Science.gov

Sample records for primary solidification phase

  1. Heterogeneous nucleation of the primary phase in the rapid solidification of Al-4.5wt%Cu alloy droplet

    NASA Astrophysics Data System (ADS)

    Maitre, A.; Bogno, A.-A.; Bedel, M.; Reinhart, G.; Henein, H.

    2015-06-01

    This paper reports on rapid solidification of Al-Cu alloys. A heterogeneous nucleation/growth model coupled with a thermal model of a falling droplet through a stagnant gas was developed. The primary undercooling as well as the number of nucleation points was compared with Al-Cu alloy droplets produced by Impulse Atomization (IA). Based on experimental results from Neutron Diffraction, secondary (eutectic) phases were obtained. Then, primary and secondary undercoolings were estimated using the metastable extensions of solidus and liquidus lines calculated by Thermo-Calc. Moreover, Synchrotron X-ray microtomography has been performed on Al-4.5wt%Cu droplets. The undercoolings are in good agreement. Results also evidence the presence of one nucleation point and are in agreement with the experimental observations.

  2. Evolution of Secondary Phases Formed upon Solidification of a Ni-Based Alloy

    NASA Astrophysics Data System (ADS)

    Zuo, Qiang; Liu, Feng; Wang, Lei; Chen, Changfeng

    2013-07-01

    The solidification of UNS N08028 alloy subjected to different cooling rates was studied, where primary austenite dendrites occur predominantly and different amounts of sigma phase form in the interdendritic regions. The solidification path and elemental segregation upon solidification were simulated using the CALPHAD method, where THERMO-CALC software packages and two classical segregation models were employed to predict the real process. It is thus revealed that the interdendritic sigma phase is formed via eutectic reaction at the last stage of solidification. On this basis, an analytical model was developed to predict the evolution of nonequilibrium eutectic phase, while the isolated morphology of sigma phase can be described using divorced eutectic theory. Size, fraction, and morphology of the sigma phase were quantitatively studied by a series of experiments; the results are in good agreement with the model prediction.

  3. Phase-field modeling of multi-phase solidification

    NASA Astrophysics Data System (ADS)

    Nestler, Britta; Wheeler, Adam A.

    2002-08-01

    A phase-field model for a general class of multi-phase metallic alloys is now proposed which describes both multi-phase solidification phenomena as well as polycrystalline grain structures. The model serves as a computational method to simulate the motion and kinetics of multiple phase boundaries and enables the visualization of the diffusion processes and of the phase transitions in multi-phase systems. Numerical simulations are presented which illustrate the capability of the phase-field model to recover a variety of complex experimental growth structures. In particular, the phase-field model can be used to simulate microstructure evolutions in eutectic, peritectic and monotectic alloys. In addition, polycrystalline grain structures with effects such as wetting, grain growth, symmetry properties of adjacent triple junctions in thin film samples and stability criteria at multiple junctions are described by phase-field simulations.

  4. Investigation of Melting and Solidification of Thin Polycrystalline Silicon Films via Mixed-Phase Solidification

    NASA Astrophysics Data System (ADS)

    Wang, Ying

    Melting and solidification constitute the fundamental pathways through which a thin-film material is processed in many beam-induced crystallization methods. In this thesis, we investigate and leverage a specific beam-induced, melt-mediated crystallization approach, referred to as Mixed-Phase Solidification (MPS), to examine and scrutinize how a polycrystalline Si film undergoes the process of melting and solidification. On the one hand, we develop a more general understanding as to how such transformations can transpire in polycrystalline films. On the other hand, by investigating how the microstructure evolution is affected by the thermodynamic properties of the system, we experimentally reveal, by examining the solidified microstructure, fundamental information about such properties (i.e., the anisotropy in interfacial free energy). Specifically, the thesis consists of two primary parts: (1) conducting a thorough and extensive investigation of the MPS process itself, which includes a detailed characterization and analysis of the microstructure evolution of the film as it undergoes MPS cycles, along with additional development and refinement of a previously proposed thermodynamic model to describe the MPS melting-and-solidification process; and (2) performing MPS-based experiments that were systematically designed to reveal more information on the anisotropic nature of Si-SiO2 interfacial energy (i.e., sigma Si-SiO2). MPS is a recently developed radiative-beam-based crystallization technique capable of generating Si films with a combination of several sought-after microstructural characteristics. It was conceived, developed, and characterized within our laser crystallization laboratory at Columbia University. A preliminary thermodynamic model was also previously proposed to describe the overall melting and solidification behavior of a polycrystalline Si film during an MPS cycle, wherein the grain-orientation-dependent solid-liquid interface velocity is identified

  5. Investigation of Melting and Solidification of Thin Polycrystalline Silicon Films via Mixed-Phase Solidification

    NASA Astrophysics Data System (ADS)

    Wang, Ying

    Melting and solidification constitute the fundamental pathways through which a thin-film material is processed in many beam-induced crystallization methods. In this thesis, we investigate and leverage a specific beam-induced, melt-mediated crystallization approach, referred to as Mixed-Phase Solidification (MPS), to examine and scrutinize how a polycrystalline Si film undergoes the process of melting and solidification. On the one hand, we develop a more general understanding as to how such transformations can transpire in polycrystalline films. On the other hand, by investigating how the microstructure evolution is affected by the thermodynamic properties of the system, we experimentally reveal, by examining the solidified microstructure, fundamental information about such properties (i.e., the anisotropy in interfacial free energy). Specifically, the thesis consists of two primary parts: (1) conducting a thorough and extensive investigation of the MPS process itself, which includes a detailed characterization and analysis of the microstructure evolution of the film as it undergoes MPS cycles, along with additional development and refinement of a previously proposed thermodynamic model to describe the MPS melting-and-solidification process; and (2) performing MPS-based experiments that were systematically designed to reveal more information on the anisotropic nature of Si-SiO2 interfacial energy (i.e., sigma Si-SiO2). MPS is a recently developed radiative-beam-based crystallization technique capable of generating Si films with a combination of several sought-after microstructural characteristics. It was conceived, developed, and characterized within our laser crystallization laboratory at Columbia University. A preliminary thermodynamic model was also previously proposed to describe the overall melting and solidification behavior of a polycrystalline Si film during an MPS cycle, wherein the grain-orientation-dependent solid-liquid interface velocity is identified

  6. Quantitative phase-field model of alloy solidification.

    PubMed

    Echebarria, Blas; Folch, Roger; Karma, Alain; Plapp, Mathis

    2004-12-01

    We present a detailed derivation and thin interface analysis of a phase-field model that can accurately simulate microstructural pattern formation for low-speed directional solidification of a dilute binary alloy. This advance with respect to previous phase-field models is achieved by the addition of a phenomenological "antitrapping" solute current in the mass conservation relation [Phys. Rev. Lett. 87, 115701 (2001)

  7. Glass Formation and Primary Solidification in Nd2Fe14B with TiC Additions

    NASA Astrophysics Data System (ADS)

    McCallum, R. W.; Willard, M. A.; Dennis, K. W.; Kramer, M. J.; Branagan, D. J.

    1996-03-01

    In bulk permanent magnets, the extrinsic properties relating to the microstructure determine the level of hard magnetic properties that is actually achieved. Alloy additions which affect the solidification behavior of the melt and then form precipitates which pin grain boundaries and therefor control grain size should be valuable in producing the uniform microstructure required for good magnetic properties. The addition of TiC to 2-14-1 results in a factor of three reduction of the quench rate required to produce amorphous material. In addition, the crystallization temperature of the glass is enhanced leading to enhanced nucleation and finer grain size during crystallization. Given the affect of TiC additions to the stochiometric melt, it is not surprising that the additions affect the range of primary solidification of the 2-14-1 phase. When TiC is added to the limit of liquid solubility, the limit 2-14-1 primary solidification is move farther from the stochiometric composition in the Nd rich region. Work at the Ames Laboratory, was supported by the U. S. Department of Energy under contract No. W-7405-ENG-82.

  8. Dual-scale phase-field simulation of Mg-Al alloy solidification

    NASA Astrophysics Data System (ADS)

    Monas, A.; Shchyglo, O.; Höche, D.; Tegeler, M.; Steinbach, I.

    2015-06-01

    Phase-field simulations of the nucleation and growth of primary α-Mg phase as well as secondary, β-phase of a Mg-Al alloy are presented. The nucleation model for α- and β-Mg phases is based on the “free growth model” by Greer et al.. After the α-Mg phase solidification we study a divorced eutectic growth of α- and β-Mg phases in a zoomed in melt channel between α-phase dendrites. The simulated cooling curves and final microstructures of α-grains are compared with experiments. In order to further enhance the resolution of the interdendritic region a high-performance computing approach has been used allowing significant simulation speed gain when using supercomputing facilities.

  9. Phase-field simulation of peritectic solidification closely coupled with directional solidification experiments in an Al-36 wt% Ni alloy.

    PubMed

    Siquieri, R; Doernberg, E; Emmerich, H; Schmid-Fetzer, R

    2009-11-18

    In this work we present experimental and theoretical investigations of the directional solidification of Al-36 wt% Ni alloy. A phase-field approach (Folch and Plapp 2005 Phys. Rev. E 72 011602) is coupled with the CALPHAD (calculation of phase diagrams) method to be able to simulate directional solidification of Al-Ni alloy including the peritectic phase Al(3)Ni. The model approach is calibrated by systematic comparison to microstructures grown under controlled conditions in directional solidification experiments. To illustrate the efficiency of the model it is employed to investigate the effect of temperature gradient on the microstructure evolution of Al-36 wt% Ni during solidification.

  10. Immiscible phase incorporation during directional solidification of hypermonotectics

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry; Merrick, Roger A.

    1993-01-01

    Solidification processes in immiscible samples were investigated by directly observing the events taking place at the solid-liquid interface during directional solidification. Visualization of these events was made possible through the use of a transparent metal analog system and a temperature gradient stage assembly fitted to an optical microscope. The immiscible transparent analog system utilized was the succinonitrile-glycerol system. This system has been shown to exhibit the same morphological transitions as observed in metallic alloys of monotectic composition. Both monotectic and hypermonotectic composition samples were directionally solidified in order to gain an improved understanding of the manner in which the excess hypermonotectic liquid is incorporated into the solidifying structure. The processing conditions utilized prevented sedimentation of the excess hypermonotectic liquid by directionally solidifying the samples in very thin (13 microns), horizontally oriented cells. High thermal gradient to growth rate ratios (G/R) were used in an effort to prevent constitutional supercooling and the subsequent formation of L(sub 2) droplets in advance of the solidification front during the growth of fibrous composite structures. Results demonstrated that hypermonotectic composites could be produced in samples up to two weight percent off of the monotectic composition by using a G/R ratio greater than or equal to 4.6 x 10(exp 4) C(s)/mm(sup 2) to avoid constitutional supercooling. For hypermonotectic samples processed with G/R ratios below 4.6 x 10(exp 4) C(s)/mm(sup 2), constitutional supercooling occurred and resulted in slight interfacial instability. For these samples, two methods of incorporation of the hypermonotectic liquid were observed and are reported. The correlation between the phase spacing, lambda, and the growth rate, R, was examined and was found to obey a relationship generally associated with a diffusion controlled coupled growth process. For

  11. Study on Solidification of Phase Change Material in Fractal Porous Metal Foam

    NASA Astrophysics Data System (ADS)

    Zhang, Chengbin; Wu, Liangyu; Chen, Yongping

    2015-02-01

    The Sierpinski fractal is introduced to construct the porous metal foam. Based on this fractal description, an unsteady heat transfer model accompanied with solidification phase change in fractal porous metal foam embedded with phase change material (PCM) is developed and numerically analyzed. The heat transfer processes associated with solidification of PCM embedded in fractal structure is investigated and compared with that in single-pore structure. The results indicate that, for the solidification of phase change material in fractal porous metal foam, the PCM is dispersedly distributed in metal foam and the existence of porous metal matrix provides a fast heat flow channel both horizontally and vertically, which induces the enhancement of interstitial heat transfer between the solid matrix and PCM. The solidification performance of the PCM, which is represented by liquid fraction and solidification time, in fractal structure is superior to that in single-pore structure.

  12. Phase Transformations During Solidification of a Laser-Beam-Welded TiAl Alloy—An In Situ Synchrotron Study

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Staron, Peter; Riekehr, Stefan; Stark, Andreas; Schell, Norbert; Huber, Norbert; Schreyer, Andreas; Müller, Martin; Kashaev, Nikolai

    2016-09-01

    An in situ highly time-resolved, high-energy X-ray diffraction investigation was carried out to observe the phase transformations of a TiAl alloy during laser beam welding. The diffraction patterns are recorded every 0.1 seconds by a fast area two-dimensional detector and plotted according to time, yielding the solidification pathway, the solid phase volume fraction, and the lattice parameter variation of different phases during the solidification and cooling process. Moreover, it is the first study that can demonstrate that the α phase without any Burgers orientation relationship, the so-called non-Burgers α, precipitates appear earlier than the Burgers α. The non-Burgers α grains are found to nucleate on the primary borides.

  13. On migration of primary/peritectic interface during interrupted directional solidification of Sn-Ni peritectic alloy.

    PubMed

    Peng, Peng; Li, Xinzhong; Li, Jiangong; Su, Yanqing; Guo, Jingjie; Fu, Hengzhi

    2016-04-14

    The migration of the primary/peritectic interface in local isothermal condition is observed in dendritic structure of Sn-Ni peritectic alloy after experiencing interrupted directional solidification. It was observed that this migration of primary Ni3Sn2/peritectic Ni3Sn4 interface towards the primary Ni3Sn2 phase was accompanied by migration of liquid film located at this interface. The migration velocity of this interface was confirmed to be much faster than that of peritectic transformation, so this migration was mostly caused by superheating of primary Ni3Sn2 phase below TP, leading to nucleation and migration of liquid film at this interface. This migration can be classified as a kind of liquid film migration (LFM), and the migration velocity at the horizontal direction has been confirmed to be much faster than that along the direction of temperature gradient. Analytical prediction has shown that the migration of liquid film could be divided into two stages depending on whether primary phase exists below TP. If the isothermal annealing time is not long enough, both the liquid film and the primary/peritectic interface migrate towards the primary phase until the superheated primary phase has all been dissolved. Then, this migration process towards higher temperature is controlled by temperature gradient zone melting (TGZM).

  14. On migration of primary/peritectic interface during interrupted directional solidification of Sn-Ni peritectic alloy

    PubMed Central

    Peng, Peng; Li, Xinzhong; Li, Jiangong; Su, Yanqing; Guo, Jingjie; Fu, Hengzhi

    2016-01-01

    The migration of the primary/peritectic interface in local isothermal condition is observed in dendritic structure of Sn–Ni peritectic alloy after experiencing interrupted directional solidification. It was observed that this migration of primary Ni3Sn2/peritectic Ni3Sn4 interface towards the primary Ni3Sn2 phase was accompanied by migration of liquid film located at this interface. The migration velocity of this interface was confirmed to be much faster than that of peritectic transformation, so this migration was mostly caused by superheating of primary Ni3Sn2 phase below TP, leading to nucleation and migration of liquid film at this interface. This migration can be classified as a kind of liquid film migration (LFM), and the migration velocity at the horizontal direction has been confirmed to be much faster than that along the direction of temperature gradient. Analytical prediction has shown that the migration of liquid film could be divided into two stages depending on whether primary phase exists below TP. If the isothermal annealing time is not long enough, both the liquid film and the primary/peritectic interface migrate towards the primary phase until the superheated primary phase has all been dissolved. Then, this migration process towards higher temperature is controlled by temperature gradient zone melting (TGZM). PMID:27075006

  15. On migration of primary/peritectic interface during interrupted directional solidification of Sn-Ni peritectic alloy

    NASA Astrophysics Data System (ADS)

    Peng, Peng; Li, Xinzhong; Li, Jiangong; Su, Yanqing; Guo, Jingjie; Fu, Hengzhi

    2016-04-01

    The migration of the primary/peritectic interface in local isothermal condition is observed in dendritic structure of Sn–Ni peritectic alloy after experiencing interrupted directional solidification. It was observed that this migration of primary Ni3Sn2/peritectic Ni3Sn4 interface towards the primary Ni3Sn2 phase was accompanied by migration of liquid film located at this interface. The migration velocity of this interface was confirmed to be much faster than that of peritectic transformation, so this migration was mostly caused by superheating of primary Ni3Sn2 phase below TP, leading to nucleation and migration of liquid film at this interface. This migration can be classified as a kind of liquid film migration (LFM), and the migration velocity at the horizontal direction has been confirmed to be much faster than that along the direction of temperature gradient. Analytical prediction has shown that the migration of liquid film could be divided into two stages depending on whether primary phase exists below TP. If the isothermal annealing time is not long enough, both the liquid film and the primary/peritectic interface migrate towards the primary phase until the superheated primary phase has all been dissolved. Then, this migration process towards higher temperature is controlled by temperature gradient zone melting (TGZM).

  16. Solidification microstructures and phase transformations in Al-Ti-Si-Mn deoxidized steel weld metals

    NASA Astrophysics Data System (ADS)

    Kluken, A. O.; Grong, Ø.; Rørvik, G.

    1990-07-01

    The present investigation is concerned with basic studies of solidification mechanisms in Al-Ti-Si-Mn deoxidized steel weld metals. Assessment of the weld metal solidification micro-structures was done on the basis of optical microscopy in combination with secondary ion mass spectrometry (SIMS), while both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for characterization of indigenous oxide inclusions. It is shown that nonmetallic inclusions play a critical role in the development of the weld metal columnar grain structure by acting as inert substrates for nucleation of delta ferrite ahead of the advancing interface. The nucleation potency of the oxides increases in the order SiO2-MnO, Al2O3-Ti2O3-SiO2-MnO, A12O3, reflecting a corresponding increase in the inclusion/liquid interfacial energy. Moreover, a shift in the peritectic reaction (which facilitates growth of the austenite grains across the phosphorus-rich boundaries of the primary delta ferrite phase) has been observed in the presence of A12O3 inclusions. Indications are that the resulting decrease in the local phosphorus concentrations at the austenite grain boundaries will strongly alter the kinetics of the subsequent solid-state transformation reactions by promoting growth of grain boundary ferrite sideplates at the expense of intragranularly nucleated acicular ferrite.

  17. Isothermal solidification stage during transient liquid-phase bonding single-crystal superalloys

    NASA Astrophysics Data System (ADS)

    Sheng, Naicheng; Liu, Jide; Jin, Tao; Sun, Xiaofeng; Hu, Zhuangqi

    2014-04-01

    In this work, the isothermal solidification stage during transient liquid-phase bonding (TLP) single-crystal superalloys has been investigated. Experiments were performed to ascertain the bonding microstructures and the kinetics during the isothermal solidification. The results have shown that the isothermal solidification stage deviates from the standard parabolic TLP models. Lots of the borides with fine, short bar and acicular morphologies formed in the diffusion affected zone (DAZ) in the thick wall and thin wall substrate specimens at the isothermal solidification stage. Electron probe microanalysis results have shown that there exists B composition peak in the DAZ. Examination of the bonding kinetics presented that there are three stages in the isothermal solidification stage: initial stage, transient stage and final stage with different growth velocity of the isothermal solidification zone (ISZ). And the relationship of the width of the ISZ with the square root of the bonding time didn't satisfy the parabolic relationship. Based on the microstructures and kinetics observed, a film ISZ mechanism is proposed, and a model is constructed to illustrate the isothermal solidification stage during bonding single-crystal superalloys.

  18. A 3-phase model for mixed columnar-equiaxed solidification in DC casting of bronze

    NASA Astrophysics Data System (ADS)

    Hao, J.; Grasser, M.; Wu, M.; Ludwig, A.; Riedle, J.; Eberle, R.

    2012-01-01

    A three-phase Eulerian approach is used to model the columnar-to-equiaxed transition (CET) during solidification in DC casting of technical bronze. The three phases are the melt, the solidifying columnar dendrites and the equiaxed grains. They are considered as spatially interpenetrating and interacting continua by solving the conservation equations of mass, momentum, species and enthalpy for all three phases. The so defined solidification model is applied to a binary CuSn6 DC casting process as a benchmark to demonstrate the model potentials. Two cases are studied: one considering only feeding flow and one including both feeding flow and equiaxed sedimentation. The simulated results of mixed columnar and equiaxed solidification are presented and discussed including the occurrence of CET, phase distribution, feeding flow, equiaxed sedimentation and their influence on macrosegregation.

  19. Thermal modeling of phase change solidification in thermal control devices including natural convection effects

    NASA Technical Reports Server (NTRS)

    Ukanwa, A. O.; Stermole, F. J.; Golden, J. O.

    1972-01-01

    Natural convection effects in phase change thermal control devices were studied. A mathematical model was developed to evaluate natural convection effects in a phase change test cell undergoing solidification. Although natural convection effects are minimized in flight spacecraft, all phase change devices are ground tested. The mathematical approach to the problem was to first develop a transient two-dimensional conduction heat transfer model for the solidification of a normal paraffin of finite geometry. Next, a transient two-dimensional model was developed for the solidification of the same paraffin by a combined conduction-natural-convection heat transfer model. Throughout the study, n-hexadecane (n-C16H34) was used as the phase-change material in both the theoretical and the experimental work. The models were based on the transient two-dimensional finite difference solutions of the energy, continuity, and momentum equations.

  20. Solidification Behavior of Polymer Solution during Membrane Preparation by Thermally Induced Phase Separation

    PubMed Central

    Ishigami, Toru; Nii, Yoko; Ohmukai, Yoshikage; Rajabzadeh, Saeid; Matsuyama, Hideto

    2014-01-01

    The solidification behavior of poly(vinylidene fluoride) (PVDF) solution during membrane preparation by thermally induced phase separation (TIPS) was investigated. Apparatus newly developed in our laboratory was used to quantitatively measure membrane stiffness during phase separation. In this apparatus, a cooling polymer solution, placed on a stage, is moved upwards and the surface of the polymer solution contacts a sphere attached to the tip of a needle. The displacement of a blade spring attached to the needle is then measured by a laser displacement sensor. Different phase separation modes, such as liquid-liquid (L-L) phase separation and solid-liquid (S-L) phase separation (polymer crystallization) were investigated. In the case of S-L phase separation, the stiffness of the solution surface began to increase significantly just before termination of crystallization. In contrast, L-L phase separation delayed solidification of the solution. This was because mutual contact of the spherulites was obstructed by droplets of polymer-lean phase formed during L-L phase separation. Thus, the solidification rate was slower for the L-L phase separation system than for the S-L phase separation system. PMID:24957124

  1. Solidification Behavior of Polymer Solution during Membrane Preparation by Thermally Induced Phase Separation.

    PubMed

    Ishigami, Toru; Nii, Yoko; Ohmukai, Yoshikage; Rajabzadeh, Saeid; Matsuyama, Hideto

    2014-01-01

    The solidification behavior of poly(vinylidene fluoride) (PVDF) solution during membrane preparation by thermally induced phase separation (TIPS) was investigated. Apparatus newly developed in our laboratory was used to quantitatively measure membrane stiffness during phase separation. In this apparatus, a cooling polymer solution, placed on a stage, is moved upwards and the surface of the polymer solution contacts a sphere attached to the tip of a needle. The displacement of a blade spring attached to the needle is then measured by a laser displacement sensor. Different phase separation modes, such as liquid-liquid (L-L) phase separation and solid-liquid (S-L) phase separation (polymer crystallization) were investigated. In the case of S-L phase separation, the stiffness of the solution surface began to increase significantly just before termination of crystallization. In contrast, L-L phase separation delayed solidification of the solution. This was because mutual contact of the spherulites was obstructed by droplets of polymer-lean phase formed during L-L phase separation. Thus, the solidification rate was slower for the L-L phase separation system than for the S-L phase separation system. PMID:24957124

  2. Phase-field study of three-dimensional steady-state growth shapes in directional solidification.

    PubMed

    Gurevich, Sebastian; Karma, Alain; Plapp, Mathis; Trivedi, Rohit

    2010-01-01

    We use a quantitative phase-field approach to study directional solidification in various three-dimensional geometries for realistic parameters of a transparent binary alloy. The geometries are designed to study the steady-state growth of spatially extended hexagonal arrays, linear arrays in thin samples, and axisymmetric shapes constrained in a tube. As a basis to address issues of dynamical pattern selection, the phase-field simulations are specifically geared to identify ranges of primary spacings for the formation of the classically observed "fingers" (deep cells) with blunt tips and "needles" with parabolic tips. Three distinct growth regimes are identified that include a low-velocity regime with only fingers forming, a second intermediate-velocity regime characterized by coexistence of fingers and needles that exist on separate branches of steady-state growth solutions for small and large spacings, respectively, and a third high-velocity regime where those two branches merge into a single one. Along the latter, the growth shape changes continuously from fingerlike to needlelike with increasing spacing. These regimes are strongly influenced by crystalline anisotropy with the third regime extending to lower velocity for larger anisotropy. Remarkably, however, steady-state shapes and tip undercoolings are only weakly dependent on the growth geometry. Those results are used to test existing theories of directional finger growth as well as to interpret the hysteretic nature of the cell-to-dendrite transition.

  3. In-situ Monitoring of Dynamic Phenomena during Solidification and Phase Transformation Processing

    SciTech Connect

    Clarke, Amy J.; Cooley, Jason C.; Morris, Christopher; Merrill, Frank E.; Hollander, Brian J.; Mariam, Fesseha G.; Patterson, Brian M.; Imhoff, Seth D.; Lee, Wah Keat; Fezzaa, Kamel; Deriy, Alex; Tucker, Tim J.; Clarke, Kester D.; Field, Robert D.; Thoma, Dan J.; Teter, David F.; Beard, Timothy V.; Hudson, Richard W.; Freibert, Franz J.; Korzekwa, Deniece R.; Farrow, Adam M.; Cross, Carl E.; Mihaila, Bogdan; Lookman, Turab; Hunter, Abigail; Choudhury, Samrat; Karma, Alain; Ott, Thomas J. Jr.; Barker, Martha R.; O'Neill, Finian; Hill, Joshua; Emigh, Megan G.

    2012-07-30

    The purpose of this project is to: (1) Directly observe phase transformations and microstructure evolution using proton (and synchrotron x-ray) radiography and tomography; (2) Constrain phase-field models for microstructure evolution; (3) Experimentally control microstructure evolution during processing to enable co-design; and (4) Advance toward the MaRIE vision. Understand microstructure evolution and chemical segregation during solidification {yields} solid-state transformations in Pu-Ga.

  4. Coupling of Atomistic and Meso-scale Phase-field Modeling of Rapid Solidification

    NASA Astrophysics Data System (ADS)

    Belak, J.; Turchi, P. E. A.; Dorr, M. R.; Richards, D. F.; Fattebert, J.-L.; Wickett, M. E.; Streitz, F. H.

    2009-03-01

    Recently, phase field models have been introduced to model the crystallography during polycrystal microstructure evolution [1,2]. Here, we assess these models with molecular dynamics and phase field simulations that overlap in time and space. Large parallel computers have enabled MD simulations of sufficient scale to observe the formation of realistic microstructure during pressure driven solidification [3]. We compare the two methods by calculating the phase field order parameter (quaternion) from the atomic coordinates and drive the evolution with the MD. Results will be presented for the solidification of tantalum. [1] R. Kobayashi and J.A. Warren, Physica A, 356, 127-132 (2005). [2] T. Pusztai, G. Bortel and L. Granasy, Europhys. Lett, 71, 131-137 (2005). [3] F. H. Streitz, J. N. Glosli, and M. V. Patel, Phys. Rev. Lett. 96, 225701 (2006).

  5. Coupling of Atomistic and Meso-scale Phase-field Modeling of Rapid Solidification

    NASA Astrophysics Data System (ADS)

    Belak, J.; Turchi, P. E. A.; Dorr, M. R.; Richards, D. F.; Fattebert, J.-L.; Wickett, M. E.; Streitz, F. H.; Tang, M.; Moelans, N.

    2009-06-01

    Recently, phase-field models have been introduced to model the crystallography during polycrystal microstructure evolution [1,2]. Here, we assess these models with molecular dynamics and phase-field simulations that overlap in time and space. Large parallel computers have enabled MD simulations of sufficient scale to observe the formation of realistic microstructure during pressure driven solidification [3]. We compare the two methods by calculating the phase field order parameter (quaternion) from the atomic coordinates and drive the evolution with the MD. Results will be presented for the solidification of tantalum. [1] R. Kobayashi and J.A. Warren, Physica A, 356, 127-132 (2005). [2] T. Pusztai, G. Bortel and L. Granasy, Europhys. Lett, 71, 131-137 (2005). [3] F. H. Streitz, J. N. Glosli, and M. V. Patel, Phys. Rev. Lett. 96, 225701 (2006).

  6. The solidification of monotectic alloys - Microstructures and phase spacings

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Hellawell, A.; Lograsso, T. A.

    1984-01-01

    The microstructures of directionally grown monotectic alloys in metallic and organic systems fall into two categories those which can form aligned fibrous composite structures with even phase spacings and fiber sections, and those in which the phase distribution is coarser and less regular. This division appears to relate to the form of the phase diagram and has been rationalized by Cahn (1977, 1979) in terms of the relative surface energies between solid and two liquids to give steady state or nonsteady state profiles. The transition in growth behavior occurs when the ratio of the monotectic temperature to that of the upper consolute temperature is approximately 0.9. Differences in phase spacings between a range of monotectic and eutectic systems are discussed in terms of the expected growth interface shapes and the factors which will influence them.

  7. Faceted growth of primary Al{sub 2}Cu crystals during directional solidification in high magnetic field

    SciTech Connect

    Li, Chuanjun; Ren, Zhongming; Shen, Yu; Wang, Qiuliang; Dai, Yinming; Wang, Hui

    2013-10-21

    The high magnetic field is widely used to modify the crystal morphology. In this work, the effect of the magnetic field on growing behavior of faceted crystals in the Al-40 wt. %Cu alloy was investigated using directional solidification technique. It was found that the faceted growth of primary Al{sub 2}Cu phase was degraded and the primary spacing was reduced upon applying the magnetic field. Additionally, the length of the mushy zone first decreased and then increased with increase of the magnetic field intensity. The quantitative analysis reveals that the shear stress induced by the fluid motion is insufficient to break the atom bonds at the solid-liquid interface. However, both of the thermoelectric magnetic convection (TEMC) and the thermoelectric magnetic force (TEMF) cause dendrites to fracture and reduce the primary spacing. The two effects also weaken the faceting growth. Moreover, the instability of the solid-liquid interface is generated by the TEMF, which further leads to degrade the faceted growth. The length of mushy zone was changed by the TEMC and reached the minimum in the magnetic field of 0.5 T, which is in good agreement with the predicted value (0.83 T)

  8. Phase-field modeling of binary alloy solidification with coupled heat and solute diffusion.

    PubMed

    Ramirez, J C; Beckermann, C; Karma, A; Diepers, H-J

    2004-05-01

    A phase-field model is developed for simulating quantitatively microstructural pattern formation in solidification of dilute binary alloys with coupled heat and solute diffusion. The model reduces to the sharp-interface equations in a computationally tractable thin-interface limit where (i). the width of the diffuse interface is about one order of magnitude smaller than the radius of curvature of the interface but much larger than the real microscopic width of a solid-liquid interface, and (ii). kinetic effects are negligible. A recently derived antitrapping current [Phys. Rev. Lett. 87, 115701 (2001)

  9. Phase field simulation on microstructure evolution in solidification and aging process of squeeze cast magnesium alloy

    NASA Astrophysics Data System (ADS)

    Pan, H. W.; Han, G. M.; Han, Z. Q.; Liu, B. C.

    2015-06-01

    Phase-field models have been developed to simulate the dendritic growth in pressurized solidification of Mg-Al alloy during squeeze casting and the precipitation of multivariant β-Mg17Al12 phases during the subsequent aging process. For the pressurized solidification, the effects of pressure on the Gibbs free energy and chemical potential of solid and liquid phases, and the solute diffusion coefficient were considered. For the precipitation during aging process, the effects of elastic strain energy, anisotropy of interfacial energy, and anisotropy of interface mobility coefficient were considered. The results showed that the dendritic growth rate tends to increase and the secondary dendrite arms are more developed as the pressure is increased from 0.1 to 100MPa, which showed a good agreement with the experimental results of direct squeeze casting of Mg-Al alloy. The 2D and 3D simulated precipitates had lath shapes with lozenge ends, and the precipitate variants were parallel to the basal plane and oriented in directions with an angular interval of 60 degrees, which is in good agreement with experimental observations.

  10. Refinement and growth enhancement of Al2Cu phase during magnetic field assisting directional solidification of hypereutectic Al-Cu alloy.

    PubMed

    Wang, Jiang; Yue, Sheng; Fautrelle, Yves; Lee, Peter D; Li, Xi; Zhong, Yunbo; Ren, Zhongming

    2016-04-19

    Understanding how the magnetic fields affect the formation of reinforced phase during solidification is crucial to tailor the structure and therefor the performance of metal matrix in situ composites. In this study, a hypereutectic Al-40 wt.%Cu alloy has been directionally solidified under various axial magnetic fields and the morphology of Al2Cu phase was quantified in 3D by means of high resolution synchrotron X-ray tomography. With rising magnetic fields, both increase of Al2Cu phase's total volume and decrease of each column's transverse section area were found. These results respectively indicate the growth enhancement and refinement of the primary Al2Cu phase in the magnetic field assisting directional solidification. The thermoelectric magnetic forces (TEMF) causing torque and dislocation multiplication in the faceted primary phases were thought dedicate to respectively the refinement and growth enhancement. To verify this, a real structure based 3D simulation of TEMF in Al2Cu column was carried out, and the dislocations in the Al2Cu phase obtained without and with a 10T high magnetic field were analysed by the transmission electron microscope.

  11. Refinement and growth enhancement of Al2Cu phase during magnetic field assisting directional solidification of hypereutectic Al-Cu alloy.

    PubMed

    Wang, Jiang; Yue, Sheng; Fautrelle, Yves; Lee, Peter D; Li, Xi; Zhong, Yunbo; Ren, Zhongming

    2016-01-01

    Understanding how the magnetic fields affect the formation of reinforced phase during solidification is crucial to tailor the structure and therefor the performance of metal matrix in situ composites. In this study, a hypereutectic Al-40 wt.%Cu alloy has been directionally solidified under various axial magnetic fields and the morphology of Al2Cu phase was quantified in 3D by means of high resolution synchrotron X-ray tomography. With rising magnetic fields, both increase of Al2Cu phase's total volume and decrease of each column's transverse section area were found. These results respectively indicate the growth enhancement and refinement of the primary Al2Cu phase in the magnetic field assisting directional solidification. The thermoelectric magnetic forces (TEMF) causing torque and dislocation multiplication in the faceted primary phases were thought dedicate to respectively the refinement and growth enhancement. To verify this, a real structure based 3D simulation of TEMF in Al2Cu column was carried out, and the dislocations in the Al2Cu phase obtained without and with a 10T high magnetic field were analysed by the transmission electron microscope. PMID:27091383

  12. Phase-field simulations of particle capture during the directional solidification of silicon

    NASA Astrophysics Data System (ADS)

    Aufgebauer, Henning; Kundin, Julia; Emmerich, Heike; Azizi, Maral; Reimann, Christian; Friedrich, Jochen; Jauß, Thomas; Sorgenfrei, Tina; Cröll, Arne

    2016-07-01

    We present a phase-field model for particle capture during directional solidification. Its predictions for critical growth velocities for particles of different sizes are compared with experimental results for capture of silicon carbide (SiC) particles during directional solidification of silicon. The phase-field model allows us to systematically test the influence of different assumptions about attractive and repulsive forces and the capture mechanisms, including the effects of particle shape and of partial engulfment of the particle by the interface. We identify common properties of models that show agreement with experiments, trying to determine the underlying physical effects by abductive inference. We find that predictions vary only slightly between models with different repulsive forces and that the shape of the particle can have a larger effect on the critical growth velocity than the exact nature of the repulsive force or the capture process. We assess to what extent a good description of experimental critical growth velocities implies that the model accurately describes the actual physical processes and propose additional ways to test the validity of models.

  13. Terfenol: A study of the phase equilibrium diagram and the solidification process

    SciTech Connect

    Anderson, M.

    1993-12-07

    Terfenol is a rare earth-iron alloy that was first developed at the Naval Ordinance Laboratory because of its rare magnetostrictive properties. Terfenol is composed of terbium and dysprosium combined with iron in a composition Tb{sub x}Dy{sub 1{minus}x}Fe{sub 2}, where x{approximately}0.3. The objective of this work was to determine the growth characteristics of Terfenol and its dependence on solidification rate, temperature gradient, and stoichiometry. Specific goals of this work were to verify the phase equilibria that is currently accepted for the systems DyFe{sub 2} and TbFe{sub 2}, and establish the phase equilibria near the composition Tb{sub 0.3}Dy{sub 0.7}Fe{sub 2}; establish that Terfenol grows directly from the liquid and that the reaction is occurring under metastable conditions; evaluate whether or not Terfenol can be grown under plane front conditions with a new radiofrequency float zone apparatus, and; determine whether or not <111> seeded crystals can be grown and <111> single crystals produced by elimination of dendrites employing growth methods capable of achieving high gradient/solidification rate ratios.

  14. Specimen analysis of Skylab, M553 experiment, flight specimens, phase C.. [on metals melting containerless solidification

    NASA Technical Reports Server (NTRS)

    Larson, D. J., Jr.

    1974-01-01

    Skylab 2 flight samples were analyzed to study containerless solidification and the effects of weightlessness on the process. A record of solute redistribution processes and of solidification terracing is reported. The solute redistribution process was highly localized, and low index, crystallographic system were suggested. Samples demonstrated that under reduced pressure and gravity conditions the anticipated solid/liquid solidification process was perturbed and superseded by solid/liquid/gas reactions during melting and solidification.

  15. Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification

    SciTech Connect

    Choi, Jeong

    2011-01-01

    The research program reported here is focused on critical issues that represent conspicuous gaps in current understanding of rapid solidification, limiting our ability to predict and control microstructural evolution (i.e. morphological dynamics and microsegregation) at high undercooling, where conditions depart significantly from local equilibrium. More specifically, through careful application of phase-field modeling, using appropriate thin-interface and anti-trapping corrections and addressing important details such as transient effects and a velocity-dependent (i.e. adaptive) numerics, the current analysis provides a reasonable simulation-based picture of non-equilibrium solute partitioning and the corresponding oscillatory dynamics associated with single-phase rapid solidification and show that this method is a suitable means for a self-consistent simulation of transient behavior and operating point selection under rapid growth conditions. Moving beyond the limitations of conventional theoretical/analytical treatments of non-equilibrium solute partitioning, these results serve to substantiate recent experimental findings and analytical treatments for single-phase rapid solidification. The departure from the equilibrium solid concentration at the solid-liquid interface was often observed during rapid solidification, and the energetic associated non-equilibrium solute partitioning has been treated in detail, providing possible ranges of interface concentrations for a given growth condition. Use of these treatments for analytical description of specific single-phase dendritic and cellular operating point selection, however, requires a model for solute partitioning under a given set of growth conditions. Therefore, analytical solute trapping models which describe the chemical partitioning as a function of steady state interface velocities have been developed and widely utilized in most of the theoretical investigations of rapid solidification. However, these

  16. Refinement and growth enhancement of Al2Cu phase during magnetic field assisting directional solidification of hypereutectic Al-Cu alloy

    NASA Astrophysics Data System (ADS)

    Wang, Jiang; Yue, Sheng; Fautrelle, Yves; Lee, Peter D.; Li, Xi; Zhong, Yunbo; Ren, Zhongming

    2016-04-01

    Understanding how the magnetic fields affect the formation of reinforced phase during solidification is crucial to tailor the structure and therefor the performance of metal matrix in situ composites. In this study, a hypereutectic Al-40 wt.%Cu alloy has been directionally solidified under various axial magnetic fields and the morphology of Al2Cu phase was quantified in 3D by means of high resolution synchrotron X-ray tomography. With rising magnetic fields, both increase of Al2Cu phase’s total volume and decrease of each column’s transverse section area were found. These results respectively indicate the growth enhancement and refinement of the primary Al2Cu phase in the magnetic field assisting directional solidification. The thermoelectric magnetic forces (TEMF) causing torque and dislocation multiplication in the faceted primary phases were thought dedicate to respectively the refinement and growth enhancement. To verify this, a real structure based 3D simulation of TEMF in Al2Cu column was carried out, and the dislocations in the Al2Cu phase obtained without and with a 10T high magnetic field were analysed by the transmission electron microscope.

  17. Refinement and growth enhancement of Al2Cu phase during magnetic field assisting directional solidification of hypereutectic Al-Cu alloy

    PubMed Central

    Wang, Jiang; Yue, Sheng; Fautrelle, Yves; Lee, Peter D.; Li, Xi; Zhong, Yunbo; Ren, Zhongming

    2016-01-01

    Understanding how the magnetic fields affect the formation of reinforced phase during solidification is crucial to tailor the structure and therefor the performance of metal matrix in situ composites. In this study, a hypereutectic Al-40 wt.%Cu alloy has been directionally solidified under various axial magnetic fields and the morphology of Al2Cu phase was quantified in 3D by means of high resolution synchrotron X-ray tomography. With rising magnetic fields, both increase of Al2Cu phase’s total volume and decrease of each column’s transverse section area were found. These results respectively indicate the growth enhancement and refinement of the primary Al2Cu phase in the magnetic field assisting directional solidification. The thermoelectric magnetic forces (TEMF) causing torque and dislocation multiplication in the faceted primary phases were thought dedicate to respectively the refinement and growth enhancement. To verify this, a real structure based 3D simulation of TEMF in Al2Cu column was carried out, and the dislocations in the Al2Cu phase obtained without and with a 10T high magnetic field were analysed by the transmission electron microscope. PMID:27091383

  18. Solidification of Mg-Zn-Y Alloys at 6 GPa Pressure: Nanostructure, Phases Formed, and Their Stability

    NASA Astrophysics Data System (ADS)

    Zhou, Haitao; Liu, Keming; Zhang, Li; Atrens, Andrej; Yu, Jiuming; Li, Xiaolong

    2016-09-01

    Mg-Zn-Y alloys solidified under high pressure were characterized using XRD, DTA, SEM, and TEM. After solidification at atmospheric pressure, Mg-6Zn-1Y consisted of α-Mg, Mg7Zn3, and Mg3YZn6, while Mg-6Zn-3Y consisted of α-Mg, Mg3Y2Zn3, and Mg3YZn6. After solidification at 6 GPa pressure, both alloys consisted of α-Mg, MgZn, and Mg12YZn. The size and the shape of the second-phase particles formed for atmospheric solidification were significantly different to those formed for solidification at 6 GPa pressure. In Mg-6Zn-1Y, the second-phase size decreased from 300 to 50 nm, and the shape changed from needle like to blocky. In Mg-6Zn-3Y, the size decreased from 100 to 50 nm and the shape changed from short rod like to small and round. After aging at 200 °C for 12 h, the new MgZn phase transformed into the intermediate MgZn2 phase. Increasing the aging time to 24 h caused the intermediate MgZn2 phase to transform into Mg7Zn3 with a size of 50 nm, while the Mg12YZn phase remained unchanged.

  19. Phase-field model for solidification of a monotectic alloy with convection

    NASA Astrophysics Data System (ADS)

    Nestler, B.; Wheeler, A. A.; Ratke, L.; Stöcker, C.

    2000-07-01

    In this paper we discuss two phase-field models for solidification of monotectic alloys, a situation in which a liquid phase L 1 may simultaneously transform into both a new liquid phase L 2 and a solid phase S via the reaction L 1→L 2+S. The first model uses three different phase-fields to characterize the three phases in the system and, in addition, a concentration field. This construction restricts the validity of the model to describe phase transitions within the vicinity of the monotectic temperature. In contrast, the second model distinguishes the two liquid phases by their concentration using a Cahn-Hilliard type model and employs only one phase-field to characterize the system as solid or liquid. This formulation enables the second model to represent a wider temperature range of the phase diagram including the miscibility gap where the spinodal decomposition L→L 1+L 2 occurs. Both our models permit the interfaces to have temperature-dependent surface energies which may induce Marangoni convection at L 1-L 2 interfaces in non-isothermal systems. By deriving a generalized stress tensor including stresses associated with the capillary forces on the diffuse interface, we extend the two monotectic phase-field models to account for convection in both liquid phases. Together with a generalized set of Navier-Stokes equations, we give a complete set of dynamic field equations to describe monotectic systems with fluid flow. Finally, we present numerical simulations of lamellar monotectic growth structures which exhibit wetting phenomena as well as coarsening and particle pushing.

  20. A thermodynamically consistent numerical method for a phase field model of solidification

    NASA Astrophysics Data System (ADS)

    Gonzalez-Ferreiro, B.; Gomez, H.; Romero, I.

    2014-07-01

    A discretization is presented for the initial boundary value problem of solidification as described in the phase-field model developed by Penrose and Fife (1990) [1] and Wang et al. (1993) [2]. These are models that are completely derived from the laws of thermodynamics, and the algorithms that we propose are formulated to strictly preserve them. Hence, the discrete solutions obtained can be understood as discrete dynamical systems satisfying discrete versions of the first and second laws of thermodynamics. The proposed methods are based on a finite element discretization in space and a midpoint-type finite-difference discretization in time. By using so-called discrete gradient operators, the conservation/entropic character of the continuum model is inherited in the numerical solution, as well as its Lyapunov stability in pure solid/liquid equilibria.

  1. Quantitative investigation of cellular growth in directional solidification by phase-field simulation.

    PubMed

    Wang, Zhijun; Wang, Jincheng; Li, Junjie; Yang, Gencang; Zhou, Yaohe

    2011-10-01

    Using a quantitative phase-field model, a systematic investigation of cellular growth in directional solidification is carried out with emphasis on the selection of cellular tip undercooling, tip radius, and cellular spacing. Previous analytical models of cellular growth are evaluated according to the phase-field simulation results. The results show that cellular tip undercooling and tip radius not only depend on the pulling velocity and thermal gradient, but also depend on the cellular interaction related to the cellular spacing. The cellular interaction results in a finite stable range of cellular spacing. The lower limit is determined by the submerging mechanism while the upper limit comes from the tip splitting instability corresponding to the absence of the cellular growth solution, both of which can be obtained from phase-field simulation. Further discussions on the phase-field results also present an analytical method to predict the lower limit. Phase-field simulations on cell elimination between cells with equal spacing validate the finite range of cellular spacing and give deep insight into the cellular doublon and oscillatory instability between cell elimination and tip splitting.

  2. Effect of solidification rate on microstructure evolution in dual phase microalloyed steel

    PubMed Central

    Kostryzhev, A. G.; Slater, C. D.; Marenych, O. O.; Davis, C. L.

    2016-01-01

    In steels the dependence of ambient temperature microstructure and mechanical properties on solidification rate is not well reported. In this work we investigate the microstructure and hardness evolution for a low C low Mn NbTi-microalloyed steel solidified in the cooling rate range of 1–50 Cs−1. The maximum strength was obtained at the intermediate solidification rate of 30 Cs−1. This result has been correlated to the microstructure variation with solidification rate. PMID:27759109

  3. A Phase-Field Solidification Model of Almost Pure ITS-90 Fixed Points

    NASA Astrophysics Data System (ADS)

    Large, M. J.; Pearce, J. V.

    2014-07-01

    A two-dimensional axisymmetric phase-field model of thermo-solutal solidification in freezing-point cells used for calibrating standard platinum resistance thermometers for realization and dissemination of the International Temperature Scale of 1990 is presented. The cell is essentially a graphite crucible containing an ingot of very pure metal (of order 99.9999 %). A graphite tube is inserted along the axis of the ingot to enable immersion of the thermometer in the metal. In this study, the metal is tin (freezing temperature of ). During the freezing of these cells, a steady, reproducible temperature is realized, with a defined temperature that can be used to calibrate thermometers with uncertainties mK. The model is applied to understand the effect of experimental parameters, such as initiation technique and furnace homogeneity, on the measured freezing curve. Results show that freezing curves whose behavior is consistent with the Scheil theory of solidification can be obtained with a specific furnace temperature profile, and provided that the freeze is of a long duration, the results are consistent with previous one-dimensional models and experiments. Morphological instability is observed with the inner interface initiation technique, causing the interface to adopt a cellular structure. This elevates the measured temperature, in accordance with the Gibbs-Thomson effect. In addition, the influence of initiation techniques on the solidification behavior is examined. The model indicates that an initially smooth inner mantle can `de-wet' from the thermometer well-forming agglomerated solid droplets, following recalescence, under certain conditions. This manifests as a measured temperature depression due to the Gibbs-Thomson effect, with a magnitude of to in simulations. The temperature rises to that of the stable outer mantle as freezing progresses and the droplets re-melt. It is demonstrated that the effect occurs below a critical mantle thickness. A physical

  4. Phase-field modeling of microstructural pattern formation during directional solidification of peritectic alloys without morphological instability.

    PubMed

    Lo, T S; Karma, A; Plapp, M

    2001-03-01

    During the directional solidification of peritectic alloys, two stable solid phases (parent and peritectic) grow competitively into a metastable liquid phase of larger impurity content than either solid phase. When the parent or both solid phases are morphologically unstable, i.e., for a small temperature gradient/growth rate ratio (G/v(p)), one solid phase usually outgrows and covers the other phase, leading to a cellular-dendritic array structure closely analogous to the one formed during monophase solidification of a dilute binary alloy. In contrast, when G/v(p) is large enough for both phases to be morphologically stable, the formation of the microstructure becomes controlled by a subtle interplay between the nucleation and growth of the two solid phases. The structures that have been observed in this regime (in small samples where convection effects are suppressed) include alternate layers (bands) of the parent and peritectic phases perpendicular to the growth direction, which are formed by alternate nucleation and lateral spreading of one phase onto the other as proposed in a recent model [R. Trivedi, Metall. Mater. Trans. A 26, 1 (1995)], as well as partially filled bands (islands), where the peritectic phase does not fully cover the parent phase which grows continuously. We develop a phase-field model of peritectic solidification that incorporates nucleation processes in order to explore the formation of these structures. Simulations of this model shed light on the morphology transition from islands to bands, the dynamics of spreading of the peritectic phase on the parent phase following nucleation, which turns out to be characterized by a remarkably constant acceleration, and the types of growth morphology that one might expect to observe in large samples under purely diffusive growth conditions.

  5. Microsegregation and Secondary Phase Formation During Directional Solidification of the Single-Crystal Ni-Based Superalloy LEK94

    NASA Astrophysics Data System (ADS)

    Lopez-Galilea, Inmaculada; Huth, Stephan; Fries, Suzana G.; Warnken, Nils; Steinbach, Ingo; Theisen, Werner

    2012-12-01

    A multicomponent phase-field method coupled to thermodynamic calculations according to the CALPHAD method was used to simulate microstructural evolution during directional solidification of the LEK94 commercial single-crystal Ni-based superalloy using a two-dimensional unit cell approximation. We demonstrate quantitative agreement of calculated microsegregation profiles and profiles determined from casting experiments as well as calculated fraction solid curves with those determined in differential thermal analysis (DTA) measurements. Finally, the role of solidification rate on dendrite morphology and precipitation of the secondary phases is investigated and a new measure of the dendrite morphology is presented to quantify the effect of back diffusion on the amount of secondary phases.

  6. Phase equillibria and solidification behaviour in the vanillin- p-anisidine system

    NASA Astrophysics Data System (ADS)

    Singh, N. B.; Das, S. S.; Gupta, Preeti; Dwivedi, M. K.

    2008-12-01

    Phase diagram of the vanillin- p-anisidine system has been studied by the thaw melt method. Congruent melting-type phase diagram exhibiting two eutectic points was obtained. Vanillin and p-anisidine react in 1:1 M ratio and form N-(4-methoxy phenyl)-4-hydroxy-3-methoxy phenyl methanimine (NHM) and water. Heats of fusion of pure components and the eutectic mixtures ( E1 and E2) were obtained from DSC studies. Jackson's roughness parameters ( α) were calculated. Excess Gibbs free energy ( GE), excess entropy ( SE) and excess enthalpy ( HE) of mixing of pre-, post- and eutectic mixtures were also calculated by using activity coefficient data. Linear velocities of solidification of components and eutectic mixtures were determined at different undercoolings. The values of excess thermodynamic functions and linear velocity data have indicated the non-ideal nature of the eutectic mixtures. Interaction energies in the gaseous state, calculated from computer simulation, have also indicated that the eutectics are non-ideal mixtures. Microstructural studies of vanillin, p-anisidine and NHM show the formation of broken lamellar type structures. However, for the eutectic E1, an irregular type and for the eutectic E2, a lamellar type structures were obtained. The effect of impurity on the microstructures of eutectic mixtures was also studied.

  7. Formation mechanism of primary phases and eutectic structures within undercooled Pb-Sb-Sn ternary alloys

    NASA Astrophysics Data System (ADS)

    Wang, Weili; Dai, Fuping; Wei, Bingbo

    2007-08-01

    The solidification characteristics of three types of Pb-Sb-Sn ternary alloys with different primary phases were studied under substantial undercooling conditions. The experimental results show that primary (Pb) and SbSn phases grow in the dendritic mode, whereas primary (Sb) phase exhibits faceted growth in the form of polygonal blocks and long strips. (Pb) solid solution phase displays strong affinity with SbSn intermetallic compound so that they produce various morphologies of pseudobinary eutectics, but it can only grow in the divorced eutectic mode together with (Sb) phase. Although (Sb) solid solution phase and SbSn intermetallic compound may grow cooperatively within ternary eutectic microstructures, they seldom form pseudobinary eutectics independently. The (Pb)+(Sb)+SbSn ternary eutectic structure usually shows lamellar morphology, but appears as anomalous eutectic when its volume fraction becomes small. EDS analyses reveal that all of the three primary (Pb), (Sb) and SbSn phases exhibit conspicuous solute trapping effect during rapid solidification, which results in the remarkable extension of solute solubility.

  8. Application of vesicular coacervate phase for microextraction based on solidification of floating drop.

    PubMed

    Moradi, Morteza; Yamini, Yadollah

    2012-03-16

    A new, efficient and environmentally friendly method for the analysis of parabens as model compounds was developed using solidified floating vesicular coacervative drop microextraction (SFVCDME). A supramolecular solvent consisting of vesicles of decanoic acid in the nano- and microscale regimes was firstly used as the solvent in solidification of floating drop microextraction. The solvent was produced from the coacervation of decanoic acid aqueous vesicles in the presence of tetrabutylammonium (Bu(4)N(+)). Methylparaben (MP), ethylparaben (EP), and propylparaben (PP) were extracted on the basis of hydrophobic and π-cation interactions and the formation of hydrogen bonds. Microliter volume of vesicular coacervative droplet was delivered to the surface of the aqueous sample, and the sample was stirred for a desired time. The sample vial was cooled by immersing it into an ice bath for 3 min. The solidified solvent was transferred into a suitable vial and melted immediately. Twenty microliter of the vesicular coacervative solvent was directly injected to high-performance liquid chromatography-ultraviolet detection, with no need to dilution or solvent evaporation. Several parameters affecting the microextraction efficiency including sample temperature, stirring rate, pH, salt effect, volume of the solvent and extraction time were investigated and optimized. Under optimum conditions, preconcentration factors and relative recoveries of the studied compounds were obtained in the range of 81-174 and 91-108%, respectively; and the performance of the method was comparable with that of solid-phase extraction as the reference method.

  9. Asymmetric Diffusional Solidification during Transient Liquid Phase Bonding of Dissimilar Materials

    NASA Astrophysics Data System (ADS)

    Ghoneim, A.; Ojo, O. A.

    2012-03-01

    A theoretical analysis of diffusional solidification during transient liquid phase (TLP) bonding of dissimilar materials was performed in conjunction with experimental verification. A fully implicit, two-dimensional, finite element numerical simulation model, without the inherent symmetry assumption, was developed and used for the theoretical calculations, and good correlations between the model predictions and experimental results were observed. The study showed that an asymmetric distribution of residual interlayer liquid during a dissimilar joining of polycrystal and single crystal alloys is attributable to a mismatch between their lattice diffusion coefficients or solute solubility, irrespective of enhanced intergranular diffusion as was assumed previously. Also, notwithstanding increased solute diffusivity with temperature, it was found that an increase in bonding temperature can result in the prolongation of processing time t f that is required to prevent the formation of deleterious eutectic during bonding of dissimilar materials. The occurrence of this seemingly anomalous behavior, however, reduces when a material is coupled with another type that exhibits a higher solute solubility or better capability of accommodating diffusing melting point depressant solute from the liquid interlayer.

  10. Application of vesicular coacervate phase for microextraction based on solidification of floating drop.

    PubMed

    Moradi, Morteza; Yamini, Yadollah

    2012-03-16

    A new, efficient and environmentally friendly method for the analysis of parabens as model compounds was developed using solidified floating vesicular coacervative drop microextraction (SFVCDME). A supramolecular solvent consisting of vesicles of decanoic acid in the nano- and microscale regimes was firstly used as the solvent in solidification of floating drop microextraction. The solvent was produced from the coacervation of decanoic acid aqueous vesicles in the presence of tetrabutylammonium (Bu(4)N(+)). Methylparaben (MP), ethylparaben (EP), and propylparaben (PP) were extracted on the basis of hydrophobic and π-cation interactions and the formation of hydrogen bonds. Microliter volume of vesicular coacervative droplet was delivered to the surface of the aqueous sample, and the sample was stirred for a desired time. The sample vial was cooled by immersing it into an ice bath for 3 min. The solidified solvent was transferred into a suitable vial and melted immediately. Twenty microliter of the vesicular coacervative solvent was directly injected to high-performance liquid chromatography-ultraviolet detection, with no need to dilution or solvent evaporation. Several parameters affecting the microextraction efficiency including sample temperature, stirring rate, pH, salt effect, volume of the solvent and extraction time were investigated and optimized. Under optimum conditions, preconcentration factors and relative recoveries of the studied compounds were obtained in the range of 81-174 and 91-108%, respectively; and the performance of the method was comparable with that of solid-phase extraction as the reference method. PMID:22305363

  11. In-Situ X-Ray Microscopy of Phase and Composition Distributions in Metal Alloys During Solidification

    NASA Technical Reports Server (NTRS)

    Kaukler, William F.; Curreri, Peter A.

    1999-01-01

    This research applies a state of the art X-ray Transmission Microscope, to image the solidification of metallic or semiconductor alloys in real-time. By employing a hard x-ray source with sub-micron dimensions, resolutions of up to 3 gm can be obtained with magnifications of over 800 X. Specimen growth conditions were optimized and the best imaging technologies applied to maintain x-ray image resolution, contrast and sensitivity. In addition, a special furnace design is required to permit controlled growth conditions and still offer maximum resolution and image contrast. We have successfully imaged in real-time: interfacial morphologies, phase growth, coalescence, incorporation of phases into the growing interface, and the solute boundary layer in the liquid at the solid-liquid inter-face. We have also measured true local growth rates and can evaluate segregation structures in the solid; a form of in-situ metallography. Composition gradients within the specimen cause vafiations in absorption of the flux such that the final image represents a spatial integral of composition (or thickness). During this study, the growth of secondary phase fibers and lameilae from eutectic and monotectic alloys have been imaged during solidification, in real-time, for the first time in bulk metal alloys. Keywords: x-ray, microscope, solidification, microfocus, real-time, microstructure

  12. A novel procedure for phase separation in dispersive liquid-liquid microextraction based on solidification of the aqueous phase.

    PubMed

    March, J G; Cerdà, V

    2016-08-15

    In this paper, an alternative for handling the organic phase after a dispersive liquid-liquid microextraction using organic solvents lighter than water is presented. It is based on solidification (at -18°C) of the aqueous phase obtained after centrifugation, and the decantation, collection and analysis of the liquid organic layer. The extraction of nicotine in toluene, and its determination in eggplant samples was conducted as a proof of concept. The study has been carried out using standards prepared in water and the formation of the dispersion was assisted by sonication. The organic extract was analysed using gas chromatography coupled to mass spectrometry. Satisfactory analytical figures of merit as: limit of detection (0.4µgL(-1), 2ngg(-1) wet sample), limit of quantification (1.2µgL(-1), 6.5ngg(-1) wet sample), within-day precision (RSD=7%), and linearity interval (up to 384µgL(-1) nicotine) were achieved. It constituted a contribution to the handling of organic extracts after microextraction processes. PMID:27260454

  13. Solidification of nano-enhanced phase change material (NEPCM) in a wavy cavity

    NASA Astrophysics Data System (ADS)

    Kashani, S.; Ranjbar, A. A.; Abdollahzadeh, M.; Sebti, S.

    2012-07-01

    The effects of surface waviness ( λ = 0, 0.125, 0.25, 0.5) and nanoparticle dispersion ( ϕ = 0, 0.05, 0.1) on solidification of Cu-water nanofluid inside a vertical enclosure are investigated numerically for different Grashof number ( Gr = 105, 106, 107). An enthalpy porosity technique is used to trace the solid and liquid interface. Comparisons with previously published works show the accuracy of the obtained results. A maximum of 25.9% relative variation of freezing time with surface waviness was observed for λ = 0.5, while the relative variation of freezing time with nanoparticles in comparison with surface waviness was negative for high values of λ. It was observed that surface waviness can be used to control the solidification time based on enhancing different mechanism of solidification.

  14. Morphologies of Primary Silicon in Hypereutectic Al-Si Alloys: Phase-Field Simulation Supported by Key Experiments

    NASA Astrophysics Data System (ADS)

    Wang, Kai; Wei, Ming; Zhang, Lijun; Du, Yong

    2016-04-01

    We realized a three-dimensional visualization of the morphology evolution and the growth behavior of the octahedral primary silicon in hypereutectic Al-20wtpctSi alloy during solidification in a real length scale by utilizing the phase-field simulation coupled with CALPHAD databases, and supported by key experiments. Moreover, through two-dimensional cut of the octahedral primary silicon at random angles, different morphologies observed in experiments, including triangle, square, trapezoid, rhombic, pentagon, and hexagon, were well reproduced.

  15. Modeling of Detached Solidification

    NASA Technical Reports Server (NTRS)

    Regel, Liya L.; Wilcox, William R.; Popov, Dmitri

    1997-01-01

    Our long term goal is to develop techniques to achieve detached solidification reliably and reproducibly, in order to produce crystals with fewer defects. To achieve this goal it is necessary to understand thoroughly the physics of detached solidification. It was the primary objective of the current project to make progress toward this complete understanding. 'Me products of this grant are attached. These include 4 papers and a preliminary survey of the observations of detached solidification in space. We have successfully modeled steady state detached solidification, examined the stability of detachment, and determined the influence of buoyancy-driven convection under different conditions. Directional solidification in microgravity has often led to ingots that grew with little or no contact with the ampoule wall. When this occurred, crystallographic perfection was usually greatly improved -- often by several orders of magnitude. Indeed, under the Soviet microgravity program the major objective was to achieve detached solidification with its resulting improvement in perfection and properties. Unfortunately, until recently the true mechanisms underlying detached solidification were unknown. As a consequence, flight experiments yielded erratic results. Within the past three years, we have developed a new theoretical model that explains many of the flight results. This model gives rise to predictions of the conditions required to yield detached solidification.

  16. In-situ x-ray microscopy of phase and composition distributions in metal alloys during solidification

    NASA Astrophysics Data System (ADS)

    Kaukler, William F.; Curreri, Peter A.

    1999-07-01

    This research applies a state of the art x-ray transmission microscope, to image the solidification of metallic or semiconductor alloys in real-time. By employing a hard x-ray source with sub-micron dimensions, resolutions of up to 2 micrometers can be obtained with magnifications of over 800 X. Specimen growth conditions were optimized and the best imaging technologies applied to maintain x-ray image resolution, contrast and sensitivity. In addition, a special furnace design is required to permit controlled growth conditions and still offer maximum resolution and image contrast. We have successfully imaged in real-time: interfacial morphologies, phase growth, coalescence, incorporation of phases into the growing interface, and the solute boundary layer in the liquid at the solid-liquid interface. We have also measured true local growth rates and can evaluate segregation structures in the solid; a form of in situ metallography. Composition gradients within the specimen cause variations in absorption of the flux such that the final image represents a spatial integration of composition. During this study, the growth of secondary phase fibers and lamellae form eutectic and monotectic alloys have been imaged during solidification, in real-time, for the first time in bulk metal alloys.

  17. Influence of solidification conditions on {gamma}{prime}-phase thermal stability in <001> single crystals of Ni-based superalloys

    SciTech Connect

    Stepanova, N.N.; Sazonova, V.A.; Rodionov, D.P.

    1999-02-05

    Operating conditions for details of the nickel-based superalloys under long-term high-temperature loading necessitate high thermal stability of the alloy structure as a whole and {gamma}{prime}-phase especially, as the latter is an essential factor of the alloy strengthening. The direct investigation of the phase stability of superalloy specimens in the range of operating temperatures is of major interest. In the present work high-temperature X-ray technique was used to study the {gamma}{prime}-phase thermal stability upon heating in the temperature range from 20 C to 1200 C for a series of <001> single crystal specimens of nickel-based superalloy ZhS 26 obtained using various regimes of the melt overheating before solidification.

  18. Effects of Manganese Content on Solidification Structures, Thermal Properties, and Phase Transformation Characteristics in Fe-Mn-Al-C Steels

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Wang, Yu-Nan; Ruan, Xiao-Ming; Wang, Rui-Zhi; Zhu, Kai; Fan, Zheng-Jie; Wang, Ying-Chun; Li, Cheng-Bin; Jiang, Xiao-Fang

    2015-04-01

    To assist developments of the continuous-casting technology of Fe-Mn-Al-C steels, the solidification structures and the thermal properties of Fe-Mn-Al-C steel ingots with different manganese contents have been investigated and the phase transformation characteristics have been revealed by FactSage (CRCT-ThermFact Inc., Montréal, Canada). The results show that the thermal conductivity of the 0Mn steel is the highest, whereas the thermal conductivity of the 8Mn steel is slightly higher than that of the 17Mn steel. Increasing the manganese content promotes a columnar solidification structure and coarse grains in steel. With the increase of manganese content, the mass fraction of austenite phase is increased. Finally, a single austenite phase is formed in the 17Mn steel. The mean thermal expansion coefficients of the steels are in the range from 1.3 × 10-5 to 2.3 × 10-5 K-1, and these values increase with the increase of manganese content. The ductility of the 17Mn steel and the 8Mn steel are higher than 40 pct in the temperature range from 873 K to 1473 K (600 °C to 1200 °C), and the cracking during the straightening operation should be avoided. However, the ductility of the 0Mn steel is lower than 40 pct at 973 K and 1123 K (700 °C and 850 °C), which indicates that the temperature of the straightening operation during the continuous-casting process should be above 1173 K (900 °C). Manganese has the effect of enlarging the austenite phase region and reducing the δ-ferrite phase region and α-ferrite phase region. At the 2.1 mass pct aluminum level, the precipitate temperature of AlN is high. Thus, the formed AlN is too coarse to deteriorate the hot ductility of steel.

  19. Solidification mechanism transition of liquid Co-Cu-Ni ternary alloy

    NASA Astrophysics Data System (ADS)

    Zang, D. Y.; Wang, H. P.; Dai, F. P.; Langevin, D.; Wei, B.

    2011-01-01

    We report a solidification mechanism transition of liquid ternary Co45Cu45Ni10 alloy when it solidifies at a critical undercooling of about 344 K. When undercooling at Δ T<344 K, the solidification process is characterized by primary S (Co) dendritic growth and a subsequent peritectic transition. The dendritic growth velocity of S (Co) dendrite increases with the rise of undercooling. However, once Δ T>344 K, the solidification velocity decreases with the increase of undercooling. In this case, liquid/liquid phase separation takes place prior to solidification. The minor L2 (Cu) droplets hinder the motion of the solidification front, and a monotectic transition may occur in the major L1 phase. These facts caused by metastable phase separation are responsible for the slow growth at high undercoolings.

  20. Stability of metastable phase and soft magnetic properties of bulk Fe-B nano-eutectic alloy prepared by undercooling solidification combined with CU-mold chilling

    NASA Astrophysics Data System (ADS)

    Yang, Changlin; Zhang, Jun; Huang, Huili; Song, Qijiao; Liu, Feng

    2015-11-01

    Bulk Fe83B17 nano-eutectic alloys were prepared by undercooling solidification combined with Cu-mold chilling method. Stable phase Fe2B and metastable phase Fe3B were found to coexist in the as-solidified microstructure. The soft magnetic properties were improved significantly by the nano-lamellar eutectic and the metastable phase and, were increased further by annealing at 1173 K for 1.5 h after which the metastable phase was decomposed completely.

  1. Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study

    NASA Astrophysics Data System (ADS)

    Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin

    2016-05-01

    We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection.

  2. Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study.

    PubMed

    Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin

    2016-05-23

    We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection.

  3. Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study.

    PubMed

    Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin

    2016-01-01

    We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection. PMID:27210816

  4. Degenerate seaweed to tilted dendrite transition and their growth dynamics in directional solidification of non-axially oriented crystals: a phase-field study

    PubMed Central

    Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin

    2016-01-01

    We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection. PMID:27210816

  5. Weld solidification cracking in 304 to 204L stainless steel

    SciTech Connect

    Hochanadel, Patrick W; Lienert, Thomas J; Martinez, Jesse N; Johnson, Matthew Q

    2010-09-15

    A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found.This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GTAW showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

  6. Weld solidification cracking in 304 to 304L stainless steel

    SciTech Connect

    Hochanadel, Patrick W; Lienert, Thomas J; Martinez, Jesse N; Martinez, Raymond J; Johnson, Matthew Q

    2010-01-01

    A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found. This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GT A W showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

  7. Two-dimensional phase-field study of competitive grain growth during directional solidification of polycrystalline binary alloy

    NASA Astrophysics Data System (ADS)

    Takaki, Tomohiro; Ohno, Munekazu; Shibuta, Yasushi; Sakane, Shinji; Shimokawabe, Takashi; Aoki, Takayuki

    2016-05-01

    Selections of growing crystals during directional solidification of a polycrystalline binary alloy were numerically investigated using two-dimensional phase-field simulations. To accelerate the simulations, parallel graphics processing unit (GPU) simulations were performed using the GPU-rich supercomputer TSUBAME2.5 at the Tokyo Institute of Technology. Twenty simulations with a combination of five sets of different seed orientation distributions and four different temperature gradients covering dendritic and cellular growth regions were performed. The unusual grain selection phenomenon, in which the unfavorably oriented grains preferentially grow instead of the favorably oriented grains, was observed frequently. The unusual selection was more remarkable in the cellular structure than in the dendritic structure.

  8. Numerical modeling of HgCdTe solidification: effects of phase diagram double-diffusion convection and microgravity level

    NASA Astrophysics Data System (ADS)

    Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

    1997-07-01

    A numerical model of HgCdTe solidification was implemented using finite the element code FIDAP. Model verification was done using both experimental data and numerical test problems. The model was used to eluate possible effects of double- diffusion convection in molten material, and microgravity level on concentration distribution in the solidified HgCdTe. Particular attention was paid to incorporation of HgCdTe phase diagram. It was found, that below a critical microgravity amplitude, the maximum convective velocity in the melt appears virtually independent on the microgravity vector orientation. Good agreement between predicted interface shape and an interface obtained experimentally by quenching was achieved. The results of numerical modeling are presented in the form of video film.

  9. Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

    NASA Technical Reports Server (NTRS)

    Ray, Ranjan; Jha, Sunil C.

    1987-01-01

    Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

  10. Solidification and fcc- to metastable hcp- phase transition in krypton under modulating dynamic pressures

    NASA Astrophysics Data System (ADS)

    Chen, Jing-Yin; Yoo, Choong-Shik; Kim, Minseob; Liermann, Hanns-Peter; Cynn, Hyunchae; Jenei, Zsolt; Evans, William

    2014-03-01

    We describe high-pressure kinetic studies of the solidification, melting and fcc-hcp transitions of Krypton under dynamic loading conditions, using a dynamic-diamond anvil cell (d-DAC) coupled with time-resolved x-ray diffraction. The time-resolved diffraction patterns and dynamic pressure responses show compression-rate dependencies associated with both the decay and growth time constants of the liquid-solid and solid-liquid transitions. According to the Avrami equation, both the solidified and melting processes are spontaneous nucleation and a rod-like (1-D) growth. Furthermore, under dynamic loading conditions, Kr-hcp forms from fcc close to the melting line. The nucleation time of fcc and hcp are very fast, with little dependence of compression rates or shorter than the time resolutions. The threshold pressure for the formation of Kr-hcp is ~ 0.8 GPa at the dynamic loadings of 0.004-13 GPa/s. This work was carried out at DESY. This work was performed under the auspices of DOE by LLNL under contracts(W-7405-Eng-48 and DE-AC52-07NA27344) and funded by the LDRD(11-ERD-046). The work at WSU was funded by NSF-DMR(1203834), DTRA(HDTRA1-12-01-0020).

  11. Sorbent Testing for Solidification of Organic Plutonium/Uranium Extraction Waste - Phase IV

    SciTech Connect

    Bickford, J.L.; Joyce, H.O.; Holmes-Burns, H.

    2006-07-01

    The U.S. Department of Energy (DOE) is evaluating various sorbents to solidify and immobilize hazardous constituents of the organic fraction of plutonium/uranium extraction (PUREX) process waste at the Savannah River Site (SRS).[5] The purpose of the solidification is to provide a cost-effective alternative to incineration of the waste. Incineration at the Consolidated Incinerator Facility (CIF) at SRS is currently identified as the treatment technology for PUREX waste. However, the CIF is not in operation at this time, so SRS is interested in pursuing alternatives to incineration for treatment of this waste. The DOE Western Environmental Technology Office in Butte, MT was designated as the facility for conducting the sorbent testing and evaluation for the organic PUREX waste surrogate. MSE Technology Applications, Inc. tested and evaluated two clay and two polymer sorbents with the capability of solidifying organic PUREX waste. A surrogate organic PUREX waste recipe was utilized, and sorbents were tested and evaluated at bench-scale, 22-liter (5-gallon) scale, and 242-liter (55-gallon) scale. This paper presents experimental results evaluating four sorbent materials including: Imbiber Beads{sup TM} IMB230301-R, Nochar A610 Petrobond{sup TM}, Petroset II{sup TM}, and Petroset II Granular{sup TM}. Previous work at SRS indicated that these products could solidify organic PUREX waste on a bench scale [1]. The sorbents were evaluated using operational criteria and final wasteform properties. Operational criteria included: sorbent capacity; sorption rate; sorbent handling; and mixing requirements. Final wasteform evaluation properties included: ignitability; thermal stability; offgas generation, leachability tests and volumetric expansion. Bench-scale tests, 22-liter (5-gallon) tests, and initial 242-liter (55-gallon) tests are complete. This paper summarizes the results of the bench-scale, 22-liter (5-gallon) scale, and 242-liter (55-gallon) scale tests performed

  12. An experimental verification of a criterion for forming metastable phases in containerless solidification

    SciTech Connect

    Kuribayashi, K.; Inatomi, Y.; Kumar, M. S. Vijaya

    2015-04-21

    On the thermodynamic condition for forming a metastable phase from undercooled melt in a containerless state, we had proposed a criterion that crystals will preferentially form if they have a smaller entropy of fusion than the entropy of fusion of equilibrium crystals (Kuribayashi et al., Mater. Sci. Eng., A 449–451, 675 (2007)). This criterion is proposed for being applied to materials that exhibit a faceted interface, such as semiconductors and oxides. However, no experimental data that support this criterion have been obtained. From this point, we used an aerodynamic levitator as a tool for forming metastable phases from undercooled melt and verified the above-mentioned criterion using LnFeO{sub 3} (Ln: lanthanide and Y) as the model material. In addition, the condition for double recalescence, which corresponds to forming metastable phases and stable phases, was discussed in terms of competitive 2D isomorphic nucleation of the metastable phase and 3D polymorphic nucleation of the stable phase.

  13. Traveling waves, two-phase fingers, and eutectic colonies in thin-sample directional solidification of a ternary eutectic alloy

    PubMed

    Akamatsu; Faivre

    2000-04-01

    We present an experimental investigation of the morphological transition of lamellar eutectic growth fronts called "formation of eutectic colonies" by the method of thin-sample directional solidification of a transparent model alloy, CBr4-C2Cl6. This morphological transition is due to the presence in the melt of traces of chemical components other than those of the base binary alloy (impurities). In this study, we use naphthalene as an impurity. The formation of eutectic colonies has generally been viewed as an impurity-driven Mullins-Sekerka instability of the envelope of the lamellar front. This traditional view neglects the strong interaction existing between the Mullins-Sekerka process and the dynamics of the lamellar pattern. This investigation brings to light several original features of the formation of eutectic colonies, in particular, the emission of long-wavelength traveling waves, and the appearance of dendritelike structures called two-phase fingers, which are connected with this interaction. We study the part played by these phenomena in the transition to eutectic colonies as a function of the impurity concentration. Recent theoretical results on the linear stability of ternary lamellar eutectic fronts [Plapp and Karma, Phys. Rev. E 60, 6865 (1999)] shed light on some aspects of the observed phenomena.

  14. Phase field simulation of a directional solidification of a ternary eutectic Mo-Si-B Alloy

    NASA Astrophysics Data System (ADS)

    Kazemi, O.; Hasemann, G.; Krüger, M.; Halle, T.

    2016-03-01

    We present a eutectic Phase-Field Model for a Mo-Si-B alloy at ternary eutectic composition (Mo-17.5Si-8B), under a constant thermal gradient. The process parameters like cooling rate and thermal gradient were obtained directly from the experimental procedure of zone melting. The equilibrium interface geometries and interface mobility were calculated using an isotropic model. The phase equilibria and the other thermodynamic parameters are obtained by linearizing the Mo-Si-B ternary phase diagram. We have investigated the effect of process parameters on the lamellar growth pattern and lamella pattern stability with respect to the Jackson-Hunt minimum undercooling spacing theory. In order to examine the generated results by the model, they were validated with experimental observed microstructures and measurements and showed to be in a good agreement with the experimental observations.

  15. Experimental study of segregation in plane front solidification and its relevance to iron meteorite solidification

    NASA Astrophysics Data System (ADS)

    Sellamuthu, R.; Goldstein, J. I.

    1983-11-01

    A directional solidification technique was developed and applied to the problem of fractional crystallization of an iron meteorite parent body. Samples of Fe-Ni alloys close to meteorite compositions and containing S, P, and C were made. The solidified structures contain secondary phases such as sulphides within the pro-eutectic single crystal austenite (taenite). As a result of these experiments, we propose that the secondary phases observed in iron meteorites were formed during primary solidification of austenite (taenite). The measured composition profiles of Ni, P and C in the alloys were used to explain the elemental distribution within a chemical group of iron meteorites. An analytical procedure was applied to determine the equilibrium distribution coefficients as a function of fraction solidified for Ni and P from the composition profiles. The distribution coefficients of Ni and P agree with previous values. These distribution coefficients are of particular interest in the determination of the elemental distributions in iron meteorites.

  16. Fundamentals of rapid solidification processing

    NASA Technical Reports Server (NTRS)

    Flemings, Merton C.; Shiohara, Yuh

    1985-01-01

    An attempt is made to illustrate the continuous change that occurs in the solidification behavior of undercooled melts, as cooling rates increase from 0.0001 K/sec to about 1000 K/sec. At the higher cooling rates, more significant changes occur as the dendrite tip temperature begins to drop from the equilibrium liquidus. Discontinuous solidification behavior changes will occur if absolute stability is reached, or a metastable phase forms, or solidification proceeds to a glass rather than to a crystalline solid, or if there is significant undercooling prior to nucleation.

  17. Effects of Manganese Content on Solidification Structures, Thermal Properties, and Phase Transformation Characteristics in Fe-Mn-C Steels

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Wang, Yu-Nan; Ruan, Xiao-Ming; Wang, Rui-Zhi; Zhu, Kai; Fan, Zheng-Jie; Wang, Ying-Chun; Li, Cheng-Bin; Jiang, Xiao-Fang

    2015-02-01

    The solidification structures and the thermal properties of Fe-Mn-C steel ingots containing different manganese contents have been investigated and the phase transformation characteristics have been revealed by Thermo-Calc to assist development of the continuous casting technology of Fe-Mn-C steels. The results show that the thermal conductivity of the 0Mn steel is higher than that of the 3Mn steel. The thermal conductivity of the 6Mn steel is the lowest in the three kinds of steels below 1023 K (750 °C) and the highest above 1173 K (900 °C). The 0Mn steel has the highest value of the proportion of equiaxed grain zone area in the three kinds of steels, whereas the 3Mn steel has the lowest value of it in the steels. Manganese has the effect of promoting the coarsening of grains. The microstructure is martensite and a little retained austenite (3.8 mass pct) in the 6Mn steel, whereas the microstructure is bainite in the 3Mn steel. The 0Mn steel is characterized by ferrite and pearlite. The mean thermal expansion coefficients of the steels are in the range from 1.0 × 10-5 to 1.6 × 10-5 K-1, and the determinations of mold tapers of the 6Mn and 3Mn steels can refer to low-carbon steel. Using RA <60 pct as the criterion, the third brittle temperature region of the 6Mn steel is 873 K to 1073 K (600 °C to 800 °C), whereas those of the 3Mn steel and the 0Mn steel are 873 K to 1123 K (600 °C to 850 °C) and 873 K to 1173 K (600 °C to 900 °C), respectively. In the 6Mn and 3Mn steels, the deformation-induced ferrite (DIF) forms in sufficient quantities cause the recovery of the ductility at the low temperature end. However, since low strains are present when straightening, sufficient quantities of DIF cannot be formed. Thus, the ductility of the 6Mn and 3Mn steels cannot be improved during the continuous casting process. Manganese has the effect of enlarging the austenite phase region and reducing the δ-ferrite phase region and α-ferrite phase region.

  18. Appearance of metastable B2 phase during solidification of Ni 50 Zr 50 alloy: electrostatic levitation and molecular dynamics simulation studies

    SciTech Connect

    Quirinale, D. G.; Rustan, G. E.; Wilson, S. R.; Kramer, M. J.; Goldman, A. I.; Mendelev, M. I.

    2015-02-04

    High-energy x-ray diffraction measurements of undercooled, electrostatically levitated Ni50Zr50 liquid droplets were performed. The observed solidification pathway proceeded through the nucleation and growth of the metastable B2 phase, which persisted for several seconds before the rapid appearance of the stable B33 phase. This sequence is shown to be consistent with predictions from classical nucleation theory using data obtained from molecular dynamics (MD) simulations. A plausible mechanism for the B2–B33 transformation is proposed and investigated through further MD simulations.

  19. Appearance of metastable B2 phase during solidification of Ni50Zr50 alloy: electrostatic levitation and molecular dynamics simulation studies.

    PubMed

    Quirinale, D G; Rustan, G E; Wilson, S R; Kramer, M J; Goldman, A I; Mendelev, M I

    2015-03-01

    High-energy x-ray diffraction measurements of undercooled, electrostatically levitated Ni50Zr50 liquid droplets were performed. The observed solidification pathway proceeded through the nucleation and growth of the metastable B2 phase, which persisted for several seconds before the rapid appearance of the stable B33 phase. This sequence is shown to be consistent with predictions from classical nucleation theory using data obtained from molecular dynamics (MD) simulations. A plausible mechanism for the B2-B33 transformation is proposed and investigated through further MD simulations. PMID:25650946

  20. The effect of heating power on impurity formation and transport during the holding phase in a Bridgman furnace for directional solidification of multi-crystalline silicon

    NASA Astrophysics Data System (ADS)

    Ellingsen, Kjerstin; Lindholm, Dag; M`Hamdi, Mohammed

    2016-06-01

    Oxygen and carbon are the most common impurities in multi-crystalline silicon. The general mechanism for formation and transport of O and C in the solidification furnace is as follows: oxygen from the silica crucible comes into the melt and combines with a silicon atom and evaporates at the gas/melt interface in the form of silicon oxide (SiO). Argon inert gas, injected into the furnace chamber, carries the SiO to the hot graphite fixtures, where it reacts with carbon to form carbon monoxide (CO) and silicon carbide (SiC). CO is carried by the gas to the melt free surface, where it dissociates into carbon and oxygen. Finally, during solidification oxygen and carbon are incorporated into the crystal. A global furnace model accounting for heat transfer, melt flow, gas flow and impurity transport has been applied to investigate the oxygen and carbon formation and transport in a vertical Bridgman furnace during the holding phase when the furnace is at its hottest. A case study is performed to investigate the effect of the applied heating power on the carbon and oxygen concentrations in the melt prior to solidification.

  1. A new liquid-phase microextraction method based on solidification of floating organic drop.

    PubMed

    Khalili Zanjani, Mohammad Reza; Yamini, Yadollah; Shariati, Shahab; Jönsson, Jan Ake

    2007-03-01

    In the present study, a new and versatile liquid-phase microextraction method is described. This method requires very simple and cheap apparatus and also a small amount of organic solvent. Eight microliters of 1-undecanol was delivered to the surface of solution containing analytes and solution was stirred for a desired time. Then sample vial was cooled by inserting it into an ice bath for 5 min. The solidified 1-undecanol was transferred into a suitable vial and immediately melted; then, 2 microL of it was injected into a gas chromatograph for analysis. Some polycyclic aromatic hydrocarbons (PAHs) were used as model compounds for developing and evaluating of the method performance. Analysis was carried out by gas chromatography/flame ionization detection (GC/FID). Several factors influencing the microextraction efficiency, such as the nature and volume of organic solvent, the temperature and volume of sample solution, stirring rate and extraction time were investigated and optimized. The applicability of the technique was evaluated by determination of trace amounts of PAHs in environmental samples. Under the optimized conditions, the detection limits (LOD) of the method were in the range of 0.07-1.67 microg L(-1) and relative standard deviations (R.S.D.) for 10 microg L(-1) PAHs were <7%. A good linearity (r(2)>0.995) in a calibration range of 0.25-300.00 microg L(-1) was obtained. After 30 min extraction duration, enrichment factors were in the range of 594-1940. Finally, the proposed method was applied to the determination of trace amounts of PAHs in several real water samples, and satisfactory results were resulted. Since very simple devices were used, this new technique is affordable, efficient, and convenient for extraction and determination of low concentrations of PAHs in water samples. PMID:17386676

  2. Macrosegregation and Grain Formation Caused by Convection Associated with Directional Solidification Through Cross-Section Increase

    NASA Technical Reports Server (NTRS)

    Ghods, Masoud; Lauer, Mark; Tewari, Surendra; Poirier, David; Grugel, Richard

    2016-01-01

    Cylindrical Al-7 wt% Silicon, Al-19 wt% Copper and Lead-6 wt% Antimony alloy samples were directionally solidified (DS) with liquid above, solid below, and gravity pointing down, in graphite crucibles having an abrupt cross-sectional increase. These alloys have similar solidification shrinkage but are expected to have different degrees of thermosolutal convection during solidification. Microstructures in the DS samples in the vicinity of the section change have been studied in order to examine the effect of convection associated with the combined influence of thermosolutal effects and solidification shrinkage. Extensive radial and axial macrosegregation associated with cross-section change is observed. It also appears that steepling and local primary alpha-phase remelting resulting from convection are responsible for stray grain formation at the reentrant corners. Preliminary results from a numerical model, which includes solidification shrinkage and thermosolutal convection in the mushy zone, indicate that these regions are prone to solutal remelting of dendrites.

  3. INCONEL 718: A solidification diagram

    NASA Astrophysics Data System (ADS)

    Knorovsky, G. A.; Cieslak, M. J.; Headley, T. J.; Romig, A. D.; Hammetter, W. F.

    1989-10-01

    As part of a program studying weldability of Ni-base superalloys, results of an integrated analytical approach are used to generate a constitution diagram for INCONEL 718* in the temperature range associated with solidification. Differential thermal analysis of wrought material and optical and scanning electron microscopy, electron probe microanalysis, and analytical electron microscopy of gas tungsten arc welds are used in conjunction with solidification theory to generate data points for this diagram. The important features of the diagram are an austenite (γ)/Laves phase eutectic which occurs at ≈19.1 wt pct Nb between austenite containing ≈9.3 wt pct Nb and a Laves phase which contains ≈22.4 wt pct Nb. The distribution coefficient for Nb was found to be ≈0.5. The solidification sequence of INCONEL 718 was found to be (1) proeutectic γ, followed by (2) a γ/NbC eutectic at ≈1250°C, followed by (3) continued γ solidification, followed by (4) a γ/Laves phase eutectic at ≈1200°C. An estimate of the volume fraction eutectic is made using the Scheil solidification model, and the fraction of each phase in the eutectic is calculated via the lever rule. These are compared with experimentally determined values and found to be in good agreement.

  4. Variational formulation and numerical accuracy of a quantitative phase-field model for binary alloy solidification with two-sided diffusion

    NASA Astrophysics Data System (ADS)

    Ohno, Munekazu; Takaki, Tomohiro; Shibuta, Yasushi

    2016-01-01

    We present the variational formulation of a quantitative phase-field model for isothermal low-speed solidification in a binary dilute alloy with diffusion in the solid. In the present formulation, cross-coupling terms between the phase field and composition field, including the so-called antitrapping current, naturally arise in the time evolution equations. One of the essential ingredients in the present formulation is the utilization of tensor diffusivity instead of scalar diffusivity. In an asymptotic analysis, it is shown that the correct mapping between the present variational model and a free-boundary problem for alloy solidification with an arbitrary value of solid diffusivity is successfully achieved in the thin-interface limit due to the cross-coupling terms and tensor diffusivity. Furthermore, we investigate the numerical performance of the variational model and also its nonvariational versions by carrying out two-dimensional simulations of free dendritic growth. The nonvariational model with tensor diffusivity shows excellent convergence of results with respect to the interface thickness.

  5. Phase-field modelling of β(Ti) solidification in Ti-45at.%Al: columnar dendrite growth at various gravity levels

    NASA Astrophysics Data System (ADS)

    Viardin, A.; Berger, R.; Sturz, L.; Apel, M.; Hecht, U.

    2016-03-01

    The effect of solutal convection on the solidification of γ titanium aluminides, specifically on β(Ti) dendrite growth, is not well known. With the aim of supporting directional solidification experiments under hyper-gravity using a large diameter centrifuge, 2D-phase field simulations of β(Ti) dendrite growth have been performed for the binary alloy Ti-45at.%Al and various gravity scenarios. Both, the direction and magnitude of the gravity vector were varied systematically in order to reveal the subtle interplay between the convective flow pattern and mushy zone characteristics. In this presentation, gravity effects are discussed for early dendrite growth. For selected cases the evolution on longer timescales is also analyse of and oscillatory modes leading to dynamically stable steady state growth are outlined. In a dedicated simulation series forced flow is superimposed, as to mimic thermally driven fluid flow expected to establish on the macroscopic scale (sample size) in the centrifugal experiments. Above a certain threshold this flow turns dominant and precludes solutally driven convective effects.

  6. Rapid solidification mechanism of highly undercooled ternary Cu40Sn45Sb15 alloy

    NASA Astrophysics Data System (ADS)

    Zhai, W.; Wang, B. J.; Lu, X. Y.; Wei, B.

    2015-10-01

    The rapid solidification of ternary Cu40Sn45Sb15 peri-eutectic type alloy was realized by glass fluxing and drop tube methods, and the corresponding maximum undercoolings are 185 K (0.22 T L) and 321 K (0.39 T L), respectively. The phase constitution of Cu40Sn45Sb15 alloy in these two rapid solidification experiments deviates from the two equilibrium phases (Sn + Cu6Sn5). In glass fluxing method, the structural morphology of Cu40Sn45Sb15 alloy is mainly characterized by a three-layer lamellar structure, which is comprised by an inner layer of long strips of primary ɛ(Cu3Sn) phase, an intermediate layer of η(Cu6Sn5) phase and an outer layer of β(SnSb) phase. As undercooling rises, this lamellar structure is remarkably refined. When small alloy droplets are containerlessly solidified during free fall in drop tube, the primary ɛ(Cu3Sn) phase grows by non-faceted mode into dendrites as droplet diameter decreases. Especially, solidification path alters in the smallest droplet with 50 μm diameter, in which η(Cu6Sn5) and Sn3Sb2 phases form directly from the metastable liquid phase by suppressing the primary ɛ phase formation and the following peri-eutectic transformation.

  7. Solidification and weldability of thermo-span{trademark} alloy

    SciTech Connect

    Robino, C.V.; Michael, J.R.

    1994-12-31

    Thermo-Span is a low coefficient of thermal expansion precipitation hardenable superalloy with high tensile and rupture strengths. The alloy is based on the Fe-Co-Ni system and utilizes chromium additions for improved environmental resistance. The solidification behavior and fusion zone hot cracking tendency of this alloy has been evaluated using differential thermal analysis, Varestraint testing, and through comparison with Inconel 718 and Incoloy 909. Solidification microstructures were characterized by optical and electron microscopy, and the solidification phases identified. Differential thermal analysis (DTA) at heating and cooling rates of 20{degrees}C/min indicated that melting of the wrought allow initiates at temperatures near 1280{degrees}C and continues to approximately 1441{degrees}C. During cooling, the alloy solidifies with two solidification events. These events are the formation of primary austenite and the formation of a terminal eutectic-like constituent at approximately 1220{degrees}C. The implications of the electron microscopy results, in terms of the hot cracking behavior, will be discussed. In summary, the weldability of Thermo-Span was found to be similar to Inconel 718 and Incoloy 909 and therefore, the alloy is likely to be amenable to similar weld processing. This was work performed at Sandia National Laboratories supported by the U.S. Department of Energy under Contract Number DE-AC04-76DP00789.

  8. Nonequilibrium solidification in undercooled Ti{sub 45}Al{sub 55} melts

    SciTech Connect

    Hartmann, H.; Galenko, P. K.; Holland-Moritz, D.; Kolbe, M.; Herlach, D. M.; Shuleshova, O.

    2008-04-01

    Ti-Al alloys are of high technological interest as light-weight high-performance materials. When produced by solidification from the liquid state, the material properties of as-solidified materials are strongly dependent on the conditions governing the solidification process. Nonequilibrium solidification from the state of an undercooled liquid may result to the formation of metastable solid materials. On the one hand undercooling under special cases may influence the phase selection behavior during solidification, and on the other hand during rapid growth of solid phases in undercooled melts nonequilibrium effects such as solute trapping and disorder trapping may occur. In the present work containerless processing by electromagnetic levitation is used to undercool Ti{sub 45}Al{sub 55} melts deeply below the liquidus temperature. The dendrite growth velocity during the solidification is measured as a function of undercooling by application of a high-speed video camera. In situ diffraction experiments at ESRF in Grenoble and microstructure investigations are performed in order to identify the primary solidified phases. The experimental findings are interpreted within current theoretical models for dendritic growth and solute trapping.

  9. Solidification Paths and Phase Components at High Temperatures of High-Zn Al-Zn-Mg-Cu Alloys with Different Mg and Cu Contents

    NASA Astrophysics Data System (ADS)

    Shu, W. X.; Hou, L. G.; Liu, J. C.; Zhang, C.; Zhang, F.; Liu, J. T.; Zhuang, L. Z.; Zhang, J. S.

    2015-11-01

    Studies were carried out systematically on a series of Al-8.5 wt pct Zn- xMg- yCu alloys ( x is about 1.5, 2.0, and 2.5 wt pct, and y is about 1.5, 2.0, 2.5, and 2.9 wt pct). The effects of alloying elements Mg and Cu on the microstructures of as-cast and homogenized alloys were investigated using the computational/experimental approach. It shows that Mg(Zn,Al,Cu)2 ( σ) phase can exist in all the as-cast alloys without any observable Mg32(Al,Zn)49/Al2Mg3Zn3 ( T) or Al2CuMg ( S) phase, whereas Al2Cu ( θ) phase is prone to exist in the alloys with low Mg and high Cu contents. Thermodynamic calculation shows that the real solidification paths of the designed alloys fall in between the Scheil and the equilibrium conditions, and close to the former. After the long-time homogenization [733 K (460 °C)/168 hours] and the two-step homogenization [733 K (460 °C)/24 hours + 748 K (475 °C)/24 hours], the phase components of the designed alloys are generally consistent with the calculated phase diagrams. At 733 K (460 °C), the phase components in the thermodynamic equilibrium state are greatly influenced by Mg content, and the alloys with low Mg content are more likely to be in single-Al phase field even if the alloys contain high Cu content. At 748 K (475 °C), the dissolution of the second phases is more effective, and the phase components in the thermodynamic equilibrium state are dominated primarily by (Mg + Cu) content, except the alloys with (Mg + Cu) ≳ 4.35 wt pct, all designed alloys are in single-Al phase field.

  10. The role of fluid flow and intermetallic phases in the formation of the primary Al-phase in AlSi alloys

    NASA Astrophysics Data System (ADS)

    Mikołajczak, P.; Ratke, L.

    2012-01-01

    In secondary AlSi alloys, the presence of small amounts of Fe causes the formation of intermetallic phases, which have a negative effect on mechanical and physical properties of castings. To understand the effect of fluid flow on the microstructure and intermetallic phases, Al-5/7/9 wt pet Si 0.2/0.5/1.0 wt pet Fe alloys have been directionally solidified under defined thermal (gradient 3 K/mm, solidification velocity 0.04 mm/s) and fluid flow (rotating magnetic field 6 mT) conditions. The primary α-Al phase and intermetallic phases were studied using light microscopy and SEM with EDX. The influence of fluid flow and intermetallic phases (β-Al5FeSi) on microstructure was characterized by changes of primary and secondary dendrite arm spacing and specific surface area of the dendrites. We observe a pronounced effect of flow on the length of the intermetallic precipitates, a macro-segregation Fe and Si and even small amounts of iron and thus intermetallics reduce possible effects of flow on microstructural parameters.

  11. Solidification of undercooled liquids

    NASA Technical Reports Server (NTRS)

    Perepezko, J. H.; Shiohara, Y.; Paik, J. S.; Flemmings, M. C.

    1982-01-01

    During rapid solidification processing (RSP) the amount of liquid undercooling is an important factor in determining microstructural development by controlling phase selection during nucleation and morphological evolution during crystal growth. While undercooling is an inherent feature of many techniques of RSP, the deepest undercoolings and most controlled studies have been possible in carefully prepared fine droplet samples. From past work and recent advances in studies of nucleation kinetics it has become clear that the initiation of crystallization during RSP is governed usually by heterogeneous sites located at surfaces. With known nucleant sites, it has been possible to identify specific pathways of metastable phase formation and microstructural development in alloys. These advances have allowed for a clearer assessment of the interplay between undercooling, cooling rate and particle size statistics in structure formation. New approaches to the examination of growth processes have been developed to follow the thermal behavior and morphology in small samples in the period of rapid crystallization and recalescence. Based upon the new experimental information from these studies, useful models can be developed for the overall solidification process to include nucleation behavior, thermodynamic constraints, thermal history, growth kinetics, solute redistribution and resulting structures. From the refinement of knowledge concerning the underlying factors that govern RSP a basis is emerging for an effective alloy design and processing strategy.

  12. Modelling Directional Solidification

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.; Regel, Liya L.; Zhou, Jian; Yuan, Weijun

    1992-01-01

    The long range goal of this program has been to develop an improved understanding of phenomena of importance to directional solidification, in order to enable explanation and prediction of differences in behavior between solidification on Earth and in space. Current emphasis is on determining the influence of perturbations on directional solidification.

  13. Modelling directional solidification

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.

    1991-01-01

    The long range goal of this program is to develop an improved understanding of phenomena of importance to directional solidification and to enable explanation and prediction of differences in behavior between solidification on Earth and in space. Current emphasis is on determining the influence of perturbations on directional solidification.

  14. A phase-field-lattice Boltzmann method for modeling motion and growth of a dendrite for binary alloy solidification in the presence of melt convection

    NASA Astrophysics Data System (ADS)

    Rojas, Roberto; Takaki, Tomohiro; Ohno, Munekazu

    2015-10-01

    In this study, a combination of the lattice Boltzmann method (LBM) and the phase-field method (PFM) is used for modeling simultaneous growth and motion of a dendrite during solidification. PFM is used as a numerical tool to simulate the morphological changes of the solid phase, and the fluid flow of the liquid phase is described by using LBM. The no-slip boundary condition at the liquid-solid interface is satisfied by adding a diffusive-forcing term in the LBM formulation. The equations of motion are solved for tracking the translational and rotational motion of the solid phase. The proposed method is easily implemented on a single Cartesian grid and is suitable for parallel computation. Two-dimensional benchmark computations show that the no-slip boundary condition and the shape preservation condition are satisfied in this method. Then, the present method is applied to the calculation of dendritic growth of a binary alloy under melt convection. Initially, the solid is stationary, and then, the solid moves freely due to the influence of fluid flow. Simultaneous growth and motion are effectively simulated. As a result, it is found that motion and melt convection enhance dendritic growth along the flow direction.

  15. Divorced Eutectic Solidification of Mg-Al Alloys

    NASA Astrophysics Data System (ADS)

    Monas, Alexander; Shchyglo, Oleg; Kim, Se-Jong; Yim, Chang Dong; Höche, Daniel; Steinbach, Ingo

    2015-08-01

    We present simulations of the nucleation and equiaxed dendritic growth of the primary hexagonal close-packed -Mg phase followed by the nucleation of the -phase in interdendritic regions. A zoomed-in region of a melt channel under eutectic conditions is investigated and compared with experiments. The presented simulations allow prediction of the final properties of an alloy based on process parameters. The obtained results give insight into the solidification processes governing the microstructure formation of Mg-Al alloys, allowing their targeted design for different applications.

  16. In situ metathesis reaction combined with liquid-phase microextraction based on the solidification of sedimentary ionic liquids for the determination of pyrethroid insecticides in water samples.

    PubMed

    Hu, Lu; Zhang, Panjie; Shan, Wanyu; Wang, Xuan; Li, Songqing; Zhou, Wenfeng; Gao, Haixiang

    2015-11-01

    A novel dispersion liquid-liquid microextraction method based on the solidification of sedimentary ionic liquids (SSIL-DLLME), in which an in situ metathesis reaction forms an ionic liquid (IL) extraction phase, was developed to determine four pyrethroid insecticides (i.e., permethrin, cyhalothrin, fenpropathrin, and transfluthrin) in water followed by separation using high-performance liquid chromatography. In the developed method, in situ DLLME was used to enhance the extraction efficiency and yield. After centrifugation, the extraction solvent, tributyldodecylphosphonium hexafluorophosphate ([P44412][PF6]), was easily collected by solidification in the bottom of the tube. The effects of various experimental parameters, the quantity of tributyldodecylphosphonium bromide ([P44412]Br), the molar ratio of [P44412]Br to potassium hexafluorophosphate (KPF6), the ionic strength, the temperature of the sample solution, and the centrifugation time, were optimized using a Plackett-Burman design to identify the significant factors that affected the extraction efficiency. These significant factors were then optimized using a central composite design. Under the optimized conditions, the recoveries of the four pyrethroid insecticides at four spiked levels ranged from 87.1% to 101.7%, with relative standard deviations (RSDs) ranging from 0.1% to 5.5%. At concentration levels between 1 and 500 µg/L, good linearity was obtained, with coefficients of determination greater than 0.9995. The limits of detection (LODs) for the four pyrethroid insecticides were in the range of 0.71-1.54 µg/L. The developed method was then successfully used for the determination of pyrethroid insecticides in environmental samples.

  17. Migration of liquid phase from the primary/peritectic interface in a temperature gradient

    NASA Astrophysics Data System (ADS)

    Peng, Peng; Li, XinZhong; Su, YanQing; Guo, JingJie

    2016-07-01

    The migration of the liquid droplets from the primary α/peritectic β interface at the peritectic temperature TP has been observed and analyzed in a Sn-Ni peritectic alloy. During the isothermal annealing stage of the interrupted directional solidification, a concentration gradient is established across the liquid droplets along the direction of the temperature gradient due to the temperature gradient zone melting. Simultaneous remelting/resolidification at the top/bottom of the liquid droplets by this concentration gradient have been confirmed to lead to migration of these droplets towards higher temperatures. The dependence of the migration distance of the liquid droplets on isothermal annealing time has been well predicted. Furthermore, since the lengths of the liquid droplet are not uniform along the direction of the temperature gradient, the remelting/resolidification rates which are dependent on the local morphology of liquid droplet are different at different local positions of the liquid droplets. It has been demonstrated that the morphology of the liquid droplet was also influenced by the morphologies of the liquid phase themselves. Therefore, the morphology of the liquid droplet itself changes from spherical to some kinds of irregular shapes during its migration.

  18. Progress with simple binary alloy solidification problems

    SciTech Connect

    Wilson, D.G.; Solomon, A.D.; Alexiades, V.

    1981-01-01

    We give a preliminary report of our studies on binary alloy solidification. In what follows we state the mathematical problem, which we assume represents the solidification of a simple binary alloy; we give a very brief introduction to two component phase diagrams, whose relations we assume hold at the solidification front; we describe our phlogiston formulation of the problem, which is derived by analogy with the enthalpy method for simpler problems; we describe the finite difference scheme, with which we computer the various constituents of our phlogiston formulation; and finally we relate our computational experience with the model so far.

  19. Cross-Permeability of the Semisolid Region in Directional Solidification: A Combined Phase-Field and Lattice-Boltzmann Simulation Approach

    NASA Astrophysics Data System (ADS)

    Böttger, B.; Haberstroh, C.; Giesselmann, N.

    2016-01-01

    Based on the results of microstructure simulations, fluid flow through the semisolid region during directional solidification of the technical Ni-base alloy 718 has been studied. Three-dimensional microstructures at different positions in the semisolid region were obtained by using a multicomponent multiphase-field model that was online coupled to a commercial thermodynamic database. For the range of five different primary dendrite distances λ 1 between 50 µm and 250 µm, the flow velocity and the permeability perpendicular to the dendrite growth direction was evaluated by using a proprietary Lattice-Boltzmann model. The commercial CFD software ANSYS FLUENT was alternatively applied for reference. Consistent values of the average flow velocity along the dendrites were obtained for both methods. From the results of the fluid flow simulations, the cross-permeability was evaluated as a function of temperature and fraction liquid for each of the five different primary dendrite distances λ 1. The obtained permeability values can be approximated by a single analytical function of the fraction liquid and λ 1 and are discussed and compared with known relations from the literature.

  20. Solidification mechanism of highly undercooled metal alloys. [tin-lead and nickel-tin alloys

    NASA Technical Reports Server (NTRS)

    Shiohara, Y.; Chu, M. G.; Macisaac, D. G.; Flemings, M. C.

    1982-01-01

    Experiments were conducted on metal droplet undercooling, using Sn-25wt%Pb and Ni-34wt%Sn alloys. To achieve the high degree of undercooling, emulsification treatments were employed. Results show the fraction of supersaturated primary phase is a function of the amount of undercooling, as is the fineness of the structures. The solidification behavior of the tin-lead droplets during recalescence was analyzed using three different hypotheses; (1) solid forming throughout recalescence is of the maximum thermodynamically stable composition; (2) partitionless solidification below the T sub o temperature, and solid forming thereafter is of the maximum thermodynamically stable composition; and (3) partitionless solidification below the T sub o temperature with solid forming thereafter that is of the maximum thermodynamically metastable composition that is possible. The T sub o temperature is calculated from the equal molar free energies of the liquid solid using the regular solution approximation.

  1. Solidification microstructure formation in HK40 and HH40 alloys

    NASA Astrophysics Data System (ADS)

    Ding, Xian-fei; Liu, Dong-fang; Guo, Pei-liang; Zheng, Yun-rong; Feng, Qiang

    2016-04-01

    The microstructure formation processes in HK40 and HH40 alloys were investigated through JmatPro calculations and quenching performed during directional solidification. The phase transition routes of HK40 and HH40 alloys were determined as L → L + γ → L + γ + M7C3 → γ + M7C3 → γ + M7C3 + M23C6→ γ + M23C6 and L → L + δ → L + δ + γ→ L + δ + γ + M23C6 δ + γ + M23C6, respectively. The solidification mode was determined to be the austenitic mode (A mode) in HK40 alloy and the ferritic-austenitic solidification mode (FA mode) in HH40 alloy. In HK40 alloy, eutectic carbides directly precipitate in a liquid and coarsen during cooling. The primary γ dendrites grow at the 60° angle to each other. On the other hand, in HH40 alloy, residual δ forms because of the incomplete transformation from δ to γ. Cr23C6 carbide is produced in solid delta ferrite δ but not directly in liquid HH40 alloy. Because of carbide formation in the solid phase and no rapid growth of the dendrite in a non-preferential direction, HH40 alloy is more resistant to cast defect formation than HK40 alloy.

  2. Modeling of the primary rearrangement stage of liquid phase sintering

    NASA Astrophysics Data System (ADS)

    Malik Tahir, Abdul; Malik, Amer; Amberg, Gustav

    2016-10-01

    The dimensional variations during the rearrangement stage of liquid phase sintering could have a detrimental effect on the dimensional tolerances of the sintered product. A numerical approach to model the liquid phase penetration into interparticle boundaries and the accompanied dimensional variations during the primary rearrangement stage of liquid phase sintering is presented. The coupled system of the Cahn–Hilliard and the Navier–Stokes equations is used to model the penetration of the liquid phase, whereas the rearrangement of the solid particles due to capillary forces is modeled using the equilibrium equation for a linear elastic material. The simulations are performed using realistic physical properties of the phases involved and the effect of green density, wettability and amount of liquid phase is also incorporated in the model. In the first step, the kinetics of the liquid phase penetration and the rearrangement of solid particles connected by a liquid bridge is modeled. The predicted and the calculated (analytical) results are compared in order to validate the numerical model. The numerical model is then extended to simulate the dimensional changes during primary rearrangement stage and a qualitative match with the published experimental data is achieved.

  3. MPS solidification model. Analysis and calculation of macrosegregation in a casting ingot

    NASA Technical Reports Server (NTRS)

    Poirier, D. R.; Maples, A. L.

    1985-01-01

    Work performed on several existing solidification models for which computer codes and documentation were developed is presented. The models describe the solidification of alloys in which there is a time varying zone of coexisting solid and liquid phases; i.e., the S/L zone. The primary purpose of the models is to calculate macrosegregation in a casting or ingot which results from flow of interdendritic liquid in this S/L zone during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, is modeled as flow through a porous medium. In Model 1, the steady state model, the heat flow characteristics are those of steady state solidification; i.e., the S/L zone is of constant width and it moves at a constant velocity relative to the mold. In Model 2, the unsteady state model, the width and rate of movement of the S/L zone are allowed to vary with time as it moves through the ingot. Each of these models exists in two versions. Models 1 and 2 are applicable to binary alloys; models 1M and 2M are applicable to multicomponent alloys.

  4. Modelling direction solidification

    NASA Technical Reports Server (NTRS)

    Wilcox, W. R.

    1986-01-01

    The overall objective of this program is to develop an improved understanding of some phenomena of importance to directional solidification. The aim of this research is also to help predict differences in behavior between solidification on Earth and solidification in space. In this report, the validity of the Burton-Primslichter equation is explored. The influence of operating variables on grain and twin generation and propagation in single crystals of In sub (x) Ga sub (1-x) Sb is also investigated.

  5. The volume change during solidification

    NASA Technical Reports Server (NTRS)

    Rittich, M.

    1985-01-01

    The liquid-solid phase transformation of solidifying metallic melts is accompanied by a volume change Delta-Vm. This volume change produces a gravity-independent microscopic flow near the solidification front. In a ground-based laboratory, solidification processes are also affected by convection due to temperature and concentration gradients. A quantitative evaluation of the effects of these flows on the formation of structure requires reproducible values of Delta-Vm. Alloys with Delta-Vm = 0 would be best suited for such an evaluation, while alloys with a constant value for Delta-Vm are still usable. Another requirement is related to a solidus-liquidus interval which is as small as possible. One-phase alloys, which would be particularly well suited, could not be found. For these reasons, alloys which solidify in two phases, as for example eutectics, have been considered, taking into account the Al-Ge system. Attention is given to the volume change at the melting point, the measurement of this change, the volume change at solidification, and applications to terrestrial technology.

  6. Analysis of macrosegregation formation and columnar-to-equiaxed transition during solidification of Al-4 wt.%Cu ingot using a 5-phase model

    PubMed Central

    Ahmadein, M.; Wu, M.; Ludwig, A.

    2015-01-01

    A 5-phase mixed columnar-equiaxed solidification model was recently introduced to predict the as-cast structure, and a series of laboratory experiments were performed previously to verify the model. The focus of the current work is to analyze the formation of macrosegregation, which accompanies the formation of the as-cast structure including the columnar-to-equiaxed transition (CET). The as-cast structure and macrosegregation map of a cylindrical Al-4 wt.% Cu ingot poured at 800 °C are used as a reference to validate the calculations. Good agreement between the calculations and the experiment regarding both the macrosegregation and CET is achieved. Thermal-solutal convection and equiaxed crystal sedimentation in such ingot are verified to be key mechanisms governing the formation of macrosegregation. The competitive equiaxed/columnar growth, the soft and hard blocking mechanisms predominate the CET. The numerical study of grid sensitivity indicates that the global segregation pattern and CET are not significantly affected by grid size; however, some fine details of the segregation map which are predicted by fine grid (~0.5 mm) are smeared or locally averaged by the coarse grid (~2 mm). Such details were also not resolved in the measurement. Future investigations are demanding. PMID:26089572

  7. Solid-Phase Extraction Followed by Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop for the Determination of Parabens.

    PubMed

    Hashemi, Beshare; Shamsipur, Mojtaba; Fattahi, Nazir

    2015-09-01

    A dispersive liquid-liquid microextraction based on solidification of floating organic drop method combined with solid-phase extraction (500-mg C18 sorbent) was developed for preconcentration and determination of some parabens. The experimental parameters influencing the extraction efficiency such as the type of extraction and disperser solvents, as well as their volumes, breakthrough volume, flow rate and salt addition were studied and optimized. The optimum experimental conditions found included: sample volume, 100 mL; KCl concentration, 1% (w/v); extraction solvent (1-undecanol) volume, 20 µL and disperser solvent (acetone) volume, 250 µL. Under the optimum experimental conditions, calibration graphs were linear in the range of 1-200 µg L(-1) with limits of detection ranged from 0.3 to 1.7 µg L(-1). The relative standard deviations were in the range of 1.2-3.1% (n = 5). The enrichment factors and absolute recoveries of parabens in different matrices were 245-1886 and 9.0-69.8%, respectively. The method was applied to the simultaneous determination of parabens in different matrices. The relative recoveries from water, shampoo and mouth rinse samples, which have been spiked at different levels of parabens, were 87.83-112.25%, 82.80-108.40% and 90.10-97.60%, respectively. PMID:25716984

  8. Chemometric assisted ultrasound leaching-solid phase extraction followed by dispersive-solidification liquid-liquid microextraction for determination of organophosphorus pesticides in soil samples.

    PubMed

    Ahmadi, Kamyar; Abdollahzadeh, Yaser; Asadollahzadeh, Mehdi; Hemmati, Alireza; Tavakoli, Hamed; Torkaman, Rezvan

    2015-05-01

    Ultrasound leaching-solid phase extraction (USL-SPE) followed by dispersive-solidification liquid-liquid microextraction (DSLLME) was developed for preconcentration and determination of organophosphorus pesticides (OPPs) in soil samples prior gas chromatography-mass spectrometry analysis. At first, OPPs were ultrasonically leached from soil samples by using methanol. After centrifugation, the separated methanol was diluted to 50 mL with double-distillated water and passed through the C18 SPE cartridge. OPPs were eluted with 1 mL acetonitrile. Thus, 1 mL acetonitrile extract (disperser solvent) and 10 µL 1-undecanol (extraction solvent) were added to 5 mL double-distilled water and a DSLLME technique was applied. The variables of interest in the USL-SPE-DSLLME method were optimized with the aid of chemometric approaches. First, in screening experiments, fractional factorial design (FFD) was used for selecting the variables which significantly affected the extraction procedure. Afterwards, the significant variables were optimized using response surface methodology (RSM) based on central composite design (CCD). Under the optimum conditions, the enrichment factors were 6890-8830. The linear range was 0.025-625 ng g(-1) and limits of detection (LODs) were between 0.012 and 0.2 ng g(-1). The relative standard deviations (RSDs) were in the range of 4.06-8.9% (n=6). The relative recoveries of OPPs from different soil samples were 85-98%.

  9. Solid-Phase Extraction Followed by Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop for the Determination of Parabens.

    PubMed

    Hashemi, Beshare; Shamsipur, Mojtaba; Fattahi, Nazir

    2015-09-01

    A dispersive liquid-liquid microextraction based on solidification of floating organic drop method combined with solid-phase extraction (500-mg C18 sorbent) was developed for preconcentration and determination of some parabens. The experimental parameters influencing the extraction efficiency such as the type of extraction and disperser solvents, as well as their volumes, breakthrough volume, flow rate and salt addition were studied and optimized. The optimum experimental conditions found included: sample volume, 100 mL; KCl concentration, 1% (w/v); extraction solvent (1-undecanol) volume, 20 µL and disperser solvent (acetone) volume, 250 µL. Under the optimum experimental conditions, calibration graphs were linear in the range of 1-200 µg L(-1) with limits of detection ranged from 0.3 to 1.7 µg L(-1). The relative standard deviations were in the range of 1.2-3.1% (n = 5). The enrichment factors and absolute recoveries of parabens in different matrices were 245-1886 and 9.0-69.8%, respectively. The method was applied to the simultaneous determination of parabens in different matrices. The relative recoveries from water, shampoo and mouth rinse samples, which have been spiked at different levels of parabens, were 87.83-112.25%, 82.80-108.40% and 90.10-97.60%, respectively.

  10. Phase-field modeling of the columnar-to-equiaxed transition in neopentylglycol-camphor alloy solidification

    NASA Astrophysics Data System (ADS)

    Viardin, A.; Sturz, L.; Zimmermann, G.; Apel, M.

    2011-12-01

    We have performed phase field simulations in order to explore the effect of equiaxed grain nucleation undercooling on the columnar to equiaxed transition "CET" in the NPG-DC alloy system. Our phase field model is based on the multiphase-field method. The simulation parameters are adapted to a microgravity experiment performed under purely diffusive growth conditions. The experimental investigation is made during the sounding rocket campaign TEXUS-47.

  11. Stability of eutectic interface during directional solidification

    SciTech Connect

    Han, S.H.

    1996-04-23

    Directional solidification of eutectic alloys shows different types of eutectic morphologies. These include lamellar, rod, oscillating and tilting modes. The growth of these morphologies occurs with a macroscopically planar interface. However, under certain conditions, the planar eutectic front becomes unstable and gives rise to a cellular or a dendritic structure. This instability leads to the cellular/dendritic structure of either a primary phase or a two-phase structure. The objective of this work is to develop a fundamental understanding of the instability of eutectic structure into cellular/dendritic structures of a single phase and of two-phases. Experimental studies have been carried out to examine the transition from a planar to two-phase cellular and dendritic structures in a ceramic system of Alumina-Zirconia (Al{sub 2}O{sub 3}-ZrO{sub 2}) and in a transparent organic system of carbon tetrabromide and hexachloroethane (CBr{sub 4}-C{sub 2}Cl{sub 6}). Several aspects of eutectic interface stability have been examined.

  12. Solidification of Au-Cu-Si alloys investigated by a combinatorial approach

    SciTech Connect

    Ding Shiyan; Schroers, Jan; Gregoire, John; Vlassak, Joost J.

    2012-06-01

    Composition libraries of Au-Cu-Si films comprising 800 composition patches were fabricated through co-sputtering deposition from elemental targets. The gold composition varies between 47% (compositions are in atomic percentage) and 81%, copper between 8% and 40%, and silicon between 6% and 36% within the library. We designed and used a high-throughput optical characterization method to detect melting and solidification based on changes in the film's contrast; further microscopy characterization reveals the microstructure. This approach reveals the composition dependence of the nucleation temperature and primary phase, which allows us to draw conclusions about glass forming ability and to identify bulk metallic glass forming compositions. Our solidification results suggest that the best glass forming composition coincides with the composition at which a transition from one primary phase to another occurs. We show that in general this transition is not at the eutectic composition but at the lowest nucleation temperature.

  13. Solidification-Rate Effects In MAR-M-246+Hf Alloy

    NASA Technical Reports Server (NTRS)

    Hamilton, David

    1988-01-01

    Under slower solidification, primary-dendrite-arm spacing increases. Report discusses experiments on influence of solidification rates on crystallographic orientation and mechanical properties of superalloy MAR-M-246+Hf. Specimens grown in directional-solidification furnace, visually examined for microstructure, and stretched to failure in tensile-testing machine. Back-reflection Laue x-ray photographs taken to determine growth orientations.

  14. Energetics of nonequilibrium solidification in Al-Sm

    NASA Astrophysics Data System (ADS)

    Zhou, S. H.; Napolitano, R. E.

    2008-11-01

    Solution-based thermodynamic modeling, aided by first-principles calculations, is employed here to examine phase transformations in the Al-Sm binary system which may give rise to product phases that are metastable or have a composition that deviates substantially from equilibrium. In addition to describing the pure undercooled Al liquid with a two-state model that accounts for structural ordering, thermodynamic descriptions of the fcc phase, and intermediate compounds ( Al4Sm-β , Al11Sm3-α , Al3Sm-δ , and Al2Sm-σ ) are reanalyzed using special quasirandom structure and first-principles calculations. The possible phase compositions are presented over a range of temperatures using a “Baker-Cahn” analysis of the energetics of solidification and compared with reports of rapid solidification. The energetics associated with varying degrees of chemical partitioning are quantified and compared with experimental observations of the metastable Al11Sm3-α primary phase and reports of amorphous solids.

  15. X-ray nano-diffraction study of Sr intermetallic phase during solidification of Al-Si hypoeutectic alloy

    SciTech Connect

    Manickaraj, Jeyakumar; Gorny, Anton; Shankar, Sumanth; Cai, Zhonghou

    2014-02-17

    The evolution of strontium (Sr) containing intermetallic phase in the eutectic reaction of Sr-modified Al-Si hypoeutectic alloy was studied with high energy synchrotron beam source for nano-diffraction experiments and x-ray fluorescence elemental mapping. Contrary to popular belief, Sr does not seem to interfere with the Twin Plane Re-entrant Edge (TPRE) growth mechanism of eutectic Si, but evolves as the Al{sub 2}Si{sub 2}Sr phase during the eutectic reaction at the boundary between the eutectic Si and Al grains.

  16. Rapid solidification of Nb-base alloys

    NASA Technical Reports Server (NTRS)

    Gokhale, A. B.; Javed, K. R.; Abbaschian, G. J.; Lewis, R. E.

    1988-01-01

    New Nb-base alloys are of interest for aerospace structural applications at high temperatures, viz, 800 to 1650 C. Fundamental information regarding the effects of rapid solidification in achieving greatly refined microstructures, extended solid solubility, suppression of embrittling equilibrium phases, and formation of new phases is desired in a number of Nb-X alloys. The microstructures and selected properties of Nb-Si and other Nb-base alloys are presented for materials both rapidly quenched from the equilibrium liquidus and rapidly solidified following deep supercooling. Electromagnetic levitation was used to achieve melting and supercooling in a containerless inert gas environment. A variety of solidification conditions were employed including splatting or drop casting of supercooled samples. The morphology and composition of phases formed are discussed in terms of both solidification history and bulk composition.

  17. Solidification of hypereutectic Al-38 wt pct Cu alloy in microgravity and in unit gravity

    SciTech Connect

    Yu, H.; Tandon, K.N.; Cahoon, J.R.

    1997-05-01

    Solidification in microgravity aboard the space shuttle Endeavour resulted in a dramatic change in the morphology of the primary Al{sub 2}Cu phase compared to ground-based solidification in unit gravity. An Al-38 wt pct Cu ingot directionally solidified at a rate of 0.015 mm/s with a temperature gradient of 1.69 K/mm exhibited large, well-formed dendrites of primary Al{sub 2}Cu phase. Ingots solidified under similar conditions in unit gravity contained primary Al{sub 2}Cu phase with smooth, faceted surfaces. The primary Al{sub 2}Cu phase spacing in the microgravity ingot was much greater than that in the unit gravity ingot, 670 {micro}m compared to 171 {micro}m. It is suggested that thermosolutal mixing in the unit gravity ingot reduces the buildup of an Al-rich layer at the solid/liquid interface, which increases the stability of the interface resulting in smooth, faceted particles of Al{sub 2}Cu phase. It is also suggested that the large difference in primary phase spacings is due mostly to the difference in morphology rather than changes in parameters that might influence dendrite ripening mechanisms. The presence or absence of gravity had no effect on the interlamellar spacing of the inter-Al{sub 2}Cu phase eutectic. The ingot solidified in microgravity exhibited almost no longitudinal macrosegregation, in agreement with the theory of inverse segregation in the absence of thermosolutal convection. The ingot solidified in unit gravity exhibited considerable longitudinal macrosegregation, with the chilled end having about 6 wt pct more Cu than the average composition. It is not clear whether the segregation results from thermosolutal convection during solidification or from sedimentation during melting.

  18. Solidification of hypermonotectic Al-In alloys under microgravity conditions

    NASA Technical Reports Server (NTRS)

    Potard, C.

    1982-01-01

    Four samples of the Al-In system having monotectic and hypermonotectic compositions that were solidified under microgravity during the NASA-SPAR IX flight of January 20, 1981, are considered. The experimental thermal and physicochemical conditions that were actually achieved are analyzed. Radiographic and metallographic observations of the samples reveal a nonregular dispersed primary phase inside the monotectic matrix. These observations are discussed in relation to capillarity and solidification aspects. A key finding is the preservation of a certain degree of dispersion of the indium primary phase. This result differs fundamentally from the results obtained under microgravity conditions on the same system and compositions (Gelles and Markworth, 1980; Alborn and Loehberg, 1979). The results are seen as clearly establishing that the space environment can be used to obtain dispersed structures from hypermonotectic alloys.

  19. Parabolic aircraft solidification experiments

    NASA Technical Reports Server (NTRS)

    Workman, Gary L. (Principal Investigator); Smith, Guy A.; OBrien, Susan

    1996-01-01

    A number of solidification experiments have been utilized throughout the Materials Processing in Space Program to provide an experimental environment which minimizes variables in solidification experiments. Two techniques of interest are directional solidification and isothermal casting. Because of the wide-spread use of these experimental techniques in space-based research, several MSAD experiments have been manifested for space flight. In addition to the microstructural analysis for interpretation of the experimental results from previous work with parabolic flights, it has become apparent that a better understanding of the phenomena occurring during solidification can be better understood if direct visualization of the solidification interface were possible. Our university has performed in several experimental studies such as this in recent years. The most recent was in visualizing the effect of convective flow phenomena on the KC-135 and prior to that were several successive contracts to perform directional solidification and isothermal casting experiments on the KC-135. Included in this work was the modification and utilization of the Convective Flow Analyzer (CFA), the Aircraft Isothermal Casting Furnace (ICF), and the Three-Zone Directional Solidification Furnace. These studies have contributed heavily to the mission of the Microgravity Science and Applications' Materials Science Program.

  20. Clinical efficacy of 2-phase versus 4-phase computed tomography for localization in primary hyperparathyroidism

    PubMed Central

    Ramirez, Adriana G.; Shada, Amber L.; Martin, Allison N.; Raghavan, Prashant; Durst, Christopher R.; Mukherjee, Sugoto; Gaughen, John R.; Ornan, David A.; Hanks, John B.; Smith, Philip W.

    2016-01-01

    Background Four-dimensional computed tomography is being used increasingly for localization of abnormal glands in primary hyperparathyroidism. We hypothesized that compared with traditional 4-phase imaging, 2-phase imaging would halve the radiation dose without compromising parathyroid localization and clinical outcomes. Methods A transition from 4-phase to 2-phase imaging was instituted between 2009 and 2010. A pre-post analysis was performed on patients undergoing operative treatment with a parathyroid protocol computed tomography, and relevant data were correlated with operative findings. Sensitivity, positive predictive value, technical success, and cure rates were calculated. The Fisher exact test or χ2 test assessed the significance of 2-phase and 4-phase imaging and operative findings. Results Twenty-seven patients had traditional four-dimensional computed tomography and 35 had modified 2-phase computed tomography. Effective radiation doses were 6.8 mSy for 2-phase and 14 mSv for 4-phase. Four-phase computed tomography had a sensitivity and positive predictive value of 93% and 96%, respectively. Two-phase computed tomography had a comparable sensitivity and positive predictive value of 97% and 94%, respectively. Eight patients with discordant imaging had an average parathyroid weight of 240 g compared with 1,300 g for all patients. Technical surgical success (90% for 4-phase computed tomography versus 91% 2-phase computed tomography) and normocalcemia rates at 6 months (88% for both) did not differ between computed tomography protocols. Computed tomography correctly predicted multiglandular disease and localization for reoperations in 88% and 90% of cases, respectively, with no difference by computed tomography protocol. Conclusion With regard to surgical outcomes and localization, 2-phase parathyroid computed tomography is equivalent to 4-phase for parathyroid localization, including small adenomas, reoperative cases, and multiglandular disease. Two-phase

  1. Examination of solidification pathways and the liquidus surface in the Nb-Ti-Al system

    NASA Astrophysics Data System (ADS)

    Leonard, Keith J.; Mishurda, Joseph C.; Vasudevan, Vijay K.

    2000-12-01

    The solidification pathways, subsequent solid-state transformations, and the liquidus surface in the Nb-Ti-Al system have been examined as part of a larger investigation of phase equilibria in Nb-Ti-Al intermetallic alloys. Fifteen alloys ranging in composition from 15 to 40 at. pct Al, with Nb to Ti ratios of 4:1, 2:1, 1.5:1, 1:1, and 1:1.5, were prepared by arc melting and the as-cast microstructures were characterized by optical microscopy (OM), microhardness, X-ray diffraction (XRD), differential thermal analysis (DTA), backscattered electron imaging (BSEI), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM). The results indicate that the range of primary β solidification is much wider than that indicated in previously reported liquidus surfaces, both experimental and calculated. Differential thermal analysis has identified the existence of a β to σ+γ transformation in three alloys where it was previously thought not to exist; confirmation was provided by high-temperature vacuum heat treatments in the single-phase β region followed by rapid quenching. The location of the boundary between the β, σ, and δ primary solidification fields has been redefined. A massive β → δ transformation, which was observed in the cast microstructure of a Nb-25Ti-25Al alloy, was repeatable through cooling following homogenization. A β → δ+σ eutectoid-like transformation in the 25 at. pct Al alloys, was detected by DTA and evaluated through microstructural analysis of heat-treated samples. Trends in the β phase with variations in composition were established for both lattice parameters and microhardness. As a result of this wider extent of the primary β solidification field, a greater possibility exists for microstructural control through thermal processing for alloys consisting of either σ+γ, β+σ, or β+δ phases.

  2. Modelling directional solidification

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.; Regel, Liya L.

    1994-01-01

    This grant, NAG8-831, was a continuation of a previous grant, NAG8-541. The long range goal of this program has been to develop an improved understanding of phenomena of importance to directional solidification, in order to enable explanation and prediction of differences in behavior between solidification on Earth and in space. Emphasis in the recently completed grant was on determining the influence of perturbations on directional solidification of InSb and InSb-GaSb alloys. In particular, the objective was to determine the influence of spin-up/spin-down (ACRT), electric current pulses and vibrations on compositional homogeneity and grain size.

  3. Microsegregation during directional solidification

    NASA Technical Reports Server (NTRS)

    Coriell, S. R.; Mcfadden, G. B.

    1984-01-01

    During the directional solidification of alloys, solute inhomogeneities transverse to the growth direction arise due to morphological instabilities (leading to cellular or dendritic growth) and/or due to convection in the melt. In the absence of convection, the conditions for the onset of morphological instability are given by the linear stability analysis of Mullins and Sekerka. For ordinary solidification rates, the predictions of linear stability analysis are similar to the constitutional supercooling criterion. However, at very rapid solidification rates, linear stability analysis predicts a vast increase in stabilization in comparison to constitutional supercooling.

  4. Phase errors in gossamer membrane primary objective gratings

    NASA Astrophysics Data System (ADS)

    Ditto, Thomas D.; Ritter, Joseph M.

    2008-07-01

    A ribbon-shaped primary objective grating (POG) telescope lends itself to deployment in space, because it can be stowed for transport on a roll. Unlike mirrors which need to be segmented for sizes beyond the diameter of the fairing or payload bay, the ribbon is a continuous integral surface transported on a drum and unfurled during deployment. A flat POG membrane abandons a standard three dimensional figure requirement of mirrors and solves the problem of making primary objectives from tensile structures. Moreover, POG telescopes enjoy relaxed surface dimensional tolerances compared with mirrors. We have demonstrated mathematically and empirically that the tolerance for flatness relaxes as the receiving angle increases toward grazing exodus where the magnification of the POG is greatest. At the same time, the tolerance for phase error is worsened as the angle of reconstruction moves toward grazing exodus. The problem will be aggravated by the rigors of the space deployment environment. We give a mathematical treatment for the flatness and phase error. We mention engineering methods that could ameliorate the error.

  5. Solidification process in melt spun Nd-Fe-B type magnets

    SciTech Connect

    Li, C.

    1998-02-23

    A generalized solidification model has been developed based on a systematic investigation on the microstructure of melt spun Nd-Fe-B alloys. Melt spinning was conducted on initial stoichiometric and TiC added Nd{sub 2}Fe{sub 14}B (2-14-1) compositions to produce under, optimally and over quenched microstructures. Microstructural characterization was carried out by TEM, SEM, Optical microscopy, XRD, DTA, VSM and DC SQUID techniques. By taking the dendritic breakup during recalescence into consideration, this generalized model has successfully explained the solidification process of the melt spun Nd-Fe-B alloys. Challenging the conventional homogeneous nucleation models, the new model explains the fine and uniform equiaxed 2-14-1 microstructure in optimally quenched ribbons as a result of the breakup of the 2-14-1 dendrites which nucleate heterogeneously from the wheel surface and grow dendritically across the ribbon thickness due to the recalescence. Besides this dendritic breakup feature, the under quenched microstructure is further featured with another growth front starting with the primary solidification of Fe phase near the free side, which results in a coarsely grained microstructure with Fe dendritic inclusions and overall variation in microstructure across the ribbon thickness. In addition, because a epitaxy exists between the Fe phase and the 2-14-1, the so-formed coarse 2-14-1 grains may be textured. C-axis texturing was observed in under quenched ribbons. As a constraint to solidification models in this system, the cause and characteristics of this phenomenon has been studied in detail to test the authors proposed model, and agreement has been found. An extension has also been made to understand the solidification process when TiC is added, which suggests that Ti and C slow down the growth front of both Fe and 2-14-1 phase.

  6. Directional Solidification of Eutectic Ceramics

    NASA Technical Reports Server (NTRS)

    Sayir, Ali

    2001-01-01

    Two major problems associated with structural ceramics are lack of damage tolerance and insufficient strength and creep resistance at very high temperatures of interest for aerospace application. This work demonstrated that the directionally solidified eutectics can have unique poly-phase microstructures and mechanical properties superior to either constituent alone. The constraining effect of unique eutectic microstructures result in higher resistance to slow crack growth and creep. Prospect of achieving superior properties through controlled solidification are presented and this technology can also be beneficial to produce new class of materials.

  7. Conditions Of Directional Solidification Affect Superalloy

    NASA Technical Reports Server (NTRS)

    Schmidt, D. D.; Alter, W. S.; Hamilton, W. D.; Parr, R. A.

    1992-01-01

    Report describes experiments to determine effects of gradient of temperature and rate of solidification on microstructure and fatigue properties of nickel-based superalloy MAR-M246(Hf). Enhancement of properties extends lifespans of objects, including turbo-pump blades of Space Shuttle Main Engines. Results indicate significant improvements in fatigue properties derived through manipulation of parameters of directional solidification. Particularly MAR-M246(Hf) for turbine blades contains small, well-dispersed blocky carbide and microstructure with small distances between dendrite arms, and without eutectic phase.

  8. Flight Planning for the International Space Station - Levitation Observation of Dendrite Evolution in Steel Ternary Alloy Rapid Solidification (LODESTARS)

    NASA Technical Reports Server (NTRS)

    Flemings, Merton C.; Matson, Douglas M.; Hyers, Robert W.; Rogers, Jan R.

    2003-01-01

    During rapid solidification, a molten sample is cooled below its equilibrium solidification temperature to form a metastable liquid. Once nucleation is initiated, growth of the solid phase proceeds and can be seen as a sudden rise in temperature. The heat of fusion is rejected ahead of the growing dendrites into the undercooled liquid in a process known as recalescence. Fe-Cr-Ni alloys may form several equilibrium phases and the hypoeutectic alloys, with compositions near the commercially important 316 stainless steel alloy, are observed to solidify by way of a two-step process known as double recalescence. During double recalescence, the first temperature rise is associated with formation of the metastable ferritic solid phase with subsequent conversion to the stable austenitic phase during the second temperature rise. Selection of which phase grows into the undercooled melt during primary solidification may be accomplished by choice of the appropriate nucleation trigger material or by control of the processing parameters during rapid solidification. Due to the highly reactive nature of the molten sample material and in order to avoid contamination of the undercooled melt, a containerless electromagnetic levitation (EML) processing technique is used. In ground-based EML, the same forces that support the weight of the sample against gravity also drive convection in the liquid sample. However, in microgravity, the force required to position the sample is greatly reduced, so convection may be controlled over a wide range of internal flows. Space Shuttle experiments have shown that the double recalescence behavior of Fe-Cr-Ni alloys changes between ground and space EML experiments. This program is aimed at understanding how melt convection influences phase selection and the evolution of rapid solidification microstructures.

  9. Melt Flow Control in the Directional Solidification of Binary Alloys

    NASA Technical Reports Server (NTRS)

    Zabaras, Nicholas

    2003-01-01

    Our main project objectives are to develop computational techniques based on inverse problem theory that can be used to design directional solidification processes that lead to desired temperature gradient and growth conditions at the freezing front at various levels of gravity. It is known that control of these conditions plays a significant role in the selection of the form and scale of the obtained solidification microstructures. Emphasis is given on the control of the effects of various melt flow mechanisms on the local to the solidification front conditions. The thermal boundary conditions (furnace design) as well as the magnitude and direction of an externally applied magnetic field are the main design variables. We will highlight computational design models for sharp front solidification models and briefly discuss work in progress toward the development of design techniques for multi-phase volume-averaging based solidification models.

  10. Solidification of eutectic system alloys in space (M-19)

    NASA Technical Reports Server (NTRS)

    Ohno, Atsumi

    1993-01-01

    It is well known that in the liquid state eutectic alloys are theoretically homogeneous under 1 g conditions. However, the homogeneous solidified structure of this alloy is not obtained because thermal convection and non-equilibrium solidification occur. The present investigators have clarified the solidification mechanisms of the eutectic system alloys under 1 g conditions by using the in situ observation method; in particular, the primary crystals of the eutectic system alloys never nucleated in the liquid, but instead did so on the mold wall, and the crystals separated from the mold wall by fluid motion caused by thermal convection. They also found that the equiaxed eutectic grains (eutectic cells) are formed on the primary crystals. In this case, the leading phase of the eutectic must agree with the phase of the primary crystals. In space, no thermal convection occurs so that primary crystals should not move from the mold wall and should not appear inside the solidified structure. Therefore no equiaxed eutectic grains will be formed under microgravity conditions. Past space experiments concerning eutectic alloys were classified into two types of experiments: one with respect to the solidification mechanisms of the eutectic alloys and the other to the unidirectional solidification of this alloy. The former type of experiment has the problem that the solidified structures between microgravity and 1 g conditions show little difference. This is why the flight samples were prepared by the ordinary cast techniques on Earth. Therefore it is impossible to ascertain whether or not the nucleation and growth of primary crystals in the melt occur and if primary crystals influence the formation of the equiaxed eutectic grains. In this experiment, hypo- and hyper-eutectic aluminum copper alloys which are near eutectic point are used. The chemical compositions of the samples are Al-32.4mass%Cu (Hypo-eutectic) and Al-33.5mass%Cu (hyper-eutectic). Long rods for the samples are

  11. Modelling directional solidification

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.

    1987-01-01

    An improved understanding of the phenomena of importance to directional solidification is attempted to enable explanation and prediction of differences in behavior between solidification on Earth and in space. Emphasis is now on experimentally determining the influence of convection and freezing rate fluctuations on compositional homogeneity and crystalline perfection. A correlation is sought between heater temperature profiles, buoyancy-driven convection, and doping inhomogeneities using naphthalene doped with anthracene. The influence of spin-up/spin-down is determined on compositional homogeneity and microstructure of indium gallium antimonide. The effect is determined of imposed melting - freezing cycles on indium gallium antimonide. The mechanism behind the increase of grain size caused by using spin-up/spin-down in directional solidification of mercury cadimum telluride is sought.

  12. Dispersive solid-phase extraction followed by vortex-assisted dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet for the determination of benzoylurea insecticides in soil and sewage sludge.

    PubMed

    Peng, Guilong; He, Qiang; Mmereki, Daniel; Lu, Ying; Zhong, Zhihui; Liu, Hanyang; Pan, Weiliang; Zhou, Guangming; Chen, Junhua

    2016-04-01

    A novel dispersive solid-phase extraction combined with vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the determination of eight benzoylurea insecticides in soil and sewage sludge samples before high-performance liquid chromatography with ultraviolet detection. The analytes were first extracted from the soil and sludge samples into acetone under optimized pretreatment conditions. Clean-up of the extract was conducted by dispersive solid-phase extraction using activated carbon as the sorbent. The vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet procedure was performed by using 1-undecanol with lower density than water as the extraction solvent, and the acetone contained in the solution also acted as dispersive solvent. Under the optimum conditions, the linearity of the method was in the range 2-500 ng/g with correlation coefficients (r) of 0.9993-0.9999. The limits of detection were in the range of 0.08-0.56 ng/g. The relative standard deviations varied from 2.16 to 6.26% (n = 5). The enrichment factors ranged from 104 to 118. The extraction recoveries ranged from 81.05 to 97.82% for all of the analytes. The good performance has demonstrated that the proposed methodology has a strong potential for application in the multiresidue analysis of complex matrices. PMID:26888089

  13. Dispersive solid-phase extraction followed by vortex-assisted dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet for the determination of benzoylurea insecticides in soil and sewage sludge.

    PubMed

    Peng, Guilong; He, Qiang; Mmereki, Daniel; Lu, Ying; Zhong, Zhihui; Liu, Hanyang; Pan, Weiliang; Zhou, Guangming; Chen, Junhua

    2016-04-01

    A novel dispersive solid-phase extraction combined with vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the determination of eight benzoylurea insecticides in soil and sewage sludge samples before high-performance liquid chromatography with ultraviolet detection. The analytes were first extracted from the soil and sludge samples into acetone under optimized pretreatment conditions. Clean-up of the extract was conducted by dispersive solid-phase extraction using activated carbon as the sorbent. The vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet procedure was performed by using 1-undecanol with lower density than water as the extraction solvent, and the acetone contained in the solution also acted as dispersive solvent. Under the optimum conditions, the linearity of the method was in the range 2-500 ng/g with correlation coefficients (r) of 0.9993-0.9999. The limits of detection were in the range of 0.08-0.56 ng/g. The relative standard deviations varied from 2.16 to 6.26% (n = 5). The enrichment factors ranged from 104 to 118. The extraction recoveries ranged from 81.05 to 97.82% for all of the analytes. The good performance has demonstrated that the proposed methodology has a strong potential for application in the multiresidue analysis of complex matrices.

  14. Simulation of metal matrix composite solidification in the presence of cooled fibers

    NASA Astrophysics Data System (ADS)

    Lee, E. K.; Amano, R. S.; Rohatgi, P. K.

    2008-09-01

    Metal matrix composite (MMC) has been well known for its superior material properties compared with traditional composite. A new method is introduced to improve the properties of MMC in the sense that the ends of the reinforcement phase of the composite are allowed to extend out of the mold and cooled by a heat sink in order to promote the rate of heat transfer through the fibers and promote the formation of primary alpha phase around the reinforcement. This paper presents the experimental results obtained from the foundry in the University of Wisconsin-Milwaukee and some numerical simulation results of the solidification process in the cast mold.

  15. Effect of the cooling rate on the mechanism and the kinetics of the phase transformations in solidification of W-Mo high-speed steels

    SciTech Connect

    Nizhnikovskaya, P.F.; Kalinushkin, E.P.; Arshava, E.V.; Yakushev, O.S.

    1988-03-01

    The stop-quenching solidification of steel R6M5, R6M5F3, R6M5K5 was studied. The furnace was a horizontal-type vacuum with a quenching tank provided with a thyristor system. The specimens were examined by optical and scanning electron microscopy and also by electron microprobe. The method of stop-quenching was found to increase the cooling rate for a fuller completion of the peritectic reaction, establish a connection between the peritectic and the eutectic reaction in high speed steels, and broaden the temperature range of peritic transformation under conditions of accelerated heat removal.

  16. Solidification microstructures: A conceptual approach

    SciTech Connect

    Trivedi, R.; Kurz, W.

    1994-01-01

    Detailed theoretical models have been developed in the literature to correlate microstructural characteristics as a function of processing parameters. These results are examined with a broad perspective to show that various laws for microstructural transitions and microstructural spacings can be represented in terms of three simple characteristic lengths of the important physical processes. Initially, the important physical processes of solute and thermal transport and capillarity effect are considered, and they are related to the microstructural lengths such as dendrite tip radius, primary and secondary spacing, and eutectic spacing. It is shown that these microstructural lengths are simply given by the geometric mean of the characteristic lengths of physical processes that are important in a given problem. New characteristic lengths that become important under rapid solidification are then developed, and how these characteristic lengths influence microstructural transition and microstructural scales is also discussed.

  17. Simulations of rapid pressure-induced solidification in molten metals

    SciTech Connect

    Patel, M V; Streitz, F H

    2003-10-14

    The process of interest in this study is the solidification of a molten metal subjected to rapid pressurization. Most details about solidification occurring when the liquid-solid coexistence line is suddenly transversed along the pressure axis remain unknown. We present preliminary results from an ongoing study of this process for both simple models of metals (Cu) and more sophisticated material models (MGPT potentials for Ta). Atomistic (molecular dynamics) simulations are used to extract details such as the time and length scales that govern these processes. Starting with relatively simple potential models, we demonstrate how molecular dynamics can be used to study solidification. Local and global order parameters that aid in characterizing the phase have been identified, and the dependence of the solidification time on the phase space distance between the final (P,T) state and the coexistence line has been characterized.

  18. Directional solidification studies in Ni-Al alloys

    SciTech Connect

    Lee, Je-hyun

    1993-05-01

    Three solid phases are involved in the phase equilibria of the intermetallic compound Ni{sub 3}Al near its melting point, {beta}, {gamma}{prime}(Ni{sub 3}Al), and {gamma}. The generally-accepted phase diagram involves a eutectic reaction between {beta}{prime} and {gamma}, but some recent studies agree with an older diagram due to Schramm, which has a eutectic reaction between the {beta} and {gamma}{prime} phases. The phase equilibria near Ni{sub 3}Al compositions was evaluated using quenched directional solidification experiments, that preserve the microstructures tonned at the solidification front, and using diffusion couple experiments. These experiments show that eutectic forms between {beta} and {gamma}{prime} phases, as in the Schramm diagram. Growth and phase transformations of these three phases are also studied in the directional solidification experiments. Microstructure analysis shows that etching of Ni{sub 3}Al({gamma}{prime}) is very sensitive to small composition variations and crystallographic orientation changes. The eutectic solidification study confirms that the equilibrium eutectic is {gamma}{prime}+{beta}, and that the metastable {gamma}+{beta} eutectic might be also produced in this system according to the impurities, solidification rates, and composition variations.

  19. The sequence of intermetallic formation and solidification pathway of an Al–13Mg–7Si–2Cu in-situ composite

    SciTech Connect

    Farahany, Saeed; Nordin, Nur Azmah; Ourdjini, Ali; Abu Bakar, TutyAsma; Hamzah, Esah; Idris, Mohd Hasbullah; Hekmat-Ardakan, Alireza

    2014-12-15

    The phase transformation sequence and solidification behaviour of an Al–13Mg–7Si–2Cu in-situ composite was examined using a combination of computer-aided cooling curve thermal analysis and interrupted quenching techniques. Five different phases were identified by analysing the derivative cooling curves, the X-ray diffraction profile, optical and scanning electron microscopy images and the corresponding energy dispersive spectroscopy. It has been found that the solidification of this alloy begins with primary Mg{sub 2}Si precipitation and continues with the formation of eutectic Al–Mg{sub 2}Si, followed by Al{sub 5}FeSi and simultaneous precipitation of Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and Al{sub 2}Cu complex intermetallic phases. The formation of the last three intermetallic compounds changes the solidification behaviour of these composites remarkably due to their complex eutectic formation reactions. The solidification of the alloy, calculated using the Factsage thermochemical analysis software, has demonstrated a good agreement with the experiments in terms of compound prediction, their weight fractions and reaction temperatures. - Highlights: • Solidification path of a commercial Al-13Mg-7Si-2Cu composite was characterized. • Five different phases were identified and then confirmed with EDS and XRD results. • Mg{sub 2}Si, Al-Mg{sub 2}Si,Al{sub 5}FeSi (β),Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} (Q) and Al{sub 2}Cu(θ) precipitated respectively. • Solidification was predicted using the Factsage thermochemical analysis software.

  20. Eutectic-Free Superalloy Made By Directional Solidification

    NASA Technical Reports Server (NTRS)

    Schmidt, Deborah Dianne

    1995-01-01

    By suitable control of thermal conditions in directional-solidification process, supperalloy structural and machine components (e.g., turbine blades) cast with microstructures enhancing resistance to fatigue. Specific version of process and thermal conditions chosen to reduce micro-segregation during solidification and to minimize or eliminate script carbide and eutectic-phase inclusions, which are brittle inclusions found to decrease resistance to fatigue.

  1. Solidification of undercooled metals

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Shiohara, Y.

    1984-01-01

    The present investigation is concerned with the subject of undercooling (i.e., supercooling) in the case of metal alloys, taking into account the effects of undercooling on microstructure and microsegregation in alloys which solidify in a crystalline manner. Techniques for obtaining a large degree of undercooling are discussed. These techniques make it possible to eliminate heterogeneous nucleants from the melt and to remove container nucleation effects. The nucleation behavior of small metal droplets is considered along with the formation of a dispersion of fine droplets in a suitable inert medium, the mixing of fine metal powders with glass powder, and the levitation melting technique. Attention is given to solidification with rapid interface velocity, aspects of dendritic morphology, and thermal measurements during solidification of undercooled droplets.

  2. Modelling directional solidification

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.

    1990-01-01

    The long range goal is to develop an improved understanding of phenomena of importance to directional solidification, to enable explanation and prediction of differences in behavior between solidification on Earth and in space. Emphasis during the period of this grant was on experimentally determining the influence of convection and freezing rate fluctuations on compositional homogeneity and crystalline perfection in the vertical Bridgman-Stockbarger technique. Heater temperature profiles, buoyancy-driven convection, and doping inhomogeneties were correlated using naphthalene doped with azulene. In addition the influence of spin-up/spin-down on compositional homogeneity and microstructure of indium gallium antimonide and the effect of imposed melting-freezing cycles on indium gallium antimonide are discussed.

  3. Microwave solidification project overview

    SciTech Connect

    Sprenger, G.

    1993-01-01

    The Rocky Flats Plant Microwave Solidification Project has application potential to the Mixed Waste Treatment Project and the The Mixed Waste Integrated Program. The technical areas being addressed include (1) waste destruction and stabilization; (2) final waste form; and (3) front-end waste handling and feed preparation. This document covers need for such a program; technology description; significance; regulatory requirements; and accomplishments to date. A list of significant reports published under this project is included.

  4. Nuclear waste solidification

    DOEpatents

    Bjorklund, William J.

    1977-01-01

    High level liquid waste solidification is achieved on a continuous basis by atomizing the liquid waste and introducing the atomized liquid waste into a reaction chamber including a fluidized, heated inert bed to effect calcination of the atomized waste and removal of the calcined waste by overflow removal and by attrition and elutriation from the reaction chamber, and feeding additional inert bed particles to the fluidized bed to maintain the inert bed composition.

  5. Microstructural Development during Directional Solidification of Peritectic Alloys

    NASA Technical Reports Server (NTRS)

    Lograsso, Thomas A.

    1996-01-01

    A thorough understanding of the microstructures produced through solidification in peritectic systems has yet to be achieved, even though a large number of industrially and scientifically significant materials are in this class. One type of microstructure frequently observed during directional solidification consists of alternating layers of primary solid and peritectic solid oriented perpendicular to the growth direction. This layer formation is usually reported for alloy compositions within the two-phase region of the peritectic isotherm and for temperature gradient and growth rate conditions that result in a planar solid-liquid interface. Layered growth in peritectic alloys has not previously been characterized on a quantitative basis, nor has a mechanism for its formation been verified. The mechanisms that have been proposed for layer formation can be categorized as either extrinsic or intrinsic to the alloy system. The extrinsic mechanisms rely on externally induced perturbations to the system for layer formation, such as temperature oscillations, growth velocity variations, or vibrations. The intrinsic mechanisms approach layer formation as an alternative type of two phase growth that is inherent for certain peritectic systems and solidification conditions. Convective mixing of the liquid is an additional variable which can strongly influence the development and appearance of layers due to the requisite slow growth rate. The first quantitative description of layer formation is a model recently developed by Trivedi based on the intrinsic mechanism of cyclic accumulation and depiction of solute in the liquid ahead of the interface, linked to repeated nucleation events in the absence of convection. The objective of this research is to characterize the layered microstructures developed during ground-based experiments in which external influences have been minimized as much as possible and to compare these results to the current the model. Also, the differences

  6. Crossover scaling of wavelength selection in directional solidification of binary alloys.

    PubMed

    Greenwood, Michael; Haataja, Mikko; Provatas, And Nikolas

    2004-12-10

    We simulate cellular and dendritic growth in directional solidification in dilute binary alloys using a phase-field model solved with adaptive-mesh refinement. The spacing of primary branches is examined for a wide range of thermal gradients and alloy compositions and is found to undergo a maximum as a function of pulling velocity, in agreement with experimental observations. We demonstrate that wavelength selection is unambiguously described by a nontrivial crossover scaling function from the emergence of cellular growth to the onset of dendritic fingers. This result is further validated using published experimental data, which obeys the same scaling function.

  7. Understanding the solidification and microstructure evolution during CSC-MIG welding of Fe–Cr–B-based alloy

    SciTech Connect

    Sorour, A.A. Chromik, R.R. Gauvin, R. Jung, I.-H. Brochu, M.

    2013-12-15

    The present is a study of the solidification and microstructure of Fe–28.2%Cr–3.8%B–1.5%Si–1.5%Mn (wt.%) alloy deposited onto a 1020 plain carbon steel substrate using the controlled short-circuit metal inert gas welding process. The as-solidified alloy was a metal matrix composite with a hypereutectic microstructure. Thermodynamic calculation based on the Scheil–Gulliver model showed that a primary (Cr,Fe){sub 2}B phase formed first during solidification, followed by an eutectic formation of the (Cr,Fe){sub 2}B phase and a body-centered cubic Fe-based solid solution matrix, which contained Cr, Mn and Si. Microstructure analysis confirmed the formation of these phases and showed that the shape of the (Cr,Fe){sub 2}B phase was irregular plate. As the welding heat input increased, the weld dilution increased and thus the volume fraction of the (Cr,Fe){sub 2}B plates decreased while other microstructural characteristics were similar. - Highlights: • We deposit Fe–Cr–B-based alloy onto plain carbon steel using the CSC-MIG process. • We model the solidification behavior using thermodynamic calculation. • As deposited alloy consists of (Cr,Fe){sub 2}B plates embedded in Fe-based matrix. • We study the effect of the welding heat input on the microstructure.

  8. MPS Solidification Model. Volume 2: Operating guide and software documentation for the unsteady model

    NASA Technical Reports Server (NTRS)

    Maples, A. L.

    1981-01-01

    The operation of solidification Model 2 is described and documentation of the software associated with the model is provided. Model 2 calculates the macrosegregation in a rectangular ingot of a binary alloy as a result of unsteady horizontal axisymmetric bidirectional solidification. The solidification program allows interactive modification of calculation parameters as well as selection of graphical and tabular output. In batch mode, parameter values are input in card image form and output consists of printed tables of solidification functions. The operational aspects of Model 2 that differ substantially from Model 1 are described. The global flow diagrams and data structures of Model 2 are included. The primary program documentation is the code itself.

  9. Stability of Detached Solidification

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.; Croell, A.

    2009-01-01

    Bridgman crystal growth can be conducted in the so-called "detached" solidification regime, where the growing crystal is detached from the crucible wall. A small gap between the growing crystal and the crucible wall, of the order of 100 micrometers or less, can be maintained during the process. A meniscus is formed at the bottom of the melt between the crystal and crucible wall. Under proper conditions, growth can proceed without collapsing the meniscus. The meniscus shape plays a key role in stabilizing the process. Thermal and other process parameters can also affect the geometrical steady-state stability conditions of solidification. The dynamic stability theory of the shaped crystal growth process has been developed by Tatarchenko. It consists of finding a simplified autonomous set of differential equations for the radius, height, and possibly other process parameters. The problem then reduces to analyzing a system of first order linear differential equations for stability. Here we apply a modified version of this theory for a particular case of detached solidification. Approximate analytical formulas as well as accurate numerical values for the capillary stability coefficients are presented. They display an unexpected singularity as a function of pressure differential. A novel approach to study the thermal field effects on the crystal shape stability has been proposed. In essence, it rectifies the unphysical assumption of the model that utilizes a perturbation of the crystal radius along the axis as being instantaneous. It consists of introducing time delay effects into the mathematical description and leads, in general, to stability over a broader parameter range. We believe that this novel treatment can be advantageously implemented in stability analyses of other crystal growth techniques such as Czochralski and float zone methods.

  10. Undercooling of materials during solidification in space

    NASA Technical Reports Server (NTRS)

    Miller, R. I.

    1976-01-01

    A theoretical research program was undertaken on the under cooling and solidification of materials under variable external field conditions. A catalog of theories and models of nucleation of solid phases in the melt is provided, as is a discussion of the relation of undercooling to intermolecular potentials, the dependence of growth rate on undercooling, the influence of undercooling on liquid-solid interface stability and solid structure, the direct effects of external fields on melts, the relation of solid physical properties to structure and the role of nucleants in solidification. Results of the theoretical analysis of several experiments related to the space processing applications program are given, and recommendations for future experiments and further theoretical developments along with procedures for correlation of theory and experiment are specified.

  11. Transport Phenomena During Equiaxed Solidification of Alloys

    NASA Technical Reports Server (NTRS)

    Beckermann, C.; deGroh, H. C., III

    1997-01-01

    Recent progress in modeling of transport phenomena during dendritic alloy solidification is reviewed. Starting from the basic theorems of volume averaging, a general multiphase modeling framework is outlined. This framework allows for the incorporation of a variety of microscale phenomena in the macroscopic transport equations. For the case of diffusion dominated solidification, a simplified set of model equations is examined in detail and validated through comparisons with numerous experimental data for both columnar and equiaxed dendritic growth. This provides a critical assessment of the various model assumptions. Models that include melt flow and solid phase transport are also discussed, although their validation is still at an early stage. Several numerical results are presented that illustrate some of the profound effects of convective transport on the final compositional and structural characteristics of a solidified part. Important issues that deserve continuing attention are identified.

  12. Solidification process for sludge residue

    SciTech Connect

    Pearce, K.L.

    1998-09-10

    This report investigates the solidification process used at 100-N Basin to solidify the N Basin sediment and assesses the N Basin process for application to the K Basin sludge residue material. This report also includes a discussion of a solidification process for stabilizing filters. The solidified matrix must be compatible with the Environmental Remediation Disposal Facility acceptance criteria.

  13. Cellular solidification in a monotectic system

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.; Curreri, P. A.

    1987-01-01

    Succinonitrile-glycerol, SN-G, transparent organic monotectic alloy is studied with particular attention to cellular growth. The phase diagram is determined, near the monotectic composition, with greater accuracy than previous studies. A solidification interface stability diagram is determined for planar growth. The planar-to-cellular transition is compared to predictions from the Burton, Primm, Schlichter theory. A new technique to determine the solute segregation by Fourier transform infrared spectroscopy is developed. Proposed models that involve the cellular interface for alignment of monotectic second-phase spheres or rods are compared with observations.

  14. Solidification phenomena of binary organic mixtures

    NASA Technical Reports Server (NTRS)

    Chang, K.

    1982-01-01

    The coalescence rates and motion of liquid bubbles in binary organic mixtures were studied. Several factors such as temperature gradient, composition gradient, interfacial tension, and densities of the two phases play important roles in separation of phases of immiscible liquids. An attempt was made to study the effect of initial compositions on separation rates of well-dispersed organic mixtures at different temperatures and, ultimately, on the homogeneity of solidification of the immiscible binary organic liquids. These organic mixtures serve as models for metallic pseudo binary systems under study. Two specific systems were investigated: ethyl salicylate - diethyl glycol and succinonitrile - water.

  15. Solidification of Al Alloys Under Electromagnetic Pulses and Characterization of the 3D Microstructures Using Synchrotron X-ray Tomography

    NASA Astrophysics Data System (ADS)

    Manuwong, Theerapatt; Zhang, Wei; Kazinczi, Peter Lobo; Bodey, Andrew J.; Rau, Christoph; Mi, Jiawei

    2015-07-01

    A novel programmable electromagnetic pulse device was developed and used to study the solidification of Al-15 pct Cu and Al-35 pct Cu alloys. The pulsed magnetic fluxes and Lorentz forces generated inside the solidifying melts were simulated using finite element methods, and their effects on the solidification microstructures were characterized using electron microscopy and synchrotron X-ray tomography. Using a discharging voltage of 120 V, a pulsed magnetic field with the peak Lorentz force of ~1.6 N was generated inside the solidifying Al-Cu melts which were showed sufficiently enough to disrupt the growth of the primary Al dendrites and the Al2Cu intermetallic phases. The microstructures exhibit a strong correlation to the characteristics of the applied pulse, forming a periodical pattern that resonates the frequency of the applied electromagnetic field.

  16. Effect of Ce melt treatment on solidification path of ZA8 alloy

    NASA Astrophysics Data System (ADS)

    Sudheer, R.; Vijeesh, V.; Prabhu, K. N.

    2016-03-01

    The solidification path of ZA8 alloy with Ce addition was characterized using Newtonian technique of thermal analysis. The solidification events were determined using cooling curve and its first derivative curve. The microstructure and chemical composition of various phases in the alloy were studied using EDS, SEM and XRD techniques. It was found that the addition of Ce did not cause formation of new phases. However, it hinders the nucleation of stable β dendrites in the alloy. The presence of Ce promotes the eutectoid phase transformation and increases the hardness of the alloy. Latent heat of solidification and heat of eutectoid transformation were found to increase on Ce addition. The upward solidification of the alloy against Cu chill was analysed. Chilling had significant influence on solidification parameters, and caused refinement of the microstructure. The addition of Ce to the melt had no effect during chill casting of the alloy.

  17. Flow Effects during Directional Solidification of Monotectic Alloys

    NASA Astrophysics Data System (ADS)

    Coriell, S. R.; Murray, B. T.; McFadden, G. B.; Andrews, J. B.

    2000-11-01

    In monotectic alloy solidification, two phases, a solid phase, α, and a liquid phase, L_2, grow cooperatively from a single liquid phase L_1. For example, during the directional solidification of the aluminum-indium monotectic system, a solid-liquid two-phase structure consisting of liquid indium rods in an aluminum rich solid matrix can be grown from an aluminum-indium melt. The indium rods subsequently solidify at a lower temperature, forming a composite material. Theoretical models developed to quantitatively predict the inter-rod spacing observed in monotectic systems are largely based on diffusive solute transport. The role played by transport due to fluid flow is not well understood. Bulk flow may result from density change upon solidification or buoyancy-driven thermosolutal convection due to the thermal and solutal gradients inherent to the solidification process. We have developed numerical models to investigate the impact of an imposed flow on the solute field in the L1 phase. In addition, we propose to model the coupled flow at the L_1--L2 interface driven by surface tension variation. For monotectic growth, since phase equilibrium is maintained at the L_1--L2 interface, the temperature, compositions, pressures, and interface curvature are related by thermodynamic constraints that do not apply in a simple mechanical system.

  18. Experimental Verification of Solidification Stress Theory

    SciTech Connect

    Solbrig, C W; Morrison, M C; SImpson, M F; Bateman, K J

    2012-04-01

    A research program is being conducted to develop a crack-free ceramic waste form (CWF) to be used for long term encasement of fission products and actinides resulting from processing spent nuclear fuel. Cracking usually occurs in the cooldown phase of the glass or ceramic formations. A crack-free formation should have more resistance to leaching than one with many cracks. In the research leading up to producing a CWF, a model was developed that proposes a permanent stress develops when the melt solidifies and that this stress can cause failure as the CWF nears room temperature. This paper reports on how the formation, CWF2, confirms the existence of this stress. The solidification stress is in addition to and of opposite sign of the thermal stress. Its derivation is reported on in Ref. 1. Cracking of the CWF would occur at low temperatures if solidification stress exists but at high temperatures if it doesn’t. If solidification stress occurs, then the cooldown rate during solidification should be reduced. If not, it should be reduced when the thermal stresses are highest. Recording cracking sounds confirm the existence of this solidification stress since cracking occurred during the low temperature phase of the cooldown. As a side purpose of this paper, a cooldown rate is proposed that should eliminate cracking in the next experiment, CWF3. CWF2 is a prototype vertical ceramic waste cylinder formed over a period of 10 days by heating a mixture of 75% zeolite, 25% glass frit in an argon atmosphere furnace through melting to 925 C and then cooling through solidification to room temperature. It is approximately 1 m high, 0.5 m in diameter, weighs about 400 kg, and is formed in a stainless steel can 0.5 cm thick. This cylinder developed many cracks on cooldown. At least 15 loud cracks were recorded over a period of 4 days at the end of cooldown when the temperatures were below 400 C. The CWF2 surface and centerline temperatures at mid height were measured which

  19. Near-congruent solidification of castings

    NASA Astrophysics Data System (ADS)

    Chaput, Kevin J.

    A study on the microstructure development of as-cast Cu-Mn alloys based around the congruent minimum at 34.6 wt % Mn and 873 °C was performed. Initially, this was to evaluate the alloy as an alternative to wide freezing range Pb and Sn bronzes that are plagued with porosity. The shallow minimum and associated narrow freezing ranges around the congruent point result in a completely cellular (non-dendritic) solidification morphology for a composition range ~3 wt % Mn about the congruent composition (C c). The degree of cellular solidification was found to depend on the mold material. Increased mold conductivity lead to a narrower composition range of complete cellular solidification. By casting alloys of different compositions into a composite mold, the effect of the mold conductivity allowed an evaluation of the congruent point reported by Gokcen. These results fit well with the constitutional supercooling criterion. While solidification at a point ideally would be planar, this was not observed even with minor deviations from the Cc. An additional study of the microstructure development along the minimum trough in the liquidus surface between the Cu-Mn and Ni-Mn binary congruent points of the Cu-Mn-Ni ternary system was conducted. This study revealed that alloys near the binary congruent minima were more cellular than alloys near the middle of the phase diagram, along the trough. As the composition approached the center of the Cu-Mn-Ni diagram, the morphology became more dendritic, characteristic of an isomorphous system. Even though these alloys did not solidify in a completely cellular manner, they were free of any microshrinkage porosity. The alloys in this study (Cu-Mn and Cu-Mn-Ni) show promise for use in structural applications due to the lack of microshrinkage porosity, potent solution strengthening of manganese and strong aging response.

  20. 30 CFR 250.916 - What are the CVA's primary duties during the design phase?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false What are the CVA's primary duties during the design phase? 250.916 Section 250.916 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION... duties during the design phase? (a) The CVA must use good engineering judgement and practices...

  1. 30 CFR 250.918 - What are the CVA's primary duties during the installation phase?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false What are the CVA's primary duties during the installation phase? 250.918 Section 250.918 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION... duties during the installation phase? (a) The CVA must use good engineering judgment and practice...

  2. 30 CFR 250.917 - What are the CVA's primary duties during the fabrication phase?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false What are the CVA's primary duties during the fabrication phase? 250.917 Section 250.917 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION... duties during the fabrication phase? (a) The CVA must use good engineering judgement and practices...

  3. Low Melt Height Solidification of Superalloys

    NASA Astrophysics Data System (ADS)

    Montakhab, Mehdi; Bacak, Mert; Balikci, Ercan

    2016-06-01

    Effect of a reduced melt height in the directional solidification of a superalloy has been investigated by two methods: vertical Bridgman (VB) and vertical Bridgman with a submerged baffle (VBSB). The latter is a relatively new technique and provides a reduced melt height ahead of the solidifying interface. A low melt height leads to a larger primary dendrite arm spacing but a lower mushy length, melt-back transition length, and porosity. The VBSB technique yields up to 38 pct reduction in the porosity. This may improve a component's mechanical strength especially in a creep-fatigue type dynamic loading.

  4. Recalescence after solidification in Ge films melted by picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Siegel, J.; Solis, J.; Afonso, C. N.

    1999-08-01

    Thin amorphous Ge films on glass substrates are irradiated by single picosecond (ps) laser pulses and the induced melting and solidification process is followed by means of real-time reflectivity measurements with ps resolution using a setup based on a streak camera. Due to the excellent time resolution achieved in single exposure, the recalescence process occurring upon solidification can be completely resolved by means of an all-optical technique. The results are consistent with the bulk nucleation of the amorphous phase in the supercooled liquid at an extremely large nucleation rate. The massive release of solidification heat causes the reheating and partial remelting of the film after its complete solidification. The occurrence of recalescence after solidification is responsible for the formation of the crystalline phase finally obtained.

  5. Microstructural Evolution and Solidification Behavior of Al-Mg-Si Alloy in High-Pressure Die Casting

    NASA Astrophysics Data System (ADS)

    Ji, Shouxun; Wang, Yun; Watson, D.; Fan, Z.

    2013-07-01

    Microstructural evolution and solidification behavior of Al-5 wt pct Mg-1.5 wt pct Si-0.6 wt pct Mn-0.2 wt pct Ti alloy have been investigated using high-pressure die casting. Solidification commences with the formation of primary α-Al phase in the shot sleeve and is completed in the die cavity. The average size of dendrites and fragmented dendrites of the primary α-Al phase formed in the shot sleeve is 43 μm, and the globular primary α-Al grains formed inside the die cavity is at a size of 7.5 μm. Solidification inside the die cavity also forms the lamellar Al-Mg2Si eutectic phase and the Fe-rich intermetallics. The size of the eutectic cells is about 10 μm, in which the lamellar α-Al phase is 0.41 μm thick. The Fe-rich intermetallic compound exhibits a compact morphology and is less than 2 μm with a composition of 1.62 at. pct Si, 3.94 at. pct Fe, and 2.31 at. pct Mn. A solute-enriched circular band is always observed parallel to the surface of the casting. The band zone separates the outer skin region from the central region of the casting. The solute concentration is consistent in the skin region and shows a general drop toward the center inside the band for Mg and Si. The peak of the solute enrichment in the band zone is much higher than the nominal composition of the alloy. The die casting exhibits a combination of brittle and ductile fracture. There is no significant difference on the fracture morphology in the three regions. The band zone is not significantly detrimental in terms of the fracture mechanism in the die casting. Calculations using the Mullins and Sekerka stability criterion reveal that the solidification of the primary α-Al phase inside the die cavity has been completed before the spherical α-Al globules begin to lose their stability, but the α-Al grains formed in the shot sleeve exceed the limit of spherical growth and therefore exhibit a dendritic morphology.

  6. Stabilization/Solidification Remediation Method for Contaminated Soil: A Review

    NASA Astrophysics Data System (ADS)

    Tajudin, S. A. A.; Azmi, M. A. M.; Nabila, A. T. A.

    2016-07-01

    Stabilization/Solidification (S/S) is typically a process that involves a mixing of waste with binders to reduce the volume of contaminant leachability by means of physical and chemical characteristics to convert waste in the environment that goes to landfill or others possibly channels. Stabilization is attempts to reduce the solubility or chemical reactivity of the waste by changing the physical and chemical properties. While, solidification attempt to convert the waste into easily handled solids with low hazardous level. These two processes are often discussed together since they have a similar purpose of improvement than containment of potential pollutants in treated wastes. The primary objective of this review is to investigate the materials used as a binder in Stabilization/Solidification (S/S) method as well as the ability of these binders to remediate the contaminated soils especially by heavy metals.

  7. Novel Directional Solidification of Hypermonotectic Alloys

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Fedoseyev, A. I.

    2000-01-01

    There are many metal alloy systems that separate into two different liquids upon cooling from a higher temperature. Uniform microstructural development during solidification of these immiscible liquids on Earth is hampered by inherent density differences between the phases. Microgravity processing minimizes settling but segregation still occurs due to gravity independent wetting and coalescence phenomena. Experiments with the transparent organic, metal analogue, succinonitrile-glycerol system were conducted in conjunction with applied ultrasonic energy. The processing parameters associated with this technique have been evaluated in view of optimizing dispersion uniformity. Characterization of the experimental results in terms of an initial modeling effort will also be presented.

  8. Novel Directional Solidification of Hypermonotectic Alloys

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Fedoseyev, A. I.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    There are many metal alloy systems that separate into two different liquids upon cooling from a higher temperature. Uniform microstructural development during solidification of these immiscible liquids on Earth is hampered by inherent density differences between the phases. Microgravity processing minimizes settling but segregation still occurs due to gravity independent wetting and coalescence phenomena. Experiments with the transparent organic, metal analogue, succinonitrile-glycerol system were conducted in conjunction with applied ultrasonic energy. The processing parameters associated with this technique have been evaluated in view of optimizing dispersion uniformity. Characterization of the experimental results in terms of an initial modeling effort will also be presented.

  9. Seaweed to dendrite transition in directional solidification.

    PubMed

    Provatas, Nikolas; Wang, Quanyong; Haataja, Mikko; Grant, Martin

    2003-10-10

    We simulate directional solidification using a phase-field model solved with adaptive mesh refinement. For small surface tension anisotropy directed at 45 degrees relative to the pulling direction we observe a crossover from a seaweed to a dendritic morphology as the thermal gradient is lowered, consistent with recent experimental findings. We show that the morphology of crystal structures can be unambiguously characterized through the local interface velocity distribution. We derive semiempirically an estimate for the crossover from seaweed to dendrite as a function of thermal gradient and pulling speed.

  10. Heat transfer-solidification kinetics modeling of solidification of castings

    NASA Astrophysics Data System (ADS)

    Stefanescu, Doru M.; Upadhya, G.; Bandyopadhyay, D.

    1990-03-01

    A close examination of the recent developments in the field of computer simulation of solidification process reveals that a combination of both macroscopic and microscopic models is necessary in order to accurately describe the solidification of castings. Currently available macroscopic models include models that describe heat transfer from metal to mold, fluid flow of liquid metal during mold filling, and stress field in the casting. At the microscopic level, the models should include more intricate issues such as solidification kinetics and fluid flow in the mushy zone. Although significant progress has been accomplished over the years in each field, the task of including all of these models into a comprehensive package is far from being complete. This paper describes the state of the art on coupling the macroscopic heat transfer (HT) and microscopic solidification kinetics (SK) models and introduces the latent heat method as a more accurate method for solving the heat source term in the heat conduction equation. A new method for calculation of fraction of solid evolved during solidification based on computer-aided cooling curve analysis (CA-CCA), as well as a method based on nucleation and growth kinetics laws, is discussed. A new nucleation model based on the concept of instantaneous nucleation, which is used to describe equiaxed eutectic solidification of commercial alloys, has been introduced. It is demonstrated that the instantaneous nucleation model agrees well with the experimental results in terms of cooling curves and of evolution of the fraction of solid during solidification. Validation results are also shown for SK models that are based on CA-CCA coupled with HT models for eutectic Al-Si and gray cast iron alloys.

  11. Solidification in a Supercomputer: From Crystal Nuclei to Dendrite Assemblages

    NASA Astrophysics Data System (ADS)

    Shibuta, Yasushi; Ohno, Munekazu; Takaki, Tomohiro

    2015-08-01

    Thanks to the recent progress in high-performance computational environments, the range of applications of computational metallurgy is expanding rapidly. In this paper, cutting-edge simulations of solidification from atomic to microstructural levels performed on a graphics processing unit (GPU) architecture are introduced with a brief introduction to advances in computational studies on solidification. In particular, million-atom molecular dynamics simulations captured the spontaneous evolution of anisotropy in a solid nucleus in an undercooled melt and homogeneous nucleation without any inducing factor, which is followed by grain growth. At the microstructural level, the quantitative phase-field model has been gaining importance as a powerful tool for predicting solidification microstructures. In this paper, the convergence behavior of simulation results obtained with this model is discussed, in detail. Such convergence ensures the reliability of results of phase-field simulations. Using the quantitative phase-field model, the competitive growth of dendrite assemblages during the directional solidification of a binary alloy bicrystal at the millimeter scale is examined by performing two- and three-dimensional large-scale simulations by multi-GPU computation on the supercomputer, TSUBAME2.5. This cutting-edge approach using a GPU supercomputer is opening a new phase in computational metallurgy.

  12. Solidification processing of intermetallic Nb-Al alloys

    NASA Technical Reports Server (NTRS)

    Smith, Preston P.; Oliver, Ben F.; Noebe, Ronald D.

    1992-01-01

    Several Nb-Al alloys, including single-phase NbAl3 and the eutectic of Nb2Al and NbAl3, were prepared either by nonconsumable arc melting in Ar or by zone processing in He following initial induction melting and rod casting, and the effect of the solidification route on the microstructure and room-temperature mechanical properties of these alloys was investigated. Automated control procedures and melt conditions for directional solidification of NbAl3 and the Nb2Al/Nb3Al eutectic were developed; high purity and stoichiometry were obtained. The effects of ternary additions of Ti and Ni are described.

  13. A mixture of massive and feathery microstructures of Ti48Al2Cr2Nb alloy by high undercooled solidification

    SciTech Connect

    Liu, Yi; Hu, Rui Kou, Hongchao; Zhang, Tiebang; Wang, Jun; Li, Jinshan

    2015-02-15

    A mixture of massive and feathery microstructures was observed in Ti48Al2Cr2Nb alloy subjected to the undercooled solidification rather than the heat treatments in most cases. Double recalescence events and primary β solidification confirmed that massive γ phase did not directly nucleate from the undercooled melt but formed during the solid-state transformations. It is believed that small white areas (aluminium-poor) along lamellar grain boundaries may be closely related to the formation of massive γ phase and feathery γ phase. High dislocation density and stacking faults were detected in massive γ phase by transmission electron microscopy. The high energy of defects and undercooling in the solid state phase transformation can provide sufficiently high driving force for the nucleation of massive γ phase. - Graphical abstract: Display Omitted - Highlights: • A mixture of massive and feathery microstructures was observed. • Massive γ formed during the solid-state transformations. • Defects and undercooling provide driving force for the nucleation of massive γ.

  14. Speciation of As(III) and As(V) in water samples by graphite furnace atomic absorption spectrometry after solid phase extraction combined with dispersive liquid-liquid microextraction based on the solidification of floating organic drop.

    PubMed

    Shamsipur, Mojtaba; Fattahi, Nazir; Assadi, Yaghoub; Sadeghi, Marzieh; Sharafi, Kiomars

    2014-12-01

    A solid phase extraction (SPE) coupled with dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) method, using diethyldithiphosphate (DDTP) as a proper chelating agent, has been developed as an ultra preconcentration technique for the determination of inorganic arsenic in water samples prior to graphite furnace atomic absorption spectrometry (GFAAS). Variables affecting the performance of both steps were thoroughly investigated. Under optimized conditions, 100mL of As(ΙΙΙ) solution was first concentrated using a solid phase sorbent. The extract was collected in 2.0 mL of acetone and 60.0 µL of 1-undecanol was added into the collecting solvent. The mixture was then injected rapidly into 5.0 mL of pure water for further DLLME-SFO. Total inorganic As(III, V) was extracted similarly after reduction of As(V) to As(III) with potassium iodide and sodium thiosulfate and As(V) concentration was calculated by difference. A mixture of Pd(NO3)2 and Mg(NO3)2 was used as a chemical modifier in GFAAS. The analytical characteristics of the method were determined. The calibration graph was linear in the rage of 10-100 ng L(-1) with detection limit of 2.5 ng L(-1). Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 80 ng L(-1) of As(ΙΙΙ) were 6.8% and 7.5%, respectively. The method was successfully applied to speciation of As(III), As(V) and determination of the total amount of As in water samples and in a certified reference material (NIST RSM 1643e). PMID:25159375

  15. Speciation of As(III) and As(V) in water samples by graphite furnace atomic absorption spectrometry after solid phase extraction combined with dispersive liquid-liquid microextraction based on the solidification of floating organic drop.

    PubMed

    Shamsipur, Mojtaba; Fattahi, Nazir; Assadi, Yaghoub; Sadeghi, Marzieh; Sharafi, Kiomars

    2014-12-01

    A solid phase extraction (SPE) coupled with dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) method, using diethyldithiphosphate (DDTP) as a proper chelating agent, has been developed as an ultra preconcentration technique for the determination of inorganic arsenic in water samples prior to graphite furnace atomic absorption spectrometry (GFAAS). Variables affecting the performance of both steps were thoroughly investigated. Under optimized conditions, 100mL of As(ΙΙΙ) solution was first concentrated using a solid phase sorbent. The extract was collected in 2.0 mL of acetone and 60.0 µL of 1-undecanol was added into the collecting solvent. The mixture was then injected rapidly into 5.0 mL of pure water for further DLLME-SFO. Total inorganic As(III, V) was extracted similarly after reduction of As(V) to As(III) with potassium iodide and sodium thiosulfate and As(V) concentration was calculated by difference. A mixture of Pd(NO3)2 and Mg(NO3)2 was used as a chemical modifier in GFAAS. The analytical characteristics of the method were determined. The calibration graph was linear in the rage of 10-100 ng L(-1) with detection limit of 2.5 ng L(-1). Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 80 ng L(-1) of As(ΙΙΙ) were 6.8% and 7.5%, respectively. The method was successfully applied to speciation of As(III), As(V) and determination of the total amount of As in water samples and in a certified reference material (NIST RSM 1643e).

  16. Solidification analysis of a centrifugal atomizer using the Al-32.7wt.% Cu alloy

    SciTech Connect

    Osborne, M.G.

    1998-02-23

    A centrifugal atomizer (spinning disk variety) was designed and constructed for the production of spherical metal powders, 100--1,000 microns in diameter in an inert atmosphere. Initial atomization experiments revealed the need for a better understanding of how the liquid metal was atomized and how the liquid droplets solidified. To investigate particle atomization, Ag was atomized in air and the process recorded on high-speed film. To investigate particle solidification, Al-32.7 wt.% Cu was atomized under inert atmosphere and the subsequent particles were examined microscopically to determine solidification structure and rate. This dissertation details the experimental procedures used in producing the Al-Cu eutectic alloy particles, examination of the particle microstructures, and determination of the solidification characteristics (e.g., solidification rate) of various phases. Finally, correlations are proposed between the operation of the centrifugal atomizer and the observed solidification spacings.

  17. The solidification microstructure of Al-Cu-Si alloys metal matrix composites

    SciTech Connect

    Garbellini, O.; Palacio, H.; Biloni, H.

    1998-12-31

    The relationship between solidification microstructure and fluidity in MMC was studied. The composites were fabricated by infiltration of liquid metal into a alumina SAFFIL fibers preform under a gas pressure, using alloys of the AlCuSi system as matrices. The fluidity was measured in terms of classic foundry practice (i.e., the distance of flow liquid metal into the preform, while solidifying). The characterization of solidification microstructure in the cast composite was analyzed and correlated with the results of fluidity. The attention was particularly focused on such effects as the presence or absence of selective nucleation, the refinement of certain solidifying phases in the presence of fibers and their influence on microstructure formation and segregation of certain elements present in the liquid at the fiber matrix interface. By comparing reinforced and non reinforced zones, it was shown that the presence of fibers resulted in a refinement of the dendritic arm spacing of the {alpha}Al phase, with nucleation of Si on the fibers and without nucleation of primary Al dendrites. The results were discussed and compared with the microstructures and fluidity test of the unreinforced Al-Cu-Si alloys.

  18. Atomistic to continuum modeling of solidification microstructures

    SciTech Connect

    Karma, Alain; Tourret, Damien

    2015-09-26

    We summarize recent advances in modeling of solidification microstructures using computational methods that bridge atomistic to continuum scales. We first discuss progress in atomistic modeling of equilibrium and non-equilibrium solid–liquid interface properties influencing microstructure formation, as well as interface coalescence phenomena influencing the late stages of solidification. The latter is relevant in the context of hot tearing reviewed in the article by M. Rappaz in this issue. We then discuss progress to model microstructures on a continuum scale using phase-field methods. We focus on selected examples in which modeling of 3D cellular and dendritic microstructures has been directly linked to experimental observations. Finally, we discuss a recently introduced coarse-grained dendritic needle network approach to simulate the formation of well-developed dendritic microstructures. The approach reliably bridges the well-separated scales traditionally simulated by phase-field and grain structure models, hence opening new avenues for quantitative modeling of complex intra- and inter-grain dynamical interactions on a grain scale.

  19. Atomistic to continuum modeling of solidification microstructures

    DOE PAGESBeta

    Karma, Alain; Tourret, Damien

    2015-09-26

    We summarize recent advances in modeling of solidification microstructures using computational methods that bridge atomistic to continuum scales. We first discuss progress in atomistic modeling of equilibrium and non-equilibrium solid–liquid interface properties influencing microstructure formation, as well as interface coalescence phenomena influencing the late stages of solidification. The latter is relevant in the context of hot tearing reviewed in the article by M. Rappaz in this issue. We then discuss progress to model microstructures on a continuum scale using phase-field methods. We focus on selected examples in which modeling of 3D cellular and dendritic microstructures has been directly linked tomore » experimental observations. Finally, we discuss a recently introduced coarse-grained dendritic needle network approach to simulate the formation of well-developed dendritic microstructures. The approach reliably bridges the well-separated scales traditionally simulated by phase-field and grain structure models, hence opening new avenues for quantitative modeling of complex intra- and inter-grain dynamical interactions on a grain scale.« less

  20. 30 CFR 250.916 - What are the CVA's primary duties during the design phase?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What are the CVA's primary duties during the design phase? 250.916 Section 250.916 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE...) Stress analyses; (vi) Material designations; (vii) Soil and foundation conditions; (viii) Safety...

  1. Teachers' Beliefs on Foreign Language Teaching Practices in Early Phases of Primary Education: A Case Study

    ERIC Educational Resources Information Center

    Caner, Mustafa; Subasi, Gonca; Kara, Selma

    2010-01-01

    The purpose of the study was to examine whether teacher beliefs would play a role in their actual practices while teaching target language in early phases of primary education, principally, in kindergarten and first grades in a state school. As it is a very broad research area, the researchers exclusively analyzed teaching practices and teaching…

  2. Biosynthesis and secretion of alpha 1 acute-phase globulin in primary cultures of rat hepatocytes.

    PubMed

    Bauer, J; Kurdowska, A; Tran-Thi, T A; Budek, W; Koj, A; Decker, K; Heinrich, P C

    1985-01-15

    Experimental inflammation in rats led to a sevenfold increase in serum levels of alpha 1 acute-phase globulin. This increase is correlated with elevated levels of translatable mRNA for alpha 1 acute-phase globulin in the liver. Biosynthesis and secretion of alpha 1 acute-phase globulin were studied in rat hepatocyte primary cultures. An intracellular form of alpha 1 acute-phase globulin with an apparent relative molecular mass of 63 500 and a secreted form of 68 000 were found. The intracellular form of alpha 1 acute-phase globulin could be deglycosylated by endoglucosaminidase H treatment indicating that its oligosaccharide chains were of the high-mannose type. The secreted form of alpha 1 acute-phase globulin was not sensitive to endoglucosaminidase H, but was susceptible to the action of sialidase reflecting carbohydrate side-chains of the complex type. Pulse-chase experiments revealed a precursor-product relationship for the high-mannose and the complex type alpha 1 acute-phase globulin. In the hepatocyte medium newly synthesized alpha 1 acute-phase globulin was detected 30 min after the pulse. Unglycosylated alpha 1 acute-phase globulin was found in the cells as well as in the medium when the transfer of oligosaccharide chains onto the polypeptide chains was blocked by tunicamycin. Tunicamycin led to a marked delay in alpha 1 acute-phase globulin secretion. PMID:2578391

  3. Solidification paths and reinforcement morphologies in melt-processed (TiB + TiC)/Ti In Situ Composites

    NASA Astrophysics Data System (ADS)

    Lu, W. J.; Zhang, D.; Wu, R. J.; Mori, H.

    2002-09-01

    A novel in situ process was developed to produce titanium matrix composites reinforced with TiB and TiC of different mole ratios in which traditional ingot metallurgy plus self-propagation hightemperature synthesis (SHS) reactions between Ti and B4C, graphite powder were used. Microstructures of (TiB+TiC)/Ti in situ composites were comprehensively characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Solidification paths were investigated using a differential scanning calorimeter (DSC). Results show that there is an apparent difference in morphologies of reinforcements. The reinforcements nucleate and grow from the melt in a way of dissolution precipitation. The different morphologies are related to their solidification paths and the particular crystal structure of the reinforcement. TiB grows along the [010] direction and forms short-fiber shape due to its B27 structure, whereas TiC with NaCl type structure grows in a dendritic, equiaxed, or near-equiaxed shape. The DSC results and analysis of the phase diagram yield three stages for the solidification paths of in situ synthesized titanium matrix composites: (1) primary phase, (2) monovariant binary eutectic, and (3) invariant ternary eutectic. The addition of graphite adjusts the solidification paths and forms more dendritic primary TiC. The addition of aluminum does not change the solidification paths. However, the reinforcements grow finer and lead to equiaxed or near-equiaxed TiC morphologies. The following consistent crystallographic relationships between TiB and titanium were observed by HRTEM, i.e., [010]TiB//[01bar 10]Ti, (100)TiB//(bar 2110)Ti, (001)TiB//(0002)Ti, (10bar 1)TiB//(4overline {22} 1)Ti and [001]TiB//[01bar 10]Ti, (0bar 10)TiB//(bar 2110)Ti, (200)TiB//(0002)Ti. The formation of the preceding crystallographic relationships is related to the growth mechanism of TiB. It also helps to minimize

  4. Quantifying hydrate solidification front advancing using method of characteristics

    NASA Astrophysics Data System (ADS)

    You, Kehua; DiCarlo, David; Flemings, Peter B.

    2015-10-01

    We develop a one-dimensional analytical solution based on the method of characteristics to explore hydrate formation from gas injection into brine-saturated sediments within the hydrate stability zone. Our solution includes fully coupled multiphase and multicomponent flow and the associated advective transport in a homogeneous system. Our solution shows that hydrate saturation is controlled by the initial thermodynamic state of the system and changed by the gas fractional flow. Hydrate saturation in gas-rich systems can be estimated by 1-cl0/cle when Darcy flow dominates, where cl0 is the initial mass fraction of salt in brine, and cle is the mass fraction of salt in brine at three-phase (gas, liquid, and hydrate) equilibrium. Hydrate saturation is constant, gas saturation and gas flux decrease, and liquid saturation and liquid flux increase with the distance from the gas inlet to the hydrate solidification front. The total gas and liquid flux is constant from the gas inlet to the hydrate solidification front and decreases abruptly at the hydrate solidification front due to gas inclusion into the hydrate phase. The advancing velocity of the hydrate solidification front decreases with hydrate saturation at a fixed gas inflow rate. This analytical solution illuminates how hydrate is formed by gas injection (methane, CO2, ethane, propane) at both the laboratory and field scales.

  5. Flight Planning for the International Space Station-Levitation Observation of Dendrite Evolution in Steel Ternary Alloy Rapid Solidification

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Matson, D. M.; Loser, W.; Hyers, R. W.; Rogers, J. R.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The paper is an overview of the status and science for the LODESTARS (Levitation Observation of Dendrite Evolution in Steel Ternary Alloy Rapid Solidification) research project. The program is aimed at understanding how melt convection influences phase selection and the evolution of rapid solidification microstructures.

  6. Numerical modeling of filling and solidification for casting problems

    SciTech Connect

    Combeau, H.; Lesoult, G.; Bourg, A.; Langlois, S.; Charbonnier, J.; Sztur, C.; Rigaut, C.

    1995-12-31

    The prediction of feeding defects by a numerical tool must take into account solidification during the filling stage of casting. Although many studies have already been devoted to the modeling of mould filling, only a few of them deal with the problem of simultaneously solving filling coupled with solidification. Moreover, when solidification is considered, the fluid flow in the mush zone is computed by increasing the viscosity in the Navier Stokes equation and the shrinkage effect is neglected. More realistic models have been developed with a drag force such as the Darcy law added to the Navier Stokes equation in order to describe the fluid flow in the mush zone, but these models have generally been used to solve solidification problems without filling. Two numerical models which take into account heat, mass and momentum transfers in metal and heat transfer in the mould are presented. These models are based on the concept of continuous equivalent medium. The first model takes into account the fluid flow in the mush zone with a Darcy term added to the Navier Stokes equation. The solid phase is considered to be fixed in this case. In the second model, the velocity of the solid phase is assumed to be equal to the velocity of the liquid phase. The results obtained with the two models are compared. The effects of various parameters, for example overheat, pressure of the liquid metal at the inlet, microstructure size, temperature range of solidification, on the tendency to form feeding defects are discussed. Predicted tendencies are in agreement with observations reported in the literature.

  7. Directional Solidification Of Monotectic Alloys

    NASA Technical Reports Server (NTRS)

    Dhindaw, B. K.; Stefanescu, D. M.; Singh, A. K.; Curreri, P. A.

    1990-01-01

    Conditions promoting formation of aligned fibers sought. Report describes experiments in directional solidification of Cu/Pb and Bi/Ga monotectic alloys. Study motivated by need to understand physical mechanism governing formation of rodlike or fiberlike aligned structures in solidifying alloy and to determine process conditions favoring such structures.

  8. Modelling the solidification of hypermonotectic alloys

    NASA Astrophysics Data System (ADS)

    Wu, Menghuai; Ludwig, Andreas; Ratke, Lorenz

    2003-09-01

    A two-phase model is developed to simulate the decomposition and spatial phase separation (microstructure evolution) during solidification of hypermonotectic alloys. The minority liquid phase, decomposing in morphology of droplets from the parent melt, is treated as the second phase, L2, while the parent melt, including the solidified monotectic matrix, is the first phase, L1. The conservation equations of mass, momentum, solute and enthalpy for both phases, and an additional transport equation for the droplets are solved. Nucleation of the droplets, diffusion-controlled growth (coarsening) and dissolution of the droplets, interphase interactions such as Marangoni (thermocapillary) force, Stokes force, solute partitioning and heat release of decomposition are modelled by the corresponding source and exchange terms in the conservation equations. The monotectic reaction is modelled by adding the latent heat on the L1 phase and applying a suitable large viscosity to the solidified monotectic matrix. The simulation results of a two-dimensional square casting with hypermonotectic composition (Al-10 wt.% Bi) under normal terrestrial and weightless conditions are presented and discussed.

  9. Interactions Between Solidification and Compositional Convection in Alloys

    NASA Technical Reports Server (NTRS)

    Davis, S. H.; Worster, M. G.; Chiareli, A. O. P.; Anderson, D. M.; Schultze, T. P.

    1998-01-01

    This project combined theoretical and experimental ground-based studies of the interactions between convection and solidification of binary melts. Particular attention was focused on the alteration of the composition and microstructure of castings caused by convective flows through the interstices of mushy layers. Two different mechanisms causing convection were investigated. (i) Compositional, buoyancy driven convection is known to cause chimneys and freckles in directionally cast alloys on Earth. The analytical studies provide quantitative criteria for the formation of chimneys that can be used to assess the expediency of producing alloys in Space. (ii) Flow of the melt is also driven by the contraction (expansion) that typically occurs during change of phase. Such convection will occur even in the absence of gravity, and may indeed be the primary cause of macrosegregation during the production of alloys in Space. The studies will employed asymptotic methods in order to determine conditions for the stability of various states of solidifying systems. Further, simple macroscopic models of complete systems were developed and solved. These analytical studies were augmented by laboratory experiments using aqueous solutions, in which the convective flows could be easily observed and the effects of convection could be readily measured. These y experiments guided the development of the theoretical models and provided data against which the predictions of the models can be tested.

  10. Community oriented primary care in Tshwane District, South Africa: Assessing the first phase of implementation

    PubMed Central

    Marcus, Tessa; Memon, Shehla; Bam, Nomonde; Hugo, Jannie

    2013-01-01

    Abstract Background Re-engineering primary health care is a cornerstone of the health sector reform initiated nationally in South Africa in 2009. Using the concept of ward based NGO-run health posts, Tshwane District, Gauteng, began implementing community oriented primary care (COPC) through ward based outreach teams (WBOT) in seven wards during 2011. Objectives This study sought to gain insight into how primary health care providers understood and perceived the first phase of implementing COPC in the Tshwane district. Method Qualitative research was performed through focus group interviews with staff of the seven health posts during September 2011 and October 2011. It explored primary health care providers’ understanding, perception and experience of COPC. Results Participants raised organisational, workplace and community relationship issues in the discussions. Organisationally, these related to the process of initiating and setting up COPC and the relationship between governmental and nongovernmental organisations. Issues that arose around the workplace related to the job situation and employment status and remuneration of health post staff. Community related issues centred on the role and relationship between service providers and their communities. Conclusion COPC touched a responsive nerve in the health care system, both nationally and locally. It was seen as an effective way to respond to South Africa's crisis of health care. Initiating the reform was inevitably a complex process. In this initial phase of implementing COPC the political commitment of governmental and nongovernmental organisations was evident. What still had to be worked through was how the collaboration would materialise in practice on the ground.

  11. Three-dimensional solidification and melting using magnetic field control

    NASA Technical Reports Server (NTRS)

    Dulikravich, George S.; Ahuja, Vineet

    1993-01-01

    A new two-fluid mathematical model for fully three dimensional steady solidification under the influence of an arbitrary acceleration vector and with or without an arbitrary externally applied steady magnetic field have been formulated and integrated numerically. The model includes Joule heating and allows for separate temperature dependent physical properties within the melt and the solid. Latent heat of phase change during melting/solidification was incorporated using an enthalpy method. Mushy region was automatically captured by varying viscosity orders of magnitude between liquidus and solidus temperature. Computational results were obtained for silicon melt solidification in a parallelepiped container cooled from above and from a side. The results confirm that the magnetic field has a profound influence on the solidifying melt flow field thus changing convective heat transfer through the boundaries and the amount and shape of the solid accrued. This suggests that development of a quick-response algorithm for active control of three dimensional solidification is feasible since it would require low strength magnetic fields.

  12. Multi-crystalline silicon solidification under controlled forced convection

    NASA Astrophysics Data System (ADS)

    Cablea, M.; Zaidat, K.; Gagnoud, A.; Nouri, A.; Chichignoud, G.; Delannoy, Y.

    2015-05-01

    Multi-crystalline silicon wafers have a lower production cost compared to mono-crystalline wafers. This comes at the price of reduced quality in terms of electrical properties and as a result the solar cells made from such materials have a reduced efficiency. The presence of different impurities in the bulk material plays an important role during the solidification process. The impurities are related to different defects (dislocations, grain boundaries) encountered in multi-crystalline wafers. Applying an alternative magnetic field during the solidification process has various benefits. Impurities concentration in the final ingot could be reduced, especially metallic species, due to a convective term added in the liquid that reduces the concentration of impurities in the solute boundary layer. Another aspect is the solidification interface shape that is influenced by the electromagnetic stirring. A vertical Bridgman type furnace was used in order to study the solidification process of Si under the influence of a travelling magnetic field able to induce a convective flow in the liquid. The furnace was equipped with a Bitter type three-phase electromagnet that provides the required magnetic field. A numerical model of the furnace was developed in ANSYS Fluent commercial software. This paper presents experimental and numerical results of this approach, where interface markings were performed.

  13. Characterization of Rapidly Solidified Al-27 Si Hypereutectic Alloy: Effect of Solidification Condition

    NASA Astrophysics Data System (ADS)

    Cai, Zhiyong; Wang, Richu; Zhang, Chun; Peng, Chaoqun; Xie, Lichuan; Wang, Linqian

    2015-03-01

    Rapidly solidified Al-27wt.%Si hypereutectic alloy was fabricated by gas atomization, and its characterization as a function of particle size was investigated. A relationship between the particle size and solidification condition was established to understand the microstructural characteristics. While the irregular primary Si phase transformed to quasi-spherical shape, and its size decreased gradually with the particle size, the primary Si morphology similar to that in ingot metallurgy sample was found from the deep-etched images. In the fine powder, the eutectic Si phase formed a network structure densely distributed in the matrix, while a tangled dendritic formed at the surface. From the distribution of the Si phase, it is suggested that the microstructure inhomogeneity increased as the particle size decreases. The structural distortion of the Al matrix was observed from x-ray diffraction patterns and differential scanning calorimetry curves. From the calculated results, an undercooling of 33 K (or interface velocity of 8 mm/s) was sufficient to suppress the primary Si to less than 2 μm in the present composition. The microhardness increased significantly while the particle size decreases. The microstructure and properties of the bulk material consolidated by hot pressing of the powders obtained were also conducted.

  14. An analytical model for solute redistribution during solidification of planar, columnar, or equiaxed morphology

    NASA Astrophysics Data System (ADS)

    Nastac, L.; Stefanescu, D. M.

    1993-09-01

    Existing models for solute redistribution (microsegregation) during solidification were reviewed. There are no analytical models that take into account limited diffusion in both the liquid and the solid phases. A new analytical mathematical model for solute redistribution was developed. Diffusion in liquid and in solid was considered. This model does not require a prescribed movement of the interface. It can be used for one-dimensional (1-D) (plate), two-dimensional (cylinder), or three-dimensional (3-D) (sphere) calculations. Thus, it is possible to calculate microsegregation at the level of primary or secondary arm spacing for columnar dendrites or for equiaxed dendrites. The solution was compared with calculations based on existing models, as well as with some available experimental data for the segregation of base elements in as cast Al-4. 9 wt pct Cu, INCONEL 718, 625, and plain carbon (0. 13 wt pct C) steel.

  15. Nucleation and solidification in static arrays of monodisperse drops.

    PubMed

    Edd, Jon F; Humphry, Katherine J; Irimia, Daniel; Weitz, David A; Toner, Mehmet

    2009-07-01

    The precise measurement of nucleation and non-equilibrium solidification are vital to fields as diverse as atmospheric science, food processing, cryopreservation and metallurgy. The emulsion technique, where the phase under study is partitioned into many droplets suspended within an immiscible continuous phase, is a powerful method for uncovering rates of nucleation and dynamics of phase changes as it isolates nucleation events to single droplets. However, averaging the behavior of many drops in a bulk emulsion leads to the loss of any drop-specific information, and drop polydispersity clouds the analysis. Here we adapt a microfluidic technique for trapping monodisperse drops in planar arrays to characterize solidification of highly supercooled aqueous solutions of glycerol. This system measured rates of nucleation between 10(-5) and 10(-2) pL(-1) s(-1), yielded an ice-water interfacial energy of 33.4 mJ m(-2) between -38 and -35 degrees C, and enabled the specific dynamics of solidification to be observed for over a hundred drops in parallel without any loss of specificity. In addition to the physical insights gained, the ability to observe the time and temperature of nucleation and subsequent growth of the solid phase in static arrays of uniform drops provides a powerful tool to discover thermodynamic protocols that generate desirable crystal structures.

  16. Spatial phase sensitivity of complex cells in primary visual cortex depends on stimulus contrast.

    PubMed

    Meffin, H; Hietanen, M A; Cloherty, S L; Ibbotson, M R

    2015-12-01

    Neurons in primary visual cortex are classified as simple, which are phase sensitive, or complex, which are significantly less phase sensitive. Previously, we have used drifting gratings to show that the phase sensitivity of complex cells increases at low contrast and after contrast adaptation while that of simple cells remains the same at all contrasts (Cloherty SL, Ibbotson MR. J Neurophysiol 113: 434-444, 2015; Crowder NA, van Kleef J, Dreher B, Ibbotson MR. J Neurophysiol 98: 1155-1166, 2007; van Kleef JP, Cloherty SL, Ibbotson MR. J Physiol 588: 3457-3470, 2010). However, drifting gratings confound the influence of spatial and temporal summation, so here we have stimulated complex cells with gratings that are spatially stationary but continuously reverse the polarity of the contrast over time (contrast-reversing gratings). By varying the spatial phase and contrast of the gratings we aimed to establish whether the contrast-dependent phase sensitivity of complex cells results from changes in spatial or temporal processing or both. We found that most of the increase in phase sensitivity at low contrasts could be attributed to changes in the spatial phase sensitivities of complex cells. However, at low contrasts the complex cells did not develop the spatiotemporal response characteristics of simple cells, in which paired response peaks occur 180° out of phase in time and space. Complex cells that increased their spatial phase sensitivity at low contrasts were significantly overrepresented in the supragranular layers of cortex. We conclude that complex cells in supragranular layers of cat cortex have dynamic spatial summation properties and that the mechanisms underlying complex cell receptive fields differ between cortical layers.

  17. Structures Self-Assembled Through Directional Solidification

    NASA Technical Reports Server (NTRS)

    Dynys, Frederick W.; Sayir, Ali

    2005-01-01

    Nanotechnology has created a demand for new fabrication methods with an emphasis on simple, low-cost techniques. Directional solidification of eutectics (DSE) is an unconventional approach in comparison to low-temperature biomimetic approaches. A technical challenge for DSE is producing microstructural architectures on the nanometer scale. In both processes, the driving force is the minimization of Gibb's free energy. Selfassembly by biomimetic approaches depends on weak interaction forces between organic molecules to define the architectural structure. The architectural structure for solidification depends on strong chemical bonding between atoms. Constituents partition into atomic-level arrangements at the liquid-solid interface to form polyphase structures, and this atomic-level arrangement at the liquid-solid interface is controlled by atomic diffusion and total undercooling due to composition (diffusion), kinetics, and curvature of the boundary phases. Judicious selection of the materials system and control of the total undercooling are the keys to producing structures on the nanometer scale. The silicon-titanium silicide (Si-TiSi2) eutectic forms a rod structure under isothermal cooling conditions. At the NASA Glenn Research Center, directional solidification was employed along with a thermal gradient to promote uniform rods oriented with the thermal gradient. The preceding photomicrograph shows the typical transverse microstructure of a solidified Si-TiSi2 eutectic composition. The dark and light gray regions are Si and TiSi2, respectively. Preferred rod orientation along the thermal gradient was poor. The ordered TiSi2 rods have a narrow distribution in diameter of 2 to 3 m, as shown. The rod diameter showed a weak dependence on process conditions. Anisotropic etch behavior between different phases provides the opportunity to fabricate structures with high aspect ratios. The photomicrographs show the resulting microstructure after a wet chemical etch and a

  18. Feedback control of unstable cellular solidification fronts.

    PubMed

    Pons, A J; Karma, A; Akamatsu, S; Newey, M; Pomerance, A; Singer, H; Losert, W

    2007-02-01

    We present a feedback control scheme to stabilize unstable cellular patterns during the directional solidification of a binary alloy. The scheme is based on local heating of cell tips which protrude ahead of the mean position of all tips in the array. The feasibility of this scheme is demonstrated using phase-field simulations and, experimentally, using a real-time image processing algorithm, to track cell tips, coupled with a movable laser spot array device to heat the tips locally. We demonstrate, both numerically and experimentally, that spacings well below the threshold for a period-doubling instability can be stabilized. As predicted by the numerical calculations, cellular arrays become stable with uniform spacing through the feedback control which is maintained with minimal heating.

  19. Segregation effects during solidification in weightless melts

    NASA Technical Reports Server (NTRS)

    Li, C.

    1973-01-01

    Two types of melt segregation effects were studied: (1) evaporative segregation, or segregation due to surface evaporation; and (2) freezing segregation, or segregation due to liquid-solid phase transformation. These segregation effects are closely related. In fact, evaporative segregation always precedes freezing segregation to some degree and must often be studied prior to performing meaningful solidification experiments. This is particularly true since evaporation may cause the melt composition, at least at the critical surface regions or layers to be affected manyfold within seconds so that the surface region or layer melting point and other thermophysical properties, nucleation characteristics, base for undercooling, and critical velocity to avoid constitutional supercooling, may be completely unexpected. An important objective was, therefore, to develop the necessary normal evaporation equations for predicting the compositional changes within specified times at temperature and to correlate these equations with actual experimental data collected from the literature.

  20. Directional solidification with heat losses

    NASA Technical Reports Server (NTRS)

    Brattkus, K.; Davis, S. H.

    1988-01-01

    The upward directional solidification of a dilute binary alloy in a tall, thin, two-dimensional slot is considered. Heat losses from the sidewalls produce curved isotherms, interface deformations, and melt convection. An asymptotic approach is used which relates the small heat loss to the thinness of the solidification cell, and solutions are obtained for the resulting melt convection, interface deflection, and the distribution of heat and solute. The model is compared to the numerical results of Chang and Brown (1983) which exclude the effects of solute buoyancy and thermodynamic equilibrium at the interface. The radial segregation at the interface (consistent with both interface shapes and temperature fields) is computed, and it is found that the radial segregation is independent of interfacial shapes; the radial segregation cannot be calculated from only a knowledge of the interface shape.

  1. Methadone induction in primary care (ANRS-Methaville): a phase III randomized intervention trial

    PubMed Central

    2012-01-01

    Background In France, the rapid scale-up of buprenorphine, an opioid maintenance treatment (OMT), in primary care for drug users has led to an impressive reduction in HIV prevalence among injecting drug users (IDU) but has had no major effect on Hepatitis C incidence. To date, patients willing to start methadone can only do so in a methadone clinic (a medical centre for drug and alcohol dependence (CSAPA) or a hospital setting) and are referred to primary care physicians after dose stabilization. This study aims to assess the effectiveness of methadone in patients who initiated treatment in primary care compared with those who initiated it in a CSAPA, by measuring abstinence from street opioid use after one year of treatment. Methods/Design The ANRS-Methaville study is a randomized multicenter non-inferiority control trial comparing methadone induction (lasting approximately 2 weeks) in primary care and in CSAPA. The model of care chosen for methadone induction in primary care was based on study-specific pre-training of all physicians, exclusion criteria and daily supervision of methadone during the initiation phase. Between January 2009 and January 2011, 10 sites each having one CSAPA and several primary care physicians, were identified to recruit patients to be randomized into two groups, one starting methadone in primary care (n = 147), the other in CSAPA (n = 48). The primary outcome of the study is the proportion of participants abstinent from street opioids after 1 year of treatment i.e. non-inferiority of primary care model in terms of the proportion of patients not using street opioids compared with the proportion observed in those starting methadone in a CSAPA. Discussion The ANRS-Methaville study is the first in France to use an interventional trial to improve access to OMT for drug users. Once the non-inferiority results become available, the Ministry of Health and agency for the safety of health products may change the the New Drug Application

  2. Cellular monotectic model solidification

    NASA Technical Reports Server (NTRS)

    Kaukler, William F.

    1987-01-01

    Succinonitrile (sn) was purified to a superior level using a fractional recrystallization method. The melting point of the best twice recrystallized sn was not raised by following with double distillation. This was tested using differential scanning calorimetry. The peak shape on melting also proved that double distillation after double recrystallization did not improve the quality. Stability and phase diagrams for succinonitrile and glycerol are presented.

  3. Solidification at the High and Low Rate Extreme

    SciTech Connect

    Meco, Halim

    2004-12-19

    The microstructures formed upon solidification are strongly influenced by the imposed growth rates on an alloy system. Depending on the characteristics of the solidification process, a wide range of growth rates is accessible. The prevailing solidification mechanisms, and thus the final microstructure of the alloy, are governed by these imposed growth rates. At the high rate extreme, for instance, one can have access to novel microstructures that are unattainable at low growth rates. While the low growth rates can be utilized for the study of the intrinsic growth behavior of a certain phase growing from the melt. Although the length scales associated with certain processes, such as capillarity, and the diffusion of heat and solute, are different at low and high rate extremes, the phenomena that govern the selection of a certain microstructural length scale or a growth mode are the same. Consequently, one can analyze the solidification phenomena at both high and low rates by using the same governing principles. In this study, we examined the microstructural control at both low and high extremes. For the high rate extreme, the formation of crystalline products and factors that control the microstructure during rapid solidification by free-jet melt spinning are examined in Fe-Si-B system. Particular attention was given to the behavior of the melt pool at different quench-wheel speeds. Since the solidification process takes place within the melt-pool that forms on the rotating quench-wheel, we examined the influence of melt-pool dynamics on nucleation and growth of crystalline solidification products and glass formation. High-speed imaging of the melt-pool, analysis of ribbon microstructure, and measurement of ribbon geometry and surface character all indicate upper and lower limits for melt-spinning rates for which nucleation can be avoided, and fully amorphous ribbons can be achieved. Comparison of the relevant time scales reveals that surface-controlled melt

  4. Shifts of Gamma Phase across Primary Visual Cortical Sites Reflect Dynamic Stimulus-Modulated Information Transfer

    PubMed Central

    Besserve, Michel; Lowe, Scott C.; Logothetis, Nikos K.; Schölkopf, Bernhard; Panzeri, Stefano

    2015-01-01

    Distributed neural processing likely entails the capability of networks to reconfigure dynamically the directionality and strength of their functional connections. Yet, the neural mechanisms that may allow such dynamic routing of the information flow are not yet fully understood. We investigated the role of gamma band (50–80 Hz) oscillations in transient modulations of communication among neural populations by using measures of direction-specific causal information transfer. We found that the local phase of gamma-band rhythmic activity exerted a stimulus-modulated and spatially-asymmetric directed effect on the firing rate of spatially separated populations within the primary visual cortex. The relationships between gamma phases at different sites (phase shifts) could be described as a stimulus-modulated gamma-band wave propagating along the spatial directions with the largest information transfer. We observed transient stimulus-related changes in the spatial configuration of phases (compatible with changes in direction of gamma wave propagation) accompanied by a relative increase of the amount of information flowing along the instantaneous direction of the gamma wave. These effects were specific to the gamma-band and suggest that the time-varying relationships between gamma phases at different locations mark, and possibly causally mediate, the dynamic reconfiguration of functional connections. PMID:26394205

  5. A multiphase solute diffusion model for dendritic alloy solidification

    SciTech Connect

    Wang, C.Y.; Beckermann, C.

    1993-12-01

    A solute diffusion model, aimed at predicting microstructure formation in metal castings, is proposed for dendritic solidification of alloys. The model accounts for the different length scales existing in a dendritic structure. This is accomplished by utilizing a multiphase approach, in which not only the various physical phases but also phases associated with different length scales are considered separately. The macroscopic conservation equations are derived for each phase using the volume averaging technique, with constitutive relations developed for the interfacial transfer terms. It is shown that the multiphase model can rigorously incorporate the growth of dendrite tips and coarsening of dendrite arms. In addition, the distinction of different length scales enables the inclusion of realistic descriptions of the dendrite topology and relations to key metallurgical parameters. Another novel aspect of the model is that a single set of conservation equations for solute diffusion is developed for both equiaxed and columnar dendritic solidification. Finally, illustrative calculations for equiaxed, columnar, and mixed columnar-equiaxed solidification are carried out to provide quantitative comparisons with previous studies, and a variety of fundamental phenomena such as recalescence, dendrite tip undercooling, and columnar-to-equiaxed transition (CET) are predicted.

  6. Fluid mechanics of directional solidification at reduced gravity

    NASA Technical Reports Server (NTRS)

    Chen, C. F.

    1992-01-01

    The primary objective of the proposed research is to provide additional groundbased support for the flight experiment 'Casting and Solidification Technology' (CAST). This experiment is to be performed in the International Microgravity Laboratory-1 (IML-1) scheduled to be flown on a space shuttle mission scheduled for 1992. In particular, we will provide data on the convective motion and freckle formation during directional solidification of NH4Cl from its aqueous solution at simulated parameter ranges equivalent to reducing the gravity from the sea-level value down to 0.1 g or lower. The secondary objectives of the proposed research are to examine the stability phenomena associated with the onset of freckles and the mechanisms for their subsequent growth and decline (to eventual demise of some) by state-of-the-art imaging techniques and to formulate mathematical models for the prediction of the observed phenomena.

  7. Flight Planning for the International Space Station-Levitation Observation of Dendrite Evolution in Steel Ternary Alloy Rapid Solidification

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Matson, D. M.; Loser, W.; Hyers, R. W.; Rogers, J. R.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The paper is an overview of the status and science for the LODESTARS research project. The program is aimed at understanding how melt convection influences phase selection and the evolution of rapid solidification microstructures

  8. Laboratory micro- and nanoscale X-ray tomographic investigation of Al–7 at.%Cu solidification structures

    SciTech Connect

    Patterson, B.M. Henderson, K.C.; Gibbs, P.J.; Imhoff, S.D.; Clarke, A.J.

    2014-09-15

    X-ray computed tomography across multiple length scales provides an opportunity to non-destructively visualize and quantify the micro- to nano-scale microstructural features of solidification structures in three dimensions. Aluminum–7 at.%copper samples were directionally solidified at three cooling rates (0.44, 0.67, and 1.33 °C/s), resulting in systematic changes in the as-solidified microstructure, which are difficult to quantify using traditional microscopic techniques. The cooling rate of a material affects its ultimate microstructure, and characterizing that microstructure is key to predicting and understanding its bulk properties. Here, two different laboratory X-ray computed tomography instruments were used to characterize as-solidified microstructures, including micro-scale computed tomography with approximately 1 mm field-of-view, ∼ 1.7 μm resolution, and nano-scale X-ray computed tomography ∼ 65 μm FOV, 150 nm resolution. Micro-scale X-ray radiography and computed tomography enabled a quantitative investigation of changes in the primary dendritic solidification structure with increasing cooling rate. Nano-scale absorption contrast X-ray computed tomography resolved the distinct phases of the lamellar eutectic structure and three dimensional measurements of the ∼ 1 μm interlamellar spacing. It is found that the lamella eutectic structure thickness is inversely proportional to the cooling rate. Nano-scale Zernike phase contrast was also used to image voids at eutectic colony boundaries. The application and resolution of these two instruments are discussed with respect to the resolvable features of the solidification structures. - Highlights: • Al–Cu eutectic is a model system for studying solidification microstructure. • X-ray computed tomography provides a 3D picture of these complex structures. • Micro-scale tomography images the primary and secondary dendritic structures. • Nano-scale tomography images the eutectic lamella and

  9. Nanoparticle Capture During Directional Solidification of Nano-Sized SiC Particle-Reinforced AZ91D Composites.

    PubMed

    Zhu, Qiaobo; Liu, Hongchang; Li, Wenzhen; Gao, Weiming; Li, Qiushu

    2015-05-01

    The capture/push behavior of a particle in front of a solidification interface was analyzed theoretically and experimentally in this work. Van der Waals force, viscous force, and force due to interfacial energy played important roles in the particle capture/push process. Directional solidification experiments were conducted with nano-sized SiC particle-reinforced AZ91D composites to observe the distribution of nanoparticles in different solidification morphologies under varied cooling rates. When the composite solidified with plane manner, the nanoparticles could be captured by the solidification front and distributed uniformly in the matrix. When solidified with columnar or equiaxial manners, the nanoparticles could be captured by the solidification front but distributed uniformly only in the grain boundary as a result of the difference in interfacial energy and wettability between SiC/α-Mg and SiC/eutectic phase. Theoretical prediction of particle capture was in agreement with the experiment results.

  10. Nanoparticle Capture During Directional Solidification of Nano-Sized SiC Particle-Reinforced AZ91D Composites.

    PubMed

    Zhu, Qiaobo; Liu, Hongchang; Li, Wenzhen; Gao, Weiming; Li, Qiushu

    2015-05-01

    The capture/push behavior of a particle in front of a solidification interface was analyzed theoretically and experimentally in this work. Van der Waals force, viscous force, and force due to interfacial energy played important roles in the particle capture/push process. Directional solidification experiments were conducted with nano-sized SiC particle-reinforced AZ91D composites to observe the distribution of nanoparticles in different solidification morphologies under varied cooling rates. When the composite solidified with plane manner, the nanoparticles could be captured by the solidification front and distributed uniformly in the matrix. When solidified with columnar or equiaxial manners, the nanoparticles could be captured by the solidification front but distributed uniformly only in the grain boundary as a result of the difference in interfacial energy and wettability between SiC/α-Mg and SiC/eutectic phase. Theoretical prediction of particle capture was in agreement with the experiment results. PMID:26505023

  11. Experimental determination of systems suitable for study as monotectic binary metallic alloy solidification models

    NASA Technical Reports Server (NTRS)

    Smith, J. E., Jr.

    1985-01-01

    Transparent binary metallic alloy solidification models are important in attempts to understand the processes causing liquid-liquid and solid-liquid phase transformations in metallic alloy systems. These models permit visual observation of the phase transformation and the processes proceding solidification. The number of these transparent monotectic binary models needs to be expanded to distinguish between the unique and general phenomena observed. The expansion of the number of accurately determined monotectic phase diagrams of model systems, and contribution to a data base for eventual use with UNIFAC group contribution methods is examined.

  12. Microstructure Evolution and Rapid Solidification Behavior of Blended Nickel-Based Superalloy Powders Fabricated by Laser Powder Deposition

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Gauvin, R.; Brochu, M.

    2016-07-01

    Laser powder deposition was performed on a substrate of Inconel 738 using blended powders of Mar M247 and Amdry DF3 with a ratio of 4:1 for repairing purposes. In the as-deposited condition, continuous secondary phases composed of γ-Ni3B eutectics and discrete (Cr, W)B borides were observed in inter-dendritic regions, and time-dependent nucleation simulation results confirmed that (Cr, W)B was the primary secondary phase formed during rapid solidification. Supersaturated solid solution of B was detected in the γ solid solution dendritic cores. The Kurz-Giovanola-Trivedi model was performed to predict the interfacial morphology and correlate the solidification front velocity (SFV) with dendrite tip radius. It was observed from high-resolution scanning electron microscopy that the dendrite tip radius of the upper region was in the range of 15 to 30 nm, which yielded a SFV of approx 30 cm/s. The continuous growth model for solute trapping behavior developed by Aziz and Kaplan was used to determine that the effective partition coefficient of B was approximately 0.025. Finally, the feasibility of the modeling results were rationalized with the Clyne-Kurz segregation simulation of B, where Clyne-Kurz prediction using a partition coefficient of 0.025 was in good agreement with the electron probe microanalysis results.

  13. Recent advances, trends and new perspectives via enthalpy-based finite element formulations for applications to solidification problems

    NASA Technical Reports Server (NTRS)

    Tamma, Kumar K.; Namburu, Raju R.

    1990-01-01

    The present paper describes recent advances and trends in finite element developments and applications for solidification problems. In particular, in comparison to traditional methods of approach, new enthalpy-based architectures based on a generalized trapezoidal family of representations are presented which provide different perspectives, physical interpretation and solution architectures for effective numerical simulation of phase change processes encountered in solidification problems. Various numerical test models are presented and the results support the proposition for employing such formulations for general phase change applications.

  14. Study on solidification of immisible alloys (M-10)

    NASA Technical Reports Server (NTRS)

    Kamio, Akihiko

    1993-01-01

    Alloying of immiscible alloys under microgravity is of interest in metallurgical processes. Several experiments investigating the alloying of immiscible alloys, such as Al-In, Al-Bi, Zn-Bi, and Zn-Pb, were done in space. Homogeneous distribution of small L2 particles in the matrix, such as an emulsion structure, was expected in the space-solidifed alloys. However, the alloys demonstrated an extremely segregated structure. To date insufficient information was obtained to explain these unexpected results. Our experiment was proposed to clarify the solidification manner of immiscible alloys and to obtain fundamental information concerning structural control of the alloys. In space, density differences between the two liquids separated in immiscible regions can be neglected, so that no sedimentation of L(sub 2) phase will take place. When the growth of the alloys is interrupted and this status is frozen by an adequate rapid cooling procedure, it will provide much information concerning decomposing homogeneous liquid and the interaction between the monotectic growth front morphology and the distribution of L(sub 2) phase. It is anticipated that the results will be useful for elucidating the monotectic solidification manner and it will be instructive to explain the segregated structures obtained in the past space experiments.

  15. Unidirectional solidification of Zn-rich Zn-Cu peritectic alloys -- 2. Microstructural length scales

    SciTech Connect

    Ma, D.; Li, Y.; Ng, S.C.; Jones, H.

    2000-05-11

    Experimental results are presented of solidification microstructure length scale including {eta}-phase cell spacing, primary {epsilon} secondary dendrite arm spacing, size of nonaligned dendrite of primary {epsilon}, and volume fraction of primary {epsilon}, as functions of alloy concentration (containing up to 7.37 wt% Cu) and growth velocity (ranging from 0.02 to 4.82 mm/s) in the unidirectional solidification of Zn-rich Zn-Cu peritectic alloys. Intercellular spacing ({lambda}) of two-phase cellular structure decreases with increasing growth velocity (V) such that {lambda}V{sup 1/2} is constant at a fixed alloy concentration in parametric agreement with the KGT and Hunt-Lu models. The value of {lambda}V{sup 1/2} varies from 216 {+-} 10 to 316 {+-} 55 {micro}m{sup 3/2}/s{sup 1/2} with decrease in alloy concentration from 4.94 to 2.17 wt% Cu. These values are much greater than for normal eutectic systems but comparable with monotectic alloys. Dendritic secondary arm spacing ({lambda}{sub 2}) of primary {epsilon} decreases with increasing V such that {lambda}{sub 2}V{sup 1/3} is constant ranging 14.9 {+-} 0.9 to 75.6 {+-} 8.1 {micro}m{sup 4/3}/s{sup 1/3} with increase in alloy concentration (C{sub 0}) from 2.17 to 7.37 wt% Cu, which is in parametric agreement with predictions of arm-coarsening theory. The volume fraction (f{sub e}) of primary {epsilon} increases with increasing V for Zn-rich Zn-3.37, 4.94 and 7.37 wt% Cu hyperperitectic alloys. Predictions of the Scheil and Sarreal-Abbaschian models show good agreement with the observed f{sub {epsilon}} for Zn-4.94 wt% Cu at moderate V from 0.19 to 2.64 mm/s, but fail at low V of less than 0.16 mm/s and at high V of greater than 3.54 mm/s. The measured average size, {Lambda}V{sup 1/2} is constant for a given alloy, increasing from (0.98 {+-} 0.04) x 10{sup 3} to (7.2 {+-} 0.7) x 10{sup 3} {micro}m{sup 3/2}/s{sup 1/2} with increase in alloy concentration from 2.17 to 4.94 wt% Cu.

  16. Optimal design of solidification processes

    NASA Technical Reports Server (NTRS)

    Dantzig, Jonathan A.; Tortorelli, Daniel A.

    1991-01-01

    An optimal design algorithm is presented for the analysis of general solidification processes, and is demonstrated for the growth of GaAs crystals in a Bridgman furnace. The system is optimal in the sense that the prespecified temperature distribution in the solidifying materials is obtained to maximize product quality. The optimization uses traditional numerical programming techniques which require the evaluation of cost and constraint functions and their sensitivities. The finite element method is incorporated to analyze the crystal solidification problem, evaluate the cost and constraint functions, and compute the sensitivities. These techniques are demonstrated in the crystal growth application by determining an optimal furnace wall temperature distribution to obtain the desired temperature profile in the crystal, and hence to maximize the crystal's quality. Several numerical optimization algorithms are studied to determine the proper convergence criteria, effective 1-D search strategies, appropriate forms of the cost and constraint functions, etc. In particular, we incorporate the conjugate gradient and quasi-Newton methods for unconstrained problems. The efficiency and effectiveness of each algorithm is presented in the example problem.

  17. Correlative characterization of primary Al{sub 3}(Sc,Zr) phase in an Al–Zn–Mg based alloy

    SciTech Connect

    Li, J.H.; Wiessner, M.; Albu, M.; Wurster, S.; Sartory, B.; Hofer, F.; Schumacher, P.

    2015-04-15

    Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al{sub 3}(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al{sub 3}(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al{sub 3}(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al{sub 3}(Sc,Zr) phases. Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al{sub 3}(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al{sub 3}(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al{sub 3}(Sc,Zr) particle enhances the heterogeneous nucleation of Al{sub 3}(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al{sub 3}(Sc,Zr) phases were observed within the α-Al matrix. • A layer by layer growth within primary Al{sub 3}(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al{sub 3}(Sc,Zr)

  18. Microstructure and solidification behavior of Ni-Mn-Ga magnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Gharghouri, Michael A.; Hyatt, Calvin V.

    2004-07-01

    In order to understand the solidification behavior of Ni-Mn-Ga alloys, ingots with different compositions were prepared by arc melting. Two series of compositions were investigated: Ni100-2xMnxGax (15<=x <=30) and Ni50Mn50-yGay (0<=y<=50). The microstructures obtained were observed and the compositions of the phases occurring in the ingots were identified by energy dispersive spectroscopy in the scanning electron microscope. Based on these observations, three solidification paths were identified: direct solidification of γ-Ni from the liquid, direct solidification of β-NiMnGa from the liquid, and solidification of β-NiMnGa phase via a peritectic reaction. It was found that the γ-Ni liquidus surface covers a large area of the ternary phase diagram. The γ-Ni liquidus boundary is located between Ni50Mn25Ga25 and Ni45Mn27.5Ga27.5 in the equal Mn and Ga alloy series, and between Ni50Mn5Ga45 and Ni50Mn10Ga40 in the 50 at.% Ni alloy series. The alloys with compositions close to the stoichiometric Ni2MnGa composition that show the magnetic shape memory effect are all covered by the γ-Ni liquidus surface. The β-NiMnGa liquidus surface covers the remaining alloy compositions.

  19. Primary ciliary dyskinesia assessment by means of optical flow analysis of phase-contrast microscopy images.

    PubMed

    Parrilla, Eduardo; Armengot, Miguel; Mata, Manuel; Sánchez-Vílchez, José Manuel; Cortijo, Julio; Hueso, José L; Riera, Jaime; Moratal, David

    2014-04-01

    Primary ciliary dyskinesia implies cilia with defective or total absence of motility, which may result in sinusitis, chronic bronchitis, bronchiectasis and male infertility. Diagnosis can be difficult and is based on an abnormal ciliary beat frequency (CBF) and beat pattern. In this paper, we present a method to determine CBF of isolated cells through the analysis of phase-contrast microscopy images, estimating cilia motion by means of an optical flow algorithm. After having analyzed 28 image sequences (14 with a normal beat pattern and 14 with a dyskinetic pattern), the normal group presented a CBF of 5.2 ± 1.6 Hz, while the dyskinetic patients presented a 1.9 ± 0.9 Hz CBF. The cutoff value to classify a dyskinetic specimen was set to 3.45 Hz (sensitivity 0.86, specificity 0.93). The presented methodology has provided excellent results to objectively diagnose PCD. PMID:24438822

  20. Refractory Boride Formation and Microstructure Evolution during Solidification of Titanium-Boron and Titanium Aluminum-Boron Alloys

    NASA Astrophysics Data System (ADS)

    Hyman, Mark Edward

    1990-01-01

    gamma-TiAl alloys targeted for use as a structural material in advanced aerospace applications lack adequate creep strength at high temperatures. Incorporation of hard refractory second phase particles (e.g. TiB _2) exhibiting large aspect ratios (i.e. needles) can increase creep strength by constraining the plastic flow of the matrix during high temperature service. Matrix microstructure evolution and refractory boride formation in binary Ti-B and Ti-(25-52) at% Al and <= ~ 6 at% B alloys during conventional solidification is examined. The effects of rapid solidification processing (RSP) on microstructure evolution and boride morphology in ternary alloys is examined in electromagnetically levitated droplets processed via gas and splat quenching. A liquidus projection near the Ti-Al edge binary is deduced from a combination of computer modelling efforts and experimental evidence. The primary fields of crystallization sequentially traversed with increasing Al content starting from the Ti-B edge binary are: TiB to Ti_3B_4 to TiB_2 and beta to alpha to gamma for B-rich (i.e. ~5 at% B) and dilute alloys, respectively. A monovariant line of the type, L to M + TiB_2 (where M = beta, alpha , and gamma) was found to run slightly below the ~1 at% B isoconcentration line near the equiatomic TiAl composition. Matrix microstructure evolution and boride formation in these ternary alloys can be explained using the proposed liquidus projection for the Ti-Al-B system. TiB_2 forms in Ti-Al-B alloys (i.e. >= 35 at% Al) with various morphologies--blocky, plate/needle and flakes--and are extensively characterized by TEM and SEM. Their growth mechanisms leading to their various morphologies is discussed. Aside from the boride phases formed, the solidification microstructures of the Ti-Al -B alloys of interest showed essentially the same constituent phases as those of binary Ti-Al alloys of similar composition. Characterization of supercooled ternary droplets dilute in B (i.e. <=1 at% B

  1. Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties

    PubMed Central

    2011-01-01

    Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure. PMID:27502650

  2. Volume phase holographic grating used for beams combination of RGB primary colors

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Zhang, Xizhao; Tang, Minxue

    2013-12-01

    Volume phase holographic grating (VPHG) has the characteristics of high diffraction efficiency, high signal to noise ratio, high wavelength and angular selectivity, low scattering , low absorption and low cost. It has been widely used in high resolution spectrometer, wavelength division multiplexing and pulse compression technique. In this paper, a novel kind of RGB primary colors beams combiner which is consisted of a transmission VPHG and a reflection VPHG as core components is proposed. The design idea of the element is described in detail. Based on the principle of VPHG, the rigorous coupled wave analysis (RCWA) and Kogelnik's coupled wave theory, diffraction properties of the transmission and reflection VPHG are studied theoretically. As an example, three primary colors at wavelengths of 632.8nm, 532nm and 476.5nm are taken into account. Dichromated gelatin (DCG) is used as the holographic recording material. The grating parameters are determined by the Bragg conditions. The TE and TM wave diffraction efficiency, the wavelength selectivity and the angular selectivity of the transmission and reflection VPHG are calculated and optimized by setting the amplitude of the index modulation (Δn) and the thickness of the gelatin layer (d) by applying Kogelnik's coupled wave theory and G-solver software, respectively. The theoretical calculating results give guidance for further manufacture of the element.

  3. Calibration artefacts in radio interferometry - III. Phase-only calibration and primary beam correction

    NASA Astrophysics Data System (ADS)

    Grobler, T. L.; Stewart, A. J.; Wijnholds, S. J.; Kenyon, J. S.; Smirnov, O. M.

    2016-09-01

    This is the third installment in a series of papers in which we investigate calibration artefacts. Calibration artefacts (also known as ghosts or spurious sources) are created when we calibrate with an incomplete model. In the first two papers of this series, we developed a mathematical framework which enabled us to study the ghosting mechanism itself. An interesting concomitant of the second paper was that ghosts appear in symmetrical pairs. This could possibly account for spurious symmetrization. Spurious symmetrization refers to the appearance of a spurious source (the antighost) symmetrically opposite an unmodelled source around a modelled source. The analysis in the first two papers indicates that the antighost is usually very faint, in particular, when a large number of antennas are used. This suggests that spurious symmetrization will mainly occur at an almost undetectable flux level. In this paper, we show that phase-only calibration produces an antighost that is N-times (where N denotes the number of antennas in the array) as bright as the one produced by phase and amplitude calibration and that this already bright ghost can be further amplified by the primary beam correction.

  4. Characterization on carbide of a novel steel for cold work roll during solidification process

    SciTech Connect

    Guo, J.; Liu, L.G.; Li, Q.; Sun, Y.L.; Gao, Y.K.; Ren, X.J.; Yang, Q.X.

    2013-05-15

    A novel steel for cold work roll was developed in this work. Its phase structures were determined by X-ray diffraction, and phase transformation temperatures during the cooling process were measured by Differential Scanning Calorimeter. The Fe–C isopleths of the steel were calculated by Thermo-Calc to preliminarily determine the characteristic temperatures of the different phases. Then the specimens were quenched at these characteristic temperatures. The typical microstructures were observed by Optical Microscopy and Field Emission Scanning Electron Microscopy with Energy Disperse Spectroscopy. The results show that α-Fe, MC, M{sub 2}C and M{sub 7}C{sub 3} precipitate when the specimen is cooled slowly to room temperature. According to the DSC curve and the Fe–C isopleths, the characteristic temperatures of the phase transformation and carbide precipitation are chosen as 1380 °C, 1240 °C, 1200 °C and 1150 °C respectively. Primary austenite precipitates at 1380 °C, then eutectic reaction occurs in residual liquid after quenching and the eutectic microstructures distribute along the crystal grain boundary. The eutectic MC is leaf-like and eutectic M{sub 2}C is fibrous-like. Both of them precipitate in ternary eutectic reaction simultaneously at 1240 °C, grow together in the form of dendrite along the crystal grain boundary. Secondary MC precipitates from the austenitic matrix at 1200 °C and nucleates at the position where eutectic MC located accompanied by the dissolving of eutectic carbides. The mixed secondary M{sub 2}C and M{sub 7}C{sub 3} precipitate at 1150 °C. The secondary M{sub 2}C is strip-like and honeycomb-like, while the M{sub 7}C{sub 3} is chrysanthemum-like and maze-like. - Highlights: • The solidification process was analyzed by Thermo-Calc, DSC, XRD and SEM observation. • Primary and secondary carbides precipitated during solidification were determined. • The three dimensional morphologies of all carbides was observed. • The

  5. Properties and solidification of decontamination wastes

    SciTech Connect

    Davis, M.S.; Piciulo, P.L.; Bowerman, B.S.; Adams, J.W.; Milian, L.

    1983-01-01

    LWRs will require one or more chemical decontaminations to achieve their designed lifetimes. Primary system decontamination is designed to lower radiation fields in areas where plant maintenance personnel must work. Chemical decontamination methods are either hard (concentrated chemicals, approximately 5 to 25 weight percent) or soft (dilute chemicals less than 1 percent by weight). These methods may have different chemical reagents, some tailor-made to the crud composition and many methods are and will be proprietary. One factor common to most commercially available processes is the presence of organic acids and chelates. These types of organic reagents are known to enhance the migration of radionuclides after disposal in a shallow land burial site. The NRC sponsors two programs at Brookhaven National Laboratory that are concerned with the management of decontamination wastes which will be generated by the full system decontamination of LWRs. These two programs focus on potential methods for degrading or converting decontamination wastes to more acceptable forms prior to disposal and the impact of disposing of solidified decontamination wastes. The results of the solidification of simulated decontamination resin wastes will be presented. Recent results on combustion of simulated decontamintion wastes will be described and procedures for evaluating the release of decontamination reagents from solidified wastes will be summarized.

  6. Double dendrite growth in solidification.

    PubMed

    Utter, Brian; Bodenschatz, E

    2005-07-01

    We present experiments on the doublon growth morphology in directional solidification. Samples used are succinonitrile with small amounts of poly(ethylene oxide), acetone, or camphor as the solute. Doublons, or symmetry-broken dendrites, are generic diffusion-limited growth structures expected at large undercooling and low anisotropy. Low anisotropy growth is achieved by selecting a grain near the {111} plane leading to either seaweed (dense branching morphology) or doublon growth depending on experimental parameters. We find selection of doublons to be strongly dependent on solute concentration and sample orientation. Doublons are selected at low concentrations (low solutal undercooling) in contrast to the prediction of doublons at large thermal undercooling in pure materials. Doublons also exhibit preferred growth directions and changing the orientation of a specific doublonic grain changes the character and stability of the doublons. We observe transitions between seaweed and doublon growth with changes in concentration and sample orientation.

  7. High gradient directional solidification furnace

    NASA Technical Reports Server (NTRS)

    Aldrich, B. R.; Whitt, W. D. (Inventor)

    1985-01-01

    A high gradient directional solidification furnace is disclosed which includes eight thermal zones throughout the length of the furnace. In the hot end of the furnace, furnace elements provide desired temperatures. These elements include Nichrome wire received in a grooved tube which is encapsulated y an outer alumina core. A booster heater is provided in the hot end of the furnace which includes toroidal tungsten/rhenium wire which has a capacity to put heat quickly into the furnace. An adiabatic zone is provided by an insulation barrier to separate the hot end of the furnace from the cold end. The old end of the furnace is defined by additional heating elements. A heat transfer plate provides a means by which heat may be extracted from the furnace and conducted away through liquid cooled jackets. By varying the input of heat via the booster heater and output of heat via the heat transfer plate, a desired thermal gradient profile may be provided.

  8. Transient Dendritic Solidification Experiment (TDSE)

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The Transient Dendritic Solidification Expepriment (TDSE) is being developed as a candidate for flight aboard the International Space Station. TDSE will study the growth of dendrites (treelike crystalline structures) in a transparent material (succinonitrile or SCN) that mimics the behavior of widely used iron-based metals. Basic work by three Space Shuttle missions of the Isothermal Dendritic Growth Expepriment (IDGE) is yielding new insights into virtually all industrially relevant metal and alloy forming operations. The TDSE is similar to IDGE, but will maintain a constant temperature while varying pressure on the dendrites. Shown here is an exploded view of major elements of TDSE. A similar view is available with labels. The principal investigator is Matthew Koss of College of the Holy Cross in Worcester, MA. Photo credit: NASA/Marshall Space Flight Center (MSFC)

  9. Transient Dendritic Solidification Experiment (TDSE)

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The Transient Dendritic Solidification Experiment (TDSE) is being developed as a candidate for flight aboard the International Space Station. TDSE will study the growth of dendrites (treelike crystalline structures) in a transparent material (succinonitrile or SCN) that mimics the behavior or widely used iron-based metals. Basic work by three Space Shuttle missions of the Isothermal Dendritic Growth Experiment (IDGE) is yielding new insights into virtually all industrially relevant metal and alloy forming operations. The TDSE is similar to IDGE, but will maintain a constant temperature while varying pressure on the dendrites. Shown here is an exploded view of major elements of the TDSE. A similar view is availble without labels. The principal investigator is Matthew Koss of College of the Holy Cross in Worcester, MA. Photo credit: NASA/Marshall Space Flight Center (MSFC)

  10. Dynamic stability of detached solidification

    NASA Astrophysics Data System (ADS)

    Mazuruk, K.; Volz, M. P.

    2016-06-01

    A dynamic stability analysis model is developed for meniscus-defined crystal growth processes. The Young-Laplace equation is used to analyze the response of a growing crystal to perturbations to its radius and a thermal transport model is used to analyze the effect of perturbations on the evolution of the crystal-melt interface. A linearized differential equation is used to analyze radius perturbations but a linear integro-differential equation is required for the height perturbations. The stability model is applied to detached solidification under zero-gravity and terrestrial conditions. A numerical analysis is supplemented with an approximate analytical analysis, valid in the limit of small Bond numbers. For terrestrial conditions, a singularity is found to exist in the capillary stability coefficients where, at a critical value of the pressure differential across the meniscus, there is a transition from stability to instability. For the zero-gravity condition, exact formulas for the capillary stability coefficients are derived.

  11. Dendritic Alloy Solidification Experiment (DASE)

    NASA Technical Reports Server (NTRS)

    Beckermann, C.; Karma, A.; Steinbach, I.; deGroh, H. C., III

    2001-01-01

    A space experiment, and supporting ground-based research, is proposed to study the microstructural evolution in free dendritic growth from a supercooled melt of the transparent model alloy succinonitrile-acetone (SCN-ACE). The research is relevant to equiaxed solidification of metal alloy castings. The microgravity experiment will establish a benchmark for testing of equiaxed dendritic growth theories, scaling laws, and models in the presence of purely diffusive, coupled heat and solute transport, without the complicating influences of melt convection. The specific objectives are to: determine the selection of the dendrite tip operating state, i.e. the growth velocity and tip radius, for free dendritic growth of succinonitrile-acetone alloys; determine the growth morphology and sidebranching behavior for freely grown alloy dendrites; determine the effects of the thermal/solutal interactions in the growth of an assemblage of equiaxed alloy crystals; determine the effects of melt convection on the free growth of alloy dendrites; measure the surface tension anisotropy strength of succinon itrile -acetone alloys establish a theoretical and modeling framework for the experiments. Microgravity experiments on equiaxed dendritic growth of alloy dendrites have not been performed in the past. The proposed experiment builds on the Isothermal Dendritic Growth Experiment (IDGE) of Glicksman and coworkers, which focused on the steady growth of a single crystal from pure supercooled melts (succinonitrile and pivalic acid). It also extends the Equiaxed Dendritic Solidification Experiment (EDSE) of the present investigators, which is concerned with the interactions and transients arising in the growth of an assemblage of equiaxed crystals (succinonitrile). However, these experiments with pure substances are not able to address the issues related to coupled heat and solute transport in growth of alloy dendrites.

  12. Microstructure analysis of Al-Si-Cu alloys prepared by gradient solidification technique

    NASA Astrophysics Data System (ADS)

    Borkar, Hemant; Seifeddine, Salem; Jarfors, Anders E. W.

    2015-03-01

    Al-Si-Cu alloys were cast with the unique gradient solidification technique to produce alloys with two cooling rates corresponding to secondary dendrite arm spacing (SDAS) of 9 and 27 μm covering the microstructural fineness of common die cast components. The microstructure was studied with optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscattered diffraction (EBSD). The alloy with higher cooling rate, lower SDAS, has a more homogeneous microstructure with well distributed network of eutectic and intermetallic phases. The results indicate the presence of Al-Fe-Si phases, Al-Cu phases and eutectic Si particles but their type, distribution and amount varies in the two alloys with different SDAS. EBSD analysis was also performed to study the crystallographic orientation relationships in the microstructure. One of the major highlights of this study is the understanding of the eutectic formation mechanism achieved by studying the orientation relationships of the aluminum in the eutectic to the surrounding primary aluminum dendrites.

  13. Inter-donor variability of phase I/phase II metabolism of three reference drugs in cryopreserved primary human hepatocytes in suspension and monolayer.

    PubMed

    den Braver-Sewradj, Shalenie P; den Braver, Michiel W; Vermeulen, Nico P E; Commandeur, Jan N M; Richert, Lysiane; Vos, J Chris

    2016-06-01

    Cytochrome P450s (CYPs), UDP-glucuronosyltransferases (UGTs) and sulfotransferases (SULTs) are the most important enzymes for metabolic clearance. Characterization of phase I and phase II metabolism of a given drug in cellular models is therefore important for an adequate interpretation of the role of drug metabolism in toxicity. We investigated phase I (CYP) and phase II (UGT and SULT) metabolism of three drugs related to drug-induced liver injury (DILI), namely acetaminophen (APAP), diclofenac (DF) and tolcapone (TC), in cryopreserved primary human hepatocytes from 5 donors in suspension and monolayer. The general phase II substrate 7-hydroxycoumarin (7-HC) was included for comparison. Our results show that the decrease in CYP, UGT and SULT activity after plating is substrate dependent. As a consequence the phase I/phase II metabolism ratio is significantly affected, with a shift in monolayer towards phase I metabolism for TC and towards phase II metabolism for APAP and DF. Inter-donor variability in drug metabolism is significant, especially in sulfation of 7-HC or APAP. As CYP, UGT and SULT metabolism may lead to bioactivation and/or detoxification of drugs, a changed ratio in phase I/phase II metabolism may have important consequences for metabolism-related toxicity. PMID:26921663

  14. Evolution of solidification texture during additive manufacturing.

    PubMed

    Wei, H L; Mazumder, J; DebRoy, T

    2015-01-01

    Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.

  15. Evolution of solidification texture during additive manufacturing

    DOE PAGESBeta

    Wei, H. L.; Mazumder, J.; DebRoy, T.

    2015-11-10

    Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Furthermore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numericalmore » modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.« less

  16. Microstructure of ceramics fabricated by unidirectional solidification

    NASA Technical Reports Server (NTRS)

    Kokubo, T.

    1984-01-01

    The unidirectional solidification methods are zone melting, crystal pulling, Bridgemen, and slow cooling. In order to obtain excellent properties (such as transparency), pores, voids and cracks must be avoided, and elimination of such defects is described.

  17. DEMONSTRATION BULLETIN - SOLIDIFICATION/ STABILIZATION PROCESS, SOLIDTECH, INC.

    EPA Science Inventory

    The Soliditech solidification/stabilization technology mixes hazardous waste materials in soils or sludges with pozzolanic material (cement, fly ash, or kiln dust), a proprietary additive called Urrichem, other proprietary additives, and water. The process is designed to aid ...

  18. Container evaluation for microwave solidification project

    SciTech Connect

    Smith, J.A.

    1994-08-01

    This document discusses the development and testing of a suitable waste container and packaging arrangement to be used with the Microwave Solidification System (MSS) and Bagless Posting System (BPS). The project involves the Rocky Flats Plant.

  19. Evolution of solidification texture during additive manufacturing

    PubMed Central

    Wei, H. L.; Mazumder, J.; DebRoy, T.

    2015-01-01

    Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components. PMID:26553246

  20. Evolution of solidification texture during additive manufacturing

    SciTech Connect

    Wei, H. L.; Mazumder, J.; DebRoy, T.

    2015-11-10

    Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Furthermore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.

  1. Advanced Automated Directional Solidification Furnace (AADSF)

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The Advanced Automated Directional Solidification Furnace (AADSF) with the Experimental Apparatus Container (EAC) attached flew during the USMP-2 mission. This assembly consists of a furnace module, a muffle tube assembly and a translation mechanism which are enclosed in the EAC. During USMP-2, the AADSF was used to study the growth of mercury cadmium telluride crystals in microgravity by directional solidification, a process commonly used on earth to process metals and grow crystals. The furnace is tubular and has three independently controlled temperature zone . The sample travels from the hot zone of the furnace (1600 degrees F) where the material solidifies as it cools. The solidification region, known as the solid/liquid interface, moves from one end of the sample to the other at a controlled rate, thus the term directional solidification.

  2. Onset of sidebranching in directional solidification.

    PubMed

    Echebarria, Blas; Karma, Alain; Gurevich, Sebastian

    2010-02-01

    We use a computationally efficient phase-field formulation [B. Echebarria, Phys. Rev. E 70, 061604 (2004)] to investigate the origin and dynamics of sidebranching in directional solidification for realistic parameters of a dilute alloy previously studied experimentally [M. Gorgelin and A. Pocheau, Phys. Rev. E 57, 3189 (1998)]. Sidebranching is found to result either from noise amplification or from deterministic oscillations that exist both in two dimensions and in a three-dimensional thin-sample geometry. The oscillatory branch of growth solutions bifurcates subcritically from the main steady-state branch of solutions and exists over a finite range of large array spacings. In contrast, noise-induced sidebranching is associated with a smooth transition where the sidebranching amplitude increases exponentially with spacing up to nonlinear saturation due to the overlap of diffusion fields from neighboring cells, as observed experimentally. In the latter case where sidebranching is noise-induced, we find that increasing the externally imposed thermal gradient reduces the onset velocity and wavelength of sidebranching, as also observed experimentally. We show that this counterintuitive effect is due to tip blunting with increasing thermal gradient that promotes noise amplification in the tip region.

  3. Minimizing Segregation during the Controlled Directional Solidification of Dendric Alloys

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Fedoseyev, Alex; Kim, Shin-Woo

    2003-01-01

    Gravity-driven convection induced in the liquid by density gradients of temperature or composition disrupts uniform dendritic growth during controlled directional solidification and promotes severe macrosegregation. The solute-rich region about the dendrite tip appears to play a pivotal role in channel initiation. Allen and Hunt referred to this region as an "initial transient" or dynamic region constituting steep concentration gradients. Experimental investigation also point to the role the tip region plays in developing microstructure. Hellawell and co-workers showed that flow-through dendritic channels could be effectively disrupted, and segregation minimized, during the gradient freezing of bulk castings by rotating the melt through a slight angle with respect to Earth's gravity vector. Adapting this principle to controlled directional solidification, it has been shown" that segregation in dendritic alloys can be minimized, and properties improved, by processing the sample near horizontal in conjunction with a slow axial rotation of the crucible. It is postulated that the observed microstructural uniformity arises by maintaining the developing solute field about the dendrite tip. Solute rejected during vertical directional solidification will rise or sink parallel to the primary dendrite arms during axial rotation setting the stage for accumulation, instabilities, and segregation. In contrast, during horizontal growth, the rejected solute will sink or rise perpendicular to the primary dendrite. Now, in the presence of a slight axial rotation, solute that was initially sinking (or rising) will find itself above (or below) its parent dendrite, i.e., still about the tip region. The following is intended to experimentally demonstrate the viability of this concept in coordination with a model that gives predictive insight regarding solute distribution about growing dendrites. Alloys based on the lead-tin eutectic system were used in this study. The system is well

  4. Effect Of Solidification Speed On Fatigue Properties

    NASA Technical Reports Server (NTRS)

    Mccay, M. H.; Schmidt, D. D.; Hamilton, W. D.; Alter, W. S.; Parr, R. A.

    1989-01-01

    Fast solidification increases fatigue life, but failure distribution becomes less predictable. Report describes effects of rate of solidification on nickel-based super-alloy MAR-M246(Hf) used in turbine blades. Based on experiments in which specimens directionally solidified at 5 cm/h and 30 cm/h, then tested for high cycle fatigue. Specimens also inspected by energy-dispersive x-ray (EDX) analysis and optical and electron microscopy.

  5. Solidification fronts in supercooled liquids: how rapid fronts can lead to disordered glassy solids.

    PubMed

    Archer, A J; Robbins, M J; Thiele, U; Knobloch, E

    2012-09-01

    We determine the speed of a crystallization (or, more generally, a solidification) front as it advances into the uniform liquid phase after the system has been quenched into the crystalline region of the phase diagram. We calculate the front speed by assuming a dynamical density functional theory (DDFT) model for the system and applying a marginal stability criterion. Our results also apply to phase field crystal (PFC) models of solidification. As the solidification front advances into the unstable liquid phase, the density profile behind the advancing front develops density modulations and the wavelength of these modulations is a dynamically chosen quantity. For shallow quenches, the selected wavelength is precisely that of the crystalline phase and so well-ordered crystalline states are formed. However, when the system is deeply quenched, we find that this wavelength can be quite different from that of the crystal, so the solidification front naturally generates disorder in the system. Significant rearrangement and aging must subsequently occur for the system to form the regular well-ordered crystal that corresponds to the free energy minimum. Additional disorder is introduced whenever a front develops from random initial conditions. We illustrate these findings with simulation results obtained using the PFC model. PMID:23030925

  6. Phase Change Characteristics of a Nanoemulsion as a Latent Heat Storage Material

    NASA Astrophysics Data System (ADS)

    Fumoto, Koji; Sato, Noriaki; Kawaji, Masahiro; Kawanami, Tsuyoshi; Inamura, Takao

    2014-10-01

    The primary objective of this study was to investigate the fundamental phase change characteristics of a nanoemulsion using differential scanning calorimetry (DSC). Tetradecane, which has a slightly higher melting point than water, was utilized as the phase change material for the nanoemulsion. The melting point of the nanoemulsion, the melting peak temperature, and latent heat were examined in detail. Regarding the fundamental phase change characteristics of the nanoemulsion, it was found that its phase change characteristics were strongly affected by the temperature-scanning rate of the DSC. Moreover, it was confirmed that the phase change behavior does not change with repeated solidification and melting.

  7. Combined effect of non-equilibrium solidification and thermal annealing on microstructure evolution and hardness behavior of AZ91 magnesium alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Z. Z.; Yang, W.; Chen, S. H.; Yu, H.; Xu, Z. F.

    2014-06-01

    Non-equilibrium solidification of commercial AZ91 magnesium alloy was performed by copper mold spray-casting technique and the thermal stability property of as-formed meta-stable microstructure was investigated by subsequent annealing at different temperatures and times. Remarkable grain refinement appears with increasing cooling rate during solidification process, which is accompanied by a visible cellular/dendrite transition for the grain morphology of primary phase. Moreover, the non-equilibrium solidified alloy exhibits obvious precipitation hardening effect upon annealing at 200 °C, and the precipitation mode of β-Mg17Al12 phase changes from discontinuous to continuous with extending isothermal time from 4 h to 16 h, which generates an increase of resultant micro-hardness value. After solid solution treatment at the elevated temperature of 420 °C, the volume fraction of β-Mg17Al12 phase decreases and a notable grain growth phenomenon occurs, which give rise to a reduction of hardness in comparison with that of as-quenched alloy.

  8. XRMON-SOL: Isothermal equiaxed solidification of a grain refined Al-20 wt%Cu alloy

    NASA Astrophysics Data System (ADS)

    Murphy, A. G.; Mathiesen, R. H.; Houltz, Y.; Li, J.; Lockowandt, C.; Henriksson, K.; Zimmermann, G.; Melville, N.; Browne, D. J.

    2016-04-01

    A novel isothermal solidification furnace (XRMON-SOL) has been developed for operation under terrestrial and microgravity conditions, using aluminium-based alloys, in conjunction with real-time in situ X-radiography. The furnace is scheduled to fly on board the MASER 13 Sounding Rocket with a view to investigating isothermal equiaxed solidification under microgravity conditions. The present work provides details of the furnace design as well as detailed analysis of pre-flight terrestrial solidification experiments investigating nucleation and growth characteristics of a thin sample of grain refined Al-20 wt%Cu alloy isothermally solidified at a constant cooling rate of -0.05 K/s. Measurements of nucleation density, nucleation undercooling, grain orientation, grain envelope evolution, primary tip growth velocities, and equiaxed grain interactions are provided. Although the effects of gravity were minimised by choice of sample orientation, we show that such effects can only be eliminated in a microgravity environment.

  9. PREFACE: Third International Conference on Advances in Solidification Processes (ICASP - 3)

    NASA Astrophysics Data System (ADS)

    Zimmermann, Gerhard; Ratke, Lorenz

    2012-01-01

    The 3rd International Conference on Advances in Solidification Processes was held in the Rolduc Abbey in the Netherlands a few kilometres away from Aachen. Around 200 scientists from 24 countries come in for the four day meeting. They found a stimulating but also relaxing environment and atmosphere, with beautiful weather and the medieval abbey inviting for walks, discussions, sitting outside and drinking a beer or wine. The contributions given at the conference reflected recent advances in various topics of solidification processes, ranging from fundamental aspects to applied casting technologies. In 20 oral sessions and a large poster session innovative results of segregation phenomena, microstructure evolution, nucleation and growth, phase formation, polyphase solidification, rapid solidification and welding, casting technology, thermophysics of molten alloys, solidification with forced melt flow and growth of single crystals and superalloys together with innovative diagnostic techniques were presented. Thereby, findings from experiments as well as from numerical modeling on different lengths scales were jointly discussed and contribute to new insight in solidification behaviour. The papers presented in this open access proceedings cover about half the oral and poster presentations given. They were carefully reviewed as in classical peer reviewed journals by two independent referees and most of them were revised and thus improved according to the reviewers comments. We think that this collection of papers presented at ICASP-3 gives an impression of the excellent contributions made. The papers embrace both the basic and applied aspects of solidification. We especially wish to express our appreciation for the team around Georg Schmitz and Margret Nienhaus organising this event and giving us their valued advice and support at every stage in preparing the conference. We also thank Lokasenna Lektorat for taking the task of checking all language-associated issues and

  10. Permeability in a state of partial solidification of aqueous solution

    NASA Astrophysics Data System (ADS)

    Okada, Masashi; Kang, Chaedong; Okiyama, Haruhiko

    A mushy region was formed by solidifying NaCl aqueous solution in a circular tube or a rectangular tube. The measurements of permeability were performed by changing volume fraction of liquid region in the mushy region. The dendritic ice in the solidification process was observed with a CCD microscope. The following results were obtained. The permeability increases with the volume fraction of liquid phase, and decreases with increasing the super-cooling degree of the solution or increasing the initial concentration of the solution, and is constant after the mushy region was formed. The arm space of dendrite becomes narrower as the super-cooling degree of the solution increases.

  11. Single-particle measurements of phase partitioning between primary and secondary organic aerosols.

    PubMed

    Robinson, Ellis Shipley; Donahue, Neil M; Ahern, Adam T; Ye, Qing; Lipsky, Eric

    2016-07-18

    Organic aerosols provide a measure of complexity in the urban atmosphere. This is because the aerosols start as an external mixture, with many populations from varied local sources, that all interact with each other, with background aerosols, and with condensing vapors from secondary organic aerosol formation. The externally mixed particle populations start to evolve immediately after emission because the organic molecules constituting the particles also form thermodynamic mixtures - solutions - in which a large fraction of the constituents are semi-volatile. The external mixtures are thus well out of thermodynamic equilibrium, with very different activities for many constituents, and yet also have the capacity to relax toward equilibrium via gas-phase exchange of semi-volatile vapors. Here we describe experiments employing quantitative single-particle mass spectrometry designed to explore the extent to which various primary organic aerosol particle populations can interact with each other or with secondary organic aerosols representative of background aerosol populations. These methods allow us to determine when these populations will and when they will not mix with each other, and then to constrain the timescales for that mixing.

  12. Casting And Solidification Technology (CAST): Directional solidification phenomena in a metal model at reduced gravity

    NASA Technical Reports Server (NTRS)

    Mccay, M. H.

    1988-01-01

    The Casting and Solidification Technology (CAST) experiment will study the phenomena that occur during directional solidification of an alloy, e.g., constitutional supercooling, freckling, and dendrite coarsening. The reduced gravity environment of space will permit the individual phenomena to be examined with minimum complication from buoyancy driven flows.

  13. Macrosegregation Caused by Convection Associated with Directional Solidification through Cross-Section Change

    NASA Technical Reports Server (NTRS)

    Ghods, M.; Lauer, M.; Tewari, S. N.; Poirier, D. R..; Grugel, R. N.

    2015-01-01

    Al-7 wt% Si and Pb-6 wt% Sb alloy samples were directionally solidified (DS), with liquid above and solid below and gravity pointing down, in cylindrical graphite crucibles through an abrupt cross-section change. Fraction eutectic distribution in the microstructure, primary dendrite spacing and primary dendrite trunk diameters have been measured in the DS samples in the vicinity of section change in order to examine the effect of convection associated with the combined influence of thermosolutal factors and solidification shrinkage. It is observed that convection not only produces extensive radial and axial macrosegregation near cross-section change, it also affects the dendritic array morphology. Primary dendrite spacing and primary dendrite trunk diameter, both, are influenced by this convection. In addition to the experimental results, preliminary results from a numerical model which includes solidification shrinkage and thermosolutal convection in the mushy zone in its analysis will also be presented

  14. 30 CFR 250.918 - What are the CVA's primary duties during the installation phase?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false What are the CVA's primary duties during the... Platforms and Structures Platform Verification Program § 250.918 What are the CVA's primary duties during... independent assessment of the installation activities. (b) Primary duties of the CVA during the...

  15. 30 CFR 250.918 - What are the CVA's primary duties during the installation phase?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 2 2014-07-01 2014-07-01 false What are the CVA's primary duties during the... Platforms and Structures Platform Verification Program § 250.918 What are the CVA's primary duties during... independent assessment of the installation activities. (b) Primary duties of the CVA during the...

  16. 30 CFR 250.918 - What are the CVA's primary duties during the installation phase?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What are the CVA's primary duties during the... Structures Platform Verification Program § 250.918 What are the CVA's primary duties during the installation... assessment of the installation activities. (b) Primary duties of the CVA during the installation...

  17. 30 CFR 250.918 - What are the CVA's primary duties during the installation phase?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false What are the CVA's primary duties during the... Platforms and Structures Platform Verification Program § 250.918 What are the CVA's primary duties during... independent assessment of the installation activities. (b) Primary duties of the CVA during the...

  18. Effects of Space Environment on Flow and Concentration During Directional Solidification

    NASA Technical Reports Server (NTRS)

    Benjapiyaporn, C.; Timchenko, V.; Leonardi, E.; deVahlDavis, G.; deGroh, H. C., III

    2000-01-01

    A study of directional solidification of a weak binary alloy (specifically, Bi - 1 at% Sn) based on the fixed grid single domain approach is being undertaken. The enthalpy method is used to solve for the temperature field over the computational domain including both the solid and liquid phases; latent heat evolution is treated with the aid of an effective specific heat coefficient. A source term accounting for the release of solute into the liquid during solidification has been incorporated into the solute transport equation. The vorticity-stream function formulation is used to describe thermosolutal convection in the liquid region. In this paper we numerically investigate the effects of g-jitter on directional solidification. A background gravity of 1 micro-g has been assumed, and new results for the effects of periodic disturbances over a range of amplitudes and frequencies on solute field and segregation have been presented.

  19. A new control method depending on primary phase angle of transcutaneous energy transmission system for artificial heart.

    PubMed

    Miura, H; Saito, I; Sato, F; Shiraishi, Y; Yambe, T; Matsuki, H

    2013-01-01

    A new control method for stabilizing output voltage of the transcutaneous energy transmission system for artificial heart is proposed. This method is primary side, is outside of the body, which is not depending on a signal transmission system from the implanted device. The impedance observed from primary side changes from inductive to capacitive and the output voltage decreases drastically when the output current is large and the coupling factor is higher than that of the optimal condition. In this case, the driving frequency should be changed to higher so that the phase angle of the primary impedance is zero degree. The preliminary examination showed that this control method can enhance the output voltage limit to twice and the feasibility of the primary side control.

  20. Icosahedral phase stabilities in Al-Cu-Ru alloys

    SciTech Connect

    Shield, J.E.; Hoppe, C.; McCallum, R.W.; Goldman, A.I. ); Kelton, K.F.; Gibbons, P.C. )

    1992-02-01

    By examining a wide region of the Al-Cu-Ru phase diagram, a thorough analysis of the compositional and thermal stability of the icosahedral phase has been completed. The primary solidification product of rapid solidification was a topologically and chemically disordered icosahedral phase with an extensive compositional region. Crystallization through exothermic events of the as-solidified materials produced crystalline phases, without the formation of the face-centered-icosahedral (FCI) phase. However, the FCI phase does form at higher temperatures through an endothermic reaction, indicating that it is a stable phase of the system, but only at elevated temperatures. Of the alloys studied, the FCI phase field was found to encompass Al{sub 65}Cu{sub 23}Ru{sub 12}, Al{sub 65}Cu{sub 20}Ru{sub 15}, Al{sub 70}Cu{sub 20}Ru{sub 10}, and Al{sub 70}Cu{sub 15}Ru{sub 15}. The transformation to the FCI phase involves an intermediate approximant phase that is very similar to the FCI structure. Also, a cubic approximant containing atomic arrangements with local icosahedral symmetry similar to {alpha}-Al Mn Si was determined to exist near the FCI phase field.

  1. Containerless undercooling and solidification in drop tubes

    NASA Technical Reports Server (NTRS)

    Lacy, L. L.; Robinson, M. B.; Rathz, T. J.

    1981-01-01

    A containerless low-gravity environment, produced within a 32 m drop tube apparatus, has been used to undercool and solidify metals, alloys or glasses by eliminating crucible induced nucleation processes. Niobium droplets with diameters in the range of 2 to 5 mm have been undercooled by 525 K which corresponds to the maximum undercooling reported by Turnbull and others on fine dispersions of low melting point metals. Solidification at large undercooling resulted in single crystalline spheres with the formation of interdendritic shrinkage channels on the sample surface rather than interior shrinkage cavities. The grain refinement as observed for Ni samples undercooled and solidified in fused silica crucibles does not occur in free-falling drops of Nb. A calculated solidification speed of undercooled Nb is compared to Ni. A solidification speed of 320 m/s is found for the Nb drops. This solidification speed is greater than or comparable to the solidification speeds calculated in splat cooled samples. Thus, a drop tube apparatus can be useful in the preparation and study of high temperature metastable compounds or alloys in bulk form.

  2. DEMONSTRATION BULLETIN: SOLIDIFICATION/STABILIZATION PROCESS, Hazcon, Inc.

    EPA Science Inventory

    The solidification/stabilization technology mixes hazardous wastes, cement, water and an additive called Chloranan. Chloranan, a nontoxic chemical, encapsulates organic molecules, rendering them ineffective in retarding or inhibiting solidification. This treatment technol...

  3. Bioprocess intensification: a potential aqueous two-phase process for the primary recovery of B-phycoerythrin from Porphyridium cruentum.

    PubMed

    Benavides, Jorge; Rito-Palomares, Marco

    2004-07-25

    A process for the primary recovery of B-phycoerythrin from Porphyridium cruentum exploiting aqueous two-phase systems (ATPS) was developed in order to reduce the number of unit operations and benefit from an increased yield of the protein product. The evaluation of system parameters such as poly(ethylene glycol) (PEG) molecular mass, concentration of PEG as well as salt, system pH and volume ratio was carried out to determine under which conditions the B-phycoerythrin and contaminants concentrate to opposite phases. PEG 1450-phosphate ATPS proved to be suitable for the recovery of B-phycoerythrin because the target protein concentrated to the top phase whilst the protein contaminants and cell debris concentrated in the bottom phase. An extraction ATPS stage comprising volume ratio (Vr) equal to 1.0, PEG 1450 24.9% (w/w), phosphate 12.6% (w/w) and system pH of 8.0 allowed B-phycoerythrin recovery with a purity of 2.9 (estimated as the relation of the 545-280 nm absorbances). The use of ATPS resulted in a primary recovery process that produced a protein purity of 2.9 +/- 0.2 and an overall product yield of 77.0% (w/w). The results reported demonstrated the practical implementation of ATPS for the design of a primary recovery process as a first step for the commercial purification of B-phycoerythrin produced by P. cruentum.

  4. MD simulations of phase stability of PuGa alloys: Effects of primary radiation defects and helium bubbles

    SciTech Connect

    Dremov, V. V.; Sapozhnikov, F. A.; Ionov, G. V.; Karavaev, A. V.; Vorobyova, M. A.; Chung, B. W.

    2013-05-14

    We present classical molecular dynamics (MD) with Modified Embedded Atom Model (MEAM) simulations to investigate the role of primary radiation defects and radiogenic helium as factors affecting the phase stability of PuGa alloys in cooling–heating cycles at ambient pressure. The models of PuGa alloys equilibrated at ambient conditions were subjected to cooling–heating cycles in which they were initially cooled down to 100 K and then heated up to 500 K at ambient pressure. The rate of temperature change in the cycles was 10 K/ns. The simulations showed that the initial FCC phase of PuGa alloys undergo polymorphous transition in cooling to a lower symmetry α'-phase. All the alloys undergo direct and reverse polymorphous transitions in the cooling–heating cycles. The alloys containing vacancies shift in both transitions to lower temperatures relative to the defect-free alloys. The radiogenic helium has much less effect on the phase stability compared to that of primary radiation defects (in spite of the fact that helium concentration is twice of that for the primary radiation defects). Lastly, this computational result agrees with experimental data on unconventional stabilization mechanism of PuGa alloys.

  5. MD simulations of phase stability of PuGa alloys: Effects of primary radiation defects and helium bubbles

    DOE PAGESBeta

    Dremov, V. V.; Sapozhnikov, F. A.; Ionov, G. V.; Karavaev, A. V.; Vorobyova, M. A.; Chung, B. W.

    2013-05-14

    We present classical molecular dynamics (MD) with Modified Embedded Atom Model (MEAM) simulations to investigate the role of primary radiation defects and radiogenic helium as factors affecting the phase stability of PuGa alloys in cooling–heating cycles at ambient pressure. The models of PuGa alloys equilibrated at ambient conditions were subjected to cooling–heating cycles in which they were initially cooled down to 100 K and then heated up to 500 K at ambient pressure. The rate of temperature change in the cycles was 10 K/ns. The simulations showed that the initial FCC phase of PuGa alloys undergo polymorphous transition in coolingmore » to a lower symmetry α'-phase. All the alloys undergo direct and reverse polymorphous transitions in the cooling–heating cycles. The alloys containing vacancies shift in both transitions to lower temperatures relative to the defect-free alloys. The radiogenic helium has much less effect on the phase stability compared to that of primary radiation defects (in spite of the fact that helium concentration is twice of that for the primary radiation defects). Lastly, this computational result agrees with experimental data on unconventional stabilization mechanism of PuGa alloys.« less

  6. Transport processes in directional solidification and their effects on microstructure development

    SciTech Connect

    Mazumder, Prantik

    1999-11-08

    The processing of materials with unique electronic, mechanical, optical and thermal properties plays a crucial role in modern technology. The quality of these materials depend strongly on the microstructure and the solute/dopant fields in the solid product, that are strongly influenced by the intricate coupling of heat and mass transfer and melt flow in the growth systems. An integrated research program is developed that include precisely characterized experiments and detailed physical and numerical modeling of the complex transport and dynamical processes. Direct numerical simulation of the solidification process is carried out that takes into account the unsteady thermo-solutal convection in the vertical Bridgman crystal growth system, and accurately models the thermal interaction between the furnace and the ampoule by appropriately using experimentally measured thermal profiles. The flow instabilities and transitions and the nonlinear evolution following the transitions are investigated by time series and flow pattern analysis. A range of complex dynamical behavior is predicted with increasing thermal Rayleigh number. The route to chaos appears as: steady convection {r_arrow} transient mono-periodic {r_arrow} transient bi-periodic {r_arrow} transient quasi-periodic {r_arrow} transient intermittent oscillation-relaxation {r_arrow} stable intermittent oscillation-relaxation attractor. The spatio-temporal dynamics of the melt flow is found to be directly related to the spatial patterns observed experimentally in the solidified crystals. The application of the model to two phase Sn-Cd peritectic alloys showed that a new class of tree-like oscillating microstructure develops in the solid phase due to unsteady thermo-solutal convection in the liquid melt. These oscillating layered structures can give the illusion of band structures on a plane of polish. The model is applied to single phase solidification in the Al-Cu and Pb-Sn systems to characterize the effect of

  7. Dendritic solidification of alloys in low gravity

    NASA Astrophysics Data System (ADS)

    Curreri, P. A.; Lee, J. E.; Stefanescu, D. M.

    1988-11-01

    Gravity-driven convective flow influences dendrite morphology, interdendritic fluid flow, dendrite interface morphology, casting macrosegregation, formation of channel type casting defects, and casting grain structure. Dendritic solidification experiments during multiple parabolic aircraft maneuvers for iron-carbon type alloys and superalloys show increased dendritic spacing in low-gravity periods. Larger dendrite spacings for low-gravity solidification have also been reported for sounding rocket and space laboratory experiments for metal-model and binary alloys. Convection decreases local solidification time and increases the rate of interdendritic solute removal. The elimination of convection in low gravity is thus expected to increase dendritic spacing. Convection's effect on dendritic arm coarsening is expected to be dependent on the coarsening mechanism. Decreased coarsening in low gravity found for Al-Cu is indicative of coarsening predominately by arm coalescence.

  8. Enthalpies of a binary alloy during solidification

    NASA Technical Reports Server (NTRS)

    Poirier, D. R.; Nandapurkar, P.

    1988-01-01

    The purpose of the paper is to present a method of calculating the enthalpy of a dendritic alloy during solidification. The enthalpies of the dendritic solid and interdendritic liquid of alloys of the Pb-Sn system are evaluated, but the method could be applied to other binaries, as well. The enthalpies are consistent with a recent evaluation of the thermodynamics of Pb-Sn alloys and with the redistribution of solute in the same during dendritic solidification. Because of the heat of mixing in Pb-Sn alloys, the interdendritic liquid of hypoeutectic alloys (Pb-rich) of less than 50 wt pct Sn has enthalpies that increase as temperature decreases during solidification.

  9. Effects of anisotropic heat conduction on solidification

    NASA Technical Reports Server (NTRS)

    Weaver, J. A.; Viskanta, R.

    1989-01-01

    Two-dimensional solidification influenced by anisotropic heat conduction has been considered. The interfacial energy balance was derived to account for the heat transfer in one direction (x or y) depending on the temperature gradient in both the x and y directions. A parametric study was made to determine the effects of the Stefan number, aspect ratio, initial superheat, and thermal conductivity ratios on the solidification rate. Because of the imposed boundary conditions, the interface became skewed and sometimes was not a straight line between the interface position at the upper and lower adiabatic walls (spatially nonlinear along the height). This skewness depends on the thermal conductivity ratio k(yy)/k(yx). The nonlinearity of the interface is influenced by the solidification rate, aspect ratio, and k(yy/k(yx).

  10. Polyethylene solidification of low-level wastes

    NASA Astrophysics Data System (ADS)

    Kalb, P. D.; Colombo, P.

    1985-02-01

    The results of an investigation on the solidification of low-level radioactive waste in polyethylene are discussed. Waste streams included those which result from advanced volume reduction technologies (dry evaporator concentrate salts and incinerator ash) and those which remain problematic for solidification using contemporary agents (ion exchange resins). Four types of commercially available low-density polyethylenes were employed which encompass a range of processing and property characteristics. Process development studies were conducted to ascertain optimal process control parameters for successful solidification. Maximum waste loadings were determined for each waste and polyethylene type. Property evaluation testing was performed on laboratory-scale specimens to assess the potential behavior of actual waste forms in a disposal environment.

  11. Development of Stable Solidification Method for Insoluble Ferrocyanides-13170

    SciTech Connect

    Ikarashi, Yuki; Masud, Rana Syed; Mimura, Hitoshi; Ishizaki, Eiji; Matsukura, Minoru

    2013-07-01

    The development of stable solidification method of insoluble ferrocyanides sludge is an important subject for the safety decontamination in Fukushima NPP-1. By using the excellent immobilizing properties of zeolites such as gas trapping ability and self-sintering properties, the stable solidification of insoluble ferrocyanides was accomplished. The immobilization ratio of Cs for K{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O saturated with Cs{sup +} ions (Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O) was estimated to be less than 0.1% above 1,000 deg. C; the adsorbed Cs{sup +} ions are completely volatilized. In contrast, the novel stable solid form was produced by the press-sintering of the mixture of Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O and zeolites at higher temperature of 1,000 deg. C and 1,100 deg. C; Cs volatilization and cyanide release were completely depressed. The immobilization ratio of Cs, under the mixing conditions of Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O:CP= 1:1 and calcining temperature: 1,000 deg. C, was estimated to be nearly 100%. As for the kinds of zeolites, natural mordenite (NM), clinoptilolite (CP) and Chabazite tended to have higher immobilization ratio compared to zeolite A. This may be due to the difference in the phase transformation between natural zeolites and synthetic zeolite A. In the case of the composites (K{sub 2-X}Ni{sub X/2}[NiFe(CN){sub 6}].nH{sub 2}O loaded natural mordenite), relatively high immobilization ratio of Cs was also obtained. This method using zeolite matrices can be applied to the stable solidification of the solid wastes of insoluble ferrocyanides sludge. (authors)

  12. Ionic liquid-assisted liquid-phase microextraction based on the solidification of floating organic droplets combined with high performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice.

    PubMed

    Yang, Miyi; Zhang, Panjie; Hu, Lu; Lu, Runhua; Zhou, Wenfeng; Zhang, Sanbing; Gao, Haixiang

    2014-09-19

    A green, simple, and efficient method, ionic liquid-assisted liquid-liquid microextraction based on the solidification of floating organic droplets (ILSFOD-LLME) collected via a bell-shaped collection device (BSCD) coupled to high performance liquid chromatography with a variable-wavelength detector, was developed for the preconcentration and analysis of seven benzoylurea insecticides (BUs) in fruit juice. In the proposed method, the low-density solvent 1-dodecanol and the ionic liquid trihexyl(tetradecyl)phosphonium hexafluorophosphate ([P14, 6, 6, 6]PF6) were used as extractant. The extraction solvent droplet was easily collected and separated by the BSCD without centrifugation. The experimental parameters were optimized by the one-factor-at-a-time approach and were followed using an orthogonal array design. The results indicated the different effects of each parameter for extraction efficiency. Under the optimal conditions in the water model, the limits of detection for the analytes varied from 0.03 to 0.28μgL(-1). The enrichment factors ranged from 160 to 246. Linearities were achieved for hexaflumuron and flufenoxuron in the range of 0.5-500μgL(-1), for triflumuron, lufenuron and diafenthiuron in the range of 1-500μgL(-1), and for diflubenzuron and chlorfluazuron in the range of 5-500μgL(-1); the correlation coefficients for the BUs ranged from 0.9960 to 0.9990 with recoveries of 75.6-113.9%. Finally, the developed technique was successfully applied to real fruit juice with acceptable results. The relative standard deviations (RSDs) of the seven BUs at two spiked levels (50 and 200μgL(-1)) varied between 0.1% and 7.3%. PMID:25124227

  13. Ionic liquid-assisted liquid-phase microextraction based on the solidification of floating organic droplets combined with high performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice.

    PubMed

    Yang, Miyi; Zhang, Panjie; Hu, Lu; Lu, Runhua; Zhou, Wenfeng; Zhang, Sanbing; Gao, Haixiang

    2014-09-19

    A green, simple, and efficient method, ionic liquid-assisted liquid-liquid microextraction based on the solidification of floating organic droplets (ILSFOD-LLME) collected via a bell-shaped collection device (BSCD) coupled to high performance liquid chromatography with a variable-wavelength detector, was developed for the preconcentration and analysis of seven benzoylurea insecticides (BUs) in fruit juice. In the proposed method, the low-density solvent 1-dodecanol and the ionic liquid trihexyl(tetradecyl)phosphonium hexafluorophosphate ([P14, 6, 6, 6]PF6) were used as extractant. The extraction solvent droplet was easily collected and separated by the BSCD without centrifugation. The experimental parameters were optimized by the one-factor-at-a-time approach and were followed using an orthogonal array design. The results indicated the different effects of each parameter for extraction efficiency. Under the optimal conditions in the water model, the limits of detection for the analytes varied from 0.03 to 0.28μgL(-1). The enrichment factors ranged from 160 to 246. Linearities were achieved for hexaflumuron and flufenoxuron in the range of 0.5-500μgL(-1), for triflumuron, lufenuron and diafenthiuron in the range of 1-500μgL(-1), and for diflubenzuron and chlorfluazuron in the range of 5-500μgL(-1); the correlation coefficients for the BUs ranged from 0.9960 to 0.9990 with recoveries of 75.6-113.9%. Finally, the developed technique was successfully applied to real fruit juice with acceptable results. The relative standard deviations (RSDs) of the seven BUs at two spiked levels (50 and 200μgL(-1)) varied between 0.1% and 7.3%.

  14. Determination of Systems Suitable for Study as Monotectic Binary Metallic Alloy Solidification Models

    NASA Technical Reports Server (NTRS)

    Smith, J. E., Jr.

    1983-01-01

    Succinonitrile-water and diethylene glycol-ethyl salicylate are two transparent systems which have been studied as monotectic binary metallic alloy solidification models. Being transparent, these systems allow for the direct observations of phase transformations and solidification reactions. The objective was to develop a screening technique to find systems of interest and then experimentally measure those systems. The succinonitrile-water system was used to check the procedures. To simulate the phase diagram of the system, two computer programs which determine solid-liquid and liquid-liquid equilibria were obtained. These programs use the UNIFAC method to determine activity coefficients and together with several other programs were used to predict the phase diagram. An experimental apparatus was developed and the succinonitrile-water phase diagram measured. The diagram was compared to both the simulation and literature data. Substantial differences were found in the comparisons which serve to demonstrate the need for this procedure.

  15. Novel Directional Solidification Processing of Hypermonotectic Alloys

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.

    1999-01-01

    Gravity driven separation precludes uniform microstructural development during controlled directional solidification (DS) processing of hypermonotectic alloys. It is well established that liquid/liquid suspensions, in which the respective components are immiscible and have significant density differences, can be established and maintained by utilizing ultrasound. A historical introduction to this work is presented with the intent of establishing the basis for applying the phenomena to promote microstructural uniformity during controlled directional solidification processing of immiscible mixtures. Experimental work based on transparent organics, as well as salt systems, will be presented in view of the processing parameters.

  16. Observations of a monotectic solidification interface morphology

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.; Frazier, D. O.

    1985-01-01

    For detailed studies of the region around a solidification interface on a microscopic scale, a very thin (essentially two-dimensional) test cell may be translated across two temperature-controlled heating/cooling blocks and viewed with a microscope. Such a device is sometimes referred to as a temperature gradient microscope stage (TGS). Of particular interest in this study is the behavior of a monotectic type solution during solidification. Succinonitrile based model systems for metallic monotectic alloys, when solidified on a TGS, form an unusual 'worm-like' micromorphology. These interfaces are observable in situ under high optical magnification during growth.

  17. Observations of a monotectic solidification interface morphology

    NASA Astrophysics Data System (ADS)

    Kaukler, W. F.; Frazier, D. O.

    1985-04-01

    For detailed studies of the region around a solidification interface on a microscopic scale, a very thin (essentially two-dimensional) test cell may be translated across two temperature-controlled heating/cooling blocks and viewed with a microscope. Such a device is sometimes referred to as a temperature gradient microscope stage (TGS). Of particular interest in this study is the behavior of a monotectic type solution during solidification. Succinonitrile based model systems for metallic monotectic alloys, when solidified on a TGS, form an unusual 'worm-like' micromorphology. These interfaces are observable in situ under high optical magnification during growth.

  18. Simultaneous Solid Phase Extraction and Derivatization of Aliphatic Primary Amines Prior to Separation and UV-Absorbance Detection

    PubMed Central

    Felhofer, Jessica L.; Scida, Karen; Penick, Mark; Willis, Peter A.; Garcia, Carlos D.

    2013-01-01

    To overcome the problem of poor sensitivity of capillary electrophoresis-UV absorbance for the detection of aliphatic amines, a solid phase extraction and derivatization scheme was developed. This work demonstrates successful coupling of amines to a chromophore immobilized on a solid phase and subsequent cleavage and analysis. Although the analysis of many types of amines is relevant for myriad applications, this paper focuses on the derivatization and separation of amines with environmental relevance. This work aims to provide the foundations for future developments of an integrated sample preparation microreactor capable of performing simultaneous derivatization, preconcentration, and sample cleanup for sensitive analysis of primary amines. PMID:24054648

  19. Thermal analysis of HGFQ using FIDAP(trademark): Solidification front motion

    NASA Technical Reports Server (NTRS)

    Woodbury, Keith A.

    1996-01-01

    The High Gradient Furnace with Quench (HGFQ) is being designed by NASA/MSFC for flight on the International Space Station. The furnace is being designed specifically for solidification experiments in metal and metallic alloy systems. The HGFQ Product development Team (PDT) has been active since January 1994 and their effort is now in early Phase B. Thermal models have been developed both by NASA and Sverdrup (support contractor) to assist in the HGFQ design effort. Both these models use SINDA as a solution engine, but the NASA model was developed using PATRAN and includes more detail than the Sverdrup model. These models have been used to guide design decisions and have been validated through experimentation on a prototypical 'Breadboard' furnace at MSFC. One facet of the furnace operation of interest to the designers is the sensitivity of the solidification interface location to changes in the furnace setpoint. Specifically of interest is the motion (position and velocity) of the solidification front due to a small perturbation in the furnace temperature. FIDAP(TM) is a commercially available finite element program for analysis of heat transfer and fluid flow processes. Its strength is in solution of the Navier-Stokes equations for incompressible flow, but among its capabilities is the analysis of transient processes involving radiation and solidification. The models presently available from NASA and Sverdrup are steady-state models and are incapable of computing the motion of the solidification front. The objective of this investigation is to use FIDAP(TM) to compute the motion of the solidification interface due to a perturbation in the furnace setpoint.

  20. Enantioseparations of primary amino compounds by high-performance liquid chromatography using chiral crown ether-based chiral stationary phase.

    PubMed

    Hyun, Myung Ho

    2013-01-01

    Liquid chromatographic resolution of racemic compounds containing a primary amino group has been known to be most successful when chiral crown ether-based chiral stationary phases (CSPs) are used. Among various crown ether-based CSPs, the stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel has been successfully applied in the resolution of various racemic compounds containing primary amino groups. In this chapter, the preparation of the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel and examples for the application to the enantioseparation of racemic compounds including α-amino acids, cyclic amines, amino alcohols, and chiral drugs are described.

  1. Enantioseparations of primary amino compounds by high-performance liquid chromatography using chiral crown ether-based chiral stationary phase.

    PubMed

    Hyun, Myung Ho

    2013-01-01

    Liquid chromatographic resolution of racemic compounds containing a primary amino group has been known to be most successful when chiral crown ether-based chiral stationary phases (CSPs) are used. Among various crown ether-based CSPs, the stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel has been successfully applied in the resolution of various racemic compounds containing primary amino groups. In this chapter, the preparation of the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel and examples for the application to the enantioseparation of racemic compounds including α-amino acids, cyclic amines, amino alcohols, and chiral drugs are described. PMID:23283776

  2. A comparison of the solidification behavior of INCOLOY 909 and INCONEL 718

    NASA Astrophysics Data System (ADS)

    Cieslak, M. J.; Headley, T. J.; Knorovsky, G. A.; Romig, A. D.; Kollie, T.

    1990-01-01

    The solidification behavior of two commercial aerospace superalloys, INCOLOY 909 and INCONEL 718, has been examined. Specifically, differential thermal analysis (DTA) revealed that INCOLOY 909 terminates solidification with the formation of a single minor constituent at ≈1198 °C. INCONEL 718 terminates solidification with the formation of two minor constituents, at ≈1257 °C and ~1185 °C, respectively. Metallography performed on the DTA samples confirmed that a single minor constituent was present in INCOLOY 909 while two minor constituents were present in INCONEL 718. Differential thermal analysis samples were also examined by electron probe microanalysis to reveal the patterns of elemental segregation. Arc welds of these alloys were examined by transmission and analytical electron microscopy (TEM and AEM). It was observed that the arc welds of INCOLOY 909 contained only a y/Laves eutectic-like constituent, while the arc welds of INCONEL 718 contained both y/Laves and γ/MC eutectic-like constituents. Compositional analyses of these minor phases revealed that all were enriched in Nb relative to the bulk alloy. The Laves phases were also enriched in Si relative to the bulk alloy concentration. Comparisons of the observed solidification sequences in these alloys with other Nb-bearing austenitic matrix alloys are made.

  3. Modeling Primary Breakup: A Three-Dimensional Eulerian Level Set/Vortex Sheet Method for Two-Phase Interface Dynamics

    NASA Technical Reports Server (NTRS)

    Herrmann, M.

    2003-01-01

    This paper is divided into four parts. First, the level set/vortex sheet method for three-dimensional two-phase interface dynamics is presented. Second, the LSS model for the primary breakup of turbulent liquid jets and sheets is outlined and all terms requiring subgrid modeling are identified. Then, preliminary three-dimensional results of the level set/vortex sheet method are presented and discussed. Finally, conclusions are drawn and an outlook to future work is given.

  4. Effects of Traveling Magnetic Field on Dynamics of Solidification

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Grugel, Richard; Motakef, Shariar

    2001-01-01

    TMF is based on imposing a controlled phase-shift in a train of electromagnets, forming a stack. Thus, the induced magnetic field can be considered to be travelling along the axis of the stack. The coupling of this traveling wave with an electrically conducting fluid results in a basic flow in a form of a single axisymmetric roll. The magnitude and direction of this flow can be remotely controlled. Furthermore, it is possible to localize the effect of this force field though activating only a number of the magnets. This force field generated in the fluid can, in principle, be used to control and modify convection in the molten material. For example, it can be used to enhance convective mixing in the melt, and thereby modify the interface shape, and macrosegregation. Alternatively, it can be used to counteract thermal and/or solutal buoyancy forces. High frequency TMF can be used in containerless processing techniques, such as float zoning, to affect the very edge of the fluid so that Marangoni flow can be counter balanced. The proposed program consists of basic fundamentals and applications. Our goal in conducting the following experiments and analyses is to establish the validity of TMF as a new tool for solidification processes. Due to its low power consumption and simplicity of design, this tool may find wide spread use in a variety of space experiments. The proposed ground based experiments are intended to establish the advantages and limitations of employing this technique. In the fundamentals component of the proposed program, we will use theoretical tools and experiments with mercury to establish the fundamental aspects of TMF-induced convection through a detailed comparison of theoretical predictions and experimental measurements of flow field. In this work, we will conduct a detailed parametric study involving the effects of magnetic field strength, frequency, wave vector, and the fluid geometry. The applications component of this work will be focused on

  5. Solidification Structure and Macrosegregation of Billet Continuous Casting Process with Dual Electromagnetic Stirrings in Mold and Final Stage of Solidification: A Numerical Study

    NASA Astrophysics Data System (ADS)

    Jiang, D.; Zhu, M.

    2016-08-01

    Coupling macroscale heat transfer and fluid flow with microscale grain nucleation and crystal growth, a mixed columnar-equiaxed solidification model was established to study the SWRT82B steel solidification structure and macrosegregation in 160 mm × 160 mm billet continuous casting with dual electromagnetic stirrings in mold and final stage of solidification (M-EMS and F-EMS). In the model, the phases of liquid, columnar, and equiaxed were treated separately and the initial growing equiaxed phase, which could move freely with liquid, was regarded as slurry. To obtain the equiaxed grains nucleation and columnar front evolution, the unit tracking method and the columnar front tracking model were built. The model was validated by magnetic induction intensity of stirrer, billet surface temperature, and carbon segregation. The equiaxed phase evolution and the solute transport with effect of fluid flow and grains transport were described in this article. The results show that the equiaxed phase ratio will not increase obviously with higher current intensity of M-EMS, while the negative segregation near the strand surface becomes more serious. The negative segregation zone near the billet center and the center positive segregation come into being with the effect of equiaxed grains sedimentation and liquid thermosolutal flow. It is also found that the liquid solute transport in the F-EMS zone becomes the main factor with higher current intensity rather than the solidification rate, and therefore, the final billet center segregation decreases first and then turns to rise with the current intensity. The optimal current intensities of M-EMS and F-EMS proposed for SWRT82B billet continuous casting are 200 and 400 A, respectively.

  6. The Role of Critical Nonwetting Fluid Saturation in Darcy-Based Models of Two-Phase Primary Drainage

    NASA Astrophysics Data System (ADS)

    Breen, S. J.; Pride, S. R.; Manga, M.

    2015-12-01

    Primary drainage is the displacement of a wetting phase by a nonwetting phase where the initial condition is fully saturated with wetting phase. The typical approach to simulating this process involves the solution of coupled mass conservation equations with Darcy-based flux terms, but this method ignores the complex pore-scale processes that influence the propagation rate and shape of drainage fronts. Therefore, we explore weaknesses in the practical application of the continuum-scale Darcy approach for modeling primary drainage by comparing 1D numerical simulations to laboratory core-scale observations. The multiphase properties of cylindrical bead packs are characterized by stepped outflow experiments and standard hydrological models are used to describe water retention and relative permeability, such as van Genuchten-Mualem. Subsequently, we generate predictions of drainage front breakthrough time with Tough2 and compare them to observations of gravitationally stabilized primary drainage at low capillary number. We find that Corey's critical nonwetting saturation parameter must be used in relative permeability curves in order to match observations, and that the best-fit value is flow-rate dependent and grid-size independent. We also argue that the value of this parameter is not constrained by current experimental methods or physical arguments, and that it is an important but irreducible source of uncertainty in the standard approach to multiphase flow. This highlights the need for a scalable model that incorporates dynamic percolation thresholds with dependency on pore-scale processes.

  7. Stability of a directional solidification front in subdiffusive media.

    PubMed

    Hamed, Mohammad Abu; Nepomnyashchy, Alexander A

    2014-01-01

    The efficiency of crystal growth in alloys is limited by the morphological instability, which is caused by a positive feedback between the interface deformation and the diffusive flux of solute at the front of the phase transition. Usually this phenomenon is described in the framework of the normal diffusion equation, which stems from the linear relation between time and the mean squared displacement of molecules 〈x2(t)〉∼K1t (K1 is the classical diffusion coefficient) that is characteristic of Brownian motion. However, in some media (e.g., in gels and porous media) the random walk of molecules is hindered by obstacles, which leads to another power law, 〈x2(t)〉∼Kαtα, where 0<α≤1. As a result, the diffusion is anomalous, and it is governed by an integro-differential equation including a fractional derivative in time variable, i.e., a memory. In the present work, we investigate the stability of a directional solidification front in the case of an anomalous diffusion. Linear stability of a moving planar directional solidification front is studied, and a generalization of the Mullins-Sekerka stability criterion is obtained. Also, an asymptotic nonlinear long-wave evolution equation of Sivashinsky's type, which governs the cellular structures at the interface, is derived.

  8. Directional solidification of eutectic composites in space environment

    NASA Technical Reports Server (NTRS)

    Yue, A. S.

    1972-01-01

    The Ni-Ni3Ta eutectic and a nickel-base alloy containing 30 wt pct Ta were solidified unidirectionally in an electron beam floating zone melting apparatus. It was found that the volume fraction of the Ni3Ta phase in the Ni-Ni3Ta eutectic mixture was increased from 7.6 to 36 volume pct in agreement with the theory as predicted. Tensile properties of the randomly solidified and unidirectionally solidified Ni-Ni3Ta eutectic were determined as function of solidification rate and temperature. It was found that the ultimate tensile strength decreased as both the test temperature and solidification rate increased. An elongation of 40 pct was obtained for a nickelbase alloy containing 30 wt at room temperature. This unusually large elongation was attributed to the superplastic behavior of the alloy. The critical currents versus the external fields at 2.5, 3.0, 3.5 and 4.2 deg for the unidirectionally solidified Pb-Sn eutectic were measured. The values of critical fields at zero critical currents were obtained by extrapolation.

  9. Stability of a directional solidification front in subdiffusive media

    NASA Astrophysics Data System (ADS)

    Hamed, Mohammad Abu; Nepomnyashchy, Alexander A.

    2014-01-01

    The efficiency of crystal growth in alloys is limited by the morphological instability, which is caused by a positive feedback between the interface deformation and the diffusive flux of solute at the front of the phase transition. Usually this phenomenon is described in the framework of the normal diffusion equation, which stems from the linear relation between time and the mean squared displacement of molecules ˜K1t (K1 is the classical diffusion coefficient) that is characteristic of Brownian motion. However, in some media (e.g., in gels and porous media) the random walk of molecules is hindered by obstacles, which leads to another power law, ˜Kαtα, where 0<α≤1. As a result, the diffusion is anomalous, and it is governed by an integro-differential equation including a fractional derivative in time variable, i.e., a memory. In the present work, we investigate the stability of a directional solidification front in the case of an anomalous diffusion. Linear stability of a moving planar directional solidification front is studied, and a generalization of the Mullins-Sekerka stability criterion is obtained. Also, an asymptotic nonlinear long-wave evolution equation of Sivashinsky's type, which governs the cellular structures at the interface, is derived.

  10. Detached Growth of Germanium by Directional Solidification

    NASA Technical Reports Server (NTRS)

    Palosz, W.; Volz, M. P.; Cobb, S.; Motakef, S.; Szofran, F. R.

    2004-01-01

    The conditions of detached solidification under controlled pressure differential across the meniscus were investigated. Uncoated and graphite- or BN-coated silica and pBN crucibles were used. Detached and partly detached growth was achieved in pBN and BN-coated crucibles, respectively. The results of the experiments are discussed based on the theory of Duffar et al.

  11. Solidification behavior during directed light fabrication

    SciTech Connect

    Thoma, D.J.; Lewis, G.K.; Nemec, R.B.

    1995-10-01

    Directed light fabrication (DLF) is a process that fuses gas delivered metal powders within a focal zone of a laser beam to produce fully dense, 3-dimensional metal components. A variety of materials have been processed with DLF, ranging from steels to tungsten, and including intermetallics such as NiAl and MoSi{sub 2}. To evaluate the processing parameters and resulting microstructures, solidification studies have been performed on defined alloy systems. For example, solidification cooling rates have been determined based upon secondary dendrite arm spacings in Fe-based alloys. In addition, eutectic spacings have been used to define growth velocities during solidification. Cooling rates vary from 10{sup 1}-10{sup 5} K s{sup {minus}1} and growth rates vary between 1--50 mm s{sup {minus}1}. As a result, process definition has been developed based upon the microstructural development during solidification. The materials explored were Ag-19Cu, Fe-24.8Ni, 316 stainless steel, Al-33Cu, W, MoSi{sub 2} and NiAl.

  12. SOLIDIFICATION/STABILIZATION: IS IT ALWAYS APPROPRIATE?

    EPA Science Inventory

    The findings of recent research and evaluation efforts are assessed to determine whether solidification/stabilization (S/S) has been properly and appropriately applied for different types of hazardous wastes. Results from these studies are mixed and, as a result, the need for pro...

  13. SOLIDIFICATION/STABILIZATION - USEPA SUPERFUND PROGRAM

    EPA Science Inventory

    The USEPA experience in using Solidification/Stabilization (S/S) Technology to remediate Superfund sites is reviewed. Included are several case studies for insitu and exsitu treatment and sites containing both metals and organics, both separately, and mixed on the same site. Co...

  14. Uncertainty Quantification of Modelling of Equiaxed Solidification

    NASA Astrophysics Data System (ADS)

    Fezi, K.; Krane, M. J. M.

    2016-07-01

    Numerical simulations of metal alloy solidification are used to gain insight into physical phenomena that cannot be observed experimentally. Often validation of such models has been done through comparison to sparse experimental data, to which agreement can be misinterpreted due to both model and experimental uncertainty. Uncertainty quantification (UQ) and sensitivity analysis are performed on a transient model of solidification of Al-4.5 wt.% Cu in a rectangular cavity, with equiaxed (grain refined) solidification morphology. This model solves equations for momentum, temperature, and species conservation; UQ and sensitivity analysis are performed for the degree of macrosegregation. A Smolyak sparse grid algorithm is used to select input values to construct a response surface fit to model outputs. The response surface is then used as a surrogate for the solidification model to determine the sensitivities and probability density functions of the model outputs. Uncertain model inputs of interest include the secondary dendrite arm spacing, equiaxed particle size, and fraction solid at which the rigid mushy zone forms. Similar analysis was also performed on a transient model of direct chill casting of the same alloy.

  15. Microstructure, corrosion behavior and cytotoxicity of biodegradable Mg-Sn implant alloys prepared by sub-rapid solidification.

    PubMed

    Zhao, Chaoyong; Pan, Fusheng; Zhao, Shuang; Pan, Hucheng; Song, Kai; Tang, Aitao

    2015-09-01

    In this study, biodegradable Mg-Sn alloys were fabricated by sub-rapid solidification, and their microstructure, corrosion behavior and cytotoxicity were investigated by using optical microscopy, scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, X-ray diffraction, immersion test, potentiodynamic polarization test and cytotoxicity test. The results showed that the microstructure of Mg-1Sn alloy was almost equiaxed grain, while the Mg-Sn alloys with higher Sn content (Sn≥3 wt.%) displayed α-Mg dendrites, and the secondary dendrite arm spacing of the primary α-Mg decreased significantly with increasing Sn content. The Mg-Sn alloys consisted of primary α-Mg matrix, Sn-rich segregation and Mg2Sn phase, and the amount of Mg2Sn phases increased with increasing Sn content. Potentiodynamic polarization and immersion tests revealed that the corrosion rates of Mg-Sn alloys increased with increasing Sn content. Cytotoxicity test showed that Mg-1Sn and Mg-3Sn alloys were harmless to MG63 cells. These results of the present study indicated that Mg-1Sn and Mg-3Sn alloys were promising to be used as biodegradable implants. PMID:26046288

  16. Microstructure, corrosion behavior and cytotoxicity of biodegradable Mg-Sn implant alloys prepared by sub-rapid solidification.

    PubMed

    Zhao, Chaoyong; Pan, Fusheng; Zhao, Shuang; Pan, Hucheng; Song, Kai; Tang, Aitao

    2015-09-01

    In this study, biodegradable Mg-Sn alloys were fabricated by sub-rapid solidification, and their microstructure, corrosion behavior and cytotoxicity were investigated by using optical microscopy, scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, X-ray diffraction, immersion test, potentiodynamic polarization test and cytotoxicity test. The results showed that the microstructure of Mg-1Sn alloy was almost equiaxed grain, while the Mg-Sn alloys with higher Sn content (Sn≥3 wt.%) displayed α-Mg dendrites, and the secondary dendrite arm spacing of the primary α-Mg decreased significantly with increasing Sn content. The Mg-Sn alloys consisted of primary α-Mg matrix, Sn-rich segregation and Mg2Sn phase, and the amount of Mg2Sn phases increased with increasing Sn content. Potentiodynamic polarization and immersion tests revealed that the corrosion rates of Mg-Sn alloys increased with increasing Sn content. Cytotoxicity test showed that Mg-1Sn and Mg-3Sn alloys were harmless to MG63 cells. These results of the present study indicated that Mg-1Sn and Mg-3Sn alloys were promising to be used as biodegradable implants.

  17. MRO's HiRISE Education and Public Outreach during the Primary Science Phase

    NASA Astrophysics Data System (ADS)

    Gulick, V. C.; Davatzes, A. K.; Deardorff, G.; Kanefsky, B.; Conrad, L. B.; HiRISE Team

    2008-12-01

    Looking back over one Mars year, we report on the accomplishments of the HiRISE EPO program during the primary science phase of MRO. A highlight has been our student image suggestion program, conducted in association with NASA Quest as HiRISE Image Challenges (http://quest.arc.nasa.gov/challenges/hirise/). During challenges, students, either individually or as part of a collaborative classroom or group, learn about Mars through our webcasts, web chats and our educational material. They use HiWeb, HiRISE's image suggestion facility, to submit image suggestions and include a short rationale for why their target is scientifically interesting. The HiRISE team gives priority to obtaining a sampling of these suggestions as quickly as possible so that the acquired images can be examined by the students. During the challenge, a special password-protected web site allows participants to view their returned images before they are released to the public (http://marsoweb.nas.nasa.gov/hirise/quest/). Students are encouraged to write captions for the returned images. Finished captions are then posted and highlighted on the HiRISE web site (http://hirise.lpl.arizona.edu) along with their class, teacher's name and the name of their school. Through these HiRISE challenges, students and teachers become virtual science team members, participating in the same process (selecting and justifying targets, analyzing and writing captions for acquired images), and using the same software tools as the HiRISE team. Such an experience is unique among planetary exploration EPO programs. To date, we have completed three HiRISE challenges and a fourth is currently ongoing. More than 200 image suggestions were submitted during the previous challenges and over 85 of these image requests have been acquired so far. Over 675 participants from 45 states and 42 countries have registered for the previous challenges. These participants represent over 8000 students in grades 2 through 14 and consist

  18. Aqueous two-phase flotation for primary recovery of bacteriocin-like inhibitory substance (BLIS) from Pediococcus acidilactici Kp10.

    PubMed

    Md Sidek, Nurul Lyana; Tan, Joo Shun; Abbasiliasi, Sahar; Wong, Fadzlie Wong Faizal; Mustafa, Shuhaimi; Ariff, Arbakariya B

    2016-08-01

    An aqueous two-phase flotation (ATPF) system based on polyethylene glycol (PEG) and sodium citrate (NaNO3C6H5O7·2H2O) was considered for primary recovery of bacteriocin-like inhibitory substance (BLIS) from Pediococcus acidilactici Kp10. The effects of ATPF parameters namely phase composition, tie-line length (TLL), volume ratio between the two phases (VR), amount of crude load (CL), pH, nitrogen gas flow rate (FR) and flotation time (FT) on the performance of recovery were evaluated. BLIS was mainly concentrated into the upper PEG-rich phase in all systems tested so far. The optimum conditions for BLIS purification, which composed of PEG 8000/sodium citrate, were: TLL of 42.6, VR of 0.4, CL of 22% (w/w), pH 7, average FT of 30min and FR of 20mL/min. BLIS was partially purified up to 5.9-fold with a separation efficiency of 99% under this optimal conditions. A maximum yield of BLIS activity of about 70.3% was recovered in the PEG phase. The BLIS from the top phase was successfully recovered with a single band in SDS-gel with molecular weight of about 10-15kDa. ATPF was found to be an effective technique for the recovery of BLIS from the fermentation broth of P. acidilactici Kp10. PMID:27262666

  19. Study on Pressurized Solidification Behavior and Microstructure Characteristics of Squeeze Casting Magnesium Alloy AZ91D

    NASA Astrophysics Data System (ADS)

    Han, Zhiqiang; Pan, Haowei; Li, Yanda; Luo, Alan A.; Sachdev, Anil K.

    2015-02-01

    Squeeze casting technology for magnesium alloys has a great application potential in automobile manufacturing and has received increasing attention from both academic and industrial communities. In this study, the pressurized solidification behavior of magnesium alloy AZ91D in squeeze casting process was investigated using computer-aided cooling curve analysis (CA-CCA). It was found that the applied pressure increased both the start and end temperatures of primary α-Mg formation but had little effect on the sizes of temperature ranges. Moreover, the applied pressure increased the start temperature and decreased the end temperature of eutectic reaction during the solidification, resulting in a larger temperature range of eutectic reaction compared with solidification under atmospheric pressure. The grains were remarkably refined, and the eutectic fraction increased with increasing applied pressure. The dendritic microstructure with a larger secondary dendrite arm spacing (SDAS) was observed under a higher applied pressure at the central part of the experimental casting. By correlating the CA-CCA and SDAS data, it was found that SDAS and the cooling rate at the maximum α-Mg growth could be fit into the power law equation in classic solidification theories.

  20. Cellular/Dendritic Transition and Microstructure Evolution during Transient Directional Solidification of Pb-Sb Alloys

    NASA Astrophysics Data System (ADS)

    Rosa, Daniel M.; Spinelli, José E.; Ferreira, Ivaldo L.; Garcia, Amauri

    2008-09-01

    Recent studies of lead-antimony alloys, used for the production of positive electrodes of lead-acid batteries, have assessed the influences of both the microstructural morphology and of solute redistribution on the surface corrosion resistance in sulfuric acid solution, and have shown that cellular structures and dendritic structures have different responses on the corrosion rate of such alloys. The present article focuses on the search of adequate solidification conditions (alloy composition, cooling rate, and solidification velocity), which determine the occurrence of a microstructural transition from the cellular to the dendritic regime during the transient unidirectional solidification of hypoeutectic Pb-Sb alloys and on the microstructural evolution after such transition. The experimental data refers to the solidification of four hypoeutectic Pb-Sb alloys (2.2, 2.5, 3, and 6.6 wt pct Sb) and of the eutectic composition. The experimental results include transient metal/mold heat-transfer coefficients, liquidus isotherm velocity, cooling rate, and cellular and dendritic spacings. It was found that the cooling rate dependence on cellular and primary dendritic spacings is characterized by an experimental law of the form λ 1 = A{\\cdot}ifmmodeexpandafterdotelseexpandafter\\.fi{T}^{{{kern 1pt} {-0.55}}}, which seems to be independent of composition where A = 60 represents the alloys undergoing a cellular growth and A = 115 can describe the dendritic growth. The sudden change on such multiplier has occurred for the Pb 2.2 wt pct Sb alloy, i.e., for the cellular/dendritic transition.

  1. Quantification of the Solidification Microstructure in Continuously-Cast High-Carbon Steel Billets

    NASA Astrophysics Data System (ADS)

    Ganguly, Suvankar; Choudhary, S. K.

    2009-06-01

    In this work, an attempt has been made to investigate the relationship between the cast microstructure and solidification variables in industrial scale, continuously-cast (CC) high-carbon steel billets. Toward these, theoretical and experimental studies are undertaken to predict the evolution of dendrite arm spacing (DAS) in the columnar zone of CC billets. Several billet samples collected from the continuous casting shop of Tata Steel are used to characterize the solidification microstructure, and interdendritic arm spacings (both primary and secondary) are measured. Macrostructural examination of the billet samples indicates predominantly columnar structure in all billets. Dendrite arm spacings vary over a wide range indicating nonuniform secondary cooling. A mathematical model is also developed to describe the relationship between dendrite structures and solidification parameters. The model considers the effect of change of volume on solidification and provides a quantitative estimation of variation of DAS as a function of distance from the product surface. Results predicted by the mathematical model are compared with the experimental measurements and good agreement can be observed in this regard, thereby establishing the authenticity of the proposed formulation.

  2. The unidirectional solidification of Al-4 wt pct Cu ingots in microgravity

    NASA Astrophysics Data System (ADS)

    Cahoon, J. R.; Chaturvedi, M. C.; Tandon, K. N.

    1998-03-01

    Three Al-4 wt pct Cu alloy ingots, 10 mm in diameter and 25-mm long, were unidirectionally solidified in microgravity during the flight of a sounding rocket, with solidification rates of about 1.6×10-4 m/s and temperature gradients of about 2600 K/m. The apparatus was comprised of three muffle furnaces, which melted the ingots prior to the launch of the rocket. Unidirectional solidification of the ingots was accomplished by chill plates attached to the furnaces, which were withdrawn from the ingots during the microgravity portion of the flight, bringing the chill plates into contact with the bases of the capsules containing the ingots. Solidification was complete in less than 4 minutes. For comparison, several ground-based ingots were solidified in unit gravity under similar conditions. Metallographic analysis of the solidified ingots showed that the macrostructures of the unit-gravity and microgravity ingots were similar, all exhibiting columnar grains. However, the microstructures were significantly different, with the microgravity ingots exhibiting primary dendrite spacings about 40 pct larger than the unit-gravity ingots and secondary dendrite arm spacings about 85 pct larger. The larger dendrite spacings for the ingots solidified in microgravity are explained by lower dendrite growth velocities. The absence of convective mixing in the microgravity ingots slightly increased temperature gradients in the liquid portion of the alloy during solidification, which resulted in decreased growth velocities.

  3. Comparison of Carbon and Hi-Z Primary Collimators for the LHC Phase II Collimation System

    SciTech Connect

    Keller, Lewis; Markiewicz, Thomas; Smith, Jeffrey; Assmann, Ralph; Bracco, Chiara; Weiler, Thomas; /Karlsruhe, Inst. Technol.

    2011-10-31

    A current issue with the LHC collimation system is single-diffractive, off-energy protons from the primary collimators that pass completely through the secondary collimation system and are absorbed immediately downbeam in the cold magnets of the dispersion suppressor section. Simulations suggest that the high impact rate could result in quenching of these magnets. We have studied replacing the 60 cm primary graphite collimators, which remove halo mainly by inelastic strong interactions, with 5.25 mm tungsten, which remove halo mainly by multiple coulomb scattering and thereby reduce the rate of single-diffractive interactions that cause losses in the dispersion suppressor.

  4. 30 CFR 250.916 - What are the CVA's primary duties during the design phase?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... the design phase? (a) The CVA must use good engineering judgment and practices in conducting an... floating facilities, Ensure that the requirements of the U.S. Coast Guard for structural integrity...

  5. 30 CFR 250.916 - What are the CVA's primary duties during the design phase?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... the design phase? (a) The CVA must use good engineering judgment and practices in conducting an... floating facilities, Ensure that the requirements of the U.S. Coast Guard for structural integrity...

  6. 30 CFR 250.916 - What are the CVA's primary duties during the design phase?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... the design phase? (a) The CVA must use good engineering judgment and practices in conducting an... floating facilities, Ensure that the requirements of the U.S. Coast Guard for structural integrity...

  7. Computer modeling of convection in the liquid metal during solidification

    NASA Technical Reports Server (NTRS)

    Lott, R. L., Jr.; Cheng, T. S.

    1988-01-01

    Numerical methods are used to study thermally/gravitationally induced convection during solidification. The primary object is aimed at understanding the flow field in the liquid metal pool due to convection. An Al-0.5Fe weight percent alloy is assumed to fill a small scale vertical rectangular enclosure model for this study. The Alternating Direction Implicit method and Successive Overrelaxation method are employed to solve these equations, which include the energy balance equation coupled with the mass and momentum equations. Both transient and steady state conditions under 1 g and low gravity (0.001 g) are investigated. The solutions for the two-dimensional isotherms and streamlines under 1 g conditions are graphically presented. The quantitative results show that the convection which occurs in the liquid metal pool is very small and is likely to have a negligible effect on the solute redistribution ahead of the solid-liquid interface.

  8. Accelerated Reader as a Literacy Catch-Up Intervention during Primary to Secondary School Transition Phase

    ERIC Educational Resources Information Center

    Siddiqui, Nadia; Gorard, Stephen; See, Beng Huat

    2016-01-01

    This paper describes an evaluation of an internet-based reading programme called Accelerated Reader (AR), which is widely used in UK schools and worldwide. AR is a whole-group reading management and monitoring programme that aims to stimulate the habit of independent reading among primary and secondary age pupils. The evaluation involved 349…

  9. Cellular solidification of transparent monotectics

    NASA Technical Reports Server (NTRS)

    Kaulker, W. F.

    1986-01-01

    Understanding how liquid phase particles are engulfed or pushed during freezing of a monotectic is addressed. The additional complication is that the solid-liquid interface is nonplanar due to constitutional undercooling. Some evidence of particle pushing where the particles are the liquid phase of the montectic was already observed. Cellular freezing of the succinonitrile-glycerol system also occurred. Only a few compositions were tested at that time. The starting materials were not especially pure so that cellular interface observed was likely due to the presence of unkown impurities, the major portion of which was water. Topics addressed include: the effort of modeling the particle pushing process using the computer, establishing an apparatus for the determination of phase diagrams, and the measurement of the temperature gradients with a specimen which will solidify on the temperature gradient microscope stage.

  10. An integrated meso-scale numerical model of melting and solidification in laser welding

    NASA Astrophysics Data System (ADS)

    Duggan, G.; Tong, M.; Browne, D. J.

    2012-01-01

    The authors present an integrated numerical model for the simulation of laser spot welding of an aluminium alloy at meso-scale in 2D. This model deals with the melting of the parent materials which form the weld pool and the subsequent solidification of the liquid metal in the pool, during the welding process. The melting of the parent materials due to the applied heating power is an important phenomenon, which determines the conditions at the onset of solidification, such as the geometry of the weld pool and the distribution of the temperature field. An enthalpy method is employed to predict the melting during the heating phase of welding. A Gaussian distribution is used to model the heat input from the laser. Once the laser beam is switched off and the melting halts, solidification commences. The UCD front tracking model [1,2] for alloy solidification is applied to predict the advancement of the columnar dendritic front, and a volume-averaging formulation is used to simulate nucleation and growth of equiaxed dendrites. A mechanical blocking criterion is used to define dendrite coherency, and the columnar-to-equiaxed transition within the weld pool is predicted.

  11. Real-Time X-Ray Transmission Microscopy for Fundamental Studies Solidification

    NASA Technical Reports Server (NTRS)

    Curreri, Peter A.; Kaukler, William F.; Sen, Subhayu; Peters, Palmer

    1998-01-01

    High resolution real-time X-ray Transmission Microscopy, XTM, has been applied to obtain information fundamental to solidification of optically opaque metallic systems. We have previously reported the measurement of solute profile in the liquid, phase growth, and detailed solid-liquid interfacial morphology of aluminum based alloys with exposure times less than 2 seconds. Recent advances in XTM furnace design have provided an increase in real-time magnification (during solidification) for the XTM from 4OX to 16OX. The increased magnification has enabled for the first time the XTM imaging of real-time growth of fibers and particles with diameters of 5 micrometers. We have applied this system to study of the kinetics of formation and morphological evolution of secondary fibers and particles in Al-Bi monotectic alloys to observe a previously unreported velocity dependent thermo-capillary depletion mechanism for Bi rich liquid which can penetrate many fiber diameters into the solid-liquid interface. In this talk we will discuss application of the XTM to the study the fundamentals of monotectic and eutectic solidification, the enhancement of XTM data with precise solid liquid interfacial temperature and thermal gradient measurement techniques, and the application of this technology to the study of the fundamentals of solidification in microgravity,

  12. Wave dynamics on directional solidification interfaces swept by a flow in a thin sample

    NASA Astrophysics Data System (ADS)

    Jiang, Tania; Georgelin, Marc; Pocheau, Alain

    2015-05-01

    The effects of a transverse flow on the dynamics of a directional solidification interface are studied experimentally in a thin sample. The set-up enables a non-intrusive visualization of the interface and an independent control of both the flow and the solidification conditions. The flow is forced in the sample from an external thermosiphon which provides an accurate steady velocity up to 1.2 mm/s. A transparent melt of succinonitrile is used with a sample depth allowing the solidification of a single layer of microstructures. Downstream inclinations of microstructures and downstream promotion of dendritic sidebranching are observed. Surprisingly, large scale traveling waves involving a wavelength of several cells or dendrites are evidenced on the interface in a large range of conditions. Two kinds of waves are evidenced, one involving a slow velocity, a weak amplitude and a sinusoidal profile, the other a large velocity, a large amplitude and a non-linear profile. Both result from the coupling between solidification and flow and induce striations in the solid phase.

  13. Compact Reconnaissance Imaging Spectrometer for Mars investigation and data set from the Mars Reconnaissance Orbiter's primary science phase

    USGS Publications Warehouse

    Murchie, S.L.; Seelos, F.P.; Hash, C.D.; Humm, D.C.; Malaret, E.; McGovern, J.A.; Choo, T.H.; Seelos, K.D.; Buczkowski, D.L.; Morgan, M.F.; Barnouin-Jha, O. S.; Nair, H.; Taylor, H.W.; Patterson, G.W.; Harvel, C.A.; Mustard, J.F.; Arvidson, R. E.; McGuire, P.; Smith, M.D.; Wolff, M.J.; Titus, T.N.; Bibring, J.-P.; Poulet, F.

    2009-01-01

    The part of the Compact Reconnaissance Imaging Spectrometer (CRISM) for Mars investigation conducted during the Mars Reconnaissance Orbiter's (MRO's) primary science phase was a comprehensive investigation of past aqueous environments, structure of the planet's crust, past climate, and current meteorology. The measurements to implement this investigation include over 9500 targeted observations of surface features taken at spatial resolutions of better than 40 m/pixel, monitoring of seasonal variations in atmospheric aerosols and trace gases, and acquisition of a 200 m/pixel map covering over 55% of Mars in 72 selected wavelengths under conditions of relatively low atmospheric opacity. Key results from these data include recognition of a diversity of aqueous mineral-containing deposits, discovery of a widespread distribution of phyllosilicates in early to middle Noachian units, the first definitive detection of carbonates in bedrock, new constraints on the sequence of events that formed Hesperian-aged, sulfate-rich layered deposits, characterization of seasonal polar processes, and monitoring of the 2007 global dust event. Here we describe CRISM's science investigations during the Primary Science Phase, the data sets that were collected and their calibration and uncertainties, and how they have been processed and made available to the scientific community. We also describe the ongoing investigation during MRO's extended science phase. Copyright 2009 by the American Geophysical Union.

  14. Dehydroepiandrosterone inhibits cell proliferation and improves viability by regulating S phase and mitochondrial permeability in primary rat Leydig cells.

    PubMed

    Liu, Lin; Wang, Dian; Li, Longlong; Ding, Xiao; Ma, Haitian

    2016-07-01

    Dehydroepiandrosterone (DHEA) is widely used as a nutritional supplement and exhibits putative anti‑aging properties. However, the molecular basis of the actions of DHEA, particularly on the biological characteristics of target cells, remain unclear. The aim of the current study was to investigate the effects of DHEA on cell viability, cell proliferation, cell cycle and mitochondrial function in primary rat Leydig cells. Adult Leydig cells were purified by Percoll gradient centrifugation, and cell proliferation was detected using a Click-iT® EdU Assay kit and cell cycle assessment performed using flow cytometry. Mitochondrial membrane potential was detected using JC-1 staining assay. The results of the current study demonstrate that DHEA decreased cell proliferation in a dose‑dependent manner, whereas it improved cell viability in a time‑dependent and dose‑dependent manner. Flow cytometry analysis demonstrated that DHEA treatment increased the S phase cell population and decreased the G2/M cell population. Cyclin A and CDK2 mRNA levels were decreased in primary rat Leydig cells following DHEA treatment. DHEA treatment decreased the transmembrane electrical gradient in primary Leydig cells, whereas treatment significantly increased succinate dehydrogenase activity. These results indicated that DHEA inhibits primary rat Leydig cell proliferation by decreasing cyclin mRNA level, whereas it improves cells viability by modulating the permeability of the mitochondrial membrane and succinate dehydrogenase activity. These findings may demonstrate an important molecular mechanism by which DHEA activity is mediated. PMID:27220727

  15. Dehydroepiandrosterone inhibits cell proliferation and improves viability by regulating S phase and mitochondrial permeability in primary rat Leydig cells

    PubMed Central

    LIU, LIN; WANG, DIAN; LI, LONGLONG; DING, XIAO; MA, HAITIAN

    2016-01-01

    Dehydroepiandrosterone (DHEA) is widely used as a nutritional supplement and exhibits putative anti-aging properties. However, the molecular basis of the actions of DHEA, particularly on the biological characteristics of target cells, remain unclear. The aim of the current study was to investigate the effects of DHEA on cell viability, cell proliferation, cell cycle and mitochondrial function in primary rat Leydig cells. Adult Leydig cells were purified by Percoll gradient centrifugation, and cell proliferation was detected using a Click-iT® EdU Assay kit and cell cycle assessment performed using flow cytometry. Mitochondrial membrane potential was detected using JC-1 staining assay. The results of the current study demonstrate that DHEA decreased cell proliferation in a dose-dependent manner, whereas it improved cell viability in a time-dependent and dose-dependent manner. Flow cytometry analysis demonstrated that DHEA treatment increased the S phase cell population and decreased the G2/M cell population. Cyclin A and CDK2 mRNA levels were decreased in primary rat Leydig cells following DHEA treatment. DHEA treatment decreased the transmembrane electrical gradient in primary Leydig cells, whereas treatment significantly increased succinate dehydrogenase activity. These results indicated that DHEA inhibits primary rat Leydig cell proliferation by decreasing cyclin mRNA level, whereas it improves cells viability by modulating the permeability of the mitochondrial membrane and succinate dehydrogenase activity. These findings may demonstrate an important molecular mechanism by which DHEA activity is mediated. PMID:27220727

  16. 30 CFR 250.917 - What are the CVA's primary duties during the fabrication phase?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... the fabrication phase? (a) The CVA must use good engineering judgment and practices in conducting an...; (vi) Structural tolerances specified and adherence to those tolerances; (vii) The nondestructive...-zone protection; (xi) Erection procedures to ensure that overstressing of structural members does...

  17. 30 CFR 250.917 - What are the CVA's primary duties during the fabrication phase?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... the fabrication phase? (a) The CVA must use good engineering judgment and practices in conducting an...; (vi) Structural tolerances specified and adherence to those tolerances; (vii) The nondestructive...-zone protection; (xi) Erection procedures to ensure that overstressing of structural members does...

  18. 30 CFR 250.917 - What are the CVA's primary duties during the fabrication phase?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... the fabrication phase? (a) The CVA must use good engineering judgment and practices in conducting an...; (vi) Structural tolerances specified and adherence to those tolerances; (vii) The nondestructive...-zone protection; (xi) Erection procedures to ensure that overstressing of structural members does...

  19. Self Assembled Structures by Directional Solidification of Eutectics

    NASA Technical Reports Server (NTRS)

    Dynys, Frederick W.; Sayir, Ali

    2004-01-01

    Interest in ordered porous structures has grown because of there unique properties such as photonic bandgaps, high backing packing density and high surface to volume ratio. Inspired by nature, biometric strategies using self assembled organic molecules dominate the development of hierarchical inorganic structures. Directional solidification of eutectics (DSE) also exhibit self assembly characteristics to form hierarchical metallic and inorganic structures. Crystallization of diphasic materials by DSE can produce two dimensional ordered structures consisting of rods or lamella. By selective removal of phases, DSE is capable to fabricate ordered pore arrays or ordered pin arrays. Criteria and limitations to fabricate hierarchical structures will be presented. Porous structures in silicon base alloys and ceramic systems will be reported.

  20. Estimates and computations for melting and solidification problems

    SciTech Connect

    Greenberg, J. M.

    2003-07-16

    In this paper we focus on melting and solidification processes described by phase-field models and obtain rigorous estimates for such processes. These estimates are derived in Section 2 and guarantee the convergence of solutions to non-constant equilibrium patterns. The most basic results conclude with the inequality (2.31). The estimates in the remainder of Section 2 illustrate what obtains if the initial data is progressively more regular and may be omitted on first reading. We also present some interesting numerical simulations which demonstrate the equilibrium structures and the approach of the system to non-constant equilibrium patterns. The novel feature of these calculations is the linking of the small parameter in the system, {delta}, to the grid spacing, thereby producing solutions with approximate sharp interfaces. Similar ideas have been used by Caginalp and Sokolovsky [1]. A movie of these simulations may be found at http:www.math.cmu.edu/math/people/greenberg.html.

  1. Modelling of binary alloy solidification in the MEPHISTO experiment

    NASA Astrophysics Data System (ADS)

    Leonardi, Eddie; de Vahl Davis, Graham; Timchenko, Victoria; Chen, Peter; Abbaschian, Reza

    2004-05-01

    A modified enthalpy method was used to numerically model experiments on solidification of a bismuth-tin alloy which were performed during the 1997 flight of the MEPHISTO-4 experiment on the US Space Shuttle Columbia. This modified enthalpy method was incorporated into an in-house code SOLCON and a commercial CFD code CFX; Soret effect was taken into account by including an additional thermo-diffusion term into the solute transport equation and the effects of thermal and solutal convection in the microgravity environment and of concentration-dependent melting temperature on the phase change processes were also included. In this paper an overview of the results obtained as part of MEPHISTO project is presented. The numerical solutions are compared with actual microprobe results obtained from the MEPHISTO experiment. To cite this article: E. Leonardi et al., C. R. Mecanique 332 (2004).

  2. Enhanced resistance against Listeria monocytogenes at an early phase of primary infection in pregnant mice: activation of macrophages during pregnancy.

    PubMed Central

    Watanabe, Y; Mitsuyama, M; Sano, M; Nakano, H; Nomoto, K

    1986-01-01

    We investigated the pregnancy-induced changes in macrophage activity which are important in the expression of host defense against infections. Several macrophage functions were examined by using Listeria monocytogenes. In pregnant mice, prolonged survival and enhanced in vivo elimination of bacteria were observed in the early phase of primary infection. Functions of peritoneal macrophages, including in vitro phagocytosis intracellular killing, glucose consumption, generation of superoxide anion, and intracellular beta-glucuronidase activity were shown to be enhanced in pregnant mice. These findings indicate that pregnancy enhances macrophage functions qualitatively. Possible mechanisms for this enhancement and the significance of macrophage activation for pregnant hosts are discussed. PMID:3011673

  3. Influence of electric current pulses on the solidification of Cu-Bi-Sn immiscible alloys

    PubMed Central

    Hongxiang, Jiang; Jie, He; Jiuzhou, Zhao

    2015-01-01

    Continuous solidification experiments were carried out with Cu-Bi-Sn alloys under the effects of Electric Current Pulses (ECPs). A model describing the microstructure evolution was developed. The formation of the microstructure in the continuously solidified alloys was calculated. The calculations demonstrated that ECPs mainly affect the solidification process through changing the energy barrier for the nucleation of the minority phase droplets (MPDs). When the matrix liquid has a lower electric conductivity compared to the MPD, the ECPs lead to a decrease in the energy barrier for the nucleation of the MPDs which then promote the formation of a finely dispersed microstructure. When the matrix liquid has a higher electric conductivity compared to the MPD, the ECPs cause an increase in the energy barrier for the nucleation and lead to the formation of a phase segregated microstructure. PMID:26228180

  4. Solidification of high temperature molten salts for thermal energy storage systems

    NASA Technical Reports Server (NTRS)

    Sheffield, J. W.

    1981-01-01

    The solidification of phase change materials for the high temperature thermal energy storage system of an advanced solar thermal power system has been examined theoretically. In light of the particular thermophysical properties of candidate phase change high temperature salts, such as the eutectic mixture of NaF - MgF2, the heat transfer characteristics of one-dimensional inward solidification for a cylindrical geometry have been studied. The Biot number for the solidified salt is shown to be the critical design parameter for constant extraction heat flux. A fin-on-fin design concept of heat transfer surface augmentation is proposed in an effort to minimize the effects of the salt's low thermal conductivity and large volume change upon fusing.

  5. Thermal control of low-pressure fractionation processes. [in basaltic magma solidification

    NASA Technical Reports Server (NTRS)

    Usselman, T. M.; Hodge, D. S.

    1978-01-01

    Thermal models detailing the solidification paths for shallow basaltic magma chambers (both open and closed systems) were calculated using finite-difference techniques. The total solidification time for closed chambers are comparable to previously published calculations; however, the temperature-time paths are not. These paths are dependent on the phase relations and the crystallinity of the system, because both affect the manner in which the latent heat of crystallization is distributed. In open systems, where a chamber would be periodically replenished with additional parental liquid, calculations indicate that the possibility is strong that a steady-state temperature interval is achieved near a major phase boundary. In these cases it is straightforward to analyze fractionation models of the basaltic liquid evolution and their corresponding cumulate sequences. This steady thermal fractionating state can be invoked to explain large amounts of erupted basalts of similar composition over long time periods from the same volcanic center and some rhythmically layered basic cumulate sequences.

  6. Solidification processing of monotectic alloy matrix composites

    NASA Technical Reports Server (NTRS)

    Frier, Nancy L.; Shiohara, Yuh; Russell, Kenneth C.

    1989-01-01

    Directionally solidified aluminum-indium alloys of the monotectic composition were found to form an in situ rod composite which obeys a lambda exp 2 R = constant relation. The experimental data shows good agreement with previously reported results. A theoretical boundary between cellular and dendritic growth conditions was derived and compared with experiments. The unique wetting characteristics of the monotectic alloys can be utilized to tailor the interface structure in metal matrix composites. Metal matrix composites with monotectic and hypermonotectic Al-In matrices were made by pressure infiltration, remelted and directionally solidified to observe the wetting characteristics of the alloys as well as the effect on structure of solidification in the constrained field of the fiber interstices. Models for monotectic growth are modified to take into account solidification in these constrained fields.

  7. Beyond Finite Size Scaling in Solidification Simulations

    SciTech Connect

    Streitz, F H; Glosli, J N; Patel, M V

    2005-05-19

    Although computer simulation has played a central role in the study of nucleation and growth since the earliest molecular dynamics simulations almost 50 years ago, confusion surrounding the effect of finite size on such simulations have limited their applicability. Modeling solidification in molten tantalum on the BlueGene/L computer, we report here on the first atomistic simulation of solidification that verifies independence from finite size effects during the entire nucleation and growth process, up to the onset of coarsening. We show that finite size scaling theory explains the observed maximal grain sizes for systems up to about 8,000,000 atoms. For larger simulations, a cross-over from finite size scaling to more physical size-independent behavior is observed.

  8. Simulation of solidification in a Bridgman cell

    NASA Technical Reports Server (NTRS)

    Dakhoul, Y. M.; Farmer, R. C.

    1984-01-01

    The Hg/Cd/Te solidification in a Bridgman cell was thermally analyzed by Continuum's VAST code. The energy equation is solved in an axisymmetric, quasi steady domain for both the molten and solid alloy regions. Alloys composition is calculated by a simplified one dimensional model to estimate its effect on melt thermal conductivity and, consequently, on the temperature field within the cell. Solidification is assumed to occur at a fixed temperature of 979 K. Simplified boundary conditions are included to model both the radiant and conductive heat exchange between the furnace walls and the alloy. Calculations are performed to show how the steady state isotherms are affected by: (1) the hot and cold furnace temperatures; (2) boundary condition parameters; and (3) the growth rate which affects the calculated alloy's composition.

  9. TEMHD Effects on Solidification Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Kao, Andrew; Pericleous, Koulis

    2012-01-01

    An unexplored potential exists to control microstructure evolution through the use of external DC magnetic fields. Thermoelectric currents form during solidification and interact with this external field to drive microscopic fluid dynamics within the inter-dendritic region. The convective heat and mass transport can lead to profound changes on the dendritic structure. In this paper the effect of high magnetic fields is demonstrated through the use of both 3-dimensional and 2-dimensional numerical models. The results show that the application of a magnetic field causes significant disruption to the dendritic morphology. Investigation into the underlying mechanism gives initial indicators of how external magnetic fields can either lead to unexpected growth behaviour, or alternatively can be used to control the evolution of microstructure in undercooled melts as encountered in levitated droplet solidification.

  10. A Phase 2 Randomized Dose-Finding Study With Esmirtazapine in Patients With Primary Insomnia.

    PubMed

    Ruwe, Frank; IJzerman-Boon, Pieta; Roth, Thomas; Zammit, Gary; Ivgy-May, Neely

    2016-10-01

    The antidepressant mirtazapine is an alternative to classical hypnotics, and this study investigated the efficacy and safety of esmirtazapine (Org 50081, the maleic acid salt of S-mirtazapine) in patients given a diagnosis of primary insomnia after acute (2-day) treatment. Patients aged 18 to 65 years with primary insomnia were randomized to receive placebo or 1.5-, 3.0-, or 4.5-mg esmirtazapine in a balanced 4-way crossover study; 2 sleep laboratory nights with polysomnography were separated by 5-day, single-blind placebo washout periods. Polysomnography-determined total sleep time (primary end point) and patient-reported total sleep time improved by at least 25 minutes with all 3 doses of esmirtazapine (P ≤ 0.001 vs placebo). Polysomnography-measured wake time after sleep onset (P ≤ 0.0001) and latency to persistent sleep also improved vs placebo (P ≤ 0.01, 3.0 and 4.5 mg). Patient-reported sleep quality improved with 3.0- and 4.5-mg esmirtazapine (P ≤ 0.01 and P ≤ 0.05, respectively, vs placebo). Morning alertness and contentment were not altered after esmirtazapine, and calmness increased with 4.5-mg esmirtazapine vs placebo. Evening questionnaires showed no difference in duration of daytime naps but reduced energy and ability to work/function after esmirtazapine treatment periods vs placebo (P < 0.05), although this effect was limited to the first night of each 2-night period. There were few adverse events, no serious adverse events, or clinically relevant treatment differences in vital signs, laboratory values, or electrocardiogram. Esmirtazapine doses of 1.5 to 4.5 mg/day significantly improved quantity and quality of sleep and were generally well tolerated, with no evidence of safety concerns or consistent pattern of residual effects. PMID:27482970

  11. Complex banded structures in directional solidification processes.

    PubMed

    Korzhenevskii, A L; Rozas, R E; Horbach, J

    2016-01-27

    A combination of theory and numerical simulation is used to investigate impurity superstructures that form in rapid directional solidification (RDS) processes in the presence of a temperature gradient and a pulling velocity with an oscillatory component. Based on a capillary wave model, we show that the RDS processes are associated with a rich morphology of banded structures, including frequency locking and the transition to chaos.

  12. Complex banded structures in directional solidification processes.

    PubMed

    Korzhenevskii, A L; Rozas, R E; Horbach, J

    2016-01-27

    A combination of theory and numerical simulation is used to investigate impurity superstructures that form in rapid directional solidification (RDS) processes in the presence of a temperature gradient and a pulling velocity with an oscillatory component. Based on a capillary wave model, we show that the RDS processes are associated with a rich morphology of banded structures, including frequency locking and the transition to chaos. PMID:26704726

  13. Microwave solidification development for Rocky Flats waste

    SciTech Connect

    Dixon, D.; Erle, R.; Eschen, V.

    1994-04-01

    The Microwave Engineering Team at the Rocky Flats Plant has developed a production-scale system for the treatment of hazardous, radioactive, and mixed wastes using microwave energy. The system produces a vitreous final form which meets the acceptance criteria for shipment and disposal. The technology also has potential for application on various other waste streams from the public and private sectors. Technology transfer opportunities are being identified and pursued for commercialization of the microwave solidification technology.

  14. Linear stability of directional solidification cells

    SciTech Connect

    Kessler, D.A. ); Levine, H. )

    1990-03-15

    We formulate the problem of finding the stability spectrum of the cellular pattern seen in directional solidification. This leads to a nonlinear eigenvalue problem for an integro-differential operator. We solve this problem numerically and compare our results to those obtained by linearizing the eigenvalue problem by employing the quasistatic approximation. Contrary to some recent claims, we find no evidence for a Hopf bifurcation to a dendritic pattern.

  15. The Equiaxed Dendritic Solidification Experiment (EDSE)

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The Equiaxed Dendritic Solidification Experiment (EDSE) is a material sciences investigation under the Formation of Microstructures/pattern formation discipline. The objective is to study the microstructural evolution of and thermal interactions between several equiaxed crystals growing dendritically in a supercooled melt of a pure and transparent substance under diffusion controlled conditions. Dendrites growing at .4 supercooling from a 2 stinger growth chamber for the EDSE in the Microgravity Development Lab (MDL).

  16. IJEMS: Iowa Joint Experiment in Microgravity Solidification

    NASA Technical Reports Server (NTRS)

    Bendle, John R.; Mashl, Steven J.; Hardin, Richard A.

    1995-01-01

    The Iowa Joint Experiment in Microgravity Solidification (IJEMS) is a cooperative effort between Iowa State University and the University of Iowa to study the formation of metal-matrix composites in a microgravity environment. Of particular interest is the interaction between the solid/liquid interface and the particles in suspension. The experiment is scheduled to fly on STS-69, Space Shuttle Endeavor on August 3, 1995. This project is unique in its heavy student participation and cooperation between the universities involved.

  17. Molecular dynamics modelling of solidification in metals

    SciTech Connect

    Boercker, D.B.; Belak, J.; Glosli, J.

    1997-12-31

    Molecular dynamics modeling is used to study the solidification of metals at high pressure and temperature. Constant pressure MD is applied to a simulation cell initially filled with both solid and molten metal. The solid/liquid interface is tracked as a function of time, and the data are used to estimate growth rates of crystallites at high pressure and temperature in Ta and Mg.

  18. Phosphate Bonded Solidification of Radioactive Incinerator Wastes

    SciTech Connect

    Walker, B. W.

    1999-04-13

    The incinerator at the Department of Energy Savannah River Site burns low level radioactive and hazardous waste. Ash and scrubber system waste streams are generated during the incineration process. Phosphate Ceramic technology is being tested to verify the ash and scrubber waste streams can be stabilized using this solidification method. Acceptance criteria for the solid waste forms include leachability, bleed water, compression testing, and permeability. Other testing on the waste forms include x-ray diffraction and scanning electron microscopy.

  19. Primary gas- and particle-phase emissions and secondary organic aerosol production from gasoline and diesel off-road engines.

    PubMed

    Gordon, Timothy D; Tkacik, Daniel S; Presto, Albert A; Zhang, Mang; Jathar, Shantanu H; Nguyen, Ngoc T; Massetti, John; Truong, Tin; Cicero-Fernandez, Pablo; Maddox, Christine; Rieger, Paul; Chattopadhyay, Sulekha; Maldonado, Hector; Maricq, M Matti; Robinson, Allen L

    2013-12-17

    Dilution and smog chamber experiments were performed to characterize the primary emissions and secondary organic aerosol (SOA) formation from gasoline and diesel small off-road engines (SOREs). These engines are high emitters of primary gas- and particle-phase pollutants relative to their fuel consumption. Two- and 4-stroke gasoline SOREs emit much more (up to 3 orders of magnitude more) nonmethane organic gases (NMOGs), primary PM and organic carbon than newer on-road gasoline vehicles (per kg of fuel burned). The primary emissions from a diesel transportation refrigeration unit were similar to those of older, uncontrolled diesel engines used in on-road vehicles (e.g., premodel year 2007 heavy-duty diesel trucks). Two-strokes emitted the largest fractional (and absolute) amount of SOA precursors compared to diesel and 4-stroke gasoline SOREs; however, 35-80% of the NMOG emissions from the engines could not be speciated using traditional gas chromatography or high-performance liquid chromatography. After 3 h of photo-oxidation in a smog chamber, dilute emissions from both 2- and 4-stroke gasoline SOREs produced large amounts of semivolatile SOA. The effective SOA yield (defined as the ratio of SOA mass to estimated mass of reacted precursors) was 2-4% for 2- and 4-stroke SOREs, which is comparable to yields from dilute exhaust from older passenger cars and unburned gasoline. This suggests that much of the SOA production was due to unburned fuel and/or lubrication oil. The total PM contribution of different mobile source categories to the ambient PM burden was calculated by combining primary emission, SOA production and fuel consumption data. Relative to their fuel consumption, SOREs are disproportionately high total PM sources; however, the vastly greater fuel consumption of on-road vehicles renders them (on-road vehicles) the dominant mobile source of ambient PM in the Los Angeles area.

  20. Multimorbidity in primary care in Portugal (MM-PT): a cross-sectional three-phase observational study protocol

    PubMed Central

    Prazeres, Filipe; Santiago, Luiz

    2014-01-01

    Introduction Multimorbidity is defined as the co-occurrence of more than one chronic disease in one person without assigning an index disease. This rapidly increasing phenomenon markedly influences patients’ overall health, has major implications for effective provision of healthcare services and has a significant economic toll on individuals and society. Since Portugal is a country with a growing ageing population, a better understanding of the role of multimorbidity should be assessed. The aim of this study is to further the knowledge of the epidemiological factors associated with multimorbidity in Portugal, chiefly its prevalence and the health and social implications. Methods and analysis This study protocol describes a primary care nationwide three-phase study. The first phase is drawn to access the prevalence and patterns of multimorbidity. In the second phase, individual parameters are assessed, such as patients’ health-related quality of life, perceived family support and unmet health needs of patients with multimorbidity. The third and last phase of this study aims to characterise general practitioners’ knowledge, awareness and practices related to multimorbidity management. Ethics and dissemination The study will be conducted in accordance with the principles expressed in the Declaration of Helsinki. It has full approval from the Ethics Committee of the Faculty of Health Sciences, University of Beira Interior, and the Ethics Committee of the Central Health Region of Portugal. Study results will be published in peer-reviewed journals and presented at national and international conferences. PMID:24531449

  1. Shape of growth cells in directional solidification.

    PubMed

    Pocheau, A; Georgelin, M

    2006-01-01

    The purpose of this study is to characterize experimentally the whole shape of the growth cells displayed in directional solidification and its evolution with respect to control parameters. A library of cells is first built up from observation of directional solidification of a succinonitrile alloy in a large range of pulling velocity, cell spacing, and thermal gradient. Cell boundaries are then extracted from these images and fitted by trial functions on their whole profile, from cell tip to cell grooves. A coherent evolution of the fit parameters with the control parameters is evidenced. It enables us to characterize the whole cell shape by a single function involving only two parameters which vary smoothly in the control parameter space. This, in particular, evidences a continuous evolution of the cell geometry at the cell to dendrite transition which denies the existence of a change of branch of solutions at the occurrence of sidebranching. More generally, this global determination of cell shape complemented with a previous determination of the position of cells in the thermal field (the cell tip undercooling) provides a complete characterization of growth solutions and of their evolutions in this system. It thus brings about a relevant framework for testing and improving theoretical and numerical understanding of cell shapes and cell stability in directional solidification.

  2. Solidification behavior of undercooled liquid aluminum oxide

    SciTech Connect

    Weber, J.K.R.; Anderson, C.D.; Merkley, D.R.; Nordine, P.C.

    1995-03-01

    Solidification of aluminum oxide from undercooled melts was investigated in containerless experiments. Specimens were levitated in a gas jet, stabilized with an acoustic positioning device, and melted with cw CO{sub 2} laser beams. Cooling curves were obtained by optical pyrometry when the laser intensity was reduced. The materials examined were high-purity Verneuil sapphire, 99.5% polycrystalline alumina, and oxide materials recovered from the effluent of an aluminum-fueled rocket motor. The degree of undercooling, the apparent temperature behavior during the thermal arrest on solidification, and the structure of the materials formed were different in argon and oxygen atmospheres. Undercooling of the sapphire and alumina materials was 360 {+-} 10 K in an oxygen atmosphere and approximately 450 K in argon. Melting and solidification of high-purity sapphire resulted in a dendritic and porous polycrystalline material in oxygen. Dense, larger crystals were obtained in argon. Products formed from 99.5% alumina were discolored and the cores were white, indicating impurity segregation effects. More reproducible behavior was observed for the sapphire and 99.5% alumina than for the tungsten-contaminated rocket motor effluent materials.

  3. Rotavirus-like particles primary recovery from insect cells in aqueous two-phase systems.

    PubMed

    Benavides, Jorge; Mena, Jimmy A; Cisneros-Ruiz, Mayra; Ramírez, Octavio T; Palomares, Laura A; Rito-Palomares, Marco

    2006-09-14

    Virus-like particles have a wide range of applications, including vaccination, gene therapy, and even as nanomaterials. Their successful utilization depends on the availability of selective and scalable methods of product recovery and purification that integrate effectively with upstream operations. In this work, a strategy based on aqueous two phase system (ATPS) was developed for the recovery of double-layered rotavirus-like particles (dlRLP) produced by the insect cell-baculovirus expression system. Polyethylene glycol (PEG) molecular mass, PEG and salt concentrations, and volume ratio (Vr, volume of top phase/volume of bottom phase) were evaluated in order to determine the conditions where dlRLP and contaminants concentrated to opposite phases. Two-stage ATPS consisting of PEG 400-phosphate with a Vr of 13.0 and a tie-line length (TLL) of 35% (w/w) at pH 7.0 provided the best conditions for processing highly concentrated crude extract from disrupted cells (dlRLP concentration of 5 microg/mL). In such conditions intracellular dlRLP accumulated in the top phase (recovery of 90%), whereas cell debris remained in the interface. Furthermore, dlRLP from culture supernatants accumulated preferentially in the interface (recovery of 82%) using ATPS with a Vr of 1.0, pH of 7.0, PEG 3350 (10.1%, w/w) and phosphate (10.9%, w/w). The purity of dlRLP from culture supernatant increased up to 55 times after ATPS. The use of ATPS resulted in a recovery process that produced dlRLP with a purity between 6 and 11% and an overall product yield of 85% (w/w), considering purification from intracellular and extracellular dlRLP. Overall, the strategy proposed in this study is simpler than traditional methods for recovering dlRLP, and represents a scalable and economically viable alternative for production processes of vaccines against rotavirus infection with significant scope for generic commercial application.

  4. Directional solidification of lead-copper immiscible alloys in a cyclic gravity environment

    NASA Technical Reports Server (NTRS)

    Shah, S.; Grugel, R. N.; Lichter, B. D.

    1988-01-01

    Hypermonotectic copper-lead alloys were directionally solidified at unit gravity on earth and also in the cyclic gravitational environment attainable during flight of NASA's KC-135 aircraft. In both cases macrosegregation developed that consisted of an initial lead-rich phase above which an aligned composite structure of apparent monotectic composition grew. Differences within these regions are examined, and the suitability of the KC-135 environment for directional solidification of monotectic alloys is discussed.

  5. Influence of surface tension effects on solidification of alloys in space and on ground

    NASA Astrophysics Data System (ADS)

    Zhang, X. M.; Zhuang, Y. X.; Zhu, L. H.; Liu, Q. Q.; Yang, H. C.; Tang, Z. M.

    1999-01-01

    Solidification experiments of AlAl3Ni and AlBi alloys were carried out in space on board a Chinese recoverable satellite. An obvious double vortical radiant structure of AlAl3Ni eutectic and a homogeneous microstructure of AlBi monotectic were obtained. Combined fluid physics and metallography, the effect of surface tension gradient driven convection on the formation of radiant eutectic structure and the Marangoni migration of second-phase droplets in the molten alloy were analyzed.

  6. Directional solidification of lead-copper immiscible alloys in a cyclic gravity environment

    NASA Astrophysics Data System (ADS)

    Shah, S.; Grugel, R. N.; Lichter, B. D.

    1988-11-01

    Hypermonotectic copper-lead alloys were directionally solidified at unit gravity on earth and also in the cyclic gravitational environment attainable during flight of NASA's KC-135 aircraft. In both cases macrosegregation developed that consisted of an initial lead-rich phase above which an aligned composite structure of apparent monotectic composition grew. Differences within these regions are examined, and the suitability of the KC-135 environment for directional solidification of monotectic alloys is discussed.

  7. Solidification studies of Nb-Ge alloys at large degrees of supercooling

    NASA Technical Reports Server (NTRS)

    Lacy, L. L.; Robinson, M. B.; Rathz, T. J.; Evans, N. D.; Bayuzick, R. J.

    1982-01-01

    A 32 meter evacuated drop tube has been used to investigate the solidification of Nb-Ge alloys after deep undercooling. Samples have been supercooled as much as 500 K below the liquidus by using free-fall conditions to eliminate crucible induced nucleation. Final microstructures are dependent on the quenching rates at the bottom of the drop tube with a striking extension of the beta phase solubility limit at the higher quenching rates.

  8. Solidification morphologies in monotectic alloys

    NASA Astrophysics Data System (ADS)

    Wang, F.; Choudhury, A.; Nestler, B.

    2012-01-01

    We model the Fe-Sn system by using a higher order polynomial to describe the free energy of the liquid, and study three different aspects in morphological evolution in the monotectic alloy. Firstly, phase separation, in which case the liquid decomposes into two, is investigated inside of the spinodal decomposition region. Secondly, we study the core-shell morphology in the Fe-Sn alloy, which arises by spinodal decomposition in 2D. Finally, stable lamellar and unstable droplet morphologies in directional solidication are investigated.

  9. High-Speed Synchrotron X-ray Imaging Studies of the Ultrasound Shockwave and Enhanced Flow during Metal Solidification Processes

    NASA Astrophysics Data System (ADS)

    Tan, Dongyue; Lee, Tung Lik; Khong, Jia Chuan; Connolley, Thomas; Fezzaa, Kamel; Mi, Jiawei

    2015-07-01

    The highly dynamic behavior of ultrasonic bubble implosion in liquid metal, the multiphase liquid metal flow containing bubbles and particles, and the interaction between ultrasonic waves and semisolid phases during solidification of metal were studied in situ using the complementary ultrafast and high-speed synchrotron X-ray imaging facilities housed, respectively, at the Advanced Photon Source, Argonne National Laboratory, US, and Diamond Light Source, UK. Real-time ultrafast X-ray imaging of 135,780 frames per second revealed that ultrasonic bubble implosion in a liquid Bi-8 wt pctZn alloy can occur in a single wave period (30 kHz), and the effective region affected by the shockwave at implosion was 3.5 times the original bubble diameter. Furthermore, ultrasound bubbles in liquid metal move faster than the primary particles, and the velocity of bubbles is 70 ~ 100 pct higher than that of the primary particles present in the same locations close to the sonotrode. Ultrasound waves can very effectively create a strong swirling flow in a semisolid melt in less than one second. The energetic flow can detach solid particles from the liquid-solid interface and redistribute them back into the bulk liquid very effectively.

  10. PHASE: a randomised, controlled trial of supervised self-help cognitive behavioural therapy in primary care.

    PubMed Central

    Richards, Ann; Barkham, Michael; Cahill, Jane; Richards, David; Williams, Chris; Heywood, Phil

    2003-01-01

    BACKGROUND: Common mental health problems account for up to 40% of all general practitioner (GP) consultations. Patients have limited access to evidence-based psychological therapies. Cognitive behavioural therapy self-help strategies offer one potential solution. AIM: To determine differences in clinical outcome, patient satisfaction and costs, between a cognitive behavioural-based self-help package facilitated by practice nurses compared to ordinary care by GPs for mild to moderate anxiety and depression. DESIGN OF STUDY: Randomised controlled trial. SETTING: Seventeen primary healthcare teams. METHOD: Patients presenting to their GP with mild to moderate anxiety and/or depression were recruited to the study and randomised to receive either a self-help intervention facilitated by practice nurses or ordinary care. The self-help intervention consisted of up to three appointments: two 1 week apart and a third 3 months later. There were no restrictions on ordinary care. RESULTS: Intention-to-treat analysis showed that patients treated with practice nurse-supported cognitive behavioural therapy self-help attained similar clinical outcomes for similar costs and were more satisfied than patients treated by GPs with ordinary care. On-treatment analysis showed patients receiving the facilitated cognitive behavioural therapy self-help were more likely to be below clinical threshold at 1 month compared to the ordinary care group (odds ratio [OR] = 3.65, 95% confidence interval [CI] = 1.87 to 4.37). This difference was less well marked at 3 months (OR = 1.36, 95% CI = 0.52 to 3.56). CONCLUSION: Facilitated cognitive behavioural self-help may provide a short-term cost-effective clinical benefit for patients with mild to moderate anxiety and depression. This has the potential to help primary care provide a choice of effective psychological as well as pharmacological treatments for mental health problems. PMID:14601351

  11. A Numerical Study of Directional Solidification and Melting in Microgravity

    NASA Technical Reports Server (NTRS)

    Chen, P. Y. P.; Timchenko, V.; Leonardi E.; deVahlDavis, G.; deGroh, H. C., III

    1998-01-01

    A computational model is presented for the study of the solidification and melting of a pure substance and of a binary alloy. The enthalpy method has been used, and incorporated into a commercial CFD code. Three examples of the use of the model are described: the three-dimensional solidification of a pure substance (succinonitrile), the results of which are compared with experiment; an example of the solidification of a bismuth-tin alloy; and a simulation of a solidification and melting experiment done in space known as the MEPHISTO program.

  12. Containerless solidification of acoustically levitated Ni-Sn eutectic alloy

    NASA Astrophysics Data System (ADS)

    Geng, D. L.; Xie, W. J.; Wei, B.

    2012-10-01

    Containerless solidification of Ni-18.7at%Sn eutectic alloy has been achieved with a single-axis acoustic levitator. The temperature, motion, and oscillation of the sample were monitored by a high speed camera. The temperature of the sample can be determined from its image brightness, although the sample moves vertically and horizontally during levitation. The experimentally observed frequency of vertical motion is in good agreement with theoretical prediction. The sample undergoes shape oscillation before solidification finishes. The solidification microstructure of this alloy consists of a mixture of anomalous eutectic plus regular lamellar eutectic. This indicates the achievement of rapid solidification under acoustic levitation condition.

  13. Solidification and microstructures of binary ice-I/hydrate eutectic aggregates

    USGS Publications Warehouse

    McCarthy, C.; Cooper, R.F.; Kirby, S.H.; Rieck, K.D.; Stern, L.A.

    2007-01-01

    The microstructures of two-phase binary aggregates of ice-I + salt-hydrate, prepared by eutectic solidification, have been characterized by cryogenic scanning electron microscopy (CSEM). The specific binary systems studied were H2O-Na2SO4, H2O-MgSO4, H2O-NaCl, and H2O-H2SO4; these were selected based on their potential application to the study of tectonics on the Jovian moon Europa. Homogeneous liquid solutions of eutectic compositions were undercooled modestly (??T - 1-5 ??C); similarly cooled crystalline seeds of the same composition were added to circumvent the thermodynamic barrier to nucleation and to control eutectic growth under (approximately) isothermal conditions. CSEM revealed classic eutectic solidification microstructures with the hydrate phase forming continuous lamellae, discontinuous lamellae, or forming the matrix around rods of ice-I, depending on the volume fractions of the phases and their entropy of dissolving and forming a homogeneous aqueous solution. We quantify aspects of the solidification behavior and microstructures for each system and, with these data articulate anticipated effects of the microstructure on the mechanical responses of the materials.

  14. Effects of the location of a cast in the furnace on flatness of the solidification front in directional solidification

    NASA Astrophysics Data System (ADS)

    Lian, Yuanyuan; Li, Dichen; Zhang, Kai

    2016-10-01

    Many defects of single crystals are caused by the nonplanar solidification front. The transverse temperature gradient at melt-crystal interface results in nonplanar solidification fronts. The location of a cast in the directional solidification furnace affects heat dissipation and thus influences the transverse temperature gradient. This paper presents a criterion and a searching algorithm to find the optimal location of the cast for flattening the solidification front. A numerical simulation was employed for the verification of our method. Additionally, the effects of the size of the cooling device of the furnace on the optimal location, the transverse temperature gradient and the solidification time were discussed. The transverse temperature gradient is reduced about 50% without increasing much solidification time when setting the cast with a varying thickness mould at the optimal location. In addition, the optimal location is mainly influenced by the radius of the cooling ring.

  15. A preliminary study on the relationship between central auditory processing and childhood primary headaches in the intercritical phase

    PubMed Central

    2013-01-01

    Background Recently, an increasing number of articles have appeared on central auditory processing disorders, but in the literature there is only one study that evaluated the possible correlation between migraine in the critical phase and central auditory processing. The aim of our study was to assess the correlation between auditory processing information and childhood primary headaches in the intercritical phase. Methods This is an observational study. We enrolled 54 patients, 30 with primary headache (migraine and tension headache) and 24 normal controls, matched for sex and age. The mean age at first observation was 9 years 10 months; the duration of observational follow-up was 2 years. Both groups had normal audiological and neurological profiles, normal peripheral hearing acuity and normal cognitive and behavioral skills. We excluded patients who had undergone pharmacological prophylactic treatment for headaches in the 6 months preceding the study and subjects with a frequency of headache lower than one every two months. After enrolment, both groups were analyzed with a computerized test battery for Speech Perception Tests in silence and in noise background to assess speech perception disabilities. In addition, with a test battery of Speech Perception Tests, we compared patients with migraines and tension-type headaches. The non-parametric χ2 test, the Mann–Whitney U-test and the Wilcoxon signed ranks test were used for statistical analysis. P-values <0.05 were considered significant and STATA 10 software was used for statistical analyses. Results Our results showed that patients with primary headache (migraine and tension-type headache), had a deficit of auditory processing in noisy background compared to control cases, but we found no significant differences when we compared patients with migraine and tension-type headache. Conclusions This is a work in progress and further studies are needed to assess the relationship between the impairment of

  16. Solidification analysis of a centrifugal atomizer using the Al-32.7wt.percent Cu alloy

    NASA Astrophysics Data System (ADS)

    Osborne, Matthew Gary

    1997-12-01

    A centrifugal atomizer (spinning disk variety) was designed and constructed for the production of spherical metal powders, 100-1000 microns in diameter in an inert atmosphere. Initial atomization experiments revealed the need for a better understanding of how the liquid metal was atomized and how the liquid droplets solidified. To investigate particle atomization, Ag was atomized in air and the process recorded on high-speed film. To investigate particle solidification, Al-32.7wt.% Cu was atomized under inert atmosphere and the subsequent particles were examined microscopically to determine solidification structure and rate. This dissertation details the experimental procedures used in producing the Al-Cu eutectic alloy particles, examination of the particle microstructures, and determination of the solidification characteristics (e.g., solidification rate) of various phases. Finally, correlations are proposed between the operation of the centrifugal atomizer and the observed solidification spacings. This research was supported in part by the Office of Basic Energy Science, USDOE. The Ames laboratory is operated by Iowa State University for the U.S. Department of Energy under contract number W-7405-Eng-82.

  17. Solidification Microstructure, Segregation, and Shrinkage of Fe-Mn-C Twinning-Induced Plasticity Steel by Simulation and Experiment

    NASA Astrophysics Data System (ADS)

    Lan, Peng; Tang, Haiyan; Zhang, Jiaquan

    2016-06-01

    A 3D cellular automaton finite element model with full coupling of heat, flow, and solute transfer incorporating solidification grain nucleation and growth was developed for a multicomponent system. The predicted solidification process, shrinkage porosity, macrosegregation, grain orientation, and microstructure evolution of Fe-22Mn-0.7C twinning-induced plasticity (TWIP) steel match well with the experimental observation and measurement. Based on a new solute microsegregation model using the finite difference method, the thermophysical parameters including solid fraction, thermal conductivity, density, and enthalpy were predicted and compared with the results from thermodynamics and experiment. The effects of flow and solute transfer in the liquid phase on the solidification microstructure of Fe-22Mn-0.7C TWIP steel were compared numerically. Thermal convection decreases the temperature gradient in the liquid steel, leading to the enlargement of the equiaxed zone. Solute enrichment in front of the solid/liquid interface weakens the thermal convection, resulting in a little postponement of columnar-to-equiaxed transition (CET). The CET behavior of Fe-Mn-C TWIP steel during solidification was fully described and mathematically quantized by grain morphology statistics for the first time. A new methodology to figure out the CET location by linear regression of grain mean size with least-squares arithmetic was established, by which a composition design strategy for Fe-Mn-C TWIP steel according to solidification microstructure, matrix compactness, and homogeneity was developed.

  18. Pre-Service Primary Science Teachers' Understandings of the Effect of Temperature and Pressure on Solid-Liquid Phase Transition of Water

    ERIC Educational Resources Information Center

    Yalcin, Fatma Aggul

    2012-01-01

    The aim of this study was to explore pre-service primary teachers' understandings of the effect of temperature and pressure on the solid-liquid phase transition of water. In the study a survey approach was used, and the sample consisted of one-hundred and three, third year pre-service primary science teachers. As a tool for data collection, a test…

  19. Prediction of solidification path and carbide precipitation in Fe-C-V-Cr-Mo-W high speed steels

    NASA Astrophysics Data System (ADS)

    Zhang, Hongwei; Gandin, Charles-André; He, Jicheng; Nakajima, Keiji

    2012-07-01

    The solidification path and precipitation of carbides in the Fe-C-V-Cr-Mo-W high speed steel system are predicted with the help of thermodynamic equilibrium calculations. The Partial Equilibrium (PE) approximation is favoured. According to experimental data for high speed steel samples, the precipitating solidification sequence of carbides, including nature, composition and amount are discussed as a function of the nominal composition of C and V. The results show that the solidification path can be reasonably predicted by the Partial Equilibrium approximation for cooling rate lower than 10 K min-1. The experimental results suffer from the sensitivity limitation of the characterization methods used when the phase fraction becomes too small.

  20. Simulation of thermos-solutal convection induced macrosegregation in a Sn-10%Pb alloy benchmark during columnar solidification

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Wu, M.; Kharicha, A.; Ludwig, A.

    2016-03-01

    In order to investigate the effect of thermo-solutal convection on the formation of macrosegregation during columnar solidification, simulations with a liquid-columnar two phase model were carried out on a 2D rectangular benchmark of Sn-10%Pb alloy. The solidification direction in the benchmark is unidirectional: (') downwards from top to bottom or (2) upwards from bottom to top. Thermal expansion coefficient, solutal expansion coefficient and liquid diffusion coefficient of the melt are found to be key factors influencing the final macrosegregation. The segregation range and distribution are also strongly influenced by the benchmark configurations, e.g. the solidifying direction (upwards or downwards) and boundary conditions, et al. The global macrosegregation range increases with the velocity magnitude of the melt during the process of solidification.

  1. A comparison of acoustic levitation with microgravity processing for containerless solidification of ternary Al-Cu-Sn alloy

    NASA Astrophysics Data System (ADS)

    Yan, N.; Hong, Z. Y.; Geng, D. L.; Wei, B.

    2015-07-01

    The containerless rapid solidification of liquid ternary Al-5 %Cu-65 %Sn immiscible alloy was accomplished at both ultrasonic levitation and free fall conditions. A maximum undercooling of 185 K (0.22 T L) was obtained for the ultrasonically levitated alloy melt at a cooling rate of about 122 K s-1. Meanwhile, the cooling rate of alloy droplets in drop tube varied from 102 to 104 K s-1. The macrosegregation was effectively suppressed through the complex melt flow under ultrasonic levitation condition. In contrast, macrosegregation became conspicuous and core-shell structures with different layers were formed during free fall. The microstructure formation mechanisms during rapid solidification at containerless states were investigated in comparison with the conventional static solidification process. It was found that the liquid phase separation and structural growth kinetics may be modulated by controlling both alloy undercooling and cooling rate.

  2. The feasibility of low-G grey solidification of nodular iron in the F-104 experimental furnace package

    NASA Technical Reports Server (NTRS)

    Curreri, P. A.; Smith, G. A.; Workman, G.

    1983-01-01

    The rationale for low-g experiments with cast iron and the need for solidification in the grey form during these experiments are reviewed. The factors which determine whether an iron melt will solidify grey or white are discussed. Cooling rate versus microstructure was studied for a nodular iron candidate material for F-104 low-g solidification. The study determined that low-g grey solidification, using the present F-104 furnace system, of the nodular iron composition studied is not feasible. Specimen microstructure strongly suggested that the F-104 furnace's gas cooling system was causing excessive localized chill resulting in the nucleation of the unwanted iron carbide phase. A change is suggested, in the quench system design, that could possibly overcome this problem.

  3. Online process control for directional solidification by ultrasonic pulse echo technique.

    PubMed

    Drevermann, A; Pickmann, C; Tiefers, R; Zimmermann, G

    2004-04-01

    A method of controlling the actual growth velocity during directional solidification based on ultrasound has been developed. For this purpose a pulse echo technique is used to measure the actual solidification rate online. This quantity is used to control the furnace velocity. Solidification experiments with metallic alloys and constant furnace velocity often result in non-steady actual solidification rates. Experiments carried out with online process control demonstrate that a really steady-state solidification with a constant solidification rate is achieved.

  4. The effect of ultrasonic vibration on the solidification of light alloys

    NASA Astrophysics Data System (ADS)

    Jian, Xiaogang

    2005-11-01

    This exposition presents a novel thermodynamical and microstructural modification to light alloys, such as aluminum alloys and magnesium alloys, by ultrasonic vibrations. An experimental apparatus which supplied a powerful 1500 Watts at 20 kHz of ultrasonic power was designed and built. Thermodynamic simulations were carried out using the Scheil model to determine the temperature versus solid fraction curve of the alloys. Thermal analysis shows that, with ultrasonic vibration, the steady growth temperature and the minimum supercooling temperature have been elevated; the recalescence time decreased significantly, which indicates a much slower growth rate of primary fcc aluminum grains. Upon ultrasonic vibration, in A356 alloy, fine globular primary aluminum grains were obtained at an unprecedented level of 20 to 40 mum; superfine globular grains less than 20 mum in size were obtained in the area near the ultrasonic radiator; the morphology of eutectic silicon in the alloy was modified from a coarse acicular plate-like form to a finely dispersed rosette-like form, with significantly reduced length, width, and aspect ratio; fine globular grains were also obtained in other aluminum alloys, including A354, 319, 6063, 6061, 2618 alloys; 670°C is the optimum casting temperature for grain refinement of 2618 alloy; not only did magnesium AM60B alloy experience a reduction in size of primary alpha-Mg grains from 760 mum to about 25˜48 mum in diameter, which is much better than other traditional grain refinement methods, but also the volume fraction of eutectic phases was reduced significantly. The mechanisms for ultrasonic influence on solidification have been studied. It was concluded that acoustically induced heterogeneous nucleation, rather than dendrite fragmentation, played a dominant role in the formation of a globular microstructure; high acoustic amplitude/intensity favors the formation of small, spherical primary aluminum grains; the casting temperature of 630

  5. Three-dimensional multiscale modeling of dendritic spacing selection during Al-Si directional solidification

    DOE PAGESBeta

    Tourret, Damien; Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Gibbs, John W.; Karma, Alain

    2015-05-27

    We present a three-dimensional extension of the multiscale dendritic needle network (DNN) model. This approach enables quantitative simulations of the unsteady dynamics of complex hierarchical networks in spatially extended dendritic arrays. We apply the model to directional solidification of Al-9.8 wt.%Si alloy and directly compare the model predictions with measurements from experiments with in situ x-ray imaging. The focus is on the dynamical selection of primary spacings over a range of growth velocities, and the influence of sample geometry on the selection of spacings. Simulation results show good agreement with experiments. The computationally efficient DNN model opens new avenues formore » investigating the dynamics of large dendritic arrays at scales relevant to solidification experiments and processes.« less

  6. Three-dimensional multiscale modeling of dendritic spacing selection during Al-Si directional solidification

    SciTech Connect

    Tourret, Damien; Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Gibbs, John W.; Karma, Alain

    2015-05-27

    We present a three-dimensional extension of the multiscale dendritic needle network (DNN) model. This approach enables quantitative simulations of the unsteady dynamics of complex hierarchical networks in spatially extended dendritic arrays. We apply the model to directional solidification of Al-9.8 wt.%Si alloy and directly compare the model predictions with measurements from experiments with in situ x-ray imaging. The focus is on the dynamical selection of primary spacings over a range of growth velocities, and the influence of sample geometry on the selection of spacings. Simulation results show good agreement with experiments. The computationally efficient DNN model opens new avenues for investigating the dynamics of large dendritic arrays at scales relevant to solidification experiments and processes.

  7. Acupuncture as a primary and independent treatment in the acute phases of sudden sensorineural hearing loss

    PubMed Central

    Jin, Yuanyuan; Lu, Ming

    2016-01-01

    Abstract Sudden sensorineural hearing loss (SSHL) is an otological emergency defined as a rapid hearing loss, seriously affects patient's social life. To data, no study has reported the treatment by acupuncture alone in the acute phase. In this report, Acupuncture and Moxibustion therapy of excitation-focus transfer is outlined. The patient was a 26-year-old young woman who had an SSHL coupled with ear fullness. The patient had no past medical history, but she had undergone variable emotions and had a history of excessive noise exposure. The patient refused to receive any medicine especially steroids and hyperbaric oxygen therapy. She just only received acupuncture treatment. Her symptoms and outcome measurements were improved every week and completely recovered after the last week. Even though the article presents a single case and is based on self-reports, there are very clear trends on how patients with SSHL responded to acupuncture treatments. PMID:27368045

  8. Characterization of particulate and vapor phase polycyclic aromatic hydrocarbons in indoor and outdoor air of primary schools

    NASA Astrophysics Data System (ADS)

    Krugly, Edvinas; Martuzevicius, Dainius; Sidaraviciute, Ruta; Ciuzas, Darius; Prasauskas, Tadas; Kauneliene, Violeta; Stasiulaitiene, Inga; Kliucininkas, Linas

    2014-01-01

    The indoor air of schools is considered as one of the most important factors affecting the health of children. The aim of the presented research was to characterize polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air of schools. The sampling campaign was conducted during the heating season of 2011/2012. Five primary schools from various urban settings in the city of Kaunas, Lithuania. 150 daily samples of particulate and vapor phases were collected during the sampling period. The ultrasonic extractions followed by the gas chromatography and mass spectroscopy (GS/MS) analyses were used for the determination of PAHs. The concentration of total PAHs in the PM2.5 fraction ranged from 20.3 to 131.1 ng m-3, while total suspended particles (TSP) fraction contained from 19.9 to 80.3 ng m-3 of total PAHs. The vapor phase concentration of PAHs ranged from 67.2 to 372.5 ng m-3. The most abundant PAH in both phases was naphthalene. In order to define sources of indoor and outdoor PAHs several source apportionment methods were applied. The analysis revealed that emissions from motor vehicles and fuel burning for heating purposes were the major sources of PAHs in the city of Kaunas.

  9. The biosynthesis of acute-phase proteins in primary cultures of rat hepatocytes.

    PubMed

    Andus, T; Gross, V; Tran-Thi, T A; Schreiber, G; Nagashima, M; Heinrich, P C

    1983-07-01

    The biosynthesis and secretion of alpha 2-macroglobulin, transferrin, alpha 1-acid glycoprotein and alpha 1-proteinase inhibitor were studied in rat hepatocyte primary cultures. After labeling with [35S]methionine, two forms, which can be separated electrophoretically differing by molecular weight, were found for each of the four glycoproteins. The following molecular weights were estimated for the intracellular precursors and the secreted forms: alpha 2-macroglobulin, 176 000 and 182 000; transferrin, 84 000 and 86 000; alpha 1-acid glycoprotein, 39 000 and 43 000-60 000; alpha 1-proteinase inhibitor, 49 000 and 54 000. Carbohydrate moieties could be removed from intracellular forms by treatment with endoglucosaminidase H indicating that their oligosaccharide chains were of the high-mannose type. The extracellular forms were sensitive to sialidase. They incorporated [3H]galactose and [3H]fucose showing that their oligosaccharide chains were of the complex type. Pulse-chase experiments revealed a precursor-product relationship for the high-mannose and the complex type glycoproteins. In the hepatocyte medium newly synthesized albumin was detected after 30 min and newly synthesized glycoproteins after 60 min. Unglycosylated alpha 2-macroglobulin (162 000), transferrin (79 000), alpha 1-acid glycoprotein (23 000), and alpha 1-proteinase inhibitor (41 000) were found in the cells as well as in the medium, when the transfer of oligosaccharide chains onto the polypeptide chains was blocked by tunicamycin. Tunicamycin led to a marked reduction of the secretion of alpha 2-macroglobulin, alpha 1-acid glycoprotein and alpha 1-proteinase inhibitor, whereas the secretion of transferrin was less affected. PMID:6602705

  10. Macrotransport-solidification kinetics modeling of equiaxed dendritic growth: Part II. Computation problems and validation on INCONEL 718 superalloy castings

    NASA Astrophysics Data System (ADS)

    Nastac, L.; Stefanescu, D. M.

    1996-12-01

    In Part I of the article, a new analytical model that describes solidification of equiaxed dendrites was presented. In this part of the article, the model is used to simulate the solidification of INCONEL 718 superalloy castings. The model was incorporated into a commercial finite-element code, PROCAST. A special procedure called microlatent heat method (MLHM) was used for coupling between macroscopic heat flow and microscopic growth kinetics. A criterion for time-stepping selection in microscopic modeling has been derived in conjunction with MLHM. Reductions in computational (CPU) time up to 90 pct over the classic latent heat method were found by adopting this coupling. Validation of the model was performed against experimental data for an INCONEL 718 superalloy casting. In the present calculations, the model for globulitic dendrite was used. The evolution of fraction of solid calculated with the present model was compared with Scheil’s model and experiments. An important feature in solidification of INCONEL 718 is the detrimental Laves phase. Laves phase content is directly related to the intensity of microsegregation of niobium, which is very sensitive to the evolution of the fraction of solid. It was found that there is a critical cooling rate at which the amount of Laves phase is maximum. The critical cooling rate is not a function of material parameters (diffusivity, partition coefficient, etc.). It depends only on the grain size and solidification time. The predictions generated with the present model are shown to agree very well with experiments.

  11. Processing of alnico permanent magnets by advanced directional solidification methods

    DOE PAGESBeta

    Zou, Min; Johnson, Francis; Zhang, Wanming; Zhao, Qi; Rutkowski, Stephen F.; Zhou, Lin; Kramer, Matthew J.

    2016-07-05

    Advanced directional solidification methods have been used to produce large (>15 cm length) castings of Alnico permanent magnets with highly oriented columnar microstructures. In combination with subsequent thermomagnetic and draw thermal treatment, this method was used to enable the high coercivity, high-Titanium Alnico composition of 39% Co, 29.5% Fe, 14% Ni, 7.5% Ti, 7% Al, 3% Cu (wt%) to have an intrinsic coercivity (Hci) of 2.0 kOe, a remanence (Br) of 10.2 kG, and an energy product (BH)max of 10.9 MGOe. These properties compare favorably to typical properties for the commercial Alnico 9. Directional solidification of higher Ti compositions yieldedmore » anisotropic columnar grained microstructures if high heat extraction rates through the mold surface of at least 200 kW/m2 were attained. This was achieved through the use of a thin walled (5 mm thick) high thermal conductivity SiC shell mold extracted from a molten Sn bath at a withdrawal rate of at least 200 mm/h. However, higher Ti compositions did not result in further increases in magnet performance. Images of the microstructures collected by scanning electron microscopy (SEM) reveal a majority α phase with inclusions of secondary αγ phase. Transmission electron microscopy (TEM) reveals that the α phase has a spinodally decomposed microstructure of FeCo-rich needles in a NiAl-rich matrix. In the 7.5% Ti composition the diameter distribution of the FeCo needles was bimodal with the majority having diameters of approximately 50 nm with a small fraction having diameters of approximately 10 nm. The needles formed a mosaic pattern and were elongated along one <001> crystal direction (parallel to the field used during magnetic annealing). Cu precipitates were observed between the needles. Regions of abnormal spinodal morphology appeared to correlate with secondary phase precipitates. The presence of these abnormalities did not prevent the material from displaying superior magnetic properties in the 7.5% Ti

  12. Processing of alnico permanent magnets by advanced directional solidification methods

    NASA Astrophysics Data System (ADS)

    Zou, Min; Johnson, Francis; Zhang, Wanming; Zhao, Qi; Rutkowski, Stephen F.; Zhou, Lin; Kramer, Matthew J.

    2016-12-01

    Advanced directional solidification methods have been used to produce large (>15 cm length) castings of Alnico permanent magnets with highly oriented columnar microstructures. In combination with subsequent thermomagnetic and draw thermal treatment, this method was used to enable the high coercivity, high-Titanium Alnico composition of 39% Co, 29.5% Fe, 14% Ni, 7.5% Ti, 7% Al, 3% Cu (wt%) to have an intrinsic coercivity (Hci) of 2.0 kOe, a remanence (Br) of 10.2 kG, and an energy product (BH)max of 10.9 MGOe. These properties compare favorably to typical properties for the commercial Alnico 9. Directional solidification of higher Ti compositions yielded anisotropic columnar grained microstructures if high heat extraction rates through the mold surface of at least 200 kW/m2 were attained. This was achieved through the use of a thin walled (5 mm thick) high thermal conductivity SiC shell mold extracted from a molten Sn bath at a withdrawal rate of at least 200 mm/h. However, higher Ti compositions did not result in further increases in magnet performance. Images of the microstructures collected by scanning electron microscopy (SEM) reveal a majority α phase with inclusions of secondary αγ phase. Transmission electron microscopy (TEM) reveals that the α phase has a spinodally decomposed microstructure of FeCo-rich needles in a NiAl-rich matrix. In the 7.5% Ti composition the diameter distribution of the FeCo needles was bimodal with the majority having diameters of approximately 50 nm with a small fraction having diameters of approximately 10 nm. The needles formed a mosaic pattern and were elongated along one <001> crystal direction (parallel to the field used during magnetic annealing). Cu precipitates were observed between the needles. Regions of abnormal spinodal morphology appeared to correlate with secondary phase precipitates. The presence of these abnormalities did not prevent the material from displaying superior magnetic properties in the 7.5% Ti

  13. Interactions of Gas-Phase Nitric/Nitrous Acids and Primary Organic Aerosol in the Atmosphere of Houston, TX

    NASA Astrophysics Data System (ADS)

    Ziemba, L. D.; Griffin, R. J.; Dibb, J. E.; Anderson, C. H.; Whitlow, S. I.; Lefer, B. L.; Flynn, J.; Rappenglück, B.

    2007-12-01

    Concentrations of aerosol and gas-phase pollutants were measured on the roof of an 18-story building during the Texas Air Quality Study II Radical and Aerosol Measurement Project (TRAMP) from August 15 through September 28, 2006. Aerosol measurements included size-resolved, non-refractory mass concentrations of ammonium, nitrate, sulfate, chloride, and organic aerosol in submicron particles using an Aerodyne quadrupole aerosol mass spectrometer (Q-AMS). Particulate water-soluble organic carbon (PWSOC) was quantified using a mist chamber/total organic carbon analysis system. Concentration data for gas-phase pollutants included those for nitric acid (HNO3), nitrous acid (HONO), and hydrochloric acid (HCl) collected using a mist chamber/ion chromatographic technique, oxides of nitrogen (NOx) collected using a chemiluminescent method, and carbon monoxide (CO) collected using an infrared gas correlation wheel instrument. Coincident increases in nitrate and organic aerosol mass concentrations were observed on many occasions throughout the measurement campaign, most frequently during the morning rush hour. Based on the lack of organic aerosol processing (defined by the ratio of m/z = 44/57 in the Q-AMS spectra), strong correlation with NOx and CO, and a lack of significant increase in PWSOC concentration, the spikes in organic aerosol were likely associated with primary organic aerosol (POA). During these events, gas-phase HNO3 concentration decreases were observed simultaneously with increases in gas-phase HONO concentrations. These data likely indicate uptake of HNO3 and subsequent heterogeneous conversion to HONO involving POA. Preliminary calculations show that HNO3 partitioning could account for the majority of the observed HONO and aerosol nitrate concentrations during these events. Q-AMS chloride and HCl data also indicate uptake of chloride by particles during these events. This phenomenon was also observed during the night, but these nocturnal events were less

  14. Spinodal decomposition and droplets entrapment in monotectic solidification.

    PubMed

    Wang, F; Choudhury, A; Strassacker, C; Nestler, B

    2012-07-21

    In this article, we present two models to simulate solidification morphologies in monotectic alloys. With the first model, we investigate the morphological evolution under the influence of spinodal decomposition. The model requires that a gradient energy contribution for the concentration field should be incorporated, in order to stabilize phase separation when the liquid concentration is inside the region of miscibility gap. The free energy of the system in this model is derived from direct interpolation of the bulk energy densities. This, however, results in simulation regions in nanometer scale due to contributions from the chemical free energy of the system to the total surface excess. With the second model, our purpose is to develop a phase-field model to simulate scales that are larger than nanometer, where the departures from equilibrium are very small resulting in phase concentrations outside the spinodal region. In view of this, we exclude the concentration gradient contribution to the grand chemical potential functional, and develop a model based on [M. Plapp, Phys. Rev. E 84, 031601 (2011); A. Choudhury and B. Nestler, Phys. Rev. E 85, 021602 (2012)]. The advantage is that the free energy excess across the interface at equilibrium disappears, and hence it is easier to derive the required surface energies with higher interface widths. Due to this benefit, we employ the method to simulate the dynamic entrapment process in the monotectic reaction and study the influence of liquid(1) - liquid(2) surface energy and undercooling on the entrapment process. PMID:22830719

  15. Modeling of microporosity formation during solidification of aluminum alloys

    NASA Astrophysics Data System (ADS)

    Wang, T.; An, D.; Zhang, Q.; Dai, T.; Zhu, M.

    2015-06-01

    A two-dimensional (2D) multi-phase cellular automaton (MCA) model is adopted to simulate the dendrite and microporosity formation during solidification of aluminium alloys. The model involves three phases of liquid, gas, and solid. The effect of liquid-solid phase transformation on the nucleation and growth of porosity, the redistribution and diffusion of solute and hydrogen, and the effects of surface tension and environmental pressure are taken into account. The growth of both dendrite and porosity is simulated using a CA approach. The diffusion of solute and hydrogen is calculated using the finite difference (FD) method. The simulations can reveal the interactive and competitive growth of dendrites and micropores, and the microsegregationof solute and hydrogen. The porosity nuclei with large size are able to grow preferentially, while the growth of the small porosity nuclei is inhibited. Gas pores grow spherically when it is enveloped by liquid. After touching with dendrites, the shapes of pores become irregular. An increased initial hydrogen concentration reduces the incubation time of porosity nucleation, but increases the final percentage of porosity and the average porosity size at the eutectic temperature. With cooling rate decreasing, the competitive growth between gas pores becomes more evident, leading to non-uniform porosity sizes, and more irregular morphology of the porosities with larger size. The simulation results are compared reasonably well with the experimental data reported in literature.

  16. The Waveform Correlation Event Detection System project, Phase II: Testing with the IDC primary network

    SciTech Connect

    Young, C.J.; Beiriger, J.I.; Moore, S.G.

    1998-04-01

    Further improvements to the Waveform Correlation Event Detection System (WCEDS) developed by Sandia Laboratory have made it possible to test the system on the accepted Comprehensive Test Ban Treaty (CTBT) seismic monitoring network. For our test interval we selected a 24-hour period from December 1996, and chose to use the Reviewed Event Bulletin (REB) produced by the Prototype International Data Center (PIDC) as ground truth for evaluating the results. The network is heterogeneous, consisting of array and three-component sites, and as a result requires more flexible waveform processing algorithms than were available in the first version of the system. For simplicity and superior performance, we opted to use the spatial coherency algorithm of Wagner and Owens (1996) for both types of sites. Preliminary tests indicated that the existing version of WCEDS, which ignored directional information, could not achieve satisfactory detection or location performance for many of the smaller events in the REB, particularly those in the south Pacific where the network coverage is unusually sparse. To achieve an acceptable level of performance, we made modifications to include directional consistency checks for the correlations, making the regions of high correlation much less ambiguous. These checks require the production of continuous azimuth and slowness streams for each station, which is accomplished by means of FK processing for the arrays and power polarization processing for the three-component sites. In addition, we added the capability to use multiple frequency-banded data streams for each site to increase sensitivity to phases whose frequency content changes as a function of distance.

  17. Characterization of solidification and weldability of Fe-29Ni-17Co alloys

    SciTech Connect

    Robino, C.V.; Hills, C.R.; Hlava, P.F.

    1992-01-01

    Applications for the controlled thermal expansion alloy Fe-29Ni-17Co often require joining by fusion welding processes. In addition, these applications usually require hermetic and high reliability joints. The small size of typical components normally dictates the use of autogenous welding processes, so that the hot cracking tendency of Fe-29Ni-17Co is of concem. The solidification behavoir and hot cracking tendency of commercial Fe-29Ni-17Co has been evaluated using diffcrential thermal analysis (DTA), Varestraint testing, light and electron microscopy, and laser welding trials. DTA and microstructural analysis indicated that the solidification of Fe-29Ni-17Co occurs as single phase austenite, does not exhibit the formation of terminal solidification phases, and results in only minimal segregation of major alloying elements. Varestraitit testing indicated that the hot cracking behavior of Fe-29Ni-17Co is similar to, though somewhat more pronounced than, 304L and 316 stainless steels. Relative to other Fe-Ni-Co and Ni-based alloys, however, the hot cracking response of this alloy is fiverable. Pulsed laser welding trials indicated that the phosphorus and sulfur levels in this heat of Fe-29Ni-17Co were insufficient to pmmote cracking in bead-on-plate welds.

  18. Characterization of solidification and weldability of Fe-29Ni-17Co alloys.

    SciTech Connect

    Robino, C.V.; Hills, C.R.; Hlava, P.F.

    1992-10-01

    Applications for the controlled thermal expansion alloy Fe-29Ni-17Co often require joining by fusion welding processes. In addition, these applications usually require hermetic and high reliability joints. The small size of typical components normally dictates the use of autogenous welding processes, so that the hot cracking tendency of Fe-29Ni-17Co is of concem. The solidification behavoir and hot cracking tendency of commercial Fe-29Ni-17Co has been evaluated using diffcrential thermal analysis (DTA), Varestraint testing, light and electron microscopy, and laser welding trials. DTA and microstructural analysis indicated that the solidification of Fe-29Ni-17Co occurs as single phase austenite, does not exhibit the formation of terminal solidification phases, and results in only minimal segregation of major alloying elements. Varestraitit testing indicated that the hot cracking behavior of Fe-29Ni-17Co is similar to, though somewhat more pronounced than, 304L and 316 stainless steels. Relative to other Fe-Ni-Co and Ni-based alloys, however, the hot cracking response of this alloy is fiverable. Pulsed laser welding trials indicated that the phosphorus and sulfur levels in this heat of Fe-29Ni-17Co were insufficient to pmmote cracking in bead-on-plate welds.

  19. Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Chen, X. F.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

  20. Solidification of ion exchange resin wastes

    SciTech Connect

    Not Available

    1982-08-01

    Solidification media investigated included portland type I, portland type III and high alumina cements, a proprietary gypsum-based polymer modified cement, and a vinyl ester-styrene thermosetting plastic. Samples formulated with hydraulic cement were analyzed to investigate the effects of resin type, resin loading, waste-to-cement ratio, and water-to-cement ratio. The solidification of cation resin wastes with portland cement was characterized by excessive swelling and cracking of waste forms, both after curing and during immersion testing. Mixed bed resin waste formulations were limited by their cation component. Additives to improve the mechanical properties of portland cement-ion exchange resin waste forms were evaluated. High alumina cement formulations dislayed a resistance to deterioration of mechanical integrity during immersion testing, thus providing a significant advantage over portland cements for the solidification of resin wastes. Properties of cement-ion exchange resin waste forms were examined. An experiment was conducted to study the leachability of /sup 137/Cs, /sup 85/Sr, and /sup 60/Co from resins modified in portland type III and high alumina cements. The cumulative /sup 137/Cs fraction release was at least an order of magnitude greater than that of either /sup 85/Sr or /sup 60/Co. Release rates of /sup 137/Cs in high alumina cement were greater than those in portland III cement by a factor of two.Compressive strength and leach testing were conducted for resin wastes solidified with polymer-modified gypsum based cement. /sup 137/Cs, /sup 85/Sr, and /sup 60/Co fraction releases were about one, two and three orders of magnitude higher, respectively, than in equivalent portland type III cement formulations. As much as 28.6 wt % dry ion exchange resin was successfully solidified using vinyl ester-styrene compared with a maximum of 25 wt % in both portland and gypsum-based cement.

  1. Effects of G-Jitter on Directional Solidification of a Binary Alloy

    NASA Technical Reports Server (NTRS)

    Benjapiyaporn, C.; Timchenko, V.; deVahlDavis, G.; deGroh, H. C., III

    1999-01-01

    A study of directional solidification of a weak binary alloy (specifically, Bi - 1 at% Sn) based on the fixed grid single domain approach is being undertaken. The enthalpy method is used to solve for the temperature field over the computational domain including both the solid and liquid phases; latent heat evolution is treated with the aid of an effective specific heat coefficient. A source term accounting for the release of solute into the liquid during solidification has been incorporated into the solute transport equation. The vorticity-stream function formulation is used to describe thermo-solutal convection in the liquid region. In this paper we present a numerical simulation of g-jitter. A background gravity of 1 microgram has been assumed, and new results for the effects of periodic disturbances over a range of amplitudes and frequencies on solute field and segregation have been presented.

  2. Simulating Solidification in Metals at High Pressure: The Drive to Petascale Computing

    SciTech Connect

    Streitz, F; Glosli, J; Patel, M

    2006-07-26

    We investigate solidification in metal systems ranging in size from 64,000 to 524,288,000 atoms on the IBM BlueGene/L computer at LLNL. Using the newly developed ddcMD code, we achieve performance rates as high as 103 TFlops, with a performance of 101.7 TFlop sustained over a 7 hour run on 131,072 cpus. We demonstrate superb strong and weak scaling. Our calculations are significant as they represent the first atomic-scale model of metal solidification to proceed, without finite size effects, from spontaneous nucleation and growth of solid out of the liquid, through the coalescence phase, and into the onset of coarsening. Thus, our simulations represent the first step towards an atomistic model of nucleation and growth that can directly link atomistic to mesoscopic length scales.

  3. Basic Research on a Latent Heat Thermal Energy Storage by Direct Contact Melting and Solidification

    NASA Astrophysics Data System (ADS)

    Saito, Akihiro; Saito, Akio; Utaka, Yoshio; Okuda, Kenichi; Katayama, Kozo

    A basic experimental research on a latent heat thermal energy storage system, utilizing a simple and effective heat exchange mechanism by a direct contact between the phase change material (PCM) and the heat transfer fluid (HTF) , was shown. In this report, authors proposed the direct contact latent heat thermal energy storage system using industrial paraffin and n-Eicosane as the PCM, and using water as the HTF. The observations were performed concerning the HTF separation from the solid PCM in the solidification process (heat discharging process), and concerning the water pass formation within the solid PCM. Then, it was confirmed that the system worked effectively by using n-Eicosane as the PCM. And authors discussed the mechanism of direct contact solidification process from experimental results.

  4. Advances in multi-scale modeling of solidification and casting processes

    NASA Astrophysics Data System (ADS)

    Liu, Baicheng; Xu, Qingyan; Jing, Tao; Shen, Houfa; Han, Zhiqiang

    2011-04-01

    The development of the aviation, energy and automobile industries requires an advanced integrated product/process R&D systems which could optimize the product and the process design as well. Integrated computational materials engineering (ICME) is a promising approach to fulfill this requirement and make the product and process development efficient, economic, and environmentally friendly. Advances in multi-scale modeling of solidification and casting processes, including mathematical models as well as engineering applications are presented in the paper. Dendrite morphology of magnesium and aluminum alloy of solidification process by using phase field and cellular automaton methods, mathematical models of segregation of large steel ingot, and microstructure models of unidirectionally solidified turbine blade casting are studied and discussed. In addition, some engineering case studies, including microstructure simulation of aluminum casting for automobile industry, segregation of large steel ingot for energy industry, and microstructure simulation of unidirectionally solidified turbine blade castings for aviation industry are discussed.

  5. Temperature Histories of Structural Steel Welds Calculated Using Solidification-Boundary Constraints

    NASA Astrophysics Data System (ADS)

    Lambrakos, S. G.

    2016-09-01

    Temperature histories of structural steel deep-penetration welds are presented, which are calculated using numerical-analytical basis functions and solidification-boundary constraints. These weld temperature histories can be adopted as input data to various types of computational procedures, which include numerical models for prediction of solid-state phase transformations and mechanical response. In addition, these temperature histories can be used parametrically for inverse thermal analysis of welds corresponding to other welding processes whose process conditions are within similar regimes. The present study applies an inverse thermal analysis procedure that uses three-dimensional constraint conditions whose two-dimensional projections are mapped within transverse cross sections of experimentally measured solidification boundaries. In addition, the present study uses experimentally measured estimates of the heat effect zone edge to examine the consistency of calculated temperature histories for steel welds.

  6. Directional solidification of Bi-Mn alloys using an applied magnetic field

    NASA Technical Reports Server (NTRS)

    Decarlo, J. L.; Pirich, R. G.

    1987-01-01

    Off-eutectic compositions of Bi-Mn were directionally solidified in applied transverse magnetic fields up to 3 kG, to determine the effects on thermal and solutal convection. Plane front directional solidification of eutectic and near-eutectic Bi-Mn results in a two-phase rodlike morphology consisting of ferromagnetic MnBi rods in a Bi solid solution matrix. Compositions of either side of the eutectic were studied in growth orientations vertically up and down. Temperature gradient was monitored during growth by means of an in-situ thermocouple. For Bi-rich compositions, the magnetic field appeared to increase mixing as determined from thermal, morphological, chemical, and magnetic analyses. For Mn-rich compositions, morphological and chemical analyses suggest some reduction in mixing due to application of the magnetic force. The capability for carrying out directional solidification of Bi-Mn in high longitudinal magnetic fields was established.

  7. Temperature Histories of Structural Steel Welds Calculated Using Solidification-Boundary Constraints

    NASA Astrophysics Data System (ADS)

    Lambrakos, S. G.

    2016-07-01

    Temperature histories of structural steel deep-penetration welds are presented, which are calculated using numerical-analytical basis functions and solidification-boundary constraints. These weld temperature histories can be adopted as input data to various types of computational procedures, which include numerical models for prediction of solid-state phase transformations and mechanical response. In addition, these temperature histories can be used parametrically for inverse thermal analysis of welds corresponding to other welding processes whose process conditions are within similar regimes. The present study applies an inverse thermal analysis procedure that uses three-dimensional constraint conditions whose two-dimensional projections are mapped within transverse cross sections of experimentally measured solidification boundaries. In addition, the present study uses experimentally measured estimates of the heat effect zone edge to examine the consistency of calculated temperature histories for steel welds.

  8. Alternating tip splitting in directional solidification.

    PubMed

    Utter, B; Ragnarsson, R; Bodenschatz, E

    2001-05-14

    We report experimental results on the tip splitting dynamics of seaweed growth in directional solidification of succinonitrile alloys. Despite the random appearance of the growth, a tip splitting morphology was observed in which the tip alternately splits to the left and to the right. The tip splitting frequency f was found to be related to the growth velocity V as a power law f~V1.5. This finding is consistent with the predictions of a tip splitting model that is also presented. Small anisotropies are shown to lead to different kinds of seaweed morphologies.

  9. Simulation of solidification in a Bridgman cell

    NASA Technical Reports Server (NTRS)

    Dakhoul, Y. M.; Farmer, R. C.

    1984-01-01

    Bridgman-type crystal growth techniques are attractive methods for producing homogeneous, high-quality infrared detector and junction device materials. However, crystal imperfections and interface shapes still must be controlled through modification of the temperature and concentration gradients created during solidification. The objective of this investigation was to study the temperature fields generated by various cell and heatpipe configurations and operating conditions. Continuum's numerical model of the temperature, species concentrations, and velocity fields was used to describe the thermal characteristics of Bridgman cell operation.

  10. [Solidification of volatile oil with graphene oxide].

    PubMed

    Yan, Hong-Mei; Jia, Xiao-Bin; Zhang, Zhen-Hai; Sun, E; Xu, Yi-Hao

    2015-02-01

    To evaluate the properties of solidifying volatile oil with graphene oxide, clove oil and zedoary turmeric oil were solidified by graphene oxide. The amount of graphene oxide was optimized with the eugenol yield and curcumol yield as criteria. Curing powder was characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The effects of graphene oxide on dissolution in vitro and thermal stability of active components were studied. The optimum solidification ratio of graphene oxide to volatile oil was 1:1. Dissolution rate of active components had rare influence while their thermal stability improved after volatile oil was solidified. Solidifying herbal volatile oil with graphene oxide deserves further study. PMID:25975033

  11. Transient magmatic convection prolonged by solidification

    NASA Technical Reports Server (NTRS)

    Brandeis, Genevieve; Marsh, Bruce D.

    1990-01-01

    Fluid dynamic experiments have been conducted on the solidification of a paraffin layer, in order to elucidate the transient stage of convection created in cooling magma by the fact that strong changes in viscosity with crystallization lock up within an inwardly propagating crust much buoyancy that would otherwise be available to drive convection. The interior of the magma remains isothermal, and the temperature decreases uniformly until it is locked at the convective liquidus; the crystals are fine hairlike dendrites without major compositional differentiations. Measurements over time are presented of crust thickness, convective velocity, and heat transfer.

  12. ORNL liquid low-level waste solidification

    SciTech Connect

    Schultz, R.M.; Monk, T.H.; du Mont, S.P.; Helms, R.E.; Keigan, M.V.; Morris, M.I.

    1987-01-01

    The solidification of LLLW at ORNL has developed two basic strategies, a near-term or backup flowsheet is planned to alleviate the immediate capacity problem for storage of concentrated LLLW and a long-term or reference flowsheet is planned to incorporate filtration of the settleable TRU and cesium and strontium decontamination of the LLLW. Presently a feasibility study is evaluating the process alternatives for segregating LLLW from remote-handled transuranic (RH-TRU) sludges, decontamination of the LLLW for beta-gamma radionuclides such as cesium and strontium, and the handling and storage of the RH-TRU sludges and decontamination media. 14 refs.

  13. Dendritic solidification of undercooled Cu-20%Pb hypomonotectic alloy

    SciTech Connect

    Dong, C.; Wei, B.

    1996-05-15

    The Cu-Pb monotectic system is the basis of an important category of wear-resistant materials especially bearing alloys. Its industrially interesting composition ranges from 10 to 50%Pb. In order to produce aligned composites or homogeneous dispersions, extensive research has been performed to investigate the solidification mechanism of Cu-Pb monotectic alloys under directional solidification or microgravity conditions. The preliminary nature of the current space experiments on Cu-Pb monotectic solidification excludes the possibility to draw any really definite conclusions about the influences of microgravity. In contrast, so far still little has been known about the undercooling behavior and rapid solidification kinetics of Cu-Pb monotectic alloys. The objective of the present work is to undercool bulk samples of Cu-Pb alloys to a significant extent and investigate their subsequent rapid solidification process. and this paper reports the related results obtained for Cu-20%Pb hypomonotectic alloy.

  14. Directional solidification studies of ternary austenitic stainless steels

    SciTech Connect

    Carder, K.H.

    1986-01-01

    The transformation of ferrite to austenite during the solidification of stainless steel welds and the subsequent tendencies toward microcracking are topics of considerable ''renewed'' interest. This revival of interest is due mainly to the use of high energy joining processes such as electron beam and laser welding into commercial practice. The rapid rates of solidification and cooling encountered in utilizing these processes have a significant effect on the amount of delta ferrite retained in the microstructure at room temperature. The present study is aimed at obtaining a correlation between solidification rates and microstructure. A directional solidification apparatus with controlled heat flows was designed and developed. This apparatus was used to determine the effect of velocity on the mode of solidification and the amount of ferrite retained in the microstructure at room temperature.

  15. Oscillatory cellular patterns in three-dimensional directional solidification.

    PubMed

    Tourret, D; Debierre, J-M; Song, Y; Mota, F L; Bergeon, N; Guérin, R; Trivedi, R; Billia, B; Karma, A

    2015-10-01

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in microgravity. Directional solidification experiments conducted onboard the International Space Station have allowed us to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 min. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (i.e., low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exists, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is observed in both

  16. Oscillatory cellular patterns in three-dimensional directional solidification

    SciTech Connect

    Tourret, D.; Debierre, J. -M.; Song, Y.; Mota, F. L.; Bergeon, N.; Guerin, R.; Trivedi, R.; Billia, B.; Karma, A.

    2015-09-11

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in micro-gravity. Directional solidification experiments conducted onboard the International Space Station have allowed for the first time to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 minutes. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (\\ie low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exist, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is

  17. Oscillatory cellular patterns in three-dimensional directional solidification

    DOE PAGESBeta

    Tourret, D.; Debierre, J. -M.; Song, Y.; Mota, F. L.; Bergeon, N.; Guerin, R.; Trivedi, R.; Billia, B.; Karma, A.

    2015-09-11

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in micro-gravity. Directional solidification experiments conducted onboard the International Space Station have allowed for the first time to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 minutes. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelatedmore » at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (\\ie low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exist, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global

  18. Oscillatory cellular patterns in three-dimensional directional solidification

    NASA Astrophysics Data System (ADS)

    Tourret, D.; Debierre, J.-M.; Song, Y.; Mota, F. L.; Bergeon, N.; Guérin, R.; Trivedi, R.; Billia, B.; Karma, A.

    2015-10-01

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in microgravity. Directional solidification experiments conducted onboard the International Space Station have allowed us to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 min. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (i.e., low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exists, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is observed in both

  19. Oscillatory cellular patterns in three-dimensional directional solidification.

    PubMed

    Tourret, D; Debierre, J-M; Song, Y; Mota, F L; Bergeon, N; Guérin, R; Trivedi, R; Billia, B; Karma, A

    2015-10-01

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in microgravity. Directional solidification experiments conducted onboard the International Space Station have allowed us to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 min. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (i.e., low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exists, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is observed in both

  20. Effect of Marangoni Convection Generated by Voids on Segregation During Low-G and 1-G Solidification

    NASA Technical Reports Server (NTRS)

    Kassemi, M.; Fripp, A.; Rashidnia, N.; deGroh, H.

    1999-01-01

    Solidification experiments, especially microgravity solidification experiments are often hampered by the evolution of unwanted voids or bubbles in the melt. Although these voids and/or bubbles are highly undesirable, there are currently no effective means of preventing their formation or eliminating their adverse effects, particularly, during low-g experiments. Marangoni Convection caused by these voids can drastically change the transport processes in the melt and, therefore, introduce enormous difficulties in interpreting the results of the space investigations. Recent microgravity experiments by Matthiesen, Andrews, and Fripp are all good examples of how the presence of voids and bubbles affect the outcome of costly space experiments and significantly increase the level of difficulty in interpreting their results. In this work we examine mixing caused by Marangoni convection generated by voids and bubbles in the melt during both 1-g and low-g solidification experiments. The objective of the research is to perform a detailed and comprehensive combined numerical-experimental study of Marangoni convection caused by voids during the solidification process and to show how it can affect segregation and growth conditions by modifying the flow, temperature, and species concentration fields in the melt. While Marangoni convection generated by bubbles and voids in the melt can lead to rapid mixing that would negate the benefits of microgravity processing, it could be exploited in some terrestrial processing to ensure effective communication between a melt/solid interface and a gas phase stoichiometry control zone. Thus we hope that this study will not only aid us in interpreting the results of microgravity solidification experiments hampered by voids and bubbles but to guide us in devising possible means of minimizing the adverse effects of Marangoni convection in future space experiments or of exploiting its beneficial mixing features in ground-based solidification.

  1. Proton Radiography Peers into Metal Solidification

    DOE PAGESBeta

    Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Cooley, Jason C.; Morris, Christopher; Merrill, Frank E.; Hollander, Brian J.; Mariam, Fesseha G.; Ott, Thomas J.; Barker, Martha R.; et al

    2013-06-19

    Historically, metals are cut up and polished to see the structure and to infer how processing influences the evolution. We can now peer into a metal during processing without destroying it using proton radiography. Understanding the link between processing and structure is important because structure profoundly affects the properties of engineering materials. Synchrotron x-ray radiography has enabled real-time glimpses into metal solidification. However, x-ray energies favor the examination of small volumes and low density metals. In this study, we use high energy proton radiography for the first time to image a large metal volume (>10,000 mm3) during melting and solidification.more » We also show complementary x-ray results from a small volume (<1mm3), bridging four orders of magnitude. In conclusion, real-time imaging will enable efficient process development and the control of the structure evolution to make materials with intended properties; it will also permit the development of experimentally informed, predictive structure and process models.« less

  2. Proton Radiography Peers into Metal Solidification

    SciTech Connect

    Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Cooley, Jason C.; Morris, Christopher; Merrill, Frank E.; Hollander, Brian J.; Mariam, Fesseha G.; Ott, Thomas J.; Barker, Martha R.; Tucker, Tim J.; Lee, Wah-Keat; Fezzaa, Kamel; Deriy, Alex; Patterson, Brian M.; Clarke, Kester D.; Montalvo, Joel D.; Field, Robert D.; Thoma, Dan J.; Smith, James L.; Teter, David F.

    2013-06-19

    Historically, metals are cut up and polished to see the structure and to infer how processing influences the evolution. We can now peer into a metal during processing without destroying it using proton radiography. Understanding the link between processing and structure is important because structure profoundly affects the properties of engineering materials. Synchrotron x-ray radiography has enabled real-time glimpses into metal solidification. However, x-ray energies favor the examination of small volumes and low density metals. In this study, we use high energy proton radiography for the first time to image a large metal volume (>10,000 mm3) during melting and solidification. We also show complementary x-ray results from a small volume (<1mm3), bridging four orders of magnitude. In conclusion, real-time imaging will enable efficient process development and the control of the structure evolution to make materials with intended properties; it will also permit the development of experimentally informed, predictive structure and process models.

  3. Method for treating materials for solidification

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Martin, Hollis L.

    1995-01-01

    A method for treating materials such as wastes for solidification to form a solid, substantially nonleachable product. Addition of reactive silica rather than ordinary silica to the material when bringing the initial molar ratio of its silica constituent to a desired ratio within a preselected range increases the solubility and retention of the materials in the solidified matrix. Materials include hazardous, radioactive, mixed, and heavy metal species. Amounts of other constituents of the material, in addition to its silica content are also added so that the molar ratio of each of these constituents is within the preselected ranges for the final solidified product. The mixture is then solidified by cement solidification or vitrification. The method can be used to treat a variety of wastes, including but not limited to spent filter aids from waste water treatment, waste sludges, combinations of spent filter aids and waste sludges, combinations of supernate and waste sludges, incinerator ash, incinerator offgas blowdown, combinations of incinerator ash and offgas blowdown, cementitious wastes and contaminated soils.

  4. The Advanced Automated Directional Solidification Furnace

    NASA Technical Reports Server (NTRS)

    Gillies, D. C.; Reeves, F. A.; Jeter, L. B.; Sledd, J. D.; Cole, J. M.; Lehoczky, S. L.

    1996-01-01

    The Advanced Automated Directional Solidification Furnace (AADSF) is a five zone tubular furnace designed for Bridgman-Stockbarger, other techniques of crystal growth involving multiple temperature zones such as vapor transport experiments and other materials science experiments. The five zones are primarily designed to produce uniform hot and cold temperature regions separated by an adiabatic region constructed of a heat extraction plate and an insert to reduce radiation from the hot to the cold zone. The hot and cold zone temperatures are designed to reach 1600 C and 1100 C, respectively. AADSF operates on a Multi-Purpose Experiment Support Structure (MPESS) within the cargo bay of the Space Shuttle on the United States Microgravity Payload (USMP) missions. Two successful flights, both employing the directional solidification or Bridgman Stockbarger technique for crystal growth have been made, and crystals of HgCdTe and PbSnTe grown in microgravity have been produced on USMP-2 and USMP-3, respectively. The addition of a Sample Exchange Mechanism (SEM) will enable three different samples to be processed on future flights including the USMP-4 mission.

  5. Proton Radiography Peers into Metal Solidification

    PubMed Central

    Clarke, Amy; Imhoff, Seth; Gibbs, Paul; Cooley, Jason; Morris, Christopher; Merrill, Frank; Hollander, Brian; Mariam, Fesseha; Ott, Thomas; Barker, Martha; Tucker, Tim; Lee, Wah-Keat; Fezzaa, Kamel; Deriy, Alex; Patterson, Brian; Clarke, Kester; Montalvo, Joel; Field, Robert; Thoma, Dan; Smith, James; Teter, David

    2013-01-01

    Historically, metals are cut up and polished to see the structure and to infer how processing influences the evolution. We can now peer into a metal during processing without destroying it using proton radiography. Understanding the link between processing and structure is important because structure profoundly affects the properties of engineering materials. Synchrotron x-ray radiography has enabled real-time glimpses into metal solidification. However, x-ray energies favor the examination of small volumes and low density metals. Here we use high energy proton radiography for the first time to image a large metal volume (>10,000 mm3) during melting and solidification. We also show complementary x-ray results from a small volume (<1 mm3), bridging four orders of magnitude. Real-time imaging will enable efficient process development and the control of structure evolution to make materials with intended properties; it will also permit the development of experimentally informed, predictive structure and process models. PMID:23779063

  6. Macrosegregation in Al-7Si alloy caused by abrupt cross-section change during directional solidification

    NASA Astrophysics Data System (ADS)

    Ghods, M.; Johnson, L.; Lauer, M.; Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

    2016-09-01

    Hypoeutectic Al-7 wt .% Si alloys were directionally solidified vertically downward in cylindrical molds that incorporated an abrupt cross-section decrease (9.5 mm to 3.2 mm diameter) which, after 5 cm, reverted back to 9.5 mm diameter in a Bridgman furnace; two constant growth speeds and thermal gradients were investigated. Thermosolutal convection and cross-section-change-induced shrinkage flow effects on macrosegregation were investigated. Dendrite clustering and extensive radial macrosegregation was seen, particularly in the larger cross-sections, before contraction and after expansion, this more evident at the lower growth speed. This alloy shows positive longitudinal macrosegregation near cross-section decrease followed by negative macrosegregation right after it; the extent of macrosegregation, however, decreases with increasing growth speed. Primary dendrite steepling intensified as solidification proceeded into the narrower section and negative longitudinal macrosegregation was seen on the re-entrant shelves at expansion. A two-dimensional model accounting for both shrinkage and thermo-solutal convection was used to simulate solidification and the resulting mushy-zone steepling and macrosegregation. The experimentally observed longitudinal and radial macrosegregation associated with the cross-section changes during directional solidification of an Al-7Si alloy is well captured by the numerical simulations.

  7. Modeling of the flow-solidification interaction in thin slab casting

    NASA Astrophysics Data System (ADS)

    Vakhrushev, A.; Wu, M.; Ludwig, A.; Tang, Y.; Hackl, G.; Nitzl, G.

    2012-07-01

    A key issue for modelling the thin slab casting (TSC) is to consider the evolution of the solid shell, which strongly interacts with the turbulent flow and in the meantime is subject to continuous deformation due to the funnel shape (curvature) of the mould. Here an enthalpy-based mixture solidification model with consideration of turbulent flow [Prescott and Incropera, ASME HTD, vol. 280, 1994, pp. 59] is employed, and further enhanced to include the deforming solid shell. The solid velocity in the fully-solidified strand shell and partially-solidified mushy zone is estimated by solving the Laplace's equation. Primary goals of this work are to examine the sensitivity of the modelling result to different model implementation schemes, and to explore the importance of the deforming and moving solid shell in the solidification. Therefore, a 2D benchmark, to mimic the solidification and deformation behaviour of the thin slab casting, is firstly simulated and evaluated. An example of 3D TSC is also presented. Due to the limitation of the current computation resources additional numerical techniques like parallel computing and mesh adaptation are necessarily applied to ensure the calculation accuracy for the full-3D TSC.

  8. Influence of a magnetic field during directional solidification of MAR-M 246 + Hf superalloy

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry; Alter, Wendy; Schmidt, Dianne

    1991-01-01

    An area that has been almost totally overlooked in the optimization of properties in directionally solidified superalloys is the control of microstructural features through the application of a magnetic field during solidification. The influence of a magnetic field on the microstructural features of a nickel-base superalloys is investigated. Studies were performed on the dendritic MAR-M 246+Hf alloy, which was solidified under both a 5 K gauss magnetic field and under no-applied-field conditions. The possible influences of the magnetic field on the solidification process were observed by studying variations in microstructural features including volume fraction, surface area, number, and shape of the carbide particles. Stereological factors analyzed also included primary and secondary dendrite arm spacing and the volume fraction of the interdendritic eutectic constituent. Microprobe analysis was performed to determine the chemistry of the carbides, dendrites, and interdendritic constituents, and how it varied between field and no-field solidification samples. Experiments involving periodic application and removal of the magnetic field were also performed in order to permit a comparison with structural variations observed in a MAR-M 246+Hf alloy solidified during KC-135 high-g, low-g maneuvers.

  9. Spatiotemporal dynamics of oscillatory cellular patterns in three-dimensional directional solidification.

    PubMed

    Bergeon, N; Tourret, D; Chen, L; Debierre, J-M; Guérin, R; Ramirez, A; Billia, B; Karma, A; Trivedi, R

    2013-05-31

    We report results of directional solidification experiments conducted on board the International Space Station and quantitative phase-field modeling of those experiments. The experiments image for the first time in situ the spatially extended dynamics of three-dimensional cellular array patterns formed under microgravity conditions where fluid flow is suppressed. Experiments and phase-field simulations reveal the existence of oscillatory breathing modes with time periods of several 10's of minutes. Oscillating cells are usually noncoherent due to array disorder, with the exception of small areas where the array structure is regular and stable.

  10. Onset of initial planar instability with surface-tension anisotropy during directional solidification.

    PubMed

    Wang, Zhijun; Wang, Jincheng; Yang, Gencang

    2009-11-01

    A simple model is presented to describe the variation of the onset of the initial planar instability with surface tension anisotropy during directional solidification. The effect of surface-tension anisotropy on the incubation time and the initial average wavelength of planar instability are predicted by the simple model quantitatively, which are also verified by phase field simulation. Investigation results reveal that surface-tension anisotropy is one of important factors in the dynamic process of planar instability. The contribution of surface-tension anisotropy to the tilting modulation is also analyzed by comparing the results from the present simple model with those from phase field simulation.

  11. Solidification Processing of Immiscible Liquids in the Presence of Applied Ultrasonic Energy

    NASA Technical Reports Server (NTRS)

    Kim, Shinwood; Grugel, R. N.

    2000-01-01

    Uniform microstructural development during solidification of immiscible liquids on Earth is hampered by inherent density differences between the phases. Microgravity processing minimizes settling but segregation still occurs due to gravity independent wetting and coalescence phenomena. Experiments with the transparent organic, metal analogue, succinonitrile-glycerol system were conducted in conjunction with applied ultrasonic energy. The processing parameters associated with this technique have been evaluated in view of optimizing dispersion uniformity. Experimental results to evaluate microstructural phase distributions, based on other liquid-liquid immiscibility systems, will also be presented.

  12. Spatiotemporal Dynamics of Oscillatory Cellular Patterns in Three-Dimensional Directional Solidification

    NASA Astrophysics Data System (ADS)

    Bergeon, N.; Tourret, D.; Chen, L.; Debierre, J.-M.; Guérin, R.; Ramirez, A.; Billia, B.; Karma, A.; Trivedi, R.

    2013-05-01

    We report results of directional solidification experiments conducted on board the International Space Station and quantitative phase-field modeling of those experiments. The experiments image for the first time in situ the spatially extended dynamics of three-dimensional cellular array patterns formed under microgravity conditions where fluid flow is suppressed. Experiments and phase-field simulations reveal the existence of oscillatory breathing modes with time periods of several 10’s of minutes. Oscillating cells are usually noncoherent due to array disorder, with the exception of small areas where the array structure is regular and stable.

  13. Characterization of Transport and Solidification in the Metal Recycling Processes

    SciTech Connect

    M. A. Ebadian; R. C. Xin; Z. F. Dong

    1997-08-06

    The characterization of the transport and solidification of metal in the melting and casting processes is significant for the optimization of the radioactively contaminated metal recycling and refining processes. . In this research project, the transport process in the melting and solidification of metal was numerically predicted, and the microstructure and radionuclide distribution have been characterized by scanning electron microscope/electron diffractive X-ray (SEWEDX) analysis using cesium chloride (CSC1) as the radionuclide surrogate. In the melting and solidification process, a resistance furnace whose heating and cooling rates are program- controlled in the helium atmosphere was used. The characterization procedures included weighing, melting and solidification, weighing after solidification, sample preparation, and SEM/EDX analysis. This analytical methodology can be used to characterize metal recycling and refining products in order to evaluate the performance of the recycling process. The data obtained provide much valuable information that is necessary for the enhancement of radioactive contaminated metal decontamination and recycling technologies. The numerical method for the prediction of the melting and solidification process can be implemented in the control and monitoring system-of the melting and casting process in radioactive contaminated metal recycling. The use of radionuclide surrogates instead of real radionuclides enables the research to be performed without causing harmfid effects on people or the community. This characterization process has been conducted at the Hemispheric Center for Environmental Technology (HCET) at Florida International University since October 1995. Tests have been conducted on aluminum (Al) and copper (Cu) using cesium chloride (CSCI) as a radionuclide surrogate, and information regarding the radionuclide transfer and distribution in melting and solidification process has been obtained. The numerical simulation of

  14. An adsorption model of the heterogeneous nucleation of solidification

    SciTech Connect

    Kim, W.T.; Cantor, B. . Oxford Centre for Advanced Materials and Composites)

    1994-09-01

    An adsorption model has been developed to describe the heterogeneous nucleation of solidification in an A-B eutectic or monotectic alloy system. The interface between A-rich [alpha] solid and B-rich liquid is treated as a mixture of A solid, B solid, A liquid and B liquid atoms, randomly distributed as a monolayer between the two phases. The interfacial energy is calculated by summing pairwise bonding energies, and is then minimized to determine the equilibrium interface solid fraction and composition. With decreasing temperature, the interface monolayer changes sharply from liquid to solid, with a composition close to pure B. This sharp onset of interface adsorption of solid B atoms corresponds to [alpha] acting as a catalyst for the heterogeneous nucleation of B-rich [beta] solid. Adsorption close to the eutectic temperature and therefore efficient nucleation catalysis is promoted by a large difference between the melting points of A and B, and a small difference between the solid and liquid immiscibilities of A and B. Predicted undercoolings for the onset of adsorption and nucleation catalysis can be obtained directly from simple phase diagram data, and give good agreement with previous measurements in the Ag-Pb and Al-Sn alloy systems.

  15. Numerical study of conjugate transient solidification in an enclosed region

    SciTech Connect

    Viswanath, R.; Jaluria, Y.

    1995-05-01

    Solidification in an enclosed space is investigated, considering conduction in the mold wall. This gives rise to a conjugate, transient problem, with the flow in the liquid driven by thermal buoyancy. An enthalpy formulation is used for the energy equation, with a porous medium approximation for the region undergoing phase change. The governing equations are solved using primitive variables in the physical space. The control volume approach is employed to discretize the equations. The numerical simulation of the phase change process is discussed in detail. The mold is subjected to different thermal conditions at the outer surface, and the effect of these on the shape of the solid-liquid interface, rate of solid formation, and rate of heat transfer quantified. Streamlines, isotherms, and velocity profiles are also obtained. The conditions under which natural convection in the melt can be neglected are investigated. The effects of important design parameters such as the mold material and width, aspect ratio of the cavity, and heat removal rate from the mold are considered in detail. A comparison is made of the important characteristics between the conjugate and nonconjugate cases. The differences in the numerical simulation of these two cases are investigated. Of particular interest are the temperature distributions that arise in the liquid, solid, and mold. It is shown that conjugate transport must be included for a realistic simulation of practical problems.

  16. Real-Time Investigation of Solidification of Metal Matrix Composites

    NASA Technical Reports Server (NTRS)

    Kaukler, William; Sen, Subhayu

    1999-01-01

    Casting of metal matrix composites can develop imperfections either as non- uniform distributions of the reinforcement phases or as outright defects such as porosity. The solidification process itself initiates these problems. To identify or rectify the problems, one must be able to detect and to study how they form. Until, recently this was only possible by experiments that employed transparent metal model organic materials with glass beads to simulate the reinforcing phases. Recent results obtained from a Space Shuttle experiment (using transparent materials) will be used to illustrate the fundamental physics that dictates the final distribution of agglomerates in a casting. We have further extended this real time investigation to aluminum alloys using X-ray microscopy. A variety of interface-particle interactions will be discussed and how they alter the final properties of the composite. A demonstration of how a solid-liquid interface is distorted by nearby voids or particles, particle pushing or engulfment by the interface, formations of wormholes, Aggregation of particles, and particle-induced segregation of alloying elements will be presented.

  17. Rapid solidification and dendrite growth of ternary Fe-Sn-Ge and Cu-Pb-Ge monotectic alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Xuehua; Ruan, Ying; Wang, Weili; Wei, Bingbo

    2007-08-01

    The phase separation and dendrite growth characteristics of ternary Fe-43.9%Sn-10%Ge and Cu-35.5%Pb-5%Ge monotectic alloys were studied systematically by the glass fluxing method under substantial undercooling conditions. The maximum undercoolings obtained in this work are 245 and 257 K, respectively, for these two alloys. All of the solidified samples exhibit serious macrosegregation, indicating that the homogenous alloy melt is separated into two liquid phases prior to rapid solidification. The solidification structures consist of four phases including α-Fe, (Sn), FeSn and FeSn2 in Fe-43.9%Sn-10%Ge ternary alloy, whereas only (Cu) and (Pb) solid solution phases in Cu-35.5%Pb-5%Ge alloy under different undercoolings. In the process of rapid monotectic solidification, α-Fe and (Cu) phases grow in a dendritic mode, and the transition “dendrite→monotectic cell” happens when alloy undercoolings become sufficiently large. The dendrite growth velocities of α-Fe and (Cu) phases are found to increase with undercooling according to an exponential relation.

  18. Solidification Behavior in Newly Designed Ni-Rich Ni-Ti-Based Alloys

    NASA Astrophysics Data System (ADS)

    Samal, Sumanta; Biswas, Krishanu; Phanikumar, Gandham

    2016-10-01

    The present investigation reports phase and microstructure evolution during solidification of novel Ni-rich Ni-Ti-based alloys, Ni60Ti40, Ni50Cu10Ti40, Ni48Cu10Co2Ti40, and Ni48Cu10Co2Ti38Ta2 during suction casting. The design philosophy of the multicomponent alloys involves judicious selection of alloying elements such as Cu, Co, and Ta in the near Ni60Ti40 eutectic alloy by replacing both Ni and Ti so that phase mixture in the microstructure remains the same from the binary to quinary alloy. The basic objective is to study the effect of addition of Cu, Co, and Ta on the phase evolution and transformation in the Ni-rich Ni-Ti-based alloys. The detailed electron microscopic studies on these suction cast alloys reveal the presence of ultrafine eutectic lamellae between NiTi and Ni3Ti phases along with dendritic NiTi and Ti2Ni phases. It has also been observed that in the binary (Ni60Ti40) alloy, the ordered NiTi (B2) phase transforms to trigonal (R) phase followed by NiTi martensitic phase (M-phase), i.e., B2 → R-phase → M-phase during solid-state cooling. However, the addition of alloying elements such as Cu, Co to the binary (Ni60Ti40) alloy suppresses the martensitic transformation of the ordered NiTi (B2) dendrite. Thus, in the ternary and quaternary alloys, the ordered NiTi (B2) phase is transformed to only trigonal (R) phase, i.e., B2 → R-phase. The secondary precipitate of Ti2Ni has been observed in all of the studied alloys. Interestingly, Ni48Cu10Co2Ti38Ta2 quinary alloy shows the disordered nature of NiTi dendrites. The experimentally observed solidification path is in good agreement with Gulliver-Scheil simulated path for binary alloy, whereas simulated solidification path deviates from the experimental results in case of ternary, quaternary, and quinary alloys.

  19. Improved Crystal Quality By Detached Solidification in Microgravity

    NASA Technical Reports Server (NTRS)

    Regel, Liya L.; Wilcox, William R.; Wang, Yaz-Hen; Wang, Jian-Bin

    2003-01-01

    Many microgravity directional solidification experiments yielded ingots with portions that grew without contacting the ampoule wall, leading to greatly improved crystallographic perfection. Our long term goals have been: (1) To develop a complete understanding of all of the phenomena of detached solidification.; (2) To make it possible to achieve detached solidification reproducibly; (3) To increase crystallographic perfection through detached solidification. We have three major achievements to report here: (1) We obtained a new material balance solution for the Moving Meniscus Model of detached solidification. This solution greatly clarifies the physics as well as the roles of the parameters in the system; (2) We achieved detached solidification of InSb growing on earth in BN-coated ampoules; (3) We performed an extensive series of experiments on freezing water that showed how to form multiple gas bubbles or tubes on the ampoule wall. However, these did not propagate around the wall and lead to fully detached solidification unless the ampoule wall was extremely rough and non-wetted.

  20. Solidification science in cast MMCs: The influence of merton flemings

    NASA Astrophysics Data System (ADS)

    Rohatgi, Pradeep; Asthana, Rajiv

    2001-09-01

    The solidification science of cast metalmatrix composites (MMC) evolved as a subset of the broad field of solidification of monolithic alloys pioneered by Merton Flemings and his students. As a result of advances in solidification, the cast MMC field has evolved from its early incarnation—employing empirical research to engineer novel materials using versatile and cost-effective casting techniques—to using solidification-science-based approaches to tailor advanced materials for application-specific needs. The current and emerging applications of cast MMCs in a variety of automotive, aerospace, electronic packaging, and consumer-good industries exemplify the maturity of the field and the materials. Innovations in composite-forming techniques and efforts at wider industrial acceptance of MMCs will undoubtedly continue. However, the scientific principles underlying the solidification microstructure evolution that governs the composite properties have become well established, to a great extent, due to Flemings’ early, pioneering work on monolithic alloys and some of his more recent studies on solidification of reinforced metals. This paper reviews some aspects of solidification of discontinuously reinforced cast metals that owe their current understanding to Flemings’ contributions, in particular, the scientific understanding of macro- and microsegregation, fluidity and rheology of multiphase slurries, and stircasting, semi-solid casting, and preform infiltration. Current research to develop and test prototype components made from cast composites, including Al-flyash, Cu-graphite, Al-graphite, Al-alumina, and SiC-Al, is also presented, along with directions for future research.

  1. The role of rapid solidification processing in the fabrication of fiber reinforced metal matrix composites

    NASA Technical Reports Server (NTRS)

    Locci, Ivan E.; Noebe, Ronald D.

    1989-01-01

    Advanced composite processing techniques for fiber reinforced metal matrix composites require the flexibility to meet several widespread objectives. The development of uniquely desired matrix microstructures and uniformly arrayed fiber spacing with sufficient bonding between fiber and matrix to transmit load between them without degradation to the fiber or matrix are the minimum requirements necessary of any fabrication process. For most applications these criteria can be met by fabricating composite monotapes which are then consolidated into composite panels or more complicated components such as fiber reinforced turbine blades. Regardless of the end component, composite monotapes are the building blocks from which near net shape composite structures can be formed. The most common methods for forming composite monotapes are the powder cloth, foil/fiber, plasma spray, and arc spray processes. These practices, however, employ rapid solidification techniques in processing of the composite matrix phase. Consequently, rapid solidification processes play a vital and yet generally overlooked role in composite fabrication. The future potential of rapid solidification processing is discussed.

  2. Long-lived magnetism from solidification-driven convection on the pallasite parent body.

    PubMed

    Bryson, James F J; Nichols, Claire I O; Herrero-Albillos, Julia; Kronast, Florian; Kasama, Takeshi; Alimadadi, Hossein; van der Laan, Gerrit; Nimmo, Francis; Harrison, Richard J

    2015-01-22

    Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally driven, implying that magnetic activity would have been short-lived. Here we report a time-series palaeomagnetic record derived from nanomagnetic imaging of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measured magnetic field characteristics and cooling rates. Solidification-driven convection was probably common among small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System. PMID:25612050

  3. Stabilization/Solidification of radioactive molten salt waste via gel-route pretreatment.

    PubMed

    Park, Hwan-Seo; Kim, In-Tae; Kim, Hwan-Young; Ryu, Seung-Kon; Kim, Joon-Hyung

    2007-02-15

    The volatilization of radionuclides during the stabilization/solidification of radioactive wastes at high temperatures is one of the major problems to be considered in choosing suitable wasteforms, process, material systems, etc. This paper reports a novel method to convert volatile wastes into nonvolatile compounds via a sol-gel process, which is different from the conventional method using metal-alkoxides and organic solvents. The material system was designed with sodium silicate (Si) as a gelling agent, phosphoric acid (P) as a catalyst/stabilizer, aluminum nitrate (Al) as a property promoter, and H20 as a solvent. A novel structural model for the chemical conversion of molten salt waste, named RPRM (Reaction Product in Reaction Module), was established, and the waste could be solidified with glass matrix via a simple procedure. The leached fraction of Cs and Sr by a PCT leaching method was 0.72% and 0.014%, respectively. In conclusion, the RPRM model isto converttargetwastes into stable and manageable products, not to obtain a specific crystalline product for each radionuclide. This paper suggested a new stabilization/solidification method for salt wastes by establishing the gel-forming material system and showing a practical example, not a new synthesis method of stable crystalline phase. This process, named "gel-route stabilization/solidification (GRSS)", will be a prospective alternative with stable chemical process on the immobilization of salt wastes and various mixed radioactive waste for final disposal.

  4. Containerless drop tube solidification and grain refinement of NiAl3

    NASA Technical Reports Server (NTRS)

    Ethridge, E. C.; Curreri, P. A.; Kelly, M.; Workman, G.; Smith, A. M.; Bond, R.

    1984-01-01

    The possibility of undercooling Ni-Al alloys below the liquidus in order to produce a single phase peritectic structure by containerless drop tube solidification was studied. Containerless process is a technique for both high purity contamination free studies as well as for investigating the undercooling and rapid solidification of alloys by suppression of heterogeneous nucleation on container walls. In order to achieve large undercoolings one must avoid heterogeneous nucleation of crystallization. It was shown that the Marshall Space Flight Center drop tubes ae unique facilities for containerless solidification experiments and large undercoolings are possible with some alloys. The original goal of undercooling the liquid metal well below the liquidus to the peritectic temperature during containerless free to form primarily NiAl3 was achieved. The microstructures were interesting from another point of view. The microstructure from small diameter samples is greatly refined. Small dendrite arm spacings such as these could greatly facilitate the annealing and solid state transformation of the alloy to nearly 10% NiAl3 by reducing the distance over which diffusion needs to occur. This could minimize annealing time and might make it economically feasible to produce NiAl3 alloy.

  5. Segregation effects during solidification in weightless melts. [effects of evaporation and solidification on crystalization

    NASA Technical Reports Server (NTRS)

    Li, C.

    1975-01-01

    Computer programs are developed and used in the study of the combined effects of evaporation and solidification in space processing. The temperature and solute concentration profiles during directional solidification of binary alloys with surface evaporation were mathematically formulated. Computer results are included along with an econotechnical model of crystal growth. This model allows: prediction of crystal size, quality, and cost; systematic selection of the best growth equipment or alloy system; optimization of growth or material parameters; and a maximization of zero-gravity effects. Segregation in GaAs crystals was examined along with vibration effects on GaAs crystal growth. It was found that a unique segregation pattern and strong convention currents exist in GaAs crystal growth. Some beneficial effects from vibration during GaAs growth were discovered. The implications of the results in space processing are indicated.

  6. Numerical simulation and experimental study of transient liquid phase bonding of single crystal superalloys

    NASA Astrophysics Data System (ADS)

    Ghoneim, Adam

    The primary goals of the research in this dissertation are to perform a systematic study to identify and understand the fundamental cause of prolonged processing time during transient liquid phase bonding of difficult-to-bond single crystal Ni-base materials, and use the acquired knowledge to develop an effective way to reduce the isothermal solidification time without sacrificing the single crystalline nature of the base materials. To achieve these objectives, a multi-scale numerical modeling approach, that involves the use of a 2-D fully implicit moving-mesh Finite Element method and a Cellular Automata method, was developed to theoretically investigate the cause of long isothermal solidification times and determine a viable way to minimize the problem. Subsequently, the predictions of the theoretical models are experimentally validated. Contrary to previous suggestions, numerical calculations and experimental verifications have shown that enhanced intergranular diffusivity has a negligible effect on solidification time in cast superalloys and that another important factor must be responsible. In addition, it was found that the concept of competition between solute diffusivity and solubility as predicted by standard analytical TLP bonding models and reported in the literature as a possible cause of long solidification times is not suitable to explain salient experimental observations. In contrast, however, this study shows that the problem of long solidification times, which anomalously increase with temperature is fundamentally caused by departure from diffusion controlled parabolic migration of the liquid-solid interface with holding time during bonding due to a significant reduction in the solute concentration gradient in the base material. Theoretical analyses showed it is possible to minimize the solidification time and prevent formation of stray-grains in joints between single crystal substrates by using a composite powder mixture of brazing alloy and base

  7. Phase selection during crystallization of undercooled liquid eutectic lead-tin alloys

    NASA Technical Reports Server (NTRS)

    Fecht, H. J.

    1991-01-01

    During rapid solidification substantial amounts of undercooling are in general required for formation of metastable phases. Crystallization at varying levels of undercooling and melting of metastable phases were studied during slow cooling and heating of emulsified PB-Sn alloys. Besides the experimental demonstration of the reversibility of metastable phase equilibra, two different principal solidification paths have been identified and compared with the established metastable phase diagram and predictions from classical nucleation theory. The results suggest that the most probable solidification path is described by the 'step rule' resulting in the formation of metastable phases at low undercooling, whereas the stable eutectic phase mixture crystallizes without metastable phase formation at high undercooling.

  8. Evaluation of the Safety and Benefit of Phase I Oncology Trials for Patients With Primary CNS Tumors

    PubMed Central

    Gounder, Mrinal M.; Nayak, Lakshmi; Sahebjam, Solmaz; Muzikansky, Alona; Sanchez, Armando J.; Desideri, Serena; Ye, Xiaobu; Ivy, S. Percy; Nabors, L. Burt; Prados, Michael; Grossman, Stuart; DeAngelis, Lisa M.; Wen, Patrick Y.

    2016-01-01

    Purpose Patients with high-grade gliomas (HGG) are frequently excluded from first-in-human solid tumor trials because of perceived poor prognosis, excessive toxicities, concomitant drug interactions, and poor efficacy. We conducted an analysis of outcomes from select, single-agent phase I studies in patients with HGG. We compared outcomes to pooled analysis of published studies in solid tumors with various molecular and cytotoxic drugs evaluated as single agents or as combinations. Patient and Methods Individual records of patients with recurrent HGG enrolled onto Adult Brain Tumor Consortium trials of single-agent, cytotoxic or molecular agents from 2000 to 2008 were analyzed for baseline characteristics, toxicities, responses, and survival. Results Our analysis included 327 patients with advanced, refractory HGG who were enrolled onto eight trials involving targeted molecular (n = 5) and cytotoxic (n = 3) therapies. At enrollment, patients had a median Karnofsky performance score of 90 and median age of 52 years; 62% were men, 63% had glioblastoma, and the median number of prior systemic chemotherapies was one. Baseline laboratory values were in an acceptable range to meet eligibility criteria. Patients were on the study for a median of two cycles (range, < one to 56 cycles), and 96% were evaluable for primary end points. During cycle 1, grade ≥ 3 nonhematologic and grade ≥ 4 hematologic toxicities were 5% (28 of 565 adverse events) and 0.9% (five of 565 adverse events), respectively, and 66% of these occurred at the highest dose level. There was one death attributed to drug. Overall response rate (complete and partial response) was 5.5%. Median progression-free and overall survival times were 1.8 and 6 months, respectively. Conclusion Patients with HGG who meet standard eligibility criteria may be good candidates for solid tumor phase I studies with single-agent molecular or cytotoxic drugs with favorable preclinical rationale and pharmacokinetic properties

  9. The effect of natural and forced melt convection on dendritic solidification in Ga-In alloys

    NASA Astrophysics Data System (ADS)

    Shevchenko, N.; Roshchupkina, O.; Sokolova, O.; Eckert, S.

    2015-05-01

    The directional solidification of Ga-25 wt%In alloys within a Hele-Shaw cell was visualized by means of X-ray radioscopy. The experimental investigations are especially focused on the impact of melt convection on the dendritic growth. Natural convection occurs during a bottom up solidification because lighter solute is rejected at the solid-liquid interface leading to an unstable density stratification. Forced convection was produced by a rotating wheel with two parallel disks containing at their inner sides a set of permanent NdFeB magnets with alternating polarization. The direction of forced melt flow is almost horizontal at the solidification front whereas local flow velocities in the range between 0.1 and 1.0 mm/s were achieved by controlling the rotation speed of the magnetic wheel. Melt flow induces various effects on the grain morphology primarily caused by the convective transport of solute. Our observations show a facilitation of the growth of primary trunks or lateral branches, suppression of side branching, dendrite remelting and fragmentation. The manifestation of all phenomena depends on the dendrite orientation, local direction and intensity of the flow. The forced flow eliminates the solutal plumes and damps the local fluctuations of solute concentration. It provokes a preferential growth of the secondary arms at the upstream side of the primary dendrite arms, whereas the high solute concentration at the downstream side of the dendrites can inhibit the formation of secondary branches completely. Moreover, the flow changes the inclination angle of the dendrites and the angle between primary trunks and secondary arms.

  10. Localized microstructures induced by fluid flow in directional solidification.

    PubMed

    Jamgotchian, H; Bergeon, N; Benielli, D; Voge, P; Billia, B; Guérin, R

    2001-10-15

    The dynamical process of microstructure localization by multiscale interaction between instabilities is uncovered in directional solidification of transparent alloy. As predicted by Chen and Davis, morphological instability of the interface is observed at inward flow-stagnation regions of the cellular convective field. Depending on the driving force of fluid flow, focus-type and honeycomb-type localized patterns form in the initial transient of solidification, that then evolves with time. In the case of solute-driven flow, the analysis of the onset of thermosolutal convection in initial transient of solidification enables a complete understanding of the dynamics and of the localization of morphological instability.

  11. Solidification Conditions and Microstructure in Continuously Cast Aluminum

    NASA Astrophysics Data System (ADS)

    Buxmann, K.; Gold, E.

    1982-04-01

    The well-known relationship between cell size or dendrite spacing and local solidification time gives the possibility of calculating the thermal parameters of solidification from the microstructure of the as-cast product. As a basis for such calculations, the dendrite spacing of different aluminum castings (DC cast ingots of different diameters, cast in conventional and electromagnetic molds; cast strip from roll casters, belt casters, and block casters; and Properzi cast rod) has been measured through their cross sections. Based on these measurements, a qualitative discussion of the thermal conditions during the solidification of these products is given, and the influence of a variation in the casting conditions discussed.

  12. Capillary-wave description of rapid directional solidification.

    PubMed

    Korzhenevskii, Alexander L; Bausch, Richard; Schmitz, Rudi

    2012-02-01

    A recently introduced capillary-wave description of binary-alloy solidification is generalized to include the procedure of directional solidification. For a class of model systems a universal dispersion relation of the unstable eigenmodes of a planar steady-state solidification front is derived, which readjusts previously known stability considerations. We moreover establish a differential equation for oscillatory motions of a planar interface that offers a limit-cycle scenario for the formation of solute bands and, taking into account the Mullins-Sekerka instability, of banded structures.

  13. Interface Shape and Convection During Solidification and Melting of Succinonitrile

    NASA Technical Reports Server (NTRS)

    Degroh, Henry C., III; Lindstrom, Tiffany

    1994-01-01

    An experimental study was conducted of the crystal growth of succinonitrile during solidification, melting, and no-growth conditions using a horizontal Bridgman furnace and square glass ampoule. For use as input boundary conditions to numerical codes, thermal profiles on the outside of the ampoule at five locations around its periphery were measured along the ampoule's length. Temperatures inside the ampoule were also measured. The shapes of the s/l interface in various two dimensional planes were quantitatively determined. Though interfaces were nondendritic and noncellular, they were not flat, but were highly curved and symmetric in only one unique longitudinal y-z plane (at x=O). The shapes of the interface were dominated by the primary longitudinal flow cell characteristic of shallow cavity flow in horizontal Bridgman; this flow cell was driven by the imposed furnace temperature gradient and caused a 'radical' thermal gradient such that the upper half of the ampoule was hotter than the bottom half. We believe that due to the strong convection, the release of latent heat does not significantly influence the thermal conditions near the interface. We hope that the interface shape and thermal data presented in this paper can be used to optimize crystal growth processes and validate numerical models.

  14. Effects of anisotropic heat conduction on solidification

    SciTech Connect

    Weaver, J.A.; Viskanta, R.

    1989-01-01

    Two-dimensional solidfication influenced by anisotropic heat conductions has been considered. The interfacial energy balance was derived to account for the heat transfer in one direction (x or y) depending on the temperature gradient in both the x and y directions. A parametric study was made to determine the effect of Stefan number, aspect ratio, initial superheat, and thermal conductivity ratios on the solidification rate. Because of the imposed boundary conditions, the interface became skewed and sometimes was not a straight line between the interface position at the upper and lower adiabatic walls (spatially nonlinear along the height). This skewness depends on the thermal conductivity ratio k/sub yy//k/sub yx/. The nonlinearity of the interface is influenced by the solidificaton rate, aspect ratio, and k/sub yy//k/sub yx/.

  15. Convection and morphological stability during directional solidification

    NASA Technical Reports Server (NTRS)

    Coriell, Sam R.; Chernov, A. A.; Murray, Bruce T.; Mcfadden, G. B.

    1994-01-01

    For growth of a vicinal face at constant velocity, the effect of anisotropic interface kinetics on morphological stability is calculated for a binary alloy. The dependence of the interface kinetic coefficient on crystallographic orientation is based on the motion and density of steps. Anisotropic kinetics give rise to traveling waves along the crystal-melt interface, and can lead to a significant enhancement of morphological stability. The stability enhancement increases as the orientation approaches a singular orientation and as the solidification velocity increases. Shear flows interact with the traveling waves and, depending on the direction of the flow, may either stabilize or destabilize the interface. Specific calculations are carried out for germanium-silicon alloys.

  16. TG1042 (Adenovirus-interferon-γ) in Primary Cutaneous B-cell Lymphomas: A Phase II Clinical Trial

    PubMed Central

    Dreno, Brigitte; Urosevic-Maiwald, Mirjana; Kim, Youn; Guitart, Joan; Duvic, Madeleine; Dereure, Olivier; Khammari, Amir; Knol, Anne-Chantal; Derbij, Anna; Lusky, Monika; Didillon, Isabelle; Santoni, Anne-Marie; Acres, Bruce; Bataille, Vincent; Chenard, Marie-Pierre; Bleuzen, Pascal; Limacher, Jean-Marc; Dummer, Reinhard

    2014-01-01

    Rational While a variety of registered therapies exist for Cutaneous T Cell Lymphoma, no such therapy is available for Cutaneous B Cell Therapy. In this context we performed a phase II, open label, multicenter, non-comparative study to evaluate the efficacy and safety of repeated intra-lesional administrations of TG1042 (adenovirus-interferon-γ) in patients with relapsing primary cutaneous B-cell lymphomas (CBCL). Method Thirteen patients have been enrolled and received intralesional injections of TG1042 containing 5×1010 viral particles into up to six lesions simultaneously. Injections were performed on days 1, 8 and 15 of each of four consecutive 28 day cycles. Results Eleven (85%) out of 13 enrolled patients showed an objective response after injections of TG1042. Seven patients (54%) exhibited complete and four (31%) displayed partial response. The median time to disease progression in the study population was 23.5 months (range 6.25 to 26+). Most commonly observed adverse events were minor to moderate flu-like symptoms, fatigue and injection site reactions. Conclusions Our study showed that treatment with TG1042 was associated with a clinical benefit in the majority of the patients with relapsing CBCL, including tumor regression, a clinically meaningful duration of response and a good treatment tolerance. Trial Registration www.clinicaltrials.gov NCT00394693 PMID:24586226

  17. The effects of marine primary biogenic organic aerosols as heterogeneous ice nuclei in mixed-phase clouds

    NASA Astrophysics Data System (ADS)

    Yun, Y.; Penner, J. E.

    2012-12-01

    There have been reports in the literature about marine primary biogenic organic aerosols (marine POA) acting as ice nuclei. These marine POA can be transported to the atmosphere through the bursting of air bubbles by breaking waves. In this study, we add marine POA as heterogeneous ice nuclei in mixed-phase clouds in a coupled general circulation model and aerosol transport model (CAM-IMPACT). The emission of the marine POA is determined by the sea salt emissions and a sea spray organic fraction function. The wet and dry deposition scheme in the CAM-IMPACT model will be extended to treat marine POA. The ice nucleation ability of the marine POA will be determined according to the in situ observation of the surface ice nuclei ratio, as well as the simulated surface concentration of marine POA and other aerosols. Several sensitivity tests will be performed on the sea salt emission flux, the sea spray organic fraction function, as well as the freezing efficiency of marine POA. The simulated ice water amount will be compared to satellite observations. This study attempts to evaluate the effect of marine biological organics as ice nuclei on a global scale.

  18. Noise and Dynamical Pattern Selection in Solidification

    NASA Technical Reports Server (NTRS)

    Kurtze, Douglas A.

    1997-01-01

    The overall goal of this project was to understand in more detail how a pattern-forming system can adjust its spacing. "Pattern-forming systems," in this context, are nonequilibrium contina whose state is determined by experimentally adjustable control parameter. Below some critical value of the control system then has available to it a range of linearly stable, spatially periodic steady states, each characterized by a spacing which can lie anywhere within some band of values. These systems like directional solidification, where the solidification front is planar when the ratio of growth velocity to thermal gradient is below its critical value, but takes on a cellular shape above critical. They also include systems without interfaces, such as Benard convection, where it is the fluid velocity field which changes from zero to something spatially periodic as the control parameter is increased through its critical value. The basic question to be addressed was that of how the system chooses one of its myriad possible spacings when the control parameter is above critical, and in particular the role of noise in the selection process. Previous work on explosive crystallization had suggested that one spacing in the range should be preferred, in the sense that weak noise should eventually drive the system to that spacing. That work had also suggested a heuristic argument for identifying the preferred spacing. The project had three main objectives: to understand in more detail how a pattern-forming system can adjust its spacing; to investigate how noise drives a system to its preferred spacing; and to extend the heuristic argument for a preferred spacing in explosive crystallization to other pattern-forming systems.

  19. Effect of a Transverse Magnetic Field on Stray Grain Formation of Ni-Based Single Crystal Superalloy During Directional Solidification

    NASA Astrophysics Data System (ADS)

    Xuan, Weidong; Liu, Huan; Lan, Jian; Li, Chuanjun; Zhong, Yunbo; Li, Xi; Cao, Guanghui; Ren, Zhongming

    2016-08-01

    The effect of a transverse magnetic field on stray grain formation during directional solidification of superalloy was investigated. Experimental results indicated that the transverse magnetic field effectively suppressed the stray grain formation on the side the primary dendrite diverges from the mold wall. Moreover, the quenched experimental results indicated that the solid/liquid interface shape was obviously changed in a transverse magnetic field. The effect of a transverse magnetic field on stray grain formation was discussed.

  20. Real-time X-ray transmission microscopy for fundamental studies solidification: Al-Al2Au eutectic

    NASA Astrophysics Data System (ADS)

    Curreri, Peter A.; Kaukler, William F.; Sen, Subhayu

    1998-01-01

    High resolution real-time X-ray Transmission Microscopy, XTM, has been applied to obtain information fundamental to solidification of optically opaque metallic systems. We have previously reported the measurement of the solute profile in the liquid, phase growth, and detailed solid-liquid interfacial morphology of aluminum based alloys with exposure times less than 2 seconds. Recent advances in XTM furnace design have provided an increase in real-time magnification (during solidification) for the XTM from 40X to 160X. The increased magnification has enabled for the first time the XTM imaging of real-time growth of fibers and particles with diameters of 5 μm. We have previously applied this system to study the kinetics of formation and morphological evolution of secondary fibers and particles in Al-Bi monotectic alloys. In this paper we present the preliminary results of the first real-time observations of fiber morphology evolution in optically opaque bulk metal sample of Aluminum-Gold eutectic alloy. These studies show that the XTM can be applied to study the fundamentals of eutectic and monotectic solidification. We are currently attempting to apply this technology in the fundamentals of solidification in microgravity.

  1. Real-time X-ray transmission microscopy for fundamental studies solidification: Al-Al{sub 2}Au eutectic

    SciTech Connect

    Curreri, Peter A.; Kaukler, William F.; Sen, Subhayu

    1998-01-15

    High resolution real-time X-ray Transmission Microscopy, XTM, has been applied to obtain information fundamental to solidification of optically opaque metallic systems. We have previously reported the measurement of the solute profile in the liquid, phase growth, and detailed solid-liquid interfacial morphology of aluminum based alloys with exposure times less than 2 seconds. Recent advances in XTM furnace design have provided an increase in real-time magnification (during solidification) for the XTM from 40X to 160X. The increased magnification has enabled for the first time the XTM imaging of real-time growth of fibers and particles with diameters of 5 {mu}m. We have previously applied this system to study the kinetics of formation and morphological evolution of secondary fibers and particles in Al-Bi monotectic alloys. In this paper we present the preliminary results of the first real-time observations of fiber morphology evolution in optically opaque bulk metal sample of Aluminum-Gold eutectic alloy. These studies show that the XTM can be applied to study the fundamentals of eutectic and monotectic solidification. We are currently attempting to apply this technology in the fundamentals of solidification in microgravity.

  2. 3D characterization by tomography of beta Al9Fe2Si2 phase precipitation in a Al6.5Si1Fe alloy

    NASA Astrophysics Data System (ADS)

    Ferdian, D.; Salvo, L.; Lacaze, J.; Tenailleau, C.; Duployer, B.; Malard, B.

    2016-03-01

    The microstructure evolution of beta phase during solidification of a synthetic Al6.5Si1Fe (wt.%) alloy has been investigated by in-situ synchrotron micro-tomography and post-mortem tomography. In-situ solidification was observed at a constant cooling rate of 10°C min-1, from above the alloy's liquidus with the melt at 618°C down to 575°C which is just above the (Al)-Si-beta invariant eutectic reaction. Primary (Al) dendrites nucleated at 608°C, followed by the formation of beta-Al9Fe2Si2 phase starting at 593°C. After a rapid growth stage until 587°C as thin plates, beta phase continued to grow at a paced rate. Thickening of the plates was also evaluated and it was observed that the decrease in the lateral growth rate of the plates did not lead to an increase of their thickening rate. It was noted that the interconnectivity between beta precipitates increased as the solidification progressed. While nucleation of beta phase has previously been reported to occur on the alumina scale formed at the outer surface of the material, it is shown from post mortem tomography that bulk nucleation can occur as well.

  3. ENGINEERING BULLETIN: SOLIDIFICATION/STABILIZATION OF ORGANICS AND INORGANICS

    EPA Science Inventory

    Solidification refers to techniques that encapsulate hazardous waste into a solid material of high structural integrity. Encapsulation involves either fine waste particles (microencapsulation) or a large block or container of wastes (macroencapsulation). Stabilization refe...

  4. Fundamentals of Alloy Solidification Applied to Industrial Processes

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Solidification processes and phenomena, segregation, porosity, gravity effects, fluid flow, undercooling, as well as processing of materials in the microgravity environment of space, now available on space shuttle flights were discussed.

  5. APPLICATIONS ANALYSIS REPORT: CHEMFIX TECHNOLOGIES, INC. - SOLIDIFICATION/STABILIZATION PROCESS

    EPA Science Inventory

    In support of the U.S. Environmental Protection Agency's (EPA) Superfund Innovative Technology Evaluation (SITE) Program, this report evaluates the Chemfix Technologies, Inc. (Chemfix), solidification/stabilization technology for on-site treatment of hazardous waste. The Chemfix ...

  6. Laser ultrasonic detection of the solidification front during casting

    SciTech Connect

    Walter, J.B.; Telschow, K.L.

    1995-10-01

    A real-time sensor that directly measures properties of the solidification front would be a valuable aid to the metal casting industry. Information needed includes solidification front location, shape, and growth dynamics. The use of contacting probes is often undesirable because it can cause contamination and probe deterioration. Noncontacting laser ultrasonics offers an attractive solution to these problems, particularly if access to the free liquid surface is available. This paper presents results of laser ultrasonic measurements of the solidification front in tin and a tin-lead alloy. The ultrasonic waves were generated and detected at the liquid surface. Tin was selected for its low melting point and the availability of a suitable furnace. Results are presented for reflections from stationary and moving solidification fronts.

  7. Technology Demonstration Summary, Chemfix Solidification/Stabilization Process, Clackamas, Oregon

    EPA Science Inventory

    ChemfIx's* patented stabilization/solidification technology was demonstrated at the Portable Equipment Salvage Company (PESC) site in Clackamas, Oregon, as part of the Superfund Innovative Technology Evaluation (SITE) program. The Chemfix process is designed to solidify and sta...

  8. SOLIDIFICATION/STABILIZATION - US ENVIRONMENTAL PROTECTION AGENCY SUPERFUND PROGRAM

    EPA Science Inventory

    This presentation outlines the Superfund program approach to site cleanup, then provides information from actual insitu and exsitu solidification/stabilization remediations to illustrate technology, equipment, field implementation, performance evaluation, cleanup specifications, ...

  9. A benchmark for the validation of solidification modelling algorithms

    NASA Astrophysics Data System (ADS)

    Kaschnitz, E.; Heugenhauser, S.; Schumacher, P.

    2015-06-01

    This work presents two three-dimensional solidification models, which were solved by several commercial solvers (MAGMASOFT, FLOW-3D, ProCAST, WinCast, ANSYS, and OpenFOAM). Surprisingly, the results show noticeable differences. The results are analyzed similar to a round-robin test procedure to obtain reference values for temperatures and their uncertainties at selected positions in the model. The first model is similar to an adiabatic calorimeter with an aluminum alloy solidifying in a copper block. For this model, an analytical solution for the overall temperature at steady state can be calculated. The second model implements additional heat transfer boundary conditions at outer faces. The geometry of the models, the initial and boundary conditions as well as the material properties are kept as simple as possible but, nevertheless, close to a realistic solidification situation. The gained temperature results can be used to validate self-written solidification solvers and check the accuracy of commercial solidification programs.

  10. Solidification of low-volume power plant sludges. Final report

    SciTech Connect

    Bell, N.E.; Halverson, M.A.; Mercer, B.M.

    1981-12-01

    A literature review was conducted to obtain information on the status of hazardous waste solidification technology and application of this technology to low-volume power plant waste sludges. Because of scarcity of sludge composition data, anticipated major components were identified primarily by chemical reactions that are known to occur during treatment of specific wastewaters. Chemical and physical properties of these sludges were critically analyzed for compatibility with several types of commercially available solidification processes. The study pointed out the need for additional information on the nature of these sludges, especially leaching characteristics and the presence of substances that will interfere with solidification processes. Laboratory studies were recommended for evaluation of solidification process which have the greatest potential for converting hazardous low-volume sludges to non-hazardous waste forms.

  11. Spinodal decomposition and droplets entrapment in monotectic solidification

    NASA Astrophysics Data System (ADS)

    Wang, F.; Choudhury, A.; Strassacker, C.; Nestler, B.

    2012-07-01

    In this article, we present two models to simulate solidification morphologies in monotectic alloys. With the first model, we investigate the morphological evolution under the influence of spinodal decomposition. The model requires that a gradient energy contribution for the concentration field should be incorporated, in order to stabilize phase separation when the liquid concentration is inside the region of miscibility gap. The free energy of the system in this model is derived from direct interpolation of the bulk energy densities. This, however, results in simulation regions in nanometer scale due to contributions from the chemical free energy of the system to the total surface excess. With the second model, our purpose is to develop a phase-field model to simulate scales that are larger than nanometer, where the departures from equilibrium are very small resulting in phase concentrations outside the spinodal region. In view of this, we exclude the concentration gradient contribution to the grand chemical potential functional, and develop a model based on [M. Plapp, Phys. Rev. E 84, 031601 (2011), 10.1103/PhysRevE.84.031601; A. Choudhury and B. Nestler, Phys. Rev. E 85, 021602 (2012)], 10.1103/PhysRevE.85.021602. The advantage is that the free energy excess across the interface at equilibrium disappears, and hence it is easier to derive the required surface energies with higher interface widths. Due to this benefit, we employ the method to simulate the dynamic entrapment process in the monotectic reaction and study the influence of liquid1 - liquid2 surface energy and undercooling on the entrapment process.

  12. Solidification of a disk-shaped crystal from a weakly supercooled binary melt.

    PubMed

    Rees Jones, David W; Wells, Andrew J

    2015-08-01

    The physics of ice crystal growth from the liquid phase, especially in the presence of salt, has received much less attention than the growth of snow crystals from the vapor phase. The growth of so-called frazil ice by solidification of a supercooled aqueous salt solution is consistent with crystal growth in the basal plane being limited by the diffusive removal of the latent heat of solidification from the solid-liquid interface, while being limited by attachment kinetics in the perpendicular direction. This leads to the formation of approximately disk-shaped crystals with a low aspect ratio of thickness compared to radius, because radial growth is much faster than axial growth. We calculate numerically how fast disk-shaped crystals grow in both pure and binary melts, accounting for the comparatively slow axial growth, the effect of dissolved solute in the fluid phase, and the difference in thermal properties between solid and fluid phases. We identify the main physical mechanisms that control crystal growth and show that the diffusive removal of both the latent heat released and the salt rejected at the growing interface are significant. Our calculations demonstrate that certain previous parametrizations, based on scaling arguments, substantially underestimate crystal growth rates by a factor of order 10-100 for low aspect ratio disks, and we provide a parametrization for use in models of ice crystal growth in environmental settings.

  13. Solidification of a disk-shaped crystal from a weakly supercooled binary melt

    NASA Astrophysics Data System (ADS)

    Rees Jones, David W.; Wells, Andrew J.

    2015-08-01

    The physics of ice crystal growth from the liquid phase, especially in the presence of salt, has received much less attention than the growth of snow crystals from the vapor phase. The growth of so-called frazil ice by solidification of a supercooled aqueous salt solution is consistent with crystal growth in the basal plane being limited by the diffusive removal of the latent heat of solidification from the solid-liquid interface, while being limited by attachment kinetics in the perpendicular direction. This leads to the formation of approximately disk-shaped crystals with a low aspect ratio of thickness compared to radius, because radial growth is much faster than axial growth. We calculate numerically how fast disk-shaped crystals grow in both pure and binary melts, accounting for the comparatively slow axial growth, the effect of dissolved solute in the fluid phase, and the difference in thermal properties between solid and fluid phases. We identify the main physical mechanisms that control crystal growth and show that the diffusive removal of both the latent heat released and the salt rejected at the growing interface are significant. Our calculations demonstrate that certain previous parametrizations, based on scaling arguments, substantially underestimate crystal growth rates by a factor of order 10-100 for low aspect ratio disks, and we provide a parametrization for use in models of ice crystal growth in environmental settings.

  14. Pulsatile instability in rapid directional solidification - Strongly-nonlinear analysis

    NASA Technical Reports Server (NTRS)

    Merchant, G. J.; Braun, R. J.; Brattkus, K.; Davis, S. H.

    1992-01-01

    In the rapid directional solidification of a dilute binary alloy, analysis reveals that, in addition to the cellular mode of Mullins and Sekerka (1964), there is an oscillatory instability. For the model analyzed by Merchant and Davis (1990), the preferred wavenumber is zero; the mode is one of pulsation. Two strongly nonlinear analyses are performed that describe this pulsatile mode. In the first case, nonequilibrium effects that alter solute rejection at the interface are taken asymptotically small. A nonlinear oscillator equation governs the position of the solid-liquid interface at leading order, and amplitude and phase evolution equations are derived for the uniformly pulsating interface. The analysis provides a uniform description of both subcritical and supercritical bifurcation and the transition between the two. In the second case, nonequilibrium effects that alter solute rejection are taken asymptotically large, and a different nonlinear oscillator equation governs the location of the interface to leading order. A similar analysis allows for the derivation of an amplitude evolution equation for the uniformly pulsating interface. In this case, the bifurcation is always supercritical. The results are used to make predictions about the characteristics of solute bands that would be frozen into the solid.

  15. Impact-activated solidification of cornstarch and water suspensions

    NASA Astrophysics Data System (ADS)

    Waitukaitis, Scott Russell

    Liquids typically offer little resistance to impacting objects . Surprisingly, dense suspensions of liquids mixed with micron-sized particles can provide tremendous impact resistance, even though they appear liquid like when left at rest or perturbed lightly. The most well-known example is a dense mixture of cornstarch and water, which can easily provide enough impact resistance to allow a full-grown person to run across its surface. Previous studies have linked this so-called ``shear thickening'' to experiments carried out under steady state shear and attributed it to hydrodynamic interactions or granular dilation. However, neither of these explanations alone can account for the stress scales required to keep a running person above the free surface. This thesis investigates the mechanism for this impact resistance in dense suspensions. We begin by studying impact directly and watching a rod as it strikes the surface of a dense suspension of cornstarch and water. Using high-speed video and embedded force and acceleration sensing, we show that the rod motion leads to the rapid growth of a solid-like object below the impact site. With X-ray videography to see the dynamics of the suspension interior and laser sheet measurements of the surface profile, we show how this solid drags on the surrounding suspension, creating substantial peripheral flow and leading to the rapid extraction of the impactor's momentum. Suspecting that the solidification below the rod may be related to jamming of the particle sub-phase, we carry out 2D experiments with macroscopic disks to show how uniaxial compression of an initially unjammed system can lead to dynamic jamming fronts. In doing so, we show how these fronts are sensitive to the system's initial packing fraction relative to the point at which it jams and also discover that the widths of these fronts are related to a diverging correlation length. Finally, we take these results back to the suspension, where we perform careful, speed

  16. Solidification of basaltic magma during flow in a dike.

    USGS Publications Warehouse

    Delaney, P.T.; Pollard, D.D.

    1982-01-01

    A model for time-dependent unsteady heat transfer from magma flowing in a dyke is developed. The ratio of solidification T to magma T is the most important parameter. Observations of volcanic fissure eruptions and study of dykes near Ship Rock, New Mexico, show that the low T at dyke margins and the rapidly advancing solidification front predicted by the model are qualitatively correct.-M.S.

  17. A comparative study of quantitative microsegregation analyses performed during the solidification of the Ni-base superalloy CMSX-10

    SciTech Connect

    Seo, Seong-Moon; Jeong, Hi-Won; Ahn, Young-Keun; Yun, Dae Won; Lee, Je-Hyun; Yoo, Young-Soo

    2014-03-01

    Quantitative microsegregation analyses were systematically carried out during the solidification of the Ni-base superalloy CMSX-10 to clarify the methodological effect on the quantification of microsegregation and to fully understand the solidification microstructure. Three experimental techniques, namely, mushy zone quenching (MZQ), planar directional solidification followed by quenching (PDSQ), and random sampling (RS), were implemented for the analysis of microsegregation tendency and the magnitude of solute elements by electron probe microanalysis. The microprobe data and the calculation results of the diffusion field ahead of the solid/liquid (S/L) interface of PDSQ samples revealed that the liquid composition at the S/L interface is significantly influenced by quenching. By applying the PDSQ technique, it was also found that the partition coefficients of all solute elements do not change appreciably during the solidification of primary γ. All three techniques could reasonably predict the segregation behavior of most solute elements. Nevertheless, the RS approach has a tendency to overestimate the magnitude of segregation for most solute elements when compared to the MZQ and PDSQ techniques. Moreover, the segregation direction of Cr and Mo predicted by the RS approach was found to be opposite from the results obtained by the MZQ and PDSQ techniques. This conflicting segregation behavior of Cr and Mo was discussed intensively. It was shown that the formation of Cr-rich areas near the γ/γ′ eutectic in various Ni-base superalloys, including the CMSX-10 alloy, could be successfully explained by the results of microprobe analysis performed on a sample quenched during the planar directional solidification of γ/γ′ eutectic. - Highlights: • Methodological effect on the quantification of microsegregation was clarified. • The liquid composition at the S/L interface was influenced by quenching. • The segregation direction of Cr varied depending on the

  18. Difference in gamma-band phase synchronization during semantic processing of visually presented words from primary and secondary languages.

    PubMed

    Kim, Kyung Hwan; Choi, Jeong Woo; Yoon, Jin

    2009-09-29

    The difference in cortical mechanisms underlying processing different languages has been of great interest. Exploration of local and global functional connections between neuronal activities originating from task-relevant areas can contribute to a more complete understanding on these processes. Semantic processing is known to involve frontal and parietal activities, and thus, functional connection between anterior-posterior regions is expected during semantic processing of visually presented words. The major purpose of this study is to investigate whether a substantial difference in gamma-band phase synchronization (GBPS) is observed during semantic processing of visually presented words from primary (Korean) and secondary (English) languages. Conventional ERP component and evoked gamma-band activity (eGBA) analyses were also performed. Word pairs with closely-related or unrelated meanings were presented to 14 Korean subjects so that N400 event-related potential (ERP) component was evoked. Other components, such as P1, N1, and late positive component, could also be identified. The N1 was shown to be larger for Korean. Response times and N400 latencies were significantly faster for Korean. eGBAs were significantly smaller in response to English at ~100 ms poststimulus, and latencies were considerably delayed. We verified significant GBPS from anterior-posterior electrode pairs, and substantial difference between the two languages emerged in the GBPS pattern during the 200-350 ms period where significant GPBS was observed from more electrode pairs for Korean. This finding indicates that differences in cortical activities due to language differences are more evident in inter-regional connectivity during semantic analysis than during other stages, such as orthographic processing.

  19. An optical study of grain formation: Casting and solidification technology (2-IML-1)

    NASA Technical Reports Server (NTRS)

    Mccay, Mary H.

    1992-01-01

    By studying the unidirectional growth of a metal-model material in microgravity, an attempt is made to characterize alloy solidification. Using holograms and supporting temperature measurements obtained during processing in the Fluids Experiment System (FES), the solute and thermal fields associated with the dendrite growth front and extraneous nucleation will be measured and compared to a theoretical (computational) model. Ground based supporting experiments include particle tracking to measure the velocity fields, and optical phase shift techniques (confocal optical signal processing, interferometry, and Schlieren) to study thermal and solutal fields.

  20. Temporal magma dynamics during solidification of the mafic-silicic complex of Isle au Haut, Maine

    NASA Astrophysics Data System (ADS)

    Patwardhan, Kaustubh

    The Isle au Haut Igneous Complex provides a unique opportunity to examine in detail the in situ physical and chemical interactions between contemporaneously emplaced mafic and silicic magmas. The complex contains a 600 m thick sequence of 11 alternating layers of gabbro and diorite (typically 15--40 m thick). Purely on the basis of density contrasts (2.65 g/cm 3 gabbro vs. 2.55 g/cm3 diorite), the entire system should have undergone wholesale instability and mixing; it is instead arrested in a grossly unstable state of interaction while molten. Chilled margins along the lower contacts of the gabbros and structural integrity of the diorite layers indicate that near liquidus gabbroic magma invaded partly crystalline, cooler diorite. Mineral assemblages, chemical analyses, and phase equilibria calculations indicate initial temperatures during emplacement of ˜1180°C (gabbro) and ˜1000°C (diorite). Conductive thermal models yield solidification timescales of 15--60 years for individual gabbro layers and about a thousand years for the entire complex. There is ample evidence for two phases of small-scale interfacial Rayleigh-Taylor type instabilities of dioritic melt into the gabbros. Phase I occurred immediately upon gabbro emplacement whereas evenly spaced, slender more silicic pipes represent a much later stage (Phase II). Pipe geometry and spacing, estimated viscosities of the gabbroic magma and silicic melt, and the sudden increase in silica near the upper contact of the diorite, all indicate a thin (˜18--53 cm) buoyant layer at the upper contact of the diorite as the source of the pipes. Compaction of the diorite produced this layer over a period of about ten years. Simultaneous solidification along the lower contact of the overlying gabbro, thickening inwards, increased viscosity enough to arrest pipe ascent after a few meters. Crystal size distribution (CSD) analyses of the gabbro layers yield crystal growth rates (G0 = 2--4 x 10-10 cm/s) and nucleation rates

  1. Solidification Processing of Immiscible Liquids in the Presence of Applied Ultrasonic Energy

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Fedoseyev, A. I.; Kim, S.

    2001-01-01

    Uniform microstructural distribution during solidification of immiscible liquids (e.g., oil and water; aluminum and lead) on Earth is hampered by inherent density differences between the phases. Microgravity processing minimizes settling but segregation still occurs due to gravity independent wetting and coalescence phenomena. Experiments with the transparent organic, metal analogue, succinonitrile-glycerol system were conducted in conjunction with applied ultrasonic energy. The processing parameters associated with this technique have been evaluated in view of optimizing dispersion uniformity. Characterization of the experimental results in terms of a modeling effort will also be presented,

  2. Effects of supercooling in the initial solidification of PbTe-SnTe solid solutions

    NASA Technical Reports Server (NTRS)

    Fripp, A. L.; Crouch, R. K.; Debnam, W. J., Jr.; Clark, I. O.; Wagner, J. B.

    1985-01-01

    Deviations from compositions anticipated by the thermal equilibrium phase diagram have been observed in Bridgman-grown crystals of Pb(1-x)Sn(x)Te, in the first to freeze region of the boule. A set of experiments were conducted to determine the extent of thermal supercooling of Pb(1-x)Sn(x)Te in a Bridgman-like configuration. The results of the compositional profiles and the supercooling measurements are consistent with a diffusionless transformation occurring at the onset of solidification, and the length of uncontrolled growth is inversely related to the temperature gradient of the furnace.

  3. SEMICONDUCTOR TECHNOLOGY: Wafer level hermetic packaging based on Cu-Sn isothermal solidification technology

    NASA Astrophysics Data System (ADS)

    Yuhan, Cao; Le, Luo

    2009-08-01

    A novel wafer level bonding method based on Cu-Sn isothermal solidification technology is established. A multi-layer sealing ring and the bonding processing are designed, and the amount of solder and the bonding parameters are optimized based on both theoretical and experimental results. Verification shows that oxidation of the solder layer, voids and the scalloped-edge appearance of the Cu6Sn5 phase are successfully avoided. An average shear strength of 19.5 MPa and an excellent leak rate of around 1.9 × 10-9 atm cc/s are possible, meeting the demands of MIL-STD-883E.

  4. Metastable bcc phase formation in the Nb-Cr-Ti system

    SciTech Connect

    Thoma, D.J.; Perepezko, J.H.

    1994-08-01

    Metastable disordered bcc phases have been formed from the melt in the Nb-Cr-Ti system where primary Laves phases would develop under equilibrium solidification conditions. Three vertical temperature-composition sections in the ternary system incorporating NbCr, were evaluated: the Nb-Cr binary, the TiCr{sub 2}-NbCr{sub 2} isoplethal section, and the NbCr{sub 2}-Ti plethal section. In the rapid solidification of NbCr{sub 2}, metastable bcc phase formation was not observed, but deviations from NbCr{sub 2} stoichiometry or alloying with Ti was found to promote bcc phase formation by decreasing the required liquid undercooling to reach the metastable bcc liquidus and solidus. The metastable phases were characterized through x-ray diffraction (XRD), and systematic deviations from Vegard`s Rule have been defined in the three plethal sections. The metastable bcc phases decompose at temperatures >800{degrees}C to uniformly refined microstructures. As a result, novel microstructural tailoring schemes are possible through the metastable precursor microstructures.

  5. Coefficients for solution of the analytical freezing equation in the range of states for rapid solidification of biological systems.

    PubMed

    Diller, K R

    1990-01-01

    Solution of the classical solidification heat transfer problem for many biological applications involves states for which roots of the transcendental equation associated with the governing differential equation are not available. These roots are calculated and presented for conditions that characterize a large ratio of solid to liquid phase thermal conductivities and diffusivities and large differences between the initial and final temperatures for the cooling process.

  6. The effects of solidification on sill propagation dynamics and morphology

    NASA Astrophysics Data System (ADS)

    Chanceaux, L.; Menand, T.

    2016-05-01

    Sills are an integral part of the formation and development of larger plutons and magma reservoirs. Thus sills are essential for both the transport and the storage of magma in the Earth's crust. However, although cooling and solidification are central to magmatism, their effects on sills have been so far poorly studied. Here, the effects of solidification on sill propagation dynamics and morphology are studied by means of analogue laboratory experiments. Hot fluid vegetable oil (magma analogue), that solidifies during its propagation, is injected as a sill in a colder layered gelatine solid (elastic host rock analogue). The injection flux and temperature are maintained constant during an experiment and systematically varied between each experiment, in order to vary and quantify the amount of solidification between each experiments. The oil is injected directly at the interface between the two gelatine layers. When solidification effects are small (high injection temperatures and fluxes), the propagation is continuous and the sill has a regular and smooth surface. Inversely, when solidification effects are important (low injection temperatures and fluxes), sill propagation is discontinuous and occurs by steps of surface-area creation interspersed with periods of momentary arrest. The morphology of these sills displays folds, ropy structures on their surface, and lobes with imprints of the leading fronts that correspond to each step of area creation. These experiments show that for a given, constant injected volume, as solidification effects increase, the area of the sills decreases, their thickness increases, and the number of propagation steps increases. These results have various geological and geophysical implications. The morphology of sills, such as lobate structures (interpretation of 3D seismic studies in sedimentary basin) and ropy flow structures (field observations) can be related to solidification during emplacement. Moreover, a non-continuous morphology

  7. SPAR VI Technical Report for Experiment 76-22: Directional Solidification of Magnetic Composites

    NASA Technical Reports Server (NTRS)

    Pirich, R. G.; Larson, D. J., Jr.

    1980-01-01

    Samples of eutectic Bi/MnBi were directionally solidified during a low-g interval aboard the SPAR 6 flight and in a l-g environment under identical furnace velocity and thermal conditions. The Bi/MnBi eutectic is characterized by a regular rod eutectic whose morphology may be sensitive to thermo-solutal convection and by its components, MnBi, which is ferromagnetic. Morphological analyses on samples show statistically smaller interrod spacings and rod diameters with respect to samples grown under identical solidification furnace conditions in l-g. An adjustment between the interrod spacing, growth velocity, and total undercooling at the solidification interface is proposed. Morphological analyses on samples grown in l-g indicate little difference between results for different growth orientations with respect to the gravity vector. The magnetic properties are significantly affected, however, by the presence of a nonequilibrium magnetic phase and the nonequilibrium phase transforms to the equilibrium ferromagnetic phase during isothermal heat treatment.

  8. Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part I. Microstructural Characterization of Rapidly Solidified Solders

    NASA Astrophysics Data System (ADS)

    Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; Handwerker, Carol A.

    2016-10-01

    Particles of Cu x Al y in Sn-Cu-Al solders have previously been shown to nucleate the Cu6Sn5 phase during solidification. In this study, the number and size of Cu6Sn5 nucleation sites were controlled through the particle size refinement of Cu x Al y via rapid solidification processing and controlled cooling in a differential scanning calorimeter. Cooling rates spanning eight orders of magnitude were used to refine the average Cu x Al y and Cu6Sn5 particle sizes down to submicron ranges. The average particle sizes, particle size distributions, and morphologies in the microstructures were analyzed as a function of alloy composition and cooling rate. Deep etching of the samples revealed the three-dimensional microstructures and illuminated the epitaxial and morphological relationships between the Cu x Al y and Cu6Sn5 phases. Transitions in the Cu6Sn5 particle morphologies from faceted rods to nonfaceted, equiaxed particles were observed as a function of both cooling rate and composition. Initial solidification cooling rates within the range of 103 to 104 °C/s were found to be optimal for realizing particle size refinement and maintaining the Cu x Al y /Cu6Sn5 nucleant relationship. In addition, little evidence of the formation or decomposition of the ternary-β phase in the solidified alloys was noted. Solidification pathways omitting the formation of the ternary-β phase agreed well with observed room temperature microstructures.

  9. Melting and solidification characteristics of a mixture of two types of latent heat storage material in a vessel

    NASA Astrophysics Data System (ADS)

    Yu, JikSu; Horibe, Akihiko; Haruki, Naoto; Machida, Akito; Kato, Masashi

    2016-11-01

    In this study, we investigated the fundamental melting and solidification characteristics of mannitol, erythritol, and their mixture (70 % by mass mannitol: 30 % by mass erythritol) as potential phase-change materials (PCMs) for latent heat thermal energy storage systems, specifically those pertaining to industrial waste heat, having temperatures in the range of 100-250 °C. The melting point of erythritol and mannitol, the melting peak temperature of their mixture, and latent heat were measured using differential scanning calorimetry. The thermal performance of the mannitol mixture was determined during melting and solidification processes, using a heat storage vessel with a pipe heat exchanger. Our results indicated phase-change (fusion) temperatures of 160 °C for mannitol and 113 and 150 °C for the mannitol mixture. Nondimensional correlation equations of the average heat transfer during the solidification process, as well as the temperature and velocity efficiencies of flowing silicon oil in the pipe and the phase-change material (PCM), were derived using several nondimensional parameters.

  10. Effect of arsenic content and quenching temperature on solidification microstructure and arsenic distribution in iron-arsenic alloys

    NASA Astrophysics Data System (ADS)

    Xin, Wen-bin; Song, Bo; Huang, Chuan-gen; Song, Ming-ming; Song, Gao-yang

    2015-07-01

    The solidification microstructure, grain boundary segregation of soluble arsenic, and characteristics of arsenic-rich phases were systematically investigated in Fe-As alloys with different arsenic contents and quenching temperatures. The results show that the solidification microstructures of Fe-0.5wt%As alloys consist of irregular ferrite, while the solidification microstructures of Fe-4wt%As and Fe-10wt%As alloys present the typical dendritic morphology, which becomes finer with increasing arsenic content and quenching temperature. In Fe-0.5wt%As alloys quenched from 1600 and 1200°C, the grain boundary segregation of arsenic is detected by transmission electron microscopy. In Fe-4wt%As and Fe-10wt%As alloys quenched from 1600 and 1420°C, a fully divorced eutectic morphology is observed, and the eutectic Fe2As phase distributes discontinuously in the interdendritic regions. In contrast, the eutectic morphology of Fe-10wt%As alloy quenched from 1200°C is fibrous and forms a continuous network structure. Furthermore, the area fraction of the eutectic Fe2As phase in Fe-4wt%As and Fe-10wt%As alloys increases with increasing arsenic content and decreasing quenching temperature.

  11. Melting and solidification characteristics of a mixture of two types of latent heat storage material in a vessel

    NASA Astrophysics Data System (ADS)

    Yu, JikSu; Horibe, Akihiko; Haruki, Naoto; Machida, Akito; Kato, Masashi

    2016-01-01

    In this study, we investigated the fundamental melting and solidification characteristics of mannitol, erythritol, and their mixture (70 % by mass mannitol: 30 % by mass erythritol) as potential phase-change materials (PCMs) for latent heat thermal energy storage systems, specifically those pertaining to industrial waste heat, having temperatures in the range of 100-250 °C. The melting point of erythritol and mannitol, the melting peak temperature of their mixture, and latent heat were measured using differential scanning calorimetry. The thermal performance of the mannitol mixture was determined during melting and solidification processes, using a heat storage vessel with a pipe heat exchanger. Our results indicated phase-change (fusion) temperatures of 160 °C for mannitol and 113 and 150 °C for the mannitol mixture. Nondimensional correlation equations of the average heat transfer during the solidification process, as well as the temperature and velocity efficiencies of flowing silicon oil in the pipe and the phase-change material (PCM), were derived using several nondimensional parameters.

  12. The influence of Nb, Ti, and Si additions on the liquidus and solidus temperatures and primary microstructure refinement in 0.3C-30Ni-18Cr cast steel

    SciTech Connect

    Piekarski, Bogdan

    2010-09-15

    This study explores the effect of niobium, titanium and silicon on the liquidus and solidus temperatures and primary structural refinement in creep-resistant 0.3C-30Ni-18Cr cast steel. Fifteen test alloys were investigated. The concentrations of niobium, titanium and silicon in these alloys ranged from 0.03 to 3.0 wt.%, 0.03 to 1.42 wt.%, and 1.39 to 4.26 wt.%, respectively. It was found that an increase of these elements in 0.3C-30Ni-18Cr cast steel lowered the beginning and ending temperatures of the solidification process, extended the range of solidification temperatures, reduced the density, and refined the microstructure, i.e., reduced the secondary dendrite arm spacing. Alloys with the highest content of the examined elements were reported to contain carbide precipitates, as well as the G phase in an as-cast state.

  13. Study of Magnetic Damping Effect on Convection and Solidification Under G-Jitter Conditions

    NASA Technical Reports Server (NTRS)

    Li, Ben Q.; deGroh, H. C.

    2001-01-01

    As shown in space flight experiments, g-jitter is a critical issue affecting solidification processing of materials in microgravity. This study aims to provide, through extensive numerical simulations and ground based experiments, an assessment of the use of magnetic fields in combination with microgravity to reduce the g-jitter induced convective flows in space processing systems. Analytical solutions and 2-D and 3-D numerical models for g-jitter driven flows in simple solidification systems with and without the presence of an applied magnetic field have been developed and extensive analyses were carried out. A physical model was also constructed and PIV measurements compared reasonably well with predictions from numerical models. Some key points may be summarized as follows: (1) the amplitude of the oscillating velocity decreases at a rate inversely proportional to the g-jitter frequency and with an increase in the applied magnetic field; (2) the induced flow oscillates at approximately the same frequency as the affecting g-jitter, but out of a phase angle; (3) the phase angle is a complicated function of geometry, applied magnetic field, temperature gradient and frequency; (4) g-jitter driven flows exhibit a complex fluid flow pattern evolving in time; (5) the damping effect is more effective for low frequency flows; and (6) the applied magnetic field helps to reduce the variation of solutal distribution along the solid-liquid interface. Work in progress includes developing numerical models for solidification phenomena with the presence of both g-jitter and magnetic fields and developing a ground-based physical model to verify numerical predictions.

  14. Interface Pattern Selection in Directional Solidification

    NASA Technical Reports Server (NTRS)

    Trivedi, Rohit; Tewari, Surendra N.

    2001-01-01

    The central focus of this research is to establish key scientific concepts that govern the selection of cellular and dendritic patterns during the directional solidification of alloys. Ground-based studies have established that the conditions under which cellular and dendritic microstructures form are precisely where convection effects are dominant in bulk samples. Thus, experimental data can not be obtained terrestrially under pure diffusive regime. Furthermore, reliable theoretical models are not yet possible which can quantitatively incorporate fluid flow in the pattern selection criterion. Consequently, microgravity experiments on cellular and dendritic growth are designed to obtain benchmark data under diffusive growth conditions that can be quantitatively analyzed and compared with the rigorous theoretical model to establish the fundamental principles that govern the selection of specific microstructure and its length scales. In the cellular structure, different cells in an array are strongly coupled so that the cellular pattern evolution is controlled by complex interactions between thermal diffusion, solute diffusion and interface effects. These interactions give infinity of solutions, and the system selects only a narrow band of solutions. The aim of this investigation is to obtain benchmark data and develop a rigorous theoretical model that will allow us to quantitatively establish the physics of this selection process.

  15. Preparation and solidification of redispersible nanosuspensions.

    PubMed

    Zhang, Xin; Guan, Jian; Ni, Rui; Li, Luk Chiu; Mao, Shirui

    2014-07-01

    To test the feasibility of preparing redispersible powders from nanosuspensions without further addition of drying protectants, Lovastatin was processed into nanosuspensions and subsequently converted into a powder form using a spray-drying process. The effects of spray-drying process parameters and stabilizers on the properties of the spray-dried powders were evaluated. The inlet air temperature was found to have the most pronounced impact; a low-inlet air temperature consistently yielded dried powders with improved redispersibility. This was attributed to the low Peclet number associated with a low-inlet air temperature, making nanoparticles less prone to aggregation and coalescence during spray drying, as evidenced by the well-defined boundary shown between nanoparticles in the SEM photomicrographs of the spray-dried microparticles. The influence of atomization pressure is significant particularly at a low-inlet air temperature. The redispersibility index value of the powder is dependent on the type of stabilizers used in the nanosuspension formulation. Spray-dried powders with acceptable redispersibility were prepared with drug concentration as high as 3%. In conclusion, with optimized process parameters and selected stabilizers, spray drying is a feasible process in the solidification of nanosuspensions with high drug loading and acceptable redispersibility.

  16. Stabilization/solidification of acid tars.

    PubMed

    Leonard, Sunday A; Stegemann, Julia A

    2010-01-01

    This work involve a systematic treatability study of the treatment of acid tars (AT), a waste generated during the processing of petroleum and petrochemical, by stabilization/solidification with Portland cement (CEM I), with the addition of high carbon fly ash (HCFA), an industrial by-product, as a novel sorbent for organic contaminants. A factorial design experiment was adopted to investigate the effects of organic content, HCFA:AT ratio, percentage CEM I addition, and curing time on response variables including unconfined compressive strength (UCS), hydraulic conductivity, porosity, and leachability-related properties of the stabilized/solidified (s/s) products, and to assess management options for the s/s products based on performance criteria adapted from regulatory and other guidance. Results show that all studied factors had significant effects on the tested properties of the s/s products. Acid tar reduced UCS, but strength increase was observed with increased curing time. Increased HCFA addition led to an improvement in hydraulic conductivity. Assessment of management options indicates that the treated acid tars could find application as controlled low-strength materials, landfill liner, and landfill daily cover. The work demonstrates how a systematic treatability study can be used to develop a S/S operating window for management of a particular waste type.

  17. Stabilization/solidification of TSCA incinerator ash

    SciTech Connect

    Spence, R.D.; Trotter, D.R.; Francis, C.L.; Morgan, I.L.

    1994-06-01

    Stabilization/solidification is a well-known waste treatment technique that utilizes different additives and processes. The Phoenix Ash Technology of the Technical Innovation Development Engineering Company is such a technique that uses Cass C fly ash and mechanical pressure to make brick waste forms out of solid wastes, such as the bottom ash from the Toxic Substances Control Act incinerator at the Oak Ridge K-25 Site. One advantage of this technique is that no volume increase over the bulk volume of the bottom ash occurs. This technique should have the same high pH stabilization for Resource Conservation and Recovery Act metals as similar techniques. Also, consolidation of the bottom ash minimizes the potential problems of material dispersion and container corrosion. The bottom ash was spiked with {sup 99}{Tc} to test the effectiveness of the bricks as a physical barrier. The {sup 99}{Tc} leachability index measured for these bricks was 6.8, typical for the pertechnetate anion in cementitious waste forms, indicating that these bricks have accessible porosity as high as that of other cementitious waste forms, despite the mechanical compression, higher waste form density, and water resistant polymer coating.

  18. Solidification effects on sill formation: An experimental approach

    NASA Astrophysics Data System (ADS)

    Chanceaux, L.; Menand, T.

    2014-10-01

    Sills represent a major mechanism for constructing continental Earth's crust because these intrusions can amalgamate and form magma reservoirs and plutons. As a result, numerous field, laboratory and numerical studies have investigated the conditions that lead to sill emplacement. However, all previous studies have neglected the potential effect magma solidification could have on sill formation. The effects of solidification on the formation of sills are studied and quantified with scaled analogue laboratory experiments. The experiments presented here involved the injection of hot vegetable oil (a magma analogue) which solidified during its propagation as a dyke in a colder and layered solid of gelatine (a host rock analogue). The gelatine solid had two layers of different stiffness, to create a priori favourable conditions to form sills. Several behaviours were observed depending on the injection temperature and the injection rate: no intrusions (extreme solidification effects), dykes stopping at the interface (high solidification effects), sills (moderate solidification effects), and dykes passing through the interface (low solidification effects). All these results can be explained quantitatively as a function of a dimensionless temperature θ, which describes the experimental thermal conditions, and a dimensionless flux ϕ, which describes their dynamical conditions. The experiments reveal that sills can only form within a restricted domain of the (θ,ϕ) parameter space. These experiments demonstrate that contrary to isothermal experiments where cooling could not affect sill formation, the presence of an interface that would be a priori mechanically favourable is not a sufficient condition for sill formation; solidification effects restrict sill formation. The results are consistent with field observations and provide a means to explain why some dykes form sills when others do not under seemingly similar geological conditions.

  19. Gas- and particle-phase primary emissions from in-use, on-road gasoline and diesel vehicles

    NASA Astrophysics Data System (ADS)

    May, Andrew A.; Nguyen, Ngoc T.; Presto, Albert A.; Gordon, Timothy D.; Lipsky, Eric M.; Karve, Mrunmayi; Gutierrez, Alváro; Robertson, William H.; Zhang, Mang; Brandow, Christopher; Chang, Oliver; Chen, Shiyan; Cicero-Fernandez, Pablo; Dinkins, Lyman; Fuentes, Mark; Huang, Shiou-Mei; Ling, Richard; Long, Jeff; Maddox, Christine; Massetti, John; McCauley, Eileen; Miguel, Antonio; Na, Kwangsam; Ong, Richard; Pang, Yanbo; Rieger, Paul; Sax, Todd; Truong, Tin; Vo, Thu; Chattopadhyay, Sulekha; Maldonado, Hector; Maricq, M. Matti; Robinson, Allen L.

    2014-05-01

    Tailpipe emissions from sixty-four unique light-duty gasoline vehicles (LDGVs) spanning model years 1987-2012, two medium-duty diesel vehicles and three heavy-duty diesel vehicles with varying levels of aftertreatment were characterized at the California Air Resources Board Haagen-Smit and Heavy-Duty Engine Testing Laboratories. Each vehicle was tested on a chassis dynamometer using a constant volume sampler, commercial fuels and standard duty cycles. Measurements included regulated pollutants such as carbon monoxide (CO), total hydrocarbons (THC), nitrogen oxides (NOx), and particulate matter (PM). Off-line analyses were performed to speciate gas- and particle-phase emissions. The data were used to investigate trends in emissions with vehicle age and to quantify the effects of different aftertreatment technologies on diesel vehicle emissions (e.g., with and without a diesel particulate filter). On average, newer LDGVs that met the most recent emissions standards had substantially lower emissions of regulated gaseous pollutants (CO, THC and NOx) than older vehicles. For example, THC emissions from the median LDGV that met the LEV2 standard was roughly a factor of 10 lower than the median pre-LEV vehicle; there were also substantial reductions in NOx (factor of ∼100) and CO (factor of ∼10) emissions from pre-LEV to LEV2 vehicles. However, reductions in LDGV PM mass emissions were much more modest. For example, PM emission from the median LEV2 vehicle was only a factor of three lower than the median pre-LEV vehicle, mainly due to the reductions in organic carbon emissions. In addition, LEV1 and LEV2 LDGVs had similar PM emissions. Catalyzed diesel particulate filters reduced CO, THC and PM emissions from HDDVs by one to two orders of magnitude. Comprehensive organic speciation was performed to quantify priority air toxic emissions and to estimate the secondary organic aerosol (SOA) formation potential. The data suggest that the SOA production from cold

  20. In Situ Study of Microstructure Evolution in Solidification of Hypereutectic Al-Si Alloys with Application of Thermal Analysis and Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Sediako, Dimitry G.; Kasprzak, Wojciech

    2015-09-01

    Understanding of the kinetics of solid-phase evolution in solidification of hypereutectic aluminum alloys is a key to control their as-cast microstructure and resultant mechanical properties, and in turn, to enhance the service characteristics of actual components. This study was performed to evaluate the solidification kinetics for three P-modified hypereutectic Al-19 pct Si alloys: namely, Al-Si binary alloy and with the subsequent addition of 2.8 pct Cu and 2.8 pct Cu + 0.7 pct Mg. Metallurgical evaluation included thermodynamic calculations of the solidification process using the FactSage™ 6.2 software package, as well as experimental thermal analysis, and in situ neutron diffraction. The study revealed kinetics of solid α-Al, solid Si, Al2Cu, and Mg2Si evolution, as well as the individual effects of Cu and Mg alloying additions on the solidification path of the Al-Si system. Various techniques applied in this study resulted in some discrepancies in the results. For example, the FactSage computations, in general, resulted in 281 K to 286 K (8 °C to 13 °C) higher Al-Si eutectic temperatures than the ones recorded in the thermal analysis, which are also ~278 K (~5 °C) higher than those observed in the in situ neutron diffraction. None of the techniques can provide a definite value for the solidus temperature, as this is affected by the chosen calculation path [283 K to 303 K (10 °C to 30 °C) higher for equilibrium solidification vs non-equilibrium] for the FactSage analysis; and further complicated by evolution of secondary Al-Cu and Mg-Si phases that commenced at the end of solidification. An explanation of the discrepancies observed and complications associated with every technique applied is offered in the paper.

  1. The effects of solidification on sill propagation dynamics and geometry

    NASA Astrophysics Data System (ADS)

    Lola, Chanceaux; Thierry, Menand

    2015-04-01

    The effects of solidification on sill propagation dynamics and geometry are studied by means of analogue laboratory experiments. Hot fluid vegetable oil (a magma analogue), that solidifies during its propagation, is injected as a sill in a colder layered gelatine solid (an elastic host rock analogue). The injection flux and temperature are maintained constant during an experiment. In order to vary the importance of solidification and quantify its effect on sill propagation, the injection flux and temperature are systematically varied between each experiment. Depending on the importance of solidification effects, two extreme behaviours for sill propagation dynamics and geometry are observed. When solidification effects are small (high injection temperatures and fluxes), the propagation is continuous and the sill has a regular and smooth surface. Inversely, when solidification effects are important (low injection temperatures and fluxes), sill propagation is discontinuous and occurs by steps. After each propagation step, the sill stalls, thickens progressively by storing hot fluid vegetable oil beneath the partially solidified intrusion, without growing neither in length nor in breadth, and after a pause, the propagation initiates again, soon followed by a new episode of momentary arrest. The geometry of these sills displays folds, ropy structures on their surface, and lobes with imprints of the leading fronts that correspond to each step of surface creation. These experiments show that for a given, constant injected volume, as solidification effects increase, the surface of the sills decreases, their thickness increases, and the number of propagation steps increases. In the same way lower solidification effects promote larger sill surfaces, lower thicknesses, and a lower number of propagation steps. These results have various geological and geophysical implications. Regarding the geometry of sills, 3D seismic studies in sedimentary basins reveal sills with lobate

  2. Successful pond closure utilizing novel solidification/stabilization technology

    SciTech Connect

    Donnelly, J.R.; Webster, W.C.

    1995-12-31

    Davy International, in joint venture with International Technology Corporation (IT-Davy), has recently completed the RCRA closure of wastewater impoundments at a major Gulf Coast refinery. These surface impoundments contained a mixture of petroleum waste sediments, free water and standing oil. In-situ solidification/stabilization (solidification) was used to produce a material which met the regulatory criteria of: achieving a bearing capacity sufficient to support earth moving equipment, the final multi-layer cap and the soil cover, immobilizing contaminants of concern namely, benzene, toluene, chrysene, naphthalene, 1-methyl naphthalene, chromium and lead. Ex-situ solidification was specified in the initial bid documents to meet the above criteria. Solidified material was to achieve an unconfined compressive strength of greater than 20 pounds per square inch (psi) and a permeability of less than 1 {times}10{sup {minus}5} centimeters per second after 7 days of curing. During the project proposal stage, IT-Davy developed a conceptual design for in-situ solidification which reduced the estimated project cost by approximately $10 million (or 33 percent). This paper reviews key elements of the project and presents results of the use of a novel solidification/stabilization process to achieve project closure criteria. Bench and field demonstration test data are given.

  3. The solidification behavior of 8090 Al-Li alloy

    SciTech Connect

    Liu, Y.L.; Hu, Z.Q.; Zhang, Y.; Shi, C.X. . Inst. of Metal Research)

    1993-10-01

    In this work, the solidification and segregation behaviors of 8090 Al-Li alloy have been investigated with differential thermal analysis (DTA) and the metallographic-electron microprobe method. The results show that 8090 Al-Li alloy has a much more complex solidification path than Al-Li binary alloy due to the addition of many alloying elements and the presence of impure elements. Solidification begins at about 635 C with the reaction of L [yields] [alpha]-Al + L[prime], and this reaction goes on to termination. The alloying element Cu and impure elements Fe and Si have a strong segregation tendency. During solidification, Cu segregates to the interdendrite and finally forms [alpha]-Al + T[sub 2] eutectic. As a result, the solidification temperature range is greatly extended. Iron and Si form the insoluble constituents Al[sub 7]Cu[sub 2]Fe, AlLiSi, etc., although their concentrations in the alloy are quite low. With the increase of Fe content, there is a eutectic reaction of [alpha]-Al/Al[sub 3]Fe at about 595 C. The formation of insoluble constituents is influenced by both concentrations of impure elements in the alloy and the cooling rate.

  4. The solidification behavior of 8090 Al-Li alloy

    NASA Astrophysics Data System (ADS)

    Liu, Y. L.; Hu, Z. Q.; Zhang, Y.; Shi, C. X.

    1993-10-01

    In this work, the solidification and segregation behaviors of 8090 Al-Li alloy have been investigated with differential thermal analysis (DTA) and the metallographic-electron microprobe method. The results show that 8090 Al-Li alloy has a much more complex solidification path than Al-Li binary alloy due to the addition of many alloying elements and the presence of impure elements. Solidification begins at about 635 °C with the reaction of L → α-Al + L', and this reaction goes on to termination. The alloying element Cu and impure elements Fe and Si have a strong segregation tendency. During solidification, Cu segregates to the interdendrite and finally forms α-Al + T2 eutectic. As a result, the solidification temperature range is greatly extended. Iron and Si form the insoluble constituents Al7Cu2Fe, AlLiSi, etc., although their concentrations in the alloy are quite low. With the increase of Fe content, there is a eutectic reaction of α-Al/Al3Fe at about 595 °C. The formation of insoluble constituents is influenced by both concentrations of impure elements in the alloy and the cooling rate.

  5. Direct formation of peritectic phase but no primary phase appearance within Ni83.25Zr16.75 peritectic alloy during free fall

    PubMed Central

    Lü, P.; Wang, H. P.

    2016-01-01

    Ni83.25Zr16.75 peritectic alloy was containerlessly solidified in a drop tube. When the droplet diameter exceeds a critical value (Dcrit), Ni7Zr2 phase primarily solidifies, followed by the peritectic reaction of Ni7Zr2 + L → Ni5Zr. Once the droplet diameter is smaller than the critical value (Dcrit), peritectic phase Ni5Zr directly solidifies from the undercooled melt by completely suppressing the nucleation and growth of Ni7Zr2 phase, which is ascribed to high undercooling and cooling rate. Additionally, peritectic phase Ni5Zr grows equiaxially in the sample solidified in a DSC at a cooling rate of 0.167 K/s. PMID:26935165

  6. Direct observation of spatially isothermal equiaxed solidification of an Al-Cu alloy in microgravity on board the MASER 13 sounding rocket

    NASA Astrophysics Data System (ADS)

    Murphy, A. G.; Mathiesen, R. H.; Houltz, Y.; Li, J.; Lockowandt, C.; Henriksson, K.; Melville, N.; Browne, D. J.

    2016-11-01

    For the first time, isothermal equiaxed solidification of a metallic alloy has been observed in situ in space, providing unique benchmark experimental data. The experiment was completed on board the MASER 13 sounding rocket, launched in December 2015, using a newly developed isothermal solidification furnace. A grain-refined Al-20 wt%Cu sample was fully melted and solidified during 360 s of microgravity and the solidification sequence was recorded using time-resolved X-radiography. Equiaxed nucleation, dendritic growth, solutal impingement, and eutectic transformation were thus observed in a gravity-free environment. Equiaxed nucleation was promoted through application of a controlled cooling rate of -0.05 K/s producing a 1D grain density of ~6.5 mm-1, uniformly distributed throughout the field of view (FOV). Primary growth slowed to a visually imperceptible level at an estimated undercooling of 7 K, after which the cooling rate was increased to -1.0 K/s for the remainder of solidification and eutectic transformation, ensuring the sample was fully solidified inside the microgravity time window. The eutectic transformation commenced at the centre of the FOV proceeding radially outwards covering the entire FOV in ~3 s Microgravity-based solidification is compared to an identical pre-flight ground-based experiment using the same sample and experiment timeline. The ground experiment was designed to minimise gravity effects, by choice of a horizontal orientation for the sample, so that any differences would be subtle. The first equiaxed nucleation occurred at an apparent undercooling of 0.6 K less than the equivalent event during microgravity. During primary equiaxed solidification, as expected, no buoyant grain motion was observed during microgravity, compared to modest grain rotation and reorientation observed during terrestrial-based solidification. However, when the cooling rate was increased from -0.05 K/s to -1.0 K/s during the latter stages of solidification, in

  7. Analysis and calculation of macrosegregation in a casting ingot. MPS solidification model. Volume 2: Software documentation

    NASA Technical Reports Server (NTRS)

    Maples, A. L.

    1980-01-01

    The software developed for the solidification model is presented. A link between the calculations and the FORTRAN code is provided, primarily in the form of global flow diagrams and data structures. A complete listing of the solidification code is given.

  8. The next phase of Title VII funding for training primary care physicians for America's health care needs.

    PubMed

    Phillips, Robert L; Turner, Barbara J

    2012-01-01

    Health care reform will add millions of Americans to the ranks of the insured; however, their access to health care is threatened by a deep decline in the production of primary care physicians. Poorer access to primary care risks poorer health outcomes and higher costs. Meeting this increased demand requires a major investment in primary care training. Title VII, Section 747 of the Public Health Service Act previously supported the growth of the health care workforce but has been severely cut over the past 2 decades. New and expanded Title VII initiatives are required to increase the production of primary care physicians; establish high-functioning academic, community-based training practices; increase the supply of well-trained primary care faculty; foster innovation and rigorous evaluation of these programs; and ultimately to improve the responsiveness of teaching hospitals to community needs. To accomplish these goals, Congress should act on the Council on Graduate Medical Education's recommendation to increase funding for Title VII, Section 747 roughly 14-fold to $560 million annually. This amount represents a small investment in light of the billions that Medicare currently spends to support graduate medical education, and both should be held to account for meeting physician workforce needs. Expansion of Title VII, Section 747 with the goal of improving access to primary care would be an important part of a needed, broader effort to counter the decline of primary care. Failure to launch such a national primary care workforce revitalization program will put the health and economic viability of our nation at risk.

  9. Microstructure Characterization and Thermal Analysis of Aluminum Alloy B206 During Solidification

    NASA Astrophysics Data System (ADS)

    Haghdadi, N.; Phillion, A. B.; Maijer, D. M.

    2015-05-01

    The solidification kinetics of a high strength B206 aluminum casting alloy as a function of cooling rates between 1 and 15 K/min has been characterized through a combination of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and optical microscopy. Three different peaks were detected in the DSC analysis, which corresponded to the nucleation of an α-Al solid solution, an Al-Cu-Fe intermetallic, and the eutectic phases. The presence of these phases was confirmed using a coupled SEM-energy dispersive spectroscopy analysis. The α-Al nucleation temperature was found to be independent of cooling rate while the eutectic and the intermetallic formation temperatures were depressed by up to 20 K (20 °C). The evolution of the fraction solid, particularly during the solidification of α-Al was also affected by the cooling rate in such a way that slower cooling was accompanied by a higher fraction solid at a given temperature. Concurrently, microscopy was used in order to quantify the variation in secondary dendrite arm spacing with cooling rate for use in numerical simulations of casting processes.

  10. Solidification and thermal behaviour of binary organic eutectic and monotectic; succinonitrile pyrene system

    NASA Astrophysics Data System (ADS)

    Rai, U. S.; Pandey, Pinky

    2003-02-01

    Transparent binary alloy models are important in metallurgical and materials science, as phase transformations can be observed during solidification. This communication concerns the solidification and thermal studies of succinonitrile (SCN)-pyrene (PY) system, which is an organic analogue of a metal-nonmetal-type system. Phase diagram of the SCN-PY system, determined by the thaw-melt method shows the formation of a monotectic and a eutectic at 143.3°C and 55.3°C with 0.025 and 0.744 mole fractions of SCN, respectively. The critical solution temperature of the system lies 48.7°C above the monotectic temperature. The growth velocity ( v) data at different undercoolings obtained from the capillary method, obey the Hillig-Turnbull equation, v= u(Δ T) n. The heats of fusion of the binary as well as single materials were obtained from the DSC (Mettler DSC-4000 system) from which the entropy of fusion, enthalpy of mixing, Jackson's roughness parameter, excess thermodynamic functions, interfacial energy and radius of the critical nucleus were calculated. The optical microphotographs of the eutectic and monotectic show their characteristic features.

  11. Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

    NASA Astrophysics Data System (ADS)

    Ahmad, R.; Asmael, M. B. A.

    2016-07-01

    The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

  12. Modeling of multiphase flow with solidification and chemical reaction in materials processing

    NASA Astrophysics Data System (ADS)

    Wei, Jiuan

    moving the side insulation layer upward. It is possible to produce high quality crystal with a good combination of heating and cooling. SiC based ceramic materials fabricated by polymer pyrolysis and synthesis becomes a promising candidate for nuclear applications. To obtain high uniformity of microstructure/concentration fuel without crack at high operating temperature, it is important to understand transport phenomena in material processing at different scale levels. In our prior work, a system level model based on reactive porous media theory was developed to account for the pyrolysis process in uranium-ceramic nuclear fabrication In this thesis, a particle level mesoscopic model based on the Smoothed Particle Hydrodynamics (SPH) is developed for modeling the synthesis of filler U3O8 particles and SiC matrix. The system-level model provides the thermal boundary conditions needed in the particle level simulation. The evolution of particle concentration and structure as well as composition of composite produced will be investigated. Since the process temperature and heat flux play the important roles in material quality and uniformity, the effects of heating rate at different directions, filler particle size and distribution on uniformity and microstructure of the final product are investigated. Uncertainty issue is also discussed. For the multiphase flow with directional solidification, a system level based on FVM is established. In this model, melt convection, temperature distribution, phase change and solidification interface can be investigated. For the multiphase flow with chemical reaction, a particle level model based on SPH method is developed to describe the pyrolysis and synthesis process of uranium-ceramic nuclear fuel. Due to its mesh-free nature, SPH can easily handle the problems with multi phases and components, large deformation, chemical reactions and even solidifications. A multi-scale meso-macroscopic approach, which combine a mesoscopic model based

  13. Modelling and simulations of ductile iron solidification- induced variations in mechanical behaviour on component and microstructural level

    NASA Astrophysics Data System (ADS)

    Olofsson, J.; Salomonsson, K.; Svensson, I. L.

    2015-06-01

    The mechanical behaviour and performance of a ductile iron component is highly dependent on the local variations in solidification conditions during the casting process. Here we show a framework which combine a previously developed closed chain of simulations for cast components with a micro-scale Finite Element Method (FEM) simulation of the behaviour and performance of the microstructure. A casting process simulation, including modelling of solidification and mechanical material characterization, provides the basis for a macro-scale FEM analysis of the component. A critical region is identified to which the micro-scale FEM simulation of a representative microstructure, generated using X-ray tomography, is applied. The mechanical behaviour of the different microstructural phases are determined using a surrogate model based optimisation routine and experimental data. It is discussed that the approach enables a link between solidification- and microstructure-models and simulations of as well component as microstructural behaviour, and can contribute with new understanding regarding the behaviour and performance of different microstructural phases and morphologies in industrial ductile iron components in service.

  14. Modeling the impact, flattening and solidification of a molten droplet on a solid substrate during plasma spraying

    NASA Astrophysics Data System (ADS)

    Zheng, Y. Z.; Li, Q.; Zheng, Z. H.; Zhu, J. F.; Cao, P. L.

    2014-10-01

    It is quite important to clearly understand the dynamic process of single splat formation for optimizing the plasma spraying process. In present study, a three-dimensional model including heat transfer and phase change was developed on Ansys Fluent 14 platform to simulate the impact, flattening and solidification of a molten droplet on a solid substrate during plasma spraying. The phase, contact pressure, temperature and velocity fields at different spreading times were presented to gain an insight into splat formation mechanism. The predicted splat morphology was in good agreement with the experimental photos. The effect of mushy zone constant, a parameter dominating the solidification behavior of fluid in Fluent, on the flattening of droplet was further investigated. Through comparing the calculated spread factor from present model with the experimental value, a mushy zone constant of 108 or 109 was found to be more appropriate for simulation on the solidification problem occurring in high-speed impact and flattening process, instead of the range of 104-107 recommended in Fluent.

  15. New Oscillatory Instability in a Mushy Layer in a Modulated Environment during the Solidification of Binary Alloys

    NASA Astrophysics Data System (ADS)

    Srimani, P. K.; Murthy, M. Vinayaka

    2011-12-01

    In this paper, the effect of gravity modulation on a new oscillatory instability in a mushy layer is discussed. During the solidification of binary mixture from a cold boundary quite often, the planar solidification front becomes unstable due to the constitutional under cooling, resulting in a mushy layer that separates completely the liquid phase from the completely solid phase. Here, the mushy layer is a reactive porous medium, whose internal structure is composed of fine—scale crystals through which the residual melt can flow. Some of the important results of the present investigation are: (i) There exists a limit for the Stefan number, which incorporates a key balance necessary for the existence of oscillatory instability under gravity modulation. (ii) The model incorporates a complex interaction of heat transfer, modulatory convection and solidification. (iii) The steady and oscillatory modes strongly depend on seven dimensionless parameters. (iv) The oscillatory instability is driven solely from the interior of the mushy layer and exists for all wave numbers. (v) A thorough discussion of the results reveals the different transition boundaries associated with the feasible combination of the parameters. (vi) The system becomes more unstable to both real and oscillatory instabilities as the Stefan number increases for a fixed of value of the modulation parameter. (vii) Modulated convection in a mushy layer could be enhanced or suppressed by a suitable choice of the governing parameters. Finally it is observed that, the results are of practical interest.

  16. Linear Stability of Binary Alloy Solidification for Unsteady Growth Rates

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.

    2010-01-01

    An extension of the Mullins and Sekerka (MS) linear stability analysis to the unsteady growth rate case is considered for dilute binary alloys. In particular, the stability of the planar interface during the initial solidification transient is studied in detail numerically. The rapid solidification case, when the system is traversing through the unstable region defined by the MS criterion, has also been treated. It has been observed that the onset of instability is quite accurately defined by the "quasi-stationary MS criterion", when the growth rate and other process parameters are taken as constants at a particular time of the growth process. A singular behavior of the governing equations for the perturbed quantities at the constitutional supercooling demarcation line has been observed. However, when the solidification process, during its transient, crosses this demarcation line, a planar interface is stable according to the linear analysis performed.

  17. Solidification Dynamics of Metal Drops in a Free Fall Environment

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Brush, L. N.; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    Comparison of experimental observations were made with numerical solutions to a model of the heat transfer and solidification kinetics associated with the cooling of a molten drop during free fall, particularly with regard to the fraction of liquid transformed. Experimentally, silver drops (99.9%, 4-9 mm diameter) were levitated, melted, and released to fall through Marshall Space Flight Center's 105m drop tube in helium - 6% hydrogen and argon atmospheres. By systematically varying the drops initial superheat the extent of solidification prior to impact ranged from complete to none during the approximately 4.6s of free fall time. Analysis reveals the relative importance of the initial parameters affecting the cooling and solidification rates within the drop. A discussion of the conditions under which the actual observations deviate from the assumptions used in the model is presented.

  18. Solidification Dynamics of Silver Drops in a Free Fall Environment

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Brush, Lucien N.

    1999-01-01

    Silver drops (99.9%, 4, 5, 7, and 9 mm diameter) were levitated, melted, and released to fall through Marshall Space Flight Center's 105m drop tube in helium - 6% hydrogen and pure argon atmospheres. By systematically varying the initial superheat condition of the drop the extent of solidification prior to impact ranged from complete to none during the approximately 4.6s of free fall time. Comparison of the experimental observations is made with numerical solutions to a model of the heat transfer and solidification kinetics associated with cooling of the drop during free fall, particularly with regard to the fraction of liquid transformed. Analysis reveals the relative importance of the initial parameters affecting the cooling and solidification rates within the drop. A discussion of the conditions under which the actual observations deviate from the assumptions used in the model is presented.

  19. Solidification Dynamics of Spherical Drops in a Free Fall Environment

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Brush, Lucien N.

    2006-01-01

    Silver drops (99.9%, 4, 5, 7, and 9 mm diameter) were levitated, melted, and released to fall through Marshall Space Flight Center's 105 meter drop tube in helium - 6% hydrogen and pure argon atmospheres. By varying a drop s initial superheat the extent of solidification prior to impact ranged from complete to none during the approx. 4.6s of free fall time. Comparison of the experimental observations is made with numerical solutions to a model of the heat transfer and solidification kinetics associated with cooling of the drop during free fall, particularly with regard to the fraction of liquid transformed. Analysis reveals the relative importance ,of the initial parameters affecting the cooling and solidification rates within the drop. A discussion of the conditions under which the actual observations deviate from the assumptions used in the model is presented.

  20. Analysis and calculation of macrosegregation in a casting ingot. MPS solidification model. Volume 3: Operating manual

    NASA Technical Reports Server (NTRS)

    Maples, A. L.

    1980-01-01

    The operation of solidification model 1 is described. Model 1 calculates the macrosegregation in a rectangular ingot of a binary alloy as a result of horizontal axisymmetric bidirectional solidification. The calculation is restricted to steady-state solidification; there is no variation in final local average composition in the direction of isotherm movement. The physics of the model are given.