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Sample records for expanded austenite experimental

  1. Magnetic properties of single crystalline expanded austenite obtained by plasma nitriding of austenitic stainless steel single crystals.

    PubMed

    Menéndez, Enric; Templier, Claude; Garcia-Ramirez, Pablo; Santiso, José; Vantomme, André; Temst, Kristiaan; Nogués, Josep

    2013-10-23

    Ferromagnetic single crystalline [100], [110], and [111]-oriented expanded austenite is obtained by plasma nitriding of paramagnetic 316L austenitic stainless steel single crystals at either 300 or 400 °C. After nitriding at 400 °C, the [100] direction appears to constitute the magnetic easy axis due to the interplay between a large lattice expansion and the expected decomposition of the expanded austenite, which results in Fe- and Ni-enriched areas. However, a complex combination of uniaxial (i.e., twofold) and biaxial (i.e., fourfold) in-plane magnetic anisotropies is encountered. It is suggested that the former is related to residual stress-induced effects while the latter is associated to the in-plane projections of the cubic lattice symmetry. Increasing the processing temperature strengthens the biaxial in-plane anisotropy in detriment of the uniaxial contribution, in agreement with a more homogeneous structure of expanded austenite with lower residual stresses. In contrast to polycrystalline expanded austenite, single crystalline expanded austenite exhibits its magnetic easy axes along basic directions.

  2. CrN precipitation and elemental segregation during the decay of expanded austenite

    NASA Astrophysics Data System (ADS)

    Manova, D.; Lotnyk, A.; Mändl, S.; Neumann, H.; Rauschenbach, B.

    2016-06-01

    Nitrogen insertion into austenitic stainless steel at elevated temperatures leads to anomalous fast nitrogen diffusion and the formation of an expanded fcc phase which is known as expanded austenite. In situ x-ray diffraction measurements during low energy nitrogen ion implantation into steel AISI 304 at 475 °C and short annealing at 575 °C were performed in conjunction with transmission electron microscopy investigations. They show the time dependent decay of this expanded phase with coalescing and growing CrN precipitates. There is elemental segregation associated with this decay where Fe is absent very early from the Cr-N containing precipitates. Ni is segregating towards the Fe-rich matrix more slowly. At the same time, the microstructure—decayed phase vs expanded austenite—is visible in SIMS cluster analysis.

  3. In-situ kinetics study on the growth of expanded austenite in AISI 316L stainless steels by XRD

    NASA Astrophysics Data System (ADS)

    Balogh-Michels, Zoltán; Faeht, Alexander; Kleiner, Simon; von Känel, Adrian; Rufer, Jean-Martin; Dommann, Alex; Margraf, Patrick; Tschopp, Gerhard; Neels, Antonia

    2017-07-01

    The formation of expanded austenite in Cr-Ni austenitic stainless steels like AISI 316L is not completely understood despite its technological relevance. In this work, we present an in-situ X-ray diffraction study on the growth kinetics of the expanded austenite. We applied a low-temperature nitrocarburizing treatment using a mixture of NH3, N2, H2, and C2H4 gases at atmospheric pressures in a novel and custom built chamber attached to a Bruker D8 Advance diffractometer. The nitrocarburizing temperature was varied between 340 and 440 °C, and the possible effects of the gas amount were also tested. The thickness of the growing layer was determined from the shrinkage of the unmodified austenite peak. The growth rate coefficient was calculated using the linear-parabolic equation. The resulting coefficients follow the Arrhenius law with the activation energy of 165 ± 12 kJ/mol. This value is in good agreement with the diffusion activation energy for heavy interstitials like carbon and nitrogen. The expanded austenite peak was modelled by a multilayer approach, where each 0.5 μm sublayer has a constant lattice parameter. The lattice expansion is analyzed as a function of the Boltzmann-variable (η = 0.5 × t-1/2). The expanded austenite layer in this metric has a constant width. Furthermore by rescaling with the lattice expansion of the first sublayer, it is possible to create a scale-independent master curve. These findings indicate that thickening of the expanded austenite is purely diffusion controlled, while the extent of strain is set by the uptake rate of the gas atoms.

  4. An experimental reciprocating expander for cryocooler application

    NASA Technical Reports Server (NTRS)

    Minta, M.; Smith, J. L., Jr.

    1985-01-01

    An experimental reciprocating expander was designed with features appropriate for cryocooler cycles. The expander has a displacer piston, simple valves, and a hydraulic/pneumatic stroking mechanism. The expander has a valve in head configuration with the valves extending out the bottom of the vacuum enclosure while the piston extends out the top. The expander was tested using a CTI 1400 liquefier to supply 13 atm in the temperature range 4.2 to 12 K. Expander efficiency was measured in the range 84 to 93% while operating the apparatus as a supercritical wet expander and in the range 91 to 93% aa a single phase expander. The apparatus can also be modified to operate as a compressor for saturated helium vapor.

  5. Autofocus imaging: Experimental results in an anisotropic austenitic weld

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Drinkwater, B. W.; Wilcox, P. D.; Hunter, A.

    2012-05-01

    The quality of an ultrasonic array image, especially for anisotropic material, depends on accurate information about acoustic properties. Inaccuracy of acoustic properties causes image degradation, e.g., blurring, errors in locating of reflectors and introduction of artifacts. In this paper, for an anisotropic austenitic steel weld, an autofocus imaging technique is presented. The array data from a series of beacons is captured and then used to statistically extract anisotropic weld properties by using a Monte-Carlo inversion approach. The beacon and imaging systems are realized using two separated arrays; one acts as a series of beacons and the other images these beacons. Key to the Monte-Carlo inversion scheme is a fast forward model of wave propagation in the anisotropic weld and this is based on the Dijkstra algorithm. Using this autofocus approach a measured weld map was extracted from an austenitic weld and used to reduce location errors, initially greater than 6mm, to less than 1mm.

  6. Formation of Expanded Austenite on a Cold-Sprayed AISI 316L Coating by Low-Temperature Plasma Nitriding

    NASA Astrophysics Data System (ADS)

    Adachi, Shinichiro; Ueda, Nobuhiro

    2015-12-01

    Low-temperature plasma nitriding at temperatures below 450 °C is commonly applied to austenitic stainless steels to enhance wear resistance, while maintaining corrosion resistance, by forming expanded austenite (known as the S-phase). In this work, low-temperature plasma nitriding of cold-sprayed AISI 316L coatings was examined. A cold-spray technique was developed to produce metal coatings with less oxidation. However, the cold-sprayed AISI 316L coating obtained by use of nitrogen gas as propellant contained many interconnected pores and cracks, and was, consequently, unsuitable as an anticorrosive coating. Therefore, laser post-treatment was used to modify the coating and increase its density to similar to that of bulk steel. The anticorrosive performance of this coating on a carbon steel substrate in NaCl solution was substantially improved. Subsequent low-temperature plasma nitriding enhanced the wear resistance by two orders of magnitude. It is concluded that cold-sprayed AISI 316L coatings treated by laser post-treatment and subsequent low-temperature plasma nitriding could be used as protective coatings under severe wear and corrosion conditions.

  7. Experimental Analysis of the Austenitic Phase in Steels by the Application of X-Ray Diffractometry

    NASA Astrophysics Data System (ADS)

    Piesova, Marianna; Czan, Andrej; Sajgalik, Michal; Czanova, Tatiana; Cep, Robert

    2016-12-01

    Uniform austenite remaining in the microstructure of the martensitic transformation is called the residual austenite. It is undesirable structure in components, due to its slow decay causes dimensional instability in these components and reducing the hardness. There is a change in volume and it generate internal stress which often appear as cracks. The residual austenite is highly undesirable component in the molded parts, as well as the production of gears and bearing components. The article deals with quantification of residual austenite in steels by using the Average peak method by X-ray diffraction. This method applies four separate peaks to determine the amount of austenite.

  8. Thermodynamic calculation and experimental verification of the carbonitride-austenite equilibrium in Ti-Nb microalloyed steels

    NASA Astrophysics Data System (ADS)

    Zou, Heilong; Kirkaldy, J. S.

    1992-02-01

    The sublattice-regular solution model has been adapted to describe the thermodynamics of complex carbonitrides. This model has been applied to titanium- and niobium-bearing microalloyed steels for calculation of the mole fraction and composition of the carbonitride precipitates and the residual solute levels in the austenite. Both experimental results and calculations show that titanium nitride predominantly forms at very high temperatures and titanium-niobium carbides go to completion at low temperatures. Quantitative agreement between the experimental measurements and the predictions for carbonitride compositions as a function of temperature is demonstrated.

  9. Austenite Grain Growth in a 2.25Cr-1Mo Vanadium-Free Steel Accounting for Zener Pinning and Solute Drag: Experimental Study and Modeling

    NASA Astrophysics Data System (ADS)

    Dépinoy, S.; Marini, B.; Toffolon-Masclet, C.; Roch, F.; Gourgues-Lorenzon, A.-F.

    2017-02-01

    Austenite grain size has been experimentally determined for various austenitization temperatures and times in a 2.25Cr-1Mo vanadium-free steel. Three grain growth regimes were highlighted: limited growth occurs at lower temperatures [1193 K (920 °C) and 1243 K (970 °C)]; parabolic growth prevails at higher temperatures [1343 K (1070 °C) and 1393 K (1120 °C)]. At the intermediate temperature of 1293 K (1020 °C), slowed down growth was observed. Classical grain growth equations were applied to the experimental results, accounting for Zener pinning and solute drag as possible causes for temperature-dependent limited growth. It was shown that Zener pinning due to AlN particles could not be responsible for limited growth, although it has some effect at lower temperatures. Instead, limited and slow growths are very likely to be the result of segregation of molybdenum atoms at austenite grain boundaries. The temperature-dependence of this phenomenon may be linked to the co-segregation of molybdenum and carbon atoms.

  10. Austenite Grain Growth in a 2.25Cr-1Mo Vanadium-Free Steel Accounting for Zener Pinning and Solute Drag: Experimental Study and Modeling

    NASA Astrophysics Data System (ADS)

    Dépinoy, S.; Marini, B.; Toffolon-Masclet, C.; Roch, F.; Gourgues-Lorenzon, A.-F.

    2017-05-01

    Austenite grain size has been experimentally determined for various austenitization temperatures and times in a 2.25Cr-1Mo vanadium-free steel. Three grain growth regimes were highlighted: limited growth occurs at lower temperatures [1193 K (920 °C) and 1243 K (970 °C)]; parabolic growth prevails at higher temperatures [1343 K (1070 °C) and 1393 K (1120 °C)]. At the intermediate temperature of 1293 K (1020 °C), slowed down growth was observed. Classical grain growth equations were applied to the experimental results, accounting for Zener pinning and solute drag as possible causes for temperature-dependent limited growth. It was shown that Zener pinning due to AlN particles could not be responsible for limited growth, although it has some effect at lower temperatures. Instead, limited and slow growths are very likely to be the result of segregation of molybdenum atoms at austenite grain boundaries. The temperature-dependence of this phenomenon may be linked to the co-segregation of molybdenum and carbon atoms.

  11. Experimental and Analytical Study of a Steam Vane Expander

    DTIC Science & Technology

    1977-02-01

    expander. Additionally, friction and to a lesser extent leakage , have been modeled in vane air compressors and in the Rovac machine utilizing techniques...Schematic Diagram of Vane Expander Model .. ......... ... 27 8. Vane Free Body Diagram ...... ................. .... 29 9. Leakage Paths for a...capability to predict transient pressure effects. 3 Peterson and McGahan [3] developed a thermodynamic model of an oil flooded sliding vane air

  12. Experimental investigation of the influence of the stress state on the mechanical stability of austenite in multiphase steels

    NASA Astrophysics Data System (ADS)

    Furnémont, Q.; Delannay, F.; Jacques, P. J.

    2003-10-01

    The transformation-induced plasticity (TRIP) effect, i.e. the mechanically activated martensitic transformation of metastable austenite, has been proven for some years to contribute very effective to the deformation process in a large variety of iron-based alloys. In order to enlighten the influence of the stress triaxiality on the kinetics of the mechanically-induced martensitic transformation in TRIP-assisted multiphase steels, several specimens presenting austenite with different mechanical stabilities were strained under different stress states (pure uniaxial tension, uniaxial tension of notched and DENT specimens and stretching). It is shown that the stress triaxiality has a large effect on the mechanical stability of austenite dispersed in a multiphase microstructure and consequently on the mechanical properties of the investigated steels.

  13. Experimental and Numerical Investigation of Flows in Expanding Channels

    SciTech Connect

    Vorobieff, Peter; Putkaradze, Vakhtang

    2008-10-24

    We present an experimental realization of the classical Jeffery-Hamel flows inside a wedge-shaped channel. We compare the measured velocity fields with the predictions of Jeffery-Hamel theory. A detailed experimental study of bifurcation diagrams for the solutions reveals the absolute stability of the pure outflow solution and an interesting hysteretic structure for bifurcations. We also observe a multiple vortex flow regime predicted earlier numerically and analytically. Experimental studies of the stability of the flow to perturbations at the channel exit are also conducted.

  14. The influence of fire exposure on austenitic stainless steel for pressure vessel fitness-for-service assessment: Experimental research

    NASA Astrophysics Data System (ADS)

    Li, Bo; Shu, Wenhua; Zuo, Yantian

    2017-04-01

    The austenitic stainless steels are widely applied to pressure vessel manufacturing. The fire accident risk exists in almost all the industrial chemical plants. It is necessary to make safety evaluation on the chemical equipment including pressure vessels after fire. Therefore, the present research was conducted on the influences of fire exposure testing under different thermal conditions on the mechanical performance evolution of S30408 austenitic stainless steel for pressure vessel equipment. The metallurgical analysis described typical appearances in micro-structure observed in the material suffered by fire exposure. Moreover, the quantitative degradation of mechanical properties was investigated. The material thermal degradation mechanism and fitness-for-service assessment process of fire damage were further discussed.

  15. Experimental and Numerical Investigation of Flows in Expanding Channels

    SciTech Connect

    Vakhtang Putkaradze Peter Vorobieff

    2004-10-28

    This is the first year progress report for our grant starting Feb. 1 2004. It describes experimental and theoretical achievements during the first year, lists the articles published during this period, as well as the progress of the graduate students supported by this grant. The timeline for the future is outlined; the current results convince us that the work will be done on time and within the budget.

  16. An experimental study of under-expanded jets

    NASA Astrophysics Data System (ADS)

    Cain, Terrence M.

    1992-10-01

    The results of an experiment conducted in turbulent underexpanded jets of nitrogen and carbon dioxide exhausted into still air from Mach 3 and Mach 5 conical nozzles are reported. The ratio of the stagnation pressure in the nozzle to the static pressure in the receiving tank was of the order 1000 which is a condition representative of rocket exhaust plumes generated at altitudes near 20 km. The Oxford gun tunnel was adapted for the project by attaching a small nozzle to its barrel. Jets were generated in the tunnel's test section, photographed with a schlieren system and traversed by a Pitot probe. The traverse mechanisms developed allow 100 mm travel during the period of 20 ms over which the tunnel stagnation pressure is constant. Methods of increasing this steady period by modification of the tunnel's driver tube are suggested. The characteristics of underexpanded jets are summarized and available experimental data is reviewed and classified using recently published plume similarity parameters. The asymmetrical nature of plumes is discussed and a physical explanation for pulse shock layer instability is given. Condensation of the plume gas is investigated. It is shown that it is unlikely that condensation occurred anywhere within the nitrogen plumes as drop growth rates are negligible at high entropy. Method of characteristics calculations of the initial plume expansion were compared with the Pitot measurements in the plume core. Variation of the nozzle exit conditions used for the boundary conditions of the method of characteristics predictions is used to demonstrate that viscous and two dimensional effects within the nozzle were not very significant in these experiments.

  17. Experimental study of cryogenic liquid turbine expander with closed-loop liquefied nitrogen system

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Sun, Jinju; Song, Peng

    2015-04-01

    A cryogenic liquid turbine expander is developed as a replacement for traditional Joule-Thomson valves used in the cryogenic systems for the purpose of energy saving. An experimental study was conducted to evaluate the performance of the turbine expander and is the subject of this paper. The test rig comprises a closed-loop liquefied nitrogen system, cryogenic liquid turbine expander unit, and its auxiliary and measuring systems. The test operating parameters of the turbine expander are determined on the basis of flow similarity rules. Pre-cooling of the liquid nitrogen system is first performed, and then the tests are conducted at different flow rates and speed ratios. The turbine expander flow rate, inlet and outlet pressure and temperature, rotational speed and shaft torque were measured. Experimental results and their uncertainties were analyzed and discussed. The following are demonstrated: (1) For both test cases, turbine expander peak isentropic efficiency is respectively 78.8% and 68.4% obtained at 89.6% and 92% of the design flow rate. The large uncertainties in isentropic efficiency are caused by the large enthalpy variations subjected to small measurement uncertainties in temperature and pressure. (2) Total efficiency and hydraulic efficiency of the turbine expander are obtained. They are essentially the same, since both include flow-related effects and also bearing losses. Comparisons of total efficiency and hydraulic efficiency were used to justify measurement uncertainties of different quantities, since the former involves the measured mass flow rate and enthalpy drop (being dependant on inlet and outlet temperature and pressure), while the latter involves the actual shaft power, volume flow rate, and inlet and outlet pressure. (3) Losses in flow passages and the shaft-bearing system have been inferred based on the measured turbine expander total efficiency, isentropic efficiency, and mechanical efficiency, which are respectively 57.6-74.8%, 62

  18. The influence of silicon and aluminum on austenite deformation behavior during fatigue and tensile loading

    NASA Astrophysics Data System (ADS)

    Lehnhoff, Gregory R.

    Advanced high strength steels (AHSS) for automobile light-weighting utilize Si and Al alloying to retain austenite in the microstructure during thermal partitioning treatments. This research project utilized fully austenitic steels with varied Si and Al compositions to understand the effect of these elements on austenite deformation response, including deformation induced martensite formation and deformation twinning. Specific focus was directed at understanding austenite deformation response during fatigue loading. Independent alloying additions of 2.5 wt pct Si and Al were made to a base steel composition of 15 Ni - 11 Cr - 1 Mn - 0.03 C (wt pct). Weak beam dark field transmission electron microscopy (TEM) imaging of dissociated dislocations was implemented to experimentally determine the influences of Si and Al on austenite stacking fault energy (SFE). The 2.5 wt pct Si alloying addition decreased the SFE by 6.4 mJ/m2, while the 2.5 wt pct Al alloying increased the SFE by 12 mJ/m2. Fully reversed, total strain controlled, low cycle fatigue (LCF) tests indicated that all four alloys underwent primary cyclic hardening and stabilization. Secondary cyclic strain hardening was correlated to BCC martensite formation using Feritscope magnetic fraction measurements of LCF specimens; the formation of 1 pct martensite led to 7 MPa of secondary hardening. TEM showed that martensite predominantly formed as parallel, irregular bands through strain induced nucleation on austenite shear bands. The austenite shear bands consisted of austenite {111} planes with concentrated dislocations, stacking faults, and/or HCP epsilon-martensite. Aluminum alloying promoted martensite formation during LCF, while Si suppressed martensite. Therefore, the strain induced nucleation process was not suppressed by the increased SFE associated with Al alloying. Tensile testing indicated that Si alloying promoted deformation twinning by lowering the SFE. Similarly to LCF loading, Al promoted

  19. Experimental investigation of the ORC system in a cogenerative domestic power plant with a scroll expanders

    NASA Astrophysics Data System (ADS)

    Kaczmarczyk, Tomasz Z.; Ihnatowicz, Eugeniusz; Żywica, Grzegorz; Kiciński, Jan

    2015-11-01

    The paper presents the results of experimental investigations of the ORC system with two scroll expanders which have been used as a source of electricity. Theworking fluidwas HFE7100 - a newly engineered fluid with a unique heat transfer and favourable environmental properties. In the ORC system three heat exchangers were used (evaporator, regenerator, condenser) and before expanders the droplet separator was installed. As a source of heat an innovative biomass boiler was used. Studies have been carried out for the expanders worked in series and in parallel. The paper presents the thermal and fluidflow properties of the ORC installation for the selected flow rates and different temperatures of the working medium. The characteristics of output electrical power, operating speed and vibrations for scroll expanders were also presented.

  20. Expanding the vision of the Experimental Forest and Range network to urban areas

    Treesearch

    J. Morgan. Grove

    2014-01-01

    After 100 years, the USDA Forest Service has emerging opportunities to expand the Experimental Forest and Range (EFR) network to urban areas. The purpose of this expansion would be to broaden the types of ecosystems studied, interdisciplinary approaches used, and relevance to society of the EFR network through long-term and large-scale social-ecological projects in...

  1. Analytical and experimental investigation of two-phase flow screw expanders for power generation

    SciTech Connect

    Taniguchi, H.; Kudo, K.; Park, I.; Kumazawa, S.

    1988-10-01

    An analytical procedure for calculating the performance of a two-phase flow screw-type expander is presented. Predicted results are compared with experimental measurements made with a recently developed prototype expander. This expander was designed for investigating the applicability of this type of machine as the expansion device in refrigeration or heat pump cycles with the objective of taking advantage of the power-producing capability of the expanding fluid. It has two rotors each with a diameter of 81.6 mm and a length of 135 mm, and was operated with Freon-12 entering at a pressure of 1.588 MPa (230.4 psia) and subcooling of between 2 and 12 K. Maximum power generated was 10 kW at a rotor speed of 3000 rpm. The internal (machine) efficiency is predicted to increase from about 30 to 70 percent as the rotor speed increases from 500 to 3000 rpm. Experimental results over the same speed range increase from 30 to 60 percent. The low experimental values at the higher rotor speeds are attributed primarily to frictional losses not included in the analysis. Estimates of the performance of machines with larger diameter rotors yielded internal efficiencies reaching 80 percent and increases in power output proportional to the square of the rotor diameter.

  2. Experimental performance of a piston expander in a small- scale organic Rankine cycle

    NASA Astrophysics Data System (ADS)

    Oudkerk, J. F.; Dickes, R.; Dumont, O.; Lemort, V.

    2015-08-01

    Volumetric expanders are suitable for more and more applications in the field of micro- and small-scale power system as waster heat recovery or solar energy. This paper present an experimental study carried out on a swatch-plate piston expander. The expander was integrated into an ORC test-bench using R245fa. The performances are evaluated in term of isentropic efficiency and filling factor. The maximum efficiency and power reached are respectively 53% and 2 kW. Inside cylinder pressure measurements allow to compute mechanical efficiency and drown P-V diagram. A semi-empirical simulation model is then proposed, calibrated and used to analyse the different sources of losses.

  3. Ignition of expandable polystyrene foam by a hot particle: an experimental and numerical study.

    PubMed

    Wang, Supan; Chen, Haixiang; Liu, Naian

    2015-01-01

    Many serious fires have occurred in recent years due to the ignition of external building insulation materials by hot metallic particles. This work studied the ignition of expandable polystyrene foam by hot metallic particles experimentally and numerically. In each experiment, a spherical steel particle was heated to a high temperature (within 1173-1373K) and then dropped to the surface of an expandable polystyrene foam block. The particles used in experiments ranged from 3mm to 7 mm in radius. The observed results for ignition were categorized into two types: "flaming ignition" and "no ignition", and the flaming ignition limit was determined by statistical analysis. According to the experimental observations, a numerical model was proposed, taking into account the reactant consumption and volatiles convection of expandable polystyrene decomposition in air. Three regimes, no ignition, unstable ignition and stable ignition, were identified, and two critical particle temperatures for separating the three regimes were determined. Comparison with the experimental data shows that the model can predict the range of critical ignition temperatures reasonably well.

  4. Tracheobronchial tree: expandable metallic stents used in experimental and clinical applications. Work in progress.

    PubMed

    Wallace, M J; Charnsangavej, C; Ogawa, K; Carrasco, C H; Wright, K C; McKenna, R; McMurtrey, M; Gianturco, C

    1986-02-01

    An expandable stainless steel stent was formulated for use in the treatment of tracheobronchial stenosis, tracheomalacia, and airway collapse following tracheal reconstruction. The stents were placed through an endotracheal tube into the trachea and bronchi of 11 healthy dogs. The stents expanded over time, substantially increasing the diameter of the lumen. Slight migration occasionally occurred, while an inflammatory reaction was noted in each animal. The stents were successfully used in the treatment of two cancer patients to dilate a postoperative bronchial stenosis that caused pneumonia and to support a tracheal graft that collapsed with respiration. Because of the stent migration in experimental studies, designs are being tested to develop stents with greater stability. These stents may be effective in overcoming stenosis caused by scarring, extrinsic compression, and collapse of reconstructed tracheobronchial structures.

  5. Experimental observations and modeling of nanoparticle formation in laser-produced expanding plasma

    SciTech Connect

    Lescoute, E.; Hallo, L.; Chimier, B.; Tikhonchuk, V. T.; Hebert, D.; Chevalier, J.-M.; Etchessahar, B.; Combis, P.

    2008-06-15

    Interaction of a laser beam with a target may generate a high velocity expanding plasma plume, solid debris, and liquid nano- and microparticles. They can be produced from plasma recombination, vapor condensation or by a direct expulsion of the heated liquid phase. Two distinct sizes of particles are observed depending on the temperature achieved in the plasma plume: Micrometer-size fragments for temperatures lower than the critical temperature, and nanometer-size particles for higher temperatures. The paper presents experimental observations of fragments and nanoparticles in plasma plumes created from gold targets. These results are compared with theoretical models of vapor condensation and microparticle formation.

  6. Correlation Between Experimental and Calculated Phase Fractions in Aged 20Cr32Ni1Nb Austenitic Stainless Steels Containing Nitrogen

    NASA Astrophysics Data System (ADS)

    Dewar, Matthew P.; Gerlich, Adrian P.

    2013-02-01

    A centrifugally cast 20Cr32Ni1Nb stainless steel manifold in service for 16 years at temperatures ranging from 1073 K to 1123 K (800 °C to 850 °C) has been characterized using scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), auger electron spectroscopy (AES), and X-ray diffraction (XRD). Nb(C,N), M23C6, and the silicide G-phases (Ni16Nb6Si7) were all identified in a conventional SEM, while the nitride Z-phase (CrNbN) was observed only in AES. M23C6, Z-phase and G-phase were characterized in XRD. Thermodynamic equilibrium calculations using ThermoCalc Version S, with the TCS Steel and Fe-alloys Database (TCFE6), and Thermotech Ni-based Superalloys Database (TTNI8) were validated by comparing experimental phase fraction results obtained from both EPMA and AES. A computational study looking at variations in the chemical composition of the alloy, and how they affect phase equilibria, was investigated. Increasing the nitrogen concentration is shown to decrease G-phase formation, where it is replaced by other intermetallic phases such as Z-phase and π-phase that do not experience liquation during pre-weld annealing treatments. Suppressing G-phase formation was ultimately determined to be a function of minimizing silicon content, and understabilizing the Nb/(C + 6/7N) ratio.

  7. In situ observations of austenite grain growth in Fe-C-Mn-Si super bainitic steel

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Xu, Guang; Zhang, Yu-long; Hu, Hai-jiang; Zhou, Lin-xin; Xue, Zheng-liang

    2013-11-01

    In situ observations of austenite grain growth in Fe-C-Mn-Si super bainitic steel were conducted on a high-temperature laser scanning confocal microscope during continuous heating and subsequent isothermal holding at 850, 1000, and 1100°C for 30 min. A grain growth model was proposed based on experimental results. It is indicated that the austenite grain size increases with austenitizing temperature and holding time. When the austenitizing temperature is above 1100°C, the austenite grains grow rapidly, and abnormal austenite grains occur. In addition, the effect of heating rate on austenite grain growth was investigated, and the relation between austenite grains and bainite morphology after bainitic transformations was also discussed.

  8. The varying porosity of braided self-expanding stents and flow diverters: an experimental study.

    PubMed

    Makoyeva, A; Bing, F; Darsaut, T E; Salazkin, I; Raymond, J

    2013-03-01

    Braided self-expandable stents and flow diverters of uniform construction may develop zones of heterogeneous porosity in vivo. Unwanted stenoses may also occur at the extremities of the device. We studied these phenomena in dedicated benchtop experiments. Five braided devices of decreasing porosity were studied. To simulate discrepancies in diameters between the landing zones of the parent vessel and the aneurysm neck area, device extremities were inserted into silicone tubes of various diameters (2-3 mm), leaving the midportion free to react to experimental manipulations, which included axial approximation of the tubes (0-7 mm), and curvature (0-135°), with or without axial compression (0-2 mm). The length of the landing zone was sequentially decreased to study terminal device stenosis. All devices adopted a conformation characterized by 3 different zones: bilateral landing zones, a middle compaction zone, and 2 transition zones. It is possible, during deployment, to compact stents and FDs to decrease porosity, but a limiting factor was the transition zone, which remained relatively unchanged and of higher porosity than the expansion zone. Length of the transition zone increased when devices were constrained in smaller tubes. Heterogeneities in porosity with compaction and curvatures were predictable and followed simple geometric rules. Extremity stenoses occurred increasingly with decreasing length of the landing zone. Braided self-expandable devices show predictable changes in porosity according to device size, vessel diameter, and curvature. Adequate landing zones are required to prevent terminal device stenosis.

  9. Nonlinear dynamics in experimental devices with compressed/expanded surfactant monolayers

    NASA Astrophysics Data System (ADS)

    Higuera, M.; Perales, J. M.; Vega, J. M.

    2014-08-01

    A theory is provided for a common experimental set up that is used to measure surface properties in surfactant monolayers. The set up consists of a surfactant monolayer (over a shallow liquid layer) that is compressed/expanded in a periodic fashion by moving in counter-phase two parallel, slightly immersed solid barriers, which vary the free surface area and thus the surfactant concentration. The simplest theory ignores the fluid dynamics in the bulk fluid, assuming spatially uniform surfactant concentration, which requires quite small forcing frequencies and provides reversible dynamics in the compression/expansion cycles. In this paper, we present a long-wave theory for not so slow oscillations that assumes local equilibrium but takes the fluid dynamics into account. This simple theory uncovers the physical mechanisms involved in the surfactant behavior and allows for extracting more information from each experimental run. The conclusion is that the fluid dynamics cannot be ignored, and that some irreversible dynamics could well have a fluid dynamic origin.

  10. Austenitic stainless steel patterning by plasma assisted diffusion treatments

    NASA Astrophysics Data System (ADS)

    Czerwiec, T.; Marcos, G.; Thiriet, T.; Guo, Y.; Belmonte, T.

    2009-09-01

    The new concept of surface texturing or surface patterning on austenitic stainless steel by plasma assisted diffusion treatment is presented in this paper. It allows the creation of uniform micro or nano relief with regularly shaped asperities or depressions. Plasma assisted diffusion treatments are based on the diffusion of nitrogen and/or carbon in a metallic material at moderate to elevated temperatures. Below 420°C, a plasma assisted nitriding treatment of austenitic stainless steel produces a phase usually called expanded austenite. Expanded austenite is a metastable nitrogen supersaturated solid solution with a disordered fcc structure and a distorted lattice. The nitrided layer with the expanded austenite is highly enriched in nitrogen (from 10 to 35 at%) and submitted to high compressive residual stresses. From mechanical consideration, it is shown that the only possible deformation occurs in the direction perpendicular to the surface. Such an expansion of the layer from the initial surface of the substrate to the gas phase is used here for surface patterning of stainless steel parts. The surface patterning is performed by using masks (TEM grid) and multi-dipolar plasmas.

  11. A Range-Expanding Shrub Species Alters Plant Phenological Response to Experimental Warming.

    PubMed

    Kopp, Christopher W; Cleland, Elsa E

    2015-01-01

    Shifts in plant species phenology (the timing of life-history events such as flowering) have been observed worldwide in concert with rising global temperatures. While most species display earlier phenology with warming, there is large variation among, and even within, species in phenological sensitivity to rising temperatures. Other indirect effects of climate change, such as shifting species composition and altered species interactions, may also be contributing to shifting plant phenology. Here, we describe how experimental warming and the presence of a range-expanding species, sagebrush (Artemisia rothrockii), interact to influence the flowering phenology (day of first and peak flowering) and production (number of flowers) of an alpine cushion plant, Trifolium andersonii, in California's White Mountains. Both first flowering and peak flowering were strongly accelerated by warming, but not when sagebrush was present. Warming significantly increased flower production of T. andersonii, but less so in the presence of sagebrush. A shading treatment delayed phenology and lowered flower production, suggesting that shading may be the mechanism by which sagebrush presence delayed flowering of the understory species. This study demonstrates that species interactions can modify phenological responses to climate change, and suggests that indirect effects of rising temperatures arising from shifting species ranges and altered species interactions may even exceed the direct effects of rising temperatures on phenology.

  12. Parameters Optimization of Laser-Induced Breakdown Spectroscopy Experimental Setup for the Case with Beam Expander

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Zhang, Lei; Fan, Juanjuan; Li, Yufang; Gong, Yao; Dong, Lei; Ma, Weiguang; Yin, Wangbao; Jia, Suotang

    2015-11-01

    Improvement of measurement precision and repeatability is one of the issues currently faced by the laser-induced breakdown spectroscopy (LIBS) technique, which is expected to be capable of precise and accurate quantitative analysis. It was found that there was great potential to improve the signal quality and repeatability by reducing the laser beam divergence angle using a suitable beam expander (BE). In the present work, the influences of several experimental parameters for the case with BE are studied in order to optimize the analytical performances: the signal to noise ratio (SNR) and the relative standard deviation (RSD). We demonstrate that by selecting the optimal experimental parameters, the BE-included LIBS setup can give higher SNR and lower RSD values of the line intensity normalized by the whole spectrum area. For validation purposes, support vector machine (SVM) regression combined with principal component analysis (PCA) was used to establish a calibration model to realize the quantitative analysis of the ash content. Good agreement has been found between the laboratory measurement results from the LIBS method and those from the traditional method. The measurement accuracy presented here for ash content analysis is estimated to be 0.31%, while the average relative error is 2.36%. supported by the 973 Program of China (No. 2012CB921603), National Natural Science Foundation of China (Nos. 61475093, 61127017, 61178009, 61108030, 61378047, 61275213, 61475093, and 61205216), the National Key Technology R&D Program of China (No. 2013BAC14B01), the Shanxi Natural Science Foundation (Nos. 2013021004-1 and 2012021022-1), the Shanxi Scholarship Council of China (Nos. 2013-011 and 2013-01), and the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi, China

  13. (R)evolution: toward a new paradigm of policy and patient advocacy for expanded access to experimental treatments.

    PubMed

    Hogan, Melissa

    2016-02-29

    In life-threatening conditions such as cancer and rare diseases, where there is no cure and no U.S. Food and Drug Administration (FDA)-approved therapy, patients sometimes seek access to an unapproved, experimental therapy through expanded access programs as their last, best hope for treatment to save their lives. Since the 1980s, the policies and the practice of expanded access have evolved, but a common challenge remains that there is no obligation, and often little incentive, for manufacturers to offer expanded access programs, especially for individual patients. In recent years, online campaigns seeking access to an experimental therapy have become more common, paralleling growth in and representing an intersection of social media, digital health, and patient advocacy.Mackey and Schoenfeld have examined the evolution of expanded access policy, practice, and trends, as well as case studies of online campaigns to access experimental therapies, to arrive at several recommendations for the future of expanded access. This commentary puts their paper in context, examines their recommendations, and suggests further reforms.Please see related article: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-016-0568-8.

  14. Precipitation hardening austenitic superalloys

    DOEpatents

    Korenko, Michael K.

    1985-01-01

    Precipitation hardening, austenitic type superalloys are described. These alloys contain 0.5 to 1.5 weight percent silicon in combination with about 0.05 to 0.5 weight percent of a post irradiation ductility enhancing agent selected from the group of hafnium, yttrium, lanthanum and scandium, alone or in combination with each other. In addition, when hafnium or yttrium are selected, reductions in irradiation induced swelling have been noted.

  15. Expanding the three Rs to meet new challenges in humane animal experimentation.

    PubMed

    Schuppli, Catherine A; Fraser, David; McDonald, Michael

    2004-11-01

    The Three Rs are the main principles used by Animal Ethics Committees in the governance of animal experimentation, but they appear not to cover some ethical issues that arise today. These include: a) claims that certain species should be exempted on principle from harmful research; b) increased emphasis on enhancing quality of life of research animals; c) research involving genetically modified (GM) animals; and d) animals bred as models of disease. In some cases, the Three Rs can be extended to cover these developments. The burgeoning use of GM animals in science calls for new forms of reduction through improved genetic modification technology, plus continued attention to alternative approaches and cost-benefit analyses that include the large numbers of animals involved indirectly. The adoption of more expanded definitions of refinement that go beyond minimising distress will capture concerns for enhancing the quality of life of animals through improved husbandry and handling. Targeting refinement to the unpredictable effects of gene modification may be difficult; in these cases, careful attention to monitoring and endpoints are the obvious options. Refinement can also include sharing data about the welfare impacts of gene modifications, and modelling earlier stages of disease, in order to reduce the potential suffering caused to disease models. Other issues may require a move beyond the Three Rs. Certain levels of harm, or numbers and use of certain species, may be unacceptable, regardless of potential benefits. This can be addressed by supplementing the utilitarian basis of the Three Rs with principles based on deontological and relational ethics. The Three Rs remain very useful, but they require thoughtful interpretation and expansion in order for Animal Ethics Committees to address the full range of issues in animal-based research.

  16. Austenite Grain Growth and the Surface Quality of Continuously Cast Steel

    NASA Astrophysics Data System (ADS)

    Dippenaar, Rian; Bernhard, Christian; Schider, Siegfried; Wieser, Gerhard

    2014-04-01

    Austenite grain growth does not only play an important role in determining the mechanical properties of steel, but certain surface defects encountered in the continuous casting industry have also been attributed to the formation of large austenite grains. Earlier research has seen innovative experimentation, the development of metallographic techniques to determine austenite grain size and the building of mathematical models to simulate the conditions pertaining to austenite grain growth during the continuous casting of steel. Oscillation marks and depressions in the meniscus region of the continuously casting mold lead to retarded cooling of the strand surface, which in turn results in the formation of coarse austenite grains, but little is known about the mechanism and rate of formation of these large austenite grains. Relevant earlier research will be briefly reviewed to put into context our recent in situ observations of the delta-ferrite to austenite phase transition. We have confirmed earlier evidence that very large delta-ferrite grains are formed very quickly in the single-phase region and that these large delta-ferrite grains are transformed to large austenite grains at low cooling rates. At the higher cooling rates relevant to the early stages of the solidification of steel in a continuously cast mold, delta-ferrite transforms to austenite by an apparently massive type of transformation mechanism. Large austenite grains then form very quickly from this massive type of microstructure and on further cooling, austenite transforms to thin ferrite allotriomorphs on austenite grain boundaries, followed by Widmanstätten plate growth, with almost no regard to the cooling rate. This observation is important because it is now well established that the presence of a thin ferrite film on austenite grain boundaries is the main cause of reduction in hot ductility. Moreover, this reduction in ductility is exacerbated by the presence of large austenite grains.

  17. Investigation of Austenitization in Low Carbon Microalloyed Steel During Continuous Heating

    NASA Astrophysics Data System (ADS)

    Gunabalapandian, Kavitha; Samanta, Santigopal; Ranjan, Ravi; Singh, Shiv Brat

    2017-02-01

    Dilatation associated with the formation of austenite from ferrite-pearlite was calculated from equilibrium phase fraction and composition. Linear thermal expansion coefficient of ferrite required for the calculation was determined by iteration of dilatation data. A good match was obtained between the calculated and experimental dilatation curves. The calculated dilatation data were used to identify the stages of austenite formation: pearlite dissolution followed by ferrite to austenite transformation which is gradual at first before becoming rapid.

  18. Predicting the Austenite Fraction After Intercritical Annealing in Lean Steels as a Function of the Initial Microstructure

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Xu, Xiaojun; Xu, Wei; van der Zwaag, Sybrand

    2014-04-01

    The final fractions of austenite after the isothermal austenite-to-ferrite transformation and its reverse transformations (including the martensite-to-austenite and the pearlite + ferrite-to-austenite transformations) in the intercritical annealing region have been studied using full equilibrium (FE), paraequilibrium (PE), and local equilibrium (LE) calculations and experiments. The LE model predictions are in a very good agreement with the experimental results, while the FE and PE model predictions deviate significantly. It is also found that the LEP/LENP transition for the austenite-to-ferrite transformation deviates from those of its reverse transformations. The magnitude of deviation increases with the increasing Mn concentration.

  19. Numerical simulation on austenitization of cast steel during heating process

    NASA Astrophysics Data System (ADS)

    Su, B.; Han, Z. Q.; Liu, B. C.; Zhao, Y. R.; Shen, B. Z.; Zhang, L. Z.

    2012-07-01

    A cellular automaton model has been developed to simulate the austenitization process of ASTM A216 WCA cast steel during heating process. The dissolution of pearlite and the transformation of ferrite into austenite were simulated. The calculation domain was divided into square cells, which are characterized by certain attributes that represent the status of each cell: pearlite (P), ferrite (α), austenite (γ) or γ /α interface. The dissolution of pearlite was described by nucleation and growth of austenite. A mixed-mode model in multicomponent system was employed to calculate the growth velocity of the γ /α interface. According to Burke and Turnbull's theory, austenite grain coarsening induced by γ /γ grain boundary migration was simulated. To validate the model, dilatometric and quenching experiments were carried out. The dilatometric experiment was conducted using a Gleeble1500D with a sample 8 mm in diameter. The temperature of the sample was measured using thermocouples welded on the sample surface. In the quenching experiments, steel samples were heated to different temperatures then dropped into a water tank immediately, and the microstructure of the samples was examined to determine the fraction of the austenite. The simulated results were compared with the experimental results and the capability of the model for quantitatively predicting the microstructure evolution of the steel in heating process was assessed.

  20. Modeling of Austenite Grain Growth During Austenitization in a Low Alloy Steel

    NASA Astrophysics Data System (ADS)

    Dong, Dingqian; Chen, Fei; Cui, Zhenshan

    2016-01-01

    The main purpose of this work is to develop a pragmatic model to predict austenite grain growth in a nuclear reactor pressure vessel steel. Austenite grain growth kinetics has been investigated under different heating conditions, involving heating temperature, holding time, as well as heating rate. Based on the experimental results, the mathematical model was established by regression analysis. The model predictions present a good agreement with the experimental data. Meanwhile, grain boundary precipitates and pinning effects on grain growth were studied by transmission electron microscopy. It is found that with the increasing of the temperature, the second-phase particles tend to be dissolved and the pinning effects become smaller, which results in a rapid growth of certain large grains with favorable orientation. The results from this study provide the basis for the establishment of large-sized ingot heating specification for SA508-III steel.

  1. A Feasibility Study on Low Temperature Thermochemical Treatments of Austenitic Stainless Steel in Fluidized Bed Furnace

    NASA Astrophysics Data System (ADS)

    Haruman, Esa; Sun, Yong; Triwiyanto, Askar; Manurung, Yupiter H. P.; Adesta, Erry Y.

    2011-04-01

    In this work, the feasibility of using an industrial fluidized bed furnace to perform low temperature thermochemical treatments of austenitic stainless steels has been studied, with the aim to produce expanded austenite layers with combined wear and corrosion resistance, similar to those achievable by plasma and gaseous processes. Several low temperature thermochemical treatments were studied, including nitriding, carburizing, combined nitridingcarburizing (hybrid treatment), and sequential carburizing and nitriding. The results demonstrate that it is feasible to produce expanded austenite layers on the investigated austenitic stainless steel by the fluidized bed heat treatment technique, thus widening the application window for the novel low temperature processes. The results also demonstrate that the fluidized bed furnace is the most effective for performing the hybrid treatment, which involves the simultaneous incorporation of nitrogen and carbon together into the surface region of the component in nitrogen and carbon containing atmospheres. Such hybrid treatment produces a thicker and harder layer than the other three processes investigated.

  2. The chick embryo as an expanding experimental model for cancer and cardiovascular research

    PubMed Central

    Kain, Kristin H.; Miller, James W.I.; Jones-Paris, Celestial R.; Thomason, Rebecca T.; Lewis, John D.; Bader, David M.; Barnett, Joey V.; Zijlstra, Andries

    2014-01-01

    A long and productive history in biomedical research defines the chick as a model for human biology. Fundamental discoveries, including the description of directional circulation propelled by the heart and the link between oncogenes and the formation of cancer, indicate its utility in cardiac biology and cancer. Despite the more recent arrival of several vertebrate and invertebrate animal models during the last century, the chick embryo remains a commonly used model for vertebrate biology and provides a tractable biological template. With new molecular and genetic tools applied to the avian genome the chick embryo is accelerating the discovery of normal development and elusive disease processes. Moreover, progress in imaging and chick culture technologies is advancing real-time visualization of dynamic biological events, such as tissue morphogenesis, angiogenesis and cancer metastasis. A rich background of information, coupled with new technologies and relative ease of maintenance suggest an expanding utility for the chick embryo in cardiac biology and cancer research. PMID:24357262

  3. Gas-Expanded Liquids: Synergism of Experimental and Computational Determinations of Local Structure

    SciTech Connect

    Charles A. Eckert; Charles L. Liotta; Rigoberto Hernandez

    2007-06-26

    This project focuses on the characterization of a new class of solvent systems called gas-expanded liquids (GXLs), targeted for green-chemistry processing. The collaboration has adopted a synergistic approach combining elements of molecular dynamics (MD) simulation and spectroscopic experiments to explore the local solvent behavior that could not be studied by simulation or experiment alone. The major accomplishments from this project are: • Applied MD simulations to explore the non-uniform structure of CO2/methanol and CO2/acetone GXLs and studied their dynamic behavior with self-diffusion coefficients and correlation functions • Studied local solvent structure and solvation behavior with a combination of spectroscopy and MD simulations • Measured transport properties of heterocyclic solutes in GXLs through Taylor-Aris diffusion techniques and compared these findings to those of MD simulations • Probed local polarity and specific solute-solvent interactions with Diels-Alder and SN2 reaction studies The broader scientific impact resulting from the research activities of this contract have been recognized by two recent awards: the Presidential Green Chemistry Award (Eckert & Liotta) and a fellowship in the American Association for the Advancement of Science (Hernandez). In addition to the technical aspects of this contract, the investigators have been engaged in a number of programs extending the broader impacts of this project. The project has directly supported the development of two postdoctoral researcher, four graduate students, and five undergraduate students. Several of the undergraduate students were co-funded by a Georgia Tech program, the Presidential Undergraduate Research Award. The other student, an African-American female graduated from Georgia Tech in December 2005, and was co-funded through an NSF Research and Education for Undergraduates (REU) award.

  4. Differences in Endothelial Injury After Balloon Angioplasty, Insertion of Balloon-Expanded Stents or Release of Self-Expanding Stents: An Electron Microscopic Experimental Study

    SciTech Connect

    Harnek, Jan; Zoucas, Evita; Carlemalm, Erik; Cwikiel, Wojciech

    1999-01-15

    Purpose: To evaluate which of six different commonly available stents inserted into an artery without percutaneous transluminal angioplasty (PTA) causes the least endothelial damage. To compare the degree of endothelial injury after insertion of such a stent with injury caused by PTA. Methods: Twelve healthy pigs were used in the experiments. In the first part of the study six different types of stents were inserted into the common iliac arteries. In the second part of the study self-expanding stents with large spaces between the wires were used. PTA was performed in the contralateral iliac artery. The pigs were killed immediately after the procedure and resected specimens examined after fixation, using scanning electron microscopy. Results: All procedures but two were accomplished successfully. More endothelium was preserved after insertion of self-expanding stents with large spaces between the wires, compared with stents with small spaces and balloon-expanded stents. After insertion of self-expanding stents with large spaces, 50.1% {+-} 16.4% of the endothelium remained intact, compared with only 5.6% {+-} 7.7% after PTA. The difference was statistically significant (p < 0.001). Conclusion: Self-expanding stents with large spaces between the wires, inserted without PTA, cause less damage to the endothelium than other stents and significantly less damage than PTA.

  5. Mechanism of antihypertensive effect of dietary potassium in experimental volume expanded hypertension in rats.

    PubMed

    Pamnani, M B; Chen, X; Haddy, F J; Schooley, J F; Mo, Z

    2000-08-01

    Dietary potassium supplementation lowers blood pressure (BP) and attenuates complications in hypertensive subjects, particularly those with the low renin volume expanded (LRVE) variety. We and others have shown that the plasma level of a digitalis like substance (DLS) is elevated in this type of hypertension. We therefore, examined the effect of increases in dietary potassium on the plasma level of endogenous DLS, myocardial and renal Na+, K+-ATPase (NKA) activities, BP, and renal excretory function in reduced renal mass (RRM)-salt hypertension in the rat, a classical model of LRVE hypertension. 70% RRM rats were divided in 4 groups, namely those consuming: 1) a sodium free and normal potassium (1.3% as KCl) diet (RRM-0 Na), 2) a normal sodium and normal potassium diet (RRM-NaK), 3) a normal sodium and high potassium (2 X normal) diet (RRM-Na2K), and 4) a normal sodium and 4 times normal potassium diet (RRM-Na4K). At the end of 4 weeks of dietary treatment, direct BP was recorded, plasma level of DLS determined by bioassay and with a radioimmunoassay for digoxin (DIF) and myocardial and renal NKA activities were measured. As expected, compared to RRM-0Na rats, RRM-NaK rats developed hypertension. BP increased significantly less in RRM-Na2K, whereas BP did not increase in RRM-Na4K rats. Hypertension in RRM-NaK rats was associated with an increase in plasma DLS and DIF and decrease in renal and myocardial NKA activities. DLS was increased (DIF was not changed) and myocardial NKA also decreased in rats consuming double potassium. However, quadrupling potassium in the diet (RRM-Na4K) normalized DLS and DIF and increased myocardial and renal NKA activities, compared to RRM-0Na rats. Also compared to RRM-0Na, water consumption, urinary volume excretion, sodium, and potassium increased in the other 3 groups, more so in RRM-Na4K rats. These data show that quadrupling the potassium in the diet prevents the BP increase in RRM rats and this is associated with diuresis

  6. Measurement and control system for cryogenic helium gas bearing turbo-expander experimental platform based on Siemens PLC S7-300

    SciTech Connect

    Li, J.; Xiong, L. Y.; Peng, N.; Dong, B.; Liu, L. Q.; Wang, P.

    2014-01-29

    An experimental platform for cryogenic Helium gas bearing turbo-expanders is established at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. This turbo-expander experimental platform is designed for performance testing and experimental research on Helium turbo-expanders with different sizes from the liquid hydrogen temperature to the room temperature region. A measurement and control system based on Siemens PLC S7-300 for this turbo-expander experimental platform is developed. Proper sensors are selected to measure such parameters as temperature, pressure, rotation speed and air flow rate. All the collected data to be processed are transformed and transmitted to S7-300 CPU. Siemens S7-300 series PLC CPU315-2PN/DP is as master station and two sets of ET200M DP remote expand I/O is as slave station. Profibus-DP field communication is established between master station and slave stations. The upper computer Human Machine Interface (HMI) is compiled using Siemens configuration software WinCC V6.2. The upper computer communicates with PLC by means of industrial Ethernet. Centralized monitoring and distributed control is achieved. Experimental results show that this measurement and control system has fulfilled the test requirement for the turbo-expander experimental platform.

  7. Measurement and control system for cryogenic helium gas bearing turbo-expander experimental platform based on Siemens PLC S7-300

    NASA Astrophysics Data System (ADS)

    Li, J.; Xiong, L. Y.; Peng, N.; Dong, B.; Wang, P.; Liu, L. Q.

    2014-01-01

    An experimental platform for cryogenic Helium gas bearing turbo-expanders is established at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. This turbo-expander experimental platform is designed for performance testing and experimental research on Helium turbo-expanders with different sizes from the liquid hydrogen temperature to the room temperature region. A measurement and control system based on Siemens PLC S7-300 for this turbo-expander experimental platform is developed. Proper sensors are selected to measure such parameters as temperature, pressure, rotation speed and air flow rate. All the collected data to be processed are transformed and transmitted to S7-300 CPU. Siemens S7-300 series PLC CPU315-2PN/DP is as master station and two sets of ET200M DP remote expand I/O is as slave station. Profibus-DP field communication is established between master station and slave stations. The upper computer Human Machine Interface (HMI) is compiled using Siemens configuration software WinCC V6.2. The upper computer communicates with PLC by means of industrial Ethernet. Centralized monitoring and distributed control is achieved. Experimental results show that this measurement and control system has fulfilled the test requirement for the turbo-expander experimental platform.

  8. An Experimental Investigation of Hollow Turbine Blades for Expandable Jet Engines

    NASA Technical Reports Server (NTRS)

    Morgan, W C; Morse, C R

    1954-01-01

    An experimental investigation was made to determine the feasibility of using hollow turbine blades in engines designed for short service life. Airfoils were fabricated from sheet material and techniques of welding and brazing attachment were investigated. The airfoils were not intended to be cooled. A principal objective was the reduction of strategic material requirements primarily as a function of direct weight reduction. The materials considered were in the density range of 0.28 to 0.31 pound per cubic inch. Three materials were used for airfoils: N-155, Inconel-X and L-605. These were attached to J47 turbine blade bases and operated to destruction at maximum service conditions of turbine speed and temperature. It was found that L-605 airfoils brazed to suitable bases satisfied the requirements for expendable engines. Service life varied from 11 to 40 hours.

  9. Effect of austenite on mechanical properties in high manganese austenitic stainless steel with two phase of martensite and austenite

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Kim, J. H.; Hwang, T. H.; Lee, J. Y.; Kang, C. Y.

    2015-05-01

    The effect of the austenite phase on mechanical properties of austenitic stainless steels was investigated using specimens with different volume fractions of retained and reversed austenite. Stainless steels with dual-phase coexisting martensite and austenite were successfully synthesized by deformation and reverse transformation treatment in the cold-rolled high manganese austenitic stainless steel and the ultrafine reverse austenite with less than 0.5 µm in size was formed by reverse transformation treatment in the temperature range of 500-750 °C for various times. With the increase of deformation degree, the volume fraction of retained austenite decreased, while that of the reversed austenite increased as the annealing time increased. From the results of the mechanical properties, it was obvious that as the volume fraction of retained and reversed austenite increased, hardness and strength rapidly decreased, while elongation increased. With regard to each austenite, reversed austenite indicated higher value of hardness and strength, while elongation suggested a lower value because of strengthening owing to grain refinement.

  10. Accurate modelling of anisotropic effects in austenitic stainless steel welds

    SciTech Connect

    Nowers, O. D.; Duxbury, D. J.; Drinkwater, B. W.

    2014-02-18

    The ultrasonic inspection of austenitic steel welds is challenging due to the formation of highly anisotropic and heterogeneous structures post-welding. This is due to the intrinsic crystallographic structure of austenitic steel, driving the formation of dendritic grain structures on cooling. The anisotropy is manifested as both a ‘steering’ of the ultrasonic beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the quantitative effects and relative impacts of these phenomena are not well-understood. A semi-analytical simulation framework has been developed to allow the study of anisotropic effects in austenitic stainless steel welds. Frequency-dependent scatterers are allocated to a weld-region to approximate the coarse grain-structures observed within austenitic welds and imaged using a simulated array. The simulated A-scans are compared against an equivalent experimental setup demonstrating excellent agreement of the Signal to Noise (S/N) ratio. Comparison of images of the simulated and experimental data generated using the Total Focusing Method (TFM) indicate a prominent layered effect in the simulated data. A superior grain allocation routine is required to improve upon this.

  11. Formation and Growth Kinetics of Reverted Austenite During Tempering of a High Co-Ni Steel

    NASA Astrophysics Data System (ADS)

    Gruber, Marina; Ressel, Gerald; Méndez Martín, Francisca; Ploberger, Sarah; Marsoner, Stefan; Ebner, Reinhold

    2016-12-01

    It is well known that high Co-Ni steels exhibit excellent toughness. Since the good toughness in these steels is supposed to be related to thin layers of austenite between martensite crystals, this work presents an experimental study corroborated with diffusional calculations to characterize the evolution of reverted austenite. Atom probe measurements were conducted for analyzing the element distribution in austenite and martensite during tempering. These results were correlated with crystallographic information, which was obtained by using transmission electron microscopy investigations. Additionally, the experimental findings were compared with kinetic calculations with DICTRA™. The investigations reveal that reverted austenite formation during tempering is connected with a redistribution of Ni, Co, Cr, and Mo atoms. The austenite undergoes a Ni and Cr enrichment and a Co depletion, while in the neighboring martensite, a zone of Ni and Cr depletion and Co enrichment is formed. The changes in the chemical composition of austenite during tempering affect the stability of the austenite against phase transformation to martensite during plastic deformation and have thus decisive influence on the toughness of the material.

  12. Relativistic DFT and experimental studies of mono- and bis-actinyl complexes of an expanded Schiff-base polypyrrole macrocycle.

    PubMed

    Zheng, Xiu-Jun; Bell, Nicola L; Stevens, Charlotte J; Zhong, Yu-Xi; Schreckenbach, Georg; Arnold, Polly L; Love, Jason B; Pan, Qing-Jiang

    2016-10-12

    The computationally- and experimentally-determined molecular structures of a bis-uranyl(vi) complex of an expanded Schiff-base polypyrrolic macrocycle [(UO2)2(L)] are in close agreement only if the pyridine in the fifth equatorial donor site on the uranium is included in the calculations. The relativistic density functional theory (DFT) calculations presented here are augmented from those on previously reported simpler frameworks, and demonstrate that other augmentations, such as the incorporation of condensed-phase media and the changes in the peripheral groups of the ligand, have only a slight effect. Synthetic routes to pure samples of the bis- and mono-uranyl(vi) complexes have been developed using pyridine and arene solvents, respectively, allowing the experimental determination of the molecular structures by X-ray single crystal diffraction; these agree well with the calculated structures. A comprehensive set of calculations has been performed on a series of actinyl AnO2(n+) complexes of this macrocyclic ligand. These include both bis- and mono-actinyl adducts for the metals U, Np and Pu, and formal oxidation states VI and V. The reduction potentials of the complexes for U, Np, and Pu, incorporating both solvation and spin-orbit coupling considerations, show the order Np > Pu > U. The agreement between experimental and computed data for U is excellent, suggesting that at this level of computation predictions made about the significantly more radiotoxic Np and Pu molecules should be accurate. A particularly unusual structure of the mononuclear plutonyl(v) complex was predicted by quantum chemical calculations, in which a twist in the macrocycle allows one of the two endo-oxo groups to form a hydrogen bond to one pyrrole group of the opposite side of the macrocycle, in accordance with this member of the set containing the most Lewis basic oxo groups.

  13. Austenite grain growth simulation considering the solute-drag effect and pinning effect

    PubMed Central

    Fujiyama, Naoto; Nishibata, Toshinobu; Seki, Akira; Hirata, Hiroyuki; Kojima, Kazuhiro; Ogawa, Kazuhiro

    2017-01-01

    Abstract The pinning effect is useful for restraining austenite grain growth in low alloy steel and improving heat affected zone toughness in welded joints. We propose a new calculation model for predicting austenite grain growth behavior. The model is mainly comprised of two theories: the solute-drag effect and the pinning effect of TiN precipitates. The calculation of the solute-drag effect is based on the hypothesis that the width of each austenite grain boundary is constant and that the element content maintains equilibrium segregation at the austenite grain boundaries. We used Hillert’s law under the assumption that the austenite grain boundary phase is a liquid so that we could estimate the equilibrium solute concentration at the austenite grain boundaries. The equilibrium solute concentration was calculated using the Thermo-Calc software. Pinning effect was estimated by Nishizawa’s equation. The calculated austenite grain growth at 1473–1673 K showed excellent correspondence with the experimental results. PMID:28179962

  14. a Study Into the Effects of AN Austenitic Weld on Ultrasonic Array Imaging Performance

    NASA Astrophysics Data System (ADS)

    Hunter, A. J.; Drinkwater, B. W.; Zhang, J.; Wilcox, P. D.

    2011-06-01

    An industrial application of ultrasonic array imaging is the inspection of austenitic welds with high inhomogeneity and anisotropy. These result in attenuation and perturbation of the signals that adversely affects imaging performance. Here, the effects of perturbations introduced by an austenitic weld on array imaging performance are investigated experimentally. It is shown that three major factors contribute to the degradation of image quality: timing errors, phase errors, and multi-path propagation and scattering.

  15. Going "social" to access experimental and potentially life-saving treatment: an assessment of the policy and online patient advocacy environment for expanded access.

    PubMed

    Mackey, Tim K; Schoenfeld, Virginia J

    2016-02-02

    Social media is fundamentally altering how we access health information and make decisions about medical treatment, including for terminally ill patients. This specifically includes the growing phenomenon of patients who use online petitions and social media campaigns in an attempt to gain access to experimental drugs through expanded access pathways. Importantly, controversy surrounding expanded access and "compassionate use" involves several disparate stakeholders, including patients, manufacturers, policymakers, and regulatory agencies-all with competing interests and priorities, leading to confusion, frustration, and ultimately advocacy. In order to explore this issue in detail, this correspondence article first conducts a literature review to describe how the expanded access policy and regulatory environment in the United States has evolved over time and how it currently impacts access to experimental drugs. We then conducted structured web searches to identify patient use of online petitions and social media campaigns aimed at compelling access to experimental drugs. This was carried out in order to characterize the types of communication strategies utilized, the diseases and drugs subject to expanded access petitions, and the prevalent themes associated with this form of "digital" patient advocacy. We find that patients and their families experience mixed results, but still gravitate towards the use of online campaigns out of desperation, lack of reliable information about treatment access options, and in direct response to limitations of the current fragmented structure of expanded access regulation and policy currently in place. In response, we discuss potential policy reforms to improve expanded access processes, including advocating greater transparency for expanded access programs, exploring use of targeted economic incentives for manufacturers, and developing systems to facilitate patient information about existing treatment options. This includes

  16. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part I. Ductility and fracture toughness

    NASA Astrophysics Data System (ADS)

    Margolin, B.; Sorokin, A.; Shvetsova, V.; Minkin, A.; Potapova, V.; Smirnov, V.

    2016-11-01

    The radiation swelling effect on the fracture properties of irradiated austenitic steels under static loading has been studied and analyzed from the mechanical and physical viewpoints. Experimental data on the stress-strain curves, fracture strain, fracture toughness and fracture mechanisms have been represented for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various swelling. Some phenomena in mechanical behaviour of irradiated austenitic steels have been revealed and explained as follows: a sharp decrease of fracture toughness with swelling growth; untypical large increase of fracture toughness with decrease of the test temperature; some increase of fracture toughness after preliminary cyclic loading. Role of channel deformation and channel fracture has been clarified in the properties of irradiated austenitic steel and different tendencies to channel deformation have been shown and explained for the same austenitic steel irradiated at different temperatures and neutron doses.

  17. Austenite Formation in a Cold-Rolled Semi-austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Celada Casero, Carola; San Martín, David

    2014-04-01

    The progress of the martensite ( α') to austenite ( γ) phase transformation has been thoroughly investigated at different temperatures during the continuous heating of a cold-rolled precipitation hardening metastable stainless steel at a heating rate of 0.1 K/s. Heat-treated samples have been characterized using different experimental complementary techniques: high-resolution dilatometry, magnetization, and thermoelectric power (TEP) measurements, micro-hardness-Vickers testing, optical/scanning electron microscopy, and tensile testing. The two-step transformation behavior observed is thought to be related to the presence of a pronounced chemical banding in the initial microstructure. This banding has been characterized using electron probe microanalysis. Unexpectedly, dilatometry measurements seem unable to locate the end of the transformation accurately, as this technique does not detect the second step of this transformation (last 20 pct of it). It is shown that once the starting ( A S) and finishing ( A F) transformation temperatures have been estimated by magnetization measurements, the evolution of the volume fractions of austenite and martensite can be evaluated by TEP or micro-hardness measurement quite reliably as compared to magnetization measurements. The mechanical response of the material after being heated to temperatures close to A S, A F, and ( A F - A S)/2 is also discussed.

  18. An alternative to the crystallographic reconstruction of austenite in steels

    SciTech Connect

    Bernier, Nicolas; Bracke, Lieven; Malet, Loïc; Godet, Stéphane

    2014-03-01

    An alternative crystallographic austenite reconstruction programme written in Matlab is developed by combining the best features of the existing models: the orientation relationship refinement, the local pixel-by-pixel analysis and the nuclei identification and spreading strategy. This programme can be directly applied to experimental electron backscatter diffraction mappings. Its applicability is demonstrated on both quenching and partitioning and as-quenched lath-martensite steels. - Highlights: • An alternative crystallographic austenite reconstruction program is developed. • The method combines a local analysis and a nuclei identification/spreading strategy. • The validity of the calculated orientation relationship is verified on a Q and P steel. • The accuracy of the reconstructed microtexture is investigated on a martensite steel.

  19. High Mn austenitic stainless steel

    DOEpatents

    Yamamoto, Yukinori [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Brady, Michael P [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN; Liu, Chain-tsuan [Knoxville, TN

    2010-07-13

    An austenitic stainless steel alloy includes, in weight percent: >4 to 15 Mn; 8 to 15 Ni; 14 to 16 Cr; 2.4 to 3 Al; 0.4 to 1 total of at least one of Nb and Ta; 0.05 to 0.2 C; 0.01 to 0.02 B; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1W; up to 3 Cu; up to 1 Si; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni, and wherein the alloy forms an external continuous scale including alumina, nanometer scale sized particles distributed throughout the microstructure, the particles including at least one of NbC and TaC, and a stable essentially single phase FCC austenitic matrix microstructure that is essentially delta-ferrite-free and essentially BCC-phase-free.

  20. Combined nano-SIMS/AFM/EBSD analysis and atom probe tomography, of carbon distribution in austenite/ε-martensite high-Mn steels.

    PubMed

    Seol, Jae-Bok; Lee, B-H; Choi, P; Lee, S-G; Park, C-G

    2013-09-01

    We introduce a new experimental approach for the identification of the atomistic position of interstitial carbon in a high-Mn binary alloy consisting of austenite and ε-martensite. Using combined nano-beam secondary ion mass spectroscopy, atomic force microscopy and electron backscatter diffraction analyses, we clearly observe carbon partitioning to austenite. Nano-beam secondary ion mass spectroscopy and atom probe tomography studies also reveal carbon trapping at crystal imperfections as identified by transmission electron microscopy. Three main trapping sites can be distinguished: phase boundaries between austenite and ε-martensite, stacking faults in austenite, and prior austenite grain boundaries. Our findings suggest that segregation and/or partitioning of carbon can contribute to the austenite-to-martensite transformation of the investigated alloy. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  1. Experimental measurements and evaluation of the expanded water repellent perlite used for the cargo containment system of LNG carrier

    NASA Astrophysics Data System (ADS)

    Li, Manfeng; Ju, Yonglin

    2017-10-01

    To minimize the water absorption and to improve the thermal insulated properties of the insulation materials used for the cargo containment systems (CCSs) of LNG carrier, a kind of expanded water-repellent perlite has been developed by coating hydrophobic membrane onto the outer surface of the expanded perlite to change its physical and chemical characteristics. Considering the CCSs operated in a wide temperature range from environmental temperature to cryogenic temperature, the thermal analysis has been conducted to quantitatively determine the thermal insulted properties of the insulation materials. Furthermore, a double-sided guarded hot plate apparatus (GHP) is specifically designed and fabricated for the measurement of the thermal conductivities of the insulation specimens operated down to liquid nitrogen temperature. The breakage ratio associated with the water absorption and the thermal conductivity of the expanded water-repellent perlite is firstly proposed, and then a series of experiments are carried out to determine the thermal conductivity of the expanded water-repellent perlite ranging from room temperature to cryogenic temperature based on the different breakage ratios.

  2. Austenite Stability Effects on Tensile Behavior of Manganese-Enriched-Austenite Transformation-Induced Plasticity Steel

    NASA Astrophysics Data System (ADS)

    Gibbs, P. J.; de Moor, E.; Merwin, M. J.; Clausen, B.; Speer, J. G.; Matlock, D. K.

    2011-12-01

    Manganese enrichment of austenite during prolonged intercritical annealing was used to produce a family of transformation-induced plasticity (TRIP) steels with varying retained austenite contents. Cold-rolled 0.1C-7.1Mn steel was annealed at incremental temperatures between 848 K and 948 K (575 °C and 675 °C) for 1 week to enrich austenite in manganese. The resulting microstructures are comprised of varying fractions of intercritical ferrite, martensite, and retained austenite. Tensile behavior is dependent on annealing temperature and ranged from a low strain-hardening "flat" curve to high strength and ductility conditions that display positive strain hardening over a range of strain levels. The mechanical stability of austenite was measured using in-situ neutron diffraction and was shown to depend significantly on annealing temperature. Variations in austenite stability between annealing conditions help explain the observed strain hardening behaviors.

  3. Computational design of precipitation strengthened austenitic heat-resistant steels

    NASA Astrophysics Data System (ADS)

    Lu, Qi; Xu, Wei; van der Zwaag, Sybrand

    2013-09-01

    A new genetic alloy design approach based on thermodynamic and kinetic principles is presented to calculate the optimal composition of MX carbonitrides precipitation strengthened austenitic heat-resistant steels. Taking the coarsening of the MX carbonitrides as the process controlling the life time for steels in high temperature use, the high temperature strength is calculated as a function of steel chemistry, service temperature and time. New steel compositions for different service conditions are found yielding optimal combinations of strength and stability of the strengthening precipitation for specific applications such as fire-resistant steels (short-time property guarantee) and creep-resistant steels (long-time property guarantee). Using the same modelling approach, the high temperature strength and lifetime of existing commercial austenitic creep-resistant steels were also calculated and a good qualitative agreement with reported experimental results was obtained. According to the evaluation parameter employed, the newly defined steel compositions may have higher and more stable precipitation strengthening factors than existing high-temperature precipitate-strengthened austenite steels.

  4. Thermal expander

    NASA Astrophysics Data System (ADS)

    Huang, Junying; Shen, Xiangying; Jiang, Chaoran; Wu, Zuhui; Huang, Jiping

    2017-08-01

    One type of thermal device, named as thermal expander, is proposed and verified through both simulation and experiment. The thermal expander performs an efficient way to expand a heat flow of line-shape front. Moreover, the thermal expander shows an advantage in rectifying a heat flow from crooked front to line-shape front, which indicates that the thermal expander could act as an efficient point-to-line heat source convertor. We suggest that the thermal expander would be of help to energy saving and emission reduction, especially in thermal circuits and thermal management.

  5. An Investigation on Low-Temperature Thermochemical Treatments of Austenitic Stainless Steel in Fluidized Bed Furnace

    NASA Astrophysics Data System (ADS)

    Haruman, E.; Sun, Y.; Triwiyanto, A.; Manurung, Y. H. P.; Adesta, E. Y.

    2012-03-01

    In this study, the feasibility of using an industrial fluidized bed furnace to perform low-temperature thermochemical treatments of austenitic stainless steels has been studied, with the aim to produce expanded austenite layers with combined wear and corrosion resistance, similar to those achievable by plasma and gaseous processes. Several low-temperature thermochemical treatments were studied, including nitriding, carburizing, combined nitriding-carburizing (hybrid treatment), and sequential carburizing and nitriding. The results demonstrate that it is feasible to produce expanded austenite layers on the investigated austenitic stainless steel by the fluidized bed heat treatment technique, thus widening the application window for the novel low-temperature processes. The results also demonstrate that the fluidized bed furnace is the most effective for performing the hybrid treatment, which involves the simultaneous incorporation of nitrogen and carbon together into the surface region of the component in nitrogen- and carbon-containing atmospheres. Such hybrid treatment produces a thicker and harder layer than the other three processes investigated.

  6. Ear-Shaped Stable Auricular Cartilage Engineered from Extensively Expanded Chondrocytes in an Immunocompetent Experimental Animal Model

    PubMed Central

    Pomerantseva, Irina; Bichara, David A.; Tseng, Alan; Cronce, Michael J.; Cervantes, Thomas M.; Kimura, Anya M.; Neville, Craig M.; Roscioli, Nick; Vacanti, Joseph P.; Randolph, Mark A.

    2016-01-01

    Advancement of engineered ear in clinical practice is limited by several challenges. The complex, largely unsupported, three-dimensional auricular neocartilage structure is difficult to maintain. Neocartilage formation is challenging in an immunocompetent host due to active inflammatory and immunological responses. The large number of autologous chondrogenic cells required for engineering an adult human-sized ear presents an additional challenge because primary chondrocytes rapidly dedifferentiate during in vitro culture. The objective of this study was to engineer a stable, human ear-shaped cartilage in an immunocompetent animal model using expanded chondrocytes. The impact of basic fibroblast growth factor (bFGF) supplementation on achieving clinically relevant expansion of primary sheep chondrocytes by in vitro culture was determined. Chondrocytes expanded in standard medium were either combined with cryopreserved, primary passage 0 chondrocytes at the time of scaffold seeding or used alone as control. Disk and human ear-shaped scaffolds were made from porous collagen; ear scaffolds had an embedded, supporting titanium wire framework. Autologous chondrocyte-seeded scaffolds were implanted subcutaneously in sheep after 2 weeks of in vitro incubation. The quality of the resulting neocartilage and its stability and retention of the original ear size and shape were evaluated at 6, 12, and 20 weeks postimplantation. Neocartilage produced from chondrocytes that were expanded in the presence of bFGF was superior, and its quality improved with increased implantation time. In addition to characteristic morphological cartilage features, its glycosaminoglycan content was high and marked elastin fiber formation was present. The overall shape of engineered ears was preserved at 20 weeks postimplantation, and the dimensional changes did not exceed 10%. The wire frame within the engineered ear was able to withstand mechanical forces during wound healing and neocartilage

  7. Ear-Shaped Stable Auricular Cartilage Engineered from Extensively Expanded Chondrocytes in an Immunocompetent Experimental Animal Model.

    PubMed

    Pomerantseva, Irina; Bichara, David A; Tseng, Alan; Cronce, Michael J; Cervantes, Thomas M; Kimura, Anya M; Neville, Craig M; Roscioli, Nick; Vacanti, Joseph P; Randolph, Mark A; Sundback, Cathryn A

    2016-02-01

    Advancement of engineered ear in clinical practice is limited by several challenges. The complex, largely unsupported, three-dimensional auricular neocartilage structure is difficult to maintain. Neocartilage formation is challenging in an immunocompetent host due to active inflammatory and immunological responses. The large number of autologous chondrogenic cells required for engineering an adult human-sized ear presents an additional challenge because primary chondrocytes rapidly dedifferentiate during in vitro culture. The objective of this study was to engineer a stable, human ear-shaped cartilage in an immunocompetent animal model using expanded chondrocytes. The impact of basic fibroblast growth factor (bFGF) supplementation on achieving clinically relevant expansion of primary sheep chondrocytes by in vitro culture was determined. Chondrocytes expanded in standard medium were either combined with cryopreserved, primary passage 0 chondrocytes at the time of scaffold seeding or used alone as control. Disk and human ear-shaped scaffolds were made from porous collagen; ear scaffolds had an embedded, supporting titanium wire framework. Autologous chondrocyte-seeded scaffolds were implanted subcutaneously in sheep after 2 weeks of in vitro incubation. The quality of the resulting neocartilage and its stability and retention of the original ear size and shape were evaluated at 6, 12, and 20 weeks postimplantation. Neocartilage produced from chondrocytes that were expanded in the presence of bFGF was superior, and its quality improved with increased implantation time. In addition to characteristic morphological cartilage features, its glycosaminoglycan content was high and marked elastin fiber formation was present. The overall shape of engineered ears was preserved at 20 weeks postimplantation, and the dimensional changes did not exceed 10%. The wire frame within the engineered ear was able to withstand mechanical forces during wound healing and neocartilage

  8. Phase transformation and stabilization of a high strength austenite

    NASA Technical Reports Server (NTRS)

    Jin, S.; Huang, D.

    1976-01-01

    An investigation of the phase transformation and the austenite stabilization in a high strength austenite has been made. An Fe-29Ni-4.3Ti austenite age-hardened by gamma-prime (Ni3Ti) precipitates showed a further increase of strength after martensitic and reverse martensitic phase transformations. The stability of ausaged austenite as well as ausaged and transformation-strengthened austenite was improved significantly through an isothermal treatment at 500 C. The Ms temperature of the strengthened austenite was restored to nearly that of annealed austenite while the austenite was hardened to R(C) 41 through precipitation and phase transformations. The observed austenite stabilization is attributed to the formation of GP zones or short-range order of less than about 10A in size.

  9. Experimental Demonstration of Collisionless Particle Acceleration Mechanisms and Entrainment of Ambient Plasma Ions by a Rapidly Expanding Diamagnetic Cavity.

    NASA Astrophysics Data System (ADS)

    Bonde, J.; Vincena, S. T.; Gekelman, W. N.

    2015-12-01

    The collisionless coupling of an expanding diamagnetic cavity to a magnetized, ambient plasma is studied in a laboratory environment using a laser-produced plasma (LPP). The seed LPP rapidly expands with velocities up to the background Alfvén speed, vexp ≤ vA. The boundary layer of the expansion is characterized with in situ diagnostics as a cylindrical version of the Ferraro-Rosenbluth current sheath. Maintenance of quasi-neutrality in this sheath forms an electric field opposing the cross-field expansion which simultaneously drives the electron current that forms the diamagnetic cavity, decelerates the LPP ions to stagnation, and accelerates ambient ions inward. The field topology across the background magnetic field is identical to that described by Bernhardt, et al. [1] for the AMPTE magnetotail barium releases. The boundary along the magnetic field, however, is shown to contain an electric field with E·B ≠ 0, which is absent in simple fluid models of diamagnetic cavities. The electric fields at this boundary help explain previous observations in the experiment of the ejection of suprathermal electrons and return currents that generated whistler- and Alfvén-wave radiation in the ambient plasma. Magnetic loops and an emissive probe measure the magnetic field and electrostatic potential along 3 dimensions while a laser-induced fluorescence scheme measures the cross-field flow of the ambient argon ions as they penetrate the diamagnetic cavity. Particle orbit solvers employing the measured fields corroborate the flow diagnostic and predict strong outflows of ambient ions with higher charge to mass ratios after diamagnetic cavity collapse. This experiment was conducted in the Large Plasma Device at the Basic Plasma Science Facility and funded by grants from the US Department of Energy and the National Science Foundation. [1] P.A. Bernhardt, R.A. Roussel-Dupre, M.B. Pongratz, J. Geophys. Res. 92, 57777 (1987).

  10. Experimental assessment of oral hygiene achieved by children wearing rapid palatal expanders, comparing manual and electric toothbrushes.

    PubMed

    Mazzoleni, S; Bonaldo, G; Pontarolo, E; Zuccon, A; De Francesco, M; Stellini, E

    2014-08-01

    The aim was to compare the efficacy of the electric versus the manual toothbrush in terms of the oral hygiene achieved by patients wearing rapid palatal expanders (RPEs). Forty patients were randomly divided into two groups; one equipped with a manual toothbrush (Group A), the other with an electric toothbrush (Group B). Each child's plaque index (PI) and gingival index (GI) were calculated at banded molar level at times T0 (before banding), T1 (a month later), T2 (3 months later) and T3 (when the expander was removed). At each appointment, the PI and GI were recorded and the patient was remotivated. The level of oral hygiene achieved by the group using an electric toothbrush produced a greater improvement in the two indexes than in the group using the manual toothbrush that showed no statistically significant improvement (PI T0-T3: P = 0.309; GI T0-T3: P = 0.141). Both indexes dropped considerably in both groups from T0 to T2, but more so in the group B. From T2 to T3, although the electric toothbrush continued to be substantially more effective, Group B showed a statistically significant deterioration in the oral hygiene (PI +20%; GI +33%). Other assessments conducted on particular areas of the tooth showed improvements in the PI (-33%) for the vestibular region, and for the GI (-57%) in the palatal region among the patients in Group B, while there were no significant changes in these indexes in Group A. Our findings show that the electric toothbrush is statistically more efficient in performing an adequate level of oral hygiene in children wearing RPE. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  11. Isothermal and Cyclic Aging of 310S Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Parrens, Coralie; Lacaze, Jacques; Malard, Benoit; Dupain, Jean-Luc; Poquillon, Dominique

    2017-06-01

    Unusual damage and high creep strain rates have been observed on components made of 310S stainless steel subjected to thermal cycles between room temperature and 1143 K (870 °C). Microstructural characterization of such components after service evidenced high contents in sigma phase which formed first from δ-ferrite and then from γ-austenite. To get some insight into this microstructural evolution, isothermal and cyclic aging of 310S stainless steel has been studied experimentally and discussed on the basis of numerical simulations. The higher contents of sigma phase observed after cyclic agings than after isothermal treatments are clearly associated with nucleation triggered by thermal cycling.

  12. Transcatheter implantation of self-expandable valved prosthesis in outlet right ventricle an experimental study in pigs.

    PubMed

    Guilhen, José Cícero Stocco; Palma, José Honório; Gaia, Diego Felipe; Araujo, Andre Telis Vilela de; Teles, Carlos Alberto; Branco, João Nelson; Buffolo, Enio

    2011-01-01

    Patients with congenital heart disease who underwent pulmonary valvotomy or surgery to open the pulmonary valve ring are prone to develop residual pulmonary insufficiency or stenosis that may lead to right heart failure with clinical deterioration. These children require multiple interventions throughout their lives, which impose a high rate of morbidity and mortality. To develop a less invasive technique for implantation of a valved prosthesis through the right ventricle. The valved prosthesis consists of an auto expanding metal stent built with nitinol, surrounded with polyester, where the three leaflets of bovine pericardium were mounted. Twelve pigs were used to perform the implants. Echocardiographic control was performed immediately after implantation and one, four, eight and 12 weeks. One animal showed reflux of moderate to severe and three mild reflux. Transvalvular gradients measured before implantation ranged from 3 to 6 mmHg and that soon after the implant was increased, ranging from 7 to 45 mmHg. There was a decrease in these gradients during follow up and in only four of the twelve animals the gradients were above 20 mmHg. Thrombus formation occurred in the prosthesis of six animals, and this was the most frequent complication. These findings highlight the need for studies with the use of anticoagulants and antiplatelet, an attempt to reduce this event. The study aims to contribute for the start of the use of prosthetic heart valves that could be implanted through minimally invasive techniques without the use of cardiopulmonary bypass.

  13. On the spheroidal graphite growth and the austenite solidification in ductile irons

    NASA Astrophysics Data System (ADS)

    Qing, Jingjing

    Evolutions of austenite and nodular/spheroidal graphite particles during solidifications of ductile irons were experimentally investigated. Spheroidal graphite particle and austenite dendrite were found nucleated independently in liquid. Austenite dendrite engulfed the spheroidal graphite particles after contact and an austenite shell formed around a spheroidal graphite particle. The graphite diameter at which the austenite shell closed around nodule was determined. Statistically determined graphite size distributions indicated multiple graphite nucleation events during solidification. Structures in a graphite nodule varied depending on the growth stages of the nodule in ductile iron. Curved graphene layers appearing as faceted growth ledges swept circumferentially around the surface of a graphite nodule at early growth stages. Mismatches between the growth fronts created gaps which divided a nodule into radially oriented conical substructures (3-D). Columnar substructure was observed in the periphery of a nodule (formed during the intermediate growth stages) on its 2-D cross section. A columnar substructure consisted of parallel peripheral grains, with their c-axes approximately parallel. Graphene layers continued building up in individual conical substructure, and a graphite nodule increased its size accordingly. Method for characterizing the crystal structures of graphite based on the selected area diffraction pattern was developed. Both hexagonal structure and rhombohedral structure were found in the spheroidal graphite particles. Possible crystallographic defects associated with hexagonal-rhombohedral structure transition were discussed. Schematic models for introducing tilt angles to the graphite lattice with basal plane tilt boundaries were constructed.

  14. Austenite grain growth kinetics in Al-killed plain carbon steels

    NASA Astrophysics Data System (ADS)

    Militzer, Matthias; Hawbolt, E. Bruce; Ray Meadowcroft, T.; Giumelli, Alan

    1996-11-01

    Austenite grain growth kinetics have been investigated in three Al-killed plain carbon steels. Experimental results have been validated using the statistical grain growth model by Abbruzzese and Lücke, which takes pinning by second-phase particles into account. It is shown that the pinning force is a function of the pre-heat-treatment schedule. Extrapolation to the conditions of a hot-strip mill indicates that grain growth occurs without pinning during conventional processing. Analytical relations are proposed to simulate austenite grain growth for Al-killed plain carbon steels for any thermal path in a hot-strip mill.

  15. Large-strain cyclic response and martensitic transformation of austenitic stainless steel at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Hamasaki, H.; Nakano, T.; Ishimaru, E.; Yoshida, F.

    2016-08-01

    Cyclic tension-compression tests were carried out for austenitic stainless steel (SUS304) at elevated temperatures. The significant Bauschinger effect was found in the obtained stress-strain curve. In addition, stagnation of deformation induced martensitic transformation was observed just after stress reversal until the equivalent stress reached the maximum value in the course of experiment. The constitutive model for SUS304 at room temperature was developed, in which homogenized stress of SUS304 was expressed by the weighed summation of stresses of austenite and martensite phases. The calculated stress-strain curves and predicted martensite volume fraction were well correlated with those experimental results.

  16. Static Recrystallized Grain Size of Coarse-Grained Austenite in an API-X70 Pipeline Steel

    NASA Astrophysics Data System (ADS)

    Sha, Qingyun; Li, Guiyan; Li, Dahang

    2013-12-01

    The effects of initial grain size and strain on the static recrystallized grain size of coarse-grained austenite in an API-X70 steel microalloyed with Nb, V, and Ti were investigated using a Gleeble-3800 thermomechanical simulator. The results indicate that the static recrystallized grain size of coarse-grained austenite decreases with decreasing initial grain size and increasing applied strain. The addition of microalloying elements can lead to a smaller initial grain size for hot deformation due to the grain growth inhibition during reheating, resulting in decreasing of static recrystallized grain size. Based on the experimental data, an equation for the static recrystallized grain size was derived using the least square method. The grain sizes calculated using this equation fit well with the measured ones compared with the equations for fine-grained austenite and for coarse-grained austenite of Nb-V microalloyed steel.

  17. Development of a System to Measure Austenite Grain Size of Plate Steel Using Laser-Based Ultrasonics

    SciTech Connect

    Lim, C. S.; Hong, S. T.; Yi, J. K.; Choi, S. G.; Oh, K. J.; Nagata, Y.; Yamada, H.; Hamada, N.

    2007-03-21

    A measurement system for austenite grain size of plate steel using laser-based ultrasonics has been developed. At first, the relationship between the ultrasonic attenuation coefficients using longitudinal waves and austenite grain size of samples was investigated in the laboratory experiments. According to the experimental results, the ultrasonic attenuation coefficients showed a good correlation with actual austenite grain sizes. For the next step, the system was installed in a hot rolling pilot plant of plate steel, and it was verified that the austenite grain size could be measured even in the environment of a hot rolling pilot plant. In the experiments, it was also confirmed that the fiber delivery system could deliver Nd:YAG laser beam of 810 mJ/pulse and ultrasonic signals could be obtained successfully.

  18. On Necking, Fracture and Localization of Plastic Flow in Austenitic Stainless Steel Sheets

    SciTech Connect

    Korhonen, A. S.; Manninen, T.; Kanervo, K.

    2007-05-17

    The forming limits of austenitic stainless steel sheets were studied in this work. It was found that the observed limit of straining in stretch forming, when both of the principal stresses are positive, is not set by localized necking, but instead by inclined shearing fracture in the through thickness direction. It appears that the forming limits of austenitic stainless steels may be predicted fairly well by using the classical localized and diffuse necking criteria developed by Hill. The strain path-dependence may be accounted for by integrating the effective strain along the strain path. The fracture criteria of Rice and Tracey and Cockcroft, Latham and Oh were also studied. The results were in qualitative agreement with the experimental observations. Recent experiments with high-velocity electrohydraulic forming of austenitic stainless steels revealed localized necks in stretch formed parts, which are not commonly observed in conventionally formed sheet metal parts.

  19. Influence of Martensite Fraction on the Stabilization of Austenite in Austenitic-Martensitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Huang, Qiuliang; De Cooman, Bruno C.; Biermann, Horst; Mola, Javad

    2016-05-01

    The influence of martensite fraction ( f α') on the stabilization of austenite was studied by quench interruption below M s temperature of an Fe-13Cr-0.31C (mass pct) stainless steel. The interval between the quench interruption temperature and the secondary martensite start temperature, denoted as θ, was used to quantify the extent of austenite stabilization. In experiments with and without a reheating step subsequent to quench interruption, the variation of θ with f α' showed a transition after transformation of almost half of the austenite. This trend was observed regardless of the solution annealing temperature which influenced the martensite start temperature. The transition in θ was ascribed to a change in the type of martensite nucleation sites from austenite grain and twin boundaries at low f α' to the faults near austenite-martensite (A-M) boundaries at high f α'. At low temperatures, the local carbon enrichment of such boundaries was responsible for the enhanced stabilization at high f α'. At high temperatures, relevant to the quenching and partitioning processing, on the other hand, the pronounced stabilization at high f α' was attributed to the uniform partitioning of the carbon stored at A-M boundaries into the austenite. Reduction in the fault density of austenite served as an auxiliary stabilization mechanism at high temperatures.

  20. Effect of Crystallographic Texture, Retained Austenite, and Austenite Grain Size on the Mechanical and Ballistic Properties of Steel Armor Plates

    DTIC Science & Technology

    1976-07-01

    after rolling recrystallizes the austenite, and changes the texture to cube orientation. The sharpness of the cube texture of recrystallized austenite...rolling at a lower temperature. Accordingly, the cube texture of the recrystallized austenite was weakened; as a result, a weakened martensite...obtained. I f . -30- 2. When the deformed austenite with a strong copper-type rolling texture was annealed, a strong cube - texture was assumed by the

  1. Experimental off-pump transventricular pulmonary valve replacement using a self-expandable valved stent: A new approach for pulmonary incompetence after repaired tetralogy of Fallot?

    PubMed

    Godart, François; Bouzguenda, Ivan; Juthier, Francis; Wautot, Fabrice; Prat, Alain; Rey, Christian; Corseaux, Delphine; Ung, Alexandre; Jude, Brigitte; Vincentelli, André

    2009-05-01

    Off-pump valve replacement using self-expandable stents is an emerging technique for pulmonary valve disease. However, significant limitations are the lack of easily available valve substitute to be inserted within the stent and, in the setting of repaired tetralogy of Fallot, the existence of huge pulmonary trunk. We report the first experimental results of a transventricular approach using a decellularized porcine xenograft mounted in a self-expandable stent. Pulmonary valve replacement was realized in 15 lambs by direct access of the infundibulum through a left thoracotomy, combined with pulmonary artery banding. Animals were followed by transthoracic echocardiography and, after control hemodynamic study, were electively killed either at day 7, month 1, or month 4 after implantation. Implantation succeeded in all lambs. Two animals died after implantation (1 pneumothorax and 1 endocarditis). Doppler echocardiographic follow-up did not show any significant transvalvular gradient and showed only mild pulmonary regurgitation. The hemodynamic control before termination revealed a systolic pulmonary valve gradient of 18.5 +/- 12.4 mm Hg at 1 week (n = 4), 13.5 +/- 10.6 mm Hg at 1 month (n = 4), and 4.3 +/- 4.9 mm Hg at 4 months (n = 5). Gross examination demonstrated the presence of connective tissue between the valved stent and pulmonary wall, which increased with time. Fifteen lambs underwent successful deployment of a self-expandable valved stent in the pulmonary position using a transventricular approach. This technique combined with pulmonary artery banding could be a therapeutic option for pulmonary insufficiency after repair of tetralogy of Fallot with a transannular patch.

  2. Stimulation of interferons and endorphins/enkephalins by electro-aerosol inhalation? An experimental approach for testing an expanded hypothesis

    NASA Astrophysics Data System (ADS)

    Wehner, A. P.

    1984-03-01

    The biological effects of endorphins/enkephalins and of interferons closely resemble those attributed to air ions and electro-aerosols. Air ions/electro-aerosols have been reported to affect brain functions and feelings of “well-being”; to have sedative and analgesic effects; to be therapeutically effective in certain viral (e.g., upper respiratory) infections; and to have tumor-attenuating effects. It is, therefore, conceivable that endorphins/enkephalins and interferons might be the mediators of these air ion/electro-aerosol effects. An experimental approach for testing this hypothesis is described. It calls for mice to be challenged with a suitable agent and to be exposed under appropriate conditions to a negatively charged aerosol of physiological saline 6 hours/day for up to 3 weeks; for the serial sacrifice of subgroups of these mice; for collecting blood and brains of the sacrificed animals; for the bioassay of the sera for interferon; and for radioimmunoassays of brains for endorphins/enkephalins. Special considerations, necessitated by the nature of the experiment, are discussed.

  3. Synchrotron x-ray studies of Austenite and Bainitic ferrite

    SciTech Connect

    Stone, H.; Peet, M.; Bhadeshia, H. K. D. H.; Withers, P.; Babu, Sudarsanam S; Specht, Eliot D

    2008-01-01

    High resolution synchrotron X-ray diffraction has been used to conduct in situ studies of the temporal evolution of phases during the isothermal growth of bainite. Two populations of austenitic material were identified: one corresponding to the initial austenite, the other to the carbon-enriched austenite associated with the bainitic ferrite. The observed lattice parameters and the asymmetry of the peaks from the residual austenite have been interpreted in terms of the carbon partitioning during the transformation. The results are contrasted with an earlier study in which the austenite unit cell appeared to split into two distinct densities prior to the onset of transformation.

  4. Nucleation kinetics of proeutectoid ferrite at austenite grain boundaries in Fe-C-X alloys

    NASA Astrophysics Data System (ADS)

    Enomoto, M.; Aaronson, H. I.

    1986-08-01

    The nucleation kinetics of proeutectoid ferrite allotriomorphs at austenite grain boundaries in Fe-0.5 at. Pct C-3 at. Pct X alloys, where X is successively Mn, Ni, Co, and Si and in an Fe-0.8 at. Pct C-2.5 at. Pct Mo alloy have been measured using previously developed experimental techniques. The results were analyzed in terms of the influence of substitutional alloying elements upon the volume free energy change and upon the energies of austenite grain boundaries and nucleus: matrix boundaries. Classical nucleation theory was employed in conjunction with the pillbox model of the critical nucleus applied during the predecessor study of ferrite nucleation kinetics at grain boundaries in Fe-C alloys. The free energy change associated with nucleation was evaluated from both the Hillert-Staffanson and the Central Atoms Models of interstitial-substitutional solid solutions. The grain boundary concentrations of X determined with a Scanning Auger Microprobe were utilized to calculate the reduction in the austenite grain boundary energy produced by the segregation of alloying elements. Analysis of these data in terms of nucleation theory indicates that much of the influence of X upon ferrite nucleation rate derives from effects upon the volume-free energy change, i.e., upon alterations in the path of the γ/(α + γ) phase boundary. Additional effects arise from reductions in austenite grain boundary energy, with austenite-forming alloying elements being more effective in this regard than ferrite-formers. By difference, the remaining influence of the alloy elements studied evidently results from their ability to diminish the energies of the austenite: ferrite boundaries enclosing the critical nucleus. The role of nucleation kinetics in the formation of a bay in the TTT diagram of Fe-C-Mo alloys is also considered.

  5. Modeling the austenite decomposition into ferrite and bainite

    NASA Astrophysics Data System (ADS)

    Fazeli, Fateh

    2005-12-01

    Novel advanced high-strength steels such as dual-phase (DP) and transformation induced plasticity (TRIP) steels, are considered as promising materials for new generation of lightweight vehicles. The superior mechanical properties of these steels, compared to classical high strength steels, are associated with their complex microstructures. The desired phase configuration and morphology can only be achieved through well-controlled processing paths with rather tight processing windows. To implement such challenging processing stages into the current industrial facilities a significant amount of development efforts, in terms of mill trials, have to be performed. Alternatively, process models as predictive tools can be employed to aid the process development' and also to design new steel grades. Knowledge-based process models are developed by virtue of the underlying physical phenomena occurring during the industrial processing and are validated with experimental data. The goal of the present work is to develop an integrated microstructure model to adequately describe the kinetics of austenite decomposition into polygonal ferrite and bainite, such that for complex thermal paths simulating those of industrial practice, the final microstructure in advanced high strength steels can reasonably be predicted. This is in particular relevant to hot-rolled DP and TRIP steels, where the intercritical ferrite evolution due to its crucial influence on the onset and kinetics of the subsequent bainite formation, has to be quantified precisely. The calculated fraction, size and spatial carbon distribution of the intercritical austenite are employed as input to characterize adequately the kinetic of the bainite reaction. Pertinent to ferrite formation, a phenomenological, physically-based model was developed on the ground of the mixed-mode approach. The model deals with the growth stage since nucleation site saturation at prior austenite grain boundaries is likely to be attained

  6. Cast alumina forming austenitic stainless steels

    DOEpatents

    Muralidharan, Govindarajan; Yamamoto, Yukinori; Brady, Michael P

    2013-04-30

    An austenitic stainless steel alloy consisting essentially of, in terms of weight percent ranges 0.15-0.5C; 8-37Ni; 10-25Cr; 2.5-5Al; greater than 0.6, up to 2.5 total of at least one element selected from the group consisting of Nb and Ta; up to 3Mo; up to 3Co; up to 1W; up to 3Cu; up to 15Mn; up to 2Si; up to 0.15B; up to 0.05P; up to 1 total of at least one element selected from the group consisting of Y, La, Ce, Hf, and Zr; <0.3Ti+V; <0.03N; and, balance Fe, where the weight percent Fe is greater than the weight percent Ni, and wherein the alloy forms an external continuous scale comprising alumina, and a stable essentially single phase FCC austenitic matrix microstructure, the austenitic matrix being essentially delta-ferrite free and essentially BCC-phase-free. A method of making austenitic stainless steel alloys is also disclosed.

  7. Austenitic stainless steels for cryogenic service

    SciTech Connect

    Dalder, E.N.C.; Juhas, M.C.

    1985-09-19

    Presently available information on austenitic Fe-Cr-Ni stainless steel plate, welds, and castings for service below 77 K are reviewed with the intent (1) of developing systematic relationships between mechanical properties, composition, microstructure, and processing, and (2) of assessing the adequacy of these data bases in the design, fabrication, and operation of engineering systems at 4 K.

  8. Optimization of Melt Treatment for Austenitic Steel Grain Refinement

    NASA Astrophysics Data System (ADS)

    Lekakh, Simon N.; Ge, Jun; Richards, Von; O'Malley, Ron; TerBush, Jessica R.

    2017-02-01

    Refinement of the as-cast grain structure of austenitic steels requires the presence of active solid nuclei during solidification. These nuclei can be formed in situ in the liquid alloy by promoting reactions between transition metals (Ti, Zr, Nb, and Hf) and metalloid elements (C, S, O, and N) dissolved in the melt. Using thermodynamic simulations, experiments were designed to evaluate the effectiveness of a predicted sequence of reactions targeted to form precipitates that could act as active nuclei for grain refinement in austenitic steel castings. Melt additions performed to promote the sequential precipitation of titanium nitride (TiN) onto previously formed spinel (Al2MgO4) inclusions in the melt resulted in a significant refinement of the as-cast grain structure in heavy section Cr-Ni-Mo stainless steel castings. A refined as-cast structure consisting of an inner fine-equiaxed grain structure and outer columnar dendrite zone structure of limited length was achieved in experimental castings. The sequential of precipitation of TiN onto Al2MgO4 was confirmed using automated SEM/EDX and TEM analyses.

  9. Study of Secondary Phase Particle Dissolution and Austenite Grain Growth on Heating Fine-Grained High-Strength IF-Steel

    NASA Astrophysics Data System (ADS)

    Jia, Hong-bin; Zhang, Hong-mei; Sun, Cheng-qian

    2016-09-01

    Dissolution of particles of second phase and growth of austenite grains in high-strength fine-grained IF-steel (0.0057% C, 0.0023% N) on heating is studied. Metallographic analysis of flat steel specimens cut from plates prepared by hot and cold rolling is performed. Steel structure is studied after holding for 10 - 60 min at different temperatures and water quenching. The quenching parameters at which the microalloying elements (Ti, Nb) dissolve completely with retention of fine-grained austenite are determined. Amathematical model of austenite grain growth is developed by nonlinear regression analysis of experimental data.

  10. Ion beam nitriding of single and polycrystalline austenitic stainless steel

    SciTech Connect

    Abrasonis, G.; Riviere, J.P.; Templier, C.; Declemy, A.; Pranevicius, L.; Milhet, X.

    2005-04-15

    Polycrystalline and single crystalline [orientations (001) and (011)] AISI 316L austenitic stainless steel was implanted at 400 deg. C with 1.2 keV nitrogen ions using a high current density of 0.5 mA cm{sup -2}. The nitrogen distribution profiles were determined using nuclear reaction analysis (NRA). The structure of nitrided polycrystalline stainless steel samples was analyzed using glancing incidence and symmetric x-ray diffraction (XRD) while the structure of the nitrided single crystalline stainless steel samples was analyzed using x-ray diffraction mapping of the reciprocal space. For identical treatment conditions, it is observed that the nitrogen penetration depth is larger for the polycrystalline samples than for the single crystalline ones. The nitrogen penetration depth depends on the orientation, the <001> being more preferential for nitrogen diffusion than <011>. In both type of samples, XRD analysis shows the presence of the phase usually called 'expanded' austenite or {gamma}{sub N} phase. The lattice expansion depends on the crystallographic plane family, the (001) planes showing an anomalously large expansion. The reciprocal lattice maps of the nitrided single crystalline stainless steel demonstrate that during nitriding lattice rotation takes place simultaneously with lattice expansion. The analysis of the results based on the presence of stacking faults, residual compressive stress induced by the lattice expansion, and nitrogen concentration gradient indicates that the average lattice parameter increases with the nitrided layer depth. A possible explanation of the anomalous expansion of the (001) planes is presented, which is based on the combination of faster nitriding rate in the (001) oriented grains and the role of stacking faults and compressive stress.

  11. A comparative study of ray tracing and CIVA simulation for ultrasonic examination of anisotropic inhomogeneous austenitic welds

    NASA Astrophysics Data System (ADS)

    Kolkoori, S. R.; Shokouhi, P.; Hoehne, C.; Rahman, M.-U.; Kreutzbruck, M.; Prager, J.

    2013-01-01

    Ultrasonic examination of anisotropic inhomogeneous austenitic welds is challenging, because of the columnar grain structure of the weld leads to beam skewing and splitting. Modeling tools play an important role in understanding the ultrasound field propagation and optimization of experimental parameters during the ultrasonic testing of austenitic welds as well as the interpretation of the test results. In this contribution, an efficient theoretical model based on the ray tracing concepts is developed to calculate the ultrasonic fields in inhomogeneous austenitic welds quantitatively. The developed model determines the ultrasound fields by taking into account the directivity of the ray source, the inhomogenity of the weld as well as ray transmission coefficients. Directivity of the ray source in columnar grained austenitic materials (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. Ray energy reflection and transmission coefficients at an interface between two general columnar grained austenitic materials are calculated in three dimensions. The ray tracing model predictions on inhomogeneous austenitic weld material are compared against those from CIVA, a commercial non-destructive modeling and simulation tool. The ultrasonic modeling tools in CIVA are based on semi-analytical solutions. For beam propagation simulation, a so-called "pencil method" is used, which involves modeling the probe as a set of individual source points, each radiating "a bundle" of diverging rays into the medium and integrating those elementary contributions. Inhomogenity in the weld region is approximated by mapping the grain orientations on weld macrograph. Simulation results for ultrasonic field profiles for an austenitic weld are shown to be in good agreement with the corresponding experimental results.

  12. Experimental characterization of next-generation expanded-bed adsorbents for capture of a recombinant protein expressed in high-cell-density yeast fermentation.

    PubMed

    Kelly, William; Garcia, Phillip; McDermott, Stefanie; Mullen, Peter; Kamguia, Guy; Jones, Gerard; Ubiera, Antonio; Göklen, Kent

    2013-01-01

    Expanded-bed adsorption (EBA) can be particularly useful in protein recovery from high-cell-density fermentation broth where conventional methods for harvest and clarification, such as continuous centrifugation and depth filtration, demand long processing times and are associated with high costs. In this work, the use of next-generation high-particle-density EBA adsorbents, including two mixed-mode resins, for the direct capture of a recombinant protein expressed in yeast at high cell densities is evaluated. Using classical experimental approaches and under different conditions (pH, salt, etc.), Langmuir isotherm parameters for these resins are obtained along with pore diffusivity values. Additional batch adsorption studies with Fastline® MabDirect, the resin that demonstrated the highest static binding capacity for the recombinant protein of interest under the conditions evaluated in this study, indicate competitive binding of nontarget proteins and approximately a 30% reduction in equilibrium binding capacity to 50 mg/mL settled bed in the presence of a 5%-10% cell concentration. Packed-bed (PB) dynamic binding capacities for the MabDirect resin (25-40 mg/mL PB) were significantly higher than for the Fastline® HSA resin and for the MabDirect MM resin in expanded-bed mode (5-10 mg/mL settled bed). Bed expansion behavior for the mMabDirect MM resin along with process yield and eluate purity are identified as a function of linear velocity and cell density, demonstrating process feasibility for pilot scale use. © 2013 International Union of Biochemistry and Molecular Biology, Inc.

  13. EXPANDED LITTLE IDA, EXPERIMENTAL RESULTS.

    DTIC Science & Technology

    propagation paths: (1) Thule, Greenland to Central New York, and (2) Coco Solo, Panama Canal Zone to Central New York. Data on mode reliability, mode loss, spectrum and noise/interference are presented and discussed. (Author)

  14. EXPANDED LITTLE IDA - EXPERIMENTAL RESULTS

    DTIC Science & Technology

    with transmitting terminals located at Thule, Greenland; Keflavik, Iceland; and Coco Solo, Panama and central receiving sites situated at the Stockbridge... Coco Solo, Panama to central New York path. A limited amount of data collected over the Thule path are discussed. Delays encountered in both

  15. Modelling grain-scattered ultrasound in austenitic stainless-steel welds: A hybrid model

    SciTech Connect

    Nowers, O.; Duxbury, D. J.; Velichko, A.; Drinkwater, B. W.

    2015-03-31

    The ultrasonic inspection of austenitic stainless steel welds can be challenging due to their coarse grain structure, charaterised by preferentially oriented, elongated grains. The anisotropy of the weld is manifested as both a ‘steering’ of the beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the influence of weld properties, such as mean grain size and orientation distribution, on the magnitude of scattered ultrasound is not well understood. A hybrid model has been developed to allow the study of grain-scatter effects in austenitic welds. An efficient 2D Finite Element (FE) method is used to calculate the complete scattering response from a single elliptical austenitic grain of arbitrary length and width as a function of the specific inspection frequency. A grain allocation model of the weld is presented to approximate the characteristic structures observed in austenitic welds and the complete scattering behaviour of each grain calculated. This model is incorporated into a semi-analytical framework for a single-element inspection of a typical weld in immersion. Experimental validation evidence is demonstrated indicating excellent qualitative agreement of SNR as a function of frequency and a minimum SNR difference of 2 dB at a centre frequency of 2.25 MHz. Additionally, an example Monte-Carlo study is presented detailing the variation of SNR as a function of the anisotropy distribution of the weld, and the application of confidence analysis to inform inspection development.

  16. Crack growth rates and fracture toughness of irradiated austenitic stainless steels in BWR environments.

    SciTech Connect

    Chopra, O. K.; Shack, W. J.

    2008-01-21

    In light water reactors, austenitic stainless steels (SSs) are used extensively as structural alloys in reactor core internal components because of their high strength, ductility, and fracture toughness. However, exposure to high levels of neutron irradiation for extended periods degrades the fracture properties of these steels by changing the material microstructure (e.g., radiation hardening) and microchemistry (e.g., radiation-induced segregation). Experimental data are presented on the fracture toughness and crack growth rates (CGRs) of wrought and cast austenitic SSs, including weld heat-affected-zone materials, that were irradiated to fluence levels as high as {approx} 2x 10{sup 21} n/cm{sup 2} (E > 1 MeV) ({approx} 3 dpa) in a light water reactor at 288-300 C. The results are compared with the data available in the literature. The effects of material composition, irradiation dose, and water chemistry on CGRs under cyclic and stress corrosion cracking conditions were determined. A superposition model was used to represent the cyclic CGRs of austenitic SSs. The effects of neutron irradiation on the fracture toughness of these steels, as well as the effects of material and irradiation conditions and test temperature, have been evaluated. A fracture toughness trend curve that bounds the existing data has been defined. The synergistic effects of thermal and radiation embrittlement of cast austenitic SS internal components have also been evaluated.

  17. Modelling grain-scattered ultrasound in austenitic stainless-steel welds: A hybrid model

    NASA Astrophysics Data System (ADS)

    Nowers, O.; Duxbury, D. J.; Velichko, A.; Drinkwater, B. W.

    2015-03-01

    The ultrasonic inspection of austenitic stainless steel welds can be challenging due to their coarse grain structure, charaterised by preferentially oriented, elongated grains. The anisotropy of the weld is manifested as both a `steering' of the beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the influence of weld properties, such as mean grain size and orientation distribution, on the magnitude of scattered ultrasound is not well understood. A hybrid model has been developed to allow the study of grain-scatter effects in austenitic welds. An efficient 2D Finite Element (FE) method is used to calculate the complete scattering response from a single elliptical austenitic grain of arbitrary length and width as a function of the specific inspection frequency. A grain allocation model of the weld is presented to approximate the characteristic structures observed in austenitic welds and the complete scattering behaviour of each grain calculated. This model is incorporated into a semi-analytical framework for a single-element inspection of a typical weld in immersion. Experimental validation evidence is demonstrated indicating excellent qualitative agreement of SNR as a function of frequency and a minimum SNR difference of 2 dB at a centre frequency of 2.25 MHz. Additionally, an example Monte-Carlo study is presented detailing the variation of SNR as a function of the anisotropy distribution of the weld, and the application of confidence analysis to inform inspection development.

  18. Pitting corrosion resistant austenite stainless steel

    DOEpatents

    van Rooyen, D.; Bandy, R.

    A pitting corrosion resistant austenite stainless steel comprises 17 to 28 wt. % chromium, 15 to 26 wt. % nickel, 5 to 8 wt. % molybdenum, and 0.3 to 0.5 wt. % nitrogen, the balance being iron, unavoidable impurities, minor additions made in the normal course of melting and casting alloys of this type, and may optionally include up to 10 wt. % of manganese, up to 5 wt. % of silicon, and up to 0.08 wt. % of carbon.

  19. Dynamic recrystallization in friction surfaced austenitic stainless steel coatings

    SciTech Connect

    Puli, Ramesh Janaki Ram, G.D.

    2012-12-15

    Friction surfacing involves complex thermo-mechanical phenomena. In this study, the nature of dynamic recrystallization in friction surfaced austenitic stainless steel AISI 316L coatings was investigated using electron backscattered diffraction and transmission electron microscopy. The results show that the alloy 316L undergoes discontinuous dynamic recrystallization under conditions of moderate Zener-Hollomon parameter during friction surfacing. - Highlights: Black-Right-Pointing-Pointer Dynamic recrystallization in alloy 316L friction surfaced coatings is examined. Black-Right-Pointing-Pointer Friction surfacing leads to discontinuous dynamic recrystallization in alloy 316L. Black-Right-Pointing-Pointer Strain rates in friction surfacing exceed 400 s{sup -1}. Black-Right-Pointing-Pointer Estimated grain size matches well with experimental observations in 316L coatings.

  20. Formability analysis of austenitic stainless steel-304 under warm conditions

    NASA Astrophysics Data System (ADS)

    Lade, Jayahari; Singh, Swadesh Kumar; Banoth, Balu Naik; Gupta, Amit Kumar

    2013-12-01

    A warm deep drawing process of austenitic stainless steel-304 (ASS-304) of circular blanks with coupled ther mal analysis is studied in this article. 65 mm blanks were deep drawn at different temperatures and thickness distribution is experimentally measured after cutting the drawn component into two halves. The process is simulated using explicit fin ite element code LS-DYNA. A Barlat 3 parameter model is used in the simulation, as the material is anisotropic up to 30 0°C. Material properties for the simulation are determined at different temperatures using a 5 T UTM coupled with a furn ace. In this analysis constant punch speed and variable blank holder force (BHF) is applied to draw cups without wrinkle.

  1. Microstructural evolution in fast-neutron-irradiated austenitic stainless steels

    SciTech Connect

    Stoller, R.E.

    1987-12-01

    The present work has focused on the specific problem of fast-neutron-induced radiation damage to austenitic stainless steels. These steels are used as structural materials in current fast fission reactors and are proposed for use in future fusion reactors. Two primary components of the radiation damage are atomic displacements (in units of displacements per atom, or dpa) and the generation of helium by nuclear transmutation reactions. The radiation environment can be characterized by the ratio of helium to displacement production, the so-called He/dpa ratio. Radiation damage is evidenced microscopically by a complex microstructural evolution and macroscopically by density changes and altered mechanical properties. The purpose of this work was to provide additional understanding about mechanisms that determine microstructural evolution in current fast reactor environments and to identify the sensitivity of this evolution to changes in the He/dpa ratio. This latter sensitivity is of interest because the He/dpa ratio in a fusion reactor first wall will be about 30 times that in fast reactor fuel cladding. The approach followed in the present work was to use a combination of theoretical and experimental analysis. The experimental component of the work primarily involved the examination by transmission electron microscopy of specimens of a model austenitic alloy that had been irradiated in the Oak Ridge Research Reactor. A major aspect of the theoretical work was the development of a comprehensive model of microstructural evolution. This included explicit models for the evolution of the major extended defects observed in neutron irradiated steels: cavities, Frank faulted loops and the dislocation network. 340 refs., 95 figs., 18 tabs.

  2. Crystallography of lath martensite and stabilization of retained austenite

    SciTech Connect

    Sarikaya. M.

    1982-10-01

    TEM was used to study the morphology and crystallography of lath martensite in low and medium carbon steels in the as-quenched and 200/sup 0/C tempered conditions. The steels have microduplex structures of dislocated lath martensite and continuous thin films of retained austenite at the lath interfaces. Stacks of laths form the packets which are derived from different (111) variants of the same austenite grain. The residual parent austenite enables microdiffraction experiments with small electron beam spot sizes for the orientation relationships (OR) between austenite and martensite. All three most commonly observed ORs, namely Kurdjumov-Sachs, Nishiyama-Wassermann, and Greninger-Troiano, operate within the same sample.

  3. The effect of niobium on the hardenability of microalloyed austenite

    NASA Astrophysics Data System (ADS)

    Fossaert, C.; Rees, G.; Maurickx, T.; Bhadeshia, H. K. D. H.

    1995-01-01

    The powerful effect that varying the extent of niobium-carbide dissolution has on the “hardenability” of microalloyed austenite is demonstrated using dilatometric measurement of the critical cooling rate required to from microstructures containing >95 Pct martensite. The results can be rationalized on the hypothesis that the hardenability of austenite is enhanced by niobium in solid solution, possibly by its segregation to austenite grain boundaries, but is decreased by precipitation of niobium-carbide particles. This effect appears analogous to that of boron in steels and is found to be independent of variations in the austenite grain size.

  4. Kinetics of Austenite Grain Growth During Heating and Its Influence on Hot Deformation of LZ50 Steel

    NASA Astrophysics Data System (ADS)

    Du, Shiwen; Li, Yongtang; Zheng, Yi

    2016-07-01

    Grain growth behaviors of LZ50 have been systematically investigated for various temperatures and holding times. Quantitative evaluations of the grain growth kinetics over a wide range of temperature (950-1200 °C) and holding time (10-180 min) have been performed. With the holding time kept constant, the average austenite grain size has an exponential relationship with the heating temperature, while with the heating temperature kept constant, the relationship between the austenite average grain size and holding time is a parabolic curve approximately. The holding time dependence of average austenite grain size obeys the Beck's equation. As the heating temperature increases, the time exponent for grain growth n increases from 0.21 to 0.39. On the basis of previous models and experimental results, taking the initial grain size into account, the mathematical model for austenite grain growth of LZ50 during isothermal heating and non-isothermal heating is proposed. The effects of initial austenite grain size on hot deformation behavior of LZ50 are analyzed through true stress-strain curves under different deformation conditions. Initial grain size has a slight effect on peak stress.

  5. Modelling the evolution of composition-and stress-depth profiles in austenitic stainless steels during low-temperature nitriding

    NASA Astrophysics Data System (ADS)

    Jespersen, Freja N.; Hattel, Jesper H.; Somers, Marcel A. J.

    2016-02-01

    Nitriding of stainless steel causes a surface zone of expanded austenite, which improves the wear resistance of the stainless steel while preserving the stainless behaviour. During nitriding huge residual stresses are introduced in the treated zone, arising from the volume expansion that accompanies the dissolution of high nitrogen contents in expanded austenite. An intriguing phenomenon during low-temperature nitriding is that the residual stresses evoked by dissolution of nitrogen in the solid state, affect the thermodynamics and the diffusion kinetics of nitrogen dissolution. In the present paper solid mechanics was combined with thermodynamics and diffusion kinetics to simulate the evolution of composition-depth and stress-depth profiles resulting from nitriding. The model takes into account a composition-dependent diffusion coefficient of nitrogen in expanded austenite, short range ordering (trapping) of nitrogen atoms by chromium atoms, and the effect of composition-induced stress on surface concentration and diffusive flux. The effect of plasticity and concentration-dependence of the yield stress was also included.

  6. Influence of temperature on layer growth as measured by in situ XRD observation of nitriding of austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Manova, D.; Günther, C.; Bergmann, A.; Mändl, S.; Neumann, H.; Rauschenbach, B.

    2013-07-01

    Investigating the formation of expanded austenite has resulted in several, different models trying to explain the particular diffusion and phase formation behaviour. However, only ex situ information, influenced by cooling and annealing processes of the samples after ion implantation has been available until now. Here, the time and temperature dependent layer growth is reported using in situ XRD measurements obtained from low energy broadbeam nitrogen ion implantation into polycrystalline austenitic stainless steel 304 in the temperature range from 300 to 500 °C for a process time of up to 1 h. Expanded austenite was observed at all temperatures without any CrN, in agreement with already published lifetime data for this metastable phase. The layer growth was derived from the time evolution of the substrate peak intensity. Using the temperature dependence of the layer growth, an activation energy of nearly 0.8 eV was estimated for the nitrogen diffusion. In contrast, a complex behaviour was observed for the lattice expansion and peak width of the expanded peak, indicating additional dynamic annealing during implantation.

  7. Prediction of the austenite-grain size of microalloyed steels based on the simulation of the evolution of carbonitride precipitates

    NASA Astrophysics Data System (ADS)

    Gorbachev, I. I.; Pasynkov, A. Yu.; Popov, V. V.

    2015-11-01

    Kinetic calculations of the evolution of carbonitride precipitates in low-alloy steels with Nb and Ti have been performed for different temperatures of austenitizing. Based on the data of the kinetic simulation of the ensembles of carbonitride precipitates, the expected size of the austenite grain has been calculated using different models. The results obtained have been compared with experimental data. It has been shown that the best agreement with the experiment is achieved for the high-temperature region (1150-1250°C) when using the Gladman model (with the parameter Z = 2) with allowance for the polydispersity of the ensemble of precipitates.

  8. Composition-dependence of stacking fault energy in austenitic stainless steels through linear regression with random intercepts

    NASA Astrophysics Data System (ADS)

    Meric de Bellefon, G.; van Duysen, J. C.; Sridharan, K.

    2017-08-01

    The stacking fault energy (SFE) plays an important role in deformation behavior and radiation damage of FCC metals and alloys such as austenitic stainless steels. In the present communication, existing expressions to calculate SFE in those steels from chemical composition are reviewed and an improved multivariate linear regression with random intercepts is used to analyze a new database of 144 SFE measurements collected from 30 literature references. It is shown that the use of random intercepts can account for experimental biases in these literature references. A new expression to predict SFE from austenitic stainless steel compositions is proposed.

  9. Investigation of Austenite-to-Ferrite Transformation in Ultralow and Low-Carbon Steel Using High-Speed Quenching Dilatometry and Thermokinetic Simulation

    NASA Astrophysics Data System (ADS)

    Imtiaz, F.; Kozeschnik, E.

    2017-07-01

    The isothermal austenite decomposition kinetics is studied in 0.004 wt pct C ultralow carbon (ULC) and 0.11 wt pct C low-carbon (LC) steel using high-speed quenching dilatometry. Standard samples of these steels are heated to austenitization temperatures of 1223 K and 1373 K (950 °C and 1100 °C) and then quenched to testing temperatures between 1163 K and 933 K (890 °C and 660 °C). The measured and calculated austenite-to-ferrite phase fractions are compared with dilatation values to analyze the ferrite nucleation and growth conditions during austenite decomposition. Ferrite evolution profiles are assessed to investigate the underlying growth kinetics. The analysis in ULC steel shows regimes of partitionless, partitioning, and two-stage transformation kinetics. In contrast, LC steel shows only diffusion-controlled transformation kinetics. The experimental results are well reproduced with thermokinetic calculations, thus supporting our interpretation of governing mechanisms during transformation.

  10. CD1d(hi)CD5+ B cells expanded by GM-CSF in vivo suppress experimental autoimmune myasthenia gravis.

    PubMed

    Sheng, Jian Rong; Quan, Songhua; Soliven, Betty

    2014-09-15

    IL-10-competent subset within CD1d(hi)CD5(+) B cells, also known as B10 cells, has been shown to regulate autoimmune diseases. Whether B10 cells can prevent or suppress the development of experimental autoimmune myasthenia gravis (EAMG) has not been studied. In this study, we investigated whether low-dose GM-CSF, which suppresses EAMG, can expand B10 cells in vivo, and whether adoptive transfer of CD1d(hi)CD5(+) B cells would prevent or suppress EAMG. We found that treatment of EAMG mice with low-dose GM-CSF increased the proportion of CD1d(hi)CD5(+) B cells and B10 cells. In vitro coculture studies revealed that CD1d(hi)CD5(+) B cells altered T cell cytokine profile but did not directly inhibit T cell proliferation. In contrast, CD1d(hi)CD5(+) B cells inhibited B cell proliferation and its autoantibody production in an IL-10-dependent manner. Adoptive transfer of CD1d(hi)CD5(+) B cells to mice could prevent disease, as well as suppress EAMG after disease onset. This was associated with downregulation of mature dendritic cell markers and expansion of regulatory T cells resulting in the suppression of acetylcholine receptor-specific T cell and B cell responses. Thus, our data have provided significant insight into the mechanisms underlying the tolerogenic effects of B10 cells in EAMG. These observations suggest that in vivo or in vitro expansion of CD1d(hi)CD5(+) B cells or B10 cells may represent an effective strategy in the treatment of human myasthenia gravis.

  11. Expanded Dengue.

    PubMed

    Kadam, D B; Salvi, Sonali; Chandanwale, Ajay

    2016-07-01

    The World Health Organization (WHO) has coined the term expanded dengue to describe cases which do not fall into either dengue shock syndrome or dengue hemorrhagic fever. This has incorporated several atypical findings of dengue. Dengue virus has not been enlisted as a common etiological agent in several conditions like encephalitis, Guillain Barre syndrome. Moreover it is a great mimic of co-existing epidemics like Malaria, Chikungunya and Zika virus disease, which are also mosquito-borne diseases. The atypical manifestations noted in dengue can be mutisystemic and multifacetal. In clinical practice, the occurrence of atypical presentation should prompt us to investigate for dengue. Knowledge of expanded dengue helps to clinch the diagnosis of dengue early, especially during ongoing epidemics, avoiding further battery of investigations. Dengue has proved to be the epidemic with the ability to recur and has a diverse array of presentation as seen in large series from India, Srilanka, Indonesia and Taiwan. WHO has given the case definition of dengue fever in their comprehensive guidelines. Accordingly, a probable case is defined as acute febrile illness with two or more of any findings viz. headache, retro-orbital pain, myalgia, arthralgia, rash, hemorrhagic manifestations, leucopenia and supportive serology. There have been cases of patients admitted with fever, altered mentation with or without neck stiffness and pyramidal tract signs. Some had seizures or status epilepticus as presentation. When they were tested for serology, dengue was positive. After ruling out other causes, dengue remained the only culprit. We have come across varied presentations of dengue fever in clinical practice and the present article throws light on atypical manifestations of dengue. © Journal of the Association of Physicians of India 2011.

  12. Isothermal austenitization of cold-rolled steel type 08

    NASA Astrophysics Data System (ADS)

    Yatsenko, A. I.; Repina, N. I.; Ginevskaya, L. A.

    1981-12-01

    Features of isothermal austenitization for cold-rolled and annealed 08 type structural steels are not the same. Deformation during cold rolling causes a reduction in the temperature for the start of austenite formation and the transformation range is extended, but it does not have a marked effect on the temperature for the end of the process.

  13. Investigation of joining techniques for advanced austenitic alloys

    SciTech Connect

    Lundin, C.D.; Qiao, C.Y.P.; Kikuchi, Y.; Shi, C.; Gill, T.P.S.

    1991-05-01

    Modified Alloys 316 and 800H, designed for high temperature service, have been developed at Oak Ridge National Laboratory. Assessment of the weldability of the advanced austenitic alloys has been conducted at the University of Tennessee. Four aspects of weldability of the advanced austenitic alloys were included in the investigation.

  14. Corrosion of austenitic alloys in aerated brines

    SciTech Connect

    Heidersbach, R.; Shi, A.; Sharp, S.

    1999-11-01

    This report discusses the results of corrosion exposures of three austenitic alloys--3l6L stainless steel, UNS N10276, and UNS N08367. Coupons of these alloys were suspended in a series of brines used for processing in the pharmaceutical industry. The effects of surface finish and welding processes on the corrosion behavior of these alloys were determined. The 316L coupons experienced corrosion in several environments, but the other alloys were unaffected during the one-month exposures of this investigation. Electropolishing the surfaces improved corrosion resistance.

  15. Concentration-Dependent Carbon Diffusivity in Austenite

    NASA Astrophysics Data System (ADS)

    Gu, Xiaoting; Michal, Gary M.; Ernst, Frank; Kahn, Harold; Heuer, Arthur H.

    2014-08-01

    The diffusion coefficient of carbon in austenite depends on the local carbon concentration. This concentration dependence is particularly noticeable during low-temperature "paraequilibrium" carburization. A critical review of the extensive literature on this topic reveals that an early paper by Asimow provides an excellent description of this substantial concentration dependence. The present analysis suggests that the marked concentration dependence of carbon diffusivity is most likely due to interstitial carbon decreasing the activation energy for carbon jumps from one interstitial site to its neighbor.

  16. Wear behavior of austenite containing plate steels

    NASA Astrophysics Data System (ADS)

    Hensley, Christina E.

    As a follow up to Wolfram's Master of Science thesis, samples from the prior work were further investigated. Samples from four steel alloys were selected for investigation, namely AR400F, 9260, Hadfield, and 301 Stainless steels. AR400F is martensitic while the Hadfield and 301 stainless steels are austenitic. The 9260 exhibited a variety of hardness levels and retained austenite contents, achieved by heat treatments, including quench and tempering (Q&T) and quench and partitioning (Q&P). Samples worn by three wear tests, namely Dry Sand/Rubber Wheel (DSRW), impeller tumbler impact abrasion, and Bond abrasion, were examined by optical profilometry. The wear behaviors observed in topography maps were compared to the same in scanning electron microscopy micrographs and both were used to characterize the wear surfaces. Optical profilometry showed that the scratching abrasion present on the wear surface transitioned to gouging abrasion as impact conditions increased (i.e. from DSRW to impeller to Bond abrasion). Optical profilometry roughness measurements were also compared to sample hardness as well as normalized volume loss (NVL) results for each of the three wear tests. The steels displayed a relationship between roughness measurements and observed wear rates for all three categories of wear testing. Nanoindentation was used to investigate local hardness changes adjacent to the wear surface. DSRW samples generally did not exhibit significant work hardening. The austenitic materials exhibited significant hardening under the high impact conditions of the Bond abrasion wear test. Hardening in the Q&P materials was less pronounced. The Q&T microstructures also demonstrated some hardening. Scratch testing was performed on samples at three different loads, as a more systematic approach to determining the scratching abrasion behavior. Wear rates and scratch hardness were calculated from scratch testing results. Certain similarities between wear behavior in scratch testing

  17. Prediction of Temperatures of Austenite Equilibrium Transformations in Steels During Thermomechanical Processing

    NASA Astrophysics Data System (ADS)

    Samadian, Pedram; Parsa, Mohammad Habibi; Ahmadabadi, M. Nili; Mirzadeh, Hamed

    2014-10-01

    Knowledge about the transformation temperatures is crucial in processing of steels especially in thermomechanical processes because microstructures and mechanical properties after processing are closely related to the extent and type of transformations. The experimental determination of critical temperatures is costly, and therefore, it is preferred to predict them by mathematical methods. In the current work, new thermodynamically based models were developed for computing the Ae3 and Acm temperatures in the equilibrium cooling conditions when austenite is deformed at elevated temperatures. The main advantage of the proposed models is their capability to predict the temperatures of austenite equilibrium transformations in steels with total alloying elements (Mn + Si + Ni + Cr + Mo + Cu) less than 5 wt.% and Si less than 1 wt.% under the deformation conditions just by using the chemical potential of constituents, without the need for determining the total Gibbs free energy of steel which requires many experiments and computations.

  18. Study of the Sensitization on the Grain Boundary in Austenitic Stainless Steel Aisi 316

    NASA Astrophysics Data System (ADS)

    Kocsisová, Edina; Dománková, Mária; Slatkovský, Ivan; Sahul, Martin

    2014-12-01

    Intergranular corrosion (IGC) is one of the major problems in austenitic stainless steels. This type of corrosion is caused by precipitation of secondary phases on grain boundaries (GB). Precipitation of the secondary phases can lead to formation of chromium depleted zones in the vicinity of grain boundaries. Mount of the sensitization of material is characterized by the degree of sensitization (DOS). Austenitic stainless steel AISI 316 as experimental material had been chosen. The samples for the study of sensitization were solution annealed on 1100 °C for 60 min followed by water quenching and then sensitization by isothermal annealing on 700 °C and 650 °C with holding time from 15 to 600 min. Transmission electron microscopy (TEM) was used for identification of secondary phases. Electron backscattered diffraction (EBSD) was applied for characterization of grain boundary structure as one of the factors which influences on DOS.

  19. Corrosion properties of S-phase layers formed on medical grade austenitic stainless steel.

    PubMed

    Buhagiar, Joseph; Dong, Hanshan

    2012-02-01

    The corrosion properties of S-phase surface layers formed in AISI 316LVM (ASTM F138) and High-N (ASTM F1586) medical grade austenitic stainless steels by plasma surface alloying with nitrogen (at 430°C), carbon (at 500°C) and both carbon and nitrogen (at 430°C) has been investigated. The corrosion behaviour of the S-phase layers in Ringer's solutions was evaluated using potentiodynamic and immersion corrosion tests. The corrosion damage was evaluated using microscopy, hardness testing, inductive coupled plasma mass spectroscopy and X-ray diffraction. The experimental results have demonstrated that low-temperature nitriding, carburising and carbonitriding can improve the localised corrosion resistance of both industrial and medical grade austenitic stainless steels as long as the threshold sensitisation temperature is not reached. Carburising at 500°C has proved to be the best hardening treatment with the least effect on the corrosion resistance of the parent alloy.

  20. A creep model for austenitic stainless steels incorporating cavitation and wedge cracking

    NASA Astrophysics Data System (ADS)

    Mahesh, S.; Alur, K. C.; Mathew, M. D.

    2011-01-01

    A model of damage evolution in austenitic stainless steels under creep loading at elevated temperatures is proposed. The initial microstructure is idealized as a space-tiling aggregate of identical rhombic dodecahedral grains, which undergo power-law creep deformation. Damage evolution in the form of cavitation and wedge cracking on grain-boundary facets is considered. Both diffusion- and deformation-driven grain-boundary cavity growth are treated. Cavity and wedge-crack length evolution are derived from an energy balance argument that combines and extends the models of Cottrell (1961 Trans. AIME 212 191-203), Williams (1967 Phil. Mag. 15 1289-91) and Evans (1971 Phil Mag. 23 1101-12). The time to rupture predicted by the model is in good agreement with published experimental data for a type 316 austenitic stainless steel under uniaxial creep loading. Deformation and damage evolution at the microscale predicted by the present model are also discussed.

  1. Evolution of microstructure and residual stress during annealing of austenitic and ferritic steels

    SciTech Connect

    Wawszczak, R.; Baczmański, A.; Marciszko, M.; Wróbel, M.; Czeppe, T.; Sztwiertnia, K.; Braham, C.; Berent, K.

    2016-02-15

    In this work the recovery and recrystallization processes occurring in ferritic and austenitic steels were studied. To determine the evolution of residual stresses during material annealing the nonlinear sin{sup 2}ψ diffraction method was used and an important relaxation of the macrostresses as well as the microstresses was found in the cold rolled samples subjected to heat treatment. Such relaxation occurs at the beginning of recovery, when any changes of microstructure cannot be detected using other experimental techniques. Stress evolution in the annealed steel samples was correlated with the progress of recovery process, which significantly depends on the value of stacking fault energy. - Highlights: • X-ray diffraction was used to determine the first order and second order stresses. • Diffraction data were analyzed using scale transition elastoplastic models model. • Stress relaxation in annealed ferritic and austenitic steels was correlated with evolution of microstructure. • Influence of stacking fault energy on thermally induced processes was discussed.

  2. Weldment for austenitic stainless steel and method

    DOEpatents

    Bagnall, Christopher; McBride, Marvin A.

    1985-01-01

    For making defect-free welds for joining two austenitic stainless steel mers, using gas tungsten-arc welding, a thin foil-like iron member is placed between the two steel members to be joined, prior to making the weld, with the foil-like iron member having a higher melting point than the stainless steel members. When the weld is formed, there results a weld nugget comprising melted and then solidified portions of the joined members with small portions of the foil-like iron member projecting into the solidified weld nugget. The portions of the weld nugget proximate the small portions of the foil-like iron member which project into the weld nugget are relatively rich in iron. This causes these iron-rich nugget portions to display substantial delta ferrite during solidification of the weld nugget which eliminates weld defects which could otherwise occur. This is especially useful for joining austenitic steel members which, when just below the solidus temperature, include at most only a very minor proportion of delta ferrite.

  3. Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by austenitic filler metal

    SciTech Connect

    Eghlimi, Abbas; Shamanian, Morteza; Eskandarian, Masoomeh; Zabolian, Azam; Szpunar, Jerzy A.

    2015-08-15

    The evolution of microstructure and texture across an as-welded dissimilar UNS S32750 super duplex/UNS S30403 austenitic stainless steel joint welded by UNS S30986 (AWS A5.9 ER309LMo) austenitic stainless steel filler metal using gas tungsten arc welding process was evaluated by optical micrography and EBSD techniques. Due to their fabrication through rolling process, both parent metals had texture components resulted from deformation and recrystallization. The weld metal showed the highest amount of residual strain and had large austenite grain colonies of similar orientations with little amounts of skeletal ferrite, both oriented preferentially in the < 001 > direction with cub-on-cube orientation relationship. While the super duplex stainless steel's heat affected zone contained higher ferrite than its parent metal, an excessive grain growth was observed at the austenitic stainless steel's counterpart. At both heat affected zones, austenite underwent some recrystallization and formed twin boundaries which led to an increase in the fraction of high angle boundaries as compared with the respective base metals. These regions showed the least amount of residual strain and highest amount of recrystallized austenite grains. Due to the static recrystallization, the fraction of low degree of fit (Σ) coincident site lattice boundaries, especially Σ3 boundaries, was increased in the austenitic stainless steel heat affected zone, while the formation of subgrains in the ferrite phase increased the content of < 5° low angle boundaries at that of the super duplex stainless steel. - Graphical abstract: Display Omitted - Highlights: • Extensive grain growth in the HAZ of austenitic stainless steel was observed. • Intensification of < 100 > orientated grains was observed adjacent to both fusion lines. • Annealing twins with Σ3 CSL boundaries were formed in the austenite of both HAZ. • Cub-on-cube OR was observed between austenite and ferrite in the weld metal.

  4. A new constitutive model for nitrogen austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Fréchard, S.; Lichtenberger, A.; Rondot, F.; Faderl, N.; Redjaïmia, A.; Adoum, M.

    2003-09-01

    Quasi-static, quasi-dynamic and dynamic compression tests have been performed on a nitrogen alloyed austenitic stainless steel. For all strain rates, a high strain hardening rate and a good ductility have been achieved. In addition, this steel owns a great strain rate sensitivity. The temperature sensitivity bas been determined between 20°C and 400°C. Microstructural analysis has been performed after different loading conditions in relation to the behaviour of the material. Johnson-Cook and Zerilli-Armstrong models have been selected to fit the experimental data into constitutive equations. These models do not reproduce properly the behaviour of this type of steel over the complete range. A new constitutive model that fits very well all the experimental data at different strain, strain rate and temperature has been determined. The model is based on empirical considerations on the separated influence of the main parameters. Single Taylor tests have been realized to validate the models. Live observations of the specimen during impact have been achieved using a special CCD camera set-up. The overall profile at different times are compared to numerical predictions using LS-DYNA code.

  5. Carbon content of austenite in austempered ductile iron

    SciTech Connect

    Chang, L.C.

    1998-06-05

    The development of austempered ductile iron (ADI) is a major achievement in cast iron technology. The austempering heat treatment enables the ductile cast iron containing mainly strong bainitic ferrite and ductile carbon-enriched austenite, with some martensite transforms from austenite during cooling down to room temperature. A key factor controlling the stability of the retained austenite can be evaluated soundly using the thermodynamics principles. It is the purpose here to demonstrate that the data of ADI from numerous sources have a similar trend.

  6. Stable atomic structure of NiTi austenite

    SciTech Connect

    Zarkevich, Nikolai A; Johnson, Duane D

    2014-08-01

    Nitinol (NiTi), the most widely used shape-memory alloy, exhibits an austenite phase that has yet to be identified. The usually assumed austenitic structure is cubic B2, which has imaginary phonon modes, hence it is unstable. We suggest a stable austenitic structure that “on average” has B2 symmetry (observed by x-ray and neutron diffraction), but it exhibits finite atomic displacements from the ideal B2 sites. The proposed structure has a phonon spectrum that agrees with that from neutron scattering, has diffraction spectra in agreement with x-ray diffraction, and has an energy relative to the ground state that agrees with calorimetry data.

  7. Stable atomic structure of NiTi austenite

    NASA Astrophysics Data System (ADS)

    Zarkevich, Nikolai A.; Johnson, Duane D.

    2014-08-01

    Nitinol (NiTi), the most widely used shape-memory alloy, exhibits an austenite phase that has yet to be identified. The usually assumed austenitic structure is cubic B2, which has imaginary phonon modes, hence it is unstable. We suggest a stable austenitic structure that "on average" has B2 symmetry (observed by x-ray and neutron diffraction), but it exhibits finite atomic displacements from the ideal B2 sites. The proposed structure has a phonon spectrum that agrees with that from neutron scattering, has diffraction spectra in agreement with x-ray diffraction, and has an energy relative to the ground state that agrees with calorimetry data.

  8. Effect of material heat treatment on fatigue crack initiation in austenitic stainless steels in LWR environments.

    SciTech Connect

    Chopra, O. K.; Alexandreanu, B.; Shack, W. J.; Energy Technology

    2005-07-31

    The ASME Boiler and Pressure Vessel Code provides rules for the design of Class 1 components of nuclear power plants. Figures I-9.1 through I-9.6 of Appendix I to Section III of the Code specify design curves for applicable structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. The existing fatigue strain-vs.-life ({var_epsilon}-N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. Under certain environmental and loading conditions, fatigue lives of austenitic stainless steels (SSs) can be a factor of 20 lower in water than in air. This report presents experimental data on the effect of heat treatment on fatigue crack initiation in austenitic Type 304 SS in LWR coolant environments. A detailed metallographic examination of fatigue test specimens was performed to characterize the crack morphology and fracture morphology. The key material, loading, and environmental parameters and their effect on the fatigue life of these steels are also described. Statistical models are presented for estimating the fatigue {var_epsilon}-N curves for austenitic SSs as a function of material, loading, and environmental parameters. Two methods for incorporating the effects of LWR coolant environments into the ASME Code fatigue evaluations are presented.

  9. The detection of flaws in austenitic welds using the decomposition of the time-reversal operator

    PubMed Central

    Cunningham, Laura J.; Mulholland, Anthony J.; Gachagan, Anthony; Harvey, Gerry; Bird, Colin

    2016-01-01

    The non-destructive testing of austenitic welds using ultrasound plays an important role in the assessment of the structural integrity of safety critical structures. The internal microstructure of these welds is highly scattering and can lead to the obscuration of defects when investigated by traditional imaging algorithms. This paper proposes an alternative objective method for the detection of flaws embedded in austenitic welds based on the singular value decomposition of the time-frequency domain response matrices. The distribution of the singular values is examined in the cases where a flaw exists and where there is no flaw present. A lower threshold on the singular values, specific to austenitic welds, is derived which, when exceeded, indicates the presence of a flaw. The detection criterion is successfully implemented on both synthetic and experimental data. The datasets arising from welds containing a flaw are further interrogated using the decomposition of the time-reversal operator (DORT) method and the total focusing method (TFM), and it is shown that images constructed via the DORT algorithm typically exhibit a higher signal-to-noise ratio than those constructed by the TFM algorithm. PMID:27274683

  10. A simplified LBB evaluation procedure for austenitic and ferritic steel piping

    SciTech Connect

    Gamble, R.M.; Wichman, K.R.

    1997-04-01

    The NRC previously has approved application of LBB analysis as a means to demonstrate that the probability of pipe rupture was extremely low so that dynamic loads associated with postulated pipe break could be excluded from the design basis (1). The purpose of this work was to: (1) define simplified procedures that can be used by the NRC to compute allowable lengths for circumferential throughwall cracks and assess margin against pipe fracture, and (2) verify the accuracy of the simplified procedures by comparison with available experimental data for piping having circumferential throughwall flaws. The development of the procedures was performed using techniques similar to those employed to develop ASME Code flaw evaluation procedures. The procedures described in this report are applicable to pipe and pipe fittings with: (1) wrought austenitic steel (Ni-Cr-Fe alloy) having a specified minimum yield strength less than 45 ksi, and gas metal-arc, submerged arc and shielded metal-arc austentic welds, and (2) seamless or welded wrought carbon steel having a minimum yield strength not greater than 40 ksi, and associated weld materials. The procedures can be used for cast austenitic steel when adequate information is available to place the cast material toughness into one of the categories identified later in this report for austenitic wrought and weld materials.

  11. Development of a Twin Crystal Membrane Coupled Conformable Phased Array for the Inspection of Austenitic Welds

    NASA Astrophysics Data System (ADS)

    Russell, J.; Long, R.; Cawley, P.

    2011-06-01

    The inspection of welded austenitic stainless steel components can be challenging. Austenitic welds contain an anisotropic, inhomogeneous grain structure which causes attenuation, scattering and beam bending. The inspection of components where the weld cap has not been removed is even more difficult due to the irregularity of the surface geometry. A twin crystal membrane coupled device has now been produced containing two linear phased arrays positioned adjacent to one another within the same housing. The arrays are angled relative to one another so that the transducer provides a pseudo-focusing effect at a depth corresponding to the beam crossing point. This type of design is used to improve the signal to noise ratio of the defect response in comparison to simple linear phased array transducer designs and to remove an internal noise signal found in linear phased array devices. Experimental results obtained from the through weld inspection of an austenitic stainless steel component with an undressed weld cap using the twin crystal membrane device are presented. These results demonstrate that small lack of side wall fusion defects can be reliably detected in large complex structures.

  12. Development of a twin crystal membrane coupled conformable phased array for the inspection of austenitic welds

    SciTech Connect

    Russell, J.; Long, R.; Cawley, P.

    2011-06-23

    The inspection of welded austenitic stainless steel components can be challenging. Austenitic welds contain an anisotropic, inhomogeneous grain structure which causes attenuation, scattering and beam bending. The inspection of components where the weld cap has not been removed is even more difficult due to the irregularity of the surface geometry. A twin crystal membrane coupled device has now been produced containing two linear phased arrays positioned adjacent to one another within the same housing. The arrays are angled relative to one another so that the transducer provides a pseudo-focusing effect at a depth corresponding to the beam crossing point. This type of design is used to improve the signal to noise ratio of the defect response in comparison to simple linear phased array transducer designs and to remove an internal noise signal found in linear phased array devices. Experimental results obtained from the through weld inspection of an austenitic stainless steel component with an undressed weld cap using the twin crystal membrane device are presented. These results demonstrate that small lack of side wall fusion defects can be reliably detected in large complex structures.

  13. Austenitic alloy and reactor components made thereof

    DOEpatents

    Bates, John F.; Brager, Howard R.; Korenko, Michael K.

    1986-01-01

    An austenitic stainless steel alloy is disclosed, having excellent fast neutron irradiation swelling resistance and good post irradiation ductility, making it especially useful for liquid metal fast breeder reactor applications. The alloy contains: about 0.04 to 0.09 wt. % carbon; about 1.5 to 2.5 wt. % manganese; about 0.5 to 1.6 wt. % silicon; about 0.030 to 0.08 wt. % phosphorus; about 13.3 to 16.5 wt. % chromium; about 13.7 to 16.0 wt. % nickel; about 1.0 to 3.0 wt. % molybdenum; and about 0.10 to 0.35 wt. % titanium.

  14. Radiation resistant austenitic stainless steel alloys

    DOEpatents

    Maziasz, P.J.; Braski, D.N.; Rowcliffe, A.F.

    1987-02-11

    An austenitic stainless steel alloy, with improved resistance to radiation-induced swelling and helium embrittlement, and improved resistance to thermal creep at high temperatures, consisting essentially of, by weight percent: from 16 to 18% nickel; from 13 to 17% chromium; from 2 to 3% molybdenum; from 1.5 to 2.5% manganese; from 0.01 to 0.5% silicon; from 0.2 to 0.4% titanium; from 0.1 to 0.2% niobium; from 0.1 to 0.6% vanadium; from 0.06 to 0.12% carbon; from 0.01 to 0.03% nitrogen; from 0.03 to 0.08% phosphorus; from 0.005 to 0.01% boron; and the balance iron, and wherein the alloy may be thermomechanically treated to enhance physical and mechanical properties. 4 figs.

  15. Radiation resistant austenitic stainless steel alloys

    DOEpatents

    Maziasz, Philip J.; Braski, David N.; Rowcliffe, Arthur F.

    1989-01-01

    An austenitic stainless steel alloy, with improved resistance to radiation-induced swelling and helium embrittlement, and improved resistance to thermal creep at high temperatures, consisting essentially of, by weight percent: from 16 to 18% nickel; from 13 to 17% chromium; from 2 to 3% molybdenum; from 1.5 to 2.5% manganese; from 0.01 to 0.5% silicon; from 0.2 to 0.4% titanium; from 0.1 to 0.2% niobium; from 0.1 to 0.6% vanadium; from 0.06 to 0.12% carbon; from 0.01% to 0.03% nitrogen; from 0.03 to 0.08% phosphorus; from 0.005 to 0.01% boron; and the balance iron, and wherein the alloy may be thermomechanically treated to enhance physical and mechanical properties.

  16. High temperature creep resistant austenitic alloy

    DOEpatents

    Maziasz, Philip J.; Swindeman, Robert W.; Goodwin, Gene M.

    1989-01-01

    An improved austenitic alloy having in wt % 19-21 Cr, 30-35 Ni, 1.5-2.5 Mn, 2-3 Mo, 0.1-0.4 Si, 0.3-0.5 Ti, 0.1-0.3 Nb, 0.1-0.5 V, 0.001-0.005 P, 0.08-0.12 C, 0.01-0.03 N, 0.005-0.01 B and the balance iron that is further improved by annealing for up to 1 hour at 1150.degree.-1200.degree. C. and then cold deforming 5-15 %. The alloy exhibits dramatically improved creep rupture resistance and ductility at 700.degree. C.

  17. Improved high temperature creep resistant austenitic alloy

    DOEpatents

    Maziasz, P.J.; Swindeman, R.W.; Goodwin, G.M.

    1988-05-13

    An improved austenitic alloy having in wt% 19-21 Cr, 30-35 Ni, 1.5-2.5 Mn, 2-3 Mo, 0.1-0.4 Si, 0.3-0.5 Ti, 0.1-0.3 Nb, 0.1-0.5 V, 0.001-0.005 P, 0.08-0.12 C, 0.01-0.03 N, 0.005-0.01 B and the balance iron that is further improved by annealing for up to 1 hour at 1150-1200/degree/C and then cold deforming 5-15%. The alloy exhibits dramatically improved creep rupture resistance and ductility at 700/degree/C. 2 figs.

  18. Fabrication and characterization of ODS austenitic steels

    NASA Astrophysics Data System (ADS)

    Xu, Yingli; Zhou, Zhangjian; Li, Ming; He, Pei

    2011-10-01

    Pure Fe, Cr, Ni, W, Ti elemental powders and nano-Y 2O 3 powders (the compositions of the mixed powders are Fe-18Cr-8Ni-2W-1Ti-0.35Y 2O 3) were processed by high energy mechanical milling. The as milled powders were consolidated by hot isostatic pressing for 3 h at 1423 K under a pressure of 200 MPa. The microstructure of the fabricated ODS austenitic steels and chemical composition of the oxide particles were examined by field emission scanning electron microscopy with energy dispersive spectrometry. The dispersed fine oxides were determined to be Y-Ti-O oxides. The tensile properties were improved significantly by oxide dispersion strengthening but the ductility deteriorated.

  19. Low-temperature creep of austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Reed, R. P.; Walsh, R. P.

    2017-09-01

    Plastic deformation under constant load (creep) in austenitic stainless steels has been measured at temperatures ranging from 4 K to room temperature. Low-temperature creep data taken from past and unreported austenitic stainless steel studies are analyzed and reviewed. Creep at cryogenic temperatures of common austenitic steels, such as AISI 304, 310 316, and nitrogen-strengthened steels, such as 304HN and 3116LN, are included. Analyses suggests that logarithmic creep (creep strain dependent on the log of test time) best describe austenitic stainless steel behavior in the secondary creep stage and that the slope of creep strain versus log time is dependent on the applied stress/yield strength ratio. The role of cold work, strain-induced martensitic transformations, and stacking fault energy on low-temperature creep behavior is discussed. The engineering significance of creep on cryogenic structures is discussed in terms of the total creep strain under constant load over their operational lifetime at allowable stress levels.

  20. Chemically Induced Phase Transformation in Austenite by Focused Ion Beam

    NASA Astrophysics Data System (ADS)

    Basa, Adina; Thaulow, Christian; Barnoush, Afrooz

    2013-11-01

    A highly stable austenite phase in a super duplex stainless steel was subjected to a combination of different gallium ion doses at different acceleration voltages. It was shown that contrary to what is expected, an austenite to ferrite phase transformation occurred within the focused ion beam (FIB) milled regions. Chemical analysis of the FIB milled region proved that the gallium implantation preceded the FIB milling. High resolution electron backscatter diffraction analysis also showed that the phase transformation was not followed by the typical shear and plastic deformation expected from the martensitic transformation. On the basis of these observations, it was concluded that the change in the chemical composition of the austenite and the local increase in gallium, which is a ferrite stabilizer, results in the local selective transformation of austenite to ferrite.

  1. Plastic Deformation Influence on Intrinsic Magnetic Field of Austenitic Biomaterials

    NASA Astrophysics Data System (ADS)

    Smetana, Milan; Čápová, Klára; Chudáčik, Vladimír; Palček, Peter; Oravcová, Monika

    2016-12-01

    This article deals with non-destructive evaluation of austenitic stainless steels, which are used as the biomaterials in medical practice. Intrinsic magnetic field is investigated using the fluxgate sensor, after the applied plastic deformation. The three austenitic steel types are studied under the same conditions, while several values of the deformation are applied, respectively. The obtained results are presented and discussed in the paper.

  2. Effect of retained austenite on high cycle fatigue behaviour of carburized 14NiCr11 steel

    NASA Astrophysics Data System (ADS)

    Jeddi, D.; Sidhom, H.; Lieurade, H.-P.

    2008-11-01

    Two vacuum carburizing treatments were applied to ductile steel 14NiCr11 to obtain equivalent hardened layers with retained austenite contents of 25% and 41%. The properties of the carburized surfaces were examined and characterized before fatigue tests and during cyclic loading. Transformation of retained austenite into martensite during loading, was evaluated by dispersive X-ray diffraction method. The effects of this transformation on the residual stresses have been measured by X ray diffraction in martensite and in retained austenite structures. It was shown that the cyclic retained austenite transformation caused a redistribution of the compressive residual stresses and an increased surface hardness that stabilized after a small number of cycles. The dependence of fatigue behaviour on surface properties was determined, and a relationship between the stabilized state and the fatigue limit is suggested. A phenomenological approach is proposed to correlate the influence of surface hardening and the stabilized residual stresses on fatigue limit of carburized specimens. The Crossland, Dang Van and Findley-Matake, multiaxial high cycle fatigue criteria were used in this approach and results have shown a good agreement with experimental data.

  3. Interpretation of high-temperature tensile properties by thermodynamically calculated equilibrium phase diagrams of heat-resistant austenitic cast steels

    NASA Astrophysics Data System (ADS)

    Jung, Seungmun; Sohn, Seok Su; Choi, Won-Mi; Lee, Byeong-Joo; Oh, Yong-Jun; Jang, Seongsik; Lee, Sunghak

    2017-01-01

    High-temperature tensile properties of three heat-resistant austenitic cast steels fabricated by varying W, Mo, and Al contents were interpreted by thermodynamically calculated equilibrium phase diagrams of austenite, ferrite, and carbides as well as microstructural analyses. A two-step calculation method was adopted to cast steel microstructures below the liquid dissolution temperature because the casting route was not an equilibrium state. Thermodynamically calculated fractions of equilibrium phases were well matched with experimentally measured fractions. Ferrites existed at room and high temperatures in both equilibrium phase diagrams and actual microstructures, which has not been reported in previous researches on austenitic cast steels. In the W2Mo1Al1 steel, 38% and 12% of ferrite existed in the equilibrium phase diagram and actual microstructure, respectively, and led to the void initiation and coalescence at ferrites and consequently to the serious deterioration of high-temperature strengths. The present equilibrium phase diagrams, besides detailed microstructural analyses, effectively evaluated the high-temperature performance by estimating high-temperature equilibrium phases, and provided an important idea on whether ferrite were formed or not in the heat-resistant austenitic cast steels.

  4. Machining and Phase Transformation Response of Room-Temperature Austenitic NiTi Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Kaynak, Yusuf

    2014-09-01

    This experimental work reports the results of a study addressing tool wear, surface topography, and x-ray diffraction analysis for the finish cutting process of room-temperature austenitic NiTi alloy. Turning operation of NiTi alloy was conducted under dry, minimum quantity lubrication (MQL) and cryogenic cooling conditions at various cutting speeds. Findings revealed that cryogenic machining substantially reduced tool wear and improved surface topography and quality of the finished parts in comparison with the other two approaches. Phase transformation on the surface of work material was not observed after dry and MQL machining, but B19' martensite phase was found on the surface of cryogenically machined samples.

  5. Migration and accumulation at dislocations of transmutation helium in austenitic steels upon neutron irradiation

    NASA Astrophysics Data System (ADS)

    Kozlov, A. V.; Portnykh, I. A.

    2016-04-01

    The model of the migration and accumulation at dislocations of transmutation helium and the formation of helium-vacancy pore nuclei in austenitic steels upon neutron irradiation has been proposed. As illustrations of its application, the dependences of the characteristics of pore nuclei on the temperature of neutron irradiation have been calculated. The results of the calculations have been compared with the experimental data in the literature on measuring the characteristics of radiation-induced porosity that arises upon the irradiation of shells of fuel elements of a 16Cr-19Ni-2Mo-2Mn-Si-Ti-Nb-V-B steel in a fast BN600 neutron reactor at different temperatures.

  6. Mechanical properties of austenitic stainless steel single crystals: Influence of nitrogen and hydrogen content

    SciTech Connect

    Sucre, Y.R.; Iost, A.; Vogt, J.B.; Najjar, D.; Chumlyakov, Y.I.

    2000-01-01

    The effect of cathodically charged hydrogen in austenitic stainless steels with or without nitrogen addition was studied by microhardness experiments carried out on single crystals. With the authors experimental conditions, it can be demonstrated that hydrogen penetration depth is near 25 {micro}m and induced a higher apparent hardness. In fact, the hardness improvement is mainly a consequence of the residual stresses induced by hydrogen diffusion. By studying the variation of hardness with the reciprocal length of the indentation print obtained with load varying between 0.5 and 200 N, it was observed that the slope (VHN vs 1/d) only depends on the aging time.

  7. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part II. Fatigue crack growth rate

    NASA Astrophysics Data System (ADS)

    Margolin, B.; Minkin, A.; Smirnov, V.; Sorokin, A.; Shvetsova, V.; Potapova, V.

    2016-11-01

    The experimental data on the fatigue crack growth rate (FCGR) have been obtained for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various radiation swelling. The performed study of the fracture mechanisms for cracked specimens under cyclic loading has explained why radiation swelling affects weakly FCGR unlike its effect on fracture toughness. Mechanical modeling of fatigue crack growth has been carried out and the dependencies for prediction of FCGR in irradiated austenitic steel with and with no swelling are proposed and verified with the obtained experimental results. As input data for these dependencies, FCGR for unirradiated steel and the tensile mechanical properties for unirradiated and irradiated steels are used.

  8. Entropic stabilization of austenite in shape memory alloys

    NASA Astrophysics Data System (ADS)

    Elliott, Ryan S.; Karls, Daniel S.

    2013-12-01

    Martensitic transformations (MTs) are the key phenomena responsible for the remarkable properties of Shape Memory Alloys (SMAs). Recent Density Functional Theory (DFT) electronic structure calculations have revealed that the austenite structure of many SMAs is a saddle-point of the material's potential energy landscape. Correspondingly, the austenite is unstable and thus unobservable at zero temperature. Thus, the observable high temperature austenite structure in many SMAs is entropically stabilized by nonlinear dynamic effects. This paper discusses the phenomenon of entropic stabilization of the austenite phase in SMAs and explicitly demonstrates it using Molecular Dynamics (MD) and a three-dimensional all-atom potential energy model whose equilibria crystal structures correspond to commonly observed SMA phases. A new technique is used to carefully select a model so that it is likely to lead to entropic stabilization of a B2 cubic austenite from a B19 orthorhombic martensite. This is accomplished by using a detailed branch-following and bifurcation (BFB) parametric study of the Morse pair potential binary alloy model. The results of the MD simulation clearly demonstrate the entropic stabilization of the B2 austenite phase at high temperature. Analysis of the dynamics of the B2 austenite phase indicates that its stabilization may be viewed as a result of individual atoms randomly visiting the B19 and αIrV phases (with only occasional visits to the B2 and L10 phases). This occurs without long-range correlations in such a way that each atom's time-average configuration corresponds to the B2 structure.

  9. Austenitic stainless steel for high temperature applications

    DOEpatents

    Johnson, Gerald D.; Powell, Roger W.

    1985-01-01

    This invention describes a composition for an austenitic stainless steel which has been found to exhibit improved high temperature stress rupture properties. The composition of this alloy is about (in wt. %): 12.5 to 14.5 Cr; 14.5 to 16.5 Ni; 1.5 to 2.5 Mo; 1.5 to 2.5 Mn; 0.1 to 0.4 Ti; 0.02 to 0.08 C; 0.5 to 1.0 Si; 0.01 maximum, N; 0.02 to 0.08 P; 0.002 to 0.008 B; 0.004-0.010 S; 0.02-0.05 Nb; 0.01-0.05 V; 0.005-0.02 Ta; 0.02-0.05 Al; 0.01-0.04 Cu; 0.02-0.05 Co; 0.03 maximum, As; 0.01 maximum, O; 0.01 maximum, Zr; and with the balance of the alloy being essentially iron. The carbon content of the alloy is adjusted such that wt. % Ti/(wt. % C+wt. % N) is between 4 and 6, and most preferably about 5. In addition the sum of the wt. % P+wt. % B+wt. % S is at least 0.03 wt. %. This alloy is believed to be particularly well suited for use as fast breeder reactor fuel element cladding.

  10. Weldable, age hardenable, austenitic stainless steel

    DOEpatents

    Brooks, J.A.; Krenzer, R.W.

    1975-07-22

    An age hardenable, austenitic stainless steel having superior weldability properties as well as resistance to degradation of properties in a hydrogen atmosphere is described. It has a composition of from about 24.0 to about 34.0 weight percent (w/o) nickel, from about 13.5 to about 16.0 w/o chromium, from about 1.9 to about 2.3 w/o titanium, from about 1.0 to about 1.5 w/ o molybdenum, from about 0.01 to about 0.05 w/o carbon, from about 0 to about 0.25 w/o manganese, from about 0 to about 0.01 w/o phosphorous and preferably about 0.005 w/o maximum, from about 0 to about 0.010 w/o sulfur and preferably about 0.005 w/o maximum, from about 0 to about 0.25 w/o silicon, from about 0.1 to about 0.35 w/o aluminum, from about 0.10 to about 0.50 w/o vanadium, from about 0 to about 0.0015 w/o boron, and the balance essentially iron. (auth)

  11. Ion-nitriding of austenitic stainless steels

    SciTech Connect

    Pacheco, O.; Hertz, D.; Lebrun, J.P.; Michel, H.

    1995-12-31

    Although ion-nitriding is an extensively industrialized process enabling steel surfaces to be hardened by nitrogen diffusion, with a resulting increase in wear, seizure and fatigue resistance, its direct application to stainless steels, while enhancing their mechanical properties, also causes a marked degradation in their oxidation resistance. However, by adaption of the nitriding process, it is possible to maintain the improved wear resistant properties while retaining the oxidation resistance of the stainless steel. The controlled diffusion permits the growth of a nitrogen supersaturated austenite layer on parts made of stainless steel (AISI 304L and 316L) without chromium nitride precipitation. The diffusion layer remains stable during post heat treatments up to 650 F for 5,000 hrs and maintains a hardness of 900 HV. A very low and stable friction coefficient is achieved which provides good wear resistance against stainless steels under diverse conditions. Electrochemical and chemical tests in various media confirm the preservation of the stainless steel characteristics. An example of the application of this process is the treatment of Reactor Control Rod Cluster Assemblies (RCCAs) for Pressurized Water Nuclear Reactors.

  12. Microstructural studies of advanced austenitic steels

    SciTech Connect

    Todd, J. A.; Ren, Jyh-Ching

    1989-11-15

    This report presents the first complete microstructural and analytical electron microscopy study of Alloy AX5, one of a series of advanced austenitic steels developed by Maziasz and co-workers at Oak Ridge National Laboratory, for their potential application as reheater and superheater materials in power plants that will reach the end of their design lives in the 1990's. The advanced steels are modified with carbide forming elements such as titanium, niobium and vanadium. When combined with optimized thermo-mechanical treatments, the advanced steels exhibit significantly improved creep rupture properties compared to commercially available 316 stainless steels, 17--14 Cu--Mo and 800 H steels. The importance of microstructure in controlling these improvements has been demonstrated for selected alloys, using stress relaxation testing as an accelerated test method. The microstructural features responsible for the improved creep strengths have been identified by studying the thermal aging kinetics of one of the 16Ni--14Cr advanced steels, Alloy AX5, in both the solution annealed and the solution annealed plus cold worked conditions. Time-temperature-precipitation diagrams have been developed for the temperature range 600 C to 900 C and for times from 1 h to 3000 h. 226 refs., 88 figs., 10 tabs.

  13. Role of nanocrystalline cerium oxide coatings on austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Zhang, Haiying

    Protective nanocrystalline cerium oxide coating has been applied to ASTM grade 304L and 304 austenitic stainless steels to improve its oxidation resistance at elevated temperatures. Experimentally, the selected alloy was exposed to 800°C/1000°C under dry air conditions. Weight changes (DeltaW/A) were monitored as a function of time and the results were compared with uncoated alloys tested under similar conditions. It was found that the oxidation resistances of 304L and 304 stainless steels were significantly improved. A comparison of the oxidation rates indicated that the nanocrystalline cerium oxide coating reduced the rate of oxidation by more than two orders of magnitude. Nevertheless, a comprehensive understanding of the mechanisms responsible for the reduction in the oxidation rate is not clear. Consequently, this work is aimed at investigating the mechanisms involved during scale growth in the presence or absence of nanocrystalline coatings. For this purpose, density functional theory was carried out in order to predict oxygen and iron diffusion microscopic activation energies and reveal the intrinsic characteristics of nanocrystalline coatings. A numerical simulation of corrosion process has also been conducted to predict the corrosion rates of alloys with and without coatings. Hence, the results from simulations are compared with the experimental outcome, and possible explanations are given to account for the reduction in the exhibited oxidation rates. The simulation results will provide a highly valuable tool for the realization of functional nanostructures and architectures "by design", particularly in the development of novel coatings, and a new approach of life assessment.

  14. Austenite decomposition in ternary manganese, molybdenum and tungsten steels

    NASA Astrophysics Data System (ADS)

    Hackenberg, Robert Errol

    A survey of austenite decomposition in Fe-(0.1, 0.2)C-(3, 4.2)Mn has revealed kinetic and morphological transitions which take place at substantial undercoolings below the paraequilibrium Ae3 temperature. An unusually long interval of transformation stasis was found in Fe-0.1C-3Mn, during which time the ferrite was free of carbides. A nodular product containing rod particles was observed in several of these alloys. The grain boundary bainite (GBB) and twin boundary bainite (TBB) morphologies at the bay in Fe-0.24C-4Mo were significantly more complex than previously assumed, with differing arrangements of bainite subunits; their thickening rates also differed. TEM revealed 10 nm steps at the bainite-austenite interfaces in GBB. Mo enrichment was found within GBB-austenite interfaces and extended ˜10 nm into the austenite. The M2C carbides are always enriched in Mo, possessing a non-equilibrium Mo content at earlier reaction times. The energies stored in the ferrite-carbide interfacial area and in carbides possessing non-equilibrium Fe/Mo ratios were considered to reduce the driving force for diffusion by up to 20%. GBB and TBB were found at and above the bay in Fe-0.3C-6.3W, while the bainite formed below the bay consisted of elongated subunits. M6C was found at all temperatures, while M2C was found only below the bay, both of which exhibited W partition. A dark-etching constituent of very high carbide density transformed the remaining pools of austenite at the late stages of reaction, a result consistent with the level of carbon in austenite rising with time. Transitions in carbide morphology were explored in Fe-0.2C-63W. At lower reaction temperatures, M6C precipitates with ferrite. At higher temperatures the cellular precipitation of quasilamellar M 6C in austenite occurs, and is considered to take place inside the ferrite + austenite + M6C three-phase field. The austenite inside the quasilamellar carbide nodules reverts to ferrite at long times, indicating a

  15. Reversed austenite for enhancing ductility of martensitic stainless steel

    NASA Astrophysics Data System (ADS)

    Dieck, S.; Rosemann, P.; Kromm, A.; Halle, T.

    2017-03-01

    The novel heat treatment concept, “quenching and partitioning” (Q&P) has been developed for high strength steels with enhanced formability. This heat treatment involves quenching of austenite to a temperature between martensite start and finish, to receive a several amount of retained austenite. During the subsequent annealing treatment, the so called partitioning, the retained austenite is stabilized due to carbon diffusion, which results in enhanced formability and strength regarding strain induced austenite to martensite transformation. In this study a Q&P heat treatment was applied to a Fe-0.45C-0.65Mn-0.34Si-13.95Cr stainless martensite. Thereby the initial quench end temperature and the partitioning time were varied to characterize their influence on microstructural evolution. The microstructural changes were analysed by dilatometer measurements, X-ray diffraction and scanning electron microscopy, including electron back-scatter diffraction. Compression testing was made to examine the mechanical behaviour. It was found that an increasing partitioning time up to 30 min leads to an enhanced formability without loss in strength due to a higher amount of stabilized retained and reversed austenite as well as precipitation hardening.

  16. Expanded Quality Management Using Information Power (EQUIP): protocol for a quasi-experimental study to improve maternal and newborn health in Tanzania and Uganda

    PubMed Central

    2014-01-01

    Background Maternal and newborn mortality remain unacceptably high in sub-Saharan Africa. Tanzania and Uganda are committed to reduce maternal and newborn mortality, but progress has been limited and many essential interventions are unavailable in primary and referral facilities. Quality management has the potential to overcome low implementation levels by assisting teams of health workers and others finding local solutions to problems in delivering quality care and the underutilization of health services by the community. Existing evidence of the effect of quality management on health worker performance in these contexts has important limitations, and the feasibility of expanding quality management to the community level is unknown. We aim to assess quality management at the district, facility, and community levels, supported by information from high-quality, continuous surveys, and report effects of the quality management intervention on the utilization and quality of services in Tanzania and Uganda. Methods In Uganda and Tanzania, the Expanded Quality Management Using Information Power (EQUIP) intervention is implemented in one intervention district and evaluated using a plausibility design with one non-randomly selected comparison district. The quality management approach is based on the collaborative model for improvement, in which groups of quality improvement teams test new implementation strategies (change ideas) and periodically meet to share results and identify the best strategies. The teams use locally-generated community and health facility data to monitor improvements. In addition, data from continuous health facility and household surveys are used to guide prioritization and decision making by quality improvement teams as well as for evaluation of the intervention. These data include input, process, output, coverage, implementation practice, and client satisfaction indicators in both intervention and comparison districts. Thus, intervention districts

  17. 75 FR 70908 - Circular Welded Austenitic Stainless Pressure Pipe From the People's Republic of China: Extension...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-19

    ... From the Federal Register Online via the Government Publishing Office ] DEPARTMENT OF COMMERCE International Trade Administration Circular Welded Austenitic Stainless Pressure Pipe From the People's Republic... of the antidumping duty order on circular welded austenitic stainless pressure pipe from the...

  18. Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

    NASA Astrophysics Data System (ADS)

    Rahmani, Mehdi; Eghlimi, Abbas; Shamanian, Morteza

    2014-10-01

    To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstätten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.

  19. Expanding the Start of the College Pipeline: Ninth-Grade Findings from an Experimental Study of the Impact of the Early College High School Model

    ERIC Educational Resources Information Center

    Edmunds, Julie A.; Bernstein, Lawrence; Unlu, Fatih; Glennie, Elizabeth; Willse, John; Smith, Arthur; Arshavsky, Nina

    2012-01-01

    Early college high schools are a new and rapidly spreading model that merges the high school and college experiences and that is designed to increase the number of students who graduate from high school and enroll and succeed in postsecondary education. This article presents results from a federally funded experimental study of the impact of the…

  20. Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel.

    PubMed

    Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

    2016-08-05

    We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α'-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α' → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α'N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance.

  1. Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel

    NASA Astrophysics Data System (ADS)

    Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

    2016-08-01

    We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α‧-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α‧ → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α‧N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance.

  2. Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel

    PubMed Central

    Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

    2016-01-01

    We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α′-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α′ → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α′N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance. PMID:27492862

  3. Simulation of an Austenite-Twinned-Martensite Interface.

    PubMed

    Kearsley, A J; Melara, L A

    2003-01-01

    Developing numerical methods for predicting microstructure in materials is a large and important research area. Two examples of material microstructures are Austenite and Martensite. Austenite is a microscopic phase with simple crystallographic structure while Martensite is one with a more complex structure. One important task in materials science is the development of numerical procedures which accurately predict microstructures in Martensite. In this paper we present a method for simulating material microstructure close to an Austenite-Martensite interface. The method combines a quasi-Newton optimization algorithm and a nonconforming finite element scheme that successfully minimizes an approximation to the total stored energy near the interface of interest. Preliminary results suggest that the minimizers of this energy functional located by the developed numerical algorithm appear to display the desired characteristics.

  4. Characterization of Austenitic Stainless Steels Deformed at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Calmunger, Mattias; Chai, Guocai; Eriksson, Robert; Johansson, Sten; Moverare, Johan J.

    2017-10-01

    Highly alloyed austenitic stainless steels are promising candidates to replace more expensive nickel-based alloys within the energy-producing industry. The present study investigates the deformation mechanisms by microstructural characterization, mechanical properties and stress-strain response of three commercial austenitic stainless steels and two commercial nickel-based alloys using uniaxial tensile tests at elevated temperatures from 673 K (400 °C) up to 973 K (700 °C). The materials showed different ductility at elevated temperatures which increased with increasing nickel content. The dominating deformation mechanism was planar dislocation-driven deformation at elevated temperature. Deformation twinning was also a noticeable active deformation mechanism in the heat-resistant austenitic alloys during tensile deformation at elevated temperatures up to 973 K (700 °C).

  5. Nickel-free austenitic stainless steels for medical applications

    PubMed Central

    Yang, Ke; Ren, Yibin

    2010-01-01

    The adverse effects of nickel ions being released into the human body have prompted the development of high-nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel in medical stainless steels, the advantages of nitrogen in stainless steels, and emphatically, the development of high-nitrogen nickel-free stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength and good plasticity, better corrosion and wear resistances, and superior biocompatibility compared to the currently used 316L stainless steel, the newly developed high-nitrogen nickel-free stainless steel is a reliable substitute for the conventional medical stainless steels. PMID:27877320

  6. High Energy Rate Forming Induced Phase Transition in Austenitic Steel

    NASA Astrophysics Data System (ADS)

    Kovacs, T.; Kuzsella, L.

    2017-02-01

    In this study, the effects of explosion hardening on the microstructure and the hardness of austenitic stainless steel have been studied. The optimum explosion hardening technology of austenitic stainless steel was researched. In case of the explosive hardening used new idea means indirect hardening setup. Austenitic stainless steels have high plasticity and can be cold formed easily. However, during cold processing the hardening phenomena always occurs. Upon the explosion impact, the deformation mechanism indicates a plastic deformation and this deformation induces a phase transformation (martensite). The explosion hardening enhances the mechanical properties of the material, includes the wear resistance and hardness [1]. In case of indirect hardening as function of the setup parameters specifically the flayer plate position the hardening increased differently. It was find a relationship between the explosion hardening setup and the hardening level.

  7. Characterization of Austenitic Stainless Steels Deformed at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Calmunger, Mattias; Chai, Guocai; Eriksson, Robert; Johansson, Sten; Moverare, Johan J.

    2017-07-01

    Highly alloyed austenitic stainless steels are promising candidates to replace more expensive nickel-based alloys within the energy-producing industry. The present study investigates the deformation mechanisms by microstructural characterization, mechanical properties and stress-strain response of three commercial austenitic stainless steels and two commercial nickel-based alloys using uniaxial tensile tests at elevated temperatures from 673 K (400°C) up to 973 K (700°C). The materials showed different ductility at elevated temperatures which increased with increasing nickel content. The dominating deformation mechanism was planar dislocation-driven deformation at elevated temperature. Deformation twinning was also a noticeable active deformation mechanism in the heat-resistant austenitic alloys during tensile deformation at elevated temperatures up to 973 K (700°C).

  8. 76 FR 43981 - Circular Welded Austenitic Stainless Pressure Pipe From the People's Republic of China: Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-22

    ... International Trade Administration Circular Welded Austenitic Stainless Pressure Pipe From the People's Republic... antidumping duty order on circular welded austenitic stainless pressure pipe from the People's Republic of..., 2010. \\1\\ See Circular Welded Austenitic Stainless Pressure Pipe From the People's Republic of...

  9. 76 FR 17819 - Circular Welded Austenitic Stainless Pressure Pipe From the People's Republic of China...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-31

    ... International Trade Administration Circular Welded Austenitic Stainless Pressure Pipe From the People's Republic... ] antidumping duty order on circular welded austenitic stainless pressure pipe (``austenitic pipe'') from the... Stainless Pressure Pipe from the People's Republic of China, 74 FR 11351 (March 17, 2009). \\2\\...

  10. Prediction of Austenite Formation Temperatures Using Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Schulze, P.; Schmidl, E.; Grund, T.; Lampke, T.

    2016-03-01

    For the modeling and design of heat treatments, in consideration of the development/ transformation of the microstructure, different material data depending on the chemical composition, the respective microstructure/phases and the temperature are necessary. Material data are, e.g. the thermal conductivity, heat capacity, thermal expansion and transformation data etc. The quality of thermal simulations strongly depends on the accuracy of the material data. For many materials, the required data - in particular for different microstructures and temperatures - are rare in the literature. In addition, a different chemical composition within the permitted limits of the considered steel alloy cannot be predicted. A solution for this problem is provided by the calculation of material data using Artificial Neural Networks (ANN). In the present study, the start and finish temperatures of the transformation from the bcc lattice to the fcc lattice structure of hypoeutectoid steels are calculated using an Artificial Neural Network. An appropriate database containing different transformation temperatures (austenite formation temperatures) to train the ANN is selected from the literature. In order to find a suitable feedforward network, the network topologies as well as the activation functions of the hidden layers are varied and subsequently evaluated in terms of the prediction accuracy. The transformation temperatures calculated by the ANN exhibit a very good compliance compared to the experimental data. The results show that the prediction performance is even higher compared to classical empirical equations such as Andrews or Brandis. Therefore, it can be assumed that the presented ANN is a convenient tool to distinguish between bcc and fcc phases in hypoeutectoid steels.

  11. Oxidation resistant high creep strength austenitic stainless steel

    DOEpatents

    Brady, Michael P.; Pint, Bruce A.; Liu, Chain-Tsuan; Maziasz, Philip J.; Yamamoto, Yukinori; Lu, Zhao P.

    2010-06-29

    An austenitic stainless steel displaying high temperature oxidation and creep resistance has a composition that includes in weight percent 15 to 21 Ni, 10 to 15 Cr, 2 to 3.5 Al, 0.1 to 1 Nb, and 0.05 to 0.15 C, and that is free of or has very low levels of N, Ti and V. The alloy forms an external continuous alumina protective scale to provide a high oxidation resistance at temperatures of 700 to 800.degree. C. and forms NbC nanocarbides and a stable essentially single phase fcc austenitic matrix microstructure to give high strength and high creep resistance at these temperatures.

  12. Uncertainty in retained austenite measurements applied to individual crystallographic orientations

    NASA Astrophysics Data System (ADS)

    Creuziger, A.; Gnäupel-Herold, T.

    2015-04-01

    A technique to measure the phase volume fraction of an individual orientation and the uncertainty in the measurement is demonstrated in this paper. The technique of complete pole figure averaging using neutron diffraction was used to assess the phase fraction of retained austenite in transformation induced plasticity (TRIP) steels and quantify the uncertainty in the phase fraction. In parallel, an ensemble of orientation distribution functions was calculated to assess crystallographic volume fractions of particular orientations and the uncertainty of these volume fractions using Monte Carlo techniques. These methods were combined to measure the retained austenite phase volume fraction of an individual orientation.

  13. Examination of carbon partitioning into austenite during tempering of bainite

    SciTech Connect

    Clarke, Amy J; Caballero, Francisca G; Miller, Michael K; Garcia - Mateo, C

    2010-01-01

    The redistribution of carbon after tempering of a novel nanocrystalline bainitic steel consisting of a mixture of supersaturated ferrite and retained austenite, has been analyzed by atom probe tomography. Direct supporting evidence of additional austenite carbon enrichment beyond that initially achieved during the bainite heat treatment was not obtained during subsequent tempering of this high carbon, high silicon steel. Evidence of competing reactions during tempering, such as the formation of carbon clusters in bainitic ferrite that signify the onset of the transitional carbides precipitation, was observed.

  14. Decomposition of supercooled austenite of powder phosphorus steels

    NASA Astrophysics Data System (ADS)

    Antsiferov, V. N.; Oglezneva, S. A.; Shatsov, A. A.

    1999-05-01

    The structure of powder phosphorus steels is investigated. New models of isothermal decomposition of super-cooled austenite are suggested which make it possible to predict the kinetics of the γ→α transformation in the pearlite and bainite temperature ranges. It is shown that mechanical alloying has a favorable effect on the formation of structure in steels. Grain disintegration accelerates the decomposition of austenite mainly due to the growth of the specific surface. At the same time, the contribution of 0.65-1.1% phosphorus additives to the process is low.

  15. Phase control of austenitic chrome-nickel steel

    SciTech Connect

    Korkh, M. K. Davidov, D. I. Korkh, J. V. Rigmant, M. B. Nichipuruk, A. P. Kazantseva, N. V.

    2015-10-27

    The paper presents the results of the comparative study of the possibilities of different structural and magnetic methods for detection and visualization of the strain-induced martensitic phase in low carbon austenitic chromium-nickel steel. Results of TEM, SEM, optical microscopy, atomic and magnetic force microscopy, and magnetic measurements are presented. Amount of the magnetic strain-induced martensite was estimated. We pioneered magnetic force microscopic images of the single domain cluster distribution of the strain-induced martensite in austenite-ferrite materials.

  16. On the constitutive model of nitrogen-containing austenitic stainless steel 316LN at elevated temperature.

    PubMed

    Zhang, Lei; Feng, Xiao; Wang, Xin; Liu, Changyong

    2014-01-01

    The nitrogen-containing austenitic stainless steel 316LN has been chosen as the material for nuclear main-pipe, which is one of the key parts in 3rd generation nuclear power plants. In this research, a constitutive model of nitrogen-containing austenitic stainless steel is developed. The true stress-true strain curves obtained from isothermal hot compression tests over a wide range of temperatures (900-1250°C) and strain rates (10(-3)-10 s(-1)), were employed to study the dynamic deformational behavior of and recrystallization in 316LN steels. The constitutive model is developed through multiple linear regressions performed on the experimental data and based on an Arrhenius-type equation and Zener-Hollomon theory. The influence of strain was incorporated in the developed constitutive equation by considering the effect of strain on the various material constants. The reliability and accuracy of the model is verified through the comparison of predicted flow stress curves and experimental curves. Possible reasons for deviation are also discussed based on the characteristics of modeling process.

  17. Strain-induced martensite to austenite reverse transformation in an ultrafine-grained Fe-Ni-Mn martensitic steel

    NASA Astrophysics Data System (ADS)

    Ghasemi-Nanesa, H.; Nili-Ahmadabadi, M.; Koohdar, H. R.; Habibi-Parsa, M.; Nedjad, S. Hossein; Alidokht, S. A.; Langdon, Terence G.

    2014-05-01

    Research was conducted to evaluate the effect of heavy cold rolling on microstructural evolution in an Fe-10Ni-7Mn (wt.%) martensitic steel. The chemical driving force for the strain-induced martensite to austenite reverse transformation was calculated using thermodynamic principles and a model was developed for estimating the effect of applied stress on the driving force of the martensite to austenite reverse transformation through heavy cold rolling. These calculations show that, in order to make a reverse transformation feasible, the applied stress on the material should supply the total driving force, both chemical and non-chemical, for the transformation. It is demonstrated that after 60% cold rolling the required driving force for the reverse transformation may be provided. Experimental results, including cold rolling and transmission electron microscopy images, are utilized to verify the thermodynamic calculations.

  18. Constitutive flow behaviour of austenitic stainless steels under hot deformation: artificial neural network modelling to understand, evaluate and predict

    NASA Astrophysics Data System (ADS)

    Mandal, Sumantra; Sivaprasad, P. V.; Venugopal, S.; Murthy, K. P. N.

    2006-09-01

    An artificial neural network (ANN) model is developed to predict the constitutive flow behaviour of austenitic stainless steels during hot deformation. The input parameters are alloy composition and process variables whereas flow stress is the output. The model is based on a three-layer feed-forward ANN with a back-propagation learning algorithm. The neural network is trained with an in-house database obtained from hot compression tests on various grades of austenitic stainless steels. The performance of the model is evaluated using a wide variety of statistical indices. Good agreement between experimental and predicted data is obtained. The correlation between individual alloying elements and high temperature flow behaviour is investigated by employing the ANN model. The results are found to be consistent with the physical phenomena. The model can be used as a guideline for new alloy development.

  19. Biocompatibility studies of low temperature nitrided and collagen-I coated AISI 316L austenitic stainless steel.

    PubMed

    Martinesi, M; Stio, M; Treves, C; Borgioli, F

    2013-06-01

    The biocompatibility of austenitic stainless steels can be improved by means of surface engineering techniques. In the present research it was investigated if low temperature nitrided AISI 316L austenitic stainless steel may be a suitable substrate for bioactive protein coating consisting of collagen-I. The biocompatibility of surface modified alloy was studied using as experimental model endothelial cells (human umbilical vein endothelial cells) in culture. Low temperature nitriding produces modified surface layers consisting mainly of S phase, the supersaturated interstitial solid solution of nitrogen in the austenite lattice, which allows to enhance surface microhardness and corrosion resistance in PBS solution. The nitriding treatment seems to promote the coating with collagen-I, without chemical coupling agents, in respect of the untreated alloy. For biocompatibility studies, proliferation, lactate dehydrogenase levels and secretion of two metalloproteinases (MMP-2 and MMP-9) were determined. Experimental results suggest that the collagen protection may be favourable for endothelial cell proliferation and for the control of MMP-2 release.

  20. Microstructural evolution of metastable austenitic steel during high-pressure torsion and subsequent heat treatment

    NASA Astrophysics Data System (ADS)

    Chen, S.; Shibata, A.; Zhao, L. J.; Gao, S.; Tian, Y. Z.; Tsuji, N.

    2014-08-01

    Metastable austenite in a Fe-24Ni-0.3C (wt.%) alloy was processed by high-pressure torsion and subsequently heat-treated. The HPT-processed material had lamellae structures composed of highly deformed austenite and deformation-induced martensite. The reverse transformation of the deformation-induced martensite and recovery/recrystallization of the retained austenite completed above 500 °C and resulted in fully annealed and single-phase austenite with different grain sizes. The ultrafine-grained and nanocrystalline austenite showed high yield strength and large ductility due to transformation-induced plasticity.

  1. Direct Observation of Austenitization in 1005 C-Mn Steel during Continuous Heating Using In Situ Synchrotron X-Ray Diffraction

    SciTech Connect

    Palmer, T. A.; Elmer, J. W.; Mayr, Peter; Specht, Eliot D

    2011-01-01

    The austenitization ( ) transformation in a 1005 C-Mn steel is monitored in real time at continuous heating rates between 1 C/sec to 10 C/sec using in situ synchrotron x-ray diffraction. Both dilatometry and the in situ x-ray diffraction experiments show that the austenitization transformation proceeds through multiple mechanisms from initiation through completion. Unlike the dilatometry experiments, the in situ x-ray diffraction experiments provide direct evidence for the phases present at specific times during the transformation. Thus, experimental validation is provided for models based on the differing kinetics of the austenitization transformation starting from a heterogeneous microstructure containing pearlite and ferrite. Beginning at temperatures below the A1 transformation temperature, the starting microstructure undergoes a recovery and recrystallization process to relieve stress imparted during the initial thermomechanical treatment of the steel. The austenitization transformation follows, beginning at temperatures above the A1 temperature, with the initial transformation proceeding as the pearlite in the microstructure is dissolved and high carbon concentration austenite is formed. Since the carbon present in the steel is localized near the original pearlite colonies, there is a pronounced heating rate dependant delay before the remaining ferrite grains begin to transform. As temperatures reach 850 C at all heating rates, the remaining ferrite transforms to austenite, since the equilibrium phase diagram indicates that higher temperatures are required to drive the transformation at these lower carbon concentrations. The transformation reaches completion at temperatures above the A3 temperature, and the last ferrite to be transformed is nearly pure iron.

  2. Reverse Austenite Transformation and Grain Growth in a Low-Carbon Steel

    NASA Astrophysics Data System (ADS)

    Garcin, Thomas; Ueda, Keiji; Militzer, Matthias

    2017-02-01

    The mechanisms controlling the reverse austenite transformation and the subsequent grain growth are examined in a low-carbon steel during slow continuous heating. The ex-situ metallographic analysis of quenched samples is complemented by in-situ dilatometry of the phase transformation and real-time laser ultrasonic measurements of the austenite grain size. Although the initial state of the microstructure (bainite or martensite) has only limited impact on the austenite transformation temperature, it has significant influence on the mean austenite grain size and the rate of grain growth. The coarsening of austenite islands during reverse transformation occurring from the martensitic microstructure is responsible for a large austenite grain structure at the completion of the austenite formation. On the other hand, a much finer austenite grain size is obtained when the austenite transforms from the bainite microstructure. Upon further heating, the rate of austenite grain growth is limited by the presence of nanometric precipitates present in the bainite microstructure leading to a significantly finer austenite grain size. These results give important guidance for the design of thermomechanical-controlled processing of heavy-gage steel plates.

  3. Solidification and solid state transformations of austenitic stainless steel welds

    SciTech Connect

    Brooks, J A; Williams, J C; Thompson, A W

    1982-05-01

    The microstructure of austenitic stainless steel welds can contain a large variety of ferrite morphologies. It was originally thought that many of these morphologies were direct products of solidification. Subsequently, detailed work on castings suggested the structures can solidify either as ferrite or austenite. However, when solidification occurs by ferrite, a large fraction of the ferrite transforms to austenite during cooling via a diffusion controlled transformation. It was also shown by Arata et al that welds in a 304L alloy solidified 70-80% as primary ferrite, a large fraction of which also transformed to austenite upon cooling. More recently it was suggested that the cooling rates in welds were sufficiently high that diffusionless transformations were responsible for several commonly observed ferrite morphologies. However, other workers have suggested that even in welds, delta ..-->.. ..gamma.. transformations are diffusion controlled. A variety of ferrite morphologies have more recently been characterized by Moisio and coworkers and by David. The purpose of this paper is to provide further understanding of the evaluation of the various weld microstructures which are related to both the solidification behavior and the subsequent solid state transformations. To accomplish this, both TEM and STEM (Scanning Transmission Electron Microscopy) techniques were employed.

  4. Advanced austenitic alloys for fossil power systems. CRADA final report

    SciTech Connect

    Swindeman, R.W.; Cole, N.C.; Canonico, D.A.; Henry, J.F.

    1998-08-01

    In 1993, a Cooperative Research and Development Agreement (CRADA) was undertaken between Oak Ridge National Laboratory and ABB Combustion Engineering t examine advanced alloys for fossil power systems. Specifically, the use of advanced austenitic stainless steels for superheater/reheater construction in supercritical boilers was examined. The strength of cold-worked austenitic stainless steels was reviewed and compared to the strength and ductility of advanced austenitic stainless steels. The advanced stainless steels were found to retain their strength to very long times at temperatures where cold-worked standard grades of austenitic stainless steels became weak. Further, the steels exhibited better long-time stability than the stabilized 300 series stainless steels in either the annealed or cold worked conditions. Type 304H mill-annealed tubing was provided to ORNL for testing of base metal and butt welds. The tubing was found to fall within range of expected strength for 304H stainless steel. The composite 304/308 stainless steel was found to be stronger than typical for the weldment. Boiler tubing was removed from a commercial boiler for replacement by newer steels, but restraints imposed by the boiler owners did not permit the installation of the advanced steels, so a standard 32 stainless steel was used as a replacement. The T91 removed from the boiler was characterized.

  5. Application of advanced austenitic alloys to fossil power system components

    SciTech Connect

    Swindeman, R.W.

    1996-06-01

    Most power and recovery boilers operating in the US produce steam at temperatures below 565{degrees}C (1050{degrees}F) and pressures below 24 MPa (3500 psi). For these operating conditions, carbon steels and low alloy steels may be used for the construction of most of the boiler components. Austenitic stainless steels often are used for superheater/reheater tubing when these components are expected to experience temperatures above 565{degrees}C (1050{degrees}F) or when the environment is too corrosive for low alloys steels. The austenitic stainless steels typically used are the 304H, 321H, and 347H grades. New ferritic steels such as T91 and T92 are now being introduced to replace austenitic: stainless steels in aging fossil power plants. Generally, these high-strength ferritic steels are more expensive to fabricate than austenitic stainless steels because the ferritic steels have more stringent heat treating requirements. Now, annealing requirements are being considered for the stabilized grades of austenitic stainless steels when they receive more than 5% cold work, and these requirements would increase significantly the cost of fabrication of boiler components where bending strains often exceed 15%. It has been shown, however, that advanced stainless steels developed at ORNL greatly benefit from cold work, and these steels could provide an alternative to either conventional stainless steels or high-strength ferritic steels. The purpose of the activities reported here is to examine the potential of advanced stainless steels for construction of tubular components in power boilers. The work is being carried out with collaboration of a commercial boiler manufacturer.

  6. Atomistic simulation of martensite-austenite phase transition in nanoscale nickel-titanium crystals

    NASA Astrophysics Data System (ADS)

    Kexel, Christian; Schramm, Stefan; Solov'yov, Andrey V.

    2015-09-01

    Shape-memory (SM) alloys can, after initial inelastic deformation, reconstruct their pristine lattice structure upon heating. The underlying phenomenon is the structural solid-solid phase transition from low-temperature lower-symmetry martensite to the high-temperature higher-symmetry austenite. Conventional nickel-titanium (NiTi) with near-equiatomic concentration already possesses an eminent importance for many applications, whereas the nanostructured equivalent can exhibit yet enhanced thermomechanical properties. However, no plausible microscopic theory of the SM effect in NiTi exists, especially for nanoscale systems. We investigate the thermally induced martensite-austenite phase transition in free equiatomic nanocrystals, comprising up to approximately 40 000 atoms, by means of molecular-dynamics simulations (MD) using a classical Gupta-type many-body scheme. Thereby we complement and extend a previously published study [D. Mutter, P. Nielaba, Eur. Phys. J. B 84, 109 (2011)]. The structural transition, revealing features of a first-order phase transition, is demonstrated. It is contrasted with the melting phase transition, a quantum solid model and bulk experimental findings. Moreover, a nucleation-growth process is observed as well as the irreversibility of the transition upon cooling.

  7. Non-equilibrium grain boundary segregation of boron in austenitic stainless steel - III. Computer simulations

    SciTech Connect

    Karlsson, L.

    1988-01-01

    A computer model has been developed to simulate non-equilibrium grain boundary segregation. The model is based on simultaneous diffusion of free vacancies, free solute atoms and vacancy-solute complexes while maintaining local equilibrium between these three entities. The driving force for segregation is the change in equilibrium vacancy concentration during cooling. A sufficient condition for grain boundary enrichment to occur is that complexes are most mobile than free solute atoms. The simulations showed that the amount and width of segregation should be strongly dependent on (i) the heat treatment temperature and cooling rate, (ii) the solute concentration, (iii) the binding energy of complexes, (iv) the vacancy formation energy and (v) the mobility of solute atoms and complexes. The maximum boundary enrichment occurs at some intermediate cooling rate. Higher mobilities, higher starting temperatures and smaller grain sizes require higher cooling rates to give maximum enrichment. The model was applied to the system boron-austenite. Good agreement between experimental results and simulations was achieved. The diffusion coefficients for boron and vacancy-boron complexes in austenite were estimated at D/sub B/ = 2.10/sup -7/ exp (-1.5(eV)/kT) and D/sub vB/ = 2.10/sup -6/ exp (-1.15(eV)/kT) (m/sup 2//s) respectively.

  8. Microstructure and Properties of Plasma Source Nitrided AISI 316 Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Li, G. Y.; Lei, M. K.

    2017-01-01

    Plasma source nitriding is a relatively new nitriding technology which can overcome those inherent shortcomings associated with conventional direct current plasma nitriding technology such as the arcing surface damage, the edging effect and the hollow cathode effect. There is considerable study on the properties of nitrided samples for laboratorial scale plasma source nitriding system; however, little information has been reported on the industrial-scale plasma source nitriding system. In this work, AISI 316 austenitic stainless steel samples were nitrided by an industrial-scale plasma source nitriding system at various nitriding temperatures (350, 400, 450 and 500 °C) with a floating potential. A high-nitrogen face-centered-cubic phase (γN) formed on the surface of nitrided sample surface. As the nitriding temperature was increased, the γN phase layer thickness increased, varying from 1.5 μm for the lowest nitriding temperature of 350 °C, to 30 μm for the highest nitriding temperature of 500 °C. The maximum Vickers microhardness of the γN phase layer with a peak nitrogen concentration of 20 at.% is about HV 0.1 N 15.1 GPa at the nitriding temperature of 450 °C. The wear and corrosion experimental results demonstrated that the γN phase was formed on the surface of AISI 316 austenitic stainless steel by plasma source nitriding, which exhibits not only high wear resistance, but also good pitting corrosion resistance.

  9. Flow Softening Index for Assessment of Dynamic Recrystallization in an Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Aashranth, B.; Samantaray, Dipti; Kumar, Santosh; Dasgupta, Arup; Borah, Utpal; Albert, Shaju K.; Bhaduri, A. K.

    2017-07-01

    The present study proposes a novel technique to assess dynamic recrystallization (DRX) and related microstructural phenomena during hot deformation of austenite. A `Flow Softening Index (FSI)' has been identified on the basis of investigations on elevated temperature deformation behaviour of austenitic stainless steel. This index corresponds to dominant microstructural phenomena at different deformation conditions. For this investigation, experimental results obtained from isothermal, constant true strain rate compression tests in a temperature range of 1173 (900)-1473 K (1200 °C) and strain rate range of 0.01-100 s-1 have been used. Resultant microstructures have been quantified using average grain size and grain size distributions. The dominant microstructural phenomena have been identified at different conditions using electron backscatter diffraction. Low FSI values are associated with the grain growth, intermediate values with DRX, and high values with the work-hardening and flow localisation phenomena. FSI also quantitatively indexes the average grain size and grain size distributions at different temperature-strain rate combinations. Analysis of the specific deformation conditions, particularly where 3.4 < FSI < 3.5, indicates a common thermo-mechanical origin of flow localisation and DRX. The potential technological implications thereof are discussed and a semi-empirical model of microstructural evolution is developed for the studied material.

  10. Atomic configuration and properties of austenitic steels at finite temperature: Effect of longitudinal spin fluctuations

    NASA Astrophysics Data System (ADS)

    Ruban, A. V.; Dehghani, M.

    2016-09-01

    High-temperature atomic configurations of fcc Fe-Cr-Ni alloys with alloy composition close to austenitic steel are studied in statistical thermodynamic simulations with effective interactions obtained in ab initio calculations. The latter are done taking longitudinal spin fluctuations (LSF) into consideration within a quasiclassical phenomenological model. It is demonstrated that the magnetic state affects greatly the alloy properties, and in particular, it is shown that the LSF substantially modify the bonding and interatomic interactions of fcc Fe-Cr-Ni alloys even at ambient conditions. The calculated atomic short-range order is in reasonable agreement with existing experimental data for Fe0.56Cr0.21Ni0.23 , which has strong preference for the (001)-type ordering between Ni and Cr atoms. A similar ordering tendency is found for the Fe0.75Cr0.17Ni0.08 alloy composition, which approximately corresponds to the widely used 304 and 316 austenitic steel grades.

  11. Microstructure and Properties of Plasma Source Nitrided AISI 316 Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Li, G. Y.; Lei, M. K.

    2016-11-01

    Plasma source nitriding is a relatively new nitriding technology which can overcome those inherent shortcomings associated with conventional direct current plasma nitriding technology such as the arcing surface damage, the edging effect and the hollow cathode effect. There is considerable study on the properties of nitrided samples for laboratorial scale plasma source nitriding system; however, little information has been reported on the industrial-scale plasma source nitriding system. In this work, AISI 316 austenitic stainless steel samples were nitrided by an industrial-scale plasma source nitriding system at various nitriding temperatures (350, 400, 450 and 500 °C) with a floating potential. A high-nitrogen face-centered-cubic phase (γN) formed on the surface of nitrided sample surface. As the nitriding temperature was increased, the γN phase layer thickness increased, varying from 1.5 μm for the lowest nitriding temperature of 350 °C, to 30 μm for the highest nitriding temperature of 500 °C. The maximum Vickers microhardness of the γN phase layer with a peak nitrogen concentration of 20 at.% is about HV 0.1 N 15.1 GPa at the nitriding temperature of 450 °C. The wear and corrosion experimental results demonstrated that the γN phase was formed on the surface of AISI 316 austenitic stainless steel by plasma source nitriding, which exhibits not only high wear resistance, but also good pitting corrosion resistance.

  12. Heat Estimation from Infrared Measurement Compared to DSC for Austenite to R Phase Transformation in a NiTi Alloy

    NASA Astrophysics Data System (ADS)

    Delobelle, V.; Favier, D.; Louche, H.

    2013-06-01

    Heat source estimations from temperature field measurements deduced from infrared imaging are increasingly used to study thermo-mechanical coupling during materials' deformation. These estimations are based on approximations of the derivative terms with respect to time and space which are involved in the heat diffusion equation. This paper proposes a first experimental validation of this method by applying it to an experimental uniform air cooling of a NiTi Shape Memory Alloy thin plate. In the studied cooling temperate range, heat sources are due to Austenite to R phase transformation. Transformation temperatures, heat sources, and energies are estimated from infrared temperature measurements and compared successfully to differential scanning calorimetry results.

  13. Research on Flow Stress During Hot Deformation Process and Processing Map for 316LN Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Guo, Baofeng; Ji, Haipeng; Liu, Xingang; Gao, Lu; Dong, Rongmei; Jin, Miao; Zhang, Qinghua

    2012-07-01

    In this study, the hot deformation behavior of austenitic stainless steel was investigated using Gleeble-3500 thermomechanical simulator at deformation temperatures in the range of 900-1200 °C and strain rates in the range of 0.001-10 s-1. The effects of initial austenitic grain size and deformation conditions on hot deformation behavior of 316LN were analyzed through true stress-strain curves under different deformation conditions. Both the constitutive equation and processing map for 316LN were obtained. The results show that, with the increase of the deformation temperature and the decrease of the strain rate, the peak stress decreases, and the initial austenitic grain size has a little influence on the peak stress. The relative error between the peak stress values calculated using the constitutive equation and the values measured is less than 10%. Using the processing map, the best hot-working condition for 316LN in the range of experimental deformation parameters appears when T = 1200 °C and dot{\\upvarepsilon } = 0.001 {{s}}^{-1}.

  14. Effect of Alloying Element Partition in Pearlite on the Growth of Austenite in High-Carbon Low Alloy Steel

    NASA Astrophysics Data System (ADS)

    Yang, Z. N.; Xia, Y.; Enomoto, M.; Zhang, C.; Yang, Z. G.

    2016-03-01

    The growth of austenite from pearlite in high-carbon low alloy steel occurs with and without alloy element redistribution depending on the amount of superheating above the eutectoid temperature. The transition temperature of austenite growth (denoted PNTT) is calculated as a function of pearlite transformation temperature and subsequent holding time, which affect the degree of partitioning in pearlite, using experimental partition coefficients k θ/ α of Mn, Cr, Co, Si, and Ni reported in the literature. PNTT is the highest in Cr-containing alloys which have the largest k θ/ α in pearlite. Post-transformation aging, usually accompanied by cementite spheroidization, leads to a marked increase of PNTT in Mn and Cr alloys. PNTT of Ni alloy does not depend on pearlite transformation temperature because practically the formation of partitioned pearlite is severely limited in this alloy for kinetic reasons. Above PNTT, austenite growth occurs fast initially, but slows down in the order of ten seconds when the ferrite disappears, and the remaining small carbide particles dissolve very slowly under the control of alloy element diffusion.

  15. Predicting the onset of transformation under noncontinuous cooling conditions. Part 2: Application to the austenite pearlite transformation

    SciTech Connect

    Pham, T.T.; Hawbolt, E.B.; Brimacombe, J.K.

    1995-08-01

    A detailed review of the additivity principle with respect to the incubation of the austenite decomposition was summarized in Part 1 of this two-part series and led to the concept of an ideal time-temperature-transformation (TTT) diagram. This curve is characteristic of the chemistry and austenite grain size in the steel and allows nonisothermal behavior to be described assuming additivity holds. The derivation of mathematical relationships between the ideal and experimental cooling data was presented in the first article. In this second article, an ideal curve for the austenite-to-pearlite transformation was derived from cooling data. The applicability of the ideal TTT curve for predicting the start of transformation under continuous cooling conditions was assessed for a range of cooling rates. Experiments were conducted under both isothermal and varying temperature conditions, including an industrial cooling schedule, using a Gleeble Thermal Simulator. Reasonable agreement was found between the predictions and the observed transformation start temperatures; predictions were consistent and compared favorably against other methods which have been frequently used to estimate the transformation start temperature for nonisothermal conditions.

  16. Grain refinement to improve impact toughness in 9Cr-1Mo steel through a double austenitization treatment

    NASA Astrophysics Data System (ADS)

    Karthikeyan, T.; Thomas Paul, V.; Saroja, S.; Moitra, A.; Sasikala, G.; Vijayalakshmi, M.

    2011-12-01

    This paper presents the results of an experimental investigation where an enhancement in Charpy impact toughness and decrease in DBTT was obtained through grain refinement in 9Cr-1Mo steel. The steel in the normalized and tempered condition (1323 K/air cool + 1023 K/2 h/air cool) had an average prior-austenite grain size of 26 μm. By designing a two-stage normalizing (1323 K/2 h/water quench + 1223 K/2 h/air cool) and tempering treatment (1023 K/2 h/air cool), a homogeneous tempered martensite microstructure with a lesser prior-austenite grain size of 12 μm could be obtained. An improvement trend in impact properties of standard sized Charpy specimens was obtained in fine-grained steel: upper shelf energy increased from 175 J to 210 J, and DBTT reduced from 243 K to 228 K. This heat treatment is unique since an attempt to carry out a single-stage low temperature normalizing treatment (1223 K/2 h/air cool) did not give a complete martensite structure, due to the incomplete dissolution of carbides during austenitization.

  17. Effect of Nb Addition to Ti-Bearing Super Martensitic Stainless Steel on Control of Austenite Grain Size and Strengthening

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoping; Langelier, Brian; Gault, Baptiste; Subramanian, Sundaresa

    2017-05-01

    The role of Nb in normalized and tempered Ti-bearing 13Cr5Ni2Mo super martensitic stainless steel is investigated through in-depth characterization of the bimodal chemistry and size of Nb-rich precipitates/atomic clusters and Nb in solid solution. Transmission electron microscopy and atom probe tomography are used to analyze the samples and clarify precipitates/atom cluster interactions with dislocations and austenite grain boundaries. The effect of 0.1 wt pct Nb addition on the promotion of (Ti, Nb)N-Nb(C,N) composite precipitates, as well as the retention of Nb in solution after cooling to room temperature, are analyzed quantitatively. (Ti, Nb)N-Nb(C,N) composite precipitates with average diameters of approximately 24 ± 8 nm resulting from epitaxial growth of Nb(C,N) on pre-existing (Ti,Nb)N particles, with inter-particle spacing on the order of 205 ± 68 nm, are found to be associated with mean austenite grain size of 28 ± 10 µm in the sample normalized at 1323 K (1050 °C). The calculated Zener limiting austenite grain size of 38 ± 13 µm is in agreement with the experimentally observed austenite grain size distribution. 0.08 wt pct Nb is retained in the as-normalized condition, which is able to promote Nb(C, N) atomic clusters at dislocations during tempering at 873 K (600 °C) for 2 hours, and increases the yield strength by 160 MPa, which is predicted to be close to maximum increase in strengthening effect. Retention of solute Nb before tempering also leads to it preferentially combing with C and N to form Nb(C, N) atom clusters, which suppresses the occurrence of Cr- and Mo-rich carbides during tempering.

  18. Effect of Nb Addition to Ti-Bearing Super Martensitic Stainless Steel on Control of Austenite Grain Size and Strengthening

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoping; Langelier, Brian; Gault, Baptiste; Subramanian, Sundaresa

    2017-03-01

    The role of Nb in normalized and tempered Ti-bearing 13Cr5Ni2Mo super martensitic stainless steel is investigated through in-depth characterization of the bimodal chemistry and size of Nb-rich precipitates/atomic clusters and Nb in solid solution. Transmission electron microscopy and atom probe tomography are used to analyze the samples and clarify precipitates/atom cluster interactions with dislocations and austenite grain boundaries. The effect of 0.1 wt pct Nb addition on the promotion of (Ti, Nb)N-Nb(C,N) composite precipitates, as well as the retention of Nb in solution after cooling to room temperature, are analyzed quantitatively. (Ti, Nb)N-Nb(C,N) composite precipitates with average diameters of approximately 24 ± 8 nm resulting from epitaxial growth of Nb(C,N) on pre-existing (Ti,Nb)N particles, with inter-particle spacing on the order of 205 ± 68 nm, are found to be associated with mean austenite grain size of 28 ± 10 µm in the sample normalized at 1323 K (1050 °C). The calculated Zener limiting austenite grain size of 38 ± 13 µm is in agreement with the experimentally observed austenite grain size distribution. 0.08 wt pct Nb is retained in the as-normalized condition, which is able to promote Nb(C, N) atomic clusters at dislocations during tempering at 873 K (600 °C) for 2 hours, and increases the yield strength by 160 MPa, which is predicted to be close to maximum increase in strengthening effect. Retention of solute Nb before tempering also leads to it preferentially combing with C and N to form Nb(C, N) atom clusters, which suppresses the occurrence of Cr- and Mo-rich carbides during tempering.

  19. In situ x-ray diffraction investigations during low energy ion nitriding of austenitic stainless steel grade 1.4571

    NASA Astrophysics Data System (ADS)

    Manova, D.; Mändl, S.; Gerlach, J. W.; Hirsch, D.; Neumann, H.; Rauschenbach, B.

    2014-09-01

    Insertion of nitrogen into austenitic stainless steel leads to anomalously fast nitrogen diffusion and the formation of an expanded face-centred cubic phase which is known to contain a large amount of mechanical stress. In situ x-ray diffraction (XRD) measurements during low energy nitrogen ion implantation into steel 316Ti at 300-550 °C allow a direct view into diffusion and phase formation. While the layer growth is directly observable from the decreasing substrate reflection intensity, the time evolution of the intensities for the expanded phase reflection is much more complex: several mechanisms including at least formation and annealing of defects, twinning, reduction of the crystal symmetry, or grain rotation may be active inside the expanded phase, besides the thermally activated decay of the metastable expanded phase. This locally varying coherence length or scattering intensity from the expanded phase is furthermore a function of temperature and time, additionally complicating the deconvolution of XRD spectra for stress and concentration gradients. As no concise modelling of this coherence length is possible at present, a simple qualitative model assuming a dependence of the scattering intensity on the depth, influence by stress and plastic flow during the nitriding process is proposed for understanding the underlying processes.

  20. What Expands in an Expanding Universe?

    PubMed

    Pacheco, José A De Freitas

    2015-01-01

    In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative) of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM) all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

  1. First-principles study of helium, carbon, and nitrogen in austenite, dilute austenitic iron alloys, and nickel

    NASA Astrophysics Data System (ADS)

    Hepburn, D. J.; Ferguson, D.; Gardner, S.; Ackland, G. J.

    2013-07-01

    An extensive set of first-principles density functional theory calculations have been performed to study the behavior of He, C, and N solutes in austenite, dilute Fe-Cr-Ni austenitic alloys, and Ni in order to investigate their influence on the microstructural evolution of austenitic steel alloys under irradiation. The results show that austenite behaves much like other face-centered cubic metals and like Ni in particular. Strong similarities were also observed between austenite and ferrite. We find that interstitial He is most stable in the tetrahedral site and migrates with a low barrier energy of between 0.1 and 0.2 eV. It binds strongly into clusters as well as overcoordinated lattice defects and forms highly stable He-vacancy (VmHen) clusters. Interstitial He clusters of sufficient size were shown to be unstable to self-interstitial emission and VHen cluster formation. The binding of additional He and V to existing VmHen clusters increases with cluster size, leading to unbounded growth and He bubble formation. Clusters with n/m around 1.3 were found to be most stable with a dissociation energy of 2.8 eV for He and V release. Substitutional He migrates via the dissociative mechanism in a thermal vacancy population but can migrate via the vacancy mechanism in irradiated environments as a stable V2He complex. Both C and N are most stable octahedrally and exhibit migration energies in the range from 1.3 to 1.6 eV. Interactions between pairs of these solutes are either repulsive or negligible. A vacancy can stably bind up to two C or N atoms with binding energies per solute atom up to 0.4 eV for C and up to 0.6 eV for N. Calculations in Ni, however, show that this may not result in vacancy trapping as VC and VN complexes can migrate cooperatively with barrier energies comparable to the isolated vacancy. This should also lead to enhanced C and N mobility in irradiated materials and may result in solute segregation to defect sinks. Binding to larger vacancy clusters

  2. Kinetic evaluation of intergranular fracture in austenitic stainless steels

    SciTech Connect

    Simonen, E.P.; Bruemmer, S.M.

    1995-12-31

    A second, higher-dose threshold exists for irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels in non-oxidizing environments. The data supporting this concept have stimulated interest in the mechanical aspects of intergranular (IG) fracture. Cracking in a non-oxidizing environment suggests that mechanically-induced IG fracture may play an important role in the IASCC mechanism under these conditions. Radiation alters deformation processes in austenitic alloys and may influence the fracture mode during either in-situ or post-irradiation straining. Radiation effects that must be considered include radiation strengthening, radiation creep and radiation-induced flow localization. The present evaluation relates these radiation-induced phenomena to IG fracture relevant to IASCC. The evaluation indicates that radiation strengthening retards matrix deformation and allows intergranular fracture to occur at higher stresses and lower temperatures than expected for unirradiated stainless steel.

  3. Laser borided composite layer produced on austenitic 316L steel

    NASA Astrophysics Data System (ADS)

    Mikołajczak, Daria; Kulka, Michał; Makuch, Natalia

    2016-12-01

    Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides) and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.

  4. Cleavage fracture of austenite induced by nitrogen supersaturation

    SciTech Connect

    Vogt, J.B.; Messai, A.; Foct, J. . Lab. de Metallurgie Physique)

    1994-09-01

    Austenitic stainless steels and more generally FCC structure materials are good candidates for cryogenic applications because they remain ductile at low temperatures. In some cases, brittleness may occasionally occur in severe and specific conditions such as hydrogen embrittlement or during stress corrosion cracking at low strain rates. The present study shows that the brittleness observed in the P900 austenitic stainless steel is associated with the presence of a high amount of nitrogen atoms. Brittle fracture occurs both intergranularly and transgranularly. Cleavage mostly on [111] planes is associated with marked slip but with the absence of rivers. The occurrence of a DBTT is explained by the converse variations of brittle rupture stress and flow stress against nitrogen content. The flow stress increases and is mainly controlled by a short range which leads the stress for brittle rupture to be reached before the plastic flow stress.

  5. Phase instability of thermally aged CrMn austenitic steels

    NASA Astrophysics Data System (ADS)

    Ruedl, E.; Sasaki, T.

    1984-05-01

    The microstructural changes taking place in several commercial Cr-Mn austenitic steels during ageing at 873 and 1073 K were examined by analytical electron microscopy. Phase identification was obtained by electron diffraction, energy dispersive X-ray analysis and electron energy loss spectrometry. It was found that the phase changes depend on the carbon and nitrogen content of the materials as well as on the presence of Mo and delta ferrite.

  6. Manganese-stabilized austenitic stainless steels for fusion applications

    DOEpatents

    Klueh, Ronald L.; Maziasz, Philip J.

    1990-01-01

    An austenitic stainless steel that is comprised of Fe, Cr, Mn, C but no Ni or Nb and minimum N. To enhance strength and fabricability minor alloying additions of Ti, W, V, B and P are made. The resulting alloy is one that can be used in fusion reactor environments because the half-lives of the elements are sufficiently short to allow for handling and disposal.

  7. Manganese-stabilized austenitic stainless steels for fusion applications

    DOEpatents

    Klueh, Ronald L.; Maziasz, Philip J.

    1990-08-07

    An austenitic stainless steel that is comprised of Fe, Cr, Mn, C but no Ni or Nb and minimum N. To enhance strength and fabricability minor alloying additions of Ti, W, V, B and P are made. The resulting alloy is one that can be used in fusion reactor environments because the half-lives of the elements are sufficiently short to allow for handling and disposal.

  8. Method for residual stress relief and retained austenite destabilization

    DOEpatents

    Ludtka, Gerard M.

    2004-08-10

    A method using of a magnetic field to affect residual stress relief or phase transformations in a metallic material is disclosed. In a first aspect of the method, residual stress relief of a material is achieved at ambient temperatures by placing the material in a magnetic field. In a second aspect of the method, retained austenite stabilization is reversed in a ferrous alloy by applying a magnetic field to the alloy at ambient temperatures.

  9. Intermetallic strengthened alumina-forming austenitic steels for energy applications

    NASA Astrophysics Data System (ADS)

    Hu, Bin

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, materials required are strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and Ni3Al precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe 2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. This research starts with microstructural and microchemical analyses of these intermetallic strengthened alumina-forming austenitic steels in a scanning electron microscope. The microchemistry of precipitates, as determined by energy-dispersive x-ray spectroscopy and transmission electron microscope, is also studied. Different thermo-mechanical treatments were carried out to these stainless steels in an attempt to further improve their mechanical properties. The microstructural and microchemical analyses were again performed after the thermo-mechanical processing. Synchrotron X-ray diffraction was used to measure the lattice parameters of these steels after different thermo-mechanical treatments. Tensile tests at both room and elevated temperatures were performed to study mechanical behaviors of this novel alloy system; the deformation mechanisms were studied by strain rate jump tests at elevated temperatures. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these alumina-forming austenitic steels after creep tests. Experiments were carried out to study the effects of boron and carbon additions in the aged alumina-forming austenitic steels.

  10. Corrosion resistance of kolsterised austenitic 304 stainless steel

    SciTech Connect

    Abudaia, F. B. Khalil, E. O. Esehiri, A. F. Daw, K. E.

    2015-03-30

    Austenitic stainless suffers from low wear resistance in applications where rubbing against other surfaces is encountered. This drawback can be overcome by surface treatment such as coating by hard materials. Other treatments such as carburization at relatively low temperature become applicable recently to improve hardness and wear resistance. Carburization heat treatment would only be justified if the corrosion resistance is unaffected. In this work samples of 304 stainless steels treated by colossal supersaturation case carburizing (known as Kolsterising) carried out by Bodycote Company was examined for pitting corrosion resistance at room temperature and at 50 °C. Comparison with results obtained for untreated samples in similar testing conditions show that there is no deterioration in the pitting resistance due to the Kolsterising heat treatment. X ray diffraction patterns obtained for Kolsterising sample showed that peaks correspond to the austenite phase has shifted to lower 2θ values compared with those of the untreated sample. The shift is an indication for expansion of austenite unit cells caused by saturation with diffusing carbon atoms. The XRD of Kolsterising samples also revealed additional peaks appeared in the patterns due to formation of carbides in the kolsterised layer. Examination of these additional peaks showed that these peaks are attributed to a type of carbide known as Hagg carbide Fe{sub 2}C{sub 5}. The absence of carbides that contain chromium means that no Cr depletion occurred in the layer and the corrosion properties are maintained. Surface hardness measurements showed large increase after Kolsterising heat treatment.

  11. Factors influencing fatigue crack propagation behavior of austenitic steels

    NASA Astrophysics Data System (ADS)

    Kim, Sangshik; Kwon, Jaeki; Kim, Youngju; Jang, Wookil; Lee, Soongi; Choi, Jongkyo

    2013-07-01

    In the present study, the fatigue crack propagation (FCP) behaviors of austenitic single phase steels, including STS304, Fe18Mn and Fe22Mn with different grain sizes ranging from 12 μm to 98 μm were investigated. The FCP tests were conducted in air at an R ratio of 0.1 using compact tension specimens and the crack paths and fracture surfaces were documented by using an SEM. The highest ΔKth value of 9.9MPa·m1/2 was observed for the Fe18Mn specimen, followed by 5.2MPa·m1/2 for the Fe22Mn specimen and 4.6MPa·m1/2 for the STS304 specimen, showing a substantial difference in the near-threshold FCP resistance for each microstructure. The crack path and fractographic analyses suggested that the near-threshold FCP behavior of these austenitic steels was largely influenced by the degree of slip planarity, as determined by stacking fault energy and grain size, rather than the tensile properties. In the Paris' regime, the slip planarity still played an important role while the tensile properties began to affect the FCP. The FCP behavior of austenitic steels with different microstructural features are discussed based on detailed fractographic and micrographic observations.

  12. Wear Behavior of Austenitic NiTi Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Yan, Lina; Liu, Yong

    2015-03-01

    This study aims to understand the wear behavior of austenitic NiTi SMA with the hope to provide a guideline for its better use for wear-resist purposes. Ball-on-disk sliding wear tests with alumina counter ball were conducted at different temperatures and under different loads. Based on the coefficients of friction, the surface wear features, temperature-dependent stress-strain curves and the estimated contact stresses, the deformation mechanisms involved in the wear process were examined. Two wear modes were identified. Mode I is temperature-sensitive and occurred when A f < T < M d. In this mode, wear process was dominated by the interplay among contact stress, temperature and shape recovery property. Results show that, when the contact stress causes either elastic deformation of austenite or stress-induced martensitic transformation, the wear resistance was improved with increasing temperature. This was originated from increased critical stress for stress-induced martensite which retards plastic deformation. However, when contact stress is higher than yield stress of stress-induced martensite, wear resistance is deteriorated. Mode II occurs when T > M d and it is less temperature-sensitive within the testing range. In this mode, the austenitic NiTi loses its superelasticity and obeys a conventional deformation sequence, and the key factor dominating the wear process is the magnitude of contact stress.

  13. Retained austenite thermal stability in a nanostructured bainitic steel

    SciTech Connect

    Avishan, Behzad; Garcia-Mateo, Carlos; Yazdani, Sasan; Caballero, Francisca G.

    2013-07-15

    The unique microstructure of nanostructured bainite consists of very slender bainitic ferrite plates and high carbon retained austenite films. As a consequence, the reported properties are opening a wide range of different commercial uses. However, bainitic transformation follows the T{sub 0} criteria, i.e. the incomplete reaction phenomena, which means that the microstructure is not thermodynamically stable because the bainitic transformation stops well before austenite reaches an equilibrium carbon level. This article aims to study the different microstructural changes taking place when nanostructured bainite is destabilized by austempering for times well in excess of that strictly necessary to end the transformation. Results indicate that while bainitic ferrite seems unaware of the extended heat treatment, retained austenite exhibits a more receptive behavior to it. - Highlights: • Nanostructured bainitic steel is not thermodynamically stable. • Extensive austempering in these microstructures has not been reported before. • Precipitation of cementite particles is unavoidable at longer austempering times. • TEM, FEG-SEM and XRD analysis were used for microstructural characterization.

  14. Corrosion resistance of kolsterised austenitic 304 stainless steel

    NASA Astrophysics Data System (ADS)

    Abudaia, F. B.; Khalil, E. O.; Esehiri, A. F.; Daw, K. E.

    2015-03-01

    Austenitic stainless suffers from low wear resistance in applications where rubbing against other surfaces is encountered. This drawback can be overcome by surface treatment such as coating by hard materials. Other treatments such as carburization at relatively low temperature become applicable recently to improve hardness and wear resistance. Carburization heat treatment would only be justified if the corrosion resistance is unaffected. In this work samples of 304 stainless steels treated by colossal supersaturation case carburizing (known as Kolsterising) carried out by Bodycote Company was examined for pitting corrosion resistance at room temperature and at 50 °C. Comparison with results obtained for untreated samples in similar testing conditions show that there is no deterioration in the pitting resistance due to the Kolsterising heat treatment. X ray diffraction patterns obtained for Kolsterising sample showed that peaks correspond to the austenite phase has shifted to lower 2θ values compared with those of the untreated sample. The shift is an indication for expansion of austenite unit cells caused by saturation with diffusing carbon atoms. The XRD of Kolsterising samples also revealed additional peaks appeared in the patterns due to formation of carbides in the kolsterised layer. Examination of these additional peaks showed that these peaks are attributed to a type of carbide known as Hagg carbide Fe2C5. The absence of carbides that contain chromium means that no Cr depletion occurred in the layer and the corrosion properties are maintained. Surface hardness measurements showed large increase after Kolsterising heat treatment.

  15. Development of cast alumina-forming austenitic stainless steels

    SciTech Connect

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer III, H. M.; Leonard, D. N.

    2016-09-06

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt. % are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt. % Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800 C - 850 C in H2O-, S-, and C- containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloy along with improved oxidation resistance typical of alumina-forming alloys. Lastly, challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

  16. Development of cast alumina-forming austenitic stainless steels

    DOE PAGES

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; ...

    2016-09-06

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt. % are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt. % Ni with good creep strength and the ability to form a protective alumina scale for use atmore » temperatures up to 800 C - 850 C in H2O-, S-, and C- containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloy along with improved oxidation resistance typical of alumina-forming alloys. Lastly, challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.« less

  17. Development of Alumina-Forming Austenitic Stainless Steels

    SciTech Connect

    Brady, Michael P; Yamamoto, Yukinori; Bei, Hongbin; Santella, Michael L; Maziasz, Philip J

    2009-01-01

    This paper presents the results of the continued development of creep-resistant, alumina-forming austenitic (AFA) stainless steel alloys, which exhibit a unique combination of excellent oxidation resistance via protective alumina (Al2O3) scale formation and high-temperature creep strength through the formation of stable nano-scale MC carbides and intermetallic precipitates. Efforts in fiscal year 2009 focused on the characterization and understanding of long-term oxidation resistance and tensile properties as a function of alloy composition and microstructure. Computational thermodynamic calculations of the austenitic matrix phase composition and the volume fraction of MC, B2-NiAl, and Fe2(Mo,Nb) base Laves phase precipitates were used to interpret oxidation behavior. Of particular interest was the enrichment of Cr in the austenitic matrix phase by additions of Nb, which aided the establishment and maintenance of alumina. Higher levels of Nb additions also increased the volume fraction of B2-NiAl precipitates, which served as an Al reservoir during long-term oxidation. Ageing studies of AFA alloys were conducted at 750 C for times up to 2000 h. Ageing resulted in near doubling of yield strength at room temperature after only 50 h at 750 C, with little further increase in yield strength out to 2000 h of ageing. Elongation was reduced on ageing; however, levels of 15-25% were retained at room temperature after 2000 h of total ageing.

  18. Researches upon the cavitation erosion behaviour of austenite steels

    NASA Astrophysics Data System (ADS)

    Bordeasu, I.; Popoviciu, M. O.; Mitelea, I.; Salcianu, L. C.; Bordeasu, D.; Duma, S. T.; Iosif, A.

    2016-02-01

    Paper analyzes the cavitation erosion behavior of two stainless steels with 100% austenitic structure but differing by the chemical composition and the values of mechanical properties. The research is based on the MDE(t) and MDER(t) characteristic curves. We studied supplementary the aspect of the eroded areas by other to different means: observations with performing optical microscopes and roughness measurements. The tests were done in the T2 vibratory facility in the Cavitation Laboratory of the Timisoara Polytechnic University. The principal purpose of the study is the identification of the elements influencing significantly the cavitation erosion resistance. It was established the effect of the principal chemical components (determining the proportion of the structural components in conformity the Schaffler diagram) upon the cavitation erosion resistance. The results of the researches present the influence of the proportion of unstable austenite upon cavitation erosion resistance. The stainless steel with the great proportion of unstable austenite has the best behavior. The obtained conclusion are important for the metallurgists which realizes the stainless steels used for manufacturing the runners of hydraulic machineries (turbines and pumps) with increased resistance to cavitation attack.

  19. Development of Cast Alumina-Forming Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer, H. M., III; Leonard, D. N.

    2016-11-01

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt.% are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt.% Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800-850°C in H2O-, S-, and C-containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloys along with improved oxidation resistance typical of alumina-forming alloys. Challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

  20. Effects of low temperature neutron irradiation on deformation behavior of austenitic stainless steels

    SciTech Connect

    Pawel, J.E.; Rowcliffe, A.F.; Alexander, D.J.; Grossbeck, M.L.; Shiba, K.

    1996-04-01

    An austenitic stainless steel, designated 316LN-IG, has been chosen for the first wall/shield (FW/S) structure for the International Thermonuclear Experimental Reactor (ITER). The proposed operational temperature range for the structure (100 to 250{degree}C) is below the temperature regimes for void swelling (400-600{degree}C) and for helium embrittlement (500-700{degree}C). However, the proposed neutron dose is such that large changes in yield strength, deformation mode, and strain hardening capacity could be encountered which could significantly affect fracture properties. Definition of the irradiation regimes in which this phenomenon occurs is essential to the establishment of design rules to protect against various modes of failure.

  1. Enhancing Hydrogen Embrittlement Resistance of Lath Martensite by Introducing Nano-Films of Interlath Austenite

    NASA Astrophysics Data System (ADS)

    Wang, Meimei; Tasan, C. Cem; Koyama, Motomichi; Ponge, Dirk; Raabe, Dierk

    2015-09-01

    Partial reversion of interlath austenite nano-films is investigated as a potential remedy for hydrogen embrittlement susceptibility of martensitic steels. We conducted uniaxial tensile tests on hydrogen-free and pre-charged medium-Mn transformation-induced plasticity-maraging steels with different austenite film thicknesses. Mechanisms of crack propagation and microstructure interaction are quantitatively analyzed using electron channelling contrast imaging and electron backscatter diffraction, revealing a promising strategy to utilize austenite reversion for hydrogen-resistant martensitic steel design.

  2. Three phase crystallography and solute distribution analysis during residual austenite decomposition in tempered nanocrystalline bainitic steels

    SciTech Connect

    Caballero, F.G.; Yen, Hung-Wei; Miller, M.K.; Cornide, J.; Chang, Hsiao-Tzu; Garcia-Mateo, C.; Yang, Jer-Ren

    2014-02-15

    Interphase carbide precipitation due to austenite decomposition was investigated by high resolution transmission electron microscopy and atom probe tomography in tempered nanostructured bainitic steels. Results showed that cementite (θ) forms by a paraequilibrium transformation mechanism at the bainitic ferrite–austenite interface with a simultaneous three phase crystallographic orientation relationship. - Highlights: • Interphase carbide precipitation due to austenite decomposition • Tempered nanostructured bainitic steels • High resolution transmission electron microscopy and atom probe tomography • Paraequilibrium θ with three phase crystallographic orientation relationship.

  3. Effects of focused ion beam milling on austenite stability in ferrous alloys

    SciTech Connect

    Knipling, K.E.; Rowenhorst, D.J.; Fonda, R.W.; Spanos, G.

    2010-01-15

    The susceptibility of fcc austenite to transform to bcc during focused ion beam milling was studied in three commercial stainless steels. The alloys investigated, in order of increasing austenite stability, were: (i) a model maraging steel, Sandvik 1RK91; (ii) an AISI 304 austenitic stainless steel; and (iii) AL-6XN, a super-austenitic stainless steel. Small trenches were milled across multiple austenite grains in each alloy using a 30 kV Ga{sup +} ion beam at normal incidence to the specimen surface. The ion beam dose was controlled by varying the trench depth and the beam current. The factors influencing the transformation of fcc austenite to bcc (listed in order of decreasing influence) were found to be: (i) alloy composition (i.e., austenite stability), (ii) ion beam dose (or trench depth), and (iii) crystallographic orientation of the austenite grains. The ion beam current had a negligible influence on the FIB-induced transformation of austenite in these alloys.

  4. The Kinetics of Formation and Decomposition of Austenite in Relation to Carbide Morphology

    NASA Astrophysics Data System (ADS)

    Alvarenga, Henrique Duarte; Van Steenberge, Nele; Sietsma, Jilt; Terryn, Herman

    2017-02-01

    The effect of the carbide morphology on the kinetics of austenite formation and its decomposition was investigated by a combination of measurements of austenite fraction by dilatometry and metallography. These measurements show that coarse carbide morphology is generated by fast cooling through the early stages of eutectoid transformation, enabling fast precipitation of pro-eutectoid ferrite, followed by slow cooling during the final stages of transformation, during the precipitation of carbides. Additionally, a strong influence of the morphology of carbides on the kinetics of austenite formation is observed. The presence of coarse carbides can determine the rate of austenite formation during intercritical annealing as a result of its slow dissolution kinetics.

  5. Effect of Austenitic and Austeno-Ferritic Electrodes on 2205 Duplex and 316L Austenitic Stainless Steel Dissimilar Welds

    NASA Astrophysics Data System (ADS)

    Verma, Jagesvar; Taiwade, Ravindra V.

    2016-11-01

    This study addresses the effect of different types of austenitic and austeno-ferritic electrodes (E309L, E309LMo and E2209) on the relationship between weldability, microstructure, mechanical properties and corrosion resistance of shielded metal arc welded duplex/austenitic (2205/316L) stainless steel dissimilar joints using the combined techniques of optical, scanning electron microscope, energy-dispersive spectrometer and electrochemical. The results indicated that the change in electrode composition led to microstructural variations in the welds with the development of different complex phases such as vermicular ferrite, lathy ferrite, widmanstatten and intragranular austenite. Mechanical properties of welded joints were diverged based on compositions and solidification modes; it was observed that ferritic mode solidified weld dominated property wise. However, the pitting corrosion resistance of all welds showed different behavior in chloride solution; moreover, weld with E2209 was superior, whereas E309L exhibited lower resistance. Higher degree of sensitization was observed in E2209 weld, while lesser in E309L weld. Optimum ferrite content was achieved in all welds.

  6. Physical and mechanical modelling of neutron irradiation effect on ductile fracture. Part 1. Prediction of fracture strain and fracture toughness of austenitic steels

    NASA Astrophysics Data System (ADS)

    Margolin, Boris; Sorokin, Alexander; Smirnov, Valeriy; Potapova, Vera

    2014-09-01

    A physical-and-mechanical model of ductile fracture has been developed to predict fracture toughness and fracture strain of irradiated austenitic steels taking into account stress-state triaxiality and radiation swelling. The model is based on criterion of plastic collapse of a material unit cell controlled by strain hardening of a material and criterion of voids coalescence due to channel shearing of voids. The model takes into account deformation voids nucleation and growth of deformation and vacancy voids. For justification of the model experimental data on fracture strain and fracture toughness of austenitic steel 18Cr-10Ni-Ti grade irradiated up to maximal dose 150 dpa with various swelling were used. Experimental data on fracture strain and fracture toughness were compared with the results predicted by the model. It has been shown that for prediction of the swelling effect on fracture toughness the dependence of process zone size on swelling should be taken into account.

  7. Functionalized expanded porphyrins

    DOEpatents

    Sessler, Jonathan L; Pantos, Patricia J

    2013-11-12

    Disclosed are functionalized expanded porphyrins that can be used as spectrometric sensors for high-valent actinide cations. The disclosed functionalized expanded porphyrins have the advantage over unfunctionalized systems in that they can be immobilized via covalent attachment to a solid support comprising an inorganic or organic polymer or other common substrates. Substrates comprising the disclosed functionalized expanded porphyrins are also disclosed. Further, disclosed are methods of making the disclosed compounds (immobilized and free), methods of using them as sensors to detect high valent actinides, devices that comprise the disclosed compounds, and kits.

  8. Expanding the Universe

    NASA Astrophysics Data System (ADS)

    Sterken, Christiaan; Leedjärv, Laurits; Tempel, Elmo

    2011-12-01

    Proceedings of the International Conference EXPANDING THE UNIVERSE, On the occasion of the 200th anniversary of the Tartu Observatory, Tartu, Estonia 2011 April 27-29. C. Sterken, L. Leedjarv, E. Tempel (Eds.)

  9. Mechanism of Austenite Formation from Spheroidized Microstructure in an Intermediate Fe-0.1C-3.5Mn Steel

    NASA Astrophysics Data System (ADS)

    Lai, Qingquan; Gouné, Mohamed; Perlade, Astrid; Pardoen, Thomas; Jacques, Pascal; Bouaziz, Olivier; Bréchet, Yves

    2016-07-01

    The austenitization from a spheroidized microstructure during intercritical annealing was studied in a Fe-0.1C-3.5Mn alloy. The austenite grains preferentially nucleate and grow from intergranular cementite. The nucleation at intragranular cementite is significantly retarded or even suppressed. The DICTRA software, assuming local equilibrium conditions, was used to simulate the austenite growth kinetics at various temperatures and for analyzing the austenite growth mechanism. The results indicate that both the mode and the kinetics of austenite growth strongly depend on cementite composition. With sufficiently high cementite Mn content, the austenite growth is essentially composed of two stages, involving the partitioning growth controlled by Mn diffusion inside ferrite, followed by a stage controlled by Mn diffusion within austenite for final equilibration. The partitioning growth results in a homogeneous distribution of carbon within austenite, which is supported by NanoSIMS carbon mapping.

  10. Experimental Analysis and Modelling of Fe-Mn-Al-C Duplex Steel Mechanical Behaviour

    SciTech Connect

    Shiekhelsouk, M. N.; Favier, V.; Cherkaoui, M.; Inal, K.; Bouaziz, O.

    2007-04-07

    A new variety of duplex steels with high content of manganese and aluminum has been elaborated in Arcelor Research. These steels contain two phases: austenite and ferrite combining the best features of austenitic and ferritic steels. In this work, four duplex steels with different chemical composition and phase volume fraction are studied. The evolution of internal stresses for the two phases has been determined by X-ray diffraction during an in situ tensile test. These measurements results were used to determine the mechanical behaviour of the duplex steel using a micromechanical approach by scale transition for tensile tests. Though a good agreement between experiments and simulations is found at the macroscopic level, the calculated internal stresses of the austenitic phase do not match experimental results. These discrepancies are attributed to (i) a bad estimation of the austenite yield stress or (ii) the presence of kinematic hardening in the austenitic phase. A new step is then proposed to test these two hypotheses.

  11. Synergistic Computational and Microstructural Design of Next- Generation High-Temperature Austenitic Stainless Steels

    SciTech Connect

    Karaman, Ibrahim; Arroyave, Raymundo

    2015-07-31

    -forming austenitic stainless steel, is fully austenitic, but possesses carbides that were not dissolvable and could not be controlled. This alloy also did not show deformation twinning. Alloy 2 was designed based on alloy 1, but was not fully austenitic and had significant traces of uncontrollable precipitates as well. Alloy 3, also designed based on alloy 1, was mainly austenitic with evolution of a second phase along the grain boundaries, but also had precipitates that were not controllable. Based on the knowledge gained from the first generation of the designed steels, two more steels, called PGAA1 and PGAA2, were proposed using genetic algorithms that, based on the modelling, were supposed to exhibit alumina-scale formation. PGAA1, however, did not demonstrate a fully austenitic structure. PGAA2 could achieve a mostly austenitic structure through thermo-mechanical processing, and was then used for oxidation tests. The oxidation tests of PGAA2, with and without nitrogen impurities, along with alloy 1, suggested that PGAA2 can form alumina-scale similar to alloy 1, but N impurity will prevent formation of such a scale, probably through formation of aluminum nitrides. For the above mentioned genetic algorithm framework of alloy design, separate models were developed for specific design criteria. For prediction of alumina formation in stainless steels, a model was constructed based off of two criteria – effective valence and third element effect. These criteria capture the thermodynamics and kinetics of alumina formation in steels. To test the efficacy and robustness of this model, they were tested against alloys in the literature which had been experimentally verified to exhibit alumina formation and the predictions were in excellent agreement with the experiments. Another meta-model for prediction of twinning in unknown steel compositions was developed by an informatics based machine learning/data mining approach. Stacking Fault Energy data was captured from the literature for a

  12. Austenite Static Recrystallization Kinetics in Microalloyed B Steels

    NASA Astrophysics Data System (ADS)

    Larrañaga-Otegui, Ane; Pereda, Beatriz; Jorge-Badiola, Denis; Gutiérrez, Isabel

    2016-06-01

    Boron is added to steels to increase hardenability, substituting of more expensive elements. Moreover, B acts as a recrystallization delaying element when it is in solid solution. However, B can interact with N and/or C to form nitrides and carbides at high temperatures, limiting its effect on both phase transformation and recrystallization. On the other hand, other elements like Nb and Ti are added due to the retarding effect that they exert on the austenite softening processes, which results in pancaked austenite grains and refined room microstructures. In B steels, Nb and Ti are also used to prevent B precipitation. However, the complex interaction between these elements and its effect on the austenite microstructure evolution during hot working has not been investigated in detail. The present work is focused on the effect the B exerts on recrystallization when added to microalloyed steels. Although B on its own leads to retarded static recrystallization kinetics, when Nb is added a large delay in the static recrystallization times is observed in the 1273 K to 1373 K (1000 °C to 1100 °C) temperature range. The effect is larger than that predicted by a model developed for Nb-microalloyed steels, which is attributed to a synergistic effect of both elements. However, this effect is not so prominent for Nb-Ti-B steels. The complex effect of the composition on recrystallization kinetics is explained as a competition between the solute drag and precipitation pinning phenomena. The effect of the microalloying elements is quantified, and a new model for the predictions of recrystallization kinetics that accounts for the B and Nb+B synergetic effects is proposed.

  13. Market Opportunities for Austenitic Stainless Steels in SO2 Scrubbers

    NASA Astrophysics Data System (ADS)

    Michels, Harold T.

    1980-10-01

    Recent U.S. federal legislation has created new opportunities for SO2 scrubbers because all coals, even low-sulfur western coals, will probably require scrubbing to remove SO2 from gaseous combustion products. Scrubbing, the chemical absorption of SO2 by vigorous contact with a slurry—usually lime or limestone—creates an aggressive acid-chloride solution. This presents a promising market for pitting-resistant austenitic stainless steels, but there is active competition from rubber and fiberglass-lined carbon steel. Since the latter are favored on a first-cost basis, stainless steels must be justified on a cost/performance or life-cost basis. Nickel-containing austenitic alloys are favored because of superior field fabricability. Ferritic stainless steels have little utility in this application because of limitations in weldability and resulting poor corrosion resistance. Inco corrosion test spools indicate that molybdenum-containing austenitic alloys are needed. The leanest alloys for this application are 316L and 317L. Low-carbon grades of stainless steel are specified to minimize corrosion in the vicinity of welds. More highly alloyed materials may be required in critical areas. At present, 16,000 MW of scrubber capacity is operational and 17,000 MW is under construction. Another 29,000 MW is planned, bringing the total to 62,000 MW. Some 160,000 MW of scrubber capacity is expected to be placed in service over the next 10 years. This could translate into a total potential market of 80,000 tons of alloy plate for new power industry construction in the next decade. Retrofitting of existing power plants plus scrubbers for other applications such as inert gas generators for oil tankers, smelters, municipal incinerators, coke ovens, the pulp and paper industry, sulfuric acid plants, and fluoride control in phosphoric acid plants will add to this large market.

  14. The Cold Gas-Dynamic Spray and Characterization of Microcrystalline Austenitic Stainless Steel

    DTIC Science & Technology

    2014-09-01

    DYNAMIC SPRAY AND CHARACTERIZATION OF MICROCRYSTALLINE AUSTENITIC STAINLESS STEEL by Jonathan F. Schiel September 2014 Thesis Advisor: Luke...MICROCRYSTALLINE AUSTENITIC STAINLESS STEEL 5. FUNDING NUMBERS DWAM31009 6. AUTHOR(S) Jonathan F. Schiel 7. PERFORMING ORGANIZATION NAME(S...spray process applied to the deposition of stainless steel coatings. Cold spray deposition is a relatively new process utilized to create corrosion

  15. Dislocation structures in the bands of localized cyclic plastic strain in austenitic 316L and austenitic-ferritic duplex stainless steels

    SciTech Connect

    Kruml, T.; Polak, J.; Obrtlik, K.; Degallaix, S.

    1997-12-01

    Dislocation structures in bands corresponding to cyclic strain localization have been studied in two types of stainless steels, single phase austenitic 316L steel and two-phase austenitic-ferritic duplex steel. Dislocation structures are documented in thin foils oriented approximately perpendicular to the active slip plane of individual grains and parallel to the primary Burgers vector. Persistent slip bands, with the structure more or less reminiscent of the well-known ladder structure, were found in austenitic grains of both steels. These bands can be correlated with the distinct surface relief consisting of extrusions, intrusions and shallow surface cracks in austenitic grains were found. The distribution of the wall and labyrinth structure embedded in the matrix structure in ferritic grains, which was proposed to be responsible for the localization of the cyclic strain, however, does not correspond to the distribution of the distinct surface slip lines on the surface.

  16. Materials compatibility of hydride storage materials with austenitic stainless steels

    SciTech Connect

    Clark, E.A.

    1992-09-21

    This task evaluated the materials compatibility of LaNi[sub 5-x]Al[sub x] (x= 0.3, 0.75) hydrides and palladium coated kieselguhr with austenitic stainless steel in hydrogen and tritium process environments. Based on observations of retired prototype hydride storage beds and materials exposure testing samples designed for this study, no materials compatibility problem was indicated. Scanning electron microscopy observations of features on stainless steel surfaces after exposure to hydrides are also commonly found on as-received materials before hydriding. These features are caused by either normal heat treating and acid cleaning of stainless steel or reflect the final machining operation.

  17. Materials compatibility of hydride storage materials with austenitic stainless steels

    SciTech Connect

    Clark, E.A.

    1992-09-21

    This task evaluated the materials compatibility of LaNi{sub 5-x}Al{sub x} (x= 0.3, 0.75) hydrides and palladium coated kieselguhr with austenitic stainless steel in hydrogen and tritium process environments. Based on observations of retired prototype hydride storage beds and materials exposure testing samples designed for this study, no materials compatibility problem was indicated. Scanning electron microscopy observations of features on stainless steel surfaces after exposure to hydrides are also commonly found on as-received materials before hydriding. These features are caused by either normal heat treating and acid cleaning of stainless steel or reflect the final machining operation.

  18. Microstructures of laser deposited 304L austenitic stainless steel

    SciTech Connect

    BROOKS,JOHN A.; HEADLEY,THOMAS J.; ROBINO,CHARLES V.

    2000-05-22

    Laser deposits fabricated from two different compositions of 304L stainless steel powder were characterized to determine the nature of the solidification and solid state transformations. One of the goals of this work was to determine to what extent novel microstructure consisting of single-phase austenite could be achieved with the thermal conditions of the LENS [Laser Engineered Net Shape] process. Although ferrite-free deposits were not obtained, structures with very low ferrite content were achieved. It appeared that, with slight changes in alloy composition, this goal could be met via two different solidification and transformation mechanisms.

  19. Formation of Widmanstätten Austenite in Strip Cast Grain-Oriented Silicon Steel

    NASA Astrophysics Data System (ADS)

    Song, Hong-Yu; Liu, Hai-Tao; Wang, Guo-Dong; Jonas, John J.

    2017-04-01

    The formation of Widmanstätten austenite was studied in strip cast grain-oriented silicon steel. The microstructure was investigated by optical microscopy and scanning electron microscopy. The orientations of the ferrite, Widmanstätten austenite, and martensite were determined using electron backscatter diffraction. The Widmanstätten austenite exhibits a lath-like shape and nucleates directly on the ferrite grain boundaries. This differs significantly from earlier work on duplex stainless steels. The orientation relationship between the Widmanstätten austenite and the parent ferrite is closer to Kurdjumov-Sachs than to Nishiyama-Wassermann. The ferrite boundaries migrate so as to accommodate the habit planes of the laths, leading to the presence of zigzag boundaries in the as-cast strip. Carbon partitioning into the Widmanstätten austenite and silicon partitioning into the parent ferrite were observed.

  20. Formation of Widmanstätten Austenite in Strip Cast Grain-Oriented Silicon Steel

    NASA Astrophysics Data System (ADS)

    Song, Hong-Yu; Liu, Hai-Tao; Wang, Guo-Dong; Jonas, John J.

    2017-02-01

    The formation of Widmanstätten austenite was studied in strip cast grain-oriented silicon steel. The microstructure was investigated by optical microscopy and scanning electron microscopy. The orientations of the ferrite, Widmanstätten austenite, and martensite were determined using electron backscatter diffraction. The Widmanstätten austenite exhibits a lath-like shape and nucleates directly on the ferrite grain boundaries. This differs significantly from earlier work on duplex stainless steels. The orientation relationship between the Widmanstätten austenite and the parent ferrite is closer to Kurdjumov-Sachs than to Nishiyama-Wassermann. The ferrite boundaries migrate so as to accommodate the habit planes of the laths, leading to the presence of zigzag boundaries in the as-cast strip. Carbon partitioning into the Widmanstätten austenite and silicon partitioning into the parent ferrite were observed.

  1. Deformation behavior of duplex austenite and ε-martensite high-Mn steel.

    PubMed

    Kwon, Ki Hyuk; Suh, Byeong-Chan; Baik, Sung-Il; Kim, Young-Woon; Choi, Jong-Kyo; Kim, Nack J

    2013-02-01

    Deformation and work hardening behavior of Fe-17Mn-0.02C steel containing ε-martensite within the austenite matrix have been investigated by means of in situ microstructural observations and x-ray diffraction analysis. During deformation, the steel shows the deformation-induced transformation of austenite → ε-martensite → α'-martensite as well as the direct transformation of austenite → α'-martensite. Based on the calculation of changes in the fraction of each constituent phase, we found that the phase transformation of austenite → ε-martensite is more effective in work hardening than that of ε-martensite → α'-martensite. Moreover, reverse transformation of ε-martensite → austenite has also been observed during deformation. It originates from the formation of stacking faults within the deformed ε-martensite, resulting in the formation of 6H-long periodic ordered structure.

  2. Texture evolution of cold rolled and reversion annealed metastable austenitic CrMnNi steels

    NASA Astrophysics Data System (ADS)

    Weidner, A.; Fischer, K.; Segel, C.; Schreiber, G.; Biermann, H.

    2015-04-01

    A thermo-mechanical process consisting of cold rolling and subsequent reversion annealing was applied to high-alloy metastable austenitic CrMnNi steels with different nickel contents. As a result of the reversion annealing ultrafine grained material with a grain size in the range between 500 nm up to 4 μm were obtained improving the strength behavior of the material. The evolution of the texture of both the cold rolled states and the reversion-annealed states was studied either by X-ray diffraction or by EBSD measurements. The nickel content has a significant influence on the austenite stability and consequently also on the amount of the martensitic phase transformation. However, the developed textures in both steel variants with different austenite stability revealed the same behavior. In both investigated steels the texture of the reverted austenite is a pronounced Bs-type texture as developed also for the deformed austenite

  3. Competition between nucleation and early growth of ferrite from austenite -- Studies using cellular automaton simulations

    SciTech Connect

    Kumar, M.; Sasikumar, R.; Nair, P.K.

    1998-11-02

    A model for the nucleation of ferrite on austenite grain boundaries and the growth of these nuclei along the grain boundary and into the grain, is developed. A cellular automaton algorithm, with transformation rules based on this model, is used to simulate the decomposition of austenite into ferrite. When performed under continuous cooling conditions, the simulations give an insight into the competition between nucleation and early growth, which determines the variation of ferrite grain size with the cooling rate and with austenite grain size. The number of ferrite grains per austenite grain, ferrite grain size and the kinetics of ferrite formation are obtained as a function of the cooling rate and austenite grain size. Contour plots of the volume fraction of ferrite in the cells at different times, enables visualization of the ferrite growth process.

  4. Effects of Retained Austenite Stability and Volume Fraction on Deformation Behaviors of TRIP Steels

    SciTech Connect

    Choi, Kyoo Sil; Soulami, Ayoub; Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

    2010-10-02

    In this paper, the separate effects of austenite stability and its volume fraction on the deformation behaviors of transformation-induced plasticity (TRIP) steels are investigated based on the microstructure-based finite element modeling method. The effects of austenite stability on the strength, ductility and formability of TRIP steels are first examined based on the microstructure of a commercial TRIP 800 steel. Then, the separate effects of the austenite volume fraction on the overall deformation behaviors of TRIP steels are examined based on the various representative volume elements (RVEs). The computational results suggest that the higher austenite stability is helpful to increase the ductility and formability, but not the UTS. However, the increase of austenite volume fraction alone is not helpful in improving the performance of TRIP steels. This may indicate that various other material factors should also be concurrently adjusted during thermo-mechanical manufacturing process in a way to increase the performance of TRIP steels, which needs further investigation.

  5. Influence of interface mobility on the evolution of Austenite-Martensite grain assemblies during annealing

    SciTech Connect

    Clarke, Amy J; Santofimia, Maria J; Speer, John G; Zhao, L; Sietsma, Jilt

    2009-01-01

    The quenching and partitioning (Q&P) process is a new heat treatment for the creation of advanced high-strength steels. This treatment consists of an initial partial or full austenitization, followed by a quench to form a controlled amount of martensite and an annealing step to partition carbon atoms from the martensite to the austenite. In this work, the microstructural evolution during annealing of martensite-austenite grain assemblies has been analyzed by means of a modeling approach that considers the influence of martensite-austenite interface migration on the kinetics of carbon partitioning. Carbide precipitation is precluded in the model, and three different assumptions about interface mobility are considered, ranging from a completely immobile interface to the relatively high mobility of an incoherent ferrite-austenite interface. Simulations indicate that different interface mobilities lead to profound differences in the evolution of microstructure that is predicted during annealing.

  6. Optimization of the use of skin expanders.

    PubMed

    Pamplona, D C; Weber, H I; Leta, F R

    2014-11-01

    Skin expansion is a physiological process that is defined as the ability of the human skin to increase its superficial area in response to stress or to a given deformation. Skin expanders are silicon bags that are implanted underneath the skin. Because the skin presents creep or relaxation, the resulting stress decreases after a time due to the imposed deformation. Skin expansions are used to reconstruct burned areas and breasts after a mastectomy or to hide scars. The question that constantly arises during skin expansion is whether it creates a sufficient amount of skin or, in other words, whether the achieved expansion is sufficient to resurface the defect. These questions are answered with information about how much new tissue is required to achieve the reconstruction in a given context and calculating the required tissue (surface area) in relationship with the volume infiltrated. Surface formulas for round and rectangular, and finite elements method for crescent skin expanders are used to calculate the relation between infiltrated volume and surface area. Those results were corrected or validated by an experimental work using 3D scanners to calculate the relation between surface area and internal volumes for the three types of expanders in question. The research provides information to determine the type, number, and volume of skin expanders necessary to obtain an extra amount of skin to repair a specific medical condition and to determine the amount of skin obtained even in cases when the expansion does not come to term. fci, Correcting factor, which corrects the mathematical formulas using the experimental results, for i skin expander; i, geometry of the expander, round (c), rectangular (r), or crescent (cresc/cr); Sd , surface of the defect; Sds , surface area of the donor site; Sfi, surface area obtained using a mathematical calculation for the i skin expander; S¯fi, surface area obtained experimentally for the i skin expander; Sfi∗, corrected surface

  7. A Three-Dimensional Cellular Automata Model Coupling Energy and Curvature-Driven Mechanisms for Austenitic Grain Growth

    NASA Astrophysics Data System (ADS)

    Wang, Min; Zhou, Jianxin; Yin, Yajun; Nan, Hai; Zhang, Dongqiao; Tu, Zhixin

    2017-10-01

    A 3D cellular automata model is used to simulate normal austenitic grain growth in this study. The proposed model considers both the curvature- and thermodynamics-driven mechanisms of growth. The 3D grain growth kinetics shows good agreement with the Beck equation. Moreover, the growth exponent and grain size distribution calculated by the proposed model coincides well with experimental and simulation results from other researchers. A linear relationship is found between the average relative grain size and the grain face number. More specifically, for average relative grain sizes exceeding 0.5, the number of faces increases linearly with relative grain size. For average relative grain sizes <0.5, this relationship is changed. Results simulated by the proposed model are translated to physical meaning by adjusting the actual temperature, space, and time for austenitic grain growth. The calibrated results are found to be in agreement with the simulation results from other research as well as the experimental results. By means of calibration of the proposed model, we can reliably predict the grain size in actual grain growth.

  8. Silicon microfabricated beam expander

    SciTech Connect

    Othman, A. Ibrahim, M. N.; Hamzah, I. H.; Sulaiman, A. A.; Ain, M. F.

    2015-03-30

    The feasibility design and development methods of silicon microfabricated beam expander are described. Silicon bulk micromachining fabrication technology is used in producing features of the structure. A high-precision complex 3-D shape of the expander can be formed by exploiting the predictable anisotropic wet etching characteristics of single-crystal silicon in aqueous Potassium-Hydroxide (KOH) solution. The beam-expander consist of two elements, a micromachined silicon reflector chamber and micro-Fresnel zone plate. The micro-Fresnel element is patterned using lithographic methods. The reflector chamber element has a depth of 40 µm, a diameter of 15 mm and gold-coated surfaces. The impact on the depth, diameter of the chamber and absorption for improved performance are discussed.

  9. Effect of hydrogen on internal friction and Young`s modulus of Fe-Cr-Mn austenitic stainless steel

    SciTech Connect

    Usui, Makoto; Asano, Shigeru

    1996-06-01

    The internal friction technique has so far been applied to studies on hydrogen behavior in iron and steel. The hydrogen cold-work peak is well known for pure iron and has also been observed in BCC iron alloys such as ferritic stainless steel and maraging steel. It provides important information about the hydrogen- dislocation interaction in the BCC iron lattice. Meanwhile, for FCC iron alloys such as austenitic stainless steel, another characteristic hydrogen internal friction peak has been found by authors` group and confirmed by several other investigators. In the present study, type 205 austenitic stainless steel (Fe-17Cr-15Mn) was chosen as a nickel-free FCC iron alloy, in which manganese is totally substituted for nickel in type 304 steel. This steel has an unstable FCC lattice as is the case of type 304 steel, in which hydrogen-induced phase transformation depends on the austenite stability. However, the present steel was confirmed to form the {var_epsilon}{sub H} phase after cathodic hydrogen charging in a similar manner to the stable FCC lattice of type 310 steel. In addition, the Fe-Cr-Mn alloy shows a marked anomaly in the temperature dependence of Young`s modulus: an abrupt drop near the Neel temperature T{sub N} and successive lowering below T{sub N}, as has been reported in the literature for some antiferromagnetic materials. The effect of hydrogen on Young`s modulus was studied by several investigators, but there was great inconsistency among their experimental results. The purpose of this paper is to confirm the hydrogen peak of internal friction in type 205 steel and to examine the effect of hydrogen on Young`s modulus of this steel.

  10. Corrosion Behavior of Platinum-Enhanced Radiopaque Stainless Steel (PERSS®) for Dilation-Baloon Expandable Coronary Stents

    SciTech Connect

    Covino, Jr., Bernard S.; Craig, Charles H.; Cramer, Stephen D.; Bullard, Sophie J.; Ziomek-Moroz, Margaret; Jablonski, Paul D.; Turner, Paul C.; Radisch, Jr., Herbert R.; Gokcen, Nev A.; Friend, Clifford M.; Edwards, Michael R.

    2002-05-01

    Dilation-balloon expandable coronary stents are commonly made of implant grade stainless steels conforming to ASTM F138/F139, e.g., Biodur? 316LS (UNS S31673). Typical of such stents is the Boston Scientific/Interventional Technologies? (BS/IVT) LP-StentTM. In 2000, BS/IVT determined that the addition of 5 to 6 wt % platinum to Biodur 316LS produced a stainless steel with enhanced radiopacity to make their stents more visible radiographically and thus more effective clinically. A goal of the program was to ensure platinum additions would not adversely affect the corrosion resistance of Biodur 316LS. The corrosion resistance of 5-6 wt % PERSS? alloys and Biodur 316LS was determined using electrochemical tests for general, pitting, crevice and intergranular corrosion. Experimental methods included ASTM A262E, F746, F2129, and potentiodynamic polarization. The 6 wt % PERSS? alloy (IVT 78) had a resistance to pitting, crevice and intergranular corrosion that was similar to the Biodur 316LS base material. IVT 78 was a single-phase austenitic alloy with no evidence of inclusions or precipitates. It was more resistant to pitting corrosion than 5 wt % PERSS? alloys. Performance of the PERSS? alloys was not a function of alloy oxygen content in the range 0.01 to 0.03 wt %.

  11. Nanostructured nickel-free austenitic stainless steel/hydroxyapatite composites.

    PubMed

    Tulinski, Maciej; Jurczyk, Mieczyslaw

    2012-11-01

    In this work Ni-free austenitic stainless steels with nanostructure and their nanocomposites with hydroxyapatite are presented and characterized by means of X-ray diffraction and optical profiling. The samples were synthesized by mechanical alloying, heat treatment and nitriding of elemental microcrystalline powders with addition of hydroxyapatite (HA). In our work we wanted to introduce into stainless steel hydroxyapatite ceramics that have been intensively studied for bone repair and replacement applications. Such applications were chosen because of their high biocompatibility and ability to bond to bone. Since nickel-free austenitic stainless steels seem to have better mechanical properties, corrosion resistance and biocompatibility compared to 316L stainless steels, it is possible that composite made of this steel and HA could improve properties, as well. Mechanical alloying and nitriding are very effective technologies to improve the corrosion resistance of stainless steel. Similar process in case of nanocomposites of stainless steel with hydroxyapatite helps achieve even better mechanical properties and corrosion resistance. Hence nanocrystalline nickel-free stainless steels and nickel-free stainless steel/hydroxyapatite nanocomposites could be promising bionanomaterials for use as a hard tissue replacement implants, e.g., orthopedic implants. In such application, the surface roughness and more specifically the surface topography influences the proliferation of cells (e.g., osteoblasts).

  12. Reducing tool wear when machining austenitic stainless steels

    SciTech Connect

    Magee, J.H.; Kosa, T.

    1998-07-01

    Austenitic stainless steels are considered more difficult to machine than carbon steels due to their high work hardening rate, large spread between yield and ultimate tensile strength, high toughness and ductility, and low thermal conductivity. These characteristics can result in a built-up edge or excessive tool wear during machining, especially when the cutting speed is too high. The practical solution is to lower the cutting speed until tool life reaches an acceptable level. However, lower machining speed negatively impacts productivity. Thus, in order to overcome tool wear at relatively high machining speeds for these alloys, on-going research is being performed to improve cutting fluids, develop more wear-resistant tools, and to modify stainless steels to make them less likely to cause tool wear. This paper discusses compositional modifications to the two most commonly machined austenitic stainless steels (Type 303 and 304) which reduced their susceptibility to tool wear, and allowed these grades to be machined at higher cutting speeds.

  13. Evaluation of Alumina-Forming Austenitic Foil for Advanced Recuperators

    SciTech Connect

    Pint, Bruce A; Brady, Michael P; Yamamoto, Yukinori; Santella, Michael L; Maziasz, Philip J; Matthews, Wendy

    2011-01-01

    A corrosion- and creep-resistant austenitic stainless steel has been developed for advanced recuperator applications. By optimizing the Al and Cr contents, the alloy is fully austenitic for creep strength while allowing the formation of a chemically stable external alumina scale at temperatures up to 900 C. An alumina scale eliminates long-term problems with the formation of volatile Cr oxy-hydroxides in the presence of water vapor in exhaust gas. As a first step in producing foil for primary surface recuperators, three commercially cast heats have been rolled to 100 m thick foil in the laboratory to evaluate performance in creep and oxidation testing. Results from initial creep testing are presented at 675 C and 750 C, showing excellent creep strength compared with other candidate foil materials. Laboratory exposures in humid air at 650 800 C have shown acceptable oxidation resistance. A similar oxidation behavior was observed for sheet specimens of these alloys exposed in a modified 65 kW microturbine for 2871 h. One composition that showed superior creep and oxidation resistance has been selected for the preparation of a commercial batch of foil. DOI: 10.1115/1.4002827

  14. Grain-boundary plane crystallography and energy in austenitic steel

    SciTech Connect

    Caul, M.; Randle, V.; Fiedler, J.

    1996-10-01

    The presence of grain boundaries in polycrystalline materials affects the materials properties and performance. Recently it has been realized that boundaries can be manipulated to give better properties, and the design and control of grain boundaries is now an area of strong research interest in the search for high performance engineering materials. Grain boundaries can be classified using the Coincident Site Lattice Model (CSL), which defines the periodicity, i.e., the degree of fit between the two lattices which constitute the boundary. Using this model it is possible to divide boundaries into categories: low angle (up to 15{degree} misorientation), CSL and random i.e., high angle non-CSL. Some CSL boundaries have been shown to have special properties: an example from recent research in the same program as that currently reported has shown that twin boundaries ({Sigma} = 3 in CSL notation) in High Nitrogen Austenitic Stainless Steels do not favor the formation of Cr{sub 2}N precipitates. The research presented here examines grain boundary inclinations of surface grains in austenitic steel specimens which have been isothermally aged at higher 700 C or 800 C. Grain boundary plane crystallography has also been obtained for the 800 C aged sample.

  15. Expanding Views on Transition.

    ERIC Educational Resources Information Center

    Repetto, Jeanne B.; Correa, Vivian I.

    1996-01-01

    This position paper proposes an expanded definition of transition, based on common components of early childhood and secondary perspectives. It advocates for a seamless model of transition service delivery for students with disabilities, including program planning, from birth through age 21. The model addresses curriculum, location of services,…

  16. Expanded Roles for HRD.

    ERIC Educational Resources Information Center

    1998

    This document contains three papers from a symposium on expanded roles for human resource development (HRD). "The Roles of Consultants in Gainsharing Firms: Empirical Results" (Eunsang Cho, Gary N. McLean) reports findings that consultants are moderately involved at the separation, preparation, evaluation, and design stages and have low…

  17. Expand Your Hiring Horizons.

    ERIC Educational Resources Information Center

    Leske, Lucy Apthorp; Archer-Martin, Nancy

    1999-01-01

    To succeed in recruiting development officers, colleges and universities must use more aggressive methods to reach alumni, people with ties to the campus, and local business people; expand their selection criteria, perhaps including candidates with little or no experience; streamline the hiring process; and train new professionals. (MSE)

  18. ExpandED Options: Learning beyond High School Walls

    ERIC Educational Resources Information Center

    ExpandED Schools, 2014

    2014-01-01

    Through ExpandED Options by TASC, New York City high school students get academic credit for learning career-related skills that lead to paid summer jobs. Too many high school students--including those most likely to drop out--are bored or see classroom learning as irrelevant. ExpandED Options students live the connection between mastering new…

  19. Study on the crystallographic orientation relationship and formation mechanism of reversed austenite in economical Cr12 super martensitic stainless steel

    SciTech Connect

    Ye, Dong; Li, Shaohong; Li, Jun; Jiang, Wen; Su, Jie; Zhao, Kunyu

    2015-11-15

    Effect of carbides and crystallographic orientation relationship on the formation mechanism of reversed austenite of economical Cr12 super martensitic stainless steel (SMSS) has been investigated mainly by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The results indicate that the M{sub 23}C{sub 6} precipitation and the formation of the reversed austenite have the interaction effect during tempering process in SMSS. The reversed austenite forms intensively at the sub-block boundary and the lath boundary within a misorientation range of 0–60°. M{sub 23}C{sub 6} has the same crystallographic orientation relationship with reversed austenite. There are two different kinds of formation modes for reversed austenite. One is a nondiffusional shear reversion; the other is a diffusion transformation. Both are strictly limited by crystallographic orientation relationship. The austenite variants are limited to two kinds within one packet and five kinds within one prior austenite grain. - Highlights: • Reversed austenite forms at martensite boundaries with misorientation of 0–60° • M{sub 23}C{sub 6} precipitation and reversed austenite formation have the interaction effect. • Two austenite variants with different orientations can be formed inside a packet. • Two reversed austenite formation modes: shear reversion; diffusion transformation.

  20. Modeling of the Recrystallization and Austenite Formation Overlapping in Cold-Rolled Dual-Phase Steels During Intercritical Treatments

    NASA Astrophysics Data System (ADS)

    Ollat, M.; Massardier, V.; Fabregue, D.; Buscarlet, E.; Keovilay, F.; Perez, M.

    2017-07-01

    Austenite formation kinetics of a DP1000 steel was investigated from a ferrite-pearlite microstructure (either fully recrystallized or cold-rolled) during typical industrial annealing cycles by means of dilatometry and optical microscopy after interrupted heat treatments. A marked acceleration of the kinetics was found when deformed ferrite grains were present in the microstructure just before austenite formation. After having described the austenite formation kinetics without recrystallization and the recrystallization kinetics of the steel without austenite formation by simple JMAK laws, a mixture law was used to analyze the kinetics of the cold-rolled steel for which austenite formation and recrystallization may occur simultaneously. In the case where the interaction between these two phenomena is strong, three main points were highlighted: (i) the heating rate greatly influences the austenite formation kinetics, as it affects the degree of recrystallization at the austenite start temperature; (ii) recrystallization inhibition above a critical austenite fraction accelerates the austenite formation kinetics; (iii) the austenite fractions obtained after a 1 hour holding deviate from the local equilibrium fractions given by Thermo-Calc, contrary to the case of the recrystallized steel. This latter result could be due to the fact that the dislocations of the deformed ferrite matrix could promote the diffusion of the alloying elements of the steel and accelerate austenite formation.

  1. Modeling of the Recrystallization and Austenite Formation Overlapping in Cold-Rolled Dual-Phase Steels During Intercritical Treatments

    NASA Astrophysics Data System (ADS)

    Ollat, M.; Massardier, V.; Fabregue, D.; Buscarlet, E.; Keovilay, F.; Perez, M.

    2017-10-01

    Austenite formation kinetics of a DP1000 steel was investigated from a ferrite-pearlite microstructure (either fully recrystallized or cold-rolled) during typical industrial annealing cycles by means of dilatometry and optical microscopy after interrupted heat treatments. A marked acceleration of the kinetics was found when deformed ferrite grains were present in the microstructure just before austenite formation. After having described the austenite formation kinetics without recrystallization and the recrystallization kinetics of the steel without austenite formation by simple JMAK laws, a mixture law was used to analyze the kinetics of the cold-rolled steel for which austenite formation and recrystallization may occur simultaneously. In the case where the interaction between these two phenomena is strong, three main points were highlighted: (i) the heating rate greatly influences the austenite formation kinetics, as it affects the degree of recrystallization at the austenite start temperature; (ii) recrystallization inhibition above a critical austenite fraction accelerates the austenite formation kinetics; (iii) the austenite fractions obtained after a 1 hour holding deviate from the local equilibrium fractions given by Thermo-Calc, contrary to the case of the recrystallized steel. This latter result could be due to the fact that the dislocations of the deformed ferrite matrix could promote the diffusion of the alloying elements of the steel and accelerate austenite formation.

  2. In-situ observation of an austenitic stainless steel weld joint during helium irradiation

    NASA Astrophysics Data System (ADS)

    Hamada, S.; Hojou, K.; Hishinuma, A.

    1993-10-01

    Microstructural evolution during helium-ion irradiation at 773 K in a weld metal sample (containing 10% δ-ferrite) of Ti-modified austenitic stainless steel was observed in-situ using a transmission electron microscope. Very fine helium bubbles formed at high number density in both δ-ferrite and austenite by a dose of 3 × 10 19ionsm-2. However, the different microstructural evolution developed in the two phases with increasing dose. Fine bubbles in δ-ferrite rapidly grew with increasing dose and coalescenced at doses beyond 9 × 10 19ionsm-2. Tiny bubbles in austenite remained very stable during irradiation to a dose of 2 × 10 20ionsm-2. The number density of bubbles was about one order of magnitude larger in austenite than that in δ-ferrite, and increased with increasing dose. Swelling became much larger in δ-ferrite than in austenite, as a result. This is the inverse phenomenon to the conventional result that swelling is lower in ferrite than in austenite. Sigma phase formed by radiation-enhancement at grain boundaries between δ-ferrite and austenite and at the interfaces within δ-ferrite at a dose 9 × 10 19ionsm-2 and grew with increasing dose. The chemical composition of σ-phase formed during irradiation showed Cr and Mo enrichment, and Fe and Ni depletion compared with σ-phase formed thermally.

  3. Recrystallization Behavior of a Heavily Deformed Austenitic Stainless Steel During Iterative Type Annealing

    NASA Astrophysics Data System (ADS)

    Ravi Kumar, B.; Sharma, Sailaja

    2014-12-01

    The study describes evolution of the recrystallization microstructure in an austenitic stainless steel during iterative or repetitive type annealing process. The starting heavily cold deformed microstructure consisted of a dual phase structure i.e., strain-induced martensite (SIM) (43 pct in volume) and heavily deformed large grained retained austenite. Recrystallization behavior was compared with Johnson Mehl Avrami and Kolmogorov model. Early annealing iterations led to reversion of SIM to reversed austenite. The microstructure changes observed in the retained austenite and in the reverted austenite were mapped by electron backscatter diffraction technique and transmission electron microscope. The reversed austenite was characterized by a fine polygonal substructure consisting of low-angle grain boundaries. With an increasing number of annealing repetitions, these boundaries were gradually replaced by high-angle grain boundaries and recrystallized into ultrafine-grained microstructure. On the other hand, recrystallization of retained austenite grains was sluggish in nature. Progress of recrystallization in these grains was found to take place by a gradual evolution of subgrains and their subsequent transformation into fine grains. The observed recrystallization characteristics suggest continuous recrystallization type process. The analysis provided basic insight into the recrystallization mechanisms that enable the processing of ultrafine-grained fcc steels by iterative type annealing. Tensile properties of the processed material showed a good combination of strength and ductility.

  4. Influence of reverted austenite on the texture and magnetic properties of 350 maraging steel

    NASA Astrophysics Data System (ADS)

    Abreu, Hamilton F. G.; Silva, Jean J.; Silva, Manoel R.; Gomes da Silva, Marcelo J.

    2015-11-01

    The aging temperature to improve magnetic properties in Maraging-350 steel (Mar-350) is limited by the onset of austenite reversion. The traditional process of cooling after aging is to remove the piece from the oven and then to air cool it. The purpose of this research was to characterize the reverted austenite and to investigate the effect of cooling below the martensite start temperature (Ms) on the magnetic properties. The Mar350 samples aged at temperatures above 550 °C, and subsequently cooled in liquid nitrogen presented less austenite than samples cooled in air, resulting in higher magnetization saturation and a lower coercive force. A combination of optical microscopy (OM), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) techniques were used to characterize the presence of reverted austenite. The crystallographic texture of both martensite and reverted austenite were analyzed. The texture of the reverted austenite coincides with the texture of the parent austenite indicating that a phenomenon of texture memory is present.

  5. The Effect of Precipitate Evolution on Austenite Grain Growth in RAFM Steel.

    PubMed

    Yan, Biyu; Liu, Yongchang; Wang, Zejun; Liu, Chenxi; Si, Yonghong; Li, Huijun; Yu, Jianxing

    2017-09-01

    To study the effects of various types of precipitates and precipitate evolution behavior on austenite (size and phase fraction) in reduced activation ferritic/martensitic (RAFM) steel, RAFM steel was heated to various austenitizing temperatures. The microstructures of specimens were observed using optical microscopy (OM) and transmission electron microscopy (TEM). The results indicate that the M23C₆ and MX precipitates gradually coarsen and dissolve into the matrix as the austenitizing temperatures increase. The M23C₆ precipitates dissolve completely at 1100 °C, while the MX precipitates dissolve completely at 1200 °C. The evolution of two types of precipitate has a significant effect on the size of austenite. Based on the Zener pinning model, the effect of precipitate evolution on austenite grain size is quantified. It was found that the coarsening and dissolution of M23C₆ and MX precipitates leads to a decrease in pinning pressure on grain boundaries, facilitating the rapid growth of austenite grains. The austenite phase fraction is also affected by the coarsening and dissolution of precipitates.

  6. The Effect of Precipitate Evolution on Austenite Grain Growth in RAFM Steel

    PubMed Central

    Yan, Biyu; Liu, Yongchang; Wang, Zejun; Liu, Chenxi; Si, Yonghong; Li, Huijun; Yu, Jianxing

    2017-01-01

    To study the effects of various types of precipitates and precipitate evolution behavior on austenite (size and phase fraction) in reduced activation ferritic/martensitic (RAFM) steel, RAFM steel was heated to various austenitizing temperatures. The microstructures of specimens were observed using optical microscopy (OM) and transmission electron microscopy (TEM). The results indicate that the M23C6 and MX precipitates gradually coarsen and dissolve into the matrix as the austenitizing temperatures increase. The M23C6 precipitates dissolve completely at 1100 °C, while the MX precipitates dissolve completely at 1200 °C. The evolution of two types of precipitate has a significant effect on the size of austenite. Based on the Zener pinning model, the effect of precipitate evolution on austenite grain size is quantified. It was found that the coarsening and dissolution of M23C6 and MX precipitates leads to a decrease in pinning pressure on grain boundaries, facilitating the rapid growth of austenite grains. The austenite phase fraction is also affected by the coarsening and dissolution of precipitates. PMID:28862680

  7. The formation of twinned austenite in Fe-10Cr-10Ni-2W maraging steel

    SciTech Connect

    Suk, J.I.; Hong, S.H.; Nam, S.W. )

    1991-12-01

    The precipitation hardening mechanisms in high strength maraging steels have been studied in detail by many investigators, but limited information is available on the formation of austenite during aging. Some investigations have been concerned with the understanding of the effect of reverted austenite formed during aging on the mechanical properties. However, only a few investigations have been reported on the morphology and crystallographic feature of austenite. Shiang and Wayman first reported the twin-related and coupled morphology of Widmanstatten austenite plates which were frequently observed in maraging steel. In addition, Ameyama et al. reported the morphology and crystallographic features of austenite formed in ferrite grain during aging in a two-phase stainless steel, and found that each side of the austenite pair of twins satisfies the Kurdjumov-Sachs (K-S) orientation relationship with the parent phase. The morphology and crystallographic features of the reverted austenite formed during aging of Fe-10Cr-10Ni-2W stainless maraging steel have been investigated in this paper. The major strengthening precipitate in Fe-10Cr-10Ni-2W maraging steels has been identified as the rod-shaped {eta}-Ni{sub 3}Ti phase in our previous study. The peculiar morphology of the austenite, i.e., twinned austenite, also has been found in our studies of maraging steel in the Fe-10Cr-10Ni-2W lath martensite. In addition, computer simulation of the diffraction pattern is used to confirm the orientation relationships, such as the Kurdjumov-Sachs (K-S) relationship, the Nishiyama-Wasserman (N-W) relationship and the twin relationship by comparisons with the experimentaly observed results.

  8. Grazing incidence beam expander

    SciTech Connect

    Akkapeddi, P.R.; Glenn, P.; Fuschetto, A.; Appert, Q.; Viswanathan, V.K.

    1985-01-01

    A Grazing Incidence Beam Expander (GIBE) telescope is being designed and fabricated to be used as an equivalent end mirror in a long laser resonator cavity. The design requirements for this GIBE flow down from a generic Free Electron Laser (FEL) resonator. The nature of the FEL gain volume (a thin, pencil-like, on-axis region) dictates that the output beam be very small. Such a thin beam with the high power levels characteristic of FELs would have to travel perhaps hundreds of meters or more before expanding enough to allow reflection from cooled mirrors. A GIBE, on the other hand, would allow placing these optics closer to the gain region and thus reduces the cavity lengths substantially. Results are presented relating to optical and mechanical design, alignment sensitivity analysis, radius of curvature analysis, laser cavity stability analysis of a linear stable concentric laser cavity with a GIBE. Fabrication details of the GIBE are also given.

  9. Grazing incidence beam expander

    NASA Astrophysics Data System (ADS)

    Akkapeddi, P. R.; Glenn, P.; Fuschetto, A.; Appert, Q.; Viswanathan, V. K.

    1985-01-01

    A Grazing Incidence Beam Expander (GIBE) telescope is being designed and fabricated to be used as an equivalent end mirror in a long laser resonator cavity. The design requirements for this GIBE flow down from a generic Free Electron Laser (FEL) resonator. The nature of the FEL gain volume (a thin, pencil-like, on-axis region) dictates that the output beam be very small. Such a thin beam with the high power levels characteristic of FELs would have to travel perhaps hundreds of meters or more before expanding enough to allow reflection from cooled mirrors. A GIBE, on the other hand, would allow placing these optics closer to the gain region and thus reduces the cavity lengths substantially. Results are presented relating to optical and mechanical design, alignment sensitivity analysis, radius of curvature analysis, laser cavity stability analysis of a linear stable concentric laser cavity with a GIBE. Fabrication details of the GIBE are also given.

  10. Expandable LED array interconnect

    DOEpatents

    Yuan, Thomas Cheng-Hsin; Keller, Bernd

    2011-03-01

    A light emitting device that can function as an array element in an expandable array of such devices. The light emitting device comprises a substrate that has a top surface and a plurality of edges. Input and output terminals are mounted to the top surface of the substrate. Both terminals comprise a plurality of contact pads disposed proximate to the edges of the substrate, allowing for easy access to both terminals from multiple edges of the substrate. A lighting element is mounted to the top surface of the substrate. The lighting element is connected between the input and output terminals. The contact pads provide multiple access points to the terminals which allow for greater flexibility in design when the devices are used as array elements in an expandable array.

  11. Discovering the Expanding Universe

    NASA Astrophysics Data System (ADS)

    Nussbaumer, Harry; Bieri, Lydia; Sandage, Foreword by Allan

    2009-03-01

    Acknowledgments; Foreword; 1. Introduction; 2. Cosmological concepts at the end of the Middle Ages; 3. Nebulae as a new astronomical phenomenon; 4. On the construction of the Heavens; 5. Island universes turn into astronomical facts: a universe of galaxies; 6. The early cosmology of Einstein and de Sitter; 7. The dynamical universe of Friedmann; 8. Redshifts: how to reconcile Slipher and de Sitter?; 9. Lemaître discovers the expanding universe; 10. Hubble's contribution of 1929; 11. The breakthrough for the expanding universe; 12. Hubble's anger about de Sitter; 13. Robertson and Tolman join the game; 14. The Einstein-de Sitter universe; 15. Are Sun and Earth older than the universe?; 16. In search of alternative tracks; 17. The seed for the Big Bang; 18. Summary and Postscript; Appendix; References; Index.

  12. Uniaxial Properties versus Temperature, Creep and Impact Energy of an Austenitic Steel

    NASA Astrophysics Data System (ADS)

    Brnic, Josip; Turkalj, Goran; Krscanski, Sanjin; Vukelic, Goran; Canadija, Marko

    2017-02-01

    In this paper, uniaxial material properties, creep resistance and impact energy of the austenitic heat-resistant steel (1.4841) are experimentally determined and analysed. Engineering stress-strain diagrams and uniaxial short-time creep curves are examined with computer-controlled testing machine. Impact energy has been determined and fracture toughness assessed. Investigated data are shown in the form of curves related to ultimate tensile strength, yield strength, modulus of elasticity and creep resistance. All of these experimentally obtained results are analysed and may be used in the design process of the structure where considered material is intended to be applied. Based on these results, considered material may be classified as material of high tensile strength (688 MPa/293 K; 326 MPa/923 K) and high yield strength (498 MPa/293 K; 283 MPa/923 K) as well as satisfactory creep resistance (temperature/stress → to strain (%) at 1,200 min: 823 K/167 MPa → to 0.25 %; 923 K/85 MPa → to 0.2 %).

  13. Effect of martensitic transformation on springback behavior of 304L austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Fathi, H.; Mohammadian Semnani, H. R.; Emadoddin, E.; Sadeghi, B. Mohammad

    2017-09-01

    The present paper studies the effect of martensitic transformation on the springback behavior of 304L austenitic stainless steel. Martensite volume fraction was determined at the bent portion under various strain rates after bending test. Martensitic transformation has a significant effect on the springback behavior of this material. The findings of this study indicated that the amount of springback was reduced under a situation of low strain rate, while a higher amount of springback was obtained with a higher strain rate. The reason for this phenomenon is that higher work hardening occurs during the forming process with the low strain rate due to the higher martensite volume fraction, therefore the formability of the sheet is enhanced and it leads to a decreased amount of springback after the bending test. Dependency of the springback on the martensite volume fraction and strain rate was expressed as formulas from the results of the experimental tests and simulation method. Bending tests were simulated using LS-DYNA software and utilizing MAT_TRIP to determine the martensite volume fraction and strain under various strain rates. Experimental result reveals good agreement with the simulation method.

  14. Expanding the HAWC Observatory

    SciTech Connect

    Mori, Johanna

    2016-08-17

    The High Altitude Water Cherenkov Gamma-Ray Observatory is expanding its current array of 300 water tanks to include 350 outrigger tanks to increase sensitivity to gamma rays above 10 TeV. This involves creating and testing hardware with which to build the new tanks, including photomultiplier tubes, high voltage supply units, and flash analog to digital converters. My responsibilities this summer included preparing, testing and calibrating that equipment.

  15. In Situ Observation of Austenite Growth During Continuous Heating in Very-Low-Carbon Fe-Mn and Ni Alloys

    NASA Astrophysics Data System (ADS)

    Enomoto, M.; Wan, X. L.

    2017-04-01

    The growth of austenite during continuous heating was observed in situ under a confocal scanning laser microscope in Fe-Mn and Ni alloys containing less than 0.01 mass pct C. The advancements of the α/ γ boundary were measured in the temperature range of ca. 40 K, which encompassed the Ae3 line of the alloys. Below Ae3, the growth rates were of the same order of magnitude as those predicted from the carbon diffusion-controlled negligible partition local equilibrium in the ( α + γ) two-phase region, whereas those observed near and above the Ae3 were ca. two orders of magnitude greater. The α/ γ boundary mobilities evaluated therefrom were somewhat smaller than those obtained previously in massive ferrite transformation during continuous cooling in the same alloys, albeit the experimental scatter was large and fell near the mobilities proposed in the literature. The α/ γ boundary migrated probably with a carbon diffusion spike ahead of the boundary and the solute drag of the carbon or alloy element is unlikely to be operative during the growth of austenite.

  16. In Situ Observation of Austenite Growth During Continuous Heating in Very-Low-Carbon Fe-Mn and Ni Alloys

    NASA Astrophysics Data System (ADS)

    Enomoto, M.; Wan, X. L.

    2017-02-01

    The growth of austenite during continuous heating was observed in situ under a confocal scanning laser microscope in Fe-Mn and Ni alloys containing less than 0.01 mass pct C. The advancements of the α/γ boundary were measured in the temperature range of ca. 40 K, which encompassed the Ae3 line of the alloys. Below Ae3, the growth rates were of the same order of magnitude as those predicted from the carbon diffusion-controlled negligible partition local equilibrium in the (α + γ) two-phase region, whereas those observed near and above the Ae3 were ca. two orders of magnitude greater. The α/γ boundary mobilities evaluated therefrom were somewhat smaller than those obtained previously in massive ferrite transformation during continuous cooling in the same alloys, albeit the experimental scatter was large and fell near the mobilities proposed in the literature. The α/γ boundary migrated probably with a carbon diffusion spike ahead of the boundary and the solute drag of the carbon or alloy element is unlikely to be operative during the growth of austenite.

  17. Measurement of ultrasonic scattering attenuation in austenitic stainless steel welds: realistic input data for NDT numerical modeling.

    PubMed

    Ploix, Marie-Aude; Guy, Philippe; Chassignole, Bertrand; Moysan, Joseph; Corneloup, Gilles; El Guerjouma, Rachid

    2014-09-01

    Multipass welds made of 316L stainless steel are specific welds of the primary circuit of pressurized water reactors in nuclear power plants. Because of their strong heterogeneous and anisotropic nature due to grain growth during solidification, ultrasonic waves may be greatly deviated, split and attenuated. Thus, ultrasonic assessment of the structural integrity of such welds is quite complicated. Numerical codes exist that simulate ultrasonic propagation through such structures, but they require precise and realistic input data, as attenuation coefficients. This paper presents rigorous measurements of attenuation in austenitic weld as a function of grain orientation. In fact attenuation is here mainly caused by grain scattering. Measurements are based on the decomposition of experimental beams into plane-wave angular spectra and on the modeling of the ultrasonic propagation through the material. For this, the transmission coefficients are calculated for any incident plane wave on an anisotropic plate. Two different hypotheses on the welded material are tested: first it is considered as monoclinic, and then as triclinic. Results are analyzed, and validated through comparison to theoretical predictions of related literature. They underline the great importance of well-describing the anisotropic structure of austenitic welds for UT modeling issues. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Observation on Formation of Fresh Martensite from the Reversed Austenite During Water-Quenching Process in Fe-0.2C-5Mn Steel

    NASA Astrophysics Data System (ADS)

    Zhao, Chuan; Zhang, Chi; Cao, Wen-Quan; Yang, Zhi-Gang; Weng, Yu-Qing

    2015-09-01

    Phase transformation behavior during intercritical annealing in Fe-0.2C-5Mn was studied. Austenite lath formed and transformed at martensite lath during annealing. XRD revealed that retained austenite amount did not always increase with time. TEM result may firstly demonstrate that reversed austenite partly changed into fresh martensite during quenching while the remained part was retained as retained austenite. The final structure consisted of ferrite, retained austenite and fresh martensite. Simulation was done by DICTRA to support TEM result.

  19. Austenite layer and precipitation in high Co-Ni maraging steel.

    PubMed

    Wang, Chenchong; Zhang, Chi; Yang, Zhigang

    2014-12-01

    In high Co-Ni maraging steel, austenite has a great effect on the fracture toughness of the steel and the precipitated carbides are the main strengthening phase. In this study, both austenite layers and precipitation were observed and their formation theory was analyzed by Thermo-Calc simulation and several reported results. TEM and HRTEM observation results showed that the thickness of the austenite layers was about 5-10 nm and the length of the needle-like precipitated carbides was less than 10nm. The carbides maintained coherent or semi-coherent relation with the matrix.

  20. A methodology suitable for TEM local measurements of carbon concentration in retained austenite

    SciTech Connect

    Kammouni, A.; Saikaly, W. Dumont, M.; Marteau, C.; Bano, X.; Charai, A.

    2008-09-15

    Carbon concentration in retained austenite grains is of great importance determining the mechanical properties of hot-rolled TRansformation Induced Plasticity steels. Among the different techniques available to measure such concentrations, Kikuchi lines obtained in Transmission Electron Microscopy provide a relatively easy and accurate method. The major problem however is to be able to locate an austenitic grain in the observed Transmission Electron Microscopy thin foil. Focused Ion Beam in combination with Scanning Electron Microscopy was used to successfully prepare a thin foil for Transmission Electron Microscopy and carbon concentration measurements from a 700 nm retained austenite grain.

  1. In-Situ NDT Measurements of Irradiation Induced Swelling PWR Core Internal Components; Phase 3: Correlation of Void Swelling and Material Properties of Austenitic Steels

    SciTech Connect

    I.Balachov; F. Garner; S-G. Kumatori-cho; Y. Isobe

    2004-04-01

    OAK-B135 The objective of the project is to examine and develop in-situ nondestructive testing (NDT) techniques for measuring irradiation induced swelling in the internal components for PWRs. This report documents the third phase effort on establishing experimental correlations of the irradiation induced void swelling and measurable material properties of austenitic steels and, eventually, correlation of swelling and signals of the developed swelling sensors. Experimental stainless steel irradiated at high neutron fluences are presented. Theoretical aspects of the influence of void swelling on electrical resistivity and ultrasound velocity are outlined. Swelling-material properties correlations were recommended for quantitative interpretation of swelling measurements.

  2. Effects of N/C Ratio on Solidification Behaviors of Novel Nb-Bearing Austenitic Heat-Resistant Cast Steels for Exhaust Components of Gasoline Engines

    NASA Astrophysics Data System (ADS)

    Zhang, Yinhui; Li, Mei; Godlewski, Larry A.; Zindel, Jacob W.; Feng, Qiang

    2017-03-01

    In order to comply with more stringent environmental and fuel consumption regulations, novel Nb-bearing austenitic heat-resistant cast steels that withstand exhaust temperatures as high as 1,323 K (1,050 °C) is urgently demanded from automotive industries. In the current research, the solidification behavior of these alloys with variations of N/C ratio is investigated. Directional solidification methods were carried out to examine the microstructural development in mushy zones. Computational thermodynamic calculations under partial equilibrium conditions were performed to predict the solidification sequence of different phases. Microstructural characterization of the mushy zones indicates that N/C ratio significantly influenced the stability of γ-austenite and the precipitation temperature of NbC/Nb(C,N), thereby altering the solidification path, as well as the morphology and distribution of NbC/Nb(C,N) and γ-ferrite. The solidification sequence of different phases predicted by thermodynamic software agreed well with the experimental results, except the specific precipitation temperatures. The generated data and fundamental understanding will be helpful for the application of computational thermodynamic methods to predict the as-cast microstructure of Nb-bearing austenitic heat-resistant steels.

  3. Effects of N/C Ratio on Solidification Behaviors of Novel Nb-Bearing Austenitic Heat-Resistant Cast Steels for Exhaust Components of Gasoline Engines

    NASA Astrophysics Data System (ADS)

    Zhang, Yinhui; Li, Mei; Godlewski, Larry A.; Zindel, Jacob W.; Feng, Qiang

    2017-01-01

    In order to comply with more stringent environmental and fuel consumption regulations, novel Nb-bearing austenitic heat-resistant cast steels that withstand exhaust temperatures as high as 1,323 K (1,050 °C) is urgently demanded from automotive industries. In the current research, the solidification behavior of these alloys with variations of N/C ratio is investigated. Directional solidification methods were carried out to examine the microstructural development in mushy zones. Computational thermodynamic calculations under partial equilibrium conditions were performed to predict the solidification sequence of different phases. Microstructural characterization of the mushy zones indicates that N/C ratio significantly influenced the stability of γ-austenite and the precipitation temperature of NbC/Nb(C,N), thereby altering the solidification path, as well as the morphology and distribution of NbC/Nb(C,N) and γ-ferrite. The solidification sequence of different phases predicted by thermodynamic software agreed well with the experimental results, except the specific precipitation temperatures. The generated data and fundamental understanding will be helpful for the application of computational thermodynamic methods to predict the as-cast microstructure of Nb-bearing austenitic heat-resistant steels.

  4. Characterization of the sodium corrosion behavior of commercial austenitic steels

    SciTech Connect

    Shiels, S.A.; Bagnall, C.; Keeton, A.R.; Witkowski, R.E.; Anantatmula, R.P.

    1980-01-01

    During the course of an on-going evaluation of austenitic alloys for potential liquid metal fast breeder reactor (LMFBR) fuel pin cladding application, a series of commercial alloys was selected for study. The data obtained led to the recognition of an underlying pattern of behavior and enabled the prediction of surface chemistry changes. The changes in surface topographical development from alloy to alloy are shown and the important role played by the element molybdenum in this development is indicated. The presentation also illustrates how a total damage equation was evolved to encompass all aspects of weight loss and metal/sodium interactions: wall thinning ferrite layer formation and intergranular attack. The total damage equation represents a significant departure from the classical description of sodium corrosion in which weight loss is simply translated into wall thinning.

  5. Austenite Formation Kinetics During Rapid Heating in a Microalloyed Steel

    SciTech Connect

    BURNETT,M.E.; DYKHUIZEN,RONALD C.; KELLEY,J. BRUCE; PUSKAR,JOSEPH D.; ROBINO,CHARLES V.

    1999-09-07

    The model parameters for the normalized 1054V1 material were compared to parameters previously generated for 1026 steel, and the transformation behavior was relatively consistent. Validation of the model predictions by heating into the austenite plus undissolved ferrite phase field and rapidly quenching resulted in reasonable predictions when compared to the measured volume fractions from optical metallography. The hot rolled 1054V1 material, which had a much coarser grain size and a non-equilibrium volume fraction of pearlite, had significantly different model parameters and the on heating transformation behavior of this material was less predictable with the established model. The differences in behavior is consistent with conventional wisdom that normalized micro-structure produce a more consistent response to processing, and it reinforces the need for additional work in this area.

  6. Surface treatment and corrosion behaviour of austenitic stainless steel biomaterial

    NASA Astrophysics Data System (ADS)

    Oravcová, M.; Palček, P.; Zatkalíková, V.; Tański, T.; Król, M.

    2017-02-01

    In this article results from corrosion behaviour of austenitic stainless steel AISI 316L after different surface treatments are published. “As received” surface and surface after grinding resulted in lower resistance to pitting corrosion in physiological solution than electrochemically polished in H3PO4+H2SO4+H2O. Electropolishing also improved the surface roughness in comparison with the “as received” surface. Deposition of Al2O3 nanometric ALD coating improves the corrosion resistance of stainless steel in chloride-containing environment by shifting the breakdown potential toward more positive values. This oxide coating not only improves the corrosion resistance but it also affects the wettability of the surface, resulting in hydrophobic surface.

  7. Fatigue crack growth in metastable austenitic stainless steels

    SciTech Connect

    Mei, Z.; Chang, G.; Morris, J.W. Jr.

    1988-06-01

    The research reported here is an investigation of the influence of the mechanically induced martensitic transformation on the fatigue crack growth rate in 304-type steels. The alloys 304L and 304LN were used to test the influence of composition, the testing temperatures 298 K and 77 K were used to study the influence of test temperature, and various load ratios (R) were used to determine the influence of the load ratio. It was found that decreasing the mechanical stability of the austenite by changing composition or lowering temperature decreases the fatigue crack growth rate. The R-ratio effect is more subtle. The fatigue crack growth rate increases with increasing R-ratio, even though this change increases the martensite transformation. Transformation-induced crack closure can explain the results in the threshold regime, but cannot explain the R-ratio effect at higher cyclic stress intensities. 26 refs., 6 figs.

  8. Direct Observations of Austenite, Bainite and Martensite Formation During Arc Welding of 1045 Steel using Time Resolved X-Ray Diffraction

    SciTech Connect

    Elmer, J; Palmer, T; Babu, S; Zhang, W; DebRoy, T

    2004-02-17

    In-situ Time Resolved X-Ray Diffraction (TRXRD) experiments were performed during stationary gas tungsten arc (GTA) welding of AISI 1045 C-Mn steel. These synchrotron-based experiments tracked, in real time, phase transformations in the heat-affected zone of the weld under rapid heating and cooling conditions. The diffraction patterns were recorded at 100 ms intervals, and were later analyzed using diffraction peak profile analysis to determine the relative fraction of ferrite ({alpha}) and austenite ({gamma}) phases in each diffraction pattern. Lattice parameters and diffraction peak widths were also measured throughout the heating and cooling cycle of the weld, providing additional information about the phases that were formed. The experimental results were coupled with a thermofluid weld model to calculate the weld temperatures, allowing time-temperature transformation kinetics of the {alpha} {yields} {gamma} phase transformation to be evaluated. During heating, complete austenitization was observed in the heat affected zone of the weld and the kinetics of the {alpha} {yields} {gamma} phase transformation were modeled using a Johnson-Mehl-Avrami (JMA) approach. The results from the 1045 steel weld were compared to those of a 1005 low carbon steel from a previous study. Differences in austenitization rates of the two steels were attributed to differences in the base metal microstructures, particularly the relative amounts of pearlite and the extent of the allotriomorphic ferrite phase. During weld cooling, the austenite transformed to a mixture of bainite and martensite. In situ diffraction was able to distinguish between these two non-equilibrium phases based on differences in their lattice parameters and their transformation rates, resulting in the first real time x-ray diffraction observations of bainite and martensite formation made during welding.

  9. Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

    SciTech Connect

    Shirdel, M.; Mirzadeh, H.; Parsa, M.H.

    2015-05-15

    A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial austenitic 304L stainless steel with emphasis on the mechanisms and the microstructural evolution. A straightforward magnetic measurement device, which is based on the measurement of the saturation magnetization, for evaluating the amount of strain-induced martensite after cold rolling and reversion annealing in metastable austenitic stainless steels was used, which its results were in good consistency with those of the X-ray diffraction (XRD) method. A new parameter called the effective reduction in thickness was introduced, which corresponds to the reasonable upper bound on the obtainable martensite fraction based on the saturation in the martensitic transformation. By means of thermodynamics calculations, the reversion mechanisms were estimated and subsequently validated by experimental results. The signs of thermal martensitic transformation at cooling stage after reversion at 850 °C were found, which was attributed to the rise in the martensite start temperature due to the carbide precipitation. After the reversion treatment, the average grain sizes were around 500 nm and the nanometric grains of the size of ~ 65 nm were also detected. The intense grain refinement led to the enhanced mechanical properties and observation of the change in the work-hardening capacity and TRIP effect behavior. A practical map as a guidance for grain refining and characterizing the stability against grain growth was proposed, which shows the limitation of the reversion mechanism for refinement of grain size. - Graphical abstract: Display Omitted - Highlights: • Nano/ultrafine grained austenitic stainless steel through martensite treatment • A parameter descriptive of a reasonable upper bound on

  10. Thermal Stability of Austenite and Properties of Quenching & Partitioning (Q&P) Treated AHSS

    NASA Astrophysics Data System (ADS)

    Wu, R. M.; Wang, L.; Jin, X. J.

    A Fe-0.2C-1.87Mn-1.42Si-0.0405Al steel subjected to an appropriate Quenching & Partitioning treatment (Q&P) exhibits the combination of high tensile strength (1311 MPa) and high elongation (13.6%). The thermal decomposition of retained austenite in the as-treated steel has been studied at an elevated temperature of 500oC by means of differential scanning calorimetry (DSC). Activation energy has been obtained by performing a Kissinger analysis method. The DSC results show that the activation energy of thermal decomposition of the retained austenite in this Q&P steel is 221.3KJ/mol, which is in a good agreement with the result of retained austenite in similar chemical composition steel subjected to a TRansformation Induced Plasticity (TRIP) treatment. This investigation helps to investigate the stability of retained austenite in Q&P steels upon cooling or under external stress.

  11. HYDROGEN-ASSISTED FRACTURE IN FORGED TYPE 304L AUSTENITIC STAINLESS STEEL

    SciTech Connect

    Switzner, Nathan; Neidt, Ted; Hollenbeck, John; Knutson, J.; Everhart, Wes; Hanlin, R.; Bergen, R.; Balch, D. K.

    2012-09-06

    Austenitic stainless steels generally have good resistance to hydrogen-assisted fracture; however, structural designs for high-pressure gaseous hydrogen are constrained by the low strength of this class of material. Forging is used to increase the low strength of austenitic stainless steels, thus improving the efficiency of structural designs. Hydrogen-assisted racture, however, depends on microstructural details associated with manufacturing. In this study, hydrogen-assisted fracture of forged type 304L austenitic stainless steel is investigated. Microstructural variation in multi-step forged 304L was achieved by forging at different rates and temperatures, and by process annealing. High internal hydrogen content in forged type 304L austenitic stainless steel is achieved by thermal precharging in gaseous hydrogen and results in as much as 50% reduction of tensile ductility.

  12. Sandblasting induced stress release and enhanced adhesion strength of diamond films deposited on austenite stainless steel

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Ye, Jiansong; Zhang, Hangcheng; Feng, Tao; Chen, Jianqing; Hu, Xiaojun

    2017-08-01

    We firstly used sandblasting to treat austenite stainless steel and then deposited a Cr/CrN interlayer by close field unbalanced magnetron sputtering on it. After that, diamond films were prepared on the interlayer. It is found that the sandblasting process induces phase transition from austenite to martensite in the surface region of the stainless steel, which decreases thermal stress in diamond films due to lower thermal expansion coefficient of martensite phase compared with that of austenite phase. The sandblasting also makes stainless steel's surface rough and the Cr/CrN interlayer film inherits the rough surface. This decreases the carburization extent of the interlayer, increases nucleation density and modifies the stress distribution. Due to lower residual stress and small extent of the interlayer's carburization, the diamond film on sandblast treated austenite stainless steel shows enhanced adhesion strength.

  13. Residual stresses and retained austenite distribution and evolution in SAE 52100 steel under rolling contact loading

    SciTech Connect

    Dommarco, R.C.; Kozaczek, K.J.; Hahn, G.T.

    1996-07-01

    Residual stresses are introduced and modified during manufacturing and also by normal use. In this paper the changes in magnitude and distribution of residual stresses, attending the strain induced transformation of retained austenite are examined. Tests were conducted on SAE 52100 bearing steel with different amounts of retained austenite in a 5-ball-rod rolling contact fatigue machine. The tests were accelerated by applying well-controlled micro- indentations on the wear track and using rough balls. The magnitude and distribution of residual stresses and retained austenite were measured using x-ray diffraction techniques. The contribution of the residual stresses and amount of retained austenite to the rolling contact fatigue life is analyzed.

  14. Role of the Bogachev - Mints Concept of Metastability of Austenite in Choosing Wear-Resistant Materials

    NASA Astrophysics Data System (ADS)

    Schastlivtsev, V. M.; Filippov, M. A.

    2005-01-01

    The significance of the Bogachev - Mints concept of metastability of austenite for the choice of strain-hardenable steel, cast iron, and facing alloys resisting mechanical kinds of wear (cavitation-, erosion-, and abrasion-induced) is discussed.

  15. Retained Austenite in SAE 52100 Steel Post Magnetic Processing and Heat Treatment

    SciTech Connect

    Pappas, Nathaniel R; Watkins, Thomas R; Cavin, Odis Burl; Jaramillo, Roger A; Ludtka, Gerard Michael

    2007-01-01

    Steel is an iron-carbon alloy that contains up to 2% carbon by weight. Understanding which phases of iron and carbon form as a function of temperature and percent carbon is important in order to process/manufacture steel with desired properties. Austenite is the face center cubic (fcc) phase of iron that exists between 912 and 1394 C. When hot steel is rapidly quenched in a medium (typically oil or water), austenite transforms into martensite. The goal of the study is to determine the effect of applying a magnetic field on the amount of retained austenite present at room temperature after quenching. Samples of SAE 52100 steel were heat treated then subjected to a magnetic field of varying strength and time, while samples of SAE 1045 steel were heat treated then subjected to a magnetic field of varying strength for a fixed time while being tempered. X-ray diffraction was used to collect quantitative data corresponding to the amount of each phase present post processing. The percentage of retained austenite was then calculated using the American Society of Testing and Materials standard for determining the amount of retained austenite for randomly oriented samples and was plotted as a function of magnetic field intensity, magnetic field apply time, and magnetic field wait time after quenching to determine what relationships exist with the amount of retained austenite present. In the SAE 52100 steel samples, stronger field strengths resulted in lower percentages of retained austenite for fixed apply times. The results were inconclusive when applying a fixed magnetic field strength for varying amounts of time. When applying a magnetic field after waiting a specific amount of time after quenching, the analyses indicate that shorter wait times result in less retained austenite. The SAE 1045 results were inconclusive. The samples showed no retained austenite regardless of magnetic field strength, indicating that tempering removed the retained austenite. It is apparent

  16. Grain refinement of a nickel and manganese free austenitic stainless steel produced by pressurized solution nitriding

    SciTech Connect

    Mohammadzadeh, Roghayeh Akbari, Alireza

    2014-07-01

    Prolonged exposure at high temperatures during solution nitriding induces grain coarsening which deteriorates the mechanical properties of high nitrogen austenitic stainless steels. In this study, grain refinement of nickel and manganese free Fe–22.75Cr–2.42Mo–1.17N high nitrogen austenitic stainless steel plates was investigated via a two-stage heat treatment procedure. Initially, the coarse-grained austenitic stainless steel samples were subjected to an isothermal heating at 700 °C to be decomposed into the ferrite + Cr{sub 2}N eutectoid structure and then re-austenitized at 1200 °C followed by water quenching. Microstructure and hardness of samples were characterized using X-ray diffraction, optical and scanning electron microscopy, and micro-hardness testing. The results showed that the as-solution-nitrided steel decomposes non-uniformly to the colonies of ferrite and Cr{sub 2}N nitrides with strip like morphology after isothermal heat treatment at 700 °C. Additionally, the complete dissolution of the Cr{sub 2}N precipitates located in the sample edges during re-austenitizing requires longer times than 1 h. In order to avoid this problem an intermediate nitrogen homogenizing heat treatment cycle at 1200 °C for 10 h was applied before grain refinement process. As a result, the initial austenite was uniformly decomposed during the first stage, and a fine grained austenitic structure with average grain size of about 20 μm was successfully obtained by re-austenitizing for 10 min. - Highlights: • Successful grain refinement of Fe–22.75Cr–2.42Mo–1.17N steel by heat treatment • Using the γ → α + Cr{sub 2}N reaction for grain refinement of a Ni and Mn free HNASS • Obtaining a single phase austenitic structure with average grain size of ∼ 20 μm • Incomplete dissolution of Cr{sub 2}N during re-austenitizing at 1200 °C for long times • Reducing re-austenitizing time by homogenizing treatment before grain refinement.

  17. Strengthening and toughening mechanisms in low-c microalloyed martensitic steel as influenced by austenite conditioning

    NASA Astrophysics Data System (ADS)

    Kennett, Shane C.

    Three low-carbon ASTM A514 microalloyed steels were used to assess the effects of austenite conditioning on the microstructure and mechanical properties of martensite. A range of prior austenite grain sizes with and without thermomechanical processing were produced in a Gleeble RTM 3500 and direct-quenched. Samples in the as-quenched, low temperature tempered, and high temperature tempered conditions were studied. The microstructure was characterized with scanning electron microscopy, electron backscattered diffraction, transmission electron microscopy, and x-ray diffraction. The uniaxial tensile properties and Charpy V-notch properties were measured and compared with the microstructural features (prior austenite grain size, packet size, block size, lath boundaries, and dislocation density). For the equiaxed prior austenite grain conditions, prior austenite grain size refinement decreases the packet size, decreases the block size, and increases the dislocation density of as-quenched martensite. However, after high temperature tempering the dislocation density decreases with prior austenite grain size refinement. Thermomechanical processing increases the low angle substructure, increases the dislocation density, and decreases the block size of as-quenched martensite. The dislocation density increase and block size refinement is sensitive to the austenite grain size before ausforming. The larger prior austenite grain size conditions have a larger increase in dislocation density, but the small prior austenite grain size conditions have the largest refinement in block size. Additionally, for the large prior austenite grain size conditions, the packet size increases with thermomechanical processing. The strength of martensite is often related to an effective grain size or carbon concentration. For the current work, it was concluded that the strength of martensite is primarily controlled by the dislocation density and dislocation substructure; which is related to a grain

  18. Heat treatment giving a stable high temperature micro-structure in cast austenitic stainless steel

    DOEpatents

    Anton, Donald L.; Lemkey, Franklin D.

    1988-01-01

    A novel micro-structure developed in a cast austenitic stainless steel alloy and a heat treatment thereof are disclosed. The alloy is based on a multicomponent Fe-Cr-Mn-Mo-Si-Nb-C system consisting of an austenitic iron solid solution (.gamma.) matrix reinforced by finely dispersed carbide phases and a heat treatment to produce the micro-structure. The heat treatment includes a prebraze heat treatment followed by a three stage braze cycle heat treatment.

  19. Corrosion And Thermal Processing In Cold Gas Dynamic Spray Deposited Austenitic Stainless Steel Coatings

    DTIC Science & Technology

    2016-06-01

    THERMAL PROCESSING IN COLD GAS DYNAMIC SPRAY DEPOSITED AUSTENITIC STAINLESS STEEL COATINGS by John A Luhn June 2016 Thesis Advisor: Sarath...REPORT TYPE AND DATES COVERED Master’s thesis 4. TITLE AND SUBTITLE CORROSION AND THERMAL PROCESSING IN COLD GAS DYNAMIC SPRAY DEPOSITED AUSTENITIC...produced by the cold gas dynamic spray process on 316L stainless steel substrates. Previous work on the use of the low-pressure cold spray process to

  20. Fundamental study of the austenite formation and decomposition in low-silicon, aluminum added TRIP steels

    NASA Astrophysics Data System (ADS)

    Garcia-Gonzalez, Jose Enrique

    2005-11-01

    TRIP (Transformation Induced Plasticity) steels are under development for automotive applications that require high strength and excellent formability. Conventional TRIP steels consist of a multiphase microstructure comprised of a ferrite matrix with a dispersion of bainite and metastable retained austenite. The high ductility exhibited by these steels results from the transformation of the metastable retained austenite to martensite during straining. In conventional TRIP steel processing, the multiphase microstructure is obtained by controlled cooling from the alpha + gamma region to an isothermal holding temperature. During this holding, bainite forms and carbon is rejected out into the austenite, which lowers the Ms temperature and stabilizes the austenite to room temperature. In this research project, a fundamental study of a low-Si, Mo-Nb added cold rolled TRIP steel with and without Al additions was conducted. In this study, the recrystallization of cold-rolled ferrite, the formation of austenite during intercritical annealing and the characteristics of the decomposition of the intercritically annealed austenite by controlled cooling rates were systematically assessed. Of special interest were: (i) the effect of the initial hot band microstructure, (ii) the formation of epitaxial ferrite during cooling from the intercritical annealing temperature to the isothermal holding temperature, (iii) the influence of the intercritically annealed austenite on the formation of bainite during the isothermal holding temperature, and (iv) the influence of the processing variables on the type, amount, composition and stability of the retained austenite. During this research study, techniques such as OM, SEM, EBSD, TEM, XRD and Magnetometry were used to fully characterize the microstructures. Furthermore, a Gleeble 3500 unit at US Steel Laboratories was used for dilatometry studies and to simulate different CGL processing routes, from which specimens were obtained to evaluate

  1. The Composition of Precipitated Austenite in 5.5 Ni Steel.

    DTIC Science & Technology

    1980-10-01

    analysis of this austenite differ cuantitatively (cont . C’D , 1473 E ,TICN OF I NO. 6SIS 3,SO.ETE 4/N 0102 LF 014 660C SECURITY CLASSIrICATION Of Tk.% Pik...quantitatively in the retained austenite compositions they reveal. On the other hand, the two techniques are in qualitative agreement both with...uncertain, the qualitative trends revealed in the variation of composition with heat treatment are both consistent and plau- sible. They indicate a co

  2. Effect of the chemical composition and austenitizing conditions on the hardenability of 35GR steel

    NASA Astrophysics Data System (ADS)

    Potapov, A. I.; Malikov, I. T.; Urazov, V. I.; Semin, A. E.

    2010-12-01

    The effect of the content of impurity elements (in particular, chromium), the heating temperature before rolling, and the austenitizing schedule on the hardenability of boron-containing 35 GR steel is studied. It is shown that a change in the heating temperature of the steel for rolling by 50-100°C does not influence the hardenability depth, which is mainly dependent on the austenitizing temperature and time and the chromium content.

  3. Microstructure inhomogeneity of Fe-31%Ni alloy and stabilization of austenite.

    PubMed

    Dzevin, Ievgenij M

    2015-01-01

    Сrystal structure and mechanism of crystallization of Fe-Ni alloys were studied by methods of X-ray diffraction and metallography. It has been found that macro- and microstructure of austenitic alloy was essentially heterogeneous at the contact and free surfaces and in the volume of a ribbon. The indentified peculiarities of the austenitic phase in different areas of the ribbon are attributed to different cooling rates and the melt crystallization conditions.

  4. Study of Ferrite During Refinement of Prior Austenite Grains in Microalloyed Steel Continuous Casting

    NASA Astrophysics Data System (ADS)

    Liu, Jiang; Wen, Guanghua; Tang, Ping

    2017-08-01

    The formation of coarse prior austenite grain is a key factor to promote transverse crack, and the susceptibility to the transverse crack can be reduced by refining the austenite grain size. In the present study, the high-temperature confocal laser scanning microscope (CLSM) was used to simulate two types of double phase-transformation technologies. The distribution and morphology of ferrites under different cooling conditions were analyzed, and the effects of ferrite distribution and morphology on the double phase-transformation technologies were explored to obtain the suitable double phase-change technology for the continuous casting process. The results indicate that, under the thermal cycle TH0 [the specimens were cooled down to 913 K (640 °C) at a cooling rate of 5.0 K/s (5.0 °C/s)], the width of prior austenite grain boundaries was thick, and the dislocation density at grain boundaries was high. It had strong inhibition effect on crack propagation; under the thermal cycle TH1 [the specimens were cooled down to 1073 K (800 °C) at a cooling rate of 5.0 K/s (5.0 °C/s) and then to 913 K (640 °C) at a cooling rate of 1.0 K/s (1.0 °C/s)], the width of prior austenite grain boundary was thin, and the dislocation density at grain boundaries was low. It was beneficial to crack propagation. After the first phase change, the developed film-like ferrite along the austenite grain boundaries improved the nucleation conditions of new austenitic grains and removed the inhibition effect of the prior austenite grain boundaries on the austenite grain size.

  5. Experimental verification of physical model of pulsed laser welding

    SciTech Connect

    Jellison, J.L.; Keicher, D.M.

    1990-01-01

    Whereas most experimental and theoretical studies of the role of convection in fusion welding have been concerned with continuous heat sources, a pulsed heat source is the focus of this study. This is primarily an experimental study of the pulsed Nd:YAG laser welding of austenitic stainless steels. 12 refs., 9 figs.

  6. On the Stability of Reversely Formed Austenite and Related Mechanism of Transformation in an Fe-Ni-Mn Martensitic Steel Aided by Electron Backscattering Diffraction and Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Koohdar, Hamidreza; Nili-Ahmadabadi, Mahmoud; Habibi-Parsa, Mohammad; Jafarian, Hamid Reza; Bhattacharjee, Tilak; Tsuji, Nobuhiro

    2017-08-01

    The stability of reversely formed austenite and related mechanism of transformation were investigated against temperature and time in an Fe-9.6Ni-7.1Mn (at. pct) martensitic steel during intercritical annealing at a dual-phase (α + γ) region. Dilatometry, electron backscattering diffraction (EBSD), atom probe tomography (APT), and X-ray diffraction (XRD) were used to characterize the mechanism of reverse transformation. It was found that under intercritical annealing at 853 K (580 °C), when the heating rate is 20 K/s (20 °C/s), reverse transformation takes place through a mixed diffusion control mechanism, i.e., controlled by bulk diffusion and diffusion along the interface, where Ni controls the diffusion as its diffusivity is lower than that of Mn in the martensite and austenite. Increasing the intercritical annealing to 873 K (600 °C) at an identical heating rate of 20 K/s (20 °C/s) showed that reverse transformation occurs through a sequential combination of both martensitic and diffusional mechanisms. The transition temperature from diffusional to martensitic transformation was obtained close to 858 K (585 °C). Experimental results revealed that the austenite formed by the diffusional mechanism at 853 K (580 °C) mainly remains untransformed after cooling to ambient temperature due to the enrichment with Ni and Mn. It was also found that the stability of the reversely formed austenite by martensitic mechanism at 873 K (600 °C) is related to grain refinement.

  7. Structure and properties of high-temperature austenitic steels for superheater tubes

    NASA Astrophysics Data System (ADS)

    Blinov, V. M.

    2009-12-01

    The structure and properties of high-temperature austenitic steels intended for superheater tubes are analyzed. Widely used Kh18N10T (AISI 304) and Kh16N13M3 (AISI 316) steels are found not to ensure a stable austenitic structure and stable properties during long-term thermal holding under stresses. The hardening of austenitic steels by fine particles of vanadium and niobium carbides and nitrides and γ'-phase and Fe2W and Fe2Mo Laves phase intermetallics is considered. The role of Cr23C6 chromium carbides, the σ phase, and coarse precipitates of an M 3B2 phase and a boron-containing eutectic in decreasing the time to failure and the stress-rupture strength of austenitic steels is established. The mechanism of increasing the stress-rupture strength of steels by boron additions is described. The chemical compositions, mechanical properties, stress-rupture strength, and creep characteristics of Russian and foreign austenitic steels used or designed for superheater tubes intended for operation under stress conditions at temperatures above 600°C are presented. The conditions are found for increasing the strength, plasticity, and thermodeformation stability of austenite in steels intended for superheater tubes operating at 700°C under high stresses for a long time.

  8. Nonisothermal Austenite Grain Growth Kinetics in a Microalloyed X80 Linepipe Steel

    NASA Astrophysics Data System (ADS)

    Banerjee, Kumkum; Militzer, Matthias; Perez, Michel; Wang, Xiang

    2010-12-01

    Nonisothermal austenite grain growth kinetics under the influence of several combinations of Nb, Ti, and Mo containing complex precipitates has been studied in a microalloyed linepipe steel. The goal of this study is the development of a grain growth model to predict the austenite grain size in the weld heat affected zone (HAZ). Electron microscopy investigations of the as-received steel proved the presence of Ti-rich, Nb-rich, and Mo-rich precipitates. The steel has then been subjected to austenitizing heat treatments to selected peak temperatures at various heating rates that are typical for thermal cycles in the HAZ. Thermal cycles have a strong effect on the final austenite grain size. Using a mean field approach, a model is proposed for the dissolution of Nb-rich precipitates. This model has been coupled to a Zener-type austenite grain growth model in the presence of pinning particles. This coupling leads to accurate prediction of the austenite grain size along the nonisothermal heating path simulating selected thermal profiles of the HAZ.

  9. Influence of Temperature and Grain Size on Austenite Stability in Medium Manganese Steels

    NASA Astrophysics Data System (ADS)

    Zhang, Yulong; Wang, Li; Findley, Kip O.; Speer, John G.

    2017-05-01

    With an aim to elucidate the influence of temperature and grain size on austenite stability, a commercial cold-rolled 7Mn steel was annealed at 893 K (620 °C) for times varying between 3 minutes and 96 hours to develop different grain sizes. The austenite fraction after 3 minutes was 34.7 vol pct, and at longer times was around 40 pct. An elongated microstructure was retained after shorter annealing times while other conditions exhibited equiaxed ferrite and austenite grains. All conditions exhibit similar temperature dependence of mechanical properties. With increasing test temperature, the yield and tensile strength decrease gradually, while the uniform and total elongation increase, followed by an abrupt drop in strength and ductility at 393 K (120 °C). The Olson-Cohen model was applied to fit the transformed austenite fractions for strained tensile samples, measured by means of XRD. The fit results indicate that the parameters α and β decrease with increasing test temperature, consistent with increased austenite stability. The 7Mn steels exhibit a distinct temperature dependence of the work hardening rate. Optimized austenite stability provides continuous work hardening in the temperature range of 298 K to 353 K (25 °C to 80 °C). The yield and tensile strengths have a strong dependence on grain size, although grain size variations have less effect on uniform and total elongation.

  10. Influence of Temperature and Grain Size on Austenite Stability in Medium Manganese Steels

    NASA Astrophysics Data System (ADS)

    Zhang, Yulong; Wang, Li; Findley, Kip O.; Speer, John G.

    2017-02-01

    With an aim to elucidate the influence of temperature and grain size on austenite stability, a commercial cold-rolled 7Mn steel was annealed at 893 K (620 °C) for times varying between 3 minutes and 96 hours to develop different grain sizes. The austenite fraction after 3 minutes was 34.7 vol pct, and at longer times was around 40 pct. An elongated microstructure was retained after shorter annealing times while other conditions exhibited equiaxed ferrite and austenite grains. All conditions exhibit similar temperature dependence of mechanical properties. With increasing test temperature, the yield and tensile strength decrease gradually, while the uniform and total elongation increase, followed by an abrupt drop in strength and ductility at 393 K (120 °C). The Olson-Cohen model was applied to fit the transformed austenite fractions for strained tensile samples, measured by means of XRD. The fit results indicate that the parameters α and β decrease with increasing test temperature, consistent with increased austenite stability. The 7Mn steels exhibit a distinct temperature dependence of the work hardening rate. Optimized austenite stability provides continuous work hardening in the temperature range of 298 K to 353 K (25 °C to 80 °C). The yield and tensile strengths have a strong dependence on grain size, although grain size variations have less effect on uniform and total elongation.

  11. On the measurement of austenite in supermartensitic stainless steel by X-ray diffraction

    SciTech Connect

    Tolchard, Julian Richard; Sømme, Astri; Solberg, Jan Ketil; Solheim, Karl Gunnar

    2015-01-15

    Sections of a 13Cr supermartensitic stainless steel were investigated to determine the optimum sample preparation for measurement of the austenite content by X-ray diffraction. The surface of several samples was mechanically ground or polished using media of grit sizes in the range 1–120 μm. The strained surface layer was afterwards removed stepwise by electropolishing, and the austenite content measured at each step. It was found that any level of mechanical grinding or polishing results in a reduction of the measured austenite fraction relative to the true bulk value, and that coarser grinding media impart greater damage and greater reduction in the measured austenite content. The results thus highlight the importance of the electropolishing step in preparation of such samples, but suggest that the American Society for Testing and Materials standard E975-03 substantially overestimates the amount of material which needs to be removed to recover the true “bulk” content. - Highlights: • Quantitative Rietveld analysis of austenite/martensite ratio in supermartensitic stainless steels • Critical evaluation of sample preparation for residual austenite measurements by X-ray diffraction • Highlighting of the importance of electropolishing as a final preparation step.

  12. Tailoring plasticity of austenitic stainless steels for nuclear applications: Review of mechanisms controlling plasticity of austenitic steels below 400 °C

    NASA Astrophysics Data System (ADS)

    Meric de Bellefon, G.; van Duysen, J. C.

    2016-07-01

    AISI 304 and 316 austenitic stainless steels were invented in the early 1900s and are still trusted by materials and mechanical engineers in numerous sectors because of their good combination of strength, ductility, and corrosion resistance, and thanks to decades of experience and data. This article is part of an effort focusing on tailoring the plasticity of both types of steels to nuclear applications. It provides a synthetic and comprehensive review of the plasticity mechanisms in austenitic steels during tensile tests below 400 °C. In particular, formation of twins, extended stacking faults, and martensite, as well as irradiation effects and grain rotation are discussed in details.

  13. Mechanism-Based Modeling for Low Cycle Fatigue of Cast Austenitic Steel

    NASA Astrophysics Data System (ADS)

    Wu, Xijia; Quan, Guangchun; Sloss, Clayton

    2017-06-01

    A mechanism-based approach—the integrated creep-fatigue theory (ICFT)—is used to model low cycle fatigue behavior of 1.4848 cast austenitic steel over the temperature range from room temperature (RT) to 1173 K (900 °C) and the strain rate range from of 2 × 10-4 to 2 × 10-2 s-1. The ICFT formulates the material's constitutive equation based on the physical strain decomposition into mechanism strains, and the associated damage accumulation consisting of crack nucleation and propagation in coalescence with internally distributed damage. At room temperature, the material behavior is controlled by plasticity, resulting in a rate-independent and cyclically stable behavior. The material exhibits significant cyclic hardening at intermediate temperatures, 673 K to 873 K (400 °C to 600 °C), with negative strain rate sensitivity, due to dynamic strain aging. At high temperatures >1073 K (800 °C), time-dependent deformation is manifested with positive rate sensitivity as commonly seen in metallic materials at high temperature. The ICFT quantitatively delineates the contribution of each mechanism in damage accumulation, and predicts the fatigue life as a result of synergistic interaction of the above identified mechanisms. The model descriptions agree well with the experimental and fractographic observations.

  14. Welding of 316L Austenitic Stainless Steel with Activated Tungsten Inert Gas Process

    NASA Astrophysics Data System (ADS)

    Ahmadi, E.; Ebrahimi, A. R.

    2015-02-01

    The use of activating flux in TIG welding process is one of the most notable techniques which are developed recently. This technique, known as A-TIG welding, increases the penetration depth and improves the productivity of the TIG welding. In the present study, four oxide fluxes (SiO2, TiO2, Cr2O3, and CaO) were used to investigate the effect of activating flux on the depth/width ratio and mechanical property of 316L austenitic stainless steel. The effect of coating density of activating flux on the weld pool shape and oxygen content in the weld after the welding process was studied systematically. Experimental results indicated that the maximum depth/width ratio of stainless steel activated TIG weld was obtained when the coating density was 2.6, 1.3, 2, and 7.8 mg/cm2 for SiO2, TiO2, Cr2O3, and CaO, respectively. The certain range of oxygen content dissolved in the weld, led to a significant increase in the penetration capability of TIG welds. TIG welding with active fluxes can increase the delta-ferrite content and improves the mechanical strength of the welded joint.

  15. Study of ultrasonic characterization and propagation in austenitic welds: The MOSAICS project

    SciTech Connect

    Chassignole, Bertrand; Recolin, Patrick; Leymarie, Nicolas; Gueudré, Cécile; Guy, Philippe; Elbaz, Deborah

    2015-03-31

    Regulatory requirements enforce a volumetric inspection of welded components of nuclear equipments. However, the multi-pass austenitic welds are characterized by anisotropic and heterogeneous structures which lead to numerous disturbances of the ultrasonic beam. The MOSAICS project supported by the ANR (French National Research Agency) aims at matching various approaches to improve the prediction of the ultrasonic testing in those welds. The first stage consists in characterizing the weld structure (determination of the columnar grain orientation and measurements of elastic constants and attenuation coefficients). The techniques of characterization provide input data for the modeling codes developed in another task of the project. For example, a 3D version of the finite elements code ATHENA is developed by EDF R and D to take into account anisotropic texture in any direction. Semi-analytical models included in CIVA software are also improved to better predict the ultrasonic propagation in highly anisotropic and heterogeneous structures. The last stage deals with modeling codes validation based on experimental inspections on representative mock-ups containing calibrated defects. The objective of this paper is to give an overview of the MOSAICS project and to present specific results illustrating the various tasks.

  16. Irradiation testing of 316L(N)-IG austenitic stainless steel for ITER

    NASA Astrophysics Data System (ADS)

    van Osch, E. V.; Horsten, M. G.; de Vries, M. I.

    1998-10-01

    In the frame work of the European Fusion Technology Programme and the International Thermonuclear Experimental Reactor (ITER), ECN is investigating the irradiation behaviour of the structural materials for ITER. The main structural material for ITER is austenitic stainless steel Type 316L(N)-IG. The operating temperatures of (parts of) the components are envisaged to range between 350 and 700 K. A significant part of the dose-temperature domain of irradiation conditions relevant for ITER has already been explored, there is, however, very little data at about 600 K. Available data tend to indicate a maximum in the degradation of the mechanical properties after irradiation at this temperature, e.g. a minimum in ductility and a maximum of hardening. Therefore an irradiation program for plate material 316L(N)-IG, its Electron Beam (EB) weld and Tungsten Inert Gas (TIG) weld metal, and also including Hot Isostatically Pressed (HIP) 316L(N) powder and solid-solid joints, was set up in 1995. Irradiations have been carried out in the High Flux Reactor (HFR) in Petten at a temperature of 600 K, at dose levels from 1 to 10 dpa. The paper presents the currently available post-irradiation test results. Next to tensile and fracture toughness data on plate, EB and TIG welds, first results of powder HIP material are included.

  17. Mechanism-Based Modeling for Low Cycle Fatigue of Cast Austenitic Steel

    NASA Astrophysics Data System (ADS)

    Wu, Xijia; Quan, Guangchun; Sloss, Clayton

    2017-09-01

    A mechanism-based approach—the integrated creep-fatigue theory (ICFT)—is used to model low cycle fatigue behavior of 1.4848 cast austenitic steel over the temperature range from room temperature (RT) to 1173 K (900 °C) and the strain rate range from of 2 × 10-4 to 2 × 10-2 s-1. The ICFT formulates the material's constitutive equation based on the physical strain decomposition into mechanism strains, and the associated damage accumulation consisting of crack nucleation and propagation in coalescence with internally distributed damage. At room temperature, the material behavior is controlled by plasticity, resulting in a rate-independent and cyclically stable behavior. The material exhibits significant cyclic hardening at intermediate temperatures, 673 K to 873 K (400 °C to 600 °C), with negative strain rate sensitivity, due to dynamic strain aging. At high temperatures >1073 K (800 °C), time-dependent deformation is manifested with positive rate sensitivity as commonly seen in metallic materials at high temperature. The ICFT quantitatively delineates the contribution of each mechanism in damage accumulation, and predicts the fatigue life as a result of synergistic interaction of the above identified mechanisms. The model descriptions agree well with the experimental and fractographic observations.

  18. Intergranular stress-corrosion cracking of austenitic stainless steels in PWR boric-acid storage systems

    SciTech Connect

    Macdonald, D.D.; Cragnolino, G.A.; Olemacher, J.; Chen, T.Y.; Dhawale, S.

    1982-08-01

    A review is presented of the available literature on the intergranular stress corrosion cracking (IGSCC) of austenitic stainless steels at temperatures below 100/sup 0/C, as well as the results of an experimental investigation of the IGSCC of Types 304, 304L, and 316L stainless steels conducted in boric acid environments of the type employed in pressurized nuclear reactors (PWRs) for nuclear shim control. The susceptibility of furnace sensitized Type 304SS to IGSCC was studied using slow strain rate tests as a function of pH, temperature, potential, and concentration of suspected contaminants: chloride, thiosulfate, and tetrathionate. Possible alternate alloys, such as Types 304L and 316L stainless steels, were also tested under those specific conditions that render Type 304SS susceptible to cracking. Corrosion potentials that can be attained in air-saturated boric acid solutions in the presence of the above mentioned species were measured in order to evaluate the propensity towards intergranular cracking under conditions simulating those that prevail in service.

  19. Use of plasma arc welding process to combat hydrogen metallic disbonding of austenitic stainless steel claddings

    SciTech Connect

    Alexandrov, O.A. ); Steklov, O.I.; Alexeev, A.V. )

    1993-11-01

    A separation type crack, metallic disbonding, occurred between austenitic stainless steel weld metal cladding and 2 1/4Cr-1Mo base metal in the hydrodesulfurizing reactor of an oil refining plant. For stainless steel cladding, the submerged arc welding (SAW) process with a strip electrode is usually applied, but the authors experimented with the plasma arc welding (PAW) process with hot wire electrode for the cladding. The metallic disbonding is considered to be attributed to hydrogen accumulation at the transition zone and has been generally studied on a laboratory scale using an autoclave. The authors used a electrolytic hydrogen charging technique for the sake of experimental simplicity and made a comparison with the results for gaseous hydrogen charging. The main conclusions obtained were follows: The PAW stainless steel weld metal cladding is more resistant to metallic disbonding with the PAW process is explained by the desirable microstructure and properties of the first layer of weld metal at the transition zone. Electrolytic hydrogen charging pretty well reproduces the results of autoclave gas phase charging.

  20. Multi-response optimization of CO 2 laser-welding process of austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Benyounis, K. Y.; Olabi, A. G.; Hashmi, M. S. J.

    2008-02-01

    Recently, laser welding of austenitic stainless steel has received great attention in industry. This is due to its widespread application in petroleum refinement stations, power plants, the pharmaceutical industry and also in households. Therefore, mechanical properties should be controlled to obtain good welded joints. The welding process should be optimized by the proper mathematical models. In this research, the tensile strength and impact strength along with the joint-operating cost of laser-welded butt joints made of AISI304 was investigated. Design-expert software was used to establish the design matrix and to analyze the experimental data. The relationships between the laser-welding parameters (laser power, welding speed and focal point position) and the three responses (tensile strength, impact strength and joint-operating cost) were established. Also, the optimization capabilities in design-expert software were used to optimize the welding process. The developed mathematical models were tested for adequacy using analysis of variance and other adequacy measures. In this investigation, the optimal welding conditions were identified in order to increase the productivity and minimize the total operating cost. Overlay graphs were plotted by superimposing the contours for the various response surfaces. The process parameters effect was determined and the optimal welding combinations were tabulated.

  1. Flux effect on the ion-beam nitriding of austenitic stainless-steel AISI 304L

    SciTech Connect

    Abrasonis, G.; Riviere, J.P.; Templier, C.; Pranevicius, L.; Barradas, N.P.

    2005-06-15

    The effect of flux and Ar pretreatment during ion-beam nitriding of austenitic stainless steel is investigated. The ion energy and temperature were 1.2 keV and 400 deg. C, respectively, the ion current densities were 0.5, 0.67, and 0.83 mA cm{sup -2}. The nitrogen distribution profiles were measured using nuclear reaction analysis. The obtained nitrogen distribution profiles were analyzed by the means of the nitrided layer thickness evolution due to sputtering and diffusion and the model of trapping-detrapping. Both approaches could fit well the experimental results, however, different diffusion coefficients have to be assumed for each current density. In addition, the diffusion coefficients are higher for higher current densities. On the other hand, it is shown that the pretreatment with Ar-ion beam at nitriding temperatures produces only a thermal effect without any other influence on the following nitrogen diffusion. The results are discussed in relation with surface and temperature effects and atomic transport mechanisms.

  2. Crack growth rates of irradiated austenitic stainless steel weld heat affected zone in BWR environments.

    SciTech Connect

    Chopra, O. K.; Alexandreanu, B.; Gruber, E. E.; Daum, R. S.; Shack, W. J.; Energy Technology

    2006-01-31

    Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of reactor pressure vessels because of their superior fracture toughness. However, exposure to high levels of neutron irradiation for extended periods can exacerbate the corrosion fatigue and stress corrosion cracking (SCC) behavior of these steels by affecting the material microchemistry, material microstructure, and water chemistry. Experimental data are presented on crack growth rates of the heat affected zone (HAZ) in Types 304L and 304 SS weld specimens before and after they were irradiated to a fluence of 5.0 x 10{sup 20} n/cm{sup 2} (E > 1 MeV) ({approx} 0.75 dpa) at {approx}288 C. Crack growth tests were conducted under cycling loading and long hold time trapezoidal loading in simulated boiling water reactor environments on Type 304L SS HAZ of the H5 weld from the Grand Gulf reactor core shroud and on Type 304 SS HAZ of a laboratory-prepared weld. The effects of material composition, irradiation, and water chemistry on growth rates are discussed.

  3. Effects of LWR coolant environments on fatigue lives of austenitic stainless steels

    SciTech Connect

    Chopra, O.K.; Gavenda, D.J.

    1997-07-01

    The ASME Boiler and Pressure Vessel Code fatigue design curves for structural materials do not explicitly address the effects of reactor coolant environments on fatigue life. Recent test data indicate a significant decrease in fatigue life of pressure vessel and piping materials in light water reactor (LWR) environments. Fatigue tests have been conducted on Types 304 and 316NG stainless steel in air and LWR environments to evaluate the effects of various material and loading variables, e.g., steel type, strain rate, dissolved oxygen (DO) in water, and strain range, on fatigue lives of these steels. The results confirm the significant decrease in fatigue life in water. The environmentally assisted decrease in fatigue life depends both on strain rate and DO content in water. A decrease in strain rate from 0.4 to 0.004%/s decreases fatigue life by a factor of {approx} 8. However, unlike carbon and low-alloy steels, environmental effects are more pronounced in low-DO than in high-DO water. At {approx} 0.004%/s strain rate, reduction in fatigue life in water containing <10 ppb D is greater by a factor of {approx} 2 than in water containing {ge} 200 ppb DO. Experimental results have been compared with estimates of fatigue life based on the statistical model. The formation and growth of fatigue cracks in austenitic stainless steels in air and LWR environments are discussed.

  4. Impact of the nanostructuration on the corrosion resistance and hardness of irradiated 316 austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Hug, E.; Prasath Babu, R.; Monnet, I.; Etienne, A.; Moisy, F.; Pralong, V.; Enikeev, N.; Abramova, M.; Sauvage, X.; Radiguet, B.

    2017-01-01

    The influence of grain size and irradiation defects on the mechanical behavior and the corrosion resistance of a 316 stainless steel have been investigated. Nanostructured samples were obtained by severe plastic deformation using high pressure torsion. Both coarse grain and nanostructured samples were irradiated with 10 MeV 56Fe5+ ions. Microstructures were characterized using transmission electron microscopy and atom probe tomography. Surface mechanical properties were evaluated thanks to hardness measurements and the corrosion resistance was studied in chloride environment. Nanostructuration by high pressure torsion followed by annealing leads to enrichment in chromium at grain boundaries. However, irradiation of nanostructured samples implies a chromium depletion of the same order than depicted in coarse grain specimens but without metallurgical damage like segregated dislocation loops or clusters. Potentiodynamic polarization tests highlight a definitive deterioration of the corrosion resistance of coarse grain steel with irradiation. Downsizing the grain to a few hundred of nanometers enhances the corrosion resistance of irradiated samples, despite the fact that the hardness of nanocrystalline austenitic steel is only weakly affected by irradiation. These new experimental results are discussed in the basis of couplings between mechanical and electrical properties of the passivated layer thanks to impedance spectroscopy measurements, hardness properties of the surfaces and local microstructure evolutions.

  5. Effect of Austenitizing Temperature on Microstructure and Mechanical Properties of Semi-High-Speed Steel Cold-Forged Rolls

    NASA Astrophysics Data System (ADS)

    Wu, Qiong; Sun, Da-Le; Liu, Chang-Sheng

    2009-10-01

    The effect of austenitizing temperature on the microstructure and mechanical properties of semi-high-speed steel (S-HSS) cold-forged rolls was investigated. Low-temperature austenitizing below 1313 K induced carbide coarsening during subsequent tempering at 973 K due to the nucleation effect of undissolved M7C3. On the other hand, the heavy dissolution of M7C3 above 1353 K caused the fine carbide formation on lath and plate boundaries, which retarded the subgrain growth during tempering. The increase in strength with increasing austenitizing temperature was attributed to the fine carbide distribution and the high dislocation density. Furthermore, as the austenitizing temperature increased, the impact energy markedly reduced, due to the large prior austenite grain size and the high strength. Finally, based on the microstructure and mechanical properties, an optimal austenitizing temperature range between 1313 and 1333 K was determined.

  6. Expanding hollow metal rings

    DOEpatents

    Peacock, Harold B [Evans, GA; Imrich, Kenneth J [Grovetown, GA

    2009-03-17

    A sealing device that may expand more planar dimensions due to internal thermal expansion of a filler material. The sealing material is of a composition such that when desired environment temperatures and internal actuating pressures are reached, the sealing materials undergoes a permanent deformation. For metallic compounds, this permanent deformation occurs when the material enters the plastic deformation phase. Polymers, and other materials, may be using a sealing mechanism depending on the temperatures and corrosivity of the use. Internal pressures are generated by either rapid thermal expansion or material phase change and may include either liquid or solid to gas phase change, or in the gaseous state with significant pressure generation in accordance with the gas laws. Sealing material thickness and material composition may be used to selectively control geometric expansion of the seal such that expansion is limited to a specific facing and or geometric plane.

  7. Mechanically expandable annular seal

    DOEpatents

    Gilmore, R.F.

    1983-07-19

    A mechanically expandable annular reusable seal assembly to form an annular hermetic barrier between two stationary, parallel, and planar containment surfaces is described. A rotatable ring, attached to the first surface, has ring wedges resembling the saw-tooth array of a hole saw. Matching seal wedges are slidably attached to the ring wedges and have their motion restricted to be perpendicular to the second surface. Each seal wedge has a face parallel to the second surface. An annular elastomer seal has a central annular region attached to the seal wedges' parallel faces and has its inner and outer circumferences attached to the first surface. A rotation of the ring extends the elastomer seal's central region perpendicularly towards the second surface to create the fluid tight barrier. A counter rotation removes the barrier. 6 figs.

  8. Mechanically expandable annular seal

    DOEpatents

    Gilmore, Richard F.

    1983-01-01

    A mechanically expandable annular reusable seal assembly to form an annular hermetic barrier between two stationary, parallel, and planar containment surfaces. A rotatable ring, attached to the first surface, has ring wedges resembling the saw-tooth array of a hole saw. Matching seal wedges are slidably attached to the ring wedges and have their motion restricted to be perpendicular to the second surface. Each seal wedge has a face parallel to the second surface. An annular elastomer seal has a central annular region attached to the seal wedges' parallel faces and has its inner and outer circumferences attached to the first surface. A rotation of the ring extends the elastomer seal's central region perpendicularly towards the second surface to create the fluidtight barrier. A counterrotation removes the barrier.

  9. Residual Stress Analysis in Girth-welded Ferritic and Austenitic Steel Pipes Using Neutron and X-Ray Diffraction

    SciTech Connect

    Hempel, Nico; Bunn, Jeffrey R; Nitschke-Pagel, Thomas; Payzant, E Andrew; Dilger, Klaus

    2016-01-01

    This paper is dedicated to the thorough experimental analysis of the residual stresses in the vicinity of tubular welds and the mechanisms involved in their formation. Pipes made of a ferritic-pearlitic structural steel and an austenitic stainless steel are investigated in this study. The pipes feature a similar geometry and are MAG welded with two passes and comparable parameters. Residual strain mappings are carried out using X-ray and neutron diffraction. The combined use of both techniques permits both near-surface and through-wall analyses of the residual stresses. The findings allow for a consistent interpretation of the mechanisms accounting for the formation of the residual stress fields due to the welding process. Since the results are similar for both materials, it can be concluded that residual stresses induced by phase transformations, which can occur in the structural steel, play a minor role in this regard.

  10. Ion-plasma nitriding of austenitic steel in a low-pressure low-frequency inductive discharge with ferrite core

    NASA Astrophysics Data System (ADS)

    Isupov, M. V.; Pinaev, V. A.; Mul, D. O.; Belousova, N. S.

    2017-05-01

    An experimental investigation of ion-plasma nitriding of austenitic stainless steel AISI 321 in a low-frequency (100 kHz) nitrogen inductive discharge has been performed for the nitrogen pressure of 7 Pa, nitrogen ion densities of 1010-1011 cm-3, sample temperatures of 440-590 °C, the densities of current on the sample surface of 1.2-3.3 mA/cm2, sample biases of -500 and -750 V. The time of ion-plasma treatment was 20 and 60 min. It is shown that even for the short (20 min.) ion-plasma treatment in the low-frequency inductive discharge, formation of nitrided layers with the thickness of up to 40 μm and microhardness of up to 9 GPa is observed.

  11. A model for determination of austenite decomposition kinetics during continuous cooling on the run-out table

    NASA Astrophysics Data System (ADS)

    Serajzadeh, S.; Mirbagheri, S. M. H.

    2006-03-01

    A model has been proposed to predict phase transformation kinetics and temperature variations on the run-out table of the hot strip rolling process. The finite element and the finite difference methods have been employed to solve equations of heat transfer and phase transformation kinetics. In order to avoid numerical instabilities in the thermal analysis, the governing conduction-convection equation is first transformed to the standard form and then the finite element method has been used to solve this equation. At the same time, a second-order rate equation is coupled with the heat transfer model for including austenite decomposition kinetics in heat transfer analysis. A comparison is made between predicted and experimental cooling curves of a low carbon steel to verify the validity of the model.

  12. Kinetics and critical conditions for initiation of dynamic recrystallization during hot compression deformation of AISI 321 austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Ghazani, Mehdi Shaban; Eghbali, Beitallah; Ebrahimi, Gholamreza

    2017-09-01

    Dynamic recrystallization behavior of AISI 321 austenitic stainless steel were studied using hot compression tests over the range of temperatures from 900 °C to 1200 °C and strain rates from 0.001 s-1 to 1 s-1. The critical strain and stress for initiation of dynamic recrystallization were determined by plotting strain hardening rate vs. stress curves and a constitutive equation describing the flow stress at strains lower than peak strain. Also, the strain at maximum flow softening was obtained and the effect of deformation conditions (Z parameter) on the critical strain and stress were analyzed. Finally, the volume fraction of dynamic recrystallization was calculated at different deformation conditions using these critical values. Results showed that the model used for predicting the kinetics of dynamic recrystallization has a great consistency with the data, in the form of θ-ɛ curves, directly acquired from experimental flow curves.

  13. Characterization of friction stir welded joint of low nickel austenitic stainless steel and modified ferritic stainless steel

    NASA Astrophysics Data System (ADS)

    Mondal, Mounarik; Das, Hrishikesh; Ahn, Eun Yeong; Hong, Sung Tae; Kim, Moon-Jo; Han, Heung Nam; Pal, Tapan Kumar

    2017-09-01

    Friction stir welding (FSW) of dissimilar stainless steels, low nickel austenitic stainless steel and 409M ferritic stainless steel, is experimentally investigated. Process responses during FSW and the microstructures of the resultant dissimilar joints are evaluated. Material flow in the stir zone is investigated in detail by elemental mapping. Elemental mapping of the dissimilar joints clearly indicates that the material flow pattern during FSW depends on the process parameter combination. Dynamic recrystallization and recovery are also observed in the dissimilar joints. Among the two different stainless steels selected in the present study, the ferritic stainless steels shows more severe dynamic recrystallization, resulting in a very fine microstructure, probably due to the higher stacking fault energy.

  14. Intermetallic Strengthened Alumina-Forming Austenitic Steels for Energy Applications

    SciTech Connect

    Hu, Bin; Baker, Ian

    2016-03-31

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, the materials required must be strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and L12 precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. Microstructural and microchemical analyses of the recently developed alumina-forming austenitic (AFA) steels (Fe-14Cr-32Ni-3Nb-3Al-2Ti-based) indicated they are strengthened by Ni3Al(Ti) L12, NiAl B2, Fe2Nb Laves phase and MC carbide precipitates. Different thermomechanical treatments (TMTs) were performed on these stainless steels in an attempt to further improve their mechanical properties. The thermo-mechanical processing produced nanocrystalline grains in AFA alloys and dramatically increased their yield strength at room temperature. Unfortunately, the TMTs didn’t increase the yield strengths of AFA alloys at ≥700ºC. At these temperatures, dislocation climb is the dominant mechanism for deformation of TMT alloys according to strain rate jump tests. After the characterization of aged AFA alloys, we found that the largest strengthening effect from L12 precipitates can be obtained by aging for less than 24 h. The coarsening behavior of the L12 precipitates was not influenced by carbon and boron additions. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these AFA steels after creep tests. Though the Laves and B2-NiAl phase precipitated along the boundaries can improve the creep properties, cracks were

  15. Characterization of the Carbon and Retained Austenite Distributions in Martensitic Medium Carbon, Low Alloy, Steel

    SciTech Connect

    Sherman, D. H.; Cross, Steven M; Kim, Sangho; Grandjean, F.; Long, G. J.; Miller, Michael K

    2007-01-01

    The retained austenite content and carbon distribution in martensite were determined as a function of cooling rate and temper temperature in steel that contained 1.31 at. pct C, 3.2 at. pct Si, and 3.2 at. pct non-iron metallic elements. Mossbauer spectroscopy, transmission electron microscopy (TEM), transmission synchrotron X-ray diffraction (XRD), and atom probe tomography were used for the microstructural analyses. The retained austenite content was an inverse, linear function of cooling rate between 25 and 560 K/s. The elevated Si content of 3.2 at. pct did not shift the start of austenite decomposition to higher tempering temperatures relative to SAE 4130 steel. The minimum tempering temperature for complete austenite decomposition was significantly higher (>650 C) than for SAE 4130 steel ({approx}300 C). The tempering temperatures for the precipitation of transition carbides and cementite were significantly higher (>400 C) than for carbon steels (100 C to 200 C and 200 C to 350 C), respectively. Approximately 90 pct of the carbon atoms were trapped in Cottrell atmospheres in the vicinity of the dislocation cores in dislocation tangles in the martensite matrix after cooling at 560 K/s and aging at 22 C. The 3.2 at. pct Si content increased the upper temperature limit for stable carbon clusters to above 215 C. Significant autotempering occurred during cooling at 25 K/s. The proportion of total carbon that segregated to the interlath austenite films decreased from 34 to 8 pct as the cooling rate increased from 25 to 560 K/s. Developing a model for the transfer of carbon from martensite to austenite during quenching should provide a means for calculating the retained austenite. The maximum carbon content in the austenite films was 6 to 7 at. pct, both in specimens cooled at 560 K/s and at 25 K/s. Approximately 6 to 7 at. pct carbon was sufficient to arrest the transformation of austenite to martensite. The chemical potential of carbon is the same in martensite

  16. Characterization of the Carbon and Retained Austenite Distributions in Martensitic Medium Carbon, High Silicon Steel

    NASA Astrophysics Data System (ADS)

    Sherman, Donald H.; Cross, Steven M.; Kim, Sangho; Grandjean, Fernande; Long, Gary J.; Miller, Michael K.

    2007-08-01

    The retained austenite content and carbon distribution in martensite were determined as a function of cooling rate and temper temperature in steel that contained 1.31 at. pct C, 3.2 at. pct Si, and 3.2 at. pct noniron metallic elements. Mössbauer spectroscopy, transmission electron microscopy (TEM), transmission synchrotron X-ray diffraction (XRD), and atom probe tomography were used for the microstructural analyses. The retained austenite content was an inverse, linear function of cooling rate between 25 and 560 K/s. The elevated Si content of 3.2 at. pct did not shift the start of austenite decomposition to higher tempering temperatures relative to SAE 4130 steel. The minimum tempering temperature for complete austenite decomposition was significantly higher (>650 °C) than for SAE 4130 steel (˜300 °C). The tempering temperatures for the precipitation of transition carbides and cementite were significantly higher (>400 °C) than for carbon steels (100 °C to 200 °C and 200 °C to 350 °C), respectively. Approximately 90 pct of the carbon atoms were trapped in Cottrell atmospheres in the vicinity of the dislocation cores in dislocation tangles in the martensite matrix after cooling at 560 K/s and aging at 22 °C. The 3.2 at. pct Si content increased the upper temperature limit for stable carbon clusters to above 215 °C. Significant autotempering occurred during cooling at 25 K/s. The proportion of total carbon that segregated to the interlath austenite films decreased from 34 to 8 pct as the cooling rate increased from 25 to 560 K/s. Developing a model for the transfer of carbon from martensite to austenite during quenching should provide a means for calculating the retained austenite. The maximum carbon content in the austenite films was 6 to 7 at. pct, both in specimens cooled at 560 K/s and at 25 K/s. Approximately 6 to 7 at. pct carbon was sufficient to arrest the transformation of austenite to martensite. The chemical potential of carbon is the same in

  17. Effect of martensite to austenite reversion on the formation of nano/submicron grained AISI 301 stainless steel

    SciTech Connect

    Karimi, M.; Najafizadeh, A.; Kermanpur, A.; Eskandari, M.

    2009-11-15

    The martensite to austenite reversion behavior of 90% cold rolled AISI 301 stainless steel was investigated in order to refine the grain size. Cold rolled specimens were annealed at 600-900 deg. C, and subsequently characterized by scanning electron microscopy, X-ray diffraction, Feritscope, and hardness measurements. The effects of annealing parameters on the formation of fully-austenitic nano/submicron grained structure and the mechanisms involved were studied. It was found that annealing at 800 deg. C for 10 s exhibited the smallest average austenite grain size of 240 {+-} 60 nm with an almost fully-austenitic structure.

  18. Correlation between mechanical properties and retained austenite characteristics in a low-carbon medium manganese alloyed steel plate

    SciTech Connect

    Chen, Jun; Lv, Mengyang; Tang, Shuai; Liu, Zhenyu; Wang, Guodong

    2015-08-15

    The effects of retained austenite characteristics on tensile properties and low-temperature impact toughness have been investigated by means of transmission electron microscopy and X-ray diffraction. It was found that only part of austenite phase formed during heat treating was left at room temperature. Moreover, the film-like retained austenite is displayed between bcc-martensite laths after heat treating at 600 °C, while the block-form retained austenite with thin hcp-martensite laths is observed after heat treating at 650 °C. It has been demonstrated that the film-like retained austenite possesses relatively high thermal and mechanical stability, and it can greatly improve low-temperature impact toughness, but its contribution to strain hardening capacity is limited. However, the block-form retained austenite can greatly enhance ultimate tensile strength and strain hardening capacity, but its contribution to low-temperature impact toughness is poor. - Highlights: • Correlation between retained austenite and impact toughness was elucidated. • The impact toughness is related to mechanical stability of retained austenite. • The effect of retained austenite on tensile and impact properties is inconsistent.

  19. Tensile and fracture properties of an Fe14Mn8Ni1Mo-0.7C fully austenitic weld metal at 4 K

    NASA Astrophysics Data System (ADS)

    Tobler, R. L.; Trevisan, R. E.; Reed, R. P.

    A fully austenitic steel butt weld 21 mm thick was produced by submerged arc welding using an experimental filler metal composition: Fe14Mn8Ni1Mo0.7C. The tensile and fracture properties of this weld were measured in liquid helium to evaluate its candidacy for applications at 4 K. The yield strength (1115 MPa) and toughness ( K lc ≈ 192 MPa m1/2) combination of this material compares favourably with existing base metal properties for AISI 304 type alloys. A conventional ductile fracture consisting of void formation and coalescence was shown by both tensile and fracture toughness specimens.

  20. Localized deformation and IASCC initiation in austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Jiao, Z.; Was, G. S.

    2008-12-01

    Localized deformation may play a key role in the underlying mechanism of irradiation assisted stress corrosion cracking (IASCC) in light water reactor core components. In this study, four austenitic alloys, 18Cr8Ni, 15Cr12Ni, 13Cr15Ni and 21Cr32Ni, with different stacking fault energies were irradiated to 1 and 5 dpa at 360 °C using 3.2 MeV protons. Interrupted constant extension rate tensile (CERT) tests were conducted in a simulated BWR environment to determine IASCC susceptibility. In order to characterize the localized deformation in slip channels and grain boundaries, parallel CERT experiments were also performed in an argon atmosphere. Results show that the IASCC susceptibility of the tested alloys increases with increasing irradiation dose and decreasing stacking fault energy. IASCC tends to initiate at locations where slip channels intersect grain boundaries. Localized deformation in the form of grain boundary sliding due to the interaction of slip channels and grain boundaries is likely the primary cause of the observed cracking initiation.

  1. Sensitization and tunneling corrosion of austenitic type 347 stainless steel

    SciTech Connect

    Teodoro, C.A.; Wolynec, S.

    1998-02-01

    Sensitization of type 347 (UNS S34700) austenitic stainless steel (SS) samples removed from forged bars was investigated using the electrochemical potentiokinetic reactivation (EPR) method and the weight-loss technique of ASTM A 262, Practice B., A normal and a low-carbon steel were investigated. After solution-annealing at 1,050 C, the two steels were submitted to sensitization treatments at 550 C, 670 C, 790 C, and 910 C for times varying from 1 h to 130 h. The steel with normal carbon content also was solution-annealed at 1.140 C and submitted to the same sensitization treatments for times varying from 1 h to 62 h. Correlation between results obtained by the two techniques was very poor. The lack of correlation was ascribed to tunneling corrosion, which is typical of forged steels, in addition to intergranular corrosion resulting from sensitization. The electrochemical test was most sensitive to corrosion by sensitization. The Practice B test did not discriminate between the two types of attack. The steel solution-annealed at higher temperature was more susceptible to sensitization.

  2. Softening and microstructural change following the dynamic recrystallization of austenite

    NASA Astrophysics Data System (ADS)

    Roucoules, C.; Hodgson, P. D.; Yue, S.; Jonas, J. J.

    1994-02-01

    To characterize the dynamic recrystallization behavior of austenite, continuous-torsion tests were carried out on a Mo steel over the temperature range 950 ‡C to {dy1000} ‡C, and at strain rates of 0.02, 0.2, and 2 s-1. Interrupted-torsion tests also were performed to study the characteristics of postdynamic recrystallization. Quenches were performed after increasing holding times to follow the development of the postdynamic microstructure. Finally, torsion simulations were carried out to assess the importance of metadynamic recrystallization in hot-strip mills. The postdynamic microstructure shows that the growth of dynamically recrystallized grains is the first change that takes place. Then metadynamically recrystallized grains appear and contribute to the softening of the material. The rate of metadynamic recrystallization and the meta-dynamically recrystallized grain size depend on strain rate and temperature and are relatively independent of strain, in contrast to the observations for static recrystallization. True dynamic recrystallization-controlled rolling (DRCR) is shown to require such short interpass times that it does not occur in isolation in hot-strip mills. As these schedules involve 20 to 80 pct softening by metadynamic recrystallization, a new concept known as metadynamic recrystallization-controlled rolling (MDRCR) is introduced to describe this type of situation.

  3. TEM studies of plasma nitrided austenitic stainless steel.

    PubMed

    Stróz, D; Psoda, M

    2010-03-01

    Cross-sectional transmission electron microscopy and X-ray phase analysis were used to study the structure of a layer formed during nitriding the AISI 316L stainless steel at temperature 440 degrees C. It was found that the applied treatment led to the formation of 6-microm-thick layer of the S-phase. There is no evidence of CrN precipitation. The X-ray diffraction experiments proved that the occurred austenite lattice expansion - due to nitrogen atoms - depended on the crystallographic direction. The cross-sectional transmission electron microscopy studies showed that the layer consisted of a single cubic phase that contained a lot of defects such as dislocations, stacking faults, slip bands and twins. The high-resolution electron microscopy observations were applied to study the defect formation due to the nitriding process. It was shown that the presence of great number of stacking faults leads to formation of nanotwins. Weak, forbidden {100} reflections were still another characteristic feature of the S-phase. These were not detected in the X-ray spectra of the phase. Basing on the high-resolution electron microscopy studies it can be suggested that the short-range ordering of the nitrogen atoms in the octahedral sites inside the f.c.c. matrix lattice takes place and gives rise to appearance of these spots. It is suggested that the cubic lattice undergoes not only expansion but also slight rombohedral distortion that explains differences in the lattice expansion for different crystallographic directions.

  4. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    PubMed

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands.

  5. Evolution of Austenite Recrystallization and Grain Growth Using Laser Ultrasonics

    NASA Astrophysics Data System (ADS)

    Sarkar, S.; Moreau, A.; Militzer, M.; Poole, W. J.

    2008-04-01

    Laser ultrasonics is a noncontacting technique with which the attenuation of ultrasonic signals can be measured and related to the grain size of the investigated material. In the present article, a laser-ultrasonic grain-size measurement technique previously developed for various C-Mn and microalloyed steels has been extended to examine austenite recrystallization and subsequent grain growth following hot deformation. The ultrasonic measurements were conducted on a low-carbon (0.05 wt pct) steel that contains Mn, Mo, and Nb as the three main alloying/microalloying elements. The grain-size data measured by ultrasonic experiments were analyzed to quantify the effect of deformation conditions on the evolution of recrystallized grain size and subsequent grain growth. A significant effect of deformation temperature, applied strain, and initial grain size on the grain-size evolution was observed, while strain rate had a negligible effect. Phenomenological modeling approaches were employed to describe the recrystallized grain-size and grain-growth behavior of the present steel.

  6. Stress corrosion cracking of austenitic stainless steel core internal welds.

    SciTech Connect

    Chung, H. M.; Park, J.-H.; Ruther, W. E.; Sanecki, J. E.; Strain, R. V.; Zaluzec, N. J.

    1999-04-14

    Microstructural analyses by several advanced metallographic techniques were conducted on austenitic stainless steel mockup and core shroud welds that had cracked in boiling water reactors. Contrary to previous beliefs, heat-affected zones of the cracked Type 304L, as well as 304 SS core shroud welds and mockup shielded-metal-arc welds, were free of grain-boundary carbides, which shows that core shroud failure cannot be explained by classical intergranular stress corrosion cracking. Neither martensite nor delta-ferrite films were present on the grain boundaries. However, as a result of exposure to welding fumes, the heat-affected zones of the core shroud welds were significantly contaminated by oxygen and fluorine, which migrate to grain boundaries. Significant oxygen contamination seems to promote fluorine contamination and suppress thermal sensitization. Results of slow-strain-rate tensile tests also indicate that fluorine exacerbates the susceptibility of irradiated steels to intergranular stress corrosion cracking. These observations, combined with previous reports on the strong influence of weld flux, indicate that oxygen and fluorine contamination and fluorine-catalyzed stress corrosion play a major role in cracking of core shroud welds.

  7. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing

    PubMed Central

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands. PMID:26601037

  8. Laser beam surface melting of high alloy austenitic stainless steel

    SciTech Connect

    Woollin, P.

    1996-12-31

    The welding of high alloy austenitic stainless steels is generally accompanied by a substantial reduction in pitting corrosion resistance relative to the parent, due to microsegregation of Mo and Cr. This prevents the exploitation of the full potential of these steels. Processing to achieve remelting and rapid solidification offers a means of reducing microsegregation levels and improving corrosion resistance. Surface melting of parent UNS S31254 steel by laser beam has been demonstrated as a successful means of producing fine, as-solidified structures with pitting resistance similar to that of the parent, provided that an appropriate minimum beam travel speed is exceeded. The use of N{sub 2} laser trail gas increased the pitting resistance of the surface melted layer. Application of the technique to gas tungsten arc (GTA) melt runs has shown the ability to raise the pitting resistance significantly. Indeed, the use of optimized beam conditions, N{sub 2} trail gas and appropriate surface preparation prior to laser treatment increased the pitting resistance of GTA melt runs to a level approaching that of the parent material.

  9. Development of Alumina-Forming Austenitic Stainless Steels

    SciTech Connect

    Yamamoto, Yukinori; Brady, Michael P; Santella, Michael L; Bei, Hongbin; Maziasz, Philip J; Pint, Bruce A

    2008-01-01

    Work in fiscal year 2008 focused on the development of creep-resistant, alumina-forming austenitic (AFA) stainless steel alloys, which exhibit a unique combination of an excellent oxidation resistance via protective alumina (Al2O3) scale formation and high-temperature creep strength through the formation of stable nano-scale MC carbides [1-8]. High levels of Nb additions (> 1 wt.% Nb) and/or Ni additions (25-30 wt.%), at Al levels of 2.5-4 wt.%, were found to correlate with increased upper-temperature limit for Al2O3 scale formation in air ( 900 aC) and air with 10% water vapor ( 800 aC). Creep resistance also showed a strong dependence on the level of Nb additions, and was correlated with volume fraction of MC-type carbides using thermodynamic computational tools. A trial heat of a 50 lb AFA alloy ingot was made using conventional single-melt vacuum techniques, and the alloy was successfully hot-rolled without any cracking [2]. This heat showed good weldability, using filler material of the same alloy.

  10. Soviet gas processing expands

    SciTech Connect

    Sagers, M.J.

    1987-09-01

    The Soviet gas processing industry expanded with the recent completion of two new gas processing plants, the Krasnoleninskiy and Noyabr'sk plants, both located in West Siberia. Both process associated gas from nearby oil fields to remove valuable liquid hydrocarbons before putting the dry gas into pipelines; previously the gas was flared or vented. These plants represent part of a major program, ongoing since the 1970s, to increase the level of utilization of the tremendous amount of valuable associated gas now being produced in West Siberia. Another major effort to develop gas processing is under way in western Kazakhstan at the Tengiz and Zhanazhol' fields. At Zhanazhol', a small gas recovery plant went into operation in late 1984 in conjunction with a separation plant with a processing capacity of 1 million tons of oil per year. A much larger enterprise to refine oil and process associated gas is under construction at the Tengiz field. This enterprise is different from the major petrochemical operation planned to use feedstocks from Tengiz; the petrochemical operation will be constructed at Kulsary, 120 kilometers from Tengiz, and produce polyethylene, polypropylene, and other plastics.

  11. High temperature stability of a 316 austenitic stainless steel coated with cerium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Mendoza Del Angel, Humberto

    Cerium oxide (CeO2-x) nanoparticles were used for coating protection on a 316 Austenitic Stainless Steel (Aust. SS) to enhance the thermal stability of the oxide films formed at high temperatures. Three simple coating methods were used, dipping, spraying and spinning in order to explore the coating film morphology, nanoparticle distribution and its effect on thermal stability of the steel substrates. Experimentally, the selected steel was exposed to 800°C/1000°C under dry air conditions. Weight changes (DeltaW/A) were monitored as a function of time and the results were compared with uncoated alloys tested under similar conditions. The cerium oxide nanoparticles used on the three methods were synthesized in the laboratory obtaining nanoparticles in the range of 3.5 to 6.2 nanometers. It was found that cerium oxide particle size is affected by temperature. In this case, the activation energy for particle growth was estimated to be around 21,1 kJ/mol. Characterization of the film morphologies before and after oxidation were carried out using Atomic Force Microscopy (AFM), Surface Profilometry, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). A comparison of the three coating methods was carried out for the particular case of the 316 Aust. SS coupons. In addition, the oxidation kinetics was experimentally investigated for the coated samples. For this purpose thermal gravimetric determinations were made at 800°C, 900°C, and 1000°C and oxidation rate constants were calculated at each temperature.

  12. Towards expanding megasonic cleaning capability

    NASA Astrophysics Data System (ADS)

    Han, Zhenxing; Ferstl, Berthold; Oetter, Günter; Dietze, Uwe; Samayoa, Martin; Dattilo, Davide

    2016-10-01

    Megasonic cleaning remains the industry's workhorse technology for particle removal on advanced 193i and extreme ultraviolet (EUV) photomasks. Several megasonic cleaning technologies and chemistries have been proposed and implemented over the years in diverse production environments. The operational range of these process technologies, over a wide array of applications, is ultimately defined by measurable capability limits. As geometries continue to scale-down and new materials are introduced, existing cleaning technologies will naturally fade out of range and new capability is ultimately required. This paper presents a novel fundamental approach for expanding cleaning capability by use of high-frequency megasonics and tenside-based additives (BASF SELECTIPUR C-series). To this end, a sonoluminescence-based experimental test bench was configured to characterize and study the effects of various process parameters on cleaning performance, with a particular emphasis on cavitation-induced damage and enhancement of particle removal capabilities. The results from the fundamental studies provide a path forward towards delivering new cleaning capability by enabling high-frequency megasonic systems and tenside-based additives.

  13. Expanding contraceptive options.

    PubMed

    1989-01-01

    The goals of Family Health International (FHI) have been to introduce a variety of birth control options to people in developing countries, and to provide information to the user on the advantages and disadvantages of each method. FHI has worked with many developing countries in clinical trials of established as well as new contraceptive methods. These trials played an important part in making 2 sterilization procedures, laparoscopy and minilaparotomy popular for women. Further research improved the methods and have made them the most popular in the world, chosen by 130 million users. FHI is doing clinical trials on a new IUD, that is a copper bearing T-shaped device called the TCu380A. they have collected data on over 10,000 women using IUD's and early analysis indicates TCu380A is more effective than others. FHI is also evaluating devices such as Norplant that will prevent pregnancy up to 5 years by implanting the capsules in the arm. More than 8,000 women are being tested to determine the acceptability of implants in different geographical locations. Other research groups are doing work in 10 additional countries: Bangladesh will expand its program to 24,000 women and Nepal to 8,000 women. Trials are also being conducted on progestogen pills, since they do not lesson the volume of milk in breast feeding. FHI has also worked to introduce creative community-based distribution channels. In one case, specially trained health workers delivered contraceptives door-to-door in over 150,000 households. They found that 2 of 3 women accepted the pills and in a follow up survey 90% were still using them. FHI is now focusing on ways to improve moving new contraceptives from clinical testing on everyday use. They will coordinate training programs, educational material, media campaigns, and efforts with other international organizations, government agencies, and family planning groups.

  14. The Artful Universe Expanded

    NASA Astrophysics Data System (ADS)

    Barrow, John D.

    2005-07-01

    Our love of art, writes John Barrow, is the end product of millions of years of evolution. How we react to a beautiful painting or symphony draws upon instincts laid down long before humans existed. Now, in this enhanced edition of the highly popular The Artful Universe , Barrow further explores the close ties between our aesthetic appreciation and the basic nature of the Universe. Barrow argues that the laws of the Universe have imprinted themselves upon our thoughts and actions in subtle and unexpected ways. Why do we like certain types of art or music? What games and puzzles do we find challenging? Why do so many myths and legends have common elements? In this eclectic and entertaining survey, Barrow answers these questions and more as he explains how the landscape of the Universe has influenced the development of philosophy and mythology, and how millions of years of evolutionary history have fashioned our attraction to certain patterns of sound and color. Barrow casts the story of human creativity and thought in a fascinating light, considering such diverse topics as our instinct for language, the origins and uses of color in nature, why we divide time into intervals as we do, the sources of our appreciation of landscape painting, and whether computer-generated fractal art is really art. Drawing on a wide variety of examples, from the theological questions raised by St. Augustine and C.S. Lewis to the relationship between the pure math of Pythagoras and the music of the Beatles, The Artful Universe Expanded covers new ground and enters a wide-ranging debate about the meaning and significance of the links between art and science.

  15. Microstructural and Stress Corrosion Cracking Characteristics of Austenitic Stainless Steels Containing Silicon

    NASA Astrophysics Data System (ADS)

    Andresen, Peter L.; Chou, Peter H.; Morra, Martin M.; Lawrence Nelson, J.; Rebak, Raul B.

    2009-12-01

    Austenitic stainless steels (SSs) core internal components in nuclear light water reactors (LWRs) are susceptible to irradiation-assisted stress corrosion cracking (IASCC). One of the effects of irradiation is the hardening of the SS and a change in the dislocation distribution in the alloy. Irradiation may also alter the local chemistry of the austenitic alloys; for example, silicon may segregate and chromium may deplete at the grain boundaries. The segregation or depletion phenomena at near-grain boundaries may enhance the susceptibility of these alloys to environmentally assisted cracking (EAC). The objective of the present work was to perform laboratory tests in order to better understand the role of Si in the microstructure, properties, electrochemical behavior, and susceptibility to EAC of austenitic SSs. Type 304 SS can dissolve up to 2 pct Si in the bulk while maintaining a single austenite microstructure. Stainless steels containing 12 pct Cr can dissolve up to 5 pct bulk Si while maintaining an austenite structure. The crack growth rate (CGR) results are not conclusive about the effect of the bulk concentration of Si on the EAC behavior of SSs.

  16. Study of biocompatibility of medical grade high nitrogen nickel-free austenitic stainless steel in vitro.

    PubMed

    Li, Menghua; Yin, Tieying; Wang, Yazhou; Du, Feifei; Zou, Xingzheng; Gregersen, Hans; Wang, Guixue

    2014-10-01

    Adverse effects of nickel ions being released into the living organism have resulted in development of high nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also improves steel properties. The cell cytocompatibility, blood compatibility and cell response of high nitrogen nickel-free austenitic stainless steel were studied in vitro. The mechanical properties and microstructure of this stainless steel were compared to the currently used 316L stainless steel. It was shown that the new steel material had comparable basic mechanical properties to 316L stainless steel and preserved the single austenite organization. The cell toxicity test showed no significant toxic side effects for MC3T3-E1 cells compared to nitinol alloy. Cell adhesion testing showed that the number of MC3T3-E1 cells was more than that on nitinol alloy and the cells grew in good condition. The hemolysis rate was lower than the national standard of 5% without influence on platelets. The total intracellular protein content and ALP activity and quantification of mineralization showed good cell response. We conclude that the high nitrogen nickel-free austenitic stainless steel is a promising new biomedical material for coronary stent development.

  17. Examination of Spheroidal Graphite Growth and Austenite Solidification in Ductile Iron

    NASA Astrophysics Data System (ADS)

    Qing, Jingjing; Richards, Von L.; Van Aken, David C.

    2016-12-01

    Microstructures of a ductile iron alloy at different solidification stages were captured in quenching experiments. Etched microstructures showed that spheroidal graphite particles and austenite dendrites nucleated independently to a significant extent. Growth of the austenite dendrite engulfed the spheroidal graphite particles after first contacting the nodule and then by forming an austenite shell around the spheroidal graphite particle. Statistical analysis of the graphite size distribution was used to determine the nodule diameter when the austenite shell was completed. In addition, multiple graphite nucleation events were discerned from the graphite particle distributions. Majority of graphite growth occurred when the graphite was in contact with the austenite. Circumferential growth of curved graphene layers appeared as faceted growth fronts sweeping around the entire surface of a spheroidal graphite particle which was at the early growth stage. Mismatches between competing graphene growth fronts created gaps, which divided the spheroidal graphite particle into radially oriented conical substructures. Graphene layers continued growing in each conical substructure to further extend the size of the spheroidal graphite particle.

  18. Deformation Mechanisms in Austenitic TRIP/TWIP Steel as a Function of Temperature

    NASA Astrophysics Data System (ADS)

    Martin, Stefan; Wolf, Steffen; Martin, Ulrich; Krüger, Lutz; Rafaja, David

    2016-01-01

    A high-alloy austenitic CrMnNi steel was deformed at temperatures between 213 K and 473 K (-60 °C and 200 °C) and the resulting microstructures were investigated. At low temperatures, the deformation was mainly accompanied by the direct martensitic transformation of γ-austenite to α'-martensite (fcc → bcc), whereas at ambient temperatures, the transformation via ɛ-martensite (fcc → hcp → bcc) was observed in deformation bands. Deformation twinning of the austenite became the dominant deformation mechanism at 373 K (100 °C), whereas the conventional dislocation glide represented the prevailing deformation mode at 473 K (200 °C). The change of the deformation mechanisms was attributed to the temperature dependence of both the driving force of the martensitic γ → α' transformation and the stacking fault energy of the austenite. The continuous transition between the ɛ-martensite formation and the twinning could be explained by different stacking fault arrangements on every second and on each successive {111} austenite lattice plane, respectively, when the stacking fault energy increased. A continuous transition between the transformation-induced plasticity effect and the twinning-induced plasticity effect was observed with increasing deformation temperature. Whereas the formation of α'-martensite was mainly responsible for increased work hardening, the stacking fault configurations forming ɛ-martensite and twins induced additional elongation during tensile testing.

  19. Investigation of Parent Austenite Grains from Martensite Structure Using EBSD in a Wear Resistant Steel

    PubMed Central

    Gyhlesten Back, Jessica; Engberg, Göran

    2017-01-01

    Crystallographic reconstruction of parent austenite grain boundaries from the martensitic microstructure in a wear resistant steel was carried out using electron backscattered diffraction (EBSD). The present study mainly aims to investigate the parent austenite grains from the martensitic structure in an as-rolled (reference) steel sample and samples obtained by quenching at different cooling rates with corresponding dilatometry. Subsequently, this study is to correlate the nearest cooling rate by the dilatometer which yields a similar orientation relationship and substructure as the reference sample. The Kurdjumov-Sachs orientation relationship was used to reconstruct the parent austenite grain boundaries from the martensite boundaries in both reference and dilatometric samples using EBSD crystallographic data. The parent austenite grain boundaries were successfully evaluated from the EBSD data and the corresponding grain sizes were measured. The parent austenite grain boundaries of the reference sample match the sample quenched at 100 °C/s (CR100). Also the martensite substructures and crystallographic textures are similar in these two samples. The results from hardness measurements show that the reference sample exhibits higher hardness than the CR100 sample due to the presence of carbides in the reference sample. PMID:28772813

  20. Investigation of austenitizing temperature on wear behavior of austempered gray iron (AGI)

    NASA Astrophysics Data System (ADS)

    Sarkar, T.; Sutradhara, G.

    2016-09-01

    This study is about finding the effect of austenitizing temperature on microstructure and wear behavior of copper alloyed austempered gray iron (AGI), and then comparing it with an as- cast (solidified) state. Tensile and wear tests specimens are prepared from as-cast gray iron material, and austenitized at different temperatures and then austempered at a fixed austempering temperature. Resulting microstructures are characterized through optical microscopy, scanning electron microscope (SEM) and X-Ray diffraction. Wear test is carried out using a block-on-roller multi-tribotester with sliding speed of 1.86 m/sec. In this investigation, wear behavior of all these austempered materials are determined and co-related with the micro structure. Hence the wear surface under scanning electron microscope showed that wear occurred mainly due to adhesion and delamination under dry sliding condition. The test results indicate that the austenitizing temperature has remarkable effect on resultant micro structure and wear behavior of austempered materials. Wear behavior is also found to be dependent on the hardness, tensile strength, austenite content and carbon content in austenite. It is shown that coarse ausferrite micro structure exhibited higher wear depth than fine ausferrite microstructure.

  1. A review on nickel-free nitrogen containing austenitic stainless steels for biomedical applications.

    PubMed

    Talha, Mohd; Behera, C K; Sinha, O P

    2013-10-01

    The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life. Metallic materials are often used as biomaterials to replace structural components of the human body. Stainless steels, cobalt-chromium alloys, commercially pure titanium and its alloys are typical metallic biomaterials that are being used for implant devices. Stainless steels have been widely used as biomaterials because of their very low cost as compared to other metallic materials, good mechanical and corrosion resistant properties and adequate biocompatibility. However, the adverse effects of nickel ions being released into the human body have promoted the development of "nickel-free nitrogen containing austenitic stainless steels" for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel and emphatically the advantages of nitrogen in stainless steel, as well as the development of nickel-free nitrogen containing stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength, better corrosion and wear resistance and superior biocompatibility in comparison to the currently used austenitic stainless steel (e.g. 316L), the newly developed nickel-free high nitrogen austenitic stainless steel is a reliable substitute for the conventionally used medical stainless steels.

  2. Residual Ferrite and Relationship Between Composition and Microstructure in High-Nitrogen Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Wang, Qingchuan; Ren, Yibin; Yao, Chunfa; Yang, Ke; Misra, R. D. K.

    2015-12-01

    A series of high-nitrogen stainless steels (HNS) containing δ-ferrite, which often retained in HNS, were studied to establish the relationship between composition and microstructure. Both ferrite and nitrogen depletions were found in the center regions of cast ingots, and the depletion of nitrogen in that area was found to be the main reason for the existence of δ-ferrite. Because of the existence of heterogeneity, the variation of microstructure with nitrogen content was detected. Hence, the critical contents of nitrogen (CCN) for the fully austenitic HNS were obtained. Then the effects of elements such as N, Cr, Mn, and Mo on austenite stability were investigated via thermodynamic calculations. The CCN of HNS alloys were also obtained by calculations. Comparing the CCN obtained from experiment and calculation, it was found that the forged microstructure of the HNS was close to the thermodynamic equilibrium. To elucidate the above relationship, by regression analysis using calculated thermodynamic data, nitrogen equivalent and a new constitution diagram were proposed. The constitution diagram accurately distinguishes the austenitic single-phase region and the austenite + ferrite dual-phase region. The nitrogen equivalent and the new constitution diagram can be used for alloying design and microstructural prediction in HNS. According to the nitrogen equivalent, the ferrite stabilizing ability of Mo is weaker than Cr, and with Mn content increases, Mn behaves as a weak austenite stabilizer first and then as a ferrite stabilizer.

  3. Influence of heating rate and temperature on austenite grain size during reheating steel

    NASA Astrophysics Data System (ADS)

    Napitupulu, Richard A. M.

    2017-09-01

    Controlling the final microstructure is one effective way to get HSLA steel with good mechanical properties. The structure of the desired item on the final microstructure depends on the initial grain size formed during the initial heating process, where to get super fine ferrite grains, it should form the initial austenite grain smooth during the heating process. Austenite grain size at the beginning of the heating process is important in order to obtain the size of the final microstructure that provides maximum mechanical properties. In this study, HSLA steel reheated to a temperature of 960°C, 1060°C and 1120°C with holding time variation of 10, 30 and 60 minutes at a heating rate of 5°C/minute, 7.5°C/minute and 10°C/minute, then water quenching. The austenite saw by using optic microscope and count by ASTM E112 method. From the results it is concluded that there is a relationship between temperatures interrelated heating, heating rate and holding time on the growth of austenite grain. The higher the temperature, the heating occur austenite grain size. While the most optimal results obtained for reheated temperature 1060°C with a heating rate 7.5°C/minute and the heating temperature 1120°C with a heating rate 5°C/minute.

  4. Influence of Ti on the Hot Ductility of High-manganese Austenitic Steels

    NASA Astrophysics Data System (ADS)

    Liu, Hongbo; Liu, Jianhua; Wu, Bowei; Su, Xiaofeng; Li, Shiqi; Ding, Hao

    2017-07-01

    The influence of Ti addition ( 0.10 wt%) on hot ductility of as-cast high-manganese austenitic steels has been examined over the temperature range 650-1,250 °C under a constant strain rate of 10-3 s-1 using Gleeble3500 thermal simulation testing machine. The fracture surfaces and particles precipitated at different tensile temperatures were characterized by means of scanning electron microscope and X-ray energy dispersive spectrometry (SEM-EDS). Hot ductility as a function of reduction curves shows that adding 0.10 wt% Ti made the ductility worse in the almost entire range of testing temperatures. The phases' equilibrium diagrams of precipitates in Ti-bearing high-Mn austenitic steel were calculated by the Thermo-Calc software. The calculation result shows that 0.1 wt% Ti addition would cause Ti(C,N) precipitated at 1,499 °C, which is higher than the liquidus temperature of high-Mn austenitic steel. It indicated that Ti(C,N) particles start forming in the liquid high-Mn austenitic steel. The SEM-EDS results show that Ti(C,N) and TiC particles could be found along the austenite grain boundaries or at triple junction, and they would accelerate the extension of the cracks along the grain boundaries.

  5. Investigation of Parent Austenite Grains from Martensite Structure Using EBSD in a Wear Resistant Steel.

    PubMed

    Gyhlesten Back, Jessica; Engberg, Göran

    2017-04-26

    Crystallographic reconstruction of parent austenite grain boundaries from the martensitic microstructure in a wear resistant steel was carried out using electron backscattered diffraction (EBSD). The present study mainly aims to investigate the parent austenite grains from the martensitic structure in an as-rolled (reference) steel sample and samples obtained by quenching at different cooling rates with corresponding dilatometry. Subsequently, this study is to correlate the nearest cooling rate by the dilatometer which yields a similar orientation relationship and substructure as the reference sample. The Kurdjumov-Sachs orientation relationship was used to reconstruct the parent austenite grain boundaries from the martensite boundaries in both reference and dilatometric samples using EBSD crystallographic data. The parent austenite grain boundaries were successfully evaluated from the EBSD data and the corresponding grain sizes were measured. The parent austenite grain boundaries of the reference sample match the sample quenched at 100 °C/s (CR100). Also the martensite substructures and crystallographic textures are similar in these two samples. The results from hardness measurements show that the reference sample exhibits higher hardness than the CR100 sample due to the presence of carbides in the reference sample.

  6. Advanced expander test bed program

    NASA Technical Reports Server (NTRS)

    Masters, A. I.; Mitchell, J. C.

    1991-01-01

    The Advanced Expander Test Bed (AETB) is a key element in NASA's Chemical Transfer Propulsion Program for development and demonstration of expander cycle oxygen/hydrogen engine technology component technology for the next space engine. The AETB will be used to validate the high-pressure expander cycle concept, investigate system interactions, and conduct investigations of advanced missions focused components and new health monitoring techniques. The split-expander cycle AETB will operate at combustion chamber pressures up to 1200 psia with propellant flow rates equivalent to 20,000 lbf vacuum thrust.

  7. Advanced expander test bed engine

    NASA Technical Reports Server (NTRS)

    Mitchell, J. P.

    1992-01-01

    The Advanced Expander Test Bed (AETB) is a key element in NASA's Space Chemical Engine Technology Program for development and demonstration of expander cycle oxygen/hydrogen engine and advanced component technologies applicable to space engines as well as launch vehicle upper stage engines. The AETB will be used to validate the high pressure expander cycle concept, study system interactions, and conduct studies of advanced mission focused components and new health monitoring techniques in an engine system environment. The split expander cycle AETB will operate at combustion chamber pressures up to 1200 psia with propellant flow rates equivalent to 20,000 lbf vacuum thrust.

  8. Effect of Plastic Pre-straining on Residual Stress and Composition Profiles in Low-Temperature Surface-Hardened Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Bottoli, Federico; Christiansen, Thomas L.; Winther, Grethe; Somers, Marcel A. J.

    2016-08-01

    The present work deals with the evaluation of the residual stress profiles in expanded austenite by applying grazing incidence X-ray diffraction (GI-XRD) combined with successive sublayer removal. Annealed and deformed ( ɛ eq=0.5) samples of stable stainless steel EN 1.4369 were nitrided or nitrocarburized. The residual stress profiles resulting from the thermochemical low-temperature surface treatment were measured. The results indicate high-residual compressive stresses of several GPa's in the nitrided region, while lower-compressive stresses are produced in the carburized case. Plastic deformation in the steel prior to thermochemical treatment has a hardly measurable influence on the nitrogen-rich zone, while it has a measurable effect on the stresses and depth of the carbon-rich zone.

  9. Computational design and analysis of high strength austenitic TRIP steels for blast protection applications

    NASA Astrophysics Data System (ADS)

    Sadhukhan, Padmanava

    Recent assessment of material property requirements for blast resistant applications, especially for the naval ship hulls, has defined the need to design steels with high stretch ductility and fragment penetration resistance, along with high strength and adequate toughness. Using a system based computational materials design approach, two series of austenitic (gamma) steels have been designed -- BA120 to exhibit high uniform ductility in tension (>20%) and SA120 to exhibit high tensile (>20%) and shear strains (>50%), with both alloys maintaining high levels of yield strength (120 ksi/827 MPa) at room temperature under Tensile and Shear stress states. BA120 is low chromium (4 wt %) high nickel (23.5 wt %) alloy while the SA120 is a high chromium design (10 wt %), both designed for non-magnetic behavior. The Thermo-Calc computational thermodynamics software in conjunction with a Ni-DATA 7 thermodynamic database has been used to model precipitation strengthening of the alloy, by quantifying the dependence of yield stress of austenitic steels on the mole fraction of the precipitated gamma' (Gamma Prime) Ni3(Ti, Al) phase. The required high strength has been achieved by the precipitation of spheroidal intermetallic gamma' -- phase of optimum diameter (15 nm) in equilibrium with the matrix at the standard aging temperature. Adequate Al and Ti with respect 5 to the Ni in the matrix ensure enough gamma' phase fraction and number density of precipitates to provide the necessary strength. The predicted gamma' precipitation strengthening to 120-130 ksi for both BA120 and SA120 has been validated through both microhardness as well as static and dynamic tensile and shear tests conducted at room temperature. 3-D LEAP analysis of the aged specimens has shown the expected size and distribution of gamma' -- precipitates with good compositional accuracy of predicted values from the thermodynamic models, for both matrix austenite and gamma'. Metastable austenitic steels have been

  10. Cast heat-resistant austenitic steel with improved temperature creep properties and balanced alloying element additions and methodology for development of the same

    DOEpatents

    Pankiw, Roman I; Muralidharan, Govindrarajan; Sikka, Vinod Kumar; Maziasz, Philip J

    2012-11-27

    The present invention addresses the need for new austenitic steel compositions with higher creep strength and higher upper temperatures. The new austenitic steel compositions retain desirable phases, such as austenite, M.sub.23C.sub.6, and MC in its microstructure to higher temperatures. The present invention also discloses a methodology for the development of new austenitic steel compositions with higher creep strength and higher upper temperatures.

  11. Effect of Strain-Induced Age Hardening on Yield Strength Improvement in Ferrite-Austenite Duplex Lightweight Steels

    NASA Astrophysics Data System (ADS)

    Song, Hyejin; Lee, Seok Gyu; Sohn, Seok Su; Kwak, Jai-Hyun; Lee, Sunghak

    2016-11-01

    Ferrite-austenite lightweight steels showing TRansformation-induced plasticity were developed by varying the aging temperature with or without prestraining, and their effects on tensile properties were investigated in relation with microstructural evolution of carbide formation. The aged steels contained austenite, pearlite, and martensite in the ferrite matrix, and the austenite volume fraction decreased with the increasing aging temperature because some austenite grains decomposed to pearlites. This austenite decomposition to pearlite was favorable for the improvement of yield strength, but negatively influenced overall tensile properties. The prestraining promoted the austenite decomposition by a diffusion-controlled phase transformation, and changed the morphology of the cementite from a long lamellar shape to a densely agglomerated particle shape. In order to obtain the large increase in yield strength as well as excellent combination of strength and ductility, the strain-induced aging treatment, i.e., prestraining followed by aging, is important like in the prestrained and 673 K (400 °C)-aged steel. This large increase in yield strength, in spite of a reduction of elongation (65 to 43 pct), was basically attributed to an appropriate amount of decomposition of austenite to pearlite ( e.g., 4 vol pct), while having sufficient austenite to martensite transformation ( e.g., 14.5 vol pct martensite).

  12. Influence of Austenitizing Heat Treatment on the Properties of the Tempered Type 410-1Mo Stainless Steel

    NASA Astrophysics Data System (ADS)

    Mabruri, E.; Syahlan, Z. A.; Sahlan; Prifiharni, S.; Anwar, M. S.; Chandra, S. A.; Romijarso, T. B.; Adjiantoro, B.

    2017-05-01

    The modified 410-1Mo stainless steel has been developed with higher tensile strength and elongation compared to the standard 410 stainless steel. This paper reports the influence of austenitizing temperature on the microstructure, hardness, impact resistance and corrosion resistance of the modified 410-1Mo steel. The steel samples were prepared by a process sequence of induction melting, hot forging, annealing, hardening, and tempering. The microstructure of the tempered steels revealed additional phase of delta ferrite at pre-austenitizing temperatures of 950 to 1050 °C and disappeared at a temperature of 1100 °C. The steels which underwent pre-austenitizing at 1100 °C showed the largest sized lath martensite and the largest amount of retained austenite. The tempered steels maintained hardness at austenitizing temperatures of 950 °C to 1000 °C and showed an increasing hardness at austenitizing temperatures from 1000 to 1100 °C. At a range of austenitizing temperatures, it was investigated that the steels exhibited higher impact resistance at 1050 °C. The tempered steels that were pre-austenitized at 950 °C and 1100 °C showed the lowest pitting potential due to the existence of carbides and coarse-high carbon martensite, respectively.

  13. Effect of precipitated austenite on the fracture of a ferritic cryogenic steel. [Fe-8Ni-2Mn-0. 1Ti

    SciTech Connect

    Frear, D.R.

    1984-05-01

    The effect of precipitated austenite on the fracture of an Fe-8Ni-2Mn-0.1Ti steel was investigated. To understand the effect an attempt was made to correlate the microstructure, mechanical properties, and the fracture surface appearance of specimens heat treated to contain austenite or be austenite-free. The fracture surfaces were quantitatively studied using a 3D imaging technique in the SEM. It was found that the presence of austenite had a beneficial influence on mechanical properties by lowering the DBTT. Part of this decrease was found to be due to the austenite gettering deleterious elements off the grain boundaries. Specimens that contained precipitated austenite were also found to have a smaller median facet size, when fractured in a brittle transgranular mode, than specimens with no austenite. The decrease in DBTT and change in fracture surface appearance is related to the austenite transforming to martensite of a different variant than the matrix which effectively grain refines the steel and raises the cleavage stress.

  14. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-09-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  15. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-01-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  16. The isothermal decomposition of austenite in hot-rolled microalloyed steels

    NASA Astrophysics Data System (ADS)

    Crooks, M. J.; Chilton, J. M.

    1984-06-01

    The isothermal decomposition of austenite has been examined in a set of 0.1 C, 1.4 Mn steels containing small amounts of Ti, V, or Nb. The volume fraction of ferrite was measured as a function of transformation temperature and holding time, after hot rolling. Precipitation of carbonitrides, in both the austenite and the ferrite, was examined by electron microscopy of extraction replicas. The decomposition is slowest in the Nb-alloyed steel, in which the start of transformation is delayed and ferrite growth rates are much lower than in the other steels. In the V-alloyed steels, ferrite growth rates are lower than in the plain carbon or Ti alloyed steels. These results are discussed in terms of the effects of carbonitride precipitation in the austenite during high temperature deformation and in the ferrite during transformation. The roles of V and Nb in solution are also considered.

  17. Solidification behavior and microstructural analysis of austenitic stainless steel laser welds

    SciTech Connect

    David, S.A.; Vitek, J.M.

    1981-01-01

    Solidification behavior of austenitic stainless steel laser welds has been investigated with a high-power laser system. The welds were made at speeds ranging from 13 to 60 mm/s. The welds sowed a wide variety of microstructural features. The ferrite content in the 13-mm/s weld varied from less than 1% at the root of the weld to about 10% at the crown. The duplex structure at the crown of the weld was much finer than the one observed in conventional weld metal. However, the welds made at 25 and 60 mm/s contained an austenitic structure with less than 1% ferrite throughout the weld. Microstructural analysis of these welds used optical microscopy, transmission electron microscopy, and analytical electron microscopy. The austenitic stainless steel welds were free of any cracking, and the results are explained in terms of the rapid solidification conditions during laser welding.

  18. Strength of "Light" Ferritic and Austenitic Steels Based on the Fe - Mn - Al - C System

    NASA Astrophysics Data System (ADS)

    Kaputkina, L. M.; Svyazhin, A. G.; Smarygina, I. V.; Kindop, V. E.

    2017-01-01

    The phase composition, the hardness, the mechanical properties at room temperature, and the resistance to hot (950 - 1000°C) and warm (550°C) deformation are studied for cast deformable "light" ferritic and austenitic steels of the Fe - (12 - 25)% Mn - (0 - 15)% Al - (0 - 2)% C system alloyed additionally with about 5% Ni. The high-aluminum high-manganese low-carbon and carbonless ferritic steels at a temperature of about 0.5 T melt have a specific strength close to that of the austenitic steels and may be used as weldable scale-resistant and wear-resistant materials. The high-carbon Fe - (20 - 24)% Mn - (5 - 9)% Al - 5% Ni - 1.5% C austenitic steels may be applied as light high-strength materials operating at cryogenic temperatures after a solution treatment and as scale- and heat-resistant materials in an aged condition.

  19. Unraveling the Effect of Thermomechanical Treatment on the Dissolution of Delta Ferrite in Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Rezayat, Mohammad; Mirzadeh, Hamed; Namdar, Masih; Parsa, Mohammad Habibi

    2016-02-01

    Considering the detrimental effects of delta ferrite stringers in austenitic stainless steels and the industrial considerations regarding energy consumption, investigating, and optimizing the kinetics of delta ferrite removal is of vital importance. In the current study, a model alloy prone to the formation of austenite/delta ferrite dual phase microstructure was subjected to thermomechanical treatment using the wedge rolling test aiming to dissolve delta ferrite. The effect of introducing lattice defects and occurrence of dynamic recrystallization (DRX) were investigated. It was revealed that pipe diffusion is responsible for delta ferrite removal during thermomechanical process, whereas when the DRX is dominant, the kinetics of delta ferrite dissolution tends toward that of the static homogenization treatment for delta ferrite removal that is based on the lattice diffusion of Cr and Ni in austenite. It was concluded that the optimum condition for dissolution of delta ferrite can be defined by the highest rolling temperature and strain in which DRX is not pronounced.

  20. Processing and characterization of a hipped oxide dispersion strengthened austenitic steel

    NASA Astrophysics Data System (ADS)

    Zhou, Zhangjian; Yang, Shuo; Chen, Wanhua; Liao, Lu; Xu, Yingli

    2012-09-01

    An oxide dispersion strengthened (ODS) austenitic steel with a nominal chemical composition of Fe-18Cr-8Ni-1Mo-0.5Ti-0.35Y2O3 (in wt.%) was prepared by mechanical alloying (MA) combined with hot isostatic pressing (HIP). The morphology of MA powders was observed by SEM. The microstructure of the HIPed ODS austenitic steels and chemical composition of the oxide particles were examined by TEM combined with an energy dispersive spectrometry. The oxide dispersion particles with sizes less than 20 nm were determined to be complex Y-Ti-Si-O oxides. The tensile test showed that the fabricated ODS austenitic steel had very high strength and good ductility. The ultimate tensile strength was around 1000 MPa with a total elongation of 33.5% at room temperature, while at temperature of 700 °C, the ultimate tensile strength still reached around 500 MPa.

  1. Examination of Austenite Solidification and Spheroidal Graphite Growth in Ni-Fe-C Alloys

    NASA Astrophysics Data System (ADS)

    Qing, J.; Richards, V. L.; Van Aken, D. C.

    The austenite phase and the spheroidal graphite in a Ni-Fe-C alloy at various solidification stages were captured by quenching experiments using spherical ceramic shell molds with inserted thermocouples. Multiple graphite nodules /spheroidal graphite particles inside an eutectic cell were observed using optical microscopy. Individual eutectic cells were differentiated by an intermetallic phase occurring within the interdendritic regions. Electron backscatter diffraction (EBSD) and orientation image mapping (OIM) analyses were performed to investigate the crystallographic orientation and the grain boundary distribution of the austenite grains surrounding individual spheroidal graphite particles. The austenite engulfment process around the spheroidal graphite was revealed by EBSD/OIM analyses. Examination of the graphite nodules extracted by deep etching experiments revealed three stages of growth for the spheroidal graphite particles.

  2. Long term corrosion resistance of alumina forming austenitic stainless steels in liquid lead

    NASA Astrophysics Data System (ADS)

    Ejenstam, Jesper; Szakálos, Peter

    2015-06-01

    Alumina forming austenitic steels (AFA) and commercial stainless steels have been exposed in liquid lead with 10-7 wt.% oxygen at 550 °C for up to one year. It is known that chromia forming austenitic stainless steels, such as 316L and 15-15 Ti, have difficulties forming protective oxides in liquid lead at temperatures above 500 °C, which is confirmed in this study. By adding Al to austenitic steels, it is in general terms possible to increase the corrosion resistance. However this study shows that the high Ni containing AFA alloys are attacked by the liquid lead, i.e. dissolution attack occurs. By lowering the Ni content in AFA alloys, it is possible to achieve excellent oxidation properties in liquid lead. Following further optimization of the microstructural properties, low Ni AFA alloys may represent a promising future structural steel for lead cooled reactors.

  3. Quantification of retained austenite by X-ray diffraction and saturation magnetization in a supermartensitic stainless steel

    SciTech Connect

    Sicupira, Felipe Lucas; Sandim, Maria José R.; Sandim, Hugo R.Z.; Santos, Dagoberto Brandão; Renzetti, Reny Angela

    2016-05-15

    The good performance of supermartensitic stainless steels is strongly dependent on the volume fraction of retained austenite at room temperature. The present work investigates the effect of secondary tempering temperatures on this phase transformation and quantifies the amount of retained austenite by X-ray diffraction and saturation magnetization. The steel samples were tempered for 1 h within a temperature range of 600–800 °C. The microstructure was characterized using scanning electron microscopy and electron backscatter diffraction. Results show that the amount of retained austenite decreased with increasing secondary tempering temperature in both quantification methods. - Highlights: • The phase transformation during secondary tempering temperatures was observed. • Phases were quantified by X-ray diffraction and DC-saturation magnetization. • More retained austenite forms with increasing secondary tempering temperature. • The retained austenite is mainly located at the grain and lath boundaries.

  4. Hot Ductility Characterization of Sanicro-28 Super-Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Mirzaei, A.; Zarei-Hanzaki, A.; Abedi, H. R.

    2016-05-01

    The hot ductility behavior of a super-austenitic stainless steel has been studied using tensile testing method in the temperature range from 1073 K to 1373 K (800 °C to 1100 °C) under the strain rates of 0.1, 0.01, and 0.001 s-1. The hot compression tests were also performed at the same deformation condition to identify the activated restoration mechanisms. At lower temperatures [ i.e., 1073 K and 1173 K (800 °C and 900 °C)], the serration of initial grain boundaries confirms the occurrence of dynamic recovery as the predominant restoration process. However, in the course of applied deformation, the initial microstructure is recrystallized at higher temperatures [ i.e., 1273 K and 1373 K (1000 °C and 1100 °C)]. In this respect, annealing the twin boundaries could well stimulate the recrystallization kinetic through initiation new annealing twins on prior annealing twin boundaries. The hot tensile results show that there is a general trend of increasing ductility by temperature. However, two regions of ductility drop are recognized at 1273 K and 1373 K (1000°C)/0.1s-1 and (1100°C)/0.01s-1. The ductility variations at different conditions of temperature and strain rate are discussed in terms of simultaneous activation of grain boundary sliding and restoration processes. The observed ductility troughs are attributed to the occurrence of grain boundary sliding and the resulting R-type and W-type cracks. The occurrence of dynamic recrystallization is also considered as the main factor increasing the ductility at higher temperatures. The enhanced ductility is primarily originated from the post-uniform elongation behavior, which is directly associated with the strain rate sensitivity of the experimental material.

  5. Three-dimensional transient thermoelectric currents in deep penetration laser welding of austenite stainless steel

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Pang, Shengyong; Shao, Xinyu; Wang, Chunming; Xiao, Jianzhong; Jiang, Ping

    2017-04-01

    The existence of thermoelectric currents (TECs) in workpieces during the laser welding of metals has been common knowledge for more than 15 years. However, the time-dependent evolutions of TECs in laser welding remain unclear. The present study developed a novel three-dimensional theoretical model of thermoelectric phenomena in the fiber laser welding of austenite stainless steel and used it to observe the time-dependent evolutions of TECs for the first time. Our model includes the complex physical effects of thermal, electromagnetic, fluid and phase transformation dynamics occurring at the millimeter laser ablated zone, which allowed us to simulate the TEC, self-induced magnetic field, Lorentz force, keyhole and weld pool behaviors varying with the welding time for different parameters. We found that TECs are truly three-dimensional, time-dependent, and uneven with a maximum current density of around 107 A/m2 located at the liquid-solid (L/S) interface near the front or bottom part of the keyhole at a laser power of 1.5 kW and a welding speed of 3 m/min. The TEC formed three-dimensional circulations moving from the melting front to solidification front in the solid part of workpiece, after which the contrary direction was followed in the liquid part. High frequency oscillation characteristics (2.2-8.5 kHz) were demonstrated in the TEC, which coincides with that of the keyhole instability (2.0-5.0 kHz). The magnitude of the self-induced magnetic field and Lorentz force can reach 0.1 mT and 1 kN/m3, respectively, which are both consistent with literature data. The predicted results of the weld dimensions by the proposed model agree well with the experimental results. Our findings could enhance the fundamental understanding of thermoelectric phenomena in laser welding.

  6. Experimental study of materials for patch graft on right ventricular outflow tract under extracorporeal circulation in dogs--comparison between Denacol EX-313-treated bovine jugular vein graft and expanded polytetrafluoroethylene (EPTFE) graft.

    PubMed

    Matsumoto, H; Sugiyama, S; Shibazaki, A; Tanaka, R; Takashima, K; Noishiki, Y; Yamane, Y

    2001-09-01

    A comparison between a bovine jugular vein treated with a hydrophilic polyepoxy compound cross-linker (Denacol), and expanded polytetrafluoroethylene (EPTFE), an artificial material, as a patch graft for the reconstruction of the right ventricular outflow tract under extracorporeal circulation in dogs, as if they had pulmonic stenosis, was made. Hemodynamic and histological examinations were conducted two weeks after the transplantation. Hemodynamic problems were not observed in either the Denacol or EPTFE groups. Macroscopically, organization of new tissue on the graft surface was more marked in the EPTFE group than in the Denacol group, and newly-formed tissue was seen surrounding the border of the graft and burying it in the EPTFE group. In the Denacol group, microscopic findings revealed the presence of inflammatory cells and fibroblasts, and an invasion of the graft by collagen fibers and elastic fibers. In the EPTFE group, there was minimal cellular infiltration of the graft and a thick layer consisting of collagen fibers and fibroblasts was observed around the graft. These results indicated that two weeks after transplantation the graft was better assimilated and organized with blood vasculature in the patch graft in the Denacol group than in the EPTFE group.

  7. Texture evolution of warm-rolled and annealed 304L and 316L austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Lindell, D.

    2015-04-01

    The brass-to-copper rolling texture transition is observed during warm rolling austenitic stainless steels. In the current paper austenitic stainless steels 304L and 316L have been subjected to warm rolling at 700°C to 90% reduction. The evolution of microstructure and texture during subsequent annealing has been studied using dilatometry and electron backscatter diffraction. Recrystallisation texture for 304L was primarily cube with some retained rolling texture while 316L only had retained rolling texture. The different behaviour between the two steels is believed to originate from differences in molybdenum content.

  8. The Formation of Martensitic Austenite During Nitridation of Martensitic and Duplex Stainless Steels

    NASA Astrophysics Data System (ADS)

    Zangiabadi, Amirali; Dalton, John C.; Wang, Danqi; Ernst, Frank; Heuer, Arthur H.

    2017-01-01

    Isothermal martensite/ferrite-to-austenite phase transformations have been observed after low-temperature nitridation in the martensite and δ-ferrite phases in 15-5 PH (precipitation hardening), 17-7 PH, and 2205 (duplex) stainless steels. These transformations, in the region with nitrogen concentrations of 8 to 16 at. pct, are consistent with the notion that nitrogen is a strong austenite stabilizer and substitutional diffusion is effectively frozen at the paraequilibrium temperatures of our experiments. Our microstructural and diffraction analyses provide conclusive evidence for the martensitic nature of these phase transformations.

  9. The features of microstructure and mechanical properties of austenitic steel after direct and reverse martensitic transformations

    NASA Astrophysics Data System (ADS)

    Litovchenko, I. Yu.; Akkuzin, S. A.; Polekhina, N. A.; Tyumentsev, A. N.; Naiden, E. P.

    2015-10-01

    The features of structural states of metastable austenitic steel after thermomechanical treatments, including low-temperature deformation, warm deformation and subsequent annealing are investigated. It is shown that under these conditions the direct (γ → α') and reverse (α' → γ) martensitic transformations occur and submicrocrystalline structural states are formed. The proposed thermomechanical treatment allows varying the strength and plastic properties of austenitic steel in a wide range. The strength of steel in submicrocrystalline state is 4-6 times higher than its original value.

  10. Nondestructive Evaluation of Strain Distribution and Fatigue Distribution from Austenitic Stainless Steel by Using Magnetic Sensors

    SciTech Connect

    Tsuchida, Y.; Enokizono, M.; Oka, M.; Yakushiji, T.

    2007-03-21

    Austenitic stainless steel transforms from austenitic crystal structure to martensitic crystal structure after applying strain or stress. Because martensitic crystal structures have magnetization, strain evaluation and fatigue evaluation can be performed by measuring magnetic properties. This paper describes the measurement of leakage magnetic flux density of remanent magnetization for the strain evaluation and the fatigue evaluation by a typical Hall element sensor for SUS 304 and SUS 304L and by a high-sensitivity thin-film flux-gate magnetic sensor for SUS 316 and SUS 316L.

  11. Plastic deformation effect of the corrosion resistance in case of austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Haraszti, F.; Kovacs, T.

    2017-02-01

    The corrosion forms are different in case of the austenitic steel than in case of carbon steels. Corrosion is very dangerous process, because that corrosion form is the intergranular corrosion. The austenitic stainless steel shows high corrosion resistance level. It knows that plastic deformation and the heat treating decrease it’s resistance. The corrosion form in case of this steel is very special and the corrosion tests are difficult. We tested the selected steel about its corrosion behaviour after high rate deformation. We wanted to find a relationship between the corrosion resistance decreasing and the rate of the plastic deformation. We wanted to show this behaviour from mechanical and electrical changing.

  12. Investigation of Strain-Induced Martensitic Transformation in Metastable Austenite using Nanoindentation

    SciTech Connect

    Ahn, T.-H.; Oh, C.-S.; Kim, D. H.; Oh, K. H.; Bei, Hongbin; George, Easo P; Han, H. N.

    2010-01-01

    Strain-induced martensitic transformation of metastable austenite was investigated by nanoindentation of individual austenite grains in multi-phase steel. A cross-section prepared through one of these indented regions using focused ion beam milling was examined by transmission electron microscopy. The presence of martensite underneath the indent indicates that the pop-ins observed on the load-displacement curve during nanoindentation correspond to the onset of strain-induced martensitic transformation. The pop-ins can be understood as resulting from the selection of a favorable martensite variant during nanoindentation.

  13. Electrochemical evaluation of sensitization in austenitic stainless steels using miniaturized specimens*1

    NASA Astrophysics Data System (ADS)

    Inazumi, T.; Bell, G. E. C.; Kiuchi, K.

    1991-03-01

    An electrochemical testing system was developed to evaluate the sensitization of neutron-irradiated austenitic stainless steels using miniaturized disk-type specimens, 3 mm in diameter and 0.25 mm thick. The system consists of a specimen holder in which a miniaturized specimen is mounted as the working electrode, a test cell designed to handle radioactive materials and waste, a computer-controlled potentiostat/galvanostat and a surface preparation equipment. Sensitization of a thermally-aged Ti-modified austenitic stainless steel was successfully detected by the single-loop electrochemical potentiokinetic reactivation (SL-EPR) method.

  14. Synthetically Focused Imaging Techniques in Simulated Austenitic Steel Welds Using AN Ultrasonic Phased Array

    NASA Astrophysics Data System (ADS)

    Connolly, G. D.; Lowe, M. J. S.; Rokhlin, S. I.; Temple, J. A. G.

    2010-02-01

    In austenitic steel welds employed in safety-critical applications, detection of defects that may propagate during service or may have occurred during welding is particularly important. In this study, synthetically focused imaging techniques are applied to the echoes received by phased arrays in order to reconstruct images of the interior of a simulated austenitic steel weld, with application to sizing and location of simplified defects. Using a ray-tracing approach through a previously developed weld model, we briefly describe and then apply three focusing techniques. Results generated via both ray-tracing theory and finite element simulations will be shown.

  15. Investigation of coatings of austenitic steels produced by supersonic laser deposition

    NASA Astrophysics Data System (ADS)

    Gorunov, A. I.; Gilmutdinov, A. Kh.

    2017-02-01

    The structure and properties of stainless austenitic steel coatings obtained by the supersonic laser deposition are studied in the paper. Implantation of the powder particles into the substrate surface and simultaneous plastic deformation at partial melting improved the mechanical properties of the coatings - tensile strength limit was 650 MPa and adhesion strength was 105 MPa. It was shown that insufficient laser power leads to disruption of the deposition process stability and coating cracking. Surface temperature increase caused by laser heating above 1300 °C resulted in coating melting. The X-ray analysis showed that radiation intensifies the cold spray process and does not cause changes in the austenitic base structure.

  16. The development of alumina-forming austenitic stainless steels for high-temperature structural use

    SciTech Connect

    Brady, Michael P; Yamamoto, Yukinori; Santella, Michael L; Maziasz, Philip J; Pint, Bruce A; Lu, Zhao Ping; Liu, Chain T; Bei, Hongbin

    2008-01-01

    Efforts at Oak Ridge National Laboratory to developAl2O3-forming austenitic (AFA) stainless steels for high-temperature (600-900 aC) structural use under aggressive oxidizing conditions are overviewed. Data obtained to date indicate the potential to achieve superior oxidation resistance to conventional Cr2O3-forming Fe- and Ni-base heat-resistant alloys, with creep strength comparable to state-of-the-art advanced austenitic stainless steels. Preliminary assessment also indicates the developed alloys are amenable to welding. Details of the alloy design approach and composition-microstructure-property relationships are presented.

  17. In-situ determination of austenite and martensite formation in 13Cr6Ni2Mo supermartensitic stainless steel

    SciTech Connect

    Bojack, A.; Zhao, L.; Morris, P.F.; Sietsma, J.

    2012-09-15

    In-situ analysis of the phase transformations in a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) was carried out using a thermo-magnetic technique, dilatometry and high temperature X-ray diffractometry (HT-XRD). A combination of the results obtained by the three applied techniques gives a valuable insight in the phase transformations during the austenitization treatment, including subsequent cooling, of the 13Cr6Ni2Mo supermartensitic stainless steel, where the magnetic technique offers a high accuracy in monitoring the austenite fraction. It was found by dilatometry that the austenite formation during heating takes place in two stages, most likely caused by partitioning of Ni into austenite. The in-situ evolution of the austenite fraction is monitored by high-temperature XRD and dilatometry. The progress of martensite formation during cooling was described with a Koistinen-Marburger relation for the results obtained from the magnetic and dilatometer experiments. Enhanced martensite formation at the sample surface was detected by X-ray diffraction, which is assumed to be due to relaxation of transformation stresses at the sample surface. Due to the high alloy content and high thermodynamic stability of austenite at room temperature, 4 vol.% of austenite was found to be stable at room temperature after the austenitization treatment. - Highlights: Black-Right-Pointing-Pointer We in-situ analyzed phase transformations and fractions of a 13Cr6Ni2Mo SMSS. Black-Right-Pointing-Pointer Higher accuracy of the austenite fraction was obtained from magnetic technique. Black-Right-Pointing-Pointer Austenite formation during heating takes place in two stages. Black-Right-Pointing-Pointer Enhanced martensite formation at the sample surface detected by X-ray diffraction.

  18. Monolithical aspherical beam expanding systems

    NASA Astrophysics Data System (ADS)

    Fuchs, U.; Matthias, Sabrina

    2014-10-01

    Beam expanding is a common task, where Galileo telescopes are preferred. However researches and customers have found limitations when using these systems. A new monolithical solution which is based on the usage of only one aspherical component will be presented. It will be shown how to combine up to five monolithical beam expanding systems and to keep the beam quality at diffraction limitation. Insights will be given how aspherical beam expanding systems will help using larger incoming beams and reducing the overall length of such a system. Additionally an add-on element for divergence and wavelength adaption will be presented.

  19. Investigation of the effect of cyclic laser heating for creating dispersed structures in the austenitic-martensitic alloys based on Fe-Cr-Ni system

    NASA Astrophysics Data System (ADS)

    Andreev, A. O.; Mironov, V. D.; Petrovskii, V. N.; Orlov, A. V.; Libman, M. A.

    2016-09-01

    The effect of cyclic laser heating on the formation of the austenite structure in the austenitic-martensitic alloys based on Fe-Cr-Ni system is investigated. It is shown that under the influence of ultra-fast laser heating on the martensite, which was formed during plastic deformation, the reverse martensitic transformation occurs, and austenite with high strength characteristics is formed. Repeated and multiple laser heating effectively grinds areas of austenite to a size close to the large nanoparticles. There is an additional increase in the strength characteristics of austenite as a result of this fragmentation.

  20. High temperature oxidation of alumina forming cast austenitic stainless steels within an environment of pure steam

    NASA Astrophysics Data System (ADS)

    Prenzlow, Elmer A.

    Steam cracking of hydrocarbons in the petrochemical industry is a multibillion dollar industry. The processes performed in these plants create byproducts that negatively affect the integrity of stainless steel piping through high temperature corrosion. Alloys used presently in industry rely on the formation of chromium oxide (chromia) as a protective layer between the bulk metal pipe and chemical byproducts. However, chromia can become susceptible to attack from aggressive species such as carbon, water vapor, and sulfur compounds, thus creating a need for a better protection method. A new series of austenitic stainless steels have been developed in recent years that, rather than forming chromia, create a protective layer of aluminum oxide (alumina) under oxidative conditions. These alloys have high nickel content for the stabilization of the austenitic phase, and a more thermodynamically stable oxide layer relative to the traditional chromia formers. Consequently, alumina forming alloys have been proposed as replacements for chromia forming alloys in the petrochemical industry. General oxidation testing has been performed on alumina forming alloys under dry and 10% water vapor conditions. However, oxidation conditions in industry resemble a 100% steam environment. Therefore, test methods to mimic such conditions are needed so that alloys can be tested and developed further for these applications. Four alloys with aluminum contents ranging from 2.6 to 3.9 wt% were cut from centrifugally cast pipes and subjected to oxidation in an environment of pure steam for up to 30 hours, at temperatures of 800 °C and 950 °C. Samples were analyzed using Raman, SEM, and EDS and showed a continuous alumina layer free of cracks. The alumina layer thickness increased with time. Additionally, larger thicknesses were observed in samples oxidized at 950 °C from those of 800 °C. Thickness measurements were used to calculate parabolic and non-parabolic oxidation rate constants

  1. Advanced expander test bed program

    NASA Technical Reports Server (NTRS)

    Riccardi, D. P.; Mitchell, J. C.

    1993-01-01

    The Advanced Expander Test Bed (AETB) is a key element in NASA's Space Chemical Engine Technology Program for development and demonstration of expander cycle oxygen/hydrogen engine and advanced component technologies applicable to space engines as well as launch vehicle upper stage engines. The AETB will be used to validate the high-pressure expander cycle concept, investigate system interactions, and conduct investigations of advanced mission focused components and new health monitoring techniques in an engine system environment. The split expander cycle AETB will operate at combustion chamber pressures up to 1200 psia with propellant flow rates equivalent to 20,000 lbf vacuum thrust. Contract work began 27 Apr. 1990. During 1992, a major milestone was achieved with the review of the final design of the oxidizer turbopump in Sep. 1992.

  2. Experimental Determination of the Austenite + Liquid Phase Boundaries of the Fe-C System

    NASA Astrophysics Data System (ADS)

    Chicco, Bruno; Thorpe, Warren R.

    1982-07-01

    Differential thermal analysis has been employed to achieve an accurate determination of the solidliquid equilibria for γ-Fe at temperatures between 1147 °C and 1430 °C and compositions in the range 1.5 to 4.42 wt pct C. Several small but significant changes to the established phase diagram have been proposed. In particular, the liquidus in the vicinity of the eutectic has been raised by approximately 15 °C and the temperature of the graphite eutectic lowered to 1150.5 °C. Consequently, the eutectic compositions have been increased to 4.39 and 4.42 wt pct C for the graphite and cementite eutectics, respectively. The possibility of some modification to the γ-solidus has also been suggested, and a revised phase diagram is presented.

  3. Austenitic stainless steel alloys having improved resistance to fast neutron-induced swelling

    DOEpatents

    Bloom, Everett E.; Stiegler, James O.; Rowcliffe, Arthur F.; Leitnaker, James M.

    1977-03-08

    The present invention is based on the discovery that radiation-induced voids which occur during fast neutron irradiation can be controlled by small but effective additions of titanium and silicon. The void-suppressing effect of these metals in combination is demonstrated and particularly apparent in austenitic stainless steels.

  4. Effect of heavy ion irradiation on microstructural evolution in CF8 cast austenitic stainless steel

    DOE PAGES

    Chen, Wei-Ying; Li, Meimei; Kirk, Marquis A.; ...

    2015-08-21

    The microstructural evolution in ferrite and austenitic in cast austenitic stainless steel (CASS) CF8, as received or thermally aged at 400 °C for 10,000 h, was followed under TEM with in situ irradiation of 1 MeV Kr ions at 300 and 350 °C to a fluence of 1.9 × 1015 ions/cm2 (~3 dpa) at the IVEM-Tandem Facility. For the unaged CF8, the irradiation-induced dislocation loops appeared at a much lower dose in the austenite than in the ferrite. At the end dose, the austenite formed a well-developed dislocation network microstructure, while the ferrite exhibited an extended dislocation structure as linemore » segments. Compared to the unaged CF8, the aged specimen appeared to have lower rate of damage accumulation. The rate of microstructural evolution under irradiation in the ferrite was significantly lower in the aged specimen than in the unaged. Finally, we attributed this difference to the different initial microstructures in the unaged and aged specimens, which implies that thermal aging and irradiation are not independent but interconnected damage processes.« less

  5. Copper modified austenitic stainless steel alloys with improved high temperature creep resistance

    DOEpatents

    Swindeman, R.W.; Maziasz, P.J.

    1987-04-28

    An improved austenitic stainless steel that incorporates copper into a base Fe-Ni-Cr alloy having minor alloying substituents of Mo, Mn, Si, T, Nb, V, C, N, P, B which exhibits significant improvement in high temperature creep resistance over previous steels. 3 figs.

  6. Effect of heavy ion irradiation on microstructural evolution in CF8 cast austenitic stainless steel

    SciTech Connect

    Chen, Wei-Ying; Li, Meimei; Kirk, Marquis A.; Baldo, Peter M.; Lian, Tiangan

    2015-08-21

    The microstructural evolution in ferrite and austenitic in cast austenitic stainless steel (CASS) CF8, as received or thermally aged at 400 °C for 10,000 h, was followed under TEM with in situ irradiation of 1 MeV Kr ions at 300 and 350 °C to a fluence of 1.9 × 1015 ions/cm2 (~3 dpa) at the IVEM-Tandem Facility. For the unaged CF8, the irradiation-induced dislocation loops appeared at a much lower dose in the austenite than in the ferrite. At the end dose, the austenite formed a well-developed dislocation network microstructure, while the ferrite exhibited an extended dislocation structure as line segments. Compared to the unaged CF8, the aged specimen appeared to have lower rate of damage accumulation. The rate of microstructural evolution under irradiation in the ferrite was significantly lower in the aged specimen than in the unaged. Finally, we attributed this difference to the different initial microstructures in the unaged and aged specimens, which implies that thermal aging and irradiation are not independent but interconnected damage processes.

  7. Influence of free forging conditions on austenitic grain growth in constructional steel

    NASA Astrophysics Data System (ADS)

    Zagulyaeva, S. V.; Potanina, V. S.; Vinograd, M. I.

    1984-02-01

    The initial period of austenitic grain growth in heating of a hot forged billet of 50G-SSh steel and of forgings after free forging is characterized by the formation of a mixed grain structure of No. 8 fine grains and No. 3-0 coarse.

  8. High temperature phase chemistries and solidification mode prediction in nitrogen-strengthened austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Ritter, Ann M.; Henry, Michael F.; Savage, Warren F.

    1984-07-01

    Nitronic 50 and Nitronic 50W, two nitrogen-strengthened stainless steels, were heat treated over a wide range of temperatures, and the compositions of the ferrite and austenite at each temperature were measured with analytical electron microscopy techniques. The compositional data were used to generate the (γ + δ phase field on a 58 pct Fe vertical section. Volume fractions of ferrite and austenite were calculated from phase chemistries and compared with volume fractions determined from optical micrographs. Weld solidification modes were predicted by reference to the Cr and Ni contents of each alloy, and the results were compared with predictions based on the ratios of calculated Cr and Ni equivalents for the alloys. Nitronic 50, which contained ferrite and austenite at the solidus temperature of 1370 °C, solidified through the eutectic triangle, and the weld microstructure was similar to that of austenitic-ferritic solidification. Nitronic 50W was totally ferritic at 1340 °C and solidified as primary delta ferrite. During heat treatments, Nitronic 50 and Nitronic 50W precipitated secondary phases, notably Z-phase (NbCrN), sigma phase, and stringered phases rich in Mn and Cr.

  9. Diffusion Couple Alloying of Refractory Metals in Austenitic and Ferritic/Martensitic Steels

    DTIC Science & Technology

    2012-03-01

    raised in the samples, the main mode was dislocation channeling [8]. b. Irradiation -Induced Precipitation and Grain Boundary Segregation In materials...centered Cubic FIB Focused Ion Beam HTGR High Temperature Gas Reactor IASCC Irradiation -assisted Stress Corrosion Cracking LMFBR Liquid Metal Fast...displacements per atom (dpa) (From [8]). Observations on irradiated austenitic steel determined that two deformation modes were present: dislocation

  10. Effect of Austenite Deformation and Continuous Cooling on Microstructure Evolution in a Pipeline Steel

    NASA Astrophysics Data System (ADS)

    Zhao, H.; Gray, J. M.; Palmiere, E. J.

    The effect of austenite deformation and continuous cooling on the evolution of microstructure in a high temperature processing (HTP) concept pipeline steel was investigated in this research. It was found that without austenite deformation, the transformed microstructure consists of blocky quasi-polygonal ferrite (QF) grains and parallel bainitic ferrite (BF) laths at a cooling rate of 0.5 °C/s. With increased cooling rates, the fraction of BF laths is raised and the microstructure reaches full BF at cooling rates of 5°C/s and higher. After austenite deformation, BF laths disappear at low cooling rates of 0.5 1°C/s and QF is the dominant phase. At a higher cooling rate of 5°C/s, the fraction of QF is reduced and acicualr ferrite (AF) becomes the main phase surrounded by QF grains. Increasing the cooling rate further, QF disappears and fthe raction of BF rises, finally leading to a BF dominant microstructure at a cooling rate of 50°C/s. Factors influencing these microstructure evolution characteristics were discussed, including segregation of niobium atoms at austenite grain boundary and the introduction of intragranular nucleation sites by deformation.

  11. Austenite Stability and Tensile Properties of Warm-Extruded Trip Steels

    DTIC Science & Technology

    1976-05-01

    ductility in war-extruded TRIP steel. The austenite stability could be adjusted, however, by a tempering treatment to remove some carbon from solid ... solution , giving tensile properties equivalent or superior to those obtained by warm rolling. Difficulties in alloy composition control or temperature

  12. High post-irradiation ductility thermomechanical treatment for precipitation strengthened austenitic alloys

    DOEpatents

    Laidler, James J.; Borisch, Ronald R.; Korenko, Michael K.

    1982-01-01

    A method for improving the post-irradiation ductility is described which prises a solution heat treatment following which the materials are cold worked. They are included to demonstrate the beneficial effect of this treatment on the swelling resistance and the ductility of these austenitic precipitation hardenable alloys.

  13. Austenitic stainless steel alloys having improved resistance to fast neutron-induced swelling

    DOEpatents

    Bloom, Everett E.; Stiegler, James O.; Rowcliffe, Arthur F.; Leitnaker, James M.

    1979-01-01

    The present invention is based on the discovery that radiation-induced voids which occur during fast neutron irradiation can be controlled by small but effective additions of titanium and silicon. The void-suppressing effect of these metals in combination is demonstrated and particularly apparent in austenitic stainless steels.

  14. Assessment of Retained Austenite in AISI D2 Tool Steel Using Magnetic Hysteresis and Barkhausen Noise Parameters

    NASA Astrophysics Data System (ADS)

    Kahrobaee, Saeed; Kashefi, Mehrdad

    2015-03-01

    Inaccurate heat treatment process could result in excessive amount of retained austenite, which degrades the mechanical properties, like strength, wear resistance, and hardness of cold work tool steel parts. Thus, to control the mechanical properties, quantitative measurement of the retained austenite is a critical step in optimizing the heat-treating parameters. X-ray diffraction method is the most frequently used technique for this purpose. This technique is, however, destructive and time consuming. Furthermore, it is not applicable to 100% quality inspection of industrial parts. In the present paper, the influence of austenitizing temperature on the retained austenite content and hardness of AISI D2 tool steel has been studied. Additionally, nondestructive magnetic hysteresis parameters of the samples including coercivity, magnetic saturation, and maximum differential permeability as well as their magnetic Barkhausen noise features (RMS peak voltage and peak position) have been investigated. The results revealed direct relations between magnetic saturation, differential permeability, and MBN peak amplitude with increasing austenitizing temperature due to the retained austenite formation. Besides, both parameters of coercivity and peak position had an inverse correlation with the retained austenite fraction.

  15. Improved expanding ring technique for determining dynamic material properties.

    PubMed

    Liang, M Z; Li, X Y; Qin, J G; Lu, F Y

    2013-06-01

    An improved expanding ring experimental technique has been described to determine dynamic material properties under conditions approximating uniform one-dimensional tensile loading. There are mainly explosive expanding ring technique and electromagnetic expanding ring technique currently, for which exist many limitations in practical applications. The work reported herein is an attempt to overcome this difficulty by lateral efficiency loading produced by projectile, made of low-density material, impacting the same material filling. The lateral efficiency loading is a convenient and effective method, which allows materials to be in uniform uniaxial stress conditions at a high stress rate. The procedure is illustrated by experiments performed on 1100-0 aluminum rings.

  16. The effect of chemical composition and austenite conditioning on the transformation behavior of microalloyed steels

    SciTech Connect

    Mousavi Anijdan, S.H.; Rezaeian, Ahmad; Yue, Steve

    2012-01-15

    In this investigation, by using continuous cooling torsion (CCT) testing, the transformation behavior of four microalloyed steels under two circumstances of austenite conditioning and non-conditioning was studied. A full scale hot-rolling schedule containing a 13-pass deformation was employed for the conditioning of the austenite. The CCT tests were then employed till temperature of {approx} 540 Degree-Sign C and the flow curves obtained from this process were analyzed. The initial and final microstructures of the steels were studied by optical and electron microscopes. Results show that alloying elements would decrease the transformation temperature. This effect intensifies with the gradual increase of Mo, Nb and Cu as alloying elements added to the microalloyed steels. As well, austenite conditioning increased the transformation start temperature due mainly to the promotion of polygonal ferrite formation that resulted from a pancaked austenite. The final microstructures also show that CCT alone would decrease the amount of bainite by inducing ferrite transformation in the two phase region. In addition, after the transformation begins, the deformation might result in the occurrence of dynamic recrystallization in the ferrite region. This could lead to two different ferrite grain sizes at the end of the CCT. Moreover, the Nb bearing steels show no sign of decreasing the strength level after the transformation begins in the non-conditioned situation and their microstructure is a mix of polygonal ferrite and bainite indicating an absence of probable dynamic recrystallization in this condition. In the conditioned cases, however, these steels show a rapid decrease of the strength level and their final microstructures insinuate that ferrite could have undergone a dynamic recrystallization due to deformation. Consequently, no bainite was seen in the austenite conditioned Nb bearing steels. The pancaking of austenite in the latest cases produced fully polygonal ferrite

  17. Mechanical properties of steels with a microstructure of bainite/martensite and austenite islands

    NASA Astrophysics Data System (ADS)

    Syammach, Sami M.

    Advanced high strength steels (AHSS) are continually being developed in order to reduce weight and improve safety for automotive applications. There is need for economic steels with improved strength and ductility combinations. These demands have led to research and development of third generation AHSS. Third generation AHSS include steel grades with a bainitic and tempered martensitic matrix with retained austenite islands. These steels may provide improved mechanical properties compared to first generation AHSS and should be more economical than second generation AHSS. There is a need to investigate these newer types of steels to determine their strength and formability properties. Understanding these bainitic and tempered martensitic steels is important because they likely can be produced using currently available production systems. If viable, these steels could be a positive step in the evolution of AHSS. The present work investigates the effect of the microstructure on the mechanical properties of steels with a microstructure of bainite, martensite, and retained austenite, so called TRIP aided bainitic ferrite (TBF) steels. The first step in this project was creating the desired microstructure. To create a microstructure of bainite, martensite, and austenite an interrupted austempering heat treatment was used. Varying the heat treatment times and temperatures produced microstructures of varying amounts of bainite, martensite, and austenite. Mechanical properties such as strength, ductility, strain hardening, and hole-expansion ratios were then evaluated for each heat treatment. Correlations between mechanical properties and microstructure were then evaluated. It was found that samples after each of the heat treatments exhibited strengths between 1050 MPa and 1350 MPa with total elongations varying from 8 pct to 16 pct. By increasing the bainite and austenite volume fraction the strength of the steel was found to decrease, but the ductility increased. Larger

  18. RESULTS OF CHARACTERIZATION TESTS OF THE SURFACES OF A COMMERCIALLY CARBURIZED AUSTENITIC STAINLESS STEEL

    SciTech Connect

    Farrell, K

    2004-01-07

    A commercial surface carburization treatment that shows promise for hardening the surfaces of the stainless steel target vessel of the Spallation Neutron Source against cavitation erosion and pitting caused by the action of pulsed pressure waves in the liquid mercury target has been investigated. To verify promotional claims for the treatment and to uncover any factors that might be of concern for the integrity of a carburized target vessel, some characterization tests of the nature of the surface layers of carburized austenitic 316LN stainless steel were conducted. The findings support most of the claims. The carburized layer is about 35 {micro}m thick. Its indentation hardness is about five times larger than that of the substrate steel and declines rapidly with depth into the layer. The surface is distorted by the treatment, and the austenite lattice is enlarged. The corrosion resistance of the carburized layer in an acid medium is greater than that for untreated austenite. The layer is not brittle; it is plastically deformable and is quite resistant to cracking during straining. Contrary to the provider's assertations, the maximum carbon content of the layer is much less than 6-7 wt% carbon, and the carbon is not simply contained in supersaturated solid solution; some of it is present in a previously unreported iron carbide phase located at the very surface. Large variations were found in the thickness of the layer, and they signify that controls may be needed to ensure a uniform thickness for treatment of the SNS target vessel. Inclusion stringers and {delta}-ferrite phase embraced in the treated layer are less resistant to chemical attack than the treated austenite. From a cavitation pitting perspective under SNS bombardment, such non-austenitic phases may provide preferential sites for pitting. The shallow depth of the hardened layer will require use of protection measures to avoid mishandling damage to the layer during assembly and installation of a target

  19. Modelling the attenuation in the ATHENA finite elements code for the ultrasonic testing of austenitic stainless steel welds.

    PubMed

    Chassignole, B; Duwig, V; Ploix, M-A; Guy, P; El Guerjouma, R

    2009-12-01

    Multipass welds made in austenitic stainless steel, in the primary circuit of nuclear power plants with pressurized water reactors, are characterized by an anisotropic and heterogeneous structure that disturbs the ultrasonic propagation and makes ultrasonic non-destructive testing difficult. The ATHENA 2D finite element simulation code was developed to help understand the various physical phenomena at play. In this paper, we shall describe the attenuation model implemented in this code to give an account of wave scattering phenomenon through polycrystalline materials. This model is in particular based on the optimization of two tensors that characterize this material on the basis of experimental values of ultrasonic velocities attenuation coefficients. Three experimental configurations, two of which are representative of the industrial welds assessment case, are studied in view of validating the model through comparison with the simulation results. We shall thus provide a quantitative proof that taking into account the attenuation in the ATHENA code dramatically improves the results in terms of the amplitude of the echoes. The association of the code and detailed characterization of a weld's structure constitutes a remarkable breakthrough in the interpretation of the ultrasonic testing on this type of component.

  20. Comparison of fracture behavior for low-swelling ferritic and austenitic alloys irradiated in the Fast Flux Test Facility (FFTF) to 180 DPA. Revision 1

    SciTech Connect

    Huang, F.H.

    1992-02-01

    Fracture toughness testing was conducted to investigate the radiation embrittlement of high-nickel superalloys, modified austenitic steels and ferritic steels. These materials have been experimentally proven to possess excellent resistance to void swelling after high neutron exposures. In addition to swelling resistance, post-irradiation fracture resistance is another important criterion for reactor material selection. By means of fracture mechanics techniques the fracture behavior of those highly irradiated alloys was characterized in terms of irradiation and test conditions. Precipitation-strengthened alloys failed by channel fracture with very low postirradiation ductility. The fracture toughness of titanium-modified austenitic stainless steel D9 deteriorates with increasing fluence to about 100 displacement per atom (dpa), the fluence level at which brittle fracture appears to occur. Ferritic steels such as HT9 are the most promising candidate materials for fast and fusion reactor applications. The upper-shelf fracture toughness of alloy HT9 remained adequate after irradiation to 180 dpa although its ductile- brittle transition temperature (DBTT) shift by low temperature irradiation rendered the material susceptible to brittle fracture at room temperature. Understanding the fracture characteristics under various irradiation and test conditions helps reduce the potential for brittle fracture by permitting appropriate measure to be taken.

  1. Comparison of fracture behavior for low-swelling ferritic and austenitic alloys irradiated in the Fast Flux Test Facility (FFTF) to 180 DPA

    SciTech Connect

    Huang, F.H.

    1992-02-01

    Fracture toughness testing was conducted to investigate the radiation embrittlement of high-nickel superalloys, modified austenitic steels and ferritic steels. These materials have been experimentally proven to possess excellent resistance to void swelling after high neutron exposures. In addition to swelling resistance, post-irradiation fracture resistance is another important criterion for reactor material selection. By means of fracture mechanics techniques the fracture behavior of those highly irradiated alloys was characterized in terms of irradiation and test conditions. Precipitation-strengthened alloys failed by channel fracture with very low postirradiation ductility. The fracture toughness of titanium-modified austenitic stainless steel D9 deteriorates with increasing fluence to about 100 displacement per atom (dpa), the fluence level at which brittle fracture appears to occur. Ferritic steels such as HT9 are the most promising candidate materials for fast and fusion reactor applications. The upper-shelf fracture toughness of alloy HT9 remained adequate after irradiation to 180 dpa although its ductile- brittle transition temperature (DBTT) shift by low temperature irradiation rendered the material susceptible to brittle fracture at room temperature. Understanding the fracture characteristics under various irradiation and test conditions helps reduce the potential for brittle fracture by permitting appropriate measure to be taken.

  2. Plant proteomics update (2007-2008): Second-generation proteomic techniques, an appropriate experimental design, and data analysis to fulfill MIAPE standards, increase plant proteome coverage and expand biological knowledge.

    PubMed

    Jorrín-Novo, Jesús V; Maldonado, Ana M; Echevarría-Zomeño, Sira; Valledor, Luis; Castillejo, Mari A; Curto, Miguel; Valero, José; Sghaier, Besma; Donoso, Gabriel; Redondo, Inmaculada

    2009-04-13

    This review is the continuation of three previously published articles [Jorrin JV, Maldonado AM, Castillejo MA. Plant proteome analysis: a 2006 update. Proteomics 2007; 7: 2947-2962; Rossignol M, Peltier JB, Mock HP, Matros A, Maldonado AM, Jorrin JV. Plant proteome analysis: a 2004-2006 update. Proteomics 2006; 6: 5529-5548; Canovas FM, Dumas-Gaudot E, Recorbet G, Jorrin J, Mock HP, Rossignol M. Plant proteome analysis. Proteomics 2004; 4: 285-298] and aims to update the contribution of Proteomics to plant research between 2007 and September 2008 by reviewing most of the papers, which number approximately 250, that appeared in the Plant Proteomics field during that period. Most of the papers published deal with the proteome of Arabidopsis thaliana and rice (Oryza sativa), and focus on profiling organs, tissues, cells or subcellular proteomes, and studying developmental processes and responses to biotic and abiotic stresses using a differential expression strategy. Although the platform based on 2-DE is still the most commonly used, the use of gel-free and second-generation Quantitative Proteomic techniques has increased. Proteomic data are beginning to be validated using complementary -omics or classical biochemical or cellular biology techniques. In addition, appropriate experimental design and statistical analysis are being carried out in accordance with the required Minimal Information about a Proteomic Experiment (MIAPE) standards. As a result, the coverage of the plant cell proteome and the plant biology knowledge is increasing. Compared to human and yeast systems, however, plant biology research has yet to exploit fully the potential of proteomics, in particular its applications to PTMs and Interactomics.

  3. Deformability of expanded polystyrene under short-term compression

    NASA Astrophysics Data System (ADS)

    Gnip, I. J.; Vaitkus, S. I.; Kersulis, V. I.; Veyelis, S. A.

    2007-09-01

    The results obtained in an experimental investigation of deformability of expanded polystyrene (EPS) under short-term compression are presented. The density of EPS varied from 13 to 28 kg/m3. The method of design of experiments was used to determine the elastic modulus and the ultimate strain (corresponding to the end of quasi-linear deformability) under compression stresses operating perpendicularly and parallel to the faces of EPS products. A graphical interpretation of the models is also presented. Based on the experimental data obtained, it was concluded that the expanded polystyrene was homogeneous in mutually perpendicular planes with respect to its deformability in compression.

  4. The influence of fine ferrite formation on the γ/α interface, fine bainite and retained austenite in a thermomechanically-processed transformation induced plasticity steel

    DOE PAGES

    Timokhina, Ilana B.; Miller, Michael K.; Beladi, Hossein; ...

    2016-03-03

    We subjected a Fe–0.26C–1.96Si–2Mn with 0.31Mo (wt%) steel to a novel thermomechanical processing route to produce fine ferrite with different volume fractions, bainite, and retained austenite. In two types of fine ferrites were found to be: (i) formed along prior austenite grain boundaries, and (ii) formed intragranularly in the interior of austenite grains. An increase in the volume fraction of fine ferrite led to the preferential formation of blocky retained austenite with low stability, and to a decrease in the volume fraction of bainite with stable layers of retained austenite. Moreover, the difference in the morphology of the bainitic ferritemore » and the retained austenite after different isothermal ferrite times was found to be responsible for the deterioration of the mechanical properties. The segregation of Mn, Mo, and C at distances of 2–2.5 nm from the ferrite and retained austenite/martensite interface on the retained austenite/martensite site was observed after 2700 s of isothermal hold. Finally, it was suggested that the segregation occurred during the austenite-to-ferrite transformation, and that this would decrease the interface mobility, which affects the austenite-to-ferrite transformation and ferrite grain size.« less

  5. Effect of lower bainite/martensite/retained austenite triplex microstructure on the mechanical properties of a low-carbon steel with quenching and partitioning process

    NASA Astrophysics Data System (ADS)

    Li, Wan-song; Gao, Hong-ye; Li, Zhong-yi; Nakashima, Hideharu; Hata, Satoshi; Tian, Wen-huai

    2016-03-01

    We present a study concerning Fe-0.176C-1.31Si-1.58Mn-0.26Al-0.3Cr (wt%) steel subjected to a quenching and partitioning (Q&P) process. The results of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile tests demonstrate that the microstructures primarily consist of lath martensite, retained austenite, lower bainite (LB), and a small amount of tempered martensite; moreover, few twin austenite grains were observed. In the microstructure, three types of retained austenite with different sizes and morphologies were observed: blocky retained austenite (~300 nm in width), film-like retained austenite (80-120 nm in width), and ultra- fine film-like retained austenite (30-40 nm in width). Because of the effect of the retained austenite/martensite/LB triplex microstructure, the specimens prepared using different quenching temperatures exhibit high ultimate tensile strength and yield strength. Furthermore, the strength effect of LB can partially counteract the decreasing strength effect of martensite. The formation of LB substantially reduces the amount of retained austenite. Analyses of the retained austenite and the amount of blocky retained austenite indicated that the carbon content is critical to the total elongation of Q&P steel.

  6. The Effects of Austenitizing Conditions on the Microstructure and Wear Resistance of a Centrifugally Cast High-Speed Steel Roll

    NASA Astrophysics Data System (ADS)

    Kang, Minwoo; Lee, Young-Kook

    2016-07-01

    The influences of austenitizing conditions on the microstructure and wear resistance of a centrifugally cast high-speed steel roll were investigated through thermodynamic calculation, microstructural analysis, and high-temperature wear tests. When the austenitizing temperature was between 1323 K and 1423 K (1050 °C and 1150 °C), coarse eutectic M2C plates were decomposed into a mixture of MC and M6C particles. However, at 1473 K (1200 °C), the M2C plates were first replaced by both new austenite grains and MC particles without M6C particles, and then remaining M2C particles were dissolved during the growth of MC particles. The wear resistance of the HSS roll was improved with increasing austenitizing temperature up to 1473 K (1200 °C) because the coarse eutectic M2C plates, which are vulnerable to crack propagation, changed to disconnected hard M6C and MC particles.

  7. Quantitative investigation into the influence of temperature on carbide and austenite evolution during partitioning of a quenched and partitioned steel

    SciTech Connect

    Pierce, Dean T.; Coughlin, D. R.; Williamson, Don L.; Kähkönen, Joonas; Clarke, A. J.; Clarke, Kester D.; Speer, J. G.; De Moor, Emmanuel

    2016-05-03

    Here, the influence of partitioning temperature on microstructural evolution during quenching and partitioning was investigated in a 0.38C-1.54Mn-1.48Si wt.% steel using Mössbauer spectroscopy and transmission electron microscopy. η-carbide formation occurs in the martensite during the quenching, holding, and partitioning steps. More effective carbon partitioning from martensite to austenite was observed at 450 than 400°C, resulting in lower martensite carbon contents, less carbide formation, and greater retained austenite amounts for short partitioning times. Conversely, greater austenite decomposition occurs at 450°C for longer partitioning times. Lastly, cementite forms during austenite decomposition and in the martensite for longer partitioning times at 450°C.

  8. Austenite Grain Structures in Ti- and Nb-Containing High-Strength Low-Alloy Steel During Slab Reheating

    NASA Astrophysics Data System (ADS)

    Roy, S.; Chakrabarti, D.; Dey, G. K.

    2013-02-01

    Austenite-grain growth was investigated in a couple of microalloyed steels, one containing Ti and the other containing Nb, Ti, and V, using different reheating temperatures between 1273 K and 1523 K (1000 °C and 1250 °C). Nature and distribution of microalloy precipitates were quantitatively analyzed before and after reheating. Interdendritic segregation (or microsegregation) during casting can result in an inhomogeneous distribution of microalloy precipitates in the as-cast slabs, which can create austenite grain size variation (even grain size bimodality) after reheating. Ti addition reduced the grain size variation; however, it could not eliminate the grain size bimodality in Nb-containing steel, due to the differential pinning effect of Nb precipitates. A model was proposed for the prediction of austenite grain size variation in reheated steel by combining different models on microsegregation during solidification, thermodynamic stability, and dissolution of microalloy precipitates and austenite grain growth during reheating.

  9. Kinetics of Ferrite Recrystallization and Austenite Formation During Intercritical Annealing of the Cold-Rolled Ferrite/Martensite Duplex Structures

    NASA Astrophysics Data System (ADS)

    Mazaheri, Y.; Kermanpur, A.; Najafizadeh, A.; Kalashami, A. Ghatei

    2016-03-01

    Ultrafine-grained, dual-phase (UFG DP) steels were produced by a new route using an uncommon cold-rolling and subsequent intercritical annealing of ferrite/martensite duplex starting microstructures. The effects of processing parameters such as rolling reduction, intercritical annealing temperature, and time on the microstructural evaluations have been studied. UFG DP steels with an average grain size of about 1 to 2 μm were achieved by short intercritical annealing of the 80 pct cold-rolled duplex microstructures. The kinetics of ferrite recrystallization and austenite formation were studied based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The proposed model for describing the isothermal austenite formation kinetics was applied successfully to the nonisothermal conditions. It was found that complete recrystallization of ferrite before the austenite formation led to the formation of a large extent randomly distributed austenite in the ferrite matrix and a chain-networked structure.

  10. Nucleation sites for ultrafine ferrite produced by deformation of austenite during single-pass strip rolling

    NASA Astrophysics Data System (ADS)

    Hurley, P. J.; Muddle, B. C.; Hodgson, P. D.

    2001-06-01

    An austenitic Ni-30 wt pct Fe alloy, with a stacking-fault energy and deformation characteristics similar to those of austenitic low-carbon steel at elevated temperatures, has been used to examine the defect substructure within austenite deformed by single-pass strip rolling and to identify those features most likely to provide sites for intragranular nucleation of ultrafine ferrite in steels. Samples of this alloy and a 0.095 wt pct C-1.58Mn-0.22Si-0.27Mo steel have been hot rolled and cooled under similar conditions, and the resulting microstructures were compared using transmission electron microscopy (TEM), electron diffraction, and X-ray diffraction. Following a single rolling pass of ˜40 pct reduction of a 2mm strip at 800 °C, three microstructural zones were identified throughout its thickness. The surface zone (of 0.1 to 0.4 mm in depth) within the steel comprised a uniform microstructure of ultrafine ferrite, while the equivalent zone of a Ni-30Fe alloy contained a network of dislocation cells, with an average diameter of 0.5 to 1.0 µm. The scale and distribution and, thus, nucleation density of the ferrite grains formed in the steel were consistent with the formation of individual ferrite nuclei on cell boundaries within the austenite. In the transition zone, 0.3 to 0.5 mm below the surface of the steel strip, discrete polygonal ferrite grains were observed to form in parallel, and closely spaced “rafts” traversing individual grains of austenite. Based on observations of the equivalent zone of the rolled Ni-30Fe alloy, the ferrite distribution could be correlated with planar defects in the form of intragranular microshear bands formed within the deformed austenite during rolling. Within the central zone of the steel strip, a bainitic microstructure, typical of that observed after conventional hot rolling of this steel, was observed following air cooling. In this region of the rolled Ni-30Fe alloy, a network of microbands was observed, typical of

  11. The effects of water vapor on the oxidation behavior of alumina forming austenitic stainless steels

    SciTech Connect

    Yanar, N. M.; Lutz, B. S.; Garcia-Fresnillo, L.; Brady, Michael P.; Meier, G. H.

    2015-08-19

    The isothermal oxidation behavior of three alumina forming austenitic (AFA) stainless steels with varying composition was studied at 650 and 800 °C in dry air and gases which contained water vapor. The AFA alloys exhibited better oxidation resistance than a “good chromia former” at 650 °C, particularly in H2O-containing atmospheres by virtue of alumina-scale formation. Although the AFA alloys were more resistant than chromia formers, their oxidation resistance was degraded at 650 °C in the presence of water vapor. In dry air the AFA alloys formed, thin continuous alumina scales, whereas in Ar–4%H2–3%H2O the areas of continuous alumina were reduced and Fe oxide-rich nodules and regions of Cr, Mn-rich oxides formed. In some regions internal oxidation of the aluminum occurred in the H2O-containing gas. The alloy OC8 had slightly better resistance than OC4 or OC5 in this atmosphere. The alumina-forming capability of the AFA alloys decreases with increasing temperature and, at 800 °C, they are borderline alumina formers, even in dry air. The oxidation resistance of all three alloys was degraded at 800 °C in atmospheres, which contained water vapor (Air–10%H2O, Ar–3%H2O and Ar–4%H2–3%H2O). The areas, which formed continuous alumina, were reduced in these atmospheres and areas of internal oxidation occurred. However, as a result of the borderline alumina-forming capability of the AFA alloys it was not possible to determine which of the H2O-containing atmospheres was more severe or to rank the alloys in terms of their performance. The experimental results indicate that the initial microstructure of the AFA alloys also plays a role in their oxidation performance. Less protective oxides formed at 800 °C when alloy OC8 was equilibrated before exposure rather than being exposed in the as-processed condition. As a result, the reason for this is the presence of different

  12. The effects of water vapor on the oxidation behavior of alumina forming austenitic stainless steels

    DOE PAGES

    Yanar, N. M.; Lutz, B. S.; Garcia-Fresnillo, L.; ...

    2015-08-19

    The isothermal oxidation behavior of three alumina forming austenitic (AFA) stainless steels with varying composition was studied at 650 and 800 °C in dry air and gases which contained water vapor. The AFA alloys exhibited better oxidation resistance than a “good chromia former” at 650 °C, particularly in H2O-containing atmospheres by virtue of alumina-scale formation. Although the AFA alloys were more resistant than chromia formers, their oxidation resistance was degraded at 650 °C in the presence of water vapor. In dry air the AFA alloys formed, thin continuous alumina scales, whereas in Ar–4%H2–3%H2O the areas of continuous alumina were reducedmore » and Fe oxide-rich nodules and regions of Cr, Mn-rich oxides formed. In some regions internal oxidation of the aluminum occurred in the H2O-containing gas. The alloy OC8 had slightly better resistance than OC4 or OC5 in this atmosphere. The alumina-forming capability of the AFA alloys decreases with increasing temperature and, at 800 °C, they are borderline alumina formers, even in dry air. The oxidation resistance of all three alloys was degraded at 800 °C in atmospheres, which contained water vapor (Air–10%H2O, Ar–3%H2O and Ar–4%H2–3%H2O). The areas, which formed continuous alumina, were reduced in these atmospheres and areas of internal oxidation occurred. However, as a result of the borderline alumina-forming capability of the AFA alloys it was not possible to determine which of the H2O-containing atmospheres was more severe or to rank the alloys in terms of their performance. The experimental results indicate that the initial microstructure of the AFA alloys also plays a role in their oxidation performance. Less protective oxides formed at 800 °C when alloy OC8 was equilibrated before exposure rather than being exposed in the as-processed condition. As a result, the reason for this is the presence of different phases in the bulk of the two specimens.« less

  13. The Change of Austenitic Stainless Steel Elements Content in the Inner Parts of VVER-440 Reactor during Operation

    NASA Astrophysics Data System (ADS)

    Smutný, Vladimír; Hep, Jaroslav; Novosad, Petr

    2009-08-01

    Neutron activation induces the element transmutation in materials surrounding the reactor active core. The objective of the present paper is to calculate and evaluate the change of austenitic stainless steel 08Ch18N10T elements content through neutron induced activation, in inner parts of VVER-440 - in the baffle and in the barrel. Particularly the content changes of Mn in austenitic stainless steel. The neutron flux density and then the neutron activation of austenitic stainless steel elements in parts at the core are calculated. Neutron activation represents a measure of austenitic stainless steel elements transmutation. The power distribution is determined as an average value of several cycles power distribution in the middle of a cycle for the NPP Dukovany. The power distribution is calculated with the code MOBY-DICK [1]. The neutron flux density is calculated with the code TORT [2]. The neutron activation of austenitic stainless steel elements in the baffle and in the barrel is calculated with the system EASY-2007 containing the code FISPACT-2007 [3]. The calculation of the changing austenitic stainless steel elements content is performed depending on the moment of the supposed end of reactor operation - 40 years. There is also necessary monitoring and benchmarking of steel element content change, because the neutron flux calculation, particularly in thermal region, shows a considerable uncertainty, e.g. [4]. The motivation for this work is the study focused to stress corrosion cracking of austenitic stainless steels induced by radiation inside PWR and BWR, e.g. [5]. The paper could be a suggestion to estimation of austenitic stainless steel corrosion damage induced by neutrons in inner parts of VVER-440 reactor.

  14. Effect of residual austenite on the tendency of incompletely aged maraging steels to embrittlement during slow deformation

    SciTech Connect

    Kardonskii, V.M.; Gorbunova, N.B.

    1986-03-01

    The authors investigate the high-strength maraging steels (HSMS) N17K10V10MT and N18V10V10MT by cyclic heat treatment and heating to temperatures of the dual-phase (alpha + gamma)-region. Embrittlement during the slow loading of incompletely aged HSMS with titanium can be reduced when approximately 20% of residual austenite is obtained in them. Maraging steel containing residual austenite in the initial state does not tend toward this type of embrittlement.

  15. Applying Ultrasonic Phased Array Technology to Examine Austenitic Coarse-Grained Structures for Light Water Reactor Piping

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2003-12-18

    Pacific Northwest Laboratory is evaluating the capabilities and limitations of phased array (PA) technology to detect service-type flaws in coarse-grained austenitic piping structures. The work is being sponsored by the U.S. Nuclear Regulatory Commission, Office of Research. This paper presents initial work involving the use of PA technology to determine the effectiveness of detecting and accurately characterizing flaws on the far-side of austenitic piping welds.

  16. The critical analysis of austenitic manganese steel T130Mn135 used for castings in the mining industry

    NASA Astrophysics Data System (ADS)

    Josan, A.; Pinca Bretotean, C.; Putan, V.

    2016-02-01

    This paper presents the critical analysis of making technology of austenitic manganese steel T130Mn135, used for castings of the type Mills hammer at a Romanian foundry. Are analyzed 11 charges of steel for castings and is determined the diagram of the heat treatment. After the applying of the heat treatment results a single-phase structure, consisting of homogeneous austenite. For all the 11 charges is presented the variation of chemical composition.

  17. Teleteach Expanded Delivery System: Evaluation.

    ERIC Educational Resources Information Center

    Christopher, G. Ronald; Milam, Alvin L.

    In order to meet the demand for Air Force Institute of Technology (AFIT) professional continuing education (PCE) courses within the School of Systems and Logistics and the School of Engineering, the Teleteach Expanded Delivery System (TEDS) for instruction of Air Force personnel at remote locations was developed and evaluated. TEDS uses a device…

  18. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G

    2015-02-03

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  19. Expanding the eukaryotic genetic code

    DOEpatents

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2017-02-28

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  20. Expanding Frontiers of Humanoid Robotics

    DTIC Science & Technology

    2000-08-01

    From the IEEE Intelligent Systems Special Issue on Humanoid Robotics , July/August 2000 GUEST EDITORS’ Expanding Frontiers of Humanoid Robotics ...Mark L. Swinson, DARPA David J. Bruemmer, Strategic Analysis Mobile robots pose a unique set of challenges to artificial intelligence researchers...the constraints of logical correctness but also some assortment of crosscutting, physical constraints. Particularly interesting among these robots

  1. Common Ground: Expanding Our Horizons.

    ERIC Educational Resources Information Center

    McDevitt, Michele J.

    In "Common Ground: Dialogue, Understanding, and the Teaching of Composition," Kurt Spellmeyer seeks to familiarize students and teachers with the linguistic and cultural no-man's-land separating them. Reinstating the value of two writing conventions often used by traditional students--expressive and commonplaces--can help expand on the…

  2. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W; Cropp, T Ashton; Anderson, J Christopher; Schultz, Peter G

    2012-05-08

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  3. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2013-01-22

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  4. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W; Cropp, T Ashton; Anderson, J Christopher; Schultz, Peter G

    2012-02-14

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  5. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2010-09-14

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  6. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2009-12-01

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  7. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W; Cropp, T Ashton; Anderson, J Christopher; Schultz, Peter G

    2009-10-27

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  8. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2009-11-17

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  9. Expanding the Universe of Education.

    ERIC Educational Resources Information Center

    Parsons, Elizabeth

    1996-01-01

    Definitions of "education" and "rural" are debunked and expanded. The three major tasks of rural education are educating people to understand their own needs, the unavoidable changes that will transform rural Australia within their lifetimes, and the range of technologies that can enhance their well-being. Presents a strategy…

  10. Emotional Giftedness: An Expanded View.

    ERIC Educational Resources Information Center

    Piechowski, Michael M.

    This paper discusses an expanded definition of the concept of emotional giftedness in children as defined by Annemarie Roeper. In contrast to examples of academic and artistic prodigies, cases are reviewed that illustrate less tangibly measured examples of children's giftedness, such as expressions of compassion, moral sensitivity, positive…

  11. Tree Decay - An Expanded Concept

    Treesearch

    Alex L. Shigo

    1979-01-01

    The purpose of this publication is to clarify further the tree decay concept that expands the classical concept to include the orderly response of the tree to wounding and infection-compartmentalization-and the orderly infection of wounds by many microorganisms-successions. The heartrot concept must be abandoned because it deals only with decay-causing fungi and it...

  12. Tree decay an expanded concept

    Treesearch

    Alex L. Shigo

    1979-01-01

    This publication is the final one in a series on tree decay developed in cooperation with Harold G. Marx, Research Application Staff Assistant, U.S. Department of Agriculture, Forest Service, Washington, D.C. The purpose of this publication is to clarify further the tree decay concept that expands the classical concept to include the orderly response of the tree to...

  13. The Expanding Frontier of Pluralism.

    ERIC Educational Resources Information Center

    King, Edmund

    1983-01-01

    Looks at the expanding frontier of pluralism in terms of reappraising the relationship of formal education to the advent of the constant change (occupational and social) accelerated by the microprocessor revolution and readjusting provisions in educational systems to meet the different needs of different populations. (AH)

  14. Expandable Shelter/Container Report.

    DTIC Science & Technology

    1973-06-01

    without removing whatever payload might be in the contai ner. Equ i pment located in the expanded porti on of the ES/C durin g norma l operat i ons is...and Supply BattalIon , Div isi on Support Coianand. In addition , divisional avIation battalions have an A Irc raft Maintenance Company. The TOE

  15. Expanded civil judicial referral procedures

    SciTech Connect

    Not Available

    1986-08-28

    The directive provides guidance on procedures for civil judicial referrals to the Department of Justice. The memorandum expands the current direct referral program, indicates that Headquarters should not establish mandatory requirements for pre-referral negotiations, mandates use of hold action cases only for strategic or tactical reasons and offers guidance on the preparation of bankruptcy cases.

  16. Finite simple groups as expanders

    PubMed Central

    Kassabov, Martin; Lubotzky, Alexander; Nikolov, Nikolay

    2006-01-01

    We prove that there exist k ∈ ℕ and 0 < ε ∈ ℝ such that every non-abelian finite simple group G, which is not a Suzuki group, has a set of k generators for which the Cayley graph Cay(G; S) is an ε-expander. PMID:16601101

  17. Monolithical aspherical beam expanding systems

    NASA Astrophysics Data System (ADS)

    Fuchs, U.

    2014-02-01

    In complex laser systems, such as those for material processing, and in basically all laboratory applications passive optical components are indispensable. Matching beam diameters is a common task, where Galileo type telescopes are preferred for beam expansion. Nevertheless researches and customers have found various limitations when using these systems. Some of them are the complicated adjustment, very small diameter for the incoming beam (1/e2), fixed and non-modifiable magnifications. Above that, diffraction-limitation is only assured within the optical design and not for the real world setup of the beam expanding system. Therefore, we will discuss limitations of currently used beam expanding systems to some extent. We will then present a new monolithical solution, which is based on the usage of only one aspherical component. It will be shown theoretically how the beam quality can be significantly improved by using aspherical lenses. As it is in the nature of things aspheres are working diffraction limited in the design, it will be shown how to combine up to five monolithical beam expanding systems and to keep the beam quality at diffraction limitation. Data of the culminated wavefront error will be presented. Last but not least insights will be given how beam expanding systems based on aspheres will help to use larger incoming beams and to reduce the overall length of such a system.

  18. Effect of Austenite Stability on Microstructural Evolution and Tensile Properties in Intercritically Annealed Medium-Mn Lightweight Steels

    NASA Astrophysics Data System (ADS)

    Song, Hyejin; Sohn, Seok Su; Kwak, Jai-Hyun; Lee, Byeong-Joo; Lee, Sunghak

    2016-06-01

    The microstructural evolution with varying intercritical-annealing temperatures of medium-Mn ( α + γ) duplex lightweight steels and its effects on tensile properties were investigated in relation to the stability of austenite. The size and volume fraction of austenite grains increased as the annealing temperature increased from 1123 K to 1173 K (850 °C to 900 °C), which corresponded with the thermodynamic calculation data. When the annealing temperature increased further to 1223 K (950 °C), the size and volume fraction were reduced by the formation of athermal α'-martensite during the cooling because the thermal stability of austenite deteriorated as a result of the decrease in C and Mn contents. In order to obtain the best combination of strength and ductility by a transformation-induced plasticity (TRIP) mechanism, an appropriate mechanical stability of austenite was needed and could be achieved when fine austenite grains (size: 1.4 μm, volume fraction: 0.26) were homogenously distributed in the ferrite matrix, as in the 1123 K (850 °C)—annealed steel. This best combination was attributed to the requirement of sufficient deformation for TRIP and the formation of many deformation bands at ferrite grains in both austenite and ferrite bands. Since this medium-Mn lightweight steel has excellent tensile properties as well as reduced alloying costs and weight savings, it holds promise for new automotive applications.

  19. Dissimilar Friction Stir Welding Between UNS S31603 Austenitic Stainless Steel and UNS S32750 Superduplex Stainless Steel

    NASA Astrophysics Data System (ADS)

    Theodoro, Maria Claudia; Pereira, Victor Ferrinho; Mei, Paulo Roberto; Ramirez, Antonio Jose

    2015-02-01

    In order to verify the viability of dissimilar UNS S31603 austenitic and UNS S32750 superduplex stainless steels joined by friction stir welding, 6-mm-thick plates were welded using a PCBN-WRe tool. The welded joints were performed in position control mode at rotational speeds of 100 to 300 rpm and a feed rate of 100 mm/min. The joints performed with 150 and 200 rpm showed good appearance and no defects. The metallographic analysis of both joints showed no internal defects and that the material flow pattern is visible only in the stirred zone (SZ) of the superduplex steel. On the SZ top, these patterns are made of regions of different phases (ferrite and austenite), and on the bottom and central part of the SZ, these patterns are formed by alternated regions of different grain sizes. The ferrite grains in the superduplex steel are larger than those in the austenitic ones along the SZ and thermo-mechanically affected zone, explained by the difference between austenite and ferrite recrystallization kinetics. The amount of ferrite islands present on the austenitic steel base metal decreased near the SZ interface, caused by the dissolving of the ferrite in austenitic matrix. No other phases were found in both joints. The best weld parameters were found to be 200 rpm rotation speed, 100 mm/min feed rate, and tool position control.

  20. Orientation relationships between M2C carbide and the austenite matrix in an Fe-Mn-AI-Mo-C alloy

    NASA Astrophysics Data System (ADS)

    Peng, Shang-Wen; Chou, Chang-Pin

    1993-05-01

    M2C carbides were observed to precipitate within the austenite matrix of an Fe-24.6Mn-6.6Al-3. IMo-1.0C alloy after quenching from 1200 °C and aging at 750 °C. By means of transmission electron microscopy (TEM) and diffraction techniques, the orientation relationships between M2C (p) and the austenite (γ) matrix were determined to be: (0001)p//(111)γ, (11- bar 20)p// (1 bar 10)γ, ( bar 1100)p//(11 bar 2)γ. M2C carbide has been reported by many researchers to precipitate from the ferrite matrix or along austenite/ferrite boundaries in alloy steels containing Mo. However, little information concerning the formation of M2C in the austenite matrix has been provided. This investigation presents the first evidence for the existence of M2C carbide wholly within the austenite matrix and its relationship to the austenite. The energy-dispersive spectrometry (EDS) analyses were performed on M2C carbides, and the results indicate that the solubility of the M2C carbide for foreign atoms other than Mo is very limited.

  1. The Mechanical and material properties of 316LN austenitic stainless steel for the fusion application in cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Sas, J.; Weiss, K.-P.; Jung, A.

    2015-12-01

    Due to the constant increase of claims for all materials used in superconducting magnets in "magnetic fusion reactors", the article deals with the possibilities of increasing the mechanical properties of austenitic stainless steel tested at cryogenic conditions that ensure the transport of Helium to magnets. The aim of the experimental plan was to increase the mechanical properties of the steel grade 316LN tested at 4.2K from the original value Steel A: YS = 1045 MPa, UTS = 1528 MPa, A = 33% to the value of YS = 1204 MPa,UTS = 1642 MPa, A = 34% and Steel B: YS = 1173 MPa, UTS = 1541 MPa, A = 28% to the value of YS = 1351 MPa, UTS = 1645 MPa, A = 17%. The increase in mechanical properties of the steel grade under examination has been made by means of heat processing in the conditions of annealing: Th1 = 625 ° C / th1 = 696 h. The mechanical properties of steel were evaluated using static tension tests at 4,2 K. The samples were placed in a cryostat filled with liquid helium. Except for the mechanical properties, there were also evaluated structural changes depending on the conditions of heat processing by light optical microscopy and EBSD (Electron Backscatter Diffraction). The increase of steel properties used in low temperatures was achieved by heat processing.

  2. The effect of antiphase boundaries on the elastic properties of Ni-Mn-Ga austenite and premartensite.

    PubMed

    Seiner, Hanuš; Sedlák, Petr; Bodnárová, Lucie; Drahokoupil, Jan; Kopecký, Vít; Kopeček, Jaromír; Landa, Michal; Heczko, Oleg

    2013-10-23

    The evolution of elastic properties with temperature and magnetic field was studied in two differently heat-treated single crystals of the Ni-Mn-Ga magnetic shape memory alloy using resonant ultrasound spectroscopy. Quenching and slow furnace cooling were used to obtain different densities of antiphase boundaries. We found that the crystals exhibited pronounced differences in the c' elastic coefficient and related shear damping in high-temperature ferromagnetic phases (austenite and premartensite). The difference can be ascribed to the formation of fine magnetic domain patterns and pinning of the magnetic domain walls on antiphase boundaries in the material with a high density of antiphase boundaries due to quenching. The fine domain pattern arising from mutual interactions between antiphase boundaries and ferromagnetic domain walls effectively reduces the magnetocrystalline anisotropy and amplifies the contribution of magnetostriction to the elastic response of the material. As a result, the anomalous elastic softening prior to martensite transformation is significantly enhanced in the quenched sample. Thus, for any comparison of experimental data and theoretical calculations the microstructural changes induced by specific heat treatment must be taken into account.

  3. Modeling of ultrasonic propagation in heavy-walled centrifugally cast austenitic stainless steel based on EBSD analysis.

    PubMed

    Chen, Yao; Luo, Zhongbing; Zhou, Quan; Zou, Longjiang; Lin, Li

    2015-05-01

    The ultrasonic inspection of heavy-walled centrifugally cast austenitic stainless steel (CCASS) is challenging due to the complex metallurgical structure. Numerical modeling could provide quantitative information on ultrasonic propagation and plays an important role in developing advanced and reliable ultrasonic inspection techniques. But the fundamental obstacle is the accurate description of the complex metallurgical structure. To overcome this difficulty, a crystal orientation map of a CCASS specimen in the 96 mm × 12 mm radial-axial cross section was acquired based on the electron backscattered diffraction (EBSD) technique and it was used to describe the coarse-grained structure and grain orientation. A model of ultrasonic propagation for CCASS was built according to the EBSD map. The ultrasonic responses of the CCASS sample were also tested. Some experimental phenomena such as structural noise and signal distortion were reproduced. The simulated results showed a good consistence with the experiments. The modeling method is expected to be effective for the precise interpretation of ultrasonic propagation in the polycrystalline structures of CCASS. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Suppression of Twinning and Phase Transformation in an Ultrafine Grained 2 GPa Strong Metastable Austenitic Steel: Experiment and Simulation

    SciTech Connect

    Shen, Yongfeng; Jia, Nan; Wang, Y. D.; Sun, Xin; Zuo, Liang; Raabe, Dierk

    2015-07-17

    An ultrafine-grained 304 austenitic 18 wt.%Cr-8 wt.%Ni stainless steel with a grain size of ~270 nm was synthesized by accumulative rolling (67 % total reduction) and annealing (550 °C, 150s). Uniaxial tensile testing at room temperature reveals an extremely high yield strength of 1890 ± 50MPa and a tensile strength of 2050 ± 30MPa, while the elongation reaches 6 ± 1%. Experimental characterization on samples with different grain sizes between 270 nm and 35 μm indicates that both, deformation twinning and martensitic phase transformation are significantly retarded with increasing grain refinement. A crystal plasticity finite element model incorporating a constitutive law reflecting the grain size-controlled dislocation slip and deformation twinning captures the micromechanical behavior of the steels with different grain sizes. Comparison of simulation and experiment shows that the deformation of ultrafine-grained 304 steels is dominated by the slip of partial dislocations, whereas for coarse-grained steels dislocation slip, twinning and martensite formation jointly contribute to the shape change.

  5. Fracture prediction in hydraulic bulging of AISI 304 austenitic steel sheets based on a modified ductile fracture criterion

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Song, H. W.; Zhang, S. H.; Cheng, M.

    2011-08-01

    The demand for weight reduction in modern vehicle construction has resulted in an increase in the application of hydroforming processes for the manufacture of automotive lightweight components. This trend led to the research of evaluation on formability of the sheet or tube hydroforming to be noted, particularly the prediction of fracture. In this study, a new proposed approach based on damage theory for fracture prediction considering the deformation history was introduced. And the modified ductile fracture criterion was applied to predict the failure for hydraulic bulging of AISI 304 austenitic steel sheets. The material parameters in terms of the function of strain rate in the failure criterion were determined from the equivalent fracture strains corresponding tensile tests under different stress conditions. Then, in the finite element simulation the effect of strain rates and their distribution as well during practical sheet metal forming process was considered. The hydraulic bulging tests were carried out to identify the fracture behavior predicted from FE analysis. A comparison between the prediction and experimental results showed that the proposed approach with a modified ductile fracture criteria can give better fracture predictions than traditional ways.

  6. The Effect of Surface Finish on Low-Temperature Acetylene-Based Carburization of 316L Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Ge, Yindong; Ernst, Frank; Kahn, Harold; Heuer, Arthur H.

    2014-12-01

    We observed a strong influence of surface finish on the efficacy of low-temperature acetylene-based carburization of AISI 316L austenitic stainless steel. Steel coupons were prepared with different surface finishes prior to carburization, from P400 SiC grit paper to 1- µm-diameter-diamond-paste. The samples with the finer surface finish developed a thicker "case" (a carbon-rich hardened surface layer) and a larger surface carbon concentration. Transmission electron microscopy revealed that the differences arose mainly from the nature of the deformation-induced disturbed layer on the steel surface. A thick (>400 nm) disturbed layer consisting of nano-crystalline grains (≈10 nm diameter) inhibits acetylene-based carburization. The experimental observations can be explained by assuming that during machining or coarse polishing, the surface oxide layer is broken up and becomes incorporated into the deformation-induced disturbed layer. The incorporated oxide-rich films retard or completely prevent the ingress of carbon into the stainless steel.

  7. Consideration of the growth mode in isochronal austenite-ferrite transformation of ultra-low-carbon Fe-C alloy

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Liu, Yongchang; Yan, Zesheng; Li, Yanli; Zhang, Lifang

    2010-01-01

    The three cooling rates of 10, 100, 200 K/min dilatometry experiments are used to investigate the kinetics of the isochronal austenite ( γ) to ferrite ( α) transformation of Fe-0.0036wt.%C alloy. “Normal transformation” and “abnormal transformation” have both been observed for transformations at different cooling rates. In accordance with the thermodynamic characteristics of the γ→ α transformation investigated here and previous kinetic considerations, a JMAK-like approach for the kinetics of isochronal phase transformations was developed that incorporates three overlapping processes: site saturation nucleation, alternate growth modes (from interface-controlled to diffusion-controlled to interface-controlled growth), as well as impingement for random distribution nuclei. The JMAK-like approach has been employed to fit the experimental results, and the fitting results show that for the γ→ α transformation of the Fe-C alloy at all applied cooling rates, the growth mode evolves in the corresponding order: from interface-controlled to diffusion-controlled growth; from interface-controlled to diffusion-controlled to interface-controlled growth; and interface-controlled growth.

  8. Ultrasonic inspection of austenitic stainless steel welds with artificially produced stress corrosion cracks

    SciTech Connect

    Dugan, Sandra; Wagner, Sabine

    2014-02-18

    Austenitic stainless steel welds and nickel alloy welds, which are widely used in nuclear power plants, present major challenges for ultrasonic inspection due to the grain structure in the weld. Large grains in combination with the elastic anisotropy of the material lead to increased scattering and affect sound wave propagation in the weld. This results in a reduced signal-to-noise ratio, and complicates the interpretation of signals and the localization of defects. Mechanized ultrasonic inspection was applied to study austenitic stainless steel test blocks with different types of flaws, including inter-granular stress corrosion cracks (IGSCC). The results show that cracks located in the heat affected zone of the weld are easily detected when inspection from both sides of the weld is possible. In cases of limited accessibility, when ultrasonic inspection can be carried out only from one side of a weld, it may be difficult to distinguish between signals from scattering in the weld and signals from cracks.

  9. Size-dependent characteristics of ultra-fine oxygen-enriched nanoparticles in austenitic steels

    NASA Astrophysics Data System (ADS)

    Miao, Yinbin; Mo, Kun; Zhou, Zhangjian; Liu, Xiang; Lan, Kuan-Che; Zhang, Guangming; Miller, Michael K.; Powers, Kathy A.; Stubbins, James F.

    2016-11-01

    Here, a coordinated investigation of the elemental composition and morphology of ultra-fine-scale nanoparticles as a function of size within a variety of austenitic oxide dispersion-strengthened (ODS) steels is reported. Atom probe tomography was utilized to evaluate the elemental composition of these nanoparticles. Meanwhile, the crystal structures and orientation relationships were determined by high-resolution transmission electron microscopy. The nanoparticles with sufficient size (>4 nm) to maintain a Y2Ti2-xO7-2x stoichiometry were found to have a pyrochlore structure, whereas smaller YxTiyOz nanoparticles lacked a well-defined structure. The size-dependent characteristics of the nanoparticles in austenitic ODS steels differ from those in ferritic/martensitic ODS steels.

  10. Magnetic Study of Martensitic Transformation in Austenitic Stainless Steel by Low Field Hysteresis Loops Analysis

    SciTech Connect

    Zhang Lefu; Takahashi, Seiki; Kamada, Yasuhiro; Kikuchi, Hiroaki; Mumtaz, Khalid; Ara, Katsuyuki; Sato, Masaya

    2005-04-09

    Magnetic method has been used to evaluate the volume percentage of {alpha}' martensitic phase in austenitic stainless steels by measuring saturation magnetization, and it is said to be a candidate NDE method. However, nondestructive detection of saturation magnetization without high magnetic field is difficult. In the current work, we present a NDE method for evaluating the magnetic properties of strain induced {alpha}' martensitic phase. Low field hysteresis loops of an austenitic stainless steels type SUS 304 after cold rolling were measured by using a yoke sensor. The results show that the initial permeability {mu}i and the relative coercive field Hcl calculated by low field hysteresis loop analysis keep monotonic relation with saturation magnetization and coercive force measured by VSM, respectively. By this method, it is possible to characterize the volume content and particle properties of {alpha}' martensitic phase in stainless steels.

  11. Stationary and quasistationary models of carbon redistribution in austenitic steel weldments: II. Polycomponent systems

    NASA Astrophysics Data System (ADS)

    Kučera, Jar; Kozák, V.; Million, B.; Stránský, K.

    1986-04-01

    In this IInd part of our paper (Czech. J. Phys. B 35 (1985) 1355) the analysis of carbon uphill diffusion data is presented. The analysed data were measured in the polycomponent steel weldments. All of the data satisfy well the conditions for stationary model application. On the basis of the present analysis the carbon diffusivities ( D {1/*}) appertaining to a non-alloyed austenite, the activity (ɛ{C/s}) and diffusion ( β {C/s}) interaction coefficients are evaluated. A “Si anomaly” in Darken's experiments is observed and discussed. On the contrary to the other substitutional elements Mn, Cr and Mo, which decrease simultaneously C-activity and C-diffusivity, silicon increases the carbon activity and, at the same time, decreases its diffusivity in the Fe-C-Xs austenitic solid solutions.

  12. Ultrafine-Grained Structure of Fe-Ni-C Austenitic Alloy Formed by Phase Hardening.

    PubMed

    Danilchenko, Vitalij

    2016-12-01

    The X-ray and magnetometry methods were used to study α-γ transformation mechanisms on heating quenched Fe-22.7 wt.% Ni-0.58 wt.% С alloy. Variation of heating rate within 0.03-80 K/min allowed one to switch from diffusive to non-diffusive mechanism of the α-γ transformation. Heating up primary austenitic single crystal specimen at a rate of less than 1.0-0.5 K/min has led to formation of aggregate of grains with different orientation and chemical composition in the reverted austenite. Significant fraction of these grains was determined to have sizes within nanoscale range.

  13. Correlation Between Microstructure and Mechanical Properties Before and After Reversion of Metastable Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Fargas, Gemma; Zapata, Ana; Roa, Joan Josep; Sapezanskaia, Ina; Mateo, Antonio

    2015-12-01

    Reversion treatments are a way to improve the mechanical response of metastable austenitic stainless steels by means of grain refinement. To effectively apply those treatments, the steel must be previously deformed to induce a significant amount of martensitic transformation. In this work, the effect of reversion treatments was studied on a commercial AISI 301LN grade subjected to an industrial cold rolling process, with thickness reductions not higher than 40 pct. Microstructural changes and evolution of both monotonic and cyclic mechanical properties were investigated after cold rolling and upon reversion treatments. Results revealed that the finer austenitic microstructure obtained after reversion leads to an interesting combination of properties, with strong increments in hardness and yield strength, and also fatigue limit improvement, as compared to the initial annealed condition.

  14. The effect of hydrogen on strain hardening and fracture mechanism of high-nitrogen austenitic steel

    NASA Astrophysics Data System (ADS)

    Maier, G. G.; Astafurova, E. G.; Melnikov, E. V.; Moskvina, V. A.; Vojtsik, V. F.; Galchenko, N. K.; Zakharov, G. N.

    2016-07-01

    High-nitrogen austenitic steels are perspective materials for an electron-beam welding and for producing of wear-resistant coatings, which can be used for application in aggressive atmospheres. The tensile behavior and fracture mechanism of high-nitrogen austenitic steel Fe-20Cr-22Mn-1.5V-0.2C-0.6N (in wt.%) after electrochemical hydrogen charging for 2, 10 and 40 hours have been investigated. Hydrogenation of steel provides a loss of yield strength, uniform elongation and tensile strength. The degradation of tensile properties becomes stronger with increase in charging duration - it occurs more intensive in specimens hydrogenated for 40 hours as compared to ones charged for 2-10 hours. Fracture analysis reveals a hydrogen-induced formation of brittle surface layers up to 6 μm thick after 40 hours of saturation. Hydrogenation changes fracture mode of steel from mixed intergranular-transgranular to mainly transgranular one.

  15. Influence of laser shock peening on irradiation defects in austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Lu, Qiaofeng; Su, Qing; Wang, Fei; Zhang, Chenfei; Lu, Yongfeng; Nastasi, Michael; Cui, Bai

    2017-06-01

    The laser shock peening process can generate a dislocation network, stacking faults, and deformation twins in the near surface of austenitic stainless steels by the interaction of laser-driven shock waves with metals. In-situ transmission electron microscopy (TEM) irradiation studies suggest that these dislocations and incoherent twin boundaries can serve as effective sinks for the annihilation of irradiation defects. As a result, the irradiation resistance is improved as the density of irradiation defects in laser-peened stainless steels is much lower than that in untreated steels. After heating to 300 °C, a portion of the dislocations and stacking faults are annealed out while the deformation twins remain stable, which still provides improved irradiation resistance. These findings have important implications on the role of laser shock peening on the lifetime extension of austenitic stainless steel components in nuclear reactor environments.

  16. Forging technology adapted to the manufacture of nuclear PWR austenitic primary piping

    SciTech Connect

    Morin, F.; Bocquet, P.; Cheviet, A.

    1997-12-31

    To increase the safety and reduce the operating costs of the primary piping of Pressurized Water Reactor power plants, Electricite de France has encouraged its French industrial partners to change the design and manufacture of components. That resulted in the manufacturing of large forged parts in austenitic stainless steel in place of castings. The main objective of such optimization is to improve the life of new power stations, increasing their safety margin, in addition to a reduction of the in service inspection and maintenance costs. The paper presents the interest in using austenitic stainless steel in place of castings and describes the manufacturing conditions of such forgings which are applied, first, to a cold leg for the Civaux 1 unit and second, to a complete loop for the Civaux 2 unit.

  17. Free energies of austenite and martensite Fe-C alloys: an atomistic study

    NASA Astrophysics Data System (ADS)

    Sak-Saracino, Emilia; Urbassek, Herbert M.

    2014-03-01

    We investigate the influence of C interstitials on the phase stability of Fe-C crystals. We employ the Meyer-Entel interatomic interaction potential which is able to reproduce the austenite-martensite phase transition for pure Fe, and supplement it by a simple pairwise Fe-C interaction potential. Using two different thermodynamic methods, we calculate the free energies of the martensite and austenite phases. We find that C destabilizes the ground-state bcc phase. The decrease in the equilibrium transformation temperature with increasing C content parallels the one found in the experiment. This destabilization is found even if C is added for a potential in which only the bcc phase is stable until the melting point; here, for sufficiently high C addition, a stable fcc phase is established in the phase diagram.

  18. Mechanical properties of 15%Mn steel with fine lamellar structure consisting of ferrite and austenite phases

    NASA Astrophysics Data System (ADS)

    Ueji, R.; Okitsu, Y.; Nakamura, T.; Takagi, Y.; Tanaka, Y.

    2010-07-01

    New steel with fine lamellar structure consisting of austenite and ferrite was developed. 15mass%Mn-3%Al-3%Si steel sheet was used in this study. First of all, the effect of the cooling rate on the microstructure was examined. The cooling at the slower speed of 100 deg/hour created the dual phase structure consisting of both austenite and ferrite. The additional rolling developed the fine lamellar duplex structure. Improvement of both the tensile strength and elongation was achieved by rolling. The strength increases furthermore by the rolling up to larger reduction. The 90% rolled sheet shows high tensile strength around 1000MPa with large elongation (15%-20%). These results indicate that the multi-phased structure with controlled lamellar morphology is beneficial for the management of both high strength and large ductility.

  19. Characterization of Service Induced Flaws on the Far Side of Austenitic Welds Using Phased Array Technology

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.

    2004-01-01

    Conventional ultrasonic testing methods continue to exhibit problems for applications involving coarse-grained structures. Pacific Northwest National Laboratory is evaluating the capabilities and limitations of phased array (PA) technology to detect service-type flaws in these coarse-grained materials. The work is being sponsored by the U.S. Nuclear Regulatory Commission, Office of Research. Work to determine detection capabilities through welds with varied grain structures is being explored to provide a better understanding of the acoustic properties of these welded structures. Piping specimens with welds fabricated in vertical and horizontal positions to simulate field conditions have been studied. The insights gained from the austenitic piping will be applied to dissimilar metal weld configurations, corrosion resistant clad piping and cast stainless steels. This paper presents results for using PA ultrasonic technology to determine the effectiveness of detecting and accurately characterizing flaws on the far-side of austenitic piping welds.

  20. High-temperature corrosion observed in austenitic coils and tubes in a direct reduction process

    SciTech Connect

    Campillo, B.; Gonzalez, C.; Hernandez-Duque, G.; Juarez-Islas, J.A.

    2000-02-01

    The subject of this study is related to the performance of austenitic steel coils and tubes, in a range of temperatures between 425 and 870 C for the transport of reducing gas, in an installation involving the direct reduction of iron-ore by reforming natural gas. Evidence is presented that metal dusting is not the only unique high-temperature corrosion mechanism that caused catastrophic failures of austenitic 304 (UNS S30400) coils and HK-40 (UNS J94204) tubes. Sensitization as well as stress corrosion cracking occurred in 304 stainless steel coils and metal dusting took place in HK-40 tubes, a high resistance alloy. The role of continuous injection of H{sub 2}S into the process is suggested to avoid the high resistance metal dusting corrosion mechanism found in this kind of installation.

  1. Size-Dependent Characteristics of Ultra-Fine Oxygen-Enriched Nanoparticles in Austenitic Steels

    SciTech Connect

    Miao, Yinbin; Mo, Kun; Zhou, Zhangjian; Liu, Xiang; Lan, Kuan-Che; Zhang, Guangming; Miller, Michael K.; Powers, Kathy A.; Stubbins, James F.

    2016-11-01

    Here, a coordinated investigation of the elemental composition and morphology of ultra-fine-scale nanoparticles as a function of size within a variety of austenitic oxide dispersion-strengthened (ODS) steels is reported. Atom probe tomography was utilized to evaluate the elemental composition of these nanoparticles. Meanwhile, the crystal structures and orientation relationships were determined by high resolution transmission electron microscopy. The nanoparticles with sufficient size (>4 nm) to maintain a Y2Ti2-xO7-2x stoichiometry were found to have a pyrochlore structure, whereas smaller YxTiyOz nanoparticles lacked a well-defined structure. The size-dependent characteristics of the nanoparticles in austenitic ODS steels differ from those in ferritic/martensitic ODS steels.

  2. High temperature corrosion of austenitic stainless steel coils in a direct reduction plant in Mexico

    SciTech Connect

    Juarez-Islas, J.A.; Campillo, B.; Chaudhary, N.; Mendoza, R.; Gonzalez, A.

    1996-08-01

    The subject of this study is related to the performance of austenitic steels coils and tubes, in a range of temperatures between 425 to 870 C for the transport of reducing gases, in an installation involving the direct reduction of iron-ore by reforming natural gas. Evidence is presented that metal dusting is not the only unique high temperature corrosion mechanism that caused catastrophic failures of austenitic 304 (UNS S30400) coils and HK-40 (UNS J94204) tubes. Sensitization as well as stress corrosion cracking occurred in 304 stainless steel coils, and metal dusting occurred in tubes of HK-40, a high resistance alloy. The role of a continuous injection of H{sub 2}S to the process is suggested to avoid the high temperature metal dusting corrosion mechanism found in these kind of installations.

  3. Processing and structure of a Nitrogen Alloyed Oxide Dispersion Strengthened Austenitic Stainless Steel by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Xu, Yingli; Zhou, Zhangjian

    2013-03-01

    Pure metallic powders of Fe, Cr, Ni, W, Ti and nano-Y2O3 powders were mechanical alloyed by high energy mechanical milling under N2 atmosphere to develop a nitrogen contained oxide dispersion strengthened austenitic steel powders. The compositions of the mixed powders are Fe-18Cr-8Ni-2W-1Ti-0.35Y2O3. The effects of milling time on nitrogen absorption were investigated. The nitrogen contents in the as-milled powders reached 0.31 wt% after milling for 60 hours and nearly 0.8 wt% after milling for 150 hours. The as-milled powders were then annealed under vacuum at 1173K and 1373 K to promote the formation of the resultant equilibrium phases. Fully austenitic structure was achieved after annealing at 1173K.

  4. Aging effects on the mechanical properties of alumina-forming austenitic stainless steels

    SciTech Connect

    Bei, Hongbin; Yamamoto, Yukinori; Brady, Michael P; Santella, Michael L

    2010-01-01

    Isothermal aging and tensile evaluation were conducted for recently developed alumina-forming austenitic stainless steels (AFAs). Microstructural observation reveals that NiAl-type B2 and Fe{sub 2}(Mo,Nb)-type Laves phase precipitates form as dominant second phases in the austenitic matrix during aging at 750 C. At room temperature these precipitates increase the strength but decrease the ductility of the AFA alloys. However, when tested at 750 C, the AFA alloys did not show strong precipitation hardening by these phases, moreover, the elongation to fracture was not affected by aging. Fracture surface and cross-sectional microstructure analysis after tensile testing suggests that the difference of mechanical behaviors between room temperature and 750 C results from the ductile-brittle transition of the B2 precipitates. At room temperature, B2 precipitates are strong but brittle, whereas they become weak but ductile above the ductile-brittle transition temperature (DBTT).

  5. Mechanical properties of a nitrogen-bearing austenitic steel during static and cycle deformation

    NASA Astrophysics Data System (ADS)

    Blinov, E. V.; Terent'ev, V. F.; Prosvirnin, D. V.

    2016-09-01

    The mechanical properties of a nitrogen-bearing corrosion-resistant austenitic steel containing 0.311% nitrogen have been studied during static and cyclic deformation. It is found that the steel having an ultimate strength of 930 MPa exhibits a plasticity of 33%. The endurance limit under repeated tension at 106 loading cycles is 400 MPa. The propagation of a fatigue crack at low and high amplitudes of cyclic deformation follows a ductile fracture mechanism with the presence of fatigue grooves.

  6. Delta ferrite-containing austenitic stainless steel resistant to the formation of undesirable phases upon aging

    DOEpatents

    Leitnaker, J.M.

    Austenitic stainless steel alloys containing delta ferrite, such as are used as weld deposits, are protected against the transformation of delta ferrite to sigma phase during aging by the presence of carbon plus nitrogen in a weight percent 0.015 to 0.030 times the volume percent ferrite present in the alloy. The formation of chi phase upon aging is controlled by controlling the Mo content.

  7. Delta ferrite-containing austenitic stainless steel resistant to the formation of undesirable phases upon aging

    DOEpatents

    Leitnaker, James M.

    1981-01-01

    Austenitic stainless steel alloys containing delta ferrite, such as are used as weld deposits, are protected against the transformation of delta ferrite to sigma phase during aging by the presence of carbon plus nitrogen in a weight percent 0.015-0.030 times the volume percent ferrite present in the alloy. The formation of chi phase upon aging is controlled by controlling the Mo content.

  8. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    SciTech Connect

    Jung, Minsu; Cho, Wontae; Park, Jihye; Jung, Jae-Gil; Lee, Young-Kook

    2014-08-15

    The variation of the C concentration in proeutectoid ferrite (α{sub PF}) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (T{sub m}) of α{sub PF} to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of α{sub PF}. The C concentration in α{sub PF} at T{sub m} in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of α{sub PF} with isothermal holding time at 775 °C in S20C steel revealed C enrichment in α{sub PF} at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in α{sub PF} during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring α{sub PF} as well as pearlitic ferrite. The supersaturated C concentration in α{sub PF} is reduced during the long-range diffusive transformation of α{sub PF} to γ. However, some of the excess C atoms still remain in α{sub PF} until α{sub PF} starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ.

  9. Magnetic-field-induced grain elongation in a medium carbon steel during its austenitic decomposition

    SciTech Connect

    Zhang, Y.D.; Esling, C.; Muller, J.; He, C.S.; Zhao, X.; Zuo, L.

    2005-11-21

    A 12-T magnetic field was applied during the austenitic decomposition in a medium plain carbon steel at a slow cooling rate. The magnetic field applied promotes proeutectoid ferrite grains to grow along the field direction and results in an elongated grain microstructure. The grain elongation is the result of the opposing contributions from the atomic dipolar interaction energy of Fe atoms and the interfacial energy.

  10. Elucidating the Effect of Alloying Elements on the Behavior of Austenitic Stainless Steels at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Naghizadeh, Meysam; Mirzadeh, Hamed

    2016-12-01

    The effect of carbon and molybdenum on elevated temperature behavior of austenitic stainless steels was studied. It was revealed that carbon does not alter the overall grain coarsening behavior but molybdenum significantly retards the growth of grains toward higher temperatures and slower kinetics and effectively increases the grain growth activation energy due to an interaction energy between Mo and grain boundaries. These observations were based on especial activation energy plots, which facilitate the interpretation of results.

  11. An improved method to identify grain boundary creep cavitation in 316H austenitic stainless steel.

    PubMed

    Chen, B; Flewitt, P E J; Smith, D J; Jones, C P

    2011-04-01

    Inter-granular creep cavitation damage has been observed in an ex-service 316H austenitic stainless steel thick section weldment. Focused ion beam cross-section milling combined with ion channelling contrast imaging is used to identify the cavitation damage, which is usually associated with the grain boundary carbide precipitates in this material. The results demonstrate that this technique can identify, in particular, the early stage of grain boundary creep cavitation unambiguously in materials with complex phase constituents.

  12. Stress Induce Martensitic Transformations in Hydrogen Embrittlement of Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Rozenak, Paul

    2013-04-01

    In austenitic type stainless steels, hydrogen concentration gradients formed during electrochemical charging and followed by hydrogen loss during aging, at room temperature, surface stresses, and martensitic phases α'-BCC and ɛ-HCP developed. The basic relationship between the X-ray diffraction peak broadening and the hydrogen gradients, formed during charging and aging at room temperature in such austenitic stainless steels, were analyzed. The results demonstrate that the impact of stresses must be considered in the discussion of phase transformations due to hydrogenation. Austenitic stainless steels based on iron-nickel-chromium, have relatively low stacking fault energy γSFE and undergo: quenching to low temperatures, plastic deformation, sensitization heat treatments, high pressure (≥3-5 × 109 Pa) by hydrogen or other gases, electrochemical charging (when the sample is cathode) and when is irradiation by various ions the samples in vacuum. All the above mentioned induce formation of ɛ and α' in the face-centered cubic (FCC) austenite γ matrix. The highest stresses cause formation of mainly α' phase and ɛ-martensite, and both are involved in plastic deformation processes and promoting crack propagation at the surface. In 310 steel, the crack propagation is based on deformation processes following ɛ-martensitic formation only. Formations of ɛ- and α'-martensites were noted along the fracture surfaces and ahead of the crack tip. The cracks propagated through the ɛ-martensitic plates, which formed along the active slip planes, while α' phase was always found in the high-stress region on the ends of the ligaments from both sides of the crack surfaces undergoing propagation.

  13. Stress Induce Martensitic Transformations in Hydrogen Embrittlement of Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Rozenak, Paul

    2014-01-01

    In austenitic type stainless steels, hydrogen concentration gradients formed during electrochemical charging and followed by hydrogen loss during aging, at room temperature, surface stresses, and martensitic phases α'-BCC and ɛ-HCP developed. The basic relationship between the X-ray diffraction peak broadening and the hydrogen gradients, formed during charging and aging at room temperature in such austenitic stainless steels, were analyzed. The results demonstrate that the impact of stresses must be considered in the discussion of phase transformations due to hydrogenation. Austenitic stainless steels based on iron-nickel-chromium, have relatively low stacking fault energy γSFE and undergo: quenching to low temperatures, plastic deformation, sensitization heat treatments, high pressure (≥3-5 × 109 Pa) by hydrogen or other gases, electrochemical charging (when the sample is cathode) and when is irradiation by various ions the samples in vacuum. All the above mentioned induce formation of ɛ and α' in the face-centered cubic (FCC) austenite γ matrix. The highest stresses cause formation of mainly α' phase and ɛ-martensite, and both are involved in plastic deformation processes and promoting crack propagation at the surface. In 310 steel, the crack propagation is based on deformation processes following ɛ-martensitic formation only. Formations of ɛ- and α'-martensites were noted along the fracture surfaces and ahead of the crack tip. The cracks propagated through the ɛ-martensitic plates, which formed along the active slip planes, while α' phase was always found in the high-stress region on the ends of the ligaments from both sides of the crack surfaces undergoing propagation.

  14. Effects of a Hydrogen Gas Environment on Fatigue Crack Growth of a Stable Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Kawamoto, Kyohei; Oda, Yasuji; Noguchi, Hiroshi; Higashida, Kenji

    In order to clarify the effects of a hydrogen gas environment on the fatigue crack growth characteristics of stable austenitic stainless steels, bending fatigue tests were carried out in a hydrogen gas, in a nitrogen gas at 1.0 MPa and in air on a SUS316L using the Japanese Industrial Standards (type 316L). Also, in order to discuss the difference in the hydrogen sensitivity between austenitic stainless steels, the fatigue tests were also carried out on a SUS304 using the Japanese Industrial Standards (type 304) metastable austenitic stainless steel as a material for comparison. The main results obtained are as follows. Hydrogen gas accelerates the fatigue crack growth rate of type 316L. The degree of the fatigue crack growth acceleration is low compared to that in type 304. The fracture surfaces of both the materials practically consist of two parts; the faceted area seemed to be brittle and the remaining area occupying a greater part of the fracture surface and seemed to be ductile. The faceted area does not significantly contribute to the fatigue crack growth rate in both austenitic stainless steels. The slip-off mechanism seems to be valid not only in air and in nitrogen, but also in hydrogen. Also, the main cause of the fatigue crack growth acceleration of both materials occurs by variation of the slip behaviour. The difference in the degree of the acceleration, which in type 316L is lower than in type 304, seems to be caused by the difference in the stability of the γ phase.

  15. The Effect of Austenitizing Conditions on the Anisotropic Embrittlement of ESR (Electroslag Remelted) 4340 Steel.

    DTIC Science & Technology

    1986-10-01

    Charpy V-notch toughness. Lower Charpy V-notch toughness associated with the quench rate of 100OF per minute was due to the presence of bainite in the...microstructure. The presence of bainite had a small effect on slow bend fracture toughness. Plate anisotropy was r .-ery small in the plane of the plate...small amounts of bainite in the sample. It appears that the sample austenitized at 16500 F had approximately 10% bainite while the samples

  16. Effects of titanium additions to austenitic ternary alloys on microstructural evolution and void swelling

    SciTech Connect

    Okita, T; Wolfer, W G; Garner, F A; Sekimura, N

    2003-12-01

    Ternary austenitic model alloys were modified with 0.25 wt.% titanium and irradiated in FFTF reactor at dose rates ranging over more than two orders in magnitude. While lowering of dose rate strongly increases swelling by shortening the incubation dose, the steady state swelling rate is not affected by dose rate. Although titanium addition strongly alters the void microstructure, swelling at {approx} 420 C does not change with titanium additions, but the sensitivity to dose rate is preserved.

  17. Phonon dispersion in austenitic stainless steel Fe18Cr12Ni2Mo

    NASA Astrophysics Data System (ADS)

    Hoelzel, M.; Danilkin, S. A.; Hoser, A.; Ehrenberg, H.; Wieder, T.; Fuess, H.

    The phonon dispersion of Fe18Cr12Ni2Mo austenitic stainless steel was measured along the symmetry directions [001], [110] and [111]. Data were analysed in the frame of the Born-von Karman model of lattice dynamics. The obtained force constants were used to evaluate the elastic constants and the engineering elastic moduli. Our results for the elastic constants confirm empirical relationships between the elastic constants found for FCC FeCrNi alloys.

  18. EBSD characterization of a hot worked 304 austenitic stainless steel under strain reversal.

    PubMed

    Jorge-Badiola, D; Iza-Mendia, A; Gutiérrez, I

    2009-07-01

    Monotonic and strain reversal hot torsion tests were performed on a 304 austenitic stainless steel, this led to changes in microstructures depending on the strain path. electron backscatter diffraction was used as the tool for characterizing the microstructures. It was possible to find some intragranular microstructural changes due to the reversal of the strain by means of several local and global misorientation-related parameters. Sigma3 boundaries also showed sensitivity to strain reversal.

  19. Alumina-Forming Austenitics: A New Class of Heat-Resistant Stainless Steels

    SciTech Connect

    Brady, Michael P; Yamamoto, Yukinori; Lu, Zhao Ping; Maziasz, Philip J; Liu, Chain T; Pint, Bruce A; Santella, Michael L

    2008-01-01

    A family of alumina (Al2O3)-forming austenitic (AFA) stainless steels is under development. These alloys offer the potential for significantly higher operating temperature and environmental durability than conventional chromia (Cr2O3)-forming stainless steels, without sacrificing other critical characteristics such as cost, creep resistance, and weldability. An overview of the alloy development approach and details of the oxidation and creep resistance properties achieved to date are presented.

  20. Hydrogen Susceptibility of Pre-strained Type 316L Austenitic Stainless Steels in Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Mati, D.; Takasaki, A.; Uematsu, S.

    2017-09-01

    This paper presents the observations made as a result of hydrogen effects in austenitic stainless steels which led to reduction of its original mechanical properties. This paper therefore seeks to understand the mechanisms and effects induced by hydrogen leading to embrittlement. The samples of Type 316L austenitic stainless steel with 20% pre-strain were charged with hydrogen through galvanostastic cathodic loading for 12, 24, 36, and 48 hours respectively, with sample as Cathode and the platinum wire as Anode. Afterwards, they were fractured under tensile test at a slow strain rates. The loss of ductility was evident as observed by the brittle nature of fracture. Small pieces were cut-off near the fracture region and examined through XRD and SEM analysis. The peak widening and slight shifting of the peak positions was observed. The surface cracking was also observed, an indication of surface-induced stresses. The severity of the effects increased with the hydrogen loading time, which is predictive of a real service conditions for austenite steels in aqueous environments.