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Sample records for activation ferritic alloys

  1. Low activation ferritic alloys

    DOEpatents

    Gelles, David S.; Ghoniem, Nasr M.; Powell, Roger W.

    1986-01-01

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  2. Low activation ferritic alloys

    DOEpatents

    Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

    1985-02-07

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  3. Charpy impact test results for low-activation ferritic alloys

    SciTech Connect

    Cannon, N.S.; Hu, W.L.; Gelles, D.S.

    1987-05-01

    The objective of this work is to evaluate the shift of the ductile to brittle transition temperature (DBTT) and the reduction of the upper shelf energy (USE) due to neutron irradiation of low activation ferritic alloys. Six low activation ferritic alloys have been tested following irradiation at 365/sup 0/C to 10 dpa and compared with control specimens in order to assess the effect of irradiation on Charpy impact properties.

  4. Neutron irradiation effects on the microstructure of low-activation ferritic alloys*1

    NASA Astrophysics Data System (ADS)

    Kimura, A.; Matsui, H.

    1994-09-01

    Microstructures of low-activation ferritic alloys, such as 2.25% Cr-2% W, 7% Cr-2% W, 9% Cr-2% W and 12% Cr-2% W alloys, were observed after FFTF irradiation at 698 K to a dose of 36 dpa. Martensite in 7% Cr-2% W, 9% Cr-2% W and 12% Cr-2% W alloys and bainite in 2.25% Cr-2% W alloy were fairly stable after the irradiation. Microvoids were observed in the martensite in each alloy but not in bainite and δ-ferrite in 12% Cr-2% W alloys. An addition of 0.02% Ti to 9% Cr-2% W alloy considerably reduced the void density. Spherical (Ta, W) and Ti-rich precipitates were observed in the Ti-added 9% Cr-2% W alloy. Precipitates observed in 9% Cr-2% W and 7% Cr-2% W alloys are mainly Cr-rich M 23C 6 (Ta, W) and Ta(W)-rich M 6C and Fe-rich Laves phase. In 2.25% Cr-2% W alloy, high density of fine (Ta, W)-rich M 2C type precipitates as well as M 6C were observed. Spherical small α' Cr-rich particles were observed in both martensite and α-ferrite in 12% Cr-2% W alloys. Correlation between postirradiation microstructure and irradiation hardening is shown and discussed for these alloys.

  5. Charpy impact test results for low activation ferritic alloys irradiated to 30 dpa

    SciTech Connect

    Schubert, L.E.; Hamilton, M.L.; Gelles, D.S.

    1996-04-01

    Miniature specimens of six low activation ferritic alloys have been impact field tested following irradiation at 370{degrees}C to 30 dpa. Comparison of the results with those of control specimens and specimens irradiated to 10 dpa indicates that degradation in the impact behavior appears to have saturated by {approx}10 dpa in at least four of these alloys. The 7.5Cr-2W alloy referred to as GA3X appears most promising for further consideration as a candidate structural material in fusion reactor applications, although the 9Cr-1V alloy may also warrant further investigation.

  6. Impurity content of reduced-activation ferritic steels and a vanadium alloy

    SciTech Connect

    Klueh, R.L.; Grossbeck, M.L.; Bloom, E.E.

    1997-04-01

    Inductively coupled plasma mass spectrometry was used to analyze a reduced-activation ferritic/martensitic steel and a vanadium alloy for low-level impurities that would compromise the reduced-activation characteristics of these materials. The ferritic steel was from the 5-ton IEA heat of modified F82H, and the vanadium alloy was from a 500-kg heat of V-4Cr-4Ti. To compare techniques for analysis of low concentrations of impurities, the vanadium alloy was also examined by glow discharge mass spectrometry. Two other reduced-activation steels and two commercial ferritic steels were also analyzed to determine the difference in the level of the detrimental impurities in the IEA heat and steels for which no extra effort was made to restrict some of the tramp impurities. Silver, cobalt, molybdenum, and niobium proved to be the tramp impurities of most importance. The levels observed in these two materials produced with present technology exceeded the limits for low activation for either shallow land burial or recycling. The chemical analyses provide a benchmark for the improvement in production technology required to achieve reduced activation; they also provide a set of concentrations for calculating decay characteristics for reduced-activation materials. The results indicate the progress that has been made and give an indication of what must still be done before the reduced-activation criteria can be achieved.

  7. Microstructural development in reduced activation ferritic alloys irradiated to 200 dpa at 420$deg;C

    NASA Astrophysics Data System (ADS)

    Gelles, D. S.

    1994-09-01

    Density change and microstructural development are reported for nine reduced activation ferritic steels covering the range 2.3 to 12Cr with varying additions of V and/or W for hardening and up to 6.5 Mn for austenite stability. Specimens were examined following irradiation in FFTF/MOTA at 420°C to a dose exceeding 200 dpa. Void swelling was found, but the swelling remained at 5% or below, with the worst case in an alloy of 9Cr-2Mn-1WV. The carbide structure pinning martensite lath boundaries remained in place.

  8. Charpy impact test results of four low activation ferritic alloys irradiated at 370{degrees}C to 15 DPA

    SciTech Connect

    Schubert, L.E.; Hamilton, M.L.; Gelles, D.S.

    1996-10-01

    Miniature CVN specimens of four low activation ferritic alloys have been impact tested following irradiation at 370{degrees}C to 15 dpa. Comparison of the results with those of control specimens indicates that degradation in the impact behavior occurs in each of these four alloys. The 9Cr-2W alloy referred to as GA3X and the similar alloy F82H with 7.8Cr-2W appear most promising for further consideration as candidate structural materials in fusion energy system applications. These two alloys exhibit a small DBTT shift to higher temperatures but show increased absorbed energy on the upper shelf.

  9. High strength ferritic alloy

    DOEpatents

    Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.

    1977-01-01

    A high-strength ferritic alloy useful for fast reactor duct and cladding applications where an iron base contains from about 9% to about 13% by weight chromium, from about 4% to about 8% by weight molybdenum, from about 0.2% to about 0.8% by weight niobium, from about 0.1% to about 0.3% by weight vanadium, from about 0.2% to about 0.8% by weight silicon, from about 0.2% to about 0.8% by weight manganese, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight sulfur, a maximum of about 0.02% by weight phosphorous, and from about 0.04% to about 0.12% by weight carbon.

  10. Further Charpy impact test results of low activation ferritic alloys, irradiated at 430{degrees}C to 67 dpa

    SciTech Connect

    Schubert, L.E.; Hamilton, M.L.; Gelles, D.S.

    1997-04-01

    Miniature CVN specimens of four ferritic alloys, GA3X, F82H, GA4X and HT9, have been impact tested following irradiation at 430{degrees}C to 67 dpa. Comparison of the results with those of the previously tested lower dose irradiation condition indicates that the GA3X and F82H alloys, two primary candidate low activation alloys, exhibit virtually identical behavior following irradiation at 430{degrees}C to {approximately}67 dpa and at 370{degrees}C to {approximately}15 dpa. Very little shift is observed in either DBTT or USE relative to the unirradiated condition. The shifts in DBTT and USE observed in both GA4X and HT9 were smaller after irradiation at 430{degrees}C to {approximately}67 dpa than after irradiation at 370{degrees}C to {approximately}15 dpa.

  11. Tantalum modified ferritic iron base alloys

    NASA Technical Reports Server (NTRS)

    Oldrieve, R. E.; Blankenship, C. P. (Inventor)

    1977-01-01

    Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.

  12. Cold worked ferritic alloys and components

    DOEpatents

    Korenko, Michael K.

    1984-01-01

    This invention relates to liquid metal fast breeder reactor and steam generator precipitation hardening fully ferritic alloy components which have a microstructure substantially free of the primary precipitation hardening phase while having cells or arrays of dislocations of varying population densities. It also relates to the process by which these components are produced, which entails solution treating the alloy followed by a final cold working step. In this condition, the first significant precipitation hardening of the component occurs during high temperature use.

  13. Delta ferrite in the weld metal of reduced activation ferritic martensitic steel

    NASA Astrophysics Data System (ADS)

    Sam, Shiju; Das, C. R.; Ramasubbu, V.; Albert, S. K.; Bhaduri, A. K.; Jayakumar, T.; Rajendra Kumar, E.

    2014-12-01

    Formation of delta(δ)-ferrite in the weld metal, during autogenous bead-on-plate welding of Reduced Activation Ferritic Martensitic (RAFM) steel using Gas Tungsten Arc Welding (GTAW) process, has been studied. Composition of the alloy is such that delta-ferrite is not expected in the alloy; but examination of the weld metal revealed presence of delta-ferrite in the weld metal. Volume fraction of delta-ferrite is found to be higher in the weld interface than in the rest of the fusion zone. Decrease in the volume fraction of delta-ferrite, with an increase in preheat temperature or with an increase in heat input, is observed. Results indicate that the cooling rate experienced during welding affects the volume fraction of delta-ferrite retained in the weld metal and variation in the delta-ferrite content with cooling rate is explained with variation in the time that the weld metal spends in various temperature regimes in which delta-ferrite is stable for the alloy during its cooling from the liquid metal to the ambient temperature. This manuscript will discuss the effect of welding parameters on formation of delta-ferrite and its retention in the weld metal of RAFM steel.

  14. Gas- and plasma-driven hydrogen permeation through a reduced activation ferritic steel alloy F82H

    NASA Astrophysics Data System (ADS)

    Zhou, Haishan; Hirooka, Yoshi; Ashikawa, Naoko; Muroga, Takeo; Sagara, Akio

    2014-12-01

    The first wall of a magnetic fusion power reactor will be subjected to hydrogen isotope permeation by the two mechanisms: one is gas-driven and the other is plasma-driven. Hydrogen transport through a reduced activation ferritic steel alloy F82H has been investigated using a steady-state laboratory-scale plasma device. Permeation parameters including permeability, solubility and diffusivity have been measured in the temperature range from 150 to 520 °C. The surface recombination coefficient for hydrogen has also been estimated by a one-dimensional steady-state permeation model with the input data taken from experiments. Using these parameters, the hydrogen plasma-driven permeation flux and inventory for a 0.5 cm thick first wall around 500 °C are estimated to be ∼1.0 × 1013 atom cm-2 s-1 and ∼2 × 1016 atom cm-3, respectively. Also, the implications of all these data on reactor operation are discussed.

  15. Joining Techniques for Ferritic ODS Alloys

    SciTech Connect

    V.G. Krishnardula; V.G. Krishnardula; D.E. Clark; T.C. Totemeier

    2005-06-01

    This report presents results of research on advanced joining techniques for ferritic oxide-dispersion strengthened alloys MA956 and PM2000. The joining techniques studied were resistance pressure welding (also known as pressure forge welding), transient liquid phase bonding, and diffusion bonding. All techniques were shown to produce sound joints in fine-grained, unrecrystallized alloys. Post-bond heat treatment to produce a coarse-grained, recrystallized microstructure resulted in grain growth across the bondline for transient liquid phase and diffusion bonds, giving microstructures essentially identical to that of the parent alloy in the recrystallized condition. The effects of bond orientation, boron interlayer thickness, and bonding parameters are discussed for transient liquid phase and diffusion bonding. The report concludes with a brief discussion of ODS joining techniques and their applicability to GEN IV reactor systems.

  16. Helium entrapment in a nanostructured ferritic alloy

    SciTech Connect

    Edmondson, Philip D; Parish, Chad M; Zhang, Yanwen; Hallen, Dr Anders; Miller, Michael K

    2011-01-01

    The nanostructured ferritic alloy 14YWT has been irradiated with He ions to simulate accumulation of He during the service life of a nuclear reactor to test the hypothesis that the large surface area for nanoclusters is a preferential nucleation site for bubbles. Transmission electron microscopy and atom probe tomography showed that high number densities of He bubbles were formed on the surface of nanoclusters and Ti(C,N) precipitates, and along grain boundaries and dislocations. At higher fluences, facetted bubbles are formed and it is postulated that the lowest energy state configuration is the truncated rhombic dodecahedron.

  17. Irradiation embrittlement of neutron-irradiated low activation ferritic steels

    NASA Astrophysics Data System (ADS)

    Kayano, H.; Kimura, A.; Narui, M.; Sasaki, Y.; Suzuki, Y.; Ohta, S.

    1988-07-01

    Effects of neutron irradiation and additions of small amounts of alloying elements on the ductile-brittle transition temperature (DBTT) of three different groups of ferritic steels were investigated by means of the Charpy impact test in order to gain an insight into the development of low-activation ferritic steels suitable for the nuclear fusion reactor. The groups of ferritic steels used in this study were (1) basic 0-5% Cr ferritic steels, (2) low-activation ferritic steels which are FeCrW steels with additions of small amounts of V, Mn, Ta, Ti, Zr, etc. and (3) FeCrMo, Nb or V ferritic steels for comparison. In Fe-0-15% Cr and FeCrMo steels, Fe-3-9% Cr steels showed minimum brittleness and provided good resistance against irradiation embrittlement. Investigations on the effects of additions of trace amounts of alloying elements on the fracture toughness of low-activation ferritic steels made clear the optimum amounts of each alloying element to obtain higher toughness and revealed that the 9Cr-2W-Ta-Ti-B ferritic steel showed the highest toughness. This may result from the refinement of crystal grains and improvement of quenching characteristics caused by the complex effect of Ti and B.

  18. High strength ferritic alloy-D53

    DOEpatents

    Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.

    1977-01-01

    A high strength ferritic alloy is described having from about 0.2% to about 0.8% by weight nickel, from about 2.5% to about 3.6% by weight chromium, from about 2.5% to about 3.5% by weight molybdenum, from about 0.1% to about 0.5% by weight vanadium, from about 0.1% to about 0.5% by weight silicon, from about 0.1% to about 0.6% by weight manganese, from about 0.12% to about 0.20% by weight carbon, from about 0.02% to about 0.1% by weight boron, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight phosphorous, a maximum of about 0.02% by weight sulfur, and the balance iron.

  19. Towards Radiation Tolerant Nanostructured Ferritic Alloys

    SciTech Connect

    Miller, Michael K; Hoelzer, David T; Russell, Kaye F

    2010-01-01

    The high temperature and irradiation response of a new class of nanostructured ferritic alloys have been investigated by atom probe tomography. These materials are candidate materials for use in the extreme environments that will be present in the next generation of power generating systems. Atom probe tomography has revealed that the yttria powder is forced into solid solution during the mechanical alloying process andsubsequently 2-nm-diameter Ti-, Y- and O-enriched nanoclusters are formedduring the extrusion process. These nanoclusters have been shown to be remarkably stable during isothermal annealing treatments up to 0.92 of the melting temperature and during proton irradiation up to 3 displacements per atom. No significant difference in sizes, compositions and number densities of the nanoclusters was also observed between the unirradiated and proton irradiated conditions. The grain boundaries were found to have high number densities of nanoclusters as well as chromium and tungsten segregation which pin the grain boundary to minimize creep and grain growth.

  20. Microstructural examination of commercial ferritic alloys at 200 dpa

    NASA Astrophysics Data System (ADS)

    Gelles, D. S.

    1996-10-01

    Microstructures and density change measurements are reported for martensitic commercial steels HT-9 and modified 9Cr1Mo (T91) and oxide dispersion strengthened ferritic alloys MA956 and MA957 following irradiation in the FFTF/MOTA at 420°C to 200 dpa. Swelling as determined by density change remains below 2% for all conditions. Microstructures are found to be stable except in recrystallized grains of MA957, which are fabrication artifacts, with only minor swelling in the martensitic steels and α' precipitation in alloys with 12% or more chromium. These results further demonstrate the high swelling resistance and microstructural stability of the ferritic alloy class.

  1. Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates

    NASA Astrophysics Data System (ADS)

    Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H.; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N.; Huang, Shenyan; Teng, Zhenke; Liu, Chain T.; Asta, Mark D.; Gao, Yanfei; Dunand, David C.; Ghosh, Gautam; Chen, Mingwei; Fine, Morris E.; Liaw, Peter K.

    2015-11-01

    There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. The present research will broaden the applications of ferritic alloys to higher temperatures.

  2. Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates

    PubMed Central

    Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H.; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N.; Huang, Shenyan; Teng, Zhenke; Liu, Chain T.; Asta, Mark D.; Gao, Yanfei; Dunand, David C.; Ghosh, Gautam; Chen, Mingwei; Fine, Morris E.; Liaw, Peter K.

    2015-01-01

    There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. The present research will broaden the applications of ferritic alloys to higher temperatures. PMID:26548303

  3. Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates

    DOE PAGESBeta

    Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H.; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N.; Huang, Shenyan; et al

    2015-11-09

    There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones.more » These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. Finally, the present research will broaden the applications of ferritic alloys to higher temperatures.« less

  4. Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates

    SciTech Connect

    Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H.; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N.; Huang, Shenyan; Teng, Zhenke; Liu, Chain T.; Asta, Mark D.; Gao, Yanfei; Dunand, David C.; Ghosh, Gautam; Chen, Mingwei; Fine, Morris E.; Liaw, Peter K.

    2015-11-09

    There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. Finally, the present research will broaden the applications of ferritic alloys to higher temperatures.

  5. Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates.

    PubMed

    Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N; Huang, Shenyan; Teng, Zhenke; Liu, Chain T; Asta, Mark D; Gao, Yanfei; Dunand, David C; Ghosh, Gautam; Chen, Mingwei; Fine, Morris E; Liaw, Peter K

    2015-01-01

    There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. The present research will broaden the applications of ferritic alloys to higher temperatures. PMID:26548303

  6. Development of low activation Ferritic steels

    NASA Astrophysics Data System (ADS)

    Noda, T.; Abe, F.; Araki, H.; Okada, M.

    1986-11-01

    Fe-(2-15)%Cr-(0-4)%W-0.1%C and Fe-9%Cr-(0-l)%V-0.1%C steels were prepared on the basis of reduced activation of ferritic steels. Tempering characteristics of these alloys were studied as a preliminary evaluation of mechanical properties. Alloys except for 12-15%Cr, 9%Cr-4%W, and 9%Cr-1%V showed a single phase of martensite. Carbides which precipitated in as-tempered steels are M 23C 6, M 6C, and W 2C for Cr-W steels and M 23C 6 and V 4C 3 for Cr-V steels. The toughness of the alloys was examined with Charpy impact test. The minimum DBTT (ductile-brittle transition temperature) was observed at around 0.25 at% of W or V concentration for 9%Cr steels. 9%Cr-V steels were superior to commercial 9%Cr-2%Mo steel in the point of toughness. The order of alloying element with a low DBTT was V > Mo > W.

  7. Unusual Thermal Stability of Nano-structured Ferritic alloys

    SciTech Connect

    Wang, Xun-Li; Liu, Chain T; Stoica, A. D.; Keiderling, Dr. Uwe; Yang, Ling; Miller, Michael K; Fu, Chong Long; Ma, Dong; An, Ke

    2012-01-01

    A scientific question vitally important to the materials community is whether there exist self-assembled nanoclusters that are thermodynamically stable at elevated temperatures. Using in-situ neutron scattering, we characterized the structure and thermal stability of a nano-structured ferritic (NSF) alloy. Nanometer sized clusters were found to persist up to ~1400 C, providing direct evidence of a thermodynamically stable alloying state for the nanoclusters. Cluster formation requires the coexistence of Y, Ti, and O without the precipitation of oxide phases. The presence of thermally stable nanoclusters at grain boundaries limits the diffusion of Fe atoms, thereby stabilizing the microstructure of the ferritic matrix at high temperatures. Our experimental results provide physical insights of the dramatically improved high-temperature mechanical properties in NSF alloy and point to a new direction in alloy design.

  8. Ferritic Fe-Mn alloy for cryogenic applications

    DOEpatents

    Hwang, Sun-Keun; Morris, Jr., John W.

    1979-01-01

    A ferritic, nickel-free alloy steel composition, suitable for cryogenic applications, which consists essentially of about 10-13% manganese, 0.002-0.01% boron, 0.1-0.5% titanium, 0-0.05% aluminum, and the remainder iron and incidental impurities normally associated therewith.

  9. The Role of Alloying Elements in Nanostructured Ferritic Steels

    SciTech Connect

    Miller, Michael K; Parish, Chad M

    2010-01-01

    The roles of the alloying elements in three nanostructured ferritic alloys (14YWT, MA957 and Eurofer 97) have been established through the characterisation of the microstructure by atom probe tomography and spectrum imaging in a transmission electron microscope. Cr, W, Mo, Ti and Y were found in the ferrite matrix and contributed to solid solution hardening. Ti, Y, C, O and N were found in high number densities of precipitates and nanoclusters both in the grain interior and on grain boundaries and thereby contributed to precipitation hardening. Cr, W and Mo were enriched at the intraparticle regions of the grain boundaries. The solute segregation and precipitation pinned the grain boundaries and contributed to the excellent creep properties of the alloys.

  10. High Temperature Fracture Characteristics of a Nanostructured Ferritic Alloy (NFA)

    SciTech Connect

    Byun, Thak Sang; Kim, Jeoung H; Ji Hyun, Yoon; Hoelzer, David T

    2010-01-01

    High temperature fracture behavior has been investigated for the nanostructured ferritic alloy 14YWT (SM10). The fracture toughness of the alloy was above 140 MPa m at low temperatures, room temperature (RT) and 200 C, but decreased to a low fracture toughness range of 52 82 MPa m at higher temperatures up to 700 C. This behavior was explained by the fractography results indicating that the unique nanostructure of 14YWT alloy produced shallow plasticity layers at high temperatures and a low-ductility grain boundary debonding occurred at 700 C.

  11. Oxidation resistance of novel ferritic stainless steels alloyed with titanium for SOFC interconnect applications

    SciTech Connect

    Jablonski, P.D.; Alman, D.E.

    2008-05-15

    Chromia (Cr2O3) forming ferritic stainless steels are being developed for interconnect application in Solid Oxide Fuel Cells (SOFC). A problem with these alloys is that in the SOFC environment chrome in the surface oxide can evaporate and deposit on the electrochemically active sites within the fuel cell. This poisons and degrades the performance of the fuel cell. The development of steels that can form conductive outer protective oxide layers other than Cr2O3 or (CrMn)3O4 such as TiO2 may be attractive for SOFC application. This study was undertaken to assess the oxidation behavior of ferritic stainless steel containing 1 weight percent (wt.%) Ti, in an effort to develop alloys that form protective outer TiO2 scales. The effect of Cr content (6–22 wt.%) and the application of a Ce-based surface treatment on the oxidation behavior (at 800° C in air+3% H2O) of the alloys was investigated. The alloys themselves failed to form an outer TiO2 scale even though the large negative {delta}G of this compound favors its formation over other species. It was found that in conjunction with the Ce-surface treatment, a continuous outer TiO2 oxide layer could be formed on the alloys, and in fact the alloy with 12 wt.% Cr behaved in an identical manner as the alloy with 22 wt.% Cr.

  12. Mechanical alloying of lanthana-bearing nanostructured ferritic steels

    SciTech Connect

    Somayeh Paseban; Indrajit Charit; Yaqiao Q. Wu; Jatuporn Burns; Kerry N. Allahar; Darryl P. Butt; James I. Cole

    2013-09-01

    A novel nanostructured ferritic steel powder with the nominal composition Fe–14Cr–1Ti–0.3Mo–0.5La2O3 (wt.%) was developed via high energy ball milling. La2O3 was added to this alloy instead of the traditionally used Y2O3. The effects of varying the ball milling parameters, such as milling time, steel ball size and ball to powder ratio, on the mechanical properties and micro structural characteristics of the as-milled powder were investigated. Nanocrystallites of a body-centered cubic ferritic solid solution matrix with a mean size of approximately 20 nm were observed by transmission electron microscopy. Nanoscale characterization of the as-milled powder by local electrode atom probe tomography revealed the formation of Cr–Ti–La–O-enriched nanoclusters during mechanical alloying. The Cr:Ti:La:O ratio is considered “non-stoichiometric”. The average size (radius) of the nanoclusters was about 1 nm, with number density of 3.7 1024 m3. The mechanism for formation of nanoclusters in the as-milled powder is discussed. La2O3 appears to be a promising alternative rare earth oxide for future nanostructured ferritic steels.

  13. The role of nickel in radiation damage of ferritic alloys

    DOE PAGESBeta

    Osetskiy, Yury N.; Anento, Napoleon; Serra, Anna; Terentyev, Dmitry

    2014-11-26

    According to the modern theory damage evolution under neutron irradiation depends on the fraction of self interstitial atoms (SIAs) produced in the form of one-dimensionally (1-D) glissile clusters. These clusters, having a low interaction cross-section with other defects, sink mainly on grain boundaries and dislocations creating the so-called production bias. It is known empirically that addition of certain alloying elements affect many radiation effects, including swelling, however the mechanisms are unknown in many cases. In this paper we report the results of an extensive multi-technique atomistic level modeling of SIA clusters mobility in bcc Fe-Ni alloys with Ni content frommore » 0.8 to 10 at.%. We have found that Ni interacts strongly with periphery of clusters affecting their mobility. The total effect is defined by all Ni atoms interacting with the cluster at the same time and can be significant even in low-Ni alloys. Thus 1nm (37SIAs) cluster is practically immobile at T < 500K in the Fe-0.8at.% Ni alloy. Increasing cluster size and Ni content enhance cluster immobilization. Furthermore, this effect should have quite broad consequences in swelling rate, matrix damage accumulation, radiation induced hardening, etc. and the results obtained help in better understanding and prediction of radiation effects in Fe-Ni ferritic alloys.« less

  14. The role of nickel in radiation damage of ferritic alloys

    SciTech Connect

    Osetskiy, Yury N.; Anento, Napoleon; Serra, Anna; Terentyev, Dmitry

    2014-11-26

    According to the modern theory damage evolution under neutron irradiation depends on the fraction of self interstitial atoms (SIAs) produced in the form of one-dimensionally (1-D) glissile clusters. These clusters, having a low interaction cross-section with other defects, sink mainly on grain boundaries and dislocations creating the so-called production bias. It is known empirically that addition of certain alloying elements affect many radiation effects, including swelling, however the mechanisms are unknown in many cases. In this paper we report the results of an extensive multi-technique atomistic level modeling of SIA clusters mobility in bcc Fe-Ni alloys with Ni content from 0.8 to 10 at.%. We have found that Ni interacts strongly with periphery of clusters affecting their mobility. The total effect is defined by all Ni atoms interacting with the cluster at the same time and can be significant even in low-Ni alloys. Thus 1nm (37SIAs) cluster is practically immobile at T < 500K in the Fe-0.8at.% Ni alloy. Increasing cluster size and Ni content enhance cluster immobilization. Furthermore, this effect should have quite broad consequences in swelling rate, matrix damage accumulation, radiation induced hardening, etc. and the results obtained help in better understanding and prediction of radiation effects in Fe-Ni ferritic alloys.

  15. Processing and characterization of oxide dispersion strengthened 14YWT ferritic alloys

    NASA Astrophysics Data System (ADS)

    West, Michael Keith

    Oxide dispersion strengthened (ODS) ferritic steels are currently being investigated as candidate materials for nuclear applications due to their increased high temperature strength and low activation characteristics. Recent studies have shown that ODS ferritic steels containing Ti exhibit enhanced high temperature properties due to the formation of a very fine dispersion of nanometer-sized oxide clusters based on Ti, Y, and O. Studies are currently underway to examine so called 14YWT alloys with nominal compositions of Fe-14Cr-3W-0.4Ti (wt. %) mechanically alloyed with 0.25 (wt.%) Y2O3. The focus of this study was to investigate how the early stages of processing of 14YWT alloys during mechanical milling, heat treatment, and consolidation affect the structure and properties of the alloys. The 14YWT alloys were milled at different times up to 80 hours, along with alloy powder compositions of Fe-14Cr + 0.25 wt.% Y2O 3 (14Y) and Fe-14Cr without Y2O3 (Fe-14Cr). The evolution of the microstructure and mechanical properties during milling was examined with a combination of optical metallography, x-ray diffraction, electron microscopy, atom probe tomography, and nanoindentation. Alloy powders were also heat treated and studied using high temperature x-ray diffraction and differential scanning calorimetry methods. Special attention was paid to milling parameters and temperature ranges which lead to the formation of nanosized oxide clusters in the alloys. Finally, the microstructure of consolidated alloys was examined and related to milling and heat treatment methods. Mechanical properties and microstructure during milling were similar in the three alloy powders examined regardless of dispersoid or alloy addition. Mechanical mixing of the alloy powders was inefficient after 40 hours of milling. Milling did not produce bulk amorphous phases but quickly reduced the crystallite size to ˜10-20 nm. Milling also resulted in relatively uniform dissolution of Y2O3. Thermal

  16. Deuterium Retention and Physical Sputtering of Low Activation Ferritic Steel

    NASA Astrophysics Data System (ADS)

    T, Hino; K, Yamaguchi; Y, Yamauchi; Y, Hirohata; K, Tsuzuki; Y, Kusama

    2005-04-01

    Low activation materials have to be developed toward fusion demonstration reactors. Ferritic steel, vanadium alloy and SiC/SiC composite are candidate materials of the first wall, vacuum vessel and blanket components, respectively. Although changes of mechanical-thermal properties owing to neutron irradiation have been investigated so far, there is little data for the plasma material interactions, such as fuel hydrogen retention and erosion. In the present study, deuterium retention and physical sputtering of low activation ferritic steel, F82H, were investigated by using deuterium ion irradiation apparatus. After a ferritic steel sample was irradiated by 1.7 keV D+ ions, the weight loss was measured to obtain the physical sputtering yield. The sputtering yield was 0.04, comparable to that of stainless steel. In order to obtain the retained amount of deuterium, technique of thermal desorption spectroscopy (TDS) was employed to the irradiated sample. The retained deuterium desorbed at temperature ranging from 450 K to 700 K, in the forms of DHO, D2, D2O and hydrocarbons. Hence, the deuterium retained can be reduced by baking with a relatively low temperature. The fluence dependence of retained amount of deuterium was measured by changing the ion fluence. In the ferritic steel without mechanical polish, the retained amount was large even when the fluence was low. In such a case, a large amount of deuterium was trapped in the surface oxide layer containing O and C. When the fluence was large, the thickness of surface oxide layer was reduced by the ion sputtering, and then the retained amount in the oxide layer decreased. In the case of a high fluence, the retained amount of deuterium became comparable to that of ferritic steel with mechanical polish or SS 316L, and one order of magnitude smaller than that of graphite. When the ferritic steel is used, it is required to remove the surface oxide layer for reduction of fuel hydrogen retention. Ferritic steel sample was

  17. Discussion on the Alloying Element Partition and Growth Kinetics of Proeutectoid Ferrite in Fe-C-Mn-X Alloys

    NASA Astrophysics Data System (ADS)

    Wei, R.; Enomoto, M.

    2011-12-01

    Experimental data on alloying element partition and growth kinetics of proeutectoid ferrite in quaternary Fe-C-Mn-Si, Ni, and Co alloys were reanalyzed using an approximate method, which permits a quick evaluation of alloy partitioning to be made. The method yielded results in good agreement with DICTRA and is applicable to Fe-C base multicomponent alloys. Differences of the predicted local condition at the α/ γ boundary from those previously presented in the alloys are noted.

  18. Investigation on the Behavior of Austenite and Ferrite Phases at Stagnation Region in the Turning of Duplex Stainless Steel Alloys

    NASA Astrophysics Data System (ADS)

    Nomani, J.; Pramanik, A.; Hilditch, T.; Littlefair, G.

    2016-06-01

    This paper investigates the deformation mechanisms and plastic behavior of austenite and ferrite phases in duplex stainless steel alloys 2205 and 2507 under chip formation from a machine turning operation. SEM images and EBSD phase mapping of frozen chip root samples detected a build-up of ferrite bands in the stagnation region, and between 65 and 85 pct, more ferrite was identified in the stagnation region compared to austenite. SEM images detected micro-cracks developing in the ferrite phase, indicating ferritic build-up in the stagnation region as a potential triggering mechanism to the formation of built-up edge, as transgranular micro-cracks found in the stagnation region are similar to micro-cracks initiating built-up edge formation. Higher plasticity of austenite due to softening under high strain is seen responsible for the ferrite build-up. Flow lines indicate that austenite is plastically deforming at a greater rate into the chip, while ferrite shows to partition most of the strain during deformation. The loss of annealing twins and activation of multiple slip planes triggered at high strain may explain the highly plastic behavior shown by austenite.

  19. Investigation on the Behavior of Austenite and Ferrite Phases at Stagnation Region in the Turning of Duplex Stainless Steel Alloys

    NASA Astrophysics Data System (ADS)

    Nomani, J.; Pramanik, A.; Hilditch, T.; Littlefair, G.

    2016-04-01

    This paper investigates the deformation mechanisms and plastic behavior of austenite and ferrite phases in duplex stainless steel alloys 2205 and 2507 under chip formation from a machine turning operation. SEM images and EBSD phase mapping of frozen chip root samples detected a build-up of ferrite bands in the stagnation region, and between 65 and 85 pct, more ferrite was identified in the stagnation region compared to austenite. SEM images detected micro-cracks developing in the ferrite phase, indicating ferritic build-up in the stagnation region as a potential triggering mechanism to the formation of built-up edge, as transgranular micro-cracks found in the stagnation region are similar to micro-cracks initiating built-up edge formation. Higher plasticity of austenite due to softening under high strain is seen responsible for the ferrite build-up. Flow lines indicate that austenite is plastically deforming at a greater rate into the chip, while ferrite shows to partition most of the strain during deformation. The loss of annealing twins and activation of multiple slip planes triggered at high strain may explain the highly plastic behavior shown by austenite.

  20. Influence of Alloy Content and Prior Microstructure on Evolution of Secondary Phases in Weldments of 9Cr-Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Thomas Paul, V.; Sudha, C.; Saroja, S.

    2015-08-01

    9Cr-Reduced Activation Ferritic-Martensitic steels with 1 and 1.4 wt pct tungsten are materials of choice for the test blanket module in fusion reactors. The steels possess a tempered martensite microstructure with a decoration of inter- and intra-lath carbides, which undergoes extensive modification on application of heat. The change in substructure and precipitation behavior on welding and subsequent thermal exposure has been studied using both experimental and computational techniques. Changes i.e., formation of various phases, their volume fraction, size, and morphology in different regions of the weldment due to prolonged thermal exposure was influenced not only by the time and temperature of exposure but also the prior microstructure. Laves phase of type Fe2W was formed in the high tungsten steel, on aging the weldment at 823 K (550 °C). It formed in the fine-grained heat-affected zone (HAZ) at much shorter durations than in the base metal. The accelerated kinetics has been understood in terms of enhanced precipitation of carbides at lath/grain boundaries during aging and the concomitant depletion of carbon and chromium and enrichment of tungsten in the vicinity of the carbides. Therefore, the fine-grained HAZ in the weldment was identified as a region susceptible for failure during service.

  1. Stability of Y–Ti–O precipitates in friction stir welded nanostructured ferritic alloys

    DOE PAGESBeta

    Yu, Xinghua; Mazumder, B.; Miller, M. K.; David, S. A.; Feng, Z.

    2015-01-19

    Nanostructured ferritic alloys, which have complex microstructures which consist of ultrafine ferritic grains with a dispersion of stable oxide particles and nanoclusters, are promising materials for fuel cladding and structural applications in the next generation nuclear reactor. This paper evaluates microstructure of friction stir welded nanostructured ferritic alloys using electron microscopy and atom probe tomography techniques. Atom probe tomography results revealed that nanoclusters are coarsened and inhomogeneously distributed in the stir zone and thermomechanically affected zone. Three hypotheses on coarsening of nanoclusters are presented. Finally, the hardness difference in different regions of friction stir weld has been explained.

  2. Detection and quantification of solute clusters in a nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Miller, M. K.; Reinhard, D.; Larson, D. J.

    2015-07-01

    A series of simulated atom probe datasets were examined with a friends-of-friends method to establish the detection efficiency required to resolve solute clusters in the ferrite phase of a 14YWT nanostructured ferritic alloy. The size and number densities of solute clusters in the ferrite of the as-milled mechanically-alloyed condition and the stir zone of a friction stir weld were estimated with a prototype high-detection-efficiency (∼80%) local electrode atom probe. High number densities, 1.8 × 1024 m-3 and 1.2 × 1024 m-3, respectively of solute clusters containing between 2 and 9 solute atoms of Ti, Y and O and were detected for these two conditions. These results support first principle calculations that predicted that vacancies stabilize these Ti-Y-O- clusters, which retard diffusion and contribute to the excellent high temperature stability of the microstructure and radiation tolerance of nanostructured ferritic alloys.

  3. Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

    DOE PAGESBeta

    Zhang, Z. W.; Yao, L.; Wang, X. -L.; Miller, M. K.

    2015-05-29

    A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. We report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using amore » combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.« less

  4. Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

    SciTech Connect

    Zhang, Z. W.; Yao, L.; Wang, X. -L.; Miller, M. K.

    2015-05-29

    A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. We report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.

  5. Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

    PubMed Central

    Zhang, Z. W.; Yao, L.; Wang, X.-L.; Miller, M. K.

    2015-01-01

    A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. Here we report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters. PMID:26023747

  6. Stability of Y Ti O Precipitates in Friction Stir Welded Nanostructured Ferritic Alloys

    DOE PAGESBeta

    Yu, Xinghua; Mazumder, Baishakhi; Miller, Michael K; David, Stan A; Feng, Zhili

    2015-01-01

    Nanostructured ferritic alloys (NFAs), which have complex microstructures consisting of ultrafine ferritic grains with a dispersion of stable oxide particles and nanoclusters (NC), are promising materials for fuel cladding and structural applications in the next generation nuclear reactor. This study evaluates microstructure of friction stir welded NFA using electron microscopy and atom probe tomography (APT) techniques. APT results revealed NCs are coarsened and inhomogeneously distributed in the stir zone. Three hypotheses on coarsening of NC are presented.

  7. Irradiation creep of various ferritic alloys irradiated {approximately}400 C in the PFR and FFTF reactors

    SciTech Connect

    Toloczko, M.B.; Garner, F.A.; Eiholzer, C.R.

    1998-03-01

    Three ferritic alloys were irradiated in two fast reactors to doses of 50 dpa or more at temperatures near 400 C. One martensitic alloy, HT9, was irradiated in both the FFTF and PFR reactors. PFR is the Prototype Fast Reactor in Dourneay, Scotland, and FFTF is the Fast Flux Test Facility in Richland, WA. D57 is a developmental alloy that was irradiated in PFR only, and MA957 is a Y{sub 2}O{sub 3} dispersion-hardened ferritic alloy that was irradiated only in FFTF. These alloys exhibited little or no void swelling at {approximately}400 C. Depending on the alloy starting condition, these steels develop a variety of non-creep strains early in the irradiation that are associated with phase changes. Each of these alloys creeps at a rate that is significantly lower than that of austenitic steels irradiated in the same experiments. The creep compliance for ferritic alloys in general appears to be {approximately}0.5 {times} 10{sup {minus}6} MPa{sup {minus}1} dpa{sup {minus}1}, independent of both composition and starting state. The addition of Y{sub 2}O{sub 3} as a dispersoid does not appear to change the creep behavior.

  8. Swelling and dislocation evolution in simple ferritic alloys irradiated to high fluence in FFTF/MOTA

    NASA Astrophysics Data System (ADS)

    Katoh, Yutai; Kohyama, Akira; Gelles, David S.

    1995-08-01

    Microstructures of a series of Fe sbnd Cr binary ferritic alloys were examined following neutron irradiation to 140 dpa at 698 K in FFTF/MOTA. The chromium concentration ranged from 3 to 18% in 3% increments and the irradiation temperature corresponded to the peak swelling condition for this alloy class. The swelling varied from 0.4 to 2.9% depending on chromium concentration, and the highest swelling was found in the Fe sbnd 9Cr alloy. The cavity microstructures corresponded to transient to early steady-state swelling regime. Dislocations were composed of networks with both a<100> and ( a/2)<111> Burgers vector and a<100> type interstitial loops. The dislocation density was negatively correlated with swelling. Explanation for the observed chromium concentration dependence of microstructural development and low swelling in the ferritic alloys will be studied in connection with the dislocation bias efficiency and the theory of sink strength ratio.

  9. Self-Consistent Model for Planar Ferrite Growth in Fe-C-X Alloys

    NASA Astrophysics Data System (ADS)

    Zurob, H. S.; Panahi, D.; Hutchinson, C. R.; Brechet, Y.; Purdy, G. R.

    2013-08-01

    A self-consistent model for non-partitioning planar ferrite growth from alloyed austenite is presented. The model captures the evolution with time of interfacial contact conditions for substitutional and interstitial solutes. Substitutional element solute drag is evaluated in terms of the dissipation of free energy within the interface, and an estimate is provided for the rate of buildup of the alloying element "spike" in austenite. The transport of the alloying elements within the interface region is modeled using a discrete-jump model, while the bulk diffusion of C is treated using a standard continuum treatment. The model is validated against ferrite precipitation and decarburization kinetics in the Fe-Ni-C, Fe-Mn-C, and Fe-Mo-C systems.

  10. The Effect of H and He on Irradiation Performance of Fe and Ferritic Alloys

    SciTech Connect

    James F. Stubbins

    2010-01-22

    This research program was designed to look at basic radiation damage and effects and mechanical properties in Fe and ferritic alloys. The program scope included a number of materials ranging from pure single crystal Fe to more complex Fe-Cr-C alloys. The range of materials was designed to examine materials response and performance on ideal/model systems and gradually move to more complex systems. The experimental program was coordinated with a modeling effort. The use of pure and model alloys also facilitated the ability to develop and employ atomistic-scale modeling techniques to understand the inherent physics underlying materials performance

  11. Detection and quantification of solute clusters in a nanostructured ferritic alloy

    DOE PAGESBeta

    Miller, Michael K.; Larson, David J.; Reinhard, D. A.

    2014-12-26

    A series of simulated atom probe datasets were examined with a friends-of-friends method to establish the detection efficiency required to resolve solute clusters in the ferrite phase of a 14YWT nanostructured ferritic alloy. The size and number densities of solute clusters in the ferrite of the as-milled mechanically-alloyed condition and the stir zone of a friction stir weld were estimated with a prototype high-detection-efficiency (~80%) local electrode atom probe. High number densities, 1.8 × 1024 m–3 and 1.2 × 1024 m–3, respectively of solute clusters containing between 2 and 9 solute atoms of Ti, Y and O and were detectedmore » for these two conditions. Furthermore, these results support first principle calculations that predicted that vacancies stabilize these Ti–Y–O– clusters, which retard diffusion and contribute to the excellent high temperature stability of the microstructure and radiation tolerance of nanostructured ferritic alloys.« less

  12. Detection and quantification of solute clusters in a nanostructured ferritic alloy

    SciTech Connect

    Miller, Michael K.; Larson, David J.; Reinhard, D. A.

    2014-12-26

    A series of simulated atom probe datasets were examined with a friends-of-friends method to establish the detection efficiency required to resolve solute clusters in the ferrite phase of a 14YWT nanostructured ferritic alloy. The size and number densities of solute clusters in the ferrite of the as-milled mechanically-alloyed condition and the stir zone of a friction stir weld were estimated with a prototype high-detection-efficiency (~80%) local electrode atom probe. High number densities, 1.8 × 1024 m–3 and 1.2 × 1024 m–3, respectively of solute clusters containing between 2 and 9 solute atoms of Ti, Y and O and were detected for these two conditions. Furthermore, these results support first principle calculations that predicted that vacancies stabilize these Ti–Y–O– clusters, which retard diffusion and contribute to the excellent high temperature stability of the microstructure and radiation tolerance of nanostructured ferritic alloys.

  13. Irradiation creep of various ferritic alloys irradiated at ˜400°C in the PFR and FFTF reactors

    NASA Astrophysics Data System (ADS)

    Toloczko, M. B.; Garner, F. A.; Eiholzer, C. R.

    1998-10-01

    Irradiation creep of three ferritic alloys at ˜400 ∘C has been studied. Specimens were in the form of pressurized tubes. In a joint US/UK creep study, two identical sets of creep specimens constructed from one heat of HT9 were irradiated in fast reactors, one in the Prototypic Fast Reactor (PFR) and the other in the Fast Flux Test Facility (FFTF). The specimens in PFR were irradiated to a dose of ˜50 dpa, whereas the specimens in FFTF were irradiated to a dose of 165 dpa. The observed swelling and creep behavior were very different in the two reactors. Creep specimens constructed from D57, a developmental alloy ferritic alloy, were also irradiated in PFR to a dose of ˜50 dpa. Creep behavior typical of previous studies on ferritic alloys was observed. Finally, creep specimens constructed from MA957, a Y 2O 3 dispersion-hardened ferritic alloy, were irradiated in FFTF to a dose of ˜110 dpa. This alloy exhibited a large amount of densification, and the creep behavior was different than observed in more conventional ferritic or ferritic-martensitic alloys.

  14. Computational Design of Creep-Resistant Alloys and Experimental Validation in Ferritic Superalloys

    SciTech Connect

    Liaw, Peter

    2014-12-31

    A new class of ferritic superalloys containing B2-type zones inside parent L21-type precipitates in a disordered solid-solution matrix, also known as a hierarchical-precipitate strengthened ferritic alloy (HPSFA), has been developed for high-temperature structural applications in fossil-energy power plants. These alloys were designed by the addition of the Ti element into a previously-studied NiAl-strengthened ferritic alloy (denoted as FBB8 in this study). In the present research, systematic investigations, including advanced experimental techniques, first-principles calculations, and numerical simulations, have been integrated and conducted to characterize the complex microstructures and excellent creep resistance of HPSFAs. The experimental techniques include transmission-electron microscopy, scanningtransmission- electron microscopy, neutron diffraction, and atom-probe tomography, which provide detailed microstructural information of HPSFAs. Systematic tension/compression creep tests revealed that HPSFAs exhibit the superior creep resistance, compared with the FBB8 and conventional ferritic steels (i.e., the creep rates of HPSFAs are about 4 orders of magnitude slower than the FBB8 and conventional ferritic steels.) First-principles calculations include interfacial free energies, anti-phase boundary (APB) free energies, elastic constants, and impurity diffusivities in Fe. Combined with kinetic Monte- Carlo simulations of interdiffusion coefficients, and the integration of computational thermodynamics and kinetics, these calculations provide great understanding of thermodynamic and mechanical properties of HPSFAs. In addition to the systematic experimental approach and first-principles calculations, a series of numerical tools and algorithms, which assist in the optimization of creep properties of ferritic superalloys, are utilized and developed. These numerical simulation results are compared with the available experimental data and previous first

  15. Studies on the activation energy from the ac conductivity measurements of rubber ferrite composites containing manganese zinc ferrite

    NASA Astrophysics Data System (ADS)

    Hashim, Mohd.; Alimuddin; Kumar, Shalendra; Shirsath, Sagar E.; Mohammed, E. M.; Chung, Hanshik; Kumar, Ravi

    2012-11-01

    Manganese zinc ferrites (MZF) have resistivities between 0.01 and 10 Ω m. Making composite materials of ferrites with either natural rubber or plastics will modify the electrical properties of ferrites. The moldability and flexibility of these composites find wide use in industrial and other scientific applications. Mixed ferrites belonging to the series Mn(1-x)ZnxFe2O4 were synthesized for different ‘x’ values in steps of 0.2, and incorporated in natural rubber matrix (RFC). From the dielectric measurements of the ceramic manganese zinc ferrite and rubber ferrite composites, ac conductivity and activation energy were evaluated. A program was developed with the aid of the LabVIEW package to automate the measurements. The ac conductivity of RFC was then correlated with that of the magnetic filler and matrix by a mixture equation which helps to tailor properties of these composites.

  16. Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy.

    PubMed

    Stoica, G M; Stoica, A D; Miller, M K; Ma, D

    2014-01-01

    Nanostructured ferritic alloys are a new class of ultrafine-grained oxide dispersion-strengthened steels that have promising properties for service in extreme environments in future nuclear reactors. This is due to the remarkable stability of their complex microstructures containing numerous Y-Ti-O nanoclusters within grains and along grain boundaries. Although nanoclusters account primarily for the exceptional resistance to irradiation damage and high-temperature creep, little is known about the mechanical roles of the polycrystalline grains that constitute the ferritic matrix. Here we report an in situ mesoscale characterization of anisotropic responses of ultrafine ferrite grains to stresses using state-of-the-art neutron diffraction. We show the experimental determination of single-crystal elastic constants for a 14YWT alloy, and reveal a strong temperature-dependent elastic anisotropy that leads to elastic softening and instability of the ferrite. We also demonstrate, from anisotropy-induced intergranular strains, that a deformation crossover exists from low-temperature lattice hardening to high-temperature lattice softening in response to extensive plastic deformation. PMID:25300893

  17. Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Stoica, G. M.; Stoica, A. D.; Miller, M. K.; Ma, D.

    2014-10-01

    Nanostructured ferritic alloys are a new class of ultrafine-grained oxide dispersion-strengthened steels that have promising properties for service in extreme environments in future nuclear reactors. This is due to the remarkable stability of their complex microstructures containing numerous Y-Ti-O nanoclusters within grains and along grain boundaries. Although nanoclusters account primarily for the exceptional resistance to irradiation damage and high-temperature creep, little is known about the mechanical roles of the polycrystalline grains that constitute the ferritic matrix. Here we report an in situ mesoscale characterization of anisotropic responses of ultrafine ferrite grains to stresses using state-of-the-art neutron diffraction. We show the experimental determination of single-crystal elastic constants for a 14YWT alloy, and reveal a strong temperature-dependent elastic anisotropy that leads to elastic softening and instability of the ferrite. We also demonstrate, from anisotropy-induced intergranular strains, that a deformation crossover exists from low-temperature lattice hardening to high-temperature lattice softening in response to extensive plastic deformation.

  18. High Frequency Properties of Ferrite/Fe-Si-Al Alloy Soft Magnetic Composites

    NASA Astrophysics Data System (ADS)

    Stergiou, Charalampos A.; Zaspalis, Vassilios

    The inclusion of Fe-Si-Al alloy particles in NiCuZn ferrite matrix was investigated with regard to the high frequency electromagnetic properties (complex permeability and permittivity). The resultant composites of relatively low density exhibit a shift of the permeability spectra to higher frequencies and an increase of dielectric polarization, which finally favour the electromagnetic wave attenuation at microwave frequencies. Thus, wider band return loss peaks are attained at frequencies above 6 GHz by thinner composite materials.

  19. A micro-alloyed ferritic steel strengthened by nanoscale precipitates

    SciTech Connect

    Shen, Yongfeng; Wang, Chong M.; Sun, Xin

    2011-10-25

    A ferritic steel with finely dispersive precipitates was investigated to reveal the fundamental strengthening mechanisms. The steel has a yield strength of 760 MPa, approximately three times higher than that of conventional Ti-bearing high strength hot-rolled sheet steels, and its ultimate tensile strength reaches 850 MPa with an elongation-to-failure value of 18%. Using energy dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM), fine carbides TiC with an average diameter of 10 nm were observed in the ferrite matrix of the 0.08%Ti steel, and some cubic M23C6 precipitates were also observed at the grain boundaries and the interior of the grains. The finely dispersive TiC precipitates in the matrix provide matrix strengthening. The estimated magnitude of precipitation strengthening is around 458 MPa, depending on the average size of the nanoscale precipitates. Dislocation densities increased from 3.42×1013 m-2 to 1.69 × 1014 m-2, respectively, with increasing tensile strain from 5.5% to 22%. The measured work-hardening behavior can be related to the observed dislocation accumulations resulting from the dispersive nano-scale precipitates.

  20. Surface modification of ferritic and Ni based alloys for improved oxidation resistance of SOFC interconnect applications

    SciTech Connect

    Jablonski, Paul D.; Alman, David E.; Kung, Steven C.

    2005-08-01

    This research is aimed at evaluating a surface modification of ferritic stainless steels (Type-430 and Crofer 22APU) and nickel-base alloys (Haynes 230) for use in the SOFC temperature range of 700 to 800°C. A surface treatment was devised to enhance the stability of the base metal oxide that forms and to reduce the oxidation rate of the materials at high temperature. Oxidation tests (in wet air; treated and untreated) were conducted at 800°C to evaulate the corrosion resistance of the alloys. It was found that the surface treatment improved the oxidation resistance of all the alloys tested. However, the treatment improved the performance of 430SS more than that of the other alloys.

  1. Effect of Alloy Composition, Surface Preparation and Exposure Conditions on the Selective Oxidation Behavior of Ferritic Fe-Cr and Fe-Cr-X Alloy

    SciTech Connect

    Meier, G H; Mu, N; Yanar, N M; Pettit, F S; Piron Abellan, J; Olszewski, T; Quadakkers, W J; Holcomb, G R

    2010-09-01

    Abstract Selective oxidation behavior of ferritic martensitic Fe–Cr base alloys, exposed in various atmospheres containing combinations of O2, CO2, and H2O, were studied at various temperatures relevant to oxy-fuel combustion. This paper begins with a discussion of the required Cr content to form a continuous external chromia scale on a simple binary Fe–Cr alloy exposed in oxygen or air based on experiments and calculations using the classic Wagner model. Then, the effects of the exposure environment and Cr content on the selective oxidation of Fe–Cr alloys are evaluated. Finally, the effects produced by alloying additions of Si, commonly present in various groups of commercially available ferritic steels, are described. The discussion compares the oxide scale formation on simple binary and ternary Fe–Cr base model alloys with that on several commercially available ferritic steels.

  2. Development of new generation reduced activation ferritic-martensitic steels for advanced fusion reactors

    NASA Astrophysics Data System (ADS)

    Tan, L.; Snead, L. L.; Katoh, Y.

    2016-09-01

    International development of reduced activation ferritic-martensitic (RAFM) steels has focused on 9 wt percentage Cr, which primarily contain M23C6 (M = Cr-rich) and small amounts of MX (M = Ta/V, X = C/N) precipitates, not adequate to maintain strength and creep resistance above ∼500 °C. To enable applications at higher temperatures for better thermal efficiency of fusion reactors, computational alloy thermodynamics coupled with strength modeling have been employed to explore a new generation RAFM steels. The new alloys are designed to significantly increase the amount of MX nanoprecipitates, which are manufacturable through standard and scalable industrial steelmaking methods. Preliminary experimental results of the developed new alloys demonstrated noticeably increased amount of MX, favoring significantly improved strength, creep resistance, and Charpy impact toughness as compared to current RAFM steels. The strength and creep resistance were comparable or approaching to the lower bound of, but impact toughness was noticeably superior to 9-20Cr oxide dispersion-strengthened ferritic alloys.

  3. Development of new generation reduced activation ferritic-martenstic steels for advanced fusion reactors

    DOE PAGESBeta

    Tan, Lizhen; Snead, Lance Lewis; Katoh, Yutai

    2016-05-26

    International development of reduced activation ferritic-martensitic (RAFM) steels has focused on 9 wt percentage Cr, which primarily contain M23C6 (M = Cr-rich) and small amounts of MX (M = Ta/V, X = C/N) precipitates, not adequate to maintain strength and creep resistance above ~500 °C. To enable applications at higher temperatures for better thermal efficiency of fusion reactors, computational alloy thermodynamics coupled with strength modeling have been employed to explore a new generation RAFM steels. The new alloys are designed to significantly increase the amount of MX nanoprecipitates, which are manufacturable through standard and scalable industrial steelmaking methods. Preliminary experimentalmore » results of the developed new alloys demonstrated noticeably increased amount of MX, favoring significantly improved strength, creep resistance, and Charpy impact toughness as compared to current RAFM steels. Furthermore, the strength and creep resistance were comparable or approaching to the lower bound of, but impact toughness was noticeably superior to 9–20Cr oxide dispersion-strengthened ferritic alloys.« less

  4. Irradiation creep of low-activation ferritic steels in FFTF/MOTA*1

    NASA Astrophysics Data System (ADS)

    Kohyama, A.; Kohno, Y.; Asakura, K.; Yoshino, M.; Namba, C.; Eiholzer, C. R.

    1994-09-01

    Irradiation creep behavior of low-activation steels, developed as structural materials for fusion reactors (JLF series steels), was investigated to obtain a fundamental understanding of these alloys under fast neutron irradiation in FFTF. (2.25-8)Cr(1-2)W bainitic steels and 12Cr-2W ferritic steels showed superior creep resistance to type-316 stainless steels under fast neutron irradiation up to 520°C. At temperatures below 460°C the creep strain increased with increasing Cr content up to 7 Cr, and further increments of Cr content up to 12% reduced the creep strain. At temperatures between 460 and 600°C, 7-8 Cr ferritic steels showed the largest creep strain. Swelling-enhanced creep, near the peak swelling temperature of 410°C, was also observed. The 9Cr-2W ferritic steel JLF-1 presented excellent properties, suggesting it as a leading candidate alloy for structural components of fusion reactors.

  5. A Micro-Alloyed Ferritic Steel Strengthened by Nanoscale Precipitates

    SciTech Connect

    Shen, Yongfeng; Wang, Chong M.; Sun, Xin

    2011-08-04

    A high strength ferritic steel with finely dispersive precipitates was investigated to reveal the fundamental strengthening mechanisms. Using energy dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM), fine carbides with an average diameter of 10 nm were observed in the ferrite matrix of the 0.08%Ti steel, and some cubic M23C6 precipitates were also observed at the grain boundaries and the interior of grains. The dual precipitate structure of finely dispersive TiC precipitates in the matrix and coarse M23C6 at grain boundaries provides combined matrix and grain boundary strengthening. The calculated amount of precipitation strengthening by the carbides was approximately 450 ~ 630 MPa, depending on the average size of nanoscale precipitates. This value is two or three times higher than that of conventional Ti-bearing high strength hot-rolled sheet steels. Dislocation densities increased from 3.42×1013 m-2 to 1.69 × 1014 m-2, espectively, with increasing tensile strain from 5.5% to 22%. The effect of the particle size, particle distribution and intrinsic particle strength have been investigated through dislocation dynamics (DD) simulations and the relationship for resolved shear stress for single crystal under this condition has been presented using simulation data. The results show that the finely dispersive precipitates can strengthen the material by pinning the dislocations up to a certain shear stress and retarding the recovery as well as annihilation of dislocations. The DD results also show that strengthening is not only a function of the density of the nano-scale precipitates but also of their size.

  6. Experimental study of the distribution of alloying elements after the formation of epitaxial ferrite upon cooling in a low-carbon steel

    SciTech Connect

    Santofimia, M.J.; Kwakernaak, C.; Sloof, W.G.; Zhao, L.; Sietsma, J.

    2010-10-15

    The distributions of carbon and substitutional elements in a low-carbon steel during the formation of epitaxial ferrite on cooling after intercritical annealing have been studied by electron probe microanalysis (EPMA). The analysis has shown that the formation of epitaxial ferrite takes place with a partial redistribution of alloying elements between the epitaxial ferrite and the austenite. This redistribution of alloying elements causes compositional gradients in the epitaxial ferrite that lead to a different etching behaviour with respect to the intercritical ferrite. Contrary to Thermo-Calc predictions, a distinct partitioning behaviour of silicon has been observed.

  7. The role of processing route on the microstructure of 14YWT nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Mazumder, B.; Parish, C. M.; Bei, H.; Miller, M. K.

    2015-10-01

    Nanostructured ferritic alloys have outstanding high temperature creep properties and enhanced tolerance to radiation damage over conventional ferritic alloys. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of α-Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of α-Fe with 50-100 μm irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embedded precipitates with the Y3Al5O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These variances can be explained by the microstructural differences and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms that retard diffusion.

  8. The role of processing route on the microstructure of 14YWT nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Mazumder, B.; Parish, C. M.; Bei, H.; Miller, M. K.

    2015-10-01

    Nanostructured ferritic alloys have outstanding high temperature creep properties and enhanced tolerance to radiation damage over conventional ferritic alloys. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of α-Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of α-Fe with 50-100 μm irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embedded precipitates with the Y3Al5O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These variances can be explained by the microstructural differences and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms that retard diffusion.

  9. Dynamical interaction of helium bubbles with cascade damage in Fe-9Cr ferritic alloy.

    SciTech Connect

    Ono, K.; Miyamoto, M.; Arakawa, K.; Birtcher, R. C.; Materials Science Division; Shimane Univ.; Osaka Univ.

    2008-12-01

    Dynamic interaction of helium bubble with cascade damage in Fe-9Cr ferritic alloy has been studied using in situ irradiation and electron microscopy. During the irradiation of the alloy by 400 keV Fe{sup +} ions at temperatures where no thermal motion takes place, induced displacement of small helium bubbles was observed: the bubbles underwent sporadic and instant displacement. The displacement was of the order of a few nanometers. The experimentally determined displacement probability of helium bubbles is consistent with the calculated probability of their dynamic interaction with sub-cascades introduced by the irradiation. Furthermore, during the irradiation of the alloy at higher temperatures, both retarded and accelerated Brownian type motions were observed. These results are discussed on the basis of dynamic interaction of helium bubbles with point defects that survive through high-energy self-ion irradiation.

  10. Ion-induced swelling of ODS ferritic alloy MA957 tubing to 500 dpa

    NASA Astrophysics Data System (ADS)

    Toloczko, M. B.; Garner, F. A.; Voyevodin, V. N.; Bryk, V. V.; Borodin, O. V.; Mel'nychenko, V. V.; Kalchenko, A. S.

    2014-10-01

    In order to study the potential swelling behavior of the ODS ferritic alloy MA957 at very high dpa levels, specimens were prepared from pressurized tubes that were unirradiated archives of tubes previously irradiated in FFTF to doses as high as 110 dpa. These unirradiated specimens were irradiated with 1.8 MeV Cr+ ions to doses ranging from 100 to 500 dpa and examined by transmission electron microscopy. No co-injection of helium or hydrogen was employed. It was shown that compared to several tempered ferritic/martensitic steels irradiated in the same facility, these tubes were rather resistant to void swelling, reaching a maximum value of only 4.5% at 500 dpa and 450 °C. In this fine-grained material, the distribution of swelling was strongly influenced by the presence of void denuded zones along the grain boundaries.

  11. Ion-induced swelling of ODS ferritic alloy MA957 tubing to 500 dpa

    SciTech Connect

    Toloczko, Mychailo B.; Garner, F. A.; Voyevodin, V.; Bryk, V. V.; Borodin, O. V.; Melnichenko, V. V.; Kalchenko, A. S.

    2014-10-01

    In order to study the potential swelling behavior of the ODS ferritic alloy MA957 at very high dpa levels, specimens were prepared from pressurized tubes that were unirradiated archives of tubes previously irradiated in FFTF to doses as high at 110 dpa. These unirradiated specimens were irradiated with 1.8 MeV Cr+ ions to doses ranging from 100 to 500 dpa and examined by transmission electron microscopy. No coinjection of helium or hydrogen was employed. It was shown that compared to several ferritic/martensitic steels irradiated in the same facility, these tubes were rather resistant to void swelling, reaching a maximum value of only 4.5% at 500 dpa and 450°C. In this fine-grained material, the distribution of swelling was strongly influenced by the presence of void denuded zones along the grain boundaries.

  12. Evaluation on Fatigue Crack Propagation of Reduced Activation Ferritic Steel (JLF-1) at High Temperature

    NASA Astrophysics Data System (ADS)

    Yoon, Han Ki; Kim, Sa Woong; Lee, Sang Pill; Katoh, Yutai; Kohyama, Akira

    Recently, reduced activation ferritic/martensitic steel, vanadium alloy and SiC/SiC composite are embossed for nuclear fusion reactor in accordance with the coolant. Especially, reduced activation ferritic/martensitic steel is very suitable material for nuclear fusion reactor, because it has low coefficient of thermal expansion and excellent heat conductivity. The objective of this study is to investigate fatigue crack propagation behavior in the Reduced Activation Ferritic Steel (JLF-1). The fatigue crack propagation behavior of the JLF-1 steel was investigated by the constant-amplitude loading test for the stress ratios R = 0.1, 0.3 and 0.5 respectively. The fatigue crack growth tests carried out at room temperature and 400°C for base metal and weld metal. The effects of stress ratio, test temperature, specimen size and TIG welding on the fatigue crack propagation behaviors for JLF-1 steel were discussed within the Paris law. Particularly, the fatigue crack propagation rate of a weld metal was similar to that of base metal at the stress ratio of 0.3. Also, the fatigue crack propagation rate of a half size specimen was similar to that of a full size specimen at the stress ratios of 0.1, 0.3 and 0.5 respectively. From this result, we can recognize that the fatigue crack propagation behavior of this material can be evaluated by using the half size specimens.

  13. System and method of forming nanostructured ferritic alloy

    DOEpatents

    Dial, Laura Cerully; DiDomizio, Richard; Alinger, Matthew Joseph; Huang, Shenyan

    2016-07-26

    A system for mechanical milling and a method of mechanical milling are disclosed. The system includes a container, a feedstock, and milling media. The container encloses a processing volume. The feedstock and the milling media are disposed in the processing volume of the container. The feedstock includes metal or alloy powder and a ceramic compound. The feedstock is mechanically milled in the processing volume using metallic milling media that includes a surface portion that has a carbon content less than about 0.4 weight percent.

  14. The development of ferritic-martensitic steels with reduced long-term activation

    NASA Astrophysics Data System (ADS)

    Ehrlich, K.; Kelzenberg, S.; Röhrig, H.-D.; Schäfer, L.; Schirra, M.

    1994-09-01

    Ferritic-martensitic 9-12% CrMoVNb steels of MANET type possess a number of advantageous properties for fusion reactor application. Their optimization has led to improved creep and fracture-toughness properties. New 9-10% CrWVTa alloys have been developed by KfK/IMF in collaboration with the SAARSTAHL GmbH which have a reduced long-term activation and show in addition superior fracture toughness properties. The calculation of dose rate and other radiological parameters with the presently available FISPACT/EAF codes, extended by KfK files for sequential reactions has shown that the long-term dose-rate in these alloys is governed by the remaining 'impurity level' of Nb and the alloying elements W and Ta. Sequential reactions — though relevant for single alloying elements like Cr, Mn, V and N — provide only a second order effect in Fe-based alloys. A challenge for the future materials development is the production of alloys with the desired narrow specification of elements and impurities, which necessitates new ways of steelmaking.

  15. Investigation of Magnetic Signatures and Microstructures for Heat-Treated Ferritic/Martensitic HT-9 Alloy

    SciTech Connect

    Henager, Charles H.; McCloy, John S.; Ramuhalli, Pradeep; Edwards, Danny J.; Hu, Shenyang Y.; Li, Yulan

    2013-05-01

    There is increased interest in improved methods for in-situ nondestructive interrogation of materials for nuclear reactors in order to ensure reactor safety and quantify material degradation (particularly embrittlement) prior to failure. Therefore, a prototypical ferritic/martensitic alloy, HT-9, of interest to the nuclear materials community was investigated to assess microstructure effects on micromagnetics measurements – Barkhausen noise emission, magnetic hysteresis measurements, and first-order reversal curve analysis – for samples with three different heat-treatments. Microstructural and physical measurements consisted of high-precision density, resonant ultrasound elastic constant determination, Vickers microhardness, grain size, and texture. These were varied in the HT-9 alloy samples and related to various magnetic signatures. In parallel, a meso-scale microstructure model was created for alpha iron and effects of polycrystallinity and demagnetization factor were explored. It was observed that Barkhausen noise emission decreased with increasing hardness and decreasing grain size (lath spacing) while coercivity increased. The results are discussed in terms of the use of magnetic signatures for nondestructive interrogation of radiation damage and other microstructural changes in ferritic/martensitic alloys.

  16. Effect of alloying on microstructure and precipitate evolution in ferritic weld metal

    NASA Astrophysics Data System (ADS)

    Narayanan, Badri Kannan

    The effect of alloying on the microstructure of ferritic weld metal produced with an self-shielded flux cored arc welding process (FCAW-S) has been studied. The welding electrode has a flux core that is intentionally alloyed with strong deoxidizers and denitriding elements such as aluminum, titanium and zirconium in addition to austenite formers such as manganese and nickel. This results in formation of microstructure consisting of carbide free bainite, retained austenite and twinned martensite. The work focuses on characterization of the microstructures and the precipitates formed during solidification and the allotropic phase transformation of the weld metal. Aluminum, manganese and nickel have significant solubility in iron while aluminum, titanium and zirconium have very strong affinity for nitrogen and oxygen. The effect of these alloying elements on the phase transformation and precipitation of oxides and nitrides have been studied with various characterization techniques. In-situ X-ray synchrotron diffraction has been used to characterize the solidification path and the effect of heating and cooling rates on microstructure evolution. Scanning Transmission Electron Microscopy (STEM) in conjunction with Energy Dispersive Spectroscopy (EDS) and Electron energy loss spectroscopy (EELS) was used to study the effect of micro-alloying additions on inclusion evolution. The formation of core-shell structure of oxide/nitride is identified as being key to improvement in toughness of the weld metal. Electron Back Scattered Diffraction (EBSD) in combination with Orientation Imaging Microscopy (OIM) and Transmission electron microscopy (TEM) has been employed to study the effect of alloying on austenite to ferrite transformation modes. The prevention of twinned martensite has been identified to be key to improving ductility for achieving high strength weld metal.

  17. Alloying Element Nitride Development in Ferritic Fe-Based Materials Upon Nitriding: A Review

    NASA Astrophysics Data System (ADS)

    Steiner, T.; Mittemeijer, E. J.

    2016-04-01

    With the aim of achieving a better understanding of the nitriding process of iron-based components (steels), as applied in engineering practice, the theoretical background and experimental observations currently available on the crystallographic, morphological, and compositional properties of the nitride precipitates in nitrided model binary and ternary, ferritic Fe-based alloys are summarily presented. Thermodynamic and kinetic considerations are employed in order to highlight their importance for the nitriding reaction and the resulting properties of the nitrided zone, thereby providing a more fundamental understanding of the nitriding process.

  18. Some microstructural characterisations in a friction stir welded oxide dispersion strengthened ferritic steel alloy

    NASA Astrophysics Data System (ADS)

    Legendre, F.; Poissonnet, S.; Bonnaillie, P.; Boulanger, L.; Forest, L.

    2009-04-01

    The goal of this study is to characterize microstructure of a friction stir welded oxide dispersion strengthened alloy. The welded material is constituted by two sheets of an yttria-dispersion-strengthened PM 2000 ferritic steel. Different areas of the friction stir welded product were analyzed using field emission gun secondary electron microscopy (FEG-SEM) and electron microprobe whereas nanoindentation was used to evaluate mechanical properties. The observed microstructural evolution, including distribution of the yttria dispersoids, after friction stir welding process is discussed and a correlation between the microstructure and the results of nanoindentation tests is established.

  19. Alloying Element Nitride Development in Ferritic Fe-Based Materials Upon Nitriding: A Review

    NASA Astrophysics Data System (ADS)

    Steiner, T.; Mittemeijer, E. J.

    2016-06-01

    With the aim of achieving a better understanding of the nitriding process of iron-based components (steels), as applied in engineering practice, the theoretical background and experimental observations currently available on the crystallographic, morphological, and compositional properties of the nitride precipitates in nitrided model binary and ternary, ferritic Fe-based alloys are summarily presented. Thermodynamic and kinetic considerations are employed in order to highlight their importance for the nitriding reaction and the resulting properties of the nitrided zone, thereby providing a more fundamental understanding of the nitriding process.

  20. Irradiation creep of various ferritic alloys irradiated at {approximately}400{degrees}C in the PFR and FFTF reactors

    SciTech Connect

    Toloczko, M.B.; Garner, F.A.; Eiholzer, C.R.

    1997-04-01

    Three ferritic alloys were irradiated in two fast reactors to doses of 50 dpa or more at temperatures near 400{degrees}C. One martensitic alloy, HT9, was irradiated in both the FFTF and PFR reactors. PFR is the Prototype Fast Reactor in Dourneay, Scotland, and FFTF is the Fast Flux Test Facility in Richland, WA. D57 is a developmental alloy that was irradiated in PFR only, and MA957 is a Y{sub 2}O{sub 3} dispersion-hardened ferritic alloy that was irradiated only in FFTF. These alloys exhibited little or no void swelling at {approximately}400{degrees}C. Depending on the alloy starting condition, these steels develop a variety of non-creep strains early in the irradiation that are associated with phase changes. Each of these alloys creeps at a rate that is significantly lower than that of austenitic steels irradiated in the same experiments. The creep compliance for ferritic alloys in general appears to be {approximately}0.5 x 10{sup {minus}6} MPa{sup {minus}1} dpa{sup {minus}1}, independent of both composition and starting state. The addition of Y{sub 2}O{sub 3} as a dispersoid does not appear to change the creep behavior.

  1. Corrosion of ferritic-martensitic steels and nickel-based alloys in supercritical water

    NASA Astrophysics Data System (ADS)

    Ren, Xiaowei

    The corrosion behavior of ferritic/martensitic (F/M) steels and Ni-based alloys in supercritical water (SCW) has been studied due to their potential applications in future nuclear reactor systems, fossil fuel power plants and waste treatment processes. 9˜12% chromium ferritic/martensitic steels exhibit good radiation resistance and stress corrosion cracking resistance. Ni-based alloys with an austenitic face-centered cubic (FCC) structure are designed to retain good mechanical strength and corrosion/oxidation resistance at elevated temperatures. Corrosion tests were carried out at three temperatures, 360°C, 500°C and 600°C, with two dissolved oxygen contents, 25 ppb and 2 ppm for up to 3000 hours. Alloys modified by grain refinement and reactive element addition were also investigated to determine their ability to improve the corrosion resistance in SCW. A duplex oxide structure was observed in the F/M steels after exposure to 25 ppb oxygen SCW, including an outer oxide layer with columnar magnetite grains and an inner oxide layer constituted of a mixture of spinel and ferrite phases in an equiaxed grain structure. An additional outermost hematite layer formed in the SCW-exposed samples when the oxygen content was increased to 2 ppm. Weight gain in the F/M steels increased with exposure temperatures and times, and followed parabolic growth kinetics in most of the samples. In Ni-based alloys after exposure to SCW, general corrosion and pitting corrosion were observed, and intergranular corrosion was found when exposed at 600°C due to formation of a local healing layer. The general oxide structure on the Ni-based alloys was characterized as NiO/Spinel/(CrxFe 1-x)2O3/(Fe,Ni). No change in oxidation mechanism was observed in crossing the critical point despite the large change in water properties. Corrosion resistance of the F/M steels was significantly improved by plasma-based yttrium surface treatment because of restrained outward diffusion of iron by the

  2. Duplex precipitates and their effects on the room-temperature fracture behaviour of a NiAl-strengthened ferritic alloy

    DOE PAGESBeta

    Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Liaw, Peter K.

    2015-03-23

    Duplex precipitates are presented in a NiAl-strengthened ferritic alloy. They were characterized by the ultra-small angle X-ray scattering and transmission electron microscope. Fine cooling precipitates with the size of several to tens of nanometres harden the matrix considerably at room temperature. Cracks are likely to initiate from precipitates, and coalesce and propagate quickly through the matrix due to the excessive hardening effect of cooling precipitates, which lead to the premature fracture of NiAl-strengthened ferritic alloys.

  3. Phase Field Modeling of Cyclic Austenite-Ferrite Transformations in Fe-C-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Zhu, Benqiang; Militzer, Matthias

    2016-08-01

    Three different approaches for considering the effect of Mn on the austenite-ferrite interface migration in an Fe-0.1C-0.5Mn alloy have been coupled with a phase field model (PFM). In the first approach (PFM-I), only long-range C diffusion is considered while Mn is assumed to be immobile during the phase transformations. Both long-range C and Mn diffusions are considered in the second approach (PFM-II). In the third approach (PFM-III), long-range C diffusion is considered in combination with the Gibbs energy dissipation due to Mn diffusion inside the interface instead of solving for long-range diffusion of Mn. The three PFM approaches are first benchmarked with isothermal austenite-to-ferrite transformation at 1058.15 K (785 °C) before considering cyclic phase transformations. It is found that PFM-II can predict the stagnant stage and growth retardation experimentally observed during cycling transformations, whereas PFM-III can only replicate the stagnant stage but not the growth retardation and PFM-I predicts neither the stagnant stage nor the growth retardation. The results of this study suggest a significant role of Mn redistribution near the interface on reducing transformation rates, which should, therefore, be considered in future simulations of austenite-ferrite transformations in steels, particularly at temperatures in the intercritical range and above.

  4. Phase Field Modeling of Cyclic Austenite-Ferrite Transformations in Fe-C-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Zhu, Benqiang; Militzer, Matthias

    2016-06-01

    Three different approaches for considering the effect of Mn on the austenite-ferrite interface migration in an Fe-0.1C-0.5Mn alloy have been coupled with a phase field model (PFM). In the first approach (PFM-I), only long-range C diffusion is considered while Mn is assumed to be immobile during the phase transformations. Both long-range C and Mn diffusions are considered in the second approach (PFM-II). In the third approach (PFM-III), long-range C diffusion is considered in combination with the Gibbs energy dissipation due to Mn diffusion inside the interface instead of solving for long-range diffusion of Mn. The three PFM approaches are first benchmarked with isothermal austenite-to-ferrite transformation at 1058.15 K (785 °C) before considering cyclic phase transformations. It is found that PFM-II can predict the stagnant stage and growth retardation experimentally observed during cycling transformations, whereas PFM-III can only replicate the stagnant stage but not the growth retardation and PFM-I predicts neither the stagnant stage nor the growth retardation. The results of this study suggest a significant role of Mn redistribution near the interface on reducing transformation rates, which should, therefore, be considered in future simulations of austenite-ferrite transformations in steels, particularly at temperatures in the intercritical range and above.

  5. Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

    SciTech Connect

    Stoica, G. M.; Stoica, A. D.; Miller, M. K.; Ma, D.

    2014-10-10

    Nanostructured ferritic alloys (NFA) are a new class of ultrafine-grained oxide dispersion-strengthened steels, promising for service in extreme environments of high temperature and high irradiation in the next-generation of nuclear reactors. This is owing to the remarkable stability of their complex microstructures containing a high density of Y-Ti-O nanoclusters within grains and along the grain boundaries. While nanoclusters have been recognized to be the primary contributor to the exceptional resistance to irradiation and high-temperature creep, very little is known about the mechanical roles of the polycrystalline grains that constitute the bulk ferritic matrix. Here we report the mesoscale characterization of anisotropic responses of the ultrafine NFA grains to tensile stresses at various temperatures using the state-of-the-art in situ neutron diffraction. We show the first experimental determination of temperature-dependent single-crystal elastic constants for the NFA, and reveal a strong temperature-dependent elastic anisotropy due to a sharp decrease in the shear stiffness constant [c'=(c_11-c_12)/2] when a critical temperature ( T_c ) is approached, indicative of elastic softening and instability of the ferritic matrix. We also show, from anisotropy-induced intergranular strain/stress accumulations, that a common dislocation slip mechanism operates at the onset of yielding for low temperatures, while there is a deformation crossover from low-temperature lattice hardening to high temperature lattice softening in response to extensive plastic deformation.

  6. Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

    DOE PAGESBeta

    Stoica, G. M.; Stoica, A. D.; Miller, M. K.; Ma, D.

    2014-10-10

    Nanostructured ferritic alloys (NFA) are a new class of ultrafine-grained oxide dispersion-strengthened steels, promising for service in extreme environments of high temperature and high irradiation in the next-generation of nuclear reactors. This is owing to the remarkable stability of their complex microstructures containing a high density of Y-Ti-O nanoclusters within grains and along the grain boundaries. While nanoclusters have been recognized to be the primary contributor to the exceptional resistance to irradiation and high-temperature creep, very little is known about the mechanical roles of the polycrystalline grains that constitute the bulk ferritic matrix. Here we report the mesoscale characterization ofmore » anisotropic responses of the ultrafine NFA grains to tensile stresses at various temperatures using the state-of-the-art in situ neutron diffraction. We show the first experimental determination of temperature-dependent single-crystal elastic constants for the NFA, and reveal a strong temperature-dependent elastic anisotropy due to a sharp decrease in the shear stiffness constant [c'=(c_11-c_12)/2] when a critical temperature ( T_c ) is approached, indicative of elastic softening and instability of the ferritic matrix. We also show, from anisotropy-induced intergranular strain/stress accumulations, that a common dislocation slip mechanism operates at the onset of yielding for low temperatures, while there is a deformation crossover from low-temperature lattice hardening to high temperature lattice softening in response to extensive plastic deformation.« less

  7. The effect of fusion-relevant helium levels on the mechanical properties of isotopically tailored ferritic alloys

    SciTech Connect

    Hankin, G.L.; Hamilton, M.L.; Gelles, D.S.

    1997-04-01

    The yield and maximum strengths of an irradiated series of isotopically tailored ferritic alloys were evaluated using the shear punch test. The composition of three of the alloys was Fe-12Cr-1.5Ni. Different balances of nickel isotopes were used in each alloy in order to produce different helium levels. A fourth alloy, which contained no nickel, was also irradiated. The addition of nickel at any isotopic balance to the Fe-12Cr base alloy significantly increased the shear yield and maximum strengths of the alloys, and as expected, the strength of the alloys decreased with increasing irradiation temperature. Helium itself, up to 75 appm over 7 dpa appears to have little effect on the mechanical properties of the alloys.

  8. TEM examination of microstructural evolution during processing of 14CrYWTi nanostructured ferritic alloys

    NASA Astrophysics Data System (ADS)

    Kishimoto, H.; Alinger, M. J.; Odette, G. R.; Yamamoto, T.

    2004-08-01

    A transmission electron microscopy (TEM) study was carried out on the co-evolution of the coarser-scale microstructural features in mechanically alloyed (MA) powders and hot isostatic press (HIP) consolidated Fe-14Cr-3W-0 and 0.4Ti-0.25Y 2O 3 nanostructured ferritic alloys (NFAs). The pancake shaped nanoscale grains in the as-MA powders are textured and elongated parallel to the particle surface. Powder annealing results in re-crystallization at 850 °C and grain growth at 1150 °C. The grains also recrystallize and may grow in the alloys HIPed at 850 °C, but appear to retain a polygonized sub-grain structure. The grains are larger and more distinct in the alloys HIPed at 1000 and 1150 °C. However, annealing resulted in bi-modal grain size distribution. Finer grains retained a significant dislocation density and populations of small precipitates with crystal structures distinct form the matrix. The grains and precipitates were much larger in alloys without Ti.

  9. Mechanical behavior of aluminum-bearing ferritic alloys for accident-tolerant fuel cladding applications

    NASA Astrophysics Data System (ADS)

    Guria, Ankan

    Nuclear power currently provides about 13% of electrical power worldwide. Nuclear reactors generating this power traditionally use Zirconium (Zr) based alloys as the fuel cladding material. Exothermic reaction of Zr with steam under accident conditions may lead to production of hydrogen with the possibility of catastrophic consequences. Following the Fukushima-Daiichi incident, the exploration of accident-tolerant fuel cladding materials accelerated. Aluminum-rich (around 5 wt. %) ferritic steels such as Fecralloy, APMT(TM) and APM(TM) are considered as potential materials for accident-tolerant fuel cladding applications. These materials create an aluminum-based oxide scale protecting the alloy at elevated temperatures. Tensile deformation behavior of the above alloys was studied at different temperatures (25-500 °C) at a strain rate of 10-3 s-1 and correlated with microstructural characteristics. Higher strength and decent ductility of APMT(TM) led to further investigation of the alloy at various combination of strain rates and temperatures followed by fractography and detailed microscopic analyses. Serrations appeared in the stress-strain curves of APMT(TM) and Fecralloy steel tested in a limited temperature range (250-400 °C). The appearance of serrations is explained on the basis of dynamic strain aging (DSA) effect due to solute-dislocation interactions. The research in this study is being performed using the funds received from the US DOE Office of Nuclear Energy's Nuclear Energy University Programs (NEUP).

  10. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Miller, M. K.; Parish, C. M.; Bei, H.

    2015-07-01

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti-Y-O-enriched nanoclusters and solute clusters, which drives the mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. The result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.

  11. The consequences of helium production on microstructural development in isotopically tailored ferritic alloys

    SciTech Connect

    Gelles, D.S.

    1996-10-01

    A series of alloys have been made adding various isotopes of nickel in order to vary the production of helium during irradiation by a two step nuclear reaction in a mixed spectrum reactor. The alloys use a base composition of Fe-12Cr with an addition of 1.5% nickel, either in the form of {sup 60}Ni which produces no helium, {sup 59}Ni which produces helium at a rate of about 10 appm He/dpa, or natural nickel ({sup Nat}Ni) which provides an intermediate level of helium due to delayed development of {sup 59}Ni. Specimens were irradiated in the HFIR at Oak Ridge, TN to {approx}7 dpa at 300 and 400{degrees}C. Microstructural examinations indicated that nickel additions promote precipitation in all alloys, but the effect appears to be much stronger at 400{degrees}C than at 300{degrees}C. There is sufficient dose by 7 dpa (and with 2 appm He) to initiate void swelling in ferritic/martensitic alloys. Little difference was found between response from {sup 59}Ni and {sup Nat}Ni. Also, helium bubble development for high helium generation conditions appeared to be very different at 300 and 400{degrees}C. At 300{degrees}C, it appeared that high densities of bubbles formed whereas at 400{degrees}C, bubbles could not be identified, possibly because of the complexity of the microstructure, but more likely because helium accumulated at precipitate interfaces.

  12. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

    SciTech Connect

    Miller, Michael K.; Parish, Chad M.; Bei, Hongbin

    2014-12-18

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti–Y–O-enriched nanoclusters and solute clusters, which drives the mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. Furthermore, the result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.

  13. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

    DOE PAGESBeta

    Miller, Michael K.; Parish, Chad M.; Bei, Hongbin

    2014-12-18

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti–Y–O-enriched nanoclusters and solute clusters, which drives themore » mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. Furthermore, the result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.« less

  14. Ferritic Alloys as Accident Tolerant Fuel Cladding Material for Light Water Reactors

    SciTech Connect

    Rebak, Raul B.

    2014-12-30

    provide hermetic seal. The replacement of a zirconium alloy using a ferritic material containing chromium and aluminum appears to be the most near term implementation for accident tolerant nuclear fuels.

  15. Effect of mechanical alloying atmosphere on the microstructure and Charpy impact properties of an ODS ferritic steel

    NASA Astrophysics Data System (ADS)

    Oksiuta, Z.; Baluc, N.

    2009-04-01

    Two types of oxide dispersion strengthened (ODS) ferritic steels, with the composition of Fe-14Cr-2W-0.3Ti-0.3Y 2O 3 (in weight percent), have been produced by mechanically alloying elemental powders of Fe, Cr, W, and Ti with Y 2O 3 particles either in argon atmosphere or in hydrogen atmosphere, degassing at various temperatures, and compacting the mechanically alloyed powders by hot isostatic pressing. It was found in particular that mechanical alloying in hydrogen yields a significant reduction in oxygen content in the materials, a lower dislocation density, and a strong improvement in the fast fracture properties of the ODS ferritic steels, as measured by Charpy impact tests.

  16. The role of processing route on the microstructure of 14YWT nanostructured ferritic alloy

    SciTech Connect

    Mazumder, B.; Parish, C. M.; Bei, H.; Miller, M. K.

    2015-06-03

    Nanostructured ferritic alloys (NFAs) have outstanding high temperature creep properties and extreme tolerance to radiation damage. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of -Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of -Fe with 50-100 m irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embedded precipitates with the Al5Y3O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These differences can be explained by the differences in the microstructure and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms retarding diffusion.

  17. The role of processing route on the microstructure of 14YWT nanostructured ferritic alloy

    DOE PAGESBeta

    Mazumder, B.; Parish, C. M.; Bei, H.; Miller, M. K.

    2015-06-03

    Nanostructured ferritic alloys (NFAs) have outstanding high temperature creep properties and extreme tolerance to radiation damage. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of -Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of -Fe with 50-100 m irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embeddedmore » precipitates with the Al5Y3O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These differences can be explained by the differences in the microstructure and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms retarding diffusion.« less

  18. Influence of solute drag on the growth of proeutectoid ferrite in Fe-C-Mn alloy

    SciTech Connect

    Enomoto, M.

    1999-10-08

    The diffusion-controlled growth of proeutectoid ferrite ({alpha}) from austenite ({gamma}) in an Fe-C-Mn alloy was simulated incorporating the possible drag effect of Mn on the migration of {alpha}:{gamma} interphase boundaries. The magnitude of drag force or the dissipation of free energy by drag was evaluated by means of Cahn and Purdy-Brechet models. The growth rate of ferrite was calculated from the flux balance equation for carbon taking into account the fact that the carbon concentration at the boundary in austenite varied with time. Whereas the time exponent of growth deviated from one-half at each moment, the overall time dependence was dictated by carbon volume diffusion in austenite. The reported differences of experimental growth rates from those calculated assuming paraequilibrium were reduced considerably by incorporating the drag of Mn, although simulation results may largely depend on the shape and depth of solute interaction potential with {alpha}:{gamma} boundaries and Mn diffusivity within the boundary, etc.

  19. Creep behavior of pack cementation aluminide coatings on Grade 91 ferritic martensitic alloy

    SciTech Connect

    Bates, Brian; Zhang, Ying; Dryepondt, Sebastien N; Pint, Bruce A

    2014-01-01

    The creep behavior of various pack cementation aluminide coatings on Grade 91 ferritic-martensitic steel was investigated at 650 C in laboratory air. The coatings were fabricated in two temperature regimes, i.e., 650 or 700 C (low temperature) and 1050 C(high temperature), and consisted of a range of Al levels and thicknesses. For comparison, uncoated specimens heat-treated at 1050 C to simulate the high temperature coating cycle also were included in the creep test. All coated specimens showed a reduction in creep resistance, with 16 51% decrease in rupture life compared to the as-received bare substrate alloy. However, the specimens heat-treated at 1050 C exhibited the lowest creep resistance among all tested samples, with a surprisingly short rupture time of < 25 h, much shorter than the specimen coated at 1050 C. Factors responsible for the reduction in creep resistance of both coated and heat-treated specimens were discussed.

  20. Fracture behavior of 9Cr nanostructured ferritic alloy with improved fracture toughness

    NASA Astrophysics Data System (ADS)

    Byun, Thak Sang; Yoon, Ji Hyun; Wee, Sung Hun; Hoelzer, David T.; Maloy, Stuart A.

    2014-06-01

    Nanostructured ferritic alloys (NFAs) have been considered as primary candidate materials for both fission and fusion reactors because of their excellent creep and irradiation resistances. It has been shown that high temperature fracture toughness could be significantly improved by appropriate thermo-mechanical treatments (TMTs). This article focuses on the static fracture behaviors of newly developed 9Cr NFAs with improved toughness. Optimal TMTs resulted in high fracture toughness at room temperature (>250 MPa √m) and in retaining higher than 100 MPa √m over a wide temperature range of 22-700 °C. Significant differences were found in fracture surfaces and fracture resistance (J-R) curves after different TMTs. Unique fracture surface features such as shallow nanoscale facets decorated with shear lips and flake-like grains were observed in high toughness specimens.

  1. Effect of tube processing methods on the texture and grain boundary characteristics of 14YWT nanostructured ferritic alloys

    DOE PAGESBeta

    Aydogan, E.; Pal, S.; Anderoglu, O.; Maloy, S. A.; Vogel, S. C.; Odette, G. R.; Lewandowski, J. J.; Hoelzer, D. T.; Anderson, I. E.; Rieken, J. R.

    2016-03-08

    In this paper, texture and microstructure of tubes and plates fabricated from a nanostructured ferritic alloy (14YWT), produced either by spray forming followed by hydrostatic extrusion (Process I) or hot extrusion and cross-rolling a plate followed by hydrostatic tube extrusion (Process II) have been characterized in terms of their effects on texture and grain boundary character. Hydrostatic extrusion results in a combination of plane strain and shear deformations which generate low intensity α- and γ-fiber components of {001}<110> and {111}<110> together with a weak ζ-fiber component of {011}<211> and {011}<011>. In contrast, multi-step plane strain deformation by hot extrusion andmore » cross-rolling of the plate leads to a strong texture component of {001}<110> together with a weaker {111}<112> component. Although the total strains are similar, shear dominated deformation leads to much lower texture indexes compared to plane strain deformations. Further, the texture intensity decreases after hydrostatic extrusion of the alloy plate formed by plane strain deformation, due to a lower number of activated slip systems during shear dominated deformation. Finally and notably, hot extruded and cross-rolled plate subjected to plane strain deformation to ~50% engineering strain creates only a modest population of low angle grain boundaries, compared to the much larger population observed following the combination of plane strain and shear deformation of ~44% engineering strain resulting from subsequent hydrostatic extrusion.« less

  2. Release of deuterium from irradiation damage in Fe-9Cr-2W ferritic alloy irradiated with deuterium ions

    NASA Astrophysics Data System (ADS)

    Ono, K.; Miyamoto, M.; Kudo, F.

    2014-09-01

    The release profile of deuterium from an Fe-9Cr-2W ferritic alloy irradiated with low-energy deuterium ions was studied by thermal desorption spectroscopy (TDS) and in situ transmission electron microscopy (TEM). It was found that one sharp TDS peak appeared at a temperature around 410 K depending on the heating rate that ranged from 1.5 to 20 K/min. The TDS peak height increased with increasing fluence from 2 × 1019 to 2 × 1021 D+/m2 with no shift of the peak temperature. A close correlation between these TDS peaks and the disappearance of dislocation loops formed by the irradiation was observed. The effects of tiny bubbles on TDS were small. These results suggest that most of the deuterium was trapped by dislocation loops, which affected the thermal stability of dislocation loops in the alloy. The dependence of TDS peak temperature on the heating rate yielded an activation energy of 0.63 ± 0.02 eV for deuterium de-trapping from dislocation loops. The retention properties of the total amount of deuterium exhibited a tendency of saturation at values on the order of 1020 D+/m2, which corresponded to a saturation tendency of the loop density.

  3. Process development for 9Cr nanostructured ferritic alloy (NFA) with high fracture toughness

    NASA Astrophysics Data System (ADS)

    Byun, Thak Sang; Yoon, Ji Hyun; Hoelzer, David T.; Lee, Yong Bok; Kang, Suk Hoon; Maloy, Stuart A.

    2014-06-01

    This article is to summarize the process development and key characterization results for the newly-developed Fe-9Cr based nanostructured ferritic alloys (NFAs) with high fracture toughness. One of the major drawbacks from pursuing ultra-high strength in the past development of NFAs is poor fracture toughness at high temperatures although a high fracture toughness is essential to prevent cracking during manufacturing and to mitigate or delay irradiation-induced embrittlement in irradiation environments. A study on fracture mechanism using the NFA 14YWT found that the low-energy grain boundary decohesion in fracture process at a high temperature (>200 °C) resulted in low fracture toughness. Lately, efforts have been devoted to explore an integrated process to enhance grain bonding. Two base materials were produced through mechanical milling and hot extrusion and designated as 9YWTV-PM1 and 9YWTV-PM2. Isothermal annealing (IA) and controlled rolling (CR) treatments in two phase region were used to enhance diffusion across the interfaces and boundaries. The PM2 alloy after CR treatments showed high fracture toughness (KJQ) at represented temperatures: 240-280 MPa √m at room temperature and 160-220 MPa √m at 500 °C, which indicates that the goal of 100 MPa √m over possible nuclear application temperature range has been well achieved. Furthermore, it is also confirmed by comparison that the CR treatments on 9YWTV-PM2 result in high fracture toughness similar to or higher than those of the conventional ferritic-martensitic steels such as HT9 and NF616.

  4. ODS Ferritic/martensitic alloys for Sodium Fast Reactor fuel pin cladding

    NASA Astrophysics Data System (ADS)

    Dubuisson, Philippe; Carlan, Yann de; Garat, Véronique; Blat, Martine

    2012-09-01

    The development of ODS materials for the cladding for Sodium Fast Reactors is a key issue to achieve the objectives required for the GEN IV reactors. CEA, AREVA and EDF have launched in 2007 an important program to determine the optimal fabrication parameters, and to measure and understand the microstructure and properties before, under and after irradiation of such cladding materials. The aim of this paper is to present the French program and the major results obtained recently at CEA on Fe-9/14/18Cr1WTiY2O3 ferritic/martensitic ODS materials. The first step of the program was to consolidate Fe-9/14/18Cr ODS materials as plates and bars to study the microstructure and the mechanical properties of the new alloys. The second step consists in producing tubes at a geometry representative of the cladding of new Sodium Fast Reactors. The optimization of the fabrication route at the laboratory scale is conducted and different tubes were produced. Their microstructure depends on the martensitic (Fe-9Cr) or ferritic (Fe-14Cr) structure. To join the plug to the tube, the reference process is the welding resistance. A specific approach is developed to model the process and support the development of the welds performed within the "SOPRANO" facility. The development at CEA of Fe-9/14/18Cr new ODS materials for the cladding for GENIV Sodium Fast Reactors is in progress. The first microstructural and mechanical characterizations are very encouraging and the full assessment and qualification of this new alloys and products will pass through the irradiation of specimens, tubes, fuel pins and subassemblies up to high doses.

  5. Low temperature embrittlement behaviour of different ferritic-martensitic alloys for fusion applications

    NASA Astrophysics Data System (ADS)

    Rieth, M.; Dafferner, B.

    1996-10-01

    In the last few years a lot of different low activation CrWVTa steels have been developed world-wide. Without irradiation some of these alloys show clearly a better low temperature embrittlement behaviour than commercial CrNiMoV(Nb) alloys. Within the MANITU project a study was carried out to compare, prior to the irradiation program, the embrittlement behaviour of different alloys in the unirradiated condition performing instrumented Charpy impact bending tests with sub-size specimens. The low activation materials (LAM) considered were different OPTIFER alloys (Forschungszentrum Karlsruhe), F82H (JAERI), 9Cr2WVTa (ORNL), and GA3X (PNL). The modified commercial 10-11% CrNiMoVNb steels were MANET and OPTIMAR. A meaningful comparison between these alloys could be drawn, since the specimens of all materials were manufactured and tested under the same conditions.

  6. Low-chromium reduced-activation ferritic steels for fusion

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.; Kenik, E.A.

    1996-04-01

    Development of reduced-activation ferritic steels has concentrated on high-chromium (8-10 wt% Cr) steels. However, there are advantages for a low-chromium steel, and initial ORNL studies on reduced-activation steels were on compositions with 2.25 to 12% Cr. Those studies showed an Fe-2.25Cr-2W-0.25V-0.1C (2 1/4Cr-2WV) steel to have the highest strenglth of the steels studied. Although this steel had the best strength, Charpy impact properties were inferior to those of an Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) and an Fe-2.25Cr-2W-0.1C (2 1/4Cr-2W) steel. Therefore, further development of the low-chromium Cr-W steels was required. These results indicate that it is possible to develop low-chromium reduced-activation ferritic steels that have tensile and impact properties as good or better than those of high-chromium (7-9% Cr) steels. Further improvement of properties should be possible by optimizing the composition.

  7. On the structure and chemistry of complex oxide nanofeatures in nanostructured ferritic alloy U14YWT

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, D.; Dickerson, P.; Odette, G. R.; Maloy, S. A.; Misra, A.; Nastasi, M. A.

    2012-06-01

    The remarkable radiation damage resistance of nanostructured ferritic alloys (NFAs) is attributed to the large numbers of matrix nanofeatures (NFs) of various types, which can enhance the recombination of displacement defects and trap transmutant helium in fine scale bubbles. Characterizing the chemistry, crystallographic structure and orientation relationships of the NFs is critical to understanding how they enhance the radiation damage resistance of NFAs. Conventional and high-resolution transmission electron microscopy and energy-dispersive spectroscopy were used to characterize the various types of NF and larger oxide phases in a model 14Cr-3 W-0.4Ti-0.25Y2O3 NFA (14YWT) hot isostatic pressed (HIP-ed) at 1150°C. Large CrTiO3 precipitates (50-300 nm) and small diffracting NFs (<5 nm) were found in this alloy. One major new result is the observation of an additional type of nanofeature (10-50 nm), orthorhombic in structure, with a square center cross-section, which constitutes a new kind of Y-Ti-oxide phase with lattice parameters different from those of known Y and Ti complex oxides. The interfaces of these particles seem to be semicoherent, while manifesting a possible orientation relationship with the BCC matrix. The ratio of Y to Ti varies between <1 and 2 for these larger NFs.

  8. Influence of displacement damage on deuterium and helium retention in austenitic and ferritic-martensitic alloys considered for ADS service

    NASA Astrophysics Data System (ADS)

    Voyevodin, V. N.; Karpov, S. A.; Kopanets, I. E.; Ruzhytskyi, V. V.; Tolstolutskaya, G. D.; Garner, F. A.

    2016-01-01

    The behavior of ion-implanted hydrogen (deuterium) and helium in austenitic 18Cr10NiTi stainless steel, EI-852 ferritic steel and ferritic/martensitic steel EP-450 and their interaction with displacement damage were investigated. Energetic argon irradiation was used to produce displacement damage and bubble formation to simulate nuclear power environments. The influence of damage morphology and the features of radiation-induced defects on deuterium and helium trapping in structural alloys was studied using ion implantation, the nuclear reaction D(3He,p)4He, thermal desorption spectrometry and transmission electron microscopy. It was found in the case of helium irradiation that various kinds of helium-radiation defect complexes are formed in the implanted layer that lead to a more complicated spectra of thermal desorption. Additional small changes in the helium spectra after irradiation with argon ions to a dose of ≤25 dpa show that the binding energy of helium with these traps is weakly dependent on the displacement damage. It was established that retention of deuterium in ferritic and ferritic-martensitic alloys is three times less than in austenitic steel at damage of ˜1 dpa. The retention of deuterium in steels is strongly enhanced by presence of radiation damages created by argon ion irradiation, with a shift in the hydrogen release temperature interval of 200 K to higher temperature. At elevated temperatures of irradiation the efficiency of deuterium trapping is reduced by two orders of magnitude.

  9. Effects of Partial Phase Transformation on Characteristics of 9Cr Nanostructured Ferritic Alloy

    SciTech Connect

    Ji Hyun, Yoon; Byun, Thak Sang; Hoelzer, David T

    2014-01-01

    The core structures of future nuclear systems require tolerance to extreme irradiation, and some critical components, for example, the fuel cladding in Sodium-cooled Fast Reactors (SFRs), have to maintain mechanical integrity to very high doses of 200 -400 dpa at high temperatures up to 700 degrees C. The high Cr nanostructured ferritic alloys (NFAs) are under intense research worldwide as a candidate core material. Although the NFAs have some admirable characteristics for high-temperature applications, their crack sensitivity is very high at high temperatures. The fracture toughness of high strength NFAs is unacceptably low above 300 degrees C. The objective of this study is to develop processes and microstructures with improved high temperature fracture toughness and ductility. To optimize the afterextrusion heat treatment condition, both the computational simulation technique on phase equilibrium and the basic microstructural and mechanical characterization have been carried out. 9 Cr-NFA was produced by the mechanical alloying of pre-alloyed Fe-9Cr base metallic powder and yttria particles, and subsequent extrusion. The post-extrusion heat-treatments of various conditions were applied to the asextruded NFA. The tensile and fracture toughness tests were conducted for as-extruded and heat-treated samples at up to 700 degrees C. Fracture toughness of the NFA has increased by more than 40% at every testing temperature after heat-treatment in the inter-critical temperature range. The increment of fracture toughness of the NFA after post-extrusion heat-treatment is attributed to the increased strength at below 500 degrees C, and an increased ductility at 700 degrees C.

  10. Evaluation of Microstructure and Mechanical Properties of Nano-Y2O3-Dispersed Ferritic Alloy Synthesized by Mechanical Alloying and Consolidated by High-Pressure Sintering

    NASA Astrophysics Data System (ADS)

    Karak, Swapan Kumar; Dutta Majumdar, J.; Witczak, Zbigniew; Lojkowski, Witold; Ciupiński, Łukasz; Kurzydłowski, K. J.; Manna, Indranil

    2013-06-01

    In this study, an attempt has been made to synthesize 1.0 wt pct nano-Y2O3-dispersed ferritic alloys with nominal compositions: 83.0 Fe-13.5 Cr-2.0 Al-0.5 Ti (alloy A), 79.0 Fe-17.5 Cr-2.0 Al-0.5 Ti (alloy B), 75.0 Fe-21.5 Cr-2.0 Al-0.5 Ti (alloy C), and 71.0 Fe-25.5 Cr-2.0 Al-0.5 Ti (alloy D) steels (all in wt pct) by solid-state mechanical alloying route and consolidation the milled powder by high-pressure sintering at 873 K, 1073 K, and 1273 K (600°C, 800°C, and 1000°C) using 8 GPa uniaxial pressure for 3 minutes. Subsequently, an extensive effort has been undertaken to characterize the microstructural and phase evolution by X-ray diffraction, scanning and transmission electron microscopy, and energy dispersive spectroscopy. Mechanical properties including hardness, compressive strength, Young's modulus, and fracture toughness were determined using micro/nano-indentation unit and universal testing machine. The present ferritic alloys record extraordinary levels of compressive strength (from 1150 to 2550 MPa), Young's modulus (from 200 to 240 GPa), indentation fracture toughness (from 3.6 to 15.4 MPa√m), and hardness (from13.5 to 18.5 GPa) and measure up to 1.5 through 2 times greater strength but with a lower density (~7.4 Mg/m3) than other oxide dispersion-strengthened ferritic steels (<1200 MPa) or tungsten-based alloys (<2200 MPa). Besides superior mechanical strength, the novelty of these alloys lies in the unique microstructure comprising uniform distribution of either nanometric (~10 nm) oxide (Y2Ti2O7/Y2TiO5 or un-reacted Y2O3) or intermetallic (Fe11TiY and Al9.22Cr2.78Y) particles' ferritic matrix useful for grain boundary pinning and creep resistance.

  11. Tensile and fracture toughness properties of the nanostructured oxide dispersion strengthened ferritic alloy 13Cr-1W-0.3Ti-0.3Y 2O 3

    NASA Astrophysics Data System (ADS)

    Eiselt, Ch. Ch.; Klimenkov, M.; Lindau, R.; Möslang, A.; Odette, G. R.; Yamamoto, T.; Gragg, D.

    2011-10-01

    The realization of fusion power as an attractive energy source requires advanced structural materials that can cope with ultra-severe thermo-mechanical loads and high neutron fluxes experienced by fusion power plant components, such as the first wall, divertor and blanket structures. Towards this end, two variants of a 13Cr-1W-0.3Ti-0.3Y 2O 3 reduced activation ferritic (RAF-) ODS steel were produced by ball milling phase blended Fe-13Cr-1W, 0.3Y 20 3 and 0.3Ti powders in both argon and hydrogen atmospheres. The milled powders were consolidated by hot isostatic pressing (HIP). The as-HIPed alloys were then hot rolled into 6 mm plates. Microstructural, tensile and fracture toughness characterization of the hot rolled alloys are summarized here and compared to results previously reported for the as-HIPed condition.

  12. R&D of low activation ferritic steels for fusion in japanese universities*1

    NASA Astrophysics Data System (ADS)

    Kohyama, Akira; Kohno, Yutaka; Asakura, Kentaro; Kayano, Hideo

    1994-09-01

    Following the brief review of the R&D of low activation ferritic steels in Japanese universities, the status of 9Cr-2W type ferritic steels development is presented. The main emphasis is on mechanical property changes by fast neutron irradiation in FFTF. Bend test, tensile test, CVN test and in-reactor creep results are provided including some data about low activation ferritic steels with Cr variation from 2.25 to 12%. The 9Cr-2W ferritic steel, denoted as JLF-1, showed excellent mechanical properties under fast neutron irradiation as high as 60 dpa. As potential materials for DEMO and beyond, innovative oxide dispersion strengthened (ODS) quasi-amorphous low activation ferritic steels are introduced. The baseline properties, microstructural evolution under ion irradiation and the recent progress of new processes are provided.

  13. Effect of friction stir welding and post-weld heat treatment on a nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Mazumder, B.; Yu, X.; Edmondson, P. D.; Parish, C. M.; Miller, M. K.; Meyer, H. M.; Feng, Z.

    2016-02-01

    Nanostructured ferritic alloys (NFAs) are new generation materials for use in high temperature energy systems, such as nuclear fission or fusion reactors. However, joining these materials is a concern, as their unique microstructure is destroyed by traditional liquid-state welding methods. The microstructural evolution of a friction stir welded 14YWT NFA was investigated by atom probe tomography, before and after a post-weld heat treatment (PWHT) at 1123K. The particle size, number density, elemental composition, and morphology of the titanium-yttrium-oxygen-enriched nanoclusters (NCs) in the stir and thermally-affected zones were studied and compared with the base metal. No statistical difference in the size of the NCs was observed in any of these conditions. After the PWHT, increases in the number density and the oxygen enrichment in the NCs were observed. Therefore, these new results provide additional supporting evidence that friction stir welding appears to be a viable joining technique for NFAs, as the microstructural parameters of the NCs are not strongly affected, in contrast to traditional welding techniques.

  14. Effect of friction stir welding and post-weld heat treatment on a nanostructured ferritic alloy

    DOE PAGESBeta

    Mazumder, Baishakhi; Yu, Xinghua; Edmondson, Philip D.; Parish, Chad M.; Miller, Michael K; Meyer, H. M.; Feng, Zhili

    2015-12-08

    Nanostructured ferritic alloys (NFAs) are new generation materials for use in high temperature energy systems, such as nuclear fission or fusion reactors. However, joining these materials is a concern, as their unique microstructure is destroyed by traditional liquid-state welding methods. The microstructural evolution of a friction stir welded 14YWT NFA was investigated by atom probe tomography, before and after a post-weld heat treatment (PWHT) at 1123K. The particle size, number density, elemental composition, and morphology of the titanium-yttrium-oxygenenriched nanoclusters (NCs) in the stir and thermally-affected zones were studied and compared with the base metal. No statistical difference in the sizemore » of the NCs was observed in any of these conditions. After the PWHT, increases in the number density and the oxygen enrichment in the NCs were observed. Therefore, these new results provide additional supporting evidence that friction stir welding appears to be a viable joining technique for NFAs, as the microstructural parameters of the NCs are not strongly affected, in contrast to traditional welding techniques.« less

  15. Effect of friction stir welding and post-weld heat treatment on a nanostructured ferritic alloy

    SciTech Connect

    Mazumder, Baishakhi; Yu, Xinghua; Edmondson, Philip D.; Parish, Chad M.; Miller, Michael K; Meyer, H. M.; Feng, Zhili

    2015-12-08

    Nanostructured ferritic alloys (NFAs) are new generation materials for use in high temperature energy systems, such as nuclear fission or fusion reactors. However, joining these materials is a concern, as their unique microstructure is destroyed by traditional liquid-state welding methods. The microstructural evolution of a friction stir welded 14YWT NFA was investigated by atom probe tomography, before and after a post-weld heat treatment (PWHT) at 1123K. The particle size, number density, elemental composition, and morphology of the titanium-yttrium-oxygenenriched nanoclusters (NCs) in the stir and thermally-affected zones were studied and compared with the base metal. No statistical difference in the size of the NCs was observed in any of these conditions. After the PWHT, increases in the number density and the oxygen enrichment in the NCs were observed. Therefore, these new results provide additional supporting evidence that friction stir welding appears to be a viable joining technique for NFAs, as the microstructural parameters of the NCs are not strongly affected, in contrast to traditional welding techniques.

  16. Response of nanostructured ferritic alloys to high-dose heavy ion irradiation

    SciTech Connect

    Parish, Chad M.; White, Ryan M.; LeBeau, James M.; Miller, Michael K.

    2014-02-01

    A latest-generation aberration-corrected scanning/transmission electron microscope (STEM) is used to study heavy-ion-irradiated nanostructured ferritic alloys (NFAs). Results are presented for STEM X-ray mapping of NFA 14YWT irradiated with 10 MeV Pt to 16 or 160 dpa at -100°C and 750°C, as well as pre-irradiation reference material. Irradiation at -100°C results in ballistic destruction of the beneficial microstructural features present in the pre-irradiated reference material, such as Ti-Y-O nanoclusters (NCs) and grain boundary (GB) segregation. Irradiation at 750°C retains these beneficial features, but indicates some coarsening of the NCs, diffusion of Al to the NCs, and a reduction of the Cr-W GB segregation (or solute excess) content. Ion irradiation combined with the latest-generation STEM hardware allows for rapid screening of fusion candidate materials and improved understanding of irradiation-induced microstructural changes in NFAs.

  17. Development of rapidly quenched brazing foils to join tungsten alloys with ferritic steel

    NASA Astrophysics Data System (ADS)

    Kalin, B. A.; Fedotov, V. T.; Sevrjukov, O. N.; Moeslang, A.; Rohde, M.

    2004-08-01

    Results on rapidly solidified filler metals for tungsten brazing are presented. A rapidly quenched foil-type filler metal based on Ni bal-15Cr-4Mo-4Fe-(0.5-1.0)V-7.5Si-1.5B was developed to braze tungsten to ferritic/martensitic Crl3Mo2NbVB steel (FS) for helium gas cooled divertors and plasma facing components. Polycrystalline W-2CeO 2 and monocrystalline pure tungsten were brazed to the steel under vacuum at 1150 °C, using a 0.5 mm thick foil spacer made of a 50Fe-50Ni alloy. As a result of thermocycling tests (100 cycles between 700 °C/20 min and air-water cooling/3-5 min) on brazed joints, tungsten powder metallurgically processed W-2CeO 2 failed due to residual stresses, whereas the brazed joint with zone-melted monocrystalline tungsten withstood the thermocycling tests.

  18. An empirical approach to strain to fracture of two-ductile-phase alloys. [Ti-Mn alloys and ferrite-martensite steels

    SciTech Connect

    Fan, Z.; Miodownik, A.P. )

    1993-04-15

    Two-ductile-phase alloys refer to the alloys comprising two phases which are plastically deformable under applied stress, for example, [alpha]-[beta] brasses, [alpha]-[beta] Ti-alloys and dual-phase steels. As a group, two-ductile-phase alloys offer an excellent combination of high strength, good ductility and promising fracture toughness. In this paper, the authors present an empirical approach to the strain to fracture of two-ductile-phase alloys, based on the microstructural characterization method developed by Fan et al. The proposed approach can predict the strain to fracture of two-ductile-phase alloys in terms of the strains to fracture of the constituent phases and the microstructural parameters, such as volume fraction, contiguity and grain size of each constituent phase. The predictions by the present approach will be compared with the experimental results in [alpha]-[beta] Ti-Mn alloys and ferrite-martensite dual-phase steels drawn from the literature. In addition, the effect of relative grain size (the grain size ratio) on the strain to fracture of two-ductile-phase alloys will be discussed.

  19. Stability of the strengthening nanoprecipitates in reduced activation ferritic steels under Fe2+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Tan, L.; Katoh, Y.; Snead, L. L.

    2014-02-01

    The stability of MX-type precipitates is critical to retain mechanical properties of both reduced activation ferritic-martensitic (RAFM) and conventional FM steels at elevated temperatures. Radiation resistance of TaC, TaN, and VN nanoprecipitates irradiated up to ∼49 dpa at 500 °C using Fe2+ is investigated in this work. Transmission electron microscopy (TEM) utilized in standard and scanning mode (STEM) reveals the non-stoichiometric nature of the nanoprecipitates. Irradiation did not alter their crystalline nature. The radiation resistance of these precipitates, in an order of reduced resistance, is TaC, VN, and TaN. Particle dissolution, growth, and reprecipitation were the modes of irradiation-induced instability. Irradiation also facilitated formation of Fe2W type Laves phase limited to the VN and TaN bearing alloys. This result suggests that nitrogen level should be controlled to a minimal level in alloys to gain greater radiation resistance of the MX-type precipitates at similar temperatures as well as postpone the formation and subsequent coarsening of Laves phase.

  20. A review of advantages of high-efficiency X-ray spectrum imaging for analysis of nanostructured ferritic alloys

    SciTech Connect

    Parish, Chad M.; Miller, Michael K.

    2014-12-09

    Nanostructured ferritic alloys (NFAs) exhibit complex microstructures consisting of 100-500 nm ferrite grains, grain boundary solute enrichment, and multiple populations of precipitates and nanoclusters (NCs). Understanding these materials' excellent creep and radiation-tolerance properties requires a combination of multiple atomic-scale experimental techniques. Recent advances in scanning transmission electron microscopy (STEM) hardware and data analysis methods have the potential to revolutionize nanometer to micrometer scale materials analysis. The application of these methods is applied to NFAs as a test case and is compared to both conventional STEM methods as well as complementary methods such as scanning electron microscopy and atom probe tomography. In this paper, we review past results and present new results illustrating the effectiveness of latest-generation STEM instrumentation and data analysis.

  1. A review of advantages of high-efficiency X-ray spectrum imaging for analysis of nanostructured ferritic alloys

    DOE PAGESBeta

    Parish, Chad M.; Miller, Michael K.

    2014-12-09

    Nanostructured ferritic alloys (NFAs) exhibit complex microstructures consisting of 100-500 nm ferrite grains, grain boundary solute enrichment, and multiple populations of precipitates and nanoclusters (NCs). Understanding these materials' excellent creep and radiation-tolerance properties requires a combination of multiple atomic-scale experimental techniques. Recent advances in scanning transmission electron microscopy (STEM) hardware and data analysis methods have the potential to revolutionize nanometer to micrometer scale materials analysis. The application of these methods is applied to NFAs as a test case and is compared to both conventional STEM methods as well as complementary methods such as scanning electron microscopy and atom probe tomography.more » In this paper, we review past results and present new results illustrating the effectiveness of latest-generation STEM instrumentation and data analysis.« less

  2. A review of advantages of high-efficiency X-ray spectrum imaging for analysis of nanostructured ferritic alloys

    NASA Astrophysics Data System (ADS)

    Parish, Chad M.; Miller, Michael K.

    2015-07-01

    Nanostructured ferritic alloys (NFAs) exhibit complex microstructures consisting of 100-500 nm ferrite grains, grain boundary solute enrichment, and multiple populations of precipitates and nanoclusters (NCs). Understanding these materials' excellent creep and radiation-tolerance properties requires a combination of multiple atomic-scale experimental techniques. Recent advances in scanning transmission electron microscopy (STEM) hardware and data analysis methods have the potential to revolutionize nanometer-to micrometer-scale materials analysis. Modern high-brightness, high-X-ray collection STEM instruments are capable of enabling advanced experiments, such as simultaneous energy dispersive X-ray spectroscopy and electron energy loss spectroscopy spectrum imaging at nm to sub-nm resolution, that are now well-established for the study of nuclear materials. In this paper, we review past results and present new results illustrating the effectiveness of latest-generation STEM instrumentation and data analysis.

  3. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-07-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1-x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1-x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1-x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1-x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  4. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-09-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1- x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1- x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1- x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1- x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  5. Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

    SciTech Connect

    Rieken, Joel

    2011-12-13

    Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O2) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand the kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from

  6. Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

    NASA Astrophysics Data System (ADS)

    Rieken, Joel Rodney

    Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O2) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand the kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from different

  7. The ferrite and austenite lattice parameters of Fe-Co and Fe-Cu binary alloys as a function of temperature

    SciTech Connect

    Velthuis, S.G.E. te; Sietsma, J.; Rekveldt, M.T.; Zwaag, S. van der; Root, J.H.

    1998-09-18

    The lattice parameters of Fe-15 Cu, Fe-2% Cu, Fe-1% Co, and Fe-2% Co binary alloys were determined by means of neutron diffraction at temperatures around the austenite-ferrite phase transformation (860--1350 K). While the thermal expansion coefficients prove to be similar to those of Fe for all alloys, Cu and Co have an opposite effect on the lattice parameter of Fe. Addition of Cu increases the lattice parameter in both ferrite ({alpha}) and austenite ({gamma}), while Co decreases the lattice parameter. For all alloys, the {alpha} {leftrightarrow} {gamma} phase transformation introduces a volume change of 1.0%. Evidence is found that both ferrite and austenite are slightly strained ({epsilon} < 8 {times} 10{sup {minus}4}) when both phases are present simultaneously.

  8. Fabrication of silver-coated cobalt ferrite nanocomposite and the study of its antibacterial activity

    NASA Astrophysics Data System (ADS)

    Kooti, M.; Saiahi, S.; Motamedi, H.

    2013-05-01

    A new silver coated cobalt ferrite nanocomposite, Ag@CoFe2O4, was prepared by a two-step procedure. In the first step, cobalt ferrite nanoparticles were synthesized by a combustion method using glycine as a fuel. This ferrite was then coated with nanosilver via chemical reduction of Ag+ solution. The as-synthesized Ag@CoFe2O4 was characterized by X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer. The antibacterial activity of this composite was investigated against some Gram-positive and Gram-negative bacteria and compared with those of silver nanoparticles and some standard antibacterial drugs.

  9. The Kinetics of Dislocation Loop Formation in Ferritic Alloys Through the Aggregation of Irradiation Induced Defects

    NASA Astrophysics Data System (ADS)

    Kohnert, Aaron Anthony

    The mechanical properties of materials are often degraded over time by exposure to irradiation environments, a phenomenon that has hindered the development of multiple nuclear reactor design concepts. Such property changes are the result of microstructural changes induced by the collision of high energy particles with the atoms in a material. The lattice defects generated in these recoil events migrate and interact to form extended damage structures. This study has used theoretical models based on the mean field chemical reaction rate theory to analyze the aggregation of isolated lattice defects into larger microstructural features that are responsible for long term property changes, focusing on the development of black dot damage in ferritic iron based alloys. The purpose of such endeavors is two-fold. Primarily, such models explain and quantify the processes through which these microstructures form. Additionally, models provide insight into the behavior and properties of the point defects and defect clusters which drive general microstructural evolution processes. The modeling effort presented in this work has focused on physical fidelity, drawing from a variety of sources of information to characterize the unobservable defect generation and agglomeration processes that give rise to the observable features reported in experimental data. As such, the models are based not solely on isolated point defect creation, as is the case with many older rate theory approaches, but instead on realistic estimates of the defect cluster population produced in high energy cascade damage events. Experimental assessments of the microstructural changes evident in transmission electron microscopy studies provide a means to measure the efficacy of the kinetic models. Using common assumptions of the mobility of defect clusters generated in cascade damage conditions, an unphysically high density of damage features develops at the temperatures of interest with a temperature dependence

  10. Tritium retention in reduced-activation ferritic/martensitic steels

    SciTech Connect

    Hatano, Y.; Abe, S.; Matsuyama, M.; Alimov, V.K.; Spitsyn, A.V.; Bobyr, N.P.; Cherkez, D.I.; Khripunov, B.I.; Golubeva, A.V.; Ogorodnikova, O.V.; Klimov, N.S.; Chernov, V.M.; Oyaidzu, M.; Yamanishi, T.

    2015-03-15

    Reduced-activation ferritic/martensitic (RAFM) steels are structural material candidates for breeding blankets of future fusion reactors. Therefore, tritium (T) retention in RAFM steels is an important problem in assessing the T inventory of blankets. In this study, specimens of RAFM steels were subjected to irradiation of 20 MeV W ions to 0.54 displacements per atom (dpa), exposure to high flux D plasmas at 400 and 600 K and that to pulsed heat loads. The specimens thus prepared were exposed to DT gas at 473 K. Despite severe modification in the surface morphology, heat loads had negligible effects on T retention. Significant increase in T retention at the surface and/or subsurface was observed after D plasma exposure. However, T trapped at the surface/subsurface layer was easily removed by maintaining the specimens in the air at about 300 K. Displacement damage led to increase in T retention in the bulk due to the trapping effects of defects, and T trapped was stable at 300 K. It was therefore concluded that displacement damages had the largest influence on T retention under the present conditions.

  11. EBSD as a tool to identify and quantify bainite and ferrite in low-alloyed Al-TRIP steels.

    PubMed

    Zaefferer, S; Romano, P; Friedel, F

    2008-06-01

    Bainite is thought to play an important role for the chemical and mechanical stabilization of metastable austenite in low-alloyed TRIP steels. Therefore, in order to understand and improve the material properties, it is important to locate and quantify the bainitic phase. To this aim, electron backscatter diffraction-based orientation microscopy has been employed. The main difficulty herewith is to distinguish bainitic ferrite from ferrite because both have bcc crystal structure. The most important difference between them is the occurrence of transformation induced geometrically necessary dislocations in the bainitic phase. To determine the areas with larger geometrically necessary dislocation density, the following orientation microscopy maps were explored: pattern quality maps, grain reference orientation deviation maps and kernel average misorientation maps. We show that only the latter allow a reliable separation of the bainitic and ferritic phase. The kernel average misorientation threshold value that separates both constituents is determined by an algorithm that searches for the smoothness of the boundaries between them. PMID:18503676

  12. Simulation of Ferrite Formation in Fe-C Alloys Based on a Three-Dimensional Mixed-Mode Transformation Model

    NASA Astrophysics Data System (ADS)

    van Bohemen, S. M. C.; Bos, C.; Sietsma, J.

    2011-09-01

    A three-dimensional mixed-mode (MM) transformation model accounting for both soft impingement and hard impingement was developed that calculates the growth kinetics of ferrite grains in an austenite matrix. The simulations are compared to the kinetics of ferrite formation in high-purity Fe-C alloys for which phase-transformation kinetics were measured isothermally by dilatometry at several temperatures in the range of 973 K to 1043 K (700 °C to 770 °C). The interface mobility is obtained from the best fit of the data at 1023 K (750 °C) for which the nucleus density N is estimated from the final microstructure. Subsequently, the experimental ferrite kinetics in Fe-0.36C at the other temperatures are simulated. The values of N extracted from the fits can be described with a nucleation model. The significance of the MM calculations is rationalized by comparing the results for Fe-0.17C with simulations assuming purely diffusion-controlled (DC) and purely interface-controlled (IC) growth. Comparison of simulated fraction curves for Fe-0.57C with the three models demonstrates that the transformation in high-carbon steels is essentially DC.

  13. Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales

    SciTech Connect

    Sun, Zhiqian; Song, Gian; Sisneros, Thomas A.; Clausen, Bjorn; Pu, Chao; Li, Lin; Gao, Yanfei; Liaw, Peter K

    2016-01-01

    An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix and elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. The study contributes to further understanding of load-partitioning characteristics in multiphase materials.

  14. Growth kinetics of grain boundary allotriomorphs of proeutectoid ferrite in Fe-C-Mn-X{sub 2} alloys

    SciTech Connect

    Tanaka, T.; Aaronson, H.I.; Enomoto, M.

    1995-03-01

    The parabolic rate constant for the thickening of grain boundary ferrite allotriomorphs at the faces of austenite grain boundaries was measured as a function of isothermal transformation temperature in three Fe-C-X{sub 1}-X{sub 2} alloys where X{sub 1} is Mn and X{sub 2} is successively Si, Ni, and Co. The results were compared with the predictions of the local equilibrium model for multi-component systems and with those derived from the theory of growth under paraequilibrium conditions. The distribution of Mn and Si in ferrite and austenite in the Fe-C-Mn-Si alloy was also measured as a function of reaction temperature with transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The observed temperature below which alloying element partition ceased was in good agreement with the local equilibrium model. Whereas the parabolic rate constant for thickening was considerably larger than the amount predicted by this theory in the alloying element diffusion-controlled regime, the opposite was true in the carbon diffusion-controlled regime. Similarly, the calculated paraequilibrium constant was usually considerably larger than that measured experimentally. Synergistic enhancements of the effects of Mn and X{sub 2} in diminishing thickening kinetics were observed for each X{sub 2}. The time-temperature-transformation (TTT) curves for the beginning of transformation were calculated from a modified Cahn analysis for the overall kinetics of grain-boundary-nucleated reactions using values of the nucleation rate and the parabolic growth rate constant computed from various models and compared with experimentally determined TTT curves.

  15. Effect of austenitizing conditions on the impact properties of an alloyed austempered ductile iron of initially ferritic matrix structure

    SciTech Connect

    Delia, M.; Alaalam, M.; Grech, M.

    1998-04-01

    The effect of austenitizing conditions on the microstructure and impact properties of an austempered ductile iron (ADI) containing 1.6% Cu and 1.6% Ni as the main alloying elements was investigated. Impact tests were carried out on samples of initially ferritic matrix structure and which had been first austenitized at 850, 900, 950, and 1,000 C for 15 to 360 min and austempered at 360 C for 180 min. Results showed that the austenitizing temperature, T{sub {gamma}}, and time, t{sub {gamma}} have a significant effect on the impact properties of the alloy. This has been attributed to the influence of these variables on the carbon kinetics. Microstructures of samples austenitized at 950 and 1,000 C contain no pro-eutectoid ferrite. The impact properties of the former structures are independent of t{sub {gamma}}, while those solution treated at 1,000 C are generally low and show wide variation over the range of soaking time investigated. For fully ausferritic structures, impact properties fall with an increase in T{sub {gamma}}. This is particularly evident at 1,000 C. As the T{sub {gamma}} increases, the amount of carbon dissolved in the original austenite increases. This slows down the rate of austenite transformation and results in coarser structures with lower mechanical properties. Optimum impact properties are obtained following austenitizing between 900 and 950 C for 120 to 180 min.

  16. Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

    DOE PAGESBeta

    Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Ghosh, Gautam; Liaw, Peter K.

    2015-11-05

    Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution bodycentered- cubic iron for high-temperature application in fossil-energy power plants. In this study, the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy was investigated at 700 - 950°C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent to differences in the matrix/precipitate compositions. The results profile the ripening process in multicomponent alloys bymore » illustrating controlling factors (i.e., interfacial energy, diffusivities, and element partitioning). As a result, the study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service.« less

  17. Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

    PubMed Central

    Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Ghosh, Gautam; Liaw, Peter K.

    2015-01-01

    Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution body-centered-cubic iron for high-temperature application in fossil-energy power plants. In this study, we investigate the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy at 700–950 °C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent on differences in the matrix/precipitate compositions. Our results profile the ripening process in multicomponent alloys by illustrating controlling factors of interfacial energy, diffusivities, and element partitioning. The study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service. PMID:26537060

  18. Dispersoid Distribution and Microstructure in Fe-Cr-Al Ferritic Oxide Dispersion-Strengthened Alloy Prepared by Friction Consolidation

    SciTech Connect

    Catalini, David; Kaoumi, Djamel; Reynolds, Anthony; Grant, Glenn J.

    2015-07-09

    INCOLOY® MA956 is a ferritic Oxide Dispersion Strengthened (ODS) alloy. Three different oxides, Y4Al2O9, YAlO3 and Y3Al5O12, have been observed in this alloy. The oxide particle sizes range from just a few up to hundreds of nm and these particles are responsible of the high temperature mechanical strength of this alloy. Mechanically alloyed MA956 powder was consolidated via Friction Consolidation using three different processing conditions. As a result, three small compacts of low porosity were produced. The compacts exhibited a refined equiaxed grain structure with grain sizes smaller than 10 µm and the desired oxide dispersion.YAlO3 and Y3Al5O12 were identified in the compacts by Scanning Electron Microscopy (SEM), Electron Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD). The size distribution of precipitates above 50 nm showed a direct proportionality between average precipitate size and grain size. The total energy input during processing was correlated with the relative amount of each of the oxides in the disks: the higher the total processing energy input, the higher the relative amount of Y3Al5O12 precipitates. The elemental composition of the oxide precipitates was also probed individually by EDS showing an aluminum enrichment trend as precipitates grow in size.

  19. Nucleation kinetics of grain boundary allotriomorphs of proeutectoid ferrite in Fe-C-Mn-X{sub 2} alloys

    SciTech Connect

    Tanaka, T.; Aaronson, H.I.; Enomoto, M.

    1995-03-01

    The steady-state nucleation rates of ferrite allotriomorphs at the ``faces`` of austenite grain boundaries were measured in Fe-C-X{sub 1}-X{sub 2} alloys, where X{sub 1} was Mn and X{sub 2} was successively Si, Ni, and Co, using techniques previously developed for counterpart studies on Fe-C and Fe-C-X alloys. The results were compared with the predictions of the classical nucleation theory, using the pillbox-shaped critical nucleus model. The volume free energy changes associated with nucleation in Fe-C-X{sub 1}-X{sub 2} quaternary systems were evaluated from the central atoms model (CAM) for both para- and orthoequilibrium modes of transformation. The nucleation process was assumed to be controlled by volume and/or grain boundary diffusion of alloying elements. The so-called synergistic effects of alloying elements were considered in terms of the volume free energy change and interfacial energies on the basis of the result of the nucleation rate measurements.

  20. Nano-sized precipitate stability and its controlling factors in a NiAl-strengthened ferritic alloy

    SciTech Connect

    Sun, Zhiqian; Song, Gian; Ilavsky, Jan; Ghosh, Gautam; Liaw, Peter K.

    2015-11-05

    Coherent B2-ordered NiAl-type precipitates have been used to reinforce solid-solution bodycentered- cubic iron for high-temperature application in fossil-energy power plants. In this study, the stability of nano-sized precipitates in a NiAl-strengthened ferritic alloy was investigated at 700 - 950°C using ultra-small angle X-ray scattering and electron microscopies. Here we show that the coarsening kinetics of NiAl-type precipitates is in excellent agreement with the ripening model in multicomponent alloys. We further demonstrate that the interfacial energy between the matrix and NiAl-type precipitates is strongly dependent to differences in the matrix/precipitate compositions. The results profile the ripening process in multicomponent alloys by illustrating controlling factors (i.e., interfacial energy, diffusivities, and element partitioning). As a result, the study provides guidelines to design and develop high-temperature alloys with stable microstructures for long-term service.

  1. Correlation of Fe/Cr phase decomposition process and age-hardening in Fe-15Cr ferritic alloys

    NASA Astrophysics Data System (ADS)

    Chen, Dongsheng; Kimura, Akihiko; Han, Wentuo

    2014-12-01

    The effects of thermal aging on the microstructure and mechanical properties of Fe-15Cr ferritic model alloys were investigated by TEM examinations, micro-hardness measurements and tensile tests. The materials used in this work were Fe-15Cr, Fe-15Cr-C and Fe-15Cr-X alloys, where X refers to Si, Mn and Ni to simulate a pressure vessel steel. Specimens were isothermally aged at 475 °C up to 5000 h. Thermal aging causes a significant increase in the hardness and strength. An almost twice larger hardening is required for embrittlement of Fe-15Cr-X relative to Fe-15Cr. The age-hardening is mainly due to the formation of Cr-rich α‧ precipitates, while the addition of minor elements has a small effect on the saturation level of age-hardening. The correlation of phase decomposition process and age-hardening in Fe-15Cr alloy was interpreted by dispersion strengthened models.

  2. Journal of Nuclear Materials - Radiation-induced segregation and phase stability in ferritic-martensitic alloy T 91

    SciTech Connect

    Jiao, Zhijie; Busby, Jeremy T; Was, Gary S; Jiao, Zhijie

    2010-01-01

    Radiation-induced segregation in ferritic martensitic alloy T 91 was studied to understand the behavior of solutes as a function of dose and temperature. Irradiations were conducted using 2 MeV protons to doses of 1, 3, 7 and 10 dpa at 400 C. Radiation-induced segregation at prior austenite grain boundaries was measured, and various features of the irradiated microstructure were characterized, including grain boundary carbide coverage, the dislocation microstructure, radiation-induced precipitation and irradiation hardening. Results showed that Cr, Ni and Si segregate to prior austenite grain boundaries at low dose, but segregation ceases and redistribution occurs above 3 dpa. Grain boundary carbide coverage mirrors radiation-induced segregation. Irradiation induces formation of Ni Si Mn and Cu-rich precipitates that account for the majority of irradiation hardening. Radiation-induced segregation behavior is likely linked to the evolution of the precipitate and dislocation microstructures. 2010 Elsevier B.V. All rights reserved

  3. First principles assessment of helium trapping in Y2TiO5 in nano-featured ferritic alloys

    NASA Astrophysics Data System (ADS)

    Jin, Yanan; Jiang, Yong; Yang, Litong; Lan, Guoqiang; Robert Odette, G.; Yamamoto, Takuya; Shang, Jiacheng; Dang, Ying

    2014-10-01

    Nano-scale Y2Ti2O7 and Y2TiO5 oxides are the major features that provide high strength and irradiation tolerance in nano-structured ferritic alloys. Here, we employ density functional theory to study helium trapping in Y2TiO5. The results suggest that helium is more deeply trapped in Y2TiO5 compared to Y2Ti2O7. Helium occupies open channels in Y2TiO5, where it weakly chemically interacts with neighboring oxygen anions, and results in less volume expansion compared to Y2Ti2O7, reducing strains in the iron matrix. The corresponding helium mobility in these channels is very high. While its ultimate fate is to form oxide/matrix interface bubbles, transient deep trapping of helium in oxides plays a major role in the ability of NFA to manage helium distribution.

  4. Effect of boron on post irradiation tensile properties of reduced activation ferritic steel (F-82H) irradiated in HFIR

    SciTech Connect

    Shiba, Kiyoyuki; Suzuki, Masahide; Hishinuma, Akimichi; Pawel, J.E.

    1994-12-31

    Reduced activation ferritic/martensitic steel, F-82H (Fe-8Cr-2W-V-Ta), was irradiated in the High Flux Isotope Reactor (HFIR) to doses between 11 and 34 dpa at 400 and 500 C. Post irradiation tensile tests were performed at the nominal irradiation temperature in vacuum. Some specimens included {sup 10}B or natural boron (nB) to estimate the helium effect on tensile properties. Tensile properties including the 0.2% offset yield stress, the ultimate tensile strength, the uniform elongation and the total elongation were measured. The tensile properties were not dependent on helium content in specimens irradiated to 34 dpa, however {sup 10}B-doped specimens with the highest levels of helium showed slightly higher yield strength and less ductility than boron-free specimens. Strength appears to go through a peak, and ductility through a trough at about 11 dpa. The irradiation to more than 21 dpa reduced the strength and increased the elongation to the unirradiated levels. Ferritic steels are one of the candidate alloys for nuclear fusion reactors because of their good thermophysical properties, their superior swelling resistance, and the low corrosion rate in contact with potential breeder and coolant materials.

  5. Soft magnetic properties of a ferritic Fe-Ni-Cr alloy

    NASA Astrophysics Data System (ADS)

    Jin, S.; Sherwood, R. C.; Chin, G. Y.; Wernick, J. H.; Bordelon, C. M.

    1984-03-01

    Technologically important applications may exist for magnetically soft alloys that possess, in addition to the appropriate magnetic properties, relatively high mechanical strength and corrosion resistance. Such an alloy can be used, for example, for certain types of telephone receiver armature applications. In the present paper, we report the magnetic and mechanical properties of the ternary Fe-3Ni-5Cr alloy. The soft magnetic properties of the alloy are significantly improved by heat treatment within the (α+γ) two-phase region. Exemplary properties after heat treatment at ˜625 °C for 2 h are Hc˜1.2 Oe, μm˜4700, yield strength ˜59 ksi, and elongation ˜30%. The alloy exhibits reasonably good corrosion resistance. Magnetic, mechanical, and electrical properties of the alloy as well as the acoustic performance of telephone receivers using it, have been found to be comparable to those of the 2V-Permendur alloy.

  6. Recent Progress of R&D Activities on Reduced Activation Ferritic/Martensitic Steels

    SciTech Connect

    Huang, Q.; Baluc, N.; Dai, Y.; Jitsukawa, S.; Kimura, A.; Konys, J.; Kurtz, Richard J.; Lindau, R.; Muroga, T.; Odette, George R.; Raj, B.; Stoller, Roger E.; Tan, L.; Tanigawa, Hiroyasu; Tavassoli, A,-A.F.; Yamamoto, Takuya; Wan, F.; Wu, Y.

    2013-01-03

    Several types of reduced activation ferritic/martensitic (RAFM) steel have been developed over the past 30 years in China, Europe, India, Japan, Russia and the USA for application in ITER TBM and future fusion DEMO and power reactors. The progress has been particularly important during the past few years with evaluation of mechanical porperties of these steels before and after irradiation and in contact with different cooling media. This paper presents recent RAFM steel results obtained in ITER partner countries in relation with different TBM and DEMO options

  7. Dispersoid Distribution and Microstructure in Fe-Cr-Al Ferritic Oxide Dispersion-Strengthened Alloy Prepared by Friction Consolidation

    NASA Astrophysics Data System (ADS)

    Catalini, David; Kaoumi, Djamel; Reynolds, Anthony P.; Grant, Glenn J.

    2015-10-01

    INCOLOY® MA956 is a ferritic oxide dispersion-strengthened alloy manufactured by mechanical alloying followed by hot extrusion in vacuum-sealed cans or by degassing and hot isostatic pressing. This could be followed by a tailored heat treatment sequence in order to obtain a desired microstructure and to allow the oxide dispersion to precipitate. Three different oxides, responsible for the high-temperature mechanical strength, have been observed in this alloy: Y4Al2O9, YAlO3, and Y3Al5O12. Their sizes range from just a few to hundreds of nanometers. In this work, mechanically alloyed MA956 powder was consolidated via friction consolidation, a single-step and potentially cheaper processing alternative. Three fully dense compacts were produced. The compacts exhibited a refined, equiaxed grain structure with grain sizes smaller than 10 µm and the desired oxide dispersion. YAlO3 and Y3Al5O12 were identified by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction. The size distribution of precipitates above 50 nm showed a direct proportionality between average precipitate size and grain size. The total energy input during processing was correlated with the relative amount of each of the oxides in the disks: the higher the total processing energy input, the higher the relative amount of Y3Al5O12 precipitates. The elemental composition of the oxide precipitates was also probed individually by EDS, showing an aluminum enrichment trend as precipitates grew in size.

  8. Modified ferritic iron alloys with improved high-temperature mechanical properties and oxidation resistance

    NASA Technical Reports Server (NTRS)

    Oldrieve, R. E.

    1975-01-01

    An alloy modification program was conducted in which the compositions of two existing Fe-Cr-Al alloys (Armco 18SR and GE-1541) were changed to achieve either improved high-temperature strength or improved fabricability. Only modifications of Armco 18SR were successful in achieving increased strength without loss of fabricability or oxidation resistance. The best modified alloy, designated NASA-18T, had twice the rupture strength of Armco 18SR at 800 and 1000 C. The NASA-18T alloy also had better oxidation resistance than Armco 18SR and comparable fabricability. The nominal composition of NASA-18T is Fe-18Cr-2Al-1Si-1.25Ta. All attempted modifications of the GE-1541 alloy were unsuccessful in terms of achieving better fabricability without sacrificing high-temperature strength and oxidation resistance.

  9. Recent status and improvement of reduced-activation ferritic-martensitic steels for high-temperature service

    DOE PAGESBeta

    Tan, L.; Katoh, Y.; Tavassoli, A. -A. F.; Henry, J.; Rieth, M.; Sakasegawa, H.; Tanigawa, H.; Huang, Q.

    2016-07-26

    Reduced-activation ferritic-martensitic (RAFM) steels, candidate structural materials for fusion reactors, have achieved technological maturity after about three decades of research and development. The recent status of a few developmental aspects of current RAFM steels, such as aging resistance, plate thickness effects, fracture toughness, and fatigue, is updated in this paper, together with ongoing efforts to develop next-generation RAFM steels for superior high-temperature performance. Additionally, to thermomechanical treatments, including nonstandard heat treatment, alloy chemistry refinements and modifications have demonstrated some improvements in high-temperature performance. Castable nanostructured alloys (CNAs) were developed by significantly increasing the amount of nanoscale MX (M = V/Ta/Ti,more » X = C/N) precipitates and reducing coarse M23C6 (M = Cr). Preliminary results showed promising improvement in creep resistance and Charpy impact toughness. We present and compare limited low-dose neutron irradiation results for one of the CNAs and China low activation martensitic with data for F82H and Eurofer97 irradiated up to ~70 displacements per atom at ~300–325 °C.« less

  10. Epitaxial Fe/Y2O3 interfaces as a model system for oxide-dispersion-strengthened ferritic alloys

    SciTech Connect

    Kaspar, Tiffany C.; Bowden, Mark E.; Wang, Chong M.; Shutthanandan, V.; Overman, Nicole R.; Van Ginhoven, Renee M.; Wirth, Brian D.; Kurtz, Richard J.

    2015-02-01

    The fundamental mechanisms underlying the superior radiation tolerance properties of oxide-dispersion-strengthened ferritic steels and nanostructured ferritic alloys are poorly understood. Thin film heterostructures of Fe/Y2O3 can serve as a model system for fundamental studies of radiation damage. Epitaxial thin films of Y2O3 were deposited by pulsed laser deposition on 8% Y:ZrO2 (YSZ) substrates with (100), (110), and (111) orientation. Metallic Fe was subsequently deposited by molecular beam epitaxy. Characterization by x-ray diffraction and Rutherford backscattering spectrometry in the channeling geometry revealed a degree of epitaxial or axiotaxial ntation for Fe(211) deposited on Y2O3(110)/YSZ(110). In contrast, Fe on Y2O3(111)/YSZ(111) was fully polycrystalline, and Fe on Y2O3(100)/YSZ(100) exhibited out-of-plane texture in the [110] direction with little or no preferential in-plane orientation. Scanning transmission electron microscopy imaging of Fe(211)/Y2O3(110)/YSZ(110) revealed a strongly islanded morphology for the Fe film, with no epitaxial grains visible in the cross-sectional sample. Well-ordered Fe grains with no orientation to the underlying Y2O3 were observed. Well-ordered crystallites of Fe with both epitaxial and non-epitaxial orientations on Y2O3 are a promising model system for fundamental studies of radiation damage phenomena. This is illustrated with preliminary results of He bubble formation following implantation with a helium ion microscope. He bubble formation is shown to preferentially occur at the Fe/Y2O3 interface.

  11. Past research and fabrication conducted at SCK•CEN on ferritic ODS alloys used as cladding for FBR's fuel pins

    NASA Astrophysics Data System (ADS)

    De Bremaecker, Anne

    2012-09-01

    In the 1960s in the frame of the sodium-cooled fast breeders, SCK•CEN decided to develop claddings made with ferritic stainless materials because of their specific properties, namely a higher thermal conductivity, a lower thermal expansion, a lower tendency to He-embrittlement, and a lower swelling than the austenitic stainless steels. To enhance their lower creep resistance at 650-700 °C arose the idea to strengthen the microstructure by oxide dispersions. This was the starting point of an ambitious programme where both the matrix and the dispersions were optimized. A purely ferritic 13 wt% Cr matrix was selected and its mechanical strength was improved through addition of ferritizing elements. Results of tensile and stress-rupture tests showed that Ti and Mo were the most beneficial elements, partly because of the chi-phase precipitation. In 1973 the optimized matrix composition was Fe-13Cr-3.5Ti-2Mo. To reach creep properties similar to those of AISI 316, different dispersions and methods were tested: internal oxidation (that was not conclusive), and the direct mixing of metallic and oxide powders (Al2O3, MgO, ZrO2, TiO2, ZrSiO4) followed by pressing, sintering, and extrusion. The compression and extrusion parameters were determined: extrusion as hollow at 1050 °C, solution annealing at 1050 °C/15 min, cleaning, cold drawing to the final dimensions with intermediate annealings at 1050 °C, final annealing at 1050 °C, straightening and final aging at 800 °C. The choice of titania and yttria powders and their concentrations were finalized on the basis of their out-of-pile and in-pile creep and tensile strength. As soon as a resistance butt welding machine was developed and installed in a glove-box, fuel segments with PuO2 were loaded in the Belgian MTR BR2. The fabrication parameters were continuously optimized: milling and beating, lubrication, cold drawing (partial and final reduction rates, temperature, duration, atmosphere and furnace). Specific non

  12. Effect of Cr content on the nanostructural evolution of irradiated ferritic/martensitic alloys: An object kinetic Monte Carlo model

    NASA Astrophysics Data System (ADS)

    Chiapetto, M.; Malerba, L.; Becquart, C. S.

    2015-10-01

    Self-interstitial cluster diffusivity in Fe-Cr alloys, model materials for high-Cr ferritic/martensitic steels, is known to be reduced in a non-monotonic way as a function of Cr concentration: it first decreases, then increases. This non-monotonic behaviour is caused by a relatively long-ranged attractive interaction between Cr atoms and crowdions and correlates well with the experimentally observed swelling in these alloys under neutron irradiation, also seen to first decrease and then increase with increasing Cr content, under comparable irradiation conditions. Moreover, recent studies reveal that C atoms dispersed in the Fe matrix form under irradiation complexes with vacancies which, in turn, act as trap for one-dimensionally migrating self-interstitial clusters. The mobility of one-dimensional migrating clusters is considered key to determine swelling susceptibility. However, no model has ever been built that quantitatively describes the dependence of swelling on Cr content, allowing for the presence of C in the matrix. In this work we developed physically-based sets of parameters for object kinetic Monte Carlo (OKMC) simulations intended to study the nanostructure evolution under irradiation in Fe-Cr-C alloys. The nanostructural evolution in Fe-C and in four Fe-Cr-C alloys (containing 2.5, 5, 9 and 12 wt.% Cr) neutron irradiated up to ∼0.6 dpa at 563 K was simulated according to the model and reference experiments were reproduced. Our model shows that the SIA cluster reduced mobility has a major influence on the nanostructural evolution: it increases the number of vacancy-SIA recombinations and thus leads to the suppression of voids formation. This provides a clear framework to interpret the non-monotonic dependence of swelling in Fe-Cr alloys versus Cr content. Our model also suggests that the amount of C in the matrix has an equally important role: high amounts of it may counteract the beneficial effect that Cr has in reducing swelling.

  13. Structure and elevated temperature properties of carbon-free ferritic alloys strengthened by a Laves phase

    NASA Technical Reports Server (NTRS)

    Bhandarkar, M. D.; Zackay, V. F.; Parker, E. R.; Bhat, M. S.

    1975-01-01

    A Laves phase, Fe2Ta, was utilized to obtain good elevated temperature properties in a carbon-free iron alloy containing 1 at. pct Ta and 7 at. pct Cr. Room temperature embrittlement resulting from the precipitation of the Laves phase at grain boundaries was overcome by spheroidizing the precipitate. This was accomplished by thermally cycling the alloys through the alpha to gamma transformation. The short-time yield strength of the alloys decreased very slowly with increase in test temperature up to 600 C, but above this temperature, the strength decreased rapidly. Results of constant load creep and stress rupture tests conducted at several temperatures and stresses indicated that the rupture and creep strengths of spheroidized 1 Ta-7 Cr alloy were higher than those of several commercial steels containing chromium and/or molybdenum carbides but lower than those of steels containing substantial amounts of tungsten and vanadium. When molybdenum was added to the base Fe-Ta-Cr alloy, the rupture and creep strengths were considerably increased.

  14. Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales

    DOE PAGESBeta

    Sun, Zhiqian; Song, Gian; Sisneros, Thomas A.; Clausen, Bjorn; Pu, Chao; Li, Lin; Gao, Yanfei; Liaw, Peter K.

    2016-03-16

    An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix andmore » elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. Furthermore, the study contributes to further understanding of load-partitioning characteristics in multiphase materials.« less

  15. Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales.

    PubMed

    Sun, Zhiqian; Song, Gian; Sisneros, Thomas A; Clausen, Bjørn; Pu, Chao; Li, Lin; Gao, Yanfei; Liaw, Peter K

    2016-01-01

    An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 °C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix and elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 °C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. The study contributes to further understanding of load-partitioning characteristics in multiphase materials. PMID:26979660

  16. Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales

    NASA Astrophysics Data System (ADS)

    Sun, Zhiqian; Song, Gian; Sisneros, Thomas A.; Clausen, Bjørn; Pu, Chao; Li, Lin; Gao, Yanfei; Liaw, Peter K.

    2016-03-01

    An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 °C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix and elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 °C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. The study contributes to further understanding of load-partitioning characteristics in multiphase materials.

  17. Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales

    PubMed Central

    Sun, Zhiqian; Song, Gian; Sisneros, Thomas A.; Clausen, Bjørn; Pu, Chao; Li, Lin; Gao, Yanfei; Liaw, Peter K.

    2016-01-01

    An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 °C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix and elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 °C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. The study contributes to further understanding of load-partitioning characteristics in multiphase materials. PMID:26979660

  18. Radiation-induced strengthening and absorption of dislocation loops in ferritic Fe-Cr alloys: the role of Cr segregation.

    PubMed

    Terentyev, D; Bakaev, A

    2013-07-01

    The understanding of radiation-induced strengthening in ferritic FeCr-based steels remains an essential issue in the assessment of materials for fusion and fission reactors. Both early and recent experimental works on Fe-Cr alloys reveal Cr segregation on radiation-induced nanostructural features (mainly dislocation loops), whose impact on the modification of the mechanical response of the material might be key for explaining quantitatively the radiation-induced strengthening in these alloys. In this work, we use molecular dynamics to study systematically the interaction of dislocations with 1/2<111> and <100> loops in all possible orientations, both enriched by Cr atoms and undecorated, for different temperatures, loop sizes and dislocation velocities. The configurations of the enriched loops have been obtained using a non-rigid lattice Monte Carlo method. The study reveals that Cr segregation influences the interaction mechanisms with both 1/2<111> and <100> loops. The overall effect of Cr enrichment is to penalize the mobility of intrinsically glissile 1/2<111> loops, modifying the reaction mechanisms as a result. The following three most important effects associated with Cr enrichment have been revealed: (i) absence of dynamic drag; (ii) suppression of complete absorption; (iii) enhanced strength of small dislocation loops (2 nm and smaller). Overall the effect of the Cr enrichment is therefore to increase the unpinning stress, so experimentally 'invisible' nanostructural features may also contribute to radiation-induced strengthening. The reasons for the modification of the mechanisms are explained and the impact of the loading conditions is discussed. PMID:23756468

  19. Development of High-Temperature Ferritic Alloys and Performance Prediction Methods for Advanced Fission Energy Systems

    SciTech Connect

    G. RObert Odette; Takuya Yamamoto

    2009-08-14

    Reports the results of a comprehensive development and analysis of a database on irradiation hardening and embrittlement of tempered martensitic steels (TMS). Alloy specific quantitative semi-empirical models were derived for the dpa dose, irradiation temperature (ti) and test (Tt) temperature of yield stress hardening (or softening) .

  20. Ab Initio Investigation of He Bubbles at the Y2Ti2O7-Fe Interface in Nanostructured Ferritic Alloys

    NASA Astrophysics Data System (ADS)

    Danielson, Thomas; Tea, Eric; Hin, Celine

    Nanostructured ferritic alloys are promising materials candidates for the next generation of nuclear reactors due to their ability to withstand high temperatures, high pressures, high neutron flux and especially, the presence of high concentrations of transmutation product helium. As helium diffuses through the matrix, large number densities of complex oxide nanoclusters, namely Y2Ti2O7, Y2O3 and Y2TiO5, act as trapping sites for individual helium atoms and helium clusters. Consequently, there is a significant decrease in the amount of helium that reaches grain boundaries, mitigating the threat of pressurized bubble formation and embrittlement. In order to understand the helium trapping mechanisms of the oxides at a fundamental level, the interface between the nanoclusters and the iron matrix must be modeled. We present results obtained using density functional theory on the Y2Ti2O7-Fe interface where the structure has been modeled based on experimental observations. Helium has been added along the interface in order to investigate the influence of helium on the structure and to obtain thermodynamic and kinetic parameters of helium along the interface.

  1. Effect of ferrite formation on abnormal austenite grain coarsening in low-alloy steels during the hot rolling process

    NASA Astrophysics Data System (ADS)

    Asahi, Hitoshi; Yagi, Akira; Ueno, Masakatsu

    1998-05-01

    Abnormal coarsening of austenite (γ) grains occurred in low-alloy steels during a seamless pipe hotrolling process. Often, the grains became several hundred micrometers in diameter. This made it difficult to apply direct quenching to produce high-performance pipes. The phenomenon of grain coarsening was successfully reproduced using a thermomechanical simulator, and the factors which affected grain coarsening were clarified. The mechanism was found to be basically strain-induced grain rowth which occurred during reheating at around 930 °C. Furthermore, once a pipe temperature decreased to the dual-phase region after the minimal hot working and prior to the reheating process, the grain coarsening was more pronounced. It was understood that the formation of ferrite along grain boundaries had the role of reducing the migration of grain boundaries into neighboring grains, leaving a strain-free, recrystallized region behind. This abnormal grain coarsening was found to be effectively prevented by an addition of Nb, the content of which varied depending on the C content. The effect of the Nb addition was confirmed by an in-line test.

  2. Effect of ferrite formation on abnormal austenite grain coarsening in low-alloy steels during hot rolling process

    SciTech Connect

    Asahi, Hitoshi; Ueno, Masakatsu; Yagi, Akira

    1998-05-01

    Abnormal coarsening of austenite ({gamma}) grains occurred in low-alloy steels during a seamless pipe hot-rolling process. Often, the grains became several hundred micrometer in diameter. This made it difficult to apply direct quenching to produce high-performance pipes. The phenomenon of grain coarsening was successfully reproduced using a thermomechanical simulator, and the factors which affected grain coarsening were clarified. The mechanism was found to be basically strain-induced grain growth which occurred during reheating at around 930 C. Furthermore, once a pipe temperature decreased to the dual-phase region after the minimal hot working and prior to the reheating process, the grain coarsening was more pronounced. It was understood that the formation of ferrite along grain boundaries had the role of reducing the migration of grain boundaries into neighboring grains, leaving a strain-free, recrystallized region behind. This abnormal grain coarsening was found to be effectively prevented by an addition of Nb, the content of which varied depending on the C content. The effect of the Nb addition was confirmed by an in-line test.

  3. Characterization of neutron-irradiated ferritic model alloys and a RPV steel from combined APT, SANS, TEM and PAS analyses

    NASA Astrophysics Data System (ADS)

    Meslin, E.; Lambrecht, M.; Hernández-Mayoral, M.; Bergner, F.; Malerba, L.; Pareige, P.; Radiguet, B.; Barbu, A.; Gómez-Briceño, D.; Ulbricht, A.; Almazouzi, A.

    2010-11-01

    Understanding the behavior of reactor pressure vessel (RPV) steels under irradiation is a mandatory task that has to be elucidated in order to be able to operate safely a nuclear power plant or to extend its lifetime. To build up predictive tools, a substantial experimental data base is needed at the nanometre scale to extract quantitative information on neutron-irradiated materials and to validate the theoretical models. To reach this experimental goal, ferritic model alloys and French RPV steel were neutron irradiated in a test reactor at an irradiation flux of 9 × 10 17 nm -2 s, doses from 0.18 to 1.3 × 10 24 nm -2 and 300 °C. The main goal of this paper is to report the characterization of the radiation-induced microstructural change in the materials by using the state-of-the-art of characterization techniques available in Europe at the nanometre scale. Possibilities, limitations and complementarities of the techniques to each other are highlighted.

  4. Microstructure and Mechanical Properties of a Nitride-Strengthened Reduced Activation Ferritic/Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Zhou, Qiangguo; Zhang, Wenfeng; Yan, Wei; Wang, Wei; Sha, Wei; Shan, Yiyin; Yang, Ke

    2012-12-01

    Nitride-strengthened reduced activation ferritic/martensitic (RAFM) steels are developed taking advantage of the high thermal stability of nitrides. In the current study, the microstructure and mechanical properties of a nitride-strengthened RAFM steel with improved composition were investigated. Fully martensitic microstructure with fine nitrides dispersion was achieved in the steel. In all, 1.4 pct Mn is sufficient to suppress delta ferrite and assure the steel of the full martensitic microstructure. Compared to Eurofer97, the steel showed similar strength at room temperature but higher strength at 873 K (600 °C). The steel exhibited very high impact toughness and a low ductile-to-brittle transition temperature (DBTT) of 243 K (-30 °C), which could be further reduced by purification.

  5. Effects of shape and size of cobalt ferrite nanostructures on their MRI contrast and thermal activation

    PubMed Central

    Joshi, Hrushikesh M.; Lin, Yen Po; Aslam, Mohammed; Prasad, P. V.; Schultz-Sikma, Elise A.; Edelman, Robert; Meade, Thomas; Dravid, Vinayak P.

    2010-01-01

    Cobalt ferrite magnetic nanostructures were synthesized via a high temperature solution phase method. Spherical nanostructures of various sizes were synthesized with the help of seed mediated growth of the nanostructures in organic phase, while faceted irregular (FI) cobalt ferrite nanostructures were synthesized via the same method but in the presence of a magnetic field. Magnetic properties were characterized by SQUID magnetometry, relaxivity measurements and thermal activation under RF field, as a function of size and shape. The results show that the saturation magnetization of the nanostructures increases with an increase in size, and the FI nanostructures exhibit lower saturation magnetization than their spherical counterparts. The relaxivity coefficient of cobalt ferrite nanostructures increases with increase in size; while FI nanostructures show a higher relaxivity coefficient than spherical nanostructures with respect to their saturation magnetization. In the case of RF thermal activation, the specific absorption rate (SAR) of nanostructures increases with increase in the size. The contribution sheds light on the role of size and shape on important magnetic properties of the nanostructures in relation to their biomedical applications. PMID:21850276

  6. ATR-A1 irradiation experiment on vanadium alloys and low activation steels

    SciTech Connect

    Tasi, H.; Strain, R.V.; Gomes, I.; Hins, A.G.; Smith, D.L.

    1996-04-01

    To study the mechanical properties of vanadium alloys under neutron irradiation at low temperatures, an experiment was designed and constructed for irradiation in the Advanced Test Reactor (ATR). The experiment contained Charpy, tensile, compact tension, TEM, and creep specimens of vanadium alloys. It also contained limited low-activation ferritic steel specimens as part of the collaborative agreement with Monbusho of Japan. The design irradiation temperatures for the vanadium alloy specimens in the experiment are {approx}200 and 300{degrees}C, achieved with passive gap-gap sizing and fill gas blending. To mitigate vanadium-to-chromium transmutation from the thermal neutron flux, the test specimens are contained inside gadolinium flux filters. All specimens are lithium-bonded. The irradiation started in Cycle 108A (December 3, 1995) and is expected to have a duration of three ATR cycles and a peak influence of 4.4 dpa.

  7. Effects of proton irradiation on nanocluster precipitation in ferritic steel containing fcc alloying additions

    SciTech Connect

    Zhang, Zhongwu; Liu, C T; Wang, Xun-Li; Miller, Michael K; Ma, Dong; Chen, Guang; Williams, J R; Chin, Bryan

    2012-01-01

    Newly-developed precipitate-strengthened ferritic steels with and without pre-existing nanoscale precipitates were irradiated with 4 MeV protons to a dose of ~5 mdpa at 50 C and subsequently examined by nanoindentation and atom probe tomography (APT). Irradiation-enhanced precipitation and coarsening of pre-existing nanoscale precipitates were observed. Copper partitions to the precipitate core along with a segregation of Ni, Al and Mn to the precipitate/matrix interface after both thermal aging and proton irradiation. Proton irradiation induces the precipitation reaction and coarsening of pre-existing nanoscale precipitates, and these results are similar to a thermal aging process. The precipitation and coarsening of nanoscale precipitates are responsible for the changes in hardness. The observation of the radiation-induced softening is essentially due to the coarsening of the pre-existing Cu-rich nanoscale precipitates. The implication of the precipitation on the embrittlement of reactor-pressure-vessel steels after irradiation is discussed.

  8. Synthesis of Water Dispersible and Catalytically Active Gold-Decorated Cobalt Ferrite Nanoparticles.

    PubMed

    Silvestri, Alessandro; Mondini, Sara; Marelli, Marcello; Pifferi, Valentina; Falciola, Luigi; Ponti, Alessandro; Ferretti, Anna Maria; Polito, Laura

    2016-07-19

    Hetero-nanoparticles represent an important family of composite nanomaterials that in the past years are attracting ever-growing interest. Here, we report a new strategy for the synthesis of water dispersible cobalt ferrite nanoparticles (CoxFe3-xO4 NPs) decorated with ultrasmall (2-3 nm) gold nanoparticles (Au NPs). The synthetic procedure is based on the use of 2,3-meso-dimercaptosuccinic acid (DMSA), which plays a double role. First, it transfers cobalt ferrite NPs from the organic phase to aqueous media. Second, the DMSA reductive power promotes the in situ nucleation of gold NPs in proximity of the magnetic NP surface. Following this procedure, we achieved a water dispersible nanosystem (CoxFe3-xO4-DMSA-Au NPs) which combines the cobalt ferrite magnetic properties with the catalytic features of ultrasmall Au NPs. We showed that CoxFe3-xO4-DMSA-Au NPs act as an efficient nanocatalyst to reduce 4-nitrophenol to 4-aminophenol and that they can be magnetically recovered and recycled. It is noteworthy that such nanosystem is more catalytically active than Au NPs with equal size. Finally, a complete structural and chemical characterization of the hetero-NPs is provided. PMID:27328722

  9. Effect of neutron irradiation at low temperature on the embrittlement of the reduced-activation ferritic steels

    NASA Astrophysics Data System (ADS)

    Rybin, V. V.; Kursevich, I. P.; Lapin, A. N.

    1998-10-01

    Effects of neutron irradiation to fluence of 2.0 × 10 24 n/m 2 ( E > 0.5 MeV) in temperature range 70-300°C on mechanical properties and structure of the experimental reduced-activation ferritic 0.1%C-(2.5-12)%Cr-(1-2)%W-(0.2-0.7)%V alloys were investigated. The steels were studied in different initial structural conditions obtained by changing the modes of heat treatments. Effect of neutron irradiation estimated by a shift in ductile-brittle transition temperature (ΔDBTT) and reduction of upper shelf energy (ΔUSE) highly depends on both irradiation condition and steel chemical composition and structure. For the steel with optimum chemical composition (9Cr-1.5WV) after irradiation to 2 × 10 24 n/m 2 ( E ⩾ 0.5 MeV) at 280°C the ΔDBTT does not exceed 25°C. The shift in DBTT increased from 35°C to 110°C for the 8Cr-1.5WV steel at a decrease in irradiation temperature from 300°C to 70°C. The CCT diagrams are presented for several reduced-activated steels.

  10. 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.

  11. Isothermal Annealing of a Thermally Stabilized Fe-Based Ferritic Alloy

    NASA Astrophysics Data System (ADS)

    Kotan, Hasan; Darling, Kris A.

    2015-09-01

    In this study, the stability and microstructural evolution, including grain size and hardness of nanocrystalline Fe91Ni8Zr1 alloyed powders, produced by ball milling, were investigated after annealing at 900 and 1000 °C for up to 24 h. Results indicate that rapid grain growth to the micron scale occurs within the first few minutes of exposure to the elevated annealing temperatures. However, despite the loss of nanocrystallinity, an extremely stable and efficient hardening effect persists, which has been found to be equal to that predicted by Hall-Petch strengthening even at the smallest grain sizes. The mechanical properties of the samples consolidated to bulk via equal channel angular extrusion at 900 °C were evaluated by uniaxial compression at room and elevated temperatures. Results reveal high compressive yield stress as well as the appearance and disappearance of a yield drop indicating the presence of coherent (GP zone like) precipitates within the microstructure. Such a hardening mechanism has implications for developing new Fe-Ni-based alloys exhibiting a combination of high strength and ductility for high temperature applications.

  12. Status of ATR-A1 irradiation experiment on vanadium alloys and low-activation steels

    SciTech Connect

    Tsai, H.; Strain, R.V.; Gomes, I.; Chung, H.; Smith, D.L.

    1997-04-01

    The ATR-A1 irradiation experiment in the Advanced Test Reactor (ATR) was a collaborative U.S./Japan effort to study at low temperatures the effects of neutron damage on vanadium alloys. The experiment also contained a limited quantity of low-activation ferritic steel specimens from Japan as part of the collaboration agreement. The irradiation was completed on May 5, 1996, as planned, after achieving an estimated neutron damage of 4.7 dpa in vanadium. The capsule has since been kept in the ATR water canal for the required radioactivity cool-down. Planning is underway for disassembly of the capsule and test specimen retrieval.

  13. Role of Y-Al oxides during extended recovery process of a ferritic ODS alloy

    DOE PAGESBeta

    Capdevila, C.; Pimentel, G.; Aranda, M. M.; Rementeria, R.; Dawson, K.; Urones-Garrote, E.; Tatlock, G. J.; Miller, Michael K.

    2015-08-04

    The microstructural stability of Y-Al oxides during the recrystallization of Fe-Cr-Al oxide dispersion strengthened alloy is studied in this work. The goal is to determine the specific distribution pattern of oxides depending where they are located: in the matrix or at the grain boundaries. It was concluded that those located at the grain boundaries yielded a faster coarsening than the ones in the matrix, although no significant differences in composition and/or crystal structure were observed. However, the recrystallization heat treatment leads to the dissolution of the Y2O3 and its combination with Al to form the YAlO3 perovskite oxide particles process,more » mainly located at the grain boundaries. Lastly, atom probe tomography analysis revealed a significant Ti build-up at the grain boundaries that might affect subsequent migration during recrystallization.« less

  14. Role of Y-Al oxides during extended recovery process of a ferritic ODS alloy

    SciTech Connect

    Capdevila, C.; Pimentel, G.; Aranda, M. M.; Rementeria, R.; Dawson, K.; Urones-Garrote, E.; Tatlock, G. J.; Miller, Michael K.

    2015-08-04

    The microstructural stability of Y-Al oxides during the recrystallization of Fe-Cr-Al oxide dispersion strengthened alloy is studied in this work. The goal is to determine the specific distribution pattern of oxides depending where they are located: in the matrix or at the grain boundaries. It was concluded that those located at the grain boundaries yielded a faster coarsening than the ones in the matrix, although no significant differences in composition and/or crystal structure were observed. However, the recrystallization heat treatment leads to the dissolution of the Y2O3 and its combination with Al to form the YAlO3 perovskite oxide particles process, mainly located at the grain boundaries. Lastly, atom probe tomography analysis revealed a significant Ti build-up at the grain boundaries that might affect subsequent migration during recrystallization.

  15. Role of Y-Al Oxides During Extended Recovery Process of a Ferritic ODS Alloy

    NASA Astrophysics Data System (ADS)

    Capdevila, C.; Pimentel, G.; Aranda, M. M.; Rementeria, R.; Dawson, K.; Urones-Garrote, E.; Tatlock, G. J.; Miller, M. K.

    2015-08-01

    The microstructural stability of Y-Al oxides during the recrystallization of Fe-Cr-Al oxide dispersion strengthened alloy is studied in this work. The goal is to determine the specific distribution pattern of oxides depending where they are located: in the matrix or at the grain boundaries. It was concluded that those located at the grain boundaries yielded a faster coarsening than the ones in the matrix, although no significant differences in composition and/or crystal structure were observed. However, the recrystallization heat treatment leads to the dissolution of the Y2O3 and its combination with Al to form the YAlO3 perovskite oxide particles process, mainly located at the grain boundaries. Finally, atom probe tomography analysis revealed a significant Ti build-up at the grain boundaries that might affect subsequent migration during recrystallization.

  16. Irradiation effects in ferritic steels

    NASA Astrophysics Data System (ADS)

    Lechtenberg, Thomas

    1985-08-01

    Since 1979 the Alloy Development for Irradiation Performance (ADIP) task funded by the US Department of Energy has been studying the 2-12Cr class of ferritic steels to establish the feasibility of using them in fusion reactor first wall/breeding blanket (FW/B) applications. The advantages of ferritic steels include superior swelling resistance, low thermal stresses compared to austenitic stainless steels, attractive mechanical properties up to 600°C. and service histories exceeding 100 000 h. These steels are commonly used in a range of microstructural conditions which include ferritic, martensitic. tempered martensitic, bainitic etc. Throughout this paper where the term "ferritic" is used it should be taken to mean any of these microstructures. The ADIP task is studying several candidate alloy systems including 12Cr-1MoWV (HT-9), modified 9Cr-1MoVNb, and dual-phased steels such as EM-12 and 2 {1}/{4}Cr-Mo. These materials are ferromagnetic (FM), body centered cubic (bcc), and contain chromium additions between 2 and 12 wt% and molybdenum additions usually below 2%. The perceived issues associated with the application of this class of steel to fusion reactors are the increase in the ductile-brittle transition temperature (DBTT) with neutron damage, the compatibility of these steels with liquid metals and solid breeding materials, and their weldability. The ferromagnetic character of these steels can also be important in reactor design. It is the purpose of this paper to review the current understanding of these bcc steels and the effects of irradiation. The major points of discussion will be irradiation-induced or -enhanced dimensional changes such as swelling and creep, mechanical properties such as tensile strength and various measurements of toughness, and activation by neutron interactions with structural materials.

  17. Absorption and Decomposition of CO2 by Active Ferrites Prepared by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Li, Shaowei; He, Zhida; Zheng, Yanjun; Chen, Changfeng

    2015-12-01

    Active ferrites, which play an important role in the catalytic decomposition of CO2, have been fabricated by atmospheric plasma spraying to incorporate FeO and anoxic iron oxide [Fe3O4-δ (0 < δ < 1)]. The complexity of phase composition, especially the presence of FeO, gives the resulting powder a greater ability to decompose CO2 when compared to hydrogen-reduced Fe3O4 or Fe2O3 particles. Spraying distance is found to play an important role in modulating the decomposition ability of the powders, while elevated temperatures can also enhance the catalytic decomposition of CO2.

  18. Irradiation-induced grain growth in nanocrystalline reduced activation ferrite/martensite steel

    SciTech Connect

    Liu, W. B.; Chen, L. Q.; Zhang, C. Yang, Z. G.; Ji, Y. Z.; Zang, H.; Shen, T. L.

    2014-09-22

    In this work, we investigate the microstructure evolution of surface-nanocrystallized reduced activation ferrite/martensite steels upon high-dose helium ion irradiation (24.3 dpa). We report a significant irradiation-induced grain growth in the irradiated buried layer at a depth of 300–500 nm, rather than at the peak damage region (at a depth of ∼840 nm). This phenomenon can be explained by the thermal spike model: minimization of the grain boundary (GB) curvature resulting from atomic diffusion in the cascade center near GBs.

  19. Interdiffusion Behavior of Al-Rich Oxidation Resistant Coatings on Ferritic-Martensitic Alloys

    SciTech Connect

    Velraj, S.; Zhang, Ying; Hawkins, W. E.; Pint, Bruce A.

    2012-06-21

    We investigated interdiffusion of thin Al-rich coatings synthesized by chemical vapor deposition (CVD) and pack cementation on 9Cr ferritic–martensitic alloys in the temperature range of 650–700°C. The compositional changes after long-term exposures in laboratory air and air + 10 vol% H2O were examined experimentally. Interdiffusion was modeled by a modified coating oxidation and substrate interdiffusion model (COSIM) program. The modification enabled the program to directly input the concentration profiles of the as-deposited coating determined by electron probe microanalysis (EPMA). Reasonable agreement was achieved between the simulated and experimental Al profiles after exposures. Moreover, the model was also applied to predict coating lifetime at 650–700°C based on a minimum Al content (Cb) required at the coating surface to re-form protective oxide scale. In addition to a Cb value established from the failure of a thin CVD coating at 700°C, values reported for slurry aluminide coatings were also included in lifetime predictions.

  20. Manufacturing development of low activation vanadium alloys

    SciTech Connect

    Smith, J.P.; Johnson, W.R.; Baxi, C.B.

    1996-10-01

    General Atomics is developing manufacturing methods for vanadium alloys as part of a program to encourage the development of low activation alloys for fusion use. The culmination of the program is the fabrication and installation of a vanadium alloy structure in the DIII-D tokamak as part of the Radiative Divertor modification. Water-cooled vanadium alloy components will comprise a portion of the new upper divertor structure. The first step, procuring the material for this program has been completed. The largest heat of vanadium alloy made to date, 1200 kg of V-4Cr-4Ti, has been produced and is being converted into various product forms. Results of many tests on the material during the manufacturing process are reported. Research into potential fabrication methods has been and continues to be performed along with the assessment of manufacturing processes particularly in the area of joining. Joining of vanadium alloys has been identified as the most critical fabrication issue for their use in the Radiative Divertor Program. Joining processes under evaluation include resistance seam, electrodischarge (stud), friction and electron beam welding. Results of welding tests are reported. Metallography and mechanical tests are used to evaluate the weld samples. The need for a protective atmosphere during different welding processes is also being determined. General Atomics has also designed, manufactured, and will be testing a helium-cooled, high heat flux component to assess the use of helium cooled vanadium alloy components for advanced tokamak systems. The component is made from vanadium alloy tubing, machined to enhance the heat transfer characteristics, and joined to end flanges to allow connection to the helium supply. Results are reported.

  1. J/sub Ic/ fracture toughness of ferritic DCI (ductile cast iron) alloys: A comparison of two versions of ASTM E 813

    SciTech Connect

    Salzbrenner, R.

    1989-05-01

    The fracture toughness of several ductile cast iron (DCI) alloys has been calculated according to two versions of the ASTM Standard covering the determination of J/sub Ic/. The original version (ASTM E 813-81) had previously been used to establish the relationship between ferritic DCI alloys and the graphite nodule spacing. The J/sub Ic/ values were recalculated by the methods of the revised version of the ASTM Standard (ASME 813-87), and were found to be 5 to 8% higher than those determined by the original standard. A linear regression analysis was used to reaffirm that the fracture toughness is directly related to the graphite nodule size or spacing. 6 refs., 8 figs., 3 tabs.

  2. Development of oxide dispersion strengthened ferritic steels for fusion

    SciTech Connect

    Mukhopadhyay, D.K.; Froes, F.H.; Gelles, D.S.

    1998-03-01

    An oxide dispersion strengthened (ODS) ferritic steel with high temperature strength has been developed in line with low activation criteria for application in fusion power systems. The composition Fe-13.5Cr-2W-0.5Ti-0.25Y{sub 2}O{sup 3} was chosen to provide a minimum chromium content to insure fully delta-ferrite stability. High temperature strength has been demonstrated by measuring creep response of the ODS alloy in uniaxial tension at 650 and 900 C in an inert atmosphere chamber. Results of tests at 900 C demonstrate that this alloy has creep properties similar to other alloys of similar design and can be considered for use in high temperature fusion power system designs. The alloy selection process, materials production, microstructural evaluation and creep testing are described.

  3. Kinetic of solute clustering in neutron irradiated ferritic model alloys and a French pressure vessel steel investigated by atom probe tomography

    NASA Astrophysics Data System (ADS)

    Meslin, E.; Radiguet, B.; Pareige, P.; Barbu, A.

    2010-04-01

    The embrittlement of reactor pressure vessel steels under neutron irradiation is partly due to the formation of solute clusters. To gain more insight into their formation mechanisms, ferritic model alloys (low copper Fe-0.08 at.% Cu, Fe-0.09 Cu-1.1 Mn-0.7 Ni (at.%), and a copper free Fe-1.1 Mn-0.7 Ni (at.%)) and a French 16MND5 reactor pressure vessel steel, were irradiated in a test reactor at two fluxes of 0.15 and 9 × 10 17 n( E> 1 MeV) m -2 s -1 and at increasing doses from 0.18 to 1.3 × 10 24 n( E> 1 MeV) m -2. Atom probe tomography analyses revealed that nanometer-size solute clusters were formed during irradiation in all the materials, even in the copper free Fe-1.1 Mn-0.7 Ni (at.%) alloy. It should be noted that solute segregation in a low-Ni ferritic material was never reported before in absence of the highly insoluble copper impurity. The manganese and nickel segregation is suggested to result from a radiation-induced mechanism.

  4. High-temperature creep rupture of low alloy ferritic steel butt-welded pipes subjected to combined internal pressure and end loadings.

    PubMed

    Vakili-Tahami, F; Hayhurst, D R; Wong, M T

    2005-11-15

    Constitutive equations are reviewed and presented for low alloy ferritic steels which undergo creep deformation and damage at high temperatures; and, a thermodynamic framework is provided for the deformation rate potentials used in the equations. Finite element continuum damage mechanics studies have been carried out using these constitutive equations on butt-welded low alloy ferritic steel pipes subjected to combined internal pressure and axial loads at 590 and 620 degrees C. Two dominant modes of failure have been identified: firstly, fusion boundary failure at high stresses; and, secondly, Type IV failure at low stresses. The stress level at which the switch in failure mechanism takes place has been found to be associated with the relative creep resistance and lifetimes, over a wide range of uniaxial stresses, for parent, heat affected zone, Type IV and weld materials. The equi-biaxial stress loading condition (mean diameter stress equal to the axial stress) has been confirmed to be the worst loading condition. For this condition, simple design formulae are proposed for both 590 and 620 degrees C. PMID:16243708

  5. Magnetic properties and adsorptive performance of manganese-zinc ferrites/activated carbon nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, B. B.; Xu, J. C.; Xin, P. H.; Han, Y. B.; Hong, B.; Jin, H. X.; Jin, D. F.; Peng, X. L.; Li, J.; Gong, J.; Ge, H. L.; Zhu, Z. W.; Wang, X. Q.

    2015-01-01

    Owing to the unique microstructure and high specific surface area, activated carbon (AC) could act as an excellent adsorbent for wastewater treatment and good carrier for functional materials. In this paper, manganese-zinc ferrites (Mn0.5Zn0.5Fe2O4: MZF) were anchored into AC by hydrothermal method, resulting in the excellent magnetic response for AC nanocomposites in wastewater treatment. All results demonstrated the magnetic nanoparticles presented a spinel phase structure and existed in the pores of AC. The saturation magnetization (Ms) of MZF/AC nanocomposites increased with the ferrites content, while the pore volume and specific surface area declined. The Sample-5 possessed the specific surface area of 1129 m2 g-1 (close to 1243 m2 g-1 of AC) and Ms of 3.96 emu g-1. Furthermore, the adsorptive performance for organic dyes was studied and 99% methylene blue was adsorbed in 30 min. The magnetic AC nanocomposites could be separated easily from solution by magnetic separation technique.

  6. Large zinc cation occupancy of octahedral sites in mechanically activated zinc ferrite powders

    SciTech Connect

    Oliver, S. A.; Harris, V. G.; Hamdeh, H. H.; Ho, J. C.

    2000-05-08

    The cation site occupancy of a mechanically activated nanocrystalline zinc ferrite powder was determined as (Zn{sub 0.55}{sup 2+}Fe{sub 0.18}{sup 3+}){sub tet}[Zr{sub 0.45}{sup 2+}Fe{sub 1.82}{sup 3+}]{sub oct}O{sub 4} through analysis of extended x-ray absorption fine structure measurements, showing a large redistribution of cations between sites compared to normal zinc ferrite samples. The overpopulation of cations in the octahedral sites was attributed to the ascendance in importance of the ionic radii over the crystal energy and bonding coordination in determining which interstitial sites are occupied in this structurally disordered powder. Slight changes are observed in the local atomic environment about the zinc cations, but not the iron cations, with respect to the spinel structure. The presence of Fe{sup 3+} on both sites is consistent with the measured room temperature magnetic properties. (c) 2000 American Institute of Physics.

  7. Hot-rolling of reduced activation 8CrODS ferritic steel

    NASA Astrophysics Data System (ADS)

    Wu, Xiaochao; Ukai, Shigeharu; Leng, Bin; Oono, Naoko; Hayashi, Shigenari; Sakasegawa, Hideo; Tanigawa, Hiroyasu

    2013-11-01

    The 8CrODS ferritic steel is based on J1-lot developed for the advanced fusion blanket material to increase the coolant outlet temperature. A hot-rolling was conducted at the temperature above Ar3 of 716 °C, and its effect on the microstructure and tensile strength in 8CrODS ferritic steel was evaluated, comparing together with normalized and tempered specimen. It was confirmed that hot-rolling leads to slightly increased fraction of the ferrite and highly improved tensile strength. This ferrite was formed by transformation from the hot-rolled austenite during cooling due to fine austenite grains induced by hot-rolling. The coarsening of the transformed ferrite in hot-rolled specimen can be attributed to the crystalline rotation and coalescence of the similar oriented grains. The improved strength of hot-rolled specimen was ascribed to the high dislocation density and replacement of easily deformed martensite with the transformed coarse ferrite.

  8. Diffusive transport parameters of deuterium through China reduced activation ferritic-martensitic steels

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Liu, Lingbo; Xiang, Xin; Rao, Yongchu; Ye, Xiaoqiu; Chen, Chang An

    2016-03-01

    Reduced Activation Ferritic/Martensitic (RAFM) steels have been considered as the most promising candidate structure materials for a fusion reactor. In the recent decades, two new types of RAFM steels, called China Low Activation Martensitic (CLAM) steel and China Low-activation Ferritic (CLF-1) steel, have been developed. The gas evolution permeation technique has been used to investigate diffusive transport parameters of deuterium through CLAM and CLF-1 over the temperature range 623 ∼ 873 K at deuterium pressure of 105 Pa. The resultant transport parameters are: Φ (mol. m-1 s-1 Pa-1/2) = 5.40 × 10-8 exp (-46.8 (kJ. mol-1)/RT), D(m2 s-1) = 3.81 × 10-7 exp(-24.0(kJ. mol-1)/RT) and S (mol. m-3 Pa-1/2) = 1.42 × 10-1 exp(-22.8(kJ. mol-1)/RT) for CLAM; while Φ(mol m-1 s-1 Pa-1/2) = 1.76 × 10-8 exp(-43.9(kJ. mol-1)/RT), D(m2. s-1) = 1.02 × 10-7 exp(-16.9(kJ. mol-1)/RT) and S(mol. m-1 Pa-1/2) = 1.73 × 10-1 exp(-27.0(kJ. mol-1) /RT) for CLF-1. The results show that CLAM is more permeable than CLF-1, thus it is easier for hydrogen isotopes to transport and be removed.

  9. HIGH TEMPERATURE BRAZING ALLOY FOR JOINT Fe-Cr-Al MATERIALS AND AUSTENITIC AND FERRITIC STAINLESS STEELS

    DOEpatents

    Cost, R.C.

    1958-07-15

    A new high temperature brazing alloy is described that is particularly suitable for brazing iron-chromiumaluminum alloys. It consists of approximately 20% Cr, 6% Al, 10% Si, and from 1.5 to 5% phosphorus, the balance being iron.

  10. Effect of mechanical restraint on weldability of reduced activation ferritic/martensitic steel thick plates

    NASA Astrophysics Data System (ADS)

    Serizawa, Hisashi; Nakamura, Shinichiro; Tanaka, Manabu; Kawahito, Yousuke; Tanigawa, Hiroyasu; Katayama, Seiji

    2011-10-01

    As one of the reduced activation ferritic/martensitic steels, the weldability of thick F82H plate was experimentally examined using new heat sources in order to minimize the total heat input energy in comparison with TIG welding. A full penetration of 32 mm thick plate could be produced as a combination of a 12 mm deep first layer generated by a 10 kW fiber laser beam and upper layers deposited by a plasma MIG hybrid welding with Ar + 2%O shielding gas. Also, the effect of mechanical restraint on the weldability under EB welding of thick F82H plate was studied by using FEM to select an appropriate specimen size for the basic test. The appropriate and minimum size for the basic test of weldability under EB welding of 90 mm thick plate might be 200 mm in length and 400 mm in width where the welding length should be about 180 mm.

  11. Development of Reduced Activation Ferritic-Martensitic Steels and fabrication technologies for Indian test blanket module

    NASA Astrophysics Data System (ADS)

    Raj, Baldev; Jayakumar, T.

    2011-10-01

    For the development of Reduced Activation Ferritic-Martensitic Steel (RAFMS), for the Indian Test Blanket Module for ITER, a 3-phase programme has been adopted. The first phase consists of melting and detailed characterization of a laboratory scale heat conforming to Eurofer 97 composition, to demonstrate the capability of the Indian industry for producing fusion grade steel. In the second phase which is currently in progress, the chemical composition will be optimized with respect to tungsten and tantalum for better combination of mechanical properties. Characterization of the optimized commercial scale India-specific RAFM steel will be carried out in the third phase. The first phase of the programme has been successfully completed and the tensile, impact and creep properties are comparable with Eurofer 97. Laser and electron beam welding parameters have been optimized and welding consumables were developed for Narrow Gap - Gas Tungsten Arc welding and for laser-hybrid welding.

  12. Tensile and creep properties of reduced activation ferritic-martensitic steel for fusion energy application

    NASA Astrophysics Data System (ADS)

    Mathew, M. D.; Vanaja, J.; Laha, K.; Varaprasad Reddy, G.; Chandravathi, K. S.; Bhanu Sankara Rao, K.

    2011-10-01

    Tensile and creep properties of a reduced activation ferritic-martensitic (RAFM) steel for Indian Test Blanket Module (TBM) to be tested in ITER have been evaluated. The tensile strength was found to decrease with temperature; the rate of decrease being slower in the intermediate temperature range of 450-650 K. Tensile ductility of the steel decreased with increase in temperature up to 650 K, followed by a rapid increase beyond 650 K. Creep studies have been carried out at 773, 823 and 873 K over a stress range of 100-300 MPa. The variation of minimum creep rate with applied stress followed a power law, ɛ = Aσ n. The ' n' value decreased with increase in temperature. The creep rupture life was found to relate inversely with minimum creep rate through the Monkman-Grant relation, t r · ɛ = constant. The tensile and creep properties of the steel were comparable with those of Eurofer 97.

  13. Mechanical property changes of low activation ferritic/martensitic steels after neutron irradiation

    NASA Astrophysics Data System (ADS)

    Kohno, Y.; Kohyama, A.; Hirose, T.; Hamilton, M. L.; Narui, M.

    Mechanical property changes of Fe- XCr-2W-0.2V,Ta ( X: 2.25-12) low activation ferritic/martensitic steels including Japanese Low Activation Ferritic/martensitic (JLF) steels and F82H after neutron irradiation were investigated with emphasis on Charpy impact property, tensile property and irradiation creep properties. Dose dependence of ductile-to-brittle transition temperature (DBTT) in JLF-1 (9Cr steel) irradiated at 646-700 K increased with irradiation up to 20 dpa and then decreased with further irradiation showing highest DBTT of 260 K at 20 dpa. F82H showed similar dose dependence in DBTT to JLF-1 with higher transition temperature than that of JLF-1 at the same displacement damage. Yield strength in JLF steels and F82H showed similar dose dependence to that of DBTT. Yield strength increased with irradiation up to 15-20 dpa and then decreased to saturate above about 40 dpa. Irradiation hardening in 7-9%Cr steels (JLF-1, JLF-3, F82H) were observed to be smaller than those in steels with 2.25%Cr (JLF-4) or 12%Cr (JLF-5). Dependences of creep strain on applied hoop stress and neutron fluence were measured to be 1.5 and 1, respectively. Temperature dependence of creep coefficient showed a maximum at about 700 K which was caused by irradiation induced void formation or irradiation enhanced creep deformation. Creep coefficient of F82H was larger than those of JLF steels above 750 K. This was considered to be caused by the differences in N and Ta concentration between F82H and JLF steels.

  14. Effects of surface conditions on the plasma-driven permeation behavior through a ferritic steel alloy observed in VEHICLE-1 and QUEST

    NASA Astrophysics Data System (ADS)

    Zhou, H.; Hirooka, Y.; Zushi, H.; Kuzmin, A.; Ashikawa, N.; Muroga, T.; Sagara, A.

    2015-08-01

    Effects of surface conditions on the plasma-driven permeation of hydrogen through a ferritic steel alloy F82H have been studied in a laboratory-scale plasma device: VEHICLE-1 and the medium-sized spherical tokamak: QUEST. Both of the surface contamination and area effects have been examined and discussed. Thick surface impurity film has been found to act as a second layer for diffusion and affect the permeation behavior in laboratory-scale and tokamak experiments. Hydrogen diffusion coefficient in the impurity layer has been estimated using the multi-layer diffusion model. A decrease in steady state permeation flux has been measured when increasing the plasma-facing surface area, which is in agreement with theoretical prediction.

  15. Elevated temperature creep properties for selected active metal braze alloys

    SciTech Connect

    Stephens, J.J.

    1997-02-01

    Active metal braze alloys reduce the number of processes required for the joining of metal to ceramic components by eliminating the need for metallization and/or Ni plating of the ceramic surfaces. Titanium (Ti), V, and Zr are examples of active element additions which have been used successfully in such braze alloys. Since the braze alloy is expected to accommodate thermal expansion mismatch strains between the metal and ceramic materials, a knowledge of its elevated temperature mechanical properties is important. In particular, the issue of whether or not the creep strength of an active metal braze alloy is increased or decreased relative to its non-activated counterpart is important when designing new brazing processes and alloy systems. This paper presents a survey of high temperature mechanical properties for two pairs of conventional braze alloys and their active metal counterparts: (a) the conventional 72Ag-28Cu (Cusil) alloy, and the active braze alloy 62.2Ag- 36.2Cu-1.6Ti (Cusil ABA), and (b) the 82Au-18Ni (Nioro) alloy and the active braze alloy Mu-15.5M-0.75Mo-1.75V (Nioro ABA). For the case of the Cusil/Cusil ABA pair, the active metal addition contributes to solid solution strengthening of the braze alloy, resulting in a higher creep strength as compared to the non-active alloy. In the case of the Nioro/Nioro ABA pair, the Mo and V additions cause the active braze alloy to have a two-phase microstructure, which results in a reduced creep strength than the conventional braze alloy. The Garofalo sinh equation has been used to quantitatively describe the stress and temperature dependence of the deformation behavior. It will be observed that the effective stress exponent in the Garofalo sinh equation is a function of the instantaneous value of the stress argument.

  16. Diffusion Bonding Beryllium to Reduced Activation Ferritic Martensitic Steel: Development of Processes and Techniques

    NASA Astrophysics Data System (ADS)

    Hunt, Ryan Matthew

    Only a few materials are suitable to act as armor layers against the thermal and particle loads produced by magnetically confined fusion. These candidates include beryllium, tungsten, and carbon fiber composites. The armor layers must be joined to the plasma facing components with high strength bonds that can withstand the thermal stresses resulting from differential thermal expansion. While specific joints have been developed for use in ITER (an experimental reactor in France), including beryllium to CuCrZr as well as tungsten to stainless steel interfaces, joints specific to commercially relevant fusion reactors are not as well established. Commercial first wall components will likely be constructed front Reduced Activation Ferritic Martensitic (RAFM) steel, which will need to be coating with one of the three candidate materials. Of the candidates, beryllium is particularly difficult to bond, because it reacts during bonding with most elements to form brittle intermetallic compounds. This brittleness is unacceptable, as it can lead to interface crack propagation and delamination of the armor layer. I have attempted to overcome the brittle behavior of beryllium bonds by developing a diffusion bonding process of beryllium to RAFM steel that achieves a higher degree of ductility. This process utilized two bonding aids to achieve a robust bond: a. copper interlayer to add ductility to the joint, and a titanium interlayer to prevent beryllium from forming unwanted Be-Cu intermetallics. In addition, I conducted a series of numerical simulations to predict the effect of these bonding aids on the residual stress in the interface. Lastly, I fabricated and characterized beryllium to ferritic steel diffusion bonds using various bonding parameters and bonding aids. Through the above research, I developed a process to diffusion bond beryllium to ferritic steel with a 150 M Pa tensile strength and 168 M Pa shear strength. This strength was achieved using a Hot Isostatic

  17. Manifestation of weak ferromagnetism and photocatalytic activity in bismuth ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Sakar, M.; Balakumar, S.; Saravanan, P.; Jaisankar, S. N.

    2013-02-01

    Bismuth ferrite (BFO) nanoparticles were synthesized by auto-ignition technique with and without adding ignition fuel such as citric acid. The presence of citric acid in the reaction mixture yielded highly-magnetic BFO/γ-Fe2O3 nanocomposite. When this composite was annealed to 650°C, a single phase BFO was formed with average crystallite size of 50 nm and showed weak ferromagnetic behavior. Conversely, the phase pure BFO prepared without adding citric acid exhibited antiferromagnetism because of its larger crystallite size of around 70 nm. The visible-light driven photocatalytic activity of both the pure BFO and BFO/γ-Fe2O3 nanocomposite were examined by degrading methyl orange dye. The pure BFO showed a moderate photocatalytic activity; while BFO/γ-Fe2O3 nanocomposite showed enhanced activity. This could be probably due to the optimal band gap ratio between BFO and γ-Fe2O3 phases reduced the recombination of electron-hole pairs which aided in the enhancement of photocatalytic activity.

  18. Manifestation of weak ferromagnetism and photocatalytic activity in bismuth ferrite nanoparticles

    SciTech Connect

    Sakar, M.; Balakumar, S.; Saravanan, P.; Jaisankar, S. N.

    2013-02-05

    Bismuth ferrite (BFO) nanoparticles were synthesized by auto-ignition technique with and without adding ignition fuel such as citric acid. The presence of citric acid in the reaction mixture yielded highly-magnetic BFO/{gamma}-Fe{sub 2}O{sub 3} nanocomposite. When this composite was annealed to 650 Degree-Sign C, a single phase BFO was formed with average crystallite size of 50 nm and showed weak ferromagnetic behavior. Conversely, the phase pure BFO prepared without adding citric acid exhibited antiferromagnetism because of its larger crystallite size of around 70 nm. The visible-light driven photocatalytic activity of both the pure BFO and BFO/{gamma}-Fe{sub 2}O{sub 3} nanocomposite were examined by degrading methyl orange dye. The pure BFO showed a moderate photocatalytic activity; while BFO/{gamma}-Fe{sub 2}O{sub 3} nanocomposite showed enhanced activity. This could be probably due to the optimal band gap ratio between BFO and {gamma}-Fe{sub 2}O{sub 3} phases reduced the recombination of electron-hole pairs which aided in the enhancement of photocatalytic activity.

  19. Study on the activated laser welding of ferritic stainless steel with rare earth elements yttrium

    NASA Astrophysics Data System (ADS)

    Wang, Yonghui; Hu, Shengsun; Shen, Junqi

    2015-10-01

    The ferritic stainless steel SUS430 was used in this work. Based on a multi-component activating flux, composed of 50% ZrO2, 12.09 % CaCO3, 10.43 % CaO, and 27.49 % MgO, a series of modified activating fluxes with 0.5%, 1%, 2%, 5%, 10%, 15%, and 20% of rare earth (RE) element yttrium (Y) respectively were produced, and their effects on the weld penetration (WP) and corrosion resistant (CR) property were studied. Results showed that RE element Y hardly had any effects on increasing the WP. In the FeCl3 spot corrosion experiment, the corrosion rates of almost all the samples cut from welded joints turned out to be greater than the parent metal (23.51 g/m2 h). However, there was an exception that the corrosion rate of the sample with 5% Y was only 21.96 g/m2 h, which was even better than parent metal. The further Energy Dispersive Spectrometer (EDS) test showed the existence of elements Zr, Ca, O, and Y in the molten slag near the weld seam while none of them were found in the weld metal, indicating the direct transition of element from activating fluxes to the welding seam did not exist. It was known that certain composition of activating fluxes effectively restrain the loss of Cr element in the process of laser welding, and as a result, the CR of welded joints was improved.

  20. Irradiation creep and swelling from 400 to 600 °C of the oxide dispersion strengthened ferritic alloy MA957

    NASA Astrophysics Data System (ADS)

    Toloczko, M. B.; Gelles, D. S.; Garner, F. A.; Kurtz, R. J.; Abe, K.

    2004-08-01

    An irradiation creep and swelling study was performed on the Y 2O 3-strengthened ODS ferritic steel MA957. Pressurized tubes were irradiated in the Fast Flux Test Facility (FFTF) to doses ranging from 40 to 110 dpa at temperatures ranging from 400 to 600 °C. None of the stress-free tubes exhibited any evidence of swelling as determined by diameter change measurements. With a few exceptions, the irradiation creep behavior is similar to that of conventional ferritic-martensitic steels. Calculated creep compliance values are equal to those of HT9 irradiated within the same temperature range, except at 600 °C where the creep rate of MA957 is about one-half the value for HT9. The magnitude of the creep transient for MA957 is comparable to HT9, again except at 600 °C where the transient is much lower for MA957.

  1. Ferrite morphology and variations in ferrite content in austenitic stainless steel welds

    SciTech Connect

    David, S.A.; Hanzelka, S.E.; Haltom, C.P.

    1981-07-01

    Four distinct ferrite morphologies have been identified in type 308 stainless steel multipass welds: vermicular, lacy, acicular, and globular. The first three ferrite types are related to transformations following solidification and the fourth is related to the shape instability of the residual ferrite. An earlier study showed that most of the ferrite observed in austenitic stainless steel welds contaning a duplex structure may be identified as residual primary ferrite resulting from incomplete delta ..-->.. ..gamma.. transformation during solidification and/or residual ferrite after Widmanstaetten austenite precipitation in primary ferrite. These modes of ferrite formation can be used to explain observed ferrite morphologies in austenitic stainless steel welds. Variations in ferrite content within the weld were related to weld metal composition, ferrite morphology, and dissolution of ferrite resulting from thermal cycles during subsequent weld passes. An investigation of the type 308 stainless steel filler metal solidified over cooling rates ranging from 7 to 1600/sup 0/C/s showed that the cooling rate of the weld metal within the freezing range of the alloy affects the amount of ferrite in the microstructure very litte. However, the scale of the solidification substructure associated with various solidification rates may influence the ferrite dissolution kinetics.

  2. Ferrite morphology and variations in ferrite content in austenitic stainless steel welds

    SciTech Connect

    David, S.A.

    1981-04-01

    Four distinct ferrite morphologies have been identified in Type 308 stainless steel multipass welds: vermicular, lacy, acicular, and globular. The first three ferrite types are related to transformations following solidfication and the fourth is related to the shape instability of the residual ferrite. An earlier study showed that most of the ferrite observed in austenitic stainless steel welds containing a duplex structure may be identified as residual primary ferrite resulting from incomplete delta ..-->.. ..gamma.. transformation during solidification and/or residual ferrite after Widmanstatten austenite precipitation in primary ferrite. These modes of ferrite formation can be used to explain observed ferrite morphologies in austenitic stainless steel welds. Variations in ferrite content within the weld were also related to weld metal composition, ferrite morphology, and dissolution of ferrite resulting from thermal cycles during subsequent weld passes. An investigation of the Type 308 stainless steel filler metal solidified over cooling rates ranging from 7 to 1600/sup 0/C/s (44.6 to 2912/sup 0/F/s) showed that the cooling rate of the weld metal within the freezing range of the alloy affects the amount of ferrite in the microstructure very little. However, the scale of the solidification substructure associated with various solidification rates may influence the ferrite dissolution kinetics.

  3. Studies on A-TIG welding of Low Activation Ferritic/Martensitic (LAFM) steel

    NASA Astrophysics Data System (ADS)

    Vasantharaja, P.; Vasudevan, M.

    2012-02-01

    Low Activation Ferritic-Martensitic steels (LAFM) are chosen as the candidate material for structural components in fusion reactors. The structural components are generally fabricated by welding processes. Activated Tungsten Inert Gas (A-TIG) welding is an emerging process for welding of thicker components. In the present work, attempt was made to develop A-TIG welding technology for LAFM steel plates of 10 mm thick. Activated flux was developed for LAFM steel by carrying out various bead-on-plate TIG welds without flux and with flux. The optimum flux was identified as one which gave maximum depth of penetration at minimum heat input values. With the optimized flux composition, LAFM steel plate of 10 mm thickness was welded in square butt weld joint configuration using double side welding technique. Optical and Scanning Electron Microscopy was used for characterizing the microstructures. Microhardness measurements were made across the weld cross section for as welded and post weld heat treated samples. Tensile and impact toughness properties were determined. The mechanical properties values obtained in A-TIG weld joint were comparable to that obtained in weld joints of LAFM steel made by Electron beam welding process.

  4. Characterization of low alloy ferritic steel–Ni base alloy dissimilar metal weld interface by SPM techniques, SEM/EDS, TEM/EDS and SVET

    SciTech Connect

    Wang, Siyan; Ding, Jie; Ming, Hongliang; Zhang, Zhiming; Wang, Jianqiu

    2015-02-15

    The interface region of welded A508–Alloy 52 M is characterized by scanning probe microscope (SPM) techniques, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM)/Energy Dispersive Spectroscopy (EDS) and scanning vibrate electrode technique (SVET). The regions along the welded A508–Alloy 52 M interface can be categorized into two types according to their different microstructures. In the type-I interface region, A508 and Alloy 52 M are separated by the fusion boundary, while in the type-II interface region, A508 and Alloy 52 M are separated by a martensite zone. A508, martensite zone and grain boundaries in Alloy 52 M are ferromagnetic while the Alloy 52 M matrix is paramagnetic. The Volta potentials measured by scanning Kelvin probe force microscopy (SKPFM) of A508, martensite zone and Alloy 52 M follow the order: V{sub 52} {sub M} > V{sub A508} > V{sub martensite}. The corrosion behavior of A508–Alloy 52 M interface region is galvanic corrosion, in which Alloy 52 M is cathode while A508 is anode. The martensite dissolves faster than Alloy 52 M, but slower than A508 in the test solution. - Highlights: • The A508–Alloy 52 M interface regions can be categorized into two types. • The chromium depleted region is observed along the Alloy 52 M grain boundary. • The Alloy 52 M grain boundaries which are close to the interface are ferromagnetic. • Martensite zone has lower Volta potential but higher corrosion resistance than A508.

  5. Magnetic properties and adsorptive performance of manganese–zinc ferrites/activated carbon nanocomposites

    SciTech Connect

    Zhang, B.B.; Xu, J.C.; Xin, P.H.; Han, Y.B.; Hong, B.; Jin, H.X.; Jin, D.F.; Peng, X.L.; Li, J.; Gong, J.; Ge, H.L.; Zhu, Z.W.; Wang, X.Q.

    2015-01-15

    Owing to the unique microstructure and high specific surface area, activated carbon (AC) could act as an excellent adsorbent for wastewater treatment and good carrier for functional materials. In this paper, manganese–zinc ferrites (Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}: MZF) were anchored into AC by hydrothermal method, resulting in the excellent magnetic response for AC nanocomposites in wastewater treatment. All results demonstrated the magnetic nanoparticles presented a spinel phase structure and existed in the pores of AC. The saturation magnetization (Ms) of MZF/AC nanocomposites increased with the ferrites content, while the pore volume and specific surface area declined. The Sample-5 possessed the specific surface area of 1129 m{sup 2} g{sup −1} (close to 1243 m{sup 2} g{sup −1} of AC) and Ms of 3.96 emu g{sup −1}. Furthermore, the adsorptive performance for organic dyes was studied and 99% methylene blue was adsorbed in 30 min. The magnetic AC nanocomposites could be separated easily from solution by magnetic separation technique. - Graphical abstract: The Sample-5 presented both good magnetic response and high BET surface area up to 1129 m{sup 2} g{sup −1} (close to AC of 1243 m{sup 2} g{sup −1}), which could be separated completely for about 60 s. MZF/AC nanocomposites (Sample-3, 4, 5) in our work could be used as the magnetic absorbents, which could be separated easily by an outer magnet after the MB adsorption. - Highlights: • Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} (MZF) as few as possible was implanted into activated carbon (AC) for the higher surface area. • Sample-5 possessed the high specific surface area (1129 m{sup 2} g{sup −1}) and the suitable Ms (3.96 emu g{sup −1}). • Methylene blue was adsorbed almost completely by MZF/AC nanocomposites in 30 min. • MZF/AC nanocomposites were separated easily from solution by magnetic separation technique.

  6. Establishing a Scientific Basis for Optimizing Compositions, Process Paths and Fabrication Methods for Nanostructured Ferritic Alloys for Use in Advanced Fission Energy Systems

    SciTech Connect

    Odette, G Robert; Cunningham, Nicholas J., Wu, Yuan; Etienne, Auriane; Stergar, Erich; Yamamoto, Takuya

    2012-02-21

    The broad objective of this NEUP was to further develop a class of 12-15Cr ferritic alloys that are dispersion strengthened and made radiation tolerant by an ultrahigh density of Y-Ti-O nanofeatures (NFs) in the size range of less than 5 nm. We call these potentially transformable materials nanostructured ferritic alloys (NFAs). NFAs are typically processed by ball milling pre-alloyed rapidly solidified powders and yttria (Y2O3) powders. Proper milling effectively dissolves the Ti, Y and O solutes that precipitate as NFs during hot consolidation. The tasks in the present study included examining alternative processing paths, characterizing and optimizing the NFs and investigating solid state joining. Alternative processing paths involved rapid solidification by gas atomization of Fe, 14% Cr, 3% W, and 0.4% Ti powders that are also pre-alloyed with 0.2% Y (14YWT), where the compositions are in wt.%. The focus is on exploring the possibility of minimizing, or even eliminating, the milling time, as well as producing alloys with more homogeneous distributions of NFs and a more uniform, fine grain size. Three atomization environments were explored: Ar, Ar plus O (Ar/O) and He. The characterization of powders and alloys occurred through each processing step: powder production by gas atomization; powder milling; and powder annealing or hot consolidation by hot isostatic pressing (HIPing) or hot extrusion. The characterization studies of the materials described here include various combinations of: a) bulk chemistry; b) electron probe microanalysis (EPMA); c) atom probe tomography (APT); d) small angle neutron scattering (SANS); e) various types of scanning and transmission electron microscopy (SEM and TEM); and f) microhardness testing. The bulk chemistry measurements show that preliminary batches of gas-atomized powders could be produced within specified composition ranges. However, EPMA and TEM showed that the Y is heterogeneously distributed and phase separated, but

  7. Photodynamic Anticancer Activities of Multifunctional Cobalt Ferrite Nanoparticles in Various Cancer Cells.

    PubMed

    Park, Bong Joo; Choi, Kyong-Hoon; Nam, Ki Chang; Ali, Anser; Min, Joe Eun; Son, Hyungbin; Uhm, Han S; Kim, Ho-Joong; Jung, Jin-Seung; Choi, Eun Ha

    2015-02-01

    To develop novel multifunctional magnetic nanoparticles (MNPs) with good magnetic properties, biocompatibility, and anticancer activities by photodynamic therapy (PDT), we synthesized multifunctional cobalt ferrite (CoFe2O4) nanoparticles (CoFe2O4-HPs-FAs) functionalized by coating them with hematoporphyrin (HP) for introducing photo-functionality and by conjugating with folic acid (FA) for targeting cancer cells. We evaluated the activities of the CoFe2O4-HPs-FAs by checking magnetic resonance imaging (MRI) in vitro, its biocompatibility, and photodynamic anticancer activities on FA receptor (FR)-positive and FR-negative cancer cell lines, Hela, KB, MCF-7, and PC-3 cells, to use for clinical applications. In this study, we have demonstrated that the CoFe2O4-HPs-FAs have good MRI and biocompatibility with non-cytotoxicity, and remarkable photodynamic anticancer activities at very low concentrations regardless of cell types. Particularly, the photo-killing abilities in 3.13 μg/mL of CoFe2O4-HPs-FAs were measured to be 91.8% (p < 0.002) for Hela, 94.5% (p < 0.007) for KB, 79.1% (p < 0.003) for MCF-7, and 71.3% (p < 0.006) for PC-3. The photodynamic anticancer activities in 6.25 and 12.5 μg/mL of CoFe2O4-HPs-FAs were measured to be over 95% (p < 0.004) to almost 100% regardless of cell types. The newly developed multifunctional CoFe2O4-HPs-FAs are effective for PDT and have potential as therapeutic agents for MRI-based PDT, because they have a high saturation value of magnetization and superparamagnetism. PMID:26349298

  8. Calcium alloy as active material in secondary electrochemical cell

    DOEpatents

    Roche, Michael F.; Preto, Sandra K.; Martin, Allan E.

    1976-01-01

    Calcium alloys such as calcium-aluminum and calcium-silicon, are employed as active material within a rechargeable negative electrode of an electrochemical cell. Such cells can use a molten salt electrolyte including calcium ions and a positive electrode having sulfur, sulfides, or oxides as active material. The calcium alloy is selected to prevent formation of molten calcium alloys resulting from reaction with the selected molten electrolytic salt at the cell operating temperatures.

  9. Characterization of TiN, TiC and Ti(C,N) in titanium-alloyed ferritic chromium steels focusing on the significance of different particle morphologies

    SciTech Connect

    Michelic, S.K.; Loder, D.; Reip, T.; Ardehali Barani, A.; Bernhard, C.

    2015-02-15

    Titanium-alloyed ferritic chromium steels are a competitive option to classical austenitic stainless steels owing to their similar corrosion resistance. The addition of titanium significantly influences their final steel cleanliness. The present contribution focuses on the detailed metallographic characterization of titanium nitrides, titanium carbides and titanium carbonitrides with regard to their size, morphology and composition. The methods used are manual and automated Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy as well as optical microscopy. Additional thermodynamic calculations are performed to explain the precipitation procedure of the analyzed titanium nitrides. The analyses showed that homogeneous nucleation is decisive at an early process stage after the addition of titanium. Heterogeneous nucleation gets crucial with ongoing process time and essentially influences the final inclusion size of titanium nitrides. A detailed investigation of the nuclei for heterogeneous nucleation with automated Scanning Electron Microscopy proved to be difficult due to their small size. Manual Scanning Electron Microscopy and optical microscopy have to be applied. Furthermore, it was found that during solidification an additional layer around an existing titanium nitride can be formed which changes the final inclusion morphology significantly. These layers are also characterized in detail. Based on these different inclusion morphologies, in combination with thermodynamic results, tendencies regarding the formation and modification time of titanium containing inclusions in ferritic chromium steels are derived. - Graphical abstract: Display Omitted - Highlights: • The formation and modification of TiN in the steel 1.4520 was examined. • Heterogeneous nucleation essentially influences the final steel cleanliness. • In most cases heterogeneous nuclei in TiN inclusions are magnesium based. • Particle morphology provides important information

  10. Status of ATR-A1 irradiation experiment on vanadium alloys and low-activation steels

    SciTech Connect

    Tsai, H.; Strain, R.V.; Gomes, I.; Smith, D.L.; Matsui, H.

    1996-10-01

    The ATR-A1 irradiation experiment was a collaborative U.S./Japan effort to study at low temperature the effects of neutron damage on vanadium alloys. The experiment also contained a limited quantity of low-activation ferritic steel specimens from Japan as part of the collaboration agreement. The irradiation started in the Advanced Test Reactor (ATR) on November 30, 1995, and ended as planned on May 5, 1996. Total exposure was 132.9 effective full power days (EFPDs) and estimated neutron damage in the vanadium was 4.7 dpa. The vehicle has been discharged from the ATR core and is scheduled to be disassembled in the next reporting period.

  11. Effects of neutron irradiation on microstructural evolution in candidate low activation ferritic steels

    NASA Astrophysics Data System (ADS)

    Kohno, Yutaka; Kohyama, Akira; Yoshino, Masahiko; Asakura, Kentaro

    1994-09-01

    Fe-(2.25-12)Cr-2W-V, Ta low activation ferritic steels (JLF series steels) were developed in the fusion materials development program of Japanese universities. Microstructural observations, including precipitation response, were performed after neutron irradiation in the FFTF/MOTA. The preirradiation microstructure was stable after irradiation at low temperature (< 683 K). Recovery of martensitic lath structure and coarsening of precipitates took place above 733 K. Precipitates observed after irradiation were the same as those in unirradiated materials in 7-9Cr steels, and no irradiation induced phase was identified. The irradiation induced shift in DBTT in the 9Cr-2W steel proved to be very small which is a reflection of stable precipitation response in these steels. A high density of fine α' precipitates was observed in the 12Cr steel which might be responsible for the large irradiation hardening found in the 12Cr steel. Void formation was observed in 7-9Cr steels irradiated at 683 K, but the amount of void swelling was very small.

  12. Influence of Prior Fatigue Cycling on Creep Behavior of Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Sarkar, Aritra; Vijayanand, V. D.; Parameswaran, P.; Shankar, Vani; Sandhya, R.; Laha, K.; Mathew, M. D.; Jayakumar, T.; Rajendra Kumar, E.

    2014-06-01

    Creep tests were carried out at 823 K (550 °C) and 210 MPa on Reduced Activation Ferritic-Martensitic (RAFM) steel which was subjected to different extents of prior fatigue exposure at 823 K at a strain amplitude of ±0.6 pct to assess the effect of prior fatigue exposure on creep behavior. Extensive cyclic softening that characterized the fatigue damage was found to be immensely deleterious for creep strength of the tempered martensitic steel. Creep rupture life was reduced to 60 pct of that of the virgin steel when the steel was exposed to as low as 1 pct of fatigue life. However, creep life saturated after fatigue exposure of 40 pct. Increase in minimum creep rate and decrease in creep rupture ductility with a saturating trend were observed with prior fatigue exposures. To substantiate these findings, detailed transmission electron microscopy studies were carried out on the steel. With fatigue exposures, extensive recovery of martensitic-lath structure was distinctly observed which supported the cyclic softening behavior that was introduced due to prior fatigue. Consequently, prior fatigue exposures were considered responsible for decrease in creep ductility and associated reduction in the creep rupture strength.

  13. Effect of silicon on the microstructure and mechanical properties of reduced activation ferritic/martensitic steel

    NASA Astrophysics Data System (ADS)

    Chen, Shenghu; Rong, Lijian

    2015-04-01

    The effect of Si in the range of 0.05-0.77 wt.% on the microstructure, tensile properties and impact toughness of reduced activation ferritic/martensitic (RAFM) steels has been investigated. An increase in Si content affected the prior austenite grain size resulting in an increase in the tensile strength at room temperature. The tensile strength of steels tested above 773 K did not change significantly with the addition of Si, which was due to the diminished carbide hardening effect and boundary strengthening effect. Detailed fractographic analysis revealed that tear fractures occurred in the samples tensile tested at room temperature, while cup and cone fractures were found in samples tensile tested at temperatures above 773 K, which were induced by the easing of dislocation pile-ups. The ductile-to-brittle transition temperature (DBTT) decreased when the Si content increased to 0.22 wt.%. However, the DBTT increased when the Si content reached 0.77 wt.% and this was due to the precipitation of Laves phase. The RAFM steel with approximately 0.22 wt.% Si content was found to possess an optimized combination of microstructure, tensile properties and impact toughness.

  14. Dynamic strain aging behavior of modified 9Cr-1Mo and reduced activation ferritic martensitic steels under low cycle fatigue

    NASA Astrophysics Data System (ADS)

    Mariappan, K.; Shankar, Vani; Sandhya, R.; Prasad Reddy, G. V.; Mathew, M. D.

    2013-04-01

    Influence of temperature and strain rate on low cycle fatigue (LCF) behavior of modified 9Cr-1Mo ferritic martensitic steel and 1.4W-0.06Ta reduced activation ferritic martensitic (RAFM) steel in normalized and tempered conditions was studied. Total strain controlled LCF tests between 300 and 873 K on modified 9Cr-1Mo steel and RAFM steel and at various strain rates on modified 9Cr-1Mo steel were performed at total strain amplitude of ±0.6%. Both the steels showed continuous cyclic softening at all temperatures. Whereas manifestations of dynamic strain aging (DSA) were observed in both the steels which decreased fatigue life at intermediate temperatures, at higher temperatures, oxidation played a crucial role in decreasing fatigue life.

  15. Deformation mechanisms in a precipitation-strengthened ferritic super alloy revealed by in situ neutron dffraction studies at elevated temperatures

    SciTech Connect

    Huang, Shenyan; Gao, Yanfei; An, Ke; Zheng, Lili; Teng, Zhenke; Wu, Wei; Liaw, Peter K.

    2015-01-01

    The ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)AlB2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.

  16. Long term high temperature oxidation characteristics of La and Cu alloyed ferritic stainless steels for solid oxide fuel cell interconnects

    NASA Astrophysics Data System (ADS)

    Swaminathan, Srinivasan; Lee, Young-Su; Kim, Dong-Ik

    2016-09-01

    To ensure the best performance of solid oxide fuel cell metallic interconnects, the Fe-22 wt.% Cr ferritic stainless steels with various La contents (0.006-0.6 wt.%) and Cu addition (1.57 wt.%), are developed. Long-term isothermal oxidation behavior of these steels is investigated in air at 800 °C, for 2700 h. Chemistry, morphology, and microstructure of the thermally grown oxide scale are examined using XPS, SEM-EDX, and XRD techniques. Broadly, all the steels show a double layer consisting of an inner Cr2O3 and outer (Mn, Cr)3O4. Distinctly, in the La-added steels, binary oxides of Cr, Mn and Ti are found at the oxide scale surface together with (Mn, Cr)3O4. Furthermore, all La-varied steels possess the metallic Fe protrusions along with discontinuous (Mn, Cr)3O4 spinel zones at the oxide scale/metal interface and isolated precipitates of Ti-oxides in the underlying matrix. Increase of La content to 0.6 wt.% is detrimental to the oxidation resistance. For the Cu-added steel, Cu is found to segregate strongly at the oxide scale/metal interface which inhibits the ingress of oxygen thereby suppressing the subscale formation of (Mn, Cr)3O4. Thus, Cu addition to the Fe-22Cr ferritic stainless steels benefits the oxidation resistance.

  17. Effect of V and Ta on the precipitation behavior of 12%Cr reduced activation ferrite/martensite steel

    SciTech Connect

    Xiao, Xiang; Liu, Guoquan; Hu, Benfu; Wang, Jinsan; Ullah, Asad

    2013-08-15

    12%Cr reduced activation ferrite/martensite steels are promising candidate materials for good corrosion and irradiation resistance used for supercritical water-cooled reactor cladding and in-core components. V and Ta are considered to have improved the creep strength of high Cr steels by precipitating as MX phase. In this paper, a series of trial products microalloyed with V and V–Ta are produced, and the microstructure is characterized after quenching at 1050 °C and tempering at 780 °C by using TEM method to investigate the effect of these elements on the precipitation behavior of 12%Cr reduced activation ferrite/martensite steel. The results from both the experimental observations and thermodynamic and kinetic calculations reveal that V and V–Ta can promote the stable MX precipitation instead of M{sub 2}X, thus increasing the volume fraction of M{sub 23}C{sub 6}. Two-phase separation behavior of the (Ta, V)(C, N) carbonitride into a Ta(V)C(N) phase and a V(Ta)N(C) phase in 12Cr3WVTa steel is observed and further discussed. - Highlights: • Microalloyed with V and V-Ta can promote the precipitation of MX instead of M{sub 2}X. • The presence of delta-ferrite in microstructure affects the morphology of MX. • Two-phase separation of MX carbonitride was observed in 12Cr3WVTa steel.

  18. Shear Punch Properties of Low Activation Ferritic Steels Following Irradiation in ORR

    SciTech Connect

    Ermi, Ruby M.; Hamilton, Margaret L.; Gelles, David S.; Ermi, August M.

    2001-10-01

    Shear punch post-irradiation test results are reported for a series of low activation steels containing Mn following irradiation in the Oak Ridge Reactor at 330 and 400 degrees centigrade to {approx}10 dpa. Alloy compositions included 2Cr, 9Cr and 12Cr steels with V to 1.5% and W to 1.0%. Comparison of results with tensile test results showed good correlations with previously observed trends except where disks were improperly manufactured because they were too thin or because engraving was faulty.

  19. Harnessing microbial subsurface metal reduction activities to synthesise nanoscale cobalt ferrite with enhanced magnetic properties

    SciTech Connect

    Coker, Victoria S.; Telling, Neil D.; van der Laan, Gerrit; Pattrick, Richard A.D.; Pearce, Carolyn I.; Arenholz, Elke; Tuna, Floriana; Winpenny, Richard E.P.; Lloyd, Jonathan R.

    2009-03-24

    Nanoscale ferrimagnetic particles have a diverse range of uses from directed cancer therapy and drug delivery systems to magnetic recording media and transducers. Such applications require the production of monodisperse nanoparticles with well-controlled size, composition, and magnetic properties. To fabricate these materials purely using synthetic methods is costly in both environmental and economical terms. However, metal-reducing microorganisms offer an untapped resource to produce these materials. Here, the Fe(III)-reducing bacterium Geobacter sulfurreducens is used to synthesize magnetic iron oxide nanoparticles. A combination of electron microscopy, soft X-ray spectroscopy, and magnetometry techniques was employed to show that this method of biosynthesis results in high yields of crystalline nanoparticles with a narrow size distribution and magnetic properties equal to the best chemically synthesized materials. In particular, it is demonstrated here that cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles with low temperature coercivity approaching 8 kOe and an effective anisotropy constant of {approx} 10{sup 6} erg cm{sup -3} can be manufactured through this biotechnological route. The dramatic enhancement in the magnetic properties of the nanoparticles by the introduction of high quantities of Co into the spinel structure represents a significant advance over previous biomineralization studies in this area using magnetotactic bacteria. The successful production of nanoparticulate ferrites achieved in this study at high yields could open up the way for the scaled-up industrial manufacture of nanoparticles using environmentally benign methodologies. Production of ferromagnetic nanoparticles for pioneering cancer therapy, drug delivery, chemical sensors, catalytic activity, photoconductive materials, as well as more traditional uses in data storage embodies a large area of inorganic synthesis research. In particular, the addition of transition metals other than

  20. Effect of heat treatment and irradiation temperature on impact behavior of irradiated reduced-activation ferritic steels

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.

    1998-03-01

    Charpy tests were conducted on eight normalized-and-tempered reduced-activation ferritic steels irradiated in two different normalized conditions. Irradiation was conducted in the Fast Flux Test Facility at 393 C to {approx}14 dpa on steels with 2.25, 5, 9, and 12% Cr (0.1% C) with varying amounts of W, V, and Ta. The different normalization treatments involved changing the cooling rate after austenitization. The faster cooling rate produced 100% bainite in the 2.25 Cr steels, compared to duplex structures of bainite and polygonal ferrite for the slower cooling rate. For both cooling rates, martensite formed in the 5 and 9% Cr steels, and martensite with {approx}25% {delta}-ferrite formed in the 12% Cr steel. Irradiation caused an increase in the ductile-brittle transition temperature (DBTT) and a decrease in the upper-shelf energy. The difference in microstructure in the low-chromium steels due to the different heat treatments had little effect on properties. For the high-chromium martensitic steels, only the 5 Cr steel was affected by heat treatment. When the results at 393 C were compared with previous results at 365 C, all but a 5 Cr and a 9 Cr steel showed the expected decrease in the shift in DBTT with increasing temperature.

  1. Irradiation Creep and Swelling from 400 C to 600 C of the Oxide Dispersion Strengthened Ferritic Alloy MA957

    SciTech Connect

    Toloczko, Mychailo B.; Gelles, David S.; Garner, Francis A.; Kurtz, Richard J.; Abe, Katsunori

    2004-04-24

    Recently, there has been a growing interest in the use of oxide dispersion strengthened (ODS) ferritic steels for fusion reactor applications. As part of an extensive study performed at PNNL on the ODS steel MA957 [1], irradiation creep tests were performed on pressurized tubes made from MA957 by two different methods. The tubes were made either by gun drilling alone or by a combination of rod drawing and gun drilling. The different fabrication methods were explored because ODS steels have been difficult to form. The pressurized tubes were irradiated in the Fast Flux Test Facility (FFTF) to doses ranging from 40 dpa to 110 dpa at temperatures ranging from 400 C to 600 C. The effective stresses resulting from the pressurization of the tubes ranged from 0 MPa to 175 MPa.

  2. Delta ferrite-containing austenitic stainless steel resistant to the formation of undesirable phases upon aging

    SciTech Connect

    Leitnaker, J.M.

    1981-05-05

    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 015-0.030 times the volume percent ferrite present in alloy. The formation of chi phase upon aging is controlled by controlling the mo content.

  3. Fractographic examination of reduced activation ferritic/martensitic steel charpy specimens irradiated to 30 dpa at 370{degrees}C

    SciTech Connect

    Gelles, D.S.; Hamilton, M.L.; Schubert, L.E.

    1996-10-01

    Fractographic examinations are reported for a series of reduced activation ferritic/Martensitic steel Charpy impact specimens tested following irradiation to 30 dpa at 370{degrees}C in FFTF. One-third size specimens of six low activation steels developed for potential application as structural materials in fusion reactors were examined. A shift in brittle fracture appearance from cleavage to grain boundary failure was noted with increasing manganese content. The results are interpreted in light of transmutation induced composition changes in a fusion environment.

  4. Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Vanaja, J.; Laha, Kinkar

    2015-10-01

    Tertiary creep deformation behavior of reduced activation ferritic-martensitic (RAFM) steels having different tungsten contents has been assessed. Creep tests were carried out at 823 K (550 °C) over a stress range of 180 to 260 MPa on three heats of the RAFM steel (9Cr-W-0.06Ta-0.22V) with tungsten content of 1, 1.4, and 2.0 wt pct. With creep exposure, the steels exhibited minimum in creep rate followed by progressive increase in creep rate until fracture. The minimum creep rate decreased, rupture life increased, and the onset of tertiary stage of creep deformation delayed with the increase in tungsten content. The tertiary creep behavior has been assessed based on the relationship, , considering minimum creep rate () instead of steady-state creep rate. The increase in tungsten content was found to decrease the rate of acceleration of tertiary parameter ` p.' The relationships between (1) tertiary parameter `p' with minimum creep rate and time spent in tertiary creep deformation and (2) the final creep rate with minimum creep rate revealed that the same first-order reaction rate theory prevailed in the minimum creep rate as well as throughout the tertiary creep deformation behavior of the steel. A master tertiary creep curve of the steels has been developed. Scanning electron microscopic investigation revealed enhanced coarsening resistance of carbides in the steel on creep exposure with increase in tungsten content. The decrease in tertiary parameter ` p' with tungsten content with the consequent decrease in minimum creep rate and increase in rupture life has been attributed to the enhanced microstructural stability of the steel.

  5. Evaluation of mechanical properties and biological response of an alumina-forming Ni-free ferritic alloy.

    PubMed

    González-Carrasco, J L; Ciapetti, G; Montealegre, M A; Pagani, S; Chao, J; Baldini, N

    2005-06-01

    PM 2000 is a Ni-free oxide dispersion strengthened Fe-20Cr-5Al alloy able to develop a fine, dense and tightly adherent alpha-alumina scale during high-temperature oxidation. Despite the high temperature involved during thermal oxidation (1100 degrees C), microstructural changes in the candidate material, a hot rolled product, hardly occurs. Consequently, the good mechanical properties of the as-received material are not significantly affected. Moreover, due to the high compressive residual stresses at the alumina scale, an increase in the fatigue limit from 500 to 530 MPa is observed. Such stresses also account for the high capability of the coating/metal system to withstand more than 1% tensile deformation without cracking. The biocompatibility of the alloy was assessed in comparison to commercial alumina. Saos-2 osteoblast-like cells were either challenged with PM 2000 particles, or seeded onto PM 2000 (with and without scale) solid samples. Viability, growth, and ALP release from cells were assessed after 3 or 7 days, while mineralization was checked at 18 days. This study has demonstrated that PM 2000 with and without scale are capable of supporting in vitro growth and function of osteoblast-like cells over a period of 18 days. Results from this study suggest that the resulting alumina/alloy system combines the good mechanical properties of the alloy with the superior biocompatibility of the alpha-alumina, for which there is very good clinical experience. PMID:15626434

  6. First principles assessment of helium trapping in Y{sub 2}TiO{sub 5} in nano-featured ferritic alloys

    SciTech Connect

    Jin, Yanan; Jiang, Yong E-mail: odette@engineering.ucsb.edu; Yang, Litong; Lan, Guoqiang; Robert Odette, G. E-mail: odette@engineering.ucsb.edu; Yamamoto, Takuya; Shang, Jiacheng; Dang, Ying

    2014-10-14

    Nano-scale Y{sub 2}Ti{sub 2}O{sub 7} and Y{sub 2}TiO{sub 5} oxides are the major features that provide high strength and irradiation tolerance in nano-structured ferritic alloys. Here, we employ density functional theory to study helium trapping in Y{sub 2}TiO{sub 5}. The results suggest that helium is more deeply trapped in Y{sub 2}TiO{sub 5} compared to Y{sub 2}Ti{sub 2}O{sub 7}. Helium occupies open channels in Y{sub 2}TiO{sub 5}, where it weakly chemically interacts with neighboring oxygen anions, and results in less volume expansion compared to Y{sub 2}Ti{sub 2}O{sub 7}, reducing strains in the iron matrix. The corresponding helium mobility in these channels is very high. While its ultimate fate is to form oxide/matrix interface bubbles, transient deep trapping of helium in oxides plays a major role in the ability of NFA to manage helium distribution.

  7. Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

    SciTech Connect

    Chou, Y. S.; Stevenson, Jeffry W.; Singh, Prabhakar

    2008-12-01

    A novel high-temperature alkaline-earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

  8. A dual ion irradiation study of helium-dpa interactions on cavity evolution in tempered martensitic steels and nanostructured ferritic alloys

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takuya; Wu, Yuan; Robert Odette, G.; Yabuuchi, Kiyohiro; Kondo, Sosuke; Kimura, Akihiko

    2014-06-01

    Cavity evolutions in a normalized and tempered martensitic steel (TMS) and two nanostructured ferritic alloys (NFA) under Fe3+ and He+ dual ion beam irradiations (DII) at 500 °C and 650 °C were characterized. The irradiation conditions encompass a wide range of displacement per atom damage (dpa), He and He/dpa. The 500 °C DII produced damage and He levels of ≈10-47 dpa and ≈400-2000 appm, respectively. Transmission electron microscopy (TEM) showed that DII of a 8Cr TMS, at 500 °C to up to 60 dpa and 2100 appm He, produced a moderate density of non-uniformly distributed cavities with bimodal sizes ranging from ≈1 nm He bubbles to ≈20 nm faceted voids, and swelling ≈0.44%. In contrast, the same irradiation conditions produced only small ≈1.3 nm diameter bubbles and swelling of ≈0.05% in the NFA MA957. Similar bubble distributions were observed in MA957 and a developmental NFA DII at 650 °C up to ≈80 dpa and ≈3900 appm He. These results demonstrate the outstanding He management capability of the oxide nano-features in the NFA. The various data trends are shown as a function of dpa, He, He/dpa and He*dpa.

  9. Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

    NASA Astrophysics Data System (ADS)

    Chou, Yeong-Shyung; Stevenson, Jeffry W.; Singh, Prabhakar

    A novel high-temperature alkaline earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO 4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor-phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor-phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in the failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in the formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

  10. Standard specification for seamless ferritic and austenitic alloy-steel boiler, superheater, and heat-exchanger tubes. ASTM standard

    SciTech Connect

    1996-04-01

    This specification is under the jurisdiction of ASTM Committee A-1 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.10 on Tubing. Current edition approved Oct. 10 and Nov. 10, 1995. 1995 and was published April 1996. Originally published as A 213-39T. Last previous edition was A 213/A 213M-94b.

  11. Impurity effects on reduced-activation ferritic steels developed for fusion applications

    NASA Astrophysics Data System (ADS)

    Klueh, R. L.; Cheng, E. T.; Grossbeck, M. L.; Bloom, E. E.

    2000-08-01

    Reduced-activation steels are being developed for fusion applications by restricting alloying elements that produce long-lived radioactive isotopes when irradiated in the fusion neutron environment. Another source of long-lived isotopes is the impurities in the steel. To examine this, three heats of reduced-activation martensitic steel were analyzed by inductively coupled plasma mass spectrometry for low-level impurities that compromise the reduced-activation characteristics: a 5-ton heat of modified F82H (F82H-Mod) for which an effort was made during production to reduce detrimental impurities, a 1-ton heat of JLF-1, and an 18-kg heat of ORNL 9Cr-2WVTa. Specimens from commercial heats of modified 9Cr-1Mo and Sandvik HT9 were also analyzed. The objective was to determine the difference in the impurity levels in the F82H-Mod and steels for which less effort was used to ensure purity. Silver, molybdenum, and niobium were found to be the tramp impurities of most importance. The F82H-Mod had the lowest levels, but in some cases the levels were not much different from the other heats. The impurity levels in the F82H-Mod produced with present technology did not achieve the low-activation limits for either shallow land burial or recycling. The results indicate the progress that has been made and what still must be done before the reduced-activation criteria can be achieved.

  12. TIG and HIP joining of Reduced Activation Ferrite/Martensitic steel for the Korean ITER-TBM

    NASA Astrophysics Data System (ADS)

    Ku, Duck Young; Oh, Seungjin; Ahn, Mu-Young; Yu, In-Keun; Kim, Duck-Hoi; Cho, Seungyon; Choi, Im-Sub; Kwon, Ki-Bum

    2011-10-01

    Korea is developing a Helium Cooled Solid Breeder Test Blanket Module for ITER. The primary candidate structural material is a Reduced Activation Ferritic/Martensitic steel. The complex TBM structure requires developing joining technologies for successful fabrication. The characteristics of Tungsten Inert Gas welding and Hot Isostatic Pressing joining of RAFM steel were investigated. Metallurgical examinations showed that the steel grain size was increased after HIP joining and recovered by post joining heat treatment. Both TIG welding and HIP joining are found to be acceptable for ITER TBM based on mechanical tests and microstructure examination.

  13. The anti-microbial activity of titania-nickel ferrite composite nanoparticles

    NASA Astrophysics Data System (ADS)

    Rana, S.; Misra, R. D. K.

    2005-12-01

    A novel approach to synthesize a new generation of composite nanoparticles consisting of a photocatalytic shell of anatase-titania and a magnetic core of nickel ferrite has been adopted combining reverse micelle and chemical hydrolysis techniques. Titania is an effective anti-microbial agent that can be directly sprayed on infected areas of the human body or environment. Unfortunately, titania is an electrical insulator and is difficult to extract from the sprayed surface after treatment. The titania photocatalytic shell provides good antimicrobial capability that renders the bacteria inactive and removes the organic pollutants, while the nickel ferrite magnetic core enables controlled delivery of composite nanoparticles through the application of a small magnetic field, encouraging their application as removable anti-microbial photocatalyst nanoparticles.

  14. Synthesis, characterization and catalytic activity of furosemide-functionalized ferrite on the sedimentation behavior of starch

    NASA Astrophysics Data System (ADS)

    Palanikumar, S.; Meenarathi, B.; Kannammal, L.; Anbarasan, R.

    2015-01-01

    Furosemide-functionalized nanoferrite was synthesized and characterized by various analytical techniques. The furosemide-functionalized ferrite was used to settle down the starch particles under three different pH. Thus, obtained starch/Fe3O4 nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The sedimentation velocity of starch in the presence of furosemide-functionalized Fe3O4 was critically compared with the available literature value and the results are discussed in detail. The high sedimentation velocity of starch under the influence of gravitational force and the external magnetic force is studied. The starch-coated ferrites exhibited the lower vibrating sample magnetometer (VSM) value. This novel research work will bring out a new methodology in the field of starch materials.

  15. Impedance spectroscopy of the oxide films formed during high temperature oxidation of a cobalt-plated ferritic alloy

    NASA Astrophysics Data System (ADS)

    Velraj, S.; Zhu, J. H.; Painter, A. S.; Du, S. W.; Li, Y. T.

    2014-02-01

    Impedance spectroscopy was used to evaluate the oxide films formed on cobalt-coated Crofer 22 APU ferritic stainless steel after thermal oxidation at 800 °C in air for different times (i.e. 2, 50, 100 and 500 h). Impedance spectra of the oxide films exhibited two or three semicircles depending on the oxidation time, which correspond to the presence of two or three individual oxide layers. Coupled with scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD), the individual oxide layer corresponding to each semicircle was determined unambiguously. Impedance spectrum analysis of the oxide films formed on the sample after thermal exposure at 800 °C in air for 2 h led to the identification of the low-frequency and high-frequency semicircles as being from Cr2O3 and Co3O4, respectively. SEM/EDS and XRD analysis of the 500-h sample clearly revealed the presence of three oxide layers, analyzed to be Co3-xCrxO4, CoCr2O4, and Cr2O3. Although the SEM images of the 50-h and 100-h samples did not clearly show the CoCr2O4 layer, impedance plots implied their presence. The oxide scales were assigned to their respective semicircles and the electrical properties of Co3-xCrxO4, CoCr2O4 and Cr2O3 were determined from the impedance data.

  16. Microstructural characterization of weld joints of 9Cr reduced activation ferritic martensitic steel fabricated by different joining methods

    SciTech Connect

    Thomas Paul, V.; Saroja, S.; Albert, S.K.; Jayakumar, T.; Rajendra Kumar, E.

    2014-10-15

    This paper presents a detailed electron microscopy study on the microstructure of various regions of weldment fabricated by three welding methods namely tungsten inert gas welding, electron beam welding and laser beam welding in an indigenously developed 9Cr reduced activation ferritic/martensitic steel. Electron back scatter diffraction studies showed a random micro-texture in all the three welds. Microstructural changes during thermal exposures were studied and corroborated with hardness and optimized conditions for the post weld heat treatment have been identified for this steel. Hollomon–Jaffe parameter has been used to estimate the extent of tempering. The activation energy for the tempering process has been evaluated and found to be corresponding to interstitial diffusion of carbon in ferrite matrix. The type and microchemistry of secondary phases in different regions of the weldment have been identified by analytical transmission electron microscopy. - Highlights: • Comparison of microstructural parameters in TIG, electron beam and laser welds of RAFM steel • EBSD studies to illustrate the absence of preferred orientation and identification of prior austenite grain size using phase identification map • Optimization of PWHT conditions for indigenous RAFM steel • Study of kinetics of tempering and estimation of apparent activation energy of the process.

  17. Study of the Structure, Composition, and Stability of Yttrium-Ti-Oxygen nm-Scale Features in Nano-Structured Ferritic Alloys

    NASA Astrophysics Data System (ADS)

    Cunningham, Nicholas John

    This work advances the understanding of the Y-Ti-O nanofeatures (NFs) in nanostructured ferritic alloys (NFAs); a class of high temperature, oxide dispersion strengthened iron alloys with applications in both advanced fission and fusion reactors. NFAs exhibit high creep strength up to 800ºC and a remarkable radiation damage tolerance and He management. However, the NFs, which are responsible for these properties, are not fully understood. This work addresses key questions including: a) what is the NF structure and composition and how are they affected by alloy composition and processing; b) what is the NFA long-term thermal stability; c) and what alternative processing paths are available to reduce costs and produce more uniform NF distributions? A detailed study using small angle neutron scattering (SANS), transmission electron microscopy (TEM-group member Y. Wu), and atom probe tomography (APT) evaluated the NF average size (), number density (N), volume fraction (f), composition, and structure in two heats of the commercial NFA MA957. The and N were ≈2.6 nm and ≈5x1023 m-3 , respectively, for both heats, with TEM indicating the NF are Y 2Ti2O7. However, SANS indicates a mixture of NF compositions or atomic densities with a difference between the heats, while APT shows compositions with ≈ 10% Cr and a Y/Ti ratio < 1. However, microscope artifacts such as preferential undercounting of Y and O or trajectory aberrations that prevent resolving Ti segregation to the NF-matrix interface could account for the discrepancy. The microstructure and NFs in MA957 were stable for long times at temperatures up to 900ºC. Notably, Ti in the matrix and some from the NFs migrates to large, Ti-rich phases. Aging at higher temperatures up to 1000ºC for 19.5 kh produced modest coarsening for ≈ 3.8 nm and ≈30% increase in grain size for a corresponding 13% reduction in microhardness. A coarsening model shows no significant NF coarsening will occur at temperatures less than

  18. Ferrite logic reliability study

    NASA Technical Reports Server (NTRS)

    Baer, J. A.; Clark, C. B.

    1973-01-01

    Development and use of digital circuits called all-magnetic logic are reported. In these circuits the magnetic elements and their windings comprise the active circuit devices in the logic portion of a system. The ferrite logic device belongs to the all-magnetic class of logic circuits. The FLO device is novel in that it makes use of a dual or bimaterial ferrite composition in one physical ceramic body. This bimaterial feature, coupled with its potential for relatively high speed operation, makes it attractive for high reliability applications. (Maximum speed of operation approximately 50 kHz.)

  19. Residual ferrite formation in 12CrODS steels

    NASA Astrophysics Data System (ADS)

    Ukai, S.; Kudo, Y.; Wu, X.; Oono, N.; Hayashi, S.; Ohtsuka, S.; Kaito, T.

    2014-12-01

    Increasing Cr content from 9 to 12 mass% leads to superior corrosion and high-temperature oxidation resistances, and usually changes microstructure from martensite to a ferrite. To make transformable martensitic type of 12CrODS steels that have superior processing capability by using α/γ phase transformation, alloy design was conducted through varying nickel content. The structure of 12CrODS steels was successfully modified from full ferrite to a transformable martensite-base matrix containing ferrite. This ferrite consists of both equilibrium ferrite and a metastable residual ferrite. It was shown that the fraction of the equilibrium ferrite is predictable by computed phase diagram and formation of the residual ferrite was successfully evaluated through pinning of α/γ interfacial boundaries by oxide particles.

  20. Effects of Grit Blasting and Annealing on the High-Temperature Oxidation Behavior of Austenitic and Ferritic Fe-Cr Alloys

    NASA Astrophysics Data System (ADS)

    Proy, M.; Utrilla, M. V.; Otero, E.; Bouchaud, B.; Pedraza, F.

    2014-08-01

    Grit blasting (corundum) of an austenitic AISI 304 stainless steel (18Cr-8Ni) and of a low-alloy SA213 T22 ferritic steel (2.25Cr-1Mo) followed by annealing in argon resulted in enhanced outward diffusion of Cr, Mn, and Fe. Whereas 3 bar of blasting pressure allowed to grow more Cr2O3 and Mn x Cr3- x O4 spinel-rich scales, higher pressures gave rise to Fe2O3-enriched layers and were therefore disregarded. The effect of annealing pre-oxidation treatment on the isothermal oxidation resistance was subsequently evaluated for 48 h for both steels and the results were compared with their polished counterparts. The change of oxidation kinetics of the pre-oxidized 18Cr-8Ni samples at 850 °C was ascribed to the growth of a duplex Cr2O3/Mn x Cr3- x O4 scale that remained adherent to the substrate. Such a positive effect was less marked when considering the oxidation kinetics of the 2.25Cr-1Mo steel but a more compact and thinner Fe x Cr3- x O4 subscale grew at 650 °C compared to that of the polished samples. It appeared that the beneficial effect is very sensitive to the experimental blasting conditions. The input of Raman micro-spectroscopy was shown to be of ground importance in the precise identification of multiple oxide phases grown under the different conditions investigated in this study.

  1. Measurement of transformation temperatures and specific heat capacity of tungsten added reduced activation ferritic-martensitic steel

    NASA Astrophysics Data System (ADS)

    Raju, S.; Jeya Ganesh, B.; Rai, Arun Kumar; Mythili, R.; Saroja, S.; Mohandas, E.; Vijayalakshmi, M.; Rao, K. B. S.; Raj, Baldev

    2009-06-01

    The on-heating phase transformation temperatures up to the melting regime and the specific heat capacity of a reduced activation ferritic-martensitic steel (RAFM) with a nominal composition (wt%): 9Cr-0.09C-0.56Mn-0.23V-1W-0.063Ta-0.02N, have been measured using high temperature differential scanning calorimetry. The α -ferrite + carbides → γ-austenite transformation start and finish temperatures, namely A c1, and A c3, are found to be 1104 and 1144 K, respectively for a typical normalized and tempered microstructure. It is also observed that the martensite start ( MS) and finish ( Mf) temperatures are sensitive to the austenitising conditions. Typical MS and Mf values for the 1273 K normalized and 1033 K tempered samples are of the order 714 and 614 K, respectively. The heat capacity CP of the RAFM steel has been measured in the temperature range 473-1273 K, for different normalized and tempered samples. In essence, it is found that the CP of the fully martensitic microstructure is found to be lower than that of its tempered counterpart, and this difference begins to increase in an appreciable manner from about 800 K. The heat capacity of the normalized microstructure is found to vary from 480 to 500 J kg -1 K -1 at 500 K, where as that of the tempered steel is found to be higher by about, 150 J kg -1 K -1.

  2. Recent activities on the compatibility of the ferritic steel wall with the plasma in the JFT-2M tokamak

    NASA Astrophysics Data System (ADS)

    Tsuzuki, K.; Sato, M.; Kawashima, H.; Isei, N.; Kimura, H.; Ogawa, H.; Miyachi, K.; Yamamoto, M.; Shibata, T.

    2002-12-01

    The compatibility of the low activation ferritic steel with a fusion plasma has been investigated in the JFT-2M tokamak. The program consists of three stages. In the first stage, the reduction of fast ion losses was well demonstrated by ferritic steel plates (FPs) outside the vacuum vessel (VV). In the second stage, 20% of the inner surface of the VV was covered by the FPs. The plasma control, stability, and impurity release were preliminary investigated. No deteriorative effect on the plasma was observed at least in the following conditions: partial covering of 20% and the normalized beta value less than 2.8. First boronization was applied to JFT-2M leading to a remarkable decrease of the oxygen impurity. After the boronization, plasmas with the highest normalized beta in JFT-2M were obtained. Thus encouraging results were gained for this stage. In the third stage, the VV was fully covered by FPs, where the ripple reduction and the plasma stability will be investigated as a full scale testing.

  3. Phase transformation and impact properties in the experimentally simulated weld heat-affected zone of a reduced activation ferritic/martensitic steel

    NASA Astrophysics Data System (ADS)

    Moon, Joonoh; Lee, Chang-Hoon; Lee, Tae-Ho; Jang, Min-Ho; Park, Min-Gu; Han, Heung Nam

    2014-12-01

    In this work, the phase transformation and impact properties in the weld heat-affected zone (HAZ) of a reduced activation ferritic/martensitic (RAFM) steel are investigated. The HAZs were experimentally simulated using a Gleeble simulator. The base steel consisted of tempered martensite through normalizing at 1000 °C and tempering at 750 °C, while the HAZs consisted of martensite, δ-ferrite and a small volume of autotempered martensite. The impact properties using a Charpy V-notch impact test revealed that the HAZs showed poor impact properties due to the formation of martensite and δ-ferrite as compared with the base steel. In addition, the impact properties of the HAZs further deteriorated with an increase in the δ-ferrite fraction caused by increasing the peak temperature. The impact properties of the HAZs could be improved through the formation of tempered martensite after post weld heat treatment (PWHT), but they remained lower than that of the base steel because the δ-ferrite remained in the tempered HAZs.

  4. Dependence of grain boundary chemistry on the irradiation dose in low activation ferritics

    NASA Astrophysics Data System (ADS)

    Kimura, A.; Charlot, L. A.; Gelles, D. S.; Jones, R. H.

    1994-09-01

    Grain boundary chemistries in low activation 9%Cr-2%Mn-1%W and 12%Cr-6%Mn-1%W steels were measured by means of Auger electron spectroscopy (AES) after irradiations in the FFTF/MOTA at 638 K up to doses of 10 and 25 dpa. In 12%Cr-6%Mn-1%W steel, grain boundary concentration of Si increased with an increase in the irradiation dose from 10 to 25 dpa. Segregation of Mn, however, appeared to saturate or even decreased with the increase. The average size of grain boundary precipitates was increased during the irradiation from 10 to 25 dpa. It is considered that beyond the 10 dpa irradiation, Mn-rich precipitates at grain boundaries absorb Mn atoms segregated at grain boundaries, resulting in the growth of grain boundary precipitates and the reduction of segregated Mn atoms in elemental form at grain boundaries. It is possible that Si atoms which may compete site with Mn atoms at grain boundaries begin to segregate at grain boundaries. In contrast, no significant change in grain boundary chemistry was recognized in 9%Cr-2%Mn-1%W alloy with the increase in irradiation dose from 10 to 25 dpa.

  5. Articles comprising ferritic stainless steels

    DOEpatents

    Rakowski, James M.

    2016-06-28

    An article of manufacture comprises a ferritic stainless steel that includes a near-surface region depleted of silicon relative to a remainder of the ferritic stainless steel. The article has a reduced tendency to form an electrically resistive silica layer including silicon derived from the steel when the article is subjected to high temperature oxidizing conditions. The ferritic stainless steel is selected from the group comprising AISI Type 430 stainless steel, AISI Type 439 stainless steel, AISI Type 441 stainless steel, AISI Type 444 stainless steel, and E-BRITE.RTM. alloy, also known as UNS 44627 stainless steel. In certain embodiments, the article of manufacture is a fuel cell interconnect for a solid oxide fuel cell.

  6. On the synthesis of copper-nickel binary alloy nanoparticles and binding silane coupling agents to magnetic ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Pritchett, Jeremy Scott

    This dissertation addresses the creation of a multifunctional nanoplatform for cancer targeting, imaging, and therapy. Magnetic oxide nanoparticles were labeled with silane coupling agents that could be used for targeting. The magnetic oxides have application as contrast enhancing agents for magnetic resonance imaging. Copper-nickel binary alloy nanoparticles were prepared for possible use in Curie temperature limited hyperthermia therapy. Spherical, single crystal iron oxide nanoparticles with average diameters of 4 nm, 6 nm, 8 nm, 11 nm, or 16 nm were prepared using published procedures. The iron oxide particle chemistry was extended to synthesize 13 nm diameter CoFe2O4, 9 nm diameter MnFe2O4, and 12 nm diameter NiFe2O4. The particles had a coating of oleic acid and oleylamine ligands. Silane coupling chemistry was used to displace these ligands with either beta-aminoethyl-gamma-aminopropyl-trimethoxysilane, triethoxysilane-PEG, or triethoxysilane-biotin. The silane ligands would allow the particles to be conjugated with a targeting group. New chemistry was developed to synthesize fcc CuNi nanoparticles with the objective of finding methods that give particles with an average size less than 50 nm, a narrow distribution of particle sizes, and control of particle composition. The particle synthesis involves the reduction of a mixture of copper(II) and nickel(II) and the reduction conditions included diol reduction, polyol synthesis, seeding by diol reduction, and oleate reduction. One of the main issues is the formation of hcp nickel particles as a containment in the method. The factors that avoided the formation of hcp nickel particles and allow only fcc particles to form were the choice of reducing agent, ratio of surfactants, and heating time. Both the oleate reduction and diol reduction gave a mixture of the hcp and fcc phases. By controlling certain reaction conditions, such as keeping the ratio of oleic acid to oleylamine 1:1 and slowly heating to reflux for

  7. Effect of pre-strain on susceptibility of Indian Reduced Activation Ferritic Martensitic Steel to hydrogen embrittlement

    NASA Astrophysics Data System (ADS)

    Sonak, Sagar; Tiwari, Abhishek; Jain, Uttam; Keskar, Nachiket; Kumar, Sanjay; Singh, Ram N.; Dey, Gautam K.

    2015-10-01

    The role of pre-strain on hydrogen embrittlement susceptibility of Indian Reduced Activation Ferritic Martensitic Steel was investigated using constant nominal strain-rate tension test. The samples were pre-strained to different levels of plastic strain and their mechanical behavior and mode of fracture under the influence of hydrogen was studied. The effect of plastic pre-strain in the range of 0.5-2% on the ductility of the samples was prominent. Compared to samples without any pre-straining, effect of hydrogen was more pronounced on pre-strained samples. Prior deformation reduced the material ductility under the influence of hydrogen. Up to 35% reduction in the total strain was observed under the influence of hydrogen in pre-strained samples. Hydrogen charging resulted in increased occurrence of brittle zones on the fracture surface. Hydrogen Enhanced Decohesion (HEDE) was found to be the dominant mechanism of fracture.

  8. Determining the shear fracture properties of HIP joints of reduced-activation ferritic/martensitic steel by a torsion test

    NASA Astrophysics Data System (ADS)

    Nozawa, Takashi; Noh, Sanghoon; Tanigawa, Hiroyasu

    2012-08-01

    Hot isostatic pressing (HIP) is a key technology used to fabricate a first wall with cooling channels for the fusion blanket system utilizing a reduced-activation ferritic/martensitic steel. To qualify the HIPped components, small specimen test techniques are beneficial not only to evaluate the thin-wall cooling channels containing the HIP joint but also to use in neutron irradiation studies. This study aims to develop the torsion test method with special emphasis on providing a reasonable and comprehensive method to determine interfacial shear properties of HIP joints during the torsional fracture process. Torsion test results identified that the torsion process shows yield of the base metal followed by non-elastic deformation due to work hardening of the base metal. By considering this work hardening issue, we propose a reasonable and realistic solution to determine the torsional yield shear stress and the ultimate torsional shear strength of the HIPped interface. Finally, a representative torsion fracture process was identified.

  9. HEAT INPUT AND POST WELD HEAT TREATMENT EFFECTS ON REDUCED-ACTIVATION FERRITIC/MARTENSITIC STEEL FRICTION STIR WELDS

    SciTech Connect

    Tang, Wei; Chen, Gaoqiang; Chen, Jian; Yu, Xinghua; Frederick, David Alan; Feng, Zhili

    2015-01-01

    Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zone mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.

  10. Thermal Diffusivity of Reduced Activation Ferritic/Martensitic Steel Determined by the Time Domain Photoacoustic Piezoelectric Technique

    NASA Astrophysics Data System (ADS)

    Zhao, Binxing; Wang, Yafei; Gao, Chunming; Sun, Qiming; Wang, Pinghuai

    2015-06-01

    The thermal diffusivity of reduced activation ferritic/martensitic steel (CLF-1), which is recognized as the primary candidate structural material for the test blanket module of the international thermal-nuclear experimental reactor, has been studied by the time-domain (TD) photoacoustic piezoelectric (PAPE) technique. The TD PAPE model based on a simplified thermoelastic theory under square-wave modulated laser excitation is presented, relating the TD PAPE signal to the modulation frequency, thermal diffusivity, and other material parameters. Thermal diffusivities of reference samples such as copper and nickel were measured and analyzed, by which the validity of the technique is verified. The thermal diffusivity of the CLF-1 sample was measured to be , which is at a medium level among the ordinary steel materials ( to and has decent heat-dissipation ability. The results show that the TD PAPE technique can provide a fast and economic way for the investigation of the thermophysical properties of fusion reactor structural materials.

  11. Alloy Design and Development of Cast Cr-W-V Ferritic Steels for Improved High-Temperature Strength for Power Generation Applications

    SciTech Connect

    Klueh, R L; Maziasz, P J; Vitek, J M; Evans, N D; Hashimoto, N

    2006-09-23

    Economic and environmental concerns demand that the power-generation industry seek increased efficiency for gas turbines. Higher efficiency requires higher operating temperatures, with the objective temperature for the hottest sections of new systems {approx} 593 C, and increasing to {approx} 650 C. Because of their good thermal properties, Cr-Mo-V cast ferritic steels are currently used for components such as rotors, casings, pipes, etc., but new steels are required for the new operating conditions. The Oak Ridge National Laboratory (ORNL) has developed new wrought Cr-W-V steels with 3-9% Cr, 2-3% W, 0.25% V (compositions are in wt.%), and minor amounts of additional elements. These steels have the strength and toughness required for turbine applications. Since cast alloys are expected to behave differently from wrought material, work was pursued to develop new cast steels based on the ORNL wrought compositions. Nine casting test blocks with 3, 9, and 11% Cr were obtained. Eight were Cr-W-V-Ta-type steels based on the ORNL wrought steels; the ninth was COST CB2, a 9Cr-Mo-Co-V-Nb cast steel, which was the most promising cast steel developed in a European alloy-development program. The COST CB2 was used as a control to which the new compositions were compared, and this also provided a comparison between Cr-W-V-Ta and Cr-Mo-V-Nb compositions. Heat treatment studies were carried out on the nine castings to determine normalizing-and-tempering treatments. Microstructures were characterized by both optical and transmission electron microscopy (TEM). Tensile, impact, and creep tests were conducted. Test results on the first nine cast steel compositions indicated that properties of the 9Cr-Mo-Co-V-Nb composition of COST CB2 were better than those of the 3Cr-, 9Cr-, and 11Cr-W-V-Ta steels. Analysis of the results of this first iteration using computational thermodynamics raised the question of the effectiveness in cast steels of the Cr-W-V-Ta combination versus the Cr

  12. Correlating size and composition-dependent effects with magnetic, Mössbauer, and pair distribution function measurements in a family of catalytically active ferrite nanoparticles

    DOE PAGESBeta

    Wong, Stanislaus; Papaefthymiou, Georgia C.; Lewis, Crystal S.; Han, Jinkyu; Zhang, Cheng; Li, Qiang; Shi, Chenyang; Abeykoon, A. M.Milinda; Billinge, Simon J.L.; Stach, Eric; et al

    2015-05-06

    The magnetic spinel ferrites, MFe₂O₄ (wherein 'M' = a divalent metal ion such as but not limited to Mn, Co, Zn, and Ni), represent a unique class of magnetic materials in which the rational introduction of different 'M's can yield correspondingly unique and interesting magnetic behaviors. Herein we present a generalized hydrothermal method for the synthesis of single-crystalline ferrite nanoparticles with 'M' = Mg, Fe, Co, Ni, Cu, and Zn, respectively, which can be systematically and efficaciously produced simply by changing the metal precursor. Our protocol can moreover lead to reproducible size control by judicious selection of various surfactants. Asmore » such, we have probed the effects of both (i) size and (ii) chemical composition upon the magnetic properties of these nanomaterials using complementary magnetometry and Mössbauer spectroscopy techniques. The structure of the samples was confirmed by atomic PDF analysis of X-ray and electron powder diffraction data as a function of particle size. These materials retain the bulk spinel structure to the smallest size (i.e., 3 nm). In addition, we have explored the catalytic potential of our ferrites as both (a) magnetically recoverable photocatalysts and (b) biological catalysts, and noted that many of our as-prepared ferrite systems evinced intrinsically higher activities as compared with their iron oxide analogues.« less

  13. Correlating size and composition-dependent effects with magnetic, Mössbauer, and pair distribution function measurements in a family of catalytically active ferrite nanoparticles

    SciTech Connect

    Wong, Stanislaus; Papaefthymiou, Georgia C.; Lewis, Crystal S.; Han, Jinkyu; Zhang, Cheng; Li, Qiang; Shi, Chenyang; Abeykoon, A. M.Milinda; Billinge, Simon J.L.; Stach, Eric; Thomas, Justin; Guerrero, Kevin; Munayco, Pablo; Munayco, Jimmy; Scorzelli, Rosa B.; Burnham, Philip; Viescas, Arthur J; Tiano, Amanda L.

    2015-05-06

    The magnetic spinel ferrites, MFe₂O₄ (wherein 'M' = a divalent metal ion such as but not limited to Mn, Co, Zn, and Ni), represent a unique class of magnetic materials in which the rational introduction of different 'M's can yield correspondingly unique and interesting magnetic behaviors. Herein we present a generalized hydrothermal method for the synthesis of single-crystalline ferrite nanoparticles with 'M' = Mg, Fe, Co, Ni, Cu, and Zn, respectively, which can be systematically and efficaciously produced simply by changing the metal precursor. Our protocol can moreover lead to reproducible size control by judicious selection of various surfactants. As such, we have probed the effects of both (i) size and (ii) chemical composition upon the magnetic properties of these nanomaterials using complementary magnetometry and Mössbauer spectroscopy techniques. The structure of the samples was confirmed by atomic PDF analysis of X-ray and electron powder diffraction data as a function of particle size. These materials retain the bulk spinel structure to the smallest size (i.e., 3 nm). In addition, we have explored the catalytic potential of our ferrites as both (a) magnetically recoverable photocatalysts and (b) biological catalysts, and noted that many of our as-prepared ferrite systems evinced intrinsically higher activities as compared with their iron oxide analogues.

  14. Dependence of the nitriding rate of ferritic and austenitic substrates on the crystallographic orientation of surface grains; gaseous nitriding of Fe-Cr and Ni-Ti alloys

    NASA Astrophysics Data System (ADS)

    Akhlaghi, M.; Jung, M.; Meka, S. R.; Fonović, M.; Leineweber, A.; Mittemeijer, E. J.

    2015-12-01

    Gaseous nitriding of ferritic Fe-Cr and austenitic Ni-Ti solid solutions reveals that the extent of the uptake of dissolved nitrogen depends on the crystallographic orientation of the surface grains of the substrate. In both ferritic and austenitic substrates, the surface nitrogen concentration and the nitriding depth decrease upon increasing the smallest angle between the surface normal and the normal of a {1 0 0} plane of the surface grain considered. This phenomenon could be ascribed to the residual compressive macrostress developed during nitriding which varies as a function of crystallographic orientation of the (surface) grains due to the elastically anisotropic nature of ferrite and austenite solid solutions investigated in this study.

  15. Effects of activating fluxes on the weld penetration and corrosion resistant property of laser welded joint of ferritic stainless steel

    NASA Astrophysics Data System (ADS)

    Wang, Yonghui; Hu, Shengsun; Shen, Junqi

    2015-10-01

    This study was based on the ferritic stainless steel SUS430. Under the parallel welding conditions, the critical penetration power values (CPPV) of 3mm steel plates with different surface-coating activating fluxes were tested. Results showed that, after coating with activating fluxes, such as ZrO2, CaCO3, CaF2 and CaO, the CPPV could reduce 100~250 W, which indicating the increases of the weld penetrations (WP). Nevertheless, the variation range of WP with or without activating fluxes was less than 16.7%. Compared with single-component ones, a multi-component activating flux composed of 50% ZrO2, 12.09% CaCO3, 10.43% CaO, and 27.49% MgO was testified to be much more efficient, the WP of which was about 2.3-fold of that without any activating fluxes. Furthermore, a FeCl3 spot corrosion experiment was carried out with samples cut from weld zone to test the effects of different activating fluxes on the corrosion resistant (CR) property of the laser welded joints. It was found that all kinds of activating fluxes could improve the CR of the welded joints. And, it was interesting to find that the effect of the mixed activating fluxes was inferior to those single-component ones. Among all the activating fluxes, the single-component of CaCO3 seemed to be the best in resisting corrosion. By means of Energy Dispersive Spectrometer (EDS) testing, it was found that the use of activating fluxes could effectively restrain the loss of Cr element of weld zone in the process of laser welding, thus greatly improving the CR of welded joints.

  16. Activity and diffusion of metals in binary aluminum alloys

    SciTech Connect

    Jao, C. S.

    1980-12-01

    To determine the activity of zinc in Zn-Al alloys, the electromotive force (emf) of the cell: Zn/ZnCl/sub 2/-KC1 (eut)/Zn,Al was measured at temperatures between 569.5 K (296.5C) and 649.5 K (376.5C). The applicability of a two-suffix Margules equation was demonstrated, in good agreement with theoretical expectations. The diffusion coefficient of Zn in Al determined from a planar diffusion model for the experimental data was about 3 x 10/sup -10/ cm/sup 2//sec to 2 x 10/sup -9/ cm/sup 2//sec in the range of temperature studied. This is higher than that found in the literature. The most plausible reason appears to be the high alumina concentration in the working electrode because of partial oxidation. Oxidation of the alloying metals was the primary cause of poor alloying between calcium/or zinc and aluminum, thereby frustrating similar measurements at a Ca-Al/or Zn-Al alloy. The literature on the activity of calcium and zinc is aluminum is reviewed.

  17. 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.

  18. 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.

  19. Development and characterization of advanced 9Cr ferritic/martensitic steels for fission and fusion reactors

    NASA Astrophysics Data System (ADS)

    Saroja, S.; Dasgupta, A.; Divakar, R.; Raju, S.; Mohandas, E.; Vijayalakshmi, M.; Bhanu Sankara Rao, K.; Raj, Baldev

    2011-02-01

    This paper presents the results on the physical metallurgy studies in 9Cr Oxide Dispersion Strengthened (ODS) and Reduced Activation Ferritic/Martensitic (RAFM) steels. Yttria strengthened ODS alloy was synthesized through several stages, like mechanical milling of alloy powders and yttria, canning and consolidation by hot extrusion. During characterization of the ODS alloy, it was observed that yttria particles possessed an affinity for Ti, a small amount of which was also helpful in refining the dispersoid particles containing mixed Y and Ti oxides. The particle size and their distribution in the ferrite matrix, were studied using Analytical and High Resolution Electron Microscopy at various stages. The results showed a distribution of Y 2O 3 particles predominantly in the size range of 5-20 nm. A Reduced Activation Ferritic/Martensitic steel has also been developed with the replacement of Mo and Nb by W and Ta with strict control on the tramp and trace elements (Mo, Nb, B, Cu, Ni, Al, Co, Ti). The transformation temperatures ( Ac1, Ac3 and Ms) for this steel have been determined and the transformation behavior of the high temperature austenite phase has been studied. The complete phase domain diagram has been generated which is required for optimization of the processing and fabrication schedules for the steel.

  20. Dynamic Strain Aging and Oxidation Effects on the Thermomechanical Fatigue Deformation of Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Nagesha, A.; Kannan, R.; Srinivasan, V. S.; Sandhya, R.; Choudhary, B. K.; Laha, K.

    2016-03-01

    Thermomechanical fatigue (TMF) behavior of a reduced activation ferritic-martensitic steel was investigated under in-phase (IP) and out-of-phase (OP) conditions under different mechanical strain amplitudes and temperature regimes. OP TMF was generally observed to result in the lowest cyclic lives compared to both IP TMF and isothermal low cycle fatigue (IF) at the maximum temperature ( T max). The stress-strain hysteresis loops under TMF were marked by extensive serrations associated with dynamic strain aging (DSA) at the strain amplitudes of ±0.4 and ±0.6 pct. The serrations were noticed during the downward ramp of temperature that resulted in IP and OP TMF exhibiting jerky flow in the compressive and tensile portions, respectively. However, no evidence of serrated flow was seen under IF cycling at any of the temperatures within the TMF cycle. The stress response during IP TMF was marked by a near-saturation regime over 65 to 70 pct of life in contrast to continuous cyclic softening in the case of OP TMF. The marked life reduction observed under OP cycling at the strain amplitudes of ±0.4 and ±0.6 pct was attributed to the deleterious influence associated with oxidation, DSA, and tensile mean stress. The findings assume importance in the context of elevated temperature fatigue design, considering the fact that the IF data at T max are deemed adequately conservative in traditional design approaches.

  1. Effect of Tungsten on Primary Creep Deformation and Minimum Creep Rate of Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Vanaja, J.; Laha, Kinkar; Mathew, M. D.

    2014-10-01

    Effect of tungsten on transient creep deformation and minimum creep rate of reduced activation ferritic-martensitic (RAFM) steel has been assessed. Tungsten content in the 9Cr-RAFM steel has been varied between 1 and 2 wt pct, and creep tests were carried out over the stress range of 180 and 260 MPa at 823 K (550 °C). The tempered martensitic steel exhibited primary creep followed by tertiary stage of creep deformation with a minimum in creep deformation rate. The primary creep behavior has been assessed based on the Garofalo relationship, , considering minimum creep rate instead of steady-state creep rate . The relationships between (i) rate of exhaustion of transient creep r' with minimum creep rate, (ii) rate of exhaustion of transient creep r' with time to reach minimum creep rate, and (iii) initial creep rate with minimum creep rate revealed that the first-order reaction-rate theory has prevailed throughout the transient region of the RAFM steel having different tungsten contents. The rate of exhaustion of transient creep r' and minimum creep rate decreased, whereas the transient strain ɛ T increased with increase in tungsten content. A master transient creep curve of the steels has been developed considering the variation of with . The effect of tungsten on the variation of minimum creep rate with applied stress has been rationalized by invoking the back-stress concept.

  2. High heat flux test of a HIP-bonded first wall panel of reduced activation ferritic steel F-82H

    NASA Astrophysics Data System (ADS)

    Hatano, T.; Suzuki, S.; Yokoyama, K.; Kuroda, T.; Enoeda, M.

    2000-12-01

    Reduced activation ferritic steel F-82H is a primary candidate structural material of DEMO fusion reactors. In fabrication technology, development of the DEMO blanket in JAERI, a hot isostatic pressing (HIP) bonding method, especially for the first wall structure with built-in cooling tubes has been proposed. A HIP-bonded F-82H first wall panel was successfully fabricated with selected manufacturing parameters. A high heat flux test of the HIP-bonded F-82H first wall panel has been performed to examine the thermo-mechanical performance of the panel including the integrity of the HIP-bonded interfaces and the fatigue behavior. A maximum heat flux of 2.7 MW/m2 was applied to accelerate the fatigue test up to 5000 cycles in test blanket inserted ITER. The maximum temperature of the panel was ∼450°C under this heat flux. Through this test campaign, no damage such as cracks was observed on the surface of the panel, and no degradation in heat removal performance was observed either from the temperature responses. The thermal fatigue lifetime of the panel was found to be longer than the fatigue data obtained by mechanical testing.

  3. Modeling C-Curves for the Growth Rate of Widmanstätten and Bainitic Ferrite in Fe-C Alloys

    NASA Astrophysics Data System (ADS)

    Leach, Lindsay; Hillert, Mats; Borgenstam, Annika

    2016-01-01

    When Zener formulated his maximum growth rate criterion for predicting the coarseness of various metallographic objects, he simplified the growth rate equations and predicted that the optimum coarseness should be twice the critical value for which all the driving force would be absorbed by interfacial energy. It is now emphasized that a composition dependence of the diffusion coefficient has a considerable influence and can result in a ratio much larger than two. Various approximations have now been removed from the growth rate equation. When applied to acicular ferrite in the Fe-C system, a C-curve for the growth rate is obtained that resembles the unusually wide C-curve obtained experimentally when information on Widmanstätten ferrite and bainite is combined. It is not necessary to explain that shape as a combination of separate curves for Widmanstätten ferrite and bainite. The main reason for the wide C-curve is the direct effect of the composition dependence of the diffusivity of carbon in austenite.

  4. Improvement of catalytic activity in selective oxidation of styrene with H{sub 2}O{sub 2} over spinel Mg–Cu ferrite hollow spheres in water

    SciTech Connect

    Tong, Jinhui; Cai, Xiaodong; Wang, Haiyan; Zhang, Qianping

    2014-07-01

    Graphical abstract: Uniform spinel Mg–Cu ferrite hollow spheres were prepared using carbon spheres as templates. Solid spinel Mg{sub 0.5}Cu{sub 0.5}Fe{sub 2}O{sub 4} ferrite nanocrystals were also prepared by sol–gel auto-combustion, hydrothermal and coprecipitation methods for comparison. The samples were found to be efficient catalysts for oxidation of styrene using hydrogen peroxide as oxidant. Especially, in the case of Mg{sub 0.5}Cu{sub 0.5}Fe{sub 2}O{sub 4} hollow spheres, obvious improvement on catalytic activity was observed and 21.2% of styrene conversion and 75.2% of selectivity for benzaldehyde were obtained at 80 °C for 6 h reaction in water. The catalyst can be magnetically separated easily for reuse and no obvious loss of activity was observed when reused in six consecutive runs. - Highlights: • Uniform spinel ferrite hollow spheres were prepared by a simple method. • The catalyst has been proved much more efficient for styrene oxidation than the reported analogues. • The catalyst can be easily separated by external magnetic field and has exhibited excellent reusability. • The catalytic system is environmentally friendly. - Abstract: Uniform spinel Mg–Cu ferrite hollow spheres were prepared using carbon spheres as templates. For comparison, solid Mg–Cu ferrite nanocrystals were also prepared by sol–gel auto-combustion, hydrothermal and coprecipitation methods. All the samples were characterized by Fourier transform infrared spectrophotometry (FT-IR), X-ray diffractometry (XRD), transmission electron microscopy (TEM) and N{sub 2} physisorption. The samples were found to be efficient catalysts for oxidation of styrene using hydrogen peroxide as oxidant. Especially, in the case of Mg{sub 0.5}Cu{sub 0.5}Fe{sub 2}O{sub 4} hollow spheres, obvious improvement on catalytic activity was observed, and 21.2% of styrene conversion and 75.2% of selectivity for benzaldehyde were obtained at 80 °C for 6 h reaction in water. The catalyst can be

  5. On the mobility of vacancy clusters in reduced activation steels: an atomistic study in the Fe-Cr-W model alloy.

    PubMed

    Bonny, G; Castin, N; Bullens, J; Bakaev, A; Klaver, T C P; Terentyev, D

    2013-08-01

    Reduced activation steels are considered as structural materials for future fusion reactors. Besides iron and the main alloying element chromium, these steels contain other minor alloying elements, typically tungsten, vanadium and tantalum. In this work we study the impact of chromium and tungsten, being major alloying elements of ferritic Fe-Cr-W-based steels, on the stability and mobility of vacancy defects, typically formed under irradiation in collision cascades. For this purpose, we perform ab initio calculations, develop a many-body interatomic potential (EAM formalism) for large-scale calculations, validate the potential and apply it using an atomistic kinetic Monte Carlo method to characterize the lifetime and diffusivity of vacancy clusters. To distinguish the role of Cr and W we perform atomistic kinetic Monte Carlo simulations in Fe-Cr, Fe-W and Fe-Cr-W alloys. Within the limitation of transferability of the potentials it is found that both Cr and W enhance the diffusivity of vacancy clusters, while only W strongly reduces their lifetime. The cluster lifetime reduction increases with W concentration and saturates at about 1-2 at.%. The obtained results imply that W acts as an efficient 'breaker' of small migrating vacancy clusters and therefore the short-term annealing process of cascade debris is modified by the presence of W, even in small concentrations. PMID:23838265

  6. Surface-engineered core-shell nano-size ferrites and their antimicrobial activity

    SciTech Connect

    Baraliya, Jagdish D. Joshi, Hiren H.

    2014-04-24

    We report the results of biological study on core-shell structured MFe{sub 2}O{sub 4} (where M = Co, Mn, Ni) nanoparticles and influence of silica- DEG dual coating on their antimicrobial activity. Spherical MFe{sub 2}O{sub 4} nanoparticles were prepared via a Co-precipitation method. The microstructures and morphologies of these nanoparticles were studied by x-ray diffraction and FTIR. The antimicrobial activity study carried out in nutrient agar medium with addition of antimicrobial synthesis compound which is tested for its activity against different types of bacteria.

  7. 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.

  8. Low cycle fatigue properties of reduced activation ferritic/martensitic steels after high-dose neutron irradiation

    NASA Astrophysics Data System (ADS)

    Gaganidze, E.; Petersen, C.; Aktaa, J.; Povstyanko, A.; Prokhorov, V.; Diegele, E.; Lässer, R.

    2011-08-01

    This paper focuses on the low cycle fatigue (LCF) behaviour of reduced activation ferritic/martensitic steels irradiated to a displacement damage dose of up to 70 dpa at 330-337 °C in the BOR 60 reactor within the ARBOR 2 irradiation programme. The influence of neutron irradiation on the fatigue behaviour was determined for the as-received EUROFER97, pre-irradiation heat-treated EUROFER97 HT and F82H-mod steels. Strain-controlled push-pull loading was performed using miniaturized cylindrical specimens at a constant temperature of 330 °C with total strain ranges between 0.8% and 1.1%. Comparison of the LCF behaviour of irradiated and reference unirradiated specimens was performed for both the adequate total and inelastic strains. Neutron irradiation-induced hardening may have various effects on the fatigue behaviour of the steels. The reduction of inelastic strain in the irradiated state compared with the reference unirradiated state at common total strain amplitudes may increase fatigue lifetime. The increase in the stress at the adequate inelastic strain, by contrast, may accelerate fatigue damage accumulation. Depending on which of the two effects mentioned dominates, neutron irradiation may either extend or reduce the fatigue lifetime compared with the reference unirradiated state. The results obtained for EUROFER97 and EUROFER97 HT confirm these considerations. Most of the irradiated specimens show fatigue lifetimes comparable to those of the reference unirradiated state at adequate inelastic strains. Some irradiated specimens, however, show lifetime reduction or increase in comparison with the reference state at adequate inelastic strains.

  9. A comparative study of different concentrations of pure Zn powder effects on synthesis, structure, magnetic and microwave-absorbing properties in mechanically-alloyed Ni-Zn ferrite

    NASA Astrophysics Data System (ADS)

    Hajalilou, Abdollah; Mazlan, Saiful Amri; Shameli, Kamyar

    2016-09-01

    In this study, a powder mixture of Zn, Fe2O3 and NiO was used to produce different compositions of Ni1-xZnxFe2O4 (x=0.36, 0.5 and 0.64) nanopowders. High-energy ball milling with a subsequent heat treatment method was carried out. The XRD results indicated that for the content of Zn, x=0.64 a single phase of Ni-Zn ferrite was produced after 30 h milling while for the contents of Zn, x=0.36 and 0.5, the desired ferrite was formed after sintering the 30 h-milled powders at 500 °C. The average crystallite size decreased with increase in the Zn content. A DC electrical resistivity of the Ni-Zn ferrite, however, decreased with increase in the Zn content, its value was much higher than those samples prepared by the conventional ceramic route by using ZnO instead of Zn. This is attributed to smaller grains size which were obtained by using Zn. The FT-IR results suggested two absorption bands for octahedral and tetrahedral sites in the range of 350-700 cm-1. The VSM results revealed that by increasing the Zn content from 0.36 to 0.5, a saturation magnetization reached its maximum value; afterwards, a decrease was observed for Zn with x=0.64. Finally, magnetic permeability and dielectric permittivity were studied by using vector network analyzer to explore microwave-absorbing properties in X-band frequency. The minimum reflection loss value obtained for Ni0.5Zn0.5Fe2O4 samples, about -34 dB at 9.7 GHz, making them the best candidates for high frequency applications.

  10. Method for making conductors for ferrite memory arrays. [from pre-formed metal conductors

    NASA Technical Reports Server (NTRS)

    Heckler, C. H.; Baba, P. D.; Bhiwandker, N. C. (Inventor)

    1974-01-01

    The ferrite memory arrays are made from pre-formed metal conductors for the ferrite arrays. The conductors are made by forming a thin sheet of a metallizing paste of metal alloy powder, drying the paste layer, bisque firing the dried sheet at a first temperature, and then punching the conductors from the fired sheet. During the bisque firing, the conductor sheet shrinks to 58 percent of its pre-fired volume and the alloy particles sinter together. The conductors are embedded in ferrite sheet material and finally fired at a second higher temperature during which firing the conductors shrink approximately the same degree as the ferrite material.

  11. Enabling Inexpensive Metallic Alloys as SOFC Interconnects: An Investigation into Hybrid Coating Technologies to Deposit Nanocomposite Functional Coatings on Ferritic Stainless Steel

    SciTech Connect

    Gannon, Paul; Gorokhovsky, Vladimir I.; Deibert, Max; Smith, Richard J.; Kayani, Asghar N.; White, P T.; Sofie, Stephen W.; Yang, Z Gary; Mccready, David E.; Visco, S.; Jacobson, C.; Kurokawa, H.

    2007-11-01

    Reduced operating temperatures (600-800°C) of Solid Oxide Fuel Cells (SOFCs) may enable the use of inexpensive ferritic steels as interconnects. Due to the demanding SOFC interconnect operating environment, protective coatings are required to increase long-term stability. In this study, large area filtered arc deposition (LAFAD) and hybrid filtered arc-assisted electron beam physical vapor deposition (FA-EBPVD) technologies were used to deposit two-segment coatings with Cr-Al-Y-O nanocomposite bottom segments and Mn-Co-O spinel-based top segments. Coatings were deposited on ferritic steels and subsequently annealed in air for various times. Surface oxidation was investigated using SEM/EDS, XRD and RBS analyses. Cr-volatilization was evaluated by transpiration and ICP-MS analysis of the resultant condensate. Time dependent Area Specific Resistance (ASR) was studied using the four-point technique. The oxidation behavior, Cr volatilization rate, and ASR of coated and uncoated samples are reported. Significant long-term (>1,000 hours) surface stability, low ASR, and dramatically reduced Cr-volatility were observed with the coated specimens. Improvement mechanisms, including the coating diffusion barrier properties and electrical conductivity are discussed.

  12. Design of tough ferritic steels for cryogenic use

    SciTech Connect

    Morris, J.W. Jr.

    1985-10-01

    This paper describes the design of ferritic steels and weldments that combine strength and toughness at cryogenic temperatures. The alloy must have a ductile-brittle transition temperature below the intended service temperature and a high fracture toughness in the ductile mode. Its systematic design uses the microstructure-property relations that govern the transition temperature and fracture toughness to identify a suitable microstructure, and then employs the microstructure-processing relations that govern its thermal response to manipulate the microstructure into the appropriate form. The procedure is illustrated by describing the heat treatments, microstructures and properties of a variety of laboratory and commercial alloys, including conventional ''9Ni'' steel, the low-Ni and Fe-Mn ferritic steels that have been developed as an alternative to 9Ni, the 12Ni steels that are promising for use at 4K, and the welding procedures and ferritic filler metals that are useful for ferritic cryogenic steels.

  13. Tensile and charpy impact properties of irradiated reduced-activation ferritic steels

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.

    1996-10-01

    Tensile tests were conducted on eight reduced-activation Cr-W steels after irradiation to 15-17 and 26-29 dpa, and Charpy impact tests were conducted on the steels irradiated to 26-29 dpa. Irradiation was in the Fast Flux Test Facility at 365{degrees}C on steels containing 2.25-12% Cr, varying amounts of W, V, and Ta, and 0.1%C. Previously, tensile specimens were irradiated to 6-8 dpa and Charpy specimens to 6-8, 15-17, and 20-24 dpa. Tensile and Charpy specimens were also thermally aged to 20000 h at 365{degrees}C. Thermal aging had little effect on the tensile behavior or the ductile-brittle transition temperature (DBTT), but several steels showed a slight increase in the upper-shelf energy (USE). After {approx}7 dpa, the strength of the steels increased and then remained relatively unchanged through 26-29 dpa (i.e., the strength saturated with fluence). Post-irradiation Charpy impact tests after 26-29 dpa showed that the loss of impact toughness, as measured by an increase in DBTT and a decrease in the USE, remained relatively unchanged from the values after 20-24 dpa, which had been relatively unchanged from the earlier irradiations. As before, the two 9Cr steels were the most irradiation resistant.

  14. Deformation Microstructure of a Reduced-Activation Ferritic/Martensitic Steel Irradiated in HFIR

    SciTech Connect

    Hashimoto, N.; Klueh, R.L.; Ando, M.; Tanigawa, H.; Sawai, T.; Shiba, K.

    2003-09-15

    In order to determine the contributions of different microstructural features to strength and to deformation mode, microstructure of deformed flat tensile specimens of irradiated reduced activation F82H (IEA heat) base metal (BM) and its tungsten inert-gas (TIG) weldments (weld metal and weld joint) were investigated by transmission electron microscopy (TEM), following fracture surface examination by scanning electron microscopy (SEM). After irradiation, the fracture surfaces of F82H BM and TIG weldment showed a martensitic mixed quasi-cleavage and ductile-dimple fracture. The microstructure of the deformed region of irradiated F82H BM contained dislocation channels. This suggests that dislocation channeling could be the dominant deformation mechanism in this steel, resulting in the loss of strain-hardening capacity. While, the necked region of the irradiated F82H TIG, where showed less hardening than F82H BM, showed deformation bands only. From these results, it is suggested that the pre-irradiation microstructure, especially the dislocation density, could affect the post-irradiation deformation mode.

  15. Spark plasma sintering synthesis of Ni1-xZnxFe2O4 ferrites: Mössbauer and catalytic study

    NASA Astrophysics Data System (ADS)

    Velinov, Nikolay; Manova, Elina; Tsoncheva, Tanya; Estournès, Claude; Paneva, Daniela; Tenchev, Krassimir; Petkova, Vilma; Koleva, Kremena; Kunev, Boris; Mitov, Ivan

    2012-08-01

    Nickel-zinc ferrite nanoparticles, Ni1-xZnxFe2O4 (x = 0, 0.2, 0.5, 0.8, 1.0) were prepared by combination of chemical precipitation and spark plasma sintering (SPS) techniques and conventional thermal treatment of the obtained precursors. The phase composition and structural properties of the obtained materials were investigated by X-ray diffraction and Mössbauer spectroscopy and their catalytic activity in methanol decomposition was tested. A strong effect of reaction medium leading to the transformation of ferrites to a complex mixture of different iron containing phases was detected. A tendency of formation of Fe-carbide was found for the samples synthesized by SPS, while predominantly iron-nickel alloys ware registered in TS obtained samples. The catalytic activity and selectivity in methanol decomposition to CO and methane depended on the current phase composition of the obtained ferrites, which was formed by the influence of the reaction medium.

  16. Low-crystalline β-FeOOH and vanadium ferrite for positive active materials of lithium secondary cells

    NASA Astrophysics Data System (ADS)

    Funabiki, Atsushi; Yasuda, Hideo; Yamachi, Masanori

    Low-crystalline β-FeOOH and vanadium ferrite were prepared by a simple hydrolysis method. XRD measurement revealed that the former material had a framework of β-FeOOH with somewhat amorphous structure, and that the latter one gave a crystalline structure analogous to that of the hydrated iron orthovanadate. From the electrochemical measurements, it was found that the low-crystalline β-FeOOH positive electrode showed a discharge capacity of 230 mAh/g in the potential range of 4.3 V and 1.6 V versus Li/Li +, and better cycle performance than the high-crystalline one. The vanadium ferrite positive electrode also showed a high discharge capacity over 300 mAh/g and superior cycle performance.

  17. Precipitation of Nb in Ferrite After Austenite Conditioning. Part II: Strengthening Contribution in High-Strength Low-Alloy (HSLA) Steels

    NASA Astrophysics Data System (ADS)

    Altuna, M. A.; Iza-Mendia, Amaia; Gutiérrez, I.

    2012-12-01

    Often, Nb contributes to the strength of a microalloyed steel beyond the expected level because of the grain size strengthening resulting from thermomechanical processing. Two different mechanisms are behind this phenomenon, and both of them have to do with the amount of Nb remaining in solution after hot rolling. The first of them is the increase of the hardenability of the steel as a result of Nb, and the second one is the fine precipitation of NbC in ferrite. Three Nb microalloyed steels were thermomechanically processed in the laboratory and coiled at different temperatures to investigate the effect of Nb content on the tensile properties. The extra strength was linearly related to the Nb remaining in solution after the hot working. The maximum contribution from Nb was reached for a coiling temperature of 873 K (600 °C).

  18. Ferrite Formation Dynamics and Microstructure Due to Inclusion Engineering in Low-Alloy Steels by Ti2O3 and TiN Addition

    NASA Astrophysics Data System (ADS)

    Mu, Wangzhong; Shibata, Hiroyuki; Hedström, Peter; Jönsson, Pär Göran; Nakajima, Keiji

    2016-08-01

    The dynamics of intragranular ferrite (IGF) formation in inclusion engineered steels with either Ti2O3 or TiN addition were investigated using in situ high temperature confocal laser scanning microscopy. Furthermore, the chemical composition of the inclusions and the final microstructure after continuous cooling transformation was investigated using electron probe microanalysis and electron backscatter diffraction, respectively. It was found that there is a significant effect of the chemical composition of the inclusions, the cooling rate, and the prior austenite grain size on the phase fractions and the starting temperatures of IGF and grain boundary ferrite (GBF). The fraction of IGF is larger in the steel with Ti2O3 addition compared to the steel with TiN addition after the same thermal cycle has been imposed. The reason for this difference is the higher potency of the TiO x phase as nucleation sites for IGF formation compared to the TiN phase, which was supported by calculations using classical nucleation theory. The IGF fraction increases with increasing prior austenite grain size, while the fraction of IGF in both steels was the highest for the intermediate cooling rate of 70 °C/min, since competing phase transformations were avoided, the structure of the IGF was though refined with increasing cooling rate. Finally, regarding the starting temperatures of IGF and GBF, they decrease with increasing cooling rate and the starting temperature of GBF decreases with increasing grain size, while the starting temperature of IGF remains constant irrespective of grain size.

  19. Ferrite Formation Dynamics and Microstructure Due to Inclusion Engineering in Low-Alloy Steels by Ti2O3 and TiN Addition

    NASA Astrophysics Data System (ADS)

    Mu, Wangzhong; Shibata, Hiroyuki; Hedström, Peter; Jönsson, Pär Göran; Nakajima, Keiji

    2016-03-01

    The dynamics of intragranular ferrite (IGF) formation in inclusion engineered steels with either Ti2O3 or TiN addition were investigated using in situ high temperature confocal laser scanning microscopy. Furthermore, the chemical composition of the inclusions and the final microstructure after continuous cooling transformation was investigated using electron probe microanalysis and electron backscatter diffraction, respectively. It was found that there is a significant effect of the chemical composition of the inclusions, the cooling rate, and the prior austenite grain size on the phase fractions and the starting temperatures of IGF and grain boundary ferrite (GBF). The fraction of IGF is larger in the steel with Ti2O3 addition compared to the steel with TiN addition after the same thermal cycle has been imposed. The reason for this difference is the higher potency of the TiO x phase as nucleation sites for IGF formation compared to the TiN phase, which was supported by calculations using classical nucleation theory. The IGF fraction increases with increasing prior austenite grain size, while the fraction of IGF in both steels was the highest for the intermediate cooling rate of 70 °C/min, since competing phase transformations were avoided, the structure of the IGF was though refined with increasing cooling rate. Finally, regarding the starting temperatures of IGF and GBF, they decrease with increasing cooling rate and the starting temperature of GBF decreases with increasing grain size, while the starting temperature of IGF remains constant irrespective of grain size.

  20. The intrinsic antimicrobial activity of citric acid-coated manganese ferrite nanoparticles is enhanced after conjugation with the antifungal peptide Cm-p5.

    PubMed

    Lopez-Abarrategui, Carlos; Figueroa-Espi, Viviana; Lugo-Alvarez, Maria B; Pereira, Caroline D; Garay, Hilda; Barbosa, João Arg; Falcão, Rosana; Jiménez-Hernández, Linnavel; Estévez-Hernández, Osvaldo; Reguera, Edilso; Franco, Octavio L; Dias, Simoni C; Otero-Gonzalez, Anselmo J

    2016-01-01

    Diseases caused by bacterial and fungal pathogens are among the major health problems in the world. Newer antimicrobial therapies based on novel molecules urgently need to be developed, and this includes the antimicrobial peptides. In spite of the potential of antimicrobial peptides, very few of them were able to be successfully developed into therapeutics. The major problems they present are molecule stability, toxicity in host cells, and production costs. A novel strategy to overcome these obstacles is conjugation to nanomaterial preparations. The antimicrobial activity of different types of nanoparticles has been previously demonstrated. Specifically, magnetic nanoparticles have been widely studied in biomedicine due to their physicochemical properties. The citric acid-modified manganese ferrite nanoparticles used in this study were characterized by high-resolution transmission electron microscopy, which confirmed the formation of nanocrystals of approximately 5 nm diameter. These nanoparticles were able to inhibit Candida albicans growth in vitro. The minimal inhibitory concentration was 250 µg/mL. However, the nanoparticles were not capable of inhibiting Gram-negative bacteria (Escherichia coli) or Gram-positive bacteria (Staphylococcus aureus). Finally, an antifungal peptide (Cm-p5) from the sea animal Cenchritis muricatus (Gastropoda: Littorinidae) was conjugated to the modified manganese ferrite nanoparticles. The antifungal activity of the conjugated nanoparticles was higher than their bulk counterparts, showing a minimal inhibitory concentration of 100 µg/mL. This conjugate proved to be nontoxic to a macrophage cell line at concentrations that showed antimicrobial activity. PMID:27563243

  1. The intrinsic antimicrobial activity of citric acid-coated manganese ferrite nanoparticles is enhanced after conjugation with the antifungal peptide Cm-p5

    PubMed Central

    Lopez-Abarrategui, Carlos; Figueroa-Espi, Viviana; Lugo-Alvarez, Maria B; Pereira, Caroline D; Garay, Hilda; Barbosa, João ARG; Falcão, Rosana; Jiménez-Hernández, Linnavel; Estévez-Hernández, Osvaldo; Reguera, Edilso; Franco, Octavio L; Dias, Simoni C; Otero-Gonzalez, Anselmo J

    2016-01-01

    Diseases caused by bacterial and fungal pathogens are among the major health problems in the world. Newer antimicrobial therapies based on novel molecules urgently need to be developed, and this includes the antimicrobial peptides. In spite of the potential of antimicrobial peptides, very few of them were able to be successfully developed into therapeutics. The major problems they present are molecule stability, toxicity in host cells, and production costs. A novel strategy to overcome these obstacles is conjugation to nanomaterial preparations. The antimicrobial activity of different types of nanoparticles has been previously demonstrated. Specifically, magnetic nanoparticles have been widely studied in biomedicine due to their physicochemical properties. The citric acid-modified manganese ferrite nanoparticles used in this study were characterized by high-resolution transmission electron microscopy, which confirmed the formation of nanocrystals of approximately 5 nm diameter. These nanoparticles were able to inhibit Candida albicans growth in vitro. The minimal inhibitory concentration was 250 µg/mL. However, the nanoparticles were not capable of inhibiting Gram-negative bacteria (Escherichia coli) or Gram-positive bacteria (Staphylococcus aureus). Finally, an antifungal peptide (Cm-p5) from the sea animal Cenchritis muricatus (Gastropoda: Littorinidae) was conjugated to the modified manganese ferrite nanoparticles. The antifungal activity of the conjugated nanoparticles was higher than their bulk counterparts, showing a minimal inhibitory concentration of 100 µg/mL. This conjugate proved to be nontoxic to a macrophage cell line at concentrations that showed antimicrobial activity. PMID:27563243

  2. Microstructural Variations Across a Dissimilar 316L Austenitic: 9Cr Reduced Activation Ferritic Martensitic Steel Weld Joint

    NASA Astrophysics Data System (ADS)

    Thomas Paul, V.; Karthikeyan, T.; Dasgupta, Arup; Sudha, C.; Hajra, R. N.; Albert, S. K.; Saroja, S.; Jayakumar, T.

    2016-03-01

    This paper discuss the microstructural variations across a dissimilar weld joint between SS316 and 9Cr-RAFM steel and its modifications on post weld heat treatments (PWHT). Detailed characterization showed a mixed microstructure of austenite and martensite in the weld which is in agreement with the phases predicted using Schaeffler diagram based on composition measurements. The presence of very low volume fraction of δ-ferrite in SS316L has been identified employing state of the art electron back-scattered diffraction technique. PWHT of the ferritic steel did not reduce the hardness in the weld metal. Thermal exposure at 973 K (700 °C) showed a progressive reduction in hardness of weld joint with duration of treatment except in austenitic base metal. However, diffusion annealing at 1073 K (800 °C) for 100 hours resulted in an unexpected increase in hardness of weld metal, which is a manifestation of the dilution effects and enrichment of Ni on the transformation characteristics of the weld zone. Migration of carbon from ferritic steel aided the precipitation of fine carbides in the austenitic base metal on annealing at 973 K (700 °C); but enhanced diffusion at 1073 K (880 °C) resulted in coarsening of carbides and thereby reduction of hardness.

  3. Neutron Absorbing Alloys

    DOEpatents

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  4. Understanding of copper precipitation under electron or ion irradiations in FeCu0.1 wt% ferritic alloy by combination of experiments and modelling

    NASA Astrophysics Data System (ADS)

    Radiguet, B.; Barbu, A.; Pareige, P.

    2007-02-01

    This work is dedicated to the understanding of the basic processes involved in the formation of copper enriched clusters in low alloyed FeCu binary system (FeCu0.1 wt%) under irradiation at temperature close to 300 °C. Such an alloy was irradiated with electrons or with ions (Fe+ or He+) in order to deconvolute the effect of displacement cascades and the associated generation of point defect clusters (ion irradiations), and the super-saturation of mono-vacancies and self-interstitial atoms (electron irradiation). The microstructure of this alloy was characterised by tomographic atom probe. Experimental results were compared with results obtained with cluster dynamic model giving an estimation of the evolution of point defects (free or agglomerated) under irradiation on the one hand and describing homogeneous enhanced precipitation of copper on the other hand. The comparison between the results obtained on the different irradiation conditions and the model suggests that the point defect clusters (dislocation loops and/or nano-voids) created in displacement cascades play a major role in copper clustering in low copper alloy irradiated at 573 K.

  5. Ferrite Nanoparticles in Pharmacological Modulation of Angiogenesis

    NASA Astrophysics Data System (ADS)

    Deshmukh, Aparna; Radha, S.; Khan, Y.; Tilak, Priya

    2011-07-01

    Nanoparticles are being explored in the targeted drug delivery of pharmacological agents : angiogenesis being one such novel application which involves formation of new blood vessels or branching of existing ones. The present study involves the use of ferrite nanoparticles for precise therapeutic modulation of angiogenesis. The ferrite nanoparticles synthesized by co-precipitation of ferrous and ferric salts by a suitable base, were found to be 10-20 nm from X-ray diffraction and TEM measurements. The magnetization measurements showed superparamagnetic behavior of the uncoated nanoparticles. These ferrite nanoparticles were found to be bio-compatible with lymphocytes and neural cell lines from the biochemical assays. The chick chorioallantoic membrane(CAM) from the shell of fertile white Leghorn eggs was chosen as a model to study angiogenic activity. An enhancement in the angiogenic activity in the CAM due to addition of uncoated ferrite nanoparticles was observed.

  6. Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

    DOEpatents

    Wright, Randy B.

    1992-01-01

    Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation).

  7. Characterizing and Modeling Ferrite-Core Probes

    NASA Astrophysics Data System (ADS)

    Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H.; Aldrin, John C.

    2010-02-01

    In this paper, we accurately and carefully characterize a ferrite-core probe that is widely used for aircraft inspections. The characterization starts with the development of a model that can be executed using the proprietary volume-integral code, VIC-3D©, and then the model is fitted to measured multifrequency impedance data taken with the probe in freespace and over samples of a titanium alloy and aluminum. Excellent results are achieved, and will be discussed.

  8. Thermally activated retainer means utilizing shape memory alloy

    NASA Technical Reports Server (NTRS)

    Grimaldi, Margaret E. (Inventor); Hartz, Leslie S. (Inventor)

    1993-01-01

    A retainer member suitable for retaining a gap filler placed in gaps between adjacent tile members is presented. One edge of the retainer member may be attached to the gap filler and another edge may be provided with a plurality of tab members which in an intermediate position do not interfere with placement or removal of the gap filler between tile members. The retainer member may be fabricated from a shape memory alloy which when heated to a specified memory temperature will thermally activate the tab members to predetermined memory positions engaging the tile members to retain the gap filler in the gap. This invention has particular application to the thermal tiles on space vehicles such as the Space Shuttle Orbiter.

  9. Corrosion performance of laser-welded austenitic-ferritic connections

    NASA Astrophysics Data System (ADS)

    Weigl, M.; Schmidt, M.

    2013-02-01

    In order to reduce the material costs of white-goods made of stainless steels, tailored constructions with unequally alloyed stainless steels shall be used. For that purpose nickel-alloyed austenitic stainless steels are supposed to be limited to zones with demanding needs for corrosions resistance, whereas nickel-free ferritic stainless steels provide an attractive cost-performance ratio for the remaining components of a system. Particularly the present article discusses the corrosion performance of austenitic-ferritic connections, welded with high-power disc lasers at accelerated feed rates, as a function of the shielding gas composition and the surface condition.

  10. Measurement of Activity of Indium in Liquid Bi-In-Sn Alloys by EMF Method

    NASA Astrophysics Data System (ADS)

    Kumar, M. R.; Mohan, S.; Behera, C. K.

    2016-08-01

    The electrochemical technique based on a molten salt electrolyte galvanic cell has been used to measure the activity of indium in liquid Bi-In-Sn alloys in the temperature range of 723 K to 855 K along three ternary sections. The activity of tin in Bi-Sn binary alloys has also been measured by the same technique in the above temperature range. The activity of indium in Bi-In-Sn alloys shows negative deviation from Raoult's law for most of the compositions and slight positive deviations for a few indium-rich compositions. The ternary excess molar free energies have been calculated by Darken's treatment. Isoactivity curves at 813 K in the ternary Bi-In-Sn alloys were derived by combining the activity data of In-Sn and Bi-In alloys. The values of excess molar free energy obtained in this study are compared with those calculated from the Muggianu model at 813 K.

  11. Measurement of Activity of Indium in Liquid Bi-In-Sn Alloys by EMF Method

    NASA Astrophysics Data System (ADS)

    Kumar, M. R.; Mohan, S.; Behera, C. K.

    2016-05-01

    The electrochemical technique based on a molten salt electrolyte galvanic cell has been used to measure the activity of indium in liquid Bi-In-Sn alloys in the temperature range of 723 K to 855 K along three ternary sections. The activity of tin in Bi-Sn binary alloys has also been measured by the same technique in the above temperature range. The activity of indium in Bi-In-Sn alloys shows negative deviation from Raoult's law for most of the compositions and slight positive deviations for a few indium-rich compositions. The ternary excess molar free energies have been calculated by Darken's treatment. Isoactivity curves at 813 K in the ternary Bi-In-Sn alloys were derived by combining the activity data of In-Sn and Bi-In alloys. The values of excess molar free energy obtained in this study are compared with those calculated from the Muggianu model at 813 K.

  12. Comminuting irradiated ferritic steel

    DOEpatents

    Bauer, Roger E.; Straalsund, Jerry L.; Chin, Bryan A.

    1985-01-01

    Disclosed is a method of comminuting irradiated ferritic steel by placing the steel in a solution of a compound selected from the group consisting of sulfamic acid, bisulfate, and mixtures thereof. The ferritic steel is used as cladding on nuclear fuel rods or other irradiated components.

  13. XXIst Century Ferrites

    NASA Astrophysics Data System (ADS)

    Mazaleyrat, F.; Zehani, K.; Pasko, A.; Loyau, V.; LoBue, M.

    2012-05-01

    Ferrites have always been a subject of great interest from point of view of magnetic application, since the fist compass to present date. In contrast, the scientific interest for iron based magnetic oxides decreased after Ørsted discovery as they where replaced by coil as magnetizing sources. Neel discovery of ferrimagnetism boosted again interest and leads to strong developments during two decades before being of less interest. Recently, the evolution of power electronics toward higher frequency, the downsizing of ceramics microstucture to nanometer scale, the increasing price of rare-earth elements and the development of magnetocaloric materials put light again on ferrites. A review on three ferrite families is given herein: harder nanostructured Ba2+Fe12O19 magnet processed by spark plasma sintering, magnetocaloric effect associated to the spin transition reorientation of W-ferrite and low temperature spark plasma sintered Ni-Zn-Cu ferrites for high frequency power applications.

  14. The role of molybdenum additions and prior deformation on acicular ferrite formation in microalloyed Nb-Ti low-carbon line-pipe steels

    SciTech Connect

    Tang Zhenghua Stumpf, Waldo

    2008-06-15

    Microstructures in Nb-Ti-microalloyed line-pipe steels with various molybdenum additions, consisted mostly of acicular ferrite plus polygonal ferrite after hot rolling and rapid cooling. Structure-sensitive surface relief after etching on shadowed extraction replicas, allowed quantification of the acicular and polygonal ferrite contents. Continuous cooling transformation diagrams of two alloys, one Mo-free and the other containing 0.22% Mo, were determined for cooling rates from 0.1 to 40 deg. C s{sup -1} without and with prior deformation of the austenite below the nil-recrystallisation temperature. Molybdenum additions slightly enhanced the acicular ferrite formation in the strain-free austenite whereas prior deformation had a much greater effect, and strongly promoted acicular ferrite formation in both alloys. Thin foil electron microscopy of acicular ferrite in these low-inclusion content alloys showed a preference for parallel acicular ferrite laths with less 'chaotically' nucleated laths.

  15. Differential cytotoxicity of copper ferrite nanoparticles in different human cells.

    PubMed

    Ahmad, Javed; Alhadlaq, Hisham A; Alshamsan, Aws; Siddiqui, Maqsood A; Saquib, Quaiser; Khan, Shams T; Wahab, Rizwan; Al-Khedhairy, Abdulaziz A; Musarrat, Javed; Akhtar, Mohd Javed; Ahamed, Maqusood

    2016-10-01

    Copper ferrite nanoparticles (NPs) have the potential to be applied in biomedical fields such as cell labeling and hyperthermia. However, there is a lack of information concerning the toxicity of copper ferrite NPs. We explored the cytotoxic potential of copper ferrite NPs in human lung (A549) and liver (HepG2) cells. Copper ferrite NPs were crystalline and almost spherically shaped with an average diameter of 35 nm. Copper ferrite NPs induced dose-dependent cytotoxicity in both types of cells, evident by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide and neutral red uptake assays. However, we observed a quite different susceptibility in the two kinds of cells regarding toxicity of copper ferrite NPs. Particularly, A549 cells showed higher susceptibility against copper ferrite NP exposure than those of HepG2 cells. Loss of mitochondrial membrane potential due to copper ferrite NP exposure was observed. The mRNA level as well as activity of caspase-3 enzyme was higher in cells exposed to copper ferrite NPs. Cellular redox status was disturbed as indicated by induction of reactive oxygen species (oxidant) generation and depletion of the glutathione (antioxidant) level. Moreover, cytotoxicity induced by copper ferrite NPs was efficiently prevented by N-acetylcysteine treatment, which suggests that reactive oxygen species generation might be one of the possible mechanisms of cytotoxicity caused by copper ferrite NPs. To the best of our knowledge, this is the first report showing the cytotoxic potential of copper ferrite NPs in human cells. This study warrants further investigation to explore the mechanisms of differential toxicity of copper ferrite NPs in different types of cells. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26918645

  16. Tensile response of low activation ferritic steels irradiated in ORR at temperatures in the range 60-400 °C

    NASA Astrophysics Data System (ADS)

    Hamilton, M. L.; Gelles, D. S.

    2002-12-01

    Post-irradiation tensile test results are reported for a series of low activation steels containing manganese following irradiation in the Oak Ridge Reactor at 60, 200, 330 and 400 °C to ˜10 dpa. Alloy compositions included 2Cr, 9Cr and 12Cr steels with V to 1.5% and W to 1.0%. Strengths are higher in all alloys for irradiation conditions below 400 °C, with peak hardening occurring following irradiation at 200 °C. The 9Cr alloy class exhibited the smallest increases in hardening. Test results were consistent with previous results obtained on fast flux test facility-irradiated specimens. Manganese does not appear to play a role in the hardening observed at these low irradiation temperatures.

  17. Influence of helium on deuterium retention in reduced activation ferritic martensitic steel (F82H) under simultaneous deuterium and helium irradiation

    NASA Astrophysics Data System (ADS)

    Yakushiji, K.; Lee, H. T.; Oya, M.; Hamaji, Y.; Ibano, K.; Ueda, Y.

    2016-02-01

    Deuterium and helium retention in Japanese reduced activation ferritic martensitic (RAFM) steel (F82H) under simultaneous D-He irradiation at 500, 625, 750, and 818 K was studied. This study aims to clarify tritium retention behavior in RAFM steels to assess their use as plasma facing materials. The irradiation fluence was kept constant at 1 × 1024 D m-2. Four He desorption peaks were observed with He retention greatest at 625 K. At T > 625 K a monotonic decrease in He retention was observed. At all temperatures a systematic reduction in D retention was observed for the simultaneous D-He case in comparison to D-only case. This suggests that He implanted at the near surface in RAFM steels may reduce the inward penetration of tritium in RAFM steels that would result in lower tritium inventory for a given fluence.

  18. Nanoporous PtRu Alloys with Unique Catalytic Activity toward Hydrolytic Dehydrogenation of Ammonia Borane.

    PubMed

    Zhou, Qiuxia; Xu, Caixia

    2016-03-01

    Nanoporous (NP) PtRu alloys with three different bimetallic components were straightforwardly fabricated by dealloying PtRuAl ternary alloys in hydrochloric acid. Selective etching of aluminum from source alloys generates bicontinuous network nanostructures with uniform size and structure. The as-made NP-PtRu alloys exhibit superior catalytic activity toward the hydrolytic dehydrogenation of ammonia borane (AB) than pure NP-Pt and NP-Ru owing to alloying platinum with ruthenium. The NP-Pt70 Ru30 alloy exhibits much higher specific activity toward hydrolytic dehydrogenation of AB than NP-Pt30 Ru70 and NP-Pt50 Ru50 . The hydrolysis activation energy of NP-Pt70 Ru30 was estimated to be about 38.9 kJ mol(-1) , which was lower than most of the reported activation energy values in the literature. In addition, recycling tests show that the NP-Pt70 Ru30 is still highly active in the hydrolysis of AB even after five runs, which indicates that NP-PtRu alloy accompanied by the network nanoarchitecture is beneficial to improve structural stability toward the dehydrogenation of AB. PMID:26573746

  19. On the Role of Alloy Composition and Sintering Parameters in the Bimodal Grain Size Distribution and Mechanical Properties of ODS Ferritic Steels

    NASA Astrophysics Data System (ADS)

    García-Junceda, Andrea; Campos, Mónica; García-Rodríguez, Nerea; Torralba, José Manuel

    2016-04-01

    A sintered 14Cr-5Al-3W oxide dispersion strengthened steel was produced by mechanical alloying and consolidated by field-assisted hot pressing. First, a nanostructured powder was developed thanks to the high-energy milling used for introducing 0.4Ti-0.25Y2O3-0.6ZrO2 into the prealloyed Fe-Cr-Al-W powder, and then the processed powders were consolidated under a low diffusive technique to better retain the microstructure inherited from milling. The effect of the addition of zirconia and of the pressure applied during sintering on the final bimodal grain microstructure and mechanical properties is assessed. Both parameters are responsible for the refinement of the microstructure by increasing the volume fraction of the ultrafine grains (0 to 400 nm), leading to an enhancement of the mechanical properties, such as the microhardness and tensile strength.

  20. The Effect of Interfacial Element Partitioning on Ferrite and Bainite Formation

    NASA Astrophysics Data System (ADS)

    Chen, Hao; van der Zwaag, Sybrand

    2016-05-01

    The formation of bainitic ferrite and that of grain boundary ferrite in low alloy steels have been two of the most important and interesting research topics in the field of solid state ferrous phase transformation for several decades, and various aspects of these two transformations have been discussed extensively in the literature. Recently, a so-called Gibbs energy balance (GEB) model was proposed by the authors to evaluate alloying element effects on the growth of bainitic ferrite and grain boundary ferrite. The model predicts a growth mode transition from paraequilibrium, negligible partitioning to partitioning during the isothermal formation of bainitic ferrite and grain boundary ferrite. Transformation stasis and bay phenomenon are well explained by the GEB model and both of them are found to be due to alloying element diffusion at the interface. This overview gives a summary of the authors' recent progress in the understanding of the growth of bainitic ferrite and grain boundary ferrite, with particular focus on the growth mode transition, the transformation stasis phenomenon and the bay phenomenon.

  1. Designation of alloy composition of reduced-activation martensitic steel

    NASA Astrophysics Data System (ADS)

    Kimura, A.; Kayano, H.; Misawa, T.; Matsui, H.

    1994-09-01

    An alloy composition of reduced-activation martensitic steel for fusion reactor is designed on the basis of the experimental results of postirradiation microstructure, mechanical properties, such as creep, fracture toughness and tensile properties, hydrogen effects and corrosion. At present, a desired composition of the steel is 0.1C-0.05Si-0.5Mn-9Cr-2W-0.25V-0.02Ti-0.05Ta- < 0.002S- < 0.002P by weight percent. Effects of the other minor elements such as Al, Zr and B are also inspected. An addition of 0.05 wt% Ta increases the high temperature strength but reduces the fracture toughness. Susceptibility to hydrogen-induced cracking is reduced by an addition of 0.03 wt% Al, though it results in a severe degradation of the fracture toughness. An addition of 30 wppm B together with the addition of 0.02 wt% Ti increases the fracture toughness. Void nucleation at grain boundaries, however, is enhanced by the B addition under the FFTF irradiation at 638 K in 10 dpa.

  2. Investigation on different oxides as candidates for nano-sized ODS particles in reduced-activation ferritic (RAF) steels

    NASA Astrophysics Data System (ADS)

    Hoffmann, Jan; Rieth, Michael; Lindau, Rainer; Klimenkov, Michael; Möslang, Anton; Sandim, Hugo Ricardo Zschommler

    2013-11-01

    Future generation reactor concepts are based on materials that can stand higher temperatures and higher neutron doses in corrosive environments. Oxide dispersion strengthened steels with chromium contents ranging from 9 to 14 wt.% - produced by mechanical alloying - are typical candidate materials for future structural materials in fission and fusion power plants.

  3. Mechanical activation of a hard magnetic Fe-Cr-Co alloy powder charge

    NASA Astrophysics Data System (ADS)

    Alymov, M. I.; Milyaev, I. M.; Sychev, A. E.; Kovalev, D. Yu.; Korneev, V. P.; Morozov, Yu. G.; Yusupov, V. S.; Bompe, T. A.

    2014-07-01

    The mechanical activation (MA) of a charge of a hard magnetic 22Kh15KT alloy is studied by wet and dry milling in a planetary mill in a medium of argon and ethyl alcohol with addition of surface-active materials and without them. It is shown that, upon dry MA, powder alloy components are alloyed with formation of two bcc solid solutions and, upon wet MA, charge particles are only intensely dispersed. Dispersion is developed at the highest degree in the first five minutes of MA.

  4. Properties of ferrites important to their friction and wear behavior

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1983-01-01

    Environmental, chemical and crystallographical effects on the fundamental nature on friction and wear of the ferrites in contact with metals, magnetic tapes and themselves are reviewed. The removal of adsorbed films from the surfaces of ferrites results in very strong interfacial adhesion and high friction in ferrite to metal and ferrite to magnetic tape contacts. The metal ferrite bond at the interface is primarily a chemical bond between the metal atoms and the large oxygen anions in the ferrite surface, and the strength of these bonds is related to the oxygen to metal bond strength in the metal oxide. The more active the metal, the higher is the coefficient of friction. Not only under adhesive conditions, but also under abrasive conditions the friction and wear properties of ferrites are related to the crystallographic orientation. With ferrite to ferrite contact the mating of highest atomic density (most closely packed) direction on matched crystallographic planes, that is, 110 directions on /110/planes, results in the lowest coefficient of friction.

  5. Alloy development for irradiation performance. Quarterly progress report for period ending December 31, 1980

    SciTech Connect

    Not Available

    1981-04-01

    Progress is reported in eight sections: analysis and evaluation studies, test matrices and test methods development, Path A Alloy Development (austenitic stainless steels), Path C Alloy Development (Ti and V alloys), Path D Alloy Development (Fe alloys), Path E Alloy Development (ferritic steels), irradiation experiments and materials inventory, and materials compatibility and hydrogen permeation studies. (DLC)

  6. Hierarchical Pd-Sn Alloy Nanosheet Dendrites: An Economical and Highly Active Catalyst for Ethanol Electrooxidation

    PubMed Central

    Ding, Liang-Xin; Wang, An-Liang; Ou, Yan-Nan; Li, Qi; Guo, Rui; Zhao, Wen-Xia; Tong, Ye-Xiang; Li, Gao-Ren

    2013-01-01

    Hierarchical alloy nanosheet dendrites (ANSDs) are highly favorable for superior catalytic performance and efficient utilization of catalyst because of the special characteristics of alloys, nanosheets, and dendritic nanostructures. In this paper, we demonstrate for the first time a facile and efficient electrodeposition approach for the controllable synthesis of Pd-Sn ANSDs with high surface area. These synthesized Pd-Sn ANSDs exhibit high electrocatalytic activity and superior long-term cycle stability toward ethanol oxidation in alkaline media. The enhanced electrocataytic activity of Pd-Sn ANSDs may be attributed to Pd-Sn alloys, nanosheet dendrite induced promotional effect, large number of active sites on dendrite surface, large surface area, and good electrical contact with the base electrode. Because of the simple implement and high flexibility, the proposed approach can be considered as a general and powerful strategy to synthesize the alloy electrocatalysts with high surface areas and open dendritic nanostructures. PMID:23383368

  7. Effect of Heat Input on Microstructure Evolution and Mechanical Properties in the Weld Heat-Affected Zone of 9Cr-2W-VTa Reduced Activation Ferritic-Martensitic Steel for Fusion Reactor

    NASA Astrophysics Data System (ADS)

    Moon, Joonoh; Lee, Chang-Hoon; Lee, Tae-Ho; Kim, Hyoung Chan

    2015-01-01

    The phase transformation and mechanical properties in the weld heat-affected zone (HAZ) of a reduced activation ferritic/martensitic steel were explored. The samples for HAZs were prepared using a Gleeble simulator at different heat inputs. The base steel consisted of tempered martensite and carbides through quenching and tempering treatment, whereas the HAZs consisted of martensite, δ-ferrite, and a small volume of autotempered martensite. The prior austenite grain size, lath width of martensite, and δ-ferrite fraction in the HAZs increased with increase in the heat input. The mechanical properties were evaluated using Vickers hardness and Charpy V-notch impact test. The Vickers hardness in the HAZs was higher than that in the base steel but did not change noticeably with increase in the heat input. The HAZs showed poor impact property due to the formation of martensite and δ-ferrite as compared to the base steel. In addition, the impact property of the HAZs deteriorated more with the increase in the heat input. Post weld heat treatment contributed to improve the impact property of the HAZs through the formation of tempered martensite, but the impact property of the HAZs remained lower than that of base steel.

  8. Computation of infinite dilute activity coefficients of binary liquid alloys using complex formation model

    NASA Astrophysics Data System (ADS)

    Awe, O. E.; Oshakuade, O. M.

    2016-04-01

    A new method for calculating Infinite Dilute Activity Coefficients (γ∞s) of binary liquid alloys has been developed. This method is basically computing γ∞s from experimental thermodynamic integral free energy of mixing data using Complex formation model. The new method was first used to theoretically compute the γ∞s of 10 binary alloys whose γ∞s have been determined by experiments. The significant agreement between the computed values and the available experimental values served as impetus for applying the new method to 22 selected binary liquid alloys whose γ∞s are either nonexistent or incomplete. In order to verify the reliability of the computed γ∞s of the 22 selected alloys, we recomputed the γ∞s using three other existing methods of computing or estimating γ∞s and then used the γ∞s obtained from each of the four methods (the new method inclusive) to compute thermodynamic activities of components of each of the binary systems. The computed activities were compared with available experimental activities. It is observed that the results from the method being proposed, in most of the selected alloys, showed better agreement with experimental activity data. Thus, the new method is an alternative and in certain instances, more reliable approach of computing γ∞s of binary liquid alloys.

  9. Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

    DOEpatents

    Wright, R.B.

    1992-01-14

    Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation). 23 figs.

  10. Corrosion behavior of nickel-containing alloys in artificial sweat.

    PubMed

    Randin, J P

    1988-07-01

    The corrosion resistance of various nickel-containing alloys was measured in artificial sweat (perspiration) using the Tafel extrapolation method. It was found that Ni, CuNi 25 (coin alloy), NiAl (colored intermetallic compounds), WC + Ni (hard metal), white gold (jewelry alloy), FN42 and Nilo Alby K (controlled expansion alloys), and NiP (electroless nickel coating) are in an active state and dissolve readily in oxygenated artificial sweat. By contrast, austenitic stainless steels, TiC + Mo2C + Ni (hard metal), NiTi (shape-memory alloy), Hastelloy X (superalloy), Phydur (precipitation hardening alloy), PdNi and SnNi (nickel-containing coatings) are in a passive state but may pit under certain conditions. Cobalt, Cr, Ti, and some of their alloys were also investigated for the purpose of comparison. Cobalt and its alloys have poor corrosion resistance except for Stellite 20. Chromium and high-chromium ferritic stainless steels have a high pitting potential but the latter are susceptible to crevice corrosion. Ti has a pitting potential greater than 3 V. Comparison between the in vitro measurements of the corrosion rate of nickel-based alloys and the clinical observation of the occurrence of contact dermatitis is discussed. PMID:3403567

  11. Evaluation of the catalytic activity of Pd-Ag alloys on ethanol oxidation and oxygen reduction reactions in alkaline medium

    NASA Astrophysics Data System (ADS)

    Oliveira, M. C.; Rego, R.; Fernandes, L. S.; Tavares, P. B.

    2011-08-01

    Pd-Ag alloys containing different amounts of Ag (8, 21 and 34 at.%) were prepared in order to evaluate their catalytic activity towards the ethanol oxidation (EOR) and oxygen reduction (ORR) reactions. A sequential electroless deposition of Ag and Pd on a stainless steel disc, followed by annealing at 650 °C under Ar stream, was used as the alloy electrode deposition process. From half-cell measurements in a 1.0 M NaOH electrolyte at ≅20 °C, it was found that alloying Pd with Ag leads to an increases of the ORR and EOR kinetics, relative to Pd. Among the alloys under study, the 21 at.% Ag content alloy presents the highest catalytic activity for the EOR and the lowest Ag content alloy (8 at.% Ag) shows the highest ORR activity. Moreover, it was found that the selectivity of Pd-Ag alloys towards ORR is sustained when ethanol is present in the electrolyte.

  12. Effect of Cu content on the antibacterial activity of titanium-copper sintered alloys.

    PubMed

    Liu, Jie; Li, Fangbing; Liu, Cong; Wang, Hongying; Ren, Baorui; Yang, Ke; Zhang, Erlin

    2014-02-01

    The phase constitution and the microstructure Ti-x Cu (x=2, 5, 10 and 25 wt.%) sintered alloys were investigated by XRD and SEM and the antibacterial activity was assessed in order to investigate the effect of the Cu content on the antibacterial activity. The results have shown that Ti2Cu was synthesized as a main secondary phase in all Ti-Cu alloys while Cu-rich phase was formed in the alloys with 5 wt.% or more copper. Antibacterial tests have showed that the Cu content influences the antibacterial rate seriously and only the alloys with 5 wt.% or high Cu have a strong and stable antibacterial rate, which indicates that the Cu content in Ti-Cu alloys must be at least 5 wt.% to obtain strong and stable antibacterial property. The Cu content also influenced the Cu ion release behavior. High Cu ion release concentration and high Cu ion release rate were observed for Ti-Cu alloys with high Cu content. It was concluded that the Cu content affects the Cu existence and the Cu ion release behavior, which in turn influences the antibacterial property. It was thought that the Cu-rich phase should play an important role in the strong antibacterial activity. PMID:24411393

  13. Impedance calculation for ferrite inserts

    SciTech Connect

    Breitzmann, S.C.; Lee, S.Y.; Ng, K.Y.; /Fermilab

    2005-01-01

    Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.

  14. Development of Lanthanum Ferrite SOFC Cathodes

    SciTech Connect

    Simner, Steve P.; Bonnett, Jeff F.; Canfield, Nathan L.; Meinhardt, Kerry D.; Shelton, Jayne P.; Sprenkle, Vince L.; Stevenson, Jeffry W.

    2003-01-01

    A number of studies have been conducted concerning compositional/microstructural modifications of a Sr-doped lanthanum ferrite (LSF) cathode and protective Sm-doped ceria (SDC) layer in an anode supported solid oxide fuel cell (SOFC). Emphasis was placed on achieving enhanced low temperature (700-800 degrees C) performance, and long-term cell stability. Investigations involved manipulation of the lanthanum ferrite chemistry, addition of noble metal oxygen reduction catalysts, incorporation of active cathode layer compositions containing Co, Fe and higher Sr contents, and attempts to optimize the ceria barrier layer between the LSF cathode and YSZ electrolyte.

  15. Electrical transport behavior of nonstoichiometric magnesium-zinc ferrite

    SciTech Connect

    Ghatak, S.; Sinha, M.; Meikap, A.K.; Pradhan, S.K.

    2010-08-15

    This paper presents the direct current conductivity, alternate current conductivity and dielectric properties of nonstoichiometric magnesium-zinc ferrite below room temperature. The frequency exponent (s) of conductivity shows an anomalous temperature dependency. The magnitude of the temperature exponent (n) of dielectric permittivity strongly depends on frequency and its value decreases with increasing frequency. The grain boundary contribution is dominating over the grain contribution in conduction process and the temperature dependence of resistance due to grain and grain boundary contribution exhibits two activation regions. The ferrite shows positive alternating current magnetoconductivity. The solid state processing technique was used for the preparation of nanocrystalline ferrite powder from oxides of magnesium, zinc and iron. The X-ray diffraction methods were used in determining the structure and composition of obtained ferrite, while multimeter, impedance analyzer, liquid nitrogen cryostat and electromagnet were used in the study of conducting and dielectric properties of ferrite.

  16. Microstructure and texture of Nb + Ti stabilized ferritic stainless steel

    SciTech Connect

    Yan Haitao Bi Hongyun; Li Xin; Xu Zhou

    2008-12-15

    The microstructure, texture and grain boundary character distribution of Nb + Ti stabilized ferritic stainless steel were analyzed using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The addition of alloying elements such as Ti and Nb to ferritic stainless steel causes the formation of TiN, NbC and Fe{sub 2}Nb. The textures of cold rolled samples were dominated by the {alpha}-fiber, while the textures of annealed samples exhibit a very strong {gamma}-fiber. The changes in texture are closely related to the grain boundary characteristics.

  17. ON QUANTIFICATION OF HELIUM EMBRITTLEMENT IN FERRITIC/MARTENSITIC STEELS

    SciTech Connect

    Gelles, David S.

    2000-12-01

    Helium accumulation due to transmutation has long been considered a potential cause for embrittlement in ferritic/martensitic steels. Three Charpy impact databases involving nickel- and boron-doped alloys are quantified with respect to helium accumulation, and it is shown that all predict a very large effect of helium production on embrittlement. If these predictions are valid, use of Ferritic/Martensitic steels for Fusion first wall applications is highly unlikely. It is therefore necessary to reorient efforts regarding development of these steels for fusion applications to concentrate on the issue of helium embrittlement.

  18. Pu-ZR Alloy high-temperature activation-measurement foil

    DOEpatents

    McCuaig, Franklin D.

    1977-08-02

    A nuclear reactor fuel alloy consists essentially of from slightly greater than 7 to about 4 w/o zirconium, balance plutonium, and is characterized in that the alloy is castable and is rollable to thin foils. A preferred embodiment of about 7 w/o zirconium, balance plutonium, has a melting point substantially above the melting point of plutonium, is rollable to foils as thin as 0.0005 inch thick, and is compatible with cladding material when repeatedly cycled to temperatures above 650.degree. C. Neutron flux densities across a reactor core can be determined with a high-temperature activation-measurement foil which consists of a fuel alloy foil core sandwiched and sealed between two cladding material jackets, the fuel alloy foil core being a 7 w/o zirconium, plutonium foil which is from 0.005 to 0.0005 inch thick.

  19. Thermodynamic activity measurements of U-Zr alloys by knudsen effusion mass spectrometry

    NASA Astrophysics Data System (ADS)

    Kanno, Masayoshi; Yamawaki, Michio; Koyama, Tadafumi; Morioka, Nobuo

    1988-06-01

    Vaporization of a series of U-Zr alloys, a fundamental subsystem of the promising metallic fuel U-Pu-Zr, was studied by using a tantalum Knudsen cell coupled with a mass spectrometer in the temperature range 1700-2060 K. Thermodynamic activities, partial molar Gibbs free energies and integral molar Gibbs free energies of mixing were calculated from the partial vapor pressures of uranium over these alloys. The activities of uranium exhibit negative deviations from ideality, especially in the uranium-rich composition region. Both the solidus and liquidus lines for this system estimated from the activities show negative deviations from the tentative phase diagram previously reported.

  20. Nickel hydroxide/cobalt-ferrite magnetic nanocatalyst for alcohol oxidation.

    PubMed

    Bhat, Pooja B; Inam, Fawad; Bhat, Badekai Ramachandra

    2014-08-11

    A magnetically separable, active nickel hydroxide (Brønsted base) coated nanocobalt ferrite catalyst has been developed for oxidation of alcohols. High surface area was achieved by tuning the particle size with surfactant. The surface area of 120.94 m2 g(-1) has been achieved for the coated nanocobalt ferrite. Improved catalytic activity and selectivity were obtained by synergistic effect of transition metal hydroxide (basic hydroxide) on nanocobalt ferrite. The nanocatalyst oxidizes primary and secondary alcohols efficiently (87%) to corresponding carbonyls in good yields. PMID:25075969

  1. Facile synthesis of PtAu alloy nanoparticles with high activity for formic acid oxidation

    SciTech Connect

    Zhang, Sheng; Shao, Yuyan; Yin, Geping; Lin, Yuehe

    2010-02-15

    We report the facile synthesis of carbon supported PtAu alloy nanoparticles with high electrocatalytic activity as the anode catalyst for direct formic acid fuel cells (DFAFCs). PtAu alloy nanopaticles are synthesized by co-reducing HAuCl4 and H2PtCl6 with NaBH4 in the presence of sodium citrate and then the nanoparticles are deposited on Vulcan XC-72R carbon support (PtAu/C). The obtained catalysts are characterized with X-ray diffraction (XRD) and transmission electron microscope (TEM), which reveal PtAu alloy formation with an average diameter of 4.6 nm. PtAu/C exhibits 8 times higher catalytic activity toward formic acid oxidation than Pt/C. The enhanced activity of PtAu/C catalyst is attributed to noncontinuous Pt sites formed in the presence of the neighbored Au sites, which promotes direct oxidation of formic acid by avoiding poison CO.

  2. A Comparison of Creep Rupture Strength of Ferritic/Austenitic Dissimilar Weld Joints of Different Grades of Cr-Mo Ferritic Steels

    NASA Astrophysics Data System (ADS)

    Laha, K.; Chandravathi, K. S.; Parameswaran, P.; Goyal, Sunil; Mathew, M. D.

    2012-04-01

    Evaluations of creep rupture properties of dissimilar weld joints of 2.25Cr-1Mo, 9Cr-1Mo, and 9Cr-1MoVNb steels with Alloy 800 at 823 K were carried out. The joints were fabricated by a fusion welding process employing an INCONEL 182 weld electrode. All the joints displayed lower creep rupture strength than their respective ferritic steel base metals, and the strength reduction was greater in the 2.25Cr-1Mo steel joint and less in the 9Cr-1Mo steel joint. Failure location in the joints was found to shift from the ferritic steel base metal to the intercritical region of the heat-affected zone (HAZ) of the ferritic steel (type IV cracking) with the decrease in stress. At still lower stresses, the failure in the joints occurred at the ferritic/austenitic weld interface. The stress-life variation of the joints showed two-slope behavior and the slope change coincided with the occurrence of ferritic/austenitic weld interface cracking. Preferential creep cavitation in the soft intercritical HAZ induced type IV failure, whereas creep cavitation at the interfacial particles induced ferritic/austenitic weld interface cracking. Micromechanisms of the type IV failure and the ferritic/austenitic interface cracking in the dissimilar weld joint of the ferritic steels and relative cracking susceptibility of the joints are discussed based on microstructural investigation, mechanical testing, and finite element analysis (FEA) of the stress state across the joint.

  3. Microstructural examination of low activation ferritic steels following irradiation in ORR at 330 and 400 °C to ˜10 dpa

    NASA Astrophysics Data System (ADS)

    Gelles, D. S.

    2004-08-01

    Microstructural examinations are reported for a series of low activation steels containing Mn following irradiation in the Oak Ridge Reactor at 330 and 400 °C to ˜10 dpa. Alloy compositions included 2% Cr, 9% Cr and 12% Cr steels with V to 1.5% and W to 1.0%. Results include compositional changes in precipitates and microstructural changes as a function of composition and irradiation temperature. It is concluded that temperatures in ORR are on the order of 50 °C higher than anticipated.

  4. Effects of Solute Nb Atoms and Nb Precipitates on Isothermal Transformation Kinetics from Austenite to Ferrite

    NASA Astrophysics Data System (ADS)

    Wang, Li; Parker, Sally; Rose, Andrew; West, Geoff; Thomson, Rachel

    2016-05-01

    Nb is a very important micro-alloying element in low-carbon steels, for grain size refinement and precipitation strengthening, and even a low content of Nb can result in a significant effect on phase transformation kinetics from austenite to ferrite. Solute Nb atoms and Nb precipitates may have different effects on transformation behaviors, and these effects have not yet been fully characterized. This paper examines in detail the effects of solute Nb atoms and Nb precipitates on isothermal transformation kinetics from austenite to ferrite. The mechanisms of the effects have been analyzed using various microscopy techniques. Many solute Nb atoms were found to be segregated at the austenite/ferrite interface and apply a solute drag effect. It has been found that solute Nb atoms have a retardation effect on ferrite nucleation rate and ferrite grain growth rate. The particle pinning effect caused by Nb precipitates is much weaker than the solute drag effect.

  5. Effect of chemical composition and ferrite content on room temperature SCC behavior of austenitic weld metals

    SciTech Connect

    Raghunatha Rao, B.; Prasad Rao, K.; Iyer, K.J.L. )

    1993-03-01

    Austenitic stainless steels are widely used in the welded condition especially in chemical, petrochemical, thermal power, and nuclear industries where they are subjected to stresses in corrosive environments. Since austenitic stainless steel weld metals invariably contain some delta ferrite to avoid hot cracking, the effect of ferrite on the stress corrosion cracking behavior is important. Austenitic weld metals with different alloy additions and different ferrite contents were investigated for their resistance to room temperature stress corrosion cracking (SCC) in 5 N H[sub 2]SO[sub 4] + 0.5 N NaCl solution. It was found that the delta ferrite content in the weld metals had a predominant effect on the SCC resistance. Higher ferrite contents increased the tendency for SCC. Post-weld heat treatment of weld metals resulted in the improvement of the SCC resistance.

  6. Effects of Solute Nb Atoms and Nb Precipitates on Isothermal Transformation Kinetics from Austenite to Ferrite

    NASA Astrophysics Data System (ADS)

    Wang, Li; Parker, Sally; Rose, Andrew; West, Geoff; Thomson, Rachel

    2016-07-01

    Nb is a very important micro-alloying element in low-carbon steels, for grain size refinement and precipitation strengthening, and even a low content of Nb can result in a significant effect on phase transformation kinetics from austenite to ferrite. Solute Nb atoms and Nb precipitates may have different effects on transformation behaviors, and these effects have not yet been fully characterized. This paper examines in detail the effects of solute Nb atoms and Nb precipitates on isothermal transformation kinetics from austenite to ferrite. The mechanisms of the effects have been analyzed using various microscopy techniques. Many solute Nb atoms were found to be segregated at the austenite/ferrite interface and apply a solute drag effect. It has been found that solute Nb atoms have a retardation effect on ferrite nucleation rate and ferrite grain growth rate. The particle pinning effect caused by Nb precipitates is much weaker than the solute drag effect.

  7. Microstructural evolution of delta ferrite in SAVE12 steel under heat treatment and short-term creep

    SciTech Connect

    Li, Shengzhi; Eliniyaz, Zumrat; Zhang, Lanting; Sun, Feng; Shen, Yinzhong; Shan, Aidang

    2012-11-15

    This research focused on the formation and microstructural evolution of delta ferrite phase in SAVE12 steel. The formation of delta ferrite was due to the high content of ferrite forming alloy elements such as Cr, W, and Ta. This was interpreted through either JMatPro-4.1 computer program or Cr{sub eq} calculations. Delta ferrite was found in bamboo-like shape and contained large amount of MX phase. It was surrounded by Laves phases before creep or aging treatment. Annealing treatments were performed under temperatures from 1050 Degree-Sign C to 1100 Degree-Sign C and various time periods to study its dissolution kinetics. The result showed that most of the delta ferrite can be dissolved by annealing in single phase austenitic region. Dissolution process of delta ferrite may largely depend on dissolution kinetic factors, rather than on thermodynamic factors. Precipitation behavior during short-term (1100 h) creep was investigated at temperature of 600 Degree-Sign C under a stress of 180 MPa. The results demonstrated that delta ferrite became preferential nucleation sites for Laves phase at the early stage of creep. Laves phase on the boundary around delta ferrite showed relatively slower growth and coarsening rate than that inside delta ferrite. - Highlights: Black-Right-Pointing-Pointer Delta ferrite is systematically studied under heat treatment and short-term creep. Black-Right-Pointing-Pointer Delta ferrite contains large number of MX phase and is surrounded by Laves phases before creep or aging treatment. Black-Right-Pointing-Pointer Formation of delta ferrite is interpreted by theoretical and empirical methods. Black-Right-Pointing-Pointer Most of the delta ferrite is dissolved by annealing in single phase austenitic region. Black-Right-Pointing-Pointer Delta ferrite becomes preferential nucleation sites for Laves phase at the early stage of creep.

  8. Probing the interaction induced conformation transitions in acid phosphatase with cobalt ferrite nanoparticles: Relation to inhibition and bio-activity of Chlorella vulgaris acid phosphatase.

    PubMed

    Ahmad, Farooq; Zhou, Xing; Yao, Hongzhou; Zhou, Ying; Xu, Chao

    2016-09-01

    The present study explored the interaction and kinetics of cobalt ferrite nanoparticles (NPs) with acid phosphatase (ACP) by utilizing diverse range of spectroscopic techniques. The results corroborate, the CoFe2O4 NPs cause fluorescence quenching in ACP by static quenching mechanism. The negative values of van't Hoff thermodynamic expressions (ΔH=-0.3293Jmol(-1)K(-1) and ΔG=-3.960kJmol(-1)K(-1)) corroborate the spontaneity and exothermic nature of static quenching. The positive value of ΔS (13.2893Jmol(-1)K(-1)) corroborate that major contributors of higher and stronger binding affinity among CoFe2O4 NPs with ACP were electrostatic. In addition, FTIR, UV-CD, UV-vis spectroscopy and three dimensional fluorescence (3D) techniques confirmed that CoFe2O4 NPs binding induces microenvironment perturbations leading to secondary and tertiary conformation changes in ACP to a great extent. Furthermore, synchronous fluorescence spectroscopy (SFS) affirmed the comparatively significant changes in microenvironment around tryptophan (Trp) residue by CoFe2O4 NPs. The effect of CoFe2O4 NPs on the activation kinetics of ACP was further examined in Chlorella vulgaris. Apparent Michaelis constant (Km) values of 0.57 and 26.5mM with activation energy values of 0.538 and 3.428kJmol(-1) were determined without and with 200μM CoFe2O4 NPs. Apparent Vmax value of -7Umml(-1) corroborate that enzyme active sites were completely captured by the NPs leaving no space for the substrate. The results confirmed that CoFe2O4 NPs ceased the activity by unfolding of ACP enzyme. This suggests CoFe2O4 NPs perturbed the enzyme activity by transitions in conformation and hence the metabolic activity of ACP. This study provides the pavement for novel and simple approach of using sensitive biomarkers for sensing NPs in environment. PMID:27209386

  9. Electrocatalytic activity of Rh-Ru alloys in electroreduction process

    SciTech Connect

    Bukherissa, S.; Belik, V.V.; Kudryashov, I.V.; Meretskii, A.M.

    1986-04-01

    The authors study the kinetics of cathodic hydrogen evolution in 1 N H/sub 2/SO/sub 4/ and of maleic acid electroreduction in C/sub 4/H/sub 4/O/sub 4/ solutions of different concentrations in 1 N H/sub 2/SO/sub 4/ as a base electrolyte at Rh-Ru alloy ingots prepared by vacuum arc melting. The results of polarization measurements for cathodic hydrogen evolution were analyzed in semilogarithmic plots of overvoltage against the logarithm of current density. Over the range of current densities from 10/sup -5/ to 10/sup -3/ A/cm/sup 2/, the polarization curves exhibit distinctly linear sections and can be described by the Tafel equation.

  10. Minimum activation martensitic alloys for surface disposal after exposure to neutron flux

    DOEpatents

    Lechtenberg, Thomas

    1985-01-01

    Steel alloys for long-term exposure to neutron flux have a martensitic microstructure and contain chromium, carbon, tungsten, vanadium and preferably titanium. Activation of the steel is held to within acceptable limits for eventual surface disposal by stringently controlling the impurity levels of Ni, Mo, Cu, N, Co, Nb, Al and Mn.

  11. Influence of DIT Parameters on the Cementite Spheroidization in a Low-Alloy Medium Carbon Steel

    NASA Astrophysics Data System (ADS)

    Arruabarrena, Jon; López, Beatriz; Rodriguez-Ibabe, Jose M.

    2016-01-01

    The influence of strain, strain rate, and temperature on deformation-induced transformation (DIT) in a low-alloy medium carbon steel is studied. The strain promotes the nucleation of ferrite (deformation-induced ferrite) and also pearlite (deformation-induced pearlite), this last being characterized by a fine interlamellar spacing and morphological instability. At strains ɛ > 0.5, intragranular nucleation activates and further ferrite nucleation over the newly created α/ γ interface takes place, which gives rise to the precipitation of cementite (deformation-induced cementite) at the ferrite boundaries. Soft annealing treatments have been performed on the microstructures obtained by DIT, and the degree of spheroidization has been quantified by image analysis techniques. In comparison to non-deformed conditions, the application of DIT results in a higher degree of spheroidization after soft annealing. Moreover, the EBSD analysis denotes that ferrite grain size refinement is achieved with respect to non-deformed conditions. The degree of spheroidization is highly influenced by the applied strain level and subsequent holding temperature.

  12. Active and passive kink mode studies in a tokamak with a movable ferromagnetic walla)

    NASA Astrophysics Data System (ADS)

    Levesque, J. P.; Hughes, P. E.; Bialek, J.; Byrne, P. J.; Mauel, M. E.; Navratil, G. A.; Peng, Q.; Rhodes, D. J.; Stoafer, C. C.

    2015-05-01

    High-resolution active and passive kink mode studies are conducted in a tokamak with an adjustable ferromagnetic wall near the plasma surface. Ferritic tiles made from 5.6 mm thick Hiperco® 50 alloy have been mounted on the plasma-facing side of half of the in-vessel movable wall segments in the High Beta Tokamak-Extended Pulse device [D. A. Maurer et al., Plasma Phys. Controlled Fusion 53, 074016 (2011)] in order to explore ferritic resistive wall mode stability. Low-activation ferritic steels are a candidate for structural components of a fusion reactor, and these experiments examine MHD stability of plasmas with nearby ferromagnetic material. Plasma-wall separation for alternating ferritic and non-ferritic wall segments is adjusted between discharges without opening the vacuum vessel. Amplification of applied resonant magnetic perturbations and plasma disruptivity are observed to increase when the ferromagnetic wall is close to plasma surface instead of the standard stainless steel wall. Rapidly rotating m / n = 3 / 1 external kink modes have higher growth rates with the nearby ferritic wall. Feedback suppression of kinks is still as effective as before the installation of ferritic material in vessel, in spite of increased mode growth rates.

  13. Active and passive kink mode studies in a tokamak with a movable ferromagnetic wall

    SciTech Connect

    Levesque, J. P.; Hughes, P. E.; Bialek, J.; Byrne, P. J.; Mauel, M. E.; Navratil, G. A.; Peng, Q.; Rhodes, D. J.; Stoafer, C. C.

    2015-05-15

    High-resolution active and passive kink mode studies are conducted in a tokamak with an adjustable ferromagnetic wall near the plasma surface. Ferritic tiles made from 5.6 mm thick Hiperco{sup ®} 50 alloy have been mounted on the plasma-facing side of half of the in-vessel movable wall segments in the High Beta Tokamak-Extended Pulse device [D. A. Maurer et al., Plasma Phys. Controlled Fusion 53, 074016 (2011)] in order to explore ferritic resistive wall mode stability. Low-activation ferritic steels are a candidate for structural components of a fusion reactor, and these experiments examine MHD stability of plasmas with nearby ferromagnetic material. Plasma-wall separation for alternating ferritic and non-ferritic wall segments is adjusted between discharges without opening the vacuum vessel. Amplification of applied resonant magnetic perturbations and plasma disruptivity are observed to increase when the ferromagnetic wall is close to plasma surface instead of the standard stainless steel wall. Rapidly rotating m/n=3/1 external kink modes have higher growth rates with the nearby ferritic wall. Feedback suppression of kinks is still as effective as before the installation of ferritic material in vessel, in spite of increased mode growth rates.

  14. Investigation of Iron-Chromium-Niobium-Titanium Ferritic Stainless Steel for Solid Oxide Fuel Cell Interconnect Applications

    SciTech Connect

    Yang, Zhenguo; Xia, Guanguang; Wang, Chong M.; Nie, Zimin; Templeton, Joshua D.; Stevenson, Jeffry W.; Singh, Prabhakar

    2008-09-01

    As part of an effort to develop cost-effective ferritic stainless steel-based interconnects for solid oxide fuel cell (SOFC) stacks, AL 441 HPTM was studied in terms of its metallurgical characteristics, oxidation behavior, and electrical performance. Minor alloying elements (Nb and Ti) captured interstitials such as C by forming carbides, stabilizing the ferritic structure and mitigating the risks of sensitization and inter-granular corrosion. Laves phases rich in Nb and Si precipitated along grain boundaries during high temperature exposure, improving the steel’s high temperature mechanical strength. The capture of Si in the Laves phase minimized the Si activity in the steel substrate and prevented formation of an insulating silica layer at the scale/metal interface. However, the relatively high oxidation rate, and thus increasing ASR over time, necessitates the application of a conductive protection layer on the steel. In particular, Mn1.5Co1.5O4 spinel protection layers drastically improved the electrical performance of the ferritic stainless steel 441, acting as barriers to chromium outward and oxygen inward diffusion.

  15. Polyhedral Palladium–Silver Alloy Nanocrystals as Highly Active and Stable Electrocatalysts for the Formic Acid Oxidation Reaction

    PubMed Central

    Fu, Geng-Tao; Liu, Chang; Zhang, Qi; Chen, Yu; Tang, Ya-Wen

    2015-01-01

    Polyhedral noble–metal nanocrystals have received much attention and wide applications as electrical and optical devices as well as catalysts. In this work, a straightforward and effective hydrothermal route for the controllable synthesis of the high-quality Pd–Ag alloy polyhedrons with uniform size is presented. The morphology, composition and structure of the Pd–Ag alloy polyhedrons are fully characterized by the various physical techniques, demonstrating the Pd–Ag alloy polyhedrons are highly alloying. The formation/growth mechanisms of the Pd–Ag alloy polyhedrons are explored and discussed based on the experimental observations and discussions. As a preliminary electrochemical application, the Pd–Ag alloy polyhedrons are applied in the formic acid oxidation reaction, which shows higher electrocatalytic activity and stability than commercially available Pd black due to the “synergistic effects” between Pd and Ag atoms. PMID:26329555

  16. Polyhedral Palladium-Silver Alloy Nanocrystals as Highly Active and Stable Electrocatalysts for the Formic Acid Oxidation Reaction

    NASA Astrophysics Data System (ADS)

    Fu, Geng-Tao; Liu, Chang; Zhang, Qi; Chen, Yu; Tang, Ya-Wen

    2015-09-01

    Polyhedral noble-metal nanocrystals have received much attention and wide applications as electrical and optical devices as well as catalysts. In this work, a straightforward and effective hydrothermal route for the controllable synthesis of the high-quality Pd-Ag alloy polyhedrons with uniform size is presented. The morphology, composition and structure of the Pd-Ag alloy polyhedrons are fully characterized by the various physical techniques, demonstrating the Pd-Ag alloy polyhedrons are highly alloying. The formation/growth mechanisms of the Pd-Ag alloy polyhedrons are explored and discussed based on the experimental observations and discussions. As a preliminary electrochemical application, the Pd-Ag alloy polyhedrons are applied in the formic acid oxidation reaction, which shows higher electrocatalytic activity and stability than commercially available Pd black due to the “synergistic effects” between Pd and Ag atoms.

  17. Contributions from research on irradiated ferritic/martensitic steels to materials science and engineering

    NASA Astrophysics Data System (ADS)

    Gelles, D. S.

    1990-05-01

    Ferritic and martensitic steels are finding increased application for structural components in several reactor systems. Low-alloy steels have long been used for pressure vessels in light water fission reactors. Martensitic stainless steels are finding increasing usage in liquid metal fast breeder reactors and are being considered for fusion reactor applications when such systems become commercially viable. Recent efforts have evaluated the applicability of oxide dispersion-strengthened ferritic steels. Experiments on the effect of irradiation on these steels provide several examples where contributions are being made to materials science and engineering. Examples are given demonstrating improvements in basic understanding, small specimen test procedure development, and alloy development.

  18. The anti-bacterial activity of titanium-copper sintered alloy against Porphyromonas gingivalis in vitro.

    PubMed

    Bai, Bing; Zhang, Erlin; Liu, Junchao; Zhu, Jingtao

    2016-01-01

    This study investigates the anti-bacterial property of Ti-Cu sintered alloys against Porphyromonas gingivalis. The anti-anaerobic property of Ti-Cu sintered alloys against P. gingivalis was investigated by antibacterial activity test, DNA measurement, DAPI staining and morphology observation. The antibacterial rates of the Ti-5Cu against P. gingivalis after 18 and 24 h incubation were 36.04 and 54.39%, and those of Ti-10Cu were 68.69 and 75.39%, which were lower than their anti-aerobic abilities. The concentration of P. gingivalis DNA gradually decreased with the increasing Cu content, which was nearly 50% after 24 h incubation on Ti-10Cu. SEM results showed that the shape of P. gingivalis changed and the bacteria broke apart with the addition of Cu and the extension of the culture time. Ti-Cu sintered alloys could not only kill anaerobic bacteria but also reduce the activity of the survived bacteria. The anti-anaerobic mechanism was thought to be in associated with the Cu ion released from Ti-Cu alloy. PMID:27477233

  19. Dielectric investigations of polycrystalline samarium bismuth ferrite ceramic

    SciTech Connect

    Palaimiene, E.; Macutkevic, J.; Banys, J.; Karpinsky, D. V.; Kholkin, A. L.

    2015-01-05

    Results of broadband dielectric investigations of samarium doped bismuth ferrite ceramics are presented in wide temperature range (20–800 K). At temperatures higher than 400 K, the dielectric properties of samarium bismuth ferrite ceramics are governed by Maxwell-Wagner relaxation and electrical conductivity. The DC conductivity increases and activation energy decreases with samarium concentration. In samarium doped bismuth ferrite, the ferroelectric phase transition temperature decreases with samarium concentration and finally no ferroelectric order is observed at x = 0.2. At lower temperatures, the dielectric properties of ferroelectric samarium doped bismuth ferrite are governed by ferroelectric domains dynamics. Ceramics with x = 0.2 exhibit the relaxor-like behaviour.

  20. Neutronics and activation analysis of lithium-based ternary alloys in IFE blankets

    DOE PAGESBeta

    Jolodosky, Alejandra; Kramer, Kevin; Meier, Wayne; DeMuth, James; Reyes, Susana; Fratoni, Massimiliano

    2016-04-09

    Here we report that an attractive feature of using liquid lithium as the breeder and coolant in fusion blankets is that it has very high tritium solubility and results in very low levels of tritium permeation throughout the facility infrastructure. However, lithium metal vigorously reacts with air and water and presents plant safety concerns. The Lawrence Livermore National Laboratory is carrying an effort to develop a lithium-based alloy that maintains the beneficial properties of lithium (e.g. high tritium breeding and solubility) and at the same time reduces overall flammability concerns. This study evaluates the neutronics performance of lithium-based alloys inmore » the blanket of an inertial fusion energy chamber in order to inform such development. 3-D Monte Carlo calculations were performed to evaluate two main neutronics performance parameters for the blanket: tritium breeding ratio (TBR), and the fusion energy multiplication factor (EMF). It was found that elements that exhibit low absorption cross sections and higher q-values such as lead, tin, and strontium, perform well with those that have high neutron multiplication such as lead and bismuth. These elements meet TBR constrains ranging from 1.02 to 1.1. However, most alloys do not reach EMFs greater than 1.15. Additionally, it was found that enriching lithium significantly increases the TBR and decreases the minimum lithium concentration by more than 60%. The amount of enrichment depends on how much total lithium is in the alloy to begin with. Alloys that performed well in the TBR and EMF calculations were considered for activation analysis. Activation simulations were executed with 50 years of irradiation and 300 years of cooling. It was discovered that bismuth is a poor choice due to achieving the highest decay heat, contact dose rates, and accident doses. In addition, it does not meet the waste disposal ratings (WDR). Some of the activation results for alloys with tin, zinc, and gallium were in

  1. Synthesis of solar active nanocrystalline ferrite, MFe 2O 4 (M: Ca, Zn, Mg) photocatalyst by microwave irradiation

    NASA Astrophysics Data System (ADS)

    Dom, Rekha; Subasri, R.; Radha, K.; Borse, Pramod H.

    2011-03-01

    For the first time, nanocrystalline photocatalysts of spinel MgFe2O4, ZnFe2O4 and orthorhombic CaFe2O4 oxides were synthesized (at low temperature ˜973 K) by microwave sintering, in one sixtieth of the time required to that of the conventional method. A significantly improved crystallinity was obtained for the samples irradiated for longer duration of time (˜10-100 min). The theoretically computed electronic structure of the MFe2O4 (M: Ca, Zn, Mg) systems was respectively correlated with the experimental results obtained from their structural and photocatalytic characterization. The photocatalytic performance was found to be affected by surface area and crystallinity of the photocatalyst. The density functional theory (DFT) calculations of MFe2O4 lattices revealed that M-ion controllably affects the density of sates of the Fe-d orbitals near the Fermi level. Consequently they play an important role in determining the band-energetics and thus the visible light photocatalytic activity for methylene blue degradation.

  2. Pack cementation coatings for alloys

    SciTech Connect

    He, Yi-Rong; Zheng, Minhui; Rapp, R.A.

    1996-08-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on a Cr-Cr{sub 2}Nb alloy in a single processing step. The morphology and composition of the coating depended both on the composition of the pack and on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi{sub 2} and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. In cyclic and isothermal oxidation in air at 700 and 1050{degrees}C, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation by the formation of a Ge-doped silica film. The codeposition and diffusion of aluminum and chromium into low alloy steel have been achieved using elemental Al and Cr powders and a two-step pack cementation process. Sequential process treatments at 925{degrees}C and 1150{degrees}C yield dense and uniform ferrite coatings, whose compositions are close to either Fe{sub 3}Al or else FeAl plus a lower Cr content, when processed under different conditions. The higher content of Al in the coatings was predicted by thermodynamic calculations of equilibrium in the gas phase. The effect of the particle size of the metal powders on the surface composition of the coating has been studied for various combinations of Al and Cr powders.

  3. The generation of wear-resistant antimicrobial stainless steel surfaces by active screen plasma alloying with N and nanocrystalline Ag.

    PubMed

    Dong, Yangchun; Li, Xiaoying; Sammons, Rachel; Dong, Hanshan

    2010-04-01

    Hospital-acquired infections (HAIs), a large proportion of which are derived from contact transmission, represent a massive global challenge. In this study a novel active screen plasma (ASP) alloying technology has been developed to generate highly durable antimicrobial surfaces by combining a wear-resistant S-phase with nanocrystalline silver for medical grade stainless steel. The phase constituent, microstructure, composition and surface roughness of the alloyed surfaces were fully characterized, and the surface hardness, wear resistance and antimicrobial efficiency of the treated surfaces were evaluated. Experimental results showed that the surface hardness and sliding wear resistance of medical grade 316LVM stainless steel can be effectively improved by the ASP alloying treatment; furthermore, the Ag alloyed S-phase can achieve 93% reduction in Escherichia coli (E. coli) after 6 h contact time. Therefore, the novel ASP alloying treatment can not only improve wear resistance but also confer antibacterial activity to stainless steel surfaces. PMID:20119942

  4. Catalytic activity of bimetallic nickel alloys for solid-oxide fuel cell anode reactions from density-functional theory

    NASA Astrophysics Data System (ADS)

    An, Wei; Gatewood, Daniel; Dunlap, Brett; Turner, C. Heath

    2011-05-01

    We present density-functional theory calculations of the chemisorption of atomic species O, S, C, H and reaction intermediates OH, SH, and CHn (n = 1, 2, and 3) on M/Ni alloy model catalysts (M = Bi, Mo, Fe, Co, and Cu). The activity of the Ni alloy catalysts for solid-oxide fuel cell (SOFC) anode oxidation reactions is predicted, based on a simple descriptor, i.e., the binding energy of oxygen. First, we find that the binding of undesirable intermediates, such as C and S, can be inhibited and the catalytic activity of planar Ni-based anodes can be tuned towards oxidation by selectively forming a bimetallic surface alloy. In particular, Cu/Ni, Fe/Ni, and Co/Ni anode catalysts are found to be most active towards anode oxidation. On the other hand, the Mo/Ni alloy surface is predicted to be the most effective catalyst in terms of inhibiting the deposition of C and S (while still preserving relatively high catalytic activity). The formation of a surface alloy, which has the alloy element enriched on the topmost surface, was found to be critical to the activity of the Ni alloy catalysts.

  5. Pack cementation diffusion coatings for iron-base alloys

    SciTech Connect

    Rapp, R.A.

    1995-02-01

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels. The Cr-Si ferrite layers have proven to be very resistant to high temperature cyclic oxidation and to pitting in aqueous solutions. The process has been patented, and is being transferred for industrial application, e.g. for water walls of utility boilers, etc. In the proposed extension of this project, the use of mixed pure metal powders in the pack will be extended to achieve similar ferrite Fe-Cr-Al coatings with excellent oxidation resistance, with the eventual transfer of the technology to industry. In other recent studies, Ni-base alloy rods were aluminized by the halide-activated pack cementation process to bring their average composition to that for the ORNL-developed Ni{sub 3}Al, for use as a welding rod. A similar effort to develop a welding rod for the ORNL Fe{sub 3}Al alloy did not yield reproducible coating compositions or growth kinetics. The continued effort to produce Duriron-type (Fe-18Si-5Cr) coatings on steels was not successful. Literature for the intrinsic diffusion coefficients suggests that this task cannot be achieved.

  6. Development of ferritic weldments for grain-refined ferritic steels for 4. 2K service

    SciTech Connect

    Kim, H.J.

    1982-11-01

    The weldability of grain-refined ferritic nickel steels designed for structural use in liquid helium was investigated. Plates of interstitial-free Fe-12Ni-0.25Ti alloy and carbon-containing 9 Ni steel were welded with 14 Ni ferritic fillers using a gas tungsten arc welding (GTAW) process with pure argon gas shielding. The ferritic weldments made have a strength closely matching those of the base plates without a significant loss in base metal toughness at temperatures as low as 4.2 K. The comparable toughness obtained in the welded region is attributed to three factors; the defect-free weldment, the chemical cleanliness of the GTAW weld deposit, and the in-process formation of an appropriate microstructure in the welded region. Special emphasis in this study was placed on changes in microstructures with respect to the characteristic of the weld thermal cycles and the effect of the resultant microstructures on low temperature toughness. In the heat-affected zone (HAZ) of multipass welded 9Ni steel, the retained (or precipitated) austenite is removed by the weld heat cycles but the sequential rapid heat cycles to successively lower peak temperatures associated with succeeding weld passes re-establish high toughness by sequentially refining the grain size and gettering carbon in the form of cementite precipitates. On the other hand, the high toughness in the HAZ of the 12Ni alloy and in the weld deposit is a direct consequence of repeated grain refinement through the overlapped austenitizing cycles and is not affected by the tempering cycles because of the carbon-free nature of these materials. 46 figures.

  7. Development of ferritic weldments for grain-refined ferritic steels for 4. 2K service

    SciTech Connect

    Kim, H.J.

    1982-01-01

    The weldability of grain-refined ferritic nickel steels designed for structural use in liquid helium was investigated. Plates of interstitial-free Fe-12Ni-0.25Ti alloy and carbon-containing 9Ni steel were welded with 14Ni ferritic fillers using a gas tungsten arc welding (GTAW) process with pure argon gas shielding. The ferritic weldments made have a strength closely matching those of the base plates without a significant loss in base metal toughness at temperatures as low as 4.2K. The comparable toughness obtained in the welded region is attributed to three factors; the defect-free weldment, the chemical cleanliness of the GTAW weld deposit, and the in-process formation of an appropriate microstructure in the welded region. Special emphasis in this study was placed on changes in microstructures with respect to the characteristic of the weld thermal cycles and the effect of the resultant microstructures on low temperature toughness. In the heat-affected zone (HAZ) of multipass welded 9Ni steel, the retained (or precipitated) austenite is removed by the weld heat cycles but the sequential rapid heat cycles to successively lower peak temperatures associated with succeeding weld passes re-establish high toughness by sequentially refining the grain size and gettering carbon in the form of cementite precipitates. On the other hand, the high toughness in the HAZ of the 12Ni alloy and in the weld deposit is a direct consequence of repeated grain refinement through the overlapped austenitizing cycles and is not affected by the tempering cycles because of the carbon-free nature of these materials.

  8. 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.

  9. Characterization of the corrosion resistance of several alloys to dilute biologically active solutions

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.

    1990-01-01

    Sulfate reducing bacteria and acid producing bacteria/fungi detected in hygiene waters increased the corrosion rate in aluminum alloy. Biologically active media enhanced the formation of pits on metal coupons. Direct observation of gas evolved at the corrosion sample, coupled with scanning electron microscopy (SEM) and energy dispersive x-ray analysis of the corrosion products indicates that the corrosion rate is increased because the presence of bacteria favor the reduction of hydrogen as the cathodic reaction through the reaction of oxygen and water. SEM verifies the presence of microbes in a biofilm on the surface of corroding samples. The bacterial consortia are associated with anodic sites on the metal surface, aggressive pitting occurs adjacent to biofilms. Many pits are associated with triple points and inclusions in the aluminum alloy microstructure. Similar bacterial colonization was found on the stainless steel samples. Fourier transform Infrared Spectroscopy confirmed the presence of carbonyl groups in pitted areas of samples exposed to biologically active waters.

  10. Cast Stainless Steel Ferrite and Grain Structure

    SciTech Connect

    Ruud, Clayton O.; Ramuhalli, Pradeep; Meyer, Ryan M.; Mathews, Royce; Diaz, Aaron A.; Anderson, Michael T.

    2012-09-01

    In-service inspection requirements dictate that piping welds in the primary pressure boundary of light-water reactors be subject to a volumetric examination based on the rules contained within the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section XI. The purpose of the inspection is the reliable detection and accurate sizing of service-induced degradation and/or material flaws introduced during fabrication. The volumetric inspection is usually carried out using ultrasonic testing (UT) methods. However, the varied metallurgical macrostructures and microstructures of cast austenitic stainless steel piping and fittings, including statically cast stainless steel and centrifugally cast stainless steel (CCSS), introduce significant variations in the propagation and attenuation of ultrasonic energy. These variations complicate interpretation of the UT responses and may compromise the reliability of UT inspection. A review of the literature indicated that a correlation may exist between the microstructure and the delta ferrite content of the casting alloy. This paper discusses the results of a recent study where the goal was to determine if a correlation existed between measured and/or calculated ferrite content and grain structure in CCSS pipe.

  11. A General Method for Multimetallic Platinum Alloy Nanowires as Highly Active and Stable Oxygen Reduction Catalysts.

    PubMed

    Bu, Lingzheng; Ding, Jiabao; Guo, Shaojun; Zhang, Xu; Su, Dong; Zhu, Xing; Yao, Jianlin; Guo, Jun; Lu, Gang; Huang, Xiaoqing

    2015-11-25

    An unconventional class of high-performance Pt alloy multimetallic nanowires (NWs) is produced by a general method. The obtained PtNi NWs exhibit amazingly specific and mass oxygen reduction reaction (ORR) activities with improvement factors of 51.1 and 34.6 over commercial Pt/C catalysts, respectively, and are also stable in ORR conditions, making them among the most efficient electrocatalysts for ORR. PMID:26459261

  12. MHD Effects of a Ferritic Wall on Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Hughes, Paul E.

    It has been recognized for some time that the very high fluence of fast (14.1MeV) neutrons produced by deuterium-tritium fusion will represent a major materials challenge for the development of next-generation fusion energy projects such as a fusion component test facility and demonstration fusion power reactor. The best-understood and most promising solutions presently available are a family of low-activation steels originally developed for use in fission reactors, but the ferromagnetic properties of these steels represent a danger to plasma confinement through enhancement of magnetohydrodynamic instabilities and increased susceptibility to error fields. At present, experimental research into the effects of ferromagnetic materials on MHD stability in toroidal geometry has been confined to demonstrating that it is still possible to operate an advanced tokamak in the presence of ferromagnetic components. In order to better quantify the effects of ferromagnetic materials on tokamak plasma stability, a new ferritic wall has been installated in the High Beta Tokamak---Extended Pulse (HBT-EP) device. The development, assembly, installation, and testing of this wall as a modular upgrade is described, and the effect of the wall on machine performance is characterized. Comparative studies of plasma dynamics with the ferritic wall close-fitting against similar plasmas with the ferritic wall retracted demonstrate substantial effects on plasma stability. Resonant magnetic perturbations (RMPs) are applied, demonstrating a 50% increase in n = 1 plasma response amplitude when the ferritic wall is near the plasma. Susceptibility of plasmas to disruption events increases by a factor of 2 or more with the ferritic wall inserted, as disruptions are observed earlier with greater frequency. Growth rates of external kink instabilities are observed to be twice as large in the presence of a close-fitting ferritic wall. Initial studies are made of the influence of mode rotation frequency

  13. Castable hot corrosion resistant alloy

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A. (Inventor); Holt, William H. (Inventor)

    1988-01-01

    Some 10 wt percent nickel is added to an Fe-base alloy which has a ferrite microstructure to improve the high temperature castability and crack resistance while about 0.2 wt percent zirconium is added for improved high temperatur cyclic oxidation and corrosion resistance. The basic material is a high temperature FeCrAl heater alloy, and the addition provides a material suitable for burner rig nozzles.

  14. Ongoing Ferritic Wall Mode studies on HBT-EP

    NASA Astrophysics Data System (ADS)

    Hughes, P. E.; Mauel, M. E.; Levesque, J. P.; Navratil, G. A.

    2015-11-01

    Low-activation ferritic steels are leading material candidates for use in next-generation fusion development experiments such as a prospective US component test facility and DEMO. Understanding the interaction of plasmas with a ferromagnetic wall will provide crucial physics for these experiments. Although the ferritic wall mode (FWM) was seen in a linear machine, ferritic steel was observed to be compatible with high-performance operation in JFT-2M. Using its high-resolution magnetic diagnostics and adjustable wall segments, HBT-EP now operates successfully with a high-permeability tiled ferritic first wall. Initial measurements showed the ferritic wall enhances the growth rate of the m/n = 3/1 kink mode. In this poster, we report results of our study of the evolution of naturally rotating modes, increased plasma response to phase-flip resonant magnetic perturbations (RMPs), and enhanced plasma disruptivity as the walls are adjusted from stainless wall to ferritic wall configuration. Supported by U.S. DOE Grant DE-FG02-86ER53222.

  15. Characterization of Irradiated Nanostructured Ferritic Steels

    SciTech Connect

    Bentley, James; Hoelzer, David T; Tanigawa, H.; Yamamoto, T.; Odette, George R.

    2007-01-01

    The past decade has seen the development of a new class of mechanically alloyed (MA) ferritic steels with outstanding mechanical properties that come, at least in part, from the presence of high concentrations (>10{sup 23} m{sup -3}) of Ti-, Y-, and O-enriched nanoclusters (NC). From the outset, there has been much interest in their potential use for applications to fission and proposed fusion reactors, not only because of their attractive high-temperature strength, but also because the presence of NC may result in a highly radiation-resistant material by efficiently trapping point defects to enhance recombination. Of special interest for fusion applications is the potential of NC to trap transmutation-produced He in high concentrations of small cavities, rather than in fewer but larger cavities that lead to greater radiation-induced swelling and other degraded properties.

  16. 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.

  17. Surface chemistry, friction and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to he surfaces of the ferrites in sliding.

  18. Method of making active magnetic refrigerant, colossal magnetostriction and giant magnetoresistive materials based on Gd-Si-Ge alloys

    DOEpatents

    Gschneidner, Jr., Karl A.; Pecharsky, Alexandra O.; Pecharsky, Vitalij K.

    2003-07-08

    Method of making an active magnetic refrigerant represented by Gd.sub.5 (Si.sub.x Ge.sub.1-x).sub.4 alloy for 0.ltoreq.x.ltoreq.1.0 comprising placing amounts of the commercially pure Gd, Si, and Ge charge components in a crucible, heating the charge contents under subambient pressure to a melting temperature of the alloy for a time sufficient to homogenize the alloy and oxidize carbon with oxygen present in the Gd charge component to reduce carbon, rapidly solidifying the alloy in the crucible, and heat treating the solidified alloy at a temperature below the melting temperature for a time effective to homogenize a microstructure of the solidified material, and then cooling sufficiently fast to prevent the eutectoid decomposition and improve magnetocaloric and/or the magnetostrictive and/or the magnetoresistive properties thereof.

  19. Zinc ferrite nanoparticles activate IL-1b, NFKB1, CCL21 and NOS2 signaling to induce mitochondrial dependent intrinsic apoptotic pathway in WISH cells

    SciTech Connect

    Saquib, Quaiser; Al-Khedhairy, Abdulaziz A.; Ahmad, Javed; Siddiqui, Maqsood A.; Dwivedi, Sourabh; Khan, Shams T.; Musarrat, Javed

    2013-12-01

    The present study has demonstrated the translocation of zinc ferrite nanoparticles (ZnFe{sub 2}O{sub 4}-NPs) into the cytoplasm of human amnion epithelial (WISH) cells, and the ensuing cytotoxicity and genetic damage. The results suggested that in situ NPs induced oxidative stress, alterations in cellular membrane and DNA strand breaks. The [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) and neutral red uptake (NRU) cytotoxicity assays indicated 64.48 ± 1.6% and 50.73 ± 2.1% reduction in cell viability with 100 μg/ml of ZnFe{sub 2}O{sub 4}-NPs exposure. The treated WISH cells exhibited 1.2-fold higher ROS level with 0.9-fold decline in membrane potential (ΔΨm) and 7.4-fold higher DNA damage after 48 h of ZnFe{sub 2}O{sub 4}-NPs treatment. Real-time PCR (qPCR) analysis of p53, CASP 3 (caspase-3), and bax genes revealed 5.3, 1.6, and 14.9-fold upregulation, and 0.18-fold down regulation of bcl 2 gene vis-à-vis untreated control. RT{sup 2} Profiler™ PCR array data elucidated differential up-regulation of mRNA transcripts of IL-1b, NFKB1, NOS2 and CCL21 genes in the range of 1.5 to 3.7-folds. The flow cytometry based cell cycle analysis suggested the transfer of 15.2 ± 2.1% (p < 0.01) population of ZnFe{sub 2}O{sub 4}-NPs (100 μg/ml) treated cells into apoptotic phase through intrinsic pathway. Over all, the data revealed the potential of ZnFe{sub 2}O{sub 4}-NPs to induce cellular and genetic toxicity in cells of placental origin. Thus, the significant ROS production, reduction in ΔΨm, DNA damage, and activation of genes linked to inflammation, oxidative stress, proliferation, DNA damage and repair could serve as the predictive toxicity and stress markers for ecotoxicological assessment of ZnFe{sub 2}O{sub 4}-NPs induced cellular and genetic damage. - Highlights: • First report on the molecular toxicity of ZnFe{sub 2}O{sub 4}-NPs in cells of placental origin • WISH cells treated with ZnFe{sub 2}O{sub 4}-NPs exhibited cytoplasmic

  20. Oxygen reduction reaction activity on Pt{111} surface alloys.

    PubMed

    Attard, Gary A; Brew, Ashley; Ye, Jin-Yu; Morgan, David; Sun, Shi-Gang

    2014-07-21

    PtM overlayers (where M=Fe, Co or Ni) supported on Pt{111} are prepared via thermal annealing in either a nitrogen/water or hydrogen ambient of dilute aqueous droplets containing M(Z+) cations directly attached to the electrode. Two different PtM phases are detected depending on the nature of the post-annealing cooling environment. The first of these consists of small (<20 nm), closely packed microcrystals comprised of a central metallic core and a shell (several monolayers thick) of mixed metal oxides/hydroxides. The second type of PtM phase is prepared by cooling in a stream of hydrogen gas. Although this second phase also consists of numerous microcrystals covering the Pt{111} electrode surface, these are both flatter than before and moreover are entirely metallic in character. A positive shift in the onset of PtM oxide formation correlates with increased activity towards the oxygen reduction reaction (ORR), which we ascribe to the greater availability of platinum metallic sites under ORR conditions. PMID:24986646

  1. Chloride Ion Activity and Susceptibility of Al Alloys 7075-T6 and 5083-H131 to Stress Corrosion Cracking

    NASA Astrophysics Data System (ADS)

    Ricker, R. E.; Lee, E. U.; Taylor, R.; Lei, C.; Pregger, B.; Lipnickas, E.

    2013-03-01

    The influence of chloride ion activity on the susceptibility of aluminum alloys 5083-H131 and 7075-T6 to stress corrosion cracking (SCC) was investigated by conducting slow strain-rate tensile tests at a strain-rate of 10-7 s-1 in naturally aerated aqueous solutions with varying NaCl mass fraction (0.001 to 20 pct) and in a 3.5 pct mass fraction NaCl solution with varying strain-rates (10-8 to 10-4 s-1). This study found that both alloys exhibited reduced strengths and failure strains (times) in the solutions compared with laboratory air. The extent of these reductions was greater in alloy 5083 for the conditions examined. The strength and ductility of both alloys decreased with chloride ion activity in a manner that indicates a chemical reaction is responsible. The strength and ductility of both alloys decreased with strain-rate in a sigmoidal manner, but the transition in alloy 7075 occurred at slower strain-rates of approximately two orders of magnitude. It was deduced that the chloride ion interacts chemically with the passivated surface in the potential gradient at the crack tip to cause SCC. While no mechanism of cracking can be eliminated on the basis of these results alone, the results are consistent with the hypothesis that the absorbed hydrogen causes cracking in alloy 7075 while cracking in 5083 is the result of a dissolution mechanism.

  2. Characterization of Low Temperature Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Arc Welds

    SciTech Connect

    Palmer, T A; Elmer, J W; Babu, S S; Vitek, J M

    2003-08-20

    Spatially Resolved X-Ray Diffraction (SRXRD) has been used to identify a previously unobserved low temperature ferrite ({delta})/austenite({gamma}) phase transformation in the heat affected zone (HAZ) of 2205 Duplex Stainless Steel (DSS) welds. In this ''ferrite dip'' transformation, the ferrite transforms to austenite during heating to peak temperatures on the order of 750 C, and re-transforms to ferrite during cooling, resulting in a ferrite volume fraction equivalent to that in the base metal. Time Resolved X-Ray Diffraction (TRXRD) and laser dilatometry measurements during Gleeble{reg_sign} thermal simulations are performed in order to verify the existence of this low temperature phase transformation. Thermodynamic and kinetic models for phase transformations, including both local-equilibrium and para-equilibrium diffusion controlled growth, show that diffusion of substitutional alloying elements does not provide a reasonable explanation for the experimental observations. On the other hand, the diffusion of interstitial alloying elements may be rapid enough to explain this behavior. Based on both the experimental and modeling results, two mechanisms for the ''ferrite dip'' transformation, including the formation and decomposition of secondary austenite and an athermal martensitic-type transformation of ferrite to austenite, are considered.

  3. Grain boundary premelting and activated sintering in binary refractory alloys

    NASA Astrophysics Data System (ADS)

    Shi, Xiaomeng

    Quasi-liquid intergranular film (IGF) which has been widely observed in ceramic systems can persist into sub-solidus region whereby an analogy to Grain boundary (GB) premelting can be made. In this work, a grain boundary (GB) premelting/prewetting model in a metallic system was firstly built based on the Benedictus' model and computational thermodynamics, predicting that GB disordering can start at 60-85% of the bulk solidus temperatures in selected systems. This model quantitatively explains the long-standing mystery of subsolidus activated sintering in W-Pd, W-Ni, W-Co, W-Fe and W-Cu, and it has broad applications for understanding GB-controlled transport kinetics and physical properties. Furthermore, this study demonstrates the necessity of developing GB phase diagrams as a tool for materials design. Subsequently, Grain boundary (GB) wetting and prewetting in Ni-doped Mo are systematically evaluated via characterizing well-quenched specimens and thermodynamic modeling. In contrast to prior reports, the delta-NiMo phase does not wet Mo GBs in the solid state. In the solid-liquid two-phase region, the Ni-rich liquid wets Mo GBs completely. Furthermore, high-resolution transmission electron microscopy demonstrates that nanometer-thick quasi-liquid IGFs persist at GBs into the single-phase region where the bulk liquid phase is no longer stable; this is interpreted as a case of GB prewetting. An analytical thermodynamic model is developed and validated, and this model can be extended to other systems. Furthermore, the analytical model was refined based upon Beneditus' model with correction in determining interaction contribution of interfacial energy. A calculation-based GB phase diagram for Ni-Mo binary system was created and validated by comparing with GB diffusivities determined through a series of controlled sintering experiments. The dependence of GB diffusivity on doping level and temperature was examined and compared with model-predicted GB phase diagram. The

  4. Controlling Hydrogen Activation, Spillover, and Desorption with Pd-Au Single-Atom Alloys.

    PubMed

    Lucci, Felicia R; Darby, Matthew T; Mattera, Michael F G; Ivimey, Christopher J; Therrien, Andrew J; Michaelides, Angelos; Stamatakis, Michail; Sykes, E Charles H

    2016-02-01

    Key descriptors in hydrogenation catalysis are the nature of the active sites for H2 activation and the adsorption strength of H atoms to the surface. Using atomically resolved model systems of dilute Pd-Au surface alloys and density functional theory calculations, we determine key aspects of H2 activation, diffusion, and desorption. Pd monomers in a Au(111) surface catalyze the dissociative adsorption of H2 at temperatures as low as 85 K, a process previously expected to require contiguous Pd sites. H atoms preside at the Pd sites and desorb at temperatures significantly lower than those from pure Pd (175 versus 310 K). This facile H2 activation and weak adsorption of H atom intermediates are key requirements for active and selective hydrogenations. We also demonstrate weak adsorption of CO, a common catalyst poison, which is sufficient to force H atoms to spill over from Pd to Au sites, as evidenced by low-temperature H2 desorption. PMID:26747698

  5. Hollow raspberry-like PdAg alloy nanospheres: High electrocatalytic activity for ethanol oxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Peng, Cheng; Hu, Yongli; Liu, Mingrui; Zheng, Yixiong

    2015-03-01

    Palladium-silver (PdAg) alloy nanospheres with unique structure were prepared using a one-pot procedure based on the galvanic replacement reaction. Their electrocatalytic activity for ethanol oxidation in alkaline media was evaluated. The morphology and crystal structure of the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Electrochemical characterization techniques, including cyclic voltammetry (CV) and chronoamperometry (CA) measurements were used to analyze the electrochemical performance of the PdAg alloy nanospheres. The SEM and TEM images showed that the PdAg alloy nanospheres exhibit a hierarchical nanostructure with hollow interiors and porous walls. Compared to the commercial Pd/C catalyst, the as-prepared PdAg alloy nanospheres exhibit superior electrocatalytic activity and stability towards ethanol electro-oxidation in alkaline media, showing its potential as a new non-Pt electro-catalyst for direct alcohol fuel cells (DAFCs).

  6. Excimer laser ablation of ferrites

    NASA Astrophysics Data System (ADS)

    Tam, A. C.; Leung, W. P.; Krajnovich, D.

    1991-02-01

    Laser etching of ferrites was previously done by scanning a focused continuous-wave laser beam on a ferrite sample in a chemical environment. We study the phenomenon of photo-ablation of Ni-Zn or Mn-Zn ferrites by pulsed 248-nm KrF excimer laser irradiation. A transfer lens system is used to project a grating pattern of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluence for ablation at the ferrite surface is about 0.3 J/cm2. A typical fluence of 1 J/cm2 is used. The etched grooves produced are typically 20-50 μm wide, with depths achieved as deep as 70 μm . Groove straightness is good as long as a sharp image is projected onto the sample surface. The wall angle is steeper than 60 degrees. Scanning electron microscopy of the etched area shows a ``glassy'' skin with extensive microcracks and solidified droplets being ejected that is frozen in action. We found that this skin can be entirely removed by ultrasonic cleaning. A fairly efficient etching rate of about 10 nm/pulse for a patterned area of about 2 mm×2 mm is obtained at a fluence of 1 J/cm2. This study shows that projection excimer laser ablation is useful for micromachining of ferrite ceramics, and indicates that a hydrodynamic sputtering mechanism involving droplet emission is a cause of material removal.

  7. Fast neutron activation analysis of oxide inclusions in magnesium alloy ingots

    NASA Astrophysics Data System (ADS)

    Fuerst, C. D.; James, W. D.

    1999-06-01

    Magnesium will have an increasingly important role to play in the automotive industry's materials strategy. In addition to its obvious use as a lightweight alternative, magnesium offers advantages in areas such as component integration and NVH (noise, vibration and harshness). Although the metallic composition of magnesium alloys has been carefully defined, there is no uniform industry standard for non-metallic inclusions, such as oxides, which are believed to adversely impact the material's strength. A definitive test has been needed, preferably one that provides a highly sensitive, calibrated, nondestructive evaluation of the metal's bulk oxide content. In response to this need, fast neutron activation analysis (FNAA) has emerged as an important tool for providing highly accurate quantitative information on the oxygen content in magnesium alloys. Oxygen levels from less than 50 to several thousand ppm have been observed in these alloys, with the highest levels concentrated at the top center of the ingot. Several operational procedures have been developed to optimize the analysis, including: a new automated, blank-free procedure which pneumatically transports machined magnesium cylinders between the irradiation and counting facilities; the use of an oxygen standard prepared from polyethylene and titanium dioxide, machined to match the sample dimensions; and implementation of new background subtraction software.

  8. A highly active and coke-resistant steam reforming catalyst comprising uniform nickel-iron alloy nanoparticles.

    PubMed

    Koike, Mitsuru; Li, Dalin; Nakagawa, Yoshinao; Tomishige, Keiichi

    2012-12-01

    Doing fine with Ni-Fe: The calcination and reduction of a hydrotalcite precursor containing Ni and Fe ions gives uniform Ni-Fe alloy nanoparticles mixed with Mg(Ni, Fe, Al)O particles. The uniformity of the Ni-Fe alloy nanoparticles is connected to the catalyst's high activity and resistance to coke formation in toluene and phenol steam reforming reactions. PMID:23135797

  9. Characterization and comparative analysis of the tensile properties of five tempered martensitic steels and an oxide dispersion strengthened ferritic alloy irradiated at ≈295 °C to ≈6.5 dpa

    DOE PAGESBeta

    Maloy, Stuart A.; Saleh, Tarik A.; Anderoglu, Osman; Romero, Tobias J.; Odette, G. Robert; Yamamoto, Takuya; Li, S.; Cole, James I.; Fielding, Randall

    2015-08-06

    Tensile test results at 25 and 300 °C on five 9-12Cr tempered martensitic steels and one 14Cr oxide dispersion strengthened alloy, that were side-by side irradiated to 6.5 dpa at 295 °C in the Advanced Test Reactor (ATR), are reported. The engineering stress–strain curves are analyzed to provide true stress–strain constitutive σ(ε) laws for all of these alloys. In the irradiated condition, the σ(ε) fall into categories of: strain softening, nearly perfectly plastic and strain hardening. Increases in yield stress (Δσy) and reductions in uniform strain ductility (eu) are observed, where as the latter can be understood in terms ofmore » the alloy's σ(ε) behavior. Increases in the average σ(ε) in the range of 0–10% strain are smaller than the corresponding Δσy, and vary more from alloy to alloy. The data are analyzed to establish relations between Δσy and coupled changes in the ultimate stresses as well as the effects of both test temperature and the unirradiated yield stress (σyu). The latter shows that higher σyu correlates with lower Δσy. In five out of six cases the effects of irradiation are generally consistent with previous observations on these alloys. However, the particular heat of the 12Cr HT-9 tempered martensitic steel in this study has a much higher eu than observed for earlier heats. The reasons for this improved behavior are not understood and may be microstructural in origin. However, it is noted that the new heat of HT-9, which was procured under modern quality assurance standards, has lower interstitial nitrogen than previous heats. As a result, notably lower interstitial solute contents correlate with improved ductility and homogenous deformation in broadly similar steels.« less

  10. Characterization and comparative analysis of the tensile properties of five tempered martensitic steels and an oxide dispersion strengthened ferritic alloy irradiated at ≈295 °C to ≈6.5 dpa

    NASA Astrophysics Data System (ADS)

    Maloy, S. A.; Saleh, T. A.; Anderoglu, O.; Romero, T. J.; Odette, G. R.; Yamamoto, T.; Li, S.; Cole, J. I.; Fielding, R.

    2016-01-01

    Tensile test results at 25 and 300 °C on five 9-12Cr tempered martensitic steels and one 14Cr oxide dispersion strengthened alloy, that were side-by side irradiated to 6.5 dpa at 295 °C in the Advanced Test Reactor (ATR), are reported. The engineering stress-strain curves are analyzed to provide true stress-strain constitutive σ(ɛ) laws for all of these alloys. In the irradiated condition, the σ(ɛ) fall into categories of: strain softening, nearly perfectly plastic and strain hardening. Increases in yield stress (Δσy) and reductions in uniform strain ductility (eu) are observed, where the latter can be understood in terms of the alloy's σ(ɛ) behavior. Increases in the average σ(ɛ) in the range of 0-10% strain are smaller than the corresponding Δσy, and vary more from alloy to alloy. The data are also analyzed to establish relations between Δσy and coupled changes in the ultimate stresses as well as the effects of both test temperature and the unirradiated yield stress (σyu). The latter shows that higher σyu correlates with lower Δσy. In five out of six cases the effects of irradiation are generally consistent with previous observations on these alloys. However, the particular heat of the 12Cr HT-9 tempered martensitic steel in this study has a much higher eu than observed for earlier heats. The reasons for this improved behavior are not understood and may be microstructural in origin. However, it is noted that the new heat of HT-9, which was procured under modern quality assurance standards, has lower interstitial nitrogen than previous heats. Notably lower interstitial solute contents correlate with improved ductility and homogenous deformation in broadly similar steels.

  11. Activation energies for oxygen reduction on platinum alloys: theory and experiment.

    PubMed

    Anderson, Alfred B; Roques, Jérôme; Mukerjee, Sanjeev; Murthi, Vivek S; Markovic, Nenad M; Stamenkovic, Vojislav

    2005-01-27

    A combined theoretical and experimental analysis of the electrode potential dependencies of activation energies is presented for the first step in oxygen reduction over platinum and platinum alloy catalysts in both polycrystalline and carbon supported form. Tafel data for several of the catalysts are used to predict potential-dependent activation energies for oxygen reduction over the 0.6-0.9 V range in strong and weak acid. Comparisons with the theoretical curve show good agreement above 0.8 V, suggesting a fairly constant preexponential factor. Arrhenius determinations of activation energies over the 0.7-0.9 V range yield little trend for weak acid, possibly because of the larger uncertainties in the Arrhenius fits, but the strong acid results have smaller uncertainties and for them the measured activation energies trend up with potential. PMID:16851081

  12. Nanocluster-associated vacancies in nanocluster-strengthened ferritic steel as seen via positron-lifetime spectroscopy

    NASA Astrophysics Data System (ADS)

    Xu, Jun; Liu, C. T.; Miller, M. K.; Chen, Hongmin

    2009-01-01

    Nanocluster-strengthened ferritic alloys are promising as structural materials because of their excellent high-temperature strength and radiation-damage resistance. Recently, Fu [Phys. Rev. Lett. 99, 225502 (2007)] predicted that vacancies play an essential role in the formation and stabilization of nanoclusters in these materials. Positron-lifetime spectroscopy has been used to test this theoretical prediction in a nanocluster-strengthened Fe-based alloy. Nanoclusters (2-4 nm in diameter) containing Ti, Y, and O have been observed in a mechanically alloyed ferritic steel by atom-probe tomography. Vacancy clusters containing four to six vacancies have also been found in this material. In contrast, no vacancy clusters were detected in similar alloys containing no nanoclusters. These results indicate that vacancies are a vital component of the nanoclusters in these alloys.

  13. A method to determine the active particle nucleation undercooling distribution in a refined alloy

    NASA Astrophysics Data System (ADS)

    Mangelinck-Noël, N.; Spinelli, J. E.; Gandin, Ch-A.; Reinhart, G.; Nguyen-Thi, H.; Billia, B.

    2012-01-01

    We propose a method to determine the active particle distribution of nucleation undercooling in a refined alloy. The experimental data used in this work are inferred from solidification experiments on a refined Al-3.5 wt% Ni alloy performed with X-ray radiography at the European Synchrotron Radiation Facility. These in situ and real time observations allow the accurate and direct determination of the grain origin (heterogeneous nucleation on particles or fragmentation), of the density and of the equiaxed front growth rate. The LGK classical dendrite growth model is used to evaluate the front undercooling (ΔTC) corresponding to the measured equiaxed front growth rate. Then, the corresponding cumulative distribution of active refining particles is determined. From this cumulative distribution, we derive the corresponding Gaussian and log-normal laws to obtain the nucleation undercooling distribution of active particles. Results are discussed and compared to available measurements in the literature. The standard particle distribution parameters (density of nuclei, mean nucleation undercooling and standard deviation) are determined. We plan to use the determined nucleation undercooling particle distribution in a stochastic CAFE model for the grain structure without preliminary adjustment of the nucleation undercooling.

  14. In vitro activation of human fibroblasts by retrieved titanium alloy wear debris.

    PubMed

    Manlapaz, M; Maloney, W J; Smith, R L

    1996-05-01

    Titanium-aluminum-vanadium wear particles isolated from the soft-issue membrane of a failed total hip arthroplasty were added to human fibroblasts in cell culture. The cellular response to particle challenge was determined by assaying for levels of interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha, prostaglandin E2, basic fibroblast growth factor, platelet-derived growth factor-AB, and transforming growth factor-beta. Collagenase and gelatinase activities were analyzed by zymography and [3H]collagen degradation. Cell viability was assessed by measuring the uptake of [3H]thymidine. Over the range of particle concentrations tested, cell viability, as demonstrated by [3H]thymidine uptake, remained unaffected. Fibroblasts exhibited a dose-dependent release of interleukin-6 in response to exposure to titanium-aluminum-vanadium particles. At 6 and 48 hours, the highest concentration of titanium alloy particles (0.189% [vol/vol]) resulted in 7-fold and 16-fold increases in interleukin-6 release, respectively, when compared with negative controls. Neither interleukin-1 beta nor tumor necrosis factor-alpha was detected in the culture medium at any particle concentration tested for both dermal and foreskin fibroblasts. The pattern of prostaglandin E2 release by fibroblasts mirrored the pattern of interleukin-6 release. Fibroblasts exposed to the highest concentration of titanium alloy particles showed an increase in collagenase activity, starting at 12 hours. When medium samples were treated with amino phenylmercuric acetate to activate latent enzymes, a statistically significant increase in collagenase activity was observed as early as 6 hours (p < 0.001). Substrate gel analysis of medium from fibroblasts stimulated by high particle concentrations also showed an increase in gelatinolytic activity when compared with unstimulated controls. Analysis of medium samples for growth factors showed an increase in basic fibroblast growth factor at low particle

  15. Features of structure-phase transformations and segregation processes under irradiation of austenitic and ferritic-martensitic steels

    NASA Astrophysics Data System (ADS)

    Neklyudov, I. M.; Voyevodin, V. N.

    1994-09-01

    The difference between crystal lattices of austenitic and ferritic steels leads to distinctive features in mechanisms of physical-mechanical change. This paper presents the results of investigations of dislocation structure and phase evolution, and segregation phenomena in austenitic and ferritic-martensitic steels and alloys during irradiation with heavy ions in the ESUVI and UTI accelerators and by neutrons in fast reactors BOR-60 and BN-600. The influence of different factors (including different alloying elements) on processes of structure-phase transformation was studied.

  16. Ferrite attenuator modulation improves antenna performance

    NASA Technical Reports Server (NTRS)

    Hooks, J. C.; Larson, S. G.; Shorkley, F. H.; Williams, B. T.

    1970-01-01

    Ferrite attenuator inserted into appropriate waveguide reduces the gain of the antenna element which is causing interference. Modulating the ferrite attenuator to change the antenna gain at the receive frequency permits ground tracking until the antenna is no longer needed.

  17. Catalysts prepared from copper-nickel ferrites for the steam reforming of methanol

    NASA Astrophysics Data System (ADS)

    Huang, Yung-Han; Wang, Sea-Fue; Tsai, An-Pang; Kameoka, Satoshi

    2015-05-01

    In this study, Fe3O4-supported Cu and Ni catalysts are prepared through reduction of Cu-Ni (Ni1-xCuxFe2O4) ferrites. The Cu-Ni ferrites, synthesized using a solid-state reaction method, are reduced at temperatures from 240 °C to 500 °C in a H2 atmosphere. All ferrites are characterized with granular morphology and a smooth particle surface before reduction. For the CuFe2O4, Ni0.5Cu0.5Fe2O4 and NiFe2O4 ferrites reduced at 240, 300, and 400 °C, respectively, nanosized Cu and/or Ni particles (5-32 nm) and mesopores (5-30 nm) are distributed and adhered on the surfaces of Fe3O4 supports. After increasing the reduction temperature of NiFe2O4 ferrite to 500 °C, the Ni particles and mesopores disappear from the Fe3O4 surfaces, which is due to the formation of a Fe-Ni alloy covering on the Fe3O4 surfaces. The CuFe2O4 ferrite after H2 reduction at 240 °C exhibits the highest H2 production rate of 149 ml STP/min g-cat at 360 °C. The existence of Ni content in the Cu-Ni ferrites enhances the reverse water gas shift reaction, and raises the CO selectivity while reducing the CO2 selectivity. Formation of a Fe-Ni alloy exaggerates the trend and poisons the H2 production rate.

  18. The influence of Cr content on the mechanical properties of ODS ferritic steels

    NASA Astrophysics Data System (ADS)

    Li, Shaofu; Zhou, Zhangjian; Jang, Jinsung; Wang, Man; Hu, Helong; Sun, Hongying; Zou, Lei; Zhang, Guangming; Zhang, Liwei

    2014-12-01

    The present investigation aimed at researching the mechanical properties of the oxide dispersion strengthened (ODS) ferritic steels with different Cr content, which were fabricated through a consolidation of mechanical alloyed (MA) powders of 0.35 wt.% nano Y2O3 dispersed Fe-12.0Cr-0.5Ti-1.0W (alloy A), Fe-16.0Cr-0.5Ti-1.0W (alloy B), and Fe-18.0Cr-0.5Ti-1.0W (alloy C) alloys (all in wt.%) by hot isostatic pressing (HIP) with 100 MPa pressure at 1150 °C for 3 h. The mechanical properties, including the tensile strength, hardness, and impact fracture toughness were tested by universal testers, while Young's modulus was determined by ultrasonic wave non-destructive tester. It was found that the relationship between Cr content and the strength of ODS ferritic steels was not a proportional relationship. However, too high a Cr content will cause the precipitation of Cr-enriched segregation phase, which is detrimental to the ductility of ODS ferritic steels.

  19. Optimization and testing results of Zr-bearing ferritic steels

    SciTech Connect

    Tan, Lizhen; Yang, Ying; Tyburska-Puschel, Beata; Sridharan, K.

    2014-09-01

    The mission of the Nuclear Energy Enabling Technologies (NEET) program is to develop crosscutting technologies for nuclear energy applications. Advanced structural materials with superior performance at elevated temperatures are always desired for nuclear reactors, which can improve reactor economics, safety margins, and design flexibility. They benefit not only new reactors, including advanced light water reactors (LWRs) and fast reactors such as sodium-cooled fast reactor (SFR) that is primarily designed for management of high-level wastes, but also life extension of the existing fleet when component exchange is needed. Developing and utilizing the modern materials science tools (experimental, theoretical, and computational tools) is an important path to more efficient alloy development and process optimization. Ferritic-martensitic (FM) steels are important structural materials for nuclear reactors due to their advantages over other applicable materials like austenitic stainless steels, notably their resistance to void swelling, low thermal expansion coefficients, and higher thermal conductivity. However, traditional FM steels exhibit a noticeable yield strength reduction at elevated temperatures above ~500°C, which limits their applications in advanced nuclear reactors which target operating temperatures at 650°C or higher. Although oxide-dispersion-strengthened (ODS) ferritic steels have shown excellent high-temperature performance, their extremely high cost, limited size and fabricability of products, as well as the great difficulty with welding and joining, have limited or precluded their commercial applications. Zirconium has shown many benefits to Fe-base alloys such as grain refinement, improved phase stability, and reduced radiation-induced segregation. The ultimate goal of this project is, with the aid of computational modeling tools, to accelerate the development of a new generation of Zr-bearing ferritic alloys to be fabricated using conventional

  20. Characterization and comparative analysis of the tensile properties of five tempered martensitic steels and an oxide dispersion strengthened ferritic alloy irradiated at ≈295 °C to ≈6.5 dpa

    SciTech Connect

    Maloy, Stuart A.; Saleh, Tarik A.; Anderoglu, Osman; Romero, Tobias J.; Odette, G. Robert; Yamamoto, Takuya; Li, S.; Cole, James I.; Fielding, Randall

    2015-08-06

    Tensile test results at 25 and 300 °C on five 9-12Cr tempered martensitic steels and one 14Cr oxide dispersion strengthened alloy, that were side-by side irradiated to 6.5 dpa at 295 °C in the Advanced Test Reactor (ATR), are reported. The engineering stress–strain curves are analyzed to provide true stress–strain constitutive σ(ε) laws for all of these alloys. In the irradiated condition, the σ(ε) fall into categories of: strain softening, nearly perfectly plastic and strain hardening. Increases in yield stress (Δσy) and reductions in uniform strain ductility (eu) are observed, where as the latter can be understood in terms of the alloy's σ(ε) behavior. Increases in the average σ(ε) in the range of 0–10% strain are smaller than the corresponding Δσy, and vary more from alloy to alloy. The data are analyzed to establish relations between Δσy and coupled changes in the ultimate stresses as well as the effects of both test temperature and the unirradiated yield stress (σyu). The latter shows that higher σyu correlates with lower Δσy. In five out of six cases the effects of irradiation are generally consistent with previous observations on these alloys. However, the particular heat of the 12Cr HT-9 tempered martensitic steel in this study has a much higher eu than observed for earlier heats. The reasons for this improved behavior are not understood and may be microstructural in origin. However, it is noted that the new heat of HT-9, which was procured under modern quality assurance standards, has lower interstitial nitrogen than previous heats. As a result, notably lower interstitial solute contents correlate with improved ductility and homogenous deformation in broadly similar steels.

  1. Effect of ferrite on cast stainless steels

    SciTech Connect

    Nadezhdin, A.; Cooper, K. ); Timbers, G. . Kraft Pulp Division)

    1994-09-01

    Premature failure of stainless steel castings in bleach washing service is attributed to poor casting quality high porosity and to a high ferrite content, which makes the castings susceptible to corrosion by hot acid chloride solutions. A survey of the chemical compositions and ferrite contents of corrosion-resistant castings in bleach plants at three pulp mills found high [delta]-ferrite levels in the austenitic matrix due to the improper balance between austenite and ferrite stabilizers.

  2. Electrical and optical properties of gadolinium doped bismuth ferrite nanoparticles

    SciTech Connect

    Mukherjee, A. Banerjee, M. Basu, S.; Pal, M.

    2014-04-24

    Multiferroic bismuth ferrite (BFO) and gadolinium (Gd) doped bismuth ferrite had been synthesized by a sol-gel method. Particle size had been estimated by Transmission electron microscopy (TEM) and found to decrease with Gd doping. We studied the temperature and frequency dependence of impedance and electric modulus and calculated the grain and grain boundary resistance and capacitance of the investigated samples. We observed that electrical activation energy increases for all the doped samples. Optical band gap also increases for the doped samples which can be used in photocatalytic application of BFO.

  3. Nature of anisotropy of impact toughness of structural steels with ferrite-pearlite structure

    NASA Astrophysics Data System (ADS)

    Goritskii, V. M.; Shneyderov, G. R.; Lushkin, M. A.

    2013-10-01

    The anisotropy of the impact toughness of low-alloy steels of various compositions and purities with a ferrite-pearlite structure has been investigated using samples of type 11 according to the Russian Standard GOST 9454-78. It has been established that the anisotropy coefficient of the impact toughness depends on the anisotropy coefficient of the work of crack propagation and is independent of the degree of striation of the ferrite-pearlite structure and the work for nucleation of the ductile crack.

  4. Deuterium and helium trapping at TiC particles in ferritic steel

    NASA Astrophysics Data System (ADS)

    Spitznagel, J. A.; Brenner, S. S.; Miller, M. K.; Choyke, W. J.

    1984-05-01

    First wall and blanket materials in Tokamak machines must accommodate increasing concentrations of helium and hydrogen isotopes. Alloy design principles point to the efficacy of trapping He and hydrogen at finely dispersed precipitates to minimize their impact on mechanical properties. Titanium carbide particles are known to trap He effectively in austenitic stainless steel. Less is known about TiC as a trap for helium and hydrogen isotopes in ferritic steels. This paper demonstrates the feasibility of directly measuring the trapping of helium and deuterium at TiC-ferrite interfaces using atom probe field ion microscopy.

  5. A complex carbonitride of niobium and vanadium in 9% Cr ferritic steels

    SciTech Connect

    Tokuno, K.; Hamada, K.; Takeda, T. ); Uemori, R. ); Itoh, K. )

    1991-01-01

    It has been considered that small additions of Nb and V have striking effects on the creep strength of high Cr ferritic steels which are used for elevated temperature services such as boilers, steam generators etc. Although Nb and V are thought to form complex precipitates which may act as obstacles for the dislocation glide, the distribution and morphology of the precipitates have not been clarified yet. Several examples of simple precipitates of V in low alloy steels were only reported. In this paper, the morphology of the complex carbonitride of Nb and V in 9% Cr ferritic steels was investigated and the role of the carbonitride on the creep strength was discussed.

  6. High power ferrite microwave switch

    NASA Technical Reports Server (NTRS)

    Bardash, I.; Roschak, N. K.

    1975-01-01

    A high power ferrite microwave switch was developed along with associated electronic driver circuits for operation in a spaceborne high power microwave transmitter in geostationary orbit. Three units were built and tested in a space environment to demonstrate conformance to the required performance characteristics. Each unit consisted of an input magic-tee hybrid, two non-reciprocal latching ferrite phase shifters, an out short-slot 3 db quadrature coupler, a dual driver electronic circuit, and input logic interface circuitry. The basic mode of operation of the high power ferrite microwave switch is identical to that of a four-port, differential phase shift, switchable circulator. By appropriately designing the phase shifters and electronic driver circuits to operate in the flux-transfer magnetization mode, power and temperature insensitive operation was achieved. A list of the realized characteristics of the developed units is given.

  7. Small high directivity ferrite antennas

    NASA Astrophysics Data System (ADS)

    Wright, T. M. B.

    A centimeter-wavelength antenna of millimetric dimensions, which uses the intrinsic angular sensitivity of ferrites, is described, with an emphasis on the modification of the material's permeability. The construction of both the ferrite film lens antenna and the ferrite film cassegrain antenna are detailed; both can be devised in a number of configurations for appropriate beam positioning and rf filtering. The antenna design, discussed primarily in the context of smart missiles, electronic warfare, and satellite systems, presents the possibility of magnetically switching between the transmit and receive modes within the antenna structure itself. Finally, it is noted that for a simple 2-dipole array the angular resolution can be two orders of magnitude higher than with the conventional techniques.

  8. Development and characterisation of a new ODS ferritic steel for fusion reactor application

    NASA Astrophysics Data System (ADS)

    Oksiuta, Z.; Olier, P.; de Carlan, Y.; Baluc, N.

    2009-08-01

    This paper describes the microstructure, tensile properties and Charpy impact resistance of a reduced activation oxide dispersion strengthened ferritic steel Fe-14Cr-2W-0.3Ti-0.3Y 2O 3 produced by mechanical alloying of a pre-alloyed, gas atomised steel powder with Y 2O 3 particles, compaction by hot extrusion at 1100 °C, hot rolling at 700 °C and heat treatment at 1050 °C for 1 h. At room temperature the material exhibits a high ultimate tensile strength of about 1420 MPa and high yield strength of about 1340 MPa in the transverse direction. In the longitudinal direction the values are about 10% lower, due to the anisotropy of the microstructure (elongated grains in the rolling direction). At 750 °C the material still exhibits relatively high yield strengths of about 325 MPa and 305 MPa in the longitudinal and transverse directions, respectively. The material exhibits reasonable uniform and total elongation values over the temperature range 23-750 °C, in both transverse and longitudinal directions. The material exhibits weak Charpy impact properties in the transverse direction. Charpy impact properties are slightly better in the longitudinal direction, with upper shelf energy of about 4.2 J and a ductile-to-brittle transition temperature of about 8.8 °C.

  9. Hydrogenation under high pressure enhancing catalytic activity of Cu-Zr amorphous alloys

    NASA Astrophysics Data System (ADS)

    Szummer, A.; Janik-Czachor, M.; Molnár, Á.; Marchuk, I.; Varga, M.; Filipek, S. M.

    2002-11-01

    High pressures of hydrogen up to 3.0 GPa and temperatures up to 373 K were used as a pretreatment to introduce structural changes in the bulk and on the surface of Cu-Zr amorphous alloys which then were examined by means of x-ray diffraction and microscopy. The hydrogenative pretreatment of high hydrogen fugacity followed by annealing at 623 K, aimed at causing desorption of hydrogen, and an eventual exposure of the samples to air at room temperature to oxidize Zr, resulted in a distinct increase of catalytic activity in the dehydrogenation of 2-propanol. A tentative mechanism to account for the enhancement of the catalytic activity induced by the above combined pretreatment is discussed.

  10. Effect of neutron irradiation on vanadium alloys

    SciTech Connect

    Braski, D.N.

    1986-01-01

    Neutron-irradiated vanadium alloys were evaluated for their susceptibility to irradiation hardening, helium embrittlement, swelling, and residual radioactivity, and the results were compared with those for the austenitic and ferritic stainless steels. The VANSTAR-7 and V-15Cr-5Ti alloys showed the greatest hardening between 400 and 600/sup 0/C while V-3Ti-1Si and V-20Ti had lower values that were comparable to those of ferritic steels. The V-15Cr-5Ti and VANSTAR-7 alloys were susceptible to helium embrittlement caused by the combination of weakened grain boundaries and irradiation-hardened grain matrices. Specimen fractures were entirely intergranular in the most severe instances of embrittlement. The V-3Ti-1Si and V-20Ti alloys were more resistant to helium embrittlement. Except for VANSTAR-7 irradiated to 40 dpa at 520/sup 0/C, all of the vanadium alloys exhibited low swelling that was similar to the ferritic steels. Swelling was greater in specimens that were preimplanted with helium using the tritium trick. The vanadium alloys clearly exhibit lower residual radioactivity after irradiation than the ferrous alloys.

  11. Highly branched PtCu bimetallic alloy nanodendrites with superior electrocatalytic activities for oxygen reduction reactions

    NASA Astrophysics Data System (ADS)

    Fu, Shaofang; Zhu, Chengzhou; Shi, Qiurong; Xia, Haibing; Du, Dan; Lin, Yuehe

    2016-02-01

    Morphology control is a promising strategy to improve the catalytic performance of Pt-based catalysts. In this work, we reported a facile synthesis of PtCu bimetallic alloy nanodendrites using Brij 58 as a template. The highly branched structures and porous features offer relatively large surface areas, which is beneficial to the enhancement of the catalytic activity for oxygen reduction reactions in fuel cells. In addition, the elimination of carbon supports showed an important effect on the stability of the catalysts. By tuning the ratio of Pt and Cu precursors, PtCu nanodendrites were almost four times more active on the basis of an equivalent Pt mass for oxygen reduction reactions than the commercial Pt/C catalyst.Morphology control is a promising strategy to improve the catalytic performance of Pt-based catalysts. In this work, we reported a facile synthesis of PtCu bimetallic alloy nanodendrites using Brij 58 as a template. The highly branched structures and porous features offer relatively large surface areas, which is beneficial to the enhancement of the catalytic activity for oxygen reduction reactions in fuel cells. In addition, the elimination of carbon supports showed an important effect on the stability of the catalysts. By tuning the ratio of Pt and Cu precursors, PtCu nanodendrites were almost four times more active on the basis of an equivalent Pt mass for oxygen reduction reactions than the commercial Pt/C catalyst. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07682j

  12. Preparation of AuPt alloy foam films and their superior electrocatalytic activity for the oxidation of formic acid.

    PubMed

    Liu, Jun; Cao, Ling; Huang, Wei; Li, Zelin

    2011-09-01

    AuPt alloy films with three-dimensional (3D) hierarchical pores consisting of interconnected dendrite walls were successfully fabricated by a strategy of cathodic codeposition utilizing the hydrogen bubble dynamic template. The foam films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Due to the special porous structure, the electronic property, and the assembly effect, the AuPt alloy foam films show superior electrocatalytic activity toward the electrooxidation of formic acid in acidic solution, and the prepared 3D porous AuPt alloy films also show high activity and long stability for the electrocatalytic oxidation of methanol, where synergistic effect plays an important role in addition to the electronic effect and assembly effect. These findings provide more insights into the AuPt bimetallic nanomaterials for electrocatalytic applications. PMID:21838240

  13. Nano-sized Superlattice Clusters Created by Oxygen Ordering in Mechanically Alloyed Fe Alloys

    PubMed Central

    Hu, Yong-Jie; Li, Jing; Darling, Kristopher A.; Wang, William Y.; VanLeeuwen, Brian K.; Liu, Xuan L.; Kecskes, Laszlo J.; Dickey, Elizabeth C.; Liu, Zi-Kui

    2015-01-01

    Creating and maintaining precipitates coherent with the host matrix, under service conditions is one of the most effective approaches for successful development of alloys for high temperature applications; prominent examples include Ni- and Co-based superalloys and Al alloys. While ferritic alloys are among the most important structural engineering alloys in our society, no reliable coherent precipitates stable at high temperatures have been found for these alloys. Here we report discovery of a new, nano-sized superlattice (NSS) phase in ball-milled Fe alloys, which maintains coherency with the BCC matrix up to at least 913 °C. Different from other precipitates in ferritic alloys, this NSS phase is created by oxygen-ordering in the BCC Fe matrix. It is proposed that this phase has a chemistry of Fe3O and a D03 crystal structure and becomes more stable with the addition of Zr. These nano-sized coherent precipitates effectively double the strength of the BCC matrix above that provided by grain size reduction alone. This discovery provides a new opportunity for developing high-strength ferritic alloys for high temperature applications. PMID:26134420

  14. Nano-sized Superlattice Clusters Created by Oxygen Ordering in Mechanically Alloyed Fe Alloys.

    PubMed

    Hu, Yong-Jie; Li, Jing; Darling, Kristopher A; Wang, William Y; VanLeeuwen, Brian K; Liu, Xuan L; Kecskes, Laszlo J; Dickey, Elizabeth C; Liu, Zi-Kui

    2015-01-01

    Creating and maintaining precipitates coherent with the host matrix, under service conditions is one of the most effective approaches for successful development of alloys for high temperature applications; prominent examples include Ni- and Co-based superalloys and Al alloys. While ferritic alloys are among the most important structural engineering alloys in our society, no reliable coherent precipitates stable at high temperatures have been found for these alloys. Here we report discovery of a new, nano-sized superlattice (NSS) phase in ball-milled Fe alloys, which maintains coherency with the BCC matrix up to at least 913 °C. Different from other precipitates in ferritic alloys, this NSS phase is created by oxygen-ordering in the BCC Fe matrix. It is proposed that this phase has a chemistry of Fe3O and a D03 crystal structure and becomes more stable with the addition of Zr. These nano-sized coherent precipitates effectively double the strength of the BCC matrix above that provided by grain size reduction alone. This discovery provides a new opportunity for developing high-strength ferritic alloys for high temperature applications. PMID:26134420

  15. Nano-sized Superlattice Clusters Created by Oxygen Ordering in Mechanically Alloyed Fe Alloys

    NASA Astrophysics Data System (ADS)

    Hu, Yong-Jie; Li, Jing; Darling, Kristopher A.; Wang, William Y.; Vanleeuwen, Brian K.; Liu, Xuan L.; Kecskes, Laszlo J.; Dickey, Elizabeth C.; Liu, Zi-Kui

    2015-07-01

    Creating and maintaining precipitates coherent with the host matrix, under service conditions is one of the most effective approaches for successful development of alloys for high temperature applications; prominent examples include Ni- and Co-based superalloys and Al alloys. While ferritic alloys are among the most important structural engineering alloys in our society, no reliable coherent precipitates stable at high temperatures have been found for these alloys. Here we report discovery of a new, nano-sized superlattice (NSS) phase in ball-milled Fe alloys, which maintains coherency with the BCC matrix up to at least 913 °C. Different from other precipitates in ferritic alloys, this NSS phase is created by oxygen-ordering in the BCC Fe matrix. It is proposed that this phase has a chemistry of Fe3O and a D03 crystal structure and becomes more stable with the addition of Zr. These nano-sized coherent precipitates effectively double the strength of the BCC matrix above that provided by grain size reduction alone. This discovery provides a new opportunity for developing high-strength ferritic alloys for high temperature applications.

  16. Cobalt ferrite nanoparticles under high pressure

    SciTech Connect

    Saccone, F. D.; Ferrari, S.; Grinblat, F.; Bilovol, V.; Errandonea, D.

    2015-08-21

    We report by the first time a high pressure X-ray diffraction and Raman spectroscopy study of cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles carried out at room temperature up to 17 GPa. In contrast with previous studies of nanoparticles, which proposed the transition pressure to be reduced from 20–27 GPa to 7.5–12.5 GPa (depending on particle size), we found that cobalt ferrite nanoparticles remain in the spinel structure up to the highest pressure covered by our experiments. In addition, we report the pressure dependence of the unit-cell parameter and Raman modes of the studied sample. We found that under quasi-hydrostatic conditions, the bulk modulus of the nanoparticles (B{sub 0} = 204 GPa) is considerably larger than the value previously reported for bulk CoFe{sub 2}O{sub 4} (B{sub 0} = 172 GPa). In addition, when the pressure medium becomes non-hydrostatic and deviatoric stresses affect the experiments, there is a noticeable decrease of the compressibility of the studied sample (B{sub 0} = 284 GPa). After decompression, the cobalt ferrite lattice parameter does not revert to its initial value, evidencing a unit cell contraction after pressure was removed. Finally, Raman spectroscopy provides information on the pressure dependence of all Raman-active modes and evidences that cation inversion is enhanced by pressure under non-hydrostatic conditions, being this effect not fully reversible.

  17. Synthesis and anti-bacterial activity of Cu, Ag and Cu-Ag alloy nanoparticles: A green approach

    SciTech Connect

    Valodkar, Mayur; Modi, Shefaly; Pal, Angshuman; Thakore, Sonal

    2011-03-15

    Research highlights: {yields} Synthesis of novel nanosized copper-silver alloys of different compositions. {yields} Completely green approach for synthesis of water soluble bimetallic nanoparticle. {yields} Interesting anti-bacterial activity of as synthesized metal and alloy nanoparticle. -- Abstract: Metallic and bimetallic nanoparticles of copper and silver in various proportions were prepared by microwave assisted chemical reduction in aqueous medium using the biopolymer, starch as a stabilizing agent. Ascorbic acid was used as the reducing agent. The silver and copper nanoparticles exhibited surface plasmon absorption resonance maxima (SPR) at 416 and 584 nm, respectively; while SPR for the Cu-Ag alloys appeared in between depending on the alloy composition. The SPR maxima for bimetallic nanoparticles changes linearly with increasing copper content in the alloy. Transmission electron micrograph (TEM) showed monodispersed particles in the range of 20 {+-} 5 nm size. Both silver and copper nanoparticles exhibited emission band at 485 and 645 nm, respectively. The starch-stabilized nanoparticles exhibited interesting antibacterial activity with both gram positive and gram negative bacteria at micromolar concentrations.

  18. High-temperature oxidation behavior of two-phase iron-manganese-aluminum alloys

    SciTech Connect

    Liu, S.Y.; Lee, C.L.; Kao, C.H.; Perng, T.P.

    2000-04-01

    Oxidation behavior of two series of two-phase Fe-Mn-Al alloys in air up to 800 C was investigated. For the first series of alloys with various ratios of ferrite-austenite, the oxidation resistance of these alloys increased as the ferrite content increased. Two layers of oxide were formed mainly on the austenite grains, and oxidation in the ferrite phase was much less severe. The other layer of the scale on austenite was enriched with Mn and Fe, while Al was concentrated in the inner layer. For the second series of alloys with nearly the same contents of ferrite and C but various contents of Cr, the addition of Cr changed the oxidation characteristics and increased the oxidation resistance. Cr assisted the formation of a dense film of alumina (Al{sub 2}O{sub 3}) to prevent further oxidation.

  19. Self-activated mesh device using shape memory alloy for periosteal expansion osteogenesis.

    PubMed

    Yamauchi, Kensuke; Takahashi, Tetsu; Tanaka, Kenko; Nogami, Shinnosuke; Kaneuji, Takeshi; Kanetaka, Hiroyasu; Miyazaki, Toshiki; Lethaus, Bernd; Kessler, Peter

    2013-07-01

    The present study evaluated the use of this self-activated shape memory alloy (SMA) device, with a focus on its effects in the region under the periosteum. Twelve Japanese white rabbits were used in this study. The device was inserted under the periosteum at the forehead. In the experimental group, the device was pushed, bent, and attached to the bone surface and fixed with a titanium screw. In control group, the device was only inserted under the periosteum. After 14 days, the screw was removed and the mesh was activated in the experimental group. Rabbits were sacrificed 5 and 8 weeks after the operation and newly formed bone was histologically and radiographically evaluated. The quantitative data by the area and the occupation of newly formed bone indicated that the experimental group had a higher volume of new bone than the control group at each consolidation period. Histologically, some newly formed bone was observed and most of the subperiosteal space underneath the device was filled with fibrous tissue, and a thin layer of immature bone was observed in the control group. In the experimental group, multiple dome-shaped bones, outlined by thin and scattered trabeculae, were clearly observed under the SMA mesh device. The use of self-activated devices for the periosteal expansion technique may make it possible to avoid donor site morbidity, trans-skin activation rods, any bone-cutting procedure, and the following intermittent activation procedure. PMID:23359561

  20. Tuning the activity of Pt(111) for oxygen electroreduction by subsurface alloying.

    PubMed

    Stephens, Ifan E L; Bondarenko, Alexander S; Perez-Alonso, Francisco J; Calle-Vallejo, Federico; Bech, Lone; Johansson, Tobias P; Jepsen, Anders K; Frydendal, Rasmus; Knudsen, Brian P; Rossmeisl, Jan; Chorkendorff, Ib

    2011-04-13

    To enable the development of low temperature fuel cells, significant improvements are required to the efficiency of the Pt electrocatalysts at the cathode, where oxygen reduction takes place. Herein, we study the effect of subsurface solute metals on the reactivity of Pt, using a Cu/Pt(111) near-surface alloy. Our investigations incorporate electrochemical measurements, ultrahigh vacuum experiments, and density functional theory. Changes to the OH binding energy, ΔE(OH), were monitored in situ and adjusted continuously through the subsurface Cu coverage. The incorporation of submonolayer quantities of Cu into Pt(111) resulted in an 8-fold improvement in oxygen reduction activity. The most optimal catalyst for oxygen reduction has an ΔE(OH) ≈ 0.1 eV weaker than that of pure Pt, validating earlier theoretical predictions. PMID:21417329

  1. A general method for multimetallic platinum alloy nanowires as highly active and stable oxygen reduction catalysts

    SciTech Connect

    Bu, Lingzheng; Ding, Jiabao; Yao, Jianlin; Huang, Xiaoqing; Guo, Shaojun; Zhang, Xu; Lu, Gang; Su, Dong; Zhu, Xing; Guo, Jun

    2015-10-13

    The production of inorganic nanoparticles (NPs) with precise control over structures has always been a central target in various fields of chemistry and physics because the properties of NPs can be desirably manipulated by their structure.[1-4] There has been an intense search for high-performance noble metal NP catalysts particular for Pt.[5-9] Precious platinum (Pt) NPs are active catalysts for various heterogeneous reactions and show particularly superior performance in both the anodic oxidation reaction and the cathodic ORR in the fuel cells, but their rare content and high cost largely impede the practical application.[10-12] A potential strategy to address this tremendous challenge is alloying Pt NPs with the transition metals (TM).[13-16]

  2. Excavated Cubic Platinum-Tin Alloy Nanocrystals Constructed from Ultrathin Nanosheets with Enhanced Electrocatalytic Activity.

    PubMed

    Chen, Qiaoli; Yang, Yanan; Cao, Zhenming; Kuang, Qin; Du, Guifen; Jiang, Yaqi; Xie, Zhaoxiong; Zheng, Lansun

    2016-07-25

    Excavated polyhedral noble-metal materials that were built by the orderly assembly of ultrathin nanosheets have both large surface areas and well-defined facets, and therefore could be promising candidates for diverse important applications. In this work, excavated cubic Pt-Sn alloy nanocrystals (NCs) with {110} facets were constructed from twelve nanosheets by a simple co-reduction method with the assistance of the surface regulator polyvinylpyrrolidone. The specific surface area of the excavated cubic Pt-Sn NCs is comparable to that of commercial Pt black despite their larger particle size. The excavated cubic Pt-Sn NCs exhibited superior electrocatalytic activity in terms of both the specific area current density and the mass current density towards methanol oxidation. PMID:27325395

  3. Active vibration control of a flexible cantilever beam using shape memory alloy actuators

    NASA Astrophysics Data System (ADS)

    Suzuki, Y.; Kagawa, Y.

    2010-08-01

    This paper demonstrates the feasibility of using shape memory alloys (SMAs) as actuators to control the vibration of a flexible cantilever beam. In a tendon mechanism, SMAs are controlled in a push-pull fashion based on H-infinity theory and taking into account the uncertainty in the actuator performance. Using this mechanism, the four vibrational modes (three bending and one torsional) of the cantilever beam can be simultaneously damped. To control bending and torsional vibrational modes of a flexible beam, we install SMAs obliquely in a beam-SMA structure, then measure and theoretically model the properties of an actuator consisting of an SMA and a spring. Using the properties of the actuator, we introduce the state equations based on the dynamic model of the proposed beam-SMA structure and design the active control system according to H-infinity theory. Finally, we experimentally verify the functioning of the system.

  4. A general method for multimetallic platinum alloy nanowires as highly active and stable oxygen reduction catalysts

    DOE PAGESBeta

    Bu, Lingzheng; Ding, Jiabao; Yao, Jianlin; Huang, Xiaoqing; Guo, Shaojun; Zhang, Xu; Lu, Gang; Su, Dong; Zhu, Xing; Guo, Jun

    2015-10-13

    The production of inorganic nanoparticles (NPs) with precise control over structures has always been a central target in various fields of chemistry and physics because the properties of NPs can be desirably manipulated by their structure.[1-4] There has been an intense search for high-performance noble metal NP catalysts particular for Pt.[5-9] Precious platinum (Pt) NPs are active catalysts for various heterogeneous reactions and show particularly superior performance in both the anodic oxidation reaction and the cathodic ORR in the fuel cells, but their rare content and high cost largely impede the practical application.[10-12] A potential strategy to address this tremendousmore » challenge is alloying Pt NPs with the transition metals (TM).[13-16]« less

  5. Electrocatalytic activity of alkyne-functionalized AgAu alloy nanoparticles for oxygen reduction in alkaline media

    NASA Astrophysics Data System (ADS)

    Hu, Peiguang; Song, Yang; Chen, Limei; Chen, Shaowei

    2015-05-01

    1-Dodecyne-functionalized AgAu alloy nanoparticles were synthesized by chemical reduction of metal salt precursors at varied initial feed ratios. Transmission electron microscopic measurements showed that the nanoparticles were all rather well dispersed with the average core diameter in the narrow range of 3 to 5 nm. X-ray photoelectron spectroscopic studies confirmed the formation of AgAu alloy nanoparticles with the gold concentration ranging from approximately 25 at% to 55 at%. Consistent results were obtained in UV-vis spectroscopic measurements where the nanoparticle surface plasmon resonance red-shifted almost linearly with increasing gold concentrations. The self-assembly of 1-dodecyne ligands on the nanoparticle surface was manifested in infrared spectroscopic measurements. Importantly, the resulting nanoparticles exhibited apparent electrocatalytic activity for oxygen reduction in alkaline media, and the performance was found to show a volcano variation in the Au content in the alloy nanoparticles, with the best performance observed for the samples with ca. 35.5 at% Au. The enhanced catalytic activity, as compared to pure Ag nanoparticles or even commercial Pt/C catalysts, was accounted for by the unique metal-ligand interfacial bonding interactions as well as alloying effects that increased metal-oxygen affinity.1-Dodecyne-functionalized AgAu alloy nanoparticles were synthesized by chemical reduction of metal salt precursors at varied initial feed ratios. Transmission electron microscopic measurements showed that the nanoparticles were all rather well dispersed with the average core diameter in the narrow range of 3 to 5 nm. X-ray photoelectron spectroscopic studies confirmed the formation of AgAu alloy nanoparticles with the gold concentration ranging from approximately 25 at% to 55 at%. Consistent results were obtained in UV-vis spectroscopic measurements where the nanoparticle surface plasmon resonance red-shifted almost linearly with increasing gold

  6. Multiferroic bismuth ferrite material core based inductive displacement sensor

    NASA Astrophysics Data System (ADS)

    Rajeswari, R.; Biswal, M. R.; Nanda, J.; Mishra, N. C.

    2012-07-01

    In this research, an inductive displacement sensor with multiferroic bismuth ferrite core has been realized. The bismuth ferrite sample is synthesized and its structural and dielectric properties are studied. A rod-shaped bismuth ferrite core is prepared and displaced through the inductor of a RLC circuit. The performance of the prepared bismuth ferrite core has been compared with a commercially available ferrite core.

  7. The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

    NASA Astrophysics Data System (ADS)

    Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

    2016-04-01

    Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

  8. Laser cladding of stainless steel with a copper-silver alloy to generate surfaces of high antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Hans, Michael; Támara, Juan Carlos; Mathews, Salima; Bax, Benjamin; Hegetschweiler, Andreas; Kautenburger, Ralf; Solioz, Marc; Mücklich, Frank

    2014-11-01

    Copper and silver are used as antimicrobial agents in the healthcare sector in an effort to curb infections caused by bacteria resistant to multiple antibiotics. While the bactericidal potential of copper and silver alone are well documented, not much is known about the antimicrobial properties of copper-silver alloys. This study focuses on the antibacterial activity and material aspects of a copper-silver model alloy with 10 wt% Ag. The alloy was generated as a coating with controlled intermixing of copper and silver on stainless steel by a laser cladding process. The microstructure of the clad was found to be two-phased and in thermal equilibrium with minor Cu2O inclusions. Ion release and killing of Escherichia coli under wet conditions were assessed with the alloy, pure silver, pure copper and stainless steel. It was found that the copper-silver alloy, compared to the pure elements, exhibited enhanced killing of E. coli, which correlated with an up to 28-fold increased release of copper ions. The results show that laser cladding with copper and silver allows the generation of surfaces with enhanced antimicrobial properties. The process is particularly attractive since it can be applied to existing surfaces.

  9. Versatility of electrospinning in the fabrication of fibrous mat and mesh nanostructures of bismuth ferrite (BiFeO3) and their magnetic and photocatalytic activities.

    PubMed

    Bharathkumar, S; Sakar, M; K, Rohith Vinod; Balakumar, S

    2015-07-21

    This study demonstrates the fabrication of electrospun bismuth ferrite (BiFeO3/BFO) fiber mat and fibrous mesh nanostructures consisting of aligned and random fibers respectively. The formation of these one dimensional (1D) nanostructures was mediated by the drum and plate collectors in the electrospinning process that yielded aligned and random nanofibers of BFO respectively. The single phase and rhombohedral crystal structure of the fabricated 1D BFO nanostructures are confirmed through X-ray diffraction (XRD) studies. X-ray photoelectron spectroscopy (XPS) studies indicated that the fabricated fibers are stoichiometric BFO with native oxidation states +3. The surface texture and morphology are analyzed using the field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) techniques. The average size of fibers in mat and mesh nanostructures is found to be 200 nm and 150 nm respectively. The band gap energy of BFO mat and mesh deduced from their UV diffuse reflectance spectra (UV-DRS) was found to be 2.44 eV and 2.39 eV, respectively, which evidenced the improved visible light receptivity of BFO mesh compared to that of the mat. Magnetization studies using a super conducting quantum interference device (SQUID) magnetometer revealed the weak ferromagnetic properties of BFO mesh and mat nanostructures that could emerge due to the dimension induced suppression of cycloidal spin structures. The photocatalytic degradation properties of the fibrous mesh are found to be enhanced compared to that of the mat. This could be attributed to the reduced band gap energy and an improved semiconductor band-bending phenomenon in the mesh that favoured the transportation of excited charge carriers to the photocatalyst-dye interfaces and the production of more number of reactive species that lead to the effective degradation of the dye molecules. PMID:26083677

  10. 46 CFR 54.25-20 - Low temperature operation-ferritic steels with properties enhanced by heat treatment (modifies...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... section VIII of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 54.01-1... 46 Shipping 2 2014-10-01 2014-10-01 false Low temperature operation-ferritic steels with... VESSELS Construction With Carbon, Alloy, and Heat Treated Steels § 54.25-20 Low temperature...

  11. 46 CFR 54.25-20 - Low temperature operation-ferritic steels with properties enhanced by heat treatment (modifies...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... section VIII of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 54.01-1... 46 Shipping 2 2011-10-01 2011-10-01 false Low temperature operation-ferritic steels with... VESSELS Construction With Carbon, Alloy, and Heat Treated Steels § 54.25-20 Low temperature...

  12. 46 CFR 54.25-20 - Low temperature operation-ferritic steels with properties enhanced by heat treatment (modifies...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... section VIII of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 54.01-1... 46 Shipping 2 2012-10-01 2012-10-01 false Low temperature operation-ferritic steels with... VESSELS Construction With Carbon, Alloy, and Heat Treated Steels § 54.25-20 Low temperature...

  13. 46 CFR 54.25-20 - Low temperature operation-ferritic steels with properties enhanced by heat treatment (modifies...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... section VIII of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 54.01-1... 46 Shipping 2 2013-10-01 2013-10-01 false Low temperature operation-ferritic steels with... VESSELS Construction With Carbon, Alloy, and Heat Treated Steels § 54.25-20 Low temperature...

  14. High-throughput design of low-activation, high-strength creep-resistant steels for nuclear-reactor applications

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Reduced-activation ferritic/martensitic steels are prime candidate materials for structural applications in nuclear power reactors. However, their creep strength is much lower than that of creep-resistant steel developed for conventional fossil-fired power plants as alloying elements with a high neutron activation cannot be used. To improve the creep strength and to maintain a low activation, a high-throughput computational alloy design model coupling thermodynamics, precipitate-coarsening kinetics and an optimization genetic algorithm, is developed. Twelve relevant alloying elements with either low or high activation are considered simultaneously. The activity levels at 0-10 year after the end of irradiation are taken as optimization parameter. The creep-strength values (after exposure for 10 years at 650 °C) are estimated on the basis of the solid-solution strengthening and the precipitation hardening (taking into account precipitate coarsening). Potential alloy compositions leading to a high austenite fraction or a high percentage of undesirable second phase particles are rejected automatically in the optimization cycle. The newly identified alloys have a much higher precipitation hardening and solid-solution strengthening at the same activity level as existing reduced-activation ferritic/martensitic steels.

  15. Effect of copper on active dissolution and pitting corrosion of 25% Cr duplex stainless steels

    SciTech Connect

    Garfias-Mesias, L.F.; Sykes, J.M.

    1998-01-01

    Electrochemical studies were made of the influence of Cu on pitting behavior and active dissolution of 25% Cr duplex stainless steels (DSS) in chloride-containing neutral and acid solutions. Alloys with increased Cu content showed higher pitting potentials (E{sub p}) in 1 M hydrochloric acid (HCl) and 3.5% sodium chloride (NaCl) solutions. In HCl, the current density in the active state also was lower for the Cu-containing alloys. However, the critical pitting temperature (CPT) in ferric chloride (FeCl{sub 3}) was not improved significantly by addition of Cu. Pitting in all environments took place preferentially in the ferrite phase.

  16. Biodegradable Mg-Cu alloy implants with antibacterial activity for the treatment of osteomyelitis: In vitro and in vivo evaluations.

    PubMed

    Li, Yang; Liu, Lina; Wan, Peng; Zhai, Zanjing; Mao, Zhenyang; Ouyang, Zhengxiao; Yu, Degang; Sun, Qi; Tan, Lili; Ren, Ling; Zhu, Zhenan; Hao, Yongqiang; Qu, Xinhua; Yang, Ke; Dai, Kerong

    2016-11-01

    Treatment of chronic osteomyelitis (bone infection) remains a clinical challenge; in particular, it requires an implantable material with improved antibacterial activity. Here, we prepared biodegradable magnesium (Mg)-copper (Cu) alloys with different Cu contents (0.05, 0.1, and 0.25 wt%) and assessed their potential for treating methicillin-resistant Staphylococcus aureus-induced osteomyelitis. We evaluated the microstructures, mechanical properties, corrosion behavior, and ion release of the alloys in vitro, and their biocompatibility and antibacterial activity in vitro and in vivo. The antibacterial activity of the Mg-Cu alloys in vitro was demonstrated by microbiological counting assays, bacterial viability assays, biofilm formation observations, and the expression of biofilm, virulence, and antibiotic-resistance associated genes. The antibacterial activity of Mg-Cu alloys in vivo was confirmed by imaging examination, microbiological cultures, and histopathology. The biocompatibility of Mg-Cu alloys was confirmed by cell proliferation, vitality, and morphology assays in vitro and Cu(2+) or Mg(2+) ion assays, blood biochemical tests, and histological evaluation in vivo. The alloy containing 0.25 wt% Cu exhibited the highest antibacterial activity among the tested alloys, with favorable biocompatibility. Collectively, our results indicate the potential utility of Mg-Cu alloy implants with 0.25 wt% Cu in treating orthopedic infections. PMID:27573133

  17. High heat flux testing of 12-14Cr ODS ferritic steels

    NASA Astrophysics Data System (ADS)

    Pintsuk, G.; Oksiuta, Z.; Linke, J.; Baluc, N.

    2010-01-01

    The thermal performance of Fe-(12-14)Cr-2W-0.3Ti-0.3Y 2O 3 ODS reduced activation ferritic steels, which are considered as candidate first wall materials for the future fusion power reactors and were manufactured by mechanical alloying in hydrogen and hot isostatic pressing, was assessed by high heat flux (HHF) testing with the electron beam JUDITH facility at the Forschungszentrum Jülich (FZJ), Germany. An analysis of the microhardness and microstructure of the specimens was done before and after HHF tests. In general, both materials present a ferritic (α-Fe, bcc) microstructure with a wide range of grain sizes from 100 to 500 nm up to a few micrometers. The coarse grains are almost dislocation-free, while the smaller ones are surrounded by tangles of dislocations. Oxide and carbide impurities (about a few hundreds nm in size) and a high density of Y-Ti-O nano-clusters, with a mean size of about 5 nm, are also present. The microhardness, density and tensile strength of the 14Cr material are slightly larger than those of the 12Cr material. HHF tests revealed that there is no difference in thermal performance, level of degradation and erosion behaviour of 12Cr and 14Cr ODS steels. The onset of melting of the materials occurs for an energy density between 1 and 1.5 MJ/m 2. Below this value only some kind of thermal etching takes place. This is a significant improvement compared to stainless steel, for which severe plastic deformation at the material surface was observed.

  18. The partitioning of alloying elements in vacuum arc remelted, Pd-modified PH 13-8 Mo alloys

    NASA Astrophysics Data System (ADS)

    Cieslak, M. J.; Vandenavyle, J. A.; Carr, M. J.; Hills, C. R.; Semarge, R. E.

    1988-12-01

    The partitioning of alloying elements in as-solidified PH 13-8 Mo stainless steel containing up to 1.02 wt pct Pd has been investigated. The as-solidified structure is composed of two major phases, martensite and ferrite. Electron probe microanalysis reveals that Mo, Cr, and Al partition to the ferrite phase while Fe, Ni, Mn, and Pd partition to the martensite (prior austenite) during solidification and cooling from the solidus. In addition to bulk segregation between phases, precipitation of the intermetallic, PdAI, in the retained ferrite is observed. Precipitation of the normal hardening phase, β-NiAl, is also observed in the retained ferrite. Partition ratios of the various alloying elements are determined and are compared with those observed previously in duplex Fe-Cr-Ni stainless steel solidification structures. The martensite start temperature (Ms) was observed to decrease with increasing Pd concentration.

  19. Characterization of ferritic G. M. A. weld deposits in 9% Ni steel for cryogenic applications

    SciTech Connect

    Mahin, K.W.

    1980-04-01

    Low temperature containment vessels of 9% Ni are normally fabricated using the shielded metal arc (S.M.A.W.) or the gas metal arc (G.M.A.W.) welding processes. Available filler metals compatible with these processes are highly alloyed austenitics, whose strength levels undermatch those of the base plate. A more efficient weld joint would be a low alloy ferritic deposit. Although acceptable matching ferritic gas tungsten arc weld (G.T.A.W.) wires have been developed, similar progress has not been made in the area of ferritic G.M.A. weld wires. Most of the prior work in this area has focused on correlating composition with mechanical properties, without a corresponding evaluation of resultant microstructure. The study presented focused on establishing correlations between chemistry, microstructure and mechanical properties for four different ferritic G.M.A. weld deposits in 9% Ni steel, with the purpose of developing a better understanding of the factors controlling the 77K (-196/sup 0/C) toughness behavior of these weld metals. Microstructural characterization was carried out using standard optical and scanning electron microscopes, as well as a variety of advanced analytical techniques, including transmission electron microscopy (T.E.M.), scanning T.E.M., Moessbauer spectroscopy and Auger electron spectroscopy.

  20. Design optimization study of a shape memory alloy active needle for biomedical applications.

    PubMed

    Konh, Bardia; Honarvar, Mohammad; Hutapea, Parsaoran

    2015-05-01

    Majority of cancer interventions today are performed percutaneously using needle-based procedures, i.e. through the skin and soft tissue. The difficulty in most of these procedures is to attain a precise navigation through tissue reaching target locations. To overcome this challenge, active needles have been proposed recently where actuation forces from shape memory alloys (SMAs) are utilized to assist the maneuverability and accuracy of surgical needles. In the first part of this study, actuation capability of SMA wires was studied. The complex response of SMAs was investigated via a MATLAB implementation of the Brinson model and verified via experimental tests. The isothermal stress-strain curves of SMAs were simulated and defined as a material model in finite element analysis (FEA). The FEA was validated experimentally with developed prototypes. In the second part of this study, the active needle design was optimized using genetic algorithm aiming its maximum flexibility. Design parameters influencing the steerability include the needle's diameter, wire diameter, pre-strain and its offset from the needle. A simplified model was presented to decrease the computation time in iterative analyses. Integration of the SMA characteristics with the automated optimization schemes described in this study led to an improved design of the active needle. PMID:25782329

  1. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction.

    PubMed

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan; Vegge, Tejs

    2015-05-01

    Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys of Au with mixed Pt-Pd skins. The activity of the binary and ternary catalysts is explained through weakening of the OH binding energy caused by solute elements. However, given the low alloy formation energies it may be difficult to tune and retain the composition under operating conditions. This is particularly challenging for alloys containing Au due to a high propensity of Au to segregate to the surface. We also show that once Au is on the surface it will diffuse to defect sites, explaining why small amounts of Au retard dissolution of Pt nanoparticles. For the PtPd thin films there is no pronounced driving force for surface segregation, diffusion to defects or surface self-assembling. On the basis of stability and activity analysis we conclude that the near surface alloy of Pd in Pt and some PdAu binary and PtPdAu ternary thin films with a controlled amount of Au are the best catalysts for oxygen reduction. PMID:25865333

  2. Catalytic Activity of Platinum Monolayer on Iridium and Rhenium Alloy Nanoparticles for the Oxygen Reduction Reaction

    SciTech Connect

    Karan, Hiroko I.; Sasaki, Kotaro; Kuttiyiel, Kurian; Farberow, Carrie A.; Mavrikakis, Manos; Adzic, Radoslav R.

    2012-05-04

    A new type of electrocatalyst with a core–shell structure that consists of a platinum monolayer shell placed on an iridium–rhenium nanoparticle core or platinum and palladium bilayer shell deposited on that core has been prepared and tested for electrocatalytic activity for the oxygen reduction reaction. Carbon-supported iridium–rhenium alloy nanoparticles with several different molar ratios of Ir to Re were prepared by reducing metal chlorides dispersed on Vulcan carbon with hydrogen gas at 400 °C for 1 h. These catalysts showed specific electrocatalytic activity for oxygen reduction reaction comparable to that of platinum. The activities of PtML/PdML/Ir2Re1, PtML/Pd2layers/Ir2Re1, and PtML/Pd2layers/Ir7Re3 catalysts were, in fact, better than that of conventional platinum electrocatalysts, and their mass activities exceeded the 2015 DOE target. Our density functional theory calculations revealed that the molar ratio of Ir to Re affects the binding strength of adsorbed OH and, thereby, the O2 reduction activity of the catalysts. The maximum specific activity was found for an intermediate OH binding energy with the corresponding catalyst on the top of the volcano plot. The monolayer concept facilitates the use of much less platinum than in other approaches. Finally, the results with the PtML/PdML/Ir2Re electrocatalyst indicate that it is a promising alternative to conventional Pt electrocatalysts in low-temperature fuel cells.

  3. Nickel Alloy Primary Water Bulk Surface and SCC Corrosion Film Analytical Characterization and SCC Mechanistic Implications

    SciTech Connect

    Morton, D.; Lewis, N.; Hanson, M.; Rice, S.; Sanders, P.

    2007-04-18

    Alloy 600 corrosion coupon tests were performed: (1) to quantify the temperature dependency of general corrosion and (2) to characterize the composition and structure of bulk surface corrosion films for comparison with ongoing primary water SCC (PWSCC) crack tip corrosion film analyses. Results suggest that the thermal activation energy of Alloy 600 corrosion is consistent with the thermal activation energy of nickel alloy PWSCC. Analytical investigations of the structure and composition of Alloy 600 bulk surface corrosion oxides revealed a duplex (inner and outer) oxide layer structure. The outer layer is discontinuous and comprised of relatively large (1 to 3 {micro}m) nickel ferrite crystals and smaller ({approx}0.1 {micro}m) chromium containing nickel ferrite crystals. The inner layer consists of a relatively continuous chromite spinel (major phase) and chromia (Cr{sub 2}O{sub 3} minor phase) which formed through non-selective oxidation. Chromia and dealloyed Alloy 600 (highly Ni enriched metal) were only observed at 337 C (640 F) and only along the boundaries of deformation induced fine grains and subcells. Specimens having deformation free surfaces exhibited continuous uniform inner chromite spinel oxide layers. Specimens with machining induced surface deformation produced non-uniform inner layer oxides (chromite spinel, Cr{sub 2}O{sub 3} and unoxidized material). PWSCC crack tip oxides, in contrast, were fine grain (no duplex structure) and consisted of both chromium rich spinels and ''NiO'' structure oxides. Generally, nickel rich oxides were more abundant under more oxidized conditions (reduced coolant hydrogen) and spinel rich crack tip oxides were favored under more reducing conditions (increased coolant hydrogen). Bulk surface corrosion film thickness did not correlate with observed SCC growth rates. These results suggest that corrosion is not the rate controlling step of PWSCC but rather that PWSCC and corrosion have a common rate controlling sub

  4. Nanoporous PdZr surface alloy as highly active non-platinum electrocatalyst toward oxygen reduction reaction with unique structure stability and methanol-tolerance

    NASA Astrophysics Data System (ADS)

    Duan, Huimei; Xu, Caixia

    2016-06-01

    Nanoporous (NP) PdZr alloy with controllable bimetallic ratio is successfully fabricated by a simple dealloying method. By leaching out the more reactive Al from PdZrAl precursor alloy, NP-PdZr alloy with smaller ligament size was generated, characterized by the nanoscaled interconnected network skeleton and hollow channels extending in all three dimensions. Upon voltammetric scan in acid solution, the dissolution of surface Zr atoms generates the highly active Pd-Zr surface alloy with a nearly pure Pd surface and Pd-Zr alloy core. The NP-Pd80Zr20 surface alloy exhibits markedly enhanced specific and mass activities as well as higher catalytic stability toward oxygen reduction reaction (ORR) compared with NP-Pd and the state-of-the-art Pt/C catalysts. In addition, the NP-Pd80Zr20 surface alloy shows a better selectivity for ORR than methanol in the 0.1 M HClO4 and 0.1 M methanol mixed solution. X-ray photoelectron spectroscopy and density functional theory calculations both demonstrate that the weakened Pd-O bond and improved ORR performances in turn depend on the downshifted d-band center of Pd due to the alloying Pd with Zr (20 at.%). The as-made NP-PdZr alloy holds prospective applications as a cathode electrocatalyst in fuel-cell-related technologies with the advantages of superior overall ORR performances, unique structure stability, and easy preparation.

  5. Potentiodynamic study of Al-Mg alloy with superhydrophobic coating in photobiologically active/not active natural seawater.

    PubMed

    Benedetti, Alessandro; Cirisano, Francesca; Delucchi, Marina; Faimali, Marco; Ferrari, Michele

    2016-01-01

    Superhydrophobic coating technology is regarded as an attractive possibility for the protection of materials in a sea environment. DC techniques are a useful tool to characterize metals' behavior in seawater in the presence/absence of coatings and/or corrosion inhibitors. In this work, investigations concerning Al-5%Mg alloy with and without a sprayed superhydrophobic coating were carried out with potentiodynamic scans in photobiologically active and not active seawater (3 weeks of immersion). In not photobiologically active seawater, the presence of the superhydrophobic coating did not prevent pitting corrosion. With time, the coating underwent local exfoliations, but intact areas still preserved superhydrophobicity. In photobiologically active seawater, on samples without the superhydrophobic coating (controls) pitting was inhibited, probably due to the adsorption of organic compounds produced by the photobiological activity. After 3 weeks of immersion, the surface of the coating became hydrophilic due to diatom coverage. As suggested by intermediate observations, the surface below the diatom layer is suspected of having lost its superhydrophobicity due to early stages of biofouling processes (organic molecule adsorption and diatom attachment/gliding). Polarization curves also revealed that the metal below the coating underwent corrosion inhibiting phenomena as observed in controls, likely due to the permeation of organic molecules through the coating. Hence, the initial biofouling stages (days) occurring in photobiologically active seawater can both accelerate the loss of superhydrophobicity of coatings and promote corrosion inhibition on the underlying metal. Finally, time durability of superhydrophobic surfaces in real seawater still remains the main challenge for applications, where the early stages of immersion are demonstrated to be of crucial importance. PMID:26319307

  6. Development of a monolithic ferrite memory array

    NASA Technical Reports Server (NTRS)

    Heckler, C. H., Jr.; Bhiwandker, N. C.

    1972-01-01

    The results of the development and testing of ferrite monolithic memory arrays are presented. This development required the synthesis of ferrite materials having special magnetic and physical characteristics and the development of special processes; (1) for making flexible sheets (laminae) of the ferrite composition, (2) for embedding conductors in ferrite, and (3) bonding ferrite laminae together to form a monolithic structure. Major problems encountered in each of these areas and their solutions are discussed. Twenty-two full-size arrays were fabricated and fired during the development of these processes. The majority of these arrays were tested for their memory characteristics as well as for their physical characteristics and the results are presented. The arrays produced during this program meet the essential goals and demonstrate the feasibility of fabricating monolithic ferrite memory arrays by the processes developed.

  7. Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Hernández-Gómez, P.; Muñoz, J. M.; Valente, M. A.; Torres, C.; de Francisco, C.

    2013-01-01

    Nickel ferrite nanoparticles were prepared by a modified sol-gel technique employing coconut oil, and then annealed at different temperatures in 400-1200 °C range. This route of preparation has revealed to be one efficient and cheap technique to obtain high quality nickel ferrite nanosized powder. Sample particles sizes obtained with XRD data and Scherrer's formula lie in 13 nm to 138 nm, with increased size with annealing temperature. Hysteresis loops have been obtained at room temperature with an inductive method. Magnetic field induced microwave absorption in nanoscale ferrites is a recent an active area of research, in order to characterize and explore potential novel applications. In the present work microwave magnetoabsorption data of the annealed nickel ferrite nanoparticles are presented. These data have been obtained with a system based on a network analyzer that operates in the frequency range 0 - 8.5 GHz. At fields up to 400 mT we can observe a peak according to ferromagnetic resonance theory. Sample annealed at higher temperature exhibits different absorption, coercivity and saturation magnetization figures, revealing its multidomain character.

  8. High Temperature Irradiation Effects in Selected Generation IV Structural Alloys

    SciTech Connect

    Nanstad, Randy K; McClintock, David A; Hoelzer, David T; Tan, Lizhen; Allen, Todd R.

    2009-01-01

    In the Generation IV Materials Program cross-cutting task, irradiation and testing were carried out to address the issue of high temperature irradiation effects with selected current and potential candidate metallic alloys. The materials tested were (1) a high-nickel iron-base alloy (Alloy 800H); (2) a nickel-base alloy (Alloy 617); (3) two advanced nano-structured ferritic alloys (designated 14YWT and 14WT); and (4) a commercial ferritic-martensitic steel (annealed 9Cr-1MoV). Small tensile specimens were irradiated in rabbit capsules in the High-Flux Isotope Reactor at temperatures from about 550 to 700 C and to irradiation doses in the range 1.2 to 1.6 dpa. The Alloy 800H and Alloy 617 exhibited significant hardening after irradiation at 580 C; some hardening occurred at 660 C as well, but the 800H showed extremely low tensile elongations when tested at 700 C. Notably, the grain boundary engineered 800H exhibited even greater hardening at 580 C and retained a high amount of ductility. Irradiation effects on the two nano-structured ferritic alloys and the annealed 9Cr-1MoV were relatively slight at this low dose.

  9. Factors affecting chromium carbide precipitate dissolution during alloy oxidation

    SciTech Connect

    Durham, R.N.; Gleeson, B.; Young, D.J.

    1998-08-01

    Ferrous alloys containing significant volume fractions of chromium carbides were formulated so as to contain an overall chromium level of 15% (by weight) but a nominal metal matrix chromium concentration of only 11%. Their oxidation at 850 C in pure oxygen led to either protective Cr{sub 2}O{sub 3} scale formation accompanied by subsurface carbide dissolution or rapid growth of iron-rich oxide scales associated with rapid alloy surface recession, which engulfed the carbides before they could dissolve. Carbide size was important in austenitic alloys: an as-cast Fe-15Cr-0.5C alloy contained relatively coarse carbides and failed to form a Cr{sub 2}O{sub 3} scale, whereas the same alloy when hot-forged to produce very fine carbides oxidized protectively. In ferritic alloys, however, even coarse carbides dissolved sufficiently rapidly to provide the chromium flux necessary to form and maintain the growth of a Cr{sub 2}O{sub 3} scale, a result attributed to the high diffusivity of the ferrite phase. Small additions of silicon to the as-cast Fe-15Cr-0.5C alloy rendered it ferritic and led to protective cr{sub 2}O{sub 3} growth. However, when the silicon-containing alloy was made austenitic (by the addition of nickel), it still formed a protective Cr{sub 2}O{sub 3} scale, showing that the principal function of silicon was in modifying the scale-alloy interface.

  10. Facile synthesis of Rh-Pd alloy nanodendrites as highly active and durable electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Qi, Yue; Wu, Jianbo; Zhang, Hui; Jiang, Yingying; Jin, Chuanhong; Fu, Maoshen; Yang, Hong; Yang, Deren

    2014-05-01

    In addition to activity, durability of Pd-based catalysts in a highly corrosive medium has become one of the most important barriers to limit their industrial applications such as low-temperature fuel cell technologies. Here, Rh with a unique capability to resist against oxidation etching was incorporated into Pd-based catalysts to enhance both their activity and durability for oxygen reduction reaction (ORR). This idea was achieved through the synthesis of the Rh-Pd alloy nanodendrites by co-reducing Rh and Pd salt precursors in oleylamine (OAm) containing cetyltrimethylammonium bromide (CTAB). In this synthesis, Rh-Pd alloy nanostructures with Rh-Pd atomic ratios from 19 : 1 to 1 : 4 were generated by varying the molar ratios of Rh and Pd salt precursors. Interestingly, this variation of the molar ratios of the precursors from Rh rich to Pd rich would lead to the shape evolution of Rh-Pd alloy from dendritic nanostructures to spherical aggregations. We found that Br- ions derived from CTAB were also indispensible to the production of Rh-Pd alloy nanodendrites. Owing to the addition of highly stable Rh as well as the radical structure with a large number of low-coordinated sites on the arms, Rh-Pd alloy nanodendrites with a Rh-Pd atomic ratio of 4 : 1 (Rh80Pd20) exhibited a substantially enhanced electrocatalytic performance towards ORR with a 5% loss of mass activity during the accelerated stability test for 10 000 cycles compared to ~50% loss of the commercial Pt/C (E-TEK).In addition to activity, durability of Pd-based catalysts in a highly corrosive medium has become one of the most important barriers to limit their industrial applications such as low-temperature fuel cell technologies. Here, Rh with a unique capability to resist against oxidation etching was incorporated into Pd-based catalysts to enhance both their activity and durability for oxygen reduction reaction (ORR). This idea was achieved through the synthesis of the Rh-Pd alloy nanodendrites by co

  11. Structural disordering of de-alloyed Pt bimetallic nanocatalysts: the effect on oxygen reduction reaction activity and stability.

    PubMed

    Spanos, Ioannis; Dideriksen, Knud; Kirkensgaard, Jacob J K; Jelavic, Stanislav; Arenz, Matthias

    2015-11-14

    Platinum bimetallic alloys are well-known for their ability to catalyze the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Pt(x)Co(1-x) colloidal nanoparticles were synthesized with varying initial Pt : Co ratios, but constant size to investigate how the initial metal composition affects their electrocatalytic performance. The results show that upon contact with acid environment the Co leaches out of the particles leading to almost identical compositions, independent of the initial differences. Surprisingly the data show a clear trend in ORR activity, although the Pt(x)Co(1-x) nanoparticles almost completely de-alloy during acid leaching, i.e. under reaction conditions in a fuel cell. To scrutinize the resulting particle structure after de-alloying we used pair distribution function (PDF) analysis and X-ray diffraction (XRD) gaining insight into the structural disorder and its dependence on the initial metal composition. Our results suggest that not only the ORR activity, but also the corrosion resistance of the synthesized NPs, are dependent on the structural disorder resulting from the de-alloying process. PMID:25537262

  12. Magnetocaloric effect in ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Poddar, P.; Gass, J.; Rebar, D. J.; Srinath, S.; Srikanth, H.; Morrison, S. A.; Carpenter, E. E.

    2006-12-01

    A comparative study of the magnetocaloric effect (MCE) is reported in two different types of chemically synthesized magnetic nanoparticle systems—cobalt ferrite and manganese zinc ferrite with mean size around 5 and 15 nm, respectively. While CoFe 2O 4 nanoparticles were synthesized using co-precipitation, the Mn 0.68Zn 0.25Fe 2.07O 4 (MZFO) nanoparticles were prepared by reverse micelle technique using AOT as surfactant. Our results indicate that the change in entropy with the change in applied magnetic field (d S/d H) is reasonably large for this class of nanoparticles and has a wide distribution over a broad temperature range covering the region above and below the blocking temperature. The maximum entropy change is influenced by the particle size, overall distribution in anisotropy and magnetic moments.

  13. Friction and wear of single-crystal manganese-zinc ferrite

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1979-01-01

    Sliding friction experiments were conducted with single crystal manganese-zinc ferrite in contact with itself and with transition metals. Results indicate mating highest atomic density directions (110) on matched crystallographic planes exhibit the lowest coefficient of friction, indicating that direction is important in the friction behavior of ferrite. Matched parallel high atomic density planes and crystallographic directions at the interface exhibit low coefficients of friction. The coefficients of friction for ferrite in contact with various metals are related to the relative chemical activity of these metals. The more active the metal, the higher the coefficient of friction. Cracking and the formation of hexagon- and rectangular-shaped platelet wear debris due to cleavages of (110) planes are observed on the ferrite surfaces as a result of sliding.

  14. Two-magnon processes and ferrimagnetic linewidth calculation in manganese ferrite

    NASA Astrophysics Data System (ADS)

    Flores, A. G.; Raposo, V.; Torres, L.; Iñiguez, J.

    1999-04-01

    A procedure has been developed to obtain the two-magnon linewidth contributions in single and polycrystalline ferrites in which, working with ferrimagnetic resonance experiments, the applied field was only slightly larger than the value required to saturate the sample. This theory has been shown to work in manganese ferrites. Single-crystal MnFe2O4 has been prepared by the floating-zone technique and polycrystalline ferrite by the ceramic method. The spinel structure and composition have been confirmed by x-ray and inductively coupled plasma spectrometry, respectively. Fitting of the experimental ferrimagnetic resonance linewidth obtained by means of the Bloch-Bloembergern formalism show errors less than 4%. The fit gave the following parameters: averaged radius of the sample surface pits, porosity in polycrystalline sample, activation energy, and values of the conductivity. The values of the activation energy imply the existence of Fe2+ cations in the sample. Additional measurements on magnetization in manganese ferrites are presented.

  15. Friction and wear of single-crystal manganese-zinc ferrite

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1979-01-01

    Sliding friction experiments were conducted with single-crystal manganese-zinc ferrite in contact with itself and with transition metals. Results indicate mating highest atomic density directions (110 line type) on matched crystallographic planes exhibit the lowest coefficient of friction indicating that direction is important in the friction behavior of ferrite. Matched parallel high atomic density planes and crystallographic directions at the interface exhibit low coefficients of friction. The coefficients of friction for ferrite in contact with various metals are related to the relative chemical activity of these metals. The more active the metal, the higher the coefficient of friction. Cracking and the formation of hexagon- and rectangular-shaped platelet wear debris due to cleavages are observed on the ferrite surfaces as a result of sliding.

  16. Effect of oxide inclusions on the solid state transformation in low-alloy steel fusion welds

    SciTech Connect

    Babu, S.S.; David, S.A.; Vitek, J.M.

    1995-12-31

    Non-metallic inclusions are known to influence the properties of low alloy steel weld metal by altering the microstructure development. Isothermal transformation kinetics of austenite to acicular ferrite and allotriomorphic ferrite were measured in reheated low alloy steel weld deposits with similar weld compositions and austenite grain size but different inclusion characteristics. Accelerated kinetics of the transformation to acicular ferrite were observed in the weld metal containing coarser titanium-rich inclusions. The results are also discussed in relation to the predictions of inclusion model. The kinetics of the transformation to allotriomorphic ferrite were not influenced by a change in the inclusion characteristics, but, rather, by a change in austenite grain size. A theoretical analysis of austenite grain development during weld cooling is considered in this work. The austenite grain size was found to depend on the driving force for transformation from 6 ferrite to austenite ({Delta}G{sup {sigma}->{gamma}}) calculated from ThermoCalc{trademark} software.

  17. Vanadium-base alloys for fusion reactor applications

    SciTech Connect

    Smith, D.L.; Loomis, B.A.; Diercks, D.R.

    1984-10-01

    Vanadium-base alloys offer potentially significant advantages over other candidate alloys as a structural material for fusion reactor first wall/blanket applications. Although the data base is more limited than that for the other leading candidate structural materials, viz., austenitic and ferritic steels, vanadium-base alloys exhibit several properties that make them particularly attractive for the fusion reactor environment. This paper presents a review of the structural material requirements, a summary of the materials data base for selected vanadium-base alloys, and a comparison of projected performance characteristics compared to other candidate alloys. Also, critical research and development (R and D) needs are defined.

  18. Multifunctionality of nanocrystalline lanthanum ferrite

    NASA Astrophysics Data System (ADS)

    Rai, Atma; Thakur, Awalendra K.

    2016-05-01

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

  19. Progress on Shape Memory Alloy Actuator Development for Active Clearance Control

    NASA Technical Reports Server (NTRS)

    DeCastro, Jonathan; Melcher, Kevin; Noebe, Ronald

    2006-01-01

    Results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine has been conducted. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 in. Design results show that an actuator comprised of 10 wires 2 in. in length is adequate for control at critical engine operating points and still exhibit acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.

  20. In vivo degradation behavior and biological activity of some new Mg-Ca alloys with concentration's gradient of Si for bone grafts

    NASA Astrophysics Data System (ADS)

    Trincă, Lucia Carmen; Fântânariu, Mircea; Solcan, Carmen; Trofin, Alina Elena; Burtan, Liviu; Acatrinei, Dumitru Mihai; Stanciu, Sergiu; Istrate, Bogdan; Munteanu, Corneliu

    2015-10-01

    Magnesium based alloys, especially Mg-Ca alloys, are biocompatible substrates with mechanical properties similar to those of bones. The biodegradable alloys of Mg-Ca provide sufficient mechanical strength in load carrying applications as opposed to biopolymers and also they avoid stress shielding and secondary surgery inherent with permanent metallic implant materials. The main issue facing a biodegradable Mg-Ca alloy is the fast degradation in the aggressive physiological environment of the body. The alloy's corrosion is proportional with the dissolution of the Mg in the body: the reaction with the water generates magnesium hydroxide and hydrogen. The accelerated corrosion will lead to early loss of the alloy's mechanical integrity. The degradation rate of an alloy can be improved mainly through tailoring the composition and by carrying out surface treatments. This research focuses on the ability to adjust degradation rate of Mg-Ca alloys by an original method and studies the biological activity of the resulted specimens. A new Mg-Ca alloy, with a Si gradient concentration from the surface to the interior of the material, was obtained. The surface morphology was investigated using scanning electron microscopy (VegaTescan LMH II, SE detector, 30 kV), X-ray diffraction (X'Pert equipment) and energy dispersive X-ray (Bruker EDS equipment). In vivo degradation behavior, biological compatibility and activity of Mg-Ca alloys with/without Si gradient concentration were studied with an implant model (subcutaneous and bony) in rats. The organism response to implants was characterized by using radiological (plain X-rays and computed tomography), biochemical and histological methods of investigation. The results sustained that Si gradient concentration can be used to control the rate of degradation of the Mg-Ca alloys for enhancing their biologic activity in order to facilitate bone tissue repair.

  1. Surface modification to improve fireside corrosion resistance of Fe-Cr ferritic steels

    DOEpatents

    Park, Jong-Hee; Natesan, Krishnamurti; Rink, David L.

    2010-03-16

    An article of manufacture and a method for providing an Fe--Cr ferritic steel article of manufacture having a surface layer modification for corrosion resistance. Fe--Cr ferritic steels can be modified to enhance their corrosion resistance to liquid coal ash and other chemical environments, which have chlorides or sulfates containing active species. The steel is modified to form an aluminide/silicide passivating layer to reduce such corrosion.

  2. Chromium and copper substituted lanthanum nano-ferrites: Their synthesis, characterization and application studies

    NASA Astrophysics Data System (ADS)

    Jauhar, Sheenu; Singhal, Sonal

    2014-10-01

    Nano-crystalline lanthanum ferrites substituted by chromium and copper having formula LaMxFe1-xO3 (M = Cr, Cu; 0.0 ⩽ x ⩽ 0.5) were synthesized using sol-gel auto-combustion method. The formation of ferrite particles was confirmed using Fourier Transform Infra-Red (FT-IR) spectra and powder X-ray Diffraction (XRD) techniques. The entire ferrite compositions were found to be pure phased with same symmetry as LaFeO3. The average crystallite size was calculated to be ∼60 nm. The ferrite compositions were observed to behave as semi-conductors, as their resistivity decreased with increasing temperature. These ferrite compositions were employed as catalysts in the decomposition of hydrogen peroxide solution (0.17 M). Pure LaFeO3 was found to have a very low catalytic activity towards the decomposition of hydrogen peroxide solution, while presence of copper in the lanthanum ferrite lattice was found to significantly enhance its catalytic activity. The rate constant in case of reactions catalysed by LaCu0.5Fe0.5O3 was nearly 25 times larger than that obtained from reactions catalysed by pure LaFeO3. However, chromium substitution was not found to influence the catalytic activity of lanthanum ferrites as chromium substituted lanthanum ferrites exhibited very low catalytic activity. This was explained on the basis of relative stability of oxidation states of the substituent ions and the presence of defects in the crystal lattice.

  3. Swelling in several commercial alloys irradiated to very high neutron fluence

    SciTech Connect

    Gelles, D.S.; Pintler, J.S.

    1983-01-01

    Swelling values have been obtained from a set of commercial alloys irradiated in EBR-II to a peak fluence of 2.5 x 10/sup 23/ n/cm/sup 2/ (E > 0.1 MeV) or approx. 125 dpa covering the range 400 to 650/sup 0/C. The alloys can be ranked for swelling resistance from highest to lowest as follows: the martensitic and ferritic alloys, the niobium based alloys, the precipitation strengthened iron and nickel based alloys, the molybdenum alloys and the austenitic alloys.

  4. Bonding of Cf/SiC composite to Invar alloy using an active cement, Ag-Cu eutectic and Cu interlayer

    NASA Astrophysics Data System (ADS)

    Lei, Zhao; Xiaohong, Li; Jinbao, Hou; Qiang, Sun; Fuli, Zhang

    2012-10-01

    The interfacial microstructures and mechanical properties of the joints formed by active cement added brazing in vacuum of Cf/SiC composite to Invar alloy, using Ag-Cu eutectic alloy and pure copper foil as braze alloy and interlayer respectively, were investigated. CuTi, Cu4Ti3, Fe2Ti and the reaction layer of TiC and Si were the predominant components at the joint interface. The maximum shear strength of the joint was 77 MPa for brazing at 850 °C for 15 min. The results show that active cement added brazing in vacuum using Ag-Cu eutectic alloy and Cu interlayer can be used successfully for joining Cf/SiC composites to Invar alloy.

  5. Kinetically-controlled growth of cubic and octahedral Rh-Pd alloy oxygen reduction electrocatalysts with high activity and durability

    NASA Astrophysics Data System (ADS)

    Yan, Yucong; Zhan, Fangwei; Du, Jingshan; Jiang, Yingying; Jin, Chuanhong; Fu, Maoshen; Zhang, Hui; Yang, Deren

    2014-11-01

    Rh is a promising candidate as an indispensible component in bimetallic catalysts due to its unique capability to resist against the aggressive corrosion from the reaction medium. However, Rh has a very strong oxygen binding ability and is generally not suitable for the oxygen reduction reaction (ORR). Here, we have demonstrated shape-controlled synthesis of Rh-Pd alloy nanocrystals with high activity and durability for ORR by retarding the reaction kinetics at an ultra-slow injection rate of metal salts using a syringe pump. Under precise control of sluggish reaction kinetics, Pd followed a preferential overgrowth along the <100> direction, whereas the growth behavior of Rh was dominant along the <111> direction. These different kinetically-controlled growth behaviors associated with Rh and Pd were essential for achieving the shape transition between the cube and the octahedron of their alloys. The Rh8Pd92 alloy octahedra exhibited the highest mass activity with a value of 0.18 mA μg-1 in terms of the equivalent Pt cost, and were two-fold higher than that of commercial Pt/C. Significantly, all Rh-Pd alloy nanocrystals were highly stable with only less than 25% loss in mass activity after 30 000 CV cycles in O2 saturated acid solution compared to ~56% loss of the commercial Pt/C (E-TEK). Indeed, the mass activity of Rh8Pd92 was 3.3 times higher than that of commercial Pt/C after the accelerated stability test (ADT). This improvement in activity and durability may arise possibly from synergistic effects between the facet and the surface composition.Rh is a promising candidate as an indispensible component in bimetallic catalysts due to its unique capability to resist against the aggressive corrosion from the reaction medium. However, Rh has a very strong oxygen binding ability and is generally not suitable for the oxygen reduction reaction (ORR). Here, we have demonstrated shape-controlled synthesis of Rh-Pd alloy nanocrystals with high activity and durability for

  6. Microstructure and Kinetics of Nitride Precipitation in a Quaternary Iron-Based Model Fe-2.82 at. pct Cr-0.13 at. pct Mo-0.18 at. pct V Alloy

    NASA Astrophysics Data System (ADS)

    Kang, C. W.; Meka, Sai Ramudu; Schacherl, R. E.; Mittemeijer, E. J.

    2015-01-01

    Internal nitride development in iron-based quaternary Fe-Cr-Mo-V alloy, as a model alloy for 31CrMoV9 steel, was investigated by performing controlled gaseous nitriding experiments. The nitride-precipitation process starts with the development of nanosized platelets of, coherent, cubic NaCl-type nitride, along {100} lattice planes of the ferrite matrix, in association with matrix-lattice dilation. The development of nitride platelets having a NaCl-type crystal structure, satisfying the Baker-Nutting orientation relationship with the ferrite matrix, and the nitrogen content of the nitrided zone suggest the development of a quaternary "mixed" (Cr x ,V y , Mo1- x-y)N nitride, similar to the development of "mixed" ternary nitrides as reported for nitrided Fe-Cr-Al and Fe-Cr-Ti alloys. In a later stage, the nitride platelets undergo discontinuous coarsening resulting in the development of a lamellar microstructure consisting of nitride and ferrite lamellae. Kinetic analysis demonstrated that the thermally activated nature of growth of the diffusion zone is controlled with about equal weights, by the diffusion of nitrogen in the substrate matrix and the matrix lattice solubility of nitrogen.

  7. Dilution and Ferrite Number Prediction in Pulsed Current Cladding of Super-Duplex Stainless Steel Using RSM

    NASA Astrophysics Data System (ADS)

    Eghlimi, Abbas; Shamanian, Morteza; Raeissi, Keyvan

    2013-12-01

    Super-duplex stainless steels have an excellent combination of mechanical properties and corrosion resistance at relatively low temperatures and can be used as a coating to improve the corrosion and wear resistance of low carbon and low alloy steels. Such coatings can be produced using weld cladding. In this study, pulsed current gas tungsten arc cladding process was utilized to deposit super-duplex stainless steel on high strength low alloy steel substrates. In such claddings, it is essential to understand how the dilution affects the composition and ferrite number of super-duplex stainless steel layer in order to be able to estimate its corrosion resistance and mechanical properties. In the current study, the effect of pulsed current gas tungsten arc cladding process parameters on the dilution and ferrite number of super-duplex stainless steel clad layer was investigated by applying response surface methodology. The validity of the proposed models was investigated by using quadratic regression models and analysis of variance. The results showed an inverse relationship between dilution and ferrite number. They also showed that increasing the heat input decreases the ferrite number. The proposed mathematical models are useful for predicting and controlling the ferrite number within an acceptable range for super-duplex stainless steel cladding.

  8. Tensile properties and deformation mechanisms of a 14Cr ODS ferritic steel

    NASA Astrophysics Data System (ADS)

    Steckmeyer, A.; Praud, M.; Fournier, B.; Malaplate, J.; Garnier, J.; Béchade, J. L.; Tournié, I.; Tancray, A.; Bougault, A.; Bonnaillie, P.

    2010-10-01

    The search for a new cladding material is part of the research studies carried out at CEA to develop a sodium-cooled fast reactor meeting the expectations of the Generation IV International Forum. In this study, the tensile properties of a ferritic oxide dispersion strengthened steel produced by hot extrusion at CEA have been evaluated. They prove the studied alloy to be as resistant as and more ductile than the other nano-reinforced alloys of literature. The effects of the strain rate and temperature on the total plastic strain of the material remind of diffusion phenomena. Intergranular damage and intergranular decohesion are clearly highlighted.

  9. X-ray photoelectron spectroscopy and friction studies of nickel-zinc and manganese-zinc ferrites in contact with metals

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1983-01-01

    X-ray photoelectron spectroscopy analysis and sliding friction experiments were conducted with hot-pressed, polycrystalline Ni-Zn and Mn-Zn ferrites in sliding contact with various transition metals at room temperature in a vacuum of 30 nPa. The results indicate that the coefficients of friction for Ni-Zn and Mn-Zn ferrites in contact with metals are related to the relative chemical activity in these metals: the more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites correlate with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite surfaces increases the coefficients of friction for the Ni-Zn and Mn-Zn ferrite-metal interfaces.

  10. Titanium oxynitride interlayer to influence oxygen reduction reaction activity and corrosion stability of Pt and Pt-Ni alloy.

    PubMed

    Tan, XueHai; Wang, Liya; Zahiri, Beniamin; Kohandehghan, Alireza; Karpuzov, Dimitre; Lotfabad, Elmira Memarzadeh; Li, Zhi; Eikerling, Michael H; Mitlin, David

    2015-01-01

    A key advancement target for oxygen reduction reaction catalysts is to simultaneously improve both the electrochemical activity and durability. To this end, the efficacy of a new highly conductive support that comprises of a 0.5 nm titanium oxynitride film coated by atomic layer deposition onto an array of carbon nanotubes has been investigated. Support effects for pure platinum and for a platinum (50 at %)/nickel alloy have been considered. Oxynitride induces a downshift in the d-band center for pure platinum and fundamentally changes the platinum particle size and spatial distribution. This results in major enhancements in activity and corrosion stability relative to an identically synthesized catalyst without the interlayer. Conversely, oxynitride has a minimal effect on the electronic structure and microstructure, and therefore, on the catalytic performance of platinum-nickel. Calculations based on density functional theory add insight with regard to compositional segregation that occurs at the alloy catalyst-support interface. PMID:25470445

  11. Numerical simulation of the activation behavior of thermal shape memory alloys

    NASA Astrophysics Data System (ADS)

    Neugebauer, Reimund; Bucht, André; Pagel, Kenny; Jung, Jakob

    2010-04-01

    Problems in using shape memory alloys (SMA) in industrial applications are often caused by the fragmentary knowledge of the complex activation behavior. To solve this problem, Fraunhofer IWU developed a Matlab®-based simulation tool to emulate the properties of a SMA wire based on the energy balance. The contained terms result of the characteristic material behavior combined with thermal, electrical, and mechanical conditions. Model validation is performed by laboratory tests. It is shown that there is almost no difference between the measured and the simulated actuator movement. Due to the good quality of the model it is possible to use it in a control loop. Knowing current and voltage enables the computation of the electrical resistance of the actuator and can therefore be used for feedback control. Implementation of the results into industrial applications is exemplified by integration of an actuator in a flap as used in air condition systems of cars. Furthermore, the SMA-based drive will be compared to an electromechanical drive.

  12. Exchange coupled ferrite nanocomposites through chemical synthesis.

    PubMed

    Dai, Qilin; Patel, Ketan; Ren, Shenqiang

    2016-08-16

    Exchange coupling between magnetically hard and soft phases has the potential to yield a large gain in the energy product. In this work, we present a scalable chemical synthetic route to produce magnetic iron oxide based nanocomposites, consisting of cobalt ferrite (CoFe2O4) and strontium ferrite (SrFe12O19) components. PMID:27476744

  13. Abnormal ferrite in hyper-eutectoid steels

    SciTech Connect

    Chairuangsri, T.; Edmonds, D.V.

    2000-04-19

    The microstructural characteristics of ultra-high carbon hyper-eutectoid Fe-C and Fe-C-Cu experimental steels have been examined after isothermal transformation in a range just beneath the eutectoid temperature. Particular attention was paid to the formation of so-called abnormal ferrite, which refers to coarse ferrite grains which can form, in hyper-eutectoid compositions, on the pro-eutectoid cementite before the pearlite reaction occurs. Thus it is confirmed that the abnormal ferrite is not a result of pearlite coarsening, but of austenite decomposition before the conditions for coupled growth of pearlite are established. The abnormal ferrite formed on both allotriomorphic and Widmanstaetten forms of pro-eutectoid cementite, and significantly, it was observed that the pro-eutectoid cementite continued to grow, despite being enclosed by the abnormal ferrite. Under certain conditions this could lead to the eventual formation of substantially reduced amounts of pearlite. Thus, a model for carbon redistribution that allows the proeutectoid cementite to thicken concurrently with the abnormal ferrite is presented. The orientation relationships between the abnormal ferrite and pro-eutectoid cementite were also determined and found to be close to those which have been reported between pearlitic ferrite and pearlitic cementite.

  14. Flash fixation of heavy metals from two industrial wastes into ferrite by microwave hydrothermal co-treatment.

    PubMed

    Chen, Dan; Mei, Chun-Yan; Yao, Li-Hua; Jin, Hong-Ming; Qian, Guang-Ren; Xu, Zhi-Ping

    2011-09-15

    Flash fixation of heavy metals from electroplating wastewater (EPW) and pickling waste liquor (PWL) into ferrite lattice can be investigated by microwave hydrothermal process. The toxicity of wastewater may be reduced by the redox reaction between Cr(VI) in electroplating wastewater and Fe(II) in pickling waste liquor. Box-Behnken design (BBD) experiment gives optimal process condition of ferrite formation as follows: wastewater volume ratio (V(PWL):V(EPW) = 0.20), pH value 11 and retention time 15 min, on which formed ferrite has a soft magnetic property with high saturation magnetization (M(s)) 47.4 emu/g. The rapid ferrite process has lower activation energy 7.01 kJ/mol according to grain growth kinetics. Concerning the environmental and economy, we introduced a new and interesting method for water remediation simultaneously synthesizing ferrite by using microwave mediated hydrothermal processes. PMID:21840124

  15. Control of Particle Size and Morphology of Cobalt-Ferrite Nanoparticles by Salt-Matrix during Annealing

    NASA Astrophysics Data System (ADS)

    Azizi, A.; Sadrnezhaad, S. K.; Mostafavi, M.

    Salt-matrix annealing of mechanically alloyed Co-ferrite nanopowder was used to modify its particle size and morphology. Efficiency improvement due to suppression of sintering and growth resulted in reduction of average particle size from 100nm for salt-less to 40nm for salt-full annealing procedure. Nanosized single-phase cobalt-ferrite particles were observed after 2h annealing at 750°C in the samples milled for 20 hours both with and without NaCl. NaCl:CoFe2O4 ratio of 10:1 resulted in cabbage-like clusters containing particles smaller than 50 nm.

  16. Effect of initial microstructure on the activation energy of second stage during austempering of ductile iron

    SciTech Connect

    Campos-Cambranis, R.E.; Narvaez Hernandez, L.; Cisneros-Guerrero, M.M.; Perez-Lopez, M.J.

    1998-03-13

    The good balance among mechanical properties of austempered ductile irons (ADI) mainly depends on the matrix microstructure, which basically consists of acicular ferrite and carbon-enriched austenite. This structure is produced by isothermal transformation of the austenite over the temperature range of 523 to 673 K. It is well accepted that during the isothermal holding, the transformation takes place in two stages. In the first stage, the austenite decomposes into acicular ferrite and carbon-enriched austenite. When the austenite is transformed at temperatures higher than 623 K, the acicular ferrite is free of carbides; at temperatures below 623 K, besides the formation of the acicular ferrite and austenite, precipitation of carbides takes place over the plates of the acicular ferrite. The mixture of ferrite and austenite is known as ausferrite being the responsible for the good mechanical properties of ADI. In this work, the ausferrite obtained above and below 623 K will be termed high and low temperature ausferrite respectively. Although ausferrite does not transform at room temperature, it is not a thermodynamically stable structure. Consequently, if the isothermal holding is extended, or if ADI is heated at high temperatures (523 to 800 K), the second stage of the austempering reaction will occur. During this stage, the carbon rich austenite will decompose into ferrite and carbides. In order to establish the maximum working temperature of ADI, it is necessary to characterize the thermal stability of ausferrite microstructure, since once stage II takes place, the mechanical properties, in particular ductility and toughness, are adversely affected. In the present work the influence of previous ausferrite microstructure (that obtained during first stage) of an alloyed ductile iron (0.6%Ni, 0.15%Mo) on the empirical activation energy of stage II is studied.

  17. Phase transformations and microstructure development in low alloy steel welds

    SciTech Connect

    Babu, S.S.; David, S.A.; Vitek, J.M.

    1995-07-01

    Microstructure development in low alloy steel welds depends on various phase transformations that are a function of weld heating and cooling. The phase changes include non-metallic oxide inclusion formation in the liquid state, weld pool solidification, and solid state transformations. In this paper the mechanism of inclusion formation during low alloy steel welding is considered and the model predictions are compared with published results. The effect of inclusions on the austenite to ferrite transformation kinetics is measured and the mechanisms of transformation are discussed. The austenite gain development is related to the driving force for transformation of {delta} ferrite to austenite.

  18. Antimicrobial Activity of Copper Alloys Against Invasive Multidrug-Resistant Nosocomial Pathogens.

    PubMed

    Eser, Ozgen Koseoglu; Ergin, Alper; Hascelik, Gulsen

    2015-08-01

    The emergence and spread of antibiotic resistance demanded novel approaches for the prevention of nosocomial infections, and metallic copper surfaces have been suggested as an alternative for the control of multidrug-resistant (MDR) bacteria in surfaces in the hospital environment. This study aimed to evaluate the antimicrobial activity of copper material for invasive MDR nosocomial pathogens isolated over time, in comparison to stainless steel. Clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) (n:4), OXA-23 and OXA-58 positive, MDR Acinetobacter baumannii (n:6) and Pseudomonas aeruginosa (n:4) were evaluated. The antimicrobial activity of coupons containing 99 % copper and a brass alloy containing 63 % copper was assessed against stainless steel. All the materials demonstrated statistically significant differences within each other for the logarithmic reduction of microorganisms. Among the three materials, the highest reduction of microorganisms was seen in 99 % copper and the least in stainless steel. The result was statistically significant especially for 0, 2, and 4 h (P = 0.05). 99 % copper showed a bactericidal effect at less than 1 h for MRSA and at 2 h for P. aeruginosa. 63 % copper showed a bactericidal effect at 24 h for P. aeruginosa strains only. Stainless steel surfaces exhibited a bacteriostatic effect after 6 h for P. aeruginosa strains only. 99 % copper reduced the number of bacteria used significantly, produced a bactericidal effect and was more effective than 63 % copper. The use of metallic copper material could aid in reducing the concentration of bacteria, especially for invasive nosocomial pathogens on hard surfaces in the hospital environment. PMID:26044991

  19. Three-dimensional hierarchical porous platinum-copper alloy networks with enhanced catalytic activity towards methanol and ethanol electro-oxidation

    NASA Astrophysics Data System (ADS)

    Fan, Yang; Liu, Pei-Fang; Zhang, Zong-Wen; Cui, Ying; Zhang, Yan

    2015-11-01

    Porous Pt-Cu alloy networks are synthesized through a one-pot hydrothermal process, with ethylene glycol as the reducing agent and the block copolymer Pluronic F127 as structure-directing agent. The structure, porosity and surface chemical state of as-prepared Pt-Cu alloy with different composition are characterized. The formation mechanism of the porous structure is investigated by time sequential experiments. The obtained Pt53Cu47 alloy possesses a unique 3D hierarchical porous network structure assembled by interconnected nanodendrites as building blocks. Because of the high surface area, concave surface topology and open porous structure, the Pt53Cu47 alloy catalyst exhibits enhanced catalytic activity towards methanol and ethanol electro-oxidation in comparison with commercial Pt black and the Pt73Cu27 alloy synthesized following the same process as Pt53Cu47.

  20. Development of ferritic steels for fusion reactor applications

    SciTech Connect

    Klueh, R.L.; Maziasz, P.J.; Corwin, W.R.

    1988-08-01

    Chromium-molybdenum ferritic (martensitic) steels are leading candidates for the structural components for future fusion reactors. However, irradiation of such steels in a fusion environment will produce long-lived radioactive isotopes that will lead to difficult waste-disposal problems. Such problems could be reduced by replacing the elements in the steels (i.e., Mo, Nb, Ni, N, and Cu) that lead to long-lived radioactive isotopes. We have proposed the development of ferritic steels analogous to conventional Cr-Mo steels, which contain molybdenum and niobium. It is proposed that molybdenum be replaced by tungsten and niobium be replaced by tantalum. Eight experimental steels were produced. Chromium concentrations of 2.25, 5, 9, and 12% were used (all concentrations are in wt %). Steels with these chromium compositions, each containing 2% W and 0.25% V, were produced. To determine the effect of tungsten and vanadium, 2.25 Cr steels were produced with 2% W and no vanadium and with 0.25% V and O and 1% W. A 9Cr steel containing 2% W, 0.25 V, and 0.07% Ta was also studied. For all alloys, carbon was maintained at 0.1%. Tempering studies on the normalized steels indicated that the tempering behavior of the new Cr-W steels was similar to that of the analogous Cr-Mo steels. Microscopy studies indicated that 2% tungsten was required in the 2.25 Cr steels to produce 100% bainite in 15.9-mm-thick plate during normalization. The 5Cr and 9Cr steels were 100% martensite, but the 12 Cr steel contained about 75% martensite with the balance delta-ferrite. 33 refs., 35 figs., 5 tabs.

  1. Hot-Pressed Ferrite-Lead Zirconate Titanate Magnetoelectric Composites

    NASA Astrophysics Data System (ADS)

    Devreugd, C. P.; Srinivasan, G.; Micheli, A. L.; Mantese, J. V.

    2004-03-01

    The electromagnetic coupling in magnetostrictive/piezoelectric is mediated by mechanical stress: magnetostriction induced mechanical deformation and piezoelectric effect induced electric fields. Composites studied so far include ferrite-lead zirconate titanate (PZT) and manganite-PZT [1-3]. Bulk or layered composites are usually synthesized by conventional sintering of mixture of powders or laminated thick films. This study is concerned with the fabrication of novel ferromagnetic-ferroelectric bulk and thin film layered composites by hot pressing together with studies on the nature of magnetoelectric interactions. The objective is to obtain defect free samples with good interface coupling. Systems studied includes Ni-Zn, Co-Zn and Co-Ni ferrites that are predicted to show high piezomagnetic and magnetomechanical couplings and PZT. Samples were prepared using aluminum oxide or high temperature alloy dies. Sintering was done at 1300 K at a pressure of 5000-7000 psi. Measurements of transverse and longitudinal ME coefficients are performed at low frequencies (10 Hz-1kHz), and at electromechanical resonance (100-300 kHz). Important results of our studies are follows. (1) Hot-pressed samples show an order of magnitude improvement in ME voltage coefficient compared to samples processed by conventional sintering. The enhancement is attributed to an increase in density, sample resistivity, and interface coupling. (2) The longitudinal coupling is stronger than the transverse effect. (3) There is a significant increase in ME interactions at electromechanical resonance. (4) Samples with Ni-Zn ferrites show the highest ME coefficients. The results are analysed using our model for a bulk composite. - supported by a grant from the National Science Foundation (DMR-0322254) 1. G. Srinivasan, E. T. Rasmussen, J. Gallegos, Yu. I. Bokhan, and V. M. Laletin, Phys. Rev. B, 64, 214408 (2001). 2. G. Srinivasan, E. T. Rasmussen, B. J. Levin, and R. Hayes, Phys. Rev. B 65, 134402 (2002). 3

  2. Effect of thermo-mechanical treatments on the microstructure and mechanical properties of an ODS ferritic steel

    NASA Astrophysics Data System (ADS)

    Oksiuta, Z.; Mueller, P.; Spätig, P.; Baluc, N.

    2011-05-01

    The Fe-14Cr-2W-0.3Ti-0.3Y 2O 3 oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steel was fabricated by mechanical alloying of a pre-alloyed, gas atomised powder with yttria nano-particles, followed by hot isostatic pressing and thermo-mechanical treatments (TMTs). Two kinds of TMT were applied: (i) hot pressing, or (ii) hot rolling, both followed by annealing in vacuum at 850 °C. The use of a thermo-mechanical treatment was found to yield strong improvement in the microstructure and mechanical properties of the ODS RAF steel. In particular, hot pressing leads to microstructure refinement, equiaxed grains without texture, and an improvement in Charpy impact properties, especially in terms of the upper shelf energy (about 4.5 J). Hot rolling leads to elongated grains in the rolling direction, with a grain size ratio of 6:1, higher tensile strength and reasonable ductility up to 750 °C, and better Charpy impact properties, especially in terms of the ductile-to-brittle transition temperature (about 55 °C).

  3. Investigation of iron-chromium-niobium-titanium ferritic stainless steel for solid oxide fuel cell interconnect applications

    NASA Astrophysics Data System (ADS)

    Yang, Zhenguo; Xia, Guan-Guang; Wang, Chong-Min; Nie, Zimin; Templeton, Joshua; Stevenson, Jeffry W.; Singh, Prabhakar

    As part of an effort to develop cost-effective ferritic stainless steel-based interconnects for solid oxide fuel cell (SOFC) stacks, both bare AISI441 and AISI441 coated with (Mn,Co) 3O 4 protection layers were studied in terms of its metallurgical characteristics, oxidation behavior, and electrical performance. The addition of minor alloying elements, in particular Nb, led to formation of Laves phases both inside grains and along grain boundaries. In particular, the Laves phase which precipitated out along grain boundaries during exposure at intermediate SOFC operating temperatures was found to be rich in both Nb and Si. The capture of Si in the Laves phase minimized the Si activity in the alloy matrix and prevented formation of an insulating silica layer at the scale/metal interface, resulting in a reduction in area-specific electrical resistance (ASR). However, the relatively high oxidation rate of the steel, which leads to increasing ASR over time, and the need to prevent volatilization of chromium from the steel necessitates the application of a conductive protection layer on the steel. In particular, the application of a Mn 1.5Co 1.5O 4 spinel protection layer substantially improved the electrical performance of the 441 by reducing the oxidation rate.

  4. Thermal activation mechanisms and Labusch-type strengthening analysis for a family of high-entropy and equiatomic solid-solution alloys

    DOE PAGESBeta

    Wu, Zhenggang; Gao, Yanfei; Bei, Hongbin

    2016-11-01

    To understand the underlying strengthening mechanisms, thermal activation processes are investigated from stress-strain measurements with varying temperatures and strain rates for a family of equiatomic quinary, quaternary, ternary, and binary, face-center-cubic-structured, single phase solid-solution alloys, which are all subsystems of the FeNiCoCrMn high-entropy alloy. Our analysis suggests that the Labusch-type solution strengthening mechanism, rather than the lattice friction (or lattice resistance), governs the deformation behavior in equiatomic alloys. First, upon excluding the Hall-Petch effects, the activation volumes for these alloys are found to range from 10 to 1000 times the cubic power of Burgers vector, which are much larger thanmore » that required for kink pairs (i.e., the thermal activation process for the lattice resistance mechanism in body-center-cubic-structured metals). Second, the Labusch-type analysis for an N-element alloy is conducted by treating M-elements (M < N) as an effective medium and summing the strengthening contributions from the rest of N-M elements as individual solute species. For all equiatomic alloys investigated, a qualitative agreement exists between the measured strengthening effect and the Labusch strengthening factor from arbitrary M to N elements based on the lattice and modulus mismatches. Furthermore, the Labusch strengthening factor provides a practical critique to understand and design such compositionally complex but structurally simple alloys.« less

  5. Long-term high temperature oxidation behavior of ODS ferritics

    NASA Astrophysics Data System (ADS)

    Pint, B. A.; Wright, I. G.

    2002-12-01

    Four oxide dispersion strengthened Fe-(13-14 at.%) Cr ferritic compositions were exposed in air and air with 10 vol.% water vapor for up to 10 000 h at 700-1100 °C. At 700-800 °C in air, the reaction rates were very low for all of the alloys compared to stainless steels. At 900 °C, a dispersion of Y 2O 3, compared to Al 2O 3, showed a distinct benefit in improving the oxidation resistance, due to a reactive element effect. However, failure occurred after 7000 h at 900 °C when only 13% Cr was present. The absence of Ti and W in one alloy appeared to result in a thinner reaction product after oxidation at 800 °C. One composition was exposed in 10 vol.% water vapor at 800 and 900 °C and in air at 1000 and 1100 °C. Under both of these conditions, there was a significant increase in the rates of oxidation. With the relatively low Cr contents in these alloys, their corrosion-limited operating temperature in air is near 900 °C.

  6. Mechanical and Electrochemical Behavior of a High Strength Low Alloy Steel of Different Grain Sizes

    NASA Astrophysics Data System (ADS)

    Ghosh, K. S.; Mondal, D. K.

    2013-08-01

    Various heat treatments applied to a fine-grained high strength low alloy (HSLA) steel resulted in producing different grain sizes. Optical and scanning electron microstructures of the different alloy states exhibited varying ferrite grains which have increased with the increase of annealing time and decrease of cooling rates. TEM structures of the as-received HSLA steel displayed characteristics microstructural features, distribution, and morphology of microalloy precipitates. Hardness and tensile strength values have decreased with the increase of grain sizes. Potentiodynamic electrochemical polarization of the different alloy states in 3.5 wt pct NaCl solution showed typical active metal/alloy behavior. Tensile specimens of the as-received and heat-treated alloy cathodically charged with hydrogen, followed by tensile testing, did not indicate any noticeable loss of ductility. FESEM fractographs of hydrogen-charged samples showed a few chain of voids in the presence of cup and cone ductile fracture features in tensile-tested samples without hydrogen charging as well.

  7. Ferrite-Martensite Band Formation During the Intercritical Annealing

    NASA Astrophysics Data System (ADS)

    Etesami, S. A.; Enayati, M. H.

    2016-02-01

    Microstructural evolution during the intercritical annealing at 740 and 770 °C for 120-900 s in a low-carbon low-alloy steel from the initial martensitic matrix was studied by electron microscopy equipped with energy dispersive x-ray spectroscopy and x-ray diffraction. It was seen that during the intercritical annealing, the martensitic structure changes to the tempered martensite with carbides. The results depicted that the temperature and time of intercritical annealing influence significantly the distribution and amount of the formed carbides. Two types of austenite morphology were identified to grow simultaneously, i.e., globular and acicular. A longer annealing time led to the coarse globular and thick acicular austenite morphology. The austenite with globular morphology nucleated preferably at prior austenite grain boundary triple and quadruple junctions. The austenite with globular and acicular morphology was developed in Mn-rich and -poor regions, respectively. The globular austenite morphology intensified the banded microstructure of ferrite-martensite dual-phase steel, whereas the acicular austenite morphology led to a more isotropic microstructure. The experimental results illustrated that the intercritical temperature is a significant factor which can contribute to intensify the banded ferrite-martensite microstructure. The volume fractions of austenite with globular and acicular morphology were quantitatively measured. The volume fraction of globular to acicular morphology of austenite was high and low at 770 and 740 °C, respectively.

  8. Decomposition Kinetics of Ferrite in Isothermally Aged SAF 2507-Type Duplex Stainless Steel

    NASA Astrophysics Data System (ADS)

    Berecz, Tibor; Fazakas, Éva; Mészáros, István; Sajó, István

    2015-12-01

    Decomposition of the ferritic phase is studied in isothermally aged SAF 2507 superduplex stainless steel (SDSS) by means of different examination methods. The ferritic phase ( δ) undergoes an eutectoid transformation into secondary austenite ( γ 2) and σ-phase between 650 and 1000 °C. Samples were treated at 900 °C because the incubation time of this transformation is the shortest at this temperature. In order to follow the microstructural changes, x-ray diffraction analysis (XRD), automated electron backscatter diffraction (EBSD), applied magnetic investigation [vibrating sample magnetometer (VSM)], micro-hardness tests, and differential thermal analysis (DTA) were used. The results of XRD and EBSD methods for phase quantification showed nearly the same amounts for all three phases. The results of applied magnetic investigation for the fraction of ferritic phase were also in good agreement with the corresponding results of XRD and EBSD methods. Decomposition of ferrite is similarly well-traceable on EBSD phase maps where the coherent ferritic areas gradually broke into pieces with increasing time of heat treatment. According to the EBSD measurements the σ-phase grains appeared and started to grow after 2 min aging time in the ferritic-austenitic matrix, usually on the boundaries of ferritic and austenitic grains. After 15 min treating time, the microstructure consisted of mainly σ- and austenitic (primary and secondary) phases with negligible amount of ferrite. Chemical composition of the σ-phase was measured by energy-dispersive x-ray spectroscopy (EDS) at different aging times. Activation energies of σ-phase precipitation and α'-phase formation were determined by the Kissinger plot, through DTA measurements; they are 243 and 261 kJ/mol, respectively. Using the results of phase quantifications, the Johnson-Mehl-Avrami equation was fitted.

  9. Effect of tetra ionic substitution on the dielectric properties of Cu-ferrite

    NASA Astrophysics Data System (ADS)

    Mazen, S. A.; Zaki, H. M.

    2003-09-01

    X-ray diffraction (XRD), of the two systems of mixed ferrites Cu1+xTixFe2-2xO4 (where x = 0.0, 0.1, 0.2, 0.3, and 0.4); indicates that the samples of x = 0 (CuFe2O4) and x = 0.1 of the Cu-Ti system were formed in tetragonal structure and all other samples of the two system were formed in the cubic system.The ac conductivity , dielectric constant , dielectric loss and the loss tangent tan δ were determined against frequency at room temperature for Cu-Ge and Cu-Ti ferrites. The measurements of and tan δ were performed over a wide range of frequency and temperature.The Maxwell-Wagner model was applied to analyze the dielectric properties of the investigated systems, according to which the dielectric parameters such as the relaxation time . A value of 1 = 5 × 10-7 s was found for Cu-Ge ferrite and 2 = 1.85 × 10-6 s for Cu-Ti ferrites. The hopping rate (g) was found to be 2 × 106 s-1 and 5.4 × 105 s-1 for the two systems Cu-Ge and Cu-Ti ferrites, respectively.The conduction of the two-ferrite systems was discussed on the basis of the hopping mechanism. The activation energy for conduction was calculated and found in the range of 0.27-0.39 eV for Cu-Ge ferrite and 0.21-0.30 eV for Cu-Ti ferrite. (

  10. Microstructural stability of a self-ion irradiated lanthana-bearing nanostructured ferritic steel

    SciTech Connect

    Pasebani, Somayeh; Charit, Indrajit; Burns, Jatuporn; Alsagabi, Sultan; Butt, Darryl P.; Cole, James I.; Price, Lloyd M.; Shao, Lin

    2015-07-01

    Thermally stable nanofeatures with high number density are expected to impart excellent high temperature strength and irradiation stability in nanostructured ferritic steels (NFSs) which have potential applications in advanced nuclear reactors. A lanthana-bearing NFS (14LMT) developed via mechanical alloying and spark plasma sintering was used in this study. The sintered samples were irradiated by Fe2+ ions to 10, 50 and 100 dpa at 30 °C and 500 °C. Microstructural and mechanical characteristics of the irradiated samples were studied using different microscopy techniques and nanoindentation, respectively. Overall morphology and number density of the nanofeatures remained unchanged after irradiation. Average radius of nanofeatures in the irradiated sample (100 dpa at 500 °C) was slightly reduced. A notable level of irradiation hardening and enhanced dislocation activity occurred after ion irradiation except at 30 °C and ≥50 dpa. Other microstructural features like grain boundaries and high density of dislocations also provided defect sinks to assist in defect removal.

  11. Current status and recent research achievements in ferritic/martensitic steels

    NASA Astrophysics Data System (ADS)

    Tavassoli, A.-A. F.; Diegele, E.; Lindau, R.; Luzginova, N.; Tanigawa, H.

    2014-12-01

    When the austenitic stainless steel 316L(N) was selected for ITER, it was well known that it would not be suitable for DEMO and fusion reactors due to its irradiation swelling at high doses. A parallel programme to ITER collaboration already had been put in place, under an IEA fusion materials implementing agreement for the development of a low activation ferritic/martensitic steel, known for their excellent high dose irradiation swelling resistance. After extensive screening tests on different compositions of Fe-Cr alloys, the chromium range was narrowed to 7-9% and the first RAFM was industrially produced in Japan (F82H: Fe-8%Cr-2%W-TaV). All IEA partners tested this steel and contributed to its maturity. In parallel several other RAFM steels were produced in other countries. From those experiences and also for improving neutron efficiency and corrosion resistance, European Union opted for a higher chromium lower tungsten grade, Fe-9%Cr-1%W-TaV steel (Eurofer), and in 1997 ordered the first industrial heats. Other industrial heats have been produced since and characterised in different states, including irradiated up to 80 dpa. China, India, Russia, Korea and US have also produced their grades of RAFM steels, contributing to overall maturity of these steels. This paper reviews the work done on RAFM steels by the fusion materials community over the past 30 years, in particular on the Eurofer steel and its design code qualification for RCC-MRx.

  12. Formation and Oxidation Performance of Low-Temperature Pack Aluminide Coatings on Ferritic-Martensitic Steels

    SciTech Connect

    Bates, Brian; Wang, Y. Q.; Zhang, Ying; Pint, Bruce A

    2009-01-01

    A pack cementation process was developed to coat commercial 9% Cr ferritic-martensitic steel T91 at temperatures below its normal tempering temperature to avoid any potential detrimental effect on the mechanical properties of the coated alloy. In order to prevent the formation of Fe{sub 2}Al{sub 5} coatings, the Al activity in the pack cementation process was reduced by substituting the pure Al masteralloy with binary Cr-Al masteralloys containing either 15 or 25 wt.% Al. When the Cr-25Al masteralloy was used, a duplex coating was formed at 700 C, consisting of a thin Fe{sub 2}Al{sub 5} outer layer and an inner layer of FeAl. With the Cr-15Al masteralloy, an FeAl coating of {approx} 12 {micro}m thick was achieved at 700 C. The pack aluminide coatings fabricated at 700 C are being evaluated in air + 10 vol.% H{sub 2}O at 650 C and 700 C to determine their long-term oxidation performance.

  13. Constitutive modeling of the mechanical behavior of high strength ferritic steels for static and dynamic applications

    NASA Astrophysics Data System (ADS)

    Abed, Farid H.

    2010-11-01

    A constitutive relation is presented in this paper to describe the plastic behavior of ferritic steel over a broad range of temperatures and strain rates. The thermo-mechanical behavior of high strength low alloy (HSLA-65) and DH-63 naval structural steels is considered in this study at strains over 40%. The temperatures and strain rates are considered in the range where dynamic strain aging is not effective. The concept of thermal activation analysis as well as the dislocation interaction mechanism is used in developing the flow model for both the isothermal and adiabatic viscoplastic deformation. The flow stresses of the two steels are very sensitive to temperature and strain rate, the yield stresses increase with decreasing temperatures and increasing strain rates. That is, the thermal flow stress is mainly captured by the yield stresses while the hardening stresses are totally pertained to the athermal component of the flow stress. The proposed constitutive model predicts results that compare very well with the measured ones at initial temperature range of 77 K to 1000 K and strain rates between 0.001 s-1 and 8500 s-1 for both steels.

  14. Microstructural stability of a self-ion irradiated lanthana-bearing nanostructured ferritic steel

    NASA Astrophysics Data System (ADS)

    Pasebani, Somayeh; Charit, Indrajit; Burns, Jatuporn; Alsagabi, Sultan; Butt, Darryl P.; Cole, James I.; Price, Lloyd M.; Shao, Lin

    2015-07-01

    Thermally stable nanofeatures with high number density are expected to impart excellent high temperature strength and irradiation stability in nanostructured ferritic steels (NFSs) which have potential applications in advanced nuclear reactors. A lanthana-bearing NFS (14LMT) developed via mechanical alloying and spark plasma sintering was used in this study. The sintered samples were irradiated by Fe2+ ions to 10, 50 and 100 dpa at 30 °C and 500 °C. Microstructural and mechanical characteristics of the irradiated samples were studied using different microscopy techniques and nanoindentation, respectively. Overall morphology and number density of the nanofeatures remained unchanged after irradiation. Average radius of nanofeatures in the irradiated sample (100 dpa at 500 °C) was slightly reduced. A notable level of irradiation hardening and enhanced dislocation activity occurred after ion irradiation except at 30 °C and ⩾50 dpa. Other microstructural features like grain boundaries and high density of dislocations also provided defect sinks to assist in defect removal.

  15. Surface oxide net charge of a titanium alloy: modulation of fibronectin-activated attachment and spreading of osteogenic cells.

    PubMed

    Rapuano, Bruce E; MacDonald, Daniel E

    2011-01-01

    In the current study, we have altered the surface oxide properties of a Ti6Al4V alloy using heat treatment or radiofrequency glow discharge (RFGD) in order to evaluate the relationship between the physico-chemical and biological properties of the alloy's surface oxide. The effects of surface pretreatments on the attachment of cells from two osteogenic cell lines (MG63 and MC3T3) and a mesenchymal stem cell line (C3H10T1/2) to fibronectin adsorbed to the alloy were measured. Both heat and RFGD pretreatments produced a several-fold increase in the number of cells that attached to fibronectin adsorbed to the alloy at a range of coating concentrations (0.001-10nM FN) for each cell line tested. An antibody (HFN7.1) directed against the central integrin binding domain of fibronectin produced a 65-70% inhibition of cell attachment to fibronectin-coated disks, indicating that cell attachment to the metal discs was dependent on fibronectin binding to cell integrin receptors. Both treatments also accelerated the cell spreading response manifested by extensive flattening and an increase in mean cellular area. The treatment-induced increases in the cell attachment activity of adsorbed fibronectin were correlated with previously demonstrated increases in Ti6Al4V oxide negative net surface charge at physiological pH produced by both heat and RFGD pretreatments. Since neither treatment increased the adsorption mass of fibronectin, these findings suggest that negatively charged surface oxide functional groups in Ti6Al4V can modulate fibronectin's integrin receptor activity by altering the adsorbed protein's conformation. Our results further suggest that negatively charged functional groups in the surface oxide can play a prominent role in the osseointegration of metallic implant materials. PMID:20884181

  16. Bactericidal activity of copper and niobium-alloyed austenitic stainless steel.

    PubMed

    Baena, M I; Márquez, M C; Matres, V; Botella, J; Ventosa, A

    2006-12-01

    Biofouling and microbiologically influenced corrosion are processes of material deterioration that originate from the attachment of microorganisms as quickly as the material is immersed in a nonsterile environment. Stainless steels, despite their wide use in different industries and as appliances and implant materials, do not possess inherent antimicrobial properties. Changes in hygiene legislation and increased public awareness of product quality makes it necessary to devise control methods that inhibit biofilm formation or to act at an early stage of the biofouling process and provide the release of antimicrobial compounds on a sustainable basis and at effective level. These antibacterial stainless steels may find a wide range of applications in fields, such as kitchen appliances, medical equipment, home electronics, and tools and hardware. The purpose of this study was to obtain antibacterial stainless steel and thus mitigate the microbial colonization and bacterial infection. Copper is known as an antibacterial agent; in contrast, niobium has been demonstrated to improve the antimicrobial effect of copper by stimulating the formation of precipitated copper particles and its distribution in the matrix of the stainless steel. Thus, we obtained slides of 3.8% copper and 0.1% niobium alloyed stainless steel; subjected them to three different heat treatment protocols (550 degrees C, 700 degrees C, and 800 degrees C for 100, 200, 300, and 400 hours); and determined their antimicrobial activities by using different initial bacterial cell densities and suspending solutions to apply the bacteria to the stainless steels. The bacterial strain used in these experiments was Escherichia coli CCM 4517. The best antimicrobial effects were observed in the slides of stainless steel treated at 700 degrees C and 800 degrees C using an initial cell density of approximately 10(5) cells ml(-1) and phosphate-buffered saline as the solution in which the bacteria came into contact with

  17. Ferritic/martensitic steels - overview of recent results

    NASA Astrophysics Data System (ADS)

    Klueh, R. L.; Gelles, D. S.; Jitsukawa, S.; Kimura, A.; Odette, G. R.; van der Schaaf, B.; Victoria, M.

    2002-12-01

    Considerable research work has been conducted on the ferritic/martensitic steels since the last International Conference on Fusion Reactor Materials in 1999. Since only a limited amount of that work can be reviewed in this paper, four areas will be emphasized: (1) the international collaboration under the auspices of the International Energy Agency (IEA) to address potential problems with ferritic/martensitic steels and to prove their feasibility for fusion, (2) the major uncertainty that remains concerning the effect of transmutation helium on mechanical properties of the steels when irradiated in a fusion neutron environment, (3) development of new reduced-activation steels beyond the F82H and JLF-1 steels studied in the IEA collaboration, and (4) work directed at developing oxide dispersion-strengthened steels for operation above 650 °C.

  18. Alloy development for irradiation performance. Quarterly progress report for period ending December 31, 1979

    SciTech Connect

    Ashdown, B.G.

    1980-04-01

    Progress is reported concerning preparation of a materials handbook for fusion, creep-fatigue of first-wall structural materials, test results on miniature compact tension fracture toughness specimens, austenitic stainless steels, Fe-Ni-Cr alloys, iron-base alloys with long-range crystal structure, ferritic steels, irradiation experiments, corrosion testing, and hydrogen permeation studies. (FS)

  19. High-temperature thermodynamic activities of zirconium in platinum alloys determined by nitrogen-nitride equilibria

    SciTech Connect

    Goodman, D.A.

    1980-05-01

    A high-temperature nitrogen-nitride equilibrium apparatus is constructed for the study of alloy thermodynamics to 2300/sup 0/C. Zirconium-platinum alloys are studied by means of the reaction 9ZrN + 11Pt ..-->.. Zr/sub 9/Pt/sub 11/ + 9/2 N/sub 2/. Carful attention is paid to the problems of diffusion-limited reaction and ternary phase formation. The results of this study are and a/sub Zr//sup 1985/sup 0/C/ = 2.4 x 10/sup -4/ in Zr/sub 9/Pt/sub 11/ ..delta..G/sub f 1985/sup 0/C//sup 0/ Zr/sub 9/Pt/sub 11/ less than or equal to -16.6 kcal/g atom. These results are in full accord with the valence bond theory developed by Engel and Brewer; this confirms their prediction of an unusual interaction of these alloys.

  20. Effect of milling atmosphere on structural and magnetic properties of Ni-Zn ferrite nanocrystalline

    NASA Astrophysics Data System (ADS)

    Hajalilou, Abdollah; Hashim, Mansor; Ebrahimi-Kahrizsangi, Reza; Masoudi Mohamad, Taghi

    2015-04-01

    Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres (argon, air, and oxygen), milling time (from 0 to 30 h) and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni-Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600 °C for 2 h leads to the formation of a single phase of Ni-Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated. Project supported by the University Putra Malaysia Graduate Research Fellowship Section.

  1. Design of Radiation-Tolerant Structural Alloys for Generation IV Nuclear Energy Systems

    SciTech Connect

    Allen, T.R.; Was, G.S.; Bruemmer, S.M.; Gan, J.; Ukai, S.

    2005-12-28

    The objective of this program is to improve the radiation tolerance of both austenitic and ferritic-martensitic (F-M) alloys projected for use in Generation IV systems. The expected materials limitations of Generation IV components include: creep strength, dimensional stability, and corrosion/stress corrosion compatibility. The material design strategies to be tested fall into three main categories: (1) engineering grain boundaries; (2) alloying, by adding oversized elements to the matrix; and (3) microstructural/nanostructural design, such as adding matrix precipitates. These three design strategies were tested across both austenitic and ferritic-martensitic alloy classes

  2. TEM microscopical examination of the magnetic domain boundaries in a super duplex austenitic-ferritic stainless steel

    SciTech Connect

    Fourlaris, G.; Gladman, T.; Maylin, M.

    1996-12-31

    It has been demonstrated in an earlier publication that significant improvements in the coercivity, maximum induction and remanence values can be achieved, by using a 2205 type Duplex austenitic-ferritic stainless steel (DSS) instead of the low alloy medium carbon steels currently being used. These improvements are achieved in the as received 2205 material, and after small amounts of cold rolling have been applied, to increase the strength. In addition, the modification of the duplex austenitic-ferritic microstructure, via a heat treatment route, results in a finer austenite `island` dispersion in a ferritic matrix and provides an attractive option for further modification of the magnetic characteristics of the material. However, the 2205 type DSS exhibits {open_quotes}marginal{close_quotes} corrosion protection in a marine environment, so that a study has been undertaken to examine whether the beneficial effects exhibited by the 2205 DSS, are also present in a 2507 type super-DSS.

  3. Structural analysis of emerging ferrite: Doped nickel zinc ferrite

    SciTech Connect

    Kumar, Rajinder; Kumar, Hitanshu; Singh, Ragini Raj; Barman, P. B.

    2015-08-28

    Ni{sub 0.6-x}Zn{sub 0.4}Co{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.033, 0.264) nanoparticles were synthesized by sol-gel method and annealed at 900°C. Structural properties of all prepared samples were examined with X-ray diffraction (XRD). The partial formation of hematite (α-Fe{sub 2}O{sub 3}) secondary phase with spinel phase cubic structure of undoped and cobalt doped nickel zinc ferrite was found by XRD peaks. The variation in crystallite size and other structural parameters with cobalt doping has been calculated for most prominent peak (113) of XRD and has been explained on the basis of cations ionic radii difference.

  4. Modeling the austenite decomposition into ferrite and bainite

    NASA Astrophysics Data System (ADS)

    Fazeli, Fateh

    2005-12-01

    during the industrial treatments. The thermodynamic boundary conditions for the kinetic model were assessed with respect to paraequilibrium. The potential interaction between the alloying atoms and the moving ferrite-austenite interface, referred to as solute drag effect, was accounted for rigorously in the model. To quantify the solute drag pressure the Purdy-Brechet approach was modified prior to its implementation into the model. (Abstract shortened by UMI.)

  5. Report on thermal aging effects on tensile properties of ferritic-martensitic steels.

    SciTech Connect

    Li, M.; Soppet, W.K.; Rink, D.L.; Listwan, J.T.; Natesan, K.

    2012-05-10

    This report provides an update on the evaluation of thermal-aging induced degradation of tensile properties of advanced ferritic-martensitic steels. The report is the first deliverable (level 3) in FY11 (M3A11AN04030103), under the Work Package A-11AN040301, 'Advanced Alloy Testing' performed by Argonne National Laboratory, as part of Advanced Structural Materials Program for the Advanced Reactor Concepts. This work package supports the advanced structural materials development by providing tensile data on aged alloys and a mechanistic model, validated by experiments, with a predictive capability on long-term performance. The scope of work is to evaluate the effect of thermal aging on the tensile properties of advanced alloys such as ferritic-martensitic steels, mod.9Cr-1Mo, NF616, and advanced austenitic stainless steel, HT-UPS. The aging experiments have been conducted over a temperature of 550-750 C for various time periods to simulate the microstructural changes in the alloys as a function of time at temperature. In addition, a mechanistic model based on thermodynamics and kinetics has been used to address the changes in microstructure of the alloys as a function of time and temperature, which is developed in the companion work package at ANL. The focus of this project is advanced alloy testing and understanding the effects of long-term thermal aging on the tensile properties. Advanced materials examined in this project include ferritic-martensitic steels mod.9Cr-1Mo and NF616, and austenitic steel, HT-UPS. The report summarizes the tensile testing results of thermally-aged mod.9Cr-1Mo, NF616 H1 and NF616 H2 ferritic-martensitic steels. NF616 H1 and NF616 H2 experienced different thermal-mechanical treatments before thermal aging experiments. NF616 H1 was normalized and tempered, and NF616 H2 was normalized and tempered and cold-rolled. By examining these two heats, we evaluated the effects of thermal-mechanical treatments on material microstructures and

  6. New findings on the atomistic mechanisms active during mechanical milling of a Fe-Y2O3 model alloy

    NASA Astrophysics Data System (ADS)

    Ressel, G.; Parz, P.; Primig, S.; Leitner, H.; Clemens, H.; Puff, W.

    2014-03-01

    In order to improve the mechanical properties at elevated temperatures, several types of steels are mechanically alloyed with yttria. The processes that are active during milling differ dependent on the individual powder constituents. Nevertheless, some theories exist which try to describe the mechanism of producing a metastable phase during milling. However, even in the system iron-yttria, the mechanisms taking place during milling are still not well understood. By using the example of a simple iron-yttria model alloy, this paper attempts to elucidate the structure of mechanically milled powder particles and, consequently, to clarify the functionality of mechanical alloying in the last stage of milling. Positron annihilation experiments on milled materials revealed "open" volumes which are enriched in yttria. Electron backscatter diffraction and atom probe tomography as complimentary techniques allowed an identification of these "open" volumes as mainly vacancies, where enrichments of Y and O occur. From these results, it can be concluded that especially vacancies are responsible for producing a metastable phase, whereby yttria is dissolved in pure iron.

  7. Hybrid LCA of a design for disassembly technology: active disassembling fasteners of hydrogen storage alloys for home appliances.

    PubMed

    Nakamura, Shinichiro; Yamasue, Eiji

    2010-06-15

    In the current recycling system of end-of-life (EoL) appliances, which is based on shredding, alloying elements tend to end up in the scrap of base metals. The uncontrolled mixing of alloying elements contaminates secondary metals and calls for dilution with primary metals. Active disassembling fastener (ADF) is a design for disassembly (DfD) technology that is expected to solve this problem by significantly reducing the extent of mixing. This paper deals with a life cycle assessment (LCA) based on the waste input-output (WIO) model of an ADF developed using hydrogen storage alloys. Special attention is paid to the issue of dilution of mixed iron scrap using pig iron in an electric arc furnace (EAF). The results for Japanese electrical and electronic appliances indicate superiority of the recycling system based on the ADF over the current system in terms of reduced emissions of CO(2). The superiority of ADF was found to increase with an increase in the requirement for dilution of scrap. PMID:20476783

  8. Nanoporous PdZr surface alloy as highly active non-platinum electrocatalyst toward oxygen reduction reaction with unique structure stability and methanol-tolerance

    NASA Astrophysics Data System (ADS)

    Duan, Huimei; Xu, Caixia

    2016-06-01

    Nanoporous (NP) PdZr alloy with controllable bimetallic ratio is successfully fabricated by a simple dealloying method. By leaching out the more reactive Al from PdZrAl precursor alloy, NP-PdZr alloy with smaller ligament size was generated, characterized by the nanoscaled interconnected network skeleton and hollow channels extending in all three dimensions. Upon voltammetric scan in acid solution, the dissolution of surface Zr atoms generates the highly active Pd-Zr surface alloy with a nearly pure Pd surface and Pd-Zr alloy core. The NP-Pd80Zr20 surface alloy exhibits markedly enhanced specific and mass activities as well as higher catalytic stability toward oxygen reduction reaction (ORR) compared with NP-Pd and the state-of-the-art Pt/C catalysts. In addition, the NP-Pd80Zr20 surface alloy shows a better selectivity for ORR than methanol in the 0.1 M HClO4 and 0.1 M methanol mixed solution. X-ray photoelectron spectroscopy and density functional theory calculations both demonstrate that the weakened Pd-O bond and improved ORR performances in turn depend on the downshifted d-band center of Pd due to the alloying Pd with Zr (20 at.%). The as-made NP-PdZr alloy holds prospective applications as a cathode electrocatalyst in fuel-cell-related technologies with the advantages of superior overall ORR performances, unique structure stability, and easy preparation.

  9. Irradiation performance of 9--12 Cr ferritic/martensitic stainless steels and their potential for in-core application in LWRs

    SciTech Connect

    Jones, R.H.; Gelles, D.S.

    1993-08-01

    Ferritic-martensitic stainless steels exhibit radiation stability and stress corrosion resistance that make them attractive replacement materials for austenitic stainless steels for in-core applications. Recent radiation studies have demonstrated that 9% Cr ferritic/martensitic stainless steel had less than a 30C shift in ductile-to-brittle transition temperature (DBTT) following irradiation at 365C to a dose of 14 dpa. These steels also exhibit very low swelling rates, a result of the microstructural stability of these alloys during radiation. The 9 to 12% Cr alloys to also exhibit excellent corrosion and stress corrosion resistance in out-of-core applications. Demonstration of the applicability of ferritic/martensitic stainless steels for in-core LWR application will require verification of the irradiation assisted stress corrosion cracking behavior, measurement of DBTT following irradiation at 288C, and corrosion rates measurements for in-core water chemistry.

  10. Development of nano-structured duplex and ferritic stainless steels by pulverisette planetary milling followed by pressureless sintering

    SciTech Connect

    R, Shashanka Chaira, D.

    2015-01-15

    Nano-structured duplex and ferritic stainless steel powders are prepared by planetary milling of elemental Fe, Cr and Ni powder for 40 h and then consolidated by conventional pressureless sintering. The progress of milling and the continuous refinement of stainless steel powders have been confirmed by means of X-ray diffraction and scanning electron microscopy. Activation energy for the formation of duplex and ferritic stainless steels is calculated by Kissinger method using differential scanning calorimetry and is found to be 159.24 and 90.17 KJ/mol respectively. Both duplex and ferritic stainless steel powders are consolidated at 1000, 1200 and 1400 °C in argon atmosphere to study microstructure, density and hardness. Maximum sintered density of 90% and Vickers microhardness of 550 HV are achieved for duplex stainless steel sintered at 1400 °C for 1 h. Similarly, 92% sintered density and 263 HV microhardness are achieved for ferritic stainless steel sintered at 1400 °C. - Highlights: • Synthesized duplex and ferritic stainless steels by pulverisette planetary milling • Calculated activation energy for the formation of duplex and ferritic stainless steels • Studied the effect of sintering temperature on density, hardness and microstructure • Duplex stainless steel exhibits 90% sintered density and microhardness of 550 HV. • Ferritic stainless steel shows 92% sintered density and 263 HV microhardness.

  11. Technical Letter Report on the Cracking of Irradiated Cast Stainless Steels with Low Ferrite Content

    SciTech Connect

    Chen, Y.; Alexandreanu, B.; Natesan, K.

    2014-11-01

    Crack growth rate and fracture toughness J-R curve tests were performed on CF-3 and CF-8 cast austenite stainless steels (CASS) with 13-14% of ferrite. The tests were conducted at ~320°C in either high-purity water with low dissolved oxygen or in simulated PWR water. The cyclic crack growth rates of CF-8 were higher than that of CF-3, and the differences between the aged and unaged specimens were small. No elevated SCC susceptibility was observed among these samples, and the SCC CGRs of these materials were comparable to those of CASS alloys with >23% ferrite. The fracture toughness values of unirradiated CF-3 were similar between unaged and aged specimens, and neutron irradiation decreased the fracture toughness significantly. The fracture toughness of CF-8 was reduced after thermal aging, and declined further after irradiation. It appears that while lowering ferrite content may help reduce the tendency of thermal aging embrittlement, it is not very effective to mitigate irradiation-induced embrittlement. Under a combined condition of thermal aging and irradiation, neutron irradiation plays a dominant role in causing embrittlement in CASS alloys.

  12. EBSD analysis of (10–12) twinning activity in Mg–3Al–1Zn alloy during compression

    SciTech Connect

    Wang, Bingshu; Deng, Liping; Guo, Ning; Xu, Zeren; Li, Qiang

    2014-12-15

    The (10–12) twinning activity of Mg–3Al–1Zn magnesium alloy during uniaxial compression at room temperature has been investigated by electron backscatter diffraction. The results indicated that the twinning activity was closely related with two angles: one was the angle between the c-axis and the compression direction and the other was the angle between the a-axis and the titling direction in the basal plane for a given relation between the c-axis and the compression direction. These two parameters can be used to explain which twinning variant will operate under the given strain path. For the grains containing a single (10–12) twinning variant, the (10–12) twinning variant occurred in a wide range of Schmid factor values (0 < Schmid factor < 0.5) and the Schmid factor rank of 1 or 2 was the most commonly observed. By contrast, for the grains containing two (10–12) twinning variants, the (10–12) twinning activity exhibited a stronger orientation dependence and the combinations of Schmid factor ranks 1–3 and 1–2 were the most commonly observed. - Highlights: • Twinning activity of AZ31 magnesium alloy was investigated by EBSD. • (10–12) twinning shows a strong orientation dependence. • Two angles can be used to explain which twin variant will operate.

  13. ENVIRONMENTALLY COMPLIANT CORROSION-ACTIVATED INHIBITOR SYSTEM FOR ALUMINUM ALLOYS - PHASE I

    EPA Science Inventory

    The federal government is estimated to spend $1 billion on painting/repainting aircraft annually. Aircraft have surfaces composed of aluminum alloys that are highly susceptible to corrosion and must be protected with corrosion-preventative treatments that typically conta...

  14. Multiply twinned AgNi alloy nanoparticles as highly active catalyst for multiple reduction and degradation reactions.

    PubMed

    Kumar, Mukesh; Deka, Sasanka

    2014-09-24

    Size dependent surface characteristics of nanoparticles lead to use of these nanomaterials in many technologically important fields, including the field of catalysis. Here Ag(1-x)Ni(x) bimetallic alloy nanoparticles have been developed having a 5-fold twinned morphology, which could be considered as an important alloy because of their excellent and unique catalytic and magnetic properties. Alloying between Ag and Ni atoms on a nanoscale has been confirmed with detailed X-ray diffraction, high resolution transmission electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and magnetization measurements. Although introduced for the first time as a catalyst due to having high active surface sites, the as-synthesized nanoparticles showed one of the best multiple catalytic activity in the industrially important (electro)-catalytic reduction of 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA) to corresponding amines with noticeable reduced reaction time and increased rate constant without the use of any large area support. Additionally the same catalyst showed enhanced catalytic activity in degradation of environment polluting dye molecules. The highest ever activity parameter we report here for Ag0.6Ni0.4 composition is 156 s(-1)g(-1) with an apparent rate constant of 31.1 × 10(-3) s(-1) in a 4-NP reduction reaction where the amount of catalyst used was 0.2 mg and the time taken for complete conversion of 4-NP to 4-aminophenol was 60 s. Similarly, an incredible reaction rate constant (115 s(-1)) and activity parameter (576.6 s(-1)g(-1)) were observed for the catalytic degradation of methyl orange dye where 15 s is the maximum time for complete degradation of the dye molecules. The high catalytic performance of present AgNi alloy NPs over the other catalysts has been attributed to size, structural (twinned defect) and electronic effects. This study may lead to use of these bimetallic nanostructures with excellent recyclable catalytic

  15. Antimicrobial Lemongrass Essential Oil-Copper Ferrite Cellulose Acetate Nanocapsules.

    PubMed

    Liakos, Ioannis L; Abdellatif, Mohamed H; Innocenti, Claudia; Scarpellini, Alice; Carzino, Riccardo; Brunetti, Virgilio; Marras, Sergio; Brescia, Rosaria; Drago, Filippo; Pompa, Pier Paolo

    2016-01-01

    Cellulose acetate (CA) nanoparticles were combined with two antimicrobial agents, namely lemongrass (LG) essential oil and Cu-ferrite nanoparticles. The preparation method of CA nanocapsules (NCs), with the two antimicrobial agents, was based on the nanoprecipitation method using the solvent/anti-solvent technique. Several physical and chemical analyses were performed to characterize the resulting NCs and to study their formation mechanism. The size of the combined antimicrobial NCs was found to be ca. 220 nm. The presence of Cu-ferrites enhanced the attachment of LG essential oil into the CA matrix. The magnetic properties of the combined construct were weak, due to the shielding of Cu-ferrites from the polymeric matrix, making them available for drug delivery applications where spontaneous magnetization effects should be avoided. The antimicrobial properties of the NCs were significantly enhanced with respect to CA/LG only. This work opens novel routes for the development of organic/inorganic nanoparticles with exceptional antimicrobial activities. PMID:27104514

  16. Effects of TiB2 particles and Ag on the activation energy of Ω phase in Al alloys

    NASA Astrophysics Data System (ADS)

    Melotti, F.; Hirst, T.; Dustan, A.; Griffiths, W. D.

    2016-03-01

    This work analyses the effects of TiB2 reinforcement particles and silver additions on the activation energy of the GP zones and the Ω phase in an aluminium matrix composite (AMC). Several additions of TiB2 and Ag were made to a 2xxx series alloy. Differential scanning calorimetry (DSC) was used to identify the temperature peaks and the Kissinger approach used to calculate activation energies. Results showed that the activation energy for the Ω phase was greatly reduced by the addition of both elements; however, the TiB2 particles were more effective. In addition, experimental results show that the lowest value of the activation energy, 68 kJmol-1, was not affected by the silver content. This value is lower than any value found in literature and suggests that the formation of the Ω phase is related to the pipe diffusion of Cu in Al.

  17. ALL-FERRITE RHIC INJECTION KICKER

    SciTech Connect

    HAHN,H.; FISCHER,W.; PTITSYN,V.I.; TUOZZOLO,J.E.

    2001-06-18

    Ion beams are transferred from the AGS into RHIC in boxcar fashion as single bunches. The nominal design assumes 60 bunches per ring but increasing the number of bunches to gain luminosity is possible, thereby requiring injection kickers with a shorter rise time. The original injection system consists of traveling-wave dielectric loaded kicker magnets and a Blumlein pulser with a rise time adequate for the present operation. Voltage breakdown in the dielectric kickers suggested the use of all-ferrite magnets. In order to minimize the conversion cost, the design of the all-ferrite kicker uses the same components as the dielectric loaded units. The all-ferrite kickers showed in bench measured good breakdown properties and a current rise time of < 50 ns. A prototype kicker has been installed in the blue ring and was tested with beam. Beam measurements indicate suitability of all-ferrite kicker magnets for upgraded operation.

  18. Ferrite HOM Absorber for the RHIC ERL

    SciTech Connect

    Hahn,H.; Choi, E.M.; Hammons, L.

    2008-10-01

    A superconducting Energy Recovery Linac is under construction at Brookhaven National Laboratory to serve as test bed for RHIC upgrades. The damping of higher-order modes in the superconducting five-cell cavity for the Energy-Recovery linac at RHIC is performed exclusively by two ferrite absorbers. The ferrite properties have been measured in ferrite-loaded pill box cavities resulting in the permeability values given by a first-order Debye model for the tiled absorber structure and an equivalent permeability value for computer simulations with solid ring dampers. Measured and simulated results for the higher-order modes in the prototype copper cavity are discussed. First room-temperature measurements of the finished niobium cavity are presented which confirm the effective damping of higher-order modes in the ERL. by the ferrite absorbers.

  19. Improved ferrite number prediction in stainless steel arc welds using artificial neural networks -- Part 2: Neural network results

    SciTech Connect

    Vitek, J.M.; Iskander, Y.S.; Oblow, E.M.

    2000-02-01

    The development of a neural network model, named FNN-1999, for predicting Ferrite Number in arc welds as a function of alloy composition is described in Part 1. In this paper, the results of the model are compared to other means of predicting Ferrite Number in stainless steel welds. It was found the accuracy of the FNN-1999 model in predicting Ferrite Number is superior to that of the WRC-1992 diagram, the Function Fit model and a preliminary neural network model developed earlier. The error in fitting the current model to the training set was 40% less than that for the WRC-1992 diagram. In addition, the FNN-1999 model removes the restriction found in WRC-1992 and many other constitution diagrams that each element's contribution to the Ferrite Number is constant, regardless of the overall composition. Examples are given that show that with this added flexibility of the FNN-1999 model, the impact of alloying additions varies as a function of concentration, and in some cases the variation can be quite significant.

  20. Ferrite insertion at Recycler Flying Wire System

    SciTech Connect

    K.Y. Ng

    2004-02-27

    Ferrite rods are installed inside the flying-wire cavity of the Recycler Ring and at entrance and exit beam pipes in order to absorb high-frequency electromagnetic waves excited by the beam. However, these rods may also deteriorate the vacuum pressure of the ring. An investigation is made to analyze the necessity of the ferrite rods at the entrance and exit beam pipes.