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Sample records for damaged bcc alloys

  1. Atomic displacements in bcc dilute alloys

    Indian Academy of Sciences (India)

    We present here a systematic investigation of the atomic displacements in bcc transition metal (TM) dilute alloys. We have calculated the atomic displacements in bcc (V, Cr, Fe, Nb, Mo, Ta and W) transition metals (TMs) due to 3d, 4d and 5d TMs at the substitutional site using the Kanzaki lattice static method. Wills and ...

  2. Metastable bcc Fe-Mn alloys produced by rf sputtering

    International Nuclear Information System (INIS)

    Sumiyama, Kenji; Kadono, Masaru; Nakamura, Yoji

    1981-01-01

    Fe sub(1-x)Mn sub(x) alloy films obtained by rf sputtering technique have been investigated by X-ray diffraction, magnetization and Moessbauer effect measurements. The single bcc phase extends up to about x = 0.2, while a bcc-fcc mixed phase appears for x = 0.2 - 0.26. The lattice constants of the bcc phase are about 0.5% larger than those of the bulk specimens. The magnetization decreases monotonically with increasing x in the bcc phase, while it decreases sharply in the bcc-fcc mixed phase. These results are consistent with the Moessbauer spectra of these alloy films. The volume fraction of bcc and fcc phases has been estimated from Moessbauer analyses as well as magnetization measurements. (author)

  3. Investigation of irradiation strengthening of bcc metals and their alloys. Progress report, January 1977--October 1977

    International Nuclear Information System (INIS)

    1977-01-01

    Progress is reported in the areas of (a) the effect of neutron damage on the dislocation kinetics in bcc metals and their alloys, and (b) the effect of 3 He on the deformation characteristics of body centered cubic metals and their alloys. Results obtained from these projects are discussed

  4. Hydrogen storage in Ti-Mn-(FeV) BCC alloys

    International Nuclear Information System (INIS)

    Santos, S.F.; Huot, J.

    2009-01-01

    Recently, the replacement of vanadium by the less expensive (FeV) commercial alloy has been investigated in Ti-Cr-V BCC solid solutions and promising results were reported. In the present work, this approach of using (FeV) alloys is adopted to synthesize alloys of the Ti-Mn-V system. Compared to the V-containing alloys, the alloys containing (FeV) have a smaller hydrogen storage capacity but a larger reversible hydrogen storage capacity, which is caused by the increase of the plateau pressure of desorption. Correlations between the structure and the hydrogen storage properties of the alloys are also discussed.

  5. Atomic displacements in bcc dilute alloys

    Indian Academy of Sciences (India)

    be attributed to the reliability of the measured distances which fall off quickly with each shell. Therefore, in ... field and electrical field gradients due to impurities in vanadium [13]. The effective .... Expanding ∆φ(| Rn' |) in power series of u(R0 n), one gets ... The results of each dilute alloy system are presented separately and ...

  6. The study on binary Mg-Co hydrogen storage alloys with BCC phase

    International Nuclear Information System (INIS)

    Zhang Yao; Tsushio, Yoshinori; Enoki, Hirotoshi; Akiba, Etsuo

    2005-01-01

    Novel Mg-Co binary alloys were successfully synthesized by mechanical alloying. These alloys were studied by X-ray diffraction (XRD), transmission electron micrograph (TEM), pressure-composition-isotherms measurements (P-C-T) and differential scanning calorimetry (DSC). Both XRD Rietveld analysis and TEM observation confirmed that these binary alloys contain BCC phase and that the BCC phase existed in the range from 37 to 80 at.% Co. The lattice parameter of the BCC phase increased with the increase of the Co content from 37 to 50 at.%. When the Co content reached 50 at.%, the lattice parameter reached a maximum value, and then turned to decrease gradually with further increase of the Co content. Most of Mg-Co BCC alloys absorbed hydrogen at 373 K under 6 MPa of hydrogen pressure. The Mg 60 Co 40 alloy showed the highest hydrogen absorption capacity, about 2.7 mass% hydrogen. However, all the Mg-Co alloys studied did not desorb hydrogen at 373 K. By means of DSC measurements and in situ XRD analysis, it was found that under 4 MPa hydrogen atmosphere, Mg 50 Co 50 alloy transformed from BCC solid solution to Mg 2 CoH 5 tetragonal hydride at 413 K

  7. Magnetic properties of metastable bcc and fcc Fe-Cu alloys produced by vapor quenching

    International Nuclear Information System (INIS)

    Sumiyama, Kenji; Yoshitake, Tsutomu; Nakamura, Yoji

    1984-01-01

    High concentration Fesub(1-x)Cusub(x) alloys have been obtained by rf sputtering technique and investigated by X-ray diffraction and magnetization measurements. The bcc phase is extended over the region with x=0-0.4, while the fcc phase with x=0.6-1.0. For x=0.4-0.6, we have the mixed phase of bcc and fcc. The lattice constant of bcc phase increases slightly and that of fcc phase decreases with increasing x. In the bcc alloys, the average magnetic moment decreases with increasing x and deviates upwards from the simple dilution law. In the fcc alloys, the magnetic moment also decreases with increasing x but it deviates downwards from the simple dilution law. The Curie temperature, Tsub(c), of the Fesub(1-x)Cusub(x) alloys decreases abruptly with increasing x: Tsub(c) is higher than 750 K for the bcc alloys, while it is lower than 320 K for the fcc alloys and become 0 K at about x=0.92. (author)

  8. Solubility of hydrogen and deuterium in bcc-uranium-titanium alloys

    International Nuclear Information System (INIS)

    Powell, G.L.; Kirkpatrick, J.R.

    1996-01-01

    For the bcc-U-Ti alloy system, H and D solubility measurements have been made on 12 alloy specimens ranging in composition from pure U to pure Ti and temperature range bounded by 900 K to 1,500 K. The results are described by a model within a standard error of 3%

  9. Hydrogen storage performance of Ti-V-based BCC phase alloys with various Fe content

    International Nuclear Information System (INIS)

    Yu, X.B.; Feng, S.L.; Wu, Z.; Xia, B.J.; Xu, N.X.

    2005-01-01

    The effect of Fe content on hydrogen storage characteristics of Ti-10Cr-18Mn-(32-x)V-xFe (x = 0, 2, 3, 4, 5) alloys has been investigated at 353 K. The X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images of the alloys present BCC and C14 two-phase structures for all of the Fe-containing alloys. With the increasing Fe content, the lattice parameters of the BCC phase decrease, which results in an increase of the hydrogen desorption plateau pressure of the alloys. Among the studied alloys, Ti-10Cr-18Mn-27V-5Fe alloy exhibits the smallest PCT plateau slope and a more suitable plateau pressure (0.1 MPa equ <1 MPa). The maximum and effective capacities of the alloy are 3.32 wt.% and 2.26 wt.%, respectively, which are higher than other reported Fe-containing BCC phase alloys. In addition, the V/Fe ratio in this alloy is close to that of (VFe) alloy, whose cost is much lower than that of pure V

  10. Ion irradiation effects on high purity bcc Fe and model FeCr alloys

    International Nuclear Information System (INIS)

    Bhattacharya, Arunodaya

    2014-01-01

    FeCr binary alloys are a simple representative of the reduced activation ferritic/martensitic (F-M) steels, which are currently the most promising candidates as structural materials for the sodium cooled fast reactors (SFR) and future fusion systems. However, the impact of Cr on the evolution of the irradiated microstructure in these materials is not well understood in these materials. Moreover, particularly for fusion applications, the radiation damage scenario is expected to be complicated further by the presence of large quantities of He produced by the nuclear transmutation (∼ 10 appm He/dpa). Within this context, an elaborate ion irradiation study was performed at 500 C on a wide variety of high purity FeCr alloys (with Cr content ranging from ∼ 3 wt.% to 14 wt.%) and a bcc Fe, to probe in detail the influence of Cr and He on the evolution of microstructure. The irradiations were performed using Fe self-ions, in single beam mode and in dual beam mode (damage by Fe ions and co-implantation of He), to separate ballistic damage effect from the impact of simultaneous He injection. Three different dose ranges were studied: high dose (157 dpa, 17 appm He/dpa for the dual beam case), intermediate dose (45 dpa, 57 appm He/dpa for dual beam case) and in-situ low dose (0.33 dpa, 3030 appm He/dpa for the dual beam case). The experiments were performed at the JANNuS triple beam facility and dual beam in situ irradiation facility at CEA-Saclay and CSNSM, Orsay respectively. The microstructure was principally characterized by conventional TEM, APT and EDS in STEM mode. The main results are as follows: 1) A comparison of the cavity microstructure in high dose irradiated Fe revealed strong swelling reduction by the addition of He. It was achieved by a drastic reduction in cavity sizes and an increased number density. This behaviour was observed all along the damage depth, up to the damage peak. 2) Cavity microstructure was also studied in the dual beam high dose

  11. First-principles study of ternary bcc alloys using special quasi-random structures

    International Nuclear Information System (INIS)

    Jiang Chao

    2009-01-01

    Using a combination of exhaustive enumeration and Monte Carlo simulated annealing, we have developed special quasi-random structures (SQSs) for ternary body-centered cubic (bcc) alloys with compositions of A 1 B 1 C 1 , A 2 B 1 C 1 , A 6 B 1 C 1 and A 2 B 3 C 3 , respectively. The structures possess local pair and multisite correlation functions that closely mimic those of the random bcc alloy. We employed the SQSs to predict the mixing enthalpies, nearest neighbor bond length distributions and electronic density of states of bcc Mo-Nb-Ta and Mo-Nb-V solid solutions. Our convergence tests indicate that even small-sized SQSs can give reliable results. Based on the SQS energetics, the predicting powers of the existing empirical ternary extrapolation models were assessed. The present results suggest that it is important to take into account the ternary interaction parameter in order to accurately describe the thermodynamic behaviors of ternary alloys. The proposed SQSs are quite general and can be applied to other ternary bcc alloys.

  12. Atomistic simulations of dislocations in a model BCC multicomponent concentrated solid solution alloy

    International Nuclear Information System (INIS)

    Rao, S.I.; Varvenne, C.; Woodward, C.; Parthasarathy, T.A.; Miracle, D.; Senkov, O.N.; Curtin, W.A.

    2017-01-01

    Molecular statics and molecular dynamics simulations are presented for the structure and glide motion of a/2〈111〉 dislocations in a randomly-distributed model-BCC Co 16.67 Fe 36.67 Ni 16.67 Ti 30 alloy. Core structure variations along an individual dislocation line are found for a/2〈111〉 screw and edge dislocations. One reason for the core structure variations is the local variation in composition along the dislocation line. Calculated unstable stacking fault energies on the (110) plane as a function of composition vary significantly, consistent with this assessment. Molecular dynamics simulations of the critical glide stress as a function of temperature show significant strengthening, and much shallower temperature dependence of the strengthening, as compared to pure BCC Fe as well as a reference mean-field BCC alloy material of the same overall composition, lattice and elastic constants as the target alloy. Interpretation of the strength versus temperature in terms of an effective kink-pair activation model shows the random alloy to have a much larger activation energy than the mean-field alloy or BCC Fe. This is interpreted as due to the core structure variations along the dislocation line that are often unfavorable for glide in the direction of the load. The configuration of the gliding dislocation is wavy, and significant debris is left behind, demonstrating the role of local composition and core structure in creating kink pinning (super jogs) and/or deflection of the glide plane of the dislocation. - Graphical abstract: Measured critical resolved shear stress scaled by the (111) shear modulus (39 GPa) necessary to achieve on-going glide as a function of temperature, for the a/2[111] screw dislocation in the model BCC Co 16.67 Fe 36.67 Ni 16.67 Ti 30 alloy. The upper and lower bounds of the critical resolved shear stress is shown in the plot. Also shown in is the measured strength for the mean-field A-atom material and BCC Fe as a function of

  13. Superconducting pinning in BCC niobium-base alloys

    International Nuclear Information System (INIS)

    Hu, S.

    1981-01-01

    The structure dependence of critical current density J/sub c/ in superconducting alloys Nb--Zr and Nb--Ti was studied by means of x-ray analysis and tensile test. Experimental results indicate that, in the absence of second phase particles, annealing increases J/sub c/ in deformed alloys due to rearrangement of dislocations into cell structure and the cell walls are effective pinning centers for magnetic flux. In the precipitation process of second phase particles, new dislocations are formed due to the relaxation of coherent stress field. These new dislocations increases the dislocation density and the flux pinning ability of the cell walls, which in turn lead to a further increase of J/sub c/. The mechanism that causes precipitates to increase the current-carrying ability in Nb--Zr and Nb--Ti alloys is therefore the same as that of cold-work deformation

  14. The physical and mechanical metallurgy of advanced O+BCC titanium alloys

    Science.gov (United States)

    Cowen, Christopher John

    deformation mechanisms as a function of stress, temperature, and strain rate. Microstructure-creep relationships for Ti-Al-Nb-xB alloys were developed with the understanding gained. A rule-of-mixtures empirical model based on constituent phase volume fractions and strain rates was developed to predict the minimum creep rates of two-phase O+BCC microstructures. The most innovative results of this thesis were produced through the development of an in-situ creep testing methodology. The creep deformation evolution was chronicled in-situ during high temperature creep experiments, while creep displacement versus time data was simultaneously obtained. The in-situ experiments revealed that prior-BCC grain boundaries were the locus of damage accumulation during creep deformation. A methodology that allows in-situ observation of surface creep deformation as a function of creep displacement has yet to be presented in the literature.

  15. Short-range order clustering in BCC Fe-Mn alloys induced by severe plastic deformation

    Science.gov (United States)

    Shabashov, V. A.; Kozlov, K. A.; Sagaradze, V. V.; Nikolaev, A. L.; Lyashkov, K. A.; Semyonkin, V. A.; Voronin, V. I.

    2018-03-01

    The effect of severe plastic deformation, namely, high-pressure torsion (HPT) at different temperatures and ball milling (BM) at different time intervals, has been investigated by means of Mössbauer spectroscopy in Fe100-xMnx (x = 4.1, 6.8, 9) alloys. Deformation affects the short-range clustering (SRC) in BCC lattice. Two processes occur: destruction of SRC by moving dislocations and enhancement of the SRC by migration of non-equilibrium defects. Destruction of SRC prevails during HPT at 80-293 K; whereas enhancement of SRC dominates at 473-573 K. BM starts enhancing the SRC formation at as low as 293 K due to local heating at impacts. The efficiency of HPT in terms of enhancing SRC increases with increasing temperature. The authors suppose that at low temperatures, a significant fraction of vacancies are excluded from enhancing SRC because of formation of mobile bi- and tri-vacancies having low efficiency of enhancing SRC as compared to that of mono vacancies. Milling of BCC Fe100-xMnx alloys stabilises the BCC phase with respect to α → γ transition at subsequent isothermal annealing because of a high degree of work hardening and formation of composition inhomogeneity.

  16. Investigation of point defects diffusion in bcc uranium and U–Mo alloys

    International Nuclear Information System (INIS)

    Smirnova, D.E.; Kuksin, A.Yu.; Starikov, S.V.

    2015-01-01

    We present results of investigation of point defects formation and diffusion in pure γ-U and γ-U–Mo fuel alloys. The study was performed using molecular dynamics simulation with the different interatomic potentials. The point defects formation and migration energies were estimated for bcc γ-U and U–9 wt.%Mo alloy. The calculated diffusivities of atoms via defects are provided for pure γ-U and for the alloy components. Analysis of simulation results shows that self-interstitial atoms play a leading role in the self-diffusion processes in the materials studied. This fact can explain a remarkably high self-diffusion mobility observed experimentally for γ-U. The self-diffusion coefficients in γ-U calculated in this assumption agree with the data measured experimentally. It is shown that alloying of γ-U with Mo increase formation energy for self-interstitial atoms and decelerate their mobility. These changes lead to decrease of self-diffusion coefficients in U–Mo alloy compared to pure U

  17. Investigation of irradiation strengthening of b.c.c. metals and their alloys. Progress report, January 1976--October 1976

    International Nuclear Information System (INIS)

    1976-01-01

    Research on irradiation of bcc metals and alloys is reported. Data and information are presented in appendixes on low temperature neutron irradiation of Nb, effects of tritium on the yield stress of Nb, multiple dislocation motion, dislocation group motion, dislocation kinetics, and computer simulation of dislocation motion

  18. Properties of grain boundaries in BCC iron and iron-based alloys

    International Nuclear Information System (INIS)

    Terentyev, D.; He, Xinfu

    2010-01-01

    The report contains a summary of work done within the collaboration established between SCK-CEN and CIEA, performed during the internship of Xinfu He (CIAE) in the period of September 2009 to June 2010. In this work, we have carried out an atomistic study addressing the properties of grain boundaries in BCC Fe and Fe-Cr alloys. Throughout this work we report on the structural and cohesive properties of grain boundaries; thermal stability; interaction of grain boundaries with He and diffusivity of He in the core of the grain boundaries; equilibrium segregation of Cr near the grain boundary zone; cleavage fracture of grain boundaries; influence of the Cr precipitates, voids and He bubbles on the structure and strength of grain boundaries.

  19. Compositional Variation of the Phonon Dispersion Curves of bcc Fe-Ga Alloys

    International Nuclear Information System (INIS)

    Zarestky, Jerel L.; Garlea, Vasile O.; Lograsso, Tom; Schlagel, D.L.; Stassis, C.

    2005-01-01

    Inelastic neutron scattering techniques have been used to measure the phonon dispersion curves of bcc Fe1-xGax x=10.8, 13.3, 16.0, 22.5 alloys as a function of Ga concentration. The phonon frequencies of every branch were found to decrease significantly with increasing Ga concentration. The softening was most pronounced for the T2 0 branch and, to a lesser extent, the L branch in the vicinity of = 2 3. The concentration dependence of the shear elastic constant C =1/2 C11-C12 , calculated from the slope of the T2 0 branch, was found to agree with the results of sound velocity measurements. For the higher concentration sample measured, 22.5 at. % Ga, new branches appeared, an effect associated with the increase in the number of atoms per unit cell.

  20. Itinerant-electron antiferromagnetism and superconductivity in bcc Cr-Re alloys

    International Nuclear Information System (INIS)

    Nishihara, Y.; Yamaguchi, Y.; Kohara, T.; Tokumoto, M.

    1985-01-01

    The magnetic and superconducting properties of bcc Cr-Re alloys with up to 40 at. % Re were studied via measurements of the magnetic susceptibility, electrical resistivity, and nuclear magnetic resonance of the Re nuclei. Antiferromagnetic order coexists with superconductivity above 18 at. % Re. The results were analyzed with the coexistence model of spin-density waves and superconductivity. In the Re-concentration range greater than 18 at. %, about 10% of the Fermi surface satisfies the nesting condition and the rest of it contributes to form the superconducting gap. This model also explains the increase in the superconducting transition temperature and the decrease in the magnetic susceptibility by annealing as a competing effect between spin-density waves and superconductivity

  1. Properties of grain boundaries in BCC iron and iron-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Terentyev, D.; He, Xinfu

    2010-08-15

    The report contains a summary of work done within the collaboration established between SCK-CEN and CIEA, performed during the internship of Xinfu He (CIAE) in the period of September 2009 to June 2010. In this work, we have carried out an atomistic study addressing the properties of grain boundaries in BCC Fe and Fe-Cr alloys. Throughout this work we report on the structural and cohesive properties of grain boundaries; thermal stability; interaction of grain boundaries with He and diffusivity of He in the core of the grain boundaries; equilibrium segregation of Cr near the grain boundary zone; cleavage fracture of grain boundaries; influence of the Cr precipitates, voids and He bubbles on the structure and strength of grain boundaries.

  2. Flow stress asymmetry and cyclic stress--strain response in a BCC Ti--V alloy

    International Nuclear Information System (INIS)

    Koss, D.A.; Wojcik, C.C.

    1976-01-01

    The cyclic stress-strain response of relatively stable bcc β-phase Ti--40 percent V alloy single crystals was studied. Flow stress asymmetry found in the alloy is attributed to the fact that screw dislocations, when gliding on a (211) plane, are more mobile in the twinning direction than in the antitwinning direction. Thus the flow stress of the crystal is greater when it is sheared in the antitwinning direction than in the twinning direction (the latter case results when crystals of the 100 orientation are stressed in tension and those of the 110 orientation are stressed in compression). Such behavior can be a result of the core of a screw dislocation being asymmetric under stress which causes the flow stress asymmetry observed. It should be noted that screw dislocations dominate the low temperature deformation structure of Ti-40V, which strongly suggests deformation is controlled by screw dislocation motion. The observation in Mo that the microyield stress is independent of crystal orientation could be a result of edge dislocation motion controlling microyield in that instance and this observation would not be inconsistent with screw dislocation motion controlling the macroscopic (epsilon/sub p/ greater than 0.05 percent) deformation measured here

  3. Converting hcp Mg-Al-Zn alloy into bcc Mg-Li-Al-Zn alloy by electrolytic deposition and diffusion of reduced lithium atoms in a molten salt electrolyte LiCl-KCl

    International Nuclear Information System (INIS)

    Lin, M.C.; Tsai, C.Y.; Uan, J.Y.

    2007-01-01

    A body-centered cubic (bcc) Mg-12Li-9Al-1Zn (wt.%) alloy was fabricated in air by electrolysis from LiCl-KCl molten salt at 500 deg. C. Electrolytic deposition of Li atoms on cathode (Mg-Al-Zn alloy) and diffusion of the Li atoms formed the bcc Mg-Li-Al-Zn alloy with 12 wt.% Li and only 0.264 wt.% K. Low K concentration in the bcc Mg alloy strip after the electrolysis process resulted from 47% atomic size misfit between K and Mg atoms and low solubility of K in Mg matrix

  4. Multi-scale Modelling of bcc-Fe Based Alloys for Nuclear Applications

    International Nuclear Information System (INIS)

    Malerba, Lorenzo

    2008-01-01

    Understanding the basic mechanisms that determine microstructure changes in neutron irradiated steels is vital for a safe lifetime management of existing nuclear reactors and a safe design of future nuclear options. Low-alloyed ferritic steels containing Cu, Ni, Mn and Si as principal solute atoms are used as structural materials for current reactor vessels. The microstructural evolution under irradiation in alloys is decided by the interplay between defect formation and thermodynamic driving forces, together determining the appearance of phase transformations (precipitation, segregation,...) and favouring or delaying the nucleation and growth of point-defect clusters, their diffusion and their mutual recombination or removal at sinks. A reliable description of the production, evolution and accumulation of radiation damage must therefore start from the atomic level and requires being able to describe multicomponent systems for timescales ranging from few picoseconds to years. This goal demands firstly the fabrication of interatomic potentials for alloys that must be both consistent with the thermodynamic properties of the system and capable of reproducing correctly the characteristic solute-point defect interactions, versus ab initio or experimental data. Secondly the performance of extensive molecular dynamics (MD) simulations, to grasp the main mechanisms of defect production, diffusion, mutual interaction, and interaction with solute atoms and impurities. Thirdly, the development of simulation tools capable of describing the microstructure evolution beyond the time-frame and length-scale of MD, while reproducing as much as possible the atomic-level origin of the mechanisms governing the evolution of the system, including phase changes. In this presentation the results of recent efforts made in this direction in the case of Fe-Cu, Fe-Cr and Fe-Ni alloys, as basic model alloys for the description of steels of technological relevance, are highlighted. In particular

  5. Retraction of 'Composition design and mechanical properties of BCC Ti solid solution alloys with low Young's modulus'

    International Nuclear Information System (INIS)

    Tulugan, Keli Mu; Park, Cheol Hong; Park, Won Jo; Qing, Wang

    2012-01-01

    The article 'Composition design and mechanical properties of BCC Ti solid solution alloys with low Young's modulus' has been retracted upon the request of the third author (Prof. Wang Qing, the first author's former advisor during his internship at DaLian University of Technology). The article was published without the third author's knowledge and consent. The corresponding author (Prof. Wonjo Park) apologizes to the third author, to the readers, and to the editorial staff of the JMST. The JMST editorial board does not tolerate such actions from authors and we will take appropriate action to prevent this from happening in the future

  6. Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W.

    Science.gov (United States)

    Li, Xiaojie; Schönecker, Stephan; Li, Ruihuan; Li, Xiaoqing; Wang, Yuanyuan; Zhao, Jijun; Johansson, Börje; Vitos, Levente

    2016-06-03

    To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W 1-x-y  Re x  Os y (0  ⩽  x, y  ⩽  6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young's modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11 , the other elastic parameters including C 12 , C 44 , Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W 1-y  Os y than in W 1-x  Re x . A strong correlation between C' and the fcc-bcc structural energy difference for W 1-x-y  Re x  Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C'. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

  7. Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in ?-Ti alloys

    NARCIS (Netherlands)

    Van Bohemen, S.M.C.; Sietsma, J.; Van der Zwaag, S.

    2006-01-01

    The formation mechanisms of two hcp ? phase morphologies in Ti-4.5Fe-6.8Mo-1.5Al have been investigated by optical microscopy (OM), atomic force microscopy (AFM), electron probe microanalysis (EPMA) and dilatometry. At relatively high temperatures primary ? forms predominantly on prior bcc ? grain

  8. Point defects in B.C.C. Fe-Al, Fe-Co, and Fe-Co-V ordered alloys

    International Nuclear Information System (INIS)

    Riviere, J.P.; Dinhut, J.F.

    1982-01-01

    Radiation damage produced at 20 K by 2.5 MeV electrons is studied in three B 2 type Fe-40 at % Al, Fe-Co, Fe-Co-V ordered alloys. The resistivity damage in Fe-40 at % Al ordered single crystals is found less effective in the directions. The results suggest that replacement collision chains are difficult to propagate along the direction. Frenkel pair creation superimposed with disordering can account for the resistivity damage in the initially ordered Fe-Co alloy. Informations concerning replacement collision sequences in direction are derived. During the recovery of all the alloys, three main stages are observed and an ordering enhancement occurs. (author)

  9. Bcc and Fcc transition metals and alloys: a central role for the Jahn-Teller effect in explaining their ideal and distorted structures.

    Science.gov (United States)

    Lee, Stephen; Hoffmann, Roald

    2002-05-01

    Transition metal elements, alloys, and intermetallic compounds often adopt the body centered cubic (bcc) and face centered cubic (fcc) structures. By comparing quantitative density functional with qualitative tight-binding calculations, we analyze the electronic factors which make the bcc and fcc structures energetically favorable. To do so, we develop a tight-binding function, DeltaE(star), a function that measures the energetic effects of transferring electrons within wave vector stars. This function allows one to connect distortions in solids to the Jahn-Teller effect in molecules and to provide an orbital perspective on structure determining deformations in alloys. We illustrate its use by considering first a two-dimensional square net. We then turn to three-dimensional fcc and bcc structures, and distortions of these. Using DeltaE(star), we rationalize the differences in energy of these structures. We are able to deduce which orbitals are responsible for instabilities in seven to nine valence electron per atom (e(-)/a) bcc systems and five and six e(-)/a fcc structures. Finally we demonstrate that these results account for the bcc and fcc type structures found in both the elements and binary intermetallic compounds of group 4 through 9 transition metal atoms. The outline of a theory of metal structure deformations based on loss of point group operation rather than translational symmetry is presented.

  10. About oxide dispersion particles chemical compatibility with areas coherent dissipation/sub-grains of bcc-alloys in Fe - (Cr, V, Mo, W systems

    Directory of Open Access Journals (Sweden)

    Udovsky A.

    2016-01-01

    Full Text Available A concept of partial magnetic moments (PMM of the iron atoms located in the first ч four coordination spheres (1÷4 CS for bcc lattice have been introduced based on analysis of results obtained by quantum-mechanical calculations (QMC for volume dependence of the average magnetic moment ferromagnetic (FM Fe. The values of these moments have been calculated for pure bcc Fe and bcc - Fe-Cr alloys. This concept has been used to formulate a three sub-lattice model for binary FM alloys of the Fe-M systems (M is an alloying paramagnetic element. Physical reason for sign change dependence of the short-range order and mixing enthalpy obtained by QMCs for Fe-(Cr, V bcc phases has been found. Using this model it has been predicted that static displacements of Fe - atoms in alloy matrix increase with increasing the of CS number and result in reducing of the area of coherent dissipation (ACD size with growth of the dimension factor (DF in the Fe-(Cr, V, Mo, W systems in agreement with the X-ray experiments. It has been shown theoretically that anisotropy of spin- density in bcc lattice Fe and DF in binary Fe - (Cr, V, Mo, W systems is main factor for origins of segregations on small angle boundaries of ACD and sub-grains boundaries To prevent the coagulation of both ACD and sub-grains, and to increase the strength of alloys, it is advisable to add oxide dispersion particles into ferrite steel taking into account their chemical compatibility and coherent interfacing with the crystalline lattice of a ferrite matrix. Application of phase diagrams for binary and ternary the Fe-(Y, Zr-O systems to verify chemical compatibility of oxide dispersion particles with ferrite matrix have been discussed

  11. Tensile properties of several 800 MeV proton-irradiated bcc metals and alloys

    International Nuclear Information System (INIS)

    Brown, R.D.; Wechsler, M.S.; Tschalar, C.

    1987-01-01

    A spallation neutron source for the 600-MeV proton accelerator facility at the Swiss Institute for Nuclear Research (SIN) consists of a vertical cylinder filled with molten Pb-Bi. The proton beam enters the cylinder, passing upward through a window in contact with the Pb-Bi eutectic liquid that must retain reasonable strength and ductility upon irradiation at about 673 K to fluence of about 1 x 10/sup 25/ protons/m/sup 2/. Investigations are underway at the 800-MeV proton accelerator at the Los Alamos Meson Physics Facility (LAMPF) to test the performance of candidate SIN window materials under appropriate conditions of temperature, irradiation, and environment. Based on considerations of chemical compatibility with molten Pb-Bi, as well as interest in identifying fundamental radiation damage mechanisms, Fe, Ta, Fe-2.25Cr-1Mo, and Fe-12Cr-1Mo(HT-9) were chosen as candidate materials. Sheet tensile samples, 0.5-mm thick, of the four materials were fabricated and heat treated. The samples were sealed inside capsules containing Pb-Bi and were proton-irradiated at LAMPF to two fluences, 4.8 and 54 x 10/sup 23/ p/m/sup 2/. The beam current was approximately equal to the 1 mA anticipated for the upgraded SIN accelerator. The power deposited by the proton beam in the capsules was sufficient to maintain sample temperatures of about 673 K. Post-irradiation tensile tests were conducted at room temperature at a strain rate of 9 x 10/sup -4/s/sup -1/. The yield and ultimate strengths increased upon irradiation in all materials, while the ductility decreased, as indicated by the uniform strain. The pure metals, Ta and Fe, exhibited the greatest radiation hardening and embrittlement. The HT-9 alloy showed the smallest changes in strength and ductility. The increase in strength following irradiation is discussed in terms of a dispersed-barrier hardening model, for which the barrier sizes and formation cross sections are calculated

  12. Neutron irradiation damage of a stress relieved TZM alloy

    International Nuclear Information System (INIS)

    Abe, K.; Masuyama, T.; Satou, M.; Hamilton, M.L.

    1992-01-01

    The objective of this work is to study defect microstructures and irradiation hardening in a stress relieved TZM alloy after irradiation in the Fast Flux Test Facility (FFTF) using the Materials Open Test Assembly (MOTA). Disk specimens of the molybdenum alloy TZM that had been stress relieved at 1199 K (929 C) for 0.9 ks (15 min.) were irradiated in the FFTF/MOTA 1F at 679, 793 and 873 K (406, 520, and 600 C) to a fast fluence of ∼9.6 x 10 22 n/cm 2 . Microstructures were observed in a transmission electron microscope (TEM). Dislocation structures consisted of isolated loops, aggregated loops (rafts) and elongated dislocations. The size of the loops increased with the irradiation temperature. Void swelling was about 1 and 2% at 793 and 873 K (520 and 600 C), respectively. A void lattice was developed in the body centered cubic (bcc) structure with a spacing of 26 - 28 nm. The fine grain size (0.5 - 2 μm) was retained following high temperature irradiation, indicating that the stress relief heat treatment may extend the material's resistance to radiation damage up to high fluence levels. Microhardness measurements indicated that irradiation hardening increased with irradiation temperature. The relationship between the microstructure and the observed hardening was determined

  13. Diffusion of titanium and niobium in b.c.c. Ti--Nb alloys

    International Nuclear Information System (INIS)

    Pontau, A.E.

    1978-01-01

    The diffusion coefficients for titanium and niobium radioactive tracers were simultaneously measured in Ti, Ti 94 6 Nb 5 4 , Ti 80 4 Nb 19 6 , and Ti 64 3 Nb 35 . 7 over the temperature range from 950 0 C to 1511 0 C using standard lathe sectioning techniques. The samples were initially heat treated by annealing above the α-β phase transition temperature and then either cooling slowly to room temperature or quenching. The room temperature crystal morphology was then examined using x-ray diffraction. Alloy concentrations were chosen both to suppress the β-α transition and to obtain the metastable ω-phase

  14. Enabling microstructural changes of FCC/BCC alloys in 2D dislocation dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Ilker Topuz, Ahmet, E-mail: aitopuz@gmail.com

    2015-03-11

    Dimension reduction procedure is the recipe to represent defects in two dimensional dislocation dynamics according to the changes in the geometrical properties of the defects triggered by different conditions such as radiation, high temperature, or pressure. In the present study, this procedure is extended to incorporate further features related to the presence of defects with a special focus on face-centered cubic/body-centered cubic alloys used for diverse engineering purposes. In order to reflect the microstructural state of the alloy on the computational cell of two dimensional dislocation dynamics, the distribution of the multi-type defects over slip lines is implemented by using corresponding strength and line spacing for each type of defect. Additionally, a simple recursive incremental relation is set to count the loop accumulation on the precipitates. In the case of continuous resistance against the motion of edge dislocations on the slip lines, an expression of friction is introduced to see its contribution on the yield strength. Each new property is applied independently on a different material by using experimental information about defect properties and grain sizes under the condition of plain strain deformation: both constant and dynamically increasing obstacle strength for precipitate coarsening in prime-aged and heat-treated copper-chromium-zirconium, internal friction in tantalum-2.5tungsten, and mixed hardening due to the presence of precipitates and prismatic loops in irradiated oxide dispersion strengthened EUROFER with 0.3% yttria.

  15. Effects of additive Pd on the structures and electrochemical hydrogen storage properties of Mg{sub 67}Co{sub 33}-based composites or alloys with BCC phase

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yao; Zhuang, Xiangyang [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Zhu, Yunfeng [College of Materials Science and Engineering, Nanjing Tech University, 5 Xinmofan Road, Nanjing 210009 (China); Zhan, Leyu [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Pu, Zhenggan [College of Materials Science and Engineering, Nanjing Tech University, 5 Xinmofan Road, Nanjing 210009 (China); Wan, Neng [SEU-FEI Nano Pico Center, Key Laboratory of MEMS of Ministry of Education, School of Electronics Science and Engineering, Southeast University, Nanjing 210096 (China); Li, Liquan [College of Materials Science and Engineering, Nanjing Tech University, 5 Xinmofan Road, Nanjing 210009 (China)

    2015-02-15

    Highlights: • Additive Pd in Mg{sub 67}Co{sub 33} benefits to form a ternary BCC alloy. • Introducing 5.0 at.% Pd in Mg{sub 67}Co{sub 33} lifts the initial discharge capacity from 10 mAh/g to maximum 530 mAh/g. • Exchange current density was increased due to the homogeneously dispersed Pd. • Additive Pd slightly enhances the hydrogen diffusion coefficient of Mg-Co-Pd composites or alloys. - Abstract: Mg{sub 67}Co{sub 33} and Mg{sub 67}Co{sub 33}-Pd composites/alloys prepared by ball milling for 120 h possess nano-crystalline with body-centered cubic (BCC) structure, which was verified by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) analyses. The introduced 5.0 at.% Pd significantly lifts the initial discharge capacity from 10 mAh g{sup -1} of Mg{sub 67}Co{sub 33} to maximum 530 mAh g{sup -1}. Pd also drives the Mg{sub 67}Co{sub 33}-Pd composite forming a full BCC alloy during ball milling. The distribution of Pd gradually becomes homogeneous with the augmentation of the ball milling time according to the analyses by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS). Exchange current density increased with the milling time and can be ascribed to the homogeneously dispersion of Pd over the surface. The introduced Pd also enhances the hydrogen diffusion coefficient of the Mg{sub 67}Co{sub 33}-Pd composites/alloys.

  16. Fatigue damage monitoring of structural aluminum alloys

    Directory of Open Access Journals (Sweden)

    С.Р. Ігнатович

    2004-01-01

    Full Text Available  Results of the experiments directed on creation of a new tool method of fatigue damage diagnostics and an estimation of a residual life of aviation designs are presented. It is shown, that the defo rmation relief formed on a surface of cladding  layer of sheets of constructional alloys Д-16АТ, 2024-Т3, 7075-Т6  can be considered as the metal damage indicator  under cyclically repeating loadings.

  17. Electronic structure of metastable bcc Cu–Cr alloy thin films: Comparison of electron energy-loss spectroscopy and first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Liebscher, C.H.; Freysoldt, C. [Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf (Germany); Dennenwaldt, T. [Institute of Condensed Matter Physics and Interdisciplinary Center for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); Harzer, T.P.; Dehm, G. [Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf (Germany)

    2017-07-15

    Metastable Cu–Cr alloy thin films with nominal thickness of 300 nm and composition of Cu{sub 67}Cr{sub 33} (at%) are obtained by co-evaporation using molecular beam epitaxy. The microstructure, chemical phase separation and electronic structure are investigated by transmission electron microscopy (TEM). The thin film adopts the body-centered cubic crystal structure and consists of columnar grains with ~50 nm diameter. Aberration-corrected scanning TEM in combination with energy dispersive X-ray spectroscopy confirms compositional fluctuations within the grains. Cu- and Cr-rich domains with composition of Cu{sub 85}Cr{sub 15} (at%) and Cu{sub 42}Cr{sub 58} (at%) and domain size of 1–5 nm are observed. The alignment of the interface between the Cu- and Cr-rich domains shows a preference for {110}-type habit plane. The electronic structure of the Cu–Cr thin films is investigated by electron energy loss spectroscopy (EELS) and is contrasted to an fcc-Cu reference sample. The experimental EEL spectra are compared to spectra computed by density functional theory. The main differences between bcc-and fcc-Cu are related to differences in van Hove singularities in the electron density of states. In Cu–Cr solid solutions with bcc crystal structure a single peak after the L{sub 3}-edge, corresponding to a van Hove singularity at the N-point of the first Brillouin zone is observed. Spectra computed for pure bcc-Cu and random Cu–Cr solid solutions with 10 at% Cr confirm the experimental observations. The calculated spectrum for a perfect Cu{sub 50}Cr{sub 50} (at%) random structure shows a shift in the van Hove singularity towards higher energy by developing a Cu–Cr d-band that lies between the delocalized d-bands of Cu and Cr. - Highlights: • Compositional fluctuations on the order of 1–5 nm in Cu- and Cr-rich domains are observed. • EELS determines a single van Hove singularity for bcc Cu–Cr solid solutions. • The electronic structure is dominated by d

  18. Damage buildup and edge dislocation mobility in equiatomic multicomponent alloys

    Energy Technology Data Exchange (ETDEWEB)

    Granberg, F., E-mail: fredric.granberg@helsinki.fi [Department of Physics, P.O. Box 43, FIN-00014 University of Helsinki (Finland); Djurabekova, F. [Department of Physics, P.O. Box 43, FIN-00014 University of Helsinki (Finland); Helsinki Institute of Physics, P.O. Box 43, FIN-00014 University of Helsinki (Finland); Levo, E.; Nordlund, K. [Department of Physics, P.O. Box 43, FIN-00014 University of Helsinki (Finland)

    2017-02-15

    Highlights: • We studied the damage buildup in equiatomic multicomponent alloys by MD simulations. • Edge dislocation mobility was lower in the studied alloys compared to elemental Ni. • Damage buildup in alloys saturated at lower levels than in elemental Ni. • Initial damage buildup is faster in alloys compared to elemental Ni. - Abstract: A new class of single phase metal alloys of equal atomic concentrations has shown very promising mechanical properties and good corrosion resistance. Moreover, a significant reduction in damage accumulation during prolonged irradiation has also been observed in these equiatomic multicomponent alloys. A comparison of elemental Ni with the two component NiFe- and the three component NiCoCr-alloy showed a substantial reduction in damage in both alloys, and an even larger difference was seen if only larger clusters were considered. One of the factors limiting the damage build-up in the alloys compared to the elemental material was seen to be dislocation mobility (Granberg et al., 2016). In this Article, we focus on a more thorough investigation of the mobility of edge dislocations in different cases of the Ni-, NiFe- and NiCoCr-samples. We find that even though the saturated amount of defects in the alloys is lower than in elemental Ni, the defect buildup in the early stages is faster in the alloys. We also find that the dislocation mobility in NiFe is lower than in Ni, at low stresses, and that the onset stress in NiFe is higher than in Ni. The same phenomenon was seen in comparison between NiFe and NiCoCr, since the three component alloy had lower dislocation mobility and higher onset stress. The dislocation velocity in elemental Ni plateaued out just under the forbidden velocity, whereas the alloys showed a more complex behaviour.

  19. Thermal Stability of Microstructure and Microhardness of Heterophase BCC-Alloys After Torsional Deformation on Bridgman Anvils

    Science.gov (United States)

    Ditenberg, I. A.; Tyumentsev, A. N.

    2018-03-01

    The results of investigations of thermal stability of microstructure and microhardness of alloys of the V-4Ti-4Cr and Mo-47Re systems, subjected to torsional deformation by high quasi-hydrostatic pressure at room temperature, are reported. It is shown that submicrocrystalline and nanocrystalline states, and the respective high values of microhardness, persist up to the upper bound ( 0.4 Tmelt) of the temperature interval of their recovery and polygonization in a single-phase state. The main factors ensuring thermal stability of highlydefective states in heterophase alloys are discussed.

  20. Lattice damage in ion-implanted silicon-germanium alloys

    International Nuclear Information System (INIS)

    Haynes, T.E.; Holland, O.W.

    1992-08-01

    The damage produced in Si 1-x Ge x alloys (0≤x≤1) by implantation of 70--100 keV 30 Si + has been measured as a function of temperature and fluence by ion channeling. For all compositions, the damage efficiency decreased sharply as the implant temperature was increased between room temperature and 150 degrees C. Furthermore, the damage efficiency in alloys of intermediate compositions (0.34≤x≤0.5) exceeds that in Ge, especially at elevated temperatures, despite the larger cascade energy density in Ge. It is shown that this behavior can be described based on a model in which the point-defect mobility is the dominant factor controlling damage retention, rather than the cascade energy density. This approach provides a framework for understanding other temperature-dependent phenomena related to damage growth in Si-Ge alloys including dose-rate effects and damage saturation in MeV implantation

  1. Stacking fault density as engineering criterion for resistance to radiation swelling of alloys' FCC- and BCC-lattice

    International Nuclear Information System (INIS)

    Zheltov, Yu.V.; Ageev, V.S.; Kolesnikov, Yu.G.

    1990-01-01

    The experimental data on influence of Mn, Cr, Ni, P, B, Ce alloying in austenitic and simultaneously Nb, V, B alloying in ferritic steels and also heat treatment on stacking fault density (SFD) are represented. In all cases besides influence of Cr in austenitic steel the increase of SFD is shown. The decrease of radiation swelling of industrial steels at the increase of their SFD, measured by X-rays, was studied. The tendency of increase of relative radiation swelling change at SFD increase at relative fluence rise is verified. It is shown that SFD may be a perspective proximate characteristics of choice of radiation-resistant steel melts within one steel quality. 14 refs.; 4 figs. (author)

  2. Thermal decomposition of the b.c.c. β-solid solution of titanium alloy containing 6.7 at% Mo, 3 at% Zr, and 1.8 at% Sn. 1

    International Nuclear Information System (INIS)

    Zakharova, M.I.; Khundzhua, A.K.; Kertesz, L.; Szasz, A.

    1981-01-01

    Changes in the crystal structure of the titanium alloy, containing 6.7 at% Mo, 3 at% Zr, and 1.8 at% Sn, during thermal decomposition are followed by means of X-ray and electron diffraction methods. Parallel to these tests the alteration in the electron structure and chemical bonds of the alloy are investigated with the help of the soft-x-ray emission (SXES) method. Attention is focussed on the at room temperature not equilibrated b.c.c. β-solid solution, on the metastable transition phase ω, and on the equilibrium phase α. (author)

  3. Interdiffusion, Intrinsic Diffusion, Atomic Mobility, and Vacancy Wind Effect in γ(bcc) Uranium-Molybdenum Alloy

    Science.gov (United States)

    Huang, Ke; Keiser, Dennis D.; Sohn, Yongho

    2013-02-01

    U-Mo alloys are being developed as low enrichment uranium fuels under the Reduced Enrichment for Research and Test Reactor (RERTR) Program. In order to understand the fundamental diffusion behavior of this system, solid-to-solid pure U vs Mo diffusion couples were assembled and annealed at 923 K, 973 K, 1073 K, 1173 K, and 1273 K (650 °C, 700 °C, 800 °C, 900 °C, and 1000 °C) for various times. The interdiffusion microstructures and concentration profiles were examined via scanning electron microscopy and electron probe microanalysis, respectively. As the Mo concentration increased from 2 to 26 at. pct, the interdiffusion coefficient decreased, while the activation energy increased. A Kirkendall marker plane was clearly identified in each diffusion couple and utilized to determine intrinsic diffusion coefficients. Uranium intrinsically diffused 5-10 times faster than Mo. Molar excess Gibbs free energy of U-Mo alloy was applied to calculate the thermodynamic factor using ideal, regular, and subregular solution models. Based on the intrinsic diffusion coefficients and thermodynamic factors, Manning's formalism was used to calculate the tracer diffusion coefficients, atomic mobilities, and vacancy wind parameters of U and Mo at the marker composition. The tracer diffusion coefficients and atomic mobilities of U were about five times larger than those of Mo, and the vacancy wind effect increased the intrinsic flux of U by approximately 30 pct.

  4. Investigation of irradiation strengthening of b.c.c. metals and their alloys. Progress report, January 1975--October 1975

    International Nuclear Information System (INIS)

    1975-01-01

    Results of studies on radiation strengthening of V, Mo, and Nb are presented. Information is included on deformation characteristics of low-temperature neutron-irradiated Nb, the effects of He 3+ on the low-temperature deformation characteristics of Nb, electron-transmission microscopic studies of the nature of neutron damage effects of post-irradiation annealing, microplasticity, thermally activated dislocation motion, production of high-purity Nb and V, early stages of flow in Mo, microplasticity in V, and effects of impurity interstitials on the lattice resistance to dislocation motion. (JRD)

  5. Damage buildup and edge dislocation mobility in equiatomic multicomponent alloys

    Science.gov (United States)

    Granberg, F.; Djurabekova, F.; Levo, E.; Nordlund, K.

    2017-02-01

    A new class of single phase metal alloys of equal atomic concentrations has shown very promising mechanical properties and good corrosion resistance. Moreover, a significant reduction in damage accumulation during prolonged irradiation has also been observed in these equiatomic multicomponent alloys. A comparison of elemental Ni with the two component NiFe- and the three component NiCoCr-alloy showed a substantial reduction in damage in both alloys, and an even larger difference was seen if only larger clusters were considered. One of the factors limiting the damage build-up in the alloys compared to the elemental material was seen to be dislocation mobility (Granberg et al., 2016). In this Article, we focus on a more thorough investigation of the mobility of edge dislocations in different cases of the Ni-, NiFe- and NiCoCr-samples. We find that even though the saturated amount of defects in the alloys is lower than in elemental Ni, the defect buildup in the early stages is faster in the alloys. We also find that the dislocation mobility in NiFe is lower than in Ni, at low stresses, and that the onset stress in NiFe is higher than in Ni. The same phenomenon was seen in comparison between NiFe and NiCoCr, since the three component alloy had lower dislocation mobility and higher onset stress. The dislocation velocity in elemental Ni plateaued out just under the forbidden velocity, whereas the alloys showed a more complex behaviour.

  6. Damage energy functions for compounds and alloys

    International Nuclear Information System (INIS)

    Parkin, D.M.; Coulter, C.A.

    1977-01-01

    The concept of the damage energy of an energetic primary knock-on atom in a material is a central component in the procedure used to calculate dpa for metals exposed to neutron and charged particle radiation. Coefficients for analytic fits to the calculated damage energy functions are given for Al 2 O 3 , Si 3 N 4 , Y 2 O 3 , and NbTi. Damage efficiencies are given for Al 2 O 3

  7. Damage percolation during stretch flange forming of aluminum alloy sheet

    Science.gov (United States)

    Chen, Zengtao; Worswick, Michael J.; Keith Pilkey, A.; Lloyd, David J.

    2005-12-01

    A multi-scale finite element (FE)-damage percolation model was employed to simulate stretch flange forming of aluminum alloys AA5182 and AA5754. Material softening and strain gradients were captured using a Gurson-based FE model. FE results were then fed into the so-called damage percolation code, from which the damage development was modelled within measured microstructures. The formability of the stretch flange samples was predicted based upon the onset of catastrophic failure triggered by profuse void coalescence within the measured second-phase particle field. Damage development is quantified in terms of crack and void areal fractions, and compared to metallographic results obtained from interrupted stretch flange specimens. Parametric study is conducted on the effect of void nucleation strain in the prediction of formability of stretch flanges to "calibrate" proper nucleation strains for both alloys.

  8. On hyper BCC-algebras

    OpenAIRE

    Borzooei, R. A.; Dudek, W. A.; Koohestani, N.

    2006-01-01

    We study hyper BCC-algebras which are a common generalization of BCC-algebras and hyper BCK-algebras. In particular, we investigate different types of hyper BCC-ideals and describe the relationship among them. Next, we calculate all nonisomorphic 22 hyper BCC-algebras of order 3 of which only three are not hyper BCK-algebras.

  9. On hyper BCC-algebras

    Directory of Open Access Journals (Sweden)

    R. A. Borzooei

    2006-01-01

    Full Text Available We study hyper BCC-algebras which are a common generalization of BCC-algebras and hyper BCK-algebras. In particular, we investigate different types of hyper BCC-ideals and describe the relationship among them. Next, we calculate all nonisomorphic 22 hyper BCC-algebras of order 3 of which only three are not hyper BCK-algebras.

  10. The development of BCC

    International Nuclear Information System (INIS)

    He Xiaoping; Yang Hailiang; Sun Jianfeng; Ren Shuqing; Zhang Jiasheng; Shi Lei; Peng Jianchang; Li Hongyu; Qiu Aici; Tang Junping; Xi'an Jiaotong Univ., Xi'an

    2004-01-01

    An analysis of principle of a BCC for measuring ion beam density and the main reasons related to the measuring accuracy were presented. An array of 13 biased charge collecrors was designed for the measurement of ion beam density of 'FLASH-II' high power ion beam source, and the data of experiments was analyzed. (authors)

  11. Smarandache hyper BCC-algebra

    OpenAIRE

    Ahadpanah, A.; Borumand Saeid, A.

    2011-01-01

    In this paper, we define the Smarandache hyper BCC-algebra, and Smarandache hyper BCC-ideals of type 1, 2, 3 and 4. We state and prove some theorems in Smarandache hyper BCC -algebras, and then we determine the relationships between these hyper ideals.

  12. Novel Concepts for Damage-Resistant Alloys in Next Generation Nuclear Power Systems

    Energy Technology Data Exchange (ETDEWEB)

    Stephen M. Bruemmer; Peter L. Andersen; Gary Was

    2002-12-27

    The discovery of a damage-resistant alloy based on Hf solute additions to a low-carbon 316SS is the highlight of the Phase II research. This damage resistance is supported by characterization of radiation-induced microstructures and microchemistries along with measurements of environmental cracking. The addition of Hf to a low-carbon 316SS reduced the detrimental impact of radiation by changing the distribution of Hf. Pt additions reduced the impact of radiation on grain boundary segregation but did not alter its effect on microstructural damage development or cracking. Because cracking susceptibility is associated with several material characteristics, separate effect experiments exploring strength effects using non-irradiated stainless steels were conducted. These crack growth tests suggest that irradiation strength by itself can promote environmental cracking. The second concept for developing damage resistant alloys is the use of metastable precipitates to stabilize the microstructure during irradiation. Three alloys have been tailored for evaluation of precipitate stability influences on damage evolution. The first alloy is a Ni-base alloy (alloy 718) that has been characterized at low neutron irradiation doses but has not been characterized at high irradiation doses. The other two alloys are Fe-base alloys (PH 17-7 and PH 17-4) that have similar precipitate structures as alloy 718 but is more practical in nuclear structures because of the lower Ni content and hence lesser transmutation to He.

  13. Micromechanics-Based Damage Analysis of Fracture in Ti5553 Alloy with Application to Bolted Sectors

    Science.gov (United States)

    Bettaieb, Mohamed Ben; Van Hoof, Thibaut; Minnebo, Hans; Pardoen, Thomas; Dufour, Philippe; Jacques, Pascal J.; Habraken, Anne Marie

    2015-03-01

    A physics-based, uncoupled damage model is calibrated using cylindrical notched round tensile specimens made of Ti5553 and Ti-6Al-4V alloys. The fracture strain of Ti5553 is lower than for Ti-6Al-4V in the full range of stress triaxiality. This lower ductility originates from a higher volume fraction of damage sites. By proper heat treatment, the fracture strain of Ti5553 increases by almost a factor of two, as a result of a larger damage nucleation stress. This result proves the potential for further optimization of the damage resistance of the Ti5553 alloy. The damage model is combined with an elastoviscoplastic law in order to predict failure in a wide range of loading conditions. In particular, a specific application involving bolted sectors is addressed in order to determine the potential of replacing the Ti-6Al-4V by the Ti5553 alloy.

  14. Radiation damage in Fe-Cr alloys: Atomistic studies

    International Nuclear Information System (INIS)

    Terentyev, Dmitry; Malerba, Lorenzo; Bonny, Giovanni; Castin, Nicolas

    2009-01-01

    High-Cr ferritic-martensitic steels are the most promising candidate structural materials for future advanced fission reactors, as well as for fusion systems, due to their better thermomechanical properties and higher radiation resistance as compared to austenitic steels. The performance of these steels, especially under irradiation, appears to be largely determined by the Cr content. For instance, the current choice of steel compositions around ∼9 wt% Cr is mainly based on the observation of a local minimum in the ductile-brittle transition temperature shift at this composition. On the other hand, reduced void swelling is observed between 3 and 12 wt% Cr. The origin of these and other Cr-dependent effects remained unexplained for a long time, thereby calling for a physical modelling effort addressing these questions. In this presentation, an overview is given on the effort made in recent years to construct a whole modelling framework, from ab initio to dislocations, to provide explanations to the above-mentioned issues. Ab initio calculations combined to the development of the interatomic potentials capable of grasping key features of Cr atoms embedded in perfect and defected Fe matrix, were required. Primary damage, defect migration, Cr mass transport, phase separation, Cr-defect segregation and dislocation-defect interactions could then be studied using fully atomistic approaches. Our research shows that many of the effects of Cr content on the behaviour of these alloys under irradiation can be attributed to the only recently highlighted high solubility of Cr in Fe (∼10 wt%), below which, in addition, Cr atoms tend to order. The presentation will clarify how this aspect, combined with the high affinity between Cr atoms and self-interstitials defects, influences and partly explain both microstructure evolution and mechanical behaviour of high-Cr steels under irradiation. (author)

  15. The Fifth International Ural seminar. Radiation damage physics of metals and alloys. Abstracts

    International Nuclear Information System (INIS)

    2003-01-01

    Presented are the abstracts of The Fifth International Ural seminar Damage physics of metals and alloys. General problems of radiation damage physics, radiation effect on change of microstucture and the properties of metals and alloys, as well as materials for nuclear and thermonuclear energetics are considered. The themes of reports are the following: correlation effects in cascades of atom-atomic collisions; radiation-induced strengthening critical current density in YBa 2 Cu 3 O 7-x superconductors; conditions of forming and hydrides growth in irradiated zirconium alloys [ru

  16. Radiation damage buildup and dislocation evolution in Ni and equiatomic multicomponent Ni-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Levo, E. [Department of Physics, P.O. Box 43, FIN-00014, University of Helsinki (Finland); Granberg, F., E-mail: fredric.granberg@helsinki.fi [Department of Physics, P.O. Box 43, FIN-00014, University of Helsinki (Finland); Fridlund, C.; Nordlund, K. [Department of Physics, P.O. Box 43, FIN-00014, University of Helsinki (Finland); Djurabekova, F. [Department of Physics, P.O. Box 43, FIN-00014, University of Helsinki (Finland); Helsinki Institute of Physics, P.O. Box 43, FIN-00014, University of Helsinki (Finland)

    2017-07-15

    Single-phase multicomponent alloys of equal atomic concentrations (“equiatomic”) have proven to exhibit promising mechanical and corrosion resistance properties, that are sought after in materials intended for use in hazardous environments like next-generation nuclear reactors. In this article, we investigate the damage production and dislocation mobility by simulating irradiation of elemental Ni and the alloys NiCo, NiCoCr, NiCoFe and NiFe, to assess the effect of elemental composition. We compare the defect production and the evolution of dislocation networks in the simulation cells of two different sizes, for all five studied materials. We find that the trends in defect evolution are in good agreement between the different cell sizes. The damage is generally reduced with increased alloy complexity, and the dislocation evolution is specific to each material, depending on its complexity. We show that increasing complexity of the alloys does not always lead to decreased susceptibility to damage accumulation under irradiation. We show that, for instance, the NiCo alloy behaves very similarly to Ni, while presence of Fe or Cr in the alloy even as a third component reduces the saturated level of damage substantially. Moreover, we linked the defect evolution with the dislocation transformations in the alloys. Sudden drops in defect number and large defect fluctuations from the continuous irradiation can be explained from the dislocation activity.

  17. A Study on Thermal Properties and α( hcp) → β( bcc) Phase Transformation Energetics in Ti-5 mass% Ta-1.8 mass% Nb Alloy Using Inverse Drop Calorimetry

    Science.gov (United States)

    Behera, Madhusmita; Raju, S.; Jeyaganesh, B.; Mythili, R.; Saroja, S.

    2010-12-01

    Accurate measurements of enthalpy increment ( H T - H 298.15) values have been made on a Ti-5 mass% Ta-1.8 mass% Nb alloy using the inverse drop calorimetry technique in the temperature range from 463 K to 1457 K. The measured enthalpy increment values show a steady increase with temperature in both α- hcp and β- bcc solid solution regions. It is found that both the onset as well the completion of the α → β phase change are demonstrated by a marked deviation of the enthalpy increment behavior from the otherwise smooth variation encountered in the respective low-temperature α- and high-temperature β-phase domains. The transformation start ( T s) and finish ( T f) temperatures of the α → β phase change are found to be (1072±10) K and (1156±10) K, respectively. In the actual α → β phase transformation region, the variation of the enthalpy with the progress of transformation is found to follow a sigmoidal shape which is in line with the diffusive nature of the phase transformation. An estimation of the total enthalpy change associated with the α → β phase transformation (Δ° H tr) has been made by assuming a simple diffusion limited kinetic model for the phase change. The net enthalpy change for the α → β transformation is found to be 76 J · g-1. The measured temperature variation of the enthalpy increment in both α- and β-phase regimes are fitted to simple analytical functional forms to obtain temperature-dependent estimates of the specific heat, C P . The total specific heat change associated with the α → β phase transformation {Δ^{circ}{CP^{α}}^{→{β}}} is estimated to be 904 J · kg-1 · K-1.

  18. Fatigue damage assessment of recycled metals and alloys | Ayensu ...

    African Journals Online (AJOL)

    Cyclic fatigue tests were conducted on recycled polycrystalline metals and alloys at room and elevated tempera-ures to determine the fatigue strength, endurance limit and endurance ratio. Annealed and polished stainless steel (Fe-18Cr-8Ni), mild steel (Fe-0.25Cr), aluminium (Al), alpha-brass (Cu-30 % Zn) and copper ...

  19. On Weak-BCC-Algebras

    Science.gov (United States)

    Thomys, Janus; Zhang, Xiaohong

    2013-01-01

    We describe weak-BCC-algebras (also called BZ-algebras) in which the condition (x∗y)∗z = (x∗z)∗y is satisfied only in the case when elements x, y belong to the same branch. We also characterize ideals, nilradicals, and nilpotent elements of such algebras. PMID:24311983

  20. Experimental and numerical characterization of anisotropic damage evolution of forged Al6061-T6 alloy

    International Nuclear Information System (INIS)

    Shen, Y.; Garnier, J.; Allais, L.; Crepin, J.; Ancelet, O.; Hiver, J.M.

    2011-01-01

    Aluminum alloy 6061-T6 (Al-Mg-Si) has been selected as the material of the vessel for the construction of Jules-Horowitz material testing reactor. Fracture mechanism of this alloy has been investigated using mechanical testing of smooth and notched tensile specimens loaded in different directions. A strong anisotropic fracture behavior has been observed. Microstructural studies using tomography and image analysis have shown a presence of anisotropic distributed coarse precipitates which is the key microstructural feature affecting the damage evolution. These observations were complemented by investigations on fractured tensile samples. A damage scenario of anisotropic growth and coalescence of voids is proposed to explain the fracture behavior associated with the distribution of precipitates. A GTN (Gurson-Tvergaard-Needleman) damage model is used to simulate this scenario and to predict damage evolution. (authors)

  1. Laser-induced damage thresholds of gold, silver and their alloys in air and water

    Energy Technology Data Exchange (ETDEWEB)

    Starinskiy, Sergey V.; Shukhov, Yuri G.; Bulgakov, Alexander V., E-mail: bulgakov@itp.nsc.ru

    2017-02-28

    Highlights: • Laser damage thresholds of Ag, Au and Ag-Au alloys in air and water are measured. • Alloy thresholds are lower than those of Ag and Au due to low thermal conductivity. • Laser damage thresholds in water are ∼1.5 times higher than those in air. • Light scattering mechanisms responsible for high thresholds in water are suggested. • Light scattering mechanisms are supported by optical reflectance measurements. - Abstract: The nanosecond-laser-induced damage thresholds of gold, silver and gold-silver alloys of various compositions in air and water have been measured for single-shot irradiation conditions. The experimental results are analyzed theoretically by solving the heat flow equation for the samples irradiated in air and in water taking into account vapor nucleation at the solid-water interface. The damage thresholds of Au-Ag alloys are systematically lower than those for pure metals, both in air and water that is explained by lower thermal conductivities of the alloys. The thresholds measured in air agree well with the calculated melting thresholds for all samples. The damage thresholds in water are found to be considerably higher, by a factor of ∼1.5, than the corresponding thresholds in air. This cannot be explained, in the framework of the used model, neither by the conductive heat transfer to water nor by the vapor pressure effect. Possible reasons for the high damage thresholds in water such as scattering of the incident laser light by the vapor-liquid interface and the critical opalescence in the superheated water are suggested. Optical pump-probe measurements have been performed to study the reflectance dynamics of the surface irradiated in air and water. Comparison of the transient reflectance signal with the calculated nucleation dynamics provides evidence that the both suggested scattering mechanisms are likely to occur during metal ablation in water.

  2. Micromechanics-Based Damage Analysis of Fracture in Ti5553 Alloy with Application to Bolted Sectors

    OpenAIRE

    Ben Bettaieb, Mohamed; Van Hoof, Thibaut; Minnebo, Hans; Pardoen, Thomas; Dufour, Philippe; Jacques, Pascal; Habraken, Anne-Marie

    2015-01-01

    A physics-based, uncoupled damage model is calibrated using cylindrical notched round tensile specimens made of Ti5553 and Ti-6Al-4V alloys. The fracture strain of Ti5553 is lower than for Ti-6Al-4V in the full range of stress triaxiality. This lower ductility originates from a higher volume fraction of damage sites. By proper heat treatment, the fracture strain of Ti5553 increases by almost a factor of two, as a result of a larger damage nucleation stress. This result proves the potential fo...

  3. Subthreshold displacement damage in copper--aluminum alloys during electron irradiation

    International Nuclear Information System (INIS)

    Drosd, R.; Kosel, T.; Washburn, J.

    1976-12-01

    During electron irradiation at low energies which results in a negligible damage rate in a pure material, lighter solute atoms are displaced, which may in turn indirectly displace solvent atoms by a focussed replacement collision or an interstitial diffusion jump. The extent to which lighter solute atoms contribute to the subthreshold damage rate has been examined by irradiating copper--aluminum alloys at high temperatures in a high voltage electron microscope. The damage rate, as measured by monitoring the growth rate of dislocation loops, at 300 kV was found to increase linearly with the aluminum concentration

  4. Self healing of damage in Fe-based alloys

    NARCIS (Netherlands)

    Zhang, S.

    2015-01-01

    Steel components can exhibit premature and low-ductility creep fracture, when exposed to high temperatures for long times. The failure arises from the formation, growth and coalescence of ultra-fine cracks and cavities. Self healing of damage is a promising new approach to enhance the lifetime of

  5. Damage in Creep Aging Process of an Al-Zn-Mg-Cu Alloy: Experiments and Modeling

    Directory of Open Access Journals (Sweden)

    Chao Lei

    2018-04-01

    Full Text Available In creep age forming (CAF, large integral panel components of high-strength aluminum alloy can be shaped and strengthened under external elastic loading at an elevated temperature through creep deformation and age hardening, simultaneously. However, the high ribbed structure on panel may induce stress concentration, inhomogeneous plastic deformation and even damage evolution on the bending rib, leading to the difficulty in controlling forming precision and material properties. Therefore, the generation and evolution of damage are necessary to be considered in the design of CAF. Taking 7050 aluminum alloy as the case material, the continuous and interrupted creep aging tests at 165 °C and three stress levels (300, 325, and 350 MPa were conducted, and the corresponding material properties, precipitate, and damage microstructures were studied by mechanical properties tests, transmission electron microscope (TEM and scanning electron microscope (SEM characterizations. With the increase of stress level, the creep deformation occurs easier, the precipitates grow up faster, the creep damage occurs earlier, the growth rate and the size of microvoids increase, the mechanical properties decrease more rapidly, and the dominant mechanism of creep fracture changes from shear to microvoid coalescence. To simulate creep aging behavior with damage, a continuum damage mechanics (CDM based model is calibrated and numerically implemented into ABAQUS solver via CREEP subroutine. The CAF of 7050 aluminum alloy panels with different height ribs were conducted by experiment and FE simulation. The forming process presents a typical stress relaxation phenomenon. The creep damage mainly occurs on the bending rib due to the severe stress concentration. With the increase of rib height, the creep strain and damage degree increase, but the springback decreases.

  6. Study on creep damage behaviors of Ni-based alloy C276

    International Nuclear Information System (INIS)

    Mao Xueping; Guo Qi; Zhang Shengyuan; Hu Suyang; Lu Daogang; Xu Hong

    2013-01-01

    High temperature creep tests were carried out for Ni-based alloy C276 at 650℃, 700℃ and 750℃, which is one of the candidate materials for the fuel cladding of the supercritical water reactor. Methods of damage mechanics were adopted to calculate and analyze these data. Damage factors calculated by Kachanov formula and Norton formula based on θ projection method were compared. The results show that the damage factors about the material are similar at the three temperatures according to Kachanov formula. The predicted creep curves calculated by θ projection method have a close agreement with the experimental data. The damages calculated by Norton formula start at about 0.3 - 0.4 lifetime, and the damage factors calculated by Kachanov formula are relatively conservative. (authors)

  7. Laser-induced damage thresholds of gold, silver and their alloys in air and water

    Science.gov (United States)

    Starinskiy, Sergey V.; Shukhov, Yuri G.; Bulgakov, Alexander V.

    2017-02-01

    The nanosecond-laser-induced damage thresholds of gold, silver and gold-silver alloys of various compositions in air and water have been measured for single-shot irradiation conditions. The experimental results are analyzed theoretically by solving the heat flow equation for the samples irradiated in air and in water taking into account vapor nucleation at the solid-water interface. The damage thresholds of Au-Ag alloys are systematically lower than those for pure metals, both in air and water that is explained by lower thermal conductivities of the alloys. The thresholds measured in air agree well with the calculated melting thresholds for all samples. The damage thresholds in water are found to be considerably higher, by a factor of ∼1.5, than the corresponding thresholds in air. This cannot be explained, in the framework of the used model, neither by the conductive heat transfer to water nor by the vapor pressure effect. Possible reasons for the high damage thresholds in water such as scattering of the incident laser light by the vapor-liquid interface and the critical opalescence in the superheated water are suggested. Optical pump-probe measurements have been performed to study the reflectance dynamics of the surface irradiated in air and water. Comparison of the transient reflectance signal with the calculated nucleation dynamics provides evidence that the both suggested scattering mechanisms are likely to occur during metal ablation in water.

  8. Slip transmission in bcc FeCr polycrystal

    Energy Technology Data Exchange (ETDEWEB)

    Patriarca, Luca, E-mail: luca.patriarca@polimi.it [Politecnico di Milano, Department of Mechanical Engineering, Via La Masa 34, I-20156 Milano (Italy); Abuzaid, Wael; Sehitoglu, Huseyin [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206W. Green St., Urbana, IL 61801 (United States); Maier, Hans J. [Institut für Werkstoffkunde, Leibniz Universität Hannover, An der Universität 2, D-30823 Garbsen (Germany)

    2013-12-20

    Grain boundaries induce heterogeneities in the deformation response of polycrystals. Studying these local variations in response, measured through high resolution strain measurement techniques, is important and can improve our understanding of fatigue damage initiation in the vicinity of grain boundaries and material hardening. In this work, strain fields across grain boundaries were measured using advanced digital image correlation techniques. In conjunction with strain measurements, grain orientations from electron back-scattered diffraction were used to establish the dislocation reactions at each boundary, providing the corresponding residual Burgers vectors due to slip transmission across the interfaces. A close correlation was found between the magnitude of the residual Burgers vector and the local strain change across the boundary. When the residual Burgers vector magnitude (with respect to the lattice spacing) exceeds 1.0, the high strains on one side of the boundary are paired with low strains across the boundary, indicating the difficulties for slip dislocations to penetrate the grain interfaces. When the residual Burgers vector approaches zero, the strain fields vary smoothly across the boundary due to limited resistance to slip transmission. The results suggest that the residual Burgers vector magnitude, which relates to the GB (Grain Boundary) resistance to slip transmission, enables a quantitative analysis of the accumulation of strain at the microstructural level and the development of strain heterogeneities across grain boundaries. The results are presented for FeCr bcc alloy which exhibits single slip per grain making the measurements and dislocation reactions rather straightforward. The work points to the need to incorporate details of slip dislocation–grain boundary interaction (slip transmission) in modeling research.

  9. Microstructure and damage behavior of W-Cr alloy under He irradiation

    Science.gov (United States)

    Huang, Ke; Luo, Lai-Ma; Zan, Xiang; Xu, Qiu; Liu, Dong-Guang; Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng

    2018-04-01

    In this study, a large-power inductively coupled plasma source was designed to perform the continuous helium ion irradiations of W-Cr binary alloy (W-20 wt%Cr) under relevant conditions of the International Thermonuclear Experimental Reactor. Surface damages and microstructures of irradiated W-20Cr were observed by using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The addition of Cr dramatically enhanced the micro-hardness of the obtained bulk materials, and the interface between the W matrix and the second phase Cr-O is a semi-coherent interface. After irradiation, the doping of Cr element effectively reduces the damage of the W matrix during the irradiation process. The semi-coherent interface between the second phase and the W matrix improves the anti-irradiation performance of the W-20Cr alloy.

  10. Hydrogen storage in TiCr1.2(FeV)x BCC solid solutions

    International Nuclear Information System (INIS)

    Santos, Sydney F.; Huot, Jacques

    2009-01-01

    The Ti-V-based BCC solid solutions have been considered attractive candidates for hydrogen storage due to their relatively large hydrogen absorbing capacities near room temperature. In spite of this, improvements of some issues should be achieved to allow the technological applications of these alloys. Higher reversible hydrogen storage capacity, decreasing the hysteresis of PCI curves, and decrease in the cost of the raw materials are needed. In the case of vanadium-rich BCC solid solutions, which usually have large hydrogen storage capacities, the search for raw materials with lower cost is mandatory since pure vanadium is quite expensive. Recently, the substitutions of vanadium in these alloys have been tried and some interesting results were achieved by replacing vanadium by commercial ferrovanadium (FeV) alloy. In the present work, this approach was also adopted and TiCr 1.2 (FeV) x alloy series was investigated. The XRD patterns showed the co-existence of a BCC solid solution and a C14 Laves phase in these alloys. SEM analysis showed the alloys consisted of dendritic microstructure and C14 colonies. The amount of C14 phase increases when the amount of (FeV) decreases in these alloys. Concerning the hydrogen storage, the best results were obtained for the TiCr 1.2 (FeV) 0.4 alloy, which achieved 2.79 mass% of hydrogen storage capacity and 1.36 mass% of reversible hydrogen storage capacity

  11. Analysis of the cyclic behavior and fatigue damage of extruded AA2017 aluminum alloy

    International Nuclear Information System (INIS)

    May, A.; Taleb, L.; Belouchrani, M.A.

    2013-01-01

    The present work is devoted to study the anisotropic behavior of an extruded aluminum alloy under cyclic loading in axial and shear directions. In first, we have studied its elastoplastic behavior through the evolution of stress–strain loops, isotropic and kinematic hardening and we have associated this behavior with the evolution of its elastic adaptation (shakedown). In second, we have studied the behavior of the material in fatigue damage using the evolution of stiffness. Finally, microstructural investigations were performed on fractured surfaces using scanning electron microscope (SEM) in order to understand the evolution of fatigue damage during cyclic loading

  12. Irradiation damage behavior of low alloy steel wrought and weld materials

    International Nuclear Information System (INIS)

    Stofanak, R.J.; Poskie, T.J.; Li, Y.Y.; Wire, G.L.

    1993-01-01

    A study was undertaken to evaluate the irradiation damage response of several different types of low alloy steel: vintage type ASTM A302 Grade B (A302B) plates and welds containing different Ni and Cu concentrations, 3.5% Ni steels similar to ASTM A508 Class 4, welds containing about 1% Ni (similar to type 105S), and 3.5% Ni steels with ''superclean'' composition. All materials were irradiated at several different irradiation damage levels ranging from 0.0003 to 0.06 dpa at 232C (450F). Complete Charpy V-notch impact energy transition temperature curves were generated for all materials before and after irradiation to determine transition temperature at 4IJ (30 ft-lb) or 47J (35 ft-lb) and the upper shelf energy. Irradiation damage behavior was measured by shift in Charpy 41J or 47J transition temperature (ΔTT4 41J or ΔTT 47J ) and lowering of upper shelf Charpy energy at a given irradiation damage level. It was found that chemical composition greatly influenced irradiation damage behavior; highest irradiation damage (greatest ΔTT) was found in an A302B type weld containing 1.28% Ni and 0.20% Cu while the least damage was found in 3.5% Ni, 0.05% Cu, superclean wrought materials. Combination of Ni and Cu was found to affect irradiation damage behavior at higher irradiation damage levels in the A302B welds where the 1.28% Ni, 0.20% Cu weld showed more damage than a 0.60% Ni, 0.31% Cu weld. For the 3.5% Ni steels, fabrication influenced irradiation behavior in that a silicon (Si) killed material showed greater irradiation damage than a low silicon material. In general, the 3.5% Ni materials with low copper showed less irradiation damage than the A302B materials

  13. Damage Tolerance Behavior of Friction Stir Welds in Aluminum Alloys

    Science.gov (United States)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process used in the fabrication of various aerospace structures. Self-reacting and conventional friction stir welding are variations of the friction stir weld process employed in the fabrication of cryogenic propellant tanks which are classified as pressurized structure in many spaceflight vehicle architectures. In order to address damage tolerance behavior associated with friction stir welds in these safety critical structures, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data describing fracture behavior, residual strength capability, and cyclic mission life capability of friction stir welds at ambient and cryogenic temperatures have been generated and will be presented in this paper. Fracture behavior will include fracture toughness and tearing (R-curve) response of the friction stir welds. Residual strength behavior will include an evaluation of the effects of lack of penetration on conventional friction stir welds, the effects of internal defects (wormholes) on self-reacting friction stir welds, and an evaluation of the effects of fatigue cycled surface cracks on both conventional and selfreacting welds. Cyclic mission life capability will demonstrate the effects of surface crack defects on service load cycle capability. The fracture data will be used to evaluate nondestructive inspection and proof test requirements for the welds.

  14. Evaluation on microscopic damage and fabrication process of shape memory alloy

    International Nuclear Information System (INIS)

    Lee, Jin Kyung; Choi, Il Kook; Park, Young Chul; Lee, Kyu Chang; Lee, Jun Hyun

    2002-01-01

    Shape memory alloy has been used to improve the tensile strength of composite by the occurrence of compressive residual stress in matrix using its shape memory effect. In order to fabricate shape memory alloy composite, TiNi alloy and Al6061 were used as reinforcing material and matrix, respectively. In this study, TiNi/Al6061 shape memory alloy composite was made by using hot press method. However, the specimen fabricated by this method had the bonding problem at tile boundary between TiNi fiber anti Al matrix when the load was applied to it. A cold rolling was imposed to the specimen to improve the bonding effort. It was found that tensile strength of specimen subjected to cold rolling was more increased than that of specimen which did not underwent cold rolling. In addition, acoustic emission technique was used to quantify the microscopic damage behavior of cold rolled TiNi/Al6061 shape memory alloy composite at high temperature.

  15. Quantification of stress-induced damage and post-fire response of 5083 aluminum alloy

    International Nuclear Information System (INIS)

    Chen, Y.; Puplampu, S.B.; Summers, P.T.; Lattimer, B.Y.; Penumadu, D.; Case, S.W.

    2015-01-01

    One of the major concerns regarding the use of lightweight materials in ship construction is the response of those materials to fire scenarios, including the residual structural performance after a fire event. This paper presents a study on creep damage evolution in 5083 marine-grade aluminum alloy and its impact on residual mechanical behavior. Tests conducted at 400 °C and pre-selected tensile stress levels were interrupted at target amplitudes of accumulated engineering creep strains to investigate the stress-induced damage using ex-situ characterization. Two-dimensional optical and electron microscopy and three-dimensional X-ray tomography were utilized on samples extracted from these test specimens to characterize the external and internal creep damage. The stress-induced damage is primarily manifested as cavitation and dynamic microstructural evolution. Cavitation morphology, orientation and grain structure evolution were investigated on three perpendicular sample surfaces. A 3D examination of the damage state provided consistent damage information to that obtained from the 2D analysis. The post-fire mechanical properties were also evaluated and linked to the microstructural change. The competing processes of cavitation and grain structure evolution were investigated to develop an understanding of the stress-induced damage associated with high temperature creep

  16. Quantification of stress-induced damage and post-fire response of 5083 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y., E-mail: yanyun@vt.edu [Department of Engineering Science & Mechanics, Virginia Tech, Blacksburg, VA 24061 (United States); Puplampu, S.B. [Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Summers, P.T.; Lattimer, B.Y. [Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061 (United States); Penumadu, D. [Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Case, S.W. [Department of Engineering Science & Mechanics, Virginia Tech, Blacksburg, VA 24061 (United States)

    2015-08-12

    One of the major concerns regarding the use of lightweight materials in ship construction is the response of those materials to fire scenarios, including the residual structural performance after a fire event. This paper presents a study on creep damage evolution in 5083 marine-grade aluminum alloy and its impact on residual mechanical behavior. Tests conducted at 400 °C and pre-selected tensile stress levels were interrupted at target amplitudes of accumulated engineering creep strains to investigate the stress-induced damage using ex-situ characterization. Two-dimensional optical and electron microscopy and three-dimensional X-ray tomography were utilized on samples extracted from these test specimens to characterize the external and internal creep damage. The stress-induced damage is primarily manifested as cavitation and dynamic microstructural evolution. Cavitation morphology, orientation and grain structure evolution were investigated on three perpendicular sample surfaces. A 3D examination of the damage state provided consistent damage information to that obtained from the 2D analysis. The post-fire mechanical properties were also evaluated and linked to the microstructural change. The competing processes of cavitation and grain structure evolution were investigated to develop an understanding of the stress-induced damage associated with high temperature creep.

  17. Welding and joining of single crystals of BCC refractory metals

    International Nuclear Information System (INIS)

    Hiraoka, Yutaka; Fujii, Tadayuki

    1989-01-01

    Welding and joining is one of key technologies for the wider utilizations of a material. In the present work, the applicability of welding and joining for a single crystal of BCC refractory metal was investigated. Electron-beam welding and tungsten-inert-gas welding by a melt-run technique, and high-temperature brazing by using brazing metals such as Mo-40%Ru alloy, vanadium or platinum were conducted for molybdenum single crystal which had been prepared by means of secondary recrystallization. 12 refs.,12 figs., 2 tabs. (Author)

  18. Impact damage resistance and damage suppression properties of shape memory alloys in hybrid composites—a review

    International Nuclear Information System (INIS)

    Angioni, S L; Meo, M; Foreman, A

    2011-01-01

    Composite materials are known to have a poor resistance to through-the-thickness impact loading. There are various methods for improving their impact damage tolerance, such as fiber toughening, matrix toughening, interface toughening, through-the-thickness reinforcements, and selective interlayers and hybrids. Hybrid composites with improved impact resistance are particularly useful in military and commercial civil applications. Hybridizing composites using shape memory alloys (SMA) is one solution since SMA materials can absorb the energy of the impact through superelastic deformation or recovery stress, reducing the effects of the impact on the composite structure. The SMA material may be embedded in the hybrid composites (SMAHC) in many different forms and also the characteristics of the fiber reinforcements may vary, such as SMA wires in woven laminates or SMA foils in unidirectional laminates, only to cite two examples. We will review the state of the art of SMAHC for the purpose of damage suppression. Both the active and passive damage suppression mechanisms will be considered. (topical review)

  19. Influence of Radiation Damage and Isochronal Annealing on the Magnetic Susceptibility of Pu1-xAmx Alloys

    International Nuclear Information System (INIS)

    McCall, Scott K.; Fluss, Michael J.; Chung, Brandon W.; Haire, Richard G.

    2008-01-01

    Results of radiation damage in Pu and Pu 1-x Am x alloys studied with magnetic susceptibility, χ(T), and resistivity are presented. Damage accumulated at low temperatures increases χ(T) for all measured alloys, with the trend generally enhanced as the lattice expands. There is a trend towards saturation observable in the damage induced magnetic susceptibility data. that is not evident in similar damage induced resistivity data taken on the same specimen. A comparison of isochronal annealing curves measured by both resistivity and magnetic susceptibility on a 4.3 at% Ga stabilized δ-Pu specimen show that Stage I annealing, where interstitials begin to move, is largely transparent to the magnetic measurement. This indicates that interstitials have little impact on the damage induced increase in the magnetic susceptibility. The isochronal annealing curves of the Pu 1-x Am x alloys do not show distinct annealing stages as expected for alloys. However, samples near 20% Am concentration show an unexpected increase in magnetization beginning when specimens are annealed to 35 K. This behavior is also reflected in a time dependent increase in the magnetic susceptibility of damaged specimens indicative of first order kinetics. These results suggest there may be a metastable phase induced by radiation damage and annealing in Pu 1-x Am x alloys. (authors)

  20. Radiation damage simulation studies of selected austenitic and ferritic/martensitic alloys for fusion reactor structural applications

    International Nuclear Information System (INIS)

    Mazey, D.J.; Walters, G.P.; Buckley, S.N.; Bullough, R.; Hanks, W.; Bolster, D.E.J.; Sowden, B.C.; Lurcook, D.; Murphy, S.M.

    1985-03-01

    Results are given of an investigation of the radiation damage stability of selected austenitic and ferritic alloys following ion bombardment in the Harwell VEC to simulate fusion-reactor exposures up to 110 dpa at temperatures from 425 deg to 625 deg C. Gas production rates appropriate to CTR conditions were simulated using a mixed beam of (4 MeV He + 2 MeV H 2 ) in the ratio 1:4 He:H. A beam of 46 MeV Ni or 20 MeV Cr ions was used in sequence with the mixed gas beam to provide a gas/damage ratio of 13 appm He/dpa at a damage rate of approx. 1 dpa/hr. The materials were investigated using TEM and comprised three austenitic alloys: European reference 316L, 316-Ti, 316-Nb; four high-nickel alloys: Fe/25 Ni/8Cr, Inconel 625, Inconel 706 and Nimonic PE16, and four ferritic/martensitic alloys: FV 448, FV 607, CRM 12 and FI. Some data were obtained for a non-magnetic structural alloy Nonmagne-30. The swelling behaviour is reported. The overall results of the study indicate that on a comparative basis the ferritic alloys are the most swelling-resistant, whilst the high-nickel alloys have an acceptable low swelling response up to 110 dpa. The 316 alloys tested have shown an unfavourable swelling response. (author)

  1. Quantitative assessment of intergranular damage due to PWR primary water exposure in structural Ni-based alloys

    International Nuclear Information System (INIS)

    Ter-Ovanessian, Benoît; Deleume, Julien; Cloué, Jean-Marc; Andrieu, Eric

    2013-01-01

    Highlights: ► IG damage occurred on Ni-base alloys during exposure at high temperature water. ► Two characterization methods yield a tomographic analysis of this IG damage. ► Connected or isolated intergranular oxygen/oxide penetrations are quantified. ► Such quantitative description provides information on IGSCC susceptibility. - Abstract: Two nickel-based alloys, alloy 718 and alloy 600, known to have different resistances to IGSCC, were exposed to a simulated PWR primary water environment at 360 °C for 1000 h. The intergranular oxidation damage was analyzed in detail using an original approach involving two characterization methods (Incremental Mechanical Polishing/Microcopy procedure and SIMS imaging) which yielded a tomographic analysis of the damage. Intergranular oxygen/oxide penetrations occurred either as connected or isolated penetrations deep under the external oxide/substrate interface as far as 10 μm for alloy 600 and only 4 μm for alloy 718. Therefore, assessing this damage precisely is essential to interpret IGSCC susceptibility.

  2. Emergency repair of severely damaged reinforced concrete columns using active confinement with shape memory alloys

    International Nuclear Information System (INIS)

    Shin, Moochul; Andrawes, Bassem

    2011-01-01

    This experimental study focuses on investigating the feasibility of utilizing spirals made of shape memory alloys (SMAs) to conduct emergency repair on severely damaged reinforced concrete (RC) columns. The thermally triggered shape memory feature of SMAs is sought in this study, to apply active confinement pressure on the column's damaged region. Two severely damaged 1/3-scale RC columns are repaired using the proposed technique and tested under a quasi-static lateral cyclic load. The repair of each column is conducted in less than 15 h, and the columns are tested 24 h after the starting of the repair process. The experimental results show that the new repair technique is successful in either fully restoring the as-built lateral strength, stiffness, and flexural ductility of the columns or making them even better. The efficacy of the proposed repair technique is mainly attributed to the ability of the SMA spirals to apply and maintain active confining pressure on the damaged region of the columns, which increases the strength of the already damaged concrete and delays its damage

  3. Modeling of Stress Development During Thermal Damage Healing in Fiber-reinforced Composite Materials Containing Embedded Shape Memory Alloy Wires

    NARCIS (Netherlands)

    Bor, Teunis Cornelis; Warnet, Laurent; Akkerman, Remko; de Boer, Andries

    2010-01-01

    Fiber-reinforced composite materials are susceptible to damage development through matrix cracking and delamination. This article concerns the use of shape memory alloy (SMA) wires embedded in a composite material to support healing of damage through a local heat treatment. The composite material

  4. Radiation response of alloy T91 at damage levels up to 1000 peak dpa

    Energy Technology Data Exchange (ETDEWEB)

    Gigax, J.G., E-mail: gigaxj@tamu.edu [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77840 (United States); Chen, T.; Kim, Hyosim [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77840 (United States); Wang, J. [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77840 (United States); Pacific Northwest National Lab, Richland, WA 99354 (United States); Price, L.M. [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77840 (United States); Aydogan, E. [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77840 (United States); Los Alamos National Lab, Los Alamos, NM 87545 (United States); Maloy, S.A. [Los Alamos National Lab, Los Alamos, NM 87545 (United States); Schreiber, D.K.; Toloczko, M.B. [Pacific Northwest National Lab, Richland, WA 99354 (United States); Garner, F.A. [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77840 (United States); Radiation Effects Consulting, Richland, WA 99354 (United States); Shao, Lin [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77840 (United States)

    2016-12-15

    Ferritic/martensitic alloys are required for advanced reactor components to survive 500–600 neutron-induced dpa. Ion-induced void swelling of ferritic/martensitic alloy T91 in the quenched and tempered condition has been studied using a defocused, non-rastered 3.5 MeV Fe-ion beam at 475 °C to produce damage levels up to 1000 peak displacements per atom (dpa). The high peak damage level of 1000 dpa is required to reach 500–600 dpa level due to injected interstitial suppression of void nucleation in the peak dpa region, requiring data extraction closer to the surface at lower dpa levels. At a relatively low peak damage level of 250 dpa, voids began to develop, appearing first in the near-surface region. With increasing ion fluence, swelling was observed deeper in the specimen, but remained completely suppressed in the back half of the ion range, even at 1000 peak dpa. The local differences in dpa rate in the front half of the ion range induce an “internal temperature shift” that strongly influences the onset of swelling, with shorter transient regimes resulting from lower dpa rates, in agreement not only with observations in neutron irradiation studies but also in various ion irradiations. Swelling was accompanied by radiation-induced precipitation of Cu-rich and Si, Ni, Mn-rich phases were observed by atom probe tomography, indicating concurrent microchemical evolution was in progress. In comparison to other ferritic/martensitic alloys during ion irradiation, T91 exhibits good swelling resistance with a swelling incubation period of about 400 local dpa.

  5. Radiation response of alloy T91 at damage levels up to 1000 peak dpa

    Energy Technology Data Exchange (ETDEWEB)

    Gigax, J. G.; Chen, T.; Kim, Hyosim; Wang, J.; Price, L. M.; Aydogan, E.; Maloy, S. A.; Schreiber, D. K.; Toloczko, M. B.; Garner, F. A.; Shao, Lin

    2016-12-01

    Ferritic/martensitic alloys are required for advanced reactor components to survive 500e600 neutroninduced dpa. Ion-induced void swelling of ferritic/martensitic alloy T91 in the quenched and tempered condition has been studied using a defocused, non-rastered 3.5 MeV Fe-ion beam at 475 C to produce damage levels up to 1000 peak displacements per atom (dpa). The high peak damage level of 1000 dpa is required to reach 500e600 dpa level due to injected interstitial suppression of void nucleation in the peak dpa region, requiring data extraction closer to the surface at lower dpa levels. At a relatively low peak damage level of 250 dpa, voids began to develop, appearing first in the near-surface region. With increasing ion fluence, swelling was observed deeper in the specimen, but remained completely suppressed in the back half of the ion range, even at 1000 peak dpa. The local differences in dpa rate in the front half of the ion range induce an “internal temperature shift” that strongly influences the onset of swelling, with shorter transient regimes resulting from lower dpa rates, in agreement not only with observations in neutron irradiation studies but also in various ion irradiations. Swelling was accompanied by radiation-induced precipitation of Cu-rich and Si, Ni, Mn-rich phases were observed by atom probe tomography, indicating concurrent microchemical evolution was in progress. In comparison to other ferritic/martensitic alloys during ion irradiation, T91 exhibits good swelling resistance with a swelling incubation period of about 400 local dpa.

  6. Effects of cavitation on damage calculations in ion-irradiated P7 alloy

    International Nuclear Information System (INIS)

    Sindelar, R.L.; Farrens, S.N.; Kulcinski, G.L.

    1985-01-01

    The purpose of this study is to investigate the effect of voids on the depth-dependent damage energy in ion-irradiated metals. Corrections to the dose at the swelling peak will be used to obtain the swelling rate of ion-irradiated 316-type stainless steels. Samples of the P7 alloy were ion-irradiated to four fluence levels up to a peak dose level of 100 dpa at 650 0 C. The depth-dependent void parameters extracted in cross section were used to model the effect of voids on the depth-dependent damage produced during 14 MeV nickel ion irradiation. An increase in the range of damage produced from the original foil surface for the target containing voids was modeled as a first-order correction to the damage profile. A second-order effect, void straggling, was shown to cause a time-dependent decrease in the damage rate at the peak swelling depth. Corrections applied to the dose at the peak swelling depth yield swelling rates approaching 0.7%/dpa

  7. Continuum damage mechanics based approach to the fatigue life prediction of cast aluminium alloy with considering the effect of porosity

    Directory of Open Access Journals (Sweden)

    Wang Xiaojia

    2018-01-01

    Full Text Available A damage mechanics based approach is applied for the study of fatigue behaviour of high pressure die cast ADC12 aluminium alloy. A damage coupled elastoplastic constitutive model is presented according to the concept of effective stress and the hypothesis of strain equivalence. An elastic fatigue damage model taking into account the pore-induced stress concentration is developed to investigate fatigue damage evolution of the specimens subjected to cyclic loading. The predicted lives for the specimens with different sizes of pores are consistent with the experimental data. The pore-induced fatigue damage and the variation of fatigue life along with the size of pores are also investigated.

  8. Creep Damage Evaluation of Titanium Alloy Using Nonlinear Ultrasonic Lamb Waves

    International Nuclear Information System (INIS)

    Xiang Yan-Xun; Xuan Fu-Zhen; Deng Ming-Xi; Chen Hu; Chen Ding-Yue

    2012-01-01

    The creep damage in high temperature resistant titanium alloys Ti60 is measured using the nonlinear effect of an ultrasonic Lamb wave. The results show that the normalised acoustic nonlinearity of a Lamb wave exhibits a variation of the 'increase-decrease' tendency as a function of the creep damage. The influence of microstructure evolution on the nonlinear Lamb wave propagation has been analyzed based on metallographic studies, which reveal that the normalised acoustic nonlinearity increases due to a rising of the precipitation volume fraction and the dislocation density in the early stage, and it decreases as a combined result of dislocation change and micro-void initiation in the material. The nonlinear Lamb wave exhibits the potential for the assessment of the remaining creep life in metals

  9. Evolution of ion damage at 773K in Ni- containing concentrated solid-solution alloys

    Science.gov (United States)

    Shi, Shi; He, Mo-Rigen; Jin, Ke; Bei, Hongbin; Robertson, Ian M.

    2018-04-01

    Quantitative analysis of the impact of the compositional complexity in a series of Ni-containing concentrated solid-solution alloys, Ni, NiCo, NiFe, NiCoCr, NiCoFeCr, NiCoFeCrMn and NiCoFeCrPd, on the evolution of defects produced by 1 MeV Kr ion irradiation at 773 K is reported. The dynamics of the evolution of the damage structure during irradiation to a dose of 2 displacements per atom were observed directly by performing the ion irradiations in electron transparent foils in a transmission electron microscope coupled to an ion accelerator. The defect evolution was assessed through measurement of the defect density, defect size and fraction of perfect and Frank loops. These three parameters were dependent on the alloying element as well as the number of elements. The population of loops was sensitive to the ion dose and alloy composition as faulted Frank loops were observed to unfault to perfect loops with increasing ion dose. These dependences are explained in terms of the influence of each element on the lifetime of the displacement cascade as well as on defect formation and migration energies.

  10. Applicability of creep damage rules to a nickel-base heat-resistant alloy Hastelloy XR

    International Nuclear Information System (INIS)

    Tsuji, Hirokazu; Nakajima, Najime; Tanabe, Tatsuhiko; Nakasone, Yuji

    1992-01-01

    A series of constant load and temperature creep rupture tests and varying load and/or temperature creep rupture tests was carried out on a nickel-base heat-resistant alloy Hastelloy XR, which was developed for applications in the High-Temperature Engineering Test Reactor, at temperatures ranging from 850 to 1000deg C in order to examine the applicability of the conventional creep damage rules, i.e., the life fraction, the strain fraction and their mixed rules. The life fraction rule showed the best applicability of these three criteria. The good applicability of the rule was considered to result from the fact that the creep strength of Hastelloy XR was not strongly affected by the change of the chemical composition and/or the microstructure during exposure to the high-temperature simulated HTGR helium environment. In conclusion the life fraction rule is applicable in engineering design of high-temperature components made of Hastelloy XR. (orig.)

  11. The effect of C concentration on radiation damage in Fe–Cr–C alloys

    Energy Technology Data Exchange (ETDEWEB)

    Meinander, A., E-mail: andrea.meinander@helsinki.fi [EURATOM-Tekes, Department of Physics, P.O. Box 43, FI-00014 University of Helsinki (Finland); Henriksson, K.O.E. [EURATOM-Tekes, Department of Physics, P.O. Box 43, FI-00014 University of Helsinki (Finland); Björkas, C. [EURATOM-Tekes, Department of Physics, P.O. Box 43, FI-00014 University of Helsinki (Finland); Institute of Energy and Climate Research – Plasma Physics, Forschungszentrum Jülich GmbH, Association EURATOM-FZJ, Partner in the Trilateral Euregio Cluster, Jülich (Germany); Vörtler, K.; Nordlund, K. [EURATOM-Tekes, Department of Physics, P.O. Box 43, FI-00014 University of Helsinki (Finland)

    2013-11-15

    Using a recently developed analytical bond-order potential for the complete ternary system, we performed molecular dynamics simulations of the primary radiation damage by displacement cascades in different Fe–Cr–C model alloys. We compared results obtained with this new potential to previous studies employing potentials for the binary Fe–Cr and Fe–C systems. We analysed the effect of C concentration on the number of Frenkel pairs produced by the cascades, as well as on clustering of vacancies and self-interstitial atoms (SIAs), and on the Cr and C content in the defects. The effect of C concentration on defect production was negligible, except at very high concentrations of over 1 at.% C. The main effect was in the Cr content of clustered SIAs, which increased with increasing C concentration.

  12. Multiscale modeling of radiation damage in Fe-based alloys in the fusion environment

    International Nuclear Information System (INIS)

    Wirth, B.D.; Odette, G.R.; Marian, J.; Ventelon, L.; Young-Vandersall, J.A.; Zepeda-Ruiz, L.A.

    2004-01-01

    Ferritic alloys represent a technologically important class of candidate materials for fusion first wall and blanket structures. A detailed understanding of the mechanisms of defect accumulation and microstructure evolution, and the corresponding effects on mechanical properties is required to predict their in-service structural performance limits. The physical processes involved in radiation damage, and its effects on mechanical properties, are inherently multiscale and hierarchical, spanning length and time scales from the atomic nucleus to meters and picosecond to decades. In this paper, we present a multiscale modeling methodology to describe radiation effects within the fusion energy environment. Selected results from atomic scale investigation are presented, focusing on (i) the mechanisms of self-interstitial dislocation loop formation with Burgers vector of a in iron relative to vanadium, (ii) helium transport and (iii) the interaction between helium and small self-interstitial clusters in iron, and (iv) dislocation-helium bubble interactions in fcc aluminum

  13. Phonon dispersion curves of BCC Ba

    International Nuclear Information System (INIS)

    Mizuki, J.; Stassis, C.; Zarestky, J.

    1985-01-01

    Ba, as well as Sr and Ca, is a divalent alkaline earth metal. At room temperature and ambient pressure, the structure of Ba is bcc, whereas that of Sr and Ca is fcc. Under pressure, the bcc phase of Ba transforms to an hcp structure at 55 kbar. Also, at 37 kbar Ba becomes a superconductor with T/sub c/ = 0.06 K. These properties are highly dependent on the position of the d bands relative to the Fermi level. Experimental investigation of the elastic and lattice dynamical properties of these metals has been hindered by difficulties in growing single crystals. However, recently the authors were able to grow several single crystals of bcc Ba of sufficient volume for inelastic neutron scattering experiments. Some of the results are summarized here

  14. Creep damage evaluation of low alloy steel weld joint by small punch creep testing

    International Nuclear Information System (INIS)

    Nishioka, Tomoya; Sawaragi, Yoshiatsu; Uemura, Hiromi

    2013-01-01

    The effect of sampling location on SPC (Small Punch Creep) tests were investigated for weld joints to establish evaluation method of Type IV creep behavior. The SPC specimen shape was 10mm diameter and 0.5mm thick round disc prepared from weld joints of 2.25Cr-1Mo low alloy steel. It was found that the center of SPC specimen should be 2mm apart from the weld interface as the recommended sampling location. Creep damage was imposed for large weld joint specimens by axial creep loading at 620degC, 52MPa with the interrupted time fraction of 0.34, 0.45, 0.64 and 0.82.SPC samples were prepared from those damaged specimens following the recommended way described in this paper. Among the various SPC tests conducted, good relationships were found for the test condition of 625degC, 200N. Namely, good relationships were obtained both between minimum deflection rate and creep life fraction, and between rupture time and creep life fraction. Consequently, creep life assessment of Type IV fracture by SPC tests could be well conducted using the sampling location and the test condition recommended in this paper. (author)

  15. Micromechanical Modeling of Grain Boundaries Damage in a Copper Alloy Under Creep

    International Nuclear Information System (INIS)

    Voese, Markus

    2015-01-01

    In order to include the processes on the scale of the grain structure into the description of the creep behaviour of polycrystalline materials, the damage development of a single grain boundary has been initially investigated in the present work. For this purpose, a special simulationmethod has been used, whose resolution procedure based on holomorphic functions. The mechanisms taken into account for the simulations include nucleation, growth by grain boundary diffusion, coalescence and shrinkage until complete sintering of grain boundary cavities. These studies have then been used to develop a simplified cavitation model, which describes the grain boundary damage by two state variables and the time-dependent development by a mechanism-oriented rate formulation. To include the influence of grain boundaries within continuum mechanical considerations of polycrystals, an interface model has been developed, that incorporates both damage according to the simplified cavitation model and grain boundary sliding in dependence of a phenomenological grain boundary viscosity. Furthermore a micromechanical model of a polycrystal has been developed that allows to include a material's grain structure into the simulation of the creep behaviour by means of finite element simulations. Thereby, the deformations of individual grains are expressed by a viscoplastic single crystal model and the grain boundaries are described by the proposed interface model. The grain structure is represented by a finite element model, in which the grain boundaries are modelled by cohesive elements. From the evaluation of experimental creep data, the micromechanical model of a polycrystal has been calibrated for a copper-antimony alloy at a temperature of 823 K. Thereby, the adjustment of the single crystal model has been carried out on the basis of creep rates of pure copper single crystal specimens. The experimental determination of grain boundary sliding and grain boundary porosity for coarse

  16. Microstructure damage evolution associated with cyclic deformation for extruded AZ31B magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Ying, E-mail: yxiong@zjut.edu.cn [Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China); College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310032 (China)

    2016-10-15

    Fatigue damage evolution of extruded AZ31B magnesium (Mg) alloy is investigated under strain-controlled tension-compression loading along the extrusion direction at various strain amplitudes, and the different cyclic deformation behaviors are observed. At the strain amplitude of 2%, the tensile peak stress displays significant cyclic softening, whereas the compressive peak stress shows consistent cyclic hardening. At 1%, moderate cyclic hardening is observed at both the tensile peak and compressive peak stresses. At 0.5%, the tensile peak stress presents stable cyclic hardening, whereas the compressive peak stress almost keeps constant. The microstructure morphologies associated with the cyclic deformation are analyzed by scanning electronic microscope (SEM). The degree of deformation twins is evaluated by analyzing X-ray diffraction (XRD) using a normalized parameter λ. The results show the fatigue crack initiation modes and its propagation modes are dependent on the strain amplitude. At 2%, grain boundary (GB) cracking and triple joint cracking are detected after 1st loading cycle. At 1%, fatigue crack initiates at grain boundary (GB cracking), twin boundary (TB cracking) and triple joint of three neighboring grains. Both grain boundary induced (GB-induced) intergranular and persistent slip band induced (PSB-induced) transgranular propagation modes play an important role in the early-stage crack growth. At 0.5%, crack initiation modes are similar to that at 1%, but GB-induced intergranular propagation mode dominates the early-stage crack growth. The effects of the microstructure (texture, grain size and uniformity) on the fatigue damage behavior are discussed.

  17. Ductile damage in aluminium alloy thin sheets: Correlation between micro-tomography observations and mechanical modeling

    International Nuclear Information System (INIS)

    Thuillier, S.; Maire, E.; Brunet, M.

    2012-01-01

    This work deals with the characterization of ductile damage in an aluminium alloy AA6016-T4 by X-ray micro-tomography, as a function of anisotropy and triaxiality. Interrupted tensile tests on notched samples with three different geometries were performed and the void volume fraction was measured for different strain values, up to rupture. It was shown that void volume fraction evolution with the strain is rather similar at 0° and 90° to RD but at 45° to RD it shows a more rapid evolution. Moreover, for the same strain level, a higher void volume fraction was recorded for a higher triaxiality ratio. Whatever the orientation and the stress triaxiality ratio, void volume fraction values range from 5×10 −4 up to 0.04. A numerical model based on Gurson–Tvergaard–Needleman constitutive equations was used to simulate the different tests. Hardening of the material was identified from macroscopic tensile test nucleation material parameters were identified by a direct method from void volume fraction evolution. It can be seen that the influence of triaxiality on void volume fraction is underestimated, though void growth is nicely predicted for the highest triaxiality ratio, for strains below 0.5. The load level was correctly predicted, except for high strain, where coalescence seems necessary to be taken into account.

  18. Damage Tolerance Assessment of Friction Pull Plug Welds in an Aluminum Alloy

    Science.gov (United States)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process used in the fabrication of cryogenic propellant tanks. Self-reacting friction stir welding is one variation of the friction stir weld process being developed for manufacturing tanks. Friction pull plug welding is used to seal the exit hole that remains in a circumferential self-reacting friction stir weld. A friction plug weld placed in a self-reacting friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data relating residual strength capability to flaw size in an aluminum alloy friction plug weld will be presented.

  19. Stress induced martensitic transformation from bcc to fcc in Ag-Zn

    International Nuclear Information System (INIS)

    Takezawa, K.; Akamatsu, R.; Marukawa, K.

    1995-01-01

    The martensitic transformation in Ag-Zn alloys of low-Zn content has been studied by optical and electron microscopic observations and by tensile tests. The β 1 phase of B2 structure transforms to the thermo-elastic martensite having 9R structure similar to Cu-based alloys upon cooling to temperature below Ms. When the β 1 phase is stretched at room temperature, the slip deformation occurs at first and then the stress-induced martensite(SIM) of wedge-like morphology forms. The SIM has the ordered fcc structure containing micro-twins. This direct transformation from bcc to fcc is a unique feature in Ag-Zn alloys. In Cu alloys, martensites of fcc structure appear only after the second transformation from the first transformation product of 9R structure. The critical stress for the martensitic transformation and a degree of order of SIM decrease as the deformation temperature rises. In Ag-Zn alloys, the martensite of disordered fcc is thermally produced also by up-quenching to a higher temperature. In the present study, the relation between martensites of ordered and disordered fcc is discussed through thermodynamical calculations. The condition for the direct transformation from bcc to fcc is also examined. (orig.)

  20. Modeling the long-term evolution of the primary damage in ferritic alloys using coarse-grained methods

    International Nuclear Information System (INIS)

    Becquart, C.S.; Barbu, A.; Bocquet, J.L.; Caturla, M.J.; Domain, C.; Fu, C.-C.; Golubov, S.I.; Hou, M.; Malerba, L.; Ortiz, C.J.; Souidi, A.; Stoller, R.E.

    2010-01-01

    Knowledge of the long-term evolution of the microstructure after introduction of primary damage is an essential ingredient in understanding mechanical property changes that occur during irradiation. Within the European integrated project 'PERFECT,' different techniques have been developed or improved to model microstructure evolution of Fe alloys under irradiation. This review paper aims to present the current state of the art of these techniques, as developed in the project, as well as the main results obtained.

  1. Assessment of the structural relations between the bcc and omega phases of Ti, Zr, Hf and other transition metals

    International Nuclear Information System (INIS)

    Aurelio, G.; Guillermet, A.F.

    2000-01-01

    The name omega (Ω) phase refers to a high-pressure structural modification of the transition metals (TMs) Ti, Zr, and Hf. In alloys of Ti, Zr and Hf with other TMs, the Ω phase can be formed and retained metastably at room temperature by quenching the bcc structure, which is usually the stable high-temperature phase in these alloy systems. As a part of a systematic investigation of the structural and bonding properties of the bcc and Ω phases, and of the bcc → Ω phase transformation in TMs and alloys, we present in this paper a detailed analysis of the structural relations between these phases in Ti, Zr, Hf and in other TMs. The approach is as follows. First, we establish the most general geometrical relations connecting the lattice parameters and interatomic distances (IDs) of the bcc and Ω structures. Next, we focus on the ratio between the relevant IDs of these phases, which are assessed on the basis of an extensive database with experimental and theoretical information. Both stable and metastable structures are considered, and various remarkable regularities in ID ratios are discussed. Finally, in the light of the systematics of ID ratios established in the present work, a discussion is made of the probable lattice parameters for the Ω phase of Hf, which are not yet accurately known from direct measurements. (orig.)

  2. Depth distribution of displacement damage in α-iron under triple beam ion irradiation

    International Nuclear Information System (INIS)

    Horton, L.L.; Bentley, J.; Jesser, W.A.

    1981-01-01

    The depth dependence of the defect structures was determined for iron irradiated at 850 0 K with 4 MeV Fe 2+ and energetic helium and deuteron ions to 10 dpa and fusion levels of helium and deuterium. From the damage profiles, a sectioning depth of 0.9 μm was selected for studies of iron and bcc iron alloys, such as ferritic steels, utilizing similar irradiation parameters. A comparison of the experimental damage profile to the deposited energy and deposited ion profiles calculated by E-DEP-1 indicated a possible overestimate of the LSS stopping power of at least 22%

  3. High Cycle Fatigue Performance in Laser Shock Peened TC4 Titanium Alloys Subjected to Foreign Object Damage

    Science.gov (United States)

    Luo, Sihai; Nie, Xiangfan; Zhou, Liucheng; Li, Yiming; He, Weifeng

    2018-03-01

    During their service, titanium alloys are likely to suffer from the foreign object damage (FOD), resulting in a decrease in their fatigue strength. Laser shock peening (LSP) has been proved to effectively increase the damage tolerance of military engine components by introducing a magnitude compressive residual stress in the near-surface layer of alloys. In this paper, smooth specimens of a TC4 titanium alloy were used and treated by LSP and subsequently exposed to FOD, which was simulated by firing a steel sphere with a nominal velocity of 300 m/s, at 90° with the leading edge of the LSP-treated region using a light gas gun. All impacted specimens were then subjected to fatigue loading. The results showed that LSP could effectively improve the fatigue strength of the damaged specimens. The effect of LSP on the fatigue strength was assessed through fracture observations, microhardness tests and residual stress analyses. The residual stresses due to the plastic deformation caused by LSP and the FOD impact, which were found to play a crucial role on the fatigue strength, were determined using the commercial software ABAQUS.

  4. Premelting hcp to bcc Transition in Beryllium

    Science.gov (United States)

    Lu, Y.; Sun, T.; Zhang, Ping; Zhang, P.; Zhang, D.-B.; Wentzcovitch, R. M.

    2017-04-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to x-ray equipment. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp → bcc transition occurs near the melting curve at 0 materials.

  5. Design and screening of nanoprecipitates-strengthened advanced ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yang, Ying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chen, Tianyi [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sridharan, K. [Univ. of Wisconsin, Madison, WI (United States); He, Li [Univ. of Wisconsin, Madison, WI (United States)

    2016-12-30

    Advanced nuclear reactors as well as the life extension of light water reactors require advanced alloys capable of satisfactory operation up to neutron damage levels approaching 200 displacements per atom (dpa). Extensive studies, including fundamental theories, have demonstrated the superior resistance to radiation-induced swelling in ferritic steels, primarily inherited from their body-centered cubic (bcc) structure. This study aims at developing nanoprecipitates strengthened advanced ferritic alloys for advanced nuclear reactor applications. To be more specific, this study aims at enhancing the amorphization ability of some precipitates, such as Laves phase and other types of intermetallic phases, through smart alloying strategy, and thereby promote the crystalline®amorphous transformation of these precipitates under irradiation.

  6. Effect of hardening induced by cold expansion on damage fatigue accumulation and life assessment of Aluminum alloy 6082 T6

    Directory of Open Access Journals (Sweden)

    Bendouba Mostefa

    2012-12-01

    Full Text Available Hole cold expansion (HCE is an effective method to extend the fatigue life of mechanical structures. During cold expansion process compressive residual stresses around the expanded hole are generated. The enhancement of fatigue life and the crack initiation and growth behavior of a holed specimen were investigated by using the 6082 Aluminum alloy. The present study suggests a simple technical method for enhancement of fatigue life by a cold expansion hole of pre-cracked specimen. Fatigue damage accumulation of cold expanded hole in aluminum alloy which is widely used in transportation and in aeronautics was analyzed. Experimental tests were carried out using pre-cracked SENT specimens. Tests were performed in two and four block loading under constant amplitude. These tests were performed by using two and four blocks under uniaxial constant amplitude loading. The increasing and decreasing loading were carried. The experimental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the 'damaged stress model', which takes into account the loading history, yields a good estimation according to the experimental results. Moreover, the error is minimized in comparison to the Miner's model.

  7. First-principles study of atomic ordering in bcc Cu-Al

    Science.gov (United States)

    Lanzini, F.; Gargano, P. H.; Alonso, P. R.; Rubiolo, G. H.

    2011-01-01

    The order-disorder transitions and phase stability in the body centered cubic structure of Cu-Al binary alloys are studied by means of theoretical methods. The total energy of different ordered compounds sharing a common bcc Bravais lattice was calculated within the framework of density functional theory. A set of effective cluster interactions was calculated through a cluster expansion (CE) of the total energies. The finite temperature phase diagram of bcc Cu-Al was obtained using the CE formalism coupled with the cluster variation method calculation of the configurational entropy. These results are confronted with a simpler semi-empirical approach based on effective pair interactions obtained from experiment. Both approaches predict a single first-order A2/DO3 transition for compositions close to Cu3Al, in agreement with the most recent experimental results.

  8. Damage structures in fission-neutron irradiated Ni-based alloys at high temperatures

    Science.gov (United States)

    Yamakawa, K.; Shimomura, Y.

    1999-01-01

    The defects formed in Ni based (Ni-Si, Ni-Cu and Ni-Fe) alloys which were irradiated with fission-neutrons were examined by electron microscopy. Irradiations were carried out at 473 K and 573 K. In the 473 K irradiated specimens, a high density of large interstitial loops and small vacancy clusters with stacking fault tetrahedra (SFT) were observed. The number densities of these two types of defects did not strongly depend on the amount of solute atoms in each alloy. The density of the loops in Ni-Si alloys was much higher than those in Ni-Cu and Ni-Fe alloys, while the density of SFT only slightly depended on the kind of solute. Also, the size of the loops depended on the kinds and amounts of solute. In 573 K irradiated Ni-Cu specimens, a high density of dislocation lines developed during the growth of interstitial loops. In Ni-Si alloys, the number density and size of the interstitial loops changed as a function of the amount of solute. Voids were formed in Ni-Cu alloys but scarcely formed in Ni-Si alloys. The number density of voids was one hundredth of that of SFT observed in 473 K irradiated Ni-Cu alloys. Possible formation processes of interstitial loops, SFT dislocation lines and voids are discussed.

  9. Damage structures in fission-neutron irradiated Ni-based alloys at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Yamakawa, K.; Shimomura, Y. [Hiroshima Univ. (Japan). Faculty of Engineering

    1999-01-01

    The defects formed in Ni based (Ni-Si, Ni-Cu and Ni-Fe) alloys which were irradiated with fission-neutrons were examined by electron microscopy. Irradiations were carried out at 473 K and 573 K. In the 473 K irradiated specimens, a high density of large interstitial loops and small vacancy clusters with stacking fault tetrahedra (SFT) were observed. The number densities of these two types of defects did not strongly depend on the amount of solute atoms in each alloy. The density of the loops in Ni-Si alloys was much higher than those in Ni-Cu and Ni-Fe alloys, while the density of SFT only slightly depended on the kind of solute. Also, the size of the loops depended on the kinds and amounts of solute. In 573 K irradiated Ni-Cu specimens, a high density of dislocation lines developed during the growth of interstitial loops. In Ni-Si alloys, the number density and size of the interstitial loops changed as a function of the amount of solute. Voids were formed in Ni-Cu alloys but scarcely formed in Ni-Si alloys. The number density of voids was one hundredth of that of SFT observed in 473 K irradiated Ni-Cu alloys. Possible formation processes of interstitial loops, SFT, dislocation lines and voids are discussed. (orig.) 8 refs.

  10. Calculation of thermodynamic equilibrium between bcc disordered solid solutions U and Mo

    International Nuclear Information System (INIS)

    Alonso, Paula R.; Rubiolo, Gerardo H.

    2003-01-01

    There is actually an interest to develop a new fuel with higher density for research reactors. Fuel plates would be obtained by dispersion, a method that requires both a very dense fuel dispersant (>15.0 g U/cm 3 ) and a very high volume loading of the dispersant (>55%). Dispersants based in gamma (BCC) stabilized uranium alloys are being investigated, as they are able to reach uranium densities of 17.0 g U/cm 3 . Among them, we focus in U(Mo) bcc solid solutions with the addition of ternary elements to stabilize gamma phase. Transition metals, 4d and 5d, of groups VII and VIII are good candidates for the ternary alloy U - Mo - X. Their relative power to stabilize gamma phase seems to be in close relation with bonding energies between atoms in the alloy. A first approach to the calculation of these energies has been performed by the semi empiric method of Miedema where only bonds between pairs are considered, neglecting ternary and quaternary bonds. There is also a lack of information concerning solubilities of the ternary elements in the ternary cubic phase. In this work we aim to calculate bonding energies between atoms in the alloy using a cluster expansion of the formation energy (T=0 K) of a series of bcc ordered compounds in the systems U-Mo-X. Then the calculation of the equilibrium phase diagram by the Cluster Variation Method will be done (CVM). We show here the first part of the investigation devoted to calculation of phases equilibria in the U Mo system Formation energies of the ordered compounds were obtained by the first principles methods TB-LMTO-ASA and FP-LAPW. Another set of bonding energies was calculated in order to fit the known experimental diagram and new formation energies for the ordered compounds were derived from them. Discrepancies between both sets are discussed. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Voyevodin, V.N.; Karpov, S.A.; Kopanets, I.E.; Ruzhytskyi, V.V. [National Science Center “Kharkov Institute of Physics and Technology” Kharkov, 1, Akademicheskaya St., Kharkov, 61108 (Ukraine); Tolstolutskaya, G.D., E-mail: g.d.t@kipt.kharkov.ua [National Science Center “Kharkov Institute of Physics and Technology” Kharkov, 1, Akademicheskaya St., Kharkov, 61108 (Ukraine); Garner, F.A. [Radiation Effects Consulting, Richland, WA (United States)

    2016-01-15

    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({sup 3}He,p){sup 4}He, 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.

  12. Simulation of Intergranular Ductile Cracking in β Titanium Alloys Based on a Micro-Mechanical Damage Model.

    Science.gov (United States)

    Li, Huan; Li, Jinshan; Tang, Bin; Fan, Jiangkun; Yuan, Huang

    2017-10-30

    The intergranular crack propagation of the lamellar structure β titanium alloys is investigated by using a modified Gurson-type damage model. The representative microstructure of the lamellar alloy, which consists of the soft α phase layer surrounding the hard grain interiors, is generated based on an advanced Voronoi algorithm. Both the normal fracture due to void growth and the shear fracture associated with void shearing are considered for the grain boundary α layer. The individual phase properties are determined according to the experimental nanoindentation result and the macroscopic stress-strain curve from a uni-axial tensile test. The effects of the strain hardening exponent of the grain interiors and the void shearing mechanism of the grain boundary α layer on fracture toughness and the intergranular crack growth behavior are emphatically studied. The computational predictions indicate that fracture toughness can be increased with increasing the strain hardening ability of the grain interiors and void shearing can be deleterious to fracture toughness. Based on the current simulation technique, qualitative understanding of relationships between the individual phase features and the fracture toughness of the lamellar alloys can be obtained, which provides useful suggestions to the heat treatment process of the β titanium alloys.

  13. Fatigue and Fracture Characterization of Aircraft Aluminum Alloys Damaged by Prior Corrosion

    National Research Council Canada - National Science Library

    Baldwin, J

    2002-01-01

    At the time of the initiation of this project, there was no comprehensive data describing corrosion's effect on the fatigue and fracture behavior of aluminum alloys typically found in aging aircraft...

  14. Microstructural studies of hydrogen and deuterium in bcc refractory metals. Final technical report

    International Nuclear Information System (INIS)

    Moss, S.C.

    1984-04-01

    Research was conducted on the microstructural atomic arrangements in alloys of hydrogen and deuterium with bcc refractory metals with emphasis on V and Nb. Because these are interstitial phases in which the host metal lattice is substantially deformed by the incorporation of the H(D) atoms, there are pronounced x-ray scattering effects. X-ray diffraction was used, with neutron scattering providing useful corollary data. One objective was to determine the phase relations, solid solution structures and phase transitions in metal-hydride alloys which depend upon the hydrogen-hydrogen interaction via the displacement field of the metal atoms. This has often included the elucidation of subtle thermodynamic properties (as in critical wetting) which are revealed in structural studies. Crystals were supplied for positron annihilation studies of the Fermi surface of H-Ta alloys which have revealed significant electronic trends. Work on alkali-graphite intercalates was initiated

  15. Numerical Simulation of Tension Properties for Al-Cu Alloy Friction Stir-Welded Joints with GTN Damage Model

    Science.gov (United States)

    Sun, Guo-Qin; Sun, Feng-Yang; Cao, Fang-Li; Chen, Shu-Jun; Barkey, Mark E.

    2015-11-01

    The numerical simulation of tensile fracture behavior on Al-Cu alloy friction stir-welded joint was performed with the Gurson-Tvergaard-Needleman (GTN) damage model. The parameters of the GTN model were studied in each region of the friction stir-welded joint by means of inverse identification. Based on the obtained parameters, the finite element model of the welded joint was built to predict the fracture behavior and tension properties. Good agreement can be found between the numerical and experimental results in the location of the tensile fracture and the mechanical properties.

  16. Gamma-induced positron annihilation spectroscopy and application to radiation-damaged alloys

    International Nuclear Information System (INIS)

    Wells, D.P.; Hunt, A.W.; Tchelidze, L.; Kumar, J.; Smith, K.; Thompson, S.; Selim, F.; Williams, J.; Harmon, J.F.; Maloy, S.; Roy, A.

    2006-01-01

    .P. Wells, et al., Nucl. Instr. and Meth. B. 241 (2005) 262]. These gamma-ray photons are then either measured with a high-resolution germanium detector (PAES) or fast scintillators (PALS) and subsequently analyzed using standard positron data analysis methods. The high penetrability of few MeV photons allows one to study defects and characterize materials in thick samples up to hundreds of g/cm2 (approximately a meter in steel), a thickness that is completely inaccessible by any other non-destructive technique. We have demonstrated the proof-of-principle of these techniques to probe tensile strain in thick steel alloys and other metals, to measure positron lifetimes in bulk samples of lead, copper and aluminium with positron lifetime spectra that are free of the surface and source background lifetimes that complicate conventional positron lifetime measurements, and demonstrated the activation technique for damage studies of copper and single-crystal iron [F.A. Selim, D.P. Wells, et al., Nucl. Instr. and Meth. B 192 (2002) 197, F.A. Selim, D.P. Wells, et al., Nucl. Instru. Meth. A 495 (2002) 154, F.A. Selim, et al., J. Rad. Phys. Chem. 68 (2004) 427]. We have also demonstrated the potential application of these techniques to 3-D imaging of defect density in thick structural materials [F.A. Selim, D.P. Wells, et al., Nucl. Instr. and Meth. B 241 (2005) 253, A.W. Hunt, D.P. Wells, et al., Nucl. Instr. and Meth. B. 241 (2005) 262

  17. Particle impact damage in the gamma based TiAl alloy TNBV3B produced via three different processing routes

    International Nuclear Information System (INIS)

    Gebhard, S.; Peters, P.W.M.; Roth-Fagaraseanu, D.; Turley, F.; Voggenreiter, H.

    2010-01-01

    The impact resistance of the TiAl alloy TNBV3B produced via three processing routes - cast, forged and extruded - has been studied on flat and airfoil-like shaped specimens making use of ballistic impact experiments. Several factors influencing the damage behaviour were investigated. The evolution of centre and edge impact induced damage in flat specimens is characterized for different energy levels. Additionally, edge impact was studied for airfoil-like shaped specimens. The results indicate that it is necessary to differentiate between the properties influencing the impact crack initiation and the impact induced crack growth. For the former, strength and ductility appear to have an important influence. A dynamic fracture toughness is probably adequate to describe impact induced crack growth. As such a property was not available an analogy is sought with crack growth behaviour under monotonic and cyclic loading based on microstructural influences found investigating the cracked surfaces after impact.

  18. Ab initio study of Cr interactions with point defects in bcc Fe

    International Nuclear Information System (INIS)

    Olsson, P.; Domain, Ch.; Wallenius, J.

    2008-01-01

    Full text of publication follows. Ferritic martensitic steels are candidate structural materials for fast neutron reactors, and in particular high-Cr reduced-activation steels. In Fe-Cr alloys, Cr plays a major role in the radiation-induced evolution of the mechanical properties. Using ab initio calculations based on density functional theory, the properties of Cr in α-Fe have been investigated. The intrinsic point defect formation energies were found to be larger in model bcc Cr as compared to those in ferromagnetic bcc Fe. The interactions of Cr with point defects (vacancy and self interstitials) have been characterised. Single Cr atoms interact weakly with vacancies but significantly with self-interstitial atoms. Mixed interstitials of any interstitial symmetry are bound. Configurations where two Cr atoms are in nearest neighbour position are generally unfavourable in bcc Fe except when they are a part of a interstitial complex. Mixed interstitials do not have as strong directional stability as pure Fe interstitials have. The effects on the results using the atom description scheme of either the ultrasoft pseudo-potential (USPP) or the projector augmented wave (PAW) formalisms are connected to the differences in local magnetic moments that the two methods predict. As expected for the Fe-Cr system, the results obtained using the PAW method are more reliable than the ones obtained with USPP. (authors)

  19. Effect of irradiation damage and helium on the swelling and structure of vanadium-base alloys

    International Nuclear Information System (INIS)

    Chung, H.M.; Loomis, B.A.; Smith, D.L.

    1993-12-01

    Swelling behavior and microstructural evolution of V-Ti, V-Cr-Ti, and V-Ti-Si alloys were investigated after irradiation at 420--600C up to 114 dpa. The alloys exhibited swelling maxima between 30 and 80 dpa and swelling decreased on irradiation to higher dpa. This is in contrast to the monotonically increasing swelling of binary alloys that contain Fe, Ni, Cr, Mo, W, and Si. Precipitation of dense Ti 5 Si 3 promotes good resistance to swelling of the Ti-containing alloys and it was concluded that Ti of >3 wt.% and 400--1000 wppm Si are necessary to effectively suppress swelling. Swelling was minimal in V-4Cr-4Ti, identified as the most promising alloy based on good mechanical properties and superior resistance to irradiation embrittlement. V-20Ti doped with B exhibited somewhat higher swelling because of He generation. Lithium atoms, generated from transmutation of 10 B, formed γ-LiV 2 O 5 precipitates and did not seem to produce undesirable effects on mechanical properties

  20. Interatomic Potential to Simulate Radiation Damage in Fe-Cr Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bonny, G.; Pasianot, R.; Terentyev, D.; Malerba, L.

    2011-03-15

    The report presents an Fe-Cr interatomic potential to model high-Cr ferritic alloys. The potential is fitted to thermodynamic and point-defect properties obtained from density functional theory (DFT) calculations and experiments. The developed potential is also benchmarked against other potentials available in literature. It shows particularly good agreement with the DFT obtained mixing enthalpy of the random alloy, the formation energy of intermetallics and experimental excess vibrational entropy and phase diagram. In addition, DFT calculated point-defect properties, both interstitial and substitutional, are well reproduced, as is the screw dislocation core structure. As a first validation of the potential, we study the precipitation hardening of Fe-Cr alloys via static simulations of the interaction between Cr precipitates and screw dislocations. It is concluded that the description of the dislocation core modification near a precipitate might have a significant influence on the interaction mechanisms observed in dynamic simulations.

  1. Interatomic Potential to Simulate Radiation Damage in Fe-Cr Alloys

    International Nuclear Information System (INIS)

    Bonny, G.; Pasianot, R.; Terentyev, D.; Malerba, L.

    2011-01-01

    The report presents an Fe-Cr interatomic potential to model high-Cr ferritic alloys. The potential is fitted to thermodynamic and point-defect properties obtained from density functional theory (DFT) calculations and experiments. The developed potential is also benchmarked against other potentials available in literature. It shows particularly good agreement with the DFT obtained mixing enthalpy of the random alloy, the formation energy of intermetallics and experimental excess vibrational entropy and phase diagram. In addition, DFT calculated point-defect properties, both interstitial and substitutional, are well reproduced, as is the screw dislocation core structure. As a first validation of the potential, we study the precipitation hardening of Fe-Cr alloys via static simulations of the interaction between Cr precipitates and screw dislocations. It is concluded that the description of the dislocation core modification near a precipitate might have a significant influence on the interaction mechanisms observed in dynamic simulations.

  2. Contact damage failure analyses of fretting wear behavior of the metal stem titanium alloy-bone cement interface.

    Science.gov (United States)

    Zhang, Lanfeng; Ge, Shirong; Liu, Hongtao; Wang, Qingliang; Wang, Liping; Xian, Cory J

    2015-11-01

    Although cemented titanium alloy is not favored currently in the Western world for its poor clinical and radiography outcomes, its lower modulus of elasticity and good biocompatibility are instrumental for its ability supporting and transforming physical load, and it is more suitable for usage in Chinese and Japanese populations due to their lower body weights and unique femoral characteristics. Through various friction tests of different cycles, loads and conditions and by examining fretting hysteresis loops, fatigue process curves and wear surfaces, the current study investigated fretting wear characteristics and wear mechanism of titanium alloy stem-bone cement interface. It was found that the combination of loads and displacement affected the wear quantity. Friction coefficient, which was in an inverse relationship to load under the same amplitude, was proportional to amplitudes under the same load. Additionally, calf serum was found to both lubricate and erode the wear interface. Moreover, cement fatigue contact areas appeared black/oxidative in dry and gruel in 25% calf serum. Fatigue scratches were detected within contact areas, and wear scars were found on cement and titanium surfaces, which were concave-shaped and ring concave/ convex-shaped, respectively. The coupling of thermoplastic effect and minimal torque damage has been proposed to be the major reason of contact damage. These data will be important for further studies analyzing metal-cement interface failure performance and solving interface friction and wear debris production issues. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Effects of prior surface damage on high-temperature oxidation of Fe-, Ni-, and Co-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL; Lowe, Tracie M [ORNL; Pint, Bruce A [ORNL

    2009-01-01

    Multi-component metallic alloys have been developed to withstand high-temperature service in corrosive environments. Some of these applications, like exhaust valve seats in internal combustion engines, must also resist sliding, impact, and abrasion. The conjoint effects of temperature, oxidation, and mechanical contact can result in accelerated wear and the formation of complex surface layers whose properties differ from those of the base metal and the oxide scale that forms in the absence of mechanical contact. The authors have investigated the effects of prior surface damage, produced by scratch tests, on the localized reformation of oxide layers. Three high-performance commercial alloys, based on iron, nickel, and cobalt, were used as model materials. Thermogravimetric analysis (TGA) was used to determine their static oxidation rates at elevated temperature (850o C). A micro-abrasion, ball-cratering technique was used to measure oxide layer thickness and to compare it with TGA results. By using taper-sectioning techniques and energy-dispersive elemental mapping, a comparison was made between oxide compositions grown on non-damaged surfaces and oxides that formed on grooves produced by a diamond stylus. Microindentation and scratch hardness data revealed the effects of high temperature exposure on both the substrate hardness and the nature of oxide scale disruption. There were significant differences in elemental distribution between statically-formed oxides and those that formed on scratched regions

  4. Investigation on the radiation damage behavior of various alloys in a fusion reactor using thorium molten salt

    International Nuclear Information System (INIS)

    Ubeyli, Mustafa; Demir, Teyfik

    2008-01-01

    In fusion reactors, one of the most important problems is the need for the frequent change of the first wall material during the reactor's operation due to the radiation damage induced by high energetic particles, especially fusion neutrons coming from fusion plasma. In order to solve this problem, in HYLIFE-II fusion reactor design, a liquid wall between the fusion plasma and first wall is used. This study presents the radiation damage behaviors of candidate structural materials (9Cr-2WVTa, V-4Cr-4Ti and W-5Re alloys) considered to be used in fusion reactors to determine the optimum thickness of the liquid wall in HYLIFE-II fusion reactor. In the liquid wall, a thorium molten salt consisting of 75%LiF-23%ThF 4 -2% 233 UF 4 was used. Calculations were carried out with respect to the variable liquid wall thickness and for an operation period of 30 years. Numerical results related to atomic displacement and helium generation damage pointed out that the liquid wall thickness should be at least 42, 66 and 81 cm for the materials, W-5Re, 9Cr-2WVTa, V-4Cr-4Ti, respectively in order not to exceed relevant damage limits after a reactor operation of 30 years

  5. Image-based creep-fatigue damage mechanism investigation of Alloy 617 at 950 °C

    Energy Technology Data Exchange (ETDEWEB)

    Tahir, Fraaz; Dahire, Sonam; Liu, Yongming, E-mail: yongming.liu@asu.edu

    2017-01-02

    Alloy 617 is a primary candidate material to be used in the next generation of nuclear power plants. Structural materials for these plants are expected to undergo creep and fatigue at temperatures as high as 950 °C. This study uses a hybrid-control creep-fatigue loading profile, as opposed to the traditional strain-controlled loading, to generate creep dominated failure. Qualitative and quantitative image analysis through SEM, EDS, and EBSD, is used to show that hybrid control testing is capable of producing creep dominated failure and that time fraction approach is not a valid indicator of creep or fatigue dominated damage. The focus of image analysis is on surface fatigue cracks and internal creep voids. A creep-fatigue damage interaction diagram based on these micro-scale features is plotted. It is shown that the classical time fraction approach suggested by the ASME code does not agree with the experimental findings and has a poor correlation with observed microscale damage features. A new definition of creep damage fraction based on an effective hold time is found to correlate well with the micro-scale image analysis.

  6. Multi Resolution In-Situ Testing and Multiscale Simulation for Creep Fatigue Damage Analysis of Alloy 617

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yongming [Arizona State Univ., Tempe, AZ (United States). School for Engineering of Matter, Transport and Energy; Oskay, Caglar [Vanderbilt Univ., Nashville, TN (United States). Dept. of Civil and Environmental Engineering

    2017-04-30

    This report outlines the research activities that were carried out for the integrated experimental and simulation investigation of creep-fatigue damage mechanism and life prediction of Nickel-based alloy, Inconel 617 at high temperatures (950° and 850°). First, a novel experimental design using a hybrid control technique is proposed. The newly developed experimental technique can generate different combinations of creep and fatigue damage by changing the experimental design parameters. Next, detailed imaging analysis and statistical data analysis are performed to quantify the failure mechanisms of the creep fatigue of alloy 617 at high temperatures. It is observed that the creep damage is directly associated with the internal voids at the grain boundaries and the fatigue damage is directly related to the surface cracking. It is also observed that the classical time fraction approach does not has a good correlation with the experimental observed damage features. An effective time fraction parameter is seen to have an excellent correlation with the material microstructural damage. Thus, a new empirical damage interaction diagram is proposed based on the experimental observations. Following this, a macro level viscoplastic model coupled with damage is developed to simulate the stress/strain response under creep fatigue loadings. A damage rate function based on the hysteresis energy and creep energy is proposed to capture the softening behavior of the material and a good correlation with life prediction and material hysteresis behavior is observed. The simulation work is extended to include the microstructural heterogeneity. A crystal plasticity finite element model considering isothermal and large deformation conditions at the microstructural scale has been developed for fatigue, creep-fatigue as well as creep deformation and rupture at high temperature. The model considers collective dislocation glide and climb of the grains and progressive damage accumulation of

  7. Experimental techniques for the study of radiation damage in metals and alloys

    International Nuclear Information System (INIS)

    Novion, C.H. de.

    1983-06-01

    In this review, one presents the main experimental techniques used to study point defects and defect clusters introduced by irradiation in metals and alloys; emphasis will be put on some recent techniques. In particular, the studies allowing to analyse the very small agglomerates of point defects (Huang and small angle scattering, positron annihilation, electron microscopy) will be compared [fr

  8. Helium ion damage in an amorphous Fe-Ni-Mo-B alloy

    International Nuclear Information System (INIS)

    Swijgenhoven, H. van; Stals, L.M.; Knuyt, G.

    1983-01-01

    Data are presented on helium gas bubble and helium blister formation for Metglas 2826MB during 5 keV He + -implantation in the temperature range 200K-600K and dose range 5.10 20 -10 22 He + /m 2 . It is concluded that amorphous alloys are less radiation resistant as has been thought earlier. (author)

  9. Influence of irradiation parameters on damage accumulation in metals and alloys

    DEFF Research Database (Denmark)

    Singh, B.N.; Zinkle, S.J.

    1994-01-01

    , helium production rate and the production rate of transmutant impurities may affect the rate and the magnitude of the damage accumulation. Possible mechanisms by which these parameters may affect the damage accumulation are described. Specific examples are given to illustrate the fact that the recoil...

  10. Development of an EAM potential for simulation of radiation damage in Fe-Cr alloys

    International Nuclear Information System (INIS)

    Wallenius, J.; Abrikosov, I.A.; Chakarova, R.; Lagerstedt, C.; Malerba, L.; Olsson, P.; Pontikis, V.; Sandberg, N.; Terentyev, D.

    2004-01-01

    We have developed a set of EAM potentials for simulation of Fe-Cr alloys. By relaxing the requirement of reproducing the pressure-volume relation at short distances and by fitting to the thermal expansion coefficients of Fe and Cr, stability of the self-interstitial could be obtained. For Cr, properties of the paramagnetic state were applied, providing a positive Cauchy pressure. Mixed Fe-Cr pair potentials were fitted to the calculated mixing enthalpy of ferromagnetic Fe-Cr. Simulation of thermal ageing in Fe-Cr alloys using the Fe-20Cr potential exhibited pronounced Cr-precipitation for temperatures below 900 K, a feature not observed at any temperature using a potential fitted to the mixing enthalpy of Fe-5Cr

  11. Development of an EAM potential for simulation of radiation damage in Fe-Cr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wallenius, J.; Abrikosov, I.A.; Chakarova, R.; Lagerstedt, C. E-mail: christina@neutron.kth.se; Malerba, L.; Olsson, P.; Pontikis, V.; Sandberg, N.; Terentyev, D

    2004-08-01

    We have developed a set of EAM potentials for simulation of Fe-Cr alloys. By relaxing the requirement of reproducing the pressure-volume relation at short distances and by fitting to the thermal expansion coefficients of Fe and Cr, stability of the <1 1 0> self-interstitial could be obtained. For Cr, properties of the paramagnetic state were applied, providing a positive Cauchy pressure. Mixed Fe-Cr pair potentials were fitted to the calculated mixing enthalpy of ferromagnetic Fe-Cr. Simulation of thermal ageing in Fe-Cr alloys using the Fe-20Cr potential exhibited pronounced Cr-precipitation for temperatures below 900 K, a feature not observed at any temperature using a potential fitted to the mixing enthalpy of Fe-5Cr.

  12. Investigation of machining damage and tool wear resulting from drilling powder metal aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Fell, H.A. [Lockheed Martin Energy Systems, Inc., Oak Ridge, TN (United States)

    1997-05-01

    This report documents the cutting of aluminum powder metallurgy (PM) parts for the North Carolina Manufacturing Extension Partnership. The parts, an aluminum powder metal formulation, were supplied by Sinter Metals Inc., of Conover, North Carolina. The intended use of the alloy is for automotive components. Machining tests were conducted at Y-12 in the machine shop of the Skills Demonstration Center in Building 9737. Testing was done on June 2 and June 3, 1997. The powder metal alloy tested is very abrasive and tends to wear craters and produce erosion effects on the chip washed face of the drills used. It also resulted in huge amounts of flank wear and degraded performance on the part of most drills. Anti-wear coatings on drills seemed to have an effect. Drills with the coating showed less wear for the same amount of cutting. The usefulness of coolants and lubricants in reducing tool wear and chipping/breakout was not investigated.

  13. Magnetic Properties Studies on Thermal Aged Fe-Cu Alloys for the Simulation of Radiation Damage

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C. K.; Kishore, M.B.; Park, D. G. [KAERI, Daejeon (Korea, Republic of); Son, De Rac. [Hannam University, Daejeon (Korea, Republic of)

    2016-05-15

    We evaluated the changes in magnetic properties due to cold rolling and thermal ageing of a Fe-1%Cu model alloy in this study. Initially, the alloy was 10% cold rolled, and isothermally aged at 400 .deg. C for 1, 10, 100 and 1000 hr. The samples were prepared at various thermal aging conditions and all the conditions were interpreted. The hysteresis loops, Magnetic Barkhausen noise (BN). The change of magnetic properties can be interpreted in terms of the domain wall motion and dislocation dynamics associated with copper rich precipitates (CRPs).The results were interpreted in terms of ageing time dependence of the precipitates evolution such as the volume fraction and size distribution. In order to evaluate the radiation embrittlement of RPV steel, A Cold rolled Fe-Cu model Alloy was prepared, The prepared samples were thermally aged by annealing at 400 .deg. C for various times, the magnetic properties of the annealed samples were measured, The Barkhausen noise and BH Loop shows a considerable trend corresponding to the Ageing time. The magnetic properties were interpreted and correlated to the CRPs formed through annealing process.

  14. Allotropic transformation bcc in equilibrium hcp in zirconium

    International Nuclear Information System (INIS)

    Akhtar, A.

    1976-01-01

    The allotropic transformation hcp(α) in equilibrium bcc(β) was examined in crystal bar zirconium. The β → α transformation is massive type in melt grown crystals of β--Zr. Upon thermal cycling through α → β → α the bcc → hcp transformation occurs frequently through a shear process and less frequently through a massive transformation. The presence of α → β transformation substructure may favor the operation of the shear mode. The hcp → bcc phase change occurs through a massive transformation. A lack of transformation memory is associated with the process of thermal cycling. 11 fig., 3 tables

  15. Understanding self ion damage in FCC Ni-Cr-Fe based alloy using X-ray diffraction techniques

    Science.gov (United States)

    Halder Banerjee, R.; Sengupta, P.; Chatterjee, A.; Mishra, S. C.; Bhukta, A.; Satyam, P. V.; Samajdar, I.; Dey, G. K.

    2018-04-01

    Using X-ray diffraction line profile analysis (XRDLPA) approach the radiation response of FCC Ni-Cr-Fe based alloy 690 to 1.5 and 3 MeV Ni2+ ion damage was quantified in terms of its microstructural parameters. These microstructural parameters viz. average domain size, microstrain and dislocation density were found to vary anisotropically with fluence. The anisotropic behaviour is mainly attributable to presence of twins in pre-irradiated microstructure. After irradiation, surface roughness increases as a function of fluence attributable to change in surface and sub-surface morphology caused by displacement cascade, defects and sputtered atoms created by incident energetic ion. The radiation hardening in case of 1.5 MeV Ni2+ irradiated specimens too is a consequence of the increase in dislocation density formed by interaction of radiation induced defects with pre-existing dislocations. At highest fluence there is an initiation of saturation.

  16. Kinetics of self-interstitial migration in bcc and fcc transition metals

    Science.gov (United States)

    Bukkuru, S.; Bhardwaj, U.; Srinivasa Rao, K.; Rao, A. D. P.; Warrier, M.; Valsakumar, M. C.

    2018-03-01

    Radiation damage is a multi-scale phenomenon. A thorough understanding of diffusivities and the migration energies of defects is a pre-requisite to quantify the after-effects of irradiation. We investigate the thermally activated mobility of self-interstitial atom (SIA) in bcc transition metals Fe, Mo, Nb and fcc transition metals Ag, Cu, Ni, Pt using molecular dynamics (MD) simulations. The self-interstitial diffusion involves various mechanisms such as interstitialcy, dumbbell or crowdion mechanisms. Max-Space Clustering (MSC) method has been employed to identify the interstitial and its configuration over a wide range of temperature. The self-interstitial diffusion is Arrhenius like, however, there is a slight deviation at high temperatures. The migration energies, pre-exponential factors of diffusion and jump-correlation factors, obtained from these simulations can be used as inputs to Monte Carlo simulations of defect transport. The jump-correlation factor shows the degree of preference of rectilinear or rotational jumps. We obtain the average jump-correlation factor of 1.4 for bcc metals and 0.44 for fcc metals. It indicates that rectilinear jumps are preferred in bcc metals and rotational jumps are preferred in fcc metals.

  17. Influence of plasma molybdenizing and shot-peening on fretting damage behavior of titanium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Chang-bin, E-mail: tcbtop@126.com [School of Metallurgy and Engineering, Xi’an University of Architecture and Technology, Xi’an, Shaanxi 710055 (China); Institute of Corrosion and Protection, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China); Liu, Dao-xin, E-mail: liudaox@nwpu.edu.cn [Institute of Corrosion and Protection, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China); Tang, Bin [Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan Shanxi 030024 (China); Zhang, Xiao-hua [Institute of Corrosion and Protection, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China); Qin, Lin [Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan Shanxi 030024 (China); Liu, Cheng-song [Institute of Corrosion and Protection, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China)

    2016-12-30

    Highlights: • Plasma molybdenizing increases FW resistance of Ti6Al4V, but reduces its FF life. • Shot-peened plasmamolybdenizing surface enhances FW and FF resistance of Ti6Al4V. • Combined treatment yields low surface-roughness & high hardness gradient distribution. • Combined treatment yields beneficial residual compressive stress & good toughness. • Anti-wear & -fatigue performance improvements for surface engineering applications. - Abstract: Effect of plasma molybdenizing and shot-peening on fretting wear and fretting fatigue behaviors of Ti6Al4V alloy was investigated. The plasma molybdenized layer composed of a dense molybdenum deposition layer and a Mo–Ti solid–solution layer can increase surface hardness by 2.8 times and cause its volume loss by fretting wear to decrease to 1/14 compared with that of the substrate. Plasma molybdenized treatment results in a significant decrease in resistance of the substrate to fretting fatigue. It is ascribed that the molybdenized layer with high hardness yields a low toughness, and its high surface roughness leads to a micro-notched effect. However, proper combination plasma molybdenizing and subsequent shot-peening may enhance the simultaneous fretting fatigue and fretting wear resistance of Ti6Al4V significantly, which can decrease the fretting wear volume loss to 1/27, and may increase the fretting fatigue life by more than 69 times. A synergistic improvement in fretting fatigue of the titanium alloy by combining surface alloying with shot-peening can be achieved. The results indicate that a beneficial residual compressive stress distribution, high surface hardness with suitable hardness gradient distribution, good apparent toughness, relatively low surface roughness, and excellent surface integrity are achieved.

  18. The Effect of Modulation Ratio of Cu/Ni Multilayer Films on the Fretting Damage Behaviour of Ti-811 Titanium Alloy.

    Science.gov (United States)

    Zhang, Xiaohua; Liu, Daoxin; Li, Xiaoying; Dong, Hanshan; Xi, Yuntao

    2017-05-26

    To improve the fretting damage (fretting wear and fretting fatigue) resistance of Ti-811 titanium alloy, three Cu/Ni multilayer films with the same modulation period thickness (200 nm) and different modulation ratios (3:1, 1:1, 1:3) were deposited on the surface of the alloy via ion-assisted magnetron sputtering deposition (IAD). The bonding strength, micro-hardness, and toughness of the films were evaluated, and the effect of the modulation ratio on the room-temperature fretting wear (FW) and fretting fatigue (FF) resistance of the alloy was determined. The results indicated that the IAD technique can be successfully used to prepare Cu/Ni multilayer films, with high bonding strength, low-friction, and good toughness, which yield improved room-temperature FF and FW resistance of the alloy. For the same modulation period (200 nm), the micro-hardness, friction, and FW resistance of the coated alloy increased, decreased, and improved, respectively, with increasing modulation ratio of the Ni-to-Cu layer thickness. However, the FF resistance of the coated alloy increased non-monotonically with the increasing modulation ratio. Among the three Cu/Ni multilayer films, those with a modulation ratio of 1:1 can confer the highest FF resistance to the Ti-811 alloy, owing mainly to their unique combination of good toughness, high strength, and low-friction.

  19. Characterisation of neutron irradiation damage in zirconium alloys - a 'Round Robin' experiment

    International Nuclear Information System (INIS)

    Kelly, P.M.; Blake, R.G.; Jostsons, A.

    1977-01-01

    The nature of the damage structure in the neutron-irradiated zirconium specimens supplied as part of an international 'Round Robin' experiment has been studied using transmission electron microscopy. The damage structure consists entirely of a/3 dislocation loops and no evidence has been found for c component loops. Both vacancy and interstitial loops were found in specimens where inside/outside contrast analysis was possible. Quantitative measurements of loop size distributions and loop concentrations are reported. All specimens exhibited corduroy contrast to varying degress. (author)

  20. Creep deformation, creep damage accumulation and residual life prediction for three low alloyed CrMo-steels

    International Nuclear Information System (INIS)

    Kondyr, A.; Sandstroem, R.; Samuelsson, A.

    1979-02-01

    A detailed analysis of creep strain results for three low alloyed steels of type 0.5 Mo, 1 Cr-0.5 Mo and 2.25 Cr-1 Mo has been undertaken. The results show that, excluding the primary stage, the true strain rate can be described by a simple analytical expression dE/dt = Aexp(B.E) where A and B are constants at constant stress and temperature. A is approximately equal to the minimum strain rate and B inversly proportional to the fracture strain. Furthermore, 1/AB equals the time t sub(r) to rupture. The residual life fraction in creep can be expressed as exp(-B.E) = 1-t/t sub(r) and a creep damage function μ is introduced as μ = 1-ABt. The expressions for strain rate and damage are shown to be a special case of the Rabotnov-Kachanov equations. The analysis has been generalized to account for multiaxial stress states, and as an example creep in a tube with internal pressure is considered. (author)

  1. Strain hardening and damage in 6xxx series aluminum alloy friction stir welds

    DEFF Research Database (Denmark)

    Simar, Aude; Nielsen, Kim Lau; de Meester, Bruno

    2010-01-01

    A friction stir weld in 6005A-T6 aluminum alloy has been prepared and analyzed by micro-hardness measurements, tensile testing and scanning electron microscopy (SEM). The locations of the various weld zones were determined by micro-hardness indentation measurements. The flow behavior of the various...... zones of the weld was extracted using micro-tensile specimens cut out parallel to the welding direction. The measured material properties and weld topology were then introduced in a fully coupled micro-mechanical finite element model, accounting for nucleation and growth of voids as well as void shape...... evolution. The model shows satisfactory preliminary results in predicting the tensile behaviour of the weld and the true strain at fracture....

  2. Damage evolution during actuation fatigue in shape memory alloys (SPIE Best Student Paper Award)

    Science.gov (United States)

    Phillips, Francis R.; Wheeler, Robert; Lagoudas, Dimitris C.

    2018-03-01

    Shape Memory Alloys (SMAs) are unique materials able to undergo a thermomechanically induced, reversible phase transformation. Additionally, SMA are subject to two types of fatigue, that is structural fatigue due to cyclic loading as experienced by most materials, as well as actuation fatigue due to repeated thermally induced phase transformation. The evolution of multiple material characteristics is presented over the actuation fatigue lifetime of NiTiHf actuators, including the accumulation of irrecoverable strain, the evolution of internal voids, and the evolution of the effective modulus of the actuator. The results indicate that all three of these material characteristics are clearly interconnected and careful analysis of each of these characteristics can help to understand the evolution of the others, as well as help to understand how actuation fatigue leads to ultimate failure of the actuator.

  3. Radiation damage and deuterium trapping in deuterium-ion-irradiated Fe–9Cr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Iwakir, Hirotomo, E-mail: iwakiri@edu.u-ryukyu.ac.jp [Faculty and Graduate School of Education, University of the Ryukyus, Nishihara, Okinawa 903-0213 (Japan); Tani, Munechika [Interdisciplinary Graduate School of Engineering Sciences, Kyusyu University, Kasuga, Fukuoka 816-8580 (Japan); Watanabe, Yoshiyuki [Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212 (Japan); Yoshida, Naoaki [Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)

    2014-01-15

    Thermal desorption of deuterium (D{sub 2}) from deuterium-ion (D{sub 2}{sup +})-irradiated Fe–9Cr was correlated with the microstructural evolution of the alloy during irradiation with 8-keV D{sub 2}{sup +} ions following annealing to determine the retention and desorption behavior of the implanted deuterium and to identify effective traps for them, particularly at high temperature. After irradiation at 573 K, a new desorption stage formed between 650 and 1100 K at higher fluences, and cavities were observed using transmission electron microscopy. The total amount of trapped deuterium following irradiation with a fluence of 3.0 × 10{sup 22} ions/m{sup 2} was 6.8 × 10{sup 17} D{sub 2}/m{sup 2}, or approximately 0.007%. These results indicate that the deuterium atoms recombined to form D{sub 2} molecules at the surfaces of the cavities.

  4. Damage structure in Nimonic PE16 alloy ion bombarded to high doses and gas levels

    International Nuclear Information System (INIS)

    Farrell, K.; Packan, N.H.

    1981-01-01

    The Nimonic PE16 alloy in solution-treated-and-aged condition was bombarded simultaneously with nickel ions and α and deuteron beams at 625 0 C to doses of 80 to 313 dpa at He/dpa = 10 and D/dpa = 25. Microstructural changes consisted of the introduction of dislocations and of cavities, and the redistribuion of γ' precipitates to these defects. Cavitational swelling remained below 1%. Cavities were represented by several distinct size classes, the smaller ones believed to be gas bubbles, and some larger ones associated with preferred growth of precipitate. Formation of bubbles at grain boundaries, and large cavities at incoherent twins intensified the possibility of mechanical separation of interfaces under high-gas irradiation conditions

  5. In situ study of heavy ion induced radiation damage in NF616 (P92) alloy

    International Nuclear Information System (INIS)

    Topbasi, Cem; Motta, Arthur T.; Kirk, Mark A.

    2012-01-01

    Highlights: ► The ferritic–martensitic alloy NF616 was irradiated in situ with 1 MeV Kr ions at 50 K and 473 K. ► The defect cluster density increases with dose and saturates at ∼6 dpa at 50 K and 473 K. ► The defect size distributions do not change with dose at this temperature range. ► Results indicate that defect cluster formation and destruction is governed by cascade impact. - Abstract: NF616 is a nominal 9Cr ferritic–martensitic steel that is amongst the primary candidates for cladding and duct applications in the Sodium-Cooled Fast Reactor, one of the Generation IV nuclear energy systems. In this study, an in situ investigation of the microstructure evolution in NF616 under heavy ion irradiation has been conducted. NF616 was irradiated to 8.4 dpa at 50 K and to 7.6 dpa at 473 K with 1 MeV Kr ions. Nano-sized defects first appeared as white dots in dark-field TEM images and their areal density increased until saturation (∼6 dpa). Dynamic observations at 50 K and 473 K showed appearance and disappearance of TEM-visible defect clusters under irradiation that continued above saturation dose. Quantitative analysis showed no significant change in the average size (∼3–4 nm) and distribution of defect clusters with increasing dose at 50 K and 473 K. These results indicate a cascade-driven process of microstructure evolution under irradiation in these alloys that involves both the formation of TEM-visible defect clusters by various degrees of cascade overlap and cascade induced defect cluster elimination. According to this mechanism, saturation of defect cluster density is reached when the rate of defect cluster formation by overlap is equal to the rate of cluster elimination during irradiation.

  6. Pivotal ERIVANCE basal cell carcinoma (BCC) study: 12-month update of efficacy and safety of vismodegib in advanced BCC.

    Science.gov (United States)

    Sekulic, Aleksandar; Migden, Michael R; Lewis, Karl; Hainsworth, John D; Solomon, James A; Yoo, Simon; Arron, Sarah T; Friedlander, Philip A; Marmur, Ellen; Rudin, Charles M; Chang, Anne Lynn S; Dirix, Luc; Hou, Jeannie; Yue, Huibin; Hauschild, Axel

    2015-06-01

    Primary analysis from the pivotal ERIVANCE BCC study resulted in approval of vismodegib, a Hedgehog pathway inhibitor indicated for treatment of adults with metastatic or locally advanced basal cell carcinoma (BCC) that has recurred after surgery or for patients who are not candidates for surgery or radiation. An efficacy and safety analysis was conducted 12 months after primary analysis. This was a multinational, multicenter, nonrandomized, 2-cohort study in patients with measurable and histologically confirmed locally advanced or metastatic BCC taking oral vismodegib (150 mg/d). Primary outcome measure was objective response rate (complete and partial responses) assessed by independent review facility. After 12 months of additional follow-up, median duration of exposure to vismodegib was 12.9 months. Objective response rate increased from 30.3% to 33.3% in patients with metastatic disease, and from 42.9% to 47.6% in patients with the locally advanced form. Median duration of response in patients with locally advanced BCC increased from 7.6 to 9.5 months. No new safety signals emerged with extended treatment duration. Limitations include low prevalence of advanced BCC and challenges of designing a study with heterogenous manifestations. The 12-month update of the study confirms the efficacy and safety of vismodegib in management of advanced BCC. Copyright © 2015 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.

  7. Damage production by fast electrons in dilute alloys of vanadium, niobium and molybdenum

    International Nuclear Information System (INIS)

    Jung, P.

    1975-01-01

    Vanadium, niobium and molybdenum samples containing about 300 ppm of zirconium were irradiated at helium temperature with electrons of energies between 0,6 and 3.1 MeV. The measured damage rates were analysed in terms of minimum threshold energy, damage function and resistivity per unit concentration of Frenkel pairs. For the minimum threshold energy T(Sub)d, values of 25+-2 eV (V) 28+-2 e V(Nb) and 34+-2 e V(Mo) were obtained. Pronounced differences between the displacement functions of molybdenum and that of niobium and vanadium are found which are explained by different stability of the defects during the irradiation at helium temperature

  8. Elemental moment variation of bcc Fe{sub x}Mn{sub 1−x} on MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Bhatkar, H.; Snow, R.J. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Arenholz, E. [Advanced Light Source, Lawrence Berkeley National Laboratories, Berkeley, CA 94720 (United States); Idzerda, Y.U., E-mail: idzerda@montana.edu [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

    2017-02-01

    We report the growth, structural characterization, and electronic structure evolution of epitaxially grown bcc Fe{sub x}Mn{sub 1−x} on MgO(001). It is observed that the 20 nm thick Fe{sub x}Mn{sub 1−x} alloy films remained bcc from 0.65≤x≤1, much beyond the bulk stability range of 0.88≤x≤1. X-ray absorption spectroscopy and X-ray magnetic circular dichroism show that both the Fe and Mn L{sub 3} binding energies slightly increase with Mn incorporation and that the elemental moment of Fe in the 20 nm crystalline bcc alloy film remain nearly constant, then shows a dramatic collapse near x~0.84. The Mn MCD intensity is found to be small at all compositions that exhibit ferromagnetism - Highlights: • Bcc Fe{sub x}Mn{sub 1−x} films were stabilized beyond bulk range by epitaxial growth on MgO. • XMCD shows negligible moment in Mn regardless of composition. • Fe moment stays constant until 84% Mn concentration. • Magnetic moment suddenly collapses before any structural change seen in RHEED.

  9. Co thin film with metastable bcc structure formed on GaAs(111 substrate

    Directory of Open Access Journals (Sweden)

    Minakawa Shigeyuki

    2014-07-01

    Full Text Available Co thin films are prepared on GaAs(111 substrates at temperatures ranging from room temperature to 600 ºC by radio-frequency magnetron sputtering. The growth behavior and the detailed resulting film structure are investigated by in-situ reflection high-energy electron diffraction and X-ray diffraction. In early stages of film growth at temperatures lower than 200 ºC, Co crystals with metastable A2 (bcc structure are formed, where the crystal structure is stabilized through hetero-epitaxial growth. With increasing the film thickness beyond 2 nm, the metastable structure starts to transform into more stable A1 (fcc structure through atomic displacements parallel to the A2{110} close-packed planes. The crystallographic orientation relationship between the A2 and the transformed A1 crystals is A1{111} || A2{110}. When the substrate temperature is higher than 400 ºC, Ga atoms of substrate diffuse into the Co films and a Co-Ga alloy with bcc-based ordered structure of B2 is formed.

  10. Cumulative damage and estimation of residual life in metallic alloys under creep

    International Nuclear Information System (INIS)

    Silveira, T.L. da.

    1980-07-01

    The mechanical behavior and fracture characteristics have been determined for a group of materials tested under conditions of creep, and the ability of various models detailed in the literature to describe these observed characteristics discussed. The parametric methods employed in formulating the indices which define the allowable stresses for design codes have been analysed, and a method of Minimum Standard Deviation (MSD) for construction of reference curves has been proposed. The constitutive equations used in the methods of analysis of creep stresses have been discussed. Finally, the accumulated damage by creep in a particular structure which had been in extended service has been characterized and, based on these observations, the methods for estimation of remaining life in industrial equipment have been analysed. (Author) [pt

  11. Structural transformation in mechanosynthesized bcc Fe-Al-Si(Ge) solid solutions during heating

    International Nuclear Information System (INIS)

    Kubalova, L.M.; Sviridov, I.A.; Vasilyeva, O.Ya.; Fadeeva, V.I.

    2007-01-01

    X-ray diffractometry and Moessbauer spectroscopy study of Fe 50 Al 25 Si 25 and Fe 50 Al 25 Ge 25 alloys obtained by mechanical alloying (MA) of elementary powders was carried out. Phase transformation during heating of synthesized products was studied using differential scanning calorimetry (DSC). After 2.5 h of MA monophase alloys containing bcc Fe(Al, Ge) solid solutions Fe(Al, Si) are formed. Fe(Al, Si) is partially ordered B2 type and Fe(Al, Ge) is completely disordered. DSC curves of synthesized alloys displayed the presence of exothermal peaks caused by phase transformation. The metastable Fe(Al, Si) solid solution transformed into FeAl 1-x Si x (B2) and FeSi 1-x Al x (B20) equilibrium phases. The Fe(Al, Ge) solid solution transformed into equilibrium phases through intermediate stage of Fe 6 Ge 3 Al 2 metastable phase formation. The Fe 6 Ge 3 Al 2 phase dissociated into three equilibrium phases: FeAl 1-x Ge x (B2), χ-Fe 6 Ge 5 and η-Fe 13 (Ge, Al) 8 (B8 2 ). The structure of Fe 6 Ge 3 Al 2 was calculated by Rietveld method, the distribution of Al and Ge in the elementary cell and its parameters were calculated. Moessbauer study showed that Fe(Al, Si) and Fe(Al, Ge) solid solutions are paramagnetic. In the equilibrium state the alloy containing Si is also paramagnetic while the alloy with Ge showed ferromagnetic properties

  12. Radiation damage studies of the FeNi alloys, pure and with impurities, by measuring magnetic properties

    International Nuclear Information System (INIS)

    Sciani, Valdir

    1978-01-01

    Radiation damage studies are interesting from various points of view, but they have two main aspects, fundamental and technological. The void formations in metals and alloys during irradiation with high energy particles is a problem of interest in Nuclear Technology. The supersaturation of vacancies is one condition for a void formation, which results in swelling as well as in changes of mechanical, electrical and magnetic properties of materials used in power reactor. Isothermal and linear annealings have been performed before, during and after irradiation with neutrons from the IEAR-1 reactor, between 400 and 500 deg C in argon atmosphere. The samples used have a following nominal compositions: Fe Ni (50 - 50% at); FeNiMo ( 50 - 50% at + 50 ppm); FeNiCr ( 49,95 - 49,95 - 0,1% at); FeNiCr (49,75 - 49,75 - 0,5% at). The initial permeability disaccommodation has been followed by Magnetic After Effect (MAE) Method, which permitted the determination of the time constants, activation energies and Curie points. From these parameters it was possible to evaluate the super saturation of vacancies, showing that the MAE can be used as practical method for the election of nuclear materials without attaining high fluences. Some observations have been performed for the sample FeNiCr (49,75 - 49,75 - 0,5% at), which showed pronounced anomalies in the initial permeability during linear annealing.(author)

  13. Transmission electron microscope study of fusion-environment radiation damage in iron and iron-chromium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Horton, L.L.S.

    1982-07-01

    A transmission electron microscopy study of radiation damage microstructures in iron and iron-chromium alloys has been performed. This study consisted of both qualitative and quantitative characterization of the dislocation and cavity microstructures, including determination of vacancy/interstitial character and Burgers vectors for dislocation loops and analysis of the cavity morphology. The effects of irradiation temperature, fluence, helium implantation, and chromium content were investigated. Neutron irradiation (iron specimens, 1 dpa, 455 to 1000 K) and triple-beam ion irradiation (Fe-10% Cr specimens, 10 dpa, 725 to 950 K; Fe-10% Cr specimens, 850 K, 0.3 to 100 dpa; and Fe, Fe-5% Cr, Fe-10% Cr specimens, 850 K, 10 dpa) were employed. In the triple-beam ion irradiation procedure, simultaneous bombardment with 4 MeV Fe/sup + +/ ions and energetic He/sup +/ and D/sub 2//sup +/ ions was used to simulate the fusion environment (10 at. ppM He/dpa and 41 at. ppM D/dpa). In addition, single-beam 4 MeV Fe/sup + +/ ion irradiations of Fe-10% Cr both with and without pre-injection of helium and deuterium were performed.

  14. Transmission electron microscope study of fusion-environment radiation damage in iron and iron-chromium alloys

    International Nuclear Information System (INIS)

    Horton, L.L.S.

    1982-07-01

    A transmission electron microscopy study of radiation damage microstructures in iron and iron-chromium alloys has been performed. This study consisted of both qualitative and quantitative characterization of the dislocation and cavity microstructures, including determination of vacancy/interstitial character and Burgers vectors for dislocation loops and analysis of the cavity morphology. The effects of irradiation temperature, fluence, helium implantation, and chromium content were investigated. Neutron irradiation (iron specimens, 1 dpa, 455 to 1000 K) and triple-beam ion irradiation (Fe-10% Cr specimens, 10 dpa, 725 to 950 K; Fe-10% Cr specimens, 850 K, 0.3 to 100 dpa; and Fe, Fe-5% Cr, Fe-10% Cr specimens, 850 K, 10 dpa) were employed. In the triple-beam ion irradiation procedure, simultaneous bombardment with 4 MeV Fe ++ ions and energetic He + and D 2 + ions was used to simulate the fusion environment (10 at. ppM He/dpa and 41 at. ppM D/dpa). In addition, single-beam 4 MeV Fe ++ ion irradiations of Fe-10% Cr both with and without pre-injection of helium and deuterium were performed

  15. 3D characterization and modeling of low cycle fatigue damage mechanisms at high temperature in a cast aluminum alloy

    International Nuclear Information System (INIS)

    Dezecot, Sebastien; Maurel, Vincent; Buffiere, Jean-Yves; Szmytka, Fabien; Koster, Alain

    2017-01-01

    Synchrotron X-ray tomography was used to monitor damage evolution in three dimensions during in situ Low Cycle Fatigue (LCF) tests at high temperature (250 °C) for an industrial material. The studied material is an AlSi7Cu3Mg aluminum alloy (close to ASTM A319) produced by Lost Foam Casting (LFC), a process which generates coarse microstructures but is nevertheless used for engine parts by the automotive industry. The volume analysis (3D images) has shown that cracks are extremely sensitive to microstructural features: coarse pores and hard particles of the eutectic regions are critical regarding respectively the main crack initiation and the crack growth. Finite Elements (FE) simulations, performed on meshes directly generated from 3D volumes and containing only pores, have revealed that mechanical fields also play a major role on the crack behavior. Initiation sites corresponded to areas of maximum inelastic strain while the crack path was globally correlated to high stress triaxiality and inelastic strain fields.

  16. Equation of state and thermodynamic properties of BCC metals

    Directory of Open Access Journals (Sweden)

    Vu Van Hung, N.T. Hoa

    2017-10-01

    Full Text Available The moment method in statistical dynamics is used to study the equation of state and thermodynamic properties of the bcc metals taking into account the anharmonicity effects of the lattice vibrations and hydrostatic pressures. The explicit expressions of the lattice constant, thermal expansion  oefficient, and the specific heats of the bcc metals are derived within the fourth order moment approximation. The termodynamic quantities of W, Nb, Fe,and Ta metals are calculated as a function of the pressure, and they are in good agreement with the corresponding results obtained from the first principles calculations and experimental results. The effective pair potentials work well for the calculations of bcc metals.

  17. Damage-based life prediction model for uniaxial low-cycle stress fatigue of super-elastic NiTi shape memory alloy microtubes

    Science.gov (United States)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-08-01

    Based on the experimental observations for the uniaxial low-cycle stress fatigue failure of super-elastic NiTi shape memory alloy microtubes (Song et al 2015 Smart Mater. Struct. 24 075004) and a new definition of damage variable corresponding to the variation of accumulated dissipation energy, a phenomenological damage model is proposed to describe the damage evolution of the NiTi microtubes during cyclic loading. Then, with a failure criterion of Dc = 1, the fatigue lives of the NiTi microtubes are predicted by the damage-based model, the predicted lives are in good agreement with the experimental ones, and all of the points are located within an error band of 1.5 times.

  18. Damage-based life prediction model for uniaxial low-cycle stress fatigue of super-elastic NiTi shape memory alloy microtubes

    International Nuclear Information System (INIS)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-01-01

    Based on the experimental observations for the uniaxial low-cycle stress fatigue failure of super-elastic NiTi shape memory alloy microtubes (Song et al 2015 Smart Mater. Struct. 24 075004) and a new definition of damage variable corresponding to the variation of accumulated dissipation energy, a phenomenological damage model is proposed to describe the damage evolution of the NiTi microtubes during cyclic loading. Then, with a failure criterion of D c = 1, the fatigue lives of the NiTi microtubes are predicted by the damage-based model, the predicted lives are in good agreement with the experimental ones, and all of the points are located within an error band of 1.5 times. (paper)

  19. Kinetics of Accumulation of Damage in Surface Layers of Lithium-Containing Aluminum Alloys in Fatigue Tests with Rigid Loading Cycle and Corrosive Effect of Environment

    Science.gov (United States)

    Morozova, L. V.; Zhegina, I. P.; Grigorenko, V. B.; Fomina, M. A.

    2017-07-01

    High-resolution methods of metal physics research including electron, laser and optical microscopy are used to study the kinetics of the accumulation of slip lines and bands and the corrosion damage in the plastic zone of specimens of aluminum-lithium alloys 1441 and B-1469 in rigid-cycle fatigue tests under the joint action of applied stresses and corrosive environment. The strain parameters (the density of slip bands, the sizes of plastic zones near fracture, the surface roughness in singled-out zones) and the damage parameters (the sizes of pits and the pitting area) are evaluated.

  20. Interactions of foreign interstitial and substitutional atoms in bcc iron from ab initio calculations

    Science.gov (United States)

    You, Y.; Yan, M. F.

    2013-05-01

    C and N atoms are the most frequent foreign interstitial atoms (FIAs), and often incorporated into the surface layers of steels to enhance their properties by thermochemical treatments. Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Nb and Mo are the most common alloying elements in steels, also can be called foreign substitutional atoms (FSAs). The FIA and FSA interactions play an important role in the diffusion of C and N atoms, and the microstructures and mechanical properties of surface modified layers. Ab initio calculations based on the density functional theory are carried out to investigate FIA interactions with FSA in ferromagnetic bcc iron. The FIA-FSA interactions are analyzed systematically from five aspects, including interaction energies, density of states (DOS), bond populations, electron density difference maps and local magnetic moments.

  1. Structural properties and stability of the bcc and omega phases in the Zr-Nb system. Pt. II. Composition dependence of the lattice parameters

    International Nuclear Information System (INIS)

    Grad, G.B.; Guillermet, A.F.; Pieres, J.J.; Cuello, G.J.; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Buenos Aires; Universidad Nacional del Comahue

    1996-01-01

    For pt.I see Guillermet, A.F., J. Nucl. Mater., vol.218, p.236-46, 1995. This paper deals with the composition dependence of the lattice parameters of the bcc and omega phases of the Zr-Nb system. The experimental part of the work comprises neutron scattering experiments on a Zr-10 at.% Nb alloy in the as-quenched state and after successive aging treatments at 773 K. This new information is combined with an extensive review of the available data, and a detailed analysis is performed of the effects of composition and heat-treatment upon the lattice parameters a Ω and c Ω of the omega phase and the lattice-parameter relations between bcc and omega. A striking behaviour is detected in the variation of a Ω with composition in low-Nb alloys. (orig.)

  2. Phase stability and microstructures of high entropy alloys ion irradiated to high doses

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Songqin [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, 100083 (China); Gao, Michael C. [National Energy Technology Laboratory, 1450 Queen Ave SW, Albany, OR, 97321 (United States); AECOM, P.O. Box 1959, Albany, OR, 97321 (United States); Yang, Tengfei [State Key Laboratory of Nuclear Physics and Technology, Center for Applied Physics and Technology, Peking University, Beijing, 100871 (China); Liaw, Peter K. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996 (United States); Zhang, Yong, E-mail: drzhangy@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, 100083 (China)

    2016-11-15

    The microstructures of Al{sub x}CoCrFeNi (x = 0.1, 0.75 and 1.5 in molar ratio) high entropy alloys (HEAs) irradiated at room temperature with 3 MeV Au ions at the highest fluence of 105, 91, and 81 displacement per atom, respectively, were studied. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) analyses show that the initial microstructures and phase composition of all three alloys are retained after ion irradiation and no phase decomposition is observed. Furthermore, it is demonstrated that the disordered face-centered cubic (FCC) and disordered body-centered cubic (BCC) phases show much less defect cluster formation and structural damage than the NiAl-type ordered B2 phase. This effect is explained by higher entropy of mixing, higher defect formation/migration energies, substantially lower thermal conductivity, and higher atomic level stress in the disordered phases.

  3. Effects of product form and boron addition on the creep damage in the modified Hastelloy X alloys in a simulated HTGR helium gas environment

    International Nuclear Information System (INIS)

    Nakasone, Yuji; Tanabe, Tatsuhiko; Tsuji, Hirokazu; Nakajima, Hajime.

    1992-01-01

    The present paper investigates early-stage-creep damage of Hastelloy XR and XR-II alloys, modified versions of Hastelloy X alloy, which have been developed in Japan as most promising candidate structural alloys for Japanese high-temperature gas-cooled reactors (HTGRs). Creep tests were made on Hastelloy XR forging, tube and XR-II tube at 1,123 to 1,273 K in a simulated HTGR helium gas environment. The tests were interrupted at different strain levels of up to 5 % in order to evaluate creep damage via intergranular voids. The void sizes along grain boundaries and the A-parameter, the ratio of the number of damaged grain boundaries, on which one or more voids are found, to that of the total grain boundaries observed are used in order to evaluate creep damage. Statistical analysis of the A-parameter as well as the void sizes reveals that the values of the parameter show wide variations and follow the Weibull distribution, reflecting spatial randomness of the voids. The void sizes along grain boundaries, on the other hand, follow the log-normal distribution. The maximum void size d max and the mean value of the A-parameter A m are calculated and plotted against interruption creep strain ε int . The resultant d max vs. ε int and A m vs. ε int diagrams show that Hastelloy XR forging had suffered more damage than Hastelloy XR tube; nevertheless, the forging has longer interruption life, or the time to reach a given interruption creep strain. The result indicates that grains may have been deformed more easily in Hastelloy XR in the form of tube than in the form of forging. The diagrams also imply that the addition of boron has suppressed the nucleation as well as the growth of voids and thus has brought about longer interruption life of Hastelloy XR-II. (author)

  4. Shear instabilities in perfect bcc crystals during simulated tensile tests

    Czech Academy of Sciences Publication Activity Database

    Černý, M.; Šesták, P.; Pokluda, J.; Šob, Mojmír

    2013-01-01

    Roč. 87, č. 1 (2013), 014117/1-014117/4 ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP108/12/0311 Institutional support: RVO:68081723 Keywords : instabilities * tensile test * bcc metals * ab initio calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013

  5. Phase Composition of a CrMo0.5NbTa0.5TiZr High Entropy Alloy: Comparison of Experimental and Simulated Data

    Directory of Open Access Journals (Sweden)

    Fan Zhang

    2013-09-01

    Full Text Available Microstructure and phase composition of a CrMo0.5NbTa0.5TiZr high entropy alloy were studied in the as-solidified and heat treated conditions. In the as-solidified condition, the alloy consisted of two disordered BCC phases and an ordered cubic Laves phase. The BCC1 phase solidified in the form of dendrites enriched with Mo, Ta and Nb, and its volume fraction was 42%. The BCC2 and Laves phases solidified by the eutectic-type reaction, and their volume fractions were 27% and 31%, respectively. The BCC2 phase was enriched with Ti and Zr and the Laves phase was heavily enriched with Cr. After hot isostatic pressing at 1450 °C for 3 h, the BCC1 dendrites coagulated into round-shaped particles and their volume fraction increased to 67%. The volume fractions of the BCC2 and Laves phases decreased to 16% and 17%, respectively. After subsequent annealing at 1000 °C for 100 h, submicron-sized Laves particles precipitated inside the BCC1 phase, and the alloy consisted of 52% BCC1, 16% BCC2 and 32% Laves phases. Solidification and phase equilibrium simulations were conducted for the CrMo0.5NbTa0.5TiZr alloy using a thermodynamic database developed by CompuTherm LLC. Some discrepancies were found between the calculated and experimental results and the reasons for these discrepancies were discussed.

  6. Moessbauer spectroscopy of Fe-Mn-Cu alloys

    International Nuclear Information System (INIS)

    Paduani, Clederson; Krause, Joao Carlos; Yoschida, M.I. Soares

    2004-01-01

    Full text: Although a continuous series of solid solutions exists between Cu and Mn, Fe and Cu are miscible only a few percent at higher temperatures. In moderately concentrated Cu-Mn alloys the Mn moments are bound to the long ranged antiferromagnetic order and the perpendicular components form an X-Y spin glass. Copper alloys are largely employed in various industrial applications. In this work we study the magnetic properties of iron-rich disordered Fe-Mn-Cu alloys with the bcc structure with the experimental techniques of X-ray diffraction (XRD), Moessbauer spectroscopy (MS) and thermogravimetry (TGA). We investigate the formation of a solid solution with the bcc structure as well as the effect of the composition on the structural and magnetic properties of these alloys. A Rietveld analysis of the XRD diffractograms indicate that all prepared samples are single phase and are well crystallized with a bcc structure. (author)

  7. Interplay between lattice distortions, vibrations and phase stability in NbMoTaW high entropy alloys

    NARCIS (Netherlands)

    Kormann, F.H.W.; Sluiter, M.H.F.

    2016-01-01

    Refractory high entropy alloys (HEA), such as BCC NbMoTaW, represent a promising materials class for next-generation high-temperature applications, due to their extraordinary mechanical properties. A characteristic feature of HEAs is the formation of single-phase solid solutions. For BCC NbMoTaW,

  8. Comparative Study by MS and XRD of Fe50Al50 Alloys Produced by Mechanical Alloying, Using Different Ball Mills

    International Nuclear Information System (INIS)

    Rojas Martinez, Y.; Perez Alcazar, G. A.; Bustos Rodriguez, H.; Oyola Lozano, D.

    2005-01-01

    In this work we report a comparative study of the magnetic and structural properties of Fe 50 Al 50 alloys produced by mechanical alloying using two different planetary ball mills with the same ball mass to powder mass relation. The Fe 50 Al 50 sample milled during 48 h using the Fritsch planetary ball mill pulverisette 5 and balls of 20 mm, presents only a bcc alloy phase with a majority of paramagnetic sites, whereas that sample milled during the same time using the Fritsch planetary ball mill pulverisette 7 with balls of 15 mm, presents a bcc alloy phase with paramagnetic site (doublet) and a majority of ferromagnetic sites which include pure Fe. However for 72 h of milling this sample presents a bcc paramagnetic phase, very similar to that prepared with the first system during 48 h. These results show that the conditions used in the first ball mill equipment make more efficient the milling process.

  9. Cr interaction in the formation of nano cluster of Y, Ti and O in bcc Fe an ab initio study

    International Nuclear Information System (INIS)

    Murali, D.; Panigrahi, B.K.; Valsakumar, M.C.; Chandra, Sharath; Sundar, C.S.

    2008-01-01

    Nanostructured ferritic alloys containing highly stable fine dispersion of yttrium oxide nano particles, produced by mechanical alloying, are promising structural materials for fast fission and fusion environments. Formation of Cr depleted and O enriched Y-Ti-O nanoclusters are observed in the atom probe analysis. Ab initio calculations based on density functional theory are carried out to understand the role of Cr atom interactions with other solute atoms (Y, Ti, O) and vacancies in the formation of nanocluster. The binding energy of clusters of Y-Ti-O in bcc Fe is found to be very high in the presence of vacancies. Our calculations are consistent with the atom probe observation of depletion of Cr atoms and enrichment of O atoms in the nanoclusters. (author)

  10. AE characterisation of damage in burn resistant β-Titanium alloy (Tl-25V-15CR-2AL-0.2C)

    International Nuclear Information System (INIS)

    Shukri Mohd; Bowen, P.

    2003-01-01

    Acoustic Emission (AE) has been used to monitor cleavage cracking in Beta Titanium alloys to gain a detailed understanding of damage mechanisms in such alloys. Damage has been characterised in situ by AE and fractography for fracture toughness and fatigue crack growth resistance tests. During fracture toughness testing, the formation of cleavage facets in as received and heat treated specimens has been monitored by using AE. The values of fracture toughness have also been compared. For as received specimens, loads were applied until fracture while for heat treated specimens, three different test sequences were employed. For the first test, the load was again applied until failure. This test was carried out to give the overall clip gauge displacement curve for this specimen and also to estimate the load at which 5% offset and any pop-in occurs. For the second test, the load was applied to the specimens and then stopped at the 5 % offset and for the last test the applied-load was removed just after pop-in. Both of these latter specimens were then post fatigued until failure and then the fractured surfaces of all specimens were analysed using SEM. For fatigue crack growth resistance tests, the tests were started at ΔK of 20 MPam 1/2 until failure. A test was also stopped at ΔK of 40 MPam 1/2 . During such tests, crack growth was monitored by measuring the potential drop across the crack. It is found that the AE technique allows the investigation of the onset of cleavage fracture in this Beta-Ti alloy. It is, in principle, possible to use this technique to monitor online the formation of such unstable cleavage cracking of this alloy. (Author)

  11. Magnetism of CrO overlayers on Fe(001)bcc surface: first principles calculations

    Science.gov (United States)

    Félix-Medina, Raúl Enrique; Leyva-Lucero, Manuel Andrés; Meza-Aguilar, Salvador; Demangeat, Claude

    2018-04-01

    Riva et al. [Surf. Sci. 621, 55 (2014)] as well as Calloni et al. [J. Phys.: Condens. Matter 26, 445001 (2014)] have studied the oxydation of Cr films deposited on Fe(001)bcc through low-energy electron diffraction, Auger electron spectroscopy and scanning tunneling microscopy. In the present work we perform a density functional approach within Quantum Expresso code in order to study structural and magnetic properties of CrO overlayers on Fe(001)bcc. The calculations are performed using DFT+U. The investigated systems include O/Cr/Fe(001)bcc, Cr/O/Fe(001)bcc, Cr0.25O0.75/Fe(001)bcc, as well as the O coverage Ox/Cr/Fe(001)bcc (x = 0.25; 0.50). We have found that the ordered CrO overlayer presents an antiferromagnetic coupling between Cr and Fe atoms. The O atoms are located closer to the Fe atoms of the surface than the Cr atoms. The ground state of the systems O/Cr/Fe(001)bcc and Cr/O/Fe(001)bcc corresponds to the O/Cr/Fe(001)bcc system with a magnetic coupling c(2 × 2). The effect of the O monolayer on Cr/Fe(001)bcc changes the ground state from p(1 × 1) ↓ to c(2 × 2) and produces an enhancement of the magnetic moments. The Ox overlayer on Cr/Fe(001)bcc produces an enhancement of the Cr magnetic moments.

  12. Diffusion of Y and Ti/Zr in bcc iron: A first principles study

    International Nuclear Information System (INIS)

    Murali, D.; Panigrahi, B.K.; Valsakumar, M.C.; Sundar, C.S.

    2011-01-01

    The diffusion of yttrium plays an important role in the kinetics of formation of oxide nanoclusters in oxide dispersion strengthened alloys. Also, the diffusivity of minor alloying elements like Ti and Zr are of special interest as they are crucial for fine dispersion of oxide nanoclusters in the ferritic matrix. These solute atoms occupy substitutional sites in bcc Fe. The diffusion coefficients of these solute atoms were calculated using Le Claire’s nine frequency model involving the vacancy mechanism. We have done detailed density functional theory calculation of the interaction of these solute atoms with vacancies (□) and estimated various migration energy barriers of the vacancies in the presence of these solute atoms using nudged elastic band method. Strikingly, compared with Zr and Ti, Y shows a very large relaxation towards first neighbor vacancy resulting in strong binding with the vacancy. The Y-□ binding energy of 1.45 eV is almost double that of Zr-□ binding energy of 0.78 eV. We have also compared the calculated diffusion coefficients of these solute atoms with the experimental values.

  13. Dose dependence of true stress parameters in irradiated bcc, fcc, and hcp metals

    Science.gov (United States)

    Byun, T. S.

    2007-04-01

    The dose dependence of true stress parameters has been investigated for nuclear structural materials: A533B pressure vessel steels, modified 9Cr-1Mo and 9Cr-2WVTa ferritic martensitic steels, 316 and 316LN stainless steels, and Zircaloy-4. After irradiation to significant doses, these alloys show radiation-induced strengthening and often experience prompt necking at yield followed by large necking deformation. In the present work, the critical true stresses for deformation and fracture events, such as yield stress (YS), plastic instability stress (PIS), and true fracture stress (FS), were obtained from uniaxial tensile tests or calculated using a linear strain-hardening model for necking deformation. At low dose levels where no significant embrittlement was detected, the true fracture stress was nearly independent of dose. The plastic instability stress was also independent of dose before the critical dose-to-prompt-necking at yield was reached. A few bcc alloys such as ferritic martensitic steels experienced significant embrittlement at doses above ∼1 dpa; and the true fracture stress decreased with dose. The materials fractured before yield at or above 10 dpa.

  14. Radiation damage simulation studies in the Harwell VEC of selected austenitic and ferritic alloys for fusion applications

    Energy Technology Data Exchange (ETDEWEB)

    Mazey, D J; Walters, G P; Buckley, S N; Hanks, W; Bolster, D E.J.; Murphy, S M

    1988-07-01

    Three austenitic (316 L, 316-Ti, 316-Nb); four high-nickel (IN 625, IN 706, PE 16, Fe-25Ni-8Cr) and four ferritic (CRM 12, FV 448, FV 607, FI) alloys have been irradiated with 46 MeV Ni or 20 MeV Cr ions in the Harwell VEC to simulated fusion-reactor doses up to 110 dpa (proportional to 10 MW-yr m/sup -2/) at temperatures from 425 to 625/sup 0/C. Gas production rates appropriate to fusion were obtained from a mixed beam of He+H/sub 2/ in the ratio 1:4 He:H with gas/dpa ratios of 13 appm He/dpa and 52 appm H/dpa. The 316 alloys showed irradiation-induced precipitation and swelling as high as 40% in ST 316-Ti after 110 dpa at 625/sup 0/C. Low swelling (e.g. <2% at 110 dpa) was observed in the high-nickel alloys. The ferritic/martensitic alloys showed negligible swelling (e.g. <0.2% in FV 607 after 100 dpa at 475/sup 0/C). The results demonstrate the high swelling behaviour of 316 alloys and the better swelling resistance of high-nickel and ferritic alloys under simulated fusion conditions.

  15. Agglomeration Versus Localization Of Hydrogen In BCC Fe Vacancies

    International Nuclear Information System (INIS)

    Simonetti, S.; Juan, A.; Brizuela, G.; Simonetti, S.

    2006-01-01

    Severe embrittlement can be produced in many metals by small amounts of hydrogen. The interactions of hydrogen with lattice imperfections are important and often dominant in determining the influence of this impurity on the properties of solids. The interaction between four-hydrogen atoms and a BCC Fe structure having a vacancy has been studied using a cluster model and a semiempirical method. For a study of sequential absorption, the hydrogen atoms were positioned in their energy minima configurations, near to the tetrahedral sites neighbouring the vacancy. VH 2 and VH 3 complexes are energetically the most stables in BCC Fe. The studies about the stability of the hydrogen agglomeration gave as a result that the accumulation is unfavourable in complex vacancy-hydrogen with more than three atoms of hydrogen. (authors)

  16. Strong, Ductile, and Thermally Stable bcc-Mg Nanolaminates.

    Science.gov (United States)

    Pathak, Siddhartha; Velisavljevic, Nenad; Baldwin, J Kevin; Jain, Manish; Zheng, Shijian; Mara, Nathan A; Beyerlein, Irene J

    2017-08-15

    Magnesium has attracted attention worldwide because it is the lightest structural metal. However, a high strength-to-weight ratio remains its only attribute, since an intrinsic lack of strength, ductility and low melting temperature severely restricts practical applications of Mg. Through interface strains, the crystal structure of Mg can be transformed and stabilized from a simple hexagonal (hexagonal close packed hcp) to body center cubic (bcc) crystal structure at ambient pressures. We demonstrate that when introduced into a nanocomposite bcc Mg is far more ductile, 50% stronger, and retains its strength after extended exposure to 200 C, which is 0.5 times its homologous temperature. These findings reveal an alternative solution to obtaining lightweight metals critically needed for future energy efficiency and fuel savings.

  17. Analysis of anisotropic damage in forged Al–Cu–Mg–Si alloy based on creep tests, micrographs of fractured specimen and digital image correlations

    Energy Technology Data Exchange (ETDEWEB)

    Gariboldi, Elisabetta, E-mail: elisabetta.gariboldi@polimi.it [Politecnico di Milano, Department of Mechanical Engineering, Via La Masa 34 20156 Milano (Italy); Naumenko, Konstantin, E-mail: konstantin.naumenko@ovgu.de [Otto-von-Guericke-University Magdeburg, Institute of Mechanics, D-39106 Magdeburg (Germany); Ozhoga-Maslovskaja, Oksana, E-mail: oksana.ozhogamaslovskaja@gmail.com [Politecnico di Milano, Department of Mechanical Engineering, Via La Masa 34 20156 Milano (Italy); Zappa, Emanuele, E-mail: emanuele.zappa@polimi.it [Politecnico di Milano, Department of Mechanical Engineering, Via La Masa 34 20156 Milano (Italy)

    2016-01-15

    The aim of this paper is to analyze anisotropic damage mechanisms in forged Al–Cu–Mg–Si alloy based on the results of creep tests. Smooth specimens are sampled in three forging directions. Creep strain vs. time curves as well as light optical microscope and scanning electron microscope observations illustrate basic features of damage growth. Flat notch specimens are sampled in different directions to analyze stress redistributions and damage in zones of stress concentration. The digital image correlation technique has been applied in situ in order to extract the strain values on the surface of the notched specimens. All observations demonstrate that the principal origins of anisotropic creep and damage are associated with elongated grains and second phase clustered particles located at grain boundaries. Longitudinal specimens possess nucleations of decohesion sites and growth of voids around second phase particles at grain boundaries. Damage evolution for radial and transverse specimens is due to the formation and growth of cracks in second phase particles orthogonal to the principal stress axis. Residual strains are confined to the notch root as well as to the flanges of advanced macrocrack, indicating the small scale yielding during the creep fracture process.

  18. Pre-melting hcp to bcc Transition in Beryllium

    OpenAIRE

    Lu, Y.; Sun, T.; Zhang, Ping.; Zhang, P.; Zhang, D. -B.; Wentzcovitch, R. M.

    2017-01-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to X-ray equipments. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp to bcc transition occurs near the melting curve at 0

  19. Radiation damage of austenitic stainless steels and zirconium alloys; Pregled radijacionog ostecenja austenitnih nerdjajucih celika i legura cirkonijuma

    Energy Technology Data Exchange (ETDEWEB)

    Stefanovic, V [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1965-11-15

    This review contains analyses of available data concerning texture deformations and radiation damage of zirconium and zircaloy-2; radiation damage, influence of neutron radiation on the mechanical properties of austenitic, ferritic and other types of stainless steels.

  20. Design of Refractory High-Entropy Alloys

    Science.gov (United States)

    Gao, M. C.; Carney, C. S.; Doğan, Ö. N.; Jablonksi, P. D.; Hawk, J. A.; Alman, D. E.

    2015-11-01

    This report presents a design methodology for refractory high-entropy alloys with a body-centered cubic (bcc) structure using select empirical parameters (i.e., enthalpy of mixing, atomic size difference, Ω-parameter, and electronegativity difference) and CALPHAD approach. Sixteen alloys in equimolar compositions ranging from quinary to ennead systems were designed with experimental verification studies performed on two alloys using x-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. Two bcc phases were identified in the as-cast HfMoNbTaTiVZr, whereas multiple phases formed in the as-cast HfMoNbTaTiVWZr. Observed elemental segregation in the alloys qualitatively agrees with CALPHAD prediction. Comparisons of the thermodynamic mixing properties for liquid and bcc phases using the Miedema model and CALPHAD are presented. This study demonstrates that CALPHAD is more effective in predicting HEA formation than empirical parameters, and new single bcc HEAs are suggested: HfMoNbTiZr, HfMoTaTiZr, NbTaTiVZr, HfMoNbTaTiZr, HfMoTaTiVZr, and MoNbTaTiVZr.

  1. Microstructure and Room-Temperature Mechanical Properties of FeCrMoVTi x High-Entropy Alloys

    Science.gov (United States)

    Guo, Jun; Huang, Xuefei; Huang, Weigang

    2017-07-01

    FeCrMoVTi x ( x values represent the molar ratio, where x = 0, 0.5, 1.0, 1.5, and 2.0) high-entropy alloys were prepared by a vacuum arc melting method. The effects of Ti element on the microstructure and room-temperature mechanical properties of the as-cast FeCrMoVTi x alloys were investigated. The results show that the prepared alloys exhibited typical dendritic microstructure and the size of the microstructure became fine with increasing Ti content. The FeCrMoV alloy exhibited a single body-centered cubic structure (BCC1) and the alloys prepared with Ti element exhibited BCC1 + BCC2 mixed structure. The new BCC2 phase is considered as (Fe, Ti)-rich phase and was distributed in the dendrite region. With the increase of Ti content, the volume fraction of the BCC2 phase increased and its shape changed from a long strip to a network. For the FeCrMoV alloy, the fracture strength, plastic strain, and hardness reached as high as 2231 MPa, 28.2%, and 720 HV, respectively. The maximum hardness of 887 HV was obtained in the FeCrMoVTi alloy. However, the fracture strength, yield stress, and plastic strain of the alloys decreased continuously as Ti content increased. In the room-temperature compressive test, the alloys showed typical brittle fracture characteristics.

  2. Damage morphology study of high cycle fatigued as-cast Mg–3.0Nd–0.2Zn–Zr (wt.%) alloy

    Energy Technology Data Exchange (ETDEWEB)

    Yue, Haiyan; Fu, Penghuai, E-mail: fph112sjtu@sjtu.edu.cn; Peng, Liming; Li, Zhenming; Pan, Jipeng; Ding, Wenjiang

    2016-01-15

    Laser scanning confocal microscopy (LSCM) and Electron back-scattered diffraction (EBSD) were applied to the study of surface morphology variation of as-cast Mg–3.0Nd–0.2Zn–Zr (NZ30K) (wt.%) alloy under tension-compression fatigue test at room temperature. Two kinds of typical damage morphologies were observed in fatigued NZ30K alloy: One was parallel lines on basal planes led by the cumulation of basal slips, called persistent slip markings (PSMs), and the other was lens shaped, thicker and in less density, led by the formation of twinning. The surface fatigue damage morphology evolution was analyzed in a statistical way. The influences of stress amplitude and grain orientation on fatigue deformation mechanisms were discussed and the non-uniform deformation among grains and the PSMs, within twinning were described quantitatively. - Highlights: • Fatigue morphology evolution was studied by Laser Scanning Confocal Microscopy. • 3D morphology of persistent slip markings and twins was characterized. • Non-uniform deformation among grains, the PSMs and twins were quantified. • Initiations of fatigue crack were clearly investigated.

  3. Microstructural characterization of EXCEL alloy

    International Nuclear Information System (INIS)

    Oroza Z E, Celiz; Saumell M, Lani; Versaci, R A; Bozzano, P B

    2012-01-01

    The microstructure of Excel alloy was studied by optical and scanning electron microscopy. X-ray diffraction was used to analyze the present phases. Characteristic peaks of α-Zr (HCP), β-Zr (BCC) and δhydride (FCC) were identified. The high relatives intensities of certain peaks suggest that samples are textured. Basal poles were dominant in radial-longitudinal planes and prismatic poles have the highest concentration in radial-tangential planes (author)

  4. Damage rates in neutron irradiated FeCo and FeCo2V ordered and disordered alloys

    International Nuclear Information System (INIS)

    Riviere, J.P.; Dinhut, J.F.

    1979-01-01

    Ordered and disordered samples of FeCo and FeCo2V alloys have been irradiated at liquid hydrogen temperature with fission neutrons up to an integrated dose of about 7.2 x 10 17 n/cm 2 (E > 1 MeV). During the irradiation, the resistivity increases continuously due to point defect production. (author)

  5. Strain ordering in BCC metals and the associated anelasticity

    International Nuclear Information System (INIS)

    Dattagupta, S.; Ranganathan, R.; Balakrishnan, R.

    1982-01-01

    The BCC to BCT transformation is thought to occur as a consequence of strain ordering due to the interaction between impurity interstitials. A Hamiltonian is given, which involves the interaction energies between the strain fields of the interstitials belonging to three distinct sublattices. In the BCT phase, one of the sublattices is preferentially occupied. The free energy of the system is calculated in the mean field approximation. In this, the BCC to BCT transformation is found to be a first-order transition at a temperature Tsub(p) that is proportional to the concentration of the interstitials and certain basic interaction parameters. The anelastic behaviour of the interacting interstitials is then studied in the region T > Tsub(p). From the anelastic strain, which is proportional to the order parameter associated with the phase transition, the static compliance is obtained. The latter obeys a Curie-Weiss type of law. The creep function, which determines the response to a constant applied stress, is found to exhibit viscous behaviour near Tsub(p). From the creep function, the frequency-dependent compliance and the internal friction are evaluated. The results predict a shift and a broadening of the internal friction peak as Tsub(p) is approached from above. The features show qualitative resemblance with the recent data on Ta-O. (author)

  6. Experimental and numerical analysis of micromechanical damage in the punching process for High-Strength Low-Alloy steels

    OpenAIRE

    ACHOURI, Mohamed; GERMAIN, Guénaël; DAL SANTO, Philippe; SAIDANE, Delphine

    2014-01-01

    Sequential sheet metal forming processes can result in the accumulation of work hardening and damage effects in the workpiece material. The mechanical strength of the final component depends on the “evolution” of these two characteristics in the different production steps. The punching process, which is usually in the beginning of the production chain, has an important impact on the stress, strain and damage states in the punched zones. It is essential that the influence of these mechanical f...

  7. Real space multiple scattering description of alloy phase stability

    International Nuclear Information System (INIS)

    Turchi, P.E.A.; Sluiter, M.

    1992-01-01

    This paper presents a brief overview of the advanced methodology which has been recently developed to study phase stability properties of substitutional alloys, including order-disorder phenomena and structural transformations. The approach is based on the real space version of the Generalized Perturbation Method first introduced by Ducastelle and Gautier, within the Korringa-Kohn-Rostoker multiple scattering formulation of the Coherent Potential Approximation. Temperature effects are taken into account with a generalized meanfield approach, namely the Cluster Variation Method. The viability and the predictive power of such a scheme will be illustrated by a few examples, among them: the ground state properties of alloys, in particular the ordering tendencies for a series of equiatomic bcc-based alloys, the computation of alloy phase diagrams with the case of fcc and bcc-based Ni-Al alloys, the calculation of antiphase boundary energies and interfacial energies, and the stability of artificial ordered superlattices

  8. Effect of positively charged particles on sputtering damage of organic electro-luminescent diodes with Mg:Ag alloy electrodes fabricated by facing target sputtering

    Directory of Open Access Journals (Sweden)

    Kouji Suemori

    2017-04-01

    Full Text Available We investigated the influence of the positively charged particles generated during sputtering on the performances of organic light-emitting diodes (OLEDs with Mg:Ag alloy electrodes fabricated by sputtering. The number of positively charged particles increased by several orders of magnitude when the target current was increased from 0.1 A to 2.5 A. When a high target current was used, many positively charged particles with energies higher than the bond energy of single C–C bonds, which are typically found in organic molecules, were generated. In this situation, we observed serious OLED performance degradation. On the other hand, when a low target current was used, OLED performance degradation was not observed when the number of positively charged particles colliding with the organic underlayer increased. We concluded that sputtering damage caused by positively charged particles can be avoided by using a low target current.

  9. Mössbauer and XRD study of the Fe65Si35 alloy obtained by mechanical alloying

    International Nuclear Information System (INIS)

    Vélez, G. Y.; Rodríguez, R. R.; Melo, C. A.; Pérez Alcázar, G. A.; Zamora, Ligia E.; Tabares, J. A.

    2011-01-01

    A study was made on the alloy Fe 65 Si 35 using x-ray diffraction and Mössbauer spectrometry. The alloy was obtained by mechanical alloying in a high energy planetary mill, with milling times of 15, 30, 50, 75 and 100 h. The results show that in the alloys two structural phases are present, a Fe-Si BCC disordered phase and ferromagnetic, and a Fe-Si SC phase, whose nature is paramagnetic and which decreases with milling time. In the temporal evolution of the milling two stages are differentiated: one between 15 and 75 h of milling, in which silicon atoms diffuse into the bcc matrix of iron and its effect is to reduce the hyperfine magnetic field; the other, after 75 h of milling, where the alloy is consolidated, the effect of the milling is only to increase the disorder of the system, increasing the magnetic order.

  10. Elastic properties of Ti-24Nb-4Zr-8Sn single crystals with bcc crystal structure

    International Nuclear Information System (INIS)

    Zhang, Y.W.; Li, S.J.; Obbard, E.G.; Wang, H.; Wang, S.C.; Hao, Y.L.; Yang, R.

    2011-01-01

    Research highlights: → The single crystals of Ti2448 alloy with the bcc crystal structure were prepared. → The elastic moduli and constants were measured by several resonant methods. → The crystal shows significant elastic asymmetry in tension and compression. → The crystal exhibits weak nonlinear elasticity with large elastic strain ∼2.5%. → The crystal has weak atomic interactions against crystal distortion to low symmetry. - Abstract: Single crystals of Ti2448 alloy (Ti-24Nb-4Zr-8Sn in wt.%) were grown successfully using an optical floating-zone furnace. Several kinds of resonant methods gave consistent Young's moduli of 27.1, 56.3 and 88.1 GPa and shear moduli of 34.8, 11.0 and 14.6 GPa for the , and oriented single crystals, and C 11 , C 12 and C 44 of 57.2, 36.1 and 35.9 GPa respectively. Uniaxial testing revealed asymmetrical elastic behaviors of the crystals: tension caused elastic softening with a large reversible strain of ∼4% and a stress plateau of ∼250 MPa, whereas compression resulted in gradual elastic stiffening with much smaller reversible strain. The crystals exhibited weak nonlinear elasticity with a large elastic strain of ∼2.5% and a high strength, approaching ∼20% and ∼30% of its ideal shear and ideal tensile strength respectively. The crystals showed linear elasticity with a small elastic strain of ∼1%. These elastic deformation characteristics have been interpreted in terms of weakened atomic interactions against crystal distortion to low crystal symmetry under external applied stresses. These results are consistent with the properties of polycrystalline Ti2448, including high strength, low elastic modulus, large recoverable strain and weak strengthening effect due to grain refinement.

  11. Triple ion-beam studies of radiation damage effects in a 316LN austenitic alloy for a high power spallation neutron source

    International Nuclear Information System (INIS)

    Lee, E.H.; Rao, G.R.; Hunn, J.D.; Rice, P.M.; Lewis, M.B.; Cook, S.W.; Farrell, K.; Mansur, L.K.

    1997-09-01

    Austenitic 316LN alloy was ion-irradiated using the unique Triple Ion Beam Facility (TIF) at ORNL to investigate radiation damage effects relevant to spallation neutron sources. The TIF was used to simulate significant features of GeV proton irradiation effects in spallation neutron source target materials by producing displacement damage while simultaneously injecting helium and hydrogen at appropriately high gas/dpa ratios. Irradiations were carried out at 80, 200, and 350 C using 3.5 MeV Fe ++ , 360 keV He + , and 180 keV H + to accumulate 50 dpa by Fe, 10,000 appm of He, and 50,000 appm of H. Irradiations were also carried out at 200 C in single and dual ion beam modes. The specific ion energies were chosen to maximize the damage and the gas accumulation at a depth of ∼ 1 microm. Variations in microstructure and hardness of irradiated specimens were studied using transmission electron microscopy (TEM) and a nanoindentation technique, respectively. TEM investigation yielded varying damage defect microstructures, comprising black dots, faulted and unfaulted loops, and a high number density of fine bubbles (typically less than 1 nm in diameter). With increasing temperature, faulted loops had a tendency to unfault, and bubble microstructure changed from a bimodal size distribution to a unimodal distribution. Triple ion irradiations at the three temperatures resulted in similar increases in hardness of approximately a factor of two. Individually, Fe and He ions resulted in a similar magnitude of hardness increase, whereas H ions showed only a very small effect. The present study has yielded microstructural information relevant to spallation neutron source conditions and indicates that the most important concern may be radiation induced hardening and associated ductility loss

  12. Triple Ion-Beam Studies of Radiation Damage Effects in a 316LN Austenitic Alloy for a High Power Spallation Neutron Source

    International Nuclear Information System (INIS)

    Lee, E.H.

    2001-01-01

    Austenitic 316LN alloy was ion-irradiated using the unique Triple Ion Beam Facility (TIF) at ORNL to investigate radiation damage effects relevant to spallation neutron sources. The TIF was used to simulate significant features of GeV proton irradiation effects in spallation neutron source target materials by producing displacement damage while simultaneously injecting helium and hydrogen at appropriately high gas/dpa ratios. Irradiations were carried out at 80, 200, and 350 C using 3.5 MeV Fe 2 , 360 keV He + , and 180 keV H + to accumulate 50 dpa by Fe, 10,000 appm of He, and 50,000 appm of H. Irradiations were also carried out at 200 C in single and dual ion beam modes. The specific ion energies were chosen to maximize the damage and the gas accumulation at a depth of ∼ 1 microm. Variations in microstructure and hardness of irradiated specimens were studied using transmission electron microscopy (TEM) and a nanoindentation technique, respectively. TEM investigation yielded varying damage defect microstructures, comprising black dots, faulted and unfaulted loops, and a high number density of fine bubbles (typically less than 1 nm in diameter). With increasing temperature, faulted loops had a tendency to unfault, and bubble microstructure changed from a bimodal size distribution to a unimodal distribution. Triple ion irradiations at the three temperatures resulted in similar increases in hardness of approximately a factor of two. Individually, Fe and He ions resulted in a similar magnitude of hardness increase, whereas H ions showed only a very small effect. The present study has yielded microstructural information relevant to spallation neutron source conditions and indicates that the most important concern may be radiation induced hardening and associated ductility loss

  13. The role of edge dislocations in the deformation of BCC metals

    International Nuclear Information System (INIS)

    Lung, C.W.

    1994-08-01

    It was widely accepted that the screw dislocation is responsible for the strong temperature dependence of the yield stresses observed in bcc metals. In this paper, we show the role of edge dislocations in the deformation of bcc metals and point out that in some cases, its main contribution to the yield stress cannot be ignored. (author). 15 refs, 2 figs, 1 tab

  14. Experimental and numerical simulations of ELM-like transient damage behaviors to different grade tungsten and tungsten alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiang, E-mail: xliu@swip.ac.cn [Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, Sichuan (China); Lian, Youyun; Chen, Lei; Chen, Zhenkui; Chen, Jiming; Duan, Xuru [Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, Sichuan (China); Fan, Jinlian [Central South University, Changsha 410083 (China); Song, Jiupeng [Xiamen Honglu Tungsten & Molybdenum Industry Co., Ltd, Xiamen (China)

    2015-08-15

    Transient heat loads, such as plasma disruptions and ELMs, could induce plastic deformations, cracking, melting, even fatigue cracks and creep of tungsten (W) surface. A high purity W, CVD-W coating, TiC dispersion strengthened and K doped tungsten alloys were tested in a 60 kW electron-beam facility by simulating the transient load events under different base temperatures. It was found that CVD-W, W-TiC and W-K alloys have higher crack thresholds than high purity W, meanwhile CVD-W is more sensitive to the crack disappearing at elevated base temperatures. On the other hand, repetitive pulse loading like ELMs can induce serious network cracks even the power density was quite lower than the crack threshold determined by a single shot. The ABAQUS code was used to simulate the crack behaviors of ITER grade pure W by a single shot and a FE-SAFE code was adopted to estimate the fatigue life under ELMs-like loads. A good agreement with experiment results was found.

  15. Phase Composition of a CrMo0.5NbTa0.5TiZr High Entropy Alloy: Comparison of Experimental and Simulated Data

    OpenAIRE

    Fan Zhang; Oleg N. Senkov; Jonathan D. Miller

    2013-01-01

    Microstructure and phase composition of a CrMo0.5NbTa0.5TiZr high entropy alloy were studied in the as-solidified and heat treated conditions. In the as-solidified condition, the alloy consisted of two disordered BCC phases and an ordered cubic Laves phase. The BCC1 phase solidified in the form of dendrites enriched with Mo, Ta and Nb, and its volume fraction was 42%. The BCC2 and Laves phases solidified by the eutectic-type reaction, and their volume fractions were 27% and 31%, respectively....

  16. Atomistic modeling of carbon Cottrell atmospheres in bcc iron

    Science.gov (United States)

    Veiga, R. G. A.; Perez, M.; Becquart, C. S.; Domain, C.

    2013-01-01

    Atomistic simulations with an EAM interatomic potential were used to evaluate carbon-dislocation binding energies in bcc iron. These binding energies were then used to calculate the occupation probability of interstitial sites in the vicinity of an edge and a screw dislocation. The saturation concentration due to carbon-carbon interactions was also estimated by atomistic simulations in the dislocation core and taken as an upper limit for carbon concentration in a Cottrell atmosphere. We obtained a maximum concentration of 10 ± 1 at.% C at T = 0 K within a radius of 1 nm from the dislocation lines. The spatial carbon distributions around the line defects revealed that the Cottrell atmosphere associated with an edge dislocation is denser than that around a screw dislocation, in contrast with the predictions of the classical model of Cochardt and colleagues. Moreover, the present Cottrell atmosphere model is in reasonable quantitative accord with the three-dimensional atom probe data available in the literature.

  17. An analytic n-body potential for bcc Iron

    Energy Technology Data Exchange (ETDEWEB)

    Pontikis, V. [Commissariat a l' Energie Atomique, DRECAM/LSI, CE de Saclay, Building 524, Room 40B, 91191 Gif-sur-Yvette Cedex (France)]. E-mail: Vassilis.Pontikis@cea.fr; Russier, V. [Centre d' Etudes de Chimie Metallurgique, CNRS UPR2801, 94407 Vitry-sur-Seine (France); Wallenius, J. [Royal Institute of Technology, Department of Nuclear and Reactor Physics, Stockholm (Sweden)

    2007-02-15

    We have developed an analytic n-body phenomenological potential for bcc iron made of two electron-density functionals representing repulsion via the Thomas-Fermi free-electron gas kinetic energy term and attraction via a square root functional similar to the second moment approximation of the tight-binding scheme. Electron-density is given by radial, hydrogen-like orbitals with effective charges taken as adjustable parameters fitted on experimental and ab-initio data. Although the set of adjustable parameters is small, prediction of static and dynamical properties of iron is in excellent agreement with the experiments. Advantages and shortcomings of this model are discussed with reference to published works.

  18. An analytic n-body potential for bcc Iron

    International Nuclear Information System (INIS)

    Pontikis, V.; Russier, V.; Wallenius, J.

    2007-01-01

    We have developed an analytic n-body phenomenological potential for bcc iron made of two electron-density functionals representing repulsion via the Thomas-Fermi free-electron gas kinetic energy term and attraction via a square root functional similar to the second moment approximation of the tight-binding scheme. Electron-density is given by radial, hydrogen-like orbitals with effective charges taken as adjustable parameters fitted on experimental and ab-initio data. Although the set of adjustable parameters is small, prediction of static and dynamical properties of iron is in excellent agreement with the experiments. Advantages and shortcomings of this model are discussed with reference to published works

  19. Neutron spectroscopy of fast hydrogen diffusion in BCC transition metals

    International Nuclear Information System (INIS)

    Richter, D.; Lottner, V.

    1979-01-01

    Quasielastic neutron scattering reveals microscopic details of both the time and space development of the H-diffusion process on an atomic scale. After outlining the method on the example of PdH/sub x/, new results on the jump geometry in bcc metals are surveyed. In particular, the anomalous diffusion behavior of H in Nb, Ta, and V at elevated temperature is emphasized, where correlated jump processes are important. The influence of impurities on the H-diffusion process is demonstrated by experiments performed on NbH/sub x/ doped with nitrogen impurities, which act as trapping centers for the diffusing hydrogen. The results are discussed in terms of a two-state random walk model which includes multiple trapping and detrapping processes. The concentration and temperature dependence of the capture and escape rates of traps are obtained

  20. Evolution of anisotropy in bcc Fe distorted by interstitial boron

    Science.gov (United States)

    Gölden, Dominik; Zhang, Hongbin; Radulov, Iliya; Dirba, Imants; Komissinskiy, Philipp; Hildebrandt, Erwin; Alff, Lambert

    2018-01-01

    The evolution of magnetic anisotropy in bcc Fe as a function of interstitial boron atoms was investigated in thin films grown by molecular beam epitaxy. The thermodynamic nonequilibrium conditions during film growth allowed one to stabilize an interstitial boron content of about 14 at .% accompanied by lattice tetragonalization. The c /a ratio scaled linearly with the boron content up to a maximum value of 1.05 at 300 °C substrate growth temperature, with a room-temperature magnetization of. In contrast to nitrogen interstitials, the magnetic easy axis remained in-plane with an anisotropy of approximately -5.1 ×106erg /cm3 . Density functional theory calculations using the measured lattice parameters confirm this value and show that boron local ordering indeed favors in-plane magnetization. Given the increased temperature stability of boron interstitials as compared to nitrogen interstitials, this study will help to find possible ways to manipulate boron interstitials into a more favorable local order.

  1. Vibrational entropies in metallic alloys

    Science.gov (United States)

    Ozolins, Vidvuds; Asta, Mark; Wolverton, Christopher

    2000-03-01

    Recently, it has been recognized that vibrational entropy can have significant effects on the phase stability of metallic alloys. Using density functional linear response calculations and molecular dynamics simulations we study three representative cases: (i) phase diagram of Al-rich Al-Sc alloys, (ii) stability of precipitate phases in CuAl_2, and (iii) phonon dynamics in bcc Zr. We find large vibrational entropy effects in all cases. In the Al-Sc system, vibrations increase the solid solubility of Sc in Al by decreasing the stability of the L12 (Al_3Sc) phase. This leads to a nearly ten-fold increase in the solid solubility of Sc in Al at T=800 K. In the Cu-Al system, our calculations predict that the tetragonal Laves phase of CuAl2 has 0.35 kB/atom higher vibrational entropy than the cubic CaF_2-type phase (the latter is predicted to be the T=0 K ground state of CuAl_2). This entropy difference causes a structural transformation in CuAl2 precipitates from the fluorite to the tetragonal Laves phase around T=500 K. Finally, we analyze the highly unusual dynamics of anharmonically stabilized bcc Zr, finding large diffuse-scattering intensity streaks between the bcc Bragg peaks.

  2. Phase transformations in the Cu.6 Pd.4 alloy

    International Nuclear Information System (INIS)

    Imakuma, K.

    1977-01-01

    Order-disorder and structural transformations in the Cu-Pd 60-40% (Cu. 6 Pd. 4 ) alloy by means of a temperature and time dependent treatment are studied. The structural transformations by x-rays diffraction are also studied, where the bcc, fcc and tetragonal phases were observed. A qualitative analyze of the resistivity kinetics are made [pt

  3. The incidence of metastatic basal cell carcinoma (mBCC) in Denmark, 1997-2010.

    Science.gov (United States)

    Nguyen-Nielsen, Mary; Wang, Lisa; Pedersen, Lars; Olesen, Anne Braae; Hou, Jeannie; Mackey, Howard; McCusker, Margaret; Basset-Seguin, Nicole; Fryzek, Jon; Vyberg, Mogens

    2015-01-01

    Few data exist on the occurrence of metastatic basal cell carcinoma (mBCC). To identify all cases of mBCC in Denmark over a 14-year period. We searched the Danish National Patient Registry covering all Danish hospitals, the Danish Cancer Registry, the National Pathology Registry and the Causes of Death Registry during the period 1997 to 2010 for potential cases of mBCC registered according to the International classification of diseases ICD-10 and the International Systemized Nomenclature of Medicine (SNOMED). We identified 126,627 patients with a history of primary basal cell carcinoma (BCC) in the registries during the 14-year study period. Using case identifications from the four registries, a total of 170 potential mBCC cases were identified. However, after a pathology review, only five cases could be confirmed, of which three were basosquamous carcinomas. The 14-year cumulative incidence proportion of mBCC was 0.0039% (95% CI 0.0016-0.0083) among individuals with a history of previous BCC (n = 126,627) and 0.0001% (95% CI 0.0000-0.0002) in the general population. MBCC is a rare disease and only a small proportion of potential cases identified in automated clinical databases or registries can be confirmed by pathology and medical record review.

  4. Influence of an external magnetic field on damage by self-ion irradiation in Fe90Cr10 alloy

    Directory of Open Access Journals (Sweden)

    Fernando José Sánchez

    2016-12-01

    Full Text Available The effect of an external magnetic field (B=0.5 T on Fe90Cr10 specimens during Fe ion irradiation, has been investigated by means of Conversion Electron Mössbauer Spectroscopy (CEMS. The analysis has revealed significant differences in the average hyperfine magnetic field (=0.3 T between non-irradiated and irradiated samples as well as between irradiations made with B (w/ B and without B (w/o B. It is considered that these variations can be due to changes in the local environment around the probe nuclei (57Fe; where vacancies and Cr distribution play a role. The results indicate that the Cr distribution in the neighbourhood of the iron atoms could be changed by the application of an external field. This would imply that an external magnetic field may be an important parameter to take into account in predictive models for Cr behaviour in Fe–Cr alloys, and especially in fusion conditions where intense magnetic fields are required for plasma confinement.

  5. A review of the irradiation evolution of dispersed oxide nanoparticles in the b.c.c. Fe-Cr system: Current understanding and future directions

    Energy Technology Data Exchange (ETDEWEB)

    Wharry, Janelle P., E-mail: jwharry@purdue.edu [Purdue University, 400 Central Drive, West Lafayette, IN 47907 (United States); Swenson, Matthew J.; Yano, Kayla H. [Boise State University, 1910 University Drive, Boise, ID 83725 (United States)

    2017-04-01

    Thus far, a number of studies have investigated the irradiation evolution of oxide nanoparticles in b.c.c. Fe-Cr based oxide dispersion strengthened (ODS) alloys. But given the inconsistent experimental conditions, results have been widely variable and inconclusive. Crystal structure and chemistry changes differ from experiment to experiment, and the total nanoparticle volume fraction has been observed to both increase and decrease. Furthermore, there has not yet been a comprehensive review of the archival literature. In this paper, we summarize the existing studies on nanoparticle irradiation evolution. We note significant observations with respect to oxide nanoparticle crystallinity, composition, size, and number density. We discuss four possible contributing mechanisms for nanoparticle evolution: ballistic dissolution, Ostwald ripening, irradiation-enhanced diffusion, and homogeneous nucleation. Finally, we propose future directions to achieve a more comprehensive understanding of irradiation effects on oxide nanoparticles in ODS alloys.

  6. Formation of soft magnetic high entropy amorphous alloys composites containing in situ solid solution phase

    Science.gov (United States)

    Wei, Ran; Sun, Huan; Chen, Chen; Tao, Juan; Li, Fushan

    2018-03-01

    Fe-Co-Ni-Si-B high entropy amorphous alloys composites (HEAACs), which containing high entropy solid solution phase in amorphous matrix, show good soft magnetic properties and bending ductility even in optimal annealed state, were successfully developed by melt spinning method. The crystallization phase of the HEAACs is solid solution phase with body centered cubic (BCC) structure instead of brittle intermetallic phase. In addition, the BCC phase can transformed into face centered cubic (FCC) phase with temperature rise. Accordingly, Fe-Co-Ni-Si-B high entropy alloys (HEAs) with FCC structure and a small amount of BCC phase was prepared by copper mold casting method. The HEAs exhibit high yield strength (about 1200 MPa) and good plastic strain (about 18%). Meanwhile, soft magnetic characteristics of the HEAs are largely reserved from HEAACs. This work provides a new strategy to overcome the annealing induced brittleness of amorphous alloys and design new advanced materials with excellent comprehensive properties.

  7. The effect of surface corrosion damage on the fatigue life of 6061-T6 aluminum alloy extrusions

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Matthew; Eason, Paul D.; Özdeş, Hüseyin; Tiryakioğlu, Murat, E-mail: m.tiryakioglu@unf.edu

    2017-04-06

    An investigation was performed where 6061-T6 extrusions were exposed to a 3.5% NaCl solution at pH 2 for 2 days and 24 days to create distinct surface flaws. The effect of these flaws on the rotating beam fatigue life was then investigated and analyzed by using Wöhler curves, Weibull statistics and scanning electron microscopy (SEM). It was determined that corrosion damage reduced the fatigue life significantly and specimens corroded for both 2-days and 24-days exhibited similar fatigue lives. Statistical analyses showed that fatigue life of all three datasets followed the 3-parameter Weibull distribution and the difference between the fatigue lives of two corroded datasets was statistically insignificant. Analysis of fracture surfaces showed that sizes of pits that led to fatigue crack initiation were very different in the two corroded datasets. Implications of the similarity in fatigue lives despite disparity in surface condition are discussed in detail in the paper.

  8. bcc transition metals under pressure: results from ultrasonic interferometry and diamond-cell experiments

    International Nuclear Information System (INIS)

    Katahara, K.W.; Manghnani, M.H.; Ming, L.C.; Fisher, E.S.

    1976-01-01

    Hydrostatic pressure derivatives of the single-crystal elastic moduli, dC/sub ij//dP, have been measured ultrasonically for b.c.c. Nb--Mo and Ta--W solid solutions. The composition dependence of various electronic properties of these alloys is known to be reasonably well approximated by a rigid-electron-band filling model where e/a, the electron per atom ratio, is the primary parameter. The results indicate that the elastic moduli and their pressure derivatives may also be calculated in such a model. In particular, the dC/sub ij//dP show relatively sharp increases at e/a compositions of 5.4 for Nb--Mo and 5.7 for Ta--W. Both compositions correspond to changes in Fermi surface topology, as deduced from existing band calculations and the rigid band assumption. The results are discussed in the light of related electronic properties and possible geophysical applications. A comparison is also made between ultrasonic results and X-ray diffraction data for Nb. Using diamond-anvil pressure cell, compression of Nb was determined by X-ray diffraction up to 55 kbar in a liquid medium under purely hydrostatic conditions, and up to 175 kbar in a solid medium under nonhydrostatic conditions. The data obtained under hydrostatic conditions agree well with the ultrasonic equation of state and shock wave data, whereas the nonhydrostatic results tend to imply either a higher bulk modulus K/sub s/ or a higher (par. deltaK/sub s//par. deltaP)/sub T/

  9. Hydrogen diffusion and trapping in bcc and fcc metals

    International Nuclear Information System (INIS)

    Richter, D.

    1979-01-01

    The fundamental aspects of the metal--hydrogen systems are described. The large number of anomalous properties are the reason for continuous scientific effort. The time scale of hydrogen motion is extremely short. The characteristic frequencies of the localized modes of hydrogen in Ta, Nb, or V are in the order of 10 -14 sec (energies between 0.1 to 0.2 eV); the jump frequencies for H-diffusion at elevated temperatures in those systems are between 10 +12 to 10 +13 sec -1 . They are comparable with the correlation times for diffusion in liquids and more than ten orders of magnitude larger than the jump times for nitrogen in Nb. Out of the large number of experimental data this paper will survey only some recent results on representative fcc and bcc metals for dilute H solutions. The nature of the elementary step in H-diffusion is described. Here the temperature and isotope dependence of the H-diffusion coefficient gives hints to the mechanism involved. The experimental results are discussed in terms of semiclassical and quantum mechanical diffusion theories

  10. Helium bubbles in bcc Fe and their interactions with irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Gai, Xiao, E-mail: X.Gai@lboro.ac.uk; Lazauskas, Tomas; Smith, Roger; Kenny, Steven D.

    2015-07-15

    The properties of helium bubbles in a body-centred cubic (bcc) Fe lattice have been examined. The atomic configurations and formation energies of different He–vacancy complexes were determined. The 0 K results show that the most energetically favourable He to Fe vacancy ratio increases from about 1:1 for approximately 5 vacancies up to about 4:1 for 36 vacancies. The formation mechanisms for small He clusters have also been considered. Isolated interstitials and small clusters can diffuse quickly through the lattice. MD simulations of randomly placed interstitial He atoms at 500 K showed clustering over the time scale of nanoseconds with He clusters containing up to 4 atoms being mobile over this time scale. He clusters containing 4 or 5 atoms were shown to eject an Fe dumbbell interstitial which could then detach from the He cluster and diffuse with the remaining He–vacancy complex being effectively immobile. Collision cascades initiated near larger bubbles showed that Fe vacancies produced by the cascades readily become part of the He–vacancy complexes. Energy barriers for He to join an existing bubble as a function of the He–vacancy ratio are also calculated. These can be larger than the diffusion barrier in the pristine lattice, but are lower when the bubbles contain excess vacancies, thus indicating that bubble growth may be kinetically constrained.

  11. Vacancy formation enthalpies in bcc and fcc FeCo by positron annihilation

    International Nuclear Information System (INIS)

    Jackman, J.A.; Kim, S.M.; Buyers, W.J.L.

    1982-01-01

    A long slit angular correlation apparatus was used to measure the peak coincidence count rate in stoichiometric FeCo from 290 K to 1510 K. The count rate did not change significantly at the order-disorder phase transition (1008 K), but decreased sharply by 3.2% at the bcc-fcc phase transition at 1258 K. The threshold temperatures for the trapping of positrons in vacancies are measured to be 1125 K for the bcc phase and 1260 K for the fcc phase. The vacancy formation enthalpies in the bcc and fcc phases are determined to be 1.45 +- 0.05 eV and 1.63 +- 0.05 eV. The activation energies for self-diffusion have been estimated from the threshold temperatures, and are found to be 2.45 eV and 2.74 eV for the bcc and fcc phases respectively. (Auth.)

  12. Damage and service life of nickel-base alloys under thermal-mechanical fatigue stress at different phase positions; Schaedigung und Lebensdauer von Nickelbasislegierungen unter thermisch-mechanischer Ermuedungsbeanspruchung bei verschiedenen Phasenlagen

    Energy Technology Data Exchange (ETDEWEB)

    Guth, Stefan

    2016-07-01

    This work considers the behaviour of two nickel-base alloys (NiCr22Co12Mo9 and MAR-M247 LC) under thermo-mechanical fatigue loading with varying phase angles between mechanical strain and temperature. The investigations focus on the characterisation of microstructures and damage mechanisms as a function of the phase angle. Based on the results, a life prediction model is proposed.

  13. Cesium under pressure: First-principles calculation of the bcc-to-fcc phase transition

    Science.gov (United States)

    Carlesi, S.; Franchini, A.; Bortolani, V.; Martinelli, S.

    1999-05-01

    In this paper we present the ab initio calculation of the structural properties of cesium under pressure. The calculation of the total energy is done in the local-density approximation of density-functional theory, using a nonlocal pseudopotential including the nonlinear core corrections proposed by Louie et al. The calculation of the pressure-volume diagram for both bcc and fcc structures allows us to prove that the transition from bcc to fcc structure is a first-order transition.

  14. Solid-liquid interface free energies of pure bcc metals and B2 phases

    Science.gov (United States)

    Wilson, S. R.; Gunawardana, K. G. S. H.; Mendelev, M. I.

    2015-04-01

    The solid-liquid interface (SLI) free energy was determined from molecular dynamics (MD) simulation for several body centered cubic (bcc) metals and B2 metallic compounds (space group: P m 3 ¯ m ; prototype: CsCl). In order to include a bcc metal with a low melting temperature in our study, a semi-empirical potential was developed for Na. Two additional synthetic "Na" potentials were also developed to explore the effect of liquid structure and latent heat on the SLI free energy. The obtained MD data were compared with the empirical Turnbull, Laird, and Ewing relations. All three relations are found to predict the general trend observed in the MD data for bcc metals obtained within the present study. However, only the Laird and Ewing relations are able to predict the trend obtained within the sequence of "Na" potentials. The Laird relation provides the best prediction for our MD data and other MD data for bcc metals taken from the literature. Overall, the Laird relation also agrees well with our B2 data but requires a proportionality constant that is substantially different from the bcc case. It also fails to explain a considerable difference between the SLI free energies of some B2 phases which have nearly the same melting temperature. In contrast, this difference is satisfactorily described by the Ewing relation. Moreover, the Ewing relation obtained from the bcc dataset also provides a reasonable description of the B2 data.

  15. Partial amorphization of an α-FeCr alloy by ball-milling

    International Nuclear Information System (INIS)

    Loureiro, J. M.; Costa, B. F. O.; Caer, G. Le; Delcroix, P.

    2008-01-01

    The structural changes of near-equiatomic α-FeCr alloys, ground in a vibratory mill in vacuum and in argon, were followed as a function of milling time. An amorphous phase forms in both cases but at a much faster rate when milling in argon than when milling in vacuum. Amorphisation by ball-milling of α-FeCr alloys is deduced to be an intrinsic phenomenon which is however speeded-up by oxygen. The amorphous phase crystallizes into a bcc Cr-rich phase and a bcc Fe-rich phase when annealed for short times.

  16. Alloying behavior and deformation twinning in a CoNiFeCrAl0.6Ti0.4 high entropy alloy processed by spark plasma sintering

    International Nuclear Information System (INIS)

    Fu, Zhiqiang; Chen, Weiping; Fang, Sicong; Zhang, Dayue; Xiao, Huaqiang; Zhu, Dezhi

    2013-01-01

    Highlights: ► CoNiFeCrAl 0.6 Ti 0.4 high entropy alloy has been synthesized via MA and SPS. ► Deformation twinning possibly occurred during MA or SPS. ► This alloy exhibits excellent mechanical properties. ► The fracture mechanism of this alloy is intergranular fracture and plastic fracture. -- Abstract: Inequi-atomic CoNiFeCrAl 0.6 Ti 0.4 high entropy alloy has been designed and fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). Alloying behavior, microstructure, phase evolution and mechanical properties of CoNiFeCrAl 0.6 Ti 0.4 alloy were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM), as well as by an Instron testing system. During MA, a supersaturated solid solution consisting of a FCC phase and a metastable BCC phase was formed. Two FCC phases (named FCC1 and FCC2) and a new BCC phase were observed after SPS. During SPS, the metastable BCC phase transformed into the FCC2 phase and the new BCC phase. Meanwhile, the FCC1 phase was the initial FCC phase which was formed during MA. Moreover, nanoscale twins obviously presented only in partial FCC1 phase after SPS. Deformation twinning may be occurred during MA or SPS. The sintered alloy with a high relative density of 98.83% exhibits excellent comprehensive mechanical properties. The yield stress, compressive strength, compression ratio and Vickers hardness of the alloy are 2.08, 2.52 GPa, 11.5% and 573 H V , respectively. The fracture mechanism of CoNiFeCrAl 0.6 Ti 0.4 high entropy alloy is mainly performed at intergranular fracture and plastic fracture mode

  17. First-principles calculations of the structural and thermodynamic properties of bcc, fcc and hcp solid solutions in the Al-TM (TM = Ti, Zr and Hf) systems: A comparison of cluster expansion and supercell methods

    International Nuclear Information System (INIS)

    Ghosh, G.; Walle, A. van de; Asta, M.

    2008-01-01

    The thermodynamic properties of solid solutions with body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed (hcp) structures in the Al-TM (TM = Ti, Zr and Hf) systems are calculated from first-principles using cluster expansion (CE), Monte-Carlo simulation and supercell methods. The 32-atom special quasirandom structure (SQS) supercells are employed to compute properties at 25, 50 and 75 at.% TM compositions, and 64-atom supercells have been employed to compute properties of alloys in the dilute concentration limit (one solute and 63 solvent atoms). In general, the energy of mixing (Δ m E) calculated by CE and dilute supercells agree very well. In the concentrated region, the Δ m E values calculated by CE and SQS methods also agree well in many cases; however, noteworthy discrepancies are found in some cases, which we argue originate from inherent elastic and dynamic instabilities of the relevant parent lattice structures. The importance of short-range order on the calculated values of Δ m E for hcp Al-Ti alloys is demonstrated. We also present calculated results for the composition dependence of the atomic volumes in random solid solutions with bcc, fcc and hcp structures. The properties of solid solutions reported here may be integrated within the CALPHAD formalism to develop reliable thermodynamic databases in order to facilitate: (i) calculations of stable and metastable phase diagrams of binary and multicomponent systems, (ii) alloy design, and (iii) processing of Al-TM-based alloys

  18. Radiation effects on BCC metals and alloys. Final report, March 1, 1970 to August 31, 1980

    International Nuclear Information System (INIS)

    Moteff, J.

    1980-12-01

    To contribute to more meaningful and self-consistent deformation and/or strengthening models, use was made of quantitative transmission electron microscopy to obtain the number density and size distribution of the various defect states in the irradiated material. With this information, the influence of defects on dislocation mobility and deformation modes was determined. In addition, by means of high temperature anneals for different time intervals, the original defect states was significantly changed so that the above dislocation-defect interaction models may be tested under many different conditions. Combinations of time at temperature and appied stress has been shown to be extremely important in the dislocation channeling phenomenon, a circumstance that is closely associated with irradiation induced embrittlement. Detailed resistivity measurements, a technique for determining defect thermal stability and recovery kinetics, was used to establish critical test temperatures

  19. Comparison between radiation effects in some fcc and bcc metals irradiated with energetic heavy ions - a review

    International Nuclear Information System (INIS)

    Iwase, A.; Ishino, S.

    2000-01-01

    It has been reported that there are substantial differences in radiation effects in fcc copper and bcc iron. Whether these differences are due to the difference in crystal structure or not is the subject of the present paper. These differences have been discussed in terms of microstructure and mechanical property changes, whereas in the present paper, results of electrical resistivity measurements are discussed in terms of damage production cross sections, defect annihilation cross sections, damage efficiency and so on during and after various ion irradiations with wide energy ranges from 1 MeV to more than 100 MeV. For crucial discussion on the effect of the difference in crystal structure, nickel and iron are compared. These metals are allotted closely in the periodic table, with similar melting points and fairly strong electron-lattice coupling, both ferromagnetic and yet with different crystal structure. It may be concluded that as far as the damage production and defect annihilation cross sections and survival ratio are concerned, the difference in crystal structure is not an essential factor. Electronic energy deposition may play an important role even for low energy ions as well as for high energies. The effect of electronic energy deposition on defect clustering is discussed

  20. Thermomechanical behavior of Fe-Mn-Si-Cr-Ni shape memory alloys modified with samarium

    International Nuclear Information System (INIS)

    Shakoor, R.A.; Khalid, F. Ahmad

    2009-01-01

    The deformation and training behavior of Fe-14Mn-3Si-10Cr-5Ni (wt.%) shape memory alloys containing samarium addition has been studied in the iron-based shape memory alloys. It is noticed that thermomechanical treatment (training) has significant influence on proof stress, critical stress and shape memory behavior of the alloys. The improvement in shape memory behavior can be attributed to the decrease in the proof stress and critical stress which facilitates the formation of ε (hcp martensite). It is also observed that alloy 2 containing samarium undergoes less softening as compared to alloy 1 with training which inhibits the formation of α (bcc martensite) and thus enhances the shape memory behavior. The excessive thermomechanical treatment with increase in the training cycle has led to the formation of α (bcc martensite) along with ε (hcp martensite) in the alloy 1 which appeared to have decline in the shape memory effect. This has been demonstrated by the examination of microstructure and identification of α (bcc martensite) martensite in the alloy 1 as compared to alloy 2

  1. Statistical study of defects caused by primary knock-on atoms in fcc Cu and bcc W using molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Warrier, M., E-mail: Manoj.Warrier@gmail.com [Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh, 530012 (India); Bhardwaj, U.; Hemani, H. [Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh, 530012 (India); Schneider, R. [Computational Science, Ernst-Moritz-Arndt University, D-17489 Greifswald (Germany); Mutzke, A. [Max-Planck-Institut für Plasmaphysik, D-17491 Greifswald (Germany); Valsakumar, M.C. [School for Engineering Sciences and Technology, University of Hyderabad, Gachibowli, Hyderabad, Telangana State, 500046 (India)

    2015-12-15

    We report on molecular Dynamics (MD) simulations carried out in fcc Cu and bcc W using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code to study (i) the statistical variations in the number of interstitials and vacancies produced by energetic primary knock-on atoms (PKA) (0.1–5 keV) directed in random directions and (ii) the in-cascade cluster size distributions. It is seen that around 60–80 random directions have to be explored for the average number of displaced atoms to become steady in the case of fcc Cu, whereas for bcc W around 50–60 random directions need to be explored. The number of Frenkel pairs produced in the MD simulations are compared with that from the Binary Collision Approximation Monte Carlo (BCA-MC) code SDTRIM-SP and the results from the NRT model. It is seen that a proper choice of the damage energy, i.e. the energy required to create a stable interstitial, is essential for the BCA-MC results to match the MD results. On the computational front it is seen that in-situ processing saves the need to input/output (I/O) atomic position data of several tera-bytes when exploring a large number of random directions and there is no difference in run-time because the extra run-time in processing data is offset by the time saved in I/O. - Highlights: • MD simulations of collision cascades in 200 random directions explored in the energy range of 1–5 keV for fcc Cu and bcc W. • 60–80 random directions must be sampled for the number of displacements produced in a collision cascade to stabilize. • In-cascade clustering of interstitials and vacancies occur. • Direction averaged distribution of interstitials and vacancies around the origin of a PKA is presented. • Comparisons with MD indicate that the recoils produced in BCA-MC simulations be checked for recombination against all vacancies created.

  2. Improved microstructure and properties of 12Cr2Ni4A alloy steel by vacuum carburization and Ti + N co-implantation

    Science.gov (United States)

    Dong, Meiling; Cui, Xiufang; Jin, Guo; Wang, Haidou; Cai, Zhaobing; Song, Shengqiang

    2018-05-01

    The carburized 12Cr2Ni4A alloy steel was implanted by Ti + N double elements implantation. The microstructure, nano-hardness and corrosion properties were investigated by EPMA, TEM, XPS, nano-hardness and electrochemistry tests in detail. The results showed that the Ti + N co-implanted layer is composed of FCC TiN and TiC phases with BCC martensite. Compared with the un-implanted layer, the Ti + N implanted layer has higher nano-hardness and better corrosion resistance. In addition, the higher nano-hardness was presented below the surface of 1800 nm compared with un-implanted layer, which is far beyond the thickness of the implanted layer. The results also indicated that the generation of nanoscale ceramic phase and structures are not the only factor to impose the influence on the nano-hardness and corrosion resistance, but the radiation damage and lattice distortion will play an important role.

  3. Comparative study of the microstructures and mechanical properties of direct laser fabricated and arc-melted Al{sub x}CoCrFeNi high entropy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Jithin, E-mail: jithin@deakin.edu.au [Institute for Frontier Materials, Deakin University, Waurn Ponds 3216 (Australia); Jarvis, Tom; Wu, Xinhua [Monash Centre for Additive Manufacturing, Monash University, Clayton 3168 (Australia); Stanford, Nicole; Hodgson, Peter; Fabijanic, Daniel Mark [Institute for Frontier Materials, Deakin University, Waurn Ponds 3216 (Australia)

    2015-05-01

    High entropy alloys (HEA) are a relatively new metal alloy system that have promising potential in high temperature applications. These multi-component alloys are typically produced by arc-melting, requiring several remelts to achieve chemical homogeneity. Direct laser fabrication (DLF) is a rapid prototyping technique, which produces complex components from alloy powder by selectively melting micron-sized powder in successive layers. However, studies of the fabrication of complex alloys from simple elemental powder blends are sparse. In this study, DLF was employed to fabricate bulk samples of three alloys based on the Al{sub x}CoCrFeNi HEA system, where x was 0.3, 0.6 and 0.85 M fraction of Al. This produced FCC, FCC/BCC and BCC crystal structures, respectively. Corresponding alloys were also produced by arc-melting, and all microstructures were characterised and compared longitudinal and transverse to the build/solidification direction by x-ray diffraction, glow discharge optical emission spectroscopy and scanning electron microscopy (EDX and EBSD). Strong similarities were observed between the single phase FCC and BCC alloys produced by both techniques, however the FCC/BCC structures differed significantly. This has been attributed to a difference in the solidification rate and thermal gradient in the melt pool between the two different techniques. Room temperature compression testing showed very similar mechanical behaviour and properties for the two different processing routes. DLF was concluded to be a successful technique to manufacture bulk HEA's.

  4. Ab initio theory of noble gas atoms in bcc transition metals.

    Science.gov (United States)

    Jiang, Chao; Zhang, Yongfeng; Gao, Yipeng; Gan, Jian

    2018-06-18

    Systematic ab initio calculations based on density functional theory have been performed to gain fundamental understanding of the interactions between noble gas atoms (He, Ne, Ar and Kr) and bcc transition metals in groups 5B (V, Nb and Ta), 6B (Cr, Mo and W) and 8B (Fe). Our charge density analysis indicates that the strong polarization of nearest-neighbor metal atoms by noble gas interstitials is the electronic origin of their high formation energies. Such polarization becomes more significant with an increasing gas atom size and interstitial charge density in the host bcc metal, which explains the similar trend followed by the unrelaxed formation energies of noble gas interstitials. Upon allowing for local relaxation, nearby metal atoms move farther away from gas interstitials in order to decrease polarization, albeit at the expense of increasing the elastic strain energy. Such atomic relaxation is found to play an important role in governing both the energetics and site preference of noble gas atoms in bcc metals. Our most notable finding is that the fully relaxed formation energies of noble gas interstitials are strongly correlated with the elastic shear modulus of the bcc metal, and the physical origin of this unexpected correlation has been elucidated by our theoretical analysis based on the effective-medium theory. The kinetic behavior of noble gas atoms and their interaction with pre-existing vacancies in bcc transition metals have also been discussed in this work.

  5. Energy barrier of bcc-fcc phase transition via the Bain path in Yukawa system

    Science.gov (United States)

    Kiyokawa, Shuji

    2018-05-01

    In the Yukawa system with the dimensionless screening parameter κ>1.5 , when bcc-fcc transition occurs via Bain path, we show that spontaneous transitions do not occur even if the system temperature reaches the transition point of bcc-fcc because it is necessary to increase once the free energy in the process of transition from bcc to fcc through Bain deformation. Here, we refer the temporary increment of the free energy during Bain deformation as Bain barrier. Since there are the Bain barriers at the transitions between bcc and fcc phases, these phases may coexist as metastable state in the wide region (not a coexistence line) of κ and the coupling constant Γ. We study the excess energy of the system and the free energy difference between bcc and fcc phases by the Monte Carlo method, where the simulation box is divided into a large number of elements with small volume and a particle in the box is restricted be placed in one of these elements. By this method, we can tabulate the values of the interparticle potential and can calculate the internal energy fast and precisely.

  6. Biological changes of APA-BCC analgesic microcapsule in cerebrospinal fluid of patients with carcinomatous pain

    International Nuclear Information System (INIS)

    Luo Yun; Li Yanling; Xue Yilong; Guo Shulong; Gao Yuhong; Cui Xin

    2005-01-01

    To explore the changes of alginate-polylysine-alginate microcapsulated bovine adrenal medullary chromaffin cells (APA-BCC microcapsules) in morphology, survival rate and leucine- enkephalin secretion after they were transplanted into CSF of cancerpain patients, the APA- BCC microcapsules were Implanted into cavitas subarachnoidealis of cancer-pain patients by conventional lumbar puncture. After 7 or 8 days, cerebrospinal fluid was collected and the morphology of the APA-BCC microcapsule, the survival rate of cells were observed and secretory volume of leucine-enkephalin was assayed by radioimmunity method. Seven days after trans- plantation, the mean VAS decreased from 8.8 to 2.4, the survival rate of cells averagely reduced from 91.2% to 89.1%, morphology of APA-BCC microcapsules did not change obviously and secretory volume of leucine-enkephalin went up 1.65 times compared with that at pretrans- plantation. In conclusion, APA-BCC can survive, secret leucine-enkephalin and produce analgesic effect after transplanted into CSF of cancer-patients. (authors)

  7. Nanoclusters in bcc-Fe containing vacancies, copper and nickel: Structure and energetics

    International Nuclear Information System (INIS)

    Al-Motasem, A.T.; Posselt, M.; Bergner, F.

    2011-01-01

    Highlights: → Fe-Cu-Ni model alloys for RPV steels. → Atomistic simulation, mainly MMC and MD simulations. → Finding the most stable configurations of defect clusters. → Energetics of clusters, formation and binding energies. → Size dependence of monomer binding energy formula as input for OKMC methods. - Abstract: The most stable atomic configuration of coherent nanoclusters in bcc-Fe formed by vacancies, Cu and Ni as well as the corresponding energetics are determined by on-lattice simulated annealing and subsequent off-lattice relaxation. An interatomic potential recently designed for investigations of radiation-induced effects in the ternary Fe-Cu-Ni system is used in the atomistic simulations. Ternary v l Cu m Ni n clusters show a core-shell structure with vacancies in the core coated by a shell of Cu atoms, followed by a shell of Ni atoms. In binary Cu m Ni n clusters the Cu core is covered by a shell of Ni atoms. On the contrary, binary v l Ni n clusters consist of a pure vacancy cluster surrounded by an agglomeration of Ni atoms. The latter is similar to a pure Ni cluster (Ni n ) and consists of Ni atoms at the second nearest neighbor distance. Because of this special arrangement of atoms v l Ni n and Ni n are also called quasi-clusters. In all clusters investigated Ni atoms may be nearest neighbors of Cu atoms but never nearest neighbors of vacancies or other Ni atoms. The atomic configurations found can be understood by the peculiarities of the binding between vacancies, Cu, Ni and Fe atoms. The structure obtained for Cu m Ni n clusters is in agreement with previous theoretical results and with indications from measurements while for the other clusters reference data are not available. It is shown that the presence of Ni atoms promotes the nucleation of clusters containing vacancies and Cu. This is in agreement with experimental observations and with recent results of atomic kinetic Monte Carlo simulations. Based on the specific atomic structure

  8. Atomistic simulation of fcc—bcc phase transition in single crystal Al under uniform compression

    International Nuclear Information System (INIS)

    Li Li; Liang Jiu-Qing; Shao Jian-Li; Duan Su-Qing; Li Yan-Fang

    2012-01-01

    By molecular dynamics simulations employing an embedded atom model potential, we investigate the fcc-to-bcc phase transition in single crystal Al, caused by uniform compression. Results show that the fcc structure is unstable when the pressure is over 250 GPa, in reasonable agreement with the calculated value through the density functional theory. The morphology evolution of the structural transition and the corresponding transition mechanism are analysed in detail. The bcc (011) planes are transited from the fcc (111-bar) plane and the (11-bar1) plane. We suggest that the transition mechanism consists mainly of compression, shear, slid and rotation of the lattice. In addition, our radial distribution function analysis explicitly indicates the phase transition of Al from fcc phase to bcc structure. (condensed matter: structural, mechanical, and thermal properties)

  9. Calculated temperature dependence of elastic constants and phonon dispersion of hcp and bcc beryllium

    Science.gov (United States)

    Hahn, Steven; Arapan, Sergiu; Harmon, Bruce; Eriksson, Olle

    2011-03-01

    Conventional first principle methods for calculating lattice dynamics are unable to calculate high temperature thermophysical properties of materials containing modes that are entropically stabilized. In this presentation we use a relatively new approach called self-consistent ab initio lattice dynamics (SCAILD) to study the hcp to bcc transition (1530 K) in beryllium. The SCAILD method goes beyond the harmonic approximation to include phonon-phonon interactions and produces a temperature-dependent phonon dispersion. In the high temperature bcc structure, phonon-phonon interactions dynamically stabilize the N-point phonon. Fits to the calculated phonon dispersion were used to determine the temperature dependence of the elastic constants in the hcp and bcc phases. Work at the Ames Laboratory was supported by the Department of Energy-Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  10. Kinetics of disorder-to-fcc phase transition via an intermediate bcc state

    International Nuclear Information System (INIS)

    Liu Yongsheng; Nie Huifen; Bansil, Rama; Steinhart, Milos; Bang, Joona; Lodge, Timothy P.

    2006-01-01

    Time-resolved small-angle x-ray scattering measurements reveal that a long-lived intermediate bcc state forms when a poly(styrene-b-isoprene) diblock copolymer solution in an isoprene selective solvent is rapidly cooled from the disordered micellar fluid at high temperature to an equilibrium fcc state. The kinetics of the epitaxial growth of the [111] fcc peak from the [110] bcc peak was obtained by fitting the scattering data to a simple model of the transformation. The growth of the [111] fcc peak agrees with the Avrami model of nucleation and growth kinetics with an exponent n=1.4, as does the initial decay of the [110] bcc peak, with an exponent n=1.3. The data were also found to be in good agreement with the Cahn model of grain boundary nucleation and growth

  11. Clean Grain Boundary Found in C14/Body-Center-Cubic Multi-Phase Metal Hydride Alloys

    Directory of Open Access Journals (Sweden)

    Hao-Ting Shen

    2016-06-01

    Full Text Available The grain boundaries of three Laves phase-related body-center-cubic (bcc solid-solution, metal hydride (MH alloys with different phase abundances were closely examined by scanning electron microscopy (SEM, transmission electron microscopy (TEM, and more importantly, electron backscatter diffraction (EBSD techniques. By using EBSD, we were able to identify the alignment of the crystallographic orientations of the three major phases in the alloys (C14, bcc, and B2 structures. This finding confirms the presence of crystallographically sharp interfaces between neighboring phases, which is a basic assumption for synergetic effects in a multi-phase MH system.

  12. Stress and stability of sputter deposited A-15 and bcc crystal structure tungsten thin films

    Energy Technology Data Exchange (ETDEWEB)

    O' Keefe, M.J.; Stutz, C.E.

    1997-07-01

    Magnetron sputter deposition was used to fabricate body centered cubic (bcc) and A-15 crystal structure W thin films. Previous work demonstrated that the as-deposited crystal structure of the films was dependent on the deposition parameters and that the formation of a metastable A-15 structure was favored over the thermodynamically stable bcc phase when the films contained a few atomic percent oxygen. However, the A-15 phase was shown to irreversibly transform into the bcc phase between 500 C and 650 C and that a significant decrease in the resistivity of the metallic films was measured after the transformation. The current investigation of 150 nm thick, sputter deposited A-15 and bcc tungsten thin films on silicon wafers consisted of a series of experiments in which the stress, resistivity and crystal structure of the films was measured as a function of temperatures cycles in a Flexus 2900 thin film stress measurement system. The as-deposited film stress was found to be a function of the sputtering pressure and presputter time; under conditions in which the as-deposited stress of the film was {approximately}1.5 GPa compressive delamination of the W film from the substrate was observed. Data from the thermal studies indicated that bcc film stress was not affected by annealing but transformation of the A-15 structure resulted in a large tensile increase in the stress of the film, regardless of the as-deposited stress of the film. In several instances, complete transformation of the A-15 structure into the bcc phase resulted in {ge}1 GPa tensile increase in film stress.

  13. Stress and stability of sputter deposited A-15 and bcc crystal structure tungsten thin films

    International Nuclear Information System (INIS)

    O'Keefe, M.J.; Stutz, C.E.

    1997-01-01

    Magnetron sputter deposition was used to fabricate body centered cubic (bcc) and A-15 crystal structure W thin films. Previous work demonstrated that the as-deposited crystal structure of the films was dependent on the deposition parameters and that the formation of a metastable A-15 structure was favored over the thermodynamically stable bcc phase when the films contained a few atomic percent oxygen. However, the A-15 phase was shown to irreversibly transform into the bcc phase between 500 C and 650 C and that a significant decrease in the resistivity of the metallic films was measured after the transformation. The current investigation of 150 nm thick, sputter deposited A-15 and bcc tungsten thin films on silicon wafers consisted of a series of experiments in which the stress, resistivity and crystal structure of the films was measured as a function of temperatures cycles in a Flexus 2900 thin film stress measurement system. The as-deposited film stress was found to be a function of the sputtering pressure and presputter time; under conditions in which the as-deposited stress of the film was approximately1.5 GPa compressive delamination of the W film from the substrate was observed. Data from the thermal studies indicated that bcc film stress was not affected by annealing but transformation of the A-15 structure resulted in a large tensile increase in the stress of the film, regardless of the as-deposited stress of the film. In several instances, complete transformation of the A-15 structure into the bcc phase resulted in ge1 GPa tensile increase in film stress

  14. Alloying behavior, microstructure and mechanical properties in a FeNiCrCo0.3Al0.7 high entropy alloy

    International Nuclear Information System (INIS)

    Chen, Weiping; Fu, Zhiqiang; Fang, Sicong; Xiao, Huaqiang; Zhu, Dezhi

    2013-01-01

    Highlights: • FeNiCrCo 0.3 Al 0.7 high entropy alloy is prepared via MA and SPS. • Two BCC phases and one FCC phase were obtained after SPS. • The two BCC phases are enriched in Fe–Cr (A2 structure) and enriched in Ni–Al (B2 structure). • Bulk FeNiCrCo 0.3 Al 0.7 HEA exhibits excellent mechanical properties. - Abstract: The present paper reports the synthesis of FeNiCrCo 0.3 Al 0.7 high entropy alloy (HEA) by mechanical alloying (MA) and spark plasma sintering (SPS) process. Alloying behavior, microstructure, mechanical properties and detailed phases of the alloy were investigated systematically. During MA, the formation of a supersaturated solid solution with body-centered cubic (BCC) structure occurred. However, partial BCC structure phase transformed into a face-center cubic (FCC) structure phase during SPS. Two BCC phases with nearly the same lattice parameter of 3.01 Å and one FCC phase with the lattice parameter of 3.72 Å were characterized in the transmission electron microscope (TEM) images. The two BCC phases which are evidently deviated from the definition of high entropy alloys (HEAs) are enriched in Fe–Cr and enriched in Ni–Al, respectively. Moreover, the FCC phase agrees well with the definition of HEAs. Bulk FeNiCrCo 0.3 Al 0.7 alloy with little porosity exhibits much better mechanical properties except compression ratio compared with other typical HEAs of FeNiCrCoAl HEA system. The yield strength, compressive strength, compression ratio and Vickers hardness of FeNiCrCo 0.3 Al 0.7 alloy are 2033 ± 41 MPa, 2635 ± 55 MPa, 8.12 ± 0.51% and 624 ± 26H v , respectively. The fracture mechanism of bulk FeNiCrCo 0.3 Al 0.7 alloy is dominated by intercrystalline fracture and quasi-cleavage fracture

  15. Surface damage mitigation of TC4 alloy via micro arc oxidation for oil and gas exploitation application: Characterizations of microstructure and evaluations on surface performance

    Science.gov (United States)

    Xie, Ruizhen; Lin, Naiming; Zhou, Peng; Zou, Jiaojuan; Han, Pengju; Wang, Zhihua; Tang, Bin

    2018-04-01

    Because of its excellent corrosion resistance, high specific strength and high tensile strength, TC4 titanium alloys used as petroleum tubes have received wide interest from material engineers after many technical investigations and estimations. However, because of its low surface hardness values, high coefficient of friction and poor wear resistance, the TC4 alloy is seldom adopted in tribological-related engineering components. In this work, micro-arc oxidation (MAO) coatings were fabricated on TC4 alloys in NaAlO2 and (NaPO3)6 electrolytes with and without ultrasonic assistance. The microstructural characterizations of the produced MAO coatings were investigated. Comparative estimations of electrochemical corrosion in CO2-saturated simulated oilfield brine and tribological behaviours on MAO coatings and TC4 alloys were conducted. The results showed that the introduction of ultrasound increased the thickness of the MAO coatings. The thickness increased by 34% and 15% in the NaAlO2 and (NaPO3)6 electrolytes, respectively. There was no significant discrepancy in phase constitutions when the MAO processes were conducted with and without ultrasonic assistance. Both MAO coatings obtained with and without ultrasonic assistance were found to improve the corrosion and wear resistance of the TC4 alloy. MAO treatments made it possible to ensure the working surface of a TC4 alloy with an enhanced surface performance for oil and gas exploitation applications.

  16. Hydrogen damage in stainless steel

    International Nuclear Information System (INIS)

    Caskey, G.R. Jr.

    1981-01-01

    Hydrogen damage has been studied in a wide variety of stainless steels. Both internal and external hydrogen damage were evaluated by ductility or J-integral under rising tensile loads and by fractography. Analysis of the data has emphasized the potential effects of strain-induced martensite on hydrogen damage. Strain-induced martensite was neither necessary nor sufficient for hydrogen damage in the alloys studied. Neither ductility loss nor fracture-mode change correlated generally with martensite formation. Alloy composition, particularly nickel and nitrogen contents, was the primary factor in resistance to hydrogen damage. Thermomechanical processing, however, could alter the degree of hydrogen damage in an alloy and was critical for optimizing resistance to hydrogen damage. 10 figures, 10 tables

  17. Study of microplasticity of bcc metals by quasirelaxation method

    International Nuclear Information System (INIS)

    Ermishkin, V.A.; Plastinin, V.M.

    1977-01-01

    The microplasticity of single crystals of tungsten of orientation and of polycrystalline wire samples of molybdenum and of a tungsten-rhenium alloy has been investigated by a new method of quasi-relaxation at room temperature. It is shown that the micro-yield limit values determined by mechanostatic hysteresis and by least quasi-relaxation stress methods agree well one with another and for W lie, in the range between 0.25 and 0.35 kg/mm 2 . A formula, based on model assumptions of the mechanism of plastic deformation, is derived to describe the deformation curve in the micro-yield range. It has been established that the micro-yield limit is not a characteristic of the material proper, as it varies as a function of the base of the tests

  18. Crystal-Structure Contribution to the Solid Solubility in Transition Metal Alloys

    DEFF Research Database (Denmark)

    Ruban, Andrei; Skriver, Hans Lomholt; Nørskov, Jens Kehlet

    1998-01-01

    The solution energies of 4d metals in other 4d metals as well as the bcc-hcp structural energy differences in random 4d alloys are calculated by density functional theory. It is shown that the crystal structure of the host plays a crucial role in the solid solubility. A local virtual bond...

  19. Evidence of eutectic crystallization and transient nucleation in Al89La6Ni5 amorphous alloy

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Jiang, Jianzhong; Lin, Z. G.

    2001-01-01

    The phase evolution with the temperature and time in the process of crystallization of Al89La6Ni5 amorphous alloy has been investigated by in situ high-temperature and high-pressure x-ray powder diffraction using synchrotron radiation. Two crystalline phases, fcc-Al and a metastable bcc-(AlNi)(11...

  20. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011){sub B3} single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Higuchi, Jumpei; Yabuhara, Osamu [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2011-09-30

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011){sub B3} single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar]{sub bcc} || GaAs(011)[011-bar]{sub B3}. The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{l_brace}011{r_brace} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011){sub B3} substrates.

  1. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011)B3 single-crystal substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Higuchi, Jumpei; Yabuhara, Osamu; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-01-01

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011) B3 single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar] bcc || GaAs(011)[011-bar] B3 . The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{011} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011) B3 substrates.

  2. Radiation damage of uranium

    International Nuclear Information System (INIS)

    Lazarevic, Dj.

    1966-11-01

    Study of radiation damage covered the following: Kinetics of electric resistance of uranium and uranium alloy with 1% of molybdenum dependent on the second phase and burnup rate; Study of gas precipitation and diffusion of bubbles by transmission electron microscopy; Numerical analysis of the influence of defects distribution and concentration on the rare gas precipitation in uranium; study of thermal sedimentation of uranium alloy with molybdenum; diffusion of rare gas in metal by gas chromatography method

  3. Determination of positions and curved transition pathways of screw dislocations in BCC crystals from atomic displacements

    Czech Academy of Sciences Publication Activity Database

    Gröger, Roman; Vítek, V.

    2015-01-01

    Roč. 643, SEP (2015), s. 203-210 ISSN 0921-5093 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : Screw dislocation * BCC metal * Dislocation pathway Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.647, year: 2015

  4. Towards an unbiased comparison of CC, BCC, and FCC lattices in terms of prealiasing

    KAUST Repository

    Vad, Viktor

    2014-06-01

    In the literature on optimal regular volume sampling, the Body-Centered Cubic (BCC) lattice has been proven to be optimal for sampling spherically band-limited signals above the Nyquist limit. On the other hand, if the sampling frequency is below the Nyquist limit, the Face-Centered Cubic (FCC) lattice was demonstrated to be optimal in reducing the prealiasing effect. In this paper, we confirm that the FCC lattice is indeed optimal in this sense in a certain interval of the sampling frequency. By theoretically estimating the prealiasing error in a realistic range of the sampling frequency, we show that in other frequency intervals, the BCC lattice and even the traditional Cartesian Cubic (CC) lattice are expected to minimize the prealiasing. The BCC lattice is superior over the FCC lattice if the sampling frequency is not significantly below the Nyquist limit. Interestingly, if the original signal is drastically undersampled, the CC lattice is expected to provide the lowest prealiasing error. Additionally, we give a comprehensible clarification that the sampling efficiency of the FCC lattice is lower than that of the BCC lattice. Although this is a well-known fact, the exact percentage has been erroneously reported in the literature. Furthermore, for the sake of an unbiased comparison, we propose to rotate the Marschner-Lobb test signal such that an undue advantage is not given to either lattice. © 2014 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.

  5. NiFe epitaxial films with hcp and fcc structures prepared on bcc-Cr underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Higuchi, Jumpei, E-mail: higuchi@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Ohtake, Mitsuru; Sato, Yoichi [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2011-09-30

    NiFe epitaxial films are prepared on Cr(211){sub bcc} and Cr(100){sub bcc} underlayers grown hetero-epitaxially on MgO single-crystal substrates by ultra-high vacuum rf magnetron sputtering. The film growth behavior and the crystallographic properties are studied by reflection high energy electron diffraction and pole figure X-ray diffraction. Metastable hcp-NiFe(11-bar 00) and hcp-NiFe(112-bar 0) crystals respectively nucleate on Cr(211){sub bcc} and Cr(100){sub bcc} underlayers, where the hcp-NiFe crystals are stabilized through hetero-epitaxial growth. The hcp-NiFe(11-bar 00) crystal is a single-crystal with the c-axis parallel to the substrate surface, whereas the hcp-NiFe(112-bar 0) crystal is a bi-crystal with the respective c-axes lying in plane and perpendicular each other. With increasing the film thickness, the hcp structure in the NiFe films starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001) close packed plane. The resulting films consist of hcp and fcc crystals.

  6. Towards an unbiased comparison of CC, BCC, and FCC lattices in terms of prealiasing

    KAUST Repository

    Vad, Viktor; Csé bfalvi, Balá zs; Rautek, Peter; Grö ller, Eduard M.

    2014-01-01

    In the literature on optimal regular volume sampling, the Body-Centered Cubic (BCC) lattice has been proven to be optimal for sampling spherically band-limited signals above the Nyquist limit. On the other hand, if the sampling frequency is below the Nyquist limit, the Face-Centered Cubic (FCC) lattice was demonstrated to be optimal in reducing the prealiasing effect. In this paper, we confirm that the FCC lattice is indeed optimal in this sense in a certain interval of the sampling frequency. By theoretically estimating the prealiasing error in a realistic range of the sampling frequency, we show that in other frequency intervals, the BCC lattice and even the traditional Cartesian Cubic (CC) lattice are expected to minimize the prealiasing. The BCC lattice is superior over the FCC lattice if the sampling frequency is not significantly below the Nyquist limit. Interestingly, if the original signal is drastically undersampled, the CC lattice is expected to provide the lowest prealiasing error. Additionally, we give a comprehensible clarification that the sampling efficiency of the FCC lattice is lower than that of the BCC lattice. Although this is a well-known fact, the exact percentage has been erroneously reported in the literature. Furthermore, for the sake of an unbiased comparison, we propose to rotate the Marschner-Lobb test signal such that an undue advantage is not given to either lattice. © 2014 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.

  7. Direct Observation of the BCC (100) Plane in Thin Films of Sphere-forming Diblock Copolymers

    Science.gov (United States)

    Ji, Shengxiang; Nagpal, Umang; Liao, Wen; de Pablo, Juan; Nealey, Paul

    2010-03-01

    In sphere-forming diblock copolymers, periodic arrays of spheres are arranged in a body-centred cubic (BCC) lattice structure in bulk. However, in thin films different surface morphologies were observed as a function of the film thickness, and the transition from the hexagonal array to the BCC (110) arrangement of spheres on film surfaces was located with respect to the increase of the film thickness. Here we report the first direct observation of the BCC (100) plane in thin films of poly (styrene-b-methyl methacrylate) diblock copolymers on homogeneous substrates. By balancing the surface energies of both blocks, the lower energy BCC (100) plane corresponding to a square arrangement of half spheres, formed on film surfaces when the film thickness was commensurate with the spacing, L100, between (100) planes or greater than 2 L100. A hexagonal arrangement of spheres was only observed when the thickness was less than 2 L100 and incommensurate with 1 L100. Monte Carlo (MC) simulation confirmed our experimental observation and was used to investigate the transition of the arrangement of spheres as a function of the film thickness.

  8. Hirsutane Sesquiterpenes from Cultures of the Basidiomycete Marasmiellus sp. BCC 22389

    Directory of Open Access Journals (Sweden)

    Masahiko Isaka

    2016-08-01

    Full Text Available Abstract Two new hirsutane sesquiterpenes, marasmiellins A (1 and B (2, were isolated from cultures of the basidiomycete Marasmiellus sp. BCC 22389. The structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data. The absolute configuration of marasmiellin B was determined by application of the modified Mosher’s method. Graphical Abstract

  9. Nucleation and growth of a BCC Fe phase deposited on a single crystal (001) Cu film

    International Nuclear Information System (INIS)

    Koike, J.

    1991-01-01

    As a thin film overlayer grows on a substrate with a different structure, the overlayer initially adopts the substrate structure and subsequently transforms to an equilibrium bulk structure. such a growth characteristic has been extensively studied in Fe/Cu bicrystals. An Fe overlayer grown on a Cu substrate is known to have the fcc structure up to a thickness of 2 nm, whereas a thicker Fe overlayer consists of submicrometer grains of the bcc-Cu has been reported in a relatively thick Fe film and was found to consist of the Nishiyama (N), Kurdjumov-Sacks (KS), or Pitsch (P), depending on the orientation of the substrate surface. However, previous studies have not explained how the bcc structure nucleates or how the observed submicrometer polycrystalline grains form. The paper provides an understanding of these two points. Transmission electron microscopy (TEM) was used to study Fe/Cu bicrystals as the Fe thickness was varied systematically. Analysis of moire fringes, which are caused by superposition of different structures, enabled us to determine the orientation relationship between the very thin Fe layer and the Cu substrate. We show that a single variant of the P orientation relationship, which accompanies atomic rearrangement parallel to the interface, predominates at the nucleation stage of the bcc structure. Nucleation of other variants of P, N, and KS occurs with increasing Fe thickness and causes the formation of the submicrometer bcc grains

  10. NiFe epitaxial films with hcp and fcc structures prepared on bcc-Cr underlayers

    International Nuclear Information System (INIS)

    Higuchi, Jumpei; Ohtake, Mitsuru; Sato, Yoichi; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-01-01

    NiFe epitaxial films are prepared on Cr(211) bcc and Cr(100) bcc underlayers grown hetero-epitaxially on MgO single-crystal substrates by ultra-high vacuum rf magnetron sputtering. The film growth behavior and the crystallographic properties are studied by reflection high energy electron diffraction and pole figure X-ray diffraction. Metastable hcp-NiFe(11-bar 00) and hcp-NiFe(112-bar 0) crystals respectively nucleate on Cr(211) bcc and Cr(100) bcc underlayers, where the hcp-NiFe crystals are stabilized through hetero-epitaxial growth. The hcp-NiFe(11-bar 00) crystal is a single-crystal with the c-axis parallel to the substrate surface, whereas the hcp-NiFe(112-bar 0) crystal is a bi-crystal with the respective c-axes lying in plane and perpendicular each other. With increasing the film thickness, the hcp structure in the NiFe films starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001) close packed plane. The resulting films consist of hcp and fcc crystals.

  11. TiAu based shape memory alloys for high temperature applications

    International Nuclear Information System (INIS)

    Wadood, Abdul; Yamabe-Mitarai, Yoko; Hosoda, Hideki

    2014-01-01

    TiAu (equiatomic) exhibits phase transformaion from B2 (ordered bcc) to thermo-elastic orthorhombic B19 martensite at about 875K and thus TiAu is categorized as high temperature shape memory alloy. In this study, recent research and developments related to TiAu based high temperature shape memory alloys will be discussed in the Introduction part. Then some results of our research group related to strengthening of TiAu based high temperature shape memory alloys will be presented. Potential of TiAu based shape memory alloys for high temperature shape memory materials applications will also be discussed

  12. TiZrNbTaMo high-entropy alloy designed for orthopedic implants: As-cast microstructure and mechanical properties.

    Science.gov (United States)

    Wang, Shao-Ping; Xu, Jian

    2017-04-01

    Combining the high-entropy alloy (HEA) concept with property requirement for orthopedic implants, we designed a Ti 20 Zr 20 Nb 20 Ta 20 Mo 20 equiatomic HEA. The arc-melted microstructures, compressive properties and potentiodynamic polarization behavior in phosphate buffer solution (PBS) were studied in detail. It was revealed that the as-cast TiZrNbTaMo HEA consisted of dual phases with bcc structure, major bcc1 and minor bcc2 phases with the lattice parameters of 0.3310nm and 0.3379nm, respectively. As confirmed by nanoindentation tests, the bcc1 phase is somewhat harder and stiffer than the bcc2 phase. The TiZrNbTaMo HEA exhibited Young's modulus of 153GPa, Vickers microhardness of 4.9GPa, compressive yield strength of σ y =1390MPa and apparent plastic strain of ε p ≈6% prior to failure. Moreover, the TiZrNbTaMo HEA manifested excellent corrosion resistance in PBS, comparable to the Ti6Al4V alloy, and pitting resistance remarkably superior to the 316L SS and CoCrMo alloys. These preliminary advantages of the TiZrNbTaMo HEA over the current orthopedic implant metals in mechanical properties and corrosion resistance offer an opportunity to explore new orthopedic-implant alloys based on the TiZrNbTaMo concentrated composition. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. High Temperature Magneto-Elastic Instability of Dislocations in bcc Iron

    International Nuclear Information System (INIS)

    Dudarev, S.; Bullough, R.; Gilbert, M.; Derlet, P.

    2007-01-01

    Full text of publication follows: Density functional calculations show that the low temperature structure of self-interstitial defects in iron is fundamentally different from the structure of self-interstitial defects in all the other bcc metals. The origin of this anomaly is associated with the magnetic part of the cohesive energy of iron, where the Stoner exchange term stabilizes the body centred cubic phase, and where the magnetic part of energy is strongly affected by the large strain associated with the core region of an interstitial defect. At elevated temperatures magnetic excitations erode the stability of the bcc phase, giving rise to the gradual softening of the 110 transverse acoustic phonon modes and to the α-γ bcc-fcc martensitic phase transition occurring at 912 deg. C at normal pressure. Elastic moduli of bcc iron vary as a function of temperature with c' = (C 11 - c 12 )/2 vanishing at the α-γ transition point. This has significant effects on the magnitude of both the elastic interactions between dislocations and other defects in the material and on the intrinsic structural stability of the dislocations and other defects themselves. To evaluate structural stability of defects at elevated temperatures we investigate elastic self-energies of dislocations in the continuum anisotropic elasticity approximation. We also develop atomistic models of dislocations and point defects based on a generalised form of the magnetic potential. By varying the magnetic part of the potential we are able to reproduce the experimentally observed variation of elastic moduli as a function of temperature, and assess relative stability of various types of defect structures. Our analysis shows that, in complete contrast to other straight dislocations, the elastic self-energy of straight 100 edge dislocations actually sharply decreases as we approach the α-γ transition, indicating that this surprising fact is a probable explanation of the frequent observation of the 100

  14. In vivo assessment of optical properties of basal cell carcinoma and differentiation of BCC subtypes by high-definition optical coherence tomography

    DEFF Research Database (Denmark)

    Boone, Marc; Suppa, Mariano; Miyamoto, Makiko

    2016-01-01

    High-definition optical coherence tomography (HD-OCT) features of basal cell carcinoma (BCC) have recently been defined. We assessed in vivo optical properties (IV-OP) of BCC, by HD-OCT. Moreover their critical values for BCC subtype differentiation were determined. The technique of semi-log plot...

  15. Interatomic spacing distribution in multicomponent alloys

    International Nuclear Information System (INIS)

    Toda-Caraballo, I.; Wróbel, J.S.; Dudarev, S.L.; Nguyen-Manh, D.; Rivera-Díaz-del-Castillo, P.E.J.

    2015-01-01

    A methodology to compute the distribution of interatomic distances in highly concentrated multicomponent alloys is proposed. By using the unit cell parameter and bulk modulus of the elements involved, the method accurately describes the distortion in the lattice produced by the interaction of the different atomic species. To prove this, density functional theory calculations have been used to provide the description of the lattice in a monophasic BCC MoNbTaVW high entropy alloy and its five sub-quaternary systems at different temperatures. Short-range order is also well described by the new methodology, where the mean error in the predicted atomic coordinates in comparison with the atomistic simulations is in the order of 1–2 pm over all the compositions and temperatures considered. The new method can be applied to tailor solid solution hardening, highly dependent on the distribution of interatomic distances, and guide the design of new high entropy alloys with enhanced properties

  16. Collective and tracer diffusion kinetics in the ternary random alloy

    International Nuclear Information System (INIS)

    Belova, I.V.; Murch, G.E.; Allnatt, A.R.

    2002-01-01

    In this study, collective and tracer diffusion kinetics is addressed for the ternary random alloy. A formal solution from the self-consistent theory of Moleko et al (Moleko L K, Allnatt A R and Allnatt E L 1989 Phil. Mag. A 59 141) is derived for collective diffusion and compared with the corresponding solution for the binary random alloy. Tracer diffusion in the ternary alloy is treated from the perspective of a special case of the quaternary random alloy. Results from Monte Carlo calculations for tracer and collective correlation factors (for the bcc ternary random alloy) are found to be in excellent agreement with this self-consistent theory but in only semi-quantitative agreement with the earlier theory of Manning (Manning J R 1971 Phys. Rev. B 4 1111). (author)

  17. Effect of Al content on structure and mechanical properties of the Al{sub x}CrNbTiVZr (x = 0; 0.25; 0.5; 1) high-entropy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yurchenko, N.Yu. [Laboratory of Bulk Nanostructured Materials, Belgorod State University, Belgorod 308015 (Russian Federation); Stepanov, N.D., E-mail: stepanov@bsu.edu.ru [Laboratory of Bulk Nanostructured Materials, Belgorod State University, Belgorod 308015 (Russian Federation); Shaysultanov, D.G. [Laboratory of Bulk Nanostructured Materials, Belgorod State University, Belgorod 308015 (Russian Federation); Tikhonovsky, M.A. [National Science Center “Kharkov Institute of Physics and Technology”, NAS of Ukraine, Kharkov, 61108 (Ukraine); Salishchev, G.A. [Laboratory of Bulk Nanostructured Materials, Belgorod State University, Belgorod 308015 (Russian Federation)

    2016-11-15

    In present study, structure and mechanical properties of the Al{sub x}CrNbTiVZr (x = 0; 0.25; 0.5; 1) high-entropy alloys after arc melting and annealing at 1200 °C for 24 h are investigated. The CrNbTiVZr alloy is composed of body centered cubic (bcc) and C15 (face centered cubic) Laves phases while the Al{sub x}CrNbTiVZr (x = 0.25; 0.5; 1) alloys consist of bcc and two C14 (hexagonal close packed) Laves phases with different chemical compositions. Thermodynamic modeling predicts existence of two phases – bcc and C15 Laves phase and broadening of single bcc phase field due to Al addition. The density of the alloys decreases with the increase of Al content. The alloys are found to be extremely brittle at room temperature and 600 °C. The alloys have high strength at temperatures of 800–1000 °C. For example, yield strength at 800 °C increases from 440 MPa for the CrNbTiVZr alloy to 1250 MPa for the AlCrNbTiVZr alloy. The experimental phase composition of the Al{sub x}CrNbTiVZr alloys is compared with predicted equilibrium phases and the factors governing the transformation of C15 to C14 Laves phases due to Al addition to the CrNbTiVZr alloy analyzed. Specific properties of the alloys are compared with other high-entropy alloys and commercial Ni-based superalloys. - Highlights: •Al{sub x}CrNbTiVZr (x = 0; 0.25; 0.5; 1) alloys are arc melted and annealed at 1200 °C. •The CrNbTiVZr alloy has bcc and C15 Laves phases. •The Al-containing alloys are composed of bcc and two C14 Laves phases. •The alloys demonstrate high specific strength at temperatures of 800 °C and 1000 °C. •The strength of the alloys increases in proportion with increase of Al content.

  18. Soft Magnetic Properties of Nanocrystalline Fe-M-(B and/or O)(M=Group IV A, V A Elements) Alloy Films

    OpenAIRE

    Hayakawa, Y.; Makino, A.; Inoue, A.; Masumoto, T.

    1996-01-01

    In Fe-M-(B and/or O)(M=group IV A, V A elements) alloy films, nanocrystalline bcc phase are formed by annealing the amorphous single phase for Fe-M-B films, whereas the bcc nanocrystals are already formed in an as-deposited state for Fe-M-O or Fe-M-B-O) films. Among Fe-M-B films with various M elements, Fe-(Zr, Hf, Nb, Ta)-B alloy films exhibit high saturation magnetization (Is) above 1.4 T and high relative permeability (|μ|) above 1000 at 1MHz. The highest |μ| of 3460 at 1MHz is obtained fo...

  19. Influence of hydrostatic pressure on BCC-lattice parameter in molybdenum, niobium and vanadium with rhenium solid solutions

    International Nuclear Information System (INIS)

    Smol'yaninova, Eh.A.; Stribuk, E.K.; Tyavlovskij, V.I.

    1987-01-01

    Data on the effect of 1.8GPa hydrostatic pressure on bcc lattice parameters of solid solutions in Mo-Re, Nb-Re, V-re systems are presented. It is shown that after the application hydrostatic pressure a decrease in bcc lattice parameter is observed and the greatest change in the lattice parameter takes place in bcc of solid solutions in the Nb-Re system (DELTA A ∼ 0.0035 nm). Analysis of the experimental data obtained on the basis of calculations made for packing density change in the above-mentioned solid solutions under the pressure is carried out

  20. Radiation behavior of high-entropy alloys for advanced reactors. Final report

    International Nuclear Information System (INIS)

    Liaw, Peter K.; Egami, Takeshi; Zhang, Chuan; Zhang, Fan; Zhang, Yanwen

    2015-01-01

    In the first task, we have demonstrated the radiation damage and the recrystallization behaviors in multicomponent alloys through molecular-dynamics simulations. It is found that by alloying with atoms of different sizes, the atomic-level strain increases, and the propensity of the radiation-induced crystalline to amorphous transition increases as the defects cluster in the cascade body. Recrystallization of the radiation induced supercooled or glass regions show that by tuning the composition and the equilibrium temperature, the multicomponent alloys can be healed. The crystalline-amorphous-crystalline transitions predict the potential high radiation resistance in multicomponent alloys. In the second task, three types of high-entropy alloys (HEAs) were fabricated from AlCoCrFeNi and AlCuCrFeNi quinary alloys. Hardness and reduced contact modulus were measured using nanoindentation tests. Heavy ion irradiation were performed using 10 MeV gold and 5 MeV nickel to study radiation effects. Al 0.5 CrCuFeNi 2 shows phase separation upon the presence of copper. Both hardness and contact modulus exhibit the same trend as increasing the applied load, and it indicates that excessive free volume may alter the growth rate of the plastic zone. The as-cast Al 0.1 CoCrFeNi specimen undergone the hot isostatic pressing (HIP) process and steady cooling rate which mitigate the quenching effect. The swelling behavior was characterized by the atomic force microscopy (AFM), and the swelling rate is approximately 0.02% dpa. Selected area diffraction (SAD) patters show irradiation-induced amorphization throughout the ion projected range. Within the peak damage region, an amorpous ring is observed, and a mixture of amorphous/ crystalline structure at deeper depth is found. The Al 0.3 CoCrFeNi HEAs shows good radiation resistance up to 60 peak dpa. No voids or dislocations are observed. The crystal structures remain face-centered-cubic (FCC) before and after 5 MeV Ni irradiation. Higher

  1. In situ 3D characterization of high temperature fatigue damage mechanisms in a cast aluminum alloy using synchrotron X-ray tomography

    International Nuclear Information System (INIS)

    Dezecot, Sebastien; Buffiere, Jean-Yves; Koster, Alain; Maurel, Vincent; Szmytka, Fabien; Charkaluk, Eric; Dahdah, Nora; El Bartali, Ahmed; Limodin, Nathalie; Witz, Jean-Francois

    2016-01-01

    Fatigue tests were performed at 250 °C on a cast AlSi7Cu3Mg aluminum alloy and monitored with Synchrotron in situ X-ray tomography in order to understand the micro-mechanisms of crack initiation and propagation. The analysis of the 3D images reveals that internal shrinkage pores are responsible for the main crack initiation. Crack propagation is mainly due to the complex and highly interconnected network of hard particles of the eutectic regions.

  2. Irradiation damage

    Energy Technology Data Exchange (ETDEWEB)

    Howe, L.M

    2000-07-01

    There is considerable interest in irradiation effects in intermetallic compounds from both the applied and fundamental aspects. Initially, this interest was associated mainly with nuclear reactor programs but it now extends to the fields of ion-beam modification of metals, behaviour of amorphous materials, ion-beam processing of electronic materials, and ion-beam simulations of various kinds. The field of irradiation damage in intermetallic compounds is rapidly expanding, and no attempt will be made in this chapter to cover all of the various aspects. Instead, attention will be focused on some specific areas and, hopefully, through these, some insight will be given into the physical processes involved, the present state of our knowledge, and the challenge of obtaining more comprehensive understanding in the future. The specific areas that will be covered are: point defects in intermetallic compounds; irradiation-enhanced ordering and irradiation-induced disordering of ordered alloys; irradiation-induced amorphization.

  3. Irradiation damage

    International Nuclear Information System (INIS)

    Howe, L.M.

    2000-01-01

    There is considerable interest in irradiation effects in intermetallic compounds from both the applied and fundamental aspects. Initially, this interest was associated mainly with nuclear reactor programs but it now extends to the fields of ion-beam modification of metals, behaviour of amorphous materials, ion-beam processing of electronic materials, and ion-beam simulations of various kinds. The field of irradiation damage in intermetallic compounds is rapidly expanding, and no attempt will be made in this chapter to cover all of the various aspects. Instead, attention will be focused on some specific areas and, hopefully, through these, some insight will be given into the physical processes involved, the present state of our knowledge, and the challenge of obtaining more comprehensive understanding in the future. The specific areas that will be covered are: point defects in intermetallic compounds; irradiation-enhanced ordering and irradiation-induced disordering of ordered alloys; irradiation-induced amorphization

  4. Plate-shaped transformation products in zirconium-base alloys

    International Nuclear Information System (INIS)

    Banerjee, S.; Dey, G.K.; Srivastava, D.

    1997-01-01

    Plate-shaped products resulting from martensitic, diffusional, and mixed mode transformations in zirconium-base alloys are compared in the present study. These alloys are particularly suitable for the comparison in view of the fact that the lattice correspondence between the parent β (bcc) and the product α (hcp) or γ-hydride (fct) phases are remarkably similar for different types of transformations. Crystallographic features such as orientation relations, habit planes, and interface structures associated with these transformations have been compared, with a view toward examining whether the transformation mechanisms have characteristic imprints on these experimental observables

  5. Mechanisms of the plastic deformation of uranium alloys at low temperature

    International Nuclear Information System (INIS)

    Le Poac, P.; Nomine, A.M.; Miannay, D.

    1976-01-01

    The mechanical characteristics of the bcc binary alloys U-6Mo, U-8Mo, U-10Mo, U-12Mo and bcc ternary alloys U-8Mo-1Ti, U-10Mo-1Ti, U-10Mo-1Zr, stressed in compression, were determined between -196 deg C and + 450 deg C. The plastic flow shear stress in non-dependent on temperature above 300 deg C. At lower temperature shear stress is highly activated, except for the alloy U-6Mo and U-12Mo. Athermal shear stress above 300 deg C is due to the hardening of the solid solution described by Mott and Nabarro. In the thermal range, the recombination of the dissociated dislocations controls the plastic deformation [fr

  6. Modelling irradiation-induced softening in BCC iron by crystal plasticity approach

    International Nuclear Information System (INIS)

    Xiao, Xiazi; Terentyev, Dmitry; Yu, Long; Song, Dingkun; Bakaev, A.; Duan, Huiling

    2015-01-01

    Crystal plasticity model (CPM) for BCC iron to account for radiation-induced strain softening is proposed. CPM is based on the plastically-driven and thermally-activated removal of dislocation loops. Atomistic simulations are applied to parameterize dislocation-defect interactions. Combining experimental microstructures, defect-hardening/absorption rules from atomistic simulations, and CPM fitted to properties of non-irradiated iron, the model achieves a good agreement with experimental data regarding radiation-induced strain softening and flow stress increase under neutron irradiation. - Highlights: • A stress- and thermal-activated defect absorption model is proposed for the dislocation-loop interaction. • A temperature-dependent plasticity theory is proposed for the irradiation-induced strain softening of irradiated BCC metals. • The numerical results of the model match with the corresponding experimental data.

  7. Simulation of He embrittlement at grain boundaries in bcc transition metals

    International Nuclear Information System (INIS)

    Suzudo, Tomoaki; Yamaguchi, Masatake

    2015-01-01

    To investigate what atomic properties largely determine vulnerability to He embrittlement at grain boundaries (GB) of bcc metals, we introduce a computational model composed of first principles density functional theory and a He segregation rate theory model. Predictive calculations of He embrittlement at the first wall of the future DEMO fusion concept reactor indicate that variation in the He embrittlement originated not only from He production rate related to neutron irradiation, but also from the He segregation energy at the GB that has a systematic trend in the periodic table. - Highlights: • We modeled He grain boundary (GB) segregation of bcc transition metals using first-principles-based rate theory. • We established the quantitative relation between He embrittlement and He segregation using GB cohesive energy. • He embrittlement was strongly dependent on He segregation energy at the GB that has a systematic trend in the periodic table.

  8. Simulation of He embrittlement at grain boundaries in bcc transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Suzudo, Tomoaki, E-mail: suzudo.tomoaki@jaea.go.jp; Yamaguchi, Masatake

    2015-10-15

    To investigate what atomic properties largely determine vulnerability to He embrittlement at grain boundaries (GB) of bcc metals, we introduce a computational model composed of first principles density functional theory and a He segregation rate theory model. Predictive calculations of He embrittlement at the first wall of the future DEMO fusion concept reactor indicate that variation in the He embrittlement originated not only from He production rate related to neutron irradiation, but also from the He segregation energy at the GB that has a systematic trend in the periodic table. - Highlights: • We modeled He grain boundary (GB) segregation of bcc transition metals using first-principles-based rate theory. • We established the quantitative relation between He embrittlement and He segregation using GB cohesive energy. • He embrittlement was strongly dependent on He segregation energy at the GB that has a systematic trend in the periodic table.

  9. Modelling irradiation-induced softening in BCC iron by crystal plasticity approach

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Xiazi [State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); CAPT, HEDPS and IFSA Collaborative Innovation Center of MoE, Peking University, Beijing 100871 (China); Terentyev, Dmitry, E-mail: dterenty@SCKCEN.BE [Structural Material Group, Institute of Nuclear Materials Science, SCK-CEN, Mol (Belgium); Yu, Long; Song, Dingkun [State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); Bakaev, A. [Structural Material Group, Institute of Nuclear Materials Science, SCK-CEN, Mol (Belgium); Duan, Huiling, E-mail: hlduan@pku.edu.cn [State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); CAPT, HEDPS and IFSA Collaborative Innovation Center of MoE, Peking University, Beijing 100871 (China)

    2015-11-15

    Crystal plasticity model (CPM) for BCC iron to account for radiation-induced strain softening is proposed. CPM is based on the plastically-driven and thermally-activated removal of dislocation loops. Atomistic simulations are applied to parameterize dislocation-defect interactions. Combining experimental microstructures, defect-hardening/absorption rules from atomistic simulations, and CPM fitted to properties of non-irradiated iron, the model achieves a good agreement with experimental data regarding radiation-induced strain softening and flow stress increase under neutron irradiation. - Highlights: • A stress- and thermal-activated defect absorption model is proposed for the dislocation-loop interaction. • A temperature-dependent plasticity theory is proposed for the irradiation-induced strain softening of irradiated BCC metals. • The numerical results of the model match with the corresponding experimental data.

  10. The Al Effects of Co-Free and V-Containing High-Entropy Alloys

    Directory of Open Access Journals (Sweden)

    Songqin Xia

    2017-01-01

    Full Text Available In this study, five-component high-entropy alloys (HEAs AlxCrFeNiV (where x denotes the molar ratio, x = 0, 0.1, 0.3, 0.5, 0.75, 1, and 1.5 were prepared using an arc-melting furnace. The effects of the addition of the Al on the crystal structures were investigated using X-ray diffraction (XRD, scanning electron microscopy (SEM, and transmission electron microscopy (TEM. Also, two non-equiatomic ratio HEAs, AlxCrFeNiV (x = 0.3, and 0.5, were systematically studied through the use of various characterization methods in the as-cast state. The Al0.3CrFeNiV alloy displayed typical duplex body-centered cubic (BCC structures, including disordered BCC (A2, and NiAl-type ordered BCC (B2 phases. Meanwhile, in regard to the Al0.5CrFeNiV alloy, this alloy was found to contain an unknown phase which was enriched in Cr and V, as well as the coherent A2/B2 phases. Both of these alloys displayed very high yield and fracture strengths. However, their compression fracture strains were approximately 10%. Also, the fracture surfaces showed mainly cleavage fracture modes.

  11. Emergence of the bcc Phase and Phase Transition in Be through Phonon Quasiparticle Calculations

    Science.gov (United States)

    Zhang, D. B., Sr.; Wentzcovitch, R. M.

    2016-12-01

    Beryllium (Be) is an important material with applications in a number of areas ranging from aerospace components to X-ray equipment. Yet a precise understanding of the phase diagram of Be remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticle properties. We find that the hcp to bcc transition occurs near the melting curve at 0

  12. Path-integral Monte Carlo study of phonons in the bcc phase of Helium-3

    OpenAIRE

    Sorkin, V.; Polturak, E.; Adler, Joan

    2006-01-01

    Using Path Integral Monte Carlo and the Maximum Entropy method, we calculate the dynamic structure factor of solid He-3 in the bcc phase at a finite temperature of T = 1.6 K and a molar volume of 21.5 cm^3. From the single phonon dynamic structure factor, we obtain both the longitudinal and transverse phonon branches along the main crystalline directions, [001], [011] and [111]. Our results are compared with other theoretical predictions and available experimental data.

  13. Atomistic model application to the problem of magnetite adhesion on iron BCC

    International Nuclear Information System (INIS)

    Forti; M; Alonso, P; Gargano, P; Rubiolo, G

    2012-01-01

    Oxide scale adhesion on a metal substrate has been investigated in the Magnetite - BCC Iron system. An Universal Binding Energy Relation (UBER) has been applied to obtain the interface energy from a fitting parameter. The interface energy thus calculated is in a reasonable order of magnitude when compared to experimental data for similar systems. This result allows this technique to be used to develop a comparative scale based on quantitative data which otherwise would require complex experiments to be obtained (author)

  14. 3D atomistic simulation of fatigue behavior of a ductile crack in bcc iron

    Czech Academy of Sciences Publication Activity Database

    Uhnáková, Alena; Machová, Anna; Hora, Petr

    2011-01-01

    Roč. 33, č. 9 (2011), s. 1182-1188 ISSN 0142-1123 R&D Projects: GA ČR(CZ) GAP108/10/0698 Institutional research plan: CEZ:AV0Z20760514 Keywords : 3D molecular dynamics * fatigue * bcc iron * mode I Subject RIV: JG - Metallurgy Impact factor: 1.546, year: 2011 http://www.sciencedirect.com/science/article/pii/S0142112311000600

  15. Curie temperatures of fcc and bcc Nickel and Permalloy: Supercell and Green's function methods

    Czech Academy of Sciences Publication Activity Database

    Yu, P.; Jin, X.F.; Kudrnovský, Josef; Wang, D. S.; Bruno, P.

    2008-01-01

    Roč. 77, č. 5 (2008), 054431/1-054431/8 ISSN 1098-0121 R&D Projects: GA MŠk OC 150; GA AV ČR IAA100100616 Institutional research plan: CEZ:AV0Z10100520 Keywords : fcc - and bcc-Ni * Permalloy * magnetic moments * Curie temperatures Subject RIV: BE - Theoretical Physics Impact factor: 3.322, year: 2008

  16. Crack-induced stress, dislocations and acoustic emission by 3-D atomistic simulation in bcc iron

    Czech Academy of Sciences Publication Activity Database

    Spielmannová, Alena; Machová, Anna; Hora, Petr

    2009-01-01

    Roč. 57, č. 14 (2009), s. 4065-4073 ISSN 1359-6454 R&D Projects: GA ČR GA101/09/1630; GA AV ČR KJB200760802; GA ČR(CZ) GA101/07/0789 Institutional research plan: CEZ:AV0Z20760514 Keywords : bcc iron * crack * dislocation emisision Subject RIV: JG - Metallurgy Impact factor: 3.760, year: 2009

  17. Behaviour and fatigue damage study of cast aluminium alloys; Etude du comportement et de l'endommagement en fatigue d'alliages d'aluminium de fonderie

    Energy Technology Data Exchange (ETDEWEB)

    Barlas, B.

    2004-02-15

    This study is aimed at determining the influence of chemical composition and heat treatment of cast aluminium alloys Al-Si-Cu-Mg on mechanical behaviour and fatigue life of structures. The industrial frame of this study concerns cylinder-heads of high efficiency diesel engines, for Renault and Montupet companies. The experimental means involved in this work are as well microscopic (TEM, microhardness, image analysis), mechanical (LCF and aniso-thermal tests, macro-hardness) and numerical (simulation of the stability of the hardening phases, behaviour and damage model identification, cylinder-head life time calculation). The link between micro and macro approaches is provided by the means of an internal microscopic variable representing thermal aging through coarsening of the precipitates and implemented into the macroscopic model. (author)

  18. Structural and magnetic properties of Fe{sub x}Ni{sub 100−x} alloys synthesized using Al as a reducing metal

    Energy Technology Data Exchange (ETDEWEB)

    Srakaew, N. [Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand); Jantaratana, P., E-mail: fscipsj@ku.ac.th [Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand); Nipakul, P. [Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand); Sirisathitkul, C. [Molecular Technology Research Unit, School of Science, Walailak University, Nakhon Si Thammarat 80161 (Thailand)

    2017-08-01

    Highlights: • Reduction by aluminum is a simple and safe route to synthesize iron-nickel alloys. • Alloy compositions with up to 90 at.% Fe can be obtained with minimal oxidation. • Morphology and magnetic properties are varied with the alloy composition. - Abstract: Iron-nickel (Fe-Ni) alloys comprising nine different compositions were rapidly synthesized from the redox reaction using aluminum foils as the reducing metal. Compared with conventional chemical syntheses, this simple approach is relatively safe and allows control over the alloy morphology and magnetic behavior as a function of the alloy composition with minimal oxidation. For alloys having low (10%–30%) Fe content the single face-centered cubic (FCC) FeNi{sub 3} phase was formed with nanorods aligned in the (1 1 1) crystalline direction on the cluster surface. This highly anisotropic morphology gradually disappeared as the Fe content was raised to 40%–70% with the alloy structure possessing a mixture of FCC FeNi{sub 3} and body-centered cubic (BCC) Fe{sub 7}Ni{sub 3}. The FCC phase was entirely replaced by the BCC structure upon further increase the Fe content to 80%–90%. The substitution of Ni by Fe in the crystals and the dominance of the BCC phase over the FCC structure gave rise to enhanced magnetization. By contrast, the coercive field decreased as a function of increasing Fe because of the reduction in shape anisotropy and the rise of saturation magnetization.

  19. Influence of the intermediate bcc phase on the evolution of superfluid inclusions in hcp matrix 3He-4He

    International Nuclear Information System (INIS)

    Birchenko, A.P.; Mikhin, N.P.; Neoneta, A.S.; Rudavskij, Eh.Ya.; Fisun, Ya.Yu.

    2016-01-01

    The evolution of liquid inclusions which are formed in the hcp matrix by rapid cooling of the 3 He- 4 He solution containing 1.05% 3 He was studied by pulse NMR. The diffusion coefficient of 3 He in the liquid was measured by two-pulses spin-echo method during evolution of the inclusions. Measurements were carried out at 1.67 K which corresponds to the bcc phase existence in the phase diagram, as well as at 1.38 K, where the bcc phase is absent. It is found that in the process of the evolution, in both cases the size of the liquid inclusions is less than diffusion length and so the diffusion is restricted. The measured restricted dif-fusion coefficient allowed to find the characteristic size of the inclusions. In the first case, during the evolution of liquid inclusions, dendrites of intermediate bcc phase is forming and the inclusions are separating into a lot of smaller droplets. Due to the rapid growth of the bcc dendrites, the droplet size decreases rapidly, and the process comes to disappearance of bcc phase and an amorphous state appearance. The results obtained by measuring the diffusion coefficient, correlated with the behavior of the spin-lattice relaxation time in such a system. In the second case at a lower temperature bcc phase is not formed, and the size of the liquid inclusions decreases very slow until the completion of their solidification.

  20. Fabry-Perot magnonic ballistic coherent transport across ultrathin ferromagnetic lamellar bcc Ni nanostructures between Fe leads

    Science.gov (United States)

    Khater, A.; Saim, L.; Tigrine, R.; Ghader, D.

    2018-06-01

    We propose thermodynamically stable systems of ultrathin lamellar bcc Ni nanostructures between bcc Fe leads, sbnd Fe[Ni(n)]Fesbnd , based on the available literature for bcc Ni overlayers on Fe(001) surfaces, and establish the necessary criteria for their structural and ferromagnetic order, for thicknesses n ≤ 6 bcc Ni monatomic layers. The system is globally ferromagnetic. A theoretical model is presented to investigate and understand the ballistic coherent scattering of Fe spin-waves, incident from the leads, at the ferromagnetic bcc Ni nanostructure. The Nisbnd Ni and Nisbnd Fe exchange are computed using the Ising effective field theory (EFT), and the magnetic ground state of the system is constructed in the Heisenberg representation. We compute the spin-wave eigenmodes localized on the bcc Ni nanostructure, using the phase field matching theory (PFMT), illustrating the effects of symmetry breaking on the confinement of localized spin excitations. The reflection and transmission scattering properties of spin-waves incident from the Fe leads, across the embedded Ni nanostructures are investigated within the framework of the same PFMT methodology. A highly refined Fabry-Perot magnonic ballistic coherent transmission spectra is observed for these sbnd Fe[Ni(n)]Fesbnd systems.

  1. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    Science.gov (United States)

    Gong, Zhiqiang; Dogar, Muhammad Mubashar Ahmad; Qiao, Shaobo; Hu, Po; Feng, Guolin

    2017-09-01

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection. The differences of summer precipitation modes of the empirical orthogonal function and the bias of atmospheric circulations over EA-NWP are analyzed to determine the reason for the precipitation prediction errors. Results indicate that the BCC_CSM could not reproduce the positive-negative-positive meridional tripole pattern from south to north that differs markedly from that observed over the last 20 years. This failure can be attributed to the bias of the BCC_CSM hindcasts of the summer EAP teleconnection and the low predictability of 500 hPa at the mid-high latitude lobe of the EAP. Meanwhile, the BCC_CSM hindcasts' deficiencies of atmospheric responses to SST anomalies over the Indonesia maritime continent (IMC) resulted in opposite and geographically shifted geopotential anomalies at 500 hPa as well as wind and vorticity anomalies at 850 hPa, rendering the BCC_CSM unable to correctly reproduce the EAP teleconnection pattern. Understanding these two problems will help further improve BCC_CSM's summer precipitation forecasting ability over EA-NWP.

  2. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    KAUST Repository

    Gong, Zhiqiang

    2017-04-05

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection. The differences of summer precipitation modes of the empirical orthogonal function and the bias of atmospheric circulations over EA-NWP are analyzed to determine the reason for the precipitation prediction errors. Results indicate that the BCC_CSM could not reproduce the positive-negative-positive meridional tripole pattern from south to north that differs markedly from that observed over the last 20 years. This failure can be attributed to the bias of the BCC_CSM hindcasts of the summer EAP teleconnection and the low predictability of 500 hPa at the mid-high latitude lobe of the EAP. Meanwhile, the BCC_CSM hindcasts\\' deficiencies of atmospheric responses to SST anomalies over the Indonesia maritime continent (IMC) resulted in opposite and geographically shifted geopotential anomalies at 500 hPa as well as wind and vorticity anomalies at 850 hPa, rendering the BCC_CSM unable to correctly reproduce the EAP teleconnection pattern. Understanding these two problems will help further improve BCC_CSM\\'s summer precipitation forecasting ability over EA-NWP.

  3. Comparative Study by MS and XRD of Fe{sub 50}Al{sub 50} Alloys Produced by Mechanical Alloying, Using Different Ball Mills

    Energy Technology Data Exchange (ETDEWEB)

    Rojas Martinez, Y., E-mail: yarojas@ut.edu.co [University of Tolima, Department of Physics (Colombia); Perez Alcazar, G. A. [University of Valle, Department of Physics (Colombia); Bustos Rodriguez, H.; Oyola Lozano, D., E-mail: doyolalozano@yahoo.com.mx [University of Tolima, Department of Physics (Colombia)

    2005-02-15

    In this work we report a comparative study of the magnetic and structural properties of Fe{sub 50}Al{sub 50} alloys produced by mechanical alloying using two different planetary ball mills with the same ball mass to powder mass relation. The Fe{sub 50}Al{sub 50} sample milled during 48 h using the Fritsch planetary ball mill pulverisette 5 and balls of 20 mm, presents only a bcc alloy phase with a majority of paramagnetic sites, whereas that sample milled during the same time using the Fritsch planetary ball mill pulverisette 7 with balls of 15 mm, presents a bcc alloy phase with paramagnetic site (doublet) and a majority of ferromagnetic sites which include pure Fe. However for 72 h of milling this sample presents a bcc paramagnetic phase, very similar to that prepared with the first system during 48 h. These results show that the conditions used in the first ball mill equipment make more efficient the milling process.

  4. Synthesis and microstructure characterization of Ni-Cr-Co-Ti-V-Al high entropy alloy coating on Ti-6Al-4V substrate by laser surface alloying

    International Nuclear Information System (INIS)

    Cai, Zhaobing; Jin, Guo; Cui, Xiufang; Liu, Zhe; Zheng, Wei; Li, Yang; Wang, Liquan

    2016-01-01

    Ni-Cr-Co-Ti-V-Al high-entropy alloy coating on Ti-6Al-4V was synthesized by laser surface alloying. The coating is composed of a B2 matrix and (Co, Ni)Ti 2 compounds with few β-Ti phases. Focused ion beam technique was utilized to prepare TEM sample and TEM observations agree well with XRD and SEM results. The formation of HEA phases is due to high temperature and rapid cooling rate during laser surface alloying. The thermodynamic parameters, ΔH mix , ΔS mix and δ as well as Δχ, should be used to predict the formation of the BCC solid solution, but they are not the strict criteria. Especially when Δχ reaches a high value (≥ 10%), BCC HEA will be partially decomposed, leading to the formation of (Co, Ni)Ti 2 compound phases. - Highlights: •Preparing HEA coating on Ti-6Al-4V by laser surface alloying is successful. •The synthesized HEA coating mainly consists of BCC HEA and (Co, Ni)Ti 2 compounds. •FIB technology was used to prepare the sample for TEM analysis. • ΔH mix , ΔS mix and δ as well as Δχ, should be all used to predict the formation of solid solution.

  5. Influence of atomic ordering on sigma phase precipitation of the Fe{sub 50}Cr{sub 50} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Vélez, G.Y., E-mail: g.y.velezcastillo@gmail.com [Universidad del Valle, Departamento de Física, A.A. 25360 Cali (Colombia); Instituto de Física, Universidad Autónoma de San Luis Potosí, avenida Manuel Nava 6, zona universitaria, 78290 San Luis Potosí, SLP México (Mexico); Pérez Alcázar, G.A. [Universidad del Valle, Departamento de Física, A.A. 25360 Cali (Colombia)

    2015-09-25

    Highlights: • σ-FeCr phase can be delayed when α-FeCr phase is ordered. • The formation of σ phase is favored by concentration gradients of α phase. • We determine the iron occupation number of the five sites of σ-Fe{sub 50}Cr{sub 50}. - Abstract: In this work we report a study of the kinetic of the formation of the σ-Fe{sub 50}Cr{sub 50} alloy which is obtained by heat treatment of α-FeCr samples with different atomic ordering. Two α-FeCr alloys were obtained, one by mechanical alloying and the other by arc-melting. Both alloys were heated at 925 K for 170 h and then quenched into ice water. Before heat treatment both alloys exhibit α-FeCr disordered structure with greater ferromagnetic behavior in the alloy obtained by mechanical alloying due to its higher atomic disorder. The sigma phase precipitation is influenced by the atomic ordering of the bcc samples: in the alloy obtained by mechanical alloying, the bcc phase is completely transformed into the σ phase; in the alloy obtained by melted the α–σ transformation is partial.

  6. Vanadium-based alloy hydrides for heat pumps, compressors, and isotope separation

    International Nuclear Information System (INIS)

    Libowitz, G.G.

    1988-01-01

    A series of body-centered cubic (b.c.c.) solid solution alloys have been developed which appears to be unusually suitable for several applications involving metal hydrides. It is normally very difficult to induce the body-centered cubic metals, Nb, V, and Ta, to react with hydrogen; in bulk form the reaction will simply not occur at room temperature. Alloys containing Nb exhibited very large hysteresis effects on hydride formation and thus are not suitable for most applications. However, the V-Ti based alloys showed relatively little hysteresis, and because of their unusual thermodynamic properties offer significant advantages for the specific applications discussed below. (orig./HB)

  7. The Current Status of Hydrogen Storage Alloy Development for Electrochemical Applications

    Science.gov (United States)

    Young, Kwo-hsiung; Nei, Jean

    2013-01-01

    In this review article, the fundamentals of electrochemical reactions involving metal hydrides are explained, followed by a report of recent progress in hydrogen storage alloys for electrochemical applications. The status of various alloy systems, including AB5, AB2, A2B7-type, Ti-Ni-based, Mg-Ni-based, BCC, and Zr-Ni-based metal hydride alloys, for their most important electrochemical application, the nickel metal hydride battery, is summarized. Other electrochemical applications, such as Ni-hydrogen, fuel cell, Li-ion battery, air-metal hydride, and hybrid battery systems, also have been mentioned. PMID:28788349

  8. The melting-diffusion correlation in the plutonium-zirconium alloys

    International Nuclear Information System (INIS)

    Zanghi, J.-P.; Calais, Daniel.

    1975-01-01

    The activation volumes for self-diffusion of Pu in b.c.c. PuZr alloys (10 and 40at%Zr) have been determined, the validity of Nachtrieb's melting-diffusion correlation was checked. Indeed, in the Pu-40at%Zr alloy, which has a pressure temperature phase diagram whose liquidus has a positive slope, the activation volume is positive, whereas in pure epsilon Pu where the slope is negative, the activation volume is negative. A self-diffusion mechanism in PuZr alloys is proposed [fr

  9. Microstructure and magnetic properties of rapidly solidified nanocrystalline Fe81Zr7B12 alloy

    International Nuclear Information System (INIS)

    Xiong, X.Y.; Muddle, B.C.; Finlayson, T.R.

    2000-01-01

    Full text: Nanocrystalline Fe-Zr-B alloys have aroused extensive research interest due to their high saturation magnetization. There have been several studies [Suzuki et al., 1994; Kim et al., 1994] of the effect of boron on the formation of nanocrystalline structure and magnetic properties, showing that the addition of boron to Fe-Zr alloys improves the glass-forming ability and refines the primary bcc α-Fe grains during crystallization. However, when the boron content is increased to 8 at.%, the magnetic permeability is observed to decrease. There has been no detailed work to date concerning the microstructural evolution and magnetic properties in those alloys with higher boron content

  10. Magnetostriction of heavily deformed Fe–Co binary alloys prepared by forging and cold rolling

    Energy Technology Data Exchange (ETDEWEB)

    Yamaura, Shin-ichi, E-mail: yamaura@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan); Nakajima, Takashi [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan); Satoh, Takenobu; Ebata, Takashi [Tohoku Steel, Co., Ltd., 23 Nishigaoka, Murata, Murata-machi, Shibata 989-1393 (Japan); Furuya, Yasubumi [North Japan Research Institute for Sustainable Energy, Hirosaki University, 2-1-3 Matsubara, Aomori 030-0813 (Japan)

    2015-03-15

    Highlights: • The as-forged Fe{sub 25}Co{sub 75} alloy shows the magnetostriction of 108 ppm. • The as-cold rolled Fe{sub 25}Co{sub 75} alloy shows the magnetostriction of 140 ppm. • Magnetostriction of Fe–Co alloy reached the maximum in a single bcc state. • Fcc phase is harmful to the increase in magnetostriction of Fe–Co alloy. • Fcc phase precipitation in Fe–Co alloy can be suppressed by cold rolling. - Abstract: Magnetostriction of Fe{sub 1−x}Co{sub x} (x = 50–90 at%) alloys prepared by forging and subsequent cold-rolling was studied as functions of alloy compositions and thermomechanical treatments. Magnetostriction of the as-forged Fe{sub 25}Co{sub 75} alloy was 108 ppm and that of the as-cold rolled Fe{sub 25}Co{sub 75} alloy measured parallel to the rolling direction (RD) was 128 ppm. The cold-rolled Fe{sub 25}Co{sub 75} alloy possessed a nearly {1 0 0}<0 1 1> texture, leading to the maximum magnetostriction of 140 ppm when measured at an angle of 45° to RD. Moreover, the fully annealed Fe{sub 25}Co{sub 75} and Fe{sub 20}Co{sub 80} alloys were gradually cold rolled and magnetostriction were measured. Results showed that the magnetostriction of those cold-rolled alloys drastically increased with increasing reduction rate. According to the XRD and TEM observations, intensity of the fcc peak gradually decreased with increasing reduction rate and that the alloys became to be in a bcc single state at a reduction rate higher than 90%, leading to a drastic increase in magnetostriction.

  11. Magnetostriction of heavily deformed Fe–Co binary alloys prepared by forging and cold rolling

    International Nuclear Information System (INIS)

    Yamaura, Shin-ichi; Nakajima, Takashi; Satoh, Takenobu; Ebata, Takashi; Furuya, Yasubumi

    2015-01-01

    Highlights: • The as-forged Fe 25 Co 75 alloy shows the magnetostriction of 108 ppm. • The as-cold rolled Fe 25 Co 75 alloy shows the magnetostriction of 140 ppm. • Magnetostriction of Fe–Co alloy reached the maximum in a single bcc state. • Fcc phase is harmful to the increase in magnetostriction of Fe–Co alloy. • Fcc phase precipitation in Fe–Co alloy can be suppressed by cold rolling. - Abstract: Magnetostriction of Fe 1−x Co x (x = 50–90 at%) alloys prepared by forging and subsequent cold-rolling was studied as functions of alloy compositions and thermomechanical treatments. Magnetostriction of the as-forged Fe 25 Co 75 alloy was 108 ppm and that of the as-cold rolled Fe 25 Co 75 alloy measured parallel to the rolling direction (RD) was 128 ppm. The cold-rolled Fe 25 Co 75 alloy possessed a nearly {1 0 0}<0 1 1> texture, leading to the maximum magnetostriction of 140 ppm when measured at an angle of 45° to RD. Moreover, the fully annealed Fe 25 Co 75 and Fe 20 Co 80 alloys were gradually cold rolled and magnetostriction were measured. Results showed that the magnetostriction of those cold-rolled alloys drastically increased with increasing reduction rate. According to the XRD and TEM observations, intensity of the fcc peak gradually decreased with increasing reduction rate and that the alloys became to be in a bcc single state at a reduction rate higher than 90%, leading to a drastic increase in magnetostriction

  12. Modelling of plastic flow localization and damage development in friction stir welded 6005A aluminium alloy using physics based strain hardening law

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Pardoen, Thomas; Tvergaard, Viggo

    2010-01-01

    of these zones was extracted from micro-tensile specimens cut parallel to the welding direction. The measured material properties and weld topology were introduced into a 3D finite element model, fully coupled with the damage model. A Voce law hardening model involving a constant stage IV is used within...

  13. Alloying behavior of iron, gold and silver in AlCoCrCuNi-based equimolar high-entropy alloys

    International Nuclear Information System (INIS)

    Hsu, U.S.; Hung, U.D.; Yeh, J.W.; Chen, S.K.; Huang, Y.S.; Yang, C.C.

    2007-01-01

    High-entropy alloys are newly developed alloys that are composed, by definition, of at least five principal elements with concentrations in the range of 5-35 at.%. Therefore, the alloying behavior of any given principal element is significantly affected by all the other principal elements present. In order to elucidate this further, the influence of iron, silver and gold addition on the microstructure and hardness of AlCoCrCuNi-based equimolar alloys has been examined. The as-cast AlCoCrCuNi base alloy is found to have a dendritic structure, of which only solid solution FCC and BCC phases can be observed. The BCC dendrite has a chemical composition close to that of the nominal alloy, with a deficiency in copper however, which is found to segregate and form a FCC Cu-rich interdendrite. The microstructure of the iron containing alloys is similar to that of the base alloy. It is found that both of these aforementioned alloys have hardnesses of about 420 HV, which is equated to their similar microstructures. The as-cast ingot forms two layers of distinct composition with the addition of silver. These layers, which are gold and silver in color, are determined to have a hypoeutectic Ag-Cu composition and a multielement mixture of the other principal elements, respectively. This indicates the chemical incompatibility of silver with the other principal elements. The hardnesses of the gold (104 HV) and silver layers (451 HV) are the lowest and highest of the alloy systems studied. This is attributed to the hypoeutectic Ag-Cu composition of the former and the reduced copper content of the latter. Only multielement mixtures, i.e. without copper segregation, form in the gold containing alloy. Thus, it may be said that gold acts as a 'mixing agent' between copper and the other elements. Although several of the atom pairs in the gold containing alloy have positive enthalpies, thermodynamic considerations show that the high entropy contribution is sufficient to counterbalance

  14. Alloy materials

    Energy Technology Data Exchange (ETDEWEB)

    Hans Thieme, Cornelis Leo (Westborough, MA); Thompson, Elliott D. (Coventry, RI); Fritzemeier, Leslie G. (Acton, MA); Cameron, Robert D. (Franklin, MA); Siegal, Edward J. (Malden, MA)

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  15. Development of Mo base alloys for conductive metal-alumina cermet applications

    International Nuclear Information System (INIS)

    Stephens, J.J.; Damkroger, B.K.; Monroe, S.L.

    1996-01-01

    A study of thermal expansion for binary Mo-V and ternary Mo-V-Fe/Mo-V-Co alloys has been conducted, with the aim of finding a composition which matches the CTE of 94% alumina ceramic. The overall goal was to identify an alloy which can be used in conductive 27 vol.% metal/73 vol.% alumina cermets. Besides thermal expansion properties, two additional requirements exist for this alloy: (1) compatibility with a hydrogen sinter fire atmosphere and (2) a single phase BCC microstructure. They have identified a ternary alloy with a nominal composition of Mo-22wt.% V-3Fe for use in cermet fabrication efforts. This paper summarizes thermal expansion properties of the various alloys studied, and compares the results with previous CTE data for Mo-V binary alloys

  16. Effects of applied strain on nanoscale self-interstitial cluster formation in BCC iron

    Science.gov (United States)

    Gao, Ning; Setyawan, Wahyu; Kurtz, Richard J.; Wang, Zhiguang

    2017-09-01

    The effect of applied strains on the configurational evolution of self-interstitial clusters in BCC iron (Fe) is explored with atomistic simulations. A novel cluster configuration is discovered at low temperatures (family of 〈 hkl 〉 loops is calculated as a function of strain. The results show that loop anisotropy is governed by the angle between the stress direction and the orientation of the 〈 111 〉 crowdions in the loop, and directly linked to the stress induced preferred nucleation of self-interstitial atoms.

  17. A numerical study of crack initiation in a bcc iron system based on dynamic bifurcation theory

    International Nuclear Information System (INIS)

    Li, Xiantao

    2014-01-01

    Crack initiation under dynamic loading conditions is studied under the framework of dynamic bifurcation theory. An atomistic model for BCC iron is considered to explicitly take into account the detailed molecular interactions. To understand the strain-rate dependence of the crack initiation process, we first obtain the bifurcation diagram from a computational procedure using continuation methods. The stability transition associated with a crack initiation, as well as the connection to the bifurcation diagram, is studied by comparing direct numerical results to the dynamic bifurcation theory [R. Haberman, SIAM J. Appl. Math. 37, 69–106 (1979)].

  18. Abnormal Strain Rate Sensitivity Driven by a Unit Dislocation-Obstacle Interaction in bcc Fe

    Science.gov (United States)

    Bai, Zhitong; Fan, Yue

    2018-03-01

    The interaction between an edge dislocation and a sessile vacancy cluster in bcc Fe is investigated over a wide range of strain rates from 108 down to 103 s-1 , which is enabled by employing an energy landscape-based atomistic modeling algorithm. It is observed that, at low strain rates regime less than 105 s-1 , such interaction leads to a surprising negative strain rate sensitivity behavior because of the different intermediate microstructures emerged under the complex interplays between thermal activation and applied strain rate. Implications of our findings regarding the previously established global diffusion model are also discussed.

  19. Comparison of void strengthening in fcc and bcc metals: Large-scale atomic-level modelling

    International Nuclear Information System (INIS)

    Osetsky, Yu.N.; Bacon, D.J.

    2005-01-01

    Strengthening due to voids can be a significant radiation effect in metals. Treatment of this by elasticity theory of dislocations is difficult when atomic structure of the obstacle and dislocation is influential. In this paper, we report results of large-scale atomic-level modelling of edge dislocation-void interaction in fcc (copper) and bcc (iron) metals. Voids of up to 5 nm diameter were studied over the temperature range from 0 to 600 K. We demonstrate that atomistic modelling is able to reveal important effects, which are beyond the continuum approach. Some arise from features of the dislocation core and crystal structure, others involve dislocation climb and temperature effects

  20. Temperature dependent magnon-phonon coupling in bcc Fe from theory and experiment.

    Science.gov (United States)

    Körmann, F; Grabowski, B; Dutta, B; Hickel, T; Mauger, L; Fultz, B; Neugebauer, J

    2014-10-17

    An ab initio based framework for quantitatively assessing the phonon contribution due to magnon-phonon interactions and lattice expansion is developed. The theoretical results for bcc Fe are in very good agreement with high-quality phonon frequency measurements. For some phonon branches, the magnon-phonon interaction is an order of magnitude larger than the phonon shift due to lattice expansion, demonstrating the strong impact of magnetic short-range order even significantly above the Curie temperature. The framework closes the previous simulation gap between the ferro- and paramagnetic limits.

  1. Estimation of the crystallographic strain limit during the reversible β ⇄ α″ martensitic transformation in titanium shape memory alloys

    Science.gov (United States)

    Zhukova, Yu. S.; Petrzhik, M. I.; Prokoshkin, S. D.

    2010-11-01

    Three methods are described to calculate the crystallographic strain limit that is determined by the maximum deformation of the crystal lattice in the reversible βbcc ⇄ α″orth martensitic transformation and ensures pseudoelastic deformation accumulation and shape recovery in Ti-Nb-Ta alloys.

  2. Effects of the sp element additions on the microstructure and mechanical properties of NiCoFeCr based high entropy alloys

    International Nuclear Information System (INIS)

    Vida, Adam; Varga, Lajos K.; Chinh, Nguyen Quang; Molnar, David; Huang, Shuo; Vitos, Levente

    2016-01-01

    The effects of the sp (Al, Ga, Ge, Sn) element additions on the microstructure and mechanical properties of equimolar NiCoFeCr High Entropy Alloys (HEAs) are investigated. The results of X-ray diffraction measurements combined with scanning electron microscopy SEM investigations, as well as the results of nanoindentation test revealed that while the structure of the basic alloy is full FCC, the addition of sp elements has changed it to a multiphase containing both FCC and BCC components, but in different scales. Accordingly, the addition of sp elements strongly increases the strength of the basic state, especially in the case of alloys where the BCC phase is dominant in the microstructure. The physical properties as the Young’s- and shear moduli of the investigated HEAs were also determined using ultrasound methods. The correlation between these two moduli suggests a general relationship for metallic alloys.

  3. Classification of different kinds of pesticide residues on lettuce based on fluorescence spectra and WT-BCC-SVM algorithm

    Science.gov (United States)

    Zhou, Xin; Jun, Sun; Zhang, Bing; Jun, Wu

    2017-07-01

    In order to improve the reliability of the spectrum feature extracted by wavelet transform, a method combining wavelet transform (WT) with bacterial colony chemotaxis algorithm and support vector machine (BCC-SVM) algorithm (WT-BCC-SVM) was proposed in this paper. Besides, we aimed to identify different kinds of pesticide residues on lettuce leaves in a novel and rapid non-destructive way by using fluorescence spectra technology. The fluorescence spectral data of 150 lettuce leaf samples of five different kinds of pesticide residues on the surface of lettuce were obtained using Cary Eclipse fluorescence spectrometer. Standard normalized variable detrending (SNV detrending), Savitzky-Golay coupled with Standard normalized variable detrending (SG-SNV detrending) were used to preprocess the raw spectra, respectively. Bacterial colony chemotaxis combined with support vector machine (BCC-SVM) and support vector machine (SVM) classification models were established based on full spectra (FS) and wavelet transform characteristics (WTC), respectively. Moreover, WTC were selected by WT. The results showed that the accuracy of training set, calibration set and the prediction set of the best optimal classification model (SG-SNV detrending-WT-BCC-SVM) were 100%, 98% and 93.33%, respectively. In addition, the results indicated that it was feasible to use WT-BCC-SVM to establish diagnostic model of different kinds of pesticide residues on lettuce leaves.

  4. Enhanced moments in bcc Co{sub 1−x}Mn{sub x} on MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Snow, R.J.; Bhatkar, H. [Department of Physics, Montana State University, Bozeman, MT 59715 (United States); N' Diaye, A.T.; Arenholz, E. [Advanced Light Source, Lawrence Berkeley Nat. Labs, Berkeley, CA 94720 (United States); Idzerda, Y.U., E-mail: Idzerda@montana.edu [Department of Physics, Montana State University, Bozeman, MT 59715 (United States)

    2016-12-01

    A 40% enhancement of the Co magnetic moment has been found for thin films of bcc Co{sub 1−x}Mn{sub x} grown by molecular beam epitaxy on a 2 nm bcc Fe buffer layer on MgO(001). Although the bcc phase cannot be stabilized in the bulk, we confirm that it is stable as an epitaxial film in the composition range x=0–0.7. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism, we show that the Co moment is a maximum of 2.38 μ{sub B} at x=0.24, while the net Mn moment remains roughly constant until x=0.24, then drops steadily. Mn is found to align parallel with Co for all ferromagnetic concentrations, up to x=0.7, where the total moment of the film abruptly collapses to zero, most likely due to the onset of the observed structural instability. - Highlights: • Stabilization of bcc Co{sub 1−x}Mn{sub x} films in the composition range of x=0 to 0.7. • Enhancement of Co moment by 40% from pure bcc Co. • Parallel alignment of Mn moment and Co moment. • Measured the elemental moment of Co and Mn as a function of composition.

  5. Inherited textures in the bcc phase furnish information about the type of transformation from the fcc phase

    International Nuclear Information System (INIS)

    Jung, V.

    1982-07-01

    Drawing annealed cylindric 18/8 Cr Ni steels, which are originally free of textures, produces the transformed phases - hcp and bcc - both showing major texture contributions with increasing stretching of the cylindric specimens. After stretching the original fcc-phase shows two orientations: [100]fcc vertical stroke vertical stroke cylinder axis and [111]fcc vertical stroke vertical stroke cylinder axis, i.e. direction of stress. In both cases the martensitic phase is produced by gliding and shear in the sequence fcc → hcp → bcc by Nishiyama-Wasserman (N-W) or Kurdjumov-Sachs (K-S) transformation in the (111)fcc planes, which enclose a small angle with direction of stress, i.e. cylinder axis. The calculated orientation distributions of the (110)bcc reflex are compared with the distribution measured by neutron diffraction to get information on the bulk material. The special K-S transformation with only 6 (110)bcc orientations shows relatively good agreement with the measured distribution, except at small angles ω between the cylinder axis and the scattering vector. This might be caused by the isotropic fraction of the fcc phase producing an anisotropic (110)bcc orientation distribution. (orig.) [de

  6. Isoelectronic substitutions and aluminium alloying in the Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor

    Science.gov (United States)

    von Rohr, Fabian O.; Cava, Robert J.

    2018-03-01

    High-entropy alloys (HEAs) are a new class of materials constructed from multiple principal elements statistically arranged on simple crystallographic lattices. Due to the large amount of disorder present, they are excellent model systems for investigating the properties of materials intermediate between crystalline and amorphous states. Here we report the effects of systematic isoelectronic replacements, using Mo-Y, Mo-Sc, and Cr-Sc mixtures, for the valence electron count 4 and 5 elements in the body-centered cubic (BCC) Ta-Nb-Zr-Hf-Ti high-entropy alloy (HEA) superconductor. We find that the superconducting transition temperature Tc strongly depends on the elemental makeup of the alloy, and not exclusively its electron count. The replacement of niobium or tantalum by an isoelectronic mixture lowers the transition temperature by more than 60%, while the isoelectronic replacement of hafnium, zirconium, or titanium has a limited impact on Tc. We further explore the alloying of aluminium into the nearly optimal electron count [TaNb] 0.67(ZrHfTi) 0.33 HEA superconductor. The electron count dependence of the superconducting Tc for (HEA)Al x is found to be more crystallinelike than for the [TaNb] 1 -x(ZrHfTi) x HEA solid solution. For an aluminum content of x =0.4 the high-entropy stabilization of the simple BCC lattice breaks down. This material crystallizes in the tetragonal β -uranium structure type and superconductivity is not observed above 1.8 K.

  7. Development of microstructure in thermomechanical processing of zirconium alloys

    International Nuclear Information System (INIS)

    Jha, S.K.; Saibaba, N.; Jayaraj, R.N.

    2009-01-01

    Zirconium based alloys are used for the manufacture of fuel tubes pressure tubes calandria tubes and other components of Pressurized Heavy Water Reactors (PHWRS). In single or two phase zirconium alloy system a variety of microstructure can be generated by suitable heat treatments by the process of equilibrium and non equilibrium phase transformations Microstructure can also be modified by alloying with α and β stabilizers. The microstructure in Zr alloys could be single hexagonal phase (α alloys) two phase bcc and hexagonal (α + β alloys) phase, single metastable martensitic microstructure and β with ω phase. The microstructural and micro textural evolution during thermo mechanical treatments depends strongly on such initial microstructure. Hot extrusion is a significant bulk deformation step which decides the initial microstructure of the alloy. It is carried out at elevated temperature i e above the recrystallization temperature, which enable imposition of large strains in single step. This deformation causes a significant change in the microstructure of the material and depends on extrusion process parameters such as temperature, strain rate (Ram speed), reduction ratio etc. In the present paper development of microstructures, microtexture and texture have been examined. An attempt is also made to optimise the hot working parameters for different Zirconium alloys with help of these studies. (author)

  8. Vibrational contribution to the thermodynamics of nanosized precipitates: vacancy-copper clusters in bcc-Fe

    International Nuclear Information System (INIS)

    Talati, Mina; Posselt, Matthias; Al-Motasem, Ahmed; Bergner, Frank; Bonny, Giovanni

    2012-01-01

    The effects of lattice vibration on the thermodynamics of nanosized coherent clusters in bcc-Fe consisting of vacancies and/or copper are investigated within the harmonic approximation. A combination of on-lattice simulated annealing based on Metropolis Monte Carlo simulations and off-lattice relaxation by molecular dynamics is applied to obtain the most stable cluster configurations at T = 0 K. The most recent interatomic potential built within the framework of the embedded-atom method for the Fe-Cu system is used. The total free energy of pure bcc-Fe and fcc-Cu as well as the total formation free energy and the total binding free energy of the vacancy-copper clusters are determined for finite temperatures. Our results are compared with the available data from previous investigations performed using many-body interatomic potentials and first-principles methods. For further applications in rate theory and object kinetic Monte Carlo simulations, the vibrational effects evaluated in the present study are included in the previously developed analytical fitting formulae. (paper)

  9. bcc-to-hcp transformation pathways for iron versus hydrostatic pressure: Coupled shuffle and shear modes

    Science.gov (United States)

    Liu, J. B.; Johnson, D. D.

    2009-04-01

    Using density-functional theory, we calculate the potential-energy surface (PES), minimum-energy pathway (MEP), and transition state (TS) versus hydrostatic pressure σhyd for the reconstructive transformation in Fe from body-centered cubic (bcc) to hexagonal closed-packed (hcp). At fixed σhyd , the PES is described by coupled shear (γ) and shuffle (η) modes and is determined from structurally minimized hcp-bcc energy differences at a set of (η,γ) . We fit the PES using symmetry-adapted polynomials, permitting the MEP to be found analytically. The MEP is continuous and fully explains the transformation and its associated magnetization and volume discontinuity at TS. We show that σhyd (while not able to induce shear) dramatically alters the MEP to drive reconstruction by a shuffle-only mode at ≤30GPa , as observed. Finally, we relate our polynomial-based results to Landau and nudge-elastic-band approaches and show they yield incorrect MEP in general.

  10. Elastic fields, dipole tensors, and interaction between self-interstitial atom defects in bcc transition metals

    Science.gov (United States)

    Dudarev, S. L.; Ma, Pui-Wai

    2018-03-01

    Density functional theory (DFT) calculations show that self-interstitial atom (SIA) defects in nonmagnetic body-centered-cubic (bcc) metals adopt strongly anisotropic configurations, elongated in the direction [S. Han et al., Phys. Rev. B 66, 220101 (2002), 10.1103/PhysRevB.66.220101; D. Nguyen-Manh et al., Phys. Rev. B 73, 020101 (2006), 10.1103/PhysRevB.73.020101; P. M. Derlet et al., Phys. Rev. B 76, 054107 (2007), 10.1103/PhysRevB.76.054107; S. L. Dudarev, Annu. Rev. Mater. Res. 43, 35 (2013), 10.1146/annurev-matsci-071312-121626]. Elastic distortions, associated with such anisotropic atomic structures, appear similar to distortions around small prismatic dislocation loops, although the extent of this similarity has never been quantified. We derive analytical formulas for the dipole tensors of SIA defects, which show that, in addition to the prismatic dislocation looplike character, the elastic field of a SIA defect also has a significant isotropic dilatation component. Using empirical potentials and DFT calculations, we parametrize dipole tensors of defects for all the nonmagnetic bcc transition metals. This enables a quantitative evaluation of the energy of elastic interaction between the defects, which also shows that in a periodic three-dimensional simple cubic arrangement of crowdions, long-range elastic interactions between a defect and all its images favor a orientation of the defect.

  11. Angular forces and melting in bcc transition metals: A case study of molybdenum

    International Nuclear Information System (INIS)

    Moriarty, J.A.

    1994-01-01

    Both the multi-ion and effective pair potentials also permit a large amount of supercooling of the liquid before the onset of freezing. With v 2 eff a bcc structure is nucleated at freezing, while with the multi-ion potentials an amorphous glasslike structure is obtained, which appears to be related to the energetically competitive A15 structure. In our second approach to melting, the multi-ion potentials have been used to obtain accurate solid and liquid free energies from quasiharmonic lattice dynamics and MD calculations of thermal energies and pressures. The resulting ion-thermal melting curve exactly overlaps the dynamically observed melting point, indicating that no superheating of the solid occurred in our MD simulations. To obtain a full melting curve, electron-thermal contributions to the solid and liquid free energies are added in terms of the density of electronic states at the Fermi level, ρ(E F ). Here the density of states for the solid has been calculated with the linear-muffin-tin-orbital method, while for the liquid tight-binding calculations have been used to justify a simple model. In the liquid ρ(E F ) is increased dramatically over the bcc solid, and the net effect of the electron-thermal contributions is to lower the calculated melting temperatures by about a factor of 2. A full melting curve to 2 Mbar has thereby been obtained and the calculated melting properties near zero pressure are in generally good agreement with experiment

  12. Multiscale modeling of dislocation processes in BCC tantalum: bridging atomistic and mesoscale simulations

    International Nuclear Information System (INIS)

    Yang, L H; Tang, M; Moriarty, J A

    2001-01-01

    Plastic deformation in bcc metals at low temperatures and high-strain rates is controlled by the motion of a/2 screw dislocations, and understanding the fundamental atomistic processes of this motion is essential to develop predictive multiscale models of crystal plasticity. The multiscale modeling approach presented here for bcc Ta is based on information passing, where results of simulations at the atomic scale are used in simulations of plastic deformation at mesoscopic length scales via dislocation dynamics (DD). The relevant core properties of a/2 screw dislocations in Ta have been obtained using quantum-based interatomic potentials derived from model generalized pseudopotential theory and an ab-initio data base together with an accurate Green's-function simulation method that implements flexible boundary conditions. In particular, the stress-dependent activation enthalpy for the lowest-energy kink-pair mechanism has been calculated and fitted to a revealing analytic form. This is the critical quantity determining dislocation mobility in the DD simulations, and the present activation enthalpy is found to be in good agreement with the previous empirical form used to explain the temperature dependence of the yield stress

  13. Structure and creep of Russian reactor steels with a BCC structure

    Science.gov (United States)

    Sagaradze, V. V.; Kochetkova, T. N.; Kataeva, N. V.; Kozlov, K. A.; Zavalishin, V. A.; Vil'danova, N. F.; Ageev, V. S.; Leont'eva-Smirnova, M. V.; Nikitina, A. A.

    2017-05-01

    The structural phase transformations have been revealed and the characteristics of the creep and long-term strength at 650, 670, and 700°C and 60-140 MPa have been determined in six Russian reactor steels with a bcc structure after quenching and high-temperature tempering. Creep tests were carried out using specially designed longitudinal and transverse microsamples, which were fabricated from the shells of the fuel elements used in the BN-600 fast neutron reactor. It has been found that the creep rate of the reactor bcc steels is determined by the stability of the lath martensitic and ferritic structures in relation to the diffusion processes of recovery and recrystallization. The highest-temperature oxide-free steel contains the maximum amount of the refractory elements and carbides. The steel strengthened by the thermally stable Y-Ti nanooxides has a record high-temperature strength. The creep rate at 700°C and 100 MPa in the samples of this steel is lower by an order of magnitude and the time to fracture is 100 times greater than that in the oxide-free reactor steels.

  14. Assessment and correction of BCC_CSM's performance in capturing leading modes of summer precipitation over North Asia

    KAUST Repository

    Gong, Zhiqiang

    2017-11-07

    This article examines the ability of Beijing Climate Center Climate System Model (BCC_CSM) in demonstrating the prediction accuracy and the leading modes of the summer precipitation over North Asia (NA). A dynamic-statistic combined approach for improving the prediction accuracy and the prediction of the leading modes of the summer precipitation over NA is proposed. Our results show that the BCC_CSM can capture part of the spatial anomaly features of the first two leading modes of NA summer precipitation. Moreover, BCC_CSM regains relationships such that the first and second mode of the empirical orthogonal function (EOF1 and EOF2) of NA summer precipitation, respectively, corresponds to the development of the El Niño and La Niña conditions in the tropical East Pacific. Nevertheless, BCC_CSM exhibits limited prediction skill over most part of NA and presents a deficiency in reproducing the EOF1\\'s and EOF2\\'s spatial pattern over central NA and EOF2\\'s interannual variability. This can be attributed as the possible reasons why the model is unable to capture the correct relationships among the basic climate elements over the central NA, lacks in its ability to reproduce a consistent zonal atmospheric pattern over NA, and has bias in predicting the relevant Sea Surface Temperature (SST) modes over the tropical Pacific and Indian Ocean regions. Based on the proposed dynamic-statistic combined correction approach, compared with the leading modes of BCC_CSM\\'s original prediction, anomaly correlation coefficients of corrected EOF1/EOF2 with the tropical Indian Ocean SST are improved from 0.18/0.36 to 0.51/0.62. Hence, the proposed correction approach suggests that the BCC_CSM\\'s prediction skill for the summer precipitation prediction over NA and its ability to capture the dominant modes could be certainly improved by choosing proper historical analogue information.

  15. The mechanism of bcc α′ nucleation in single hcp ε laths in the fcc γ → hcp ε → bcc α′ martensitic phase transformation

    International Nuclear Information System (INIS)

    Yang, Xu-Sheng; Sun, Sheng; Zhang, Tong-Yi

    2015-01-01

    High Resolution Transmission Electron Microscopy (HRTEM) and Molecular Dynamics (MD) simulations were conducted here to study the plastic deformation induced γ (fcc) → ε (hcp) → α′ (bcc) martensitic transformation in 304 stainless steels for the α′ nucleation from single hcp-ε laths. Results elucidate that the underlying microscopic mechanism for the α′ nucleation from single hcp-ε laths obeys the Bogers–Burgers–Olson–Cohen “3T/8–T/3” model. In particular, the atomic-scale observations clearly show the Kurdyumov–Sachs (K–S) lattice orientation relation (OR) and Pitsch OR at the γ/α′ interfaces, the lattice rotation inside an α′ martensitic inclusion, the transition lattice and the reverse shear-shuffling induced continuous lattice elastic deformation at the diffuse ε/α′ interface, which caters the 3T/8 and T/3 shears and sheds atomic process insight into the mechanism of the martensitic transformation

  16. A Micropillar Compression Methodology for Ductile Damage Quantification

    NARCIS (Netherlands)

    Tasan, C.C.; Hoefnagels, J.P.M.; Geers, M.G.D.

    2012-01-01

    Microstructural damage evolution is reported to influence significantly the failures of new high-strength alloys. Its accurate quantification is, therefore, critical for (1) microstructure optimization and (2) continuum damage models to predict failures of these materials. As existing methodologies

  17. A micropillar compression methodology for ductile damage quantification

    NARCIS (Netherlands)

    Tasan, C.C.; Hoefnagels, J.P.M.; Geers, M.G.D.

    2012-01-01

    Microstructural damage evolution is reported to influence significantly the failures of new high-strength alloys. Its accurate quantification is, therefore, critical for (1) microstructure optimization and (2) continuum damage models to predict failures of these materials. As existing methodologies

  18. Giant magnetoresistive properties of FexAu100-x alloys produced by mechanical alloying

    International Nuclear Information System (INIS)

    Socolovsky, L.M.; Sanchez, F.H.; Shingu, P.H.

    2001-01-01

    The Fe x Au 100- x alloys were produced for the first time by mechanical alloying. Resistance of samples with iron concentrations of x=15, 20, 25, and 30 at% were measured at 77 K under an applied field of 14 kOe. A maximum in magnetoresistive ratio (Δρ/ρ) of 3.5% was obtained for Fe 25 Au 75 . Samples were annealed in order to enhance magnetoresistive properties. These samples exhibit larger ratios, primarily due to the elimination of defects. X-ray diffraction Moessbauer spectroscopy and magnetoresistance measurements were performed, in order to correlate bulk and hyperfine magnetic properties with crystalline structure. X-ray diffractograms show an FCC structure, with no evidence for a BCC one

  19. Influence of Ti addition and sintering method on microstructure and mechanical behavior of a medium-entropy Al0.6CoNiFe alloy

    International Nuclear Information System (INIS)

    Fu, Zhiqiang; Chen, Weiping; Chen, Zhen; Wen, Haiming; Lavernia, Enrique J.

    2014-01-01

    The influence of Ti addition and sintering method on the microstructure and mechanical behavior of a medium-entropy alloy, Al 0.6 CoNiFe alloy, was studied in detail. Alloying behavior, microstructure, phase evolution and mechanical properties of Al 0.6 CoNiFe and Ti 0.4 Al 0.6 CoNiFe alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as by mechanical testing. During the mechanical alloying (MA) process, a supersaturated solid solution consisting of both BCC and FCC phases was formed in the Al 0.6 CoNiFe alloy. With Ti addition, the Ti 0.4 Al 0.6 CoNiFe alloy exhibited a supersaturated solid solution with a single FCC phase. Following hot pressing (HP), the HP sintered (HP’ed) Al 0.6 CoNiFe bulk alloy was composed of a major BCC phase and a minor FCC phase. The HP’ed Ti 0.4 Al 0.6 CoNiFe alloy exhibited a FCC phase, two BCC phases and a trace unidentified phase. Nanoscale twins were present in the HP’ed Ti 0.4 Al 0.6 CoNiFe alloy, where deformation twins were observed in the FCC phase. Our results suggest that the addition of Ti facilitated the formation of nanoscale twins. The compressive strength and Vickers hardness of HP’ed Ti 0.4 Al 0.6 CoNiFe alloy were slightly lower than the corresponding values of the HP’ed Al 0.6 CoNiFe alloy. In contrast with HP’ed Al 0.6 CoNiFe alloy, spark plasma sintered (SPS’ed) Al 0.6 CoNiFe alloy exhibited a major FCC phase and a minor BCC phase. Moreover, the SPS’ed Al 0.6 CoNiFe alloy exhibited a lower compressive strength and Vickers hardness, but singificantly higher plasticity, as compared to those of the HP’ed counterpart material

  20. Effect of B addition to hypereutectic Ti-based alloys

    International Nuclear Information System (INIS)

    Louzguina-Luzgina, Larissa V.; Louzguine-Luzgin, Dmitri V.; Inoue, Akihisa

    2009-01-01

    The structure and mechanical properties of Ti-Fe-B and Ti-Fe-Co-B alloys produced in the shape of the arc-melted ingots of about 25 mm diameter and 10 mm height are studied. The hypereutectic alloys showed excellent compressive mechanical properties. The structures of the high-strength and ductile hypereutectic alloys studied by X-ray diffractometry and scanning electron microscopy were found to consist of the primary cubic cP2 intermetallic compound (TiFe-phase or a solid solution on its base) and a dispersed eutectic consisting of this cP2 intermetallic compound + BCC cI2 β-Ti supersaturated solid solution phase. The addition of B increased mechanical strength. Si causes embrittlement owing to the formation of alternative intermetallic compounds. The structure and deformation behaviour were studied

  1. Deformation and fracture of an alpha/beta titanium alloy

    International Nuclear Information System (INIS)

    Morcelli, Aparecido Edilson; Andrade, Arnaldo Homobono Paes de; Lobo, Raquel de Moraes

    2010-01-01

    Titanium alloys are used in the aero-spatial, energy and biomaterial industries among others and exhibit high specific strength and fracture toughness. Their mechanical properties show a strong dependence on the microstructure, especially on the size and morphology of the constituent phases. An experimental evaluation was done to a better understanding of that influence using some techniques like as transmission electron microscopy (TEM), both low and high resolution (HR), scanning electron microscopy (SEM), coupled to electron back-scattering diffraction (EBSD), X-ray diffraction (XRD) and optical microscopy (OM). Some in-situ TEM deformation studies were also done. The alloy was submitted to two heat treatment conditions to get different phases distribution. An hcp phase (alpha) in coexistence with a bcc phase (beta) was observed after both treatments as well the occurrence of twins, stacking faults and dislocations arrangements. The work then discusses the influence of these features on the overall alloy strength. (author)

  2. Hydrogenation properties and microstructure of Ti-Mn-based alloys for hybrid hydrogen storage vessel

    International Nuclear Information System (INIS)

    Shibuya, Masachika; Nakamura, Jin; Akiba, Etsuo

    2008-01-01

    Ti-Mn-based AB 2 -type alloys which are suitable for a hybrid hydrogen storage vessel have been synthesized and evaluated hydrogenation properties. As the third element V was added to Ti-Mn binary alloys. All the alloys synthesized in this work mainly consist of the C14 Laves and BCC phase. In the case of Ti0.5V0.5Mn alloy, the amounts of hydrogen absorption was 1.8 wt.% at 243 K under the atmosphere of 7 MPa H 2 , and the hydrogen desorption pressure was in the range of 0.2-0.4 MPa at 243 K. The hydrogen capacity of this alloy did not saturate under 7 MPa H 2 and seems to increase with hydrogen pressure up to 35 MPa that is estimated working pressure of the hybrid hydrogen storage vessel

  3. Effect of composition on the structure and properties of Ti-Co-Cr alloys

    Directory of Open Access Journals (Sweden)

    T. Matković

    2010-01-01

    Full Text Available The present work is a study of six as-cast Ti-Co-Cr alloys in the Ti-rich region with the purpose of examining the possibility of obtaining a new β-type Ti-alloys. Two experimental alloys Ti80Co10Cr10 and Ti70Co10Cr20 are nearly single-phases and are identified as bcc β-Ti phase. They also display the lowest hardness values and the best corrosion properties. The present study indicates that the region of biomedically-acceptable ternary Ti-rich alloys is situated within lower concentrations of alloying elements, i.e. about 10 at.% Co and 20 at. % Cr.

  4. Contribution of Lattice Distortion to Solid Solution Strengthening in a Series of Refractory High Entropy Alloys

    Science.gov (United States)

    Chen, H.; Kauffmann, A.; Laube, S.; Choi, I.-C.; Schwaiger, R.; Huang, Y.; Lichtenberg, K.; Müller, F.; Gorr, B.; Christ, H.-J.; Heilmaier, M.

    2018-03-01

    We present an experimental approach for revealing the impact of lattice distortion on solid solution strengthening in a series of body-centered-cubic (bcc) Al-containing, refractory high entropy alloys (HEAs) from the Nb-Mo-Cr-Ti-Al system. By systematically varying the Nb and Cr content, a wide range of atomic size difference as a common measure for the lattice distortion was obtained. Single-phase, bcc solid solutions were achieved by arc melting and homogenization as well as verified by means of scanning electron microscopy and X-ray diffraction. The atomic radii of the alloying elements for determination of atomic size difference were recalculated on the basis of the mean atomic radii in and the chemical compositions of the solid solutions. Microhardness (μH) at room temperature correlates well with the deduced atomic size difference. Nevertheless, the mechanisms of microscopic slip lead to pronounced temperature dependence of mechanical strength. In order to account for this particular feature, we present a combined approach, using μH, nanoindentation, and compression tests. The athermal proportion to the yield stress of the investigated equimolar alloys is revealed. These parameters support the universality of this aforementioned correlation. Hence, the pertinence of lattice distortion for solid solution strengthening in bcc HEAs is proven.

  5. Grain Refinement and Texture Mitigation in Low Boron Containing TiAl-Alloys

    Science.gov (United States)

    Hecht, Ulrike; Witusiewicz, Victor T.

    2017-12-01

    Controlling the grain size and texture of lamellar TiAl-alloys is essential for well-balanced creep and fatigue properties. Excellent refinement and texture mitigation are achieved in aluminum lean alloys by low boron additions of 0.2 at.%. This amount is sufficient to promote in situ formation of ultrafine borides during the last stages of body centered cubic (BCC) solidification. The borides subsequently serve as nucleation sites for hexagonal close packed (HCP) during the BCC-HCP phase transformation. Bridgman solidification experiments with alloy Ti-43Al-8Nb-0.2C-0.2B were performed under a different growth velocity, i.e., cooling rate, to evaluate the HCP grain size distribution and texture. For slow-to-moderate cooling rates, about 65% of HCP grains are randomly oriented, despite the pronounced texture of the parent BCC phase resulting from directional solidification. For high cooling rates, obtained by quenching, texture mitigation is less pronounced. Only 28% of the HCP grains are randomly oriented, the majority being crystallographic variants of the Burgers orientation relationship.

  6. Electron microscopy investigations of rapidly solidified Fe-Zr-B-Cu alloys

    International Nuclear Information System (INIS)

    Majumdar, B.; Arvindha Babu, D.; Akhtar, D.

    2010-01-01

    Rapidly solidified Fe-based nanocrystalline soft magnetic materials possess a unique combination of properties i,e high permeability, saturation and Curie temperature and very low coercivity which are otherwise not attainable in conventional soft magnetic materials. The alloys are processed by producing amorphous phase through melt spinning route followed by a partial devitrification for incorporation of nanocrystalline phase in the amorphous matrix. In this paper, detailed electron microscopic investigations of melt spun Fe-Zr-B-Cu alloys are presented. Melt spun ribbons of Fe 99-x-y Zr x BCu 1 alloys with x+y = 11 and x+y = 13 were prepared under different wheel speed conditions and then vacuum annealed for 1 h at different temperatures. The microstructure changes from completely amorphous to a cellular/dendritic bcc solid solution coexisting with the amorphous phase at intercellular/dendritic regions when Zr/B ratio or the process parameters are varied. Annealing leads to the precipitation of nanocrystalline bcc-Fe phase from both amorphous phase and already existing bcc solid solution. (author)

  7. Residual stresses caused by head-on and 45° foreign object damage for a laser shock peened Ti–6Al–4V alloy aerofoil

    International Nuclear Information System (INIS)

    Zabeen, S.; Preuss, M.; Withers, P.J.

    2013-01-01

    This paper investigates the effect on the residual stresses of foreign object damage (FOD) to a previously laser shock peened (LSP) leading edge (LE). FOD was introduced onto the LE of the aerofoil-shaped specimen through ballistic impacts of a cube edge at angles of 0° and 45° to the leading edge. The residual stress distribution was mapped around the FOD notch by synchrotron X-ray diffraction. The results suggest that for both impact angles, the FOD event superimposed a significant additional residual stress on top of the pre-existing stress associated with the LSP process. In particular, the compressive stress was found to be largest directly beneath the notch and the tensile region, seen previously for unpeened aerofoils beneath the compressive zone, was absent due to the pre-existing peening stress field. This may help to explain the improved fatigue strength observed previously. It is shown that the FOD notch created by 45° impact was asymmetric in shape and smaller in depth compared to that created at 0°. The residual stresses were somewhat larger for the 0° impact condition than for 45° partly due to the larger notch depth introduced in the former case.

  8. The effect of hydrogen on the superconducting and structural properties of b.c.c. Nb-Ru alloys

    International Nuclear Information System (INIS)

    Robbins, C.G.; Ishikawa, M.; Treyvaud, A.; Muller, J.

    1975-01-01

    The superconducting transition temperature (Tsub(c)) has been measured before and after the introduction of hydrogen into Nbsub((1-x))Rusub(x) (0.20<=x<=0.33). In all cases, the presence of appreciable amounts of this interstitial component led to a sharp increase in the Tsub(c). All the evidence suggests that conversion of the host metal lattice to f.c.c. is necessary for the appearance of the elevated Tsub(c). (author)

  9. Elastic constants of bcc austenite and 2H orthorhombicmartensite in CuAlNi shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Sedlák, Petr; Seiner, Hanuš; Landa, Michal; Novák, Václav; Šittner, Petr

    2005-01-01

    Roč. 53, č. 5 (2005), s. 3643-3661 ISSN 1359-6454 R&D Projects: GA ČR GA106/03/1073 Institutional research plan: CEZ:AV0Z20760514 Keywords : SMA * ultrasonics * material properties Subject RIV: JJ - Other Materials Impact factor: 3.430, year: 2005

  10. Link between structural and mechanical stability of fcc- and bcc-based ordered MgeLi alloys

    CSIR Research Space (South Africa)

    Phasha, MJ

    2010-06-01

    Full Text Available ) pseudopotential method, embodied in the CASTEP code [10]. The Hohenberg-Kohn-Sham density functional theory (DFT) [11] was used 5 within the GGA formalism [12] to describe the electronic exchange-correlation interactions. We used the recent PBE form..., Int. J. Quantum Chem. 77 (2000) 895. [11] P. Hohenberg and W. Kohn, Phys. Rev. 136, B 864 (1964), W. Kohn and L.J. Sham, Phys. Rev. 140 (1965) A 1133. [12] J.P. Perdew and Y. Wang, Phys. Rev. B 45 (1992) 13244. [13] J.P. Perdew, K. Burke and M...

  11. Fatigue crack micromechanisms in a Cu-Zn-Al shape memory alloy with pseudo-elastic behavior

    Directory of Open Access Journals (Sweden)

    Vittorio Di Cocco

    2015-10-01

    Full Text Available Shape memory property characterizes the behavior of many Ti based and Cu based alloys (SMAs. In Cu-Zn-Al SMAs, the original shape recovering is due to a bcc phase that is stable at high temperature. After an appropriate cooling process, this phase (β-phase or austenitic phase transforms reversibly into a B2 structure (transition phase and, after a further cooling process or a plastic deformation, it transforms into a DO3 phase (martensitic phase. In β-Cu-Zn-Al SMAs, the martensitic transformation due to plastic deformation is not stable at room temperature: a high temperature “austenitization” process followed by a high speed cooling process allow to obtain a martensitic phase with a higher stability. In this work, a Cu-Zn-Al SMA in “as cast” conditions has been microstructurally and metallographically characterized by means of X-Ray diffraction and Light Optical Microscope (LOM observations. Fatigue crack propagation resistance and damaging micromechanisms have been investigated corresponding to three different load ratios (R=0.10, 0.50 and 0.75

  12. Study of the multiple exchange frequencies in bcc 3He by thermodynamic measurements

    International Nuclear Information System (INIS)

    Bernier, M.; Suaudeau, E.; Roger, M.

    1987-08-01

    To study the multiple exchange hamiltonian of solid 3 He we measured the contribution of the spin exchange to the pressure of bcc solid in various magnetic fields (O≤ H≤ 7.5T). Due to the nature of the atomic exchange of a fermion system this contribution is a strong function of the spin polarization. The characteristic frequencies of the exchange hamiltonian are obtained by fitting the pressure measurements with the results of a statistical calculation using a high temperature series expansion of the hamiltonian in a temperature range where both the magnetic effect is significant and the expansion converges (7mK < T < 30mK). We discuss the results obtained for two molar volumes

  13. Atomistic studies of nucleation of He clusters and bubbles in bcc iron

    International Nuclear Information System (INIS)

    Yang, L.; Deng, H.Q.; Gao, F.; Heinisch, H.L.; Kurtz, R.J.; Hu, S.Y.; Li, Y.L.; Zu, X.T.

    2013-01-01

    Atomistic simulations of the nucleation of He clusters and bubbles in bcc iron at 800 K have been carried out using the newly developed Fe–Fe interatomic potential, along with Ackland potential for the Fe–Fe interactions. Microstructure changes were analyzed in detail. We found that a He cluster with four He atoms is able to push out an iron interstitial from the cluster, creating a Frenkel pair. Small He clusters and self-interstitial atom (SIA) can migrate in the matrix, but He-vacancy (He-V) clusters are immobile. Most SIAs form clusters, and only the dislocation loops with a Burgers vector of b = 1/2 appear in the simulations. SIA clusters (or loops) are attached to He-V clusters for He implantation up to 1372 appm, while the He-V cluster–loop complexes with more than one He-V cluster are formed at the He concentration of 2057 appm and larger

  14. Effects of applied strain on nanoscale self-interstitial cluster formation in BCC iron

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Ning; Setyawan, Wahyu; Kurtz, Richard J.; Wang, Zhiguang

    2017-09-01

    The effect of applied strains on the configurational evolution of self-interstitial clusters in BCC iron (Fe) is explored with atomistic simulations. A novel cluster configuration is discovered at low temperatures (<600 K), which consists of <110> dumbbells and <111> crowdions in a specific configuration, resulting in an immobile defect. The stability and diffusion of this cluster at higher temperatures is explored. In addition, an anisotropy distribution factor of a particular [hkl] interstitial loop within the family of loops is calculated as a function of strain. The results show that loop anisotropy is governed by the angle between the stress direction and the orientation of the <111> crowdions in the loop, and directly linked to the stress induced preferred nucleation of self-interstitial atoms.

  15. Indium-defect interactions in FCC and BCC metals studied using the modified embedded atom method

    Energy Technology Data Exchange (ETDEWEB)

    Zacate, M. O., E-mail: zacatem1@nku.edu [Northern Kentucky University, Department of Physics, Geology, and Engineering Technology (United States)

    2016-12-15

    With the aim of developing a transferable potential set capable of predicting defect formation, defect association, and diffusion properties in a wide range of intermetallic compounds, the present study was undertaken to test parameterization strategies for determining empirical pair-wise interaction parameters in the modified embedded atom method (MEAM) developed by Baskes and coworkers. This report focuses on indium-solute and indium-vacancy interactions in FCC and BCC metals, for which a large set of experimental data obtained from perturbed angular correlation measurements is available for comparison. Simulation results were found to be in good agreement with experimental values after model parameters had been adjusted to reproduce as best as possible the following two sets of quantities: (1) lattice parameters, formation enthalpies, and bulk moduli of hypothetical equiatomic compounds with the NaCl crystal structure determined using density functional theory and (2) dilute solution enthalpies in metals as predicted by Miedema’s semi-empirical model.

  16. Calculation of elastic constants of BCC transition metals: tight-binding recursion method

    International Nuclear Information System (INIS)

    Masuda, K.; Hamada, N.; Terakura, K.

    1984-01-01

    The elastic constants of BCC transition metals (Fe, Nb, Mo and W) are calculated by using the tight-binding d band and the Born-Mayer repulsive potential. Introducing a small distortion characteristic to C 44 (or C') elastic deformation and calculating the energy change up to second order in the atomic displacement, the shear elastic constants C 44 and C' are determined. The elastic constants C 11 and C 12 are then calculated by using the relations B=1/3(C 11 + 2C 12 ) and C'=1/2(C 11 -C 12 ), where B is the bulk modulus. In general, the agreement between the present results and the experimental values is satisfactory. The characteristic elasticity behaviour, i.e. the strong Nsub(d) (number of d electrons) dependence of the observed anisotropy factor A=C 44 /C', will also be discussed. (author)

  17. Nuclear spin relaxation due to hydrogen diffusion in b.c.c. metals

    International Nuclear Information System (INIS)

    Faux, D.A.; Hall, C.K.

    1989-01-01

    We present Monte Carlo simulation results for the proton-proton contribution to the T 1 -1 relaxation rate for hydrogen spins diffusing on the tetrahedral sites of a b.c.c. metal. It is assumed that each hydrogen blocks all sites to the zeroth (no multiple-occupancy), second or third neighbour and that longer-range interactions may be neglected. Comparisons are made to the BPP and Torrey models. It is found that both the BPP and Torrey models give reasonable values for the peak height but that their predictions for the peak position and the high- and low-temperature limit are in error, particularly for large blocking distances. (orig.)

  18. Vacancy-mediated fcc/bcc phase separation in Fe1 -xNix ultrathin films

    Science.gov (United States)

    Menteş, T. O.; Stojić, N.; Vescovo, E.; Ablett, J. M.; Niño, M. A.; Locatelli, A.

    2016-08-01

    The phase separation occurring in Fe-Ni thin films near the Invar composition is studied by using high-resolution spectromicroscopy techniques and density functional theory calculations. Annealed at temperatures around 300 ∘C ,Fe0.70Ni0.30 films on W(110) break into micron-sized bcc and fcc domains with compositions in agreement with the bulk Fe-Ni phase diagram. Ni is found to be the diffusing species in forming the chemical heterogeneity. The experimentally determined energy barrier of 1.59 ±0.09 eV is identified as the vacancy formation energy via density functional theory calculations. Thus, the principal role of the surface in the phase separation process is attributed to vacancy creation without interstitials.

  19. Thermodynamic properties of bcc crystals at high temperatures: The transition metals

    International Nuclear Information System (INIS)

    MacDonald, R.A.; Shukla, R.C.

    1985-01-01

    The second-neighbor central-force model of a bcc crystal, previously used in lowest-order anharmonic perturbation theory to calculate the thermodynamic properties of the alkali metals, is here applied to the transition metals V, Nb, Ta, Mo, and W. The limitations of the model are apparent in the thermal-expansion results, which fall away from the experimental trend above about 1800 K. The specific heat similarly fails to exhibit the sharp rise that is observed at higher temperatures. A static treatment of vacancies cannot account for the difference between theory and experiment. The electrons have been taken into account by using a model that specifically includes d-band effects in the electron ground-state energy. The results thus obtained for the bulk moduli are quite satisfactory. In the light of these results, we discuss the prerequisites for a better treatment of metals when the electrons play an important role in determining the thermodynamic properties

  20. The glide of screw dislocations in bcc Fe: Atomistic static and dynamic simulations

    International Nuclear Information System (INIS)

    Chaussidon, Julien; Fivel, Marc; Rodney, David

    2006-01-01

    We present atomic-scale simulations of screw dislocation glide in bcc iron. Using two interatomic potentials that, respectively, predict degenerate and non-degenerate core structures, we compute the static 0 K dependence of the screw dislocation Peierls stress on crystal orientation and show strong boundary condition effects related to the generation of non-glide stress components. At finite temperatures we show that, with a non-degenerate core, glide by nucleation/propagation of kink-pairs in a {1 1 0} glide plane is obtained at low temperatures. A transition in the twinning region, towards an average {1 1 2} glide plane, with the formation of debris loops is observed at higher temperatures

  1. Comparison of interface structure of BCC metallic (Fe, V and Nb) films on MgO (100) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Du, J.L. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Zhang, L.Y. [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049 (China); Fu, E.G., E-mail: efu@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Ding, X., E-mail: dingxd@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049 (China); Yu, K.Y., E-mail: kyyu@cup.edu.cn [Department of Materials Science and Engineering, China University of Petroleum, Beijing 102249 (China); Wang, Y.G. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wang, Y.Q.; Baldwin, J.K. [Experimental Physical Sciences Directorate, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Wang, X.J. [State Key Laboratory of Advanced Optical Communication Systems and Networks, Peking University, Beijing 100871 (China); Xu, P. [Department of Chemistry, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 (China)

    2017-07-15

    Highlights: • The difference of BCC metal/MgO(100) interface configuration with various lattice mismatches is identified by experiments and simulations in terms of dislocations and work of separation. • The strength of bonds along interface is found to be the fundamental factor to determine the interface configurations between BCC metal and MgO substrate. • The combination of experiments and simulations shows that the O-atop model is the actual match type between BCC metal and MgO substrate. - Abstract: This study systematically investigates the interface structure of three body-centered-cubic (BCC) metallic (Fe, V and Nb) films grown on MgO(100) substrates through experiments and simulations. Orientation relationships of their interfaces with the different lattice mismatches exhibit cube-on-cube configurations. The misfit dislocations at these three interfaces exhibit different characteristics. High resolution TEM (HRTEM), combined with first principle calculations, demonstrates the O-atop match type between metal atoms and MgO substrates for the first time. The fundamental mechanism in determining the interface configuration is discussed in terms of the work of separation and delocalization of atomic charge density.

  2. Assessment and correction of BCC_CSM's performance in capturing leading modes of summer precipitation over North Asia

    KAUST Repository

    Gong, Zhiqiang; Dogar, Muhammad Mubashar; Qiao, Shaobo; Hu, Po; Feng, Guolin

    2017-01-01

    in the tropical East Pacific. Nevertheless, BCC_CSM exhibits limited prediction skill over most part of NA and presents a deficiency in reproducing the EOF1's and EOF2's spatial pattern over central NA and EOF2's interannual variability. This can be attributed

  3. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    KAUST Repository

    Gong, Zhiqiang; Dogar, Muhammad Mubashar; Qiao, Shaobo; Hu, Po; Feng, Guolin

    2017-01-01

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection

  4. SCC, Bowen's disease and BCC arising on chronic radiation dermatitis due to radiation therapy for tinea pedis

    International Nuclear Information System (INIS)

    Aoki, Eri; Aoki, Mikako; Ikemura, Akiko; Igarashi, Tsukasa; Suzuki, Kayano; Kawana, Seiji

    2000-01-01

    We reported a case who developed three different types of skin cancers: SCC, BCC, and Bowen's disease, on the chronic radiation dermatitis. He had been treated for his tinea pedis et palmaris with radiotherapy in 1940's. It is very ratre that three different types of skin cancers arise in the same patient. This is a second case reported in Japan. (author)

  5. Microstructural characterisation of high-entropy alloy AlCoCrFeNi fabricated by laser engineered net shaping

    Energy Technology Data Exchange (ETDEWEB)

    Kunce, I., E-mail: ikunce@wat.edu.pl [Department of Advanced Materials and Technology, Military University of Technology, 2 Kaliskiego Str., 01-908 Warsaw (Poland); Polanski, M.; Karczewski, K. [Department of Advanced Materials and Technology, Military University of Technology, 2 Kaliskiego Str., 01-908 Warsaw (Poland); Plocinski, T.; Kurzydlowski, K.J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, 141 Wołoska Str., 02-507 Warsaw (Poland)

    2015-11-05

    Laser engineered net shaping (LENS) was used to produce thin-walled samples of the high-entropy alloy AlCoCrFeNi from a prealloyed powder. To determine the effect of the cooling rate during solidification on the microstructure of the alloy, different laser scanning rates were used. A microstructural study of the surfaces of the sample walls was performed using X-ray diffraction analysis and optical and scanning/transmission electron microscopy. The crystal structure of the alloy was determined to be a body-centred cubic (bcc)-derivative B2-ordered type. The microstructure of the alloy produced by LENS was dendritic. Further, it was found that with an increase in the laser scanning rate from 2.5 to 40 mm s{sup −1}, the average grain size decreased from 108.3 ± 32.4 μm to 30.6 ± 9.2 μm. The maximum cooling rate achieved during the laser cladding of the alloy was 44 × 10{sup 3} K s{sup −1}. The electron microscopy study of the alloy showed the presence of precipitates. The morphology of the disordered bcc (Fe, Cr)-rich precipitates in the ordered B2 (Al, Ni)-rich matrix changed in the dendritic and interdendritic regions from fine and spherical (with a diameter of less 100 nm) to spinodal (with the thickness being less than 100 nm). The LENS- produced AlCoCrFeNi alloy exhibited an average microhardness of approximately 543 HV0.5; this was approximately 13% higher than the hardness in the as-cast state and can be attributed to the grain refinemet in the LENS- produced alloy. Moreover, it was found that increasing the cooling rate during laser cladding increasess the microhardness of the alloy. - Highlights: • Laser-engineered net shaping is used to produce samples of AlCoCrFeNi alloy. • The alloy has a body-centred cubic (bcc)-derivative B2-ordered crystal structure. • Electron microscopy images of the alloy show the presence of precipitates. • The microhardness of the laser-clad alloy is higher than that of the as-cast alloy. • The cooling rate

  6. Hyperfine Interactions and Some Magnetic Properties of Nanocrystalline Co40Fe50Ni10 and Co50Fe45Ni5 Alloys Prepared by Mechanical Synthesis and Subsequently Heat Treated

    International Nuclear Information System (INIS)

    Pikula, T.; Oleszak, D.; Pekala, M.

    2011-01-01

    Co 40 Fe 50 Ni 10 and Co 50 Fe 45 Ni 5 ternary alloys were prepared by mechanical alloying method. To check the stability of their structure thermal treatment was applied subsequently. As X-ray diffraction studies proved the final products of milling were the solid solutions with bcc lattice and the average grain sizes ranged of tens of nanometers. After heating of the Co 50 Fe 45 Ni 5 alloy up to 993 K the mixture of two solid solutions with bcc and fcc lattices was formed. In other cases thermal treatment did not change the type of the crystalline lattice. Moessbauer spectroscopy revealed hyperfine magnetic field distributions which reflected the different possible atomic surroundings of 57 Fe isotopes. Results of the macroscopic magnetic measurements proved that both investigated alloys had relatively good soft magnetic properties. (authors)

  7. Some aspects of thermally induced martensite in Fe-30% Ni-5% Cu alloy

    International Nuclear Information System (INIS)

    Guener, M.; Gueler, E.; Yasar, E.; Aktas, H.

    2007-01-01

    Kinetical, morphological, crystallographical and several thermal properties of thermally induced martensite in the austenite phase of Fe-30% Ni-5% Cu alloy were investigated. Scanning electron microscope (SEM), transmission electron microscope (TEM) and differential scanning calorimetry (DSC) techniques were used during study. Kinetics of the transformation was found to be as athermal type. SEM and TEM observations revealed α' (BCC) martensite formation in the austenite phase of alloy by thermal effect. These thermally induced α' martensites exhibited a thin plate-like morphology with twinnings

  8. Influence of Annealing on Microstructure and Mechanical Properties of Refractory CoCrMoNbTi0.4 High-Entropy Alloy

    Science.gov (United States)

    Zhang, Mina; Zhou, Xianglin; Zhu, Wuzhi; Li, Jinghao

    2018-04-01

    A novel refractory CoCrMoNbTi0.4 high-entropy alloy (HEA) was prepared via vacuum arc melting. After annealing treatment at different temperatures, the microstructure evolution, phase stability, and mechanical properties of the alloy were investigated. The alloy was composed of two primary body-centered cubic structures (BCC1 and BCC2) and a small amount of (Co, Cr)2Nb-type Laves phase under different annealing conditions. The microhardness and compressive strength of the heat-treated alloy was significantly enhanced by the solid-solution strengthening of the BCC phase matrix and newborn Laves phase. Especially, the alloy annealed at 1473 K (1200 °C) achieved the maximum hardness and compressive strength values of 959 ± 2 HV0.5 and 1790 MPa, respectively, owing to the enhanced volume fraction of the dispersed Laves phase. In particular, the HEAs exhibited promising high-temperature mechanical performance, when heated to an elevated temperature of 1473 K (1200 °C), with a compressive fracture strength higher than 580 MPa without fracture at a strain of more than 20 pct. This study suggests that the present refractory HEAs have immense potential for engineering applications as a new class of high-temperature structural materials.

  9. Microstructure, thermophysical and electrical properties in AlxCoCrFeNi (0 ≤ x ≤2) high-entropy alloys

    International Nuclear Information System (INIS)

    Chou, H.-P.; Chang, Y.-S.; Chen, S.-K.; Yeh, J.-W.

    2009-01-01

    Al x CoCrFeNi (0 ≤ x ≤2) alloys were prepared by an arc remelter and investigated. With increasing x, the Al x CoCrFeNi alloys change from single FCC phase to single BCC phase with a transition duplex FCC/BCC region. The weak X-ray diffraction intensities indicate severe X-ray scattering effect of lattice in these high-entropy alloys. Electrical conductivity and thermal conductivity much smaller than those of pure component metals is ascribed as due to this lattice effect. The behavior of electrical conductivity and thermal conductivity can be divided into three parts according to microstructure. Both values of electrical conductivity and thermal conductivity decrease with increasing x in single-phase regions. Values of electrical conductivity and thermal conductivity are even higher than those in the duplex phase region because of the additional scattering effect of FCC/BCC phase boundaries in the alloys. Relative contribution of electron and phonon to electrical resistivity and thermal conductivity is evaluated in this study. It is shown that both electron and phonon components are comparable in these high-entropy alloys, and their transport properties are similar to that of semi-metal.

  10. Initiation of cleavage in a low alloy steel: effect of a ductile damage localized around inclusions; Declenchement du clivage dans un acier faiblement allie: role de l'endommagement ductile localise autour des inclusions

    Energy Technology Data Exchange (ETDEWEB)

    Carassou, S

    2000-07-01

    The fracture mechanism in a low alloy steel, used in the pressurised water reactor vessel, has been studied in the ductile to brittle transition temperature range. We used the local approach of fracture in conjunction with both fractographic observations and numerical simulations. Previous studies suggested the onset of cleavage to be favoured by the presence of nearby manganese sulphide (MnS) clusters: the ductile damaged zone localised inside a cluster increases the stress around it, and so contribute to the triggering of cleavage due to nearby classical sites, like carbides. The experimental study of size dependence and anisotropy on the global fracture behaviour, together with fractographic observations, give here the proof of the influence of MnS clusters on the onset of cleavage in this steel. Fracture behaviour of pre-cracked specimens tested in the transition regime has then been simulated, by three dimensional finite element method computations. Ductile tearing process preceding the cleavage onset at those temperatures regime was well reproduced by the Rousselier's model. Failure probabilities, related to given stress states, has been given by post-processor calculations, using a probabilistic model based on the specific cleavage fracture process. Fracture toughness scatter of the steel, tested in the transition regime, is then well reproduced by those calculations. However, the critical cleavage stress of an elementary volume, that scales for the fracture process, is still assumed to be temperature dependant. Numerical simulations of the local fracture process suggest that this temperature effect can partly be explained by the temperature dependant decrease of the stress amplification due to the MnS clusters. (author)

  11. Mössbauer study of alloy Fe{sub 67.5}Ni{sub 32.5}, prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Benitez Rodríguez, Edson Daniel, E-mail: edbenitezr@ut.edu.co; Bustos Rodríguez, Humberto; Oyola Lozano, Dagoberto; Rojas Martínez, Yebrail Antonio [University of Tolima, Department of Physics (Colombia); Pérez Alcázar, German Antonio [University of Valle, Department of Physics (Colombia)

    2015-06-15

    We present the study of effect of the particle size on the structural and magnetic properties of the Fe{sub 67.5}Ni{sub 32.5} alloy, prepared by mechanical alloying (MA). After milling the powders during 10 hours they were separated by sieving using different meshes. The refinement of the X-ray patterns showed the coexistence of the BCC (Body Centered Cubic) and the FCC (Face Centered Cubic) phases in all samples with lattice parameters and crystallite sizes independent of the mean particle size. However, big particles presented bigger volumetric fraction of BCC grains. The Mossbauer spectra were fitted with a broad sextet corresponding to the ferromagnetic BCC phase, a hyperfine magnetic field distribution and a broad singlet which correspond to the ferromagnetic and paramagnetic sites of the FCC phase, respectively. Hysteresis loops showed a magnetically, soft behavior for all the samples, however, the saturation magnetization values are smaller for the original powder and for the powders with small, mean, particle size due to the dipolar magnetic interaction and the smaller mean magnetic moment, respectively. These effects were proved by Henkel plots that were made to the samples.

  12. VANADIUM ALLOYS

    Science.gov (United States)

    Smith, K.F.; Van Thyne, R.J.

    1959-05-12

    This patent deals with vanadium based ternary alloys useful as fuel element jackets. According to the invention the ternary vanadium alloys, prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal conductivity, low neutron capture cross section, good corrosion resistance, good welding and fabricating properties, low expansion coefficient, and high strength.

  13. Progressive degradation of alloy 690 and the development of a significant improvement in alloy 800CR

    International Nuclear Information System (INIS)

    Staehle, Roger W.; Arioka, Koji; Tapping, Robert

    2015-01-01

    The present most widely used alloys for tubing in steam generators and structural materials in water cooled reactors are Alloy 690 and Alloy 800. However, both alloys, while improved over Alloy 600 may not meet the needs of longer range applications in the range of 80-100 years. Alloy 690 sustains damage resulting from the formation of cavities at grain boundaries which eventually cover about 50% of the area of the grain boundaries with the remainder covering being covered with carbides. The cavities seem to nucleate on the carbides leaving the grain boundaries a structure of cavities and carbides. Such a structure will lead the Alloy 690 to fail completely. Normal Alloy 800 does not produce such cavities and probably retains a large amount of its corrosion resistance but does sustain progressive SCC at low rate. A new alloy, 800CR, has been developed in a collaboration among Arioka, Tapping, and Staehle. This alloy is based on a Cr composition of 23.5-27% with the remainder retaining the previous Alloy 800 composition. 800CR sustains a crack velocity about 100 times less than Alloy 690 and a negligible rate of initiation. The 800CR, alloy is now seeking a patent. (authors)

  14. Recombination radius of a Frenkel pair and capture radius of a self-interstitial atom by vacancy clusters in bcc Fe

    International Nuclear Information System (INIS)

    Nakashima, Kenichi; Stoller, Roger E; Xu, Haixuan

    2015-01-01

    The recombination radius of a Frenkel pair is a fundamental parameter for the object kinetic Monte Carlo (OKMC) and mean field rate theory (RT) methods that are used to investigate irradiation damage accumulation in irradiated materials. The recombination radius in bcc Fe has been studied both experimentally and numerically, however there is no general consensus about its value. The detailed atomistic processes of recombination also remain uncertain. Values from 1.0a 0 to 3.3a 0 have been employed as a recombination radius in previous studies using OKMC and RT. The recombination process of a Frenkel pair is investigated at the atomic level using the self-evolved atomistic kinetic Monte Carlo (SEAKMC) method in this paper. SEAKMC calculations reveal that a self-interstitial atom recombines with a vacancy in a spontaneous reaction from several nearby sites following characteristic pathways. The recombination radius of a Frenkel pair is estimated to be 2.26a 0 by taking the average of the recombination distances from 80 simulation cases. In addition, we apply these procedures to the capture radius of a self-interstitial atom by a vacancy cluster. The capture radius is found to gradually increase with the size of the vacancy cluster. The fitting curve for the capture radius is obtained as a function of the number of vacancies in the cluster. (paper)

  15. Effect of reversible hydrogen alloying and plastic deformation on microstructure development in titanium alloys

    International Nuclear Information System (INIS)

    Murzinova, M.A.

    2011-01-01

    Hydrogen leads to degradation in fracture-related mechanical properties of titanium alloys and is usually considered as a very dangerous element. Numerous studies of hydrogen interaction with titanium alloys showed that hydrogen may be considered not only as an impurity but also as temporary alloying element. This statement is based on the following. Hydrogen stabilizes high-temperature β-phase, leads to decrease in temperature of β→α transformation and extends (α + β )-phase field. The BCC β-phase exhibits lower strength and higher ductility in comparison with HCP α -phase. As a result, hydrogen improves hot workability of hard-to-deform titanium alloys. Hydrogen changes chemical composition of the phases, kinetics of phase transformations, and at low temperatures additional phase transformation (β→α + TiH 2 ) takes place, which is accompanied with noticeable change in volumes of phases. As a result, fine lamellar microstructure may be formed in hydrogenated titanium alloys after heat treatment. It was shown that controlled hydrogen alloying improves weldability and machinability of titanium alloys. After processing hydrogenated titanium preforms are subjected to vacuum annealing, and the hydrogen content decreases up to safe level. Hydrogen removal is accompanied with hydrides dissolution and β→α transformation that makes possible to control structure formation at this final step of treatment. Thus, reversible hydrogen alloying of titanium alloys allows to obtain novel microstructure with enhanced properties. The aim of the work was to study the effect of hydrogen on structure formation, namely: i) influence of hydrogen content on transformation of lamellar microstructure to globular one during deformation in (α+β)-phase field; ii) effect of dissolved hydrogen on dynamic recrystallization in single α- and β- phase regions; iii) influence of vacuum annealing temperature on microstructure development. The work was focused on the optimization of

  16. High strength and high electrical conductivity Cu–Cr system alloys manufactured by hot rolling–quenching process and thermomechanical treatments

    International Nuclear Information System (INIS)

    Xia Chengdong; Zhang Wan; Kang Zhanyuan; Jia Yanlin; Wu Yifeng; Zhang Rui; Xu Genying; Wang Mingpu

    2012-01-01

    Highlights: ► HR–Q and thermomechanical treatments are successfully developed to manufacture Cu–Cr system alloys. ► Ordered fcc structure Cr precipitates are considered to be precursors of equilibrium bcc Cr precipitates. ► The Cr precipitates are responsible for the improvement of properties. ► Additions of Zr, Mg and Si bring about significant improvement in properties of Cu–Cr alloy. ► Good properties are ascribed to grain boundary strengthening, strain hardening and precipitation hardening. - Abstract: Cu–Cr system alloy strips were manufactured by an online hot rolling–quenching (HR–Q) process and subsequent thermomechanical treatments. The microstructure and properties of the alloys were investigated by observations of optical microscopy and transmission electron microscopy, and measurements of microhardness and electrical conductivity. The results show that the HR–Q process and thermomechanical treatments are successfully developed to manufacture Cu–Cr system alloy strips with good combinations of strength, conductivity and softening resistance. Ordered fcc structure Cr precipitates, which are decomposed from the thermomechanical treated alloys, are considered to be precursors to the formation of equilibrium bcc Cr precipitates and responsible for the improvement of properties during near peak aging. Small additions of Zr, Mg and Si effectively improve the hardness and softening resistance of Cu–Cr alloy, and slightly reduce the electrical conductivity. The achievement of high strength and high electrical conductivity in the alloys is ascribed to the interactions of grain boundary strengthening, strain hardening and precipitation hardening.

  17. Electronic structure and phase equilibria in ternary substitutional alloys

    International Nuclear Information System (INIS)

    Traiber, A.J.S.; Allen, S.M.; Waterstrat, R.M.

    1996-01-01

    A reliable, consistent scheme to study phase equilibria in ternary substitutional alloys based on the tight-binding approximation is presented. With electronic parameters from linear muffin-tin orbital calculations, the computed density of states and band structures compare well with those from more accurate abinitio calculations. Disordered alloys are studied within the tight-binding coherent-potential approximation extended to alloys; energetics of ordered systems are obtained through effective pair interactions computed with the general perturbation method; and partially ordered alloys are studied with a novel simplification of the molecular coherent-potential approximation combined with the general perturbation method. The formalism is applied to bcc-based Zr-Ru-Pd alloys which are promising candidates for medical implant devices. Using energetics obtained from the above scheme, we apply the cluster- variation method to study phase equilibria for particular pseudo- binary alloys and show that results are consistent with observed behavior of electronic specific heat coefficient with composition for Zr 0.5 (Ru, Pd) 0.5

  18. Characteristic of fretting damage in metal material

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.; Zhi, F.

    1988-10-01

    The fretting fatigue experiment of LC4 high strength aluminum alloy is described. An SEM examination of the fractology and morphology of fretting damage is carried out as well as an EDAX analysis of the chemical composition of fretting particles. The results show that many loose oxide particles were produced and accumulated in the fretting damage region. 10 references.

  19. A linear model of ductile plastic damage

    International Nuclear Information System (INIS)

    Lemaitre, J.

    1983-01-01

    A three-dimensional model of isotropic ductile plastic damage based on a continuum damage variable on the effective stress concept and on thermodynamics is derived. As shown by experiments on several metals and alloys, the model, integrated in the case of proportional loading, is linear with respect to the accumulated plastic strain and shows a large influence of stress triaxiality [fr

  20. Effect of alloying elements on martensitic transformation in the binary NiAl(β) phase alloys

    International Nuclear Information System (INIS)

    Kainuma, R.; Ohtani, H.; Ishida, K.

    1996-01-01

    The characteristics of the B2(β) to L1 0 (β') martensitic transformation in NiAl base alloys containing a small amount of third elements have been investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It is found that in addition to the normal L1 0 (3R) martensite, the 7R martensite is also present in the ternary alloys containing Ti, Mo, Ag, Ta, or Zr. While the addition of third elements X (X: Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Ta, W, and Si) to the binary Ni 64 Al 36 alloy stabilizes the parent β phase, thereby lowering the M s temperature, addition of third elements such as Co, Cu, or Ag destabilizes the β phase, increasing the M s temperature. The occurrence of the 7R martensite structure is attributed to solid solution hardening arising from the difference in atomic size between Ni and Al and the third elements added. The variation in M s temperature with third element additions is primarily ascribed to the difference in lattice stabilities of the bcc and fcc phases of the alloying elements

  1. Nonswelling alloy

    Science.gov (United States)

    Harkness, S.D.

    1975-12-23

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses.

  2. Nonswelling alloy

    International Nuclear Information System (INIS)

    Harkness, S.D.

    1975-01-01

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses

  3. Preparation and characterization of Ti-15Zr-12.5Mo alloy for use as biomaterial

    International Nuclear Information System (INIS)

    Lourenco, M.L.; Correa, D.R.N.; Grandini, C.R.

    2014-01-01

    Titanium alloys exhibit favorable properties for biomedical applications. With the zirconium and molybdenum addition, the microstructure and mechanical properties can be changed. Moreover, these alloying elements have certified non-toxicity. The aim of this paper is to prepare and characterize the microstructure and some mechanical properties of Ti-15Zr-12,5Mo (wt%). The alloy was produced by arc-melting and heat treated at 1000 °C for 24 h. Chemical analysis was made by ICP-OES, EDS and density measurements. The crystalline structure and microstructure were analyzed by X-ray diffraction, optical and scanning electron microscopy. An analysis of the mechanical properties was evaluated by Vickers microhardness measurements. The alloy presented a β-type structure (bcc crystalline structure), with the formation of typical equiaxial grains, with higher hardness value than the cp-Ti. (author)

  4. Phase characterisation and mechanical behaviour of Fe–B modified Cu–Zn–Al shape memory alloys

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo Alaneme

    2017-04-01

    Full Text Available The microstructures, phase characteristics and mechanical behaviour of Cu–Zn–Al alloys modified with Fe, B, and Fe–B mixed micro-alloying additions has been investigated. Cu–Zn–Al alloys were produced by casting with and without the addition of the microelements (Fe, B and Fe–B. The alloys were subjected to a homogenisation – cold rolling – annealing treatment schedule, before the alloys were machined to specifications for tensile test, fracture toughness, and hardness measurement. Optical, scanning electron microscopy and X-ray diffraction analysis were utilised for microstructural and phase characterisation of the alloys. A distinct difference in grain morphology was observed in the alloys produced – the unmodified alloy had predominantly needle-like lath martensite structure with sharp grain edges while significantly larger transverse grain size and curve edged/near elliptical grain shape was observed for the modified Cu–Zn–Al alloys. Cu–Zn with fcc structure was the predominant phase identified in the alloys while Cu–Al with bcc structure was the secondary phase observed. The hardness of the unmodified Cu–Zn–Al alloy was higher than that of the modified alloys with reductions in hardness ranging between 32.4 and 51.5%. However, the tensile strength was significantly lower than that of the modified alloy grades (28.37–52.74% increase in tensile strength was achieved with the addition of micro-alloying elements. Similarly, the percent elongation and fracture toughness (10–23% increase of the modified alloy was higher than that of the unmodified alloy grade. The modified alloy compositions mostly exhibited fracture features indicative of a fibrous micro-mechanism to crack initiation and propagation, characterised by the prevalence of dimpled rupture.

  5. First-principles calculation for the effect of hydrogen atoms on the mobility of a screw dislocation in BCC iron

    International Nuclear Information System (INIS)

    Itakura, Mitsuhiro; Kaburaki, Hideo; Yamaguchi, Masatake; Endo, Tatsuro; Higuchi, Kenji; Ogata, Shigenobu; Kimizuka, Hajime

    2012-01-01

    Effect of hydrogen atoms on the mobility of a screw dislocation in BCC iron has been evaluated using the first-principles calculation. The stable position of a hydrogen atom is found to be near the screw dislocation core and inside the core respectively when the dislocation is at the easy-core or hard-core configuration in BCC iron. The intrinsically unstable hard-core configuration of the screw dislocation is stabilized when a hydrogen atom is trapped inside the core. On the basis of this first-principles result, an elastic string model of a dislocation is developed to predict the kink motion in the presence of a hydrogen atom. It is found that a double-kink formation is facilitated when a hydrogen atom is located near a dislocation line, however, a kink motion is retarded when a hydrogen atom is behind the kink. (author)

  6. Investigation of the structural and hydrogenation properties of disordered Ti-V-Cr-Mo BCC solid solutions

    International Nuclear Information System (INIS)

    Raufast, C.; Planté, D.; Miraglia, S.

    2014-01-01

    Highlights: • Materials synthesis and structural analysis of selected compositions of TiVCr(Mo) bcc samples. • Extraction of the thermodynamics relevant parameters for hydride formation and dissociation state of Ti 0.3 V 1.7 Cr 0.7 Mo 0.3 sample. • Discussion of the hydrides practicability. - Abstract: Selected compositions in the Ti-Cr-V-Mo system (with the BCC structure-type) have been synthesized and characterized for structural (crystalline structure, solidification microstructure) and thermodynamic properties (equilibrium and reversible hydrogen storage capacity). We present as well the effect of co-melting with a so-called activating phase that results in a secondary phase development and a subsequent enhancement of the hydrogen sorption kinetics. Ageing properties and applicability of such materials for hybrid hydrogen storage systems are also discussed

  7. Impact of Intragranular Substructure Parameters on the Forming Limit Diagrams of Single-Phase B.C.C. Steels

    Directory of Open Access Journals (Sweden)

    Gérald Franz

    2013-11-01

    Full Text Available An advanced elastic-plastic self-consistent polycrystalline model, accounting for intragranular microstructure development and evolution, is coupled with a bifurcation-based localization criterion and applied to the numerical investigation of the impact of microstructural patterns on ductility of single-phase steels. The proposed multiscale model, taking into account essential microstructural aspects, such as initial and induced textures, dislocation densities, and softening mechanisms, allows us to emphasize the relationship between intragranular microstructure of B.C.C. steels and their ductility. A qualitative study in terms of forming limit diagrams for various dislocation networks, during monotonic loading tests, is conducted in order to analyze the impact of intragranular substructure parameters on the formability of single-phase B.C.C. steels.

  8. A systematic study on the interfacial energy of O-line interfaces in fcc/bcc systems

    International Nuclear Information System (INIS)

    Dai, Fuzhi; Zhang, Wenzheng

    2013-01-01

    Habit planes between face-centered cubic (fcc)/body-centered cubic (bcc) phases usually exhibit irrational orientations, which often agree with the O-line criterion. Previously, energy calculation was made to test whether the habit planes were energetically favorable, but the values of the energy were found very sensitive to the initial atomic configuration in an irrationally orientated interface. In this paper, under the O-line condition, simple selection criteria are proposed to define and remove interfacial interstitials and vacancies in the initial atomic configuration. The criteria are proved to be effective in obtaining robust energy results. Interfacial energies of two types of O-line interfaces in fcc/bcc systems are calculated following the criteria. The observed transformation crystallography of precipitates in Ni–Cr and Cu–Cr systems can be explained consistently as the irrational habit plane in each system is associated with the lowest energy O-line interface. (paper)

  9. Magnetic ordering of four particle exchange model in BCC 3He

    International Nuclear Information System (INIS)

    Ishikawa, Koji; Okada, Isamu

    1978-01-01

    The low temperature magnetic ordering of BCC 3 He within the mean field approximation was studied. A model including four particle exchange interactions was considered. Two types of cyclic quadrupole exchange process, planar and folded, were taken into account. Assuming four sublattices, it was considered to minimize the spin energy with respect to the classical spin vector and to find out four ordered states at the absolute zero point. They are antiferromagnetic (AF), weak ferromagnetic (WF) and two kinds of simple cubic antiferromagnetic states (SCAF). The condition for the existence of each ordered state is given, and the free energies of the ordered states are calculated in the mean field approximation. The transition between AF or SCAF and the paramagnetic states is of the first order. The phase diagram is drawn in the parameter space. The phase diagram was obtained numerically at Hetherington and Willard's value and at its neighbouring values. The difference between the present result and HW's is that of magnetic field direction in the perpendicular simple cubic antiferromagnetic states. The second order transition disappears, and the WF state changes gradually into AF state. With respect to the first order transition, the transition temperature increases with magnetic field. In this case, a critical magnetic field exists. (Kato, T

  10. Effect of orientation of prismatic dislocation loops on interaction with free surfaces in BCC iron

    Science.gov (United States)

    Fikar, Jan; Gröger, Roman; Schäublin, Robin

    2017-12-01

    The prismatic loops appear in metals as a result of high-energy irradiation. Understanding their formation and interaction is important for quantification of irradiation-induced deterioration of mechanical properties. Characterization of dislocation loops in thin foils is commonly made using transmission electron microscopy (TEM), but the results are inevitably influenced by the proximity of free surfaces. The prismatic loops are attracted to free surfaces by image forces. Depending on the type, shape, size, orientation and depth of the loop in the foil, they can escape to the free surface creating denuded loop-free zones and thus invalidating TEM observations. In our previous studies we described a simple general method to determine the critical depth and the critical stress to move prismatic dislocation loops. The critical depths can be further used to correct measurements of the loop density by TEM. Here, we use this procedure to compare 〈100〉 loops and 1/2 〈111〉 loops in body-centered cubic (BCC) iron. The influences of the interatomic potential and the loop orientation are studied in detail. The difference between interstitial and vacancy type loop is also investigated.

  11. Amylase Production from Thermophilic Bacillus sp. BCC 021-50 Isolated from a Marine Environment

    Directory of Open Access Journals (Sweden)

    Altaf Ahmed Simair

    2017-06-01

    Full Text Available The high cost of fermentation media is one of the technical barriers in amylase production from microbial sources. Amylase is used in several industrial processes or industries, for example, in the food industry, the saccharification of starchy materials, and in the detergent and textile industry. In this study, marine microorganisms were isolated to identify unique amylase-producing microbes in starch agar medium. More than 50 bacterial strains with positive amylase activity, isolated from marine water and soil, were screened for amylase production in starch agar medium. Bacillus sp. BCC 021-50 was found to be the best amylase-producing strain in starch agar medium and under submerged fermentation conditions. Next, fermentation conditions were optimized for bacterial growth and enzyme production. The highest amylase concentration of 5211 U/mL was obtained after 36 h of incubation at 50 °C, pH 8.0, using 20 g/L molasses as an energy source and 10 g/L peptone as a nitrogen source. From an application perspective, crude amylase was characterized in terms of temperature and pH. Maximum amylase activity was noted at 70 °C and pH 7.50. However, our results show clear advantages for enzyme stability in alkaline pH, high-temperature, and stability in the presence of surfactant, oxidizing, and bleaching agents. This research contributes towards the development of an economical amylase production process using agro-industrial residues.

  12. Strain Fields And Crystallographic Characteristics Of Interstitial Dislocation Loops of Various Geometry In BCC Iron

    International Nuclear Information System (INIS)

    Sivak, Alexander B.; Chernov, Viatcheslav M.; Romanov, Vladimir A.

    2008-01-01

    The formation energy, the relaxation volume, the dipole-force tensor, the self strain tensor and strain fields of interstitial dislocation loops in bcc iron (clusters of self interstitial atoms) have been calculated by molecular statics. Hexagonal and square dislocation loops of different types with different Burgers vectors, directions of dislocation segments and habit planes containing up to ∼2500 self-interstitials have been considered. Analytical expressions describing size dependence of the formation energy, the relaxation volume and the self strain tensor for the loops stated have been obtained. The most energetically favorable loops are hexagonal loops with Burgers vector a/2 and habit plane {11x}, where x takes values in the range from 0 to 1 depending on the loop size. The formation energy of a loops with and dislocation segments is ∼14% and 23% greater than that of hexagonal a/2 loops at N>500, respectively. The analysis of the formation energies of a/2 and a loops demonstrated that the nucleation of an a loop by joining of two a/2 loops is possible when the total number of constituent self-interstitials in these loops is larger than 13

  13. Interface Mediated Nucleation and Growth of Dislocations in fcc-bcc nanocomposite

    Science.gov (United States)

    Zhang, Ruifeng; Wang, Jian; Beyerlein, Irene J.; Germann, Timothy C.

    2011-03-01

    Heterophase interfaces play a crucial role in determining material strength for nanostructured materials because they can block, store, nucleate, and remove dislocations, the essential defects that enable plastic deformation. Much recent theoretical and experimental effort has been conducted on nanostructured Cu-Nb multilayer composites that exhibited extraordinarily high strength, ductility, and resistance to radiation and mechanical loading. In decreasing layer thicknesses to the order of a few tens of nanometers or less, the deformation behavior of such composites is mainly controlled by the Cu/Nb interface. In this work, we focus on the cooperative mechanisms of dislocation nucleation and growth from Cu/Nb interfaces, and their interaction with interface. Two types of experimentally observed Cu/Nb incoherent interfaces are comparatively studied. We found that the preferred dislocation nucleation sites are closely related to atomic interface structure, which in turn, depend on the orientation relationship. The activation stress and energies for an isolated Shockley dislocation loop of different sizes from specific interface sites depend strongly on dislocation size, atomic interface pattern, and loading conditions. Such findings provide important insight into the mechanical response of a wide range of fcc/bcc metallic nanocomposites via atomic interface design.

  14. Identifying self-interstitials of bcc and fcc crystals in molecular dynamics

    Science.gov (United States)

    Bukkuru, S.; Bhardwaj, U.; Warrier, M.; Rao, A. D. P.; Valsakumar, M. C.

    2017-02-01

    Identification of self-interstitials in molecular dynamics (MD) simulations is of critical importance. There exist several criteria for identifying the self-interstitial. Most of the existing methods use an assumed cut-off value for the displacement of an atom from its lattice position to identify the self-interstitial. The results obtained are affected by the chosen cut-off value. Moreover, these chosen cut-off values are independent of temperature. We have developed a novel unsupervised learning algorithm called Max-Space Clustering (MSC) to identify an appropriate cut-off value and its dependence on temperature. This method is compared with some widely used methods such as effective sphere (ES) method and nearest neighbor sphere (NNS) method. The cut-off radius obtained using our method shows a linear variation with temperature. The value of cut-off radius and its temperature dependence is derived for five bcc (Cr, Fe, Mo, Nb, W) and six fcc (Ag, Au, Cu, Ni, Pd, Pt) crystals. It is seen that the ratio of the cut-off values "r" to the lattice constant "a" lies between 0.23 and 0.3 at 300 K and this ratio is on an average smaller for the fcc crystals. Collision cascade simulations are carried out for Primary knock-on Atom (PKA) energies of 5 keV in Fe (at 300 K and 1000 K) and W (at 300 K and 2500 K) and the results are compared using the various methods.

  15. On the Secrecy Capacity Region of the Block-Fading BCC with Limited CSI Feedback

    KAUST Repository

    Hyadi, Amal

    2017-02-07

    In this work, we examine the secrecy capacity region of the block-fading broadcast channel with confidential messages (BCC) when the transmitter has limited knowledge of the channel. In particular, we consider a two-user communication system where the transmitter has one common message to be transmitted to both users and one confidential message intended to only one of them. The confidential message has to be kept secret from the other user to whom the information is not intended. The transmitter is not aware of the channel state information (CSI) of neither channel and is only provided by limited CSI feedback sent at the beginning of each fading block. Assuming an error-free feedback link, we characterize the secrecy capacity region of this channel and show that even with a 1-bit CSI feedback, a positive secrecy rate can still be achieved. Then, we look at the case where the feedback link is not error- free and is rather a binary erasure channel (BEC). In the latter case, we provide an achievable secrecy rate region and show that as long as the erasure event is not a probability 1 event, the transmitter can still transmit the confidential information with a positive secrecy rate.

  16. MD and BCA simulations of He and H bombardment of fuzz in bcc elements

    Science.gov (United States)

    Klaver, T. P. C.; Zhang, S.; Nordlund, K.

    2017-08-01

    We present results of MD simulations of low energy He ion bombardment of low density fuzz in bcc elements. He ions can penetrate several micrometers into sparse fuzz, which allows for a sufficient He flux through it to grow the fuzz further. He kinetic energy falls off exponentially with penetration depth. A BCA code was used to carry out the same ion bombardment on the same fuzz structures as in MD simulations, but with simpler, 10 million times faster calculations. Despite the poor theoretical basis of the BCA at low ion energies, and the use of somewhat different potentials in MD and BCA calculations, the ion penetration depths predicted by BCA are only ∼12% less than those predicted by MD. The MD-BCA differences are highly systematic and trends in the results of the two methods are very similar. We have carried out more than 200 BCA calculation runs of ion bombardment of fuzz, in which parameters in the ion bombardment process were varied. For most parameters, the results show that the ion bombardment process is quite generic. The ion species (He or H), ion mass, fuzz element (W, Ta, Mo, Fe) and fuzz element lattice parameter turned out to have a modest influence on ion penetration depths at most. An off-normal angle of incidence strongly reduces the ion penetration depth. Increasing the ion energy increases the ion penetration, but the rate by which ion energy drops off at high ion energies follows the same exponential pattern as at lower energies.

  17. Microstructural and magnetic characterization of iron precipitation in Ni-Fe-Al alloys

    International Nuclear Information System (INIS)

    Duman, Nagehan; Mekhrabov, Amdulla O.; Akdeniz, M. Vedat

    2011-01-01

    The influence of annealing on the microstructural evolution and magnetic properties of Ni 50 Fe x Al 50-x alloys for x = 20, 25, and 30 has been investigated. Solidification microstructures of as-cast alloys reveal coarse grains of a single B2 type β-phase and typical off eutectic microstructure consisting of proeutectic B2 type β dendrites and interdendritic eutectic for x = 20 and x > 20 at.% Fe respectively. However, annealing at 1073 K results in the formation of FCC γ-phase particles along the grain boundaries as well as grain interior in x = 20 at.% Fe alloy. The volume fraction of interdentritic eutectic regions tend to decrease and their morphologies start to degenerate by forming FCC γ-phase for x > 20 at.% Fe alloys with increasing annealing temperatures. Increasing Fe content of alloys induce an enhancement in magnetization and a rise in the Curie transition temperature (T C ). Temperature scan magnetic measurements and transmission electron microscopy reveal that a transient rise in the magnetization at temperatures well above the T C of the alloys would be attributed to the precipitation of a nano-scale ferromagnetic BCC α-Fe phase. Retained magnetization above the Curie transition temperature of alloy matrix, together with enhanced room temperature saturation magnetization of alloys annealed at favorable temperatures support the presence of ferromagnetic precipitates. These nano-scale precipitates are shown to induce significant precipitation hardening of the β-phase in conjunction with enhanced room temperature saturation magnetization in particular when an annealing temperature of 673 K is used. - Research Highlights: → Evolution of microstructure and magnetic properties with varying Fe content. → Transient rise in magnetization via the formation of ferromagnetic phase. → Enhancements in saturation magnetization owing to precipitated ferromagnetic phase. → Nanoscale precipitation of ferromagnetic BCC α-Fe confirmed by TEM.

  18. Spheroidization behavior of dendritic b.c.c. phase in Zr-based モ-phase composite

    Directory of Open Access Journals (Sweden)

    Sun Guoyuan

    2013-03-01

    Full Text Available The spheroidization behavior of the dendritic b.c.c. phase dispersed in a bulk metallic glass (BMG matrix was investigated through applying semi-solid isothermal processing and a subsequent rapid quenching procedure to a Zr-based モ-phase composite. The Zr-based composite with the composition of Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 was prefabricated by a water-cooled copper mold-casting method and characterized by X-ray diffraction (XRD and scanning electron microscope (SEM. The results show that the composite consists of a glassy matrix and uniformly distributed fine dendrites of the モ-Zr solid solution with the body-centered-cubic (b.c.c. structure. Based on the differential scanning calorimeter (DSC examination results, and in view of the b.c.c. モ-Zr to h.c.p. メ-Zr phase transition temperature, a semi-solid holding temperature of 900 ìC was determined. After reheating the prefabricated composite to the semi-solid temperature, followed by an isothermal holding process at this temperature for 5 min, and then quenching the semi-solid mixture into iced-water; the two-phase microstructure composed of a BMG matrix and uniformly dispersed spherical b.c.c. モ-Zr particles with a high degree of sphericity was achieved. The present spheroidization transition is a thermodynamically autonomic behavior, and essentially a diffusion process controlled by kinetic factors; and the formation of the BMG matrix should be attributed to the rapid quenching of the semi-solid mixture as well as the large glass-forming ability of the remaining melt in the semi-solid mixture.

  19. Pre-melting hcp to bcc Transition in Beryllium: A Study by First-Principles Phonon Quasiparticle Approach

    Science.gov (United States)

    Zhang, D. B., Sr.

    2017-12-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to X-ray equipments. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp to bcc transition occurs near the melting curve at 0

  20. Growth of a brittle crack (001) in 3D bcc iron crystal with a Cu nano-particle

    Czech Academy of Sciences Publication Activity Database

    Uhnáková, Alena; Machová, Anna; Hora, Petr; Červená, Olga

    2014-01-01

    Roč. 83, February (2014), s. 229-234 ISSN 0927-0256 R&D Projects: GA ČR GA101/09/1630 Institutional support: RVO:61388998 Keywords : brittle crack extension * 3D * mode I * bcc iron * Cu nano-particle * molecular dynamics * acoustic emission Subject RIV: JG - Metallurgy Impact factor: 2.131, year: 2014 http://www.sciencedirect.com/science/article/pii/S0927025613006575

  1. 3D atomistic simulation of fatigue behavior of a ductile crack in bcc iron loaded in mode II

    Czech Academy of Sciences Publication Activity Database

    Uhnáková, Alena; Pokluda, J.; Machová, Anna; Hora, Petr

    2012-01-01

    Roč. 61, AUG 2012 (2012), s. 12-19 ISSN 0927-0256 R&D Projects: GA ČR(CZ) GAP108/10/0698 Institutional research plan: CEZ:AV0Z20760514 Keywords : fatigue * mode II * bcc iron * molecular dynamic simulations Subject RIV: JG - Metallurgy Impact factor: 1.878, year: 2012 http://www.sciencedirect.com/science/article/pii/S0927025612001929

  2. Crystal plasticity model for BCC iron atomistically informed by kinetics of correlated kinkpair nucleation on screw dislocation

    Science.gov (United States)

    Narayanan, Sankar; McDowell, David L.; Zhu, Ting

    2014-04-01

    The mobility of dislocation in body-centered cubic (BCC) metals is controlled by the thermally activated nucleation of kinks along the dislocation core. By employing a recent interatomic potential and the Nudged Elastic Band method, we predict the atomistic saddle-point state of 1/2 screw dislocation motion in BCC iron that involves the nucleation of correlated kinkpairs and the resulting double superkinks. This unique process leads to a single-humped minimum energy path that governs the one-step activation of a screw dislocation to move into the adjacent {110} Peierls valley, which contrasts with the double-humped energy path and the two-step transition predicted by other interatomic potentials. Based on transition state theory, we use the atomistically computed, stress-dependent kinkpair activation parameters to inform a coarse-grained crystal plasticity flow rule. Our atomistically-informed crystal plasticity model quantitatively predicts the orientation dependent stress-strain behavior of BCC iron single crystals in a manner that is consistent with experimental results. The predicted temperature and strain-rate dependencies of the yield stress agree with experimental results in the 200-350 K temperature regime, and are rationalized by the small activation volumes associated with the kinkpair-mediated motion of screw dislocations.

  3. Microstructural origins of high strength and high ductility in an AlCoCrFeNi2.1 eutectic high-entropy alloy

    International Nuclear Information System (INIS)

    Gao, Xuzhou; Lu, Yiping; Zhang, Bo; Liang, Ningning; Wu, Guanzhong; Sha, Gang; Liu, Jizi; Zhao, Yonghao

    2017-01-01

    Recent studies indicate that eutectic high-entropy alloys can simultaneously possess high strength and high ductility, which have potential applications in industrial fields. Nevertheless, microstructural origins of the excellent strength–ductility combination remain unclear. In this study, an AlCoCrFeNi 2.1 eutectic high-entropy alloy was prepared with face-centered cubic (FCC)(L1 2 )/body-centered-cubic (BCC)(B2) modulated lamellar structures and a remarkable combination of ultimate tensile strength (1351 MPa) and ductility (15.4%) using the classical casting technique. Post-deformation transmission electron microscopy revealed that the FCC(L1 2 ) phase was deformed in a matter of planar dislocation slip, with a slip system of {111} <110>, and stacking faults due to low stacking fault energy. Due to extreme solute drag, high densities of dislocations are distributed homogeneously at {111} slip plane. In the BCC(B2) phase, some dislocations exist on two {110} slip bands. The atom probe tomography analysis revealed a high density of Cr-enriched nano-precipitates, which strengthened the BCC(B2) phase by Orowan mechanisms. Fracture surface observation revealed a ductile fracture in the FCC(L1 2 ) phase and a brittle-like fracture in the BCC(B2) lamella. The underlying mechanism for the high strength and high ductility of AlCoCrFeNi 2.1 eutectic high-entropy alloy was finally analyzed based on the coupling between the ductile FCC(L1 2 ) and brittle BCC(B2) phases.

  4. Strain aging in tungsten heavy alloys

    International Nuclear Information System (INIS)

    Dowding, R.J.; Tauer, K.J.

    1991-01-01

    This paper reports on tungsten heavy alloys which are two-phase mixtures of body center cubic (BCC) tungsten surrounded by a face center cubic (FCC) matrix. The matrix is most often composed of nickel and iron in a ratio of 70:30 but, occasionally, the matrix may also contain cobalt or copper. Nickel, however, is always the primary matrix component. The tungsten heavy alloy is fabricated through powder metallurgy techniques. Elemental powders are blended, pressed to shape, and sintered. Depending upon the tungsten content, the sintering temperatures are usually in the range of 1450 degrees C to 1525 degrees C. These temperatures are high enough that, as a result, the matrix is at the liquid phase and the process is known as liquid phase sintering. At the liquid phase temperature, the matrix becomes saturated with tungsten, but this does not change the FCC character of the matrix. The sintering is usually done in a hydrogen atmosphere furnace in order to reduce the oxides on the tungsten powder surfaces and create clean, active surfaces which will enhance the adherence between the tungsten and the matrix. The hydrogen atmosphere also creates the presence of excess dissolved hydrogen in the alloy. It has been shown that the hydrogen degrades the toughness and ductility of the heavy alloy. A post-sintering vacuum heat treatment is generally required to insure that there is no residual hydrogen present. The as-sintered tensile strength of a 90% tungsten, 7% nickel, 3% iron alloy (90W) is in the range of 800 to 940 MPa and can be increased significantly by cold working, usually rolling or swaging. Swaging to reductions in area of 20% can result in tensile strengths of 1250 MPa or more. As the strength increases, the elongation, which may have been 30% or more, decreases to less than 5%

  5. Electronic structure of disordered Fe-V alloys

    International Nuclear Information System (INIS)

    Krause, J.C.; Paduani, C.; Schaff, J.; Costa, M.I. Jr. da

    1998-01-01

    The first-principles discrete variational method is employed to investigate the electronic structure and local magnetic properties of disordered Fe-V alloys. The spin-polarized case is considered in the formalism of the local-spin-density approximation, with the exchange-correlation term of von Barth endash Hedin. The effect on the local magnetic properties of adding V atoms in the immediate neighborhood of iron atoms is investigated. The partial density of states, hyperfine field (H c ), magnetic moment (μ), and isomer shift are obtained for the central atom of the cluster. For the impurity V atom in the bcc iron host the calculated values for H c and μ are -203 kG and -0.86μ B , respectively. The isolated Fe atom in a bcc vanadium host exhibits a collapsed moment and acts as a receptor for electrons. In ordered alloys the calculations indicate also a vanishing moment at iron sites. copyright 1998 The American Physical Society

  6. Enhanced upper critical fields in binary Nb-Ti alloys

    International Nuclear Information System (INIS)

    Hariharan, Y.; Sastry, V.S.; Janawadkar, M.P.; Radhakrishnan, T.S.

    1986-01-01

    The authors report the enhancement of H/sub c2/ in quenched and suitably heat treated binary Nb-65 at % Ti alloys. The inherent metastability of the bcc β phase and its instability towards athermal ω are used to realise high values of normal state resistivity ε/sub n/. The consequences of this on the upper critical field have been experimentally determined by the measurement of dH/sub c2//dT at T/sub c/ and of T/sub c/. These together with our similar measurements on Nb-83 at % Ti alloy to which at 1 at % N was added (to retain it in the β phase) are analysed in terms of the existing theories for upper critical fields. It is shown that a peak in H/sub c2/(o) occurs at 17 - 18 T when ε/sub n/ has a value of approximately 100 μΩcm

  7. Fission neutron damage rates and efficiencies in several metals

    International Nuclear Information System (INIS)

    Klabunde, C.E.; Coltman, R.R. Jr.

    1981-11-01

    Initial rates of resistivity-measured low-temperature damage production by fission-spectrum fast neutrons have been determined for 14 metals in the same very well characterized irradiation facility. Six of these metals were fcc, 5 bcc, and 3 hcp. Most were of quite high purity. Observed damage rates, after correction for all known extraneous resistivity-producing effects, were compared with rates predicted by the damage calculation code RECOIL, using parameters chosen from the literature. These parameters, effective displacement threshold energy, E/sub d/, and Frenkel-pair resistivity, rho/sub F/, were in many cases only best estimates, the further refinement of which may be aided by the present results. Damage efficiencies (measured/predicted rates) follow the same trends by crystal classes as seen in other fast-neutron studies

  8. Electrical Resistance Alloys and Low-Expansion Alloys

    DEFF Research Database (Denmark)

    Kjer, Torben

    1996-01-01

    The article gives an overview of electrical resistance alloys and alloys with low thermal expansion. The electrical resistance alloys comprise resistance alloys, heating alloys and thermostat alloys. The low expansion alloys comprise alloys with very low expansion coefficients, alloys with very low...... thermoelastic coefficients and age hardenable low expansion alloys....

  9. Magnetic Properties of Nanocrystalline FexCu1-x Alloys Prepared by Ball Milling

    International Nuclear Information System (INIS)

    Yousif, A.; Bouziane, K.; Elzain, M. E.; Ren, X.; Berry, F. J.; Widatallah, H. M.; Al Rawas, A.; Gismelseed, A.; Al-Omari, I. A.

    2004-01-01

    X-ray diffraction, Moessbauer and magnetization measurements were used to study Fe x Cu 1-x alloys prepared by ball-milling. The X-ray data show the formation of a nanocrystalline Fe-Cu solid solution. The samples with x≥0.8 and x≤0.5 exhibit bcc or fcc phase, respectively. Both the bcc and fcc phases are principally ferromagnetic for x≥0.2, but the sample with x=0.1 remains paramagnetic down to 78 K. The influence of the local environment on the hyperfine parameters and the local magnetic moment are discussed using calculations based on the discrete-variational method in the local density approximation.

  10. On the segregation behavior of tin and antimony at grain boundaries of polycrystalline bcc iron

    Czech Academy of Sciences Publication Activity Database

    Lejček, Pavel; Šandera, P.; Horníková, J.; Pokluda, J.; Godec, M.

    2016-01-01

    Roč. 363, Feb (2016), 140-144 ISSN 0169-4332 R&D Projects: GA ČR GAP108/12/0144 Institutional support: RVO:68378271 Keywords : grain boundary segregation * tin * antimony * Fe based alloy * AES quantification Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.387, year: 2016

  11. Phase stability and elastic properties of Cr-V alloys

    Science.gov (United States)

    Gao, M. C.; Suzuki, Y.; Schweiger, H.; Doǧan, Ö. N.; Hawk, J.; Widom, M.

    2013-02-01

    V is the only element in the periodic table that forms a complete solid solution with Cr and thus is particularly important in alloying strategy to ductilize Cr. This study combines first-principles density functional theory calculations and experiments to investigate the phase stability and elastic properties of Cr-V binary alloys. The cluster expansion study reveals the formation of various ordered compounds at low temperatures that were not previously known. These compounds become unstable due to the configurational entropy of bcc solid solution as the temperature is increased. The elastic constants of ordered and disordered compounds are calculated at both T = 0 K and finite temperatures. The overall trends in elastic properties are in agreement with measurements using the resonant ultrasound spectroscopy method. The calculations predict that addition of V to Cr decreases both the bulk modulus and the shear modulus, and enhances the Poisson’s ratio, in agreement with experiments. Decrease in the bulk modulus is correlated to decrease in the valence electron density and increase in the lattice constant. An enhanced Poisson’s ratio for bcc Cr-V alloys (compared to pure Cr) is associated with an increased density of states at the Fermi level. Furthermore, the difference charge density in the bonding region in the (110) slip plane is highest for pure Cr and decreases gradually as V is added. The present calculation also predicts a negative Cauchy pressure for pure Cr, and it becomes positive upon alloying with V. The intrinsic ductilizing effect from V may contribute, at least partially, to the experimentally observed ductilizing phenomenon in the literature.

  12. Phase stability and elastic properties of Cr-V alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gao, M C; Suzuki, Y; Schweiger, H; Doğan, Ö N; Hawk, J; Widom, M

    2013-01-23

    V is the only element in the periodic table that forms a complete solid solution with Cr and thus is particularly important in alloying strategy to ductilize Cr. This study combines first-principles density functional theory calculations and experiments to investigate the phase stability and elastic properties of Cr–V binary alloys. The cluster expansion study reveals the formation of various ordered compounds at low temperatures that were not previously known. These compounds become unstable due to the configurational entropy of bcc solid solution as the temperature is increased. The elastic constants of ordered and disordered compounds are calculated at both T = 0 K and finite temperatures. The overall trends in elastic properties are in agreement with measurements using the resonant ultrasound spectroscopy method. The calculations predict that addition of V to Cr decreases both the bulk modulus and the shear modulus, and enhances the Poisson’s ratio, in agreement with experiments. Decrease in the bulk modulus is correlated to decrease in the valence electron density and increase in the lattice constant. An enhanced Poisson’s ratio for bcc Cr–V alloys (compared to pure Cr) is associated with an increased density of states at the Fermi level. Furthermore, the difference charge density in the bonding region in the (110) slip plane is highest for pure Cr and decreases gradually as V is added. The present calculation also predicts a negative Cauchy pressure for pure Cr, and it becomes positive upon alloying with V. The intrinsic ductilizing effect from V may contribute, at least partially, to the experimentally observed ductilizing phenomenon in the literature.

  13. Martensitic Transformation in a β-Type Mg-Sc Alloy

    Science.gov (United States)

    Ogawa, Yukiko; Ando, Daisuke; Sutou, Yuji; Somekawa, Hidetoshi; Koike, Junichi

    2018-03-01

    Recently, we found that a Mg-Sc alloy with a bcc (β) phase exhibits superelasticity and a shape memory effect at low temperature. In this work, we examined the stress-induced and thermally induced martensitic transformation of the β-type Mg-Sc alloy and investigated the crystal structure of the thermally induced martensite phase based on in situ X-ray diffraction (XRD) measurements. The lattice constants of the martensite phase were calculated to be a = 0.3285 nm, b = 0.5544 nm, and c = 0.5223 nm when we assumed that the martensite phase has an orthorhombic structure (Cmcm). Based on the lattice correspondence between a bcc and an orthorhombic structures such as that in the case of β-Ti shape memory alloys, we estimated the transformation strain of the β Mg-Sc alloy. As a result, the transformation strains along the 001, 011, and 111 directions in the β phase were calculated to be + 5.7, + 8.8, and + 3.3%, respectively.

  14. Martensitic Transformation in a β-Type Mg-Sc Alloy

    Science.gov (United States)

    Ogawa, Yukiko; Ando, Daisuke; Sutou, Yuji; Somekawa, Hidetoshi; Koike, Junichi

    2017-12-01

    Recently, we found that a Mg-Sc alloy with a bcc (β) phase exhibits superelasticity and a shape memory effect at low temperature. In this work, we examined the stress-induced and thermally induced martensitic transformation of the β-type Mg-Sc alloy and investigated the crystal structure of the thermally induced martensite phase based on in situ X-ray diffraction (XRD) measurements. The lattice constants of the martensite phase were calculated to be a = 0.3285 nm, b = 0.5544 nm, and c = 0.5223 nm when we assumed that the martensite phase has an orthorhombic structure (Cmcm). Based on the lattice correspondence between a bcc and an orthorhombic structures such as that in the case of β-Ti shape memory alloys, we estimated the transformation strain of the β Mg-Sc alloy. As a result, the transformation strains along the 001, 011, and 111 directions in the β phase were calculated to be + 5.7, + 8.8, and + 3.3%, respectively.

  15. XPS study on the electronic structure of hydrided Ti-V, Ti-Nb and Ti-Mo alloys

    International Nuclear Information System (INIS)

    Tanaka, Kazuhide; Aoki, Hiromasa

    1989-01-01

    Effects of hydrogenation on the core and valence electronic structures of β(bcc)-stabilized Ti-25at%V, Ti-50at%Nb and Ti-20at%Mo alloys are studied with XPS technique using monochromatized Al K α radiation. Small but uniform binding-energy shifts are observed upon hydrogenation for all the core spectra measured. Their valence-band spectra are significantly distorted, providing an evidence of the formation of metal-hydrogen bonding bands in these Ti alloys. Interrelations between the core binding-energy shifts and the valence-band distortion are discussed. (orig.)

  16. Determinants of adherence to therapies among Malaysian women with breast cancer: MyBCC Cohort

    Directory of Open Access Journals (Sweden)

    Mao Li Cheng

    2017-12-01

    Full Text Available Background: Breast cancer therapies have been progressively advancing to improve the breast cancer survival over the last few decades. However, non-adherence to cancer treatments has shown to be associated with reduced treatment effectiveness, increased mortality, and increased health care costs. The aim of the study is to understand the determinants of adherence to therapies among Malaysian breast cancer patients. Methods: This was a secondary analysis of all newly diagnosed Malaysian breast cancer patients recruited into a prospective cohort study in Universiti Malaya Medical Centre, MyBCC cohort, from 1st February 2012 to 31st December 2015. The MyBCC cohort study has ethics approval, MEC number 896.150. The treatment options (surgery, chemotherapy, radiotherapy, and overall therapies, surgical options, socio-demographic characteristics, clinical signs and symptoms, traditional and complementary medicine, and psychosocial assessments were measured using Hospital Anxiety and Depression Scale (HADS and Multidimensional Scale of Perceived Social Support (MSPSS. Results: In total, 467 patients were analysed. The adherence to surgery was 93.8%, chemotherapy 87.7%, radiotherapy 89.1%, and overall therapies 65.8% respectively. Breast conserving surgery was associated with adherence to surgery compared to mastectomy (adjusted OR 5.48 [95% CI 1.00, 30.09], p = 0.034, radiotherapy (adjusted OR 5.44 [95% CI 1.17, 25.16], p = 0.030 and overall therapies (adjusted OR 2.45 [95% CI 1.04, 5.78], p = 0.041. Time from diagnosis to surgery of less than 60 days was associated with adherence to surgery (adjusted OR 49.98 [95% CI 8.47, 289.05], p less than 0.0001 and overall therapies (adjusted OR 9.38 [95% CI 1.26, 69.73], p = 0.029. Adherence to chemotherapy associated with no surgery (adjusted OR 0.15 [95% CI 0.03, 0.70], p = 0.016. Adherence to radiotherapy was associated with financial reimbursement (adjusted OR 4.34 [95% CI 1.03, 18.26], p = 0.045 and

  17. Developing precipitation hardenable high entropy alloys

    Science.gov (United States)

    Gwalani, Bharat

    . Furthermore, precipitation of bcc based ordered phase B2 in Al0.3CoCrFeNi can further strengthen the alloy. Fine-tuning the microstructure by thermo-mechanical treatments achieved a wide range of mechanical properties in the same alloy. The Al0.3CoCrFeNi HEA exhibited ultimate tensile strength (UTS) of ˜250 MPa and ductility of ˜65%; a UTS of ˜1100 MPa and ductility of ˜30%; and a UTS of 1850 MPa and a ductility of 5% after various thermo-mechanical treatments. Grain sizes, precipitates type and size scales manipulated in the alloy result in different strength ductility combinations. Henceforth, the alloy presents a fertile ground for development by grain boundary strengthening and precipitation strengthening, and offers very high activation energy of grain growth aptly suitable for high-temperature applications.

  18. High-throughput computational search for strengthening precipitates in alloys

    International Nuclear Information System (INIS)

    Kirklin, S.; Saal, James E.; Hegde, Vinay I.; Wolverton, C.

    2016-01-01

    The search for high-strength alloys and precipitation hardened systems has largely been accomplished through Edisonian trial and error experimentation. Here, we present a novel strategy using high-throughput computational approaches to search for promising precipitate/alloy systems. We perform density functional theory (DFT) calculations of an extremely large space of ∼200,000 potential compounds in search of effective strengthening precipitates for a variety of different alloy matrices, e.g., Fe, Al, Mg, Ni, Co, and Ti. Our search strategy involves screening phases that are likely to produce coherent precipitates (based on small lattice mismatch) and are composed of relatively common alloying elements. When combined with the Open Quantum Materials Database (OQMD), we can computationally screen for precipitates that either have a stable two-phase equilibrium with the host matrix, or are likely to precipitate as metastable phases. Our search produces (for the structure types considered) nearly all currently known high-strength precipitates in a variety of fcc, bcc, and hcp matrices, thus giving us confidence in the strategy. In addition, we predict a number of new, currently-unknown precipitate systems that should be explored experimentally as promising high-strength alloy chemistries.

  19. Absorption of hydrogen by vanadium-palladium alloys

    International Nuclear Information System (INIS)

    Artman, D.; Lynch, J.F.; Flanagan, T.B.

    1976-01-01

    Pressure composition isotherms (273-373 K) have been determined for the absorption of hydrogen by a series of six palladium alloys (f.c.c) in the composition range from 1 to 8 at.% vanadium. At a given hydrogen content, the equilibrium hydrogen pressure progressively increases with vanadium content. Thermodynamic parameters for the absorption of hydrogen are reported at infinite dilution of hydrogen and for the formation of the nonstoichiometric hydride from the hydrogen-saturated alloy. The relative, partial molar enthalpy of solution of hydrogen at infinite dilution increases slightly with vanadium content. The presence of vanadium, which absorbs hydrogen itself in its normal b.c.c. structure, greatly inhibits the ability of palladium to absorb hydrogen. For example, the isobaric solubility of hydrogen (1 atm, 298K) decreases from H/Pd=0.7 (palladium) to 0.024 (V(6%)-Pd). The lattice expansion due to the presence of interstitial hydrogen has been determined by X-ray diffraction. From these data it can be concluded that the formation of two non-stoichiometric hydride phases does not occur at vanadium contents greater that 5 at.% (298 K). Electrical resistance has been measured as a function of the hydrogen content of the alloys. The electrical resistance increases more markedly with hydrogen content for these alloys than for any of the palladium alloys previously examined. (Auth.)

  20. Development of a new formulation of interferons (HEBERPAG for BCC treatment

    Directory of Open Access Journals (Sweden)

    Bello-Rivero I

    2013-12-01

    Full Text Available Purpose: This work is aimed to show briefly, the clinical development of a new pharmaceutical formulation of interferons for the treatment of basal cell carcinoma. Methods: A rationale design of the combination of IFN-α2b and -γ based in their anti-proliferative synergism on several tumors cell lines identified adequate proportions to be combined to obtain the best clinical results. The potential mechanism of antitumoral effect was studied by qPCR mRNA quantification. HEBERPAG (anti-proliferative synergistic combination of co-formulated recombinant interferons-α2b and –γ was used in clinical trials in adult patients with non-melanoma skin cancer. Trials were conducted after approval by the ethics review boards of the institutions participating in trials; and the patients gave their written informed consent to be enrolled in the studies and receive HEBERPAG. Results: HEBERPAG inhibits the proliferation of several tumor cell lines in vitro and in vivo. The combination has improved pharmacodinamic properties. Several clinical trials have demonstrated the efficacy of HEBERPAG in BCC, with excellent cosmetic effect and well tolerable, mild side effects. HEBERPAG was approved by State Control Center for Drug, Medical Equipment and Devises in Cuba, for the treatment of basal cell carcinoma of any subtype, size and localization, and adjuvant to other treatments, surgical or not. After 3-year follow-up, a recurrence rate of 0.03% was detected in treated patients. Conclusions: HEBERPAG is a novel formulation of IFNs, more potent than separated IFNs for the treatment of basal cell carcinoma, with more rapid and prolonged clinical effect and excellent cosmetic effect and safety profile.

  1. Identifying self-interstitials of bcc and fcc crystals in molecular dynamics

    International Nuclear Information System (INIS)

    Bukkuru, S.; Bhardwaj, U.; Warrier, M.; Rao, A.D.P.; Valsakumar, M.C.

    2017-01-01

    Identification of self-interstitials in molecular dynamics (MD) simulations is of critical importance. There exist several criteria for identifying the self-interstitial. Most of the existing methods use an assumed cut-off value for the displacement of an atom from its lattice position to identify the self-interstitial. The results obtained are affected by the chosen cut-off value. Moreover, these chosen cut-off values are independent of temperature. We have developed a novel unsupervised learning algorithm called Max-Space Clustering (MSC) to identify an appropriate cut-off value and its dependence on temperature. This method is compared with some widely used methods such as effective sphere (ES) method and nearest neighbor sphere (NNS) method. The cut-off radius obtained using our method shows a linear variation with temperature. The value of cut-off radius and its temperature dependence is derived for five bcc (Cr, Fe, Mo, Nb, W) and six fcc (Ag, Au, Cu, Ni, Pd, Pt) crystals. It is seen that the ratio of the cut-off values “r” to the lattice constant “a” lies between 0.23 and 0.3 at 300 K and this ratio is on an average smaller for the fcc crystals. Collision cascade simulations are carried out for Primary knock-on Atom (PKA) energies of 5 keV in Fe (at 300 K and 1000 K) and W (at 300 K and 2500 K) and the results are compared using the various methods. - Highlights: • Max-Space Clustering (MSC) method is developed to identify interstitials in crystals. • MSC provides a structured way to identify the temperature dependent cut-off radius. • It is compared with widely used sphere methods and found to be better. • MSC coupled with graph tree optimization can be used to obtain diffusion trajectory. • Cascade simulations of Fe, W are carried out and results are compared with various methods.

  2. Identifying self-interstitials of bcc and fcc crystals in molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bukkuru, S., E-mail: srinivasaraobukkuru@gmail.com [Dept. of Nuclear Physics, Andhra University, Visakhapatnam 530003 (India); Bhardwaj, U., E-mail: haptork@gmail.com [Computational Analysis Division, BARC, Visakhapatnam 530012, Andhra Pradesh (India); Warrier, M., E-mail: manoj.warrier@gmail.com [Computational Analysis Division, BARC, Visakhapatnam 530012, Andhra Pradesh (India); Rao, A.D.P., E-mail: adp_rao_99@yahoo.com [Dept. of Nuclear Physics, Andhra University, Visakhapatnam 530003 (India); Valsakumar, M.C., E-mail: mc.valsakumar@gmail.com [IIT Palakkad, Kozhippara P.O., Palakkad 678557, Kerala (India)

    2017-02-15

    Identification of self-interstitials in molecular dynamics (MD) simulations is of critical importance. There exist several criteria for identifying the self-interstitial. Most of the existing methods use an assumed cut-off value for the displacement of an atom from its lattice position to identify the self-interstitial. The results obtained are affected by the chosen cut-off value. Moreover, these chosen cut-off values are independent of temperature. We have developed a novel unsupervised learning algorithm called Max-Space Clustering (MSC) to identify an appropriate cut-off value and its dependence on temperature. This method is compared with some widely used methods such as effective sphere (ES) method and nearest neighbor sphere (NNS) method. The cut-off radius obtained using our method shows a linear variation with temperature. The value of cut-off radius and its temperature dependence is derived for five bcc (Cr, Fe, Mo, Nb, W) and six fcc (Ag, Au, Cu, Ni, Pd, Pt) crystals. It is seen that the ratio of the cut-off values “r” to the lattice constant “a” lies between 0.23 and 0.3 at 300 K and this ratio is on an average smaller for the fcc crystals. Collision cascade simulations are carried out for Primary knock-on Atom (PKA) energies of 5 keV in Fe (at 300 K and 1000 K) and W (at 300 K and 2500 K) and the results are compared using the various methods. - Highlights: • Max-Space Clustering (MSC) method is developed to identify interstitials in crystals. • MSC provides a structured way to identify the temperature dependent cut-off radius. • It is compared with widely used sphere methods and found to be better. • MSC coupled with graph tree optimization can be used to obtain diffusion trajectory. • Cascade simulations of Fe, W are carried out and results are compared with various methods.

  3. Decrease Risk Behavior HIV Infected on Construction Laborers with Behavior Change Communication (BCC Approach

    Directory of Open Access Journals (Sweden)

    Purwaningsih Purwaningsih

    2016-09-01

    The purpose of this study was to determine the effectiveness of BCC approach to the reduction of contracting HIV risk behavior in the construction laborers. Method: This study used operational research design. In this study measures the effectiveness of behavior change of construction workers on the prevention of HIV transmission by comparing the behavior of the construction workers before and after the intervention. The subjects of this study were 150 people risk group of construction workers who work and are spread throughout the city of Surabaya. This research was carried out into three phases, namely, phase preintervention research, intervention research, and post-intervention phase of the study. Implemented in the first year and second year praintervensi stage implemented intervention and post-intervention phases. Result: The results of this study showed that 72% of construction workers is productive (18–35 years and visit his family more than once a month (38%. There is 20% of construction workers had sex with commercial sex workers and no one was using drugs. By 50% of construction workers never get information about HIV/AIDS and as many as 48% never use the services of HIV/AIDS. Discussion: External motivation construction workers associated with the utilization of behavioral HIV/AIDS services with sufficient correlation. Strong external motivation is influenced by risk behaviors of HIV/AIDS were conducted and the desire to get help. Weak external motivation is influenced by a lack of exposure to information related to HIV/AIDS services. The results of the FGD stakeholders have the perception is the same if a construction worker is a high risk group of contracting HIV. Most of the construction workers not have enough knowledge for the prevention of HIV transmission because they do not have access to HIV care and behavior are at risk of contracting HIV by construction workers. Keywords: construction workers, behavior change communication, behavior

  4. Dissolving, trapping and detrapping mechanisms of hydrogen in bcc and fcc transition metals

    Directory of Open Access Journals (Sweden)

    Yu-Wei You

    2013-01-01

    Full Text Available First-principles calculations are performed to investigate the dissolving, trapping and detrapping of H in six bcc (V, Nb, Ta, Cr, Mo, W and six fcc (Ni, Pd, Pt, Cu, Ag, Au metals. We find that the zero-point vibrations do not change the site-preference order of H at interstitial sites in these metals except Pt. One vacancy could trap a maximum of 4 H atoms in Au and Pt, 6 H atoms in V, Nb, Ta, Cr, Ni, Pd, Cu and Ag, and 12 H atoms in Mo and W. The zero-point vibrations never change the maximum number of H atoms trapped in a single vacancy in these metals. By calculating the formation energy of vacancy-H (Vac-Hn complex, the superabundant vacancy in V, Nb, Ta, Pd and Ni is demonstrated to be much more easily formed than in the other metals, which has been found in many metals including Pd, Ni and Nb experimentally. Besides, we find that it is most energetically favorable to form Vac-H1 complex in Pt, Cu, Ag and Au, Vac-H4 in Cr, Mo and W, and Vac-H6 in V, Nb, Ta, Pd and Ni. At last, we examine the detrapping behaviors of H atoms in a single vacancy and find that with the heating rate of 10 K/min a vacancy could accommodate 4, 5 and 6 H atoms in Cr, Mo and W at room temperature, respectively. The detrapping temperatures of all H atoms in a single vacancy in V, Nb, Ta, Ni, Pd, Cu and Ag are below room temperature.

  5. Annealing effects on structure and mechanical properties of CoCrFeNiTiAlx high-entropy alloys

    International Nuclear Information System (INIS)

    Zhang, K B; Fu, Z Y; Zhang, J Y; Wang, W M; Lee, S W; Niihara, K

    2011-01-01

    Novel CoCrFeNiTiAl x (x:molar ratio, other elements are equimolar) high-entropy alloys were prepared by vacuum arc melting and these alloys were subsequently annealed at 1000 deg. C for 2 h. The annealing effects on structure and mechanical properties were investigated. Compared with the as-cast alloys, there are many complex intermetallic phases precipitated from the solid solution matrix in the as-annealed alloys with Al content lower than Al 1.0 . Only simple BCC solid solution structure appears in the as-annealed Al 1.5 and Al 2.0 alloys. This kind of alloys exhibit high resistance to anneal softening. Most as-annealed alloys possess even higher Visker hardness than the as-cast ones. The as-annealed Al 0.5 alloys shows the highest compressive strength while the Al 0 alloy exhibits the best ductility, which is about 2.6 GPa and 13%, respectively. The CoCrFeNiTiAl x high-entropy alloys possess integrated high temperature mechanical property as well.

  6. Effect of cooling rate on the phase structure and magnetic properties of Fe{sub 26.7}Co{sub 28.5}Ni{sub 28.5}Si{sub 4.6}B{sub 8.7}P{sub 3} high entropy alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Ran; Sun, Huan; Chen, Chen [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Han, Zhenhua [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710068 (China); Li, Fushan, E-mail: fsli@zzu.edu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China)

    2017-08-01

    Highlights: • High entropy alloy with amorphous phase and FCC solid solution phase are successfully developed respectively. • The amorphous phase exhibits better soft magnetic properties than that of the solid solution phase. • The BCC phase transformed into FCC phase, and then into BCC phase was found in this HEA. - Abstract: The effect of cooling rate on phase structure and magnetic properties of the Fe{sub 26.7}Co{sub 28.5}Ni{sub 28.5}Si{sub 4.6}B{sub 8.7}P{sub 3} high entropy alloy (HEA) was investigated. The HEA forms into amorphous phase by melt spinning method at high cooling rate and FCC solid solution phase at low cooling rate. The soft magnetic properties of the amorphous phase (saturation magnetization B{sub s} of 1.07T and coercivity H{sub c} of 4 A/m) are better than that of the solid solution phase (B{sub s} of 1.0 T and H{sub c} of 168 A/m). In order to study the phase evolution of the present HEA, anneal experiments were conducted. It is found that crystallization products of amorphous phase are solid solution phase which constitute much of FCC and a small amount of BCC. BCC phase transforms into FCC phase, and then into BCC phase with the increase of annealing temperature.

  7. Low temperature study of mechanically alloyed Fe{sub 67.5}Ni{sub 32.5} Invar sample

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, J.L. [Departamento de Física, Universidad del Valle, A. A. 25360, Cali (Colombia); Valderruten, J.F. [Departamento de Ingeniería, Universidad Cooperativa de Colombia, Bucaramanga (Colombia); Pérez Alcázar, G.A., E-mail: gpgeperez@gmail.com [Departamento de Física, Universidad del Valle, A. A. 25360, Cali (Colombia); Colorado, H.D. [Departamento de Física, Universidad del Valle, A. A. 25360, Cali (Colombia); Romero, J.J. [Instituto de Microelectrónica de Madrid, CNM, CSIC, C/Isaac Newton 8, Tres Cantos, 28760 Madrid (Spain); González, J.M. [Unidad Asociada ICMM-IMA, Apdo. 155, Las Rozas, 28230 Madrid (Spain); Greneche, J.M. [LUNAM, Université du Maine, Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, 72085 Le Mans, Cedex 9 (France); Marco, J.F. [Instituto de Química-Física ' ' Rocasolano' ' , CSIC, C/Serrano 119, 28006 Madrid (Spain)

    2015-07-01

    The study at low temperatures of powder of the Invar alloy, Fe{sub 67.5}Ni{sub 32.5}, produced by mechanical alloying, shows that the sample presents two structural phases, the Fe–Ni BCC and the Fe–Ni FCC. The {sup 57}Fe Mössbauer spectra obtained in this sample at different temperatures were fitted considering two hyperfine magnetic field distributions. The first one having the larger mean field and only one peak (at ca. 35 T, varying with T), is associated with the BCC phase, and the second one, presenting several broad peaks (distributed between 10 and 35 T), is associated to the FCC phase. A singlet, which is associated to low spin Fe sites of the FCC phase, was also considered. The mean hyperfine magnetic field of the BCC phase increases monotonically as temperature decreases, while that of the FCC phase presents an anomaly near 75 K. The real part of the ac magnetic susceptibility temperature scans presents a peak whose position increases from 31 to 39 K, when the ac field frequency increases from 100 to 5000 Hz. These results permit to associate the detected anomaly to the occurrence of a reentrant spin glass transition. - Highlights: • XRD detect the BCC and FCC nanocrystalline phases in the Invar Fe{sub 67.5}Si{sub 32.5}. • Mössbauer spectra were fitted with two HMFDs and a singlet. • The MHMF and the isomer shift of the FCC structure present a kink near 61 K. • Magnetic susceptibility proved that this anomaly corresponds to a RSG- F transition. • The Invar composition of the MA Fe{sub 67.5}Si{sub 32.5} alloy presents the frustration phenomena.

  8. Effect of aluminum on the microstructure and properties of two refractory high-entropy alloys

    International Nuclear Information System (INIS)

    Senkov, O.N.; Senkova, S.V.; Woodward, C.

    2014-01-01

    The microstructure, phase composition and mechanical properties of the AlMo 0.5 NbTa 0.5 TiZr and Al 0.4 Hf 0.6 NbTaTiZr high-entropy alloys are reported. The AlMo 0.5 NbTa 0.5 TiZr alloy consists of two body-centered cubic (bcc) phases with very close lattice parameters, a 1 = 326.8 pm and a 2 = 332.4 pm. One phase was enriched with Mo, Nb and Ta and another phase was enriched with Al and Zr. The phases formed nano-lamellae modulated structure inside equiaxed grains. The alloy had a density of ρ = 7.40 g cm −3 and Vickers hardness H v = 5.8 GPa. Its yield strength was 2000 MPa at 298 K and 745 MPa at 1273 K. The Al 0.4 Hf 0.6 NbTaTiZr had a single-phase bcc structure, with the lattice parameter a = 336.7 pm. This alloy had a density ρ = 9.05 g cm −3 , Vickers microhardness H v = 4.9 GPa, and its yield strength at 298 K and 1273 K was 1841 MPa and 298 MPa, respectively. The properties of these Al-containing alloys were compared with the properties of the parent CrMo 0.5 NbTa 0.5 TiZr and HfNbTaTiZr alloys and the beneficial effects from the Al additions on the microstructure and properties were outlined. A thermodynamic calculation of the solidification and equilibrium phase diagrams was conducted for these alloys and the calculated results were compared with the experimental data

  9. On the recovery of neutron irradiation defects of some metals and alloys

    International Nuclear Information System (INIS)

    Mohamed, H.G.; Matta, M.K.

    2001-01-01

    This work deals with the recovery of mechanical properties of neutron irradiated material to the pre-irradiating values. Rate of migration of defects responsible for radiation hardening and those inducing radiation embrittlement is analyzed. Role of crystalline structure is also studied. Materials of FCC crystal structure used in these investigations are pure Cu, Cu-5 at. % , Al, Cu-5 at. % Si, some Ni base binary alloys and some austenitic stainless steels mainly of AISI types 304 and 316. Among materials of BCC crystalline structure Fe-6 wt % Cr alloy is used. Alloys with CPH structure used in the present investigations are Zr-l wt. % Nb and Mg - 4.8 wt % Li alloys. History of material is studied such as cold worked state and annealed condition. Character of alloying elements and their amounts were of interest in this study. The result showed that the higher the percentage radiation hardening, the slower is the migration of radiation defects. Irradiated pure metals recovered at a higher temperature than alloys. Cold work accelerated the migration of radiation defects. The amount of alloying elements had little effect on the recovery temperatures. Character of solute alloying elements (substitutional or interstitial) revealed sensitive effect on the migration of radiation defects. Rate of migration of defects causing hardening can be different from those causing embrittlement. (author)

  10. Radiation damage of uranium; Radijaciono ostecenje urana

    Energy Technology Data Exchange (ETDEWEB)

    Lazarevic, Dj [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1966-11-15

    Study of radiation damage covered the following: Kinetics of electric resistance of uranium and uranium alloy with 1% of molybdenum dependent on the second phase and burnup rate; Study of gas precipitation and diffusion of bubbles by transmission electron microscopy; Numerical analysis of the influence of defects distribution and concentration on the rare gas precipitation in uranium; study of thermal sedimentation of uranium alloy with molybdenum; diffusion of rare gas in metal by gas chromatography method.

  11. Powder Metallurgy Processing of a WxTaTiVCr High-Entropy Alloy and Its Derivative Alloys for Fusion Material Applications.

    Science.gov (United States)

    Waseem, Owais Ahmed; Ryu, Ho Jin

    2017-05-16

    The W x TaTiVCr high-entropy alloy with 32at.% of tungsten (W) and its derivative alloys with 42 to 90at.% of W with in-situ TiC were prepared via the mixing of elemental W, Ta, Ti, V and Cr powders followed by spark plasma sintering for the development of reduced-activation alloys for fusion plasma-facing materials. Characterization of the sintered samples revealed a BCC lattice and a multi-phase structure. The selected-area diffraction patterns confirmed the formation of TiC in the high-entropy alloy and its derivative alloys. It revealed the development of C15 (cubic) Laves phases as well in alloys with 71 to 90at.% W. A mechanical examination of the samples revealed a more than twofold improvement in the hardness and strength due to solid-solution strengthening and dispersion strengthening. This study explored the potential of powder metallurgy processing for the fabrication of a high-entropy alloy and other derived compositions with enhanced hardness and strength.

  12. Phase transitions in alloys of the Ni-Mo system

    International Nuclear Information System (INIS)

    Ustinovshikov, Y.; Shabanova, I.

    2011-01-01

    Graphical abstract: The structure of Ni-20 at.% Mo and Ni-25 at.% Mo alloys was studied by methods of TEM and XPS. It is shown that at high temperatures the tendency toward phase separation takes place in the alloys and crystalline bcc Mo particles precipitate in the liquid solution. At 900 deg. C and below, the tendency toward ordering leads to the dissolution of Mo particles and precipitation of the particles of Ni 3 Mo, Ni 2 Mo or Ni 4 Mo chemical compounds. Highlights: → 'Chemical' phase transition 'ordering-phase separation' is first discovered in alloys of the Ni-Mo system. → It is first shown that the phase separation in the alloys studied begins at temperatures above the liquidus one. → The formation of Ni 3 Mo from A1 has gone through the intervening stage of the Ni 4 Mo and Ni 2 Mo coexistence. - Abstract: The structure of Ni-20 at.% Mo and Ni-25 at.% Mo alloys heat treated at different temperatures was studied by the method of transmission electron microscopy. X-ray photoelectron spectroscopy was used to detect the sign of the chemical interaction between Ni and Mo atoms at different temperatures. It is shown that at high temperatures the tendency toward phase separation takes place. The system of additional reflections at positions {1 1/2 0} on the electron diffraction patterns testifies that the precipitation of crystalline bcc Mo particles begins in the liquid solution. At 900 deg. C and below, the tendency toward ordering leads to the precipitation of the particles of the chemical compounds. A body-centered tetragonal phase Ni 4 Mo (D1 a ) is formed in the Ni-20 at.% Mo alloy. In the Ni-25 at.% Mo alloy, the formation of the Ni 3 Mo (D0 22 ) chemical compound from the A1 solid solution has gone through the intervening stage of the Ni 4 Mo (D1 a ) and Ni 2 Mo (Pt 2 Mo) formation.

  13. Analysis of radiation damaged nanocrystals

    International Nuclear Information System (INIS)

    Sitek, J.; Dekan, J.; Sedlackova, K.; Sagatova, A.

    2014-01-01

    Ribbon-shaped specimens of the master alloy were prepared by planar flow casting. The ribbons with nominal composition of (Fe_1_-_xN_x)_8_1Nb_7B_1_2 (x = 0, 0.25, 0.5, 0.75) were about 25 μm thick and 10 mm wide. To achieve nanocrystalline state, the amorphous ribbons were annealed in vacuum at the temperature of 550 grad C for 1 hour. Samples were irradiated by neutrons in nuclear reactor with fluence of 10"1"6 n/cm"2 and 10"1"7 n/cm"2. and by electrons in linear accelerator with dose 1 MGy at the Slovak Medical University. Moessbauer spectra were collected in transmission geometry by a conventional constant-acceleration spectrometer with a "5"7Co(Rh) source. All spectra were measured at room temperature and evaluated by the CONFIT program, which allows simultaneous treatment of crystalline and residual amorphous phase by means of individual lines and distribution of hyperfine components. After summarizing all obtained results, the fluence 10"1"6 n/cm"2 is still not sufficiently high significantly damage amorphous and crystalline structure. This fluence more or less modify the structure than damage. After fluence 10"17"n/cm"2 we observed beginning of the. structural damage. Our results show, that high electron dose also modify the structure of nanocrystaline alloys. In further study of this alloy it would be necessary to find the limit of electron dose under that the alloy is resistant against electron's damage. From point of view Moessbauer spectroscopy the most sensitive parameter is direction of net magnetic moment. (authors)

  14. Chloride removal from plutonium alloy

    International Nuclear Information System (INIS)

    Holcomb, H.P.

    1983-01-01

    SRP is evaluating a program to recover plutonium from a metallic alloy that will contain chloride salt impurities. Removal of chloride to sufficiently low levels to prevent damaging corrosion to canyon equipment is feasible as a head-end step following dissolution. Silver nitrate and mercurous nitrate were each successfully used in laboratory tests to remove chloride from simulated alloy dissolver solution containing plutonium. Levels less than 10 ppM chloride were achieved in the supernates over the precipitated and centrifuged insoluble salts. Also, less than 0.05% loss of plutonium in the +3, +4, or +6 oxidation states was incurred via precipitate carrying. These results provide impetus for further study and development of a plant-scale process to recover plutonium from metal alloy at SRP

  15. Effect of thermal cycling on the microstructure of a directionally solidified Fe, Cr, Al-TaC eutectic alloy

    Science.gov (United States)

    Harf, F. H.; Tewari, S. N.

    1977-01-01

    Cylindrical bars (1.2 cm diameter) of Fe-13.6Cr-3.7Al-9TaC (wt %) eutectic alloy were directionally solidified in a modified Bridgman type furnace at 1 cm/h. The alloy microstructure consisted of aligned TaC fibers imbedded in a bcc Fe-Cr-Al matrix. Specimens of the alloy were thermally cycled from 1100 to 425 C in a burner rig. The effects of 1800 thermal cycles on the microstructure was examined by scanning electron microscopy, revealing a zig-zag shape of TaC fibers aligned parallel to the growth direction. The mechanism of carbide solution and reprecipitation on the (111) easy growth planes, suggested previously to account for the development of irregular serrations in Co-Cr-Ni matrix alloys, is believed to be responsible for these zig-zag surfaces.

  16. NEUTRON-INDUCED SWELLING OF Fe-Cr BINARY ALLOYS IN FFTF AT ∼400 DEGREES C

    International Nuclear Information System (INIS)

    Garner, Francis A.; Greenwood, Lawrence R.; Okita, Taira; Sekimura, Naoto; Wolfer, W. G.

    2002-01-01

    The purpose of this effort is to determine the influence of dpa rate, He/dpa ratio and composition on the void swelling of simple binary Fe-Cr alloys. Contrary to the behavior of swelling of model fcc Fe-Cr-Ni alloys irradiated in the same FFTF-MOTA experiment, model bcc Fe-Cr alloys do not exhibit a dependence of swelling on dpa rate at approximately 400 degrees C. This is surprising in that an apparent flux-sensitivity was observed in an earlier comparative irradiation of Fe-Cr binaries conducted in EBR-II and FFTF. The difference in behavior is ascribed to the higher helium generation rates of Fe-Cr alloys in EBR-II compared to that of FFTF, and also the fact that lower dpa rates in FFTF are accompanied by progressively lower helium generation rates.

  17. Underwater laser beam welding of Alloy 690

    International Nuclear Information System (INIS)

    Hino, Takehisa; Tamura, Masataka; Kono, Wataru; Kawano, Shohei; Yoda, Masaki

    2009-01-01

    Stress Corrosion Clacking (SCC) has been reported at Alloy 600 welds between nozzles and safe-end in Pressurized Water Reactor (PWR) plant. Alloy 690, which has higher chromium content than Alloy 600, has been applied for cladding on Alloy 600 welds for repairing damaged SCC area. Toshiba has developed Underwater Laser Beam Welding technique. This method can be conducted without draining, so that the repairing period and the radiation exposure during the repair can be dramatically decreased. In some old PWRs, high-sulfur stainless steel is used as the materials for this section. It has a high susceptibility of weld cracks. Therefore, the optimum welding condition of Alloy 690 on the high-sulfur stainless steel was investigated with our Underwater Laser Beam Welding unit. Good cladding layer, without any crack, porosity or lack of fusion, could be obtained. (author)

  18. Superconducting alloys

    International Nuclear Information System (INIS)

    Bowers, J.E.

    1976-01-01

    Reference is made to superconductors having high critical currents. The superconductor described comprises an alloy consisting of a matrix of a Type II superconductor which is a homogeneous mixture of 50 to 95 at.% Pb and 5 to 40 at.%Bi and/or 10 to 50 at.%In. Dispersed in the matrix is a material to provide pinning centres comprising from 0.01% to 20% by volume of the alloy; this material is a stable discontinuous phase of discrete crystalline particles of Cu, Mn, Te, Se, Ni, Ca, Cr, Ce, Ge or La, either in the form of the element or a compound with a component of the matrix. These particles should have an average diameter of not more than 2μ. A method for making this alloy is described. (U.K.)

  19. Anisotropy migration of self-point defects in dislocation stress fields in BCC Fe and FCC Cu

    International Nuclear Information System (INIS)

    Sivak, A.B.; Chernov, V.M.; Dubasova, N.A.; Romanov, V.A.

    2007-01-01

    Spatial dependence of the interaction energies of self-point defects (vacancies and self interstitial atoms in stable, metastable and saddle point configurations) with edge dislocations in slip systems {1 1 0} and {1 0 0} in BCC Fe and {1 1 1} in FCC Cu was calculated using the anisotropic theory of elasticity and molecular statics (hybrid method). The migration pathways of vacancies and SIA ( dumbbell in Fe and dumbbell in Cu) along which the migration of the defects with the lowest energy barriers were defined in the presence of the dislocation stress fields. These pathways are significantly different in the stress fields of dislocations

  20. A new parameterization for ice cloud optical properties used in BCC-RAD and its radiative impact

    International Nuclear Information System (INIS)

    Zhang, Hua; Chen, Qi; Xie, Bing

    2015-01-01

    A new parameterization of the solar and infrared optical properties of ice clouds that considers the multiple habits of ice particles was developed on the basis of a prescribed dataset. First, the fitting formulae of the bulk extinction coefficient, single-scatter albedo, asymmetry factor, and δ-function forward-peak factor at the given 65 wavelengths as a function of effective radius were created for common scenarios, which consider a greater number of wavelengths and are more accurate than those used previously. Then, the band-averaged volume extinction and absorption coefficients, asymmetry factor and forward-peak factor of ice cloud were derived for the BCC-RAD (Beijing Climate Center radiative transfer model) using a parameter reference table. Finally, the newly developed and the original schemes in the BCC-RAD and the commonly used Fu Scheme of ice cloud were all applied to the BCC-RAD. Their influences on radiation calculations were compared using the mid-latitude summer atmospheric profile with ice clouds under no-aerosol conditions, and produced a maximum difference of approximately 30.0 W/m 2 for the radiative flux, and 4.0 K/d for the heating rate. Additionally, a sensitivity test was performed to investigate the impact of the ice crystal density on radiation calculations using the three schemes. The results showed that the maximum difference was 68.1 W/m 2 for the shortwave downward radiative flux (for the case of perpendicular solar insolation), and 4.2 K/d for the longwave heating rate, indicating that the ice crystal density exerts a significant effect on radiation calculations for a cloudy atmosphere. - Highlights: • A new parameterization of the radiative properties of ice cloud was obtained. • More accurate fitting formulae of them were created for common scenarios. • The band-averaged of them were derived for our radiation model of BCC-RAD. • We found that there exist large differences of results among different ice schemes. • We found

  1. Temperature dependence of enthalpies and entropies of formation and migration of mono-vacancy in BCC iron

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Haohua; Woo, C.H., E-mail: chungho@cityu.edu.hk

    2014-12-15

    Entropies and enthalpies of vacancy formation and diffusion in BCC iron are calculated for each temperature directly from free-energies using phase-space trajectories obtained from spin–lattice dynamics simulations. Magnon contributions are found to be particularly substantial in the temperature regime near the α−β (ferro/para-magnetic) transition. Strong temperature dependence and singular behavior can be seen in this temperature regime, reflecting magnon softening effects. Temperature dependence of the lattice component in this regime is also much more significant compared to previous estimations based on Arrhenius-type fitting. Similar effects on activation processes involving other irradiation-produced defects in magnetic materials are expected.

  2. Structural and magnetic properties of FeCoC system obtained by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Rincón Soler, A. I. [Universidad Tecnológica de Pereira, Fac. de Ciencias, Depto. de Física (Colombia); Rodríguez Jacobo, R. R., E-mail: rrrodriguez@uao.edu.co [Universidad Autónoma de Occidente, Fac. de Ciencias Básicas, Depto. de Física (Colombia); Medina Barreto, M. H.; Cruz-Muñoz, B. [Universidad Tecnológica de Pereira, Fac. de Ciencias, Depto. de Física (Colombia)

    2017-11-15

    Fe{sub 96−X}Co{sub X}C{sub 4} (x = 0, 10, 20, 30, 40 at. %) alloys were obtained by mechanical alloying of Fe, C and Co powders using high-energy milling. The structural and magnetic properties of the alloy system were analyzed by X-ray diffraction, Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM) and Mössbauer Spectrometry at room temperature. The X-ray diffraction patterns showed a BCC-FeCoC structure phase for all samples, as well as a lattice parameter that slightly decreases with Co content. The saturation magnetization and coercive field were analyzed as a function of Co content. The Mössbauer spectra were fitted with a hyperfine magnetic field distribution showing the ferromagnetic behavior and the disordered character of the samples. The mean hyperfine magnetic field remained nearly constant (358 T) with Co content.

  3. Proofs of cluster formation and transitions in liquid metals and alloys

    International Nuclear Information System (INIS)

    Filippov, E.S.

    1985-01-01

    Calculational and experimental proofs are presented indicating to existence of clusters in liquid metals and alloys. Systems of liquid alloys both on the base of ferrous metals and non-ferrous metals (Fe-C, Ni-C, Co-C, Fe-Ni, Ni-Mo, Co-Cr, Co-V as well as In-Sn, Bi-Sn, Si-Ge and others) are studied experimentally. It is shown that the general feature of the systems studied is sensitivity of a volume to change in structure, to replacement fcc structure on bcc or to initiation-dissociation of intermetallic compounds AxBy. It is shown that both in pure liquid metals and in their.alloys there are clusters as ordered aggregate of atoms

  4. Effects of reactive element additions and sulfur removal on the oxidation behavior of FECRAL alloys

    International Nuclear Information System (INIS)

    Stasik, M.C.; Pettit, F.S.; Meier, G.H.; Smialek, J.L.

    1994-01-01

    The results of this study have shown that desulfurization of FeCrAl alloys by hydrogen annealing can result in improvements in cyclic oxidation comparable to that achieved by doping with reactive elements. Moreover, specimens of substantial thicknesses can be effectively desulfurized because of the high diffusivity of sulfur in bcc iron alloys. The results have also shown that there is less stress generation during the cyclic oxidation of Y-doped FeCrAl compared to Ti-doped or desulfurized FeCrAl. This indicates that the growth mechanism, as well as the strength of the oxide/alloy interface, influences the ultimate oxidation morphology and stress state which will certainly affect the length of time the alumina remains protective

  5. Microstructures and mechanical properties of two-phase alloys based on NbCr{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Chen, K.C.; Kotula, P.G.; Cady, C.M.; Mauro, M.E.; Thoma, D.J.

    1999-07-01

    A two-phase, NbCrTi alloy (bcc + C15 Laves phase) has been developed using several alloy design methodologies. In efforts to understand processing-microstructure-property relationships, different processing routes were employed. The resulting microstructures and mechanical properties are discussed and compared. Plasma arc melted (PAM) samples served to establish baseline, as-cast properties. In addition, a novel processing technique, involving decomposition of a supersaturated and metastable precursor phase during hot isostatic pressing (HIP), was used to produce a refined, equilibrium two-phase microstructure. Quasi-static compression tests as a function of temperature were performed on both alloy types. Different deformation mechanisms were encountered based upon temperature and microstructure.

  6. Martensitic Transformation and Superelasticity in Fe-Mn-Al-Based Shape Memory Alloys

    Science.gov (United States)

    Omori, Toshihiro; Kainuma, Ryosuke

    2017-12-01

    Ferrous shape memory alloys showing superelasticity have recently been obtained in two alloy systems in the 2010s. One is Fe-Mn-Al-Ni, which undergoes martensitic transformation (MT) between the α (bcc) parent and γ' (fcc) martensite phases. This MT can be thermodynamically understood by considering the magnetic contribution to the Gibbs energy, and the β-NiAl (B2) nanoprecipitates play an important role in the thermoelastic MT. The temperature dependence of critical stress for the MT is very small (about 0.5 MPa/°C) due to the small entropy difference between the parent and martensite phases in the Fe-Mn-Al-Ni alloy, and consequently, superelasticity can be obtained in a wide temperature range from cryogenic temperature to about 200 °C. Microstructural control is of great importance for obtaining superelasticity, and the relative grain size is among the most crucial factors.

  7. Structural and magnetic properties of FeCoC system obtained by mechanical alloying

    International Nuclear Information System (INIS)

    Rincón Soler, A. I.; Rodríguez Jacobo, R. R.; Medina Barreto, M. H.; Cruz-Muñoz, B.

    2017-01-01

    Fe 96−X Co X C 4 (x = 0, 10, 20, 30, 40 at. %) alloys were obtained by mechanical alloying of Fe, C and Co powders using high-energy milling. The structural and magnetic properties of the alloy system were analyzed by X-ray diffraction, Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM) and Mössbauer Spectrometry at room temperature. The X-ray diffraction patterns showed a BCC-FeCoC structure phase for all samples, as well as a lattice parameter that slightly decreases with Co content. The saturation magnetization and coercive field were analyzed as a function of Co content. The Mössbauer spectra were fitted with a hyperfine magnetic field distribution showing the ferromagnetic behavior and the disordered character of the samples. The mean hyperfine magnetic field remained nearly constant (358 T) with Co content.

  8. Vanadium alloys for fusion reactor applications

    International Nuclear Information System (INIS)

    Mattas, R.F.; Loomis, B.A.; Smith, D.L.

    1992-01-01

    This paper reports that fusion reactors will produce a severe operating environment for structural materials. The material should have good mechanical strength and ductility to high temperature, be corrosion resistant to the local environment, have attractive thermophysical properties to accommodate high heat loads, and be resistant to neutron damage. Vanadium alloys are being developed for such applications, and they exhibit desirable properties in many areas Recent progress in vanadium alloy development indicates good strength and ductility to 700 degrees C, minimal degradation by neutron irradiation, and reduced radioactivity compared with other candidate alloy systems

  9. Radiation behavior of high-entropy alloys for advanced reactors. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, Peter K. [Univ. of Tennessee, Knoxville, TN (United States); Egami, Takeshi [Univ. of Tennessee, Knoxville, TN (United States); Zhang, Chuan [CompuTherm, LLC, Madison, WI (United States); Zhang, Fan [CompuTherm, LLC, Madison, WI (United States); Zhang, Yanwen [Univ. of Tennessee, Knoxville, TN (United States)

    2015-04-30

    In the first task, we have demonstrated the radiation damage and the recrystallization behaviors in multicomponent alloys through molecular-dynamics simulations. It is found that by alloying with atoms of different sizes, the atomic-level strain increases, and the propensity of the radiation-induced crystalline to amorphous transition increases as the defects cluster in the cascade body. Recrystallization of the radiation induced supercooled or glass regions show that by tuning the composition and the equilibrium temperature, the multicomponent alloys can be healed. The crystalline-amorphous-crystalline transitions predict the potential high radiation resistance in multicomponent alloys. In the second task, three types of high-entropy alloys (HEAs) were fabricated from AlCoCrFeNi and AlCuCrFeNi quinary alloys. Hardness and reduced contact modulus were measured using nanoindentation tests. Heavy ion irradiation were performed using 10 MeV gold and 5 MeV nickel to study radiation effects. Al0.5CrCuFeNi2 shows phase separation upon the presence of copper. Both hardness and contact modulus exhibit the same trend as increasing the applied load, and it indicates that excessive free volume may alter the growth rate of the plastic zone. The as-cast Al0.1CoCrFeNi specimen undergone the hot isostatic pressing (HIP) process and steady cooling rate which mitigate the quenching effect. The swelling behavior was characterized by the atomic force microscopy (AFM), and the swelling rate is approximately 0.02% dpa. Selected area diffraction (SAD) patters show irradiation-induced amorphization throughout the ion projected range. Within the peak damage region, an amorpous ring is observed, and a mixture of amorphous/ crystalline structure at deeper depth is found. The Al0.3CoCrFeNi HEAs shows good radiation resistance up to 60 peak dpa. No voids or dislocations are observed. The crystal structures remain face-centered-cubic (FCC) before and

  10. Silicon Alloying On Aluminium Based Alloy Surface

    International Nuclear Information System (INIS)

    Suryanto

    2002-01-01

    Silicon alloying on surface of aluminium based alloy was carried out using electron beam. This is performed in order to enhance tribological properties of the alloy. Silicon is considered most important alloying element in aluminium alloy, particularly for tribological components. Prior to silicon alloying. aluminium substrate were painted with binder and silicon powder and dried in a furnace. Silicon alloying were carried out in a vacuum chamber. The Silicon alloyed materials were assessed using some techniques. The results show that silicon alloying formed a composite metal-non metal system in which silicon particles are dispersed in the alloyed layer. Silicon content in the alloyed layer is about 40% while in other place is only 10.5 %. The hardness of layer changes significantly. The wear properties of the alloying alloys increase. Silicon surface alloying also reduced the coefficient of friction for sliding against a hardened steel counter face, which could otherwise be higher because of the strong adhesion of aluminium to steel. The hardness of the silicon surface alloyed material dropped when it underwent a heating cycle similar to the ion coating process. Hence, silicon alloying is not a suitable choice for use as an intermediate layer for duplex treatment

  11. Nature of the interfaces between the constituent phases in the high entropy alloy CoCrCuFeNiAl

    Energy Technology Data Exchange (ETDEWEB)

    Welk, Brian A.; Williams, Robert E.A.; Viswanathan, Gopal B. [Center for the Accelerated Maturation of Materials, Department of Materials Science and Engineering, The Ohio State University, 1305 Kinnear Road, Columbus, OH 43212 (United States); Gibson, Mark A. [CSIRO, Private Bag 33, Clayton, Victoria 3169 (Australia); Liaw, Peter K. [Department of Materials Science and Engineering, The University of Tennessee, 414 Ferris Hall, 1508 Middle Drive, Knoxville, TN 37996 (United States); Fraser, Hamish L., E-mail: fraser.3@osu.edu [Center for the Accelerated Maturation of Materials, Department of Materials Science and Engineering, The Ohio State University, 1305 Kinnear Road, Columbus, OH 43212 (United States)

    2013-11-15

    The interfaces between the phase separated regions in the dendritic grains of laser-deposited samples of the high entropy alloy CoCrCuFeNiAl have been studied using aberration-corrected analytical (scanning) transmission electron microscopy ((S)TEM). The compositional variations have been determined using energy dispersive x-ray spectroscopy (EDS) in (S)TEM. It was found that between B2, consisting mainly of Al, Ni, Co, and Fe, and disordered bcc phase, consisting mainly of Cr and Fe, there is a transition region, approximately 1.5 nm in width, over which the chemical composition changes from the B2 to that of the bcc phase. The crystal structure of this interfacial region is also B2, but with very different sublattice occupancy than that of the adjacent B2 compound. The structural aspects of the interface between the ordered B2 phase and the disordered bcc phase have been characterized using high angle annular dark-field (HAADF) imaging in STEM. It has been determined that the interfaces are essentially coherent, with the lattice parameters of the two B2 regions and the disordered bcc phase being more or less the same, the uncertainty arising from possible relaxations from the proximity of the surfaces of the thin foils used in imaging of the microstructures. Direct observations show that there is a planar continuity between all three constituent phases. - Highlights: • In the dendritic grains, there are two dominant phases, one with the ordered B2 structure, and the other disordered bcc. • From the intensity ratios in HAADF, the B2 phase appears to have a stoichiometry of the form Al(Ni, Co, and Fe). • Energy dispersive x-ray spectroscopy reveals the presence of an ordered interface transition region between the two phases. • Nanodiffraction in the Titan shows that the interface region is also ordered with the B2 crystal structure based on C.

  12. Searching for Next Single-Phase High-Entropy Alloy Compositions

    Directory of Open Access Journals (Sweden)

    David E. Alman

    2013-10-01

    Full Text Available There has been considerable technological interest in high-entropy alloys (HEAs since the initial publications on the topic appeared in 2004. However, only several of the alloys investigated are truly single-phase solid solution compositions. These include the FCC alloys CoCrFeNi and CoCrFeMnNi based on 3d transition metals elements and BCC alloys NbMoTaW, NbMoTaVW, and HfNbTaTiZr based on refractory metals. The search for new single-phase HEAs compositions has been hindered by a lack of an effective scientific strategy for alloy design. This report shows that the chemical interactions and atomic diffusivities predicted from ab initio molecular dynamics simulations which are closely related to primary crystallization during solidification can be used to assist in identifying single phase high-entropy solid solution compositions. Further, combining these simulations with phase diagram calculations via the CALPHAD method and inspection of existing phase diagrams is an effective strategy to accelerate the discovery of new single-phase HEAs. This methodology was used to predict new single-phase HEA compositions. These are FCC alloys comprised of CoFeMnNi, CuNiPdPt and CuNiPdPtRh, and HCP alloys of CoOsReRu.

  13. U-Zr alloy: XPS and TEM study of surface passivation

    Science.gov (United States)

    Paukov, M.; Tkach, I.; Huber, F.; Gouder, T.; Cieslar, M.; Drozdenko, D.; Minarik, P.; Havela, L.

    2018-05-01

    Surface reactivity of Uranium metal is an important factor limiting its practical applications. Bcc alloys of U with various transition metals are much less reactive than pure Uranium. So as to specify the mechanism of surface protection, we have been studying the U-20 at.% Zr alloy by photoelectron spectroscopy and transmission electron microscopy. The surface was studied in as-obtained state, in various stages of surface cleaning, and during an isochronal annealing cycle. The analysis based on U-4f, Zr-3p, and O-1 s spectra shows that a Zr-rich phase segregates at the surface at temperatures exceeding 550 K, which provides a self-assembled coating. The comparison of oxygen exposure of the stoichiometric and coated surfaces shows that the coating is efficiently preventing the oxidation of uranium even at elevated temperatures. The coating can be associated with the UZr2+x phase. TEM study indicated that the coating is about 20 nm thick. For the clean state, the U-4f core-level lines of the bcc alloy are practically identical to those of α-U, revealing similar delocalization of the 5f electronic states.

  14. Radiation-induced segregation in binary and ternary alloys

    International Nuclear Information System (INIS)

    Okamoto, P.R.; Rehn, L.E.

    1979-01-01

    A review is given of our current knowledge of radiation-induced segregation of major and minor elements in simple binary and ternary alloys as derived from experimental techniques such as Auger electron spectroscopy, secondary-ion mass spectroscopy, ion-backscattering, infrared emissivity measurements and transmission electron microscopy. Measurements of the temperature, dose and dose-rate dependences as well as of the effects of such materials variables as solute solubility, solute misfit and initial solute concentration has proved particularly valuable in understanding the mechanisms of segregation. The interpretation of these data in terms of current theoretical models which link solute segregation behavior to defect-solute binding interactions and/or to the relative diffusion rates of solute and solvent atoms the interstitial and vacancy migration mechanisms has, in general, been fairly successful and has provided considerable insight into the highly interrelated phenomena of solute-defect trapping, solute segregation, phase stability and void swelling. Specific examples in selected fcc, bcc and hcp alloy systems are discussed with particular emphasis given to the effects of radiation-induced segregation on the phase stability of single-phase and two-phase binary alloys and simple Fe-Cr-Ni alloys. (Auth.)

  15. Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

    Science.gov (United States)

    Na, Suok-Min; Yoo, Jin-Hyeong; Lambert, Paul K.; Jones, Nicholas J.

    2018-05-01

    High-entropy alloys (HEAs) containing multiple principle alloying elements exhibit unique properties so they are currently receiving great attention for developing innovative alloy designs. In FeCoNi-based HEAs, magnetic behaviors strongly depend on the addition of alloying elements, usually accompanied by structural changes. In this work, the effect of non-magnetic components on the ferromagnetic transition and magnetic behaviors in equiatomic FeCoNiCrX (X=Al, Ga, Mn and Sn) HEAs was investigated. Alloy ingots of nominal compositions of HEAs were prepared by arc melting and the button ingots were cut into discs for magnetic measurements as functions of magnetic field and temperature. The HEAs of FeCoNiCrMn and FeCoNiCrSn show typical paramagnetic behaviors, composed of solid solution FCC matrix, while the additions of Ga and Al in FeCoNiCr exhibit ferromagnetic behaviors, along with the coexistence of FCC and BCC phases due to spinodal decomposition. The partial phase transition in both HEAs with the additions of Ga and Al would enhance ferromagnetic properties due to the addition of the BCC phase. The saturation magnetization for the base alloy FeCoNiCr is 0.5 emu/g at the applied field of 20 kOe (TC = 104 K). For the HEAs of FeCoNiCrGa and FeCoNiCrAl, the saturation magnetization significantly increased to 38 emu/g (TC = 703 K) and 25 emu/g (TC = 277 K), respectively. To evaluate the possibility of solid solution FCC and BCC phases in FeCoNiCr-type HEAs, we introduced a parameter of valence electron concentration (VEC). The proposed rule for solid solution formation by the VEC was matched with FeCoNiCr-type HEAs.

  16. Corrosion and oxidation of vanadium-base alloys

    International Nuclear Information System (INIS)

    Loomis, B.A.; Wiggins, G.

    1983-10-01

    The corrosion of several V-base alloys on exposure at elevated temperatures to helium environments containing hydrogen and/or water vapor are presented. These results are utilized to discuss the consequences of the selection of certain radiation-damage resistant, V-base alloys for structural materials applications in a fusion reactor

  17. SIMS as a new methodology to depth profile helium in as-implanted and annealed pure bcc metals?

    Energy Technology Data Exchange (ETDEWEB)

    Gorondy-Novak, S. [CEA, DEN, Service de Recherches de Métallurgie Physique, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Jomard, F. [Groupe d' Etude de la Matière Condensée, CNRS, UVSQ, 45 avenue des Etats-Unis, 78035 Versailles cedex (France); Prima, F. [PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie Paris, 75005 Paris (France); Lefaix-Jeuland, H., E-mail: helene.lefaix@cea.fr [CEA, DEN, Service de Recherches de Métallurgie Physique, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France)

    2017-05-01

    Reliable He profiles are highly desirable for better understanding helium behavior in materials for future nuclear applications. Recently, Secondary Ions Mass Spectrometry (SIMS) allowed the characterization of helium distribution in as-implanted metallic systems. The Cs{sup +} primary ion beam coupled with CsHe{sup +} molecular detector appeared to be a promising technique which overcomes the very high He ionization potential. In this study, {sup 4}He depth profiles in pure body centered cubic (bcc) metals (V, Fe, Ta, Nb and Mo) as-implanted and annealed, were obtained by SIMS. All as-implanted samples exhibited a projected range of around 200 nm, in agreement with SRIM theoretical calculations. After annealing treatment, SIMS measurements evidenced the evolution of helium depth profile with temperature. The latter SIMS results were compared to the helium bubble distribution obtained by Transmission Electron Microscopy (TEM). This study confirmed the great potential of this experimental procedure as a He-depth profiling technique in bcc metals. Indeed, the methodology described in this work could be extended to other materials including metallic and non-metallic compounds. Nevertheless, the quantification of helium concentration after annealing treatment by SIMS remains uncertain probably due to the non-uniform ionization efficiency in samples containing large bubbles.

  18. Anharmonic correlated Debye model high-order expanded interatomic effective potential and Debye-Waller factors of bcc crystals

    Energy Technology Data Exchange (ETDEWEB)

    Van Hung, Nguyen, E-mail: hungnv@vnu.edu.vn [Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Hue, Trinh Thi [Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Khoa, Ha Dang [School of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet, Hanoi (Viet Nam); Vuong, Dinh Quoc [Quang Ninh Education & Training Department, Nguyen Van Cu, Ha Long, Quang Ninh (Viet Nam)

    2016-12-15

    High-order expanded interatomic effective potential and Debye-Waller factors (DWFs) for local vibrational amplitudes in X-ray absorption fine structure (XAFS) of bcc crystals have been studied based on the anharmonic correlated Debye model. DWFs are presented in terms of cumulant expansion up to the fourth order and the many-body effects are taken into account in the present one-dimensional model based on the first shell near neighbor contribution approach used in the derivations of the anharmonic effective potential and XAFS cumulants where Morse potential is assumed to describe the single-pair atomic interaction. Analytical expressions for the dispersion relation, correlated Debye frequency and temperature and four first temperature-dependent XAFS cumulants have been derived based on the many-body perturbation approach. Thermodynamic properties and anharmonic effects in XAFS of bcc crystals described by the obtained cumulants have been in detail discussed. The advantage and efficiency of the present theory are illustrated by good agreement of the numerical results for Mo, Fe and W with experiment.

  19. Local structure and phase transformation in Zr and Ti based bcc solutions

    International Nuclear Information System (INIS)

    Chang, A.L.J.

    1975-01-01

    High resolution direct lattice imaging and dark field electron microscopy were used to examine the omega phase transformation in Zr--Nb alloys. Direct lattice imaging demonstrates the existence of three subvariants within each omega variant. The kinematic intensity sum, which is evaluated based on the combination of certain atomic arrangements, was carried out to include both untransformed beta phase and the omega phase. An ordered sequence of subvariants was found to be responsible for the diffraction effects in high Nb content alloys. However, the existence of such an ordered sequence among omega subvariants could not be checked out because of the small size of the omega regions. Omega domains of different variant do not interweave. Isolated particles with diameters of 3 to 5 A also are present away from the domains. As the Nb content is increased the omega domains decrease in size while the isolated particles (3 to 5 A) are present over the entire range studied, from 8 to 30 wt percent Nb. It is suggested that fluctuations in structure occur between the beta and omega phases. The isolated particles, also changing with time, are believed to be images of single or small groups of displaced atoms. (Diss. Abstr. Int., B)

  20. Magnetic Properties of Nanocrystalline Fe{sub x}Cu{sub 1-x} Alloys Prepared by Ball Milling

    Energy Technology Data Exchange (ETDEWEB)

    Yousif, A.; Bouziane, K., E-mail: bouzi@squ.edu.om; Elzain, M. E. [Sultan Qaboos University, Physics Department, College of Science (Oman); Ren, X.; Berry, F. J. [The Open University, Department of Chemistry (United Kingdom); Widatallah, H. M. [Sudan Atomic Energy Commission, Institute of Nuclear Research (Sudan); Al Rawas, A.; Gismelseed, A.; Al-Omari, I. A. [Sultan Qaboos University, Physics Department, College of Science (Oman)

    2004-12-15

    X-ray diffraction, Moessbauer and magnetization measurements were used to study Fe{sub x}Cu{sub 1-x} alloys prepared by ball-milling. The X-ray data show the formation of a nanocrystalline Fe-Cu solid solution. The samples with x{>=}0.8 and x{<=}0.5 exhibit bcc or fcc phase, respectively. Both the bcc and fcc phases are principally ferromagnetic for x{>=}0.2, but the sample with x=0.1 remains paramagnetic down to 78 K. The influence of the local environment on the hyperfine parameters and the local magnetic moment are discussed using calculations based on the discrete-variational method in the local density approximation.

  1. Generalized Rate Theory for Void and Bubble Swelling and its Application to Plutonium Metal Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Allen, P. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wolfer, W. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-16

    In the classical rate theory for void swelling, vacancies and self-interstitials are produced by radiation in equal numbers, and in addition, thermal vacancies are also generated at the sinks, primarily at edge dislocations, at voids, and at grain boundaries. In contrast, due to the high formation energy of self-interstitials for normal metals and alloys, their thermal generation is negligible, as pointed out by Bullough and Perrin. However, recent DFT calculations of the formation energy of self-interstitial atoms in bcc metals have revealed that the sum of formation and migration energies for self-interstitials atoms (SIA) is of the same order of magnitude as for vacancies. The ratio of the activation energies for thermal generation of SIA and vacancies is presented. For fcc metals, this ratio is around three, but for bcc metals it is around 1.5. Reviewing theoretical predictions of point defect properties in δ-Pu, this ratio could possibly be less than one. As a result, thermal generation of SIA in bcc metals and in plutonium must be taken into considerations when modeling the growth of voids and of helium bubbles, and the classical rate theory (CRT) for void and bubble swelling must be extended to a generalized rate theory (GRT).

  2. Hydrogen-plasticity in the austenitic alloys; Interactions hydrogene-plasticite dans les alliages austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    De lafosse, D. [Ecole Nationale Superieure des Mines, Lab. PECM-UMR CNRS 5146, 42 - Saint-Etienne (France)

    2007-07-01

    This presentation deals with the hydrogen effects under stresses corrosion, in austenitic alloys. The objective is to validate and characterize experimentally the potential and the limits of an approach based on an elastic theory of crystal defects. The first part is devoted to the macroscopic characterization of dynamic hydrogen-dislocations interactions by aging tests. then the hydrogen influence on the plasticity is evaluated, using analytical classic models of the elastic theory of dislocations. The hydrogen influence on the flow stress of bcc materials is analyzed experimentally with model materials. (A.L.B.)

  3. Moessbauer study of Fe-Al disordered alloys near the critical concentration

    International Nuclear Information System (INIS)

    Bohorquez, A.; Tabares, J.A.; Perez Alcazar, G.A.; Gancedo, J.R.

    1994-01-01

    Disordered bcc Fe 1-q Al q alloys in the composition range 0.5≤q≤0.6 were studied by Moessbauer effect measurements. The Moessbauer spectra at 300 K of all the samples consist of two paramagnetic sites, one is a singlet and the other a doublet with quadrupole splitting. The results can be interpreted by considering that the sites of this disordered system are arranged near the configurations of the Fe and Al sites of the Fe-Al ordered system. (orig.)

  4. MAPPING FLOW LOCALIZATION PROCESSES IN DEFORMATION OF IRRADIATED REACTOR STRUCTURAL ALLOYS - FINAL REPORT. Nuclear Energy Research Initiative Program No. MSF99-0072. Period: August 1999 through September 2002. (ORNL/TM-2003/63)

    Energy Technology Data Exchange (ETDEWEB)

    Farrell, K.

    2003-09-26

    Metals that can sustain plastic deformation homogeneously throughout their bulk tend to be tough and malleable. Often, however, if a metal has been hardened it will no longer deform uniformly. Instead, the deformation occurs in narrow bands on a microscopic scale wherein stresses and strains become concentrated in localized zones. This strain localization degrades the mechanical properties of the metal by causing premature plastic instability failure or by inducing the formation of cracks. Irradiation with neutrons hardens a metal and makes it more prone to deformation by strain localization. Although this has been known since the earliest days of radiation damage studies, a full measure of the connection between neutron irradiation hardening and strain localization is wanting, particularly in commercial alloys used in the construction of nuclear reactors. Therefore, the goal of this project is to systematically map the extent of involvement of strain localization processes in plastic deformation of three reactor alloys that have been neutron irradiated. The deformation processes are to be identified and related to changes in the tensile properties of the alloys as functions of neutron fluence (dose) and degree of plastic strain. The intent is to define the role of strain localization in radiation embrittlement phenomena. The three test materials are a tempered bainitic A533B steel, representing reactor pressure vessel steel, an annealed 316 stainless steel and annealed Zircaloy-4 representing reactor internal components. These three alloys cover the range of crystal structures usually encountered in structural alloys, i.e. body-centered cubic (bcc), face-centered cubic (fcc), and close-packed hexagonal (cph), respectively. The experiments were conducted in three Phases, corresponding to the three years duration of the project. Phases 1 and 2 addressed irradiations and tensile tests made at near-ambient temperatures, and covered a wide range of neutron fluences

  5. Evaluation of copper alloys for fusion reactor divertor and first wall components

    DEFF Research Database (Denmark)

    Fabritsiev, S.A.; Zinkle, S.J.; Singh, B.N.

    1996-01-01

    This paper presents a critical analysis of the main factors of radiation damage limiting the possibility to use copper alloys in the ITER divertor and first wall structure. In copper alloys the most significant types of radiation damage in the proposed temperature-dose operation range are swellin...

  6. Comparative study of radiation damage accumulation in Cu and Fe

    International Nuclear Information System (INIS)

    Caturla, M.J.; Soneda, N.; Alonso, E.; Wirth, B.D.; Diaz de la Rubia, T.; Perlado, J.M.

    2000-01-01

    Bcc and fcc metals exhibit significant differences in behavior when exposed to neutron or heavy ion irradiation. Transmission electron microscopy (TEM) observations reveal that damage in the form of stacking fault tetrahedra (SFT) is visible in copper irradiated to very low doses, but that no damage is visible in iron irradiated to the same total dose. In order to understand and quantify this difference in behavior, we have simulated damage production and accumulation in fcc Cu and bcc Fe. We use 20 keV primary knock-on atoms (PKAs) at a homologous temperature of 0.25 of the melting point. The primary damage state was calculated using molecular dynamics (MD) with empirical, embedded-atom interatomic potentials. Damage accumulation was modeled using a kinetic Monte Carlo (kMC) algorithm to follow the evolution of all defects produced in the cascades. The diffusivities and binding energies of defects are input data for this simulation and were either extracted from experiments, the literature, or calculated using MD. MD simulations reveal that vacancy clusters are produced within the cascade core in the case of copper. In iron, most of the vacancies do not cluster during cooling of the cascade core and are available for diffusion. In addition, self-interstitial atom (SIA) clusters are produced in copper cascades but those observed in iron are smaller in number and size. The combined MD/kMC simulations reveal that the visible cluster densities obtained as a function of dose are at least one order of magnitude lower in Fe than in Cu. We compare the results with experimental measurements of cluster density and find excellent agreement between the simulations and experiments when small interstitial clusters are considered to be mobile as suggested by recent MD simulations

  7. Radiation damage

    CERN Document Server

    Heijne, Erik H M; CERN. Geneva

    1998-01-01

    a) Radiation damage in organic materials. This series of lectures will give an overview of radiation effects on materials and components frequently used in accelerator engineering and experiments. Basic degradation phenomena will be presented for organic materials with comprehensive damage threshold doses for commonly used rubbers, thermoplastics, thermosets and composite materials. Some indications will be given for glass, scintillators and optical fibres. b) Radiation effects in semiconductor materials and devices. The major part of the time will be devoted to treat radiation effects in semiconductor sensors and the associated electronics, in particular displacement damage, interface and single event phenomena. Evaluation methods and practical aspects will be shown. Strategies will be developed for the survival of the materials under the expected environmental conditions of the LHC machine and detectors. I will describe profound revolution in our understanding of black holes and their relation to quantum me...

  8. Extraordinary high strength Ti-Zr-Ta alloys through nanoscaled, dual-cubic spinodal reinforcement.

    Science.gov (United States)

    Biesiekierski, Arne; Ping, Dehai; Li, Yuncang; Lin, Jixing; Munir, Khurram S; Yamabe-Mitarai, Yoko; Wen, Cuie

    2017-04-15

    While titanium alloys represent the current state-of-the-art for orthopedic biomaterials, concerns still remain over their modulus. Circumventing this via increased porosity requires high elastic admissible strains, yet also limits traditional thermomechanical strengthening techniques. To this end, a novel β-type Ti-Zr-Ta alloy system, comprised of Ti-45Zr-10Ta, Ti-40Zr-14Ta, Ti-35Zr-18Ta and Ti-30Zr-22Ta, was designed and characterized mechanically and microstructurally. As-cast, this system displayed extremely high yield strengths and elastic admissible strains, up to 1.4GPa and potentially 1.48%, respectively. This strength was attributed to a nanoscaled, cuboidal structure of semi-coherent, dual body-centered cubic (BCC) phases, arising from the thermodynamics of interaction between Ta and Zr; this morphology occurring with dual BCC-phases is heretofore unreported in Ti-based alloys. Further, cell proliferation investigated by MTS assay suggests this was achieved without sacrificing biocompatibility, with no significant difference to either empty-well or commercially-pure Ti controls noted. The current research details microstructural, mechanical, and biological investigations into four novel biomedical alloys in a hitherto uninvestigated region of the Ti-Zr-Ta alloy system; Ti-45Zr-10Ta, Ti-40Zr-14Ta, Ti-35Zr-18Ta and Ti-30Zr-22Ta. We find that the investigated alloys display 0.2% yield strengths of up to 1.40GPa and elastic admissible strains of up to 1.48%, along with biological properties comparable to that seen in the conventional metallic biomaterial ASTM Grade-2 CP-Ti, achieved in the complete absence of traditional thermomechanical processing techniques. This is attributed to the presence of a dual-BCC cuboidal nanostructure, achieved via spinodal decomposition; while similar structures have been reported in e.g. Ni-based superalloys, we believe this is the first such structure investigated in a Ti-based material. As such, this work is felt to be of

  9. The irradiation hardening of Ni-Mo-Cr and Ni-W-Cr alloy under Xe26+ ion irradiation

    Science.gov (United States)

    Chen, Huaican; Hai, Yang; Liu, Renduo; Jiang, Li; Ye, Xiang-xi; Li, Jianjian; Xue, Wandong; Wang, Wanxia; Tang, Ming; Yan, Long; Yin, Wen; Zhou, Xingtai

    2018-04-01

    The irradiation hardening of Ni-Mo-Cr and Ni-W-Cr alloy was investigated. 7 MeV Xe26+ ion irradiation was performed at room temperature and 650 °C with peak damage dose from 0.05 to 10 dpa. With the increase of damage dose, the hardness of Ni-Mo-Cr and Ni-W-Cr alloy increases, and reaches saturation at damage dose ≥1 dpa. Moreover, the damage dose dependence of hardness in both alloys can be described by the Makin and Minter's equation, where the effective critical volume of obstacles can be used to represent irradiation hardening resistance of the alloys. Our results also show that Ni-W-Cr alloy has better irradiation hardening resistance than Ni-Mo-Cr alloy. This is ascribed to the fact that the W, instead of Mo in the alloy, can suppress the formation of defects under ion irradiation.

  10. Elastic-modulus enhancement during room-temperature aging and its suppression in metastable Ti–Nb-Based alloys with low body-centered cubic phase stability

    International Nuclear Information System (INIS)

    Tane, M.; Hagihara, K.; Ueda, M.; Nakano, T.; Okuda, Y.

    2016-01-01

    Changes in the elastic properties during room-temperature aging (RT aging) of metastable Ti–Nb-based alloy single crystals with low body-centered cubic (bcc)-phase stability were investigated. The elastic stiffness components of Ti–Nb–Ta–Zr alloys with different Nb concentrations were measured by resonant ultrasound spectroscopy during RT aging; the results revealed that shear moduli c ′ and c 44 were increased by RT aging. In the alloy with the lowest Nb concentration, i.e., with the lowest bcc phase stability, shear moduli c ′ and c 44 were enhanced by the largest amount. The increase rates were ∼5% for 1.1 × 10 7  s (127 days), whereas the bulk modulus was hardly changed by aging. In Ti–Nb–Ta–Zr–O alloys with different oxygen concentrations, shear moduli c ′ and c 44 of the alloy with the lowest oxygen concentration increased most significantly. Moreover, the electrical resistivity of Ti–Nb–Ta–Zr and Ti–Nb–Ta–Zr–O alloys was increased by RT aging. Importantly, the enhancements of shear moduli and electrical resistivity were suppressed by increases in the bcc-phase stability (i.e., increase in the Nb concentration) and oxygen concentration; these factors are known to suppress ω (hexagonal) phase formation. However, transmission electron microscopy (TEM) observations revealed that only a diffuse ω structure—an ω-like lattice distortion—was formed after RT aging. On the basis of alloying element effects, TEM observations, and analysis of the changes in elastic properties by using a micromechanics model, it was deduced that the enhancements of shear moduli and electrical resistivity were possibly caused by the formation of a diffuse ω structure.

  11. The effect of Mn and B on the magnetic and structural properties of nanostructured Fe60Al40 alloys produced by mechanical alloying.

    Science.gov (United States)

    Rico, M M; Alcázar, G A Pérez; Zamora, L E; González, C; Greneche, J M

    2008-06-01

    The effect of Mn and B on the magnetic and structural properties of nanostructured samples of the Fe60Al40 system, prepared by mechanical alloying, was studied by 57Fe Mössbauer spectrometry, X-ray diffraction and magnetic measurements. In the case of the Fe(60-x)Mn(x)Al40 system, 24 h milling time is required to achieve the BCC ternary phase. Different magnetic structures are observed according to the temperature and the Mn content for alloys milled during 48 h: ferromagnetic, antiferromagnetic, spin-glass, reentrant spin-glass and superparamagnetic behavior. They result from the bond randomness behaviour induced by the atomic disorder introduced by the MA process and from the competitive interactions of the Fe-Fe ferromagnetic interactions and the Mn-Mn and Fe-Mn antiferromagnetic interactions and finally the presence of Al atoms acting as dilutors. When B is added in the Fe60Al40 alloy and milled for 12 and 24 hours, two crystalline phases were found: a prevailing FeAl BCC phase and a Fe2B phase type. In addition, one observes an additional contribution attributed to grain boundaries which increases when both milling time and boron composition increase. Finally Mn and B were added to samples of the Fe60Al40 system prepared by mechanical alloying during 12 and 24 hours. Mn content was fixed to 10 at.% and B content varied between 0 and 20 at.%, substituting Al. X-ray patterns show two crystalline phases, the ternary FeMnAl BCC phase, and a (Fe,Mn)2B phase type. The relative proportion of the last phase increases when the B content increases, in addition to changes of the grain size and the lattice parameter. Such behavior was observed for both milling periods. On the other hand, the magnetic hyperfine field distributions show that both phases exhibit chemical disorder, and that the contribution attributed to the grain boundaries is less important when the B content increases. Coercive field values of about 10(2) Oe slightly increase with boron content

  12. Beta decomposition processes in Hf-rich Hf--Nb alloys

    International Nuclear Information System (INIS)

    Jones, W.B.; Taggart, R.; Polonis, D.H.

    1978-01-01

    The decomposition of the bcc β-phase by both athermal and isothermal processes has been investigated in Hf-rich Hf--Nb alloys. An all β-phase structure is retained in chill-cast alloys containing 30 to 50 at.% Nb (Cb), although electron diffraction streaking effects and the behavior of the temperature coefficient of electrical resistivity indicate the presence of a bcc lattice instability similar to that reported in solute lean Ti and Zr alloys. Aging a Hf 0 . 65 Nb 0 . 35 alloy at 400 and 600 0 C resulted in the direct precipitation of a fine dispersion of α-phase needles; this morphology differs from the discs of transition α (α/sub t/) which Carpenter et al observed in Nb-rich Nb 0 . 68 Hf 0 . 32 . During continued aging, the needles grow selectively to form colonies or groups of needles in which both the individual needles and the groups of needles have major axes aligned along (110)/sub β/ type directions. The initial α-phase particles exhibit the Burgers orientation relationship with the parent matrix; continued aging changes the electron diffraction patterns in a way that is similar to that observed in aged Ti--Mo and Ti--Mo--Al alloys where they were attributed to the α-phase having a different crystallographic relationship to the β-phase (Type 2 α-phase). The observed changes in the electron diffraction patterns of aged Hf 0 . 65 Nb 0 . 35 cannot be described as resulting from strained Burgers α-phase

  13. ANALYSIS OF DECREASE MACHINABILITY POSSIBLE CAUSES FOR CLAIMED ALLOY

    Directory of Open Access Journals (Sweden)

    Nataša Náprstková

    2016-09-01

    Full Text Available The Faculty of Production Technology and Management is often asked by companies with a request to solve a specific technical task. One of these tasks was the analysis of aluminum alloy worsened machinability when the rods from this alloy exhibited against assumption significantly worse (longer chips during machining. The alloy was complaint and, of course, it created economic damage. Obviously, the company was interested in the causes of this alloy behavior change that could possibly generate future complaints procedures to defend itself better, or to avoid mistakes in the production of the material. At the faculty analysis that could contribute to identifying the cause of the worsened machinability were done.

  14. Evaluation of non-conformities of hip prostheses made of titanium alloys and stainless steel

    International Nuclear Information System (INIS)

    Bezerra, Ewerton de Oliveira Teotonio; Nascimento, Jose Jeferson da Silva; Luna, Carlos Bruno Barreto; Morais, Crislene Rodrigues da Silva; Campos, Karla Valeria Miranda de

    2017-01-01

    A large number of metallic alloys has satisfactory behavior when used to manufacture implants for hip prostheses. However, they must be in conformity with standards, to ensure their quality for long periods without losing its functionality. Therefore, this paper aims to study the non-conformities in two hip prostheses, one of titanium and other stainless steel according to standards. The implants studied passed by X-ray diffraction (XRD), X-ray fluorescence, tensile test and optical microscopy (OM). Specimens for the tensile test were made according to ASTM E 8M, as well, MO samples passed by metallographic procedure. The results evidenced that some chemical compositions showed in relation to the standards. The XRD analysis showed peaks of austenite and absence of ferrite for the stainless steel, while the titanium alloy presents an alpha phase (HCP) more significant than the beta phase (BCC). The stainless steel alloys and titanium have yield strength and tensile strength that meet the standards. On the other hand, the elastic modulus of the titanium alloy and stainless steel, comes to be ten times greater than the human bone. Therefore, the high modulus of elasticity of the alloys, favors bone resorption problems. The stainless steel microstructure is typical of an austenitic matrix, while the titanium alloy presents α + β microstructure. (author)

  15. Tort Damages

    NARCIS (Netherlands)

    L.T. Visscher (Louis)

    2008-01-01

    textabstractAbstract: In this Chapter, I provide an overview of Law and Economics literature regarding tort damages. Where necessary, attention is also spent to rules of tort liability. Both types of rules provide behavioral incentives to both injurers and victims, with respect to their level of

  16. Layer texture of hot-rolled BCC metals and its significance for stress-corrosion cracking of main gas pipelines

    Science.gov (United States)

    Perlovich, Yu. A.; Isaenkova, M. G.; Krymskaya, O. A.; Morozov, N. S.

    2016-10-01

    Based on data of X-ray texture analysis of hot-rolled BCC materials it was shown that the layerwise texture inhomogeneity of products is formed during their manufacturing. The effect can be explained by saturation with interstitial impurities of the surface layer, resulting in dynamical deformation aging (DDA). DDA prevents the dislocation slip under rolling and leads to an increase of lattice parameters in the external layer. The degree of arising inhomogeneity correlates with the tendency of hot-rolled sheets and obtained therefrom tubes to stress-corrosion cracking under exploitation, since internal layers have a compressive effect on external layers, and prevents opening of corrosion cracks at the tube surface.

  17. Beyond chemical accuracy: The pseudopotential approximation in diffusion Monte Carlo calculations of the HCP to BCC phase transition in beryllium.

    Energy Technology Data Exchange (ETDEWEB)

    Shulenburger, Luke [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mattsson, Thomas Kjell Rene [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Desjarlais, Michael Paul [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-01-01

    Motivated by the disagreement between recent diffusion Monte Carlo calculations of the phase transition pressure between the ambient and beta-Sn phases of silicon and experiments, we present a study of the HCP to BCC phase transition in beryllium. This lighter element provides an opportunity for directly testing many of the approximations required for calculations on silicon and may suggest a path towards increasing the practical accuracy of diffusion Monte Carlo calculations of solids in general. We demonstrate that the single largest approximation in these calculations is the pseudopotential approximation and after removing this we find excellent agreement with experiment for the ambient HCP phase and results similar to careful calculations using density functional theory for the phase transition pressure.

  18. A New Approach to Reducing Search Space and Increasing Efficiency in Simulation Optimization Problems via the Fuzzy-DEA-BCC

    Directory of Open Access Journals (Sweden)

    Rafael de Carvalho Miranda

    2014-01-01

    Full Text Available The development of discrete-event simulation software was one of the most successful interfaces in operational research with computation. As a result, research has been focused on the development of new methods and algorithms with the purpose of increasing simulation optimization efficiency and reliability. This study aims to define optimum variation intervals for each decision variable through a proposed approach which combines the data envelopment analysis with the Fuzzy logic (Fuzzy-DEA-BCC, seeking to improve the decision-making units’ distinction in the face of uncertainty. In this study, Taguchi’s orthogonal arrays were used to generate the necessary quantity of DMUs, and the output variables were generated by the simulation. Two study objects were utilized as examples of mono- and multiobjective problems. Results confirmed the reliability and applicability of the proposed method, as it enabled a significant reduction in search space and computational demand when compared to conventional simulation optimization techniques.

  19. Application of generalized non-Schmid yield law to low-temperature plasticity in bcc transition metals

    International Nuclear Information System (INIS)

    Lim, H; Weinberger, C R; Battaile, C C; Buchheit, T E

    2013-01-01

    In this work, a generalized yield criterion that captures non-Schmid effects is proposed and implemented into a finite element crystal plasticity model to simulate plastic deformation of single and polycrystals. The parameters required for the constitutive formulation were calibrated to deformation experiments on single crystals. This model is used to investigate the effects of non-Schmid effects on the predictions of the stress–strain response and texture evolution in body-centered-cubic (bcc) metals. The non-Schmid contributions are required to accurately predict the stress–strain response of single crystals, and the concomitant non-associativity of the flow also increases the tendency of localization in polycrystal deformations. (paper)

  20. The electronic structure and bonding of a H-H pair in the vicinity of a BCC Fe bulk vacancy

    Energy Technology Data Exchange (ETDEWEB)

    Juan, A.; Pistonesi, C.; Brizuela, G. [Universidad Nacional del Sur, Bahia Blanca (Argentina). Departamento de Fisica; Garcia, A.J. [Universidad Nacional del Sur, Bahia Blanca (Argentina). Departamento de Ciencias de la Computacion

    2003-09-01

    The H-Fe interaction near a bcc Fe vacancy is analysed using a semi-empirical theoretical method. Calculations were performed using a Fe{sub 86} cluster with a vacancy. Hydrogen atoms are positioned in their local energy minima configurations. Changes in the electronic structure of Fe atoms near a vacancy were analysed for the system without H, with one H and with two H atoms. Fe atoms surrounding the vacancy weaken their bond when hydrogen is present. This is due to the formation of H-Fe bonds. Hydrogen influences only its nearest-neighbour Fe atoms. The H-H interaction was also analysed. For H-H distance of 0.82 Angstrom an H-H association is formed, while H-Fe interaction and Fe-Fe weakening is markedly reduced, when compared with other H-H interactions. (author)

  1. Effect of Ti/Cr content on the microstructures and hydrogen storage properties of Laves phase-related body-centered-cubic solid solution alloys

    Energy Technology Data Exchange (ETDEWEB)

    Young, K., E-mail: kwo.young@basf.com [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Wong, D.F. [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States); Department of Chemical Engineering and Materials Science, Wayne State University, MI 48202 (United States); Wang, L. [BASF/Battery Materials-Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309 (United States)

    2015-02-15

    Highlights: • Influences of Ti/Cr to BCC to hydrogen storage properties were reported. • A new activation using hydrogen pressure at 5 MPa was developed. • A discharge capacity of 463 mA h g{sup −1} was reported on a C14(36%)/BCC(64%) alloy. • Increase in Ti/Cr increases storage capacity and decreases high-rate performance. • The high-rate performance was dominated by the surface reaction. - Abstract: A series of BCC/C14 mixed phase alloys with the chemical composition of Ti{sub 13.6+x}Zr{sub 2.1}V{sub 44}Cr{sub 13.2−x}Mn{sub 6.9}Fe{sub 2.7}Co{sub 1.4}Ni{sub 15.7}Al{sub 0.3}, x = 0, 2, 4, 6, 8, 10, and 12, was fabricated, and their structural, gaseous phase and electrochemical hydrogen storage properties were studied. Raising the maximum pressure for measuring the gaseous hydrogen storage capacity allowed these alloys to reach full activation, and the maximum discharge capacities ranged from 375 to 463 mA h g{sup −1}. As the Ti/Cr ratio in the alloy composition increased, the maximum gaseous hydrogen storage capacity improved due to the expansion in both BCC and C14 unit cells. However, reversibility decreased due to the higher stability of the hydride phase, as indicated by the lower equilibrium pressures measured for these alloys. As with most other metal hydride alloys, the electrochemical capacities measured at 50 and 4 mA g{sup −1} fell between the boundaries set by the maximum and reversible gaseous hydrogen storage capacities. The poorer high-rate dischargeability observed with higher Ti/Cr ratios was attributed to the lower surface exchange current (less catalytic). Two other negative impacts observed with higher Ti/Cr ratios in the alloy composition are poorer cycle stability and lower open-circuit voltage.

  2. Development of a Knowledge Base of Ti-Alloys From First-Principles and Thermodynamic Modeling

    Science.gov (United States)

    Marker, Cassie

    An aging population with an active lifestyle requires the development of better load-bearing implants, which have high levels of biocompatibility and a low elastic modulus. Titanium alloys, in the body centered cubic phase, are great implant candidates, due to their mechanical properties and biocompatibility. The present work aims at investigating the thermodynamic and elastic properties of bcc Tialloys, using the integrated first-principles based on Density Functional Theory (DFT) and the CALculation of PHAse Diagrams (CALPHAD) method. The use of integrated first-principles calculations based on DFT and CALPHAD modeling has greatly reduced the need for trial and error metallurgy, which is ineffective and costly. The phase stability of Ti-alloys has been shown to greatly affect their elastic properties. Traditionally, CALPHAD modeling has been used to predict the equilibrium phase formation, but in the case of Ti-alloys, predicting the formation of two metastable phases o and alpha" is of great importance as these phases also drastically effect the elastic properties. To build a knowledge base of Ti-alloys, for biomedical load-bearing implants, the Ti-Mo-Nb-Sn-Ta-Zr system was studied because of the biocompatibility and the bcc stabilizing effects of some of the elements. With the focus on bcc Ti-rich alloys, a database of thermodynamic descriptions of each phase for the pure elements, binary and Ti-rich ternary alloys was developed in the present work. Previous thermodynamic descriptions for the pure elements were adopted from the widely used SGTE database for global compatibility. The previous binary and ternary models from the literature were evaluated for accuracy and new thermodynamic descriptions were developed when necessary. The models were evaluated using available experimental data, as well as the enthalpy of formation of the bcc phase obtained from first-principles calculations based on DFT. The thermodynamic descriptions were combined into a database

  3. The anti-mycobacterial activity of the cytochrome bcc inhibitor Q203 can be enhanced by small-molecule inhibition of cytochrome bd.

    NARCIS (Netherlands)

    Lu, P.; Asseri, A.H.O.; Kremer, Martijn; Maaskant, Janneke; Ummels, Roy; Lill, H.; Bald, D.

    2018-01-01

    Mycobacterial energy metabolism currently attracts strong attention as new target space for development of anti-tuberculosis drugs. The imidazopyridine Q203 targets the cytochrome bcc complex of the respiratory chain, a key component in energy metabolism. Q203 blocks growth of Mycobacterium

  4. 3D atomistic studies of fatigue behaviour of edge crack (0 0 1) in bcc iron loaded in mode i and II

    Czech Academy of Sciences Publication Activity Database

    Machová, Anna; Pokluda, J.; Uhnáková, Alena; Hora, Petr

    2014-01-01

    Roč. 66, September (2014), s. 11-19 ISSN 0142-1123 R&D Projects: GA ČR(CZ) GAP108/10/0698 Institutional support: RVO:61388998 Keywords : fatigue crack growth * bcc iron * 3D atomistic simulations * molecular dynamics Subject RIV: JQ - Machines ; Tools Impact factor: 2.275, year: 2014 www.elsevier.com/locate/ijfatigue

  5. Radiation damages in superconducting materials

    International Nuclear Information System (INIS)

    Heinz, W.; Seibt, E.

    1978-01-01

    Radiation damage investigations of technical superconductors are reported and discussed with respect to their main properties like critical current jsub(c), transition temperature Tsub(c), upper critical field Bsub(c2), pinning and annealing behaviour. Ordered A15 type alloys (like Nb 3 Sn and V 3 Ga) show significant reductions of all critical parameters above a threshold of about 2x10 21 m -2 with 50 MeV deuterons corresponding to 2x10 22 neutrons/m 2 (Esub(n)>0.1 MeV). Pure metals and disordered B1 type alloys (like Nb or NbTi) show only a small linear decrease in critical parameters (except Bsub(c2) of niobium). Experimental results are compared with theoretical calculations. (author)

  6. Experimental and Modeling Damage Limits Study for Straight Ti-3A1-2.5V Tubes

    National Research Council Canada - National Science Library

    Gupta, Mool C; Lin, Yaomin; Ni, Kan; Wong, Teh-Hwa; Woodland, Kevin; Grose, Tim; Spidel, Tom; Stone, Bill; Yu, Michael; Taylor, Bob; Lei, Charles; Williams, Reanne

    2007-01-01

    To insure the safety of the V-22 aircraft over long period of operation, damage limits should be established for Ti alloy hydraulic tubes In a previous report, the damage limit results for straight...

  7. Aeronautical requirements for Inconel 718 alloy

    Science.gov (United States)

    Elefterie, C. F.; Guragata, C.; Bran, D.; Ghiban, B.

    2017-06-01

    The project goal is to present the requirements imposed by aviation components made from super alloys based on Nickel. A significant portion of fasteners, locking lugs, blade retainers and inserts are manufactured from Alloy 718. The thesis describes environmental factors (corrosion), conditions of external aggression (salt air, intense heat, heavy industrial pollution, high condensation, high pressure), mechanical characteristics (tensile strength, yield strength and fatigue resistance) and loadings (tensions, compression loads) that must be satisfied simultaneously by Ni-based super alloy, compared to other classes of aviation alloys (as egg. Titanium alloys, Aluminum alloys). For this alloy the requirements are strength durability, damage tolerance, fail safety and so on. The corrosion can be an issue, but the fatigue under high-magnitude cyclic tensile loading it’s what limits the lifetime of the airframe. Also, the excellent malleability and weldability characteristics of the 718 system make the material physical properties tolerant of manufacturing processes. These characteristics additionally continue to provide new opportunities for advanced manufacturing methods.

  8. Radiation damage of structural materials

    International Nuclear Information System (INIS)

    Koutsky, J.; Kocik, J.

    1994-01-01

    Maintaining the integrity of nuclear power plants (NPP) is critical in the prevention or control of severe accidents. This monograph deals with both basic groups of structural materials used in the design of light-water nuclear reactors, making the primary safety barriers of NPPs. Emphasis is placed on materials used in VVER-type nuclear reactors: Cr-Mo-V and Cr-Ni-Mo-V steel for reactor pressure vessels (RPV) and Zr-Nb alloys for fuel element cladding. The book is divided into seven main chapters, with the exception of the opening one and the chapter providing phenomenological background for the subject of radiation damage. Chapters 3-6 are devoted to RPV steels and chapters 7-9 to zirconium alloys, analyzing their radiation damage structure, changes of mechanical properties due to neutron irradiation as well as factors influencing the degree of their performance degradation. The recovery of damaged materials is also discussed. Considerable attention is paid to a comparison of VVER-type and western-type light-water materials

  9. Research on modulated structure alloys

    International Nuclear Information System (INIS)

    Tsujimoto, Tokuzo; Saito, Kazuo; Hashimoto, Kenki

    1982-01-01

    Research was carried out for the purposes of clarifying the cause of modulated structure formation, developing the structure control method utilizing modulated structure and clarifying the suitability of modulated structure alloys as radiation damage-resisting materials. The research on structure control method encountered a difficulty in the analysis of experimental results, bu the following results were obtained in the other items. The method of solving a diffusion equation including a nonlinear term was found in course of the clarification of the cause of modulated structure formation. As a means of detecting faint unevenness in solid solution, of which the deviation of composition is a few %, the structure analysis method utilizing magnetic property was developed. This method was applied to Ni-9.6 at.% Ti alloy, and the process of expanding amplitude in composition variation in spinodal decomposition and the formation of solute atomshort region at the time of nucleation-growth were confirmed. Utilizing the high energy electron beam generated in a superhigh voltage electron microscope, electron beam irradiation experiment was carried out on precipitation hardening alloys with modulated structure. As the result, it was found that in Ni-Ti alloy, the amount of void swelling resistance showed the change with the increase of modulated structure period. (Kako, I.)

  10. Effect of thermo-mechanical processing on microstructure and mechanical properties of U - Nb - Zr alloys: Part 2 - U - 3 wt % Nb - 9 wt % Zr and U - 9 wt% Nb - 3 wt% Zr

    Science.gov (United States)

    Morais, Nathanael Wagner Sales; Lopes, Denise Adorno; Schön, Cláudio Geraldo

    2018-04-01

    The present work is the second and final part of an extended investigation on Usbnd Nb - Zr alloys. It investigates the effect of mechanical processing routes on microstructure of alloys U - 3 wt % Nb - 9 wt % Zr and U - 9 wt% Nb - 3 wt% Zr, through X-ray diffraction and scanning electron microscopy, completing the investigation, which started with alloy U - 6 wt% Nb - 6 wt% Zr in part 1. Mechanical properties are determined using microhardness and bending tests and correlated with the developed microstructures. The results show that processing sequence, in particular the inclusion of a 1000 °C heat treatment step, affects significantly the microstructure and mechanical properties of these alloys alloy in different ways. Microstructural characterization shows that both alloys present significant volume fraction of precipitates of a body-centered cubic (BCC) γ-Nb-Zr rich phase in addition the uranium-rich matrix. Bending tests show that sample ductility does not correlate necessarily with hardness and that the key factor appears to be the amount of the γ-Nb-Zr precipitates, which controls the matrix microstructure. Samples with a monoclinic α″ cellular microstructure and/or with the tetragonally-distorted BCC phase (γ0), although not strictly ductile, showed the largest allowed strains-before-break and complete elastic recovery of the broken pieces, pointing out to the macroscopic observation of superelasticity.

  11. Synthesis and Characterization of High-Entropy Alloy AlFeCoNiCuCr by Laser Cladding

    Directory of Open Access Journals (Sweden)

    Xiaoyang Ye

    2011-01-01

    Full Text Available High-entropy alloys have been recently found to have novel microstructures and unique properties. In this study, a novel AlFeCoNiCuCr high-entropy alloy was prepared by laser cladding. The microstructure, chemical composition, and constituent phases of the synthesized alloy were characterized by SEM, EDS, XRD, and TEM, respectively. High-temperature hardness was also evaluated. Experimental results demonstrate that the AlFeCoNiCuCr clad layer is composed of only BCC and FCC phases. The clad layers exhibit higher hardness at higher Al atomic content. The AlFeCoNiCuCr clad layer exhibits increased hardness at temperature between 400–700°C.

  12. Dynamics of the HCP/BCC phase transition and of the diffusion in zirconium: a model based on a tight-binding potential

    International Nuclear Information System (INIS)

    Willaime, F.

    1991-09-01

    We have developed an N-body interatomic potential, based on the second moment approximation of the tight-binding scheme, by fitting its four adjustable parameters to the cohesive energy, atomic volume, and elastic constants of hcp-Zr. We then showed that various properties of this potential compare favorably with those of zirconium in both the low temperatures hcp phase and the high temperature bcc phase. Such is the case in particular for the elastic constants, the phonon dispersion curves, the thermal expansion, and the melting temperature. We reproduced by molecular dynamics (MD) simulations on this potential the hcp/bcc phase transformation in both ways. It indeed occurs following the mechanism predicted by Burgers. We find a vibrational entropy of transformation equal to 0.13 k B . Our calculations suggest that in real zirconium the electronic contribution to the transformation entropy is important. We show that some interatomic potential lead to a higher value of the vibrational entropy in the hcp phase than in the bcc phase. We specified the dynamics of the vacancy migration in the bcc phase. The atomic jumps are almost exclusively nearest neighbour ones. The walk of the vacancy becomes strongly correlated at high temperatures. The vacancy jump frequency is very large and has a perfectly arrhenian behaviour. There is no evicence of a dynamical lowering of the vacancy migration barrier: the static and dynamic values of the vacancy migration energy are almost equal, both being unusually small (0.3 eV). The self diffusion coefficent of our model for the vacancy mechanism reproduces an anomalous fast diffusion close to that measured experimentally in bcc-Zr. In our model at high temperatures the time interval between successive jumps is almost equal to the time of flight. The migration events will therefore influence the formation of the vacancies [fr

  13. Irradiation assisted stress corrosion cracking of HTH Alloy X-750 and Alloy 625

    International Nuclear Information System (INIS)

    Mills, W.J.; Lebo, M.R.; Bajaj, R.; Kearns, J.J.; Hoffman, R.C.; Korinko, J.J.

    1994-01-01

    In-reactor testing of bolt-loaded precracked compact tension specimens was performed in 360 degree C water to determine effect of irradiation on the SCC behavior of HTH Alloy X-750 and direct aged Alloy 625. Out-of-flux and autoclave control specimens provided baseline data. Primary test variables were stress intensity factor, fluence, chemistry, processing history, prestrain. Results for the first series of experiments were presented at a previous conference. Data from two more recent experiments are compared with previous results; they confirm that high irradiation levels significantly reduce SCC resistance in HTH Alloy X-750. Heat-to-heat differences in IASCC were related to differences in boron content, with low boron heats showing improved SCC resistance. The in-reactor SCC performance of Alloy 625 was superior to that for Alloy X-750, as no cracking was observed in any Alloy 625 specimens even though they were tested at very high K 1 and fluence levels. A preliminary SCC usage model developed for Alloy X-750 indicates that in-reactor creep processes, which relax stresses but also increase crack tip strain rates, and radiolysis effects accelerate SCC. Hence, in-reactor SCC damage under high flux conditions may be more severe than that associated with postirradiation tests. In addition, preliminary mechanism studies were performed to determine the cause of IASCC In Alloy X-750

  14. TEM study of amorphous alloys produced by ion implantation

    International Nuclear Information System (INIS)

    Johnson, E.; Grant, W.A.; Wohlenberg, P.; Hansen, P.; Chadderton, L.T.

    1978-01-01

    Ion implantation is a technique for introducing foreign elements into surface layers of solids. Ions, as a suitably accelerated beam, penetrate the surface, slow down by collisions with target atoms to produce a doped layer. This non-equilibrium technique can provide a wide range of alloys without the restrictions imposed by equilibrium phase diagrams. This paper reports on the production of some amorphous transition metal-metalloid alloys by implantation. Thinned foils of Ni, Fe and stainless steel were implanted at room temperature with Dy + and P + ions at doses between 10 13 - 10 17 ions/cm 2 at energies of 20 and 40 keV respectively. Transmission electron microscopy and selected area diffraction analysis were used to investigate the implanted specimens. Radial diffracted intensity measurements confirmed the presence of an amorphous implanted layer. The peak positions of the maxima are in good agreement with data for similar alloys produced by conventional techniques. Only certain ion/target combinations produce these amorphous layers. Implantations at doses lower than those needed for amorphization often result in formation of new crystalline phases such as an h.c.p. phase in nickel and a b.c.c. phase in stainless steel. (Auth.)

  15. Creep damage development in welded X20 and P91

    Energy Technology Data Exchange (ETDEWEB)

    Brett, Steve; Holmstrom, Stefan; Hald, John; Borg, Ulrik; Aakjaer Jensen, Soeren; Vulpen, Rijk Van; Degnan, Craig; Vinter Dahl, Kristian; Vilhelmsen, Tommy

    2011-03-15

    The Martensitic steel X20CrMoV121 (hereinafter called X20) and the modified 9Cr1Mo steel (hereinafter called P91) have been used for a number of years in high temperature applications since they posses superior creep strength compared to low alloyed steels. Due to the simple fact that very few failures were observed, almost no knowledge as to the evolution of creep damage in welds were available despite long operation times exceeding well over 100.000 hours. It has been suggested that X20 will develop creep damage in a different manner compared to low alloyed steel, i.e damage initiation should be slow followed by accelerated growth. The research work presented in this report included systematic investigations of the first components of X20, which has developed creep during long-term operation. All of the investigated components showed creep damage evolution similar to low alloy steels

  16. Translating VDM to Alloy

    DEFF Research Database (Denmark)

    Lausdahl, Kenneth

    2013-01-01

    specifications. However, to take advantage of the automated analysis of Alloy, the model-oriented VDM specifications must be translated into a constraint-based Alloy specifications. We describe how a sub- set of VDM can be translated into Alloy and how assertions can be expressed in VDM and checked by the Alloy...

  17. Quantum statistical vibrational entropy and enthalpy of formation of helium-vacancy complex in BCC W

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Haohua [Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, 519082, Zhuhai (China); Woo, C.H., E-mail: chung.woo@polyu.edu.hk [ME Department, The Hong Kong Polytechnic University, Hong Kong SAR (China)

    2016-12-15

    High-temperature advance-reactor design and operation require knowledge of in-reactor materials properties far from the thermal ground state. Temperature-dependence due to the effects of lattice vibrations is important to the understanding and formulation of atomic processes involved in irradiation-damage accumulation. In this paper, we concentrate on the formation of He-V complex. The free-energy change in this regard is derived via thermodynamic integration from the phase-space trajectories generated from MD simulations based on the quantum fluctuation-dissipation relation. The change of frequency distribution of vibration modes during the complex formation is properly accounted for, and the corresponding entropy change avoids the classical ln(T) divergence that violates the third law. The vibrational enthalpy and entropy of formation calculated this way have significant effects on the He kinetics during irradiation.

  18. Radiation damage of structural materials

    CERN Document Server

    Koutsky, Jaroslav

    1994-01-01

    Maintaining the integrity of nuclear power plants is critical in the prevention or control of severe accidents. This monograph deals with both basic groups of structural materials used in the design of light-water nuclear reactors, making the primary safety barriers of NPPs. Emphasis is placed on materials used in VVER-type nuclear reactors: Cr-Mo-V and Cr-Ni-Mo-V steel for RPV and Zr-Nb alloys for fuel element cladding. The book is divided into 7 main chapters, with the exception of the opening one and the chapter providing a phenomenological background for the subject of radiation damage. Ch

  19. Electronic properties of γ-U and superconductivity of U–Mo alloys

    International Nuclear Information System (INIS)

    Tkach, I.; Kim-Ngan, N.-T.H.; Warren, A.; Scott, T.; Gonçalves, A.P.; Havela, L.

    2014-01-01

    Highlights: • The bcc phase of uranium was stabilized to low temperature in U–Mo alloys. • Ultrafast cooling was utilized. • Negative coefficient dρ/dT indicates very strong disorder. • The alloys are superconducting with T c ≈ 2.1 K. • They exhibit high critical field exceeding 5 T. - Abstract: Fundamental electronic properties of γ-Uranium were determined using Mo doping combined with ultrafast (splat) cooling, which allowed stabilization of the bcc structure to low temperatures. The Sommerfeld coefficient γ e is enhanced to 16 mJ/mol K 2 from 11 mJ/mol K 2 for α-U. Magnetic susceptibility remains weak and T-independent, ≈5 × 10 −8 m 3 /mol. The Mo-doped γ-U exhibits a conventional BCS superconductivity with T c ≈ 2.1 K and critical field exceeding 5 T for 15 at.% Mo. This type of superconductivity is qualitatively different from the one found for pure U splat, which has T c higher than 1 K but the weak specific heat anomaly proves that it is not real bulk effect

  20. Magnetic properties of nanocrystalline Fe–10%Ni alloy obtained by planetary ball mills

    International Nuclear Information System (INIS)

    Hamzaoui, Rabah; Elkedim, Omar

    2013-01-01

    Highlights: •Solid solution formation accompanied by a grain refinement for nanocrystalline Fe-Ni. •The shock mode process (SMP) prevails when Ω > >ω. •The friction mode process (FMP) is stronger when Ω < <ω. •The FMP leads to the formation of alloys exhibiting a soft magnetic behavior. -- Abstract: Planetary ball mill PM 400 from Retsch (with different milling times for Ω = 400 rpm, ω = 800 rpm) and P4 vario ball mill from Fritsch (with different milling conditions (Ω/ω), Ω and ω being the disc and the vial rotation speeds, respectively) are used for obtaining nanocrystalline Fe–10wt% Ni. The structure and magnetic properties are studied by using X-ray diffraction, SEM and hysteresis measurements, respectively. The bcc-Fe(Ni) phase formation is identified by X-ray diffraction. The higher the shock power and the higher milling time are, the larger the bcc lattice parameter and the lower the grain size. The highest value of the coercivity is 1600 A/m for Fe–10 wt.%Ni (with shock mode (424 rpm/100 rpm) after 36 h of milling), while the lowest value is 189 A/m for (400 rpm/800 rpm) after 72 h of milling. The milling performed in the friction mode has been found to lead the formation of alloys exhibiting a soft magnetic behavior for nanocrystalline Fe–10%Ni

  1. Supporting data for senary refractory high-entropy alloy CrxMoNbTaVW

    Directory of Open Access Journals (Sweden)

    B. Zhang

    2015-12-01

    Full Text Available This data article is related to the research paper entitled “senary refractory high-entropy alloy CrxMoNbTaVW [1]”. In this data article, the pseudo-binary Cr-MoNbTaVW phase diagram is presented to show the impact of Cr content to the senary Cr-MoNbTaVW alloy system; the sub-lattice site fractions are presented to show the disordered property of the Cr-MoNbTaVW BCC structures; the equilibrium and Scheil solidification results with the actual sample elemental compositions are presented to show the thermodynamic information of the melted/solidified CrxMoNbTaVW samples; and the raw EDS scan data of the arc-melted CrxMoNbTaVW samples are also provided.

  2. Evidence of eutectic crystallization and transient nucleation in Al89La6Ni5 amorphous alloy

    International Nuclear Information System (INIS)

    Zhuang, Y. X.; Jiang, J. Z.; Lin, Z. G.; Mezouar, M.; Crichton, W.; Inoue, A.

    2001-01-01

    The phase evolution with the temperature and time in the process of crystallization of Al 89 La 6 Ni 5 amorphous alloy has been investigated by in situ high-temperature and high-pressure x-ray powder diffraction using synchrotron radiation. Two crystalline phases, fcc-Al and a metastable bcc-(AlNi) 11 La 3 -like phase, were identified after the first crystallization reaction, revealing a eutectic reaction instead of a primary reaction suggested in the literature. Time-dependent nucleation in the amorphous alloy is detected and the experimental data can be fitted by both the Zeldovich's and Kashchiev's transient nucleation models with transient nucleation times of 220 and 120 min, respectively. Copyright 2001 American Institute of Physics

  3. Role of samarium additions on the shape memory behavior of iron based alloys

    International Nuclear Information System (INIS)

    Shakoor, R.A.; Khalid, F. Ahmad; Kang, Kisuk

    2011-01-01

    Research highlights: → The effect of samarium contents on shape memory behavior has been studied. → Addition of samarium increases the strength, c/a ratio and ε (hcp martensite). → Addition of samarium retards the nucleation of α (bcc martensite). → Improvement in shape memory effect with the increase in samarium contents. - Abstract: The effect of samarium contents on shape memory behavior of iron based shape memory alloys has been studied. It is found that the strength of the alloys increases with the increase in samarium contents. This effect can be attributed to the solid solution strengthening of austenite by samarium addition. It is also noticed that the shape memory effect increases with the increase in samarium contents. This improvement in shape memory effect presumably can be regarded as the effect of improvement in strength, increase in c/a ratio and obstruction of nucleation of α in the microstructure.

  4. Development of Metallic Sensory Alloys

    Science.gov (United States)

    Wallace Terryl A.; Newman, John A.; Horne, Michael R.; Messick, Peter L.

    2010-01-01

    Existing nondestructive evaluation (NDE) technologies are inherently limited by the physical response of the structural material being inspected and are therefore not generally effective at the identification of small discontinuities, making the detection of incipient damage extremely difficult. One innovative solution to this problem is to enhance or complement the NDE signature of structural materials to dramatically improve the ability of existing NDE tools to detect damage. To address this need, a multifunctional metallic material has been developed that can be used in structural applications. The material is processed to contain second phase sensory particles that significantly improve the NDE response, enhancing the ability of conventional NDE techniques to detect incipient damage both during and after flight. Ferromagnetic shape-memory alloys (FSMAs) are an ideal material for these sensory particles as they undergo a uniform and repeatable change in both magnetic properties and crystallographic structure (martensitic transformation) when subjected to strain and/or temperature changes which can be detected using conventional NDE techniques. In this study, the use of a ferromagnetic shape memory alloy (FSMA) as the sensory particles was investigated.

  5. Phase transition of Ni-Mn-Ga alloy powders prepared by vibration ball milling

    International Nuclear Information System (INIS)

    Tian, B.; Chen, F.; Tong, Y.X.; Li, L.; Zheng, Y.F.; Liu, Y.; Li, Q.Z.

    2011-01-01

    Research highlights: → The vibration ball milling with a high milling energy introduces the atomic disorder and large lattice distortion in the alloy during milling and makes the formation of disordered fcc structure phase in the alloy. → The transition temperature and activation energy for disordered fcc → disordered bcc are ∼320 o C and 209 ± 8 kJ/mol, respectively. → The alloy powders annealed at 800 o C for 1 h show a one-stage martensitic transformation with quite lower latent heat compared to the bulk alloy. - Abstract: This study investigated the phase transformation of the flaky shaped Ni-Mn-Ga powder particles with thickness around 1 μm prepared by vibration ball milling and post-annealing. The SEM, XRD, DSC and ac magnetic susceptibility measurement techniques were used to characterize the Ni-Mn-Ga powders. The structural transition of Heusler → disordered fcc occurred in the powders prepared by vibration ball milling (high milling energy) for 4 h, which was different from the structural transition of Heusler → disordered fct of the powders fabricated by planetary ball milling (low milling energy) for 4 h. The two different structures after ball milling should be due to the larger lattice distortion occurred in the vibration ball milling process than in the planetary ball milling process. The structural transition of disordered fcc → disordered bcc took place at ∼320 o C during heating the as-milled Ni-Mn-Ga powders, which was attributed to the elimination of lattice distortion caused by ball milling. The activation energy for this transition was 209 ± 8 kJ/mol. The Ni-Mn-Ga powder annealed at 800 o C mainly contained Heusler austenite phase at room temperature and showed a low volume of martensitic transformation upon cooling. The inhibition of martensitic transformation might be attributed to the reduction of grain size in the annealed Ni-Mn-Ga particles.

  6. Direct prediction of the solute softening-to-hardening transition in W–Re alloys using stochastic simulations of screw dislocation motion

    Science.gov (United States)

    Zhao, Yue; Marian, Jaime

    2018-06-01

    Interactions among dislocations and solute atoms are the basis of several important processes in metal plasticity. In body-centered cubic (bcc) metals and alloys, low-temperature plastic flow is controlled by screw dislocation glide, which is known to take place by the nucleation and sideward relaxation of kink pairs across two consecutive Peierls valleys. In alloys, dislocations and solutes affect each other’s kinetics via long-range stress field coupling and short-range inelastic interactions. It is known that in certain substitutional bcc alloys a transition from solute softening to solute hardening is observed at a critical concentration. In this paper, we develop a kinetic Monte Carlo model of screw dislocation glide and solute diffusion in substitutional W–Re alloys. We find that dislocation kinetics is governed by two competing mechanisms. At low solute concentrations, nucleation is enhanced by the softening of the Peierls stress, which dominates over the elastic repulsion of Re atoms on kinks. This trend is reversed at higher concentrations, resulting in a minimum in the flow stress that is concentration and temperature dependent. This minimum marks the transition from solute softening to hardening, which is found to be in reasonable agreement with experiments.

  7. Steel alloys

    International Nuclear Information System (INIS)

    Bloom, E.E.; Stiegler, J.O.; Rowcliffe, A.F.; Leitnaker, J.M.

    1977-01-01

    The invention deals with a fuel element for fast breeder reactors. It consits essentially of a uranium oxide, nitride, or carbide or a mixture of these fuels with a plutonium or thorium oxide, nitride, or carbide. The fuel elements are coated with an austenitic stainless steel alloy. Inside the fuel elements, vacancies or small cavities are produced by neutron effects which causes the steel coating to swell. According to the invention, swelling is prevented by a modification of type 304, 316, 321, or 12 K 72HV commercial steels. They consist mainly of Fe, Cr, and Ni in a ratio determined by a temary diagram. They may also contain 1.8 to 2.3% by weight of Mo and a fraction of Si (0.7 to 2% by weight) and Ti(0.10 to 0.5% by weight) to prevent cavity formation. They are structurally modified by cold working. (IHOE) [de

  8. A damage-tolerant glass.

    Science.gov (United States)

    Demetriou, Marios D; Launey, Maximilien E; Garrett, Glenn; Schramm, Joseph P; Hofmann, Douglas C; Johnson, William L; Ritchie, Robert O

    2011-02-01

    Owing to a lack of microstructure, glassy materials are inherently strong but brittle, and often demonstrate extreme sensitivity to flaws. Accordingly, their macroscopic failure is often not initiated by plastic yielding, and almost always terminated by brittle fracture. Unlike conventional brittle glasses, metallic glasses are generally capable of limited plastic yielding by shear-band sliding in the presence of a flaw, and thus exhibit toughness-strength relationships that lie between those of brittle ceramics and marginally tough metals. Here, a bulk glassy palladium alloy is introduced, demonstrating an unusual capacity for shielding an opening crack accommodated by an extensive shear-band sliding process, which promotes a fracture toughness comparable to those of the toughest materials known. This result demonstrates that the combination of toughness and strength (that is, damage tolerance) accessible to amorphous materials extends beyond the benchmark ranges established by the toughest and strongest materials known, thereby pushing the envelope of damage tolerance accessible to a structural metal.

  9. The microstructure and mechanical properties of Al-containing 9Cr ODS ferritic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guangming [School of Materials Science and Engineering, University of Science and Technology, Beijing, Beijing 100083 (China); Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 (United States); Zhou, Zhangjian, E-mail: zhouzhj@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology, Beijing, Beijing 100083 (China); Mo, Kun [Nuclear Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Wang, Pinghuai [Fusion Reactor & Materials Division, Southwestern Institute of Physics, Chengdu, Sichuan 610041 (China); Miao, Yinbin [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 (United States); Li, Shaofu; Wang, Man [School of Materials Science and Engineering, University of Science and Technology, Beijing, Beijing 100083 (China); Liu, Xiang [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 (United States); Gong, Mengqiang [School of Materials Science and Engineering, University of Science and Technology, Beijing, Beijing 100083 (China); Almer, Jonathan [X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Stubbins, James F. [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 (United States)

    2015-11-05

    In this study, a 9Cr oxide-dispersion strengthened (ODS) alloy with additional corrosion resistant element Al was fabricated by mechanical alloying (MA) and hot pressing (HP) to explore the impact of Al on the microstructure and mechanical property of a 9Cr ODS alloy. It is found that the Al completely dissolved into the Fe–Cr matrix after milling for 30 h. The minor phases in the Al-containing 9Cr ODS ferritic alloy were investigated by a high-energy X-ray, and were identified to be orthorhombic-YAlO{sub 3} (YAP), bcc-Y{sub 3}Al{sub 5}O{sub 12} (YAG), monoclinic-Al{sub 2}Y{sub 4}O{sub 9} (YAM), and hexagonal-YAlO{sub 3} (YAH). These phases were further confirmed by selected area diffraction pattern (SADP), energy dispersive spectroscopy (EDS), and high resolution transmission electron microscopy (HRTEM). In addition, their volume fractions were also calculated from the integrated intensities. According to the analysis of the particles and their formation sequences, the larger particles (greater than 100 nm) are identified as mainly YAG and Al{sub 2}O{sub 3} particles, while the particles with small size (less than 30 nm) are likely primarily YAM, YAH, and YAP particles. The yielding strength (YS) and ultimate tensile strength (UTS) at RT are 563 MPa and 744 MPa, respectively, while the YS and UTS at 700 °C are 245 MPa and 276 MPa, respectively. Although the addition Al in ODS alloys decreases the strength at RT, the values at high temperature are similar to those obtained for 9Cr ODS alloys strengthened by fine Y–Ti–O particles. - Graphical abstract: Synchrotron X-ray diffraction line profile of the 9CrAl ODS alloy; (Ferrite matrix phases, along with minor phases, orthorhombic YAlO{sub 3} (yttrium aluminum perovskite, YAP), bcc Y{sub 3}Al{sub 5}O{sub 12} (yttrium aluminum garnet, YAG), monoclinic Al{sub 2}Y{sub 4}O{sub 9} (yttrium aluminum monoclinic, YAM), and hexagonal YAlO{sub 3} (yttium aluminum hexagonal, YAH) were recognized.). - Highlights: • The

  10. Hydrogen absorption/desorption properties in the TiCrV based alloys

    Directory of Open Access Journals (Sweden)

    A. Martínez

    2012-10-01

    Full Text Available Three different Ti-based alloys with bcc structure and Laves phase were studied. The TiCr1.1V0.9, TiCr1.1V0.45Nb0.45 and TiCr1.1V0.9 + 4%Zr7Ni10 alloys were melted in arc furnace under argon atmosphere. The hydrogen absorption capacity was measured by using aparatus type Sievert's. Crystal structures, and the lattice parameters were determined by using X-ray diffraction, XRD. Microestructural analysis was performed by scanning electron microscope, SEM and electron dispersive X-ray, EDS. The hydrogen storage capacity attained a value of 3.6 wt. (% for TiCr1.1V0.9 alloy in a time of 9 minutes, 3.3 wt. (% for TiCr1.1V0.45Nb0.45 alloy in a time of 7 minutes and 3.6 wt. (% TiCr1.1V0.9 + 4%Zr7Ni10 with an increase of the hydrogen absorption kinetics attained in 2 minutes. This indicates that the addition of Nb and 4%Zr7Ni10 to the TiCrV alloy acts as catalysts to accelerate the hydrogen absorption kinetics.

  11. An all aluminum alloy UHV components

    International Nuclear Information System (INIS)

    Sugisaki, Kenzaburo

    1985-01-01

    An all aluminum components was developed for use with UHV system. Aluminum alloy whose advantage are little discharge gas, easy to bake out, light weight, little damage against radieactivity radiation is used. Therefore, as it is all aluminum alloy, baking is possible. Baking temperature is 150 deg C in case of not only ion pump, gate valve, angle valve but also aluminum components. Ion pump have to an ultrahigh vacuum of order 10 -9 torr can be obtained without baking, 10 -10 torr order can be obtained after 24 hour of baking. (author)

  12. Plasticity of oxide dispersion strengthened ferritic alloys

    International Nuclear Information System (INIS)

    Zakine, C.; Prioul, C.; Alamo, A.; Francois, D.

    1993-01-01

    Two 13%Cr oxide dispersion strengthened (ODS) ferritic alloys, DT and DY, exhibiting different oxide particle size distribution and a χ phase precipitation were studied. Their tensile properties have been tested from 20 to 700 C. Experimental observations during room temperature tensile tests performed in a scanning electronic microscope have shown that the main damage mechanism consists in microcracking of the χ phase precipitates on grain boundaries. These alloys are high tensile and creep resistant between 500 and 700 C. Their strongly stress-sensitive creep behaviour can be described by usual creep laws and incorporating a threshold stress below which the creep rate is negligible. (orig.)

  13. Microstructural Evolution of AlCoCrFeNiSi High-Entropy Alloy Powder during Mechanical Alloying and Its Coating Performance.

    Science.gov (United States)

    Tian, Lihui; Fu, Ming; Xiong, Wei

    2018-02-23

    High-entropy alloys (HEAs) are promising structural materials due to their excellent comprehensive performances. The use of mechanically alloyed powders to deposit HEA coatings through atmospheric plasma spraying (APS) is an effective approach that can broaden the application areas of the HEAs. In this paper, a ductility-brittleness AlCoCrFeNiSi system was chosen as an object of study, and the detailed evolution of the surface morphology, particle size distribution, and microstructure of the powder during mechanical alloying was investigated. An AlCoCrFeNiSi HEA coating was deposited using powder milled for 10 h, which can be used as an ideal feedstock for APS. The surface morphology, microstructure, microhardness, and wear behavior of the coating at room temperature were investigated. The results showed that as the milling time increased, the particle size first increased, and then decreased. At the milling time of 10 h, simple body-centered cubic (BCC) and face-centered cubic (FCC) solid solution phases were formed. After spraying, the lamellar structure inside a single particle disappeared. An ordered BCC phase was detected, and the diffraction peaks of the Si element also disappeared, which indicates that phase transformation occurred during plasma spraying. A transmission electron microscopy analysis showed that nanometer crystalline grains with a grain size of about 30 nm existed in the APS coating. For the coating, an average microhardness of 612 ± 41 HV was obtained. Adhesive wear, tribo-oxidation wear, and slight abrasion wear took place during the wear test. The coating showed good wear resistance, with a volume wear rate of 0.38 ± 0.08 × 10 -4 mm³·N -1 ·m -1 , which makes it a promising coating for use in abrasive environments.

  14. Neutron and PIMC determination of the longitudinal momentum distribution of HCP, BCC and normal liquid 4He

    International Nuclear Information System (INIS)

    Blasdell, R.C.; Ceperley, D.M.; Simmons, R.O.

    1993-07-01

    Deep inelastic neutron scattering has been used to measure the neutron Compton profile (NCP) of a series of condensed 4 He samples at densities from 28.8 atoms/nm 3 (essentially the minimum possible density in the solid phase) up to 39.8 atoms/nm 3 using a chopper spectrometer at the Argonne National Laboratory Intense Pulsed Neutron Source. At the lowest density, the NCP was measured along an isochore through the hcp, bcc, and normal liquid phases. Average atomic kinetic energies are extracted from each of the data sets and are compared to both published and new path integral Monte-Carlo (PIMC) calculations as well as other theoretical predictions. In this preliminary analysis of the data, account is taken of the effects of instrumental resolution, multiple scattering, and final-state interactions. Both our measurements and the PIMC theory show that there are only small differences in the kinetic energy and longitudinal momentum distribution of isochoric helium samples, regardless of their phase or crystal structure

  15. Atomistic simulations of screw dislocations in bcc tungsten: From core structures and static properties to interaction with vacancies

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Ke [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beihang University, Beijing 100191 (China); Niu, Liang-Liang [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beihang University, Beijing 100191 (China); Department of Nuclear Engineering and Radiological Science, University of Michigan, Ann Arbor, MI 48109 (United States); Jin, Shuo, E-mail: jinshuo@buaa.edu.cn [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beihang University, Beijing 100191 (China); Shu, Xiaolin [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beihang University, Beijing 100191 (China); Xie, Hongxian [School of Mechanical Engineering, Hebei University of Technology, Tianjin 300132 (China); Wang, Lifang; Lu, Guang-Hong [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beihang University, Beijing 100191 (China)

    2017-02-15

    Atomistic simulations have been used to investigate the core structures, static properties of isolated 1/2 <1 1 1> screw dislocations, and their interaction with vacancies in bcc tungsten (W) based on three empirical interatomic potentials. Differential displacement maps show that only one embedded atom method potential is able to reproduce the compact non-degenerate core as evidenced by ab initio calculations. The obtained strain energy and stress distribution from atomistic simulations are, in general, consistent with elasticity theory predictions. In particular, one component of the calculated shear stress, which is not present according to elasticity theory, is non-negligible in the core region of our dislocation model. The differences between the results calculated from three interatomic potentials are in details, such as the specific value and the symmetry, but the trend of spatial distributions of static properties in the long range are close to each other. By calculating the binding energies between the dislocations and vacancies, we demonstrate that the dislocations act as vacancy sinks, which may be important for the nucleation and growth of hydrogen bubbles in W under irradiation.

  16. Differentiation of Leishmania (Viannia) panamensis and Leishmania (V.) guyanensis using BccI for hsp70 PCR-RFLP.

    Science.gov (United States)

    Montalvo Alvarez, Ana Margarita; Nodarse, Jorge Fraga; Goodridge, Ivón Montano; Fidalgo, Lianet Monzote; Marin, Marcel; Van Der Auwera, Gert; Dujardin, Jean-Claude; Bernal, Iván Darío Velez; Muskus, Carlos

    2010-05-01

    Leishmania panamensis and Leishmania guyanensis are two species of the subgenus Viannia that are genetically very similar. Both parasites are usually associated with cutaneous leishmaniasis, but also have the potential to cause the mucocutaneous form of the disease. In addition, the study of foci and consequently the identification of vectors and probable reservoirs involved in transmission require a correct differentiation between both species, which is important at epidemiological level. We explored the possibility of identifying these species by using restriction fragment length polymorphisms (RFLP) in the gene coding for heat-shock protein 70 (hsp70). Previously, an hsp70 PCR-RFLP assay proved to be very effective in differentiating other Leishmania species when HaeIII is used as restriction enzyme. Based on hsp70 sequences analysis, BccI was found to generate species-specific fragments that can easily be recognized by agarose gel electrophoresis. Using the analysis of biopsies, scrapings, and parasite isolates previously grouped in a cluster comprising both L. panamensis and L. guyanensis, we showed that our approach allowed differentiation of both entities. This offers the possibility not only for identification of parasites in biological samples, but also to apply molecular epidemiology in certain countries of the New World, where several Leishmania species could coexist. Copyright 2009 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.

  17. Grain size engineering of bcc refractory metals: Top-down and bottom-up-Application to tungsten

    International Nuclear Information System (INIS)

    Kecskes, L.J.; Cho, K.C.; Dowding, R.J.; Schuster, B.E.; Valiev, R.Z.; Wei, Q.

    2007-01-01

    We have used two general methodologies for the production of ultrafine grained (UFG) and nanocrystalline (NC) tungsten (W) metal samples: top-down and bottom-up. In the first, Equal channel angular extrusion (ECAE), coupled with warm rolling has been used to fabricate UFG W, and high pressure torsion (HPT) was used to fabricate NC W. We demonstrate an abrupt shift in the deformation mechanism, particularly under dynamic compressive loading, in UFG and NC W. This novel deformation mechanism, a dramatic transition from a uniform deformation mode to that of localized shearing, is shared by other UFG and NC body-centerd cubic (BCC) metals. We have also conducted a series of bottom-up experiments to consolidate powdered UFG W precursors into solid bodies. The bottom-up approach relies on rapid, high-temperature consolidation, specifically designed for UFG and NC W powders. The mechanical property results from the top-down UFG and NC W were used as minimum property benchmarks to guide and design the experimental protocols and parameters for use in the bottom-up procedures. Preliminary results, showing rapid grain growth during the consolidation cycle, did not achieve full density in the W samples. Further development of high-purity W nanopowders and appropriate grain-growth inhibitors (e.g., Zener pinning) will be required to successfully produce bulk-sized UFG and NC W samples

  18. An MD simulation of interactions between self-interstitial atoms and edge dislocation in bcc transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, H. (Aomori Public College, 153-4 Yamazaki, Goushi-zawa, Aomori 030-01 (Japan)); Rafii-Tabar, H. (Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980 (Japan)); Kawazoe, Y. (Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980 (Japan)); Matsui, H. (Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980 (Japan))

    1994-09-01

    According to our model on the mechanism of dislocation bias reduction based on the interaction of dumbbell self-interstitial atoms (SIAs) with dislocation, the bias is significantly different depending on the dumbbell configuration in the dislocation strain field. A large-scale molecular dynamics (MD) simulation is performed to reveal the stability and the mechanism of diffusion of dumbbell SIAs near the edge dislocation core in bcc iron. Most SIAs take the crowdion configuration parallel to the Burgers vector in the expansion side of the dislocation. Such crowdions are stable in the temperature range of this simulation, i.e. between 373 and 473 K, making one-dimensional random to-and-fro motion parallel to the dislocation Burgers vector staying at several atomic layers below'' the dislocation core. This means that the SIA does not approach the dislocation core. These results suggest that the stable configuration of SIAs is seriously affected by the dislocation resulting in a reduction of bias factor. ((orig.))

  19. An MD simulation of interactions between self-interstitial atoms and edge dislocation in bcc transition metals

    International Nuclear Information System (INIS)

    Kamiyama, H.; Rafii-Tabar, H.; Kawazoe, Y.; Matsui, H.

    1994-01-01

    According to our model on the mechanism of dislocation bias reduction based on the interaction of dumbbell self-interstitial atoms (SIAs) with dislocation, the bias is significantly different depending on the dumbbell configuration in the dislocation strain field. A large-scale molecular dynamics (MD) simulation is performed to reveal the stability and the mechanism of diffusion of dumbbell SIAs near the edge dislocation core in bcc iron. Most SIAs take the crowdion configuration parallel to the Burgers vector in the expansion side of the dislocation. Such crowdions are stable in the temperature range of this simulation, i.e. between 373 and 473 K, making one-dimensional random to-and-fro motion parallel to the dislocation Burgers vector staying at several atomic layers ''below'' the dislocation core. This means that the SIA does not approach the dislocation core. These results suggest that the stable configuration of SIAs is seriously affected by the dislocation resulting in a reduction of bias factor. ((orig.))

  20. Analysis and diagnosis of basal cell carcinoma (BCC) via infrared imaging

    Science.gov (United States)

    Flores-Sahagun, J. H.; Vargas, J. V. C.; Mulinari-Brenner, F. A.

    2011-09-01

    conjugated gradients method could be useful in the definition of a better safety margin in the surgery for the removal of the lesion, both minimizing esthetics damage to the patient and possibly avoiding basal cell carcinoma recurrence.