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1.
The interdiffusion coefficients in bcc (α) and fcc (γ) Fe-Ni alloys below their Curie temperatures have been calculated based on the magnetic contribution to the free energy for
interdiffusion. The free energy for interdiffusion due to magnetic ordering in bcc Fe-Ni alloys is positive. The calculated
interdiffusion coefficients in bcc Fe-Ni alloys fit the experimental data quite well. In fcc Fe-Ni alloys, the magnetic contribution
to interdiffusion depends on both temperature and composition and is abnormal for Ni compositions in the Invar region. The
free energy of vacancy formation is positive and the free energy of vacancy migration is negative, due to the effect of magnetic
ordering. The interdiffusion coefficient in the ferromagnetic phase is lower than that extrapolated from the paramagnetic
phase for Ni compositions of 50 at. pct and greater and is higher than that extrapolated from the paramagnetic phase for Ni
compositions of 40 at. pct and lower. 相似文献
2.
S. S. K. Balam H. Q. Dong T. Laurila V. Vuorinen A. Paul 《Metallurgical and Materials Transactions A》2011,42(7):1727-1731
Incremental diffusion couple experiments are conducted to determine the average interdiffusion coefficient and the intrinsic
diffusion coefficients of the species in the Ni6Nb7 (μ phase) in the Ni-Nb system. Further, the tracer diffusion coefficients are calculated from the knowledge of thermodynamic
parameters. The diffusion rate of Ni is found to be higher than that of Nb, which indicates higher defect concentration in
the Ni sublattice. 相似文献
3.
E. Perez D. D. KeiserJr. Y. H. Sohn 《Metallurgical and Materials Transactions A》2011,42(10):3071-3083
U-Mo dispersion and monolithic fuels are being developed to fulfill the requirements for research reactors, under the Reduced
Enrichment for Research and Test Reactors program. In dispersion fuels, particles of U-Mo alloys are embedded in the Al-alloy
matrix, while in monolithic fuels, U-Mo monoliths are roll bonded to the Al-alloy matrix. In this study, interdiffusion and
microstructural development in the solid-to-solid diffusion couples, namely, U-15.7 at. pct Mo (7 wt pct Mo) vs pure Al, U-21.6 at. pct Mo (10 wt pct Mo) vs pure Al, and U-25.3 at. pct Mo (12 wt pct Mo) vs pure Al, annealed at 873 K (600 °C) for 24 hours, were examined in detail. Scanning electron microscopy (SEM), transmission
electron microscopy (TEM), and electron probe microanalysis (EPMA) were employed to examine the development of a very fine
multiphase interaction layer with an approximately constant average composition of 80 at. pct Al. Extensive TEM was carried
out to identify the constituent phases across the interaction layer based on selected area electron diffraction and convergent
beam electron diffraction (CBED). The cubic-UAl3, orthorhombic-UAl4, hexagonal-U6Mo4Al43, and cubic-UMo2Al20 phases were identified within the interaction layer that included two- and three-phase layers. Residual stress from large
differences in molar volume, evidenced by vertical cracks within the interaction layer, high Al mobility, Mo supersaturation,
and partitioning toward equilibrium in the interdiffusion zone were employed to describe the complex microstructure and phase
constituents observed. A mechanism by compositional modification of the Al alloy is explored to mitigate the development of
the U6Mo4Al43 phase, which exhibits poor irradiation behavior that includes void formation and swelling. 相似文献
4.
Shigenari Hayashi Wen Wang Daniel J. Sordelet Brian Gleeson 《Metallurgical and Materials Transactions A》2005,36(7):1769-1775
The effect of platinum addition on the interdiffusion behavior of γ-Ni + γ′-Ni3Al alloys was studied by using diffusion couples comprised of a Ni-Al-Pt alloy mated to a Ni-Al, Ni-Al-Cr, or Ni-based commercial
alloy. The commercial alloys studied were CMSX-4 and CMSX-10. Diffusion annealing was at 1150 °C for up to 100 hours. An Al-enriched
γ′-layer often formed in the interdiffusion zone of a given couple during diffusion annealing due to the uphill diffusion of
Al. This uphill diffusion was ascribed to Pt addition decreasing the chemical activity of aluminum in the γ + γ′ alloys. For a given diffusion couple end member, the thickening kinetics of the γ′ layer that formed increased with increasing Pt content in the Ni-Al-Pt γ + γ′ alloy. The γ′-layer thickening kinetics in diffusion couples with Cr showed less of a dependence on Pt concentration. Inference of a negative
effect of Pt and positive effect of Cr on the Al diffusion in this system enabled explanation of the observed interdiffusion
behaviors. There was no or minimal formation of detrimental topologically close-packed (TCP) phases in the interdiffusion
zone of the couples with CMSX-4 or CMSX-10. An overlay Pt-modified γ + γ′ coating on CMSX-4 showed excellent oxidation resistance when exposed to air for 1000 hours at 1150 °C. Moreover, the Al
content in the coating was maintained at a relatively high level due to Al replenishment from the CMSX-4 substrate. 相似文献
5.
Concentration profiles that develop in a ternary diffusion couple during an isothermal anneal can be analyzed directly for
average ternary interdiffusion coefficients. A new analysis is presented for the determination of average values for the main
and cross-interdiffusion coefficients over selected regions in the diffusion zone from an integration of interdiffusion fluxes,
which are calculated directly from experimental concentration profiles. The analysis is applied to selected isothermal diffusion
couples investigated with α (fcc) Cu-Ni-Zn alloys at 775 °C, β (bcc) Fe-Ni-Al alloys at 1000 °C, and γ (fcc) Ni-Cr-Al alloys at 1100 °C. Average ternary interdiffusion coefficients treated as constants are calculated over composition
ranges on either side of the Matano plane and examined for the diffusional interactions among the diffusing components. The
ternary interdiffusion coefficients determined from the new analysis are observed to be consistent with those determined by
the Boltzmann-Matano analysis at selected compositions in the diffusion zone. The ternary interdiffusion coefficients are
also employed in analytical solutions based on error functions for the generation of concentration profiles for the selected
diffusion couples. The generated profiles are a good representation of the experimental profiles including those exhibiting
uphill diffusion or zero-flux plane (ZFP) development for the individual components. Uncertainties in the values of the interdiffusion
coefficients calculated on the basis of the new analysis are found to be minimal. 相似文献
6.
Interdiffusion was investigated with solid-solid diffusion couples in theα (fcc) region of the quaternary Ni-Cr-Co-Mo system at 1300 °C for the determination of diffusion paths and diffusional interactions
among the components. The concentration profiles for a given couple exhibited a common cross-over composition, Yc, which reflected the relative depths of diffusion in the terminal alloys. Interdiffusion fluxes were calculated directly
from the concentration profiles, and the quaternary interdiffusion coefficients were calculated at selected compositions.
Ni and Co exhibited uphill diffusion against their individual concentration gradients in a direction opposite to the interdiffusion
of Cr. Quaternary diffusion paths were presented as a set of partial diffusion paths on the basis of relative concentration
variables. 相似文献
7.
8.
Taufiq Hidayat Peter C. Hayes Evgueni Jak 《Metallurgical and Materials Transactions B》2012,43(1):14-26
Ferrous calcium silicate slags, whose principal components are “FeO
x
”-CaO-SiO2, are widely used in copper smelting and converting operations. In the current study, high-temperature equilibration and rapid
quenching techniques were used to study the phase equilibria of the ferrous calcium silicate slags. The compositions of phases
in the slags were measured accurately using electron probe X-ray microanalysis (EPMA). The phase equilibria of the system
have been characterized at oxygen partial pressures between 10−5 atm and 10−7 atm at selected temperatures between 1473 K and 1623 K (1200 °C and 1350 °C). The effects of oxygen partial pressure and temperature
on the compositions of phases in the slags are presented. 相似文献
9.
Somasurendra Kumar Balam Aloke Paul 《Metallurgical and Materials Transactions A》2010,41(9):2175-2179
The diffusion characteristics of the Fe–Nb system were investigated using the diffusion couple technique. The average interdiffusion
coefficient was calculated for the Fe2Nb Laves and the FeNb μ phases. The possible diffusion mechanism was predicted by using the calculated values of the activation energy for diffusion.
Kirkendall marker experiments were conducted to determine the relative mobilities of the species. Fe was found to have a faster
diffusion rate than Nb in both phases. 相似文献
10.
D. Arvindha Babu B. Majumdar A. P. Srivastava B. Ramakrishna Rao D. Srivastava B. S. Murthy D. Akhtar 《Metallurgical and Materials Transactions A》2011,42(2):508-516
Melt-spun ribbons of Fe99–x–y
Zr
x
B
y
Cu1 alloys with x + y = 11 and x + y = 13 were prepared under similar experimental conditions and characterized for structure and soft magnetic properties. Substitution
of Zr by B changes the structure of as-spun ribbons from completely amorphous to cellular bcc solid solution coexisting with
the amorphous phase at intercellular regions and then to completely dendritic solid solution. The glass forming ability (GFA)
of the Fe-Zr-B-Cu system, evaluated from thermodynamic properties such as enthalpy of mixing and mismatch entropy, is found
to be in good agreement with the experimental observations. Annealing of all ribbons leads to the precipitation of nanocrystalline
bcc α-Fe phase from both amorphous phase and already existing bcc solid solution. A window of alloy compositions that exhibit the
best combination of soft magnetic properties (high saturation magnetization and low coercivity) was identified. 相似文献
11.
Louis S. Castleman 《Metallurgical and Materials Transactions A》1981,12(12):2031-2037
An analysis has been made of ternary diffusing systems to determine the possibility that individual diagonal interdiffusion
coefficient elements of thek(2D) (k = 1,2,3) interdiffusion coefficient matrices can be negative. It is shown that in ternary diffusing systems, in which the
concentration-penetration curves are monotonic, as many as three of the six diagonal coefficients can be negative. It is further
shown that several ternary diffusing systems having a negative diagonal interdiffusion coefficient matrix element have already
in fact been determined experimentally. 相似文献
12.
Yoshiaki Iijima Kazutomo Hoshino Ken-Ichi Hirano 《Metallurgical and Materials Transactions A》1977,8(6):997-1001
Interdiffusion coefficients in copper-titanium alloys have been determined by Matano's method in the temperature range between
973 and 1283 K on (pure Cu)-(Cu-1.98 at. pct Ti alloy) and (pure Cu)-(Cu-2.91 at. pct Ti alloy) couples. Temperature dependence
of the impurity diffusion coefficient of titanium in copper, determined by extrapolation of the concentration dependence of
the interdiffusion coefficient to zero mole fraction of titanium, is expressed by the following Arrhenius equation along with
the probable errors:D
Ti/Cu=(0.693
−0.135
+0.169
)×10−4exp[−(196±2)kJ mol−1/RT] m2/s.
The difference in the activation energies for the impurity diffusion of the 3d-transition metals and self-diffusion in copper
has been calculated by applying LeClaire's model with the oscillating potential of the impurity atom in copper. The calculated
values agree well with the experimental values including the present one.
Kazutomo Hoshino, formerly Graduate Student, Tohoku University 相似文献
13.
14.
Diffusion studies were carried out in the Fe-Ni-Al system at 1000 °C with solid-solid diffusion couples assembled with β (B2), β′ (bcc), and γ (fcc) single-phase alloys for the development of diffusion structures, diffusion paths, and for the determination of interdiffusion
and intrinsic diffusion coefficients. The diffusion structures were examined by optical and scanning electron microscopy,
and the concentration profiles were determined by electron microprobe analysis. Diffusion couples included several series
of β vs γ and β′ vs γ diffusion couples characterized by a common terminal alloy bonded to several terminal alloys with varying compositions. The
development of planar and nonplanar interfaces, as well as two-phase layers, as observed in various couples, were related
to the diffusion paths. The interdiffusion fluxes of individual components were calculated directly from the experimental
concentration profiles, and the diffusional interactions among components were examined in the light of zero-flux planes (ZFPs)
and flux reversals, which were identified in several couples. Ternary interdiffusion coefficients (
(i, j = Al, Ni)), with Fe considered as the dependent concentration variable, were evaluated at composition points of the intersection
of diffusion paths of single-phase couples and of multiphase couples that developed planar interfaces. The interdiffusion
coefficients were the largest in magnitude for the β′ alloys, especially near the β/β′ miscibility gap, and decreased for the β and γ alloys. In the β and γ phases, the main interdiffusion coefficient for Al was larger than those for Ni and Fe. Also, Fe interdiffused faster than
Ni in the Fe-rich β and β′ phases. The cross-interdiffusion coefficients (
and
) were negative in all three phases. In general, the
coefficients were larger in magnitude than the
coefficients; however, the magnitude of
was greater than that of
near the β/(β + γ) phase boundary on the ternary isotherm. In the β phase, the magnitude of
(i, j=Al, Ni) coefficients increased over 1 to 2 orders of magnitude with a decrease in the Al concentration and increase in the
Fe/Ni concentration ratio. Interdiffusion coefficients, extrapolated from the ternary coefficients for binary alloys, were
consistent with those in literature. Intrinsic diffusion coefficients were also determined at selected compositions. In addition,
tracer diffusion coefficients were estimated for the binary Fe-Al and Ni-Al alloys at selected compositions, from an extrapolation
of ternary interdiffusion coefficients. 相似文献
15.
Formation and Stability of Equiatomic and Nonequiatomic Nanocrystalline CuNiCoZnAlTi High-Entropy Alloys by Mechanical Alloying 总被引:1,自引:0,他引:1
Varalakshmi S. Kamaraj M. Murty B.S. 《Metallurgical and Materials Transactions A》2010,41(10):2703-2709
Nanocrystalline equiatomic high-entropy alloys (HEAs) have been synthesized by mechanical alloying in the Cu-Ni-Co-Zn-Al-Ti
system from the binary CuNi alloy to the hexanary CuNiCoZnAlTi alloy. An attempt also has been made to find the influence
of nonequiatomic compositions on the HEA formation by varying the Cu content up to 50 at. pct (Cu
x
NiCoZnAlTi; x = 0, 8.33, 33.33, 49.98 at. pct). The phase formation and stability of mechanically alloyed powder at an elevated temperature
(1073 K [800 °C] for 1 hour) were studied. The nanocrystalline equiatomic Cu-Ni-Co-Zn-Al-Ti alloys have a face-centered cubic
(fcc) structure up to quinary compositions and have a body-centered cubic (bcc) structure in a hexanary alloy. In nonequiatomic
alloys, bcc is the dominating phase in the alloys containing 0 and 8.33 at. pct of Cu, and the fcc phase was observed in alloys
with 33.33 and 49.98 at. pct of Cu. The Vicker’s bulk hardness and compressive strength of the equiatomic nanocrystalline
hexanary CuNiCoZnAlTi HEA after hot isostatic pressing is 8.79 GPa, and the compressive strength is 2.76 GPa. The hardness
of these HEAs is higher than most commercial hard facing alloys (e.g., Stellite, which is 4.94 GPa). 相似文献
16.
17.
18.
19.
Growth of silicides and interdiffusion in the Mo-Si system 总被引:1,自引:0,他引:1
Solid-solid diffusion couples assembled with disks of Mo and Si were annealed at selected temperatures, over the temperature
range from 900 °C to 1350 °C, for the development of diffusion structure and determination of interdiffusion coefficients
for the silicides of Mo. Layers of MoSi2 and Mo5Si3 were observed to form in the diffusion zone; the MoSi2 layer was one to two orders of magnitude larger in thickness than the Mo5Si3 layer. The MoSo2 layer developed a columnar microstructure with evidence of texture and preferential growth of grains in the direction of
diffusion. The Si-to-Mo ratio, determined by microprobe analysis across the thickness of the MoSi2 layer, varied within the approximate range from 1.9 to 2.0. From the concentration profiles, integrated interdiffusion coefficients
as well as energies of activation for interdiffusion were determined for the silicide layers. On the basis of the observed
stoichiometric range for the MoSi2 phase, average values of the interdiffusion coefficients were also estimated. Relations are derived between the growth-rate
constant and the integrated interdiffusion coefficient for the MoSi2 phase. The evaluated activation energies for interdiffusion in the MoSi2 and Mo5Si3 phases are 130±20 and 210±10 kJ/mol, respectively. 相似文献