Interdiffusion and Atomic Mobility Studies in Ni-Rich fcc Ni-Co-Al Alloys

The ternary interdiffusion coefficients in fcc Ni-Co-Al alloys at 1373 K were determined using Whittle and Green method together with electronic-probe microanalysis. With the help of DICTRA software, the experimental diffusion coefficients were critically assessed to obtain the atomic mobilities of Ni, Co and Al in fcc Ni-Co-Al alloys. Comprehensive comparisons between calculated and experimental diffusion coefficients showed that the experimental data could be well reproduced by the atomic mobilities obtained in the present work. The developed diffusion mobilities were further validated by the calculation of the concentration profiles and diffusion paths in diffusion couples.     

Ni-Nb-Ti三元系富Ni侧fcc相的互扩散及原子迁移率参数研究

本研究利用EPMA技术测定了Ni-Nb-Ti三元系富Ni侧合金在1000℃下的扩散数据,并使用Whittle and Green方法计算了Ni-Nb-Ti三元系在1000℃下的互扩散系数。通过DICTRA软件优化得到Ni-Nb-Ti三元系的fcc相的原子迁移率参数,运用优化得到的的原子迁移率计算出的互扩散系数与实验数据具有较好的一致性,从而验证了所得的原子迁移率参数的可靠性。同时通过运用迁移率参数拟合各扩散偶的的浓度-距离曲线和扩散路径,进一步验证了参数的合理性。     

Co-Cr-V三元系富Co侧fcc相的互扩散及原子迁移率参数研究

本研究制备了一系列Co-Cr-V合金,在1200℃下扩散处理259200 s。利用EPMA技术测定了各扩散偶的浓度-距离曲线,并根据测得的浓度-距离曲线用Whittle and Green方法计算了Co-Cr-V三元系在1200℃下的互扩散系数。基于本研究的实验数据和文献报道的热力学信息和相关子二元系的动力学参数,利用DICTRA软件优化得到Co-Cr-V体系fcc相的扩散迁移率参数。运用优化得到的原子迁移率参数计算互扩散系数,并与实验数据比对,取得较好的一致性,从而验证了所得迁移率参数的可靠性。同时运用该迁移率参数计算了各扩散偶的浓度-距离曲线和扩散路径,计算结果与实验数据均符合良好,进一步验证了参数的合理性和准确性。     

Interdiffusion and Diffusion Mobility for Fcc Ni-Co-Mo Alloys

Ternary fcc Ni-Co-Mo diffusion couples annealed at 1273 and 1473 K have been scanned to measure composition profiles by using electron probe microanalysis. The interdiffusion coefficients were extracted using the Whittle–Green method from the measured composition profiles of the ternary diffusion couples. Based on the diffusion coefficients reported in the literature and data determined in the present work, the diffusion mobilities for fcc Ni-Co-Mo alloys were assessed. In addition, diffusion paths and composition profiles were simulated with presently assessed mobility parameters. In general, reasonable agreements have been reached and the resulted mobility database can be used to investigate the diffusion behavior of the ternary fcc Ni-Co-Mo alloys in wide composition and temperature ranges.     

Interdiffusion and Atomic Mobilities of fcc Co-V-Mo Alloys: Measurement and Modeling

Based on 18 bulk diffusion couples, the composition-dependent interdiffusion coefficients in the fcc Co-V-Mo alloys at 1273, 1373 and 1473 K were obtained from the intersection points of the diffusion couples by means of EPMA technique coupled with the Whittle and Green method. With the experimentally determined interdiffusion coefficients and the critically reviewed experimental diffusivities available in the literature, the atomic mobilities of fcc Co-V-Mo alloys were assessed by means of Diffusion Controlled Transformation (DICTRA) software. The quality of the assessed atomic mobilities was confirmed by the comprehensive comparisons between various DICTRA-calculated diffusion behaviors and the experimental ones, including concentration profiles and diffusion paths.     

Computational Study of Atomic Mobility in Co-Fe-Ni Ternary Fcc Alloys

The generalized Boltzmann-Matano method has been used to evaluate the interdiffusion coefficients at 1100 °C for the fcc phase of the Co-Fe-Ni ternary system from the concentration profiles developed from single-phase diffusion couple. The evaluated interdiffusion coefficients, together with other experimental data in the literature, have been assessed to develop an atomic mobility database for the fcc phase of the Co-Fe-Ni ternary. The atomic mobility database, in conjunction with the CALPHAD-base thermodynamics, has been used to simulate a number of ternary diffusion couple experiments. Comprehensive comparisons between the calculated and experimental data show that excellent agreement is obtained not only for the general diffusion data of ternary diffusion couple, such as the interdiffusion coefficients and the concentration profiles, but also for much of in-depth diffusion behavior, like the diffusion path, the interdiffusion flux and the shift of the Kirkendall plane.     

Determination and assessment of ternary interdiffusion coefficients from individual diffusion couples

Two pairs of diffusion couples were assembled with α (fcc) Cu-Ni-Zn alloys characterized by similar thermodynamic activities for Cu and annealed at 775 °C. One pair of couples exhibited intersecting diffusion paths, and the other pair showed overlapping path segments. They were analyzed for interdiffusion fluxes, zero-flux-planes, and ternary interdiffusion coefficients directly from the concentration profiles. The analysis was based on converting profiles of concentrations to profiles of interdiffusion fluxes and evaluating moments of interdiffusion fluxes for the determination of interdiffusion coefficients over selected composition ranges. For the pair with intersecting diffusion paths, ternary interdiffusion coefficients were determined from the individual couples in the region of their common composition; these coefficients were in agreement with each other and with those determined by the Boltzmann-Matano analysis. For the pair of couples with overlapping diffusion path segments, interdiffusion coefficients calculated from each couple over the common path segment agreed with each other. In addition, the interdiffusion coefficients calculated over various composition regions were used to regenerate the concentration profiles of the individual couples. All calculations were carried out with the aid of a computer program called MultiDiFlux, which was developed by Dayananda and Ram-Mohan as a free educational and research tool for analysis of multicomponent diffusion.     

Study of Diffusion and Marker Movement in fcc Ag-Au Alloys

On the basis of the published CALPHAD-type thermodynamic parameters, the atomic mobilities of Ag and Au in face-centered cubic (fcc) Ag-Au alloys are critically assessed, where self-diffusion coefficients, impurity diffusion coefficients, tracer diffusion coefficients, interdiffusion coefficients and concentration curves are simultaneously optimized. Good agreements are obtained by comprehensive comparisons between the calculated and experimentally measured values. In addition, the developed mobilities are successfully used to study inert marker movement for one-dimensional and two-dimensional cases. It is believed that the obtained parameters can provide helpful guidance for material designs.     

Interdiffusion and Atomic Mobilities in fcc Co-Ga and Co-V Alloys

On the basis of Co/Co-10Ga, Co/Co-12Ga, and Co/Co-10V (at.%) diffusion couples, interdiffusion coefficients in the face-centered cubic (fcc) phase of the Co-Ga and Co-V binary systems were investigated in the temperature range between 1273 and 1573 K by means of the den Broeder method. Based on available thermodynamic information, the interdiffusion data were assessed to develop the atomic mobilities for the fcc Co-Ga and Co-V alloys using the DICTRA software package, and their validity was tested by simulating concentration–distance profiles.     

Atomic Mobilities and Diffusivities in fcc Co-Cr-Ti Alloys

In order to develop the atomic mobilities for the fcc phase of the Co-Cr-Ti alloys, interdiffusivities were determined with diffusion couples annealed at 1323 K for 100 h, the results of which were then critically assessed using the DICTRA software. From comprehensive comparisons between the calculated and the experimentally measured diffusion coefficients, good agreements can be obtained. The obtained atomic mobilities for fcc Co-Cr-Ti alloys are further verified through numerically simulated concentration profiles in diffusion couples, where the kinetic characteristics can be fully reproduced.     

Interdiffusion and Atomic Mobilities in bcc Ti-Ga and Ti-Cu Alloys

On the basis of three groups of Ti/Ti-10 at.% Ga and Ti/Ti-7 at.% Cu diffusion couples, respectively, interdiffusion coefficients in the bcc Ti-Ga and Ti-Cu binary alloys in the temperature range of 1273-1573 K were evaluated by means of the den Broeder method. Based on various reported experimental and the present measured diffusion coefficients as well as the available thermodynamic information, accurate atomic mobilities in the bcc Ti-Ga and Ti-Cu alloys were assessed via the DICTRA simulation package. A semi-empirical correlation was employed in the present work for the self-diffusivities in the hypothetical bcc Ga and Cu. Comparision between the calculated and measured diffusion coefficients indicated that most of the experimental information can be reasonably reproduced. The developed diffusion mobilities were further validated by the prediction of the concentration-distance profiles.     

Assessment of the Atomic Mobilities in fcc Cu-Fe and Cu-Ti Alloys

The experimentally measured diffusion coefficients of fcc Cu-Fe and Cu-Ti alloys in the published literature were reviewed critically in the present work. On the basis of the available thermodynamic information, the atomic mobilities of Cu, Fe, and Ti in fcc Cu-Fe and Cu-Ti alloys as a function of temperature and composition were assessed in terms of the CALPHAD method using the DICTRA^® software. The optimized mobility parameters are presented. The calculated diffusion coefficients show an excellent agreement with the experimental data. The composition-distance profiles of the Cu-Ti binary diffusion couples reported in the literature were also predicted using the assessed mobility parameters. Overall good agreement is achieved between the experimental results and simulations.     

Diffusion and Atomic Mobilities in fcc Ni-Sn Alloys

The composition-distance profiles in face-centered cubic (fcc) Ni-Sn alloys at 1173, 1223, 1273, and 1323 K were measured by means of electronic probe microanalysis (EPMA) using Ni/Ni-7.3at.%Sn diffusion couples. Based on the available thermodynamic information and various experimental diffusion coefficients, the atomic mobilities of Ni and Sn in fcc Ni-Sn alloys were assessed as a function of temperature and composition in terms of the CALPHAD method using the DICTRA^® software package. Optimized mobility parameters are presented. Comparisons between the calculated and measured diffusion coefficients show that most of the experimental information can be reproduced reasonably. The obtained mobility parameters can also predict satisfactorily the composition-distance profiles of the Ni/Ni-7.3at.%Sn diffusion couples determined in the present work.     

Assessment of Atomic Mobilities in fcc Al-Ag-Zn Alloys

Based on various experimental diffusivities of fcc Al-Ag-Zn alloys available in the literature and the thermodynamic parameter evaluated in the present work, atomic mobilities of Al, Ag and Zn in the fcc Al-Ag-Zn system were assessed as a function of composition and temperature with the aid of DICTRA software. Comparison between the calculated diffusivities and the corresponding experimental data indicates that the presently obtained atomic mobilities can reproduce most of the diffusivities, such as tracer diffusivities, impurity diffusivities and interdiffusivities in both binary and ternary systems. The reliability of the atomic mobilities was further verified via comparisons between the model-predicted concentration-distance profiles of the binary and ternary diffusion couples and the experimentally measured ones. Good agreement between the calculated and the measured concentration-distance profiles indicates that the presently obtained atomic mobilities are reliable. The diffusion paths can be also reproduced by the presently obtained atomic mobilities.     

Ni-Cr-W三元系富Ni侧fcc相的互扩散及原子迁移率参数研究

利用电子探针微量分析与Whittle-Green方法确定了在1200℃下退火72 h的Ni-Cr-W三元合金体系的互扩散系数。通过DICTRA软件包对实验互扩散系数进行评估以确定原子迁移率。通过全面分析比较模型预测的扩散特性和实验数据的良好一致性验证了原子迁移率的合理性。Ni-Cr-W三元体系中的扩散现象,如扩散路径和浓度-距离曲线可以通过获得的原子迁移率合理地描述,进一步证明了本研究所获得的原子迁移率参数的可靠性。     

Assessment of Atomic Mobilities for bcc Phase of Ti-Al-V System

Experimental diffusion data in the literature, in conjunction with existing CALPHAD-based thermodynamic parameters, were used to assess the atomic mobilities for the bcc phase of the Ti-Al-V system by using the DICTRA software. Good agreement was obtained from a comprehensive comparison between the calculated and experimental diffusion coefficients. The atomic mobilities database developed was further validated by appropriate predictions of some diffusion behavior resulting from interdiffusion, especially the concentration profile of diffusion couples.