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A high-throughput experimental approach is presented to extract the anisotropic interdiffusion coefficient by combining information over the composition profiles obtained by the electron probe microanalysis (EPMA) and the grain orientation spectrum by the electron backscatter diffraction (EBSD) on polycrystalline diffusion couples. Following the forward-simulation scheme, the interdiffusion coefficients in grains with diverse orientation are obtained and subsequently used to determine the anisotropic interdiffusion coefficients perpendicular () and parallel () to the c axis of the hcp Mg lattice in a Mg–Al alloy as a function of the Al solute content at 673 K and 723 K, respectively. It was found that the interdiffusion coefficients generally increased with the Al content and the rotation angle with respect to the c axis with a valley point around at 723 K. And it was noticed that diffusion along the basal plane was always faster than along the c axis. A comprehensive explicit expression of the interdiffusion coefficients was provided as a function of Al content, grain orientation and temperature. The anisotropic impurity diffusion coefficients of Al in hcp Mg derived by the extrapolation of the results in this paper are in good agreement with first principles calculations in the literature.

A CALPHAD-type thermodynamic assessment of the Al-C-Mn system was carried out in the present work. Special attention was paid to the ternary κ-phase with the aid of ab initio calculations. The enthalpies of formation at 0 K of all end-members of the κ phase were derived from the ab initio calculations and utilized in the present optimization. The κ phase was modeled as an ordered form of the fcc structure for the substitutional sub-lattices, employing the following formula within the framework of compound energy formalism: (Al,Mn)0.25(Al,Mn)0.25(Al,Mn)0.25(Al,Mn)0.25(C,Va)0.25. With the present optimized model parameters, the wide homogeneity range of the κ phase was reproduced satisfactorily. Comparison between the predicted and measured phase equilibria as well as the ab initio calculation results validates the present optimized model parameters., QC 20180524

The thermodynamic database of the Fe-C-Mn-Si system has been developed in the framework of the CALPHAD approach. The sub-ternary systems have been carefully evaluated and revised based on available experimental data. A satisfactory description of the liquid phase in the Fe-C-Si system has been obtained. The C-Mn-Si system was assessed treating the liquid phase as a substitutional solution. Phase equilibria in the C-Mn-Si system, especially those involving the liquid phase, can he well described. Based on the extrapolation of the experimental data in the quaternary system, the Fe-Mn-Si system has been modified to agree well with experimental data at high temperatures. The comparison between the calculated and measured phase transformation temperatures confirms the reliability of the present quaternary database. Additionally, the solidification process of Fe-0. 16C-1. 5 M n-1. 5 Si ( wt. % Yo) alloy was simulated by using the thermodynamic database developed., QC 20190207

The phase equilibria, thermodynamic properties and diffusion mobilities of the Fe-Co system were carefully assessed through the CALPHAD methods. As an indispensable tool, the first-principles calculations were carried out to study the magnetic moments and the enthalpies of mixing of the bcc_A2, bcc_B2, fcc_A1 and hcp_A3 phases as well as the point defect types of the bcc_B2 phase. In order to verify the heat capacities reported in the literature, new measurements were conducted in a high-temperature calorimetric apparatus using the three-dimensional calorimetric method. Because of the revision of the thermodynamic parameters in the present work, the diffusion mobilities for the fcc_Al phase were reassessed. The diffusion mobilities for the bcc_A2 phase were established for the first time based on the experimental diffusion coefficients. For the low temperature bcc_B2 phase, the diffusion couple experiments conducted in the present work show that the diffusion process is sluggish and the interdiffusion coefficients are difficult to determine. Therefore the tracer diffusivities of Co and Fe in the Fe-Co alloys were used to assess the diffusion mobilities for the bcc_B2 phase, while the composition-distance profile of one diffusion couple was served as a validation of its diffusion mobilities., QC 20180207

In order to simulate the diffusional phase transformations involving the fcc and bcc phases for microalloyed steels, the diffusion mobilities for fcc and bcc Fe˗Mo and Fe˗Mn˗Mo alloys were experimentally investigated and critically assessed. The diffusion-couple technique was employed to extract the interdiffusion coefficients in Fe˗Mo and Fe˗Mn˗Mo alloys with the Sauer-Freise and Whittle-Green methods. Based on the present experimental interdiffsivities, the mobility parameters for the fcc and bcc phases in the Fe˗Mo and Fe˗Mn˗Mo systems were optimized using the traditional method. Simultaneously, a direct method was developed and utilized to directly fit mobilities to the diffusion profiles rather than the diffusivities in the present work. The satisfactory description of the diffusion behavior in the Fe˗Mo and Fe˗Mn˗Mo systems has confirmed the reliability of the direct method. Particularly, the two sets of diffusion mobilities obtained with both methods could simulate the diffusion phenomenon between the fcc and bcc phases in the Fe˗Mo and Fe˗Mn˗Mo systems successfully., QC 20180524

The Al-C-Fe system was assessed in the framework of the CALPHAD approach. Through the critical review of thermochemical properties of liquid Al-Fe alloys, the binary Al-Fe description was revised to agree better with the experimental data. The partitioning model based on the Compound Energy Formalism (CEF) was utilized to describe the disordered and ordered bcc, fcc and κ phases. Moreover, ab initio calculations were performed to determine the enthalpies of formation of the ordered structures based on the bcc and fcc lattices in the binary Al-Fe and for the end-members of the κ phase in the ternary Al-C-Fe system. In order to simplify the database, the present work also employed a two-sublattice model to describe the B2 ordered phase in the Al-Fe system, which can be applied easily to diffusion simulations. Comprehensive comparison between the model-predicted and experimental data confirms that the present evaluation describe the Al-C-Fe system satisfactorily, especially the κ phase., QC 20170621

QC 20180524