Jin Zhanpeng

An analytic MEAM model for all BCC transition metals

A new pair potential is proposed, and a new analytic MEAM is developed by adding a modification term to total energy with the pair potential. The model can reproduce the shear moduli of all BCC transition metals accurately, especially the negative Cauchy pressure for the metal Cr. The mono- and di-vacancy formation and migration energies for all BCC transition metals are calculated with the model. The calculations are in agreement with the available experimental data.

A thermodynamic calculation of the Ni-Nb phase diagram

Abstract An optimized set of thermodynamic functions of the Ni-Nb system has been obtained using phase diagram data and thermodynamic data from the literature. The excess free energies of solution phases, liquid and two terminal solid solutions (Ni) and (Nb), were described by the Redlich-Kister formula. Two compound phases, Ni 3 Nb and Ni 6 Nb 7 , were described by the Wagner-Schottky model: Ni 3 Nb was modelled with two sublattices assuming anti-structure atoms on both sublattices, and Ni 6 Nb 7 was modelled with four sublattices after the formula (Ni,Nb) 2 (Nb,Ni) 1 (Ni) 4 (Nb) 6 , where the second atoms in the first and second brackets are anti-structure atoms. Optimization and calculation were performed alternately with different selections of data in order to get the most acceptable compromise between the scattered experimental data. The calculated phase diagram agrees very well with the experimental values from the literature.

A reassessment of the TiNi system

Abstract The Ti-Ni system has been reevaluated. A subregular solution model is used for the liquid and regular ones for the terminal solid solutions ((α Ti), (β Ti),(Ni)). The compounds, Ti 2 Ni and TiNi 3 , are treated as line compounds, while TiNi is described by a three-sublattice model. For (Ni), the magnetic contribution to the Gibbs energy is considered.Almost all of the experimental phase diagram data and thermochemical data are employed in the optimization. A consistent set of parameters describing the system is presented, and a comparison with the experimental data is shown.It is demonstrated that some important improvements have been made compared with previous assessments.

Optimization and calculation of the ZrO2-MgO system

Abstract The experimentally determined phase diagram data in the ZrO 2 -MgO system have been critically evaluated. An optimal set of thcrmodynamic functions for this system has been obtained using the selected phase diagram data from the literature. The Gibbs free energies are described by the following models: a regular solution model for the liquid and tetragonal ZrO 2 solid solution, and a subregular solution model for cubic ZrO 2 solid solution. The terminal solid solutions based on monoclinic ZrO 2 and MgO are treated as pure oxides in view of the negligible solubilities. A consistent set of parameters describing the system is presented, and comprehensive companions with the experimental data are made. It is shown that most of the experimental information is satisfactorily accounted for by the present thermodynamic description.

Calculation of the ZrO2-CaO-MgO phase diagram

Abstract A thermodynamic evaluation of the ZrO[ 2 -MgO system has been conducted and combined with the previous descriptions of the ZrO 2 -CaO and MgO-CaO systems to calculate the ZrO 2 -CaO-MgO phase diagram by means of Bonnierś equation. The calculated results are shown by isothermal sections, a projection of the Liquidus surfaces, and a reaction scheme. Comparisons between the computed and experimental diagrams demonstrate that the calculations reasonably account for the experimental data and no ternary parameter is necessary for the description of the ZrO 2 -CaO-MgO system.

Thermodynamic modeling of intermetallic compounds in the Ni-Nb system

There are three intermetallic compounds in the Ni{sub 3}Nb, Ni{sub 6}Nb{sub 7}, and Ni{sub 8}Nb. Several attempts have been made to describe the Ni-Nb phase diagram by means of a thermodynamic approach. Kaufman and Nesor modeled the intermetallic compounds as line compounds. The compound Ni{sub 6}Nb{sub 7} was predicted to melt congruently, contrary to experimental data. In the work of Chevalier the homogeneity ranges of the compound phases were not considered, and the calculated (Ni) solvus overestimated the solubility of Nb. Although Ni{sub 6}Nb{sub 7} phase was described with a sublattice model, its nonzero width has not been predicted. This paper reports that a stoichiometric phase can usually be regarded as composed of two or more sublattices, the sites of each one being occupied by a certain element. If the phase has a small range of homogeneity, different species, which are sufficiently similar in size, shape, electronegativity, etc., may form mixtures on several of the sublattices.

Thermodynamics of the massive, bainitic and martensitic transformations in FeC, FeNi, FeCr and FeCu alloys

Abstract The γ → α transformation in pure iron and iron alloys with dilute alloying elements is a five-staged process, each stage has its own transformation-start temperature and transformation product: the first and second stages are a massive-type and a bainitic-type transformation respectively, while the subsequent stages (3, 4 and 5) are martensitic transformations. Thermodynamic calculation reveals that the driving force varies linearly with the transformation-start temperature for each stage of the transformation in FeC, FeNi, FeCr and FeCu alloys. Based on the linear relations, the calculated M a , B s and M s are in good agreement with experimental points.

Phase equilibria in the Mo-Ni-Co and Mo-Ni-Fe systems at 1000°C

Abstract The phase equilibria in the Mo-Ni-Co and Mo-Ni-Fe ternary systems at 1000 °C were investigated by means of a diffusion triple technique and electron microprobe analysis. Five phases coexist in each ternary system and the experimental information obtained was used to construct the isothermal cross-sections through the phase diagrams at 1000 °C.

A study of the isothermal section of the WNiCo system at 1300°C

Abstract An experimental study of the isothermal section of the WNiCo system at 1300°C has been made using the diffusion triple technique and electron microprobe analysis. It was determined that three single-phase regions (α, μ and γ), three two-phase regions ( α + γ , α + μ and μ + γ ) and one three-phase region ( α + μ + γ ) are included in the section.

Evolution of microstructure and diffusion paths in the molybdenum-steel explosion weld interface during heat treatment

Abstract The carbide layers formed in the bond interface of the explosively welded molybdenum-steel composite after heat treatment between 973 and 1273 K was examined metallgraphically and analyzed using an electron microprobe technique. The diffusion paths at 973, 1023 and 1273 K were constructed and interpreted by means of the FeMoC equilibrium phase diagram assuming that local equilibrium is established at all the phase boundaries.