Diffusion Kinetics In The Ni-Ti-X(X=Al,Cu And Cr) Systems And Thermodynamic Descriptions For Pb-S And Bi-S Binary Systems

Since the 1980s, the innovation of materials has an increasing impact on advancement of modern technology and rapid development of world economy. The improvement of industrialization level increasingly demands innovative materials with better performance. Nickel-based superalloy, developed in the late 1930s, is a kind of important modern material with excellent comprehensive mechanical properties. It exhibits outstanding resistance to erosion and corrosion at elevated temperatures, thus widely used in aircraft engine blade, turbine disk, combustion chamber, etc. A lot of nickel-based superalloy systems have been researched in our country with the development in more than one century. However, the growing development of power, transportation, aviation and aerospace industry requires nickel-base superalloy with better performances. Additionally, such superalloy works under high temperature, which exists difficulties in experimental studies. Therefore, it is particularly important to further understand the relationship between microstructure, processing and performance of nickel-based superalloy, perfect their thermodynamics and kinetics database, and study such novel nickel-based materials in virtue of modern material design method.Modern material design method bases on thermodynamics calculation and diffusion kinetics simulation. Thermodynamics and kinetics database provides fundamental information in a lot of research work, such as processing simulation in physical metallurgy, prediction in structures and properties of materials. Phase equilibrium, metastable phase equilibrium, pseudo equilibrium, various thermodynamic properties and thermodynamic factors of multi-component alloy system can be achieved by the established thermodynamic database. Various diffusion coefficients, such as self-diffusion coefficient, impurity diffusion coefficient, intrinsic diffusion coefficient and mutual diffusion coefficient can be obtained from dynamic database. The application of thermodynamic and kinetic database for multi-component alloy system in innovative materials research avoids the blindness and repetitiveness of much experimental work, improves the efficiency of material design, and significantly reduces workforce and materials resources involved in material research and development. At present, related kinetic database of nickel base alloy is still not complete. Therefore, it has important theoretical value and practical significance in novel nickel-based material research and development to establish its kinetic database by calculating diffusion kinetics. Three key nickel-based ternary systems i.e. fcc Ni-Cu-Ti, fcc Ni-Al-Ti, and fcc Ni-Cr-Ti, are studied in this paper, aiming at establishing the accurate atomic mobility databases of such key systems. Based on the experimental diffusion information, the atomic mobility parameters for these systems are accurately assessed in DICTRA (Diffusion Controlled TRAnsformations) by combining the critically reviewed thermodynamic and kinetic information. Further validation concerning the quality and accuracy of atomic mobilities obtained in this work is conducted with computational simulations for concentration profiles, the results of which are compared with experimental data. In addition, thermodynamic parameters of Pb-S and Bi-S binary systems are also studied in this work by thermodynamic optimization.