Bulk and Grain Boundary Diffusion in Intermetallic Compounds of the Systems Ni-AI and Ti-AI

摘要

Bulk and grain boundary (GB) self-diffusion (Ni, Ti) in nickel- and titanium-aluminides was comprehensively investigated as a function of temperature and composition of corresponding alloys. Radiotracer measurements were combined with secondary ion mass spectrometry (SIMS) to cover a broader temperature interval. The compounds with different structures, such as B'2 (NiAl), LI_2 (Ni_3Al), D0_(19) (Ti_3Al), and L1_0 (TiAl), were investigated which provided an additional insight into the interdependence of the diffusion behavior and the diffusion mechanisms on structure and ordering. The compositional dependence of the diffusivity allowed to establish the effect of constitutional defects in these compounds. To interpret Al diffusion the interdiffusion data were used as well as the results on diffusion of Al-substituting impurities (Ga, Ge). The exhaustive experimental data form a basis for the subsequent theoretical analysis. A systematics in the diffusion behavior of Ti-and Ni-aluminides is proposed. GB self-diffusion in Ni- and Ti-aluminides was investigated. The available experimental data are analyzed.