Masahiko Kato*, Hisaoki Sasano** and Toshiyuki Suzuki*
* Department of Mechanical Engineering, Graduate School of Engineering, Kogakuin University, Tokyo 163-8677 ** National Research Institute for Metals, Tsukuba 305-0047Interdiffusion in single-phase Ti3Al has been investigated using a vapor-solid diffusion couple in the temperature range between 1086 and 1345 K. Aluminum was diffused by a chemical transportation technique in which aluminum chloride was used as the carrier gas. The results show that the interdiffusion coefficients at temperatures above 1209 K are almost the same at both sides of stoichiometry. However, the diffusion mode below 1132 K is completely different from that above 1209 K. Although the diffusion layer is formed uniformly in the surface of the base metal above 1209 K, the new crystal grains which are obviously different from the grains in the base metal are formed in the surface of the base metal below 1132 K. As the result, aluminum diffuses along the newly formed crystal grain boundary. This means that the interdiffusion below 1132 K must be controlled by a grain boundary diffusion mechanism instead of the lattice diffusion above 1209 K.
intermetallic compound, interdiffusion, Ti3Al, vapor-solid diffusion couple, grain boundary diffusion