Abstract
Microstructures, mechanical properties, and crystal structures of Ti-(50-52)mol%Al alloys containing Sn up to 5mol% as a third element have been studied by using an optical microscope, a transmission electron microscope, a micro-Vickers hardness tester, and an X-ray diffractometer. Results obtained are as follows: The amount of Ti3Al (α2) phase existing in as-cast alloys was decreased by addition of Sn and it disappeared by anannealing for 604.8ks at 1273K. But the Ti3Sn phase formed in the cast alloys containings Sn did not disappear by the annealing. The Ti6Sn5 phase was formed in the Ti-50mol%Al-5mol%Sn alloy by the annealing. Both of the lattice parameter c and the axial ratio c/a of the LlO-type Al-rich intermetallic compound TiAl (γ phase) increased with increasing Sn content. Tin atoms in the γ phase occupy predominantly in the Ti site. The amount of mutual exchanges of Ti and Al atoms in lattice sites increased with increasing Sn content in the γ phase.
