Abstract:Elemental Ti, Al powders were hot pressed in Ar atmosphere at various temperatures in order to produce Ti-48Al (%) alloy. The microstructure evolution has been studied in this article through optical microscopy, scanning electron microscopy, EDAX analysis, X-ray diffraction analysis and TEM observation. Results show that reaction between elemental Ti and Al is mainly controlled by diffusion. After hot pressing at 800℃, the reaction between Ti and Al powders is incomplete. The hot pressed microstructure mainly consists of Ti₃Al phase and TiAl phase. The higher the hot pressing temperature is, the higher the rate of reactive diffusion and the more complete the crystallization of TiAl and Ti₃Al will be. After hot pressing at 1300℃, the Ti₃Al phase is island like. TEM observation shows that the island like Ti₃Al phase and the TiAl matrix are all composed of fine grains. After hot pressing at 1400℃, the microstructure consists of largeγgrains and coarse lamellar microstructure. Therefore, 1 300℃seems to be the premium temperature for reaction synthesis of TiAl based alloy.

Key words: TiAl based alloy　hot press　powder metallurgy