Microstructure evolution of TiAl composite powder during low temperature high-energy milling

Microstructures and morphologies of two kinds of powders Ti-47Al(at%) and Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%) PREPARED by high-energy mechanical alloying at low-temperature were investigated. The results show that the particle size can be effectively controlled by decreasing of the milling temperature and that high quality fine and uniform powders with composite structure can be gained by mutual acting of low temperature condition and alloy elements. The particle size of Ti-45Al-2Cr-2Nb-lB-0.5Ta after milling 12 h at low temperature (-140--5)°C without process control agent can be effectively refined to get fine and uniform powders with composite structure. The grain sizes of Ti an Al are about 16 nm and 9 nm, respectively. However, Ti and Al in Ti-47Al(at%) after milling 5.2 h at the same conditions are far from composite and component uniform. No new phase was found at the milling conditions in the two constitutions. Low temperature and alloy element play an important role in mechanical alloying without process control agent.