Formation of Nanocrystalline Intermetallic Compounds for Ti-Al-Si System by Mechanical Alloying

Amorphous phase was obtained by mechanical alloying of Ti-Al-Si powders with four different composition. The structure evolution of the as-milled amorphous phase during the annealing treatment is classified into three stages:the first is partial crystallization of amorphous phase producing Ti₅Si₃ phase; the second is crystallization of the rest amorphous phase producing the corresponding titanium aluminides according to the relative amount of Ti and Al in the elemental mixture; and the last one is grain growth of all the phase in powders. The crystallization result in formation of Ti₃Al,TiAl and Al₃Ti according the powder composition. Ti₅Si₃ is the only silicide produced by crystallization reaction. The annealing treatment (less than 800℃ for A3, A4 and A5, and 750℃ for A6) shows that the grain size of all the phases fall in nanometer range.