Stoichiometry effects: on the deformation of binary TiAl alloys

Abstract

The room temperature deformation behavior and microstructure of Ti48Al52 and Ti52Al48 alloys are compared. The material was fabricated by rapid solidification melt spinning, and examined in both as-cast and consolidated forms. The Ti52Al48 alloy exhibited enhanced strength and ductility in both forms in bend tests compared with the Ti48Al52 alloy. The microstructure of the Ti52Al48 alloy was two-phase γ–TiAl and α2–Ti3Al. The Ti48Al52 alloy was single-phase γ–TiAl and had a larger grain size than the previous alloy. The microstructure of the Ti52Al48 alloy after room temperature deformation consisted primarily of {111} mechanical twins and a/2〈110〉 perfect dislocations. The comparable Ti48Al52 alloy microstructure contained fewer twins, and many more a〈101〉 and a/2〈112〉 superdislocations were present in addition to a/2〈110〉 dislocations. The superdislocations had dissociated and formed sessile faulted dipoles. The possible reasons for the differences in microstructure and mechanical behavior between these two alloys are discussed.