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.