Structure and Mechanical Properties of the Hot Pressed Compact of Ti-rich TiAl Powder Produced by the Plasma Rotating Electrode Process

The structure and the compressive mechanical properties of the Ti-rich TiAl (approximately Ti-47at%Al) compact produced by vacuum hot pressing of PREPed powder were investigated and compared with those of the compact having approximately stoichiometric TiAl composition (Stoi-TiAl compact) in the previous study. Ti-rich TiAl compact showed ultra-fine microduplex structure (average grain diameter 2 μm) consisting of equiaxed γ grain and the grain which was composed of (γ+α2) lamellar structure. Such a Ti-rich TiAl compact indicated higher strength and better ductility than those of the Stoi-TiAl compact at room temperature. However, at high-temperature such as 1 223 K, flow stress of the Ti-rich TiAl was lower than that of the Stoi-TiAl compact. During the deformation of the Ti-rich TiAl compact at 1 223 K, dynamic recrystallization (DR) which introduced a certain extent of grain refinement was occurred. This compact exhibited larger m value than 0.3 at 1 223 K, and was presumed to be deformed by superplastic flow closely related to DR.