Abstract
In the present paper, the author describes the reviews of our recent studies on Ti-rich TiAl intermetallics through two kinds of powder processing routs, plasma rotating electrode process (PREP) and mechanical alloying (MA) process. The HIPed billet of the PREPed powder can be isothermally hot forged to the 78% deformed sound pancake at 950°C and initial strain rate of 3.8×10-4/s by a manner of superplastic hot forging. The pancake consists of γ+α2 microduprex structure, and showed a large elongation to failure value such as 445% by tensile fracture test at 1000°C and initial strain rate of 2.8×10-4/s. From these results, it is presumed that the PREP-HIPed billet can be used as a material for superplastic hot forging to a complicated part. As-HIPed billet of the MA(150hr processed)-powder showed the similar γ+α2 microduplex structure. The results of detailed analysis of high-temperature deformation behavior of this material indicated that, the flow of the material satisfy the condition of fine grain superplasticity controlled by lattice diffusion. It seems to be possible to improve the formability of the intermetallics in the other alloy systems by controlling the structure as has been done in the present case of Ti-rich TiAl alloys.
