Microstructural Evolution Mechanisms of TiAl Based Alloy Prepared by Spark Plasma Sintering

Using atomizing spherical Ti47Al2Cr2Nb0.2W prealloyed powder with plasma rotating electrode as starting material, TiAl-based alloy was prepared by SPS technology at different sintering temperatures (1100℃, 1200℃, 1250℃, 1300℃). The microstructure evolution of the pre-alloyed powder during densification was systematically studied by XRD, SEM and TEM and the effects of different sintering temperatures on mechanical properties were also investigated. The results show that when the sintering temperature exceeds 1200℃, there is a small amount of high temperature residual B2 phase in the microstructure, and the β phase (B2 phase) content increases with the increase of sintering temperature. The alloy has the highest compressive fracture strength, tensile fracture strength and fracture strain at 1100℃, which are 2367 MPa, 600 MPa and 2.25%, respectively. The α2 phase, β phase and γ phase have the following crystallographic relationship: (0001)α2//{111}γ//{110}β, α2//γ//β. Deformation induced α2→γ phase transformation and deformation twin formation occur in the sample sintered at 1300℃. © 2019, Science Press. All right reserved.