Deformability and microstructure transformation of PM TiAl alloy prepared by pseudo-HIP technology

Microstructures and deformation properties of Ti-46Al-(Cr, Nb, W, B) alloy consolidated by pseudo-HIP technology were investigated. The results show that the pseudo-HIP temperature has a significant effect on microstructures. When the sintering temperature is 1 100 °C, the microstructure of as-pseudo-HIPped alloy is similar to that of the prealloyed powder and the interfaces of these powder particles are still discernible, but a near γ microstructure appears in particles. Increasing the pressing temperature to 1 200 °C develops successfully a homogeneous and fine-grained duplex microstructure. A typically fully lamellar microstructure with residual β phase is developed at 1 300 °C. The compact exhibits excellent deformation properties at elevated temperatures. When the compression temperature is higher than 1 100 °C, high quality products without cracks can be obtained even if the engineering compression strain is up to 0.8 at strain rates of 10−2–10−3 s−1. It can be established that the mechanical twinning and matrix deformation due to ordinary dislocation slip/climb contribute to the whole hot deformation.