Hot packed-rolling process of high-Nb TiAl alloy and its microstructure evolution

A novel hot pack-rolling process was developed in the wrought TiAl based alloy containing high content of Nb. The microstructure was studied using field-emission scanning electron microscopy (FE-SEM). The whole reduction of the sheet was up to more than 80% and the thickness of sheet was 1.9 mm. The production condition was nearly isothermal rolling at high temperature within the (α+γ) phase field, and the rolling speed was less than 80 mm · s^-1. The observation by FE-SEM showed the microstructure of the hot-rolled sheet was uniform and the average grain size increased after the hot rolling. The band structure in the wrought TiAl alloy disappeared because of the dynamic and statical recrystallization occurred during the hot rolling. The measurement of EBSD showed that some <100> a-axes of γ-TiAl grains paralleled to RD (rolling direction), and the orientation of other grains was of random distribution. In the rolled sheets of high-Nb TiAl with equiaxed microstructure, the main texture component was a modified cube texture {100}<010> where the a-axis paralleled to RD of the sheet. This texture component was caused by dynamic recrystallization.