Development of Microstructure and Texture Heterogeneities during Static Annealing of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy Preformed by Hot Working

The effect of annealing temperature on the development of microstructure and texture in an α+β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) preformed by hot working was investigated with the aid of electron back-scattered diffraction and X-ray diffraction measurements. It is shown that considerable microstructure and texture heterogeneities were developed in the cross-section of the hot-worked rod due to the non-uniform deformation. Subsequent annealing at 940 °C and 990 °C led to homogeneous microstructures with globular α grains, whereas a typical lamellar α+β microstructure was obtained after annealing at 1040 °C. In the latter case, the Burgers orientation relationship was well preserved between the two phases in a single colony. The α lamellar within a given colony depicted similar crystallographic orientations and the boundary α grains shared the orientation of one of the neighboring α lamellar. In contrast, subsequent annealing had very limited effect on the main features of the textures, indicating strong inheritance of the texture heterogeneity in annealing. It is thus crucial to control the hot working process in order to achieve a high level of texture homogeneity in the final parts.