Effects of TiB on the variant selection and spheroidization of secondary α phases at different cooling rates in TiB-TC25G composites

The evolution of the texture and microstructure of TiB-TC25G composites, heat-treated in the high α+β phase field, have been studied with different cooling rates. The present study found that the size of α colonies and the thickness of individual secondary α laths increased with decreasing cooling rates. Slow cooling induces the formation of equiaxed secondary α grains in the β matrix of TiB-TC25G composites. Attributed to the TiB, the intensity of α texture in TiB-TC25G composites decreased with decreasing cooling rate, which is inconsistent with the results of variant selection during the β→α phase transformation in traditional titanium alloys. The misorientation analysis suggested that some of the equiaxed secondary α grains do not follow the Burgers orientation relationship (BOR) with the parent β grain. In this study, the role of TiB in influencing variant selection and the morphology of the secondary α phase with different cooling rates were analyzed.