Formation and crystallography of nano/ultrafine-trimorphic structure in metastable β titanium alloy Ti-5Al-5Mo-5V-3Cr-0.5Fe processed by dynamic deformation at low temperature

The dynamic beta -> alpha phase transformation of metastable beta titanium alloy Ti-5553 during the hot deformation process was investigated, including the crystallographic orientation relationship between alpha phase and beta matrix and the variant selection mechanism of nanoscale alpha precipitates. It is revealed that nano/ultrafine-trimorphic structure can be successfully produced dynamically Ti-5553 alloy through warm compression without severe plastic deformation or subsequent aging treatment. Ultrafine equiaxed alpha/beta grains do not respect Burgers orientation relationship were observed in the slip bands together with the remaining regions consisting of the lamellar a structure maintaining the Burgers orientation relationship with beta matrix. Moreover, the irregular a grains were mainly attributed to the fragmentation of a lamellae in some areas. There was variation in the proportion and distribution of the precipitates in the different areas depending on deformation. Furthermore, the strain induced variant selection of alpha I happened drastically.