Investigation of microstructural evolution in a selective laser melted Ti6Al4V alloy induced by an ultrasonic surface rolling process

Surface modification treatment was carried out on a selective laser melted Ti6Al4V alloy using an ultrasonic surface rolling process (USRP). The results showed that a deformed layer with a gradient microstructure was produced near the surface, in which the microstructure changed from a coarse lamellar a structure to ultrafine lamellar grains, ultrafine equiaxed grains and nanograins. Moreover, there was a decrease in the intensity of the texture from the matrix to the surface. Furthermore, the dislocation density in the deformed layer first increased and then decreased from the matrix to the surface. The deformed layer exhibited a much higher hardness than the matrix, which was ascribed to grain boundary strengthening and dislocation strengthening.