Surface microstructure and stress characteristics in pure titanium after high-current pulsed electron beam irradiation

Abstract

The specimens of polycrystalline pure titanium are irradiated by high-current pulsed electron beam (HCPEB). Surface microstructures and defects induced by HCPEB irradiation are investigated by using X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy technique. The XRD results show that the high value of stress (GPa order) is introduced into the irradiated surface layer, and the characteristics of preferential orientations (100), (102) and (103) are present after HCPEB treatment. The surface microstructure observations indicate that martensitic transformation occurs in the irradiated surface and a large number of plate martensite structures are formed in the irradiated surface. Moreover, strong plastic deformation is triggered by HCPEB treatment. After one pulse, (100) type slip bands are formed in the interior of grain, which leads to the increase of dislocation density. After multi- pulses, deformation microstructures change significantly, and the number of deformation twins increases evidently. The formation of these deformation structures produces a significant effect both on the evolution of surface textures and on grain refinement, which improves the mechanical performance of irradiated surface. It is suggested that HCPEB technique is an effective approach to surface hardening for pure titanium.