Influence of high-energy shot peening on the microstructure and mechanical properties of Ti-6Al-4V welded joints

In this study, Ti-6Al-4V welded joints were subjected to a high-energy shot peening (HESP) treatment. The structural characteristics of the Ti-6Al-4V welded joints were investigated by optical microscopy (OM) and x-ray diffraction (XRD). The Rockwell hardness and residual stress in different regions of the Ti-6Al-4V welded joints were assessed before and after treatment. Tension tests were then performed to investigate the effect of HESP on the welded samples. Experimental results showed that an Surface nanocrystallization (SNC) layer can be prepared on a Ti-6Al-4V welded joint via HESP. The average grain size of the SNC layer was approximately 30 nm after HESP. HESP also resulted in a higher surface hardness compared with that of the original sample. After treatment, surface compressive residual stresses formed in welded joints, and the residual peak stress of the weld zone was decreased from 650 MPa to -638 MPa. The surface hardness and surface residual stress were distributed more uniformly on the surface of the welded joint. After treatment, the tensile properties were improved.