Void shrinking process and mechanisms of the diffusion bonded Ti–6Al–4V alloy with different surface roughness

The diffusion bonding of Ti–6Al–4V alloy with different surface roughness was performed at 5 and 10 MPa. The influence of surface roughness on the void shrinking process and mechanisms was investigated. The average void size increases as the R_a increases from 0.33 to 0.44 μm, while it decreases as the R_a increases to 0.46 μm because of the decreasing of R_λq. The void shrinking mechanisms were analyzed by using the dynamic model of void shrinking. Power-law creep is a dominant mechanism on void shrinking, of which the contribution decreases as the R_a increases from 0.33 to 0.44 μm, while it increases as the R_a increases to 0.46 μm. The influence of surface roughness on the contribution of plastic deformation and surface source mechanism on void shrinking is not significant while that on the contribution of interface source mechanism is dependent on the imposing pressure. The optimizing surface roughness is with a R_a of 0.33 μm and R_λq of 5.38 μm in this study.