Deformation of single and multiple laser peened TC6 titanium alloy

Laser peening without coating (LPwC) was done on the titanium TC6 alloy at a wavelength of 532 nm using an Nd:YAG laser. The laser power densities of 3, 6 and 9 GW cm−2 were used to peen the samples. Samples were also peened multiple times (1, 3 and 5 passes) at 6 GW cm−2. Microhardness showed an overall 23% increase from the baseline value. Further, softening of α phase in the bulk was observed above 6 GW cm−2 in the samples peened once and above 1 pass in multiply peened samples. A similar trend was observed from the residual stress analysis of the samples. The maximum compressive residual stress was −1780 MPa at a depth of 50 μm at 9 GW cm−2. The observed softening of α phase was proposed due to adiabatic heating. Microstructural changes due to adiabatic heating resulting in increased β volume fractions were observed and confirmed by synchrotron radiation measurements.