Experimental investigation of laser shock peening on TC17 titanium alloy for thin-wall workpieces

To study the performance and microstructure of TC17 thin-walled parts in shock wave and its reflection wave induced by laser, TC17 titanium alloy samples are processed using YAG laser with the wavelength of 1064 nm, pulse energy of 7J and pulse width of 15ns. Thus, its residual stress, microhardness and microstructure of overlapping shock with different thickness are obtained. The results show that with the thickness increasing, the front micro-hardness increases, and the reverse micro-hardness increases firstly and then decreases. The variation of residual stress with the thickness is consistent with the micro-hardness. The front residual stress maximum reaches -496.5MPa at the thickness of 5mm, and the reverse residual stress maximum reaches -171.1MPa at the thickness of 2mm. With the increase of thickness, the distribution of surface dislocations is more uniform, the grain refinement effect is more obvious, and the strengthening effect is the better. The causes of the variation of the double-sided residual stress field with the thickness are explained by theoretical analysis of the propagation and reflection of the shock wave in the material. The conclusions of this investigation have significance for the optimization of laser shock peening thin-wall workpieces.