Laser shock peening is conducted to enhance the mechanical properties of metals. Efficient optical absorption of metal surface is desirable to increase the laser shock peening depth. In this work, a method is proposed to regulate the absorption behavior by surface colorizing to increase the affected depth and magnitude of nanosecond laser shock peening (NLSP). Colorized samples are fabricated with high absorption of 400–1500 nm, which is 89% higher than that of un-colorized samples. This regulated optical response is attributed to the multi-reflection/absorption behavior within nano-to-microscale structures. Nano-to-microscale structure-based approaches offer controllable concurrent tailoring of a higher residual stress depth and greater magnitude. Black samples exhibit higher affected depth (64.71%) and magnitude (17.87%) values for the compressive residual stress than un-colorized samples with unit peak power density after NLSP. Experimental results show that coarse grains are refined on surfaces, and the depths of grain refinement and dislocation propagation increase for colorized samples, which exhibit a regulated surface optical behavior. Therefore, this study represents a promising approach that the regulation of surface optical absorption of metals can be incorporated into the improvement of laser shock peening depth.

optical absorption regulation,laser shock peening,affected depth,grain refinement,dislocation generation