Effect of confinement on surface modification for laser peen forming without protective coating

In this study, multiple laser peen forming (LPF) experiments were conducted for micro-bending aluminum alloy 1060, OHFC copper, and commercially pure titanium specimens under confinement media of water and air. Surface morphological and compositional changes as well as the mechanical properties of the treated specimens were experimentally analyzed to determine the effect of confinement during LPF. Significantly different surface morphological characteristics were captured and quantitatively analyzed. Clear feed mark patterns were found to be caused by the laser pulse feed for all materials under air confinement. Under water confinement, specimen surfaces appeared in a tarnished, featureless surface texture without showing any feed marks. The mechanisms of laser-material interaction during LPF were studied for various materials under different confinement media. The surface chemical composition change was investigated on the surface and in depth. More chemical composition change was observed under air confinement than under water, while it was limited within the topmost 10-30 nm under both water and air confinement.