Effect of processing environment on laser-induced darkening evolution in magnesium alloy

Laser-induced darkening effect is an important phenomenon for Mg alloys to provide potential engineering applications in product identification, photocatalysts, and bio-optical implants. This work reports darkening evolution on Mg alloy by KrF excimer laser irradiation. Effort was made to study how processing environment influence morphological evolution and chemical variation of laser-irradiated surface. All irradiated surfaces were characterized using Talysurf surface profiler, atomic force microscope, scanning electron microscope and energy dispersive X-ray spectrometer. The results showed that oxygen content played a critical role in determining darkening effect on the Mg alloy, and surface morphology transferred from network structures to granular structures and protruding oxide particles when darkening occurred. Mechanism of laser-induced darkening in Mg alloy was further discussed.