ABSTRACT
This chapter describes the current research and development in laser surface processing of magnesium (Mg) alloys. The processes, challenges, and research issues in short pulse and ultrashort pulse laser processing of Mg AZ91D and Mg AZ31B are discussed. Some new insights on the laser-induced surface structural changes and surface coloration in relation to the surface morphologies are presented. A nanosecond pulse Nd:YAG laser is used to discuss the beam interaction with AZ91D Mg alloy. The formation of micron-size craters with a broad distribution of sizes has been observed during the nanosecond pulse processing. The formation mechanism of the microcraters is discussed, which may be caused by the combined effect of explosive volume boiling and generation of cavitation bubbles during laser melting. A femtosecond ultrafast laser is discussed for its interactions with AZ31B Mg alloy. Iridescent effect of AZ31B Mg alloy is observed on the surface induced by scanning the femtosecond laser beam in an atmospheric environment. The experimental results reveal that the surface coloration is mainly attributed to the nanoripples with a broad distribution of periods acting as diffraction gratings, which leads to interference colors. The intensity of the structural colors is significantly influenced by the morphology evolution of the ripple structures in the fs laser processing. Finally, the process of laser melting deposition of a rare earth-based Mg alloy is presented. A continuous-wave CO2 laser is used to study the microstructure evolution and mechanical properties enhancement of the rare earth-based Mg alloys by LMD.
