This study investigates the microstructural and functional evolution of hot-extruded ZX21 and ZXM211 magnesium alloys subjected to laser surface melting (LSM). The effects of grain size, crystallographic texture, solute enrichment, and secondary phase characteristics on corrosion resistance and microhardness are systematically examined. LSM homogenizes the microstructure, weakens basal texture, and enables a uniform distribution of secondary phases, shifts corrosion toward less localized corrosion attack. Mn’s high melting point and low diffusivity favored solute retention in α-Mg during LSM, limiting second phase precipitations and promoting grain coarsening. Although potentiodynamic polarization indicated a higher average corrosion rate for LSM-treated ZXM211, the corrosion mode was more uniform, consistent with a lower second-phase fraction and a topology in which Ca₂Mg₆Zn₃ embedded within Mg₂Ca limits effective cathode exposure and mitigates microgalvanic intensification. Despite these favorable microstructural changes, secondary precipitation strengthening remains negligible, and no significant improvement in hardness is observed post-LSM, though both as-extruded and LSM-treated states retained high microhardness.

Biodegradable implants from magnesium (Mg) alloys have emerged in the biomedical field especially in the orthopedic and cardiovascular stent applications owing to their low density, high specific strength, excellent machinability, good biocompatibility, and biodegradability. The primary shortcoming of Mg-based implants is their low corrosion resistance in the physiological environment, which results in premature mechanical integrity loss before adequate healing and the production of excessive hydrogen gas, which is harmful to the body tissues and negatively affects the biocompatibility of the implant. Laser surface modification has recently received attention because it can improve the surface properties such as surface chemistry, roughness, topography, corrosion resistance, wear resistance, hydrophilicity, and thus cell response to the surface of the material. The composition and microstructures including textures and phases of laser-treated surfaces depend largely on the laser processing parameters (input laser power, laser scan velocity, frequency, pulse duration, pressure, gas circulation, working time, spot size, beam focal position, and laser track overlap) and the thermophysical properties of the substrate (solubility, melting point, and boiling point). This review investigates the impacts of various laser surface modification techniques including laser surface melting, laser surface alloying, laser cladding, laser surface texturing, and laser shock peening, and highlights their significance in improving the surface properties of biodegradable Mg alloys for implant applications. Additionally, we explore how different laser process parameters affect its composition, microstructure, and surface properties in each laser surface modification technique.