EFFECT OF Nd:YAG LASER MELTING ON SURFACE ENERGY OF AZ91D Mg ALLOY

Laser surface melting is known to alter surface energy and wettability of a few engineering materials, but its effect on magnesium alloys has never been reported. Effort was made to study how Nd:YAG laser irradiation influenced surface energy of an AZ91D magnesium alloy. Contact angle measurement was carried out using three types of liquids to make it possible to calculate the surface energy quantitatively based upon the acid–base theory. The laser irradiation was found to enhance surface wettability significantly and lead to a drastic increase in surface energy from 25.82 to 40.78 mJ/m2. The change in surface property was attributed to the laser-induced refinement of α-Mg and β-Mg17Al12 phases and enrichment of Al in the microstructure.