Laser-processing-induced phase transformation in Zn-Al-based alloy

Microstructure and phase transformation of a furnace-cooled eutectoid Zn-Al-based alloy were studied after laser beam bombardment using low-angle x-ray diffraction (XRD) and backscattered scanning electron microscopy (BSEM). It was found that the microstructure of the laser-beam-treated specimen consisted mainly of the supersaturated Zn-rich β′sphase particulates of about 1-2 μm in diameter. Three structure morphologies were observed. Microcracking occurred in the laser-beam-affected zone during laser processing. Two laser-processing-induced phase transformations, i.e., decomposition of the η′FCphase and a four-phase transformation, were detected using XRD and BSEM techniques, similar to phase transformations that occurred in the same eutectoid Zn-Al-based alloy after various thermal and thermomechanical processing procedures.