Surface morphology and structural characterization of high-purity iron irradiated with Nd:YAG pulsed laser

Abstract

Mechanically polished 4N pure iron specimens were irradiated under a vacuum of 10−3Torr with Q-switched pulsed Nd:YAG laser for a number of laser shots ranging from 500 to 1500 with an increment of 250 shots. Surface morphology of laser irradiated specimens was examined by both optical and scanning electron microscopes. Heat affected area and its perimeter were found to increase with the increase in number of laser shots. Scanning electron micrographs revealed the formation of cracks, pits, and ripples as well as hydrodynamic and exfoliational sputtering of the material. Rose-like structure was developed on the target surface exposed to 500 laser shots due to the molten material movement caused by laser-induced plasma-recoil pressure. Substantial amorphization in the target occured on irradiation with 1000 laser shots. XRD study of the irradiated specimens revealed that crystallite size decreases while dislocation line density and microstrain increase on increasing the number of laser shots.