The effect of Nd:YAG laser parameters on the microstructure, hot cracking susceptibility and elemental evaporation of surface melted AZ80 magnesium-based alloy

Abstract

Laser surface melting (LSM) is an environmentally-safe technique in which melting and solidification occur in a very short reaction time, without affecting the bulk of the material. On the other hand, today, the use of magnesium as a very light metal, with excellent specific resistance, excellent sound damping and good casting ability, etc., has been expanded. Also, having low absorption of laser beams, strong tendency to oxidation, high thermal conductivity, etc are important drawbacks of these alloys. Today there is widespread agreement on the better resistance to hot cracking of magnesium alloys with Nd:YAG laser due to its shorter wavelength by comparison with CO2 laser. This research aims to investigate the effect of Nd:YAG laser surface melting parameters on the microstructural, phase changes and hot cracking susceptibility of the AZ80 magnesium base alloy. The results of current research showed that sample 5 with voltage, frequency, pulse duration and gas flow rate of 250V, 10 Hz, 4 ms, 5lit/min, respectively, and constant speed of 1 mms showed a remelted zone with minimum hot cracks and other defects. In conclusion by controlling the laser parameters such as pulse duration, shielding gas flow rate, laser frequency, scanning rate and the laser power, the susceptibility to hot cracking including both solidification and liquation cracking are significantly decreased.