Tailored Surface Characteristics of AZ91 Mg Alloy Induced by Laser Surface Melting

The AZ91 Mg alloy was surface melted by a DPSS Nd:YVO4 laser using different pulse lengths. Characterization of the Mg alloy and laser melted layers was accomplished utilizing XRD, SEM, and EDS. The impact of laser surface melting (LSM) on hardness and corrosion characteristics was investigated using hardness tester and potentiodynamic polarization test, respectively. The results indicated that LSM clearly reduced the crystallite size of alpha-Mg to be in the range of 206-251 nm for the laser melted layers compared to 369 nm for the Mg alloy. The highest melted layer thickness of 13.7 mu m was obtained using a pulse length of 100 nm. The concentration of Al and Zn in the melted layers changed with increasing pulse length due to the evaporation of Mg. The hardness was enhanced due to the LSM, especially with a decrease in the pulse length owing to the rapid solidification where the highest hardness value of 89.1 HV0.1 was observed using a pulse length of 15 ns. The LSM significantly boosted the corrosion resistance of Mg alloy mainly owing to the increase in Al concentration. The corroded surface of all laser melted layers was characterized by a sponge-like structure. [GRAPHICS] .

Automated summary

The AZ91 Mg alloy was surface melted using a DPSS Nd:YVO4 laser with different pulse lengths. Characterization of the alloy and laser melted layers was done using XRD, SEM, and EDS. The impact of laser surface melting (LSM) on hardness and corrosion characteristics was investigated through hardness testing and potentiodynamic polarization test. Results showed that LSM reduced the crystallite size of alpha-Mg and increased hardness. Moreover, LSM improved the corrosion resistance of the Mg alloy.