Microstructure and Dry Sliding Wear Behavior of Mg-Y-Zn Alloy Modified by Laser Surface Melting

Mg-11Y-2.5Zn alloy was surface-melted using a 6.0 kW continuous wave CO2 laser as a heat-generating source. X-ray diffractometer, laser optical microscopy, and Vickers hardness indentation were used to characterize the microstructure and hardness of the Mg-11Y-2.5Zn alloy. The results show that the microstructure in the laser-melted zone can be greatly refined and hardness is slightly improved. Dry sliding tests were performed on the as cast and laser surface-melted Mg-11Y-2.5Zn alloys using a pin-on-disk configuration. Coefficients of friction and wear rates were measured within a load range of 20-320 N at a sliding velocity of 0.785 m/s. Laser surface-melted Mg-11Y-2.5Zn alloy exhibited good wear resistance when compared with the as cast one under given applied load conditions, which has been explained by refining of the microstructure in the melted zone. Morphologies of worn surface on the as cast and laser surface-melted Mg-11Y-2.5Zn alloys were examined using scanning electron microscopy. Four wear mechanisms, namely abrasion, delamination, thermal softening, and melting, have operated.