Wear and corrosion resistance of a laser powder bed fused AZ91D magnesium matrix composite with TiC reinforcement

The surface performance of magnesium alloys significantly influences their service properties and life in extremely harsh environments. Ceramic modified magnesium alloys cause microstructure refinement and phase variations, affecting their corrosion and wear resistance. In this work, the AZ91D magnesium alloy and a TiC-reinforced magnesium matrix composite were manufactured via laser powder bed fusion (LPBF) to investigate the effect of TiC addition on the relative density, microstructure, wear and electrochemical corrosion resistance of the alloy. The results show that the TiC addition improves the densification of the composite, decreasing the porosity to 0.04 % and promoting the precipitation of Mg17Al12 in the matrix. The grains change from coarse columnar to fine equiaxed ones and a mean size of similar to 4.2 mu m is obtained. The composite exhibits high elastic modulus of 54 +/- 1 GPa, microhardness of 108 +/- 1 HV0.2, and nanohardness of 1.5 +/- 0.03 GPa. The wear resistance of the TiC/AZ91D composite increases with a decrease of the coefficient of friction and wear rate. This is because the TiC addition increases the hardness of the alloys and induces oxide formation, and promotes a change from abrasive wear to oxidative wear. The TiC/AZ91D composite exhibits a uniform corrosion film, and high galvanic corrosion resulting from the precipitation of beta-Mg17Al12, leading to a slight decrease in overall corrosion resistance. This work offers an insight into the laser additive manufacturing of magnesium matrix composites with good surface properties for applications in extremely harsh environments.