Laser surface forming of AlCoCrCuFeNi particle reinforced AZ91D matrix composites

• LMI was used to produce AlCoCrCuFeNi metal particles reinforced MMC on AZ91D.
• AlCoCrCuFeNi HEA metal reinforcements were stable in the formed MMC.
• The mixing enthalpy played an important role in the formation of MMC.
• The tribological properties of MMC were significantly improved.
• The reinforcing particles and AZ91D had different wear mechanisms.

Traditionally, the laser melt injection (LMI) technique can only be used for forming ceramic particles reinforced metal matrix composites (MMCs) for enhancing surface properties of lightweight engineering materials. In this research, the LMI method was employed to form metal particles reinforced MMCs on AZ91D instead. This was viable because of the unique properties of the AlCoCrCuFeNi high-entropy alloy (HEA) metal particles used. The large difference in melting point between the HEA and the substrate material (AZ91D), and the limited reaction and the lack of fusion between the HEA and Mg have made it possible that a metal particles reinforced AZ91D composite material was produced. The reason of limited reaction was considered mainly due to the relatively high mixing enthalpy between the HEA constituent elements and Mg. Although there was some melting occurred at the particles surface with some solute segregation found in the vicinity close to the surface, intermetallic compounds were not observed. With regard to the wear resistance of the MMCs, it was found that when the volume fraction of the reinforcement phase, i.e. the HEA particles, reached about 0.4, the wear volume loss of the coating was only one-seventh of that of the substrate material.