Interface microstructure and mechanical properties of zinc-aluminum thermal diffusion coating on AZ31 magnesium alloy

The zinc-aluminum (Zn-Al) alloy coating with excellent wear and corrosion resistance was fabricated on the surface of magnesium substrate (AZ31) using thermal diffusion technique. The microstructure, phase constitution and chemical composition were investigated. The experimental observation exhibited that the interfacial microstructures were composed of network eutectic structures and lamellar eutectoid structures at heating temperature of 350 °C for holding time of 30 min under 0.1 MPa in a vacuum of 10−3 Pa. X-ray diffraction (XRD) pattern analysis identified that α-Mg, Mg7Zn3 and MgZn phases were formed in the diffusion layer. The interdiffusion of Mg and Al atoms were restricted by Mg-Zn intermetallic compounds (IMCs). The value of microhardness at the diffusion layer increased due to the formation of Mg-Zn eutectic phases. This technique is beneficial to improving poor wear and corrosion resistance of magnesium alloy.