Characterisation and mechanical properties of Al/SiC metal matrix composite coatings formed on ZE41 magnesium alloys by laser cladding

Abstract

Metal matrix composite coatings on light alloys are in high demand in the transport industry to reduce the weight of vehicles without a reduction in mechanical properties. Composite coatings with various mixtures of Al, Si, Ti and SiC could be a good option for this application but the high reactivity between the melted aluminium and the reinforcement must be avoided. This study provides a solution for this problem for laser cladding composite coatings on ZE41 magnesium alloys. The method employed consists of the addition of different alloying elements (silicon or titanium) to the composite matrix to avoid Al4C3 formation. A dilution of magnesium from the substrate in the aluminium coating matrix takes place and it produces an important effect in the matrixreinforcement reactions. The microstructure and mechanical properties of the coatings are analysed. The reaction mechanisms are also determined. Al4C3 formation is avoided and the mechanical properties are improved. Introduction The increased awareness of the need to save energy is one of the most important reasons for the development and research of magnesium alloys. The interest in this topic has increased since the 1990s [1,2] because of the oil crisis. Environmental legislation related to polluting gas emission from transport vehicles is becoming more restrictive. For this reason, the aeronautic and automotive transport sectors have been forced to reduce the weight of their components by employing lighter materials [3–5]. Lights alloys, like magnesium, are attracting high attention due to their reduced density, which provides them with high specific values of stiffness and strength. Nevertheless, the use of these alloys is limited because of their low superficial properties. The superficial property modification in these alloys could increase the variety of applications in which they could be used. This study provides a solution for this problem by fabricating aluminium matrix composite (Al-MMC) coatings on magnesium alloys. In previous research, laser cladding with Al/SiC particles (SiCp) on aluminium alloys was successfully carried out [6]. SiC, in the shape of particles, is an excellent reinforcement