Plasticity of light metal matrix composites under anodic polarization

Light metal matrix composites (MMCs), reinforced with ceramic particles, demonstrate an improvement in strength, elasticity, and wear resistance with regards to matrix alloys. Unfortunately, the plasticity of MMCs is rather low, and their hardness is relatively high. Therefore, there are serious problems in formability and machinability of these materials. In the present study, an improvement in the surface plasticity of such light MMCs as Al 6063-10% SiC (AMC) and Mg AZ31-10% SiC (MgMC) as well as the high-strength Al 7075 T6 alloy under anodic polarization was observed. To assess the effect of polarization on plasticity of composites, the relative Vickers hardness (RVH) was used, which was found as the square of the ratio of the depth of penetration of the indenter into the metal in air and in the electrolyte. In the acid electrolyte 0.3 M HCl + 0.6 M NaCl, both composites demonstrated a very intense drop in RVH at low current densities (≤1 mA cm^-2), while in tap water a small effect of anodic polarization on the relative hardness was obtained. Corrosion rate of an AMC in 0.6 M NaCl solution was much higher with respect to matrix alloy.