Microhardness, Microstructure and Electrochemical Efficiency of an Al (Zn/xMg) Alloy after Thermal Treatment

The influence of Mg on the microhardness, microstructure and electrochemical efficiency of Al(Zn/xMg) alloys have been investigated. Al(Zn/xMg) alloys were prepared by metal mould casting method to diminish the process cost and to generate an alloy with homogenous microstructure and less casting porosity. Vickers hardness, X-ray diffraction, scanning electron microscopy and transmission electron microscopy were performed to determine the Mg influence on the AlZn alloy. Electrochemical efficiency was used to relate the influence of Mg with the thermal treatment on the corrosion behavior of the Al(Zn/xMg) alloy. The results reveals the presence of Al32(MgZn)49 phase for two events; the first is when the Mg content is above 5.49% in as-cast condition, and the second after the thermal treatment is carried out at 450 °C for 5 h. The results also show that the microhardness and electrochemical efficiency have been influenced by the presence of Al32(MgZn)49 phase. The addition of Mg modifies the microstructure, increases the content of Al32(MgZn)49 phase and improves the electrochemical efficiency.