Effects of Zn on microstructure, mechanical properties and corrosion behavior of Mg-Zn alloys

In this study, binary Mg-Zn alloys were fabricated with high-purity raw materials and by a clean melting process. The effects of Zn on the microstructure, mechanical property and corrosion behavior of the as-cast Mg-Zn alloys were studied using direct observations, tensile testing, immersion tests and electrochemical evaluations. Results indicate that the microstructure of Mg-Zn alloys typically consists of primary alpha-Mg matrix and MgZn intermetallic phase mainly distributed along grain boundary. The improvement in mechanical performances for Mg-Zn alloys with Zn content until 5% of weight is corresponding to fine grain strengthening, solid solution strengthening and second Phase strengthening. Polarization test has shown the beneficial effect of Zn element on the formation of a protective film on the surface of alloys. Mg-5Zn alloy exhibits the best anti-corrosion property. However, further increase of Zn content until 7% of weight deteriorates the corrosion rate which is driven by galvanic couple effect. (C) 2012 Elsevier B.V. All rights reserved.