Effects of Sn and Ca additions on microstructure, mechanical properties, and corrosion resistance of the as-cast Mg-Zn-Al-based alloy

Effects of Sn and Ca additions on microstructure, mechanical properties, and corrosion resistance of the as-cast Mg-6Zn-2Al-based alloy were investigated by SEM, XRD, tensile tests, electrochemical measurements, etc. The higher the Sn content, the higher the yield strength of the Mg-6Zn-2Al-based alloy. Trace Ca addition refined both grains and divorced eutectics in the Mg-Zn-Sn-Al alloys, leading to the best combination of strength and plasticity. Moreover, its influence was more significant for the alloy with a higher Sn content. Furthermore, the combined addition had a beneficial effect on the corrosion resistance improvement of the Mg-6Zn-2Al alloy. The Mg-6Zn-2Al-3Sn-0.2Ca alloy was the most corrosion-resistant alloy among the nine alloys studied, better than AZ91 and ZA85. It could be ascribed to the decrease and the refinement of divorced eutectics, the higher hydrogen overvoltage of Sn and the Ca grain refinement.