Effects of processing parameters on microstructure and mechanical properties of squeeze-cast Mg-12Zn-4Al-0.5Ca alloy

In this paper, a new magnesium alloy Mg-12Zn-4Al-0.5Ca (ZAX12405) was prepared by squeeze casting. The effects of processing parameters including applied pressure, pouring temperature and dwell time on the microstructure and mechanical properties of squeeze-cast ZAX12405 alloy were investigated. It was found that squeeze-cast ZAX12405 alloy exhibited finer microstructure and much better mechanical properties than gravity casting alloy. Increasing the applied pressure led to significant cast densification and a certain extent of grain refinement in the microstructure, along with obvious promotion in mechanical properties. Lowering the pouring temperature refined the microstructure of ZAX12405 alloy, but deteriorated the cast densification, resulting in that the mechanical properties firstly increased and then decreased. Increasing the dwell time promoted cast densification and mechanical properties just before the solidification process ended. A combination of highest applied pressure (120 MPa), medium pouring temperature (650 degrees C) and dwell time (30 s) brought the highest mechanical properties, under which the ultimate tensile strength (UTS), yield strength (YS) and elongation to failure (E-f) of the alloy reached 211 MPa, 113 MPa and 5.2% at room temperature. Comparing with the gravity casting ZAX12405 alloy, the UTS and E-f increased 40% and 300%, respectively. For squeeze-cast Mg-12Zn-4Al-0.5Ca alloy, cast densification was considered more important than microstructure refinement for the promotion of mechanical properties. (C) 2014 Elsevier Ltd. All rights reserved.