Effect of Zn and Solution and Aging on Microstructure and Properties of Mg-4Al-2Ca Alloy

In order to research the influence of Zn on microstructure and mechanical properties of alloys, Mg-4Al-2Ca-xZn alloys were designed by adding Zn alloying element to the alloy. The important results show that the microstructure of the as-cast Mg-4Al-2Ca-xZn(x=0, 2, 4, 6) alloy without Zn is mainly composed of α-Mg, β-Mg17Al12and trace of Al2Ca. Adding Zn(2%, 4%, 6%) to the alloy, Al2Ca phase increases in the microstructure; Mg32(Al, Zn)49, MgZn phases and a small amount of Mg5Zn2Al2compounds are found in the microstructure; With Zn increasing, the primary α-Mg phase for the alloy is significantly refined. When Zn content is 6%, the primary α-Mg phase for the alloy is refined with equiaxed morphology. In the case of the same aging time, the increase of Zn element greatly refined the α-Mg phase, and phase boundary precipitates gradually reduced; Aging at 180 ℃, the results show that when the aging time is 72 h, the hardness of Mg-4Al-2Ca-xZn(x=0, 2, 4, 6) alloy reaches 72.9 HB, 75.1 HB, 80.7 HB and 83.9 HB with x increasing, respectively. In the case of the same aging time, the hardness of Mg-4Al-2Ca-6Zn alloy is the largest. The hardness for the Zn-containing Mg-4Al-2Ca alloy is generally higher than that of no Zn-containing of Mg-4Al-2Ca alloy.