Mg-6Zn-xCu铸造合金的显微组织及力学性能研究

Study on Microstructure and Mechanics Properties of As-cast Mg-6Zn-xCu Alloys

采用金属型铸造方法制备了Mg-6Zn-xCu(x=1%、3%、5%)镁合金,并通过光学显微镜、X射线衍射和扫描电镜及力学性能测试等手段研究了Cu含量对合金的显微组织和力学性能的影响。结果表明:Cu在合金中主要以CuMgZn相存在,且随着Cu量的增加,其数量增加;在凝固过程中,CuMgZn富集在已结晶的α-Mg表面,阻碍了其长大,从而细化了晶粒,但过量的CuMgZn偏聚晶界偏聚,引起局部的应力集中,对合金的力学性能产生负面影响;随着Cu含量的增加,合金的力学性能逐渐降低,加入1%Cu时,合金的抗拉强度和伸长率达到最大值,分别为208MPa和13.5%;随着Cu含量的增加,拉伸断口由准解理断裂向解理断裂和沿晶断裂转变。

Mg-6Zn-xCu （1,3 and 5wt.% ） alloys have been prepared by metal mould casting method. The effect of Cu content on microstructure and mechanics properties of alloys have been investigated by OM, SEM, XRD and mechanics apparatus. The results showed that the CuMgZn phases were formed when added Cu elements inalloys, and the amount of CuMgZn compounds increased with increasing of Cu content. Due to the CuMgZn compounds enriched on the surface of α-Mg during solidification, the growth of α-Mg was difficultl and then grains were refined effectively. But an excess of CuMgZn compounds precipitates at grain boundaries resulted in local stress concentration, thus it was detrimental to the mechanics properties of alloys. Consequently, with addition of 1% Cu, the values of ultimate tensile strength and elongation were 208MPa and 13.5% respectively. The tensile fracture surfaces changed from quasi-cleavage to cleavage and intergranular fracture with increase of Cu content.