Sb对Mg-8Al-12Zn-2Si合金组织与性能的影响

Effects of Sb Addition on Microstructure and Mechanical Properties of Mg-8Al-12Zn-2Si Alloy

采用X-ray衍射仪、光学显微镜(OM)、扫描电镜(SEM)及拉伸试验机等,研究了Sb含量对Mg-8Al-12Zn-2Si铸态合金显微组织及性能的影响。结果表明,合金主要由α-Mg、β-Mg_(17)Al_(12)、Mg_2Zn_(11)和Mg_2Si相组成。合金添加0.2%~0.8%Sb时,Mg_2Si颗粒由原来粗大的十字状、花瓣状和骨骼状逐渐转变为细小的颗粒及短棒状,最大颗粒尺寸由铸态的50μm减小至10μm;当Sb含量增加到1.0%时,Mg_2Si出现粗化,最大颗粒尺寸约30μm。相应地,合金的拉伸强度、屈服强度和伸长率出现先提高后降低,断裂形式为准解理脆性断裂。

The effects of Sb content on microstructure and mechanical properties of alloy Mg-8Al-12Zn-2Si was investigated by means of X-ray diffraction, optical microscopy, scanning electron microscopy and mechanical tests. The results show that the microstructure of the as-cast Mg-8Al-12Zn-2Si alloy consists of the phases of α-Mg matrix, β-Mg17Al12, Mg2Zn11 and Mg2Si. After adding 0.2%-0.8%Sb （mass fraction）, the morphology of the phase Mg2Si changes from primary coarse crosswise, petal-like and skeleton-like to fine polygonal particle and short rod, and the maximum particle size of Mg2Si decreases from 50 μm to 10 μm. The phase Mg2Si becomes coarse when Sb content is increased to 1.0% and the maximum particle size of Mg2Si is around 30 μm. Accordingly, the ultimate tensile strength, yield strength and elongation of the alloys increase at first and then decreases. The fracture mechanism of the alloy is quasi-cleavage brittle fracture.