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采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)和拉伸试验机研究了Si含量变化对Mg-4Al-1Zn-xSi(x=0.5,1.0,2.0,质量分数,%,下同)合金显微组织和力学性能的影响。结果表明:随着Si含量的增加,合金中的α-Mg基体组织逐渐细化;β-Mg17Al12相由点状(块状)逐渐转变为网状分布于晶界上;大量粗大的汉字状Mg2Si相沿晶界或穿晶分布。Si含量从0.5%增加到1.0%和2.0%时,α-Mg基体晶粒的平均尺寸从25μm分别细化到20μm和10μm;汉字状Mg2Si颗粒的平均尺寸从5μm分别增大到10μm和100μm;合金的硬度逐渐提高;其抗拉强度、屈服强度和伸长率先降低后升高;合金拉伸断裂形式为准解理脆性断裂。
The effect of Si content on the microstructures of Mg-4Al-1Zn-xSi (x = 0.5,1.0,2.0, mass fraction, %, The same below) alloy microstructure and mechanical properties. The results show that the microstructure of α-Mg matrix in the alloy is gradually refined with the increase of Si content. The β-Mg17Al12 phase is gradually changed from dot-like (block) to reticular distribution on the grain boundary. A large number of coarse Chinese characters Mg2Si Phase along the grain boundary or transgranular distribution. When the content of Si increased from 0.5% to 1.0% and 2.0%, the average size of α-Mg matrix grains was refined from 25μm to 20μm and 10μm, respectively. The average size of Chinese-character Mg2Si particles increased from 5μm to 10μm and 100μm, respectively. The hardness of the alloy gradually increased; its tensile strength, yield strength and elongation decreased first and then increased; tensile fracture of alloy was quasi-cleavage brittle fracture.