采用光学显微镜、扫描电镜(附EDAX能量分散光谱系统)和差示扫描量热仪(DSC)等分析手段研究了不同Si含量(0～1.61 wt%)对Mg-8Zn-4Al-0.3Mn(ZA84)合金时效过程的影响.结果表明,合金经固溶处理后显微硬度较铸态下提高了8%左右,其Mg2Si、τ(Mg32(Al,Zn)49)等相基本未溶入基体中.随着ZA84合金中加入Si量的增加,合金的析出相形成激活能呈增加趋势,峰值时效时间由ZA84合金的2 h左右推迟至8 h左右,析出相粗化时间较ZA84合金推迟4 h以上.合金中加入不同含量Si后其峰值时效显微硬度提高幅度为4%～12%.
Effect of silicon on the evolution of microstructure and mechanical properties of Mg-8Zn-4Al-0.3Mn(ZA84)alloy in aging process was investigated by means of optical microscopy,scanning electron microscopy(SEM),energy dispersive X-ray analysis(EDAX)and differential scanning calorimetry(DSC)analysis.The results show that as compared to the as-cast alloys,microhardness enhances about 8% and part dissolution of Mg2Si and τ(Mg32(Al,Zn)49)phases into α(Mg)matrix is observed for the alloys solution-treated at 335 ℃ for 12 h.With the increasing silicon content in ZA84 alloy,the activation energy of precipitation increases,consequently,the aging process is delayed,and microhardness of the alloys peak-aged enhances by 4%-12%.
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