摘要
采用Al-10％Sr对Al-20％Si合金进行变质处理,研究Sr对Al-20％Si合金的铸态组织和硬度的影响.Sr可以同时细化Al-20％Si合金中的初晶硅和共晶硅,当Sr的添加量达到0.4％时,初晶硅晶粒细化效果最明显,初晶硅的形貌由大的板块状变为变态后的细的鱼骨状,共晶硅由长针状变为颗粒状.X射线衍射分析表明,在变质后的合金中生成了 Al2Si2Sr相.扫描电镜分析表明,当Sr添加量为0.4％时,Al-20％Si合金样品中出现了白色的菱形组织Al2Si2Sr相,即XRD测试分析中的Al-Si-Sr三元相.硬度试验表明,当Sr的添加量为0.4％时,Al-20％Si合金的硬度达到最大值64 HB,随着Sr添加量的进一步增加,其硬度呈现下降趋势.
Abstract
Al-10％Sr was adopted as modifier to refine Al-20％Si alloy in this paper,and the effect of different additive amount of Sr on the cast structure and properties of Al-20％Si alloy was investigated.The results showed that Sr can simultaneously refine both primary and eutectic silicon in Al-20％Si alloy.When the addition of Sr reaches 0.4％,the grain size of primary silicon is obviously refined.The morphology of primary silicon changes from large plate to fine fishbone,and eutectic silicon changes from long needle to dot.X-ray diffraction(XRD)analysis indicated the formation of Al2Si2Sr phase in the modified alloy.Scanning electron microscopy analysis showed that when the Sr addition amount is 0.4％,white diamond shaped Al2Si2Sr phase appears in the Al-20％Si alloy sample,which is the Al-Si-Sr ternary phase revealed by XRD analysis.The results of hardness test showed that the hardness of Al-20％Si alloy reaches the maximum value of 64 HB when the addition of Sr is 0.4％.With the further increase of Sr addition,the hardness of Al-20％Si alloy shows a downward trend.
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