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制备了3种不同铒元素含量的Al-Mg-Si合金,利用显微组织观察(OM)、扫描电镜(SEM)、能谱分析(EDS)、X射线衍射物相分析(XRD)、硬度测试与差热分析(DSC)等分析测试手段,研究元素Er在Al-Mg-Si合金中的存在形式,并运用Miedema模型对Er在Al-Mg-Si合金中的热力学行为进行了分析。结果表明:在Al-Mg-Si合金中,Er元素的添加可以有效细化铸态晶粒,减小枝晶间距。Al-Mg-Si-Er合金凝固过程时可形成α(Al)+Er5Si3初生共晶组织,显微组织呈鱼骨状,合金中大量Er5Si3相的形成,使可时效析出的Mg2Si相减少,合金硬度值减小。原子亲和力和金属间化合物生成焓的计算结果显示Er-Si原子之间的亲和力大于Mg-Er和Al-Er原子之间的亲和力,且铒硅二元金属间化合物生成焓负值更大,熔点更高,因此,在Al-Mg-Si-Er合金中,Er原子与Si原子优先形成铒硅相。
Three kinds of Al-Mg-Si alloys with different erbium content were prepared and characterized by means of OM, SEM, EDS, XRD, hardness test And differential thermal analysis (DSC). The thermodynamic behavior of Er in Al-Mg-Si alloy was analyzed by Miedema model. The results show that in the Al-Mg-Si alloy, the addition of Er can effectively refine the as-cast grains and reduce the dendrite spacing. The α (Al) + Er5Si3 primary eutectic microstructure was formed during the solidification of Al-Mg-Si-Er alloy. The microstructure of the Al-Mg-Si-Er alloy was fish bone. The formation of a large amount of Er5Si3 phase in the alloy decreased the aging precipitated Mg2Si phase. Hardness value decreases. The calculated results of atomic affinity and enthalpy of formation of intermetallic compounds show that the affinity between Er-Si atoms is greater than the affinity between Mg-Er and Al-Er atoms, and the formation enthalpy of erbium-silicon binary intermetallic compounds has a negative value greater. The melting point Therefore, in the Al-Mg-Si-Er alloy, Er atoms and Si atoms preferentially form the erbium silicon phase.