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对Al-Cu-Li铸态合金进行单级和双级均匀化处理,通过光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)、X衍射(XRD)和差热分析(DSC)研究合金元素分布和微观组织演化。结果表明:Al-Cu-Li合金铸态组织存在严重枝晶偏析,由晶内到晶界Cu元素分布十分不均匀,Mg、Zn、Mn和Ag变化不明显。晶界处存在大量的非平衡共晶相,主要包括Al_2Cu、含有少量Mg元素的Al_2Cu相,以及Al_2Cu Mg相。经双级均匀化(495℃/24 h+515℃/_24 h)处理后,大部分非平衡共晶相和部分第二相(Al_2Cu Mg和Al_2Cu Li)溶解到合金基体,但仍有部分富-Fe和富-Mn相残留在晶界不能回溶。Al_2Cu Mg相的熔点低于Al_2Cu相,两者分别在495和515℃先后溶解。通过均匀化动力学分析,确定Al-Cu-Li铝锂合金最佳的均匀化制度为495℃/24 h+515℃/24 h,该双级均匀化制度与动力学分析结果一致。
The as-cast Al-Cu-Li alloys were homogenized by one-stage and two-stage homogenization. The microstructures were characterized by OM, SEM, EDS, XRD and DSC ) Studied alloying elemental distribution and microstructure evolution. The results show that the as-cast microstructure of Al-Cu-Li alloy has serious dendritic segregation. The distribution of Cu element from the grain boundary to the grain boundary is not uniform and the changes of Mg, Zn, Mn and Ag are insignificant. There are a large number of non-equilibrium eutectic phases in the grain boundary, including Al 2 Cu, Al 2 Cu phase containing a small amount of Mg, and Al 2 Cu Mg phase. After two-stage homogenization (495 ℃ / 24 h + 515 ℃ / 24 h), most of the unbalanced eutectic phase and some of the second phase (Al 2 Cu Mg and Al 2 Cu Li) dissolved into the alloy matrix, -Fe and rich-Mn phase residue in the grain boundary can not be dissolved. The melting point of Al2Cu Mg phase is lower than that of Al2Cu phase, which dissolves successively at 495 and 515 ℃, respectively. The homogenization kinetics of Al-Cu-Li Al-Li alloy was determined to be 495 ℃ / 24 h + 515 ℃ / 24 h by homogenization kinetic analysis. The two-stage homogenization system is consistent with the kinetic analysis.