【摘要】 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Al₂Cu、含有少量Mg元素的Al₂Cu相,以及Al₂Cu 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（Al₂Cu Mg和Al₂Cu 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。Al₂Cu Mg相的熔点低于Al₂Cu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。更多还原

【Abstract】 The microstructure evolution and composition distribution of the industrially cast Al-Cu-Li alloy during single-step and tow-step homogenization were investigated by optical microscopy（OM）, scanning electron microscopy（SEM）, energy dispersive spectrometry（EDS）, X-ray diffraction（XRD） and differential scanning calorimetry（DSC）. The results show that severe dendrite segregation exists in the Al-Cu-Li as-cast alloy. Cu distributes unevenly from the grain boundary to inside. But the changes of Mg,Zn, Mn and Ag are not obvious. At the grain boundary, there are a large amount of coarse nonequilibrium eutectic phases Al₂ Cu,Al₂Cu containing a trace of Mg and Al₂ Cu Mg phase. After the optimized two-step homogenization treatment, most of the nonequilibrium eutectic phase and second phase（Al₂Cu Mg and Al₂ Cu Li） dissolve into α（Al） matrix. A small amount of Fe-rich and Mn-rich phase are still distributed at the grain boundaries. Al₂ Cu Mg phase melting point is lower than that of Al₂ Cu phase. Al₂ Cu Mg and Al₂ Cu phase gradually dissolve into the matrix at 495 and 515 °C, respectively. The suitable homogenization treatment for the Al-Cu-Li alloy is 495 °C /24 h + 515 °C/24 h. The results of homogenization can be described by homogenization kinetic analysis,which agrees well with experimental observation.更多还原