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 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 Al_2 Cu,Al_2Cu containing a trace of Mg and Al_2 Cu Mg phase. After the optimized two-step homogenization treatment, most of the nonequilibrium eutectic phase and second phase（Al_2Cu Mg and Al_2 Cu Li） dissolve into α（Al） matrix. A small amount of Fe-rich and Mn-rich phase are still distributed at the grain boundaries. Al_2 Cu Mg phase melting point is lower than that of Al_2 Cu phase. Al_2 Cu Mg and Al_2 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.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2017年第1期28-34,共7页
Rare Metal Materials and Engineering
