(中南大学 粉末冶金国家重点实验室，长沙 410083)
摘 要: 通过电子背散射衍射实验对复合添加稀土元素Yb和过渡族元素Zr或Cr的Al-Zn-Mg-Cu超高强合金的晶粒尺寸、晶界类型、晶界特性进行研究，分析了微合金化后的晶界特性对合金力学性能和局部腐蚀(晶间腐蚀和剥落腐蚀)的影响。结果表明：与复合添加Yb和Cr相比，复合添加Yb和Zr的Al-Zn-Mg-Cu合金具有最佳的再结晶抑制效果；高温固溶-时效处理后，合金晶粒尺寸由40 μm显著细化到2.3 μm，再结晶程度从98%下降到3%，Σ27晶界所占比例大幅提高，小角度晶界所占比例由8%提高到51%；亚晶界上的析出相与晶内的析出相近似，合金的力学性能和耐腐蚀性能显著提高，使得合金拉伸断裂时，沿晶断裂分数大幅降低，合金的力学性能和耐腐蚀性能显著提高。
关键字: 稀土Yb；过渡族元素；电子背散射衍射；力学性能；腐蚀
（State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China）
Abstract:The electron backscatter diffraction (EBSD) experiments were conducted to study the grain size, grain boundary types and feature in Al-Zn-Mg-Cu super high-strength alloys by complex additions of rare earth element Yb and transition element Zr or Cr. The effect of grain boundary character on the mechanical properties and localized corrosion (Intergranular corrosion and exfoliation corrosion) of Al-Zn-Mg-Cu alloy was investigated. The results show that, comparing with Yb and Cr addition, the recrystallization of Al matrix can be strongly inhibited by complex additions of Yb and Zr to Al-Zn-Mg-Cu alloy. After high temperature solution-T6 temper, the average grain size and recrystallized volume fraction decrease from 40 μm and 98% to 2.3 μm and 3%, respectively. The Σ27 accounted for the highest proportion of grain boundaries, the proportion of small-angle grain boundaries increases from 8% to 51%. The precipitates on the subgrain boundaries are similar with those in the grain, leading to the decrease of the volume fraction of fracture along recrystallized grain, and the mechanical properties and resistance to corrosion of the alloys increase sharply.
Key words: rare earth Yb; transition element; electron backscatter diffraction; mechanical property; corrosion
