Precipitation sequence of η phase along low-angle grain boundaries in Al-Zn-Mg-Cu alloy during artificial aging  

Al-Zn-Mg-Cu合金在时效过程中η相沿小角晶界的析出序列(英文)

作　　者：李茂华[1] 杨延清[1] 冯宗强[1] 黄斌[1] 罗贤[1] 娄菊红[1] 汝继刚[2] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,西安710072 [2]北京航空材料研究院,北京100095

出　　处：《Transactions of Nonferrous Metals Society of China》2014年第7期2061-2066,共6页中国有色金属学报（英文版）

基　　金：Project(51071122)supported by the National Natural Science Foundation of China;Project(B08040)supported by the Program of Introducing Talents of Discipline to Universities,China("111"Project)

摘　　要：The precipitation sequence of η（MgZn2） phase along low-angle grain boundaries in Al-Zn-Mg-Cu alloy was investigated by examining samples aged at 135 ℃ for various times from 5 min to 6 h. High resolution transmission electron microscopy （HRTEM） observations and energy dispersive X-ray spectroscopy （EDX） analysis indicate that the precipitation sequence of η phase along low-angle grain boundaries should be supersaturated solid solution （SSS）→vacancy-rich clusters （VRC）→GP Ⅱ zones→η＇→η. Based on the theory of non-equilibrium grain boundary segregation （NGS） and non-equilibrium grain boundary co-segregation （NGCS）, the excessive solute elements gradually segregate to the grain boundaries by the diffusion of the solute-vacancy complex during aging treatment. The grain boundary segregation plays an important role in the nucleation and growth of VRC, GP Ⅱ zones, η＇ phase as well as η phase.采用高分辨透射电子显微镜和高角环形暗场扫描透射电子显微镜结合X射线能谱仪,研究Al-Zn-Mg-Cu合金η相沿小角晶界的析出序列。试样在135°C分别时效5 min到6 h。结果表明,η相在小角晶界的析出序列是:SSS→VRC→GP II区→η′→η。基于非平衡晶界偏析和非平衡晶界共偏析理论,在Al-Zn-Mg-Cu合金时效过程中,通过溶质-空位对的扩散,大量的沉淀形成元素偏析到晶界。这种晶界偏析在VRC、GP II区、η′相和η相的形核和生长中起重要作用。

关 键 词：Al-Zn-Mg-Cu alloy AGING low-angle grain boundaries grain boundary segregation precipitation sequence 

分 类 号：TG146.21[一般工业技术—材料科学与工程] TG156.92[金属学及工艺—金属材料]