(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 中南大学 有色金属材料科学与工程教育部重点实验室，长沙 410083；
3. 中南大学 有色金属先进结构材料与协同创新中心，长沙 410083；
4. 河南航天精工制造有限公司，信阳 464000)
摘 要: 通过电导率、力学性能测试和慢应变速率拉伸试验，结合扫描电镜(SEM)、电子背散射衍射(EBSD)等微观组织表征方法，研究固溶处理对紧固件用Al-Zn-Mg-Cu合金挤压棒材电导率、力学性能和应力腐蚀性能的影响。结果表明：强化固溶较单级固溶处理，合金具有较好的电导率和力学性能。随着强化固溶中二级固溶时间的延长和一级、二级固溶温度的提高，电导率和伸长率随之提高，硬度和强度随之降低。其中，二级固溶时间的影响最大，其次是二级固溶温度，一级固溶温度的影响最小。随着二级固溶时间的延长和温度的提高，应力腐蚀敏感指数(ISSRT)先减小后增大，主要因为残余粗大相减少，降低腐蚀敏感性，而后再结晶分数提高和晶粒长大，恶化应力腐蚀性能。在满足紧固件用Al-Zn-Mg-Cu合金对电导率要求(≥38.0%IACS)的基础上，获得良好综合性能适宜的热处理工艺为：((450 ℃, 1 h)+(490 ℃, 1 h))固溶处理+ ((120 ℃, 5 h)+(177 ℃, 16 h))时效处理，合金的抗拉强度、硬度、电导率和应力腐蚀敏感指数分别为532.8 MPa、158.0 HV、38.5%IACS和ISSRT为2.0%。
关键字: Al-Zn-Mg-Cu合金；组织；强化固溶；应力腐蚀性能
（1. School of Material Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China;
3. Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China;
4. Henan Aerospace Precision Machining Co., Ltd., Xinyang 464000, China）
Abstract:The effects of solution treatment on conductivity, mechanical properties and stress corrosion resistance of the Al-Zn-Mg-Cu alloy extruded bars for fasteners were investigated by electrical conductivity, mechanical properties and slow strain rate tensile tests, combined with scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD). The results show that the alloys treated by enhanced solution have better conductivity and mechanical properties than single-stage solution treated alloys. The conductivity and elongation increase and the hardness and strength decrease with the extending of secondary solution time and the increasing of primary and secondary solution temperature. While the second solution time has the most influential on conductivity and mechanical properties of alloys, which is followed by second solution temperature, and first solution temperature has the least effect. The stress corrosion sensitivity index (ISSRT) decreases and then increases with the extending of the second solution time and the increasing of temperature. The decrease of residual coarse phase is the mainly responsible for the decreasing of corrosion sensitivity. And then, the crystallization fraction increases and the grain grows, which worsens the stress corrosion performance. On the basis of meeting the requirements of the conductivity(≥38.0%IACS) of Al-Zn-Mg-Cu alloy used for fasteners, the suitable heat treatment process for good comprehensive properties are ((450 ℃, 1 h)+(490 ℃, 1 h)) solution treatment+((120 ℃, 5 h)+(177 ℃, 16 h)) aging treatment. The tensile strength, hardness and conductivity of the alloy are 532.8 MPa, 158.0HV and 38.5%IACS, respectively, ISSRT is 2.0%.
Key words: Al-Zn-Mg-Cu alloy; structure; enhanced solid solution; stress corrosion resistance
