(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 中南大学 轻合金研究院，长沙 410083；
3. 中南大学 高性能复杂制造国家重点实验室，长沙 410083)
摘 要: 采用硬度测试、拉伸性能测试、透射电镜分析(TEM)、扫描电镜(SEM)断口形貌观察以及疲劳性能测试等研究3种时效工艺对轨道交通用Al-Zn-Mg-Cu合金组织和性能的影响。结果表明：三级时效(120 ℃, 0.5 h, WC)+(65 ℃, 240 h)+(120 ℃, 24 h)态合金的抗拉强度达到640.2 MPa，高于二级时效(120 ℃, 4 h)+(175 ℃, 6 h)态合金的477.7 MPa和四级时效(105 ℃, 7 h)+(120 ℃, 7 h)+(155 ℃, 4 h)+(175 ℃, 4 h)态合金的483.5 MPa；二级时效和四级时效态合金中微米量级第二相粒子数量多，且尺寸较大；而三级时效态合金中，无论是微米量级第二相还是晶内η′析出相，其尺寸都小于二级和四级时效态合金的；3种时效工艺疲劳试验试样的裂纹源均起于试样表层，在频率50 Hz、应力比为-1的加载条件下，二级时效、三级时效和四级时效态合金的疲劳极限分别约为 145、239和180 MPa。
关键字: 7050铝合金；时效工艺；拉伸性能；疲劳极限
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Light Alloy Research Institute, Central South University, Changsha 410083, China;
3. State Key Laboratory of High Performance and Complex Manufacturing, Central South University, Changsha 410083, China）
Abstract:The effects of aging system on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy for rail transportation were investigated by hardness measurement, tensile test, transmission electron microscopy, scanning electron microscopy observation and fatigue performance tests. The results show that after the three-stage aging (120 ℃, 0.5 h, WC)+(65 ℃, 240 h)+(120 ℃, 24 h) treatment, the tensile strength of alloy is 640.2 MPa, which is higher than 477.7 MPa of the two-stage aging (120 ℃, 4 h)+(175 ℃, 6 h) and 483.5 MPa of the four-stage aging (105 ℃, 7 h)+(120 ℃, 7 h)+(155 ℃, 4 h)+(175 ℃, 4 h). The two-stage aging and four-stage aging samples have the larger number of second phase particles and larger size. However, for the three-stage aging samples, whether it is the micron scale second phase, or intragranular η′ precipitates, their sizes are less than those of the two-stage and four-stage aging samples. The crack sources of three kinds of samples in the aging process fatigue test all start on the sample surfaces. The fatigue limits of the two-stage aging, three-stage aging and four-stage aging alloys are about 145 MPa, 239 MPa and 180 MPa, respectively.
Key words: Al-Zn-Mg-Cu alloy; aging system; tensile property; fatigue life
