(1. 中南大学 轻合金研究院，长沙 410083； 2. 中南大学 材料科学与工程学院，长沙 410083； 3. 中南大学 有色金属先进结构材料与制造协同创新中心，长沙 410083)
摘 要: 采用电导率实验与慢应变速率拉伸实验研究自然时效对Al-Zn-Mg合金型材应力腐蚀断裂的影响，通过扫描电镜、透射电镜等显微组织分析揭示其性能变化的机理。结果表明：Al-Zn-Mg合金型材的电导率随着自然时效时间的延长呈下降趋势，停放至28 d左右基本达到稳定状态，稳定后合金的内、外表层电导率分别为32.20(IACS)%与31.50(IACS)%。自然时效后再进行人工时效((90 ℃, 12 h)+(169 ℃, 11 h))，Al-Zn-Mg合金型材的抗拉强度(Rm)随自然时效时间的延长而显著降低，但合金的抗应力腐蚀性能明显提高；自然时效后，合金内晶界无沉淀析出带变宽(PFZ)，晶界析出相尺寸与间距变大。
关键字: Al-Zn-Mg合金型材；自然时效；电导率；力学性能；应力腐蚀性能
（1. Light Alloy Research Institute, Central South University, Changsha 410083, China; 2. School of Material Science and Engineering, Central South University, Changsha 410083, China; 3. Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China）
Abstract:The effect of natural aging time on stress corrosion cracking of aluminum alloy was investigated by means of electrical conductivity and slow rate tension testing (SSRT). The changing mechanism was analyzed by scanning electron microcopy (SEM) and transmission electron microcopy (TEM). The results show that the electrical conductivity of alloy decreases during natural aging time at room temperature and reaches a stable value after natural aging about 28 d. The electrical conductivities of different surfaces of alloy are 32.2(IACS)% and 31.5(IACS)%, respectively. The stress corrosion cracking resistance can be improved after natural aging time at room temperature. The strength decreases sharply. The grain boundary precipitates distribute coarsely and sparsely after natural aging time about 28 d. The precipitate free zone (PFZ) width becomes broaden, and the alloy possesses the best resistance to SCC.
Key words: Al-Zn-Mg aluminum alloy; room temperature parking; electrical conductivity; mechanical property; stress corrosion cracking
