新型Al-Zn-Mg-Cu合金型材回归再时效处理的组织与性能

采用拉伸、硬度、电导率测试和透射电镜分析等方法研究了不同回归处理工艺对Al-Zn-Mg-Cu合金型材组织与性能的影响。结果表明,采用120℃×24 h+180℃×45 min+120℃×24 h回归再时效处理后,合金的抗拉强度、屈服强度、伸长率和电导率分别为613.5 MPa、599 MPa、11.1%和39.2%IASC。与T6态相比,合金在抗拉强度和伸长率相当的情况下,屈服强度和电导率显著提高,合金的抗应力腐蚀性能明显改善。合金晶内为细小的η’相和η相,晶界沉淀相断续分布,伴有较窄的晶界无析出带。

Microstructure and properties during retrogression and re-aging treatment of a new type Al-Zn-Mg-Cu alloy profile

The effect of retrogression and re-aging(RRA) treatment on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy profile was studied by tensile,hardness,electrical conductivity test and transmission electron microscopy.The results show that suitable RRA treatment is pre-aging at 120 ℃ for 24 h,retrogression at 180 ℃ for 45 min,and then re-aging at 120 ℃ for 24 h.In this condition,the tensile strength,yield strength,elongation and electrical conductivity of the alloy profile is 613.5 MPa,599 MPa,11.1% and 39.2%IACS,respectively.Compared to T6 state,the yield strength and electrical conductivity are increased obviously with similar tensile strength and elongation.The stress corrosion cracking(SCC) resistance of alloy is improved significantly.After RRA treatment,the major precipitates in intracrystalline of the alloy are fine η′ and η phases.Discontinuous grain boundary precipitates and narrow precipitate-free zones(PFZ) along the grain boundary are observed clearly.