添加微量Ag对高Zn超高强铝合金微观组织和力学性能的影响

Effect of small addition of silver on microstructure and mechanical properties of high-zinc super-high strength aluminum alloy

探讨了添加微量Ag对高 Zn超高强 Al Zn Mg Cu合金微观组织和力学性能的影响。采用力学拉伸实验、能谱分析、扫描电镜和透射电镜等手段对不同热处理方式的合金进行了分析。结果表明: 向合金中添加微量Ag会促进粗大相的形成, 消耗合金元素Zn、Mg, 对合金力学性能不利。在采用相同的固溶时效工艺时, 加Ag合金的抗拉强度降低了近40 MPa。但另一方面, Ag可以提高合金的固溶处理温度, 使残留的粗大相在更高的固溶温度下较充分固溶, 降低Ag对合金力学性能的不利影响。采用高温固溶处理后, 加Ag合金T6态抗拉强度与不加Ag合金相当, 但塑性有所下降。在时效过程中, 微量Ag会促进过渡相的形成, 并提高GP区和过渡相的稳定性, 但使合金到达峰值的时间延长。

The effect of small addition of silver on a high-zinc super-high strength Al-Zn-Mg-Cu aluminum alloy was investigated. The mechanical properties of the investigated alloys with or without silver addition undergoing different heat treatment were tested by tensile test. Using transmission electronic microscope (TEM), scanning electronic microscope (SEM) and its energy dispersive spectrometry (EDS), the microstructures of both alloys were analyzed. The results show that small addition of silver promotes the formation of coarse constituent particles within the alloy and consumes hardening alloying elements of Zn and Mg, which may decrease the mechanical properties of the alloy. When the same solid-solution heat treatment and ageing process are employed to the silver-bearing alloy and the silver-free one, the tensile strength of the former alloy at peak-aged condition is decreased by about 40MPa compared to the latter. However, the solution annealing temperature can be increased due to small addition of Ag. When the silver-bearing alloy is solutionized on a higher temperature and aged subsequently, the remained coarse particles in its microstructure can be solutionized into the matrix more sufficiently, and thus makes the alloy obtain a same level of the tensile strength as the silver-free one at peak-age hardening, while its elongation ratio slightly decreases. During ageing, trace addition of Ag enhances the formation of metastable phases and stablizes GP zones and metastable phases to a higher temperature. However, small addition of Ag prolongs the ageing time reaching the peak-age hardening for the studied alloy.