力學性能的影響
(中南大學 材料科學與工程學院, 長沙 410083)
摘 要: 探討了添加微量Ag對高Zn超高強Al-Zn-Mg-Cu合金微觀組織和力學性能的影響。 采用力學拉伸實驗、能譜分析、 掃描電鏡和透射電鏡等手段對不同熱處理方式的合金進行了分析。 結(jié)果表明： 向合金中添加微量Ag會促進粗大相的形成， 消耗合金元素Zn、 Mg， 對合金力學性能不利。 在采用相同的固溶時效工藝時， 加Ag合金的抗拉強度降低了近40 MPa。 但另一方面， Ag可以提高合金的固溶處理溫度， 使殘留的粗大相在更高的固溶溫度下較充分固溶，降低Ag對合金力學性能的不利影響。采用高溫固溶處理后， 加Ag合金T6態(tài)抗拉強度與不加Ag合金相當， 但塑性有所下降。 在時效過程中，微量Ag會促進過渡相的形成， 并提高GP區(qū)和過渡相的穩(wěn)定性， 但使合金到達峰值的時間延長。
關(guān)鍵字: Al-Zn-Mg-Cu合金; 微觀組織; 力學性能； 微量Ag
（ School of Materials Science and Engineering,
Central South University, Changsha 410083, China）
Abstract: 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.
Key words: Al-Zn-Mg-Cu alloy; microstructure; mechanical properties; small addition of Ag
