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采用熔铸法制备了Zn含量分别为12wt%、14wt%、16wt%和18wt%的4种高锌Al-Zn-Cu合金,并对合金的显微组织、相组成和力学性能进行了详细分析,重点探讨了合金中Zn的存在形式及其对力学性能的影响。结果表明,4种不同锌含量的合金均由花瓣状的α-Al枝晶和晶界相Al_2Cu组成,尽管Zn含量的增加导致晶界Al_2Cu相的数量增加以及α-Al枝晶的细化,但Zn主要以固溶形式存在于固溶体相α-Al中。Zn含量的增加显著提高Al-Zn-Cu合金的强度而明显降低塑性的主要原因可归于Zn对α-Al固溶体的固溶强化效应。Al-Zn-Cu合金的断裂由韧窝状断裂向解理断裂转变。
Four kinds of high-zinc Al-Zn-Cu alloys with Zn content of 12wt%, 14wt%, 16wt% and 18wt% were prepared by the cast method. The microstructure, phase composition and mechanical properties of the alloy were analyzed in detail. The existence of Zn in the alloy and its influence on the mechanical properties were mainly discussed. The results show that all the four alloys with different zinc contents consist of petaloid α-Al dendrite and grain boundary phase Al 2 Cu. Although the amount of Al 2 Cu phase in the grain boundary increases and the grain refinement of α-Al dendrite increases with the increase of Zn content, However, Zn exists mainly as a solid solution in the solid solution phase α-Al. The main reason for the significant decrease in ductility of Al-Zn-Cu alloy with the increase of Zn content is attributed to the solid-solution strengthening effect of Zn on α-Al solid solution. The fracture of Al-Zn-Cu alloy changes from dimpled fracture to cleavage fracture.