Al-xZn-2.6Mg合金的显微组织演变与力学性能

Microstructural evolution and mechanical properties of Al-xZn-2.6Mg alloy

  • 摘要: 基于7A62铝合金设计Al-xZn-2.6Mg(x=6.8、 7.1、 7.4)合金,研究Zn含量对铸造、热轧和固溶时效合金显微组织和力学性能的影响,并分析其时效析出行为。结果表明:随Zn含量从6.8%提高至7.4%,铸造合金中第二相含量提高、尺寸增大并趋于网状分布;热轧合金平均晶粒尺寸从20.8 μm减至9.9 μm,且晶界平均取向差和大角度晶界的比例逐渐增加;经固溶时效处理,合金中析出的η′-MgZn2相体积分数明显提高,但尺寸基本保持恒定。由于细晶强化、固溶强化和沉淀强化的共同作用,7.4%Zn合金的力学性能最优,屈服强度、抗拉强度和延伸率分别达到570.9、616.8 MPa和9.7%。

     

    Abstract: Al-xZn-2.6Mg (x=6.8, 7.1, 7.4) alloys were designed based on the 7A62 aluminum alloy. The effects of Zn content on the microstructure and mechanical properties of as-cast, hot-rolled and solution-aged alloys were investigated, and their aging precipitation behavior was also analyzed. The results show that with the increase of Zn content from 6.8% to 7.4%, the content and size of secondary phase in the as-cast alloy increased, and its distribution tended to be mesh-like. The average grain size of the hot-rolled alloys decreased from 20.8 μm to 9.9 μm, and the average misorientation difference of grain boundaries and the proportion of the large angle grain boundaries increased gradually. After solution and aging treatment, the volume fraction of η′-MgZn2 phase precipitated in the alloy was significantly increased, but its size was basically constant. The mechanical properties of 7.4% Zn alloy were the best, with the yield strength, tensile strength, and elongation reaching 570.9, 616.8 MPa and 9.7%, respectively, due to the joint action of fine grain strengthening, solid solution strengthening and precipitation strengthening.

     

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