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采用力学性能测试和电子显微分析技术研究了不同加工处理条件下Al-5.4Zn-2.0-Mg-0.25Cu-0.1Sc-0.1Zr合金的显微组织及性能演变。结果表明:在半连续激冷铸造条件下,铸锭存在晶界偏析,形成了富Zn、Mg的非平衡相和富Fe、Si、Mn的杂质相;经470℃、12 h均匀化处理后,富Zn、Mg的非平衡相溶入基体,仅剩下少量富Fe、Si、Mn的杂质相;与此同时,铸锭合金固溶体分解析出纳米级的Al3(Sc,Zr)相,470℃、12 h是研究合金合适的铸锭均匀化制度;铸锭热变形过程中,随试验温度升高合金强度逐渐降低,伸长率则先增加而后降低,350~400℃的温度范围内合金具有较稳定的热变形抗力和塑性,是合宜的热变形温度范围;合金冷轧板材经470℃、1 h固溶处理后,热变形过程中形成的大量非平衡相溶入基体形成过饱和固溶体,时效过程中脱溶顺序为αsss(α过饱和固溶体)→GP区→η′相→η相。合金板材最佳固溶-时效工艺为(470℃,1 h)固溶+(120℃,24 h)时效,在此条件下,试验合金的抗拉强度、屈服强度和伸长率分别可达533 MPa、494 MPa和15%。试验合金的高强度主要来源于η′相析出强化、添加微量Sc和Zr引起的亚晶强化和亚结构强化以及Al3(Sc,Zr)相的弥散强化。
The microstructure and property evolution of Al-5.4Zn-2.0-Mg-0.25Cu-0.1Sc-0.1Zr alloy under different processing conditions were studied by mechanical properties testing and electron microscopy. The results show that there are segregation of grain boundaries in the ingot under semi-continuous chilled casting condition, forming Zn, Mg-enriched non-equilibrium phase and Fe, Si and Mn-rich impurities phase. After being homogenized at 470 ℃ for 12 h, , Zn, Mg-rich non-equilibrium phase into the matrix, leaving only a small amount of impurities rich in Fe, Si, Mn; at the same time, the solid solution of ingot alloy precipitation nanometer scale Al3 (Sc, Zr) ℃ and 12 h, respectively. During the hot deformation of ingot, the strength of the alloy gradually decreased with the increase of the test temperature, while the elongation increased first and then decreased. The alloy in the temperature range of 350-400 ℃ Has a stable thermal deformation resistance and plasticity, is the appropriate temperature range of heat deformation; alloy cold-rolled sheet by 470 ℃, 1 h solution treatment, the thermal deformation of the formation of a large number of non-equilibrium phase into the matrix to form a supersaturated solid solution , The desolventizing sequence in the aging process is αsss (α supersaturated solid solution) → GP zone → η ’phase → η phase. The best solution-aging process of alloy sheet is (470 ℃, 1 h) solution + (120 ℃, 24 h) aging. Under these conditions, the tensile strength, yield strength and elongation of the alloy can reach 533 MPa, 494 MPa and 15%. The high strength of the test alloy mainly comes from the η ’phase precipitation strengthening, the subgrain strengthening and substructure strengthening caused by the addition of trace amounts of Sc and Zr, and the dispersion strengthening of the Al3 (Sc, Zr) phase.