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采用透射电镜、电子探针、拉伸和硬度测试等方法对铸态Al-6Mg-0.2Sc-0.15Zr(质量分数, %)合金在等温退火过程中的硬化行为进行了研究. 结果表明, 退火过程中Mg分布的变化对合金强度影响不大,细小、弥散的Al₃(Sc, Zr)沉淀相的析出产生了显著的沉淀强化作用.合金在300 ℃下退火, Al₃(Sc, Zr)沉淀相粗化速率较慢,经过24 h处理后其直径为5 nm, 合金屈服强度相对退火前提高约90 MPa;随着退火温度的升高, Al₃(Sc, Zr)相在退火过程中发生不同程度的粗化.450 ℃/24 h处理后沉淀相直径增大至约30 nm, Al₃(Sc, Zr)相引起的沉淀强化作用下降至30 MPa. 铸态Al-6Mg-0.2Sc-0.15Zr合金经过 300 ℃/3 h退火处理后可获得最大的沉淀强化效果.

Addition of minor Sc and Zr to the Al–Mg alloys can effectively improve the recrystallization temperature and strength of the alloys due to the formation of L12 structured Al₃(Sc, Zr) precipitates. To optimize the mechanical properties of the Al–Mg–Sc–Zr alloys, it is important to understand the precipitation behavior of the Al₃(Sc, Zr) precipitates and the corresponding strengthening effect during the annealing of Al–Mg–Sc–Zr alloys. In this work, isothermal annealing at the temperatures between 250 and 450 ℃ was conducted to study the precipitation behavior of Al₃(Sc, Zr) particles in the as–cast Al–6Mg–0.2Sc–0.15Zr alloy (mass fraction, %). The results show that dramatic precipitation hardening occurred with the formation of the coherent Al₃(Sc, Zr) precipitates during the annealing. Precipitation rocess of the Al₃(Sc, Zr) accelerates with the increase of the annealing temperature. After the sample was annealed at 300 ℃ for 24 h, the Al₃(Sc, Zr) particles were in a size of 5 nm ad the yield strength of the as–cast alloy can be increased by 90 MPa. Severe coarsening of Al₃(Sc, Zr) occurred when the annealing temperature is bove 400 ℃. After annealed at 450 ℃ for 24 h, average particle size of Al₃(Sc, Zr) particles was found increase to 30 nm, wth the corresponding precipitation strengthening effect to be about 30 MPa.