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研究了铸态Al-4.51Zn-1.77Mg合金在不同均匀化工艺条件下的显微组织的演变规律。结果表明:铸态Al-4.51Zn-1.77Mg合金的DSC曲线在476℃附近出现明显的吸热峰;(460~510℃)×24 h均匀化处理后,476℃附近的吸热峰消失。铸态合金晶粒之间包围着大量的枝晶网络,枝晶臂之间存在着大量的非平衡共晶。随均匀化温度的升高,非平衡共晶逐渐回溶到基体中;高于480℃时,晶粒内部和晶界处开始出现形状不规则的复熔粒子,合金出现过烧。在470℃进行均匀化处理,1 h后大部分第二相已回溶到基体中,随均匀化时间的延长,第二相含量逐渐减少;但24 h后,随时间延长第二相含量无明显变化。根据合金的均匀化动力学方程计算出适合实验合金的均匀化制度为470℃×26 h,与实验结果基本相符。
The microstructure evolution of as-cast Al-4.51Zn-1.77Mg alloy under different homogenization conditions was studied. The results show that the DSC curve of as-cast Al-4.51Zn-1.77Mg alloy shows obvious endothermic peak near 476 ℃. The endothermic peak near 476 ℃ disappears after homogenization at 460-510 ℃ for 24 h. A large amount of dendrite network is surrounded by as-cast alloy grains, and a large amount of non-equilibrium eutectic exists between the dendrite arms. With the increase of the homogenization temperature, the unbalanced eutectic gradually dissolved back into the matrix. When the temperature was above 480 ℃, irregularly shaped refractory particles began to appear at the grain boundaries and at grain boundaries. After homogenization at 470 ℃, the majority of the second phase was dissolved back into the matrix after 1 h. The content of the second phase decreased with the extension of the homogenization time, but the content of the second phase decreased with time after 24 h obvious change. According to the homogenization kinetics equation of the alloy, the homogenization system of the suitable alloy is calculated to be 470 ℃ × 26 h, which is basically consistent with the experimental results.