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采用半固态等温热处理方法,研究了Al-Zn-Mg-Cu合金在加热到两相区温度等温保温过程中的组织粗化规律。回归拟合结果表明,α(Al)晶粒平均直径与等温时间近似满足方程:■-■=Kt,粗化速率系数K随等温温度升高而增大,其在610和620℃下对应的值分别为14811.4和17836.3μm4/s。实验合金组织的多边化、球化和粗化现象是同时发生的,组织粗化以晶粒合并长大和Ostwald熟化的方式进行。等温前期粗化以合并为主,但随着晶间液相增多,合并变得困难,导致等温后期粗化速率下降。
The semi-solid isothermal heat treatment method was used to study the microstructure roughening of Al-Zn-Mg-Cu alloy during the isothermal heat-up to the two-phase zone. Regression fitting results show that the average diameter of α (Al) grains and isothermal time approximately satisfy the equation: ■ - ■ = Kt, the coarsening rate coefficient K increases with increasing isothermal temperature, which corresponds to 610 and 620 ℃ The values were 14811.4 and 17836.3 μm 4 / s, respectively. The polygation, spheroidization and coarsening of the experimental alloy structure occur simultaneously, and the coarsening of the structure takes place in the manner of grain coalescence and Ostwald ripening. Cohesion is mainly dominated by coarsening in the early isothermal phase, but as the interphase liquid phase increases, merging becomes more difficult, resulting in a decrease in the coarsening rate during the late isothermal phase.