7A55铝合金晶界析出相的非等温回归动力学(英文)

Non-isothermal retrogression kinetics for grain boundary precipitate of 7A55 aluminum alloy

采用TEM研究了7A55合金回归过程中晶界析出相的动力学行为。研究结果表明:晶界析出相的粗化遵循"LSW"理论,即晶界相平均尺寸的三次方与回归温度呈线性关系,且晶界相的粗化速率随着回归温度的升高而增大。计算得到7A55合金晶界析出相的粗化激活能为(115.2±1.3)kJ/mol。将7A55铝合金薄板的理论回归制度(190°C,45 min)作为参考,基于"LSW"理论和"等动力学"处理方法,建立了包含Arrhenius方程形式的7A55铝合金晶界相非等温回归模型。当初始晶界相尺寸r0已知时,利用该模型可成功预测非等温回归阶段任意时间点的晶界相平均尺寸r(t)。在此基础上,最终建立了一种7A55铝合金厚板高向组织均匀性的通用表征方法。

The retrogression kinetics for grain boundary precipitate （GBP） of 7A55 aluminum alloy was investigated by transmission electron microscopy （TEM） observation. The results reveal that the coarsening behavior of GBP obeys “LSW” theory, namely, the cube of GBP average size has a linear dependence relation to retrogression time, and the coarsening rate accelerates at the elevated retrogression temperature. The GBP coarsening activation energy Qo of （115.2±1.3） kJ/mol is obtained subsequently. Taking the retrogression treatment schedule of 190℃, 45 min derived from AA7055 thin plate as reference, the non-isothermal retrogression model for GBP coarsening behavior is established based on “LSW”theory and “iso-kinetics” solution, which includes an Arrhenius form equation. After that, the average size of GBP r（t） is predicted successfully at any non-isothermal process T（t） when the initial size of GBP r0 is given. Finally, the universal characterization method for the microstructure homogeneity along the thickness direction of TA55 aluminum alloy thick plate is also set up.