高Zn含量Al-Zn-Mg-Cu合金均匀化过程中显微结构演变研究（英文）

Microstructure Evolution of a High Zinc Containing Al-Zn-Mg-Cu Alloy during Homogenization

对一种高Zn含量Al-Zn-Mg-Cu合金进行均匀化处理,通过光学显微镜(OM)、差热分析(DSC)、扫描电镜(SEM)和X射线衍射(XRD)研究合金的显微结构演变。使用扩散动力学模型推导均匀化动力学方程,用于确认最佳均匀化参数。结果表明:合金的铸态组织中存在严重偏析,非平衡共晶结构包含α(Al)、Mg(Zn,Cu,Al)_2、S(Al_2CuMg)、θ(Al_2Cu)和富Fe相。当前研究表明均匀化过程中没有发生Mg(Zn,Cu,Al)_2相向S(Al_2CuMg)相的转变,Mg(Zn,Cu,Al)_2相直接回溶。随着均匀化的进行,θ(Al_2Cu)相溶入基体。均匀化后富Fe相仍残留,但随着保温时间的延长,富Fe相中的Zn、Mg元素逐渐减少或消失。最佳均匀化参数为440℃/12 h+468℃/24 h,这与均匀化动力学的分析相一致。

The microstructural evolution of a high Zn-containing Al-Zn-Mg-Cu alloy during homogenization was investigated by optical microscopy, differential scanning calorimetry, scanning electron microscope and X-ray diffraction. A homogenization kinetic equation derived from a diffusion kinetic model was established to confirm the optimum homogenization parameter. Results indicate that severe segregation exists in the as-cast alloy. The non-equilibrium eutectics consist of a（Al）, Mg（Zn, Cu, Al）2, S（Al2CuMg）, θ（Al2Cu） and Fe-enriehed phases. In the present work, no transformation from Mg（Zn,Cu,Al）2 to S（Al2CuMg） phases occurs during homogenization and Mg（Zn, Cu, Al）2 phases directly dissolve into the matrix. θ（Al2Cu） phases dissolve into the matrix while Fe-enriched phases still exist after homogenization. In addition, the contents of Zn and Mg elements in Fe-enriched phases are reduced or even disappear by prolonging the holding time of homogenization. The proper homogenization parameter is 440℃/12 h ＋ 468 ℃/24 h, which is in consistent with the results of homogenization kinetic analysis.