摘要
采用光学显微镜(OM)、扫描电镜(SEM)、差示扫描量热仪(DSC)表征,研究了均匀化过程中Al-Zn-Mg-Cu合金的微观组织演变。结果表明,铸态合金晶界中存在大量难溶相Al7Cu2Fe及非平衡共晶相Mg(Zn,Cu,Al)2、Al2CuMg相,在经过420℃/8 h的单级均匀化处理后,部分难溶相和非平衡共晶相回溶到基体中,但还存在大量枝晶偏析,继续进行470℃/36 h第二级均匀化后,非平衡共晶组织和枝晶偏析完全消除。合金的平均晶粒尺寸在两个阶段的均匀化中呈现随时间延长而增加的趋势,基体中残留相及共晶组织的面积分数随保温时长增加而减小,第二级均匀化达到36 h时,相面积分数仅为0.34%,表明均匀化已经非常充分。经过均匀化动力学分析,得出在第二级均匀化温度为470℃时,第二相充分回溶所需保温时间约为37 h,与均匀化的实验结果吻合。
The microstructure evolution of Al-Zn-Mg-Cu alloy during homogenization was studied by optical microscopy(OM),scanning electron microscopy(SEM)and differential scanning calorimetry(DSC)characterization.The results show that a large amount of Al7Cu2Fe insoluble phases and Mg(Zn,Cu,Al)2 nonequilibrium eutectic phases,Al2CuMg phases exist in the crystal boundary of the cast state alloy.After the single-stage homogenization treatment at 420℃/8 h,some of the refractory and non-equilibrium eutectic phases are back-dissolved into the matrix,but a large amount of dendrite segregation still exist,and the non-equilibrium eutectic microstructure and dendrite segregation are even completely eliminated after the second-stage homogenization at 470℃/36 h is continued.The average grain size of the alloy shows a tendency to increase with time in the two stages of homogenization,and the area fraction of residual phase and eutectic microstructure in the matrix decrease with the increase of holding time,and the area fraction of phase is only 0.34%when the second-stage homogenization reaches 36 h,indicating that the homogenization is very adequate.After the homogenization kinetic analysis,it is concluded that at the second homogenization temperature of 470℃,the holding time required for the second phase to fully diffuse back into solution is about 37 h,which is consistent with the homogenization experimental results.
作者
黄元春
严积珺
赵永兴
聂昌昌
马尚坤
吴镇力
HUANG Yuanchun;YAN Jijun;ZHAO Yongxing;NIE Changchang;MA Shangkun;WU Zhenli(Institute of Light Alloy Research,Central South University,Changsha 410083,China;School of Mechanical and Electrical Engineering,Central South University,Changsha 410083,China;State Key Laboratory of High Performance Complex Manufacturing,Changsha 410083,China)
出处
《热加工工艺》
北大核心
2024年第15期8-14,共7页
Hot Working Technology
基金
国家自然科学基金项目(U1837207)。
