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利用光学显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、能谱分析(EDS)、差示扫描量热(DSC)、X射线物相分析(XRD)研究了7449高纯高强韧铝合金均匀化热处理制度及其微观组织演变。结果表明:7449合金铸锭组织存在枝晶偏析,Zn,Cu原子沿晶界偏析严重,非平衡共晶相沿晶界呈连续网状分布,共晶相组成为α(Al)+Mg(AlZnCu)2四元相,初始回溶温度为477℃;合金经不同均匀化热处理后,非平衡共晶相发生回溶,且析出弥散分布的Al3Zr粒子。研究了不同的均匀化热处理制度对7449合金微观组织的影响,均匀化热处理温度越高,合金非平衡共晶相回溶效果越好,合金经(440℃/12 h)+(470℃/24 h)均匀化热处理后第二相回溶充分,且析出弥散的Al3Zr粒子,抑制后续加工和固溶处理过程中的再结晶。最终确定合金合理的均匀化热处理制度为(440℃/12 h)+(470℃/24 h)。
The microstructure of 7449HP was studied by OM, SEM, TEM, EDS, DSC and XRD. Homogenization Heat Treatment System and Microstructure Evolution of High Strength and Ductility Aluminum Alloy. The results show that there exists dendritic segregation in the ingot of 7449 alloy. The segregation of Zn and Cu atoms along the grain boundaries is serious. The unbalanced eutectic phases are continuously reticulate distributed along the grain boundaries. The eutectic composition is α (Al) + Mg (AlZnCu) 2 tetragonal phase, the initial temperature of the solution was 477 ℃; after homogenization heat treatment, the unbalanced eutectic phase was dissolved back and the dispersed Al3Zr particles were precipitated. The effects of different homogenization heat treatment systems on the microstructure of 7449 alloy were studied. The higher the homogenization heat treatment temperature, the better the non-equilibrium eutectic phase solution dissolution. The alloy was heated at (440 ℃ / 12 h) + (470 ℃ / 24 h) After homogenization heat treatment, the second phase is fully dissolved and the dispersed Al3Zr particles are precipitated, inhibiting the recrystallization in the subsequent processing and solution treatment. Finally, the reasonable homogenization heat treatment system for the alloy was determined as (440 ℃ / 12 h) + (470 ℃ / 24 h).