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采用扫描示差量热法(DSC)、扫描电镜(SEM)、光学显微镜(OM)和能谱分析(EDS)等手段研究了含微量Zr的Al-Cu-Mg-Ag合金铸态与不同均匀化热处理态的显微组织演化和成分分布,测定了该合金铸态组织中的低熔点共晶相的成分和熔化温度,确定了该合金的均匀化处理制度和过烧温度。结果表明:Al-Cu-Mg-Ag-Zr合金铸态组织晶界上主要的非平衡相为Al2Cu,其熔点为523.52℃。合金经420℃×6h一级均匀化处理后,Al3Zr粒子在基体内二次析出且弥散分布。经515℃×24h二级均匀化处理后,晶界上的非平衡相大部分溶入基体,枝晶偏析基本消除,晶内各元素分布均匀。该合金的最佳均匀化制度为420℃×6h+515℃×24h,均匀化过烧温度为520℃。
The as-cast and homogenized Al-Cu-Mg-Ag alloys containing trace amounts of Zr were investigated by scanning calorimetry (DSC), scanning electron microscopy (SEM), optical microscopy (OM) and energy dispersive spectroscopy (EDS) The microstructure evolution and compositional distribution of the as-cast microstructure were investigated. The composition and melting temperature of the low-melting eutectic phase in the as-cast microstructure of the alloy were determined. The homogenization treatment and over-burning temperature were determined. The results show that the main non-equilibrium phase in the as-cast Al-Cu-Mg-Ag-Zr alloy is Al2Cu with a melting point of 523.52 ℃. After homogenization of the alloy at 420 ℃ for 6h, the Al3Zr particles were precipitated and diffused in the matrix. After the secondary homogenization at 515 ℃ for 24h, most of the unbalanced phases in the grain boundary dissolve into the matrix, and the dendritic segregation is basically eliminated, and the elements in the crystal are evenly distributed. The best homogenization system of the alloy is 420 ℃ × 6h + 515 ℃ × 24h, the homogenization over-burning temperature is 520 ℃.