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研究凝固过程中冷却速度对Al-7Si-0.3Mg-0.15Fe合金凝固参数和组织的影响。为了获得不同的冷却速度,设计了5个不同厚度阶梯的阶梯间。通过计算机辅助热分析法得到冷却速度和凝固参数。结果显示,冷却速度越高,初生α(Al)的形核温度、共晶反应温度以及固相线的温度都越低。当冷却速度由0.19℃/s增加到6.25℃/s时,二次枝晶臂间距(SDAS)从68μm下降到20μm,初生相的体积分数也下降5%。铁相的平均长度由28μm下降到18um,并且提高了铁相在基体中的分布均匀性。此外,冷却速度的提高,有利于促进共晶硅向纤维状分支结构的转变,减少了基体中的块状和板状共晶硅。
The effect of cooling rate on the solidification parameters and microstructure of Al-7Si-0.3Mg-0.15Fe alloy during solidification was investigated. In order to obtain different cooling rates, five steps of different thickness steps are designed. The cooling rate and solidification parameters were obtained by computer-aided thermal analysis. The results show that the higher the cooling rate, the lower the nucleation temperature, the eutectic reaction temperature and the solidus temperature of primary α (Al). When the cooling rate increased from 0.19 ℃ / s to 6.25 ℃ / s, the secondary dendrite arm spacing (SDAS) decreased from 68μm to 20μm, and the volume fraction of primary phase decreased by 5%. The average length of the iron phase is reduced from 28 μm to 18 μm and the distribution uniformity of the iron phase in the matrix is increased. In addition, the cooling rate is increased, is conducive to promoting the eutectic silicon to the fibrous branched structure of the transition, reducing the matrix of bulk and plate eutectic silicon.