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结合数值模拟与实验研究了常规条件下Al-Bi偏晶合金难混溶区的凝固过程,分析了Bi含量对Al-Bi偏晶合金显微组织演变的影响。结果表明,成分为Al-10%Bi合金试样下部组织中富Bi液滴的平均直径和体积分数分别是成分为Al-5%Bi合金试样下部组织中富Bi液滴平均直径和体积分数的1.1倍和12.8倍,且Al-10%Bi合金试样下部聚集了大量的大尺寸富Bi液滴,其显微组织均匀性较差;成分为Al-5%Bi的合金试样中富Bi液滴的平均尺寸较小,显微组织较均匀;偏晶点成分的Al-3.4%Bi偏晶合金显微组织中无大尺寸富Bi液滴生成,显微组织均匀。分析表明,富Bi相含量的增加导致液滴受重力作用增强,加剧了难混溶区液-液相分离和分解的凝固行为,增大了富Bi液滴的尺寸和数量,液滴受到的Ostwald熟化和碰撞凝并的作用增强,促使大量的大尺寸富Bi液滴聚集在试样下部,加重了偏晶合金显微组织的宏观偏析。
The solidification process of Al-Bi amorphous alloy under normal conditions was studied by numerical simulation and experiments. The effect of Bi content on the microstructure evolution of Al-Bi amorphous alloy was analyzed. The results show that the average diameter and volume fraction of Bi-rich droplets in the lower microstructure of the Al-10% Bi alloy are the average diameters and volume fractions of the Bi-rich droplets in the substructure of the Al-5% Bi alloy, respectively Times and 12.8 times, and a large number of large-size Bi rich droplets accumulate in the lower part of the Al-10% Bi alloy sample, and the microstructure homogeneity is poor. In the Al-5% Bi alloy sample, Bi-rich droplets The microstructure of the Al-3.4% Bi amorphous alloy with partial crystallite was uniform and the microstructure was uniform. The analysis shows that the increase of the Bi-rich phase leads to the enhancement of the droplet gravity, aggravates the solidification behavior of the liquid-liquid phase separation and decomposition in the immiscible zone, increases the size and amount of the Bi-rich droplets, Ostwald aging and collision coagulation enhanced, prompting a large number of large-size Bi-rich droplets gathered in the lower part of the sample, aggravating the macroscopic segregation of the devitrified alloy microstructure.