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在常规重力条件下利用超频感应加热炉对Al-10%Bi过偏晶合金难混溶区的宏观偏析进行研究。结果表明,合金试样上部和中部位置的富Bi相液滴的最大直径随时间呈线性增大,试样下部液滴的最大直径随时间呈指数形式增大,试样上、中、下部位的液滴密度随时间呈指数规律递减。分析表明,合金凝固的初始阶段,形核、扩散长大和Ostwald熟化是影响凝固组织的主导因素;在合金凝固的中、后期,重力迁移和碰撞凝并开始起主导作用,加剧液滴的粗化速率,导致相同时刻试样不同位置的富Bi液滴分布的差异逐渐增大,造成了重力条件下最终凝固组织的宏观偏析。
The macroscopic segregation of Al-10% Bi over-miscrystallization alloy was studied by conventional over-frequency induction furnace. The results show that the maximum diameter of the Bi-rich droplets in the upper and middle parts of the alloy increases linearly with time, and the maximum diameter of the droplets in the lower part of the alloy increases exponentially with time. The upper, The droplet density decreases exponentially with time. The analysis shows that nucleation, diffusion growth and Ostwald ripening are the dominant factors affecting the solidification structure in the initial stage of alloy solidification. During the middle and late phases of alloy solidification, gravity migration and collisional condensation begin to play a dominant role, which aggravates the coarsening of droplets Velocity, the difference of Bi-rich droplets distribution at different positions of the sample at the same time gradually increases, causing the macroscopic segregation of the final solidified structure under the gravity condition.