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对Al-Bi偏晶点成分合金(Al-3.4%Bi,质量分数)开展了逆重力方向的定向凝固实验,考察了凝固速度对合金凝固组织的影响,分析了试样凝固组织形成过程.结果表明:Al-Bi偏晶点成分合金定向凝固时在固-液界面前沿液相内形成溶质Bi富集层,并发生液-液相变,少量相液滴在Marangoni迁移、Stokes沉积和试样自身下拉运动共同作用下进行空间迁移,当凝固速度较快时,凝固界面前沿所有尺寸的少量相液滴均向凝固界面迁移,合金凝固后少量相粒子尺寸呈现单峰分布;当试样凝固速度较慢时,部分少量相液滴在长大过程中其合速度方向按:指向凝固界面-背离凝固界面-再指向凝固界面顺序随液滴尺寸变化,合金凝固后少量相粒子尺寸分布呈现2个峰;当凝固速度较快时,少量相粒子平均尺寸随凝固速度V_0近似呈∝V_0~(-1/2)指数关系变化,随着凝固速度的下降,与V_0间的关系向∝V_0~(-1/3)指数关系趋近.
Directional solidification experiments were carried out in the direction of gravity against the Al-Bi amorphous component (Al-3.4% Bi, mass fraction), the influence of solidification rate on the solidified structure of the alloy was investigated, and the formation of the solidified structure was analyzed. It is shown that when the Al-Bi deviatoric alloy is directionally solidified, the solute Bi enriched layer is formed in the liquid front of the solid-liquid interface, and the liquid-liquid phase change, the migration of a few phase droplets in Marangoni, the Stokes deposition and the sample When the solidification speed is fast, a small amount of phase droplets of all sizes at the front of the solidification interface migrate to the solidification interface. After the solidification, a small number of phase particles exhibit a unimodal distribution. When the solidification rate Slower, some of the small amount of phase droplets grew up in the direction of their combined speed by: point to the solidification interface - away from the solidification interface - and then point to the solidification interface with the size of the droplet size changes, the solidification of small phase particles showed two size distribution Peak. When the solidification rate is fast, the average size of minor phase particles changes exponentially with the solidification rate of V_0, and as the solidification rate decreases, and V_0 relationship to αV_0 ~ ( -1/3) The exponential relationship approaches.