中文摘要：

对Al-3.4%Bi（质量分数）偏晶点成分合金开展了定向凝固实验,并对其凝固组织形成过程进行分析.结果表明,Al-Bi偏晶点成分合金定向凝固时在凝固界面前沿液相内形成溶质Bi富集层,并在该区域内发生液液相变.当试样凝固速度较慢时,合金凝固后弥散相粒子尺寸呈现双峰分布;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,合金凝固后弥散相粒子尺寸呈现单峰分布.

英文摘要：

Directional solidification experiments are carried out with Al-3.4%Bi alloy and the microstructure evolution mechanism is investigated.The results demonstrate that a solute-rich layer forms in front of the solidification interface and the liquid-liquid decomposition occurs at the same region.When the alloy is solidified at a relatively low velocity,the size distribution of the minority phase particles shows two peaks.When the alloy is solidified at a high velocity so that the minority phase droplets of all sizes in front of the solidification interface migrate to the solidification interface,the size distribution of the minority phase particles shows only one peak.