(重庆大学 材料科学与工程学院，重庆 400030)
摘 要: 研究Al-24%Si合金铸态组织中五星柱状初生Si的立体形貌及生长机制。结果表明：混合酸腐蚀后，五星柱状初生Si内部出现平行于表层晶面、层层堆叠的生长迹线，与螺旋式生长线存在明显差别，表明Si晶生长所依靠的台阶源并不是螺旋位错形成的；层错堆垛在五角多面体Si晶核生长面{111}上产生高度分别为δ(111)/3和2δ(111)/3的亚台阶，两类亚台阶交替产生的过程为Si晶的生长提供永不消失的台阶源；萃取得到的五星柱状初生Si的完整形貌显示其生长终端界面形态与五角多面体晶核一致，呈五角多面凹坑状；八面体团簇五重凝并形成的五角多面体晶核，以层错在各{111}生长面产生的两类亚台阶为生长台阶源，层层堆砌长大形成五星柱状初生Si。
关键字: 五星柱状初生Si；层状生长迹线；亚台阶生长理论
primary Si in hypereutectic Al-24%Si alloy
（College of Materials Science and Engineering, Chongqing University, Chongqing 40030, China）
Abstract:The stereo-morphology and growth mechanism of five-pyramid prismatic-shaped primary Si in hypereutectic Al-24%Si alloy were investigated. The results show that the growth traces of the five-pyramid prismatic-shaped primary Si exists layer by layer, paralleling with the surface crystal plane. It is quite different from the growth trace of the screw dislocation growth. The growth step sources required for Si phase are supplied by δ(111)/3 and 2δ(111)/3 sub-steps, which creates on {111} growth surface of silicon crystal by stacking faults. Two kinds of sub-steps created by turns can supply the lasting growth step sources for Si phase. The growth ending interface morphology of primary Si is five-pyramid polyhedron pit-shaped, which likes the nucleus coagulated by octahedrons. Therefore, the sub-step theory can explain the growth mechanism of the five-pyramid prismatic-shaped primary Si.
Key words: five-pyramid prismatic-shaped primary Si; layer growth trace; sub-step growth theory
