(重慶大學(xué) 材料科學(xué)與工程學(xué)院，重慶 400030)
摘 要: 研究Al-24%Si合金鑄態(tài)組織中五星柱狀初生Si的立體形貌及生長機(jī)制。結(jié)果表明：混合酸腐蝕后，五星柱狀初生Si內(nèi)部出現(xiàn)平行于表層晶面、層層堆疊的生長跡線，與螺旋式生長線存在明顯差別，表明Si晶生長所依靠的臺(tái)階源并不是螺旋位錯(cuò)形成的；層錯(cuò)堆垛在五角多面體Si晶核生長面{111}上產(chǎn)生高度分別為δ(111)/3和2δ(111)/3的亞臺(tái)階，兩類亞臺(tái)階交替產(chǎn)生的過程為Si晶的生長提供永不消失的臺(tái)階源；萃取得到的五星柱狀初生Si的完整形貌顯示其生長終端界面形態(tài)與五角多面體晶核一致，呈五角多面凹坑狀；八面體團(tuán)簇五重凝并形成的五角多面體晶核，以層錯(cuò)在各{111}生長面產(chǎn)生的兩類亞臺(tái)階為生長臺(tái)階源，層層堆砌長大形成五星柱狀初生Si。
關(guān)鍵字: 五星柱狀初生Si；層狀生長跡線；亞臺(tái)階生長理論
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
