过共晶Al-Si合金中球团状初生Si的形成机理  

Formation Mechanism of Spheroidal Primary Si in Hypereutectic Al-Si Alloys

作　　者：董光明[1] 廖恒成[2] 孙国雄[2] 

机构地区：[1]中国矿业大学机电工程学院 [2]东南大学材料科学与工程学院

出　　处：《特种铸造及有色合金》2009年第5期412-414,共3页Special Casting & Nonferrous Alloys

摘　　要：根据杂质原子诱发共生的成对孪晶理论,变质剂原子在Si晶体内诱发的共生成对孪晶大大降低了初生Si生长时的各向异性,使得变质后的过共晶Al-Si合金中的初生Si最终生长为球团状。Na原子吸附在共生成对孪晶间的晶格紊乱区——亚晶界,形成了初生Si内部的富Na带。亚晶界对初生Si强度的消弱、富Na带对亚晶界强度的进一步降低、以及α(Al)、Si二相间热膨胀系数的差异造成的热应力是初生Si开裂的原因。球团状初生Si内部的裂纹是在合金凝固结束后的固态收缩阶段形成的。Primary Si phase was finally evolved into spheroidal structure in the modified hypereutectic Al-Si alloy,which was attributed to the coupled twins induced by modifier atom in silicon crystal greatly decreasing anisotropy of primary Si phase growth based on the theory of coupled twins induced by impurity atom.Na-enriched region can be observed in primary Si phase as a result of Na atom absorbed at sub-boundary in coupled twin.Crack of primary Si phase is attributed to sub-boundary decreasing strength of primary Si and Na-enriched region deteriorating further strength of sub-boundary as well as existing thermal stress resulting from difference of thermal expansion coefficient between α-Al phase and Si phase.Crack in spheroidal primary Si appears in solid contract after the hypereutectic Al-Si alloys solidification.

关 键 词：过共晶AL-SI合金 球团状初生Si 共生成对孪晶 

分 类 号：TG146.21[一般工业技术—材料科学与工程]