(1. 兰州理工大学 甘肃省有色金属新材料省部共建国家重点实验室，兰州 730050；
2. 东北大学 材料与冶金学院，沈阳 110819)
摘 要: 采用光学显微镜等手段对Mg和Mn复合变质处理后的过共晶Al-Si合金显微组织及形貌进行观察。结果表明：随着Si含量的增加，Al-Si合金中有粗大的不规则板条状的初生硅和长条状的共晶硅生成，且随Si含量的增加，合金的抗拉强度呈下降趋势，布氏硬度则逐渐增加；在Al-20Si合金中添加0.9%Mg后，合金中的初生硅和共晶硅得到明显细化，合金的力学性能提高；0.9Mg-xMn的加入可同时变质Al-20Si合金的初生硅和共晶硅，初生硅的形状由星形和不规则形状变为块状，共晶硅由长针状变成球状或短棒状；0.9Mg-0.5Mn复合加入后，合金的铸态抗拉强度最高，达到了210 MPa，较Al-20Si和Al-20Si-0.9Mg合金分别提高64%和37%；热处理以后的抗拉强度达到345 MPa，较铸态的提高64%。
关键字: 铝硅合金；Mg；Mn；显微组织；力学性能
（1. State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology,
Lanzhou 730050, China;
2. School of Materials and Metallurgy, Northeastern University, Shenyang 110819, China）
Abstract:By means of optical micrograph and other instruments, the microstructures and shapes of transcocrystallized Al-Si alloy treated by Mg and Mn complex modifications were studied. The results indicate that the mass coarse and irregular lath-shaped primary silicon and slim strip eutectic silicon phase are found with the Si content increasing. In addition, the tensile strength decreases gradually when the Si content increasing. However, the hardness increases. The primary and eutectic silicon phases are refined when adding 0.9% Mg to Al-20Si alloy, and the mechanical properties are remarkably improved. SEM and OM results show that 0.9Mg-xMn can effectively refine the primary and eutectic silicon in alloy. The morphology of primary silicon after modification is transformed from pentalpha and irregular shape to block. A majority of eutectic silicon is changed from acicular or lamellar morphology to small short rod. By adding 0.9%Mg and 0.5% Mn elements, the tensile strength reaches 210 MPa, which increases by 64% and 37% relative to those of Al-20Si and Al-20Si-0.9Mg alloys, respectively, and the heat treatment tensile strength reaches 345 MPa, increases by 64% relative to that of the as-cast alloy.
Key words: Al-Si alloy; Mg; Mn; microstructure; mechanical property
