(1. 蘭州理工大學 甘肅省有色金屬新材料省部共建國家重點實驗室，蘭州 730050；
2. 東北大學 材料與冶金學院，沈陽 110819)
摘 要: 采用光學顯微鏡等手段對Mg和Mn復合變質(zhì)處理后的過共晶Al-Si合金顯微組織及形貌進行觀察。結果表明：隨著Si含量的增加，Al-Si合金中有粗大的不規(guī)則板條狀的初生硅和長條狀的共晶硅生成，且隨Si含量的增加，合金的抗拉強度呈下降趨勢，布氏硬度則逐漸增加；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顯細化，合金的力學性能提高；0.9Mg-xMn的加入可同時變質(zhì)Al-20Si合金的初生硅和共晶硅，初生硅的形狀由星形和不規(guī)則形狀變?yōu)閴K狀，共晶硅由長針狀變成球狀或短棒狀；0.9Mg-0.5Mn復合加入后，合金的鑄態(tài)抗拉強度最高，達到了210 MPa，較Al-20Si和Al-20Si-0.9Mg合金分別提高64%和37%；熱處理以后的抗拉強度達到345 MPa，較鑄態(tài)的提高64%。
關鍵字: 鋁硅合金；Mg；Mn；顯微組織；力學性能
（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
