(1. 蘭州理工大學 材料科學與工程學院，蘭州 730050； 2. 蘭州理工大學 省部共建有色金屬先進加工與再利用國家重點實驗室，蘭州 730050)
摘 要: 采用光學顯微鏡、掃描電子顯微鏡、電子探針及力學性能測試，研究了不同比例的混合稀土Pr和Y對過共晶Al-20Si合金顯微組織與力學性能的影響。結果表明：Al-20Si合金中添加稀土Pr和Y能使合金中粗大的塊狀及五瓣星狀初生Si變質為細小的塊狀和部分粒化；當Pr和Y按質量比1:1的比例混合(0.5%Pr、0.5%Y，質量分數(shù))時，細化效果最為顯著，初生Si尺寸由96 μm減小到41 μm，減小57.3%，共晶Si由粗大的針片狀變質為類蠕點狀；此時，合金的抗拉強度由93 MPa提高到143 MPa，伸長率從1.12%提高到2.79%，分別提高53.8%和149%。
關鍵字: Al-20Si合金；混合稀土；顯微組織；力學性能
（1. School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China; 2. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:By optical microscopy, scanning electron microscopy, electron probe analysis and mechanical property test, the effects of mischmetal Pr and Y on the microstructure and mechanical properties of hypereutectic Al-20Si alloy were investigated. The results show that the addition of mischmetal Pr and Y can effectively modify the primary Si from coarse polygonal and star-like shape to fine blocky shape with smooth edges and corners. When the mass ratio of mischmetal Pr and Y is 1:1 (0.5%Pr, 0.5%Y (mass fraction)), the consequence of modification is the best on primary silicon and eutectic silicon, the size of primary silicon reduces by 57.3% from 96 μm to 41 μm. In addition, the morphology of eutectic silicon changes from coarse platelet-like/needle-like structure to fine fibrous structure and worm-like. The ultimate tensile strength increases by 53.8% from 93 MPa to 143 MPa, and the elongation increases by 149% from 1.12% to 2.79%, respectively.
Key words: Al-20Si alloy; mischmetal; microstructure; mechanical property
