(東北大學(xué) 材料與冶金學(xué)院，沈陽 110004)
摘 要: 采用單一稀土元素Nd對過共晶Al-17.5%Si合金進(jìn)行變質(zhì)；采用掃描電鏡、金相顯微鏡、電子探針、透射電鏡及X射線衍射等方法對變質(zhì)前后合金的微觀組織、成分和相組成進(jìn)行分析；并對變質(zhì)前后合金的斷口形貌進(jìn)行分析。結(jié)果表明：加入0.3%Nd(質(zhì)量分?jǐn)?shù))到過共晶Al-17.5%Si合金中可同時變質(zhì)初生硅和共晶硅，經(jīng)過變質(zhì)處理后，初生硅的形狀由星形和不規(guī)則形狀變?yōu)閴K狀，尺寸由40~60 μm減小到10~30 μm，共晶硅由長針狀變成球狀或短棒狀；初生硅區(qū)域的主要成分是硅，中心邊緣幾乎檢測不到Nd元素，Nd沿晶界分布；與未變質(zhì)合金相比，經(jīng)0.3%Nd變質(zhì)后的Al-17.5%Si合金硅相上孿晶密度增大，變質(zhì)后的合金中沒有生成新相，α(Al)相和硅相的晶格常數(shù)變大；經(jīng)0.3%Nd變質(zhì)后，合金的整體性能大幅度提高，抗拉強(qiáng)度提高了35.8%，從120 MPa提高到163 MPa，伸長率從0.8%提高到2.2%，提高了175%。
關(guān)鍵字: 過共晶鋁硅合金；稀土；釹；變質(zhì)；初生硅；力學(xué)性能
hypereutectic Al-17.5%Si alloy modified with Nd
（School of Materials and Metallurgy, Northeastern University, Shenyang 110004, China）
Abstract:Pure Nd was adopted to modify the hypereutectic Al-17.5%Si alloy. The morphology, composition and phase of alloys before and after modification were analyzed by SEM, OM, EPMA, TEM and XRD. The fracture morphologies of the alloy were analyzed by SEM before and after modification. The results show that 0.3% Nd, mass fraction) can effectively refine the primary and eutectic silicon in alloy. The morphology of primary silicon after modification transforms from pentalpha and irregular shape to block, and the grain size of primary silicon is refined from 40−60 μm to 10−30 μm. A majority of eutectic silicon changes from acicular or lamellar morphology to small short rod. No Nd is detected in the center and edge of silicon, Nd distributes along the grain boundary. The twinning density in modified Si crystals is much higher than that of the initial sample. No new phase forms, and the lattices of silicon and aluminum increase after modification. The tensile strength of the alloy modified by 0.3%Nd increases by about 35.8% from 120 MPa to 163 MPa, and its elongation increases by about 175% from 0.8% to 2.2%.
Key words: hypereutectic Al-Si alloys; rare earth; neodymium; modification; primary silicon; mechanical properties
