过共晶铸造A1-Si-Cu-Mg-Fe合金组织性能研究

Study on the Microstructure and Mechanical Properties of Hypereutectic A1-Si-Cu-Mg-Fe Alloys

通过正交试验和单因素试验,考察了Cu、Mg、Zn、Ni和Fe对Al-18Si过共晶铝硅合金室温及高温(350℃)力学性能的影响规律,利用光学金相显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDX)对合金中富Cu相、富Fe相的组织组成进行了分析.结果表明:Cu、Mg是提高Al-18Si过共晶铝硅合金室温及高温强度的主要因素;Zn含量增加明显降低合金350℃时的高温强度,改善合金的室温和高温延伸率;Fe降低合金的室温强度,显著提高合金的高温强度;当Cr∶Fe=0.35∶1,Mn∶Cr=2∶1,含铁0.8%～1.2%时,Al-18Si-4.0Cu-0.7Mg-0.2Zn-1.0Ni-(0.8～1.2)Fe合金力学性能σb(25℃)>310MPa,延伸率δ5(25℃)≥0.75%,σb(350℃)>130MPa,延伸率δ5(350℃)>1.5%;合金中富铜相主要以块状Al2Cu相和白灰色花卉状Al5Si6Cu2Mg8相存在,富铁相主要以三叶草状、树枝状和棒状Al5Si(Cr,Mn,Fe)相存在.

The effects of Cu,Mg,Zn,Ni and Fe on the mechanical properties of Al-18 Si alloys at room temperature and 350 ℃ have been studied by orthorhombic experimental and the single factor experiment analysis. The micro-structures mainly composed of rieh Cu and Fe in the alloys have also been analyzed by optical microscope（OM）, scanning electron microscopy （SEM） and energy spectrum analyzer （EDX）. The results show that Cu and Mg are the most important factors for improving the tensile strength of hypereuteetic Al-18 Si alloy at room temperature and high temperature. Increasing of Zn content reduces the strength of the alloy at 350℃obviously,and improves the elongation rate at room temperature and 350 ℃. With the increase of Fe concentration from 0. 8%to 1.2% ,the strength of the alloy reduces at room temperature,however,improves significantly at 350 ℃. Under the condition of Cr ： Fe=0. 35 ： 1 and Mn ： Cr=2 ： 1 ,the best tensile properties of Al-18Si-4.0Cu-0. 7Mg-0. 2Zn-1.0Ni-Mn-Cr -（0. 841. 2） Fe alloy are obtained, i. e. σb（25 C） ）〉310 MPa,δ5（250σ） ≥0. 75% ,σu（350℃） ）〉130 MPa and δ5（350℃） ）〉1.5 %. The copper-rich phases are mainly existed in the massive Al2Cu phase and the white with gray flowers like Al5 Si6 Cu2 Mgs phase in the alloy, while the iron-rich phase existed mainly in the clover-like, dendritic or rod Al5 Si （Cr, Mn, Fe） phase.