李浩 林冲 费卓铭 朱文波 吴和保

(武汉工程大学机电工程学院)

摘要:研究了不同La含量对Al-8.5Si-3.5Cu-1.2Fe合金显微组织和力学性能的影响。结果表明，La的加入能变质α-Al、共晶Si相和针状β-Al₅FeSi相，且会生成AlSiFeLa相。当La含量为0.6%时，变质效果最佳，T6态La含量为0.6%的合金的最大抗拉强度为233 MPa。α-Al相一次枝晶臂平均长度由181.3 μm减至55.2 μm，共晶Si相尺寸由13.0 μm缩短至6.9 μm，β-Al₅FeSi相尺寸由24.2 μm减至14.7 μm。当La含量超过0.6%时，β-Al₅FeSi相有变粗大的趋势，合金强度下降。T6热处理后，合金成分没有变化，但β-Al₅FeSi相出现溶断现象，且端部钝化，共晶Si转变为颗粒状。

关键词：AlSi合金；La变质；组织；力学性能

中图分类号:TG146.21;TG113.25   文献标志码    A

DOI:10.15980/j.tzzz.2020.06.025

Effects of La Addition on Microstructure and Mechanical Properties of  Al-8.5Si-3.5Cu-1.2Fe Alloy

Li Hao, Lin Chong, Fei Zhuoming, Zhu Wenbo, Wu Hebao

(School of Mechanical and Electrical Engineering, Wuhan Institute of Technology)

Abstract:The microstructure and mechanical properties of Al-8.5Si-3.5Cu-1.2Fe alloy with different La contents were investiagted. The results reveal that with La addition, the formation of AlSiFeLa phases can be observed Meanwhile the α-Al, eutectic Si phase and needlelike β-Al₅FeSi phase all can be refined. With addition of 0.6% La, the modification effect is desirable and the ultimate tensile strength of the T6 treated alloy reaches 233 MPa. The length of α-Al primary dendrite arm is decreased from 181.3 μm to 55.2 μm, and the size of eutectic Si phase is decreased from 13.0 μm to 6.9 μm, and the size of β-Al₅FeSi phase is decreased from 24.2 μm to 14.7 μm. With the content of La more than 0.6%, the morphology of β-Al₅FeSi phase becomes coarse again, so the strength of the alloy is decreased. After T6 treatment, there is absent change in the phase composition of the alloy. However, the fragmentation of β-Al₅FeSi phase can be observed by diffusion of solute atoms and matrix atoms at points such as crevice locations or the tips, and the morphology of eutectic Si phase is transformed into granular structure.

Key Words: Al Si Alloy, La Modification, Microstructure, Mechanical Properties