La变质对Al-8.5Si-3.5Cu-1.2Fe合金组织和性能的影响

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

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233MPa。α-Al相一次枝晶臂平均长度由181.3μm减至55.2μm,共晶Si相尺寸由13.0μm缩短至6.9μm,β-Al5FeSi相尺寸由24.2μm减至14.7μm。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。

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 theα-Al,eutectic Si phase and needle-likeβ-Al5FeSi phase all can be refined.With addition of 0.6%La,the modification effect is desirable and the ultimate tensile strength of the T6treated alloy reaches 233MPa.The length ofα-Al primary dendrite arm is decreased from 181.3μm to 55.2μm,and the size of eutectic Si phase is decreased from 13.0μm to 6.9μm,and the size ofβ-Al5FeSi phase is decreased from 24.2μm to 14.7μm.With the content of La more than 0.6%,the morphology ofβ-Al5FeSi phase becomes coarse again,so the strength of the alloy is decreased.After T6treatment,there is absent change in the phase composition of the alloy.However,the fragmentation ofβ-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.