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-Al

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FeSi 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 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 of β-Al

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FeSi phase is decreased from 24.2μm to 14.7μm.With the content of La more than 0.6%

the morphology of β-Al

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FeSi 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-Al

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FeSi 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.