Effect of Ce-rich Rare Earth on Solidification Microstructure of Multicomponent Al-Si Piston Alloy
The effect of Ce-rich rare earth(0.1wt%,0.3wt%,0.5wt%)on the solidification microstructure of multivariate near-eutectic Al-11.5Si-4Cu-2Ni-1Mg-0.5Fe(wt%)piston alloy was studied by DSC,optical microscopy and scanning electron microscopy.It is found that the addition of Ce-rich rare earth has obvious effects on the solidification temperature,morphology and volume fraction of eutectic silicon and various second phases of the alloy.The addition of Ce-rich rare earth reduces the Al-Si eutectic temperature and increases the precipitation temperature of T-Al9FeNi phase and δ-Al3CuNi phase.When the addition of Ce-rich rare earth is 0.3wt%,the modification effect of eutectic silicon is best,T-Al9FeNi phase changes from the initial lath shape to the small block shape,the volume fraction decreases to 3.22vol%,and the δ-Al3CuNi phase changes from the initial flake shape to fishbone shape,the volume fraction increases to 6.47vol%.La and Ce atoms in the Ce-rich rare earth are enriched at the front of the solid-liquid interface during the solidification process,which increases the compositional supercooling and refines the eutectic structure.When the content of Ce-rich rare earth is 0.5wt%,long needle-like rare earth-rich phase appears in the alloy.
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