Effects of Sc Content on Microstructure and Creep Properties of Al-Si Series Piston Alloy

The effects of adding different content of Sc (0wt%, 0.2wt%,0.4wt%and 0.6wt%)on the microstructure and creep properties of complex Al-Si piston aluminum alloy were investigated.The results show that Sc element forms in piston aluminum alloy to form a blocky Sc-rich phase identified as ScSiNi phase, which has two existence forms, one existing independently in the matrix and another being tightly bound to the primary Si.The size of α-Al and primary Si in the cast alloy added with different content of Sc reduces by different degrees, at the same time, the δ-Al₃CuNi phase shape occurs by Cluster fish bone-like to bar rod shape to cluster fish bone-like. The alloy with 0.2wt%Sc, the steady-state creep rate is substantially reduced under 350 ℃and 25 MPa stress, when the dislocation motion is the dominant factor. After adding 0.6wt%Sc to the alloy, crystal boundary sliding is the dominant factor, and the creep resistance of the alloy reduces.