Modification effect of Sr on the microstructures and mechanical properties of Al–10.5Si–2.0Cu recycled alloy for die casting

The effect of Sr addition on the microstructure and mechanical properties of Al–10.5Si–2.0Cu (in wt%) recycled die-casting alloy was studied. With increasing Sr content, the morphology of the eutectic Si evolved from coarse acicular → lamellar → fine fibrous shapes. Sr addition significantly improved the mechanical properties, with the tensile strength being increased from 209 to 237 MPa and the elongation from 2.0 to 4.1%. This improvement was associated with the morphological evolution of the eutectic Si and was qualitatively evaluated by using a quality index.

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► Morphology of the eutectic Si changed to fine fibrous form by addition of Sr.
► UTS, elongation and e-conductivity of the alloy were enhanced by modification of Si.
► Optimum Sr content is 0.03pct and holding time of 150 min.
► More addition of Sr and increase holding time did not affect the modification of Si.