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

[Display omitted] ► 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. 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.