Hot Deformation Combined with Heat Treatment on the Microstructure and Mechanical Behavior of (Ce + Yb)-Modified Al-Si-Mg-Cu-Cr Casting Alloy

This study enhances the strength and ductility of (Ce + Yb)-modified Al-Si-Mg-Cu-Cr casting alloy by integrating hot deformation and heat treatment. In addition, the synergistic effects of hot deformation and heat treatment on the microstructure and mechanical behavior were thoroughly investigated. As-solutionized alloys were subjected to hot deformation examinations at temperatures ranging from 250 to 450 °C and strain rates varying between 0.0005-0.0125 s −1 . The results revealed that the flow stress increased as the temperature decreased, and the strain rate increased. The maximum ultimate tensile strength (UTS), yield strength (YS) and elongation (El) of as-solutionized, hot deformed at 250 °C, strain rate of 0.0025 s −1 and aged alloy were 353, 296 MPa and 11.4%, respectively, higher by 79.1, 193.1 and 96.6% than the as-cast alloy. The interactions between Ce- and/or Yb-rich precipitates, the high-density dislocations induced by hot deformation and the creation of substructures such as subgrains are primarily responsible for the increase in strength. Finally, the high strength of the (Ce + Yb)-modified alloy after hot deformation and heat treatment is primarily attributed to the synergistic strengthening of several factors through solid solution strengthening, precipitation strengthening, substructural strengthening and work hardening.