Synergistic effect of hot rolling and T6 Heat Treatment on the Mechanical Behaviour of Gravity Die Cast A356 Alloy

Vollständiger Abstract

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Secondary processing techniques offer a practical approach for improving the performance of cast aluminium alloys without introducing reinforcement particles. This study investigated the individual and synergistic effects of hot rolling and T6 heat treatment on the mechanical behaviour of gravity die-cast A356 alloy. The alloy was produced by gravity die casting and subsequently subjected to four processing conditions: as-cast, hot rolled, T6 treated, and hot rolled followed by T6 treatment. Mechanical characterisation was performed through tensile and hardness testing, while optical microscopy was used to examine the corresponding microstructural evolution. The results showed that hot rolling significantly improved ductility through microstructural refinement and defect closure, whereas T6 heat treatment substantially enhanced strength and hardness through precipitation hardening. The combined hot rolling and T6 treatment produced the best overall mechanical performance, increasing the ultimate tensile strength from approximately 118 MPa in the as-cast condition to about 248 MPa while simultaneously improving elongation from approximately 7% to 11%. The combined treatment also exhibited the highest hardness, longest time to fracture (273.599 s), and greatest total deformation (5.471 mm), indicating superior resistance to crack initiation and propagation. Optical microstructural observations confirmed progressive refinement and improved structural homogeneity following secondary processing. The study demonstrates that the sequential application of hot rolling and T6 heat treatment generates a synergistic strengthening effect, providing an industrially scalable strategy for enhancing the performance of gravity die cast A356 alloy for lightweight structural and automotive applications.