Influence of Mg, Sr, TiB, and Cu Additions on the Microstructure and Mechanical Behavior of A356 Alloy Wheels

Abstract

This research investigates the influence of magnesium (Mg), strontium (Sr), titanium boride (TiB), and copper (Cu) additions on the mechanical and microstructural behavior of A356 aluminum alloy wheel components produced by low-pressure casting and subjected to T6 heat treatment. Tensile and hardness tests were performed across three critical wheel regions to evaluate localized performance variations caused by casting conditions. Results demonstrate that increasing Mg content from 0.05 wt.% to 0.15 wt.% leads to a measurable decrease in ductility, with elongation reductions of 0.3–0.7% depending on the region, while simultaneously increasing hardness through Mg₂Si precipitation strengthening. Sr additions at realistic modification levels (0.005–0.015 wt.%) produced a clear transition of eutectic Si from acicular to spheroidized morphology, improving yield strength by approximately 15–20 MPa, particularly in the inner flange. Copper additions enhanced tensile and yield strength through precipitation hardening, although excessive Cu levels reduced ductility due to the presence of coarse intermetallic phases. Overall, the findings demonstrate that controlled additions of Mg, Sr, TiB, and Cu significantly influence the regional mechanical response of A356 alloy wheels. The study highlights the importance of localized microstructural analysis for optimizing alloy design and improving casting performance.