Evolution of the Young's Modulus of Al-7Si-4Cu Alloy with Increasing Temperature by Various Strengthening Approaches

Despite the crucial role of Young's modulus in the structural performance of Al alloys, the effects of common strengthening approaches on its evolution, particularly at elevated temperatures, remain largely unexplored. In this study, an Al-7Si-4Cu alloy was modified by hot deformation, micro-alloying with 0.3 wt.% Sc, alloying with 4 wt.% Ni, and reinforcement with 0.8 vol.% Al₂O₃ nanoparticles. The effects of these strengthening approaches on the microstructure and the evolution of Young's modulus from room temperature to 350 °C were examined. It was found that the Young's modulus of the alloys decreased with the increase in temperature, while this tendency is much more obvious when the temperature exceeds 250 °C. The results showed that hot deformation markedly refines the α-Al grains while the Young's modulus stays largely unchanged. The Sc addition leads to the formation of the W phase but has no significant effect on the Young's modulus. In contrast, the addition of Ni substantially increases the Young's modulus through the formation of Al₃CuNi intermetallic particles, with the Young's modulus increasing from 72.15 to 76.47 GPa. With the addition of Al₂O₃ particles, the decreasing magnitude of Young's modulus is optimized when the temperature is higher than 250 °C. This work may be referred to when designing high-modulus Al alloys by considering the utilization of various strengthening concepts.