Research Progress of Metamorphic Treatment of Hypereutectic Aluminum-Silicon Alloys

Hypereutectic aluminum-silicon (Al-Si) alloys are widely employed in high-end engineering applications, such as automotive engine pistons and aerospace structural components, due to their advantageous properties including low thermal expansion coefficient, high specific strength, excellent castability, and superior wear resistance. The mechanical performance of these alloys is critically influenced by the morphological characteristics of silicon phases, particularly the size, distribution, and geometric features of primary silicon crystals and eutectic silicon networks. This review systematically evaluates recent international research advancements in microstructure optimization of hypereutectic Al-Si alloys. It comprehensively discusses various modification strategies, such as non-rare-earth element modification, rare-earth compound modification and composite modification systems combining multiple alloying elements. Additionally, advanced processing techniques are analyzed, including rapid solidification technologies, ultrasonic vibration treatment during solidification, mechanical stirring processes and high-temperature melt treatment. These approaches have demonstrated effectiveness in refining silicon phase morphologies and improving alloy performance. However, significant challenges remain in achieving uniform microstructure refinement for large-scale castings, particularly in maintaining phase stability during industrial production. Future research should prioritize the development of novel modification systems and integrated processing technologies that can simultaneously optimize both primary and eutectic silicon phases.