The Effect of Si Content on the Microstructure and Thermal Conductivity of Al-XSi-3Cu-5Mg Alloys Produced by Laser Additive Manufacturing

High-silicon aluminum alloys are widely utilized in heat dissipation devices due to their outstanding thermophysical properties and represent a major focus in thermal management research. The incorporation of silicon imparts numerous beneficial attributes to the alloy; however, an excessive amount of silicon may result in a decline in thermal conductivity. To investigate the optimal silicon content within the alloy system, this study employed laser additive manufacturing to fabricate Al-Si-3Cu-5Mg alloys with varying silicon concentrations. Comprehensive microstructural characterization was conducted, alongside systematic evaluations of wear resistance and thermal performance. The results demonstrate that as the silicon content increases, hardness rises progressively from 134 HV to 326 HV, the friction coefficient decreases from 0.5 to approximately 0.22, and wear resistance is significantly enhanced. Meanwhile, thermal conductivity exhibits a linear decreasing trend, dropping from 227 W/(m·K) to around 140 W/(m·K), and shows an inverse relationship with the coefficient of thermal expansion. These phenomena are attributed to the complex interactions between silicon and the added copper and magnesium elements during the additive manufacturing process. This study provides valuable insights for optimizing alloy compositions to improve the efficiency of heat sinks in industrial applications. Furthermore, a mathematical model for calculating thermal conductivity is developed, and a thorough comparison with experimentally measured values indicates that the model offers a satisfactory interpretation of the experimental outcomes.