The role of Si additions to the solidification process, microstructure evolution, thermo-physical and mechanical properties of hypereutectic Al–Ni alloy are systematically investigated. It reveals that the Si addition has a significant impact on the solidification process and microstructure of the alloy, and consequently the thermo-physical and mechanical properties. As the Si addition increases, the dendritic eutectic and blocky primary Si phases will be formed. It turns out that the thermal conductivity (TC) of the alloy degrades due to the precipitation of large and blocky Si phases, while the thermal expansion property is improved. The ultimate tensile strength (UTS) of the Al–10Ni-xSi alloys is improved initially, followed by degradation due to greater precipitation of the Si phase, the elongation (EI) is inevitably damaged. The alloy with 15 wt% Si exhibits the TC of 162 ± 3 W/(m·K) at 25 °C, CTE of 14.3 ± 0.1 × 10−6/K (@25–100 °C), UTS of 205 ± 5 MPa, EI of 3.9 ± 0.1% and Vickers hardness of 186 ± 4 HV. We successfully obtained an as-cast Al alloy with excellent thermo-physical and favorable mechanical properties, potentially for thermal management materials.
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