Strengthening mechanism of particle gradation in 55 vol% SiCp/6061Al composites fabricated by semi-solid hot isostatic pressing

[Display omitted] •Semi-solid hot isostatic pressing (HIP) was proposed for the fabrication of 55 vol.% SiCp/6061Al composites.•The strength and Young's modulus of the composite at the optimum SiCp gradation are 373.09 MPa and 188.62 GPa, respectively.•The thermal and mechanical properties of composites were analyzed using theoretical models and finite element methods. High-volume fraction SiCp/Al composites are widely used in aerospace, optical, and electronic packaging industries due to their high specific strength, superior specific stiffness, and low coefficient of thermal expansion. Hot isostatic pressing (HIP), as a near-net shaping process, enables a low-cost fabrication of difficult-to-machine composites with complex shapes and high performance. This paper investigates the effects of SiCp gradation (with 40 μm:10 μm ratios of 1:0, 3:1, 2:1, 1:1, 1:2, 1:3, and 0:1) on the microstructure, relative density, and thermal and mechanical properties of 55 vol% SiCp/6061Al composites during semi-solid HIP. Results show that the SiC11/6061Al (with 40 μm:10 μm ratio of 1:1) sample achieves a high relative density (99.07 %) and demonstrates excellent mechanical performance (ultimate tensile strength of 373.09 MPa and Young’s modulus of 188.62 GPa). Compared to other engineering materials, this composite offers significantly higher specific stiffness and specific strength while maintaining favorable thermal conductivity and a low coefficient of thermal expansion. Finite element simulation of uniaxial tensile behavior indicates that powder gradation optimizes load transfer. This work provides guidance for HIP forming of high-performance 55 vol% SiCp/6061Al composite components.