Gas-induced semi-solid processing of A356 with in-situ polymer-derived ceramic reinforcement for improved mechanical performance

This research proves the production of SiCN-reinforced A356 aluminum composites through a Gas-Induced Semi-Solid (GISS) process coupled with in-situ pyrolysis of a polymer-derived ceramic (PDC) precursor, poly(urea-methyl-vinyl)silazane (PUVMS). The molten alloy was argon-purged at 610 °C for 5–15 s to create semi-solid conditions and enable the formation of SiCN. Optical and SEM examinations showed that 10 s purged composite (4LMMC10S) had well-refined, nearly globular α-Al grains (38 µm, shape factor = 0.81) and well-distributed SiCN particles. Density tests verified 99 % relative density, whereas shorter (5 s) and longer (15 s) purging resulted in incomplete degassing and particle agglomeration, respectively. The optimized composite possessed a tensile strength of 230 MPa, yield strength of 120 MPa, and elongation of 5.4 %, which is equivalent to ∼ 59 % strength improvement relative to the base alloy. The mechanical improvement is mainly owed to grain refinement and interfacial load-transfer strengthening mechanism at the matrix–reinforcement interface. This new GISS–PDC path presents a feasible method to manufacture high-density, fine-grained aluminum composites with enhanced strength–ductility synergy.