Synthesis and Characterization of AA6351/SiC Composites Using Ball Milling Combined with Hot Extrusion

<div>In this investigation, AA6351 alloy matrix composites with a larger volume proportion of SiC (20 wt%) were fabricated and tested for microstructure and mechanical behavior. Composites were hot extruded from mechanically milled matrix and reinforcements. Hot extrusion uniformly distributed reinforcements in the matrix and strengthened phase interaction. Mechanical ball milling causes AA6351 powder to become more homogeneous, reducing the mean particle size from 38.66 ± 2.31 μm to 23.57 ± 2.31 μm due to particle deformation. The micrograph shows that the SiC particles are equally dispersed in the AA6351 matrix, avoiding densification and reinforcing phase integration issues during hot extrusion. In hot extrusion, SiC particles are evenly distributed in the matrix, free of pores, and have strong metallurgical bonds, resulting in a homogenous composite microstructure. SiC powders and mechanical milling increase microhardness and compressive strength, giving MMC-A 54.9% greater than AA6351 alloy (as unmilled). With 175.82% strength and ductility, MMC-B outperforms MMC-A. This shows that coarse-grain AA6351 improves the composite’s compressive strength and ductility. This study improves mechanical performance by employing mechanical milling and hot extrusion to get fine AA6351 matrix grain size and homogenous SiC reinforcement.</div>