Effects of hot extrusion on compressive strength and densification of aluminium-based metal matrix composites

Metal matrix composites (MMC) made from powder metallurgy (PM) require post-processing to improve the mechanical properties or achieve the final shape. In this experimental study, Aluminium metal matrix composite (Al-MMC) was first fabricated through PM, followed by a hot extrusion process to study the effects of extrusion on compressive strength and density. Hot extrusion of Al-MMC results in microstructure refinement, enhanced dispersion of reinforcement particles and improved mechanical properties. The experimental findings revealed that hot extrusion of Al-MMC resulted in densification, reflected as an average improvement of 5% in the density. An average improvement of up to 22% was observed in the compressive strength of the Al-MMC. Therefore, hot extrusion can be considered an effective post-processing method for enhancing the Al-MMC fabricated through PM. It was also found experimentally that the extrusion ratio also affects the mechanical properties and performance of Al-MMC. It was revealed that the compressive strength is enhanced with an increase in extrusion ratio. It is also important to note that the PM process is one of the processes which offers reasonable control over the utilisation of starting material. Hence, reinforcement retention is higher than other methods like stir casting.