Liquid-Phase Sintering and Properties of PIMed 10-20 vol.% SiCp-Reinforced Aluminium Composites

Abstract

Liquid-phase sintering and properties of powder injection moulded aluminium composite reinforced with SiCp has been investigated via thermal-phase analyses and hardness property. Mixing of 10 and 20 vol.% SiCp and aluminium powder was done via ball milling prior to feedstock preparation at 55% solid loading. Powder injection moulding was carried out at 170°C, followed by solvent and thermal debinding. The brown samples were sintered in a nitrogen atmosphere at 650–660°C, prior to age-hardening. Experimental result shows relatively high % linear shrinkage of 9.9–21.9 % and high % volumetric shrinkage of 34.5–46.5%. Thermal analysis indicates the formation of the liquid around 632 °C, facilitating liquid phase sintering. The composite microstructures consists of uniformly distributed SiCp throughout the densified aluminium matrix. SiCp addition scales up SiCp clustering, accompanying with gap porosity. The composite reinforced with 10 vol.% SiCp possesses higher sintered density at 2.63 g/cm3, yielding 93.1% theoretical. However the maximum macro Vickers hardness was measured at 164.2 Hv for 20 vol.% SiCp – reinforced aluminium composite in the age-hardened condition. Liquid phase sintering was found effective for the microstructure evolution of the PIMed composite, rendering densification. Hardening is influenced by SiCp addition and the roles of AlN, Al2Cu and Mg2Si precipitates.