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

¹ School of Metallurgical Engineering, Suranaree University of Technology, 111 University Avenue, Muang, Nakhon Ratchasima, 30000, Thailand
² The Metallurgy and Materials Science Research Institute, Chulalongkorn University, Phayatai Road, Patumwan, Bangkok, 10330, Thailand

^a Tapany Patcharawit: tapany@sut.ac.th

Abstract

Liquid-phase sintering and properties of powder injection moulded aluminium composite reinforced with SiC_p has been investigated via thermal-phase analyses and hardness property. Mixing of 10 and 20 vol.% SiC_p 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 SiC_p throughout the densified aluminium matrix. SiC_p addition scales up SiC_p clustering, accompanying with gap porosity. The composite reinforced with 10 vol.% SiC_p 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.% SiC_p – 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 SiC_p addition and the roles of AlN, Al₂Cu and Mg₂Si precipitates.