Phase Evolution - Property Relationships of PIMed 5 - 40 Vol.% SiCp - Reinforced Aluminium Composite

Abstract

Abstract Microstructure-mechanical property relationships of powder injection molded aluminium composite reinforced with 5 - 40 vol.% silicon carbide particulate (SiCp) has been investigated via thermal and phase analyses along with density and hardness testing. The samples were injection molded and sintered at 645 - 800 °C in N2 atmosphere. Thermal analysis showed endothermic reactions around 632 - 643 °C, related to liquid phase formation. Exothermic reactions about 458 - 461 °C and weight gains around 471 - 479 °C were plausibly associated with AlN formation, which facilitated liquid phase sintering. The composite microstructure exhibited close interfaces between SiCp - Al and Al - Al for 5 - 20 vol.% SiCp addition. Higher SiCp addition however led to SiCp clustering, creating large pores and unreacted SiCp - SiCp interface, which prohibited both liquid flow and rearrangement of the solid grains and pore filling during liquid phase sintering. Optimum SiCp addition was achieved at 15 vol.%, giving the maximum bulk density at 2.68 g.cm−3 or at 94.2 % theoretical density. The maximum macro Vickers hardness values at 138.9 and 166.6 Hv were obtained in the as - sintered and age - hardened conditions respectively.