Fracture toughness (K_1C) and tensile properties of as-cast and age-hardened aluminium (6063)silicon carbide particulate composites

The tensile and fracture behavior of as-cast and age-hardened aluminium (6063), silicon carbide particulate composites produced, using borax additive and a two step stir casting method, was investigated. Al (6063), SiC_p composites having 3, 6, 9, and 12 volume percent of SiC were produced, and sample representatives of each composition were subjected to age-hardening treatment at 1800 °C for 3 hours. Tensile and Circumferential Notched Tensile (CNT) specimens were utilized for tension testing to evaluate, respectively, the tensile properties and fracture toughness of the composites. Experimental results show that the ageing treatment resulted in little improvement in the tensile strength of the composites. The tensile strength and yield strength increased to almost the same magnitude with an increase in SiC volume percent for both as-cast and age-hardened conditions. The increase was, however, more significant for the 9 and 12 volume percent SiC reinforcement. The strain to fracture was less sensitive to volume percent SiC reinforcement and ageing treatment, with values less than 12% strain to fracture observed in all cases. The fracture toughness, however, improved significantly with ageing treatment (as-cast K1C=6.63-6.71MPam12; ageing treatment K1C=7.57-8.2MPam12).