The Effect of Silicon Carbide Particulates on Tensile, Fatigue, Impact and Final Fracture Behaviour of 2618 Aluminium Alloy Matrix Composites

In this paper, the tensile, high cycle fatigue (HCF), Impact and fracture behaviour of Aluminium alloy 2618(AA 2618) reinforced with particulates of Silicon Carbide (SiCp) is discussed. AA 2618/SiCp metal matrix composites (MMCs) were fabricated by two-step mixing of stir casting method followed by forging operation. A significant increase of the elastic modulus and tensile strength in the MMCs respect to the unreinforced alloys were evidenced by the tensile tests, while the elongation at fracture decreased. Temperature effects on the tensile properties at 120�C and 200�C were studied. The high cycle fatigue tests showed a marginal increase in fatigue life over the unreinforced alloys. A SEM analysis of the fracture surfaces showed that tensile feature was controlled by micro-void coalescence, interfacial decohesion and fracture of reinforcing particles, whereas fatigue was controlled by interfacial decohesion at the matrix-particle interface. The impact behaviour of the composites was affected by clustering of particles, particle cracking and weak matrix-reinforcement bonding. Agglomeration of the particles reduced the impact strength. The effect of particle size is invariant to the impact strength.