Friction Stir Welding of Al–Cu Alloy Metal Matrix Composites Reinforced with B₄C and Graphite Particle Fabricated by Stir Casting and Thixoforming Method

Abstract

Aluminum with high strength, improved corrosion resistance, lightweight-to-strength ratio, and toughness provides a technical challenge in the joining process. An attempt to weld Al–Cu alloy metal matrix composite reinforced with B₄C and graphite particle by friction stir welding (FSW). In this paper, stir casting and thixoforming method are used for fabricating AA2017 and its composite, which was reinforced with varying B₄C (0.5, 1 and 1.5 wt%) and constant graphite (1 wt%). The addition of B₄C improves the wear resistance, and graphite acts as solid lubricant for aluminum matrix. The microstructures of metal matrix composites studied by optical microscopy with the absence of defects and porosity and X-ray diffraction (XRD) patterns revealed the presence of reinforcement particles. SEM image confirms the reinforcement particles are well distributed and act as a bonding agent with the metal matrix. The hardness of composites AA2017+1.5% B₄C+1% graphite increased up to 19% compared to base alloy. The maximum increase in tensile strength from 224 to 251 MPa with strength increased up to 15.64%, in addition to 1 wt% boron carbide and 1 wt% graphite, was observed. The increase in B₄C particle generally increases the hardness and decreases the tensile strength and vice versa, due clustering of particles and segregation.