Processing and evaluation of nano SiC reinforced aluminium composite synthesized through ultrasonically assisted stir casting process

Abstract

Aluminium composites were synthesized through an ultrasonically assisted stir casting method by reinforcing 0.5 wt%SiC, 1.0 wt%SiC, 1.5 wt%SiC and 2.0 wt%SiC nanoparticles. Ultrasonication was carried out to the composite melt to refine the grain size and to achieve uniform nano-SiC dispersion in the aluminium matrix. Scanning electron microscopy (SEM) reveals the uniform dispersion of nano-SiC particles in the 0.5 wt%, 1.0 wt% and 1.5 wt% SiC reinforced compose. However, the X-Ray Diffraction (XRD) peaks confirm the Al2Cu intermetallic phases in the Al- 2.0 wt% SiC composite. The mechanical properties of the synthesized composites were significantly enhanced with the incorporation of SiC reinforcements and the maximum hardness and ultimate tensile strength (U.T.S) of 163 BHN and 431 MPa was attained for 1.5 wt% SiC reinforced composite. Nevertheless, the generated brittle agglomeration at 2.0 wt% SiC reinforcements decreases the mechanical properties of the composite due to the variation of thermal expansion coefficients between the matrix and the agglomerations. The yield strength of the fabricated Al– SiC composites was analyzed through different strengthening mechanisms. Results concluded that the yield strength contribution due to thermal mismatch is more influenced followed by the Orowan strengthening and grain refinement strengthening mechanism. In addition to this, the contribution of the strengthening mechanisms was found to be increased with the addition of SiC nanoparticles. Fractography investigation for the fractured tensile specimens reveals the ductile fracture for unreinforced aluminium and brittle fracture for the SiC-reinforced composites due to the presence of cleavage texture of the fractured surfaces of Al–SiC nanocomposites.

Keywords

• Nano-SiC reinforcements
• Stir-casting
• Mechanical properties
• Metal matrix composite