Microstructure and mechanical behaviour of in situ fabricated AA6061-TiC metal matrix composites

AA6061-TiC composites were developed by in situ reaction of molten AA6061 alloy with potassium hexafluorotitanate salt and pure graphite at a temperature of 900 °C. The in situ composites were subjected to hot forging at 500 °C and uniform strain rate of 0.0115 mm s−1 with degree of deformation of 65%. Both cast and forged in situ composites were subjected to grain size analysis and scanning electron microscopy studies to study the dispersion of TiC particles. Mechanical properties like Brinell hardness and tensile properties were evaluated to measure the effect of TiC particles on the AA6061 matrix. Microstructure of forged composites revealed uniform dispersion of TiC particles without forming any lumps at any particular regions. Brinell hardness and tensile strength of cast and forged in situ composites increased with increasing TiC particle content. The improved mechanical properties were attributed to good dispersion of TiC particles, grain refinement of the matrix and dislocation strengthening. Every fracture developed in cast ones was due to inter-dendritic cracking while in the case of forged ones it had mixed mode of fracture with dominating ductile nature.