Study on the mechanical behaviour of LM24 alloy reinforced with ZrB 2 and fly ash hybrid composites using stir casting technique

The objective of the present investigation is to develop zirconium diboride (ZrB2) and fly ash-reinforced LM24 aluminium alloy-based hybrid composites through the stir casting process. The study was conducted with different weight percentages of ZrB2 (2.5, 5, and 7.5 wt%) with the fixed fly ash content of 2.5 wt%. The microscope analysis showed a fine dispersion of fly ash as well as ZrB2 particles in the aluminium matrix. It was assessed that the incorporation of reinforcements led to an enhancement of hardness up to the maximum value of 127 BHN for the hybrid composite containing a total of 10 wt% reinforcements, which is 38% higher than that of the unreinforced LM24 alloy. The ultimate tensile strength also increased, and it was found to be enhanced by upto 12.2% more than the matrix alloy. Nevertheless, these improvements were obtained at a rather significant decrease in ductility of the composites, with the LM24 alloy remaining ductile as a counterpart. Furthermore, lower impact strength was observed for the hybrid composites; a fractographic study revealed that the failure was due to brittle fracture. The hybrid composite with 10 wt% reinforcement exhibited the lowest impact energy absorption of 1.6 J, which is 36% lower than the LM24 alloy.