Effect of particles size variation of graphite on mechanical properties of piston materials

This work investigates the influence of varying graphite particle sizes on the mechanical properties of pistons, crucial components of internal combustion engines. Graphite sourced from used batteries were ball milled for durations of 3, 6, and 9 hours to achieve size reduction. These milled graphite particles are then dispersed into molten pistons to create composites. Additionally, a control sample comprising an aluminum (AI) alloy without graphite is included for comparison. Particle size analysis reveals graphite sizes of 125 µm, 90 µm, and <90 µm for milling durations of 3, 6, and 9 hours, respectively. The chemical composition of the ingot used as the base material for the pistons comprises 85% Al, 11.37% Si, and trace elements. The composite pistons undergo testing for hardness and tensile strength, with results indicating significant enhancement in mechanical properties with decreasing graphite particle size. Specifically, compared to the control sample, the composite with graphite particles <90 µm exhibits a notable 53% increase in tensile strength (140.44 MPa) and a 2.5% increase in hardness (48.67 HRB). These findings emphasize the potential for optimizing piston performance by controlling graphite particle size during production, highlighting the beneficial relationship between reduced graphite particle size and improved mechanical properties.