Effect of Thickness Reduction on the Hardness and Wear Resistance of Cold Rolled Aluminium 6061 Plates

Abstract

This study investigates the effects of varying thickness reductions on the micro hardness and wear resistance of Al 6061 alloy steel plates. Initial 20 mm thick plates were cold rolled to achieve reductions of 10%, 25%, 50% and 75%. Vickers Hardness Number (VHN) testing revealed that micro hardness improved up to a 50% reduction, attributed to strain hardening and grain refinement. However, a significant decline in VHN was observed at a 75% reduction, likely due to over-hardening and microstructural degradation. Wear resistance was evaluated using a pin-on-disc wear tester. Results demonstrated enhanced wear resistance for samples with up to 50% reduction, indicated by lower volumetric wear rates. This improvement correlates with increased surface hardness and reduced plastic deformation observed in field emission scanning electron microscope analysis. Conversely, samples with a 75% reduction exhibited poor wear resistance, characterized by higher wear rates and severe wear track damage, including deep grooves and surface fractures. The study concludes that optimal thickness reduction can significantly enhance the microhardness and wear resistance of Al 6061 alloy. However, excessive reduction beyond 50% leads to detrimental effects on microstructure and wear performance. This research underscores the importance of carefully controlling cold rolling parameters to achieve desirable material properties for practical applications in industries requiring high wear resistance.