Enhancement of Surface Hardness and Tensile Properties of Al2024 Alloy Through Modified Age Hardening Path

This study investigates the alteration made in the solutionising step of age hardening to witness timed quench hardness number distribution along the cross section of the cylindrical surface, higher at the surface and lower at the core region of Al2024 alloy. Specimens are heated above solvus temperature of the alloy i.e., at 550 °C, quenched by the modified novel method and aged at temperature range 120–240 C isothermally for 3-time durations (6, 10, and 14h). Optical microscopy images are analyzed to verify the microscopic flaws present and SEM images confirm the variation in grain size across the cross section of modified age hardened specimen. Vickers hardness, tensile and Charpy impact tests are performed to plot hardness number distribution along the heat treated cylindrical specimens, tensile property and impact resistance of the specimen to failure respectively. Aging at 180 °C shows a good aging temperature with reasonably elevated hardness observation during 10h of aging. Aging at 120 °C shows poor demonstration of aging kinetics whereas aging at 240 °C shows lesser increase in surface hardness with faster over aging phenomena. At 180 °C aging shows 50% reduction in impact resistance data during conventional peak age hardened whereas 100% improvement in modified peak age hardened specimens over that of untreated one. Also, at the same aging temperature, nearly 100% improvement in ductility (%elongation at peak) without any sacrifice in UTS is observed. Phase analysis shows prominent peaks for the intermetallic phases like, AlCu, AlCu 4 and Al 2 CuMg in aged alloy. Upto 14% enhance in surface hardness is observed while aging in the targeted temperature range. The result substantiates the hardness, tensile and impact tests result with the microstructure of heat-treated specimen.