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A technique to achieve an excellent strength-ductility balance in AA2024 alloy

Roodgari Mohammad Reza, Jamaati Roohollah

Archives of Civil and Mechanical Engineering

2023

Vol. 23, no. 1

art. no. e12, 2023

In the current study, the microstructure and mechanical properties of AA2024 alloy produced by a new technique consisting of solution treatment, instantly followed by asymmetric cold rolling with a reduction of 65%, and subsequent artificial aging (heat treatment) with four temperatures of 190, 300, 400, and 500 °C was investigated. The additional shear strain in asymmetric rolling led to the formation of a high amount of shear bands in the microstructure of AA2024 alloy. During aging treatment at the temperature of 300 °C, recrystallization was locally started in the shear bands. The grain morphology of the rolled sample was not much changed after aging at the temperature of 190 and 300 °C. However, the samples aged at 400 and heat-treated at 500 °C had different microstructures. In addition, with increasing the temperature to 500 °C, numerous dispersoids were formed in the microstructure of the AA2024 alloy. The sample after aging treatment at 190 °C had the maximum hardness, yield strength, and ultimate tensile strength of 207.4 HV, 481.7 MPa, and 605.1 MPa, respectively, along with a desirable elongation (7.9%). By increasing the aging temperature, the hardness and strength of the alloy considerably decreased. The aging treatment at 400 and heat treatment at 500 °C led to the complete elimination of the strain hardening effect and recurrence of Portevin-Le Chatelier (PLC) in the stress-strain curves. The fracture mode was often a ductile mode for all samples. By increasing the aging temperature, the number and size of dimples increased. As a consequence, the processing technique used in the present study resulted in an excellent strength-ductility balance due to an appropriate combination of strain hardening and precipitation hardening.