Investigation on the Effect of Retrogression and Re-aging on Microstructure and Mechanical Properties of 2024 Aluminum Alloys

In the current study, a new artificial aging process, Retrogression and re-aging (RRA), which is a multi-step precipitation hardening, was utilized to investigate its effect on microstructure and mechanical properties of Al2024 alloys and compare the results with conventional T6. The microstructural evolution during heat treatment was studied by SEM and TEM, and tension test and hardness test were used to investigate the mechanical properties of specimens. The results showed that RRA process has improved the mechanical properties of Al2024 in comparison with T6. Yield stress, UTS, elongations and brinell hardness in RRA samples are higher than T6. The microstructural investigation revealed that during RRA, more secondary particles solute in matrix and more and finer S and theta phase precipitate. It was also observed that in RRA samples, S and theta phases have better distribution in Al matrix.