Influence of strain rates and aging time on microstructure and hardness of integrally compressed 6082 aluminum alloy

Abstract

In this study, an in-depth analysis of the microstructure and hardness of 6082 aluminum alloy under a novel solution-forging integrated process was conducted by performing a series of isothermal uniaxial compression tests at various strain rates and aging durations. The results indicated that the highest hardness was 125.0 ± 1.2 HV at peak aging with a forming strain rate of 10 s−1; a 16.1% improvement compared to the conventional T6 forming process. The deformation reduced the subsequent peak aging time from 8 h in the conventional process to 6 h. In addition, the composite phases, including short-range disordered B'/U2 phase and composite phase with multiple structures, were also observed under a strain rate of 10 s−1 with 6 h of aging. As the strain rate increased, the grain size increased, accompanied by an increase in dislocation density. For the integrated process, the deformation microstructure would inherit to the aging state and affect the precipitation kinetics during aging, including grain morphology, dislocation density, and the aging precipitated phase, especially for the formation of composite phase; these were the main reasons for the higher hardness after ageing when compared to the hardness of the alloy under traditional T6 state.