Effect of Severe Plastic Deformation and Aging States on Microstructure and Mechanical Properties of 2024 Aluminum Alloy

Al2024 aluminum alloy is subjected to equal channel angular pressing (ECAP) as severe plastic deformation in the quenched and overaged states to analyze the effect of different ECAP-based thermomechanical processes on microstructure and mechanical properties of the alloy. Application of ECAP process to both overaged and quenched samples brings about significant grain refinement in the microstructures. Aging the overaged + ECAPed sample at 180 degrees C for 24 h results in a partially aged (underaged) microstructure with GPB (Guinier-Preston-Bagaryatsky) zone, semicoherent S '', and S ' precipitates. Such a microstructural alteration is achieved in the quenched + ECAPed sample after aging at 100 degrees C for 7 h. 225 HV hardness as the highest hardness value reported in the Al2024 alloy subjected to thermomechanical processes including ECAP and aging steps is achieved after aging the quenched + ECAPed sample at 100 degrees C for 7 h. For both cases (overaged + ECAP and quenched + ECAP), strength-plasticity matching is achieved in the ECAP + underaged state where the microstructure consists of GPB zones, semicoherent S '', and S ' precipitates rather than incoherent S precipitates. Such a strength-plasticity matching is attributed to the planar slip in the underaged samples rather than cross-slip that occurs in the overaged samples.