Effect of deformation amount on microstructure and properties of AA2024-T8I4 with deep cryogenic treatment

Abstract

To simultaneously improve the mechanical properties and corrosion resistance of AA2024 aluminum alloy, a T8I4 with deep cryogenic treatment (DCT) process is proposed, which includes solution heat-treatment, cold-drawing deformation, pre-aging, DCT and re-aging. The microstructure of AA2024 is observed by confocal laser scanning microscope, scanning electron microscopy and transmission electron microscopy. The properties of AA2024 are studied by hardness measurement, tensile test, friction and wear test, exfoliation corrosion test, intergranular corrosion test and electrochemical corrosion test. On comparison with T6, AA2024-T8I4 +DCT obviously increases its hardness, tensile strength and wear resistance. AA2024-T8I4 +DCT has similar corrosion resistance to T7X two-stage aging. According to comprehensive analysis, the MPts in AA2024-T8I4 +DCT with 3 % deformation amount have the maximum pinning force to the dislocations, and the alloy has the largest hardness, strength and the best wear resistance. The discontinuous grain boundary precipitates in AA2024-T8I4 +DCT with 1 % deformation amount are discontinuous and fine, and the precipitate free zone is not obvious, which makes the corrosion difficult to develop. The alloy has the shallowest intergranular corrosion depth, the smallest corrosion rate and the best corrosion resistance