The role of cryogenic dipping prior to ECAP in the microstructure, secondary-phase precipitation, mechanical properties and corrosion resistance of AA6012 (Al-Mg-Si-Pb)

Literature on ECAP generally deals with room temperature or high-temperature deformation regimes. Very few data on low-temperature SPD processes have been published. This study presents some experimental results on the effect of cryogenic treatment prior to ECAP-BC on microstructure modification, mechanical response, and corrosion behaviour of an AA6012 Al-Mg-Si-Pb alloy. This type of Pb-bearing AA6000-series alloy, is produced and used for its marked post-extrusion machinability. The mechanical properties were inferred by nanoindentation to measure hardness, H, and local elastic modulus, Er. These data were presented in form of maps to account for the whole H and Er evolution with cumulative strain. The experimental results showed significant microstructure differences between the cryogenic treated ECAP condition and the conventional ECAP at room temperature. These differences were also correlated with electron microscopy inspections, XRD. Finally, the cryogenic treatment prior ECAP also affected the alloy corrosion behaviour.