Influence of electropulsing treatment combined with pre-deformation on ageing behavior and mechanical properties of 5A90 Al-Li alloy

The electropulsing treatment (EPT) combined with pre-deformation, an environmentally-friendly and efficient method, was designed as a novel ageing process for improving the mechanical properties of the 5A90 Al-Li alloy. Compared with the conventional ageing treatment, the EPT could remarkably shorten the peak ageing time of the alloy by enhancing the coarsening of delta'-Al3Li strengthening precipitates. Particularly, the combination of EPT and pre-deformation could increase the strength of the alloy dramatically with a slight decrease in elongation by increasing the size and volume fraction of delta' phase. The increase in strength was attributed to the combination of the coarsening of delta' precipitates induced by electropulsing, the Ostwald ripening process promoted by pipe diffusion and the localized Joule heating effect contributing to the diffusion, while the decrease in elongation mainly resulted from the formation of coarse beta-Al3Mg2 phase particles accelerated by electropulsing. Based on the diffusion kinetics, the associated mechanisms including the coarsening of delta' precipitates induced by interaction between the electropulsing and vacancies, the promoting effect of pipe diffusion on the Ostwald ripening process and the influence of localized Joule heating were discussed theoretically and schematically. (C) 2019 Elsevier B.V. All rights reserved.