Characterization of 14YWT oxide dispersion strengthened structural materials under electrically-assisted tension

Abstract

In this study, we investigated the use of an electrically-assisted (EA) forming process to reduce the forming force of ODS ferritic steels. The effects of a continuous electric current on 14YWT, which is a kind of ODS material, during plastic deformation were evaluated. First, EA uniaxial tension tests show that the electric current is able to reduce the flow stress of 14YWT. 14YWT exhibits a ductility minimum at a current density of 34.5 A/mm2 which is consistent with fractography results. Hardness measurements and TEM results indicate that oxide particles are stable during the EA process. Second, microstructure analysis was performed on the sample in its as-received state and after current treatment. The microstructures are stable when subjected to high current density. Third, a thermal model was developed to predict the Joule heating temperatures. The temperatures were compared with the experimental results. Finally, a temperature-dependent hardening model was used to explore the mechanisms acting during EA deformation. Since the model can accurately predict the yield strength of 14YWT under EA conditions without the incorporation of non-thermal effects, it can be concluded that the reduction in yield strength is due to the Joule heating generated under continuous current loading conditions. An oven-heated pure thermal tension test was conducted to confirm this conclusion. The findings generated from this study will result in the development of innovative manufacturing processes such as the electrically-assisted tube forming processes.