Effect of Pulsed Electric Current on TRIP-Aided Steel

In the present study, the tensile deformation behavior of transformation-induced plasticity (TRIP)-aided steel under pulsed electric current is investigated. When a pulsed electric current is applied to the specimen during entire tensile deformation, a significant reduction of elongation is observed. The reason is that the mechanically induced martensitic transformation (MIMT) effect does not work properly as the stability of retained austenite phase increases due to temperature rise by the applied electric current. To improve the ductility of the TRIP-aided steel, the pulsing pattern of electric current is modified to apply the electric current only in the early stage of deformation immediately before the phase transformation of retained austenite phase begins to take place. As a result, the elongation is significantly increased by delaying the MIMT effect and making it work properly in the latter stage of deformation. Also, the electrically-induced annealing effect, which occurs in the early stage of deformation where a dislocation plasticity occurs dominantly, contributes to the improvement of elongation. The modified pulsing pattern suggested in the present study provides an easy-to-implement technique to improve the formability of the TRIP-aided steel.