Influence of strain rate on the mechanical behaviour of high-manganese TWIP steel tested using a flywheel machine

Abstract The present study investigates the dynamic tensile behaviour of a high-manganese austenitic TWIP steel (X45MnAl20-4) using a flywheel-based testing system, with emphasis on strain rate effects. Dynamic tensile tests with strain rates ranging from approximately 300 to 950 s −1 . The force vs. time signals were recorded during the course of tests. This allowed the true stress–true strain diagrams to be determined. It has been established that the propagation of elastic stress waves within the test stand construction caused oscillations in the σ true -ε true curves. The smoothing of these oscillations has been approached through the utilisation of a power function as an approximation. The influence of strain rate on the tested steel characteristics such as flow stress, plastic deformation work, and absorbed energy (SEA and VEA) was quantitatively evaluated on the basis of the obtained σ true -ε true curves. Microscopic observations confirmed that mechanical twinning is the predominant deformation mechanism in the steel studied, with increased twinning density and multisystem twinning under dynamic conditions. A comparison of the X45MnAl20-4 steel with other TWIP steels and DP steel has shown that it exhibits a competitive specific SEA value. This confirms its suitability for use in structural components operating under dynamic loading conditions. The findings of the study underscore the significance of accurate measurement data interpretation and selection of suitable correction methods when analysing the dynamic mechanical responses of TWIP steels by means of a flywheel machine.