Effects of cyclic pre-straining on mechanical properties of an austenitic microalloyed high-Mn twinning-induced plasticity steel

摘要

The current work was undertaken for gaining insight into the influence of cyclic pre-straining on monotonic flow of a 0.6C-22Mn-0.0.3V (in wt-%) TWIP steel. Fully reversed tension-compression strain-controlled cycling at four strain amplitudes until the saturation stage was used for pre-straining. The yield and tensile strength and elongation of these cyclically pre-strained samples were measured and compared to those of the non-pre-strained sample. Dislocation structures of the cyclically pre-strained samples were examined using transmission electron microscopy. Cyclic hardening resulting in a saturation stage around the mid-life took place during cycling, the degree depending on the strain amplitude. Tensile testing of cyclically pre-strained samples showed that the yield strength increased by 28% by pre-straining at the strain amplitude of 0.5% for 250 cycles, while the plastic strain amplitude was only 0.15%, the monotonic yield strength increased by 28%, from 500 to 640 MPa. Pre-straining at the 2% amplitude for 40 cycles even doubled the yield strength. The dislocation structure consisting of dislocation cells with a very low number of mechanical twins was found to be a reason for the pronounced strengthening.