Effect of Grain Size on the Local Deformation Behavior Associated with the Discontinuous Yielding in a High Mn Austenitic Steel

The discontinuous characteristics of the yielding behavior in a high Mn austenitic steel was examined in specimens with different grain sizes. In the stress–strain curves of the fine-grained specimens, both the stress drop and Lüders strain were observed, but as the grain size increases it becomes difficult to distinguish the signals related to the yield point phenomena. The effect of grain size on the local deformation behavior was quantitatively investigated using both the digital image correlation method and a simple displacement analysis method. While the velocity of the Lüders band was higher, the amount of Lüders strain was decreased with increasing the grain size. The results are mainly related to the degree of strain concentration during Lüders band propagation. Based on the interactions between the dislocations and grain boundaries, the effect of grain size on the overall discontinuous yielding behavior was discussed.