The dynamic behavior of three high manganese steels with very different stacking faultenergy (SFE) values (4-30 mJ/m2) were studied using high strain rate torsional tests. The hotrolledmicrostructure of the steel with the lowest SFE of 4 mJ/m2 consisted of a duplex mixture ofaustenite and ε-martensite, but those of the other two steels were fully austenitic. The deformedmicrostructures were stu...