In Situ Characterization of Deformation Behavior of Austenitic High Manganese Steels

The mechanical properties of high manganese steels are linked to their hardening mechanisms and their intrinsic behavior during deformation. The characterization of mechanical properties is influenced by the localization of plastic flow and the effect of this localization on the material. Depending on grain size, temperature, and extrinsic strain rate localization of strain, adiabatic heating, and hardening vary in spatial and temporal extent. Even at small strain rates the adiabatic heating of samples reaches temperatures more than 100?K over initial testing temperature due to the sharp localization and last but not least this heating is also dependent on the tested sample size. Furthermore, temperature influences the activated mechanisms of plastic flow. The characterization of temperature increase, strain distribution, and local hardening is pursued in tensile tests with application of infrared thermography. With those techniques it is possible to gather correlations between local strain and temperature. The analysis of dynamic strain ageing effects is also carried out by evaluation of the instantaneous strain rate, the strain rate in the gauge length, in dependence of stress in different alloys, as well as at different strain rate regimes. Thus it is possible to distinguish the onset of TRIP, TWIP and DSA.