Solid solution softening at high strain rates in Si- and/or Mn-added interstitial free steels Original Research Article

In order to understand the high strain rate properties of high strength steel sheets, stress–strain relations of Fe, Fe–Mn and Fe–Si at high strain rates were investigated. The addition of Mn and Si caused both solid solution hardening at lower strain rates and a decrease of strain rate sensitivity of the flow stress. In addition, the ductility at high strain rates was improved by the addition of solute atoms, an effect which can be related to the decrease in the strain rate sensitivity of the flow stress. Thermal activation analysis revealed that the Peierls–Nabarro mechanism controls the strain rate sensitivity of these steels. The effects of solid solution were discussed based on the theories proposed to explain alloy softening at low temperatures.