Inverse grain size dependence of critical strain for serrated flow in a Fe–Mn–C twinning-induced plasticity steel

Abstract

The grain size dependence of critical strain for serrations associated with dynamic strain aging has been examined in a twinning-induced plasticity steel. Tensile tests were conducted at various deformation temperatures and strain rates in a Fe–17Mn–0.6C steel (mass%) with grain sizes 3.5, 10, 23, 37, and 44 µm. In addition, the carbon concentration varied from 0.3 to 0.8 in the Fe–17Mn–xC steels with coarse grains. The critical strain for the onset of serrations was found to show an inverse grain size dependence, i.e., the critical strain increased with the decrease in grain size, the opposite of what occurs in conventional alloys.

Keywords:

• austenitic steel
• twinning-induced plasticity steel
• dynamic strain aging
• grain size
• plastic deformation
• tensile testing
• mechanical behavior

Acknowledgments

Motomichi Koyama acknowledges a Research Fellowship of the Japan Society for the Promotion of Science for Young Scientists. The Materials Manufacturing and Engineering Station and the Materials Analysis Station at the National Institute for Materials Science supported this study through the production of the samples and by carrying out the analysis of the chemical compositions.