Intermittency and Deformation Band Propagation in an Austenitic FeMnC TWIP Steel

Plastic deformation of austenitic FeMnC TWIP steels exhibits complex spatiotemporal patterns associated with the occurrence of deformation bands and the concomitant fluctuations of the deforming stress. Although the plastic instability is a generic property of these steels and is usually attributed to interaction of dislocations with solutes (the Portevin-Le Chatelier effect), both the kinematics of the deformation bands and the characteristic shape of stress serrations observed in the carbon-containing TWIP steel at room temperature manifest unusual features. The nature of these peculiarities and the mechanism of jerky flow in such steels are unclear. In the present work, an attempt is made to get an insight into the jerky flow in the Fe22Mn0.6C steel by studying the time series characterizing the evolution of plastic deformation at various scales: stress-time curves, local strain field, and acoustic emission accompanying the deformation processes. Stress and strain fluctuations related to two distinct scale ranges are detected and characterized.