Nucleation and Propagation of Portevin-Le Châtelier Bands in Austenitic Steel with Twinning Induced Plasticity

Twinning induced plasticity (TWIP) steels have high manganese content and exhibit extreme strain hardening and elongation. Tensile flow curves show serrations due to dynamic strain aging associated with solute-dislocation interactions. Highly inhomogeneous plastic flow is manifested by Portevin-Le Chatelier (PLC) band nucleation and propagation. In this research, TWIP steel tensile specimens were quasi-statically deformed to fracture at room temperature. Images of one specimen surface were recorded with a variable framing rate high speed digital camera and custom image acquisition software. A digital image correlation technique was used to compute incremental strain rate maps that enabled study of PLC band nucleation and propagation. The impact of tensile specimen geometry on the location of band nucleation along the specimen gauge section was also explored. Fracture surfaces and material chemistry were examined with SEM and energy dispersive mapping.