The nonlinear analysis of Portevin-Le Chatelier (PLC) effect: An application to medium Mn steel

• Multifractal provides an effective method for quantitative analysis of PLC effect in medium manganese steel. • The nonlinear characteristics of local stress jump in PLC effect are consistent with multifractal dynamic system. • The chaos of plastic instability system of medium manganese steel depends on strain rate and austenite content. The instability of plastic flow in medium manganese steel was investigated through uniaxial tensile tests conducted at room temperature across various strain rates. The Portvin-Le Chatelier (PLC) effect was analyzed using statistical methods and a multifractal approach. The findings indicate that the zigzag stress–strain curves associated with instability plastic flow exhibit typical multifractal characteristics. Furthermore, the multifractal analysis quantifies the influence of strain rate and initial phase composition on the instability characteristics of the stress–strain curves. Specifically, it was observed that lower strain rates and austenite content correspond to a chaotic state, whereas higher strain rates and austenite content result in self-organizing critical dynamics. Finally, the underlying physical mechanisms driving these differing modes of behavior are discussed, with a focus on their relationship to strain rate and the initial austenitic phase fraction.