Mechanisms of types B and C serrations in the tensile flow curve of C-bearing high Mn steel

Abstract

In the present study, the mechanisms of types B and C serrations in the tensile curves of C-bearing high Mn steel were investigated. Many tensile tests were performed at various temperatures (313–573 K) with two different initial strain rates (ε˙ini = 1 × 10−3 and 1 × 10−4/s). Type B serrations appeared in a lower tensile temperature range compared to type C serrations. Whereas a critical strain for type B serrations (ecB) was similar to yield strain regardless of tensile temperature and strain rate, a critical strain for type C serrations (ecC) increased with increasing tensile temperature, indicating the inverse PLC behavior of ecC. The inverse PLC behavior of ecC was explained by the intensified dynamic strain aging (DSA) model. The repetition of rapid aging and easy breakaway causes the discontinuous propagation of the PLC band with flickering, thereby resulting in type B serrations.

Keywords

• High Mn steel
• Dynamic strain aging
• Serration
• Portevin-Le chatelier effect
• C diffusion
• Digital image correlation