On the effect of microstructural heterogeneity on yield point phenomena in architectured steel: Revealed by in-situ micro-digital image correlation (μDIC)

Lüders banding in carbon steel is a manifestation of discontinuous yielding and limits the formability and surface quality of the steel. In this study, we explore the role of microstructure heterogeneity in suppressing the formation of Luder band. A ferritic steel was processed by decarburization, cold rolling, and controlled annealing to induce partial recrystallization and develop a heterogeneous grain structure. This micro-architectured material resembles a functionally graded structure and inhibits the propagation of Lüders bands. We propose a simple model in which heterogeneity disrupts the spatial coherence of yield front propagation. Suppression of Lüders bands was confirmed through tensile testing with micro- digital image correlation (DIC) and in-situ micro-tensile testing in Scanning Electron Microscopy (SEM). This heterostructure engineering approach demonstrates a viable alternative strategy for tuning the deformation behavior of ferritic steel.