Mechanistic Insights Into Strain‐Controlled Low‐Cycle Fatigue of 22MnB5 Steel: Microstructure and Constitutive Modeling

ABSTRACT

22MnB5 boron steel is widely used in hot‐stamped automotive structural components owing to its high strength and excellent crashworthiness. This study investigates the cyclic deformation behavior of cold‐rolled 22MnB5 steel under uniaxial low‐cycle fatigue at strain amplitudes of 0.4% and 0.6%, representative of cyclic loading during forming and service. The specimen tested at 0.4% exhibited initial cyclic softening followed by hardening, whereas the 0.6% specimen showed initial hardening, subsequent softening, and pronounced secondary hardening. Interrupted fatigue tests combined with EBSD and XRD established a direct correlation between strain amplitude–dependent cyclic response and the corresponding microstructure and texture evolution. Higher strain amplitudes resulted in greater intragranular deformation, reflected by increased grain average misorientation, while cube {100}<001> and copper {112}<111> texture components progressively increased with cycling. These findings provide mechanistic insights for optimizing forming strategies and improving the fatigue durability of hot‐stamped automotive components.