Cracking induced by second phases in a continuously cast micro-alloyed steel: Experiments and crystal plasticity modeling

Transverse corner cracks in continuously cast micro-alloyed slab are closely associated with second-phase particles, yet their micro-scale geometric and spatial effects remain poorly quantified. In this study, a systematic framework integrating experimental characterization with crystal plasticity (CP) simulations was developed to decouple the independent effects of particle size, morphology, and spatial distribution on cracking susceptibility. Experimentally, quantitative characterization of austenite size, ferrite film thickness, and particle characteristics provided geometric parameters for numerical modeling, and high temperature tensile data served for model calibration. Numerically, a novel multiphase coupled model was developed by integrating CP for austenite with continuum damage mechanics coupled J 2 plasticity for ferrite. Validated by industrial comparisons, the proposed framework accurately captured heterogeneous strain distribution and intergranular damage evolution. Simulation results reveal a dual competitive effect of particle number, where increasing particle number accelerates damage initiation yet unexpectedly retards propagation by disrupting the continuity of crack path. Morphologically, square particles induce a peak plastic strain approximately 3.3 times higher and a damage propagation rate 4.4 times faster than circular ones. Notably, an inverse size effect is observed, whereby local damage is minimized at a critical particle size of 3 μm for both morphologies. Furthermore, spatial clustering amplifies the morphology-induced damage gap by 3.0 times. Once the cluster index exceeds 0.6, square particles trigger exponential damage aggravation, driving a damage transition from linear bridging to blocky coalescence. This study establishes a quantitative mapping between precipitation characteristics and micro-damage evolution, providing critical metallurgy insights for process optimization and advanced alloy design.