Investigating carbide characteristics effect on multiscale mechanical behavior of AISI 420 steel using crystal plasticity simulation

Understanding the impact of precipitates on the mechanical behavior of material is crucial for effective material design and application. This research focuses on AISI 420 stainless steel, characterized by a ferritic matrix with dispersed carbides in its annealed state. This study employs a multiphase crystal plasticity (CP) model to systematically investigate the influence of variations in carbide characteristics, including their fraction at grain boundaries (GBs), number, average size, and volume fraction, on multiscale mechanical behavior. The workflow includes generating representative volume elements (RVEs) from the microstructure of the as-received AISI 420 steel, calibrating constitutive parameters within the CP model, and validating the CP-RVE model against experimental textures and mechanical properties. A novel method is introduced to capture anisotropic behavior by accurately replicating the experimental approach. Subsequently, diverse RVEs are generated by modifying carbide characteristics to evaluate their impact on stress-strain curves, anisotropic behavior, and micromechanical interactions, while preserving the characteristics of ferrites. The results are compared with experiments and theoretical insights. The findings reveal that an increase in either the fraction of carbides at GBs or the carbide volume fraction enhances the steel’s strength. Empirical equations are derived to predict these effects on mechanical properties efficiently. Moreover, increasing the carbide volume fraction leads to more inhomogeneous strain and stress distributions in both carbides and ferrites, while reducing anisotropy (Lankford coefficient). This study highlights the potential of the CP-RVE model as a tool for exploring macroscale behavior and studying the influence of microstructural features.