Mechanical Properties of Fine-Grained Low Alloy Steel Investigated by Crystal Plasticity Finite Element Method

Fine-grained low-alloy steels are prepared via hot rolling, warm rolling, and subsequent annealing in the intercritical zone, resulting in a microstructure consisting of a ferritic matrix and spherical cementite. Characterization of microstructure and mechanical properties indicated that when the average grain sizes decreased from 4.5 to 1.5 μm, a continuous improvement in yield strength and tensile strength was observed. Grain-refinement and precipitation strengthening of cementite are the key reasons for the significant increase in strength. Using crystal plasticity finite element methods, quasi-static tensile simulations were performed on steels with various grain sizes, and a set of crystal plasticity parameters suitable for fine-grained low-alloy steels was obtained. The simulation of size effects was innovatively performed by modifying the single-crystal strength based on the Hall–Petch relationship, and the simulations were in good agreement with the tested results. This provides a new, cost-effective, time-efficient, and highly reliable method for exploring the relationship between the mechanical properties and microstructure of fine-grained steel with complex microstructures.