Crystal plasticity constitutive modeling of temperature-dependent strengthening behavior of dual-heterogeneous carbon steel

Materials processed using tempforming (TF) technology exhibit exceptional strength-toughness synergy due to their dual-heterogeneous structure (grain morphology and dislocation density). This study employs a nonlocal crystal plasticity constitutive model to simulate the tensile behavior of TF-processed 45-grade steel under varying rolling temperatures, revealing the mechanisms by which dislocation strengthening, precipitation strengthening, back stress strengthening, and texture effects govern the tensile mechanical response. Results indicate that the high yield strength is dominated by dislocation strengthening and precipitation strengthening, while geometrically necessary dislocation (GND) strengthening and back stress strengthening effects primarily function during plastic deformation stages. Rolling temperature critically modulates the contributions of these mechanisms: with increasing rolling temperature, dislocation, back stress, and precipitation strengthening diminish, whereas GND strengthening intensifies. Microstructural analysis demonstrates that morphological disparities between elongated and equiaxed grains induce deformation heterogeneity, leading to preferential GND accumulation at the grain boundaries between elongated and equiaxed grains. Texture evolution analysis reveals that low and high temperature rolling promotes fiber texture formation, enhancing material strength, whereas intermediate temperature rolling generates mixed textures that degrade performance. This study supplemented the mechanical behavior of medium carbon steel under different rolling temperatures by simulating the uniaxial tensile properties and strengthening mechanism of TF process 45-grade steel, providing guidance for the regulation of the TF process in experimental research.