This paper attempts to predict how the microstructural features and mechanical properties of the individual constituents affect the deformation behavior and formability of ferrite-pearlite steels under quasi-static loading at room temperature. For this purpose, finite element simulations using representative volume elements (RVEs) based on the real microstructures were implemented to model the flow behavior of the ferrite-pearlite steels with various microstructural morphologies (non-banded and banded). The homogenized flow curves obtained from the RVEs subjected to periodic boundary conditions together with displacement boundary conditions were validated with the experimental results of the uniaxial tensile tests. Then, the initial microstructural inhomogeneity and Johnson–Cook damage criteria were employed for both non-banded and banded RVEs to estimate the onset of plastic instability under different loading paths ranging from uniaxial tension to equi-biaxial tension. Finally, the forming limit diagrams of both ferritic-pearlitic microstructures were predicted, which show a good agreement with the experimental results of the Nakazima stretch-forming tests (less than 13 pct error). It implies that the initial microstructural inhomogeneity criterion adequately enables to predict the plastic instability in the ferritic-pearlitic steel sheets without using any damage or failure criterion. The most commonly observed damage mechanism is the severe plastic deformation of the ferrite grains near the pearlite colonies due to the strength contrast between ferrite and pearlite. Another significant finding is that the microstructural morphology has a crucial influence on the strain partitioning, strain localization, and formability of the ferritic-pearlitic steels.

本文试图预测在室温下准静态载荷下，各个成分的显微组织特征和力学性能如何影响铁素体-珠光体钢的变形行为和可成形性。为此，基于真实的微观结构，使用代表体积元素（RVE）进行了有限元模拟，以模拟具有各种微观结构形态（非带状和带状）的铁素体-珠光体钢的流动行为。通过单轴拉伸试验的实验结果验证了从周期性边界条件和位移边界条件共同作用的RVE获得的均匀流动曲线。然后，对于非带状和带状的RVE，均采用了初始的微观结构不均匀性和Johnson-Cook破坏准则，以估计从单轴拉力到等双轴拉力的不同载荷路径下塑性不稳定性的开始。最后，预测了两个铁素体-珠光体微结构的成形极限图，与中岛拉伸成形试验的实验结果（误差小于13 pct）具有很好的一致性。这意味着初始的微观结构不均匀性标准足以预测铁素体-珠光体钢板中的塑性不稳定性，而无需使用任何破坏或破坏标准。最常见的破坏机理是珠光体菌落附近的铁素体晶粒发生严重的塑性变形，这是由于铁素体与珠光体之间的强度差异所致。另一个重要发现是，显微组织形态对铁素体-珠光体钢的应变分配，应变局部化和可成形性具有至关重要的影响。