Deformation band localization modes, uniform tensile strength, and uniform elongation of Ferrite-Martensite Dual-Phase (DP) steels are analyzed by finite element (FE) study. Treating the microstructure inhomogeneity as the sole cause of imperfection, failure initiation is predicted as the natural fallout of plastic instability caused by load drop because of localized plastic strain in the Representative Volume Element (RVE) during straining. Strain partitioning between two phases (ferrite matrix and martensite island) are investigated on RVEs, and it reveals that the increase of martensite yield stress decreases the plastic deformation and increases the stress state in martensite. Whereas, a decrease in martensite island volume fraction (V_m) results in the reduction of plastic deformation and stress state in the island. Studies are then carried out to investigate the effects of the ferrite-martensite flow properties and martensite volume fraction on the macroscopic tensile deformation behavior and band localization of DP steels. Micromechanical based FE simulation results emphasize that an increase in initial yield strength and volume fraction of martensite increases the ultimate tensile stress (UTS) with the decrease in uniform elongation. Similarly, as the hardening rate of ferrite increases, it increases the ultimate tensile stress (UTS) and uniform elongation. Additionally, deformation band localization modes alter from inclined to perpendicular to the loading axis with an increase in martensite volume fraction and initial yield strength of martensite. The knowledge of this work can be used to design DP steels with desired mechanical properties.

通过有限元（FE）研究分析了铁素体-马氏体双相（DP）钢的变形带局部化模式，均匀的拉伸强度和均匀的延伸率。将微观结构的不均匀性视为缺陷的唯一原因，由于在应变过程中代表体积单元（RVE）中局部塑性应变，载荷下降引起的塑性不稳定性自然会发生破坏，从而预测了破坏的开始。在RVEs上研究了两相（铁素体基体和马氏体岛）之间的应变分配，结果表明，马氏体屈服应力的增加会减小塑性变形并增加马氏体的应力状态。而马氏体岛体积分数（V _m）可减少岛中的塑性变形和应力状态。然后进行研究以研究铁素体-马氏体流动特性和马氏体体积分数对DP钢的宏观拉伸变形行为和能带局部化的影响。基于微机械的有限元模拟结果强调，马氏体初始屈服强度和体积分数的增加会随着均匀伸长率的降低而增加极限拉伸应力（UTS）。同样，随着铁素体硬化速率的增加，铁素体的极限拉伸应力（UTS）和均匀伸长率也会增加。另外，随着马氏体体积分数和马氏体初始屈服强度的增加，变形带局部化模式从倾斜方向变为垂直于加载轴。