35. Micromechanics of Dual-Phase Steels: Deformation, Damage, and Fatigue

Ferritic–martensitic dual-phase (DP) steels are increasingly being used in various automotive components because of their favorable material behavior for lightweight and crash-safe designs. DP steels deform with strong strain and stress partitioning at the microscale. Deformation pattern of ferrite and martensite phases under tensile loading condition is the most important issue which can be effective on the prediction of mechanical behavior of DP steel. Deformation pattern and strain localization play an important role in the process of damage initiation and final fracture. Failure in DP steels is a phenomenon that has been extensively investigated in the last decade through experimental tests and simulation methods. Experimental procedures have shown that failure has a ductile pattern and that shear failure of ferrite matrix is dominant in these materials. On the other hand, experimental findings have shown that failure due to fatigue loading occurred with different pattern comparing to the other loading conditions. To understand and improve DP steels, it is important to identify connections between the microstructural parameters and the mechanical behavior of these materials at macroscale. This work provides a detailed micromechanical investigation of DP steels focusing on micro-deformation, micro-damage, and micro-fatigue analysis of DP steels based on experimental and numerical approaches to highlight the current and future directions and open problems about these materials.