Damage and fracture of dual-phase steels: Influence of martensite volume fraction

The influence of the martensite volume fraction (Vm) on the damage and fracture behavior of dual-phase steels was studied by combining experiments and micromechanical modeling. A transition in the dominating damage mechanism is observed when varying Vm. Martensite fracture dominates the void nucleation process at high Vm, while interface decohesion prevails at low Vm. Damage accumulation accelerates when Vm increases, resulting in a decrease of the fracture strain. Brittle fracture areas are observed in uniaxial tensile specimens for a sufficiently high Vm. The damage mechanisms and evolution are rationalized using a micromechanical analysis based on periodic finite element cell calculations. The results show that Vm is a key factor for controlling the balance between strength and fracture resistance.