Crack path morphology in dual-phase steel

摘要

Intercritical heat treatment (ICHT) and thermomechanical processing (TMP) were used on steel having 0.16% C to vary the morphology, distribution of ferrite, and martensite phases, in order to study the resistance to fatigue crack propagation and crack path morphology in dual-phase steel. A crack growth rate has been determined at ∼10−10 to 10−3 m per cycle in ICHT and TMP samples. The tortuous morphology of the crack path was observed in unrolled materials, which resulted in reduction of the crack driving force from crack deflection and increased the ΔK th. In thermomechanical processed materials, the crack tended to cross the martensite and the crack path become less circuitous, resulting in decrease a threshold stress intensity factor (ΔK th) as compared with unrolled material.