A study of the deformation and fracture of a dual-phase steel

A metallographic study of the tensile deformation and fracture of a commercial dual-phase steel shows that extensive plastic deformation of the martensite occurs mainly in the neck of the tensile specimen. The average load-transfer stress in martensite was roughly calculated from a shear-lag model, and it was found that it exceeds the estimated martensite yield stress value at strains corresponding to the ultimate uniform elongation, and beyond. Ductile fracture begins with void formation at martensite ferrite interfaces, most frequently at the poles of closely spaced martensite particles situated o ferrite grain boundaries. Large inclusions and martensite banding also affect the fracture process