The use of dual-phase steels has been limited in a number of applications, due to failure during sheared edge stretching. Previous investigations have studied the properties of dual-phase steels, especially regarding the mechanical properties of the individual phases or constituents, the strain partitioning to the microconstituents during loading, and the decohesion at the interface during loading. On the basis of the literature review, a hypothesis is developed in which failure in sheared edge stretching is the result of a sequence of events. Cracking first develops in the hard constituent, cracks grow in the interface between the hard constituent and ferrite, and relative movement of ferrite relative to the hard constituent increases the rate of cracking. In the present study, a single steel was heat treated to produce different amounts of hard constituent within the ferrite matrix in order to better understand the behavior of dual-phase steels during sheared edge stretching. The results of the study are consistent with the proposed hypothesis. It was found that in contrast to other studies, increased strength of the hard constituent retards crack initiation. Crack growth increased with increasing surface area of hard constituent-ferrite interfaces and increasing movement of ferrite relative to the hard constituent.
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