An in-situ scanning electron microscopy study of the bonding between MnS inclusions and the matrix during tensile deformation of hot-rolled steels

The bonding between manganese sulfide (MnS) inclusions and the surrounding steel matrix was investigated by in-situ tensile testing in a scanning electron microscope (SEM) at room temperature. Tests were carried out for two different orientations of the inclusions with respect to the loading axis. The orientation was created during a hot cross rolling operation of the test material. Straining was performed along both longitudinal (L) and short transverse (S) directions. The investigation showed that the bond between the MnS inclusions and the matrix is weak. This was particularly seen in the S test direction where the sulfides, lying perpendicular to the load axis, delaminated from the matrix at very low applied stresses. The MnS inclusions in longitudinal tests instead fractured at high stress levels close to the yield stress.