The shear mode of ductile fracture in materials with few inclusions

The mechanism of the shear mode of ductile fracture has been investigated in sheet tensile specimens of an α brass containing few inclusions. The techniques of optical metallography, scanning electron microscopy and transmission electron microscopy of both thin foils and replicas were all used in order to obtain as complete a picture of the fracture mechanism as possible. It was found that a zone of shear deformation, made up of many intense shear bands, developed across the specimen neck and fracture occurred within this zone along the shear bands. These shear bands consisted of material with a fine subgrain structure. No voids were found in the necked region of either deformed or fractured specimens yet the fracture surfaces were covered with elongated dimples. It is therefore suggested that the dimples on the fracture surface are not a precursor of the fracture but form only during the final process of separation.