Neutron diffraction measurement of the residual stress in the cementite and ferrite phases of cold-drawn steel wires

Abstract

The residual stress state in both the cementite and ferrite phases of cold-drawn pearlitic wires has been measured by neutron diffraction. The phase microstress in the axial direction is obtained. It is found that the cementite lamellae are subjected to a high tensile stress, up to 2000 MPa, after cold drawing. Measurements on etched wires showed that the phase microstress is nearly constant with the distance to the wire axis. Combination of these data with complementary X-ray diffraction measurements on the ferrite determines the response of each phase to the macrostress or an applied stress. Additionally, the peak broadening and texture of both phases have been studied using the neutron diffraction technique. The texture is less sharp in the cementite than in the ferrite. In the cold-drawn samples the diffraction peaks are very broad, which suggests plastic deformation of the cementite lamellae.