X-RAY-MEASUREMENT OF LATTICE STRAINS IN TEXTURED LOW-CARBON STEEL UNDER UNIAXIAL LOADING

Abstract

To examine the effect of relative crystallite misorientations on the inhomogeneous deformation behavior, lattice strains in the crystallites of a textured low-carbon steel are measured by an in situ X-ray diffraction method under uniaxial loading. Internal microstresses of the crystallites are also determined from the lattice strains measured along different directions of the crystallites. The low-carbon steel has the rolling texture of orientation relationship: {211}[01(1) over bar], {111}[2 (1) over bar (1) over bar], and {100}[011]. Different lattice stress-strain curves are obtained from the different crystallite groups, which show dissimilarity in the proportionality constant between the stress and lattice strain and the elastic limit of each crystallite group. The external elastic limit can be calculated from averaging the individual lattice yield points of each crystallite groups. Triaxial stress states are developed in the crystallites in the entire range of the elastic and plastic regions during uniaxial loading. The residual stresses of the specimen unloaded at a strain level of about 3 pct are in a biaxial stress state.