Correlating in-plane strength anisotropy with its microstructural counterpart for a hot rolled line pipe steel

Abstract

The present study focuses on the microstructural entities, emphasizing the role of precipitates on the in-plane directional tensile responses, including the strain hardening behaviour of a hot rolled X-65 Line pipe graded steel. Tensile samples have been prepared from four different directions lying on the RD-TD (rolling direction-transverse direction) plane at the varying angle of 0°, 30°, 60°, and 90° with respect to the RD of the hot-rolled plate. Superior mechanical properties have been evidenced in the 90° sample compared to other orientations in terms of maintaining yield continuity and better strength-ductility combination. The yielding behaviour and tensile response have been explained from the viewpoint of grain/grain boundary characteristics, dislocation-precipitation interaction, and elasto-plastic incompatibility across grain boundaries. The role of interaction of dislocations with fine precipitates along with the Elastic Modulus (EM) and Schmid Factor (SF) differences across high angle grain boundaries (HAGBs) have been found to be significant in determining the superiority of the mechanical properties of 90° sample.