Effect of Microstructural and Crystallographic Texture Parameters on the Fracture Energy Absorption of X90 Pipeline Steel

The microstructure, substructure, and crystallographic texture of X90 pipeline steel were studied using optical and electron microscopy, electron backscatter diffraction (EBSD), and X-ray texture analysis. Fracture energy absorption was measured by drop-weight tear testing. The preferred grains orientation and substructure characteristics within lath bainite bands were analyzed. A comparative assessment was carried out for misorientation angles, the extent of low-angle grain boundaries, lattice distortions, and microhardness within and between lath bainite bands. Correlations between fracture energy absorption in drop-weight tear tests and both the fraction of bainitic bands and specific texture parameters, such as the volume fraction of grains with the {001} component and the volume fraction of grains with the || TD orientation were established.