Role of delamination and crystallography on anisotropy of Charpy toughness in API-X80 steel

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2012-06, Vol.546, p.314-322
• Main Authors: Joo, M.S., Suh, D.-W., Bae, J.H., Bhadeshia, H.K.D.H.
• Format: Article
• Language: English
• Subjects: Anisotropic properties; Applied sciences; Crystallographic texture; Delamination; Exact sciences and technology; Fractures; Linepipe; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; X80 steel
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2012.03.079

► Role of delamination established using special Charpy test orientations. ► Demonstrated reduction in anisotropy using special orientations. ► Confirmed a component of anisotropy due to texture. The orientation dependence of Charpy toughness has been investigated in API-X80 linepipe steel. The occurrence of delamination and preferential alignment of {100} cleavage planes are found to contribute to the observed anisotropy in Charpy properties. Delamination is also related to the presence of banding in the hot-rolled alloy, and the additional plasticity it entails during the process of fracture leads to an effective increase in toughness. As a consequence, the toughness is worst when the Charpy specimen is machined at 45° to the rolling direction because the extent of delamination at that orientation is minimal. The rolling and transformation textures also lead to a greater propensity of {100} ferrite planes parallel to the fracture surface for the 45° orientation, leading to a further decrease in toughness. Some revealing results are also reported for unconventional Charpy test orientations in which the notch is prepared parallel to the plate.