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The transformation between the face centered cubic austenitic and hexagonal close-packed martensitic phases during high-pressure torsion processing was observed in a Fe-Mn-C-Al twinning-induced plasticity steel. This phase transformation was not found in the same material processed by unidirectional compressive and tensile deformation. Initiated by the high-pressure loading, the martensite phase initially increased with torsional strain but diminished subsequently. Texture evolution of the austenitic phase was compared with the ideal texture distribution of face-centered cubic materials after shear deformation.

In oil and gas and other industries, valve bodies are often manufactured using a 2.25Cr-1Mo steel which, if welded, requires post-weld heat treatment (PWHT) in order to restore toughness. The safe operation and longterm integrity of such welds is critically dependent on achieving adequate toughness across the welded joint.In this work, mock-ups were manufactured for the purpose of assessing the effects of the weld heat input on toughness. The assessment was made by carrying out crack tip opening displacement (CTOD) and Charpyimpact tests in different metallurgical regions and, after testing, by examining the fracture surfaces using optical-and scanning-electron microscopy, and energy-dispersive spectroscopy. There did not appear to be an effect of weld heat input on toughness at a test temperature of +20°C. However, for the case where a high weld heat input was employed, the toughness of the weld metal dropped by close to 50% when the temperature was decreased to -20°C. These results suggest that inadequate control of the welding process may lead to significant variability in weld toughness, and that high weld heat inputs should be avoided when welding or buttering 2.25Cr-1Mo steel components.