Concurrent microstructural evolution of ferrite and austenite in a duplex stainless steel processed by high-pressure torsion

• Published in: Acta materialia Vol. 63; pp. 16 - 29
• Main Authors: Cao, Y., Wang, Y.B., An, X.H., Liao, X.Z., Kawasaki, M., Ringer, S.P., Langdon, T.G., Zhu, Y.T.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.01.2014; Elsevier
• Subjects: Applied sciences; De-twinning; Exact sciences and technology; Grain refinement; High-pressure torsion; Metals. Metallurgy; Steel; Twinning; Twinning; Steel; De-twinning; Grain refinement; High-pressure torsion; Grain size; Austenitic ferritic steel; Ferrite; Stainless steel; Austenite; Duplex stainless steel; Microstructure; Dual phase steel; Torsion
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2013.09.030

A duplex stainless steel with approximately equal volume fractions of ferrite and austenite was processed by high-pressure torsion. Nano-indentation, electron backscatter diffraction and transmission electron microscopy were used to investigate the hardness and microstructure evolutions of the steel. Despite the different strain-hardening rates of individual ferrite and austenite, the microstructures of the two phases evolved concurrently in such a way that the neighbouring two phases always maintained similar hardness. While the plastic deformation and grain refinement of ferrite occurred mainly via dislocation activities, the plastic deformation and grain refinement process of austenite were more complicated and included deformation twinning and de-twinning in coarse grains, grain refinement by twinning and dislocation–twin interactions, de-twinning in ultrafine grains and twin boundary subdivision.