On the Heterogeneity of Local Shear Strain Induced by High‐Pressure Torsion

• Published in: Advanced engineering materials Vol. 22; no. 1
• Main Authors: Jiang, Wei, Zhou, Hao, Cao, Yang, Nie, Jinfeng, Li, Yusheng, Zhao, Yonghao, Kawasaki, Megumi, Langdon, Terence G., Zhu, Yuntian
• Format: Journal Article
• Language: English
• Published: 01.01.2020
• Subjects: deformation twinning; high-pressure torsion; microstructures; shear strains; steels
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.201900477

A ductile duplex stainless steel consisting of a ferrite phase and an austenitic phase is chosen as a model material to investigate the development of shear strain patterns under high‐pressure torsion. Systematic analysis on the macroscopic and microscopic heterogeneities of local shear strain reveals that complex shear patterns can be developed only above a high strain level where the grain sizes are already refined to a steady state. It is concluded that grain boundary‐mediated deformation mechanisms provide sufficient freedom for reshaping the austenite phase domains, and thus the intrinsic factor required for the formation of these complicated shear patterns is well‐developed ultrafine grains and/or nanograins. High‐pressure torsion induces very complicated shear strain patterns such as shear bands, shear vortices, and shear turbulence, whereas shear turbulence can be effectively accommodated by dislocation slip and/or deformation twinning. The high local shear strains associated with shear bands and shear vortices are accommodated by grain boundary‐mediated deformation mechanisms in addition to the conventional deformation mechanisms.