Formation of Micro Shear Bands During Severe Plastic Deformation of BCC Alloys

In this work, tendencies of pure Niobium, Fe-20Cr stainless steel, and Ti-36Nb- 2Ta-3Zr to formation of micro shear bands inside their microstructures during severe plastic deformation are compared with their mechanical properties. For this purpose, strain hardening behavior and strain rate sensitivity of flow stress of these alloys were measured using tension tests and nano-indentation tests, respectively. Microstructures of the alloys were studied using electron backscattering diffraction method before and after imposition of severe plastic deformation. Results show that increase of the strain hardening exponent and/or strain rate sensitivity of flow stress causes decrease of tendency to formation of micro shear bands during deformation. Moreover, formation of micro shear bands can be approximately predicted using a parameter previously proposed for prediction of formation of macro shear bands.