Shear localization and shear banding: A review about the complex interplay between material, microstructural and process variables

Shear localization and shear band formation in metals, alloys and composites is an important deformation phenomenon most commonly associated with high strain rate deformation. It generally occurs as a thermo-mechanical instability where thermal softening due to adiabatic heating subdues strain hardening. The review presents different facets of strain localization and eventual shear band formation in various materials primarily including pure metals, alloys and composites. It starts with the dependence of shear band formation on materials parameters (e.g. crystal structure, stacking fault energy, c/a ratio, twining and TRIP effect etc.) and process variables (strain rate, stress states etc.) are presented. Effect of microstructural heterogeneities like twinning, grain boundary, phase boundary, particulates etc. are then discussed along with orientation variables (micro- and bulk texture etc.). Various aspects of microstructure and texture evolution due to strain localization in and around the shear bands are further demonstrated e.g. heat accumulation leading to dynamic recrystallization, phase transformation amorphization, evolution of Brass type texture due to shear banding etc. Theoretical simulations and modeling efforts pertaining to shear band formation, mostly crystal plasticity finite element based and resulting texture evolution is presented. Finally, an extensive review is carried out about the shear location and shear band formation for various metallic nanolayered composites. The present review therefore should be useful in understanding the root causes of shear localization and shear band formation e.g. during fabricating components for fracture-critical applications.