Dynamic recrystallization in adiabatic shear banding: effective-temperature model and comparison to experiments in ultrafine-grained titanium

TL;DR

This paper develops an effective-temperature model for dynamic recrystallization within adiabatic shear bands, successfully matching experimental observations in ultrafine-grained titanium and providing a thermodynamic framework for understanding shear banding and recrystallization.

Contribution

It reformulates the Langer-Bouchbinder-Lookman continuum theory to include grain boundary creation, offering a new thermodynamic perspective on shear banding and recrystallization.

Findings

Model closely matches experimental results in ultrafine-grained titanium.

Recrystallization is explained as an entropic effect from dislocation and grain boundary competition.

Provides a systematic, thermodynamically consistent description of shear band formation.

Abstract

Dynamic recrystallization (DRX) is often observed in conjunction with adiabatic shear banding (ASB) in polycrystalline materials. The recrystallized nanograins in the shear band have few dislocations compared to the material outside of the shear band. In this paper, we reformulate the recently-developed Langer-Bouchbinder-Lookman (LBL) continuum theory of polycrystalline plasticity and include the creation of grain boundaries. While the shear-banding instability emerges because thermal heating is faster than heat dissipation, recrystallization is interpreted as an entropic effect arising from the competition between dislocation creation and grain boundary formation. We show that our theory closely matches recent results in sheared ultrafine-grained titanium. The theory thus provides a thermodynamically consistent way to systematically describe the formation of shear bands and recrystallized grains therein.