Grain size reduction by dynamic recrystallization: can it result in major rheological weakening?

Abstract

It is widely believed that grain size reduction by dynamic recrystallization can lead to major rheological weakening and associated strain localization by bringing about a switch from grain size insensitive dislocation creep to grain size sensitive diffusion creep. Recently, however, we advanced the hypothesis that, rather than a switch, dynamic recrystallization leads to a balance between grain size reduction and grain growth processes set up in the neighborhood of the boundary between the dislocation creep field and the diffusion creep field. In this paper, we compare the predictions implied by our hypothesis with those of other models for dynamic recrystallization. We also evaluate the full range of models against experimental data on a variety of materials. We conclude that a temperature dependence of the relationship between recrystallized grain size and flow stress cannot be neglected a priori. This should be taken into account when estimating natural flow stresses using experimentally calibrated recrystallized grain size piezometers. We also demonstrate experimental support for the field boundary hypothesis. This support implies that significant weakening by grain size reduction in localized shear zones is possible only if caused by a process other than dynamic recrystallization (such as syntectonic reaction or cataclasis) or if grain growth is inhibited.

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

“…12), viscosity will remain constant with depth. Because the dominant deformation mechanism in the northern Baja California lithosphere is transitional between dislocation creep and diffusion creep, any grain size reduction is not expected to result in a major change in strength or viscosity of the lower crust (De Bresser et al, 2001).…”

Exhumation of (ultra-)high-pressure terranes: concepts and mechanisms

“…The mechanisms responsible for deformation-induced grain size reduction include cataclasis, metamorphic reactions and dynamic recrystallization (De Bresser et al, 2001). Cataclasis is a brittle grain-size-reducing mechanism and is therefore not relevant to the discussion of high-pressure rock exhumation, which initiates in the ductile field.…”

“…Dynamic recrystallization leads to weakening and strain localization by generating a change from dislocation creep (which is insensitive to grain size) to diffusion creep (which is sensitive to grain size; De Bresser et al, 2001). However, significant weakening by grain size reduction may only be possible when caused by syntectonic reaction recrystallization or cataclasis rather than dynamic recrystallization (De Bresser et al, 2001).…”

“…However, significant weakening by grain size reduction may only be possible when caused by syntectonic reaction recrystallization or cataclasis rather than dynamic recrystallization (De Bresser et al, 2001). Alternatively, weakening may only occur if grain growth is inhibited.…”

Characterization of Compound Particles Formed during Thin Slab Direct Rolling of Ti-added Nb HSLA Steel

“…The activation of dynamic recrystallization and subsequent meta-dynamic recrystallization (MDRX) softening can be used to induce a faster microstructural refinement. [3][4][5] In Nb-added high strength low alloy (HSLA) steels the strengthening is achieved mainly by grain refinement and, to a lesser extent, precipitation strengthening. The grain refinement is obtained by thermo-mechanical controlled processing (TMCP) during hot rolling in the non-recrystallization temperature range in the finishing tandem mill section of a conventional HSM.…”