Deformation microstructures and selected examples of their recrystallization

Abstract

The elements that are needed to describe a deformation structure—grains, grain boundaries, macroscale banding within crystals, cell blocks, geometrically necessary boundaries and incidental dislocation boundaries (cell boundaries)—are presented and described for fcc metals and alloys of medium to high stacking fault energy. Pertinent to this quantitative description are the local orientations, structural morphology, different boundary misorientations and spacings as a function of strain and deformation conditions. Three specific examples are given in which particular aspects of the deformation structure are shown to direct the recrystallization behavior. Copyright © 2001 John Wiley & Sons, Ltd; first published by Risø National Laboratory.

The mechanics of deformation–induced subgrain–dislocation structures in metallic crystals at large strains

“…Specifically, we consider microstructures that may be described as simple or sequential laminates (Kohn & Strang 1986a-c, Kohn 1991Ortiz & Repetto 1999;Ortiz et al 2000). While other types of microstructures cannot be ruled out a priori, sequential lamination does appear to suffice for the purpose of mathematically describing the vast majority of dislocation structures that are observed at large strains Hughes 2001;Hughes & Hansen 1993, 2001.…”

“…The dislocation structures that form in metallic crystals at large strains have been extensively investigated by (see also Hughes 2001and Hughes & Hansen 1993, 2001. The dislocation structures observed at large strains in a wide variety of metals are regular lamellar structures containing arrays of so-called geometrically necessary boundaries, i.e.…”

“…In the interest of analytical tractability, we restrict our attention to microstructures in the form of sequential laminates (Kohn 1991;Kohn & Strang 1986a-c). These microstructures are amenable to an effective analytical evaluation, and suffice to give mathematical description to the microstructures observed by , Hughes (2001) and Hughes & Hansen (1993, 2001.…”

“…In this paper, the predictions of the constrained theory are compared against the experimental observations of , Hughes (2001) and Hughes & Hansen (1993, 2001 on deformation-induced subgrain-dislocation structures. Some of these experiments are somewhat complex and involve a number of factors that are extraneous to the theory, such as the polycrystalline structure of the samples and others.…”

Finite element analysis of geometrically necessary dislocations in crystal plasticity

“…In particular, the GND energy is homogeneous of degree one in the slip strains. Such models indeed arise from rigorous multiscale analysis as the macroscopic limit of discrete dislocation models [19] and are unique among strain-gradient models of crystal plasticity in that they allow for the formation of sharp dislocation walls, in keeping with a vast body of observational evidence pertaining to dislocation structures in crystals [20][21][22][23][24][25][26][27]. Models of the type considered here may also be built from phenomenological considerations such as a line-tension approximation for the dislocation self-energy [28,29].…”