A simple model for dynamic recrystallization during severe plastic deformation

Le, Khanh Chau; Kochmann, Dennis M.

doi:10.1007/s00419-008-0280-z

Cited by 15 publications

(17 citation statements)

References 18 publications

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“…Before RX starts, grain size is approximately uniform and constant, equal to the initial value 0 d d = [6]. Experiments show that in this stage the biggest contribution to strain hardening is due to the continuous increase of dislocation density due to their multiplication at sources [14,15].…”

Section: Prior To Recrystallizationmentioning

confidence: 95%

“…The proposed model, based on a simple one developed by Le and Kochmann [6] for continuous dynamic recrystallization (CDRX), describes the evolution of the dislocation density and the grain size on a thermodynamically consistent basis, as follows. Plastic deformation causes the dislocation density to increase by dislocation multiplication at sources in the material and, as noted above, can also cause the grain size to change due to RX.…”

Section: Proposed Modelmentioning

confidence: 99%

“…Consider the energy conservation during plastic deformation, but neglect the elastic strain energy of the macroscopic deformation as it is stored reversibly (see [6] for more details). Thus only dissipative terms are included, giving…”

Section: Proposed Modelmentioning

confidence: 99%

“…From now on, microstructural evolution is divided into two main stages: prior to Recrystallization, and during Recrystallization (equivalent to Stage I and Stage II respectively in the model proposed by Le and Kochmann [6]). …”

Section: Proposed Modelmentioning

confidence: 99%

“…This phenomenon can be achieved in several ways, the most common one being the activation of recrystallization (RX) by severe plastic deformation (SPD), with a consequent decrease in the average diameter of the grains. A thermodynamically consistent model for RX during SPD, inspired by Le and Kochmann [6], is proposed in this paper; it is described in Section 2, its calibration is reported in Section 3, computational results derived from the model are reported in Section 4 and compared with experiments on machining for the Aluminium Alloy Al 6061-T6 [1], a discussion on the model and its comparison with other models is reported in Section 5 and its implementation in a finite element code is reported in Section 6. This processes are able to create grain sizes in the range of nanometers, and such nanostructured materials are known to have much higher strength than those having grain size on the micron scale.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Continuous dynamic recrystallization during severe plastic deformation

Bacca

Hayhurst

McMeeking

2015

Mechanics of Materials

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Severe plastic deformation (strains > 100%) has been shown to create significant grain refinement in polycrystalline materials, leading to a nanometric equiaxed crystalline structure for such metals as aluminum, copper and nickel alloys. This process, termed continuous dynamic recrystallization, is governed by evolution of the dislocation structure, which creates new grain boundaries from dislocation walls. In the proposed model, plasticity occurs which firstly involves dislocation multiplication, leading to strain hardening limited by dynamic recovery. After a critical dislocation density is reached new grain boundaries are formed by condensation of walls of dislocations, creating a new stable configuration that is favored due to a reduction of the system free energy. This evolution of the microstructure continues to develop, with a consequent progressive decrease in the average grain diameter. The proposed model provides a quantitative prediction of the evolution of the average grain size, as well as the dislocation density, during continued plastic strain. The model can be calibrated by use of results from any experiment that involves large plastic deformation of metals, subject to negligible annealing effects. In this paper, the model has been calibrated, and consequently validated, through experiments on machining of Al 6061-T6.

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Section: Prior To Recrystallizationmentioning

confidence: 95%

Section: Proposed Modelmentioning

confidence: 99%

Section: Proposed Modelmentioning

confidence: 99%

Section: Proposed Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Continuous dynamic recrystallization during severe plastic deformation

Bacca

Hayhurst

McMeeking

2015

Mechanics of Materials

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High‐temperature deformation and recrystallization: A variational analysis and its application to olivine aggregates

Hackl

Renner

2013

JGR Solid Earth

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[1] We develop a framework for a variational analysis of microstructural evolution during inelastic high-temperature deformation accommodated by dislocation mechanisms and diffusive mass transport. A polycrystalline aggregate is represented by a distribution function characterizing the state of individual grains by three variables, dislocation density, grain size, and elastic strain. The aggregate's free energy comprises elastic energy and energies of lattice distortions due to dislocations and grain boundaries. The work performed by the external loading is consumed by changes in the number of defects and their migration leading to inelastic deformation. The variational approach minimizes the rate of change of free energy with the evolution of the state variables under constraints on the aggregate volume, on a relation between changes in plastic strain and dislocation density, and on the form of the dissipation functionals for defect processes. The constrained minimization results in four basic evolution equations, one each for the evolution in grain size and dislocation density and flow laws for dislocation and diffusion creep. Analytical steady state scaling relations between stress and dislocation density and grain size (piezometers) are derived for quasi-homogeneous materials characterized by a unique relation between grain size and dislocation density. Our model matches all currently available experimental observations regarding high-temperature deformation of olivine aggregates with plausible values for the involved micromechanical model parameters. The relation between strain rate and stress for olivine aggregates maintaining a steady state microstructure is distinctly nonlinear in stark contrast to the majority of geodynamical modeling relying on linear relations, i.e., Newtonian behavior.Citation: Hackl, K., and J. Renner (2013), High-temperature deformation and recrystallization: a variational analysis and its application to olivine aggregates,

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Consistency of dynamic recrystallization models from the perspective of physical metallurgy and continuum mechanics

Bambach

Klinge

2017

Proc Appl Math and Mech

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Dynamic recrystallization (DRX) is characterized by the nucleation and growth of new grains, which takes place concurrently to plastic deformation. DRX processes are used in industrial hot forming operations to control the microstructure and properties of the workpiece. Various models have been developed that consider the coupled evolution of microstructure and flow stress during hot deformation processes, some from a perspective of physical metallurgy, some from continuum mechanics. It is widely accepted that the onset of DRX is characterized by an inflection point of the strain hardening rate as a function of stress. This criterion was derived by Poliak and Jonas using results from the thermodynamics of irreversible processes. The present paper analyses the conditions that need to be met by DRX models to be consistent with the criterion by Poliak and Jonas. It is shown that for models which use classical Avrami kinetics to describe the evolution of the recrystallized volume fraction, the Avrami exponent should exceed a value of 3 to ensure that the Poliak-Jonas criterion is not violated. Based on this observation, a framework for consistent DRX kinetics is presented and discussed.

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A simple model for dynamic recrystallization during severe plastic deformation

Cited by 15 publications

References 18 publications

Continuous dynamic recrystallization during severe plastic deformation

Continuous dynamic recrystallization during severe plastic deformation

High‐temperature deformation and recrystallization: A variational analysis and its application to olivine aggregates

Consistency of dynamic recrystallization models from the perspective of physical metallurgy and continuum mechanics

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