A mesoscale study on the thermodynamic effect of stress on martensitic transformation

Marketz, Franz; Fischer, Franz Dieter

doi:10.1007/bf02664665

Cited by 66 publications

(32 citation statements)

References 13 publications

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“…At the microscale, PTs in elastoplastic materials were investigated in [3,11,12,13,14] using the principle of the minimum of Gibbs free energy (similar to PT in elastic materials) and sharp interfaces, while plasticity was described within continuum flow theory for an isotropic material.…”

Section: Introductionmentioning

confidence: 99%

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Javanbakht

Levitas

2016

Phys. Rev. B

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Pressure and shear strain-induced phase transformations (PTs) in a nanograined bicrystal at the evolving dislocations pile-up have been studied utilizing phase field approach (PFA).The complete system of PFA equations for coupled martensitic PT, dislocation evolution, and mechanics at large strains is presented and solved using finite element method (FEM). The nucleation pressure for high pressure phase (HPP) under hydrostatic condition near single dislocation was determined to be 15.9 GPa. Under shear, a dislocations pile-up that appears in the left grain creates strong stress concentration near its tip and significantly increases the local thermodynamic driving force for PT, which causes nucleation of HPP even at zero pressure. At pressures of 1.59 and 5 GPa and shear, a major part of a grain transforms to HPP.When dislocations are considered in the transforming grain as well, they relax stresses and lead to a slightly smaller stationary HPP region than without dislocations. However, they strongly suppress nucleation of HPP and require larger shear. Unexpectedly, the stationary HPP morphology is governed by the simplest thermodynamic equilibrium conditions, which do not contain contributions from plasticity and surface energy. These equilibrium conditions are fulfilled either for the majority of points of phase interfaces or (approximately) in terms of stresses averaged over the HPP region or for the entire grain, despite the strong heterogeneity of stress fields. The major part of the driving force for PT in the stationary state is due to deviatoric stresses rather than pressure. While the least number of dislocations in a pile-up to nucleate HPP linearly decreases with increasing the applied pressure, the least corresponding shear strain depends on pressure nonmonotonously. Surprisingly, the ratio of kinetic coefficients for PT and dislocations affect stationary solution and nanostructure. Consequently, there are multiple stationary solutions under the same applied load and PT and deformation processes are path dependent. With an increase in the size of the sample by a factor of two, 2 no effect was found on the average pressure and shear stress and HPP nanostructure, despite the different number of dislocations in a pile-up. Obtained results represent a nanoscale basis for understanding and description of PTs under compression and shear in rotational diamond anvil cell and high pressure torsion.

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Section: Introductionmentioning

confidence: 99%

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Javanbakht

Levitas

2016

Phys. Rev. B

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“…In the past decades, various constitutive models have been proposed to elucidate the complex interactive mechanisms that occur in steels assisted by transformation-induced plasticity; see e.g., [4,10,11,16,21,22,26]. In most cases, the models are developed within a small-strain, isotropic elastoplasticity framework.…”

Section: Introductionmentioning

confidence: 99%

Crystallographically based model for transformation-induced plasticity in multiphase carbon steels

Tjahjanto

Turteltaub

Suiker

2007

Continuum Mech. Thermodyn.

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The microstructure of multiphase steels assisted by transformation-induced plasticity consists of grains of retained austenite embedded in a ferrite-based matrix. Upon mechanical loading, retained austenite may transform into martensite, as a result of which plastic deformations are induced in the surrounding phases, i.e., the ferrite-based matrix and the untransformed austenite. In the present work, a crystallographically based model is developed to describe the elastoplastic transformation process in the austenitic region. The model is formulated within a large-deformation framework where the transformation kinematics is connected to the crystallographic theory of martensitic transformations. The effective elastic stiffness accounts for anisotropy arising from crystallographic orientations as well as for dilation effects due to the transformation. The transformation model is coupled to a single-crystal plasticity model for a face-centered cubic lattice to quantify the plastic deformations in the untransformed austenite. The driving forces for transformation and plasticity are derived from thermodynamical principles and include lower-length-scale contributions from surface and defect energies associated to, respectively, habit planes and dislocations. In order to demonstrate the essential features of the model, simulations are carried out for austenitic single crystals subjected to basic loading modes. To describe the elastoplastic response of the ferritic matrix in a multiphase steel, a crystal plasticity model for a body-centered cubic lattice is adopted. This model includes the effect of nonglide stresses in order to reproduce the asymmetry of slips in the twinning and antitwinning directions that characterizes the behavior of this type of lattices. The models for austenite and ferrite are combined to simulate the microstructural behavior of a multiphase steel. The results of the simulations show the relevance of including plastic deformations in the austenite in order to predict a more realistic evolution of the transformation process.

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“…In the last decades, various micromechanically-based models for martensitic transformations have been developed, see e.g., [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. However, these models mainly focus upon mechanically-driven martensitic transformations, without taking into account the effect of temperature variations on the transformation behavior.…”

Section: Introductionmentioning

confidence: 99%

Transformation-induced plasticity in multiphase steels subjected to thermomechanical loading

Tjahjanto¹,

Turteltaub²,

Suiker³

et al. 2008

Philosophical Magazine

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A mesoscale study on the thermodynamic effect of stress on martensitic transformation

Cited by 66 publications

References 13 publications

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Crystallographically based model for transformation-induced plasticity in multiphase carbon steels

Transformation-induced plasticity in multiphase steels subjected to thermomechanical loading

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