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Phase field modeling of martensitic transformation- Effect of grain and twin boundaries
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.ORCID iD: 0000-0003-3336-1462
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.ORCID iD: 0000-0002-7656-9733
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.ORCID iD: 0000-0002-4521-6089
##### Abstract [en]

In this work we are presenting, for the first time, the elasto-plastic phase field modeling and simulation of the martensitic transformation in a polycrystalline material including the effect of grain and twin boundaries. The phase field microelasticity theory proposed by Khachaturyan is used to perform 2D and 3D simulations of FCC$\rightarrow$BCT martensitic transformation in an Fe-0.3\%C polycrystalline alloy, incorporating the effect of both coherent and incoherent boundaries. The effect of plastic accommodation is also introduced into the model, by solving a time dependent equation, during the solid-to-solid phase transformation. It is found that the given phase field model, with the effect of grain boundaries, not only respects the morphological features of martensite but it also conforms well with the physics of the problem. Different sets of simulations are performed to validate the model and it is concluded that the given model can correctly predict the evolution of martensitic microstructure in a polycrystal as opposed to the previous models where the effects of grain and twin boundaries are neglected.

##### Keywords [en]
Martensitic transformation; Polycrystal; Grain boundaries; Phase field modeling; Simulations.
##### National Category
Materials Engineering
##### Identifiers
OAI: oai:DiVA.org:kth-118448DiVA, id: diva2:606216
##### Note

QS 2013

Available from: 2013-02-18 Created: 2013-02-18 Last updated: 2013-02-19Bibliographically approved
##### In thesis
1. Phase change with stress effects and flow
Open this publication in new window or tab >>Phase change with stress effects and flow
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
##### Abstract [en]

In this thesis two kinds of phase change i.e., solid state phase transformation in steels and solid-to-liquid phase transformation in paraffin, have been modeled and numerically simulated. The solid state phase transformation is modeled using the phase field theory while the solid-to-liquid phase transformation is modeled using the Stokes equation and exploiting the viscous nature of the paraffin, by treating it as a liquid in both states.The theoretical base of the solid state, diffusionless phase transformation or the martensitic transformation comes from the Khachaturyan's phase field microelasticity theory. The time evolution of the variable describing the phase transformation is computed using the time dependent Ginzburg-Landau equation. Plasticity is also incorporated into the model by solving another time dependent equation. Simulations are performed both in 2D and 3D, for a single crystal and a polycrystal. Although the model is valid for most iron-carbon alloys, in this research an Fe-0.3\%C alloy is chosen.In order to simulate martensitic transformation in a polycrystal, it is necessary to include the effect of the grain boundary to correctly capture the morphology of the microstructure. One of the important achievements of this research is the incorporation of the grain boundary effect in the Khachaturyan's phase field model. The developed model is also employed to analyze the effect of external stresses on the martensitic transformation, both in 2D and 3D. Results obtained from the numerical simulations show good qualitative agreement with the empirical observations found in the literature.The microactuators are generally used as a micropump or microvalve in various miniaturized industrial and engineering applications. The phase transformation in a paraffin based thermohydraulic membrane microactuator is modeled by treating paraffin as a highly viscous liquid, instead of a solid, below its melting point.  The fluid-solid interaction between paraffin and the enclosing membrane is governed by the ALE technique. The thing which sets apart the presented model from the previous models, is the use of geometry independent and realistic thermal and mechanical properties. Numerical results obtained by treating paraffin as a liquid in both states show better conformity with the experiments, performed on a similar microactuator. The developed model is further employed to analyze the time response of the system, for different input powers and geometries of the microactuator.

##### Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. p. x, 58
##### Series
Trita-MEK, ISSN 0348-467X ; 2013:04
##### Keywords
Martensitic transformation, phase-field method, polycrystal, stress-effects, microactuator, finite-element simulations.
##### National Category
Materials Engineering Mechanical Engineering
##### Identifiers
urn:nbn:se:kth:diva-118451 (URN)978-91-7501-655-9 (ISBN)
##### Public defence
2013-03-13, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
##### Note

QC 20130219

Available from: 2013-02-19 Created: 2013-02-18 Last updated: 2013-02-19Bibliographically approved

#### Open Access in DiVA

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#### Authority records BETA

Amberg, GustavBorgenstam, Annika

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Malik, AmerAmberg, GustavBorgenstam, AnnikaÅgren, John
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Cite
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