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Mark Aindow - One of the best experts on this subject based on the ideXlab platform.
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interfacial dislocation mechanism for diffusional phase Transformations exhibiting martensitic crystallography formation of tial ti3al lamellae
Acta Materialia, 2000Co-Authors: R.c. Pond, P Shang, T T Cheng, Mark AindowAbstract:Abstract The displacive–Diffusive Transformation, which gives rise to lamellar γ-TiAl+α2-Ti3Al microstructures, has been analysed theoretically. Using the formulation due to Hirth and Pond, the shear produced and extent of diffusional flux associated with interfacial defect motion can be quantified in terms of the Burgers vectors, step heights of the defects and the chemical compositions of the adjacent crystals. Moreover, this formulation also enables the effects of chemical composition, misfit at the interface and ordering to be investigated systematically. It is shown that for the defects observed on such interfaces in recent high-resolution transmission electron microscopy studies, their motion would lead to the conservation of sites and, correspondingly, to equal and opposite fluxes of Ti and Al atoms. Consequently, although this Transformation is diffusional, it exhibits crystallographic features consistent with martensitic processes.
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Interfacial dislocation mechanism for diffusional phase Transformations exhibiting martensitic crystallography: formation of TiAl + Ti3Al lamellae
Acta Materialia, 2000Co-Authors: R.c. Pond, P Shang, T T Cheng, Mark AindowAbstract:Abstract The displacive–Diffusive Transformation, which gives rise to lamellar γ-TiAl+α2-Ti3Al microstructures, has been analysed theoretically. Using the formulation due to Hirth and Pond, the shear produced and extent of diffusional flux associated with interfacial defect motion can be quantified in terms of the Burgers vectors, step heights of the defects and the chemical compositions of the adjacent crystals. Moreover, this formulation also enables the effects of chemical composition, misfit at the interface and ordering to be investigated systematically. It is shown that for the defects observed on such interfaces in recent high-resolution transmission electron microscopy studies, their motion would lead to the conservation of sites and, correspondingly, to equal and opposite fluxes of Ti and Al atoms. Consequently, although this Transformation is diffusional, it exhibits crystallographic features consistent with martensitic processes.
Jong Won Choi - One of the best experts on this subject based on the ideXlab platform.
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thermo mechanical metallurgical modeling for hot press forming in consideration of the prior austenite deformation effect
International Journal of Plasticity, 2014Co-Authors: Jong Won Choi, Frederic BarlatAbstract:Abstract In this study, a prior austenite grain refinement model was incorporated into semi-empirical Diffusive Transformation kinetics for application to hot-press forming. In particular, the kinetics equations were modified to include the effects of boron addition and austenite deformation on Transformation behaviors during forming. To simulate the hot-press forming process, a thermo-mechanical-metallurgical model was formulated implicitly and implemented into the finite element program ABAQUS using the user subroutines UMAT and UMATHT. This nonconventional finite element modeling is appropriate to consider thermal- and Transformation-associated strains. The proposed model was validated through simple finite element simulation examples, i.e., dilatometry simulation with and without external loading, and hot torsion and quenching of a rod. Finally, the hot-press forming of a U-channel-type part was simulated to study the effect of austenite deformation on the phase kinetics, hardness and residual stress. The simulation results showed that the austenite deformation had considerable influence on the final strength and residual stress distribution in the hot-press formed sheet, which resulted from an increase in ferritic phases due to the modified kinetics. In particular, the austenite deformation effect was more noticeable in the side-wall region of the U-channel where plastic deformation was the most severe.
Frederic Barlat - One of the best experts on this subject based on the ideXlab platform.
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thermo mechanical metallurgical modeling for hot press forming in consideration of the prior austenite deformation effect
International Journal of Plasticity, 2014Co-Authors: Jong Won Choi, Frederic BarlatAbstract:Abstract In this study, a prior austenite grain refinement model was incorporated into semi-empirical Diffusive Transformation kinetics for application to hot-press forming. In particular, the kinetics equations were modified to include the effects of boron addition and austenite deformation on Transformation behaviors during forming. To simulate the hot-press forming process, a thermo-mechanical-metallurgical model was formulated implicitly and implemented into the finite element program ABAQUS using the user subroutines UMAT and UMATHT. This nonconventional finite element modeling is appropriate to consider thermal- and Transformation-associated strains. The proposed model was validated through simple finite element simulation examples, i.e., dilatometry simulation with and without external loading, and hot torsion and quenching of a rod. Finally, the hot-press forming of a U-channel-type part was simulated to study the effect of austenite deformation on the phase kinetics, hardness and residual stress. The simulation results showed that the austenite deformation had considerable influence on the final strength and residual stress distribution in the hot-press formed sheet, which resulted from an increase in ferritic phases due to the modified kinetics. In particular, the austenite deformation effect was more noticeable in the side-wall region of the U-channel where plastic deformation was the most severe.
R.c. Pond - One of the best experts on this subject based on the ideXlab platform.
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interfacial dislocation mechanism for diffusional phase Transformations exhibiting martensitic crystallography formation of tial ti3al lamellae
Acta Materialia, 2000Co-Authors: R.c. Pond, P Shang, T T Cheng, Mark AindowAbstract:Abstract The displacive–Diffusive Transformation, which gives rise to lamellar γ-TiAl+α2-Ti3Al microstructures, has been analysed theoretically. Using the formulation due to Hirth and Pond, the shear produced and extent of diffusional flux associated with interfacial defect motion can be quantified in terms of the Burgers vectors, step heights of the defects and the chemical compositions of the adjacent crystals. Moreover, this formulation also enables the effects of chemical composition, misfit at the interface and ordering to be investigated systematically. It is shown that for the defects observed on such interfaces in recent high-resolution transmission electron microscopy studies, their motion would lead to the conservation of sites and, correspondingly, to equal and opposite fluxes of Ti and Al atoms. Consequently, although this Transformation is diffusional, it exhibits crystallographic features consistent with martensitic processes.
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Interfacial dislocation mechanism for diffusional phase Transformations exhibiting martensitic crystallography: formation of TiAl + Ti3Al lamellae
Acta Materialia, 2000Co-Authors: R.c. Pond, P Shang, T T Cheng, Mark AindowAbstract:Abstract The displacive–Diffusive Transformation, which gives rise to lamellar γ-TiAl+α2-Ti3Al microstructures, has been analysed theoretically. Using the formulation due to Hirth and Pond, the shear produced and extent of diffusional flux associated with interfacial defect motion can be quantified in terms of the Burgers vectors, step heights of the defects and the chemical compositions of the adjacent crystals. Moreover, this formulation also enables the effects of chemical composition, misfit at the interface and ordering to be investigated systematically. It is shown that for the defects observed on such interfaces in recent high-resolution transmission electron microscopy studies, their motion would lead to the conservation of sites and, correspondingly, to equal and opposite fluxes of Ti and Al atoms. Consequently, although this Transformation is diffusional, it exhibits crystallographic features consistent with martensitic processes.
Lakhdar Taleb - One of the best experts on this subject based on the ideXlab platform.
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(0) Save to: more options Evaluation of microstructure-based Transformation plasticity models from experiments on 100C6 steel
Computational Materials Science, 2012Co-Authors: Abdeladhim Tahimi, Fabrice Barbe, Lakhdar Taleb, R. Quey, Alain GuilletAbstract:The main characteristics of quasi-isothermal Diffusive Transformation from austenite to pearlite in a 100C6 steel have been determined from experimental tests. The parameters of constitutive laws and kinetics of phase Transformation of different micromechanical models of phase Transformation could then be identified. The models are classified according to the prevailing assumptions: mean- or full-field approach, regular or heterogeneous microstructural morphology, macro-homogeneous constitutive laws or crystal plasticity. A comparative analysis in terms of Transformation-induced plasticity (TRIP) is performed in order to conclude on the relevance of the different models as regards experiments and to show how the principal assumptions of TRIP modelling can affect the predictions
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Evaluation of microstructure-based Transformation plasticity models from experiments on 100C6 steel
Computational Materials Science, 2012Co-Authors: Abdeladhim Tahimi, Fabrice Barbe, Romain Quey, Lakhdar Taleb, Alain GuilletAbstract:The main characteristics of quasi-isothermal Diffusive Transformation from austenite to pearlite in a 100C6 steel have been determined from experimental tests. The parameters of constitutive laws and kinetics of phase Transformation of different micromechanical models of phase Transformation could then be identified. The models are classified according to the prevailing assumptions: mean- or full-field approach, regular or heterogeneous microstructural morphology, macro-homogeneous constitutive laws or crystal plasticity. A comparative analysis in terms of Transformation-induced plasticity (TRIP) is performed in order to conclude on the relevance of the different models as regards experiments and to show how the principal assumptions of TRIP modelling can affect the predictions.
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Numerical modelling of the plasticity induced during Diffusive Transformation. An ensemble averaging approach for the case of random arrays of nuclei
European Journal of Mechanics - A Solids, 2008Co-Authors: Fabrice Barbe, Romain Quey, Lakhdar Taleb, Eduardo Souza De CursiAbstract:Abstract The grounds of a numerical modelling of the mechanical consequences of Diffusive phase Transformation in solids have been established by Leblond [Leblond, J.B., Mottet, G., Devaux, J.C., 1986. A theoretical and numerical approach to the plastic behavior of steels during phase Transformations I: derivation of general relations, J. Mech. Phys. Solids 34 (4) 395–409] and Ganghoffer [Ganghoffer, J.F., Denis, S., Gautier, E., Simon, A., Sjostrom, S., 1993. Finite element calculation of the micromechanics of a diffusional Transformation, Eur. J. Mech. A Solids 12 (1) 21–32]: this modelling resorts to the FE method to evaluate the stress and strain fields which ensure the mechanical equilibrium between a diffusionaly growing phase and its parent phase. It has been the subject of a thorough analysis in [Barbe, F., Quey, R., Taleb, L., 2007. Numerical modelling of the plasticity induced during Diffusive Transformation. Case of a cubic array of nuclei, Eur. J. Mech. A Solids 26, 611–625] which has evidenced the main limit underlying this modelling with regard to physics, relative to the fact that nuclei are implicitly positioned according to a periodic array. The present work proposes, in details, an extension to the case of nuclei instantaneously appearing at random positions in a quasi infinite homogeneous medium. It constitutes a fundamental step towards a numerical modelling explicitly taking into account the crystalline plasticity and the morphology of the transforming medium.
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FE determination of the plasticity induced during Diffusive Transformation in the case of nucleation at random locations and instants
Computational Materials Science, 2008Co-Authors: H. Hoang, Fabrice Barbe, Romain Quey, Lakhdar TalebAbstract:Abstract The evolution of Transformation Induced Plasticity (TRIP) in a steel where the parent phase has been strain-hardened, for a martensitic as well as a bainitic Transformation, can only be predicted with models taking into account the interaction between classical plasticity and TRIP. One of the most famous, due to Leblond [J.B. Leblond, Int. J. Plasticity 5 (1989) 573–591], does not provide satisfying predictions in the experimental cases of pre-hardening explored by Taleb and Petit-Grostabussiat [L. Taleb, S. Petit-Grostabussiat, J. Phys. IV 12 (2002) Pr11–187–194; L. Taleb, S. Petit, Int. J. Plasticity 22 (2006) 110–130]. This has motivated the development of alternative approaches based on Finite Element (FE) analysis, which calculates equilibrium at the local scale of the interaction between phases without adopting any particular assumption on stress and strain fields. Our studies concern in particular diffusional Transformation where the last improvement has consisted in introducing a new law to govern the kinetics of nucleation: whereas previous works were based on the assumption of site saturation (instantaneous nucleation), it is considered here that nucleation happens randomly in space as well as in time, with a controlled probability distribution and evolution in time.
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Numerical modelling of the plasticity induced during Diffusive Transformation. Case of a cubic array of nuclei
European Journal of Mechanics - A Solids, 2007Co-Authors: Fabrice Barbe, Romain Quey, Lakhdar TalebAbstract:Abstract The experimental work of Taleb and Petit-Grostabussiat [Taleb, L., Petit-Grostabussiat, S., 2002. Elastoplasticity and phase Transformations in ferrous alloys: some discrepancies between experiments and modeling. J. Phys. IV 12 (11), 187–194; Taleb, L., Petit, S., 2006. New investigations on Transformation induced plasticity and its interaction with classical plasticity. Int. J. Plasticity 22 (1), 110–130] has shown evidence that the evolution of Transformation Induced Plasticity (TRIP) in a low carbon steel (16MND5) could be significantly influenced by the loading history of the parent phase, for a martensitic as well as a bainitic Transformation. Furthermore, estimates from the Leblond model – one of the few micromechanical models currently found in different Finite Element (FE) softwares – have appeared to be in disagreement with experiments in these cases where the parent phase has been strain hardened. This has motivated the development of alternative approaches based on FE computations. This paper presents our first investigations about simulations of Diffusive Transformations with FE in an idealized case: the parent and the product phase are considered as two homogeneous materials with given elastoplastic properties and density; the Transformation takes place at the same instant at predefined elements constituting the nuclei; then it progresses at a uniform rate by changing the material properties of the layer of elements surrounding the nuclei. In the basic configuration of modelling, the volume of discretization stands for a unit cell of a periodic cellular array, with a single central nucleus. In a more complex configuration, which is introduced shortly here and to be presented in details in the paper under preparation [Barbe, F., Quey, R., Taleb, L., Souza de Cursi, E., 2006. Numerical modelling of the plasticity induced during Diffusive Transformation. Case of a random instantaneous array of nuclei, in preparation], the volume of computation contains few to several nuclei at random locations. For both configurations, results in terms of effective (mean) TRIP as a function of the volume fraction of product phase are in correct quantitative and qualitative agreement with experimental results.