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Physically Based Constitutive Model of Ti-6Al-4V for Arbitrary Phase Composition
Mechanics of Sold Materials, Luleå University of Technology, SE-971 87, Luleå, Sweden.
University West, Department of Engineering Science, Avdelningen för svetsteknologi (SV). (PTW)ORCID iD: 0000-0002-3687-7782
Mechanics of Sold Materials, Luleå University of Technology, SE-971 87, Luleå, Sweden.
(English)Article in journal (Other academic) Submitted
Abstract [en]

The main challenge in producing aerospace components using Ti-6Al-4V alloy is to employ the optimum process window of deformation rate and temperature in order to achieve desired material properties. Understanding the microstructure property relationship qualitatively is not enough to achieve this goal. Developing advanced material models to be used in manufacturing process simulation is the key to iteratively computeand optimize the process. The focus in this work is on physically based flow stress models coupled with microstructure evolution models. Such a model can be used to simulate processes involving complex and cyclic thermo-mechanical loading

Keyword [en]
Finite Element Method, Dislocation density, Vacancy concentration, Ti-6Al-4V, Alpha, Beta
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-9345OAI: oai:DiVA.org:hv-9345DiVA: diva2:927835
Note

Ingår i avhandling

Available from: 2016-05-13 Created: 2016-05-13 Last updated: 2016-05-13Bibliographically approved
In thesis
1. Microstructure model for Ti-6Al-4V used in simulation of additive manufacturing
Open this publication in new window or tab >>Microstructure model for Ti-6Al-4V used in simulation of additive manufacturing
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is devoted to microstructure modelling of Ti-6Al-4V. The microstructure and the mechanical properties of titanium alloys are highly dependent on the temperature history experienced by the material. The developed microstructure model accounts for thermaldriving forces and is applicable for general temperature histories. It has been applied to study wire feed additive manufacturing processes that induce repetitive heating and cooling cycles.The microstructure model adopts internal state variables to represent the microstructure through microstructure constituents' fractions in finite element simulation. This makes it possible to apply the model efficiently for large computational models of general thermomechanical processes. The model is calibrated and validated versus literature data. It is applied to Gas Tungsten Arc Welding -also known as Tungsten Inert Gas welding-wire feed additive manufacturing process.Four quantities are calculated in the model: the volume fraction of phase, consisting of Widmanstätten, grain boundary, and martensite. The phase transformations during cooling are modelled based on diffusional theory described by a Johnson-Mehl-Avrami-Kolmogorov formulation, except for diffusionless martensite formation where the Koistinen-Marburger equation is used. A parabolic growth rate equation is used for the to transformation upon heating. An added variable, structure size indicator of Widmanstätten, has also been implemented and calibrated. It is written in a simple Arrhenius format.The microstructure model is applied to in finite element simulation of wire feed additive manufacturing. Finally, coupling with a physically based constitutive model enables a comprehensive and predictive model of the properties that evolve during processing.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2016. 159 p.
Series
Doctoral thesis / Luleå University of Technology, ISSN 1402-1544
Keyword
Titanium alloy, Ti-6Al-4V, Welding, Metal deposition, Additive manufacturing, Wire feed, Finite Element Method, Microstructure model, Johnson-Mehl-Avrami- Kolmogorov, Thermally driven
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9346 (URN)978-91-7583-579-2 (ISBN)978-91-7583-580-8 (ISBN)
Public defence
2016-05-24, E246, Luleå tekniska universitet, Luleå, 09:30 (English)
Opponent
Supervisors
Available from: 2016-05-13 Created: 2016-05-13 Last updated: 2016-05-13Bibliographically approved

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Charles Murgau, Corinne
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