Microstructure Model for Ti-6Al-4V used in Simulation of Additive Manufacturing

176 Pages·2016·11.5 MB·English

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THESIS FOR DEGREE OF PHILOSOPHY DOCTOR IN ENGINEERING
Microstructure Model for Ti-6Al-4V used
in Simulation of Additive Manufacturing
CORINNE CHARLES MURGAU
May 2016
Mechanics of Solid Materials
Department of Engineering Sciences and Mathematics
LULEÅ UNIVERSITY OF TECHNOLOGY
971 87 Luleå, Sweden
Phone number [phone]
Microstructure Model for Ti-6Al-4V used
in Simulation of Additive Manufacturing
CORINNE CHARLES MURGAU

(cid:148) 2016 Corinne Charles Murgau

Division of Mechanics of Solid Materials
Department of Engineering Sciences and Mathematics
Luleå University of Technology
Sweden
Phone: [phone]

Printed by Luleå University of Technology, Graphic Production 2016

ISSN 1402-1544
ISBN 978-917583-579-2 (print)
ISBN 978-91-7583-580-8 (pdf)

Luleå 2016

www.ltu.se
ABSTRACT
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 thermal
driving 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 thermo-
mechanical 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 (cid:302) phase, consisting of
Widmanstätten (cid:302), grain boundary (cid:302), and martensite (cid:302). The phase transformations during
cooling are modelled based on diffusional theory described by a Johnson-Mehl-Avrami-
Kolmogorov formulation, except for diffusionless (cid:302) martensite formation where the
Koistinen-Marburger equation is used. A parabolic growth rate equation is used for the (cid:302) to
(cid:533) transformation upon heating. An added variable, structure size indicator of Widmanstätten
(cid:302), 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.

Keywords: Titanium alloy, Ti-6Al-4V, Welding,Metal deposition, Additive manufacturing,
Wire feed, Finite Element Method, Microstructure model, Johnson-Mehl-Avrami-
Kolmogorov, Thermally driven

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ACKNOWLEDGMENTS
This thesis summarises my doctoral studies carried out at University West (Högskolan Väst,
HV), Trollhättan, during the years 2005-2013. During this period I was registered as a
graduate student at Luleå University of Technology (LTU), division for Material Mechanics.
The work was supervised by Professor Lars-Erik Lindgren at LTU, by Associate Professor
Niklas Järvstråt at HV during the years 2005-2009 and by Research Associate Robert
Pederson at LTU during the years 2009-2016. An appreciated collaboration with GKN
aerospace Sweden AB (Volvo Aero Corporation 2005-2013) throughout this work is to be
mentioned.
The work was financed by the European Union through the research project VERDI1 and the
research project AFFIX2. The region of Västra Götaland (Sweden) through the project
INNside3 and VINNOVA4 foundation through the NFFP project MDReg5 are also
acknowledged for their financial support. The author would like to thank the research
environment Production Technology West at University West for financial support during the
years 2008-2012 and 2015-2016.
Professor Lars-Erik Lindgren, and his group, especially Bijish Babu and Andreas Lundbäck,
are gratefully thanked for their guidance and collaboration. I wish to express my gratitude to
Niklas Järvstråt for his time and support as well as for the advising discussions throughout
the first part of this work. I also would like to thank Robert Pederson for all the support and
supervision given on the metallurgical field. I appreciated that you stand up when supervision
transition were needed. Anna-Karin Christiansson and Mikael Ericsson are thanked for their
encouragements and helps along the following up meetings that took me through the end of
this work. Thanks to all of you for believing in me more than I do.
Finally, I would like to express my family for their understanding and encouragement. Warm
thanks to my friends and colleagues at University West for their technical support as well as
for their encouragements throughout this journey. I would also like to express my gratitude
to all who have helped me master Swedish language and traditions that became part of me.

Corinne Charles Murgau
Trollhättan, Sweden, May 2016

1 VERDI: European 6th Framework Programme funded research project "Virtual Engineering for Robust manufacturing
with Design Integration" (2002-2006) under contract n° AST4-CT-2005-516046 - http://www.verdi-fp6.org
2 AFFIX: European 6th Framework Programme funded research project "Aligning, Holding and Fixing Flexible and
Difficult to Handle Components" (2006-2010) under contract n° NMP-NI-4-2004-026670- http://www.affix-ip.eu
3 INNside 1-4: Region Västra Götaland 7th Framework programme funded research project (2007-2011). "Innovative
svetsning och bearbetning för lättviktsdesign"
4 VINNOVA: Swedish Governmental Agency for Innovation Systems - http://www.vinnova.se/en/
5 MDreg: Swedish VINNOVA Nationella Flygtekniska ForskningsProgrammet funded research project (2009-2013)
under contract n° 2009-01330

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PUBLICATIONS
The thesis comprises introductory chapters and the five appended papers listed below.

Paper A
Development of a Microstructure Model for Metal Deposition of Titanium Alloy Ti-6Al-4V
Corinne Charles and Niklas Järvstråt

In Proceedings of the 11th World Conference on Titanium (Ti-2007), Kyoto, Japan, 3-7 June
2007

Paper B
Modelling Ti-6Al-4V microstructure by evolution laws implemented as finite element
subroutines: Application to TIG metal deposition
Corinne Charles and Niklas Järvstråt

In Proceedings of the 8th International Conference on Trends in Welding Research,
Pine Mountain, GA, USA, 1-6 June 2008

Paper C
A model for Ti–6Al–4V microstructure evolution for arbitrary temperature changes
Corinne Charles Murgau, Robert Pederson and Lars-Erik Lindgren

Published in Modelling and Simulation in Materials Science and Engineering, 20(5), 055006

Paper D
Temperature and microstructure evolution in Gas Tungsten Arc Welding wire feed additive
manufacturing of Ti-6Al-4V
Corinne Charles Murgau, Andreas Lundbäck, Pia Åkerfeldt and Robert Pederson

To be submitted for publication.

Paper E
Physically based constitutive model of Ti-6Al-4V for arbitrary phase composition
Bijish Babu, Corinne Charles Murgau and Lars-Erik Lindgren

To be submitted for publication.

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