Microstructure-Property Optimization in Metallic Glasses

100 Pages·2015·9.693 MB·English

by  Baran Sarac (auth.)

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Baran Sarac
Microstructure-Property
Optimization in Metallic
Glasses
1 3
Baran Sarac
Institute für Complex Materials
Leibniz Institute IFW Dresden
Dresden
Germany
ISSN 2190-5053 ISSN 2190-5061 (electronic)
Springer Theses
ISBN 978-3-319-13032-3 ISBN 978-3-319-13033-0 (eBook)
DOI 10.1007/978-3-319-13033-0
Library of Congress Control Number: 2014958305
Springer Cham Heidelberg New York Dordrecht London
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Foreword
This thesis consists of an in-depth study of investigating microstructure–property
relationships in bulk metallic glasses using a novel quantitative approach by which
influence of the second phase features on mechanical properties can be indepen-
dently and systematically analyzed. We adopted this strategy to evaluate and opti-
mize the elastic and plastic deformation, as well as the overall toughness of cellular
honeycombs under in-plane compression and porous heterostructures under uniaxi-
al tension. The first study revealed three major deformation zones in cellular metal-
lic glass structures, where deformation changes from collective buckling showing
nonlinear elasticity to localized failure exhibiting a brittle-like deformation, and
finally to global sudden failure with negligible plasticity as the length to thickness
ratio of the ligaments increases. For the second case, it has been found that spacing
and size of the pores, the pore configuration within the matrix, and the overall width
of the sample determines the extent of deformation, where the optimized values are
attained for pore diameter to spacing ratio of one with AB-type pore stacking.
In general, this versatile concept can also provide an insight to a wide range of
problems including very complicated microstructural architectures, stochastic foam
designs found in nature, as well as flaw tolerance and sensitivity studies of different
classes of materials.
Yale University, Department of Prof. Jan Schroers
Mechanical Engineering and Materials Science (Supervisor of Dr. Baran Sarac)
v
Acknowledgements
I take this opportunity to extend my gratitude to the people who have been instru-
mental in the successful completion of this thesis. I would like to express my deep-
est appreciation to my advisor, Prof. Jan Schroers, who has been abundantly helpful
and has offered invaluable assistance and support. He is not only a successful scien-
tist, but also a role model for the young scientists of our generation with his energy
and dedication to his work. I will forever value our scientific discussions, and will
always be inspired by his vision and perception of life.
I take immense pleasure in thanking Prof. Corey S. O’Hern and Prof. Aaron
M. Dollar for serving on my advisory committee and providing me guidance and
feedback on my thesis research. I would like to show my greatest appreciation to
my external committee member, Prof. Robert D. Conner. I am also grateful to my
former committee member, Prof. Ainissa G. Ramirez for her contributions and sup-
port in my special investigations and my area exam. I would also like to express my
gratitude to Prof. John B. Morrell who acted as a committee member in my disserta-
tion progress presentations.
Many thanks to our former postdoc, Dr. Golden Kumar, who has recently be-
come a professor at Texas Technical University, for his vast contributions and his
insightful comments about my research throughout my PhD.
I would like to thank Prof. Jamie Guest at Johns Hopkins University, who uti-
lized computational algorithm to structurally optimize cellular structures. Special
thanks to Dr. Amish Desai for providing me silicon templates and contributing to
the revision of my paper about blow-molding of metallic glasses. I also thank A.J.
Barnes, who sent me superplastically formable aluminum alloy pieces to generate
heterostructures.
I would like to thank all of the undergraduate researchers who have worked/been
working in my research projects and providing me experimental data. I owe thanks
to my current and previous colleagues, friends, as well as many other people in our
department and school, for their valuable ideas, support and assistance throughout
my PhD study.
Finally, yet importantly, I would like to express my heartfelt thanks to my be-
loved parents, Nes’e Sarac and Prof. A. Sezai Sarac, for their blessings and guid-
ance.
vii
Article Note (Parts of this Thesis)
Parts of this thesis have been published in the following journal articles:
• Sarac, B., Schroers, J., “Designing Tensile Ductility in Metallic Glasses”, Nature
Communications, 06/2013, vol. 4, pp. 1–7, DOI: 10.1038/ncomms3158.
• Sarac, B., Schroers, J., “From brittle to ductile: Density optimization of Zr-
based bulk metallic glass cellular structures”, Scripta Materialia, 06/2013, vol.
68, pp. 921–924, DOI: 10.1016/j.scriptamat.2013.02.030.
• Sarac, B., Ketkaew, J., Popnoe, D. O. and Schroers, J., “Honeycomb Structures
of Bulk Metallic Glasses”, Advanced Functional Materials, 04/2012, vol. 22,
pp. 3161–3169, DOI: 10.1002/ adfm.201200539.
• Sarac, B., Kumar, G., Hodges, T., Ding, S., Desai, A., and Schroers, J., “Three-
Dimensional Shell Fabrication Using Blow Molding of Bulk Metallic Glass”,
Journal of Microelectromechanical Systems, 02/2011, vol. 20, pp. 28–36, DOI:
10.1109/JMEMS.2010.2090495.
ix
Contents
1 General Introduction ................................................................................ 1
1.1 Motivation and Scope of Complex Materials .................................... 1
1.2 A n Overview of Metallic Glasses (MGs) ........................................... 3
1.3 Processing of MGs ............................................................................. 5
1.4 Mechanical Property Enhancement in MG Composites .................... 10
References ................................................................................................... 12
2 Fabrication Methods of Artificial Microstructures ............................... 17
2.1 M etallic Glass (MG) Alloy Synthesis ................................................ 17
2.2 S ilicon Mold Fabrication ................................................................... 18
2.3 Fabrication Methods of MG Artificial Microstructures ..................... 19
Conclusions ................................................................................................. 24
References ................................................................................................... 28
3 Structural Characterization of Metallic Glasses .................................... 29
3.1 Formability Test ................................................................................. 29
3.2 Thermal Analysis ............................................................................... 30
3.3 Structural Analysis ............................................................................. 31
3.4 Bend Test ............................................................................................ 34
Conclusions ................................................................................................. 35
References ................................................................................................... 36
4 Artificial Microstructure Approach ........................................................ 37
4.1 Objectives .......................................................................................... 37
4.2 Periodic Cellular Structures of MGs .................................................. 38
4.2.1 M G Cellular Structure Sample ............................................... 39
4.2.2 In-Plane Compression Test .................................................... 40
4.2.3 Euler Buckling Instability ...................................................... 41
4.2.4 Results and Discussion .......................................................... 42
4.2.5 General Findings and Conclusions ........................................ 59
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xii Contents
4.3 T oughening Mechanisms in MGs ...................................................... 60
4.3.1 U niaxial Tensile Test .............................................................. 61
4.3.2 I nvestigation of MG Composites Using FEM Analysis ........ 72
4.3.3 G eneral Findings and Conclusions ........................................ 75
References ................................................................................................... 77
5 General Conclusions and Outlook ........................................................... 81
5.1 General Conclusions .......................................................................... 81
5.2 P ush the Limit: 3D Metallic Glass Structures .................................... 82
5.3 M ultiple Material Artificial Microstructures ..................................... 83
5.4 N onperiodic Cellular Structures and Flaw Tolerance ........................ 85
5.5 Algorithmic Topological Optimization .............................................. 86
5.6 F racture Toughness in MG Heterostructures ..................................... 86
5.7 O ther Application Fields of MG Heterostructures ............................. 87
References ................................................................................................... 88
Index ................................................................................................................. 89