Effect of grain refiners on squeeze casting of magnesium alloy AM60

146 Pages·2015·9.64 MB·English

University of Windsor
Scholarship at UWindsor
Electronic Theses and Dissertations
2014
Effect of grain refiners on squeeze casting of
magnesium alloy AM60
Yanda Zou
University of Windsor
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5153.
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EFFECT OF GRAIN REFINERS ON SQUEEZE CASTING
OF MAGNESIUM ALLOY AM60

By
Yanda Zou

A Thesis
Submitted to the Faculty of Graduate Studies
through the Department of Mechanical, Automotive and Materials Engineering
in Partial Fulfillment of the Requirements for
the Degree of Master of Applied Science
at the University of Windsor

Windsor, Ontario, Canada
2014
© 2014 Yanda Zou
EFFECT OF GRAIN REFINERS ON SQUEEZE CASTING
OF MAGENSIUM ALLOY AM60
by
Yanda Zou

APPROVED BY:
______________________________________________
X. Chen
Department Electrical and Computer Engineering

______________________________________________
X. Nie
Department of Mechanical, Automotive and Materials Engineering

______________________________________________
H. Hu, Advisor
Department of Mechanical, Automotive and Materials Engineering

May 13, 2014
DECLARATION OF ORIGINALITY

I hereby certify that I am the sole author of this thesis and that no part of this
thesis has been published or submitted for publication.
I certify that, to the best of my knowledge, my thesis does not infringe upon
anyone’s copyright nor violate any proprietary rights and that any ideas, techniques,
quotations, or any other material from the work of other people included in my thesis,
published or otherwise, are fully acknowledged in accordance with the standard
referencing practices. Furthermore, to the extent that I have included copyrighted
material that surpasses the bounds of fair dealing within the meaning of the Canada
Copyright Act, I certify that I have obtained a written permission from the copyright
owner(s) to include such material(s) in my thesis and have included copies of such
copyright clearances to my appendix.
I declare that this is a true copy of my thesis, including any final revisions, as
approved by my thesis committee and the Graduate Studies office, and that this thesis has
not been submitted for a higher degree to any other University or Institution.

iii
ABSTRACT

The effect of hexachloroethane (C Cl ) and calcium carbide (CaC ) as grain
2 6 2
refiners added into the squeeze casting AM60 magnesium alloys was investigated in this
study. The results of thermal analysis and microstructural analysis indicate the occurrence
of heterogeneous nucleation of primary magnesium during solidification. The
microstructural analysis suggests that the nucleation behaviors of C Cl /CaC -treated
2 6 2
AM60 alloys may be attributed to the increase in nuclei and nucleation rate during the
solidification of the magnesium alloy. Grain size measurements indicated that both C Cl
2 6
and CaC have the capability to unify the average grain sizes of squeeze cast magnesium
2
alloy AM60 among different section thicknesses. The tensile testing indicate the
improved tensile properties especially in the thick sections. The corrosion tests showed
an increase in corrosion resistance as the grain refiners were added into the squeeze cast
alloy AM60.

iv
DEDICATION

I dedicate this thesis to my parents and my girlfriend. Their love and support
during my study in University of Windsor has given me strength and motivated me
through difficult times during the research period.

v
ACKNOWLEDGEMENTS

First of all, I would like to thank my supervisor Dr. Henry Hu for giving me the
opportunity to join the casting group in University of Windsor, for his excellent
supervision of this research work.
Great thanks to the program reader, Dr. Xueyuan Nie, and the outside program
reader, Dr. Xiang Chen for taking the time to review my thesis and giving me the
suggestions for this study.
Many thanks to the department technicians including Mr. Andy Jenner and Mr.
Matthew St. Louis for the sample preparation and the tensile test, Mr. Gang Li’s advises
on microstructure analysis, and Ms. Sharon Lackie’s help for the SEM training, and also
to the classmates in the casting group including Xuzhi Zhang, Meng Wang and Bojun
Xiong, for their great help on the experiment of this research.
Finally, I would like to express my sincerest gratitude to my family for their love,
support and encouragement.

vi
TABLE OF CONTENTS

DECLARATION OF ORIGINALITY .......................................................................... iii
ABSTRACT .......................................................................................................................iv
DEDICATION.................................................................................................................... v
ACKNOWLEDGEMENTS .............................................................................................vi
LIST OF TABLES ............................................................................................................ix
LIST OF FIGURES ........................................................................................................... x
CHAPTER 1: INTRODUCTION ..................................................................................... 1
1.1 Research Background ................................................................................................. 1
1.2 Objectives of this research ......................................................................................... 2
1.3 Thesis Layout ............................................................................................................. 3
CHAPTER 2: LITERATURE REVIEW ........................................................................ 4
2.1 Metallurgical Aspects of Magnesium Alloys ............................................................. 4
2.2 Die Casting Process .................................................................................................... 6
2.2.1 Die Casting .......................................................................................................... 6
2.2.2 Advantages of Die Casting .................................................................................. 8
2.2.3 Disadvantages of Die Casting.............................................................................. 9
2.3 Squeeze Casting Process ............................................................................................ 9
2.3.1 Squeeze Casting Concept .................................................................................... 9
2.3.2 Squeeze Casting Process ................................................................................... 10
2.3.3 Squeeze Casting vs Die Casting ........................................................................ 13
2.3.4 Effect of section Thickness on Tensile Properties of Magnesium Alloys ......... 17
2.4 Grain Refinement of Magnesium Alloys ................................................................. 20
2.4.1 Aluminum Free and Aluminum Containing Magnesium Alloys ...................... 20
2.4.2 Grain Refinement of Aluminum-Free Magnesium Alloys ................................ 21
vii
2.4.3 Grain Refinement of Aluminum Contain Magnesium Alloys........................... 22
2.5 Summary .................................................................................................................. 38
CHAPTER 3: EXPERIMENTAL PROCEDURES ..................................................... 40
3.1 Materials and Processing .......................................................................................... 40
3.2 Thermal Analysis ..................................................................................................... 41
3.3 Microstructure Analysis ........................................................................................... 43
3.4 Tensile Testing ......................................................................................................... 44
3.5 Potentiodynamic Polarization Testing ..................................................................... 46
CHAPTER 4: RESULTS AND DISCUSSION ............................................................. 48
4.1 Appearance of Squeeze casting Products ................................................................. 48
4.2 Solidification of magnesium alloy AM60 ................................................................ 49
4.2.1 Cooling Curve Analysis ..................................................................................... 49
4.2.2 DSC Analysis .................................................................................................... 54
4.3 Tensile Behaviour .................................................................................................... 55
4.3.1 Tensile Behaviour of cylindrical coupon ........................................................... 55
4.3.2 Tensile behaviour of 5-step casting ................................................................... 59
4.4 Microstructure Analysis ........................................................................................... 67
4.4.1 Magnesium alloy AM60 .................................................................................... 67
4.4.2 Grain structure of alloy AM60 cast in cylindrical mould .................................. 69
4.4.3 Grain refining mechanisms ................................................................................ 78
4.5 Fracture surface analysis .......................................................................................... 83
4.6 Inclusion analysis ..................................................................................................... 87
4.7 Corrosion test ........................................................................................................... 90
4.8 Summary .................................................................................................................. 93
CHAPTER 5: CONCLUSIONS ..................................................................................... 94
CHAPTER 6: FUTURE WORK .................................................................................... 96
REFERENCES ................................................................................................................. 97
APPENDICES: ADDITIONAL FIGURES ................................................................. 108
VITA AUCTORIS ......................................................................................................... 129
viii
LIST OF TABLES

Table 2-1 Grain refining method for casting magnesium alloys ....................................... 39
Table 3-1 Chemical composition of cast alloy AM60 ....................................................... 40
Table 3-2 Chemical properties of C Cl and CaC ............................................................ 41
2 6 2
Table 4-1 DSC analysis results of AM60 and C Cl /CaC -treated AM60 alloy ............... 55
2 6 2
Table 4-2 Tensile properties of AM60 C Cl -treated and CaC -treated specimens .......... 56
2 6 2
Table 4-3 Best fit parameters of power law equation ........................................................ 59
Table 4-4 Tensile properties of squeeze casting alloy AM60 in different thicknesses ..... 61
Table 4-5 Tensile properties of grain refined squeeze casting AM60 in different
thicknesses ......................................................................................................................... 64
Table 4-6 Grain size measurements of the untreated and treated squeeze cast Mg alloy
AM60 ................................................................................................................................. 78
Table 4-7 Characteristic values for the polarization curves in Figure 4-37 ....................... 93

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