Improving the Corrosion Resistance of a High-Strength Aluminum-Copper Casting Alloy" (2009)
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University of Windsor Scholarship at UWindsor Electronic Theses and Dissertations Theses, Dissertations, and Major Papers 2009 Improving the Corrosion Resistance of a High-Strength Aluminum- Copper Casting Alloy Madhavan Manivannan University of Windsor Follow this and additional works at: https://scholar.uwindsor.ca/etd Recommended Citation Manivannan, Madhavan, "Improving the Corrosion Resistance of a High-Strength Aluminum-Copper Casting Alloy" (2009). Electronic Theses and Dissertations. 7891. https://scholar.uwindsor.ca/etd/7891 This online database contains the full-text of PhD dissertations and Masters’ theses of University of Windsor students from 1954 forward. These documents are made available for personal study and research purposes only, in accordance with the Canadian Copyright Act and the Creative Commons license—CC BY-NC-ND (Attribution, Non-Commercial, No Derivative Works). 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Improving the Corrosion Resistance of a High-Strength Aluminum-Copper Casting Alloy By Madhavan Manivannan 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 2009 © 2009 Madhavan Manivannan DECLARATION OF CO-AUTHORSHIP /PREVIOUS PUBLICATION This thesis includes [ISSN. 1442-0139, Paper 019] original paper that has been previously published in peer reviewed conference proceedings, as follows: Thesis Publication title Publication status* Chapter M. Manivannan., J.H. Sokolowski and D.O. Northwood, An investigation of the effect of various heat treatments on the corrosion Chapter 4 resistance of a high-strength Aluminum- published Copper casting alloy, Corrosion & Prevention 2008, Wellington, New Zealand, November 16- 19, 2008. Conference Proceedings, ISSN. 1442-0139, Paper 019, p. 1-10 I hereby declare that this thesis incorporates the outcome of a joint research under the supervision of Dr. Jerry H. Sokolowski and Dr. Derek O. Northwood. I am aware of the University of Windsor Senate Policy on Authorship and I certify that I have properly acknowledged the contribution of other researchers to my thesis, and have obtained written permission from each of the co-authors to include the above material in my thesis. I certify that, with the above qualification, this thesis, and the research to which it refers, is the product of my own work. I certify that I have obtained a written permission from the copyright owner(s) to include the above published material(s) in my thesis. I certify that the above material describes work completed during my registration as graduate student at the University of Windsor. I declare 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, iii 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. 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 of Institution. iv ABSTRACT The B206 alloy (up to 5 wt% Cu) is the strongest aluminum foundry alloy in current use. B206 alloy can be used in a number of automotive applications, e.g. suspension knuckles and vehicle control arms, to reduce vehicle weight. Elimination of hot tearing has reawakened the interest in the 206 alloy family. However, the B206 alloy is susceptible to intergranular/pitting corrosion which restricts its current applications. A heterogeneous distribution of Cu-containing intermetallic precipitates in the as-cast condition resulted in severe intergranular corrosion. The improved 3-step ST + 2-step AA provides better corrosion resistance compared to 2-step ST + 1-step AA. Longer first step AA time eliminated intergranular corrosion but resulted in low level pitting corrosion. The elongation was found to decrease with the increase in AA temperature and time. It is difficult to obtain both excellent corrosion resistance and elongation (510%) for the overaged condition. v ACKNOWLEDGEMENTS 1. The author wishes to express his sincere gratitude to Dr. Derek O. Northwood and Dr. Jerry H. Sokolowski for their support, supervision and valuable discussions throughout this work. 2. This research was funded by AUT021, a member of the Network of Centres of Excellence of Canada program, United States Council for Automotive Research (USCAR) through Dr. J. H. Sokolowski and the Natural Sciences and Engineering Research Council of Canada (NSERC) through a Discovery Grant awarded to Dr. D. O. Northwood. 3. I would like to sincerely thank all the collaborators in this thesis project especially from Dr. W. Kasprzak, Marta Aniolek, Mr. Blair Warnock, Dr. J. Fred Major (from Novelis), Dr. Geoffrey K. Sigworth & Eric McCarty (USCAR representatives), Dr. J. Szpunar & Mr. N.A.P. Kiran Kumar (McGill University) for their technical support. Thanks are also given to Dr. Glenn Byczynski & Dr. Robert Mackay (from Nemak). I greatly appreciate the valuable opportunities and assistance received from the Nemak of Canada Corporation, Windsor. 4. I would like to extend my thanks to the Advisory Committee Dr. Paul Henshaw, Dr. Xueyuan Nie and Dr. Henry Hu for their support. 5. I wish to express my appreciation to Ms. Ellen Moosberger and Ms. Barbara Tattersall for their assistance. Also the assistance of Mr. J. Robinson and the entire Technical Support Centre (U of W) was invaluable. Thanks to Mr. Daniel Szablewski and Mr. Nathan D. Reade for their support during my studies. I also wish to acknowledge the SEM analysis work from JEOL. vi TABLE OF CONTENTS DECLARATION OF CO-AUTHORSHIP/PREVIOUS PUBLICATION iii ABSTRACT v ACKNOWLEDGEMENTS vi LIST OF TABLES xi LIST OF FIGURES xiii LIST OF ABBREVIATIONS xxii CHAPTER 1: INTRODUCTION 1 1.1 General Background 1 1.2 Objectives 2 2: LITERATURE REVIEW 3 2.1 Introduction 3 2.2 Key Alloying and Impurity elements 4 2.2.1 Copper 4 2.2.2 Manganese 4 2.2.3 Magnesium 5 2.2.4 Silicon 5 2.2.5 Iron 5 2.2.6 Tin 6 2.2.7 Titanium 6 2.2.8 Nickel 6 2.3 History of Casting Al-Cu alloy 6 2.3.1 Al-Cu phase diagram 6 2.3.1.1 B206 alloy 7 2.3.1.2 Solidification reactions of 206.2 alloy 8 2.4 Casting Technology 8 2.4.1 Permanent Mold Casting Process 8 2.4.2 Hot-cracking of Al-Cu-Mn-Mg alloy 9 2.4.2.1 Effect of Silicon on the fluidity and hot cracking of Aluminum-Copper alloy 9 2.4.2.2 Fatigue crack growth in cast Al-Cu alloy A206 with different levels of porosity 10 2.5 Heat Treatment of Al-Cu alloys 10 2.5.1 Solution Treatment 10 2.5.2 Precipitation hardening 11 2.5.3 Natural Aging 12 2.5.4 Artificial Aging (AA) 12 2.5.4.1 Single stage Artificial Aging (AA) 12 2.5.4.2 Multi-stage Artificial Aging (AA) 14 2.5.5 Effect of Si on the microstructure and mechanical properties of AI-4.5%Cu alloys 16 2.5.6 Effect of Cu and Si on mechanical properties in Al-Cu-Si-Mg alloys 17 2.5.7 Chemistry/Property relationship in AA206 alloy 18 2.5.8 Mechanical properties of B206 alloy 18 2.6 Corrosion of Al-Cu alloys 19 2.6.1 Immersion testing of heat treated 201 alloys in NaCI/H202 corrosive solution 20 2.6.2 Stress Corrosion Cracking 21 2.6.2.1 Intergranular stress corrosion behaviour of Al-Cu-Mg-Ag alloys 21 2.6.2.2 Pitting corrosion of Al-Cu alloys 23 2.6.2.3 Copper redeposition during the dissolution in NaCI solution 25 2.6.2.4 Effect of quench delay time on corrosion behaviour of Al 2024 alloy....26 2.6.2.5 Stress Corrosion Cracking (SCC) after 2-step aging 26 2.7 Quality index of Al alloys 27 2.7.1 Caceres analytical model 27 2.7.2 Quality index by Murat Tiryakioglu 29 2.7.3 Ductility potential of 206 alloys 30 2.7.4 Quality index of B206 alloy 31 3: EXPERIMENTAL DETAILS 32 3.1 Tensile test bar casting 32 3.1.1 Chemical Composition of B206 alloy specimens 32 3.2 UMSA platform 33 3.3 First Series Heat Treatment 35 viii 3.3.1 2-step Solution Treatment (ST) 35 3.3.2 Natural Aging (NA) followed by 1-step Artificial Aging (AA) 36 3.4 Second Series Heat Treatment 38 3.5 Third Series Heat Treatment 38 3.5.1 Modified 3-step Solution Treatment 38 3.5.2 Aging (Natural + Artificial) 39 3.6 Corrosion Test Sample Preparation 42 3.7 Corrosion Testing Methods 42 3.7.1 Immersion corrosion Testing 42 3.7.2 Potentiodynamic Testing 43 3.7.3 Tribocorrosion tests 44 4: RESULTS AND DISCUSSIONS 47 4.1 As-cast Structure analysis before the immersion corrosion test 47 4.2 As-cast Structure analysis after the immersion corrosion test 51 4.3 Metallographic Analysis of corrosion mode and severity for First Series Heat Treatment conditions 54 4.4 Mechanical Properties analysis for second series heat treatments 64 4.5 Metallographic Analysis for third series heat treatments 66 4.5.1 Heat Treatment and corrosion test data for the machined samples 66 4.5.2 Heat Treatment and corrosion test data for the non machined samples 70 4.6 Comparison of immersion corrosion behaviour of heat treated samples subjected to 2 vs.