Rapid Infrared Thermal Processing of AA 2618 and AA 6061 Forgings a Dissertation Presented to the Faculty of the Russ College Of
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Rapid Infrared Thermal Processing of AA 2618 and AA 6061 Forgings A dissertation presented to the faculty of the Russ College of Engineering and Technology of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy Vamadevan Gowreesan November 2008 © 2008 Vamadevan Gowreesan. All Rights Reserved. 2 This dissertation titled Rapid Infrared Thermal Processing of AA 2618 and AA 6061 Forgings by VAMADEVAN GOWREESAN has been approved for the Department of Mechanical Engineering and the Russ College of Engineering and Technology by Frank F. Kraft Associate Professor of Mechanical Engineering Dennis Irwin Dean, Russ College of Engineering and Technology 3 ABSTRACT GOWREESAN, VAMADEVAN, Ph.D., November 2008, Integrated Engineering Rapid Infrared Thermal Processing of AA 2618 and AA 6061 Forgings (150 pp.) Director of Dissertation: Frank F. Kraft Application of rapid heating methods for the thermal processing of aluminum alloy forgings is investigated in this work. Differential scanning calorimeter analysis of rapid heating of wrought aluminum alloys and laboratory simulation of solution treatment of wrought aluminum alloys were performed. The results showed that rapid heating accelerated the solutionizing of second phases in the alloys. Based on the results of these studies and practical limitation at the shop floor, optimized thermal processing cycles with an infrared furnace for AA 2618 and AA 6061 forgings were determined. Prototype forgings were produced and thermally processed with the proposed infrared heating cycles in addition to prototype forgings processed with conventional heat treatment. Mechanical testing was performed from samples obtained from the prototype forgings and measured mechanical properties were compared to understand the effect of thermal processing for shorter duration with rapid infrared heating. The results showed that short solution treatment with rapid infrared heating can produce forgings with mechanical properties comparable to that of conventionally processed forgings. The energy savings resulting from the short solution treatment with rapid infrared heating are also analyzed. The acceleration of the dissolution of second phase particles with rapid infrared heating has been attributed to the thermal stresses arising from mismatch of thermal expansions of the aluminum matrix and the second phases during rapid heating. 4 Approved:_______________________________________________________________ Frank F. Kraft Associate Professor of Mechanical Engineering 5 To my wife, parents, brothers, And also to all those teachers starting with the one who transformed an alphabet-hating five year old boy into one who could write, to those who teach 800 level courses. 6 ACKNOWLEDGEMENTS I am greatly indebted to my academic advisor Dr. Frank Kraft for his guidance and encouragement in my endeavors. What I learned from him helps me in my professional work very much. I am grateful for Dr. Khairul Alam, Dr. Daniel Gulino, Dr. Hugh Richardson and Dr. Horatio Castillo for agreeing to serve on the dissertation steering committee. Their input and suggestions brought some additional insights into the work. This research work would not have been possible without the financial support by EMTEC (Edison Materials Technology Center), Forging Industry Association (FIA) and John C. Baker Fund of Ohio University. Their financial contribution and support are greatly appreciated. I would like to acknowledge other project partners for their contributions, namely Rob Mayer of Queen City Forging Company, Puja Kadolkar of Oak Ridge National Laboratory, Percy Gros of EMTEC and George Mochnal of Forging Industry Association. Rob Mayer deserves a special appreciation for sharing some of his results with us. It had been a great privilege and pleasure working on this project. Dr. Jay Gunasekera is also acknowledged for his involvement in this research work. I would like to take this opportunity to thank Devon Polin for sharing part of the experimental work load in this project. Mihnea Anghelescu is also acknowledged for his help with DSC work. I wish to express my sincere appreciation to the ever-helpful Stephanie Walker and Randy Mulford. 7 TABLE OF CONTENTS Page ABSTRACT ................................................................................................................... 3 ACKNOWLEDGEMENTS ........................................................................................... 6 LIST OF TABLES ....................................................................................................... 11 LIST OF FIGURES ...................................................................................................... 12 CHAPTER 1: INTRODUCTION ................................................................................. 19 1.0 Introduction ..................................................................................................... 19 1.1 Research Summary ......................................................................................... 19 1.2 Background Information ................................................................................. 20 1.2.1 Forging Process ................................................................................ 20 1.2.2 Forging Stock ................................................................................... 22 1.2.3 Preheating of the Forging Stocks ..................................................... 22 1.2.4 Forging Steps ................................................................................... 23 1.3 Heat Treatment ................................................................................................ 23 1.3.1 Precipitation Hardening ................................................................... 24 1.3.2 Grain Refinement ............................................................................. 26 1.3.3 Conventional Heating ...................................................................... 26 1.3.4 Infrared Heating ............................................................................... 27 1.4 Scope of the Work .......................................................................................... 28 1.4.1 Theoretical Basis of Infrared Thermal Processing ........................... 29 1.4.2 Determination of Optimal Rapid Infrared Thermal Processing for the Forgings ......................................................................................................... 29 1.4.3 Comparisons of Mechanical Properties ........................................... 30 1.5 Significance of the Work ................................................................................ 31 1.6 Objectives ....................................................................................................... 32 1.7 Outline of the Dissertation .............................................................................. 33 CHAPTER 2: Literature Review .................................................................................. 34 2.0 Introduction ..................................................................................................... 34 2.1 Thermal Processing of Alloys with Rapid Heating ............................ 35 2.1.1 Rapid Heating of Titanium .............................................................. 35 8 2.1.2 Rapid Heating of Steels ................................................................... 37 2.2 Recent Applications of Rapid Heating Methods for Thermal Processing of Aluminum Alloys.................................................................................................. 38 2.3 Solution Heat Treatment ................................................................................. 41 2.4 DSC Studies on Thermal Processing of Aluminum Alloys ............................ 45 CHAPTER 3: Savings in energy and processing time ................................................. 49 3.0 Introduction ..................................................................................................... 49 3.1 Modeling of Heat Transfer.............................................................................. 49 CHAPTER 4: DSC Experimentation and analysis ....................................................... 51 4.0 Introduction ..................................................................................................... 51 4.1 Differential Scanning Calorimeter .................................................................. 51 4.2 Experimentation .............................................................................................. 52 4.3 Chemical Composition of the Alloy Samples ................................................. 54 4.4 Results and Analysis ....................................................................................... 56 4.4.1 Net Energy Transfer at Different Temperatures .............................. 57 4.4.2 Variation of Specific Heat Capacities .............................................. 62 4.5 Conclusions ..................................................................................................... 64 CHAPTER 5: Physical Simulation of Solution Treatment with Rapid Heating .......... 66 5.0 Introduction ..................................................................................................... 66 5.1 Materials ......................................................................................................... 66 5.2 Experimental Procedure .................................................................................