Al-Si Alloys (eBook)

Dr. Francisco C. Robles Hernandez has a BSc, a MSc. and a PhD in Materials Science and Engineering. He conducted his BSc and MSc at the Instituto Politecnico Nacional in Mexico City. After that he went to the University of Windsor to conduct his PhD. His PhD work is in the influence of electromagnetic stirring with or without vibration (ES or ESV) on Al-Si alloys, particularly hypereutectic. ES and ESV methods are applied during solidification as a means of soundness improvements and microstructure refinement and positive influence in mechanical properties and service characteristics. The work on Al-Si alloys had a direct focus on automotive applications. After completion of his PhD he moved to the Transportation Technology Center, Inc. as a Principal Investigator and a Chief Metallurgist. Later he relocated to the University of Houston as an Assistant Professor and he is currently an Associate Professor with tenure. He has authored more than 200 documents including conferences presentations, proceedings, books, patents, journal papers and industrial reports.Dr. Martin Herrera conducted his BSc in Chemical Engineering at Mexican Army (Escuela Militar de Ingenieros-Universidad del Ejercito y Fuerza Aerea) in Mexico City. Then he made his MSc in Metallurgy Engineering Science at the Instituto Politecnico Nacional also in Mexico City. Later he studied his PhD in Materials Science and Engineering at Ecole Nationale Superieure des Mines de Paris in Paris, France. After graduating from his BSc, he worked for the Army at the Direccion General de Industria Militar where he held various positions including the Head and project leader of the Applied Research Center and Technology Development for the Mexican Military Industry. Once he retired from the Army he moved to Centro de Investigacion en Materiales Avanzados in Chihuahua Mexico as a full-time researcher. His current research consists on powder metallurgy of metallic alloys and composites, especially aluminum and magnesium base. Dr. Herrera has authored or co-authored around 120 publications including journal papers, proceedings, conference presentations, books, and basic science and technological projects. He has been thesis advisor of doctoral, master and bachelor students.Dr. Robert Mackay began his formal education with a BSc in Physics at the University of Prince Edward Island, an MSc in Geophysics at Memorial University of Newfoundland and then a MEng in Metallurgical Engineering at McGill University, Montreal, Quebec. He then began his career in the metal casting industry at Oberdorfer Industries Limited, Syracuse, New York, as a product engineer and then moved to Haley Industries Limited, Haley, Ontario, as a process engineer with a focus on aerospace magnesium and aluminum castings. From there he started a Graduate Student Internship with Ford Motor Company while simultaneously working on a PhD degree in Materials Engineering at the University of Windsor. His area of focus in his PhD Dissertation was the improvement of High Cycle Fatigue (HCF) performance in cast aluminum engine blocks for the light truck segment. In 2003, after completing his PhD, he joined Nemak as a Metallurgical & Heat Treatment Specialist where he supervises a Metallurgical Laboratory technical team that supports alloy development, process optimization and defect/warranty characterization for several Nemak facilities in Canada, US and Mexico. Dr. Mackay is also a former Adjunct Professor at the Mechanical, Automotive and Materials Engineering Department at the University of Windsor. To date, Dr. Mackay has authored or co-authored nearly 60 publications from work stemming mainly for metal casting science and its application to product development and/or manufacturing. Dr. Mackay has served extensively in the Detroit-Windsor Chapter of the American Foundry Society (AFS) as a three term Chairman, one term as Vice Chairman, and finally a two time Board of Director Member.

Dedication 5
Authorship Statement 8
Bio-sketches 9
Acknowledgments 12
Contents 13
Chapter 1: Al-Si Alloys, Minor, Major, and Impurity Elements 17
1.1 General Overview: Aluminum Silicon Alloys 17
1.2 Alloy Designations 19
1.3 ASTM Standards for Testing AL-SI Castings 19
1.4 Effect of Main Chemical Constituents of AL-SI Hypereutectic Alloys 20
1.5 Major Alloying Elements 20
1.5.1 Silicon 20
1.5.2 Copper 22
1.5.3 Nickel 25
1.5.4 Magnesium 25
1.5.5 Zinc 26
1.6 Impurity Elements 26
1.6.1 Iron 26
1.6.2 Manganese 27
References 28
Chapter 2: Thermal Analysis 32
2.1 Introduction 32
2.2 Thermal Analysis Procedure 34
2.3 Heat Exchange Conditions 34
2.4 Experimental Results and Thermal Analysis Algorithms 36
2.5 Applications of the Thermal Analysis Algorithms 44
2.6 Thermal Analysis, Quench Testing, and Optical Microscopy 49
2.7 Characterization: Optical and Scanning Electron Microscopy 51
References 58
Chapter 3: Metal Casting Process 64
3.1 Casting Processes: Overview 64
3.2 High Pressure Die Casting Process 66
3.3 Lost Foam Process 72
3.4 Sand Casting and Precision Sand Casting Process 76
3.5 Aerospace Sand Casting Applications 77
3.6 Precision Sand for Automotive Applications 81
3.7 Semi-Permanent Molding Process 83
3.8 Permanent Mold Process 89
3.9 Investment Casting Process 91
3.10 Casting Process Selection 93
3.11 Heat Treatment Process for Aluminum Castings 94
References 96
Chapter 4: Powder Metallurgy 97
4.1 Introduction to Mechanical Milling 97
4.2 Al-Si Alloys 99
4.3 Powder Production Methods 100
4.4 Mechanical Alloying 102
4.5 Consolidation Methods 107
4.6 Sintering 111
References 120
Chapter 5: Liquid and Semisolid Melt Treatment: Electromagnetic Stirring 125
5.1 Introduction to Electromagnetic Stirring 125
5.2 Electromagnetic Stirring (ES) Principle 126
5.3 Mechanical and Ultrasonic Stirring 129
5.4 Electromagnetic Stirring and Vibration 129
5.5 Discussion of Silicon Modification 138
References 142
Chapter 6: Mechanical Properties 147
6.1 Mechanical Strength and Durability Assessment 148
6.2 Tensile Testing Properties 148
6.2.1 Tensile Test Sample Geometries for Casting 152
6.2.2 Precision Sand with Implemented Chill 152
6.2.3 Tensile Properties of Casting Sections Where Cylindrical Samples Are Not Possible 154
6.3 Weibull Statistical Method for Treating Tensile Test Data 157
6.3.1 Examples of Weibull Statics Used in Aluminum Castings 158
6.4 Fatigue Durability of Aluminum Castings 162
6.4.1 Fatigue Staircase Generation for Al-Si Castings 167
6.5 Weld Repair of Aluminum Castings 171
References 175
Chapter 7: Applications in the Automotive and Aerospace Industries 177
7.1 Aluminum Alloys: A Brief History 177
7.2 Casting Quality Requirements 179
7.3 Applications of Aluminum Castings in Automotive and Aerospace Industries 181
7.4 Impact of Aluminum Cost on Casting Processes 184
7.5 Aerospace 184
7.6 Automotive 184
References 185
Chapter 8: Principles of Solidification 186
8.1 Aluminum Alloy Systems 186
8.2 Alloy Designations 188
8.3 Solidification Sequence of Al-Si Alloys 190
8.4 Primary-Phase Evolution: ?-Al Dendritic Structure 191
8.4.1 Effect of Silicon Concentrations 195
8.4.2 Effect of Iron Concentrations 197
8.4.3 Effect of Copper Concentrations 200
8.4.4 Effect of Magnesium Concentration 201
8.4.5 Si Eutectic Modifiers: Strontium, Antimony, and Sodium 202
8.4.6 Grain Refinement 203
8.5 Mechanism for Pore Development 204
8.6 Hydrogen Concentrations: Measurement and Established Thresholds 206
8.7 Methods of Hydrogen Absorption 208
8.8 Kinetics for Oxide Generation 210
8.9 Titanium Boride (TiB2) Inclusions 211
8.10 Strontium-Based Inclusions 212
8.11 Reduced Pressure Test Methodology 212
8.12 Methods for Degassing 218
References 221
Chapter 9: Grain Refinement 224
9.1 Introduction to Grain Refinement 224
9.2 Chemical Grain Refinement 225
9.2.1 Principles and Grain Growth Restriction Factor 225
9.2.2 Grain Refinement of Aluminum-Rich Phases 226
9.3 Silicon in Liquid and Semisolid States 228
9.3.1 Structure in the Liquid State 228
9.3.2 Al-Si Hypereutectic Alloys 228
9.3.3 Primary Si Growth 233
9.4 Silicon Modification Methods 235
9.4.1 Chemical Modification of Si Rich Phases 235
9.4.2 Thermal Modification 238
9.4.3 Mechanical Modification 240
References 241
Erratum to: Al-Si Alloys: Automotive, Aeronautical, and Aerospace ApplicationsFrancisco C. Robles Hernandez, Jose Martin Herrera Ramírez, and Robert Mackay 248
Index 249