Welding Metallurgy of Aluminium Alloys

Preface vii

List of Abbreviations ix

1 Aluminum Alloys: Fundamentals of Welding Metallurgy 1

1.1 Introduction 1

1.1.1 Aluminum–Copper Alloys 4

1.1.2 Aluminum–Zinc–Magnesium Alloys 4

1.1.3 Aluminum–Magnesium–Silicium 4

1.1.4 Aluminum–Lithium Alloys 5

1.2 Weldability 5

1.2.1 Aluminum Oxide 6

1.2.2 Hydrogen and Pore Formation 7

1.2.2.1 Effects of Porosity on the Mechanical Behavior 10

1.2.3 Hot Cracking 10

1.3 Thermal Cycle and Its Effect on the Weld Zone 23

1.4 Welding of Aluminum to Other Metals 30

References 31

2 Arc Welding Processes 37

2.1 Introduction 37

2.2 Processes 38

2.2.1 TIG Welding 38

2.2.2 Plasma Arc Welding 39

2.2.3 MIG Welding 40

2.3 Modifications to the Processes 42

2.3.1 Negative-Pole and Positive-Pole TIG Welding 42

2.3.2 Keyhole TIG (K-TIG) Welding 42

2.3.3 Activated-Flux TIG (A-TIG) Welding 44

2.3.4 Double-Wire MIG Welding 44

2.3.5 Indirect Electric Arc 46

2.3.6 Cold Metal Transfer (CMT) Welding 47

2.3.7 Positive-Pole Plasma Welding 47

2.3.8 Hyperbaric Welding 48

2.4 Hybrid Welding 48

2.4.1 Plasma-MIG Welding 49

2.4.2 TIG-MIG Welding 51

2.5 Protective Gases 52

2.6 Filler Material 53

2.7 Grain Refinement in the Weld 53

2.8 Grain Structure 59

2.9 Defects During Arc Welding 60

2.9.1 Segregation 60

2.9.2 Smut 61

2.9.3 Pores 62

2.9.4 Hot Cracking 62

2.10 Welding of Dissimilar Metals 64

2.11 Simulation of the Arc Welding Processes 67

References 72

3 Beam Welding Processes 83

3.1 Introduction 83

3.2 Laser Systems 87

3.3 Defects Formation During Laser Welding of Al Alloys 88

3.3.1 Mechanism of Pore Formation 88

3.3.2 Hot Cracking in Laser Welding 93

3.4 Shielding Gases in Laser Welding 96

3.5 Modifications to Laser Welding of Al 98

3.5.1 Multi-spot Laser Beam Welding 98

3.5.2 Micro-laser Welding 99

3.5.3 Pulsed Laser Beam Welding 99

3.5.4 Hybrid Laser Welding 103

3.5.5 Oscillation Laser Beam Welding 104

3.5.6 Vibration-Assisted Laser Beam Welding 105

3.5.7 Hot-Wire Laser Welding 106

3.6 Special Cases of Al Welding 107

3.6.1 Additive Manufacturing 107

3.6.2 Cast Aluminum 107

3.6.3 Welding of Aluminum to Dissimilar Materials 108

3.7 Simulation of Laser Welding 109

References 115

4 Resistance Welding Process 125

4.1 Introduction 125

4.2 Weld Zones 131

4.2.1 Nugget Zone 131

4.2.2 Thermo-Mechanically Affected Zone (TMAZ) 133

4.3 Defects During RSW of Al Alloys 135

4.4 RSW of Dissimilar Aluminum Alloys 137

4.5 RSW of Al to Dissimilar Metals 139

4.6 Modifications to RSW for Welding Al Alloys 144

4.7 Simulation of the Process 149

4.8 Evaluation of the Joints 152

References 155

5 Solid-State Welding Process 163

5.1 Introduction 163

5.2 FSW of Al Alloys 164

5.3 FSW of Al-Matrix Composites 172

5.4 FSW of Al to Dissimilar Materials 175

5.5 Joint Design 180

5.6 Simulation of the Process 184

References 186

Index 193