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Welding Metallurgy Third Edition de S Kou

Welding Metallurgy Third Edition

Autor S Kou
en Limba Engleză Hardback – 25 noi 2020
Discover the extraordinary progress that welding metallurgy has experienced over the last two decades Welding Metallurgy, 3rd Edition is the only complete compendium of recent, and not-so-recent, developments in the science and practice of welding metallurgy. Written by Dr. Sindo Kou, this edition covers solid-state welding as well as fusion welding, which now also includes resistance spot welding. It restructures and expands sections on Fusion Zones and Heat-Affected Zones. The former now includes entirely new chapters on microsegregation, macrosegregation, ductility-dip cracking, and alloys resistant to creep, wear and corrosion, as well as a new section on ternary-alloy solidification. The latter now includes metallurgy of solid-state welding. Partially Melted Zones are expanded to include liquation and cracking in friction stir welding and resistance spot welding. New chapters on topics of high current interest are added, including additive manufacturing, dissimilar-metal joining, magnesium alloys, and high-entropy alloys and metal-matrix nanocomposites. Dr. Kou provides the reader with hundreds of citations to papers and articles that will further enhance the reader's knowledge of this voluminous topic. Undergraduate students, graduate students, researchers and mechanical engineers will all benefit spectacularly from this comprehensive resource. The new edition includes new theories/methods of Kou and coworkers regarding: · Predicting the effect of filler metals on liquation cracking · An index and analytical equations for predicting susceptibility to solidification cracking · A test for susceptibility to solidification cracking and filler-metal effect · Liquid-metal quenching during welding · Mechanisms of resistance of stainless steels to solidification cracking and ductility-dip cracking · Mechanisms of macrosegregation · Mechanisms of spatter of aluminum and magnesium filler metals, · Liquation and cracking in dissimilar-metal friction stir welding, · Flow-induced deformation and oscillation of weld-pool surface and ripple formation · Multicomponent/multiphase diffusion bondingDr. Kou's Welding Metallurgy has been used the world over as an indispensable resource for students, researchers, and engineers alike. This new Third Edition is no exception.
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Specificații

ISBN-13: 9781119524816
ISBN-10: 1119524814
Pagini: 688
Dimensiuni: 203 x 254 x 34 mm
Greutate: 2.43 kg
Ediția:3rd Edition
Editura: Wiley
Locul publicării:Hoboken, United States

Notă biografică

Sindo Kou, PhD, is Professor and former Chair of the Department of Materials Science and Engineering at the University of Wisconsin. He graduated from MIT with a doctorate in metallurgy. He is a Fellow of American Welding Society and ASM International. He received the William Irrgang Memorial Award (2018), the Honorary Membership Award (2016), and the Comfort A. Adams Lecture Award (2012) from the American Welding Society (AWS); the Yoshiaki Arata Award (2017) from the International Institute of Welding (IIW); the Bruce Chalmers Award (2013) from The Minerals, Metals & Materials Society (TMS); the John Chipman Award (1980) from the Iron and Steel Society of AIME; and Chancellor's Award for Distinguished Teaching (1999) from the University of Wisconsin-Madison. His technical papers won the Warren F. Savage Memorial Award (4 times), Charles H. Jennings Memorial Award (4 times), William Spraragen Award (3 times), A.F. Davis Silver Medal Award, and James F. Lincoln Gold Medal of AWS; and the Magnesium Technology Best Paper Award of TMS.

Cuprins

Preface to Third Edition xxi Part I Introduction 1 1 Welding Processes 3 1.1 Overview 3 1.1.1 Fusion Welding Processes 3 1.1.1.1 Power Density of Heat Source 4 1.1.1.2 Welding Processes and Materials 5 1.1.1.3 Types of Joints and Welding Positions 7 1.1.2 Solid-State Welding Processes 8 1.2 Gas Welding 8 1.2.1 The Process 8 1.2.2 Three Types of Flames 9 1.2.2.1 Neutral Flame 9 1.2.2.2 Reducing Flame 9 1.2.2.3 Oxidizing Flame 9 1.2.3 Advantages and Disadvantages 10 1.3 Arc Welding 10 1.3.1 Shielded Metal Arc Welding 10 1.3.1.1 Functions of Electrode Covering 10 1.3.1.2 Advantages and Disadvantages 11 1.3.2 Gas-Tungsten Arc Welding 11 1.3.2.1 The Process 11 1.3.2.2 Polarity 12 1.3.2.3 Electrodes 13 1.3.2.4 Shielding Gases 13 1.3.2.5 Advantages and Disadvantages 13 1.3.3 Plasma Arc Welding 14 1.3.3.1 The Process 14 1.3.3.2 Arc Initiation 14 1.3.3.3 Keyholing 15 1.3.3.4 Advantages and Disadvantages 15 1.3.4 Gas-Metal Arc Welding 16 1.3.4.1 The Process 16 1.3.4.2 Shielding Gases 16 1.3.4.3 Modes of Metal Transfer 17 1.3.4.4 Advantages and Disadvantages 18 1.3.5 Flux-Cored Arc Welding 18 1.3.5.1 The Process 18 1.3.6 Submerged Arc Welding 19 1.3.6.1 The Process 19 1.3.6.2 Advantages and Disadvantages 20 1.3.7 Electroslag Welding 20 1.3.7.1 The Process 20 1.3.7.2 Advantages and Disadvantages 21 1.4 High-Energy-Beam Welding 21 1.4.1 Electron Beam Welding 21 1.4.1.1 The Process 21 1.4.1.2 Advantages and Disadvantages 23 1.4.2 Laser Beam Welding 24 1.4.2.1 The Process 24 1.4.2.2 Reflectivity 24 1.4.2.3 Shielding Gas 25 1.4.2.4 Laser-Assisted Arc Welding 25 1.4.2.5 Advantages and Disadvantages 26 1.5 Resistance Spot Welding 26 1.6 Solid-State Welding 27 1.6.1 Friction Stir Welding 27 1.6.2 Friction Welding 29 1.6.3 Explosion and Magnetic-Pulse Welding 31 1.6.4 Diffusion Welding 31 Examples 32 References 33 Further Reading 34 Problems 35 2 Heat Flow in Welding 37 2.1 Heat Source 37 2.1.1 Heat Source Efficiency 37 2.1.1.1 Definition 37 2.1.1.2 Measurements 38 2.1.1.3 Heat Source Efficiencies in Various Welding Processes 41 2.1.2 Melting Efficiency 42 2.1.3 Power Density Distribution of Heat Source 43 2.1.3.1 Effect of Electrode Tip Angle 43 2.1.3.2 Measurements 43 2.2 Heat Flow During Welding 45 2.2.1 Response of Material to Welding Heat Source 45 2.2.2 Rosenthal's Equations 45 2.2.2.1 Rosenthal's Two-Dimensional Equation 46 2.2.2.2 Rosenthal's Three-Dimensional Equation 47 2.2.2.3 Step-by-Step Application of Rosenthal's Equations 48 2.2.3 Adams' Equations 49 2.3 Effect of Welding Conditions 49 2.4 Computer Simulation 52 2.5 Weld Thermal Simulator 53 2.5.1 The Equipment 53 2.5.2 Applications 54 2.5.3 Limitations 54 Examples 54 References 57 Further Reading 59 Problems 59 3 Fluid Flow in Welding 61 3.1 Fluid Flow in Arcs 61 3.1.1 Sharp Electrode 61 3.1.2 Flat-End Electrode 63 3.2 Effect of Metal Vapor on Arcs 63 3.2.1 Gas.Tungsten Arc Welding 63 3.2.2 Gas.Metal Arc Welding 65 3.3 Arc Power- and Current-Density Distributions 68 3.4 Fluid Flow in Weld Pools 69 3.4.1 Driving Forces for Fluid Flow 69 3.4.2 Heiple's Theory for Weld Pool Convection 71 3.4.3 Physical Simulation of Fluid Flow and Weld Penetration 72 3.4.4 Computer Simulation of Fluid Flow and Weld Penetration 75 3.5 Flow Oscillation and Ripple Formation 77 3.6 Active Flux GTAW 80 3.7 Resistance Spot Welding 81 Examples 84 References 85 Further Reading 88 Problems 88 4 Mass and Filler-Metal Transfer 91 4.1 Convective Mass Transfer in Weld Pools 91 4.2 Evaporation of Volatile Solutes 94 4.3 Filler-Metal Drop Explosion and Spatter 96 4.4 Spatter in GMAW of Magnesium 100 4.5 Diffusion Bonding 100 Examples 103 References 104 Problems 105 5 Chemical Reactions in Welding 107 5.1 Overview 107 5.1.1 Effect of Nitrogen, Oxygen, and Hydrogen 107 5.1.2 Protection Against Air 107 5.1.3 Evaluation of Weld Metal Properties 108 5.2 Gas-Metal Reactions 111 5.2.1 Thermodynamics of Reactions 111 5.2.2 Hydrogen 113 5.2.2.1 Magnesium 113 5.2.2.2 Aluminum 113 5.2.2.3 Titanium 116 5.2.2.4 Copper 116 5.2.2.5 Steels 116 5.2.3 Nitrogen 118 5.2.3.1 Steel 118 5.2.3.2 Titanium 121 5.2.4 Oxygen 121 5.2.4.1 Magnesium 121 5.2.4.2 Aluminum 121 5.2.4.3 Titanium 121 5.2.4.4 Steel 122 5.3 Slag-Metal Reactions 125 5.3.1 Thermochemical Reactions 125 5.3.1.1 Decomposition of Flux 125 5.3.1.2 Removal of S and P from Liquid Steel 126 5.3.2 Effect of Flux on Weld Metal Oxygen 127 5.3.3 Types of Fluxes, Basicity Index, and Weld Metal Properties 127 5.3.4 Basicity Index 128 5.3.5 Electrochemical Reactions 130 Examples 135 References 136 Further Reading 140 Problems 140 6 Residual Stresses, Distortion, and Fatigue 141 6.1 Residual Stresses 141 6.1.1 Development of Residual Stresses 141 6.1.1.1 Stresses Induced By Welding 141 6.1.1.2 Welding 141 6.1.2 Analysis of Residual Stresses 143 6.2 Distortion 145 6.2.1 Cause 145 6.2.2 Remedies 146 6.3 Fatigue 147 6.3.1 Mechanism 147 6.3.2 Fractography 147 6.3.3 S-N Curves 150 6.3.4 Effect of Joint Geometry 150 6.3.5 Effect of Stress Raisers 151 6.3.6 Effect of Corrosion 152 6.3.7 Remedies 152 6.3.7.1 Shot Peening 152 6.3.7.2 Reducing Stress Raisers 153 6.3.7.3 Laser Shock Peening 154 6.3.7.4 Use of Low-Transformation-Temperature Fillers 154 Examples 154 References 155 Further Reading 156 Problems 156 Part II The Fusion Zone 157 7 Introduction to Solidification 159 7.1 Solute Redistribution During Solidification 159 7.1.1 Directional Solidification 159 7.1.2 Equilibrium Segregation Coefficient k 159 7.1.3 Four Cases of Solute Redistribution 161 7.2 Constitutional Supercooling 166 7.3 Solidification Modes 168 7.4 Microsegregation Caused by Solute Redistribution 171 7.5 Secondary Dendrite Arm Spacing 174 7.6 Effect of Dendrite Tip Undercooling 177 7.7 Effect of Growth Rate 178 7.8 Solidification of Ternary Alloys 178 7.8.1 Liquidus Projection 178 7.8.2 Solidification Path 179 7.8.3 Ternary Magnesium Alloys 180 7.8.4 Ternary Fe-Cr-Ni Alloys 182 7.8.4.1 Fe-Cr-Ni Phase Diagram 182 7.8.4.2 Solidification Paths 185 7.8.4.3 Microstructure 186 Examples 189 References 191 Further Reading 193 Problems 193 8 Solidification Modes 195 8.1 Solidification Modes 195 8.1.1 Temperature Gradient and Growth Rate 195 8.1.2 Variations in Growth Mode Across Weld 197 8.2 Dendrite Spacing and Cell Spacing 200 8.3 Effect of Welding Parameters 201 8.3.1 Solidification Mode 201 8.3.2 Dendrite and Cell Spacing 202 8.4 Refining Microstructure Within Grains 203 8.4.1 Arc Oscillation 203 8.4.2 Arc Pulsation 205 Examples 205 References 206 Further Reading 207 Problems 207 9 Nucleation and Growth of Grains 209 9.1 Epitaxial Growth at the Fusion Line 209 9.2 Nonepitaxial Growth at the Fusion Line 212 9.2.1 Mismatching Crystal Structures 212 9.2.2 Nondendritic Equiaxed Grains 213 9.3 Growth of Columnar Grains 214 9.4 Effect of Welding Parameters on Columnar Grains 215 9.5 Control of Columnar Grains 218 9.6 Nucleation Mechanisms of Equiaxed Grains 219 9.6.1 Microstructure Around Pool Boundary 219 9.6.2 Dendrite Fragmentation 220 9.6.3 Grain Detachment 222 9.6.4 Heterogeneous Nucleation 222 9.6.5 Effect of Welding Parameters on Heterogeneous Nucleation 225 9.6.6 Surface Nucleation 228 9.7 Grain Refining 228 9.7.1 Inoculation 228 9.7.2 Weld Pool Stirring 229 9.7.2.1 Magnetic Weld Pool Stirring 229 9.7.2.2 Ultrasonic Weld Pool Stirring 229 9.7.3 Arc Pulsation 232 9.7.4 Arc Oscillation 232 9.8 Identifying Grain-Refining Mechanisms 233 9.8.1 Overlap Welding Procedure 233 9.8.2 Identifying the Grain-Refining Mechanism 235 9.8.3 Effect of Arc Oscillation on Dendrite Fragmentation 236 9.8.4 Effect of Arc Oscillation on Constitutional Supercooling 236 9.8.5 Effect of Composition on Grain Refining by Arc Oscillation 238 9.9 Grain-Boundary Migration 238 Examples 239 References 240 Further Reading 245 Problems 246 10 Microsegregation 247 10.1 Microsegregation in Welds 247 10.2 Effect of Travel Speed on Microsegregation 249 10.3 Effect of Primary Solidification Phase on Microsegregation 252 10.4 Effect of Maximum Solid Solubility on Microsegregation 253 Examples 259 References 261 Further Reading 262 Problems 262 11 Macrosegregation 263 11.1 Macrosegregation in the Fusion Zone 263 11.2 Quick Freezing of One Liquid Metal in Another 265 11.3 Macrosegregation in Dissimilar-Filler Welding 265 11.3.1 Bulk Weld-Metal Composition 265 11.3.2 Mechanism I 267 11.3.3 Mechanism II 270 11.4 Macrosegregation in Dissimilar-Metal Welding 279 11.4.1 Mechanism I 279 11.4.2 Mechanism II 283 11.5 Reduction of Macrosegregation 286 11.6 Macrosegregation in Multiple-Pass Welds 287 References 290 Further Reading 291 Problems 291 12 Some Alloy-Specific Microstructures and Properties 293 12.1 Austenitic Stainless Steels 293 12.1.1 Microstructure Evolution in Stainless Steels 293 12.1.2 Mechanisms of Ferrite Formation 294 12.1.3 Prediction of Ferrite Content 296 12.1.4 Effect of Cooling Rate 297 12.1.4.1 Changes in Solidification Mode 297 12.1.4.2 Dendrite Tip Undercooling 301 12.2 Low-Carbon, Low-Alloy Steels 301 12.2.1 Microstructure Development 301 12.2.2 Factors Affecting Microstructure 302 12.2.3 Weld Metal Toughness 306 12.3 Ultralow Carbon Bainitic Steels 306 12.4 Creep-Resistant Steels 308 12.5 Hardfacing of Steels 311 References 319 Further Reading 321 Problems 321 13 Solidification Cracking 323 13.1 Characteristics of Solidification Cracking 323 13.2 Theories of Solidification Cracking 323 13.2.1 Criterion for Cracking Proposed by Kou 327 13.2.2 Index for Crack Susceptibility Proposed by Kou 328 13.2.3 Previous Theories 330 13.3 Binary Alloys and Analytical Equations 331 13.4 Solidification Cracking Tests 334 13.4.1 Varestraint Test 334 13.4.2 Controlled Tensile Weldability Test 336 13.4.3 Transverse-Motion Weldability Test 337 13.4.4 Circular-Patch Test 341 13.4.5 Houldcroft Test 342 13.4.6 Cast-Pin Test 343 13.4.7 Ring-Casting Test 344 13.4.8 Other Tests 344 13.5 Solidification Cracking of Stainless Steels 345 13.5.1 Primary Solidification Phase 345 13.5.2 Mechanism of Crack Resistance 346 13.6 Factors Affecting Solidification Cracking 350 13.6.1 Primary Solidification Phase 350 13.6.2 Grain Size 350 13.6.3 Solidification Temperature Range 351 13.6.4 Back Diffusion 354 13.6.5 Dihedral Angle 355 13.6.6 Grain-Boundary Angle 359 13.6.7 Degree of Restraint 360 13.7 Reducing Solidification Cracking 360 13.7.1 Control of Weld Metal Composition 360 13.7.2 Control of Weld Microstructure 363 13.7.3 Control of Welding Conditions 365 13.7.4 Control of Weld Shape 366 Examples 367 References 370 Further Reading 376 Problems 376 14 Ductility-Dip Cracking 379 14.1 Characteristics of Ductility-Dip Cracking 379 14.2 Theories of Ductility-Dip Cracking 381 14.3 Test Methods 382 14.4 Ductility-Dip Cracking of Ni-Base Alloys 384 14.4.1 Grain-Boundary Sliding 384 14.4.2 Grain-Boundary Misorientation 386 14.4.3 Grain-Boundary Tortuosity and Precipitates 386 14.4.4 Grain Size 388 14.4.5 Factors Affecting Ductility-Dip Cracking 390 14.5 Ductility-Dip Cracking of Stainless Steels 390 Examples 392 References 394 Further Reading 396 Problems 396 Part III The Partially Melted Zone 399 15 Liquation in the Partially Melted Zone 401 15.1 Formation of the Partially Melted Zone 401 15.2 Liquation Mechanisms 403 15.2.1 Mechanism I: Alloy with Co > CSM 404 15.2.2 Mechanism II: Alloy with Co CSM and no AxBy or Eutectic 405 15.2.3 Mechanism III: Alloy with Co CSM and AxBy or Eutectic 405 15.2.4 Additional Mechanisms of Liquation 409 15.3 Directional Solidification of Liquated Material 411 15.4 Grain-Boundary Segregation 411 15.5 Loss of Strength and Ductility 413 15.6 Hydrogen Cracking 414 15.7 Effect of Heat Input 414 15.8 Effect of Arc Oscillation 415 Examples 416 References 417 Problems 418 16 Liquation Cracking 419 16.1 Liquation Cracking in Arc Welding 419 16.1.1 Crack Susceptibility Tests 421 16.1.1.1 Varestraint Testing 421 16.1.1.2 Circular-Patch Testing 422 16.1.1.3 Hot Ductility Testing 423 16.1.2 Mechanism of Liquation Cracking 423 16.1.3 Predicting Effect of Filler Metal on Crack Susceptibility 424 16.1.4 Factors Affecting Liquation Cracking 430 16.1.4.1 Filler Metal 430 16.1.4.2 Heat Source 430 16.1.4.3 Degree of Restraint 431 16.1.4.4 Base Metal 431 16.2 Liquation Cracking in Resistance Spot Welding 434 16.3 Liquation Cracking in Friction Stir Welding 434 16.4 Liquation Cracking in Dissimilar-Metal FSW 439 Examples 445 References 446 Problems 449 Part IV The Heat-Affected Zone 451 17 Introduction to Solid-State Transformations 453 17.1 Work-Hardened Materials 453 17.2 Heat-Treatable Al Alloys 455 17.3 Heat-Treatable Ni-Base Alloys 458 17.4 Steels 461 17.4.1 Fe-C Phase Diagram and CCT Diagrams 461 17.4.2 Carbon Steels 463 17.4.3 Dual-Phase Steels 470 17.5 Stainless Steels 471 17.5.1 Types of Stainless Steels 471 17.5.2 Sensitization of Unstabilized Grades 473 17.5.3 Sensitization of Stabilized Grades 473 17.5.4 sigma-Phase Embrittlement 475 Examples 475 References 475 Problems 477 18 Heat-Affected-Zone Degradation of Mechanical Properties 479 18.1 Grain Coarsening 479 18.2 Recrystallization and Grain Growth 480 18.3 Overaging in Al Alloys 483 18.3.1 Al-Cu-Mg (2000-Series) Alloys 483 18.3.1.1 Microstructure and Strength 483 18.3.1.2 Effect of Welding Parameters or Process 488 18.3.2 Al-Mg-Si (6000-Series) Alloys 489 18.3.2.1 Microstructure and Strength 489 18.3.2.2 Effect of Welding Processes and Parameters 491 18.3.3 Al-Zn-Mg (7000-Series) Alloys 492 18.4 Dissolution of Precipitates in Ni-Base Alloys 494 18.5 Martensite Tempering in Dual-Phase Steels 498 Examples 500 References 500 Further Reading 502 Problems 502 19 Heat-Affected-Zone Cracking 505 19.1 Hydrogen Cracking in Steels 505 19.1.1 Cause 505 19.1.2 Appearance 506 19.1.3 Susceptibility Tests 507 19.1.4 Remedies 508 19.1.4.1 Preheating 508 19.1.4.2 Postweld Heating 509 19.1.4.3 Bead Tempering 509 19.1.4.4 Use of Low-H Processes and Consumables 509 19.1.4.5 Use of Lower-Strength Filler Metals 509 19.1.4.6 Use of Austenitic-Stainless-Steel Filler Metals 510 19.2 Stress-Relief Cracking in Steels 510 19.3 Lamellar Tearing in Steels 514 19.4 Type-IV Cracking in Grade 91 Steel 517 19.5 Strain-Age Cracking in Ni-Base Alloys 519 Examples 524 References 524 Further Reading 527 Problems 528 20 Heat-Affected-Zone Corrosion 529 20.1 Weld Decay of Stainless Steels 529 20.2 Weld Decay of Ni-Base Alloys 533 20.3 Knife-Line Attack of Stainless Steels 534 20.4 Sensitization of Ferritic Stainless-Steel Welds 536 20.5 Stress Corrosion Cracking of Austenitic Stainless Steels 537 20.6 Corrosion Fatigue of Al Welds 538 Examples 538 References 539 Further Reading 540 Problems 540 Part V Special Topics 541 21 Additive Manufacturing 543 21.1 Heat and Fluid Flow 543 21.2 Residual Stress and Distortion 545 21.3 Lack of Fusion and Gas Porosity 547 21.4 Grain Structure 550 21.5 Solidification Cracking 550 21.6 Liquation Cracking 553 21.7 Graded Transition Joints 558 21.8 Further Discussions 560 Examples 560 References 561 Further Reading 563 Problems 564 22 Dissimilar-Metal Joining 565 22.1 Introduction 565 22.2 Arc and Laser Joining 565 22.2.1 Al-to-Steel Arc Brazing 566 22.2.1.1 Effect of Lap Joint Gap 569 22.2.1.2 Effect of Heat Input 575 22.2.1.3 Effect of Ultrasonic Vibration 577 22.2.1.4 Effect of Preheating 578 22.2.1.5 Effect of Postweld Heat Treatment 578 22.2.1.6 Butt Joint 579 22.2.2 Al-to-Steel Laser Brazing 579 22.2.3 Al-to-Steel Laser Welding 580 22.2.4 Mg-to-Steel Brazing 582 22.2.5 Al-to-Mg Welding 583 22.3 Resistance Spot Welding 583 22.3.1 Al-to-Steel RSW 583 22.3.2 Mg-to-Steel RSW 586 22.3.3 Al-to-Mg RSW 588 22.4 Friction Stir Welding 589 22.4.1 Al-to-Cu FSSW 589 22.4.2 FSSW of Al to Galvanized Steel 592 22.4.3 Effect of Coating on Al-to-Steel FSSW 597 22.5 Other Solid-State Welding Processes 603 22.5.1 Friction Welding 603 22.5.2 Explosion Welding 606 22.5.3 Magnetic Pulse Welding 607 Examples 608 References 609 Further Reading 612 Problems 612 23 Welding of Magnesium Alloys 613 23.1 Spatter 613 23.1.1 Spatter in Mg GMAW 613 23.1.2 Mechanism of Spatter 614 23.1.3 Elimination of Spatter 614 23.1.4 Irregular Weld Shape and Its Elimination 617 23.2 Porosity 618 23.2.1 Porosity in Mg GMAW 618 23.2.2 Mechanisms of Porosity Formation and Elimination 620 23.2.3 Comparing Porosity in Al and Mg Welds 621 23.3 Internal Oxide Films 622 23.3.1 Mechanism 622 23.3.2 Remedies 624 23.4 High Crowns 625 23.4.1 Mechanism of High-Crown Formation 625 23.4.2 Reducing Crown Height 627 23.5 Grain Refining 628 23.5.1 Ultrasonic Weld Pool Stirring 628 23.5.2 Arc Pulsation 629 23.5.3 Arc Oscillation 629 23.6 Solidification Cracking 629 23.7 Liquation Cracking 629 23.7.1 A Simple Test for Crack Susceptibility 631 23.7.2 Effect of Filler Metals 634 23.7.3 Effect of Grain Size 636 23.8 Heat-Affected Zone Weakening 636 Examples 638 References 640 Further Reading 641 Problems 641 24 Welding of High-Entropy Alloys and Metal-Matrix Nanocomposites 643 24.1 High-Entropy Alloys 643 24.1.1 Solidification Microstructure 643 24.1.2 Weldability 644 24.2 Metal-Matrix Nanocomposites 646 24.2.1 Nanoparticles Increasing Weld Size 646 24.2.2 Nanoparticles Refining Microstructure 648 24.2.3 Nanoparticles Reducing Cracking During Solidification 650 24.2.4 Nanoparticles Allowing Friction Stir Welding 651 Examples 653 References 654 Further Reading 655 Problems 655 Appendix A: Analytical Equations for Susceptibility to Solidification Cracking 657 Index 659