Since the publication of the first edition of this book in 1987, there has been much new progress made in welding metallurgy. The purpose for the second edition is to update and improve the first edition. Examples of improvements include (1) much sharper photomicrographs and line drawings; (2) integration of the phase diagram, thermal cycles, and kinetics with the microstructure to explain microstructural development and defect formation in welds; and (3) additional exercise problems. Specific revisions are as follows.
In Chapter 1 the illustrations for all welding processes have been redrawn to show both the overall process and the welding area. In Chapter 2 the heat source efficiency has been updated and the melting efficiency added. Chapter 3 has been revised extensively, with the dissolution of atomic nitrogen, oxygen, and hydrogen in the molten metal considered and electrochemical reactions added.
Chapter 4 has also been revised extensively, with the arc added, and with flow visualization, arc plasma dragging, and turbulence included in weld pool convection. Shot peening is added to Chapter 5. Chapter 6 has been revised extensively, with solute redistribution and microsegregation expanded and the solidification path added. Chapter 7 now includes nonepitaxial growth at the fusion boundary and formation of nondendritic equiaxed grains. In Chapter 8 solidification modes are explained with more illustrations.
Chapter 9 has been expanded significantly to add ferrite formation mechanisms, new ferrite prediction methods, the effect of cooling rate, and factors affecting the austenite–ferrite transformation. Chapter 10 now includes the effect of both solid-state diffusion and dendrite tip undercooling on microsegregation. Chapter 11 has been revised extensively to include the effect of eutectic reactions, liquid distribution, and ductility of the solidifying metal on solidification cracking and the calculation of fraction of liquid in multicomponent alloys.
Chapter 12 has been rewritten completely to include six different liquation mechanisms in the partially melted zone (PMZ), the direction and modes of grain boundary (GB) solidification, and the resultant GB segregation. Chapter 13 has been revised extensively to include the mechanism of PMZ cracking and the effect of the weld-metal composition on cracking. Chapter 15 now includes the heat-affected zone (HAZ) in aluminum– lithium–copper welds and friction stir welds and Chapter 16 the HAZ of Inconel 718.
Chapter 17 now includes the effect of multiple-pass welding on reheat cracking and Chapter 18 the grain boundary chromium depletion in a sensitized austenitic stainless steel. The author thanks the National Science Foundation and NASA for supporting his welding research, from which this book draws frequently. He also thanks the American Welding Society and ASM International for permissions to use numerous copyrighted materials.
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