This article reviews the classical models for the pseudo-steady-state temperature distribution of the thermal field around moving point and line sources. These include thick- and thin-plate models and the medium-thick-plate model. The analytical solutions to the differential heat flow equation under conditions applicable to fusion welding are provided. The article also provides an overview of the factors affecting heat flow in a real welding situation using the analytical modeling approach because this makes it possible to derive relatively simple equations that provide the required background for an understanding of the temperature-time pattern.

Rheology is defined as the study of the flow and deformation of matter. This article begins with an examination of flow behavior. It describes the geometries and methods employed for rheological testing of polymers in their molten state. It also discusses materials that are predominantly in the solid state and the methods employed for solids testing. Examples of unidirectional and dynamic oscillatory testing are provided for different mechanical behaviors.

Friction stir welding (FSW) involves plastic deformation at high strain rates and elevated temperatures with resultant microstructural changes leading to joining. This article provides a link between deformation and FSW process parameters and summarizes the results of experimental temperature measurements during FSW of various metals. It considers the physical explanation of the heat input during FSW and the possible methods of their estimation. The article presents the experimental results of two analytical models, supplemented by experimental/numerical flow models on material flow during FSW. The types of defects, processing parameters affecting the generation of these defects, and results of theoretical models and simulations to understand the formation and control of defects during FSW are discussed. The article concludes with information on the microstructure and its distribution produced during FSW.

Neutrons are a principal tool for the study of lattice vibrational spectra in materials. This article provides a detailed account of fission and spallation methods of neutron production that are capable of producing sufficient intensity to be useful in neutron scattering research. It describes the instrumentation required for, and advancements made in, neutron powder diffraction. The article further explains the texture and residual stress (macrostresses and microstresses) problems that are analyzed using the neutron powder diffraction method. It also outlines the single-crystal neutron diffraction technique, and provides examples of the applications of neutron diffraction.

The term isomorphous refers to metals that are completely miscible in each other in both the liquid and solid states. This article discusses the construction of simple phase diagrams by using the appropriate points obtained from time-temperature cooling curves. It describes the two methods to determine a phase diagram with equilibrated alloys: the static method and the dynamic method. The article illustrates the construction of phase boundaries according to the Gibbs' phase rule and describes the calculation methods that allow the prediction of the phases present, the chemical compositions of the phases present, and the amounts of phases present. Phase diagrams provide useful information for understanding alloy solidification. The article provides two simple models that can describe the limiting cases of solidification behavior.

This article describes the fundamental concepts of heat treatment simulation, including the physical events and their interactions, the heat treatment simulation software, and the commonly used simulation strategies. It summarizes material data needed for heat treatment simulations and discusses reliable data sources as well as experimental and computational methods for material data acquisition. The article provides information on the process data needed for accurate heat treatment simulation and the methods for their determination. Methods for validating heat treatment simulations are also discussed with an emphasis on the underlying philosophy for the selection and design of validation tests. The article also discusses the applications, capabilities, and limitations of heat treatment simulations via selected industrial case studies for a better understanding of the effect of microstructure, distortion, residual stress, and cracking in gears, shafts, and bearing rings.

This article discusses the microstructural processes that take place during plastic deformation and presents a plain phenomenological and general description of the cyclic stress-strain (CSS) response. It emphasizes the microstructural aspects of cyclic loading on single-phase materials tested in initially soft, dislocation-poor conditions resulting from a prior heat treatment. The article discusses deformation-induced phase transformations in austenitic stainless steels and commercial age-hardened aluminum alloys. It describes the interaction of dislocations and the strengthening of second-phase particles. The article also provides a description of the framework used to model the CSS response on a physical basis.

This article discusses the three different modeling approaches for grain structures formed during solidification of metallic alloys: direct modeling of dendritic structure, direct modeling of grain structure, and indirect modeling of grain structure. The main construction bases, the scale at which it applies, and the mathematical background are presented for each modeling approach. The article concludes with a table that presents a comparison of the main inputs/outputs, approximations, numerical methods, kinetics laws, and applications for the three approaches to modeling of dendritic grain solidification.

This article reviews the various aspects of the simulation of solidification microstructures and grain textures. It describes the grain structures and morphology of dendrites or eutectics that compose the internal structure of the grains. A particular emphasis has been put on the simulation of defects related to grain textures and microstructures. The article provides information on the application of the most important simulation approaches and the status of numerical simulation.

This article reviews the fundamental solidification concepts for understanding microstructural evolution in fusion welds. The common concepts, namely, nucleation, competitive grain growth, constitutional supercooling, solute redistribution, and rapid solidification, depend on the solidification parameters during welding, are discussed. The article discusses important solidification parameters, including temperature gradient, solid/liquid interface growth rate, and cooling rate.

Catastrophic failure best typifies the characteristic behavior of brittle solids in the presence of cracks or crack-like flaws under ambient conditions. This article provides a description of the concepts of fracture mechanics of brittle solids and focuses on the various testing methods developed to characterize the fracture behavior of brittle solids with examples. These include the fracture toughness test method and R-curve test method at ambient and elevated temperatures. The article also includes information on the evaluation of fracture-toughness test results and the behavior of R-curve.

This article describes the structure of coatings produced by plasma spraying, vapor deposition, and electrodeposition processes. The main techniques used for microstructure assessment are introduced. The relationship between the microstructure and property is also discussed. The experimental techniques for microstructural characterization include metallographic technique, X-ray diffraction, electron, microscopies, and porosimetry.

This article discusses tools that are used for the systematic optimization of engineering designs. It focuses on the practical application of optimization technology in a computer-aided engineering environment. The article presents numerical optimization algorithms and provides some background on how these algorithms make decisions when searching for the optimal design. It also provides information on structural optimization, topology optimization, materials processing optimization, multidisciplinary optimization, and global optimization.

The heat treatment of steel is based on the physical metallurgical principles that relate to its processing, properties, and structure. The microstructures that result from the heat treatment of steel are composed of one or more phases in which the atoms of iron, carbon, and other elements in steel are associated. This article describes the phases of heat treated steel, and provides information on effect of temperature change and the size of carbon atoms relative to that of iron atoms during the heat treatment.

This article reviews the topic of computational thermodynamics and introduces the calculation of solidification paths for casting alloys. It discusses the calculation of thermophysical properties and the fundamentals of the modeling of solidification processes. The article describes several commonly used microstructure simulation methods and presents ductile iron casting as an example to demonstrate the ability of microstructure simulation. The predictions for the major defects of casting, such as porosity, hot tearing, and macrosegregation, are highlighted. Finally, several industry applications are presented.

This article provides a discussion on the operation of various methods and sensors that have been used or have the potential to be used for on-line, real-time monitoring of localized corrosion. These include the electrochemical noise (ECN) method, nonelectrochemical methods, the galvanically coupled differential flow cell, galvanically coupled crevice cell, coupled multielectrode sensor, and electrochemical biofilm activity sensor.