This article discusses three distinct mechanisms of bonding for solid-state (forge) welding processes, namely, contaminant displacement/interatomic bonding, dissociation of retained oxides, and decomposition of the interfacial structure. It explains the processes that can be characterized as having two stages: heating and forging. The article also includes a table that illustrates weld strengths as a function of annealing temperature for a range of materials.

Thermodynamic descriptions have become available for a large number of alloy systems and allow the calculation of the phase diagrams of multicomponent alloys. This article begins with a discussion on three laws of thermodynamics: the Law of Conservation of Energy, the Second Law of Thermodynamics, and the Third Law of Thermodynamics. It informs that for transformations that occur at a constant temperature and pressure, the relative stability of the system is determined by its Gibbs free energy. The article describes the Gibbs free energy of a single-component unary system and the Gibbs free energy of a binary solution. It schematically illustrates the structure of a binary solid solution with interatomic bonds and shows how the equilibrium state of an alloy can be obtained from the free-energy curves at a given temperature. The article concludes with information on the construction of eutectic and binary phase diagrams from Gibbs free-energy curves.

This article summarizes a physical model of an interface structure and shows how the model helps in optimizing atomistic modeling studies. It presents the orientation relationship of the interface structure to define the mutual crystallographic position of adjacent crystals. The article describes the model-informed atomistic modeling of the interface structures for interpolating the results of atomistic modeling to predict the properties of interfaces. Theories to predict low-energy orientation relationships are described. The article discusses the use of the localization parameter, such as shear modulus, bonding energy, and transformations, for prediction of interface structures. It provides information on the application of the atomistic modeling of interface structure to predict interface reaction mechanisms.

The diffraction pattern of any material contains structural and chemical property information that can be extracted using radial distribution function analysis. This article provides an introduction to the technique and presents several examples highlighting various ways in which it can be used. It begins with a discussion on the principles of diffraction and scattering and the effectiveness of x-ray, neutron, and electron energy sources for different types of measurements. It provides information on data collection and reduction and explains how to create atomic distribution plots from intensity and scattering angle data. The article also presents application parameters for defining short distances and background intensity and describes a procedure for generating pair distribution functions.

This article describes a method to predict mechanical properties of cast iron materials and illustrates how to use the predictions in computer-aided tools for the analysis of castings subjected to load. It outlines some ways to predict the hardness and elastic modulus of cast iron without going into dislocation theory. The article discusses modeling of hardness in cast iron based on a regular solution equation in which the properties of each phase depend on chemical composition and coarseness. It describes the evaluation of material parameters from the tensile stress-strain curve. The article concludes with an illustration of a finite-element method (FEM) model containing heterogeneous mechanical properties using local material definitions.

Properties of an engineering material have a characteristic range of values that are conveniently displayed on materials selection charts. This article describes the plotting of data on these charts. It discusses the features of various types of material property charts, namely, modulus-density, strength-density, fracture toughness-density, modulus-strength, specific stiffness-specific strength, fracture toughness-modulus, fracture toughness-strength, loss coefficient-modulus, thermal conductivity-thermal diffusivity, thermal expansion-thermal conductivity, thermal expansion-modulus, and normalized strength-thermal expansion charts. The article examines the use of material property charts in presenting information in a compact and easily accessible manner.

The primary goal of single-crystal x-ray diffraction is to determine crystal structure and the arrangement of atoms in a unit cell. This article discusses the diffraction of light through line gratings and explains the significance of crystal symmetry, space groups, and diffraction intensities. It also addresses phase and crystallographic analysis along with related challenges, and presents several application examples highlighting various experimental techniques.

Joining is key to the manufacture of large or complex devices or assemblies; construction of large and complex structures; and repair of parts, assemblies, or structures in service. This article describes the three forces for joining: physical, chemical, and mechanical. It provides an overview of the joining processes, namely, mechanical fastening, integral attachment, adhesive bonding, welding, brazing, and soldering. The article concludes with information on the various aspects of joint design and location that determine the selection of a suitable joining method.

This article presents an overview of the science and engineering of materials along with suitable definitions, descriptions, and examples for better understanding for corrosionists with limited field knowledge. It begins with a detailed description of various categories of engineering materials and moves into the discussion of physical properties of materials, such as the phases, strength, conductivity, and wear. The article describes the methods used in the fabrication of engineering materials and summarizes the materials and their properties in a tabular form. The article concludes with information on material design, materials applications, and materials failure analysis.

This article describes measurement techniques for the three basic types of adhesion: fundamental adhesion, thermodynamic adhesion, and practical adhesion. It discusses common measurement methods for each type of adhesion with the main focus on practical adhesion testing of coatings and thin films. The article provides an insight into the mechanisms of environmentally induced interfacial degradation by discussing the fundamental aspects of adhesion between two dissimilar materials. It examines the use of adhesion tests in the evaluation of stress-corrosion cracking within bimaterial interfaces. Testing techniques for <i>in situ</i> environmental testing of thin-film adhesion are also reviewed.

Cold pressure welding can be accomplished by deforming in a lap or butt configuration, drawing, extrusion, and rolling. This article provides a discussion on cold pressure lap welding, cold pressure butt welding and cold pressure welding in drawing process with illustrations. It provides information on the combinations of metals that can be successfully cold welded.

This article first describes surface forces, and the methods of measuring them, followed by a discussion on adhesion. It discusses the instrumental requirements and techniques, including Atomic Force Microscopy (AFM), used for the measurement of surface forces. Measurements of surface roughness, with AFM, can provide a precise picture of surface roughness and can be used as input for contact mechanics computer models. The article also describes microscale adhesion and adhesion measurement methods using microelectromechanical systems technologies. It reviews certain considerations used for the measurement of adhesion, such as fundamental adhesion measurements, history dependence and sample preparation, and practical adhesion measurements. The article describes various arrangements that can be employed in adhesion tests.

This article discusses three typical repair types for composite structures: temporary repairs, adhesively bonded repairs, and bolted repairs. It contains a table that lists general design requirements and considerations for the repair of composite structures. The article describes ten steps for an engineering repair approach to effectively restore structural integrity to damaged composite components. Management, validation and certification of repairs are also discussed. The article presents the design guidelines for analyzing the damage and possible strategies for making a repair. It reviews three repair schemes used in repair design analysis, namely, core replacement, adhesively bonded patch, and mechanically fastened patch. The article also emphasizes the various pitfalls and problems in repair design for composite structures.

This article discusses different types of joining processes, including welding, brazing, soldering, mechanical fastening, and adhesive bonding. It examines two broad classes of welding: fusion welding and solid-state welding. The article discusses the process selection considerations for welding, brazing, and soldering. It also describes joint design considerations such as selection of weld joints and welds.

This article reviews quantifying adhesion, bonding, and interfacial characterization and strength in a solid-state welding process. It discusses metal-metal configurations and provides information on experimental work carried out in measuring the mechanical properties of interfaces based on theoretical analysis. A discussion on the properties affecting adhesion is also provided.

Thermal spray coating involves certain precoating operations, such as cleaning, surface preparation, and masking, that are critical to the overall quality of the coating system. In addition to these, certain other elements are considered prior to the coating, namely, customer requirements, coating function, part geometry, substrate metallurgy, structure, and thermal history. This article provides a detailed account of the various processes of surface preparation, namely, cleaning, roughening, dry abrasive grit blasting, and machining and macro roughening processes. It outlines the masking and fixturing techniques and stripping of coatings.

This article discusses the most fundamental building-block level, atomic level, molecular considerations, intermolecular structures, and supermolecular issues. It contains a table that shows the structures and lists the properties of selected commodity and engineering plastics. The article describes the effects of structure on thermal and mechanical properties. It reviews the chemical, optical, and electrical properties of engineering plastics and commodity plastics. An explanation of important physical properties, many of which are unique to polymers, is also included. The factors that must be considered when processing engineering thermoplastics are discussed. These include melt viscosity and melt strength; crystallization; orientation, die swell, shrinkage, and molded-in stress; polymer degradation; and polymer blends.

This article explains how to design a joint or conduct a joining process so that components can be produced most efficiently and without defects. The joining processes include mechanical fastening, adhesive bonding, welding, brazing, and soldering. The article discusses the selection and application of good design practices based on the understanding of process-related manufacturing aspects such as accessibility, quality, productivity, and overall manufacturing cost. It provides several examples of selected parts and joining processes to illustrate the advantages of a specific design practice in improving manufacturability.

This article begins with a description of the advantages and disadvantages of thermal spraying. It provides a discussion on the importance of substrate processing prior to coating and the role of undercutting in repair. The article reviews the steps for substrate preparation, namely, cleaning, roughening, masking, and preheating. Information on the equipment and process variables of dry abrasive grit blasting are also provided. The article describes the roles of spray stream and the spray pattern for all thermal spray processes. It discusses the defects arising from poor temperature control and from the variables influencing the manipulation of the spray torch. The article concludes with helpful information on calculating the process efficiency of thermal spraying.