This article defines crystallographic terms and concepts, including crystal structure, unit cell, structure symbols, lattice, space-group notation, and atom position. It schematically illustrates the atom positions, prototypes, structure symbols, space-group notations, and lattice parameters for some of the simple metallic crystals. A table that lists the crystal structures of various metal elements is presented. The crystal structures are described by the Pearson symbols for crystal system, space lattice, total number of atoms per unit cell, and prototype structure. The article tabulates the assorted structure types of metallurgical interest arranged according to Pearson symbol. It also provides information on crystal defects in all real crystals, explaining some significant ones, such as point defects, line defects, stacking faults, and twins.

This article focuses on laboratory atomic force microscopes (AFMs) used in ambient air and liquid environments. It begins with a discussion on the origin of AFM and development trends occurring in AFM. This is followed by a section on the general principles of AFM and a comprehensive list of AFM scanning modes. There is a brief description of how each mode works and what types of applications can be made with each mode. Some of the processes involved in preparation of samples (bulk materials and those placed on a substrate) scanned in an AFM are then presented. The article provides information on the factors applicable to the accuracy and precision of AFM measurements. It ends by discussing the applications for AFMs in the fields of science, technology, and engineering.

Heat treating furnaces require different control systems and integration for achieving optimum technical results and enabling safe operation. This article focuses on atmosphere furnaces, with some coverage on controls for vacuum furnaces. Heat treating operations require reliable monitoring and control of motion and position of various mechanical components with the help of mechanical limit switches, proximity sensors, and distance- and position-measuring devices. Using inputs from both flow meters and sensors, such as thermocouples and oxygen sensors, flow measurement control systems must be able to adjust the flow of gases for process optimization. The operator interface of a furnace-control system displays critical information such as the furnace temperature, atmosphere status, alarms, electronic chart recorders, recipe, and maintenance. A supervisory control and data-acquisition (SCADA) system is used to monitor, collect, and store data from multiple pieces of equipment.

Chemical elements are the basic chemical substances; that is, they cannot be decomposed by chemical change or made by chemical union. These elements follow a periodic pattern related to the atomic mass of each that allows them to be arranged into a convenient table. This article includes a series of tables: the first gives the names and symbols of the elements in alphabetical order and the second lists the elements in order by atomic number and give the atomic weight for each. The periodic table of the elements also is included in the article.

Spray casting, also known as spray forming, is a niche casting process for the manufacture of preforms. This article lists commercial examples of alloys manufactured by spray casting and provides sequential steps of the spray casting process. Gas atomization is a chaotic, stochastic process that always produces a wide range of droplet diameters. The article schematically illustrates typical log-normal droplet diameter probability density distribution on a mass or volume basis obtained by gas atomization. It also illustrates the changes in solid fraction during the spray casting process as a function of axial distance from the point of droplet atomization. The article concludes with a section on occurrence of macrosegregation and coarsening in spray cast preforms.

Crystal structure is the arrangement of atoms or molecules in the solid state that involves consideration of defects, or abnormalities, in idealized atomic/molecular arrangements. The three-dimensional aggregation of unit cells in the crystal forms a space lattice or Bravais lattice. This article provides a brief review of the terms and basic concepts associated with crystal structures. It also discusses some of the significant defects obstructing plastic flow in real crystals, namely point defects, line defects, stacking faults, twins, and cold work. Several tables in the article provide information on the crystal structures and lattice parameters of allotropes of metallic elements.

This article provides a clear but nonexhaustive description of the general principle of atomic emission, with a particular focus on instrumentation, and summarizes the main characteristics of the inductively coupled plasma optical emission spectrometer technique. Basic atomic theory as well as the instrument characteristics and their influence on the instrument performances are presented. The advantages, drawbacks, and developments of this technique are discussed, and, finally, alternative techniques and examples of applications are provided.

Sputtering is a nonthermal vaporization process in which the surface atoms are physically ejected from a surface by momentum transfer from an energetic bombarding species of atomic/molecular size. It uses a glow discharge or an ion beam to generate a flux of ions incident on the target surface. This article provides an overview of the advantages and limitations of sputter deposition. It focuses on the most common sputtering techniques, namely, diode sputtering, radio-frequency sputtering, triode sputtering, magnetron sputtering, and unbalanced magnetron sputtering. The article discusses the fundamentals of plasma formation and the interactions on the target surface. A comparison of reactive and nonreactive sputtering is also provided. The article concludes with a discussion on the several methods of process control and the applications of sputtered films.

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 crystal structure of a material is an important aspect of corrosion and oxidation processes. This article provides a general introduction to the crystal structure of materials, providing information on the crystal systems, lattice dimensions, nomenclature, and solid-solution mechanisms used to characterize structures. It illustrates the unit cells and ion positions for some simple metal crystals, arranged alphabetically according to Pearson symbol. The space lattice and crystal system, space-group notation, and prototype for each crystal are also illustrated.

Alloy phase diagrams are useful for the development, fabrication, design and control of heat treatment procedures that will produce the required mechanical, physical, and chemical properties of new alloys. They are also useful in solving problems that arise in their performance in commercial applications, thus improving product predictability. This article describes different equilibrium phase diagrams (unary, binary, and ternary) and microstructures, description terms, and general principles of reading alloy phase diagrams. Further, the article discusses plotting schemes; areas in a phase diagram; and the position and shapes of the points, lines, surfaces, and intersections, which are controlled by thermodynamic principles and properties of all phases that comprise the system. It also illustrates the application of the stated principles with suitable phase diagrams.

Transmission electron microscopy (TEM) approach enables essentially simultaneous examination of microstructural features through imaging from lower magnifications to atomic resolution and the acquisition of chemical and crystallographic information from small regions of the thin specimen. This article discusses fundamentals of the technique, especially for solving materials problems. Background information is provided to help understand basic operations and principles, including instrumentation, the physics of signal generation and detection, image formation, electron diffraction, and spectrometry techniques with data analysis.

This article briefly discusses popular techniques for metals characterization. It begins with a description of the most common techniques for determining chemical composition of metals, namely X-ray fluorescence, optical emission spectroscopy, inductively coupled plasma optical emission spectroscopy, high-temperature combustion, and inert gas fusion. This is followed by a section on techniques for determining the atomic structure of crystals, namely X-ray diffraction, neutron diffraction, and electron diffraction. Types of electron microscopies most commonly used for microstructural analysis of metals, such as scanning electron microscopy, electron probe microanalysis, and transmission electron microscopy, are then reviewed. The article contains tables listing analytical methods used for characterization of metals and alloys and surface analysis techniques. It ends by discussing the objective of metallography.

This article provides an overview of chemistry and chemical interactions necessary to understand protective coatings. It includes information on elements, atoms, molecules, types of bonding, valence electrons, functional groups, polymer formation, and chemical bonding structures.

Ion-beam-assisted deposition (IBAD) refers to the process wherein evaporated atoms produced by physical vapor deposition are simultaneously struck by an independently generated flux of ions. This article discusses the energy utilization of this process. It describes the physical and chemical processes occurring at the film-vacuum interface during IBAD and dual-ion-beam sputtering with illustrations. The article also reviews the methods used for large-area, high-volume implementation of IBAD and the modes of film formation for IBAD. It contains a table that presents information on deposition and synthesis of inorganic compounds by IBAD and concludes with a discussion on the improved coating properties, advantages, limitations, and applications of IBAD.

This article describes the integration of thermodynamic modeling, mobility database, and phase-transformation crystallography into phase-field modeling and its combination with transformation texture modeling to predict phase equilibrium, phase transformation, microstructure evolution, and transformation texture development during heat treatment of multicomponent alpha/beta and beta titanium alloys. It includes quantitative description of Burgers orientation relationship and path, discussion of lattice correspondence between the alpha and beta phases, and determination of the total number of Burgers correspondence variants and orientation variants. The article also includes calculation of the transformation strain with contributions from defect structures developed at alpha/beta interfaces as a precipitates grow in size. In the CALculation of PHAse Diagram (CALPHAD) framework, the Gibbs free energies and atomic mobilities are established as functions of temperature, pressure, and composition and serve directly as key inputs of any microstructure modeling. The article presents examples of the integrated computation tool set in simulating microstructural evolution.

This article endeavors to familiarize the reader with a selection of different ionization designs and instrument components to provide knowledge for sorting the various analytical strategies in the field of solid analysis by mass spectrometry (MS). It begins with a description of the general principles of MS. This is followed by sections providing a basic understanding of instrumentation and discussing the operating requirements as well as practical considerations related to solid sample analysis by MS. Instrumentation discussed include the triple quadrupole mass spectrometer and the time-of-flight mass spectrometer. Inductively coupled plasma and thermal ionization MS provide atomic information, and direct analysis in real-time and matrix-assisted laser-desorption ionization MS are used to analyze molecular compositions. The article describes various factors pertinent to ionization methods, namely glow discharge mass spectrometry and secondary ion mass spectrometry. It concludes with a section on various examples of applications and interpretation of MS for various materials.

This article focuses on the modes of operation, physical basis, sample requirements, properties characterized, advantages, and limitations of common characterization methods that are used to evaluate the physical morphology and chemical properties of component surfaces for medical devices. The methods include light microscopy, scanning electron microscopy, atomic force microscopy, energy-dispersive x-ray spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy.

Diffusion is the process by which molecules, atoms, ions, point defects, or other particle types migrate from a region of higher concentration to one of lower concentration. This article focuses on the diffusivity data and modeling of lattice diffusion in solid-state materials, presenting their diffusion equations. It discusses different methods for evaluating the diffusivity of a material, including the measurement of diffusion coefficients, composition profiles, and layer growth widths. The article reviews the various types of direct and indirect diffusion experiments to extract tracer, intrinsic, and chemical diffusivities. It provides information on the applications of single-phase and multiphase diffusion.

Modeling of structure formation in casting of alloys involves several length scales, ranging from the atomic level to macroscopic scale. Intermediate length scales are used to define the microstructure of the growing phases and the grain structure. This article discusses the principles and applications of phase field method and cellular automaton method for modeling the direct evolution of structure at the intermediate length scales, where transport phenomena govern the spatial and temporal evolution of the structure that involves nucleation and growth.