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, explaining some significant ones, such as point defects, line defects, stacking faults, and twins.

This article, to develop an understanding of the underlying mechanisms governing deformation at elevated temperatures, discusses the phenomenological effects resulting from temperature-induced thermodynamic and kinetic changes. It describes the deformation behavior of engineering materials using expressions known as constitutive equations that relate the dependence of stress, temperature, and microstructure on deformation. The article reviews the characteristics of creep deformation and mechanisms of creep, such as power-law creep, low temperature creep, power-law breakdown, diffusional creep, twinning during creep deformation, and deformation mechanism maps. It discusses the creep-strengthening mechanisms for most structural engineering components. The article provides a description of the microstructural modeling of creep in engineering alloys.

Plastic deformation can occur in metals from various mechanisms, such as slip, twinning, diffusion creep, grain-boundary sliding, grain rotation, and deformation-induced phase transformations. This article emphasizes on the mechanism of slip and twinning under cold working conditions. It discusses the factors on which the structures developed during plastic deformation depend. These factors include crystal structure, amount of deformation, composition, deformation mode, and deformation temperature and rate. The article illustrates the microstructural features that appear after substantial deformation when revealed through metallographic investigation.

This article provides a description of the microscale models and mechanisms for deformation and fracture. Macroscale and microscale appearances of ductile and brittle fracture are discussed for various specimen geometries and loading conditions. The article reviews the general geometric factors and materials aspects that influence the stress-strain behavior and fracture of ductile metals. It highlights fractures arising from manufacturing imperfections and stress raisers. The article presents a root cause failure analysis case history to illustrate some of the fractography concepts.