Coextrusion is defined as the simultaneous extrusion of two or more metals to form an integral product that can be carried out using conventional extrusion or drawing equipment at a temperature appropriate to the metal system being formed. This article discusses the applications, billet configurations, and metal flow modes of coextrusion. It presents the analytical studies of coextrusion: deformation energy methods, lower-bound (slab) analyses, upper-bound analyses, and finite-element analyses. These studies are used to identify the regime of material properties and process variables for which sound extrusions can be obtained. The article concludes with a discussion on the state-of-the-art of coextrusion that assists in developing process models, which accurately describe both the macroscopic and microscopic aspects of a process.

This article begins with a description of indirect and direct semisolid metalworking processes. It then provides information on alloy compositions of common aluminum semisolid metalworking alloys and primary die-cast magnesium alloys in a tabular form. The article describes the macroscopic examination of defects, which occur in semisolid metalworking with illustrations. It discusses the macroscopic examination of gating systems and semisolid feedstocks. The article also provides information on feedstock microstructures, direct semisolid metalworking component microstructures, and indirect semisolid metalworking component microstructures of series 300 aluminum casting alloys and magnesium die-casting alloys.

This article focuses on the various technology drivers for finishing methods, namely, tolerance, consistency, surface quality, and productivity. Every finishing method may be viewed as a manufacturing system consisting of four input categories: machine tool, processing tool, work material, and operational factors. The article provides a classification of finishing as a surface generation process and addresses the characteristics of the generated surfaces and the methods used to measure them. It describes the thermomechanical interactions occurring between the processing tool and the work material in the presence of machine tool and operational factors.

Microstructure and crystallographic texture are the key material features used in the continuous endeavor to relate the processing of a metal with its final properties. This article emphasizes several aspects of deformation microstructures, namely, microstructural evolution, dislocation boundaries, and macroscopic properties. It discusses three different microstructural types: cell blocks, TL blocks, and equiaxed subgrains. The article also emphasizes the behavior of metals and single-phase alloys processed under plastic deformation (dislocation slip) conditions. It provides information on the microstructural parameters, measurement techniques, and microstructural relationships, which assist in predicting the mechanical properties and recrystallization behavior of materials. The article concludes with an analysis of the general relationship between the microstructural parameters and properties.

Examination of a damaged component involves a chain of activities that, first and foremost, requires good observation and documentation. Following receipt and documentation, the features of damage can be recorded and their cause(s) investigated, as this article briefly describes, for typical types of damage experienced for metallic components. This article discusses the processes involved in visual or macroscopic examination of damaged material; the interpretation of fracture features, corrosion, and wear damage features; and the analysis of base material composition. It covers the processes involved in the selection of metallurgical samples, the preparation and examination of metallographic specimens in failure analysis, and the analysis and interpretation of microstructures. Examination and evaluation of polymers and ceramic materials in failure analysis are also briefly discussed.

Particle image analysis of metal powders can be easily performed with optical macroscopes and microscopes. This article provides examples of the particle image analysis on powders used in the powder metallurgy industry.

The cracking process occurs slowly over the service life from various crack growth mechanisms such as fatigue, stress-corrosion cracking, creep, and hydrogen-induced cracking. Each of these mechanisms has certain characteristic features that are used in failure analysis to determine the cause of cracking or crack growth. This article discusses the macroscopic and microscopic basis of understanding and modeling fracture resistance of metals. It describes the four major types of failure modes in engineering alloys, namely, dimpled rupture, ductile striation formation, cleavage or quasicleavage, and intergranular failure. Certain fundamental characteristics of fracture observed in precipitation-hardening alloys, ferrous alloys, titanium alloys are also discussed.

The metallographic specimen preparation process for microstructural investigations of cast iron specimens usually consists of five stages: sampling, cold or hot mounting, grinding, polishing, and etching with a suitable etchant to reveal the microstructure. This article describes the general preparation of metallographic specimens and the methods of macroscopic and microscopic examination. Usually, gray-scale (black-and-white) metallography is sufficient for microstructural analysis of cast irons. The article discusses the use of color metallography of gray irons and ductile irons. It also presents application examples of color metallography.

This article discusses the numerical simulation of the forming of aluminum alloy sheet metals. The macroscopic and microscopic aspects of the plastic behavior of aluminum alloys are reviewed. The article presents constitutive equations suitable for the description of aluminum alloy sheets. It explains testing procedures and analysis methods that are used to measure the relevant data needed to identify the material coefficients. The article describes the various formulations of finite element methods used in sheet metal forming process simulations. Stress-integration procedures for both continuum and crystal-plasticity mechanics are also discussed. The article also provides various examples that illustrate the simulation of aluminum sheet forming.

This article commences with a discussion on the characteristics of stress-corrosion cracking (SCC) and describes crack initiation and propagation during SCC. It reviews the various mechanisms of SCC and addresses electrochemical and stress-sorption theories. The article explains the SCC, which occurs due to welding, metalworking process, and stress concentration, including options for investigation and corrective measures. It describes the sources of stresses in service and the effect of composition and metal structure on the susceptibility of SCC. The article provides information on specific ions and substances, service environments, and preservice environments responsible for SCC. It details the analysis of SCC failures, which include on-site examination, sampling, observation of fracture surface characteristics, macroscopic examination, microscopic examination, chemical analysis, metallographic analysis, and simulated-service tests. It provides case studies for the analysis of SCC service failures and their occurrence in steels, stainless steels, and commercial alloys of aluminum, copper, magnesium, and titanium.

This article commences with a summary of fatigue processes and mechanisms. It focuses on fractography of fatigue. Characteristic fatigue fracture features that can be discerned visually or under low magnification are described. Typical microscopic features observed on structural metals are presented subsequently, followed by a brief discussion of fatigue in nonmetals. The article reviews the various macroscopic and microscopic features to characterize the history and growth rate of fatigue in metals. It concludes with a description of fatigue of polymers and composites.

In cast iron, residual stresses normally arise due to hindered thermal contraction, meaning that they are associated with the presence of constraints that prevent the natural, free volumetric variation of the material upon solid-state cooling. This article explains their mechanism of formation by introducing the scalar relation, known as the additive strain decomposition. The main factors influencing casting deformation are volume changes during solidification and cooling, phase transformations, alloy composition, thermal gradients, casting geometry, and mold stability. The article reviews the dimensional stability in cast iron and discusses macroscopic and microscopic stresses in cast iron.

Fatigue failure of engineering components and structures results from progressive fracture caused by cyclic or fluctuating loads. Fatigue is an important potential cause of mechanical failure, because most engineering components or structures are or can be subjected to cyclic loads during their lifetime. This article focuses on fractography of fatigue. It provides an abbreviated summary of fatigue processes and mechanisms: fatigue crack initiation, fatigue crack propagation, and final fracture,. Characteristic fatigue fracture features that can be discerned visually or under low magnification are then described. Typical microscopic features observed on structural metals are presented subsequently, followed by a brief discussion on fatigue in polymers and polymer-matrix composites.

This article provides an overview of the origin of metallography. It presents information on how to select a section from a specimen and prepare it for macroscopic analysis. The article describes the macroscopic analysis of steel fracture surfaces with emphasis on ductile, brittle, and fatigue fracture with illustrations. It discusses microanalysis with a focus on the method of light microscopy and includes information of scanning electron microscope in fractography. The article also explains the characteristics of solidification, transformation, deformation structures, and discontinuities that are present in a microstructure. It concludes with information on image analysis.

This article discusses a set of experimental and computational studies aimed at understanding the effect of various processing parameters on the extent of burr and other defect formation during sheet edge-shearing and slitting processes. It describes the development of experimentally validated finite-element models for analyzing the classes of shearing processes. The article also discusses the use of microstructural characterization with stereology to render three-dimensional volumetric parameters. It concludes with information on the numerical simulation of an edge-shearing process, along with sensitivity studies with respect to process and tool parameters.