This article provides an overview of exogenous and indigenous inclusions. It discusses the general concepts of phase diagrams, thermochemical relationships, and reaction rates, along with their practical significance. The article describes the most common techniques for controlling the occurrence of inclusions in any cast metal. The article provides a discussion on the inclusions in ferrous and nonferrous alloys. The ferrous and nonferrous alloys include steels, cast irons, aluminum alloys, copper alloys, and magnesium alloys.

This article illustrates equilibrium phase diagram for the aluminum-silicon system showing metastable extensions of the liquidus and solidus lines. It describes the classification and microstructure of the aluminum-silicon eutectic. The article presents the theories of solidification and chemical modification of the aluminum-silicon eutectic.

This article begins with a schematic illustration of a eutectic system in which the two components of the system have the same crystal structure. Eutectic systems form when alloying additions cause a lowering of the liquidus lines from both melting points of the pure elements. The article describes the aluminum-silicon eutectic system and the lead-tin eutectic system. It discusses eutectic morphologies in terms of lamellar and fibrous eutectics, regular and irregular eutectics, and the interpretation of eutectic microstructures. The article examines the solidification of a binary alloy of exactly eutectic composition. It concludes with a discussion on terminal solid solutions.

This article presents the binary eutectic phase diagram to understand the various structures that evolve in a binary eutectic system during solidification. It describes the various classifications and solidification principles of the eutectic structures. Formation of halos in eutectic microstructures of most alloy systems is also discussed.

This article discusses the two extremes of solute redistribution that results in microsegregation. The solute redistribution includes equilibrium solidification, nonequilibrium Gulliver-Scheil solidification, and nonequilibrium solidification with back diffusion. The measurement and kinetics of microsegregation are discussed for the binary isomorphous systems: titanium-molybdenum; binary eutectic systems: aluminum-copper and aluminum-silicon; binary peritectic systems: copper-zinc; multicomponent eutectic systems: Al-Si-Cu-Mg; and for systems with both eutectic and peritectic reactions: Fe-C-Cr and nickel-base superalloy.

Similar to the eutectic group of invariant transformations is a group of peritectic reactions, in which a liquid and solid phase decomposes into a solid phase on cooling through the peritectic isotherm. This article describes the equilibrium freezing and nonequilibrium freezing of peritectic alloys. It informs that peritectic reactions or transformations are very common in the solidification of metals. The article discusses the formation of peritectic structures that can occur by three mechanisms: peritectic reaction, peritectic transformation, and direct precipitation of beta from the melt. It provides a discussion on the peritectic structures in iron-base alloys and concludes with information on multicomponent systems.

This article focuses on aspects important for the commercial production of castings. It discusses the modification process in hypoeutectic and eutectic alloys that differ only in the relative volume fraction of primary aluminum and aluminum-silicon eutectic. The article explains how modification changes porosity formation in a casting. It describes the mechanisms responsible for silicon modification, as well as the modifications and changes in eutectic nucleation and eutectic grain structure. The article reviews the usage of strontium during process steps in foundry practices. The growth of silicon eutectic is described to explain effects ancillary to silicon modification. The article also discusses the effects of elements, such as phosphorus, antimony, bismuth, magnesium, boron, and calcium, on the silicon structure.

This article reviews the solubilities of the common gases present in ferrous metals, such as cast irons, and nonferrous metals, such as aluminum, copper, magnesium, and their alloys. The kinetics of the relevant reactions, reactions during solidification, and possible methods of control or removal of the dissolved gases are discussed. The most common method for removing hydrogen from aluminum, copper, and magnesium is inert gas flushing. The article concludes with a discussion on overcoming gas porosity in ferrous and nonferrous metals.

This article describes the allotropic modification and atmospheric corrosion of pure tin. Corrosion of pure tin due to oxidation reaction, and reaction with the other gases, water, acids, bases, and other liquid media, is discussed. The article provides information on corrosion behavior on soft solders, pewter, bearing alloys, tin-copper alloys, and tin-silver alloys. It reviews the influence of corrosion on immersion tin coating, tin-cadmium alloy coatings, tin-cobalt coatings, tin-copper coatings, tin-lead coatings, tin-nickel coatings, and tin-zinc coatings. The general properties and corrosion resistance of tinplate are summarized. The article also describes the methods of corrosion testing of coatings; these include an analysis of coating thickness measurements, porosity and rust resistance testing, solderability test, and specific special tests.

Cast iron, which usually refers to an in situ composite of stable eutectic graphite in a steel matrix, includes the major classifications of gray iron, ductile iron, compacted graphite iron, malleable iron, and white iron. This article discusses melting, pouring, desulfurization, inoculation, alloying, and melt treatment of these major ferrous alloys as well as carbon and alloy steels. It explains the principles of solidification by describing the iron-carbon phase diagram, and provides a pictorial presentation of the basic microstructures and processing steps for cast irons.

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 begins with a discussion on the effects of alloying and impurity elements on the properties of aluminum cast alloys and their chemical compositions. It describes various means of structural control, namely, chemistry control, control of element ratios based on the stoichiometry of intermetallic phases, and control of solidification conditions. The article discusses the modification and grain refinement of aluminum-silicon alloys by the use of modifiers and refiners to influence eutectic and hypereutectic structures in aluminum-silicon alloys. It provides information on the foundry alloys for specific casting applications. The article concludes with a discussion on the heat treatment practices and properties of aluminum casting alloys.

Monotectic alloys can be classified based on the difference between the critical temperature and the monotectic temperature. This article begins with a schematic illustration of monotectic reaction in copper-lead system. It discusses the solidification structures of monotectics and illustrates the monotectic solidification for low-dome alloys. The forming mechanism of the banded structure of copper-lead alloy in upward directional solidification is also described.

This article describes the three solidification mechanisms of peritectic structures, namely, peritectic reaction, peritectic transformation, and direct precipitation. It discusses the theoretical analysis, which shows that the rate of the peritectic transformation is influenced by the diffusion rate and the extension of the beta-phase region in the phase diagram. The article provides information on peritectic transformations in multicomponent systems.

In some phase diagrams, the appearance of several reactions is the result of the presence of intermediate phases. These are phases whose chemical compositions are intermediate between two pure metals, and whose crystalline structures are different from those of the pure metals. This article describes the order-disorder transformation that typically occurs on cooling from a disordered solid solution to an ordered phase. It provides a table that lists selected superlattice structures and alloy phases that order according to each superlattice. The article informs that spinodal decomposition has been particularly useful in the production of permanent magnet materials, because the morphologies favor high magnetic coercivities. It also describes the theory of spinodal decomposition with a simple binary phase diagram.

Cast irons may be compared with steels in their reactions to hardening. However, because cast irons (except white iron) contain graphite and substantially higher percentages of silicon, they require higher austenitizing temperatures. This article describes the effect of heat treatment processes such as annealing, normalizing, surface hardening, tempering, stress relieving, quenching, and austempering, on hardness and tensile properties of cast irons, namely gray irons, ductile irons, malleable irons, and austenitic irons.

A sliding bearing (plain bearing) is a machine element designed to transmit loads or reaction forces to a shaft that rotates relative to the bearing. This article explains the role of wear damage mechanisms in the design and selection of bearing materials, and its relationship with bearing material properties. Sliding bearings are commonly classified by terms that describe their application; they also are classified according to material construction, as single-metal, bimetal, or trimetal sliding bearings. The article further provides detailed tabular data on the designation and composition of the following types of bearing materials: tin-base alloys, lead-base alloys, copper-base alloys, and aluminum-base alloys. It also briefly discusses the following types of bearing materials: zinc-base alloys, silver-base alloys, gray cast irons, cemented carbides, and nonmetallic bearing materials.

This article reviews high-temperature corrosion of furnace parts used in heat-treating furnaces. It provides a comparison of cast and wrought materials in the context of their general considerations, advantages, and applications. The article provides information on the heat-resistant alloys used for parts that go through the furnaces, including trays, fixtures, conveyor chains and belts, and quenching fixtures and parts, and the parts that remain in the furnace such as combustion tubes, radiant tubes, burners, thermowells, roller and skid rails, baskets, pots, retorts, muffles, and drive and idler drums. The article also reviews the material characteristics of silicon/silicon carbide composite and reaction-bonded silicon carbide as used in radiant tubes.

The melting process often includes refining and treating the metal. The choice of which type of melting to use depends on a number of factors: type of alloy being melted, the local cost of electric power, and local environmental regulations. This article discusses the principles, furnace types, charging practices of metal melting methods, namely induction melting, cupola melting, arc melting, crucible melting, reaction melting, and vacuum melting, and the refractories and charging practice of reverberatory furnaces. Molten metal treatment of steels and aluminum also is discussed in the article.

Ceramic-matrix composites (CMCs) are being developed for a number of high-temperature and high-performance applications in industrial, aerospace, and energy conservation sectors. This article focuses on processing, fabrication, testing, and characterization methods of CMCs, namely, discontinuously reinforced composites and continuous-fiber-reinforced composites. Processing methods include cold pressing, sintering, hot pressing, reaction bonding, melt infiltration, directed metal oxidation, sol-gel and polymer pyrolysis, self-propagating high-temperature synthesis and joining. A table summarizes the properties of various ceramic reinforcements and industrial applications of these composites.