Eutectoid and peritectoid transformations are classified as solid-state invariant transformations. This article focuses primarily on the structures from eutectoid transformations with emphasis on the classic iron-carbon system of steel. It reviews peritectoid phase equilibria that are very common in several binary systems. The addition of substitutional alloying elements causes the eutectoid composition and temperature to shift in the iron-carbon system. The article graphically illustrates the effect of various substitutional alloying elements on the eutectoid transformation temperature and effective carbon content. The partitioning effect of substitutional alloying elements, such as chromium, manganese, and silicon, in pearlitic steel is also illustrated.

This article illustrates the three techniques for producing glassy metals, namely, liquid phase quenching, atomic or molecular deposition, and external action technique. Devitrification of an amorphous alloy can proceed by several routes, including primary crystallization, eutectoid crystallization, and polymorphous crystallization. The article demonstrates a free-energy versus composition diagram that summarizes many of the devitrification routes. It provides a historical review of the corrosion behavior of fully amorphous and partially devitrified metallic glasses. The article describes the general corrosion behavior and localized corrosion behavior of transition metal-metal binary alloys, transition metal-metalloid alloys, and amorphous simple metal-transition metal-rare earth metal alloys. It concludes with a discussion on the environmentally induced fracture of glassy alloys, including hydrogen embrittlement and stress-corrosion cracking.

This article presents an outline of the physical metallurgical principles that are associated with heat treating of steels. It describes the iron-carbon phase diagram and various types of transformation diagrams, including isothermal transformation diagrams, continuous heating transformation diagrams, and continuous cooling transformation diagrams. The primary design criteria for heat treating of steels this article covers are the minimization of distortion and undesirable residual stresses. The article presents the theoretical and empirical guidelines to understand sources of common heat-treating defects and how they can be controlled. It also presents an example to demonstrate how thermal and transformation-induced strains cause dimensional changes and residual stresses.

This article introduces the mechanism of diffusion and the common types of heat treatments such as annealing and precipitation hardening, which are applicable to most ferrous and nonferrous systems. Three distinct processes occur during annealing: recovery, recrystallization, and grain growth. The article also describes the various types of solid-state transformations such as isothermal transformation and athermal transformation, resulting from the heat treatment of nonferrous alloys. It provides information on the homogenization of chemical composition within a cast structure.

The application of phase diagrams is instrumental in solid-state transformations for the processing and heat treatment of alloys. A unary phase diagram plots the phase changes of one element as a function of temperature and pressure. This article discusses the unary system that can exist as a solid, liquid, and/or gas, depending on the specific combination of temperature and pressure. It describes the accomplishment of conversion between weight percentage and atomic percentage in a binary system by the use of formulas. The article analyzes the effects of alloying on melting/solidification and on solid-state transformations. It explains the construction of phase diagrams by the Gibbs phase rule and the Lever rule. The article also reviews the various types of alloy systems that involve solid-state transformations. It concludes with information on the sources of phase diagram.

Of the various thermal processing methods for steel, heat treating has the greatest overall impact on control of residual stress and on dimensional control. This article provides an overview of the effects of material- and process-related parameters on the various types of failures observed during and after heat treating of quenched and tempered steels. It describes phase transformations of steels during heating, cooling of steel with and without metallurgical transformation, and the formation of high-temperature transformation products on the surface of a carburized part. The article illustrates the use of carbon restoration on decarburized spring steels. Different geometric models for carbide formation are shown schematically. The article also describes the different microstructural features such as grain size, microcracks, microsegregation, and banding.

This article describes the different types of precipitation and transformation processes and their effects that can occur during heat treatment of various nonferrous alloys. The nonferrous alloys are aluminum alloys, copper alloys, magnesium alloys, nickel alloys, titanium alloys, cobalt alloys, zinc alloys, and heat treatable silver alloys, gold alloys, lead alloys, and tin alloys. It also provides a detailed discussion on the effects due to precipitation and transformation processes in these non-ferrous alloys.

This article discusses the general characteristics, primary and secondary fabrication methods, product forms, and corrosion resistance of zirconium and hafnium. It describes the physical metallurgy of zirconium and its alloys, providing details on allotropic transformation and anisotropy that profoundly influences the engineering properties of zirconium and its alloys. Tables listing the values for chemical composition and tensile properties for nuclear and nonnuclear grades of zirconium are also provided.

The term shape memory alloys (SMAs) refers to the group of metallic materials that demonstrate the ability to return to some previously defined shape or size when subjected to the appropriate thermal procedure. Materials that exhibit shape memory only upon heating are referred to as having a one-way shape memory. Some materials also undergo a change in shape upon recooling. These materials have a two-way shape memory. This article discusses the general characteristics of SMAs by using typical transformation versus temperature curve. It describes the processing, applications and properties (mechanical and physical) of commercial SMA alloys, namely nickel-titanium alloys and copper-base alloys.

Titanium and its alloys are used in various applications owing to its high strength, stiffness, good toughness, low density, and good corrosion resistance. This article discusses the applications of titanium and titanium alloys in gas turbine engine components, aerospace pressure vessels, optic-system support structures, prosthetic devices, and applications requiring corrosion resistance and high strength. It explains the effects of alloying elements in titanium alloys as they play an important role in controlling the microstructure and properties and describes the secondary phases and martensitic transformations formed in titanium alloy systems. Information on commercial and semicommercial grades and alloys of titanium is tabulated. The article also discusses the different grades of titanium alloys such as alpha, near-alpha alloys, alpha-beta alloys, beta alloys, and advanced titanium alloys (titanium-matrix composites and titanium aluminides).

Thermomechanical processing (TMP) refers to various metal forming processes that involve careful control of thermal and deformation conditions to achieve products with required shape specifications and good properties. This article describes TMP methods in producing hot-rolled steel and reviews how improvements in the strength and toughness depend on the synergistic effect of microalloy additions and on carefully controlled thermomechanical conditions. It discusses TMP variables and the general distinctions between conventional hot rolling and common types of controlled-rolling schedules. The article describes the metallurgical processes in grain refinement of austenite steel by hot working, such as recovery and recrystallization and strain-induced transformation. The grain refinement in high strength low alloy steel by alloy addition is also discussed. The article provides an outline on the key stages of deformation, and the required metallurgical information at each of these stages.

The response of titanium and titanium alloys to heat treatment depends on the composition of the metal, the effects of the alloying elements on the alpha-beta crystal transformation, and the thermomechanical processing utilized during processing of the alloy. This article provides a detailed discussion on the effects of heat treatment on the mechanical properties for three general classes of titanium alloys, namely, alpha and near-alpha titanium alloys, alpha-beta alloys, and beta alloys.

This article provides a detailed discussion on heat treatment of titanium alloys such as alpha alloys, alpha-beta alloys, and beta and near-beta alloys. Common processes include stress-relief, annealing, solution treating, aging, quenching, and age hardening. It provides information on the effects of alloying elements on alpha/beta transformation. The article also discusses the heat treating procedures, and the furnaces used for heat treating titanium and titanium alloys.

This article introduces the different types, distinctions, and grades of commercially pure titanium and titanium alloys. It describes three types of alloying elements: alpha stabilizers, beta stabilizers, and neutral additions. The article discusses the basic categories of titanium alloys, namely, alpha and near-alpha titanium alloys, beta and near-beta titanium alloys, and alpha-beta titanium alloys. It also describes the general microstructural features of titanium alloys.

Alloy cast irons are casting alloys based on the Fe-C-Si system that contain one or more alloying elements added to enhance one or more useful properties. This article discusses the composition of different types of alloy cast iron, including white cast irons, corrosion-resistant cast irons, heat-resistant cast irons, and abrasion-resistant cast irons. It provides information on the effect of the alloying element on their high-temperature properties. The article also discusses the microstructure and mechanical properties of alloy cast irons.

The properties of copper alloys occur in unique combinations found in no other alloy system. This article focuses on the major and minor alloying additions and their impact on the properties of copper. It describes major alloying additions, such as zinc, tin, lead, aluminum, silicon, nickel, beryllium, chromium, and iron. The article discusses minor alloying additions, including antimony, bismuth, selenium, manganese, and phosphorus. Copper alloys can be cast by many processes, including sand casting, permanent mold casting, precision casting, high-pressure die casting, and low-pressure die casting. The article provides information on the types of copper castings and tabulates the nominal chemical composition and mechanical properties of several cast alloys.

Bronzes generally are used to describe many different copper-base alloys in which the major alloying addition is neither zinc nor nickel. They are generally classified by their major alloying elements, for example, tin bronzes with phosphorus used as a deoxidizer, aluminum bronzes, nickel-aluminum bronzes, silicon bronzes, and beryllium bronzes. This article briefly discusses the types, hardening mechanisms, heat treatment processes, applications, and mechanical properties of these bronzes and high-copper alloys.

This article provides a detailed discussion on the heat treatment processes for titanium and titanium alloys. These processes are age hardening, solution treatment, aging, and annealing. The article illustrates the characteristics of equilibrium phase diagrams that are important for understanding the heat treatment of titanium alloys. It explains the types of metastable phases encountered in titanium alloys. The article also provides information on the equilibrium phase relationships and properties of titanium alloys.

This article is a pictorial representation of commonly observed microstructures in iron-base alloys (carbon and alloy steels, cast irons, tool steels, and stainless steels) that occur as a result of variations in chemical analysis and processing. It reviews a wide range of common and complex mixtures of constituents (single or combination of two phases) that are encountered in iron-base alloys and the complex structure that is observed in these microstructures. The single-phase constituents discussed in the article include austenite, ferrite, delta ferrite, cementite, various alloy carbides, graphite, martensite, and a variety of intermetallic phases, nitrides, and nonmetallic inclusions. The article further describes the two-phase constituents including, tempered martensite, pearlite, and bainite and nonmetallic inclusions in steel that consist of two or more phases.

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.