This article discusses a tool for the conversion of measurements made against various reference electrodes at different temperatures. It reviews different electrode potential temperature coefficients, namely, isothermal temperature coefficient and thermal temperature coefficient. The article contains a table that lists the electrode potentials and conversion factors for various reference electrodes.

Hot-die forging and isothermal forging are unique forging methods developed to forge materials that are difficult or impossible to forge by conventional means. This article presents a comparative study on hot-die forging and isothermal forging. It discusses forging parameters, process selection considerations, design guidelines, alloy types and selection, and the advantages and disadvantages of hot-die forging and isothermal forging. The article discusses the application of the finite-element analysis modeling to design.

This article discusses two types of hot-tension tests, namely, the Gleeble test and conventional isothermal hot-tension test, as well as their equipment. It summarizes the data for hot ductility, strength, and hot-tension for commercial alloys. The article presents isothermal hot-tension test data, which helps to gain information on a number of material parameters and material coefficients. It details the effect of test conditions on flow behavior. The article briefly describes the detailed interpretation of data from the isothermal hot-tension test using numerical model. It also explains the cavitation mechanism and failure modes that occur during hot-tension testing.

This article provides information on the salt baths used for a variety of heat treatments, including heating, quenching, interrupted quenching (austempering and martempering), case hardening, and tempering. It describes two general types of salt bath systems for steel hardening: the first type uses atmosphere austenitizing followed by salt quench and the second type employs austenitizing salt baths with rapid transfer to the quench salt. The article provides a detailed account on the construction, advantages and disadvantages, and limitations of isothermal quenching furnaces, submerged-electrode furnaces, immersed-electrode furnaces, and externally heated furnaces. It discusses the important applications of various furnace designs, including the austempering of ductile iron, the hardening of tool steels, and the isothermal annealing of high-alloy steels.

Thermal inspection comprises all methods in which heat-sensing devices or substances are used to detect irregular temperatures. Inspection of workpieces can be used to detect flaws and undesirable distribution of heat during service. Though there are several methods of thermal inspection and many types of temperature-measuring devices and substances, this article focuses only on thermography, which is the mapping of isotherms, or contours of equal temperature, over a test surface, and on thermometry, which is the measurement of temperature. Thermography techniques can be classified as contact thermographic methods using cholesteric liquid crystals, thermally quenched phosphors, and heat-sensitive paints, and noncontact techniques using hand-held infrared scanners, high-resolution infrared imaging systems, and thermal wave interferometer systems. Contact thermometric inspection devices include bolometers, thermocouples, thermopiles, and meltable substances, whereas radiometers and pyrometers come under the noncontact category.

High-temperature corrosion can occur in numerous environments and is affected by various parameters such as temperature, alloy and protective coating compositions, stress, time, and gas composition. This article discusses the primary mechanisms of high-temperature corrosion, namely oxidation, carburization, metal dusting, nitridation, carbonitridation, sulfidation, and chloridation. Several other potential degradation processes, namely hot corrosion, hydrogen interactions, molten salts, aging, molten sand, erosion-corrosion, and environmental cracking, are discussed under boiler tube failures, molten salts for energy storage, and degradation and failures in gas turbines. The article describes the effects of environment on aero gas turbine engines and provides an overview of aging, diffusion, and interdiffusion phenomena. It also discusses the processes involved in high-temperature coatings that improve performance of superalloy.

Heat treatment of aluminum alloys is assessed by various quality-assurance methods that include metallographic examination, hardness measurements, mechanical property tests, corrosion-resistance tests, and electrical conductivity testing. The use of hardness measurements in the quality assurance of heat treated aluminum products is effectively used in conjunction with the measurement of surface electrical conductivity. This article provides a detailed discussion of the error sources in eddy-current conductivity measurements. It also presents useful information on the variation of electrical conductivity of alloy 2024 samples as a function of aging time at different isothermal holding temperatures.

This article lists functions of lubricants common to the majority of applications and processes. It discusses the lubricant candidates widely used in forging: conversion coatings with soaps (stearate compounds) and molybdenum disulfide for cold forging; oil-based thick, film oil or polymerbased lubricants and molybdenum disulfide for warm application; graphite suspensions in oil or water for hot forging steels; and glass films for titanium and superalloys hot forgings. The article describes the applications of lubricants in warm extrusion and forging, hot forging of steel, hot forging of aluminum, isothermal and hot die forging, and the extrusion of steel.

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 material data for forging can be divided into two categories, namely, mechanical properties and thermophysical properties. This article describes the flow characteristics of key engineering materials, such as steels, aluminum alloys, copper alloys, titanium alloys, and nickel-base superalloys. It discusses the thermophysical properties for designing or optimizing a metalworking process: specific heat, coefficient of thermal expansion, thermal conductivity/diffusivity, and density.

Thermomechanical are used to gain insight into the causes of problems that arise during a given thermomechanical process. This article provides examples to demonstrate how significant the parameters were selected for specific tests. It examines the types of problems that can occur during a thermomechanical process. The article provides information on the thermophysical properties, which include specific heat, coefficient of thermal expansion, thermal conductivity/diffusivity, and density. It concludes with examples that illustrate how the various considerations in testing are successfully used to solve practical thermomechanical processing problems.

This article discusses the fundamental aspects of phase-field microstructure modeling. It describes the evolution of microstructure modeling, including nucleation, growth, and coarsening. The article reviews two approaches used in the modeling nucleation of microstructure: the Langevin force approach and explicit nucleation algorithm. Calculation of activation energy and critical nucleus configuration is discussed. The article presents the deterministic phase-field kinetic equations for modeling growth and coarsening of microstructure. It also describes the material-specific model inputs, chemical free energy and kinetic coefficients, for phase-field microstructure modeling. The article provides four examples that illustrate some aspects of phase-field modeling.

The heat treatment of steel involves a number of processes (such as stress relieving, normalizing, annealing etc) to condition the microstructure and obtain desired properties. This article discusses typical heat treating process control procedures for carbon and low-alloy steels, as well as the importance of time, and temperature control in heat treatment. Temperature Uniformity Survey, a testing procedure intended to map variations in temperature throughout the furnace work zone, helps in precise control of temperature. The article focuses on the measuring instruments used to determine gas pressure, vacuum level, gas flow, and gas composition. It focuses on their measuring quenchant characteristics, including bulk temperature, viscosity, composition, and cooling efficiency. The article describes the procedures for detecting variability in the incoming product. It presents, through an example, the general application of design of experiments techniques to locate and tune vital process parameters. The devices used in the control process of mechanical components are also reviewed.

Thermomechanical fatigue (TMF) is the general term given to the material damage accumulation process that occurs with simultaneous changes in temperature and mechanical loading. TMF may couple cyclic inelastic deformation accumulation, temperature-assisted diffusion within the material, temperature-assisted grain-boundary evolution, and temperature-driven surface oxidation, among other things. This article discusses some of the major aspects and challenges of dealing with TMF life prediction. It describes the damage mechanisms of TMF and covers various experimental techniques to promote TMF damage mechanisms and elucidate mechanism coupling interactions. In addition, life modeling in TMF conditions and a practical application of TMF life prediction are presented.

This article describes the use of compression tests, namely, cylindrical compression, ring compression, and plane-strain compression tests at elevated temperatures. It discusses the effects of the temperature, strain rate, and deformation heating on metals during the cylindrical compression test, with the help of flow curves. The article illustrates the testing apparatus used in the cylindrical compression test. It describes the issues regarding friction and temperature, and strain-rate control with proper test equipment and experimental planning during the ring compression test and plane-strain compression test. The article also reviews the testing conditions, procedures, and advantages of hot plane-strain compression test.

This article examines the high-temperature oxidation of silica-forming ceramics under constant temperature and cyclic conditions. The effects of water vapor, impurities, and molten salts are discussed. The article describes the oxidation and corrosion of silica-forming composites, oxide ceramics, non-silica forming nitrides, carbides, and borides. The performance of environmental barrier coatings by material type is also discussed. The article also explains the effects of oxidation and corrosion on the mechanical properties of ceramic-matrix composites. It concludes with information on high-temperature applications, wear properties, and the microscopic analyses of advanced ceramics.

Thermal analysis provides a powerful tool for researchers and engineers in determining both unknown and reproducible behavioral properties of polymer molecules. This article covers the thermal analysis and thermal properties of engineering plastics with respect to chemical composition, chain configuration, conformation of the base polymers, processing of the base polymers with or without additives; and the response to chemical, physical, and mechanical stresses of base polymers as unfilled, shaped articles or as components of composite structures. It also describes thermal analysis techniques, including differential scanning calorimetry, thermogravimetric analysis, thermomechanical analysis, and rheological analysis. This article also summarizes the basic thermal properties used in the application of engineering plastics, such as thermal conductivity, temperature resistance, thermal expansion, specific heat, and the determination of glass transition temperatures. It concludes with a discussion of the thermal and related properties of nine thermostat resin systems divided into three groups by low, medium, and high service temperature capabilities.

Alloys based on ordered intermetallic compounds constitute a unique class of metallic material that form long-range ordered crystal structures below a critical temperature. Aluminides, a unique class of ordered intermetallic materials, possesses many attributes like low densities, high melting points, and good high-temperature strength that make them an attractive material for high-temperature structural application. This article discusses the properties, chemical composition, corrosion resistance, processing, fabrication, alloying effects and crystallographic data of nickel aluminides (Ni3Al and NiAl), iron aluminides (Fe3Al and FeAl) and titanium aluminides (alpha-2 alloys, orthorhombic alloys, and gamma alloys).

This article introduces the fundamental concepts of chemical thermodynamics and chemical kinetics in describing presolidification phenomena. For metallurgical systems, the most important thermodynamic variables are enthalpy and Gibbs free energy. A qualitative demonstration of the interrelationship between phase diagrams and thermodynamics is presented. The article discusses processes that generally limit the rates of chemical processes. These include nucleation of the product phase and interphase mass transport. The article provides a discussion on the dissolution of alloy with melting point lower than bath temperature and dissolution of alloy that is solid at bath temperatures.