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.

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.

Copper and copper alloys are used extensively in structural applications in which they are subject to moderately elevated temperatures. At relatively low operating temperatures, these alloys can undergo thermal softening or stress relaxation, which can lead to service failures. This article is a collection of curves and tables that present data on thermal softening and stress-relaxation in copper and copper alloys. Thermal softening occurs over extended periods at temperatures lower than those inducing recrystallization in commercial heat treatments. Stress relaxation occurs because of the transformation of elastic strain in the material to plastic, or permanent strain.

Quenching and partitioning (Q&P) steel is a term used to describe a series of C-Si-Mn, C-Si-Mn-Al, or other steels subjected to the quenching and partitioning heat treatment process. This article discusses the Q&P steel's chemical compositions and mechanical properties, and provides an overview of the important background and product characteristics with a focus on the automotive sheet steel application. It schematically represents the continuous annealing process, consequent phase-transformation behaviors, and forming-limit curves of Q&P steels. The article describes the parameters associated with resistance spot welding, laser welding, and metal active gas welding. It also provides useful information of retained austenite volume fraction measured by x-ray diffraction and electron backscatter diffraction. The article also examines microstructure evolution during tensile testing at different strain levels using electron backscatter diffraction.

This article discusses the microstructural processes that take place during plastic deformation and presents a plain phenomenological and general description of the cyclic stress-strain (CSS) response. It emphasizes the microstructural aspects of cyclic loading on single-phase materials tested in initially soft, dislocation-poor conditions resulting from a prior heat treatment. The article discusses deformation-induced phase transformations in austenitic stainless steels and commercial age-hardened aluminum alloys. It describes the interaction of dislocations and the strengthening of second-phase particles. The article also provides a description of the framework used to model the CSS response on a physical basis.

This article presents an overview of the techniques used in the design for heat treatment and discusses the primary criteria for design: minimization of distortion and undesirable residual stresses. It provides theoretical and empirical guidelines to understand the sources of common heat treat defects. A simple example is presented to demonstrate how thermal and phase-transformation-induced strains cause dimensional changes and residual stresses. The article concludes with a discussion on the heat treatment process modeling technology.

Austempered ductile iron (ADI) results from a specialty heat treatment of ductile cast iron. This article discusses the production of austempered ductile iron by heat treatment. The austempered ductile iron grades, according to ISO 17804 and EN 1564, are presented in a table. For economic reasons, or to avoid metallurgical problems, combinations of alloys are often used to achieve the desired hardenability in austempered ductile iron. The article provides information on the alloy combinations for austempered ductile iron. The mechanical properties, fracture toughness, fatigue, and abrasion resistance of the austempered ductile iron are discussed. The article concludes with information on the applications for austempered ductile iron.

This article focuses on the fractography of Nitinol, a shape memory alloy of nickel and titanium, in superelastic biomedical applications, which primarily comprise drawn and/or laser-cut wire and tube components. Overload fracture, hydrogen embrittlement fracture, and fatigue fracture are discussed in detail.

This article focuses on the specific aspects of nitinol that are of interest to medical device designers. It describes the physical metallurgy, physical properties, and tensile properties of the nitinol. The article discusses the factors influencing superelastic shape memory effects, fatigue, and corrosion in medical device design. It reviews the biocompatibility of nitinol based on corrosion behavior. The article explains the general principles, potential pitfalls, and key properties for manufacturing, heat treatment, and processing of nitinol.

This article examines residual stresses in quenched and surface-hardened steels by focusing on its theoretical background, formation mechanisms of residual stress, effects of tempering and cryogenic cooling on residual stress, effects of residual stress on the service performance of components, and measurement, computation, and relaxation of residual stress.

Bending fatigue of carburized steel components is a result of cyclic mechanical loading. This article reviews the alloying and processing factors that influence the microstructures and bending fatigue performance of carburized steels. These include austenitic grain size, surface oxidation, retained austenite, subzero cooling, residual stresses, and shot peening. The article describes the analysis of bending fatigue behavior of the steels based on S-N curves that represents a stress-based approach to fatigue. It discusses the types of specimen used to evaluate bending fatigue in carburized steels. The stages of fatigue and fracture of the steels, namely crack initiation, stable crack propagation, and unstable crack propagation, are reviewed. The article analyzes the intergranular fracture at the prior-austenite grain boundaries of high-carbon case microstructures that dominates bending fatigue crack initiation and unstable crack propagation of direct-quenched carburized steels.

This article discusses the history of shape memory alloys (SMAs) along with their properties, capabilities, and crystallography, including phase transformations that occur during thermal treatment. It describes the thermomechanical behaviors of SMAs and explains how to characterize them using differential scanning calorimeter (DSC) techniques as well as other methods. The article examines the most common shape memory alloys, namely, nickel-titanium and copper-base SMAs, and provides information on their respective properties.

Martensite is a metastable structure that forms during athermal (nonisothermal) conditions. This article reviews the crystallographic theory, morphologies, orientation relationships, habit plane, and transformation temperature of ferrous martensite microstructures. It examines the stages of the tempering process involved in ferrous martensite. The article also describes the formation of the martensite structure in nonferrous systems. It concludes with a discussion on shape memory alloys.

In the case of steels, heat treatment plays a fundamental role because no other process step can manipulate the microstructure in order to fulfill such a wide variety of possible in-service conditions. This article addresses heat treatment with regard to hardening and subsequent tempering of steel components in order to optimize tribological properties. It focuses on the heat treatment of tempering and bearing steels and on volume changes that take place due to phase transformations. Plastic deformations that occur due to shrinking and phase transformation are also discussed. The article also describes the generation of thermal, transformation, and hardening residual stresses.

This article discusses four types of defects in materials that have been fusion welded and that have been the focus of much attention because of the magnitude of their impact on product quality. These include hot cracks, heat-affected zone (HAZ) microfissures, cold cracks, and lamellar tearing. These defects, all of which manifest themselves as cracks, are characteristic of phenomena that occur at certain temperature intervals specific to a given alloy. The article presents selected alloy 625 compositions used in weldability study.

Fusion welding induces residual stresses and distortion, which may result in loss of dimensional control, costly rework, and production delays. In thermal analysis, conductive heat transfer is considered through the use of thermal transport, heat-input, and material models that provide values for the applied welding heat input. This article describes how the solid-phase transformations that occur during the thermal cycle produced by welding lead to irreversible plastic deformation known as transformation plasticity. Residual stress and welding distortion are also discussed.

The design of structural components with nominally brittle materials is largely determined by their elastic moduli, density, and tensile strength. This article discusses some of the factors involved in the design and reliability through considerations of toughness and ductility of nominally brittle materials. It describes toughening by various bridging mechanisms, as well as process zone effects and their interaction with the bridging rupture zone. The article explains the phenomena that give rise to exceptional toughness and notch-insensitive mechanical behavior. It provides a schematic illustration of a basic cell model to characterize the inelastic strains that occur in ceramic-matrix composites and their dependence on the interface friction.