Quenching is a widely used technique to strengthen titanium alloys. This article presents the metallurgical and structural background underlying the specific techniques applied in the quenching of various titanium alloys, and the ways to control and reduce residual stresses induced from quenching or other thermal or mechanical processes. It discusses the types and microstructures of titanium alloys, namely, alpha, alpha-beta, and beta alloys, and describes the general effects of the various heat treatments. The article provides information on quenching media, quenching rate, section size, and martensitic transformation in quenched titanium alloys. It shows how residual stresses in titanium alloys are evaluated and controlled. Finally, the article describes the stress-relief treatments used to reduce residual stresses.

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.

The process of case hardening of steel includes three consecutive steps of heat treatment: heating; the thermochemical process with the enrichment of the surface area during the carburizing or carbonitriding stage with carbon and nitrogen; and the subsequent quenching process for hardening. This article provides a model-based description of the development of residual stresses during case hardening. It also describes the influence and effects of residual stresses and distortion in hardening, carburizing, and nitriding processes of the steel.

X-ray diffraction (XRD) residual-stress analysis is an essential tool for failure analysis. This article focuses primarily on what the analyst should know about applying XRD residual-stress measurement techniques to failure analysis. Discussions are extended to the description of ways in which XRD can be applied to the characterization of residual stresses in a component or assembly and to the subsequent evaluation of corrective actions that alter the residual-stress state of a component for the purposes of preventing, minimizing, or eradicating the contribution of residual stress to premature failures. The article presents a practical approach to sample selection and specimen preparation, measurement location selection, and measurement depth selection; measurement validation is outlined as well. A number of case studies and examples are cited. The article also briefly summarizes the theory of XRD analysis and describes advances in equipment capability.

This article describes the fundamental concepts of heat treatment simulation, including the physical events and their interactions, the heat treatment simulation software, and the commonly used simulation strategies. It summarizes material data needed for heat treatment simulations and discusses reliable data sources as well as experimental and computational methods for material data acquisition. The article provides information on the process data needed for accurate heat treatment simulation and the methods for their determination. Methods for validating heat treatment simulations are also discussed with an emphasis on the underlying philosophy for the selection and design of validation tests. The article also discusses the applications, capabilities, and limitations of heat treatment simulations via selected industrial case studies for a better understanding of the effect of microstructure, distortion, residual stress, and cracking in gears, shafts, and bearing rings.

This article provides a detailed account of x-ray diffraction (XRD) residual-stress techniques. It begins by describing the principles of XRD stress measurement, followed by a discussion on the most common methods of XRD residual-stress measurement. Some of the procedures required for XRD residual-stress measurement are then presented. The article provides information on measurement of subsurface stress gradients and stress relaxation caused by layer removal. The article concludes with a section on examples of applications of XRD residual-stress measurement that are typical of industrial metallurgical, process development, and failure analysis investigations undertaken at Lambda Research.

The presence of macroscopic residual stresses in heat treatable aluminum alloys can give rise to machining distortion, dimensional instability, and increased susceptibility to in-service fatigue and stress-corrosion cracking. This article details the residual-stress magnitudes and distributions introduced into aluminum alloys by thermal operations associated with heat treatment. The available technologies by which residual stresses in aluminum alloys can be relieved are also described. The article shows why thermal stress relief is not a feasible stress-reduction technology for precipitation-hardened alloys. It examines the consequences of aging treatments on the residual stress, namely, annealing, precipitation heat treatment, and cryogenic treatment. The article provides information on uphill quenching, which attempts to reverse thermal gradients encountered during quenching. It examines how quench-induced residual stresses in heat treatable aluminum alloys are reduced when sufficient load is applied to cause plastic deformation. The article also shows how plastic deformation reduces residual stress.

This article discusses the advantages, disadvantages, applications, and selection criteria of various technologies and transduction modalities that can generate and detect ultrasonic waves. These include piezoelectric transducers, electromagnetic acoustic transducers (EMATs), laser ultrasound phased array transducers, magnetostriction transducers, and couplants. The article discusses four basic types of search units with piezoelectric transducers. These include the straight-beam contact type, the angle-beam contact type, the dual-element contact type, and the immersion type. The article concludes with information on immersion or contact type focused search units.

The properties of carbon and alloy steels are dependent on the relationships between chemical composition, processing, and microstructure. This article discusses the effects of alloying and residual elements on the mechanical properties of carbon and alloy steels. Tables listing values for the mechanical properties of selected carbon and alloy steels in the hot-rolled, normalized, annealed, and quenched-and tempered condition are provided.

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 provides a useful guide for measuring residual macrostress on coatings. The most commonly used measurement methods are mechanical deflection, X-ray diffraction, and hole-drilling strain-gage. After a discussion on the origins of residual stress, the article describes the fundamental principles and presents examples of practical measurements for each method.

This article provides an explanation on how crystal plasticity is implemented within finite element formulations by the use of physical length scales: crystal scale and continuum scale. It provides theoretical formulations for kinematic framework for deforming crystals and polycrystals, elastic and plastic behaviors of single crystals, refinements to the single-crystal constitutive, and crystal-scale finite-element. The article also presents examples that illustrate the capabilities of the formulations at the length scales.

Several methods are developed for the numerical solution of partial differential equations, namely, meshed-solution methods such as the finite-element method (FEM), finite-difference method, and boundary-element method; and numerical algorithms consisting of so-called meshed-solution methods. This article introduces the methods of so-called meshed solutions, with an emphasis on the FEM. It presents some basic differential equations that are used to model the responses of structures, components, processes, or systems with emphasis on continuum mechanics. The article provides an outline on the mathematical principles of solving differential equations. It also reviews linear structural problems to illustrate the concept of the FEMs.

This article provides a summary of the overall development of the finite element method (FEM) and its contribution to the materials forming industry. It presents an overview of FEM methodologies and applications in the order of their usage in typical manufacturing (bulk forming process) process sequence: primary materials processing, hot forging and cold forming, and product assembly. The article discusses the material fracture and dies stress analysis and presents the optimization techniques used in 2-D and 3-D preform die design.

When complex designs, transient loadings, and nonlinear material behavior must be evaluated, computer-based techniques are used. This is where the finite-element analysis (FEA) is most applicable and provides considerable assistance in design analysis as well as failure analysis. This article provides a general view on the applicability of finite-element modeling in conducting analyses of failed components. It highlights the uses of finite-element modeling in the area of failure analysis and design, with emphasis on structural analysis. The discussion covers the general development and both general- and special-purpose applications of FEA. The special-purpose applications of FEA covered are piping and pressure vessel analysis, impact analysis, and microelectronic and microelectromechanical systems analysis. The article provides case histories that involved the use of FEA in failure analysis.

Heat treatment simulation helps to predict heat treatment results such as component microstructures, properties, residual stresses, and distortion, and thereby assists in reducing experimental effort in defining heat treatment parameters. This article discusses the modeling and simulation of age hardening as being the most important heat treatment to strengthen aluminum alloys. It provides information on the heat treatment simulation model, the yield strength model based on the responsible strengthening mechanisms, and the flow curve model based on mechanical tests. The article also discusses simulation of the quenching process, and provides examples for aluminum quenching simulation.

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.

X-ray diffraction (XRD) is the most extensively used method for identifying and characterizing various aspects of metals related to the arrangements and spacings of their atoms for bulk structural analysis. XRD techniques are also applicable to ceramics, geologic materials, and most inorganic chemical compounds. This article describes the operating principles and types of XRD analyses, along with information about the threshold sensitivity and precision, limitations, sample requirements, and capabilities of related techniques. The necessary instrumentation for XRD analyses include the Debye-Scherrer camera and the X-ray diffractometer. The article also describes the uses of XRD analyses, such as the identification of phases or compounds in metals and ceramics; detection of order and disorder transformation; determination of lattice parameters and changes in lattice parameters due to alloying and temperature effects; measurement of residual stresses; characterization of crystallite size and perfection; characterization of preferred orientations; and determination of single crystal orientations.

Quenching refers to the rapid cooling of metal from the solution treating temperature, typically between 465 and 565 deg C (870 and 1050 deg F) for aluminum alloys. This article provides an overview on the appropriate quenching process and factors used to determine suitable cooling rate. It describes the quench sensitivity and severity of alloys, quench mechanisms and the different types of quenchants used in immersion, spray, and fog quenching. The article provides a detailed description of the quench-factor analysis that mainly includes residual stress and distortion, which can be controlled by proper racking. It concludes with information on agitation and the quench tank system used in the quenching of aluminum alloys.

Heat treating of stainless steel produces changes in physical condition, mechanical properties, and residual stress level and restores maximum corrosion resistance when that property has been adversely affected by previous fabrication or heating. This article focuses on annealing of different types of stainless steels such as austenitic, ferritic, duplex, martensitic, and precipitation-hardening, and on the heat treatment of superalloys and refractory metals. It discusses the recommended procedures for solution annealing, austenite conditioning, transformation cooling, and age tempering of precipitation-hardening stainless steels. The article also lists general recommendations for the annealing temperatures of tantalum, niobium, molybdenum, tungsten, and their alloys.