Creep occurs in any metal or alloy at a temperature where atoms become sufficiently mobile to allow the time-dependent rearrangement of structure. This chapter begins with a section on creep curves, covering the three distinct stages: primary, secondary, and tertiary. It then provides information on the stress-rupture test used to measure the time it takes for a metal to fail at a given stress at elevated temperature. The major classes of creep mechanism, namely Nabarro-Herring creep and Coble creep, are then covered. The chapter also provides information on three primary modes of elevated fracture, namely, rupture, transgranular fracture, and intergranular fracture. The next section focuses on some of the metallurgical instabilities caused by overaging, intermetallic phase precipitation, and carbide reactions. Subsequent sections address creep life prediction and creep-fatigue interaction and the approaches to design against creep.

This chapter familiarizes readers with the mechanisms involved in creep and how they are related to fatigue behavior. It explains that what we observe as creep deformation is the gradual displacement of atoms in the direction of an applied stress aided by diffusion, dislocation movement, and grain boundary sliding. It describes these mechanisms in qualitative terms, explaining how they are driven by thermal energy and how they can be analyzed using creep curves and deformation maps. In addition, it examines the types of damage associated with creep, presents a number of creep strain and strain rate equations, explains how to determine creep constants, and reviews the findings of several studies on cyclic loading. It also discusses the development of a novel test that measures the cyclic creep-rupture resistance of materials in tension and compression.

This chapter compares and contrasts the high-temperature behaviors of metals and composites. It describes the use of creep curves and stress-rupture testing along with the underlying mechanisms in creep deformation and elevated-temperature fracture. It also discusses creep-life prediction and related design methods and some of the factors involved in high-temperature fatigue, including creep-fatigue interaction and thermomechanical damage.

This chapter provides a detailed overview of the creep behavior of metals and how to account for it when determining the remaining service life of components. It begins with a review of creep curves, explaining how they are plotted and what they reveal about the operating history, damage mechanisms, and structural integrity of the test sample. In the sections that follow, it discusses the effects of stress and temperature on creep rate, the difference between diffusional and dislocation creep, and the use of time-temperature-stress parameters for data extrapolation. It explains how to deal with time dependent deformation in design, how to estimate cumulative damage under changing conditions, and how to assess the effect of multiaxial stress based on uniaxial test data. It also includes information on rupture ductility, creep fracture, and creep-crack growth and their effect on component life and performance.

This chapter discusses the composition, properties, and uses of crystalline ceramics, glasses, clay, and concrete mixes. It also discusses the carbon structure of diamond, graphite, fullerenes, and nanotubes.

This chapter considers various behaviors of microstructural interfaces from a thermodynamics viewpoint. It discusses energy of surface and interface, the Gibbs-Thomson Effect, grain-boundary segregation, smooth and rough interfaces, and grain growth.

After shaping and first-stage binder removal, the component (with remaining backbone binder) is heated to the sintering temperature. Further heating induces densification, evident as dimensional shrinkage, pore rounding, and improved strength. This chapter begins with a discussion on the events that are contributing to sintering densification, followed by a discussion on the driving forces, such as surface energy, and high-temperature atomic motion as well as the factors affecting these processes. The process of microstructure evolution in sintering is then described, followed by a discussion on the tools used for measuring bulk properties to monitor sintering and density. The effects of key parameters, such as particle size, oxygen content, sintering atmosphere, and peak temperature, on the sintered properties are discussed. Further, the chapter covers sintering cycles and sintering practices adopted as well as provides information on dimensional control and related concerns of sintering. Cost issues associated with sintering are finally covered.

This chapter explains how to achieve accurate, sharp delineation of the microstructure of metals using appropriate etching and contrasting techniques. It covers a variety of methods, including chemical etching, heat tinting, gas contrasting, vapor deposition, magnetic etching, ion bombardment, and dislocation etch pitting.