This chapter discusses the structural alloys being used for cryogenic applications in commercially significant quantities. It emphasizes the practical considerations involved in the material selection process and provides the information necessary to make preliminary selections of alloys most suitable for the intended cryogenic application. The chapter provides general information on a class or group of alloys, their representative mechanical and physical properties, and their fabrication characteristics. The materials covered are austenitic stainless steels, nickel steels, aluminum alloys, and other metals and alloys.

Composite systems for cryogenic applications are discussed in this chapter. This chapter emphasizes filamentary-reinforced composites because they are the most widely used composite materials. It begins with a discussion on the approach to designing and fabricating with low-pressure laminate composites. This is followed by a section providing an overview of the materials in modern cryogenic technology. Then, the chapter describes the effect of cryogenic temperatures on materials properties; it also introduces the various joining techniques developed for composite materials. The effects of radiation on the properties of the materials are covered as well as the processes involved in testing laminates at cryogenic temperatures. Finally, the chapter provides information available on concrete aggregate composites.

This chapter concentrates on very low-temperature martensitic transformations, which are of great concern for cryogenic applications and research. The principal transformation characteristics are reviewed and then elaborated. The material classes or alloy systems that exhibit martensitic transformations at very low temperatures are discussed. In particular, the martensitic transformations and their effects in austenitic stainless steels, iron-nickel alloys, practical superconductors, alkali metals, solidified gases, and polymers are discussed.

This chapter reviews the concepts of fracture mechanics and their application to materials evaluation and the design of cryogenic structures. Emphasis is placed on an explanation of technology, a review of fracture mechanics testing methods, and a discussion on the many factors contributing to the fracture behavior of materials at cryogenic temperatures. Three approaches of elastic-plastic fracture mechanics are covered, namely the crack opening displacement, the J-integral, and the R-curve methods. The chapter also discusses the influence of thermal and metallurgical effects on toughness at low temperatures.

This chapter details low-temperature test procedures and equipment. It discusses the role temperature plays in the properties of typical engineering materials. The effect that lowering the temperature of a solid has on the mechanical properties of a material is summarized for three principal groups of engineering materials: metals, ceramics, and polymers (including fiber-reinforced polymers). The chapter describes the factors that influence the selection of tensile testing procedures for low-temperature evaluation, along with a comparison of tensile and compression tests. It covers the parameters and standards related to low-temperature tensile testing. The chapter discusses the factors involved in controlling test temperature. Finally, the chapter discusses the safety issues concerning the use of cooled methanol, liquid-nitrogen, and liquid helium.

This article provides an overview of austenitic manganese steels. It describes the standard composition ranges of commercial products and explains how various alloying elements affect mechanical properties, processing, and performance. The article also discusses special grades of manganese steels and the types of applications for which they have been developed.

This chapter provides an overview of the state of the art in high-pressure cold spray equipment, including both spray systems and gas supply systems. The chapter describes the commercial cold spray systems developed by companies such as Cold Gas Technology (CGT) GmbH, Plasma Giken Company Ltd, Impact Innovations GmbH, and ASB Industries. Typical helium and nitrogen gas systems used in high-pressure cold spray processing are reviewed.

This chapter defines low-temperature and cryogenic steels and describes their alloy classifications and their ambient and low-temperature properties. These steels include ferritic carbon and low alloy steels, martensitic low alloy steels, martensitic high alloy steels, and austenitic high alloy steels.

The technology of fabricating composite hardware and structures by filament winding has evolved empirically through the development and manufacturing of specific components. This chapter reviews areas of technology used in building composite parts and discusses the processes from which the current technology was derived. The discussion covers quality control requirements for composite fabrication technology and cleanliness standards in the workplace. It describes technology developed for specific components, including satellites struts, aircraft hydraulic cylinders, drill pipe, drive shafts, couplings, and cryogenic tubing.

The mechanical properties of a material describe the relations between the stresses acting on the material and its resulting deformations. Stresses capable of producing permanent deformations, which remain after the stresses are removed, are considered in this chapter. The effects of cryogenic temperatures on the mechanical properties of metals and alloys are reviewed in this chapter; the effects on polymers and glasses are discussed briefly. The fundamental mechanisms controlling temperature-dependent mechanical behavior, phenomena encountered in low-temperature testing, and the mechanical properties of some representative engineering metals and alloys are described. Modifications of test procedures for low temperatures and sources of data are also included.

This chapter provides a view of magnetism in materials used at low temperatures. The discussion covers the concepts, definitions, and systems of units that are unique to the study of magnetic properties. The chapter provides a description of some of the techniques and devices used for determining magnetic properties.

This chapter presents topics pertaining to resistance at cryogenic temperatures: measurement, the resistive mechanisms, and available data. The chapter also presents brief descriptions of the various mechanisms that are operative in producing resistance at low temperatures. The alloys discussed are the nondilute mixtures of metals. An introduction to low-temperature electrical properties of specific metals and alloys is included.

This chapter reviews the major marine applications of stainless steels, including the desalination equipment, shipping containers, and heat exchangers that handle seawater.

Titanium alloys are classified according to the amount of alpha and beta phase material retained in their structures at room temperature. This chapter discusses the metallurgy, composition, processing, and properties of titanium and its alloys. It provides information on melting, forging, casting, heat treating, and secondary fabrication. It also discusses the advantages and disadvantages of titanium and its alloys in various applications.

The chapter presents an overview of the properties and operational limits of superconductive materials, as well as techniques used to fabricate practical superconducting wires. It introduces six properties: critical temperature, critical magnetic field, critical current density, stability, ac loss, and mechanical characteristics; for each property, typical data are provided and the experimental methods used to measure it are briefly described. The properties of the superconducting composites are tied together in the chapter to summarize their effect on superconductor material selection and the geometrical design of superconducting composites. The chapter also contains a reference guide to composite-design factors with links to the relevant chapter sections where each design consideration is addressed.

This chapter discusses the compatibility problems that arise from chemical or physical interactions between liquefied gases and the common materials used in their production, storage, transportation, distribution, and use. The discussion covers the compatibility of materials with liquid oxygen and liquid fluorine. Hydrogen-environment embrittlement is unique to low-temperature hydrogen systems and is also discussed.

This chapter discusses three measurements parameters: temperature, strain, and magnetic field strength. It stresses the measurement of temperature because it is the primary variable in nearly all low-temperature material properties. The chapter contains information on methods and auxiliary materials. Areas of frequent concern, such as thermal contact, heat leak, thermal anchoring, thermal conductivity of greases, insulators, lead wires, ground loops, and feedthroughs are also reviewed. The chapter provides an overview and historical development of temperature scales because the practical use of all thermometers is associated with some approximation of the thermodynamic temperature scale. A short section is devoted to types of temperature measuring devices. The characteristics of commercially available resistance-type strain gauges at low temperatures are stressed.

Specific heat and thermal expansion are closely related. Following a discussion on thermal expansion theory, methods of measurement techniques are presented along with their advantages and disadvantages. The results of the measurements are then summarized for three classes of materials: metallics, nonmetallics, and composites. Because predicting thermal expansion values for unmeasured or novel materials is useful, the chapter also describes the means of making educated guesses for low-temperature values. A short discussion on how thermal expansion data can be used is followed by a section describing where such data can be found.

This chapter summarizes the progress that has been made in the study of high-entropy alloy (HEA) systems and the process-structure-property relationships that define them. It describes the various ways HEAs can be strengthened and explains how alloying elements influence tensile and yield strength, fracture toughness, and fracture strength. It discusses the stages of plastic deformation in HEAs and the role of dislocations and twinning in the evolution of microstructure. It reviews some of the work that has been done on fatigue behaviors and the methods developed to assess fatigue performance. It discusses the influence of defects on fatigue life, the effect of temperature and grain size on fatigue-crack propagation, and the role of nanotwinning in crack-growth retardation. It describes the methods used to produce HEAs in bulk and powder form and to apply them as protective coatings and films. It also identifies potential applications based on properties such as strength, hardness, density, wear resistance, high-temperature stability, and biocompatibility.