The term heat treatable alloys is used in reference to alloys that can be hardened by heat treatment, and this chapter briefly describes the major types of heat treatable nonferrous alloys. The discussion provides a general description of annealing cold-worked metals and describes some of the common nonferrous alloys that can be hardened through heat treatment. The nonferrous alloys covered include aluminum alloys, cobalt alloys, copper alloys, magnesium alloys, nickel alloys, and titanium alloys.

Titanium alloys are generally resistant to stress-corrosion cracking (SCC), but under certain conditions, the potential for problems exists. This chapter identifies the types of service environments where titanium alloys have exhibited signs of SCC. It begins by describing the nominal composition, designation, and grade of nearly two dozen commercial titanium alloys and the different types of media (including oxidizers, organic compounds, hot salt, and liquid metal) in which SCC has been observed. It discusses the mechanical and metallurgical factors that influence SCC behavior and examines the cracking and fracture mechanisms that appear to be involved. The chapter also includes information on SCC test standards and provides detailed guidelines on how to prevent or mitigate the effects of SCC.

This chapter provides a detailed account of crevice corrosion of metals. It begins by describing various critical factors influencing crevice corrosion. This is followed by a section presenting selected examples of crevice corrosion of stainless steel, nickel alloys, aluminum alloys, and titanium alloys in different environments. Methods that have been developed for differentiating and ranking the resistance of alloys toward crevice corrosion are then reviewed. The chapter concludes by discussing various strategies for the prevention of crevice corrosion, namely design awareness, use of inhibitors, and potential control methods.

This chapter discusses some of the metallurgical factors that affect corrosion of weldments and describes a few considerations for selected nonferrous alloy systems: aluminum, titanium, tantalum, and nickel.

Hydrogen damage is a form of environmentally assisted failure that results most often from the combined action of hydrogen and residual or applied tensile stress. This chapter classifies the various forms of hydrogen damage, summarizes the various theories that seek to explain hydrogen damage, and reviews hydrogen degradation in specific ferrous and nonferrous alloys. The preeminent theories for hydrogen damage are based on pressure, surface adsorption, decohesion, enhanced plastic flow, hydrogen attack, and hydride formation. The specific alloys covered are iron-base, nickel, aluminum, copper, titanium, zirconium, vanadium, niobium, and tantalum alloys.

This chapter provides an overview of the production and use of titanium and its significance as an engineering material. It begins by identifying important deposits and ores and assessing current and future production capacities and how they align with global consumption trends. It then describes the physical and mechanical properties of pure titanium and numerous grades of wrought titanium alloys and explains how they compare with other aerospace materials in terms of processing complexity and cost. The chapter also includes information on extractive metallurgy, current and emerging processes, product forms, and related costs.

This chapter discusses the basic principles of alloying and their practical application in the production of titanium mill products and engineered parts. It begins with a review of the atomic and crystal structure of titanium and the conditions for interstitial and substitutional alloying. It then describes the different classes of alloying elements, their effect on mechanical properties and behaviors, and their influence on phase transitions and transformations. The chapter also discusses the role of intermetallic compounds and their effect on crystal structure and creep behavior.

Titanium alloys respond well to heat treatment be it to increase strength (age hardening), reduce residual stresses, or minimize tradeoffs in ductility, machinability, and dimensional and structural stability (annealing). This chapter describes the phase transformations associated with these processes, explaining how and why they occur and how they are typically controlled. It makes extensive use of phase diagrams and cooling curves to illustrate the effects of alloying and quenching on beta-to-alpha transformations and the conditions that produce metastable phases. It also examines several time-temperature-transformation diagrams, which account for the effect of cooling rate.

Titanium, like other metals, can be shaped, formed, and strengthened through deformation processes. This chapter describes the structural changes that occur in titanium during deformation and how they can be controlled. It discusses the role of slip, dislocations, and twinning, the effect of grain size and crystal orientation, the concept of texture strengthening, and the principles of strain hardening and superplasticity. It also discusses the effect of annealing and the difference between recrystallization and neocrystallization processes.

This chapter discusses the factors that govern the mechanical properties of titanium, beginning with the morphology of the alpha phase. It explains that the shape of the alpha phase has a significant effect on many properties, including hardness, tensile strength, toughness, and ductility as well as creep, fatigue strength, and fatigue crack growth rate. It also discusses the influence of other titanium phases and the properties of titanium-based intermetallic compounds, metal-matrix composites, and shape-memory alloys.

The practical application of metals and alloys is guided largely by information obtained through the study of their microstructure. This chapter examines a wide range of titanium microstructures, identifying characteristic features and explaining what they reveal about processing, properties, and performance. It includes images of elongated and equiaxed structures, primary alpha, transformed beta, and metastable phases as well as spheroidal and intergranular beta, alpha case, and intermetallic compounds. It also defines important terms and provides step-by-step procedures for preparing titanium for metallographic analysis.

Casting is the most economical processing route for producing titanium parts, and unlike most metals, the properties of cast titanium are on par with those of wrought. This chapter covers titanium melting and casting practices -- including vacuum arc remelting, consumable electrode arc melting, electron beam hearth melting, rammed graphite mold casting, sand casting, investment casting, hot isostatic pressing, weld repair, and heat treatment -- along with related equipment, process challenges, and achievable properties and microstructures. It also explains how titanium parts are produced from powders and how the different methods compare with each other and with conventional production techniques. The methods covered include powder injection molding, spray forming, additive manufacturing, blended elemental processing, and rapid solidification.

Most integrated titanium mills have primary working equipment designed specifically for titanium. This chapter describes the forging, rolling, and extruding equipment used to produce titanium mill products and sheds light on the corresponding process, structure, property relationships.

This chapter discusses the equipment and processes used to convert titanium billet and bar into useful shapes or more refined product forms. These secondary working operations include open-die, closed-die, hot-die and isothermal forging as well as ring rolling and extruding. The chapter describes each method in detail and how it affects the microstructure and mechanical properties of various titanium alloys. It also discusses the propensity of titanium to react with oxygen and hydrogen when heated and explains how to mitigate the effects.

This chapter describes the equipment and processes used to form titanium alloy parts. It discusses the advantages and disadvantages of hot and cold forming, the factors that influence formability, and the effect of forming temperature and lubricants. It describes common processes, including brake forming, stretch forming, deep drawing, and spin forming as well as roll forming, drop-hammer forming, tube bulging and bending, and superplastic forming. It also discusses dimpling and joggling and the use of hot sizing to correct springback.

This chapter discusses the various methods used to join titanium alloy assemblies, focusing on welding processes and procedures. It explains how welding alters the structure and properties of titanium and how it is influenced by composition, surface qualities, and other factors. It describes several welding processes, including arc welding, resistance welding, and friction stir welding, and addresses related issues such as welding defects, quality control, and stress relieving. The chapter also covers mechanical fastening techniques along with adhesive bonding and brazing.

This chapter familiarizes readers with the machining characteristics of titanium and the implementation of machining and shaping processes. It explains why titanium alloys are more difficult to machine than other metals and how it impacts the equipment and procedures that can be used. It describes the basic machining requirements for titanium in terms of tool geometry and materials, machine setup rigidity, cutting speeds and feed rates, and surface conditions, and explains how the requirements are met in practice in milling, turning, drilling, surface grinding, and broaching operations. The chapter also covers chemical and electrochemical machining processes as well as flame cutting.

This chapter discusses the corrosion behavior of titanium, the types of corrosion that can occur, and the effect of alloying on corrosion resistance. It explains that, due to its tenacious oxide film, titanium has excellent corrosion resistance in oxidizing environments and that the resistance can be extended into the “reducing-acid” region by adding a small amount of palladium. It describes how different grades of titanium respond to different forms of attack, including uniform, crevice, and galvanic corrosion. It also identifies applications where corrosion is often a concern.