This article examines the composition and properties of magnesium and its alloys. It discusses alloy and temper designations, applications and product forms, and commercial alloy systems, and explains how alloying elements affect physical and mechanical properties, processing characteristics, and corrosion behaviors.

Stress-corrosion cracking (SCC) in magnesium alloys was first reported in the 1930s and, within ten years, became the focus of intense study. This chapter provides a summary of all known work published since then on the nature of SCC in magnesium alloys and how it is related to composition, microstructure, and heat treatment. It describes the types of environments where magnesium alloys are most susceptible to SCC and the effect of contributing factors such as temperature, strain rate, and applied and residual stresses. The chapter also discusses crack morphology and what it reveals, provides information on proposed cracking mechanisms, and presents a practical approach for preventing SCC.

This chapter discusses the effects of metallurgical factors on the corrosion resistance of magnesium alloys. The factors are chemical composition, heat treating, grain size, and cold-work effects. The chapter describes the causes of corrosion failures in magnesium alloys, namely heavy-metal contamination, blast residues, flux inclusions, and galvanic attack.

Magnesium, by volume, is two-thirds the weight of aluminum and one-quarter the weight of steel. It also has good damping capacity, giving it an edge over other metals in high-vibration environments. This chapter discusses the basic metallurgy, alloy designations, compositions, and mechanical properties of cast and wrought magnesium alloys. It also describes the processes used to produce magnesium parts, the causes and effects of corrosion, and the use of protective coatings and treatments.

This chapter describes the effect of temperature and strain rate on the mechanical properties and forming characteristics of aluminum and magnesium sheet materials. It discusses the key differences between isothermal and nonisothermal warm forming processes, the factors that affect heat transfer, die heating techniques, and press systems. It also discusses the effect of forming temperature, punch velocity, blank size, and other parameters on deep drawing processes, making use of both experimental and simulated data.

Magnesium occupies the highest anodic position on the galvanic series and can be subject to severe corrosion. The corrosion problem is due to the impurity elements iron, nickel, and copper. However, the use of higher-purity magnesium alloys has led to corrosion resistance approaching that of some of the competing aluminum casting alloys. This chapter begins with a general overview of magnesium metallurgy and alloy designations and moves on to discuss in detail the nominal compositions, mechanical properties, heat treatment, fabrication, and corrosion protection of magnesium casting alloys and wrought magnesium alloys. It also discusses the nominal compositions, properties, and applications of commercially pure zinc, zinc casting alloys, and wrought zinc alloys.

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.

This appendix contains tables listing the approximate composition of materials for the extrusion process. The materials covered are aluminum alloys, magnesium and magnesium alloys, copper and copper alloys, cobalt alloys, nickel and nickel alloys, iron alloys, steels, lead, tin, zinc alloys, molybdenum, niobium, tantalum, zirconium alloys, titanium, and titanium alloys.

This chapter describes the formability and forming characteristics of low-carbon sheet steels, coated sheet steels, stainless steels, and aluminum and magnesium alloys. It provides property data as well as flow stress curves for numerous grades of each material and explains how composition, microstructure, and processing methods influence forming behaviors.

This chapter describes important requirements for ferrous and nonferrous alloys used for gears. Wrought surface-hardening and through-hardening carbon and alloy steels are the most widely used of all gear materials and are emphasized in this chapter. The processing characteristics of gear steels and the bending fatigue strength and properties of carburized steels are reviewed. In addition to wrought steels, the chapter provides information on the other iron-base alloys that are used for gears, namely cast carbon and alloy steels, gray and ductile cast irons, powder metallurgy irons and steels, stainless steels, and tool steels. In terms of nonferrous alloys, the chapter addresses copper-base alloys, die cast aluminum alloys, zinc alloys, and magnesium alloys.

Precipitation hardening is used extensively to strengthen aluminum alloys, magnesium alloys, nickel-base superalloys, beryllium-copper alloys, and precipitation-hardening stainless steels. This chapter discusses two types of particle strengthening: precipitation hardening, which takes place during heat treatment; and true dispersion hardening, which can be achieved by mechanical alloying and powder metallurgy consolidation. It provides information on the three steps of precipitation hardening of aluminum alloys: solution heat treating, rapid quenching, and aging.

This appendix contains flow stress data (in the form of flow curves) obtained by viscous pressure bulge tests conducted on various grades of sheet steel as well as aluminum and magnesium alloys.

Aluminum casting alloy compositions parallel those of wrought alloys in many respects. However, because work hardening plays no significant role in the development of casting properties, the use and purposes of some alloying elements differ in casting alloys versus wrought alloys. This chapter provides information on specifications and widely used designation systems and alloy nomenclature for aluminum casting alloys. It describes the composition of seven basic families of aluminum casting alloys: aluminum-copper, aluminum-silicon-copper, aluminum-silicon, aluminum-silicon-magnesium, aluminum-magnesium, aluminum-zinc-magnesium, and aluminum-tin. The chapter discusses the effects of alloying elements on the properties of cast aluminum. It provides information on various alloys that are grouped with respect to their applications or major performance characteristics.

The hot-working process extrusion is used to produce semifinished products in the form of bar, strip, and solid sections, as well as tubes and hollow sections. The first part of this chapter describes the composition, properties, and applications of tin and lead extruded products with a deformation temperature range of 0 to 300 deg C and magnesium and aluminum extruded products with a working temperature range of 300 to 600 deg C. The second part focuses on copper alloy extruded products, extruded titanium alloy products, and extruded products in iron alloys with a working temperature range of 600 to 1300 deg C.

Nonferrous alloys are heat treated for a variety of reasons. Heat treating can reduce internal stresses, redistribute alloying elements, promote grain formation and growth, produce new phases, and alter surface chemistry. This chapter describes heat treatment processes and how nonferrous alloys respond to them. It provides information on aluminum, cobalt, copper, magnesium, nickel, and titanium alloys and their composition, microstructure, properties, and processing characteristics.

Engineers have many materials to choose from when dealing with weight-related design constraints. The list includes aluminum, beryllium, magnesium, and titanium alloys as well as engineering plastics, structural ceramics, and polymer-, metal-, and ceramic-matrix composites. This chapter provides a brief overview of these lightweight materials, discussing their primary advantages along with their properties, behaviors, and limitations.

This appendix provides a list of etch compositions and procedures that reveal the macrostructure of aluminum, beryllium, bismuth, antimony, cobalt, copper, lead, magnesium, nickel, tin, titanium, zinc, and their respective alloys as well as iron, steel, noble metals, refractory metals, silicon, zirconium, and hafnium.

Compared with other deformation processes used to produce semifinished products, the hot-working extrusion process has the advantage of applying pure compressive forces in all three force directions, enhancing workability. The available variations in the extrusion process enable a wide spectrum of materials to be extruded. This chapter focuses on the processes involved in the extrusion of semifinished products in various metals and their alloys, namely tin, lead, lead-base soft solders, tin-base soft solders, zinc, magnesium, aluminum, copper, titanium, zirconium, iron, nickel, and powder metals. It discusses their properties and applications as well as suitable equipment for extrusion. It further discusses the processes involved in the extrusion of semifinished products in exotic alloys and extrusion of semifinished products from metallic composite materials.

This chapter describes the properties and uses of aluminum, magnesium, titanium, and other nonferrous alloys. It also discusses the effect of cold working and the process of annealing, including recovery, recrystallization, and grain growth.

All materials are susceptible to corrosion or some form of environmental degradation. Although no single material is suitable for all applications, usually there are a variety of materials that will perform satisfactorily in a given environment. The intent of this chapter is to review the corrosion behavior of the major classes of metals and alloys as well as some nonmetallic materials, describe typical corrosion applications, and present some unique weaknesses of various types of materials. It also aims to point out some unique material characteristics that may be important in material selection, and discuss, where appropriate, the characteristic forms of corrosion that attack specific materials. The materials addressed in this chapter include carbon steels, weathering steels, and alloy steels; nickel, copper, aluminum, titanium, lead, magnesium, tin, zirconium, tantalum, niobium, and cobalt and their alloys; polymers; and other nonmetallic materials, including rubber, carbon and graphite, and woods.