This chapter describes the mechanisms, characteristics, and prevention of intergranular and exfoliation corrosion in various aluminum alloys. It discusses susceptible alloys and recommended tempers and presents several examples of exfoliation in aircraft components. It also explains how the two forms of corrosion are related to stress-corrosion cracking.

Aluminum is protected by a barrier oxide film that, if damaged, reforms immediately in most environments. Despite this inherent corrosion resistance, there are conditions where aluminum alloys, like many materials, are subject to the effects of stress-corrosion cracking (SCC). This chapter describes those conditions, focusing initially on the effects of alloying elements and temper on solution potential and how it compares to other metals. It then addresses the issue of intergranular corrosion and its role in SCC. It explains how factors such as stress loads, grain structure, and environment determine whether or not stress-corrosion cracking develops in a susceptible alloy. It also provides stress-corrosion ratings for many alloys, tempers, and product forms and includes information on hydrogen-induced cracking.

Environmentally assisted cracking is a generic term that includes various cracking phenomena such as stress-corrosion cracking (SCC), corrosion fatigue cracking, and liquid-metal embrittlement. This chapter describes these cracking mechanisms beginning with SCC and the factors that influence its formation. It covers alloy selection and mitigation techniques and includes examples of SCC in aircraft components. The chapter also addresses corrosion fatigue, explaining how different environments and operating conditions affect crack propagation, fatigue strength, and fatigue life. It includes information on liquid-metal embrittlement as well.

This chapter provides basic engineering information on aluminum alloys with an emphasis on their use in applications where weight is a significant design factor. It discusses the advantages and limitations of various types of aluminum along with their compositions, designations, and achievable strengths. It explains how some alloys are hardened through solution strengthening and cold working, while others are strengthened by precipitation hardening. It also describes production and fabrication processes such as melting, casting, rolling, forging, forming, extruding, heat treating, and joining, and includes a section on the causes and effects of corrosion and how they are typically controlled.

This chapter describes the use of standardized tests to determine the susceptibility of aluminum alloys to specific forms of corrosion, including pitting, intergranular corrosion, filiform corrosion, exfoliation corrosion, and stress-corrosion cracking.

Aluminum is the second most widely used metal in the world. It is readily available, offers a wide range of properties, and can be shaped, coated, and joined using a variety of methods. This chapter discusses some of the key attributes of wrought and cast aluminum alloys and the classifications, designations, and grades of available product forms. It also explains how aluminum alloys are used in aerospace, automotive, rail, and marine applications as well as in building and construction, electrical products, manufacturing equipment, packaging, and consumer durables such as appliances and furniture.

This appendix contains composition limit data for wrought aluminum and aluminum alloys.

This article discusses the composition, structures, properties, and behaviors of aluminum alloys and explains how they correspond to specific alloying elements. It begins with an overview of the general characteristics of wrought and cast aluminum alloys, the four-digit classification system by which they are defined, and the applications for which they are suited. It then explains how primary alloying elements, second-phase constituents, and impurities affect yield strength, phase formation, and grain size and how they induce structural changes that help refine certain alloys. The article also explains how primary alloying elements affect corrosion and wear behaviors and how they influence fabrication processes such as forming, forging, welding, brazing, and soldering.

This chapter provides information and data on the fatigue and fracture properties of steel, aluminum, and titanium alloys. It explains how microstructure, grain size, inclusions, and other factors affect the fracture toughness and fatigue life of these materials and the extent to which they can be optimized. It also discusses the effect of metalworking and heat treatment, the influence of loading and operating conditions, and factors such as corrosion damage that can accelerate crack growth rates.