Chapter 11: Applications and Processing of Metal Alloys

Steel compositions are organized by carbon content into distinct categories including low-carbon, medium-carbon, and high-carbon variants, each exhibiting different combinations of strength and ductility that directly correlate to their carbon concentration. The chapter explains how alloying elements and thermal processing modify steel properties such as hardness, corrosion resistance, and the ability to harden during quenching, a characteristic known as hardenability. Stainless steels are further subdivided into ferritic, austenitic, and martensitic microstructural classes, while tool steels are highlighted for their exceptional hardness and resistance to wear in cutting and stamping applications. Cast iron variants including gray, ductile, white, malleable, and compacted graphite types are discussed through their graphite morphologies, which fundamentally determine their mechanical behavior. The chapter then transitions to nonferrous alloy systems encompassing copper-based materials such as brasses and bronzes, lightweight aluminum alloys including those strengthened by lithium, magnesium alloys for weight-critical structures, and titanium alloys available in alpha, beta, and alpha-beta phases for demanding aerospace and biomedical environments. Additional coverage includes refractory metals that maintain strength at extreme temperatures, nickel-based and cobalt-based superalloys engineered for turbine engines, and noble metals prized for chemical stability. The fabrication methods section explores forming operations such as forging, rolling, extrusion, and drawing that plastically deform metals into useful shapes, alongside casting techniques including sand casting, investment casting, die casting, and continuous casting for producing geometrically complex components. Powder metallurgy and additive manufacturing technologies are presented as modern approaches for precision manufacturing and design flexibility. The thermal processing section details annealing variants such as process annealing, stress relief, normalizing, and spheroidizing that restore ductility or refine grain structures. Hardenability assessment through the Jominy end-quench test illustrates how steel composition and part geometry influence quenching effectiveness. Precipitation hardening mechanisms in aluminum-copper systems demonstrate how controlled aging creates high-strength materials through microscopic strengthening phases. The chapter concludes by illustrating how alloy selection, processing methods, and thermal treatment strategies integrate to optimize material properties for diverse applications ranging from structural infrastructure to aerospace components and medical devices.