This chapter discusses the advantages, limitations, and applications of various aluminum casting processes, namely green sand casting process, air set or no-bake molding process, vacuum molding process, evaporative foam casting process, and die casting process. The processes covered also include gravity permanent molding, low-pressure permanent molding, counter pressure, squeeze casting, investment casting, rapid prototype casting, cast forge hybrid, and semisolid metal processes.

This chapter is a collection of tables listing: cast alloy designations of Aluminum Association, along with their general applications; the chemical compositions of the frequently used alloys for gravity permanent molds, low-pressure permanent molds, squeeze castings, and die castings; the typical tensile properties of die cast alloys; and the designations of different heat treatments and their description. The tables also list the temperatures and times of typical heat treatment cycles for different permanent mold cast alloys; typical components in sand, gravity, and low-pressure permanent mold castings and die castings, the functional requirements of each process, and the corresponding suitable alloys and heat treatments; and alloys that are high vacuum die cast for structural castings. The chapter also presents examples of photomicrographs of some alloys cast by different processes.

Almost all metals and alloys are produced from liquids by solidification. For both castings and wrought products, the solidification process has a major influence on both the microstructure and mechanical properties of the final product. This chapter discusses the three zones that a metal cast into a mold can have: a chill zone, a zone containing columnar grains, and a center-equiaxed grain zone. Since the way in which alloys partition on freezing, it follows that all castings are segregated to different categories. The different types of segregation discussed include normal, gravity, micro, and inverse. The chapter also provides information on grain refinement and secondary dendrite arm spacing and porosity and shrinkage in castings. It concludes with a brief overview of six of the most important casting processes in industries: sand casting, plaster mold casting, evaporative pattern casting, investment casting, permanent mold casting, and die casting.

This chapter provides information on comparative attributes of sand molds and metal molds for aluminum casting. The cooling rates and microstructures obtained with each mold type are discussed. In addition, the chapter explains why sand castings work successfully in certain applications.

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.

This chapter covers the practices and procedures used for shape casting metals and alloys. It begins with a review of the factors that influence solidification and contribute to the formation of casting defects. It then describes basic melting methods, including induction, cupola, crucible, and vacuum melting, and common casting techniques such as sand casting, plaster and shell casting, evaporative pattern casting, investment casting, permanent mold casting, cold and hot chamber die casting, squeeze casting, semisolid metal processing, and centrifugal casting.

This chapter is an atlas of microstructures observed in AlSi7Mg, AlSi11, and Al21CuNiMg modified with either eutectic (strontium, sodium) or hypereutectic (phosphorus) silicon crystals. The microstructure images reveal the as-cast state of gravity castings made in sand and metal molds, before and after modification. The chapter also provides composition data and includes callouts identifying various phase constituents in the interdendritic eutectic microstructure.

This chapter begins with information on the historical development of aluminum alloy castings. It then covers the basic factors involved in the selection of a casting process. This is followed by sections describing the various categories of casting processes and their variants: expendable mold gravity-feed casting, nonexpendable (permanent) mold gravity feed casting, and pressure die casting. Next, the chapter describes the technologies used to produce premium engineered castings and when such castings may be relevant. The chapter concludes with descriptions of other process technologies used with castings, including metallurgical bonding, metal-matrix composites, and hot isostatic pressing.

This chapter begins with information on the historical development of aluminum alloy castings. It then covers the basic factors involved in the selection of a casting process. This is followed by sections describing the various categories of casting processes and their variants: expendable mold gravity-feed casting, nonexpendable (permanent) mold gravity feed casting, and pressure die casting. Next, the chapter describes the technologies used to produce premium engineered castings and when such castings may be relevant. The chapter concludes with descriptions of other process technologies used with castings, including metallurgical bonding, metal-matrix composites, and hot isostatic pressing.

Casting is one of the most economical manufacturing processes for providing shape to components of machinery and is used in a wide range of industries. This chapter is a brief account of the advantages, applications, limitations, and market growth of aluminum casting. It also provides information on the process of conversion of steel and iron parts to aluminum.

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.

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.

This chapter describes cast steel features that may be identified or attributed to component failure during heat treatment or subsequent processing or service, namely porosity (generated by the presence of gas as well as by shrinkage pores), decarburization, cold joint, and inclusions.

Titanium castings are used in a wide range of aerospace, chemical process, marine, biomedical, and automotive applications. This chapter provides an overview of titanium casting and associated processes and how they compare with other manufacturing methods. It also discusses the role heat treating and its effect on the tensile properties of different titanium alloys.

The commercial relevance of cast irons is best understood in the context of the iron-carbon phase diagram, where their composition places them near the eutectic point, which sheds light on why they melt at lower temperatures than steel and why they can be cast into more intricate shapes. This chapter examines these unique properties and how they are derived. It begins by describing the basic metallurgy of cast iron, focusing on the eutectic reaction. It explains how to control the reaction and thus properties of cast iron by overcooling and inoculation. The chapter also discusses composition, microstructure, heat treatments, and the classification and casting characteristics of white, gray, ductile, malleable, compacted graphite, and special cast irons.

This chapter first introduces the various factors that may alter the physical and mechanical properties of aluminum castings that are addressed in the other chapters in the book. Then, it presents the historical development of aluminum castings, followed by a discussion on the advantages and limitations of aluminum castings. Next, the chapter describes the major trends that are influencing the increased use of aluminum castings. Finally, it introduces the considerations involved in the selection of an appropriate aluminum alloy and casting process for a given application.

This chapter first introduces the various factors that may alter the physical and mechanical properties of aluminum castings that are addressed in the other chapters in the book. Then, it presents the historical development of aluminum castings, followed by a discussion on the advantages and limitations of aluminum castings. Next, the chapter describes the major trends that are influencing the increased use of aluminum castings. Finally, it introduces the considerations involved in the selection of an appropriate aluminum alloy and casting process for a given application.

This chapter serves as a study and guide on the main phase constituents of cast aluminum-silicon alloys, alpha-Al solid solution and Si crystals. The first section focuses on the structure of Al-Si castings in the as-cast state, covering the morphology of the alpha-Al solid solution grains and the process by which they form. It describes how cooling rates, temperature gradients, and local concentrations influence the topology of the crystallization front, and how they play a role in determining the morphology and dispersion degree of the grains observed in cross sections of cast parts. It also describes the mechanism behind dendritic grain crystallization and how factors such as surface tension, capillary length, and lattice symmetry affect dendritic arm size and spacing. The section that follows examines the morphology of the silicon crystals that form in aluminum-silicon castings and its effect on properties and processing characteristics. It discusses the faceted nature of primary Si crystals and the modification techniques used to optimize their shape. It also describes the morphology of the (alpha-Al + Si) eutectic, which can be lamellar or rodlike in shape, and explains how it can be modified through temperature control or alloy additions to improve properties such as tensile strength and plasticity and reduce shrinkage.

This chapter discusses the various factors pertinent to gravity permanent mold (GPM) castings, along with their advantages, limitations, and significance. The discussion covers the geometric factors, process and manufacturing elements, gating practices, and feeding principles of and pouring systems in GPM. The influences of mold coatings on GPM and low pressure permanent mold castings are described. The chapter also discusses various processes involved in the engineering of core boxes and cooling of GPM for casting integrity and cycle time control. It provides information on some of the processes involved in post-casting operations, namely de-coring and de-gating. The key design aspects for consideration in water quenching during the T6 heat treatment are reviewed. The chapter also provides information on two critical cycle events important in engineering at the manufacturing facility: tipper cycle planning and table or cell cycle planning.

The inspection of castings normally involves checking for shape and dimensions, coupled with aided and unaided visual inspection for external discontinuities and surface quality. This chapter discusses methods for determining surface quality, internal discontinuities, and dimensional inspection. Casting defects including porosity, oxide films, inclusions, hot tears, metal penetration, and surface defects are reviewed. Liquid penetrant inspection, magnetic particle inspection, eddy current inspection, radiographic inspection, ultrasonic inspection, and leak testing for castings are discussed. The chapter provides information on the procedures involved in the inspection of castings that are limited to visual and dimensional inspections, weight testing, and hardness testing. It also discusses the use of computer equipment in foundry inspection operations.