This chapter examines the microstructure of metallic components produced by casting and compares them with microstructures achieved by means of powder metallurgy. It shows how metals and alloys obtained by various processing routes differ in terms of grain size, secondary phases, oxide and carbide dispersions, porosity, dendritic formation, and properties such as hardness, toughness, tensile strength, and yield strength.

Phase diagrams serve as a map to the phases present in an alloy at different temperatures and compositions. They also help in assessing mechanical properties, selecting heat treat temperatures, warning of possible solidification problems, and identifying routes for creating desired microstructures. This chapter familiarizes readers with the information contained in binary phase diagrams and the methods used to extract it. It explains how thermocouple measurements are used to determine liquidus, solidus, and eutectic reaction lines, how differential scanning calorimetry shows where phase reactions occur, and how x-ray diffraction identifies the actual phases present. It demonstrates the use of tie lines for determining phase composition at different temperatures and the application of the level rule to calculate phase fractions. It also discusses the CALPHAD method and presents computed binary phase diagrams that account for the presence of inclusions, oxygen content, and secondary phases.

This appendix contains sample problems with worked solutions pertaining to the use of binary phase diagrams. The problems require the determination of favorable temperatures and compositions, the amount and composition of phases in an alloy at a given temperature, the amount of a certain phase in different steels, and the microstructure developed in different alloys.

This chapter describes the processes and alloys used in the casting of aluminum components, the advantages and disadvantages of the different shape-casting methods, and the major factors that influence alloy selection for shape-casting applications. An overview of the heat treatment of cast products is also included.

This chapter discusses the crystal structures of steel and cast iron, the iron-iron carbide equilibrium diagram, microconstituents or phases in the iron-iron carbide phase diagram, the iron-carbon carbide-silicon equilibrium diagram of cast irons, and the influence on microstructure by base elements and alloying elements. Graphitization, cooling rates, and heat treatment effects are covered. There also is discussion on inoculation benefits, flake graphite types and typical applications, evolution of cast iron types, ASTM specification A247 for graphite shapes, and selection of the best molding process. A large table lists typical material choices for various applications.

The casting engineer contributes to a successful component design by offering expertise in molding, core making, and material characteristics and by recommending the most suitable casting process to use to meet quality and cost targets. The casting engineer's responsibilities include recommending locator positioning; advising about lugs, hooks, or holes for casting handling through all processes; determining the choice of a parting plane and pouring orientation; designing cores for accurate positioning, suitable venting, and proper cleaning; guiding decisions about wall thicknesses and junctions; making suggestions about casting design to eliminate distortion; optimizing the gating design for slag-free metal; and establishing the feeding techniques to eliminate shrink porosity. This chapter provides the guidelines for these responsibilities. In addition, the guidelines for the use of chaplets and chills in cast iron castings; guidelines for drafts, machine stock, tolerances, and contraction or shrink rule; and guidelines for pattern layouts and nesting are also covered.

Ductile iron has far superior mechanical properties compared to gray iron as well as significantly improved castability and attractive cost savings compared to cast steel. This chapter begins with information on graphite morphology and matrix type. It then discusses the advantages and applications of ductile iron. Next, the effects of various factors on the grades, chemistry, matrix, and mechanical properties of ductile iron are covered. This is followed by a section detailing the ductile iron treatment methods and the quality control methods used. Guidelines for gating and feeder design are then provided. Further, the chapter addresses the technology of ductile iron castings, including the performance and geometric attributes, molding and core-making processes used, material grades, mechanical properties, and chemical compositions of a few applications. Finally, it describes ductile iron casting defects and presents practical cases of problem-solving.

Compacted graphite iron (GCI) is a cast iron grade that is engineered through graphite morphology modifications to achieve a combination of thermal and mechanical properties that are in between those of flake graphite iron and ductile iron. This chapter discusses the advantages of compacted graphite iron over gray iron and ductile iron. It presents examples of low- and high-frequency thermal cycling, both of which affect the thermal stresses that castings are exposed to during temperature fluctations. Information on optimum carbon and silicon ranges as well as mechanical property standards for CGI are provided. The chapter describes the critical factors that control CGI and discusses methods of CGI manufacturing.

The existence of austenite and ferrite, along with carbon alloying, is fundamental in the heat treatment of steel. In view of the importance of structure and its formation to heat treatment, this chapter describes the various microstructures that form in steels, the various factors that determine the formation of microstructures during heat treatment processing of steel, and some of the characteristic properties of each of the microstructures. The discussion also covers the constitution of iron during heat treatment and the phases of heat-treated steel with elaborated information on iron phase transformation, hysteresis in heating and cooling, ferrite and austenite as two crystal structures of solid iron, and the diffusion coefficient of carbon.

The decomposition of austenite, during controlled cooling or quenching, produces a wide variety of microstructures in response to such factors as steel composition, temperature of transformation, and cooling rate. This chapter provides a detailed discussion on the isothermal transformation and continuous cooling transformation diagrams that characterize the conditions that produce the various microstructures. It discusses the mechanism and process variables of quenching of steel, explaining the factors involved in the mechanism of quenching. In addition, the chapter provides information on the causes and characteristics of residual stresses, distortion, and quench cracking of steel.

This chapter introduces the key powder fabrication attributes to assist in the identification of the right powders for an application. First, it describes the characteristics of engineering powders such as particle size distribution, powder shape and packing density, surface area, powder flow and rheology, and chemical analysis. The chapter then describes the general categories of powder fabrication methods, namely mechanical comminution, electrochemical precipitation, thermochemical reaction, and phase change and atomization. It provides information on the two largest contributors to powder price, namely raw material cost and conversion cost. The applicability of various processes to specific material systems is mentioned throughout this chapter.

This chapter describes the metallurgy, composition, and properties of steels and other alloys. It provides information on the atomic structure of metals, the nature of alloy phases, and the mechanisms involved in phase transformations, including time-temperature effects and the role of diffusion, nucleation, and growth. It also discusses alloying, heat treating, and defect formation and briefly covers condenser tube materials.

Many of the structural characteristics of steel products are a result of changes that occur during solidification, particularly volume contractions and solute redistribution. This chapter discusses the solidification process and how it affects the quality and behaviors of steel. It explains how steel shrinks as it solidifies, causing issues such as pipe and voids, and how differences in the solubility of solid and liquid steel lead to compositional heterogeneities or segregation. It describes the dendritic nature of solidification, peritectic and eutectic reactions, microporosity, macro- and microsegregation, and hot cracking, as well as the effects of solidification and remelting on castings, ingots, and continuous cast products. It explains how to determine where defects originate in continuous casters and how to control alumina, sulfide, and nitride inclusions.

Heat treatment is the most common way of altering the mechanical, physical, and even chemical properties of steels. This chapter describes the changes that occur in carbon and low-alloy steels during conventional heat treatments. It explains how austenite decomposition largely defines the final microstructure, and how the associated phase transformations are driven by nucleation and growth processes. It describes diffusionless and diffusive growth mechanisms and provides detailed information on the properties, structure, and behaviors of the transformation products produced, namely martensite and bainite. It also discusses the formation of austenite, the control and measurement of austenitic grain size, the characteristics of ferritic microstructures, and the methods used to classify ferrite morphology.

This chapter discusses the effects of hot working on the structure and properties of steel. It explains how working steels at high temperatures promotes diffusion, which helps close cavities and pores, and how it changes the shape and distribution of segregates, offsetting their effect. It describes the effect of hot working on nonmetallic inclusions and the many properties influenced by them. It discusses the recrystallization mechanism by which hot working produces microstructural changes and explains how to control it by adjusting temperature, degree of reduction, and cooling rates. It describes special cases of segregation, including banding and why it occurs, and the application of closed die forging. The chapter also presents several examples of hot working defects, including forging laps, cracks, and overheated or burned steel.