This chapter summarizes the progress that has been made in the study of high-entropy alloy (HEA) systems and the process-structure-property relationships that define them. It describes the various ways HEAs can be strengthened and explains how alloying elements influence tensile and yield strength, fracture toughness, and fracture strength. It discusses the stages of plastic deformation in HEAs and the role of dislocations and twinning in the evolution of microstructure. It reviews some of the work that has been done on fatigue behaviors and the methods developed to assess fatigue performance. It discusses the influence of defects on fatigue life, the effect of temperature and grain size on fatigue-crack propagation, and the role of nanotwinning in crack-growth retardation. It describes the methods used to produce HEAs in bulk and powder form and to apply them as protective coatings and films. It also identifies potential applications based on properties such as strength, hardness, density, wear resistance, high-temperature stability, and biocompatibility.

This chapter, presented in a question-and-answer format, covers many practical aspects of high-entropy alloys (HEAs). It provides clear and concise answers to more than 50 questions, imparting knowledge on alloying elements, heat treatments, diffusion mechanisms, phase formation, lattice distortion, crystal and grain structures, structure-property relationships, microstructure control, and characterization methods. It likewise explains how to calculate the effect of strengthening processes on the mechanical properties of HEAs and offers insights on how to balance strength, ductility, and density for specific applications. It also provides information on twinning behaviors, stacking faults, elastic properties, coating and film deposition methods, manufacturing challenges, and the use of computational techniques for alloy design.

This chapter covers the practical aspects of machining, particularly for turning, milling, drilling, and grinding operations. It begins with a discussion on machinability and its impact on quality and cost. It then describes the dimensional and surface finish tolerances that can be achieved through conventional machining methods, the mechanics of chip formation, the factors that affect tool wear, the selection and use of cutting fluids, and the determination of machining parameters based on force and power requirements. It also includes information on nontraditional machining processes such as electrical discharge, abrasive jet, and hydrodynamic machining, laser and electron beam machining, ultrasonic impact grinding, and electrical discharge wire cutting.

This chapter discusses coating technologies that are applicable to beryllium, including physical and chemical vapor deposition, thermal evaporation, electroplating, sputtering, ion plating, and plasma arc spraying. It describes the advantages and disadvantages of each method and the effect of temperature, pressure, and other process variables on the microstructures and properties developed.

This chapter explains how the presence of intermediate phases affects the melting behavior of binary alloys and the transformations that occur under different rates of cooling. It begins by examining the phase diagrams of magnesium-lead and copper-zinc, noting some of the complexities associated with intermediate phases. It then discusses the difference between ordered and disordered phases and how they are accounted for on phase diagrams. It describes how the atoms in a disordered solution may arrange themselves into an ordered array, forming a superlattice in the process of cooling, and goes on to identify the most common superlattice structures and their corresponding alloy phases. It also discusses the factors that limit the formation of superlattices along with the kinetics of spinodal decomposition and its effect on microstructure development.

This chapter is a detailed account of various attributes related to mixing and testing of powder-binder feedstocks. Mixing parameters and their effects on feedstock properties is discussed. The attributes reviewed include mixture homogeneity, wetting, powder-binder ratio, feedstock density, elastic modulus, rheological behavior, particle size, formulation control, feedstock mixing, and feedstock properties. The chapter also provides information on the processes involved in feedstock preparation and testing.

Materials used in joining, whether solders, fluxes, or atmospheres, are becoming increasingly subjected to restrictions on the grounds of health, safety, and pollution concerns. These regulations can limit the choice of materials and processes that are deemed acceptable for industrial use. The chapter addresses this issue with a focus on soldering fluxes. The chapter also describes factors related to soldering under a protective atmosphere, provides information on chemical fluxes for soldering of various metals, and discusses the processes involved in fluxless soldering processes.