nonuniformity in deformation affects the microstructure and the properties of the forged disk. The solution to this problem is to control the speed of the forging operation, thus minimizing the contact time of the workpiece and dies and the temperature loss at the workpiece surface. The end result is uniform deformation and uniform microstructure and properties in the forged part.

The identification of process components provides a useful overview. However, several hundred individual unit manufacturing processes are commercially used in manufacturing operations. In order to discuss these processes in more detail, it is necessary to classify them using some common features. Many such classifications or taxonomies have been presented in the relevant technical literature. The taxonomy chosen for this study emphasizes the physical process by which the configuration or structure of a material is changed. The subsequent discussion of unit processes will be organized according to this taxonomy. Five families of physical processes make up this taxonomy:

• Mass-change processes remove or add material by mechanical, electrical, or chemical means. Included in this family are the traditional processes of plating, machining, and grinding, as well as nontraditional removal processes such as electrodischarge and electrochemical machining.
• Phase-change processes produce a solid part from material originally in the liquid or vapor phase. The casting of metals, infiltration of composites, and injection molding of polymers represent this family. (Phase changes in the solid state are considered to belong to the structure-change process family.)
• Structure-change processes alter the microstructure of a workpiece, either throughout its bulk or in a localized area, such as its surface. Heat treatment and surface hardening are commercial processes representative of this family. Solid-state phase changes are considered part of this family.
• Deformation processes alter the shape of a solid workpiece without changing its mass or composition. Classical metalworking processes of rolling and forging fall into this category, as do the sheet-forming processes of deep drawing and ironing.
• Consolidation processes combine materials such as particles, filaments, or solid sections to form a part or component. Powder metallurgy, ceramic molding, and polymer-matrix composite pressing are examples of consolidation processes. Joining processes, such as welding and brazing, also belong to this process family.