Abstract

Operations performed on consolidated metals and alloys are referred to as metal treatments and are usually mechanical or thermal. Mechanical treatments involve changes in shape by forming or machining. Forming entails plastic deformation, which changes the metal microstructure. Plastic deformation can be imparted by hot or cold working. The amount of deformation that can be tolerated is established by workability testing. Primary forming operations convert cast ingots into wrought blooms, billets, bars, or slabs; secondary forming operations produce shapes. Machinability, which indicates the ease or difficulty with which a material can be machined to a given shape, is influenced by metallurgical factors in addition to machining parameters.

In thermal treatments, heat is applied to alter structures and properties, as in annealing or in precipitation hardening, whereby substantial increases in strength can be achieved. Heat treatment of some metals such as steels involves an allotropic transformation. Surface treatments such as shot peening are sometimes used to enhance surface performance. Thermomechanical processing may also be employed. The metals treatment industry is continuously evaluating worker exposure and improving efficiency of treatment processes. Powder metallurgical processes for superalloys are described.