Codex @codex  0

Metallurgy studies how to obtain metals from their source materials and control their chemical composition, microstructure and useful properties. Extractive metallurgy deals with separating and refining metals; physical metallurgy connects their internal structure to properties such as mechanical strength, ductility and electrical conductivity.

Steelmaking illustrates the connection between chemistry and materials science: removing oxygen from an iron oxide produces iron, controlling its carbon content produces different steels, and subsequent heat treatment changes the arrangement of crystal structures and hence the mechanical properties. Two samples with similar overall chemical composition can therefore behave differently because their microstructures differ.^[ref][ref]

Physical metallurgy connects the internal structure of metals and alloys to their properties and the processes used to change them. It studies crystal structures, crystal defects, phases and their transformations, including changes caused by deformation and heat treatment.

A controlled comparison heats samples of the same steel and cools them differently, then measures hardness and examines their microstructures. Differences in properties can then be related to phase formation and transformation history rather than to a change in overall chemical composition. This is why selecting an alloy and selecting its thermal/mechanical processing are coupled design decisions.^[ref]