What determines a metal's mechanical properties, such as strength and ductility?

The crystal structure of a metal is fundamental to its mechanical properties, including strength and ductility. Metals can exist in different crystalline forms, such as body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close-packed (HCP). Each of these structures influences how atoms are arranged in the metal, which in turn affects how the metal deforms under stress.

In a crystalline structure, the arrangement of atoms, the types of slip systems available, and the way dislocations move have a direct impact on properties like yield strength and the ability to stretch (ductility). For example, FCC structures generally provide higher ductility because they have more slip systems available for dislocation motion compared to BCC structures, which can be more brittle at room temperature.

While chemical composition, temperature during processing, and impurities do affect a metal's properties, the crystal structure is paramount as it establishes the fundamental framework through which these properties are expressed. The way the atoms are packed influences how dislocations move, how external stresses are distributed, and ultimately how the material will behave under mechanical loads. Therefore, the crystal structure plays a critical role in determining the overall mechanical characteristics of metals.