Fundamental concepts of metals science Properties of metals Metallic crystal structures What is crystalline lattice? Atomic bonding in solids Lattice parameters Crystal systems Polymorphism of metals Anisotropy Imperfections in solids

Imperfections in solids Idealized solid and real crystalline solids What are imperfections in crystal structures? Classification of crystalline defects Point defects Linear defects Interfacial defects Volume imperfections Imperfections and strength of crystalline solids

Classification of imperfections in solids

Point defects Self-interstitial

Point defects

Linear defects Edge dislocation

Linear defects Screw dislocation

Linear defects Mixed dislocation

Linear defects Dislocations in a titanium alloy (transmission electron micrograph, 51,450 x)

Linear defects Strength depends on the dislocation density: 1 – idealized crystal, 2 – single crystals, 3 – annealed metals (polycrystalline solids), 4 – hardened metals

Interfacial defects Grain boundaries

Grain boundary acts as a barrier to dislocation motion Interfacial defects Grain boundary acts as a barrier to dislocation motion

Grain boundaries in iron are made visible by etching Interfacial defects Grain boundaries in iron are made visible by etching

Nonmetallic inclusions Volume, or bulk defects Nonmetallic inclusions

Nonmetallic inclusions Volume, or bulk defects Nonmetallic inclusions

Nonmetallic inclusions are the sites of crack formation Volume, or bulk defects Nonmetallic inclusions are the sites of crack formation