Chapter 4 Terms

Imperfections

various defects within crystalline materials

Crystalline defect

a lattice irregularity having one or more of its dimensions on the order of an atomic diameter.

Point defects

defects associated with one or two atomic positions.

Vacancy

one normally occupied site but from which an atom is missing.

self-interstitial

an atom from the crystal that is crowded into a small void space that under ordinary circumstances is not occupied.

Alloys

where impurity atoms have been added intentionally to impart specific characteristics to the material.

Solid solution

The addition of impurity atoms to a metal

Solvent

the element or compound that is present in the greatest amount; on occasion, solvent atoms are also called host atoms.

Solute

an element or compound present in a minor concentration.

dislocation

a linear or one-dimensional defect around which some of the atoms are misaligned.

Edge dislocation

a linear defect that centers on the line that is defined along the end of the extra half-plane of atoms.

Screw dislocation

Formed by a shear stress that is applied to produce the distortion.

Interfacial defects

boundaries that have two dimensions and normally separate regions of the materials that have different crystal structures and/or crystallographic orientations

External surface

along which the crystal structure terminates.

Phase boundaries

multiphase materials in which a different phase exists on each side of the boundary.

Twin boundary

a special type of grain boundary across which there is a specific mirror lattice symmetry; that is, atoms on one side of the boundary are located in mirror-image positions to those of the atoms on the other side.

Grain boundary

the boundary separating two small grains or crystals having different crystallographic orientations in polycrystalline materials.