Annealing Raising the temperature of a material so that recrystallization and grain growth begin, and then permitting the material’s temperature to slowly decrease back to room temperature.

Brittle Fracture A fracture of the material where layers of atoms break apart completely during stress without the presence of plastic deformation.

Brittleness The measurement of how prone a material is to result in a brittle fracture when placed under stress.

Compressive Stress Stress that involves the squeezing or compression of a material.

Dislocation The appearance of a defect in a crystal which results from an incomplete sheet of atoms.

Ductile A quality which describes the capability of a material to undergo extreme amounts of plastic deformation before fracturing.

Ductile Fracture Layers of atoms break apart completely due to stress resulting from plastic deformation that causes the material to fracture.

Elastic Deformation A change in the shape of a material from its original shape caused by stress which does not result in the permanent rearrangement of the atoms within the material. In other words, when the stress is removed the material returns to its original shape.

Grain An individual, small crystallite which is a part of a larger polycrystalline material made up of numerous grains.

Grain boundary a thin layer of atoms located in between two separate crystals or grains of a polycrystalline material.

Hardness The capacity of a substance to be scratched or penetrated by another.

Metal Fatigue when blemishes in a material propagate as tears and result in a fracture

Metallic bonds Bonding that occurs in metals. Electrons are shared among atoms and the atoms are bound together because of this sharing.

Plastic deformation Atoms in a material are permanently rearranged due to a stress induced change. Removal of stress does not result in a restoration of the original shape.

Polycrystalline Made of many individual crystallites.

Quench rapid cooling of a material from a high temperature quickly, so that the material cannot assume its normal low temperature state.

Shear strain A material’s angle of bend resulting from a shear stress.

Shear stress A stress in which the top and bottom of a material are pushed in opposite horizontal directions.

Slip In a crystal, one street of atoms slides across another sheet of atoms resulting in a plastic deformation.

Strain the change in a materials length divided by its original length. It is caused by an applied stress.

Stress Force exerted on a material divided by the cross-sectional area over which the force is exerted.

Supersaturated Containing more of a substance than is normally possible.

Surface tension An inward tension acting to make a surface as small as possible. It appears when a surface has extra potential energy.

Temper to relieve trapped stresses by baking a material at moderate temperatures.

Tensile strength Amount of tensile stress a material can handle before developing a fracture.

Tensile stress Stress due to tension.

Toughness Measure of mechanical energy that can be withstood by a material before a fracture develops.

Work hardening Hardening that occurs when extensive manipulation reduces the size of grains in a polycrystalline material.

Yield strength Amount of stress necessary to cause plastic deformation.