Materials Science Flashcards

Which crystal defect is formed when an atom is missing from its lattice site?

Answer: Vacancy defect

A vacancy defect (Schottky defect in ionic crystals) occurs when an atom is missing from its normal lattice position.

What is the primary strengthening mechanism in cold-worked metals?

Answer: Dislocation density increase

Cold working increases dislocation density, causing dislocations to impede each other's motion and thereby strengthening the metal.

The elastic modulus of a material is best described as:

Answer: The ratio of stress to strain in the elastic region

Young's modulus (elastic modulus) is defined as the ratio of uniaxial stress to strain within the elastic (reversible) deformation range.

Which type of polymer chain arrangement leads to the highest crystallinity?

Answer: Isotactic

Isotactic polymers, where all substituents are on the same side of the backbone, pack most efficiently and achieve the highest degree of crystallinity.

In a eutectic binary alloy system, the eutectic reaction is best described as:

Answer: A single liquid transforming into two solids simultaneously

At the eutectic point, a single liquid phase transforms simultaneously into two distinct solid phases at a fixed temperature.

Which bonding type is primarily responsible for the high melting point of diamond?

Answer: Covalent bonding

Diamond's extremely high melting point results from its three-dimensional network of strong, directional covalent C–C bonds.

A material that exhibits a linear stress-strain curve up to fracture with no plastic region is classified as:

Answer: Brittle

Brittle materials fracture within the elastic region without significant plastic deformation, showing no yield point on the stress-strain curve.