Engineering Materials Final Vocabulary

Weak Force

Forces of interaction between atoms with unstable nuclei. To attain stability, an unstable atomic nucleus loses energy by emitting a radiation (process is known as radioactive decay of atom). In this process, a neutron in the nucleus changes into a proton and an electron. Responsible for the radioactive decay of atom.

Substitutional Solid Solution

In which the solute (impurities) atoms substitute the hosting atoms.

Grain Boundary

Separates two grains or crystals having different crystallographic orientations in polycrystalline materials.

Liquidus Line

Line that separates the liquid phase from the solid-liquid mixture in a phase diagram.

Solidus Line

Line that separates the solid phase from the solid-liquid mixture in a phase diagram.

Slip Plane

Crystallographic plane along which the dislocation line moves.

Isothermal transformation

Phase transformation process in which the temperature of the alloy is held constant throughout the duration of the transformation.

Bainite Structure

Non-lamellar structure consisting of a-ferrite matrix and elongated particles (needles) of cementite (Fe3C).

Elasticity

Material behavior, where the material recovers its original shape and dimensions upon removing the applied load (stress).

Yield Strength

Stress value at the initiation of the plastic zone. At the yield point the material starts to experience plastic deformation.

Solid Solution

New solid that is formed due to the insertion of impurities inside the structure of the hosting material. The crystal structure of the hosting material is maintained, and no new structures are formed.

Dislocation

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

Phase Transformation

A change in the phase of the material upon altering (or changing) temperature or pressure.

Interdiffusion (Impurity Diffusion)

Process where atoms of one metal diffuse into another.

Self-diffusion

Occurs for pure metals where all atoms of the same type migrate from a region of a high concentration to another region of low concentration of the metal.

Hardness

Material ability to withstand the penetration of other materials to its surface. Can also be defined as the material resistance to being scratched.

Anisotropic Material

Material whose properties along one direction are different from those along the transverse direction.

Engineering Stress

Force divided by the original area that is subjected to the force.

Ductility

Material ability to deform with no fracture.

Fatigue Strength

Stress level at which failure will occur at a specified number of cycles.

Material Processing

To develop or synthesize the material with a certain structure and properties.

Electromagnetic Force

The attraction force between the nucleus (positive charge) and the electrons (negative charge) around it, keeping the electrons traveling in a continuous and definite orbit.

Strong Force

The force that opposes the electromagnetic force of repulsion between protons. Keeps protons together to form the nucleus.

Gravity Force

Weakest of the four forces within the atom. Holds the electrons around the nucleus, helping the electromagnetic forces in holding the atom as one part.

Crystal

Composition of atoms, ions, or molecules, which are arranged in a periodic three-dimensional pattern over large atomic distances.

Unit Cell

Basic structural unit or building block of the crystal structure, and it is chosen to represent the symmetry of the crystal structure such that, when it is repeated, the overall crystal structure is formed.

Coordination Number

Property of a crystal structure, which is the number of nearest-neighbor (or touching) atoms of an atom.

Atomic Packing Factor (APF)

Sum of the volumes of all atoms within a unit cell divided by the overall unit cell volume.

Interstitial Solid Solution

In which the solute (impurity) atoms are inserted between the atomic sites.

Burgers Vector

Represents the magnitude and direction of the lattice distortion resulting from a dislocation in the crystal lattice.

Phase Diagram

Graphical representation of the relationships among temperature (and sometimes pressure), composition, and quantities of the phases of an alloy.

Solvus Line

Line of the solid solubility limit, separating one solid phase from the solid mixture with another solid phase in a phase diagram.

Equilibrium Cooling

Process in which the cooling of an alloy occurs very slowly, wherein phase equilibrium is continuously maintained.

Natural Polymers

Organic materials derived from plants and animals including wood, rubber, cotton, wool, leather, silk, proteins, enzymes, starches, and cellulose.

Synthetic Polymers

Materials that are synthesized from small organic molecules, which include plastics, rubbers, and fiber materials.

Twin Boundary

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 of the atoms on the other side.

Diffusion

Process of the transfer (or transport) of mass (such as atoms) either within a specific material or from one to another material.

Vacancy Diffusion

Atom leaves a normal lattice position to an adjacent vacant lattice site or vacancy.

Interstitial Diffusion

Atom migrates from an interstitial position to a neighboring one that is empty.

Slip

Process by which plastic deformation is produced by dislocation motion.

Slip Direction

Direction of the dislocation line movement.

Anelastic Deformation

Non-permanent, time-dependent deformation, in which the material takes some time to recover the developed strain.

Isotropic Material

Material whose properties are the same in all directions.

Solubility Limit

Maximum concentration of solute (impurity) atoms that may dissolve in the solvent (host substance) to form a solid solution at some specific temperature.

Phase

Homogenous portion of a system that has uniform physical and chemical characteristics.

Nonequilibrium Cooling

Process in which the cooling of an alloy occurs at rates higher than the diffusional rates required for the compositional readjustments of the alloy. Results in gradient compositions for one or more of the phases.

Coarse Pearlite

Pearlite with thick layers of both the a-ferrite and Fe3C phases. Obtained by isothermal transformation at temperatures just below the eutectoid temperature.

Fine Pearlite

Pearlite with thin layers of both the a-ferrite and Fe3C phases. Obtained by the isothermal transformation in the vicinity of 540 C.

Pearlite Structure

Obtained by cooling (at relatively slow) of y-austenite to a temperature below the eutectoid temperature.

Spheroidite Structure

Microstructure of steel consisting of a-ferrite matrix and spherical-like particles of cementite (Fe3C).

Fracture

Material failure mode in which the solid part is separated into two or more pieces due to an applied stress that is static (constant or slowly varying with time) and at low temperatures.

Slip System

Combination of the slip plane and slip direction associated with a dislocation motion.

Elastic Deformation

Non-permanent deformation that is totally recovered upon removing the applied load (stress).

Plastic Deformation

Permanent deformation after the removal of the applied load (stress).

Plasticity

Material behavior, where the material does not recover its original shape or dimensions upon removing the applied load (stress), exhibiting a permanent deformation.

Engineering Strain

Material deformation in reference to its original shape or dimensions.

True Stress

Force divided by the instantaneous area that is subjected to the force.

True Strain

Material deformation in reference to its instantaneous shape or dimensions.

Young's Modulus

Measure of the material elasticity. The slope of the linear stress-strain function within the elastic region.

Proportional Limit

The stress at the end of the proportional (linear) stress-strain line.

Tensile Strength

Maximum value of stress that the material can withstand before fracture.

Resilience

Capacity of the material to absorb and store energy when it is deformed elastically.

Modulus of Resilience

Strain energy per unit volume required to stress the material from a zero-stress state up to yielding.

Ductile Material

Material that experiences large plastic deformation before fracture.

Brittle Material

Material that experiences very little plastic deformation (or no plastic deformation) before fracture.

Fatigue

Form (mode) of material failure that occurs in materials subjected to dynamic and fluctuating stresses (cyclic stresses).

Fatigue/Endurance Limit

Stress below which fatigue failure will not occur.

Fatigue Life

Number of cycles required to cause fatigue failure of the material when subjected to a specific stress level.