MS&E #10 Phase transformations
22 flashcards · Physics · by Kristóf Nagy
tempered martensite
Martensite that has been partially transformed by heating to relieve internal stresses and improve toughness.
thermally activated
A process requiring an input of thermal energy to overcome an energy barrier and initiate a reaction or transformation.
growth (phase particle)
The expansion of a nucleus into a growing particle during nucleation and growth.
free energy
The amount of energy available to do useful work. In metallurgy, it often refers to the difference in energy between two phases.
transformation diagram
A graphical representation of the isothermal transformation behavior of a steel, depicting the start and finish times of various transformations.
kinetics
The study of the rates of reactions and processes. In metallurgy, it often refers to the rates of phase transformations.
isothermal transformation
A heat treatment process involving holding a steel at a constant temperature for a period of time to promote transformation.
nucleation
The initial stage of phase transformation, where a small nucleus of the new phase forms within the old phase.
continuous cooling
A heat treatment process involving controlled cooling from the austenitizing temperature at a selected rate.
phase transformation
A change in the crystal structure of a material, often accompanied by a change in properties.
plain carbon steel
A steel that contains only carbon and iron, with no other alloying elements.
diagram
A graphical representation of the isothermal transformation behavior of a steel, depicting the start and finish times of various transformations.
transformation rate
The rate at which a phase transformation occurs. It is often expressed as the partial derivative of the extent of transformation with respect to time.
supercooling
Cooling a liquid or solid below its equilibrium temperature without it transforming into a more stable phase.
superheating
Heating a substance above its equilibrium temperature without it vaporizing.
spheroidite
A microstructure that forms during prolonged heating of a eutectoid steel. It is composed of spherical inclusions of cementite in a matrix of ferrite.
martensite
A microstructure that forms during rapid cooling or quenching of austenite in steel. It is a supersaturated solid solution of carbon in alpha ferrite with a tetragonal crystal lattice.
bainite
A microstructure that forms during the isothermal transformation of austenite in steel. Bainite is composed of thin platelets of alpha ferrite and iron carbides arranged in a characteristic pattern.
coarse pearlite
A microstructure that forms during the slow cooling of hypereutectoid steels. It is composed of alternating layers of ferrite and cementite, with the cementite layers being relatively thick compared to fine pearlite.
athermal transformation
A transformation that is independent of temperature and time, meaning that the transformation starts and completes at the same temperature regardless of how quickly or slowly the transformation occurs.
fine pearlite
A microstructure that forms during the slow cooling of hypoeutectoid steels. It is composed of alternating layers of ferrite and cementite, with the cementite layers being relatively thin compared to coarse pearlite.
alloy steel
A steel that contains significant quantities of elements other than carbon, such as nickel, chromium, or molybdenum, added to improve the steel's properties.