Chapter 10 phase transformations Flashcards
nucleation
nucleation, the initial process that occurs in the formation of a crystal from a solution, a liquid, or a vapor, in which a small number of ions, atoms, or molecules become arranged in a pattern characteristic of a crystalline solid, forming a site upon which additional particles are deposited as the crystal grows.
supercooling
and
superheating
Supercooling - A liquid cooled below its freezing point without the solid phase separating out is in a metastable supercooled state
Superheating - A liquid heating above its boiling point or a saturated vapor heated after all traces of liquid have evaporated is superheated.
phase transformations
10 1 phase trans
homogeneous vs heterogeneous
A phase is any part of a sample that has a uniform composition and properties.
homogeneous mixture - a pure substance consists of a single phase.
heterogeneous mixture - consists of two or more phases. When oil and water are combined, they do not mix evenly, but instead, form two separate layers.
in solidification, what are the two nucleation types
10 2 solidification
Homogeneous Nucleation & Energy Effects
10 3 Homogeneous Nucleation
Solidification formula
Solidification is the process of transformation of a liquid to a solid.
10 4 solid formula
rate of phase transformation
10 5 rate of phase
what is the Avrami equation
The Avrami equation describes how solids transform from one phase to another at constant temperature.
It can specifically describe the kinetics of crystallisation, can be applied generally to other changes of phase in materials, like chemical reaction rates, and can even be meaningful in analyses of ecological systems.
rate of phase transformation
graph
10 6 rate of phase graph
temperature dependence of transformation rate
10 7 temp dependance
Transformations & Undercooling
Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid.
10 8 undercooling
define pearlite
Pearlite is essentially a composite microstructure consisting of cementite layers (which are hard and brittle) sandwiched between ferrite layers (which are soft and ductile).
The Fe-Fe3C Eutectoid Transformation
10 9 fe fe3
