Two-Component (Binary) Systems (Chapter 4) Flashcards
What is Gibbs phase rule?
f = c + n - @
What is the “f” in Gibbs phase rule?
Degree of freedom
What is the “c” in Gibbs phase rule?
The number of the system
What is the “n” in Gibbs phase rule?
The number of independent variables that change the system (P, T)
What is the “@” in Gibbs phase rule?
The number of phases
Tie line
The line connecting the two equilibrium phases at the same temperature
The lever principle
Determines the relative quantities of two phases co-existing along a tie line
Equilibrium crystallization vs Fractional crystallization
Eq = Crystals are always in equilibrium with the melt and the final composition is the same as the original composition
Frac = Crystals are not in equilibrium and they are separated from the melt. Final composition is different than the original composition.
What is a binary eutectic system?
The two components do not form solid solution but there is a low point on the liquidus (eutectic point)
What happens at the eutectic point?
The solidus and the liquidus coincide. All solid phases melt instantly. ** Melt composition **
True or False: Eutectic point = Te
True
Equilibrium crystallization creates what kind of texture?
Equigranular
Fractional crystallization creates what kind of texture?
Porphyritic (phenocrysts + groundmass)
What happens in a partially melting system?
The system moves in the opposite direction (upwards)
What happens during fractional partial melt?
It becomes a unary system (no melting occurs in between)
