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In Cigar shape diagram there are three different regions: 1. Liquid (single phase). 2. Liquid + solid (double phase). 3.
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Phase diagrams 0.44 wt% of carbon in Fe microstructure of a lead–tin alloy of eutectic composition
A phase may be defined as a homogeneous portion of a system that has uniform physical and chemical characteristics What is a phase?
The Gibbs Phase Rule This rule represents a criterion for the number of phases that will coexist within a system at equilibrium. C – # of components (material that is single phase; has specific stoichiometry; and has a defined melting/evaporation point) N – # of variable thermodynamic parameter (Temp, Pressure, Electric & Magnetic Field) P max
Gibbs Phase Rule – example Phase Diagram of Water C = 1 N = 1 (fixed pressure or fixed temperature) P = 2 1 atm. boiling sublimation melting fixed pressure ( 1 atm) solid liquid vapor 0 0 C 100 0 C fixed pressure (0.0060373atm=611.73 Pa) Ice Ih vapor 0.01 0 C fixed temperature (0.01 oC) vapor liquid solid 611.73 Pa 10 (^9) Pa
Full solubility (Cigar shape diagram) Partially solubility (eutectic diagram)
Full Solubility (Cigar shaped diagram)
A copper–nickel alloy of composition 35 wt% Ni – 65 wt% Cu is slowly cooled from 1300 oC (a)At what temperature does the first solid phase form?
You start to heat solution of 60 wt% of Cr 2 O 3 from room temperature up to 2200 oC a)What is the melting Temp of pure? Al 2 O 3 and of pure Cr 2 O 3?
W 100 44 56 %
Partially solubility (eutectic diagram) Single phase Double phase Three phases
Microstructure obtained with different compositions
Primary α eutectic α
You start with 10 kg solution of 10 wt% Sn - 90 wt% Pb at 200 oC a)How many phases do you have?
Complex Diagrams