Introduction to Phase Diagrams

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Introduction to Phase Diagrams
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Phase Diagrams
Apollo 11 Metal-sulfide Particle
Gibeon Iron Meteorite
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Components and PhasesP F C 2
Components The elements or compounds
which are mixed initially (e.g., Al and
Cu) Phases The physically and
chemically distinct material regions that
result (e.g., a and b).
Aluminum- Copper Alloy
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Phase Diagrams
Tell us about phases as function of T, Co, P.
For this course --binary systems just
2 components. --independent variables T and
Co (P 1 atm).
Phase Diagram for Cu-Ni system
Binary Isomorphous System
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Phase Diagrams and Types of Phases
Rule 1 If we know T and Co, then we know
--the and types of phases present.
Examples
Cu-Ni phase diagram
Adapted from Fig. 9.2(a), Callister 6e. (Fig.
9.2(a) is adapted from Phase Diagrams of Binary
Nickel Alloys, P. Nash (Ed.), ASM International,
Materials Park, OH, 1991).
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Phase Diagrams Composition of Phases
Rule 2 If we know T and Co, then we know
--the composition of each phase.
Cu-Ni system
Examples
Adapted from Fig. 9.2(b), Callister 6e. (Fig.
9.2(b) is adapted from Phase Diagrams of Binary
Nickel Alloys, P. Nash (Ed.), ASM International,
Materials Park, OH, 1991.)
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Phase Composition
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Phase Diagrams Weight Fractions of Phases
Rule 3 If we know T and Co, then we know
--the amount of each phase (given in wt).
Cu-Ni system
Examples
27wt
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Phase Diagrams Weight Fractions of Phases
If we know T and Co, then we know
--the amount of each phase (given in wt).
Cu-Ni system
Examples
27wt
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Example Cooling in a Cu-Ni Binary
Consider Co 35wtNi.
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Cored versus Equilibrium Phases
Ca changes as we solidify. Cu-Ni case
First a to solidify has Ca 46wtNi. Last a to
solidify has Ca 35wtNi.
Fast rate of cooling Cored structure
Slow rate of cooling Equilibrium structure
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Binary-Eutectic Systems
has a special composition with a min. melting T.
2 components
Cu-Ag system
Ex. Cu-Ag system

3 single phase regions

L, a, b

Limited solubility

a mostly Cu


b mostly Ag

• 3 two phase regions
• L a
• L b
• a b