How can we determine the most stable phase from a free energy curve?
The phase that has the lowest free Gibbs energy for that temperature.
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Which phase is most stable below T_m?
The solid phase.
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Which phase is most stable above T_m?
The liquid phase.
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What is ΔG_mix for an isomorphous (+real) system?
ΔG_mix = x_A*x_B*Ω +RT(x_A*ln(x_A)+x_B*ln(x_B))
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What is the most stable phase in solid state for an alloy?
A homogeneous solid solution of the two components.(well anything that allows the G to be at its lowest point for the given composition).
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How is the total G for a 2-phase system found?
A common tangent is drawn linking the two phases G curves.( a straight line)
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What is the significance of a common tangent?
It produces the lowest possible G for the system as a whole. Where lines meet the G curves defines the composition of each phase.
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What can be made from G curves at different temperatures?
A temperature against composition phase diagram.
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What happens is the system is not isomorphous?
A positive ΔH_mix can be caused by unfavourable interactions between atoms.
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What are the effects of ΔH_mix being positive?
As T reduces ΔH_mix becomes more significant, The G curve turns upwards at intermediate compositions resulting in a curve with two minimas and one maxima.
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Other cards in this set
Card 2
Front
Which phase is most stable below T_m?
Back
The solid phase.
Card 3
Front
Which phase is most stable above T_m?
Back
Card 4
Front
What is ΔG_mix for an isomorphous (+real) system?
Back
Card 5
Front
What is the most stable phase in solid state for an alloy?
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