Phase Diagrams Flashcards
Interpreting phase diagrams and how they are used/were used
What is a phase?
A material with a uniform structure on an atomic scale, not necessarily homogenous composition
What are axes of a phase diagram?
y-axis = pressure x-axis = temperature
Why is pressure often not really taken into account?
Need massive changes in pressure for change in phase
Where is the triple point of a water phase diagram?
P of 0.006 atm, T of 0.01oC
What is a triple point?
Where all 3 phases can exist
Historically, what did they use instead of a phase diagram?
Mechanical property and composition graph; ductility on left y-axis, extension on right y-axis, composition of x-axis
How are phases related to mechanical properties of a Cu-Al diagram?
α phase = ductility
β phase = high TS, poor ductility
γ1 + γ2 phases = poor TS, poor ductility
What are the conventions of naming?
Left to right, go along Greek alphabet; α β γ δ
What was the first Cu alloy, and when was it used?
Cu-As; ~3000BC, for ~100 years
What is the modern Cu alloy?
Cu-Sn; bronze
What is equilibrium?
No further driving force for change
What is allotropy?
A material changes structure under different conditions
What is a phase equilibrium diagram?
A diagram which tells us what phases should exist for given conditions of T and composition (under assumed equilibrium conditions)
