Simple Phase Diagrams Flashcards
What do phase diagrams normally show?
Solid and liquid states
What phase boundary limits the bottom of the liquid phase?
Liquidus boundary
What is the solidus line?
The line giving the upper limit of the single phase solid field
Define isomorphous
Single-structured
Define an arrest point
A shelf in the cooling curve caused by the release of latent heat during state change
Eutectic Point
The lower limit of the single-phase liquid field formed by the intersection of two liquidus lines
Field (phase diagram context)
Any region in which the phases present are fixed
What can you guarantee when crossing a binary phase diagram at a given temperature?
Crossing a phase boundary will take you from a one phase field to a two phase field (or vice versa)
How are single phase regions labelled?
Either with a Greek character, or bracketed element symbol (eg (Pb) for lead rich solution)
How do you find the phase composition of a constitution point in a two phase field in a binary phase diagram
Follow a horizontal line across the phase boundaries on each side of the field into the single phase fields; the point is composed of a combination of the single phases at the points where the tie-line meets the field boundary
What is a tie-line?
A horizontal (constant temperature) crossing a field in a phase diagram, and passing through a given constitution point
What is the lever rule
The length of the tie line on either side of a constitution point divided by the overall length of the tie line gives the proportion of the constitution point that is made up by the phase at the opposite end of the tie line to the given portion of tie line (make sense?)
Eutectoid point
The lower limit of a single-phase solid field (as opposed to liquid for eutectic point) formed by two falling phase boundaries
Peritectic point
Maximum temperature at which a single phase forms; a liquid must be in one of the fields bordering the point, or it is a peritectoid point
