Phase diagram analysis

Question

The figure is a portion of the titanium copper phase diagram for which only single-phase regions are labeled. Specify all temperature composition points at which eutectics, eutectoids, peritectics and congruent phase transformations occur.

I think i've found the eutectic and congruent point. (aprox 960 and 980 celsius) but how do I find the eutectoid and peritectic point?

Sorry for blurry image!

Answer 1

Assuming that the fields marked by x are solid and y is liquid, these are the points:

1. a: eutectic point. Cooling will turn the single liquid into two solids. The point is between the composition of the two solids involved.
2. b: eutectoid point. Cooling will turn the single solid into two solids.
3. c: peritectic point. Cooling from immediately to the left will turn the solid into a liquid and a solid. The point is outside the composition of the two solids involved.
4. d: congruent point: A solid will melt at this point to a liquid of the same composition.
5. e: incongruent melting points. A solid will melt to a liquid and a solid. Note that the left one is intimately associated with the peritectic point.

There are no peritectoid points in this diagram. A peritectoid point is similar to a peritectic point, but with all phases solid.