Continuous Cooling Transformation (CTT) Curves
It is possible to get martensite below the critical cooling rate because the TTT diagram represents isothermal behaviour
- this is good for understanding phase behaviour but does not represent what occurs in heat treatment where cooling is continuous
In such cases CCT diagrams are used which can be derived from TTT diagrams
- these show what would happen if a sample is allowed to cool continuously rather than being held at a fixed temperature