A chart of the time needed to reach specified transformation fractions after cooling to, and holding at, a fixed temperature. Its curves are not themselves continuous-cooling histories; estimating a critical cooling rate from their nose is an approximation.
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An Isothermal Transformation Diagram (often referred to as an IT diagram or TTT diagram for Time-Temperature-Transformation) is a graphical representation used in materials science and metallurgy to illustrate the phase changes of a material, typically steel, as it is cooled or heated under isothermal (constant temperature) conditions. ### Key Aspects of Isothermal Transformation Diagrams: 1. **Axes**: The diagram typically features temperature on the vertical axis and time on the horizontal axis.