Time-temperature-transformation (TTT diagrams) are generated from percentage transformation vs logarithm of time measurements and are useful for understanding the transformations of an alloy steel that is cooled isothermally. An isothermal transformation diagram is only valid for one specific composition of material, and only if the temperature is held constant during the transformation, and strictly with rapid cooling to that temperature. Though usually used to represent transformation kinetics for steels, they also can be used to describe the kinetics of crystallization in ceramic or other materials. a) Sketch and label each phase in the TTT diagram for an eutectoid composition steel (0.77% C)
b) Sketch a path on this diagram to produce the following microstructure. i. time-temperature path that will produce 100% pearlite ii. time-temperature path that will produce 100% bainite iii. time-temperature path that will produce 50% bainite and 50% martensite iv. time-temperature path that will produce 50% pearlite and 50% martensite time-temperature path that will produce 100% martensite V.
