1. (a) Outline the principles and essential differences betweenContinuous Cooling Transformation and Isothermal TransformationDiagrams
  (b) Using the TTT diagram for a plain carbon steelwith 0.53%wt C, define the nature of the final microstructure (interms of micro-constituents present and approximate percentages) ofsmall samples (5 x 5 x 5 mm) subjected to the followingtime-temperature heat treatments.In each case, assume that thespecimen was austenitised at 860?C and held at this temperaturelong enough to achieve a homogeneous austenitic structure prior tocooling.
(i) Rapidly cool to 500oC, hold for 7s, rapidly coolto 400oC, hold for 103s and water quench to room temperature.
(ii) Rapidly cool to 400oC, hold for 7s and waterquench to room temperature.
(iii) Rapid cooling to room temperature within 1s.
(iv) Rapidly cool to 650oC, hold for 1h and waterquench to room temperature.
(v) Rapidly cool to 400oC, hold for 1s, followed bywater quenching to room temperature.
