Answer Happy

Q1 (a) Choose a composition other than the eutectoid and with the aid of illustrated sketches distinguish in detail between three of the following four terms: Equilibrium, Non-Equilibrium, Isothermal and Continuous Cooling. In your answer explain how the phases present evolve. (12 marks) (b) The following figure (Figure Q1) shows a Time Temperature Transformation diagram for a eutectoid steel. A eutectoid steel which in spherical shape and 100 mm in diameter is heated to 750°C until it is completely austenitic throughout is then dropped into water at 5°C. Choose three different cooling rates from the surface to the core of the sphere. With the corresponding Continuous Cooling Transformation diagram show and explain how the phases evolve with cooling for each of your three different cooling rates. (8 marks) (c) Using your three cooling curves what would the corresponding hardenability curve look like? Justify your decision. (5 marks) (25 marks) 800 A Eutectoid temperature 1400 700 A 1200 600 Р 1000 500 B Temperature (°C) 800 Temperature (°F) 400 A 300 600 M(start) 200 50% M + A 400 M(50%) M(90%) 100 200 0 10-1 1 10 105 102 103 104 Time (s) Figure Q1. TTT Diagram for Eutectoid Steel.