For a Fe-C alloy with a eutectoid composition, an austenite was rapidly cooled down to 450°C, held for 10 sec, and quenched to room temperature. What is the final microstructure based on its TTT curve? Temperature of Transformation, C 700 600 500 400 300 Aes Aer 10 10² 10³ 104 105 seconds T Austenite stable 200 50%- 100 ME 675 P 100% completed 1 1sec F+B Coarse Pearlite - Fine Pearlite -Upper Bainite (Feathery) Lower Bainite Martensite +Bainite L Martensite 1min 1hr Transformation Time (Log. Scale) O a. 50% bainite and 50% martensite O b. 50% austenite and 50% bainite O c. 100% bainite O d. 100% martensite Fine more Acicular Rapid Etching Bainitic Pearlitic A Slow Etching Martensitic V.P.H. 210 320 450 700 750

Calculate the amounts of solid phases of ferrite and cementite present in pearlite.

QI/ Draw a thermal equilibrium diagram for the binary alloy system (Si –Au), from the following data:- a- Si melts at 1414 °C, and Au melts at 1064 °C , and identify all phases are present in the diagram. b- Eutectic is formed at 360°C containing 20 Wt% Si -80 Wt% Au . c- Determine the amount of each phase for the alloy which consist 60 Wt% Si- 40Wt % Au at 1200 °C and 800 °C ,then determine the amount of eutectic at 200 °C?

Question 4 A segment of the Fe/C alloy phase diagram is shown below: Composition (at% C) 15 Temperature (°C) 0 1600 1400 1200 1000 800 600 400 1538°C 0 (Fe) 8 Y 912°C -1493 C 1394-C Y. Austenite 0.76 0.022 a, Ferrite 1 y+L 2 2.14 10 1147 C at Fe₂C L 4.30 Y+Fe3C 4 3 Composition (wt% C) 727°C 20 Cementite (Fe-C) 5 6 25 2500 2000 1500 1000 6.70 Temperature (°F) a) What are the equilibrium phases, compositions and relative fractions of the Fe-C alloy at an average composition Ccarbon of 2% and a temperature of 730 °C? b) What are the equilibrium phases, compositions and relative fractions of the Fe-C alloy at an average composition Ccarbon of 2% and a temperature of 725 °C? 7 c) Sketch the microstructure of the alloy obtained by quick cooling of the alloy from the conditions in part a) to the conditions in part b). Be sure to identify the phases in your sketch.