SECTION A Question 1 (22 marks) Figure 1 displays the phase diagram for iron-carbon alloys. An alloy with composition (by weight percent) of 4.3% C is held at a given temperature (See Figure 1). Temperature (°C) 0 1600 1538°C 1493°C 1400 8 Composition (at % C) 5 10 15 20 25 L 2500 1394°C Y+L 1200- 1147°C 2.14 4130 y. Austenite 2000 1000 - 800 600 912°C La Y 0.76 0.022 a, Ferrite a+ FezC y+ Fe₂C 727°C 1500 Cementite (FegC) 1000 Temperature ("F) 400 0 (Fe) 1(a) (4 marks) 2 3 Composition (wt% C) 4 Figure 1: Phase diagram of Fe-C alloy 5 6 6.70 What is the common name for Fe-C alloys at this composition? What is the main advantage at this composition? 1(b) (4 marks) pro eutectaid cementite hyperatodoid composte eutectic Identify the dominant phase at temperature of 1200°C and 1000°C. Sketch the microstructure of the composite for each temperature. The alloy is then slowly cooled to room temperature (extrapolate the phase diagram). 1(c) (5 marks) How many phases are present? Describe each of the phases. 1(d) (3 marks) Calculate the composition of each of the phase(s). 1(e) (6 marks) What is the weight fraction of each phase? Justify your answer. ECM3160 1/4