Description
1. Compare the diffusion coefficients for hydrogen and nitrogen in FCC iron at 1200 oC and explain the difference in their values. (3 marks)
2. A 0.02 % C steel is to be carburized at 1200 oC in 4 hours with a point 0.6 mm beneath the surface reaching 0.45 % C. Calculate the carbon content required at the surface of the steel. Consider that the steel is made of FCC iron. (3 marks)
3. Which of the following oxides is expected to have the largest solid solubility in CaO? a) MgO, b) NiO and c) FeO. (3marks)
4. Determine the liquidus temperature, solidus temperature, and freezing range for the following MgO-FeO ceramic compositions. (Figure 1) a) MgO-10wt% FeO; b) MgO-45wt% FeO; c) MgO-60wt% FeO; d) MgO-90wt% FeO. (2marks)
5. a) Determine the phases present, the composition of each phase, and the amount of each phase in wt% for the following MgO-FeO ceramics at 2000 oC. (Figure 1) i) MgO-20 wt%FeO; ii) MgO-50 wt%FeO; iii) MgO-60 wt%FeO; and iv) MgO-90 wt%FeO. b) Consider an alloy of 40 wt% Au and 60 wt% Ag. Calculate the composition of the alloy in at.%. (3marks)
