A steel alloy containing Fe, 4 wt% Si, 0.7 wt% C and traces of other elements has been cooled to equilibrium. Assume that there are no changes in the positions of the other boundaries between phases due to the addition of Si. The cementite composition is 6.67 wt% C.

a- Is silicon a gamma-gene or alpha-gene element? Explain.

b- What is the eutectoid carbon composition of this alloy?

c- What is the proeutectoid phase of its microstructure?

d- Calculate, at room temperature, the composition in ferrite and cementite phases of this alloy.

e- Calculate, at room temperature, the relative amounts of the proeutectoid and pearlite constituents of this alloy.

f- From what % C will an alloy with 4 wt% Si have a cast iron structure?

Fe-C diagram with Si addition 1500 1400 1300 1200 Temperature (C) MY N 1100 8% Si 6,5% Si 1000 900 Si 2% Si 800 carbon 0.25% Si steel 700 600 0,2 0,4 06 1,2 1,4 1,6 1,8 0.6 1.0 %C Fe