Question

5. Three steels with a composition of Fe-0.2 wt.% C, Fe-0.76 wt.% C and Fe-1.1 wt.% C are produced by melting and slowly cooling down to room temperature. By referring the phase diagram provided in figure 3, what would you expect in terms of phase changes (solidification sequence) in all three alloys as the temperature of the alloys reduces from melting temperature to room temperature? What will be the approximate weight fraction of each of those micro constituents at room temperature for the three steels? 1600 1538°C -1493°C 1400 8 L 1394°C 7+L 1200 1147°C 2.14 4.30 y, Austenite Temperature (°C) 1000 (912°C y + Fe3c 800 + 727°C 0.76 600 0.022 a, Ferrite a + Fezc Cementite (Fe3C) 400 0 (Fe) 1 2 5 6 6.7 3 4 Composition (wt% C) Figure 2: Fe-C Phase Diagram (Ref: Mat. Sc. and Eng., W.D. Callister)

Answer 1

5) during phase change of .2%of c

liuid metal changes to (delta plus liquid ) than after cooling goes to solid austenite during cooling austenite convert into solide mixture of (gamma plus autenite )

further cooling to room tempreture formation of alpha plus cementite at the end

during .76 % of c

liquid convert into austenite solid and some portion of liquid further cooling make all alloy into autenite solid

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cooling at 727 c tempreture austenite converted into cememtite and alpha solide

at 1.1% of c

liquid conerted into some portin to austenite solide then further cooling all alloy converted into austenite and cementite and then converted into alpha and cementite