PSI - Issue 14

Neeta Paulose et al. / Procedia Structural Integrity 14 (2019) 649–655 Neeta Paulose etal. / Structural Integrity Procedia 00 (2018) 000–000

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cycle A specimen, δ ferrite pools are less than as cast condition spreading semi continuously (Fig. 3b) and with Cycle B, δ Ferrite are like isolated cores (Fig.3 c). The size of ferrite is smaller in heat treated condition than in as cast structure.

a

b

Fig.3. (a)As Cast CF 8C (b) Heat treated Cycle A

c

Fig.3 (c) Heat treated Cycle B

3.2 Elemental Analysis Three major phases (Austenite matrix,  Ferrite and Carbide) is seen in as cast and heat treated CF 8C samples. It is known that, nickel manganese, carbon and nitrogen are austenite stabilizer. They will try to segregate more in austenite maritx compared to ferrite phase. Similarly elements chromium, silicon, molybedenum, and niobium are ferrite stabilizer and will try to diffuse more in ferrite phase compared to austenite phase. From elemental analysis study it is found that both austenite matrix and δ ferrite phase contains iron, chromium, carbon, nickel, silicon and niobium in all three conditions (As cast, Cycle A and Cycle B). Solute partition ratios (element in δ ferrite/element in Austenite matrix) of nickel, manganese, chromium, silicon, molybedenum and niobium in all three condition is given in Table.2. It is seen that heat treatment effect the solute partitioning. Austenite stabilizer element nickel and manganese concentration decreases and δ stabilizer elements chromium, silicon and molybedenum concentration increases in δ ferrite phase by heat treatment. The effect is more prominent in cycle B. Niobium is not much