Correct Answer - Option 4 : Chromium
Concept:
Ferrite stabilizers: some alloying elements tend to stabilize the ferrite phase in preference to austenite. Many of these elements have the same crystal structure as ferrite (BCC). They reduce the extent of the austenite area on the equilibrium diagram by forming a gamma loop. Austenite is enclosed within the loop.
eg: Cr, Si, Mo, W, V, Ti etc.
Austenite stabilizers: These enlarge the area of the austenite phase on the phase diagram. a critical amount of these alloying elements results in Austenite even at room temperature.
eg: Mn, Ni, C, N etc.
Effect on eutectoid temperature and composition: Ferrite stabilizers raise the eutectoid temperature to above 727°C, Austenite stabilizers lowers the eutectoid tempersture to below 727°C.
Both Ferrite and Austenite stabilizers decrease the eutectoid composition from 0.77% to lower values.
