Question

Which one of the following elements is ferrite stabilizer?

• A. Nickel
• B. Copper
• C. Chromium
• D. Manganese

Hint:

To remember the stabilizers:
- Austenite stabilizers are generally elements that favor FCC structure (like Ni, Mn, Cu).
- Ferrite stabilizers are elements that favor BCC structure (like Cr, Mo, W, V, Si).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify which of the given alloying elements acts as a ferrite stabilizer in steel metallurgy.
Alloying elements in iron-carbon systems are classified based on their influence on the stability of the phases (ferrite and austenite) and how they modify the iron-carbon phase diagram.

Step 2: Detailed Explanation:

• Classification of Alloying Elements:
Alloying elements added to steel generally fall into two categories: Austenite stabilizers and Ferrite stabilizers.

• Austenite Stabilizers:
These elements expand the gamma-phase ($\gamma$-iron, austenite) region on the phase diagram.
They lower the eutectic/eutectoid transition temperature, stabilizing the Face-Centered Cubic (FCC) austenite structure down to lower temperatures.
Examples include Nickel (Ni), Manganese (Mn), Copper (Cu), and Cobalt (Co).
Therefore, Options (A), (B), and (D) are austenite stabilizers.

• Ferrite Stabilizers:
These elements restrict the gamma-phase region and expand the alpha-phase ($\alpha$-iron, ferrite) region.
They raise the eutectoid temperature and promote the formation of the Body-Centered Cubic (BCC) ferrite structure.
At higher concentrations, they can completely close the gamma-phase field, creating a "closed gamma loop".
Examples include Chromium (Cr), Silicon (Si), Molybdenum (Mo), Tungsten (W), Vanadium (V), and Titanium (Ti).
Thus, Chromium is a highly effective and classic ferrite stabilizer.

Step 3: Final Answer:
Chromium is a ferrite stabilizer.