Crystal structure of iron at room temperature At ordinary (room) temperature, does iron exhibit a body-centred cubic (bcc) crystal structure?

Introduction / Context:
Iron exhibits allotropic transformations: its crystal structure changes with temperature. Understanding these phases is crucial in metallurgy and heat treatment of steels, where phase transformations determine mechanical properties.

Given Data / Assumptions:

• Consider pure iron (no alloying elements).
• Room temperature conditions (~20–30 °C).
• Ambient pressure.

Concept / Approach:

Pure iron has the following phases: α-Fe (ferrite) is bcc from room temperature up to about 912 °C; γ-Fe (austenite) is fcc from ~912 °C to ~1394 °C; δ-Fe is bcc again from ~1394 °C to the melting point. Thus, at room temperature, iron is indeed bcc (α-Fe).

Step-by-Step Solution:

Verification / Alternative check:

X-ray diffraction data and iron–carbon phase diagrams confirm the bcc structure of ferrite at room temperature.

Why Other Options Are Wrong:

• “False” contradicts the α-Fe phase field.
• “Only above 912 °C” describes austenite (fcc), not bcc.
• Curie temperature concerns magnetism, not lattice type.

Common Pitfalls:

Confusing magnetic transition (Curie point ~770 °C) with structural change at 912 °C.

Final Answer:

True