Allotropic iron — temperature range for gamma (γ) iron Gamma-iron (austenite) occurs in pure iron between which of the following temperature ranges?

Introduction / Context:
Pure iron exhibits multiple allotropic forms as temperature changes: alpha (α), gamma (γ), and delta (δ). Recognizing the temperature ranges is essential for understanding steel heat treatments and phase transformations.

Given Data / Assumptions:

• Pure iron under equilibrium conditions (no alloying additions).
• Standard conversion temperatures: ~910°C and ~1403°C for α↔γ and γ↔δ transitions.

Concept / Approach:
Below ~910°C, iron is α (ferrite, BCC). Between ~910°C and ~1403°C, iron is γ (austenite, FCC). Above ~1403°C up to the melting point (~1538°C), iron is δ (BCC). Thus, the correct interval for gamma-iron is 900–1400°C (rounded choices).

Step-by-Step Solution:
Match phase names to temperature ranges using standard Fe phase chart.γ-Fe exists between about 910°C and 1403°C → select the closest option bounds.Therefore, choose 900°C to 1400°C.

Verification / Alternative check:
Fe–C diagrams and basic metallurgy texts universally place γ-Fe in this interval for pure iron.

Why Other Options Are Wrong:

• 400–600°C and 600–900°C: temperatures below the α→γ transformation.
• 1400–1530°C: corresponds to δ-iron region up to melting.
• 200–770°C: includes the Curie temperature region for α-Fe, not γ-Fe.

Common Pitfalls:
Confusing the Curie point (~770°C, magnetic transition) with structural allotropic transitions.

Final Answer:
900°C to 1400°C