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GATE 2025 MT – Question 23

Metallurgical Thermodynamics · Phase equilibria and phase diagrams · 1 mark · Multiple choice

In the Fe–C system, the invariant reaction $\text{Liquid}+\delta\rightleftharpoons\gamma$ takes place at 1493 °C. This reaction is called ________.

  1. eutectic
  2. eutectoid
  3. peritectic
  4. monotectic

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Show answer and explanation

Correct answer: (C) peritectic

Explanation

A peritectic reaction combines a liquid and an existing solid to form a different solid at an invariant temperature. Liquid+δ→γ has exactly this structure. A eutectic instead produces two solids from one liquid. Therefore **peritectic, C**.