The GATE Grind

GATE 2019 MT – Question 23

Physical Metallurgy · Diffusion in solids · 1 mark · Multiple choice

Which element diffuses fastest in iron at 1100°C?

  1. Ni
  2. Co
  3. Cr
  4. C

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Correct answer: (D) C

Explanation

Carbon is a small interstitial solute in iron, so it can move between interstitial sites without the slower vacancy-mediated substitutional exchange required by Ni, Co and Cr. Its diffusion is consequently fastest among these choices. Select D.

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