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GATE 2021 MT – Question 29

Physical Metallurgy · Nucleation solidification and transformations · 1 mark · Numerical answer

For homogeneous spherical-solid nucleation in liquid at fixed undercooling, a 20% rise in nucleus surface energy causes a ______ % increase in critical radius (nearest integer).

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Correct answer: 20 to 20

Explanation

At fixed undercooling, r*=2γ/|ΔGv|. The bulk driving force is unchanged, so a 20% rise in γ gives a **20%** rise in critical radius. The nucleation barrier would instead scale as γ³.