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GATE 2021 MT – Question 41

Physical Metallurgy · Crystal defects and interfaces · 2 marks · Multiple choice

Without external stress, which statement about point-defect/dislocation interaction is FALSE?

  1. An oversized solute preferentially migrates below an edge-dislocation slip plane
  2. A spherically symmetric point defect interacts with both hydrostatic and shear stress fields of a dislocation
  3. A point defect can modify the local elastic modulus and thereby change interaction energy
  4. Vacancies are attracted to the compressive region of a dislocation

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Show answer and explanation

Correct answer: (B) A spherically symmetric point defect interacts with both hydrostatic and shear stress fields of a dislocation

Explanation

An isotropic spherical dilation couples to hydrostatic stress, not a pure shear stress field in the simple elastic size-misfit model.

Thus **B** is false. Oversized solutes favor tensile regions, while vacancies favor compressive regions.