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GATE 2025 MT – Question 26

Mechanical Behaviour of Materials · Dislocations and strengthening · 1 mark · Multiple select

With reference to edge and screw dislocations, which of the following statements is/are CORRECT?

  1. Both edge and screw dislocations can leave the slip plane by climb.
  2. Burgers vector of a screw dislocation is parallel to its line vector.
  3. Both edge and screw dislocations can leave the slip plane by cross-slip.
  4. Strain energy per unit length of an edge dislocation is higher than that of a screw dislocation.

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Show answer and explanation

Correct answer: (B) Burgers vector of a screw dislocation is parallel to its line vector.; (D) Strain energy per unit length of an edge dislocation is higher than that of a screw dislocation.

Explanation

A screw dislocation has its Burgers vector parallel to its line, so B is true. With equal Burgers magnitude and elastic constants, edge energy is the screw energy divided by 1−ν and is higher, so D is true. Climb is characteristic of edge components; cross-slip requires screw character. Thus **B,D**.