Question

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

• A. Both edge and screw dislocations can leave the slip plane by climb.
• B. Burgers vector of a screw dislocation is parallel to its line vector.
• C. Both edge and screw dislocations can leave the slip plane by cross-slip.
• D. Strain energy per unit length of an edge dislocation is higher than that of a screw dislocation.

Hint:

Remember: climb is edge only, cross slip is screw only. Burgers vector parallel means screw, perpendicular means edge.

Answer 1

The Correct Option is B, D

Step 1: Recall key points.
- In an edge dislocation, the Burgers vector is perpendicular to the dislocation line.
- In a screw dislocation, the Burgers vector is parallel to the dislocation line.
- Edge dislocations can move out of the slip plane by climb, but screw dislocations cannot climb.
- Screw dislocations can move out of the slip plane by cross slip, edge dislocations cannot.
- Strain energy per unit length of an edge dislocation is slightly higher than that of a screw dislocation. Step 2: Verify each option.
- (A) False, climb is possible for edge only.
- (B) True, definition of screw dislocation.
- (C) False, cross slip occurs only in screw dislocation.
- (D) True, edge dislocation has higher strain energy.
Step 3: Conclusion.
Correct statements are (B) and (D). \[ \boxed{\text{Correct: (B) and (D)}} \]