For an edge dislocation, the slip direction is along the direction of applied shear stress.

• A. In the same direction as the applied shear stress
• B. Perpendicular to the applied shear stress
• C. Opposite to the applied shear stress
• D. At a 45-degree angle to the applied shear stress

Answer: (A)

Dislocation glide is driven by the resolved shear stress on a slip system, and the motion occurs along the Burgers vector within the slip plane. For an edge dislocation, the Burgers vector is perpendicular to the dislocation line, and slip proceeds in the Burgers vector direction. When the applied shear stress is oriented along that slip direction in the slip plane, the resolved shear stress is maximized, giving a strong driving force for glide in that exact direction. If the shear is perpendicular or at an angle, the driving force for motion along the Burgers vector is reduced, so motion would not align with the applied shear as effectively. Thus, the slip direction being in the same direction as the applied shear stress reflects the direct relationship between the Burgers vector (the slip direction) and the driving force for dislocation glide.