Differences between Crystal Slip and Twinning

Comparison between crystal slip and twinning can be done in aspects like defect type, seen in, change in crystal axis, stress requirement, visibility and for occurrence threshold value of stress.

S.no
Slip
Twinning
1 Crystal slip is a line defect. Twinning is a surface defect grain boundary defect.
2 During slip, all atoms in a block move the same distance. During twinning, the atoms in each successive plane in a block move through different distances proportional to their distance from twinning plane.
3 Slip is commonly observed in Body centered Cubic (BCC) and Face Centered Cubic (FCC) metals. Twinning is commonly observed in Hexagonal Close Packing (HCP) metals.
4 After the slip, the crystal axis remains the same. After twinning, the crystal axis is deformed.
5 The slipped crystal lattice has the same orientation. The twinned crystal lattice is the minor image of the original lattice.
6 The stress required for slip is comparatively low. The stress required for twinning is comparatively more.
7 The stress necessary to propagate slip is usually higher than the stress required to start slip. The stress necessary to propagate twinning is lesser than that required starting it.
8 Slip can be seen as thin lines when viewed under microscope. Twinning can be seen as broad lines when viewed under microscope.
9 For slipping to occur, a threshold valve of stress called critical resolved shear stress is required. For twinning to occur, no such threshold valve of stress is required.
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