What is the Difference Between Slip and Twinning?

Slip and twinning are two different mechanisms of plastic deformation in materials. Here are the main differences between them:

• Slip:
• Involves the sliding of crystal blocks over one another along various crystallographic planes referred to as slip planes.
• Occurs in Face-centered cubic (FCC) and body-centered cubic (BCC) crystal structures.
• Requires less stress.
• During slip, every atom in the block moves by the same amount.
• There is no change in the central axis during slip.
• The orientation of the slipped crystal lattice is the same.
• Slip is observed as thin lines under the microscope.
• Occurs in several milliseconds.
• Twinning:
• Involves a portion of the crystals adopting an orientation that is clearly and symmetrically connected to the direction of the remaining untwined lattice.
• Occurs in Hexagonal close-packing (HCP) metals.
• Requires more stress compared to slipping.
• The atoms in each succeeding plane of a block move through different distances proportional to how far they are from the central axis.
• A deformation in the central axis occurs in twinning.
• The twinned crystal lattice is just a minor image of the original lattice.
• Twinning is observed as broad lines under the microscope.
• Occurs in a few microseconds.

In summary, slip involves the sliding of crystal blocks along specific planes and is observed in FCC and BCC structures, while twinning involves the adoption of a new crystal orientation and is observed in HCP structures. Slip requires less stress and occurs more slowly than twinning, with the slipped crystal lattice maintaining the same orientation.

Comparative Table: Slip vs Twinning

The key difference between slip and twinning is the manner in which atoms in a block move during the deformation process. Here is a table summarizing the differences between slip and twinning:

Slip is a deformation process where all atoms in a block move the same distance, while in twinning, the atoms in each successive plane in a block move through different distances proportional to their position. Slip occurs in metals with different slip systems, such as face-centred cubic, body-centred cubic, and hexagonal close-packed systems. Twinning, on the other hand, involves different types of twinning, including contact twins, merohedral twinning, and penetration twins. Slip and twinning are fundamental deformation mechanisms in metals and alloys, and their competition is influenced by factors such as preloaded stress and temperature.