What is the Difference Between Annealing Twins and Deformation Twins?

The main difference between annealing twins and deformation twins lies in their formation processes and characteristics:

Annealing Twins:

• Form as a result of a change in the crystal system during cooling.
• Do not cause any deformation, so strain energy minimization is not an issue.
• Shape is determined by the need to minimize interfacial energy.
• Tend to be straight and not lenticular (lens-shaped).
• Annealing twins do not cause any deformation, so there is no strain field contrast visible at their tips.

Deformation Twins:

• Form as a result of stress on the crystal after it has formed.
• Cause deformation and are associated with strain energy.
• Shape is determined by the need to minimize strain energy.
• Tend to be lenticular (lens-shaped) with sharply pointed ends to minimize long-range elastic strains.
• Deformation twins cause deformation, so there is a strain field contrast visible at their tips.

In summary, annealing twins are formed during cooling and do not cause deformation, while deformation twins are formed due to stress on the crystal after it has formed and cause deformation. Annealing twins are typically straight, while deformation twins are lenticular in shape.

Comparative Table: Annealing Twins vs Deformation Twins

Here is a table comparing annealing twins and deformation twins:

Annealing twins are formed as a result of a change in the crystal system during annealing heat treatment, while deformation twins form as a result of stress on the crystal after the crystal has formed. Annealing twins are flat, minimizing strain energy, and typically occur in low-SFE materials during annealing. On the other hand, deformation twins are lenticular, minimizing strain energy, and occur in low-SFE materials due to plastic deformation.