I know that annealing twins occur during heat treatment and deformation twins during plastic deformation, but what are the fundamental differences? Are there differences in their ability to accommodate dislocations and improve strain hardening? Is there a difference in their interfacial energies considering a coherent deformation twin and coherent annealing twin?
Also how do the lengths of these twins vary?
Annealing twins are formed during hot processing of low stacking fault energy metals, such as copper, brass and austenitic stainless steels. Annealing twins have insignificant or a little effect on the strain hardening property of the materials.
However, Mechanical twins are formed during deformation of moderate SFE materials of order 25 mJ/m2, such as high Mn TWIP steels. Mechanical twins are formed dynamically during straining, Consequently, Dynamic Hall-Petch relation is effective during straining. As a result, the strain hardening significantly increases.
Hi Atef, The twinning (of course deformation twins) contribution to strain hardening is very minimal and it amounts to about 250 MPa only!! Even for TWIP steels, the significant contribution comes from the dislocations. There are some papers and we also found the same.
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