Cryorolling

Cryorolling is one of the potential techniques to produce nanostructured bulk materials from its bulk counterpart at cryogenic temperatures. It can be defined as rolling that is carried out at cryogenic temperatures. Nanostructured materials are produced chiefly by severe plastic deformation processes. The majority of these methods require large plastic deformations (strains much larger than unity). In case of cryorolling, the deformation in the strain hardened metals is preserved as a result of the suppression of the dynamic recovery. Hence large strains can be maintained and after subsequent annealing, ultra-fine-grained structure can be produced.

Advantages

Comparison of cryorolling and rolling at room temperature:

* In Cryorolling, the strain hardening is retained up to the extent to which rolling is carried out. This implies that there will be no dislocation annihilation and dynamic recovery. Whereas in rolling at room temperature, dynamic recovery is inevitable and softening takes place.
* The flow stress of the material differs for the sample which is subjected to cryorolling. A cryorolled sample has a higher flow stress compared to a sample subjected to rolling at room temperature.
* Cross slip and climb of dislocations are effectively suppressed during cryorolling leading to high dislocation density which is not the case for room temperature rolling.
* The corrosion resistance of the cryorolled sample comparatively decreases due to the high residual stress involved.
* The number of electron scattering centres increases for the cryorolled sample and hence the electrical conductivity decreases significantly.
* The cryorolled sample shows a high dissolution rate.
* Ultra-fine-grained structures can be produced from cryorolled samples after subsequent annealing.