4. Conclusion

Various techniques have been tried and tested for the manufacture of ultra-fine grain and nanostructured materials. Channel angular extrusion is one of the most-used techniques as it allows manufacturing products of an interesting size where the grain size does not reach nanometric dimensions. Techniques exploiting electrolytic deposition should be developed.

The intervention of Coble creep and grain boundary sliding below a critical grain size does not enable reaching the yield strength that the Hall-Petch effect suggests for nanostructured materials. Their lack of strain hardening promotes plastic instabilities and ductility is therefore very small. The endurance limit of ultra-fine grained material is higher than that of standard grain size materials. However, their resistance to crack propagation as well as their low-cycle fatigue plastic lifespan is deteriorated....