MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF ULTRAFINE-GRAINED MATERIALS

Some ultrafine-grained materials produced by severe plastic deformation were studied and compared to literature results for those obtained by other processes. In particular, comparisons between various as-prepared microstructures and between their evolutions during heat treatments were conducted. It was found that the high internal elastic strains probably arises from a metastable state of grain boundaries. Recovery of such microstructures occurs first by grain boundary recovery and by grain growth. The high level of internal elastic strains as well as the very fine scale of the microstructure should play an important role in the unusual mechanical behaviour of ultrafine-grained materials.