Viscous nature of deformation of ultra-fine grain aluminum processed by equal-channel angular pressing

Deformation and microstructural evolution of ultra-fine grained (UFG) aluminum produced by equal-channel angular pressing has been examined over a wide range of strain-rates at room temperature and liquid nitrogen temperature (77 K). Elevated strain-rate sensitivity of UFG structures at both temperatures was revealed and compared with the coarse-grain counterparts. Results indicated that this enhanced viscous nature may be attributed in part to an increase in dislocation density as well as to some sort of reaction related to grain boundary diffusivity.