Pure aluminum with different grain size distributions by consolidation of particles using equal-channel angular pressing with back pressure

Equal-channel angular pressing (ECAP) with back pressure was used to consolidate particles into bulk materials. In the present study, fully dense bulk aluminum was consolidated from nanoparticles and mixtures of nano and microparticles in varying proportions to obtain different grain size distributions. These materials were processed by ECAP for four passes at 673 K with the application of a constant back pressure of 200 MPa. Mechanical tests showed that hardness and strength increased significantly with increasing volume fraction of the nanoparticles while ductility decreased. Transmission electron microscopy examination and X-ray diffraction analysis showed Al nanocrystals of the order of 10 nm in the material consolidated from 100% nanoparticles whereas a bimodal distribution of grain sizes was observed in the mixtures.