Hutchins, Cathleen Ruth (2007-08). Consolidation of copper and aluminum micro and nanoparticles via equal channel angular extrusion. Master's Thesis.
Ultrafine grained (UFG), and nanocrystalline (nc) materials are of interest because of the high strength, compared with coarse grained counterparts. Several current methods to fabricate UFG and nc materials result in samples too small for practical use. In addition, the fabrication of nc materials, in particular, is difficult, and defects in the material causes significant reduction in strength and ductility of these materials. The present study uses Equal Channel Angular Extrusion (ECAE) to produce relatively large consolidates of UFG and nc materials.
ECAE has been used to consolidate micro and nanocrystalline powders. The behavior of consolidated pure Cu and aluminum alloys in the nano and micron size were explored. The effects of different routes, extrusion temperature, and post-ECAE processing on microstructure and mechanical behavior were studied. Processing parameters were explored to determine the influence of each parameter on the consolidation performance. The goals of experimenting with different processing parameters were to increase the ductility of the material, while maintaining relatively strong specimens. Comparisons were made with a recently developed powder compaction constitutive model and corresponding simulations.
ECAE of microcrystalline powders produced relatively ductile materials, with high strength. Swaging of these consolidated powders produced samples which were softer and less ductile in tension, than the non-swaged samples.
ECAE produced effective consolidation of Cu nanoparticles with average sizes of 100 nm, with an ultimate tensile strength of 680 MPa, with a fracture strain as much as 10%, which is higher than previously reported 7% [Haouaoui, 2005].