Consolidation of dispersion strengthened nanostructured copper via hot extrusion

Nanostructured copper-based powders were prepared by mechanical synthesis. The powder particle size distribution was characterised by sieving. The microstructure was characterised with optical and scanning electron microscopy. The grain (crystallite) size was determined with X-ray diffraction, using the Scherrer method. The mechanical properties were assessed with microhardness measurements. The stability of the nanostructure was tested with heat treatment up to 800 degreesC. Both the X-ray determination of grain size and the microhardness measurements indicate negligible grain coarsening up to 800 degreesC. Powders were vacuum encapsulated in copper, and extruded at temperatures in the range of 500 to 600 degreesC. The microstructure was again characterised after extrusion. The prior particle boundaries of the powders were usually not seen and porosity was very small. The extrudates showed hardness values of up to 193 VHN. The viability of consolidation of nanostructured copper-based powders by hot extrusion, without significant grain coarsening, was demonstrated. The detailed analysis of the nanostructure, namely with transmission electron microscopy, is still on the way.