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The ultrafine Cu–3 vol.% Al2O3 and Cu–3 vol.% MgO powders with comparable nanocrystalline structures were prepared by thermo-chemical technique and mechanical milling followed by hot extrusion. The study compares an influence of the two different oxide dispersoids on strengthening of the copper matrix after thermo-deformation consolidation of the powders into bulk compacts and annealing of the compacts at elevated temperatures. The as-extruded Cu–Al2O3 alloy exhibits a homogeneous, thermal stable nanostructure up to 900 °C due to the dispersed alumina nano-particles that effectively strengthen crystallite / grain boundaries and inhibit grain growth. In the Cu–MgO material, the MgO particles are less efficient barriers against the grain growth due to their agglomeration into coarser particles (>50 nm) during the consolidation. A negative role here is a weak coherence of particle / matrix interface. The as-extruded Cu – MgO alloy is characterized by a bimodal grain size microstructure, a low hardness and it is structurally stable only up to 200 °C due to the recrystallization processes. The results indicate that the choice of a suitable dispersoid for the given matrix is one of the deciding factors for thermal stabilization of the nano-grains.
Keywords: dispersion strengthening, Cu–Al2O3, Cu–MgO, nanostructure, thermal stability© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.