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The multiple hardening mechanisms of a copper matrix have been presented and discussed. The prealloyed ball milled Cu-3 wt.%Al and the atomized Cu-0·6 wt.%Ti-2·5 wt.%TiB 2 powders have been used as starting materials. Dispersoid particles Al 2 O 3 and TiB 2 were formed in situ. The powders have been hot consolidated. Optical microscopy, SEM, TEM, and X-ray diffraction analysis were performed for microstructural characterization. Increase in microhardness of Cu-3 wt.%Al compacts is a consequence of the crystallite size refinement and the presence of Al 2 O 3 particles. High hardening of Cu-0·6 wt.%Ti-2·5 wt.%TiB 2 is a consequence of the presence of modular structure, Cu 4 Ti (m) , and TiB 2 particles.

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In order to produce the composite powder analyzed in this paper, two prealloys were melted and afterwards gas atomized. The obtained TiB2-reinforced copper powder was consolidated by hot isostatic pressing (HIP). Since it is known that a decrease in the size of the reinforcing phase can cause an increase in hardness of composites, the main aim of the experimental work was to obtain as small particles of the dispersed phase as possible by using standard powder metallurgy techniques. Microstructure and microhardness of the ascast prealloys, as-atomized powder and HIP-ed compacts were examined. The results of these examinations revealed that TiB2 particles about 10 nm in size were in-situ formed and homogenously dispersed in the copper matrix. As a consequence of the TiB2 formation, the microhardness of Cu-TiB2 composite was significantly improved

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