Microstructure and magnetic properties of Cu 90− x Co 10 Ni x –7.5% SmCo 5 composite alloys prepared by mechanical alloying and hot pressing

Abstract

Nanocrystalline composites of Cu_90−xCo₁₀Ni _x (x = 0, 10, 20 wt-%) alloys reinforced with 7.5 wt-% of intermetallic SmCo₅ particles were prepared by several processing steps. The production of these alloys started with the synthesis of Cu_90−xCo₁₀Ni _x powder alloys by mechanical alloying of pure Cu, Co and Ni in a planetary mill for 30 h at 250 rev min⁻¹. As a second step, intermetallic SmCo₅ particles were added, and additional milling was performed for 10 h. The resulting powders of both milling processes were characterised by means of an X-ray diffraction method, a scanning electron microscopy and an electron probe microanalysis. As a final fabrication step, Cu_90−xCo₁₀Ni _x –7.5% SmCo₅ alloy powders were consolidated by hot pressing under 88 MPa for 75 min at 750°C in an argon atmosphere. The resulting compacts are reinforced by the precipitation of Co(Ni) during consolidation, and the presence of second-phase particles of oxides and intermetallic SmCo₅.