Properties of copper matrix reinforced with nano- and micro-sized Al(2)O(3) particles
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The mixture of electrolytic copper powder with 5 wt.% of commercial Al(2)O(3) powder (average particle size: 15 and 0.75 mu m, respectively) and the inert gas atomized prealloyed copper powder (average particle size: 30 mu m) containing 2.5 wt.% aluminum were separately milled in air up to 20 h in the planetary ball mill. During milling aluminum in the prealloyed copper powders was oxidized in situ by internal oxidation with oxygen from the air forming very fine nano-sized Al(2)O(3) particles. The internal oxidation of 2.5 wt.% aluminum generated 4.7 wt.% of Al(2)O(3) in the copper matrix. Powders and compacts were characterized by light and scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction analysis. Microhardness and electrical conductivity were also included in measurements. The microhardness of Cu-2.5 wt.% Al compacts was 3.6 times higher than that of compacts processed from electrolytic copper powder. This increase in microhardness is a c...onsequence of a fine dispersion of Al(2)O(3) particles and refined grain structure. The average values of electrical conductivity of compacts processed from Cu-5 wt.% Al(2)O(3) and Cu-2.5 wt.% Al powders previously milled for 20 h and were 88% and 70% IACS, respectively, which is a rather significant increase if compared with values of 60% and 23% IACS of compacts processed from as-received and non-milled powders. The microhardness of 20-h milled compacts decreases with the heat treatment at 800 degrees C. Due to the effect of nano-sized Al(2)O(3) Particles Cu-2.5 wt.% Al compacts show lower decrease in microhardness. The results are discussed in terms of the effect of Al(2)O(3) Particle size and fine grain structure on the reinforcing of the copper matrix. (C) 2007 Elsevier B.V. All fights reserved.