Strength and thermal stability of Cu-Al2O3 composite obtained by internal oxidation

Abstract

The objective of the work is to study the effects of the high-energy milling on strengthening, thermal stability and electrical conductivity of Cu-Al2O3 composite. The prealloyed copper powders, atomized in inert gas and containing 3 wt. % Al, were milled up to 20 h in the planetary ball mill to oxidize in situ aluminium with oxygen from the air. Composite compacts were obtained by hot-pressing in an argon atmosphere at 800 degrees C for 3 h under the pressure of 35 MPa. The microstructural characterization was performed by the optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction analysis (XRD). The microhardness, electrical conductivity and density measurements were also carried out. The effect of internal oxidation and high-energy milling on strengthening of Cu-Al2O3 composite was significant, The increase of the microhardness of composite compacts (292 HV) is almost threefold comparing to compacts processed from the as-received Cu-3 wt. % Al powder (102 HV). The grain size of Cu-Al2O3 compacts processed from 5 and 20 h-milled powders was 75 and 45 nm, respectively. The small increase in the grain size and the small microhardness drop indicate the high thermal stability of Cu-Al2O3 composite during high-temperature exposure at 800 degrees C.