Abstract
A new process is proposed and tested in order to prepare an Al2O3-dispersion-strengthened copper, combining the mechanical alloying and following heat-treatment. The mechanical alloying was carried out with an attritor using powders of electrolytic pure Cu, gas-atomized Cu-8 mass% Al master alloy and Cu2O as starting materials. By mechanical alloying for 72.0 ks, homogeneous Cu-Al-O solid solutions or nanometer order mixtures of each starting material substances were obtained. These powders were then converted to the A12O3-dispersion-strengthened copper by heating, in vacuum, below the temperature of 1273 K. The dispersed particles precipitated by heat-treatment were γ-Al2O3 under the temperature of 1073 K, and γ-Al2O3 and small amount of α-Al2O3 at 1173 K for 3.6 ks, and α-Al2O3, γ-Al2O3 and Fe(Al, Cr)2O4 at 1273 K for 3.6 ks. These dispersed particles have a tendency to aggregate. The hardness value of Al2O3-dispersion-strengthened copper corresponding to 4.13 oxide vol%, heat treated below the temperature of 973 K, showed the highest value among the samples studied in the present work. The Al2O3-dispersion-strengthened copper powders obtained in this study had tendency to sweat pure Cu at the powder particle surface by heat-treatment. The occurrence of sweating resulted in a marked decrease in the hardness values of Al2O3-dispersion-strengthened alloys.
