Characterization of nanostructured CuCr bulk composites prepared by high-energy mechanical alloying

In this paper, the structure and properties of metal matrix composite materials on the basis of copper reinforced with chromium (20-50 wt%) were investigated. Raw materials consisted of grinded copper chips 5000 μm in size and chromium particles with an initial size of 10 μm. The composites were produced by mechanical alloying in a high-energy planetary mill with a quasi-cylindrical grinding body followed by hot pressing at 650°С. The milling duration was 1-10 h. It was shown that microstructure refinement occurs in the composites with an increase in chromium content and milling time. The structure of Cu-50 wt% Cr bulk materials after mechanical alloying for 5 h followed by hot pressing consists of the Cu and Cr-rich phases with average crystallite sizes of 37 and 28 nm, respectively. During short time milling the hardness of this composite increases to 600 HV due to the high intensity of mechanical alloying. At the same time, its wear resistance increases almost by 30 times in comparison with 1 h milling. On the contrary, electrical conductivity decreases after mechanical alloying.