Preparation of CuCr pseudo-alloys by deposition of copper from a solution onto chromium powders with simultaneous mechanical activation of the mixture

: CuCr composite particles were obtained using the method of copper deposition from the solution of its sulfate onto chromium powder particles with the simultaneous mechanical activation (MA) of the mixture in an AGO-2 planetary ball mill for Powder Metallurgy and Functional Coatings  4  2020 5 minutes. CuSO 4 ·5H 2 O concentration in the solution with complete copper reduction provided a molar ratio of Cu/Cr = 1. Since deposited fine crystalline copper is highly active and rapidly oxidizes to Cu 2 O oxide in air, the obtained composite powders were washed, dried, and stored in an argon atmosphere. After drying, the mixture was subjected to additional MA for 5 minutes. Composite particles with a laminate structure begin to form in the solution during MA. Tablets were pressed with a diameter of 3 mm, height of up to 1.5 mm, and density of 4.2–4.5 g/cm 3 from the powders obtained. Samples were sintered in an argon atmosphere at 700– 1400 °С. For comparison of microstructures, samples were also sintered from mixtures of Cr and Cu metal powders with a volume ratio of chromium to copper of 50 : 50 obtained by simple mixing in a porcelain mortar for 20 minutes and MA for 10 minutes. Three areas of the alloy structure formation can be distinguished depending on the heating temperature. At heating temperatures below the eutectic melting point, composite particles are sintered at certain points. At heating temperatures above the liquidus temperature, the alloy melts with its phases separated; one part of the sample consists of copper enriched in chromium, and the other part consists of chromium enriched in copper. At intermediate heating temperatures, liquid phase sintering occurs accompanied by phase separation. Copper-enriched chromium particles become spherical and are located in a chromium-enriched copper matrix. Comparison of samples sintered under the same conditions from powder mixtures obtained by different methods showed that a more uniform and fine-grained structure is obtained in samples with deposited copper.