| Popis: |
Methods of the X-ray phase analysis, as well as optical and scanning electron microscopy supplemented by construction of the distribution maps for such chemical elements as oxygen and copper demonstrated presence in the structure of the PR-BrX brand powder made of bronze with the FСС lattice of oxygen-containing phases, i.e., copper oxides (CuO, Cu2O) located along the grain boundaries and on the powder particle surface. Using these methods demonstrated that annealing in the ammonia at a temperature of 450 °C promoted reduction of the oxide phases to the single-phase structure of the initial solid solution. It was found out that the presence of oxides on the powder particles surface and grain boundaries inside these particles made the oxidized powder unsuitable for use in the selective laser melting technology. This is due to reduction of the oxides, and, consequently, to the outgassing and excessive porosity of objects during the laser 3D printing. It was proved that reductive annealing in ammonia formed a single-phase structure of powder particles based on the FCC copper, which made it possible to grow objects with small porosity not exceeding 2.5 % using various laser processing modes |
