The obtaining nanopowder pseudo-ligatures Cu–(SiC+Si3N4) for modification and reinforcement of aluminum alloys

Abstract

The paper studies mechanical mixing and subsequent compaction of a powder mixture consisting of a powdered carrying agent (electrolytic copper having particles size of 20–100 µm) and a nanopowder modifying composition (silicon carbide powders (SiC) – 50÷70 %, silicon nitride (Si3N4) – 20÷30 %, sodium hexafluoroaluminate (Na3AlF6) – 10÷20 %) having particles size of 70–100 nm, obtained using azide self-propagating high-temperature synthesis technology. Modifying agent content in powder mixtures was 2,5, 5, 10 and 15 %. Mechanical mixing was carried out for 30–45 min at a rate of 150 rpm using the «Pulverizette-5» planetary mill. The study analyzes intermixing of initial powder components. It determines some physical and technological properties of powder mixtures obtained, such as granulometric composition, density, bulk mass, flowability. Nanopowder pseudo-ligatures briquettes are formed of Cu–(SiC + Si3N4) powder mixtures with various content of the modifying agent by cold pressing in a cylindrical press mold using the PSU-50 hydraulic press at a pressure of 85–310 MPa. The study determines dependencies of relative density and porosity of briquettes on compaction pressure. It presents microstructures of pressed pseudo-ligatures at the maximum compaction pressure. Obtained nanopowder pseudo-ligatures briquettes with a diameter of 25 mm, up to 2 mm in height, weighing 5 g, with a relative density of 53–85 % and porosity of 15–47 are intended for subsequent introduction into aluminum melt for further modification.