Application of PAP-2 aluminum powder to produce powdered composite materials: The features of technology, structure, and physicomechanical properties of composites. Part I. Process approaches providing the formation of composite materials and applied procedures for determining their physicomechanical properties

Abstract

Composites Al/Al₂O₃ (lamellar cermet matrix)–filler (discrete metallic fibers, duralumin chips, graphite particles, fused corundum grains, and technical alumina spherulites) are fabricated. To form the lamellar cermet matrix, industrially produced PAP-2 aluminum powder was used. This powder consists of scaled particles with stearin coating (the specific surface of the powder is 4.1322 m²/g, and its particle size varies from 0.03 to 10 μm). In order to form the composites, the following main process operations were used: heat treatment of the PAP-2 powder in air to burn out stearin from the particle surface and replace it with a passivating alumina film, mixing of the thus formed powder product with a filler, and compaction and reaction sintering of powder billets in the filtration burning mode in air. To fabricate the Al/Al₂O₃–C composite, a new approach based on the saponification chemical reaction of stearin is proposed. This reaction runs between stearin on the surface of aluminum particles and caustic soda, which is the product of hydrolysis of the diluted liquid glass introduced into initial powder. The reaction products (sodium stearate and glycerol) are decomposed during the subsequent heat treatment in air with the formation of a coke residue on the particle surface. The physicochemical properties of the composites were determined using standard and conventional procedures.