Study of synthesis products in mechanically activated mixtures of copper titanides with carbon

Abstract

Metal matrix composites reinforced with dispersed carbide particles have an optimal combination of strength and wear resistance. The composites are used as structural materials, wear-resistant materials and coatings as well as functional materials. Copper matrix composites for electrical purposes are strengthened with particles of refractory compounds (carbides, borides, silicides). They are used to manufacture breaking electrical contacts which have increased resistance to erosion under the electric arc exposure. The highest arc erosion resistance is achieved by composites with a structure, in which submicron particles of refractory compounds are homogeneously distributed in the copper matrix. Powder technologies are used to obtain the copper matrix composites. A large number of publications concerns with the production of copper matrix composites strengthened by dispersed particles of titanium diboride. The composite powder was obtained by self-propagating high- temperature synthesis (SHS) occurring through mechanically activated mixtures of titanium, copper and carbon. The synthesis products were compacted by spark plasma sintering (SPS). In the present work, the microstructure, elemental and phase composition of the products of the synthesis reaction occurring through mechanically activated reactant powder mixtures of copper titanides with carbon (soot) subjected to additional heat treatment were studied using the methods of X-ray diffraction, optical and scanning electron microscopy. Copper matrix composites strengthened by carbide particles were obtained by copper reduction from intermetallic compounds (copper titanides) via reaction: TimCun+ C → TiC + Cu. The use of the copper titanides instead of titanium and copper powders eliminates the blocking of surface titanium-carbon reaction by copper during the mechanical activation of titanium-copper-carbon powder mixtures. This ensures a more complete conversion of titanium carbide in the synthesis reaction. It is established that the dispersion of the carbide phase in the structure of the synthesized ‘titanium carbide-copper binder’ composite depends on the elemental ratio of titanium and copper in the reaction mixtures. With an equiatomic content of titanium and copper the synthesis results in a matrix-type composite, in the structure of which submicron (less than 300 nm) carbide inclusions are homogeneously distributed throughout the copper binder. Unreacted copper and titanium in the titanide powders do not prevent the attainment of target phase composition of the synthesis products that include only titanium carbide and copper.