The work is devoted to solving the actual scientific and technical problem - the creation of macroheterogenic composites of polyfunctional applications. In order to create new metal-ceramic composite materials for the manufacture of contact welding electrodes and maintaining high electrical conductivity, the possibility of creating copper and aluminum metal-ceramic composites with doping with their powder LaB6-TiB2 composite material is considered. Given that the strength of materials is primarily determined by defects in the microstructure, it is important to find out the effects of the defects of the crystalline structure of the matrix phase and the material of the fibers on the mechanical properties. Since the greatest defect is the grain boundaries, then the possibility of creating materials with reinforced grain boundaries is explored. It is important to find out the characteristics of these structural parameters and the possibility of strengthening the interphase boundaries, depending on the methods of obtaining composites of various bulk forms. Solving the problem of manufacturing reinforced ceramic materials can be realized by obtaining powders with an eutectic structure, which is a composite of ceramic matrix with regularly located monocrystalline fibers of another refractory compound. It was first established that under conditions of high-speed cooling from 102 to 105 °C /s during crystallization from the melt of the eutectic alloy of the LaB6-11wt.% TiB2 with an excess of 1 wt.% boron, the diameter of the fibers of the reinforcing phase TiB2 decreases in 4-5 times and their number increases by 2-2.5 times.
The influence of concentration and kinetic supercooling, annealing temperature on morphology, crystallographic orientation, stress-deformed state, phase composition and mechanical properties of ceramic composites of LaB6-TiB2, LaB6-ZrB2 systems have been investigated. It was found that the overlay of mechanical vibrations on the crystal of the eutectic alloy during float zone melting affects the concentration of components in the melt before the growth front of the crystal and leads to the deviation of the matrix and fibers from the direction of growth given by the seed crystal and the even distribution of ZrB2 fibers, an increase in the average diameter by ~ 20% and a change in their morphology.
It was shown, that the annealing at 1200°С, 1400°С and 1600°С reduces the amount of thermal stresses that are formed when cooled from the crystallization temperature due to the difference in the magnitude of the coefficients of the thermal expansion of the phase components of the reinforced composite materials of LaB6-TiB2, LaB6-ZrB2 systems and LaB6-HfB2, and as a result of uneven cooling of the composite material. It is shown that the thermal expansion of LaB6-MeB2 composites depends on the nature of the phase components and the internal residual thermo-mechanical stresses that arise at the boundary of the matrix-fiber section during cooling from the melting temperature. Moreover, the more different the coefficients of thermal expansion of the matrix and fibers, so at higher temperatures, the thermal characteristics of the matrix phase and the composite are aligned and the residual stresses in the composite is reduced. In this work by atomization obtained an isotropically-reinforced powdered composite with less in 3 times the size of the reinforcing component of TiB2, 2-3 times with residual macrostresses, with a stoichiometric phase composition, a better substructure at the macrolevel and a higher strength, than composites, obtained by directionally crystallization.
Application of the obtained LaB6-TiB2 powdered ceramic composite, as a strengthening phase, has allowed increasing the strength of metal matrices in 2-2.5 times and maintaining plasticity as the metal. When using a powdered composite with an etched matrix phase LaB6, due to the reinforcement of the grain boundaries at the interface of the composite-metal matrix, the strength increases by more than 2 times. The electric resistance of the metal-matrix composites LaB6-TiB2-Cu is at the copper level.
