omposites with a Matrix Based on Niobium and Molybdenum Reinforced with Sapphire Fibers

Single-crystal sapphire fibers are obtained by the Stepanov/edge-defined film-fed growth (EFG) method. The procedure for obtaining them is described. Mechanical testing of the fibers is carried out according to the presented scheme, and the dependences of the limiting deformation and strength of the fibers on the length are determined. The dependences are of the power-law type and decrease with the length of the fibers. The strength of the obtained fibers corresponds to the international standard and meets the conditions for their use as reinforcing fibers for high-temperature composite materials. From blanks containing layer-by-layer unidirectionally arranged sapphire fibers, niobium powder, and metal foils of molybdenum and aluminum, layered-fibrous composites are obtained by solid-phase diffusion welding under load. Using scanning electron microscopy with X-ray analysis, the structure of the composites is studied. It is found that, in addition to the initial components, it includes intermetallic compounds of niobium, molybdenum, and aluminum, as well as solid solutions of these metals formed during the technological process. As a result of mechanical testing of the composite samples, deformation curves of load-deformation dependences are obtained, which, together with the developed fracture surfaces, indicate the nonbrittle nature of the fracture of composites containing brittle components. The dependences of the strength of the composites on temperature in the range of 20-1400degree celsius are obtained, which meet the requirements for high-temperature structural materials of this kind.