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

Single-crystal sapphire fibers were obtained by the Stepanov method/EFG – Edge defined Film-fed Growth. The procedure for obtaining them is described. Mechanical testings of the fibers were carried out according to the presented scheme, and the dependences of the ultimate deformation and strength of the fibers on the length were determined. The dependences are power-law, and decrease with the length of the fibers. The strength of the obtained fibers corresponds to the world level and meets the conditions for their use as reinforcing for high-temperature composite materials. From workpieces containing layer-by-layer unidirectionally arranged sapphire fibers, niobium powder, metal foils of molybdenum and aluminum, layered-fibrous composites were obtained by solid-phase diffusion welding under load. Using scanning electron microscopy with X-ray analysis, the structure of the composites was studied, it was 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 in the technological process. As a result of mechanical testing of composite samples, deformation curves of load-deflection dependences were obtained, which, together with developed fracture surfaces, indicate the non-brittle nature of the fracture of composites containing brittle components. The dependences of the strength of composites on temperature in the range of 20–1400°C are obtained, which meet the requirements for high-temperature structural materials of this kind.