Refractory composites based on Nb-Al₂O₃ have been developed for applications as thermo-mechanically highly stressed components in metal producing industries. Such refractory components have to withstand extreme conditions, where they are exposed not only to high temperatures but also to challenges such as oxidation, high thermal and mechanical stresses, and creep. Their high-temperature mechanical behavior is determined by the choice of raw materials (particle size distribution), composition, manufacturing technology, thermal treatment and postprocessing. The resulting physical (density, porosity, electrical conductivity) and thermal properties (thermal conductivity, shrinkage during sintering) are crucial to design sophisticated solutions. In this study, the high-temperature mechanical properties of coarse- as well as fine-grained Nb-Al₂O₃ refractory composite materials produced using three different manufacturing methods: casting, extrusion, and field-assisted sintering (FAST) were evaluated. Cylindrical specimens were subjected to compressive loads, and further tests including creep and stress-relaxation were conducted at temperatures up to 1500°C. The results indicate that the particle size of the raw materials, the manufacturing technology and the resulting porosity of the components significantly affect the deformation behavior of the Nb-Al₂O₃ refractory composites.

Keywords: refractory composites, mechanical properties, creep, porosity