Characterization of high-temperature compressive behaviour of field-assisted sintered niobium-alumina refractory composites

Nb-Al$_2$O$_3$ refractory composites have attracted significant attention due to their excellent performance at elevated temperatures. The incorporation of both metallic (Nb) and ceramic (Al$_2$O$_3$) phases enhances interest in these materials, i.e., the combination of the high toughness and plasticity of niobium with the refractoriness, high hardness, thermal stability, and oxidation resistance of alumina. In this study, the high-temperature mechanical behaviour of Nb-Al$_2$O$_3$ composites produced via field-assisted sintering (FAST) was investigated under compressive loading. Composites containing alumina particles of different sizes were subjected to compressive tests up to 1350 °C. The results were evaluated with respect to Nb content, alumina particle size, applied stress, and test temperature. Initial and post-mortem microstructural analyses were carried out to characterise the deformation behaviour. It was observed that an increase in the metal content led to an enhancement of plasticity, while changes in alumina particle size influenced the deformation behaviour.