In situ synthesis, microstructure, mechanical properties and thermal shock resistance of (ZrB2 + SiC)/Zr2[Al(Si)]4C5 composites

Abstract

Dense (ZrB2+SiC)/Zr2[Al(Si)]4C5 composites with adjustable content of (ZrB2+SiC) reinforcements (0–30vol.%) were prepared by in situ hot-pressing. The microstructure, room and high temperature mechanical and thermal physical properties, as well as thermal shock resistance of the composites were investigated and compared with monolithic Zr2[Al(Si)]4C5 ceramic. ZrB2 and SiC incorporated by in situ reaction significantly improve the mechanical properties of Z2[Al(Si)]4C5 by the synergistic action of many mechanisms including particulate reinforcement, crack deflection, branching, bridging, “self-reinforced” microstructure and grain-refinement. With (ZrB2+SiC) content increasing, the flexural strength, toughness and Vickers hardness show a nearly linear increase from 353 to 621MPa, 3.88 to 7.85MPa·m1/2, and 11.7 to 16.7GPa, respectively. Especially, the 30vol.% (ZrB2+SiC)/Zr2[Al(Si)]4C5 composite retains a high modulus up to 1511°C (357GPa, 86% of that at 25°C) and superior strength (404MPa) at 1300°C in air. The composite shows higher thermal conductivity (25–1200°C) and excellent thermal shock resistance at ΔT up to 550°C. Superior properties render the composites a promising prospect as ultra-high-temperature ceramics.