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

Abstract Dense (ZrB 2 + SiC)/Zr 2 [Al(Si)] 4 C 5 composites with adjustable content of (ZrB 2 + SiC) reinforcements (0–30 vol.%) 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 Zr 2 [Al(Si)] 4 C 5 ceramic. ZrB 2 and SiC incorporated by in situ reaction significantly improve the mechanical properties of Z 2 [Al(Si)] 4 C 5 by the synergistic action of many mechanisms including particulate reinforcement, crack deflection, branching, bridging, “self-reinforced” microstructure and grain-refinement. With (ZrB 2 + SiC) content increasing, the flexural strength, toughness and Vickers hardness show a nearly linear increase from 353 to 621 MPa, 3.88 to 7.85 MPa·m 1/2 , and 11.7 to 16.7 GPa, respectively. Especially, the 30 vol.% (ZrB 2 + SiC)/Zr 2 [Al(Si)] 4 C 5 composite retains a high modulus up to 1511 °C (357 GPa, 86% of that at 25 °C) and superior strength (404 MPa) 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.