关键词: 碳化硅纤维, 高温原位拉伸强度, 拉伸性能, 微观结构, 晶粒粗化

Abstract: Continuous silicon carbide (SiC) ceramic fibres serve as reinforcements for composites used in aerospace and advanced nuclear energy applications. High-temperature tensile performance is a key property for ceramic fibres employed in extreme environments. However, reports on the in-situ high-temperature tensile properties of SiC fibres remain limited. In this study, in-situ high-temperature tensile tests using both cold-grip and hot-grip methods were employed to systematically investigate the relationships among composition, microstructure, and mechanical properties of SiC fibres from room temperature up to 2000 ℃ under different atmospheres. The high-temperature tensile strength of fibre tows is influenced by the atmosphere. At 1200 ℃, oxidation in air causes the tensile strength to decrease from 1632 MPa at room-temperature value to 417 MPa, retaining 44.4% of the original strength. In contrast, in an argon atmosphere at the same temperature, the tensile strength is 843 MPa, corresponding to a retention rate of 89.7%. In an argon atmosphere, the tensile strength retentions at 1400 ℃ and 1600 ℃ are 76.1% and 63.5%, respectively. Above 1700 ℃, the tensile strength decreases significantly, owing to rapid coarsening of β-SiC grains and the formation of pore defects from the decomposition of some amorphous phases. At 2000 ℃, the fiber strength drops to only 331 MPa, only retaining 22.5% of its original strength. This study reveals that SiC fibres exhibit relatively high strength retention in argon below 1600 ℃, and elucidates the mechanisms governing the evolution of high-temperature mechanical properties above 1700 ℃, including grain coarsening, partial phase decomposition and phase transformation. Therefore, this study provides critical fundamental data to support the high-temperature engineering application of domestic SiC fibres.

Key words: silicon carbide fibre, in-situ high-temperature tensile strength, tensile property, microstructure, grain coarsening