Effect of Argon Atmosphere Heat Treatment on Mechanical Properties and Microstructural Evolution of Shicolon-II SiC Fibers

Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance. Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes. This study presents a comprehensive investigation into evolution of the mechanical properties, surface microstructure, and composition of Shicolon-II fibers subjected to argon heat treatment at temperatures ranging from 1300 ℃ to 1700 ℃. The Shicolon-II fibers are composed of small-sized β-SiC grains, SiC x O y amorphous phase, and a minor amount of graphite microcrystals. Following treatment in an argon atmosphere at 1300 ℃, the fibers maintain a monofilament tensile strength of 3.620 GPa, corresponding to a retention of 98.32%. This strength diminishes to 2.875 GPa, equating to a retention of 78.08%, after treatment at 1500 ℃. The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains. Furthermore, creep resistance is an essential factor influencing the long-term performance of composite materials. After treatment at temperatures above 1400 ℃, the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains. This study offers valuable theoretical insights into high-temperature applications of second-generation fibers, contributing to an enhanced understanding of their performance under extreme conditions.