Impact of heat treatment on microstructure and tensile strength of monofilaments and bundles of aluminosilicate fibers

Abstract Continuous alumina fiber serves as the reinforcement phase within the Al 2 O 3 /oxide composite system, and its behavior at elevated temperatures significantly influences the mechanical properties of the composite. This study focuses on a novel type of continuous aluminosilicate fiber (AF18) to investigate the effects of heat treatment temperature (ranging from 1100°C to 1400°C) and duration (2/4/8 h) on the microstructure and mechanical properties of the monofilament. Acknowledging that fibers typically exist in bundles within the composite material, the study further examines the changes in tensile strength of these bundles following heat treatment at various temperatures. The findings indicate that both the heat treatment temperature and duration contribute to an increase in grain size and an enhancement in the surface roughness of the fiber, with the temperature having a more pronounced effect than the duration. The tensile strength of the original fiber monofilament is measured at 2.08 GPa, while the tensile strength of the tow exhibits a reduction of approximately 10% compared to the monofilament, with the degree of attenuation correlating with the heat treatment conditions. Notably, with 8 h of heat treatment at 1200°C, the fiber retains approximately 70% of its tensile strength, demonstrating its capacity for long‐term temperature resistance.