Tensile Creep Behavior of SiC‐Based Fibers With a Low Oxygen Content

Abstract

The creep behavior of Hi‐Nicalon, Hi‐Nicalon S, and Tyranno SA3 fibers is investigated at temperatures up to 1700°C. Tensile tests were carried out on a high‐capability fiber testing apparatus in which the fiber is heated uniformly under vacuum. Analysis of initial microstructure and composition of fibers was performed using various techniques. All the fibers experienced a steady‐state creep. Primary creep was found to be more or less significant depending on fiber microstructure. Steady‐state creep was shown to result from grain‐boundary sliding. Activation energy and stress exponents were determined. Creep mechanisms are discussed on the basis of activation energy and stress exponent data. Finally, tertiary creep was observed at very high temperatures. Tertiary creep was related to volatilization of SiC. Results are discussed with respect to fiber microstructure.

Creep of Hi-Nicalon S Ceramic Fiber Tows at 800 deg C in Air and in Silicic Acid-Saturated Steam

“…Here the grain boundary or the lattice diffusion happens so quickly that the creation and annihilation of point defects at the grain boundary controls the process [4,134,135]. SA3 and Hi-Nicalon T M S fibers at various tempertures in a vacuum [138]. Evidence of all three stages of creep was found, with primary creep due, primarily, to viscoelastic deformation of carbon at the grain boundaries.…”

“…In other circles, such as organic (polymer) matrix composites, the term "creep" is used to describe a broader set of behaviors that result in permanent deformation of a Creep of Tyranno T M SA3 and Hi-Nicalon T M S fibers at 850 MPa (123 ksi) [138], reproduced with permission from Wiley.…”

“…Table 7. Power law creep parameters for third generation non-oxide fibers [138], data reproduced with permission from Wiley.…”

Micromechanical modeling of the elastic behavior of unidirectional CVI SiC/SiC composites

“…In order to avoid the limits due to the brittle nature of the monolithic SiC, while retaining its performances at high temperature and after irradiation, the material is studied under its composite form (Katoh et al, 2007). Particularly, the last generations of SiC/SiC composites currently developed are based on near-stoichiometric SiC fibers (Hi-Nicalon S or Tyranno-SA3 fibers) which present very stable properties (Sauder and Lamon, 2007;Sha et al, 2004). Several processes are still under consideration to deposit the SiC matrix within the woven fibrous preform (Naslain, 2004) and improve the thermo-mechanical behavior of the composite.…”

Low Pressure Joining of SiCf/SiC Composites Using Ti3AlC2 or Ti3SiC2 MAX Phase Tape

“…12,13) Accordingly, to increase the fiber's strength, it's very important to decrease the residual defects during the production process. Tyranno SA (produced by Ube Industries, Ltd.) is synthesized by a conversion process from an amorphous Si-Al-C-O fiber into SiC-polycrystalline fiber.…”