Abstract
Irradiation creep beyond the transient regime was investigated for various silicon carbide (SiC) materials. The materials examined included polycrystalline or monocrystalline high-purity SiC, nanopowder sintered SiC, highly crystalline and near-stoichiometric SiC fibers (including Hi-Nicalon Type S, Tyranno SA3, isotopically-controlled Sylramic and Sylramic-iBN fibers), and a Tyranno SA3 fiber-reinforced SiC matrix composite fabricated through a nano-infiltration transient eutectic phase process. Neutron irradiation experiments for bend stress relaxation tests were conducted at irradiation temperatures ranging from 430 to 1180 °C up to 30 dpa with initial bend stresses of up to ∼1 GPa for the fibers and ∼300 MPa for the other materials. Initial bend stress in the specimens continued to decrease from 1 to 30 dpa. Analysis revealed that (1) the stress exponent of irradiation creep above 1 dpa is approximately unity, (2) the stress normalized creep rate is ∼1 × 10-7 [dpa-1 MPa-1] at 430-750 °C for the range of 1-30 dpa for most polycrystalline SiC materials, and (3) the effects on irradiation creep of initial microstructures - such as grain boundary, crystal orientation, and secondary phases - increase with increasing irradiation temperature.
| Original language | English |
|---|---|
| Pages (from-to) | 97-111 |
| Number of pages | 15 |
| Journal | Journal of Nuclear Materials |
| Volume | 478 |
| DOIs | |
| State | Published - Sep 1 2016 |
Funding
This work was supported by the Office of Fusion Energy Sciences, U.S. Department of Energy , under contract DE-C05-00OR22725 with UT-Battelle, LLC, and the US–Japan TITAN Collaboration on Fusion Blanket Technology and Materials . Research was supported in part by the High Flux Isotope Reactor, which is sponsored by the Office of Basic Energy Sciences, U.S. Department of Energy . The authors would like to gratefully acknowledge contributions to pre- and post-irradiation experiments from F. C. Montgomery, C. M. Silva, A. M. Williams, P. S. Tedder, C. Shih and M. R. McAlister at Oak Ridge National Laboratory, and M. Fukuda at Tohoku University.