Creep grain boundary sliding

R. Raj and M.F. Ashby. On grain boundary sliding and diffusional creep. Metall. Trans., 2 1113-1127, 1971. 

Duclos, R., Crampon, J., and Carry, C., Grain-boundary sliding and accommodation mechanism during creep of yttria-stabilized zirconia , Phil. Mag. Lett., 2002, 82, 529-33. 

Langdon, T.G., The significance of grain boundary sliding in creep and superplasticity , Metal Forum, 1981, 4, 14-23. 

Fine-grained materials, when subjected to high temperatures and low applied stresses, deform by mutual accommodation of grains assisted by grain boundary sliding and transport of matter (diffusion). Under conditions where lattice diffusion dominates, the diffusional creep rate is reasonably well characterized by the Nabarro-Herring creep process. (For a review of this and other classical creep mechanisms, see Refs. 5 and 6.) Here the strain rate is expressed as... 

F. W. Crossman and M. F. Ashby, The Non-Uniform Flow of Polycrystals by Grain Boundary Sliding Accommodated by Power Law Creep, Acta Metall., 23, 425-440 (1975). 

TADB-derived ceramic fibers, with the idealized composition SiBNsC, do not reach the E-modulus of the most advanced SiC fibers at room temperature. However, they are clearly superior to the latter in a crucial point, namely the drop of the E-modulus and of the creep resistance at high temperatures. SiC fibers already lose a large part of their mechanical strength below 1400 °C, as can be measured by creep resistance. These limitations are fundamental in nature, since they are related to grain boundary sliding and thus to the crystallinity of SiC. In contrast, amorphous SiBNsC fibers do not show any grain boundaries and, moreover, the concentration of microstructural flaws is extremely low. 

---