HIGH-TEMPERATURE FRACTURE

Deformation and fracture of materials at elevated temperatures are time-dependent processes. For different loading modes, cyclic or monotonous, cracks can nucleate on the free surface by localized corrosion at particles or interfaces or by cavity nucleation, growth and linkage in the interior of the material. In this short keynote paper corrosion effects are only discussed briefly. The main part is focused on cavity nucleation and growth. On the basis of recent measurements of cavity size distribution functions as a function of temperature, load and strain in bicrystals, bimaterial interfaces and directionally solidified oxygen-dispersion strengthened alloys, cavity growth by diffusion (quasi-equilibrium and crack-like cavities) and creep is discussed. In addition, experimental results on the effects of cavity nucleation on growth and the influence of cavity linkage on residual life are reported. These results are discussed from the viewpoint of predicting rupture life.