Rolf Sandström

By Rolf Sandström and Junjing He

Cavitation plays an important role in plants operating at high temperatures since the cavitation controls the creep failure of engineering alloys. In the past it has been difficult to predict the cavitation behaviour with the help of basic models, since critical models have been missing. Recently new models have been formulated for grain boundary sliding, cavity nucleation and cavity growth to fill this gap. These models are reviewed in this chapter. It is shown that the new models can quantitatively predict cavitation for austenitic stainless steels, where detailed experimental information is available.

Part of the book: Study of Grain Boundary Character

By Rolf Sandström

Analysis of creep properties has traditionally been made with empirical methods involving a number of adjustable parameters. This makes it quite difficult to make predictions outside the range of the original data. In recent years, the author has formulated basic models for prediction of creep properties, covering dislocation, particle and solid solution hardening. These models do not use adjustable parameters. In the present chapter, these models are further developed and utilised. The dislocation mobilities play an important role. The high-temperature climb mobility is extended to low temperatures by taking vacancies generated by plastic deformation into account. This new expression verifies the validity of the combined climb and glide mobility that has been used so far. By assuming that the glide rate is controlled by the climb of the jogs, a dislocation glide mobility is formulated. The role of the mobilities is analysed, and various creep properties are derived. For example, secondary creep rates and strain versus time curves are computed and show good agreement with experimental data.

Part of the book: Creep