High temperature mechanical strength and microstructural stability of advanced 9-12%Cr steels and ODS steels.
The present study proposes a comparison between several martensitic and ferritic steels in terms of creep strength and cyclic softening effect. The damage mechanisms are identified using fractographic observations and the microstructural evolutions are observed by TEM. The effects of a modified chemical composition on the high temperature mechanical behaviour are studied.
Effects of cyclic deformation on subgrain evolution and creep in 9–12% Cr-steels
Abstract Power plant components from modern 9–12% CrMoV-steels having fine precipitate stabilized subgrain structure undergo cyclic deformation as well as creep during service. The present work studies changes in subgrain structure due to cyclic straining and their effects on the creep behaviour in 12CrMoWVNbN10-1-1 steel. It was found that the cyclic plastic straining causes significant coarsening of the subgrain structure. Presence of hold periods during deformation significantly increases the extent of coarsening. Evolution of subgrain structure during cyclic deformation has been treated by extending the phenomenological law known from creep. Subgrain coarsening induced by cyclic deformation leads to significant increase in the resistance against creep.
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.