This work is a study into the possibilities of self healing of early stage creep damage (i.e. grain boundary pores) in iron based model alloys by site-specific precipitation of substitutionally dissolved Cu atoms. The precipitation of copper is found to occur in the form of (a) spherical nanoscale precipitates within the matrix, (b) decoration of dislocations and/or (sub)grain boundaries and (c) precipitation at free creep cavity surfaces. Due to the comparable atomic size of Cu and Fe the copper precipitation is found to be only weakly site specific and does not have a strong preference for creep cavity surfaces. The addition B and N to the Fe-Cu alloys generally retards the Cu diffusion along dislocations and (sub)grain boundaries. This does not change the overall precipitation mechanism, but modifies the precipitation rate and distribution over the potential precipitation sites. No indications were found for an independent healing mechanism for creep damage by BN precipitation within creep cavities for the studied ferritic Fe-Cu alloys. The defect-induced precipitation of Cu was only weakly affected by the introduction of about 0.1 wt.% C in the alloy.
This chapter summarises the main findings of the work already published in the open literature.
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