The effects of microstructure on creep behaviour-A study through synchrotron X-ray tomography

A preliminary study has been carried out to investigate the influence of microstructure on creep behaviour using an Fe-Ni-Cr steel alloy as a model material. Creep rupture tests and synchrotron X-ray tomography were performed on as-cast (AC) and ex-service (ES) specimens. The results indicate that the combination of larger cavity volume and lower ductility in the AC specimen was attributed to initial microstructural differences in terms of carbide size and distribution. The location, orientation and shape of the voids were also considered to be important microstructural features as voids on grain boundaries were seen to have coalesced preferentially along the plane normal to the loading axis to form 'wedge' shaped voids.