Characterization of Fe-Cr alloys using SANS, nanoindentation and ultrasound

Ferritic/martensitic Cr-steels are candidate structural materials for future nuclear applications. Fe-Cr alloys serve as model alloys for the investigation of the effect of Cr on microstructure, properties and irradiation behaviour. Industrial purity Fe-Cr alloys of Cr levels of 2.5, 5, 9 and 12 at% were produced at SCK•CEN Mol within the MIRE project and characterized with respect to composition, microstructure, dislocation arrangement and tensile properties [M. Matijasevic et al., JNM 377 (2008) 147]. The present contribution is devoted to the complementary characterization of the same set of materials by means of small angle neutron scattering (SANS), depth-sensing nanoindentation and sound velocity measurements.
SANS experiments were performed in the wide range of scattering vectors from 0.03 to 3 nm 1 using three different sample-detector distances. Incoherent and coherent scattering were identified and discussed as a function of Cr content. Depth-sensing nanoindentation was performed at maximum loads ranging from 1 to 500 mN and supplemented with Vickers hardness. Interestingly, some of the curves representing the load dependence of nanohardness for different Cr contents cross one another indicating an effect of Cr on the indentation-size effect. The velocity of both longitudinal and shear waves was measured using the ultrasound pulse-echo technique. The polycrystalline averages of the elastic constants were estimated as a function of Cr. First results on the effect of both ion and neutron irradiation will also be presented.