Microhardness and microstructure of He-irradiated nickel and amorphous Ni40Fe40P14B6

The aim of this work is the study of possible changes after irradiation in the sub-surface structure and the microhardness of nickel and amorphous nickel alloy Ni40Fe40P14B6 (Met Glasssup(R) 2826). The samples have been irradiated at room temperature with a 50 keV helium ion beam to doses ranging from 1015 to 1017 He ions/cm2. These dosages are smaller than the critical dose (3 x 1017He ion/cm2) for blister formation at this energy. The microhardness of nickel increases with dose whereas no change is observable in Met Glasssup(R) 2826. The irradiated samples have also been investigated under a transmission electron microscope. The increase in the microhardness of Ni is attributed to the formation of interestitial loops which interact with dislocations giving rise to the observed complex dislocation net work. Again, no change in the microstructure of Met Glasssup(R) 2826 is observed, indicating that irradiation does not drastically affect the disordered state. Transformation to polycrystallanity is ruled out by electron diffraction data. (author)