Neutron Small-Angle-Scattering Studies of Metal Alloys Produced by Solid State Reaction

We have used neutron Small Angle Scattering (SAS) experiments to investigate the changes in large scale structures (in the size range 50-1000 A) which accompany the Mechanical Alloying (MA) of pure metallic powders and the Mechanical Milling (MM) of intermetallic compounds. New results on NiTi MA treated alloys are presented, and a comparison is made between our neutron SAS data on NiMo, NiTi, and FeTi alloys. These suggest that amorphization reactions are initiated after the formation of highly convoluted two-phase structures characterized by linear dimensions down to 150-50 A. We have found that the SAS intensity can often be expressed as a power law of the scattering vector Q exp -g and that the magnitude of g is related to the degree of amorphization in the MA treated samples. The values of g obtained lie in a range which suggests that both surface fractals and volume fractals are useful concepts for describing the inner morphology of these new alloys. (Author)