Local structure around a nitrogen atom for Cr–N and V–N amorphous alloys prepared by mechanical alloying

Abstract Cr 81 N 19 and V 76 N 24 amorphous alloys were prepared by mechanical alloying under nitrogen gas atmosphere. Detailed structures for the two samples were studied by neutron diffraction. A coherent scattering length for the N atom for neutron scattering is much larger than that of the Cr atom, and moreover that of the V atom is negative and very small compared to those of Cr and N atoms. Radial distribution functions (RDF(r)) clearly indicate a positive peak around 2 A for the Cr–N system and also a negative peak around 2 A for the V–N system. In contrast, only very small positive peak in the vicinity of 2 A was observed in RDF(r)s by X-ray diffraction with Mo-Kα radiation for the Cr–N and V–N systems. Therefore, these peaks can be identified as Cr–N and V–N correlations, respectively. Areas of the positive Cr–N and negative V–N peaks mean the coordination numbers of metal atoms (Cr or V) around a N atom, which were calculated to be 5.5 and 5.1 atoms for the Cr–N and V–N systems. The results indicate that the N atom absorbed during the mechanical alloying (MA) process is located at the center of polyhedra formed by 4 and 6 metal atoms for stabilizing the amorphous structure.