Observation of Nitrogen Induced Amorphization of the V-Cu System by EXAFS, X-ray and Neutron Diffractions

概要

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Mechanical alloying (MA) of V_<70>Cu_<30> powders which is characterized by a positive heat of mixing was carried out under the N_2 gas atmosphere. The structure factor S^X(Q) observed by X-ray diffraction gradually changes into a structure characteristic of an amorphous state with increasing milling time. This indicates the amorphization induced by nitrogen. The S^N(Q) by neutron diffraction after 200 hours of milling also confirmed the formation of an amorphous phase with the residual pure Cu. Since the coherent scattering length of the V atom in the neutron diffraction is negligibly small, crystalline peaks can be easily identified as the fcc Cu. A drastic change of the EXAFS profile around a V atom was more clearly observed than that around a Cu atom. These results allow us to conclude that the bcc solid solution is formed at the early stage of milling and then that the amorphization gradually proceeds in the subsequent stage of milling by incorporating N atoms into the bcc solid solution.amorphousstructuremechanical alloyingneutron scattering
東北大学の論文
1997-03-25