X-ray-absorption fine structure study on devitrification of ultrafine amorphous Ni-B alloys - art. no. 224201

X-ray-absorption fine structure (XAFS), x-ray diffraction, and differential thermal analysis have been combined to investigate the structure of ultraf ine amorphous Ni70B30 alloy during the crystallization process. The XAFS re sults demonstrate that a fee-like nanocrystalline Ni phase with a medium-ra nge order is formed at 573 K where the first exothermic process is observed . We confirmed that the metastable intermediate states consist of the two p hases, i.e., nanocrystalline Ni and crystalline Ni3B alloy. The results sup port the Riveiro et al.'s scenario [J. Magn. Magn. Mater. 188, 153 (1998)] for the devitrification of NiB alloy, in that crystalline phases of Ni3B an d Ni-rich NiB alloy are formed as the intermediate states. Based on the com plementary information obtained by the three techniques, we present a simpl e mechanism of crystallization process for the ultrafine amorphous Ni70B30 alloy.