Annealed crystallization of ultrafine amorphous NiB alloy studied by XAFS

XAFS has been used to investigate the local structure evolutions of ultrafine amorphous NiB alloy during the annealed crystallization process. A nanocrystalline Ni phase with the local structure of crystalline Ni-like and a crystalline Ni3B, have been produced for ultrafine amorphous NiB alloy under the annealed temperature of 573 K. The results rule out Rojo et al.'s devitrification mechanism of Ni80B20 amorphous alloy in which they considered that an amorphous pure Ni phase is formed in the first exothermic process. However, our results are almost identical with Riveiro et al.'s conclusion in which the intermediate state is interpreted as two metastable crystalline phases of Ni3B and Ni-rich NiB alloy. With the annealed temperature going onto 773 K, the ultrafine NiB sample is further decomposed and crystallized into crystalline Ni with long-range order.