日本金属学会誌

J. Japan Inst. Metals, Vol. 63, No. 3 (1999),
pp. 367-374

Formation of Nanocrystalline Structure in Amorphous Fe-Cu-Nb-Si-B Alloys

Yoshihiro Takahara

Department of Materials Science and Engineering, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550

Abstract:

We have investigated the formation and its kinetics of nanocrystalline structure in amorphous Fe74Cu1Nb3.5Si13B8.5 alloy by differential scanning calorimetry, electrical resistivity measurement, X-ray diffraction and transmission electron microscopy.
The solid solution bcc-Fe(Si) phase including Si appeared as the primary crystal during isothermal annealing at 773 K. The maximum grain size of the crystalline phase was about 26 nm after annealing for 360 ks. The volume fraction of the nanocrystalline phase after the annealing was estimated to be about 70% from the analysis of X-ray diffraction profiles. A progressive increase in the Si content of the solid solution bcc-Fe(Si) during crystallization has been revealed. We estimated the diffusivity D from the annealing time dependence of the largest grain size, and obtained D=2.0{×}10-20 m2/s. This value agrees with the diffusivity for Nb volume diffusion in bcc-Fe at 773 K, which means that Nb diffusion is the rate-determining process for the growth of the bcc-Fe(Si) crystals. On the other hand, the DSC curves measured for the formation of nanocrystalline structure were well reproduced by the grain growth model proposed by Chen and Spaepen.


(Received July 24, 1998; In Final Form October 21, 1998)

Keywords:

amorphous alloy, nanocrystalline structure, grain growth, kinetics, iron-copper-niobium-silicon-boron alloy, differential scanning calorimetry


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