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The microstructure of the nanocrystalline \Fe78B13Si9 alloy, prepared by means of high-current-density electropulsing from the parent amorphous alloy (2605S-2), has been investigated by Mössbauer spectroscopy along with X-ray diffraction and transmission electron microscopy. The experimental results show that nanocrystalline \Fe78B13Si9 alloy is uniformly composed of the grains about 23 nm in diameter, with an interfacial component. Two crystalline phases are a disordered α-Fe(Si) solid solution with an Si concentration of 11.3 at.% and t -Fe2B. The interface phase is ferromagnetic Fe6.7B4.1Si2.2 with large number of voids, and is estimated to be about 1.3 nm thick with four to five atomic layers. The examination of a comparable isothermally annealed amorphous \Fe78B13Si9 sample reveals that the crystalline of the amorphous \Fe78B13Si9 alloy and its ultrafine grain structure should be attributed mainly to the electromagnetic effect from high-current-density electropulsing. The mechanism involved is discussed.

The amorphous Fe78B13Si9 (Metglas 2605S‐2) alloy is treated by high current density electropulsing and the preliminary, partial, and full nanocrystallization can be achieved at temperatures lower than the bulk crystallization temperature by isothermal annealing. Analysis of Mössbauer spectra along with XRD measurement and TEM observation is presented. The preliminary crystalline product is the disordered b.c.c. Fe‐based solid solution, probably containing a trace amount of B. In the partially and fully crystallized samples, α‐Fe(Si), t‐Fe2B, and also a small amount of t‐Fe3B appear. The hyperfine magnetic field distribution P(H) of the residual amorphous phase in the crystallized sample takes a distinct bimodal type. It was suggested that the secondary peak at the higher field side can be associated with Fe‐rich clusters in the residual amorphous phase of the preliminarily crystallized sample and that the lower field side is caused by the local segregation of some Si and B atoms in the residual amorphous phase excluded during the crystallization processes of the partially and fully nanocrystallized samples.

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An inverted torsion pendulum is used to study the high temperature internal friction of Al‐0.073 wt% Zr alloy. Two internal friction peaks well separated from each other, the bamboo boundary peak and the conventional grain boundary peak, are observed in the original internal friction curve when the size of some grains is larger than the diameter of the specimen. The height of the bamboo boundary peak increases while that of the grain boundary peak decreases with increasing number of bamboo‐like grains. The bamboo boundary peak in the completely bamboo‐structured specimen decreases linearly in height with increasing size of bamboo grains, until the peak is completely absent in the single crystal specimen. The peak temperature of the bamboo boundary peak and the associated activation energy are 690 K (fp = 0.29 Hz) and 3.20 eV when bamboo grains coexist with fine grains, and 635 K (fp = 0.31 Hz) and 2.74 eV when the complete bamboo structure is formed, respectively. Combining the electron microscopic observation of the second phase particles in boundaries, it is suggested that the bamboo boundary peak is originated by the stress relaxation of the particle‐bearing boundary.