The control of nanocrystal formation in amorphous alloys is of particular importance for the development of advanced nanocrystalline materials. In the present study, the authors succeeded in controlling α-Fe and Nd2Fe14B nanocrystallization processes in amorphous Nd9Fe85B6 by a combination of severe plastic deformation at room temperature and subsequent thermal annealing. The α-Fe∕Nd2Fe14B nanocomposite magnets prepared by this approach possess homogeneously distributed nanocrystals with a small size, 15nm for α-Fe phase and 26nm for Nd2Fe14B, and therefore show enhanced magnetic properties as compared to those prepared by directly annealing amorphous Nd9Fe85B6.

A high number density ͑ϳ10 23 m −3 ͒ of ␣-Fe nanocrystals with a size below 10 nm has been induced in amorphous Nd 9 Fe 85 B 6 by high-pressure torsion deformation ͑HPTD͒ at room temperature. The amorphous Nd 9 Fe 85 B 6 subjected to HPTD presents a quite different crystallization behavior as compared with the nondeformed alloy. The growth activation energies E g = 0.9 eV for ␣-Fe nanocrystals and 0.5 eV for Nd 2 Fe 14 B nanocrystals are determined from the annealing time dependence of their size. The ␣-Fe/ Nd 2 Fe 14 B nanocomposite magnets prepared by the combination of HPTD and subsequent thermal annealing show enhanced magnetic properties due to a small grain size as compared with the magnets prepared by directly annealing amorphous Nd 9 Fe 85 B 6 .

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The influence of hydrogen on the deformation ahead of the crack tip and the crack propagation were observed and studied in situ under transmission electron microscopy with dynamic tensile deformation for bridge steel. The results show that hydrogen can promote local plastic deformation ahead of the crack tip and change the mode of crack propagation so that the crack will propagate in a zigzag path.