Engineering nanocrystalline materials from amorphous precursors

Various processes have been developed for the production of nanocrystalline materials. One interesting technique is the “nano-crystallization” of amorphous precursors. For example, new soft magnetic nanocrystalline materials, with a composition such as Fe87Zr7Cu1B5, are based on the thermal crystallization of an amorphous ribbon. In this work, we show that with a sufficient understanding of the amorphous nature of an alloy we can design a specific crystallization process that will produce a unique nanostructured material. Two examples of such design are presented here. The first involves the possibilities of using mechanical energy to induce crystallization of an amorphous alloy. For amorphous Fe90Zr10, it is possible to produce a partly nanocrystalline material having an average crystal size of about 2 to 4 nm and a unique structure. The second looks at the effects of the atmosphere on the nano-structure during the annealing of amorphous Fe87Zr7Cu1B5. In this case, elemental reactivity could be used to trigger a specific crystallization path. These examples show that nano-crystallization can open the door to the design of complex and unique nanocrystalline materials.