Structure of the nanocrystalline Fe_(41)Ni_(20)Co_(20)Zr_7B_(12)alloy formed by ball milling

摘要

High-energy ball milling technique with subsequent heat treatment were used to prepare the nanocrystalline Fe_(41)Ni_(20)Co_(20)Zr_7B_(12) alloy. The powder samples were obtained by mechanical milling of the melt-spun amorphous ribbon and by mechanical alloying of the mixture of pure elemental powders with the corresponding composition. Combined X-ray diffraction and Mossbauer spectroscopy measurements allowed the structural characterization of the samples. The powder prepared from the ribbon remained amorphous after milling for 27 h, while the milling of the mixture of crystalline elements for 200 h led to the formation of the nanocrystalline iron-based random solid solution. Differential scanning calorimetry results revealed three exothermic peaks, however, crystallization temperatures determined for the nanocrystalline powder were much lower that those obtained for the amorphous one. The first two stages correspond to the formation of the bcc FeCo nanograins. Annealing at higher temperatures caused the crystallization of the bcc phase followed by the formation of the iron-based borides. The magnetization measurements performed as a function of temperature confirmed the amorphous and crystalline states of the ball milled ribbon and mechanically alloyed elemental powders, respectively. The Curie temperature of the amorphous ribbon is markedly higher than that of the amorphous powder.