Thermomagnetic and Mossbauer Studies of Structural Transformations Caused in the Amorphous Nd_9Fe_(85)B_5 Alloy by Severe Plastic Deformation and Annealing

摘要

Thermomagnetic analysis and Mossbauer spectroscopy were used to study the effect of severe plastic deformation (SPD) by high-pressure torsion (HPT) and subsequent annealing on structural transfor-mations and formation of magnetic properties of rapidly quenched Nd_9Fe_(85)B_6 alloy. The HPT of the Nd_9Fe_(85)B_6 amorphous alloy was found to result in the precipitation of α-Fe nanocrystals and in changes in the structural state of the residual amorphous phase A'. In the annealed samples, there was revealed a great amount of nonequilibrium phases with different magnetizations. The total content of nonequilibrium phases depends on the annealing temperature and affects the exchange interaction between magnetically soft α-Fe nanocrystals and Nd_2Fe_(14)B nanocrystalline grains. The results obtained in this study can explain the differ-ences between the high level of hysteresis properties of nanocrystalline materials, which was predicted theo-retically, and low magnitudes realized in practice.