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Mechanical spectroscopy studies of partially amorphous Nd60Fe30Al10 alloys

✍ Scribed by Germán C. Tarnowski; Horacio Salva; Ada A. Ghilarducci; Silvia E. Urreta; Orlando V. Billoni; Luis M. Fabietti


Publisher
Elsevier Science
Year
2004
Tongue
English
Weight
567 KB
Volume
354
Category
Article
ISSN
0921-4526

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✦ Synopsis


The hard magnetic properties of melt spun Nd 60 Fe 30 Al 10 alloys are attributed to a major matrix nominally amorphous for X-ray diffraction, composed by two metastable nanosized ($5 nm) phases with different intrinsic magnetic properties. This composite system is investigated for the first time by mechanical spectroscopy techniques in the temperature range between 50 K and 450 K (1 kHz) where large annealing effects and two damping phenomena are detected. The as-cast microstructure irreversibly changes during annealing above 330 K, leading to a large modulus recovery accompanied by a reduction in the internal friction level. A relatively large relaxation effect is observed about 290 K, evidenced by a narrow internal friction peak with the corresponding step in the elastic modulus; this peak remains stable under thermal cycling between 200 K and 300 K but is affected by aging at 330 K and practically vanishes after heating to 450 K. Another internal friction peak is observed at about 250 K which has associated an anomalous modulus effect; in this temperature range, the internal friction and the elastic modulus exhibit heating/cooling hysteresis, which strongly depends on the extreme temperatures of the thermal cycle, a behavior frequently associated to first-order phase transformations.


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Glass forming ability (GFA) of Nd 60 TM 30 Al 10 (TM = Fe, Co, Ni, Cu or Mn) alloys was studied. From X-ray diffraction measurement, highly textured Nd nanocrystallites are observed on the free surfaces of the Fe-, Mn-melt-spun ribbons, while the Co-, Ni-, Cu-melt-spun ribbons are fully amorphous. A