Mechanical spectroscopy studies of partially amorphous Nd60Fe30Al10 alloys

• Published in: Physica. B, Condensed matter Condensed matter, 2004-12, Vol.354 (1-4), p.220-223
• Main Authors: TARNOWSKI, German C, SALVA, Horacio, GHILARDUCCI, Ada A, URRETA, Silvia E, BILLONI, Orlando V, FABIETTI, Luis M
• Format: Article
• Language: English
• Subjects: Amorphous and quasicrystalline magnetic materials; Anelasticity, internal friction, stress relaxation, and mechanical resonances; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Magnetic properties and materials; Mechanical and acoustical properties of condensed matter; Physics; Studies of specific magnetic materials
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2004.09.052

The hard magnetic properties of melt spun Nd60Fe30Al10 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.