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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.43  No.8 (2002)  >  pp.1966-1973

MATERIALS TRANSACTIONS
<<Previous article Vol.43  No.8 (2002)   pp.1966 - 1973 Next article>>

Magnetic Properties and Phase Transformations of Bulk Amorphous Fe-Based Alloys Obtained by Different Techniques

Mihai Stoica1), Jarmila Degmová1)4), Stefan Roth1), Jürgen Eckert1), Helgard Grahl1), Ludwig Schultz1), Alain Reza Yavari2), Åke Kvick3) and Guido Heunen3)
1) IFW Dresden, Institute for Metallic Materials
2) LTPCM (CNRS umr 5614), Institut National Polytechnique de Grenoble
3) European Synchrotron Radiation Facilities ESRF
4) Department of Nuclear Physics and Technology, Slovak University of Technology


Bulk amorphous Fe65.5Cr4Mo4Ga4P12C5B5.5 rods with diameters of 1.5–3 mm were prepared by copper mold casting. Besides casting, bulk amorphous Fe77Al2.14Ga0.86P8.4C5B4Si2.6 samples in the shape of discs (diameter of 10 mm and thickness of 3 mm) were prepared from melt-spun ribbons by high-energy ball milling and subsequent compaction of the resulting powders in the supercooled liquid region. The as-cast amorphous FeCrMoGaPCB samples exhibit a low coercivity, below 10 A·m−1. In the case of the FeAlGaPCBSi alloy, the milling-induced stress causes significant differences in coercivity between the ribbons and the powders. The relatively low coercivity of about 5–10 A·m−1 characteristic for the melt-spun ribbons increases after 1 hour of ball milling to a value of about 2200 A·m−1. Subsequent annealing of the ball-milled powders leads to a decrease of Hc by a factor of 10 to about 220–250 A·m−1. The bulk samples prepared by hot pressing of the crushed ribbons show a coercivity of about 120–140 A·m−1. For both alloys, thermal stability measurements show a distinct glass transition, followed by a supercooled liquid region of 60 K for Fe65.5Cr4Mo4Ga4P12C5B5.5 and of 30 K for Fe77Al2.14Ga0.86P8.4C5B4Si2.6. For the Fe65.5Cr4Mo4Ga4P12C5B5.5 alloy, crystallization of the amorphous phase as observed by in-situ X-ray diffraction measurements in transmission configuration occurs via the formation of a metastable intermediate phase. The phases observed in the crystalline state obtained by heating do not correspond to those occurring after slow cooling.


Keyword:
iron-based alloys, melt-spun ribbons, ball-milled powders, supercooled-liquid region, coercivity, hot pressing, amorphous rods

Received: February 25, 2002
Accepted: April 15, 2002 , Published online: September 06, 2005
Copyright (c) 2005 The Japan Institute of Metals

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