Metal treatment – Stock – Magnetic
Reexamination Certificate
2000-02-09
2001-10-09
Sheehan, John (Department: 1742)
Metal treatment
Stock
Magnetic
C420S435000, C420S440000
Reexamination Certificate
active
06299703
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to articles comprising magnetostrictive alloys, in particular, cobalt-iron-based magnetostrictive alloys.
2. Discussion of the Related Art
One application for highly magnetostrictive materials is magnetostrictive transducers, which convert electrical energy into mechanical energy or vice versa. Such transducers are useful for ultrasonic sound generators, magnetostrictive tuning in optical systems, acoustic delay lines, and other actuators and sensors. See, e.g., F. Claeyssen et al.,
J. of Alloys and Compound
, Vol. 258, 61 (1997).
Important requirements for practical application of magnetostrictive materials include the capability to provide high saturation magnetostriction in low applied fields, ease of fabrication into a desired shape, e.g., ductility and formability of the material, and low cost. The magnetostriction of Co—Fe alloys has been studied in previous work (see, e.g., R. C. Hall,
Trans. Metal. Soc. AIME
, Vol. 218, 268 (1960)). For example, a saturation magnetostriction of 130×10
−6
under a field of ~2000 Oe has been obtained on a cold rolled Co-30% Fe tape after 95% deformation (see E. A. Nesbitt,
J. Appl. Phys
., Vol. 21, 879 (1950)).
High saturation magnetostriction values in excess of 1000×10
−6
have been reported for TbFe
2
and other iron rare-earth compounds known as giant magnetostriction materials or terfenol. See, e.g., A. E. Clark,
Ferromagnetic Materials I
, edited by E. P. Wohlfarth, North Holland, Amsterdam, Chapter 7, 531 (1980), and R. E. Newnham,
MRS Bulletin
, 20 (May 1997). These materials, however, are brittle and require the use of a high magnetic field, typically 1000 Oe or higher, to obtain high magnetostriction. More recently, large magnetic-field-induced strains have been observed in magnetic shape memory alloys such as Ni
2
MnGa. See, e.g., R. C. O'Handley,
J. Appl. Phys
., Vol. 83, 3263 (1998) and J. K. Ulakko et al.,
Appl. Phys. Lett
., Vol. 69, 1966 (1996). These intermetallics, however, generally require single crystals or high magnetic fields to exhibit substantial magnetostriction.
Thus, improved magnetostrictive materials are desired, particular materials which not only exhibit good magnetostriction at relatively low applied field, but which are also capable of relatively easy formation, handling, and incorporation into devices.
SUMMARY OF THE INVENTION
The invention provides an alloy exhibiting high magnetostriction in relatively low applied magnetic fields, the alloy capable of being formed in a relatively easy manner and having desirable physical properties. Specifically, the Co—Fe alloy of the invention exhibits a magnetostriction of at least 100×10
−6
in a magnetic field less than 400 Oe, advantageously in a magnetic field less than 100 Oe. The alloy is formed by plastically deforming the alloy, e.g., by cold rolling, to a reduction in cross-sectional area of at least 50%, and then heat treating the alloy to induce recrystallization. This combination of plastic deformation and recrystallization was found to provide desirable grain growth and microstructure. Moreover, the alloy is capable of being quenched from the heat treatment temperature to provide useful ductility. The resultant alloy is useful in a variety of device components, including transducers, frequency filters, signal delay lines, and optical fiber grating devices.
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F. Claeyssen, et al., “Actuators transducers and motors based on giant magnetostrictive materials”,Journal of Alloys and Compounds, vol. 258, 61, (1997).
A. E. Clark,Ferromagnetic MaterialsI, edited by E.P. Wohlfarth, North Holland, Amsterdam, Ch. 7, 531 (1980).
R. E. Newnham, “Molecular Mechanisms in Smart Materials”,MRS Bulletin, 20, (1997).
R. C. O'Handley, “Model for strain and magnetization in magnetic shape-memory alloys”,Journal of Applied Physics, vol. 83, No. 6, 3263 (1998).
R.C. Hall “Magnetic Anisotrophy and Magnetostriction of Ordered and Disordered Cobalt-Iron Alloys”,Trans. Metall. Society of AIME, vol. 218, 268 (1960).
K. Ullakko, et al., “Large magnetic-field-induced stains in Ni2MnGa single crystals”,Appl. Phys. Lett.vol. 69, No. 13, 1966 (1996).
Chen Li-Han
Jin Sung-ho
Klemmer Timothy J.
Mavoori Hareesh
Agere Systems Guardian Corp.
Rittman Scott J.
Sheehan John
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