Magnetostrictive material

Details Magnetostrictive material Magnetostrictive material

1998-10-14

2001-11-06

Sheehan, John (Department: 1742)

Metal treatment

Stock

Magnetic

C075S246000

Reexamination Certificate

active

06312530

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magnetostrictive materials used for ultrasonic vibration elements, actuators and sensors. The present invention particularly relates to a magnetostrictive material primarily containing iron, a rare earth element, and a transition metal.
2. Description of the Related Art
Alloys RT
2
composed of a specified rare earth element R and a specified transition metal T are known as magnetostrictive materials having a large magnetostrictive constant. Among them, the alloy having a composition Tb
0.26
Dy
0.74
Fe
2
has a large magnetic susceptibility and a large electromechanical coupling coefficient due to low magnetocrystalline anisotropy, and is known as a super-magnetostrictive material having excellent magnetostrictive characteristics. Recently, Tb-Fe-based magnetostrictive materials have also been studied. The materials are produced by annealing quenched amorphous ribbons to form precipitates of fine crystalline phases in order to reduce magnetocrystalline anisotropy.
A magnetostrictive material composed of the Tb
0.26
Dy
0.74
Fe
2
alloy is produced through many production steps as follows. The alloy is melted by high frequency melting or arc melting, the melt is cooled into a given shape, and the product is annealed for a prolonged period to remove process strain. Thus, the process cost is inevitably high.
An effective method for raising the electromechanical coupling coefficient of such a magnetostrictive material is to orient the axis for easy magnetization (hereinafter referred to as the “easy axis”) of crystal grains in the texture. Such a means, however, requires high-skill technologies with high production costs. Further, the magnetostrictive material is disadvantageous with respect to workability or processability because of its high mechanical strength and low toughness.
Since the Tb-Fe-based magnetostrictive material including fine crystalline textures is produced as a ribbon, materials having shapes other than a ribbon are obtainable with difficulty.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a magnetostrictive material which has high workability and excellent magnetostrictive characteristics, and which can be formed into desired shapes at low production costs.
A magnetostrictive material in accordance with the present invention is produced by annealing an alloy consisting essentially of an amorphous phase and comprising Fe, Dy, and Tb as primary components, at least one element selected from the group consisting of Ta, Nb, Zr, Hf, V, W, Mo, Si and B and/or at least one element selected from the group consisting of Cr, Al, Ga, Ge, Cu, Au, Ag, Pt, Pd, Os, Ir, and Rh.
The magnetostrictive material may be a compact formed by compacting and sintering the powder of the alloy consisting essentially of the amorphous phase so as to precipitate fine crystalline phases having an average crystal grain size of 100 nm or less.
The compact may be formed by compacting and sintering the powder of the alloy consisting essentially of the amorphous phase by means of a softening phenomenon when the alloy is crystallized.
The compact may be formed by compacting and sintering the powder under a stress of the alloy consisting essentially of the amorphous phase when the alloy is crystallized.
Preferably, the magnetostrictive material has magnetic anisotropy in the direction of the pressure which is applied to the magnetostrictive material.
Preferably, the compact has a relative density of 90% or more.
Preferably, the compact is formed by sintering and simultaneously annealing the powder of the alloy consisting essentially of the amorphous phase so as to precipitate fine crystalline phases having an average crystal grain size of 100 nm or less.
Preferably, the temperature of the annealing is in a range of 400° C. to 800° C.
Preferably, the alloy is represented by the formula:
(T
1-a-b
DY
a
Tb
b
)
100-x-y
M
x
E
y
wherein T denotes at least one element selected from the group consisting of Fe, Co and Ni; M denotes at least one element selected from the group consisting of Ta, Nb, Zr, Hf, V, W, Mo, Si and B; E denotes at least one element selected from the group consisting of Cr, Al, Ga, Ge, Cu, Au, Ag, Pt, Pd, Os, Ir, and Rh; 0≦a≦0.5; 0≦b≦0.5; 0.1≦a+b≦0.5; 0 atomic percent≦x≦10 atomic percent; 0 atomic percent≦y≦10 atomic percent; and 2 atomic percent≦x+y≦20 atomic percent.


REFERENCES:
patent: 4152178 (1979-05-01), Malekzadeh et al.
patent: 5110376 (1992-05-01), Kobayashi et al.
patent: 5336337 (1994-08-01), Funayama et al.
patent: 8027545A (1996-01-01), None
patent: 8-27545 (1996-01-01), None

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