JPH0551704A - Ultra-magnetostrictive alloy - Google Patents

Abstract

PURPOSE:To obtain an ultra-magnetostrictive alloy having high Curie temp. and superior magnetostrictive properties by incorporating rare earth elements, Fe and/or Co, and at least one element among B, C, and N in specific proportions. CONSTITUTION:An alloy having a composition represented by a general formula RXT100-X-YMY [where R means at least one kind among rare earth elements including Y, T means Fe and/or Co, M means at least one element among B, C, and N, and the symbols (X) and (Y) stand for, by atom, 20-60% and 0-30%, respectively] is used and rare earth elements and Fe or Co are melted in the above proportion and an ingot of the resulting molten metal is machined and subjected to crystal control melting in an atmosphere containing N gas, such as N gas, NH3 gas, and CN gas, to incorporate N, or, an alloy containing rare earth elements and Fe or Co and further containing specific amounts of B, C, etc., is refined and an ingot of the resulting molten alloy is subjected to homogenizing heat treatment. By this method, the ultra-magnetostrictive alloy where coercive force is reduced without deteriorating magnetostrictive properties and other magnetic properties can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a giant magnetostrictive alloy used for a magnetic-mechanical displacement conversion device or the like, and more particularly to a giant magnetostrictive alloy having an improved Curie temperature.

[0002]

2. Description of the Related Art A displacement control actuator is applied as an application of magnetostriction in which a magnetic body is deformed when an external magnetic field is applied to the magnetic body.
Magnetostrictive oscillators, magnetostrictive sensors, magnetostrictive filters, ultrasonic delay lines, etc. Conventionally, Ni-based alloys, Fe-Co alloys, ferrites, etc. have been used.

In recent years, along with the progress of measurement engineering and the development of precision machinery field, it is necessary to develop a displacement drive unit which is indispensable for micro displacement control of micron order. A magnetic-mechanical conversion device using a magnetostrictive alloy is promising as one of the driving mechanisms of this displacement driving unit. However, the conventional magnetostrictive alloy does not have a sufficient absolute amount of displacement, and as a micron-order precision displacement control drive unit material, it is not satisfactory not only in terms of absolute drive displacement but also in precision control.

In response to such demands, a rare earth-transition metal based magnetostrictive alloy has been attracting attention and studied as a high magnetostrictive material. (Japanese Patent Publication No. 61-33892, U.S. Pat. No. 4)
378258 specification etc.)

However, such a magnetostrictive alloy does not have a sufficiently high Curie temperature. For example, a rare earth-iron alloy has a low magnetostrictive characteristic in a low temperature range, and a rare earth-cobalt alloy is difficult to use in a high temperature environment. However, a magnetostrictive material having excellent magnetostrictive properties in a wide temperature range has not been obtained.

[0006]

As described above, the conventional rare earth-transition metal-based magnetostrictive alloy has a problem that the Curie temperature is not sufficiently high and good magnetostrictive characteristics cannot be obtained in a wide temperature range. The present invention has been made in view of the above points, and an object thereof is to provide a giant magnetostrictive alloy having a high Curie temperature and excellent magnetostrictive properties.

[0007]

The present invention provides a general formula expressed in atomic%: R _x T _100-xy M _y (R is at least one rare earth element containing Y, T is Fe or Co) At least one kind of element, M is at least one kind of element among B, C, and N, 20 ≦ x ≦ 60, 0 <y ≦ 30), and is a giant magnetostrictive alloy.

As the rare earth element (R) containing Y,
Y, La, Ce, Pr, Nb, Pm, Sm, Eu, C
d, Tb, Dy, Ho, Er, Tm, Yb and Lu are used, and at least one of them is Pr, N
d, Sm, Tb, Dy, Ho, Er, TbDy, TbH
o, TbPr, SmYb, TbDyHo, TbDyP
r, TbPrHo are preferred.

Fe and / or Co is used as at least one element (T) of Fe and Co. It is possible to replace a part of this with other transition elements such as Ni and Mn. However, if it is replaced excessively, the Curie temperature is lowered, so that it is necessary to be 50% or less in atomic% with respect to Fe and Co. is there. X in the above general formula is less than 20 or 6
When it exceeds 0, the main phase is decreased and the magnetostrictive characteristic is deteriorated. More preferable x is in the range of 25-40.

The giant magnetostrictive alloy is generally composed of a Laves phase and a grain boundary, which are the main phases responsible for the magnetostrictive characteristics.
The element is a so-called infiltration type element that penetrates into the lattice of the main phase,
Modulates the band structure of the transition element, in particular, increases the magnetic polarization of d-electrons and enhances the exchange interaction between d-electron spins, and thus improves the Curie temperature of the giant magnetostrictive alloy.
This effect can be obtained by adding a very small amount of M element,
It becomes significant when y in the above general formula is 3 or more. On the other hand, if the content is increased, it becomes difficult to form a solid solution in the main phase, and it precipitates at the grain boundaries, but when it is present at the grain boundaries, the resistivity increases and the frequency characteristics are improved. However, when it exceeds 30, it is excessively present in the grain boundary and deteriorates the magnetostrictive property. More preferable y is in the range of 10 to 25.
Note that hydrogen, oxygen, phosphorus, and the like are similar interstitial elements, and the inclusion of up to the same amount is allowable. A method for producing a giant magnetostrictive alloy in which M in the general formula is N will be described below.

First, a predetermined atomic ratio of R element and Fe, C
At least one element of o is prepared and dissolved by high frequency induction melting or the like. Subsequently, after subjecting this ingot to a sample having a desired shape by cutting or the like, crystal controlled dissolution in nitrogen or a gas compound containing nitrogen,
For example, floating zone dissolution and Bridgman dissolution are performed. The pressure of the nitrogen or the gas containing nitrogen is 0.01a.
The growth rate of the crystal is preferably 0.1 mm / hr to 300 mm / hr. As the nitrogen or a gas containing nitrogen, for example, nitrogen, ammonia gas, or cyan gas is desirable.

The single crystal or unidirectionally solidified material obtained by such a method penetrates into the crystal lattice. Such a nitrogen compound is usually obtained by heat-treating a powdery sample in a nitrogen atmosphere, but in that case, it is very difficult to produce a bulky sample, especially a unidirectionally solidified material or a single crystal. On the other hand, the above-described method involves crystal controlled melting, for example, floating zone melting and Bridgman melting, because the molten metal involves nitrogen contained in the atmosphere,
Nitrogen is homogeneously incorporated into the alloy, and the unidirectionally solidified material and the single crystal can also obtain an alloy containing nitrogen uniformly.

[0013]

The giant magnetostrictive alloy according to the present invention has a general formula expressed in atomic%: R _x T _100-xy M _y (R is at least one rare earth element containing Y, and T is at least Fe or Co. One kind of element, M is at least one kind of element among B, C, and N, and 20 ≦ x ≦ 60, 0 <y ≦ 30), and therefore has a high Curie temperature and excellent magnetostrictive characteristics. Have.

In particular, M in the above general formula is nitrogen (N).
The above-mentioned giant magnetostrictive alloy acts on the magnetic anisotropy of the rare earth-iron-based Laves type compound by the nitrogen and further acts on the crystal structure thereof, so that the coercive force is reduced without deteriorating the magnetostrictive characteristics and other magnetic characteristics. be able to.

[0015]

EXAMPLES Examples of the present invention will be described below. Example 1

Alloys having the compositions shown in Table 1 were prepared by arc melting and then subjected to a homogenizing heat treatment at 900 ° C. for 1 week, and the sample was cut to obtain a size of 10 × 10.
A test piece (No. 1 to 5 mm) having the composition shown in Table 1 below.
7). Here, No. 6 and 7 are conventional B or C
Is not included and is manufactured as a comparative example.

The magnetostriction value and the Curie temperature of each test piece prepared by the above method were measured. The results are also shown in Table 1 below. The magnetostriction value and the Curie temperature were evaluated as follows. The magnetostriction characteristics are obtained by using an anti-magnetic gauge, and the magnetic field is generated by an opposed magnetic pole type electromagnet.
It was evaluated in a magnetic field applied with kOe. The magnetostriction value is No. 6
The magnetostriction value of 1 is standardized and displayed. The Curie temperature was obtained from the temperature characteristic of magnetization.

[0018]

[Table 1]

As is clear from Table 1, the test pieces (Nos. 1 to 5) made of the giant magnetostrictive alloy of the present invention have a higher Curie temperature than those of the comparative examples (Nos. 6 and 7), and It can be seen that the magnetostriction value is larger than that of the comparative example.

Further, No. 1 which is the giant magnetostrictive alloy of the present invention is used.
No. 1 which is a giant magnetostrictive alloy of Comparative Example 1 and Comparative Example. 6 about diameter 1
A rod-shaped sample having a length of 0 mm and a length of 30 mm was prepared and the frequency characteristic of the displacement amount was evaluated. As the magnetic field applying means, a sinusoidal alternating current was passed through the air-core coil, and the frequency was varied with a constant current. The amount of displacement is measured using an optical displacement meter without contact, and
Normalized by the amount of displacement at 0 Hz. As a result, it is shown in FIG.

As is apparent from FIG. 1, the giant magnetostrictive alloy of the present invention has a smaller change in displacement amount with respect to frequency as compared with that of the comparative example, and it is understood that a good displacement amount can be obtained even in a high frequency region. Example 2

After alloys having the compositions shown in Table 2 below were prepared by arc melting, they were pulverized to a particle size of 100 μm or less, heat-treated at 500 ° C. for 1 hour in a nitrogen atmosphere at 1 atmosphere, and then 1 atmosphere after press molding. 1200 ℃ × 2 in the nitrogen atmosphere of
One test piece (N
o. 8-12). The magnetostriction value and Curie temperature of the test pieces (Nos. 8 to 12) thus produced were determined by the same method as in Example 1. As a result, the results are shown in Table 2 below.

[0023]

[Table 2] As is clear from Table 2, the test pieces (Nos. 8 to 12) made of the giant magnetostrictive alloy of the present invention have the same effects as those of the above-described Example 1. Example 3

Tb, Dy, Sm, Ho, Pr, Er, F
e, Co, Mn, Al, Zr, Ni, B, and P were mixed so as to have the compositions shown in Table 3 below, and high-frequency induction melting was performed using an alumina crucible in an argon atmosphere. A seed alloy was prepared. Then, after cutting out a sample having a diameter of 6 mm and a length of 50 mm from each of the above alloys, 1
Floating zone dissolution in nitrogen atmosphere at atmospheric pressure Growth rate 10μ
It was performed under the condition of m / sec.

The coercive force of the obtained samples (Nos. 1 to 9) was measured using a vibrating sample magnetometer. Also, a test piece similar to that of Example 1 was taken out from the sample,
The magnetostriction value and the Curie temperature were obtained by the same method as in Example 1. The results are shown in Table 3 below. Table 3
Indicates the coercive force of each alloy before dissolution in the floating zone in a nitrogen atmosphere.

[0026]

[Table 3]

As is clear from Table 3, the test pieces (Nos. 1 to 9) made of the giant magnetostrictive alloy of the present invention are 10 to 20.
It can be seen that it has a low coercive force of Oe, a high Curie temperature, and a large magnetostriction value.

Further, No. 1 in Table 3 above. The alloy of the present invention having the composition of No. 1 and melted in a floating zone in a nitrogen atmosphere and No. 3 in Table 3 above. 4 mm in diameter and 10 mm in length from an alloy (comparative example) having a composition of No. 1 before melting in a floating zone in a nitrogen atmosphere.
A rod-shaped sample of mm was prepared, incorporated into a magnetostrictive actuator, and evaluated for micro displacement characteristics. The actuator comprises an air-core coil as a magnetic field generating means, a DC bias applying permanent magnet, a temperature control spiral water cooling pipe, a yoke, and a stay. For the measurement, a control current was supplied to the air-core coil, and a minute displacement at that time was measured. During the measurement, cooling water controlled at a constant temperature was supplied from a constant temperature bath to keep the temperature constant. FIG. 2 shows a change in the displacement amount by the rod-shaped sample of the present invention, and FIG. 3 shows a change in the displacement amount by the rod-shaped sample of the comparative example. As is clear from FIGS. 2 and 3, it can be seen that the sample of the present invention has a displacement characteristic with extremely small hysteresis as compared with the sample of the comparative example.

[0029]

As described above, according to the present invention, it is possible to provide a giant magnetostrictive alloy having a high Curie temperature and excellent magnetostrictive properties. Particularly, according to the giant magnetostrictive alloy in which M in the general formula is nitrogen (N), the nitrogen acts on the magnetic anisotropy of the rare earth-iron-based Laves type compound, and further acts on the crystal structure thereof, so that the magnetostrictive characteristic The coercive force can be reduced without deteriorating other magnetic properties.

[Brief description of drawings]

1 is a No. 1 shown in Table 1. No. 1 sample piece and No. 1 sample piece.
6 is a diagram showing frequency characteristics of the sample piece 6 (comparative example). FIG.

FIG. 2 shows No. 1 shown in Table 3. FIG. 3 is a diagram showing a micro displacement characteristic of a rod-shaped sample of an alloy (invention) having the composition of No. 1 and melted in a floating zone in a nitrogen atmosphere.

FIG. 3 shows No. FIG. 3 is a diagram showing a minute displacement characteristic of a rod-shaped sample of an alloy (comparative example) having a composition of No. 1 and not dissolved in a floating zone in a nitrogen atmosphere.

Front page continuation (72) Inventor Masashi Sahashi 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki City, Kanagawa Prefecture Toshiba Research Institute Ltd.

Claims (1)

[Claims] 1. A general formula expressed in atomic%: R _x T _100-xy.
M _y (R is at least one of rare earth elements including Y,
T is at least one element of Fe and Co, M is B,
At least one element of C and N, 20 ≦ x ≦ 60,
0 <y ≦ 30), which is a giant magnetostrictive alloy.