JPH06184709A - Magnetostorictive material and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily manufacture a magnetostorictive material having small temp. dependency of the magnetostorictive quantity by bringing molten alloy for raw material composed of the specific atomic ratios of Pr, Nd, Fe, etc., into contact with a base body for cooling, rapidly quenching and applying hot- working. CONSTITUTION:The molten alloy for raw material having the atomic ratio composition shown with the formular (PrxNd1-x) Ty (T: one or more kinds among Fe, Co and Ni, 0<x<1, 1.0<=y.f2.0) is rapidly quenched by bringing into contact with the base body for cooling, such as cooling rolls, to manufacture a strip-like quenched alloy. Successively, if necessary after pulverizing by using plasma activating sintering device, etc., the hotworking is applied at >= about 100kgf/cm<2> impressed pressure and about 500-850oC holding temp. and then, this material is cooled to room temp. By this method, the magnetostorictive material having small temp. dependency of the magnetostorictive quantity and easily manufacturable is obtd.

Description

Detailed Description of the Invention

[0001]

This invention relates to magnetostrictive materials, namely,
The present invention relates to a magnetic material whose length changes when an external magnetic field is applied, and a manufacturing method thereof.

[0002]

2. Description of the Related Art When an external magnetic field is applied to a magnetic material, the magnetic material expands or contracts. This is called magnetostriction. Magnetostriction is applied to, for example, a displacement control or drive actuator, an ultrasonic wave generation magnetostrictive oscillator, an ultrasonic delay line, an ultrasonic wave filter, a variable frequency resonator, various sensors, and the like.

A magnetostrictive material is required to have a high magnetostriction amount at a low magnetic field strength, a high material strength, etc. according to the purpose and application, and it is also necessary to have excellent corrosion resistance. As a conventionally known magnetostrictive material, which has a saturated magnetostriction amount of 300 × 10 ⁻⁶ or more at room temperature,

(I) Iron and rare earth elements (Tb, Sm, Dy,
Alloys with Ho, Er, Tm) (U.S. Pat. No. 4,375,375)
372 specification, 4,152,178 specification, 3,949,351 specification, 4,308,47 specification.
No. 4, etc.),

(Ii) Alloys of iron group elements and Mn with Tb and Sm (US Pat. No. 4,378,258),

(Iii) Ti, V, Cr, Mn, Ni, C
u, Nb, Mo, Ta, W, C, Si, Ge, Sn,
B, In, La, Ce, Pr, Nd, Sm, Gd, T
b, Eu, Dy, Ho, Er, Yb, Lu, Tm, at least one, a magnetostrictive material consisting of Fe, Al and Co, and Ti, V, Cr, Mn, Co, Ni, Cu, Nb, M
o, Ta, W, C, Si, Ge, Sn, B, In, L
a, Ce, Pr, Nd, Sm, Gd, Eu, Er, Y
at least one of b, Lu and Tm, Tb, Dy, Ho and Fe
And a magnetostrictive material (Japanese Patent Laid-Open No. 53-64798)

And the like. These magnetostrictive materials are
Fe ₂ Laves-type intermetallic compound, which is an intermetallic compound of Fe and a rare earth element R, or one in which another element such as a transition metal is added, and is a conventionally used magnetostrictive material such as nickel or ferrite. It has a saturation magnetostriction value λ s that is one to two orders of magnitude higher than that, and is called a giant magnetostrictive material.

Of the RFe ₂ Laves type intermetallic compounds, T
bFe ₂ has a large magnetostriction amount when the external magnetic field strength is high, for example, when the external magnetic field strength is about 20 to 25 kOe, but the magnetostriction amount is not sufficient when the magnetic field strength is low. Therefore, Tb
(Tb, Dy) Fe _{2 in} which a part of is replaced by Dy is widely used as a magnetostrictive material having an improved magnetostriction amount at low magnetic field strength. Further, SmFe ₂ is used as a negative magnetostrictive material.

When a device using such a magnetostrictive material is used outdoors, it is necessary to assume a considerably wide operating temperature range. For example, a device utilizing magnetostriction is applied to various valves for automobiles and the like, but in this case, it is necessary to guarantee a substantially linear operation from a high temperature of about 150 ° C to a low temperature of about 50 ° C below zero. However, (Tb, Dy) Fe
No. ₂ has poor temperature characteristics, and at the optimum composition ratio of Tb and Dy at room temperature, the magnetic anisotropy changes at a low temperature of 0 ° C. or less, so that the amount of magnetostriction is significantly reduced. Therefore,
Improvement of temperature characteristics of magnetostrictive materials is required for use in equipment that is used severely. Further, when used in a refrigeration facility or the like, a large amount of magnetostriction is required at, for example, -40 ° C or lower.

By the way, among the RFe ₂ Laves-type intermetallic compounds, those having an extremely large theoretical value of λs are CeF.
e ₂ and PrFe ₂ (sensor technology 1990 2
The monthly issue, page 36), is expected to outperform conventional giant magnetostrictive materials. Also, Pr and Ce are T
It has more resources and is cheaper than b.

However, 32,000 is required for the synthesis of PrFe _2.
Ultra high pressure of about 35000 atm and high temperature heat treatment of about 1000 ° C. are required. CeFe ₂ is promising as a material having a large magnetostriction amount at a low temperature, but it requires a long time for synthesis and its Curie temperature is lower than room temperature, so that its use is limited.

Under these circumstances, the present inventors first
(Pr, Ce)-(Fe, Co, Ni) system and (N
A magnetostrictive material of d, Ce)-(Fe, Co, Ni) system has been proposed (Japanese Patent Application No. 3-292544). However, in these compositions, the magnetostriction amount at a low temperature is extremely large, but the temperature dependency of the magnetostriction amount is rather large, and the magnetostriction amount decreases relatively rapidly at a high temperature.

[0013]

SUMMARY OF THE INVENTION The present invention has been made under the circumstances as described above, and an object thereof is to provide a magnetostrictive material having a small temperature dependence of the magnetostriction and easy to manufacture.

[0014]

These objects are achieved by the present invention described in (1) to (4) below. (1) A magnetostrictive material having an atomic ratio composition represented by the following formula (I). Formula (I) (Pr _x Nd _1-x ) T _y (In the above formula (I), T is at least one of Fe, Co and Ni, and 0 <x <1, 1.0 ≦ y ≦ 2. ．
It is 0. (2) A magnetostrictive material having an atomic ratio composition represented by the following formula (II). Formula (II) (Pr _x Nd _1-x ) _1-z Ce _z T _y (In the above formula (II), T is at least one of Fe, Co and Ni, and 0 <x <1, 1. 0 ≦ y ≦ 2.
0 and 0 <z ≦ 0.5. (3) A method for producing the magnetostrictive material according to (1) or (2), which comprises contacting a molten base material alloy with a cooling substrate to quench the material, and subjecting the resulting quenched alloy to hot working. A method of manufacturing a magnetostrictive material, comprising: (4) The method for producing a magnetostrictive material according to (3), wherein the quenched alloy is crushed and then hot-worked.

[0015]

In the present invention, in the RFe ₂ Laves type intermetallic compound, Pr and Nd as R or Ce in addition to these are combined. Among the magnetostrictive materials of the present invention, the (Pr _x Nd _1-x ) T _y composition has extremely small temperature dependence of the magnetostriction amount. On the other hand, (Pr _x Nd _1-x ) _1-z C
In the e _z T _y composition, the temperature dependence of the magnetostriction amount is (Pr _x Nd
_1-x) T _y becomes slightly larger than the composition, so improves the magnetostriction amount of a low magnetic field strength of more than about 1 kOe, which is advantageous in practical use.

Further, the magnetostrictive material of the present invention does not require heat treatment at ultrahigh pressure and high temperature, and is easy to manufacture.

[0017]

Specific Structure The specific structure of the present invention will be described in detail below.

The magnetostrictive material of the present invention has an atomic ratio composition represented by the following formula (I). Formula (I) (Pr _x Nd _1-x ) T _{y In the} above formula (I), T is 1 of Fe, Co and Ni.
0 or more and 0 <x <1, preferably 0.2 ≦ x ≦
0.9, more preferably 0.4 ≦ x ≦ 0.8, 1.0 ≦
y ≦ 2.0, preferably 1.5 ≦ y ≦ 2.0.

If x is too small, the amount of magnetostriction becomes small. x
If is too large, the ratio of the different phases other than RFe ₂ (R is a rare earth element) becomes high and the magnetostriction amount decreases unless the pressure during hot working described later is made extremely high. This is x
It is most remarkable when = 1.

When y is less than the above range, the rare earth element-rich phase increases, and when it exceeds the above range, a heterogeneous phase such as RFe ₇ phase occurs, and the magnetostriction amount decreases in both cases.

Since T has a Curie point at room temperature or higher, it is preferable to use Fe alone or a part of Fe replaced with Co. Further, since it is considered that the strength is improved by making a rare earth element and an alloy thereof by substituting Mn, Cr, Mo, etc., these elements may be contained.

The present invention also includes a magnetostrictive material having an atomic ratio composition represented by the following formula (II). Formula (II) (Pr _x Nd _1-x ) _1-z Ce _z T _{y In the} above formula (II), T, x and y are the above formula (I).
And 0 <z ≦ 0.5, preferably 0.1 ≦ z
≦ 0.4.

If z is too small, the effect of addition of Ce becomes insufficient, and if z is too large, the Curie temperature becomes low, and the amount of magnetostriction from normal temperature to high temperature becomes small.

The reason for limiting x and y in the formula (II) is the same as in the formula (I).

The method for producing the magnetostrictive material of the present invention is not particularly limited, but it is preferable to use a method of hot working after rapid quenching.

In this method, first, a molten alloy material is brought into contact with a cooling substrate such as a cooling roll to be rapidly cooled to produce a quenched alloy in the form of ribbons, flakes, particles, or the like.
The quenching conditions are not particularly limited and may be appropriately determined according to the alloy composition and the like. Although the structure structure of the quenched alloy varies depending on the cooling rate, it is usually in an amorphous state or a state in which fine crystals such as rare earth element simple substance and RFe ₇ phase are mixed.

Next, after crushing if necessary, hot working is performed. The hot working conditions are not particularly limited, but the applied pressure is 100 kgf / cm ² or more, especially 1000 kgf / cm ²
The above is preferable. In the present invention, the applied pressure during hot working is 20000 kgf / cm ² or less, particularly 100
A large amount of magnetostriction can be obtained even when it is set to 00 kgf / cm ² or less. The holding temperature of the work piece is preferably 500 to
The temperature is 850 ° C, more preferably about 600 to 750 ° C. After hot working, cool to room temperature.

A normal hot press may be used for hot working, but if plasma activated sintering (PAS) is used because it can be densified in a short time and can be heated at a high speed,
Oxidation can be prevented and it is advantageous in terms of cost. In plasma activated sintering, quenched alloy particles are activated in plasma and then sintered. In this case, the plasma generation method and the plasma-activated sintering apparatus used are not particularly limited, but a plasma-activated sintering apparatus 1 shown in FIG. 1 will be described as a preferred example.

First, the quenched alloy particles 5 are put between the punches 3 in the mold 4 of the apparatus 1. Then, the material is pressed with the punches 3 and 3, and an electric current is applied between the electrodes 2 and 2 in a vacuum to generate plasma, and then an energizing current is applied to sinter. It should be noted that the plasma generation current usually has a pulse width of 20 × 10
A pulse current of about ^{−3 to} 900 × 10 ⁻³ seconds is used.

The more detailed mechanism is as follows.

When the pulse voltage applied between the electrodes 2 and 2 reaches a predetermined value, dielectric breakdown occurs at the contact surface between the electrode and the quenched alloy particles and the contact surface between the quenched alloy particles, and a discharge is generated. At this time, the surface of the quenched alloy particles is sufficiently purified by the electrons ejected from the cathode and the ion bombardment generated at the anode. Also, the discharge impact pressure due to the spark is applied to the particles. The discharge impact pressure then distorts the particles and improves the atomic diffusion rate.

The Joule heat due to the subsequent energizing current spreads around the contact point and facilitates the plastic deformation of the quenched alloy particles. In particular, since the atoms in the contact portion are activated and are in a state of being easily moved, the particle gaps are approached and the atoms start diffusion only by applying pressure to the quenched alloy particles. In addition, since there is an electric field, the metal ions easily move electrically.

As a result, the sintering time can be shortened and the particles can be prevented from being oxidized.

The various conditions in such plasma activated sintering are usually preferably set as follows.

Pressing pressure: 1000 kgf / cm ² or more,
It is preferably 2000 kgf / cm ² or more, and in view of productivity, the upper limit is preferably 20000 kgf / cm ² , more preferably 10000 kgf / cm ² Plasma generation time: about 1 to 3 minutes Plasma atmosphere: 10 ^-3 to 10 ^-5 Torr Maximum temperature during sintering: 500 to 850 ° C Holding time at maximum temperature: 0 to 10 minutes Energizing current: 1500 to 3000A

The above description is only an example. In addition to this, the atmosphere may be an inert gas such as Ar, N ₂ gas whose oxygen partial pressure is controlled, etc., an apparatus using other conditions, and plasma generation. It is appropriately selected depending on the method.

By the hot working as described above, R
A polycrystalline magnetostrictive material composed of Fe ₂ phase crystal grains and rare earth element-rich crystal grain boundaries can be obtained, but the magnetostrictive material of the present invention may be a single crystal.

Other general alloy production methods such as arc melting method, Bridgman method, unidirectional solidification method, zone melting method, high frequency melting method, powder metallurgy method and centrifugal casting method are suitable. A method may be selected to produce the magnetostrictive material of the present invention. These manufacturing methods are described, for example, in US Pat. Nos. 4,308,474 and 3,949,35.
No. 1, No. 4,378,258, No. 4,375,372, No. 4,158,368
No. 4,152,178, No. 4,152,178
609,402, 4,374,665, JP-B-61-33892, and JP-A-58-3.
No. 294, etc. The magnetostrictive material produced by these methods is preferably annealed as necessary.

The magnetostrictive material of the present invention may be anisotropy if necessary.

[0040]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

<Temperature Characteristic of Magnetostriction Amount> The molten alloy material was rapidly cooled at a high speed by a single roll method to obtain a flaky alloy. Then, the quenched alloy was sintered using the plasma activated sintering apparatus having the configuration shown in FIG. 1 to prepare a magnetostrictive material sample having an atomic ratio composition shown in FIGS. The plasma generation method and sintering conditions were as follows.

Plasma generation method: pulse width 30 × 10 ^-3
Pulse current per ^second Pressing pressure: 10000 kgf / cm ² Plasma generation time: 1 minute Plasma activated sintering atmosphere: After vacuuming to 5 × 10 ⁻⁵ Torr, introducing Ar gas Maximum temperature during sintering: 670 ° C. ( Sintered body temperature) Hold time at maximum temperature: 5 minutes Current: 2000A

With respect to each sample, the magnetostriction amount was measured while changing the environmental temperature, and the magnetostriction amount and its change rate α = (λ ₂
−λ ₁ ) / (T ₂ −T ₁ ) was calculated. However, λ ₁ and λ ₂ are magnetostriction amounts [ppm] (external magnetic field strength H = 0.4 kOe) at temperatures T ₁ and T ₂ , respectively, and T ₂
−T ₁ = 20 [° C.]. The magnetostriction amount was measured with a strain gauge. Figure 2 shows the relationship between temperature and magnetostriction.
FIG. 3 shows the relationship between temperature and the magnetostriction change rate α.

For comparison, a (Tb, Dy) -Fe system sample was prepared in the same manner as above. The magnetostriction change rate α was also obtained for this comparative sample. The results are also shown in FIG.

From these results, (Tb, Dy) -Fe
In the system sample, the amount of magnetostriction changes greatly due to temperature changes,
Further, the (Pr, Ce) -Fe based sample also shows a relatively large magnetostriction change, while the (Pr, Nd, C) of the present invention.
It can be seen that the e) -Fe based sample has a small change in magnetostriction due to temperature changes, and in particular, the (Pr, Nd) -Fe based sample is extremely small.

<Change in magnetostriction amount by addition of Ce> (Pr, N
The relationship between the Ce addition amount and the magnetostriction amount of the d, Ce) -Fe system sample was obtained. External magnetic field strength H during measurement is 0.4 kOe
And the environmental temperature was 25 ° C. Results are shown in FIG.

From the results shown in FIG. 5, it is recognized that the amount of magnetostriction is increased by adding Ce.

From the results of the above examples, the effect of the present invention is clear.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a plasma activated sintering apparatus used for manufacturing a magnetostrictive material of the present invention.

FIG. 2 is a graph showing the relationship between temperature and magnetostriction amount.

FIG. 3 is a graph showing the relationship between temperature and magnetostriction amount.

FIG. 4 is a graph showing the relationship between temperature and magnetostriction change rate α.

FIG. 5 is a graph showing the relationship between the amount of Ce added and the amount of magnetostriction.

[Explanation of symbols]

 1 Plasma Activated Sintering Device 2 Electrode 3 Punch 4 Form 5 Quenched Alloy Particles

Claims (4)

[Claims] 1. A magnetostrictive material having an atomic ratio composition represented by the following formula (I). Formula (I) (Pr _x Nd _1-x ) T _y (In the above formula (I), T is at least one of Fe, Co and Ni, and 0 <x <1, 1.0 ≦ y ≦ 2. .0.) 2. A magnetostrictive material having an atomic ratio composition represented by the following formula (II). Formula (II) (Pr _x Nd _1-x ) _1-z Ce _z T _y (In the above formula (II), T is at least one of Fe, Co and Ni, and 0 <x <1, 1. 0 ≦ y ≦ 2.0 and 0 <z ≦ 0.5.) 3. A method for producing a magnetostrictive material according to claim 1 or 2, further comprising the step of bringing a molten raw material alloy into contact with a cooling substrate to quench it, and subjecting the resulting quenched alloy to hot working. A method of manufacturing a magnetostrictive material, comprising: 4. The method for producing a magnetostrictive material according to claim 3, wherein hot working is performed after crushing the quenched alloy.