JPH01246342A - Supermagnetostrictive material and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the title material having high absolute value of satulated magnetostriction and having excellent mechanical strength by quenching the molten metal of an alloy constituted of transition metals such as Fe, Ni and Co and lanthanoids into the shape of powder having fine crystal grains and converting it into a block by hot pressing treatment, etc. CONSTITUTION:The molten metal of an alloy expressed by the general formula RTx (in the formula, R denotes at least one kind of lanthanoids among La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, T denotes at least one kind among the transition metals such as Fe, Ni and Co and X satisfies 1.0<=X<=9.0 by atomic mol number) is quenched at a cooling speed of 10<3>-10<5> deg.C/sec and is converted into the shape of a thin strip or flake having an extremely fine structure of <=15mum crystal grain size. It is ground into the shape of powder having 200mum average grain size, and as the starting material, is converted into a block by a hot pressing method or a hot isostatic pressing method, by which the supermagnetostrictive material having extremely high absolute value of the saturated magnetostriction and having high mechanical strength and density for fine crystal grains can be manufactured.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a giant magnetostrictive material and a method for manufacturing the same, and relates to a novel giant magnetostrictive material that has a large absolute value of saturation magnetostriction and excellent mechanical strength, and its method. Regarding the manufacturing method.

(Prior Art) Magnetostrictive materials that can convert magnetization changes into shape changes (and vice versa) have long been used as materials for ultrasonic oscillators, for example, by taking advantage of their properties. Recently, it was discovered that materials made of rare earth elements and transition metals exhibit enormous magnetostriction, and as the trend towards lighter, thinner, and smaller materials progresses in various technical fields, materials are being used to fine-tune and control various devices. It is newly attracting attention.

By the way, conventionally known methods for manufacturing giant magnetostrictive materials are roughly divided into the following cutting method and powder method.

In the former method, a magnetic alloy of a predetermined composition is first melted, and then the melt is cooled to prepare an ingot in which the single crystal or crystal grains of the alloy are solidified with their crystal axes oriented in one direction. . Since this ingot is an extremely brittle material and cannot be hot worked, the ingot is cut and polished to cut out material in a predetermined shape. In addition, as a modification of this method, a method is also used in which the melt of the magnetic alloy described above is sucked up using, for example, a quartz tube and solidified as it is within the quartz tube.

Next, in the latter method, the above-mentioned ingot is pulverized into fine powder with a predetermined particle size, the obtained fine powder is filled into a mold and preformed, and then this molded body is sintered under predetermined conditions. This sintered body is later processed into a predetermined shape.

(Problem B to be solved by the invention) However, in the case of the former method, when solidifying the alloy liquid, it is necessary to orient the crystal axes of the growing crystal grains in one direction. It is necessary to set the solidification rate low.

That is, in the case of this method, the productivity during ingot preparation is low and there is little industrial merit.

Further, when cutting and polishing the ingot, a large amount of cutting and polishing loss inevitably occurs.

Moreover, there is also the problem that a high degree of skill is required to cut out a material with uniform properties.

Furthermore, in the case of the method of sucking up the alloy liquid using a quartz tube or the like, there is a restriction that it is not possible to manufacture materials with large shapes or materials with complicated shapes.

In the case of the latter powder method, rare earth elements are primarily contained in the alloy, so if oxygen gets mixed into the atmosphere during the handling process of the fine powder, oxidation of the rare earth elements will proceed rapidly and the fine powder may catch fire. This may even lead to an explosion. Therefore, to prevent this, explosion-proof equipment and other auxiliary equipment are essential.

Further, the density of the sintered body obtained by this method is about 95% of the theoretical density, and voids remain inside the sintered body. Therefore, its mechanical strength is low and it is brittle, which often causes breakage during use.Furthermore, since it has voids, its oxidation resistance is low, and it sometimes rusts.

By the way, recently, the development of magnetostrictive materials with a large absolute value of saturation magnetostriction has been progressing, and one of these materials has a composition of the following formula: RITI, + (where R' is SII, Tb5D
Intermetallic compounds represented by lanthanide elements such as V, T' are transition metals such as Fe, Go, and Ni, and Xo is the number of atomic moles, usually around 2, are attracting attention.

Among these compounds, SmFez has a large absolute value of saturation magnetostriction (1λ, 1) of 1000 x 10-'' (measurement conditions: measurement temperature is room temperature, applied magnetic field is 10KO,);
Highly valuable as a giant magnetostrictive material.

It is true that this material has a large value of 1λ, 1, but its crystal grains are usually as large as several 100 μm, so in the magnetostrictive material manufactured from this SmFet, the grain boundary accumulated strain is large. (The problem is that the fracture stress is small and the mechanical strength is low.

This can be said to be because, as described above, the crystal grain size becomes coarse due to the unidirectional solidification treatment performed during the preparation of the ingot.

The present invention solves the problems related to conventional materials as described above, and provides a novel giant magnetostrictive material having a &llll iso structure, which has fine crystal grains and therefore excellent mechanical strength, and a method for manufacturing the same. purpose.

(Means for Solving the Problems) As a result of extensive research in order to solve the above problems, the present inventors used an alloy powder with the composition described below and a small crystal grain size as a raw material, and the following We discovered that materials hot pressed or hot isostatically pressed by this method have high IJ,l and excellent mechanical strength, and we have developed the Zhao magnetostrictive material of the present invention and its manufacturing method. It was.

That is, the giant magnetostrictive material of the present invention has the following formula: RTx (wherein, R is La, Ce, Pr, Nd, S
m, Eu, Gd, Tb5Dy, Ho, Er, T
represents at least one lanthanide element selected from the group of m, Yb, and Lu; T represents at least one transition metal selected from the group of Fe, Co, and Ni;
is a number satisfying the relationship of 1.0≦x≦9.0 in terms of atomic moles), and has a crystal grain size of 15 μm or less, and its manufacturing method includes:
For an alloy with the above composition, a cooling rate of 1 (1' to 10"C/se
The method is characterized in that a ribbon or flake of the alloy is prepared by applying the molten metal quenching method described in c. Preferably, the powder obtained after pulverizing the ribbon or flakes is subjected to hot pressing treatment or hot isostatic pressing treatment to form a block, and further, the ribbon or flakes are subjected to hot plastic deformation processing. This is what we do.

First, the giant magnetostrictive material of the present invention is composed of the intermetallic compound represented by RTx, in which case the transition metal: T
When the number of atomic moles (x) of is less than 1.0, and 9.0
If it is larger, the magnetostriction will become extremely small and the objective will not be achieved.The preferred range of X is 1.5 to 2.5.

Particularly preferable compositions include, for example, SyoF, 8. .

can be given.

Furthermore, in this material, the crystal grain size of the intermetallic compound is set within a range of 15 μm or less. The crystal grain size here refers to the value measured by the method specified in JIS G-0552. If it is larger than 15 μm, the mechanical strength of the obtained material will decrease, making it difficult to process it into a predetermined shape depending on the application. This is because cracks, chips, etc. sometimes occur, which is inconvenient.

The giant magnetostrictive material of the present invention can be manufactured as follows.

That is, a molten metal quenching method is applied to an alloy having the above-mentioned composition to prepare a ribbon or flake of the alloy.

In the molten metal quenching method in this case, the cooling rate of the alloy liquid is set within the range of 103 to 10"C/sec. If the cooling rate is lower than 103C/sec, the resulting The crystal grains of the alloy become coarse and the grain size becomes larger than 15 μm,
In addition, if the cooling rate is greater than 10'''C/sec,
This is because the obtained ribbon or flake becomes partially amorphous and therefore requires annealing. In addition,
This step is carried out in an inert gas atmosphere such as A1 or in vacuum.

Further, following the above steps, the ribbon or flakes obtained as described above may be ground into powder with a predetermined particle size. This is carried out while preventing external contamination from machines etc. so that the average particle size of the obtained powder is about 200 μm. Note that, prior to this pulverization treatment, the ribbon or flakes may be annealed at a predetermined temperature at the end of their crystallization temperature to remove distortion accumulated during the preparation of the ribbon or flakes.

In addition, hot pressing (H
P) treatment or hot isostatic pressing (HIP) treatment may be performed to form blocks.

At this time, when the powder is subjected to HP treatment, it is preferable to preform the powder in the following way. Namely, in a vacuum or an inert atmosphere, the powder is coated with a binder such as zinc stearate. Appropriate amount (e.g. 0.
The mixed powder obtained by adding about 5% by weight) is filled into a mold of a predetermined shape and molded at room temperature with a press pressure of 2 to 10 ton/cd.

The conditions during HP processing are appropriately selected depending on the desired composition, density, mechanical strength, etc. of the block-shaped giant magnetostrictive material obtained, but the temperature during pressing is usually 500 to 900°C.
, preferably 600~700°C, press pressure 0.5~
5 ton/c+i, preferably about 2 ton/d.

Next, when performing HIP treatment, use the powder described above for carbon steel, austenitic stainless steel! l (e.g. SUS
304), the whole can is sealed, and hydrostatic pressure is applied to the can in a pressure medium to densify the can.The temperature applied at this time is 500 to 9
Preferably, the 00°C5 pressure is about 2000 atmospheres.

By the above-mentioned HP treatment and HIP treatment, a block-shaped giant magnetostrictive material with properly oriented crystal axes and high mechanical strength can be obtained. In order to increase the size, it is preferable to further perform hot plastic deformation as described below.

That is, hot extrusion molding, hot isostatic pressure processing is performed on the block material obtained by HP treatment and HIP treatment,
Alternatively, hot upset processing may be applied, or processing that directly causes hot plastic deformation of powder produced by molten metal quenching (e.g. hot extrusion, hot isostatic pressing, hot upset processing) The applied temperature at this time is usually 500 to 900°C, the applied pressure is preferably about 10 ton/cj, and the processing rate is preferably 50% or more. (Embodiment of the invention) Implementation Examples 1-3 Alloys of the indicated compositions were melted in a high frequency induction furnace and the resulting melt was injected onto a high speed rotating copper roll to prepare flakes. The cooling rate of the melt is shown in the table.

The obtained flakes were crushed in A, atmosphere, and the average particle size was 1.
It was made into a powder of 50 μm.

Next, this powder was mixed with 0.5% by weight of zinc stearate, filled into a mold with a diameter of 30 cm, and preformed at a pressure of 8 tons/d to form pellets with a diameter of 30 m and a height of 10 mm.

This pellet was placed in a mold with a diameter of 32 cm, and in a vacuum,
The pellets were subjected to HP treatment at a temperature of 850° C. and a pressure of 2 ton/cd to obtain pellets with a diameter of 32 mm and a thickness of 1 wm.

Various properties of the obtained pellets were measured according to the following specifications.

Crystal grain size (μm): After mirror polishing the cut surface of each sample, the surface was observed with a microscope (400 magnification).

Saturation magnetostriction (1λ): Cut the pellet using a blade such as a water-cooled emery diamond cutter to cut out specimens for saturation magnetostriction measurement with a length of 5 m and a width of 5 cm and a length of 30 m. 1λ,1 was measured under the following conditions.

Mechanical Strength 2 The bending strength of the specimens described above was measured.

In addition, the strength was determined qualitatively by observing the presence or absence of chips on the cut surface when cutting out the specimen.

Density (%): The true density of each specimen was calculated using X-rays and expressed as a percentage of the theoretical density of each specimen.

The above results are summarized in the table.

Example 4.5 Flakes were prepared by applying the molten metal rapid cooling method to an alloy having the indicated composition, and the flakes were ground in the same manner as in Examples 1 to 3 to obtain powder with an average particle size of 150 μm.

The cooling rate when applying the molten metal quenching method is as shown.

The powder was then filled into a carbon steel can body with a diameter of 50 m and a depth of 30 m, and the can body was sealed with a lid. Next, this can body was set in a HIP device where the pressure medium was A1, and the temperature was raised to 700°.
It was pressed at a C1 pressure of 2 ton/c-.

Regarding the obtained blocks, the crystal grain size, saturation magnetostriction, mechanical strength, and density were measured in the same manner as in Examples 1 to 3, and the results are shown in the table.

Example 6.7 The pellets of Example 1 were subjected to a temperature of 700″ C1 extrusion ratio of 7.0.
(S, /S, where So: cross-sectional area of the initial test piece, S:
The processing was carried out under the following conditions (cross-sectional area of the test piece after processing). The obtained material was designated as Example 5.

The alloy composition is Tb*, Jys, Je+, scO*,
Pellets were produced in the same manner as in Example 3, except that the results were +Nie, +, and then the pellets were subjected to hot upset processing at a temperature of 670°C and a pressure of 1.5 ton/cj. . The obtained sample was designated as Example 6.

Each characteristic of these samples was determined in the same manner as in Examples 1 to 3, and the results are shown in the table.

Comparative Example 1 Composition: An alloy of SmFez was prepared and the cooling rate was 200%.
An ingot was prepared by slow cooling at a temperature of 1.5 C/hr. Samples having the same shape as in Examples 1 to 3 were cut from this ingot, and each characteristic was measured in the same manner. The results are shown in the table.

Comparative Example 2 The alloy liquid of Comparative Example 1 was sucked up by a quartz tube with a diameter of 5.0 m, and then cooled to produce a rod with a diameter of 5.0 m and a length of 2.0 m. This characteristic is shown in the table.

Comparative Example 3 A graphite crucible was placed on a cooling copper plate, and Comparative Example 1 was placed in it.
A unidirectionally cooled rod was produced by injecting the alloying liquid and moving a vertically movable high-frequency induction heating coil placed around the outer periphery of the crucible from bottom to top to achieve a cooling rate of 100°C/hr. did. This characteristic is shown in the table.

(The following is a blank space) (Effects of the invention) As is clear from the above explanation, the giant magnetostrictive material of the present invention has
Its configuration is the following formula: RTx (wherein, R is La,
Ce, Pr, Nd5SIISEu,, Gd, T
b, Dy, Ilo.

represents at least one lanthanide element selected from the group of Er, Tm, Yb, and Lu, and T is Fe5CoS
represents at least one transition metal selected from the group of Ni; It is characterized by having a diameter of 15 pm or less, and the method for producing it is characterized in that the alloy having the above composition has a cooling rate of 103 to
The method is characterized in that a ribbon or flake of the alloy is prepared by applying a molten metal rapid cooling method of 10'° (:/sec), and further, the ribbon or flake is crushed and the obtained powder is heated. Because it is characterized by being made into blocks by applying an intermediate press treatment or a hot isostatic press treatment,
This material has a much larger absolute value of saturation magnetostriction than conventional materials, and at the same time, because it has a high density, its mechanical strength is high and it can be processed into various shapes. In particular, those subjected to hot plastic deformation have a high degree of crystal orientation and a high absolute value of saturation magnetostriction, and are desirable as giant magnetostrictive materials.

The uninvented giant magnetostrictive material can be used, for example, in computer terminal hammer printers, camera autofocus fine adjustment, VTR and CD tracking position control, robot functional parts, and even ion tunnel microscope focus fine adjustment. It can be used in fields that require fine adjustment of magnetic changes and shape (dimensional) changes, such as industrial applications, and its industrial value is extremely large.

Claims (4)

[Claims] (1) The following formula: RT_x (wherein, R is La, Ce
, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho,
At least one selected from the group of Er, Tm, Yb, and Lu
represents a lanthanide element, T represents at least one transition metal selected from the group of Fe, Co, and Ni, and x
A giant magnetostrictive material, characterized in that it has a composition represented by the number of atomic moles (expressing a number satisfying the relationship 1.0≦x≦9.0), and has a crystal grain size of 15 μm or less. (2) The following formula: RT_x (wherein, R is La, Ce
, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho,
At least one selected from the group of Er, Tm, Yb, and Lu
represents a lanthanide element, T represents at least one transition metal selected from the group of Fe, Co, and Ni, and x
is the number of atomic moles that satisfies the relationship 1.0≦x≦9.0), and the cooling rate is 10^3.
A method for producing a giant magnetostrictive material, characterized in that a ribbon or flake of the alloy is prepared by applying a molten metal quenching method at ~10^5°C/sec. (3) The method for producing a giant magnetostrictive material according to claim 2, wherein the powder obtained after pulverizing the ribbon or flakes is subjected to hot pressing treatment or hot isostatic pressing treatment to form blocks. (4) The method for producing a giant magnetostrictive material according to claim 2 or 3, wherein the ribbon or flake is subjected to hot plastic deformation.