JPH0468372B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a magnetostrictive alloy suitable for a minute displacement control element. (Prior Art) In recent years, machining accuracy in mechanical work has improved markedly and is moving from the micron order to the submicron order, and this is already a common situation in the field of electronic devices. Furthermore, as we enter the era of mechatronics, problems related to ultra-fine processing and minute displacement control are becoming important not only in the above-mentioned field of electronic engineering but also in the field of mechanical engineering. In other words, in the case of measuring devices and various mechanical devices, displacement of each component due to temperature changes is unavoidable. means that a displacement of about 10 ppm/℃ can always occur,
Various devices have flexible moving parts (e.g. joints) and rotating parts (e.g. gears, motors)
In the case of equipment, errors due to play in contact between parts are unavoidable, metal generally exhibits a history of deformation under load, and various devices are freed from mechanical vibration. There are limits to this, especially if the device itself has a built-in vibration source, and it is theoretically impossible to prevent vibration and distance fluctuations caused by it. A control element is required. Furthermore, with the rapid development of optical information processing and optical recording equipment, the need for minute displacement control elements is increasing more and more. Conventionally, such micro-displacement control elements include:
Depending on the form of the displacement generating part, the types shown in Table 1 have been proposed and put into practical use.

[Structure of the invention]

(Means for Solving the Problems) The magnetostrictive alloy of the present invention includes, for example, a magnetic coil wound in a hollow shape and a displacement generating member coaxially inserted into the hollow part of the magnetic coil and displaced. It is used as a displacement generating member of the minute displacement control element with iron (Fe) 13.0 to 40% by weight, manganese (Mn) 0.01 to 16.4% by weight, and terbium (Tb).
0.1 to 25% by weight, the remainder substantially consisting of disprosium (Dy), and the main phase is a cubic Laves compound, and the crystals are oriented in the approximately [111] direction of the cubic Laves compound. It is a magnetostrictive alloy. First, an example of the structure of a control element using the alloy of the present invention will be explained with reference to FIG. In FIG. 1, 1 is a rod-shaped displacement generating member, and 2 is an excitation coil for magnetizing the displacement generating portion to generate a length displacement. The excitation coil 2 is constructed by winding a conducting wire (for example, formal copper wire) of a predetermined diameter a necessary number of times, and making the inside hollow. The number of turns of the coil at this time is determined based on the relationship with the strength of the magnetic field to be created in the displacement generating member 1. A rod-shaped magnetic alloy having a predetermined length is coaxially inserted into the hollow portion of the magnetic coil 2 to constitute the displacement generating member 1 . The length of the displacement generating member 1 at this time is determined based on the relationship between the magnitude of the displacement to be controlled and the magnitude of magnetostriction of the member. In addition, the displacement generating member 1 is supported in the hollow part of the excitation coil 2 by a bearing material 3 having excellent lubrication performance, such as a ball bearing, a graphite material, or a Teflon material. It is designed so that it can be easily slid even if something happens. The amount of displacement of the displacement generating member 1 is determined by a first displacement transmission shaft 4 made of, for example, soft magnetic iron, which is disposed in contact with an end of the member, and a first displacement transmission shaft 4 made of, for example, non-magnetic stainless steel, which is in contact with an end of the transmission shaft 4. It is transmitted to the outside of the system via the second displacement transmission shaft 5 made of steel. In order to prevent magnetic flux from leaking from both ends when a magnetic field is applied to the displacement generating member 1, the outer periphery of the magnetic coil 2 is provided with a demagnetizing field that controls or eliminates the demagnetizing field generated in the displacement generating member 1. In order to increase the efficiency of the magnetic coil 2, it is preferable to provide a yoke made of soft magnetic iron, for example. Furthermore, before magnetizing the displacement generating part 1 with the excitation coil 2, a bias is applied to the outer periphery of the excitation coil 2 in order to magnetize the displacement generation member 1 to some extent in advance and use it in a magnetostrictive characteristic region with good linearity. More preferably, a coil 6 is provided. Alternatively, a permanent magnet may be used. The magnetostrictive alloy will be explained in detail below. First, Tb and Dy are rare earth elements that have extremely large crystal anisotropy and are essential components for improving the magnetostriction properties of magnetic alloys. however,
Tb alone and Dy alone are alloys consisting only of Tb and Dy.
Although both exhibit excellent magnetostriction properties at low temperatures, they have the problem that they do not exhibit magnetostriction at temperatures above room temperature. On the other hand, Tb and Dy form Laves-type intermetallic compounds with reduction metals such as Fe and Mn.
This allows the excellent magnetostrictive properties of Tb, Dy-Tb, and Dy alloys to be brought to room temperature. This is because the broadly defined ferromagnetic phase is stabilized up to room temperature in a form that is included in the Laves type intermetallic compound. For example, the temperature at which the ferromagnetic phase disappears in Dy is 179K (-94℃), but in Dy
In the case of DyFex, a labase-type intermetallic compound with Fe, it is 635 K (358°C). The saturation magnetostriction values (λ) of Labase type intermetallic compounds of various rare earth elements and Fe in a chamber (25° C.) are shown in Table 2.

[Table] As is clear from Table 2, the saturation magnetostriction values of these Labase-type intermetallic compounds are orders of magnitude larger than that of Ni, a typical conventional magnetostrictive metal (30×10 ^-6 ). . However, when the above-mentioned labase-type intermetallic compound is single-phase, its mechanical properties
In particular, the workability and toughness are extremely poor, which poses a problem in terms of practicality. Furthermore, in order to obtain the saturation magnetostriction values shown in Table 2, a strong magnetic field of several tens of KOe is required, and for example, when an electric/magnetic conversion operation is performed using a solenoid type magnet of about 100 Oe/A, Dozens of times require a second current of 100A or more
Since the power consumption of KW is unavoidable, there is a big obstacle in terms of practicality. The present inventors discovered that Tb, Dy, and Tb-Dy alloys have excellent magnetostrictive properties, and that these elements and Fe,
Based on the premise that the Labase type intermetallic compound with Mn can guarantee stable magnetostriction properties at room temperature, and that the amount of magnetostriction can be improved in each step by crystal orientation, we have carried out various studies described below. We have now discovered an alloy useful as a displacement generating member for micro displacement control elements. First, (Tby Dy _(1-y) ) 1.33 (Fe _1-x Mn _x ) ₂ (x, y
represent Mn concentration and Tb concentration, respectively. ) The magnetostrictive properties of the alloy shown in (2) were measured while varying x and y. Some of the results are shown in FIGS. 2 and 3. In the diagram, the dimension of the characteristic is x=
0, y-0, that is, the magnetostriction properties at room temperature of the Labase-type intermetallic compound of Dy _1.33 Fe ₂ are shown as relative values when 10. As is clear from Figure 2, alloying of Mn is
In the magnetostrictive properties at room temperature and in a low magnetic field (below 2 KO _e ), a remarkable improvement in the magnetostrictive properties is seen in the region of y = 0.2, that is, 13% by weight of Tb or less. In particular, x
=0.2, 1=0.2 alloy; (Tb _0.2 Dy _0.8 ) _1.33 (Fe _0.8
Mn _0.2 ) ₂ is currently known to have the highest magnetostrictive properties. It was found that the value was higher than that of Tb _0.3 Dy _0.7 Fe ₂ , and its toughness was significantly improved. Furthermore, as is clear from FIG. 3, the properties of the alloy obtained by alloying Dy with Tb are significantly improved regardless of the size of x. Especially x=
At 0.2, the effect of Tb alloying is remarkable. The magnetic alloy of the present invention is of the Tb-Dy-Fe-Mn system developed based on the above experimental progress. In the magnetic alloy, Fe and Mn form a Laves type intermetallic compound with Tb and Dy, and Tb, Dy,
The excellent magnetostrictive properties of Tb-Dy alloy are stabilized and improved in the temperature range above room temperature. At this time, if the composition ratio of Fe is less than 13.0% by weight, sufficient magnetostrictive properties cannot be obtained, and if it exceeds 40% by weight, the toughness of the alloy deteriorates significantly and becomes brittle. Mn
When the composition ratio is 0.01% by weight or more, the effect of improving magnetostrictive properties is exhibited, but when the composition ratio exceeds 16.4% by weight, the magnetostrictive properties are deteriorated. By alloying with Dy, Tb improves the overall magnetostrictive properties compared to the case of Dy alone. The composition ratio is
The effect is exhibited at 0.1% by weight or more, but if it exceeds 25% by weight, the magnetic properties will deteriorate. In the magnetostrictive alloy according to the present invention, the remainder is
Although it is composed of Dy, there is no problem even if there is a trace amount of contaminants (for example, C, O, N, rare earth elements, Y, La) that inevitably accompany the alloy adjustment. Note that although it is possible to obtain a relatively large magnetostriction with the alloy composition as described above, the characteristics can be further improved by crystallizing the alloy. Magnetostrictive alloys have the required characteristics of high magnetostriction and low saturation magnetic field. In order to obtain a low saturation magnetic field, the axis of easy magnetization must be close to the direction of the applied magnetic field,
The anisotropy energy (absolute value) is small,
is necessary. The axis of easy magnetization differs depending on the constituent elements, and for example, in the present invention, it is [100] in the binary system of Dy and Fe, which are the main components. In addition, the anisotropic energy differs depending on the composition, and the anisotropy energy differs depending on the composition.
It has a negative value in the element system. If a Tb-Fe system with a positive value is added to this to form a ternary system, the absolute value can be reduced, but the axis of easy magnetization will shift from [100]. Furthermore, Mn is added to these systems to improve magnetostriction properties.
However, the details of its behavior have not yet been clarified, and it has been difficult to optimize its composition and crystal orientation. Therefore, the inventors experimentally tried to optimize these values, and found that the Dy-Fe system having an easy axis of magnetization of [100] has the following properties as specified in the present invention.
When Tb and Mn are added, an easy axis of magnetization is obtained approximately in the [111] direction, the anisotropy energy can be made sufficiently small, and magnetostriction can also be obtained with a sufficiently large value compared to the case without orientation. That is, it has been found that it is most preferable in terms of both magnetostriction and saturation magnetic field to orient the material having the above-mentioned composition in the approximately [111] direction of the cubic Laves compound as the main phase. The alloy of the present invention can be obtained by, for example, melting it by a vacuum induction heating method, making it into an ingot, and unidirectionally solidifying this ingot at an appropriate G value (temperature gradient at the solid-liquid interface) in, for example, a Bridgeman furnace. In order to create a displacement generating member, it can be created by performing a predetermined cutting process. Note that any method can be used for crystal orientation, regardless of the unidirectional solidification. Further, hot or cold working may be performed, or the obtained alloy may be crushed and then pressed in a magnetic field and fired. By combining this member with the coil portion shown in FIG. 1, a minute displacement control element is manufactured. (Example) Examples of the present invention will be described below. Thirty types of alloy samples having the compositions shown in Table 3 were prepared, and each of these samples was melted in a vacuum induction heating furnace. After the molten metal is cooled and made into an ingot, it is charged into an alumina tube with an inner diameter of 12 mm and a length of 250 mm.
Solidification was performed unilaterally in a modified Bridzmann furnace equipped with a tantalum heater at a constant rate of 60 mm/hr in an argon atmosphere. Note that this speed is 10mm/min ~ 100
It can be displaced about mm/hr. At this time, the G value near the solid-liquid interface was about 80°C/cm. The solidification orientation of the obtained unidirectionally solidified material was approximately the [111] easy axis of magnetization, which is the crystal orientation of the cubic Laves compound. For each unidirectionally solidified material
After uniform treatment at 800°C for 120 hours, a round bar with a diameter of 8 mm and a length of 100 mm was cut into a displacement generating member. Sample numbers 1 to 14 are examples according to the present invention, and the others are comparative examples. Note that sample numbers 31 and 32 have the same composition as sample number 1, but the orientation direction of the crystals was changed. Using these round bars, minute displacement control elements having the structure shown in FIG. 1 were assembled, and the characteristics of each element were investigated. Here, the bearing material has an outer diameter of 10 mm, an inner diameter of 8 mm, and a length of
100mm Teflon tube, excitation coil 1mm in diameter
20,000 times/m around the outer circumference of the Teflon tube.
Winding with a total DC resistance of 5Ω, excitation capacity of 250
Oe/A, the bias coil arranged around its outer circumference has a number of turns of 10,000 turns/m and an excitation capacity of 150
It was Oe/A. Characteristic evaluation of the control element is performed using 1A in the bias coil.
The experiment was conducted under a bias magnetic field of 125 Oe and a current of 125 Oe. In this state, the excitation coil is 0.5A (input power 6W)
When driving power is applied to the bar material (magnetostrictive alloy)
The amount of displacement (μm) was measured. The results are shown in Table 3.

【table】

〔Effect of the invention〕

As is clear from the above description, the magnetostrictive alloy of the present invention has a large amount of strain and is very effective. In addition, displacement generating members using this material have excellent linearity, have a significantly small displacement history, can be operated with small input power, and have a large amount of distortion, which allows the entire element to be miniaturized. Therefore, it is extremely useful in the fields of optical information processing, optical recording equipment, and precision machine tools that require precision control on the submicron order.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway schematic diagram showing a preferred example of a minute displacement control element according to the present invention. FIGS. 2 and 3 are diagrams showing the relationship between x, y and magnetic properties of (TbyDy _(1-y)1.33 Fe _1-x Mn _x ) _2, respectively. FIG. 4 is a diagram showing the relationship between the drive current and the amount of strain, and FIG. 5 is a diagram showing the relationship between the magnitude of the electric field and the amount of strain for electrostrictive materials and piezoelectric materials shown for comparison. 1... Displacement generating member (magnetostrictive alloy), 2... Excitation coil, 3... Bearing material, 4, 5... Displacement transmission shaft,
6...Bias coil.

Claims (1)

[Scope of Claims] 1 Consisting of 13.0 to 40% by weight of iron, 0.01 to 16.4% by weight of manganese, 0.1 to 25% by weight of terbium, and the remainder substantially disprosium, and the main phase is a cubic laves compound, A magnetostrictive alloy characterized by crystal orientation in the [111] direction of a cubic Laves compound. 2. The magnetostrictive alloy according to claim 1, wherein the axis of easy magnetization is approximately in the [111] direction. 3. The magnetostrictive alloy according to claim 1 or 2, wherein the crystal orientation is obtained by directional solidification.