JPS6133892B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a terbium-disprodium-based giant magnetostrictive alloy that exhibits excellent magnetostrictive properties and excellent toughness. It has been known that when a magnetic body is magnetized, the length of the magnetic body changes in response to changes in the internal magnetic arrangement, that is, when an external magnetic field is applied, magnetostriction occurs.
This magnetostriction is applied to magnetostrictive filters, magnetostrictive sensors, ultrasonic delay lines, magnetostrictive vibrators, etc. Nickel-based alloys, iron-cobalt alloys, ferrite, and the like are used as magnetostrictive materials constituting these devices. In recent years, with advances in measurement engineering and development in the field of precision machinery, there has been a need to develop a displacement drive unit that is indispensable for minute displacement control on the micron order. A magneto-mechanical conversion device using a magnetostrictive material is promising as one of the drive mechanisms for the displacement drive unit. However, conventionally known magnetostrictive materials do not have a sufficient absolute amount of displacement, and are not satisfactory as materials for drive parts for precise displacement control on the micron order, not only in terms of absolute drive displacement but also in terms of precision control. . Also, if we focus only on the amount of displacement of the magnetostrictive material,
Rare earth and iron intermetallic compounds form nickel-based alloys.
Although it is known to exhibit magnetostriction of nearly 100 times, it is not satisfactory as a drive part material because the conversion efficiency of electrical input energy into mechanical displacement is extremely poor and the material is brittle. Ta. The present inventors carried out studies based on these points, and as a result, iron of 8% to 38% by weight, manganese of 0.01% to 25% by weight, and 0.1% to 35% by weight
of terbium and the remainder disprosium and incidental impurities, and the weight ratio of terbium to disprosium ((terbium weight)/
(disprosium weight)) is in the range of 0.001 to 0.5, and is composed of 50% by volume or more of a Laves type intermetallic compound phase and the balance of rare earth metal α phase mainly composed of terbium and disprosium. We have discovered a terbium-disprosium-based giant magnetostrictive alloy consisting of a two-phase alloy structure. That is, the present invention provides a terbium-disprosium-based giant magnetostrictive alloy that has excellent magnetostrictive properties and toughness and is particularly suitable as a magnetostrictive material that is a main component of a magneto-mechanical displacement conversion device for a precision displacement control drive unit. With the goal. To explain the present invention in detail below, in the alloy according to the present invention, terbium and disprosium belong to rare earth elements (lanthanides), and unlike 3d transition metals such as iron and nickel, because of the strong orbital angular momentum of 4f electrons. It has extremely large crystal anisotropy and is an essential component for obtaining excellent magnetostriction properties, and at the same time is the main alloy component that provides excellent toughness. However, terbium, disprosium alone,
Alternatively, although the terbium-disprosium alloy exhibits excellent magnetostriction properties at low temperatures,
It does not exhibit magnetostriction in the temperature range above room temperature, making it impossible to obtain satisfactory characteristics. Iron and manganese, which are the main alloying (additional) elements of the alloy of the present invention, form a Laves type intermetallic compound with terbium and disprosium, and in the temperature range above room temperature in terbium, disprosium, and terbium-disprosium alloys. This significantly improves the magnetostrictive properties, leading to satisfactory properties. The reason for limiting the alloy composition ranges of iron and manganese to 8% to 38% by weight of iron and 0.01% to 25% by weight of manganese is that both iron and manganese must contain less than 8% by weight of iron and 0.01% by weight, respectively. If the amount of manganese is less than 38% by weight, sufficient improvement in magnetostrictive properties will not be obtained, and if the amount of iron is more than 38% by weight, the toughness will significantly deteriorate and the material will become brittle.
If manganese exceeds 25% by weight, the magnetostrictive properties deteriorate, so the alloy composition is limited to the above range. In addition, the range of terbium alloy composition has been increased from 0.1% by weight to 35% by weight.
The reason why the weight ratio of terbium and disprosium ((terbium weight)/(disprosium weight)) is limited to 0.001 or more and 0.5 or less is as follows: The magnetostrictive properties are further improved by iron and manganese, and a terbium-disprosium-based alloy exhibiting excellent magnetostrictive properties is realized, but with less than 0.1% by weight terbium, the magnetostrictive properties are not improved. First, if terbium exceeds 35% by weight, deterioration of the magnetostrictive properties is observed, so the content is limited to 0.1% by weight or more and 35% by weight or less. Furthermore, even within the above-mentioned limited range of terbium, if the weight ratio of terbium and disprosium is not within the range of 0.001 or more and 0.5 or less, no improvement in magnetostrictive properties can be obtained, so this was added to the limited range. In addition, if the volume percent of the Laves type intermetallic compound found in the alloy of the present invention is less than 50%, although the toughness and other mechanical properties are excellent, satisfactory magnetostriction properties cannot be obtained. It is limited to include Laves-type intermetallic compounds. Next, the reason why the transition metal additive elements in the alloy of the present invention are limited to iron and manganese will be explained based on experimental data. Disprosium and terbium metals form Laves-type intermetallic compounds with transition metals such as iron and manganese. By creating Laves-type intermetallic compounds, the excellent magnetostrictive properties of rare earth metals and alloys such as terbium-disprosium alloys can be brought to temperatures above room temperature. This is because the ferromagnetic phase in a broad sense is stabilized up to temperatures above room temperature. The temperature at which the ferromagnetic phase disappears is 179 K (-94° C.) in disprosium, to give an example of rare earth metals. On the other hand, in the case of DyFe ₂ in the Laves type intermetallic compound
It is 635K (358℃). As described above, transition metals form Laves-type intermetallic compounds when rare earth metals are alloyed, and bring excellent magnetostrictive properties to temperatures above room temperature. Table 1 shows the saturation magnetostriction values of the Laves type intermetallic compounds at room temperature.

[Table] At first glance, it can be seen that these values are orders of magnitude larger than the saturation magnetostriction value of 30×10 ^-6 for conventional magnetostrictive metals, such as nickel. However, the mechanical properties of single-phase Laves-type intermetallic compounds are extremely poor, especially in workability and toughness, and the properties are far different from those of practical alloys. In addition, in order to obtain the saturation magnetostriction values shown in Table 1, a strong magnetic field of tens of kilo Oersteds is required, and if a solenoid-type magnet with a per ampere of about 100 Oersteds is used and electric-magnetic conversion is performed, the magnetic field will exceed 100 Amps. This requires a large current of several tens of kilowatts, which poses a major obstacle in practical use. One of the measures to improve workability and toughness is to alloy the transition metal constituting the Laves-type intermetallic compound with iron and manganese. Furthermore, as a means to further improve workability and toughness, it is possible to improve the fracture toughness value by dispersing a highly ductile rare earth metal α phase, particularly an α-disprosium phase, in the Laves type intermetallic compound. However, improvements in toughness and workability due to the dispersion of this α-terbium-disprosium phase are limited to the above-mentioned iron-manganese-rare earth metal/alloy system based on the thermal equilibrium phase diagram. The phase diagram for the transition metal-rare earth metal system is shown in Figure 1, where there is no compound with a higher rare earth metal element concentration than the DyMn ₂ Laves type intermetallic compound on the rare earth metal side, such as the disprosium-manganese system, and the phase diagram shown in Figure 1. On the rare earth metal side, such as the disprosium-cobalt system shown in Figure 2,
DyCo ₂ It is broadly classified into systems in which compounds of higher rare earth elements exist than Laves type intermetallic compounds. The alloy systems that can be applied to the alloy products of the present invention are limited to alloy systems that exhibit a disprosium-manganese type phase diagram, but alloy systems that satisfy this include iron-manganese rare earth alloy systems. That is why. Next, we will discuss rare earth metals and transition metals in Laves-type intermetallic compounds, especially changes in magnetostrictive properties due to alloying of disprosium with terbium as a rare earth metal, and alloying of iron with manganese as a transition metal, and α- We will explain the change in magnetostrictive properties when toughness is improved by terbium-disprosium. In Figures 3 and 4 (TbyDy _{(1 - y)} ) _1.33
(Fe ₁ - _x Mnx) Each x value (manganese concentration), each y of _{the 2} systems
Magnetostrictive properties at various values (terbium concentration) are shown.
Alloying of manganese is done at room temperature, especially on the low magnetic field side (2kOe
Regarding the magnetostrictive properties (below), when y is about 0.2 and the terbium concentration is lower than about 13% by weight, a remarkable improvement in the magnetostrictive properties was observed due to the alloying of iron with manganese. In addition, in Figure 3, the magnetostrictive properties are the magnetostrictive properties of Dy _{1. 33} Fe ₂ at room temperature.
Shown as a relative value when set to 10. _{( Tb 0.2 Dy 0.8} ) _1.33
(Fe _0.8 Mn _0.2 ) ₂ exhibits the best magnetostrictive properties among the materials whose magnetostrictive properties are _currently known _.
It exceeds Tb _0.3 Dy _{0.7 Fe 2 .} In addition
Compared to Tb ₀ . ₃ Dy ₀ . ₇ Fe ₂ which is brittle,
(Tb _{0.2 Dy 0.8 ) 1.33 (} Fe _{0.8 Mn 0.2} ) ₂ was found to have significantly improved _{toughness .} On the other hand, when alloying terbium, the magnetostriction properties at room temperature, particularly in the low magnetic field (below 2 kOe), are significantly reduced, regardless of the x value or the manganese concentration, as disprosium becomes alloyed with terbium. Improvement was observed. In addition, the effect of terbium alloying was noticeable when x was 0.1 and 0.2, especially when x=0.2. The magnetostrictive characteristics in Figure 4 are
It is expressed as a relative value when the magnetostriction property of Dy ₁ . ₃₃ Fe ₂ at room temperature is set to 10. As a result, _the above Tb _0.3 Dy _{0.7 Fe 2}
It exhibits excellent magnetostrictive properties at low terbium concentrations compared to . Rare earth metals are rare metal resources on earth.
In recent years, effective utilization of limited resources has become a technical issue. In this sense as well, lowering the concentration of terbium, which is one of the rarest and most expensive metals among rare earth lanthanides, has great practical and technical significance. Also _, (Tb _0.2 Dy _0.8 ) ₍ Fe _{0.8 Mn 0.2} ) ₂ ―α ₍ Tb―
Figure 5 shows the magnetostrictive characteristics of the Dy) system. The magnetostrictive properties (Tb _{0.2 Dy 0.8 )} (Fe _0.8 Mn _0.2 ) ₂ are expressed as relative values when _the magnetostrictive properties at room temperature are taken as 10 _. α-(terbium-disprosium) volume percent
It can be seen that when it exceeds 50%, the magnetostrictive properties deteriorate rapidly. Based on the above experimental facts, the composition of the alloy of the present invention was limited. Next, examples of the present invention will be described, and comparative examples will also be described in order to confirm the effects of the present invention. Example 1 No.2-1 to No.2- in Tables 2, 3, and 4
14, No. 3-1 ~ No. 3-14, No. 4-1 ~ No. 4-14,
A total of 42 types of alloys (14 types each) were prepared, and after arc melting each alloy was homogenized at 800℃ for 120 hours, a test piece with a thickness of 3 mm, width of 6 mm, and length of 15 mm was created by cutting. The magnetostrictive properties were measured.

【table】

【table】

【table】

[Table] Magnetostrictive properties were measured by the strain gauge method using a core magnet and inserting the above sample into a part of a magnetic circuit. The No. 2 series has a (terbium)/(disprosium) weight ratio of 0.1, and the No. 3 series has a (terbium)/(disprosium) weight ratio of 0.1.
The 0.2, No. 4 series has a (terbium)/(disprosium) weight ratio of 0.3. The measurement results are shown in Tables 5, 6, and 7.

【table】

【table】

【table】

[Table] Comparative Example 1 Fourteen types of alloys with the compositions shown in No. 5-1 to No. 5-14 in Table 8 were prepared, and as in the example, after arc melting 800
After homogenizing at ℃ for 120 hours, a test piece with a thickness of 3 mm, width of 6 mm, and length of 15 mm was prepared by cutting, and then the magnetostrictive properties were measured under the same conditions as in the example.
The magnetostrictive properties were also measured for conventionally used nickel, iron-cobalt alloys, and iron-palladium alloys having the compositions shown in No. 5-15 to No. 5-17 in Table 8. The results are also listed in Table 9.

[Table] Main ingredients include and disprosium
It is not the α phase. (RT ₃ phase))

【table】

[Table] When comparing the magnetostriction properties, we focused on the magnetostriction value on the low magnetic field side, calculated the static magnetostriction value at an applied magnetic field of 2 kOe, and compared the magnetostriction properties of DyFe ₂ shown in No. 5-5 to 10 The value is expressed as a relative value using this as a standard. As is clear from the results of Example 1 above, the terbium-disprosium-based giant magnetostrictive alloy according to the present invention has significantly improved properties at room temperature and in a low magnetic field (low electrical input) compared to the magnetostrictive properties of DyFe ₂ . It has been confirmed that this will be done. Compared to the nickel 5-17 of Comparative Example 1, the alloy of the present invention, 3- of Example 1-2
9. In Example 4-10 of Example 1-3, the magnetostrictive properties are improved by about 8 to 9 times, that is, by nearly one order of magnitude compared to the conventionally most used magnetostrictive material. Taking the example of materials for precision micro-displacement drives, this fact means that while conventionally it was possible to precisely control displacement up to 40 μm over 1 m, if the same length (1 m) is used,
In addition to enabling precise displacement control of about 400 μm, if the same displacement (40 μm) is to be precisely controlled, the length is only 10 cm, which allows for miniaturization, and this size is also an important factor in determining whether it can be put into practical use. . Furthermore, the magnetostrictive properties of the alloy of the present invention are as follows:
It also significantly exceeds the magnetostrictive properties of the iron-cobalt alloy shown in No. 15 and the iron-palladium alloy shown in Comparative Example 5-16. In addition, the alloy of the present invention is an alloy that further improves the magnetostrictive properties by nearly three times that of the disprosium-based giant magnetostrictive alloy previously proposed by the present inventors who investigated improvements in the magnetostrictive properties and toughness of DyFe ₂ . Figure 6 shows the alloy of the present invention, 3-9 of Example 1-2,
4-10 of Example 1-3 and Laves-type intermetallic compound with excellent magnetostrictive properties although fragile
Tb _{0.3 Dy 0.7 Fe 2} exhibits magnetostrictive properties on the low magnetic field ₍ low electrical input energy) side, but the alloy of the present _invention has properties superior to Tb _0.3 Dy _0.7 Fe ₂ on the low electrical input side. It exhibits excellent linearity with respect to electrical input, and has extremely advantageous characteristics in high-speed AC control. In addition, although the above example shows only the improvement of magnetostrictive properties, when applying a giant magnetostrictive alloy as shown in Example 1 to precision displacement drive members or powerful ultrasonic generation members, toughness in addition to magnetostrictive properties is practically important. It becomes a big problem. Below is Example 1, Table 2, and Table 3.
The present invention alloy and Comparative Example 2 shown in Tables 4 and 4,
Examples of improving the toughness of the alloys shown in Table 10 will be described.

[Table] Example 2 No.2-1 to No.2-14 in Table 2, No.3-1 in Table 3
~3-14, Table 4 No.4-1 to 4-14, 14 types each,
A total of 42 types of alloys are prepared, and after arc melting each
After homogenization treatment at 800°C for 120 hours, a 10mm x 100mm test piece was created by cutting. As a comparative evaluation method for toughness, we adopted a drop test on an uneven iron plate, and tested the same shape (almost the same weight).
Test pieces A (0.5m), B (1m), C (2m),
D (3 m) was allowed to fall naturally from four different potential energy positions, and the presence or absence of breakage was examined. The results are shown in Table 11. In addition, the toughness is indicated by an X mark if the product was broken when dropped from a position A or below, a △ mark if a product was broken when dropped from a position A or above B or below, and a △ mark if the product was broken when dropped from a position B or above. Items that break when dropped from a higher position are marked with ○, items that are broken when dropped from position C or higher and lower than position D are marked with ◎, items that break when dropped from position D or higher, or those that do not cause destruction at all. Indicated by ↑.

[Table] Comparative Example 2 In order to confirm the effect of manganese alloying and rare earth metal concentration on toughness in the alloy of the present invention,
Alloys No. 10-1 to No. 10-5 in Table 10 were prepared under the same conditions as in Example 2, and then tested under the same conditions. The test results are shown in Table 12.

[Table] As is clear from the results of Example 2 above, toughness was significantly improved by alloying manganese and by increasing the rare earth metal concentration higher than the rare earth metal concentration in the Laves type intermetallic compound stoichiometric composition. There is. In other words, the terbium-disprosium-based alloy consisting of the terbium-disprosium-iron-manganese system, which is the alloy of the present invention, has a high resistance to the brittleness of intermetallic compounds due to the dispersion of α-(Tb-Dy), which is rich in alloying ductility of manganese. This has made it possible to overcome the toughness and provide toughness that is suitable for practical use. In addition, by having a rare earth metal concentration higher than the rare earth metal concentration in the stoichiometric composition, it is possible to improve oxidation resistance and corrosion resistance at room temperature. As explained above, the terbium-disprosium-iron-manganese terbium-disprosium-based alloy according to the present invention has extremely superior magnetostrictive properties compared to the properties of conventional magnetostrictive materials, and is a practical material with good toughness and oxidation resistance. It also satisfies the essential factors, and has extremely excellent properties especially as a constituent material for drive units for micron-order minute displacement control, vibrators for generating powerful ultrasonic waves, sensors, etc.

[Brief explanation of the drawing]

Figure 1 is a disprosium-manganese alloy phase diagram, Figure 2 is a disprosium-cobalt alloy phase diagram, and Figure 3 is (TbyDy _{(1 - y)} ) _1.33
Figure 4 is a curve diagram showing the relationship between manganese concentration and magnetostriction properties at (Fe _{1 - x} Mnx) _2. Figure ₄ shows the relationship between terbium concentration and magnetostriction at ( _{TbyDy ( 1} - _y) ) ₁ . _A curve diagram showing the relationship with the _{characteristics} , Figure 5 is α(Tb-Dy)-Tb _0.2 Dy _0.8 )
(Fe _0.8 Mn _{0.2 ) 2} A curve diagram showing _the relationship between α-(Tb _- Dy) volume percentage and magnetostriction properties, Figure 6 shows _{the alloy of the present invention and Tb 0.3 Dy 0.7} Fe ₂ A curve diagram showing the magnetostriction characteristics on the low magnetic field side of .

Claims (1)

[Claims] 1 8wt%~38wt% iron and 0.01wt%~
Consists of 25% by weight of manganese, 0.1% to 35% by weight of terbium, and the remainder disprosium and incidental impurities, and the weight ratio of terbium to disprosium ((terbium/(disprosium weight)) is 0.001 or more and 0.5 or less A terbium-disprosium group consisting of a two-phase alloy structure consisting of a Laves-type intermetallic compound phase of 50% or more by volume and a rare earth metal α phase mainly composed of terbium and disprosium. Magnetostrictive alloy.