JP3630164B2 - Magnetic alloy material and method for producing the same - Google Patents

Description

  The present invention relates to a magnetic alloy material suitably used as a magnetic refrigeration working substance or a magnetostrictive material and a method for producing the same.

In recent years, composition formula: La _1-z RE _z (Fe _1-x A _xy TM _y ) ₁₃ (A = at least one element of Al, Si, Ga, Ge, Sn 0.05 ≦ x ≦ 0.2) , TM is a magnetic alloy represented by at least one element of transition metal elements 0 ≦ y ≦ 0.1, RE is at least one element of rare earth elements excluding La, 0 ≦ z ≦ 0.1) (Hereinafter referred to as “LaFe ₁₃ -based magnetic alloy”) has a NaZn ₁₃ type crystal structure and exhibits a large magnetocaloric effect and magnetovolume effect near the Curie temperature (Tc). As a magnetostrictive material, it is considered promising (for example, Patent Document 1, Patent Document 2, and Non-Patent Document 1).

The LaFe ₁₃ series magnetic alloy has been conventionally produced by, for example, subjecting a cast alloy obtained by arc melting or high frequency melting to a heat treatment in vacuum at 1050 ° C. for about 168 hours.
JP 2000-54086 A JP 2002-69596 A “The strong magnetic volume and magnetocaloric effect of the itinerant electron metamagnetism La (FexSi1-x) 13 compound”, Maya Fujita, et al., Materia, Vol. 41, No. 4, pp. 269-275, 2002

However, the conventional method for producing a LaFe ₁₃ series magnetic alloy has the following problems.

A cast alloy obtained from a molten alloy having a predetermined composition has two or more coarse crystals including an α-Fe phase in which a part of A and TM in the above composition formula is dissolved and a phase composed of the remainder. It has an intricate organization of phases (for example, see FIG. 6A described later). A compound phase having a NaZn ₁₃ type crystal structure (hereinafter referred to as “LaFe ₁₃ type compound phase”) is generated from the interface of these coarse crystal phases (see, for example, FIG. 6B described later). Therefore, in order to obtain a LaFe ₁₃ -based magnetic alloy (intermetallic compound) from a structure having such a coarse crystal phase, as described above, homogenization (hereinafter referred to as “homogenization” by high-temperature heat treatment at a high temperature). Sometimes referred to as “heat treatment”. Since the homogenization heat treatment for a long time is indispensable, there is a problem that the LaFe ₁₃ series magnetic alloy is poor in mass productivity.

  In addition, the alloy surface is deteriorated by corrosion such as oxidation during the long-time homogenization heat treatment, and as a result, there is a problem that the magnetocaloric effect and the magnetovolume effect are deteriorated.

  Further, the cast alloy is generally massive, and the homogenization heat treatment is also carried out in bulk. Magnetic refrigeration work materials are often used in granular form (powder) to increase the heat exchange efficiency with heat exchange liquids (eg, liquids with high specific heat such as aqueous antifreeze), whereas bulk cast alloys are The grindability is poor, which causes a reduction in production efficiency.

The present invention has been made in view of such various points, and its main object is to provide a method for producing a LaFe ₁₃ -based magnetic alloy material with higher efficiency than before.

Method for producing a magnetic alloy material of the present invention includes the steps of preparing a melt of an alloy material having a predetermined composition, by quenching a melt of the alloy material, the composition _{formula: Fe 100-abc RE a A} b TM c (RE is selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm, and at least one rare earth element containing 90 atomic% or more of La, A Is at least one element selected from the group consisting of Al, Si, Ga, Ge and Sn, TM is at least selected from the group consisting of Sc, Ti, V, Cr, Mn, Co, Ni, Cu and Zn 1 type transition metal element, 5 atomic% ≦ a ≦ 10 atomic%, 4.7 atomic% ≦ b ≦ 18 atomic%, 0 atomic% ≦ c ≦ 9 atomic%) are formed. And in the quenched alloy, The compound phase having AZN ₁₃ type crystal structure includes a step of forming 70 vol% or more, by the above-described object is achieved.

  In a preferred embodiment, the step of forming the compound phase includes a step of heat-treating the quenched alloy at a temperature of 400 ° C. or higher and 1200 ° C. or lower for a time of 1 second or longer and 100 hours or shorter.

  The heat treatment step is preferably a step of heat-treating the quenched alloy for 10 minutes or more.

It is preferable to form a compound phase having a NaZn ₁₃ type crystal structure having a homogeneous structure throughout the heat treatment step.

In one embodiment, the quenched alloy preferably has the compound phase having a NaZn ₁₃ type crystal structure immediately after quenching.

The cooling rate in the step of forming the quenched alloy is preferably 1 × 10 ² ° C./second or more and 1 × 10 ⁸ ° C./second or less.

  The quenched alloy is preferably in the form of a ribbon having a thickness of 10 μm to 300 μm.

  In a preferred embodiment, the magnetic alloy raw material has a magnetocaloric effect.

  In a preferred embodiment, the method further includes a step of pulverizing the quenched alloy.

  It is preferable that Curie temperature Tc which shows a magnetic phase transition exists in the range of 180K or more and 330K or less. A plurality of magnetic alloy materials having different Curie temperatures Tc can be obtained by including Co as TM in the composition formula and controlling the ratio of Co.

  In one embodiment, the half-value width ΔTc of the temperature region causing the magnetic phase transition is 30K or more.

  The magnetic alloy material according to the present invention is manufactured by any one of the above-described manufacturing methods, and can be particularly suitably used as a magnetic refrigeration working substance.

According to the present invention, a method for producing a LaFe ₁₃ -based magnetic alloy material with higher production efficiency than before is provided. In particular, if a process for forming a ribbon-like quenching alloy is employed, the pulverization property can be improved, so that a magnetic alloy material can be produced with high efficiency as a magnetic refrigeration working substance used as a powder.

Hereinafter, an embodiment of a method for producing a magnetic alloy material (LaFe ₁₃ -based magnetic alloy) according to the present invention will be described.

Method for producing a magnetic alloy material of the present invention includes a first step of preparing a melt of an alloy material having a predetermined composition, by quenching a melt of the alloy material, the composition _{formula: Fe 100-abc RE a A} b TM _c (RE is selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm, and at least one rare earth element containing 90 atomic% or more of La, A is at least one element selected from the group consisting of Al, Si, Ga, Ge and Sn, and TM is selected from the group consisting of Sc, Ti, V, Cr, Mn, Co, Ni, Cu and Zn A quenched alloy having a composition represented by at least one transition metal element, 5 atomic% ≦ a ≦ 10 atomic%, 4.7 atomic% ≦ b ≦ 18 atomic%, 0 atomic% ≦ c ≦ 9 atomic%) A second step to form and N in the quenched alloy Compound phase having a Zn ₁₃ type crystal structure (i.e., LaFe ₁₃ type compound phase) encompasses a third step of forming a 70% by volume or more.

The method for producing a LaFe ₁₃ -based magnetic alloy according to the present invention employs a rapid cooling method (liquid quenching method) in the second step. The quenched alloy has a higher compositional uniformity than the cast alloy, and a multiphase structure (see FIG. 6A) composed of coarse crystal phases found in the cast alloy is not observed. For example, even when the quenched alloy is pulverized to have a particle size of 10 μm to 300 μm, for example, by heat treatment, 70% by volume or more of each particle is composed of a LaFe ₁₃ type compound phase.

Of course, a magnetic alloy material in which 90% by volume or more is composed of a LaFe ₁₃ type compound phase can be obtained by adjusting heat treatment conditions and the like. In the above composition formula, when a is out of the above range, the LaFe ₁₃ type compound phase cannot be formed by 70 vol% or more. If b is less than 4.7 atomic%, the LaFe ₁₃ type compound phase is not formed, and if it exceeds 18 atomic%, the magnetocaloric effect (or magnetovolume effect) cannot be obtained sufficiently. Further, even if c is out of the above range, the magnetocaloric effect (or magnetovolume effect) cannot be sufficiently obtained, and a magnetic alloy material having sufficient characteristics as a magnetic refrigeration working material (or magnetostrictive material) cannot be obtained.

The third step typically includes a step of subjecting the quenched alloy obtained in the second step to a heat treatment at a temperature of 400 ° C. or higher and 1200 ° C. or lower for a period of 1 second or longer and 100 hours or shorter. Since the quenched alloy obtained in the second step has a more uniform structure than the cast alloy, the heat treatment time required for making the entire quenched alloy into a LaFe ₁₃ -based magnetic alloy can be shortened. For example, the heat treatment time can be reduced to 24 hours or less, and can be further reduced to about 5 minutes. In order to improve the characteristics, it is preferable to form a LaFe ₁₃ type compound phase having a homogeneous structure throughout the alloy. In order to form a LaFe ₁₃ type compound phase having a homogeneous structure throughout the alloy, it is preferable to heat-treat for 10 minutes or more. For example, as will be described later, for a quenched alloy obtained by adjusting the roll surface speed within a range of 3 m / second or more and 30 m / second or less, if heat treatment is performed for 10 minutes or more, almost all of the alloy is obtained. A LaFe ₁₃ type compound phase having a homogeneous structure can be formed. If the heat treatment is performed for more than 90 minutes, the α-Fe phase may increase, so the heat treatment time is preferably 90 minutes or less.

The heat treatment temperature is set so that a predetermined LaFe ₁₃ series magnetic alloy is formed in relation to the treatment time. However, if the temperature is lower than 400 ° C., the treatment time is longer than 100 hours, and it is not preferable. If the temperature exceeds 1200 ° C., surface deterioration due to oxidation or the like, and volatilization of specific elements become remarkable. In consideration of shortening the heat treatment time to about 1 hour, it is preferable to perform the heat treatment at a temperature of 900 ° C. or higher and 1200 ° C. or lower. In order to suppress oxidation, the atmosphere is preferably a vacuum (eg, 10 ⁻² Pa or less) or an inert gas (particularly, rare gas) atmosphere.

The first step in the production method of LaFe ₁₃ based magnetic alloy according to the present invention, for example, it is performed in the same way as conventional.

When the manufacturing method according to the present embodiment is used, the heat treatment time can be shortened, so that productivity is improved. Furthermore, since deterioration due to oxidation or the like of the surface of the LaFe ₁₃ -based magnetic alloy is suppressed during the heat treatment, there is little deterioration in characteristics. For example, in a LaFe ₁₃ series magnetic alloy obtained by heat-treating a cast alloy for a long time, a layer several mm from the surface cannot be used as a magnetic refrigeration working material, but the quenching obtained by the embodiment of the present invention is used. Alloys (especially ribbon-like quenched alloys and alloy ribbons) can be used as magnetic refrigeration materials as they are. Therefore, a cost reduction effect can be obtained by improving the yield of expensive raw materials. Further, as will be described later, if a ribbon-like quenched alloy is produced, the pulverization performance is superior to that of a cast alloy, so that the process time required for the pulverization process can be shortened.

The LaFe ₁₃ series magnetic alloy has a large magnetocaloric effect or magnetovolume effect because it exhibits a magnetic phase transition close to the primary phase transition near the Curie temperature. In order to increase the magnetocaloric effect or magnetovolume effect It is desirable to form as many LaFe ₁₃ type compound phases as possible that exhibit a magnetic phase transition close to the primary phase transition. Conventionally, since the LaFe ₁₃ type compound phase is formed from the interface between the coarse α-Fe phase and the grain boundary phase contained in the alloy (as-cast alloy) obtained by the casting method, it is homogeneous for a long time. The treatment was necessary.

On the other hand, as a method for producing an alloy, a rapid cooling method is known together with a casting method. However, even if the quenching method is used, the α-Fe phase is likely to be produced in the same manner as in the casting method, the compositional deviation may occur through the quenching process, and a metastable phase other than the LaFe ₁₃ type compound phase is produced. Therefore, there is no report that a LaFe ₁₃ -based magnetic alloy is manufactured by using a rapid cooling method.

As a result of the study by the present inventors, when the rapid cooling method is used, a uniform and fine structure is formed as described above, and a LaFe ₁₃ type compound phase is already generated in the state immediately after the rapid cooling, as illustrated later as an example. The However, the LaFe ₁₃ type compound phase may be formed by heat treatment after making the state immediately after quenching (as-cast) an amorphous structure.

The cooling rate in the step of forming the quenched alloy is preferably 1 × 10 ² ° C./second or more and 1 × 10 ⁸ ° C./second or less. When the cooling rate is slower than 1 × 10 ² ° C./second, a multiphase structure including a relatively coarse α-Fe phase is formed as in the conventional casting method, and a homogenization heat treatment exceeding 100 hours is required. Become. On the other hand, if the cooling rate is faster than 1 × 10 ⁸ ° C./second, the thickness of the quenched alloy is reduced, resulting in a decrease in production efficiency.

  As a liquid quenching method that can obtain such a cooling rate, a gas atomizing method, a single roll quenching method, a twin roll quenching method, a strip casting method, a melt spinning method, or the like can be used. In particular, when a melt spinning method, a strip casting method, or the like is used, a ribbon-like quenched alloy having a thickness of 20 μm to 200 μm can be manufactured with high efficiency.

  For example, a quenching alloy can be produced by a melt spinning method using the quenching apparatus shown in FIG. In order to prevent oxidation of a raw material alloy containing rare earth elements (La and RE in the above composition formula) and Fe that are easily oxidized, it is preferable to perform the quenching step in an inert gas atmosphere. As the inert gas, a rare gas such as helium or argon or nitrogen can be used. Note that since nitrogen is relatively easy to react with rare earth elements, it is preferable to use a rare gas such as helium or argon.

  The rapid cooling apparatus shown in FIG. 1 includes a raw material alloy melting chamber 1 and a rapid cooling chamber 2 capable of maintaining a vacuum or an inert gas atmosphere and adjusting the pressure. FIG. 1A is an overall configuration diagram, and FIG. 1B is a partially enlarged view.

  As shown in FIG. 1 (a), the melting chamber 1 includes a melting furnace 3 for melting a raw material 20 blended so as to have a desired alloy composition at a high temperature, and a hot water storage container 4 having a hot water discharge nozzle 5 at the bottom. And a blended raw material supply device 8 for feeding the blended raw material into the melting furnace 3 while suppressing the entry of air. The hot water storage container 4 has a heating device (not shown) that stores the molten alloy 21 of the raw material alloy and can maintain the temperature of the hot water at a predetermined level.

  The quenching chamber 2 includes a rotary cooling roll 7 for rapidly cooling and solidifying the molten metal 21 discharged from the hot water nozzle 5.

  In this apparatus, the atmosphere in the melting chamber 1 and the quenching chamber 2 and the pressure thereof are controlled within a predetermined range. Therefore, atmospheric gas supply ports 1b, 2b, and 8b and gas exhaust ports 1a, 2a, and 8a are provided at appropriate locations in the apparatus. In particular, the gas exhaust port 2a is connected to a pump in order to control the absolute pressure in the quenching chamber 2 within a range of 30 kPa to normal pressure (atmospheric pressure) (preferably 100 kPa or less). By changing the pressure in the melting chamber 1, the injection pressure of the molten metal coming out of the nozzle 5 can be adjusted.

  The melting furnace 3 can be tilted, and the molten metal 21 is appropriately poured into the hot water storage container 4 through the funnel 6. The molten metal 21 is heated in the hot water storage container 4 by a heating device (not shown).

  The hot water discharge nozzle 5 of the hot water storage container 4 is disposed in the partition wall between the melting chamber 1 and the quenching chamber 2 and causes the molten metal 21 in the hot water storage container 4 to flow down to the surface of the cooling roll 7 positioned below. The orifice diameter of the hot water nozzle 5 is set within a range of 0.5 mm to 4.0 mm. By adjusting the orifice diameter and / or the pressure difference between the melting chamber 1 and the quenching chamber 2 (for example, 10 kPa or more) according to the viscosity of the molten metal 21, the molten metal 21 is smoothly discharged. According to the apparatus used in this embodiment, the molten alloy supply rate can be set to 1.5 to 10 kg / min. When the supply rate exceeds 10 kg / min, the molten metal quenching rate becomes slow, and there is a disadvantage that a multiphase structure is formed. A more preferable supply rate of the molten alloy is 2 to 8 kg / min.

  The cooling roll 7 is preferably formed from Cu, Fe, or an alloy containing Cu or Fe. If the cooling roll is made of a material other than Cu or Fe, the releasability of the quenched alloy from the cooling roll is deteriorated, and therefore the quenched alloy may be wound around the roll. The diameter of the cooling roll 7 is, for example, 300 mm to 500 mm. The water cooling capacity of the water cooling device provided in the cooling roll 7 is calculated and adjusted according to the solidification latent heat per unit time and the amount of hot water.

First, a melt 21 of a predetermined raw material alloy is produced and stored in the hot water storage container 4 of the melting chamber 1 in FIG. Next, the molten metal 21 is discharged from the hot water nozzle 5 onto the water-cooled roll 7 in the reduced-pressure Ar atmosphere, rapidly cooled by contact with the cooling roll 7, and solidified. To obtain a homogeneous structure as described above, it is preferable that the cooling rate of the molten alloy with ^{1 × 10 2 ~1 × 10 8} ℃ / sec, and ^{1 × 10 2 ~1 × 10 6} ℃ / sec More preferably.

  The time during which the molten alloy 21 is cooled by the cooling roll 7 corresponds to the time from when the alloy comes into contact with the outer peripheral surface of the rotating cooling roll 7 until it leaves, during which time the temperature of the alloy decreases and supercooling occurs. Become liquid. Thereafter, the supercooled alloy leaves the cooling roll 7 and flies in an inert atmosphere. While the alloy is in the form of a ribbon, the temperature is further reduced as a result of the heat being taken away by the atmospheric gas. In the present embodiment, the pressure of the atmospheric gas is set within the range of 10 kPa to normal pressure.

  In the present embodiment, the roll surface speed is adjusted within a range of 3 m / sec or more and 30 m / sec or less, and the atmosphere gas pressure is set to 30 kPa or more in order to enhance the secondary cooling effect by the atmosphere gas. A ribbon-like quenched alloy having a texture can be obtained. If the roll surface speed is less than 3 m / sec, the time for the homogenization heat treatment becomes longer, and the surface of the quenched ribbon may be deteriorated by corrosion such as oxidation, and if it exceeds 30 m / sec, the quenched ribbon is too thin. As a result, the volume ratio of the portion of the homogeneous structure excluding the deteriorated layer on the surface may be reduced.

  In addition, the rapid cooling method of the molten alloy used in the present invention is not limited to the above-described single roll method, and a strip casting method which is a rapid cooling method in which the flow rate is not controlled by the nozzle orifice may be used. In the case of the strip casting method, since the nozzle orifice is not used, there are advantages that the molten metal supply rate is increased and stabilization is easy. However, atmospheric gas is likely to be caught between the cooling roll and the molten metal, and the cooling rate on the quenching surface side may be uneven. In order to solve such a problem, it is necessary to reduce the atmospheric pressure of the space in which the cooling roll is placed to the above-described range and suppress the entrainment of the atmospheric gas. Further, although the production efficiency is lowered, a gas atomizing method may be used.

According to the manufacturing method of the LaFe ₁₃ series magnetic alloy of the embodiment according to the present invention, the magnetocaloric effect in which the magnetic entropy change (−ΔS _mag ) when the external magnetic field is changed from 0 T to 1 T exceeds 5 JK ⁻¹ kg ⁻¹ is achieved. A magnetic refrigeration working material can be obtained. According to the manufacturing method described above, a thin LaFe ₁₃ magnetic quenching alloy can be obtained, so that a granular (powdered) magnetic refrigeration working material can be manufactured with high manufacturing efficiency.

According to the embodiment of the present invention, a LaFe ₁₃ -based magnetic alloy having a Curie temperature Tc at which a magnetic phase transition occurs is in a range of 180K or higher, or 190K or higher and 330K or lower is obtained. LaFe ₁₃ -based magnetic alloys having different Curie temperatures Tc can be obtained by including Co as TM in the composition formula and controlling the ratio of Co. For example, when the ratio of Co (corresponding to c in the composition formula) is 9, Tc = 330K is obtained. In this specification, the magnetic phase transition refers to a transition from ferromagnetism to paramagnetism, ferromagnetism to antiferromagnetism, or antiferromagnetism to paramagnetism.

In addition, the LaFe ₁₃ -based magnetic alloy obtained by an embodiment of the present invention has a relatively wide temperature region in which a magnetic phase transition occurs, and for example, obtains a LaFe ₁₃ -based magnetic alloy having a half-value width ΔTc of 30 K or more in the transition temperature region. be able to. Therefore, according to the present embodiment, the magnetic refrigeration apparatus can be configured even when a single LaFe ₁₃ -based magnetic alloy is used as the magnetic refrigeration working material. Of course, a plurality of LaFe ₁₃ -based magnetic alloys having different compositions (different Tc) may be used depending on the operating temperature range. For example, a MnAs-based magnetic refrigeration working material (Japanese Patent Laid-Open No. 2003-028532) is used. Fewer types of alloys can cover the same operating temperature range. Moreover, the regenerative heat exchanger and the magnetic refrigeration apparatus described in Japanese Patent Application Laid-Open No. 2003-028532 can be configured using the LaFe ₁₃ based magnetic alloy according to the present embodiment.

The LaFe ₁₃ -based magnetic alloy according to the present invention is particularly preferably used as a magnetic refrigeration working material, but can also be suitably used as a magnetostrictive material as disclosed in, for example, Patent Document 1 and Patent Document 2.

Hereinafter, shows an experimental example will be described an embodiment of the method of LaFe ₁₃ based magnetic alloy according to the present invention, the present invention is not limited thereto.

(Experimental example 1)
[Production process of raw material alloy melt]
Predetermined amounts of La, Fe and Si raw materials were blended so that a LaFe ₁₃ type compound phase having a composition of La (Fe _0.88 Si _0.12 ) ₁₃ was obtained, and a cast alloy was produced using a high frequency melting furnace. The cast alloy obtained at this stage is designated as sample (e).

[Rapid cooling process]
Using an experimental machine having the same configuration as that shown in FIG. 1, about 10 g of molten cast alloy was injected from a quartz nozzle having a diameter of 0.8 mm onto a Cu roll rotating at 20 m / second to produce an alloy ribbon. The ribbon alloy obtained here is designated as sample (a).

[Heat treatment process]
Sample (a) was wrapped in Nb foil, placed in a quartz tube, and subjected to heat treatment at 1000 ° C. for 1 hour while being evacuated with a rotary pump (substantially a vacuum of 10 Pa or less). The obtained quenched alloy is designated as sample (b).

Sample (a) was enclosed in a quartz tube evacuated to 10 ⁻² Pa or less and quenched at 1050 ° C. for 24 hours as sample (c), and quenched at 120 hours for sample (c) d).

About 10 g of sample (e) (casting alloy) was sealed in a quartz tube evacuated to 10 ⁻² Pa or less, and a casting alloy that was heat treated at 1050 ° C. for 1, 24, and 120 hours was used as sample (f), Let it be a sample (g) and a sample (h).

[Evaluation]
The crystal structure of each sample was evaluated by an X-ray diffraction method (XRD method). The powder which grind | pulverized each sample to 150 micrometers or less was used. Cu was used for the target. The scan speed was 4.0 ° / min, the sampling width was 0.02 °, and the measurement range was 20 to 80 °.

  Table 1 summarizes the heat treatment conditions of the obtained samples (a) to (h) and the formation phase in the alloy.

  Moreover, the form and composition distribution of each sample were evaluated using an electron beam microanalyzer (EPMA). A sample for EPMA observation was prepared as follows. An EPMA sample was prepared by impregnating each sample alloy with an epoxy resin and polishing the surface, followed by Au deposition with a thickness of about 20 nm. The acceleration voltage of EPMA was 15 kV. The irradiation current is B.I. E. I. (Reflected electron image) was 1.0 nA.

The magnetic properties (magnetocaloric effect) of each sample were evaluated. A material having a large magnetocaloric effect is preferred for the magnetic refrigeration material. Magnetic entropy change −ΔS _mag is used to evaluate the magnetocaloric effect. In general, the greater the -ΔS _mag , the greater the magnetocaloric effect. Using a high magnetic field VSM (sample vibration magnetometer), a magnetization (M) -temperature (T) curve was measured under an applied magnetic field having a constant intensity from 0T to 1T at intervals of 0.2T. -ΔS _mag was calculated using Equation (1).
-ΔS _mag = ∫ ₀ ^H (∂M / ∂T) _H dH (1)
(Where -ΔS _mag is the magnetic entropy change, H is the magnetic field, M is the magnetization, and T is the absolute temperature.)

FIG. 2 shows the XRD measurement results of samples (a), (b), (c) and (d) prepared using the quenched alloy. Further, FIG. 3 shows the temperature dependence of −ΔS _mag obtained for the sample (c). Further, a reflected electron image (BEI) of the sample (c) by EPMA is shown in FIG.

  For comparison, FIG. 5 shows the XRD measurement results of samples (e), (f), (g) and (h) prepared using a cast alloy. In addition, reflected electron images (BEI) of samples (e) and (h) by EPMA are shown in FIGS. FIG. 6B shows a backscattered electron image of a sample having a heat treatment time of 8 hours.

  The difference in structure between the quenched alloy sample of the embodiment of the present invention and the conventional cast alloy sample will be described by comparing FIG. 2 and FIG.

As can be seen from FIG. 2, in the quenched alloy according to the example, a LaFe ₁₃ type compound phase (◯ in the figure) is formed immediately after quenching (sample (a)). In the sample (a), (La, Fe, Si) compound phases (▲ in the figure) and α-Fe phases composed of La, Fe, and Si are also formed. When heat treatment is performed for 1 hour (sample (b)), the (La, Fe, Si) compound phase almost disappears and the α-Fe phase also decreases. Thereafter, when the heat treatment time is lengthened, there is almost no change except that the intensity of the peak derived from the α-Fe phase is slightly increased. In this case, almost all of the rapidly cooled alloy is LaFe ₁₃ after about 1 hour heat treatment. It turns out that it is a type compound phase. Moreover, when the backscattered electron image of the sample (c) shown in FIG. 4 is seen, it has a substantially uniform composition distribution over the whole ribbon except that many Fe exist in the edge part of a ribbon. I understand that.

Moreover, as can be seen from the temperature dependence of the magnetic entropy change −ΔS _mag shown in FIG. 3, the quenched alloy according to the example (sample (c)) shows a large magnetic entropy change. -ΔS _mag from 0T to 1T was 7.5 Jkg ⁻¹ K ⁻¹ . Currently, Gd (gadolinium) used in a magnetic refrigeration tester operating near room temperature is about −ΔS _mag = 3 Jkg ⁻¹ K ⁻¹ from 0T to 1T, which is a large magnetic entropy change. It can be seen that It should be noted that -ΔS _mag obtained for the sample after removing the oxide layer (thickness of about 2 mm) on the surface of the sample (h) prepared using the cast alloy was 19 Jkg ⁻¹ K ⁻¹ . The reason why -ΔS _{mag of} sample (c) is lower than that of sample (h) is considered to be due to the presence or absence of the oxide layer on the surface. Considering the industrial applicability, it is considered that the effect of shortening the heat treatment time, the raw material cost, and the simplification of the pulverization process are larger than the decrease of -ΔS _mag . Further, as can be seen from FIG. 3, the half-value width ΔTc of the temperature region where the magnetic phase transition of the sample (c) occurs is 30K or more, and there is an advantage that the operating temperature range as a magnetic refrigeration working material is wide.

On the other hand, when the XRD measurement results of the samples (e) to (h) prepared using the conventional cast alloy shown in FIG. 5 and the reflected electron image shown in FIG. 6 are viewed, the cast alloy (sample (e) ) Has no LaFe ₁₃ type compound phase, and as the heat treatment proceeds, the (La, Fe, Si) compound phase and α-Fe phase gradually decrease, and a LaFe ₁₃ type compound phase is formed. I can see the situation. Further, as can be seen from a comparison between FIG. 5 and FIG. 2, in the sample (b) obtained by heat-treating the quenched alloy for 1 hour, the (La, Fe, Si) compound phase disappears almost completely, but the casting In the sample (g) obtained by heat-treating the alloy for 24 hours, the (La, Fe, Si) compound phase remains.

Thus, it can be seen that by using a quenched alloy, a LaFe ₁₃ based magnetic alloy having a LaFe ₁₃ type compound phase as a main phase can be obtained by a short heat treatment.

  Furthermore, the results of experiments conducted to determine the optimum heat treatment time will be described.

(Experimental example 2)
[Sample preparation]
In the same manner as in Experimental Example 1 described above, a predetermined amount of La, Fe, and Si raw materials are blended so that a LaFe ₁₃ type compound phase having a composition of La (Fe _0.88 Si _0.12 ) ₁₃ is obtained, and a high frequency melting furnace is used. A cast alloy was produced. About 10 g of the molten cast alloy thus obtained was sprayed from a quartz nozzle having a diameter of 0.8 mm onto a Cu roll rotating at 20 m / sec to obtain a ribbon alloy sample (i).

  Samples (j), (k), (l), and (b) were obtained by heat-treating samples (i) at 1050 ° C. for 1 minute, 5 minutes, 10 minutes, 30 minutes, and 60 minutes, respectively, in an Ar stream. Sample (m) and sample (n) were used.

Further, similarly to the above-described method, a cast alloy having a composition of La (Fe _1-x Si _x ) ₁₃ (x = 0.10, 0.11, 0.12, 0.13, 0.14) is produced. did. A ribbon alloy was produced from each cast alloy according to the method described above. However, here, the rotational speed of the Cu roll was 10 m / sec.

  The obtained ribbon alloy was wrapped in Nb foil and heat-treated at 1050 ° C. for 1 hour in an Ar stream, and the obtained ribbon alloys were sample (o), sample (p), sample (q) and sample (r), respectively. And sample (s).

On the other hand, for comparison, about 10 g of the above-mentioned cast alloy was sealed in a quartz tube evacuated to 10 ⁻² Pa or less and heat-treated at 1050 ° C. for 120 hours, respectively, sample (t) and sample (u) Sample (v), sample (w) and sample (x).

  Table 2 summarizes the compositions and preparation conditions of the samples (i) to (s) of the examples according to the present invention and the samples (t) to (x) of the comparative examples.

[Evaluation]
Each sample was evaluated in the same manner as in Experimental Example 1. FIG. 7 shows the results of evaluating the crystal structures of sample (i), sample (j), sample (k), sample (l), sample (m) and sample (n) by XRD.

As can be seen from FIG. 7, when the alloy ribbon (sample (i)) immediately after quenching is subjected to heat treatment, the α-Fe phase is reduced even if the heat treatment time is only 1 minute (sample (j)). Observed clearly. From this, it is considered that even in a very short time (for example, 1 second), the effect of increasing the LaFe ₁₃ type compound phase can be obtained more than immediately after the rapid cooling.

  Even if the heat treatment time is further increased, the intensity of the peak derived from the α-Fe phase does not change until the heat treatment time is 1 hour (sample (n)). As described above with reference to FIG. 2, when the heat treatment time is 24 hours (sample (c)), the α-Fe phase increases conversely. From the dependence of the diffraction peak intensity derived from the α-Fe phase on the heat treatment time, it is considered that the α-Fe phase does not increase until the heat treatment time is about 1 hour. That is, the optimum heat treatment time for the quenched alloy is about 1 hour or less.

  Next, the results of observing the fracture surfaces of sample (i), sample (k), and sample (n) with a field emission scanning electron microscope (FE-SEM) are shown in FIGS. 8A, 8B, and 8C. Shown in

  As can be seen from FIG. 8 (a), a particulate microstructure of 1 μm or less is observed in the alloy ribbon (sample (i)) immediately after quenching, but in the sample (k) subjected to heat treatment for 5 minutes. As can be seen from FIG. 8B, a relatively large particulate structure of about 1 μm is formed. Furthermore, in the sample (n) with a heat treatment time of 1 hour, as shown in FIG.

As described above, by performing the heat treatment, the α-Fe phase is decreased, the LaFe ₁₃ type compound phase is increased, and the structure is homogenized.

  FIG. 9 shows sample (o), sample (p), sample (q), sample (r), sample (s) and sample (t) of comparative example, sample (u), sample (v), The result of having evaluated the magnetic characteristic (magnetocaloric effect) of the sample (w) and the sample (x) is shown.

And the temperature dependence of the magnetic entropy change -Derutaesu _mag of each sample of Example, a comparison between the temperature dependence of the magnetic entropy change -Derutaesu _mag of each sample of the comparative example corresponding Both of -Derutaesu _mag at 205K or less The maximum value is 15 to 21 Jkg ⁻¹ K ⁻¹ , and when it exceeds 205 K, the maximum value of −ΔS _mag is 9 Jkg ⁻¹ K ⁻¹ or less, which is almost the same value. That is, according to the embodiment of the present invention, the quenched alloy is heat-treated for 1 hour, so that the temperature dependence of the magnetic entropy change -ΔS _mag equivalent to that obtained by heat-treating the cast alloy for 120 hours according to the conventional manufacturing method is obtained. It was possible to produce a LaFe ₁₃ series magnetic alloy material.

According to the present invention, it is possible to produce a LaFe ₁₃ -based magnetic alloy material with higher production efficiency than before. Therefore, it is possible to provide a magnetic refrigeration working substance and a magnetostrictive material at a lower price than before, and for example, it is possible to provide a magnetic refrigeration apparatus at a practical cost. Since the magnetic refrigeration apparatus does not use a refrigerant unlike the gas compression type, the magnetic refrigeration apparatus is environmentally friendly and has a feature that high energy conversion efficiency can be obtained by using a permanent magnet material in combination.

(A) is sectional drawing which shows the example of whole structure of the apparatus used for the method of manufacturing the quenching alloy by this invention, (b) is an enlarged view of the part by which rapid solidification is performed. It is a figure which shows the measurement result of XRD of the sample (a), (b), (c) and (d) produced using the quenching alloy. It is a diagram showing temperature dependence of the resulting -Derutaesu _mag for sample (c) was prepared using the rapidly solidified alloy. It is a photograph which shows the reflected-electron image (BEI) by EPMA of the sample (c) produced using the quenching alloy. It is a figure which shows the measurement result of XRD of the samples (e), (f), (g), and (h) produced using the casting alloy. It is a photograph which shows the reflected electron image (BEI) by EPMA of the sample produced using the casting alloy. It is a figure which shows the measurement result of XRD of sample (i), samples (j), (k), (l), (m), and (n) produced using the quenching alloy. It is a photograph which shows the structure of the torn surface by FE-SEM of sample (i), (k), and (n) produced using the quenching alloy. A graph (top) showing the temperature dependence of -ΔS _mag obtained for sample (o), sample (p), sample (q), sample (r) and sample (s) produced using the ribbon alloy; , (Graph) showing the temperature dependence of -ΔS _mag obtained for sample (t), sample (u), sample (v), sample (w) and sample (x) prepared using a cast alloy is there.

Explanation of symbols

1b, 2b, 8b, and 9b Atmospheric gas supply port 1a, 2a, 8a, and 9a Gas exhaust port 1 Melting chamber 2 Quenching chamber 3 Melting furnace 4 Hot water storage vessel 5 Hot water discharge nozzle 6 Funnel 7 Rotating cooling roll 21 Molten metal 22 Alloy ribbon

Claims (12)

Preparing a molten alloy raw material having a predetermined composition;
By quenching a melt of the alloy material, the composition _{formula: Fe 100-abc RE a A} b TM c (RE is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er And at least one rare earth element selected from the group consisting of Tm and containing 90 atomic% or more of La, A is Si , TM is Co , 5 atomic% ≦ a ≦ 10 atomic%, 4.7 atomic% ≦ b ≦ 18 Forming a quenched alloy having a composition represented by: atomic%, 0 atomic% ≦ c ≦ 9 atomic%);
Forming 70% by volume or more of a compound phase having a NaZn ₁₃ type crystal structure in the quenched alloy;
A method for producing a magnetic alloy material, comprising: 2. The magnetic alloy according to claim 1, wherein the step of forming the compound phase includes a step of heat-treating the quenched alloy at a temperature of 900 ° C. to 1200 ° C. for a time of 1 second to 100 hours. Material manufacturing method.   The method for producing a magnetic alloy material according to claim 2, wherein the heat treatment step is a step of heat-treating the quenched alloy for 10 minutes or more. The method for producing a magnetic alloy according to claim 2, wherein a compound phase having a NaZn ₁₃ type crystal structure having a homogeneous structure is formed throughout the heat treatment step. 5. The method for producing a magnetic alloy material according to claim 1, wherein the quenched alloy has the compound phase having a NaZn ₁₃ type crystal structure immediately after quenching. The method for producing a magnetic alloy material according to any one of claims 1 to 5, wherein a cooling rate in the step of forming the quenched alloy is 1 x 10 ² ° C / second or more and 1 x 10 ⁸ ° C / second or less.   The method for producing a magnetic alloy material according to any one of claims 1 to 6, wherein the quenched alloy is a ribbon having a thickness of 10 µm to 300 µm.   The said magnetic alloy raw material is a manufacturing method of the magnetic alloy material in any one of Claim 1 to 7 which has a magnetocaloric effect.   The method for producing a magnetic alloy material according to claim 1, further comprising a step of pulverizing the quenched alloy.   The method for producing a magnetic alloy material according to any one of claims 1 to 9, wherein a Curie temperature Tc exhibiting a magnetic phase transition is in a range of 180K to 330K. The method for producing a magnetic alloy material according to any one of claims 1 to 10 , wherein a half-value width ΔTc of a temperature region causing a magnetic phase transition is 30K or more. The magnetic alloy material manufactured by the manufacturing method in any one of Claim 1 to 11 .