JP2004100043A - Magnetic alloy material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an LaFe<SB>13</SB>based magnetic alloy material at an efficiency higher than that in the conventional one. <P>SOLUTION: The method comprises a stage where the molten metal of an alloy raw material having a prescribed composition is prepared; a stage where the molten metal of the alloy raw material is rapidly cooled to form a rapidly cooled alloy having a composition expressed by the compositional formula of Fe<SB>100-a-b-c</SB>RE<SB>a</SB>A<SB>b</SB>TM<SB>c</SB>(RE is at least one kind of rare earth element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm, and includes La by ≥90; A is at least one kind of element selected from the group consisting of Al, Si, Ga, Ge and Sn; TM is at least one kind of transition metal element selected from the group consisting of Sc, Ti, V, Cr, Mn, Co, Ni, Cu and Zn; and 5 atomic%≤a≤10 atomic%, 4.7 atomic%≤b≤18 atomic%, and 0 atomic%≤c≤9 atomic%); and a stage where a compound phase with an NaZn<SB>13</SB>type crystal structure is formed in the rapidly cooled alloy by ≥70 atomic%. <P>COPYRIGHT: (C)2004,JPO

Description

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

Recently, the composition _{formula: La 1-z RE z (} Fe 1-x A xy TM y) 13 (A = Al, Si, Ga, Ge, at least one element 0.05 ≦ x ≦ among Sn 0.2 , TM is a magnetic alloy (0 ≦ y ≦ 0.1) of at least one of transition metal elements, and RE is a magnetic alloy (0 ≦ z ≦ 0.1 of at least one of rare earth elements other than La). Hereinafter, referred to as “LaFe ₁₃ -based magnetic alloy”) has a NaZn ₁₃ type crystal structure, and exhibits a large magnetocaloric effect and a large magneto-volume effect near the Curie temperature (Tc). And, as a magnetostrictive material, it is promising (for example, Patent Document 1, Patent Document 2, and Non-Patent Document 1).

Conventionally, LaFe ₁₃ -based magnetic alloys have been produced, for example, by subjecting a cast alloy obtained by arc melting or high frequency melting to heat treatment at 1050 ° C. for about 168 hours in a vacuum.
JP 2000-54086 A JP-A-2002-69596 "Strong magnetic volume and magnetocaloric effect of itinerant electron metamagnetic La (FexSi1-x) 13 compound", Maya Fujita et al., Materia, 41, 4, 269-275, 2002

However, the conventional method for producing a LaFe ₁₃ -based 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 constituted by the remainder. It has an organization in which phases are intricately complicated (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 an interface between these coarse crystal phases (for example, see 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”) is performed at a high temperature for a long time. Heat treatment ”). Since the long-time homogenizing heat treatment is indispensable, there has been a problem that the LaFe ₁₃ -based magnetic alloy has poor mass productivity.

の 間 に In addition, during the long-time homogenizing heat treatment, the alloy surface is deteriorated by corrosion such as oxidation, and as a result, there is a problem that the magnetocaloric effect and the magnetic volume effect are deteriorated.

Furthermore, the cast alloy is generally in a lump, and the homogenization heat treatment is also performed in the lump. Magnetic refrigeration working materials are often used in granular (powder) form in order to increase the heat exchange efficiency with heat exchange liquids (for example, liquids having a large specific heat such as aqueous antifreeze). Poor grindability is a factor that lowers production efficiency.

The present invention has been made in view of the above points, and a main object thereof 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, and TM is at least one selected from the group consisting of Sc, Ti, V, Cr, Mn, Co, Ni, Cu and Zn. Forming a quenched alloy having a composition represented by one kind of transition metal element, 5 atomic% ≦ a ≦ 10 atomic%, 4.7 atomic% ≦ b ≦ 18 atomic%, 0 atomic% ≦ c ≦ 9 atomic%) And during the quenching 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 subjecting the quenched alloy to a heat treatment at a temperature of 400 ° C. to 1200 ° C. for a time of 1 second to 100 hours.

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

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

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./sec or more and 1 × 10 ⁸ ° C./sec or less.

急 The quenched alloy is preferably in the form of a ribbon having a thickness of 10 µm or more and 300 µm or less.

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.

キ ュ It is preferable that the Curie temperature Tc indicating the magnetic phase transition is in the range of 180K to 330K. A plurality of magnetic alloy materials having different Curie temperatures Tc can be obtained by including Co as TM in the above composition formula and controlling the ratio of Co.

に お い て In one embodiment, the half width ΔTc of the temperature region where the magnetic phase transition occurs is 30K or more.

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

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, when a process for forming a strip-shaped quenched alloy is employed, the pulverizability can be improved, and therefore, a magnetic alloy material can be produced with high efficiency as a magnetic refrigeration working material 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 of forming 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.

In the method for producing a LaFe ₁₃ -based magnetic alloy according to the present invention, a quenching method (liquid quenching method) is employed in the second step. The quenched alloy has higher composition uniformity than the cast alloy, and the multi-phase structure (see FIG. 6 (a)) composed of a coarse crystal phase found in the cast alloy is not observed. For example, even if the quenched alloy is pulverized into particles having a particle size of 10 μm to 300 μm, for example, by heat treatment, 70% by volume or more of each particle comes to be composed of the LaFe ₁₃ type compound phase.

Of course, by adjusting the heat treatment conditions and the like, a magnetic alloy material having 90% by volume or more of the LaFe ₁₃ type compound phase can be obtained. In addition, in the above composition formula, if a is out of the above range, 70% by volume or more of the LaFe ₁₃ type compound phase cannot be formed. When b is less than 4.7 atomic%, a LaFe ₁₃ type compound phase is not formed, and when b exceeds 18 atomic%, a sufficient magnetocaloric effect (or magneto-volume effect) cannot be obtained. Further, if c is outside the above range, a sufficient magnetocaloric effect (or magnetovolume effect) cannot be 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 to 1200 ° C for a time of 1 second to 100 hours. Since the quenched alloy obtained in the second step has a more uniform structure than the cast alloy, it is possible to reduce the heat treatment time required for making the entire quenched alloy a LaFe ₁₃ -based magnetic alloy. For example, the heat treatment time can be set 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 over the entire alloy. In order to form a LaFe ₁₃ type compound phase having a homogeneous structure throughout the entire alloy, it is preferable to perform heat treatment for 10 minutes or more. For example, as described later, for a quenched alloy obtained by adjusting the roll surface speed within a range of 3 m / sec or more and 30 m / sec or less, if heat treatment is performed for 10 minutes or more, almost the entire alloy is obtained. A LaFe ₁₃ type compound phase having a homogeneous structure can be formed. Note that 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 as to form a predetermined LaFe ₁₃ -based magnetic alloy in relation to the treatment time. However, when the temperature is lower than 400 ° C., the treatment time exceeds 100 hours, and it is not preferable. In consideration of shortening the heat treatment time to about one hour, it is preferable to perform the heat treatment at a temperature of 900 ° C. or more and 1200 ° C. or less. In order to suppress oxidation, the atmosphere is preferably in a vacuum (eg, 10 ⁻² Pa or less) or an inert gas (particularly, a rare gas) atmosphere.

The first step in the method for producing a LaFe ₁₃ -based magnetic alloy according to the present invention is performed, for example, by the same method as the conventional method.

When the manufacturing method according to the present embodiment is used, the heat treatment time can be shortened, so that the productivity is improved. Further, deterioration of the LaFe ₁₃ -based magnetic alloy surface due to oxidation or the like during the heat treatment is also suppressed, so that there is little deterioration in characteristics. For example, a LaFe ₁₃ -based magnetic alloy obtained by subjecting a cast alloy to heat treatment for a long time cannot use a layer several mm from the surface as a magnetic refrigeration working material, but the quenching obtained by the embodiment of the present invention. Alloys (especially thin strip quenched alloys and alloy thin strips) can be used as they are as magnetic refrigeration working materials. 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-shaped quenched alloy is produced, the pulverizability is superior to that of a cast alloy, so that an advantage that the process time required for the pulverization step can be shortened is also obtained.

The LaFe ₁₃ based magnetic alloy has a large magnetocaloric effect or magnetovolume effect because it shows a magnetic phase transition close to the first-order phase transition near the Curie temperature. It is desired to form as many as possible LaFe ₁₃ -type compound phases exhibiting a magnetic phase transition close to the first-order phase transition. Conventionally, a LaFe ₁₃ type compound phase is formed from an interface between a coarse α-Fe phase and a grain boundary phase contained in an alloy (as-cast alloy) obtained by a casting method, so that a long-time homogenization is required. Treatment was required.

On the other hand, a quenching method as well as a casting method is known as a method for producing an alloy. However, even when the quenching method is used, the α-Fe phase is easily generated similarly to the casting method. In addition, there is a possibility that a composition shift occurs due to the quenching process, and a metastable phase other than the LaFe ₁₃ type compound phase is generated. However, there is no report that a LaFe ₁₃ -based magnetic alloy was manufactured by using the quenching method.

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

The cooling rate in the step of forming the quenched alloy is preferably 1 × 10 ² ° C./sec or more and 1 × 10 ⁸ ° C./sec or less. If the cooling rate is lower than 1 × 10 ² ° C./sec, a multi-phase structure containing a relatively coarse α-Fe phase is formed similarly to the conventional casting method, and a homogenizing heat treatment exceeding 100 hours is required. Become. On the other hand, if the cooling rate is higher than 1 × 10 ⁸ ° C./sec, the thickness of the quenched alloy becomes small, which is not preferable because the production efficiency is reduced.

液体 As a liquid quenching method capable of obtaining 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 strip-shaped quenched alloy having a thickness of 20 μm or more and 200 μm or less can be manufactured with high efficiency.

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

(1) The quenching apparatus shown in FIG. 1 includes a raw material alloy melting chamber 1 and a quenching 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. 1A, a 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 tapping nozzle 5 at the bottom. And a blending material supply device 8 for supplying the blending material into the melting furnace 3 while suppressing the entry of the atmosphere. The hot water storage container 4 has a heating device (not shown) that stores the molten metal 21 of the raw material alloy and can maintain the temperature of the molten metal at a predetermined level.

The quenching chamber 2 is provided with a rotary cooling roll 7 for rapidly solidifying the molten metal 21 discharged from the tapping nozzle 5.

に お い て In this apparatus, the atmosphere and the pressure in the melting chamber 1 and the quenching chamber 2 are controlled within a predetermined range. For this purpose, the atmosphere gas supply ports 1b, 2b, and 8b and the gas exhaust ports 1a, 2a, and 8a are provided at appropriate places 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 from the nozzle 5 can be adjusted.

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

(4) The tapping nozzle 5 of the hot water storage container 4 is disposed on a 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 located below. The orifice diameter of tapping nozzle 5 is set in the range of 0.5 mm or more and 4.0 mm or less. By adjusting the orifice diameter and / or the pressure difference (for example, 10 kPa or more) between the melting chamber 1 and the quenching chamber 2 according to the viscosity of the molten metal 21, the molten metal 21 can be smoothly discharged. According to the apparatus used in the present embodiment, the supply rate of the molten alloy can be set to 1.5 to 10 kg / min. If the supply rate exceeds 10 kg / min, the quenching speed of the molten metal becomes slow, which causes a disadvantage that a multiphase structure is formed. A more preferred 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 a 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 the quenched alloy may be wound around the roll, which is not preferable. 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 and the amount of hot water per unit time.

First, a molten metal 21 of a predetermined raw material alloy is prepared 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 tapping nozzle 5 onto the water-cooled roll 7 in a 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 Is more preferable.

The time during which the molten alloy 21 is cooled by the cooling roll 7 corresponds to the time from the contact of the alloy to the outer peripheral surface of the rotating cooling roll 7 until the alloy is separated, during which time the temperature of the alloy decreases and the supercooling occurs. Become liquid. Thereafter, the supercooled alloy leaves the cooling roll 7 and flies in an inert atmosphere. The alloy is deprived of heat by the ambient gas while flying in the form of a ribbon, which further reduces its temperature. In the present embodiment, the pressure of the atmosphere gas is set in a range from 10 kPa to normal pressure.

In this embodiment, the uniformity is obtained by adjusting the roll surface speed within the range of 3 m / sec or more and 30 m / sec or less, and setting the atmosphere gas pressure to 30 kPa or more to enhance the secondary cooling effect by the atmosphere gas. A strip-shaped quenched alloy having a structure can be obtained. When the roll surface speed is less than 3 m / sec, the time of the homogenization heat treatment is prolonged, and the surface of the quenched ribbon may be deteriorated by corrosion such as oxidation. When it exceeds 30 m / sec, the quenched ribbon becomes too thin. Therefore, there is a possibility that the ratio of the volume of the portion of the homogeneous structure excluding the degraded layer on the surface is reduced.

The quenching method of the molten alloy used in the present invention is not limited to the one-roll method described above, and a strip casting method, which is a quenching 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 is an advantage that the molten metal supply rate is increased and the melt is easily stabilized. However, entrainment of the atmosphere gas between the cooling roll and the molten metal is likely to occur, 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 in the space in which the cooling roll is placed to the above-described range to suppress the entrainment of the atmospheric gas. Although the production efficiency is reduced, a gas atomizing method may be used.

According to the manufacturing method of the LaFe ₁₃ -based magnetic alloy of the embodiment according to the present invention, when the external magnetic field is changed from 0T to 1T, the change in magnetic entropy (−ΔS _mag ) exceeds 5 JK ⁻¹ kg ^−1. Magnetic refrigeration working material having According to the above-described manufacturing method, a strip-shaped LaFe ₁₃ -based magnetic quenched alloy can be obtained, so that a granular (powder-like) 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 180K or more, or 190K or more and within 330K or less is obtained. LaFe ₁₃ -based magnetic alloys having different Curie temperatures Tc can be obtained by containing Co as TM in the above composition formula and controlling the ratio of Co. For example, when the ratio of Co (corresponding to c in the above composition formula) is 9, Tc = 330K is obtained. In this specification, the magnetic phase transition refers to a transition from ferromagnetic to paramagnetic, from ferromagnetic to antiferromagnetic, or from antiferromagnetic to paramagnetic.

Further, the LaFe ₁₃ -based magnetic alloy obtained according to an embodiment of the present invention has a relatively wide temperature range in which a magnetic phase transition occurs, and for example, obtains a LaFe ₁₃ -based magnetic alloy having a half-width ΔTc of 30 K or more in the transition temperature range. be able to. Therefore, according to the present embodiment, a magnetic refrigeration apparatus can be configured even if a single LaFe ₁₃ -based magnetic alloy is used as the magnetic refrigeration work material. Of course, a plurality of LaFe ₁₃ -based magnetic alloys having different compositions (different Tc) may be used according to the operating temperature range. For example, a MnAs-based magnetic refrigeration working material (Japanese Patent Application Laid-Open No. 2003-028532) is used. Fewer alloys can cover the same operating temperature range. Further, the regenerative heat exchanger and the magnetic refrigerator described in JP-A-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 Documents 1 and 2.

Hereinafter, specific examples of the method for producing a LaFe ₁₃ -based magnetic alloy according to the present invention will be described with reference to experimental examples, but the present invention is not limited thereto.

(Experimental example 1)
[Making process of raw material alloy]
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 referred to as a sample (e).

[Quenching process]
Using an experimental machine having the same configuration as that of FIG. 1, a molten metal of about 10 g of a massive casting alloy was injected from a quartz nozzle having a diameter of 0.8 mm onto a Cu roll rotating at 20 m / sec to produce an alloy ribbon. The thin ribbon alloy obtained here is used as a sample (a).

[Heat treatment process]
The sample (a) was wrapped in an Nb foil, placed in a quartz tube, and heat-treated at 1000 ° C. for 1 hour while evacuating (substantially 10 Pa or less) with a rotary pump. The obtained quenched alloy is used as a sample (b).

The sample (a) was sealed in a quartz tube evacuated to 10 ⁻² Pa or less and heat-treated at 1050 ° C. for 24 hours as a sample (c), and the quenched alloy heat-treated for 120 hours was used as a sample ( d).

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

[Evaluation]
The crystal structure of each sample was evaluated by an X-ray diffraction method (XRD method). Powders obtained by pulverizing each sample to 150 μm or less were 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 phases generated in the alloy.

形態 The morphology and composition distribution of each sample were evaluated using an electron beam microanalyzer (EPMA). A sample for EPMA observation was prepared as follows. Each of the sample alloys was impregnated with an epoxy resin and polished on the surface, and then subjected to Au evaporation to a thickness of about 20 nm to obtain EPMA samples. The accelerating voltage of EPMA was 15 kV. Irradiation current is B. E. FIG. I. (Reflection electron image) was set to 1.0 nA.

The magnetic properties (magnetoretic effect) of each sample were evaluated. As the magnetic refrigeration working material, a material having a large magnetocaloric effect is preferable. For the evaluation of the magnetocaloric effect, a magnetic entropy change-ΔS _mag is used. In general, the larger -ΔS _mag is, the larger the magnetocaloric effect is. The magnetization (M) -temperature (T) curve was measured using a high magnetic field VSM (sample vibrating magnetometer) under an applied magnetic field of a constant strength set at 0.2T intervals from 0T to 1T, and the following results were obtained from the measurement results. -ΔS _mag was calculated using equation (1).
−ΔS _mag = ∫ ₀ ^H (∂M / ∂T) _H dH (1)
(Here, -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 the samples (a), (b), (c) and (d) produced using the quenched alloy. FIG. 3 shows the temperature dependence of -ΔS _mag obtained for sample (c). FIG. 4 shows a backscattered electron image (BEI) of the sample (c) by EPMA.

ＸFor comparison, FIG. 5 shows the XRD measurement results of the samples (e), (f), (g) and (h) produced using the cast alloy. 6A and 6C show the backscattered electron images (BEI) of the samples (e) and (h) by EPMA. FIG. 6B also shows a backscattered electron image of the sample in which the heat treatment time is 8 hours.

(5) 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), a (La, Fe, Si) compound phase composed of La, Fe, and Si (、 in the figure) and an α-Fe phase were 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. After that, when the heat treatment time is increased, almost no change is observed except for a slight increase in the intensity of the peak derived from the α-Fe phase. In this case, almost all of the quenched alloy becomes LaFe _{13 by} heat treatment for about 1 hour. It turns out that it is a type compound phase. In addition, the reflection electron image of the sample (c) shown in FIG. 4 shows that the ribbon has a substantially uniform composition distribution throughout the ribbon except that a large amount of Fe is present at the end of the ribbon. You can see that.

Further, as can be seen from the temperature dependence of the magnetic entropy change -ΔS _mag shown in FIG. 3, the quenched alloy (sample (c)) according to the example shows a large magnetic entropy change. −ΔS _mag from 0T to 1T was 7.5 Jkg ⁻¹ K ⁻¹ . At present, 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, and a large change in magnetic entropy is compared with this. It can be seen that it has In addition, −ΔS _mag obtained for the sample after removing the oxide layer (thickness: about 2 mm) on the surface of the sample (h) manufactured using the cast alloy was 19 Jkg ⁻¹ K ⁻¹ . It is considered that the reason why −ΔS _{mag of the} sample (c) is lower than that of the sample (h) is due to the presence or absence of an oxide layer on the surface. Considering the industrial applicability, it is considered that the effect of shortening the heat treatment time, reducing the cost of raw materials, and further simplifying the pulverization process is greater than the reduction of -ΔS _mag . Further, as can be seen from FIG. 3, the half 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 the magnetic refrigeration working material is wide.

On the other hand, the XRD measurement results of the samples (e) to (h) prepared using the conventional cast alloy shown in FIG. 5 and the reflected electron images shown in FIG. 6 show that 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 the α-Fe phase gradually decrease to form a LaFe ₁₃ type compound phase. You can see the situation. As can be seen from a comparison between FIG. 5 and FIG. 2, in the sample (b) in which the quenched alloy was heat-treated for 1 hour, the (La, Fe, Si) compound phase almost completely disappeared, whereas 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-time heat treatment.

Furthermore, the result of an experiment for obtaining an optimum heat treatment time will be described.

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

Sample (j), sample (k), sample (l), and the ribbon alloy obtained by heat-treating sample (i) in an Ar gas stream at 1,050 ° C. for 1, 5, 10, 30, and 60 minutes, respectively. Sample (m) and sample (n) were used.

Further, similarly to the above method, producing 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) did. From each cast alloy, a thin strip alloy was produced according to the method described above. However, here, the rotation speed of the Cu roll was 10 m / sec.

The obtained ribbon alloy was wrapped in an Nb foil, and heat-treated at 1050 ° C. for 1 hour in an Ar gas flow, and the obtained ribbon alloy was 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. , Sample (v), sample (w) and sample (x).

Table 2 shows 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 XRD evaluation of the crystal structures of Sample (i), Sample (j), Sample (k), Sample (l), Sample (m), and Sample (n).

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

、 Even if the heat treatment time is further extended, the peak intensity 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 reaches 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 optimal heat treatment time for the quenched alloy is about 1 hour or less.

Next, the results of observing the fracture surfaces of the sample (i), the sample (k), and the 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), in the alloy ribbon (sample (i)) immediately after the quenching, a particulate microstructure of 1 μm or less is observed, but in the sample (k) subjected to the heat treatment for 5 minutes. As can be seen from FIG. 8B, a relatively large particulate structure of about 1 μm is formed. Further, in the sample (n) in which the heat treatment time was set to 1 hour, as shown in FIG. 8 (c), no particulate structure was observed and the sample had a homogeneous structure.

Thus, by performing the heat treatment, the α-Fe phase is reduced, and the LaFe ₁₃ type compound phase is increased, so that the structure is homogenized.

FIG. 9 shows sample (o), sample (p), sample (q), sample (r), sample (s) and sample (t), sample (u), sample (v), and comparative example of the example. The result of having evaluated the magnetic characteristic (magnetoretic effect) of sample (w) and 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 It can be seen that the maximum value is 15 to 21 Jkg ^-1 K ^-1 , and that when the temperature 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 is equivalent to that obtained by heat-treating the cast alloy for 120 hours according to the conventional manufacturing method. A LaFe ₁₃ -based magnetic alloy material having the same was produced.

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 the magnetic refrigeration working material and the magnetostrictive material at a lower price than before, and for example, it is possible to provide a magnetic refrigeration apparatus at a practical cost. The magnetic refrigerating apparatus is environmentally friendly because it does not use a refrigerant unlike the gas compression type, and has the characteristics that a high energy conversion efficiency can be obtained by using a permanent magnet material together.

(A) is a sectional view showing an example of an entire configuration of an apparatus used for a method of manufacturing a rapidly cooled alloy according to the present invention, and (b) is an enlarged view of a portion where rapid solidification is performed. It is a figure which shows the measurement result of XRD of the samples (a), (b), (c) and (d) produced using the quenched 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 reflection electron image (BEI) by EPMA of the sample (c) produced using the quenched 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 reflection electron image (BEI) by EPMA of the sample manufactured using the casting alloy. It is a figure which shows the measurement result of the XRD of the sample (i), the sample (j), (k), (l), (m) and (n) produced using the quenched alloy. It is a photograph which shows the structure of the fracture surface by FE-SEM of the samples (i), (k), and (n) produced using the quenched alloy. A graph (upper part) showing the temperature dependence of -ΔS _mag obtained for the sample (o), the sample (p), the sample (q), the sample (r) and the sample (s) manufactured using the ribbon alloy. , A sample (t), a sample (u), a sample (v), a sample (w), and a sample (x) produced using a cast alloy are shown in a graph (lower part) showing the temperature dependence of −ΔS _mag obtained. is there.

Explanation of reference numerals

1b, 2b, 8b, and 9b Atmosphere gas supply ports 1a, 2a, 8a, and 9a Gas exhaust port 1 Melting chamber 2 Quenching chamber 3 Melting furnace 4 Hot water storage tank 5 Hot water nozzle 6 Roth 7 Rotary cooling roll 21 Molten metal ribbon

Claims (13)

A step of preparing a molten 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 La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er And Tm, 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 Sc , Ti, V, Cr, Mn, Co, Ni, Cu and Zn, at least one transition metal element, 5 at% ≦ a ≦ 10 at%, 4.7 at% ≦ b ≦ 18 Atomic%, 0 atomic% ≦ c ≦ 9 atomic%) to form a quenched alloy having a composition represented by:
Forming a compound phase having a NaZn ₁₃ type crystal structure in the quenched alloy at 70% by volume or more;
A method for producing a magnetic alloy material, comprising: The magnetic alloy according to claim 1, wherein the step of forming the compound phase includes a step of subjecting the quenched alloy to a heat treatment at a temperature of 400 ° 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. 4. The method for producing a magnetic alloy according to claim 2, wherein the heat treatment step forms a compound phase having a NaZn ₁₃ type crystal structure having a homogeneous structure throughout. 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 claim 1, wherein a cooling rate in the step of forming the quenched alloy is 1 × 10 ² ° C./sec or more and 1 × 10 ⁸ ° C./sec 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 thin ribbon having a thickness of 10 µm or more and 300 µm or less. The method according to any one of claims 1 to 7, wherein the magnetic alloy material has a magnetocaloric effect. The method for producing a magnetic alloy material according to any one of claims 1 to 8, 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 the Curie temperature Tc indicating a magnetic phase transition is in a range of 180 K or more and 330 K or less. 11. The method for producing a magnetic alloy material according to claim 1, wherein Co is contained as TM in the composition formula. The method for producing a magnetic alloy material according to any one of claims 1 to 11, wherein the half-width ΔTc of the temperature region where the magnetic phase transition occurs is 30K or more. A magnetic alloy material produced by the production method according to any one of claims 1 to 12.