WO1992020829A1 - Magnetostrictive powder composite and methods for the manufacture thereof - Google Patents

Magnetostrictive powder composite and methods for the manufacture thereof Download PDF

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Publication number
WO1992020829A1
WO1992020829A1 PCT/SE1992/000331 SE9200331W WO9220829A1 WO 1992020829 A1 WO1992020829 A1 WO 1992020829A1 SE 9200331 W SE9200331 W SE 9200331W WO 9220829 A1 WO9220829 A1 WO 9220829A1
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Prior art keywords
composite material
magnetostrictive
material according
grains
powder
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PCT/SE1992/000331
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French (fr)
Inventor
Tord Cedell
Original Assignee
Proengco Ab
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Publication date
Application filed by Proengco Ab filed Critical Proengco Ab
Priority to JP4510169A priority Critical patent/JPH06507676A/en
Priority to EP92917301A priority patent/EP0663961A1/en
Publication of WO1992020829A1 publication Critical patent/WO1992020829A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/58—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising fillers only, e.g. particles, powder, beads, flakes, spheres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/58—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising fillers only, e.g. particles, powder, beads, flakes, spheres
    • B29C70/62—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising fillers only, e.g. particles, powder, beads, flakes, spheres the filler being oriented during moulding
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/02—Granular materials, e.g. microballoons
    • C04B14/34—Metals, e.g. ferro-silicon
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/02—Granular materials, e.g. microballoons
    • C04B14/36—Inorganic materials not provided for in groups C04B14/022 and C04B14/04 - C04B14/34
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/0094—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with organic materials as the main non-metallic constituent, e.g. resin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C49/00—Alloys containing metallic or non-metallic fibres or filaments
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/0302—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity characterised by unspecified or heterogeneous hardness or specially adapted for magnetic hardness transitions
    • H01F1/0306—Metals or alloys, e.g. LAVES phase alloys of the MgCu2-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
    • H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
    • H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
    • H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
    • H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
    • H01F1/26—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated by macromolecular organic substances
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N35/00—Magnetostrictive devices
    • H10N35/80—Constructional details
    • H10N35/85—Magnetostrictive active materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2791/00—Shaping characteristics in general
    • B29C2791/004—Shaping under special conditions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2791/00—Shaping characteristics in general
    • B29C2791/004—Shaping under special conditions
    • B29C2791/008—Using vibrations during moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
    • B29K2105/12—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts of short lengths, e.g. chopped filaments, staple fibres or bristles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
    • B29K2105/16—Fillers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2503/00—Use of resin-bonded materials as filler
    • B29K2503/04—Inorganic materials
    • B29K2503/06—Metal powders, metal carbides or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0003—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular electrical or magnetic properties, e.g. piezoelectric
    • B29K2995/0008—Magnetic or paramagnetic

Definitions

  • the invention relates partly to a magnetostrictive
  • the powder composite according to the preamble to claim 1 is preferably used as a magnetostrictive element in sound projectors and vibration generators, transducers, actuators and in various types of linear motors.
  • Permanent magnets usually compounds of rare earth
  • SmCo 5 and Nd 2 Fe 14 B are passive devices used for generating a magnetic field.
  • Permanent magnets are magnetized initially and posses
  • Nd 2 Fe 14 B magnets developed by
  • General Motors are used in the starter motors of their cars and trucks.
  • Magnetostrictive powder composite is an active device consisting of rare earth metals (RE) and transition metals (Fe, Ni, Co and Mn), (RE) x Fe 1-x , which changes its length extremely much when exposed to an external magnetic field.
  • RE rare earth metals
  • Fe, Ni, Co and Mn transition metals
  • Fe x Fe 1-x which changes its length extremely much when exposed to an external magnetic field.
  • traditional magnetostrictive materials such as Fe and Ni which display magnetostrictive change in length of 9 ⁇ m/m and 40 ⁇ m/m respectively
  • a magnetostrictive powder composite displays length changes of more than 1000 ⁇ m/m and is therefore called giant magnetostrictive material.
  • the magnetostrictive powder composite is used to generate large and fast movements of high precision and large force. In most applications this large force is used to increase change in length and to generate larger movements.
  • Magnetostrictive powder composite is usually used in high frequency applications (up to 60 kHz), e.g.
  • the purpose of the magnetostrictive composite is that it should work as an acoustic projector i.e. to generate fast mechanical movements and ultrasound.
  • Magnetostrictive powder composite is initially a
  • the material constituting the magnetostrictive powder composite has low remanence and low coercive force.
  • Magnetic powder composite has been put forward with a purpose to increase the bandwidth of the casted giant magnetostrictive material available on the market.
  • Magnetostrictive powder composite can manage a frequency region of 0 - 60 kHz, while casted giant magnetostrictive material only can manage 0 - 2 kHz.
  • Giant magnetostrictive alloys made of terbium, dysprosium and iron are usually called Terfenol-D.
  • Giant magnetostrictive powder composite is used in:
  • Magnetostrictive powder composite according to the invention presented has not been known of before.
  • the patent documents US, A, 4865 660, DK, B, 157 222, FR, A, 2065 359 and EP, Al, 175 535 do certainly refer to magnetic powder composite materials, which nevertheless all are permanet magnets and which find their applications because of their capability to maintain permanent
  • Magnetostrictive properties are not
  • the magnetostrictive materials are manufactured in the form of rods by casting.
  • the casted rods hereby get brittle characteristics and are beacuse of this very difficult to machine with conventional techniques.
  • the rods are brittle and can only withstand very small tensional stress.
  • magnetostrictive rods like for instance Terfenol-D rods
  • magnetostrictive rod it is difficult to magnetize homogeneously such a rod by the use of permanent magnets applied at its ends.
  • permanent magnets applied at its ends.
  • the low permeability of the casted rod also causes
  • the powder composite is so tough that it can be shaped with a conventional cutting technique.
  • aluminium oxide, silicon carbide, Kevlar, carbon, glass or titanium are pressed into the rod and aligned longitudinally or perpendicularly, tensile strength and elastic modulus will be increased.
  • the invention utilizes such binding agents which wet said grains and bind them together and
  • Ceramics and oxides preferably rare earth oxides because of a high reactivity of Terfenol-D, can also be used as an
  • magnets can be achieved if a powder of a permanent magnet type, preferably Nd 2 Fe 14 B, is mixed with the magnetostrictive powder, preferably along the rod axis, in order to decrease the leakage flux. This will make it possible to manufacture rods with length/diameter ratios larger than 3:1.
  • a powder of a permanent magnet type preferably Nd 2 Fe 14 B
  • coated iron, nickel, cobalt or amorphous iron like for instance metglas, or alloys of these, can be pressed into the rod ends.
  • Magnetostrictive powder composite can be directly
  • the invention provides for the following advantages:
  • the composite can be lowered, so that it can glide easier against other objects. Also, its chemical resistance can be increased by coating the magnetostrictive powder composite, after it has been pressed, with a thin layer of non-organic material, such as aluminium oxide or an organic material, such as teflon, or if during pressing the composite surface is provided with a powder coating made of the above mentioned organic or non-organic materials.
  • non-organic material such as aluminium oxide or an organic material, such as teflon
  • the strength of the magnetic powder composite can be
  • Fig 1 shows a magnetostrictive composite rod 1 which, besides the magnetostrictive powder, possible coating and a binder, also has permanent magnets 2 of a conventional type at the rod ends and aligned permanent magnet powder 3, mainly along the longitudinal axis of rod 1, which makes the working magnetization in the composite rod 1 more homogeneous.
  • Fig 2 shows a magnetostrictive composite rod 1, an excitation coil for generating magnetizing field 4 and iron powder, coated with a thin electrically insulating layer of Fe 2 O 3 or equivalent material, which has been pressed into the ends 5 of the rod 1.
  • Fig 3 shows a magnetostrictive composite rod 1 with longitudinal fibre reinforcement 6 which, besides
  • the magnetostrictive composite material according to the invention must exhibit low anisotropic energy and high magnetostriction in order to find practical use. It is therefore important to minimize the anisotropic energy and at the same time to optimize the room temperature magnetostriction of the composite material.
  • a number of composite materials with chemical composition (RE) x T 1-x where RE represents one or a mixture of several rare earth metals, T represents Fe, Ni, Co or Mn or a mixture of two or more of these metals and x assuming a value 0 ⁇ x ⁇ 1 represents atomic fraction, will have the mentioned properties.
  • RE represents one or a mixture of several rare earth metals
  • T represents Fe, Ni, Co or Mn or a mixture of two or more of these metals and x assuming a value 0 ⁇ x ⁇ 1 represents atomic fraction
  • x, y, z and w represent atomic fractions within 0.1 ⁇ x ⁇ 1.0
  • the composite material is cooled down, with the magnetizing field still being applied, to a temperature below its Curie temperature.
  • the composite material can be further improved if it is exposed to external vibrations during pressing. This will increase the density and the permeability as well as facilitate the magnetic alignement of the magnetostrictive grains.
  • isostatic pressing which usually means a lower pressing force than in the above described method.
  • This isostatic pressing can be improved by magnetically aligning the magnetostrictive grains before the composite material has been pressed and before the binder has been cured. This is achieved by applying the magnetizing field along the working direction of the magnetostrictive powder composite.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Power Engineering (AREA)
  • Composite Materials (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Dispersion Chemistry (AREA)
  • Metallurgy (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Inorganic Chemistry (AREA)
  • Powder Metallurgy (AREA)
  • Hard Magnetic Materials (AREA)
  • Soft Magnetic Materials (AREA)

Abstract

Magnetostrictive powder composite and method for the manufacturing of the magnetostrictive powder composite. The powder composite according to the invention is preferably used as a magnetostrictive element in sound projectors and vibration generators, transducers, actuators and in linear motors. The powder composite consists of magnetostrictive powder grains with chemical composition (RE)xT1-x, where RE represents one or a mixture of several rare earth metals, T represents Fe, Ni, Co or Mn or a mixture of these metals and x represents atomic fraction assuming a value between 0 and 1, whereby the grains are held together by a binder. The powder composite is formed in such a way that it exhibits a homogeneous magnetic flux, has a good strength and can be made with a built-in precompression. It can be equipped with coolant channels and/or with coil loops. The powder composite is produced by pressing together the magnetostrictive powder grains and the binder in order to plastically deform the grains, either completely or partially, which causes the magnetic domains in the grains to align perpendicularly to the applied compression pressure. In an alternative mode of execution according to the invention isostatic pressing is used.

Description

MAGNETOSTRICTIVE POWDER COMPOSITE AND METHODS FOR THE
MANUFACTURE THEREOF.
The invention relates partly to a magnetostrictive
powder composite according to the preamble to claim 1, and partly to a method for the manufacturing of the magnetostrictive powder composite according to the preamble to claims 16 and 17. The powder composite according to the invention is preferably used as a magnetostrictive element in sound projectors and vibration generators, transducers, actuators and in various types of linear motors.
To clarify the difference between permanent magnets and magnetostrictive powder composites, key properties and areas of applications for both materials are listed below:
PERMANENT MAGNETS:
Properties
1. Permanent magnets, usually compounds of rare earth
metals and transition metals (Fe, Ni, Co) like for
instance SmCo5 and Nd2Fe14B, are passive devices used for generating a magnetic field.
2. Permanent magnets can only generate static magnetic
fields.
3. Permanent magnets are magnetized initially and posses
high remanence and high coercive force. Unreasonably high energy would be needed to change the magnetic
field, which makes it practically impossible to use permanent magnets for purposes other than to generate static magnetic fields.
4. Permanent magnets do not need an electric current
flowing in a coil or a solenoid to generate and
maintain the magnetic field.
Application areas
A. Permanent magnets are used for generation of large
static fields in situations where it is difficult to provide electric power or where the availability of electric power is limited, or where geometrical
constraints such as space restrictions generate their use rather than electromagnets. B. The main applications of permanent magnets are in electric motors (in which electric energy is
converted into mechanical energy), generators (in which mechanical energy is converted into electrical energy), loudspeakers, control devices for electron beams such as in TV sets, magnetic levitation systems, and various forms of holding magnets such as door catches. For example Nd2Fe14B magnets developed by
General Motors are used in the starter motors of their cars and trucks.
MAGNETOSTRICTIVE POWDER COMPOSITE:
Properties
1. Magnetostrictive powder composite is an active device consisting of rare earth metals (RE) and transition metals (Fe, Ni, Co and Mn), (RE)xFe1-x, which changes its length extremely much when exposed to an external magnetic field. In contrast to traditional magnetostrictive materials, such as Fe and Ni which display magnetostrictive change in length of 9 μm/m and 40 μm/m respectively, a magnetostrictive powder composite displays length changes of more than 1000 μm/m and is therefore called giant magnetostrictive material.
Beacause of this, the magnetostrictive powder composite is used to generate large and fast movements of high precision and large force. In most applications this large force is used to increase change in length and to generate larger movements.
2. Magnetostrictive powder composite is usually used in high frequency applications (up to 60 kHz), e.g.
for ultrasonics. In this application the purpose of the magnetostrictive composite is that it should work as an acoustic projector i.e. to generate fast mechanical movements and ultrasound.
3. Magnetostrictive powder composite is initially a
material with low ferromagnetism. Magnetic moments within the magnetic domains in the material are randomly oriented i.e. the material is not magnetized as in the case of the above mentioned permanent magnets. For a powder composite to produce a length change one has to apply mechanical stress on the material to rotate magnetic domains relative the direction of the applied stress, as well as to apply a high magnetic field by feeding current into a coil surrounding the material. Typical magnetic fields are 1 - 8 kOe.
4. The material constituting the magnetostrictive powder composite has low remanence and low coercive force.
Chemical composition of the powder is chosen so that the anisotropic energy is minimized. If one omitted to do so it would be very difficult to use the
material in practice.
5. Magnetic powder composite has been put forward with a purpose to increase the bandwidth of the casted giant magnetostrictive material available on the market.
Magnetostrictive powder composite can manage a frequency region of 0 - 60 kHz, while casted giant magnetostrictive material only can manage 0 - 2 kHz. Giant magnetostrictive alloys made of terbium, dysprosium and iron are usually called Terfenol-D.
Application areas
Giant magnetostrictive powder composite is used in:
A.
- acoustic underwater sound projectors for high
frequencies,
- acoustic projectors for ultrasound applications
(20 - 60 kHz),
- vibration generators (0 - 60 kHz),
- positioners (to generate fast, high precision motion), and
B.
- wide bandwidth sound projectors and vibrators in which the amplitude does not change with frequency or load, which is the case with conventional electromagnets.
Magnetostrictive powder composite according to the invention presented has not been known of before. For example the patent documents US, A, 4865 660, DK, B, 157 222, FR, A, 2065 359 and EP, Al, 175 535 do certainly refer to magnetic powder composite materials, which nevertheless all are permanet magnets and which find their applications because of their capability to maintain permanent
magnetization. Magnetostrictive properties are not
mentioned in the above referred documents. The fact that the materials mentioned in these documents include powder grains of rare earth metals and transition metals is of no importance in this context.
When using conventional magnetostrictive materials and in particular alloys of type (RE)xT1-x, where RE represents one or a mixture of several rare earth metals, T represents Fe, Ni, Co or Mn or a mixture of two or more of these metals and x assuming a value 0 < x≤ 1 represents atomic fraction, below mentioned rods, the following inconveniences will be manifested:
1. The magnetostrictive materials are manufactured in the form of rods by casting. The casted rods hereby get brittle characteristics and are beacuse of this very difficult to machine with conventional techniques.
2. Scrap from crashed rods is difficult to reuse.
3. The rods are brittle and can only withstand very small tensional stress.
4. Due to a relatively low resistivity of casted
magnetostrictive rods, like for instance Terfenol-D rods, in order to increase the frequency performance of the said rods, it is often neccessary to slice the rods and to glue them together again in order to decrease the electrically conductive cross section of the material and to thereby decrease eddy current losses.
5. Due to the low permeablity of a conventional casted
magnetostrictive rod it is difficult to magnetize homogeneously such a rod by the use of permanent magnets applied at its ends. Usually a fairly homogeneous
magnetic flux can only be achieved if the rod length is not larger than 3 times its diameter.
6. The low permeability of the casted rod also causes
magnetization at the rod ends to be lower compared to the rod centre when a conventional coil is used to magnetize the rod.
7. So far it has only been possible to produce magnetostrictive elements in form of rods with circular cross sections. This causes a large material wastage and a costly machining if another geometrical form is
required.
By either crushing the scrapped magnetostrictive rods in an oxygen free atmosphere, or crushing magnetostrictive ingots or directly atomizing magnetostrictive powder or by hydrogen decrepitation producing a magnetostrictive powder, and thereafter pressing the crushed scrap or powder
together with a binder, all of the above accounted
inconveniences can be decreased or eliminated. To maximize the magnetostriction one can magnetically align the
material before it is pressed isostatically and the binder has been cured. This is accomplished by applying a
magnetizing field along the working direction of the magnetostrictive powder composite.
The above mentioned disadvantages 1 - 6 with the
existing technique are matched by the following advantages if the invention is utilized:
1. The powder composite is so tough that it can be shaped with a conventional cutting technique.
2. Scrap from crushed rods can be ground in an oxygen free atmosphere and thereafter reused for new rods.
3. If for example reinforcement fibres, preferably of
aluminium oxide, silicon carbide, Kevlar, carbon, glass or titanium, are pressed into the rod and aligned longitudinally or perpendicularly, tensile strength and elastic modulus will be increased.
4. By coating the grain surface with an electrically
insulating material or by using a binder that insulates the grains from each other, eddy current losses can be decreased. The invention utilizes such binding agents which wet said grains and bind them together and
possibly also form an electrically conducting layer between the powder grains or between the grain agglomerates. These requirements are fulfilled e.g. by a number of known resins and thermoplastics. Ceramics and oxides, preferably rare earth oxides because of a high reactivity of Terfenol-D, can also be used as an
insulating coating.
5. A homogeneous magnetic field generated by permanent
magnets can be achieved if a powder of a permanent magnet type, preferably Nd2Fe14B, is mixed with the magnetostrictive powder, preferably along the rod axis, in order to decrease the leakage flux. This will make it possible to manufacture rods with length/diameter ratios larger than 3:1.
6. To avoid lowering of magnetization at the rod ends high permeability and high resistivity powder grains,
preferably of coated iron, nickel, cobalt or amorphous iron, like for instance metglas, or alloys of these, can be pressed into the rod ends.
7. Magnetostrictive powder composite can be directly
pressed to a final shape, whereby expensive material wastage is avoided.
In addition, the invention provides for the following advantages:
- The surface friction of the magnetostrictive powder
composite can be lowered, so that it can glide easier against other objects. Also, its chemical resistance can be increased by coating the magnetostrictive powder composite, after it has been pressed, with a thin layer of non-organic material, such as aluminium oxide or an organic material, such as teflon, or if during pressing the composite surface is provided with a powder coating made of the above mentioned organic or non-organic materials.
- The strength of the magnetic powder composite can be
increased by coating its surfaces, which are in contact with other objects and thereby are exposed to a
mechanical load, with a layer made of e.g. aluminium oxide or silicon carbide. - In addition, by the use of powder technology, additional coil loops and/or coolant channels can be integrated into the pressed form.
Different embodiments of the invention are shown
in the enclosed figures.
Fig 1 shows a magnetostrictive composite rod 1 which, besides the magnetostrictive powder, possible coating and a binder, also has permanent magnets 2 of a conventional type at the rod ends and aligned permanent magnet powder 3, mainly along the longitudinal axis of rod 1, which makes the working magnetization in the composite rod 1 more homogeneous.
Fig 2 shows a magnetostrictive composite rod 1, an excitation coil for generating magnetizing field 4 and iron powder, coated with a thin electrically insulating layer of Fe2O3 or equivalent material, which has been pressed into the ends 5 of the rod 1. With this design a homogeneous magnetic flux in the composite rod 1 is achieved.
Fig 3 shows a magnetostrictive composite rod 1 with longitudinal fibre reinforcement 6 which, besides
reinforcing the rod 1 and increasing its strength against tensile stress, also makes it possible to build in a prestress into the rod 1.
The magnetostrictive composite material according to the invention must exhibit low anisotropic energy and high magnetostriction in order to find practical use. It is therefore important to minimize the anisotropic energy and at the same time to optimize the room temperature magnetostriction of the composite material. A number of composite materials with chemical composition (RE)xT1-x, where RE represents one or a mixture of several rare earth metals, T represents Fe, Ni, Co or Mn or a mixture of two or more of these metals and x assuming a value 0 < x ≤ 1 represents atomic fraction, will have the mentioned properties. At evaluating different compositions of magnetostrictive composite rods 1 according to the invention the applicant has found that the following compositions A) - F) give good such properties in the composite rods: A) TbxDy1-xFe2-w
wherein x and w represent atomic fractions within
0.2 ≤ x≤ 1.0 and 0≤ w≤ 0.5.
B) TbxHo1-xFe2-w
wherein x and w represent atomic fractions within
0.1≤ x≤ 1.0 and 0≤ w≤ 0.2.
C) SmxDy1-xFe2-w
wherein x and w represent atomic fractions within
0.8 ≤ x≤ 1.0 and 0 ≤ w ≤ 0.2.
D) SmxHo1-xFe2-w
wherein x and w represent atomic fractions within
0.6 ≤ x≤ 1.0 and 0≤ w≤ 0.2.
E) TbxHoyDyzFe2-w
wherein x, y, z and w represent atomic fractions within 0.1 ≤ x ≤ 1.0,
0 ≤ y≤ 0.9,
0 ≤ z ≤ 0.8,
and 0 ≤ w≤ 0.2
and x + y + z = 1.
F) SmxHoyDyzFe2-w
wherein x, y, z, and w represent atomic fractions within
0.6 ≤ x≤ 1.0,
0 ≤ Y≤ 0.4,
0≤ z ≤ 0.4,
and 0 ≤ w≤ 0.2
and x + y + z = 1.
Although some particularly favourable compositions of magnetostrictive composite materials are accounted for in the above it is understood that even other compositions with good properties are contained within the scope of the invention.
In order to improve the magnetostrictive composite material described by the invention, to increase the derivative dλ/dH, where λ is magnetostriction and H is the magnetizing field, as well as magnetostriction at
saturation one can, after pressing and after the binder has been cured, expose the magnetostrictive composite material to the following heat treatment: - composite material is heated to a temperature above its Curie temperature, which means about 400°C,
- thereafter, a magnetizing field of 40 kA/m amplitude is applied,
- finally the composite material is cooled down, with the magnetizing field still being applied, to a temperature below its Curie temperature.
The composite material can be further improved if it is exposed to external vibrations during pressing. This will increase the density and the permeability as well as facilitate the magnetic alignement of the magnetostrictive grains.
The above described method of manufacture of the magnetostrictive powder composite according to the
invention often demands high pressing forces. In an alternative mode of execution according to the invention isostatic pressing is used, which usually means a lower pressing force than in the above described method.
In said alternative method, the magnetostrictive powder grains and the binder are pressed together
isostatically, at which the composite material is directly pressed to an arbitrary final shape.
This isostatic pressing can be improved by magnetically aligning the magnetostrictive grains before the composite material has been pressed and before the binder has been cured. This is achieved by applying the magnetizing field along the working direction of the magnetostrictive powder composite.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Claims

PATENT CLAIMS
1. Magnetostrictive powder composite consisting of magnetostrictive powder grains with chemical composition
(RE)xT1-x, where RE represents one or a mixture of several rare earth metals, T represents Fe, Ni, Co or Mn or a mixture of two or more of these metals and x represents atomic fraction assuming a value between 0 and 1,
characterized in that the magnetostrictive grains are held together by a binder, the binder is such that it wets the magnetostrictive grains and is preferably a resin or a thermoplastic, the grains are prevented from electric contact with each other by the binder and/or an
electrically insulating layer, preferably ceramics or oxides, in particular rare earth oxides, that encapsulates each one of the magnetostrictive powder grains.
2. Magnetostrictive composite material according to claim 1, characterized in that it has chemical composition TbxDy1-xFe2-w
wherein x and w represent atomic fractions within
0.2≤ x≤ 1.0 and 0 ≤ w≤ 0.5.
3. Magnetostrictive composite material according to claim 1, characterized in that it has chemical composition TbxHo1-xFe2-w
wherein x and w represent atomic fractions within
0.1 ≤ x ≤ 1.0 and 0 ≤ w≤ 0.2.
4. Magnetostrictive composite material according to claim 1, characterized in that it has chemical composition
SmxDy1-xFe2-w
wherein x and w represent atomic fractions within
0.8≤ x≤ 1.0 and 0≤ w≤ 0.2.
5. Magnetostrictive composite material according to claim 1, characterized in that it has chemical composition SmxHo1-xFe2-w
wherein x and w represent atomic fractions within
0.6 ≤ x≤ 1.0 and 0≤ w≤ 0.2.
6. Magnetostrictive composite material according
to claim 1, characterized in that it has chemical
composition TbxHoyDyzFe2-w
wherein x, y, z and w represent atomic fractions within 0.1 ≤ x≤ 1.0,
0 ≤ y≤ 0.9,
0 ≤ z ≤ 0.8,
and 0 ≤ w ≤ 0.2
and x + y + z = 1.
7. Magnetostrictive composite material according to claim 1, characterized in that it has chemical composition SmxHoyDyzFe2-w
wherein x, y, z and w represent atomic fractions within 0.6≤ x≤ 1.0,
0 ≤ y≤ 0.4,
0≤ z ≤ 0.4,
and 0 ≤ w≤ 0.2
and x + y + z = 1.
8. Magnetostrictive composite material according to any of the above claims characterized in that it has a rod shape.
9. Magnetostrictive composite material according to claim 8, characterized in that the rod has an arbitrary cross section.
10. Magnetostrictive composite material according to any of the above claims, characterized in that the opposite ends of the composite material contain high permeability, or high permeability and high resistivity powder grains, preferably of surface coated iron, nickel, cobalt or amorphous iron like for example metglas, or alloys of such, which make said ends into electrical insulators, even at high frequencies.
11. Magnetostrictive composite material according to any of the above claims, characterized in that the
composite material also includes fibres, preferably of aluminium oxide, silicon carbide, Kevlar, carbon, glass or titanium, oriented lonqitudinally or transversally in the composite material, intended as mechanical reinforcement and/or strength improvement against tensile stresses and/or as means to produce a prestress in the composite material and/or as means to increase elastic modulus of the
composite material.
12. Magnetostrictive composite material according to any of the above claimes, characterized in that the
composite material also includes permanent magnet powder grains, preferably of Nd2Fe14B, in such concentration and at such locations in the composite material, preferably along the axis of the composite material, that it has a
homogeneous operating magnetization.
13. Magnetostrictive composite material according to any of the above claims, characterized in that the
composite material is formed with coolant channels and/or with coil loops.
14. Magnetostrictive composite material according to any of the above claims, characterized in that the
composite material, with the aim to lower its surface friction so that it can glide easier against other objects and to increase its chemical resistance, is after pressing coated with a thin layer of a non-organic material, such as aluminium oxide, or an organic material, such as teflon, or that during the pressing its surface is provided with a surface layer consisting of a powder of said organic or non-organic materials.
15. Magnetostrictive composite material according to any of the above claims, characterized in that the
composite material, aimed at increasing its strength, has its surfaces that are in contact against other objects and thereby are exposed to mechanical stresses, coated with a surface layer of powder, preferably aluminium oxide or silicon carbide.
16. Method for the manufacturing of the magnetostrictive composite material according to any of the above claims, characterized in that the magnetostrictive powder grains and the binder are pressed together at a pressure that is at least high enough to plastically deform the grains, either completely or partially, which causes the magnetic domains in the grains to align perpendicularly to the applied compression force, and that the composite material is directly pressed into a final arbitrary shape.
17. Method for the manufacturing of the magnetostrictive composite material according to any of claims 1-15, characterized in that the magnetostrictive powder grains and the binder are isostatically pressed together, and the composite material thereby is pressed into a final arbitrary shape.
18. Method for the manufacturing of the composite material according to claim 17, characterized in that the magnetic alignement of the magnetostrictive powder grains takes place by applying a magnetizing field along the working axis of the magnetostrictive powder composite, before the composite material has been pressed and before the binder has been cured.
19. Method for the manufacturing of the magnetostrictive composite material according to any of claims 16-18, characterized in that high permeability, or high permeability and high resistivity, powder grains,
preferably of surface coated iron, nickel, cobalt or amorphous iron like for example metglas, or alloys of these, had been pressed into the opposing ends of the composite material in such a way that said ends are
made into electrical insulators, which provides a more homogeneous magnetic flux inside the composite material.
20. Method for the manufacturing of the magnetostrictive composite material according to any of claims 16-19, characterized in that the magnetostrictive powder grains are pressed together with fibres, preferably of aluminium oxide, silicon carbide, Kevlar, carbon, glass or titanium, which are preferably oriented longitudinally or transversally in the composite material, in such a way that said fibres act as mechanical reinforcement and/or strength improvement against tensile stresses and/or as means of producing a prestress in the composite material and/or as means of increasing elastic modulus of the composite material.
21. Method for the manufacturing of the magnetostrictive composite material according to any of claims 16-20, characterized in that the powder grains,
preferably of Nd2Fe14B, in such concentration and at such locations in the composite material, preferably along the axis of the composite material, are added during its manufacture, that the composite material has a homogeneous operating magnetization, and that the permanent magnetic powder grains are oriented by means of an external magnetic field.
22. Method for the manufacturing of the magnetostrictive composite material according to any of claims 16-21, characterized in that the composite material, with the aim to decrease its surface friction so that it can glide easier against other objects and to increase its chemical resistance, after the pressing is coated with a thin layer of non-organic materials, such as aluminium oxide, or an organic material, such as teflon, or that during the pressing its surface is provided with a surface layer consisting of a powder of said organic or nonorganic materials.
23. Method for the manufacturing of the magnetostrictive composite material according to any of claims 16-22, characterized in that the composite material, with the purpose to increase its strength, has its surfaces that are in contact against other objects and thereby are exposed to mechanical stresses coated with a surface layer of powder, preferably of aluminium oxide or silicon carbide.
24. Method for the manufacturing of the magnetostrictive composite material according to any of claims 16-23, characterized in that the magnetostrictive composite undergoes the following heat treatment after it has been pressed and the binder has been cured in order to increase its derivative dΛ/dH, where A is the magnetostriction and H is the magnetizing field as well as its saturation
magnetostriction:
- the composite material is heated to a temperature above its Curie temperature, which means about 400°C, thereafter, a magnetizing field with an amplitude of 40 kA/m is applied,
- finally, the composite material is cooled down,.
said magnetizing field still being applied, to a
temperature below its Curie temperature.
25. Method for the manufacturing of the magnetostrictive composite material according to any of claims 16-24, characterized in that the composite material is exposed to external vibrations during the pressing, at which its density and its permeability are increased as well as the magnetic alignement of the magnetostrictive grains is facilitated.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PCT/SE1992/000331 1991-05-22 1992-05-19 Magnetostrictive powder composite and methods for the manufacture thereof WO1992020829A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP4510169A JPH06507676A (en) 1991-05-22 1992-05-19 Magnetostrictive powder composite material and its manufacturing method
EP92917301A EP0663961A1 (en) 1991-05-22 1992-05-19 Magnetostrictive powder composite and methods for the manufacture thereof

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9101535A SE468655B (en) 1991-05-22 1991-05-22 MAGNETOSTRICTIVE COMPOSITION OF POWDER MATERIAL
SE9101535-4 1991-05-22

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JP (1) JPH06507676A (en)
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CA (1) CA2102501A1 (en)
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WO (1) WO1992020829A1 (en)

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WO1995035176A1 (en) * 1994-06-22 1995-12-28 Valtion Teknillinen Tutkimuskeskus Method for the manufacture of a magnetostrictive material
EP0817286A1 (en) * 1996-07-01 1998-01-07 General Motors Corporation Magnetostrictive composites
WO1999015281A2 (en) * 1997-09-19 1999-04-01 Etrema Products, Inc. Multilayer magnetostrictive transducer and magnetostrictive composite material for same
WO2006007882A1 (en) * 2004-07-17 2006-01-26 Carl Freudenberg Kg Magnetostrictive element and use thereof

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JP6056634B2 (en) * 2013-04-25 2017-01-11 富士通株式会社 Power generator

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US4644310A (en) * 1984-03-22 1987-02-17 Allied Corporation Actuator system having magnetomechanical cantilever beam formed of ferromagnetic amorphous material
US4845450A (en) * 1986-06-02 1989-07-04 Raytheon Company Self-biased modular magnetostrictive driver and transducer
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FR2065359A5 (en) * 1969-10-13 1971-07-23 Western Electric Co Polymeric coating on ferromagnetic particl - es to prevent oxidation
US4152178A (en) * 1978-01-24 1979-05-01 The United States Of America As Represented By The United States Department Of Energy Sintered rare earth-iron Laves phase magnetostrictive alloy product and preparation thereof
US4644310A (en) * 1984-03-22 1987-02-17 Allied Corporation Actuator system having magnetomechanical cantilever beam formed of ferromagnetic amorphous material
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Publication number Priority date Publication date Assignee Title
WO1995035176A1 (en) * 1994-06-22 1995-12-28 Valtion Teknillinen Tutkimuskeskus Method for the manufacture of a magnetostrictive material
EP0817286A1 (en) * 1996-07-01 1998-01-07 General Motors Corporation Magnetostrictive composites
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US5993565A (en) * 1996-07-01 1999-11-30 General Motors Corporation Magnetostrictive composites
WO1999015281A2 (en) * 1997-09-19 1999-04-01 Etrema Products, Inc. Multilayer magnetostrictive transducer and magnetostrictive composite material for same
WO1999015281A3 (en) * 1997-09-19 2000-02-10 Etrema Products Inc Multilayer magnetostrictive transducer and magnetostrictive composite material for same
WO2006007882A1 (en) * 2004-07-17 2006-01-26 Carl Freudenberg Kg Magnetostrictive element and use thereof
US8502635B2 (en) 2004-07-17 2013-08-06 Carl Freudenberg Kg Magnetostrictive element and use thereof

Also Published As

Publication number Publication date
AU1870692A (en) 1992-12-30
SE468655B (en) 1993-02-22
EP0663961A1 (en) 1995-07-26
CA2102501A1 (en) 1992-11-23
SE9101535L (en) 1992-11-23
SE9101535D0 (en) 1991-05-22
JPH06507676A (en) 1994-09-01

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