JP4602210B2 - Magnesium-based metallic glass alloy-metal particle composite with ductility - Google Patents

Description

The present invention relates to a magnesium-based metallic glass alloy-metal particle composite material. More specifically, the present invention relates to a magnesium-based metallic glass alloy-metal particle composite material having ductility while being rapidly solidified from a molten metal.

It is known that a “metallic glass alloy” can be obtained in a specific composition by rapidly solidifying a molten alloy. To date, many metallic glass alloys have been obtained for palladium-based alloys, lanthanoid-based alloys, zirconium-based alloys, iron group element-based alloys, or magnesium-based alloys.

In Zr-based metallic glass alloys, etc., attempts have been made to eliminate the defects of metallic glass alloys without plastic elongation and improve ductility by dispersing and compounding particles of about 100 μm or less such as ZrC (Patent Literature). 1, 2). As described in Patent Documents 1 and 2, the substances dispersed in the metallic glass alloy of the parent phase are oxides and carbides having high hardness. In addition, a mixed powder of amorphous alloy powder and metal powder having high ductility such as copper can be integrated by compression in the supercooled liquid region of the amorphous alloy to improve the stretch rate and fracture toughness at room temperature. Known (Patent Document 3).

On the other hand, an amorphous alloy ribbon having a thickness of several tens of μm does not show elongation in a tensile test, but is known to have toughness under special stresses such as adhesion bending. As a method of making a high-strength alloy ribbon with high strength while maintaining its toughness, W of 1-5μm in size
A method of dispersing carbide particles such as C and fine powders such as Fe and W is known (Patent Document 4).

Magnesium-based metallic glass alloys have low specific gravity and light weight, and are expected to be applied to various fields as new types of metallic glass alloys different from conventional zirconium-based metallic glass alloys. Among them, in an alloy system in which a rare earth metal is added to magnesium, a high-strength Mg-based metallic glass alloy as disclosed in Patent Documents 5 and 6 has been developed and is expected to be applied to structural materials. Yes.

WO02 / 27055 A1 WO96 / 04134 (JP2000 / 509098T) Japanese Patent Laid-Open No. 2003-221657 JP 59-47352 A Japanese Patent Laid-Open No. 3-10041 JP 2001-254157 A

Magnesium-based metallic glass alloy has a high strength also proof stress (sigma _0.2) is more than 700MPa under compressive load, although the thin strip of the sample is toughness can contact bending in mechanical materials testing compression test, etc. The elongation at room temperature did not show an elongation corresponding to plastic deformation, and the room temperature breaking elongation was almost 0%, which caused the same failure as brittle materials. Therefore, a large safety factor has to be taken when designing the member, and it has been impossible to practically produce a member or a material for plastic working that makes use of high strength while being rapidly solidified.

Accordingly, an object of the present invention is to provide a high-strength magnesium-based metal glass alloy cast material having ductility while rapidly solidified from a molten metal, and a material for plastic working made of such a cast material.

Conventionally, with regard to crystalline alloys, a particle dispersion type in which oxides and inclusions with a size of several μm to several tens of μm are dispersed in the alloy as a method for improving the strength to prevent dislocation movement and strengthen the material. Alloys are known. However, this method usually improves the strength, but the ductility does not improve or decreases compared to the alloy before dispersion. Metallic glass alloys do not have dislocations, so they cannot be equated with ordinary crystal alloys and can be expected to improve strength when nanometer-sized particles are dispersed. Does not improve.

The present inventors have confirmed that ductility is not exhibited even when oxide or carbide particles are dispersed in a magnesium-based metallic glass alloy. However, certain metals, namely Ti, Co,
It has been found that when particles of a predetermined size of at least one metal element selected from Fe or Zr are dispersed, the magnesium-based metallic glass alloy has a large ductility although there is no effect of improving the strength. The present invention has been completed.

That is, this invention consists of the structure described in the following item.
(1) in the composition formula _{Mg 100-abc Ln a M b} X c ( wherein, Ln is, Y, Gd, Tb, Dy , Ho,
One or more elements selected from Er and Tm, M is one or two elements selected from Cu and Ag
Species element, X is one or more elements selected from Pd and Zn, 5 ≦ a <15, 15 ≦ b
<35, 0 ≦ c <10, and 25 ≦ a + b + c <45), an average particle diameter of one or more elements selected from Ti, Co, Fe, and Zr is 20 μm
A magnesium-based metal glass alloy-metal particle composite material characterized in that metal spherical particles of less than 400 μm are dispersed, and the elongation at room temperature is 5% or more as cast.

(2) The volume fraction of the metal spherical particles with respect to the metal glass alloy-metal particle composite is 5% or more and 5
The magnesium-based metallic glass alloy-metal particle composite material according to (1) above, which is less than 0%.

(3) Magnesium-based metallic glass alloy-metal particles according to (1) or (2) above, wherein the yield strength (σ _0.2 ) is 800 MPa or more under compressive load and the room temperature breaking elongation is 20% or more. Body composite material.

(4) A plastic working material comprising the magnesium-based metallic glass alloy-metal particle composite material according to any one of (1) to (3).

(5) Cooling rate at which crystallization does not occur after plastic processing of the magnesium-based metal glass alloy-metal particle composite material according to any one of (1) to (3) above in the supercooled liquid temperature region of the metal glass alloy. A product made of a magnesium-based metallic glass alloy-metal particle composite material having a room-temperature elongation at break of 5% or more obtained by cooling at a temperature of 5%.

The magnesium-based metallic glass alloy-metal particle composite material of the present invention is obtained by mixing and melting metal raw material powder and lump and Ti, Co, Fe, or Zr element particles as an alloy composition of the matrix, It can be easily obtained by casting using a technique such as casting or high pressure die casting. Even when the raw material for the parent phase is dissolved, the Ti, Co, Fe, and Zr grains tend to phase separate into Mg, which is the main element of the parent phase. The body is not dissolved in the molten metal, and the shape of the granule is maintained. When the granule component is dissolved in the parent phase, the glass forming ability is lowered and the parent phase becomes brittle.

At the time of dissolution of the matrix phase, on the surface of the metal spherical particles, Ln elements other than magnesium of the matrix phase (one or more selected from Y, Gd, Tb, Dy, Ho, Er and Tm), M element (Cu, 1 type or 2 types selected from Ag) and the element of the metal spherical particles can react only on the surface of the metal spherical particles, and the metal glass alloy and the metal spherical particles can be sufficiently wetted. . For this reason,
It becomes a composite material in which the metallic glass alloy of the matrix and the metal spherical particles are firmly adhered. When relatively large metal spherical particles are dispersed and interspersed in the parent phase of the metal glass alloy, it is considered that the continuity of the parent phase is impaired and the strength is usually lowered. In the granular composite material, strength reduction is suppressed, and the high strength and high ductility of the magnesium-based metallic glass matrix can be achieved.

Magnesium-based metallic glass alloy with a composite of metallic glass alloy and spherical metal particles
It is considered that there are various factors that the metal particle composite material has both strength and ductility. According to the observation of the fracture surface, the fracture surface pattern generated by the brittle fracture of the magnesium-based metallic glass alloy is complicated near the metal spherical particles, so the brittle fracture of the parent phase occurs at the nanometer scale. However, in view of the fact that the progress of the fracture can be stopped in the vicinity of the metal spherical particles and that the metal spherical particles are observed to be crushed and deformed, there is resistance when the spherical particles are deformed. It is inferred that ductility is caused by the occurrence. However, there is a possibility of having both high strength and high ductility for other reasons, and the reason for having both high strength and high ductility does not limit the present invention.

Practically, the magnesium-based metallic glass alloy-metal particle composite of the present invention uses an alloy composition having a high glass-forming ability as a matrix phase, and when heated and heated, before the metallic glass alloy crystallizes. A supercooled liquid state is produced in a certain temperature range. In this supercooled liquid state, the viscosity decreases and softens, so that molding and processing while maintaining the glass state are facilitated. For this reason, even if a technique such as forging is used, the matrix phase is easily deformed, so that the metal spherical particles in the matrix phase are not affected, and the product can be easily plastically processed into a target shape. After processing, cooling is performed at a cooling rate at which the matrix phase does not crystallize, so that the properties of the metallic glass alloy are not lost and the ductility is not lost. Therefore, the magnesium-based metallic glass alloy-metal particle composite material of the present invention is industrially beneficial.

Although the magnesium-based metallic glass alloy has high strength, it did not show break elongation according to plastic deformation, and a member that makes use of high strength could not be practically produced. Characteristics of Magnesium-Based Metallic Glass Alloys with a Relatively Simple Method of Mixing the Molten-Metallic Metallic Glass Alloy-Metal Grain Composite Matrix Alloy Melt to Form a Composite of Metallic Glass Alloy and Metal Spherical Particles The magnesium-based metallic glass alloy having remarkable room temperature plastic elongation, that is, room temperature breaking elongation, was successfully achieved without any loss of the above.

In the present invention, even when the metal spherical particles are dispersed in the metallic glass alloy of the parent phase,
Since the parent phase needs to maintain the glass state, the composition of the metallic glass alloy to be the parent phase is limited.

Since the magnesium-based metallic glass alloy-metal particle composite material of the present invention is characterized by being able to obtain members having various shapes by a method such as a rapid solidification casting method, it has a high glass forming ability. There is a need. Among the known composition ranges shown in Patent Documents 1 and 2, a composition having particularly high glass-forming ability is limited to the composition of the parent phase. When it deviates from the composition range which is limited as the alloy composition of the present invention, it has a problem of embrittlement because the metallic glass alloy of the parent phase tends to be crystallized. Cannot be used.

That is, in the parent phase alloy, Mg needs to be 55 atom% or more and less than 75 atom%, and more preferably 60 atom% or more and less than 70 atom%. Y, Gd, Tb, Dy, Ho
One or more elements selected from Er and Tm must be 5 atomic% or more and less than 15 atomic%, more preferably 8 atomic% or more and less than 12 atomic%. The content of these elements is 5
If it is less than 15% or more than 15% by atom, the ability to form an amorphous material is lowered, and 5 mm is obtained by using a die casting method.
Even if a bulk material of φ or larger is produced, an amorphous single-phase bulk material cannot be obtained.

Further, at least one element selected from Cu and Ag is 15 atomic% to 35 atomic%.
It is necessary to be less than 20% by atom, and more preferably 20 atom% or more and less than 30 atom%. When the content of these elements is less than 15 atomic% or more than 35 atomic%, the amorphous forming ability is reduced, and even if a bulk material having a diameter of 5 mmφ or more is produced by using a die casting method, amorphous element Phase bulk material is not obtained.

One or two elements selected from Zn and Pd are less than 10 atomic%, more preferably less than 5 atomic%. Zn and Pd are elements that improve the glass-forming ability. By adding these elements, it is possible to produce a metallic glass alloy casting material with an amorphous volume fraction of 100% in diameter or thickness of 10 mm or more. it can. However, the heat resistance strength is slightly reduced by the addition of Zn, and since Pd is expensive, the magnesium-based metallic glass alloy of the present invention-
When producing a metal particle composite material, it is desirable to add as needed when the glass forming ability is insufficient.

The spherical metal particles dispersed in the matrix, which is a major feature of the present invention, are limited as follows. The metal spherical particles need to be composed of one or more elements selected from Ti, Zr, Co, and Fe. These elements are elements that tend to phase-separate with magnesium, but at the time of melting the parent phase alloy during melting of the parent phase alloy and at the time of casting, the parent phase is not melted into the molten metal glass alloy. It is important that the metallic glass alloy and the spherical metal particles become wet. In addition, although there is no clear definition about the term of a granular material, generally several dozen micrometer or more is called a "granule", and about 3 micrometer-several dozen micrometer is called "powder." 1985.
Kodansha), so this example was followed in this specification.

When pure metals or alloys other than the metal spherical particles composed of these elements are used, the metal spherical particles dissolve during the melting of the matrix alloy, and at the same time, the dissolved atoms form the matrix glass alloy. Even when the performance deteriorates or does not melt, the surface of the metal spherical particles does not get wet with the magnesium-based metallic glass alloy of the parent phase, so that the metal spherical particles do not act to provide ductility as a composite material. For example, refractory metals such as Nb, V, Mo, and W do not melt, but the metal particles do not get wet with the molten metal, so that the metal particles in the cast material are peeled off from the parent phase and develop ductility. do not do.

Furthermore, the average particle diameter of the metal spherical particles is preferably 20 μm or more and less than 400 μm. The average particle size of the metal spherical particles of the present invention is expressed as the average particle size of the spherical particle material added to the melt. The average particle diameter of the metal spherical particles in the composite material is, for example, an arbitrary 0 as observed with a scanning electron microscope.
. It can be obtained by a method of calculating by observing 5 fields of view of 2 mm × 0.3 mm and averaging the particle diameters of all metal particles present in the field of view. There is substantially no difference between the average particle size measured by this method and the average particle size of the spherical granular material.

When the average particle diameter of the metal spherical particles is less than 20 μm, the surface area of the metal spherical particles tends to be large, and it tends to be difficult to mix the metal spherical particles into the matrix alloy, and the average particle diameter is 400 μm or more. When it is, there exists a tendency which produces the fall of the intensity | strength of a composite material, and the reduction | decrease of elongation. The most preferable average particle size of the metal spherical particles is 50 μm or more and less than 200 μm. As such metal spherical particles, those produced by a gas atomizing method or a plasma atomizing method are generally commercially available, and these commercially available products can be used in the present invention.

The spherical metal particles of Ti, Zr, Co, and Fe are not limited to pure metal particles, and are equivalent to the pure metal spherical particles without melting into the molten metal glass alloy of the parent phase. As long as wetting between the metallic glass alloy and the spherical metal particles is observed and the ductility of the room temperature breaking elongation is 5% or more, these metals are mainly coated with these metals or dissimilar particles. You may have done.

The magnesium-based metallic glass alloy-metal particle composite material of the present invention can be selected from various strengths and elongations depending on the type, average particle size, and mixing ratio of the metal spherical particles. In the case of spherical metal particles made of pure Ti and having a particle size of 100 μm, no plastic elongation is observed when the mixing ratio of the spherical metal particles in the composite material is less than 5%. When the rate is 5% or more and less than 30%, it is possible to obtain a magnesium-based metal glass alloy-metal particle composite having a yield strength (σ _0.2 ) of 700 MPa or more and a room temperature breaking elongation of 5% or more in a compression test. Furthermore, when the mixing ratio of the metal spherical particles is 20% or more and less than 40%, a magnesium-based metal glass alloy-metal particle composite having a yield strength of 600 MPa or more and a room temperature breaking elongation of 20% or more is obtained. Obtainable.

The magnesium-based metal glass alloy-metal particle composite material of the present invention is obtained by, for example, dissolving a metal glass alloy serving as a parent phase in an argon atmosphere, and mixing a predetermined metal spherical particle into the molten metal to form a parent phase alloy. Can be produced. In melting, since it is necessary to uniformly disperse the metal spherical particles, melting by high frequency induction melting that also has the stirring effect of the molten metal is desirable. When the stirring effect is small due to the frequency of high frequency induction melting, or when another melting method is selected, it is possible to uniformly disperse the metal spherical particles even using a method of mechanically applying vibration from the outside. .

By cooling and solidifying the matrix alloy from a molten state using a mold casting method in various molds, the magnesium-based metal glass alloy-metal particle composite material of the present invention can be obtained.
For the production of a large casting material, die casting using a Cu mold having a high cooling rate is preferable, and further, a die casting method using a high-pressure die casting apparatus capable of casting in a high-pressure state is preferable.

In the present invention, when these mold casting methods are used, they can be easily manufactured under the manufacturing conditions used in each conventionally known manufacturing method. For example, the mother phase alloy is melted in a ceramic crucible also serving as a ceramic nozzle having a pore diameter of 1 mm to 3.0 mm in an argon atmosphere, and then the molten metal is poured at an ejection pressure of 0.2 to 5.0 kg / cm ² in the argon atmosphere. From nozzle to C
By ejecting into a u-made mold, a magnesium-based metallic glass alloy-metal particle composite casting can be obtained.

Furthermore, since the magnesium-based metallic glass alloy-metal particle composite material of the present invention uses a composition excellent in glass forming ability for the matrix phase, a twin roll method, a groove quenching method, or the like other than the above is used. However, magnesium-based metallic glass alloy-metal particle composites having various large shapes such as thick plates and metal wires can be easily obtained.

Next, the present invention will be described more specifically with reference to examples and comparative examples. Alloys having various compositions shown in Table 1 were produced by melting in an argon atmosphere. Specifically, after inserting pure metals composed of each element forming the parent phase into a magnesia crucible, in a melting furnace with a vacuum chamber, after evacuation, argon gas was injected to a pressure of -0.02 MPa, It melt | dissolved over 10 minutes maintaining at about 700 degreeC in atmosphere, and it poured into the casting_mold | template made from Fe, and was set as the raw material alloy of a metal glass alloy.

Next, the raw material alloy is pulverized to a size of about 5 to 10 mm, inserted into a magnesia crucible at the same time as the metal spherical particles at a predetermined mixing ratio, evacuated, and then injected with argon gas to a pressure of -0.02 MPa. Then, it was melted over 10 minutes while maintaining at about 600 ° C. in an argon gas atmosphere, and then poured into an Fe mold to prepare a raw material alloy of a magnesium-based metal glass alloy-metal particle composite material.

Table 1 shows the types of metal spherical particles, the average particle size and volume fraction of the metal spherical particles.
As the metal spherical particles, metal spherical particles produced by the atomizing method manufactured by Kojundo Chemical Laboratory Co., Ltd. were used. The average particle size of the metal spherical particles shown in Table 1 is the average particle size obtained by observation with a scanning electron microscope as described above, and is substantially the same as the average particle size of the raw metal spherical particles. It was.
The produced raw material alloy was melted in a quartz crucible which also served as a nozzle having a hole diameter of 2.0 mm, and then 600
The molten metal was extruded from a nozzle into a Cu mold having a diameter of 2 mm at a jet pressure of 1.0 kg / cm ² in an argon atmosphere at 0 ° C. to produce a rod-shaped cast material having the composition shown in Table 1. Comparative Example 1 is a conventional magnesium-based metallic glass alloy in which metal spherical particles are not mixed.

Next, after cutting these produced cast materials into 1 mm width in the circumferential direction, phases were identified by an X-ray diffraction method. Moreover, the diffraction peak of the metal spherical particle was previously acquired only with the metal spherical particle. Judgment of phase has a broad peak peculiar to metallic glass alloys, and when the diffraction peak obtained only from the metal spherical particles and the diffraction peak obtained from the cast material coincide, it is judged as glass and metal spherical particles. In Table 1, (glass + particles) is indicated. In addition, when a diffraction peak different from the peak of only the broad peak and the spherical metal particles appears, the crystal phase is judged and the same diffraction peak as the peak of the crystalline phase and the spherical metal particles appears. When it is, it was judged as a mixed phase of a crystal phase and a metal spherical particle phase. The results are shown in Table 1.

Moreover, the cast material of 2 mmφ shown in Examples 1 to 13 and Comparative Example 1 was cut to a length of 5 mm, and a compression test was performed at room temperature. In the compression test, 1 × 10 ^-5 by Instron tensile tester
The yield strength and plastic elongation were determined by performing a test at a strain rate of. The results are also shown in Table 1.

As is apparent from Table 1, the cast material made of the magnesium-based metallic glass alloy-metal particle composite material of Examples 1 to 13 is a 2 mmφ bulk material, both of which are made of a glass phase and metal spherical particles. This was a magnesium-based metallic glass alloy-metal particle composite. Comparative Example 1 has no plastic elongation, whereas the Magnesium-based metallic glass alloy-metal particle composites of Examples 1 to 13 have a yield strength exceeding 600 MPa and room temperature breaking elongation of 5% or more in any composition. And is ductile although its strength is slightly lower than that of conventional Mg-based metallic glass alloys. As shown in Comparative Example 2, when Cu metal spherical particles that are not metal spherical particles used in the present invention are used, Cu melts into the molten metal to reduce the glass-forming ability, thereby obtaining a metal glass alloy. Can not.

Among the examples in Table 1, the true stress-true strain curve of Example 12 having the largest plastic elongation is shown in FIG.
FIG. 2 shows a scanning electron microscope image and a composition image of the fractured section after the fracture. As shown in FIG. 1, even when the stress is higher than the yield strength, the strength increases while increasing, and no brittle fracture behavior is observed. In addition, after breaking, as seen in FIG. 2, it was possible to observe that the spherical particles before the test were crushed and deformed, and the metal spherical particles contributed to the improvement of ductility. It is clear.

Example 14, Comparative Example 3 and Comparative Example 4, Comparative Example 5
In order to confirm that the glass forming ability of the parent phase was not lowered by mixing the metal spherical particles, as in Example 1, Mg ₆₅ Gd ₁₀ Cu ₂₅ (atomic%) was used as the parent phase and Ti metal was used. An alloy raw material in which 40% by volume of spherical particles are mixed is prepared, and is 5 mm in diameter (Example 14) and 6 mm in diameter by die casting.
A cast material of (Comparative Example 3) was produced. Moreover, as Comparative Example 4 and Comparative Example 5, casting materials in which metal spherical particles were not mixed were similarly produced. Phase identification was determined by X-ray diffraction as in Example 1.

As shown in Table 2, the Mg ₆₅ Gd ₁₀ Cu ₂₅ magnesium-based metallic glass alloy can obtain a glass phase having a diameter of 5 mm as shown in Comparative Examples 4 and 5 when metallic spherical particles are not mixed. The maximum diameter that can be made. On the other hand, even when the metal spherical particles are mixed, the parent phase is a glass phase up to a diameter of 5 mm as shown in Example 14 and Comparative Example 3 even though the metal spherical particles are mixed. The glass forming ability of the metallic glass alloy phase is not reduced by mixing the spherical metal particles.
[Comparative Example 6]

Similar to the example of Patent Document 2 (WO96 / 04134), a cast material of a magnesium-based metallic glass alloy in which TiC particles were dispersed was produced. The specific mixing method of the parent phase alloy and TiC particles is as follows:
The same as in Example 1, the magnesium-based metallic glass alloy has Mg ₆₅ Gd ₁₀ Cu ₂₅ (figures atomic%)
The powder was mixed at a volume ratio of 40% by volume using TiC.

The obtained alloy was in a crystalline phase, and as a result of measurement in the same manner as in Examples, the strength was 580 MPa, and ductility was not obtained. According to the example of Patent Document 2, “TiC is sufficiently wet”, but TiC particles are detached from the magnesium-based metal of the parent phase when the cast material is cut and polished for cross-sectional observation. It was a state, and it could not be said that TiC was sufficiently wet.

The magnesium-based metallic glass alloy-metal particle composite of the present invention exhibits plastic elongation by using a high-strength alloy with excellent glass-forming ability as the matrix and dispersing metal spherical particles suitable for the matrix. However, it has the same strength as the conventional magnesium metal glass alloy. In addition, the magnesium-based metallic glass alloy-metal particle composite material of the present invention can provide a casting material having various shapes and a plastic working material made of the casting material by making the mold into an arbitrary shape. .

It is a graph which shows the true stress-true strain curve of the magnesium group metal glass alloy-metal particle composite material of Example 12. It is a drawing substitute photograph which shows the scanning electron microscope image and composition image of the fracture | rupture cross section after the fracture | rupture by the compression test of the magnesium group metal glass alloy-metal particle composite material of Example 12.

Claims (5)

In the composition formula _{Mg 100-abc Ln a M b} X c ( wherein, Ln is Y, Gd, Tb, Dy, Ho, one or more elements selected from Er and Tm, M is selected Cu, from Ag One or two elements, X is one or more elements selected from Pd and Zn, 5 ≦ a <15, 15 ≦ b <35
, 0 ≦ c <10, and 25 ≦ a + b + c <45).
And an average particle diameter of at least 20 μm consisting of one or more elements selected from Co, Fe and Zr 4
A magnesium-based metal glass alloy-metal particle composite material, characterized in that metal spherical particles less than 00 μm are dispersed, and the elongation at room temperature is 5% or more as cast. The magnesium-based metal glass alloy-metal particle composite according to claim 1, wherein the volume fraction of the metal spherical particles with respect to the metal glass alloy-metal particle composite is 5% or more and less than 50%. The magnesium-based metallic glass alloy-metal particle composite according to claim 1 or 2, wherein the proof stress (σ _0.2 ) is 800 MPa or more under a compressive load and the room temperature breaking elongation is 20% or more. A material for plastic working, comprising the magnesium-based metallic glass alloy-metal particle composite material according to any one of claims 1 to 3. It is obtained by plastically processing the magnesium-based metallic glass alloy-metal granular composite material according to any one of claims 1 to 3 in a supercooled liquid temperature region of the metallic glass alloy and then cooling at a cooling rate that does not crystallize. Further, a product comprising a magnesium-based metallic glass alloy-metal particle composite material having a room temperature breaking elongation of 5% or more.

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