JP4094030B2 - Super high strength Ni-based metallic glass alloy - Google Patents

Description

The present invention relates to a Ni-based metallic glass alloy having a large amorphous forming ability and an ultrahigh strength.

“Metallic glass” has realized the dream of making amorphous alloys in bulk. That is, an alloy having a very high glass-forming ability was found in the Pd—Si—Cu alloy in the 1980s. Furthermore, since 1990, alloys with a practical alloy composition and a very high glass forming ability have been found. In general, in an “amorphous alloy”, crystallization proceeds before reaching the glass transition point by heating, and the glass transition cannot be observed experimentally. On the contrary,"
A clear glass transition is observed in the “metal glass” by heating, and the temperature range of the supercooled liquid region up to the crystallization temperature reaches several tens of K.

For the first time with this physical property, a bulk amorphous alloy can be made by a method of casting into a copper mold having a slow cooling rate. Such an amorphous alloy is particularly called a “metal glass”, although it is a metal, it is a stable amorphous material like oxide glass and can be easily plastically deformed (viscous flow) at high temperatures. Because.

“Metal glass” has a high amorphous forming ability, that is, has a characteristic that can be manufactured by cooling and solidifying a so-called bulk metal casting made of a glass phase and having a larger size from a molten metal by copper mold casting or the like. Is. Further, since the viscosity of the alloy decreases when heated to a supercooled liquid state, it has a characteristic that it can be plastically processed into an arbitrary shape by a method such as closed forging. "Metallic glass" is a material that does not have these characteristics and is essentially different from "amorphous alloys" such as conventional amorphous alloy ribbons and fibers, and is very useful as a material for various industrial products. .

The present inventors previously described Ni-PM (M is one or more of Ti, Zr, Hf, Nb, or Ta) -based Ni excellent in amorphous forming ability, workability, and mechanical strength. A base metal glass alloy (Patent Document 1) was developed. Moreover, the Ni-Nb type metal glass alloy (patent documents 2, 3, non-patent document 1) was opened. The compression test results of these Ni—Nb-based metallic glass alloys are shown in FIG. Ni-T
An i-Zr metallic glass alloy (Patent Document 4) has been developed. Furthermore, in 2003, a Ni—Nb—Sn-based metallic glass alloy with high glass stability and excellent amorphous forming ability was developed (Non-Patent Document 2), but this Ni-based metallic glass alloy is very brittle. It cannot be said that it has excellent mechanical properties and high thermal stability against crystallization.

Furthermore, the present inventors have reported that a bulk metallic glass alloy having a diameter of 0.5 mm can be manufactured in a Ni—Si—B based alloy (Non-patent Document 3). Furthermore, the inventors have
A Ni-Ta-Ti- (Zr, Hf) -based high strength Ni-based metallic glass alloy having a compressive strength of 2800 to 3180 MPa was developed (Patent Document 5). Recently, Ni-Cu with 5mm diameter
-Ti-Zr-Al metallic glass alloy was reported (Non-Patent Document 4), but compressive strength (σf)
Is as small as about 2300-2400 MPa.

Japanese Unexamined Patent Publication No. 2000-87197 Japanese Unexamined Patent Publication No. 2000-345309 Japanese Patent Laid-Open No. 2001-49407 Japanese Patent Laid-Open No. 2002-105608 JP-A-2005-298858 Mater.Trans.43 (2002) 708 APPL. PHYS. LETT. 82 (7): 1030-1032, FEB. 17 (2003) Mater.Trans.44 (2003) 1425 Acta Mater. 52,3493 (2004)

As described above, several Ni-based bulk metallic glass alloys have been produced so far, but it has been difficult to produce bulk metallic glass alloys having large dimensions (ie, high glass forming ability) and high strength. . Therefore, the present invention provides Ni having both high glass forming ability and high strength.
An object is to provide a base metal glass alloy.

In order to solve the above-mentioned problems, the present inventors have studied on an optimum composition, and as a result,
The present inventors have found that a Ni-based metallic glass alloy that exhibits the above-described supercooled liquid region ΔTx and that has an unprecedented high strength and that can solve the above-described problems has been obtained. That is, the present invention is a Ni-based metallic glass alloy represented by the following composition formula.
_{Formula: [(Ni 1-x Fe} x) 0.75 B 0.25-a Si a] 100 _over y Nb _y (wherein,
0.1 ≦ x ≦ 0.5, 0.04 ≦ a ≦ 0.06, 3.0 ≦ y ≦ 4.5 (atomic%))

The Ni-based metallic glass alloy of the present invention has a temperature interval of the supercooled liquid represented by the equation: ΔTx = Tx−Tg (where Tx is the crystallization start temperature and Tg is the glass transition temperature) The conversion temperature Tg / Tl (Tl is the liquidus temperature) is 0.54 or higher. The Ni-based metallic glass alloy of the present invention is a rod or plate having a diameter or thickness of 1.0 mm or more and a volume ratio of the amorphous phase of 100% by a die casting method.

The Ni-based metallic glass alloy of the present invention has excellent mechanical properties at room temperature, with a compressive strength of 3500 MPa or more and a Vickers hardness (load: 0.98 N, holding time: 15 seconds) of 1000 Hv or more. In addition, a high-strength cast product having a glass phase volume fraction of 100% can be produced by a die casting method using the Ni-based metallic glass alloy of the present invention. Furthermore, a high-strength processed product with a volume fraction of the glass phase of 100% can be produced by plastic processing using this alloy in a supercooled liquid state.

The “supercooled liquid region” in this specification is defined by the temperature interval between the glass transition temperature Tg and the crystallization start temperature Tx obtained by performing differential scanning calorimetry at a heating rate of 40 K / min. Is. The “supercooled liquid region” is a numerical value indicating resistance to crystallization, that is, amorphous stability and workability. This alloy has a supercooled liquid region ΔTx of 40K or more.
The “equivalent vitrification temperature” in the present specification is the alloy liquidus temperature (Tl) obtained by performing differential calorimetry (DTA) at a glass transition temperature (Tg) and a heating rate of 5 K / min. It is defined by the ratio of The “converted vitrification temperature” is a numerical value indicating the amorphous forming ability.

The alloy generally improves its mechanical properties by making it amorphous, but in the Ni-based metallic glass alloy of the present invention, a massive sample having a compressive strength exceeding 3500 MPa at room temperature was easily obtained. . This value of 3500 MPa or more is larger than any of the Ni-based glass alloys reported so far.

Thus, it is estimated that the mechanism by which high intensity | strength is obtained will be as follows. It is known that the strength of metallic glass is mainly due to the bonding force between elements. The atomic numbers of Fe and Ni are 26 and 28, respectively, and the arrangement of extranuclear electrons is 1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 3d ⁶ 4s ² and 1 respectively.
s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 3d ⁸ 4s ² The electrons in the 3d bands of Fe and Ni are 6 and 8, respectively. The 3d band can accept up to 10 electrons. That is, 3d band is still vacant in Fe than Ni. Therefore, extranuclear electrons (s electrons) from B and Si tend to enter the 3d band due to the increase in Fe content, and a strong sd mixed bond is formed. As a result, the strength increases with increasing Fe content up to about X = 0.4. In particular, [(Ni _0.6 F
e _0.4 ) _0.75 B _0.2 Si _0.05 ] ₉₆ Nb _{4 with} a composition of 383
It exhibits an ultra-high strength of 6 MPa, which is the highest value among various Ni-based metallic glass alloys. If X is more than 0.5, it is not preferable because it becomes brittle and plastic deformation is difficult.

The increase in glass forming ability due to the increase in Fe content is considered to be because the Ni—Fe based alloy composition is located in a closer eutectic composition. The addition of Fe brings the alloy composition closer to the eutectic point as shown in FIG. Near the eutectic composition, the liquidus temperature is low, Tg / Tl is increased, and the glass forming ability is improved.

Since the Ni-based alloy composition of the present invention exhibits a supercooled liquid region of 30K or more, it has a large amorphous forming ability, and a plate-like material having a thickness of 1 mm or more or a rod-like material having a diameter of 1 mm or more by a die casting method. Can be easily manufactured. Moreover, it has high strength and high hardness. from these things,
INDUSTRIAL APPLICABILITY The present invention can provide a practically useful Ni-based metallic glass alloy that has excellent plastic workability and excellent mechanical properties.

Next, an embodiment of the present invention will be described. The alloy composition of the present invention has the formula: [(Ni _1-x Fe
_x ) _0.75 B _0.25-a Si _a ] _100-y Nb _y (where 0.1 ≦ x ≦ 0.5,0
. 04 ≦ a ≦ 0.06, 3.0 ≦ y ≦ 4.5 (atomic%)). This alloy is based on five components of Ni: nickel, Fe: iron, B: boron, Si: silicon, and Nb: niobium.

In the Ni—Fe-based metallic glass alloy of the present invention, Ni and Fe as the main components are elements that form the basis of the ultra-high-strength bulk metallic glass alloy of the present invention. Among these five elements, the total content of Ni and Fe is about 71.6-72.8 at% by calculation based on the above formula, and N
The ratio of i and Fe is such that the value of x indicating the atomic ratio of Fe when the total number of atoms of Ni and Fe elements is 1, 0.1 ≦ x ≦ 0.5, more preferably 0.20. ≦ x ≦ 0.40.

In the above formula, when x that defines the Fe content is less than 0.1, ΔTx and Tg / Tl decrease, the glass forming ability decreases, and the mechanical strength is not sufficient. When x exceeds 0.5, embrittlement occurs and plastic workability deteriorates.

In the above alloy composition of the present invention, the metalloid elements B and Si are elements responsible for forming an amorphous phase, and are important for obtaining a stable amorphous structure. Both B and Si need to be contained, and if one of them is out of the above composition range, the glass forming ability is inferior and it is difficult to form a bulk glass alloy. In the composition of the alloy of the present invention, the total amount of B + Si is about 23.9-2.
It is 4.3 at% and becomes a composition close to the eutectic point.

In the above alloy composition formula of the present invention, the addition of Nb is effective in improving the glass forming ability. In the alloy composition of the present invention, Nb is added in the range of 3.0 atomic% to 4.5 atomic%. Outside this range, Nb less than 3.0 atomic% is not preferable because the temperature interval ΔTx of the supercooled liquid disappears, and if it exceeds 4.5 atomic%, glass forming ability is decreased. Absent.

In the above alloy composition of the present invention, due to deviation from the composition range, the glass forming ability is inferior, crystal nuclei are generated and grown from the molten metal to the solidification process, and the glass phase has a mixed crystal phase. Moreover, if it leaves | separates greatly from this composition range, a glass phase will not be obtained but will become a crystal phase.

In the above alloy composition of the present invention, since the glass forming ability is high, a metal glass round bar with a glass phase of 100% of a maximum diameter of 3 mm can be produced by casting with a copper mold, but the diameter is obtained by the rotating underwater spinning method at the same cooling rate. A metal glass alloy of particles up to a diameter of 0.6 mm can be produced by a fine line up to 0.55 mm and an atomizing method.

The Ni-based glass alloy of the present invention is cooled and solidified from a molten state by various methods such as a known single-roll method, twin-roll method, spinning in a rotating liquid, and atomizing method, and is in the form of a ribbon, filament, or granular material. An amorphous solid can be obtained. Moreover, since the Ni-based metallic glass alloy of the present invention has a large amorphous forming ability, the volume fraction of the glass phase can be adjusted by adjusting not only the above-mentioned known production method but also the cooling conditions and the product thickness. Bulk high strength cast products of various shapes that are 100% can be produced.

That is, a metallic glass alloy product having an arbitrary shape can be obtained by filling and casting molten metal into a mold such as a copper mold. For example, in a typical mold casting method, an alloy is melted in a quartz tube in an argon atmosphere, and then a molten metal is added in an amount of 0.5 to 1.5 kg · f / cm ^2.
A metallic glass alloy lump can be obtained by filling and solidifying a copper mold with a jet pressure of a certain degree. Furthermore, a manufacturing method such as a die casting method and a squeeze casting method can also be applied. Moreover, using the alloy of the present invention, high strength processed products having various shapes with a volume fraction of the glass phase of 100% are produced by plastic working such as pressing, forging, rolling, etc. in a supercooled liquid state. Can do.

1 was fabricated by the melt spinning process _{[(Ni 1-x Fe x} ) B 0.2 Si 0.05
] D of ₉₆ Nb ₄ composition glass alloy (where x = 0, 0.1, 0.2, 0.3, 0.4)
SC curve is shown. And the glass transition temperature (Tg) of the sample and the crystallization start temperature (Tx) were measured with the differential scanning calorimeter (DSC). The supercooled liquid region (Tx−Tg) was calculated from these values. The liquidus temperature (Tl) was measured by differential thermal analysis (DTA). The conversion vitrification temperature (Tg / Tl) was calculated from these values.

Tg gradually decreases from 770K to 745K as the Fe content increases, but Tx maintains a substantially constant value of 795K, and ΔTx is in the range of 25K to 50K. In addition, x
It can be seen that crystallization of = 0.3 and 0.4 alloys occurs mostly through a single exothermic reaction.
Therefore, it is understood that the thermal stability against crystallization of the supercooled liquid increases with increasing Fe content.

FIG. 2 shows the DTA curve of the alloy of the present invention. No Fe (Ni _0.75 B _0.2 Si _0.05 ) ₉₆
It can be seen that the Nb ₄ alloy has Tm (melting point) and Tl of 1275K and 1446K, respectively, and the maximum temperature range between Tm and Tl is 171K. In addition, the alloy exhibits several endothermic peaks. Therefore, it is suggested that the composition of this alloy is far from the eutectic point. By replacing Ni by Fe with a value of x = 0.1, Tm and Tl drop significantly from 1275K to 1243K and from 1446K to 1408K, respectively, and the DTA curve shows two endothermic peaks. [(Ni _0.9 Fe _0.1 ) B _0.2 Si _0.05 ]
It suggests that the ₉₆ Nb ₄ alloy is simpler than that of the Fe-free alloy.

Even if the Fe content was further increased to x = 0.2, 0.3, and 0.4, the Tm was about 12
Maintains an almost constant value of 32K. However, the alloy with Fe addition x = 0.3 shows a slightly higher Tm of 1237K. Therefore, the Fe content is x = 0.2, 0.3 and 0.
It is understood that the alloy of 4 is close to the eutectic point and has a Tm of about 1232K. On the other hand, Tl gradually decreases from 1381K, and the alloy with the Fe addition amount of x = 0.4 has the lowest Tl = 1348.
K, the temperature interval between Tm and Tl is the smallest at 118K.

Furthermore, it can be seen that the two endothermic peaks in the DTA curve change to almost one endothermic peak at x = 0.4. All these changes indicate that the alloy composition approaches the eutectic point with increasing Fe content, and the alloy composition with x = 0.4 Fe content is closer to the eutectic point compared to the other alloy compositions. Means that.

<Comparative example 1, Examples 1-4>
Examples of the present invention will be described below. A material comprising the alloy composition shown in Table 1 (Comparative Example 1
In Examples 1 to 4), a raw material alloy was melted by an arc melting method. FIG. 6 shows a schematic configuration of the apparatus used for producing the rod-shaped sample by the copper mold casting method as seen from the side.

First, a molten alloy having a predetermined composition is formed by arc melting, and the molten alloy is remelted in a quartz tube in an argon atmosphere at a temperature of 1600 K to 1800 K, and then a diameter of 0.5 to 3 mm by a copper mold casting method. A rod-shaped sample having a length of about 40 mm was prepared. For casting, the molten alloy was filled in a quartz tube 3 having a small hole (hole diameter: 0.5 to 4 mm) at the tip, and heated and melted by the high frequency generating coil 4. Thereafter, the copper mold 6 in which the quartz tube 3 is provided with a vertical hole 5 as a casting space.
It was installed directly above.

Next, the molten metal 1 in the quartz tube 3 is pressurized with argon gas (0.1 to 1.0 Kg / cm ² ).
Was ejected from the small hole 2 of the quartz tube 3, injected into the hole of the copper mold 6 and allowed to solidify as it was to obtain a cast rod. Comparative Example 1 is an alloy that does not contain Fe. The critical diameter for forming the glassy single phase is 1 mm in Example 1 (x = 0.2), 2 mm in Example 2 (x = 0.2), and 2.5 mm in Example 3 (x = 0.3). In Example 4 (x = 0.4), it was 3 mm.

FIG. 3 shows XRD patterns of cast alloy bars having diameters of Example 2 (2 mm), Example 3 (2.5 mm), and Example 4 (3 mm). Only a broad peak with no crystal peak is seen for all these bulk samples, indicating the formation of a glass phase within a diameter range of up to 3 mm.

Confirmation of the amorphization of the sample was performed by X-ray diffraction. In addition, the volume ratio (Vf-amo.) Of the amorphous phase contained in the sample is compared with a ribbon having a thickness of about 20 μm in which the calorific value at the time of crystallization using DSC is completely amorphized. It was evaluated by. As shown in Table 1, conversion vitrification temperature (
Tg / Tl) and γ parameter (Tx / (Tg + Tl)) were 0.541 to 0.553 and 0.366 to 0.380, respectively.

A compression test piece was prepared using an alloy bar having a diameter of 2 mm, and a compression test (σf) was measured by performing a compression test at room temperature using an Instron type testing machine. Moreover, Vickers hardness Hv (a load and time are 0.98 N and 15 seconds, respectively) was measured.

FIG. 4 shows a strain rate of 5 × 10 ^{− for} an alloy bar having a diameter of 2 mm and a length of 40 mm having the composition of Example 4.
The true stress-true strain curve of the compression test at ⁴ s ⁻¹ is shown. As shown in FIG. 4, each alloy bar has the same characteristics, that is, elastic deformation to a strain of about 0.02, followed by a small plastic deformation of about 0.001, and then a final break. Show. Young's modulus (E), yield strength (
σy), compressive strength (σf), elastic elongation (εe) and plastic elongation (εp) are each 186 GP
a, 3778 MPa, 3836 MPa, 0.02 and 0.001.

In FIG. 5, the optical structure photograph which shows the fracture surface by the compression test of the metallic glass alloy material of Example 4 is shown. As can be seen in the photo, a vein pattern has developed on the fracture surface, the viscosity of the fracture part decreases during fracture, the liquid state is reproduced, and the fracture proceeds like a slip. To some degree of plastic deformation. On the other hand, in the sample having no vein pattern, breakage occurs at a stretch and does not show plastic deformation. The Fe-based metallic glass alloy and the Co-based metallic glass alloy break with almost no plastic deformation.

Table 1 summarizes the critical diameter, thermal stability, and mechanical properties of the alloys of Comparative Example 1 and Examples 1-4. Hv of the alloy of Comparative Example 1 is 972, but the alloys of Examples 1 to 4 are Hv 1053-1
It is in the range of 130. The mechanical properties of the metal glass alloys of Examples 2 to 4 are respectively Ε = 1
72-186 GPa, σy = 3598-3778 MPa, σf = 3683-3836 MP
a.

<Comparative Examples 2-7>
Each alloy composition shown in Table 2 that deviates from the alloy composition of the present invention was die-cast in the same manner as in the examples. Each sample was crystalline at the diameters shown in Table 2.

The Ni-based metallic glass alloy of the present invention has a high strength and a high glass forming ability, and can produce a foil with a larger size. For example, a brazing material for joining large parts, for example, a pressure sensor, a torque sensor, It is particularly useful as a structural material or functional material that requires miniaturization and high strength such as a micromotor gear.

It is a DSC curve figure of the metallic glass alloy material of this invention. It is a DTA curve of the metallic glass alloy material of invention. The XRD pattern of the rod-shaped sample of Examples 2-4 is shown. It is a true stress-true strain curve figure by the compression test of the metallic glass alloy material of Example 4. It is a drawing substitute optical structure photograph which shows the fracture surface by the compression test of the metallic glass alloy material of Example 4. It is the schematic which looked at the apparatus used for producing the alloy sample of a cast bar by the die casting method from the side. It is a stress-strain curve figure by the compression test of the Ni-Nb-Ti- (Zr, Hf) type metal glass alloy material of a prior art example.

Claims (6)

_{Formula: [(Ni 1-x Fe} x) 0.75 B 0.25-a Si a] 100 _over y Nb _y (wherein,
0.1 ≦ x ≦ 0.5, 0.04 ≦ a ≦ 0.06, 3.0 ≦ y ≦ 4.5 (atomic%))
An ultrahigh-strength Ni-based metallic glass alloy characterized by having a composition represented by: ΔTx = Tx−Tg (where Tx is the crystallization start temperature and Tg is the glass transition temperature), the temperature interval of the supercooled liquid is 30K or more, and the converted vitrification temperature Tg / Tl (Tl is the liquid phase) The ultrahigh-strength Ni-based metallic glass alloy according to claim 1, wherein the linear temperature is 0.54 or more. 2. The ultrahigh strength Ni-based metallic glass alloy according to claim 1, wherein the volume fraction of the glass phase is 100% in the thickness or diameter range of 2 mm to 3 mm. The ultrahigh strength Ni-based metallic glass alloy according to claim 1, wherein the compressive strength is 3500 MPa or more at room temperature, and the Vickers hardness (load: 0.98 N, holding time: 15 seconds) is 1000 Hv or more. A cast product, wherein the volume fraction of the glass phase made of the metallic glass alloy according to any one of claims 1 to 4 cast by a die casting method is 100%. A processed product, wherein the volume fraction of the glass phase obtained by plastic processing of the metallic glass alloy according to any one of claims 1 to 4 in a supercooled liquid state is 100%.

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