WO2021070502A1

WO2021070502A1 - High-ductility molybdenum alloy material

Info

Publication number: WO2021070502A1
Application number: PCT/JP2020/032395
Authority: WO
Inventors: 一平安達; 瀧田　朋広; 角倉　孝典; 正寛長江
Original assignee: 株式会社アライドマテリアル
Priority date: 2019-10-08
Filing date: 2020-08-27
Publication date: 2021-04-15
Also published as: JPWO2021070502A1

Abstract

A molybdenum alloy material according to the present invention contains molybdenum, zirconia, and yttria, wherein: the zirconia content is 0.7% by mass to 13.6% by mass; the yttria content is 0.03 times to 0.08 times the zirconia content; and the ratio (11-1)/(111) of the ratio of the peak height of an (11-1) plane of tetragonal zirconia T and the peak height of a (111) plane of monoclinic zirconia M in X-ray diffraction is 10 or greater.

Description

High ductility molybdenum alloy material

This disclosure relates to molybdenum alloy materials. This application claims priority based on Japanese Patent Application No. 2019-185321, which is a Japanese patent application filed on October 8, 2019. All the contents of the Japanese patent application are incorporated herein by reference.

Conventionally, the molybdenum alloy material has been described, for example, in JP-A-2010-215933 (Patent Document 1), Journal of the Japan Institute of Metals, Vol. 52, No. 8 (1988), 803-809, "HIP-treated Mo-ZrO _2- based sintered material. "Structure and Mechanical Properties" (Non-Patent Document 1) and Journal of the Japan Institute of Metals, Vol. 50, No. 9 (1986) 828-833 "t → m transformation _{of ZrO 2} _{and tetragonal ZrO in Mo-ZrO 2-} based sintered materials" _{About the residue of 2} ”(Non-Patent Document 2).

Japanese Unexamined Patent Publication No. 2010-215933

The molybdenum alloy material contains molybdenum, zirconia (ZrO ₂ ) and yttria (Y ₂ O ₃ ), and the content of zirconia is 0.7% by mass or more and 13.6% by mass or less, and the content of yttria is that of zirconia. The content is 0.03 times or more and 0.08 times or less, and in X-ray diffraction, the peak height of the (11-1) plane of the zirconia tetragonal T and the peak of the (111) plane of the zirconia tetragonal M The ratio to height (11-1) / (111) is 10 or more.

FIG. 1 is a diagram showing a sintered body 200 and a test piece 100 extending in the x direction cut out from the sintered body 200. FIG. 2 is a diagram showing a sintered body 200 and a test piece 100 extending in the y direction cut out from the sintered body 200. FIG. 3 is a diagram showing a sintered body 200 and a test piece 100 extending in the z direction cut out from the sintered body 200.

[Issues to be resolved by this disclosure]
However, conventionally, it has not been possible to produce a molybdenum alloy material having high ductility.
[Effect of this disclosure]
The above molybdenum alloy material has high ductility.

<Knowledge of the present inventor>
The present inventor has repeated studies for improving the ductility of the molybdenum alloy material. Patent Document 1 describes in paragraphs [0110] to [0113] that a molybdenum plate having a thickness of 0.2 mm, an outer shape of 2.1 mm, a length of 7 mm, and a cup shape having good drawability was obtained. The elongation of this molybdenum alloy material is small. Paragraph number [0127] discloses that the elongation is 10-12% when the angle with respect to the elongation direction is 0 °, 16-18% when it is 45 °, and 6.0-8.0% when it is 90 °. Has been done.

Since the molybdenum sintered material has a brittle grain boundary and an equiaxed structure, cracks easily propagate and ductility is low. In Patent Document 1, an attempt was made to improve ductility by devising plastic working in order to overcome low ductility. As a result, a rolled material having a fibrous structure, improved brittleness at grain boundaries, less likely to propagate cracks, and higher ductility was obtained.

However, the plastic working of Patent Document 1 is cold working. As a result, the slip surfaces of the (111) plane are accumulated. Then, ductility anisotropy occurs, and the elongation in a certain direction is enhanced, but the problem that the elongation in the direction orthogonal to it is small remains, and the improvement in ductility cannot be overcome.

The present inventor has found that ductility is improved by dispersing a large amount _{of zirconia (ZrO 2} ) in a molybdenum alloy in a tetragonal state. The conventional molybdenum alloy material cannot disperse a large amount of tetragonal zirconia in the Mo alloy.

As a result, a molybdenum alloy material having high ductility in the X, Y, and Z directions could be obtained. It is considered that the ductility was improved because the abundance of tetragonal zirconia that expresses the transformation strengthening mechanism in the molybdenum alloy is large. Conventionally, the Mo alloy material has a problem that the elongation at room temperature is small, or the elongation in one direction is high but the elongation in the other direction is small. In rolled materials, the elongation in one direction is high, but the elongation in the other direction is small. The elongation of the molybdenum alloy material in which unstabilized or partially stabilized zirconia is dispersed is small.

The highly ductile molybdenum alloy material can be used for plastic working of complicated shapes. A molybdenum alloy material having high ductility is desired as a measure against cracking of a holder for a hot extrusion die, a cold extrusion die, and the like.

<Molybdenum alloy material of the present disclosure>
[composition]
The composition of the molybdenum alloy material is zirconia = 0.7% by mass or more and 13.6% by mass or less, yttria concentration = zirconia concentration × a, and the balance is impurities of 0.01% by mass or less and molybdenum. Ceria (CeO ₂ ), Calcia (CaO), and Magnesia (MgO) also show the same effect as yttria. Therefore, yttria may be replaced with at least one of ceria, calcia and magnesia.

The content of zirconia is 0.7% by mass or more and 13.6% by mass or less. Within this range, high elongation (the average value in the X, Y, and Z directions is 30% or more) can be obtained.

Preferably, the content of zirconia is 1.3% by mass or more and 8.2% by mass or less. More preferably, it is 1.3% by mass or more and 5% by mass or less. Within this range, the average value of elongation in the X, Y, and Z directions is preferably 35% or more, more preferably 40% or more. If the content of zirconia is less than 0.7% by mass, the amount of zirconia is small and the transformation strengthening is difficult to function. When the content of zirconia exceeds 13.6% by mass, zirconia aggregates and becomes a base point of cracks.

The coefficient a is 0.03 or more and 0.08 or less. When the coefficient a is less than 0.03, a part of zirconia becomes monoclinic. When the coefficient a exceeds 0.08, a part of zirconia becomes cubic.

Accessories (Aluminum (Al), Chromium (Cr), Copper (Cu), Iron (Fe), Manganese (Mn), Nickel (Ni), Lead (Pb), Tin (Sn), Silicon (Si), Sodium (Na) ) And potassium (K)), the total amount is preferably 0.01% by mass or less. If it exceeds 0.01% by mass, impurities may be the starting point of fracture and the mechanical properties may be deteriorated.

[Measurement of composition]
The method for measuring the composition is as follows.

Zirconia is measured by the ICP (Inductively Coupled Plasma) method. Zirconium in the molybdenum alloy was measured using ICPS-8100 type (Shimadzu Corporation), and the converted value was obtained assuming that the total amount of zirconium was zirconia.

Yttria is measured by the ICP method. Y in the Mo alloy was measured using ICPS-8100 type (Shimadzu Corporation), and the converted value was obtained assuming that Y was totally yttria.

For impurities, aluminum, calcium, chromium, copper, iron, magnesium, manganese, nickel, lead, tin, silicon, sodium, and potassium were measured by the ICP method using ICPS-8100 type (Shimadzu Corporation).

Molybdenum was obtained according to the analysis method for molybdenum materials (JIS H 1404: 2001), and from the whole, aluminum, calcium, chromium, copper, iron, magnesium, manganese, nickel, lead, tin, silicon, sodium, It excludes the contents of potassium, ittoria and zirconia.

[X-ray diffraction intensity]
The ratio (11-1) / (111) of the peak height of the (11-1) plane of the zirconia tetragonal T to the peak height of the (111) plane of the zirconia monoclinic crystal M is 10 or more. Within this range, the room temperature elongation can be increased.

The shape of the measurement sample is a rectangular parallelepiped of 10 x 20 x 2 mm. This rectangular parallelepiped is cut out from the sintered body, and the measurement surface is electropolished by the following method, and then XRD (X-ray difficulty) measurement is performed.

The method of electropolishing is as follows.
A mixed solution of methyl alcohol (95%) 100 cm ³ , sulfuric acid (1.84 g / cm ³ ) 10 cm ³ , and hydrofluoric acid (40%) 1 cm ³ is used as the electrolytic solution. A stainless steel cathode was used as the electrode, and a DC current of 50-60 V was passed through 10-20 Sec.

[Measurement of XRD]
The XRD measurement method is as follows.

Measured using X'Part manufactured by PHILIPS. The setting conditions are X-ray tube: Cu tube, primary side optical system (solar slit 0.04 rad, PDS fixed 1/2 °, mask 15 mm, ASS 1 °), light receiving side optical system (FASS 8 mm, solar slit 0.04 rad, Filter Ni, X-ray detector PIXcel), X-ray output was set to 50 mA, 40 kV. The measurement conditions were start angle 20 °, end angle 70 °, step size 0.02, and time per step 20s.

For data processing, use HighScore Plus Ver.3 (PANalytical) and specify the background (minimum significance 1.00, minimum peak chip 0.01, maximum peak chip 1.00, peak base width 2.00, method 2). After the minimum value of the next derivative), peak search, K-Alpha2 separation, automatic background specification, and profile fitting are performed. From the obtained peak intensity curve from which the background was removed, the peak height intensity of the (11-1) plane of the zirconia tetragonal crystal T and the (111) plane of the zirconia monoclinic crystal M was read, and the ratio was calculated.

[Growth]
The average value of elongation of the molybdenum alloy material in the three directions (one direction is set to be 90 ° with respect to the other) is preferably 30% or more. It is more preferably 35% or more, still more preferably 40% or more. Within this range, forging and drawing workability to complicated shapes are improved.

The method for measuring the elongation is as follows.
From the obtained sintered body, a tensile test piece having a thickness of 2 mm, a distance between reference points of 8 mm, and a width of 3 mm was cut out. FIG. 1 is a diagram showing a sintered body 200 and a test piece 100 extending in the x direction cut out from the sintered body 200. FIG. 2 is a diagram showing a sintered body 200 and a test piece 100 extending in the y direction cut out from the sintered body 200. FIG. 3 is a diagram showing a sintered body 200 and a test piece 100 extending in the z direction cut out from the sintered body 200. As shown in FIGS. 1 to 3, the test piece 100 was cut out from a substantially central portion of the cubic sintered body 200.

After polishing the surface of each test piece 100 with # 800 SiC abrasive paper, it is set in an Instron universal testing machine (model number 5867 type), and the crosshead speed is 0 at room temperature (20 degrees) in the atmospheric atmosphere. A tensile test was performed at .32 mm / min. The maximum stress and elongation at break were determined from the stress-strain diagram obtained by the tensile test.

The average tensile strength of the Mo alloy material in the three directions (one direction is set to be 90 ° with respect to the other) is preferably 650 MPa or more. Within this range, it can be used for members that require strength, such as holders for hot extrusion dies. The density of the Mo alloy material is preferably 95% or more. If the density is less than 95%, the void becomes the starting point and cracks occur, so that the ductility may not be improved.

[Measurement of relative density]
The method for measuring the relative density is as follows.

It was measured by the in-liquid weighing method (JIS Z 8804: 2012).
<Manufacturing method of molybdenum alloy material of the present disclosure>
Hereinafter, the manufacturing conditions of the present disclosure will be described.

Manufacturing method of Mo alloy material (1) : Refer to sample 3 and other sample conditions (Table 1).

(1) Powder mixing process of Mo alloy material [raw material powder]
Mo powder manufactured by Allied Material having a Fsss particle size of 5 μm and a purity of 99.9% by the Fisher method was used.

It was added to Mo in the form of zirconium (IV) butoxide (about 85% 1-butanol solution) manufactured by Wako Pure Chemical Industries, and yttrium (III) butoxide solution manufactured by Sigma-Aldrich.

[Weighing / mixing]
Weigh 50.0 g of Mo, 1.28 g of zirconium (IV) butoxide, 0.19 g of yttrium (III) butanol, and 20 cm ^{3 of} solvent: Wako Pure Chemical's butanol solution (99.0%), and use the following method. Wet mixed. Zirconium (IV) butoxide and yttrium (III) butoxide were diluted with butanol in a glove box (humidity of 20% or less). The solution prepared with Mo was put into an alumina mortar and manually mixed with an alumina pestle for 5 to 10 minutes.

The mixed slurry was dried using a hot plate at 80-100 ° C. in an air atmosphere with stirring. This step from weighing to drying was repeated "number of times" in Table 1 to obtain a predetermined amount of powder. For sample numbers 2, 4 to 23, the same steps from weighing to drying were repeated "number of times" in Table 1 to obtain a predetermined amount of powder. For sample number 1, only Mo was weighed according to Table 1.

(2) Mo alloy material molding-sintering process [molding / sintering]
Using a hot press manufactured by Kurata Giken, 300 g of each of the dry powders of sample numbers 1 to 23 was put into a mold of 30 mm × 30 mm, and molded / sintered at ^{1900 ° C × 1 hr, nitrogen atmosphere, 49 kN / cm 2.} did.

The sintering temperature is preferably 1700-1900 ° C. If it exceeds this, the crystal grains may become coarse and the ductility may decrease.

Manufacturing method of Mo alloy material (Part 2) : Sample 30 (see Table 2)

(1) Powder mixing process of Mo alloy material [raw material powder]
Mo powder manufactured by Allied Materials Co., Ltd. having an Fsss particle size of 5 μm and a purity of 99.9% by the Fisher method was used.

As YSZ, YSZ (TZ-3YS-E) powder manufactured by Tosoh Co., Ltd. having a surface area of 7 m ^{2 / g was used.}
[mixture]
985.7 g of Mo powder and 14.3 g of YSZ powder were weighed.

Using an automatic mortar ANM-1000 type (mortar material: alumina) manufactured by Nikko Kagaku, 300 g of Mo powder and 14.3 g of YSZ were mixed for 1 h. Then, 685.7 g of Mo powder and the mixed powder were mixed for 1 hour with an Invar China shaker mixer manufactured by Mitamura RIKEN INDUSTRY. The powder of sample number 30 was obtained.

(2) Mo alloy material molding-sintering process [molding / sintering]
Using a hot press manufactured by Kurata Giken, 300 g of dry powder of sample number 30 was put into a mold of 30 mm × 30 mm, and molded and sintered at ^{1900 ° C. × 1 hr, nitrogen atmosphere, 49 kN / cm 2.}

Manufacturing method of Mo alloy material (Part 3) : Conditions for sample 28 and other samples (see Table 3)

(1) Powder Mixing Step of Mo Alloy Material TMO-10 type Mo powder manufactured by Allied Materials Co., Ltd. having an Fsss particle size of 0.9 μm and a purity of 99.9% by the Fisher method was used.

A zirconia powder manufactured by Nippon Kagaku Ceramics Co., Ltd. with an Fsss particle size of 20 nm by the Fisher method was used.

[mixture]
123.3 g of Mo powder and 1.70 g of zirconia powder were weighed.

Ball mill mixing was performed using a planetary ball mill manufactured by FRITSCH. Weighed powder, balls (material: cemented carbide, φ8 mm balls 160 g, φ40 mm balls 737 g) and alcohol were put into a pot and mixed in an air atmosphere for 50 hours. After mixing, it was naturally dried in the air. This weighing and mixing step was repeated for the “number of ball mills” in Table 3 to obtain a predetermined amount of powder.
(2) Mo alloy material molding-sintering process [molding]
Using a 30 mm × 30 mm mold, powder molding was performed at 200 MPa. As a result, a powder compact was obtained.

[Sintering]
The powder compact was sintered in a hydrogen atmosphere at a temperature of 1000 ° C. for 2 hours. Furthermore the green compact _H 2 -Ar gas mixture _(H 2: 10vol%) atmosphere, and sintered for 1 hour at a temperature 1600 ° C.. The sintered body was pressurized by HIP (Hot Isostatic Pressing) under the conditions of an argon atmosphere, a temperature of 1500 ° C., and a pressure of 100 MPa for 1 hour. Then, the sintered body was heat-treated in a hydrogen-argon mixed gas at a temperature of 1400 ° C. for 1 hour. As a result, a molybdenum alloy material was obtained.

Molybdenum alloy materials were obtained for Sample Nos. 24 to 27 and 29 by the same method. In Sample Nos. 24 to 26, YSZ was used instead of zirconia. As YSZ, YSZ (TZ-3YS-E) powder manufactured by Tosoh Co., Ltd. having a surface area of 7 m ^{2 / g was used.}

[Evaluation of alloy composition, alloy density and XRD characteristics]
The alloy composition, alloy density and XRD characteristics of the molybdenum alloy materials of sample numbers 1 to 30 produced in Tables 1 to 3 are described in the paragraphs of [Measurement of composition], [Measurement of relative density] and [Measurement of XRD] above. Measured according to description. The results are shown in Tables 4 to 6.

In Table 4, "T / M ratio (XRD peak intensity ratio of alloy)" means the peak height of the (11-1) plane of the zirconia tetragonal T and the peak of the (111) plane of the zirconia monoclinic crystal M. The ratio to the height (11-1) / (111) is shown.

The molybdenum alloys of sample numbers 1 to 30 were used as sintered bodies 200 as shown in FIGS. 1 to 3, and a test piece 100 was cut out from the sintered body 200, and the elongation at break and the maximum stress were measured. The results are shown in Tables 7 to 9.

In Tables 7 to 9, the content of zirconia is 0.7% by mass or more and 13.6% by mass or less, the content of yttria is 0.03 times or more and 0.08 times or less of the content of zirconia, and X. In line diffraction, the ratio (11-1) / (111) of the peak height of the (11-1) plane of the zirconia tetragonal T to the peak height of the (111) plane of the zirconia monoclinic crystal M is 10 or more. It was found that there was an excellent elongation at break and a high level of maximum stress.

It should be considered that the embodiments and examples disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

100 test pieces, 200 sintered body.

Claims

High ductile molybdenum alloys include molybdenum, zirconia and yttria.
The content of zirconia is 0.7% by mass or more and 13.6% by mass or less, and the content of yttria is 0.03 times or more and 0.08 times or less of the content of zirconia.
In X-ray diffraction, the ratio (11-1) / (111) of the peak height of the (11-1) plane of the zirconia tetragonal T to the peak height of the (111) plane of the zirconia monoclinic crystal M is 10 or more. High ductility molybdenum alloy material.
The highly ductile molybdenum alloy material according to claim 1, wherein the content of zirconia is 1.3% by mass or more and 8.2% by mass or less.
The highly ductile molybdenum alloy material according to claim 2, wherein the content of zirconia is 1.3% by mass or more and 5% by mass or less.
The highly ductile molybdenum alloy material according to any one of claims 1 to 3, which contains impurities and the total amount of impurities is 0.01% by mass or less.
The highly ductile molybdenum alloy material according to claim 4, wherein the impurities include at least one of aluminum, chromium, copper, iron, manganese, nickel, lead, tin, silicon, sodium, and potassium.