JPWO2013018714A1 - Transition metal carbide-containing alloy manufacturing method, transition metal carbide-containing tungsten alloy, and alloy manufactured by the manufacturing method - Google Patents

Abstract

Alloys, especially alloys with significantly improved low temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement by introducing a recrystallized microstructure into tungsten material and significantly strengthening weak grain boundaries in the recrystallized microstructure Develop materials. At least one selected from carbides of Group IVA, Group VA or Group VIA transition metals and a metal raw material are mechanically alloyed, and the raw material powder obtained in the mechanical alloying step is sintered by hot isostatic pressing. The alloy obtained in the step of subjecting the alloy obtained in the sintering step to plastic deformation of 60% or more at a strain rate of 500 ° C. or more and 2000 ° C. or less, 10 −5 s −1 or more and 10 −2 s −1 or less. By manufacturing, an alloy material in which low temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement are greatly improved can be obtained.

Description

  The present invention relates to a transition metal carbide-containing alloy manufacturing method, a transition metal carbide-containing tungsten alloy, and an alloy manufactured by the above manufacturing method, and in particular, superplastic deformation is exerted on the alloy to develop superplasticity due to intergranular cracking. , A method for producing an alloy that has a high recrystallization fracture strength and has a recrystallized structure, so that there is little decrease in strength and ductility even when heated to a high temperature, and low temperature brittleness, recrystallization brittleness and neutron irradiation brittleness can be remarkably improved And an alloy produced by the production method, particularly a tungsten alloy.

  Tungsten and tungsten alloys have numerous advantages that other metals cannot follow, such as having the highest melting point of 3410 ° C. among metals. However, since the problem of embrittlement (low temperature embrittlement, recrystallization embrittlement, irradiation embrittlement) has not been solved for many years, it has never been used as a structural material so far, and it can be used as a high temperature structural material in an extreme environment. Is blocked.

  All of these embrittlements are caused by “grain boundary embrittlement” in which the crystal grain boundaries are weak and are easily broken from the grain boundaries. The cause of grain boundary embrittlement is tungsten, which is the metal with the strongest degree of covalent bonding. In addition to the fact that grain boundaries are inherently high energy and weak (easy to break), intrusion type in air such as nitrogen and oxygen Since the gas element has an extremely low solid solubility in tungsten, it tends to segregate and precipitate at the grain boundary, further weakening the grain boundary and promoting embrittlement.

  As a result, as shown in FIG. 1A, a normal metal undergoes plastic deformation (permanent deformation) before it breaks, so that almost the entire temperature range becomes the ductile temperature region. On the other hand, as shown in FIG. 1B, tungsten has a covalent bond with a very strong interatomic bond direction, so that the grain boundary is essentially weak, causing a ductile brittle transition and ductile brittleness. The transition temperature (ductile-britlet transition temperature, hereinafter abbreviated as “DBTT”) is also high. Therefore, the lower the temperature at which the Peierls stress (yield strength) required for the motion of screw dislocations in tungsten rises sharply (low temperature embrittlement), and it becomes more prominent in the recrystallized structure where extremely weak grain boundaries are formed. (Recrystallization embrittlement). Furthermore, when irradiation defects are introduced by irradiation with high-energy particles such as neutrons, dislocation rolling is inhibited by the accumulation of irradiation defects within the crystal grains and at the grain boundaries, which further promotes grain boundary embrittlement. (Irradiation embrittlement).

  Therefore, in order to improve low temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement at the same time, a recrystallized microstructure containing high-density sites (sinks: grain boundaries and dispersed particles) that can eliminate irradiation defects is introduced. However, it is necessary to change weak grain boundaries in the recrystallized microstructure to extremely strong grain boundaries that are difficult to break.

In order to solve the problems of embrittlement due to neutron irradiation and recrystallization of tungsten, and low temperature embrittlement, the present inventors mechanically alloyed W-TiC having ultrafine crystal grains in an Ar atmosphere and an H ₂ atmosphere ( (MA) method and hot isostatic pressing (HIP) method, it has been found that effects such as improved room temperature toughness can be obtained (see Non-Patent Documents 1 and 2). However, even the tungsten material produced by the above method is still not sufficient for practical use.

  On the other hand, as a method for improving the durability and the like of a refractory metal, a refractory metal such as Mo, W, Nb, Ta, V, and Cr has a melting point of 1500 ° C. or higher and a particle size ≦ 1.5 μm. By containing 0.005 to 10% by mass of one or several compounds or mixtures selected from the group of oxides, nitrides, carbides, borides, silicates or aluminates of It is known to improve (see Patent Document 1). However, what is disclosed in Patent Document 1 is to improve the heat resistance and creep resistance of a refractory metal at a high temperature, and does not improve low temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement. .

  Further, the present inventors have dispersed molybdenum alloy ultrafine particles of IVa group transition metal carbide having a particle size of 10 nm or less in a molybdenum alloy by 0.05 mol or more and 5 mol% or less, and having a crystal particle size of 1 μm or less. The inventors have found that the strength of the alloy can be increased, and that the strength is hardly lowered even when heated to a high temperature, and that low temperature brittleness, recrystallization brittleness and neutron irradiation brittleness can be improved, and a patent application has been filed (see Patent Document 2). However, molybdenum described in Patent Document 2 is a material that exhibits ductility at room temperature even if it is a pure metal, and has a melting point that is 800 ° C. higher than that of molybdenum and is an extremely brittle material. Is a material with completely different properties and manufacturing conditions.

  Further, in Patent Document 2, in order to improve ductility, molybdenum requires the introduction / existence of a work deformation structure by plastic working (forging, rolling, etc.). As a result, the recrystallization temperature is lowered and anisotropy occurs. On the other hand, tungsten is related to ductility improvement in a recrystallized state that does not include any work-deformed structure, and therefore has no anisotropy, and therefore is essentially different.

JP-T-1-502680 JP-A-8-85840

Outline of the Japan Institute of Metals, Vol. 148, p235 Outline of the Japan Institute of Metals, Vol. 143, p322

  The present inventors conducted extensive research and found that transition metal carbide-containing alloys produced by mechanical alloying (MA) method and hot isostatic pressing (HIP) method were further crushed by grain boundaries by superplastic deformation. By re-strengthening the recrystallized random grain boundaries, it is possible to introduce a recrystallized microstructure into the alloy and reinforce the weak grain boundaries in the recrystallized microstructure, resulting in low temperature embrittlement, It was found that recrystallization embrittlement and irradiation embrittlement were greatly improved. In addition, the recrystallization random grain boundary strengthening process using grain boundary cracking due to superplastic deformation can be applied to all alloys, but among them, it is effective in improving the brittleness of tungsten, which is extremely brittle. Also found new. The present invention has been made based on these new findings.

  That is, an object of the present invention is to provide a method for producing a transition metal carbide-containing alloy in which low temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement are greatly improved. Another object of the present invention is to provide an alloy produced by the production method. Furthermore, another object of the present invention is to provide a transition metal carbide-containing tungsten alloy in which low temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement are greatly improved.

  The present invention relates to a method for producing a transition metal carbide-containing alloy, a transition metal carbide-containing tungsten alloy, and an alloy produced by the production method described below.

(1) At least one selected from carbides of group IVA, group VA or group VIA transition metal and a metal material mechanically alloyed, hot isostatic pressing of the raw material powder obtained in the mechanical alloying step The alloy obtained in the sintering step and the alloy obtained in the sintering step is subjected to plastic deformation of 60% or more at a strain rate of 500 ° C. or more and 2000 ° C. or less, 10 ⁻⁵ s ⁻¹ or more and 10 ⁻² s ⁻¹ or less. A method for producing an alloy comprising the steps of:
(2) The method for producing an alloy as described in (1) above, including a step of degassing the carbide and metal raw material of the transition metal by heating before the step of mechanical alloying.
(3) In a tungsten alloy containing at least one selected from carbides of Group IVA, Group VA, and Group VIA transition metals in an amount of 0.25 mass% to 5 mass%, the oxygen content is 950 mass ppm or less, and the nitrogen content The amount is 60 mass ppm or less, 80% or more of the area ratio of the tungsten phase is equiaxed grains having a grain size of 0.05 μm or more and 10 μm or less, and a ductile brittle transition temperature by three-point bending is 500 K or less, Tungsten alloy characterized by being capable of plastic deformation above temperature.
(4) The carbide orientation in the tungsten alloy structure and 90% or more of the orientation of the tungsten matrix are carbides of {111} W // {110} transition metal, <110> W // <111> transition The tungsten alloy according to (3) above, which has a (Kurdjumov-Sachs) orientation relationship of a metal carbide.
(5) The full width at half maximum of the diffraction surface (220) reflection in X-ray diffraction is 3 ° or less, or the number of dislocations in the crystal grains is 50 or less by observation with a transmission electron microscope (3) Or a tungsten alloy according to (4).
(6) The tungsten alloy according to any one of (3) to (5) above, wherein the maximum bending strength by three-point bending is 1470 MPa or more.
(7) An alloy produced by the production method described in (1) or (2) above.

  According to the present invention, transition metal carbide and alloy powder are processed by mechanical alloying (MA) method and hot isostatic pressing (HIP) method, and further, superplastic deformation that can maximize the use of grain boundary wrinkling. (1) Grain boundary strength (intergranular bond strength) of alloys in recrystallized structure, especially tungsten, by promoting and optimizing carbide grain boundary precipitation and grain boundary segregation in recrystallized fine grain structure Can be achieved, and high strength and toughness can be realized. (2) Since it is originally in a recrystallized state, there is little change in structure even when heated to high temperatures, so there is very little reduction in strength and ductility, and there is a risk of recrystallization embrittlement. (3) Irradiation embrittlement can be greatly improved. (4) When tungsten is used as the alloy, the crystal grain size of the tungsten alloy grows to about 0.05-10 μm, so the yield point. Moderately lowered That effect is given, it can be plastically deformable tungsten alloy in the vicinity of room temperature, an effect equal.

FIG. 1 is a diagram showing the relationship between the strength and temperature of normal metal and tungsten. FIG. 2 is a diagram showing the principle of superplastic deformation. FIG. 3 is a diagram showing an outline of plastic working for the purpose of introducing a work deformation structure using dislocations as carriers, and as a result, lowering the recrystallization temperature and causing anisotropy. FIG. 4 is a diagram showing an outline of the GSMM process. FIG. 5 shows the three-point bending deformation behavior of Example 4 (DBTT: 310K) and Example 6 (DBTT: 420K) at a temperature of 400K. FIG. 6 shows the three-point bending deformation behavior of Example 4 at 300K. FIG. 7 shows X-ray diffraction patterns of Example 2 (GSMM-treated) and Comparative Example 1 (no GSMM-treated). FIG. 8 is a photograph-substituting drawing and shows transmission electron micrographs of Comparative Example 1 and Example 2. FIG. 9 shows X-ray diffraction patterns of as-HIP bodies before the GSMM treatment of Example 5 (GSMM-treated) and Example 5. FIG. 10 is a photograph-substituting drawing and is a transmission electron micrograph of the tungsten alloy of Example 2.

  The present invention includes a step of degassing the raw material by heating, if necessary, and a step of mechanically alloying (MA) the raw material obtained in the degassing step (hereinafter sometimes referred to as “MA step”). The raw powder obtained in the mechanical alloying step is sintered (HIP) by hot isostatic pressing (hereinafter sometimes referred to as “HIP step”), and obtained in the sintering step. The obtained alloy may be described as a process of strengthening a recrystallized random grain boundary using superplastic deformation (hereinafter referred to as a “GSMM process”. Grain boundary is a grain boundary). Abbreviation of Sliding-based Microstructural Modification)), and further, according to the method Manufactured alloy is characterized by a particularly tungsten alloy. The present invention will be described more specifically.

First, the raw material used for this invention is demonstrated. Examples of transition metal carbides used in the present invention include transition metal carbides selected from the group IVA, VA, and VIA. Particularly, the carbides are formed before the brittle W ₂ C in which the diffusion rate of the constituent elements is high and brittle. Titanium carbide, zirconium carbide, niobium carbide, tantalum carbide, and the like are preferable because they are easily formed or the formed carbide is thermally stable. These Group IVA, Group VA and Group VIA transition metal carbides (hereinafter sometimes simply referred to as “transition metal carbides”) may be used alone or in combination.

  The amount of transition metal carbide added to the alloy is preferably 0.25% by mass or more and 5% by mass or less. If the added amount of transition metal carbide is less than 0.25% by mass, the effect of suppressing the strengthening of the grain boundaries and the movement of the grain boundaries at high temperatures is poor, and the recrystallization temperature is increased or the crystal grains after recrystallization Not only is the effect of suppressing coarsening poor, but the improvement of low-temperature brittleness, recrystallization brittleness, and neutron irradiation brittleness, and high-temperature strength are insufficient. On the other hand, if the added amount of transition metal carbide exceeds 5% by mass, the alloy becomes brittle, which is not preferable.

Examples of raw materials for alloys other than transition metal carbide include at least one selected from tungsten, molybdenum, vanadium, yttrium, chromium, niobium, tantalum, titanium, zirconium, hafnium, etc., or stainless steel, iron, etc. The manufacturing method of the invention is particularly useful for Group VIA transition metals such as tungsten. The alloy raw material powder preferably has a Fischer particle size of 2 μm or more. This will be described in detail in the manufacturing method described later. If the oxygen or nitrogen concentration in the manufactured alloy is high, it is necessary to (1) greatly improve low temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement. Inhibits grain boundary precipitation and segregation of certain transition metal carbides, (2) promotes the formation of W ₂ C, which itself is brittle and acts as a starting point for fracture, (3) pores where oxygen and nitrogen act as a starting point for fracture It is because it forms. Therefore, in order to strengthen weak grain boundaries in the recrystallized microstructure in the alloy, it is essential to keep the oxygen and nitrogen contents contained between the powders of the alloy raw material low, and a degassing step described later In addition to the above, it is preferable that the raw material has the above-mentioned particle size. However, it is not necessarily 2 μm or more, and may be 1 μm or less as long as the atmosphere management is performed so as to suppress impurity contamination.

Next, each process of the manufacturing method of this invention is demonstrated. The process of degassing the raw material by heating is a process performed to reduce the oxygen and nitrogen content finally contained as impurities in the alloy. In the raw material powder preparation stage, air (especially moisture) in the raw material powder. It is for performing sufficient deaeration. In this degassing step, the degree of harmfulness caused by oxygen and nitrogen varies depending on the metal material, and therefore the degassing conditions may be adjusted as appropriate depending on the metal material. For example, vanadium absorbs and dissolves oxygen and nitrogen and becomes brittle (environmental embrittlement) even when heated in an ultra-high vacuum, so the deaeration process is performed at a considerably low temperature or unnecessary, and SUS316L Then, it is not necessary to carry out strictly. On the other hand, in the case of tungsten, as described above, oxygen and nitrogen remaining in the alloy precipitate and segregate at weak recrystallized grain boundaries to promote grain boundary embrittlement (recrystallization embrittlement), For example, when using a commercially available tungsten powder as a raw material, it forms a pore and acts as a starting point of destruction. For example, a container for preparing a raw material powder (produced with Mo or the like for mounting powder) It is desirable that the raw material powder is evacuated to 10 ⁻⁴ Pa or less and the raw material powder is deaerated at 800 ° C. to 1,500 ° C. in a state where the raw material powder is placed on the boat. However, for example, when using tungsten having a sufficiently low oxygen and nitrogen concentration as a raw material, such as an ultra-high purity W powder manufactured by Plansee Japan Co., Ltd., an inert gas or a reducing gas (such as moisture contained in both) It is possible to omit the deaeration step by eliminating the mixing of oxygen and nitrogen, such as by opening the raw material in an atmosphere) and performing the MA step.

  The degassing time is desirably 120 minutes if 800 ° C. or higher, and 90 minutes or more if 950 ° C. or higher. When the degassing temperature is less than 800 ° C., gas desorption is not sufficient, and when it exceeds 1,500 ° C., a reaction with a degassing container (a boat made of Mo or the like) is likely to occur. Undesirably, after the aggregation starts, another problem occurs in the subsequent process.

  In the case of a tungsten alloy, the oxygen content in the produced alloy is 950 ppm or less, preferably 850 ppm or less, more preferably 300 ppm or less, and the nitrogen content is 60 ppm or less, preferably 50 ppm or less. When the content of oxygen and nitrogen in the alloy is not more than the above numerical values, it is possible to produce a densified alloy. Note that oxygen and nitrogen in the tungsten alloy are contained in the raw material powder stage at about three times as much as the finally produced alloy. Therefore, in terms of process management, it is desirable to manage the process so that oxygen is about 3000 ppm or less and nitrogen is about 180 ppm or less at the end of the raw material powder deaeration process.

  After the deaeration process, the MA process is performed. In this MA process, the raw material is further powdered, and until the powder is encapsulated and HIPed, it can be operated in an inert gas or reducing gas atmosphere to prevent oxygen and nitrogen contamination. preferable. Examples of the inert gas include Ar, helium, and neon, and examples of the reducing gas include hydrogen.

  In the MA process, mechanical high energy is imparted to the alloy and the transition metal carbide raw material powder, so that the transition metal carbide is homogeneously decomposed and dissolved in an atomic form in the alloy structure of the parent phase, and at the same time, the parent phase. In the process for producing the (alloy) ultrafine-grained powder, for example, a three-axis vibration ball mill, a planetary ball mill, an attritor or the like is used. In the MA treatment, usually, balls and raw material powder are placed in a pot, and the pot is rotated or vibrated on a ball mill mount to mechanically impart high energy to the raw material powder. Even systems that do not dissolve in equilibrium can be forcibly dissolved, and crystal grains can be made ultrafine (10 to 30 nm) at room temperature. In addition, in order to remove impurities on the inner wall and ball surface of the pot used in the MA process, only the pot and the ball are vacuum heated at 150 to 200 ° C. for 3 to 10 hours before putting the raw material powder into the pot. Also good.

  The processing conditions of the MA process, that is, the processing time, the number of revolutions, the material of the ball, the diameter, the mass ratio of the total mass of the ball and the total mass of the raw material powder, the ratio of the total internal volume of the container and the total volume of the ball, The transition metal carbide is uniformly decomposed and dissolved in the alloy, the crystal grain size of the parent phase metal is made ultrafine, and the effect of mixing the container and ball material into the raw material powder during the MA process is suppressed. In order to suppress the mixing amount to a negligible amount, or even if mixing does not affect the subsequent material properties, conditions may be set as appropriate.

In the HIP process, the MA powder produced in the MA process is isotropically pressurized with Ar gas, while the alloy powder refined in the MA process has a relatively low temperature at which it is difficult for grains to grow and is harmful to the alloy. Sintering without exposure to the atmosphere composed of impurities precipitates and segregates transition metal carbides that were forcibly dissolved during the MA process, and prevents the growth of ultrafine grains due to its pinning effect, and recrystallization This is a process for producing equiaxed ultrafine grains of an alloy matrix in which transition metal carbides are grain boundary precipitated and segregated without distortion. Specifically, MA powder is sealed in a metal container made of mild steel, SUS, Ti, Nb, Ta or the like in the above-described inert gas or reducing gas atmosphere, and the sealed gas is exhausted thoroughly (vacuum degree). Is usually 10 ⁻⁴ to 10 ⁻⁶ Pa), and then sintered at 1350 to 1400 ° C. and 100 to 1000 MPa for 1 to 5 hours to obtain an alloy having the above structure. In addition, in order to remove impurities on the inner wall of the metal container used in the HIP process, the metal container alone may be vacuum heated at 500 to 1000 ° C. for 1 to 3 hours before putting the MA powder into the metal container. Good.

  The GSMM process replaces weak grain boundaries in the recrystallized microstructure with strong heterogeneous interfaces with transition metal carbides or strong grain boundaries where transition metal carbide constituents are precipitated and segregated. Precipitation and knitting at the boundary increases the grain boundary bonding force, so the fracture strength increases and the effect of improving brittleness is obtained. In addition, the GSMM process increases the crystal grain size to an appropriate size to lower the yield strength (deformation strength) and make ductility easier (reducing the burden on the grain boundaries), and residual pores that tend to act as a starting point for fracture In addition to the effect of removing (1 to 3% after HIP), a dispersion strengthened alloy containing precipitates (vanadium, stainless steel, etc.) also has an effect of strengthening the interface (boundary surface) with different types of precipitates. In the present invention, in order to promote and optimize grain boundary precipitation / segregation of transition metal carbide, the effect of grain boundary waviness at high temperature is used. FIG. 2 is a diagram showing the principle of superplastic deformation due to grain boundary wrinkling. Grain boundary wobbling means that when a shear stress τ is applied to the crystal structure of FIG. 2 (1), FIG. 2 (2) → (3) → As shown in (4), it means that the crystal is displaced and deformed while maintaining the equiaxed shape without generating or disappearing the crystal grain. By repeating such grain boundary cracking a very large number of times, transition metal carbide precipitates and sinters at the grain boundary, and the fracture strength at the weak recrystallized grain boundary exceeds the yield strength (deformation strength). As a result of the increase, the alloy becomes elongated.

  However, grain boundary cracking is a non-uniform deformation and conversely promotes embrittlement by the formation of cracks at the grain boundary triple point accompanying grain boundary cracking (high temperature embrittlement generally seen in copper alloys and the like). Therefore, it is very important in the present invention to use superplastic deformation that has a very large amount of deformation until breakage and that can make the most of grain boundary cracking. As described above, grain boundary cracking is a non-uniform deformation, and usually embrittlement is promoted by crack formation at the triple point of grain boundary accompanying grain boundary cracking. However, the superplastic deformation of the present invention can be achieved by setting the temperature and strain rate (the amount obtained by dividing the test piece deformation rate by the size of the test piece to correct the strain) under certain conditions described later. A relaxation mechanism that does not progress to the formation of cracks works, and elongation of several hundred percent occurs. In order to promote and optimize the grain boundary precipitation / segregation of transition metal carbide, it is more effective to perform GSMM for a longer time than to perform for a short time.

  As described above, superplastic deformation is a deformation mode in which elongation of several hundreds of percent occurs due to intergranular breakage and can maintain equiaxed crystal grains even after deformation. `` Transition and rotation of crystal grains due to active grain boundary movement promotes and optimizes transition metal carbide grain boundary precipitation and grain boundary segregation, and maintains an isotropic recrystallized structure with little anisotropy. '' Is possible. In the present invention, this “strengthening treatment method of recrystallized random grain boundaries using superplastic deformation capable of maximizing the use of grain boundary wrinkling” is defined as GSMM (Grain boundary Sliding-based Microstructural Modification).

  Fig. 3 shows a wide range of applications, including tungsten, which has been widely used for high toughness. The purpose is to introduce a deformed structure using dislocations as a carrier. It is a figure which shows the outline of the "plastic processing to bring." “Dislocation” means a linear lattice defect, and the characteristics of the plastic working are (1) that a specific crystallographic surface can slide in a specific crystallographic direction with a small stress, and (2) a slip. It has a new ability to multiply dislocations in the process of movement, and (3) an elastic strain field (for example, an elastic strain that occurs around different sizes of different atoms, and all the dislocations have an elastic strain field around them) And has a very strong interaction. For this reason, as shown in FIGS. 3 (1) and (2), when deformation is applied by applying a tensile stress to the material, the material is warped as shown in FIG. 3 (3), and dislocations are generated in the material. As a result, the density of dislocations increases, and as a result, the stress necessary for further sliding movement of the dislocations, that is, the stress for plastic deformation of the alloy increases to reach the breaking strength, and FIG. ) As shown in FIG. “Structure with increased dislocation density due to deformation” is called a processed deformed structure or processed structure, but increasing the dislocation density means increasing the strain field inside the material (crystal), resulting in a high internal energy. And materials with a high internal energy state are easy to release internal energy, so if you add heat (increase the temperature), the internal energy will be released with a little heat (with a slight increase in temperature). One process is recrystallization. Therefore, the recrystallization temperature decreases in the processed structure. Note that many of the upper limits of elongation by “plastic processing that aims to introduce a work deformation structure using dislocations as a carrier and as a result lowers the recrystallization temperature and causes anisotropy” is about several tens of percent, especially when it is elongated. But it is much smaller than 100%.

  On the other hand, in the superplastic deformation due to grain boundary, the recrystallized grain structure with less strain is maintained after the deformation, so that the internal energy basically does not increase. In the GSMM process of the present invention, the crystal grains grow (increased by an order of magnitude) because the processing is performed at a temperature higher than the HIP temperature. Internal energy will also be high, and grain growth will reduce internal energy.

  As described above, the GSMM of the present invention is a new structure control method that achieves high toughness by strengthening weak recrystallized grain boundaries that are the cause of grain boundary embrittlement. Are essentially different, and the fracture strength and elongation to fracture of the alloy after treatment are completely different.

In the GSMM process, as shown in FIG. 4, the alloy produced in the HIP process is sandwiched between BN—SiC composite plates, and a high temperature of 500 ° C. to 2000 ° C. (40% of the melting point of each alloy measured at an absolute temperature). It is performed by applying a pressure at a strain rate of 10 ⁻⁵ s ⁻¹ to 10 ⁻² s ⁻¹ and applying plastic deformation of 60% or more. The temperature is preferably adjusted as appropriate according to the melting point of each alloy as described above. For example, in the case of tungsten and molybdenum, 1200 ° C to 2000 ° C is preferable, and tungsten is more preferably 1400 ° C to 2000 ° C. . In the case of vanadium or SUS316L, a temperature of 800 ° C. to 1500 ° C. is preferable. In the case of tungsten, if the temperature is less than 1400 ° C., the alloy may break during compression deformation, and if it exceeds 2000 ° C., the industrially produced apparatus becomes undesirably large. Further, if the strain rate is slower than 10 ⁻⁵ s ⁻¹ , there is an effect, but it takes too much time, so it is not industrial, and if it is larger than 10 ⁻² s ⁻¹ , the alloy may be destroyed, which is not desirable. Note that the plastic deformation of 60% or more means that the elongation (strain) of the test piece due to plastic deformation is 60% or more, and the elongation is the length (ΔL) of the test piece extended to the initial length (ΔL). Divided by L) and multiplied by 100 to display%. As long as the above-mentioned temperature, strain rate, and plastic deformation can be imparted, tensile deformation or torsional deformation may be used instead of pinching with a plate.

  The transition metal carbide is necessary for maintaining the crystal grains of the alloy matrix as dispersed particles and developing superplastic deformation. Also, the transition metal carbide / alloy matrix (matrix) heterophase interface satisfies the Kurdjumov-Sachs orientation relationship, thereby forming a high-strength heterophase interface. When tungsten is used as the alloy raw material, the orientation of transition metal carbide existing in the tungsten alloy structure and 90% or more of the orientation of the tungsten matrix is {111} W // {110} transition metal carbide, <110> It is desirable to have a (Kurdjumov-Sachs) orientation relationship of W / <111> transition metal carbonization. If there are 10% or more of transition metal carbide particles not satisfying the Kurdjumov-Sachs orientation relationship, sufficient maximum bending strength (about 1470 MPa) cannot be obtained at room temperature.

  The crystal grain size of an alloy produced by the production method of the present invention, particularly a tungsten alloy, grows to about 0.05 to 10 μm. As a result, the effect of appropriately lowering the yield point is imparted, and a tungsten alloy that can be plastically deformed even near room temperature can be obtained. In the case of a tungsten alloy, the ductile brittle transition temperature (non-ductile transition temperature: DBTT) by three-point bending can be lowered to about 500 K by being produced by the production method of the present invention, and above the ductile brittle transition temperature, Plastic deformation is possible.

  The crystal grain size can be determined by subjecting a photograph taken with a general transmission electron microscope from the central portion of the sample cross section to image processing using commercially available image processing software (for example, Image Pro). The average particle size may be obtained only for the tungsten phase. Since average information could be obtained by counting tungsten crystal grains having an area ratio of 80% or more, it was measured statistically.

  In regions where the area ratio is less than 20%, it is difficult to count tungsten crystal grains (because it is difficult to see the crystal grain boundaries that are the boundaries of the crystal grains, it is difficult to judge whether they should be regarded as crystal grain boundaries, and if they are counted finely, etc.) Even if there is such a problem, the characteristics of each material can be clarified as long as the average tungsten particle size in a region with an area ratio of 80% or more can be calculated. The crystal grain size can be measured as a stable average grain size by counting approximately 300 or more tungsten crystal grains and calculating the area. In short, the crystal grain size can be measured in a wide area of 80% or more of the total field of view of many photographs taken with a transmission electron microscope. As a result, 80% or more of the measured crystal grains have a grain size of 0.05 to 10 μm. If it is in range.

  If the average particle size is less than 0.05 μm, the yield strength becomes extremely high, so that plastic deformation becomes extremely difficult, the yield of processing and manufacturing decreases, and it is not industrial. On the other hand, even when the average particle diameter exceeds 10 μm, plastic deformation is extremely difficult to occur. In order to enable plastic deformation near room temperature, it is necessary to appropriately adjust the processing rate range to be within an appropriate range during plastic deformation for high toughness (that is, during GSMM processing). In order to reduce the average particle diameter, the temperature during GSMM treatment may be lowered. To increase the average particle diameter, the temperature during GSMM treatment may be increased.

  One of the points to be noted in the present invention is that excellent properties (breaking strength, ductility, etc.) could be obtained in a structure in which sufficient recrystallization occurred, which is anisotropic as a metal structure. This is because there are no equiaxed grains. The equiaxed crystal grain in the present invention means that the aspect ratio (ratio of length and width of crystal grains) is 2 or less when the metal structure is observed two-dimensionally in any cross section. .

  The alloy manufacturing method and the manufactured alloy shown in the following examples are uniaxial simple compression deformations as shown in FIG. 4, but they can realize superplastic deformation that can make maximum use of grain boundary deformation. For example, it is not limited to simple tension compression. Depending on the required shape of the alloy member, for example, if it is a plate shape, it is possible to apply rolling reduction.

<Identification of the amount of transition metal carbide required for the development of superplasticity>
<Experiment 1>
Add a TiC powder (manufactured by Soekawa Riken Co., Ltd.) with an average particle diameter of 0.7 μm to tungsten powder (manufactured by Allied Materials Co., Ltd.) with an average particle diameter of 4 μm by the Fischer method, put it in a molybdenum boat Degassing was performed by heating at 950 ° C. for 1.5 hours in a hydrogen atmosphere under high vacuum (<1 × 10 ⁻⁴ Pa). Next, in a hydrogen atmosphere, the mixture was mixed in a TZM (titanium, zirconium-containing molybdenum alloy) container (pot) and a triaxial vibration type ball mill (Topology Systems TKMAC1200) for 70 hours at a rotational speed of 360 rpm. Ing (MA) treatment. In addition, in order to specify a suitable addition range of the TiC powder, eight samples were subjected to MA treatment so that the content of the TiC powder was 0 to 6.0% by mass.

  Next, the MA-treated powder was placed in a molybdenum boat and heated at 950 ° C. under high vacuum for 1.5 hours to degas hydrogen mixed in the tungsten and TiC powder during the MA treatment. The deaerated powder was sealed in a HIP capsule (made of mild steel) and vacuum-sealed, and then subjected to HIP treatment at 1350 ° C. and 196 MPa for 3 hours in an argon gas to obtain a sintered body. Hereinafter, the obtained sintered body is referred to as “as-HIP body”.

From this as-HIP body, dimensions 0.4 × 4 × 16 mm (parallel portion length: 5 mm. T. Kuubara, H. Kurishita, M. Hasegawa, Development of an Ultra-Fine Grained V-1.7 mass% Y Alloy Disp. With Yttrium Compounds Having Superior Ductility and High Strength, Mater. Sci. Eng. A 417 (2006) 16-23. The entire surface was mechanically polished with water-resistant paper (up to # 1500) and the four edges were chamfered, and then mounted on a tensile test piece jig to perform a high temperature tensile test. The tensile test jig is a shoulder support (R part) type of the test piece, and alignment is guaranteed by a method that converts the compression load on the jig into the tensile load on the test piece, so that the test piece can be mounted on the jig with a single touch. Is possible. The test piece was heated by high frequency induction heating using a graphite susceptor, and the surface temperature of the test piece was constantly observed and recorded with a two-color radiation thermometer (Chino, model 1R-AQ). In the tensile test, an electric actuator type testing machine R1362 manufactured by Instron was used, and the initial strain rate was 5 × 10 ⁻⁴ / s (crosshead speed: 0.0025 mm / s) at three temperatures of 1500 ° C., 1600 ° C., and 1700 ° C. s) It was performed under a vacuum of 5 × 10 ⁻⁴ Pa or less, and the load weight and elongation (%) accompanying the tensile test were measured. When the oxygen and nitrogen concentrations in the samples were measured using the infrared absorption and thermal conductivity method of LECO-TC600, the oxygen concentration of each sample was 850 ppm or less and the nitrogen concentration was 50 ppm or less. The results are shown in Table 1. In the table, “> 160” means that the material does not break even if it is deformed by 160%.

<Experiment 2>
The test was performed in the same manner as in Experiment 1 except that the hydrogen in Experiment 1 was changed to argon and nine samples were used in which the TiC content was partially changed. The results are shown in Table 2.

  From the above Experiment 1 and Experiment 2, the amount of TiC necessary for the development of superplasticity at 1600 ° C. to 1700 ° C. (the elongation at break is 100% or more) is 0 for the as-HIP body of the hydrogen atmosphere MA-treated powder. It was found to be 0.7-5% by mass in an as-HIP body in an argon atmosphere at 25-5% by mass. When the amount of TiC is less than these ranges, the weak grain boundaries occupy the majority of the grain boundaries of the tungsten phase, and the presence of second phase grains that suppress the grain boundary migration is rare, so the grain growth of the tungsten phase. Becomes faster and the crystal grains become coarser. The TiC phase is indispensable for the maintenance of fine equiaxed grains necessary for superplastic deformation and the rotation and movement of grains during grain boundaries. When the grain boundary cracking that is uniform deformation occurs, a grain boundary crack is formed and grows, and the breaking strain is reduced.

  On the contrary, when the amount of TiC exceeds these ranges, the contact frequency between the TiC phases increases, and the existence ratio of the TiC / TiC interface increases. The TiC phase is considered to have a lower plastic deformability than the tungsten matrix and the TiC / TiC interface is less likely to slip. Therefore, overload is applied to the harmony of the tungsten phase with respect to the continuous grain boundary of the tungsten grains, and grain boundary (interface) cracks are generated, so that the elongation at break is also reduced.

<Experiment 3>
The test was conducted in the same manner as in Experiment 1, except that the content of zirconium carbide, niobium carbide, tantalum carbide, or a mixture thereof was changed and the high temperature tensile elongation was performed only at 1600 ° C instead of the titanium carbide in Experiment 1. It was. The results are shown in Table 3.

  As is apparent from Table 3, it was found that the elongation characteristics were improved even when about 0.25 to 5 mass% of transition metal carbide other than Ti was added to the alloy.

<Example 1>
An as-HIP body was produced in the same manner as Sample No. 5 in <Experiment 1> except that the degassing conditions were heating at 1050 ° C. under high vacuum (1 × 10 ⁻⁴ Pa) for 1.5 hours. Next, with respect to the sintered body having a diameter of about 9 to 10 mm and a height of about 20 mm cut out from the produced as-HIP material by wire cutting, weak randomness is obtained by utilizing superplastic deformation that makes the best use of grain boundary deformation. In order to reinforce the grain boundary, at a temperature of 1650 ° C. and a strain rate of 0.5 to 2 × 10 ⁻⁴ s ⁻¹ (superplastic behavior is more likely to occur as the strain rate is slower. The plate was produced by compressing and deforming to a thickness of about 3.5 mm (diameter of about 21 to 23 mm) by selecting the speed at which the response (increase in deformation stress) was most easily tested. The sintered body was heated by high-frequency induction heating using a graphite susceptor under vacuum, and an electric actuator type testing machine R1362 manufactured by Instron was used for the high-temperature compression deformation. A piece having a size of 1 × 1 × 20 mm was cut out from the plate material in a direction perpendicular to the compression direction, and the surface and the edge were polished with water-resistant paper up to # 1500 to prepare a bending test piece. The oxygen concentration of the test piece measured using the infrared absorption and thermal conductivity method of LECO-TC600 was 40 ppm, and the nitrogen concentration was 30 ppm. Next, the test piece was subjected to a three-point bending test in a flow range of room temperature to 600 ° C., a crosshead speed of 0.001 mm / s, and a high purity Ar-4% H ₂ flow atmosphere. The three-point bending test uses a Shimadzu fatigue tester / servo pulser EHF2 type (capacity 5 tons), and a LVDT (Linear Variable Differential Transformer) with a span of ± 2.5 mm is connected to the actuator head, with a capacity of 5 tons. A shear type load cell having a load capacity of 5 kN was attached immediately below the load cell, and the test was controlled by a static test application program. An infrared image furnace (manufactured by ULVAC) was used for heating the test piece, and the temperature of the test piece and the atmosphere (position several mm away from the test piece) were measured for a dummy test piece spot-welded with a thermocouple in advance. In actual tests, the temperature of the atmosphere was controlled and measured. The bending strength was measured at room temperature, and the minimum value of the measured values for an average of five bending test pieces was the minimum bending strength, and the maximum value was the maximum bending strength. The DBTT measures the plastic strain at each temperature while increasing the test temperature from room temperature by about 50 ° C., records the change, approximates one-dimensionally, and sets the temperature extrapolated to zero plastic strain. It was. In order to obtain one DBTT, it is necessary to change the test temperature and measure the amount of plastic strain, and 3 to 5 test pieces having the same impurity concentration and the same structure were prepared and measured.

<Examples 2 to 7>
The degassing conditions were as follows: heating at 950 ° C. for 1.5 hours in Example 2, heating at 950 ° C. for 1 hour in Example 3, heating at 900 ° C. for 1 hour in Example 4, and 1.50 at 850 ° C. in Example 5. Heating for 5 hours, heating at 850 ° C. for 1 hour in Example 6, heating at 800 ° C. for 1 hour in Example 7, and changing the oxygen content and nitrogen content in the tungsten alloy in the same procedure as in Example 1. Test pieces were prepared, and oxygen content, nitrogen content, minimum and maximum bending strengths at room temperature, and DBTT were measured.

<Comparative Example 1>
Measurement was performed in the same manner as in Example 2 except that the test piece was made of an as-HIP body without being subjected to compression deformation treatment.
<Comparative example 2>
A test piece was prepared and measured in the same procedure as in Example 1 except that the TiC content was 1.1% by mass and the deaeration treatment was not performed.

  Table 4 shows the measurement results of Examples 1 to 7 and Comparative Examples 1 and 2.

  As is clear from Table 4, the lower the oxygen and nitrogen concentrations, the stronger the bending strength of the GSMM-treated tungsten alloy. Furthermore, it has been clarified that by subjecting an as-HIP body to plastic deformation, DBTT is remarkably lowered and ductility can be obtained even at low temperatures.

<Three-point bending deformation behavior test>
FIG. 5 shows the three-point bending deformation behavior of Example 4 (DBTT: 310 K) and Example 6 (DBTT: 420 K) at a temperature of 400 K, and FIG. 6 shows the three-point bending deformation behavior of Example 4 at 300 K. ing. As apparent from FIGS. 5 and 6, at a temperature lower than the DBTT temperature of the obtained alloy, it breaks without exhibiting ductility. Therefore, in addition to the GSMM (by compression) treatment, the oxygen content and the nitrogen content are reduced. It became clear that it was necessary.

<X-ray diffraction pattern test>
FIG. 7 compares the X-ray diffraction patterns of Example 2 (GSMM-treated) and Comparative Example 1 (no GSMM-treated). When both were compared, a large intensity difference was observed in the TiC peak, which indicates that TiC precipitation progressed during the GSMM treatment. This was also confirmed from a transmission electron microscope.

<Transmission electron micrograph>
(1) in FIG. 8 is a transmission electron micrograph of Comparative Example 1, (2) is a transmission electron micrograph of Example 2, and (3) is an enlarged photograph of the “←” portion of (2). As is clear from the photograph, in the tungsten alloy treated with GSMM, TiC grain boundary precipitation was confirmed in the alloy, and at the same time, it was also confirmed that the constituent elements of TiC were solid solution segregated at the grain boundaries.

<X-ray diffraction pattern test>
FIG. 9 compares the X-ray diffraction patterns of the as-HIP body before the GSMM treatment of Example 5 (GSMM-treated) and Example 5. Although it is shown that TiC precipitation similarly progressed by the GSMM treatment, unlike the case of FIG. 7, W ₂ C, which is a carbide harmful to ductility (that is, easily broken), is formed. It is considered that a part of C liberated from TiC reacted with surrounding tungsten due to the oxygen content between TiC and tungsten due to the increase in the amount of oxygen.

<Confirmation of equiaxed recrystallized grains>
A thin film having a diameter of 3 mm, a thickness of about 50 μm, and a minute hole at the center was prepared from the tungsten alloy of Example 2 by electropolishing (Tenupol), and then observed with a transmission electron microscope (JEOL2000) at an acceleration voltage of 200 kV. . 10 (1) shows the observation direction of the transmission electron microscope, FIG. 10 (2) is a photograph of the sample observed from above (that is, from a direction parallel to the compression direction), and FIG. 10 (3) is the sample from the side. It is the photograph observed (from the direction perpendicular to the compression direction). Both are bright-field images and the observation magnification is about 10,000 times. As can be seen from FIG. 10, the crystal grains were equiaxed grains, and the aspect ratio of the crystal grains was in the range of 1-2.

  Further, when the above-mentioned thin film was observed by further enlarging the diffraction conditions and the observation magnification, no dislocation was observed in most of the crystal grains, and even in the observed crystal grains, the number of dislocations was often as few as 1 to 3 in many cases. It was. From the above observation results, it is clear that the structure of the invention is a recrystallized structure. It is clear that the number of dislocations in the recrystallized tungsten crystal grains is 50 or less compared to the fact that there are 1000 or more dislocations in the tungsten crystal grains that contain a deformed structure and are not recrystallized. It became clear that the characteristics of tungsten crystal grains without distortion were exhibited if this was satisfied.

  Moreover, the state without distortion was also confirmed from the XRD measurement using Rigaku RAD II-B. Although the XRD measurement results include the effect of fine crystal grains, the diffraction width of the diffraction peak increases if the strain is large in an unrecrystallized state. For example, as a result of examining the XRD results obtained by measuring the tungsten alloy (recrystallized structure) of Example 2 and a commercially available pure tungsten stress relief treatment material under the condition of a Cu tube 40 kV 30 mA solar slit 1 °, the lattice constant was set to 0. When the full width at half maximum exceeds 3 ° in (220) diffraction of tungsten at 11188 nm, strain remains and it is not a recrystallized structure (commercial pure tungsten stress relief treatment material), and the full width at half maximum is 3 ° or less. It became clear that there was no distortion and it was a recrystallized structure.

<Confirmation of particle size>
A thin film having a diameter of 3 mm, a thickness of about 50 μm, and a minute hole at the center was produced from the tungsten alloys produced in Examples 1 to 7 by electrolytic polishing (Tenupol), and then accelerated voltage by a transmission electron microscope (JEOL2000). Observed at 200 kV. In the transmission micrographs of all examples, the crystal grain size can be measured at 80% or more of the entire field of view of the photograph, and it can be confirmed that 80% or more of the measured crystal grains are in the range of 0.05 to 10 μm. It was.

<Confirmation of carbide orientation and tungsten matrix orientation in tungsten alloy structure>
Unlike the case shown in <Confirmation of particle size> above, bright field images, dark field images, and limited field diffraction at a high magnification of several hundred thousand times for many fields containing one carbide particle in the tungsten matrix. The pattern was photographed and the orientation relation between carbide and tungsten matrix was analyzed. As a result, in the transmission micrographs of all the examples, the orientation of carbides present in the tungsten alloy structure and 90% or more of the orientation of the tungsten matrix are {111} W // {110} transition metal carbides, < It was confirmed that the (Kurdjumov-Sachs) orientation relationship of 110> W / <111> transition metal carbide was satisfied.

<Example 8>
As alloy raw material powder, vanadium: yttrium: tungsten: TiC = 89.8: 1.4: 8.0: 0.8 was weighed and blended, and then placed on a Mo boat and 1 at 200 ° C. Time deaeration treatment was performed. Next, the container / ball (material: TZM (Mo-0.5Ti-0.1Zr)) used for MA treatment is baked at 150-200 ° C. for 10 hours under high vacuum, and then the blended raw material powder is It was put into a container together with the balls, and MA treatment was performed for 70 hours in a purified hydrogen atmosphere by a triaxial vibration type ball mill. In order to remove hydrogen mixed in from the atmosphere during MA, dehydrogenation treatment was performed at 600 ° C. for 1 hour under a vacuum of 1 × 10 ⁻⁴ Pa or less. Thereafter, packed in a hydrogen atmosphere MA treated vanadium alloy powder into a vacuum heating degassing were HIP capsule (manufactured by mild steel) in advance at 900 ° C., at room temperature, while degassing under vacuum, high vacuum HIP capsule (2x10 ^-5 Vacuum sealed under Pa). Therefore, the inside of the HIP capsule is in a high vacuum sealed state. This was subjected to HIP treatment at 1000 ° C. and 196 MPa in argon gas for 3 hours to obtain a sintered body having a relative density of 99.5% or more, and then a tensile test piece similar to that in Example 1 was cut out from the sintered body. In order to reinforce weak random grain boundaries by utilizing superplastic deformation making the best use of grain boundary deformation, GSMM treatment was performed at a temperature of 1300 ° C. and a strain rate of 0.5 to 2 × 10 ⁻⁴ s ⁻¹ . The obtained specimens were subjected to a tensile test using a Shimadzu servo pulsar EHF type 2 at room temperature and an initial strain rate of 1 × 10 ⁻³ / s, yield strength, tensile strength, uniform elongation, elongation at break (total elongation ) Was measured.

<Comparative Example 3>
A test piece was prepared and measured in the same procedure as in Example 8 except that the GSMM treatment was not performed.

<Example 9>
As alloy raw material powder, SUS316L of mass ratio of SUS316L: TiC = 98: 2 (manufactured by Soekawa Rikagaku Co., Ltd.) and TiC, degassing treatment at 450 ° C. for 1.5 hours, dehydrogenation treatment after MA treatment The sample was heated at 450 ° C. for 1.5 hours, the heating temperature during vacuum sealing of the HIP capsule was 750 ° C., the HIP process was performed at 850 to 900 ° C. for 3 hours, and the GSMM process was performed at 950 ° C. A test piece was prepared and measured.

<Comparative example 4>
A test piece was prepared and measured in the same procedure as in Example 9 except that the GSMM treatment was not performed.

  Table 5 shows the measurement results of Examples 8 to 9 and Comparative Examples 3 to 4.

  As can be seen from Table 5, both the GSMM-treated vanadium alloy and stainless steel alloy have improved uniform elongation and elongation at break more than twice, and GSMM treatment can improve the elongation properties of various metals or alloys including tungsten. Became clear.

  By subjecting the alloy to GSMM treatment, the low temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement of alloys, especially tungsten, can be greatly improved, so high temperature structural materials, molybdenum substitute materials, and thermal fusion experimental reactors It is expected that the use of alloys, especially tungsten, in extreme environments exposed to severe heat loads, such as plasma facing materials, high-temperature test jigs, and sputtered neutron source solid rotating targets, is expected.

Claims (7)

At least one selected from carbides of Group IVA, Group VA or Group VIA transition metals and a metal raw material are mechanically alloyed, and the raw material powder obtained in the mechanical alloying step is sintered by hot isostatic pressing. A step of subjecting the alloy obtained in the sintering step to a plastic deformation of 60% or more at a strain rate of 500 ° C. or more and 2000 ° C. or less, 10 ⁻⁵ s ⁻¹ or more and 10 ⁻² s ⁻¹ or less, The manufacturing method of the alloy characterized by including.   The method for producing an alloy according to claim 1, further comprising a step of degassing the transition metal carbide and the metal raw material by heating before the mechanical alloying step.   In a tungsten alloy containing 0.25 mass% or more and 5 mass% or less of at least one selected from the group IVA, VA, and VIA transition metal carbides, the oxygen content is 950 mass ppm or less, and the nitrogen content is 60 Mass ppm or less, 80% or more of the area ratio of the tungsten phase is equiaxed grains having a grain size of 0.05 μm or more and 10 μm or less, and a ductile brittle transition temperature by three-point bending is 500 K or less. A tungsten alloy characterized by being plastically deformable.   90% or more of the orientation of carbides present in the tungsten alloy structure and the orientation of the tungsten matrix is a carbide of {111} W // {110} transition metal, <110> W // <111> transition metal carbide The tungsten alloy according to claim 3, which has a (Kurdjumov-Sachs) orientation relationship.   5. The full width at half maximum of diffraction surface (220) reflection in X-ray diffraction is 3 ° or less, or the number of dislocations in crystal grains is 50 or less by observation with a transmission electron microscope. The tungsten alloy described.   The maximum bending strength by three-point bending is 1470 MPa or more, The tungsten alloy as described in any one of Claims 3-5 characterized by the above-mentioned.   An alloy manufactured by the manufacturing method according to claim 1.

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