WO2013018714A1 - Method for manufacturing alloy containing transition metal carbide, tungsten alloy containing transition metal carbide, and alloy manufactured by said method - Google Patents
Method for manufacturing alloy containing transition metal carbide, tungsten alloy containing transition metal carbide, and alloy manufactured by said method Download PDFInfo
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- WO2013018714A1 WO2013018714A1 PCT/JP2012/069190 JP2012069190W WO2013018714A1 WO 2013018714 A1 WO2013018714 A1 WO 2013018714A1 JP 2012069190 W JP2012069190 W JP 2012069190W WO 2013018714 A1 WO2013018714 A1 WO 2013018714A1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/05—Mixtures of metal powder with non-metallic powder
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/14—Both compacting and sintering simultaneously
- B22F3/15—Hot isostatic pressing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
- C22C27/04—Alloys based on tungsten or molybdenum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
- C22C32/0047—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents
- C22C32/0052—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents only carbides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
- C22F1/18—High-melting or refractory metals or alloys based thereon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
Definitions
- 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.
- 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.
- embrittlement low temperature embrittlement, recrystallization embrittlement, irradiation embrittlement
- 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.
- embrittlements are all caused by “grain boundary embrittlement”, where the crystal grain boundaries are weak and easily break from the grain boundaries.
- the cause of grain boundary embrittlement is tungsten, which is the metal with the strongest degree of covalent bonding.
- 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.
- a normal metal undergoes plastic deformation (permanent deformation) before breaking, so that almost the entire temperature range becomes the ductile temperature region.
- 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-britch transition temperature, hereinafter abbreviated as “DBTT”) is also high.
- 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 ⁇ m.
- 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 ⁇ m.
- 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 ⁇ m 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).
- 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.
- molybdenum requires the introduction and presence of a deformed structure by plastic working (forging, rolling, etc.) in order to improve ductility. As a result, the recrystallization temperature is lowered and anisotropy occurs.
- 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.
- 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.
- MA mechanical alloying
- HIP hot isostatic pressing
- 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.
- the present invention has been made based on these new findings.
- the present invention relates to a transition metal carbide-containing alloy manufacturing method, transition metal carbide-containing tungsten alloy, and an alloy manufactured by the manufacturing method described below.
- 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.
- 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 ⁇ m or more and 10 ⁇ m 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.
- 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 as described in (3) above which has a (Kurdjumov-Sachs) orientation relationship of a metal carbide.
- the full width at half maximum of reflection of diffraction plane (220) 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 (3) Or a tungsten alloy according to (4).
- 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.
- MA mechanical alloying
- HIP hot isostatic pressing
- 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.
- 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.
- Irradiation embrittlement can be greatly improved.
- the crystal grain size of the tungsten alloy grows to about 0.05-10 ⁇ m.
- Moderately reduced Causing effect is applied can be a 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. 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 the as-HIP body 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 the recrystallized random grain boundary using superplastic deformation (hereinafter referred to as a “GSMM process”) that can make the best use of the grain boundary deformation.
- GSMM is a grain boundary.
- An abbreviation of “Sliding-based Microstructural Modification”), and the method More manufactured alloy is characterized by particularly tungsten alloy. The present invention will be described more specifically.
- 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 ⁇ m 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.
- the raw material has the above-mentioned particle size. However, it is not necessarily 2 ⁇ m or more, and may be 1 ⁇ m or less as long as the atmosphere management is performed so as to suppress impurity contamination.
- 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.
- air especially moisture
- 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.
- 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.
- oxygen and nitrogen remaining in the alloy precipitate and segregate at weak recrystallized grain boundaries to promote grain boundary embrittlement (recrystallization embrittlement)
- tungsten when using a commercially available tungsten powder as a raw material, it forms a pore and acts as a starting point of destruction.
- a container for preparing a raw material powder (produced with Mo or the like for mounting powder) It is desirable to evacuate to 10 ⁇ 4 Pa or less while the raw material powder is placed on a boat, and to degas the raw material powder at 800 ° C. to 1,500 ° C.
- tungsten having a sufficiently low oxygen and nitrogen concentration 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 deaeration time is desirably 120 minutes if it is 800 ° C or higher, and 90 minutes or more if it is 950 ° C or higher.
- 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.
- a degassing container a boat made of Mo or the like
- 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.
- 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.
- 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.
- the MA process is performed after the deaeration 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.
- the inert gas include Ar, helium, and neon
- the reducing gas include hydrogen.
- the transition metal carbide raw material powder 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.
- a three-axis vibration ball mill, a planetary ball mill, an attritor or the like is used.
- 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.
- 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.
- conditions may be set as appropriate.
- 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.
- 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.
- 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.
- 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 ⁇ 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.
- 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.
- 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.
- 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.
- it is more effective to perform GSMM for a longer time than to perform for a short time.
- 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.
- this “strengthening treatment method of recrystallized random grain boundaries using superplastic deformation capable of maximizing the use of grain boundary deformation” is defined as GSMM (Grain boundary Sliding-basic 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.
- the recrystallized grain structure with less strain is maintained after the deformation, so that the internal energy basically does not increase.
- the crystal grains grow (increased by an order of magnitude) because the process is performed at a temperature higher than the HIP temperature.
- the crystal grain boundary is a highly strained region, the more crystal grain boundaries are present. Internal energy will also be high, and grain growth will reduce internal energy.
- 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.
- the alloy produced in the HIP process is sandwiched between BN—SiC composite plates as shown in FIG. 4, and a high temperature of 500 ° C. to 2000 ° C. (40% of the melting point of each alloy measured at an absolute temperature).
- the pressure is applied at a strain rate of 10 ⁇ 5 s ⁇ 1 to 10 ⁇ 2 s ⁇ 1 and plastic deformation of 60% or more is performed.
- 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, it is preferably 1200 ° C. to 2000 ° C., and tungsten is more preferably 1400 ° C. to 2000 ° C. .
- a temperature of 800 ° C. to 1500 ° C. is preferable.
- 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 lower than 10 ⁇ 5 s ⁇ 1 , there is an effect, but it takes too much time and is not industrial, and if it is higher than 10 ⁇ 2 s ⁇ 1 , the alloy may be destroyed, which is not desirable.
- 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 ( ⁇ L) of the test piece extended to the initial length ( ⁇ L). Divided by L) and multiplied by 100 to display%.
- strain strain
- 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.
- the transition metal carbide / alloy matrix (matrix) heterophase interface satisfies the Kurdjumov-Sachs orientation relationship, thereby forming a high-strength heterophase interface.
- 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> W // ⁇ 111> (Kurdjumov-Sachs) orientation relationship of transition metal carbonization is desirable. 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 grows to about 0.05 to 10 ⁇ m.
- 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.
- the ductile brittle transition temperature non-ductile transition temperature: DBTT
- DBTT non-ductile transition temperature
- the crystal grain size can be obtained 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).
- 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.
- 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 ⁇ m. If it is in range.
- the average particle size is less than 0.05 ⁇ m, 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.
- the average particle size exceeds 10 ⁇ m, plastic deformation is extremely difficult to occur.
- the temperature during GSMM treatment may be lowered.
- 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.
- it is not limited to simple tension compression.
- the required shape of the alloy member for example, if it is a plate shape, it is possible to apply rolling reduction.
- the MA-treated powder was put 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.
- the obtained sintered body is referred to as “as-HIP body”.
- 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).
- the amount of TiC required for superplastic development at 1600 ° C. to 1700 ° C. is 0 for the as-HIP body of hydrogen atmosphere MA-treated powder. It was found to be 0.5 to 5% by mass, and 0.7 to 5% by mass in an as-HIP body in an argon atmosphere.
- 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.
- a grain boundary crack is formed and grows, and the breaking strain is reduced.
- the contact frequency between TiC phases increases, and the presence 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 a grain boundary (interface) crack is generated, so that the elongation at break is also reduced.
- Example 1> An as-HIP body was prepared 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.
- 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 is weakly randomized by utilizing superplastic deformation that makes the best use of grain boundary deformation.
- the 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.
- 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 measure the amount of plastic strain by changing the test temperature. Three to five 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.
- 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.
- 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.
- 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
- FIG. 6 shows the three-point bending deformation behavior of Example 4 at 300 K. ing.
- 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.
- 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.
- 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.
- a thin film having a diameter of 3 mm, a thickness of about 50 ⁇ m, 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.
- JEOL2000 transmission electron microscope
- FIG. 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)
- 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.
- the crystal grains were equiaxed grains, and the aspect ratio of the crystal grains was in the range of 1-2.
- 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.
- a thin film having a diameter of 3 mm, a thickness of about 50 ⁇ m, and a minute hole at the center was prepared from the tungsten alloys prepared in Examples 1 to 7 by electrolytic polishing (Tenupol), and then accelerated voltage was measured by a transmission electron microscope (JEOL2000). Observed at 200 kV.
- 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 ⁇ m. It was.
- 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.
- TZM Mo-0.5Ti-0.1Zr
- 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.
- Example 2 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.
- GSMM treatment was performed at a temperature of 1300 ° C. and a strain rate of 0.5-2 ⁇ 10 ⁇ 4 s ⁇ 1 .
- the obtained test piece was subjected to a tensile test using a servo pulsar EHF2 type manufactured by Shimadzu under conditions of 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.
- 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 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.
- 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.
- 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.
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Abstract
Description
(2)前記メカニカルアロイングする工程の前に、前記遷移金属の炭化物及び金属原料を加熱により脱気する工程を含むことを特徴とする上記(1)に記載の合金の製造方法。
(3)IVA族、VA族、VIA族遷移金属の炭化物から選ばれる少なくとも1種を0.25質量%以上5質量%以下含むタングステン合金において、酸素の含有量が950質量ppm以下、窒素の含有量が60質量ppm以下であり、タングステン相の面積比の80%以上が粒径0.05μm以上10μm以下の等軸結晶粒であり、3点曲げによる延性脆性遷移温度が500K以下であり、その温度以上で塑性変形可能であることを特徴とするタングステン合金。
(4)タングステン合金組織中に存在する炭化物の方位と、タングステンのマトリクスの方位の90%以上が、{111}W//{110}遷移金属の炭化物,<110>W//<111>遷移金属の炭化物の(Kurdjumov-Sachs)方位関係であることを特徴とする上記(3)に記載のタングステン合金。
(5)X線回折での回折面(220)反射の半値全幅が3°以下であること、あるいは透過電子顕微鏡観察により結晶粒内の転位が50本以下であることを特徴とする上記(3)又は(4)に記載のタングステン合金。
(6)3点曲げによる最大曲げ強度が1470MPa以上であることを特徴とする上記(3)~(5)の何れか一に記載のタングステン合金。
(7)上記(1)又は(2)に記載の製造方法により製造された合金。 (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 And the alloy obtained in the sintering step is subjected to plastic deformation of 60% or more at a strain rate of 500 −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 as described in (3) above, which has a (Kurdjumov-Sachs) orientation relationship of a metal carbide.
(5) The full width at half maximum of reflection of diffraction plane (220) 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 (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.
<実験1>
フィッシャー法による平均粒径4μmのタングステン粉末((株)アライドマテリアル社製)に、平均粒径0.7μmのTiC粉末(添川理化学(株)社製)を添加し、モリブデン製ボートに入れて、水素雰囲気、高真空下(<1x10-4Pa)950℃で1.5時間加熱し脱気処理を行った。次いで、水素雰囲気で、TZM(チタン、ジルコニウム入りモリブデン合金)製の容器(ポット)と3軸加振型ボールミル(トポロジーシステムズ製TKMAC1200)で70時間、回転数360rpmの条件下で混合してメカニカルアロイング(MA)処理した。なお、TiC粉末の好適な添加範囲を特定するため、TiC粉末の含有量が0~6.0質量%となるように8通りの試料をMA処理した。 <Identification of the amount of transition metal carbide required for the development of superplasticity>
<
Add a TiC powder (manufactured by Soekawa Rika Co., Ltd.) with an average particle diameter of 0.7 μm to tungsten powder (manufactured by Allied Material 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, mixing was performed 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 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.
実験1の水素をアルゴンに変更し、TiCの含有量を一部変えた9通りの試料を用いた以外は、実験1と同様に試験を行った。結果を表2に示す。 <
The test was performed in the same manner as in
実験1の炭化チタンに変え、炭化ジルコニウム、炭化ニオブ、炭化タンタル又はそれらの混合物の含有量を変えて添加し、高温引張り伸びを1600℃のみで行った以外は、実験1と同様に試験を行った。結果を表3に示す。 <
The test was conducted in the same manner as in
脱気条件を、高真空下(1x10-4Pa)1050℃で、1.5時間加熱、とした以外は、上記<実験1>の試料番号5と同様に、as-HIP体を作製した。次に、作製したas-HIP材からワイヤーカットにより切り出した直径約9~10mm、高さ約20mmの当該焼結体について、粒界辷りを最大限に活用した超塑性変形を利用して弱いランダム粒界を強化するために、温度1650℃、歪速度0.5~2x10-4s-1で(超塑性挙動は歪速度が遅いほど起こりやすいので、少しずつ歪速度を増加しながら材料の示す応答(変形応力の上昇)をみて最も実験しやすい速度を選択)、厚さ約3.5mm(直径約21~23mm)まで圧縮変形し、板材を作製した。焼結体の加熱は、真空下でグラファイトサセプタを用いた高周波誘導加熱により行い、その高温圧縮変形にはインストロン社製電気アクチュエータ式試験機R1362型を用いた。この板材から圧縮方向に垂直に寸法1×1×20mmの片を切り出し、#1500までの耐水紙で表面およびエッジを研磨し、曲げ試験片を作製した。LECO-TC600の赤外線吸収、熱伝導度法を用いて測定した試験片の酸素濃度は40ppm、窒素濃度は30ppmであった。次いで、試験片を、室温~600℃の温度範囲、クロスヘッドスピード0.001mm/s、高純度Ar-4%H2のflow雰囲気下で3点曲げ試験を行った。3点曲げ試験は、島津製作所製の疲労試験機・サーボパルサーEHF2型(容量5トン)を用い、スパン±2.5mmのLVDT(Linear Variable Differential Transformer)をアクチュエーターヘッドに連結し、容量5トンのロードセルの直下に荷重容量5kNのせん断型ロードセルを取りつけ、静的試験のアプリケーションプログラムにより試験の制御を行った。試験片の加熱には赤外線イメージ炉(アルバック製)を用い、あらかじめ熱電対を点溶接したダミーの試験片について試験片の温度および雰囲気(試験片から数mm離れた位置)の温度を測定しておき、実際の試験では、雰囲気の温度を制御、計測した。曲げ強度は室温で測定し、平均5本の曲げ試験片に対する測定値の最小値を最小曲げ強度、最大値を最大曲げ強度とした。また、DBTTは試験温度を室温から約50℃ずつ増加しながら各温度で塑性歪量を測定してその変化を記録し、一次元的に近似して、塑性歪ゼロに外挿した温度をDBTTとした。なお、一つのDBTTを求めるには試験温度を変えて塑性歪量を測定する必要があり、不純物濃度と組織が同じ試験片を3~5本準備して測定を行った。 <Example 1>
An as-HIP body was prepared in the same manner as Sample No. 5 in <
脱気条件を、実施例2では、950℃で1.5時間加熱、実施例3では950℃で1時間加熱、実施例4では900℃で1時間加熱、実施例5では850℃で1.5時間加熱、実施例6では850℃で1時間加熱、実施例7では800℃で1時間加熱し、タングステン合金中の酸素量及び窒素量を変更した以外は、実施例1と同様の手順で試験片を作製し、酸素量、窒素量、室温での最小曲げ強度及び最大曲げ強度、並びにDBTTを測定した。 <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.
圧縮変形処理をせず、as-HIP体で試験片を作製した以外は、実施例2と同様の手順で測定をした。
<比較例2>
TiCの含有量を1.1質量%とし、脱気処理を行わなかった以外は、実施例1と同じ手順で試験片を作製し、測定した。 <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.
図5は、実施例4(DBTT:310K)及び実施例6(DBTT:420K)の温度400Kにおける3点曲げ変形挙動を示し、図6は、実施例4の300Kにおける3点曲げ変形挙動を示している。図5及び図6から明らかなように、得られた合金のDBTT温度より低い温度では、延性を示さずに破断することから、GSMM(圧縮による)処理に加え、酸素量及び窒素量を低くすることが必要であることが明らかとなった。 <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.
図7は、実施例2(GSMM処理済み)及び比較例1(GSMM処理なし)のX線回折パターンを比較したものである。両者を比較するとTiCピークに大きな強度差がみられたが、これは、GSMM処理時にTiCの析出が進行したことを示している。このことは、透過電子顕微鏡からも確認された。 <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.
図8の(1)は比較例1、(2)は実施例2の透過電子顕微鏡写真で、(3)は(2)の「←」部分の拡大写真である。写真から明らかなように、GSMM処理したタングステン合金は、合金中にTiCの粒界析出が確認され、同時にTiCの構成元素が粒界に固溶偏析していることも確認された。 <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.
図9は、実施例5(GSMM処理済み)及び実施例5のGSMM処理前のas-HIP体のX線回折パターンを比較したものである。GSMM処理により、同様にTiCの析出が進行したことを示しているが、図7の場合と異なり、延性に有害な(すなわち、破壊しやすい)炭化物であるW2Cが形成されている。酸素量の増加により、TiCとタングステンの間で酸素の関与により、TiCから遊離した一部のCが周囲のタングステンと反応したものと考えられる。 <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.
実施例2のタングステン合金から、直径3mm、厚さが約50μmで中央部に微小な孔をもつ薄膜を電解研磨(テヌポール)により作製した後、透過電子顕微鏡(JEOL2000)により加速電圧200kVで観察した。図10(1)は透過電子顕微鏡の観察方向を示し、図10(2)はサンプルを上から(すなわち、圧縮方向と平行な方向から)観察した写真、図10(3)はサンプルを横から(圧縮方向と垂直な方向から)観察した写真である。いずれも明視野像で、観察倍率は約1万倍である。図10からわかるように、結晶粒は等軸粒であり、結晶粒のアスペクト比は1~2の範囲にあった。 <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.
実施例1~7で作製したタングステン合金から、直径3mm、厚さが約50μmで中央部に微小な孔をもつ薄膜を電解研磨(テヌポール)により作製した後、透過電子顕微鏡(JEOL2000)により加速電圧200kVで観察した。全ての実施例の透過顕微鏡写真において、写真の全視野の80%以上で結晶粒径を測定でき、測定した結晶粒の80%以上が粒径0.05~10μmの範囲であることが確認できた。 <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 prepared from the tungsten alloys prepared in Examples 1 to 7 by electrolytic polishing (Tenupol), and then accelerated voltage was measured by a transmission electron microscope (JEOL2000). Observed at 200 kV. In 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.
上記<粒径の確認>で示した場合と異なり、タングステン母相の中に炭化物粒子1個を含む多くの視野について、数10万倍の高倍率で明視野像、暗視野像、制限視野回折パターンを撮影し、炭化物とタングステン母相の方位関係を解析した。その結果、全ての実施例の透過顕微鏡写真において、タングステン合金組織中に存在する炭化物の方位と、タングステンのマトリクスの方位の90%以上が、{111}W//{110}遷移金属炭化物,<110>W//<111>遷移金属炭化物の(Kurdjumov-Sachs)方位関係を満たすことが確認できた。 <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.
合金原料粉末として、バナジウム:イットリウム:タングステン:TiC=89.8:1.4:8.0:0.8の質量比となるように秤量配合したのち、Mo製ボートに載せ、200℃で1時間脱気処理を行った。次に、MA処理に使用する容器・ボール(材質:TZM(Mo-0.5Ti-0.1Zr))を高真空下、150~200℃で10時間、ベーキング処理してから、配合原料粉末をボールとともに容器に入れ、3軸加振型ボールミルにより、純化した水素雰囲気で70時間、MA処理を行った。MA時に雰囲気から混入した水素を除くために600℃で1時間、1x10-4Pa以下の真空下で脱水素処理を行った。その後、あらかじめ900℃で真空加熱脱気したHIPカプセル(軟鋼製)にMA処理済みのバナジウム合金粉末を水素雰囲気で詰め、室温、真空下で脱気しながら、HIPカプセルを高真空(2x10-5Pa)のもとで真空封止した。したがって、HIPカプセル内は高真空の密閉状態にある。これをアルゴンガス中、1000℃、196MPaで3時間HIP処理して、相対密度99.5%以上の焼結体とした後、その焼結体から実施例1と同様の引張試験片を切り出し、粒界辷りを最大限に活用した超塑性変形を利用して弱いランダム粒界を強化するために、温度1300℃、歪速度0.5~2x10-4s-1でGSMM処理した。得られた試験片を、島津製のサーボパルサーEHF2型を用いて、室温、1x10-3/sの初期歪速度の条件で引張試験し、降伏強度、引張強度、均一伸び、破断伸び(全伸び)を測定した。 <Example 8>
The alloy raw material powder was weighed and blended so as to have a mass ratio of vanadium: yttrium: tungsten: TiC = 89.8: 1.4: 8.0: 0.8, 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 in 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 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 0.5-2 × 10 −4 s −1 . The obtained test piece was subjected to a tensile test using a servo pulsar EHF2 type manufactured by Shimadzu under conditions of 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.
GSMM処理をしなかった以外は、実施例8と同様の手順で試験片の作製・測定を行った。 <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.
合金原料粉末として、質量比でSUS316L:TiC=98:2のSUS316L(添川理化学(株)社製)及びTiCを用い、脱気処理を450℃で1.5時間、MA処理後の脱水素処理を450℃で1.5時間、HIPカプセルの真空封止時の加熱温度を750℃、HIP処理を850~900℃で3時間、GSMM処理を950℃で行った以外は、実施例8と同様に試験片を作製・測定を行った。 <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 Except that the heating temperature during vacuum sealing of the HIP capsule was 750 ° C., the HIP treatment was carried out at 850 to 900 ° C. for 3 hours, and the GSMM treatment was carried out at 950 ° C. for 1.5 hours at 450 ° C. A test piece was prepared and measured.
GSMM処理をしなかった以外は、実施例9と同様の手順で試験片の作製・測定を行った。 <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.
Claims (7)
- IVA族、VA族又はVIA族遷移金属の炭化物から選ばれる少なくとも1種及び金属原料をメカニカルアロイングする工程、前記メカニカルアロイングする工程で得られた原料粉末を熱間等方圧プレスにより焼結する工程、前記焼結する工程で得られた合金を500℃以上2000℃以下、10-5s-1以上10-2s-1以下の歪速度で、60%以上の塑性変形を施す工程、を含むことを特徴とする合金の製造方法。 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 −5 s −1 or more and 10 −2 s −1 or less, at a temperature of 500 ° C. or more and 2000 ° C. or less, The manufacturing method of the alloy characterized by including.
- 前記メカニカルアロイングする工程の前に、前記遷移金属の炭化物及び金属原料を加熱により脱気する工程を含むことを特徴とする請求項1に記載の合金の製造方法。 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.
- IVA族、VA族、VIA族遷移金属の炭化物から選ばれる少なくとも1種を0.25質量%以上5質量%以下含むタングステン合金において、酸素の含有量が950質量ppm以下、窒素の含有量が60質量ppm以下であり、タングステン相の面積比の80%以上が粒径0.05μm以上10μm以下の等軸結晶粒であり、3点曲げによる延性脆性遷移温度が500K以下であり、その温度以上で塑性変形可能であることを特徴とするタングステン合金。 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.
- タングステン合金組織中に存在する炭化物の方位と、タングステンのマトリクスの方位の90%以上が、{111}W//{110}遷移金属の炭化物,<110>W//<111>遷移金属の炭化物の(Kurdjumov-Sachs)方位関係であることを特徴とする請求項3に記載のタングステン合金。 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.
- X線回折での回折面(220)反射の半値全幅が3°以下であること、あるいは透過電子顕微鏡観察により結晶粒内の転位が50本以下であることを特徴とする請求項3又は4に記載のタングステン合金。 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.
- 3点曲げによる最大曲げ強度が1470MPa以上であることを特徴とする請求項3~5の何れか一項に記載のタングステン合金。 The tungsten alloy according to any one of claims 3 to 5, wherein the maximum bending strength by three-point bending is 1470 MPa or more.
- 請求項1又は2に記載の製造方法により製造された合金。 An alloy produced by the production method according to claim 1 or 2.
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EP12819524.5A EP2737966A4 (en) | 2011-07-29 | 2012-07-27 | Method for manufacturing alloy containing transition metal carbide, tungsten alloy containing transition metal carbide, and alloy manufactured by said method |
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