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Method for manufacturing alloy containing transition metal carbide, tungsten alloy containing transition metal carbide, and alloy manufactured by said method

a technology of transition metal carbide and manufacturing method, which is applied in the field of manufacturing method of tungsten alloy containing transition metal carbide, and alloy manufactured by said method, which can solve the problems of affecting the practical use of these materials as high-temperature structural materials in extreme environments, affecting the performance of the alloy, and affecting the quality of the alloy, etc., to achieve the effect of improving the grain boundary strength of the alloy in the recrystallized structur

Inactive Publication Date: 2014-05-29
TOHOKU UNIV
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  • Abstract
  • Description
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  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a method of improving the strength and toughness of tungsten alloy by creating a fine-grained structure through hot isostatic pressing and mechanical alloying. The method also reduces the chance of grain boundary embrittlement and resolves irradiation embrittlement. Additionally, the method allows for a decrease in yield strength and enables the production of tungsten alloy that can undergo plastic deformation at room temperature. The treatment results in a much stronger and more durable tungsten alloy.

Problems solved by technology

However, the materials have not been used for structure due to an inability to resolve problems with persisting embrittlement (low-temperature embrittlement, recrystallization embrittlement, and irradiation embrittlement), which has hampered practical use of these materials as high-temperature structural materials in extreme environments.
The cause of grain boundary embrittlement is that tungsten is a metal having an extremely high degree of covalent bond character, and the grain boundaries are substantially weaker (tend to fracture) due to their high energies.
Additionally, interstitial gas elements contained in air such as nitrogen and oxygen have extremely low solubility in tungsten, and thus tend to segregate and precipitate at the grain boundaries, which further weakens the grain boundaries and promotes embrittlement.
Moreover, when lattice defects are introduced by high-energy particle irradiation using neutrons or the like, such irradiation induced defects accumulate inside the crystal grains or at the grain boundaries and impede dislocation slip, resulting in the promotion of grain boundary embrittlement (irradiation embrittlement).
However, the tungsten materials manufactured by the above methods still were not adequate for practical use.
However, patent document 1 discloses an improvement in the heat resistance and creep resistance of high-melting metals at high temperatures, not a remedy for low-temperature embrittlement, recrystallization embrittlement, or irradiation embrittlement.
However, the molybdenum described in patent document 2 is a material that exhibits ductility at room temperature, even as a pure metal, and has completely different properties and manufacture conditions in comparison to tungsten, which is an extremely brittle material having a high melting point that is 800° C. higher than that of molybdenum.
With tungsten, on the other hand, the issue is ductility improvement in a recrystallized equiaxed structure that is in a recrystallized state with absolutely no work-deformed structure and therefore no anisotropy.

Method used

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  • Method for manufacturing alloy containing transition metal carbide, tungsten alloy containing transition metal carbide, and alloy manufactured by said method
  • Method for manufacturing alloy containing transition metal carbide, tungsten alloy containing transition metal carbide, and alloy manufactured by said method
  • Method for manufacturing alloy containing transition metal carbide, tungsten alloy containing transition metal carbide, and alloy manufactured by said method

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embodiments

[0062]With the methods for manufacturing the alloys and the manufactured alloys of the embodiments described below, as shown in FIG. 4, simple compressive deformation was carried out along one axis, but deformation is not restricted to simple compression, provided that superplastic deformation allowing maximal utilization of grain boundary sliding can be realized. Depending on the shape of the alloy product that is desired, for example, reduction by rolling can be employed for sheet-form materials, for example.

[0063]Characterization of transition metal carbide amount required for manifesting superplasticity

experiment 1

[0064]TiC powder with an average particle diameter of 0.7 μm (manufactured by Soekawa Chemical Co., Ltd.) was added to tungsten powder with an average particle diameter of 4 μm (Manufactured by A.L.M.T. Corp.) using the Fischer method. The material was introduced into a molybdenum boat in a hydrogen atmosphere and was then subjected to a degassing treatment by heating for 1.5 h at 950° C. under high vacuum (−4 Pa). Next, the material was subjected to a mechanical alloying (MA) treatment by mixing for 70 h at a vibration frequency of 360 cycles / min (6 Hz) in a TZM (titanium, zirconium-containing molybdenum alloy) container (pot) using a tri-axial vibrating ball mill (TKMAC 1200, manufactured by Topology Systems). In order to characterizes the appropriate TiC powder addition range, eight MA treatment sample runs were carried out with TiC powder contents of 0 to 6.0 mass %.

[0065]Next, the MA-treated powder was introduced into a molybdenum boat and was heated for 1.5 h at 950° C. under ...

experiment 2

[0067]The same test as in Experiment 1 was carried out, with the exception that the hydrogen in Experiment 1 was changed to argon, and nine samples were used in which the TiC content was varied. The results are shown in Table 2

TABLE 21500° C.1600° C.1700° C.TiC contentElongationElongationElongationSample No.Mass %(%)(%)(%)90255100.25377110.5304060120.75070>160130.870110>160141.1120>160>160151.570>160>1601655070>160176103060

[0068]Experiment 1 and Experiment 2 above show that the TiC amount required for manifestation of superplasticity at 1600 to 1700° C. (elongation at break:100% or greater) is 0.25 to 5 mass % with the as-HIPed compacts produced from powder that was MA-treated in hydrogen atmosphere, and 0.7 to 5 mass % with those produced using an argon atmosphere. If the TiC amount is below these ranges, then weak grain boundaries occur in great numbers among the grain boundaries of the tungsten phase, and there are few grains of a second phase that inhibit grain boundary movement...

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Abstract

The present invention relates to the development of an alloy material with significantly improved low-temperature brittleness, recrystallization brittleness, and irradiation brittleness by the introduction of a recrystallization microstructure into an alloy, particularly a tungsten material, to significantly strengthen a weak grain boundary of the recrystallization microstructure. The present invention comprises the steps of: mechanically alloying at least one species selected from a group-IVA, VA, or VIA transition metal carbide and a metallic raw material; sintering base powders obtained through the mechanically alloying step, by using a hot isostatic press; and performing plastic deformation of at least 60% on the alloy obtained through the sintering step, at a strain rate between 10−5 s−1 and 10−2 S−1 and at a temperature between 500° C. and 2,000° C. It is therefore possible to obtain an alloy material with significantly improved low-temperature brittleness, recrystallization brittleness, and irradiation brittleness.

Description

TECHNICAL FIELD[0001]The present invention relates to a method for manufacturing an alloy containing transition metal carbide, a tungsten alloy containing transition metal carbide, and an alloy manufactured by said method. In particular, the present invention relates to a method for manufacturing an alloy that manifests superplasticity due to grain boundary sliding when the alloy is made to undergo superplastic deformation, that exhibits high recrystallization fracture strength, that has little decrease in strength or ductility, even when heated to high temperatures due to its recrystallized structure, and which has dramatically remedied low-temperature embrittlement, recrystallization embrittlement, and neutron irradiation embrittlement, as well as an alloy that has been manufactured by this manufacturing method, in particular, a tungsten alloy.BACKGROUND ART[0002]Tungsten and tungsten alloys have melting points of as high as 3410° C. which are the highest of any metal. These mater...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C1/05C22C27/04
CPCB22F3/15C22C27/04C22F1/18C22C32/0052B22F2998/10C22C1/1084C22C1/05
Inventor KURISHITA, HIROAKIARAKAWA, HIDEOMATSUO, SATORU
Owner TOHOKU UNIV
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