Alloy for hydrogen-resistant member, method for producing same, hydrogen-resistant member, hydrogen-embrittlement-resistant alloy, and alloy design method

Abstract

An alloy for a hydrogen-resistant member to be used in a hydrogen-resistant member having resistance to hydrogen embrittlement comprises a fundamental component composed of one or more iron group elements, and a low-hydrogen-affinity component composed of one or more metal elements of a metal element group having a lower affinity for hydrogen than the iron group elements. The average value of the enthalpy of mixing with hydrogen, which is calculated based on the enthalpy of mixing with hydrogen and atomic ratio of each of all metal elements contained in the chemical composition of the alloy for a hydrogen-resistant member, is −20 [kJ / mol] or greater.

Description

Alloy for hydrogen-resistant member and manufacturing method thereof, hydrogen-resistant member, hydrogen embrittlement-resistant alloy, and alloy design method

[0001] The present invention relates to an alloy for hydrogen-resistant members.

[0002] Research has been conducted to realize a hydrogen energy society. Patent documents 1 and 2 describe techniques for suppressing hydrogen embrittlement of materials.

[0003] Zhang, B., et al., Nat Commun, (2022), 13, 3858.M. Koyama, et al., International Journal of Hydrogen Energy, (2019), 44, 31, 17163-17167.

[0004] There is a strong demand for the development of materials that are resistant to hydrogen embrittlement.

[0005] In order to solve the above problems, one aspect of the present invention provides an alloy for hydrogen resistant components, which is used for hydrogen resistant components having hydrogen embrittlement resistance, and includes a basic component consisting of one or more iron-group elements and a low-hydrogen affinity component consisting of one or more metal elements from a group of metal elements having a lower affinity for hydrogen than the iron-group elements. The basic component accounts for 50% or more in atomic ratio in the chemical composition of the alloy for hydrogen resistant components. The average value of the mixing enthalpy with hydrogen of all metal elements contained in the chemical composition, calculated based on the mixing enthalpy with hydrogen and the atomic ratio of each metal element, is -20 kJ / mol or more.

[0006] In order to solve the above problems, a hydrogen embrittlement resistant alloy according to one embodiment of the present invention has the composition formula Fe, ａ Co ｂ Ni ｃ Cu ｄ Al ｅ and the balance being impurities. The hydrogen embrittlement resistant alloy has a chemical composition represented by the following equation: a+b+c+d+e=100, where a=21.0≦a≦23.0, 20.0≦b≦22.0, 17.0≦c≦19.0, 25.0≦d≦27.0, and 12.0≦e≦14.0. The hydrogen embrittlement resistant alloy has an FCC structure.

[0007] In order to solve the above-mentioned problems, an alloy design method in one embodiment of the present invention is an alloy design method for designing an alloy, and includes: an acquisition step of acquiring information on the mixing enthalpy with hydrogen for each element that can be contained in the alloy; a first selection step of selecting one or more iron-group elements as basic components; a second selection step of selecting one or more metal elements from a group of metal elements that have a lower affinity for hydrogen than the iron-group elements as low-hydrogen-affinity components; and a determination step of determining a chemical composition such that the average value of the mixing enthalpy with hydrogen, calculated based on the mixing enthalpy with hydrogen and atomic ratios of each of all metal elements in the alloy, including the basic components and the low-hydrogen-affinity components, is −20 kJ / mol or more.

[0008] According to one aspect of the present invention, a material having resistance to hydrogen embrittlement can be realized.

[0009] 11 is a diagram showing the value of the mixing enthalpy with hydrogen for each metal element, appended to the periodic table. It is a diagram showing XRD profiles obtained by XRD measurement of the alloys of Examples 1 and 2 and Comparative Examples 1 and 2. It is a diagram showing a table of the analysis results of the XRD profile of FIG. 2. It is a diagram showing SEM images and composition analysis results of the alloys of Examples 1 and 2 and Comparative Examples 1 and 2. It is a diagram showing a table of the values ​​of each parameter calculated based on the composition analysis results of FIG. 4. It is a diagram showing the measurement results of the amount of absorbed hydrogen for the alloys of Examples 1 and 2 and Comparative Examples 1 and 2. It is a diagram showing the measurement results of slow strain rate tensile tests of test specimens before and after a hydrogen charging test for the alloys of Examples 1 and 2 and Comparative Examples 1 and 2. It is a diagram showing the hydrogen sensitivity index calculated based on the measurement results of FIG. 7. It is a diagram showing the measurement results of slow strain rate tensile tests using test specimens in a hydrogen charging environment for the alloys of Example 1 and Comparative Example 1. It is a diagram showing XRD profiles obtained by XRD measurement of the alloy of Example 3. It is a diagram showing an SEM image and composition analysis results of the alloy of Example 3. It is a diagram showing a table of the values ​​of each parameter calculated based on the composition analysis results of FIG. 11.

[0010] An embodiment of the present invention will be described below with reference to the drawings. However, the following description is intended to provide a better understanding of the gist of the invention, and is not intended to limit the present invention unless otherwise specified.

[0011] In the following description, prior to describing the alloy for hydrogen resistant members in the embodiments of the present invention, the findings of the present invention will be briefly described.

[0012] (Summary of the findings of the invention) Hydrogen embrittlement is a phenomenon that significantly reduces the strength and ductility of metallic materials. Toward the realization of a hydrogen energy society, the development of materials that are resistant to hydrogen embrittlement is required. "Hydrogen embrittlement resistance" refers to the property of being less likely to show a decrease in ductility in an environment where hydrogen is present (hydrogen environment), and can also be referred to as hydrogen embrittlement resistance.

[0013] Generally, hydrogen embrittlement progresses through a process in which hydrogen is adsorbed onto the surface of a material and a process in which hydrogen penetrates into the material. Hereinafter, hydrogen adsorbed onto the surface of a material will be referred to as surface-adsorbed hydrogen H ａｄ The hydrogen that penetrates into the material is called the penetrated hydrogen H ａｂ This is sometimes referred to as hydrogen embrittlement. Many years of research have led to the proposal of various mechanistic models for hydrogen embrittlement. For example, the mechanism proposed is that hydrogen increases dislocation mobility (Hydrogen-Enhanced Localized Plasticity: HELP mechanism) and hydrogen reduces interfacial cohesion (Hydrogen-Enhanced Decohesion: HEDE mechanism). However, the details of the hydrogen embrittlement mechanism are still unclear, and the mechanism may differ depending on the type of material. Therefore, it remains difficult to predict the hydrogen embrittlement resistance of materials.

[0014] For example, it has been proposed to use the Ni equivalent formula, which is also an index of austenite stability, as an index for predicting the hydrogen embrittlement resistance of austenitic stainless steels, but the types of metals to which such an index can be applied are limited.

[0015] In this situation, the present inventors have conducted extensive research into a method for designing alloys with hydrogen embrittlement resistance based on a new index that can be universally applied to any alloy type. As a result, they have obtained the following novel findings and have conceived the present invention.

[0016] That is, the inventors came up with the idea of ​​using the enthalpy of mixing of various elements with hydrogen in designing an alloy resistant to hydrogen embrittlement. Hereinafter, the enthalpy of mixing with hydrogen will be referred to as ΔH Ｘ－Ｈ (X: element) The enthalpy of mixing with hydrogen ΔH Ｘ－Ｈ is an index showing the affinity of each element with hydrogen.

[0017] Based on the above idea, the present inventors have calculated the enthalpy of mixing with hydrogen, ΔH Ｘ－Ｈ The absolute value of is small (ΔH Ｘ－Ｈ The alloy was designed and manufactured to have a chemical composition where σ approaches 0. The hydrogen embrittlement resistance of the manufactured alloy was tested, and surprisingly, the new finding was obtained that the amount of hydrogen that penetrated into the alloy was significantly reduced, demonstrating excellent hydrogen embrittlement resistance. It was also demonstrated that the alloy exhibits excellent hydrogen embrittlement resistance whether manufactured by casting or additive manufacturing.

[0018] For example, Fe ２０ Co ２０ Ni ２０ Cr ２０ Mn ２０ It has been reported that alloys having the above chemical composition (so-called Cantor alloys) exhibit relatively high hydrogen embrittlement resistance (H. Luo, et al., Materials Today, (2018), Volume 21, Issue 10, pp. 1003-1009). The alloys manufactured using the novel alloy design method discovered by the present inventors exhibited significantly superior hydrogen embrittlement resistance compared to the Cantor alloys (see the Examples below for details).

[0019] Conventionally, due to the properties of hydrogen (hydrogen atoms, protons), surface adsorption of hydrogen H ａｄ and interstitial hydrogen H ａｂThere was a fixed idea that it was difficult to reduce the amount of hydrogen. To suppress hydrogen embrittlement in alloys, measures have been proposed, such as hydrogen trapping using fine compounds (see Non-Patent Document 1 above) and suppressing hydrogen localization by refining crystal grains (see Non-Patent Document 2 above). These measures are based on the premise that hydrogen is absorbed in the alloy, and aim to prevent hydrogen from localizing at specific locations in the material (making it less likely that embrittled locations will occur).

[0020] In contrast, the findings of the present inventors overturn conventional ideas and propose a new method to reduce the amount of hydrogen absorbed in the alloy. In the alloy design method newly proposed by the present inventors, the mixing enthalpy ΔH Ｘ－Ｈ The type and composition of elements constituting the alloy are designed using the above as an index. The above-mentioned new alloy design method is innovative in that it can provide an alloy with significantly excellent hydrogen embrittlement resistance, which cannot be achieved by conventional alloy design methods. Furthermore, according to the above-mentioned new alloy design method, the mixing enthalpy ΔH Ｘ－Ｈ Therefore, the new alloy design method is not limited to specific alloy types, but can be applied to a wide range of alloy types. Alloys with excellent hydrogen embrittlement resistance developed using this method will have a significant impact on hydrogen-related industries and products.

[0021] The alloys designed based on the novel alloy design method may be known in terms of their chemical composition, but it has not been known that such alloys have excellent hydrogen embrittlement resistance, and this has been difficult to predict using conventional methods.

[0022] Hereinafter, an alloy for a hydrogen-resistant member according to one embodiment of the present invention will be described.

[0023] (Alloy for Hydrogen-Resistant Components) An alloy for hydrogen-resistant components in one embodiment of the present invention (hereinafter sometimes simply referred to as "alloy for hydrogen-resistant components") is used for hydrogen-resistant components having hydrogen embrittlement resistance (hydrogen embrittlement resistance characteristics). Hydrogen-resistant components are components used under conditions generally referred to as hydrogen environments. The temperature and hydrogen partial pressure in hydrogen environments are not particularly limited. Examples of hydrogen-resistant components include hydrogen tanks, pressure vessels, high-pressure hydrogen gas equipment, hydrogen pressure accumulators, fuel cells, hydrogen gas detection equipment, as well as sliding components, valves, and joints used in hydrogen environments. Of course, the hydrogen-resistant component may also be other components.

[0024] In one embodiment of the present invention, an alloy for a hydrogen-resistant component includes a base component consisting of one or more iron-group elements and a low-hydrogen-affinity component. The base component accounts for 50% or more of the atomic ratio in the chemical composition of the alloy for a hydrogen-resistant component. The iron-group elements are a collective term for the three elements iron, cobalt, and nickel. Regarding the chemical composition of the alloy, the atomic ratio (atomic fraction) and the mole fraction can be used interchangeably.

[0025] The low hydrogen affinity component is composed of one or more metal elements from a group of metal elements that have a lower affinity with hydrogen than iron group elements. As described above, the affinity with hydrogen is determined by the enthalpy of mixing with hydrogen, ΔH Ｘ－Ｈ The enthalpy of mixing ΔH of various metal elements with hydrogen can be used as an index for comparison. Ｘ－Ｈ For example, the enthalpies of mixing ΔH of various elements with hydrogen are listed in a known document (A. Takeuchi, et al., Materials Transactions, (2005), Vol. 46, No. 12, 2817-2829). Ｘ－Ｈ A value of may be used.

[0026] FIG. 1 shows the enthalpy of mixing ΔH of each metal element with hydrogen. Ｘ－Ｈ This figure shows the values ​​of carbon, nitrogen, and phosphorus, which are non-metallic elements, added to the periodic table. In Figure 1, the values ​​are also added for reference. All values ​​added in Figure 1 are in kJ / mol.

[0027] In one embodiment of the present invention, the alloy for hydrogen-resistant components has a mixing enthalpy ΔH with hydrogen of each of all metal elements contained in the chemical composition of the alloy for hydrogen-resistant components. Ｘ－Ｈ and the enthalpy of mixing with hydrogen ΔH calculated based on the atomic ratio Ｘ－Ｈ The average value of the hydrogen-resistant alloy is -20 kJ / mol or more. The average value can also be considered as a weighted average value. For the sake of convenience, the average value of the hydrogen-resistant alloy is expressed as the average value of the mixing enthalpy with hydrogen, AVΔH. Ｘ－Ｈ The average value of the enthalpy of mixing with hydrogen, AVΔH Ｘ－Ｈ is -20 [kJ / mol] or more, the average value of the mixing enthalpy with hydrogen AVΔH Ｘ－Ｈ is closer to 0 than -20 [kJ / mol] (AVΔH Ｘ－Ｈ (including cases where the energy is -20 kJ / mol).

[0028] In the following description, the units may be omitted for the sake of simplicity. Ｘ－Ｈ and AVΔH Ｘ－Ｈ All values ​​are in kJ / mol.

[0029] Enthalpy of mixing of iron group elements with hydrogen ΔH Ｘ－Ｈ The value of -23 (see FIG. 1) can be adopted for the metal element group FMG. Hereinafter, the metal element group FMG, which is a candidate for the low hydrogen affinity component and has a lower affinity for hydrogen than the iron group elements, will be referred to as the first metal element group FMG. The first metal element group FMG is the metal element group FMG that is selected from the metal elements in the second to sixth periods and the first to fifteenth groups of the periodic table, by referring to the table shown in FIG. 1, and has a mixing enthalpy ΔH Ｘ－Ｈ It consists of a metal element with a mixing enthalpy ΔH greater than -23. Ｘ－Ｈ is greater than -23, the enthalpy of mixing with hydrogen ΔH Ｘ－Ｈ is a negative value closer to 0 than -23, or ΔH Ｘ－Ｈ is 0 or a positive value. The first metal element group FMG has a mixing enthalpy ΔH Ｘ－ＨThe first metal element group FMG includes metalloid elements (boron, silicon, germanium, arsenic) having a mixing enthalpy ΔH with hydrogen of 0.05 to 0.23. The first metal element group FMG does not need to include antimony (Sb). Furthermore, referring to the table shown in FIG. 1, rhodium (Rh) has a mixing enthalpy ΔH with hydrogen of 0.05 to 0.23. Ｘ－Ｈ Since the value of is −23 (the same value as the iron group elements), it is not included in the first metal element group FMG.

[0030] Hereinafter, in this specification, among the metal elements in the second to sixth periods and the first to fifteenth groups of the periodic table, the enthalpy of mixing with hydrogen, ΔH Ｘ－Ｈ A group consisting of metal elements with a mixing enthalpy ΔH with hydrogen in the table shown in FIG. 1 is referred to as a second metal element group SMG. For convenience of explanation, a group consisting of all metal elements other than iron group elements, the first metal element group FMG, and the second metal element group SMG is referred to as a third metal element group TMG. The third metal element group TMG includes metal elements in the seventh period of the periodic table, metal elements in the seventh period of the periodic table, metal elements in the Ｘ－Ｈ This includes the metalloids for which the blank is given (selenium, antimony, tellurium, polonium, and astatine).

[0031] The alloy for hydrogen-resistant members has a chemical composition that is substantially composed of the basic components and the low hydrogen affinity components, and has an average value AVΔH of the mixing enthalpy of the alloy with hydrogen. Ｘ－Ｈ The hydrogen resistant component alloy may be composed of, for example, the basic component, the low hydrogen affinity component, and an impurity element, and in this case, the content of the impurity element may be, for example, 1% or less in atomic ratio in the chemical composition of the hydrogen resistant component alloy. Examples of the impurity element include metal elements included in the second metal element group SMG or the third metal element group TMG, and non-metal elements.

[0032] The alloy for hydrogen resistant components may have a chemical composition consisting of the basic components, the low hydrogen affinity components, and the remainder. The remainder refers to components other than the basic components and the low hydrogen affinity components in the chemical composition of the alloy for hydrogen resistant components. The remainder may be the impurities or may be intentionally added components.

[0033] The alloy for hydrogen resistant components may contain, as the remaining component, one or more metal elements selected from the second metal element group SMG or the third metal element group TMG, or a non-metal element. The content of the remaining component may be, for example, 5% or less, 3% or less, or 1% or less in atomic ratio in the chemical composition of the alloy for hydrogen resistant components. The alloy for hydrogen resistant components may contain, as the remaining component, one or more metal elements selected from the second metal element group SMG or the third metal element group TMG, or a non-metal element. Ｘ－Ｈ The silicon dioxide may contain one or more non-metallic elements having a valence greater than −23, selected from the group consisting of carbon, nitrogen and phosphorus.

[0034] The content of the low hydrogen affinity component in the chemical composition of the alloy for hydrogen resistant components may be, for example, 45% or more, 47% or more, or 49% or more in atomic ratio. In relation to the basic components, the upper limit of the content of the low hydrogen affinity component is set to less than 50%.

[0035] Alloys for hydrogen-resistant components may be manufactured by common methods. For example, whether they are manufactured by casting or additive manufacturing (such as laser powder bed fusion), the alloys for hydrogen-resistant components manufactured by either method exhibit the following properties: average enthalpy of mixing with hydrogen, AVΔH Ｘ－Ｈ By ensuring that the tensile strength is -20 kJ / mol or more, the amount of hydrogen that penetrates into the alloy in a hydrogen environment can be effectively reduced. As a result, the alloy for hydrogen-resistant components is less likely to experience a decrease in ductility in a hydrogen environment. Therefore, a material with excellent hydrogen embrittlement resistance can be realized.

[0036] Furthermore, alloys for hydrogen-resistant components can have relatively high strength because they contain one or more iron-group elements as basic components. Using alloys for hydrogen-resistant components, hydrogen-resistant components with high strength in hydrogen environments can be manufactured. Such hydrogen-resistant components are more stable and easier to use in hydrogen environments. Therefore, they are of great significance in the hydrogen-related industry.

[0037] The alloy for a hydrogen-resistant member according to one embodiment of the present invention can be subjected to cathodic hydrogen charging using a 0.1 M NaOH aqueous solution at a current of 20 mA / cm ２When a hydrogen introduction test was conducted in which hydrogen was charged at a current density of 1000 kJ / cm2 for 18 hours, the amount of absorbed hydrogen was 3 ppm by weight or less. The test by the cathodic hydrogen charging method will be described in more detail in the examples below.

[0038] For example, a comparison between a general Ni-based alloy and a Cantor alloy is as follows: An Ni-based superalloy called Inconel 718, which is an example of a general Ni-based alloy, has an average value of the mixing enthalpy with hydrogen, AVΔH Ｘ－Ｈ The Cantor alloy has an average value of the enthalpy of mixing with hydrogen, AVΔH Ｘ－Ｈ is about -26. The average value AVΔH of the enthalpy of mixing with hydrogen is Ｘ－Ｈ In alloys with a relatively small σ (a large negative value), it is difficult to reduce the amount of hydrogen that penetrates into the alloy. For example, in the case of the Cantor alloy, when a hydrogen introduction test was performed using the cathodic hydrogen charging method, the amount of hydrogen that penetrated into the alloy was as large as about 10 ppm by weight.

[0039] One aspect of the present invention was conceived by discovering that an alloy of specific components has an attribute of having excellent hydrogen embrittlement resistance when placed in a selected external environment, i.e., a hydrogen environment, and by finding an application for the alloy as a hydrogen-resistant component.

[0040] Furthermore, the alloy for a hydrogen-resistant component according to one embodiment of the present invention may have a chemical composition that further satisfies the condition that the entropy of configuration, determined by the number of types of all metal elements contained in the chemical composition and their atomic ratios, is greater than 1.5R (R is the gas constant). Alloys having such a chemical composition are sometimes called high-entropy alloys. The entropy of configuration, also called the entropy of mixing, is calculated using the following formula:

[0041]

[0042] Here, ΔS ｍｉｘ is the configurational entropy (mixing entropy), R is the gas constant (8.314 [J / K mol]), and x ｉ is the mole fraction of each component, and n is the number of constituent elements.

[0043] High-entropy alloys are typically multi-element solid solutions containing five or more metal elements, allowing for a high degree of freedom in alloy design. By having a chemical composition that corresponds to a high-entropy alloy, alloys for hydrogen-resistant components experience, for example, increased crystal lattice distortion. This may make it less likely for the HELP mechanism to occur. While the detailed mechanism is not yet clear, the above-described configuration may facilitate improved hydrogen embrittlement resistance in alloys for hydrogen-resistant components.

[0044] An alloy for a hydrogen-resistant component according to one embodiment of the present invention may include a microstructure having an FCC structure. The microstructure may have a half-width of the strongest diffraction peak of 1.0° or less in X-ray diffraction measurement. Such a microstructure can be formed, for example, by manufacturing the alloy for a hydrogen-resistant component using an additive manufacturing method. For example, when the alloy for a hydrogen-resistant component is manufactured by laser powder bed fusion, the molten part is rapidly solidified, making segregation less likely to occur. This facilitates the formation of a uniform metal structure. As a result, a microstructure is formed.

[0045] The alloy for hydrogen-resistant components has a fine structure, which makes it difficult for low-hydrogen affinity components to localize (they exist in a dispersed state). This effectively reduces the amount of hydrogen that penetrates into the alloy. The alloy for hydrogen-resistant components has an FCC structure, which makes it easy to maintain high ductility even at low temperatures, such as the temperature of liquefied hydrogen (approximately -253°C). Therefore, the alloy can be suitably used for liquefied hydrogen storage tanks.

[0046] Generally, a technique known as the parameter method is used in the alloy design of high-entropy alloys. The parameter method is a method of systematically and statistically organizing the empirically obtained constituent elements and composition ratios of high-entropy alloys, as well as their physical properties, into a database, and predicting alloy systems that are likely to form multi-component solid solutions using empirical parameters necessary for the formation of multi-component solid solutions. Since the parameter method is well known, a detailed explanation will be omitted, but a brief explanation of the empirical parameters is as follows.

[0047] The enthalpy of mixing is calculated by the following formula:

[0048]

[0049] Here, ΔH ｍｉｘ is the enthalpy of mixing in the alloy, and ΔH ｉｊ is the equiatomic composition ratio A in the binary alloy A-B ５０ B ５０ is the entropy of mixing in the liquid phase of the alloy, and x ｉ and x ｊ is the mole fraction of each component, and n is the number of constituent elements. ｍｉｘ ) is the enthalpy of mixing with hydrogen (ΔH Ｘ－Ｈ ) is used in distinction from

[0050] The delta parameter is an index representing the atomic radius ratio of the constituent elements, and is calculated by the following formula:

[0051]

[0052] where δ is the delta parameter and r ｉ is the atomic radius of the i-th atom, r (bar above) is the average atomic radius calculated from the composition ratio of the atomic radii of each element, and x ｉ is the mole fraction of each component, and n is the number of constituent elements.

[0053] The omega parameter is ΔS ｍｉｘ and ΔH ｍｉｘ It is a dimensionless index related to the melting point, including

[0054]

[0055] where Ω is the omega parameter, (T ｍ ) ｉ is the melting point of the i-th atom, T ｍ is the average melting point calculated from the composition ratio of the melting points of each element, and x ｉ is the mole fraction of each component, and n is the number of constituent elements.

[0056] The VEC value is an index representing the valence electron concentration and is calculated by the following formula.

[0057]

[0058] Here, (VEC) ｉ is the total number of electrons per atom in the valence band including d electrons in each component element, and x ｉ is the mole fraction of each component, and n is the number of constituent elements. The VEC value of the alloy is calculated by (VEC) for each element. ｉ In the parameter method, it is empirically known that when VEC≦6.87, the alloy is a single BCC phase, when 6.87<VEC≦8.0, the alloy is a two-phase BCC and FCC phase, and when 8.0≦VEC, the alloy is a single FCC phase.

[0059] In one embodiment of the alloy for hydrogen-resistant components of the present invention, the microstructure may have the following chemical composition: the enthalpy of mixing calculated based on the chemical composition of the microstructure is greater than -20 kJ / mol and less than 5 kJ / mol, the delta parameter is less than 6.6%, the omega parameter is 1.1 or more, the VEC value is 8.0 or more, and the average value of the enthalpy of mixing with hydrogen, AVΔH, is Ｘ－Ｈ may be −20 kJ / mol or more.

[0060] By designing the chemical composition of the alloy so as to have the above structure, it becomes easier to make the microstructure a single-phase FCC structure.

[0061] Furthermore, the alloy for a hydrogen resistant component according to one embodiment of the present invention may have a first phase and a second phase. The first phase and the second phase each contain the aforementioned basic component and a low-hydrogen-affinity component. Both the first phase and the second phase may have an average enthalpy of mixing with hydrogen of −20 kJ / mol or more and an FCC structure. The alloy for a hydrogen resistant component may have, for example, a dendritic structure, and one of the first phase and the second phase may be a dendritic phase and the other an interdendritic phase. Such a metal structure can be formed, for example, by producing the alloy for a hydrogen resistant component using a casting method. Segregation is likely to occur when the molten portion is cooled and solidified relatively slowly. However, the alloy for a hydrogen resistant component may have other metal structures.

[0062] In one embodiment of the alloy for a hydrogen resistant component of the present invention, the first and second phases may both have the following chemical compositions. That is, the enthalpy of mixing calculated based on the respective chemical compositions of the first and second phases may be greater than -20 kJ / mol and less than 5 kJ / mol, the delta parameter value may be less than 6.6%, the omega parameter value may be 1.1 or greater, and the VEC value may be 8.0 or greater. This makes it easier for both the first and second phases in the metallographic structure to have an FCC structure.

[0063] An alloy for a hydrogen-resistant component according to one embodiment of the present invention may include a phase having a BCC structure and a phase having an FCC structure. The phase having a BCC structure includes the aforementioned basic component and a component with a low hydrogen affinity. The phase having an FCC structure may include the aforementioned basic component and a component with a low hydrogen affinity, and have a chemical composition with a higher VEC value than the phase having a BCC structure. The phase having a BCC structure and the phase having an FCC structure may have the following chemical compositions. That is, the enthalpy of mixing calculated based on the respective chemical compositions of the phase having a BCC structure and the phase having an FCC structure is greater than -20 kJ / mol and less than 5 kJ / mol, the delta parameter value is less than 6.6%, the omega parameter value is 1.1 or greater, and the average value of the enthalpy of mixing with hydrogen, AVΔH, is Ｘ－Ｈ may be −20 kJ / mol or more.

[0064] As described above, the alloy for a hydrogen-resistant component may contain both a phase having a BCC structure and a phase having an FCC structure. Even if the alloy has a chemical composition that forms such a two-phase structure in the metal structure, both the phase having the BCC structure and the phase having the FCC structure have an average value AVΔH of the mixing enthalpy with hydrogen. Ｘ－Ｈ By making the hydrogen embrittlement resistance of the alloy equal to or greater than -20 kJ / mol, the amount of hydrogen that penetrates into the alloy can be reduced, and therefore the alloy can be used for hydrogen-resistant components that exhibit high resistance to hydrogen embrittlement.

[0065] The alloy for a hydrogen resistant member according to one aspect of the present invention may contain Cu as a component with low hydrogen affinity, and the phase having the FCC structure may have a higher Cu concentration than the phase having the BCC structure.

[0066] An alloy for a hydrogen resistant component according to one embodiment of the present invention may contain Fe, Co, and Ni as basic components, Cu and Al as low-hydrogen affinity components, and may have the following chemical composition: the enthalpy of mixing calculated based on the chemical composition of the alloy for a hydrogen resistant component may be greater than -20 kJ / mol and less than 5 kJ / mol, the delta parameter may be less than 6.6%, the omega parameter may be 1.1 or greater, and the VEC value may be 8.0 or greater. Thus, the alloy for a hydrogen resistant component may have an FCC structure.

[0067] By using the alloy for hydrogen resistant components according to one embodiment of the present invention as a material, it is possible to manufacture hydrogen resistant components that have excellent resistance to hydrogen environments. The alloy for hydrogen resistant components tends to maintain excellent hydrogen embrittlement resistance even if the metal structure is changed by processing, heating, or other treatment. Therefore, there is also an effect that the hydrogen resistant components can be easily manufactured. Hydrogen resistant components containing the alloy for hydrogen resistant components according to one embodiment of the present invention are also included in the scope of the present invention.

[0068] In an alloy for a hydrogen resistant component according to one aspect of the present invention, the delta parameter value may be, for example, smaller than 6.6% and larger than 0.4%. In an alloy for a hydrogen resistant component according to one aspect of the present invention, the total number of metal elements contained in the chemical composition may be, for example, 5 or more and 20 or less. In an alloy for a hydrogen resistant component according to one aspect of the present invention, the entropy of configuration ΔS ｍｉｘ may be, for example, greater than 1.5R and equal to or less than 3.0R.

[0069] (Method for Manufacturing Alloy for Hydrogen-Resistant Member) An example of a method for manufacturing an alloy for a hydrogen-resistant member according to one aspect of the present invention is as follows: The method for manufacturing an alloy for a hydrogen-resistant member includes the steps of preparing raw materials, preparing a mixed composition by mixing the raw materials so as to have the aforementioned chemical composition, and producing the alloy for a hydrogen-resistant member by melting and solidifying the mixed composition using a casting method or an additive manufacturing method.

[0070] The raw material may be, for example, in powder form, piece form, or other form. The powdered raw material may be a pure metal powder or an alloy powder. The piece form raw material may be a pure metal or alloy chip or wire. The specific methods for preparing the raw material and preparing the mixed composition are not particularly limited. For example, in additive manufacturing, spherical particles produced by a gas atomization method or the like may be used as the raw material. Another major advantage of the alloy for hydrogen-resistant components in one embodiment of the present invention is that it is sufficient to have chemical components designed by a novel alloy design method, and no special manufacturing method is required.

[0071] (Hydrogen Embrittlement Resistant Alloy) The present inventors have conceived the following hydrogen embrittlement resistant alloy as an example based on a novel alloy design method. The hydrogen embrittlement resistant alloy in one aspect of the present invention has the composition formula Fe, ａ Co ｂ Ni ｃ Cu ｄ Al ｅ The alloy has a chemical composition represented by the formula (1), with the balance being impurities, and has an FCC structure. The chemical composition satisfies the following conditions: 21.0≦a≦23.0, 20.0≦b≦22.0, 17.0≦c≦19.0, 25.0≦d≦27.0, and 12.0≦e≦14.0, where a+b+c+d+e=100. It cannot be said that such a hydrogen embrittlement-resistant alloy is known per se, and the fact that it has excellent hydrogen embrittlement resistance was discovered for the first time by the present inventors.

[0072] In one embodiment of the present invention, the hydrogen embrittlement resistant alloy has an average value of mixing enthalpy with hydrogen of −20 kJ / mol or more, calculated based on the mixing enthalpy with hydrogen and the atomic ratio of each of all metal elements contained in the above chemical composition.

[0073] (Alloy Design Method) The alloy design method based on the above-described novel findings can be summarized as follows. The alloy design method according to one aspect of the present invention is an alloy design method for designing an alloy, and includes an acquisition step, a first selection step, a second selection step, and a determination step, in this order. In the acquisition step, the mixing enthalpy ΔH of each element that can be contained in the alloy with hydrogen is calculated. Ｘ－Ｈ In the first selection step, one or more iron group elements are selected as the basic components, and in the second selection step, one or more elements from a group of metal elements having a lower affinity for hydrogen than the iron group elements are selected as the low hydrogen affinity components.

[0074] In the determination step, an average value AVΔH of the mixing enthalpy with hydrogen is calculated based on the mixing enthalpy with hydrogen and the atomic ratio of each of all metal elements in the alloy, including the basic component selected in the first selection step and the low hydrogen affinity component selected in the second selection step. Ｘ－Ｈ The chemical composition is determined so that the kinetic energy of the ion beam is -20 kJ / mol or more.

[0075] An embodiment of the present invention will be described below, but the present invention is not limited to the following embodiment.

[0076] (Example 1) The alloy of Example 1 was produced as follows. First, Fe was mixed with the alloy by gas atomization. ２２ Co ２１ Ni １８ Cu ２６ Al １３Powder particles of an alloy having the above chemical composition were produced. Specifically, a gas atomization apparatus equipped with a melting chamber and a spray chamber was used. The chamber of the gas atomization apparatus was evacuated and then replaced with an inert gas. Then, in the melting chamber, raw metal was melted by high-frequency induction melting to obtain the above chemical composition. Next, a pressure difference was created between the melting chamber and the spray chamber, and the stopper was released, causing the molten metal to flow downward, and high-pressure gas was sprayed onto the molten metal, producing spherical alloy powder particles having the above chemical composition.

[0077] The alloy was fabricated by laser powder bed fusion using the prepared alloy powder particles. The conditions for the laser powder bed fusion were: layer thickness 0.06 mm, laser power 180-360 W, scanning speed 600-1400 mm / s, and scanning pitch width 0.08 mm. The laser scanning direction was rotated 67° for each layer.

[0078] (Example 2) The alloy of Example 2 has the same chemical composition as Example 1 and was produced as follows. First, pure metal raw materials with a purity of 99.9% or more were prepared for each of Fe, Co, Ni, Cu, and Al. ２２ Co ２１ Ni １８ Cu ２６ Al １３ The alloy was produced by arc melting. Ten melting cycles were carried out for homogenization.

[0079] (Comparative Examples 1 and 2) As comparative examples, Fe ２０ Co ２０ Ni ２０ Cr ２０ Mn ２０ A Cantor alloy having the above chemical composition was produced in the same manner as in Example 1 to prepare an alloy for Comparative Example 1, and in the same manner as in Example 2 to prepare an alloy for Comparative Example 2.

[0080] (Test Method) The alloys of Examples 1 and 2 and Comparative Examples 1 and 2 were used as test materials and tested as follows.

[0081] For each test material, powder X-ray diffraction measurement was performed to obtain an XRD pattern. In addition, the metal structure was observed and composition was analyzed using a scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDS).

[0082] Hydrogen embrittlement resistance evaluation: A hydrogen charging test was carried out on each test material using the cathodic hydrogen charging method. Specifically, a three-electrode method using a potentiostat was adopted, with the test piece as the cathode, the counter electrode as Pt, the standard electrode as an Ag / AgCl electrode, and a 0.1 M NaOH solution. The current density was 20 mA / cm. ２ The battery was charged for 18 hours.

[0083] The test pieces before and after the hydrogen charging test were subjected to quantitative temperature programmed gas desorption analysis using a temperature programmed gas desorption analyzer (TDS) to measure the amount of absorbed hydrogen in the test pieces.

[0084] The hydrogen embrittlement resistance was evaluated by both a slow strain rate tensile test using a test specimen after hydrogen charging (hereinafter referred to as slow strain rate tensile test 1) and a slow strain rate tensile test using a test specimen in a hydrogen charging environment (hereinafter referred to as slow strain rate tensile test 2).

[0085] In the case of the slow strain rate tensile test 1, the test piece after the hydrogen charging test was subjected to strain rate measurement at a strain rate of 1 × 10 using an autograph (Shimadzu AG-X). －４ The tensile test was carried out at 1000 MPa (mm / sec) until the test piece broke.

[0086] The slow strain rate tensile test 2 was carried out as follows. That is, a tensile test was carried out while hydrogen charging was carried out in the same manner as the hydrogen charging test. Specifically, while hydrogen charging was being carried out, a strain rate of 1 × 10 was applied using an autograph (Shimadzu AG-X). －４ The tensile test was carried out at a strain rate of 1 / 2 mm / sec until the test piece broke. The method of the slow strain rate tensile test 2 can be described, for example, in a known literature (S. Aomatsu and R. Matsumoto, ISIJ International, (2014), 54, 2411-2415).

[0087] Mechanical evaluation: The plastic strain of each specimen was also measured before the hydrogen charging test. The specimens of each specimen before the hydrogen charging test were subjected to strain rate of 1 × 10 in vacuum using an autograph (Shimadzu AG-X). －４ A slow strain rate tensile test was carried out at 1000 MPa (mm / sec) until the test piece broke.

[0088] (Evaluation) Figure 2 shows the XRD profiles of the alloys of Examples 1 and 2 and Comparative Examples 1 and 2. The analysis results of the XRD profiles are shown in Figure 3. As shown in Figures 2 and 3, the main peak of the FCC structure was confirmed in the XRD profile of each alloy, and the lattice constants obtained by experiment were in good agreement with the calculated values ​​obtained by Vegard's law. The peak half-width in Figure 3 is the value calculated for the main peak of the XRD profile. It can be seen that the alloys produced by laser powder bed fusion have narrower peak half-widths than the alloys produced by arc melting, indicating a strong tendency toward a single phase.

[0089] Figure 4 shows SEM images and compositional analysis results for the alloys of Examples 1 and 2 and Comparative Examples 1 and 2. In Figure 4, the designed composition (charged composition) is indicated by a dotted line in the graph showing the compositional analysis results. Furthermore, Figure 5 shows the values ​​of each parameter calculated based on the compositional analysis results. As shown in Figures 4 and 5, the alloys produced by the arc melting method (Example 2, Comparative Example 2) had a dendritic structure. In contrast, the alloys produced by the laser powder bed fusion method (Example 1, Comparative Example 1) had a fine structure, with no dendritic structure observed.

[0090] Figure 6 shows the results of measuring the amount of absorbed hydrogen in the alloys of Examples 1 and 2 and Comparative Examples 1 and 2. The amount of absorbed hydrogen on the vertical axis of Figure 6 corresponds to the amount of hydrogen introduced into the alloy in the hydrogen introduction test (introduced hydrogen amount). As shown in Figure 6, the alloys of Examples 1 and 2 have a significantly reduced amount of absorbed hydrogen compared to the alloys of Comparative Examples 1 and 2.

[0091] Figure 7 shows the results of slow strain rate tensile tests of test pieces before and after the hydrogen charging test for the alloys of Examples 1 and 2 and Comparative Examples 1 and 2. As shown in Figure 7, the alloys of Examples 1 and 2 showed almost no decrease in ductility after the hydrogen charging test and had excellent hydrogen embrittlement resistance. In contrast, the alloys of Comparative Examples 1 and 2 showed a significant decrease in ductility after the hydrogen charging test.

[0092] The hydrogen sensitivity index HEI was calculated based on the results shown in Fig. 7. The hydrogen sensitivity index HEI was calculated using the following formula.

[0093]

[0094] where ε ｆＨ is the value of the plastic strain of the specimen after the hydrogen charging test, and ε ｆ０ is the value of plastic strain of the test specimen before the hydrogen charging test.

[0095] Fig. 8 is a diagram showing the hydrogen sensitivity index calculated based on the measurement results of Fig. 7. As shown in Fig. 8, it can be seen that the alloys of Examples 1 and 2 have significantly smaller values ​​of the hydrogen sensitivity index HEI than the alloys of Comparative Examples 1 and 2.

[0096] 9 shows the measurement results of slow strain rate tensile tests using test pieces in a hydrogen charging environment for the alloys of Example 1 and Comparative Example 1. As shown in Fig. 9, it can be seen that the alloy of Example 1 exhibits excellent hydrogen embrittlement resistance even against an external load in a hydrogen environment (hydrogen exposure environment).

[0097] (Example 3) The alloy of Example 3 is Fe ２０ Co ２０ Ni ２０ Cu ２０ Al ２０ The alloy of Example 3 had the following chemical composition and was produced by the same method as in Example 2. The alloy of Example 3 was subjected to metallographic analysis.

[0098] Fig. 10 shows an XRD profile obtained by XRD measurement of the alloy of Example 3. Fig. 11 shows an SEM image and composition analysis results of the alloy of Example 3. Fig. 12 also shows the values ​​of each parameter calculated based on the composition analysis results. In Fig. 11, the designed composition (charged composition) is shown by a dotted line in the graph.

[0099] 10 to 12, main peaks of the FCC structure and the BCC structure were confirmed in the XRD profile of the alloy of Example 3, and the presence of a multiphase structure was confirmed in the SEM image of the alloy of Example 3. The relatively dark areas in the SEM image are phases having a BCC structure, and the relatively white areas are phases having an FCC structure.

[0100] In the alloy of Example 3, the average value AVΔH of the mixing enthalpy with hydrogen was found to be 0.01 in both the phase having the BCC structure and the phase having the FCC structure. Ｘ－Ｈ On the other hand, in the phase having the FCC structure, the Cu concentration was relatively higher than in the phase having the BCC structure, and conversely, the Al concentration was relatively lower.

[0101] When the above-mentioned hydrogen embrittlement resistance evaluation test was performed on the alloy of Example 3, the following can be said. That is, the alloy of Example 3, like the alloys of Examples 1 and 2, has relatively higher hydrogen embrittlement resistance (i.e., the amount of hydrogen penetration into the alloy is relatively small) than the alloys of Comparative Examples 1 and 2. This is supported by the composition analysis results in FIGS. 5 and 12 and the hydrogen embrittlement resistance evaluation of the alloys of Examples 1 and 2.

[0102] [Summary] The alloy for hydrogen resistant components in aspect 1 of the present invention is an alloy for hydrogen resistant components used in hydrogen resistant components having hydrogen embrittlement resistance properties, and includes a basic component consisting of one or more iron group elements and a low hydrogen affinity component consisting of one or more metal elements from a group of metal elements having a lower affinity for hydrogen than the iron group elements, wherein the basic component is contained in a chemical composition of the alloy for hydrogen resistant components at an atomic ratio of 50% or more, and the average value of the mixing enthalpy with hydrogen, calculated based on the mixing enthalpy with hydrogen and the atomic ratio of each of all metal elements contained in the chemical composition, is -20 kJ / mol or more.

[0103] In the alloy for hydrogen-resistant components according to aspect 2 of the present invention, in accordance with aspect 1, the entropy of configuration determined by the number of types of all metal elements contained in the chemical composition and their atomic ratios is greater than 1.5R (R is the gas constant).

[0104] In a third aspect of the present invention, the alloy for a hydrogen-resistant component according to the first or second aspect includes a microstructure having an FCC structure, and in an X-ray diffraction measurement, the half-width of the most intense diffraction peak is 1.0° or less.

[0105] The alloy for hydrogen-resistant components in aspect 4 of the present invention is the alloy for hydrogen-resistant components in aspect 2 or 3, which comprises a microstructure having an FCC structure, wherein the microstructure has an enthalpy of mixing calculated based on the chemical composition of the microstructure that is greater than -20 kJ / mol and less than 5 kJ / mol, a delta parameter value which is an index representing the atomic radius ratio that is less than 6.6%, an omega parameter value which is an index relating to the melting point that is 1.1 or more, a VEC value which is an index representing the valence electron concentration that is 8.0 or more, and an average value of the enthalpy of mixing with hydrogen that is -20 kJ / mol or more.

[0106] The alloy for hydrogen-resistant components in aspect 5 of the present invention is the alloy for hydrogen-resistant components in aspect 2, which has a first phase and a second phase containing the basic component and the low hydrogen affinity component, and both of the first phase and the second phase have an average value of mixing enthalpy with hydrogen of -20 kJ / mol or more and have an FCC structure.

[0107] The alloy for hydrogen-resistant components in aspect 6 of the present invention is the alloy for hydrogen-resistant components in aspect 2 or 5, which has a first phase and a second phase containing the basic component and the low hydrogen affinity component, and the first phase and the second phase have an enthalpy of mixing calculated based on their respective chemical compositions that is greater than -20 kJ / mol and less than 5 kJ / mol, a delta parameter value which is an index representing the atomic radius ratio is less than 6.6%, an omega parameter value which is an index relating to the melting point is 1.1 or more, and a VEC value which is an index representing the valence electron concentration is 8.0 or more.

[0108] The alloy for hydrogen-resistant components in Aspect 7 of the present invention is the alloy for hydrogen-resistant components in Aspect 2, comprising: a phase having a BCC structure containing the basic component and the low-hydrogen-affinity component; and a phase having an FCC structure containing the basic component and the low-hydrogen-affinity component and having a chemical composition in which the VEC value, which is an index representing the valence electron concentration, is higher than that of the BCC structure phase, wherein the phase having the BCC structure and the phase having the FCC structure have an enthalpy of mixing greater than -20 kJ / mol and less than 5 kJ / mol, a delta parameter value, which is an index representing the atomic radius ratio, less than 6.6%, an omega parameter value, which is an index relating to the melting point, of 1.1 or more, and an average value of the enthalpy of mixing with hydrogen of -20 kJ / mol or more, calculated based on their respective chemical compositions.

[0109] The alloy for hydrogen-resistant components in aspect 8 of the present invention is the alloy for hydrogen-resistant components in aspect 2 or 7, comprising: a phase having a BCC structure containing the basic component and the low hydrogen affinity component; and a phase having an FCC structure containing the basic component and the low hydrogen affinity component and having a chemical composition in which the VEC value, an index representing the valence electron concentration, is higher than that of the BCC structure phase, wherein the low hydrogen affinity component contains Cu, and the FCC structure phase has a higher Cu concentration than the BCC structure phase.

[0110] The alloy for hydrogen-resistant components in aspect 9 of the present invention is, in any one of aspects 2 to 8, an alloy in which the basic components consist of Fe, Co, and Ni, the low hydrogen affinity components include Cu and Al, the enthalpy of mixing calculated based on the chemical composition is greater than -20 kJ / mol and less than 5 kJ / mol, the delta parameter value, which is an index representing the atomic radius ratio, is less than 6.6%, the omega parameter value, which is an index relating to the melting point, is 1.1 or more, and the VEC value, which is an index representing the valence electron concentration, is 8.0 or more, and the alloy has an FCC structure.

[0111] In Aspect 10 of the present invention, the alloy for hydrogen-resistant members is, in any one of Aspects 1 to 9, a cathode hydrogen charging method using a 0.1 M NaOH aqueous solution at 20 mA / cm ２ When a hydrogen introduction test was conducted in which hydrogen was charged at a current density of 1000 kJ / cm for 18 hours, the amount of absorbed hydrogen was 3 ppm by weight or less.

[0112] A hydrogen-resistant member according to an eleventh aspect of the present invention includes the alloy for a hydrogen-resistant member according to any one of the first to tenth aspects.

[0113] A method for producing an alloy for a hydrogen-resistant component in Aspect 12 of the present invention is the method for producing an alloy for a hydrogen-resistant component in any one of Aspects 1 to 10, and includes the steps of preparing raw materials, preparing a mixed composition by mixing the raw materials so as to have the above-mentioned chemical composition, and producing the alloy for a hydrogen-resistant component by melting and solidifying the mixed composition using a casting method or an additive manufacturing method.

[0114] The hydrogen embrittlement resistant alloy according to aspect 13 of the present invention has the composition formula Fe: ａ Co ｂ Ni ｃ Cu ｄ Al ｅ and the balance consisting of impurities, wherein the chemical composition satisfies 21.0≦a≦23.0, 20.0≦b≦22.0, 17.0≦c≦19.0, 25.0≦d≦27.0, and 12.0≦e≦14.0, where a+b+c+d+e=100, and the alloy has an FCC structure.

[0115] The hydrogen embrittlement resistant alloy of aspect 14 of the present invention is the alloy of aspect 13, wherein the average value of the mixing enthalpy with hydrogen calculated based on the mixing enthalpy with hydrogen and the atomic ratio of each of all metal elements contained in the chemical composition is −20 kJ / mol or more.

[0116] The alloy design method in aspect 15 of the present invention includes an acquisition step of acquiring information on the mixing enthalpy with hydrogen for each element that can be contained in the alloy; a first selection step of selecting one or more iron-group elements as basic components; a second selection step of selecting one or more metal elements from a group of metal elements that have a lower affinity for hydrogen than the iron-group elements as low-hydrogen-affinity components; and a determination step of determining a chemical composition such that the average value of the mixing enthalpy with hydrogen, calculated based on the mixing enthalpy with hydrogen and atomic ratios of each of all metal elements in the alloy, including the basic components and the low-hydrogen-affinity components, is −20 kJ / mol or more.

[0117] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the above description are also included in the technical scope of the present invention.

Claims

1. An alloy for hydrogen-resistant components used in hydrogen-resistant components having hydrogen embrittlement resistance properties, comprising a basic component consisting of one or more iron-group elements and a low-hydrogen affinity component consisting of one or more metal elements from a group of metal elements that have a lower affinity for hydrogen than the iron-group elements, wherein the basic component accounts for 50% or more in atomic ratio in the chemical composition of the alloy for hydrogen-resistant components, and the average value of the mixing enthalpy with hydrogen, calculated based on the mixing enthalpy with hydrogen and atomic ratio of each of all metal elements contained in the chemical composition, is -20 kJ / mol or more.

2. An alloy for hydrogen-resistant components according to claim 1, wherein the entropy of the configuration determined by the number of types of all metal elements contained in the chemical composition and their atomic ratios is greater than 1.5R (R is the gas constant).

3. An alloy for use in a hydrogen-resistant component according to claim 2, which comprises a microstructure having an FCC structure, and in X-ray diffraction measurement, the half-width of the most intense diffraction peak of said microstructure is 1.0° or less.

4. An alloy for hydrogen-resistant components according to claim 3, wherein the microstructure has an enthalpy of mixing calculated based on the chemical composition of the microstructure that is greater than -20 kJ / mol and less than 5 kJ / mol, a delta parameter value which is an index representing the atomic radius ratio that is less than 6.6%, an omega parameter value which is an index relating to the melting point that is 1.1 or more, a VEC value which is an index representing the valence electron concentration that is 8.0 or more, and an average value of the enthalpy of mixing with hydrogen that is -20 kJ / mol or more.

5. An alloy for hydrogen-resistant components according to claim 2, having a first phase and a second phase containing said basic component and said low hydrogen affinity component, wherein both said first phase and said second phase have an average value of mixing enthalpy with hydrogen of -20 kJ / mol or more and have an FCC structure.

6. An alloy for hydrogen-resistant components according to claim 5, wherein the first phase and the second phase have an enthalpy of mixing calculated based on their respective chemical compositions that is greater than -20 kJ / mol and less than 5 kJ / mol, a delta parameter value which is an index representing the atomic radius ratio that is less than 6.6%, an omega parameter value which is an index relating to the melting point that is 1.1 or more, and a VEC value which is an index representing the valence electron concentration that is 8.0 or more.

7. An alloy for a hydrogen-resistant component according to claim 2, comprising: a phase having a BCC structure containing said basic component and said low-hydrogen affinity component; and a phase having an FCC structure containing said basic component and said low-hydrogen affinity component, and having a chemical composition in which the VEC value, an index representing valence electron concentration, is higher than that of said BCC structure phase, wherein the phase having the BCC structure and the phase having the FCC structure each have an enthalpy of mixing calculated based on their respective chemical compositions: greater than -20 kJ / mol and less than 5 kJ / mol; a delta parameter value, an index representing the atomic radius ratio, less than 6.6%; an omega parameter value, an index relating to the melting point, of 1.1 or more; and an average value of the enthalpy of mixing with hydrogen of -20 kJ / mol or more.

8. An alloy for a hydrogen-resistant component according to claim 7, wherein the low hydrogen affinity component contains Cu, and the phase having the FCC structure has a higher Cu concentration than the phase having the BCC structure.

9. An alloy for a hydrogen-resistant component according to claim 2, wherein the basic components consist of Fe, Co, and Ni, the low hydrogen affinity components include Cu and Al, and the alloy has an FCC structure, wherein the enthalpy of mixing calculated based on the chemical composition is greater than -20 kJ / mol and less than 5 kJ / mol, the delta parameter value, which is an index representing the atomic radius ratio, is less than 6.6%, the omega parameter value, which is an index relating to the melting point, is 1.1 or more, and the VEC value, which is an index representing the valence electron concentration, is 8.0 or more.

10. Cathodic hydrogen charging was performed using a 0.1 M NaOH aqueous solution at 20 mA / cm ２ 2. The alloy for hydrogen-resistant members according to claim 1, wherein the amount of absorbed hydrogen is 3 ppm by weight or less when a hydrogen introduction test is carried out in which hydrogen is charged at a current density of 1000 ppm for 18 hours.

11. A hydrogen-resistant member comprising the alloy for hydrogen-resistant members according to any one of claims 1 to 10.

12. A method for producing an alloy for a hydrogen-resistant component according to any one of claims 1 to 10, comprising the steps of: preparing raw materials; preparing a mixed composition by mixing the raw materials so as to have the chemical composition; and producing the alloy for a hydrogen-resistant component by melting and solidifying the mixed composition using a casting method or an additive manufacturing method.

13. The atomic ratio of the composition formula is Fe. ａ Co ｂ Ni ｃ Cu ｄ Al ｅ and the balance consisting of impurities, wherein the chemical composition satisfies the following conditions, where a+b+c+d+e=100: 21.0≦a≦23.0, 20.0≦b≦22.0, 17.0≦c≦19.0, 25.0≦d≦27.0, and 12.0≦e≦14.0; and the hydrogen embrittlement resistant alloy has an FCC structure.

14. A hydrogen embrittlement resistant alloy as set forth in claim 13, wherein the average value of the enthalpy of mixing with hydrogen, calculated based on the enthalpy of mixing with hydrogen and the atomic ratio of each of all metal elements contained in said chemical composition, is -20 kJ / mol or more.

15. A method for designing an alloy, comprising: an acquisition step of acquiring information on the mixing enthalpy with hydrogen for each element that can be contained in the alloy; a first selection step of selecting one or more iron-group elements as basic components; a second selection step of selecting one or more metal elements from a group of metal elements that have a lower affinity with hydrogen than the iron-group elements as low-hydrogen-affinity components; and a determination step of determining a chemical composition such that the average value of the mixing enthalpy with hydrogen, calculated based on the mixing enthalpy with hydrogen and atomic ratios of each of all metal elements in the alloy, including the basic components and the low-hydrogen-affinity components, is -20 kJ / mol or more.

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