Additive manufacturing low-stress high-entropy alloy design system and method based on lattice mismatch

Abstract

The invention relates to the technical field of additive manufacturing, in particular to an additive manufacturing low-stress high-entropy alloy design system and method based on lattice mismatch, which are used for effectively reducing interface stress of gradient materials, and the method comprises the following steps: analyzing a matrix crystal structure, and determining a high-entropy alloy crystal structure type consistent with the matrix crystal structure; based on a high-entropy alloy crystal structure, a high-entropy alloy virtual lattice approximate structure model is established; performing structure geometric optimization on the model to obtain a high-entropy alloy lattice constant under a stable structure; according to the obtained lattice constants, the proportion of all elements of the high-entropy alloy is adjusted by comparing the lattice constants of the base body, and the redesigned high-entropy alloy is calculated till the lattice mismatch degree of the high-entropy alloy and the base body is low; and gradient design is conducted on the designed high-entropy alloy with the low lattice mismatch degree and the base body, and the design result of the low lattice mismatch degree and the low interface stress of the additive manufacturing high-entropy alloy gradient material is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a system and method for designing low-stress high-entropy alloys for additive manufacturing based on lattice mismatch. Background Art

[0002] High entropy alloys, also known as multi-principal high entropy alloys, are composed of five or more elements. With their excellent mechanical properties, corrosion resistance and thermal stability, they are widely used in aerospace materials, automotive industry, and nuclear energy fields. High entropy alloys can achieve autonomous and controllable crystal structure through composition design. By introducing a composition gradient transition between the matrix material and the high entropy alloy, the material properties and functions can be changed from one side to the other along the thickness direction, thereby giving the material better mechanical, physical and chemical properties.

[0003] When the lattice constants of two different materials differ greatly, the lattice mismatch at the interface is high, which easily generates high interface stress. When the lattice constants of two different materials are close or tend to be consistent, the atoms on both sides of the interface are highly similar in arrangement and distribution, the lattice distortion in the interface area is low, and the interface stress on the material is low, which significantly improves the stability of the material interface.

[0004] At present, the research on high entropy alloy gradient materials mainly alleviates the stress concentration at the interface caused by thermal stress by changing the composition ratio of the matrix and high entropy alloy. However, simply changing the volume content of each material in the spatial position cannot effectively reduce the interface stress caused by the lattice mismatch of the material. Therefore, it is necessary to use the first-principles calculation tools to accurately design and control the lattice mismatch between the high entropy alloy and the matrix, so as to obtain a high entropy alloy with a low lattice mismatch with the matrix. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned background technology, the present invention proposes a system and method for designing low-stress high-entropy alloys for additive manufacturing based on lattice mismatch, which provides theoretical support for the design of high-entropy alloy gradient materials in the field of additive manufacturing, so as to achieve more efficient material design and development.

[0006] The technical solution of the present invention to solve the above problems is:

[0007] The present invention proposes a method for designing a low-stress high-entropy alloy system for additive manufacturing based on lattice mismatch, which is special in that:

[0008] It includes virtual lattice approximation (VCA) structural model unit, structural optimization unit and gradient material design unit.

[0009] The virtual lattice approximation (VCA) structural model unit is used to establish a disordered high-entropy alloy crystal structure model by defining mixed atoms; the structural optimization unit is used to find the lowest energy model of the disordered high-entropy alloy crystal structure, obtain the material lattice constant in a stable state, and continuously adjust the high-entropy alloy composition optimization to achieve a low lattice mismatch standard; the gradient material design unit is used to obtain a design result of low lattice mismatch and low interface stress for additively manufactured high-entropy alloys.

[0010] In addition, the present invention also proposes a method for designing a low-stress high-entropy alloy system for additive manufacturing based on the lattice mismatch, which is special in that it includes the following steps:

[0011] Step 1: Analyze the matrix crystal structure and determine the high entropy alloy crystal structure type that is consistent with the matrix crystal structure;

[0012] Step 2: Based on the high entropy alloy crystal structure, a high entropy alloy virtual lattice approximation (VCA) structure model is established;

[0013] Step 3: Optimize the structural geometry of the model in step 2 to obtain the lattice constant of the high entropy alloy under the stable structure;

[0014] Step 4: According to the lattice constant obtained in step 3, the proportion of each element in the high entropy alloy is adjusted by comparing it with the lattice constant of the matrix, and the redesigned high entropy alloy is substituted into step 2 for calculation until the lattice mismatch between the high entropy alloy and the matrix is ​​low;

[0015] Step 5: Perform gradient design on the designed high entropy alloy and matrix with lower lattice mismatch, and obtain the design results of low lattice mismatch and low interface stress of additively manufactured high entropy alloy gradient materials.

[0016] Furthermore, the above step 1 is specifically that, in order to effectively reduce the lattice mismatch, materials with similar atomic arrangement and distribution characteristics in space should be selected. Based on this consideration, the crystal structure of the high entropy alloy and the matrix material should be consistent. The proportion of each element in the high entropy alloy is designed according to the material function, and the multi-principal element high entropy alloy design theory is combined to determine whether it can form a stable single-phase solid solution, and the high entropy alloy empirical judgment formula is used to determine,

[0017]

[0018] In the formula, c i is the atomic percentage of element i, (VEC) i is the number of valence electrons of the ith element, and VEC is the average number of valence electrons in the high entropy alloy.

[0019] Furthermore, the above-mentioned step 2 of establishing a virtual lattice approximate structural model of a high entropy alloy is specifically to construct a unit cell of a crystal structure, and use a virtual lattice approximation (VCA) model for each atom in the unit cell according to the designed high entropy alloy element ratio. The model is characterized in that different types of atoms are mixed to occupy the same lattice position, and the atomic ratio reflects the doping ratio or solid solution composition of the elements in the actual material. The model can complete complex calculations within one unit cell.

[0020] Furthermore, the above-constructed single-phase high-entropy alloy virtual lattice approximation (VCA) structural model and geometric optimization use first-principles calculation software, which allows the establishment of a disordered crystal structure by defining mixed atoms.

[0021] Furthermore, the above step 3 is specifically to find the high entropy alloy structure with the lowest energy by refining the geometric shape of the unit cell, so as to obtain the high entropy alloy lattice constant under the stable structure. The geometric optimization task in the first principle calculation software is an iterative calculation process, which specifically reduces the magnitude of the calculated force and stress until they are less than the defined convergence tolerance.

[0022] Furthermore, the matrix lattice constant value of the above step 4 is obtained from standard powder diffraction data.

[0023] Furthermore, the above step 4 adjusts the ratio of each element in the high entropy alloy specifically by adjusting the atomic ratio according to the application requirements of the designed high entropy alloy, and simultaneously changing the doping ratio of each element in the unit cell to rebuild the model.

[0024] Furthermore, after the above step 4 completes the composition adjustment of the high entropy alloy, it is necessary to combine the multi-principal component high entropy alloy design theory again to determine whether the new high entropy alloy system can form a stable single-phase solid solution.

[0025] Furthermore, in the above step 4, the calculation formula for the lattice mismatch between the high entropy alloy and the matrix is ​​defined as:

[0026]

[0027] In the formula, δ represents the lattice mismatch, a su b strate represents the lattice constant of the matrix, a HEA Represents the lattice constant of the high entropy alloy.

[0028] Furthermore, the high entropy alloy that meets the design results of step 4 is subjected to gradient material design with the matrix, and by designing different composition ratios of the two materials, a design result of low lattice mismatch and low interface stress for additively manufactured high entropy alloy gradient material is obtained.

[0029] Advantages of the present invention:

[0030] The present invention proposes a design method for low-stress high-entropy alloys for additive manufacturing based on lattice mismatch, which is used to effectively reduce the interface stress of gradient materials, provide theoretical support for the design of high-entropy alloy gradient materials in the field of additive manufacturing, and achieve more efficient material design and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the lattice mismatch between the high entropy alloy and the matrix material due to different lattice constants, a is the matrix material, b is the high entropy alloy;

[0032] Figure 2 It is a schematic diagram of the virtual lattice approximation (VCA) structural model of high entropy alloy and matrix material;

[0033] Figure 3 It is a schematic diagram of the composition change of high entropy alloy gradient materials manufactured by additive manufacturing;

[0034] Figure 4 This is a schematic diagram of the change in atomic lattice mismatch during the gradient transition between a low-mismatch high-entropy alloy and the matrix material. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] The present invention proposes a lattice mismatch-based additive manufacturing low-stress high-entropy alloy design system, which includes a virtual lattice approximation (VCA) structural model unit, a structural optimization unit and a gradient material design unit.

[0037] The virtual lattice approximation (VCA) structure model unit is used to establish a disordered high entropy alloy crystal structure model by defining mixed atoms. The unit designs the proportion of each element in the high entropy alloy according to the material function, combines the multi-principal element high entropy alloy design theory to determine whether it can form a stable single-phase solid solution, and uses the high entropy alloy empirical judgment formula to determine,

[0038]

[0039] In the formula, c i is the atomic percentage of element i, (VEC) i is the number of valence electrons of the ith element, and VEC is the average number of valence electrons in the high entropy alloy.

[0040] The structure optimization unit is used to find the lowest energy model of the disordered high entropy alloy crystal structure, obtain the material lattice constant in a stable state, and continuously adjust the high entropy alloy composition to achieve a low lattice mismatch standard.

[0041] The gradient material design unit is used to obtain a design result of low lattice mismatch and low interface stress for additively manufactured high entropy alloy.

[0042] The present invention also proposes a method for designing a system for additively manufacturing low-stress high-entropy alloys based on the lattice mismatch, comprising the following steps:

[0043] Step 1: Analyze the matrix crystal structure and determine the high entropy alloy crystal structure type that is consistent with the matrix crystal structure;

[0044] Step 2: Based on the high entropy alloy crystal structure, establish a high entropy alloy virtual lattice approximation (VCA) structure model, see Figure 1 ;

[0045] Step 3: Optimize the structural geometry of the model in step 2 to obtain the lattice constant of the high entropy alloy under the stable structure;

[0046] Step 4: According to the lattice constant obtained in step 3, the proportion of each element in the high entropy alloy is adjusted by comparing it with the lattice constant of the matrix, and the redesigned high entropy alloy is substituted into step 2 for calculation until the lattice mismatch between the high entropy alloy and the matrix is ​​low;

[0047] Step 5: Perform gradient design on the designed high entropy alloy and matrix with lower lattice mismatch, and obtain the design results of low lattice mismatch and low interface stress of additively manufactured high entropy alloy gradient materials.

[0048] Furthermore, the above step 1 is specifically that, in order to effectively reduce the lattice mismatch, materials with similar atomic arrangement and distribution characteristics in space should be selected. Based on this consideration, the crystal structure of the high entropy alloy and the matrix material should be consistent. The proportion of each element in the high entropy alloy is designed according to the material function, and the multi-principal element high entropy alloy design theory is combined to determine whether it can form a stable single-phase solid solution, and the high entropy alloy empirical judgment formula is used to determine,

[0049]

[0050] In the formula, c i is the atomic percentage of element i, (VEC)i is the number of valence electrons of the ith element, and VEC is the average number of valence electrons in the high entropy alloy.

[0051] Furthermore, the above-mentioned step 2 of establishing a virtual lattice approximate structural model of a high entropy alloy is specifically to construct a unit cell of a crystal structure, and use a virtual lattice approximation (VCA) model for each atom in the unit cell according to the designed high entropy alloy element ratio. The model is characterized in that different types of atoms are mixed to occupy the same lattice position, and the atomic ratio reflects the doping ratio or solid solution composition of the elements in the actual material. The model can complete complex calculations within one unit cell.

[0052] Furthermore, the above-constructed single-phase high-entropy alloy virtual lattice approximation (VCA) structural model and geometric optimization use first-principles calculation software, which allows the establishment of a disordered crystal structure by defining mixed atoms.

[0053] Furthermore, the above step 3 is specifically to find the high entropy alloy structure with the lowest energy by refining the geometric shape of the unit cell, so as to obtain the high entropy alloy lattice constant under the stable structure. The geometric optimization task in the first principle calculation software is an iterative calculation process, which specifically reduces the magnitude of the calculated force and stress until they are less than the defined convergence tolerance.

[0054] Furthermore, the matrix lattice constant value of the above step 4 is obtained from standard powder diffraction data.

[0055] Furthermore, the above step 4 adjusts the ratio of each element in the high entropy alloy specifically by adjusting the atomic ratio according to the application requirements of the designed high entropy alloy, and simultaneously changing the doping ratio of each element in the unit cell to rebuild the model.

[0056] Furthermore, after the above step 4 completes the composition adjustment of the high entropy alloy, it is necessary to combine the multi-principal component high entropy alloy design theory again to determine whether the new high entropy alloy system can form a stable single-phase solid solution.

[0057] Furthermore, in the above step 4, the calculation formula for the lattice mismatch between the high entropy alloy and the matrix is ​​defined as:

[0058]

[0059] In the formula, δ represents the lattice mismatch, a su b strate represents the lattice constant of the matrix, a HEA Represents the lattice constant of the high entropy alloy.

[0060] Furthermore, the high entropy alloy that meets the design results of step 4 is subjected to gradient material design with the matrix, and by designing different composition ratios of the two materials, a design result of low lattice mismatch and low interface stress for additively manufactured high entropy alloy gradient material is obtained.

[0061] Example

[0062] A low-stress material design method for lattice mismatch of gradient materials between AlCrFeNiV high-entropy alloy and austenitic stainless steel matrix for additive manufacturing. This example is applied to the development and design of gradient materials between austenitic stainless steel and high-entropy alloy for additive manufacturing.

[0063] Select Al9Cr, a high entropy alloy with the same crystal structure as austenitic stainless steel 17 Fe 25 Ni 46 V3 is the initial VCA structure model. According to the empirical judgment formula of high entropy alloy in multi-principal element high entropy alloy design theory:

[0064]

[0065] Determine the high entropy alloy Al9Cr 17 Fe 25 Ni 46 V3 tends to form a stable single FCC solid solution phase.

[0066] According to the high entropy alloy Al9Cr 17 Fe 25 Ni 46 The V3 element ratio for each atom in the unit cell is used to establish the FCC crystal structure using the virtual lattice approximation (VCA) model in the first-principles design software Material Studio, such as Figure 2 Specifically, the proportion of elements in each atom is 9at% Al, 17at% Cr, 25at% Fe, 46at% Ni, and 3at% V.

[0067] The Al9Cr 17 Fe 25 Ni 46The V3 high entropy alloy model was selected, and the geometry optimization calculation of the unit cell was performed using the Geometry Optimization Task of the CASTEP module in the software Material Studio to obtain the high entropy alloy lattice constant under the stable structure. The proton balance equation PBE functional under the generalized gradient approximation (GGA) was selected to set the exchange correlation function between electrons and electrons, and the interaction between electrons and ions was treated by the norm-conserving pseudopotential in the first principles. The cutoff energy of the expanded plane wave function and the k-point mesh size in the Brillouin zone will be selected through convergence testing.

[0068] According to the obtained Al9Cr 17 Fe 25 Ni 46 The lattice constant of V3 high entropy alloy is larger than that of austenitic stainless steel. Combined with the design requirements of FCC high entropy alloy, Al and Ni elements are both FCC structures, which play an important role in material design. In addition, the increase in Al content will lead to the transformation of FCC structure to BCC structure. Therefore, the atomic proportions of Al and Ni elements are adjusted without changing the doping ratios of other elements in the unit cell, and the model is rebuilt.

[0069] The high entropy alloy with adjusted composition was verified again by the empirical judgment formula of high entropy alloy, and it was determined that the adjusted high entropy alloy tended to form a stable single FCC solid solution phase.

[0070] Repeat the above steps until the lattice mismatch between the AlCrFeNiV high entropy alloy and the austenitic stainless steel is low, and its final composition is Al 8.1 Cr 17 Fe 25 Ni 46.9 V3, and the accuracy of the high entropy alloy lattice constant design was verified by experiments. The experiment used the laser directed energy deposition preparation method to deposit Al on an austenitic stainless steel substrate. 8.1 Cr 17 Fe 25 Ni 46.9 V3 high entropy alloy. The prepared high entropy alloy was polished and tested by X-ray diffraction. The experimental data was consistent with the results obtained by the calculation software.

[0071] The designed Al 8.1 Cr 17 Fe 25 Ni 46.9The gradient material design of V3 high entropy alloy and austenitic stainless steel is carried out. By designing different composition ratios of the two materials, a design result of low lattice mismatch and low interface stress of high entropy alloy gradient material for additive manufacturing is obtained. The gradient transition diagram is shown in the figure. Figure 3 , Figure 4 Schematic diagram of the atomic lattice mismatch change during the gradient transition between an atomically designed low-mismatch high-entropy alloy and a matrix material.

[0072] The above descriptions are merely embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related system fields, are also included in the protection scope of the present invention.

Claims

1. A design system for additively manufactured low-stress high-entropy alloys based on lattice mismatch, characterized by: It includes virtual lattice approximation (VCA) structural model unit, structural optimization unit and gradient material design unit; The virtual lattice approximation (VCA) structure model unit is used to establish a disordered high entropy alloy crystal structure model by defining mixed atoms; The structural optimization unit is used to find the lowest energy model of the disordered high-entropy alloy crystal structure, obtain the material lattice constant in a stable state, and continuously adjust the high-entropy alloy composition to achieve the low lattice mismatch standard; The gradient material design unit is used to obtain the design results of low lattice mismatch and low interface stress for additively manufactured high entropy alloy.

2. A design method for additively manufactured low-stress high-entropy alloys based on lattice mismatch, which is special in that it includes the following steps: Step 1: Analyze the matrix crystal structure and determine the high entropy alloy crystal structure type that is consistent with the matrix crystal structure; Step 2: Based on the high entropy alloy crystal structure, establish a high entropy alloy virtual lattice approximate structure model; Step 3: Optimize the structural geometry of the model in step 2 to obtain the lattice constant of the high entropy alloy under the stable structure; Step 4: According to the lattice constant obtained in step 3, the proportion of each element in the high entropy alloy is adjusted by comparing it with the lattice constant of the matrix, and the redesigned high entropy alloy is substituted into step 2 for calculation until the lattice mismatch between the high entropy alloy and the matrix is ​​low; Step 5: Perform gradient design on the designed high entropy alloy and matrix with lower lattice mismatch, and obtain the design results of low lattice mismatch and low interface stress of additively manufactured high entropy alloy gradient materials.

3. The design method of low stress high entropy alloy for additive manufacturing based on lattice mismatch according to claim 2 is characterized in that: Specifically, step 1 is to design the proportion of each element of the high entropy alloy according to the material function, and determine whether it can form a stable single-phase solid solution by combining the multi-principal element high entropy alloy design theory, and use the high entropy alloy empirical judgment formula to determine, In the formula, c i is the atomic percentage of element i, (VEC) i is the number of valence electrons of the ith element, and VEC is the average number of valence electrons in the high entropy alloy.

4. The design method for low-stress high-entropy alloys for additive manufacturing based on lattice mismatch according to claim 3 is characterized in that: The step 2 of establishing a virtual lattice approximate structural model of a high entropy alloy is specifically to construct a unit cell of a crystal structure, and use a virtual lattice approximate model for each atom in the unit cell according to the designed high entropy alloy element ratio. The model is characterized in that different types of atoms are mixed to occupy the same lattice position, and the atomic ratio reflects the doping ratio or solid solution composition of the elements in the actual material. The model can complete complex calculations within one unit cell.

5. The design method for low stress high entropy alloys for additive manufacturing based on lattice mismatch according to claim 4 is characterized in that: Specifically, step 3 is to find the high entropy alloy structure with the lowest energy by refining the geometric shape of the unit cell, so as to obtain the high entropy alloy lattice constant under the stable structure.

6. The design method of low stress high entropy alloy for additive manufacturing based on lattice mismatch according to claim 5 is characterized in that: The matrix lattice constant value of step 4 is obtained from standard powder diffraction data.

7. The design method for low stress high entropy alloys for additive manufacturing based on lattice mismatch according to claim 6 is characterized in that: In step 4, adjusting the ratio of each element in the high entropy alloy specifically involves adjusting the atomic ratio of the designed high entropy alloy according to the application requirements, and simultaneously changing the doping ratio of each element in the unit cell to re-establish the model.

8. The design method for low stress high entropy alloys for additive manufacturing based on lattice mismatch according to claim 7 is characterized in that: After completing the composition adjustment of the high entropy alloy in step 4, it is necessary to combine the multi-principal component high entropy alloy design theory again to determine whether the new high entropy alloy system can form a stable single-phase solid solution.

9. The design method for low stress high entropy alloys for additive manufacturing based on lattice mismatch according to claim 8 is characterized in that: In step 4, the formula for calculating the lattice mismatch between the high entropy alloy and the matrix is ​​defined as: In the formula, δ represents the lattice mismatch, a su b strate represents the lattice constant of the matrix, a HEA Represents the lattice constant of the high entropy alloy.

10. The design method of low stress high entropy alloy for additive manufacturing based on lattice mismatch according to claim 9 is characterized in that: Specifically, step 5 is to perform gradient material design on the high entropy alloy and the matrix that meet the design results of step 4, and obtain the design result of low lattice mismatch and low interface stress of the additively manufactured high entropy alloy gradient material by designing different composition ratios of the two materials.

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