A method for preparing a metal component with dual gradient of structure and stress

Abstract

The present invention relates to a method for preparing a dual-gradient metal component of organization and stress, comprising: obtaining a mapping relationship between microstructure and additive manufacturing process parameters; performing additive manufacturing on a metal component with gradient organization according to the mapping relationship; removing internal stress from the metal component with gradient organization to obtain a zero-stress gradient microstructure metal component; using laser impact to introduce residual compressive stress on the surface of the zero-stress gradient microstructure metal component to obtain a dual-gradient metal component of organization and stress. The purpose of the method for preparing a dual-gradient metal component of organization and stress is to solve the problem that the existing gradient metal materials have relatively poor comprehensive performances in terms of strength, surface fatigue resistance and wear resistance.

Description

Technical Field

[0001] The invention relates to the technical field of gradient material preparation, and in particular to a method for preparing a metal component with dual gradients of structure and stress. Background Art

[0002] Gradient materials refer to new materials with uniform or non-uniform components inside, different regions showing differentiated properties, and meeting special use requirements. As far as gradient metal materials are concerned, common gradient metal materials include metal materials with gradient microstructures and metal materials with gradient stress structures. Gradient microstructures can achieve both high strength and toughness of materials, especially the structure with a gradient transition from fine surface grains to coarse internal grains, which can provide excellent plasticity from fine surface grains and good strength from coarse core grains. Gradient stress can improve the surface performance of materials, especially the structure with a gradient transition from surface compressive stress to core tensile stress, which can neutralize part of the out-of-service load with surface compressive stress, delay the time for surface damage of materials, and improve fatigue, wear and other performance.

[0003] Patent CN113510248B discloses a patent for preparing a titanium alloy integral blade disk with gradient structure by adjusting the overlap distance, powder feeding rate, laser spot size, melt pool overlap rate, laser power and other process parameters, but it does not have gradient stress distribution. Patent CN104588650B discloses a functional gradient part additive manufacturing method based on three-dimensional heterogeneous powder laying, which realizes the precise control of the material composition at each point in the part, but it also does not have gradient stress distribution. Patent CN106825574B discloses a metal gradient material laser shock forging composite additive manufacturing method, which uses laser shock mainly to avoid or reduce defects such as pores, unfusion and shrinkage.

[0004] Therefore, the inventor provides a method for preparing a metal component with dual gradient of structure and stress. Summary of the invention

[0005] (1) Technical issues to be solved

[0006] The embodiment of the present invention provides a method for preparing a metal component with dual gradients in structure and stress, which solves the technical problem that the existing gradient metal materials have relatively poor comprehensive performances in strength, surface fatigue resistance and wear resistance.

[0007] (2) Technical solution

[0008] The present invention provides a method for preparing a metal component with dual gradient of structure and stress, comprising the following steps:

[0009] Obtain the mapping relationship between microstructure and additive manufacturing process parameters;

[0010] According to the mapping relationship, additive manufacturing is performed on the metal component with gradient structure;

[0011] Removing internal stress from the metal component with gradient structure to obtain a zero-stress gradient microstructure metal component;

[0012] Laser shock is used to introduce residual compressive stress into the surface layer of the zero stress gradient microstructure metal component to obtain a metal component with dual gradient of structure and stress.

[0013] Furthermore, the step of obtaining a mapping relationship between the microstructure and the additive manufacturing process parameters specifically includes the following steps:

[0014] Calculating the cumulative input energy of the test block to be processed, and determining the average grain size of the test block to be processed by metallographic method;

[0015] Utilizing the average grain size and the accumulated input energy to respectively perform parameterized representation on the microstructure and the additive manufacturing process parameters, and obtaining a first parameter formula and a second parameter formula;

[0016] A mapping relationship between the average grain size and the accumulated input energy is obtained according to the first parameter formula and the second parameter formula.

[0017] Furthermore, the calculation of the cumulative input energy of the test block to be processed specifically includes the following steps:

[0018] The test block to be processed is prepared by setting the laser power, and the processing time is recorded;

[0019] The accumulated input energy is calculated according to the set power and the processing time.

[0020] Furthermore, the step of obtaining a mapping relationship between the average grain size and the accumulated input energy according to the first parameter formula and the second parameter formula specifically includes the following steps:

[0021] Obtaining the mapping relationship between the average grain size and the cumulative input energy by least square method and nonlinear function fitting;

[0022] According to the mapping relationship, a mapping relationship between the average grain size and the additive manufacturing process parameters is obtained.

[0023] Furthermore, the additive manufacturing of the metal component with gradient structure is performed according to the mapping relationship, specifically:

[0024] The cumulative input energy E1 is used to prepare an additive layer with a thickness of Δh1, and the corresponding grain size is d1. The cumulative input energy E2 is used to prepare an additive layer with a thickness of Δh2, and the corresponding grain size is d2. The cumulative input energy E3 is used to prepare an additive layer with a thickness of Δh3, and the corresponding grain size is d3. And so on, a metal additive component with a uniform gradient structure is obtained.

[0025] Furthermore, the additive manufacturing of the metal component with gradient structure is performed according to the mapping relationship, specifically:

[0026] The cumulative input energy E1 is used to prepare an additive layer with a thickness of Δh1, and the corresponding grain size is d1. The cumulative input energy E2 is used to prepare an additive layer with a thickness of Δh2, and the corresponding grain size is d2. The cumulative input energy E1 is used to prepare an additive layer with a thickness of Δh1, and the corresponding grain size is d1. And so on, a metal additive component with a repeated gradient structure is obtained.

[0027] Furthermore, the internal stress of the metal component with gradient structure is removed to obtain the metal component with zero stress gradient microstructure, specifically:

[0028] Thermal aging and / or vibration aging are used to remove the internal stress of the metal component with gradient structure, so as to obtain the zero-stress gradient microstructure metal component.

[0029] Furthermore, the laser shock is used to introduce residual compressive stress into the surface layer of the zero stress gradient microstructure metal component to obtain a microstructure and stress dual gradient metal component, specifically:

[0030] The zero stress gradient microstructure metal component is impacted once or multiple times by using a pulsed laser to introduce residual compressive stress into its surface layer, thereby obtaining the structure and stress dual gradient metal component.

[0031] Furthermore, before the laser shock treatment, an absorption layer is arranged on the surface to be impacted of the zero stress gradient microstructure metal component and a deionized water constraint layer is applied.

[0032] Furthermore, after obtaining the metal component with dual gradient of structure and stress, the method further comprises:

[0033] The distribution of residual stress along the depth direction is determined by non-destructive or destructive residual stress detection methods.

[0034] (3) Beneficial effects

[0035] In summary, the present invention uses laser shock to additively manufacture metal components with gradient structures, which can reduce internal defects of additively manufactured components and improve the safety and reliability of additively manufactured components. The prepared metal gradient components have both gradient microstructure and gradient stress distribution. The gradient microstructure can achieve strong and tough synergy, and the gradient stress distribution can improve surface performance. The combination of the two expands the application scenarios of metal gradient components to a wider range. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a schematic flow chart of a method for preparing a metal component with dual gradients of structure and stress provided by an embodiment of the present invention;

[0038] Figure 2 It is a schematic structural diagram of a metal component with dual gradient of organization and stress provided in Example 1 of the present invention;

[0039] Figure 3 It is a structural schematic diagram of a metal component with dual gradient of structure and stress provided in Example 2 of the present invention.

[0040] In the figure:

[0041] 1-first additive layer; 2-second additive layer; 3-third additive layer; 4-first surface to be impacted; 5-second surface to be impacted; 6-first surface residual compressive stress layer; 7-first central core tensile stress layer; 8-fourth additive layer; 9-fifth additive layer; 10-sixth additive layer; 11-seventh additive layer; 12-third surface to be impacted; 13-second surface residual compressive stress layer; 14-second central core tensile stress layer. DETAILED DESCRIPTION

[0042] The following is a further detailed description of the embodiments of the present invention in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments, and covers any modification, replacement and improvement of parts, components and connection modes without departing from the spirit of the present invention.

[0043] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0044] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0045] Figure 1 1 is a flow chart of a method for preparing a metal component with dual gradient of structure and stress provided by an embodiment of the present invention. The method may include the following steps:

[0046] S100, obtaining a mapping relationship between microstructure and additive manufacturing process parameters;

[0047] S200, performing additive manufacturing on a metal component having a gradient structure according to a mapping relationship;

[0048] S300, removing internal stress from a metal component with a gradient structure to obtain a metal component with a zero stress gradient microstructure;

[0049] S400, using laser shock to introduce residual compressive stress into the surface layer of a metal component with a zero stress gradient microstructure, to obtain a metal component with a dual gradient of structure and stress.

[0050] In the above-mentioned embodiment, by using laser shock to additively manufacture metal components with gradient structures, the internal defects of the additively manufactured components can be reduced, and the safety and reliability of the use of the additively manufactured components can be improved. The prepared metal gradient components have both gradient microstructure and gradient stress distribution. The gradient microstructure can achieve strong and tough synergy, and the gradient stress distribution can improve the surface performance. The combination of the two expands the application scenarios of metal gradient components to a wider range.

[0051] As an optional implementation, in step S100, obtaining a mapping relationship between microstructure and additive manufacturing process parameters specifically includes the following steps:

[0052] S101, calculating the cumulative input energy of the test block to be processed, and determining the average grain size of the test block to be processed by metallographic method;

[0053] S102, using the average grain size and the accumulated input energy to respectively perform parameterized representation of the microstructure and the additive manufacturing process parameters to obtain a first parameter formula and a second parameter formula;

[0054] S103, obtaining a mapping relationship between the average grain size and the accumulated input energy according to the first parameter formula and the second parameter formula.

[0055] In the above embodiment, a laser, arc, electron beam or the like is used as a heat source to melt the metal powder along a specific path, the average grain size d is used to parameterize the microstructure, and the cumulative energy input E (Formula 1) is used to parameterize the additive manufacturing process parameters:

[0056] E = ηPt(1);

[0057] In the formula, η is the power efficiency coefficient, P is the power used in the additive manufacturing process, and t is the time required to prepare components of the same shape and volume. The mapping relationship between E and d is further obtained through the least squares method, nonlinear function fitting and other methods, thereby obtaining the mapping relationship between the average grain size d and the additive manufacturing process parameters (Formula 2):

[0058] d=f(E)(2).

[0059] As an optional implementation, in step S200, additive manufacturing is performed on the metal component with the gradient structure according to the mapping relationship, specifically:

[0060] The cumulative input energy E1 is used to prepare an additive layer with a thickness of Δh1, and the corresponding grain size is d1. The cumulative input energy E2 is used to prepare an additive layer with a thickness of Δh2, and the corresponding grain size is d2. The cumulative input energy E3 is used to prepare an additive layer with a thickness of Δh3, and the corresponding grain size is d3. And so on, a metal additive component with a uniform gradient structure is obtained.

[0061] In the above embodiment, a metal additive component with a uniform gradient structure having a thickness of H is obtained, and the grain size distribution of the metal additive component is d1, d2, d3, ..., d n , H=Δh1+Δh2+Δh3+…+Δh n .

[0062] As an optional implementation, in step S200, additive manufacturing is performed on the metal component with the gradient structure according to the mapping relationship, specifically:

[0063] The cumulative input energy E1 is used to prepare an additive layer with a thickness of Δh1, and the corresponding grain size is d1. The cumulative input energy E2 is used to prepare an additive layer with a thickness of Δh2, and the corresponding grain size is d2. The cumulative input energy E1 is used to prepare an additive layer with a thickness of Δh1, and the corresponding grain size is d1. And so on, a metal additive component with a repeated gradient structure is obtained.

[0064] In the above embodiment, a metal additive component with a repeated gradient structure having a thickness of H is obtained, and the grain size distribution of the metal additive component is d1, d2, d1, d2, ..., d1, d2,

[0065] As an optional implementation, in step S300, the internal stress of the metal component with gradient structure is removed to obtain a metal component with zero stress gradient microstructure, specifically: thermal aging and / or vibration aging are used to remove the internal stress of the metal component with gradient structure to obtain a metal component with zero stress gradient microstructure.

[0066] In the above implementation, physical methods such as thermal aging and vibration aging are used to remove the internal stress of the gradient microstructure metal component, and finally obtain a gradient microstructure metal component with a near zero stress state. Thermal aging needs to strictly select a suitable temperature according to the type of material, and before vibration aging, it is necessary to calculate its natural frequency in advance according to the size of the part through finite element numerical simulation.

[0067] Among them, the thermal aging step mainly includes heating, insulation and cooling processes, among which the heating and cooling processes need to control the temperature change rate.

[0068] Among them, the vibration aging steps mainly include natural frequency solution, slow speed increase, high speed increase, and slow speed decrease stages.

[0069] As an optional implementation, in step S400, residual compressive stress is introduced into the surface layer of the zero stress gradient microstructure metal component by laser shock to obtain a dual gradient metal component of structure and stress. Specifically, a pulsed laser is used to impact the zero stress gradient microstructure metal component once or multiple times to introduce residual compressive stress into its surface layer to obtain a dual gradient metal component of structure and stress.

[0070] In the above-mentioned embodiment, the main steps of laser shock peening include: laser parameter selection, absorption layer arrangement, constraint layer setting, laser path planning, laser shock and part chemical cleaning.

[0071] As an optional implementation, before laser shock treatment, an absorption layer is provided on the surface to be impacted of the zero stress gradient microstructure metal component and a deionized water constraint layer is applied.

[0072] As an optional implementation, after obtaining the dual-gradient metal component of structure and stress, it also includes: using a non-destructive or destructive residual stress detection method to determine the distribution of residual stress along the depth direction.

[0073] Example 1

[0074] Step 1: Mapping of additive manufacturing microstructure and process parameters. Laser was used to select and melt the additive TC4 titanium alloy. First, two levels of laser power (P1 and P2) were set from high to low. Two test blocks with length, width and height of a, b and c were prepared by adjusting the process parameters such as powder feeding amount, spot diameter and scanning speed. The required time was recorded as t1 and t2, and the cumulative input energy was calculated as E1 and E2 according to formula (1). The corresponding grain sizes were determined by metallographic method as d1 and d2.

[0075] Step 2: Additive manufacturing of metal components with gradient structures. The third additive layer 3 is prepared using the additive manufacturing parameters corresponding to the cumulative input energy E1 in step 1, and then the first additive layer 1 is prepared using the additive manufacturing parameters corresponding to the cumulative input energy E2 in step 1, and finally the second additive layer 2 is prepared using the additive manufacturing parameters corresponding to the cumulative input energy E2 in step 1, thereby completing the manufacturing of metal additive components with gradient structures.

[0076] Step 3: Removal of internal stress of additively manufactured gradient metal components. Perform stress relief annealing on the metal additive component with gradient structure prepared in step 2 to obtain a metal additive component in a zero stress state.

[0077] Step 4: Gradient stress implantation of additively manufactured gradient metal components. Laser shock peening is used to process the metal additive component manufacturing in a zero stress state. Before the shock treatment, an absorption layer is arranged on the first surface to be impacted 4, a deionized water constraint layer is applied, and then the shock is performed; the second surface to be impacted 5 is impacted in the same way to prepare the following. Figure 2 Dual gradient metal components shown.

[0078] Step 5: Gradient stress test characterization. The electrolytic polishing peeling method is used to obtain different depth layers of the additively manufactured gradient metal component after laser shock, and the residual stress of different depth layers is measured by X-ray diffraction to obtain the surface residual compressive stress layer 6 and the central core tensile stress layer 7.

[0079] Through the above five steps, the preparation of a dual-gradient metal component with a gradient microstructure of different grain sizes d1-d2-d1 and a gradient stress distribution of residual compressive stress-residual tensile stress-residual compressive stress is completed.

[0080] Example 2

[0081] Step 1: Mapping of additive manufacturing microstructure and process parameters. Laser was used to select and melt the additive TC4 titanium alloy. First, two levels of laser power (P3, P4, P5, P6) were set from high to low. Two test blocks with length, width and height of a, b and c were prepared by adjusting the process parameters such as powder feeding amount, spot diameter and scanning speed. The required time was recorded as t3, t4, t5 and t6 respectively. The cumulative input energy was calculated as E3, E4, E5 and E6 according to formula (1). The corresponding grain sizes were determined by metallographic method as d3, d4, d5 and d6 respectively.

[0082] Step 2: Additive manufacturing of metal components with gradient structure. The fourth additive layer 8 is prepared using the additive manufacturing parameters corresponding to the cumulative input energy E3 in step 1, and then the fifth additive layer 9 is prepared using the additive manufacturing parameters corresponding to the cumulative input energy E4 in step 1, the sixth additive layer 10 is prepared using the additive manufacturing parameters corresponding to the cumulative input energy E5 in step 1, and the seventh additive layer 11 is prepared using the additive manufacturing parameters corresponding to the cumulative input energy E6 in step 1, thereby completing the manufacturing of metal additive components with gradient structure.

[0083] Step 3: Removal of internal stress of additively manufactured gradient metal components. Perform vibration aging to remove stress on the metal additive component with gradient structure prepared in step 2 to obtain a metal additive component in a zero stress state.

[0084] Step 4: Gradient stress implantation of additively manufactured gradient metal components. Laser shock peening is used to process the metal additive component manufacturing in a zero stress state. Before the shock treatment, an absorption layer is arranged on the third surface to be impacted 12, a deionized water constraint layer is applied, and then the impact is performed to prepare the following. Figure 3 Dual gradient metal components shown.

[0085] Step 5: Gradient stress test characterization. Electrolytic polishing and delamination are used to obtain different depth layers of the additively manufactured gradient metal component after laser shock, and X-ray diffraction is used to measure the residual stress of different depth layers to obtain the surface residual compressive stress layer 13 and the central core tensile stress layer 14.

[0086] Through the above five steps, the preparation of the organization / stress dual gradient metal component with gradient microstructure of different grain sizes d3-d4-d5-d6 and gradient stress distribution of residual compressive stress-residual tensile stress-residual compressive stress is completed.

[0087] It should be clear that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. In addition, for the sake of brevity, a detailed description of known methods and technologies is omitted here.

[0088] The above are only embodiments of the present application and are not limited to the present application. For those skilled in the art, the present application may have various changes and variations without departing from the scope of the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for preparing a metal component with dual gradient of structure and stress, characterized in that: The method comprises the following steps: Obtain the mapping relationship between microstructure and additive manufacturing process parameters; According to the mapping relationship, additive manufacturing is performed on the metal component with gradient structure; Using thermal aging and / or vibration aging to remove the internal stress of the metal component with gradient structure to obtain a zero-stress gradient microstructure metal component; Using a pulsed laser to impact the zero stress gradient microstructure metal component once or multiple times, introducing residual compressive stress on its surface layer, and obtaining a metal component with dual structure and stress gradients; The step of obtaining a mapping relationship between microstructure and additive manufacturing process parameters specifically includes the following steps: Calculating the cumulative input energy of the test block to be processed, and determining the average grain size of the test block to be processed by metallographic method; Utilizing the average grain size and the accumulated input energy to respectively perform parameterized representation on the microstructure and the additive manufacturing process parameters, and obtaining a first parameter formula and a second parameter formula; According to the first parameter formula and the second parameter formula, obtaining a mapping relationship formula between the average grain size and the accumulated input energy; The calculation of the cumulative input energy of the test block to be processed specifically includes the following steps: The test block to be processed is prepared by setting the laser power, and the processing time is recorded; Calculating the accumulated input energy according to the set power and the processing time; The step of obtaining a mapping relationship between the average grain size and the accumulated input energy according to the first parameter formula and the second parameter formula specifically includes the following steps: Obtaining the mapping relationship between the average grain size and the cumulative input energy by least square method and nonlinear function fitting; According to the mapping relationship, a mapping relationship between the average grain size and the additive manufacturing process parameters is obtained.

2. The method for preparing a metal component with dual gradient of structure and stress according to claim 1, characterized in that: The method of performing additive manufacturing on a metal component with a gradient structure according to the mapping relationship is specifically as follows: Using the cumulative input energy E 1 Preparation thickness is Δh 1 additive layer, the corresponding grain size is d1, using the cumulative input energy E 2 Preparation thickness is Δh 2 additive layer, the corresponding grain size is d2, using the cumulative input energy E 3 Preparation thickness is Δh 3, the corresponding grain size is d3, and so on, to obtain a metal additive component with a uniform gradient structure.

3. The method for preparing a metal component with dual gradient of structure and stress according to claim 1, characterized in that: The method of performing additive manufacturing on a metal component with a gradient structure according to the mapping relationship is specifically as follows: Using the cumulative input energy E 1 Preparation thickness is Δh 1 additive layer, the corresponding grain size is d1, using the cumulative input energy E 2 Preparation thickness is Δh 2 additive layer, the corresponding grain size is d2, using the cumulative input energy E 1 Preparation thickness is Δh 1, and its corresponding grain size is d1, and so on, to obtain a metal additive component with a repeated gradient structure.

4. The method for preparing a metal component with dual gradient of structure and stress according to claim 1, characterized in that: Before laser shock treatment, an absorption layer is arranged on the surface to be impacted of the zero stress gradient microstructure metal component and a deionized water constraint layer is applied.

5. The method for preparing a metal component with dual gradient of structure and stress according to claim 1, characterized in that: After obtaining the dual-gradient metal component of structure and stress, the method further comprises: The distribution of residual stress along the depth direction is determined by non-destructive or destructive residual stress detection methods.

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