A method for regulating the mechanical properties of additively manufactured NiTi alloy components

Abstract

The present invention discloses a method for regulating the mechanical properties of an additive manufactured nickel-titanium alloy component, belonging to the technical field of laser additive manufacturing, and comprising the following steps: Step 1: Prepare a nickel-titanium alloy component through a powder bed powder feeding laser additive manufacturing process; Step 2: Perform heat treatment on the nickel-titanium alloy component. The heat treatment temperature is between 300°C and 550°C, and the heat treatment time is between 0.1 h and 3 h. During the heat treatment, an external load is applied to the nickel-titanium alloy component. The direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component, and the stress magnitude applied to the nickel-titanium alloy component should be in the range of 0.2 - 10 N / mm<supgt;2< / supgt; to achieve the regulation of the mechanical properties of the nickel-titanium alloy component. This method can effectively regulate the mechanical properties of the nickel-titanium alloy component and further promote the application of the nickel-titanium alloy component in the field of buffer energy absorption.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser additive manufacturing, and specifically relates to a method for regulating the mechanical properties of additively manufactured nickel-titanium alloy components. Background Art

[0002] Due to its shape memory effect, superelasticity, high damping properties, etc., nickel-titanium alloy is widely used in the fields of aerospace, medical treatment, mechanical manufacturing, etc. It is currently the shape memory alloy with the best memory performance, the widest application range, and the largest application amount. However, due to the high hardness of nickel-titanium alloy, the martensitic phase transformation process and microstructure are easily affected by machining behavior and thermal conditions, and its cutting performance is poor. It is very difficult to obtain nickel-titanium alloy components with complex structures through primary casting or secondary processing. In recent years, laser additive manufacturing technology has been widely used to fabricate nickel-titanium alloy components with complex structures. Among them, the powder bed fusion laser additive manufacturing process has attracted much attention because of its ability to form components with uniform composition, high precision, and excellent performance.

[0003] Nickel-titanium shape memory alloy exhibits good deformation ability due to its phase transformation output strain, and at the same time has excellent shape recovery function. Therefore, nickel-titanium alloy can be used as a new type of buffer energy-absorbing material for recycling. However, its poor machinability severely limits its application prospects. Commonly used nickel-titanium alloys mostly appear in simple configurations, such as wires, tubes, plates, etc. Laser additive manufacturing is expected to promote the application of nickel-titanium shape memory alloy in the field of buffer energy absorption.

[0004] Existing studies have shown that the mechanical properties of laser additive manufactured nickel-titanium alloy samples cannot reach the corresponding level prepared by traditional metallurgical methods. However, the advantage of additive manufacturing is that it can integrally near-net shape components with complex structures, and the complex structural factors will cause the components to be unable to perform secondary processing such as rolling and stamping, and the mechanical properties cannot be further regulated by traditional methods. Of course, if the process parameters and processing strategies in the laser additive manufacturing process are changed, the mechanical properties of the components may also be changed or further regulated. However, if the processing parameters are changed, the structural parameters of the components themselves will also be changed accordingly. Due to the existence of the above problems, there is currently no effective means to significantly regulate the mechanical properties of complex nickel-titanium components. Therefore, for laser additive manufactured nickel-titanium alloy components, a post-treatment method that does not require deformation treatment and only needs to in-situ regulate the mechanical properties of the component materials can be developed to achieve the purpose of overall regulating the mechanical properties of nickel-titanium alloy components. Summary of the Invention

[0005] To overcome the above problems, the present invention provides a method for regulating the mechanical properties of additively manufactured NiTi alloy components. By means of short-time heat treatment and changing the weight of the external load, the size, morphology and phase relationship between the nano-precipitates and the matrix phase of the additively manufactured NiTi alloy are adjusted, so as to effectively regulate the mechanical properties of the additively manufactured NiTi alloy components. This method can effectively regulate the mechanical properties of NiTi alloy components and further promote the application of NiTi alloy components in the field of buffer energy absorption.

[0006] A method for regulating the mechanical properties of additively manufactured NiTi alloy components, comprising the following steps:

[0007] Step 1: Prepare a NiTi alloy component by a powder bed laser additive manufacturing process;

[0008] Step 2: Heat-treat the NiTi alloy component at a temperature between 300°C and 550°C for a time between 0.1 h and 3 h. During the heat treatment, an external load is applied to the NiTi alloy component, and the direction of the applied external load is parallel to the forming direction of the NiTi alloy component. The stress magnitude applied to the NiTi alloy component should be between 0.2 and 10 N / mm 2 to achieve the regulation of the mechanical properties of the NiTi alloy component.

[0009] Preferably, the atomic percentage of the raw material components of the NiTi alloy component is 50.5% - 51.5% for nickel element, and the rest is titanium element.

[0010] Preferably, in Step 2, the heat treatment time is between 0.1 h and 1 h, and the heat treatment temperature is between 300°C and 400°C.

[0011] The beneficial effects of the present invention are as follows:

[0012] While this method improves the compressive strength of the additively manufactured NiTi alloy component, it does not sacrifice the ductility of the NiTi alloy component, maintaining a good strength-ductility relationship of the NiTi alloy component;

[0013] This method is a method for in-situ regulating the mechanical properties of NiTi alloy components, and does not require changing the structural parameters of the NiTi alloy components, and is widely applicable to NiTi alloy components obtained by additive manufacturing methods;

[0014] This operation method is simple and highly practical, and is also applicable to NiTi alloy components with complex structures. Just according to the main bearing capacity direction of compression or tension, change the direction of the external load during heat treatment, and the mechanical properties of complex NiTi alloy components can also be regulated. For large or small additively manufactured NiTi alloy components, just adjust the magnitude of the external load according to the size and weight of the component, and the mechanical properties of the component can also be regulated. Description of the Drawings

[0015] Figure 1 Is the three-dimensional configuration diagram of the embodiment of the present invention;

[0016] Figure 2 Is the schematic diagram of the embodiment of the present invention parallel to the forming direction;

[0017] Figure 3 Is the schematic diagram of the embodiment of the present invention perpendicular to the forming direction;

[0018] Figure 4 Is the schematic diagram of the external load in the method of the present invention;

[0019] Figure 5 Is the schematic diagram of the control mode of the external load during the short-time heat treatment process of the embodiment of the present invention;

[0020] Figure 6 Is the schematic diagram of the external load of the special post-treatment method of the comparative example of the present invention;

[0021] Figure 7 Is the compression force-strain curve of the NiTi alloy component of Example 17 of the present invention that is originally printed and not subjected to any post-treatment;

[0022] Figure 8 Is the compression force-strain curve of the NiTi alloy component of Example 4 of the present invention that is heat-treated at 350 °C for 0.5 h and simultaneously subjected to a 10 N external load for post-treatment;

[0023] Figure 9 Is the compression force-strain curve of the NiTi alloy component of Example 7 of the present invention that is heat-treated at 350 °C for 0.5 h and simultaneously subjected to a 20 N external load for post-treatment;

[0024] Figure 10 Is the compression force-strain curve of the NiTi alloy component of Example 2 of the present invention that is heat-treated at 300 °C for 1 h and simultaneously subjected to a 10 N external load for post-treatment;

[0025] Figure 11 Is the compression force-strain curve of the NiTi alloy component of Comparative Example 1 of the present invention that is heat-treated at 350 °C for 0.5 h but not subjected to an external load for post-treatment;

[0026] Figure 12 Is the compression force-strain curve of the NiTi alloy component of Comparative Example 2 of the present invention that is heat-treated at 350 °C for 0.5 h and simultaneously subjected to a 10 N external load, but the load direction is along the direction perpendicular to the forming direction;

[0027] Figure 13 Is the compression force-strain curve of the NiTi alloy component of Comparative Example 3 of the present invention that is heat-treated at 500 °C for 0.5 h but not subjected to an external load for post-treatment;

[0028] Figure 14 For Comparative Example 4 of the present invention, heat treatment is carried out at 500 °C for 0.5 h while applying an external load of 10 N, but the load direction is along the compression force-strain curve of the NiTi alloy component perpendicular to the forming direction;

[0029] Figure 15 It is a statistical chart of the mechanical property test of the embodiment of the present invention;

[0030] Figure 16 It is a statistical chart of the mechanical property test of the comparative example of the present invention. Specific Embodiments

[0031] To make the objectives, technical solutions and advantages 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 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 those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention. The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0033] Please refer to Figures 1 to 16 As shown, a method for regulating the mechanical properties of an additive manufactured NiTi alloy component includes the following steps:

[0034] Step 1: Prepare a NiTi alloy component by a powder bed laser additive manufacturing process;

[0035] Step 2: Heat-treat the NiTi alloy component. The heat treatment temperature is between 300 °C and 550 °C, and the heat treatment time is between 0.1 h and 3 h. During the heat treatment, an external load is applied to the NiTi alloy component, and the direction of the applied external load is parallel to the forming direction of the NiTi alloy component. The stress magnitude applied to the NiTi alloy component should be between 0.2 and 10 N / mm 2 within the range to achieve the regulation of the mechanical properties of the NiTi alloy component.

[0036] The atomic percentage of the raw material components of the NiTi alloy component is 50.5% - 51.5% for nickel element, and the rest is titanium element.

[0037] It has been found through experiments that short-term heat treatment alone cannot effectively regulate the mechanical properties of additive manufactured NiTi alloy components; specifically, when the NiTi alloy components are heat-treated at different temperatures and for different times within the temperature range of 300°C - 550°C, due to the uncertain precipitation positions and uneven growth of nano-precipitates, not only the mechanical properties of the NiTi alloy components are not improved, but the mechanical properties of the NiTi alloy components are deteriorated instead.

[0038] The present invention does not limit the specific operation of heat treatment, as long as the time and temperature of heat treatment meet the limitations of the present invention. In the present invention, the above operation can be carried out using a vacuum tube furnace.

[0039] In order to further improve the mechanical properties of NiTi alloy components, when the heat treatment time is 0.1h - 1h and the heat treatment temperature is between 300°C and 400°C, with the same external load maintained, the mechanical properties of the NiTi alloy components will be further improved. While the compressive strength is increased, the elastic recovery after unloading will also increase.

[0040] In some specific embodiments, when the heat treatment time is 1h - 3h and the heat treatment temperature is between 300°C and 400°C, with the same external load maintained, the compressive strength of the NiTi alloy components can be further improved, but at the same time, the compressible deformation amount of the NiTi alloy components is reduced.

[0041] In some specific embodiments, when the heat treatment time is 0.1 - 1h and the heat treatment temperature is between 400 - 550°C, with the same external load maintained, both the compressive strength and the compressible deformation amount of the NiTi alloy components can be reduced.

[0042] In some specific embodiments, when the heat treatment time is 0.1 - 1h and the heat treatment temperature is between 300 - 400°C, while increasing the external load during heat treatment, both the compressive strength and the recovery deformation amount after unloading are lower than those of the NiTi alloy components after post-treatment with a smaller external load, but larger than those of the directly prepared NiTi alloy components. It can be seen that under the same heat treatment conditions, by changing the magnitude of the external load, the mechanical properties of the NiTi alloy components obtained by the additive manufacturing method can be regulated.

[0043] Hereinafter, the mechanical properties of the NiTi alloy components regulated by this method will be introduced in detail through specific examples.

[0044] Example 1

[0045] The NiTi alloy component is heat-treated at 300°C for 0.5h. During the heat treatment, a load of 10N is applied to the NiTi alloy component. The direction of the applied external load is parallel to the forming direction of the NiTi alloy component. The stress per unit area on the NiTi alloy component is 2N / mm 2, a NiTi alloy component is obtained.

[0046] Example 2

[0047] The NiTi alloy component is heat-treated at 300 °C for 1 h. During the heat treatment, a load of 10 N is applied to the NiTi alloy component, and the direction of the applied external load is parallel to the forming direction of the NiTi alloy component. The stress per unit area on the NiTi alloy component is 2 N / mm 2 , a NiTi alloy component is obtained.

[0048] Example 3

[0049] The NiTi alloy component is heat-treated at 300 °C for 2 h. During the heat treatment, a load of 10 N is applied to the NiTi alloy component, and the direction of the applied external load is parallel to the forming direction of the NiTi alloy component. The stress per unit area on the NiTi alloy component is 2 N / mm 2 , a NiTi alloy component is obtained.

[0050] Example 4

[0051] The NiTi alloy component is heat-treated at 350 °C for 0.5 h. During the heat treatment, a load of 10 N is applied to the NiTi alloy component, and the direction of the applied external load is parallel to the forming direction of the NiTi alloy component. The stress per unit area on the NiTi alloy component is 2 N / mm 2 , a NiTi alloy component is obtained.

[0052] Example 5

[0053] The NiTi alloy component is heat-treated at 350 °C for 1 h. During the heat treatment, a load of 10 N is applied to the NiTi alloy component, and the direction of the applied external load is parallel to the forming direction of the NiTi alloy component. The stress per unit area on the NiTi alloy component is 2 N / mm 2 , a NiTi alloy component is obtained.

[0054] Example 6

[0055] The NiTi alloy component is heat-treated at 350 °C for 2 h. During the heat treatment, a load of 10 N is applied to the NiTi alloy component, and the direction of the applied external load is parallel to the forming direction of the NiTi alloy component. The stress per unit area on the NiTi alloy component is 0.2 N / mm 2 , a NiTi alloy component is obtained.

[0056] Example 7

[0057] The nickel-titanium alloy component is heat-treated at 350°C for 0.5 h. During the heat treatment, a load of 20 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 4 N / mm 2 , obtaining a nickel-titanium alloy component.

[0058] Example 8

[0059] The nickel-titanium alloy component is heat-treated at 350°C for 0.5 h. During the heat treatment, a load of 50 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 10 N / mm 2 , obtaining a nickel-titanium alloy component.

[0060] Example 9

[0061] The nickel-titanium alloy component is heat-treated at 400°C for 0.25 h. During the heat treatment, a load of 10 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 2 N / mm 2 , obtaining a nickel-titanium alloy component.

[0062] Example 10

[0063] The nickel-titanium alloy component is heat-treated at 400°C for 0.5 h. During the heat treatment, a load of 10 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 2 N / mm 2 , obtaining a nickel-titanium alloy component.

[0064] Example 11

[0065] The nickel-titanium alloy component is heat-treated at 450°C for 0.25 h. During the heat treatment, a load of 10 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 2 N / mm 2 , obtaining a nickel-titanium alloy component.

[0066] Example 12

[0067] The nickel-titanium alloy component is heat-treated at 450°C for 0.5 h. During the heat treatment, a load of 10 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 2 N / mm2 , a nickel-titanium alloy component is obtained.

[0068] Example 13

[0069] The nickel-titanium alloy component is heat-treated at 500 °C for 0.25 h. During the heat treatment, a load of 10 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 2 N / mm 2 , a nickel-titanium alloy component is obtained.

[0070] Example 14

[0071] The nickel-titanium alloy component is heat-treated at 500 °C for 0.5 h. During the heat treatment, a load of 10 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 2 N / mm 2 , a nickel-titanium alloy component is obtained.

[0072] Example 15

[0073] The nickel-titanium alloy component is heat-treated at 550 °C for 0.25 h. During the heat treatment, a load of 10 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 2 N / mm 2 , a nickel-titanium alloy component is obtained.

[0074] Example 16

[0075] The nickel-titanium alloy component is heat-treated at 550 °C for 0.5 h. During the heat treatment, a load of 10 N is applied to the nickel-titanium alloy component, and the direction of the applied external load is parallel to the forming direction of the nickel-titanium alloy component. The stress per unit area on the nickel-titanium alloy component is 2 N / mm 2 , a nickel-titanium alloy component is obtained.

[0076] Example 17

[0077] Example 17 is a nickel-titanium alloy component directly prepared by an additive manufacturing method without any treatment.

[0078] The relevant mechanical properties of the above examples are detected, and the results are shown in Figure 15 as follows.

[0079] According to Figure 15 , it can be known that the present invention regulates the mechanical properties of the nickel-titanium alloy component by changing the heat treatment time and the magnitude of the external load during heat treatment, and directionally generating nano-precipitates during heat treatment according to the forming direction of additive manufacturing.

[0080] To prove the authenticity and reliability of the present invention, several comparative examples were set up for mechanical testing, and the post-treatment conditions of the comparative examples are described as follows.

[0081] Comparative Example 1

[0082] The Ni-Ti alloy component was only heat-treated at 350 °C for 0.5 h to obtain the Ni-Ti alloy component.

[0083] Comparative Example 2

[0084] The Ni-Ti alloy component was heat-treated at 350 °C for 0.5 h. During the heat treatment, a load of 10 N was applied to the Ni-Ti alloy component, and the direction of the applied external load was perpendicular to the forming direction of the Ni-Ti alloy component. The stress per unit area on the Ni-Ti alloy component was 0.2 N / mm 2 , to obtain the Ni-Ti alloy component.

[0085] Comparative Example 3

[0086] The Ni-Ti alloy component was only heat-treated at 400 °C for 0.5 h to obtain the Ni-Ti alloy component.

[0087] Comparative Example 4

[0088] The Ni-Ti alloy component was only heat-treated at 500 °C for 0.5 h to obtain the Ni-Ti alloy component.

[0089] Comparative Example 5

[0090] The Ni-Ti alloy component was heat-treated at 400 °C for 0.5 h. During the heat treatment, a load of 10 N was applied to the Ni-Ti alloy component, and the direction of the applied external load was perpendicular to the forming direction of the Ni-Ti alloy component. The stress per unit area on the Ni-Ti alloy component was 0.2 N / mm 2 , to obtain the Ni-Ti alloy component.

[0091] Comparative Example 6

[0092] The Ni-Ti alloy component was heat-treated at 500 °C for 0.5 h. During the heat treatment, a load of 10 N was applied to the Ni-Ti alloy component, and the direction of the applied external load was perpendicular to the forming direction of the Ni-Ti alloy component. The stress per unit area on the Ni-Ti alloy component was 0.2 N / mm 2 , to obtain the Ni-Ti alloy component.

[0093] The above comparative examples were subjected to mechanical testing, and the test results are shown in Figure 16 .

[0094] According to Figure 16It can be seen that the mechanical properties of a nickel-iron alloy component obtained by an additive manufacturing method cannot be regulated only by changing the heat treatment temperature without applying an external load. During the heat treatment process, if the direction of the external load is perpendicular to the forming direction of the nickel-titanium alloy component, it will basically not affect the phase relationship between the nano-precipitation phase and the matrix phase of the parent phase, and the purpose of regulating the mechanical properties cannot be achieved.

[0095] According to Figure 7 - Figure 10 and Figure 11 - Figure 14 It can be seen that the Young's modulus of a nickel-titanium alloy component directly prepared by an additive manufacturing method is about 228 Mpa, the compressive strength after 50% deformation is about 152 Mpa, and the recovery deformation amount after unloading is 36%. After heat-treating the nickel-titanium alloy component at 350 °C for 0.5 h and applying a 10 N load simultaneously, the Young's modulus of the nickel-titanium alloy component rises to about 311 Mpa, the compressive strength after 50% deformation is about 194 Mpa, and the recovery deformation amount after unloading reaches about 60%. Comparative Example 1 and Comparative Example 2 respectively show the mechanical properties of a nickel-titanium alloy component without an external load applied and a nickel-titanium alloy component with an external load applied along the direction perpendicular to the forming direction, and no obvious changes occur. As Figure 9 shown, when the weight of the external load is further increased, the compressive strength and the recovery rate after unloading will decrease accordingly.

Claims

1. A method for regulating the mechanical properties of an additively manufactured nickel-titanium alloy component, characterized in that: It includes the following steps: Step 1: Prepare a nickel-titanium alloy component through a powder bed powder feeding laser additive manufacturing process; Step 2: Heat-treat the Ni-Ti alloy component. The heat treatment temperature is between 300°C and 550°C, and the heat treatment time is between 0.1 h and 3 h. During the heat treatment, an external load is applied to the Ni-Ti alloy component. The direction of the applied external load is parallel to the forming direction of the Ni-Ti alloy component, and the stress magnitude applied to the Ni-Ti alloy component is between 0.2 and 10 N / mm 2 within the range to achieve the regulation of the mechanical properties of the Ni-Ti alloy component.

2. A method for regulating the mechanical properties of an additive manufactured nickel-titanium alloy component according to claim 1, characterized in that: The atomic percentage of the raw material components of the nickel-titanium alloy component is 50.5% - 51.5% for nickel element, and the rest is titanium element.

3. A method for regulating the mechanical properties of an additively manufactured nickel-titanium alloy component according to claim 1, characterized in that: In Step 2, the heat treatment time is between 0.1 h and 1 h, and the heat treatment temperature is between 300 °C and 400 °C.

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