Method for improving bonding quality of additive manufacturing heterogeneous material gradient composite structure interface

Abstract

The invention provides a method for improving the interface bonding quality of an additive manufacturing heterogeneous material gradient composite structure, which comprises the following steps: printing a first metal material on a substrate by using a first heat source to obtain a first metal layer; printing a second metal material on the surface of the first metal layer by using a second heat source to obtain a composite structure of the second metal layer and the first metal layer; a third heat source is used for heating the surface of the second metal layer, the interface of the first metal layer and the second metal layer is heated to the expected temperature, and the roller is used for synchronously rolling the surface of the second metal layer; and printing a second metal material on the surface of the rolled second metal layer by using a second heat source until the target part is formed. According to the method, no new intermetallic compound is introduced into the gradient composite structure interface, a new third heat source is introduced to heat and control the temperature of the second metal layer, the roller is used for synchronously rolling the surface of the second metal layer, and the defects of holes and cracks of the heterogeneous material gradient composite structure interface are effectively eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and particularly to a method for improving the interfacial bonding quality of a gradient composite structure of heterogeneous materials in additive manufacturing. Background Art

[0002] With the continuous high-speed development of fields such as China's aerospace, shipbuilding and marine, and automotive industries, the performance requirements for related components, especially the main load-bearing components, have been gradually improved, the structures have become increasingly complex and integrated, and single metals or alloys are difficult to meet their requirements for the comprehensive properties of materials. A gradient composite structure refers to a whole structural component made of two metal materials with different properties. By designing the layout of different materials in the structural component, the active regulation of the properties of the gradient composite structure can be realized. The preparation technologies and processes of gradient composite structures mainly include laser welding, friction stir welding, explosion welding, diffusion welding, rolling, and additive manufacturing, etc. Additive manufacturing, also known as "3D printing", is a technology for manufacturing components by rapidly forming raw materials under the heating of a focused heat source and accumulating materials layer by layer. Using additive manufacturing technology, objects with complex and customized geometric shapes that cannot be produced by traditional methods can be rapidly manufactured. In addition, additive manufacturing can realize the customized regulation of the microstructure and mechanical properties of different regions of the target component.

[0003] There are significant differences in the physical properties of heterogeneous materials such as melting point, thermal conductivity, and coefficient of thermal expansion. During the bonding process of heterogeneous materials, defects such as cracks and pores and residual stresses are easily generated; it is difficult to avoid the formation of a large number of brittle intermetallic compound phases during the bonding of heterogeneous materials, which will weaken the mechanical properties of the gradient composite structure. Due to the extremely large temperature gradient in the molten pool during the additive manufacturing process, the micro-region temperature distribution is uneven, and it is easy to form large-area columnar crystal structures and defects such as pores and cracks. The repeated heat input and high cooling rate during the additive manufacturing process result in high residual stresses in the printed parts, which further promotes the generation of interfacial cracks in the gradient composite structure, making it more difficult to form the gradient composite structure.

[0004] In the prior art, through the method of optimizing process parameters, the interfacial defects of the additive manufacturing gradient composite structure are reduced; usually, intermediate layers or alloy partitions are prepared between heterogeneous materials by means of welding, laser cladding, hot dip plating, flame wire spraying, etc. to avoid direct contact between different materials, regulate the type of intermetallic compounds at the bonding interface, and inhibit the growth of brittle phases. However, the gradient composite structure prepared only by optimizing process parameters still has problems such as uneven microstructure, anisotropic mechanical properties, and relatively large tensile residual stresses; the addition of intermediate layers or partitions also introduces new intermetallic compounds at the interface of the heterogeneous material gradient composite structure, and the interface composition is still mainly composed of brittle phases, and the problems of defects, uneven microstructure, and residual stresses cannot be solved. Summary of the Invention

[0005] In view of this, the present invention provides a method for improving the interfacial bonding quality of additive manufactured heterogeneous material gradient composite structures, so as to solve the problems in the above-mentioned background technology that the gradient composite structures prepared only by optimizing process parameters still have problems such as uneven microstructure, mechanical property anisotropy, and large tensile residual stress; and the addition of an intermediate layer or a partition also introduces new intermetallic compounds at the interface of the heterogeneous material gradient composite structure, the interface composition is still mainly composed of brittle phases, and the problems of defects, uneven microstructure, and residual stress cannot be solved.

[0006] The technical solution of the present invention is realized as follows: The present invention provides a method for improving the interfacial bonding quality of additive manufactured heterogeneous material gradient composite structures, including: Printing a first metal material on a substrate using a first heat source to obtain a first metal layer, where the main elements of the first metal material and the substrate are the same; Printing a second metal material on the surface of the first metal layer using a second heat source to obtain a composite structure of the second metal layer and the first metal layer, where the melting point of the second metal material is lower than that of the first metal material, and the main elements of the second metal material and the first metal material are different; Heating the surface of the second metal layer using a third heat source to raise the temperature of the interface between the first metal layer and the second metal layer to an expected temperature, and synchronously rolling the surface of the second metal layer using a rolling mill; Printing the second metal material on the surface of the rolled second metal layer using the second heat source until the target component is formed.

[0007] Based on the above technical solutions, preferably, the heating of the surface of the second metal layer using the third heat source to raise the temperature of the interface between the first metal layer and the second metal layer to an expected temperature specifically includes: If an intermetallic compound phase is formed between the main elements of the first metal material and the second metal material and the melting point of the intermetallic compound phase is lower than the melting points of the two, the expected temperature is above the melting point of the intermetallic compound phase but lower than the melting point of the second metal material; If the melting point of the intermetallic compound phase formed between the main elements of the first metal material and the second metal material is higher than the melting point of the second metal material, the expected temperature is above 0.3 times the melting point of the intermetallic compound phase but lower than the melting point of the second metal material.

[0008] Based on the above technical solutions, preferably, the synchronous rolling of the surface of the second metal material using the rolling mill includes: under the action of the rolling mill, the surface deformation of the second metal layer reaches 5% - 60% of the single-layer printing thickness of the second metal material.

[0009] Based on the above technical solutions, preferably, the rolling mill moves synchronously with the third heat source, and the distance between the rolling mill and the third heat source is 2 - 6 cm.

[0010] Based on the above technical solutions, preferably, heating the surface of the second metal layer using the third heat source includes: when the third heat source moves, it performs rapid scanning synchronously, and the scanning direction is perpendicular to the moving path.

[0011] Based on the above technical solutions, preferably, the moving path of the third heat source is the same as or opposite to that when the second heat source prints the second metal material; the moving speed of the third heat source is 2 - 30 mm / s.

[0012] Based on the above technical solutions, preferably, the effective heating range of the third heat source is 0.8 - 5 times the width of a single pass when the second metal material is printed, and the width of the rolling mill is 0.8 - 1 times the effective heating range of the third heat source.

[0013] Based on the above technical solutions, preferably, the first heat source, the second heat source, and the third heat source are moving focused heat sources, and a single heat source or a combined heat source among laser, arc, plasma arc, and ion beam is adopted.

[0014] Based on the above technical solutions, preferably, the first metal material is one of nickel and nickel - based alloys, cobalt and cobalt - based alloys, titanium and titanium - alloy, steel, copper and copper alloys, aluminum and aluminum alloys; the second metal material is one of nickel and nickel - based alloys, cobalt and cobalt - based alloys, titanium and titanium - alloy, steel, copper and copper alloys, aluminum and aluminum alloys, magnesium and magnesium alloys.

[0015] Based on the above technical solutions, preferably, the forms of the printing raw materials of the first metal material and the second metal material are wire or powder.

[0016] The method for improving the interfacial bonding quality of the additive - manufactured heterogeneous material gradient composite structure of the present invention has the following beneficial effects compared with the prior art: (1) By using the second heat source to print the second metal material on the surface of the first metal layer, a composite structure of the second metal layer and the first metal layer is obtained. By regulating the interfacial structure between the first metal layer and the second metal layer, the bonding quality between the two is improved, and no new intermetallic compounds are introduced at the interface of the gradient composite structure. By using the third heat source to heat the surface of the second metal layer, the interface between the first metal layer and the second metal layer is heated to the expected temperature. During the additive manufacturing process, a new heat source is introduced to heat and control the temperature of the interface of the heterogeneous material gradient composite structure, which can fully improve the absorption efficiency of different materials for the heat source. At the same time of heating, a rolling mill is used to synchronously roll the surface of the second metal layer, which can eliminate interface defects while refining and homogenizing the interface structure, eliminate the anisotropy of the mechanical properties at the interface of the gradient composite structure, realize the improvement of the interfacial bonding performance of the additive - manufactured heterogeneous material gradient composite structure, effectively eliminate the pore and crack defects at the interface of the heterogeneous material gradient composite structure, and introduce compressive residual stress to inhibit interface cracking; (2) If an intermetallic compound phase with a melting point lower than the melting points of both the first and second metal materials is formed between the main elements of the first and second metal materials, and the expected temperature is above the melting point of the intermetallic compound phase but lower than the melting point of the second metal material, ensure that the intermetallic compound phase can melt while the second metal layer does not melt; When the melting point of the intermetallic compound phase formed between the main elements of the first and second metal materials is higher than the melting point of the second metal material, the expected temperature is above 0.3 times the melting point of the intermetallic compound phase but lower than the melting point of the second metal material, that is, the expected temperature is above the recrystallization temperature of the intermetallic compound phase, ensure that the intermetallic compound can recrystallize while the second metal layer does not melt, reducing strain; Through the above setting of the expected temperature, after synchronously rolling the surface of the second metal layer using a roller, it is possible to refine and homogenize the interface structure while eliminating interface defects, eliminate the anisotropy of the mechanical properties of the interface of the gradient composite structure, and achieve the improvement of the interface bonding performance of the gradient composite structure of heterogeneous materials in additive manufacturing; (3) Under the action of the roller, the surface deformation of the second metal layer reaches 5% - 60% of the single-layer printing thickness of the second metal material to eliminate interface defects and densify the structure, and introduce compressive residual stress to the interface or cause the interface structure to recrystallize under thermal deformation; (4) Through the third heat source, rapid scanning is synchronously performed during movement, and the scanning direction is perpendicular to the movement path, thereby increasing the effective heating range of the third heat source for the interface; (5) The effective heating range of the third heat source is 0.8 - 5 times the width of a single pass during the printing of the second metal material, and the width of the roller is 0.8 - 1 times the effective heating range of the third heat source, ensure that the area rolled by the roller is within the heating range of the third heat source, improve the synchronization of rolling and heating, and improve the reliability and stability of the device. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a schematic flow chart of the method for improving the interface bonding quality of the gradient composite structure of heterogeneous materials in the embodiments of the present invention; Figure 2 It is a schematic principle diagram of the method for improving the interface bonding quality of the gradient composite structure of heterogeneous materials in the embodiments of the present invention; Figure 3Schematic diagram of the principle of the method for improving the interfacial bonding quality of the additive manufacturing aluminum / magnesium gradient composite structure in Application Example 1 of the present invention; Figure 4 Schematic diagram of the principle of the method for improving the interfacial bonding quality of the additive manufacturing titanium / aluminum gradient composite structure in Application Example 2 of the present invention. Specific embodiments

[0019] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all 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 protection scope of the present invention.

[0020] Referring to Figures 1-4 As shown, an embodiment of the present invention provides a method for improving the interfacial bonding quality of an additive manufacturing heterogeneous material gradient composite structure, including: Step S1: Printing a first metal material on a substrate using a first heat source to obtain a first metal layer, where the main elements of the first metal material and the substrate are the same; Specifically, in step S1, the first metal material is printed on the substrate to a certain thickness using the first heat source, as shown in (a), (b), and (c) in Figure 2 The first heat source is a moving focused heat source, and a single heat source or a combined heat source among laser, arc, plasma arc, and ion beam is used. The first metal material is one of nickel and nickel-based alloys, cobalt and cobalt-based alloys, titanium and titanium alloys, steel, copper and copper alloys, and aluminum and aluminum alloys. The process parameters used by the first heat source to form the first metal layer are the optimized process parameters when no pores and cracks are present; Before step S1, the following preparatory work is also required: The surface of the substrate is polished successively with 80-mesh, 240-mesh, 500-mesh, and 1000-mesh sandpapers, and then the substrate is fixed on the printing platform through a fixture; Step S2: Printing a second metal material on the surface of the first metal layer using a second heat source to obtain a composite structure of the second metal layer and the first metal layer, where the melting point of the second metal material is lower than that of the first metal material, and the main elements of the second metal material and the first metal material are different; Specifically, in step S2, a layer of the second metal material is printed on the surface of the first metal material using the second heat source to obtain the second metal layer, as shown in Figure 2As shown in (d), the second metal material is one of nickel and nickel-based alloys, cobalt and cobalt-based alloys, titanium and titanium alloys, steel, copper and copper alloys, aluminum and aluminum alloys, and magnesium and magnesium alloys; the second heat source is a moving focused heat source, using a single heat source or a combined heat source among laser, arc, plasma arc, and ion beam; the process parameters used when the second heat source forms the second metal material are the optimized process parameters when there are no holes and crack defects. Step S3: Heat the surface of the second metal layer with a third heat source to raise the temperature at the interface between the first metal layer and the second metal layer to the expected temperature, and synchronously roll the surface of the second metal layer with a rolling mill. In step S3, as Figure 2 shown in (e), the third heat source is a moving focused heat source, using a single heat source or a combined heat source among laser, arc, plasma arc, and ion beam; Step S4: Use the second heat source to print the second metal material on the surface of the second metal layer after the above rolling until the target component is formed. The operations in step S4 are as shown in Figure 2 (f), (g), and (h) in

[0021] In some embodiments, in step S3, heating the surface of the second metal layer with the third heat source to raise the temperature at the interface between the first metal layer and the second metal layer to the expected temperature specifically includes: if an intermetallic compound phase with a melting point lower than the melting points of the two main elements of the first metal material and the second metal material is formed between the two main elements, the expected temperature is above the melting point of the intermetallic compound phase but lower than the melting point of the second metal material. Through the setting of the above expected temperature, it is ensured that the intermetallic compound phase can melt, while the second metal layer does not melt. After synchronously rolling the surface of the second metal layer with a rolling mill, it is possible to refine and homogenize the interface structure while eliminating interface defects, eliminate the anisotropy of the mechanical properties of the gradient composite structure interface, and achieve the improvement of the interface bonding performance of the additive manufacturing heterogeneous material gradient composite structure.

[0022] In other embodiments, in step S3, heating the surface of the second metal layer with the third heat source to raise the temperature at the interface between the first metal layer and the second metal layer to the expected temperature specifically includes: if the melting point of the intermetallic compound phase formed between the two main elements of the first metal material and the second metal material is higher than the melting point of the second metal material, the expected temperature is above 0.3 times the melting point of the intermetallic compound phase but lower than the melting point of the second metal material. That is, the expected temperature is above the recrystallization temperature of the intermetallic compound phase, ensuring that the intermetallic compound can recrystallize while the second metal layer does not melt, reducing strain. After synchronously rolling the surface of the second metal layer with a rolling mill, it is possible to refine and homogenize the interface structure while eliminating interface defects, eliminate the anisotropy of the mechanical properties of the gradient composite structure interface, and achieve the improvement of the interface bonding performance of the additive manufacturing heterogeneous material gradient composite structure.

[0023] In some embodiments, in step S3, the synchronous rolling of the surface of the second metal material using the rolling mill includes: under the action of the rolling mill, the deformation amount on the surface of the second metal layer reaches 5% - 60% of the single-layer printing thickness of the second metal material. Through the setting of the above deformation amount, interface defects can be eliminated and tissue densification can be achieved, and compressive residual stress can be introduced to the interface or the interface tissue can recrystallize under the action of thermal deformation, inhibiting interface cracking and improving the quality of the gradient composite structure interface.

[0024] In some embodiments, the rolling mill moves synchronously with the third heat source, and the distance between the rolling mill and the third heat source is 2 - 6 cm. The rolling mill is behind the third heat source. The second metal layer is first heated and then rolled by the rolling mill. Through the distance between the rolling mill and the third heat source, there is a spacing between the rolling mill and the third heat source, but the spacing is not too large to cause the temperature at the corresponding position to not meet the requirements when the rolling mill reaches the third metal layer, improving reliability and stability.

[0025] In some embodiments, heating the surface of the second metal layer using the third heat source includes: when the third heat source moves, it synchronously performs rapid scanning, and the scanning direction is perpendicular to the moving path. For the case where the interface area between the first metal layer and the second metal layer is large, when the third heat source moves, it synchronously performs rapid scanning, and the scanning direction is perpendicular to the moving path, thereby increasing the effective heating range of the third moving heat source for the interface and improving the heating efficiency.

[0026] In some embodiments, the moving path of the third heat source is the same as or opposite to that of the second heat source when printing the second metal material; the moving speed of the third heat source is 2 - 30 mm / s. Through the setting of the above parameters, the third heat source can uniformly heat the second metal layer while ensuring the heating efficiency, improving stability and reliability.

[0027] In some embodiments, the effective heating range of the third heat source is 0.8 - 5 times the width of a single pass during the printing of the second metal material, and the width of the rolling mill is 0.8 - 1 times the effective heating range of the third heat source. Through the setting of the above parameters, it is ensured that the second metal layer can be covered by the effective heating range of the third heat source, and the entire second metal layer can be heated by the third heat source, with good heating uniformity. It is ensured that the area rolled by the rolling mill is within the heating range of the third heat source, improving the synchronization of rolling and heating and the reliability and stability of the device.

[0028] In some embodiments, the forms of the printing raw materials of the first metal material and the second metal material are wire or powder. The form of the printing raw materials can be wire or powder, with good compatibility for the form and a wider applicable range, improving applicability.

[0029] In some embodiments, the first heat source, the second heat source, and the third heat source can be the same heat source during actual use, or can be reasonably selected according to the absorption efficiency of the printing material for the heat source.

[0030] Application Example 1 This embodiment provides a method for improving the interfacial bonding quality of an additive manufacturing aluminum / magnesium gradient composite structure. Combining Figure 3 as shown, the method includes the following steps: Step S11: Use 80-mesh, 240-mesh, 500-mesh, and 1000-mesh sandpapers to polish the surface of the Al 6061 aluminum alloy substrate in sequence, and then fix the substrate on the printing platform through a fixture; Step S12: Use a first laser heat source to print multiple layers of AlSi10Mg aluminum alloy blocks on the substrate. The melting point of the AlSi10Mg aluminum alloy is 660°C. The printing raw material AlSi10Mg aluminum alloy is powder, and the powder diameter is between 5 and 78 μm. The laser power is 275 W, the laser spot diameter is 110 μm, the scanning speed is 1500 mm / s, the scanning pitch is 0.09 mm, and the layer thickness is 0.03 mm; Step S13: Use a second laser heat source to print a layer of ZK60 magnesium alloy on the surface of the AlSi10Mg aluminum alloy. As Figure 3 shown in (a), the melting point of the ZK60 magnesium alloy is 649°C. The printing raw material ZK60 magnesium alloy is powder, and the powder diameter is between 10 and 90 μm. The laser power is 80 W, the laser spot diameter is 80 μm, the scanning speed is 600 mm / s, the scanning pitch is 0.06 mm, and the layer thickness is 0.03 mm. Two aluminum-magnesium intermetallic compound layers, Al3Mg2 and Al12Mg17, are formed at the interface between the AlSi10Mg aluminum alloy and the ZK60 magnesium alloy. The melting points of the two aluminum-magnesium intermetallic compound phases, Al3Mg2 and Al12Mg17, are 453°C and 460°C respectively. Due to the uneven temperature distribution at different positions of the printed part during the additive manufacturing process and the difference in the solidification time of each region of the molten pool, holes exist, and there are different degrees of deformation at different positions of the printed part, resulting in the existence of residual stress. And the aluminum-magnesium intermetallic compound is a brittle phase and will crack under the action of residual stress, as Figure 3 shown in (a) and (b); Step S14: Use a third laser heat source to heat the surface of the ZK60 magnesium alloy. The laser spot diameter is 3 mm, the laser power is 100 W, the scanning speed is 5 mm / s, and the temperature range of the aluminum / magnesium interface layer corresponding to the effective laser heating area is between 460 and 649°C, so that the Al3Mg2 and Al12Mg17 aluminum-magnesium intermetallic compound layers formed at the interface between the AlSi10Mg aluminum alloy and the ZK60 magnesium alloy are melted, but the ZK60 magnesium alloy does not melt. As Figure 3As shown in (c), the surface of ZK60 magnesium alloy is subjected to hot rolling deformation synchronously using rollers. The reduction is 60% of the single-layer thickness of the printed ZK60 magnesium alloy, which is 0.018 mm, and the roller width is 3 mm. Under the action of the third laser heat source, the aluminum-magnesium intermetallic compound layer in the interface layer melts, and the pore and crack defects are reduced and eliminated. Combining the roller pressure to generate thermal deformation in the acting area further eliminates the pore and crack defects, densifies the interface structure. Moreover, during the thermal deformation process, the interface structure recrystallizes and is refined and homogenized. In addition, the tensile residual stress in the area of thermal deformation under the action of the roller pressure is eliminated, and the residual stress state changes to a compressive stress state. Thus, the interface bonding quality of the additive manufactured aluminum / magnesium gradient composite structure is improved; Step S15: Subsequently, continue the additive manufacturing process on the surface of the rolled ZK60 magnesium alloy using the second laser heat source in Step S13 until the component is formed.

[0031] Application Example 2 This example proposes a method for improving the interface bonding quality of an additive manufactured titanium / aluminum gradient composite structure. Combining Figure 4 As shown, it includes the following steps: Step S21: Polish the surface of the pure titanium substrate successively with 80-mesh, 240-mesh, 500-mesh, and 1000-mesh sandpapers, and then fix the substrate on the printing platform through a fixture; Step S22: Print multiple layers of Ti6Al4V titanium alloy blocks on the substrate using an electron beam heat source. The melting point of Ti6Al4V titanium alloy is 1668 °C. The printed raw material Ti6Al4V titanium alloy is powder with a diameter between 50 and 105 μm, an electron beam current of 18 mA, a scanning speed of 2400 mm / s, a scanning pitch of 0.12 mm, and a layer thickness of 0.1 mm; Step S23: Print a layer of AA5087 aluminum alloy on the surface of Ti6Al4V titanium alloy using a laser heat source. The melting point of AA5087 aluminum alloy is 589 °C, as Figure 4As shown in Figure 4 (a), the printing raw material AA5087 aluminum alloy is in wire form, with a wire diameter of 1 mm, a laser power of 4000 W, a laser spot diameter of 1.6 mm, a wire feeding speed of 10 m / min, a scanning speed of 1 m / min, a scanning pitch of 1.7 mm, and a layer thickness of 2.4 mm. Three titanium-aluminum intermetallic compound layers, namely Al3Ti, TiAl, and TiAl3, are formed at the interface between the Ti6Al4V titanium alloy and the AA5087 aluminum alloy. The melting point of the TiAl phase, which has the highest melting point among the three titanium-aluminum intermetallic compound phases of Al3Ti, TiAl, and TiAl3, is 1456 °C. Due to the uneven temperature distribution at different positions of the printed part during the additive manufacturing process and the difference in the solidification time of each region of the molten pool, holes exist, and different degrees of deformation occur at different positions of the printed part, resulting in the existence of residual stress. Since the titanium-aluminum intermetallic compound is a brittle phase, it will crack under the action of residual stress, as shown in Figure 4 (a) and (b); Step S24: Heat the surface of the AA5087 aluminum alloy using a laser heat source. The laser spot diameter is 3 mm, the laser power is 500 W, the scanning speed is 3 mm / s, and the temperature range of the effective laser heating area is between 0.3 times the melting point of the titanium-aluminum intermetallic compound phase (437 °C) and the melting point of the AA5087 aluminum alloy (589 °C), that is, above the recrystallization temperature of the titanium-aluminum intermetallic compound phase. As shown in Figure 4 (c), simultaneously use a rolling mill to perform hot deformation on the surface of the AA5087 aluminum alloy. The reduction in thickness is 50% of the single-layer thickness of the printed AA5087 aluminum alloy, which is 1.2 mm, and the width of the rolling mill is 3 mm. Under the action of the laser heat source and the rolling mill pressure, thermal deformation and recrystallization occur at the interface between the titanium alloy and the aluminum alloy, and the hole and crack defects are reduced or eliminated, and the interface structure becomes denser and more uniform. In addition, the tensile residual stress in the area of thermal deformation under the action of the rolling mill pressure is eliminated, and the residual stress state changes to a compressive stress state. Thereby improving the interface bonding quality of the additive manufacturing titanium / aluminum gradient composite structure; Step S25: Subsequently, use the laser heat source in Step S23 to continue the additive manufacturing process on the surface of the rolled AA5087 aluminum alloy until the component is formed.

[0032] In summary, a method for improving the interface bonding quality of an additive manufacturing heterogeneous material gradient composite structure provided by the present invention can eliminate the hole and crack defects at the interface of the additive manufacturing heterogeneous material gradient composite structure, introduce compressive residual stress to inhibit interface cracking, specifically control the temperature and perform thermal deformation on the interface of the heterogeneous material gradient composite structure, and can refine and homogenize the interface structure while eliminating interface defects, eliminate the anisotropy of the mechanical properties of the gradient composite structure interface, and achieve the improvement of the interface bonding performance of the additive manufacturing heterogeneous material gradient composite structure.

[0033] ​The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for improving the interface bonding quality of a heterogeneous material gradient composite structure manufactured by additive manufacturing, characterized in that: include: Printing a first metal material on a substrate using a first heat source to obtain a first metal layer, wherein the first metal material and the substrate have the same main element; Using a second heat source to print a second metal material on the surface of the first metal layer to obtain a composite structure of the second metal layer and the first metal layer, wherein the melting point of the second metal material is lower than that of the first metal material, and the main elements of the second metal material and the first metal material are different; Using a third heat source to heat the surface of the second metal layer, so that the interface between the first metal layer and the second metal layer is heated to a desired temperature, and using a roller to synchronously roll the surface of the second metal layer; the desired temperature is lower than the melting point of the second metal material; A second heat source is used to print a second metal material on the surface of the second metal layer after rolling until the target component is formed.

2. The method for improving the interface bonding quality of the additively manufactured heterogeneous material gradient composite structure according to claim 1, characterized in that: The method of using the third heat source to heat the surface of the second metal layer so that the interface between the first metal layer and the second metal layer is heated to a desired temperature specifically includes: If an intermetallic compound phase with a lower melting point than the first metal material and the second metal material is formed between the main elements of the first metal material and the second metal material, the expected temperature is above the melting point of the intermetallic compound phase but lower than the melting point of the second metal material; If the melting point of the intermetallic compound phase formed between the main elements of the first metal material and the second metal material is higher than the melting point of the second metal material, the expected temperature is above 0.3 times the melting point of the intermetallic compound phase but lower than the melting point of the second metal material.

3. The method for improving the interface bonding quality of the additively manufactured heterogeneous material gradient composite structure according to claim 1, characterized in that: The synchronous rolling of the surface of the second metal material using a rolling roller includes: under the action of the rolling roller, the surface deformation of the second metal layer reaches 5% to 60% of the single-layer printing thickness of the second metal material.

4. The method for improving the interface bonding quality of the additively manufactured heterogeneous material gradient composite structure according to claim 1, characterized in that: The rolling roller moves synchronously with the third heat source, and the distance between the rolling roller and the third heat source is 2~6cm.

5. The method for improving the interface bonding quality of the additively manufactured heterogeneous material gradient composite structure according to claim 4, characterized in that: The method of using the third heat source to heat the surface of the second metal layer includes: the third heat source performs rapid scanning synchronously while moving, and the scanning direction is perpendicular to the moving path.

6. The method for improving the interface bonding quality of the additively manufactured heterogeneous material gradient composite structure according to claim 5, characterized in that: The moving path of the third heat source is the same as or opposite to that of the second heat source when printing the second metal material; the moving speed of the third heat source is 2~30mm / s.

7. The method for improving the interface bonding quality of the additively manufactured heterogeneous material gradient composite structure according to claim 6, characterized in that: The effective heating range of the third heat source is 0.8 to 5 times the width of a single pass when printing the second metal material, and the width of the rolling roller is 0.8 to 1 times the effective heating range of the third heat source.

8. The method for improving the interface bonding quality of the additively manufactured heterogeneous material gradient composite structure according to claim 1, characterized in that: The first heat source, the second heat source and the third heat source are mobile focused heat sources, using a single heat source or a combined heat source of laser, electric arc, plasma arc, or ion beam.

9. The method for improving the interface bonding quality of the additively manufactured heterogeneous material gradient composite structure according to claim 1, characterized in that: The first metal material is one of nickel and nickel-based alloys, cobalt and cobalt-based alloys, titanium and titanium alloys, steel, copper and copper alloys, aluminum and aluminum alloys; the second metal material is one of nickel and nickel-based alloys, cobalt and cobalt-based alloys, titanium and titanium alloys, steel, copper and copper alloys, aluminum and aluminum alloys, magnesium and magnesium alloys.

10. The method for improving the interface bonding quality of a heterogeneous material gradient composite structure manufactured by additive manufacturing according to any one of claims 1 to 9, characterized in that: The printing raw material form of the first metal material and the second metal material is wire or powder.

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