Porous high-entropy alloy structure layer for strengthening aluminum / steel heterogeneous interface connection and selective laser melting forming method of porous high-entropy alloy structure layer

Abstract

The invention discloses a porous high-entropy alloy structure layer for strengthening aluminum / steel heterogeneous interface connection and a selective laser melting forming method of the porous high-entropy alloy structure layer, and belongs to the field of high-entropy alloy materials. The porous high-entropy alloy structure layer comprises FeCoCrNiMn high-entropy alloy and is of a single cubic array stacking structure formed through selective laser melting. The selective laser melting forming method comprises the steps that a porous cubic structure model is designed through Majics three-dimensional software and guided into selective laser melting manufacturing equipment, a metal powder rapid forming system is started, FeCoCrNiMn high-entropy alloy powder is subjected to selective laser melting forming, and the high-strength and high-toughness high-entropy alloy coating is obtained. By effectively controlling the laser power and the three-dimensional model parameters, free energy of an alloy system is effectively reduced, formation of intermetallic compounds is inhibited, the mechanical property of aluminum / steel dissimilar metal connection is improved, and the method has wide application prospects in the aspect of aluminum / steel dissimilar metal connection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high-entropy alloy materials, and particularly relates to a porous high-entropy alloy structure layer for strengthening aluminum / steel heterogeneous interface connection and a laser selective melting forming method thereof. BACKGROUND

[0002] As a multi-principal element alloy material, high-entropy alloy (HEA) has many unique characteristics and advantages in microstructure and performance. High-entropy alloy has a "high-entropy effect" in thermodynamics, which can promote the formation of high-entropy solid solution; has a "lattice distortion effect" in microstructure, which can cause solid solution strengthening to improve strength; and has a "cocktail effect" in performance, which is conducive to optimizing the performance of the alloy. With the rapid transformation of the automobile industry and the further improvement of energy saving and emission reduction requirements for lightweight, the demand and development of lightweight alloy structural parts have also changed greatly. Lightweight high-entropy alloy can take advantage of its light weight and high strength to replace structural plates, seat frames, gearbox tooth hubs and other components in automobiles, effectively reducing the weight of automobiles, saving traditional automobile oil consumption and improving the endurance of new energy vehicles.

[0003] Laser selective melting forming (SLM) is an advanced rapid forming technology. Based on the discrete-accumulation forming principle, according to the three-dimensional model data of the computer, the metal powder is melted and accumulated layer by layer by using a high-energy laser beam, and finally a solid part is obtained. Compared with the traditional electric arc melting process, laser selective melting forming technology can directly complete the preparation of various small-size and complex-structure metal components, and is a high-efficiency and low-cost preparation process. Using a high-energy density laser beam, the pre-set powder layer is selectively scanned according to the three-dimensional model data, and is melted and accumulated layer by layer until the final metal part is prepared. The laser spot used in the laser selective melting forming process is small, and the surface precision and relative density of the formed part are high, overcoming the defect of poor surface precision of the parts prepared by laser melting deposition technology. At the same time, laser selective melting technology has unique advantages in preparing precise and complex components, personalized customized structural parts and component gradient composite materials. SUMMARY

[0004] In view of the aluminum / steel heterogeneous metal interlayer connection problem in the prior art, the main purpose of the present application is to provide a porous high-entropy alloy structure layer for strengthening aluminum / steel heterogeneous interface connection. A porous cubic structure is constructed by Magics three-dimensional software, and a porous FeCoCrNiMn high-entropy alloy coating structure is prepared by laser selective melting forming technology, which is used to enhance the connection of aluminum / steel heterogeneous metals and reduce the generation of intermetallic compounds.

[0005] Another object of the present application is to provide a laser selective melting forming method of the porous high-entropy alloy structure layer, which effectively controls laser energy power and three-dimensional model data parameters, solves the problems of un-melted powder particles in the internal part of the formed piece, surface-attached metal powder and unevenness of the high-entropy alloy in the laser selective melting forming process, and thus obtains a porous high-entropy alloy structural piece with good surface quality and forming.

[0006] To achieve the above object, the present application adopts the following technical solutions.

[0007] In a first aspect, the present application provides a FeCoCrNiMn high-entropy alloy for strengthening aluminum / steel heterogeneous interface connection, which comprises the following elements in atomic percentage: Fe: 19.98%, Co: 21.06%, Cr: 18.24%, Ni: 21.03%, and Mn: 19.69%, and the purity of the raw materials of Fe, Co, Cr, Ni and Mn is not less than 99.98%.

[0008] Preferably, the powder particle size of the FeCoCrNiMn high-entropy alloy is 15-50 um.

[0009] In a second aspect, the present application provides a porous high-entropy alloy structure layer for strengthening aluminum / steel heterogeneous interface connection, which comprises the FeCoCrNiMn high-entropy alloy for strengthening aluminum / steel heterogeneous interface connection and is a single cubic array stacked structure formed by laser selective melting.

[0010] In a third aspect, the present application provides a laser selective melting forming method of the porous high-entropy alloy structure layer for strengthening aluminum / steel heterogeneous interface connection, which comprises the following steps:

[0011] (1) Raw material preparation: weigh the raw materials of the FeCoCrNiMn high-entropy alloy, which comprises the following elements in atomic percentage: Fe: 19.98%, Co: 21.06%, Cr: 18.24%, Ni: 21.03%, and Mn: 19.69%, and the purity of the raw materials of Fe, Co, Cr, Ni and Mn is not less than 99.98%, mix uniformly, and obtain high-entropy alloy powder;

[0012] (2) Put the high-entropy alloy powder into a vacuum drying oven and heat to 60-80℃, keep warm for 10-12 h, remove the water therein, and introduce argon gas with a purity of 99.9% as a protective gas to prevent oxidation, and obtain dried high-entropy alloy powder;

[0013] (3) Start the metal powder rapid forming system, take 45# steel as the substrate, set the coaxial powder feeding deposition process parameters under the protection of pure argon gas, including: laser power: 90~120 W, spot diameter: 50 um, scanning speed: 800~1100mm / s, scanning interval: 50 um, powder thickness of each layer: 0.02 mm;

[0014] (4) A porous cube structure model is constructed by Magics three-dimensional software, slicing decomposition is performed, and the laser scanning path and scanning mode of the slice section are set; the dried high-entropy alloy powder is placed on the 45# steel substrate, the coaxial powder feeding deposition process set in step (3) is combined with the laser scanning path, and the high-entropy alloy powder is melted and formed on the 45# steel substrate by using laser selective melting forming, and the laser beam and the powder feeding are in the form of layer-by-layer powder laying and face-by-face scanning, so that the accumulation forming is formed, and a porous high-entropy alloy structure layer is obtained.

[0015] Preferably, in step (2), the powder particle size of the FeCoCrNiMn high-entropy alloy is 15~50 um.

[0016] Preferably, in step (4), the thickness of the porous high-entropy alloy structure layer is 1.0 mm, and the size is 100mm×50mm.

[0017] Compared with the prior art, the present application constructs a porous cube structure by Magics three-dimensional software, and uses laser selective melting forming technology to prepare a porous FeCoCrNiMn high-entropy alloy structure layer, which is used for enhancing the connection of aluminum / steel heterogeneous metals, reducing the generation of intermetallic compounds, and improving the connection strength of aluminum / steel heterogeneous metals, and the beneficial effects at least lie in:

[0018] 1. The present application uses the laser selective melting forming process to optimize the data of the three-dimensional model and regulate and control the laser power, scanning interval, scanning speed and other process parameters of the metal powder rapid forming system, so as to obtain a porous high-entropy alloy structure layer, which has excellent forming surface quality and mechanical properties, and effectively avoids the problems of randomness, high cost and serious powder waste caused by the preparation of high-entropy alloy by traditional process.

[0019] 2. The laser selective melting forming process adopted by the present application is a high-efficiency and low-cost preparation process, and the laser spot used in the laser selective melting forming process is small, so that the surface precision and relative density of the formed part are high, and the problem of poor surface precision of the parts prepared by the laser selective melting forming technology is overcome.

[0020] 3. The porous high-entropy alloy structure layer prepared by the method can reduce the free energy of the alloy system, inhibit the formation of intermetallic compounds, facilitate the formation of solid solution at the aluminum / steel interface, and improve the strength of the aluminum / steel heterogeneous metal connection, and has a wide application prospect in aluminum / steel heterogeneous metal connection. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A three-dimensional model schematic diagram of the laser selective melting forming of the porous high-entropy alloy structure layer in the examples.

[0022] Figure 2 The surface forming conditions of the formed parts of the porous high-entropy alloy structure layer formed by laser selective melting with a height of 1.0 mm and different powers in the examples; (a) laser power 60 W; (c) laser power 70 W; (e) laser power 80 W; (g) laser power 90 W; (i) laser power 120 W; (b), (d), (f), (h), (j) are the microstructure observed by confocal microscopy corresponding to (a), (c), (e), (g), (i).

[0023] Figure 3 The actual conditions of (a) the laser selective melting forming of HEA as an intermediate layer to strengthen the aluminum / steel heterogeneous metal connection interface in the examples; (b) the macroscopic morphology of aluminum / steel direct connection; (c) the cross-sectional macroscopic morphology of aluminum / HEA / steel connection.

[0024] Figure 4 The nanohardness cloud distribution of the aluminum / HEA interface (left) and the average nanohardness of the reaction layer of the aluminum / steel connection interface with and without the HEA intermediate layer (right) in the examples, wherein HEA-0 is without the HEA intermediate layer, and HEA-1 is with the HEA intermediate layer, and the thickness of the intermediate layer is 1 mm. DETAILED DESCRIPTION

[0025] In order to more fully understand the technical solutions, objectives and advantages of the present application, the following will further describe the technical effects of the present application in detail and completely in combination with the drawings and specific examples. Obviously, the described examples are only a part of the examples of the present application, but not all. It should be noted that other examples obtained by those skilled in the art without departing from the concept of the present application all belong to the protection scope of the present application.

[0026] The following examples propose a method of laser selective melting forming of a porous HEA intermediate layer to strengthen the aluminum / steel heterogeneous interface connection, and the steps are as follows:

[0027] (1) Raw material preparation: the raw materials of FeCoCrNiMn high-entropy alloy are weighed, and the element composition is Fe: 19.98%, Co: 21.06%, Cr: 18.24%, Ni: 21.03%, and Mn: 19.69% according to the atomic percentage, and the purity of Fe, Co, Cr, Ni and Mn is not less than 99.98%, and the mixture is uniform, to obtain a high-entropy alloy powder;

[0028] (2) The high-entropy alloy powder is first placed in a vacuum drying oven and heated to 60-80℃, and the moisture is removed, and the flowability of the high-entropy alloy powder is ensured, and 99.9% argon protective gas is introduced to prevent the high-entropy alloy powder from being oxidized, to obtain a high-entropy alloy powder with a particle size of 15-50um for SLM forming;

[0029] (3) Start the metal powder rapid forming system, select 45# steel as the substrate, and use the coaxial powder feeding deposition method under the protection of pure argon gas, and the process parameters include: laser power: 90-120 W, spot diameter: 50 μm, scanning speed: 800-1100 mm / s, scanning interval: 50 um, and each layer powder thickness: 0.02 mm;

[0030] (4) The imported Magics three-dimensional model is sliced and decomposed by computer, and the scanning path and scanning mode of the corresponding slice section are set, and the dried high-entropy alloy powder is placed on the 45# steel substrate, and the high-entropy alloy powder is melted and formed on the 45# steel substrate through the process of step (3) and the set laser scanning path, and the laser beam and the powder feeding are used in a layer-by-layer powder laying and face-by-face scanning manner, and finally the high-entropy alloy powder is accumulated and formed to obtain a porous high-entropy alloy structure layer, which is a single cubic array stacking structure, which can effectively improve the connection strength of aluminum / steel heterogeneous metal.

[0031] Example 1

[0032] As Figure 1 shown, the present embodiment proposes a method for preparing a porous HEA intermediate layer reinforced aluminum / steel heterogeneous interface by laser selective melting forming, and the steps are as follows:

[0033] First step, substrate preparation: before laser selective melting forming, the 45# steel substrate is cleaned and polished with 400#-800# sandpaper, the purpose is to remove the surface oxidation layer, and then the 45# steel substrate is wiped with anhydrous ethanol with an alcohol content of not less than 95.5%, to remove surface dirt and prevent contamination of the high-entropy alloy forming part.

[0034] Second step, model preparation: the porous cube structure is optimized by Majics three-dimensional software, each layer of the porous high-entropy alloy structure is sliced according to the printing thickness in the three-dimensional software, and finally the format is converted into a CLS format file and imported into the metal powder rapid prototyping system.

[0035] Third step: laser selective melting forming of the porous high-entropy alloy structure layer. The particle size of the high-entropy alloy powder is 15-50 um, and the laser selective melting forming parameters are as follows: laser power: 120 W, spot diameter: 50 um, porous high-entropy alloy height: 1.0 mm, scanning speed: 1000 mm / s, scanning interval: 50 um, 45# steel substrate is preheated to 150 DEG C, pure argon is introduced as a protective gas during the preparation process, and finally the porous high-entropy alloy structure layer is obtained, as shown in Figure 3 (c) shown, the surface is shaped flat, the quality is good, and there is no powder adhesion.

[0036] Comparative example 1

[0037] The porous high-entropy alloy coating is prepared by traditional high-temperature sintering.

[0038] As shown in Figure 2 , the surface shaping of the formed piece of the porous high-entropy alloy structure layer prepared by laser selective melting under different powers at a HEA height of 1.0 mm; (a) laser power 60 W; (c) laser power 70 W; (e) laser power 80 W; (g) laser power 90 W; (i) laser power 120 W; (b), (d), (f), (h), (j) are the microstructure observed by confocal microscope corresponding to (a), (c), (e), (g), (i), it is found that when the height of the porous high-entropy alloy structure layer is 1.0 mm, the un-melted powder particles gradually decrease within a certain range with the increase of the laser power.

[0039] Under the condition that the laser power remains unchanged, the Majics three-dimensional software is used to design the porous cube structure with a height of 0.5 mm, 0.8 mm, 1.0 mm and 1.5 mm, respectively. During the laser selective melting forming process, with the gradual increase of the height, the surface of the porous high-entropy alloy structure is more flat and smooth, and there is no powder adhesion. After many experiments, the best height is finally selected as 1.0 mm, and the size is 100 mm x 50 mm.

[0040] As shown in Figure 3As shown in the figure, the actual situation of preparing HEA as an intermediate layer to strengthen the aluminum / steel heterogeneous metal connection interface by laser selective melting, the macroscopic morphology of aluminum / steel direct connection and the cross-sectional macroscopic morphology of aluminum / HEA / steel connection are compared, it is found that the high-entropy alloy coating prepared by traditional sintering has harsh conditions, and high temperature will cause the high-entropy alloy coating to be brittle, the sintering temperature is generally about 1000-1200 DEG C, the process is more complicated, and the requirement for holding time is higher. And the random freedom of the formed porous high-entropy alloy coating is high, and the surface roughness is large.

[0041] As shown in the figure, Figure 4 The distribution of the aluminum / HEA interface nanohardness cloud chart (left figure) and the average nanohardness of the aluminum / steel connection interface reaction layer with or without HEA intermediate layer (right figure) show that the highest hardness of the aluminum / steel connection interface reaction layer is only 12.40 GPa, compared with 23.81 GPa of the aluminum / steel reaction layer (Ma Jingtao, Wang Tao, Chen Chong, etc. Effect of high-entropy alloy coating on the microstructure and properties of aluminum / steel liquid-solid composite bimetal), the HEA as an intermediate layer can effectively alleviate stress concentration and avoid the generation of brittle intermetallic compounds, thereby strengthening the aluminum / steel heterogeneous interface connection performance.

[0042] In summary, the present application provides a method for laser selective melting to prepare a porous HEA intermediate layer to strengthen the aluminum / steel heterogeneous interface connection, first, the Majics three-dimensional software is used to optimize the porous high-entropy alloy structure, and then the porous high-entropy alloy structure layer is prepared by a metal powder rapid forming system, the surface is smooth and the quality is good, which improves the defects such as raw material waste, random forming and poor surface precision in the traditional preparation process of high-entropy alloy, and at the same time, an effective regulation method for strengthening the mechanical properties of aluminum / steel heterogeneous metal connection is obtained.

[0043] The above is only a preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A FeCoCrNiMn high-entropy alloy for strengthening aluminum / steel heterogeneous interface connection, characterized in that, The elemental composition in atomic percentage is: Fe: 19.98%, Co: 21.06%, Cr: 18.24%, Ni: 21.03%, and Mn: 19.69%, and the purity of the raw materials of Fe, Co, Cr, Ni, and Mn is not less than 99.98%.

2. The FeCoCrNiMn high-entropy alloy for strengthening aluminum / steel dissimilar interface connection according to claim 1, characterized in that, The powder particle size of the FeCoCrNiMn high-entropy alloy is 15-50 um.

3. A porous high-entropy alloy structural layer for strengthening aluminum / steel dissimilar interface joint, characterized in that, The FeCoCrNiMn high-entropy alloy for strengthening aluminum / steel heterogeneous interface connection according to claim 1 or 2.

4. The porous high-entropy alloy structural layer for strengthening aluminum / steel dissimilar interface connection according to claim 3, characterized in that, It is a single cubic array stacked structure formed by laser selective melting.

5. The method for laser powder bed fusion forming of porous high-entropy alloy structural layer for strengthening aluminum / steel dissimilar interface joint according to claim 3 or 4, characterized in that, It comprises the following steps: (1) Raw material preparation: weigh the raw materials of the FeCoCrNiMn high-entropy alloy, and the elemental composition in atomic percentage is: Fe: 19.98%, Co: 21.06%, Cr: 18.24%, Ni: 21.03%, and Mn: 19.69%, and the purity of the raw materials of Fe, Co, Cr, Ni, and Mn is not less than 99.98%, mix uniformly, and obtain high-entropy alloy powder; (2) Put the high-entropy alloy powder into a vacuum drying oven and heat to 60-80℃, and keep warm for 10-12 h to remove the water therein, and introduce argon gas with a purity of 99.9% as a protective gas to prevent oxidation, and obtain dried high-entropy alloy powder; (3) Start the metal powder rapid forming system, use 45# steel as the substrate, set the coaxial powder feeding deposition process parameters in a pure argon protective atmosphere, including: laser power: 90-120 W, spot diameter: 50 um, scanning speed: 800-1100 mm / s, scanning interval: 50 um, and powder thickness of each layer: 0.02 mm; (4) Build a porous cubic structure model by Magics three-dimensional software, slice decomposition, and set the laser scanning path and scanning mode of the slice section; put the dried high-entropy alloy powder on the 45# steel substrate, combine the coaxial powder feeding deposition process set in step (3) with the laser scanning path, and use laser selective melting to form the high-entropy alloy powder on the 45# steel substrate, and the laser beam and the powder feeding adopt the way of layer-by-layer powder laying and face-by-face scanning to form a stacked structure, and obtain a porous high-entropy alloy structure layer.

6. The method of claim 5, wherein the laser selective melting is performed by using a laser beam having a diameter of 100-200 μm. In step (2), the powder particle size of the FeCoCrNiMn high-entropy alloy is 15-50 um.

7. The method of claim 5, wherein the laser selective melting is performed in a vacuum or in an inert gas atmosphere. In step (4), the thickness of the porous high-entropy alloy structure layer is 1.0 mm, and the size is 100 mm x 50 mm.

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