A process for additive manufacturing of nanoscale metal parts by equal channel angular pressing-friction stir molding

Abstract

The present invention provides a process for manufacturing nanoscale metal parts by equal-axis angular extrusion (EAP)-friction stir additive manufacturing (FSAM), comprising the following steps: extruding a metal billet using an EAP process to refine the grain size of the billet to a first nanometer size range, thereby obtaining a first bar stock; using the first bar stock as the raw material, using a FAM process to deposit, layer by layer, in an upward growth manner starting from the first layer according to a preset procedure until the final layer is deposited, thereby obtaining a metal part having a nanocrystalline grain size; wherein the grain size is further refined by the action of FAM, and the grain size of the metal part is within a second nanometer size range. The present invention utilizes EAP combined with FAM technology, using nanosized alloy billets as the raw material, and utilizing FAM technology to directly obtain nanoscale grains in the formed metal part, thereby achieving nanosized alloy additive manufacturing.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a process for additively manufacturing nanoscale metal parts by equal-channel angular extrusion-friction stir manufacturing. Background Art

[0002] Manufacturing larger structural parts using traditional machining methods (forging or casting) is difficult and costly. Chemical milling and mechanical milling require high equipment capacity and process levels, and also suffer from low efficiency, poor machining accuracy, high costs, large deformation, and the inability to meet design requirements. Therefore, metal additive manufacturing has emerged.

[0003] At present, the metal additive manufacturing methods that are being studied more include laser, electron beam and arc additive manufacturing. They are all metal additive manufacturing based on melting connection. During the manufacturing process, problems such as metallurgical defects and anisotropy caused by solid-liquid phase transition may occur.

[0004] The microstructure of metal parts formed using laser additive manufacturing (LAM) displays columnar crystals surrounded by fine equiaxed crystals. This is due to the rapid scanning speed, which prevents the heat remaining in the deposited layer from dissipating quickly. The high-temperature layer of the previous layer acts as a high-temperature tempering agent for the next deposited layer. As the deposited layer thickness increases, the heat accumulates, increasing the overall sample temperature. This, in turn, increases the tempering temperature of the subsequent layer, and the closer the structure of the subsequent layer approaches the equilibrium solidification structure, resulting in columnar crystal growth. As the deposited material nears the top layer, the overheated sample is rapidly cooled by air, forming fine equiaxed crystals. This remelting-induced columnar crystal structure is coarse and results in strong anisotropy in the macro- and microstructures and mechanical properties. This reduces the forming processability, mechanical properties, and structural performance, limiting the use of the parts produced.

[0005] Electron beam additive manufacturing (EBAM) can reduce stress concentration in parts, minimize porosity during the molding process, and improve molding quality and mechanical properties. However, this method's repeated melting results in excessive energy input, leading to excessively high melt pool temperatures and affecting melt pool stability. The resulting metal parts exhibit subtle grain boundaries of the original β columnar crystals. The α phase, in addition to its needle-like shape, also exhibits dendritic and long strip-like distribution, with significant size variation between α phases. Furthermore, the molten pool's agitation generates significant recoil pressure, shattering some of the melt into numerous small droplets under impact. During rapid solidification, numerous voids are not promptly filled with liquid metal, forming pores that severely impact the product's mechanical properties.

[0006] Arc additive manufacturing technology offers advantages such as high material utilization, high manufacturing efficiency, strong process adaptability, and low manufacturing costs, making it suitable for the production of large, thin-walled aerospace components. However, due to the varying thermal cycles caused by remelting, this method can lead to microstructural inhomogeneities in different regions of the component. The microstructure is primarily composed of fine columnar and equiaxed crystals, while the majority of grains within the deposited layer are coarse equiaxed crystals. This results in significant size and morphological inhomogeneities in the sample microstructure, significantly impacting the mechanical properties of the product.

[0007] The three processes mentioned above cannot be used directly in some production applications because the remelting process can lead to defects such as microstructure and mechanical properties, affecting the product. To address this problem, other processes are generally used to enhance mechanical properties. For example, forging can refine the raw cast grains, increase grain boundaries, increase metal strength, improve hardness, and improve the mechanical properties of the metal. However, the strengthening effect of this method is still limited and does not reach the level of nanocrystalline.

[0008] Friction stir additive manufacturing (FSAM) is a solid-phase metal additive manufacturing method that can overcome the inherent defects of melt joining in metal additive manufacturing. Compared with other additive manufacturing technologies, friction stir additive manufacturing has the following advantages: (1) Good molding effect. Under the action of mechanical stirring and heat input, the microstructure of the material in the additive area after friction stir is fine and uniform grains, so the mechanical properties are excellent; (2) Small residual deformation and stress. Because FSAM is a solid-phase additive manufacturing method, the material does not melt and solidify during the processing process, so the residual deformation and stress are extremely low; (3) Energy saving and environmental protection. Because the FSAM process does not require a high-energy heat source and the material does not melt, it saves more energy. In addition, no smoke and harmful gases are generated during the processing, which is more environmentally friendly.

[0009] Compared with the above three methods, the material will not melt during the FSAM process and will not cause the above-mentioned microstructural problems. However, due to the limitations of processes such as forging and pressing, this method is still difficult to obtain nanocrystals. Summary of the Invention

[0010] The purpose of the present invention is to address the shortcomings of the existing technology and provide a process for manufacturing nano-scale metal parts through equal-diameter angular extrusion-stir friction additive manufacturing. The process adopts equal-diameter angular extrusion process + stir friction additive manufacturing technology, uses nano-sized alloy rods as raw materials, and uses stir friction additive manufacturing technology to enable the formed metal parts to directly obtain nano-scale grains, thereby realizing nano-sized alloy additive manufacturing.

[0011] According to the purpose of the present invention, a process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing is provided, comprising the following steps:

[0012] An equal-channel angular extrusion process is used to extrude the metal rod blank, so that the grain size of the metal rod blank is refined to a first nanometer size range, thereby obtaining a first rod stock;

[0013] Using the first bar as the raw material, a friction stir additive manufacturing process is adopted to deposit layer by layer in an upward growth manner starting from the first layer according to a preset program until the last layer is deposited, thereby obtaining a metal part with a nanocrystalline grain size;

[0014] The grain size is further refined by the effect of stir friction, and the grain size of the metal part is within the second nanometer size range.

[0015] As an optional implementation, the first nanometer size interval is [200 nm, 500 nm].

[0016] As an optional implementation, the second nanometer size interval is [100 nm, 300 nm].

[0017] As an optional embodiment, the metal type is any one of aluminum alloy, magnesium alloy or titanium alloy.

[0018] As an optional embodiment, the specific process of equal channel angular extrusion includes:

[0019] The first end of the preheated metal billet is placed in the inlet of the upper die of the equal channel extrusion die, and the metal billet is completely squeezed into the lower die by downward pressure until the second end of the metal billet is squeezed out of the outlet, completing one extrusion pass;

[0020] Then, the second end of the metal rod blank is placed into the inlet of the upper die of the equal channel extrusion die, and the metal rod blank is completely squeezed into the lower die by downward pressure until the first end of the metal rod blank is squeezed out of the outlet, completing the second extrusion;

[0021] Among them, one extrusion pass and two extrusion passes constitute an extrusion cycle, and the extrusion cycle of the metal bar billet is T≥2.

[0022] As an optional embodiment, when the metal type is aluminum alloy and magnesium alloy, the preheating temperature of the metal bar blank is 250-350°C.

[0023] As an optional embodiment, when the metal type is titanium alloy, the preheating temperature of the metal bar blank is 600-750°C.

[0024] As an optional embodiment, the extrusion speed is 3 to 5 mm / s.

[0025] As an optional embodiment, the equal channel angular extrusion process uses a die with an internal intersection angle φ of 90° to 120° and an external angle Ψ of 10° to 30°.

[0026] As an optional embodiment, the specific conditions of the friction stir additive manufacturing process include:

[0027] The stirring head travel speed is 100-1000 mm / min, the stirring head rotation speed is 500-900 r / min, the bar feeding speed is 1-200 mm / min, the stirring head downward pressure is 1-10 mm, and the top forging force is 10-200 KN.

[0028] As an optional embodiment, the metal bar blank further includes a heat treatment before the extrusion process, and a process of removing oxide scale by grinding after the heat treatment; wherein,

[0029] When the metal type is aluminum alloy, the metal bar is solution treated at 450-480℃ for 2h, and then aged at 120-155℃ for 16h;

[0030] When the metal type is magnesium alloy, the metal bar blank is solution treated at 500-530℃ for 16 hours and then subjected to subsequent aging heat treatment with aging parameters of 200-260℃ at intervals of 4 hours up to 96 hours;

[0031] When the metal type is titanium alloy, the metal bar blank is solution treated at 700-750° C. for 30 minutes.

[0032] It can be seen from the above technical solution of the present invention that the process of manufacturing nano-scale metal parts by equal-diameter angular extrusion-stir friction additive manufacturing proposed by the present invention first adopts equal-diameter angular extrusion technology to process the metal bar blank, so that the alloy bar undergoes strong plastic deformation, refines the grains, and refines the grains of the metal bar blank to the nanocrystalline level. Then, the nano-sized alloy bar is used as the raw material for stir friction additive manufacturing. Under the action of intense stir friction, the material structure undergoes huge plastic deformation, generates a large amount of plastic deformation energy, and the metal material undergoes a violent recovery recrystallization process. Therefore, the grains after stir friction additive manufacturing are finer and more uniform, and nanocrystalline metal parts are directly obtained with excellent performance. In addition, the nano-grains manufactured by equal-diameter angular extrusion contribute to the metal flow in the stir friction process through the sliding mechanism of the crystal during the plastic deformation process, which can more conveniently manufacture ultrafine grains.

[0033] The present invention adopts stir friction additive manufacturing technology, which can overcome the problems of porosity and poor density of the molded parts. Since the metal raw material does not melt during the process, it has the advantages of small residual stress and less damage to the material itself. At the same time, due to the low process temperature, it has the advantage of saving energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a process flow chart of the process of manufacturing nano-scale metal parts through equal channel angular extrusion-stir friction additive manufacturing of the present invention.

[0035] Figure 2 It is a schematic structural diagram of the die for equal channel angular extrusion used in an exemplary embodiment of the present invention.

[0036] Figure 3 is a schematic diagram of friction stir additive manufacturing in an exemplary embodiment of the present invention.

[0037] Figure 4 Schematic diagram of parts prepared in an embodiment of the present invention; Figure 4 a in the figure is the front view. Figure 4 b in the figure is a top view.

[0038] Figure 5 a and b are respectively the microstructure diagrams of 1420 aluminum-lithium alloy before and after equal channel angular extrusion in Example 1 of the present invention.

[0039] Figure 6 a and b are the microstructure diagrams of the final parts obtained in Comparative Example 1 and Example 1 of the present invention, respectively.

[0040] Figure 7 a and b are microstructure diagrams of the Mg-10Gd-6Y-1.5Zn-0.5Zr rare earth magnesium alloy before and after equal channel angular extrusion in Example 2 of the present invention.

[0041] Figure 8 a and b are the microstructure diagrams of the final parts obtained in Comparative Example 2 and Example 2 of the present invention, respectively.

[0042] Figure 9 a and b are the microstructure diagrams of TA15 titanium alloy before and after equal channel angular extrusion in Example 3 of the present invention.

[0043] Figure 10 a and b are the microstructure diagrams of the final parts obtained in Comparative Example 3 and Example 3 of the present invention, respectively. DETAILED DESCRIPTION

[0044] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0045] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to be comprehensive. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of a number of ways.

[0046] Equal channel angular pressing (ECAP) is a method of preparing ultrafine-grained materials by large plastic deformation. Compared with traditional metal plastic processing methods, the ECAP process can apply lower pressure without changing the cross-sectional area of ​​the material, and obtain pure shear deformation through multiple extrusion passes, thereby refining the grains and improving the mechanical properties.

[0047] Currently, extensive research using ECAP has been conducted on metals such as aluminum, copper, magnesium, and titanium, as well as their alloys. A series of tests have shown that ECAP can significantly refine grain size, resulting in higher mechanical strength. Compared to other methods for preparing ultrafine-grained materials (such as vapor phase processing, high-energy ball milling, and amorphous crystallization), the ECAP process offers numerous advantages. These include overcoming the porosity and poor density inherent in samples prepared by other methods, as well as the impurities and difficulty in producing large-sized billets caused by ball milling. This has played a significant role in both experimental research and production applications.

[0048] However, the ECAP process can only form metal into bars and cannot directly produce metal parts.

[0049] Therefore, the present invention provides a process for manufacturing nano-scale metal parts through equal-axis angular extrusion-friction stir additive manufacturing. The equal-axis angular extrusion process + friction stir additive manufacturing technology is adopted. The equal-axis angular extrusion technology is used to refine the grains of the metal bar blank to the nanoscale, thereby achieving the purpose of strengthening the strength and hardness of the alloy. On this basis, the friction stir additive manufacturing technology is further used to fully utilize the equal-axis angular extruded metal bar blank, and the nanocrystals can be preserved while being made into parts, and even further refined.

[0050] Combine Figure 1 As shown, in one preferred embodiment of the present invention, a process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing is provided, comprising the following steps:

[0051] An equal-channel angular extrusion process is used to extrude the metal rod blank, so that the grain size of the metal rod blank is refined to a first nanometer size range, thereby obtaining a first rod stock;

[0052] Using the first bar as the raw material, a friction stir additive manufacturing process is adopted to deposit layer by layer in an upward growth manner starting from the first layer according to a preset program until the last layer is deposited, thereby obtaining a metal part with a nanocrystalline grain size;

[0053] The grain size is further refined by the effect of stir friction, and the grain size of the metal part is within the second nanometer size range.

[0054] As an optional implementation, the first nanometer size interval is [200 nm, 500 nm].

[0055] As an optional implementation, the second nanometer size interval is [100 nm, 300 nm].

[0056] As an optional embodiment, the metal type is any one of aluminum alloy, magnesium alloy or titanium alloy.

[0057] As an optional embodiment, the specific process of equal channel angular extrusion includes:

[0058] The first end of the preheated metal billet is placed in the inlet of the upper die of the equal channel extrusion die, and the metal billet is completely squeezed into the lower die by downward pressure until the second end of the metal billet is squeezed out of the outlet, completing one extrusion pass;

[0059] Then, the second end of the metal rod blank is placed into the inlet of the upper die of the equal channel extrusion die, and the metal rod blank is completely squeezed into the lower die by downward pressure until the first end of the metal rod blank is squeezed out of the outlet, completing the second extrusion;

[0060] Among them, one extrusion pass and two extrusion passes constitute an extrusion cycle, and the extrusion cycle of the metal bar billet is T≥2.

[0061] As an optional embodiment, when the metal type is aluminum alloy and magnesium alloy, the preheating temperature of the metal bar blank is 250-350°C.

[0062] As an optional embodiment, when the metal type is titanium alloy, the preheating temperature of the metal bar blank is 600-750°C.

[0063] As an optional embodiment, the extrusion speed is 3 to 5 mm / s.

[0064] As an optional embodiment, the equal channel angular extrusion process uses a die with an internal intersection angle φ of 90° to 120° and an external angle Ψ of 10° to 30°.

[0065] As an optional embodiment, the specific conditions of the friction stir additive manufacturing process include:

[0066] The stirring head travel speed is 100-1000 mm / min, the stirring head rotation speed is 500-900 r / min, the bar feeding speed is 1-200 mm / min, the stirring head downward pressure is 1-10 mm, and the top forging force is 10-200 KN.

[0067] As an optional embodiment, the metal bar blank further includes a heat treatment before the extrusion process, and a process of removing oxide scale by grinding after the heat treatment; wherein,

[0068] When the metal type is aluminum alloy, the metal bar is solution treated at 450-480℃ for 2h, and then aged at 120-155℃ for 16h;

[0069] When the metal type is magnesium alloy, the metal bar blank is solution treated at 500-530℃ for 16 hours and then subjected to subsequent aging heat treatment with aging parameters of 200-260℃ at intervals of 4 hours up to 96 hours;

[0070] When the metal type is titanium alloy, the metal bar blank is solution treated at 700-750° C. for 30 minutes.

[0071] In other optional embodiments, during the friction stir additive manufacturing process, each deposited layer is surface machined to obtain a smooth surface while removing the oxide layer.

[0072] In other optional embodiments, the metal rod blank that has completed the extrusion process is surface-polished and then cleaned and dried to obtain a first rod stock.

[0073] In an exemplary embodiment of the present invention, a process for manufacturing nanoscale metal parts by equal channel angular pressing-friction stir additive manufacturing is provided, comprising the following steps:

[0074] (1) The obtained ingot is processed into a metal billet with a diameter of 12 mm and a length of 60 mm by wire cutting, and the metal billet is pre-processed.

[0075] It can be understood that the preparation process of the ingot is the existing technology in this field. For example, the raw materials are smelted to form the ingot. The smelting process is the existing technology in this field and will not be described in detail here.

[0076] The process of pre-processing of metal bar billets is as follows:

[0077] When the metal type is aluminum alloy, the metal bar is solution treated at 450-480℃ for 2h, and then aged at 120-155℃ for 16h;

[0078] When the metal type is magnesium alloy, the metal bar blank is solution treated at 500-530℃ for 16 hours and then subjected to subsequent aging heat treatment with aging parameters of 200-260℃ at intervals of 4 hours up to 96 hours;

[0079] When the metal type is titanium alloy, the metal bar blank is solution treated at 700-750° C. for 30 minutes.

[0080] Through heat treatment, defects such as looseness and pores are eliminated to make the grains uniform. After heat treatment, the oxide scale on the surface of the metal bar blank is removed by grinding to complete the pretreatment of the metal bar blank.

[0081] (2) A commercially available equal-diameter angular extrusion die was used, with an inner die angle of φ = 90° and an outer die angle of Ψ = 30°. In preparation for the extrusion experiment, the inner surface of the extrusion die, the pretreated metal billet, and the extrusion rod were lubricated with a lubricant (e.g., a mixed solution of MoS2 and engine oil).

[0082] In an alternative embodiment, the mold is Figure 2 As shown, the main body of the mold consists of three parts: an extrusion rod 1, an upper mold 2 and a lower mold 3. The upper mold 2 and the lower mold 3 are respectively provided with channels, and the channels in the upper mold 2 and the lower mold 3 are connected; when in use, the metal bar blank enters from the upper mold inlet 21, and the downward pressure of the extrusion rod 1 extrudes the metal bar blank to the outlet 31, completing the extrusion process.

[0083] (3) Debug the extrusion machine and conduct ECAP experiments.

[0084] First, the pretreated metal bar blank is preheated again;

[0085] The first end of the preheated metal billet is placed into the upper die inlet 21 of the equal channel extrusion die. The extrusion rod 1 uses downward pressure to completely extrude the metal billet into the lower die at an extrusion speed of 3 to 5 mm / s until the second end of the metal billet is extruded out of the outlet 31, completing one extrusion pass.

[0086] Then, the second end of the metal bar blank is placed into the upper die inlet 21 of the equal channel extrusion die. The extrusion rod 1 uses downward pressure to completely extrude the metal bar blank into the lower die at an extrusion speed of 3 to 5 mm / s until the first end of the metal bar blank is extruded out of the outlet 31, completing the second extrusion process.

[0087] Then, the first end of the metal bar blank is placed into the upper die inlet 21 of the equal channel extrusion die. The extrusion rod 1 uses downward pressure to completely squeeze the metal bar blank into the lower die at an extrusion speed of 3 to 5 mm / s until the second end of the metal bar blank is squeezed out of the outlet 31, completing three extrusion passes.

[0088] Then, the second end of the metal rod blank is placed into the upper die inlet 21 of the equal channel extrusion die. The extrusion rod 1 uses downward pressure to completely extrude the metal rod blank into the lower die at an extrusion speed of 3 to 5 mm / s until the first end of the metal rod blank is extruded out of the outlet 31, completing four extrusion passes.

[0089] (5) The samples that completed the extrusion test were polished with 600#, 1000#, 1500#, 2000#, 3000#, and 5000# water sandpaper in sequence until the scratch directions on the sample surface were consistent. Then, they were polished with diamond with a grain size of 0.25μm until the sample surface was bright and without obvious scratches. Then, they were ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove the residual polishing agent and impurities on the sample surface. After taking out, they were blown dry with a hair dryer for microstructural observation and analysis of the material grain refinement mechanism.

[0090] (6) Using the friction stir additive manufacturing technology, the metal rod blank obtained in step (5) is used as the raw material, and the parts are manufactured by depositing layer by layer in an upward growth manner starting from the first layer according to a preset program until the last layer is deposited.

[0091] like Figure 3 As shown, in a typical embodiment of the present invention, the structure of the stirring head 4 used for stir friction treatment can adopt the existing stir friction head structure, and a channel for a cylindrical metal rod 5 is set in the center to send the metal rod to the lower position of the stirring head 4, and stir friction treatment is performed through the stirring needle set at the lower end of the stirring head 4.

[0092] Combine Figure 3 In the illustrated embodiment, a channel for a cylindrical metal rod is provided in the stirring head 4 , and an example of depositing the deposition layer 7 layer by layer in an upward growth manner on the substrate 6 is exemplarily shown.

[0093] The process parameters are as follows: agitator travel speed of 100 to 1000 mm / min, agitator rotation speed of 500 to 900 rpm, bar feed speed of 1 to 200 mm / min, agitator downward pressure of 1 to 10 mm, and a forging force of 10 to 200 kN. During the manufacturing process, surface processing is performed after each layer is deposited to achieve a smooth surface and remove the oxide layer.

[0094] For better understanding, the present invention is further described below with reference to several specific examples, but the processing technology is not limited thereto, and the content of the present invention is not limited thereto.

[0095] The equal diameter angular extrusion die used in the following embodiments has an inner angle of φ = 90° and an outer angle of Ψ = 30°; the printed part is a thin-walled, topless cylindrical part with a diameter of 8 mm, a height of 10 mm, and a wall thickness of 2 mm. Figure 4 shown.

[0096] Example 1

[0097] In this embodiment, equal channel angular extrusion-stirring additive manufacturing is used to manufacture nanostructured 1420 aluminum-lithium alloy parts. The composition of the 1420 aluminum-lithium alloy is: Li 1.8wt%, Mg 4.5wt%, Zr 0.08wt%, Fe 0.2wt%, Si 0.15wt%, Ti 0.1wt%, Cu 0.05wt%, and Al 93.12wt%.

[0098] The specific steps are as follows:

[0099] (1) The above metal raw materials (purity of 99.9%) were placed in an electric furnace, heated to 800°C, and smelted into 1420 aluminum-lithium alloy ingots.

[0100] (2) The smelted ingot is processed into a metal bar with a diameter of 12 mm and a length of 60 mm by wire cutting, and then solution treated at 473 ° C for 2 h, aged at 135 ° C for 16 h, and cooled in the furnace to eliminate defects such as looseness and porosity and make the grains uniform.

[0101] (3) Use sandpaper to polish the surface of the metal rod blank and lubricate the inner surface of the mold, the metal rod blank, and the extrusion rod with lubricant (a mixed solution of MoS2 and engine oil).

[0102] (4) The extrusion machine is debugged and the metal bar blank is preheated to 250°C. The first end of the metal bar blank is then placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely extrude the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the second end of the metal bar blank is extruded out of the outlet, completing one extrusion pass.

[0103] Then, the second end of the metal bar blank is placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the first end of the metal bar blank is squeezed out of the outlet, completing the second extrusion.

[0104] Then, the first end of the metal bar blank is placed into the inlet of the upper die of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the second end of the metal bar blank is squeezed out of the outlet, completing three extrusion passes.

[0105] Then the second end of the metal rod blank is placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal rod blank into the lower die at an extrusion speed of 5 mm / s until the first end of the metal rod blank is squeezed out of the outlet, completing four extrusion passes.

[0106] (5) The metal rod blanks that completed the extrusion experiment were polished with 600#, 1000#, 1500#, 2000#, 3000#, and 5000# water sandpaper in turn until the scratch directions on the sample surface were consistent. Then, they were polished with diamond with a grain size of 0.25μm until the sample surface was bright and without obvious scratches. Then, they were ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove the residual polishing agent and impurities on the sample surface. After being taken out, they were blown dry with a hair dryer for microstructural observation and the grain refinement mechanism of the material after four passes of equal-diameter angular extrusion was analyzed.

[0107] (6) Friction stir additive manufacturing technology is used to manufacture parts using the metal rod blank obtained in step (5) as raw material. During the manufacturing process, surface processing is performed after each layer is deposited to obtain a smooth surface and remove the oxide layer until a formed part is obtained.

[0108] The process parameters of friction stir are as follows:

[0109] The travel speed is 800mm / min; the stirring head speed is 600r / min; the bar feeding speed is 120mm / min; the stirring head downward pressure is 1mm, and the top forging force is 100KN.

[0110] Example 2

[0111] In this embodiment, the nanostructured magnesium alloy part is manufactured by equal channel angular extrusion-stirring additive manufacturing, which includes the following raw materials in percentage by weight: 82 wt% Mg, 10 wt% Gd, 6 wt% Y, 1.5 wt% Zn, and 0.5 wt% Zr.

[0112] The specific steps are as follows:

[0113] (1) The above-mentioned metal raw materials (purity of 99.9%) were placed in an electric furnace, heated to 760° C., and smelted into Mg-10Gd-6Y-1.5Zn-0.5Zr rare earth magnesium alloy ingots.

[0114] (2) The smelted ingot was processed into metal billets with a diameter of 12 mm and a length of 60 mm by wire cutting, and the metal billets were solution treated at 510 °C for 16 h, and subsequently subjected to aging heat treatment with an aging parameter of 220 °C at intervals of 4 h until 96 h.

[0115] (3) Use sandpaper to polish the surface of the metal rod blank and lubricate the inner surface of the mold, the metal rod blank, and the extrusion rod with lubricant (a mixed solution of MoS2 and engine oil).

[0116] (4) The extrusion machine is debugged and the metal bar blank is preheated to 250°C. The first end of the metal bar blank is then placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely extrude the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the second end of the metal bar blank is extruded out of the outlet, completing one extrusion pass.

[0117] Then, the second end of the metal bar blank is placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the first end of the metal bar blank is squeezed out of the outlet, completing the second extrusion.

[0118] Then, the first end of the metal bar blank is placed into the inlet of the upper die of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the second end of the metal bar blank is squeezed out of the outlet, completing three extrusion passes.

[0119] Then the second end of the metal rod blank is placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal rod blank into the lower die at an extrusion speed of 5 mm / s until the first end of the metal rod blank is squeezed out of the outlet, completing four extrusion passes.

[0120] (5) The samples that completed the extrusion experiment were polished with 600#, 1000#, 1500#, 2000#, 3000#, and 5000# water sandpaper in turn until the scratch directions on the sample surface were consistent. Then, they were polished with diamond with a grain size of 0.25μm until the sample surface was bright and without obvious scratches. Then, they were ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove the residual polishing agent and impurities on the sample surface. After being taken out, they were blown dry with a hair dryer and the microstructure was observed to analyze the grain refinement mechanism of the material after four passes of equal-diameter angular extrusion.

[0121] (6) Friction stir additive manufacturing technology is used to manufacture parts using the metal rod blank obtained in step (5) as raw material. During the manufacturing process, surface processing is performed after each layer is deposited to obtain a smooth surface and remove the oxide layer until a formed part is obtained.

[0122] The process parameters of friction stir are as follows:

[0123] The travel speed is 1000mm / min; the stirring head speed is 700r / min; the bar feeding speed is 150mm / min; the stirring head downward pressure is 2mm, and the top forging force is 150KN.

[0124] Example 3

[0125] In this embodiment, the nanostructured titanium alloy part is manufactured by equal channel angular extrusion-stirring additive manufacturing, including the following raw materials in percentage by weight: Al 6.44wt%, V 1.98wt%, Zr 1.98wt%, Mo 1.73wt%, Fe 0.03wt%, O 0.11wt%, H 0.002wt%, N 0.004wt%, C 0.017wt%, Si 0.04wt%, and Ti 87.667wt%.

[0126] The specific steps are as follows:

[0127] (1) Each metal raw material (purity of 99.9%) was placed in an electric furnace, heated to 960°C, and smelted into TA15 ingots.

[0128] (2) The smelted ingot is processed into a metal billet with a diameter of 12 mm and a length of 60 mm by wire cutting, and the metal billet is subjected to a solution treatment of annealing at 750 ° C for 30 min and cooled in the furnace to eliminate defects such as looseness and porosity and make the grains uniform.

[0129] (3) Use sandpaper to polish the surface of the metal rod blank and lubricate the inner surface of the mold, the metal rod blank, and the extrusion rod with lubricant (a mixed solution of MoS2 and engine oil).

[0130] (4) The extrusion machine is debugged and the metal bar blank is preheated to 600°C. The first end of the metal bar blank is then placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely extrude the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the second end of the metal bar blank is extruded out of the outlet, completing one extrusion pass.

[0131] Then, the second end of the metal bar blank is placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the first end of the metal bar blank is squeezed out of the outlet, completing the second extrusion.

[0132] Then, the first end of the metal bar blank is placed into the inlet of the upper die of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal bar blank into the lower die at an extrusion speed of 5 mm / s until the second end of the metal bar blank is squeezed out of the outlet, completing three extrusion passes.

[0133] Then the second end of the metal rod blank is placed into the upper die inlet of the equal channel extrusion die. The extrusion rod uses downward pressure to completely squeeze the metal rod blank into the lower die at an extrusion speed of 5 mm / s until the first end of the metal rod blank is squeezed out of the outlet, completing four extrusion passes.

[0134] (5) The samples that completed the extrusion experiment were polished with 600#, 1000#, 1500#, 2000#, 3000#, and 5000# water sandpaper in sequence until the scratch directions on the sample surface were consistent. Then, they were polished with diamond with a grain size of 0.25μm until the sample surface was bright and without obvious scratches. Then, they were ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove the residual polishing agent and impurities on the sample surface. After being taken out, they were blown dry with a hair dryer. Microstructural observation was carried out to analyze the grain refinement mechanism of the material after four passes of equal channel angular extrusion.

[0135] (6) Friction stir additive manufacturing technology is used to manufacture parts using the metal rod blank obtained in step (5) as raw material. During the manufacturing process, surface processing is performed after each layer is deposited to obtain a smooth surface and remove the oxide layer until a formed part is obtained.

[0136] The process parameters of friction stir are as follows:

[0137] The travel speed is 500mm / min; the stirring head speed is 900r / min; the bar feeding speed is 100mm / min; the stirring head downward pressure is 5mm, and the top forging force is 200KN.

[0138] Comparative Example 1

[0139] The nanostructured 1420 aluminum-lithium alloy parts were manufactured by friction stir additive manufacturing. The composition of the 1420 aluminum-lithium alloy was the same as that in Example 1.

[0140] The specific steps are as follows:

[0141] (1) The above metal raw materials (purity of 99.9%) were placed in an electric furnace, heated to 800°C, and smelted into 1420 aluminum-lithium alloy ingots.

[0142] (2) The smelted ingot is processed into a metal bar with a diameter of 12 mm and a length of 60 mm by wire cutting, and then solution treated at 473 ° C for 2 h, aged at 135 ° C for 16 h, and cooled in the furnace to eliminate defects such as looseness and porosity and make the grains uniform.

[0143] (3) The metal rod blank was polished with 600#, 1000#, 1500#, 2000#, 3000#, and 5000# water sandpaper in turn until the scratch directions on the sample surface were consistent. It was then polished with diamond with a grain size of 0.25μm until the sample surface was bright and without obvious scratches. It was then ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove the residual polishing agent and impurities on the sample surface. After being taken out, it was blown dry with a hair dryer and used as the raw material for stir friction additive manufacturing. The stir friction additive manufacturing technology was used to manufacture parts. During the manufacturing process, surface processing was performed after each layer was deposited to obtain a smooth surface and remove the oxide layer until a formed part was obtained.

[0144] The process parameters of friction stir are as follows:

[0145] The travel speed is 800mm / min; the stirring head speed is 600r / min; the bar feeding speed is 120mm / min; the stirring head downward pressure is 1mm, and the top forging force is 100KN.

[0146] Comparative Example 2

[0147] The nanostructured magnesium alloy parts were manufactured by friction stir additive manufacturing, and the magnesium alloy composition was the same as that in Example 2.

[0148] The specific steps are as follows:

[0149] (1) The above-mentioned metal raw materials (purity of 99.9%) were placed in an electric furnace, heated to 760° C., and smelted into Mg-10Gd-6Y-1.5Zn-0.5Zr rare earth magnesium alloy ingots.

[0150] (2) The ingots were processed into metal billets with a diameter of 12 mm and a length of 60 mm using wire cutting, and the metal billets were solution treated at 510 °C for 16 h and subsequently subjected to aging heat treatment with an aging parameter of 220 °C at intervals of 4 h until 96 h.

[0151] (3) The metal rod blank was polished with 600#, 1000#, 1500#, 2000#, 3000#, and 5000# water sandpaper in turn until the scratch directions on the sample surface were consistent. It was then polished with diamond with a grain size of 0.25μm until the sample surface was bright and without obvious scratches. It was then ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove the residual polishing agent and impurities on the sample surface. After being taken out, it was blown dry with a hair dryer and used as the raw material for stir friction additive manufacturing. The stir friction additive manufacturing technology was used to manufacture parts. During the manufacturing process, surface processing was performed after each layer was deposited to obtain a smooth surface and remove the oxide layer until a formed part was obtained.

[0152] The process parameters of friction stir are as follows:

[0153] The travel speed is 1000mm / min; the stirring head speed is 700r / min; the bar feeding speed is 150mm / min; the stirring head downward pressure is 2mm, and the top forging force is 150KN.

[0154] Comparative Example 3

[0155] The nanostructured titanium alloy parts were manufactured by friction stir additive manufacturing, and the titanium alloy composition was the same as that in Example 3.

[0156] The specific steps are as follows:

[0157] (1) Each metal raw material (purity of 99.9%) was placed in an electric furnace, heated to 960°C, and smelted into TA15 ingots.

[0158] (2) The smelted ingot is processed into a metal billet with a diameter of 12 mm and a length of 60 mm by wire cutting, and the metal billet is subjected to a solution treatment of annealing at 750 ° C for 30 min and cooled in the furnace to eliminate defects such as looseness and porosity and make the grains uniform.

[0159] (3) The metal rod blank was polished with 600#, 1000#, 1500#, 2000#, 3000#, and 5000# water sandpaper in turn until the scratch directions on the sample surface were consistent. It was then polished with diamond with a grain size of 0.25μm until the sample surface was bright and without obvious scratches. It was then ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove the residual polishing agent and impurities on the sample surface. After being taken out, it was blown dry with a hair dryer and used as the raw material for stir friction additive manufacturing. The stir friction additive manufacturing technology was used to manufacture parts. During the manufacturing process, surface processing was performed after each layer was deposited to obtain a smooth surface and remove the oxide layer until a formed part was obtained.

[0160] The process parameters of friction stir are as follows:

[0161] The travel speed is 500mm / min; the stirring head speed is 900r / min; the bar feeding speed is 100mm / min; the stirring head downward pressure is 5mm, and the top forging force is 200KN.

[0162] microstructure

[0163] Figure 5 Figures a and b are the microstructures of 1420 Al-Li alloy before and after equal channel angular extrusion.

[0164] By comparison, it can be seen that after four extrusion passes, the grains are greatly refined, and at the same time the grains are refined, the second phase is broken, and the initial slender particles are transformed into smaller and more numerous rice-like particles distributed in the aluminum alloy matrix, and the distribution of the second phase is more uniform.

[0165] Figure 6 a and b are the microstructure diagrams of the final parts of Comparative Example 1 and Example 1, respectively.

[0166] Depend on Figure 6 As shown in Figures a and b, friction stir additive manufacturing (FSAM) leads to dynamic recrystallization, resulting in smaller, uniformly equiaxed grains with no apparent directionality. Furthermore, it is clearly observed that the ECAP + FSM technology can achieve nanocrystalline grains, significantly enhancing performance.

[0167] Figure 7 Figures a and b are the microstructures of Mg-10Gd-6Y-1.5Zn-0.5Zr rare earth magnesium alloy before and after equal channel angular extrusion.

[0168] By comparison, it can be seen that after four extrusions, the grains show obvious refinement, and it can be observed that the size of most recrystallized grains is significantly smaller than the size of the second phase. The grain refinement effect is very obvious, and the phenomenon of coarse grains wrapped by fine grains appears, showing a network distribution.

[0169] Figure 8 a and b are the microstructure diagrams of the final parts of Comparative Example 2 and Example 2, respectively.

[0170] By comparison, it can be seen that under the action of dynamic recrystallization, the grains will be refined. Figure 8 Compared with a in Figure 8 The grain refinement of b is particularly obvious, and most of the grains are nanocrystalline. This phenomenon is caused by the ECAP treatment, which greatly increases the degree of grain refinement.

[0171] Figure 9 Figures a and b are the microstructures of TA15 titanium alloy before and after equal channel angular pressing.

[0172] By comparison, it can be seen that during extrusion, dislocation accumulation and reorganization occurred inside the sample, forming subgrains and complete fine equiaxed crystals, thereby refining the grains. At the same time, recovery and dynamic recrystallization occurred inside the sample during the ECAP deformation process, which also promoted the refinement of the grains.

[0173] Figure 10 a and b are the microstructure diagrams of the final parts of Comparative Example 3 and Example 3, respectively.

[0174] By comparison, it can be seen that, similar to the previous two examples, under the premise of adopting ECAP, the dynamic recrystallization of the manufactured products is more obvious, the grain refinement effect is more significant, and the mechanical properties of titanium alloy are also improved to a certain extent.

[0175] Performance Testing

[0176] The mechanical properties of the final parts of Examples 1, 2, 3 and Comparative Examples 1, 2, 3 were tested, and the results are shown in Table 1.

[0177] Table 1 Mechanical properties and average grain size data of each workpiece

[0178]

[0179] From the results in Table 1 and the microstructure test results, it can be seen that after combining friction stir additive manufacturing with ECAP technology, the tensile strength of aluminum alloy increased by 11.2%, the yield strength increased by 9.6%, the average grain size was reduced to 152nm, and the elongation increased by 11.8%; for magnesium alloy, the tensile strength increased by 10.1%, the yield strength increased by 8.6%, the average grain size was reduced to 118nm, and the elongation increased by 7.2%; for titanium alloy, the tensile strength increased by 9.7%, the yield strength increased by 11%, the average grain size was reduced to 305nm, and the elongation increased by 10.2%.

[0180] It can be seen from this that the grain size of the product manufactured using the ECAP+FSAM technology of the present invention can reach nanometers, and its various performances will also be greatly improved.

[0181] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing, characterized in that: The following steps are involved: Extruding the metal rod blank using an equal-channel angular extrusion process to refine the grain size of the metal rod blank to a first nanometer size range, thereby obtaining a first rod material; wherein the first nanometer size range is [200 nm, 500 nm]; Using the first bar as the raw material, a friction stir additive manufacturing process is adopted to deposit layer by layer in an upward growth manner starting from the first layer according to a preset program until the last layer is deposited, thereby obtaining a metal part with a nanocrystalline grain size; The grain size is further refined by the stir friction, and the grain size of the metal part is in a second nanometer size range, and the second nanometer size range is [100nm, 300nm]. By using equal-channel angular extrusion technology to refine the grains of metal billets to the nanoscale, and then using stir friction additive manufacturing technology to make parts from the equal-channel angular extruded metal billets while preserving the nanocrystals in the parts; The specific conditions of the friction stir additive manufacturing process include: The stirring head travel speed is 100~1000mm / min, the stirring head speed is 500~900 r / min, the bar feeding speed is 1~200mm / min, the stirring head downward pressure is 1~10mm, and the top forging force is 10~200KN.

2. The process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing according to claim 1, characterized in that: The metal type is any one of aluminum alloy, magnesium alloy or titanium alloy.

3. The process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing according to claim 1, characterized in that: The specific process of equal channel angular extrusion includes: The first end of the preheated metal billet is placed in the inlet of the upper die of the equal channel extrusion die, and the metal billet is completely squeezed into the lower die by downward pressure until the second end of the metal billet is squeezed out of the outlet, completing one extrusion pass; Then, the second end of the metal rod blank is placed into the inlet of the upper die of the equal channel extrusion die, and the metal rod blank is completely squeezed into the lower die by downward pressure until the first end of the metal rod blank is squeezed out of the outlet, completing the second extrusion; Among them, one extrusion pass and two extrusion passes constitute an extrusion cycle, and the extrusion cycle of the metal bar billet is T≥2.

4. The process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing according to claim 3, characterized in that: When the metal type is aluminum alloy and magnesium alloy, the preheating temperature of the metal bar billet is 250~350℃.

5. The process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing according to claim 3, characterized in that: When the metal type is titanium alloy, the preheating temperature of the metal bar blank is 600~750℃.

6. The process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing according to claim 3, characterized in that: The extrusion speed is 3~5mm / s.

7. The process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing according to claim 1, characterized in that: The internal angle φ of the die used in the equal diameter angular extrusion process is 90°~120°, and the external angle Ψ=10°~30°.

8. The process for manufacturing nanoscale metal parts by equal channel angular extrusion-friction stir additive manufacturing according to claim 1, characterized in that: The metal bar blank also includes a heat treatment before extrusion, and a process of removing oxide scale by grinding after heat treatment; wherein, When the metal type is aluminum alloy, the metal billet is solution treated at 450-480℃ for 2 h, and then aged at 120-155℃ for 16 h. When the metal type is titanium alloy, the metal bar blank is solution treated at 700~750℃ for 30 min.

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