A low-cost short-process preparation method of a large and complex component

Abstract

The application discloses a low-cost short-process preparation method of large complex components and belongs to the technical field of material processing. The method takes a cast alloy plate as an initial material, adopts friction stir welding to weld the initial material, and then adopts multi-pass friction stir processing (i.e. single-plate friction stir welding) on the large-size plate after welding to obtain a large-size component with integral superplastic forming capability, and adopts superplastic forming to prepare a large-size complex component, and the preparation process is shown in Fig. 1. The method can convert small cast alloy plates with cast defects and coarse structures into large-size fine-grain plates with integral superplastic forming capability, and finally forms large-size complex components. The method has the advantages of short preparation process, high material utilization rate, low cost and no limitation on the size of the initial plate, and can be applied to titanium alloys, steel, aluminum alloys, magnesium alloys, high-entropy alloys and other various alloys with superplasticity, and is favorable for industrial production and application of large-size complex components.

Description

Technical Field

[0001] This invention relates to the field of materials processing technology, and specifically to a low-cost, short-process preparation method for large, complex components. Background Technology

[0002] Superplastic forming, a process capable of shaping complex structural parts, stands out among many plastic processing techniques due to its superior characteristics compared to traditional plastic forming methods, such as low deformation resistance, near-net-shape forming, significant weight reduction in formed components, and one-time forming. Currently, the fabrication of complex components from superplastic alloy sheets using superplastic forming is widely used, such as aircraft panels, hatches, and doors. However, for extremely large and complex components, such as large satellite skins and large aircraft air intake lips, the current sheet metal fabrication technology limits the size of the sheet metal, making it impossible to fabricate them using superplastic forming from a single sheet.

[0003] Fine equiaxed / ultrafine-grained structures and a high proportion of high-angle grain boundaries are crucial conditions for materials to achieve superplastic properties. Therefore, preparing fine-grained / ultrafine-grained superplastic sheets and increasing the proportion of high-angle grains are prerequisites for achieving superplasticity and performing superplastic forming. Currently, existing fine-grained preparation techniques are insufficient for producing ultra-large-sized fine-grained / ultrafine-grained superplastic sheets. For large and complex components, multiple components can be superplastically formed and then welded together; however, welding damages the overall performance of the component, leading to significant residual stress and deformation, affecting the assembly accuracy, and greatly limiting the practical application of large and complex components. To prepare large-size titanium alloy sheets with superplastic forming capabilities, Wu et al. [Patent 202111282326.4] disclosed a superplastic forming process for preparing large-size titanium alloy components. This process involves first performing friction stir welding on commercially available superplastic rolled titanium alloy sheets to obtain fine equiaxed grains in the weld nugget area. The entire welded sheet is then annealed. By utilizing the difference in microstructure coarsening rates between the weld nugget and the base material during annealing, a similar microstructure is achieved across the entire sheet, resulting in similar superplastic deformation capabilities in different regions of the large-size welded plate. However, this method requires the original titanium alloy sheet to be a rolled sheet with a superplastic fine-grained structure to maintain its superplasticity after subsequent annealing. This method requires commercially available superplastic fine-grained titanium alloy sheets as raw materials, but the preparation of these sheets still suffers from the problems of traditional rolled sheet preparation, such as long process flow, the need for coordination of multiple equipment, complex and cumbersome process, and low material yield. This significantly limits the engineering application of this method. Furthermore, the prolonged annealing process of this method will also lead to coarsening of the entire board's microstructure, thereby reducing the overall mechanical properties of the board.

[0004] Therefore, there is an urgent need to invent a low-cost, short-process preparation method for large and complex components, namely, to use a short-process preparation method to prepare large-size superplastic alloy plates with uniform and fine microstructure from cast alloy raw materials, and then to use superplastic forming to prepare large and complex components. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost, short-process method for manufacturing large and complex components. This method can obtain large-size superplastic plates with uniform fine / ultra-fine grain structures from small-sized cast alloy raw materials, and ultimately achieve the fabrication of high-performance large components. Moreover, the process is simple, efficient, and low-cost, and the original plate size of large and complex structural parts is not limited by the processing method.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A low-cost, short-process fabrication method for large, complex components, comprising the following steps:

[0008] (1) Multiple cast alloy plates are subjected to friction stir welding to obtain large-size alloy welded plates. Using cast alloy plates as raw materials can significantly reduce the cost of raw materials, and welding can be used to connect small-size plates into large-size plates, thereby breaking through the limitation of raw material plate size.

[0009] (2) After welding, the large-size alloy plate is subjected to multi-pass friction stir processing to eliminate defects in the overall cast plate, improve compositional segregation and microstructure inhomogeneity, refine grains, and prepare a large-size superplastic plate with a uniform and fine microstructure. Because the cast microstructure is coarse and usually accompanied by compositional segregation, microstructure inhomogeneity, and casting defects, the base material of the cast microstructure plate usually does not have superplasticity. This step can eliminate casting defects through the large plastic deformation method of multi-pass friction stir processing, so that the microstructure of the processed area is greatly refined and the composition and microstructure are homogenized. In addition, the microstructure of the weld after welding is completely different from that of the original cast base material. However, since the basic principle of friction stir welding is the same as that of processing, the microstructure of the entire large-size welded plate (including the weld and the base material) can be processed into a uniform and consistent special fine microstructure through multi-pass friction stir processing, thereby giving the entire large-size plate excellent superplastic forming ability.

[0010] (3) The large-size superplastic alloy sheet is integrally superplastically formed to produce large-size complex components. Since steps (1) and (2) produce large-size sheets with excellent superplastic forming capabilities, large-size complex components can be prepared in step (3) by using a suitable superplastic forming process.

[0011] The parameters for friction stir welding in steps (1)-(2) above are the same as those for multi-pass friction stir processing. Specifically, the shoulder size of the stirring tool is 8-15 mm, the stirring pin size is 3-8 mm, the rotation speed of the stirring tool is 200-1000 rpm, and the welding speed is 25-300 mm / min. Since superplasticity requires a low grain size, the heat input corresponding to the parameters of friction stir welding and friction stir processing used in this invention is relatively low. Therefore, the size of the stirring tool is small and matched with a lower rotation speed and an appropriate welding speed.

[0012] The welding process described in steps (1)-(2) can be carried out in atmospheric, vacuum, water, or even dry ice, liquid nitrogen, liquid helium, and organic solvent media. By combining low heat input welding parameters with different cooling media, a special fine-grained structure with excellent superplastic forming ability can be achieved.

[0013] In step (2) above, the width of the overlap area between two passes before and after multi-pass overlapping processing is 1 / 5 to 4 / 5 of the width of the friction stir processing area in each pass. If the overlap area is too small, there will be unprocessed areas between the two passes. The unprocessed areas are the original cast structure, which results in a lack of superplasticity in some areas of the entire plate, making it impossible to obtain subsequent superplastic forming applications. If the overlap area is too large, the number of processing passes required to process the entire plate will be very large, resulting in low production efficiency. In addition, if the overlap area is too large, there will be too many processing passes in the entire plate processing area, which will easily lead to the entire processing area being affected by multiple heat accumulations, resulting in a significant increase in grain size, which will lead to excessive grain coarsening and failure to obtain superplasticity. Therefore, the width of the overlap area must be within the above range to ensure the microstructure required by this application and achieve superplasticity of large-size plates.

[0014] The large-size plates obtained in steps (1)-(2) above have an equiaxed microstructure with a grain size of 0.01–5 micrometers and high-angle grain boundaries exceeding 80%. The microstructure is fine and equiaxed with high-angle grain boundaries (mismatch angle not less than 15°). ° A high proportion of grain boundaries is beneficial for obtaining excellent superplastic forming capabilities. Therefore, this invention ensures that the obtained grain size, grain morphology, and high angle ratio are within the above-mentioned range through a specific combination of welding and processing parameters, thus guaranteeing the realization of subsequent superplastic forming.

[0015] In step (3) above, the superplastic deformation temperature range is 175–1000℃, and the strain rate is 1×10⁻⁶. -4 ~1×10 - 1 s -1The gas pressure for superplastic forming is 0.1–5 MPa. Materials must exhibit high superplasticity within a specific temperature range and a certain strain rate range (or gas pressure). Excessively high strain rates hinder grain boundary slip, leading to localized necking and making it difficult to achieve high superplastic elongation. Conversely, excessively low strain rates result in severe grain coarsening and a significant increase in grain boundary slip resistance, thus preventing the attainment of high superplastic elongation.

[0016] The alloys to which this invention applies include titanium alloys, aluminum alloys, magnesium alloys, steel, high-entropy alloys, and all other alloys with superplastic deformation capabilities.

[0017] The design mechanism of this invention is as follows:

[0018] This invention solves the problem of large-size plate fabrication by using friction stir welding (FSW) with relatively low heat input to connect small-size cast plates into large-size plates. By combining this with multi-pass friction stir processing (i.e., single-plate FSW), the intense friction between the stirring tool and the cast plate generates heat and causes significant deformation, eliminating casting defects, refining grains, and homogenizing composition and microstructure. Based on the principle that FSW and FSW processes share the same fundamental principle, resulting in identical microstructure between the weld nugget and the processed area, and through appropriate combinations of FSW and processing parameters, a unique microstructure with suitable grain size, morphology, and high angle ratio is achieved across the entire large-size welded plate. This yields large-size fine-grained or ultra-fine-grained plates with excellent superplastic forming capabilities. Furthermore, superplastic forming is performed at appropriate temperatures and under appropriate gas pressures (or strain rates), ultimately producing large, complex components from these large-size plates.

[0019] Compared to other traditional processes, the method of this invention can produce fine equiaxed microstructures with a high proportion of high-angle grain boundaries, which is more conducive to superplastic forming. Furthermore, the use of small-sized cast alloy plates as raw materials significantly reduces the cost of superplastic sheets; and the welding method to connect small-sized plates into large-sized plates overcomes the size limitations of raw materials; and the process can be carried out on the same equipment, greatly reducing the difficulty of preparing large-sized titanium alloy superplastic sheets. In addition, this process has a short flow, high efficiency, high material utilization, and uniform microstructure, which can overcome the size limitations of sheet materials and ultimately produce large-sized complex structural components, which is of great significance for the low-cost preparation of high-performance large and complex components for industrial use.

[0020] The advantages of this invention are:

[0021] 1. Compared with traditional high-pressure torsion, equal-channel angular extrusion, and dynamic plastic deformation, which are difficult to prepare large-size superplastic sheets, friction stir welding and multi-pass friction stir processing can overcome the size limitations of the sheet and prepare large-size fine-grained / ultra-fine-grained alloy sheets with superplastic deformation capabilities.

[0022] 2. Traditional methods for preparing superplastic fine-grained sheets: as-cast state - homogenization annealing - billet preparation - multiple (hot rolling - heat treatment) - heat treatment - multiple cold rolling - heat treatment. This process is lengthy, complex, has a long production cycle, high cost, requires multiple pieces of equipment, and has a low yield. In contrast, this invention uses friction stir welding and multi-pass friction stir processing to prepare superplastic sheets. This process can be completed on the same equipment, with a short process flow, simple process, high material utilization, high production efficiency, and low cost, making it suitable for industrial production and applications.

[0023] 3. Compared with the traditional rolling method for preparing plates and then using superplastic forming to prepare complex components, which is limited by the size of the plate and cannot produce large-sized (e.g., several meters in diameter) complex components, the method of this invention can overcome the size limitation. It can combine friction stir welding to increase the size of the plate and friction stir processing to prepare fine / ultra-fine grain structure in a short process. The method of this invention can have both welding and processing functions, overcome the limitation of plate size, and finally use superplastic forming to prepare large complex components.

[0024] 4. Compared with cast alloys, the high-proportion, high-angle grain boundary large-size fine / ultra-fine grain alloy components prepared by friction stir welding and multi-pass friction stir processing have excellent superplastic forming capabilities and have broad application prospects in large and complex components such as satellite skin, aircraft air intake lips, aircraft landing gear doors, aircraft wing ribs and fuselage components, and integral turbine disks. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the low-cost, short-process fabrication of large, complex components according to the present invention.

[0026] Figure 2 Images showing the microstructure of large-sized titanium alloy formed components; including: (a) metallographic microstructure of the cross-section of the multi-pass machining zone of the titanium alloy; (b) grain size diagram of the machining zone; and (c) grain size diagram of the transition zone.

[0027] Figure 3 Images showing the microstructure of large-size high-entropy alloy formed components; including: (a) metallographic microstructure of the cross-section of the multi-pass machining zone of the high-entropy alloy; (b) grain size diagram of the machining zone; and (c) grain size diagram of the transition zone.

[0028] Figure 4 A schematic diagram of the process for preparing fine-grained plates using traditional methods.

[0029] Figure 5 Superplastic tensile curves of titanium alloys and high-entropy alloys subjected to friction stir processing; wherein: (a) 600℃ and 3×10 -4 s -1 (a) Superplastic tensile curves of titanium alloy at strain rates; (b) 1000℃ and 3×10 -2 s -1 Superplastic tensile curves of high-entropy alloys under strain rates. Detailed Implementation

[0030] To further understand the present invention, examples are described in conjunction with the present invention. However, the examples are only for further elaboration of the present invention and are not intended to limit the scope of the claims of the present invention.

[0031] Example 1

[0032] This embodiment presents a low-cost, short-process fabrication method for large, complex components. The process is as follows: Figure 1 The specific process is as follows:

[0033] Two 2mm thick cast TC4 titanium alloy plates were fixed on the welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 11mm and a needle root diameter of 5mm was used for friction stir welding of the cast TC4 alloy. The stirring tool rotated at 300 rpm, and the welding speed was 50 mm / min. The resulting large alloy plate was then subjected to multiple passes of friction stir machining under the same parameters, with a 40% overlap between the two multi-pass machining zones.

[0034] Technical effects: such as Figure 2 As shown, this embodiment ultimately obtains a titanium alloy sheet with a high-angle grain boundary ratio of 90% and a grain size of 1.1 micrometers, which has a uniform microstructure. After superplastic forming at 900°C, a complex structural component of titanium alloy is obtained.

[0035] Example 2

[0036] Two 3mm thick as-cast high-entropy alloy plates were fixed on the welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 12mm and a needle root diameter of 5mm was used for friction stir welding of the as-cast high-entropy alloy plates. The stirring tool rotated at 400 rpm, and the welding speed was 50 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining under the same parameters, with an overlap of 35% between the two multi-pass machining zones.

[0037] Technical effects: such as Figure 3 As shown, this embodiment ultimately yields a high-entropy alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 2μm, exhibiting a uniform microstructure.

[0038] Example 3

[0039] Two 3mm thick cast aluminum alloy plates were fixed on the welding machine platform. H13 steel with a shoulder diameter of 15mm and a needle root diameter of 8mm were used for friction stir welding of the cast aluminum alloy. The stirring tool rotated at 800 rpm, and the welding speed was 100mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 30% overlap between the two multi-pass processing zones.

[0040] Technical results: A uniform aluminum alloy sheet with a high-angle grain boundary ratio of 90% and a grain size of 4μm was finally obtained. After superplastic forming at 400℃, a complex structural part with a uniform microstructure was obtained.

[0041] Example 4

[0042] Two 3mm thick cast magnesium alloy plates were fixed on the welding machine platform. H13 steel needles with a shoulder diameter of 8mm and a root diameter of 3mm were used for friction stir welding of the cast magnesium alloy. The stirring tool rotated at 600 rpm, and the welding speed was 80 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 50% overlap between the two multi-pass processing zones.

[0043] Technical Results: A magnesium alloy sheet with a high-angle grain boundary ratio of 90% and a grain size of 5μm was obtained, exhibiting a uniform microstructure. After superplastic forming at 425℃, a complex structural component with a uniform microstructure was obtained. For different alloys, friction stir welding, combined with multi-pass friction stir processing, requires appropriate stirring pin size and reasonable friction stir processing parameters to obtain a complex structural component with a uniform microstructure.

[0044] Comparative Example 1

[0045] Two 2mm thick cast TC4 titanium alloy plates were fixed on the welding machine platform. A tungsten-rhenium alloy tool with an 11mm shoulder diameter was used for friction stir welding of the cast TC4 alloy. The stirring tool rotated at 400 rpm, and the welding speed was 70 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining at a rotation speed of 300 rpm and a welding speed of 50 mm / min. The overlap area between the two multi-pass machining zones was 40%.

[0046] Technical effects and analysis: Different parameters lead to uneven microstructure in the weld and multi-pass processing areas. During superplastic forming at 900℃, the sheet metal cannot deform uniformly. Therefore, maintaining consistent welding and processing parameters is crucial for achieving a uniform microstructure in large-size bulk alloys.

[0047] Comparative Example 2

[0048] Two 3mm thick cast aluminum alloy plates were fixed on the welding machine platform. H13 steel with a shoulder diameter of 20mm and a root diameter of 10mm was used for friction stir welding of the cast aluminum alloy. The stirring tool rotated at 800 rpm, and the welding speed was 100mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining under the same parameters, with a 30% overlap between the two multi-pass machining zones.

[0049] Technical Results and Analysis: The final product was an aluminum alloy sheet with a grain size of 10 μm. Due to the large grain size, superplasticity could not be achieved. Therefore, maintaining reasonable shoulder and pin dimensions is a crucial factor for complex structural components in large-size bulk alloys.

[0050] Comparative Example 3

[0051] Two 3mm thick cast aluminum alloy plates were fixed on the welding machine platform. H13 steel with a shoulder diameter of 6mm and a root diameter of 2mm was used for friction stir welding of the cast aluminum alloy. The stirring tool rotated at 800 rpm, and the welding speed was 100mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining under the same parameters, with a 30% overlap between the two multi-pass machining zones.

[0052] Technical effects and analysis: Due to insufficient heat input caused by the small shoulder, a defect-free machining area cannot be obtained. Therefore, maintaining reasonable shoulder and pin dimensions is an important factor for complex structural components made of large-size bulk alloys.

[0053] Comparative Example 4

[0054] Traditional methods for preparing superplastic fine-grained sheets are complex, such as... Figure 4 As shown, after homogenization annealing of the alloy ingot, it is forged into a billet. After billeting, the sample is subjected to multiple rolling and high-temperature annealing cycles, followed by rough cold rolling, intermediate annealing, finish rolling, and finally annealing to prepare a superplastic fine-grained titanium alloy plate.

[0055] Technical Effects and Analysis: The complex process of traditional methods presents challenges such as long preparation time, high difficulty, high cost, and low production efficiency. Furthermore, the process involves coordinating multiple pieces of equipment, resulting in low material yield. In contrast, this invention employs a simpler process with shorter flow, higher production efficiency, lower cost, and higher material yield for preparing superplastic sheets using friction stir welding and multi-pass friction stir processing. This makes it suitable for industrial production and applications.

[0056] Example 5

[0057] Two 2mm thick cast TC4 titanium alloy plates were fixed on the welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 11mm and a needle root diameter of 5mm was used for friction stir welding of the cast TC4 alloy. The stirring tool rotated at 200 rpm, and the welding speed was 25mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining under the same parameters, with a 40% overlap between the two multi-pass machining zones.

[0058] Technical results: A titanium alloy sheet with a high-angle grain boundary ratio of 91% and a grain size of 420 nanometers was finally obtained. After superplastic forming at 650℃, a complex structural part with a uniform microstructure was obtained.

[0059] Comparative Example 5

[0060] Two 2mm thick cast TC4 titanium alloy plates were fixed on the welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 11mm and a needle root diameter of 5mm was used for friction stir welding of the cast TC4 alloy. The stirring tool rotated at 150 rpm, and the welding speed was 10mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining under the same parameters, with a 40% overlap between the two multi-pass machining zones.

[0061] Technical effects and analysis: Due to the improper matching of rotational speed and welding speed, it is impossible to obtain a defect-free large-size machining area. Therefore, maintaining a reasonable match between rotational speed and welding speed is an important factor in obtaining excellent properties of large-size bulk alloys.

[0062] Example 6

[0063] Two 2mm thick cast aluminum alloy plates were fixed on the welding machine platform. Using an H13 steel tool with a 12mm shoulder diameter and a 4mm needle root diameter, friction stir welding was performed on the cast aluminum alloy. The stirring tool rotated at 1000 rpm, and the welding speed was 300 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 40% overlap between the two multi-pass processing zones.

[0064] Technical results: The final product is an aluminum alloy sheet with a high-angle grain boundary ratio of 95% and a grain size of 3 micrometers. After superplastic forming at 400℃, a complex structural part with a uniform microstructure is obtained.

[0065] Comparative Example 6

[0066] Two 2mm thick cast aluminum alloy plates were fixed on the welding machine platform. Using an H13 steel tool with a 12mm shoulder diameter and a 4mm needle root diameter, friction stir welding was performed on the cast aluminum alloy. The stirring tool rotated at 1500 rpm, and the welding speed was 500 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 40% overlap between the two multi-pass processing zones.

[0067] Technical effects and analysis: Due to the improper matching of rotational speed and welding speed, it is impossible to obtain a large-size machining area without defects. Therefore, maintaining a reasonable match between rotational speed and welding speed is an important factor in obtaining large-size bulk alloys without defects.

[0068] Example 7

[0069] Two 2mm thick cast TC4 titanium alloy plates were fixed on the welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 11mm and a needle root diameter of 5mm was used for friction stir welding of the cast TC4 alloy. The stirring tool rotated at 400 rpm, and the welding speed was 40mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining under the same parameters, with a 20% overlap between the two multi-pass machining zones.

[0070] Technical results: A titanium alloy sheet with a high-angle grain boundary ratio of 90% and a grain size of 2 micrometers was finally obtained. After superplastic forming at 900℃, a complex structural part with a uniform microstructure was obtained.

[0071] Example 8

[0072] Two 2mm thick cast TC4 titanium alloy plates were fixed on the welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 11mm and a needle root diameter of 5mm was used for friction stir welding of the cast TC4 alloy. The stirring tool rotated at 400 rpm, and the welding speed was 40mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining under the same parameters, with an 80% overlap between the two multi-pass machining zones.

[0073] Technical results: A uniform aluminum alloy sheet with a high-angle grain boundary ratio of 92% and a grain size of 2.8 micrometers was finally obtained. After superplastic forming at 900℃, a complex structural part with uniform microstructure was obtained.

[0074] Comparative Example 7

[0075] Two 2mm thick cast TC4 titanium alloy plates were fixed on the welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 11mm and a needle root diameter of 5mm was used for friction stir welding of the cast TC4 alloy. The stirring tool rotated at 400 rpm, and the welding speed was 40mm / min. The welded alloy plates were then subjected to multiple passes of friction stir machining under the same parameters, with an overlap of 10% between the two multi-pass machining zones.

[0076] Technical effects and analysis: Due to the limited overlap, an effective machining depth cannot be achieved. Therefore, maintaining a reasonable overlap width is a crucial factor in obtaining large-size bulk alloys.

[0077] Comparative Example 8

[0078] Two 2mm thick cast TC4 titanium alloy plates were fixed on the welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 11mm and a needle root diameter of 5mm was used for friction stir welding of the cast TC4 alloy. The stirring tool rotated at 400 rpm, and the welding speed was 40mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 90% overlap between the two multi-pass machining zones.

[0079] Technical effects and analysis: Excessive overlap significantly reduces production efficiency, hindering industrial production and application. Therefore, maintaining a reasonable overlap width is crucial for obtaining large-size bulk alloys.

[0080] Example 9

[0081] Two 2mm thick as-cast TC4 titanium alloy plates were fixed on a welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 11mm and a needle root diameter of 5mm was used for friction stir welding of the as-cast TC4 alloy. The stirring tool rotated at 300 rpm, and the welding speed was 50 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 40% overlap between the two multi-pass processing zones. This resulted in a titanium alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 1.1 micrometers, exhibiting a uniform microstructure. The plate was then processed at 600℃ and 3×10⁻⁶ mm. -4 s -1 Superplastic forming at strain rate

[0082] Technical effects: such as Figure 5 As shown in a, at 600℃ and 3×10 -4 s -1 A superplastic elongation of 780% was obtained after superplastic forming at the strain rate.

[0083] Example 10

[0084] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3 High-entropy alloy was fixed on a welding machine platform. A truncated cone tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multi-pass friction stir welding under the same parameters, with a 35% overlap between the two multi-pass processing zones. This yielded an aluminum alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further processed at 1000℃ and 3×10⁻⁶ mm. -2 s -1 Superplastic forming of large-sized bulk high-entropy alloys under strain rate.

[0085] Technical effects: such as Figure 5As shown in b, at 1000℃ and 3×10 -2 s -1 A superplastic elongation of 1000% was obtained after superplastic forming at the strain rate.

[0086] Example 11

[0087] Two 3mm thick cast aluminum alloy plates were fixed on a welding machine platform. Friction stir welding was performed using an H13 steel tool with a shoulder diameter of 12mm and a needle root diameter of 4mm. The stirring tool rotated at 400 rpm, and the welding speed was 200 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 30% overlap between the two multi-pass processing zones. This yielded a uniform aluminum alloy plate with a high-angle grain boundary ratio of 92% and a grain size of 3 micrometers. The plate was then further processed at 175℃ and 1×10⁻⁶ mm. -4 s -1 Superplastic forming of large-sized bulk aluminum alloys under strain rate.

[0088] Technical effect: at 175℃ and 1×10 -4 s -1 A superplastic elongation of 420% was obtained after superplastic forming at the strain rate.

[0089] Comparative Example 9

[0090] Two 3mm thick cast aluminum alloy plates were fixed on a welding machine platform. Using an H13 steel tool with a shoulder diameter of 12mm and a needle root diameter of 4mm, friction stir welding was performed on the cast aluminum alloy. The stirring tool rotated at 400 rpm, and the welding speed was 200 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 30% overlap between the two multi-pass processing zones. This yielded a uniform aluminum alloy plate with a high-angle grain boundary ratio of 92% and a grain size of 3 micrometers. The plate was then further processed at 150℃ and 1×10⁻⁶ mm. -4 s -1 Superplastic forming of large-sized bulk aluminum alloys under strain rate.

[0091] Technical effects and analysis: at 150℃ and 1×10 -4 s -1 Superplasticity cannot be achieved at excessively low strain rates because grain boundary slip cannot occur effectively at such low temperatures. Therefore, appropriate superplastic deformation temperature and strain rate are crucial factors for large-size bulk alloys to possess superplastic properties.

[0092] Comparative Example 10

[0093] Two 3mm thick cast aluminum alloy plates were fixed on the welding machine platform. Friction stir welding was performed using an H13 steel tool with a shoulder diameter of 12mm and a needle root diameter of 4mm. The stirring tool rotated at 400 rpm, and the welding speed was 200 mm / min. The welded alloy plates were then subjected to multiple passes of friction stir welding under the same parameters, with a 30% overlap between the two multi-pass processing zones. This yielded a uniform aluminum alloy plate with a high-angle grain boundary ratio of 92% and a grain size of 3 micrometers. The plate was then further processed at 175℃ and 3×10⁻⁶ mm. -5 s -1 Superplastic forming of large-sized bulk aluminum alloys under strain rate.

[0094] Technical effects and analysis: at 175℃ and 3×10 -5 s -1 Superplasticity cannot be achieved at excessively low strain rates because excessively slow strain rates lead to grain growth. Therefore, appropriate superplastic deformation temperature and strain rate are crucial factors for large-size bulk alloys to possess superplastic properties.

[0095] Example 12

[0096] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3 High-entropy alloy was fixed on a welding machine platform. A truncated conical tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multiple passes of friction stir welding under the same parameters, with a 35% overlap between the two multi-pass processing zones. This yielded an aluminum alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further processed at 1000℃ and 1×10⁻⁶ mm. -1 s -1 Superplastic forming of large-sized bulk high-entropy alloys under strain rate.

[0097] Technical effect: at 1000℃ and 1×10 -1 s -1 A superplastic elongation of 300% was obtained after superplastic forming at a strain rate.

[0098] Comparative Example 11

[0099] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3High-entropy alloy was fixed on a welding machine platform. A truncated conical tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multi-pass friction stir machining under the same parameters, with a 35% overlap between the two multi-pass machining zones. This yielded an aluminum alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further processed at 1100℃ and 1×10⁻⁶ mm. -1 s -1 Superplastic forming of large-sized bulk high-entropy alloys under strain rate.

[0100] Technical effects and analysis: at 1100℃ and 1×10 -1 s -1 At high strain rates, grain growth occurs due to the higher deformation temperature. Therefore, appropriate superplastic deformation temperature and strain rate are crucial factors for large-size bulk alloys to possess superplastic properties.

[0101] Comparative Example 12

[0102] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3 High-entropy alloy was fixed on a welding machine platform. A truncated conical tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multi-pass friction stir machining under the same parameters, with a 35% overlap between the two multi-pass machining zones. This yielded an aluminum alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further processed at 1100℃ and 3×10⁻⁶ mm. -1 s -1 Superplastic forming of large-sized bulk high-entropy alloys under strain rate.

[0103] Technical effects and analysis: at 1100℃ and 3×10 -1 s -1 At high strain rates, the rapid strain rate leads to severe stress concentration, making it impossible to achieve superplastic properties. Therefore, appropriate superplastic deformation temperature and strain rate are crucial factors for large-size bulk alloys to possess superplastic properties.

[0104] Example 13

[0105] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3High-entropy alloy was fixed on a welding machine platform. A truncated conical tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multiple passes of friction stir welding under the same parameters, with a 35% overlap between the two multi-pass processing zones. This resulted in a high-entropy alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further tested at 1000℃ and 3×10⁻⁶ mm. -2 s -1 1000% superplasticity was achieved at the strain rate. Superplastic forming was then performed under a gas pressure of 0.5 MPa.

[0106] Technical effect: After superplastic forming under a gas pressure of 0.5 MPa, a complex structural part with uniform microstructure is obtained.

[0107] Example 14

[0108] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3 High-entropy alloy was fixed on a welding machine platform. A truncated conical tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multiple passes of friction stir welding under the same parameters, with a 35% overlap between the two multi-pass processing zones. This resulted in a high-entropy alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further tested at 1000℃ and 3×10⁻⁶ mm. -2 s -1 A superplasticity of over 800% was achieved at the strain rate. Superplastic forming was performed under a gas pressure of 0.1 MPa.

[0109] Technical effect: After superplastic forming under a gas pressure of 0.1 MPa, a complex structural part with uniform structure is obtained.

[0110] Example 15

[0111] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3 High-entropy alloy was fixed on a welding machine platform. A truncated conical tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multiple passes of friction stir welding under the same parameters, with a 35% overlap between the two multi-pass processing zones. This resulted in a high-entropy alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further tested at 1000℃ and 3×10⁻⁶ mm. -2s -1 A superplasticity of over 800% was achieved at the specified strain rate. Superplastic forming was then performed under a gas pressure of 5 MPa.

[0112] Technical effect: After superplastic forming under a gas pressure of 5MPa, a complex structural part with uniform structure is obtained.

[0113] Comparative Example 13

[0114] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3 High-entropy alloy was fixed on a welding machine platform. A truncated conical tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multiple passes of friction stir welding under the same parameters, with a 35% overlap between the two multi-pass processing zones. This resulted in a high-entropy alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further tested at 1000℃ and 3×10⁻⁶ mm. -2 s -1 A superplasticity of over 800% was achieved at the strain rate. Superplastic forming was performed under a gas pressure of 0.05 MPa.

[0115] Technical effect: During superplastic forming at a gas pressure of 0.05 MPa, the relatively low gas pressure leads to severe grain growth, resulting in poor superplastic forming performance. Therefore, appropriate gas pressure is a crucial factor in the fabrication of complex components from large-size bulk alloys.

[0116] Comparative Example 14

[0117] Two 3 mm thick as-cast CoCrFeNiAl 0.2 Cu 0.3 High-entropy alloy was fixed on a welding machine platform. A truncated conical tungsten-rhenium alloy tool with a shoulder diameter of 12 mm and a needle root diameter of 5 mm was used for friction stir welding of the cast high-entropy alloy. The stirring tool rotated at 600 rpm, and the welding speed was 30 mm / min. The welded alloy plate was then subjected to multiple passes of friction stir welding under the same parameters, with a 35% overlap between the two multi-pass processing zones. This resulted in a high-entropy alloy plate with a high-angle grain boundary ratio of 90% and a grain size of 800 nm, exhibiting a uniform microstructure. The plate was then further tested at 1000℃ and 3×10⁻⁶ mm. -2 s -1 A superplasticity of over 800% was achieved at the specified strain rate. Superplastic forming was then performed under a gas pressure of 6 MPa.

[0118] Technical implications: During superplastic forming at a gas pressure of 6 MPa, the high gas pressure results in poor rheological properties of the material during deformation. Therefore, appropriate gas pressure is a crucial factor in fabricating complex components from large-sized bulk alloys.

[0119] As demonstrated by the above examples and comparative examples, the combination of friction stir welding and multi-pass friction stir processing is a simple and efficient method for obtaining large-size fine-grained / ultra-fine-grained structural components. The large-size superplastic sheets prepared by this method exhibit excellent superplastic deformation capacity and deformation uniformity, and can be further processed into large-size components through subsequent superplastic forming. It should be noted that although numerous invention patents and papers have been published on the individual techniques of friction stir welding, friction stir processing, and superplastic forming, this invention requires appropriate friction stir processing parameters combined with reasonable superplastic deformation parameters to obtain superplastic sheets and then to perform superplastic forming to obtain complex components. It is not simply a matter of combining friction stir processing and superplastic forming techniques to obtain highly superplastic sheets.

[0120] It should be noted that, based on the embodiments of the present invention, any improvements and modifications proposed by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A low-cost, short-process fabrication method for large, complex components, characterized in that: The method includes the following steps: (1) Multiple cast alloy plates are joined together by friction stir welding to form a large-sized alloy welded plate; (2) The large-size alloy welded plate obtained in step (1) is subjected to multiple passes of stir friction processing to eliminate defects in the overall cast plate, improve compositional segregation and microstructure inhomogeneity, and prepare a large-size superplastic plate with uniform fine microstructure on the whole plate. (3) The large-size superplastic sheet prepared in step (2) is subjected to integral superplastic forming to prepare large-size complex components; During the welding process in steps (1)-(2), the shoulder size of the stirring tool is 8~15 mm, the size of the stirring needle is 3~8 mm, and the rotation speed of the stirring tool is 200~1000 rpm; The welding speed is 25~300 mm / min.

2. The low-cost, short-process fabrication method for large, complex components according to claim 1, characterized in that: The large-size plate obtained in steps (1)-(2) has an equiaxed microstructure with a grain size of 0.01~5 micrometers and a high-angle grain boundary ratio of more than 80%; the high-angle grain boundaries are those with a mismatch angle of not less than 15 degrees. o Grain boundaries.

3. The low-cost, short-process fabrication method for large, complex components according to claim 1, characterized in that: The parameters for friction stir welding in step (1) are the same as those for multi-pass friction stir processing in step (2).

4. The low-cost, short-process fabrication method for large, complex components according to claim 1, characterized in that: Welding can be performed in atmospheric, vacuum, water, or even dry ice, liquid nitrogen, liquid helium, and organic solvent media.

5. The low-cost, short-process fabrication method for large, complex components according to claim 1, characterized in that: In step (2), when performing multi-pass friction stirring, the overlap width between two consecutive passes is 1 / 5 to 4 / 5 of the width of the friction stirring processing area in each pass.

6. The low-cost, short-process fabrication method for large, complex components according to claim 1, characterized in that: In step (3), the superplastic deformation temperature range is 175~1000℃, and the strain rate is 1×10⁻⁶. -4 ~1×10 -1 s -1 The gas pressure for superplastic forming is 0.1~5MPa.

7. The low-cost, short-process fabrication method for large, complex components according to claim 1, characterized in that: The alloy is a titanium alloy, aluminum alloy, magnesium alloy, or steel.

8. The low-cost, short-process fabrication method for large, complex components according to claim 1, characterized in that: The alloy is a high-entropy alloy.

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