Manufacturing method of high-strength aluminum-lithium alloy plate

Abstract

The invention belongs to the technical field of aluminum alloy processing, and particularly relates to a manufacturing method of a high-strength aluminum-lithium alloy plate, a non-homogenized casting blank is subjected to ultralow-temperature rolling, high-temperature rough rolling, ultralow-temperature finish rolling and aging treatment, the casting blank is made of aluminum-lithium alloy, the rolling temperature of ultralow-temperature rolling and ultralow-temperature finish rolling ranges from-196 DEG C to-100 DEG C, the temperature of high-temperature rough rolling ranges from-20 DEG C to-30 DEG C, and the temperature of high-temperature rough rolling ranges from-20 DEG C to-30 DEG C; the rolling temperature of the high-temperature rough rolling is 360-480 DEG C, and the total deformation is not less than 80%; the aluminum alloy plate is finer in crystal grain, higher in strength, better in ductility, higher in forming precision and better in surface quality.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy processing, and specifically relates to a method for manufacturing a high-strength aluminum-lithium alloy plate. Background Art

[0002] Aluminum-lithium alloys have become important materials in the aerospace field due to their unique lightweight characteristics and excellent mechanical properties. Aluminum-lithium alloys are widely used in aerospace structures, especially in situations where high strength, low density and excellent corrosion resistance are required. However, the processing performance of aluminum-lithium alloys is relatively complex, mainly manifested in the significant differences in the microstructure evolution and mechanical properties of the alloys under different processing conditions. In particular, during the processing of aluminum-lithium alloys, the presence of the eutectic phase has a significant impact on the mechanical properties, formability and final product quality of the alloy.

[0003] At present, there have been many studies and applications on the processing technology of aluminum-lithium alloys. Generally speaking, the existing aluminum-lithium alloy rolling technology mainly relies on homogenization treatment and cold rolling or hot rolling to control the shape and properties of alloy plates. However, since aluminum-lithium alloys contain a certain proportion of lithium elements, the alloy plasticity during hot working is poor, especially during rolling at conventional temperatures, cracks and surface quality problems are prone to occur.

[0004] First, since some eutectic phases in the ingot are very large, conventional homogenization treatment cannot completely eliminate them. As a result, aluminum-lithium alloys are prone to cracking during large deformation rolling. Secondly, although single high-temperature rolling can make the alloy have better formability, there are certain difficulties in controlling the grain size and uniformity, and the forming accuracy and surface quality of the plate at high temperature are sometimes difficult to guarantee. Although conventional cold rolling treatment can achieve better forming accuracy and surface quality, it requires the alloy to have sufficient formability, otherwise it is easy to crack. Therefore, the existing technology still has great limitations in improving the formability, grain refinement and performance optimization of aluminum-lithium alloys, and there is an urgent need for a new rolling process that can solve these problems at the same time. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for manufacturing a high-strength aluminum-lithium alloy plate with finer grains, higher strength, better elongation, higher forming accuracy and better surface quality.

[0006] An embodiment of the present invention provides a method for manufacturing a high-strength aluminum-lithium alloy plate, wherein an unhomogenized ingot is subjected to ultra-low temperature rolling, high-temperature rough rolling, ultra-low temperature finishing rolling and aging treatment, wherein the material of the ingot is an aluminum-lithium alloy, and the rolling temperatures of the ultra-low temperature rolling and ultra-low temperature finishing rolling are -196°C to -100°C, and the rolling temperature of the high-temperature rough rolling is 360°C to 480°C, and the total deformation is not less than 80%.

[0007] Preferably, the aluminum-lithium alloy is an aluminum-copper-lithium alloy, more preferably a 2195 aluminum-copper-lithium alloy.

[0008] Preferably, the temperature of the ultra-low temperature rolling or ultra-low temperature finish rolling is -180°C to -150°C.

[0009] Preferably, the total deformation of the ultra-low temperature rolling is 30-50%, the ultra-low temperature rolling has 3-6 rolling passes, and the reduction in each pass is 10-25%.

[0010] Preferably, the temperature of the high temperature rough rolling is 400-450° C., the total deformation of the high temperature rough rolling is 50-70%, the high temperature rough rolling has 2-5 rolling passes, and the reduction in each pass is 20-30%.

[0011] Preferably, the total deformation of the ultra-low temperature finishing rolling is 20-30%, the ultra-low temperature finishing rolling is performed 2-3 times, and the reduction in each time is 10-15%.

[0012] Preferably, the aging treatment is T8 aging treatment.

[0013] Preferably, the T8 aging treatment is pre-deformation after solution treatment and then artificial aging.

[0014] Preferably, the solution treatment is carried out for 1 to 3 hours at a temperature 30 to 50° C. lower than the solidus temperature of the aluminum-lithium alloy.

[0015] Preferably, the pre-deformation temperature is room temperature, and the pre-deformation amount is 3-7%; the artificial aging temperature is 150-170°C, and the time is 20-36h.

[0016] The beneficial effect of the present invention is that the present invention first breaks the eutectic phase in the alloy by performing ultra-low temperature cold rolling on the aluminum-lithium alloy ingot that has not been homogenized, thereby avoiding the problem that the eutectic phase fails to be effectively melted during the traditional homogenization process. Through the coordination of ultra-low temperature cold rolling and high temperature rough rolling, the eutectic phase in the alloy is broken and converted into particle nucleation points, which greatly promotes dynamic recrystallization. This not only accelerates the refinement of the grains, but also effectively controls the uniformity of the grains, avoids the defects of excessively large or uneven grains in traditional processes, and improves the overall performance of the alloy. In the high temperature rough rolling stage, the aluminum-lithium alloy has a strong deformation ability at a relatively high temperature, which promotes the good formability of the material. At the same time, through precise ultra-low temperature finishing rolling, the forming accuracy is further adjusted and the grains are refined. This process scheme enables the finished product to have higher dimensional accuracy and uniform mechanical properties, and is suitable for high-requirement fields such as aerospace.

[0017] The aluminum-lithium alloy of the present invention cannot be homogenized or solution treated before the ultra-low temperature cold rolling. Otherwise, the eutectic phase is difficult to completely dissolve in the subsequent process. In addition, the eutectic phase cannot be broken into small particles, and cannot provide nucleation points for dynamic recrystallization during high-temperature rough rolling. During high-temperature rough rolling, the rolling temperature needs to be carried out at a relatively high temperature, otherwise the broken eutectic phase particles cannot be fully dissolved, and dynamic recrystallization cannot be achieved, which will significantly reduce the mechanical properties of the plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a scan of the ingot used in the present invention.

[0019] Figure 2 This is a grain morphology diagram of Example 1 of the present invention.

[0020] Figure 3 This is a grain morphology diagram of comparative example 1 of the present invention.

[0021] Figure 4 This is a grain morphology diagram of comparative example 2 of the present invention.

[0022] Figure 5 This is a grain morphology diagram of comparative example 3 of the present invention.

[0023] Figure 6 The engineering stress-strain curves of the embodiment of the present invention, comparative example 1, comparative example 2 and comparative example 3 are shown. DETAILED DESCRIPTION

[0024] The present invention provides a method for manufacturing a high-strength aluminum-lithium alloy plate, comprising: performing ultra-low temperature rolling on an aluminum-lithium alloy ingot that has not been homogenized to obtain a slab with a broken eutectic phase; performing high-temperature rough rolling to obtain a slab with a large deformation amount; then performing ultra-low temperature finishing rolling to obtain a slab with good surface quality, high forming accuracy, and fine grain structure; and finally heat treating the obtained slab to obtain a high-strength aluminum-lithium alloy plate. The present invention is suitable for heat-treatable aluminum-lithium alloys that can be strengthened, especially aluminum-copper-lithium alloys with T1 phase as the main strengthening phase.

[0025] The present invention will be further described in detail below with reference to specific embodiments.

[0026] Example 1 In the manufacturing method of a high-strength aluminum-lithium alloy plate described in this embodiment, the alloy grade used is 2195 alloy, and the alloy composition mass percentage is: Si: 0.03, Fe: 0.04, Cu: 4.1, Mn: 0.04, Mg: 0.28, Zr: 0.13, Ag: 0.26, Li: 0.9, and the rest is Al. The initial state of the alloy used is an unhomogenized ingot, and the initial structure is as follows Figure 1 shown.

[0027] The alloy was processed into a billet of 120×80×60 mm (length 120 mm, width 80 mm, height 60 mm).

[0028] The billet is immersed in liquid nitrogen for 30 minutes; then the billet is subjected to ultra-low temperature rolling; liquid nitrogen spraying is maintained during the rolling process; the billet temperature is measured after every two passes; after the billet temperature is higher than -150°C, it is immersed in liquid nitrogen for 10 minutes, and then the ultra-low temperature rolling process is repeated.

[0029] The ultra-low temperature rolling was carried out for 4 passes with a total deformation of 50%. The specific deformation of each pass is shown in Table 1.

[0030] Table 1 Ultra-low temperature rolling process

[0031] The slab after ultra-low temperature rolling was kept at 480°C for 1 hour; After the insulation, the slab was subjected to high temperature rough rolling; the billet temperature was measured after every two passes; the billet temperature was returned to the furnace for annealing after it was lower than 360°C, and then the high temperature rough rolling process was repeated. The high temperature rough rolling was performed for a total of 4 passes, with a total deformation of 66.6%; the specific deformation of each pass is shown in Table 2.

[0032] Table 2 High temperature rough rolling process

[0033] The plate after high temperature rough rolling was immersed in liquid nitrogen again for 30 minutes and then ultra-low temperature rolling was performed again. The process was the same as the above ultra-low temperature rolling. This ultra-low temperature rolling was performed for 2 passes with a total deformation of 25%; the specific deformation of each pass is shown in Table 3.

[0034] Table 3 Ultra-low temperature finishing rolling process

[0035] The final sheet thickness is 6 mm and the total deformation is 90%.

[0036] The plate was subjected to T8 treatment. The specific system is: solution treatment at 510℃ for 1h; 3% tensile pre-deformation at room temperature; artificial aging at 160℃ for 24h.

[0037] The grain morphology of the plate is shown in Figure 2 As shown in Figure 2, the grain structure is equiaxed fine-grained structure.

[0038] Tensile specimens were taken from the T8 treated sheet and subjected to uniaxial tensile test at room temperature. The yield strength was 627 MPa, the tensile strength was 653 MPa, and the elongation was 12.43%.

[0039] Comparative Example 1 The material used in Comparative Example 1 is the alloy after homogenization treatment of the ingot used in Example 1, and the homogenization treatment system is to increase the temperature from room temperature to 500°C at a rate of 0.85°C / min and keep it at that temperature for 24 hours. The homogenized alloy is cut into the same size as the ingot in Example 1.

[0040] The billet is subjected to high temperature rolling. The high temperature rolling temperature and process are the same as those in Example 1. The high temperature rolling process flow is a combination of all rolling process flows in Example 1. The specific process flow is shown in Table 4. The total deformation amount is 90%.

[0041] Table 4 High temperature rolling process of comparative example 1

[0042] The plate after high temperature rolling is subjected to T8 treatment, which is the same as that in Example 1.

[0043] The grain morphology of the plate is shown in Figure 3 As shown in Figure 1, the grain structure is a coarse and long rolled structure.

[0044] Tensile specimens were taken from the T8 treated sheet and subjected to uniaxial tensile test at room temperature. The yield strength was 564MPa, the tensile strength was 582MPa, and the elongation was 10.82%.

[0045] Comparative Example 2 Comparative Example 2 is different from Example 1 in that Comparative Example 2 is subjected to homogenization treatment, and the homogenization treatment system is: heating from room temperature to 500°C at a heating rate of 0.85°C / min, and keeping the temperature for 24 hours. The homogenized alloy is cut into the same size as the billet of Example 1. Then ultra-low temperature rolling, high temperature rough rolling, ultra-low temperature finishing rolling and aging treatment are performed, and the steps of ultra-low temperature rolling, high temperature rough rolling, ultra-low temperature finishing rolling and aging treatment are the same as those of Example 1.

[0046] The grain morphology of the plate is shown in Figure 4 As shown in Figure 2, the grain structure is an elongated rolling structure.

[0047] Tensile specimens were taken from the T8 treated sheet and subjected to uniaxial tensile test at room temperature. The yield strength was 578 MPa, the tensile strength was 600 MPa, and the elongation was 10.4%.

[0048] Comparative Example 3 Compared with Example 1, Comparative Example 3 is different in that the rolling temperature of high-temperature rough rolling in Comparative Example 3 is 300° C., and the rest is the same as Example 1.

[0049] The final grain morphology of the plate is shown in Figure 5 , the grain structure is equiaxed coarse-grained structure.

[0050] Tensile specimens were taken from the T8 treated sheet and subjected to uniaxial tensile test at room temperature. The yield strength was 584 MPa, the tensile strength was 606 MPa, and the elongation was 11.26%.

[0051] The engineering stress-strain curves of Example 1 and Comparative Examples 1-3 are shown in Figure 6 .

[0052] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0053] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A method for manufacturing a high-strength aluminum-lithium alloy plate, characterized in that: The non-homogenized ingot is subjected to ultra-low temperature rolling, high temperature rough rolling, ultra-low temperature finishing rolling and aging treatment. The material of the ingot is aluminum-lithium alloy. The rolling temperatures of the ultra-low temperature rolling and ultra-low temperature finishing rolling are -196°C to -100°C, the rolling temperature of the high temperature rough rolling is 360°C to 480°C, and the total deformation is not less than 80%.

2. The manufacturing method according to claim 1, characterized in that: The aluminum-lithium alloy is an aluminum-copper-lithium alloy.

3. The manufacturing method according to claim 1, characterized in that: The temperature of the ultra-low temperature rolling or ultra-low temperature finish rolling is -180°C to -150°C.

4. The manufacturing method according to claim 1, characterized in that: The total deformation of the ultra-low temperature rolling is 30-50%, the rolling passes of the ultra-low temperature rolling are 3-6 times, and the reduction amount of each pass is 10-25%.

5. The manufacturing method according to claim 1, characterized in that: The temperature of the high temperature rough rolling is 400-450° C., the total deformation of the high temperature rough rolling is 50-70%, the rolling passes of the high temperature rough rolling are 2-5 times, and the reduction amount of each pass is 20-30%.

6. The manufacturing method according to claim 1, characterized in that: The total deformation of the ultra-low temperature finishing rolling is 20-30%, the rolling passes of the ultra-low temperature finishing rolling are 2-3 times, and the reduction amount of each pass is 10-15%.

7. The manufacturing method according to claim 1, characterized in that: The aging treatment is T8 aging treatment.

8. The manufacturing method according to claim 7, characterized in that: The T8 aging treatment is to perform pre-deformation after solution treatment and then perform artificial aging.

9. The manufacturing method according to claim 8, characterized in that: The solution treatment is carried out for 1 to 3 hours at a temperature 30 to 50° C. lower than the solidus temperature of the aluminum-lithium alloy.

10. The manufacturing method according to claim 8, characterized in that: The pre-deformation temperature is room temperature, and the pre-deformation amount is 3-7%; the artificial aging temperature is 150-170°C, and the time is 20-36h.

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