Large-specification Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity and preparation process of large-specification Mg-Gd-based magnesium alloy thick plate

Abstract

The invention relates to a large-specification Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity and a preparation process of the large-specification Mg-Gd-based magnesium alloy thick plate. The preparation process comprises the following steps: S1, preserving the heat of an Mg-Gd-based magnesium alloy ingot subjected to solid solution at a certain temperature for 2 hours before forging to obtain a blank; s2, an upper hammer anvil and a lower hammer anvil are preheated to a certain temperature through heated iron blocks, multi-heating-number large-deformation forging is conducted on the blank, the blank is separated from the upper hammer anvil and the lower hammer anvil through heat preservation cotton during forging, the pressing speed is 10-15 mm / s, pressing is conducted by 10 mm each time, the intermediate annealing temperature is 450-500 DEG C, the heat preservation time is 30-60 min, and a forged plate is obtained; s3, the forged plate is put into hot water at the temperature of 70-80 DEG C to be quenched, and a quenched plate is obtained; and S4, high-temperature aging treatment is conducted, specifically, isothermal aging treatment is conducted on the quenched plate at the temperature of 225-250 DEG C, the heat preservation time is 10-20 h, water cooling is conducted, and the large-specification Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity is obtained. According to the method, the thick plate with matched strength and plasticity is obtained through high-temperature aging treatment, after aging treatment, high-density fine cylindrical surface precipitated phases are dispersed and distributed in a magnesium matrix, and the percentage of elongation of the thick plate after aging is improved.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal material processing, and in particular to a large-size Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity and a preparation process thereof. Background Art

[0002] Magnesium (Mg) alloys are generally considered to be the lightest metal structural materials. Against the backdrop of the continuous advancement of the "dual carbon" goals and the urgent need to reduce the weight of major equipment, magnesium alloys are regarded as key materials with great application prospects in aerospace, transportation and other fields. However, the absolute strength of traditional magnesium alloys is low, and their plasticity is poor due to the limited slip system in the close-packed hexagonal structure matrix. Therefore, the development of magnesium alloys with excellent mechanical properties such as strength and plasticity is one of the necessary prerequisites for their use as structural materials.

[0003] Extrusion, rolling and forging are very effective in improving the mechanical properties of alloys. Forging, in particular, has an overwhelming advantage over other technical means in manufacturing large or differently shaped parts. Magnesium-gadolinium (Mg-Gd) based alloys are typical age-hardening alloys, but usually after aging, the elongation of the alloy will drop significantly to less than 4%, which greatly limits the application of magnesium alloys.

[0004] To this end, the present application provides a large-sized Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity and a preparation process thereof. Summary of the invention

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention produces large-sized Mg-Gd-based alloy thick plates with matched strength and plasticity through a high-temperature, multi-fire, large-deformation forging process and a high-temperature short-time aging heat treatment process, thereby solving the technical problems of difficult preparation of thick plates, low elongation after aging, and anisotropy.

[0006] In order to achieve the above object, the present invention provides the following technical solutions.

[0007] A large-size Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity, comprising the following mass percentage compositions:

[0008] Gd7~15wt.%, Y0~5wt.%, Zn0~2wt.%, Zr0.3~0.5wt.%, Cu≤0.05%, Si≤0.05%, Ni≤0.005%, and the balance is Mg.

[0009] Ingot solution process: keep at 500℃~520℃ for 12 hours, water cooling, the water temperature is 70℃~80℃.

[0010] A preparation process of a large-sized Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity, comprising the following specific steps:

[0011] S1: Before forging, a large-sized Mg-Gd-based magnesium alloy ingot with good solid solution and matching strength and plasticity is kept at a certain temperature for 2 hours to obtain a billet;

[0012] S2: Use heated iron blocks to preheat the upper and lower hammer anvils to a certain temperature, use a 20MN upper pressure fast forging machine to perform multiple fires and large deformation forging on the billet, use insulation cotton to separate the billet from the upper and lower hammer anvils during forging, press down at a speed of 10mm / s to 15mm / s, press down 10mm each time, the intermediate annealing temperature is 450℃ to 500℃, and the holding time is 30min to 60min to obtain the forged plate;

[0013] S3: placing the forged plate into hot water at 70° C. to 80° C. for quenching to obtain a quenched plate;

[0014] S4: High temperature aging treatment: The quenched plate is subjected to isothermal aging treatment at 225°C to 250°C for 10h to 20h, and water-cooled to obtain a large-size Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity.

[0015] Optionally, in step S2, the preheating temperature is 480°C to 500°C.

[0016] Optionally, in step S2, the upper and lower anvils are preheated to 350°C to 400°C.

[0017] Optionally, in step S2, the multi-fire large deformation forging is as follows: in the first fire, the roughing reduction is 15% to 20%, and the heat preservation is performed for 1 hour after forging; in the second fire, the drawing forging is performed in the radial direction, and the two mutually perpendicular radial directions of the cylindrical forging blank are used as equivalent forging directions, the reduction in each direction is 20% to 30%, and shaping is performed, and the heat preservation is performed for 45 minutes to 60 minutes after forging; in the third fire, the highest direction is roughened, the reduction is 30% to 35%, the cross section is shaped into a square, and the heat preservation is performed for 45 minutes to 60 minutes after forging; in the fourth fire, one of the radial directions is selected for forging, and the downward pressure is spread along the short side, and the reduction is 20% to 25%, and then the blank is rotated 90 degrees parallel to the anvil, and the downward pressure is continued, the reduction is 10% to 15%, and the total reduction is 30% to 60%, and the heat preservation is performed for 30 minutes to 45 minutes after forging;

[0018] Optionally, if subsequent firing is required, the fourth firing step is repeated, and the total reduction is controlled at 45% to 60%.

[0019] Optionally, the yield strength of the large-size Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity is ≥320MPa, the tensile strength is ≥380MPa, and the elongation is ≥10%.

[0020] The beneficial effects of the present invention are:

[0021] On the one hand, the present invention effectively suppresses the dynamic precipitation of coarse Mg-Gd phases through high temperature forging, and the interpass annealing reduces the density of defects such as dislocations inside the alloy, improves the degree of recrystallization, and makes subsequent deformation easier. On the other hand, the precipitated second phase can be dissolved back into the matrix, so that more aging phases can be precipitated in the subsequent aging process, and a better aging strengthening effect is obtained.

[0022] Furthermore, the large deformation (the maximum deformation between firings, i.e. the reduction, can reach 60%) and the spreading process (spreading in two perpendicular directions) refine the grains of the plate, so that similar grain structures are obtained in all directions, thereby reducing the mechanical anisotropy of the thick plate.

[0023] Furthermore, after aging treatment, high-density fine columnar precipitation phases are dispersed in the magnesium matrix, which effectively hinders dislocation slip and mechanical twinning, thereby improving the elongation of Mg-Gd-based magnesium alloy thick plates after aging. Unlike the elongation of Mg-Gd-based alloys that drops sharply to 4% after conventional low-temperature aging, the elongation of the plate after high-temperature aging treatment is ≥10%.

[0024] Furthermore, after aging at 250° C. for 10 h to 20 h, the Mg—Gd-based magnesium alloy thick plate of the present invention has a yield strength of ≥320 MPa, a tensile strength of ≥380 MPa, and an elongation of ≥10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The metallographic structure diagram of a large-sized Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity prepared in Example 2 of the present invention;

[0026] Figure 2 This is a stress-strain curve of a large-sized Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity prepared in Example 2 of the present invention after aging. DETAILED DESCRIPTION

[0027] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0028] Example 1

[0029] An ingot with an alloy composition of Mg-12Gd-0.3Zr was obtained by semi-continuous casting. The alloy size was Φ200mm×400mm. The solid solution process was 520℃ for 12 hours and water-cooled at 80℃.

[0030] Before forging, the Φ200mm×400mm Mg-12Gd-0.3Zr ingot with solid solution was kept at 500℃ for 2h, and the upper and lower hammer anvils were preheated to 400℃ with heated iron blocks. The billet was subjected to multi-fire large deformation forging using a 20MN upper pressure fast forging machine. During forging, the billet was separated from the upper and lower hammer anvils by insulation cotton. The pressing speed was 10mm / s, and the pressing was 10mm each time. The intermediate annealing temperature was 500℃. In the first fire, the roughing reduction was 20%, and the heat was kept for 1h after forging. In the second fire, the drawing forging was carried out along the radial direction, and the two mutually perpendicular radial directions of the cylindrical forging billet were used as equivalent forging directions. The reduction in each direction was 20%, and the forging direction was 100mm. The blank is shaped and kept warm for 60 minutes after forging. The third fire is upsetting in the highest direction with a reduction of 30%, and the cross section is shaped into a square, and kept warm for 60 minutes after forging. The fourth fire is forging in one of the radial directions, and the billet is pressed down and spread along the short side with a reduction of 25%. Then the blank is rotated 90° parallel to the anvil, and continued to be pressed down with a reduction of 15%, and kept warm for 45 minutes after forging. The fifth and sixth fires repeat the steps of the fourth fire, and the total reduction of each fire is controlled at 45%. After forging, the plate is placed in hot water at 70°C to 80°C for quenching, and the forged plate is aged at 250°C for 10 hours to obtain a large-size Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity.

[0031] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the alloy prepared in Example 1 of the present invention was tested for room temperature mechanical properties. The tensile direction was parallel to the plate surface. The test results are listed in Table 1.

[0032] Example 2

[0033] An ingot with an alloy composition of Mg-14Gd-0.3Zr was obtained by semi-continuous casting. The alloy size was Φ200mm×400mm. The solid solution process was 520℃ for 12 hours and water-cooled at 80℃.

[0034] Before forging, the solution-solutionized Φ200mm×400mm Mg-14Gd-0.3Zr ingot was kept at 500℃ for 2h, and the upper and lower hammer anvils were preheated to 400℃ with heated iron blocks. A 20MN upper pressure fast forging machine was used to perform multi-fire large deformation forging on the billet. During forging, the billet was separated from the upper and lower hammer anvils with insulation cotton. The pressing speed was 10mm / s, and the pressing was 10mm each time. The intermediate annealing temperature was 500℃. In the first fire, the roughing reduction is 20%, and the billet is kept warm for 1 hour after forging; in the second fire, the drawing forging is carried out in the radial direction, and the two mutually perpendicular radial directions of the cylindrical forging billet are used as equivalent forging directions, the reduction in each direction is 20%, and shaping is carried out, and the billet is kept warm for 60 minutes after forging; in the third fire, the highest direction is upsetting, the reduction is 30%, and the cross section is shaped into an approximate square, and the billet is kept warm for 60 minutes after forging; in the fourth fire, one of the radial directions is selected for forging, and the billet is pressed down and spread along the short side with a reduction of 25%, and then the billet is rotated 90° parallel to the anvil, and the pressure is continued to be 15%, and the billet is kept warm for 45 minutes after forging; the steps of the fourth fire are repeated in the fifth and sixth fires, and the total reduction of each fire is controlled at 45%; after forging, the plate is placed in hot water at 70℃~80℃ for quenching; the forged plate is aged at 250℃ for 10 hours to obtain a large-size Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity.

[0035] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the room temperature mechanical properties test of the alloy thick plate prepared in Example 2 of the present invention was carried out. The tensile direction was parallel to the plate surface. The test results are listed in Table 1.

[0036] like Figure 1 As shown, the Mg-Gd-based magnesium alloy thick plate in this embodiment is composed of large unrecrystallized grains and small recrystallized grains, which is a typical bimodal structure. The bimodal structure is conducive to the alloy to obtain better mechanical properties; and Figure 2 It can be seen that the tensile strength of the alloy thick plate is 426.8MPa, and the yield strength is 365.7MPa, wherein the elongation after aging can still be as high as 12.6%. It can be seen that the aging elongation of this embodiment far exceeds the aging elongation of 4% of the Mg-Gd-based alloy in the prior art. Obviously, this embodiment 2 exhibits excellent strength-plastic matching.

[0037] Example 3

[0038] An ingot with an alloy composition of Mg-9Gd-4Y-1.2Zn-0.3Zr (VW94) was obtained by semi-continuous casting. The alloy size was Φ200mm×400mm. The solid solution process was 520℃ for 12 hours and water-cooled at 80℃.

[0039] Before forging, the VW94 ingot with a solid solution size of Φ200mm×400mm was kept at 500℃ for 2h, and the upper and lower hammer anvils were preheated to 400℃ with heated iron blocks. A 20MN upper pressure fast forging machine was used to perform multi-fire large deformation forging on the billet. During forging, the billet was separated from the upper and lower hammer anvils with insulation cotton. The pressing speed was 10mm / s, and the pressing was 10mm each time. The intermediate annealing temperature was 500℃. In the first fire, the roughing reduction is 20%, and the forging is kept warm for 1 hour; in the second fire, the drawing forging is carried out in the radial direction, and the two mutually perpendicular radial directions of the cylindrical forging billet are used as equivalent forging directions, the reduction in each direction is 20%, and shaping is carried out, and the forging is kept warm for 60 minutes; in the third fire, the highest direction is upsetting, the reduction is 30%, the cross section is shaped into an approximate square, and the forging is kept warm for 60 minutes; in the fourth fire, one of the radial directions is selected for forging, and the billet is pressed and spread along the short side with a reduction of 25%, and then the billet is rotated 90° parallel to the anvil, and the pressing is continued with a reduction of 15%, and the forging is kept warm for 45 minutes; the fifth and sixth fires repeat the steps of the fourth fire, and the total reduction of each fire is controlled at 45%; after forging, the plate is placed in hot water at 70℃~80℃ for quenching; the forged plate is aged at 250℃ for 10 hours to obtain a large-size Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity.

[0040] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the room temperature mechanical properties of the alloy thick plates prepared in Examples 1 to 3 of the present invention were tested. The tensile direction was parallel to the plate surface. The test results are listed in Table 1.

[0041] Table 1 Room temperature mechanical properties of alloy thick plates prepared in Examples 1 to 3

[0042] Example Tensile strength(MPa) Yield strength (MPa) Elongation(%) Example 1 388.3 320.8 13.2 Example 2 426.8 365.7 12.6 Example 3 411.6 370.2 13.3

[0043] From the results in Table 1, it can be seen that after aging at 250°C, the elongation of the alloy thick plates of Examples 1 to 3 did not decrease significantly, and the elongation of the alloy thick plates of Examples 1 to 3 were all higher than 10%, which indicates that the high-temperature short-time aging treatment in the above embodiments is superior to the traditional low-temperature aging.

[0044] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A large-sized Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity, characterized in that: It includes the following mass percentage composition: Gd7~15wt.%, Y0~5wt.%, Zn0~2wt.%, Zr0.3~0.5wt.%, Cu≤0.05%, Si≤0.05%, Ni≤0.005%, and the balance is Mg.

2. A process for preparing a large-sized Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity, used for preparing the large-sized Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity as claimed in claim 1, characterized in that: The preparation process comprises the following specific steps: S1: Before forging, a large-sized Mg-Gd-based magnesium alloy ingot with good solid solution and matching strength and plasticity is kept at a certain temperature for 2 hours to obtain a billet; S2: Use heated iron blocks to preheat the upper and lower hammer anvils to a certain temperature, use a 20MN upper pressure fast forging machine to perform multiple fires and large deformation forging on the billet, use insulation cotton to separate the billet from the upper and lower hammer anvils during forging, press down at a speed of 10mm / s to 15mm / s, press down 10mm each time, the intermediate annealing temperature is 450℃ to 500℃, and the holding time is 30min to 60min to obtain the forged plate; S3: placing the forged plate into hot water at 70° C. to 80° C. for quenching to obtain a quenched plate; S4: High temperature aging treatment: The quenched plate is subjected to isothermal aging treatment at 225°C to 250°C for 10h to 20h, and water-cooled to obtain a large-size Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity.

3. The process for preparing a large-sized Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity as claimed in claim 2, characterized in that: In the step S2, the preheating temperature is 480°C to 500°C.

4. The process for preparing a large-sized Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity as claimed in claim 2, characterized in that: In step S2, the upper and lower anvils are preheated to 350°C to 400°C.

5. The process for preparing a large-sized Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity as claimed in claim 2, characterized in that: In step S2, the multi-fire large deformation forging is as follows: in the first fire, the roughing reduction is 15% to 20%, and the forging is kept warm for 1 hour; in the second fire, the drawing forging is performed along the radial direction, and the two mutually perpendicular radial directions of the cylindrical forging blank are used as equivalent forging directions, the reduction in each direction is 20% to 30%, and shaping is performed, and the forging is kept warm for 45 minutes to 60 minutes; in the third fire, the highest direction is roughened, the reduction is 30% to 35%, the cross section is shaped into a square, and the forging is kept warm for 45 minutes to 60 minutes; in the fourth fire, one of the radial directions is selected for forging, and the short side is pressed down and spread, the reduction is 20% to 25%, and then the blank is rotated 90 degrees parallel to the anvil, and the pressing is continued, the reduction is 10% to 15%, the total reduction is 30% to 60%, and the forging is kept warm for 30 minutes to 45 minutes.

6. The process for preparing a large-sized Mg-Gd-based magnesium alloy thick plate with matching strength and plasticity as claimed in claim 5, characterized in that: If subsequent firing is required, the fourth firing step is repeated, and the total reduction is controlled at 45% to 60%.

7. The process for preparing a large-sized Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity as claimed in any one of claims 2 to 6, characterized in that: The yield strength of the large-sized Mg-Gd-based magnesium alloy thick plate with matched strength and plasticity is ≥320MPa, the tensile strength is ≥380MPa, and the elongation is ≥10%.

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