Creep age forming method of rare earth magnesium alloy and application

Abstract

The application provides a rare earth magnesium alloy creep age forming method and application, and the method comprises the following steps: (1) performing heating treatment on the rare earth magnesium alloy until the creep temperature is reached; (2) performing creep forming on the rare earth magnesium alloy reaching the creep temperature under a first tensile stress; and (3) performing aging treatment on the rare earth magnesium alloy under the creep temperature and the first tensile stress; wherein in the step (1), the rare earth magnesium alloy is selected from any one of Mg-9Gd rare earth magnesium alloy, Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy and Mg-4.3Y-2.9Nd-1.0Gd-0.5Zr rare earth magnesium alloy, and the creep temperature is 200-240 DEG C; and in the step (2), the first tensile stress is 150-250 MPa. The method can improve the formability of the rare earth magnesium alloy, optimize the microstructure and mechanical properties of the alloy, and significantly improve the strength and plasticity of the alloy.

Description

Technical Field

[0001] This invention relates to the field of forming and strengthening technology of metallic materials, and in particular to a creep aging forming method and its application for rare earth magnesium alloys. Background Technology

[0002] With the rapid development of high-end manufacturing industries such as aerospace, automotive, and electronics, the demand for high-performance magnesium alloy materials is increasing. Magnesium alloys are widely used in lightweight structural materials due to their low density, high specific strength, good damping performance, and excellent machinability. However, traditional magnesium alloys suffer from insufficient strength and creep resistance at high temperatures, limiting their application in higher temperatures and more complex working conditions. To meet the demands of modern industry for high-performance magnesium alloys, developing a magnesium alloy and its forming process that can maintain high strength and good creep resistance at high temperatures is particularly important.

[0003] In recent years, rare earth elements have been widely used in magnesium alloys to improve their performance due to their unique physical and chemical properties. The addition of rare earth elements (such as Gd, Y, and Nd) to magnesium alloys can significantly improve their mechanical properties, corrosion resistance, and high-temperature stability. However, the forming process of rare earth magnesium alloys still faces challenges. Traditional forming methods (such as casting, forging, and extrusion) often struggle to simultaneously optimize the alloy's microstructure and mechanical properties, especially at high temperatures. Furthermore, traditional processes can lead to high residual stress and inhomogeneous microstructure, thus affecting the alloy's final properties.

[0004] Calcium can form intermetallic compounds with magnesium in magnesium alloys, such as Mg2Ca. These compounds can play a role in precipitation strengthening, thereby improving the strength of the alloy. For example, in some rare earth magnesium alloys, the tensile strength and yield strength are significantly improved after adding an appropriate amount of calcium. CN117987708A discloses a magnesium-gadolinium-neodymium-calcium-zirconium alloy, which, by mass percentage, includes the following elemental composition: gadolinium 3-6%, neodymium 0.5-2%, calcium 0.1-1.5%, zirconium 0.2-0.8%, with the balance being magnesium. This invention reduces the gadolinium content of the heavy rare earth element to below 6 wt%, and adds a small amount of the less dense light rare earth element (neodymium) and the inexpensive alkaline earth metal element (calcium). By utilizing the synergistic effect of these heterogeneous elements, the solid solubility of each element in magnesium is reduced. Combined with low-temperature positive extrusion and short-term creep aging treatment, the precipitation of nanoscale second phase is promoted, resulting in a large number of nanoscale second phases being uniformly distributed in the magnesium matrix. This promotes dynamic recrystallization, refines the microstructure, and enhances the mechanical properties of the magnesium alloy, giving the magnesium-gadolinium-neodymium-calcium-zirconium alloy both high strength and high plasticity.

[0005] The aforementioned methods primarily target calcium-containing rare-earth magnesium alloys, utilizing the synergistic effect of rare-earth elements and calcium, combined with low-temperature positive extrusion and short-term creep aging treatment. However, for calcium-free rare-earth magnesium alloys, how to significantly improve their formability while maintaining high strength remains a pressing issue. Summary of the Invention

[0006] The main objective of this invention is to provide a creep aging forming method and its application for rare earth magnesium alloys, in order to solve the problems of poor formability and difficult processing of calcium-free rare earth magnesium alloys under high strength conditions. The method of this invention can simultaneously realize creep flow and aging strengthening of magnesium alloys during the forming process, improve their plasticity and mechanical properties, and enhance forming accuracy and mechanical stability of components.

[0007] To achieve the above objectives, the present invention provides a method for creep aging forming of rare earth magnesium alloys, comprising the following steps:

[0008] (1) Heat the rare earth magnesium alloy until it reaches the creep temperature;

[0009] (2) The rare earth magnesium alloy that has reached the creep temperature is subjected to creep forming under a first tensile stress;

[0010] (3) The rare earth magnesium alloy is subjected to aging treatment under the creep temperature and the first tensile stress conditions;

[0011] In step (1), the rare earth magnesium alloy is selected from any one of Mg-9Gd rare earth magnesium alloy, Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy, and Mg-4.3Y-2.9Nd-1.0Gd-0.5Zr rare earth magnesium alloy, and the creep temperature is 200-240℃.

[0012] In step (2), the first tensile stress is 150-250 MPa;

[0013] In step (3), the time for the time-sensitive processing is 6-24 hours.

[0014] Furthermore, in step (1), the conditions for the heating treatment also include a heating rate of 1-10℃ / min.

[0015] Furthermore, in step (2), the first tensile stress is 200-250 MPa.

[0016] Preferably, in step (2), the creep deformation condition further includes: the loading rate of the first tensile stress is 10-20 N / s.

[0017] Furthermore, in step (3), the time for the aging process is 10-24 hours.

[0018] Furthermore, in step (3), the method further includes: after the aging treatment of the rare earth magnesium alloy is completed, the first tensile stress is unloaded.

[0019] Furthermore, in step (3), the unloading rate of the first tensile stress is 50-200 N / s.

[0020] Furthermore, the rare earth magnesium alloy is Mg-9Gd rare earth magnesium alloy, the creep temperature is 220-230℃, the first tensile stress is 200-225MPa, and the aging treatment time is 6-12 hours.

[0021] Furthermore, the rare earth magnesium alloy is a Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy, and the creep temperature is 200-205℃, the first tensile stress is 240-250MPa, and the aging treatment time is 20-22 hours.

[0022] The present invention also provides an application of the aforementioned rare earth magnesium alloy creep aging forming method in the casting forming process, forging forming process or extrusion forming process of magnesium alloy.

[0023] The beneficial effects of this invention are as follows:

[0024] The creep aging forming method for rare earth magnesium alloys provided by this invention targets several specific calcium-free rare earth magnesium alloys. During the creep process, by combining creep forming and aging strengthening treatments and optimizing the process parameters of creep forming and aging treatment, a synergistic effect between dynamic softening and aging strengthening of the alloy is achieved. The creep forming stage promotes grain boundary or dislocation strengthening of the alloy, while the aging treatment stage precipitates strengthening phases (such as Mg5Gd, Mg7Gd, Mg...). 24 Y5, Mg 12 The method of this invention can enhance the strength and hardness of calcium- and rare-earth magnesium alloys by using Nd and other minerals. Therefore, the method of this invention can improve the formability of calcium- and rare-earth magnesium alloys, optimize their microstructure and mechanical properties, and significantly improve their strength and plasticity.

[0025] Compared with traditional processes, the method of the present invention can effectively improve the formability of alloys while maintaining high strength and good plasticity. In addition, the method of the present invention can simplify the heat treatment process without reducing performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 The process flow diagram of the creep aging forming method for rare earth magnesium alloys provided by the present invention.

[0028] Figure 2 The images show the microstructure of rare earth magnesium alloys before and after creep aging treatment in Example 2 and Comparative Example 2. Specifically, (a1) shows the crystal orientation distribution of the sample before creep aging in Example 2, (b1) shows the crystal orientation distribution of the sample after creep aging in Example 2, (a2) shows the morphology of the artificially aged precipitates in Comparative Example 2, and (b2) shows the morphology of the creep-aged precipitates in Comparative Example 2.

[0029] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Moreover, the technical solutions of the various embodiments of this invention can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0032] As mentioned above, this invention provides a method for creep aging forming of rare earth magnesium alloys, comprising the following steps:

[0033] (1) Heat the rare earth magnesium alloy until it reaches the creep temperature;

[0034] (2) The rare earth magnesium alloy that has reached the creep temperature is subjected to creep forming under a first tensile stress;

[0035] (3) The rare earth magnesium alloy is subjected to aging treatment under the creep temperature and the first tensile stress conditions;

[0036] In step (1), the rare earth magnesium alloy is selected from any one of Mg-9Gd rare earth magnesium alloy, Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy, and Mg-4.3Y-2.9Nd-1.0Gd-0.5Zr rare earth magnesium alloy, and the creep temperature is 200-240℃.

[0037] In step (2), the first tensile stress is 150-250 MPa;

[0038] In step (3), the time for the time-sensitive processing is 6-24 hours.

[0039] When the creep temperature is too high, the nucleation and growth rate of precipitated phases accelerates, which can easily lead to coarsening of the precipitated phases and a decrease in the strength or plasticity of the alloy after creep aging. In addition, if the creep temperature is too high, the surface of the calcium-free rare earth magnesium alloy may be oxidized, reducing the surface quality of the component after creep aging. On the other hand, if the creep temperature is too low, the nucleation rate of precipitated phases decreases, resulting in insufficient precipitation. Furthermore, dislocation movement becomes difficult, which may lead to dislocation pile-up, forming large internal stresses that make it difficult to meet the strength and toughness requirements of the component. Moreover, if the temperature is too low, the actual creep amount of the component will be reduced, significantly increasing the time cost of creep aging. In this invention, the creep temperature can be, for example, any value between 200℃, 205℃, 210℃, 215℃, 220℃, 225℃, 230℃, 235℃, 240℃ or 200-240℃. The inventors of this invention have discovered through research that, combined with the performance characteristics of calcium-free rare earth magnesium alloys, setting the creep temperature in the range of 200-240℃ can better promote grain boundary or dislocation strengthening of the alloy, thereby significantly improving the tensile strength, yield strength and other mechanical properties of rare earth magnesium alloys, as well as improving the ductility and formability of rare earth magnesium alloys.

[0040] The creep mechanism of magnesium alloys changes under different temperature and stress conditions. This invention utilizes the synergistic effect of creep temperature and creep stress to concentrate the creep mechanism of rare earth magnesium alloys primarily on dislocation slip. When the creep stress is too high, dislocations proliferate and move extensively within the alloy, accelerating creep deformation and even leading to creep fracture, thereby compromising the structural and performance integrity of the component. Conversely, when the creep stress is too low, dislocation movement is insufficient, and the alloy mainly creeps through a diffusion mechanism, resulting in slower creep deformation and maintaining good dimensional stability. However, long-term low-stress creep may lead to the accumulation of vacancies within the alloy, triggering crack initiation and propagation, thus reducing the strength and toughness of the alloy after creep deformation. The inventors of this invention have discovered that by setting the creep deformation stress of several specific rare earth magnesium alloys selected in this invention within the range of 150-250 MPa and matching the creep temperature of 200-240℃, rare earth magnesium alloys with excellent tensile strength, yield strength, and other mechanical properties can be obtained.

[0041] This invention targets several calcium-free rare-earth magnesium alloys. Through the synergistic effect of creep forming and aging treatment, it enhances the grain boundary or dislocation strengthening effect of the rare-earth magnesium alloys, while simultaneously utilizing the precipitation orientation effect to significantly improve the alloy's strength. If the aging treatment time is too long, the precipitated phases coarsen and may even undergo structural transformation, changing from metastable strengthening phases to stable phases, thus reducing the alloy's strength and toughness after creep aging. Conversely, if the aging treatment time is too short, the precipitated phases are insufficiently precipitated, and the volume fraction and spatial distribution characteristics of the precipitated phases fail to meet the alloy's strength and toughness requirements. The inventors of this application have discovered that aging the specific rare-earth magnesium alloys used in this invention under creep temperatures of 200-240℃ and creep stresses of 150-250MPa, with the aging treatment time controlled within 6-24 hours, can simultaneously achieve creep flow and age strengthening of the magnesium alloy, further improving its plasticity and mechanical properties, thereby enhancing forming accuracy and the mechanical stability of magnesium alloy components.

[0042] The method of this invention achieves a synergistic effect between dynamic softening and age-hardening of the alloy during creep forming by optimizing and adjusting the creep temperature, stress, and aging time. The creep stage promotes grain boundary or dislocation strengthening, while the aging stage strengthens the alloy through the precipitation of strengthening phases (such as Mg5Gd, Mg7Gd, Mg...). 24 Y5, Mg 12 (e.g., Nd) can be used to enhance the strength and hardness of the alloy.

[0043] In some specific embodiments, the rare earth element in the rare earth magnesium alloy is selected from at least one of Gd, Y, and Nd.

[0044] It should be noted that the three rare earth elements, Gd, Y, and Nd, all have significant effects on refining grains, improving mechanical properties, and enhancing the microstructure in magnesium alloys. They significantly improve the overall performance of magnesium alloys through mechanisms such as solid solution strengthening, precipitation strengthening, and inhibiting the formation of harmful phases. The specific roles of the aforementioned three rare earth elements in rare earth magnesium alloys are as follows:

[0045] Gd (gadolinium) is a rare earth element, silvery-white in color, with strong magnetism and superconductivity at low temperatures. Adding Gd to magnesium alloys can have the following effects: (1) it can significantly refine the grain size of magnesium alloys and improve their microstructure; (2) the addition of Gd can significantly increase the tensile strength and elongation of magnesium alloys; (3) the stable phases formed by Gd (such as the Al2Gd phase) can significantly improve the creep resistance of the alloy; (4) in Mg-Gd alloys, the addition of Gd can promote the formation of age-accelerated precipitates (such as the β” phase), further improving the strength of the alloy.

[0046] Yttrium (Y) is a rare earth element, silvery-gray in color, commonly used in the manufacture of alloys, specialty glasses, and electronic and optical devices. Y acts as a nucleation site for heterogeneous formation, significantly refining the grain size of magnesium alloys, thereby improving their strength and toughness. Adding Y to magnesium alloys also significantly increases their tensile and yield strength. Simultaneously, Y reduces the formation of coarse, discontinuous phases (such as the Mg5(Gd, Y, Zn) phase) while promoting the formation of beneficial LPSO (long-period stacked ordered) phases, further enhancing the alloy's high-temperature performance. Furthermore, the addition of Y improves the alloy's thermal stability, resulting in better performance at high temperatures.

[0047] Nd (neodymium) is a rare earth element, silvery-white in color, and readily oxidizes in air. Nd can significantly refine the grain size of magnesium alloys, thereby improving their strength and toughness. Adding Nd to magnesium alloys can significantly increase their tensile strength and yield strength, and also promote the precipitation of phases such as Mg. 12 The formation of (Nd, Zn) phases further enhances the strength of the alloy. Simultaneously, Nd can also bind coarse continuous phases (such as Mg) together. 17 Al 12 The phase transforms into a fine, discontinuous distribution phase, thereby improving the microstructure of the alloy.

[0048] It should be noted that the present invention does not impose any particular limitation on the type of rare earth magnesium alloy, and rare earth magnesium alloys well known to those skilled in the art can be used. According to a particularly preferred embodiment, the rare earth magnesium alloy is selected from Mg-Gd alloys, Mg-Y alloys, Mg-Nd alloys, or rare earth magnesium alloys composed of at least two rare earth elements selected from Gd, Y, and Nd with Mg.

[0049] According to a particularly preferred embodiment, the rare earth magnesium alloy is selected from at least one of Mg-9Gd rare earth magnesium alloy, Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy, and Mg-4.3Y-2.9Nd-1.0Gd-0.5Zr rare earth magnesium alloy.

[0050] It should be noted that the rare earth magnesium alloy used in this invention can be obtained commercially or prepared by conventional methods. Exemplarily, the preparation method of the rare earth magnesium alloy includes the following steps: pure magnesium ingots are added to a resistance furnace. Once the magnesium ingots are completely melted and the furnace temperature reaches 700–800°C, under the protection of an SF6 / CO2 mixed gas (volume ratio 1:99) and MgCl2 flux, intermediate alloys such as Mg-30Gd, Mg-30Y, Mg-30Nd, and Mg-30Zr are added sequentially to the melt. Then, argon gas is introduced into the furnace for refining and slag removal. After standing for about 1 hour, magnesium alloy ingots are cast. The magnesium alloy ingots can be directly creep-aged after homogenization treatment; or, after homogenization treatment, the billet can be extruded and rolled into magnesium alloy plates before creep aging.

[0051] According to a particularly preferred embodiment, in step (1), the heating treatment conditions further include a heating rate of 1-10℃ / min. The heating rate can be, for example, any value between 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, or 1-10℃ / min.

[0052] According to a particularly preferred embodiment, in step (2), the first tensile stress is 200-250 MPa. Preferably, in step (3), the aging treatment time is 10-24 hours. The first tensile stress can be, for example, any value between 200 MPa, 205 MPa, 210 MPa, 215 MPa, 220 MPa, 225 MPa, 230 MPa, 235 MPa, 240 MPa, 245 MPa, 250 MPa, or 200-250 MPa; the aging treatment time can be, for example, any value between 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, or 10-24 hours. The inventors have found that by adopting this preferred embodiment, rare earth magnesium alloys with superior mechanical properties such as tensile strength and yield strength can be obtained.

[0053] According to a particularly preferred embodiment of the present invention, the rare earth magnesium alloy is a Mg-9Gd rare earth magnesium alloy, the creep temperature is 220-230℃, the first tensile stress is 200-225MPa, and the aging treatment time is 6-12 hours. The inventors have found that, under this preferred condition, the Mg-9Gd rare earth magnesium alloy, after creep aging forming, not only improves the elongation but also significantly enhances the alloy's tensile strength and yield strength, among other mechanical properties.

[0054] According to another particularly preferred embodiment of the present invention, the rare earth magnesium alloy is a Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy, with a creep temperature of 200-205℃, a first tensile stress of 240-250MPa, and an aging treatment time of 20-22 hours. The inventors have found that, compared with artificial aging, this preferred embodiment synergistically improves the strength and toughness of the alloy.

[0055] In some specific embodiments, in step (2), the creep deformation condition further includes: the loading rate of the first tensile stress is 10-20 N / s. The loading rate can be, for example, 10 N / s, 11 N / s, 12 N / s, 13 N / s, 14 N / s, 15 N / s, 16 N / s, 17 N / s, 18 N / s, 19 N / s, 20 N / s or any value between 10 and 20.

[0056] According to a particularly preferred embodiment, in step (3), the method further includes: after the aging treatment of the rare earth magnesium alloy is completed, the first tensile stress is unloaded.

[0057] According to a particularly preferred embodiment, in step (3), the unloading rate of the first tensile stress is 50-200 N / s.

[0058] In some specific embodiments, in step (3), the method further includes: after the first tensile stress is unloaded, the rare earth magnesium alloy is cooled.

[0059] The present invention does not particularly limit the cooling method; any cooling method well known to those skilled in the art can be used, as long as it can achieve the purpose of cooling to room temperature. For example, in step (3), the method further includes: after the first tensile stress is unloaded, the rare earth magnesium alloy is cooled by air or water until it reaches room temperature.

[0060] The creep aging process route diagram for rare earth magnesium alloys provided by this invention is as follows: Figure 1As shown, by controlling the creep temperature at 200-240℃ and the stress during creep at 150-250MPa, and controlling the aging time at 6-24 hours, the formability of rare earth magnesium alloy components can be synergistically prepared. This invention improves the overall properties of rare earth magnesium alloys, including enhancing their ductility and formability. Compared to conventional artificial aging, creep aging achieves a higher strengthening effect for rare earth magnesium alloys.

[0061] The present invention also provides an application of the aforementioned rare earth magnesium alloy creep aging forming method in the casting forming process, forging forming process or extrusion forming process of magnesium alloy.

[0062] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all raw materials and instruments used are commercially available products.

[0063] Example 1

[0064] This embodiment provides a creep aging forming method for rare earth magnesium alloys, wherein the rare earth magnesium alloy is a Mg-9Gd rare earth magnesium alloy; specifically, it includes the following steps:

[0065] The Mg-9Gd rare earth magnesium alloy was heated to 225℃ at a heating rate of 5℃ / min, and then a first tensile stress of 225MPa was applied at a loading rate of 10N / s to induce creep deformation. The Mg-9Gd rare earth magnesium alloy was then subjected to aging treatment at a temperature of 225℃ and a first tensile stress of 225MPa for 10 hours. After the aging treatment, the first tensile stress was unloaded at an unloading rate of 50N / s, and the Mg-9Gd rare earth magnesium alloy sample was allowed to cool naturally to room temperature.

[0066] Comparative Example 1

[0067] This comparative example follows the method of Example 1, except that no first tensile stress is applied, i.e., artificial aging treatment is used; specifically, it includes the following steps:

[0068] The Mg-9Gd rare earth magnesium alloy was heated to 225℃ at a heating rate of 5℃ / min. The Mg-9Gd rare earth magnesium alloy was then subjected to aging treatment at 225℃ for 10 hours. After the aging treatment was completed, the Mg-9Gd rare earth magnesium alloy sample was naturally cooled to room temperature.

[0069] Example 2

[0070] This embodiment provides a creep aging forming method for rare earth magnesium alloys, wherein the rare earth magnesium alloy type is Mg-7.5Gd-1.5Y-0.4Zr; specifically, it includes the following steps:

[0071] The Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy was heated to 200℃ at a heating rate of 10℃ / min, and then a first tensile stress of 250MPa was applied at a loading rate of 15N / s to induce creep deformation. The Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy was then subjected to aging treatment at a temperature of 200℃ and a first tensile stress of 250MPa for 21 hours. After the aging treatment, the first tensile stress was unloaded at an unloading rate of 70N / s, and the Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy sample was naturally cooled to room temperature.

[0072] Comparative Example 2

[0073] This comparative example follows the method of Example 2, except that no first tensile stress is applied, i.e., artificial aging treatment is used; specifically, it includes the following steps:

[0074] The Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy was heated to 200℃ at a heating rate of 10℃ / min. Then, the Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy was aged at 200℃ for 21 hours. After the aging treatment, the Mg-7.5Gd-1.5Y-0.4Zr rare earth magnesium alloy sample was naturally cooled to room temperature.

[0075] Example 3

[0076] This embodiment provides a creep aging forming method for rare earth magnesium alloys, which is carried out with reference to the method in Embodiment 1, except that the aging treatment time is 12 hours.

[0077] Example 4

[0078] This embodiment provides a creep aging forming method for rare earth magnesium alloys, which is carried out with reference to the method in Embodiment 1, except that the aging treatment time is 7.5 hours.

[0079] Example 5

[0080] This embodiment provides a creep aging forming method for rare earth magnesium alloys, which is carried out with reference to the method in Embodiment 1, except that the first tensile stress is 150 MPa.

[0081] Comparative Example 3

[0082] This comparative example provides a creep aging forming method for rare earth magnesium alloys, which is carried out with reference to the method in Example 1, except that the aging treatment time is 5 hours.

[0083] Comparative Example 4

[0084] This comparative example provides a creep aging forming method for rare earth magnesium alloys, which is carried out with reference to the method in Example 1, except that the first tensile stress is 75 MPa.

[0085] Comparative Example 5

[0086] This comparative example provides a creep aging forming method for rare earth magnesium alloys, which is carried out with reference to the method in Example 1, except that the rare earth magnesium alloy is the extrusion sample obtained in Example 1 of CN117987708A.

[0087] Analysis example 1

[0088] The rare earth magnesium alloy samples obtained after creep aging forming in the examples and comparative examples were subjected to performance testing. The untreated Mg-9Gd rare earth magnesium alloy in Example 1 was used as the control group. The performance testing included tensile strength, yield strength and elongation. The specific test results are shown in Table 1.

[0089] The test method for tensile strength is GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test at room temperature";

[0090] The test method for yield strength is GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test at room temperature";

[0091] The test method for elongation is GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test method at room temperature".

[0092] Table 1

[0093]

[0094]

[0095] By comparing the control group, Example 1, and Comparative Example 1, it can be seen that the rare earth magnesium alloy after aging treatment exhibits significant improvements in both strength and ductility. Specifically, by comparing Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, it can be seen that compared to conventional artificial aging, the tensile strength, yield strength, and elongation of the rare earth magnesium alloy after creep forming are all significantly improved. Therefore, the calcium-free rare earth magnesium alloy treated by the method of this invention exhibits higher strength and ductility.

[0096] By comparing Examples 1, 3-5, and Comparative Examples 3-4, it can be seen that the method of the present invention achieves creep flow and aging strengthening of magnesium alloys simultaneously during the forming process by specifically adjusting the creep temperature, stress, and aging time. Through the synergistic effect between the dynamic softening and aging strengthening of the alloy, the grain boundary or dislocation strengthening effect of the rare earth magnesium alloy is enhanced. At the same time, by utilizing the precipitation orientation effect, the strength and toughness of the alloy are significantly improved.

[0097] By comparing Example 1 and Comparative Example 5, it can be seen that the present invention, by combining creep forming and aging strengthening treatments and optimizing the process parameters of creep forming and aging treatment in the creep process, is very beneficial to improving the formability of calcium-free rare earth magnesium alloys and can also significantly improve their strength and plasticity. However, when calcium-containing magnesium gadolinium neodymium alloys are treated with the method of the present invention, it may promote the precipitation and aggregation of the second phase (such as calcium compounds) in the alloy, and also lead to the generation of a large number of dislocations inside the alloy, increasing the dislocation density, thereby inducing plastic deformation and crack initiation, and also affecting the mechanical properties of the alloy.

[0098] Analysis example 2

[0099] Observe the microstructure of the rare earth magnesium alloys before and after creep aging treatment in Example 2 and Comparative Example 2. See the specific results below. Figure 2 .

[0100] exist Figure 2 In the diagram, (a1) shows the crystal orientation distribution of the sample before creep aging in Example 2, (b1) shows the crystal orientation distribution of the sample after creep aging in Example 2, (a2) shows the morphology of the artificially aged precipitated phase in Comparative Example 2, and (b2) shows the morphology of the creep-aged precipitated phase in Comparative Example 2.

[0101] By comparing the crystal orientation evolution of rare earth magnesium alloys before and after creep aging, and the differences in morphology of precipitated phases between artificial aging and creep aging, it can be seen that rare earth magnesium alloys do indeed exhibit orientation precipitation effects after being treated by the creep aging process of this invention, thereby effectively improving the ductility and strength of rare earth magnesium alloys.

[0102] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0103] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for creep aging forming of rare earth magnesium alloys, characterized in that, Includes the following steps: (1) The rare earth magnesium alloy is heated until the creep temperature is reached; the rare earth magnesium alloy is Mg-9Gd rare earth magnesium alloy, the creep temperature is 220-230℃, and the heating rate of the heating treatment is 3-7℃ / min. (2) The rare earth magnesium alloy that has reached the creep temperature is subjected to creep forming under a first tensile stress; the first tensile stress is 220-230 MPa, and the loading rate of the first tensile stress is 10-15 N / s; (3) The rare earth magnesium alloy is subjected to aging treatment under the creep temperature and the first tensile stress conditions; the aging treatment time is 7.5-12 hours.

2. The creep aging forming method for rare earth magnesium alloys according to claim 1, characterized in that, Step (3) further includes: after the aging treatment of the rare earth magnesium alloy is completed, the first tensile stress is unloaded.

3. The creep aging forming method for rare earth magnesium alloys according to claim 2, characterized in that, In step (3), the unloading rate of the first tensile stress is 50-200 N / s.

4. The application of the rare earth magnesium alloy creep aging forming method as described in any one of claims 1-3 in the casting forming process, forging forming process or extrusion forming process of magnesium alloy.

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