High-strength high-temperature-resistant wrought magnesium alloy and preparation method thereof

Abstract

The invention discloses a high-strength high-temperature-resistant wrought magnesium alloy and a preparation method thereof, and relates to the technical field of magnesium alloy preparation. The magnesium alloy comprises the following components in percentage by mass: 8.0%-10.0% of Gd; 2.5% to 4.0% of Y; 1.5% to 3.0% of Zn; 0.3% to 0.8% of Zr; 0.1% to 0.5% of Nd; the total mass percentage content of the Gd and the Y is 11.5%-13.5%; zn / (Gd + Y) is equal to 0.15 to 0.3; the balance is magnesium and other inevitable impurity elements. The magnesium alloy disclosed by the invention has ultrahigh strength and plasticity and good hot working formability, can be used for preparing products with complex shapes through a simple process and a forging processing method, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy preparation, and in particular to a high-strength, high-temperature-resistant deformable magnesium alloy and a preparation method thereof. Background Art

[0002] Lightweighting is a key development direction for aerospace equipment and a key technology for achieving maneuverable trajectory changes and long-duration, high-speed flight. As the lightest metal structural material, magnesium alloys offer unique advantages, including high specific strength, high specific stiffness, and high thermal conductivity.

[0003] Research has shown that rare earth elements (REEs) significantly strengthen magnesium alloys and significantly improve their high-temperature performance. However, existing commercial high-strength, heat-resistant magnesium alloys, such as WE43, WE54, and VW83M, suffer from common challenges such as difficulty in plastic forming large, complex structures, severe strength-to-size effects and anisotropy, and high processing costs. This results in their widespread use in aerospace equipment as castings. Therefore, the challenge of preparing ultra-high-strength, high-temperature-resistant magnesium alloys by rationally adding REEs and controlling their proportions remains a major research challenge.

[0004] Chinese patent application CN107858616A discloses a high-strength, high-ductility Mg-Gd-Y-Zn-Nd-Zr cast magnesium alloy and its preparation method. The cast magnesium alloy consists of the following components, by mass percentage: Gd: 8.8-9.8%, Y: 0.8-2.8%, Zn: 0.8-1.5%, Nd: 0.1-0.3%, Zr: 0.4-0.6%, with a total impurity element content of <0.1%, and the balance being Mg. The magnesium alloy is produced by solution heat treating the ingot, cooling it to room temperature, then artificially aging it, and then cooling it back to room temperature. However, the cast magnesium alloy only has a yield strength of 240-300 MPa, a tensile strength of 340-370 MPa, and an elongation of 7-10.5%. Its room-temperature tensile strength does not reach 400 MPa, and its yield strength does not exceed 300 MPa, failing to meet the increasingly stringent strength and weight reduction requirements for aerospace structural components.

[0005] Chinese patent application CN 114107849A discloses a method for preparing a high-strength and tough Mg-Gd-Y-Zn-Zr wrought magnesium alloy. This method uses semi-continuous casting to produce an ingot, which is then subjected to homogenization, quenching, extrusion deformation, and aging treatments. During extrusion, high-pressure air is applied to the discharge channel or outlet, as well as to the extrusion rod, to achieve rapid cooling of the sample surface, limiting the coarsening of recrystallized grains and dynamic precipitation phases in the alloy and improving the alloy's strength and elongation. This method uses extrusion rather than forging for plastic deformation. While extrusion can significantly improve the alloy's strength and plasticity, it is subject to significant size restrictions, making it impractical for the preparation of complex structural parts and limiting its application scenarios. Furthermore, this method does not address high-temperature performance requirements, making it unclear whether the alloy can withstand the high-temperature service environment (200-300°C) encountered during high-speed flight of missile weapons.

[0006] Chinese patent document CN 112410632A discloses a Mg-Gd-Y-Nd high-strength and toughness rare earth magnesium alloy and its preparation method. The magnesium alloy has a chemical composition, by mass percentage, of: Gd: 6.5-10 wt.%, Y: 1.5-2.5 wt.%, Nd: 1.5-2.5 wt.%, Ag: 0.2-0.5 wt.%, Sc: 0.05-0.1 wt.%, Zr: 0.35-0.55 wt.%, Zn: 0-0.3 wt.%, with the remainder being Mg; the mass ratio of Gd, Y, and Nd is (4-4.3):1:1. The magnesium alloy in this scheme also contains components such as Ag and Sc. The preparation method is primarily through casting, followed by solution treatment, heat treatment, and cooling to room temperature. The final product's yield strength, tensile strength, and elongation still require improvement.

[0007] Therefore, the room temperature tensile strength of the magnesium alloy disclosed in the prior art does not reach 400 MPa, and the yield strength does not exceed 300 MPa, which cannot meet the increasingly stringent requirements for strength and weight reduction of aerospace structural parts, and its high-temperature performance cannot meet the requirements of high-temperature service environment (200-300°C); it is urgent to develop a high-strength and heat-resistant magnesium alloy. Summary of the Invention

[0008] In view of the defects of the existing technology, the technical problem to be solved by the present invention is: to provide a high-strength, high-temperature resistant deformable magnesium alloy and a preparation method thereof, wherein the magnesium alloy has excellent room temperature strength and plasticity, as well as excellent heat resistance; and the magnesium alloy can be used to prepare products with complex shapes through simple forging processing, and the product processing application scenarios are wide.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a high-strength, high-temperature resistant deformable magnesium alloy comprising the following components in percentage by mass:

[0011] Gd: 8.0%~10.0%;

[0012] Y: 2.5% to 4.0%;

[0013] Zn: 1.5% to 3.0%;

[0014] Zr: 0.3% to 0.8%;

[0015] Nd: 0.1%~0.5%;

[0016] Moreover, the total mass percentage of Gd and Y is: 11.5% to 13.5%; Zn / (Gd+Y)=0.15 to 0.3;

[0017] The balance is magnesium and other inevitable impurity elements.

[0018] For unavoidable impurity elements, the content of a single element is controlled not to exceed 0.01%, and the total amount of impurity elements is controlled not to exceed 0.1%.

[0019] Preferably, in the magnesium alloy provided by the present invention, the mass percentage content of Gd is controlled to be 8.5%-9.5%, the mass percentage content of Y is controlled to be 2.8%-3.8%, and the mass percentage content of (Gd+Y) is controlled to be 11.8%-13.4%.

[0020] Preferably, in the magnesium alloy provided by the present invention, the mass percentage content of Zn is controlled to be 1.5-2.0%; and the mass percentage ratio of Zn / (Gd+Y) is controlled to be 0.2-0.25.

[0021] This is mainly based on the following considerations:

[0022] Because Gd has a high solid solubility in the magnesium matrix, reaching 23.5 wt.% at 548°C, and its solid solubility decreases sharply with decreasing temperature, it has great potential for precipitation strengthening. Gd and Mg can form high-melting-point compounds, such as Mg5Gd, Mg3Gd, Mg2Gd, and MgGd, which effectively hinder dislocation slip and exhibit good high-temperature stability. Y has a maximum solid solubility of 11.5 wt.% in the magnesium matrix and also decreases sharply with decreasing temperature. Its addition imparts significant ageing-strengthening effects on magnesium. Y and Gd have very similar atomic radii. When Y atoms are added to Mg-Gd alloys, they replace Gd atoms. The solid solubility of Gd decreases with increasing Y content, leading to an increase in the volume fraction of the precipitated phase during isothermal aging, effectively improving the alloy's strength. By manipulating the Gd and Y content, the formation of high-melting-point compounds within the alloy can be controlled, improving both the room-temperature and high-temperature properties of the alloy. However, although the addition of Gd and Y can effectively improve the alloy properties, high concentrations of rare earth elements will lead to increased density and cost of magnesium alloys.

[0023] Based on this, the solution of the present invention uses cheap and lightweight Zn to replace part of the rare earth elements, which can form a long period ordered structure (LPSO phase) with the rare earth elements. The magnesium alloy of the present invention preferably controls Zn in this phase to further improve the strength and plasticity of the alloy, and has good high-temperature stability and still exists after solution treatment at 500°C. The formation of the LPSO phase requires sufficient Zn atoms as smaller interstitial atoms to be embedded in the lattice distortion gaps caused by RE atoms. The periodic and orderly stacking of RE and Zn atoms forms the LPSO structure. When the Zn content is too low, it is difficult to precipitate the LPSO phase. When the Zn content is too high, the LPSO phase of the magnesium matrix is ​​greatly reduced and the strength decreases. Therefore, regulating the ratio of Zn / (Gd+Y) can effectively regulate the LPSO phase structure, thereby optimizing the recrystallization behavior and mechanical properties of the alloy.

[0024] Preferably, in the magnesium alloy provided by the present invention, the mass percentage content of Zr is controlled to be 0.4% to 0.7%.

[0025] This is because Zr has a significant grain-refining effect on magnesium alloys and is often added to magnesium alloys along with rare earth elements to produce high-performance magnesium alloys. Adding an appropriate amount of Zr to Mg-Gd alloys can significantly refine the alloy grains and improve alloy properties. However, excessive Zr (≥1% wt.) can form coarse Zn-Zr compounds, which can reduce the alloy's mechanical properties.

[0026] Preferably, in the magnesium alloy provided by the present invention, the mass percentage content of Nd is controlled to be 0.1% to 0.3%.

[0027] This is because the maximum solid solubility of Nd in magnesium is 3.6%. The present invention forms a high temperature stable phase - Mg in the alloy by adding 0.1-0.3% Nd trace element. 12 Nd improves the high temperature mechanical properties of the alloy. When the Nd content is too high, it will affect the main strengthening phases Mg5 (Gd / Y) and Mg 24 The precipitation of (Gd / Y)5 is not conducive to the mechanical properties of the alloy.

[0028] In a second aspect, the present invention provides a method for preparing the high-strength, high-temperature resistant deformable magnesium alloy as described above, comprising the following steps:

[0029] S1. Semi-continuous casting: After the raw materials are melted, they are semi-continuously cast to obtain magnesium alloy ingots;

[0030] S2. Homogenization heat treatment: subjecting the magnesium alloy ingot to a two-step homogenization heat treatment, firstly solution treatment and then aging treatment, to obtain a magnesium alloy ingot after homogenization heat treatment;

[0031] S3, multi-directional forging: the magnesium alloy ingot after homogenization heat treatment is subjected to multi-directional forging to obtain a forged magnesium alloy part, wherein the multi-directional forging step comprises at least a first forging at 480-500° C. and a second forging at 450-470° C.;

[0032] S4. Aging heat treatment: The magnesium alloy forgings are kept at 190℃~230℃ for 24~72h for aging treatment.

[0033] The raw material melting process is usually carried out in a melting furnace, and the multi-stage casting process is usually carried out on a hydraulic press.

[0034] Furthermore, in step S1, the process of smelting the raw materials includes:

[0035] (1) Under the protection of an inert atmosphere, the melting temperature is raised to 590-610°C, a preset proportion of pure magnesium ingots are added, and after the magnesium ingots are melted, the melting temperature is continued to be raised;

[0036] (2) After the smelting temperature rises to 700-730°C, add a preset proportion of pure zinc ingots and refining agent, introduce inert gas and stir after melting, remove the bottom slag after refining, and continue to increase the smelting temperature;

[0037] (3) After the melting temperature rises to 750-770°C, Mg-Gd master alloy, Mg-Y master alloy, Mg-Nd master alloy, Mg-Zr master alloy and refining agent are added in proportion. After the melting is completed, inert gas is introduced for stirring. After the refining is completed, the bottom slag is removed;

[0038] (4) the smelting temperature is reduced to 650-670 DEG C, and the temperature is kept static, the oxide skin and the bottom slag are removed, then the smelting temperature is increased to 750-770 DEG C, and the temperature is kept static, the oxide skin and the bottom slag are removed.

[0039] Since the high rare earth magnesium alloy in the prior art has the common problems of difficulty in plastic forming of large complex structure, serious strength size effect and anisotropy, and high processing cost, the application of the magnesium alloy provided in the present application to aerospace equipment is usually in the form of casting, and the plastic processing mode of forging is adopted for the magnesium alloy, so that the plastic processing product has better comprehensive mechanical properties and product quality consistency, and can better meet the requirements of lightweight structure design of equipment.

[0040] Preferably, the inert gas in steps (2) and (3) is argon, which has low comprehensive cost and good effect.

[0041] Preferably, the refining agent in steps (2) and (3) is RJ-5.

[0042] Further, the conditions of the first step of solid solution treatment in the homogenization heat treatment in step S2 are that the temperature is kept at 480-500 DEG C for 20-28 h, and the conditions of the second step of aging treatment are that the temperature is kept at 210-240 DEG C for 12-24 h.

[0043] Further, in the multi-stage casting process of step S3, the reduction speed is 5-10 mm / s, the upsetting and drawing reversing frequency is 1-3 times, the upsetting single-pass reduction amount is 25%-35%, the drawing single-pass reduction amount is 10%-20%, the total forging pass is greater than or equal to 30, the axial direction of the forging blank after each reversing is perpendicular to the axial direction of the ingot before forging, and the blank height-diameter ratio after each reversing is 1.2-2.5.

[0044] Preferably, in order to improve plasticity and reduce deformation resistance, the magnesium alloy is made to be easy to deform by heating to avoid cracking, and the magnesium alloy ingot after homogenization heat treatment is preheated in a resistance furnace before multi-directional forging.

[0045] Further, the first fire forging and the second fire forging further comprise an intermediate annealing step, the temperature of the intermediate annealing step is 460-470 DEG C, and the annealing time is 2-4 hours.

[0046] Preferably, in step S4, the temperature of the aging heat treatment is 200-220 DEG C, and the time is 48-72 hours.

[0047] The present application has the following beneficial effects:

[0048] (1) The present invention provides a high-strength, high-temperature-resistant Mg-Gd-Y-Zn-Nd-Zr deformable magnesium alloy and a preparation method thereof. By designing a certain alloying composition and combining it with a reasonable homogenization heat treatment process, a forging process, and an aging heat treatment process, a Mg-Gd-Y-Zn-Nd-Zr deformable magnesium alloy with both improved strength and plasticity is obtained, and it has excellent high-temperature resistance. The room temperature tensile strength reaches above 450 MPa, the yield strength reaches above 340 MPa, and the elongation exceeds 10%. At 200°C, the tensile strength can still reach above 380 MPa, the yield strength reaches above 280 MPa, and the elongation exceeds 15%. The tensile strength at 300°C can still reach above 280 MPa.

[0049] (2) The present invention optimizes the processing technology and adopts semi-continuous casting, "solid solution + aging" homogenization heat treatment, two-fire multi-directional forging, and aging heat treatment to prepare the magnesium alloy. The magnesium alloy has excellent processing performance and a simple preparation process. It is suitable for large-scale production and multi-scenario applications. It can prepare blanks for structural parts with complex structures and has broad prospects in the fields of aerospace and weapon equipment.

[0050] (3) Compared with the Mg-Gd-Y-Zn-Zr magnesium alloy disclosed in CN 114107849 A, the Mg-Gd-Y-Zn-Nd-Zr magnesium alloy provided by the present invention can be formed by forging, has a wide range of applications, and can better meet the stringent service index requirements of aerospace structural parts. It can realize the typical application of ultra-high-strength and high-temperature resistant magnesium alloys in key structural parts such as missile weapon cabins and solve the bottleneck problem of weight reduction in aerospace equipment, which has great engineering application value.

[0051] In summary, the magnesium alloy of the present invention has ultra-high strength and plasticity, good hot working formability, can be used to prepare products with complex shapes by forging through simple processes, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The metallographic diagrams of the magnesium alloys prepared according to the embodiments of the present invention are shown in FIG. Figure 1 (a) is the metallographic diagram of the magnesium alloy of Example 1, Figure 1 (b) is the metallographic diagram of the magnesium alloy of Example 2, Figure 1 (c) is the metallographic diagram of the magnesium alloy of Example 3, Figure 1 (d) is the metallographic image of the magnesium alloy of Example 4.

[0053] Figure 2 The metallographic diagrams of the magnesium alloys prepared in the comparative example are shown in FIG. Figure 2 (a) is the metallographic diagram of the magnesium alloy of Comparative Example 1, Figure 2 (b) is the metallographic image of the magnesium alloy of Comparative Example 2. DETAILED DESCRIPTION

[0054] As used herein:

[0055] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0056] The conjunction "consisting of" excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0057] When a parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0058] In these examples, parts and percentages are by mass unless otherwise indicated.

[0059] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. Where specific conditions are not specified in the examples, the methods are carried out according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, they are conventional products that can be purchased commercially.

[0061] The present invention first provides a high-strength, high-temperature resistant deformable magnesium alloy, comprising the following components in percentage by mass: Gd: 8.0% to 10.0%; Y: 2.5% to 4.0%; Zn: 1.5% to 3.0%; Zr: 0.3% to 0.8%; Nd: 0.1% to 0.5%; and the total mass percentage of Gd and Y is: 11.5% to 13.5%; Zn / (Gd+Y)=0.15 to 0.3; the balance is magnesium and other inevitable impurity elements. Preferably, the mass percentage content of Gd is controlled to be 8.5%-9.5%, the mass percentage content of Y is controlled to be 2.8%-3.8%, and the mass percentage content of (Gd+Y) is controlled to be 11.8%-13.4%; the mass percentage content of Zn is controlled to be 1.5-2.0%; the mass percentage ratio of Zn / (Gd+Y) is controlled to be 0.2-0.25; the mass percentage content of Zr is controlled to be 0.4-0.7%; and the mass percentage content of Nd is controlled to be 0.1-0.3%.

[0062] The present invention is described with reference to the following examples. The mass percentage composition of the magnesium alloys in the following examples and comparative examples is shown in Table 1:

[0063] Table 1 Mass percentage composition of each embodiment and comparative example

[0064]

[0065] The master alloys used in the preparation processes of the following examples and comparative examples are Mg-(20-40) wt% Gd, Mg-(20-40) wt% Y, Mg-(20-40) wt% Nd, and Mg-(20-40) wt% Zr master alloys. These master alloys are composed of two elements, primarily to facilitate the precise addition of refractory metals, reactive metals, or high-melting-point metals to the base metal melt. The following examples and comparative examples utilize master alloys composed of two elements: Mg-20 wt% Gd, Mg-20 wt% Y, Mg-20 wt% Nd, and Mg-20 wt% Zr.

[0066] Example 1

[0067] This embodiment provides a magnesium alloy, the mass percentage composition of each component of which is shown in Table 1, and is prepared by the following preparation method:

[0068] S1. Semi-continuous casting:

[0069] (1) Under the protection of inert atmosphere argon, heat the melting furnace to 610℃, add pure magnesium ingot, and continue to heat the melting furnace after the magnesium ingot is melted.

[0070] (2) After the smelting furnace is heated to 730°C, pure zinc ingots and refining agent RJ-5 are added. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed and the smelting furnace is continued to heat up.

[0071] (3) After the melting furnace is heated to 770°C, Mg-Gd master alloy, Mg-Y master alloy, Mg-Nd master alloy, Mg-Zr master alloy and refining agent RJ-5 are added in proportion. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed.

[0072] (4) Cool the smelting furnace to 670°C, let it stand to cool down, and remove the oxide scale and bottom slag; then continue to heat the smelting furnace to 770°C, let it stand to heat up, and remove the oxide scale and bottom slag.

[0073] The refining furnace is covered and sealed, the draft tube is heated, and argon gas is passed to press the magnesium alloy melt into the crystallizer to start casting. After the casting is completed, the ingot is taken out by a crane.

[0074] S2. Homogenization heat treatment: The magnesium alloy ingot obtained in step 1 is subjected to homogenization heat treatment. The temperature of the first step of homogenization heat treatment is 490° C. and kept warm for 26 hours. The temperature of the second step of aging treatment is 210° C. and kept warm for 24 hours.

[0075] S3. Multi-directional forging: The magnesium alloy ingot is placed in a resistance furnace for preheating, the resistance furnace temperature is set to 490°C, and kept warm for 8 hours; a hydraulic press is used to perform two-fire multi-directional forging on the ingot, the first fire forging temperature is 500°C, the second fire forging temperature is 450°C, the intermediate annealing temperature is 460°C, and the heat preservation is 4 hours; the pressing speed is 8 mm / s, the number of upsetting and drawing reversals is 2 times, the upsetting single pass pressing amount is 25%, the drawing single pass pressing amount is 15%, the total number of forging passes is 35, and after each reversal, the axial direction of the forging blank is perpendicular to the axial direction of the ingot before forging, and the billet height-to-diameter ratio after each reversal is 1.8.

[0076] S4. Aging heat treatment: Place the magnesium alloy forging blank into a resistance furnace for aging heat treatment. The aging heat treatment temperature is 230° C. and the time is 72 hours.

[0077] Example 2

[0078] This embodiment provides a magnesium alloy, the mass percentage composition of each component of which is shown in Table 1, and is prepared by the following preparation method:

[0079] S1. Semi-continuous casting:

[0080] (1) Under the protection of inert atmosphere argon, heat the melting furnace to 590℃, add pure magnesium ingot, and continue to heat the melting furnace after the magnesium ingot is melted.

[0081] (2) After the smelting furnace is heated to 700°C, pure zinc ingots and refining agent RJ-5 are added. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed and the smelting furnace is continued to heat up.

[0082] (3) After the melting furnace is heated to 750°C, Mg-Gd master alloy, Mg-Y master alloy, Mg-Nd master alloy, Mg-Zr master alloy and refining agent RJ-5 are added in proportion. After the melting is completed, argon is introduced for stirring. After the refining is completed, the bottom slag is removed.

[0083] (4) Cool the smelting furnace to 650℃, let it stand and cool down, and remove the oxide scale and bottom slag. Continue to heat the smelting furnace to 750℃, let it stand and heat up, and remove the oxide scale and bottom slag.

[0084] The refining furnace is covered and sealed, the draft tube is heated, and argon gas is passed to press the magnesium alloy melt into the crystallizer to start casting. After the casting is completed, the ingot is taken out by a crane.

[0085] S2. Homogenization heat treatment: The magnesium alloy ingot obtained in step 1 is subjected to homogenization heat treatment. The temperature of the first step of homogenization heat treatment is 500° C. and kept warm for 20 hours. The temperature of the second step of aging treatment is 240° C. and kept warm for 20 hours.

[0086] S3. Multi-directional forging: The magnesium alloy ingot is placed in a resistance furnace for preheating, the temperature of the resistance furnace is set to 480°C, and kept warm for 8 hours; a hydraulic press is used to perform two-fire multi-directional forging on the ingot, the forging temperature of the first fire is 480°C, the forging temperature of the second fire is 470°C, the intermediate annealing temperature is 470°C, and the temperature is kept warm for 2 hours; the pressing speed is 9 mm / s, the number of reversals between upsetting and drawing is 2 times, the single-pass downsetting reduction is 30%, the single-pass downsetting reduction is 10%, and the total number of forging passes is 35. After each reversal, the axial direction of the forging blank is perpendicular to the axial direction of the ingot before forging, and the aspect ratio of the blank after each reversal is 1.9.

[0087] S4. Aging heat treatment: Place the magnesium alloy forging blank into a resistance furnace for aging heat treatment. The aging heat treatment temperature is 190° C. and the time is 60 hours.

[0088] Example 3

[0089] This embodiment provides a magnesium alloy, the mass percentage composition of each component of which is shown in Table 1, and is prepared by the following preparation method:

[0090] S1. Semi-continuous casting:

[0091] (1) Under the protection of inert atmosphere argon, heat the melting furnace to 600℃, add pure magnesium ingot, and continue to heat the melting furnace after the magnesium ingot is melted.

[0092] (2) After the smelting furnace is heated to 720℃, pure zinc ingots and refining agent RJ-5 are added. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed and the smelting furnace is continued to heat up.

[0093] (3) After the melting furnace is heated to 760°C, Mg-Gd master alloy, Mg-Y master alloy, Mg-Nd master alloy, Mg-Zr master alloy and refining agent RJ-5 are added in proportion. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed.

[0094] (4) Cool the smelting furnace to 660℃, let it stand and cool down, and remove the oxide scale and bottom slag. Continue to heat the smelting furnace to 760℃, let it stand and heat up, and remove the oxide scale and bottom slag.

[0095] The refining furnace is covered and sealed, the draft tube is heated, and argon gas is passed to press the magnesium alloy melt into the crystallizer to start casting. After the casting is completed, the ingot is taken out by a crane.

[0096] S2. Homogenization heat treatment: The magnesium alloy ingot obtained in step 1 is subjected to homogenization heat treatment. The temperature of the first step of homogenization heat treatment is 490° C. and kept warm for 24 hours. The temperature of the second step of aging treatment is 220° C. and kept warm for 15 hours.

[0097] S3. Multi-directional forging: The magnesium alloy ingot is placed in a resistance furnace for preheating, the resistance furnace temperature is set to 495°C, and kept warm for 8 hours; a hydraulic press is used to perform two-fire multi-directional forging on the ingot, the first fire forging temperature is 495°C, the second fire forging temperature is 465°C, the intermediate annealing temperature is 470°C, and the heat is kept for 2 hours; the pressing speed is 8 mm / s, the number of upsetting and drawing reversals is 3 times, the upsetting single pass pressing amount is 35%, the drawing single pass pressing amount is 15%, the total number of forging passes is 30, and after each reversal, the axial direction of the forging blank is perpendicular to the axial direction of the ingot before forging, and the billet height-to-diameter ratio after each reversal is 2.0.

[0098] S4. Aging heat treatment: Place the magnesium alloy forging blank into a resistance furnace for aging heat treatment. The aging heat treatment temperature is 220° C. and the time is 24 hours.

[0099] Example 4

[0100] This embodiment provides a magnesium alloy, the mass percentage composition of each component of which is shown in Table 1, and is prepared by the following preparation method:

[0101] S1. Semi-continuous casting:

[0102] (1) Under the protection of inert atmosphere argon, heat the melting furnace to 610℃, add pure magnesium ingot, and continue to heat the melting furnace after the magnesium ingot is melted.

[0103] (2) After the smelting furnace is heated to 730°C, pure zinc ingots and refining agent RJ-5 are added. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed and the smelting furnace is continued to heat up.

[0104] (3) After the melting furnace is heated to 760°C, Mg-Gd master alloy, Mg-Y master alloy, Mg-Nd master alloy, Mg-Zr master alloy and refining agent RJ-5 are added in proportion. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed.

[0105] (4) Cool the smelting furnace to 660℃, let it stand to cool down, and remove the oxide scale and bottom slag. Continue to heat the smelting furnace to 760℃, let it stand to heat up, and remove the oxide scale and bottom slag.

[0106] The refining furnace is covered and sealed, the draft tube is heated, and argon gas is passed to press the magnesium alloy melt into the crystallizer to start casting. After the casting is completed, the ingot is taken out by a crane.

[0107] S2. Homogenization heat treatment: The magnesium alloy ingot obtained in step 1 is subjected to homogenization heat treatment. The temperature of the first step of homogenization heat treatment is 480° C. and kept warm for 28 hours. The temperature of the second step of aging treatment is 220° C. and kept warm for 12 hours.

[0108] S3. Multi-directional forging: The magnesium alloy ingot is placed in a resistance furnace for preheating, the temperature of the resistance furnace is set to 490°C, and kept warm for 8 hours; a hydraulic press is used to perform two-fire multi-directional forging on the ingot, the forging temperature of the first fire is 490°C, the forging temperature of the second fire is 460°C, the intermediate annealing temperature is 470°C, and the temperature is kept warm for 2 hours; the pressing speed is 8 mm / s, the number of reversals of upsetting and drawing is 3 times, the single-pass pressing amount of upsetting is 30%, the single-pass pressing amount of drawing is 20%, and the total number of forging passes is 32. After each reversal, the axial direction of the forging blank is perpendicular to the axial direction of the ingot before forging, and the aspect ratio of the blank after each reversal is 1.6.

[0109] S4. Aging heat treatment: Place the magnesium alloy forging blank into a resistance furnace for aging heat treatment. The aging heat treatment temperature is 220° C. and the time is 48 hours.

[0110] Comparative Example 1

[0111] This comparative example provides a magnesium alloy, the mass percentage composition of each component of which is shown in Table 1, which is prepared by the following preparation method:

[0112] S1. Semi-continuous casting:

[0113] (1) Under the protection of inert atmosphere argon, heat the melting furnace to 610℃, add pure magnesium ingot, and continue to heat the melting furnace after the magnesium ingot is melted.

[0114] (2) After the melting furnace is heated to 760°C, Mg-Gd master alloy, Mg-Y master alloy, Mg-Nd master alloy, Mg-Zr master alloy and refining agent RJ-5 are added in proportion. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed.

[0115] (3) Cool the smelting furnace to 660℃, let it stand to cool down, and remove the oxide scale and bottom slag. Continue to heat the smelting furnace to 770℃, let it stand to heat up, and remove the oxide scale and bottom slag.

[0116] The refining furnace is covered and sealed, the draft tube is heated, and argon gas is passed to press the magnesium alloy melt into the crystallizer to start casting. After the casting is completed, the ingot is taken out by a crane.

[0117] S2. Homogenization heat treatment: The magnesium alloy ingot obtained in step 1 is subjected to homogenization heat treatment. The temperature of the first step of homogenization heat treatment is 480° C. and kept warm for 28 hours. The temperature of the second step of aging treatment is 220° C. and kept warm for 12 hours.

[0118] S3. Multi-directional forging: The magnesium alloy ingot is placed in a resistance furnace for preheating, the resistance furnace temperature is set to 490°C, and kept warm for 8 hours; a hydraulic press is used to perform two-fire multi-directional forging on the ingot, the first fire forging temperature is 490°C, the second fire forging temperature is 460°C, the intermediate annealing temperature is 470°C, and the heat is kept for 2 hours; the pressing speed is 8 mm / s, the number of upsetting and drawing reversals is 2 times, the upsetting single pass pressing amount is 30%, the drawing single pass pressing amount is 20%, the total number of forging passes is 32, and after each reversal, the axial direction of the forging blank is perpendicular to the axial direction of the ingot before forging, and the billet height-to-diameter ratio after each reversal is 1.7.

[0119] S4. Aging heat treatment: Place the magnesium alloy forging blank into a resistance furnace for aging heat treatment. The aging heat treatment temperature is 220° C. and the time is 48 hours.

[0120] Comparative Example 2

[0121] This embodiment provides a magnesium alloy, the mass percentage composition of each component of which is shown in Table 1, and is prepared by the following preparation method:

[0122] S1. Semi-continuous casting:

[0123] (1) Under the protection of inert atmosphere argon, heat the melting furnace to 600℃, add pure magnesium ingot, and continue to heat the melting furnace after the magnesium ingot is melted.

[0124] (2) After the smelting furnace is heated to 720℃, pure zinc ingots and refining agent RJ-5 are added. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed and the smelting furnace is continued to heat up.

[0125] (3) After the melting furnace is heated to 760°C, Mg-Gd master alloy, Mg-Y master alloy, Mg-Nd master alloy, Mg-Zr master alloy and refining agent RJ-5 are added in proportion. After the melting is completed, argon gas is introduced for stirring. After the refining is completed, the bottom slag is removed.

[0126] (4) The melting furnace is cooled to 660°C, and allowed to cool down. The oxide scale and bottom slag are removed. The melting furnace is further heated to 760°C, and allowed to cool down. The oxide scale and bottom slag are removed. The refining furnace is sealed with a lid, the draft tube is heated, and argon gas is passed to press the magnesium alloy melt into the crystallizer. Casting begins. After the casting is completed, the ingot is removed by a crane.

[0127] S2. Homogenization heat treatment: The magnesium alloy ingot obtained in step 1 is subjected to homogenization heat treatment. The temperature of the first step of homogenization heat treatment is 490° C. and kept warm for 24 hours. The temperature of the second step of aging treatment is 220° C. and kept warm for 15 hours.

[0128] S3. Multi-directional forging: Place the magnesium alloy ingot in a resistance furnace for preheating, set the resistance furnace temperature to 490℃, and keep it warm for 8 hours; use a hydraulic press to perform single-fire multi-directional forging on the ingot, and the forging temperature is 490℃; the pressing speed is 8mm / s, the number of reversals between upsetting and drawing is 1, the single-pass downsetting reduction is 20%, the single-pass downsetting reduction is 10%, and the total number of forging passes is 20. After each reversal, the axial direction of the forging blank is perpendicular to the axial direction of the ingot before forging, and the billet height-to-diameter ratio after each reversal is 1.3.

[0129] S4. Aging heat treatment: Place the magnesium alloy forging blank into a resistance furnace for aging heat treatment. The aging heat treatment temperature is 220° C. and the time is 24 hours.

[0130] In order to verify the feasibility and effectiveness of the present invention, the following tests were performed on the magnesium alloy samples prepared in the above embodiments and comparative examples:

[0131] 1. Metallographic (OM) analysis

[0132] The magnesium alloy samples prepared in the examples and comparative examples were subjected to metallographic microscopic analysis. Figure 1-2 As shown, Figure 1 (a) is the magnesium alloy of Example 1, Figure 1 (b) is the magnesium alloy of Example 2, Figure 1(c) is the magnesium alloy of Example 3, Figure 1 (d) is the magnesium alloy of Example 4; Figure 2 (a) is the magnesium alloy of Comparative Example 1, Figure 2 (b) is the magnesium alloy of Comparative Example 2.

[0133] As can be seen from the figure, the Figure 1 The grain structures of the magnesium alloys (a), 1(b), 1(c), and 1(d) are similar, with a high degree of grain refinement and good elongation due to the presence of LPSO phase due to the addition of Zn.

[0134] Figure 2 The magnesium alloy of Comparative Example 1 shown in (a) has a high degree of grain refinement, but due to the lack of Zn addition and the absence of LPSO phase, the elongation is low; Figure 2 The magnesium alloy of Comparative Example 2 shown in (b) has coarse grains and low strength due to insufficient multi-directional forging deformation.

[0135] 2. Tests of tensile strength, yield strength and elongation at room temperature (25°C) and high temperature (200°C).

[0136] Please briefly describe the specific test methods for tensile strength, yield strength, and elongation, or cite the test methods in the corresponding standards (specify the standard number). Room temperature mechanical properties were tested in accordance with GB / T 228.1-2021, and high temperature mechanical properties were tested in accordance with GB / T 228.2-2015. The experimental results are shown in Tables 1 and 2.

[0137] Table 1 Room temperature mechanical properties of magnesium alloys in Examples 1-4

[0138]

[0139] Table 2 Room temperature mechanical properties of magnesium alloys in comparative examples 1-2

[0140]

[0141] As shown in Tables 1-2 above, Comparative Example 1, which did not add Zn but followed the process of the present invention, resulted in a lower elongation. Comparative Example 2, which reduced the number of fires and deformation during the multi-directional forging process, also resulted in a lower strength.

[0142] In summary, the scheme of the present application can obtain the Mg-Gd-Y-Zn-Nd-Zr wrought magnesium alloy with the improved strength and plasticity by optimizing the alloy component design, equipping the reasonable homogenization heat treatment process, forging process and aging heat treatment process, and has excellent high temperature resistance. The tensile strength at room temperature reaches above 450MPa, the yield strength reaches above 340MPa, and the elongation is more than 10%; the tensile strength at 200 DEG C high temperature can still reach above 380MPa, the yield strength reaches above 280MPa, and the elongation is more than 15%.

[0143] The above has described the embodiments of the present application, the above description is exemplary, is not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A high-strength, high-temperature-resistant deformable magnesium alloy, characterized in that: The following components are included in mass percentage: Gd: 8.0%~10.0%; Y：2.5％～4.0％； Zn: 1.5% to 3.0%; Zr：0.3％～0.8％； Nd: 0.1%~0.5%; Moreover, the total mass percentage of Gd and Y is: 11.5% to 13.5%; Zn / (Gd+Y)=0.15 to 0.3; The balance is magnesium and other inevitable impurity elements.

2. The high-strength, high-temperature-resistant deformable magnesium alloy according to claim 1, characterized in that: The mass percentage content of Gd is controlled to be 8.5%-9.5%, the mass percentage content of Y is controlled to be 2.8%-3.8%, and the mass percentage content of (Gd+Y) is controlled to be 11.8%-13.4%.

3. The high-strength, high-temperature-resistant deformable magnesium alloy according to claim 2, characterized in that: The mass percentage content of Zn is controlled to be 1.5-2.0%; the mass percentage ratio of Zn / (Gd+Y) is controlled to be 0.2-0.

25.

4. The high-strength, high-temperature-resistant deformable magnesium alloy according to claim 1, characterized in that: The mass percentage content of Zr is controlled to be 0.4-0.7%.

5. The high-strength, high-temperature-resistant deformable magnesium alloy according to claim 1, characterized in that: The mass percentage content of Nd is controlled to be 0.1-0.3%.

6. A method for preparing a high-strength, high-temperature resistant deformable magnesium alloy according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Semi-continuous casting: After the raw materials are melted, they are semi-continuously cast to obtain magnesium alloy ingots; S2. Homogenization heat treatment: subjecting the magnesium alloy ingot to a two-step homogenization heat treatment, firstly solution treatment and then aging treatment, to obtain a magnesium alloy ingot after homogenization heat treatment; S3, multi-directional forging: the magnesium alloy ingot after homogenization heat treatment is subjected to multi-directional forging to obtain a forged magnesium alloy part, wherein the multi-directional forging step comprises at least a first forging at 480-500° C. and a second forging at 450-470° C.; S4. Aging heat treatment: The magnesium alloy forgings are kept at 190℃~230℃ for 24~72h for aging treatment.

7. The preparation method according to claim 6, characterized in that In step S1, the process of smelting the raw materials includes: (1) Under the protection of an inert atmosphere, the melting temperature is raised to 590-610°C, a preset proportion of pure magnesium ingots are added, and after the magnesium ingots are melted, the melting temperature is continued to be raised; (2) After the smelting temperature rises to 700-730°C, add a preset proportion of pure zinc ingots and refining agent, introduce inert gas and stir after the melting is completed, remove the bottom slag after the refining is completed, and continue to increase the smelting temperature; (3) After the melting temperature rises to 750-770°C, Mg-Gd master alloy, Mg-Y master alloy, Mg-Nd master alloy, Mg-Zr master alloy and refining agent are added in proportion. After the melting is completed, inert gas is introduced for stirring. After the refining is completed, the bottom slag is removed; (4) Lower the smelting temperature to 650-670°C, let it stand and cool down, and remove the oxide scale and bottom slag; then raise the smelting temperature to 750-770°C, let it stand and heat up, and remove the oxide scale and bottom slag.

8. The preparation method according to claim 6, characterized in that The conditions for the first step of the homogenization heat treatment in step S2, the solution treatment, are: keeping warm at 480-500°C for 20-28 hours; the conditions for the second step of the aging treatment are: keeping warm at 210-240°C for 12-24 hours.

9. The preparation method according to claim 6, characterized in that In the multi-stage casting process of step S3, the pressing speed is 5-10 mm / s, the number of reversals of upsetting and drawing is 1-3 times, the pressing amount of a single upsetting pass is 25%-35%, the pressing amount of a single drawing pass is 10%-20%, the total forging passes are ≥30 passes, and after each reversal, the axial direction of the forging blank is perpendicular to the axial direction of the ingot before forging, and the aspect ratio of the blank after each reversal is 1.2-2.

5.

10. The preparation method according to claim 6, characterized in that Between the first forging and the second forging in step S3, an intermediate annealing step is also included. The temperature of the intermediate annealing step is 460-470° C. and the annealing time is 2-4 hours.

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