A magnesium-gadolinium-neodymium-calcium-zirconium alloy, its preparation method and application

Abstract

This invention belongs to the field of magnesium alloy technology, specifically relating to a magnesium-gadolinium-neodymium-calcium-zirconium alloy, its preparation method, and its applications. The magnesium-gadolinium-neodymium-calcium-zirconium alloy provided by this invention comprises the following elemental components by mass percentage: 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 content of the heavy rare earth element gadolinium 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). Utilizing the synergistic effect of these dissimilar elements, the solid solubility of each element in magnesium is reduced. Combined with low-temperature positive extrusion and short-term creep aging treatment, this promotes the precipitation of nanoscale second phases, resulting in a large number of nanoscale second phases 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.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy technology, specifically relating to a magnesium-gadolinium-neodymium-calcium-zirconium alloy, its preparation method, and its application. Background Technology

[0002] The "dual carbon" goals and vision have made lightweighting of mass transportation vehicles such as automobiles and rail transit an urgent priority. Magnesium and its alloys are currently the lightest metallic structural materials, possessing advantages such as low density, high specific strength and specific stiffness, and easy recyclability. They are hailed as "green structural materials" of the 21st century and have demonstrated significant application value and promising prospects in transportation, energy, aerospace, and other fields. However, the low absolute strength and poor low-temperature deformation capacity of magnesium alloys greatly limit the application of magnesium and magnesium alloys.

[0003] Precipitation strengthening and grain refinement are effective ways to improve the strength of magnesium alloys. Precipitation strengthening can be achieved through alloying and heat treatment; the addition of alloying elements can induce the precipitation of second phases, thus producing a precipitation strengthening effect. Rare earth magnesium alloys have attracted widespread attention due to their good age-hardening effect; however, the high price of rare earth elements hinders industrial applications. To reduce costs, it is necessary to develop high-strength, low-alloy Mg-RE magnesium alloys. However, low rare earth content results in insufficient motivation for second phase precipitation. Therefore, increasing the amount of second phase in low-rare earth content magnesium alloys becomes crucial for designing low-cost, high-performance magnesium alloys.

[0004] To obtain a fine-grained microstructure and further improve the properties of magnesium alloys through grain refinement strengthening, extrusion, a simple and efficient plastic deformation method, is often employed. However, in the extrusion process, increasing the extrusion temperature reduces the strength of the magnesium alloy, leading to increased costs or reduced final product efficiency. Therefore, it is necessary to develop new high-performance magnesium alloys for low-temperature extrusion. Although low-temperature extrusion can effectively improve the strength of magnesium alloys, it creates significant residual stress, reducing plasticity. Heat treatment is an effective means to eliminate residual stress, promote the precipitation of precipitates, and improve the mechanical properties of magnesium alloys. Traditional aging treatment precipitates a large amount of second phase, forming precipitation strengthening and effectively improving strength. However, traditional aging treatment requires a long time, which significantly reduces the productivity of the actual magnesium alloy forming process and increases energy consumption and production costs. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a magnesium-gadolinium-neodymium-calcium-zirconium alloy, its preparation method and application. The magnesium-gadolinium-neodymium-calcium-zirconium alloy provided by the present invention has both high strength and high plasticity. The preparation method, based on the effective alloying element design, combines low-temperature extrusion and creep aging, which can effectively shorten the preparation time and reduce the cost.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a magnesium-gadolinium-neodymium-calcium-zirconium alloy, comprising the following elemental components by mass percentage:

[0008] Gadolinium 3-6%, neodymium 0.5-2%, calcium 0.1-1.5%, zirconium 0.2-0.8%, with the balance being magnesium.

[0009] This invention also provides a method for preparing the magnesium-gadolinium-neodymium-calcium-zirconium alloy described above, comprising the following steps:

[0010] According to the elemental composition of the magnesium-gadolinium-neodymium-calcium-zirconium alloy described in the above technical solution, the alloy liquid of the metal raw material and the refining agent are mixed and refined under a protective gas. The resulting refined alloy liquid is then cast to obtain an alloy ingot.

[0011] The alloy ingot was subjected to solution heat treatment and quenching in sequence to obtain the extrusion sample;

[0012] The sample to be extruded is placed in an extrusion die and preheated and extruded sequentially to obtain an extruded sample;

[0013] The preheating temperature is 300–330°C;

[0014] The extrusion temperature is 300–330°C;

[0015] The extruded specimen was subjected to tensile-compressive cyclic stress creep aging to obtain a magnesium-gadolinium-neodymium-calcium-zirconium alloy.

[0016] The tensile-compression cyclic stress creep aging time is 0.5 to 16 hours.

[0017] Preferably, the refining agent comprises the following components in parts by mass: 49 parts potassium chloride, 24 parts calcium chloride, 14 parts barium chloride, 6 parts gadolinium chloride, 5 parts calcium fluoride, and 2 parts sodium chloride.

[0018] Preferably, the protective gas comprises sulfur hexafluoride and carbon dioxide; the volume ratio of sulfur hexafluoride to carbon dioxide is 1:99.

[0019] Preferably, the method for preparing the alloy liquid of the metal raw material includes the following steps:

[0020] Pure magnesium is heated for a period of time to obtain molten magnesium;

[0021] Pure gadolinium was added to the magnesium liquid and heated in two stages to obtain a magnesium-gadolinium mixture.

[0022] A magnesium-zirconium master alloy was added to the magnesium-gadolinium mixture and heated in three stages to obtain a magnesium-gadolinium-zirconium mixture.

[0023] Magnesium-neodymium master alloy and magnesium-calcium master alloy are added to the magnesium-gadolinium-zirconium mixture and heated in four stages to obtain an alloy liquid of metal raw materials.

[0024] The first-stage heating, second-stage heating, third-stage heating, and fourth-stage heating are all carried out under a protective gas atmosphere.

[0025] Preferably, the solution heat treatment temperature is 500-530℃ and the holding time is 4-8h; the quenching is performed with water at 25℃.

[0026] Preferably, the preheating holding time is 60 minutes.

[0027] Preferably, the extrusion ratio is 16:1, and the extrusion speed is 1 mm / s.

[0028] Preferably, the temperature for the tensile-compressive cyclic stress creep aging is 250°C, and the stress value is 50–100 MPa.

[0029] The present invention also provides the application of the magnesium-gadolinium-neodymium calcium-zirconium alloy described in the above technical solution or the magnesium-gadolinium-neodymium calcium-zirconium alloy prepared by the preparation method described in the above technical solution in lightweight equipment.

[0030] This invention provides a magnesium-gadolinium-neodymium-calcium-zirconium alloy, comprising the following components by mass percentage: gadolinium 3-6%, neodymium 0.5-2%, calcium 0.1-1.5%, zirconium 0.2-0.8%, with the balance being magnesium. In this invention, the gadolinium content is reduced to below 6 wt.%, and a small amount of the less dense light rare earth element (neodymium) and the inexpensive alkaline earth metal element (calcium) are added. Utilizing the synergistic effect of these dissimilar elements, the solid solubility of each element in magnesium is reduced. Combined with lower-temperature positive extrusion and short-term creep aging treatment, the precipitation of nanoscale second phases is promoted. The abundant precipitated nanoscale second phases are uniformly distributed in the magnesium matrix, promoting dynamic recrystallization, refining the microstructure, and enhancing the mechanical properties of the magnesium alloy. This results in a magnesium-gadolinium-neodymium-calcium-zirconium alloy possessing both high strength and high plasticity. The results of the examples show that the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared by this invention exhibits a typical bimodal microstructure (composed of fine dynamically recrystallized grains and dynamically recrystallized grains elongated along the extrusion direction) after extrusion deformation and creep aging. The grain size is approximately 1.52 μm, the yield strength is approximately 285.68 MPa, and the elongation is approximately 16.56%. This invention achieves a high balance between strength and plasticity in the low-cost preparation of magnesium-gadolinium-neodymium-calcium-zirconium alloy, effectively expanding the research and development of this alloy system in the scientific research field and possessing broad market application prospects.

[0031] This invention also provides a method for preparing the aforementioned magnesium-gadolinium-neodymium-calcium-zirconium alloy. This method, through low-temperature extrusion, achieves grain refinement while introducing a large number of crystal defects such as dislocations, providing ample nucleation sites and high driving energy for the precipitation of the second phase. Combined with creep aging, it effectively integrates conventional aging treatment with creep forming, introducing stress during aging to increase dislocation concentration, providing nucleation sites for the second phase precipitation, and accelerating the diffusion of solute atoms. Without grain growth, it promotes the precipitation of a large number of nanoscale second phases in a short time, significantly shortening the peak aging time and achieving a synergistic effect of solid solution strengthening, grain refinement strengthening, and Orowan strengthening, thus simultaneously improving the strength and plasticity of the magnesium alloy. Compared to high-strength, high-rare-earth magnesium alloys and complex and expensive large plastic deformation techniques, the preparation method provided by this invention has advantages such as low cost, simple process, and short process flow, greatly saving costs and possessing certain economic benefits and application potential. Attached Figure Description

[0032] Figure 1 This is a flowchart of the method for preparing magnesium-gadolinium-neodymium-calcium-zirconium alloy according to the present invention;

[0033] Figure 2 A schematic diagram of the specimen used for tensile-compressive cyclic stress creep aging;

[0034] Figure 3 Optical micrograph (OM) of the magnesium gadolinium-zirconium alloy prepared in Comparative Example 1;

[0035] Figure 4 Optical micrograph (OM) of the magnesium gadolinium neodymium zirconium alloy prepared in Comparative Example 2;

[0036] Figure 5 Optical micrograph (OM) of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 1;

[0037] Figure 6 The image shows a scanning electron microscope (SEM) image of the magnesium-gadolinium-zirconium alloy prepared in Comparative Example 1.

[0038] Figure 7 Scanning electron microscopy (SEM) image of the magnesium gadolinium neodymium zirconium alloy prepared in Comparative Example 2;

[0039] Figure 8 Scanning electron microscopy (SEM) image of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 1;

[0040] Figure 9 Transmission electron microscopy (TEM) image of the magnesium gadolinium neodymium zirconium alloy prepared for Comparative Example 2;

[0041] Figure 10 Transmission electron microscopy (TEM) image of the magnesium gadolinium neodymium calcium zirconium alloy prepared in Example 1;

[0042] Figure 11 This is a schematic diagram of a specimen for room temperature tensile property testing.

[0043] Figure 12 Tensile stress-strain diagram of the magnesium-gadolinium-zirconium alloy prepared for Comparative Example 1 at room temperature;

[0044] Figure 13 Tensile stress-strain diagram of the magnesium-gadolinium-neodymium-zirconium alloy prepared in Comparative Example 2 at room temperature;

[0045] Figure 14 The tensile stress-strain diagram of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 1 at room temperature;

[0046] Figure 15 The tensile stress-strain diagram of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 2 at room temperature;

[0047] Figure 16 The tensile stress-strain diagram of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 3 at room temperature. Detailed Implementation

[0048] This invention provides a magnesium-gadolinium-neodymium-calcium-zirconium alloy, comprising the following elemental components by mass percentage:

[0049] Gadolinium 3-6%, neodymium 0.5-2%, calcium 0.1-1.5%, zirconium 0.2-0.8%, with the balance being magnesium.

[0050] In this invention, the magnesium-gadolinium-neodymium-calcium-zirconium alloy preferably comprises the following elemental components by mass percentage:

[0051] Gadolinium 4-5%, neodymium 0.5-1.5%, calcium 0.5-1.5%, zirconium 0.4-0.6%, with the balance being magnesium.

[0052] 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. The large number of precipitated nanoscale second phases are uniformly distributed in the magnesium matrix, promoting dynamic recrystallization, making the microstructure more refined, and enhancing the mechanical properties of the magnesium alloy. This results in a magnesium-gadolinium-neodymium-calcium-zirconium alloy that simultaneously possesses high strength and high plasticity.

[0053] This invention also provides a method for preparing the magnesium-gadolinium-neodymium-calcium-zirconium alloy described above, comprising the following steps:

[0054] According to the elemental composition of the magnesium-gadolinium-neodymium-calcium-zirconium alloy described in the above technical solution, the alloy liquid of the metal raw material and the refining agent are mixed and refined under a protective gas. The resulting refined alloy liquid is then cast to obtain an alloy ingot.

[0055] The alloy ingot was subjected to solution heat treatment and quenching in sequence to obtain the extrusion sample;

[0056] The sample to be extruded is placed in an extrusion die and preheated and extruded sequentially to obtain an extruded sample;

[0057] The preheating temperature is 300–330°C;

[0058] The extrusion temperature is 300–330°C;

[0059] The extruded specimen was subjected to tensile-compressive cyclic stress creep aging to obtain a magnesium-gadolinium-neodymium-calcium-zirconium alloy.

[0060] The tensile-compression cyclic stress creep aging time is 0.5 to 16 hours.

[0061] Unless otherwise specified, the present invention does not have special requirements on the source of the raw materials used in the preparation, and commercially available products well known to those skilled in the art can be used.

[0062] According to the elemental composition of the magnesium-gadolinium-neodymium-calcium-zirconium alloy described in the above technical solution, the present invention mixes the alloy liquid of the metal raw material with the refining agent and refines it under a protective gas to obtain a refined alloy liquid.

[0063] In this invention, the refining agent preferably comprises the following components by mass: 49 parts potassium chloride, 24 parts calcium chloride, 14 parts barium chloride, 6 parts gadolinium chloride, 5 parts calcium fluoride, and 2 parts sodium chloride; the mass of the refining agent is preferably 0.5 to 1.5% of the total mass of the alloy liquid of the metal raw materials, more preferably 0.8 to 1.2%.

[0064] In this invention, the protective gas preferably comprises sulfur hexafluoride and carbon dioxide; the volume ratio of sulfur hexafluoride and carbon dioxide is preferably 1:99.

[0065] Before refining, the present invention preferably dries the refining agent. The present invention does not have any particular limitation on the drying process; any drying process well known in the art can be used.

[0066] In this invention, the method for preparing the alloy liquid of the metal raw material preferably includes the following steps:

[0067] Pure magnesium is heated for a period of time to obtain molten magnesium;

[0068] Pure gadolinium was added to the magnesium liquid and heated in two stages to obtain a magnesium-gadolinium mixture.

[0069] A magnesium-zirconium master alloy was added to the magnesium-gadolinium mixture and heated in three stages to obtain a magnesium-gadolinium-zirconium mixture.

[0070] Magnesium-neodymium master alloy and magnesium-calcium master alloy are added to the magnesium-gadolinium-zirconium mixture and heated in four stages to obtain an alloy liquid of metal raw materials.

[0071] The first-stage heating, second-stage heating, third-stage heating, and fourth-stage heating are all carried out under a protective gas atmosphere.

[0072] Under a protective gas atmosphere, the present invention preferably involves heating pure magnesium in a single stage to obtain molten magnesium. In this invention, the purity of the pure magnesium is preferably not less than 99.99%; the pure magnesium is preferably pure magnesium block; the temperature of the single-stage heating is preferably 720°C, and the holding time is 30 minutes; the present invention does not have a specific limitation on the holding time of the single-stage heating, as long as the solid raw material is completely melted into a liquid state.

[0073] After the heating process is completed, the present invention preferably removes the slag from the surface of the magnesium liquid.

[0074] After obtaining the magnesium liquid, the present invention preferably adds pure gadolinium to the magnesium liquid for two-stage heating to obtain a magnesium-gadolinium mixture. In the present invention, the purity of the pure gadolinium is preferably not less than 99.99%; the pure gadolinium is preferably pure gadolinium particles; the particle size of the pure gadolinium particles is preferably 0.5-2 mm, more preferably 1-1.5 mm; the temperature of the two-stage heating is preferably 780°C, and the holding time is preferably 30 min; the present invention does not have a special limitation on the holding time of the two-stage heating, as long as the solid raw material is completely melted into a liquid state.

[0075] After the two-stage heating is completed, the present invention preferably removes the scum from the surface of the magnesium-gadolinium mixture.

[0076] After obtaining the magnesium-gadolinium mixture, the present invention preferably adds a magnesium-zirconium master alloy to the magnesium-gadolinium mixture and performs three-stage heating to obtain a magnesium-gadolinium-zirconium mixture. In the present invention, the zirconium mass percentage in the magnesium-zirconium master alloy is preferably not less than 30.00%; the temperature of the three-stage heating is preferably 780°C, and the holding time is preferably 20 minutes; the present invention does not have a special limitation on the holding time of the three-stage heating, as long as the solid raw materials are completely melted into a liquid state.

[0077] After the three-stage heating is completed, the present invention preferably removes the scum from the surface of the magnesium-gadolinium-zirconium mixture.

[0078] After obtaining the magnesium-gadolinium-zirconium mixture, the present invention preferably adds a magnesium-neodymium master alloy and a magnesium-calcium master alloy to the magnesium-gadolinium-zirconium mixture and performs four-stage heating to obtain an alloy liquid of the metal raw materials. In the present invention, the mass percentage of neodymium in the magnesium-neodymium master alloy is preferably not less than 30.00%; the mass percentage of calcium in the magnesium-calcium master alloy is preferably not less than 30.00%; the temperature of the three-stage heating is preferably 750°C, and the holding time is preferably 20 min; the present invention does not have a special limitation on the holding time of the four-stage heating, as long as the solid raw materials are completely melted into a liquid state.

[0079] After the four-stage heating is completed, the present invention preferably removes the slag from the surface of the alloy liquid of the metal raw material.

[0080] A refining agent was added to the magnesium-gadolinium-neodymium-calcium-zirconium mixture, and the mixture was heated in five stages. After cooling, the liquid was discharged to obtain an alloy liquid.

[0081] In this invention, the refining process is preferably carried out by adding a refining agent to the alloy liquid of the metal raw material, refining under a protective gas, cooling and then discharging the liquid to obtain a refined alloy liquid.

[0082] In this invention, after adding the refining agent, it is preferable to maintain the temperature at 750°C and stir the mixture of the refining agent and the metal raw material alloy liquid; the stirring rate is preferably 2-3 rad / s, more preferably 3 rad / s; the stirring time is preferably 1-2 min, more preferably 2 min; the refining temperature is preferably 750°C, and the holding time is preferably 25 min; the cooling is preferably reduced to 720°C; this invention does not have a special limitation on the holding time for refining, as long as the solid raw material is completely melted into a liquid state.

[0083] After the refining is completed, the present invention preferably removes the scum from the surface of the refined alloy liquid.

[0084] After the refining is completed, the present invention preferably discharges the liquid when the temperature inside the smelting furnace drops to 720°C.

[0085] In this invention, the equipment used for preparing and refining the alloy liquid of the metal raw material is preferably a smelting furnace and a crucible; the crucible is preferably a steel crucible; preferably, when the temperature in the smelting furnace reaches 300°C, the pure magnesium block is placed in the crucible, then placed in the smelting furnace, and a protective gas is introduced into the smelting furnace.

[0086] Before preparing the alloy liquid of the metal raw materials, the present invention preferably removes the oxides from the surface of the pure magnesium, pure gadolinium, magnesium-neodymium master alloy, magnesium-calcium master alloy, and magnesium-zirconium master alloy and then dries them; the preferred removal method is polishing. The present invention does not have any particular limitation on the drying process, and a drying process well known in the art can be used.

[0087] Before preparing the alloy liquid of the metal raw materials, the present invention preferably pre-treats the crucible; the pre-treatment preferably involves preheating the crucible to 300°C in a heating furnace, then sequentially applying coating I and coating II to the inner wall of the crucible. When the crucible temperature decreases and the coatings can no longer adhere to the crucible surface, the crucible is returned to the heating furnace to dry, and the above steps are repeated twice. In the present invention, coating I preferably comprises the following components by mass: 17 parts talc, 1 part water glass, and 82 parts water; coating II preferably comprises the following components by mass: 8 parts zinc oxide, 3 parts water glass, and 89 parts water.

[0088] This invention prevents impurities on the inner wall of the crucible from contaminating the solution by pre-treating the crucible.

[0089] After obtaining the refined alloy liquid, the present invention pours the refined alloy liquid to obtain an alloy ingot.

[0090] In this invention, the casting is preferably performed by pouring the refined alloy liquid into a casting mold.

[0091] Before casting, the present invention preferably preheats the casting mold and sprays it with paint I and paint II, then dries it; the preheating temperature is preferably 180-210℃, more preferably 190-200℃. The present invention does not have any particular limitation on the casting mold; any casting mold well-known in the art can be used. The present invention also does not have any particular limitation on drying; any drying process well-known in the art can be used to dry the paint.

[0092] After obtaining the alloy ingot, the present invention performs solution heat treatment and quenching on the alloy ingot in sequence to obtain the sample to be extruded.

[0093] In this invention, the solution heat treatment temperature is preferably 500-530℃, more preferably 510-520℃, and the holding time is 4-8h, more preferably 5-7h; the quenching is preferably performed with water at 25℃.

[0094] Before performing solution heat treatment, the present invention preferably removes the casting defects at both ends of the alloy ingot; the removal is preferably performed using a wire cutting machine.

[0095] After the quenching is completed, the present invention preferably performs machining on the quenched alloy ingot to obtain the extrusion sample.

[0096] In this invention, the machining is preferably performed by turning to remove the oxide scale from the surface of the quenched alloy ingot, followed by polishing. This invention does not impose any particular limitations on the turning and polishing processes; any turning and polishing methods well-known in the art can be used.

[0097] After obtaining the sample to be extruded, the present invention places the sample to be extruded in an extrusion mold and preheats and extrudes it in sequence to obtain the extruded sample.

[0098] Before placing the sample to be extruded into the extrusion die, the present invention preferably applies a lubricant to the sample to be extruded and the extrusion die; in the present invention, the lubricant is preferably graphite and petroleum jelly; the mass ratio of graphite to petroleum jelly is preferably 1:1.5.

[0099] In this invention, the sample to be extruded is preferably a cylindrical ingot with a diameter of Φ40mm×40mm; the preheating temperature is 300~330℃, preferably 310~320℃, and the holding time is preferably 60min.

[0100] In this invention, the extrusion temperature is 300-330°C, preferably 310-320°C; the extrusion ratio is preferably 16:1; and the extrusion speed is preferably 1 mm / s.

[0101] The present invention does not have any particular limitation on the extrusion die; any extrusion die well known in the art can be used.

[0102] After obtaining the extruded specimen, the present invention subjectes the extruded specimen to tensile-compressive cyclic stress creep aging to obtain a magnesium-gadolinium-neodymium-calcium-zirconium alloy.

[0103] In this invention, the temperature of the tensile-compression cyclic stress creep aging is preferably 250°C, the stress value is preferably 50-100 MPa, more preferably 70-90 MPa; the time of the tensile-compression cyclic stress creep aging is 0.5-16 h, preferably 2-5 h; and the stress value is less than the yield strength of the extrusion specimen.

[0104] In this invention, the preferred method for the tensile-compression cyclic stress creep aging is as follows: the extrusion specimen is cut into a rectangular plate-shaped specimen using a wire cutting machine, the oxide layer on the surface of the plate-shaped specimen is removed with sandpaper, and the resulting plate-shaped specimen with the oxide layer removed is hung in an RDL100 high-temperature creep testing machine equipped with an air-circulating environmental chamber. The square wave load mode is selected, and the temperature and stress values ​​are set to perform tensile-compression cyclic stress creep aging. The computer system will record the parameters during the test in real time. The specimen used for the tensile-compression cyclic stress creep aging is preferably a rectangular plate-shaped specimen with dimensions of 3mm × 10mm × 60mm.

[0105] The creep aging process used in this invention effectively combines conventional aging treatment with creep forming. Stress is introduced during the aging process to increase dislocation concentration, provide nucleation sites for the precipitation of the second phase, and accelerate the diffusion of solute atoms, thereby promoting the precipitation of the second phase. This significantly shortens the peak aging time while achieving integrated forming and forming manufacturing.

[0106] Figure 1 This is a flowchart of the method for preparing magnesium-gadolinium-neodymium-calcium-zirconium alloy according to the present invention. Figure 1 As shown, this invention involves mixing raw materials of corresponding elements, melting and casting them, removing defects from the beginning and end of the resulting alloy ingot, performing solution heat treatment, removing the surface oxide scale, applying lubricant to the extrusion sample and extrusion die, and then extruding. The resulting extruded sample is cut into rectangular plates using a wire cutting machine, and then subjected to tensile-compression cyclic stress creep aging to obtain a magnesium-gadolinium-neodymium-calcium-zirconium alloy. A schematic diagram of the sample used for tensile-compression cyclic stress creep aging is shown below. Figure 2 As shown.

[0107] This invention achieves grain refinement through low-temperature extrusion while introducing numerous crystal defects such as dislocations, providing ample nucleation sites and high driving energy for the precipitation of the second phase. Combined with creep aging, it promotes the rapid precipitation of a large number of nanoscale second phases without grain growth, achieving a synergistic effect of solid solution strengthening, grain refinement strengthening, and Orowan strengthening, thus simultaneously improving the strength and plasticity of magnesium alloys. Therefore, for magnesium alloys, with low rare earth element addition and low alloying degree, combining low-temperature extrusion and creep aging, a low-cost, high-strength, and high-plasticity magnesium-gadolinium-neodymium-calcium-zirconium alloy can be developed, thereby accelerating the industrial production of magnesium alloys and broadening their application fields. Compared with high-strength, high-rare-earth magnesium alloys and complex and expensive large plastic deformation techniques, this method has advantages such as low cost, simple process, and short process flow, significantly saving costs and demonstrating considerable economic benefits and application potential.

[0108] The present invention also provides the application of the magnesium-gadolinium-neodymium calcium-zirconium alloy described in the above technical solution or the magnesium-gadolinium-neodymium calcium-zirconium alloy prepared by the preparation method described in the above technical solution in lightweight equipment.

[0109] The present invention does not impose any special limitations on the application of the magnesium-gadolinium-neodymium-calcium-zirconium alloy in lightweight equipment; any application method known in the art can be used.

[0110] In this invention, the lightweight equipment is preferably applied in one or more of the following fields: transportation, energy, and aerospace.

[0111] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0112] Example 1

[0113] The following master alloys were prepared by mixing 99.9 wt.% pure magnesium blocks, 99.9 wt.% pure gadolinium particles (1 mm in diameter), magnesium-neodymium master alloy (30 wt.% Nd), magnesium-calcium master alloy (30 wt.% Ca), and magnesium-zirconium master alloy (30 wt.% Zr) according to the alloy composition ratio of 93.5 wt.% Mg, 4 wt.% Gd, 1 wt.% Nd, 1 wt.% Ca, and 0.5 wt.% Zr (by mass percentage). The steel crucible was then preheated to 300°C in a furnace. Coating I (by mass percentage) was then applied sequentially to the inner wall of the crucible. The crucible is prepared by mixing 17 parts talc, 1 part water glass, and 82 parts water, and coating II (by weight, including 8 parts zinc oxide, 3 parts water glass, and 89 parts water). Once the crucible temperature decreases and the coating can no longer adhere to the crucible surface, the crucible is returned to the heating furnace to dry. This process is repeated twice. Oxides on the surfaces of pure magnesium, pure gadolinium, magnesium-neodymium master alloys, magnesium-calcium master alloys, and magnesium-zirconium master alloys are removed by grinding. The oxide-removed metal and refining agent are then placed in an oven to dry. When the temperature in the melting furnace reaches 300°C, the pure magnesium block is placed in the crucible, then placed in the melting furnace, and the melting process begins. A protective gas (sulfur hexafluoride and carbon dioxide in a volume ratio of 1:99) is introduced into the furnace, and the temperature is raised to 720°C for a first stage of heating, held for 30 minutes until the solid raw materials are completely melted into a liquid alloy. The surface scum is then removed. The temperature is then raised to 780°C, pure gadolinium granules are added, and a second stage of heating is performed, held for 30 minutes. After removing the surface scum, the temperature is maintained at 780°C, and a magnesium-zirconium master alloy is added for a third stage of heating, held for 20 minutes. The surface scum is then removed, and the temperature is lowered to 750°C. A magnesium-neodymium master alloy and a magnesium-calcium master alloy are added, held for 20 minutes, and the surface oxide float is removed. The slag was removed, and the resulting alloy liquid was obtained from the metal raw materials. The refining agent (by mass, including 49 parts potassium chloride, 24 parts calcium chloride, 14 parts barium chloride, 6 parts gadolinium chloride, 5 parts calcium fluoride, and 2 parts sodium chloride; the amount used was 1% of the total mass of pure magnesium, pure gadolinium, magnesium-neodymium master alloy, magnesium-calcium master alloy, and magnesium-zirconium master alloy) was slowly sprinkled into the alloy liquid of the metal raw materials. At the same time, the alloy liquid was rapidly stirred at a speed of 3 rad / s for 2 minutes, and the temperature was maintained at 750℃ for refining and holding for 25 minutes. After removing the surface slag, the liquid was discharged when the temperature in the furnace dropped to 720℃, and the refined alloy liquid was obtained.

[0114] The casting mold is preheated to 200°C, then coated with paint I and paint II and dried. The refined alloy liquid is poured into the preheated casting mold (which has been coated) to obtain a cylindrical alloy ingot. The casting defects at both ends of the alloy ingot are removed using a wire cutting machine. The ingot is then placed in a heat treatment furnace for solution heat treatment at 520°C for 6 hours, followed by water quenching at 25°C. The resulting quenched alloy ingot is then machined to remove the surface oxide scale and polished to obtain a cylindrical ingot (Φ40mm×40mm in diameter) to be extruded. The extruded ingot and extrusion mold are coated with a lubricant (graphite and petroleum jelly in a 1:1.5 mass ratio) and placed in the extrusion mold, preheated to 32°C. After holding at 0℃ for 60 minutes, extrusion was performed at a temperature of 320℃, an extrusion ratio of 16:1, and an extrusion speed of 1mm / s to obtain an extruded specimen. The extruded specimen was then cut into 3mm×10mm×60mm rectangular plate-shaped specimens using a wire cutting machine. The oxide layer on the surface of the plate-shaped specimens was removed with sandpaper. The specimens were then hung in an RDL100 high-temperature creep testing machine equipped with an air-circulating environmental chamber. The test was conducted using a square wave load mode, with a test temperature of 250℃ and a stress value of 75MPa (less than the yield strength of the specimen). Tensile-compression cyclic stress creep aging was performed for 2 hours. The computer system recorded all parameters during the test in real time. After the extruded specimens were heat-treated, a magnesium-gadolinium-neodymium-calcium-zirconium alloy was obtained.

[0115] Example 2

[0116] After mixing 99.9 wt.% pure magnesium blocks, 99.9 wt.% pure gadolinium particles (1 mm in diameter), magnesium-neodymium master alloy (30 wt.% Nd), magnesium-calcium master alloy (30 wt.% Ca), and magnesium-zirconium master alloy (30 wt.% Zr) according to the alloy composition ratio of 93.5 wt.% Mg, 4 wt.% Gd, 1.5 wt.% Nd, 0.5 wt.% Ca, and 0.5 wt.% Zr (mass percentage content), a steel crucible was preheated to 300°C in a furnace. Then, coating I (using the formula...) was applied sequentially to the inner wall of the crucible. The crucible is prepared by mass fractions, including 17 parts talc, 1 part water glass, and 82 parts water, and coating II (by mass fractions, including 8 parts zinc oxide, 3 parts water glass, and 89 parts water). Once the crucible temperature decreases and the coating can no longer adhere to the crucible surface, the crucible is returned to the heating furnace for drying. This process is repeated twice. Oxides on the surfaces of pure magnesium, pure gadolinium, magnesium-neodymium master alloys, magnesium-calcium master alloys, and magnesium-zirconium master alloys are removed by grinding. The oxide-removed metal and refining agent are then placed in an oven for drying. When the temperature in the melting furnace reaches 300°C, the pure magnesium block is placed in the crucible, then placed in the melting furnace, and... A protective gas (sulfur hexafluoride and carbon dioxide in a volume ratio of 1:99) is introduced into the melting furnace, and the temperature is raised to 720°C for a first stage of heating, held for 30 minutes, until the solid raw materials are completely melted into a liquid alloy. The surface scum is then removed. The temperature is then raised to 780°C, pure gadolinium granules are added, and a second stage of heating is performed, held for 30 minutes. After removing the surface scum, the temperature is maintained at 780°C, and a magnesium-zirconium master alloy is added for a third stage of heating, held for 20 minutes. The surface scum is then removed, and the temperature is lowered to 750°C. Magnesium-neodymium master alloy and magnesium-calcium master alloy are added and held for 20 minutes, and the surface oxide is removed. The scum is removed, and the alloy liquid of the metal raw materials is obtained. The refining agent (by mass parts, including 49 parts potassium chloride, 24 parts calcium chloride, 14 parts barium chloride, 6 parts gadolinium chloride, 5 parts calcium fluoride and 2 parts sodium chloride; the amount is 1% of the total mass of pure magnesium, pure gadolinium, magnesium-neodymium master alloy, magnesium-calcium master alloy and magnesium-zirconium master alloy) is slowly sprinkled into the alloy liquid of the metal raw materials. At the same time, the alloy liquid is rapidly stirred at a speed of 3 rad / s for 2 min, the temperature is maintained at 750℃, and the refining is held at this temperature for 25 min. After the surface scum is removed, the liquid is discharged when the temperature in the furnace drops to 720℃ to obtain the refined alloy liquid.

[0117] The casting mold is preheated to 200°C, then coated with paint I and paint II and dried. The refined alloy liquid is poured into the preheated casting mold (which has been coated) to obtain a cylindrical alloy ingot. The casting defects at both ends of the alloy ingot are removed using a wire cutting machine. The ingot is then placed in a heat treatment furnace for solution heat treatment at 520°C for 6 hours, followed by water quenching at 25°C. The resulting quenched alloy ingot is then machined to remove the surface oxide scale and polished to obtain a cylindrical ingot (Φ40mm×40mm in diameter) to be extruded. The extruded ingot and extrusion mold are coated with a lubricant (graphite and petroleum jelly in a 1:1.5 mass ratio) and placed in the extrusion mold, preheated to 32°C. After holding at 0℃ for 60 minutes, extrusion was performed at a temperature of 320℃, an extrusion ratio of 16:1, and an extrusion speed of 1mm / s to obtain an extruded specimen. The extruded specimen was then cut into 3mm×10mm×60mm rectangular plate-shaped specimens using a wire cutting machine. The oxide layer on the surface of the plate-shaped specimens was removed with sandpaper. The specimens were then hung in an RDL100 high-temperature creep testing machine equipped with an air-circulating environmental chamber. The test was conducted using a square wave load mode, with a test temperature of 250℃ and a stress value of 75MPa (less than the yield strength of the specimen). Tensile-compression cyclic stress creep aging was performed for 2 hours. The computer system recorded all parameters during the test in real time. After the extruded specimens were heat-treated, a magnesium-gadolinium-neodymium-calcium-zirconium alloy was obtained.

[0118] Example 3

[0119] 99.9 wt.% pure magnesium blocks, 99.9 wt.% pure gadolinium particles (approximately 1 mm in diameter), magnesium-neodymium master alloy (30 wt.% Nd), magnesium-calcium master alloy (30 wt.% Ca), and magnesium-zirconium master alloy (30 wt.% Zr) were batched according to the alloy composition ratio of 93.5 wt.% Mg, 4 wt.% Gd, 0.5 wt.% Nd, 1.5 wt.% Ca, and 0.5 wt.% Zr (mass percentage content). After preheating a steel crucible to 300°C in a furnace, coating I was sequentially applied to the inner wall of the crucible. The mixture consists of 17 parts talc, 1 part water glass, and 82 parts water by weight, and coating II (8 parts zinc oxide, 3 parts water glass, and 89 parts water by weight). Once the crucible temperature decreases and the coating can no longer adhere to the crucible surface, the crucible is returned to the heating furnace for drying. This process is repeated twice. Oxides on the surfaces of pure magnesium, pure gadolinium, magnesium-neodymium master alloys, magnesium-calcium master alloys, and magnesium-zirconium master alloys are removed by grinding. The oxide-removed metal and refining agent are then placed in an oven for drying. When the temperature in the melting furnace reaches 300°C, the pure magnesium block is placed in the crucible, then placed in the melting furnace, and... A protective gas (sulfur hexafluoride and carbon dioxide in a volume ratio of 1:99) is introduced into the melting furnace, and the temperature is raised to 720°C for a first stage of heating, held for 30 minutes, until the solid raw materials are completely melted into a liquid alloy. The surface scum is then removed. The temperature is then raised to 780°C, pure gadolinium granules are added, and a second stage of heating is performed, held for 30 minutes. After removing the surface scum, the temperature is maintained at 780°C, and a magnesium-zirconium master alloy is added for a third stage of heating, held for 20 minutes. The surface scum is then removed, and the temperature is lowered to 750°C. Magnesium-neodymium master alloy and magnesium-calcium master alloy are added and held for 20 minutes, and the surface oxide is removed. The scum is removed, and the alloy liquid of the metal raw materials is obtained. The refining agent (by mass parts, including 49 parts potassium chloride, 24 parts calcium chloride, 14 parts barium chloride, 6 parts gadolinium chloride, 5 parts calcium fluoride and 2 parts sodium chloride; the amount is 1% of the total mass of pure magnesium, pure gadolinium, magnesium-neodymium master alloy, magnesium-calcium master alloy and magnesium-zirconium master alloy) is slowly sprinkled into the alloy liquid of the metal raw materials. At the same time, the alloy liquid is rapidly stirred at a speed of 3 rad / s for 2 min, the temperature is maintained at 750℃, and the refining is held at this temperature for 25 min. After the surface scum is removed, the liquid is discharged when the temperature in the furnace drops to 720℃ to obtain the refined alloy liquid.

[0120] The casting mold is preheated to 200°C, then coated with paint I and paint II and dried. The refined alloy liquid is poured into the preheated casting mold (which has been coated) to obtain a cylindrical alloy ingot. The casting defects at both ends of the alloy ingot are removed using a wire cutting machine. The ingot is then placed in a heat treatment furnace for solution heat treatment at 520°C for 6 hours, followed by water quenching at 25°C. The resulting quenched alloy ingot is then machined to remove the surface oxide scale and polished to obtain a cylindrical ingot (Φ40mm×40mm in diameter) to be extruded. The extruded ingot and extrusion mold are coated with a lubricant (graphite and petroleum jelly in a 1:1.5 mass ratio) and placed in the extrusion mold, preheated to 32°C. After holding at 0℃ for 60 minutes, extrusion was performed at a temperature of 320℃, an extrusion ratio of 16:1, and an extrusion speed of 1mm / s to obtain an extruded specimen. The extruded specimen was then cut into 3mm×10mm×60mm rectangular plate-shaped specimens using a wire cutting machine. The oxide layer on the surface of the plate-shaped specimens was removed with sandpaper. The specimens were then hung in an RDL100 high-temperature creep testing machine equipped with an air-circulating environmental chamber. The test was conducted using a square wave load mode, with a test temperature of 250℃ and a stress value of 75MPa (less than the yield strength of the specimen). Tensile-compression cyclic stress creep aging was performed for 2 hours. The computer system recorded all parameters during the test in real time. After the extruded specimens were heat-treated, a magnesium-gadolinium-neodymium-calcium-zirconium alloy was obtained.

[0121] Comparative Example 1

[0122] After mixing 99.9 wt.% pure magnesium blocks, 99.9 wt.% pure gadolinium particles (1 mm in diameter), and a magnesium-zirconium master alloy (30 wt.% Zr) according to the alloy composition ratio of 93.5 wt.% Mg, 6 wt.% Gd, and 0.5 wt.% Zr (mass percentage content), a steel crucible was preheated to 300°C in a furnace. Then, coating I (comprising 17 parts talc, 1 part water glass, and 82 parts water by mass) and coating... Material II (by mass, comprising 8 parts zinc oxide, 3 parts water glass, and 89 parts water), after the crucible temperature decreases and the coating can no longer adhere to the crucible surface, the crucible is returned to the heating furnace for drying. This process is repeated twice. Oxides on the surfaces of pure magnesium, pure gadolinium, and the magnesium-zirconium master alloy are removed by grinding. The oxide-removed metal and refining agent are then placed in an oven for drying. When the temperature in the melting furnace reaches 300°C, the pure magnesium block is placed in the crucible, then into the melting furnace, and a protective gas is introduced into the furnace. A mixture of sulfur hexafluoride and carbon dioxide (volume ratio 1:99) is heated to 720°C and held for 30 minutes until the solid raw material is completely melted into a liquid alloy. Surface dross is then removed. The temperature is then raised to 780°C, pure gadolinium granules are added, and a second heating stage is performed, held for 30 minutes. Surface dross is removed, and the temperature is maintained at 780°C. A magnesium-zirconium master alloy is added, and a third heating stage is performed, held for 20 minutes. Surface dross is removed again to obtain the alloy liquid of the metallic raw material. The liquid is then cooled to 750°C. The refining agent (by mass, including 49 parts potassium chloride, 24 parts calcium chloride, 14 parts barium chloride, 6 parts gadolinium chloride, 5 parts calcium fluoride, and 2 parts sodium chloride; the amount used is 1% of the total mass of pure magnesium, pure gadolinium, and magnesium-zirconium master alloy) is slowly sprinkled into the alloy liquid of the metal raw materials. At the same time, the alloy liquid is stirred rapidly at a speed of 3 rad / s for 2 minutes, and the temperature is maintained at 750℃. The refining is held at this temperature for 25 minutes. After removing the surface slag, the liquid is discharged when the temperature inside the furnace drops to 720℃ to obtain the refined alloy liquid.

[0123] The casting mold is preheated to 200°C, then coated with paint I and paint II and dried. The refined alloy liquid is poured into the preheated casting mold (preheated to 200°C and coated with paint) to obtain a cylindrical alloy ingot. The casting defects at both ends of the alloy ingot are removed using a wire cutting machine. The ingot is then placed in a heat treatment furnace for solution heat treatment at 520°C for 6 hours, followed by water quenching at 25°C. The resulting quenched alloy ingot is machined to remove surface oxide scale and then polished to obtain a cylindrical ingot (Φ40mm×40mm in diameter) to be extruded. A lubricant (graphite and...) is applied to the extruded sample and the extrusion mold. After applying Vaseline, the sample is placed in an extrusion mold and preheated to 320℃. After holding at this temperature for 60 minutes, it is extruded at a temperature of 320℃, an extrusion ratio of 16:1, and an extrusion speed of 1mm / s to obtain an extruded specimen. The extruded specimen is then cut into 3mm×10mm×60mm rectangular plate-shaped specimens using a wire cutting machine. The oxide layer on the surface of the plate-shaped specimens is removed with sandpaper. The specimens are then hung in an RDL100 high-temperature creep testing machine equipped with an air-circulating environmental chamber. The test is conducted using a square wave load mode, a test temperature of 250℃, and a stress value of 75MPa (less than the yield strength of the specimen). The specimens undergo tensile-compressive cyclic stress creep aging for 2 hours to obtain a magnesium-gadolinium-zirconium alloy.

[0124] Comparative Example 2

[0125] 99.9 wt.% pure magnesium blocks, 99.9 wt.% pure gadolinium particles (1 mm in diameter), magnesium-neodymium master alloy (30 wt.% Nd), and magnesium-zirconium master alloy (30 wt.% Zr) were prepared according to the alloy composition ratio of 93.5 wt.% Mg, 4 wt.% Gd, 2 wt.% Nd, and 0.5 wt.% Zr (mass percentage content). After preheating the steel crucible to 300°C in a heating furnace, coating I (comprising 17 parts talc and 1 part water glass by mass) was applied sequentially to the inner wall of the crucible. Add 82 parts water) and coating II (by mass, comprising 8 parts zinc oxide, 3 parts water glass, and 89 parts water). When the crucible temperature decreases and the coating can no longer adhere to the crucible surface, return the crucible to the heating furnace for drying. Repeat the above steps twice. Remove oxides from the surfaces of pure magnesium, pure gadolinium, magnesium-neodymium master alloys, and magnesium-zirconium master alloys by grinding. Place the oxide-removed metal and refining agent in an oven for drying. When the temperature in the smelting furnace reaches 300°C, place the pure magnesium block in the crucible, place it in the smelting furnace, and introduce a protective gas (volume ratio of...) into the smelting furnace. A mixture of sulfur hexafluoride and carbon dioxide (1:99) is heated to 720°C and held for 30 minutes until the solid raw material is completely melted into a liquid alloy. The surface scum is then removed. The temperature is then raised to 780°C, pure gadolinium particles are added, and the mixture is heated for another 30 minutes. The surface scum is removed, and the temperature is maintained at 780°C. A magnesium-zirconium master alloy is added and heated for 20 minutes. The surface scum is removed, and the temperature is lowered to 750°C. A magnesium-neodymium master alloy is added and held for 20 minutes. The surface oxide scum is then removed, yielding the final metal raw material. After the gold liquid is poured, the refining agent (by mass, including 49 parts potassium chloride, 24 parts calcium chloride, 14 parts barium chloride, 6 parts gadolinium chloride, 5 parts calcium fluoride, and 2 parts sodium chloride; the amount is 1% of the total mass of pure magnesium, pure gadolinium, magnesium-neodymium master alloy, magnesium-calcium master alloy, and magnesium-zirconium master alloy) is slowly sprinkled into the alloy liquid of the metal raw materials. At the same time, the alloy liquid is stirred rapidly at a speed of 3 rad / s for 2 minutes, the temperature is maintained at 750℃, and the refining is carried out at this temperature for 25 minutes. After removing the surface slag, the liquid is discharged when the temperature in the furnace drops to 720℃ to obtain the refined alloy liquid.

[0126] Preheat the casting mold to 200°C, then spray with coatings I and II and dry. Pour the refined alloy liquid into the preheated and coated casting mold to obtain a cylindrical alloy ingot. Cut off the casting defects at both ends of the alloy ingot with a wire cutter, place it in a heat treatment furnace for solution heat treatment at 520°C, hold for 6 hours, and then quench it with water at 25°C. After quenching, the resulting alloy ingot is machined to remove the oxide scale on the surface and then polished to obtain the extrusion sample (a cylindrical ingot with a diameter of Φ40mm×40mm). Apply lubricant (graphite and petroleum jelly in a mass ratio of 1:1.5) to the extrusion sample and the extrusion mold, then place them in the extrusion mold and preheat to 30°C. After holding at 20℃ for 60 minutes, the sample was extruded at 320℃ with an extrusion ratio of 16:1 and an extrusion speed of 1 mm / s to obtain an extruded specimen. The extruded specimen was then cut into 3 mm × 10 mm × 60 mm rectangular plate-shaped specimens using a wire cutting machine. The oxide layer on the surface of the plate-shaped specimens was removed with sandpaper. The specimens were then hung in an RDL100 high-temperature creep testing machine equipped with an air-circulating environmental chamber. The test was conducted using a square wave load mode, with a test temperature of 250℃ and a stress value of 75 MPa (less than the yield strength of the specimen). Tensile-compression cyclic stress creep aging was performed for 2 hours. The computer system recorded all parameters during the test in real time. After the extruded specimens were heat-treated, a magnesium-gadolinium-neodymium-zirconium alloy was obtained.

[0127] Organizational performance testing

[0128] (1) Figure 3 Optical micrograph (OM) of the magnesium-gadolinium-zirconium alloy prepared in Comparative Example 1. Figure 3 As shown, the microstructure of the magnesium gadolinium zirconium alloy can be observed to consist of fine dynamically recrystallized grains and non-dynamically recrystallized grains elongated along the extrusion direction, with an average grain size of 5.30 μm.

[0129] Figure 4 Optical micrograph (OM) of the magnesium-gadolinium-neodymium-zirconium alloy prepared in Comparative Example 2. Figure 4 As shown, the microstructure of the magnesium gadolinium neodymium zirconium alloy consists of fine dynamically recrystallized grains and non-dynamically recrystallized grains elongated along the extrusion direction. Compared with Comparative Example 1, the grains are significantly finer, with an average grain size of 3.11 μm.

[0130] Figure 5 Optical micrograph (OM) of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 1. Figure 5 As shown, the microstructure of the magnesium gadolinium neodymium calcium zirconium alloy can be observed to consist of fine dynamically recrystallized grains and non-dynamically recrystallized grains elongated along the extrusion direction. The grain size is further refined, with an average grain size of 1.52 μm.

[0131] (2) Figure 6The image shows a SEM image of the magnesium-gadolinium-zirconium alloy prepared in Comparative Example 1. Figure 6 It can be seen that the amount of precipitated phase in magnesium-gadolinium-zirconium alloy is small.

[0132] Figure 7 The image shows a SEM image of the magnesium-gadolinium-neodymium-zirconium alloy prepared in Comparative Example 2. Figure 9 The TEM image shows the magnesium-gadolinium-neodymium-zirconium alloy prepared in Comparative Example 2. Figure 7 and Figure 9 It can be seen that the number of precipitates in magnesium gadolinium neodymium zirconium alloy is significantly increased, but the precipitates are relatively coarse.

[0133] Figure 8 This is a SEM image of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 1. Figure 10 The TEM image of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 1 is shown below. Figure 8 and Figure 10 As shown, the number of precipitates in the magnesium-gadolinium-neodymium-calcium-zirconium alloy is significantly increased, and a large number of nano-sized precipitates appear.

[0134] (3) The alloys prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to tensile property tests at room temperature. The test specimens were as follows: Figure 11 As shown in Table 1, the test results are as follows. Figures 12-16 As shown.

[0135] Table 1. Alloy properties of the examples and comparative examples

[0136] state Yield strength / MPa Tensile strength / MPa Elongation / % Comparative Example 1 188.33 256.07 14.89 Comparative Example 2 232.98 287.76 19.27 Example 1 285.68 350.19 16.56 Example 2 248.62 302.2 18.26 Example 3 303.15 361.85 12.87

[0137] Figure 12 The tensile stress-strain diagram of the magnesium-gadolinium-zirconium alloy prepared for Comparative Example 1 at room temperature is shown. Figure 12 As shown, the magnesium-gadolinium-zirconium alloy prepared in Comparative Example 1 has a tensile yield strength of 188.33 MPa, a tensile strength of 256.07 MPa, and an elongation of only 14.89% at room temperature. At this point, the alloy exhibits poor strength-plasticity synergy.

[0138] Figure 13 The tensile stress-strain diagram of the magnesium-gadolinium-neodymium-zirconium alloy prepared in Comparative Example 2 at room temperature is shown. Figure 13 As shown, the magnesium-gadolinium-neodymium-zirconium alloy prepared in Comparative Example 2 has a tensile yield strength of 232.98 MPa, a tensile strength of 287.76 MPa, and an elongation of 19.27% ​​at room temperature. Compared with Comparative Example 1, it begins to show good strength-toughness synergy.

[0139] Figure 14 The image shows the tensile stress-strain diagram at room temperature for the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 1. Figure 14As shown, the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 1 has a tensile yield strength of 285.68 MPa, a tensile strength of 350.19 MPa, and an elongation of 16.56% at room temperature, exhibiting good strength-plasticity synergy.

[0140] Figure 15 This is a tensile stress-strain diagram of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 2 at room temperature. Figure 15 As shown, the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 2 has a tensile yield strength of 248.62 MPa, a tensile strength of 302.2 MPa, and an elongation of 18.26% at room temperature, exhibiting good strength-plasticity synergy.

[0141] Figure 16 This is a tensile stress-strain diagram of the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 3 at room temperature. Figure 16 As shown, the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared in Example 3 has a tensile yield strength of 303.15 MPa, a tensile strength of 361.85 MPa, and an elongation of 12.87% at room temperature, exhibiting good strength-plasticity synergy.

[0142] In Comparative Examples 1 and 2, the alloy microstructure also exhibited a bimodal structure, and the grain size refinement was more pronounced after the addition of Nd. However, the grain size was significantly larger than that of Example 1, and the amount of precipitated phase was significantly less, resulting in lower alloy performance. This is because a large number of nano-sized granular second phases precipitated in Example 1 after creep aging treatment. These second phases effectively pinned grain boundaries and inhibited grain growth. Simultaneously, the nano-sized second phases were dispersed, resulting in uniform strain distribution, reduced stress concentration, and reduced crack initiation at grain boundaries during deformation, thus improving alloy plasticity. The synergistic effect of grain refinement strengthening after extrusion and precipitation strengthening after creep aging treatment resulted in a high level of alloy strength. Using the method of this invention, relatively excellent mechanical properties were obtained in Examples 2 and 3, indicating that the combined addition of Nd and Ca elements in the Mg-Gd-0.5Zr series magnesium alloys helps to improve the mechanical properties of magnesium alloys. In summary, the magnesium-gadolinium-neodymium-calcium-zirconium alloy (Mg-Gd-Nd-Ca-Zr alloy) prepared by this invention exhibits good strength-ductility matching.

[0143] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A magnesium-gadolinium-neodymium-calcium-zirconium alloy, characterized in that, The composition includes the following elements by mass percentage: Gadolinium 3-6%, neodymium 0.5-2%, calcium 0.1-1.5%, zirconium 0.2-0.8%, balance magnesium; The preparation method of the magnesium-gadolinium-neodymium-calcium-zirconium alloy includes the following steps: According to the elemental composition of the magnesium-gadolinium-neodymium-calcium-zirconium alloy, the alloying liquid of the metal raw materials and the refining agent are mixed. The alloy is refined under a protective atmosphere, and the resulting refined alloy liquid is poured to obtain an alloy ingot. The alloy ingot was subjected to solution heat treatment and quenching in sequence to obtain the extrusion sample; The solution heat treatment temperature is 500~530℃, and the holding time is 4~8h; the quenching is performed with water at 25℃. The sample to be extruded is placed in an extrusion die and preheated and extruded sequentially to obtain an extruded sample; The preheating temperature is 300~330℃; The extrusion temperature is 300~330℃; The extruded specimen was subjected to tensile-compressive cyclic stress creep aging to obtain a magnesium-gadolinium-neodymium-calcium-zirconium alloy. The tensile-compression cyclic stress creep aging time is 0.5~16h; the tensile-compression cyclic stress creep aging temperature is 250℃.

2. The method for preparing the magnesium-gadolinium-neodymium-calcium-zirconium alloy according to claim 1, characterized in that, Includes the following steps: According to the elemental composition of the magnesium-gadolinium-neodymium-calcium-zirconium alloy, the alloying liquid of the metal raw materials and the refining agent are mixed. The alloy is refined under a protective atmosphere, and the resulting refined alloy liquid is poured to obtain an alloy ingot. The alloy ingot was subjected to solution heat treatment and quenching in sequence to obtain the extrusion sample; The solution heat treatment temperature is 500~530℃, and the holding time is 4~8h; the quenching is performed with water at 25℃. The sample to be extruded is placed in an extrusion die and preheated and extruded sequentially to obtain an extruded sample; The preheating temperature is 300~330℃; The extrusion temperature is 300~330℃; The extruded specimen was subjected to tensile-compressive cyclic stress creep aging to obtain a magnesium-gadolinium-neodymium-calcium-zirconium alloy. The tensile-compression cyclic stress creep aging time is 0.5~16h; the tensile-compression cyclic stress creep aging temperature is 250℃.

3. The preparation method according to claim 2, characterized in that, The refining agent comprises the following components by mass: 49 parts potassium chloride, 24 parts calcium chloride, 14 parts barium chloride, 6 parts gadolinium chloride, 5 parts calcium fluoride, and 2 parts sodium chloride.

4. The preparation method according to claim 2, characterized in that, The protective gas comprises sulfur hexafluoride and carbon dioxide; the volume ratio of sulfur hexafluoride to carbon dioxide is 1:

99.

5. The preparation method according to any one of claims 2 to 4, characterized in that, The method for preparing the alloy liquid of the metal raw material includes the following steps: Pure magnesium is heated for a period of time to obtain molten magnesium; Pure gadolinium was added to the magnesium liquid and heated in two stages to obtain a magnesium-gadolinium mixture. A magnesium-zirconium master alloy was added to the magnesium-gadolinium mixture and heated in three stages to obtain a magnesium-gadolinium-zirconium mixture. Magnesium-neodymium master alloy and magnesium-calcium master alloy are added to the magnesium-gadolinium-zirconium mixture and heated in four stages to obtain an alloy liquid of metal raw materials. The first-stage heating, second-stage heating, third-stage heating, and fourth-stage heating are all carried out under a protective gas atmosphere.

6. The preparation method according to claim 2, characterized in that, The preheating holding time is 60 minutes.

7. The preparation method according to claim 2, characterized in that, The extrusion ratio is 16:1, and the extrusion speed is 1 mm / s.

8. The preparation method according to claim 2, characterized in that, The stress value for the tensile-compressive cyclic stress creep aging is 50~100MPa.

9. The application of the magnesium-gadolinium-neodymium-calcium-zirconium alloy of claim 1 or the magnesium-gadolinium-neodymium-calcium-zirconium alloy prepared by any one of claims 2 to 8 in lightweight equipment.

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