A cast rare earth magnesium alloy and a method for producing the same

Abstract

The application provides a cast rare earth magnesium alloy and a preparation method thereof, and relates to the technical field of magnesium alloys. The cast rare earth magnesium alloy comprises the following elements in percentage by mass: the content of Gd element is 4.5-6.50%, the content of Y element is 0.5-2.0%, the content of Nd element is 0.05-1.2%, the content of Er element is 0.05-0.5%, the content of Zn element is 0.3-1.2%, the content of Zr element is 0.3-0.6%, the total content of unavoidable impurities is less than or equal to 0.1%, the content of single impurity is less than 0.05%, and the balance is Mg element. In the application, the addition of Gd element, Y element, Nd element and Er element can weaken the basal texture of the magnesium alloy and improve the plasticity. Controlling the content of each element in the above range is helpful to improve the interaction between the elements, thereby helping the magnesium alloy to realize good strength-plasticity synergy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnesium alloy, in particular to a cast rare earth magnesium alloy and a preparation method thereof. BACKGROUND

[0002] Rare earth magnesium alloy has important application prospect and development potential in the field of aerospace and other fields due to its excellent lightweight characteristics, high temperature mechanical properties and corrosion resistance. The addition of rare earth elements in magnesium alloy can significantly refine the grain, improve the mechanical strength and improve the thermal stability. Traditional magnesium alloy (such as AZ series) has poor room temperature plasticity and toughness due to the limitation of hexagonal close-packed (HCP) crystal structure, and is prone to cracking during processing, which has problems such as difficulty in product forming, low yield and insufficient reliability. In the field of aerospace, the plasticity of materials is crucial, which directly affects the fracture resistance, energy absorption characteristics and processing formability of components under complex load (such as impact, vibration, thermal cycle). High plasticity materials can relieve stress concentration through uniform deformation, avoid brittle failure and improve component reliability. Especially in extreme service environment, good plasticity can ensure that the material still maintains structural integrity when micro-cracks expand or local stress exceeds the limit, which is crucial for flight safety and life. Therefore, improving the plasticity of magnesium alloy is one of the core directions to break through the bottleneck of its application in aerospace.

[0003] Magnesium alloy can significantly improve plasticity after deformation processes such as rolling, forging and extrusion. Although deformed rare earth magnesium alloy has extremely significant plasticity advantage, it has the following disadvantages: ① complex preparation process, high processing cost; ② limited forming ability, difficult to prepare deep cavity, thin wall or special-shaped parts; ③ significant anisotropy, magnesium alloy will form strong basal texture during deformation, resulting in large difference in mechanical properties in different directions, affecting the reliability of components; ④ low material utilization, deformed magnesium alloy is prone to produce edge waste during product processing, causing material waste; ⑤ low production efficiency, limited by the hexagonal close-packed crystal structure of magnesium alloy, magnesium alloy usually chooses a lower deformation rate to improve the yield, which leads to low production efficiency of magnesium alloy deformation products. Compared with deformed magnesium alloy, cast magnesium alloy has weaker anisotropy, can directly near-net shape complex structure parts, reduce processing cost, improve raw material utilization and production efficiency, and has significant low cost and high efficiency advantage. In addition, high plasticity cast rare earth magnesium alloy can realize large deformation processing at lower temperature and higher strain rate than traditional deformation process, which reduces energy consumption and equipment requirements; excellent plasticity can effectively inhibit deformation cracking and improve material utilization. High plasticity cast rare earth magnesium alloy also has the potential to prepare precision complex structure parts through "near-net casting + local precision deformation" composite process. Therefore, it is urgent to develop high plasticity cast rare earth magnesium alloy to meet the demand for low cost, lightweight and high reliability materials in high-end fields such as aerospace. SUMMARY

[0004] The main object of the present application is to provide a cast rare earth magnesium alloy and a preparation method thereof, so as to solve the problem of poor plasticity of the rare earth magnesium alloy in the prior art.

[0005] In order to achieve the above object, according to one aspect of the present application, a cast rare earth magnesium alloy is provided, which comprises the following elements in percentage by mass: the content of Gd element is 4.5-6.50%, the content of Y element is 0.5-2.0%, the content of Nd element is 0.05-1.2%, the content of Er element is 0.05-0.5%, the content of Zn element is 0.3-1.2%, the content of Zr element is 0.3-0.6%, the total content of unavoidable impurities is ≤0.1%, the content of single impurity is less than 0.05%, and the balance is Mg element.

[0006] Further, the cast rare earth magnesium alloy comprises the following elements in percentage by mass: the content of Gd element is 5.83-6.47%, the content of Y element is 0.69-1.81%, the content of Nd element is 0.11-0.21%, the content of Er element is 0.09-0.49%, the content of Zn element is 0.47-0.55%, the content of Zr element is 0.32-0.41%, the total content of unavoidable impurities is ≤0.1%, the content of single impurity is less than 0.05%, and the balance is Mg element.

[0007] Further, the mass ratio of the Gd element to the Y element is (3-10):1; and / or, the cast rare earth magnesium alloy further comprises 0.05-0.1% of Sc element.

[0008] Further, the mass ratio of the Nd element, the Er element and the Sc element is (0.11-1.14):(0.06-0.49):0.08.

[0009] Further, the total content of the Gd element, the Y element, the Nd element, the Er element and the Sc element is 6-9%.

[0010] According to another aspect of the present application, a preparation method of the aforementioned cast rare earth magnesium alloy is provided, which comprises: sequentially melting, casting, solid solution treatment, quenching treatment and aging treatment of the metal raw material of the cast rare earth magnesium alloy according to the proportion, so as to obtain the cast rare earth magnesium alloy.

[0011] Further, the temperature of the melting is 750-780℃.

[0012] Further, the preparation method further comprises: ultrasonic treatment of the melt during the melting, the frequency of the ultrasonic treatment is 20-22kHz, and the time of the ultrasonic treatment is 10-20min.

[0013] Further, the temperature of the above-mentioned solid solution treatment is 470-500 DEG C, the holding time is 6-8h; and / or, the temperature of the aging treatment is 200-230 DEG C, the holding time is 12-24h; and / or, the temperature of the cooling medium of the quenching treatment is 70-80 DEG C.

[0014] Further, the heating process of the above-mentioned solid solution treatment comprises: heating to 450-460 DEG C at a heating rate of 15-20 DEG C / min, holding for 5-10 min, and then heating to the required temperature of the solid solution treatment at a heating rate of 5-7 DEG C / min for solid solution treatment; and / or, the heating process of the aging treatment comprises: heating to 180-190 DEG C at a heating rate of 15-20 DEG C / min, holding for 5-10 min, and then heating to the required temperature of the aging treatment at a heating rate of 5-7 DEG C / min for aging treatment.

[0015] By adding Gd element, Y element, Nd element and Er element in the technical solution of the present application, the basal texture of the magnesium alloy can be weakened and the plasticity can be improved. Gd element is the core strengthening element, and the solid solubility in the magnesium matrix is high. Gd element can control the magnesium alloy lattice parameters through solid solution, optimize the deformation coordination, reduce the critical shear stress difference between the basal plane and the column plane slip, and at the same time induce the lattice axis ratio to reduce, promote the cooperative activation of basal plane slip and column plane slip, thereby significantly improve the plasticity. With the increase of the addition amount of Gd element, a large amount of second phase will be formed in the magnesium alloy matrix, which will improve the strength of the magnesium alloy, but the plasticity will decrease, so the addition amount of Gd element should be controlled. Y element can significantly improve the yield strength of the magnesium alloy. This is because the solid solubility of Y element in the magnesium matrix is lower than that of Gd element, so it is easier to form second phase in the magnesium alloy by adding Y element, which hinders the dislocation movement, so the plasticity of the magnesium alloy is very sensitive to the content of Y element, therefore the addition amount of Y element should not be too high. The addition of Nd element can improve the plasticity of the alloy, but the solid solubility of Nd element in the magnesium alloy is lower than that of Gd element and Y element, and excessive addition will form a large amount of brittle second phase, which will affect the plasticity of the alloy. Er element has a large solid solubility in the magnesium alloy, but excessive addition of Er element is not conducive to the improvement of plasticity. The key role of Zn element is to improve the flowability of the magnesium alloy melt and induce the formation of long-period ordered stacking phase. The purpose of improving the plasticity is achieved by the deformation coordination of the twisted ordered stacking phase, but the increase of the content of Zn element will lead to the coarsening of the ordered stacking phase, and at the same time, Zn element will consume the strengthening element Gd by forming Zn-Gd compound, thereby leading to the decrease of the performance of the alloy, so the content of Zn should not be too high. Zr is an effective grain refiner of the magnesium alloy, and its addition is helpful to refine the magnesium alloy grains and improve the plasticity and strength of the magnesium alloy. Controlling the content of each element within the above-mentioned range is helpful to improve the interaction between the elements, thereby helping to make the magnesium alloy have higher plasticity under the condition of meeting the requirements of tensile strength and yield strength. DETAILED DESCRIPTION

[0016] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below in combination with the embodiments.

[0017] As analyzed in the background art of the present application, the problem of poor plasticity of rare earth magnesium alloy in the prior art, in order to solve the problem, the present application provides a cast rare earth magnesium alloy and a preparation method thereof.

[0018] In a typical embodiment of the present application, a cast rare earth magnesium alloy is provided, which comprises the following elements in mass percentage: the content of Gd element is 4.5-6.50%, the content of Y element is 0.5-2.0%, the content of Nd element is 0.05-1.2%, the content of Er element is 0.05-0.5%, the content of Zn element is 0.3-1.2%, the content of Zr element is 0.3-0.6%, the total content of unavoidable impurities is ≤0.1%, the content of single impurity is lower than 0.05%, and the balance is Mg element.

[0019] In the present application, the addition of Gd element, Y element, Nd element and Er element can weaken the basal texture of magnesium alloy and improve the plasticity. Gd element is the core strengthening element, and has high solid solubility in magnesium matrix. Gd element can control the magnesium alloy lattice parameters through solid solution, optimize the deformation coordination, reduce the critical shear stress difference between basal plane and column plane slip, and induce the reduction of lattice axis ratio, thereby promoting the coordinated activation of basal plane slip and column plane slip, so as to significantly improve the plasticity. With the increase of the addition amount of Gd element, a large amount of second phase will be formed in the magnesium alloy matrix, which will improve the strength of the magnesium alloy, but the plasticity will decrease, so the addition amount of Gd element should be controlled. Y element can significantly improve the yield strength of the magnesium alloy. This is because the solid solubility of Y element in the magnesium matrix is lower than that of Gd element, so it is easier to form second phase in the magnesium alloy to hinder dislocation movement by adding Y element, so the plasticity of the magnesium alloy is very sensitive to the content of Y element, and therefore the addition amount of Y element should not be too high. The addition of Nd element can improve the plasticity of the alloy, but since the solid solubility of Nd element in the magnesium alloy is lower than that of Gd element and Y element, excessive addition will form a large amount of brittle second phase to affect the plasticity of the alloy. Er element has a large solid solubility in the magnesium alloy, but excessive addition of Er element is not conducive to the improvement of plasticity. The key role of Zn element is to improve the flowability of the magnesium alloy melt and induce the formation of long-period ordered stacking phase. The purpose of improving the plasticity is achieved by the deformation coordination of the twisted ordered stacking phase, but the increase of the content of Zn element will lead to the coarsening of the ordered stacking phase, and the Zn element will consume the strengthening element Gd by forming Zn-Gd compound, thereby causing the performance of the alloy to decrease, so the content of Zn should not be too high. Zr is an effective grain refiner for magnesium alloy, and its addition is helpful to refine the magnesium alloy grains and improve the plasticity and strength of the magnesium alloy. Controlling the content of each element within the above range is helpful to improve the interaction between the elements, thereby helping the magnesium alloy to have high plasticity while meeting the requirements of tensile strength and yield strength.

[0020] In order to further improve the plasticity of the magnesium alloy, in an embodiment of the present application, the cast rare earth magnesium alloy includes the following elements in mass percentage: the content of Gd element is 5.83-6.47%, the content of Y element is 0.69-1.81%, the content of Nd element is 0.11-0.21%, the content of Er element is 0.09-0.49%, the content of Zn element is 0.47-0.55%, the content of Zr element is 0.32-0.41%, the total content of unavoidable impurities is ≤0.1%, the content of single impurity is less than 0.05%, and the balance is Mg element.

[0021] In an embodiment of the present application, the mass ratio of the above-mentioned Gd element to Y element is (3-10):1, and specifically can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 and a range value between any two ratios.

[0022] Gd element can more effectively change the lattice parameter of magnesium alloy due to its higher solid solubility, optimize the deformation compatibility of the alloy, narrow the difference between the critical shear stress of basal slip and that of prismatic slip, thereby promoting the diversification of slip mechanism and improving the plasticity of the alloy. Y has a relatively low solid solubility and hinders dislocation movement more by forming a second phase to improve the strength of the alloy. Controlling the mass ratio of Gd element to Y element within the above range is helpful to further balance the strength and plasticity of the magnesium alloy.

[0023] In an embodiment of the present application, the cast rare earth magnesium alloy described above further comprises 0.05-0.1% of Sc element.

[0024] Sc element has a high solid solubility in magnesium alloy, and its addition is helpful to activate the pyramidal slip system, thereby facilitating the improvement of plasticity.

[0025] In an embodiment of the present application, the mass ratio of the above Nd element, Er element and Sc element is (0.11-1.14):(0.06-0.49):0.08.

[0026] Nd and Er elements can induce the formation of specific types of second phases in the magnesium matrix, which can weaken basal texture and activate non-basal slip. Sc element has a high solid solubility and can refine grains and promote the activation of non-basal slip. Controlling the mass ratio of Nd element, Er element and Sc element within the above range is helpful to improve the interaction among the three, thereby further improving the plasticity of the magnesium alloy while maintaining good strength and thermal stability.

[0027] In an embodiment of the present application, the total content of the above Gd element, Y element, Nd element, Er element and Sc element is 6-9%.

[0028] Controlling the total content of Gd element, Y element, Nd element, Er element and Sc element within the above range is helpful to control the formation of brittle phases in the alloy, promote the formation of ordered stacking phases and the precipitation of nano-strengthening phases, thereby further improving the strength and plasticity of the magnesium alloy.

[0029] In an embodiment of the present application, the mass ratio of the above Zn element to Zr element is (0.7-2.5):1, specifically 0.7:1, 0.9:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 1.9:1, 2.1:1, 2.3:1, 2.5:1 and any range value between any two ratio values.

[0030] The element Zn can induce the formation of long-period ordered stacking phase, which can improve the plastic deformation ability of the alloy through the kink mechanism, and the element Zr can effectively refine the grains and improve the thermal stability and plasticity of the alloy. Controlling the mass ratio of the elements Zn and Zr in the above range can help to promote the plastic deformation mechanism and optimize the grain refinement, thereby further improving the overall plasticity and strength of the alloy.

[0031] In an embodiment of the present application, the tensile strength of the cast rare earth magnesium alloy is 218-242 MPa, preferably 221-242 MPa; and / or, the yield strength of the cast rare earth magnesium alloy is 106-131 MPa; and / or, the elongation of the cast rare earth magnesium alloy is 20.1-28.0%, preferably 21.5-28.0%.

[0032] The cast rare earth magnesium alloy with the above tensile strength, yield strength and elongation is more suitable for use in the field of aerospace.

[0033] In another typical embodiment of the present application, a preparation method of the aforementioned cast rare earth magnesium alloy is provided, which comprises: sequentially melting, casting, solid solution treatment, quenching treatment and aging treatment of the metal raw materials of the cast rare earth magnesium alloy according to the proportions to obtain the cast rare earth magnesium alloy.

[0034] The preparation method of the cast rare earth magnesium alloy of the present application is simple, low in cost and suitable for mass production.

[0035] In an embodiment of the present application, the temperature of the melting is 750-780℃.

[0036] Controlling the temperature of the melting in the above range can help to reduce the entry of Fe in the crucible and hydrogen in the air into the melt under the condition that each raw material is fully melted, thereby reducing the impurity content of the cast rare earth magnesium alloy.

[0037] In an embodiment of the present application, the preparation method further comprises: ultrasonic treatment of the melt during the melting, the frequency of the ultrasonic treatment being 20-22 kHz, and the time of the ultrasonic treatment being 10-20 min.

[0038] The acoustic cavitation and acoustic streaming of the ultrasonic wave can promote the homogenization of the melt, reduce the sedimentation of the element Zr and the gas inclusion in the magnesium alloy melt, thereby helping to improve the purity of the magnesium alloy. Controlling the frequency and time of the ultrasonic treatment in the above range can help to improve the efficiency of the ultrasonic treatment.

[0039] In order to further improve the purity of the magnesium alloy and the uniformity of the distribution of each component in the magnesium alloy, thereby improving the strength and plasticity of the magnesium alloy, in an embodiment of the present application, the melting and casting include: weighing the pure magnesium, the magnesium gadolinium intermediate alloy, the magnesium yttrium intermediate alloy, the magnesium neodymium intermediate alloy, the magnesium erbium intermediate alloy, the magnesium scandium intermediate alloy, the magnesium zirconium intermediate alloy and the pure zinc raw material according to the component ratio and the loss on ignition, and baking the raw material, the operating tool and the casting mold at 200℃ for 20min; placing the pure magnesium in a crucible and putting it into a pit-type electric resistance furnace to be heated with the furnace, when the furnace temperature reaches 500℃, introducing the CO2+SF6 (volume ratio is 99.5:0.5) protective gas and covering a layer of chloride protective flux, and continuing to heat to 700℃ to completely melt the magnesium ingot; after the magnesium alloy melt is heated to 750℃, adding the magnesium gadolinium intermediate alloy, the magnesium yttrium intermediate alloy, the magnesium neodymium intermediate alloy, the magnesium erbium intermediate alloy, the magnesium scandium intermediate alloy and the pure zinc, after the intermediate alloy and the pure zinc are completely melted, using an ultrasonic amplitude horn to probe into the melt to perform ultrasonic treatment on the magnesium alloy melt, the frequency of the ultrasonic treatment is 20~22kHz, and the treatment time is 5~10min; heating the magnesium alloy melt to 780℃, adding the magnesium zirconium intermediate alloy, after the magnesium zirconium intermediate alloy is melted, performing ultrasonic treatment for 5~10min, then refining, skimming the slag, and keeping warm for 10min; after the magnesium alloy melt is cooled to 720℃ and kept still for 10min, performing magnesium alloy mold casting to obtain a magnesium alloy ingot.

[0040] In an embodiment of the present application, the temperature of the solid solution treatment is 470~500℃, and the holding time is 6~8h; and / or, the temperature of the aging treatment is 200~230℃, and the holding time is 12~24h; and / or, the temperature of the cooling medium of the quenching treatment is 70~80℃.

[0041] Controlling the temperature and time of the solid solution treatment in the above range helps to promote the re-dissolution of the rare earth phase in the as-cast alloy and inhibit the excessive growth of the grains. Controlling the temperature and time of the aging treatment in the above range helps to inhibit the excessive growth of the precipitated phase, thereby helping to improve the plasticity of the magnesium alloy. Controlling the temperature of the cooling medium of the quenching treatment in the above range helps to reduce the generation of cracks and improve the integrity and reliability of the magnesium alloy.

[0042] In order to reduce the temperature of the furnace from rising too fast after reaching the target value, and reduce the influence of temperature fluctuation on the solution treatment and aging treatment, in an embodiment of the present application, the temperature rising process of the solution treatment comprises: rising the temperature to 450-460℃ at a temperature rising rate of 15-20℃ / min, and keeping the temperature for 5-10min, and then rising the temperature to the temperature required for the solution treatment at a temperature rising rate of 5-7℃ / min for the solution treatment; and / or, the temperature rising process of the aging treatment comprises: rising the temperature to 180-190℃ at a temperature rising rate of 15-20℃ / min, and keeping the temperature for 5-10min, and then rising the temperature to the temperature required for the aging treatment at a temperature rising rate of 5-7℃ / min for the aging treatment.

[0043] The solution treatment and the aging treatment are carried out in an inert gas, which can be helium or argon.

[0044] The beneficial effects of the present application will be further illustrated below in combination with embodiments.

[0045] Embodiment 1

[0046] The pure magnesium, magnesium gadolinium intermediate alloy, magnesium yttrium intermediate alloy, magnesium neodymium intermediate alloy, magnesium erbium intermediate alloy, magnesium zirconium intermediate alloy and pure zinc raw materials are weighed according to the component ratio and the burning loss, and the raw materials, operating tools and casting molds are all baked at 200℃ for 20min; the pure magnesium is placed in a crucible and put into a pit-type resistance furnace for rising with the furnace, when the furnace temperature reaches 500℃, the CO2+SF6 (volume ratio of 99.5:0.5) protective gas is introduced and covered with a layer of chloride protective flux, and then the temperature is continuously raised to 700℃ to completely melt the magnesium ingot; after the magnesium alloy melt is heated to 750℃, the magnesium gadolinium intermediate alloy, the magnesium yttrium intermediate alloy, the magnesium neodymium intermediate alloy, the magnesium erbium intermediate alloy and the pure zinc are added, and after the intermediate alloy and the pure zinc are completely melted, the magnesium alloy melt is treated by ultrasonic treatment by using an ultrasonic amplitude bar probe, the frequency of the ultrasonic treatment is 20kHz, and the treatment time is 5min; the magnesium alloy melt is heated to 780℃, the magnesium zirconium intermediate alloy is added, and after the magnesium zirconium intermediate alloy is melted, the ultrasonic treatment is performed for 5min, and then the refining and slagging are performed, and the temperature is kept for 10min; the magnesium alloy melt is cooled to 720℃ and kept for 10min, and then the magnesium alloy mold casting is performed, and the magnesium alloy ingot is obtained.

[0047] The magnesium alloy ingot is placed in a muffle furnace at 25°C, and then vacuum pumping (-0.1 MPa) and argon filling are performed. After the argon pressure in the furnace reaches 0.01 MPa, the argon filling is stopped, and the temperature is raised at a rate of 15°C / min. The temperature is raised to 450°C, and the temperature is maintained for 5 min. The temperature is raised to 500°C at a rate of 5°C / min for solid solution treatment, and the temperature is maintained for 6 h. Then, the solid solution alloy is quenched in hot water at 80°C. The solid solution alloy is placed in a muffle furnace at 25°C, and then vacuum pumping (-0.1 MPa) and argon filling are performed. After the argon pressure in the furnace reaches 0.01 MPa, the argon filling is stopped, and the temperature is raised at a rate of 15°C / min. The temperature is raised to 180°C, and the temperature is maintained for 5 min. The temperature is raised to 225°C at a rate of 5°C / min for aging treatment, and the temperature is maintained for 24 h. Then, the cast rare earth magnesium alloy is obtained by air cooling. The cast rare earth magnesium alloy contains, by mass percent, 5.83% of Gd element, 1.81% of Y element, 0.11% of Nd element, 0.09% of Er element, 0.47% of Zn element, 0.32% of Zr element, ≤0.1% of total content of unavoidable impurities, <0.05% of content of single impurity, and the balance of Mg element.

[0048] Example 2

[0049] The difference from Example 1 is that the ratio among the pure magnesium, magnesium gadolinium intermediate alloy, magnesium yttrium intermediate alloy, magnesium neodymium intermediate alloy, magnesium erbium intermediate alloy, magnesium scandium intermediate alloy, magnesium zirconium intermediate alloy, and pure zinc raw materials is adjusted. The solid solution treatment temperature is 470°C, the holding time is 8 h, the aging treatment temperature is 210°C, and the holding time is 24 h. Finally, the cast rare earth magnesium alloy is obtained. The cast rare earth magnesium alloy contains, by mass percent, 4.83% of Gd element, 1.54% of Y element, 0.26% of Nd element, 0.11% of Er element, 0.53% of Zn element, 0.43% of Zr element, 0.08 of Sc element, ≤0.1% of total content of unavoidable impurities, <0.05% of content of single impurity, and the balance of Mg element. The mass ratio of Gd element to Y element is 3.1:1. The mass ratio of Nd element, Er element, and Sc element is 0.26:0.11:0.08. The total content of Gd element, Y element, Nd element, Er element, and Sc element is 6.82%.

[0050] Example 3

[0051] The difference from Example 1 is that the proportions of pure magnesium, magnesium-gadolinium master alloy, magnesium-yttrium master alloy, magnesium-neodymium master alloy, magnesium-erbium master alloy, magnesium-zirconium master alloy and pure zinc raw materials are adjusted, the temperature of the solid solution treatment is 500℃, the holding time is 8h, the temperature of the aging treatment is 230℃, and the holding time is 12h. Finally, a cast rare earth magnesium alloy is obtained, which contains the following elements in percentage by mass: 6.50% of Gd element, 1.16% of Y element, 0.65% of Nd element, 0.48% of Er element, 0.41% of Zn element, 0.53% of Zr element, ≤0.1% of total content of unavoidable impurities, less than 0.05% of content of single impurity, and the balance of Mg element.

[0052] Example 4

[0053] The difference from Example 1 is that the proportions of pure magnesium, magnesium-gadolinium master alloy, magnesium-yttrium master alloy, magnesium-neodymium master alloy, magnesium-erbium master alloy, magnesium-zirconium master alloy and pure zinc raw materials are adjusted, the temperature of the solid solution treatment is 500℃, the holding time is 8h, the temperature of the aging treatment is 230℃, and the holding time is 24h. Finally, a cast rare earth magnesium alloy is obtained, which contains the following elements in percentage by mass: 6.03% of Gd element, 1.93% of Y element, 0.18% of Nd element, 0.06% of Er element, 0.63% of Zn element, 0.58% of Zr element, ≤0.1% of total content of unavoidable impurities, less than 0.05% of content of single impurity, and the balance of Mg element.

[0054] Example 5

[0055] The difference from Example 1 is that the proportions of pure magnesium, magnesium-gadolinium master alloy, magnesium-yttrium master alloy, magnesium-neodymium master alloy, magnesium-erbium master alloy, magnesium-zirconium master alloy and pure zinc raw materials are adjusted, the temperature of the solid solution treatment is 480℃, the holding time is 8h, the temperature of the aging treatment is 200℃, and the holding time is 24h. Finally, a cast rare earth magnesium alloy is obtained, which contains the following elements in percentage by mass: 5.13% of Gd element, 1.51% of Y element, 1.14% of Nd element, 0.15% of Er element, 1.18% of Zn element, 0.49% of Zr element, ≤0.1% of total content of unavoidable impurities, less than 0.05% of content of single impurity, and the balance of Mg element.

[0056] Example 6

[0057] The difference from example 1 is that the ratio of pure magnesium, magnesium gadolinium master alloy, magnesium yttrium master alloy, magnesium neodymium master alloy, magnesium erbium master alloy, magnesium zirconium master alloy and pure zinc raw materials is adjusted, the temperature of solid solution treatment is 470℃, the holding time is 8h, the temperature of aging treatment is 210℃, and the holding time is 12h. Finally, a cast rare earth magnesium alloy is obtained, which contains the following elements in mass percentage: 6.47% of Gd element, 0.69% of Y element, 0.21% of Nd element, 0.49% of Er element, 0.55% of Zn element, 0.41% of Zr element, ≤0.1% of total content of unavoidable impurities, less than 0.05% of content of single impurity, and the balance of Mg element.

[0058] Example 7

[0059] The difference from example 1 is that the ratio of pure magnesium, magnesium gadolinium master alloy, magnesium yttrium master alloy, magnesium neodymium master alloy, magnesium erbium master alloy, magnesium zirconium master alloy and pure zinc raw materials is adjusted, the temperature of solid solution treatment is 480℃, the holding time is 6h, the temperature of aging treatment is 220℃, and the holding time is 12h. Finally, a cast rare earth magnesium alloy is obtained, which contains the following elements in mass percentage: 5.47% of Gd element, 1.08% of Y element, 0.31% of Nd element, 0.16% of Er element, 0.61% of Zn element, 0.39% of Zr element, ≤0.1% of total content of unavoidable impurities, less than 0.05% of content of single impurity, and the balance of Mg element.

[0060] Example 8

[0061] The difference from example 1 is that the ratio of pure magnesium, magnesium gadolinium master alloy, magnesium yttrium master alloy, magnesium neodymium master alloy, magnesium erbium master alloy, magnesium zirconium master alloy and pure zinc raw materials is adjusted, the temperature of solid solution treatment is 490℃, the holding time is 8h, the temperature of aging treatment is 220℃, and the holding time is 24h. Finally, a cast rare earth magnesium alloy is obtained, which contains the following elements in mass percentage: 4.55% of Gd element, 1.47% of Y element, 0.51% of Nd element, 0.39% of Er element, 0.49% of Zn element, 0.47% of Zr element, ≤0.1% of total content of unavoidable impurities, less than 0.05% of content of single impurity, and the balance of Mg element.

[0062] Example 9

[0063] The difference from example 1 is that the ratio of pure magnesium, magnesium gadolinium master alloy, magnesium yttrium master alloy, magnesium neodymium master alloy, magnesium erbium master alloy, magnesium zirconium master alloy and pure zinc raw materials is adjusted, the temperature of solid solution treatment is 500℃, the holding time is 8h, the temperature of aging treatment is 225℃, the holding time is 24h, and finally a cast rare earth magnesium alloy is obtained, which contains the following elements in percentage by mass: 6.07% of Gd element, 1.19% of Y element, 0.49% of Nd element, 0.31% of Er element, 0.52% of Zn element, 0.37% of Zr element, ≤0.1% of total content of unavoidable impurities, less than 0.05% of content of single impurity, and the balance of Mg element.

[0064] Example 10

[0065] The difference from example 1 is that the ratio of pure magnesium, magnesium gadolinium master alloy, magnesium yttrium master alloy, magnesium neodymium master alloy, magnesium erbium master alloy, magnesium zirconium master alloy and pure zinc raw materials is adjusted, the temperature of solid solution treatment is 500℃, the holding time is 8h, the temperature of aging treatment is 220℃, the holding time is 24h, and finally a cast rare earth magnesium alloy is obtained, which contains the following elements in percentage by mass: 5.57% of Gd element, 1.46% of Y element, 1.03% of Nd element, 0.08% of Er element, 0.53% of Zn element, 0.55% of Zr element, ≤0.1% of total content of unavoidable impurities, less than 0.05% of content of single impurity, and the balance of Mg element.

[0066] Example 11

[0067] The difference from example 2 is that the ratio of magnesium gadolinium master alloy and magnesium yttrium master alloy is adjusted, and finally a cast rare earth magnesium alloy is obtained, which contains 5.79% of Gd element, 0.58% of Y element, and the mass ratio of Gd element to Y element is 10:1.

[0068] Example 12

[0069] The difference from example 2 is that the ratio of magnesium gadolinium master alloy and magnesium yttrium master alloy is adjusted, and finally a cast rare earth magnesium alloy is obtained, which contains 4.5% of Gd element, 1.87% of Y element, and the mass ratio of Gd element to Y element is 2.4:1.

[0070] Example 13

[0071] The difference from example 2 is that the addition of magnesium scandium master alloy is cancelled, and finally a cast rare earth magnesium alloy is obtained.

[0072] Example 14

[0073] The difference from example 2 is that the ratio of magnesium neodymium master alloy and magnesium erbium master alloy is adjusted, and finally a cast rare earth magnesium alloy is obtained, the content of Nd element is 0.05%, the content of Er element is 0.32%, and the mass ratio of Nd element, Er element and Sc element is 0.05:0.32:0.08.

[0074] Comparative example 1

[0075] The difference from example 1 is that the ratio of pure magnesium, magnesium gadolinium master alloy, magnesium yttrium master alloy, magnesium neodymium master alloy, magnesium erbium master alloy, magnesium zirconium master alloy and pure zinc raw material is adjusted, and finally a cast rare earth magnesium alloy is obtained, the cast rare earth magnesium alloy includes the following elements in mass percentage: 5.74% of Gd element, 3.11% of Y element, 0.10% of Nd element, 0.11% of Er element, 0.51% of Zn element, 0.35% of Zr element, the total content of unavoidable impurities is ≤0.1%, the content of single impurity is less than 0.05%, and the balance is Mg element.

[0076] Comparative example 2

[0077] The difference from example 1 is that the ratio of pure magnesium, magnesium gadolinium master alloy, magnesium yttrium master alloy, magnesium neodymium master alloy, magnesium erbium master alloy, magnesium zirconium master alloy and pure zinc raw material is adjusted, and finally a cast rare earth magnesium alloy is obtained, the cast rare earth magnesium alloy includes the following elements in mass percentage: 7.15% of Gd element, 2.37% of Y element, 1.15% of Nd element, 0.10% of Er element, 0.45% of Zn element, 0.38% of Zr element, the total content of unavoidable impurities is ≤0.1%, the content of single impurity is less than 0.05%, and the balance is Mg element.

[0078] Comparative example 3

[0079] The difference from example 1 is that the ratio of pure magnesium, magnesium gadolinium master alloy, magnesium yttrium master alloy, magnesium neodymium master alloy, magnesium erbium master alloy, magnesium zirconium master alloy and pure zinc raw material is adjusted, the solid solution treatment temperature is 480℃, the holding time is 8h, the aging treatment temperature is 210℃, and the holding time is 24h, and finally a cast rare earth magnesium alloy is obtained, the cast rare earth magnesium alloy includes the following elements in mass percentage: 4.08% of Gd element, 0.55% of Y element, 0.13% of Nd element, 0.06% of Er element, 0.49% of Zn element, 0.45% of Zr element, the total content of unavoidable impurities is ≤0.1%, the content of single impurity is less than 0.05%, and the balance is Mg element.

[0080] Comparative example 4

[0081] The difference from example 1 is that the addition of magnesium-erbium intermediate alloy is cancelled, and finally the cast rare earth magnesium alloy is obtained,

[0082] Performance test

[0083] The cast rare earth magnesium alloy prepared by the example and the comparative example is processed into a rod-shaped tensile sample of a national standard size (a gauge length L o = 50mm, a diameter d o = 10mm), and the tensile strength, the yield strength and the elongation are tested by using the method of GB / T 228.1-2021, and the test results are shown in Table 1.

[0084] Table 1

[0085]

[0086] From the above description, it can be seen that the above-mentioned examples of the present application achieve the following technical effects:

[0087] In the present application, the addition of Gd element, Y element, Nd element and Er element can weaken the basal texture of magnesium alloy and improve the plasticity. Gd element is the core strengthening element, and has high solid solubility in magnesium matrix. Gd element can control the lattice parameters of magnesium alloy through solid solution, optimize the deformation compatibility, reduce the critical shear stress difference between basal slip and prismatic slip, and induce the reduction of lattice axis ratio, thereby promoting the coordinated activation of basal slip and prismatic slip, and significantly improving the plasticity. With the increase of the addition amount of Gd element, a large amount of second phase will be formed in the magnesium alloy matrix, which will improve the strength of the magnesium alloy, but the plasticity will decrease, so the addition amount of Gd element should be controlled. Y element can significantly improve the yield strength of magnesium alloy. This is because the solid solubility of Y element in magnesium matrix is lower than that of Gd element, so it is easier to form second phase in magnesium alloy to hinder dislocation movement by adding Y element, so the plasticity of magnesium alloy is very sensitive to the content of Y element, and the addition amount of Y element should not be too high. The addition of Nd element can improve the plasticity of the alloy, but the solid solubility of Nd element in magnesium alloy is lower than that of Gd element and Y element, and excessive addition will form a large amount of brittle second phase to affect the plasticity of the alloy. Er element has a large solid solubility in magnesium alloy, but excessive addition of Er element is not conducive to the improvement of plasticity. The key role of Zn element is to improve the flowability of magnesium alloy melt and induce the formation of long-period ordered stacking phase. The purpose of improving plasticity is achieved by the deformation coordination of the twisted ordered stacking phase, but the increase of Zn content will lead to the coarsening of the ordered stacking phase, and Zn element will consume the strengthening element Gd by forming Zn-Gd compound, thereby reducing the performance of the alloy, so the content of Zn should not be too high. Zr is an effective grain refiner for magnesium alloy, and its addition is helpful to refine the magnesium alloy grains and improve the plasticity and strength of the magnesium alloy. Controlling the content of each element within the above range is helpful to improve the interaction between elements, thereby helping the magnesium alloy to have high plasticity while meeting the requirements of tensile strength and yield strength.

[0088] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cast rare earth magnesium alloy characterized by, The casting rare earth magnesium alloy comprises the following elements in percentage by mass: The content of the Gd element is 4.5-6.50%, the content of the Y element is 0.5-2.0%, the content of the Nd element is 0.05-1.2%, the content of the Er element is 0.05-0.5%, the content of the Zn element is 0.3-1.2%, the content of the Zr element is 0.3-0.6%, the total content of inevitable impurities is ≤0.1%, the content of a single impurity is less than 0.05%, and the balance is the Mg element; the mass ratio of the Gd element to the Y element is (3-10):1, and the casting rare earth magnesium alloy further comprises 0.05-0.1% of the Sc element.

2. The cast rare earth magnesium alloy according to claim 1, characterized by, The casting rare earth magnesium alloy comprises the following elements in percentage by mass: the content of the Gd element is 5.83-6.47%, the content of the Y element is 0.69-1.81%, the content of the Nd element is 0.11-0.21%, the content of the Er element is 0.09-0.49%, the content of the Zn element is 0.47-0.55%, the content of the Zr element is 0.32-0.41%, the total content of inevitable impurities is ≤0.1%, the content of a single impurity is less than 0.05%, and the balance is the Mg element.

3. The cast rare earth magnesium alloy according to claim 1, characterized by, The mass ratio of the Nd element, the Er element and the Sc element is (0.11-1.14):(0.06-0.49):0.

08.

4. The cast rare earth magnesium alloy according to any one of claims 1 to 3, characterized in that, The total content of the Gd element, the Y element, the Nd element, the Er element and the Sc element is 6-9%.

5. A method of producing the cast rare earth magnesium alloy as claimed in any one of claims 1 to 4, characterized by, The preparation method comprises: The metal raw material of the casting rare earth magnesium alloy is sequentially subjected to melting, casting, solid solution treatment, quenching treatment and aging treatment according to the proportion, so as to obtain the casting rare earth magnesium alloy.

6. The method of producing a cast rare earth magnesium alloy according to claim 5, characterized by, The temperature of the melting is 750-780 ℃.

7. The method of producing a cast rare earth magnesium alloy according to claim 6, characterized by, The preparation method further comprises: ultrasonic treatment of the melt during the melting, the frequency of the ultrasonic treatment is 20-22 kHz, and the time of the ultrasonic treatment is 10-20 min.

8. The method of producing a cast rare-earth magnesium alloy according to any one of claims 5 to 7, characterized in that, The temperature of the solid solution treatment is 470-500 ℃, and the holding time is 6-8 h; And / or, the temperature of the aging treatment is 200-230 ℃, and the holding time is 12-24 h; And / or, the temperature of the cooling medium of the quenching treatment is 70-80 ℃.

9. The method of producing a cast rare earth magnesium alloy according to claim 8, characterized by, The temperature rising process of the solid solution treatment comprises: rising the temperature to 450-460 ℃ at a temperature rising rate of 15-20 ℃ / min, holding for 5-10 min, and then rising to the temperature required for the solid solution treatment at a temperature rising rate of 5-7 ℃ / min to perform the solid solution treatment; And / or, the temperature rising process of the aging treatment comprises: rising the temperature to 180-190 ℃ at a temperature rising rate of 15-20 ℃ / min, holding for 5-10 min, and then rising to the temperature required for the aging treatment at a temperature rising rate of 5-7 ℃ / min to perform the aging treatment.

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