A composite deformation process for synergistically improving the strength and plasticity of a dual-phase magnesium-lithium alloy

Abstract

The present invention discloses a composite deformation process for improving the strength and plasticity of a dual-phase magnesium-lithium alloy, comprising the following steps: subjecting a magnesium-lithium alloy ingot to homogenization treatment and solid solution water quenching treatment in sequence, then preheating a magnesium-lithium alloy round bar, and then placing it in an extruder for extrusion deformation, cutting the extruded bar and subjecting it to composite deformation of variable temperature mixed hot rolling + room temperature rolling, with a total deformation of 70%, to obtain a dual-phase magnesium-lithium alloy plate with a thickness of 2 mm, and then subjecting the rolled plate to aging treatment. The present invention can effectively refine the grains, enhance the strength of the magnesium-lithium alloy without losing plasticity, and improve the synergistic effect of the strength and plasticity of the magnesium-lithium alloy. The preparation method is simple, the cost is low, and it is convenient for the promotion and use of magnesium-lithium alloys.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material preparation and processing, and in particular relates to a composite deformation process for synergistically improving the strength and plasticity of a dual-phase magnesium-lithium alloy. Background Art

[0002] Magnesium-lithium alloys have the advantages of low density, good plasticity, high specific strength and specific modulus, good low-temperature toughness, insensitivity to notches, low anisotropy, good thermal conductivity, good electrical conductivity, and good electromagnetic shielding. Magnesium-lithium alloys are the preferred high-performance magnesium alloy lightweight structural materials in the aerospace field. However, magnesium-lithium alloys have low absolute strength, poor mechanical property stability, difficulty in achieving a balance between strength and plasticity, difficulty in matching strength and density, and poor corrosion resistance, which greatly limit the application of magnesium-lithium alloys.

[0003] Dual-phase magnesium-lithium alloys have the moderate strength of single-phase α-Mg magnesium-lithium alloys and the excellent room-temperature processability of single-phase β-Li magnesium-lithium alloys. However, the plastic deformation of the α-Mg and β-Li matrix phases of the dual-phase magnesium-lithium alloys is not synchronized, which makes it more difficult to improve the strength of the magnesium-lithium alloys. Furthermore, the coarse grains of the matrix phase of the dual-phase magnesium-lithium alloys are also a factor that limits the improvement of the mechanical properties of the magnesium-lithium alloys.

[0004] At present, there is no relevant report that the strength of magnesium-lithium alloy can reach 300MPa or above through conventional deformation process and is suitable for industrial production. The research group of Nanjing University of Science and Technology (Yang Y, Chen X, Nie J, et al. Ac hieving ultra-strong Magnesium-lithium alloys by low-strain rotary swaging [J]. Materials Research Letters, 2021, 9 (6): 255-262.) used rotary swaging technology to prepare a kind of strength up to 405MPa and elongation of about 5%, but rotary swaging technology is mostly used for pipes and shaft parts, and the size of the prepared material is relatively small and the cost is relatively high. Patent document CN113502422B discloses high-strength and toughness magnesium-lithium alloy and its preparation method, mentioning that the magnesium-lithium alloy extrusion is hot-rolled, and then the hot-rolled plate is friction-processed to obtain a magnesium-lithium alloy with a strength higher than 300MPa and an elongation of about 20%, but the friction processing mainly acts on the surface of the material, and the patent processing technology is relatively complicated, and the economic investment is relatively large. Summary of the invention

[0005] The present invention develops a composite deformation process that improves the strength and plasticity of dual-phase magnesium-lithium alloys without sacrificing the plasticity of magnesium-lithium alloys, is economically applicable, and is easy to operate. It is suitable for factory assembly line deformation processing, shortens the factory preparation cycle, and improves the factory's economic benefits. In order to improve the strength and plasticity of dual-phase magnesium-lithium alloy materials, the present invention proposes the following technical solutions:

[0006] A composite deformation process for synergistically improving the strength and plasticity of a dual-phase magnesium-lithium alloy, wherein a magnesium-lithium alloy is prepared according to the following mass percentages: Li: 7%-9%, Al: 3%-5%, and the rest is magnesium and unavoidable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0007] S1, homogenizing the magnesium-lithium alloy ingot and then performing a solid solution treatment;

[0008] S2, mechanically cutting the heat-treated ingot into an extruded cylinder and performing surface milling treatment, preheating the cylinder, and then extruding the preheated cylinder, and water quenching the extruded magnesium-lithium alloy after extrusion;

[0009] S3, hot rolling the extruded magnesium-lithium alloy with a deformation amount of 60%;

[0010] S4. After hot rolling, the plate cooled to room temperature is subjected to room temperature rolling deformation, with a deformation amount of 10%.

[0011] As a supplement to the technical solution, the temperature of the homogenization treatment in step S1 is 250°C-300°C, the insulation time is 1.5h-4h, and the cooling method is air cooling.

[0012] As a supplement to the technical solution, the solution treatment temperature in step S1 is 350°C-420°C, the holding time is 1.5h-3h, and the cooling method is water quenching.

[0013] As a supplement to the technical solution, the extrusion ratio in step S2 is 10:1-45:1, the extrusion temperature is 260°C-300°C, and the extrusion rate is 0.5-1.5 mm / s.

[0014] As a supplement to the technical solution, the hot rolling process in step S3 adopts variable temperature mixed hot rolling, including the following steps:

[0015] The first hot rolling process: temperature is 260℃-300℃, deformation is 40%, and reduction per pass is 15%-25%

[0016] Cooling control: Use a controlled cooling device to spray water for cooling, the cooling rate is controlled at 5-10℃ / min, and the cooling termination temperature is controlled to be about 5℃ higher than the second hot rolling temperature;

[0017] The second hot rolling process: temperature 50℃-100℃, deformation amount 20%, and reduction amount of each pass 5%-15%.

[0018] As a supplement to the technical solution, the room temperature rolling process in S4 is as follows: the temperature is 25° C., the deformation is 10%, and the reduction in each pass is 1%-5%.

[0019] As a supplement to the technical solution, step S5 is also included: subjecting the rolled plate to aging treatment.

[0020] As a supplement to the technical solution, the aging treatment temperature in step S5 is 50°C-150°C, the insulation time is 0.5h-16h, and the cooling method is air cooling.

[0021] Beneficial effects: The present invention subjects the ingot to medium-temperature extrusion at an extrusion temperature of 260°C-300°C, so that the β-Li phase in the dual-phase magnesium-lithium alloy undergoes maximum dynamic recrystallization, thereby improving the degree of grain refinement, and then performs rapid water quenching to prevent the growth of β-phase grains. At the same time, part of the coarse α-Mg phase is mechanically crushed to achieve the effect of refining the α-Mg phase, and part of the α-Mg phase undergoes dynamic recrystallization to improve the degree of α-Mg phase refinement and improve the mechanical properties. In another aspect of the present invention, in order to further improve the mechanical properties of the magnesium-lithium alloy, the present invention performs variable temperature mixed hot rolling on the basis of extrusion. The first hot rolling process enables the atoms in the magnesium-lithium alloy to obtain a certain activity, thereby providing power for the movement of dislocations. At the same time, low pass-high pressure can reduce the grain growth time, thereby avoiding the defect of decreased mechanical properties caused by grain growth, and introducing a large number of dislocations into the magnesium-lithium alloy material matrix, thereby improving The strength of magnesium-lithium alloy; after cooling to 50-100°C, a second hot rolling is carried out to promote the precipitation of strengthening phase, limit the process of Zn atoms replacing magnesium atoms, and further increase the dislocation density of the material matrix, and then water quenching is carried out to prevent the growth of grain structure, and further improve the strength of magnesium-lithium alloy; when the plate is cooled to 25°C, room temperature rolling is carried out to further refine the α-Mg phase, improve the work hardening effect of the two-phase magnesium-lithium alloy, and increase the proportion of strain-induced phase structure in the β phase of the magnesium-lithium alloy to obtain a large number of subgrain boundaries and nano-precipitated phases, greatly refine the phase structure of the two-phase magnesium-lithium alloy and hinder crack propagation, thereby optimizing the strength and plasticity of the magnesium-lithium alloy; finally, according to the requirements of component strength and plasticity, aging strengthening or aging softening treatment can be carried out, which can effectively adjust the matching of strength and plasticity of magnesium-lithium alloy, improve the service life of magnesium-lithium alloy structure materials, and broaden the application field of magnesium-lithium alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a step diagram of the present invention.

[0023] Figure 2 It is the tensile strength and elongation of the magnesium-lithium alloy under different aging conditions of the present invention. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention will be described in detail below.

[0025] like Figure 1 As shown, the present invention proposes a composite deformation process for synergistically improving the strength and plasticity of a dual-phase magnesium-lithium alloy. According to an embodiment of the present invention, the method includes:

[0026] First, a magnesium-lithium alloy is prepared according to the following mass percentages: Li: 7%-9%, Al: 3%-5%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0027] S1. Perform homogenization treatment on the magnesium-lithium alloy ingot: the homogenization treatment temperature is 250°C-300°C, the holding time is 1.5h-4h, and the cooling method is air cooling.

[0028] Then the solution treatment is carried out, the solution treatment temperature is 350℃-420℃, the holding time is 1.5h-3h, and the cooling method is water quenching.

[0029] S2. Mechanically cut the heat-treated ingot into an extruded cylinder and perform surface milling, preheat the cylinder, and then extrude the preheated cylinder, and then water quench the extruded magnesium-lithium alloy after extrusion. The extrusion ratio is 10:1-45:1, the extrusion temperature is 260℃-300℃, and the extrusion rate is 0.5-1.5mm / s.

[0030] S3, subjecting the extruded magnesium-lithium alloy to mixed hot rolling at variable temperature, with a deformation amount of 60%. The variable temperature rolling adopts two hot rolling processes.

[0031] The first hot rolling process: the temperature is 260℃-300℃, the deformation is 40%, and the reduction in each pass is 15%-25%, so that the atoms in the magnesium-lithium alloy can obtain a certain activity and provide power for the dislocation movement. At the same time, low pass-high reduction can reduce the grain growth time and introduce a large number of dislocations into the magnesium-lithium alloy material matrix;

[0032] Cooling control: Use a controlled cooling device to spray water for cooling, the cooling rate is controlled at 5-10℃ / min, and the cooling termination temperature is controlled to be about 5℃ higher than the second hot rolling temperature;

[0033] The second hot rolling process: temperature 50℃-100℃, deformation 20%, reduction of 5%-15% per pass, water quenching after hot rolling to promote the precipitation of strengthening phase, limit the process of Zn atoms replacing magnesium atoms, and further increase the dislocation density of the material matrix, and then water quenching to prevent grain growth.

[0034] S4. After hot rolling, the plate cooled to room temperature is subjected to room temperature rolling deformation. The room temperature rolling process is as follows: temperature is 25° C., deformation is 10%, and reduction in each pass is 1%-5%.

[0035] S5. Perform aging treatment on the rolled plate: the aging treatment temperature is 50°C-150°C, the insulation time is 0.5h-16h, and the cooling method is air cooling.

[0036] The embodiments of the present invention are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0037] Example 1

[0038] Embodiment 1 After the cast magnesium-lithium alloy is heat treated, the magnesium-lithium alloy is processed by using the process of extrusion+hot rolling+room temperature rolling.

[0039] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0040] S1. Perform homogenization treatment on the magnesium-lithium alloy ingot: temperature 250°C, holding time 4h, cooling method is air cooling;

[0041] Then the solution treatment is carried out: the temperature is 350℃, the holding time is 3h, and the cooling method is water quenching;

[0042] S2, mechanically cutting the heat-treated cylinder and performing surface milling, preheating the cylinder, and then extruding the preheated cylinder, the extrusion temperature is 260° C., the extrusion ratio is 35:1, the extrusion rate is 1 mm / s, and the extruded magnesium-lithium alloy is water quenched after extrusion;

[0043] S3, hot rolling the extruded sample: the temperature is 260°C, the deformation is 60%, and the reduction in each pass is 25%;

[0044] S4. Roll the hot-rolled plate at room temperature: the temperature is 25° C., the deformation is 10%, and the reduction in each pass is 3%, and finally a 2 mm magnesium-lithium alloy plate is obtained.

[0045] Example 2

[0046] Example 2 After the cast magnesium-lithium alloy is heat treated, the magnesium-lithium alloy is processed by using the process of extrusion + variable temperature mixed hot rolling + room temperature rolling.

[0047] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0048] S1. Perform homogenization treatment on the magnesium-lithium alloy ingot: temperature 250°C, holding time 4h, cooling method is air cooling;

[0049] Then the solution treatment is carried out: the temperature is 350℃, the holding time is 3h, and the cooling method is water quenching;

[0050] S2, mechanically cutting the heat-treated cylinder and performing surface milling, preheating the cylinder, and then extruding the preheated cylinder, the extrusion temperature is 260° C., the extrusion ratio is 35:1, the extrusion rate is 1 mm / s, and the extruded lithium alloy is water quenched after extrusion;

[0051] S3, subjecting the extruded sample to variable temperature mixed hot rolling deformation:

[0052] The first hot rolling process: temperature is 260℃, deformation is 40%, and reduction is 25% per pass;

[0053] Intermediate cooling control: Use the controlled cooling device for water spray cooling, the cooling rate is controlled at 5℃ / min, and the cooling end temperature is controlled at around 55℃;

[0054] The second hot rolling process: temperature is 50°C, deformation is 20%, and reduction is 15% per pass.

[0055] S4. Roll the hot-rolled plate at room temperature: the temperature is 25° C., the deformation is 10%, and the reduction in each pass is 3%, and finally a 2 mm magnesium-lithium alloy plate is obtained.

[0056] Example 3

[0057] Embodiment 3 After the cast magnesium-lithium alloy is heat treated, the magnesium-lithium alloy is processed by adopting the process of extrusion + variable temperature mixed hot rolling + room temperature rolling + aging.

[0058] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0059] S1. Perform homogenization treatment on the magnesium-lithium alloy ingot: temperature 250°C, holding time 4h, cooling method is air cooling;

[0060] Then the solution treatment is carried out: the temperature is 350℃, the holding time is 3h, and the cooling method is water quenching;

[0061] S2, mechanically cutting the heat-treated cylinder and performing surface milling, preheating the cylinder, and then extruding the preheated cylinder, the extrusion temperature is 260° C., the extrusion ratio is 35:1, the extrusion rate is 1 mm / s, and the extruded lithium alloy is water quenched after extrusion;

[0062] S3, subjecting the extruded sample to variable temperature mixed hot rolling deformation:

[0063] The first hot rolling process: temperature is 260℃, deformation is 40%, and reduction is 25% per pass;

[0064] Cooling control: Use the controlled cooling device to spray water for cooling, the cooling rate is controlled at 5℃ / min, and the cooling end temperature is controlled at around 55℃;

[0065] The second hot rolling process: temperature is 50°C, deformation is 20%, and reduction is 15% per pass.

[0066] S4, rolling the hot-rolled plate at room temperature: the temperature is 25° C., the deformation is 10%, and the reduction per pass is 3%, and finally a 2 mm magnesium-lithium alloy plate is obtained;

[0067] S5. Aging treatment: temperature is 50℃, holding time is 2h, cooling method is air cooling.

[0068] Example 4

[0069] Example 4 After the cast magnesium-lithium alloy is heat treated, the magnesium-lithium alloy is processed by a process of extrusion + variable temperature mixed hot rolling + room temperature rolling + aging.

[0070] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0071] S1. Perform homogenization treatment on the magnesium-lithium alloy ingot: temperature 250°C, holding time 4h, cooling method is air cooling;

[0072] Then the solution treatment is carried out: the temperature is 350℃, the holding time is 3h, and the cooling method is water quenching;

[0073] S2, mechanically cutting the heat-treated cylinder and performing surface milling, preheating the cylinder, and then extruding the preheated cylinder, the extrusion temperature is 260° C., the extrusion ratio is 35:1, the extrusion rate is 1 mm / s, and the extruded magnesium-lithium alloy is water quenched after extrusion;

[0074] S3, subjecting the extruded sample to variable temperature mixed hot rolling deformation:

[0075] The first hot rolling process: temperature is 260℃, deformation is 40%, and reduction is 25% per pass;

[0076] Cooling control: Use the controlled cooling device to spray water for cooling, the cooling rate is controlled at 5℃ / min, and the cooling end temperature is controlled at around 55℃;

[0077] The second hot rolling process: temperature is 50°C, deformation is 20%, and reduction is 15% per pass.

[0078] S4, rolling the hot-rolled plate at room temperature: the temperature is 25° C., the deformation is 10%, and the reduction per pass is 3%, and finally a 2 mm magnesium-lithium alloy plate is obtained;

[0079] S5. Aging treatment: temperature is 50℃, holding time is 16h, cooling method is air cooling.

[0080] The tensile strength and elongation performance test results of the magnesium-lithium alloy sheets prepared in Examples 1 to 3 and Comparative Examples 1 to 6 are shown in Table 1 below. The tensile strength and elongation of the magnesium-lithium alloy under different processes.

[0081] Comparative Example 1

[0082] Comparative Example 1 is a pure cast magnesium-lithium alloy.

[0083] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest are magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot.

[0084] Comparative Example 2

[0085] Comparative Example 2: After the cast magnesium-lithium alloy is heat treated, the magnesium-lithium alloy is processed by an extrusion process.

[0086] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0087] S1. Perform homogenization treatment on the magnesium-lithium alloy ingot: temperature 250°C, holding time 4h, cooling method is air cooling;

[0088] Then the solution treatment is carried out: the temperature is 350℃, the holding time is 3h, and the cooling method is water quenching;

[0089] S2. Cut the heat-treated machine into an extruded cylinder and perform surface milling, preheat the cylinder, and then extrude the preheated cylinder at an extrusion temperature of 260°C, an extrusion ratio of 35:1, and an extrusion rate of 1 mm / s. After extrusion, the extruded lithium alloy is water quenched.

[0090] Comparative Example 3

[0091] Comparative Example 3: After the cast magnesium-lithium alloy is heat treated, the magnesium-lithium alloy is processed by hot rolling.

[0092] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0093] S1. Perform homogenization treatment on the magnesium-lithium alloy ingot: temperature 250°C, holding time 4h, cooling method is air cooling;

[0094] Then the solution treatment is carried out: the temperature is 350℃, the holding time is 3h, and the cooling method is water quenching;

[0095] S2. Hot rolling the heat-treated magnesium-lithium alloy ingot at a temperature of 260° C., a deformation amount of 70%, and a reduction amount of 25% per pass.

[0096] Comparative Example 4

[0097] Comparative Example 4: After the cast magnesium-lithium alloy was heat treated, the magnesium-lithium alloy was processed by a conventional hot rolling + room temperature rolling process.

[0098] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0099] S1: homogenizing the magnesium-lithium alloy ingot: temperature 250°C, holding time 4h, cooling method is air cooling;

[0100] Then the solution treatment is carried out: the temperature is 350℃, the holding time is 3h, and the cooling method is water quenching;

[0101] S2: The heat-treated magnesium-lithium alloy ingot is hot rolled at a temperature of 260° C., a deformation amount of 60%, and a reduction amount of 25% per pass.

[0102] S3. Roll the hot-rolled plate at room temperature: the temperature is 25°C, the reduction in each pass is 3%, and the deformation is 10%.

[0103] Comparative Example 5

[0104] Comparative Example 5: After the cast magnesium-lithium alloy is heat treated, the magnesium-lithium alloy is processed by a conventional extrusion + hot rolling process.

[0105] A magnesium-lithium alloy is prepared according to the following mass percentages: Li: 8%, Al: 3%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed:

[0106] S1: homogenizing the magnesium-lithium alloy ingot: temperature 250°C, holding time 4h, cooling method is air cooling;

[0107] Then the solution treatment is carried out: the temperature is 350℃, the holding time is 3h, and the cooling method is water quenching;

[0108] S2, mechanically cutting the heat-treated cylinder and performing surface milling, preheating the cylinder, and then extruding the preheated cylinder, the extrusion temperature is 260° C., the extrusion ratio is 35:1, the extrusion rate is 1 mm / s, and the extruded magnesium-lithium alloy is water quenched after extrusion;

[0109] S3. The extruded sample is subjected to hot rolling deformation: the temperature is 260°C, the deformation amount is 70%, and the reduction amount per pass is 25%.

[0110] Table 1 Tensile strength and elongation of magnesium-lithium alloy under different processes

[0111]

[0112] According to Table 1 above, it can be seen that the strength of magnesium-lithium alloy after deformation processing is greatly improved compared with the cast state, the elongation of conventional extruded magnesium-lithium alloy is higher than that of conventional hot-rolled magnesium-lithium alloy, the strength of conventional hot-rolled magnesium-lithium alloy is higher than that of conventional extruded magnesium-lithium alloy, and the strength of conventional hot-rolled + room temperature rolled magnesium-lithium alloy is the highest, but the elongation is only 6.4%.

[0113] The strength of the magnesium-lithium alloy in the conventional extrusion + hot rolling state is higher than that in the extrusion deformation or hot rolling deformation state, and the elongation decreases less. The strength and elongation of the conventional extrusion + hot rolling + room temperature rolling state are improved to a certain extent compared with the conventional extrusion + hot rolling, and the strength of the magnesium-lithium alloy in the extrusion + variable temperature mixed hot rolling + room temperature rolling state is improved to a certain extent compared with the conventional extrusion + hot rolling + room temperature rolling state magnesium-lithium alloy, and the elongation decreases less. In summary, the composite deformation process of extrusion + mixed rolling at different temperatures of the present invention overcomes the contradiction between strength and plasticity, and achieves the goal of synergistically improving the strength and plasticity of the dual-phase magnesium-lithium alloy.

[0114] like Figure 2 As shown in the figure, the tensile strength and elongation of the magnesium-lithium alloy in the deformation process under different aging conditions of the present invention. In order to further improve the strength of the magnesium-lithium alloy, the magnesium-lithium alloy sheet is subjected to aging treatment. Figure 2 It can be found that with the increase of aging treatment time, the strength first increases and then decreases, and the elongation first decreases and then increases. The strength of the magnesium-lithium alloy after aging for 2h is the largest, and the elongation remains above 10%. As the aging time reaches 15h-16h, the change trend of strength and elongation tends to be gentle. The aging strengthening stage can increase the strength of the magnesium-lithium alloy by 12MPa, and the aging softening stage can increase the elongation of the magnesium-lithium alloy by 6.4%. This patent adopts conventional deformation technology to compositely process magnesium-lithium alloy, adjusts the matching of strength and plasticity of magnesium-lithium alloy, and combines aging treatment technology to obtain magnesium-lithium alloy with high strength and good plasticity, which has certain innovation.

[0115] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A composite deformation process for improving the strength and plasticity of a dual-phase magnesium-lithium alloy, characterized in that: The magnesium-lithium alloy is prepared according to the following mass percentages: Li: 7%-9%, Al: 3%-5%, and the rest is magnesium and inevitable impurities, wherein the purity of magnesium and aluminum is 99.99%, and the impurity content in the magnesium-lithium alloy material is less than 0.02%; the prepared magnesium-lithium alloy raw material is melted and cast into a magnesium-lithium alloy ingot, and then the following composite deformation process is performed: S1, homogenizing the magnesium-lithium alloy ingot and then performing a solid solution treatment; S2, mechanically cutting the heat-treated ingot into an extruded cylinder and performing surface milling treatment, preheating the cylinder, and then extruding the preheated cylinder, and water quenching the extruded magnesium-lithium alloy after extrusion; S3, hot rolling the extruded magnesium-lithium alloy, with a deformation of 60%, using variable temperature mixed hot rolling, comprising the following steps: The first hot rolling process: temperature is 260℃-300℃, deformation is 40%, and reduction is 15%-25% per pass. Cooling control: Use a controlled cooling device to spray water for cooling, control the cooling rate at 5-10℃ / min, and control the cooling termination temperature to be 5℃ higher than the second hot rolling temperature; The second hot rolling process: temperature 50℃-100℃, deformation 20%, reduction 5%-15% per pass; S4. After hot rolling, the plate cooled to room temperature is subjected to room temperature rolling deformation, with a deformation amount of 10%.

2. A composite deformation process for synergistically improving strength and plasticity of a dual-phase magnesium-lithium alloy as claimed in claim 1, characterized in that: The homogenization treatment temperature in step S1 is 250° C.-300° C., the heat preservation time is 1.5 h-4 h, and the cooling method is air cooling.

3. A composite deformation process for improving the strength and plasticity of a dual-phase magnesium-lithium alloy as claimed in claim 1, characterized in that: The solution treatment temperature in step S1 is 350° C.-420° C., the holding time is 1.5 h-3 h, and the cooling method is water quenching.

4. A composite deformation process for improving the strength and plasticity of a dual-phase magnesium-lithium alloy as claimed in claim 1, characterized in that: The extrusion ratio in step S2 is 10:1-45:1, the extrusion temperature is 260° C.-300° C., and the extrusion rate is 0.5-1.5 mm / s.

5. A composite deformation process for improving the strength and plasticity of a dual-phase magnesium-lithium alloy as claimed in claim 1, characterized in that: The room temperature rolling process in S4 is as follows: the temperature is 25° C. and the reduction amount per pass is 1%-5%.

6. A composite deformation process for improving the strength and plasticity of a dual-phase magnesium-lithium alloy as claimed in claim 1, characterized in that: The method further comprises step S5: subjecting the rolled plate to aging treatment.

7. A composite deformation process for improving the strength and plasticity of a dual-phase magnesium-lithium alloy as claimed in claim 6, characterized in that: The aging treatment temperature in step S5 is 50° C.-150° C., the holding time is 0.5 h-16 h, and the cooling method is air cooling.

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