CN115125423B - High-strength Gao Chengxing magnesium-lithium alloy and preparation method and application thereof - Google Patents
High-strength Gao Chengxing magnesium-lithium alloy and preparation method and application thereof Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C23/00—Alloys based on magnesium
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- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon
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Abstract
The invention belongs to the technical field of magnesium-lithium alloy material preparation, and particularly relates to a high-strength Gao Chengxing magnesium-lithium alloy, and a preparation method and application thereof. Aiming at the problems existing in the prior art, the invention provides the high-strength Gao Chengxing magnesium-lithium alloy, and aims at the defect that the traditional Mg-Li-Al-Zn magnesium-lithium alloy has insufficient comprehensive mechanical properties, and the defects of effective improvement of the comprehensive mechanical properties of the Mg-Li-Al-Zn magnesium-lithium alloy, improvement of age softening phenomenon and poor mechanical durability are overcome by adding mixed RE and trace Ag elements and Zr elements. The high-strength high-formability magnesium-lithium alloy consists of the following components in percentage by mass: 4.5-11.5% of Li, 0.5-2.2% of Al, 2.5-5.5% of Zn, 0.1-3% of RE, 0.1-1.2% of Ag, 0.01-0.2% of Zr, RE being lanthanum-cerium misch metal, the total content of Al and Zn should not exceed 5%, the impurity content should be less than 0.01%, and the balance being Mg. The magnesium-lithium alloy plate prepared by the method has the advantages of high tensile strength, good plasticity, stable mechanical property and excellent room-temperature stamping forming capability, and the preparation method is simple and has strong operability.
Description
Technical Field
The invention belongs to the technical field of magnesium-lithium alloy material preparation, and particularly relates to a high-strength Gao Chengxing magnesium-lithium alloy, and a preparation method and application thereof.
Background
The magnesium-lithium alloy is the lightest metal structural material at present, and has the advantages of low density, high specific strength and specific rigidity, good damping and shock absorption performance, good heat conductivity, good electromagnetic shielding effect and the like. The alloy is lighter than the common magnesium alloy by 1/4 to 1/3, the density is only 1/2 of the density of the aluminum alloy and 1/5 of the density of steel, the alloy meets the requirement of light structural materials, and is widely favored in the fields of aerospace, electronic communication, weaponry and the like. With the continuous maturity of magnesium-lithium alloy application, the product form of the magnesium-lithium alloy is not limited to simple forgings, plates, bars and the like, the demand of various magnesium-lithium alloy structural members with complex shapes is continuously increased, and the demand on the formability of the magnesium-lithium alloy is higher.
Curved surface type structural members are one of the most common structural members, and the processing technology thereof is very representative of the consideration of the formability of materials. The curved structural member is mainly obtained by three modes of casting, precision machining and plastic deformation. At present, the casting process of the magnesium-lithium alloy is still immature, and the interface reaction problem of the magnesium-lithium alloy melt and the film shell in the casting process is not solved properly; the cutting allowance required by precisely processing and producing curved structural members by using thick plates or forgings is large, and the consumption can reach 90 percent at most, so the processing mode has high cost and low efficiency, and simultaneously, the generated dust is harmful to the environment and human body; in contrast, the stamping forming is a more feasible method, and curved surface parts with uniform wall thickness and good comprehensive mechanical properties can be rapidly produced.
In the prior art, the magnesium alloy formability research is mainly based on the traditional wrought magnesium alloy, and the magnesium lithium alloy is less researched. For example, chinese patent publication No. CN109182859a discloses a method for preparing a magnesium alloy sheet with high formability by composite deformation, which includes two heat treatments, one compression deformation and two rolling deformations, wherein the material is AZ31-0.3Mn, and the cupping value after deformation is 5.3; chinese patent publication No. CN113444945a discloses a high plasticity, high formability magnesium alloy sheet material with annular divergent structure and preparation method, comprising Zn:0.5 to 2 percent, li: 1-3%, gd: 0.1-1%, the balance being Mg, the maximum value of the alloy cupping is 7.3; chinese patent publication No. CN109844152a discloses a high formability magnesium alloy sheet and a method for preparing the same, comprising Zn: 0-3%, ca:0 to 1.5 percent, mn:0 to 1.0 percent and the balance of Mg, wherein the maximum cupping value of the alloy is 9.0, the ultimate tensile strength of the alloy is 254MPa, the yield strength is 185MPa, and the elongation is 22.2 percent.
The above researches are based on the deformed magnesium alloy, and because the magnesium alloy belongs to a close-packed Hexagonal (HCP) crystal structure, the slippage system is less, the deformation is difficult, the forming performance and the plastic improvement are relatively limited, and the forming preparation of the magnesium alloy structural member is restricted. And when Li element is added into the magnesium alloy, the density is reduced, the lattice symmetry is increased, and the forming capability is obviously improved.
However, at the same time, magnesium-lithium alloys having high plasticity or high formability have a problem that the strength is too low, such as LZ91N, LA103M, and are difficult to be applied in mass as parts of a load-carrying structure. However, the high-strength magnesium-lithium alloy developed at present is generally low in elongation and low in formability, for example, researches by Liang et al develop a magnesium-lithium alloy with a tensile strength of 315MPa and an elongation of 3.4% (see Liang X, xiang P, hao J I, et al Transactions of Nonferrous Metals Society of China,2021,31 (4): 925-938.); for another example, chinese patent publication No. CN112442620A discloses a 300 MPa-grade magnesium-lithium alloy material and a preparation method thereof, wherein the tensile strength of the alloy is 307MPa at the highest, and the density is 1.54g/cm 3 The elongation was 13%.
Based on the above problems, it is necessary to develop a high-strength Gao Chengxing magnesium-lithium alloy, improve the production efficiency of magnesium-lithium alloy forming parts, realize the weight reduction substitution of curved surface parts, and expand the application field thereof.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides the high-strength Gao Chengxing magnesium-lithium alloy, and aims at the defect that the traditional Mg-Li-Al-Zn magnesium-lithium alloy has insufficient comprehensive mechanical properties, and the defects of effective improvement of the comprehensive mechanical properties of the Mg-Li-Al-Zn magnesium-lithium alloy, improvement of age softening phenomenon and poor mechanical durability are overcome by adding mixed RE and trace Ag elements and Zr elements.
Meanwhile, the invention also provides a preparation method of the high-strength Gao Chengxing magnesium-lithium alloy plate, which is characterized in that the magnesium-lithium alloy plate with small grain size, uniform structure, high tensile strength and high elongation is obtained by carrying out composite plastic deformation such as forging, extrusion and rolling on the Mg-Li-Al-Zn-RE-Ag-Zr magnesium-lithium alloy, and then the magnesium-lithium alloy plate with good strength and formability can be obtained under the condition of less influence on strength by a cold-hot circulation treatment mode.
The invention further provides application of the magnesium-lithium alloy plate with high strength and high formability.
Based on the above purpose, the invention adopts the following technical scheme:
the high-strength Gao Chengxing magnesium-lithium alloy consists of the following components in percentage by mass: 4.5 to 11.5 percent of Li,0.5 to 2.2 percent of Al,2.5 to 5.5 percent of Zn,0.1 to 3 percent of RE,0.1 to 1.2 percent of Ag,0.01 to 0.2 percent of Zr, RE being lanthanum-cerium mixed rare earth, the total content of Al and Zn being not more than 5 percent, the content of impurities being less than 0.01 percent, and the balance being Mg.
Specifically, in lanthanum-cerium mixed rare earth RE, the mass ratio La: ce is more than or equal to 60:30.
The preparation method of the high-strength Gao Chengxing magnesium-lithium alloy plate comprises the following steps:
(1) Vacuum melting and casting: preparing the required components of the magnesium-lithium alloy according to the mass percentage, vacuumizing, filling argon, smelting and casting, and obtaining a homogeneous magnesium-lithium alloy cast ingot after the cast ingot is cooled;
(2) And (3) deformation heat treatment: and (3) machining the magnesium-lithium alloy ingot obtained in the step (1) to remove the surface oxide layer, and then sequentially performing forging, extrusion, rolling and cold-hot cycle treatment to obtain the magnesium-lithium alloy plate with high strength and high formability.
Specifically, the vacuum melting and casting in the step (1) specifically comprises the following steps: vacuumizing to 10Pa in a vacuum reaction furnace, charging argon to the vacuum degree of 50kPa, heating to 650-800 ℃ for smelting for 30-90min, standing for 10-30min, and casting to obtain the Gao Chunjing magnesium-lithium alloy cast ingot.
Specifically, the ingot obtained in the step (1) is subjected to homogenization treatment before forging in the step (2), and the ingot is placed in a table heat treatment furnace and subjected to homogenization treatment for 2-6 hours at the temperature of 350-400 ℃ under the protection of nitrogen.
Specifically, the forging process in the step (2) is as follows: heating the cast ingot obtained in the step (1) to 280-420 ℃, preserving heat for 2-12 h, then cooling to 190-280 ℃ for multidirectional forging, wherein the forging ratio is (2-5.5): 1, final forging temperature is 150-250 ℃, and after forging, water cooling is carried out to room temperature, so as to obtain the forged rod with the diameter of 90-180 mm.
Specifically, the extrusion process in the step (2) is as follows: and (3) machining the forged bar to remove the surface oxide layer, heating to 200-300 ℃ and preserving heat for 30-100 min, then extruding, wherein the extrusion ratio is 10-60, the extrusion speed is 20-120 mm/min, and then air-cooling or water-cooling to room temperature to obtain the extruded plate with the thickness of 10-25 mm.
Specifically, the rolling process in the step (2) is as follows: heating the extruded plate obtained by extrusion to 300-450 ℃ and preserving heat for 10-210 min, then cooling to 180-280 ℃ and carrying out cross rolling, reversing the plate by 90 degrees after each pass of rolling to carry out the next pass, wherein the single pass of rolling is 25-50% and the total rolling is 70-95%, and finally obtaining the magnesium-lithium alloy plate with the thickness of 1.5-3.0 mm.
Specifically, the cold-hot cycle treatment process in the step (2) is as follows: and (3) placing the rolled plate in a cold and hot circulation furnace, carrying out cold and hot circulation at the temperature of at least 150 ℃ and at the temperature of at most 150 ℃, wherein the single circulation time is 2-20h, the single circulation temperature change rate is-5 ℃/min, and the heat preservation is carried out for 20-30min at the lowest temperature and the highest temperature, wherein two circulation are carried out, the medium of the cold and hot circulation is liquid nitrogen, and the plate is taken out and is recovered to the room temperature after the cold and hot circulation treatment is finished.
The magnesium-lithium alloy plate with high strength and high formability is prepared by the method, and the thickness of the magnesium-lithium alloy plate is 1.5-3.0 mm.
The high-strength high-formability magnesium-lithium alloy plate is applied to the preparation of industrial product shells or aerospace curved surface parts.
Specifically, the industrial product shell is a luggage shell or a portable electronic product shell.
Specifically, the aerospace curved surface part is a satellite electronic device tray and other products.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention prepares the Mg-Li-Al-Zn-RE-Ag-Zr high-strength high-formability magnesium-lithium alloy, and the main element content is controlled as follows: li (4.5-11.5 wt.%), al (0.5-3.5 wt.%) and Zn (2.5-5.5 wt.%) are the results of optimizing the density, strength and plasticity, wherein the Li content is between 4.5 and 11.5, so that the lattice symmetry of the alloy is obviously improved, the strength and the formability can be effectively balanced, and the density of the alloy is reduced; the Al content is 0.5-3.5 wt.% and the Zn content is 2.5-5.5 wt.%, so that the low density of the alloy is maintained, and the alloy can be dissolved in a matrix to effectively improve the strength of the alloy.
2. The magnesium-lithium alloy with high strength and high formability is prepared by adding mixed RE element, ag element and Zr element on the basis of Mg-Li-Al-Zn alloy. The addition of the fine dispersed intermetallic compound formed by the mixed RE element can not only generate solid solution strengthening effect, but also improve the thermal stability and recrystallization temperature of the alloy, and in addition, the price of the mixed rare earth is lower than that of single rare earth, so that the cost can be effectively reduced; the addition of the trace Ag element can improve the aging softening phenomenon of the alloy, improve the mechanical durability of the material and prolong the service life of the structural member; the trace addition of Zr element can bring about good fine grain strengthening effect.
3. According to the preparation method of the high-strength high-formability magnesium-lithium alloy, disclosed by the invention, the alloy structure can be effectively regulated and controlled by adopting a means of vacuum casting and forging/extruding/rolling composite plastic deformation, so that the strength and the plasticity are both realized. Vacuum casting to obtain high purity homogeneous cast ingot and to improve the metallurgical quality of alloy material obviously; the forging/extrusion/rolling composite plastic deformation effectively refines grains and weakens the anisotropy phenomenon of the alloy plate. The thermal-mechanical treatment means has the advantages of simple processing procedure, strong operability and low industrialization difficulty.
4. The preparation method of the high-strength high-formability magnesium-lithium alloy, disclosed by the invention, combines the traditional plastic deformation means with the heat treatment means with multi-stage temperature, is different from the traditional annealing means, adopts a cold-hot circulation treatment mode with the temperature of-150 ℃ to 150 ℃, can effectively improve stress concentration caused by the final plastic deformation stage, further improves the ductility of the alloy under the condition of keeping the high strength of the alloy, so that excellent formability is obtained, and meanwhile, the aging softening phenomenon of the magnesium-lithium alloy is inhibited to a certain extent, and the mechanical durability of the alloy is effectively improved.
The method has the advantages of simple process, easy operation, low and controllable production cost and good practical application prospect in the field of aerospace new materials.
Drawings
FIG. 1 is an as-cast microstructure of a magnesium-lithium alloy according to example 3 of the present invention;
FIG. 2 is a graph of tensile stress-strain at room temperature for rolled magnesium-lithium alloy sheets according to example 3 and example 4;
FIG. 3 is a graph showing the cupping test results of the rolled magnesium-lithium alloy sheet described in examples 1-4;
fig. 4 is a diagram of a finished luggage case and a shell made of the magnesium-lithium alloy described in example 3.
Detailed Description
The present invention will be described in further detail below in order to make the objects, technical solutions and effects of the present invention more clear and distinct. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. The raw materials used in the following examples are all common commercial products.
Example 1
The high-strength Gao Chengxing magnesium-lithium alloy consists of the following components in percentage by mass: li:5.2%, al:1%, zn:1%, ag:0.8%, zr:0.05 percent of lanthanum-cerium mixed rare earth RE, 1.0 percent of La: ce (mass ratio) =90:10, total amount of impurity elements Si, fe, cu and Ni is less than 0.01wt.%, balance Mg.
The preparation method of the high-strength high-formability magnesium-lithium alloy comprises two stages of vacuum smelting and casting and thermomechanical treatment (forging, extrusion, rolling and the like), wherein Li element, al element and Zn element are respectively added in the form of a simple substance of lithium, a simple substance of aluminum and a simple substance of zinc, and RE, ag and Zr are respectively added in the form of intermediate alloy MgRe 30 、AlAg 40 、MgZr 30 Is added in the form of (a) and specifically comprises the following steps:
(1) Vacuum casting: proportioning the magnesium-lithium alloy elements, placing the mixture in a vacuum induction furnace after proportioning, vacuumizing to 10Pa, filling argon to 50kPa, heating to 720 ℃ for smelting for 70min, standing for 10min, casting, taking out the cast ingot after the cast ingot is cooled, and obtaining a high-purity homogeneous cast ingot;
(2) Forging and extrusion treatment: turning the magnesium-lithium alloy cast ingot obtained in the step (1), removing a surface oxide skin layer, then placing the cast ingot in a table heat treatment furnace, homogenizing at 400 ℃ for 4 hours under the protection of nitrogen, taking out the cast ingot, keeping the temperature for 2 hours after the temperature of the cast ingot is reduced to 280 ℃, and forging, wherein the forging technological parameters are as follows: the forging ratio is 2, the final forging temperature is 200-250 ℃, until a forging rod with the diameter of 120mm is obtained, and the forging rod is rapidly cooled to room temperature; the obtained forging bar is put into a table heat treatment furnace to be heated to 220 ℃ after the oxide layer is removed by turning, and is kept for 60 minutes, and then is extruded, wherein the extrusion technological parameters are as follows: the extrusion ratio is 25, the extrusion rate is 85mm/min, and then the extrusion plate with the thickness of 20mm is obtained by water cooling to room temperature;
(3) Rolling and cold cycle treatment: placing the extruded plate obtained in the step (2) into a heat treatment furnace, reheating to 380 ℃, preserving heat for 15min, cooling to 220 ℃ and rolling, reversing the plate by 90 degrees after one pass of rolling for the next pass, and rolling for 30% of single pass of rolling until a rolled plate with the thickness of 2mm is obtained; and then placing the rolled plate with the thickness of 2mm into a cold-hot circulation furnace, carrying out cold-hot circulation at the temperature of at least 90 ℃ and at most 110 ℃, wherein the single circulation time is 6 hours, the single circulation temperature change rate is +/-0.67 ℃/min, and the temperature is respectively kept for 30 minutes at the temperature of-90 ℃ and 110 ℃, carrying out two circulation, wherein the medium of the cold-hot circulation is liquid nitrogen, and finally obtaining the magnesium-lithium alloy plate with high strength and high formability.
The magnesium-lithium alloy obtained in example 1 was subjected to a rolling state mechanical property test and a cupping test by referring to the methods in national standard GB/T16865-2013 samples and methods for tensile test of deformed aluminum, magnesium and processed products thereof, GB/T4156-2007 Metal Material-sheet and thin strip-Eleksen cup test, and the results were: tensile strength 343.2MPa, yield strength 318.4MPa, elongation 29.2% and cupping value 9.1mm. The cup burst test is a bulging process for simulating a material, the cup burst value obtained by the test can be used as a bulging forming performance index of the material, the forming capacity of the material can be intuitively represented, and the larger the cup burst value is, the better the bulging forming performance is.
Example 2
The high-strength Gao Chengxing magnesium-lithium alloy consists of the following components in percentage by mass: li:7.2%, al:1%, zn:1%, ag:0.8%, zr:0.05 percent of lanthanum-cerium mixed rare earth RE, 1.5 percent of La: ce (mass ratio) =90:10, the total amount of impurity elements Si, fe, cu and Ni being less than 0.01wt.%. The balance being Mg.
The preparation method of the high-strength high-formability magnesium-lithium alloy comprises two stages of vacuum smelting and casting and thermomechanical treatment (forging, extrusion, rolling and the like), wherein Li element, al element and Zn element are respectively added in the form of a simple substance of lithium, a simple substance of aluminum and a simple substance of zinc, and RE, ag and Zr are respectively added in the form of intermediate alloy MgRe 30 、AlAg 40 、MgZr 30 Is added in the form of (a) and specifically comprises the following steps:
(1) Vacuum casting: proportioning the magnesium-lithium alloy elements, placing the mixture in a vacuum induction furnace after proportioning, vacuumizing to 10Pa, filling argon to 50kPa, heating to 750 ℃ for smelting for 80min, standing for 20min, casting, taking out the cast ingot after the cast ingot is cooled, and obtaining a high-purity homogeneous cast ingot;
(2) Forging and extrusion treatment: turning the magnesium-lithium alloy cast ingot obtained in the step (1), removing a surface oxide skin layer, then placing the cast ingot in a table heat treatment furnace, homogenizing at 380 ℃ for 4 hours under the protection of nitrogen, taking out the cast ingot, keeping the temperature for 6 hours after the temperature of the cast ingot is reduced to 250 ℃, and forging, wherein the forging technological parameters are as follows: the forging ratio is 3.5, the final forging temperature is 190-240 ℃ until a forging rod with the diameter of 120mm is obtained, and the forging rod is quickly cooled to room temperature; the obtained forging bar is put into a desk type heat treatment furnace to be heated to 200 ℃ after the oxide layer is removed by turning, and is kept for 60 minutes, and then is extruded, wherein the extrusion technological parameters are as follows: the extrusion ratio is 25, the extrusion rate is 85mm/min, and then the extrusion plate with the thickness of 20mm is obtained by water cooling to room temperature;
(3) Rolling and cold cycle treatment: placing the extruded plate obtained in the step (2) into a heat treatment furnace, reheating to 370 ℃, preserving heat for 15min, cooling to 210 ℃ and rolling, reversing the plate by 90 degrees after one pass of rolling for the next pass, wherein the rolling reduction of a single pass is 40%, and obtaining a rolled plate with the thickness of 2 mm; and then placing the rolled plate with the thickness of 2mm into a cold and hot circulation furnace, carrying out cold and hot circulation at the temperature of at least 95 ℃ and at most 105 ℃, wherein the single circulation time is 6 hours, the single circulation temperature change rate is +/-0.67 ℃/min, and the temperature is respectively kept for 30 minutes at the temperature of minus 95 ℃ and 105 ℃, carrying out two circulation, wherein the medium of the cold and hot circulation is liquid nitrogen, and finally obtaining the magnesium-lithium alloy plate with high strength and high formability.
The magnesium-lithium alloy obtained in example 2 was subjected to a rolling state mechanical property test and a cupping test by referring to the methods in national standard GB/T16865-2013 samples and methods for tensile test of deformed aluminum, magnesium and processed products thereof and GB/T4156-2007 metallic materials-sheet and thin strip-Eleksen cup test, and the results were: tensile strength 327.5MPa, yield strength 306.3MPa, elongation 33.7% and cupping value 9.7mm.
Example 3
The high-strength Gao Chengxing magnesium-lithium alloy consists of the following components in percentage by mass: li:9.2%, al:1%, zn:1%, ag:0.8%, zr:0.05 percent of lanthanum-cerium mixed rare earth RE, 1.5 percent of La: ce (mass ratio) =90:10, the total amount of impurity elements Si, fe, cu and Ni being less than 0.01wt.%. The balance being Mg.
The preparation method of the high-strength high-formability magnesium-lithium alloy comprises two stages of vacuum smelting and casting and thermomechanical treatment (forging, extrusion, rolling and the like), wherein Li element, al element and Zn element are respectively added in the form of a simple substance of lithium, a simple substance of aluminum and a simple substance of zinc, and RE, ag and Zr are respectively added in the form of intermediate alloy MgRe 30 、AlAg 40 、MgZr 30 Is added in the form of (a) and specifically comprises the following steps:
(1) Vacuum casting: proportioning the magnesium-lithium alloy elements, placing the mixture in a vacuum induction furnace after proportioning, vacuumizing to 10Pa, filling argon to 50kPa, heating to 780 ℃ for smelting for 60min, standing for 30min, casting, taking out the cast ingot after the cast ingot is cooled, and obtaining a high-purity homogeneous cast ingot;
(2) Forging and extrusion treatment: turning the magnesium-lithium alloy cast ingot obtained in the step (1), removing a surface oxide skin layer, then placing the cast ingot in a table heat treatment furnace, homogenizing at 380 ℃ for 4 hours under the protection of nitrogen, taking out the cast ingot, keeping the temperature for 8 hours after the temperature of the cast ingot is reduced to 250 ℃, and forging, wherein the forging technological parameters are as follows: the forging ratio is 3.5, the final forging temperature is 200-250 ℃, until a forging rod with the diameter of 120mm is obtained, and the forging rod is rapidly cooled to room temperature; the obtained forging bar is put into a desk type heat treatment furnace to be heated to 200 ℃ after the oxide layer is removed by turning, and is kept for 60 minutes, and then is extruded, wherein the extrusion technological parameters are as follows: the extrusion ratio is 30, the extrusion rate is 85mm/min, and then the extrusion plate with the thickness of 20mm is obtained by water cooling to room temperature;
(3) Rolling and cold cycle treatment: placing the extruded plate obtained in the step (2) into a heat treatment furnace, reheating to 360 ℃, preserving heat for 15min, cooling to 210 ℃ and rolling, reversing the plate by 90 degrees after one pass of rolling for the next pass, and rolling for a single pass with the rolling reduction of 50% until a rolled plate with the thickness of 2mm is obtained; and then placing the rolled plate with the thickness of 2mm into a cold-hot circulation furnace, carrying out cold-hot circulation at the temperature of least 100 ℃ and at the temperature of most 100 ℃, wherein the single circulation time is 6 hours, the single circulation temperature change rate is +/-0.67 ℃/min, and the temperature is respectively kept for 30 minutes at the temperature of minus 100 ℃ and 100 ℃, carrying out two circulation, wherein the medium of the cold-hot circulation is liquid nitrogen, and finally obtaining the magnesium-lithium alloy plate with high strength and high formability.
The magnesium-lithium alloy obtained in example 3 was subjected to a rolling state mechanical property test and a cupping test by referring to the methods in national standard GB/T16865-2013 samples and methods for tensile test of deformed aluminum, magnesium and processed products thereof and GB/T4156-2007 metallic materials-sheet and thin strip-Eleksen cup test, and the results were: the tensile strength is 321.7MPa, the yield strength is 302.3MPa, the elongation is 43.9%, and the cupping value is 11.1mm.
Example 4
The high-strength Gao Chengxing magnesium-lithium alloy consists of the following components in percentage by mass: li:11.2%, al:2%, zn:1%, ag:0.8%, zr:0.05 percent of lanthanum-cerium mixed rare earth RE, 1.0 percent of La: ce (mass ratio) =90:10, the total amount of impurity elements Si, fe, cu and Ni being less than 0.01wt.%. The balance being Mg.
The preparation method of the high-strength high-formability magnesium-lithium alloy comprises the following steps ofIn two stages of empty smelting, casting and thermomechanical treatment (forging, extrusion, rolling, etc.), li element, al element and Zn element are respectively added in the form of simple substance of lithium, simple substance of aluminum and simple substance of zinc, and RE, ag and Zr are respectively used as intermediate alloy MgRe 30 、AlAg 40 、MgZr 30 Is added in the form of (a) and specifically comprises the following steps:
(1) Vacuum casting: proportioning the magnesium-lithium alloy elements, placing the mixture in a vacuum induction furnace after proportioning, vacuumizing to 10Pa, filling argon to 50kPa, heating to 750 ℃ for smelting for 60min, standing for 10min, casting, taking out the cast ingot after the cast ingot is cooled, and obtaining a high-purity homogeneous cast ingot;
(2) Forging and extrusion treatment: turning the magnesium-lithium alloy cast ingot obtained in the step (1), removing a surface oxide skin layer, then placing the cast ingot in a table heat treatment furnace, homogenizing at 350 ℃ for 4 hours under the protection of nitrogen, taking out the cast ingot, keeping the temperature for 12 hours after the temperature of the cast ingot is reduced to 200 ℃, and forging the cast ingot, wherein the forging technological parameters are as follows: forging ratio is 4, final forging temperature is 170-200 ℃, until obtaining a forging rod with diameter of 120mm, and rapidly cooling to room temperature; the obtained forging bar is put into a table heat treatment furnace to be heated to 180 ℃ after the oxide layer is removed by turning, and is kept for 60 minutes, and then is extruded, wherein the extrusion technological parameters are as follows: the extrusion ratio is 35, the extrusion rate is 100mm/min, and then the extrusion plate with the thickness of 20mm is obtained by water cooling to room temperature;
(3) Rolling and cold cycle treatment: placing the extruded plate obtained in the step (2) into a heat treatment furnace, reheating to 350 ℃, preserving heat for 15min, cooling to 200 ℃ and rolling, reversing the plate by 90 degrees after one pass of rolling for the next pass, and rolling for a single pass with the rolling reduction of 50% until a rolled plate with the thickness of 2mm is obtained; and then placing the rolled plate with the thickness of 2mm into a cold and hot circulation furnace, carrying out cold and hot circulation at the temperature of at least 120 ℃ and at most 80 ℃, wherein the single circulation time is 6 hours, the single circulation temperature change rate is +/-0.67 ℃/min, and the temperature is respectively kept for 30 minutes at the temperature of at least 120 ℃ and at the temperature of 80 ℃, carrying out two circulation, wherein the medium of the cold and hot circulation is liquid nitrogen, and finally obtaining the magnesium-lithium alloy plate with high strength and high formability.
The magnesium-lithium alloy obtained in example 4 was subjected to a rolling state mechanical property test and a cupping test by referring to the methods in national standard GB/T16865-2013 samples and methods for tensile test of deformed aluminum, magnesium and processed products thereof, GB/T4156-2007 Metal Material-sheet and thin strip-Eleksen cup test, and the results were: tensile strength 307.1MPa, yield strength 283.6MPa, elongation 49.8% and cupping value 11.3mm.
FIG. 1 is a microstructure diagram of an as-cast magnesium-lithium alloy of example 3. As can be seen from FIG. 1, the as-cast 9.2Li-1Al-1Zn-1.5RE-0.8Ag-0.05Zr alloy obtained in example 3 has fine grain size, uniform distribution of alpha-Mg phase and beta-Li phase in all directions, pure alpha-Mg phase component, and uniform distribution of second phase in the beta-Li phase and at the interface of two phases.
Fig. 2 is a graph of tensile stress-strain at room temperature of rolled magnesium-lithium alloy plates according to example 3 and example 4, from which it can be concluded that: the ultimate tensile strength of the magnesium-lithium alloy plates obtained by the preparation methods of the embodiment 3 and the embodiment 4 is 321.7MPa and 307.1MPa respectively, the elongation percentage is 43.9% and 49.8% respectively, and the magnesium-lithium alloy plates can still maintain higher ductility when used as 300 MPa-level alloy, and meanwhile, the strength and the formability of the alloy are both considered.
FIG. 3 shows the results of the cupping test of the rolled magnesium-lithium alloy plates of examples 1 to 4, and shows that the cupping values of the rolled plates with the thickness of 2mm prepared in examples 1, 2, 3 and 4 are 9.7mm, 9.1mm, 11.1mm and 11.3mm respectively, and the rolled plates have good bulging forming capacity.
The proportions and performances of the elements in the magnesium-lithium alloys in examples 1, 2, 3 and 4 are shown in table 1, and it can be seen from table 1 that the alloy with four different components has an ultimate tensile strength of more than 300MPa and a higher cupping value after being treated by the process, which indicates that the preparation method of the invention can effectively consider both the strength and the forming performance of the alloy.
TABLE 1
Application example 1
Luggage has wide market demands as a necessity for moving, traveling, going on business, etc. of modern people. The materials of the trunk sold in the market at present mainly comprise cloth, leather, plastic, aluminum alloy, titanium alloy and the like, and the cloth and leather trunk is easy to break, waterproof, dirt-proof and easy to deform; the strength of the plastic luggage case is not high, the weight cannot be borne, the aesthetic property is inferior to that of the metal luggage case, meanwhile, the service life of the plastic luggage case is limited due to the characteristic that plastic products are easy to age, and the plastic luggage case cannot be recycled after being damaged; the aluminum alloy luggage case is heavy in weight and poor in portability, and the burden is increased for traveling. The titanium alloy luggage case has high strength and good corrosion resistance, but has heavier mass, complex manufacturing process and high cost, and cannot be recycled, so that the cost performance is low.
The magnesium-lithium alloy obtained in the embodiment 3 of the invention has the tensile strength as high as 321.7MPa, has the characteristic of high strength, and meets the daily requirement of the trunk; density is only 1.48g/cm 3 The weight of the metal luggage case can be greatly reduced; the elongation rate reaches 49.8%, the cupping value reaches 11.3mm, and the stamping forming of the magnesium-lithium alloy suitcase body can be realized.
Compared with cloth, leather and plastic luggage, the magnesium-lithium alloy of the embodiment 3 of the invention is adopted as the processing material of the luggage, and the strength, the aesthetic property, the recycling rate and the like are greatly improved; meanwhile, compared with aluminum alloy and titanium alloy luggage cases, the weight of the luggage case is greatly reduced, the processing resilience is effectively reduced, and the processing process is more environment-friendly. The magnesium-lithium alloy in the embodiment 3 is used for replacing aluminum alloy with the same volume and dosage, the weight of the prepared luggage case is reduced by more than 1/2, and the luggage case has the characteristics of portability and durability, and brings better experience to traveling.
While specific embodiments of the invention have been described above, it should be understood that the invention is not limited to the particular embodiments described above. Various changes or modifications may be made by one skilled in the art within the scope of the claims without affecting the spirit of the invention.
Claims (7)
1. The high-strength Gao Chengxing magnesium-lithium alloy is characterized by comprising the following components in percentage by mass: 4.5-11.5% of Li, 0.5-2.2% of Al, 2.5-5.5% of Zn, 0.1-3% of RE, 0.1-1.2% of Ag, 0.01-0.2% of Zr, RE being lanthanum-cerium misch metal, the total content of Al and Zn not exceeding 5%, the impurity content being less than 0.01%, and the balance being Mg;
in the lanthanum-cerium mixed rare earth RE, the mass ratio of La to Ce is more than or equal to 2:1;
the high-strength high-formability magnesium-lithium alloy is prepared by the following steps:
(1) Vacuum melting and casting: proportioning all components of the required magnesium-lithium alloy according to mass percentage, vacuumizing, charging argon, smelting and casting, and cooling to obtain a homogeneous magnesium-lithium alloy cast ingot;
(2) And (3) deformation heat treatment: machining the magnesium-lithium alloy ingot obtained in the step (1) to remove a surface oxide layer, and then sequentially performing forging, extrusion, rolling and cold-hot cycle treatment to obtain the magnesium-lithium alloy ingot;
the cold and hot circulation treatment process in the step (2) comprises the following steps: and (3) carrying out cold and hot circulation on the rolled plate at the temperature of the lowest temperature of-150 ℃ and the highest temperature of 150 ℃, wherein the single circulation time is 2-20h, the single circulation temperature change rate is-5 ℃/min, and the heat preservation is carried out for 20-30min at the lowest temperature and the highest temperature, and the two circulation is carried out, wherein the medium of the cold and hot circulation is liquid nitrogen.
2. The method for producing a high-strength high-formability magnesium lithium alloy sheet according to claim 1, comprising the steps of:
(1) Vacuum melting and casting: proportioning all components of the required magnesium-lithium alloy according to mass percentage, vacuumizing, charging argon, smelting and casting, and cooling to obtain a homogeneous magnesium-lithium alloy cast ingot;
(2) And (3) deformation heat treatment: machining the magnesium-lithium alloy ingot obtained in the step (1) to remove a surface oxide layer, and then sequentially forging, extruding, rolling and carrying out cold and hot circulation treatment to obtain a magnesium-lithium alloy plate with high strength and high formability;
the cold and hot circulation treatment process in the step (2) comprises the following steps: and (3) carrying out cold and hot circulation on the rolled plate at the temperature of the lowest temperature of-150 ℃ and the highest temperature of 150 ℃, wherein the single circulation time is 2-20h, the single circulation temperature change rate is-5 ℃/min, and the heat preservation is carried out for 20-30min at the lowest temperature and the highest temperature, and the two circulation is carried out, wherein the medium of the cold and hot circulation is liquid nitrogen.
3. The method according to claim 2, wherein the vacuum melting and casting in the step (1) comprises the specific steps of: vacuumizing to 10Pa, charging argon to the vacuum degree of 50kPa, heating to 650-800 ℃ for smelting for 30-90min, standing for 10-30min, and casting.
4. The method of claim 2, wherein the forging process in step (2) is: heating the cast ingot obtained in the step (1) to 280-420 ℃, preserving heat for 2-12 h, and then cooling to 190-280 ℃ for multidirectional forging, wherein the forging ratio is (2-5.5): and 1, performing final forging at 150-250 ℃, and performing water cooling to room temperature after forging to obtain a forged rod with the diameter of 90-180 mm.
5. The method according to claim 2, wherein the extrusion process in step (2) is: and (3) machining the forged bar to remove the surface oxide layer, heating to 200-300 ℃, preserving heat for 30-100 min, extruding at an extrusion ratio of 10-60 and an extrusion speed of 20-120 mm/min, and then air-cooling or water-cooling to room temperature to obtain the extruded plate with the thickness of 10-25 mm.
6. The method according to claim 2, wherein the rolling process in step (2) is: and heating the extruded plate obtained by extrusion to 300-450 ℃, preserving heat for 10-210 min, cooling to 180-280 ℃ and rolling, wherein the rolling single-pass rolling reduction is 25-50%, and the total rolling reduction is 70-95%, so that the magnesium-lithium alloy plate with the thickness of 1.5-3.0 mm is finally obtained.
7. The application of the magnesium-lithium alloy plate with high strength and high formability prepared by the method in preparing industrial product shells or aerospace curved surface parts.
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