CN114540681A - High-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member and preparation method thereof - Google Patents

High-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member and preparation method thereof Download PDF

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CN114540681A
CN114540681A CN202111643741.8A CN202111643741A CN114540681A CN 114540681 A CN114540681 A CN 114540681A CN 202111643741 A CN202111643741 A CN 202111643741A CN 114540681 A CN114540681 A CN 114540681A
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lithium alloy
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corrosion
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CN114540681B (en
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王俊升
田光元
杨兴海
张弛
王硕
苏辉
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Beijing Institute of Technology BIT
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Abstract

The invention discloses a high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy and a preparation method thereof, belonging to the technical field of metal material magnesium alloy. The high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy comprises the following chemical components in percentage by mass: al: 1-4.5 wt.%, Gd: 0.1-3.5 wt.%, Y: 0.5-8 wt.%, Li: 5-12 wt.%, Zn: 0.2-4.2 wt.%, Mn: 0.1-3.5 wt.%, the balance Mg and non-removable impurities. The preparation method comprises a raw material preparation stage, a raw material preheating stage, a heat treatment furnace atmosphere adjustment stage, a vacuum smelting stage, a vacuum tube furnace atmosphere adjustment stage and a heat treatment stage. The invention forms a precipitated phase with high modulus through the preparation method, and improves the comprehensive performance in a coupling mode of solid solution strengthening, fine grain strengthening and the like; the beta-Li phase is utilized to form a compact surface film and the corrosion resistance such as grain refinement and the like.

Description

High-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member and preparation method thereof
Technical Field
The invention belongs to the technical field of metal material magnesium alloy, and relates to a high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member and a preparation method thereof.
Background
Compared with other metal structure materials, the magnesium-lithium alloy is lightest and has the density of 1.25-1.65g/cm3In between, it is half of aluminum alloy, and is three-fourths of the traditional magnesium alloy. Meanwhile, the Mg-Li alloy has the characteristics of high specific strength, high specific rigidity, good cold and hot deformation performance, weak mechanical anisotropy, good low-temperature mechanical property and the like, and is highly valued in industrial structural parts in high and new technical fields of aerospace, aviation, electronics, military and the like in various countries in the world. It is anticipated that the level of research on magnesium lithium alloys will be critical to future development.
In the research aspect of magnesium-lithium alloy, some foreign countries start earlier. Magnesium-lithium alloys have been increasingly used in non-structural and sub-structural components such as armored vehicles and aerospace since the 40's of the 20 th century. In the last century, a large amount of research on magnesium-lithium alloys was conducted from the middle of the 60 s to the later of the 90 s, and alloys such as MA18 and MA21 were developed. The research on the magnesium-lithium alloy starts from the middle of the 80's in the last century, and the contents comprise the heat treatment and aging behavior of the alloy, the influence and superplasticity of alloying elements and the like.
Besides the characteristics of common magnesium alloy, the magnesium-lithium alloy also has the following unique characteristics:
(1) because lithium element is added into the magnesium-lithium alloy, on one hand, the c/a axial ratio of magnesium crystal lattice can be reduced, and the symmetry of the close-packed hexagonal crystal lattice is improved; on the other hand, as the lithium content increases, the BCC- β Li phase will appear in the matrix, increasing the plasticity and ductility of the magnesium-lithium alloy.
(2) When the lithium content is below 5.7 wt.%, the alloy consists of an α -Mg single phase; when the lithium content is between 5.7 and 10.3 wt.%, the alloy consists of two phases, alpha-Mg and beta-Li; when the lithium content exceeds 10.3 wt.%, the alloy consists of a β -Li single phase.
(3) The alpha-Mg phase is a close-packed hexagonal structure, so that the strength of the magnesium-lithium alloy can be obviously improved, but the alpha-Mg phase has few lattice slip systems and poor plasticity. The beta-Li phase has a BCC structure, has more slip systems, and can obviously improve the plasticity and the ductility of the magnesium-lithium alloy.
However, the magnesium-lithium alloy still has the technical defects of low engineering absolute strength, low elastic modulus, poor corrosion resistance and the like so far, and compared with the traditional magnesium alloy, the preparation and processing process of an industrial structural part is difficult, so that the engineering application and further development of the magnesium-lithium alloy are severely restricted.
At present, aiming at the problem of low strength of the structural part in the magnesium-lithium alloy industry at home and abroad, although the strength, the modulus and the elongation of the magnesium-lithium alloy can be improved by using composite strengthening such as dispersion strengthening, solid solution strengthening, fine grain strengthening and the like through alloying, heat treatment, deformation processing, composite particle adding and the like, a plurality of problems still exist; and the strength, modulus and corrosion resistance of the magnesium-lithium alloy are improved on the basis of ensuring low density.
At present, the content selection and preparation method of the defective magnesium-lithium alloy are researched a lot, and the specific details are as follows:
chinese patent CN 113355574A discloses a rapid aging-strengthening high-strength high-toughness magnesium-lithium alloy, which not only has less light element selection, but also is added with heavy rare earth elements Gd and Li, so that the prepared magnesium-lithium alloy has higher density and is not suitable for being used as a light alloy structural material in the technical field of low-density, high-strength and high-modulus two-phase magnesium-lithium alloys; and when the content of the heavy rare earth element Gd exceeds 8 wt.%, the excessive addition causes the sharp increase of the density of the magnesium-lithium alloy, and the magnesium-lithium alloy is not suitable for the technical field.
Chinese patent CN107523770B discloses a heat treatment process for improving the performance of a long-range structure ordered-phase reinforced dual-phase magnesium-lithium alloy, which is to perform solution treatment on an as-cast long-range structure ordered-phase magnesium-lithium alloy through a reasonable solid solution system without considering the synergistic improvement of strength and elastic modulus by the solution treatment and aging treatment, so that the tensile strength of the obtained magnesium-lithium alloy is less than 300MPa at 120-.
Chen(Chen Z.,Bao C G,Wu G Q,et al.Effect of YAl2Particles on the Corrosion Behavior of Mg–Li Matrix Composite in NaCl Solution[J]Mateials 2019) by reacting Al2The corrosion resistance of the Mg-Li alloy in a NaCl solution is researched by adding Y intermetallic compound particles into the Mg-Li alloy to obtain Al2The Y particles can promote the surface of the Mg-Li alloy to form a compact film and hinder the further enlargement of the pitting corrosion, thereby improving the corrosion resistance of the alloy. However, in the practical application process, the intermetallic compound particles are easy to generate brittle fracture at the interface joint of the magnesium-lithium alloy particles and the magnesium-lithium alloy particles, and are particularly not suitable for structural members with high requirements on plasticity, so that the application range of the magnesium-lithium alloy particles is greatly limited. And the Mg-Li alloy has higher lithium content, a dual-phase aluminum lithium alloy cannot be formed, and whether the corrosion resistance is improved or not can be applied to the dual-phase aluminum lithium alloy with low density, high strength and high modulus in the field of industrial structural members is unknown.
Chinese patent CN 113528911A discloses a method for preparing an anti-aging, high-strength, high-toughness and corrosion-resistant dual-phase magnesium-lithium alloy, wherein a cast ingot obtained by smelting needs to be sequentially subjected to extrusion deformation processing, hot rolling processing and stirring friction processing accompanied with cooling assistance to finally obtain a product; obviously, the product is not a casting organization structure, the preparation process is complex, the ingot casting needs to be subjected to complex hot processing, and the plate obtained by extrusion deformation and hot rolling is simple in structure and is not suitable for preparing high-strength high-modulus corrosion-resistant structural members with complex shapes.
In addition, at present, because magnesium and lithium elements in the magnesium-lithium alloy are active metals, the smelting process is difficult, the process is complex, the corrosion resistance is poor, and micro-current corrosion can be formed in the dual-phase magnesium-lithium alloy, so that the wide application of the magnesium-lithium alloy is severely restricted.
In summary, in the research on the magnesium-lithium alloy, in order to meet the technical requirement of high strength or high elongation of the dual-phase magnesium-lithium alloy, microalloying, heat treatment and hot working are adopted, but the strength, elongation, high modulus and corrosion resistance of the dual-phase magnesium-lithium alloy cannot be synergistically improved while the low density of the dual-phase magnesium-lithium alloy is controlled, so that the tensile strength, yield strength, elongation, high modulus and corrosion resistance are highly matched.
Disclosure of Invention
In order to solve the defects and shortcomings of the prior art, the invention provides a high-strength high-modulus biphase magnesium-lithium alloy and a preparation method thereof, which can be used for obtaining the high-strength high-modulus biphase magnesium-lithium alloy meeting the target requirements of low density, high strength, high elongation and high modulus by reasonably controlling and selecting the content and proportion of alloy elements, alloying, vacuum casting, heat treatment and other processes in a combined and synergistic manner.
The invention provides the following technical scheme:
a high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member comprises the following chemical components in percentage by mass: al: 1-5 wt.%, Gd: 0.1-3.5 wt.%, Y: 0.5-8 wt.%, Li: 5-12 wt.%, Zn: 0.2-4.2 wt.%, Mn: 0.1-3.5 wt.%, the balance Mg and unavoidable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
Preferably, the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member comprises the following chemical components in percentage by mass: al: 2.0-4.5 wt.%, Gd: 1.5-3.0 wt.%, Y: 2.0-4.0 wt.%, Li: 6-8.5 wt.%, Zn: 3.5-4.2 wt.%, Mn: 0.2-3.0 wt.%, the balance Mg and unavoidable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
The content of Li element and the proportion of alloy elements are reasonably controlled, so that the matrix of the magnesium-lithium alloy can keep smaller density and the matrix phase of alpha + beta phases in the matrix, and the magnesium-lithium alloy can improve the alloy strength (alpha-Mg) and the plasticity and the machinability (beta-Li). Meanwhile, the beta-Li phase can generate a compact LiOH film layer in the corrosion process to make up loose Mg (OH) generated by the alpha-Mg phase2Etching ofThe product can improve the corrosion resistance of the matrix. By adding two alloy elements with high solid solubility of Al and Zn, the solid solution strengthening effect and the fine grain strengthening effect can be achieved, and the corrosion performance of the magnesium-lithium alloy is improved. And the added Al element can form a high-modulus disperse second phase (Al) with other alloy elements (Gd and Y)2RE) distributed at the grain boundary, so that the elastic modulus of the magnesium-lithium alloy is improved, excessive Zn element can be prevented from being added, and the density of the alloy is reduced. By simultaneously adding two mixed rare earth elements of Gd and Y, a high-strength high-modulus intermetallic compound (Mg) with high stability can be generated in the magnesium-lithium alloy5RE), the mechanical property of the alloy is improved, and Gd and Y are added to purify the melt, refine the crystal grains, form a high-modulus quasicrystal strengthening phase with corrosion resistance with Zn element, and improve the corrosion resistance and the mechanical property of the alloy. The production cost can also be reduced by adding the mixed rare earth elements.
The simultaneous addition of Al and Zn elements not only can refine grains, but also can generate a high-modulus phase (MgLi)2Al and MgLi2Zn); al element and Li element can also form Al-Li precipitation strengthening phase, and the elasticity modulus and strength of the magnesium-lithium alloy are improved.
The addition of Mn element with corrosion resistance can not only refine the grain structure to become a heterogeneous nucleation core of the magnesium-lithium alloy, inhibit the growth of alpha-Mg phase, but also form a high-modulus second phase (Al) with Al element8Mn5) The magnesium-lithium alloy is distributed near the crystal boundary to block alpha-Mg and beta-Li phases and avoid galvanic corrosion, so that the elastic modulus, the strength and the corrosion resistance of the magnesium-lithium alloy are improved.
Preferably, the structure of the biphase magnesium-lithium alloy of the high-strength high-modulus corrosion-resistant structural part is mainly alpha-Mg, beta-Li and Al2RE(Gd,Y)，Al8Mn5The AlLi has alpha phase in 50-80 wt%, beta phase in 20-50 wt% and total alpha phase plus beta phase not more than 96 wt%.
Preferably, the performance of the dual-phase magnesium-lithium alloy of the high-strength high-modulus corrosion-resistant structural member is as follows: the density is 1.37-1.75g/cm3Tensile strength of 300-400MPa, yield strength260MPa, elongation of 21-42%, elastic modulus of 62-75GPa, and corrosion potential Ecorr1.63 to 1.35V, and the corrosion current density is icorr＝5-12μA/cm2。
The preparation method of the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following steps:
s1 raw material preparation stage
Weighing pure Mg, pure Al, pure Li, pure Zn, Mg-Gd intermediate alloy, Mg-Y intermediate alloy and Mg-Mn intermediate alloy as raw materials according to the mass percentage of the chemical components of the raw materials in the high-strength high-modulus biphase magnesium-lithium alloy structural component, and polishing surface oxides;
s2 stage of preheating raw materials
Putting the raw materials and the crucible weighed in the step S1 into a heat treatment furnace for preheating so as to dry the moisture of the raw materials;
s3, adjusting the atmosphere of the heat treatment furnace
Putting the raw materials preheated in the step S2 into different positions of a vacuum smelting furnace according to factors of melting point, oxidation degree, density, adding quantity and volatilizable degree, then opening a cooling system, covering a furnace cover, starting vacuumizing, then opening a protective gas valve, and introducing protective gas;
s4, vacuum melting stage
Setting the smelting temperature of the vacuum smelting furnace after the step S3, starting heating smelting, stirring and standing after the magnesium-lithium alloy raw material is completely molten, and then cooling to the casting temperature to start casting a magnesium-lithium alloy cast ingot;
s5, adjusting the atmosphere of the vacuum tube furnace
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, opening a vacuum pump, and then introducing protective gas;
s6, heat treatment stage
And (5) setting the heat treatment temperature of the vacuum tube furnace after the step S5, and then carrying out a solution aging heat treatment process to finally obtain the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural member.
Preferably, in the step S1, pure Mg, pure Al, pure Li, pure Zn and a Mg master alloy, wherein the purities of pure Mg, pure Al, pure Li and pure Zn are all 99.966-99.999%.
Preferably, in step S1, the content of Gd, Y and Mn in the Mg-Gd, Mg-Y, Mg-Mn master alloy is 20-50 wt.%.
Preferably, the preheating temperature in the step S2 is 100-250 ℃, and the preheating time is 1.5-2.5 h.
Preferably, in the step S3, the raw materials are added into the crucible at different positions in the vacuum melting furnace according to the melting point, the easy oxidation degree, the density, the adding amount, the easy volatilization degree and the like of the raw materials; considering that Li is easy to volatilize and has low melting point, a small block of pure Mg is placed at the bottom, then Mg intermediate alloy is placed, pure Zn and pure Al are placed, and finally pure Li is placed; .
Preferably, the temperature-rising smelting in the step S4 adopts a gradient heating mode.
Preferably, the vacuum melting stage in step S4 is:
s401, setting the smelting temperature to 710 and 790 ℃, and setting the heating power to 50-100%;
s402, starting heating in a gradient heating mode until the raw materials are completely melted, stirring for 10-30min, and standing for 5-20 min;
and S403, stopping stirring, then, cooling to the pouring temperature, and finally, pouring to obtain the magnesium-lithium alloy ingot.
Preferably, the solution aging heat treatment process in step S6 is: after the solid solution treatment is carried out for 2-24h at the temperature of 300-500 ℃, water or oil bath is used for rapid cooling, and then the magnesium-lithium alloy ingot after the solid solution treatment is subjected to aging treatment for 5-24h at the temperature of 100-250 ℃.
Preferably, the solution aging heat treatment process in step S6 is: after solid solution treatment is carried out for 8-12h at the temperature of 400-450 ℃, water is used for rapid cooling, and then the magnesium-lithium alloy ingot after the solid solution treatment is subjected to aging treatment for 15-20h at the temperature of 100-150 ℃.
Compared with the prior art, the invention has the following beneficial effects:
in the scheme, the content of Li element and the alloy proportion are controlled, so that an alpha + beta two-phase matrix phase exists in the matrix, and the beta-Li phase not only can provide a compact oxide film for the magnesium-lithium alloy to improve the corrosion resistance of the alloy, but also can improve the plasticity and the ductility of the matrix. Meanwhile, alloying elements such as Al, Zn, Mn, Gd, Y and the like are added, so that the solid solution strengthening effect can be achieved, a high-modulus precipitation strengthening phase can be generated in a matrix, and the strength and the plasticity of the magnesium-lithium alloy can be greatly improved by combining various modes such as solid solution treatment, aging heat treatment and the like, and meanwhile, the elastic modulus and the corrosion resistance of the magnesium-lithium alloy can be greatly improved, so that the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy is obtained, and the high-strength high-toughness corrosion-resistant two-phase magnesium-lithium alloy is suitable for meeting the requirements of light weight, high strength, high toughness and corrosion resistance for industrial structural members.
The invention can refine crystal grains and promote high modulus Al by simultaneously adding Gd and Y2Y, MgZn2Gd (Y) and the like; the alpha-Mg and the beta-Li in the matrix are matched to synergistically improve the properties of the magnesium-lithium alloy, such as strength, plasticity, modulus and the like, and prolong the service life of the magnesium-lithium alloy. Meanwhile, the addition of rare earth elements can purify impurity elements in the melt and improve the corrosion resistance of the alloy.
According to the invention, by simultaneously adding Al and Zn, the alpha-Mg in the magnesium-lithium matrix tends to be equiaxial, the beta-Li phase is refined, and a stable phase and a quasicrystal phase can be generated to further improve the mechanical property and corrosion resistance of the magnesium-lithium alloy. Meanwhile, the Mn element is added, so that the yield strength of the magnesium-lithium alloy can be improved, harmful metal impurities are removed, crystal grains are refined, and a high-modulus strengthening phase Al is formed with Al8Mn5。
In addition, the added Al may form Al with Li3Li high modulus phase and Mg continuous generation of high modulus Mg in crystal17Al12And precipitating a strengthening phase to obtain the high-strength high-modulus magnesium-lithium alloy.
According to the preparation method of the magnesium-lithium alloy structural member, mechanical properties such as strength and the like of the magnesium-lithium alloy are improved by forming a precipitation phase with high modulus, solid solution strengthening, fine grain strengthening and other coupling modes on the magnesium-lithium alloy through vacuum melting, simple microalloying and heat treatment processes, corrosion resistance of the alloy is improved by forming a compact surface film by using a beta-Li phase and refining grains and the like, and finally the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy which is improved in a synergistic manner is achieved.
The high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural part has excellent strength, plasticity and corrosion resistance: the density is 1.37-1.75g/cm3The tensile strength is 300-400MPa, the yield strength is 260-350MPa, the elongation is 21-42%, the elastic modulus is 62-75GPa, and the corrosion potential is Ecorr-1.63 to-1.35V, corrosion current density icorr＝5-12μA/cm2。
In a word, the method adopts a mode of combining micro-alloying with heat treatment, has the advantages of low cost, high efficiency, simple operation, high raw material utilization rate, wide application range and the like, can synergistically improve the strength, elongation, elastic modulus and corrosion resistance of the biphase magnesium-lithium alloy while controlling the low density of the biphase magnesium-lithium alloy structural member, ensures that the matching effects of high tensile strength, high yield strength, high elongation, high elastic modulus and high corrosion resistance are excellent, and is beneficial to industrial large-scale production and popularization.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is an as-cast microstructure of a high-strength high-modulus corrosion-resistant dual-phase Mg-Li alloy structural member according to example 1 of the present invention;
FIG. 2 is a tensile curve of a high-strength high-modulus corrosion-resistant dual-phase Mg-Li alloy structural member of example 1 of the present invention in a heat-treated state;
FIG. 3 is a corrosion graph of a high strength and high modulus corrosion resistant dual phase Mg-Li alloy structural member of example 1 of the present invention in a heat treated state;
FIG. 4 is an as-cast microstructure of a high-strength high-modulus corrosion-resistant dual-phase Mg-Li alloy structural member according to example 2 of the present invention.
Detailed Description
The technical solutions and the technical problems to be solved in the embodiments of the present invention will be described below with reference to the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the patent of the invention, not all embodiments.
Example 1
The high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following chemical components in percentage by mass: al: 4 wt.%, Gd: 2 wt.%, Y: 2.5 wt.%, Li: 8.5 wt.%, Zn: 4.2 wt.%, Mn: 0.2 wt.%, the balance Mg and inevitable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
The preparation method of the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following steps:
s1 raw material preparation stage
Weighing Mg-20 wt.% Gd intermediate alloy containing 2 wt.% Gd, Mg-25 wt.% Y intermediate alloy containing 2.5 wt.% Y, Mg-50 wt.% Mn intermediate alloy containing 0.2 wt.% Mn, 4 wt.% pure Al, 8.5 wt.% pure Li, 4.2 wt.% pure Zn and the balance of pure Mg according to the mass percentage of chemical components of raw materials in the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural component; and removing the surface oxide;
s2 stage of preheating raw materials
Putting the raw materials and the crucible weighed in the step S1 into a heat treatment furnace, and preheating for 2 hours at 200 ℃ to dry the moisture of the raw materials;
s3, adjusting the atmosphere of the heat treatment furnace
Putting the raw materials preheated in the step S2 into different positions of a crucible according to factors such as melting point, oxidation degree, density and the like, putting the raw materials into a vacuum melting furnace, putting small pure Mg blocks at the bottom of the crucible in consideration of the fact that Li is easy to volatilize and has low melting point, then putting Mg intermediate alloy, putting pure Zn and pure Al, and finally putting pure Li; and turn on to coolThe system is covered with a furnace cover, and vacuum pumping is started until the vacuum degree reaches 10-3Pa, then opening a protective gas valve, and introducing high-purity argon until the gas pressure in the furnace is increased to more than 0.5 MPa;
s4, vacuum melting stage
Setting the melting temperature to 780 ℃ through the heat treatment of the step S3, starting heating and melting in a gradient heating mode, stirring for 20min and standing for 10min after the magnesium-lithium alloy raw material is completely melted, then cooling to the casting temperature, and finally casting into a magnesium-lithium alloy ingot;
s5, adjusting the atmosphere of the vacuum tube furnace
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, opening a vacuum pump, vacuumizing for more than 3 times until the vacuum degree reaches 10-3Pa, introducing argon protective gas, and increasing the argon pressure to be more than 0.5 MPa;
s6, heat treatment stage
And (4) carrying out solution treatment on the vacuum tube furnace after the step S5 at 450 ℃ for 10h, then rapidly cooling by using water or oil bath, and then carrying out aging treatment on the magnesium-lithium alloy cast ingot after the solution treatment at 130 ℃ for 20h to obtain the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member of the embodiment.
The cast microstructure of the biphase magnesium-lithium alloy structural member is shown in figure 1, and the structure mainly comprises alpha-Mg, beta-Li and Al2RE(Gd,Y)，Al8Mn5AlLi, wherein the alpha phase accounts for 55% and the beta phase accounts for 41%; the overall performance is shown in fig. 2: the density was 1.65g/cm3Tensile strength is 351MPa, yield strength is 283MPa, elongation is 21.2 percent, and elastic modulus is 65.8 GPa; as shown in FIG. 3, the corrosion potential is Ecorr1.52V, corrosion current density icorr＝8μA/cm2。
Example 2
The high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following chemical components in percentage by mass: al: 3 wt.%, Gd: 1.5 wt.%, Y: 3.5 wt.%, Li: 7 wt.%, Zn: 3.5 wt.%, Mn: 2 wt.%, the balance Mg and unavoidable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
The preparation method of the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following steps:
s1 raw material preparation stage
Weighing 1.5 wt.% of Gd-containing Mg-30 wt.% of Gd intermediate alloy, 3.5 wt.% of Y-containing Mg-40 wt.% of Y intermediate alloy, 2 wt.% of Mn-25 wt.% of Mn intermediate alloy, 3 wt.% of pure Al, 7 wt.% of pure Li, 3.5 wt.% of pure Zn and the balance of pure Mg according to the mass percentage of chemical components of raw materials in the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member; and removing the surface oxide;
s2 stage of preheating raw materials
Putting the raw materials and the crucible weighed in the step S1 into a heat treatment furnace, and preheating for 1.8 hours at 190 ℃ to dry the moisture of the raw materials;
s3, adjusting the atmosphere of the heat treatment furnace
Putting the raw materials preheated in the step S2 into different positions of a crucible according to factors such as melting point, oxidation degree, density and the like, putting the raw materials into a vacuum smelting furnace, wherein in consideration of the fact that Li is volatile and has low melting point, small pure Mg blocks are placed at the bottom of the crucible, then putting Mg intermediate alloy, then putting pure Zn and pure Al, and finally putting pure Li; opening the cooling system, covering the furnace cover, and vacuumizing until the vacuum degree reaches 10-3Pa, then opening a protective gas valve, and introducing high-purity argon until the gas pressure in the furnace is increased to more than 0.5 MPa;
s4, vacuum melting stage
Setting the smelting temperature to 730 ℃ through the heat treatment of the step S3, starting heating and smelting in a gradient heating mode, stirring for 30min and standing for 5min after the magnesium-lithium alloy raw material is completely molten, then cooling to the casting temperature, and finally casting into a magnesium-lithium alloy ingot;
s5, adjusting the atmosphere of the vacuum tube furnace
Putting the magnesium-lithium alloy ingot obtained in the step S4 into a vacuum tube furnace, opening a vacuum pump, vacuumizing for more than 3 times, and when the vacuum degree reaches 10-3Pa, then introducing argon protective gas, and increasing the pressure of the argon to 0.5MPa or above;
s6, heat treatment stage
And (4) carrying out solution treatment on the vacuum tube furnace after the step S5 at 430 ℃ for 8h, then rapidly cooling the vacuum tube furnace by using water or oil bath, and then carrying out aging treatment on the magnesium-lithium alloy cast ingot after the solution treatment at 100 ℃ for 20h to obtain the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member of the embodiment.
The cast microstructure of the biphase magnesium-lithium alloy structural member is shown in figure 4, and the microstructure mainly comprises alpha-Mg, beta-Li and Al2RE(Gd,Y)，Al8Mn5AlLi, wherein alpha phase accounts for 65% and beta phase accounts for 31%; comprehensive properties: the density was 1.60g/cm3Tensile strength of 356MPa, yield strength of 263MPa, elongation of 25%, elastic modulus of 67.8GPa, corrosion potential Ecorr1.45V, corrosion current density icorr＝10μA/cm2。
Example 3
The high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following chemical components in percentage by mass: al: 5 wt.%, Gd: 1.5 wt.%, Y: 4 wt.%, Li: 8.5 wt.%, Zn: 4.2 wt.%, Mn: 1 wt.%, the balance Mg and unavoidable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
The preparation method of the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following steps:
s1 raw material preparation stage
Weighing 1.5 wt.% of Gd-containing Mg-40 wt.% of Gd intermediate alloy, 4 wt.% of Y-containing Mg-33 wt.% of Y intermediate alloy, 1 wt.% of Mn-43 wt.% of Mn intermediate alloy, 5 wt.% of pure Al, 8.5 wt.% of pure Li, 4.2 wt.% of pure Zn and the balance of pure Mg according to the mass percentage of chemical components of raw materials in the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member; and removing the surface oxide;
s2 stage of preheating raw materials
Putting the raw materials and the crucible weighed in the step S1 into a heat treatment furnace, and preheating for 2.2 hours at 130 ℃ to dry the moisture of the raw materials;
s3, adjusting the atmosphere of the heat treatment furnace
Putting the raw materials preheated in the step S2 into different positions of a crucible according to factors such as melting point, oxidation degree, density and the like, putting the raw materials into a vacuum smelting furnace, wherein in consideration of the fact that Li is volatile and has low melting point, small pure Mg blocks are placed at the bottom of the crucible, then putting Mg intermediate alloy, then putting pure Zn and pure Al, and finally putting pure Li; opening the cooling system, covering the furnace cover, and vacuumizing until the vacuum degree reaches 10-3Pa, then opening a protective gas valve, and introducing high-purity argon until the gas pressure in the furnace is increased to more than 0.5 MPa;
s4, vacuum melting stage
Setting the smelting temperature to 790 ℃ in the heat treatment after the step S3, starting heating and smelting in a gradient heating mode, stirring for 25min and standing for 20min after the magnesium-lithium alloy raw material is completely molten, then cooling to the casting temperature, and finally casting into a magnesium-lithium alloy ingot;
s5, adjusting the atmosphere of the vacuum tube furnace
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, opening a vacuum pump, vacuumizing for more than 3 times until the vacuum degree reaches 10-3Pa, introducing argon protective gas, and increasing the argon pressure to be more than 0.5 MPa;
s6, heat treatment stage
And (4) carrying out solution treatment on the vacuum tube furnace after the step S5 at 400 ℃ for 12h, then rapidly cooling by using water or oil bath, and then carrying out aging treatment on the magnesium-lithium alloy cast ingot after the solution treatment at 100 ℃ for 20h to obtain the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member of the embodiment.
The cast microstructure of the biphase magnesium-lithium alloy structural part mainly comprises alpha-Mg, beta-Li and Al2RE(Gd, Y)，Al8Mn5AlLi, wherein alpha phase accounts for 50% and beta phase accounts for 46%; comprehensive properties: the density is 1.5g/cm3Tensile strength of 400MPa, yield strength of 350MPa, elongation of 35%, elastic modulus of 70.2GPa, corrosion potential Ecorr-1.535V, corrosion current density icorr＝11μA/cm2。
Example 4
The high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following chemical components in percentage by mass: al: 2 wt.%, Gd: 3 wt.%, Y: 2 wt.%, Li: 6 wt.%, Zn: 4.2 wt.%, Mn: 3 wt.%, the balance Mg and unavoidable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
The preparation method of the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following steps:
s1 raw material preparation stage
Weighing 3 wt.% of Gd-containing Mg-33 wt.% of Gd intermediate alloy, 2 wt.% of Y-containing Mg-35 wt.% of Y intermediate alloy, 3 wt.% of Mn-23 wt.% of Mn intermediate alloy, 2 wt.% of pure Al, 6 wt.% of pure Li, 4.2 wt.% of pure Zn and the balance of pure Mg according to the mass percentage of chemical components of raw materials in the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural component; and removing the surface oxide;
s2, stage of preheating raw material
Putting the raw materials and the crucible weighed in the step S1 into a heat treatment furnace, and preheating for 1.8 hours at 200 ℃ to dry the moisture of the raw materials;
s3, adjusting the atmosphere of the heat treatment furnace
Putting the raw materials preheated in the step S2 into different positions of a crucible according to factors such as melting point, oxidation degree, density and the like, putting the raw materials into a vacuum melting furnace, putting small pure Mg blocks at the bottom of the crucible in consideration of the fact that Li is easy to volatilize and has low melting point, then putting Mg intermediate alloy, putting pure Zn and pure Al, and finally putting pure Li; opening the cooling system, covering the furnace cover, and vacuumizing until the vacuum degree reaches 10-3Pa, then opening a protective gas valve, and introducing high-purity argon until the gas pressure in the furnace is increased to more than 0.5 MPa;
s4, vacuum melting stage
Setting the melting temperature to 780 ℃ through the heat treatment of the step S3, starting heating and melting in a gradient heating mode, stirring for 30min and standing for 10min after the magnesium-lithium alloy raw material is completely melted, then cooling to the casting temperature, and finally casting into a magnesium-lithium alloy ingot;
s5, adjusting the atmosphere of the vacuum tube furnace
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, opening a vacuum pump, vacuumizing for more than 3 times until the vacuum degree reaches 10-3Pa, introducing argon protective gas, and increasing the argon pressure to be more than 0.5 MPa;
s6, heat treatment stage
And (4) carrying out solution treatment on the vacuum tube furnace after the step S5 at 430 ℃ for 10h, then rapidly cooling by using water or oil bath, and then carrying out aging treatment on the magnesium-lithium alloy cast ingot after the solution treatment at 150 ℃ for 20h to obtain the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member of the embodiment.
The cast microstructure of the biphase magnesium-lithium alloy structural member mainly comprises alpha-Mg, beta-Li and Al2RE(Gd, Y)，Al8Mn5AlLi, wherein the alpha phase accounts for 85 percent, and the beta phase accounts for 11 percent; comprehensive properties: the density is 1.58g/cm3Tensile strength of 310MPa, yield strength of 280MPa, elongation of 30%, elastic modulus of 69.7GPa, corrosion potential Ecorr1.40V, corrosion current density icorr＝6μA/cm2。
Example 5
The high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following chemical components in percentage by mass: al: 4.5 wt.%, Gd: 3.3 wt.%, Y: 3.7 wt.%, Li: 7.3 wt.%, Zn: 3.7 wt.%, Mn: 2.5 wt.%, the balance Mg and unavoidable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
The preparation method of the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following steps:
s1 raw material preparation stage
Weighing 3.3 wt.% of Gd-containing Mg-47 wt.% of Gd intermediate alloy, 3.7 wt.% of Y-containing Mg-36 wt.% of Y intermediate alloy, 2.5 wt.% of Mn-26 wt.% of Mn intermediate alloy, 4.5 wt.% of pure Al, 7.3 wt.% of pure Li, 3.7 wt.% of pure Zn and the balance of pure Mg according to the mass percentage of chemical components of raw materials in the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member; and removing the surface oxide;
s2 stage of preheating raw materials
Putting the raw materials and the crucible weighed in the step S1 into a heat treatment furnace, and preheating for 2.5 hours at 150 ℃ to dry the moisture of the raw materials;
s3, adjusting the atmosphere of the heat treatment furnace
Putting the raw materials preheated in the step S2 into different positions of a crucible according to factors such as melting point, oxidation degree, density and the like, putting the raw materials into a vacuum smelting furnace, wherein in consideration of the fact that Li is volatile and has low melting point, small pure Mg blocks are placed at the bottom of the crucible, then putting Mg intermediate alloy, then putting pure Zn and pure Al, and finally putting pure Li; opening the cooling system, covering the furnace cover, and vacuumizing until the vacuum degree reaches 10-3Pa, then opening a protective gas valve, and introducing high-purity argon until the gas pressure in the furnace is increased to more than 0.5 MPa;
s4, vacuum melting stage
Setting the smelting temperature to 740 ℃ through the heat treatment of the step S3, starting heating and smelting in a gradient heating mode, stirring for 25min after the magnesium-lithium alloy raw material is completely molten, standing for 9min, cooling to the casting temperature, and finally casting into a magnesium-lithium alloy ingot;
s5, adjusting the atmosphere of the vacuum tube furnace
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, opening a vacuum pump, vacuumizing for more than 3 times until the vacuum degree reaches 10-3Pa, introducing argon protective gas, and increasing the argon pressure to be more than 0.5 MPa;
s6, heat treatment stage
After the vacuum tube furnace processed in step S5 is subjected to solution treatment at 460 ℃ for 8 hours, the magnesium-lithium alloy ingot is rapidly cooled by water or oil bath, and then the magnesium-lithium alloy ingot after solution treatment is subjected to aging treatment at 160 ℃ for 18 hours, so as to obtain the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member of the embodiment.
The cast microstructure of the biphase magnesium-lithium alloy structural member mainly comprises alpha-Mg, beta-Li and Al2RE(Gd, Y)，Al8Mn5，AlLi, wherein alpha phase accounts for 68% and beta phase accounts for 28%; comprehensive properties: the density is 1.45g/cm3Tensile strength of 370MPa, yield strength of 300MPa, elongation of 31%, elastic modulus of 69.2GPa, corrosion potential Ecorr1.51V, corrosion current density icorr＝10.2μA/cm2。
Example 6
The high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following chemical components in percentage by mass: al: 3.5 wt.%, Gd: 2.5 wt.%, Y: 3.4 wt.%, Li: 8 wt.%, Zn: 4.0 wt.%, Mn: 0.6 wt.%, the balance Mg and inevitable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
The preparation method of the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural part comprises the following steps:
s1 raw material preparation stage
Weighing 0.1-3.5 wt.% Gd-containing Mg-20-50 wt.% Gd intermediate alloy, 0.5-8 wt.% Y intermediate alloy, 0.1-3.5 wt.% Mn intermediate alloy, 1-5 wt.% pure Al, 5-12 wt.% pure Li, 0.2-4.2 wt.% pure Zn and the balance of pure Mg according to the mass percentage of the chemical components of the raw materials in the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member; and removing the surface oxide;
s2 stage of preheating raw materials
Putting the raw materials and the crucible weighed in the step S1 into a heat treatment furnace, and preheating for 2 hours at 180 ℃ to dry the moisture of the raw materials;
s3, adjusting the atmosphere of the heat treatment furnace
Putting the raw materials preheated in the step S2 into different positions of a crucible according to factors such as melting point, oxidation degree, density and the like, putting the raw materials into a vacuum smelting furnace, wherein in consideration of the fact that Li is volatile and has low melting point, small pure Mg blocks are placed at the bottom of the crucible, then putting Mg intermediate alloy, then putting pure Zn and pure Al, and finally putting pure Li; opening the cooling system, covering the furnace cover, and vacuumizing until the vacuum degree reaches 10-3Pa, then opening a protective gas valve, and introducing high-purity argon until the gas pressure in the furnace is increased toAbove 0.5 MPa;
s4, vacuum melting stage
Setting the melting temperature to 770 ℃ in the heat treatment after the step S3, starting heating and melting in a gradient heating mode, stirring for 15min and standing for 18min after the magnesium-lithium alloy raw material is completely melted, then cooling to the casting temperature, and finally casting into a magnesium-lithium alloy ingot;
s5, adjusting the atmosphere of the vacuum tube furnace
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, opening a vacuum pump, vacuumizing for more than 3 times until the vacuum degree reaches 10-3Pa, introducing argon protective gas, and increasing the argon pressure to be more than 0.5 MPa;
s6, heat treatment stage
And (4) carrying out solution treatment on the vacuum tube furnace after the step S5 at 440 ℃ for 12h, then rapidly cooling by using water or oil bath, and then carrying out aging treatment on the magnesium-lithium alloy cast ingot after the solution treatment at 180 ℃ for 15h to obtain the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member of the embodiment.
The cast microstructure of the biphase magnesium-lithium alloy structural member mainly comprises alpha-Mg, beta-Li and Al2RE(Gd, Y)，Al8Mn5AlLi, wherein alpha phase accounts for 59% and beta phase accounts for 37%; comprehensive properties: the density is 1.37g/cm3Tensile strength of 380MPa, yield strength of 330MPa, elongation of 34%, elastic modulus of 71.5GPa, corrosion potential Ecorr-1.44V, corrosion current density icorr＝8μA/cm2。
In the scheme, the content of Li element and the alloy proportion are controlled, so that an alpha + beta two-phase matrix phase exists in the matrix, and the beta-Li phase not only can provide a compact oxide film for the magnesium-lithium alloy to improve the corrosion resistance of the alloy, but also can improve the plasticity and the ductility of the matrix. Meanwhile, alloying elements such as Al, Zn, Mn, Gd, Y and the like are added, so that the solid solution strengthening effect can be achieved, a high-modulus precipitation strengthening phase can be generated in a matrix, and the strength and the plasticity of the magnesium-lithium alloy can be greatly improved by combining various modes such as solid solution treatment, aging heat treatment and the like, and meanwhile, the elastic modulus and the corrosion resistance of the magnesium-lithium alloy can be greatly improved, so that the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy is obtained, and the high-strength high-toughness corrosion-resistant two-phase magnesium-lithium alloy is suitable for meeting the requirements of light weight, high strength, high toughness and corrosion resistance for industrial structural members.
The invention can refine crystal grains and promote high modulus Al by simultaneously adding Gd and Y2Y, MgZn2Gd (Y) and the like; the alpha-Mg and the beta-Li in the matrix are matched to synergistically improve the properties of the magnesium-lithium alloy, such as strength, plasticity, modulus and the like, and prolong the service life of the magnesium-lithium alloy. Meanwhile, the addition of rare earth elements can purify impurity elements in the melt and improve the corrosion resistance of the alloy.
According to the invention, by simultaneously adding Al and Zn, the alpha-Mg in the magnesium-lithium matrix tends to be equiaxial, the beta-Li phase is refined, and a stable phase and a quasicrystal phase can be generated to further improve the mechanical property and corrosion resistance of the magnesium-lithium alloy. Meanwhile, the Mn element is added, so that the yield strength of the magnesium-lithium alloy can be improved, harmful metal impurities are removed, crystal grains are refined, and a high-modulus strengthening phase Al is formed with Al8Mn5。
In addition, the added Al may form Al with Li3Li high modulus phase and Mg continuous generation of high modulus Mg in crystal17Al12And precipitating a strengthening phase to obtain the high-strength high-modulus magnesium-lithium alloy.
According to the preparation method of the magnesium-lithium alloy structural member, mechanical properties such as strength and the like of the magnesium-lithium alloy are improved by forming a precipitation phase with high modulus, solid solution strengthening, fine grain strengthening and other coupling modes on the magnesium-lithium alloy through vacuum melting, simple microalloying and heat treatment processes, corrosion resistance of the alloy is improved by forming a compact surface film by using a beta-Li phase and refining grains and the like, and finally the high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy which is improved in a synergistic manner is achieved.
The high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural part has excellent strength, plasticity and resistanceCorrosion property: the density is 1.37-1.75g/cm3The tensile strength is 300-400MPa, the yield strength is 260-350MPa, the elongation is 21-42%, the elastic modulus is 62-75GPa, and the corrosion potential is Ecorr-1.63 to-1.35V, corrosion current density icorr＝5-12μA/cm2。
In a word, the method adopts a mode of combining micro-alloying with heat treatment, has the advantages of low cost, high efficiency, simple operation, high raw material utilization rate, wide application range and the like, can synergistically improve the strength, elongation, elastic modulus and corrosion resistance of the biphase magnesium-lithium alloy while controlling the low density of the biphase magnesium-lithium alloy structural member, ensures that the matching effects of high tensile strength, high yield strength, high elongation, high elastic modulus and high corrosion resistance are excellent, and is beneficial to industrial large-scale production and popularization.
The foregoing is a preferred embodiment of the present invention, and it should be noted that it is obvious to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and these modifications and improvements should be considered as the protection scope of the present invention.

Claims (10)

1. The high-strength high-modulus corrosion-resistant two-phase magnesium-lithium alloy structural member is characterized by comprising the following chemical components in percentage by mass: al: 1-5 wt.%, Gd: 0.1-3.5 wt.%, Y: 0.5-8 wt.%, Li: 5-12 wt.%, Zn: 0.2-4.2 wt.%, Mn: 0.1-3.5 wt.%, the balance being Mg and unavoidable impurities; wherein: the content of the inevitable impurities is less than or equal to 0.03 wt%.
2. The high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member according to claim 1, wherein the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member has a structure mainly comprising α -Mg, β -Li, Al2RE(Gd,Y)，Al8Mn5The AlLi has alpha phase in 50-80 wt%, beta phase in 20-50 wt% and total alpha phase plus beta phase not higher than 96 wt%.
3. The high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member according to claim 1, wherein the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member has the following properties: the density is 1.37-1.75g/cm3The tensile strength is 300-400MPa, the yield strength is 260-350MPa, the elongation is 21-42%, the elastic modulus is 62-75GPa, and the corrosion potential is Ecorr-1.63 to-1.35V, corrosion current density icorr＝5-12μA/cm2。
4. A method for preparing a high-strength high-modulus corrosion-resistant dual-phase mg-li alloy structural member according to any one of claims 1 to 3, wherein the method comprises the following steps:
s1 raw material preparation stage
Weighing pure Mg, pure Al, pure Li, pure Zn, Mg-Gd intermediate alloy, Mg-Y intermediate alloy and Mg-Mn intermediate alloy as raw materials according to the mass percentage of the chemical components of the raw materials in the high-strength high-modulus biphase magnesium-lithium alloy structural component, and polishing surface oxides;
s2 stage of preheating raw materials
Putting the raw materials and the crucible weighed in the step S1 into a heat treatment furnace for preheating so as to dry the moisture of the raw materials;
s3, adjusting the atmosphere of the heat treatment furnace
Putting the raw materials preheated in the step S2 into different positions of a vacuum smelting furnace according to factors of melting point, oxidation degree, density, adding quantity and volatility, then opening a cooling system, covering a furnace cover, starting vacuumizing, then opening a protective gas valve, and introducing protective gas;
s4, vacuum melting stage
Setting the smelting temperature of the vacuum smelting furnace after the step S3, starting heating smelting, stirring and standing after the magnesium-lithium alloy raw material is completely molten, and then cooling to the casting temperature to start casting a magnesium-lithium alloy cast ingot;
s5, adjusting the atmosphere of the vacuum tube furnace
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, opening a vacuum pump, and then introducing protective gas;
s6, heat treatment stage
And (5) setting the heat treatment temperature of the vacuum tube furnace after the step S5, and then carrying out a solution aging heat treatment process to finally obtain the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural member.
5. The method of claim 4, wherein the content of Gd, Y and Mn in the Mg-Gd, Mg-Y, Mg-Mn master alloy is 20-50 wt.% in the step S1.
6. The method as claimed in claim 4, wherein the preheating temperature in step S2 is 100-250 ℃ and the preheating time is 1.5-2.5 h.
7. The method for preparing the high-strength high-modulus corrosion-resistant biphase magnesium-lithium alloy structural member according to claim 4, wherein different positions of the vacuum melting furnace in the step S3 are that small pure Mg blocks are placed at the bottom, then Mg intermediate alloy is placed, pure Zn and pure Al are placed, and finally pure Li is placed; .
8. The method for preparing a high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member according to claim 4, wherein the temperature-rising smelting in the step S4 adopts a gradient heating mode.
9. The method for preparing a high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member according to claim 4, wherein the vacuum melting stage in the step S4 is as follows:
s401, setting the smelting temperature to 710 and 790 ℃, and setting the heating power to 50-100%;
s402, starting heating in a gradient heating mode until the raw materials are completely melted, stirring for 10-30min, and standing for 5-20 min;
and S403, stopping stirring, then, cooling to the pouring temperature, and finally, pouring to obtain the magnesium-lithium alloy ingot.
10. The method for preparing the high-strength high-modulus corrosion-resistant dual-phase magnesium-lithium alloy structural member according to claim 4, wherein the solution aging heat treatment process in the step S6 is as follows: after solution treatment is carried out for 2-24h at the temperature of 300-500 ℃, water or oil bath is used for rapid cooling, and then the magnesium-lithium alloy ingot after solution treatment is subjected to aging treatment for 5-24h at the temperature of 100-250 ℃.
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