CN114540686B - Multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy and preparation method thereof - Google Patents
Multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy and preparation method thereof Download PDFInfo
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- C22C23/00—Alloys based on magnesium
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- C22C1/03—Making non-ferrous alloys by melting using master alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
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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
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- 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
Abstract
The invention discloses a multi-element microalloyed high-strength high-modulus biphase magnesium lithium alloy and a preparation method thereof, wherein the multi-element microalloyed high-strength high-modulus biphase magnesium lithium alloy comprises the following elements in percentage by mass: al:1-5wt.%, gd:0.1-2wt.%, Y:0.5-3wt.%, li:5-12wt.%, zn:0.2-3wt.%, mn:0.1-0.8wt.%, sn:0.1-1.5wt.%, pr:0.1-1.5wt.%, nd:0.1-1.5wt.%, balance Mg and impurities; the content of impurities
0.03wt%. The method has the advantages of low price, high efficiency, advanced and simple process, high raw material yield, wide application range and the like, can ensure the low density and light weight of the magnesium-lithium alloy, and simultaneously obviously improves the mechanical properties of the multielement microalloying biphase magnesium-lithium alloy, such as strength, elongation, elastic modulus, plasticity and the like. The invention is suitable for the field of magnesium alloy materials.
Description
Technical Field
The invention belongs to the field of magnesium alloy materials, and particularly relates to a multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy and a preparation method thereof.
Background
With the increasing requirements for light weight and environmental protection of weaponry, alloy materials with ultra-high strength are receiving attention. Among them, the Mg-Li alloy is the lightest of the structural materials and has the density of 1.25-1.65g/cm 3 ) Only half of the aluminum alloy material. Compared with other metal materials, the Mg-Li alloy has high specific strength and specific stiffness, good damping property, machinability and electromagnetic shielding property, has huge market application prospect in the high and new technical fields of aerospace, 3C industry, military, communication and the like, and particularly, the Mg-Li alloy can rise rapidly under the conditions that the current natural resources are increasingly deficient and the magnesium resource reserves are rich.
At present, many research reports on magnesium-lithium alloys are reported, specifically as follows:
chinese patent CN 107541626A discloses a multi-element microalloy grain refinement type magnesium-lithium alloy and its preparation, which is characterized in that a small amount of composite blocks are added into LA141 magnesium-lithium alloy to make the material multi-element microalloy, although the magnesium-lithium alloy can be microalloyed, the addition of the composite blocks can cause brittle fracture of the alloy, and the interface bonding strength between the alloy and the magnesium-lithium alloy matrix is not high, so that the alloy is not suitable for engineering application with high requirement on plasticity.
Chinese patent CN 112746210B discloses a multi-element microalloyed magnesium alloy, a preparation method thereof and a plate extrusion forming process, wherein alloying elements are added for alloying and the extrusion process is used for improving the mechanical property of Mg-6Zn-1Gd-0.12Y-0.21Nd-0.03Ca alloy, but the synergistic improvement of alloy strength, elastic modulus and density is not considered, the addition of a large amount of Zn element can obviously improve the density of the magnesium alloy and form a second phase with low modulus, is not beneficial to industrial lightweight application and material application of high-modulus structural members, and cannot meet the use working conditions of actual complex industrial structural members.
Chinese patent CN 110029254B discloses a multi-element microalloyed double-phase magnesium-lithium alloy and a preparation method thereof, and the strength of the alloy is improved by microalloying, extrusion forming and other methods of various alloy elements, so that the strength of the obtained magnesium-lithium alloy is 220-250MPa, is lower than 300MPa, has the yield strength of 140-190MPa, is lower than 200MPa, and still cannot meet the complex working conditions of industrial application. Meanwhile, the preparation method is complex, complicated hot processing needs to be carried out on the cast ingot, and the plate obtained by extrusion deformation and hot rolling is simple in structure and is not suitable for application requiring high-strength high-modulus low-density materials.
Aiming at the defects of low strength, low elastic modulus, large preparation difficulty and the like of the existing Mg-Li alloy, how to improve the mechanical properties of the Mg-Li alloy such as strength, modulus and the like is particularly important.
Disclosure of Invention
In order to solve the defects and shortcomings, the invention provides a multi-element microalloyed high-strength high-modulus biphase magnesium-lithium alloy and a preparation method thereof, wherein the mechanical property of the magnesium-lithium alloy is improved by regulating and controlling the Li element content and proportion in the magnesium-lithium alloy, multi-element alloying, vacuum centrifugal smelting, heat treatment and other processes and utilizing strengthening mechanisms such as solid solution strengthening, aging strengthening, dispersion strengthening, fine grain strengthening and the like, so that the multi-element alloying high-strength high-modulus biphase magnesium-lithium alloy with the requirements of low density, high strength, high elongation and high modulus is prepared, and the large-scale application of Mg-Li alloy materials in the fields of aerospace, precision instruments, missiles and the like is met.
In order to achieve the above object, the first aspect of the present invention provides the following solutions:
a multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following elements in percentage by mass: al:1-5wt.%, gd:0.1-2wt.%, Y:0.5-3wt.%, li:5-12wt.%, zn:0.2-3wt.%, mn:0.1-0.8wt.%, sn:0.1-1.5wt.%, pr:0.1-1.5wt.%, nd:0.1-1.5wt.%, balance Mg and impurities;
the content of impurities
0.03wt%。
As an embodiment of the invention, the microstructure of the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is mainly
-Mg，
-Li，Al 2 RE(Nd，Gd，Y，Pr)，Mg 3 (Nd, Pr, Sn)，Al 8 Mn 5 ，AlLi，Mg 24 Y 5 ，MgZn(Gd，Y)，Li 17 Sn 4 ，MgLi 2 Al and MgLi 2 Zn；
Wherein the content of the first and second substances,
-Mg in a proportion of 30-80%,
-a Li proportion of 30-70%,
phase actuation
The total proportion of phases does not exceed 95%.
As an embodiment of the invention, the properties of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy are as follows: the density is 1.3-1.9g/cm 3 The tensile strength is 280-430MPa, the yield strength is 240-360MPa, the elongation is 15-35%, and the elastic modulus is 60-75GPa.
A method for preparing the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy of the first aspect of the invention, which comprises the following steps:
s1: raw material selection
According to the composition and the mass percentage of each element in the multi-element microalloyed high-strength high-modulus biphase magnesium-lithium alloy, pure Mg, pure Al, pure Zn, pure Sn, mg-Li intermediate alloy, mg-Gd intermediate alloy, mg-Y intermediate alloy, mg-Mn intermediate alloy, mg-Pr intermediate alloy and Mg-Nd intermediate alloy are used as raw materials for weighing, and a grinding machine is used for grinding surface oxides to keep the metal luster for the later use;
s2: stage of preheating raw materials
Wrapping the raw materials weighed in the step S1 with aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating, and reserving for later use;
s3: charging phase
Firstly, placing the preheated crucible and the metal copper mold in the step S2 into a vacuum centrifugal casting furnace with argon protection, then placing the preheated raw materials into different positions of the crucible in the centrifugal casting furnace, then opening a cold water circulator and covering a furnace cover, and starting to vacuumize the atmosphere in the furnace to 10 DEG C -3 Below Pa, then filling protective gas argon into the furnace;
s4: vacuum centrifugal smelting stage
After the step S3, adjusting the heating current and power of the centrifugal casting furnace, starting to heat and melt the raw material, firstly heating at low power until the crucible is red hot, then heating at high power until the raw material is melted, starting to preserve heat, then setting the centrifugal casting speed and starting to cast to obtain a magnesium-lithium alloy ingot, and monitoring the temperature change in the furnace by using an infrared thermometer in the whole process;
s5: stage of heat treatment
Putting the magnesium-lithium alloy ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the atmosphere in the furnace to 10 DEG -3 Introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; setting heat treatment temperature, and then carrying out solid solution aging heat treatment process to finally obtain the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
As an embodiment of the invention, in the step S1, the mass purities of pure Mg, pure Al, pure Sn and pure Zn are all 99.90-99.999%;
in the step S1, the mass contents of Li, gd, Y, mn, pr and Nd in the Mg-Li intermediate alloy, the Mg-Gd intermediate alloy, the Mg-Y intermediate alloy, the Mg-Mn intermediate alloy, the Mg-Pr intermediate alloy and the Mg-Nd intermediate alloy in the raw materials are all 10-50wt.%.
As an embodiment of the invention, in the step S2, the preheating temperature is 80-250 ℃, and the preheating time is 0.5-2h;
in step S2, the crucible is: graphite crucibles, BN crucibles or stainless steel crucibles.
In step S3, different positions of the crucible in the centrifugal casting furnace are placed in the crucible according to the melting point, the degree of easy oxidation, the density, the adding amount, the degree of easy volatilization and other factors of the raw materials; considering that Li is active and inflammable, and the upper part temperature is relatively low in the crucible heating process, small pure Mg blocks are placed at the bottom, then Mg-Gd, mg-Y, mg-Mn, mg-Pr and Mg-Nd intermediate alloys are placed, pure Zn and pure Al are placed, and finally the Mg-Li intermediate alloy is placed.
As an embodiment of the present invention, the vacuum centrifugal melting stage in step S4 includes:
s401: the heating current is 1.0-5.0A, and the heating power is 50-100%;
s402: the raw materials are heated and melted by adopting a gradient heating mode, the raw materials are firstly heated to be red hot in a crucible at low power, and the power is as follows: 50% -70%; heating to melt by adopting high power, wherein the high power is as follows: 70% -100%;
s403: the heat preservation temperature is as follows: 730-780 ℃, and the heat preservation time is as follows: 15-30min;
s404: the centrifugal casting speed is as follows: 300-500 rpm.
As an embodiment of the present invention, the heat treatment stage in step S5 includes:
s501: the solid solution treatment adopts two-stage solid solution treatment. The solid solution temperature is 300-500 ℃, and after the solid solution time is 2-48h, the steel plate is rapidly cooled and quenched by water or oil bath;
s502: the aging temperature is as follows: 80-250 ℃ and aging time of 1-24h, and then obtaining the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
The technical scheme provided by the invention at least brings the following beneficial effects:
in the scheme, the multi-element microalloyed high-strength high-modulus biphase magnesium-lithium alloy provided by the invention has specific micro metallographic structure morphology, refined as-cast structure grains and Mg 3 Nd，Mg 5 Gd、Al 8 Mn 5 The phase is distributed in the crystal boundary, and obviously, the grains are refined and dispersed.
The invention controls the content and the proportion of the Li element and the multi-element alloying element to ensure that the Li element and the multi-element alloying element exist in the matrix at the same time
Two-phase matrix phase, BCC with darker color in metallographic picture
Improves the elongation and plasticity of the alloy, and simultaneously improves the HCP-
The phase improves the strength of the alloy. Meanwhile, al, zn, mn, gd, Y and N are added under the condition of ensuring the low density of the alloyd. Alloying elements such as Sn and Pr not only can play a role of solid solution strengthening, but also can generate high-modulus precipitation strengthening phases in a matrix, and the phases are in crystal boundaries and BCC-
The phase formation can hinder dislocation movement and slippage, and the strength and plasticity of the magnesium-lithium alloy can be greatly improved by combining various modes such as solution treatment, aging heat treatment and the like, and the elastic modulus of the magnesium-lithium alloy is also greatly improved by the high-modulus second phases. The multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy and the preparation method thereof provided by the invention can obtain the high-strength high-modulus two-phase magnesium-lithium alloy by adding multi-element alloying elements under the condition of ensuring the low density of the magnesium-lithium alloy, and are suitable for meeting the industrial requirements of light-weight, high-strength and high-toughness lithium-magnesium alloys.
By simultaneously adding rare earth elements Gd, Y, nd and Pr, the invention can refine crystal grains, avoid partial polymerization of alloy components and form Al with high modulus and fine dispersion distribution 2 Y（Gd，Pr）、MgZn 2 Gd（Y）、Mg 3 Nd、Al 3 Pr and the like to obviously improve the elastic modulus of the alloy. Simultaneous collaboration
-Mg and
the Li matrix phase improves the mechanical properties of the magnesium-lithium alloy, such as strength, plasticity, modulus and the like. And rare earth elements are added, so that the texture formed in the plastic deformation process can be weakened, and a fine grain structure is formed. Moreover, the rare earth elements are added, so that impurity elements in the melt can be purified, and the corrosion resistance of the alloy is improved.
The invention can form MgLi by adding Al and Zn simultaneously 2 Al and MgLi 2 The Zn phase improves the strength of the alloy, and can also generate a stable phase and a quasicrystal phase to further improve the mechanical property and the elongation of the magnesium-lithium alloy. The addition of Mn and Sn can raise the yield strength of Mg-Li alloyRemove harmful metal impurities, refine grains and form a high-modulus strengthening phase Al with Al 8 Mn 5 With Li to form Li 17 Sn 4 High modulus phase.
In addition, the added Al may form Al with Li 3 The Li and AlLi high modulus phase is cooperated with the multi-element alloying elements through fine grain strengthening, solid solution strengthening, dispersion strengthening, second phase strengthening and the like to obtain the multi-element microalloying high-strength high-modulus biphase magnesium-lithium alloy.
The preparation method of the multi-element microalloying high-strength high-modulus two-phase magnesium-lithium alloy provided by the invention adopts the vacuum centrifugal smelting, the multi-element microalloying and the heat treatment process to form the precipitated phase with high modulus, solid solution strengthening, fine grain strengthening and other coupling modes to improve the mechanical properties of the alloy, such as strength and the like.
The properties of the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy are as follows: the density is 1.3-1.9g/cm 3 The tensile strength is 280-430MPa, the yield strength is 240-360MPa, the elongation is 15-35%, and the elastic modulus is 60-75GPa.
In a word, the method adopts a mode of combining centrifugal casting, multi-element microalloying and heat treatment, has the advantages of low price, high efficiency, advanced and simple process, high raw material yield, wide application range and the like, can ensure the low density and light weight of the magnesium-lithium alloy, obviously improves the mechanical properties of strength, elongation, elastic modulus, plasticity and the like of the multi-element microalloyed dual-phase magnesium-lithium alloy, and can meet the requirements of the fields of military affairs, medical treatment, aviation and the like on light-weight high-strength high-modulus alloy materials.
Drawings
FIG. 1 is an as-cast microstructure of a multi-microalloyed high strength high modulus two-phase Mg-Li alloy in example 1 of the invention;
FIG. 2 is an as-cast microstructure of the multi-component microalloyed high strength high modulus two-phase magnesium lithium alloy of example 2 of the invention;
FIG. 3 is an as-cast microstructure of the multi-microalloyed high strength high modulus two-phase Mg-Li alloy of example 3 in accordance with the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below.
Example 1
The multielement microalloyed high-strength high-modulus biphase magnesium-lithium alloy comprises the following elements in percentage by mass: al:2wt.%, gd:0.9wt.%, Y:3wt.%, li:6.5wt.%, zn:2wt.%, mn:0.5wt.%, sn:0.2wt.%, pr:0.2wt.%, nd:1wt.%, the balance Mg and unavoidable impurities; wherein: the inevitable impurity content
0.03wt%。
The preparation method of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following steps:
s1, selecting raw materials
Weighing 2wt.% of pure Al, 2wt.% of pure Zn, 0.2wt.% of pure Sn, 6.5wt.% of Li-containing Mg-20wt.% of Li intermediate alloy, 0.9wt.% of Gd-containing Mg-30wt.% of Gd intermediate alloy, 3wt.% of Y-containing Mg-30wt.% of Y intermediate alloy, 0.5wt.% of Mn-8 wt.% of Mn intermediate alloy, 0.2wt.% of Pr-25 wt.% of Pr intermediate alloy and 1wt.% of Nd-containing Mg-25wt.% of Nd intermediate alloy as raw materials according to the component and the mass percentage thereof in the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy, and grinding the surface oxide by using a grinding machine to keep metallic luster for later use;
s2, preheating raw materials
Wrapping the raw materials weighed in the step S1 with aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating at 200 ℃ for 2 hours, and reserving for the next step;
s3, charging stage
Firstly, the crucible and the metal copper mold preheated in the step S2 are put into a vacuum centrifugal casting furnace with argon protection, and then the preheated raw materials are put into the furnace according to the melting point of the raw materialsThe oxidation degree, the density, the adding amount, the volatile degree and other factors are put into different positions of a crucible in the centrifugal casting furnace; considering that Li is more active and flammable and the upper temperature is relatively low in the crucible heating process, small pure Mg blocks are placed at the bottom, then Mg-Gd, mg-Y, mg-Mn, mg-Pr and Mg-Nd intermediate alloys are placed, pure Zn and pure Al are placed, and finally the Mg-Li intermediate alloy is placed; then the cold water circulator is opened and the furnace cover is closed, and the furnace atmosphere is vacuumized to 10 DEG -3 Below Pa, then filling protective gas argon into the furnace;
s4, vacuum centrifugal smelting stage
And S3, adjusting the heating current of the centrifugal casting furnace to be 2.0A and the power to be 50%, starting to heat and melt the raw materials, heating the raw materials at low power (50%) until the crucible is red hot, heating the raw materials at high power (90%) until the raw materials are melted, starting to preserve heat, keeping the temperature at 780 ℃ for 15min, setting the centrifugal casting speed at 350 r/min, and starting to pour to obtain the magnesium-lithium alloy ingot. Monitoring the temperature change in the furnace by adopting an infrared thermometer in the whole process;
s5, heat treatment stage
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the furnace atmosphere to 10 DEG -3 Below Pa, introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; carrying out a solid solution aging heat treatment process, wherein the solid solution temperature is as follows: the solid solution time is 5h at 350 ℃; the aging temperature is as follows: the aging time is as follows at 100 ℃: and 5h, finally obtaining the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
The as-cast microstructure of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is shown in figure 1, and the microstructure mainly comprises
-Mg，
-Li，Al 2 RE(Nd，Gd，Y，Pr)，Mg 3 (Nd, Pr, Sn)，Al 8 Mn 5 ，AlLi，Mg 24 Y 5 ，MgZn(Gd，Y)，Li 17 Sn 4 ，MgLi 2 Al and MgLi 2 Zn, of which
The proportion of the phases is 60 percent,
the proportion of the phases is 30 percent; the comprehensive properties are as follows: the density is 1.65g/cm 3 The tensile strength was 351MPa, the yield strength was 283MPa, the elongation was 21.2%, and the elastic modulus was 65.8GPa.
Example 2
The multielement microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following elements in percentage by mass: al:4wt.%, gd:0.5wt.%, Y:3wt.%, li:5wt.%, zn:2wt.%, mn:0.8wt.%, sn:0.9wt.%, pr:0.2wt.%, nd:0.5wt.%, the balance Mg and inevitable impurities; wherein: the inevitable impurity content
0.03wt%。
The preparation method of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following steps:
s1, selecting raw materials
Weighing 4wt.% of pure Al, 2wt.% of pure Zn, 0.9wt.% of pure Sn, 5wt.% of Li-containing Mg-30wt.% of Li intermediate alloy, 0.5wt.% of Gd-containing Mg-30wt.% of Gd intermediate alloy, 3wt.% of Y-containing Mg-30wt.% of Y intermediate alloy, 0.8wt.% of Mn-10 wt.% of Mn intermediate alloy, 0.2wt.% of Pr-25 wt.% of Pr intermediate alloy and 0.5wt.% of Nd-containing Mg-30wt.% of Nd intermediate alloy as raw materials according to the element compositions and the mass percentages thereof in the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy, and grinding surface oxides by using a grinding machine to keep metallic luster for later use;
s2, preheating raw materials
Wrapping the raw materials weighed in the step S1 with aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating at 150 ℃ for 2 hours, and reserving for the next step;
s3, charging stage
Firstly, putting the crucible and the metal copper mold preheated in the step S2 into a vacuum centrifugal casting furnace protected by argon, then putting the preheated raw materials into the furnace, and putting the raw materials into different positions of the crucible in the centrifugal casting furnace according to factors such as 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 more active and inflammable, and the upper part temperature is relatively low in the crucible heating process, small pure Mg blocks are placed at the bottom, then Mg-Gd, mg-Y, mg-Mn, mg-Pr and Mg-Nd intermediate alloys are placed, pure Zn and pure Al are placed, and finally the Mg-Li intermediate alloy is placed; then the cold water circulator is opened and the furnace cover is closed, and the furnace atmosphere is vacuumized to 10 DEG -3 Below Pa, then filling protective gas argon into the furnace;
s4, vacuum centrifugal smelting stage
And S3, adjusting the heating current of the centrifugal casting furnace to be 2.5A and the power to be 60%, starting to heat and melt the raw material, heating the raw material at low power (60%) until the crucible is red hot, heating the raw material at high power (95%) until the raw material is melted, starting to preserve heat, keeping the temperature at 730 ℃ for 30min, setting the centrifugal casting speed at 400 rpm, and starting to pour to obtain the magnesium-lithium alloy ingot. Monitoring the temperature change in the furnace by adopting an infrared thermometer in the whole process;
s5, heat treatment stage
Putting the magnesium-lithium alloy ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the atmosphere in the furnace to 10 DEG -3 Introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; carrying out a solid solution aging heat treatment process, wherein the solid solution temperature is as follows: the solid solution time is 6h at 360 ℃; the aging temperature is as follows: 120 ℃, and the aging time is as follows: and 3h, finally obtaining the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
The as-cast microstructure of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is shown in figure 2, and the microstructure mainly comprises
-Mg，
-Li，Al 2 RE(Gd，Y，Pr)，Mg 3 (Nd, Pr, Sn)，Al 8 Mn 5 ，AlLi，Mg 24 Y 5 ，MgZn(Gd，Y，Sn)， Li 17 Sn 4 ，MgLi 2 Al and MgLi 2 Zn, of which
The proportion of the phases is 74 percent,
the proportion of the phases is 20 percent; the comprehensive performance is as follows: the density is 1.55g/cm 3 The tensile strength was 300MPa, the yield strength was 260MPa, the elongation was 21.2%, and the elastic modulus was 68GPa.
Example 3
The multielement microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following elements in percentage by mass: al:4wt.%, gd:1wt.%, Y:1.5wt.%, li:6wt.%, zn:2.5wt.%, mn:0.6wt.%, sn:0.2wt.%, pr:1wt.%, nd:0.5wt.%, the balance Mg and inevitable impurities; wherein: the inevitable impurity content
0.03wt%。
The preparation method of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following steps:
s1, selecting raw materials
Weighing 4wt.% of Al pure Al, 2.5wt.% of Zn pure Zn, 0.2wt.% of Sn pure Sn, 6wt.% of Li-20 wt.% of Mg intermediate alloy, 1wt.% of Gd-30 wt.% of Mg intermediate alloy, 1.5wt.% of Y-30 wt.% of Y intermediate alloy, 0.6wt.% of Mn-10 wt.% of Mn intermediate alloy, 1wt.% of Pr-25 wt.% of Pr intermediate alloy, 0.5wt.% of Nd-25 wt.% of Nd intermediate alloy as raw materials, grinding surface oxides by using a grinding machine, and keeping metallic luster for later use;
s2, preheating raw materials
Wrapping the raw materials weighed in the step S1 by using aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating at 200 ℃ for 1h, and reserving for the next step;
s3, charging stage
Firstly, putting the crucible and the metal copper mold preheated in the step S2 into a vacuum centrifugal casting furnace protected by argon, then putting the preheated raw materials into the furnace, and putting the raw materials into different positions of the crucible in the centrifugal casting furnace according to factors such as 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 more active and flammable and the upper temperature is relatively low in the crucible heating process, small pure Mg blocks are placed at the bottom, then Mg-Gd, mg-Y, mg-Mn, mg-Pr and Mg-Nd intermediate alloys are placed, pure Zn and pure Al are placed, and finally the Mg-Li intermediate alloy is placed; then the cold water circulator is opened and the furnace cover is closed, and the furnace atmosphere is vacuumized to 10 DEG -3 Below Pa, then filling protective gas argon into the furnace;
s4, vacuum centrifugal smelting stage
And S3, adjusting the heating current of the centrifugal casting furnace to be 3A and the power to be 50%, starting to heat and melt the raw material, heating at low power (50%) until the crucible is red hot, then heating at high power (95%) until the raw material is melted, starting to preserve heat, keeping the temperature at 780 ℃ for 30min, setting the centrifugal casting speed at 400 rpm, and starting to pour to obtain the magnesium-lithium alloy ingot. Monitoring the temperature change in the furnace by adopting an infrared thermometer in the whole process;
s5, heat treatment stage
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the furnace atmosphere to 10 DEG -3 Below Pa, introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; carrying out a solid solution aging heat treatment process, wherein the solid solution temperature is as follows: the solid solution time is 8h at 350 ℃; the aging temperature is as follows: 80 ℃, and the aging time is as follows: and 5h, finally obtaining the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
The as-cast microstructure of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is shown in FIG. 3, and the microstructure mainly comprises
-Mg，
-Li，Al 2 RE(Nd，Gd，Y，Pr)，Mg 3 (Nd, Pr, Sn)，Al 8 Mn 5 ，AlLi，Mg 24 Y 5 ，MgZn(Gd，Y)，Li 17 Sn 4 ，MgLi 2 Al and MgLi 2 Zn, of which
The proportion of the phase is 55 percent,
the proportion of the phases is 41 percent; the comprehensive properties are as follows: the density is 1.69g/cm 3 The tensile strength was 330MPa, the yield strength was 283MPa, the elongation was 23% and the elastic modulus was 65GPa.
Example 4
The multielement microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following elements in percentage by mass: al:3wt.%, gd:1.5wt.%, Y:3wt.%, li:10wt.%, zn:2.5wt.%, mn:0.8wt.%, sn:0.5wt.%, pr:1wt.%, nd:0.4wt.%, the balance Mg and unavoidable impurities; wherein: the inevitable impurity content
0.03wt%。
The preparation method of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following steps:
s1, selecting raw materials
Weighing 3wt.% of pure Al, 2.5wt.% of pure Zn, 0.5wt.% of pure Sn, 1.0 wt.% of Li-containing Mg-20wt.% of Li intermediate alloy, 1.5wt.% of Gd-containing Mg-30wt.% of Gd intermediate alloy, 3wt.% of Y-containing Mg-30wt.% of Y intermediate alloy, 0.8wt.% of Mn-10 wt.% of Mn intermediate alloy, 1wt.% of Pr-25 wt.% of Pr intermediate alloy and 0.4wt.% of Nd-containing Mg-25wt.% of Nd intermediate alloy as raw materials according to the component compositions and the mass percentages thereof in the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy, and grinding the surface oxide by using a grinding machine to keep the metallic luster for the later use;
s2, preheating raw materials
Wrapping the raw materials weighed in the step S1 by using aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating at 180 ℃ for 1h, and reserving for the next step;
s3, charging stage
Firstly, putting the crucible and the metal copper mold preheated in the step S2 into a vacuum centrifugal casting furnace protected by argon, then putting the preheated raw materials into the furnace, and putting the raw materials into different positions of the crucible in the centrifugal casting furnace according to factors such as 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 more active and flammable and the upper temperature is relatively low in the crucible heating process, small pure Mg blocks are placed at the bottom, then Mg-Gd, mg-Y, mg-Mn, mg-Pr and Mg-Nd intermediate alloys are placed, pure Zn and pure Al are placed, and finally the Mg-Li intermediate alloy is placed; then the cold water circulator is opened and the furnace cover is closed, and the furnace atmosphere is vacuumized to 10 DEG -3 Below Pa, then filling protective gas argon into the furnace;
s4, vacuum centrifugal smelting stage
And S3, adjusting the heating current of the centrifugal casting furnace to be 2.5A and the power to be 60%, starting to heat and melt the raw material, heating the raw material at low power (60%) until the crucible is red hot, heating the raw material at high power (90%) until the raw material is melted, starting to preserve heat, keeping the heat preservation temperature at 750 ℃ for 20min, setting the centrifugal casting speed at 450 rpm, and starting to pour to obtain the magnesium-lithium alloy ingot. Monitoring the temperature change in the furnace by adopting an infrared thermometer in the whole process;
s5, heat treatment stage
Putting the magnesium-lithium alloy ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the atmosphere in the furnace to 10 DEG -3 Below Pa, introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; carrying out a solid solution aging heat treatment process, wherein the solid solution temperature is as follows: the solid solution time is 8h at 350 ℃; the aging temperature is as follows: 80 ℃, and the aging time is as follows: and 5h, finally obtaining the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
The as-cast microstructure of the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is mainly
-Mg，
-Li，Al 2 RE(Nd，Gd，Y，Pr)，Mg 3 (Nd, Pr, Sn)，Al 8 Mn 5 ，AlLi，Mg 24 Y 5 ，MgZn(Gd，Y)，Li 17 Sn 4 ，MgLi 2 Al and MgLi 2 Zn, of which
The proportion of the phase is 40 percent,
the proportion of the phases is 55 percent; the comprehensive performance is shown in figure 2: the density was 1.75g/cm 3 The tensile strength was 351MPa, the yield strength was 270MPa, the elongation was 26%, and the elastic modulus was 66GPa.
Example 5
The multielement microalloyed high-strength high-modulus biphase magnesium-lithium alloy comprises the following elements in percentage by mass: al:3.5wt.%, gd:0.5wt.%, Y:2.5wt.%, li:8wt.%, zn:1.5wt.%, mn:0.9wt.%, sn:0.5wt.%, pr:0.5wt.%, nd:0.6wt.%, the balance Mg and inevitable impurities; wherein: the inevitable impurity content
0.03wt%。
The preparation method of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following steps:
s1, selecting raw materials
Weighing 3.5wt.% of Al pure Al, 1.5wt.% of Zn pure Zn, 0.5wt.% of Sn pure Sn, 8wt.% of Li-containing Mg-20wt.% of Li intermediate alloy, 0.5wt.% of Gd-containing Mg-30wt.% of Gd intermediate alloy, 2.5wt.% of Y-containing Mg-30wt.% of Y intermediate alloy, 0.9wt.% of Mn-10 wt.% of Mn intermediate alloy, 0.5wt.% of Pr-25 wt.% of Pr intermediate alloy, 0.6wt.% of Nd-containing Mg-25wt.% of Nd intermediate alloy as raw materials, grinding surface oxides by a grinding machine, maintaining metallic luster, and using for the later step;
s2, preheating raw materials
Wrapping the raw materials weighed in the step S1 with aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating at 200 ℃ for 2 hours, and reserving for the next step;
s3, charging stage
Firstly, putting the crucible and the metal copper mold preheated in the step S2 into a vacuum centrifugal casting furnace with argon protection, then putting the preheated raw materials into the furnace, and putting the raw materials into different positions of the crucible in the centrifugal casting furnace according to factors such as melting point, easy oxidation degree, density, adding amount, easy volatilization degree and the like of the raw materials; considering that Li is more active and flammable and the upper temperature is relatively low in the crucible heating process, small pure Mg blocks are placed at the bottom, then Mg-Gd, mg-Y, mg-Mn, mg-Pr and Mg-Nd intermediate alloys are placed, pure Zn and pure Al are placed, and finally the Mg-Li intermediate alloy is placed; then the cold water circulator is opened and the furnace cover is closed, and the furnace atmosphere is vacuumized to 10 DEG -3 Below Pa, then filling protective gas argon into the furnace;
s4, vacuum centrifugal smelting stage
And S3, adjusting the heating current of the centrifugal casting furnace to be 4.5A and the power to be 50%, starting to heat and melt the raw material, heating the raw material at low power (50%) until the crucible is red hot, heating the raw material at high power (99%) until the raw material is melted, starting to preserve heat, keeping the temperature at 730 ℃ for 30min, setting the centrifugal casting speed at 450 rpm, and starting to pour to obtain the magnesium-lithium alloy ingot. Monitoring the temperature change in the furnace by adopting an infrared thermometer in the whole process;
s5, heat treatment stage
Putting the magnesium-lithium alloy ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the atmosphere in the furnace to 10 DEG -3 Introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; carrying out a solid solution aging heat treatment process, wherein the solid solution temperature is as follows: the solid solution time is 5h at 340 ℃; the aging temperature is as follows: 150 ℃, and the aging time is as follows: and 3h, finally obtaining the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
The as-cast microstructure of the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is mainly
-Mg，
-Li，Al 2 RE(Nd，Gd，Y，Pr)，Mg 3 (Nd, Pr, Sn)，Al 8 Mn 5 ，AlLi，Mg 24 Y 5 ，MgZn(Gd，Y)，Li 17 Sn 4 ，MgLi 2 Al and MgLi 2 Zn, of which
The proportion of the phase is 48 percent,
the proportion of the phases is 44%; the overall performance is shown in fig. 2: the density is 1.78g/cm 3 The tensile strength was 345MPa, the yield strength was 280MPa, the elongation was 23%, and the elastic modulus was 70GPa.
Example 6
The multielement microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following elements in percentage by mass: al:2.5wt.%, gd:1wt.%, Y:1.5wt.%, li:12wt.%, zn:2wt.%, mn:0.5wt.%, sn:0.5wt.%, pr:0.9wt.%, nd:1wt.%, the balance Mg and unavoidable impurities; wherein: the inevitable impurity content
0.03wt%。
The preparation method of the multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following steps:
s1, selecting raw materials
Weighing 2.5wt.% of Al pure Al, 2.5wt.% of Zn pure Zn, 0.5wt.% of Sn pure Sn, 12wt.% of Li-containing Mg-20wt.% of Li intermediate alloy, 1wt.% of Gd-30 wt.% of Gd intermediate alloy, 1.5wt.% of Y-30 wt.% of Y intermediate alloy, 0.5wt.% of Mn-10 wt.% of Mn intermediate alloy, 0.9wt.% of Pr-20 wt.% of Pr intermediate alloy, 1wt.% of Nd-30 wt.% of Nd intermediate alloy as raw materials, grinding surface oxides by a grinding machine, maintaining metallic luster, and using for later steps;
s2, raw material preheating stage
Wrapping the raw materials weighed in the step S1 by using aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating at 150 ℃ for 2 hours for later use;
s3, charging stage
Firstly, putting the crucible and the metal copper mold preheated in the step S2 into a vacuum centrifugal casting furnace protected by argon, then putting the preheated raw materials into the furnace, and putting the raw materials into different positions of the crucible in the centrifugal casting furnace according to factors such as 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 more active and inflammable, and the upper part temperature is relatively low in the crucible heating process, small pure Mg blocks are placed at the bottom, then Mg-Gd, mg-Y, mg-Mn, mg-Pr and Mg-Nd intermediate alloys are placed, pure Zn and pure Al are placed, and finally the Mg-Li intermediate alloy is placed; then the cold water circulator is opened and the furnace cover is closed, and the furnace atmosphere is vacuumized to 10 DEG -3 Below Pa, then filling protective gas argon into the furnace;
s4, vacuum centrifugal smelting stage
And S3, adjusting the heating current of the centrifugal casting furnace to be 4A and the power to be 60%, starting to heat and melt the raw material, heating to the red heat of the crucible at low power (60%), then heating to the raw material melting at high power (100%), starting to preserve heat at 780 ℃ for 20min, setting the centrifugal casting speed to be 500 r/min, and starting to pour to obtain the magnesium-lithium alloy ingot. Monitoring the temperature change in the furnace by adopting an infrared thermometer in the whole process;
s5, heat treatment stage
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the furnace atmosphere to 10 DEG -3 Introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; carrying out a solid solution aging heat treatment process, wherein the solid solution temperature is as follows: the solid solution time is 24 hours at 400 ℃; the aging temperature is as follows: at 120 ℃, the aging time is as follows: and 5h, finally obtaining the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
The as-cast microstructure of the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is mainly
-Mg，
-Li，Al 2 RE(Nd，Gd，Y，Pr)，Mg 3 (Nd, Pr, Sn)，Al 8 Mn 5 ，AlLi，Mg 24 Y 5 ，MgZn(Gd，Y)，Li 17 Sn 4 ，MgLi 2 Al and MgLi 2 Zn, of which
The proportion of the phases is 35 percent,
the proportion of the phases is 55 percent; the comprehensive performance is shown in figure 2: the density is 1.63g/cm 3 The tensile strength was 343MPa, the yield strength was 290MPa, the elongation was 25%, and the elastic modulus was 68GPa.
In the scheme, the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy provided by the invention has specific micro metallographic structure morphology and as-cast structure crystalsGrain refinement, mg 3 Nd，Mg 5 Gd、Al 8 Mn 5 The phase is distributed in the crystal boundary, and obviously, the grains are refined and dispersed.
The invention controls the content and the proportion of the Li element and the multi-element alloying element to ensure that the Li element and the multi-element alloying element exist in the matrix at the same time
Two-phase matrix phase, BCC-
The elongation and the plasticity of the alloy are improved, and the HCP-
The phase improves the strength of the alloy. Meanwhile, under the condition of ensuring the low density of the alloy, alloying elements such as Al, zn, mn, gd Y, nd, sn, pr and the like are added, so that the effect of solid solution strengthening can be achieved, high-modulus precipitation strengthening phases can be generated in the matrix, and the phases are in the crystal boundary and BCC-
The phase formation can block dislocation movement and slippage, and the strength and plasticity of the magnesium-lithium alloy can be greatly improved by combining various modes such as solution treatment, aging heat treatment and the like, and the elastic modulus of the magnesium-lithium alloy is also greatly improved by the high-modulus second phase. The multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy and the preparation method thereof provided by the invention can obtain the high-strength high-modulus two-phase magnesium-lithium alloy by adding multi-element alloying elements under the condition of ensuring the low density of the magnesium-lithium alloy, and are suitable for meeting the industrial requirements of light weight, high strength and high toughness.
The invention can refine crystal grains, avoid the segregation of alloy components and form Al with fine dispersion distribution and high modulus by simultaneously adding rare earth elements (Gd, Y, nd and Pr) 2 Y（Gd，Pr）、MgZn 2 Gd（Y）、Mg 3 Nd、Al 3 Pr and the like to obviously improve the elastic modulus of the alloy. Simultaneously cooperate with a-Mg and b-Li matrix phase to improve magnesiumThe strength, plasticity, modulus and other mechanical properties of the lithium alloy. And rare earth elements are added, so that the texture formed in the plastic deformation process can be weakened, and a fine grain structure is formed. Moreover, the rare earth elements are added, so that impurity elements in the melt can be purified, and the corrosion resistance of the alloy is improved.
The invention can form MgLi by adding Al and Zn simultaneously 2 Al and MgLi 2 The Zn phase improves the strength of the alloy, and can also generate a stable phase and a quasicrystal phase to further improve the mechanical property and the elongation of the magnesium-lithium alloy. The addition of Mn and Sn elements can improve the yield strength of the magnesium-lithium alloy, remove harmful metal impurities, refine crystal grains and form a high-modulus strengthening phase Al together with Al 8 Mn 5 With Li to form Li 17 Sn 4 High modulus phase.
In addition, the added Al may form Al with Li 3 The high modulus phase of Li and AlLi is cooperated with the multiple alloying elements through fine grain strengthening, solid solution strengthening, dispersion strengthening, second phase strengthening and the like to obtain the multiple microalloying high-strength high-modulus two-phase magnesium-lithium alloy.
The preparation method of the multi-element microalloyed high-strength high-modulus biphase magnesium-lithium alloy provided by the invention adopts the vacuum centrifugal smelting, multi-element microalloying and heat treatment processes to form a precipitated phase with high modulus, solid solution strengthening, fine grain strengthening and other coupling modes to improve the mechanical properties of the alloy, such as strength and the like.
The properties of the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy are as follows: the density is 1.3-1.9g/cm 3 The tensile strength is 280-430MPa, the yield strength is 240-360MPa, the elongation is 15-35%, and the elastic modulus is 60-75GPa.
In a word, the method adopts a mode of combining centrifugal casting, multi-element microalloying and heat treatment, has the advantages of low price, high efficiency, advanced and simple process, high raw material yield, wide application range and the like, can ensure the low density and light weight of the magnesium-lithium alloy, obviously improves the mechanical properties of strength, elongation, elastic modulus, plasticity and the like of the multi-element microalloyed dual-phase magnesium-lithium alloy, and can meet the requirements of the fields of military affairs, medical treatment, aviation and the like on light-weight high-strength high-modulus alloy materials.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.
Claims (4)
1. The multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is characterized in that the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy comprises the following elements in percentage by mass: al:1-5wt.%, gd:0.1-2wt.%, Y:0.5-3wt.%, li:5-12wt.%, zn:0.2-3wt.%, mn:0.1-0.8wt.%, sn:0.1-1.5wt.%, pr:0.1-1.5wt.%, nd:0.1-1.5wt.%, the balance Mg and impurities;
the content of the impurities
0.03wt%；
The tissue structure of the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy is mainly
-Mg，
-Li，Al 2 RE(Nd，Gd，Y，Pr)，Mg 3 (Nd, Pr, Sn)，Al 8 Mn 5 ，AlLi，Mg 24 Y 5 ，MgZn(Gd，Y)，Li 17 Sn 4 ，MgLi 2 Al and MgLi 2 Zn；
Wherein the content of the first and second substances,
-Mg in a proportion of 30-80%,
-a Li proportion of 30-70%,
phase C
The total proportion of phases does not exceed 95%;
the method for multi-element microalloying the high-strength high-modulus two-phase magnesium-lithium alloy comprises the following steps:
s1: raw material selection
Weighing pure Mg, pure Al, pure Zn, pure Sn, mg-Li intermediate alloy, mg-Gd intermediate alloy, mg-Y intermediate alloy, mg-Mn intermediate alloy, mg-Pr intermediate alloy and Mg-Nd intermediate alloy as raw materials according to the component and the mass percentage of each element in the multi-element microalloying high-strength high-modulus two-phase magnesium-lithium alloy, and polishing surface oxides by using a grinding machine to keep the metal luster for the later use;
s2: stage of preheating raw materials
Wrapping the raw materials weighed in the step S1 with aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating, and reserving for later use;
s3: charging phase
Firstly, placing the preheated crucible and the metal copper mold in the step S2 into a vacuum centrifugal casting furnace with argon protection, then placing the preheated raw materials into different positions of the crucible in the centrifugal casting furnace, then opening a cold water circulator and covering a furnace cover, and starting to vacuumize the atmosphere in the furnace to 10 DEG C -3 Below Pa, then filling protective gas argon into the furnace;
s4: vacuum centrifugal smelting stage
After the step S3, adjusting the heating current and power of the centrifugal casting furnace, starting to heat and melt the raw material, firstly heating at low power until the crucible is red hot, then heating at high power until the raw material is melted, starting to preserve heat, then setting the centrifugal casting speed and starting to cast to obtain a magnesium-lithium alloy ingot, and monitoring the temperature change in the furnace by adopting an infrared thermometer in the whole process;
s5: stage of heat treatment
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the furnace atmosphere to 10 DEG -3 Introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; setting heat treatment temperature, and then carrying out a solid solution aging heat treatment process to finally obtain multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy;
the vacuum centrifugal smelting stage in the step S4 comprises the following steps:
s401: the heating current is 1.0-5.0A, and the heating power is 50-100%;
s402: the raw materials are heated and melted by adopting a gradient heating mode, the raw materials are firstly heated to be red hot in a crucible at low power, and the power is as follows: 50% -70%; heating to melt by adopting high power, wherein the high power is as follows: 70% -100%;
s403: the heat preservation temperature is as follows: 730-780 ℃, and the heat preservation time is as follows: 15-30min;
s404: the centrifugal casting speed is as follows: 300-500 rpm;
the heat treatment stage in step S5 includes:
s501: the solution treatment adopts two-stage solution treatment; the solid solution temperature is 300-500 ℃, and after the solid solution time is 2-48h, the steel plate is rapidly cooled and quenched by water or oil bath;
s502: the aging temperature is as follows: aging for 1-24h at 80-250 ℃ to obtain multi-microalloyed high-strength high-modulus two-phase magnesium-lithium alloy;
the properties of the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy are as follows: the density is 1.3-1.9g/cm 3 The tensile strength is 280-430MPa, the yield strength is 240-360MPa, the elongation is 15-35%, and the elastic modulus is 60-75GPa.
2. A method of making the multi-microalloyed high strength high modulus dual phase magnesium lithium alloy defined in claim 1, the method including:
s1: raw material selection
Weighing pure Mg, pure Al, pure Zn, pure Sn, mg-Li intermediate alloy, mg-Gd intermediate alloy, mg-Y intermediate alloy, mg-Mn intermediate alloy, mg-Pr intermediate alloy and Mg-Nd intermediate alloy as raw materials according to the component and the mass percentage of each element in the multi-element microalloying high-strength high-modulus two-phase magnesium-lithium alloy, and polishing surface oxides by using a grinding machine to keep the metal luster for the later use;
s2: stage of preheating the raw materials
Wrapping the raw materials weighed in the step S1 with aluminum foil, putting the wrapped raw materials, a crucible and a metal copper mold into a heat treatment furnace for preheating, and reserving for later use;
s3: charging phase
Firstly, placing the preheated crucible and the metal copper mold in the step S2 into a vacuum centrifugal casting furnace with argon protection, then placing the preheated raw materials into different positions of the crucible in the centrifugal casting furnace, then opening a cold water circulator and covering a furnace cover, and starting to vacuumize the atmosphere in the furnace to 10 DEG C -3 Below Pa, then filling protective gas argon into the furnace;
s4: vacuum centrifugal smelting stage
After the step S3, adjusting the heating current and power of the centrifugal casting furnace, starting to heat and melt the raw material, firstly heating at low power until the crucible is red hot, then heating at high power until the raw material is melted, starting to preserve heat, then setting the centrifugal casting speed and starting to cast to obtain a magnesium-lithium alloy ingot, and monitoring the temperature change in the furnace by using an infrared thermometer in the whole process;
s5: stage of heat treatment
Putting the magnesium-lithium alloy cast ingot obtained in the step S4 into a vacuum tube furnace, and then vacuumizing the furnace atmosphere to 10 DEG -3 Below Pa, introducing protective gas into the furnace until the gas pressure reaches the atmospheric pressure; setting heat treatment temperature, and then carrying out solid solution aging heat treatment process to finally obtain the multi-element microalloyed high-strength high-modulus two-phase magnesium-lithium alloy.
3. The method according to claim 2, wherein in step S1, the mass purities of pure Mg, pure Al, pure Sn and pure Zn are all 99.90-99.999%;
in the step S1, the mass contents of Li, gd, Y, mn, pr and Nd in the Mg-Li intermediate alloy, the Mg-Gd intermediate alloy, the Mg-Y intermediate alloy, the Mg-Mn intermediate alloy, the Mg-Pr intermediate alloy and the Mg-Nd intermediate alloy in the raw materials are all 10-50wt.%.
4. The method according to claim 2, wherein in step S2, the preheating temperature is 80-250 ℃ and the preheating time is 0.5-2h;
in step S2, the crucible is: graphite crucibles, BN crucibles or stainless steel crucibles.
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