CN108998700B - Ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and preparation method thereof - Google Patents

Ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and preparation method thereof Download PDF

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CN108998700B
CN108998700B CN201810854570.5A CN201810854570A CN108998700B CN 108998700 B CN108998700 B CN 108998700B CN 201810854570 A CN201810854570 A CN 201810854570A CN 108998700 B CN108998700 B CN 108998700B
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CN108998700A (en
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吴量
李险峰
陈东
周聪
马乃恒
王浩伟
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Shanghai Jiaotong University
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Abstract

The invention provides an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof, wherein the aluminum-lithium-based composite material comprises a matrix alloy and a reinforcing phase; the matrix alloy comprises the following elements in percentage by mass: 2.5-3.5% of Li, 1-2.5% of Cu, 0.4-0.5% of Mg, 0.15-0.2% of Sc, 0.15-0.2% of Zr, 0-0.2% of Cd, less than 0.2% of total impurity element content and the balance of Al; the reinforcing phase is TiB2. The preparation method comprises the following steps: preparation of TiB by in-situ autogenous reaction2a/Al base metal alloy; then TiB is added2Smelting Al base alloy, pure aluminum and intermediate alloy such as Al-Cu, Al-Li and the like to obtain a composite material, and carrying out specific solid solution and aging treatment to obtain the composite material. The composite material has higher strength and elastic modulus, lower density and lower cost.

Description

Ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and preparation method thereof
Technical Field
The invention relates to the field of metal materials and metallurgy, in particular to an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof.
Background
The rapid development in the aerospace field puts higher requirements on the specific strength, specific stiffness and damage tolerance of materials, and further, the improvement of the structural quality and the comprehensive mechanical property of aerospace products becomes a major topic in the field. One of the ideal materials is: an aluminum lithium alloy. Lithium is the lightest metal element in the nature, and the density of the lithium is only 0.53g/cm31/5 for aluminum only; lithium element is therefore also the most effective metal element for achieving weight reduction of the aluminum alloy member. Studies have shown that for every 1% wt.% lithium addition to an aluminum alloy, the alloy density is reduced by about 3% and the elastic modulus is increased by about 6%, and the sumThe gold has good hardening effect after solid solution and aging. Among them, the wrought aluminum-lithium alloy has high strength and plasticity and is widely applied to the aerospace field, however, the wrought material has inevitable short plates: the anisotropy is severe, the content of Li is low, the weight reduction effect of Li cannot be fully exerted, and due to the limitation of the shape of the part, some complex components can only be produced by adopting a casting molding method, so that the research on casting aluminum lithium alloy is gradually increased in recent years. Currently, there is less research associated with casting aluminum lithium alloys. The influence of alloy elements on the performance of cast aluminum-lithium alloy is researched by Shanghai university of traffic Chen' an waves and the like, and an Al-3Li-2Cu-0.3Mn-0.2Zr-0.2Sc alloy with excellent performance is developed, but the yield strength is only 300Mpa, and further popularization and application of cast aluminum-lithium alloy are severely restricted.
Another class of materials that have gained much attention in the aerospace field are ceramic particle reinforced aluminum matrix composites, which exhibit excellent properties such as low density, high specific strength and stiffness, high elastic modulus, good wear resistance, high thermal conductivity, and low coefficient of thermal expansion. By combining two ways of improving the material performance (adding Li element and ceramic particles), and through the complementary advantages and the enhanced advantages of the aluminum-lithium alloy and the aluminum-based composite material, the ceramic particle reinforced aluminum-lithium-based composite material is developed. However, in conventional composites, the reinforcement is often prepared prior to casting of the composite, and thus conventional composites may be referred to as ex situ composites. The size and morphology of the reinforcing phase in the ex-situ composite thus depends on the state of the original powder, which typically has a particle size on the scale of a few microns to tens of microns, with few occurrences on the nanometer scale. In addition, the major disadvantages to be overcome include interfacial reaction between the particles and the substrate, poor wettability between the particles and the substrate due to surface contamination of the added particles, and the like. There are a number of problems to be overcome in the current ex situ production methods.
Disclosure of Invention
Aiming at overcoming the defects in the prior art and solving the problems in the ex-situ production method, the aluminum lithium-based composite material used by the invention is mainly prepared by an in-situ self-generation (in situ) methodCompared with the traditional ex-situ production method, the composite material prepared by the in-situ self-generation method has the following advantages that (a) the in-situ self-generation reinforced particles have good thermodynamic stability in a matrix, and the degradation of the material in the high-temperature service process is slowed down; (b) the contact interface of the reinforcement and the matrix is clean and tidy, so that the interface combination is more stable; (c) the micro-nano scale particle reinforced aluminum matrix composite can be prepared by in-situ self-generation, the particles are distributed in the matrix more uniformly, and the obtained composite has better comprehensive performance. Second, TiB2Has the advantages of high hardness, high modulus, chemical stability and the like; the ceramic particles in the aluminum matrix composite material prepared by the in-situ self-generating method are submicron, round in shape and good in interface combination. Therefore, the nano ceramic particles are synthesized in situ in the aluminum-lithium alloy, and the mechanical properties such as the elastic modulus, the yield strength, the compressive micro-creep resistance and the like of the nano ceramic particles are expected to be greatly improved on the basis of the aluminum-lithium alloy.
The invention aims to provide an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof. By adding alloying elements (Li, Cu, Mg, Sc, Zr and Cd) and subsequent solution aging treatment, the cast aluminum-lithium-based composite material with excellent mechanical property is obtained, and the composite material has higher elastic modulus and higher strength than a matrix aluminum-lithium alloy, is simple in process operation, low in cost and suitable for batch production.
The purpose of the invention is realized by the following technical scheme:
in a first aspect, the present invention provides an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material, which comprises a matrix alloy and a reinforcing phase distributed in the matrix alloy; the matrix alloy comprises the following elements in percentage by mass based on the total weight of the aluminum-lithium based composite material: 2.5-3.5% of Li, 1-2.5% of Cu, 0.4-0.5% of Mg0.15-0.2% of Sc, 0.15-0.2% of Zr, 0-0.2% of Cd, less than 0.2% of total impurity element content and the balance of Al; the reinforcing phase is TiB2。
Preferably, the matrix alloy comprises the following elements in percentage by mass based on the total weight of the aluminum-lithium based composite material: 2.5 to 3.5 percent of Li, 1 to 2 percent of Cu, 0.4 to 0.5 percent of Mg, 0.15 to 0.2 percent of Sc, 0.15 to 0.2 percent of Zr, 0.1 to 0.2 percent of Cd, less than 0.2 percent of total content of impurity elements and the balance of Al.
Li is the metal with the lowest density in the nature, and Li is selected as the main alloy element to reduce the density and improve the rigidity of the material, and plays a role in precipitation strengthening in the aging process; cu element as main aging precipitation strengthening phase T1(Al2CuLi)、θ(Al2Cu) is used. The trace elements Sc, Zr and Cd are added, the main functions are to refine crystal grains and improve the plasticity of the material, and the Al and the grain can be added in the aging stage3Li forming Al3(Scx，Zry，Li1-x-y) The composite particles improve the mechanical property of the material. In addition, although Mn is a potential element capable of improving the plasticity of the aluminum-lithium alloy, the Al20Cu2Mn3 dispersed phase precipitated by the homogenization of the Al-Li-Cu alloy inevitably consumes the Cu element in an aluminum matrix, and reduces the precipitation of an alloy aging strengthening phase T1-Al2CuLi and theta-Al 2Cu, thereby reducing the alloy strength. In addition, when the content of the Mn element exceeds a certain value, primary hard and brittle Al20Cu2Mn3 can be formed at the boundary of the grain boundary, and the mechanical property of the alloy is seriously damaged.
Preferably, the impurity elements include one or more of Fe, Si, K, and Na.
Preferably, the TiB2The content in the aluminum lithium-based composite material is 1 to 15 wt% (relative to the aluminum lithium-based composite material). If the content is too low (less than 1 wt%), it is difficult to achieve an effective toughening effect; if the content is too high (more than 15 wt%), the plasticity of the alloy is seriously impaired and the manufacturing process is made difficult.
In a second aspect, the invention provides a preparation method of an ultralight high-modulus high-strength cast aluminum-lithium-based composite material, which comprises the following steps:
s1 preparation of TiB by in situ autogenous reaction2Al base metal alloy as raw material;
s2, weighing Al-Cu intermediate alloy, Al-Mg intermediate alloy and Al-Li master alloy, Al-Sc master alloy, Al-Zr master alloy, Al-Cd master alloy, TiB2Al base alloy and pure aluminum;
s3, mixing the TiB2Putting Al base alloy and pure aluminum into a crucible for melting, sequentially adding Al-Cu intermediate alloy, Al-Mg intermediate alloy, Al-Zr intermediate alloy, Al-Sc intermediate alloy and Al-Cd intermediate alloy under the condition of 750-760 ℃ (if the temperature is low, the intermediate alloy is insufficiently melted, and the primary phase is thick, if the temperature is too high, the burning loss is aggravated, and the subsequent smelting and casting are difficult), stirring uniformly after completely melting, and uniformly scattering a covering agent on the surface of a melt;
s4, adding the Al-Li intermediate alloy into the melt obtained after the treatment in the step S3 under the protective atmosphere, after the Al-Li intermediate alloy is completely melted, removing the surface scum, scattering a covering agent, and uniformly stirring;
and S5, refining the melt processed in the step S4, standing, and then casting into a mold to obtain a casting.
Preferably, the preparation method further comprises the step of carrying out double-stage solution treatment on the casting obtained in the step S5.
Preferably, the two-stage solution treatment comprises a first stage solution treatment and then a second stage solution treatment; wherein the first stage of solution treatment is solution treatment at 460-500 ℃ for 32 hours, and the second stage of solution treatment is solution treatment at 520-540 ℃ for 24 hours. The solid solution treatment at 460-500 ℃ for 32h is to eliminate coarse second phases (mainly Al) precipitated in the non-equilibrium solidification process2Cu and Al2CuLi), if the temperature is lower than the temperature range, the solid solution time is prolonged and a good solid solution effect cannot be obtained; if the temperature is higher than the temperature range, the material may be over-fired, which may greatly impair the performance of the material. Based on the fact that the material has high solute element content, in order to improve the supersaturation degree of the solid solution to the maximum extent, the temperature of 520-540 ℃ is selected for solid solution for 24 hours to be used as the second-stage solid solution treatment, and similarly, the temperature is lower than the temperature range, so that the high supersaturation degree cannot be obtained, and the temperature is higher than the temperature range, so that overburning can be caused.
Preferably, the preparation method further comprises the step of carrying out double-stage solution treatment on the casting obtained in the step S5 and then carrying out single-stage aging treatment.
Preferably, the single-stage aging treatment is carried out at 170-190 ℃ for 24-32 h. The aluminum-lithium based composite material is aging-strengthened, and the mechanical property of the aluminum-lithium based composite material is greatly influenced by an aging process. When the aging temperature is lower, the time for reaching the same mechanical property is much longer at higher temperature, the time and the economic cost are increased, and when the aging temperature is higher, the nano precipitated phase is not uniformly distributed and is easy to coarsen, and the plasticity of the material is damaged. And long-time aging is carried out at the temperature of 170-190 ℃, so that the time and the economic cost are increased, the occurrence of no precipitation zone in a crystal boundary is promoted, and the premature failure of the material is caused.
Preferably, in step S3, the Al-Cu master alloy contains Cu in an amount of 49 to 50 wt%, the Al-Li master alloy contains Li in an amount of 9 to 11 wt%, the Al-Mg master alloy contains Mg in an amount of 8.9 to 10.6 wt%, the Al-Zr master alloy contains Zr in an amount of 4 to 5 wt%, the Al-Sc master alloy contains Sc in an amount of 2 to 3 wt%, and the Al-Cd master alloy contains Cd in an amount of 9 to 10 wt%.
Preferably, in steps S3 and S4, the covering agent includes LiCl and LiF in a mass ratio of 3: 1. The aluminum lithium alloy adopts a mixture of LiCl and LiF as a covering agent, the covering agent is melted on the surface of the melt in the melting process, and the melted covering agent forms a layer of protective film on the surface of the melt to separate the melt from oxygen and water vapor in the air, so that the reaction of the melt with the oxygen and the water vapor is prevented.
Preferably, in step S4, the protective atmosphere is argon.
Preferably, in step S5, the refining includes not cutting off power with C2Cl6Or refining for 5-8 minutes by argon; the standing time is 3-5 minutes; the casting is carried out by preheating a steel mould to 180-200 ℃. The casting process adopts argon protection.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention effectively combines the advantages of in-situ melt autogenous preparation of the micro-nano particle reinforced aluminum-based composite material and the light high-modulus high-strength aluminum-lithium alloy. The micro-nano particle reinforced aluminum-based composite material base material is prepared by an in-situ melt autogenous method, and then the aluminum-lithium-based composite material is further prepared, so that the obtained material has the advantages of the micro-nano particle reinforced aluminum-based composite material base material and the aluminum-lithium-based composite material.
(2) The trace elements Sc, Zr and Cd are added, the main functions are to refine crystal grains and improve the plasticity of the material, and the Al and the grain can be added in the aging stage3Li forming Al3(Scx，Zry，Li1-x-y) The composite particles improve the mechanical property of the material.
(3) The components of the material are optimized, and a preferable scheme is obtained by adjusting the mass fraction of the reinforcing particles and researching the distribution ratio of various alloy elements such as Li, Cu, Mg, Sc, Zr, Cd and the like.
(4) The smelting adopts the double protection of flux and argon, and the casting process adopts the protection of argon, thereby greatly reducing the hydrogen absorption and oxidation of the material and improving the mechanical property of the material.
(5) According to the invention, the micro-nano ceramic reinforced particles are introduced into the aluminum-lithium alloy, so that the effect of refining grains can be achieved, the refining effect is more obvious than that of the traditional refiner, the fine grain strengthening effect is achieved, and the cost is reduced.
(6) The solid solution and aging behaviors of the material at different temperatures and time are systematically researched, so that a preferable solid solution treatment and aging treatment scheme is obtained, and the maximum solid solution strengthening and aging strengthening effects are obtained.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a photomicrograph of an ultra-light high-modulus high-strength cast aluminum-lithium matrix composite material of example 1; wherein, fig. 1a is a microscopic metallographic structure photograph of the lithium-based composite material, and the magnification is 200 x; FIG. 1b is a microscopic scanning electron microscope image of the aluminum lithium-based composite material; the upper right inset of fig. 1b is a microscopic topography of the ceramic reinforcing particles at the nanometer scale.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
Example 1
The embodiment relates to an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof. The preparation method specifically comprises the following steps:
firstly, TiB is prepared by in-situ autogenous molten salt reaction2The Al base material comprises the following specific steps: pure aluminum as matrix material, NaBF4And Na2TiF6As a reaction mix salt, supplemented with Na3AlF6、LiF3、LiCl3As a reaction auxiliary agent, the proportion is 2:1:1, the total amount is 10 percent of the reaction mixed salt, the reaction auxiliary agent is added at the temperature of 760 ℃, and the reaction time is 30 min; rotationally blowing argon gas for stirring, wherein the rotating speed of a rotor is 300r/min, and the flow of the argon gas is 10L/min; the pulse magnetic field intensity is controlled at 1.5T, and the high-energy ultrasonic field intensity is controlled at 200W/m2Preparing TiB2And (3) reinforcing the pure aluminum composite material in situ.
Then, the base material, pure aluminum, Al-Mg intermediate alloy and Al-Cu intermediate alloy are preheated to about 200 ℃, and then TiB is added2Putting the Al base material and pure aluminum into a molybdenum crucible for melting. And after the aluminum ingot is melted, adding Al-Cu intermediate alloy at 750-760 ℃, adding the Al-Mg intermediate alloy into the aluminum liquid after the temperature of the aluminum liquid is raised to 750-760 ℃ again, and preserving heat for 5min after the temperature is stabilized. And after the heat preservation is finished, sequentially adding an Al-Zr intermediate alloy and an Al-Sc intermediate alloy at 750-760 ℃, stirring uniformly after the Al-Zr intermediate alloy and the Al-Sc intermediate alloy are completely melted, and scattering a covering agent (3: 1: LiCl: LiF) onto the surface of the melt. And then, adding the Al-Li intermediate alloy into the melt under the argon protection environment, stirring uniformly after the Al-Li intermediate alloy is completely melted, removing the surface scum, and scattering a covering agent. After the temperature of the melt is reduced to 730-740 ℃, under the protection of argon, the temperature of the melt is reduced to C twice2Cl6Refining the melt by using a refining agent for 5-8 minutes, skimming floating slag after refining is finished, spreading a covering agent, and cooling to 710 ℃Standing at 720 deg.C for 5 min. And removing the covering agent on the surface of the melt after standing is finished, and casting the melt into a mold preheated to 200 ℃ under the protection of argon to obtain a casting.
And (3) carrying out solid solution treatment on the composite material casting, wherein the solid solution treatment process is 460 ℃/32h +520 ℃/24h, and finally carrying out water quenching to obtain the solid solution material. The chemical analysis shows that the material comprises the following components (wt%):
Li Cu Mg Sc Zr Cd Ti B Al
3.02 1.47 0.46 0.16 0.18 — 4.23 1.98 balance of
Wherein, TiB2The content in the aluminum lithium-based composite material was 6.14 wt%.
The solid solution state room temperature mechanical property, the elastic modulus and the density of the cast aluminum-lithium based composite material are as follows:
tensile strength: 332Mpa, yield strength: 191Mpa, elongation: 8 percent;
modulus of elasticity: 91.2Gpa, density: 2.59g/cm3。
The yield of Li is 87%.
FIG. 1 is a photomicrograph of an ultra-lightweight, high modulus, high strength cast aluminum lithium matrix composite material of this example, from FIG. 1a it can be seen that the Al-Cu-Li-x alloy matrix α -Al dendrite is substantially spheroidized, and further, a portion of the TiB which is repelled to the dendritic gaps by the solidification front is2The particles can block the growth of matrix grains, so that the matrix structure can be refined to a certain degree, and the average grain size is about 45 mu m. Fig. 1b shows the spatial distribution and typical morphology of the enhanced particles, with most of the particles concentrated at the grain boundaries, the particle sizes varying from a few nanometers to hundreds of nanometers, and the shapes mostly being tetragonal and equiaxed hexagons.
Example 2
The embodiment relates to an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof. The preparation method specifically comprises the following steps:
firstly, TiB is prepared by in-situ autogenous molten salt reaction2Al base material, preheating base material, pure aluminum, Al-Mg intermediate alloy and Al-Cu intermediate alloy to about 200 ℃, and then TiB2Putting the Al base material and pure aluminum into a molybdenum crucible for melting. And after the aluminum ingot is melted, adding Al-Cu intermediate alloy at 750-760 ℃, adding the Al-Mg intermediate alloy into the aluminum liquid after the temperature of the aluminum liquid is raised to 750-760 ℃ again, and preserving heat for 5min after the temperature is stabilized. And after the heat preservation is finished, sequentially adding Al-Zr, Al-Sc and Al-Cd intermediate alloys at the temperature of 750-760 ℃, stirring uniformly after the intermediate alloys are completely melted, and scattering a covering agent (3: 1: LiCl: LiF) onto the surface of the melt. Then, adding Al-Li intermediate alloy into the melt under the argon protection environment, and stirring the mixture after the Al-Li intermediate alloy is completely meltedHomogenizing, removing floating slag on the surface, and spreading covering agent. After the temperature of the melt is reduced to 730-740 ℃, under the protection of argon, the temperature of the melt is reduced to C twice2Cl6Refining the melt by using a refining agent for 5-8 minutes, removing floating slag after refining is finished, scattering a covering agent, cooling to 710-720 ℃, and standing for 5 minutes. And removing the covering agent on the surface of the melt after standing is finished, and casting the melt into a mold preheated to 200 ℃ under the protection of argon to obtain a casting.
And (3) carrying out solid solution treatment on the composite material casting, wherein the solid solution treatment process is 480 ℃/32h +535 ℃/24h, and finally carrying out water quenching to obtain the solid solution material. The chemical analysis shows that the material comprises the following components (wt%):
Li Cu Mg Sc Zr Cd Ti B Al
3.08 1.54 0.46 0.17 0.17 0.19 4.34 2.01 balance of
Wherein, TiB2The content in the aluminum lithium-based composite material was 6.3 wt%.
The solid solution state room temperature mechanical property, the elastic modulus and the density of the cast aluminum-lithium based composite material are as follows:
tensile strength: 357Mpa, yield strength: 235Mpa, elongation: 7.2 percent;
modulus of elasticity: 90.8Gpa, density: 2.63g/cm3。
The yield of Li is 83%.
Example 3
The embodiment relates to an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof. The preparation method specifically comprises the following steps:
firstly, TiB is prepared by in-situ autogenous molten salt reaction2Al base material, preheating base material, pure aluminum, Al-Mg intermediate alloy and Al-Cu intermediate alloy to about 200 ℃, and then TiB2Putting the Al base material and pure aluminum into a molybdenum crucible for melting. And after the aluminum ingot is melted, adding Al-Cu intermediate alloy at 750-760 ℃, adding the Al-Mg intermediate alloy into the aluminum liquid after the temperature of the aluminum liquid is raised to 750-760 ℃ again, and preserving heat for 5min after the temperature is stabilized. And after the heat preservation is finished, sequentially adding Al-Zr, Al-Sc and Al-Cd intermediate alloys at the temperature of 750-760 ℃, stirring uniformly after the intermediate alloys are completely melted, and scattering a covering agent (3: 1: LiCl: LiF) onto the surface of the melt. And then, adding the Al-Li intermediate alloy into the melt under the argon protection environment, stirring uniformly after the Al-Li intermediate alloy is completely melted, removing the surface scum, and scattering a covering agent. After the temperature of the melt is reduced to 730-740 ℃, under the protection of argon, the temperature of the melt is reduced to C twice2Cl6Refining the melt by using a refining agent for 5-8 minutes, removing floating slag after refining is finished, scattering a covering agent, cooling to 710-720 ℃, and standing for 5 minutes. Removing the covering agent on the surface of the melt after the standing is finished,the melt was cast into a mold preheated to 200 ℃ under argon.
The solid solution treatment process of the composite material is 460 ℃/32h +520 ℃/24h, and the composite material is aged for 30h at 175 ℃ after water quenching. The chemical analysis shows that the material comprises the following components (wt%):
Li Cu Mg Sc Zr Cd Ti B Al
2.97 1.46 0.44 0.16 0.19 0.20 4.12 1.96 balance of
Wherein, TiB2The content in the aluminum lithium-based composite material was 5.98 wt%.
The solid solution state room temperature mechanical property, the elastic modulus and the density of the cast aluminum-lithium based composite material are as follows:
tensile strength: 430Mpa, yield strength: 345Mpa, elongation: 2.1 percent;
modulus of elasticity: 91.4Gpa, density: 2.61g/cm3。
The yield of Li is 88%.
Example 4
The embodiment relates to an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof. The preparation method specifically comprises the following steps:
firstly, TiB is prepared by in-situ autogenous molten salt reaction2Al base material, preheating base material, pure aluminum, Al-Mg intermediate alloy and Al-Cu intermediate alloy to about 200 ℃, and then TiB2Putting the Al base material and pure aluminum into a molybdenum crucible for melting. And after the aluminum ingot is melted, adding Al-Cu intermediate alloy at 750-760 ℃, adding the Al-Mg intermediate alloy into the aluminum liquid after the temperature of the aluminum liquid is raised to 750-760 ℃ again, and preserving heat for 5min after the temperature is stabilized. And after the heat preservation is finished, sequentially adding Al-Zr, Al-Sc and Al-Cd intermediate alloys at the temperature of 750-760 ℃, stirring uniformly after the intermediate alloys are completely melted, and scattering a covering agent (3: 1: LiCl: LiF) onto the surface of the melt. And then, adding the Al-Li intermediate alloy into the melt under the argon protection environment, stirring uniformly after the Al-Li intermediate alloy is completely melted, removing the surface scum, and scattering a covering agent. After the temperature of the melt is reduced to 730-740 ℃, under the protection of argon, the temperature of the melt is reduced to C twice2Cl6Refining the melt by using a refining agent for 5-8 minutes, removing floating slag after refining is finished, scattering a covering agent, cooling to 710-720 ℃, and standing for 5 minutes. And removing the covering agent on the surface of the melt after standing is finished, and casting the melt into a die preheated to 200 ℃ under the protection of argon.
The solid solution treatment process of the composite material is 460 ℃/32h +520 ℃/24h, and the composite material is aged for 32h at 175 ℃ after water quenching. The chemical analysis shows that the material comprises the following components (wt%):
Li Cu Mg Sc Zr Cd Ti B Al
3.01 1.55 0.48 0.18 0.15 0.18 4.21 1.97 balance of
Wherein, TiB2The content in the aluminum lithium-based composite material was 6.11 wt%.
The solid solution state room temperature mechanical property, the elastic modulus and the density of the cast aluminum-lithium based composite material are as follows:
tensile strength: 439Mpa, yield strength: 372Mpa, elongation: 1.2 percent;
modulus of elasticity: 90.9Gpa, density: 2.60g/cm3。
The yield of Li is 86%.
Example 5
The embodiment relates to an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof. The preparation method specifically comprises the following steps:
firstly, TiB is prepared by in-situ autogenous molten salt reaction2Al base material, preheating base material, pure aluminum, Al-Mg intermediate alloy and Al-Cu intermediate alloy to about 200 ℃, and then TiB2Putting the Al base material and pure aluminum into a molybdenum crucible for melting. And after the aluminum ingot is melted, adding Al-Cu intermediate alloy at 750-760 ℃, adding the Al-Mg intermediate alloy into the aluminum liquid after the temperature of the aluminum liquid is raised to 750-760 ℃ again, and preserving heat for 5min after the temperature is stabilized. And after the heat preservation is finished, sequentially adding Al-Zr, Al-Sc and Al-Cd intermediate alloys at the temperature of 750-760 ℃, stirring uniformly after the intermediate alloys are completely melted, and scattering a covering agent (3: 1: LiCl: LiF) onto the surface of the melt. And then, adding the Al-Li intermediate alloy into the melt under the argon protection environment, stirring uniformly after the Al-Li intermediate alloy is completely melted, removing the surface scum, and scattering a covering agent. After the temperature of the melt is reduced to 730-740 ℃, under the protection of argon, the temperature of the melt is reduced to C twice2Cl6Refining the melt by using a refining agent for 5-8 minutes, removing floating slag after refining is finished, scattering a covering agent, cooling to 710-720 ℃, and standing for 5 minutes. And removing the covering agent on the surface of the melt after standing is finished, and casting the melt into a die preheated to 200 ℃ under the protection of argon.
The solid solution treatment process of the composite material is 460 ℃/32h +520 ℃/24h, and the composite material is aged for 32h at 175 ℃ after water quenching. The chemical analysis shows that the material comprises the following components (wt%):
Li Cu Mg Sc Zr Cd Ti B Al
2.56 2.49 0.46 0.15 0.18 0.19 4.27 1.93 balance of
Wherein, TiB2The content in the aluminum lithium-based composite material was 6.2 wt%.
The solid solution state room temperature mechanical property, the elastic modulus and the density of the cast aluminum-lithium based composite material are as follows:
tensile strength: 447MPa, yield strength: 388Mpa, elongation: 2.1 percent;
modulus of elasticity: 90.2Gpa, density: 2.66g/cm3。
Example 6
The embodiment relates to an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof. The preparation method is substantially identical to example 5, except that: the casting is subjected to solution treatment at 500 ℃/32h +540 ℃/24h, and is aged for 24h at 190 ℃ after water quenching.
The solid solution state room temperature mechanical property, the elastic modulus and the density of the cast aluminum-lithium based composite material are as follows:
tensile strength: 426Mpa, yield strength: 394MPa, elongation: 1.1 percent;
modulus of elasticity: 90.2Gpa, density: 2.66g/cm3。
Example 7
The embodiment relates to an ultra-light high-modulus high-strength cast aluminum-lithium-based composite material and a preparation method thereof. The preparation method is substantially identical to example 5, except that: the casting is subjected to solution treatment at 480 ℃/32h +530 ℃/24h, and is aged for 28h at 180 ℃ after water quenching.
The solid solution state room temperature mechanical property, the elastic modulus and the density of the cast aluminum-lithium based composite material are as follows:
tensile strength: 445Mpa, yield strength: 379Mpa, elongation: 1.6 percent;
modulus of elasticity: 90.2Gpa, density: 2.66g/cm3。
Comparative example 1
The present comparative example provides a cast aluminum lithium based composite material and a method of making the same. The preparation method is substantially identical to example 3, except that: in the present comparative example, the Sc content in the composition of the aluminum lithium-based composite material was 0.1%.
Comparative example 2
The present comparative example provides a cast aluminum lithium based composite material and a method of making the same. The preparation method is substantially identical to example 3, except that: in the present comparative example, the Zr content in the composition of the aluminum lithium-based composite material was 0.13%.
Comparative example 3
The present comparative example provides a cast aluminum lithium based composite material and a method of making the same. The preparation method is substantially identical to example 3, except that: in the present comparative example, the content of Cd in the composition of the aluminum lithium-based composite material was 0.22%.
Comparative example 4
The present comparative example provides a cast aluminum lithium based composite material and a method of making the same. The preparation method is substantially identical to example 3, except that: in this comparative example, the casting was not subjected to solution treatment and aging treatment.
Comparative example 5
The present comparative example provides a cast aluminum lithium based composite material and a method of making the same. The preparation method is substantially identical to example 3, except that: in this comparative example, the casting was subjected to aging treatment without being subjected to solid solution treatment.
Comparative example 6
The present comparative example provides a cast aluminum lithium based composite material and a method of making the same. The preparation method is substantially identical to example 3, except that: in this comparative example, the solution treatment process was 460 ℃/32h, followed by aging.
Results of Performance testing
TABLE 1 results of the Performance test of comparative examples 1 to 6
Figure BDA0001748239810000101
Figure BDA0001748239810000111
From the results in table 1 above, it can be seen from comparison of comparative example 1 and example 3 that when the content of the trace element Sc in the aluminum lithium-based composite material is too low, a severe decrease in tensile strength and plasticity is caused; comparing comparative example 2 and example 3, it is known that when the content of the trace element Zr in the aluminum lithium-based composite material is too low, a decrease in strength and plasticity is caused; comparing comparative example 3 with example 3, it is known that when the content of the trace element Cd in the aluminum lithium-based composite material is excessively high, a decrease in strength is caused; comparing comparative example 4 and example 3, it is known that when the aluminum lithium-based composite material is not subjected to the solution treatment and the aging treatment, severe insufficiency of strength and plasticity is caused; comparing comparative example 5 with example 3, it is known that when the aluminum lithium-based composite material is subjected to aging treatment without being subjected to solution treatment, severe insufficiency of strength and plasticity is caused; comparing comparative example 6 and example 3, it is known that when the aluminum lithium-based composite material is subjected to only one-stage solution treatment, the improvement of strength and plasticity is low.
In addition, although the aluminum lithium-based composite material prepared in the embodiment 1-2 is subjected to the solution treatment only and is not subjected to the aging treatment, the comprehensive performance of the aluminum lithium-based composite material prepared in the embodiment 1-2 is obviously better than that of the comparative examples 4-6. Meanwhile, the comprehensive performance of the aluminum lithium-based composite materials prepared in examples 3 to 7 is obviously superior to that of comparative examples 1 to 6.
The composite material prepared by the invention is composed of nano TiB2The ceramic material consists of ceramic particles, Li, Cu, Mg, Sc, Zr, Cd, impurity elements and the balance of Al, wherein the mass percentages of the impurity elements are Li, Cu, Mg, Sc, Zr and Cd, and the balance of Al. It is characterized in that firstly, in-situ self-generated reaction is utilized to prepare TiB2a/Al base metal alloy; and then smelting Al-Cu, Al-Li, Al-Mg, Al-Sc, Al-Zr, Al-Cd intermediate alloy, TiB2/Al base metal and pure aluminum to obtain a composite material, and performing specific two-stage solution treatment, water quenching treatment and single-stage aging treatment to obtain the ultra-light high-modulus high-strength cast aluminum-lithium-based composite material. Compared with the traditional aluminum-lithium alloy and composite material, the nano-particle aluminum-lithium-based composite material prepared by the invention has higher strength and elastic modulus, lower density and low cost, and has huge application prospect in the aerospace field.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (6)

1. The preparation method of the ultra-light high-modulus high-strength cast aluminum-lithium-based composite material is characterized in that the aluminum-lithium-based composite material comprises a matrix alloy and a reinforcing phase distributed in the matrix alloy; the matrix alloy comprises the following elements in percentage by mass based on the total weight of the aluminum-lithium based composite material: li 2.5-3.5%, Cu 1-2.5%, Mg0.4-0.5%, Sc 0.15-0.2%, Zr 0.15 ∞0.2 percent of Cd 0-0.2 percent, less than 0.2 percent of total content of impurity elements and the balance of Al; the reinforcing phase is TiB2Said TiB2The content of the aluminum-lithium-based composite material is 1-15 wt%, and the impurity elements comprise one or more of Fe, Si, K and Na;
the preparation method of the aluminum lithium-based composite material comprises the following steps:
s1 preparation of TiB by in situ autogenous reaction2Al base metal alloy as raw material;
s2, weighing Al-Cu intermediate alloy, Al-Mg intermediate alloy, Al-Li intermediate alloy, Al-Sc intermediate alloy, Al-Zr intermediate alloy, Al-Cd intermediate alloy and TiB according to the proportion2Al base alloy and pure aluminum;
s3, mixing the TiB2Melting Al base metal alloy and pure aluminum in a crucible, sequentially adding Al-Cu intermediate alloy, Al-Mg intermediate alloy, Al-Zr intermediate alloy, Al-Sc intermediate alloy and Al-Cd intermediate alloy at the temperature of 750-760 ℃, stirring uniformly after completely melting, and uniformly scattering a covering agent on the surface of the melt;
s4, adding the Al-Li intermediate alloy into the melt obtained after the treatment in the step S3 under the protective atmosphere, after the Al-Li intermediate alloy is completely melted, removing the surface scum, scattering a covering agent, and uniformly stirring;
s5, refining and standing the melt obtained after the treatment in the step S4, casting the melt into a mold to obtain a casting, and carrying out double-stage solution treatment on the obtained casting, wherein the double-stage solution treatment comprises first-stage solution treatment and then second-stage solution treatment; wherein the first stage of solution treatment is solution treatment at 460-500 ℃ for 32 hours, and the second stage of solution treatment is solution treatment at 520-540 ℃ for 24 hours.
2. The method for preparing the ultra-light weight high-modulus high-strength cast aluminum-lithium-based composite material as claimed in claim 1, wherein the method further comprises a step of performing two-stage solution treatment on the casting obtained in the step S5 and then performing single-stage aging treatment.
3. The preparation method of the ultra-light high-modulus high-strength cast aluminum-lithium-based composite material as claimed in claim 2, wherein the single-stage aging treatment is carried out at 170-190 ℃ for 24-32 h.
4. The method for preparing the ultra-light weight, high modulus and high strength cast aluminum-lithium based composite material according to claim 1, wherein in step S3, the Al-Cu master alloy contains 49-50 wt% of Cu, the Al-Li master alloy contains 9-11 wt% of Li, the Al-Mg master alloy contains 8.9-10.6 wt% of Mg, the Al-Zr master alloy contains 4-5 wt% of Zr, the Al-Sc master alloy contains 2-3 wt% of Sc, and the Al-Cd master alloy contains 9-10 wt% of Cd.
5. The method of preparing an ultra-light weight, high modulus, high strength cast aluminum lithium matrix composite as claimed in claim 1, wherein the covering agent comprises LiCl and LiF in a mass ratio of 3:1 in steps S3 and S4.
6. The method of claim 1, wherein the refining step S5 includes uninterrupted use of C2Cl6Or refining for 5-8 minutes by argon; the standing time is 3-5 minutes; the casting is carried out by preheating a steel mould to 180-200 ℃.
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