A high-rare-earth heat-resistant magnesium-lithium alloy based on plastic deformation and a preparation method thereof

Abstract

The application discloses a high-rare-earth heat-resistant magnesium-lithium alloy based on plastic deformation and a preparation method thereof, relates to the technical field of magnesium-lithium alloy preparation, and the magnesium-lithium alloy comprises the following components in percentage by mass: Li 2-11%, Al 3-10%, Y 2-10%, Gd 5-15% and Sc 0-3%, and the balance is Mg. The application further provides a preparation method of the magnesium-lithium alloy. In the application, high-content rare-earth elements consume Al elements in the solidification process, thereby reducing the precipitation of adverse AlLi phases and improving the thermal stability of the magnesium-lithium alloy; meanwhile, plastic deformation is performed on the high-rare-earth heat-resistant magnesium-lithium alloy through a plastic deformation process, so that the best mechanical properties are obtained.

Description

Technical Field

[0001] This invention relates to the field of magnesium-lithium alloy preparation technology, specifically to a high rare-earth heat-resistant magnesium-lithium alloy based on plastic deformation and its preparation method. Background Technology

[0002] Magnesium-lithium alloys are the lightest metallic structural materials, with a density of approximately 1.3 g / cm³. 3 -1.65g / cm 3 Magnesium-lithium alloys are 1 / 4 to 1 / 3 lighter than ordinary magnesium alloys and 1 / 3 to 1 / 2 lighter than aluminum alloys. Furthermore, they possess excellent thermal conductivity, damping and shock absorption properties, and electromagnetic shielding performance, making them highly promising for applications in aerospace, military, automotive, 3C industries, and medical devices. However, magnesium-lithium alloys exhibit high chemical reactivity, relatively low absolute strength, poor corrosion resistance and oxidation resistance, and are prone to over-aging and metastable strengthening phase decomposition into softening phases at slightly higher temperatures (50-70℃), leading to excessive creep under relatively small external forces. Alloying and plastic deformation are currently the most commonly used strengthening methods. Reported literature indicates that magnesium-lithium alloys generally have low strength. Researchers generally believe that rare earth elements can form Al-RE phases with Al, inhibiting the formation of AlLi softening phases. Although the softening inhibition gradually increases with increasing rare earth element content, a large amount of Al-RE phase will deteriorate the plastic processing performance of magnesium-lithium alloys. Therefore, the rare earth element content in magnesium-lithium alloys generally does not exceed 10 wt.%. For example, patent CN 115161526A provides a magnesium-lithium alloy composition with a tensile strength of 260 MPa, in which the rare earth element Ce content is 0.5 wt.%-1 wt.%; patent CN 110343923A provides a magnesium-lithium alloy composition with a tensile strength of 180-300 MPa, in which the mass fraction of alloying elements is less than 7 wt.%, of which the rare earth element Ce content is 0-1.5 wt.% and the La content is 0-3 wt.%; patent CN 115584419A proposes a heat-resistant dual-phase magnesium-lithium alloy in which the rare earth element content is 0.3-0.8 wt.%; and patent CN 115652156A provides a novel Mg-Gd-Li-Y-Al alloy in which the rare earth element Gd content is 3-6 wt.% and the Y content is 0.5-1.5 wt.%. Since the concept of high-entropy alloys was proposed in 2004, the compositional space of alloys has become increasingly extensive. With the exploration of unknown space, many new high-performance alloys have been developed, but their components are mainly transition elements. Inspired by the design concept of high-entropy alloys, this invention proposes a new type of heat-resistant magnesium-lithium alloy, namely a magnesium-lithium alloy with a rare earth content higher than 10 wt.%. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a high rare-earth heat-resistant magnesium-lithium alloy based on plastic deformation and its preparation method. By consuming Al elements during solidification with a high content of rare-earth elements, the precipitation of unfavorable AlLi phases is reduced, thereby improving the thermal stability of the magnesium-lithium alloy. Simultaneously, the high rare-earth heat-resistant magnesium-lithium alloy is plastically deformed through a plastic deformation process to obtain optimal mechanical properties.

[0004] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation is provided, comprising the following components by mass percentage: Li 2-11%, Al 3-10%, Y 2-10%, Gd 5-15% and Sc 0-3%, with the balance being Mg.

[0005] Furthermore, the high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation comprises the following components by mass percentage: Li 9.3%, Al 3.6%, Y 5.2%, Gd 11% and Sc 2.6%, with the balance being Mg.

[0006] Furthermore, the as-cast microstructure of the high rare earth heat-resistant magnesium-lithium alloy includes a magnesium-lithium matrix phase and an Al-RE phase.

[0007] Furthermore, the magnesium-lithium matrix phases are α-Mg phase, α+β phase and β-Li phase.

[0008] Furthermore, the rare earth element content in the high rare earth heat-resistant magnesium-lithium alloy is higher than 10%.

[0009] This invention also provides a method for preparing the above-mentioned high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation, comprising the following steps:

[0010] Magnesium-lithium alloy ingots were obtained by melting elemental Mg, elemental Li, elemental Al, Mg-Y master alloy, Mg-Gd master alloy, and Mg-Sc master alloy, and then plastically deformed to obtain high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation.

[0011] Furthermore, in a mixed atmosphere of carbon dioxide and sulfur tetrafluoride, elemental Mg, elemental Al, Mg-Y master alloy, Mg-Gd master alloy, and Mg-Sc master alloy are heated and melted at 800°C, then cooled to 700°C, elemental Li is added after being wrapped in aluminum foil, mechanically stirred for 4-6 minutes, then heated to 740°C, a refining agent is added, mechanically stirred for 4-6 minutes, and finally heated to 800°C and held for 10 minutes before casting to obtain a magnesium-lithium alloy ingot.

[0012] Furthermore, the carbon dioxide content in the mixed atmosphere is 99%.

[0013] Furthermore, plastic deformation can be achieved through rolling, extrusion, or equal-diameter angular extrusion.

[0014] Furthermore, during rolling, the temperature is 25-300℃, the reduction per pass is 0.5-1mm, and the total reduction is 20-80%.

[0015] Furthermore, during extrusion, the material is preheated and held at 100-350℃ for 10-30 minutes, and then extruded at 100-350℃ followed by water cooling.

[0016] Furthermore, during equal diameter angular extrusion, the BC path is used for deformation, the deformation temperature is 100-300℃, and the number of deformation passes is 1-8.

[0017] Furthermore, preheat and maintain the temperature at 100-350℃ for 5-10 minutes.

[0018] Furthermore, the material is immediately placed in water to cool after each deformation process.

[0019] The present invention has the following beneficial effects:

[0020] 1. This invention utilizes the content and ratio of various elements in an alloy to obtain a high-strength and ductile magnesium-lithium alloy; the amount of Li added involves synergistic combination with other alloying elements. The designed content of Li balances the increase in mass brought about by high-density rare earth elements, maintaining the lightweight characteristics of the alloy; the addition of rare earth elements generates an Al-RE second phase, achieving the effects of refining grain size, improving the thermal stability of the alloy, and ensuring the high strength of the alloy.

[0021] 2. The high content of rare earth elements and Al have a more negative mixing enthalpy, which means that the inter-element bonding force is strong. During the solidification process, a large amount of Al elements are consumed first, reducing the precipitation of unfavorable AlLi phase. The generated Al-RE phase helps to refine the grains and improve the thermal stability of the alloy.

[0022] 3. The magnesium-lithium matrix and Al-RE phase particles form a simple composite structure similar to "particle reinforcement." The matrix provides plasticity, while the Al-RE second phase acts as a reinforcing agent, balancing the alloy's strength and plasticity. The combination of lightweight Li elements and high-density rare earth elements leverages the excellent strengthening effect of rare earth elements while ensuring the alloy's low density.

[0023] 4. Through plastic deformation, it achieves strengthening and toughening effects such as grain refinement and precipitation strengthening, significantly improving the mechanical properties of the alloy; the alloy density reaches 1.5-1.7 g / cm³. 3 After plastic deformation, the tensile strength is 240-350MPa and the elongation is 5-50%. Attached Figure Description

[0024] Figure 1 The microstructure of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 1 is shown.

[0025] Figure 2The mechanical property test results of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 1 are shown below.

[0026] Figure 3 The microstructure of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 2 is shown.

[0027] Figure 4 The mechanical property test results of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 2 are shown below.

[0028] Figure 5 The microstructure of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 3 is shown.

[0029] Figure 6 The mechanical property test results of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 3 are shown below.

[0030] Figure 7 The mechanical property test results of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 4 are shown below.

[0031] Figure 8 The mechanical properties test results of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 5 are shown. Detailed Implementation

[0032] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0033] Example 1

[0034] A high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation comprises the following components by mass percentage: Li 2.3%, Al 8%, Y 6%, Gd 11%, with the balance being Mg.

[0035] The above-mentioned method for preparing high rare earth heat-resistant magnesium-lithium alloys based on plastic deformation includes the following steps:

[0036] (1) In a mixed atmosphere of carbon dioxide (99%) and sulfur tetrafluoride, elemental Mg, elemental Al, Mg-Y30, and Mg-Gd30 master alloy were heated and melted at 800°C, then cooled to 700°C, elemental Li was wrapped in aluminum foil and added, mechanically stirred for 5 min, then heated to 740°C, a refining agent was added, mechanically stirred for 5 min, and finally heated to 800°C and held for 10 min, and cast to obtain a cylindrical magnesium-lithium alloy ingot with a diameter of 60 mm.

[0037] (2) The ingot was wire-cut into a cylindrical shape according to the extrusion die size. The die was kept at 300℃ for 2 hours and the sample was kept at 300℃ for 10 minutes. Then, extrusion was carried out with an extrusion ratio of 11:1. After extrusion, the sample was immediately placed in water to cool, and the high rare earth heat-resistant magnesium-lithium alloy Mg-2.3Li-8Al-11Gd-6Y based on plastic deformation was obtained.

[0038] The microstructure of the obtained high rare earth heat-resistant magnesium-lithium alloy Mg-2.3Li-8Al-11Gd-6Y based on plastic deformation is as follows: Figure 1 As shown; referring to GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature", the mechanical properties of the alloy in different states were tested, and the results are as follows. Figure 2 As shown. Among them, Figure 2 The upper middle section is in a compressed state.

[0039] Depend on Figure 1-2 It can be seen that the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 1 has a tensile strength of 208 MPa and an elongation of 17.5%; the tensile strength in the extruded state is 269 MPa and the elongation is 18.8%.

[0040] Example 2

[0041] A high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation comprises the following components by mass percentage: Li 4.6%, Al 8%, Y 6%, Gd 11%, with the balance being Mg.

[0042] The above-mentioned method for preparing high rare earth heat-resistant magnesium-lithium alloys based on plastic deformation includes the following steps:

[0043] (1) In a mixed atmosphere of carbon dioxide (99%) and sulfur tetrafluoride, elemental Mg, elemental Al, Mg-Y30, and Mg-Gd30 master alloy were heated and melted at 800°C, then cooled to 700°C, elemental Li was wrapped in aluminum foil and added, mechanically stirred for 5 min, then heated to 740°C, a refining agent was added, mechanically stirred for 5 min, and finally heated to 800°C and held for 10 min, and cast to obtain a cylindrical magnesium-lithium alloy ingot with a diameter of 60 mm.

[0044] (2) The ingot was wire-cut into a cylindrical shape according to the extrusion die size. The die was kept at 300℃ for 2 hours and the sample was kept at 300℃ for 10 minutes. Then, extrusion was carried out with an extrusion ratio of 11:1. After extrusion, the sample was immediately placed in water to cool, and the high rare earth heat-resistant magnesium-lithium alloy Mg-4.6Li-8Al-11Gd-6Y based on plastic deformation was obtained.

[0045] The microstructure of the obtained high rare earth heat-resistant magnesium-lithium alloy Mg-4.6Li-8Al-11Gd-6Y based on plastic deformation is as follows: Figure 3As shown; referring to GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature", the mechanical properties of the alloy in different states were tested, and the results are as follows. Figure 4 As shown. Among them, Figure 4 The upper middle section is in a compressed state.

[0046] Depend on Figure 3-4 It can be seen that the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 2 has a tensile strength of 217 MPa and an elongation of 13.6%; the tensile strength in the extruded state is 284 MPa and the elongation is 15.8%.

[0047] Example 3

[0048] A high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation comprises the following components by mass percentage: Li 9.3%, Al 3.6%, Y 5.2%, Gd 11% and Sc 2.6%, with the balance being Mg.

[0049] The above-mentioned method for preparing high rare earth heat-resistant magnesium-lithium alloys based on plastic deformation includes the following steps:

[0050] (1) In a mixed atmosphere of carbon dioxide (99%) and sulfur tetrafluoride, elemental Mg, elemental Al, Mg-Y30, Mg-Gd30 and Mg-Sc30 master alloys were heated and melted at 800℃, then cooled to 700℃, elemental Li was wrapped in aluminum foil and added, mechanically stirred for 5 min, then heated to 740℃, added refining agent, mechanically stirred for 5 min, and finally heated to 800℃ and held for 10 min, and cast to obtain a cylindrical magnesium-lithium alloy ingot with a diameter of 60 mm.

[0051] (2) The ingot was wire-cut into a cylindrical shape according to the extrusion die size. The die was kept at 300℃ for 2 hours and the sample was kept at 300℃ for 10 minutes. Then, extrusion was carried out with an extrusion ratio of 11:1. After extrusion, the sample was immediately placed in water to cool, and a high rare earth heat-resistant magnesium-lithium alloy Mg-9.3Li-3.6Al-2.6Sc-11Gd-5.2Y based on plastic deformation was obtained.

[0052] The microstructure morphology of the obtained high rare-earth heat-resistant magnesium-lithium alloy Mg-9.3Li-3.6Al-2.6Sc-11Gd-5.2Y based on plastic deformation is as follows: Figure 5 As shown; referring to GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature", the mechanical properties of the alloy in different states were tested, and the results are as follows. Figure 6 As shown. Among them, Figure 6 The upper middle section is in a compressed state.

[0053] Depend on Figure 5-6It can be seen that the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 3 has a tensile strength of 107 MPa and an elongation of 32%; the tensile strength in the extruded state is 242 MPa and the elongation is 28%.

[0054] Example 4

[0055] A high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation comprises the following components by mass percentage: Li 4.6%, Al 8%, Y 6%, Gd 11%, with the balance being Mg.

[0056] The above-mentioned method for preparing high rare earth heat-resistant magnesium-lithium alloys based on plastic deformation includes the following steps:

[0057] (1) In a mixed atmosphere of carbon dioxide (99%) and sulfur tetrafluoride, elemental Mg, elemental Al, Mg-Y30, and Mg-Gd30 master alloy were heated and melted at 800°C, then cooled to 700°C, elemental Li was wrapped in aluminum foil and added, mechanically stirred for 5 min, then heated to 740°C, a refining agent was added, mechanically stirred for 5 min, and finally heated to 800°C and held for 10 min, and cast to obtain a cylindrical magnesium-lithium alloy ingot with a diameter of 60 mm.

[0058] (2) The ingot was wire-cut into blocks of 6mm×10mm×10mm. The sample was kept in a muffle furnace at 300℃ for 1h without heating the rolls. After the heat preservation, it was rolled with a reduction of 1mm per pass. After rolling, the sample was placed in a muffle furnace at 300℃ for 5min and rolled again to obtain a high rare earth heat-resistant magnesium-lithium alloy Mg-4.6Li-8Al-6Y-11Gd based on plastic deformation.

[0059] Referring to GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature", the mechanical properties of alloys rolled from 6 mm to 3 mm thickness were tested with a total strain of 50%. The results are as follows: Figure 7 As shown.

[0060] Depend on Figure 7 It can be seen that the as-cast high rare earth heat-resistant magnesium-lithium alloy obtained in Example 4 has a tensile strength of 305 MPa and an elongation of 8%.

[0061] Example 5

[0062] A high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation comprises the following components by mass percentage: Li 4.6%, Al 8%, Y 6%, Gd 11%, with the balance being Mg.

[0063] The above-mentioned method for preparing high rare earth heat-resistant magnesium-lithium alloys based on plastic deformation includes the following steps:

[0064] (1) In a mixed atmosphere of carbon dioxide (99%) and sulfur tetrafluoride, elemental Mg, elemental Al, Mg-Y30, and Mg-Gd30 master alloy were heated and melted at 800°C, then cooled to 700°C, elemental Li was wrapped in aluminum foil and added, mechanically stirred for 5 min, then heated to 740°C, a refining agent was added, mechanically stirred for 5 min, and finally heated to 800°C and held for 10 min, and cast to obtain a cylindrical magnesium-lithium alloy ingot with a diameter of 60 mm.

[0065] (2) Equal diameter angular extrusion: The ingot is wire-cut into a round bar with a diameter of 11mm according to the size of the equal channel corner mold. The mold is kept at 300℃ for 2h. The sample is subjected to equal diameter angular extrusion without heating. After deformation, the sample is placed in water to cool, and a high rare earth heat-resistant magnesium-lithium alloy Mg-4.6Li-8Al-6Y-11Gd based on plastic deformation is obtained.

[0066] Referring to GB / T228-2002 "Metallic Materials - Tensile Testing at Room Temperature", the mechanical properties of the alloy after two passes of equal diameter angular extrusion were tested, and the results are as follows: Figure 8 As shown.

[0067] Depend on Figure 8 It can be seen that the rolled tensile strength of the high rare earth heat-resistant magnesium-lithium alloy obtained in Example 5 is 305 MPa, and the elongation is 8%.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high rare earth heat resistant magnesium-lithium alloy based on plastic deformation, characterized in that, The high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation comprises the following components in percentage by mass: Li 2.3-4.6%, Al 8-10%, Y 6-10%, Gd 5-15%, and Sc 0-3%, and the balance of Mg; the high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation is prepared by the following steps: melting Mg element, Li element, Al element, Mg-Y intermediate alloy, Mg-Gd intermediate alloy, and Mg-Sc intermediate alloy to obtain a magnesium-lithium alloy ingot, and performing plastic deformation to obtain the high rare earth heat-resistant magnesium-lithium alloy based on plastic deformation; the plastic deformation is rolling, extrusion, or equal-diameter angular extrusion; the sample is not heated and is subjected to equal-diameter angular extrusion, the BC path is deformed during the equal-diameter angular extrusion, the deformation temperature is 100-300℃, and the deformation pass is 1-8; during rolling, the temperature is 300℃, the reduction per pass is 0.5-1mm, and the total reduction is 20-80%; during extrusion, the sample is preheated at 100-350℃ for 10-30min, and then is extruded at 100-350℃, and is water-cooled.

2. The plastic deformation based high rare earth heat resistant Mg-Li alloy according to claim 1, wherein, The as-cast structure of the high rare earth heat-resistant magnesium-lithium alloy comprises a magnesium-lithium matrix phase and an Al-RE phase.

3. The plastic deformation based high rare earth heat resistant Mg-Li alloy according to claim 2, wherein, The magnesium-lithium matrix phase is an α-Mg phase, an α+β phase, and a β-Li phase.

4. The plastic deformation based high rare earth heat resistant Mg-Li alloy according to claim 1, wherein, The Mg element, the Al element, the Mg-Y intermediate alloy, the Mg-Gd intermediate alloy, and the Mg-Sc intermediate alloy are heated and melted at 800℃ in a mixed atmosphere of carbon dioxide and sulfur tetrafluoride, then are cooled to 700℃, the Li element is added after being wrapped with aluminum foil, mechanical stirring is performed for 4-6min, the temperature is then increased to 740℃, a refining agent is added, mechanical stirring is performed for 4-6min, the temperature is finally increased to 800℃ and is kept for 10min, and then the magnesium-lithium alloy ingot is poured.

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