High-strength low-thermal-expansion magnesium alloy as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of alloy casting, and relates to a high-strength low-thermal-expansion magnesium alloy and a preparation method and application thereof. The magnesium alloy comprises the following components in percentage by weight: 14-16% of Y, 4.5-5.5% of Cu and the balance of Mg, the invention also discloses a preparation method of the magnesium alloy, which comprises the following steps: proportioning alloy raw materials, smelting, alloying, carrying out melt treatment and quenching to obtain a magnesium alloy product; the magnesium alloy disclosed by the invention has excellent room-temperature mechanical properties and extremely low thermal expansion coefficient, and is particularly suitable for manufacturing precision parts which need to keep high dimensional stability, light weight and high specific strength in a wide temperature range; the composite material can be applied to various parts, such as satellite optical platform parts, train track fastener systems, natural gas storage tank connecting pipeline systems, new energy automobile battery jackets, inertial navigation system frames, high-precision aerospace sensor shells, photoetching machine workpiece table parts and / or high-end communication equipment shielding cases or heat dissipation substrates, and has huge application prospects.

Description

Technical Field

[0001] This invention relates to the field of alloy casting technology, and specifically to a high-strength, low-thermal-expansion magnesium alloy, its preparation method, and its applications. Background Technology

[0002] Magnesium alloys, as the lightest commercially available metallic engineering materials, have a density of approximately 1.74 g / cm³, which is 2 / 3 the density of aluminum alloys and 1 / 4 the density of steel, giving them a significant advantage in structural lightweighting. However, traditional magnesium alloys such as AZ91D and AM60B generally suffer from low absolute strength, weak high-temperature creep resistance, poor corrosion resistance, and a high coefficient of thermal expansion (typically 25–28 × 10⁻⁶). -6 Magnesium alloys suffer from problems such as high coefficient of thermal expansion (C / K), resulting in poor dimensional stability and a mismatch with the coefficient of thermal expansion of commonly used metals, which can easily lead to stress concentration and failure at joints. Currently, alloying or adding low / negative thermal expansion phases are commonly used to reduce the coefficient of thermal expansion of magnesium alloys. However, excessive addition can damage their mechanical properties and lightweight advantages, severely limiting the application of magnesium alloys in precision engineering fields that require high dimensional stability.

[0003] Therefore, there is an urgent need for a magnesium alloy material that can simultaneously achieve high strength and low coefficient of thermal expansion while maintaining good casting performance and plasticity. Summary of the Invention

[0004] One objective of this invention is to address the problem that existing magnesium alloy materials cannot simultaneously achieve high strength and low thermoplasticity, and to provide a magnesium alloy material with high strength, high ductility, low density, and low thermal expansion. The second objective of this invention is to provide a method for preparing a high-strength, low-thermal-expansion magnesium alloy material.

[0005] A third objective of this invention is to provide an application of a high-strength, low-thermal-expansion magnesium alloy material in component materials that maintain high stability, lightweight, and high specific strength over a wide temperature range.

[0006] To achieve the first objective of the invention, the present invention can be implemented by the following technical solution: a high-strength, low-thermal-expansion magnesium alloy, comprising the following components by weight percentage: Y 14-16%, Cu 4.5-5.5%, with the balance being Mg.

[0007] The beneficial effects of adopting the above technical solution are as follows: This invention uses magnesium as the matrix and alloys it with yttrium (Y) and copper (Cu) with a specific content to obtain a Mg-Y-Cu alloy that has both excellent room temperature mechanical properties and an extremely low coefficient of thermal expansion (CTE). This alloy is particularly suitable for manufacturing components that need to maintain high dimensional stability, lightweight and high specific strength over a wide temperature range, such as satellite optical platforms, inertial navigation system frames, train track fasteners, natural gas storage tank connection pipeline systems, new energy vehicle battery pack shells, high-precision aerospace sensor shells, lithography machine workpiece stage components and / or high-end communication equipment shielding covers and heat dissipation substrates, etc.

[0008] This invention effectively improves the overall performance of magnesium alloys by adding rare earth elements. Yttrium, as an important heavy rare earth element, can significantly refine the grains of magnesium alloys and form a second phase with high thermal stability (such as Mg). 24 Y5), thereby improving the room temperature and high temperature strength of magnesium alloys; furthermore, this invention, based on specific amounts of magnesium and copper, adds a specific amount of rare earth element Y to form a certain long-period stacked ordered structure (LPSO) within the alloy body. The long-period stacked ordered (LPSO) phase, through its atomic-scale L... 12 Strongly bonded atomic clusters (such as Y8Cu6) and long-period stacking structures enhance interatomic bonding forces and crystal structure rigidity. These ordered nanoclusters can strongly constrain atomic thermal vibrations, significantly reducing the thermal expansion coefficient of the material. At the same time, they act as hard barriers to hinder dislocation movement, thereby improving strength and elastic modulus to a certain extent. In the microstructure of this invention, LPSO laths or mesh structures form a coherent interface with the magnesium matrix, constituting a two-phase composite system. This not only improves mechanical properties through load transfer mechanisms, but its interfacial strain field also constrains the thermal expansion of the magnesium matrix.

[0009] Furthermore, the LPSO phase can activate non-basal plane slip and has the ability to twist and deform, improving plasticity and toughness while maintaining high strength. This phase also has high thermal stability and can produce a pinning effect on grain boundaries, thereby jointly improving the high-temperature creep resistance of the alloy. This multi-scale synergistic effect from atomic bonding, nano-ordered clusters, periodic stacking structure to microstructure enables LPSO-strengthened magnesium alloys to have low thermal expansion, high strength, high elastic modulus and good plasticity.

[0010] First-principles calculations show that among various 14H-LPSO phases, Cu exhibits higher electronegativity, significantly different from both Mg and Y. When Cu and Y coexist in an ordered layer, a strong Mg-Y-Cu localized bond is easily formed. This bond has a higher covalent component and directionality, effectively suppressing the interatomic spacing expansion caused by thermal vibrations. This leads to the formation of a 14H-type LPSO phase (Mg...) within the Mg-Y-Cu system. 72Y8Cu6 has a lower intrinsic coefficient of thermal expansion, thus yielding the magnesium alloy of the present invention that combines high strength and low coefficient of thermal expansion. In one specific embodiment of the present invention, a high-strength, low-thermal-expansion magnesium alloy is provided, comprising the following components by weight percentage: Y 15%, Cu 5%, and the balance being Mg. To achieve the second objective, the present invention can be implemented through the following technical solution: providing a method for preparing a thermally expandable magnesium alloy, comprising: Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots, Cu is added in the form of pure copper blocks, and Y is added in the form of Mg-Y master alloy; Under a protective gas environment, pure magnesium ingots are heated to complete melting and held at 740-780℃ for 15-20 min. Then, Mg-Y master alloy and pure copper are added in sequence, stirred evenly, and held at the temperature for 30-45 min to obtain the melt. The melt temperature is stabilized within the range of 740-760℃, and then water-cooled and quenched to obtain the product.

[0011] In one specific embodiment of the present invention, the protective gas is a mixture of SF6 and CO2 or high-purity argon; in the mixture of SF6 and CO2, the volume ratio of SF6 to CO2 is 1:199.

[0012] To achieve the third objective of the invention, the present invention provides the application of a high-strength, low-thermal-expansion magnesium alloy in the preparation of component materials that maintain high stability, lightweight and high specific strength over a wide temperature range.

[0013] In one specific embodiment of the present invention, the components include satellite optical platform components, train track fasteners, natural gas storage tank connection pipeline systems, new energy vehicle battery pack shells, inertial navigation system frames, high-precision aerospace sensor shells, lithography machine workpiece stage components, and / or high-end communication equipment shielding covers or heat dissipation substrates. Attached Figure Description

[0014] Figure 1 The room temperature tensile curves (yield strength and tensile strength) of the magnesium alloys prepared in Example 1 and Comparative Examples 1-4 of this invention are curves showing the change of Y content. Figure 2 The graph shows the thermal expansion curves of the magnesium alloys prepared in Example 1 and Comparative Examples 1-4 of the present invention as a function of Y content in the range of room temperature to 300°C. Figure 3 A comparison chart of the average coefficient of thermal expansion of the magnesium alloys prepared in Example 1 and Comparative Examples 1-4 of the present invention within the range of 25℃-300℃; Figure 4The as-cast alloy metallographic structure of the magnesium alloys prepared in Example 1 and Comparative Examples 1-4 of this invention; Figure 5 The XRD patterns of the magnesium alloys prepared in Example 1 and Comparative Examples 1 and 3 are shown below. Figure 6 The images shown are scanning electron microscope (SEM), backscattered electron (BSE), and energy dispersive spectroscopy (EDS) images of magnesium alloys in the as-cast state prepared in Example 1 and Comparative Examples 1 and 3 of this invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0016] Example 1 A high-strength, low-thermal-expansion magnesium alloy comprises, by weight percentage, the following components: Y 15%, Cu 5%, and Mg 80%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 760°C for 15 minutes. Then, Mg-Y master alloy and pure copper are added in sequence. Mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved. The stirring time is not less than 5 minutes to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 30 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0017] Example 2 A high-strength, low-thermal-expansion magnesium alloy comprises, by weight percentage: Y 14%, Cu 5.5%, and Mg 80.5%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 740°C for 20 minutes; then Mg-Y master alloy and pure copper are added in sequence; mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved, and the stirring time is not less than 5 minutes to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 45 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0018] Example 3 A high-strength, low-thermal-expansion magnesium alloy comprises, by weight percentage, the following components: Y 16%, Cu 5%, and Mg 79%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 780℃ for 20 minutes; then Mg-Y master alloy and pure copper are added in sequence; mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved, and the stirring time is not less than 5 minutes to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 30 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0019] Example 4 A high-strength, low-thermal-expansion magnesium alloy comprises, by weight percentage, the following components: Y 15%, Cu 4.5%, and Mg 80.5%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 760°C for 15 minutes; then preheated Mg-Y master alloy and pure copper are added in sequence; mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved, and the stirring time is not less than 5 minutes to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 45 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0020] Example 5 A high-strength, low-thermal-expansion magnesium alloy comprises, by weight percentage, the following components: Y 15%, Cu 4%, and Mg 81%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 760℃ for 15-20 min; then preheated Mg-Y master alloy and pure copper are added in sequence; mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved, and the stirring time is not less than 5 min to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 30 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0021] Comparative Example 1 A high-strength, low-thermal-expansion magnesium alloy comprises, by weight percentage, the following components: Y 1%, Cu 5%, and Mg 94%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 760°C for 15 minutes; then preheated Mg-Y master alloy and pure copper are added in sequence; mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved, and the stirring time is not less than 5 minutes to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 30 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0022] Comparative Example 2 A high-strength, low-thermal-expansion magnesium alloy comprises, by weight percentage, the following components: Y 3%, Cu 5%, and Mg 92%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 760°C for 20 minutes; then preheated Mg-Y master alloy and pure copper are added in sequence; mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved, and the stirring time is not less than 5 minutes to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 30 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0023] Comparative Example 3 A high-strength, low-thermal-expansion magnesium alloy, comprising the following components by weight percentage: Y 5%, Cu 5%, and Mg 90%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 760°C for 15 minutes; then preheated Mg-Y master alloy and pure copper are added in sequence; mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved, and the stirring time is not less than 5 minutes to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 30 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0024] Comparative Example 4 A high-strength, low-thermal-expansion magnesium alloy, comprising the following components by weight percentage: Y 10%, Cu 5%, and Mg 85%; The preparation method of the above-mentioned high-strength, low-thermal-expansion magnesium alloy includes the following steps: (1) Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots (≥99.95%), Cu is added in the form of pure copper blocks (≥99.9%), and Y is added in the form of Mg-Y master alloy (Y content: 30% by mass); all raw materials are surface cleaned to remove oxide scale and oil stains; (2) Melting and alloying: In a resistance furnace or induction furnace with a protective atmosphere (a mixture of SF6 and CO2 with a volume fraction of 0.5-1.5% and a volume ratio of SF6 to CO2 of 1:199; or high-purity argon), pure magnesium ingots are heated to complete melting and held at 760°C for 20 minutes; then preheated Mg-Y master alloy and pure copper are added in sequence; mechanical stirring is used to ensure that the alloying elements are fully diffused and dissolved, and the stirring time is not less than 5 minutes to ensure that the melt composition is uniform. (3) Melt treatment: The homogenized melt is kept at a constant temperature for 30 minutes to allow the slag to float to the surface. (4) Quenching: The temperature of the melt is stabilized in the range of 740-760℃, and the mold is water-cooled and quenched to obtain the product.

[0025] The magnesium alloy composition tables of Examples 1-5 and Comparative Examples 1-4 are shown in the table below.

[0026] Table 1. Alloy composition of Examples 1-5 and Comparative Examples 1-4 (wt. % represents mass fraction)

[0027] Experimental Example 1) Sample preparation Pure magnesium, Mg-30Y master alloy, and pure Cu were weighed according to the mass fraction of the magnesium alloy formulation components. For both the comparative and example samples, 500 grams of raw materials were prepared per sample. After weighing, the surface of the raw materials was polished to remove surface impurities and oxides. Then, the pure magnesium ingot was placed in a stainless steel crucible, which was then placed in a resistance furnace at 720°C. SF6 and CO2 protective gases (SF6 to CO2 volume ratio 1:199) were introduced into the furnace. After the pure magnesium ingot melted, the Mg-30Y master alloy and pure Cu were added, and the furnace temperature was raised to 760°C. The high temperature helps impurities in the melt settle. After holding at 760°C for 30 minutes, the slag on the surface of the melt was removed. The melt was then stirred for 5 minutes using a stirrer to ensure uniform element distribution. The melt was held at this temperature for another 30 minutes, and then the crucible was removed and water-cooled.

[0028] (2) Performance testing and morphological characterization Thermal expansion test samples were machined into cylinders with a diameter of φ5 mm × 25 mm, and tensile samples were machined into round bar specimens with a gauge length of 25 mm and a diameter of 5 mm according to GB / T 228.1-2021 standard. The tests were conducted using a Netzsch DIL 502 Expedis Classic thermal dilatometer with a temperature range of 25℃ to 300℃ and a heating rate of 5 K / min. Mechanical property tests were performed on a universal testing machine, with a strain rate of 1.5 mm / s achieved by controlling the displacement of the crossbeam. The sample density was determined by the water displacement method.

[0029] Combined with Table 2 Figure 1 The results show that with the increase of Y content, the yield strength and tensile strength of the alloy both show an upward trend, while the elongation shows an initial increase followed by a decrease. Figure 2 and Figure 3 The figures show the thermal expansion curves and average coefficient of thermal expansion (CTE) of magnesium alloys in the range of 25-300℃, respectively, indicating that the introduction of Y element can effectively reduce the overall CTE of the material.

[0030] like Figures 4-5 As shown, metallographic analysis indicates that when the Y content is below 5 wt.%, the second phase in the alloy exhibits a network distribution; when the Y content exceeds 5 wt.%, obvious strip-shaped second phases begin to appear in the microstructure. Combined with XRD and SEM-EDS analysis results, this strip-shaped phase is confirmed to be a strengthening phase with a long-period packed ordered structure (LPSO). With increasing Y content, the number of LPSO phases gradually increases, while the content of Mg2Cu phase decreases accordingly. XRD patterns show that when the Y content reaches 15 wt.%, diffraction peaks of the Mg2Cu phase are no longer detectable. (See also...) Figure 6 , Figure 6 SEM images also revealed that when the Y content was 1%, no strip-shaped LPSO phase was formed inside the alloy, only a network of Mg2Cu phase. When the Y content reached 15%, no bright white Mg2Cu phase appeared, and the second phase was almost entirely LPSO phase. Since the LPSO phase content was relatively high at this point, some LPSO phases were combined together to form blocks. Because the characteristic thermal expansion coefficient of the LPSO phase is lower than that of the Mg2Cu phase, the CTE value of the alloy also decreased sharply with the change of Y content. As a nanoscale lamellar reinforcing phase formed in a magnesium matrix, the LPSO phase exerts multiple positive effects on alloy properties due to its unique atomically ordered stacking structure. Firstly, its nanosheet structure strongly hinders dislocation movement within the magnesium matrix, significantly enhancing alloy strength. Secondly, the LPSO phase itself activates non-matrix slip systems and forms kink bands during deformation; this unique deformation mechanism helps maintain the plasticity of the magnesium alloy while improving strength. Furthermore, the well-bonded interface between the LPSO phase and the magnesium matrix effectively pins grain boundaries, refining the microstructure. Therefore, in this magnesium alloy system, the formation and development of the LPSO phase not only reduces the overall thermal expansion coefficient of the magnesium alloy through its low expansion characteristics but also achieves a good balance between strength and plasticity through the aforementioned multiple strengthening mechanisms.

[0031] In summary, by controlling the Y content, the microstructure of the alloy can be guided from being dominated by the Mg2Cu phase to being dominated by the LPSO phase. This transformation not only utilizes the lower inherent coefficient of thermal expansion of the LPSO phase to further reduce the CTE of the alloy, but also achieves a comprehensive improvement in the mechanical properties of the alloy while reducing the coefficient of thermal expansion through the unique strengthening mechanism of the LPSO phase.

[0032] The performance test results of the products prepared in Examples 1-5 and Comparative Examples 1-4 of this invention are shown in Table 2.

[0033] Table 2. Room temperature performance test results of magnesium alloys prepared in Examples 1-5 and Comparative Examples 1-4

[0034] In summary, this invention uses magnesium as the matrix and employs alloying design with a specific high content of yttrium (Y) and copper (Cu) to obtain a Mg-Y-Cu alloy that combines excellent room-temperature mechanical properties with an extremely low coefficient of thermal expansion (CTE). This alloy is particularly suitable for manufacturing precision components that require high dimensional stability, lightweight, and high specific strength over a wide temperature range, such as satellite optical platforms, train track fasteners, natural gas storage tank connection pipeline systems, new energy vehicle battery packs, inertial navigation system frames, high-precision aerospace sensor housings, lithography machine workpiece stage components, and / or high-end communication equipment shielding covers and heat dissipation substrates.

Claims

1. A high-strength, low-thermal-expansion magnesium alloy, characterized in that, The components, by weight percentage, include the following: Y14-16%, Cu 4.5-5.5%, with the balance being Mg.

2. The high-strength, low-thermal-expansion magnesium alloy according to claim 1, characterized in that, The components, by weight percentage, include the following: Y 15%, Cu 5%, with the balance being Mg.

3. The method for preparing the high-strength, low-thermal-expansion magnesium alloy according to any one of claims 1-2, characterized in that, include: Prepare raw materials according to the weight percentage of magnesium alloy components, wherein Mg is added in the form of pure magnesium ingots, Cu is added in the form of pure copper blocks, and Y is added in the form of Mg-Y master alloy; Under a protective gas environment, pure magnesium ingots are heated to complete melting and held at 740-780℃ for 15-20 minutes. Then, Mg-Y master alloy and pure copper are added in sequence, stirred evenly, and held at the temperature for 30-45 minutes to obtain the melt. The melt temperature is stabilized within the range of 740-760℃, and then water-cooled and quenched to obtain the product.

4. The method for preparing a high-strength, low-thermal-expansion magnesium alloy according to claim 3, characterized in that, The protective gas is a mixture of SF6 and CO2 or high-purity argon; in the mixture of SF6 and CO2, the volume ratio of SF6 to CO2 is 1:

199.

5. Application of the high-strength, low-thermal-expansion magnesium alloy according to any one of claims 1-2 in material components that maintain high stability, lightweight and high specific strength over a wide temperature range.

6. The application according to claim 5, characterized in that, The components include satellite optical platform components, train track fastening systems, natural gas storage tank connection pipeline systems, new energy vehicle battery pack shells, inertial navigation system frames, high-precision aerospace sensor shells, lithography machine workpiece stage components, and / or high-end communication equipment shielding covers or heat dissipation substrates.

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