Magnesium-based composite material with controllable thermal expansion coefficient and preparation method

Abstract

The invention discloses a magnesium-based composite material with a controllable thermal expansion coefficient and a preparation method, and belongs to the field of composite materials. The composite material comprises a negative thermal expansion reinforcing body and a magnesium matrix, the volume percentage content alpha of the negative thermal expansion reinforcing body in the composite material is more than 0 and less than or equal to 50vol.%, and the balance is the magnesium matrix. The negative thermal expansion material is used for reinforcing the magnesium-based composite material, the negative thermal expansion material can effectively compensate high positive thermal expansion of magnesium, the high thermal expansion coefficient of magnesium is remarkably reduced through a low-content second phase, the effect of inhibiting high CTE of magnesium is extremely remarkable, and the ordered and controllable low-thermal-expansion even zero-thermal-expansion magnesium-based composite material is achieved; and meanwhile, magnesium-based composite materials with different components and different thermal expansion coefficients can be accurately designed according to requirements, and the magnesium-based composite materials can be applied to environments with different strength requirements and different thermal expansion requirements.

Description

Technical Field

[0001] This invention relates to a magnesium-based composite material with a controllable coefficient of thermal expansion and its preparation method, belonging to the field of composite material technology. Background Technology

[0002] Against the backdrop of increasingly urgent global demands for reduced energy consumption and carbon emission control, metallic materials that combine lightweight properties with excellent comprehensive performance have become a research hotspot across various industries, especially in transportation, aerospace, and other fields with stringent requirements for lightweight materials, where their application demand is growing daily. While aluminum alloys are widely used lightweight metallic materials in modern industry due to their high strength, light weight, versatility, and ease of shaping, magnesium, with a density only 2 / 3 that of aluminum, and magnesium alloys possessing excellent shock absorption, superior machinability, good electromagnetic shielding, and excellent die-casting fluidity, has thus attracted widespread attention.

[0003] However, magnesium alloys suffer from significant defects in thermal expansion characteristics: their coefficient of thermal expansion (CTE) at room temperature is as high as 26 ppm / ℃, and this value increases dramatically with increasing temperature. This defect directly leads to two problems: first, it severely affects the dimensional stability and accuracy of magnesium-based structural components in environments with drastic temperature fluctuations; second, it easily causes a mismatch in the coefficient of thermal expansion with commonly used structural materials such as aluminum, copper, and steel, thereby inducing thermal stress and ultimately leading to deformation, cracking, and other damage in structural components, greatly limiting the application range of magnesium alloys under complex temperature conditions.

[0004] To address the aforementioned thermal expansion issue, existing technologies have proposed controlling the coefficient of thermal expansion (CTE) of magnesium alloys through alloying, such as adding alloying elements like Si, Zn, Zr, Nd, and Gd to the magnesium matrix. Specifically, patents CN109182855A, CN108486446A, and CN114672711A disclose methods for reducing the CTE of magnesium alloys by adding Zr, Si, and Gd alloying elements to the magnesium matrix, resulting in relatively low-CTE magnesium alloys. However, firstly, the low-CTE second phase precipitated after alloying with these elements is itself a positively expanding material. Simply reducing lattice vibration energy through alloying the second phase to control the CTE has limited effectiveness, and adding large amounts of alloying elements can lead to other problems, such as performance changes and increased costs. Secondly, if these second phases have low melting points or are exposed to high temperatures, they are prone to decomposition within the magnesium matrix, causing significant fluctuations in the CET value of the magnesium alloy at different temperatures, resulting in unstable CET performance. In addition, existing technologies have proposed a technical solution to prepare low-thermal-expansion magnesium-based composite materials by introducing low-thermal-expansion brittle reinforcing phases, such as SiC, Al2O3, and AlN. However, this solution also requires the addition of a relatively high content of reinforcing agents to achieve the desired low-thermal-expansion effect. Furthermore, the introduction of a high content of brittle reinforcing phases can lead to the magnesium alloy's mechanical properties failing to meet the requirements of practical engineering applications.

[0005] Negative thermal expansion materials exhibit the characteristic of shrinking volume with increasing temperature. Theoretically, applying them to the preparation of magnesium-based composite materials can compensate for the high positive thermal expansion of the magnesium matrix, thereby suppressing the ultra-high thermal expansion coefficient of the magnesium matrix with a lower reinforcement content, and ultimately obtaining magnesium-based composite materials with low or even zero thermal expansion. Patents CN114892037A, CN114875262A, CN117210732A, and CN117230353A all disclose the preparation of low or near-zero thermal expansion composite materials by combining negative thermal expansion materials with a magnesium matrix; however, without exception, all employ a vacuum hot-pressing sintering method. Because vacuum hot pressing involves a long heating and holding process, and negative thermal expansion materials generally suffer from weak bonding energy and insufficient chemical stability, their structural stability is poor, making them prone to decomposition at high temperatures. Furthermore, the chemically reactive nature of magnesium facilitates a violent interfacial reaction between the two materials, damaging their structure and causing them to lose their thermal expansion compensation function. This significantly weakens their ability to suppress the thermal expansion of the magnesium matrix, making it impossible to achieve stable preparation of low thermal expansion magnesium-based composite materials. Patent CN109112442A discloses a multi-scale reinforced low / negative thermal expansion magnesium-based composite material, which uses a pressure infiltration method to impregnate molten magnesium-based material into a reinforcement made of fibers and negative thermal expansion particles. However, this method has a complex preparation process and produces a 2.5D composite material, which has defects in Z-axis properties.

[0006] Therefore, how to achieve precise control of the thermal expansion coefficient of magnesium-based composite materials has become a technical problem that needs to be solved. Summary of the Invention

[0007] This invention addresses the issue of how to achieve precise control over the coefficient of thermal expansion of magnesium-based alloys by proposing a magnesium-based composite material with a controllable coefficient of thermal expansion and its preparation method. This aims to solve at least one of the technical problems existing in the prior art, such as the high and unstable coefficient of thermal expansion of magnesium-based alloys, as well as the unstable preparation methods and complex processes.

[0008] First, the present invention provides a magnesium-based composite material with a controllable coefficient of thermal expansion. The composite material includes a negative thermal expansion reinforcement and a magnesium matrix. The volume percentage α of the negative thermal expansion reinforcement in the composite material is: 0 < α ≤ 50 vol.%, with the remainder being the magnesium matrix.

[0009] Optionally, the negative thermal expansion reinforcement is one or more of the following: ceramic materials, intermetallic compounds, and alloys with a negative average linear expansion coefficient or volumetric expansion coefficient at t℃ (-150℃ < t < 500℃).

[0010] Optionally, the ceramic material is selected from at least one of the following chemical formulas: aα₂O₈, where a represents one or more of the chemical elements Zr, Hf, Sn, Ti, Eu, Er, and Yb, and α represents one or more of the chemical elements W, Mo, and V; bβ₂O₇, where b represents one or more of the chemical elements Zr, Th, and Ce, and β represents one or more of the chemical elements P, Mo, and V; c₂γ₃O₇ 12 In the formula, c represents one or more of the chemical elements Sc, Dy, Y, Er, Yb, and Lu, and γ represents one or more of the chemical elements W and Mo; the chemical formula is dδO5, where d represents one or more of the chemical elements Nb and Ta, and δ represents one or more of the chemical elements V and P; the chemical formula is eε2P3O 12 In the formula, e represents one or more of the chemical elements Na, K, Nb, Rb, and Cs, and ε represents one or more of the chemical elements Zr, Ti, and Hf; the chemical formula f2ζ2O7, where f represents one or more of the chemical elements Cu, Mn, Fe, Co, Ni, Mg, and Zn, and ζ represents one or more of the chemical elements P and V; the chemical formula g2O(PO4)2, where g represents one or more of the chemical elements U and Th; the chemical formula hθF6, where h represents one or more of the chemical elements Ca, Mn, Fe, Zn, Co, Ni, Mg, Yb, and Ti, and θ represents one or more of the chemical elements Zr, Hf, and Nb; the chemical formula i(CN)2, where i represents one or more of the chemical elements Zn and Cd; the chemical formula jB(CN)4, where j represents one or more of the chemical elements Cu and Ag; chemical formula kτ(CN)6, where k represents one or more of the chemical elements Y, Fe, Ga, Sc, Ti, La, Sm, Ho, Lu, Er, Cs, Rb, Cd, Mn, Co, Ni, and Zn, and τ represents one or more of the chemical elements Fe, Co, Pt, Cd, Ni, Cu, and Zn; chemical formula Mn3lN, where l is one or more of Zn, Cu, Ga, Sn, Si, Ge, and Fe, and compounds formed by partial substitution of the Mn position in chemical formula Mn3lN by any one or two elements V, Cr, Fe, Co, Ni, Cu, and Zn; Zn[Ag(CN)2]2, CaZr4P6O 24 , Si(NCN)2, ReO3, SiO2, Cu2O, Ag2O, ScF3;

[0011] Intermetallic compounds are selected from at least one of the following chemical formulas: Zr y Nb 1-y Fe2, Hf y Nb 1-y Fe2, Hf 1-y Ta yFe2,Sc 1-y Ti y Fe2, CrTe y Se 1-y LaFe 13-x Si x LaFe 13-x Al x , Mn3Ge, Mn-Co-Ge series, Fe-Mn-Ga series, Ni-Mn-Ga series, RCo2, R2Fe 14 B, R2Fe 17 , RCo3, RFe 12 , R3Fe 29 In the chemical formula, y is any value from 0 to 1, x is any value from 0 to 13, and R is one or more rare earth elements; and intermetallic compounds formed by partially replacing the Fe, Co, or Mn sites in the above chemical formula with any one or two elements selected from Si, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Hf, and Ta.

[0012] The alloy is selected from at least one of the following combinations of elements: Fe-Ni, Fe-Pt, Cr-Fe, Ni-Ti, Ti-Nb.

[0013] Optionally, the magnesium matrix is ​​one or more of magnesium alloys or pure magnesium with a magnesium mass percentage of 50 wt% or more, and the purity of the pure magnesium is 99.0 wt% or more.

[0014] Secondly, the present invention also provides a method for preparing the above-mentioned magnesium-based composite material with controllable thermal expansion coefficient, comprising the following steps:

[0015] Step S1: Convert the volume fraction of the magnesium-based composite material to be prepared into weight, and weigh the negative thermal expansion reinforcement powder and magnesium matrix powder accordingly.

[0016] Step S2: Mix the three powders weighed in step S1 evenly to obtain composite powder;

[0017] Step S3: Load the composite powder from step S2 into a sintering mold and move it into the furnace. Adjust the furnace environment, heat up, keep warm or keep warm and pressurize to carry out solid-phase sintering, cool with the furnace, and take it out at room temperature to obtain magnesium-based composite material.

[0018] Optionally, in step S1, the average particle size of the negative thermal expansion reinforcing powder is 0.1~500μm; the average particle size of the magnesium matrix powder is 0.1~500μm.

[0019] Optionally, in step S3, solid-state sintering is carried out in a spark plasma sintering furnace.

[0020] Optionally, the furnace environment in the spark plasma sintering furnace is 1×10 -3 A vacuum environment of ~50 Pa or an atmospheric pressure of 10~1×10 3 Pa is a protective gas among nitrogen, argon, and helium.

[0021] Optionally, the heating rate is 50~200℃ / min, the holding temperature is 350~580℃, and the holding time is 1~10min.

[0022] Optionally, the pressure applied is 1~150MPa.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] 1. The advantage of this invention is that it uses a negative thermal expansion material to reinforce magnesium-based composite materials. The negative thermal expansion material can effectively compensate for the high positive thermal expansion of magnesium, and achieve a significant reduction in the high thermal expansion coefficient of magnesium by using a low content of the second phase. The effect of suppressing the high CTE of magnesium is extremely significant, and an ordered and controllable low thermal expansion or even zero thermal expansion magnesium-based composite material is realized. At the same time, magnesium-based composite materials with different compositions and different thermal expansion coefficients can be precisely designed as needed, which is beneficial for application in environments with different strength requirements and different thermal expansion requirements.

[0025] 2. The introduction of a low proportion of negative thermal expansion brittle phase into the magnesium-based composite material of the present invention ensures that the composite material as a whole can still maintain the inherent properties of the magnesium matrix, such as the low density and mechanical properties of magnesium alloys.

[0026] 3. The Zn2P2O7-reinforced pure magnesium matrix composite material of the present invention, wherein the negative expansion material Zn2P2O7 reduces the coefficient of thermal expansion and also improves the strength in the pure magnesium matrix.

[0027] 4. By adjusting the appropriate ratio, the magnesium-based composite material of the present invention can achieve precise matching with the structural materials used in aerospace, so that structural components will not be damaged by deformation, cracking or other phenomena due to mismatch in thermal expansion coefficients.

[0028] 5. This invention employs spark plasma sintering technology in solid-state sintering. By rapidly heating, holding for a short time, and rapidly cooling down, the chemical reaction between the highly chemically reactive magnesium and the negative thermal expansion material is avoided. This helps to maintain the structure of the negative thermal expansion material, thereby ensuring that it exerts its effect of inhibiting the thermal expansion of the magnesium matrix. At the same time, solid-state sintering can also achieve relatively precise control over the volume fraction of the negative thermal expansion reinforcement and the magnesium matrix.

[0029] 6. This invention provides a magnesium-based composite material with a controllable coefficient of thermal expansion and a preparation method thereof. The method is simple, rapid, highly operable, and easy to implement in engineering applications, solving the problem that the application of existing magnesium-based materials is limited due to their high coefficient of thermal expansion. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 The images show the XRD patterns of the magnesium-based composite materials in Examples 1-3.

[0032] Figure 2 The graphs show the linear expansion test curves of the magnesium-based composite materials in Examples 1-3.

[0033] Figure 3 This is a microstructure diagram of the magnesium-based composite material in Example 3;

[0034] In the figure, 1-negative thermal expansion reinforcement Zn2P2O7; 2-WE43 magnesium alloy matrix. Detailed Implementation

[0035] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be described in detail below with reference to specific embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of the invention.

[0036] The present invention provides a magnesium-based composite material with a controllable coefficient of thermal expansion. The material comprises a negative thermal expansion reinforcement and a magnesium matrix, wherein the volume percentage α of the negative thermal expansion reinforcement is: 0 < α ≤ 50 vol.%, and the remainder is the magnesium matrix.

[0037] Negative thermal expansion reinforcement is one or more of the following: ceramic materials, intermetallic compounds, and alloys with a negative average linear expansion coefficient or volumetric expansion coefficient at t℃ (-150℃ < t < 500℃).

[0038] Specifically, the negative thermal expansion reinforcement is selected from: (1) ceramic materials: chemical formula aα2O8, where a represents one or more of the chemical elements Zr, Hf, Sn, Ti, Eu, Er, Yb, and α represents one or more of the chemical elements W, Mo, V; chemical formula bβ2O7, where b represents one or more of the chemical elements Zr, Th, Ce, and β represents one or more of the chemical elements P, Mo, V; chemical formula c2γ3O 12In the formula, c represents one or more of the chemical elements Sc, Dy, Y, Er, Yb, and Lu, and γ represents one or more of the chemical elements W and Mo; the chemical formula is dδO5, where d represents one or more of the chemical elements Nb and Ta, and δ represents one or more of the chemical elements V and P; the chemical formula is eε2P3O 12 In the formula, e represents one or more of the chemical elements Na, K, Nb, Rb, and Cs, and ε represents one or more of the chemical elements Zr, Ti, and Hf; the chemical formula f2ζ2O7, where f represents one or more of the chemical elements Cu, Mn, Fe, Co, Ni, Mg, and Zn, and ζ represents one or more of the chemical elements P and V; the chemical formula g2O(PO4)2, where g represents one or more of the chemical elements U and Th; the chemical formula hθF6, where h represents one or more of the chemical elements Ca, Mn, Fe, Zn, Co, Ni, Mg, Yb, and Ti, and θ represents one or more of the chemical elements Zr, Hf, and Nb; the chemical formula i(CN)2, where i represents one or more of the chemical elements Zn and Cd; the chemical formula jB(CN)4, where j represents one or more of the chemical elements Cu and Ag; chemical formula kτ(CN)6, where k represents one or more of the chemical elements Y, Fe, Ga, Sc, Ti, La, Sm, Ho, Lu, Er, Cs, Rb, Cd, Mn, Co, Ni, and Zn, and τ represents one or more of the chemical elements Fe, Co, Pt, Cd, Ni, Cu, and Zn; chemical formula Mn3lN, where l is one or more of Zn, Cu, Ga, Sn, Si, Ge, and Fe, and compounds formed by partial substitution of the Mn position in chemical formula Mn3lN by any one or two elements V, Cr, Fe, Co, Ni, Cu, and Zn; Zn[Ag(CN)2]2, CaZr4P6O 24 , Si(NCN)2, ReO3, SiO2, Cu2O, Ag2O, ScF3, ZrW2O8, ZrMo2O8, ZrV2O8, Cu2P2O7, Cu2V2O7, ThV2O7, CeV2O7, etc.

[0039] (2) Intermetallic compounds are selected from: Zr y Nb 1-y Fe2, Hf y Nb 1-y Fe2, Hf 1-y Ta y Fe2,Sc 1-y Ti y Fe2, CrTe y Se 1-y LaFe 13-x Si x LaFe13-x Al x , Mn3Ge, Mn-Co-Ge series, Fe-Mn-Ga series, Ni-Mn-Ga series, RCo2, R2Fe 14 B, R2Fe 17 , RCo3, RFe 12 , R3Fe 29 In the chemical formula, y is any value from 0 to 1, x is any value from 0 to 13, and R is one or more rare earth elements, such as rare earth elements La, Ce, Dy, Ho, Yb, etc.; and intermetallic compounds formed by partially replacing the Fe, Co, or Mn sites in the above-mentioned intermetallic compounds with any one or two elements from Si, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Hf, and Ta.

[0040] (3) The alloys are selected from: Fe-Ni, Fe-Pt, Cr-Fe, Ni-Ti, Ti-Nb, etc.

[0041] The magnesium matrix is ​​one or more of magnesium alloys or pure magnesium with a magnesium mass percentage of 50 wt% or more, and the purity of the pure magnesium is 99.0 wt% or more. The magnesium alloys include, for example, AZ series magnesium alloys (aluminum-zinc series magnesium alloys), AM series magnesium alloys (aluminum-manganese series magnesium alloys), AS series magnesium alloys (aluminum-silicon series magnesium alloys), AE series magnesium alloys (aluminum-rare earth series magnesium alloys), WE series magnesium alloys (yttrium-rare earth series magnesium alloys), ZK series magnesium alloys (zinc-zirconium series magnesium alloys), Mg-Li series magnesium alloys, Mg-Al-Ca series magnesium alloys, or magnesium alloys of other compositions. Among them, AZ series magnesium alloys, such as AZ91 and AZ31; AM series magnesium alloys, such as AM60 and AM50; AS series magnesium alloys, such as AS41 and AS21; AE series magnesium alloys, such as AE44; WE series magnesium alloys, such as WE43 and WE54; ZK series magnesium alloys, such as ZK60; and Mg-Al-Ca series magnesium alloys, such as AJ62 and AXJ530.

[0042] It should be noted that the main role of negative thermal expansion reinforcement in magnesium matrix composites is to adjust the coefficient of thermal expansion. Other properties of magnesium matrix composites, besides the coefficient of thermal expansion, mainly come from the magnesium matrix itself. That is, the appropriate magnesium matrix material is selected based on the specific requirements of the overall performance of the magnesium matrix composite. For example, if a magnesium matrix composite with a controllable coefficient of thermal expansion and good overall performance is selected, the magnesium matrix tends to be AZ series or WE series magnesium alloys; if a magnesium matrix composite with a controllable coefficient of thermal expansion and good corrosion resistance is selected, the magnesium matrix tends to be AM series magnesium alloys; if a magnesium matrix composite with a controllable coefficient of thermal expansion and good high-temperature performance is selected, the magnesium matrix tends to be AE series or AS series magnesium alloys; and if a magnesium matrix composite with a controllable coefficient of thermal expansion and high strength is selected, the magnesium matrix tends to be ZK series magnesium alloys, etc.

[0043] Negative thermal expansion reinforcements exhibit "thermal contraction and cold expansion" properties within the operating temperature range of material parts. Within this range, both the average linear expansion coefficient and the volumetric expansion coefficient are negative. Negative thermal expansion materials can be composited with a magnesium matrix to create materials with controllable thermal expansion coefficients. By adjusting their volume ratio, magnesium-based composite materials with different thermal expansion coefficients can be obtained to meet various application conditions, such as low-thermal-expansion materials and zero-thermal-expansion materials. For example, a magnesium-based composite material of 5 vol% Zn₂P₂O₇ + 95 vol% WE₄₃ magnesium alloy achieves a thermal expansion coefficient of 23.0 ppm / ℃ at 100–140℃, while maintaining a coefficient of 1.94 g / cm³. 3 The low-density magnesium-based composite material of 15 vol% Zn2P2O7 + 85 vol% WE43 magnesium alloy achieves a coefficient of thermal expansion of 11.1 ppm / ℃ at 100~140℃, while maintaining a coefficient of thermal expansion of 2.16 g / cm³. 3 The low-density magnesium-based composite material of 25 vol% Zn2P2O7 + 75 vol% WE43 magnesium alloy achieves a coefficient of thermal expansion of 0.468 ppm / ℃ at 100~140℃, while maintaining a coefficient of thermal expansion of 2.40 g / cm³. 3 Low density; a magnesium-based composite material of 10 vol% Zn₂P₂O₇ + 90 vol% pure magnesium achieves a coefficient of thermal expansion of 21.1 ppm / ℃ at 70–160℃, while maintaining a coefficient of thermal expansion of 2.01 g / cm³. 3 It has low density, a compressive strength of 216 MPa, and a fracture strain of 16.0%; the magnesium-based composite material of 30 vol% Zn2P2O7 + 70 vol% pure magnesium achieves a coefficient of thermal expansion of 12.1 ppm / ℃ at 70~160℃, and maintains a coefficient of thermal expansion of 2.51 g / cm³. 3 It has low density, a compressive strength of 382 MPa, and a fracture strain of 9.57%. The chemical composition of WE43 magnesium alloy, by mass percentage, is: 3.7~4.3% Y, 2.4~4.4% RE, 0.4~1.0 Zr%, with the balance being Mg, where RE is a Nd-rich mixed heavy rare earth element.

[0044] The present invention also provides a method for preparing the above-mentioned magnesium-based composite material with controllable thermal expansion coefficient, comprising the following steps:

[0045] Step S1: Convert the volume fraction of the magnesium-based composite material to be prepared into weight, and weigh the negative thermal expansion reinforcement powder and magnesium matrix powder accordingly.

[0046] Step S2: Mix the two powders weighed in step S1 evenly to obtain composite powder;

[0047] Step S3: Load the composite powder from step S2 into a sintering mold and move it into the furnace. Adjust the furnace environment, heat up, keep warm or keep warm and pressurize to carry out solid-phase sintering, cool with the furnace, and take it out at room temperature to obtain magnesium-based composite material.

[0048] Specifically, in step S1, firstly, the total volume is calculated according to the dimensions of the magnesium-based composite material to be prepared; then, the volumes of the negative thermal expansion reinforcement and the magnesium matrix are calculated according to the volume fraction; finally, the weights of the respective materials are calculated based on the volumes and true densities of the negative thermal expansion reinforcement and the magnesium matrix.

[0049] The negative thermal expansion reinforcing powder is one or more of the following: ceramic powder, intermetallic compound powder, and alloy powder, with a negative average linear expansion coefficient or volume expansion coefficient at t℃ (-150℃ < t < 500℃). The average particle size of the negative thermal expansion reinforcing powder is 0.1~500μm. Specifically, the negative thermal expansion reinforcing powder is selected from: (1) ceramic powder: chemical formula aα2O8, where a represents one or more of the chemical elements Zr, Hf, Sn, Ti, Eu, Er, and Yb, and α represents one or more of the chemical elements W, Mo, and V; chemical formula bβ2O7, where b represents one or more of the chemical elements Zr, Th, and Ce, and β represents one or more of the chemical elements P, Mo, and V; chemical formula c2γ3O 12 In the formula, c represents one or more of the chemical elements Sc, Dy, Y, Er, Yb, and Lu, and γ represents one or more of the chemical elements W and Mo; the chemical formula is dδO5, where d represents one or more of the chemical elements Nb and Ta, and δ represents one or more of the chemical elements V and P; the chemical formula is eε2P3O 12In the formula, e represents one or more of the chemical elements Na, K, Nb, Rb, and Cs, and ε represents one or more of the chemical elements Zr, Ti, and Hf; the chemical formula f2ζ2O7, where f represents one or more of the chemical elements Cu, Mn, Fe, Co, Ni, Mg, and Zn, and ζ represents one or more of the chemical elements P and V; the chemical formula g2O(PO4)2, where g represents one or more of the chemical elements U and Th; the chemical formula hθF6, where h represents one or more of the chemical elements Ca, Mn, Fe, Zn, Co, Ni, Mg, Yb, and Ti, and θ represents one or more of the chemical elements Zr, Hf, and Nb; the chemical formula i(CN)2, where i represents one or more of the chemical elements Zn and Cd; the chemical formula jB(CN)4, where j represents one or more of the chemical elements Cu and Ag; chemical formula kτ(CN)6, where k represents one or more of the chemical elements Y, Fe, Ga, Sc, Ti, La, Sm, Ho, Lu, Er, Cs, Rb, Cd, Mn, Co, Ni, and Zn, and τ represents one or more of the chemical elements Fe, Co, Pt, Cd, Ni, Cu, and Zn; chemical formula Mn3lN, where l is one or more of Zn, Cu, Ga, Sn, Si, Ge, and Fe, and compounds formed by partial substitution of the Mn position in chemical formula Mn3lN by any one or two elements V, Cr, Fe, Co, Ni, Cu, and Zn; Zn[Ag(CN)2]2, CaZr4P6O 24 、Si(NCN)2, ReO3, SiO2, Cu2O, Ag2O, ScF3, ZrW2O8, ZrMo2O8, ZrV2O8, Cu2P2O7, Cu2V2O7, ThV2O7, CeV2O7, etc.; (2) Intermetallic compound powders are selected from: Zr y Nb 1-y Fe2, Hf y Nb 1-y Fe2, Hf 1-y Ta y Fe2,Sc 1-y Ti y Fe2, CrTe y Se 1-y LaFe 13-x Si x LaFe 13-x Al x , Mn3Ge, Mn-Co-Ge series, Fe-Mn-Ga series, Ni-Mn-Ga series, RCo2, R2Fe 14 B, R2Fe 17 , RCo3, RFe 12 , R3Fe 29In the chemical formula, y is any value from 0 to 1, x is any value from 0 to 13, and R is one or more rare earth elements, such as rare earth elements La, Ce, Dy, Ho, Yb, etc.; and intermetallic compounds formed by replacing the Fe site, Co site or Mn site in the above intermetallic compounds with any one or two elements from Si, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Hf, Ta; (3) Alloy powder is selected from: Fe-Ni, Fe-Pt, Cr-Fe, Ni-Ti, Ti-Nb, etc.

[0050] The magnesium matrix powder is one or more of magnesium alloy powder or pure magnesium powder, with a magnesium content of 50 wt% or more. The purity of the pure magnesium powder is 99.0 wt% or higher. The magnesium alloy powder includes, for example, AZ series magnesium alloys (aluminum-zinc series magnesium alloys), AM series magnesium alloys (aluminum-manganese series magnesium alloys), AS series magnesium alloys (aluminum-silicon series magnesium alloys), AE series magnesium alloys (aluminum-rare earth series magnesium alloys), WE series magnesium alloys (yttrium-rare earth series magnesium alloys), ZK series magnesium alloys (zinc-zirconium series magnesium alloys), Mg-Li series magnesium alloys, Mg-Al-Ca series magnesium alloys, or magnesium alloy powders of other compositions. The average particle size of the magnesium matrix powder is 0.1~500 μm.

[0051] Specifically, in step S3, the solid-state sintering is carried out in a spark plasma sintering furnace.

[0052] The furnace environment in the spark plasma sintering furnace is 1×10 -3 A vacuum environment of ~50 Pa or an atmospheric pressure of 10~1×10 3Pa uses a protective gas selected from nitrogen, argon, and helium. The sintering mold used is a cylindrical graphite or steel mold, axially compressible, with an inner diameter of 6~300mm. The heating rate is 50~200℃ / min, such as 60℃ / min, 80℃ / min, 100℃ / min, 120℃ / min, 140℃ / min, 160℃ / min, 180℃ / min, etc.; the temperature is 350~580℃, such as 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, etc.; the holding time is 1~10min, such as 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, etc. If heat preservation and pressure are applied, the applied pressure is 1~150MPa, such as 5MPa, 10MPa, 20MPa, 30MPa, 50MPa, 70MPa, 80MPa, 100MPa, 120MPa, 140MPa, etc. The spark plasma sintering furnace is cooled with the assistance of circulating water, so the cooling rate after sintering and heat preservation is above 100℃ / min.

[0053] It should be noted that the discharge plasma sintering of the present invention has a heating rate of 50°C / min or higher, a holding time of less than 10 minutes, and a cooling rate of 100°C / min or higher, while the conventional vacuum hot pressing sintering has a heating rate of less than 25°C / min and a holding time of more than 50 minutes. The present invention effectively avoids the chemical reaction between the highly chemically reactive magnesium and the negative thermal expansion material by rapidly heating, holding for a short time, and rapidly cooling, thereby maintaining the structure and negative thermal expansion properties of the negative thermal expansion material.

[0054] The magnesium-based composite material prepared in this invention effectively suppresses the interfacial reactions commonly found in composite materials through a rapid heating-short-time holding-rapid cooling process strategy. This also prevents the decomposition of the negative thermal expansion phase at high temperatures, thus ensuring the compensating effect of the negative thermal expansion material on the high positive thermal expansion coefficient of the magnesium matrix. Secondly, the overall thermal expansion coefficient of the composite material gradually decreases with increasing negative thermal expansion material content. For example, when the negative thermal expansion material content is only 5%, the thermal expansion coefficient of the composite material can be reduced to 23.0 ppm / ℃; when the negative thermal expansion material content increases to 25%, this invention successfully prepares a zero-expansion magnesium-based composite material, a breakthrough that is difficult to achieve with existing magnesium alloys or traditional low-expansion phase reinforced magnesium-based composite materials. Finally, the introduction of a low proportion of brittle phase ensures that the composite material as a whole still maintains the inherent properties of the magnesium matrix, such as the low density and mechanical properties of magnesium alloys.

[0055] Example 1

[0056] A magnesium-based composite material with a controllable coefficient of thermal expansion, comprising a negative thermal expansion reinforcement Zn₂P₂O₇ and a magnesium matrix WE43 magnesium alloy, wherein the volume percentage (α) of the negative thermal expansion reinforcement is 5 vol.%, with the balance being the magnesium matrix. The chemical composition of the WE43 magnesium alloy, by mass percentage, is: 4.0% Y, 3.3% RE, 0.5% Zr%, with the balance being Mg, wherein RE is a Nd-rich Nd and Gd mixed heavy rare earth element.

[0057] A method for preparing the above-mentioned magnesium-based composite material with controllable thermal expansion coefficient includes the following steps:

[0058] Step S1: Convert the volume fraction of the magnesium-based composite material to be prepared into weight, and weigh the negative thermal expansion reinforcement powder and magnesium matrix powder accordingly.

[0059] Precast magnesium-based composite material with a volume of 24 cm³ 3 Weigh out 5g of negative thermal expansion reinforced Zn2P2O7 powder and 41g of magnesium matrix WE43 magnesium alloy powder. The average particle size of Zn2P2O7 powder is 50μm, and the average particle size of WE43 magnesium alloy powder is 30μm.

[0060] Step S2: Mix the two powders weighed in step S1 evenly to obtain composite powder;

[0061] Step S3: Load the composite powder from step S2 into a sintering mold and move it into the furnace. Adjust the furnace environment, keep it warm or apply pressure to carry out solid-phase sintering, cool it with the furnace, and take it out at room temperature to obtain the magnesium-based composite material.

[0062] Solid-state sintering was carried out in a spark plasma furnace at a depth of 1×10⁻⁶. -3 The vacuum environment was controlled at 50 MPa, and the sintering mold used was a cylindrical graphite mold with an inner diameter of 50 mm. The pressure applied during sintering was 50 MPa, the heating rate was 100 °C / min, the temperature was 450 °C, and the holding time was 5 min.

[0063] XRD tests were performed on the magnesium-based composite material of this embodiment. Figure 1 This includes the XRD pattern of the magnesium-based composite material in this embodiment, from... Figure 1 As can be seen, the phase composition of this composite material consists only of the characteristic diffraction peaks of the matrix WE43 magnesium and the negative thermal expansion phase Zn2P2O7, with no newly generated impurity phases detected. This result is attributed to the advantages of the rapid heating-short holding-rapid cooling process of spark plasma sintering.

[0064] The coefficient of thermal expansion of the magnesium-based composite material in this embodiment was tested using a linear thermal dilatometer. Figure 2The test curves of this embodiment are included, and the test results are shown in Table 1. When the amount of negative thermal expansion material added is only 5%, the coefficient of thermal expansion of the composite material can be reduced to 23.0 ppm / ℃, which is highly matched with the coefficient of thermal expansion of lightweight metal aluminum (23.5 ppm / ℃), while its density is only 72% of that of aluminum.

[0065] The magnesium-based composite material in this embodiment is based on the Archimedes' method of drainage, utilizing 1×10 -5 Density tests were performed using an analytical balance with g-precision precision, and the results are shown in Table 1.

[0066] Example 2

[0067] A magnesium-based composite material with a controllable coefficient of thermal expansion, comprising a negative thermal expansion reinforcement Zn₂P₂O₇ and a magnesium matrix WE43 magnesium alloy, wherein the volume percentage (α) of the negative thermal expansion reinforcement is 15 vol.%, with the balance being the magnesium matrix. The chemical composition of the WE43 magnesium alloy, by mass percentage, is: 4.0% Y, 3.3% RE, 0.5% Zr%, with the balance being Mg, wherein RE is a Nd-rich Nd and Gd mixed heavy rare earth element.

[0068] A method for preparing the above-mentioned magnesium-based composite material with controllable thermal expansion coefficient includes the following steps:

[0069] Step S1: Convert the volume fraction of the magnesium-based composite material to be prepared into weight, and weigh the negative thermal expansion reinforcement powder and magnesium matrix powder accordingly.

[0070] Precast magnesium-based composite material with a volume of 3cm³ 3 Weigh out 2g of negative thermal expansion reinforced Zn2P2O7 powder and 5g of magnesium matrix WE43 magnesium alloy powder. The average particle size of Zn2P2O7 powder is 50μm, and the average particle size of Mg-Y magnesium alloy powder is 30μm.

[0071] Step S2: Mix the two powders weighed in step S1 evenly to obtain composite powder;

[0072] Step S3: Load the composite powder from step S2 into a sintering mold and move it into the furnace. Adjust the furnace environment, keep it warm or apply pressure to carry out solid-phase sintering, cool it with the furnace, and take it out at room temperature to obtain the magnesium-based composite material.

[0073] Solid-state sintering was carried out in a spark plasma furnace at a depth of 1×10⁻⁶. -3 The vacuum environment was controlled at 50 MPa, and the sintering mold used was a cylindrical graphite mold with an inner diameter of 20 mm. The pressure applied during sintering was 50 MPa, the heating rate was 100 °C / min, the temperature was 450 °C, and the holding time was 5 min.

[0074] XRD tests were performed on the magnesium-based composite material of this embodiment. Figure 1 This includes the XRD test pattern of the magnesium-based composite material in this embodiment, from... Figure 1 As can be seen, the phase composition of this composite material consists only of the characteristic diffraction peaks of the matrix WE43 magnesium and the negative thermal expansion phase Zn2P2O7, with no newly generated impurity phases detected. This result is attributed to the advantages of the rapid heating-short holding-rapid cooling process of spark plasma sintering.

[0075] The coefficient of thermal expansion of the magnesium-based composite material in this embodiment was tested using a linear thermal dilatometer. Figure 2 The test curves of this embodiment are included, and the test results are shown in Table 1.

[0076] The magnesium-based composite material in this embodiment is based on the Archimedes' method of drainage, utilizing 1×10 -5 Density tests were performed using an analytical balance with g-precision precision, and the results are shown in Table 1.

[0077] Example 3

[0078] A magnesium-based composite material with a controllable coefficient of thermal expansion comprises a negative thermal expansion reinforcement Zn₂P₂O₇ and a magnesium matrix WE43 magnesium alloy (Mg-4%Y-3.3%RE(Nd,Gd)-0.5Zr%), wherein the volume percentage α of the negative thermal expansion reinforcement is 25 vol.%, and the balance is the magnesium matrix. The chemical composition of the WE43 magnesium alloy, by mass percentage, is: 4.0%Y, 3.3%RE, 0.5Zr%, and the balance is Mg, wherein RE is a Nd-rich Nd and Gd mixed heavy rare earth element.

[0079] A method for preparing the above-mentioned magnesium-based composite material with controllable thermal expansion coefficient includes the following steps:

[0080] Step S1: Convert the volume fraction of the magnesium-based composite material to be prepared into weight, and weigh the negative thermal expansion reinforcement powder and magnesium matrix powder accordingly.

[0081] The volume of the prefabricated magnesium-based composite material is 0.374 cm³. 3 Weigh out 0.393g of negative thermal expansion reinforced Zn2P2O7 powder and 0.519g of magnesium matrix WE43 magnesium alloy powder. The average particle size of Zn2P2O7 powder is 50μm, and the average particle size of WE43 magnesium alloy powder is 30μm.

[0082] Step S2: Mix the two powders weighed in step S1 evenly to obtain composite powder;

[0083] Step S3: Load the composite powder from step S2 into a sintering mold and move it into the furnace. Adjust the furnace environment, keep it warm or apply pressure to carry out solid-phase sintering, cool it with the furnace, and take it out at room temperature to obtain the magnesium-based composite material.

[0084] Solid-state sintering was carried out in a spark plasma furnace at a depth of 1×10⁻⁶. -3 The sintering environment was in a vacuum of 50 MPa, and the sintering mold used was a cylindrical graphite mold with an inner diameter of 12.6 mm. The pressure applied during the sintering process was 50 MPa, the heating rate was 100 °C / min, the temperature was 450 °C, and the holding time was 5 min.

[0085] XRD tests were performed on the magnesium-based composite material of this embodiment. Figure 1 This includes the XRD test pattern of the magnesium-based composite material in this embodiment, from... Figure 1 As can be seen, the phase composition of this composite material consists only of the characteristic diffraction peaks of the matrix WE43 magnesium and the negative thermal expansion phase Zn2P2O7, with no newly generated impurity phases detected. This result is attributed to the advantages of the rapid heating-short holding-rapid cooling process of spark plasma sintering.

[0086] The coefficient of thermal expansion of the magnesium-based composite material in this embodiment was tested using a linear thermal dilatometer. Figure 2 The test curves of this embodiment are included, and the test results are shown in Table 1.

[0087] The magnesium-based composite material in this embodiment is based on the Archimedes' method of drainage, utilizing 1×10 -5 Density tests were performed using an analytical balance with g-precision precision, and the results are shown in Table 1.

[0088] Figure 3 This is a microstructure diagram of the magnesium-based composite material in this embodiment. Figure 3 As can be seen, the negative thermal expansion material Zn2P2O71 is uniformly dispersed in the continuous WE43 magnesium alloy matrix 2. In backscattered imaging mode, no interfacial reaction layer characterizing impurity phases was observed at the particle edges. This phenomenon further confirms that the spark plasma sintering process can effectively suppress interfacial reactions, thereby protecting the structural integrity of the negative thermal expansion material and ensuring its efficient compensation for the high positive thermal expansion coefficient of the magnesium matrix, ultimately achieving the preparation of zero-expansion magnesium-based composite materials.

[0089] Example 4

[0090] A magnesium-based composite material with a controllable coefficient of thermal expansion, comprising a negative thermal expansion reinforcement Zn2P2O7 and a pure magnesium matrix, wherein the volume percentage α of the negative thermal expansion reinforcement is 10 vol.%, and the remainder is the magnesium matrix.

[0091] A method for preparing the above-mentioned magnesium-based composite material with controllable thermal expansion coefficient includes the following steps:

[0092] Step S1: Convert the volume fraction of the magnesium-based composite material to be prepared into weight, and weigh the negative thermal expansion reinforcement powder and magnesium matrix powder accordingly.

[0093] The volume of the prefabricated magnesium-based composite material is 0.374 cm³. 3 Weigh out 0.157g of negative thermal expansion reinforced Zn2P2O7 powder and 0.606g of magnesium matrix pure magnesium powder. The average particle size of Zn2P2O7 powder is 20μm, the average particle size of pure magnesium powder is 30μm, and the purity of pure magnesium is 99.5wt%.

[0094] Step S2: Mix the two powders weighed in step S1 evenly to obtain composite powder;

[0095] Step S3: Load the composite powder from step S2 into a sintering mold and move it into the furnace. Adjust the furnace environment, keep it warm or apply pressure to carry out solid-phase sintering, cool it with the furnace, and take it out at room temperature to obtain the magnesium-based composite material.

[0096] Solid-state sintering was carried out in a spark plasma furnace at a depth of 1×10⁻⁶. -3 The sintering environment was in a vacuum of 70 MPa, and the sintering mold used was a cylindrical graphite mold with an inner diameter of 12.6 mm. The pressure applied during the sintering process was 70 MPa, the heating rate was 100 °C / min, the temperature was 420 °C, and the holding time was 3 min.

[0097] The coefficient of thermal expansion of the magnesium-based composite material in this embodiment was tested using a linear thermal dilatometer, and the test results are shown in Table 1. The compressive strength of the magnesium-based composite material in this embodiment was tested according to GB / T 7314-2017, and the test results are shown in Table 1.

[0098] The magnesium-based composite material in this embodiment is based on the Archimedes' method of drainage, utilizing 1×10 -5 Density tests were performed using an analytical balance with g-precision precision, and the results are shown in Table 1.

[0099] Example 5

[0100] A magnesium-based composite material with a controllable coefficient of thermal expansion, comprising a negative thermal expansion reinforcement Zn2P2O7 and a pure magnesium matrix, wherein the volume percentage α of the negative thermal expansion reinforcement is 30 vol.%, and the remainder is the magnesium matrix.

[0101] A method for preparing the above-mentioned magnesium-based composite material with controllable thermal expansion coefficient includes the following steps:

[0102] Step S1: Convert the volume fraction of the magnesium-based composite material to be prepared into weight, and weigh the negative thermal expansion reinforcement powder and magnesium matrix powder accordingly.

[0103] The volume of the prefabricated magnesium-based composite material is 0.374 cm³. 3Weigh out 0.471 g of negative thermal expansion reinforced Zn2P2O7 powder and 0.471 g of magnesium matrix pure magnesium powder. The average particle size of Zn2P2O7 powder is 20 μm, the average particle size of pure magnesium powder is 30 μm, and the purity of pure magnesium is 99.5 wt%.

[0104] Step S2: Mix the two powders weighed in step S1 evenly to obtain composite powder;

[0105] Step S3: Load the composite powder from step S2 into a sintering mold and move it into the furnace. Adjust the furnace environment, keep it warm or apply pressure to carry out solid-phase sintering, cool it with the furnace, and take it out at room temperature to obtain the magnesium-based composite material.

[0106] Solid-state sintering was carried out in a spark plasma furnace at a depth of 1×10⁻⁶. -3 The sintering environment was in a vacuum of 70 MPa, and the sintering mold used was a cylindrical graphite mold with an inner diameter of 12.6 mm. The pressure applied during the sintering process was 70 MPa, the heating rate was 100 °C / min, the temperature was 420 °C, and the holding time was 3 min.

[0107] The coefficient of thermal expansion of the magnesium-based composite material in this embodiment was tested using a linear thermal dilatometer, and the test results are shown in Table 1. The compressive strength of the magnesium-based composite material in this embodiment was tested according to GB / T 7314-2017, and the test results are shown in Table 1.

[0108] The magnesium-based composite material in this embodiment is based on the Archimedes' method of drainage, utilizing 1×10 -5 Density tests were performed using an analytical balance with g-precision precision, and the results are shown in Table 1.

[0109] Table 1. Properties of magnesium-based composite materials in Examples 1-5

[0110]

[0111] As shown in Table 1, firstly, the coefficients of thermal expansion of the magnesium-based composites in Examples 1-5 are all lower than those of the magnesium matrix. Furthermore, the coefficients of thermal expansion decrease further with increasing volume content of the negative thermal expansion reinforcement. In Example 3, with the addition of 25 vol.% of the negative thermal expansion reinforcement, the coefficient of thermal expansion is 0.468 ppm / ℃, achieving zero expansion. This fully demonstrates that the present invention, through the proportioning design of the negative thermal expansion reinforcement and the magnesium matrix, can achieve orderly and controllable expansion of the magnesium-based composite material from low to zero. Secondly, the density of the magnesium-based composites in Examples 1-5 increases accordingly with the addition ratio of the negative thermal expansion material, but remains at a low level, all lower than the density of aluminum or aluminum alloys, thus maintaining the inherent low-density characteristics of magnesium or magnesium alloys. Thirdly, the compressive strength of the magnesium-based composites in Examples 4-5 is higher than that of pure magnesium matrix, indicating that the negative expansion material Zn₂P₂O₇ not only reduces the coefficient of thermal expansion but also improves the strength in the pure magnesium matrix. Finally, the coefficients of thermal expansion of the magnesium-based composite materials in Examples 2 and 5 are 11.1 ppm / ℃ and 12.1 ppm / ℃, respectively, which can be precisely matched with structural materials used in aerospace, such as 14-4PH stainless steel (12.5 ppm / ℃), Q235 steel (12.2 ppm / ℃), 18Ni300 steel (12 ppm / ℃), pure iron (11.8 ppm / ℃), 9Cr steel (11.7 ppm / ℃), 45# steel (11.3 ppm / ℃), HTCS130 steel (11.1 ppm / ℃), 410 steel (11 ppm / ℃), GCr15 steel (10.9 ppm / ℃), etc., so that structural components will not suffer from deformation, cracking or other damage due to mismatch in coefficients of thermal expansion.

[0112] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this invention, and these modifications or substitutions should all be covered within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope defined in the claims.

Claims

1. A magnesium-based composite material with a controllable coefficient of thermal expansion, characterized in that, The composite material includes a negative thermal expansion reinforcement and a magnesium matrix. The volume percentage α of the negative thermal expansion reinforcement in the composite material is: 0 < α ≤ 50 vol.%, with the remainder being the magnesium matrix.

2. The composite material according to claim 1, characterized in that, The negative thermal expansion reinforcement is one or more of the following: ceramic materials, intermetallic compounds, and alloys, where the average linear expansion coefficient or volumetric expansion coefficient is negative at t℃ (-150℃ < t < 500℃).

3. The material according to claim 2, characterized in that, The ceramic material is selected from at least one of the following chemical formulas: aα₂O₈, where a represents one or more of the chemical elements Zr, Hf, Sn, Ti, Eu, Er, and Yb, and α represents one or more of the chemical elements W, Mo, and V; bβ₂O₇, where b represents one or more of the chemical elements Zr, Th, and Ce, and β represents one or more of the chemical elements P, Mo, and V; c₂γ₃O₇ 12 In the formula, c represents one or more of the chemical elements Sc, Dy, Y, Er, Yb, and Lu, and γ represents one or more of the chemical elements W and Mo; the chemical formula dδO5, where d represents one or more of the chemical elements Nb and Ta, and δ represents one or more of the chemical elements V and P; the chemical formula eε2P3O 12 In the formula, e represents one or more of the chemical elements Na, K, Nb, Rb, and Cs, and ε represents one or more of the chemical elements Zr, Ti, and Hf; the chemical formula f2ζ2O7, where f represents one or more of the chemical elements Cu, Mn, Fe, Co, Ni, Mg, and Zn, and ζ represents one or more of the chemical elements P and V; the chemical formula g2O(PO4)2, where g represents one or more of the chemical elements U and Th; the chemical formula hθF6, where h represents one or more of the chemical elements Ca, Mn, Fe, Zn, Co, Ni, Mg, Yb, and Ti, and θ represents one or more of the chemical elements Zr, Hf, and Nb; the chemical formula i(CN)2, where i represents one or more of the chemical elements Zn and Cd; the chemical formula jB(CN)4, where j represents one or more of the chemical elements Cu and Ag; chemical formula kτ(CN)6, where k represents one or more of the chemical elements Y, Fe, Ga, Sc, Ti, La, Sm, Ho, Lu, Er, Cs, Rb, Cd, Mn, Co, Ni, and Zn, and τ represents one or more of the chemical elements Fe, Co, Pt, Cd, Ni, Cu, and Zn; chemical formula Mn3lN, where l is one or more of Zn, Cu, Ga, Sn, Si, Ge, and Fe, and compounds formed by partial substitution of the Mn position in chemical formula Mn3lN by any one or two elements V, Cr, Fe, Co, Ni, Cu, and Zn; Zn[Ag(CN)2]2, CaZr4P6O 24 , Si(NCN)2, ReO3, SiO2, Cu2O, Ag2O, ScF3; The intermetallic compound is selected from at least one of the following chemical formulas: Zr y Nb 1-y Fe2, Hf y Nb 1-y Fe2, Hf 1-y Ta y Fe2, Sc 1-y Ti y Fe2, CrTe y Se 1-y LaFe 13-x Si x LaFe 13-x Al x , Mn3Ge, Mn-Co-Ge series, Fe-Mn-Ga series, Ni-Mn-Ga series, RCo2, R2Fe 14 B, R2Fe 17 , RCo3, RFe 12 , R3Fe 29 In the chemical formula, y is any value from 0 to 1, x is any value from 0 to 13, and R is one or more rare earth elements; and intermetallic compounds formed by partially replacing the Fe, Co, or Mn sites in the above chemical formula with any one or two elements selected from Si, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Hf, and Ta. The alloy is selected from at least one of the following element combinations: Fe-Ni, Fe-Pt, Cr-Fe, Ni-Ti, Ti-Nb.

4. The composite material according to claim 1, characterized in that, The magnesium matrix is ​​one or more of magnesium alloys or pure magnesium with a magnesium mass percentage of 50 wt% or more, and the purity of the pure magnesium is 99.0 wt% or more.

5. A method for preparing a magnesium-based composite material with a controllable coefficient of thermal expansion, characterized in that, The method is used to prepare the composite material according to any one of claims 1 to 4, and the method includes the following steps: Step S1: Convert the volume fraction of the magnesium-based composite material to be prepared into weight, and weigh the negative thermal expansion reinforcement powder and magnesium matrix powder accordingly. Step S2: Mix the three powders weighed in step S1 evenly to obtain composite powder; Step S3: Load the composite powder from step S2 into a sintering mold and move it into the furnace. Adjust the furnace environment, heat up, keep warm or keep warm and pressurize to carry out solid-phase sintering, cool with the furnace, and take it out at room temperature to obtain magnesium-based composite material.

6. The method according to claim 5, characterized in that, In step S1, the average particle size of the negative thermal expansion reinforced powder is 0.1~500μm; the average particle size of the magnesium matrix powder is 0.1~500μm.

7. The method according to claim 5, characterized in that, In step S3, the solid-phase sintering is carried out in a spark plasma sintering furnace.

8. The method according to claim 7, characterized in that, The furnace environment in the spark plasma sintering furnace is 1×10⁻⁶. -3 A vacuum environment of ~50 Pa or an atmospheric pressure of 10~1×10 3 Pa is a protective gas among nitrogen, argon, and helium.

9. The method according to claim 7, characterized in that, The heating rate is 50~200℃ / min, the holding temperature is 350~580℃, and the holding time is 1~10min.

10. The method according to claim 7, characterized in that, The applied pressure is 1~150MPa.

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