Nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material and preparation method thereof

Abstract

The invention provides a nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material which comprises an alloy matrix, the alloy matrix comprises Mg, Al and hollow glass microspheres evenly distributed in the alloy matrix, and the volume fraction of the hollow glass microspheres in the composite foam material is 30%-60%. The invention further discloses a method for preparing the nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material. The method comprises the following steps that 1, nickel plating is conducted on the hollow glass microspheres, 2, uniform mixing is conducted, 3, forming and pre-pressing are conducted, 4, spark plasma sintering is conducted, demolding is conducted after cooling, and the composite foam material is obtained. The invention provides a novel composite foam material and a preparation path thereof, and the composite foam material has remarkable technical progress significance and application and popularization value.

Description

Technical Field

[0001] The invention relates to the field of metal-based composite materials, and in particular to a nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material and a preparation method thereof. Background Art

[0002] Metal-based composite foam materials are a new type of structural and functional integrated materials with porous structure, light weight, high strength and outstanding energy absorption capacity. They are widely used in aerospace, rail transportation, automotive cushioning and protection fields.

[0003] Hollow glass microspheres, due to their low density, excellent sphericity, and dimensional stability, are often incorporated as reinforcements into metal-matrix composites. They effectively create closed-cell foam structures and reduce the overall density of the material. However, the interfacial bonding between conventional microspheres and metal powders is poor, and microspheres are prone to falling off, breaking, or interfacial voids during sintering, resulting in poor structural continuity and unstable mechanical properties of the finished product.

[0004] To improve the interfacial bonding between microspheres and substrates, some studies have used electroless plating to deposit metal coatings on the microsphere surfaces, typically nickel. While electroless plating can improve interfacial wettability, it suffers from significant process contamination, poor coating uniformity, difficulty in thickness control, and insufficient adhesion, limiting its application in engineering-scale batch production.

[0005] Magnetron sputtering, a physical vapor deposition technique, offers fast deposition rates, dense coatings, controllable processes, and environmental friendliness, making it suitable for constructing high-quality metal coatings on microparticle surfaces. Depositing a dense nickel layer on the surface of hollow glass microspheres using magnetron sputtering is expected to effectively improve interfacial bonding and stabilize the structural morphology. However, the application of this technique in microsphere-reinforced metal-matrix composite foams is still underdeveloped, and the bonding mechanism between the coating and the substrate and its impact on material properties remain under-researched.

[0006] In terms of sintering densification, conventional hot pressing suffers from slow heating rates, low density, and non-uniform microstructure, making it difficult to achieve rapid densification of microsphere-reinforced composites at relatively low temperatures. Spark plasma sintering (SPS) offers rapid heating, short sintering times, and low-temperature densification. This technology can achieve excellent microstructure uniformity and mechanical properties while minimizing the risk of microsphere breakage, making it a potential sintering process for these materials.

[0007] Therefore, there is an urgent need to develop a preparation method for magnesium-aluminum-based composite foam materials based on the combination of magnetron sputtering nickel-plated hollow microspheres and spark plasma sintering, so as to improve the interface bonding quality of the composite materials, control the uniformity of the pore structure and achieve the synergistic optimization of high density and high performance. Summary of the Invention

[0008] The purpose of the present invention is to provide a nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material and a preparation method thereof. In order to solve the problems of weak interface bonding, structural instability and performance fluctuation existing in the traditional preparation route, a new composite foam material and its preparation route are provided, which has significant technological advancement significance and application promotion value.

[0009] In order to achieve the above object, the present invention provides the following technical solutions: A nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material comprises: an alloy matrix comprising Mg and Al, and hollow glass microspheres uniformly distributed in the alloy matrix, wherein the volume fraction of the hollow glass microspheres in the composite foam material is 30% to 60%, and the overall density range is 1.25 g / cm 3 ~1.60g / cm 3 .

[0010] Furthermore, in the above-mentioned nickel-plated hollow microsphere reinforced magnesium-aluminum based composite foam material, in the alloy matrix, the mass ratio of Mg to Al is 1:1, and the total mass of Mg and Al exceeds 99 wt.%.

[0011] Furthermore, in the above-mentioned nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material, the particle size of the hollow glass microspheres is 5μm to 30μm, and the main components of the hollow glass microspheres include 50 to 90 wt.% SiO2, 5 to 35 wt.% Al2O3, 4 to 10 wt.% K2O, 1 to 5 wt.% CaO and 0 to 12 wt.% B2O3, and the surface of the hollow glass microspheres is covered with a nickel coating with a thickness of 80nm to 120nm.

[0012] Furthermore, in the above-mentioned nickel-plated hollow microspheres reinforced magnesium-aluminum composite foam material, the interface region between the hollow glass microspheres and the alloy matrix forms (Ni,Mg)2SiO4, CaMgSi2O6, Mg2Si and Mg 17 Al 12 Intermetallic reaction phase, wherein the nickel coating reacts with the alloy matrix at the interface to form a (Ni,Mg)2SiO4 metallurgical bonding phase.

[0013] Furthermore, in the above nickel-plated hollow microspheres reinforced magnesium-aluminum based composite foam material, the compressive strength of the composite foam material is 150MPa to 230MPa, and the energy absorption per unit volume is not less than 70MJ / m 3 .

[0014] Also disclosed is a method for preparing the nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material, comprising the following steps: step 1, nickel-plating the hollow glass microspheres, and depositing a nickel coating with a thickness of 80 nm to 120 nm on the surface of the hollow glass microspheres by magnetron sputtering; step 2, uniformly mixing the nickel-plated hollow glass microspheres and magnesium-aluminum alloy powder, and mixing them in a ratio so that the volume fraction of the hollow glass microspheres is 30% to 60%; step 3, forming and pre-pressing, loading the uniformly mixed hollow glass microspheres and magnesium-aluminum alloy powder into a graphite mold and pre-pressing them; step 4, spark plasma sintering, sintering in a vacuum state at 380° C. to 450° C. and 10 MPa to 20 MPa, with a holding time of 20 min to 40 min, and demolding after cooling to obtain the composite foam material.

[0015] Furthermore, in the above-mentioned method for preparing nickel-plated hollow microspheres reinforced magnesium-aluminum-based composite foam material, in step 1, during magnetron sputtering, a multi-target system is used, the sputtering power is 150W to 250W, and the gas pressure is 0.2 to 0.4 Pa. In step 2, before mixing, anhydrous ethanol is added to the hollow glass microspheres and magnesium-aluminum alloy powder, and the mass ratio of the hollow glass microspheres and magnesium-aluminum alloy powder to anhydrous ethanol is 2:1 to 3:1.

[0016] Furthermore, in the above method for preparing nickel-plated hollow microspheres reinforced magnesium-aluminum composite foam material, in step 4, the sintering process is carried out at a vacuum degree not higher than 10 -2 Pa, and a graphite paper insulation layer is laid on the inner wall of the graphite mold and the contact surface of the upper and lower pressure heads.

[0017] Furthermore, in the above-mentioned method for preparing nickel-plated hollow microspheres reinforced magnesium-aluminum-based composite foam material, in step 4, the spark plasma sintering adopts a current control mode, the heating rate is 75°C / min to 90°C / min, and the pressurization rate is 0.5 Pa / h≤5 Pa / h.

[0018] The technical solution of the present invention has the following advantages: improved interface bonding quality, pore structure uniformity and overall mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings and the accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. Among them: Figure 1 This is a scanning electron microscope (SEM) image of the un-nickel-plated microspheres used in the present invention, showing that the microspheres have uniform particle size and good sphericity.

[0020] Figure 2This is a scanning electron microscope (SEM) image of the nickel-plated hollow microspheres prepared in the present invention, showing that the microspheres have uniform particle size and good sphericity.

[0021] Figure 3 This is a cross-sectional SEM image of the overall structure of the composite foam material prepared by the present invention, showing that the nickel-plated hollow microspheres are evenly distributed in the matrix and the pore structure is complete.

[0022] Figure 4 It is an EDS line scan image of the interface area of the composite foam material, reflecting the diffusion and interface reaction behavior of Ni, Mg, and Si elements between the coating and the substrate.

[0023] Figure 5 Quasi-static compressive stress-strain curves at different sintering temperatures when the volume fraction of nickel-plated hollow microspheres is 40%, the volume fraction of magnesium-aluminum composite foam material is 60%, the sintering pressure is 10 MPa, and other parameters are the same as those in Example 1.

[0024] Figure 6 Quasi-static compressive stress-strain curves at different sintering temperatures when the volume fraction of nickel-plated hollow microspheres is 40%, the volume fraction of magnesium-aluminum composite foam material is 60%, the sintering pressure is 15 MPa, and other parameters are the same as those in Example 1.

[0025] Figure 7 Quasi-static compressive stress-strain curves at different sintering temperatures when the volume fraction of nickel-plated hollow microspheres is 40%, the volume fraction of magnesium-aluminum composite foam material is 60%, the sintering pressure is 20 MPa, and other parameters are the same as those in Example 1.

[0026] Figure 8 This is the CT scanning slice microstructure of the composite foam material obtained in Example 1.

[0027] Figure 9 The density comparison of composite foam materials obtained under different sintering temperatures and pressures is performed with the volume fraction of nickel-plated hollow microspheres being 40%, the volume fraction of magnesium-aluminum-based composite foam material being 60%, and other parameters being the same as those in Example 1.

[0028] Figure 10 The present invention compares the compressive strength trends of composite foam materials obtained under different sintering temperatures and pressures, with the volume fraction of nickel-plated hollow microspheres being 40% and the volume fraction of magnesium-aluminum-based composite foam material being 60%, and other parameters being the same as those in Example 1. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0030] According to an embodiment of the present invention, a nickel-plated hollow microsphere reinforced magnesium-aluminum-based composite foam material is provided, comprising: an alloy matrix comprising Mg and Al, and hollow glass microspheres uniformly distributed in the alloy matrix, wherein the volume fraction of the hollow glass microspheres in the composite foam material is 30% to 60%.

[0031] In the alloy matrix, the mass ratio of Mg to Al is 1:1, the total mass of Mg and Al exceeds 99 wt.%, and the remainder is impurities such as Fe, Mn, Zn, Cl and HCl insolubles.

[0032] The measured density of the magnesium-aluminum alloy powder is 2.1153 g / cm³, and the particle size is 45 μm.

[0033] like Figure 1 As shown, the hollow glass microspheres have a sphericity exceeding 95% and a density of 0.69 g / cm³. The particle size of the hollow glass microspheres ranges from 5μm to 30μm. This particle size range facilitates uniform dispersion of the microspheres during mixing with the magnesium-aluminum alloy powder, reducing the risk of agglomeration and sedimentation. It also effectively controls the breakage rate during sintering, thereby maintaining the integrity of the closed-cell structure. Furthermore, smaller hollow microspheres increase local porosity and effectively disperse stress, while larger particles enhance structural support, thereby optimizing the overall load-bearing properties of the composite material.

[0034] The main components of the hollow glass microspheres include 50-90 wt.% SiO2, 5-35 wt.% Al2O3, 4-10 wt.% K2O, 1-5 wt.% CaO and 0-12 wt.% B2O3, and the surface of the hollow glass microspheres is coated with a nickel coating with a thickness of 80nm to 120nm. Figure 2 As shown, the nickel coating is continuous and dense, evenly covering the surface of the hollow glass microspheres.

[0035] The porosity of the composite foam material is 30% to 60%, and the overall density range is 1.25 g / cm 3 ~1.60g / cm 3 .

[0036] The interface area between the hollow glass microspheres and the alloy matrix forms (Ni, Mg) 2 SiO 4 , CaMgSi 2 O 6 , Mg 2 Si and Mg 2 O 6 during the sintering process. 17 Al 12The nickel coating reacts with the alloy substrate at the interface to form a (Ni, Mg)2SiO4 metallurgical bonding phase, achieving effective interfacial metallurgical bonding. A (Ni, Mg)2SiO4 metallurgical bonding phase is formed between the nickel coating of the hollow microspheres and the alloy substrate. The nickel coating of the composite material forms a transition zone at the interface with the substrate, possessing an intermetallic compound structure and improving interfacial bonding strength.

[0037] The compressive strength of the composite foam material is 150MPa to 230MPa, and the energy absorption per unit volume is not less than 70MJ / m 3 .

[0038] The present invention also discloses a method for preparing a nickel-plated hollow microsphere reinforced magnesium-aluminum based composite foam material, comprising the following steps: Step 1: Nickel-plating the hollow glass microspheres. Step 1.1 Raw Material Preparation: Spherical hollow glass microspheres are selected as the reinforcement phase. The main components of these hollow glass microspheres are SiO2, Na2O, and CaO. The particle size ranges from 5 to 30 μm, and the sphericity is greater than 95%. The matrix powder is a magnesium-aluminum alloy powder with a mass ratio of Mg to Al of 1:1 and a powder particle size of 45 μm.

[0039] Step 1.2 Microsphere pretreatment: The hollow glass microspheres were ultrasonically cleaned in anhydrous ethanol for 30 min to remove impurities and adsorbed particles, and then dried in a constant temperature drying oven at 80°C for 4 h.

[0040] Step 1.3 Nickel plating: A nickel coating with a thickness of 80 nm to 120 nm is deposited on the surface of the hollow glass microspheres by magnetron sputtering.

[0041] In step 1.3, during the magnetron sputtering process, a multi-target structure is used to improve the deposition efficiency, the sputtering power is set to 150W to 250W, and the working gas pressure is controlled at 0.2 to 0.4Pa to ensure the formation of a nickel coating with a dense structure and uniform thickness.

[0042] The nickel plating process is carried out by DC magnetron sputtering. The target material used is a high-purity Ni target with a metal purity of not less than 99.95%. Before sputtering, the chamber is evacuated to a vacuum degree better than 5×10 -3 Pa, and then high-purity argon (purity of 99% to 99.99%) is introduced as the working atmosphere. The working pressure range of magnetron sputtering is stabilized at 0.2 to 0.4 Pa, and the deposition time is controlled between 30 and 60 min to obtain the ideal coating structure and performance.

[0043] Step 2: Mix evenly. The nickel-plated hollow glass microspheres and magnesium-aluminum alloy powder are uniformly mixed in a ratio such that the volume fraction of the hollow glass microspheres is 30% to 60%, preferably 40%.

[0044] In step 2, the hollow glass microspheres and magnesium-aluminum alloy powder are dried before mixing to remove moisture and impurities, preventing defects such as gas inclusions during the subsequent sintering process. Anhydrous ethanol is added to the dried hollow glass microspheres and magnesium-aluminum alloy powder at a mass ratio of 2:1 to 3:1 (total powder mass: ethanol mass) to improve mixing uniformity and effectively inhibit particle agglomeration, thereby enhancing the overall dispersibility of the composite powder. The mixing is performed using a low-speed ball mill at a speed of 200 to 300 rpm for 1 to 2 hours.

[0045] Step 3: Pre-pressing The uniformly mixed hollow glass microspheres and magnesium-aluminum alloy powder were loaded into a graphite mold and pre-pressed. The inside of the graphite mold was lined with graphite paper to prevent reaction and adhesion. The mold diameter was 15 mm and the pre-pressing pressure was set to 5 MPa.

[0046] Step 4, Spark Plasma Sintering (SPS), Sintering under vacuum conditions at 380°C to 450°C, preferably 420°C, 10MPa to 20MPa, preferably 15MPa, with a holding time of 20min to 40min. In step 4, the sintering process is carried out at a vacuum degree not higher than 10 -2 Pa or high purity argon gas conditions, A graphite paper insulation layer is laid on the inner wall of the graphite mold and the contact surface of the upper and lower pressure heads to prevent powder from sticking to the mold, reduce heat loss and improve sintering temperature uniformity.

[0047] In step 4, the spark plasma sintering adopts a current control mode, a heating rate of 75° C. / min to 90° C. / min, and a pressurization rate of 0.5 Pa / h ≤ 5 Pa / h.

[0048] Step 5: demoulding and cooling. The cooling method is furnace cooling, and after sintering, the furnace is cooled to room temperature. After cooling, the mold is demoulded to obtain a composite foam material, so as to avoid thermal stress concentration causing material cracking or microsphere damage.

[0049] The composite foam material was removed, the surface was polished with sandpaper, and the samples were numbered and saved for subsequent performance testing.

[0050] Among them, the nickel plating process parameters in step 1, the moderate pre-pressing in step 3, and the reasonably set temperature, pressure, holding time and other parameters in step 4 work together to ensure that the hollow glass microspheres maintain at least part of their original morphology during the sintering process and do not undergo large-scale cracking, which is beneficial to the stability of the closed-cell structure.

[0051] like Figure 3As shown, the prepared composite foam material exhibits a typical closed-cell structure with uniform pore distribution and no apparent agglomeration of the microspheres within the matrix. The total porosity of the material is controlled between 30% and 60%, and the density is between 1.25 and 1.60 g / cm³. The pore size is primarily derived from the gaps between the unbroken microspheres and the sintered interface.

[0052] During the sintering process, the nickel-plated layer undergoes a metallurgical reaction with the magnesium-aluminum alloy matrix, forming stable intermetallic phases such as (Mg,Ni)2SiO4 and Mg2Ni. This interfacial bonding zone exhibits a continuous transitional structure, avoiding interfacial voids and delamination caused by physical contact. The nickel-plated hollow microspheres exhibit excellent thermal stability within the composite foam structure, with no noticeable flaking or agglomeration of the coating, and the structure remains intact.

[0053] The material exhibits an obvious three-stage compression behavior under quasi-static compression and has good structural energy absorption properties. Figure 10 As shown, the compressive strength of the material is 150-230 MPa, and the energy absorption capacity per unit volume is not less than 80 MJ / m 3 .

[0054] At the same volume fraction, the compressive strength of nickel-plated microsphere-reinforced foams increased by approximately 15% to 25% compared to unplated samples. The thickness of the nickel layer is positively correlated with the degree of interfacial reaction, and proper control of the coating thickness can achieve a balance between improved wettability and metallurgical bonding.

[0055] As the volume fraction increases, the material density gradually decreases and the strength decreases slightly, but the energy absorption capacity still maintains a high level within a certain range.

[0056] Combined with CT scan analysis (such as Figure 8 As shown in Figure 3, the microspheres are highly evenly distributed within the matrix, with no apparent aggregation or accumulation. SEM / EDS observations reveal uniform diffusion of Ni at the interface, while Mg and Si interact to form a stable bonding zone.

[0057] The micro-fracture morphology shows ductile tearing characteristics, indicating that the interface bonding effectively inhibits the propagation of crack source.

[0058] The process of the present invention has good repeatability, and the fluctuation range of the performance of the obtained material is less than ±5%.

[0059] The method is compatible with other magnesium alloy matrix systems, such as AZ91, AZ31, and ZK60, enabling process versatility and expansion. It can also be applied to different types of hollow microspheres (such as alumina and ceramic microspheres) to replace glass microspheres for structural control.

[0060] The material can be used in engineering fields such as automobile buffer energy absorption components, train anti-collision devices, aerospace structural core materials, and personal protective armor.

[0061] The preparation process does not require binders or fluxes, avoiding the introduction of impurities and making the process environmentally friendly and green. The described preparation pathway can be combined with data-driven optimization methods (such as machine learning models) for performance prediction and process design.

[0062] Example 1, verification of basic low temperature parameter conditions This example uses a 30% volume fraction of nickel-plated hollow glass microspheres (particle size 5-30 μm). A continuous and dense nickel coating approximately 100 nm thick is deposited on the microspheres by magnetron sputtering. The substrate is a 1:1 Mg:Al alloy powder with a particle size of approximately 45 μm. After drying, the powder is wet-mixed with anhydrous ethanol and press-fitted into a 15 mm φ graphite mold.

[0063] The sintering process was carried out by spark plasma sintering (SPS) technology, with the temperature set at 380°C, the applied pressure at 10 MPa, and the vacuum degree at less than 10 -2 Pa, heating rate 78℃ / min~83℃ / min, holding temperature 30 min. Samples were demoulded and sampled after cooling in the furnace.

[0064] Scanning electron microscopy (SEM) observations of the material revealed an intact foam structure, with the microspheres maintaining a substantially spherical morphology and good interfacial bonding. No large-scale voids or microsphere shedding were observed. Energy dispersive spectroscopy (EDS) line scans revealed a tendency for Ni to diffuse into the matrix at the interface, with the bonding zone exhibiting a continuous transition.

[0065] The density of the material was measured to be 1.45 g / cm 3 The quasi-static compression test shows that the material compressive strength is 165.27 MPa and the energy absorption per unit volume is 72.3 MJ / m 3 , showing a three-stage compression behavior and a stable platform area, indicating that the material has good structural and mechanical properties under basic process conditions.

[0066] Example 2, Optimal Process Window Verification Based on Example 1, the microsphere volume fraction was increased to 40%, the nickel coating thickness was maintained at 120 nm, and other mixing and ball milling methods were the same. The SPS sintering temperature was set to 420°C, the pressure was adjusted to 15 MPa, and the other parameters remained the same.

[0067] SEM images show uniform distribution of hollow microspheres within the material, with a low sphere breakage rate. At the interface, the coating is continuously embedded in the matrix, forming a metallurgical bond. EDS analysis reveals a mixed diffusion zone of Ni, Mg, and Si at the interface. X-ray diffraction (XRD) analysis confirms the formation of (Mg, Ni)₂SiO₄, demonstrating a clear interface bonding mechanism.

[0068] The material density was measured to be 1.39 g / cm 3 Compression tests show that the compressive strength is increased to 191.98 MPa and the energy absorption per unit volume is 84.7 MJ / m 3 The ductility of the curved platform area is good, and the fracture observation shows obvious tearing characteristics, and the bonding layer is continuous without peeling.

[0069] The comprehensive structural observation and performance results show that the SPS sintering temperature is 420℃ and the pressure is 15 MPa, the material microstructure integrity and interface bonding state are optimal, which is the preferred process window parameter of the present invention.

[0070] Example 3: Verification of medium-high temperature and medium pressure conditions Based on Example 2, the volume fraction of the hollow glass microspheres was increased to 50%, and the nickel coating thickness was set to 110 nm. The SPS sintering temperature was set to 400°C, the applied pressure was adjusted to 15 MPa, the heating rate was 75°C / min, and the holding time was 30 min. Other parameters were the same as in Example 1.

[0071] Scanning electron microscopy (SEM) of the material revealed that the hollow glass microspheres were uniformly distributed within the matrix, maintaining good integrity, with no significant large-scale cracking or delamination observed. Energy dispersive spectroscopy (EDS) analysis revealed that at the interface between the nickel coating and the magnesium-aluminum alloy substrate, the Ni, Mg, and Si elements diffused uniformly, forming a stable metallurgical bonding phase (Mg, Ni)2SiO4. XRD results further confirmed the formation of this metallurgical phase.

[0072] The density of the material was measured to be 1.41 g / cm 3 The porosity is about 50%. The compression test results show that the compressive strength reaches 180.45 MPa and the energy absorption per unit volume reaches 79.5 MJ / m 3 The platform area of the compression curve shows good stability and ductility, the fracture characteristics show obvious ductile tearing, and the interface bonding layer is continuous and uniform without obvious defects.

[0073] The results of this example further demonstrate that appropriately increasing the volume fraction (50%) and adopting medium-high temperature and medium pressure (400°C, 15 MPa) conditions can achieve an optimal balance between the material's structural stability and comprehensive mechanical properties.

[0074] Figures 5 to 7 (The horizontal axis represents strain, and the vertical axis represents stress) shows the sintering pressure of 10 MPa ( Figure 5 )、15 MPa( Figure 6 ) and 20 MPa ( Figure 7Stress-strain curves of nickel-plated hollow microsphere-reinforced magnesium-aluminum composite foams prepared at different sintering temperatures (380°C, 400°C, 420°C, and 450°C) during quasi-static compression. These curves exhibit a typical three-stage characteristic, including a linear elastic region, a stable plateau region, and a region of rapid densification. Specifically, the following are the characteristics: At a lower temperature (380°C): the platform area of the curve is short and slightly fluctuates, and the material shows a certain brittle failure trend, indicating that the material densification degree is low and the interface bonding is not sufficient; At moderate temperatures (400℃~420℃): the platform area of the curve is wide and relatively stable, reflecting good plasticity and uniform compression deformation. This indicates that under this condition, the interface is tightly bonded, the structure is stable, and the comprehensive mechanical properties are excellent. Under high temperature (450°C) conditions: the material curve shows an obvious compression platform, but then the stress increases rapidly and fluctuates greatly, accompanied by obvious brittle failure characteristics, and local rupture or overreaction occurs on the microspheres and interfaces, reflecting that the slightly high temperature leads to interface instability.

[0075] These results intuitively demonstrate the influence of different sintering parameters on the mechanical properties of the material, and clearly indicate that the sintering parameters proposed in the present invention (especially the conditions of 400℃~420℃ and 15 MPa) can effectively obtain a composite foam material with stable structure and excellent performance.

[0076] Figure 8 The microstructure of the slices of the composite foam material prepared under the conditions of Example 1 obtained by CT scanning is shown, which shows that the microspheres are evenly distributed in the matrix, and no obvious microsphere agglomeration or interface defects are observed. This verifies that the preparation process proposed in the present invention achieves ideal pore structure distribution and microstructural integrity on a macro scale, and effectively improves the overall homogeneity of the material.

[0077] Figure 9 The density comparison chart clearly shows the effect of different sintering temperatures and pressures (380°C to 450°C, 10-20 MPa) on the material density at the same microsphere volume fraction (40% volume fraction of hollow glass microspheres). The results show that: The material density corresponding to the lower sintering temperature (380 °C) is relatively low, indicating that the material has high porosity and insufficient density; When the sintering temperature is increased to around 420℃, the material density is at a medium level, the structure is uniform and dense, and the pore distribution is reasonable; However, when the temperature and pressure are too high (such as 450°C and above 20 MPa), the material density increases significantly, but the structural stability decreases, and the microspheres rupture and interface excessive diffusion are obvious.

[0078] Figure 10(Comparison of compressive strength) shows the Figure 9 The compressive strength change trend of the material under the corresponding conditions, combined with Figure 9 The data reveals: Under the sintering condition of 380℃, the compressive strength is relatively low and the structure is not fully dense; The compressive strength reaches its peak value in the range of 400℃~420℃, indicating that the structure is stable and the interface bonding is good; Under high temperature conditions of 450℃, although the density of the material is improved, the compressive strength decreases instead, indicating that the excessively high temperature and pressure conditions destroy the microsphere structure and interface continuity, resulting in a brittle failure mode.

[0079] comprehensive Figure 9 and Figure 10 From the comparison results, it can be seen that the moderate sintering conditions proposed in the present invention (especially around 420°C and 15 MPa) comprehensively balance the density and mechanical properties, avoid the defects of insufficient densification at low temperature and structural damage at high temperature, and are significantly better than the effects of other parameter combinations, reflecting the scientific nature and superiority of the selection of preparation process parameters of the present invention.

[0080] Comparative Example 1: Verification of interface instability under over-temperature and over-pressure conditions On the basis of Example 2, in order to investigate the effect of sintering temperature and pressure outside the range of the present invention on the interfacial stability of the composite foam material, the SPS sintering temperature in this example was adjusted to 460°C (exceeding the upper limit of the protection range of 450°C), the pressure was increased to 22 MPa (exceeding the upper limit of the protection range of 20 MPa), and the nickel plating layer thickness and mixing process parameters remained the same as in Example 2.

[0081] SEM observations revealed that under these sintering conditions, a large number of hollow glass microspheres exhibited obvious cracking, the nickel coating on the surface of the microspheres exhibited significant shedding and peeling, and cracks, voids, and obvious structural defects occurred in the interface bonding area. EDS elemental analysis further confirmed that excessive diffusion of the Ni element occurred in the interface area, resulting in discontinuous and uneven distribution of the metallurgical bonding phase ((Ni,Mg)2SiO4), which seriously damaged the integrity of the interface structure.

[0082] Further tests showed that under these conditions, the porosity of the material decreased to about 12% and the density increased to about 1.60 g / cm 3 Quasi-static compression tests showed that the compressive strength of the material dropped significantly to about 150 MPa, and the energy absorption per unit volume dropped to about 60 MJ / m 3 The compression curve shows obvious brittle failure characteristics, and the overall toughness and structural stability of the material are significantly reduced.

[0083] This comparative example shows that when the SPS sintering temperature and pressure exceed the preferred ranges defined in the present invention (temperature: 380°C to 450°C, pressure: 10 MPa to 20 MPa), the structural stability and mechanical properties of the nickel-plated hollow microsphere-reinforced magnesium-aluminum-based composite foam material will be significantly reduced, thereby verifying the rationality and necessity of the protection parameter range of the present invention.

[0084] Comparative Example 2: Comparative verification of non-nickel-plated hollow microspheres To verify the effect of nickel plating on interfacial bonding and performance, this example used uncoated hollow glass microspheres (particle size 5-30 μm) at a volume fraction of 40%. These were mixed and milled under the same conditions as a 1:1 Mg:Al matrix powder. The sintering temperature was set at 420°C and the pressure was 15 MPa, using the same process parameters as in Example 2.

[0085] SEM images show that there is a clear gap between the microspheres and the matrix, and the interface lacks a transition layer; some microspheres have peeling, voids, and unsintered bonding areas on their edges. Figure 4 As shown, EDS line scan did not detect the formation of intermetallic compounds, Ni element was missing, and the interface bonding completely relied on physical contact.

[0086] The compressive strength test result was 149.36 MPa, which is much lower than that of the nickel-plated microsphere sample. The compression failure morphology showed a through-break with no tough buffer zone.

[0087] The comparative results show that nickel-plated hollow microspheres not only improve the interface bonding ability, but also stabilize the morphology and structure of the microspheres during the sintering process, effectively enhancing the compressive strength and energy absorption capacity of the composite material, which is an important technical means of the present invention.

[0088] The core innovation of this invention lies in: using magnetron sputtering technology to deposit a dense nickel layer on the surface of hollow glass microspheres, effectively enhancing the interfacial bonding ability with the magnesium-aluminum matrix; combining the spark plasma sintering (SPS) process to control the sintering behavior, achieving the coordinated unity of microsphere structure maintenance and material densification; and finally obtaining a new magnesium-aluminum-based composite foam material with a closed-cell structure, strong interfacial bonding, excellent compressive resistance and high energy absorption capacity.

[0089] The technical route proposed in the present invention is universal and controllable, suitable for the expanded application of different types of metal matrices and reinforced hollow microsphere materials, and has good engineering promotion prospects and industrialization value.

[0090] The material and preparation process described in the present invention have comprehensive advantages such as strong interface bonding, uniform structure, good density, excellent mechanical properties, and batch preparation, and are suitable for the engineering application needs of high-performance porous structure materials.

[0091] Nickel-plated hollow microspheres reinforced magnesium-aluminum based composite foam materials are suitable for high-energy absorption structural components, including automobile anti-collision beams, aviation protection buffer structures, rail vehicle energy-absorbing wall panels and individual protective armor shell structures.

[0092] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A nickel-plated hollow microsphere reinforced magnesium-aluminum based composite foam material, characterized in that: include: an alloy matrix comprising Mg and Al, Hollow glass microspheres uniformly distributed in the alloy matrix, Wherein, the volume fraction of the hollow glass microspheres in the composite foam material is 30% to 60%. The porosity of the composite foam material is 30% to 60%, and the overall density range is 1.25 g / cm 3 ~1.60g / cm 3 .

2. The nickel-plated hollow microsphere reinforced magnesium-aluminum based composite foam material according to claim 1, characterized in that: In the alloy matrix, the mass ratio of Mg to Al is 1:1, and the total mass of Mg and Al exceeds 99 wt.%.

3. The nickel-plated hollow microsphere reinforced magnesium-aluminum based composite foam material according to claim 1, characterized in that: The particle size of the hollow glass microspheres is 5 μm to 30 μm. The main components of the hollow glass microspheres include 50-90 wt.% SiO2, 5-35 wt.% Al2O3, 4-10 wt.% K2O, 1-5 wt.% CaO and 0-12 wt.% B2O3. The surface of the hollow glass microspheres is covered with a nickel coating with a thickness of 80nm to 120nm.

4. The nickel-plated hollow microsphere reinforced magnesium-aluminum based composite foam material according to claim 3, characterized in that: The interface area between the hollow glass microspheres and the alloy matrix forms (Ni, Mg) 2 SiO 4 , CaMgSi 2 O 6 , Mg 2 Si and Mg 2 O 6 during the sintering process. 17 Al 12 Intermetallic reaction phase, The nickel coating reacts with the alloy substrate at the interface to form a (Ni, Mg) 2 SiO 4 metallurgical bonding phase.

5. The nickel-plated hollow microsphere reinforced magnesium-aluminum based composite foam material according to claim 1, characterized in that: The compressive strength of the composite foam material is 150MPa to 230MPa, and the energy absorption per unit volume is not less than 70MJ / m 3 .

6. A method for preparing the nickel-plated hollow microsphere reinforced magnesium-aluminum based composite foam material according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Nickel-plating the hollow glass microspheres. A nickel coating with a thickness of 80 nm to 120 nm is deposited on the surface of the hollow glass microspheres by magnetron sputtering; Step 2: Mix evenly. The nickel-plated hollow glass microspheres and magnesium-aluminum alloy powder are uniformly mixed in a ratio such that the volume fraction of the hollow glass microspheres is 30% to 60%; Step 3: Pre-pressing The uniformly mixed hollow glass microspheres and magnesium-aluminum alloy powder are placed into a graphite mold and pre-pressed; Step 4, spark plasma sintering, Sintering under vacuum conditions at 380℃~450℃, 10MPa~20MPa, holding time 20min~40min, After cooling, the composite foam material is demoulded.

7. The method for preparing nickel-plated hollow microspheres reinforced magnesium-aluminum based composite foam material according to claim 6, characterized in that: In step 1, during magnetron sputtering, a multi-target system is used, the sputtering power is 150W to 250W, and the gas pressure is 0.2 to 0.4Pa. In step 2, before mixing, anhydrous ethanol is added to the hollow glass microspheres and the magnesium-aluminum alloy powder, and the mass ratio of the hollow glass microspheres and the magnesium-aluminum alloy powder to the anhydrous ethanol is 2:1 to 3:

1.

8. The method for preparing nickel-plated hollow microspheres reinforced magnesium-aluminum based composite foam material according to claim 6, characterized in that: In step 4, the sintering process is carried out at a vacuum degree not higher than 10 -2 Pa, A graphite paper insulation layer is laid on the inner wall of the graphite mold and the contact surface of the upper and lower pressure heads.

9. The method for preparing nickel-plated hollow microspheres reinforced magnesium-aluminum based composite foam material according to any one of claims 7 to 8, characterized in that: In step 4, the spark plasma sintering adopts a current control mode, a heating rate of 75° C. / min to 90° C. / min, and a pressurization rate of 0.5 Pa / h ≤ 5 Pa / h.

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