A method for preparing a carbon-reinforced high-performance magnesium alloy

Abstract

The application discloses a preparation method of carbon-reinforced high-performance magnesium alloy and relates to the technical field of new material preparation of magnesium alloy. The magnesium alloy powder is used as raw material, phenolic resin is uniformly coated on the surface of magnesium alloy powder particles, then the coated magnesium alloy powder is heated to 700 DEG C under the induction of a pulse electric field, the phenolic resin is decomposed and carbonized, and a carbon network structure is formed in the magnesium alloy matrix, the magnesium alloy melt is pressure-formed in a preheated forming mold after heat preservation for 30 minutes, and the carbon-reinforced high-performance magnesium alloy material is obtained.

Description

Technical Field

[0001] This invention relates to the field of magnesium alloy new material preparation technology, and in particular to a method for preparing carbon-reinforced high-performance magnesium alloy materials by heating and melting magnesium alloy powder particles coated with phenolic resin under pulsed electric field induction. Background Technology

[0002] Magnesium alloys are lightweight metallic structural materials with a range of advantages, including high specific strength, high specific stiffness, good electromagnetic shielding, and biocompatibility, making them widely used in aerospace, electronic communications, and life sciences. However, magnesium alloys also have significant drawbacks, namely, relatively low elastic modulus, fatigue strength, and impact values, as well as poor high-temperature performance, which limits their further development and application.

[0003] To address these issues, numerous studies have been conducted. For example, adding ceramic particles such as silicon carbide and titanium carbide to magnesium alloys can improve their strength and stiffness, but this significantly reduces their plasticity, severely altering their metallic properties and characteristics.

[0004] In recent years, methods such as liquid method, solid method, and in-situ method have been used to add graphene to prepare magnesium alloy materials. However, due to the large specific surface area of ​​graphene and its non-wetting and incompatibility with magnesium alloy melt, graphene is extremely difficult to disperse in magnesium alloy. Moreover, graphene and magnesium do not react chemically in the molten state and cannot form a chemical bond, making it difficult for graphene to be uniformly dispersed in magnesium alloy melt. Therefore, it has little effect on improving the performance of magnesium alloy. Summary of the Invention

[0005] To overcome the shortcomings and defects in the current technology for preparing high-performance magnesium alloys, this invention proposes a method for preparing carbon-strengthened high-performance magnesium alloys. This invention uses phenolic resin to coat the surface of magnesium alloy powder particles. The coated magnesium alloy powder is then heated and melted under a pulsed electric field, causing the phenolic resin to decompose and carbonize, forming a carbon network structure within the magnesium alloy powder matrix, thereby improving the various properties of the magnesium alloy. The process steps are as follows:

[0006] (1) The phenolic resin is used to coat the surface of magnesium alloy powder with a particle size of less than 3 mm, and the amount of phenolic resin coating is 1% to 2% of the weight of the magnesium alloy powder;

[0007] (2) The magnesium alloy powder coated with phenolic resin is heated to 700°C or above under the action of a pulsed electric field and kept at that temperature for at least 30 minutes, so that the magnesium alloy is fully melted into a magnesium alloy melt, and the phenolic resin is decomposed and carbonized to form a carbon network structure in the magnesium alloy matrix.

[0008] (3) The magnesium alloy melt is injected into a preheated molding die and pressed into shape;

[0009] The magnesium alloy powder is Mg-Al-Zn, wherein: Al: 3.3%~3.7%, Zn: 0.4%~0.6%;

[0010] The phenolic resin has the following characteristics: hydroxymethyl content 9%–15%, free phenol content ≤1%, moisture content ≤1%, and ash content 0.3%–0.5%.

[0011] The coated magnesium alloy powder of the present invention is prepared by crushing magnesium alloy into powder particles smaller than 3 mm and loading them into a mixer, weighing 500 g of magnesium alloy powder and adding 1.5% phenolic resin, and then stirring for 15 min or more to make the phenolic resin uniformly coat the surface of the magnesium alloy powder particles.

[0012] The method of melting the coated magnesium alloy powder under pulsed electric field induction described in this invention involves loading the coated magnesium alloy powder into a crucible, placing the crucible in an electric furnace, applying a pulsed electric field of 100V / mm to 150V / mm strength to both ends of the crucible, heating the electric furnace to 700℃ at a heating rate of 2℃ / min, and holding the temperature at 700℃ for at least 30min to allow the coated magnesium alloy powder to fully melt into a magnesium alloy melt and form a carbon network structure in its matrix.

[0013] The present invention injects the magnesium alloy melt into a molding die preheated to 400 °C and pressurizes it into a carbon-strengthened high-performance magnesium alloy material, with a molding pressure of 80 MPa.

[0014] The main properties of the carbon-reinforced high-performance magnesium alloy material prepared by this invention are significantly improved compared with those of magnesium alloy materials prepared by traditional methods. Specifically, the elastic modulus is increased by 46%, the yield strength is increased by 53%, and the tensile strength is increased by 37%. Attached Figure Description

[0015] Figure 1 A micrograph is shown after phenolic resin is coated onto the surface of magnesium alloy particles;

[0016] Figure 2 The microstructure formed by rapid cooling after melting of magnesium alloy is shown, in which a carbon network structure is formed in the magnesium alloy matrix. Detailed Implementation

[0017] The present invention will be described in detail below through inventive concept and specific embodiments, but the listed embodiments do not limit other implementations of the present invention.

[0018] This invention addresses a novel research topic in materials and technologies: improving the various properties of magnesium alloys through carbon strengthening technology. The effective results achieved through numerous experiments lie in how to introduce carbon components into the magnesium alloy matrix, ensure their uniform distribution, and form a carbon network structure within the magnesium alloy powder.

[0019] As demonstrated in the heating experiment, there are three heating stages. As the heating temperature increases, the magnesium alloy begins to melt at around 463℃, while the phenolic resin also begins to undergo carbonization and decomposition. In the first stage, from room temperature to 300℃, the physical dehydration of the phenolic resin and the removal of unreacted monomers, hydroxyl groups, and methylene groups are the main processes, with the decomposition products surrounding the surface of the magnesium alloy particles. In the second stage, from 300℃ to 600℃, decarburization and aromatization occur, methylene bonds break, and gases such as CO, CO2, and CH4 are generated. The decarburization products are dispersed into the magnesium alloy melt under the agitation of the decomposition gases. In the third stage, from 600℃ to 1200℃, the magnesium alloy melts, and the conjugated aromatic rings further stack to form a graphite-like microcrystalline structure. The carbon network structure formed by this graphite-like microcrystalline structure effectively improves the various properties of the magnesium alloy.

[0020] Because phenolic resin decomposes stepwise, various charged groups are generated in the magnesium alloy melt before it is completely decomposed and carbonized. Therefore, under the action of a pulsed electric field, these charged groups can migrate directionally, allowing them to be uniformly dispersed in the magnesium alloy melt. Furthermore, unlike graphite, the charged groups also improve the wettability between the phenolic resin decomposition products and the magnesium alloy melt.

[0021] When the temperature rises to 700℃, the conjugated aromatic rings uniformly dispersed in the magnesium alloy melt further stack, and the carbonization process is basically completed, forming a graphite-like microcrystalline structure with a small number of functional groups. This forms a carbon network structure that strengthens the magnesium alloy matrix, laying the foundation for improving the various strength properties of the magnesium alloy material. The temperature is held at 700℃ for at least 30 minutes to fully melt the coated magnesium alloy powder into a magnesium alloy melt. After the holding period, the magnesium alloy melt is injected into a preheated mold at 400℃ and pressurized at a molding pressure of 80 MPa to form a carbon-reinforced high-performance magnesium alloy material.

[0022] Example 1

[0023] Using magnesium-aluminum alloy (Mg-Al-Zn), wherein Al: 3.5% and Zn: 0.5%, and phenolic resin: hydroxymethyl content 12%, free phenol content ≤1%, moisture ≤1%, and ash content 0.3%, as raw materials, the magnesium alloy was pulverized to less than 3mm, and 500g was weighed and loaded into a small mixer. 7.5g of 1.5% phenolic resin was added to the mixer, and the mixture was stirred for 15 minutes to ensure the phenolic resin was evenly coated on the surface of the magnesium alloy powder particles. Figure 1Micrographs are shown of magnesium alloy particles coated with phenolic resin. The phenolic resin-coated magnesium alloy powder was placed in a rectangular corundum crucible, which was then placed in a box furnace. A pulsed electric field of 100 V / mm was applied along the rectangular direction of the crucible at both ends. The furnace was heated to 700°C at a heating rate of 2°C / min and held at this temperature for 30 min to fully melt the magnesium alloy and form a carbon network structure within the molten magnesium. Figure 2 The microstructure formed by rapid cooling after melting of magnesium alloy is shown, revealing a carbon network structure within the magnesium alloy matrix. After holding at the temperature, the molten magnesium alloy is injected into a preheated mold and pressurized for shaping.

[0024] In this embodiment, the molding die has a diameter of 80 mm. The molded body is processed into a cylindrical sample with a diameter of 60 mm and a length of 40 mm. Then, after homogenization and hot extrusion, it is processed into a sample for measuring Young's modulus, yield strength, tensile strength and elongation at break.

[0025] Table 1 shows the measurement results for each embodiment and comparative example. The magnesium alloy powder raw material, heating and melting process, and molding and extrusion conditions for the comparative example samples were the same as in Example 1, except that the magnesium alloy powder used was not coated with phenolic resin and no pulsed electric field was applied during the heating and melting process.

[0026] Table 1 Results of Examples and Comparative Examples

[0027]

[0028] As can be seen from the results in the table, the magnesium alloy samples prepared using this embodiment have significantly improved properties. The Young's modulus, yield strength, and tensile strength are increased by 41%, 50%, and 36%, respectively, compared with magnesium alloys prepared by traditional methods, while the elongation at break is reduced by 36%.

[0029] Example 2

[0030] The phenolic resin raw material, magnesium-aluminum alloy, and heating and melting process used in this embodiment are the same as those in Example 1, except that the amount of phenolic resin coating is changed to 2%. The measurement results are shown in Table 1.

[0031] Compared with the sample with a phenolic resin coating amount of 1.5%, increasing the phenolic resin coating amount to 2% had no significant effect on the Young's modulus, yield strength, tensile strength and elongation at break of the sample.

[0032] Example 3

[0033] The raw materials, heating and melting process, and molding and extrusion conditions used in this embodiment are the same as in Example 1, except that the amount of phenolic resin coating is reduced to 1%. The measurement results are shown in Table 1.

[0034] Compared with the sample with a phenolic resin coating amount of 1.5%, when the phenolic resin coating amount was reduced to 1%, the Young's modulus, yield strength and tensile strength of the magnesium alloy sample decreased slightly, indicating that increasing the phenolic resin coating amount from 1% to 1.5% has a promoting effect on improving the performance of magnesium alloy.

[0035] Example 4

[0036] The raw materials, heating and melting process, and molding and extrusion conditions used in this embodiment are the same as in Example 1, except that the pulse electric field strength is increased to 150V / mm. The measurement results are shown in Table 1.

[0037] As can be seen from the results in the table, when the pulse electric field strength is increased from 100V / mm to 150V / mm, the Young's modulus, yield strength and tensile strength of the magnesium alloy sample increase slightly, but the magnitude is small. This indicates that when the pulse electric field strength is higher than 100V / mm, further increasing the pulse electric field strength has little effect on the properties of the magnesium alloy.

[0038] Example 5

[0039] The raw materials, heating and melting process, and molding and extrusion conditions used in this embodiment are the same as in Example 1, except that the pulse electric field strength is set to 50V / mm. The measurement results are shown in Table 1.

[0040] As can be seen from the table, when the pulsed electric field strength is below 100 V / mm, increasing the pulsed electric field strength has a significant impact on the properties of magnesium alloys, indicating that the pulsed electric field strength is also an important parameter affecting the properties of magnesium alloys. Therefore, designing the pulsed electric field strength in the range of 100 V / mm to 150 V / mm is a reasonable range obtained from experimental data.

[0041] This invention introduces carbon components into a magnesium alloy matrix and melts them through pulsed electric field-induced heating, forming a carbon network structure in the magnesium alloy powder. The carbon-reinforced high-performance magnesium alloy material prepared has significantly improved main properties compared with magnesium alloy materials prepared by traditional methods, such as an increase of 46% in elastic modulus, 53% in yield strength, and 37% in tensile strength, thereby making its application range wider.

[0042] This invention is not limited to the above embodiments. Various modifications and variations can be made without departing from the design concept of this invention, and all such changes and modifications fall within the protection scope of this invention.

Claims

1. A method for preparing carbon-strengthened high-performance magnesium alloy, characterized in that, A phenolic resin coating is applied to the surface of magnesium alloy powder. The coated magnesium alloy powder is then heated and melted under a pulsed electric field, causing the phenolic resin to decompose and carbonize, forming a carbon network structure within the magnesium alloy matrix, thereby improving the various properties of the magnesium alloy. The process steps are as follows: (1) The phenolic resin is used to coat the surface of magnesium alloy powder with a particle size of less than 3 mm, and the amount of phenolic resin coating is 1% to 2% of the weight of the magnesium alloy powder; (2) The magnesium alloy powder coated with phenolic resin is heated to 700°C or above under the action of a pulsed electric field and kept at that temperature for at least 30 minutes, so that the magnesium alloy is fully melted into a magnesium alloy melt, and the phenolic resin is decomposed and carbonized to form a carbon network structure in the magnesium alloy matrix. (3) The magnesium alloy melt is injected into a preheated molding die and pressed into shape; The magnesium alloy powder is Mg-Al-Zn, wherein: Al: 3.3%~3.7%, Zn: 0.4%~0.6%; The phenolic resin has the following characteristics: hydroxymethyl content 9%–15%, free phenol content ≤1%, moisture content ≤1%, and ash content 0.3%–0.5%.

2. The method for preparing carbon-strengthened high-performance magnesium alloy according to claim 1, characterized in that, The coated magnesium alloy powder is prepared by crushing magnesium alloy into powder particles smaller than 3 mm and loading them into a mixer. 500 g of magnesium alloy powder is weighed and 1.5% phenolic resin is added. The mixture is then stirred for 15 minutes or more to ensure that the phenolic resin is evenly coated on the surface of the magnesium alloy powder particles.

3. The method for preparing carbon-strengthened high-performance magnesium alloy according to claim 1, characterized in that, The process of heating and melting the coated magnesium alloy powder under the induction of the pulsed electric field involves loading the coated magnesium alloy powder into a crucible, placing the crucible in an electric furnace, applying a pulsed electric field of strength of 100V / mm to 150V / mm to both ends of the crucible, and heating the electric furnace to 700℃ at a heating rate of 2℃ / min. The temperature is then maintained at 700℃ for at least 30 minutes to allow the coated magnesium alloy powder to fully melt into a magnesium alloy melt and form a carbon network structure in its matrix.

4. The method for preparing carbon-strengthened high-performance magnesium alloy according to claim 1 or 3, characterized in that, The magnesium alloy melt is injected into a molding die preheated to 400 °C and pressurized to form a carbon-reinforced high-performance magnesium alloy material; the molding pressure is 80 MPa.

5. The method for preparing carbon-strengthened high-performance magnesium alloy according to claim 4, characterized in that, The main performance improvements of the carbon-reinforced high-performance magnesium alloy material are as follows: the elastic modulus is increased by 46%, the yield strength by 53%, and the tensile strength by 37%.

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