Structural member, preparation method thereof and electronic equipment

Abstract

The invention provides a preparation method of a structural member. The method comprises the steps that metal raw materials in a first state are obtained, the first state represents a mixed state of a solid state and a liquid state, and the metal raw materials comprise magnesium, aluminum and yttrium; and under the preset technological conditions, the metal raw materials in the first state are formed and cooled, the metal layer in the second state is obtained, the preset technological conditions comprise the vacuum condition, and the metal layer is composed of the metal raw materials.

Description

Technical Field

[0001] The present disclosure relates to the technical field of metal forming, and in particular to a structural component and a preparation method thereof, and an electronic device. Background Art

[0002] As more and more consumers have higher and higher requirements for electronic equipment and consumer electronic products, the requirements for the molding process and surface treatment process of the appearance structural parts of electronic equipment are also getting higher and higher.

[0003] Some electronic equipment structural parts use magnesium alloy thixoforming or extrusion molding combined with a painting process. Due to reasons such as the solidification and reaction of the molten metal, there are more holes in the metal layer. Summary of the invention

[0004] One aspect of the present disclosure provides a method for preparing a structural part, comprising: obtaining a metal raw material in a first state, the first state representing a mixed state of a solid state and a liquid state, the metal raw material comprising magnesium, aluminum and yttrium. Under preset process conditions, the metal raw material in the first state is formed, and cooled to obtain a metal layer in a second state, the preset process conditions including a vacuum condition, and the metal layer is composed of the metal raw material.

[0005] Optionally, obtaining the metal raw material in the first state includes: obtaining the metal raw material in the first state under a preset temperature condition, the preset temperature condition is 605° C.~615° C., so that the liquid phase ratio of the metal raw material is 45%~60%.

[0006] Optionally, the mass fraction of the elements in the metal raw material includes at least one of the following: the mass fraction of aluminum is 8.5% to 9.5%. The mass fraction of yttrium is 0.2% to 0.3%. And / or the metal layer includes an aluminum-magnesium eutectic structure and an yttrium-containing oxide film.

[0007] Optionally, under preset process conditions, forming the metal raw material in the first state includes: evacuating the mold to a vacuum degree of less than or equal to 40 mbar, and injecting the metal raw material in the first state into the evacuated mold.

[0008] Optionally, the preset process conditions further include at least one of injection pressure, injection speed, mold temperature, holding pressure time, and demolding agent concentration. Under the preset process conditions, the metal raw material in the first state is molded and cooled to obtain a metal layer in the second state, and further includes at least one of the following: Inject the metal raw material in the first state into the mold under the condition that the injection pressure is 16.5 MPa to 17 MPa. Inject the metal raw material in the first state into the mold under the condition that the injection speed is 1500 mm / s to 2000 mm / s. Hold the pressure on the metal raw material in the first state under the condition that the mold temperature is 260°C to 300°C. Hold the pressure on the metal raw material in the first state for 0.5 s to 0.7 s. After the metal raw material in the first state is cooled to the metal layer in the second state, demold the metal layer with a demolding agent having a concentration of 1:20 to 1:10.

[0009] Optionally, the structural member preparation method further includes: preparing a protective layer on one side of the metal layer, at least part of the protective layer is a transparent layer, and the yttrium-containing oxide film is located on the side of the metal layer close to the protective layer.

[0010] Optionally, the metal layer includes a first part and a second part in different planes, and the area of the first part is larger than that of the second part. Preparing a protective layer on one side of the metal layer includes: performing oxidation treatment on the surface of the first part to obtain an oxide layer. Spraying an organic coating on the oxide layer to obtain a first protective layer. After performing high-gloss treatment on the surface of the second part, performing electrophoretic treatment on the high-gloss surface to obtain a second protective layer.

[0011] Optionally, after performing high-gloss treatment on the surface of the second part, performing electrophoretic treatment on the high-gloss surface to obtain a second protective layer includes: placing the high-gloss surface as the cathode in the electrophoresis tank. Performing electrophoretic treatment on the high-gloss surface with acrylic resin, wherein the voltage used for the electrophoretic treatment is 48 V to 52 V, and the electrophoretic time is 110 s to 130 s.

[0012] Optionally, the structural member preparation method further includes: performing at least one of polishing and degreasing and wax removal operations on the high-gloss surface. Among them, the components of the polishing paste used for the polishing operation include silicon carbide, stearic acid, dispersant, and methyl silicone oil, and the components of the chemical solution used for the degreasing and wax removal operation include sodium citrate, sodium hydroxide, disodium EDTA, borax, surfactant, and corrosion inhibitor.

[0013] Another aspect of the present disclosure provides an electronic device, including: a structural member, which is a part of the body of the electronic device and is used to fix at least one of a display device and an input device. Among them, the structural member includes at least one of a metal layer and a protective layer provided on one side of the metal layer. The protective layer belongs to the outer surface of the electronic device. The pore diameter of the holes in the metal layer is less than 10 μm, and at least part of the protective layer is a transparent layer. The metal layer is composed of a metal raw material including magnesium, aluminum, and yttrium. Description of the Drawings

[0014] Through the following description of the embodiments of the present disclosure with reference to the drawings, the above and other objects, features, and advantages of the present disclosure will become clearer. In the drawings:

[0015] Figure 1 Schematically shows a flowchart of a method for preparing a structural member according to an embodiment of the present disclosure;

[0016] Figure 2 Schematically shows a flowchart of a method for obtaining a metal raw material in a first state according to an embodiment of the present disclosure;

[0017] Figure 3A 、 Figure 3B 、 Figure 3C 、 Figure 3D Schematically shows a cross-sectional scanning electron microscope image and an appearance comparison diagram of metal layers with different aluminum components according to an embodiment of the present disclosure;

[0018] Figure 4 Schematically shows a flowchart of a method for forming a metal raw material in a first state according to an embodiment of the present disclosure;

[0019] Figure 5 Schematically shows a flowchart of a method for forming a metal raw material in a first state according to another embodiment of the present disclosure;

[0020] Figure 6 Schematically shows a flowchart of a method for preparing a structural member according to another embodiment of the present disclosure;

[0021] Figure 7 Schematically shows a flowchart of a method for preparing a protective layer according to an embodiment of the present disclosure;

[0022] Figure 8 Schematically shows a flowchart of a method for obtaining a second protective layer according to an embodiment of the present disclosure;

[0023] Figure 9 Schematically shows a flowchart of a method for preparing a structural member according to still another embodiment of the present disclosure;

[0024] Figure 10A scanning electron microscope image schematically showing a cross-section of a metal layer and a protective layer of a structural member according to an embodiment of the present disclosure. Detailed implementation manners

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0026] The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0027] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0028] Some block diagrams and / or flowcharts are shown in the accompanying drawings. It should be understood that some blocks or combinations thereof in the block diagrams and / or flowcharts can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when executed by the processor, these instructions can create a device for implementing the functions / operations illustrated in these block diagrams and / or flowcharts.

[0029] Therefore, the technology of the present disclosure can be implemented in the form of hardware and / or software (including firmware, microcode, etc.). In addition, the technology of the present disclosure can take the form of a computer program product on a computer-readable medium storing instructions, which can be used by or in conjunction with an instruction execution system. In the context of the present disclosure, a computer-readable medium can be any medium that can contain, store, transmit, propagate, or transport instructions. For example, a computer-readable medium can include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, components, or propagation media. Specific examples of computer-readable media include: magnetic storage devices such as magnetic tapes or hard disk drives (HDDs); optical storage devices such as compact discs (CD-ROMs); memories such as random access memories (RAMs) or flash memories; and / or wired / wireless communication links.

[0030] Embodiments of the present disclosure provide a method for preparing a structural member for reducing holes in a metal layer. The method for preparing the structural member includes obtaining a metal raw material in a first state, where the first state represents a mixed state of solid and liquid, and the metal raw material includes magnesium, aluminum, and yttrium. Under preset process conditions, the metal raw material in the first state is formed and cooled to obtain a metal layer in a second state. The preset process conditions include a vacuum condition, and the metal layer is composed of an aluminum-magnesium eutectic structure and a yttrium-containing oxide film. By adopting a semi-solid vacuum forming method and combining a magnesium alloy material doped with aluminum and yttrium, while refining the grains of the metal layer, the gas in the forming process is discharged by using a high-vacuum condition, thereby reducing the holes in the prepared metal layer.

[0031] Figure 1 A flowchart of the method for preparing a structural member according to an embodiment of the present disclosure is schematically shown.

[0032] According to an embodiment of the present disclosure, as Figure 1 shown, the method for preparing the structural member of this embodiment includes, for example, operations S110 to S120.

[0033] In operation S110, a metal raw material in a first state is obtained, where the first state represents a mixed state of solid and liquid, and the metal raw material includes magnesium, aluminum, and yttrium.

[0034] In operation S120, under preset process conditions, the metal raw material in the first state is formed and cooled to obtain a metal layer in a second state. The preset process conditions include a vacuum condition, and the metal layer is composed of the metal raw material.

[0035] In some embodiments, magnesium, aluminum, and yttrium can be mixed in a certain proportion and heated to a semi-solid state (i.e., the first state), at which time the metal raw material is in a mixed state of solid and liquid.

[0036] The semi-solid metal raw material can be placed in a vacuum environment (such as a sealed mold), and can be formed under vacuum conditions by a pressure forming device (such as a die-casting machine) to reduce gas residue during the forming process of the semi-solid metal raw material.

[0037] During the semi-solid forming process, the metal raw material has good fluidity, and at the same time, the presence of solid particles can help the gas escape and reduce gas residue. The vacuum environment reduces the gas content in the metal raw material, avoiding the gas being wrapped inside the metal during the forming process to form holes. Under vacuum conditions, the metal raw material has better fluidity, can fill the mold cavity more tightly, and form a dense metal layer. Due to vacuum assistance, the pressure of metal filling is greatly reduced, which is beneficial to improving the mold life and reducing production costs. At the same time, this method is more environmentally friendly, and the impurities and defects in the waste materials and scrapped workpieces generated are significantly lower than those of the traditional scheme, which is more conducive to recycling.

[0038] Table 1 Results of the holes in the metal layer with or without vacuum conditions

[0039]

[0040] As can be seen from Table 1, under the same conditions, when the vacuum degree is, for example, 40 mbr, there are fewer holes in the metal layer of the fabricated structural member, meeting the finished product appearance standard (no visible holes to the naked eye). Under non-vacuum conditions, shrinkage cavities visible to the naked eye are generated in the metal layer.

[0041] Among them, the absence of visible holes to the naked eye can be understood as being based on the general attention and cognition of those of ordinary skill in the art. If those of ordinary skill in the art cannot perceive the hole defects through visual perception without the aid of tools, it can be understood that there are no visible holes to the naked eye in the present application.

[0042] After forming, the metal raw material is cooled to transform it from a semi-solid state to a solid state (the second state), forming a metal layer composed of, for example, an aluminum-magnesium eutectic structure and a yttrium-containing oxide film, etc.

[0043] During the cooling process, the formed aluminum-magnesium eutectic structure (α-Mg + β-Mg 17 Al 12 ) can refine the grains, and thus can fill the microvoids in the metal layer, reducing the formation of holes. The formation process of the eutectic structure is accompanied by uniform solidification, further reducing the probability of hole generation.

[0044] Under the same conditions (such as the vacuum semi-solid forming process, the same process parameters, and the liquid phase ratio of the metal raw material), other metal combinations (such as magnesium-aluminum alloy (without yttrium), magnesium-zinc alloy, magnesium-lithium alloy, etc.) cannot achieve the effect of reducing the holes in the metal layer of the magnesium-aluminum-yttrium alloy.

[0045] For example, magnesium-zinc alloy is prone to thermal cracking tendency during solidification, resulting in cracks and holes in the metal layer. Although the addition of zinc can improve the strength, it will reduce the fluidity and filling ability of the alloy, increasing the hole defects.

[0046] Another example is that although magnesium-lithium alloy has a lower density, it is prone to segregation and hole defects during solidification. Lithium has a high chemical activity and is easy to react with oxygen to form oxides, resulting in more oxidation inclusions and holes in the metal layer.

[0047] After demolding, the metal layer is exposed to air, and yttrium can react with oxygen to form a dense yttrium-containing oxide film. This oxide film covers the surface of the metal layer, effectively preventing external gases (such as oxygen, water vapor, etc.) from further penetrating into the metal interior, thereby reducing pores caused by subsequent oxidation or gas residue. At the same time, the yttrium-containing oxide film has high density and chemical stability, and can fill the microscopic defects (such as tiny pores or cracks, etc.) on the surface of the metal layer, thereby improving the surface quality of the metal layer. The formation process of the oxide film is accompanied by volume expansion, and this expansion can further compress the microscopic voids inside the metal layer, reducing the number and size of pores.

[0048] In this embodiment, through the vacuum semi-solid forming process, combined with the formation of the aluminum-magnesium eutectic structure and the yttrium-containing oxide film, the pore defects in the metal layer are effectively reduced.

[0049] Figure 2 A method flow chart for obtaining a metal raw material in a first state according to an embodiment of the present disclosure is schematically shown.

[0050] According to an embodiment of the present disclosure, as Figure 2 shown, in addition to including the operations S110~S120 described above with reference to Figure 1 description, the method of this embodiment can also obtain the metal raw material in the first state, for example, through the operation S211. For the sake of brevity of description, the description of the operations S110~S120 is omitted here, and subsequent related method embodiments can be analogized in this way and will not be elaborated.

[0051] In the operation S211, the metal raw material in the first state is obtained under a preset temperature condition, and the preset temperature condition can be 605°C~615°C, so that the liquid phase ratio of the metal raw material can be 45%~60%.

[0052] In some embodiments, magnesium, aluminum, and yttrium can be mixed in a certain proportion and heated to 605°C~615°C, such as 605°C, 610°C, 615°C, etc., to make the metal raw material in a semi-solid state (the first state). At this time, the liquid phase ratio of the metal raw material can be controlled at 45%~60%, such as 45%, 50%, 55%, 60%, etc.

[0053] By controlling the temperature of the metal raw material, the ratio of solid and liquid in the metal raw material reaches the best balance, ensuring fluidity and avoiding segregation caused by complete melting. When the liquid phase ratio is 45%~60%, the metal raw material has good fluidity, can fully fill the mold cavity, and reduce pore defects caused by insufficient filling.

[0054] In the semi-solid state, the presence of solid particles can inhibit the flow of liquid metal, avoid compositional segregation caused by density differences of elements such as magnesium, aluminum, and yttrium, thereby improving the uniformity of the metal layer. During the semi-solid forming process, the presence of solid particles can also reduce the shrinkage rate of the metal and reduce pores and cracks caused by shrinkage.

[0055] Transfer the semi-solid metal raw material to a vacuum forming device and perform die-casting under vacuum conditions.

[0056] For example, during the forming process, a pressure device (such as a die-casting machine) can be used to apply pressure to the metal raw material to fill the mold cavity, while the vacuum environment reduces gas residues.

[0057] After forming, the metal raw material can be cooled to room temperature to transform it from the semi-solid state to the solid state (the second state), forming a metal layer composed of an aluminum-magnesium eutectic structure.

[0058] After demolding, the metal layer is exposed to the air, and yttrium can react with oxygen to form a dense yttrium-containing oxide film covering the surface of the metal layer.

[0059] In this embodiment, by heating the metal raw material to 605°C - 615°C and controlling the liquid phase ratio at 45% - 60%, combined with the vacuum semi-solid forming process, the fluidity of the metal raw material can be optimized, compositional segregation and gas residues can be reduced, thereby significantly reducing pore defects in the metal layer. The yttrium-containing oxide film generated after demolding can further protect the surface of the metal layer and fill microscopic defects, ultimately obtaining a high-quality and dense structural part.

[0060] Figures 3A - 3D Schematically shows the cross-sectional scanning electron microscope images and appearance comparison diagrams of metal layers with different aluminum components according to embodiments of the present disclosure.

[0061] According to an embodiment of the present disclosure, the elemental mass fraction ratios of the metal raw material may include at least one of the following: the mass fraction ratio of aluminum may be 8.5% - 9.5%. The mass fraction ratio of yttrium may be 0.2% - 0.3%. And / or the metal layer may include an aluminum-magnesium eutectic structure and a yttrium-containing oxide film.

[0062] In some embodiments, magnesium, aluminum, and yttrium can be mixed in the following mass fraction ratios: the mass fraction ratio of aluminum may be 8.5% - 9.0%, such as 8.5%, 9%, 9.5%, etc., the mass fraction ratio of yttrium may be 0.2% - 0.3%, such as 0.2%, 0.25%, 0.3%, etc., and the rest may be magnesium.

[0063] Exemplarily, the mass fraction ratio of aluminum may be 8.5% - 9.5%.

[0064] The mass fraction of aluminum within this range can promote the formation of the aluminum-magnesium eutectic structure, which has a dense microstructure and can effectively fill the microscopic voids in the metal layer, reducing pore defects. The addition of aluminum can also enhance the strength and corrosion resistance of the metal layer while avoiding an increase in brittleness caused by excessive aluminum content.

[0065] As a trace alloying element, yttrium can refine the grain structure of the metal layer, improving the density and mechanical properties of the metal layer. After demolding, yttrium can react with oxygen to form a dense yttrium-containing oxide film that covers the surface of the metal layer, preventing the infiltration of external gases (such as oxygen, water vapor, etc.) and reducing pores caused by subsequent oxidation or corrosion. The yttrium-containing oxide film has high chemical stability and can significantly improve the oxidation resistance of the metal layer.

[0066] For example, the influence of the aluminum component on the pore structure in the metal layer can be verified in four formulations, as shown in Tables 2, 3, 4, and 5 below, and they respectively correspond to Figures 3A - 3D .

[0067] Table 2 Metal Raw Material Formulation 1

[0068]

[0069] Table 3 Metal Raw Material Formulation 2

[0070]

[0071] Table 4 Metal Raw Material Formulation 3

[0072]

[0073] Table 5 Metal Raw Material Formulation 4

[0074]

[0075] As can be seen from Tables 2, 3, 4, and 5, when the Al content is too low, the fluidity of the material is poor, resulting in more shrinkage cavities and porosity in the base material, as Figure 3A shown. For example, Figure 3A the upper dotted box in represents the external view of the metal layer, and the lower dotted box represents the scanning electron microscope image of the cross-section of the metal layer and the protective layer. Figure 3B , Figure 3C , Figure 3D Similarly. When the Al content is relatively high, the liquid phase ratio is large, causing liquid phase gas entrainment during the forming process. At the same time, during the solidification shrinkage process, local parts of the metal cannot be compensated, resulting in shrinkage cavities, as Figure 3D shown. In the metal layer with a moderate Al content, there are no obvious pores, and the product appearance is good, as Figure 3B and Figure 3C shown.

[0076] It is understandable that, as shown in Table 2, Table 3, Table 4, and Table 5 above, in addition to the above three elements, the metal raw material may also contain other elements or impurities.

[0077] Among them, the addition of manganese (Mn) and silicon (Si) can have a positive impact on the structure and properties of the metal raw material, while Fe, Cu, and Ni may be possible impurity elements.

[0078] Manganese can form fine intermetallic compounds with elements such as aluminum and magnesium (such as Al 6 Mn). These compounds can serve as heterogeneous nucleation sites to refine the grain structure of the metal layer. The refined grain structure can improve the strength and toughness of the metal layer while reducing the pore defects at the grain boundaries.

[0079] In addition, the solid solution strengthening effect of manganese can significantly improve the strength and hardness of the metal layer. The intermetallic compounds formed by manganese and aluminum, magnesium (such as Al 6 Mn) can further strengthen the mechanical properties of the metal layer. Manganese can form stable compounds with impurity elements (such as iron), reducing the adverse effects of impurities on corrosion resistance. The addition of manganese can also improve the oxidation resistance of the metal layer, further enhancing its corrosion resistance. And the addition of manganese can reduce the hot cracking tendency of the metal layer during solidification, reducing cracks and pores caused by thermal stress.

[0080] Silicon can form Mg 2 Si phase with magnesium and aluminum. This phase is evenly distributed in the metal layer and can promote the formation of eutectic structure. The formation of eutectic structure can further improve the compactness of the metal layer, reducing pore defects. Mg 2 Si phase has high hardness and wear resistance, which can improve the wear resistance of the metal layer. And Mg 2 Si phase has high stability at high temperatures, which can improve the high-temperature strength and creep resistance of the metal raw material during the forming process.

[0081] In addition, the addition of silicon can improve the fluidity of the metal raw material, making it easier to fill the mold cavity during the forming process and reducing pore defects caused by insufficient filling. Silicon can also reduce the solidification shrinkage rate of the metal raw material, reducing pores and cracks caused by shrinkage.

[0082] It should be noted that when manganese and silicon are added simultaneously, manganese and silicon can produce a synergistic effect, further optimizing the compactness and mechanical properties of the metal layer, etc.

[0083] The mixed metal raw material can be heated to 605°C to 615°C to make it in a semi-solid state (the first state), and the liquid phase ratio can be controlled at 45% to 60%.

[0084] The semi-solid metal raw material can be transferred to a vacuum forming device, for example, die-casting is carried out under the condition that the vacuum degree ≤ 70 mbar. During the forming process, a pressure device (such as a die-casting machine) can be used to apply pressure to the metal raw material to make it fill the mold cavity, and at the same time, the vacuum environment reduces gas residue.

[0085] After forming, the metal raw material can be cooled to room temperature to change from semi-solid state to solid state (the second state), forming a metal layer composed of an aluminum-magnesium eutectic structure.

[0086] After demolding, the metal layer is exposed to the air, and yttrium can react with oxygen to form a dense yttrium-containing oxide film covering the surface of the metal layer.

[0087] In this embodiment, by controlling the mass fraction ratio of aluminum, for example, 8.5% - 9.5%, and the mass fraction ratio of yttrium, for example, 0.2% - 0.3%, combined with the vacuum semi-solid forming process, the formation of the aluminum-magnesium eutectic structure can be optimized, the grain structure can be refined, and a yttrium-containing oxide film can be generated, thereby reducing the pore defects in the metal layer. This method not only improves the density and mechanical properties of the metal layer, but also enhances its oxidation resistance and corrosion resistance, and finally obtains high-quality structural parts.

[0088] Figure 4 A method flow chart for forming a metal raw material in the first state according to an embodiment of the present disclosure is schematically shown.

[0089] According to an embodiment of the present disclosure, as Figure 4 shown, for example, the metal raw material in the first state can be formed under preset process conditions by operating S421 - S422.

[0090] In operation S421, the mold can be evacuated to a vacuum degree, for example, less than or equal to 40 mbar.

[0091] In operation S422, the metal raw material in the first state can be injected into the evacuated mold.

[0092] In some embodiments, for example, magnesium, aluminum, and yttrium are mixed according to the following mass fraction ratio: the mass fraction ratio of aluminum can be 8.0%, the mass fraction ratio of yttrium can be 0.25%, and the rest can be magnesium.

[0093] The mixed metal raw material can be heated to 610 °C to make it in a semi-solid state (the first state), and the liquid phase ratio can be controlled at 45% - 60%.

[0094] For example, evacuating the forming mold can make the vacuum degree in the mold ≤ 40 mbar (i.e., ≤ 4000 Pa), such as 20 mbar, 30 mbar, 40 mbar, etc., to reduce the gas residue in the mold cavity.

[0095] In industrial production of consumer electronics products, for example, due to reasons such as cost or technology, conditions of ultra-high vacuum (such as less than 100 mbar) are less frequently used for forming structural parts.

[0096] In this embodiment, for example, a high-temperature resistant sealing ring can be added inside the mold structure to provide a sealed vacuum environment for the vacuum thixomolding process, and the vacuum degree can reach 30 mbar to 50 mbar.

[0097] The vacuum environment inside the mold can effectively remove the gas in the cavity, preventing the gas from being wrapped inside the metal during the filling process of the metal raw material to form holes. The vacuum environment reduces the resistance of the gas to the flow of the metal raw material, enabling the metal raw material to fill the mold cavity more smoothly and reducing defects caused by insufficient filling. The vacuum environment also reduces the chance of oxygen contacting the metal raw material, preventing the metal raw material from oxidizing during the forming process, thereby reducing oxide inclusions and holes.

[0098] The semi-solid metal raw material can be injected into the evacuated mold, and a pressure device (such as a die-casting machine) is used to apply pressure to the metal raw material to make it fully fill the mold cavity.

[0099] After forming, the metal raw material can be cooled to room temperature to transform it from a semi-solid state to a solid state (the second state), forming a metal layer composed of an aluminum-magnesium eutectic structure.

[0100] After demolding, the metal layer is exposed to the air, and yttrium can react with oxygen to form a dense yttrium-containing oxide film covering the surface of the metal layer.

[0101] Some relevant experimental result data of this embodiment are shown in Table 6 below.

[0102] Table 6 Results of holes in metal layers with different vacuum degrees

[0103]

[0104] As can be seen from Table 6, under the same conditions, for example, when the vacuum degree is 20 mbr to 40 mbr, there are fewer holes in the metal layer of the prepared structural part, meeting the finished product appearance standard (no visible hole defects to the naked eye).

[0105] This embodiment can significantly reduce gas residue, optimize the fluidity of the metal raw material, and improve the density of the metal layer by evacuating the mold to a vacuum degree of, for example, ≤40 mbar and combining with the semi-solid forming process. The synergistic effect of the aluminum-magnesium eutectic structure and the yttrium-containing oxide film can further reduce hole defects and improve the quality and performance of the metal layer.

[0106] Figure 5 Schematically shows a method flow chart for forming a metal raw material in a first state according to another embodiment of the present disclosure.

[0107] According to an embodiment of the present disclosure, the preset process conditions may further include at least one of injection pressure, injection speed, mold temperature, holding pressure time, and demolding agent concentration. For example, Figure 5 as shown, for example, it is also possible to form the metal raw material in the first state under the preset process conditions by operating at least one of S521 to S525, and cooling to obtain a metal layer in the second state.

[0108] In operation S521, the metal raw material in the first state can be injected into the mold under the condition that the injection pressure is 16.5 MPa to 17 MPa.

[0109] In operation S522, the metal raw material in the first state can be injected into the mold under the condition that the injection speed is 1500 mm / S to 2000 mm / S.

[0110] In operation S523, the metal raw material in the first state can be held under pressure under the condition that the mold temperature is 260 °C to 300 °C.

[0111] In operation S524, the metal raw material in the first state can be held under pressure for 0.5 s to 0.7 s.

[0112] In operation S525, after the metal raw material in the first state is cooled to a metal layer in the second state, a demolding agent with a concentration of 1:20 to 1:10 can be used to demold the metal layer.

[0113] In some embodiments, for example, magnesium, aluminum, yttrium, etc. are mixed in the following mass fraction ratios: the mass fraction of aluminum can be 6.0%, the mass fraction of yttrium can be 0.3%, the mass fraction of manganese can be 0.2%, and the rest can be magnesium.

[0114] The mixed metal raw material can be heated to 605 °C to make it in a semi-solid state (first state), and the liquid phase ratio can be controlled at 45% to 60%.

[0115] The molding mold can be evacuated so that the vacuum degree in the mold is about 20 mbar (i.e., 2000 Pa) to reduce the gas residue in the mold cavity.

[0116] The semi-solid metal raw material can be injected into the mold under the condition that the injection pressure is 16.5 MPa to 17 MPa (such as 16.5 MPa, 17 MPa, etc.).

[0117] Higher injection pressure can enable the metal raw material to fully fill every corner of the mold cavity when injecting into the mold, reducing holes and defects caused by insufficient filling. Under high-pressure conditions, the fluidity of the metal raw material is better, and it can fill the mold cavity more tightly, forming a dense metal layer.

[0118] The metal raw material can be rapidly injected into the mold under the condition that the injection speed is 1500 mm / s - 2000 mm / s (such as 1500 mm / s, 1600 mm / s, 1700 mm / s, 1800 mm / s, 1900 mm / s, 2000 mm / s, etc.), so that the metal raw material fully fills the mold cavity.

[0119] High-speed injection can reduce the heat loss of the metal raw material during the filling process, avoiding the decrease in fluidity caused by temperature reduction. High-speed injection can also reduce the contact time between the metal raw material and the possible gas in the mold cavity, reducing the probability of gas being wrapped inside the metal to form holes.

[0120] Under the condition that the mold temperature is 260°C - 300°C (such as 260°C, 270°C, 280°C, 290°C, 300°C, etc.), the metal raw material injected into the mold can be held under pressure for 0.5 s - 0.7 s (such as 0.5 s, 0.6 s, 0.7 s, etc.), so that the metal raw material fully solidifies in the cavity and reduces shrinkage defects.

[0121] A higher mold temperature can delay the solidification speed of the metal raw material, enabling it to solidify evenly in the cavity and reducing shrinkage holes and cracks caused by rapid cooling. An appropriate mold temperature can also reduce cold shut and flow marks on the surface of the metal layer, improving the surface finish.

[0122] In addition, during the pressure holding process, the metal raw material can continue to fill the voids generated by solidification shrinkage under the action of pressure, reducing shrinkage holes and cracks. Pressure holding can enable the metal raw material to fully solidify in the cavity, forming a dense metal layer.

[0123] The metal raw material can be cooled to room temperature, transforming it from a semi-solid state to a solid state (the second state), forming a metal layer composed of an aluminum-magnesium eutectic structure.

[0124] After the metal layer is cooled to the second state, a mold release agent with a concentration of, for example, 1:20 - 1:10 (such as 1:20, 1:15, 1:10, etc.) can be used to demold the metal layer, enabling the metal layer to be demolded smoothly and with good surface quality.

[0125] An appropriate mold release agent concentration can reduce the friction between the metal layer and the mold, enabling the metal layer to be demolded smoothly and without surface damage. The mold release agent can also prevent the surface of the metal layer from adhering to the mold, reducing surface defects and improving the finish of the metal layer.

[0126] The partial relevant experimental result data of this embodiment are shown in Table 7 below.

[0127] Table 7 Hole Results of Metal Layers with Different Preparation Parameters

[0128]

[0129] As can be seen from Table 7, under parameter conditions such as a vacuum degree of 20 mbr to 40 mbr, an injection pressure of 16.5 MPa to 17 MPa, and an injection temperature (i.e., the temperature of the semi-solid metal raw material) of 605 °C to 615 °C, there are fewer holes in the metal layer of the fabricated structural member, meeting the finished product appearance standard.

[0130] In this embodiment, for example, by controlling the injection pressure, injection speed, mold temperature, holding pressure time, and release agent concentration, combined with the vacuum semi-solid forming process, the filling quality, solidification process, and demolding effect of the metal raw material can be optimized. This method not only reduces hole and shrinkage defects but also improves the density and surface quality of the metal layer, and is applicable to the fabrication of high-performance and low-defect structural members.

[0131] Figure 6 A flowchart of a method for fabricating a structural member according to another embodiment of the present disclosure is schematically shown.

[0132] According to an embodiment of the present disclosure, as Figure 6 shown, the method for fabricating a structural member of this embodiment may further include operation S610.

[0133] In operation S610, a protective layer can be fabricated on one side of the metal layer. At least a part of the protective layer can be a transparent layer, and the yttrium-containing oxide film can be located on the side of the metal layer close to the protective layer.

[0134] In some embodiments, for example, magnesium, aluminum, and yttrium are mixed in the following mass fraction ratios: the mass fraction ratio of aluminum can be 7.0%, the mass fraction ratio of yttrium can be 0.2%, the mass fraction ratio of manganese can be 0.2%, the mass fraction ratio of silicon can be 0.02%, and the rest can be magnesium.

[0135] The mixed metal raw material can be heated to 605 °C to make it in a semi-solid state (the first state), and the liquid phase ratio can be controlled between 45% and 60%.

[0136] The semi-solid metal raw material can be transferred to a vacuum forming device and die-cast under the condition that the vacuum degree can be 40 mbar.

[0137] After forming, the metal raw material can be cooled to room temperature, causing it to transform from a semi-solid state to a solid state (second state), forming a metal layer composed of an aluminum-magnesium eutectic structure.

[0138] A protective layer can be prepared on one side of the metal layer. The protective layer can include at least a partially transparent layer (such as transparent ceramics or transparent polymers, etc.). The yttrium-containing oxide film can be located on the side of the metal layer close to the protective layer as a transition layer between the metal layer and the protective layer.

[0139] The transparent protective layer can display the luster and texture of the metal layer, enhancing the visual effect. The design of the transparent protective layer can make the structural member have both functionality and aesthetics, and can be applicable to fields such as consumer electronics and decorations.

[0140] For example, the material of the transparent layer can be transparent ceramics or transparent polymers. These materials have high light transmittance, wear resistance, and weather resistance, and can effectively protect the metal layer and remain transparent for a long time.

[0141] For example, as a transition layer, the yttrium-containing oxide film can improve the bonding force between the metal layer and the protective layer, preventing the protective layer from peeling off. The yttrium-containing oxide film has high chemical stability and antioxidant properties, can protect the metal layer from corrosion and oxidation, and at the same time reduce the risk of the protective layer being damaged due to the expansion of pore defects in the metal layer, extending the service life of the transparent layer.

[0142] In addition, the surface of the protective layer can also be surface-treated (such as polishing or coating, etc.) to improve the light transmittance and aesthetics of the transparent layer. Through polishing or coating treatment, the light transmittance and surface smoothness of the transparent layer can be further improved, making it more beautiful.

[0143] In this embodiment, for example, by preparing a transparent protective layer on one side of the metal layer and using the yttrium-containing oxide film as a transition layer, not only can the luster and texture inside the metal layer be displayed, enhancing the aesthetics of the product, but also the bonding force between the protective layer and the metal layer can be enhanced, extending the service life of the transparent layer. This method can be applicable to application scenarios with high requirements for aesthetics and durability, such as consumer electronics, decorations, and display devices, etc.

[0144] Figure 7 Schematically shows a flowchart of a method for preparing a protective layer according to an embodiment of the present disclosure.

[0145] According to an embodiment of the present disclosure, the metal layer can include a first part and a second part in different planes. The area of the first part can be larger than the area of the second part. For example, Figure 7 as shown, for example, a protective layer can also be prepared on one side of the metal layer through operations S711~S713.

[0146] In operation S711, the surface of the first part can be oxidized to obtain an oxide layer.

[0147] In operation S712, an organic coating can be sprayed on the oxide layer to obtain a first protective layer.

[0148] In operation S713, for example, after performing a high-gloss treatment on the surface of the second part, an electrophoretic treatment can be carried out on the high-gloss surface to obtain a second protective layer.

[0149] In some embodiments, for example, magnesium, aluminum, yttrium, etc. are mixed in the following mass fraction ratios: the mass fraction ratio of aluminum can be 9.0%, the mass fraction ratio of yttrium can be 0.2%, the mass fraction ratio of silicon can be 0.04%, and the rest can be magnesium.

[0150] The mixed metal raw materials can be heated to 610 °C to make them in a semi-solid state (the first state), and the liquid phase ratio can be controlled between 45% and 60%.

[0151] The semi-solid metal raw materials can be transferred to a vacuum forming device and die-cast under a vacuum condition of, for example, 30 mbar.

[0152] After forming, the metal raw materials can be cooled to room temperature to change from the semi-solid state to the solid state (the second state), forming a metal layer composed of an aluminum-magnesium eutectic structure.

[0153] The first part (the larger area part) of the metal layer can be oxidized to form a dense oxide layer. And an organic coating (such as polyurethane or epoxy resin, etc.) can be sprayed on the oxide layer to form a first protective layer.

[0154] The oxidation treatment can form a dense oxide layer (such as Al 2 O 3 or MgO, etc.) on the metal surface, improving the corrosion resistance and wear resistance of the metal layer. The oxide layer, for example, as a transition layer, can enhance the bonding force between the organic coating and the metal layer and prevent the coating from peeling off.

[0155] The organic coating (such as polyurethane or epoxy resin, etc.) has good weather resistance, wear resistance, and decorative properties, can protect the metal layer and enhance the appearance texture. The organic coating can also be formulated with colors and gloss according to requirements to meet different design needs.

[0156] Performing a high-gloss treatment (such as polishing or laser treatment, etc.) on the second part (the smaller area part) of the metal layer can make its surface reach a high-gloss effect. And an electrophoretic treatment can be carried out on the high-gloss surface to form a second protective layer.

[0157] The high-gloss treatment (such as polishing or laser treatment, etc.) can make the metal surface reach a mirror effect, improving the gloss and aesthetics of the metal layer. The high-gloss surface can reflect light, enhancing the visual attraction of the product.

[0158] Electrophoresis treatment can form a uniform protective layer on the high-gloss surface, improving the corrosion resistance and wear resistance of the metal layer. The electrophoretic coating has high adhesion and uniformity, can cover the microscopic defects of the high-gloss surface, and further improve the surface quality.

[0159] At the same time, through zoning treatment, the most suitable protective layer process can be selected according to the functional requirements of different areas (such as corrosion resistance, wear resistance, aesthetics, etc.) to optimize the overall performance. The organic coating of the first part and the high-efficiency electrophoretic coating of the second part can be combined, which not only meets the practical requirements of the product, but also improves the aesthetics of the product.

[0160] In this embodiment, for example, by performing oxidation treatment and organic coating spraying on the first part of the metal layer, and performing high gloss treatment and electrophoresis treatment on the second part, the corrosion resistance, wear resistance and aesthetics of the metal layer can be improved. This partitioning treatment method not only optimizes the performance of the protective layer, but also makes the structural parts both practical and decorative, and can be applied to application scenarios with high requirements for performance and appearance, such as electronic products, automotive parts and decorative devices.

[0161] Figure 8 A flow chart of a method for obtaining a second protective layer according to an embodiment of the present disclosure is schematically shown.

[0162] According to an embodiment of the present disclosure, for example, after the surface of the second part is subjected to highlight processing, Figure 8 As shown, for example, the high gloss surface may be subjected to electrophoresis treatment through operations S8131-S8132 to obtain a second protective layer.

[0163] In operation S8131, the high gloss surface may be placed in an electrophoresis tank as a cathode.

[0164] In operation S8132, the high gloss surface may be electrophoretically treated with acrylic resin, wherein the voltage used for the electrophoresis treatment may be 48V to 52V, and the electrophoresis time may be 110s to 130s.

[0165] In some embodiments, magnesium, aluminum, and yttrium are mixed in the following mass fraction ratios: the mass fraction of aluminum may be 8.5%, the mass fraction of yttrium may be 0.3%, and the rest may be magnesium.

[0166] The mixed metal raw materials can be heated to 605°C to be in a semi-solid state (first state), and the liquid phase ratio can be controlled at 45% to 60%.

[0167] The semi-solid metal raw material can be transferred to a vacuum forming device and die-casted under a vacuum degree of, for example, 10 mbar.

[0168] After forming, the metal raw material can be cooled to room temperature, causing it to transform from a semi-solid state to a solid state (the second state), forming a metal layer composed of an aluminum-magnesium eutectic structure.

[0169] The first part (the part with a larger area) of the metal layer can be oxidized to form a dense oxide layer. And an organic coating (such as polyurethane or epoxy resin, etc.) can be sprayed on the oxide layer to form a first protective layer.

[0170] The second part (the part with a smaller area) of the metal layer can be subjected to CNC (Computer Numerical Control) high-gloss treatment to make its surface reach a high-gloss effect. And the high-gloss surface can be used as the cathode and placed in an electrophoresis tank. For example, electrophoresis treatment can be carried out using an acrylic resin. The electrophoresis voltage can be 48V - 52V, such as 48V, 49V, 50V, 51V, 52V, etc., and the electrophoresis time can be 110s - 130s, such as 110s, 120s, 130s, etc., to form a uniform second protective layer.

[0171] The electrophoresis voltage is, for example, 48V - 52V, which can ensure the uniformity of the coating while avoiding coating defects (such as pinholes or orange peel phenomena, etc.) caused by too high voltage. The electrophoresis time is, for example, 110s - 130s, which can enable the acrylic resin to be fully deposited on the high-gloss surface to form a protective layer with a moderate thickness and excellent performance.

[0172] In this embodiment, for example, by oxidizing and spraying an organic coating on the first part of the metal layer, and performing high-gloss treatment and electrophoresis treatment on the second part with appropriate materials and parameters, the corrosion resistance, wear resistance, and aesthetics of the metal layer can be improved.

[0173] Figure 9 A flowchart of a method for preparing a structural member according to another embodiment of the present disclosure is schematically shown.

[0174] According to an embodiment of the present disclosure, as Figure 9 shown, the method for preparing a structural member of this embodiment may further include operation S910.

[0175] In operation S910, at least one of polishing and degreasing and wax removal operations can be performed on the high-gloss surface. Among them, the composition of the polishing paste used in the polishing operation may include silicon carbide, stearic acid, dispersant, and methyl silicone oil, and the composition of the chemical solution used in the degreasing and wax removal operation may include sodium citrate, sodium hydroxide, disodium EDTA, borax, surfactant, and corrosion inhibitor.

[0176] In some embodiments, for example, magnesium, aluminum, and yttrium are mixed in the following mass fraction ratios: the mass fraction of aluminum can account for 6.5%, the mass fraction of yttrium can account for 0.3%, and the rest can be magnesium.

[0177] The mixed metal raw materials can be heated to 605 °C to make them in a semi-solid state (the first state), and the liquid phase ratio can be controlled between 45% and 60%.

[0178] The semi-solid metal raw materials can be transferred to a vacuum forming device and die-cast under a vacuum degree of, for example, 20 mbar.

[0179] After forming, the metal raw materials can be cooled to room temperature to change from the semi-solid state to the solid state (the second state), forming a metal layer composed of an aluminum-magnesium eutectic structure.

[0180] The first part (the part with a larger area) of the metal layer can be oxidized to form a dense oxide layer. And an organic coating (such as polyurethane or epoxy resin, etc.) can be sprayed on the oxide layer to form a first protective layer.

[0181] The second part (the part with a smaller area) of the metal layer can be subjected to a high-gloss treatment (such as CNC machining or laser treatment, etc.) to make its surface reach a high-gloss effect. Then, the high-gloss surface can be polished using a polishing paste (the composition includes, for example, silicon carbide, stearic acid, dispersant, and methyl silicone oil, etc.) for polishing to further improve the surface finish. The polished high-gloss surface can also be subjected to a degreasing and dewaxing operation, and the surface can be cleaned using a chemical solution (the composition includes, for example, sodium citrate, sodium hydroxide, disodium EDTA, borax, surfactant, and corrosion inhibitor, etc.) to remove the residual polishing paste and impurities.

[0182] For example, the relevant parameters for degreasing and dewaxing can be: pH 10 - 11, temperature 50 °C - 55 °C, time 5 min.

[0183] The silicon carbide in the polishing paste can be used as an abrasive, which can effectively remove the microscopic protrusions and scratches on the high-gloss surface and further improve the surface finish. Stearic acid and methyl silicone oil can be used as lubricants, which can reduce the frictional heat during the polishing process and prevent surface damage. The dispersant can evenly disperse the components in the polishing paste and improve the consistency of the polishing effect. Through polishing, the roughness of the high-gloss surface is further reduced, the light reflection is more uniform, and a mirror effect is formed.

[0184] At the same time, sodium citrate, sodium hydroxide, and disodium EDTA in the chemical solution for degreasing and dewaxing can effectively dissolve the grease and wax residues in the polishing paste, making the surface clean. Borax and surfactant can enhance the cleaning ability of the chemical solution and remove the tiny particles and impurities on the surface. The corrosion inhibitor can prevent the metal surface from being corroded during the cleaning process and improve the quality of the high-gloss surface.

[0185] The polished high-gloss surface can be subjected to an electrophoresis treatment to form a second protective layer.

[0186] In this embodiment, for example, by subjecting a first portion of the metal layer to oxidation treatment and organic coating spraying, and subjecting a second portion to high-gloss treatment, polishing, degreasing and wax removal, and electrophoresis treatment, the corrosion resistance, wear resistance and aesthetics of the metal layer can be further improved.

[0187] Figure 10 A scanning electron microscope image schematically showing a cross-section of a metal layer and a protective layer of a structural member according to an embodiment of the present disclosure is shown.

[0188] Another aspect of the present disclosure provides a structural member, which can be prepared by the method of any embodiment of the present disclosure, and for example includes at least one of a metal layer 1 and a protective layer 2 provided on one side of the metal layer 1. Among them, the pore diameter in the metal layer 1 is, for example, less than 10 μm, and at least part of the protective layer 2 is a transparent layer. The metal layer 1 is, for example, composed of an aluminum-magnesium eutectic structure and a yttrium-containing oxide film, and the yttrium-containing oxide film is, for example, located on the side of the metal layer 1 close to the protective layer 2.

[0189] In some embodiments, a structural member can be prepared based on the preparation method of the above embodiment. The structural member can include at least one of a metal layer and a protective layer, and for example, it can be a metal layer or a composite layer of a metal layer and a protective layer.

[0190] The metal layer can be composed of an aluminum-magnesium eutectic structure and a yttrium-containing oxide film, as Figure 10 shown, the pore diameter therein can reach less than 10 μm (no obvious pores are seen at this resolution), and it has high density and low defect rate. The yttrium-containing oxide film can be located on the side of the metal layer close to the protective layer and serve as a transition layer between the metal layer and the protective layer.

[0191] The aluminum-magnesium eutectic structure has a dense microstructure, can effectively fill the microvoids in the metal layer, and reduce pore defects. The formation process of the eutectic structure is accompanied by uniform solidification, further reducing the probability of pore generation.

[0192] For example, the pore diameter less than 10 μm indicates that the metal layer has high density, can significantly improve the mechanical properties and durability of the structural member. The small-diameter pores can also reduce stress concentration and improve the fatigue resistance of the structural member.

[0193] The yttrium-containing oxide film can be located on the side of the metal layer close to the protective layer, can improve the bonding force between the metal layer and the protective layer, and prevent the protective layer from peeling off. The yttrium-containing oxide film has high chemical stability and antioxidant property, and can protect the metal layer from corrosion and oxidation.

[0194] The protective layer can be provided on one side of the metal layer, and at least part of the protective layer can be a transparent layer (such as transparent ceramics or transparent polymers, etc.).

[0195] The transparent layer can display the eutectic structure of aluminum and magnesium inside the metal layer and the structure of the yttrium-containing oxide film, enabling the structural component to exhibit metallic luster and texture, and enhancing the visual effect. The transparent layer has high light transmittance, wear resistance, and weather resistance, and can effectively protect the metal layer and remain transparent for a long time.

[0196] For example, through zonal treatment (such as an organic coating in the first part and a high-photoelectrophoretic coating in the second part), the performance of the protective layer can be optimized according to the functional requirements of different regions, meeting both practicality requirements and enhancing aesthetics.

[0197] The structural component can be applied to fields such as consumer electronics (such as mobile phone frames, laptop computer casings, etc.), automotive parts (such as interior and exterior parts like the motor housing of new energy vehicles, support components for the central control display screen, etc.), structural components and decorative devices for 5G communication base stations (such as luxury accessories, home decoration items, etc.), and has both practicality and decorativeness.

[0198] The structural component of this embodiment, for example, is prepared by adopting the method in the above embodiment, and has high density, low defect rate, and excellent aesthetics. The eutectic structure of aluminum and magnesium and the yttrium-containing oxide film in the metal layer improve the mechanical properties and corrosion resistance of the structural component, while the transparent protective layer displays the luster and texture of the metal layer, enhancing the visual effect.

[0199] Another aspect of the present disclosure provides an electronic device, for example, including: a structural component, which can be part of the body of the electronic device and can be used to fix at least one of a display device and an input device. Among them, the structural component can be prepared by adopting the method of any embodiment of the present disclosure, and the structural component can include at least one of a metal layer and a protective layer provided on one side of the metal layer. The protective layer belongs to the outer surface of the electronic device. The pore diameter in the metal layer can be less than 10 μm, and at least part of the protective layer can be a transparent layer. The metal layer can be composed of a metal raw material including magnesium, aluminum, and yttrium.

[0200] In some embodiments, for example, the structural component can be part of the body of the electronic device and is used to fix a display device (such as a screen) and an input device (such as a keyboard or a touchpad, etc.). The structural component can include a metal layer and a protective layer provided on one side of the metal layer, and the protective layer belongs to the outer surface of the electronic device.

[0201] The metal layer can be composed of an eutectic structure of aluminum and magnesium and a yttrium-containing oxide film, the pore diameter therein can be less than 10 μm, and it has high density and low defect rate. The yttrium-containing oxide film can be located on the side of the metal layer close to the protective layer and serve as a transition layer between the metal layer and the protective layer.

[0202] At least a part of the protective layer can be a transparent layer (such as transparent ceramics or transparent polymers, etc.), which can display the luster and texture of the metal layer. The protective layer can be subjected to high-gloss treatment, polishing, degreasing and wax removal, and electrophoresis treatment, with high smoothness and wear resistance, and can resist scratches and abrasions in daily use.

[0203] For example, the electronic device can be a laptop computer. The structural member can be used to fix the display screen and the keyboard, and at the same time can be used as a part of the device's housing. The transparent protective layer can be located on the side surface of the device, displaying the unique structure inside the metal layer, that is, a magnesium alloy workpiece with a high-brightness side wall and non-high-brightness in other areas, improving the appearance texture of the laptop computer. The high-brightness side wall can be prepared by using the method for preparing the structural member of the present disclosure, and other parts can not be used; or all areas can be high-brightness magnesium alloy workpieces.

[0204] The transparent protective layer and the high-gloss surface improve the texture of the electronic device, and thus can improve the market competitiveness of the product. The high-density metal layer and the wear-resistant protective layer can improve the durability of the electronic device and extend its service life. At the same time, the aluminum-magnesium alloy metal layer has a low density, which can realize the lightweight design of the electronic device and improve its portability.

[0205] The electronic device of this embodiment, for example, by using the method for preparing the structural member in the above embodiment, has high density, low defect rate and excellent aesthetics. The aluminum-magnesium eutectic structure and the yttrium-containing oxide film in the metal layer improve the mechanical properties and corrosion resistance of the structural member, while the transparent protective layer displays the luster and texture of the metal layer, improving the visual effect of the device. Such an electronic device has the characteristics of aesthetics, durability and lightweight, and can be applied to consumer electronic products, such as laptop computers, smart phones and tablet computers, etc.

[0206] It can be understood that based on the excellent performance characteristics of the magnesium alloy of the present disclosure (such as high density, low defect rate, lightweight, high strength and corrosion resistance, etc.), in addition to the above-mentioned electronic devices, the magnesium alloy structural members and the corresponding structural member preparation methods of the present disclosure can also be applied in many other fields.

[0207] For example, body structural members in the automotive industry, such as door frames, roof brackets, chassis components, etc., can utilize the lightweight characteristics of magnesium alloy to reduce the weight of the whole vehicle and improve fuel efficiency. Power system components, such as engine mounts, transmission cases, etc., can utilize the high strength and corrosion resistance of magnesium alloy to improve the durability of the components. Interior parts, such as dashboard brackets, seat skeletons, etc., can utilize the high-gloss surface and aesthetics of magnesium alloy to improve the interior decoration texture.

[0208] For another example, fuselage structural components in the aerospace field, such as cabin door frames, wing ribs, brackets, etc., can utilize the lightweight characteristics of magnesium alloys to reduce the weight of the aircraft and improve fuel efficiency. Engine components, such as engine casings, blade brackets, etc., can utilize the high-temperature performance and corrosion resistance of magnesium alloys to improve the reliability of the components.

[0209] For another example, surgical instruments in the medical device field, such as surgical forceps, scissors, etc., can utilize the lightweight and biocompatibility of magnesium alloys to improve the convenience and safety of surgical operations. Implants, such as bone nails, bone plates, etc., can utilize the degradability and biocompatibility of magnesium alloys to reduce the risk of secondary surgery. The outer shells of medical devices, such as the outer shells of CT machines, MRI devices, etc., can utilize the high strength and aesthetics of magnesium alloys to enhance the texture and durability of the devices.

[0210] In some embodiments of the present disclosure, die-castings with an overall high-gloss metal surface can be surface-treated, for example, with reference to the following process flow.

[0211] 1.01 Prepare semi-solid metal raw materials

[0212] Magnesium, aluminum, and yttrium can be mixed in a certain proportion and heated to a semi-solid state, at which time the metal raw material can be in a mixed state of solid and liquid.

[0213] 1.02 Vacuum forming of semi-solid metal raw materials

[0214] The semi-solid metal raw material can be placed in a vacuum environment (such as a sealed mold), and can be formed under vacuum conditions by a pressure forming device (such as a die-casting machine) to reduce gas residues during the forming process of the semi-solid metal raw material.

[0215] 1.03 Cool and demold to obtain a structural component (die-casting)

[0216] After forming, the metal raw material can be cooled to transform it from a semi-solid state to a solid state, forming a metal layer composed of an aluminum-magnesium eutectic structure. After demolding, the metal layer is exposed to the air, and yttrium can react with oxygen to form a dense yttrium-containing oxide film. This oxide film covers the surface of the metal layer and can effectively prevent external gases (such as oxygen, water vapor, etc.) from further penetrating into the metal interior, thereby reducing pores caused by subsequent oxidation or gas residues.

[0217] 1.04 Mechanical high-gloss treatment

[0218] To achieve a high-gloss metal surface for the die-casting, a CNC numerical control center can be used to perform high-speed CNC fine machining on the surface of the die-casting to expose the metal substrate and present good flatness and gloss.

[0219] 1.05 Polishing treatment

[0220] A polishing wheel can be used to polish the surface of die-cast parts to form a high-gloss metal surface. During the polishing process, polishing paste can be used, and the polishing paste can include at least one of vaseline, paraffin wax, and stearic acid.

[0221] 1.06 Wax removal treatment

[0222] A wax remover can be used to perform wax removal treatment on the polished surface.

[0223] 1.07 Heat treatment

[0224] The die-cast parts after polishing can be heat-treated to make the polishing paste that has penetrated into the micropores of the die-cast parts overflow. The heat treatment temperature can be 150°C to 250°C, and the heat treatment holding time can be 10 min to 40 min.

[0225] 1.08 Degreasing treatment

[0226] After heat treatment, various oils and related pollutants, such as oil and dust, are likely to exist on the surface of the die-cast parts. Through degreasing treatment, the surface of the die-cast parts can be further cleaned, and the adhesion and uniformity of the subsequent protective film can be improved.

[0227] 1.09 Preparation of conversion film

[0228] A transparent conversion film can be formed at the high-gloss treatment position as the primer layer of the protective film. Exemplarily, a ceramic conversion film can be formed at the high-gloss treatment position through transparent chemical conversion process.

[0229] 1.10 Preparation of polymer film

[0230] A wet film can be formed at the high-gloss treatment position by spraying or electrophoretic coating, and then it can be dried at 150°C to 200°C to obtain a protective film to protect the high-gloss position. Exemplarily, transparent cathodic electrophoresis can be used, and the workpiece can be used as the cathode for coating. An anodic electrophoretic layer can be deposited on the surface of the transparent chemical conversion film to protect the high-gloss position, so as to obtain the die-cast parts after surface treatment.

[0231] In some embodiments of the present disclosure, die-cast parts with a locally high-gloss metal surface can be surface-treated with reference to the following process flow. At this time, the locally high-gloss metal surface area has a different paint film from other areas.

[0232] 2.01 Preparation of semi-solid metal raw material

[0233] Magnesium, aluminum, and yttrium can be mixed in a certain proportion and heated to a semi-solid state, at which time the metal raw material can be in a mixed state of solid and liquid.

[0234] 2.02 Vacuum forming of semi-solid metal raw material

[0235] The semi-solid metal raw material can be placed in a vacuum environment (such as a sealed mold), and can be formed under vacuum conditions by a pressure forming device (such as a die-casting machine) to reduce gas residue during the forming process of the semi-solid metal raw material.

[0236] 2.03 Cool and demold to obtain a structural part (die-casting)

[0237] After forming, the metal raw material can be cooled to transform it from semi-solid to solid state, forming a metal layer composed of an aluminum-magnesium eutectic structure. After demolding, the metal layer is exposed to the air, and yttrium can react with oxygen to form a dense yttrium-containing oxide film. This oxide film covers the surface of the metal layer and can effectively prevent external gases (such as oxygen, water vapor, etc.) from further penetrating into the metal interior, thereby reducing pores caused by subsequent oxidation or gas residue.

[0238] 2.04 Grinding

[0239] The die-casting can be ground to remove the rough surface, make the surface of the die-casting uniform, and facilitate subsequent processing.

[0240] 2.05 Pretreatment

[0241] The die-casting can be pretreated by a chemical conversion process or a micro-arc oxidation process to remove the oxide film on the surface of the die-casting and form a protective layer on the surface.

[0242] 2.06 Spraying or electrophoretic coating

[0243] The die-casting can be coated by a conventional electrophoretic or spraying process to achieve good protection of the die-casting.

[0244] 2.07 Local pattern processing

[0245] The local surface of the die-casting can be subjected to CNC high-gloss treatment and / or laser processing, and the local area can be polished to form a high-gloss metal surface. A polishing paste can be used during the polishing process, and the polishing paste can include at least one of petrolatum, paraffin wax, and stearic acid.

[0246] 2.08 Dewaxing treatment

[0247] The surface after polishing treatment can be subjected to dewaxing treatment using a dewaxing agent.

[0248] 2.09 Heat treatment

[0249] The die-casting after polishing treatment can be heat-treated to make the polishing paste infiltrated into the micropores of the die-casting overflow. The temperature of the heat treatment can be 150°C to 250°C, and the heat preservation time of the heat treatment can be 10 min to 40 min.

[0250] 2.10 Degreasing treatment

[0251] After heat treatment, various kinds of oils and related pollutants, such as grease and dust, are likely to exist on the surface of die-castings. Through degreasing treatment, the surface of die-castings can be further cleaned, and the adhesion and uniformity of the subsequent protective film can be improved.

[0252] 2.11 Preparation of conversion film

[0253] A transparent conversion film can be formed at the high-gloss treatment position as the primer layer of the protective film. Exemplarily, a ceramic conversion film can be formed at the high-gloss treatment position through transparent chemical conversion process.

[0254] 2.12 Preparation of polymer film

[0255] A wet film can be formed at the high-gloss treatment position by spraying or electrophoretic coating, and then it can be dried at 150°C to 200°C to obtain a protective film for protecting the high-gloss position. Exemplarily, transparent cathodic electrophoresis can be adopted, and the workpiece can be used as the cathode for coating. An anodic electrophoretic layer can be deposited on the surface of the transparent chemical conversion film to protect the high-gloss position, so as to obtain a die-casting with surface treatment.

[0256] In some embodiments of the present disclosure, die-castings with locally high-gloss metal surfaces can also be surface-treated with reference to the following process flow. At this time, the locally high-gloss metal surface area has the same paint film as other areas.

[0257] 3.01 Preparation of semi-solid metal raw material

[0258] Magnesium, aluminum and yttrium can be mixed in a certain proportion and heated to a semi-solid state. At this time, the metal raw material can be in a mixed state of solid and liquid.

[0259] 3.02 Vacuum forming of semi-solid metal raw material

[0260] The semi-solid metal raw material can be placed in a vacuum environment (such as a sealed mold), and can be formed under vacuum conditions by a pressure forming device (such as a die-casting machine) to reduce gas residue during the forming process of the semi-solid metal raw material.

[0261] 3.03 Cooling and demolding to obtain a structural part (die-casting)

[0262] After forming, the metal raw material can be cooled to transform it from a semi-solid state to a solid state, forming a metal layer composed of an aluminum-magnesium eutectic structure. After demolding, the metal layer is exposed to the air, and yttrium can react with oxygen to form a dense yttrium-containing oxide film. This oxide film covers the surface of the metal layer and can effectively prevent external gases (such as oxygen, water vapor, etc.) from further penetrating into the metal interior, thereby reducing pores caused by subsequent oxidation or gas residue.

[0263] 3.04 Grinding

[0264] The die-castings can be ground to remove the rough surface, make the surface of the die-castings uniform, and facilitate subsequent processing.

[0265] 3.05 Polishing

[0266] The surface of the die-castings can be polished using a polishing wheel to form a high-gloss metal surface. A polishing paste can be used during the polishing process, and the polishing paste can include at least one of vaseline, paraffin wax, and stearic acid.

[0267] 3.06 Wax removal treatment

[0268] The surface after polishing treatment can be subjected to wax removal treatment using a wax remover.

[0269] 3.07 Heat treatment

[0270] The die-castings after polishing treatment can be heat-treated to make the polishing paste that has penetrated into the micropores of the die-castings overflow. The temperature of the heat treatment can be 150°C to 250°C, and the heat preservation time of the heat treatment can be 10 min to 40 min.

[0271] 3.08 Local area masking

[0272] The local areas that need to have a high-gloss metal surface can be masked using a UV ink process or a photoresist process.

[0273] Exemplarily, the entire surface of the die-castings can be sprayed with UV ink so that the treated surface of the die-castings is completely covered and wrapped. After baking and surface drying, the ink has non-fluidity. At this time, a film with a mask can be placed on the local area with a high-gloss metal surface, and the whole piece can be placed in an ultraviolet exposure machine. Through UV light irradiation, the ink at the irradiated part undergoes crosslinking and curing, and there is no crosslinking at the unirradiated part. The method of spraying a developing solution can also be used to remove the ink in the uncrosslinked part, exposing the die-casting substrate. The crosslinked pattern ink layer can be retained until the next process section to achieve local area masking of the die-castings.

[0274] 3.09 Overall sandblasting

[0275] The surface of the die-cast part can be sandblasted to obtain a uniformly sandblasted surface. During the sandblasting process, the part without ink protection will be impacted by quartz sand to form a hemispherical rough surface, and finally reach the required roughness inside, such as a surface with a roughness of Ra = 1.2μm. The pattern with ink protection can resist the impact of quartz sand and remain unchanged. Exemplarily, the sandblasting pressure can be 3Mpa - 5Mpa, the sandblasting time can be 2min - 3min, and the sand number can be 180#.

[0276] 3.10 Removal of masking in local areas

[0277] The remaining ink pattern can be removed using an ink remover to expose the underlying high-gloss metal surface.

[0278] 3.11 Degreasing treatment

[0279] Various oils, greases, and related pollutants, such as grease and dust, are likely to exist on the surface of die-cast parts. Through degreasing treatment, the surface of die-cast parts can be further cleaned, and the adhesion and uniformity of the subsequent protective film can be improved.

[0280] 3.12 Preparation of conversion film

[0281] A transparent conversion film can be formed at the high-gloss treatment position as the primer layer of the protective film. Exemplarily, a ceramic conversion film can be formed at the high-gloss treatment position through a transparent chemical conversion process.

[0282] 3.13 Preparation of polymer film

[0283] A wet film can be formed at the high-gloss treatment position by spraying or electrophoretic coating, and then it can be dried at 150°C - 200°C to obtain a protective film to protect the high-gloss position. Exemplarily, transparent cathodic electrophoresis can be used, and the workpiece can be used as the cathode for coating. An anodic electrophoretic layer can be deposited on the surface of the transparent chemical conversion film to protect the high-gloss position, so as to obtain a die-cast part with surface treatment.

[0284] For details not described in the product embodiment part, they are similar to those in the method embodiment part. Please refer to the method embodiment part, and details will not be repeated here.

[0285] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The appended method claims present the elements of various steps in an exemplary order and are not limited to a specific order or hierarchy.

[0286] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., are only references to the directions in the accompanying drawings and are not used to limit the protection scope of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. When it may cause confusion in the understanding of the present disclosure, the conventional structures or configurations will be omitted. And the shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual sizes, proportions, and actual positional relationships.

[0287] In the above detailed description, various features are combined in a single embodiment to simplify the present disclosure. This method of disclosure should not be construed as reflecting an intention that the embodiments of the claimed subject matter require more features than those clearly recited in each claim. On the contrary, as reflected in the appended claims, the present disclosure is in a state of having fewer features than all the features of the disclosed single embodiment. Therefore, the appended claims are hereby expressly incorporated into the detailed description, where each claim stands alone as a separate preferred embodiment of the present disclosure.

[0288] In addition, the terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present disclosure, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. Regarding the term "comprising" used in the specification or claims, the coverage of this word is similar to the term "including", as explained when "including" is used as a transitional word in the claims. Any term "or" used in the specification of the claims is to mean "non-exclusive or".

[0289] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above description is only specific embodiments of the present disclosure and is not used to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A method for preparing a structural part, comprising: Obtaining a metal raw material in a first state, wherein the first state is characterized by a mixed state of solid and liquid, the metal raw material comprising magnesium, aluminum, and yttrium; Under preset process conditions, the metal raw material in the first state is formed and cooled to obtain a metal layer in the second state, the preset process conditions include vacuum conditions, and the metal layer is composed of the metal raw material.

2. The method according to claim 1, wherein: The step of obtaining the metal raw material in the first state comprises: The metal raw material in the first state is obtained under a preset temperature condition, wherein the preset temperature condition is 605° C. to 615° C., so that the liquid phase ratio of the metal raw material is 45% to 60%.

3. The method according to claim 2, wherein: The element mass fraction ratio of the metal raw material includes at least one of the following: The mass fraction of aluminum is 8.5% to 9.5%; The mass fraction of yttrium is 0.2% to 0.3%; and / or The metal layer includes an aluminum-magnesium eutectic structure and an yttrium-containing oxide film.

4. The method according to claim 1, wherein: The step of forming the metal raw material in the first state under the preset process conditions includes: Evacuate the mold to a vacuum degree of less than or equal to 40mbar; The metal raw material in the first state is injected into the vacuumed mold.

5. The method according to claim 4, wherein: The preset process conditions further include at least one of injection pressure, injection speed, mold temperature, holding time and release agent concentration. Under the preset process conditions, the metal raw material in the first state is molded and cooled to obtain a metal layer in the second state, and at least one of the following is also included: Under the condition that the injection pressure is 16.5MPa-17MPa, injecting the metal raw material in the first state into the mold; Injecting the metal raw material in the first state into the mold at an injection speed of 1500 mm / s to 2000 mm / s; Under the condition that the mold temperature is 260° C. to 300° C., the metal raw material in the first state is maintained under pressure; Maintaining the pressure of the metal raw material in the first state for 0.5s to 0.7s; After the metal raw material in the first state is cooled to the metal layer in the second state, the metal layer is demolded using a demoulding agent with a concentration of 1:20 to 1:

10.

6. The method according to claim 1, wherein: The method further comprises: A protective layer is prepared on one side of the metal layer, at least a portion of the protective layer is a transparent layer, and the yttrium-containing oxide film is located on a side of the metal layer close to the protective layer.

7. The method according to claim 6, wherein: The metal layer includes a first part and a second part in different planes, the area of ​​the first part is larger than the area of ​​the second part, and the step of preparing a protective layer on one side of the metal layer includes: performing oxidation treatment on the surface of the first part to obtain an oxide layer; Spraying an organic coating on the oxide layer to obtain a first protective layer; After the surface of the second part is subjected to highlight treatment, the highlight surface is subjected to electrophoresis treatment to obtain a second protective layer.

8. The method according to claim 7, wherein: After the surface of the second part is subjected to highlight treatment, the highlight surface is subjected to electrophoresis treatment to obtain a second protective layer, including: Placing the high gloss surface as a cathode in an electrophoresis tank; The high gloss surface is electrophoretically treated with acrylic resin, wherein the voltage used for the electrophoresis treatment is 48V-52V, and the electrophoresis time is 110s-130s.

9. The method according to claim 7, wherein: The method further comprises: Performing at least one of polishing and degreasing and dewaxing on the high gloss surface; The polishing paste used in the polishing operation includes silicon carbide, stearic acid, dispersant and methyl silicone oil, and the liquid medicine used in the degreasing and dewaxing operation includes sodium citrate, sodium hydroxide, disodium EDTA, borax, surfactant and corrosion inhibitor.

10. An electronic device comprising: A structural member, the structural member is a part constituting a body of the electronic device and is used to fix at least one of a display device and an input device; The structural member includes at least one of a metal layer and a protective layer disposed on one side of the metal layer, the protective layer belongs to the outer surface of the electronic device, the hole diameter in the metal layer is less than 10 μm, and at least part of the protective layer is a transparent layer; The metal layer is composed of metal raw materials including magnesium, aluminum, and yttrium.

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