CN115029596B - Self-assembled nano sheet material for PCB-level shielding case material and preparation method thereof - Google Patents

Self-assembled nano sheet material for PCB-level shielding case material and preparation method thereof Download PDF

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CN115029596B
CN115029596B CN202210708593.1A CN202210708593A CN115029596B CN 115029596 B CN115029596 B CN 115029596B CN 202210708593 A CN202210708593 A CN 202210708593A CN 115029596 B CN115029596 B CN 115029596B
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magnesium
casting
magnesium alloy
pcb
asynchronous rolling
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CN115029596A (en
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冯中学
李同曼
张超
董学懋
徐静
钟莉萍
薛宝帅
赵珊
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Kunming University of Science and Technology
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C23/00—Alloys based on magnesium
    • C22C23/06—Alloys based on magnesium with a rare earth metal as the next major constituent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/20—Controlling or regulating processes or operations for removing cast stock
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/0551—Flake form nanoparticles
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/03—Making non-ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/0213—Electrical arrangements not otherwise provided for
    • H05K1/0216—Reduction of cross-talk, noise or electromagnetic interference
    • H05K1/0218—Reduction of cross-talk, noise or electromagnetic interference by printed shielding conductors, ground planes or power plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention discloses a self-assembled nano sheet material for a PCB-level shielding case material and a preparation method thereof, belonging to the field of composite boards. The invention is based on the growth morphology and orientation characteristics of LPSO/alpha-Mg nano-platelets in Mg-Zn-Y alloy, and the 'soft-hard' mechanical characteristics thereof. And the growth direction is controlled by controlling the heat flow direction, so that the multi-reflection nano lamellar structure is constructed. Meanwhile, asynchronous rolling with high shear stress is introduced, the number of nano sheets and interface area in unit volume are increased, the interface reflection loss of the magnesium alloy is improved, and the high-frequency electromagnetic shielding performance of the magnesium alloy is improved. The material prepared by the method has electromagnetic shielding efficiency of more than 60dB under the frequency band of 30-6000MHz, and has excellent full-frequency electromagnetic shielding performance. The material overcomes the shortages of insufficient high-frequency electromagnetic shielding performance of common PCB-level shielding cover materials such as copper oxide, stainless steel and the like, and has the characteristics of good casting formability, strong feasibility and the like.

Description

Self-assembled nano sheet material for PCB-level shielding case material and preparation method thereof
Technical Field
The invention relates to the technical field of composite boards, in particular to a self-assembled nano sheet material for a PCB-level shielding case material and a preparation method thereof.
Background
The magnetic shield is made of a material for shielding a magnetic field. Magnetic shielding is divided into three cases: magnetostatic shielding, low frequency electromagnetic shielding, and high frequency electromagnetic shielding. Different shielding materials are selected according to different situations in practice. Magnetostatic shielding: in order to concentrate the stray magnetic field on the shield shell, the shield should have as high a permeability as possible. All magnetically soft materials with high magnetic permeability, such as electromagnetic pure iron, spheroidal graphite cast iron, permalloy, silicon steel, soft magnetic ferrite and the like, can be selected in principle. The design is selected according to the magnetic shielding requirement, price, shell strength, processing performance and the like, comprehensively considering; low frequency electromagnetic shielding: besides shielding static magnetic, it also needs to shield the changing electromagnetic field, such as power frequency electromagnetic field. In addition to the high permeability, high conductivity is also required. The ideal material is permalloy, and the large shielding cover is preferably made of electromagnetic pure iron in consideration of price and processing factors. When the nickel content in permalloy is higher than 40%, the permeability and the conductivity are good. In addition, iron-aluminum alloy containing about 15% -16% of aluminum is also a commonly used magnetic screen material; high frequency electromagnetic shielding: the shielding principle is Lenz's law, and the induced electromagnetic field in the shielding cover is applied to counteract external electromagnetic interference, and good conductor is selected to manufacture the shielding cover, such as aluminum, copper, etc.
In recent years, the problem of high-frequency electromagnetic wave harm is endless, and the problems of electromagnetic wave interference and harm to human health exist in both a 5G system and communication equipment which are iterated rapidly. The presence of a Printed Circuit Board (PCB) reduces, among other things, the interference of the electromagnetic field on the internal devices and, on the other hand, the influence of the electromagnetic field of the devices on the outside. At present, the PCB-level shielding cover high-frequency electromagnetic shielding material mainly selects copper foil with better electrical property and radiation-proof shielding property, the electromagnetic shielding property can reach 40-60dB, but the material is increasingly strict in pursuit of high-frequency electromagnetic shielding property in the face of rapid development in the current age.
Therefore, how to prepare a shielding case material with better high-frequency electromagnetic shielding performance is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a self-assembled nano sheet material for a PCB-level shielding case material and a preparation method thereof, aiming at overcoming the defects of the prior art, and solving the problem that the high-frequency electromagnetic shielding performance of the PCB-level shielding case material in the prior art is lower.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a self-assembled nano sheet material for a PCB-level shielding case material, which is Mg 98～99 Zn 0.3～0.6 Y 0.6～1.2 The magnesium alloy comprises the following elements of Mg, zn and Y in a mass ratio of 98-99: 0.3 to 0.6:0.6 to 1.2.
The invention also provides a preparation method of the self-assembled nano sheet material for the PCB-level shielding case material, which comprises the following steps:
1) Under the protective atmosphere, melting magnesium, and then deslagging and purifying to obtain magnesium liquid;
2) In CO 2 And SF (sulfur hexafluoride) 6 Heating the magnesium solution to 750-800 ℃ under the mixed atmosphere, and sequentially adding zinc and Mg-Y intermediate alloy for smelting to obtain mixed solution;
3) Cooling the mixed solution to 700-710 ℃ for casting;
4) Pulling a cast magnesium alloy ingot;
5) And annealing and multi-pass asynchronous rolling deformation treatment are sequentially carried out on the pulled casting blank, so that the material is obtained.
Preferably, the melting temperature of magnesium in the step 1) is 665-685 ℃.
Preferably, the smelting time in the step 2) is 30 to 40 minutes.
Preferably, the cooling rate in the casting process is 20-65 ℃/s, and the casting speed is 80-100 mm/min.
Preferably, the speed of pulling the blank in the step 4) is 5-15 cm/min.
Preferably, the annealing temperature in the step 5) is 760 to 780K, and the annealing time is 4 to 6 hours.
Preferably, the preheating treatment is further performed before the multi-pass asynchronous rolling deformation treatment in the step 5), wherein the preheating temperature is 380-420 ℃, and the preheating time is 10-20 min.
Preferably, the thickness of the magnesium alloy sheet material before the multi-pass asynchronous rolling deformation treatment in the step 5) is 1.0-1.5 mm; the multi-pass asynchronous rolling deformation treatment is three-pass asynchronous rolling deformation treatment; and after the three times of asynchronous rolling deformation treatment, the thickness of the thin plate is reduced to 0.3-0.7 mm.
Preferably, the speed of the asynchronous rolling in the step 5) is 90 to 110mm/s, and the rolling reduction is 18 to 25%.
The beneficial effects of the invention include:
1) The invention selects magnesium alloy with rich resources, easy recovery, high specific strength, specific rigidity and excellent full-frequency electromagnetic shielding performance, and prepares the nano-scale LPSO/alpha-Mg lamellar structure which grows in parallel along the heat flow direction and has good orientation consistency after semi-continuous casting. The high-frequency electromagnetic shielding performance of the material is improved by the synergistic effect of the orientation, thickness and interface combination condition of the nano-scale LPSO/alpha-Mg lamellar structure. In comparison, the magnesium alloy is selected as the high-frequency electromagnetic shielding material of the PCB-level shielding case, so that on one hand, the magnesium mineral resources in China are rich, and the development trend of magnesium in the future is exponentially increased; on the other hand, the nanoscale lamellar structure generated in situ inside the magnesium alloy crystal grains realizes the effective span from the macroscopic scale to the atomic size, and the high-frequency electromagnetic shielding efficiency can reach 60-110dB under the frequency band of 30-6000 MHz.
2) The design of the lamellar structure of the invention selects pure magnesium, pure zinc and intermediate alloy of Mg-25wt% Y as raw materials, and prepares Mg by semi-continuous casting x Zn y Y z Magnesium alloy, wherein the mass ratio of Zn to Y is 1:2. the invention successfully controls the percentage of each element component in the magnesium alloyPreparing Mg 98-99 Zn 0.3-0.6 Y 0.6-1.2 The magnesium alloy has the advantages that a large number of nano-scale lamellar structures which grow in parallel along the heat flow direction and are randomly distributed in the orientation are distributed in the magnesium alloy crystal grains in the component proportion, so that the shape and structure controllability of the self-assembled nano-scale lamellar structure PCB shielding cover material is realized by controlling the components of alloy elements and the proportion design.
3) The nanoscale alpha-Mg/LPSO lamellar structure prepared by the semi-continuous casting method realizes the span from a macroscopic scale to an atomic size, and meets the severe requirements on the performance, the weight, the thickness and the like of the novel PCB-level shielding case high-frequency electromagnetic shielding material. The invention adopts a semi-continuous casting and asynchronous rolling process treatment scheme, and has the characteristics of simple process, low cost and good forming property.
4) The invention increases the rolling pass, the thickness of the material is continuously thinned, the orientation of the nano lamellar structure gradually tends to be consistent, the effective interface layer of the nano LPSO phase and the matrix alpha-Mg is continuously increased, the high-frequency electromagnetic shielding performance of the material is greatly improved, the tensile strength can reach 180-273 Mpa, the elongation rate can reach 2-3%, and the electromagnetic shielding performance can reach 60-110dB (30-6000 MHz).
Drawings
FIG. 1 is Mg after semi-continuous casting obtained in step 5) of example 1 98.5 Zn 0.5 Y 1.0 Magnesium alloy cross-section micro-morphology diagram: (a) a metallographic microstructure; (b) a metallographic microscopic partial magnified view; (c) SEM microstructural map; (d) SEM microscopic structure partial enlarged view.
FIG. 2 is a graph of Mg for the various passes in example 1 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding performance of the alloy under the full frequency band of 30-6000 MHz.
FIG. 3 is Mg for different rolling passes in example 1 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding performance of the alloy is between 30 and 1500MHz frequency band.
FIG. 4 is a graph of Mg for the various passes in example 1 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding performance of the alloy is between 1500 and 4500MHz frequency band.
FIG. 5 is a graph of Mg for the various passes in example 1 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding performance of the alloy is between 4500 and 6000 MHz.
FIG. 6 shows the Mg after three times of asynchronous rolling deformation treatment in example 1 98.5 Zn 0.5 Y 1.0 Tensile strength and elongation graphs of the alloy.
Detailed Description
The invention provides a self-assembled nano sheet material for a PCB-level shielding case material, which is Mg 98～99 Zn 0.3～0.6 Y 0.6～1.2 The magnesium alloy comprises the following elements of Mg, zn and Y in a mass ratio of 98-99: 0.3 to 0.6:0.6 to 1.2.
In the invention, the Mg 98～99 Zn 0.3～0.6 Y 0.6～1.2 The mass ratio of Zn to Y in the magnesium alloy is 1:1.5 to 2.5, preferably 1:1.8 to 2.3, more preferably 1:2.
the invention also provides a preparation method of the self-assembled nano sheet material for the PCB-level shielding case material, which comprises the following steps:
1) Under the protective atmosphere, melting magnesium, and then deslagging and purifying to obtain magnesium liquid;
2) In CO 2 And SF (sulfur hexafluoride) 6 Heating the magnesium solution to 750-800 ℃ under the mixed atmosphere, and sequentially adding zinc and Mg-Y intermediate alloy for smelting to obtain mixed solution;
3) Cooling the mixed solution to 700-710 ℃ for casting;
4) Pulling a cast magnesium alloy ingot;
5) And annealing and multi-pass asynchronous rolling deformation treatment are sequentially carried out on the pulled casting blank, so that the material is obtained.
In the present invention, the melting temperature of magnesium in the step 1) is 665 to 685 ℃, preferably 670 to 680 ℃, and more preferably 672 to 678 ℃.
In the present invention, the protective atmosphere in the step 1) is preferably argon and/or CO 2 。
The proportion of the magnesium, zinc and Mg-Y intermediate alloy in the step 1) is as followsThe mass ratio of Mg, zn and Y elements is 98-99: 0.3 to 0.6:0.6 to 1.2 of Mg 98～99 Zn 0.3～0.6 Y 0.6～1.2 The magnesium alloy is the standard.
In the present invention, the melting time in the step 2) is 30 to 40min, preferably 35min.
In the present invention, step 2) is said CO 2 And SF (sulfur hexafluoride) 6 CO in a mixed atmosphere of (2) 2 The mass fraction of (2) is 0.5 to 1%, preferably 0.6 to 1%, more preferably 0.7 to 0.9%.
In the invention, in the step 2), the temperature of the magnesium solution is raised to 750-800 ℃, zinc and Mg-Y intermediate alloy are sequentially added for smelting, and the temperature after the temperature is raised is preferably 755-790 ℃, and more preferably 760-780 ℃.
The invention lowers the temperature of the mixed solution to 700-710 ℃ for casting, preferably 705-708 ℃.
In the invention, the cooling rate in the casting process is 20-65 ℃/s, preferably 25-60 ℃/s, more preferably 30-55 ℃/s, the casting speed is 80-100 mm/min, preferably 85-98 mm/min, more preferably 88-95 mm/min; the pouring process is cooled in a water cooling mode to ensure that the growth position of the nano lamellar structure is along the heat flow direction, and finally, a large-sized die Cheng Zhuding with the diameter of 260mm and the length of 800-1000 mm is poured.
In the present invention, the speed of pulling the blank in the step 4) is 5 to 15cm/min, preferably 9 to 11cm/min, and more preferably 10cm/min.
In the present invention, the annealing temperature in the step 5) is 760 to 780K, preferably 763 to 778K, more preferably 765 to 775K, and the annealing time is 4 to 6 hours, preferably 4.5 to 5.5 hours, more preferably 5 hours.
In the invention, the nanoscale blocky LPSO phase (18R) at the grain boundary of the magnesium alloy material after the annealing treatment is converted into the nanoscale lamellar LPSO phase (14H).
In the invention, the magnesium alloy is cut into a magnesium alloy sheet with the length and width of 80X 80-100X 100mm and the thickness of 1.0-1.5 mm before the multi-pass asynchronous rolling deformation treatment in the step 5); the length and width are preferably 85×85 to 95×95mm, and more preferably 90×90mm; the thickness is preferably 1.0 to 1.4mm, and more preferably 1.1 to 1.3mm.
In the present invention, the preheating treatment is further performed before the multi-pass asynchronous rolling deformation treatment in the step 5), wherein the preheating temperature is 380-420 ℃, preferably 390-410 ℃, further preferably 395-405 ℃, and the time is 10-20 min, preferably 12-18 min, further preferably 14-16 min.
In the invention, the thickness of the magnesium alloy sheet material before the multi-pass asynchronous rolling deformation treatment in the step 5) is 1.0-1.5 mm, preferably 1.0-1.4 mm, and more preferably 1.1-1.3 mm; the multi-pass asynchronous rolling deformation treatment is performed in three times, and the thickness of the thin plate is reduced to 0.3-0.7 mm, preferably 0.4-0.68 mm, and more preferably 0.45-0.65 mm after the three times of asynchronous rolling deformation treatment.
In the present invention, the speed of the asynchronous rolling in the step 5) is 90 to 110mm/s, preferably 95 to 105mm/s, more preferably 100mm/s, and the rolling reduction is 18 to 25%, preferably 19 to 23%, more preferably 20%.
According to the invention, as the rolling pass is increased, the thickness of the material is continuously thinned, and the orientation of the nano-scale lamellar structure gradually tends to be consistent, so that the effective interface layer of the nano-scale LPSO phase and the matrix alpha-Mg is continuously increased, and the high-frequency electromagnetic shielding performance of the material is greatly improved.
The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
1) Removing an oxide layer on the surface of the magnesium, zinc and Mg-25wt% Y intermediate alloy material by adopting a mechanical polishing mode; the mass ratio of the Mg, zn and Y elements is 98.5:0.5:1.0, fully melting magnesium at 670 ℃ in a well-type resistance furnace filled with protective atmosphere argon to obtain magnesium liquid;
2) In CO 2 (0.5% mass fraction) and SF 6 Heating the magnesium solution to 775 ℃, sequentially adding zinc and Mg-Y intermediate alloy, and smelting for 40min to obtain a mixed solution;
3) Cooling the mixed solution to 700 ℃ for casting, and simultaneously opening a cooling water valve of a crystallizer to adjust the temperature to 250m 3 Medium cooling water quantity per h; controlling the inclination speed of the crucible to be 15 degrees, leading the molten metal to flow into the crystallizer at the speed of 25t/h, and forming Mg with the diameter of 260mm and the length of 0.9 m under the condition that the cooling speed is 40 ℃/s and the casting speed is 90mm/min 98.5 Zn 0.5 Y 1.0 Starting a blank pulling system after magnesium alloy ingot casting;
4) Controlling the rotating speed of an electric winch to be 150r/min, and pulling the cast magnesium alloy cast ingot at a pulling speed of 10 cm/min;
5) To pulled out Mg 98.5 Zn 0.5 Y 1.0 Sampling along the radial center and edge of a magnesium alloy casting blank, and observing a metallographic structure;
6) Annealing the pulled casting blank for 5 hours at 770K;
7) Mg annealed in step 6) 98.5 Zn 0.5 Y 1.0 Cutting magnesium alloy into thin plate with length of 90×90mm and thickness of 1.2mm, cleaning surface with acetone, polishing surface of the dried thin plate, and removing surface oxide layer;
8) Placing the treated magnesium alloy sheet into a temperature control box, and preheating for 15 minutes at 400 ℃; the asynchronous rolling speed is adjusted to 100mm/s, the rolling reduction is 20%, and the preheated sheet is subjected to one-pass, two-pass and three-pass asynchronous rolling deformation treatment respectively; after three passes, the obtained Mg 98.5 Zn 0.5 Y 1.0 The thickness of the magnesium alloy sheet is reduced to 0.61mm, the tensile strength can reach 185MPa, the elongation rate can reach 3.1%, and the electromagnetic shielding performance can reach 60-110dB in the whole frequency band of 30-6000 MHz.
Example 2
1) Removing an oxide layer on the surface of the magnesium, zinc and Mg-25wt% Y intermediate alloy material by adopting a mechanical polishing mode; the mass ratio of the Mg, zn and Y elements is 98.2:0.6:1.2, fully melting magnesium in a well-type resistance furnace filled with protective atmosphere argon at 665 ℃ to obtain magnesium liquid;
2) In CO 2 (0.8% mass fraction) and SF 6 Is a mixed atmosphere of (2)Heating the magnesium solution to 750 ℃, sequentially adding zinc and Mg-Y intermediate alloy, and smelting for 35min to obtain a mixed solution;
3) Cooling the mixed solution to 710 ℃ for casting, and simultaneously opening a cooling water valve of a crystallizer to adjust the thickness to 200m 3 Medium cooling water quantity per h; controlling the inclination speed of the crucible to be 10 degrees, enabling the molten metal to flow into the crystallizer at the speed of 26t/h, and forming Mg with the diameter of 260mm and the length of 1 meter under the conditions that the cooling speed is 20 ℃/s and the casting speed is 80mm/min 98.2 Zn 0.6 Y 1.2 Starting a blank pulling system after magnesium alloy ingot casting;
4) Controlling the rotating speed of the electric winch to be 140r/min, and pulling the cast magnesium alloy cast ingot at the pulling speed of 8 cm/min;
5) To pulled out Mg 98.2 Zn 0.6 Y 1.2 Sampling the casting blank along the radial center and the edge, and observing a metallographic structure;
6) Annealing the pulled casting blank for 4 hours at 760K;
7) Mg annealed in step 6) 98.2 Zn 0.6 Y 1.2 Cutting magnesium alloy into thin plate with the length of 100X 100mm and the thickness of 1.0mm, cleaning the surface by using acetone, polishing the surface of the dried thin plate, and removing a surface oxide layer;
8) Placing the treated magnesium alloy sheet into a temperature control box, and preheating for 13 minutes at 390 ℃; the asynchronous rolling speed is adjusted to 95mm/s, the rolling reduction is 17%, and the preheated sheet is subjected to one-pass, two-pass and three-pass asynchronous rolling deformation treatment respectively; after three passes, the obtained Mg 98.2 Zn 0.6 Y 1.2 The thickness of the magnesium alloy sheet was reduced to 0.57mm. Example 2 Mg after asynchronous Rolling deformation treatment 98.2 Zn 0.6 Y 1.2 The mechanical properties and electromagnetic shielding properties of the magnesium alloy were the same as those of example 1.
Example 3
1) Removing an oxide layer on the surface of the magnesium, zinc and Mg-25wt% Y intermediate alloy material by adopting a mechanical polishing mode; the mass ratio of the Mg, zn and Y elements is 99:0.3: under 0.7, fully melting magnesium at 685 ℃ in a well-type resistance furnace filled with argon in a protective atmosphere to obtain magnesium liquid;
2) In CO 2 (1.0% by mass) and SF 6 Heating the magnesium solution to 790 ℃, sequentially adding zinc and Mg-Y intermediate alloy, and smelting for 30min to obtain a mixed solution;
3) Cooling the mixed solution to 705 ℃ for casting, and simultaneously opening a cooling water valve of a crystallizer to adjust the temperature to 300m 3 Medium cooling water quantity per h; the tilting speed of the crucible is controlled to be 19 DEG, molten metal flows into the crystallizer at a speed of 28t/h, and Mg with a diameter of 260mm and a length of 0.8 m is formed at a cooling rate of 50 ℃/s and a casting speed of 100mm/min 99 Zn 0.3 Y 0.7 Starting a blank pulling system after magnesium alloy ingot casting;
4) Controlling the rotating speed of an electric winch to be 155r/min, and pulling a cast magnesium alloy ingot at a pulling speed of 12 cm/min;
5) To pulled out Mg 99 Zn 0.3 Y 0.7 Sampling the casting blank along the radial center and the edge, and observing a metallographic structure;
6) Annealing the pulled casting blank at 780K for 6 hours;
7) Mg annealed in step 6) 99 Zn 0.3 Y 0.7 Cutting magnesium alloy into thin plate with length of 80×80mm and thickness of 1.5mm, cleaning surface with acetone, polishing surface of the dried thin plate, and removing surface oxide layer;
8) Placing the treated magnesium alloy sheet into a temperature control box, and preheating for 20 minutes at 420 ℃; the asynchronous rolling speed is adjusted to 110mm/s, the rolling reduction is 25%, and the preheated sheet is subjected to one-pass, two-pass and three-pass asynchronous rolling deformation treatment respectively; after three passes, the obtained Mg 99 Zn 0.3 Y 0.7 The thickness of the magnesium alloy sheet was reduced to 0.63mm. EXAMPLE 3 Mg after asynchronous Rolling deformation treatment 99 Zn 0.3 Y 0.7 The mechanical properties and electromagnetic shielding properties of the magnesium alloy were the same as those of example 1.
From the above embodiments, the present invention provides a self-assembled nano-sheet material for a PCB-grade shield can material and a method for preparing the same. As in example 1 of FIG. 1Mg after semicontinuous casting obtained in step 5) 98.5 Zn 0.5 Y 1.0 The magnesium alloy section microscopic morphology diagram shows that a large number of nanoscale LPSO phases which grow in parallel to each other along the heat flow direction are distributed in the crystal grain, and the self-assembled nanoscale alpha-Mg/LPSO lamellar structure realizes the effective span from the macroscopic scale to the atomic scale. Compared with the common solidified alloy, the nano lamellar growth form and the alpha-Mg/LPSO lamellar structure interface layer formed in the crystal grain are beneficial to improving the electromagnetic shielding efficiency of the magnesium alloy. The cross-sectional microscopic morphology of the magnesium alloy after semi-continuous casting obtained in examples 2 to 3 was the same as that shown in fig. 1 in example 1. As shown in FIG. 2, between the full frequency bands of 30-6000MHz, different rolling passes Mg 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding effectiveness of the magnesium alloy reaches 55 dB-105 dB, and the electromagnetic shielding performance is excellent. In FIG. 3, between 30 and 1500MHz in the low frequency band, mg 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding effectiveness of the magnesium alloy is between 90 and 105dB, and the electromagnetic shielding effectiveness slowly decreases along with the increase of the frequency; FIG. 4 is a chart showing Mg between 1500 and 4500MHz in the medium frequency range 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding effectiveness of the magnesium alloy is reduced from 89-100 dB to 57-64 dB; in FIG. 5, the electromagnetic shielding performance is slowly increased between the high frequency band 4800 MHz and the high frequency band 6000 MHz; and adopts two-pass and three-pass asynchronous rolling deformation treatment of Mg 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding performance of the magnesium alloy in the high frequency range 4800-6000 MHz is obviously better than that of the magnesium alloy which is not subjected to rolling deformation treatment and is subjected to one-time rolling deformation treatment, because the orientation of the lamellar structure can be changed through the rolling deformation process, thereby improving the electromagnetic shielding performance of the magnesium alloy; mg adopting two-pass asynchronous rolling deformation treatment 98.5 Zn 0.5 Y 1.0 The electromagnetic shielding performance of the magnesium alloy can reach 64-83 dB in the high frequency band 4800-6000 MHz. The reasonable processing technology and optimal technological parameters are controlled, and the breakthrough of the electromagnetic shielding performance of the magnesium alloy under the ultra-high frequency band is expected to be realized.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (7)

1. A self-assembled nano sheet material for a PCB-level shielding case material is characterized in that the material is Mg 98～ 99 Zn 0.3～0.6 Y 0.6～1.2 The magnesium alloy comprises the following elements of Mg, zn and Y in a mass ratio of 98-99: 0.3 to 0.6:0.6 to 1.2;
the preparation method of the self-assembled nano sheet material for the PCB-level shielding case material comprises the following steps:
1) Under the protective atmosphere, melting magnesium, and then deslagging and purifying to obtain magnesium liquid;
2) In CO 2 And SF (sulfur hexafluoride) 6 Heating the magnesium solution to 750-800 ℃ under the mixed atmosphere, and sequentially adding zinc and Mg-Y intermediate alloy for smelting to obtain mixed solution;
3) Cooling the mixed solution to 700-710 ℃ for casting;
4) Pulling a cast magnesium alloy ingot;
5) Annealing and multi-pass asynchronous rolling deformation treatment are sequentially carried out on the pulled casting blank, and the material is obtained;
the cooling rate in the casting process is 20-65 ℃/s, and the casting speed is 80-100 mm/min;
the speed of pulling the blank in the step 4) is 5-15 cm/min;
the speed of asynchronous rolling in the step 5) is 90-110 mm/s, and the rolling reduction is 18-25%.
2. The method for preparing the self-assembled nano sheet material for the PCB-level shielding case material as set forth in claim 1, which is characterized by comprising the following steps:
1) Under the protective atmosphere, melting magnesium, and then deslagging and purifying to obtain magnesium liquid;
2) In CO 2 And SF (sulfur hexafluoride) 6 Under the mixed atmosphere of (2), the temperature of the magnesium solution is raised to 750-800 ℃, and the magnesium solution is sequentially added into zinc and Mg-YSmelting the intermediate alloy to obtain a mixed solution;
3) Cooling the mixed solution to 700-710 ℃ for casting;
4) Pulling a cast magnesium alloy ingot;
5) Annealing and multi-pass asynchronous rolling deformation treatment are sequentially carried out on the pulled casting blank, and the material is obtained;
the cooling rate in the casting process is 20-65 ℃/s, and the casting speed is 80-100 mm/min;
the speed of pulling the blank in the step 4) is 5-15 cm/min;
the speed of asynchronous rolling in the step 5) is 90-110 mm/s, and the rolling reduction is 18-25%.
3. The method according to claim 2, wherein the melting temperature of magnesium in step 1) is 665-685 ℃.
4. A method according to claim 2 or 3, wherein the smelting time in step 2) is 30-40 min.
5. The method according to claim 4, wherein the annealing temperature in step 5) is 760 to 780K and the annealing time is 4 to 6 hours.
6. The method according to claim 5, wherein the preheating treatment is performed before the multi-pass asynchronous rolling deformation treatment in step 5), the preheating temperature is 380-420 ℃, and the preheating time is 10-20 min.
7. The method according to claim 6, wherein the thickness of the magnesium alloy sheet material before the multi-pass asynchronous rolling deformation treatment in the step 5) is 1.0-1.5 mm; the multi-pass asynchronous rolling deformation treatment is three-pass asynchronous rolling deformation treatment; and after the three times of asynchronous rolling deformation treatment, the thickness of the thin plate is reduced to 0.3-0.7 mm.
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