A high-strength magnesium alloy and a method for manufacturing the same

Abstract

The application relates to a high-strength magnesium alloy and a preparation method thereof, and belongs to the technical field of magnesium alloys. The preparation method of the high-strength magnesium alloy comprises the following steps: (1) metal raw materials containing Mg and Mn metal elements are smelted and cast in a protective gas to obtain an alloy ingot; and (2) the alloy ingot obtained in the step (1) is heated and melted, sprayed to the surface of a rotating roller by using a single-roller strip casting method, and rapidly cooled and solidified to obtain a magnesium alloy strip. The preparation method does not need a solid solution treatment and a deformation process such as multiple rolling, the magnesium alloy prepared by the method has good mechanical properties, the tensile strength can be more than 400 MPa after further artificial aging treatment, the preparation steps are saved, and the alloy cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloys, and in particular to a high-strength magnesium alloy and a preparation method thereof. Background Art

[0002] The only high-strength magnesium alloy developed based on this γ″ basal plane precipitation phase reported so far is the Mg-Gd(-Y)-Ag(-Zr) series magnesium alloy. The existing technology is that this series of alloys undergoes solution treatment and subsequent multiple rolling deformation, and the specific steps include: (1) solution treatment at 500℃ for 12 hours, and oil cooling to room temperature. (2) before each hot rolling, keep warm in a 450℃ furnace for 15 minutes, and then hot roll on a conventional hot rolling mill, with each rolling reduction less than 5%, and air cool to room temperature after rolling. The high-density nano-spacing γ″ basal plane precipitation phase in the alloy obtained after the total rolling reduction exceeds 60% makes its tensile strength exceed 400MPa.

[0003] Magnesium alloys containing a high-density γ″ basal plane precipitation phase can be prepared by spray casting combined with a long artificial aging treatment, but the overall process is still long, and the tensile strength of the prepared magnesium alloy has not been explored.

[0004] However, the existing Mg-Gd-Y-Ag-Zr alloy contains the expensive element Ag, which increases the alloy manufacturing cost. The alloy also requires solution treatment and multiple rolling steps, which increases its cost. There are no reports of non-Ag magnesium alloys based on γ″ basal plane precipitation that can achieve a tensile strength exceeding 400 MPa.

[0005] Therefore, it is very necessary to develop a preparation method for magnesium alloys with lower raw material cost, simple preparation method, and the ability to produce γ″ basal plane precipitation phase and maintain a tensile strength of more than 400 MPa. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of the prior art and provide a high-strength magnesium alloy and a method for preparing the same. The method of the present invention does not require deformation processes such as solution treatment and multiple rolling processes. The resulting magnesium alloy has high tensile strength, simple preparation steps, and low alloy cost.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides a method for preparing a high-strength magnesium alloy, comprising the following steps:

[0009] (1) melting and casting a metal raw material in a protective gas to obtain an alloy ingot; the metal raw material comprises metal elements Mg and Mn; and the Mn accounts for 1-2% by mass of the metal raw material;

[0010] (2) heating and melting the alloy ingot obtained in step (1), and rapidly solidifying it by a single-roller strip-spinning method to obtain a magnesium alloy strip, namely a magnesium alloy;

[0011] The single-roller strip-throwing method is as follows: the molten alloy ingot is sprayed onto the surface of a rotating roller, rapidly cooled and solidified; in the single-roller strip-throwing method, the circumferential speed of the roller is 5-15m / s.

[0012] First, the metal raw materials containing Mg and Mn are melted and cast. The melting temperature is generally 740°C. Stirring is used to fully melt the alloy and mix the various alloy components. This ensures that the alloy ingot can maintain its uniform state after the initial melting when it is remelted and recast in subsequent processing. The alloy ingot is then heated until it is completely melted and a sprayable liquid alloy is formed. The liquefied master alloy is sprayed onto a rotating single roller. As the roller rotates continuously, the liquefied alloy contacts the roller and cools and deposits rapidly on the roller surface, forming a magnesium alloy strip.

[0013] Since the solubility of Mn in Mg alloys is relatively low, rapid cooling and solidification can achieve solid solution strengthening. At the same time, the formation of an oversaturated solidified body reduces the precipitation of Mn particles, promotes the formation of γ″ basal plane precipitation phase, and produces an alloy strip with high tensile strength.

[0014] By using the single-roller strip-spinning process described above and controlling the roller's circumferential speed within the aforementioned range, continuous solidification and deposition can be achieved, forming a high-strength magnesium alloy strip. When the roller's circumferential speed is below 5 m / s, the alloy strength decreases. When the roller's circumferential speed is above 15 m / s, a continuously deposited magnesium alloy strip cannot be obtained, and the resulting alloy strip has excessive defects, making it unsuitable for further processing or use.

[0015] The preparation method is simple to operate, has low raw material costs, eliminates the need for solution treatment and multiple rolling processes, and consumes minimal energy. The resulting Mg-Mn alloy exhibits high strength exceeding 350 MPa, demonstrating its potential application in the research and development of high-performance, low-cost rare earth magnesium alloys.

[0016] Preferably, in step (1), the protective gas is argon, which can provide an inert atmosphere to protect the metal components from oxidation.

[0017] Preferably, in step (1), the metal raw material further comprises the metal elements Gd, Y, and Zn. In the resulting Mg-Gd-Y-Zn-Mn alloy, Mn atoms occupy the positions of some Zn atoms in the crystal structure, which can promote the formation of γ″ basal plane precipitation phase in the Mg-Gd-Y-Zn structure, more effectively hinder dislocation movement, and achieve the effect of strengthening the magnesium alloy.

[0018] Further preferably, in step (1), the metal raw material comprises the following components in mass percentage: 9.22-9.63% Gd, 3.99-4.17% Y, 1.13-1.33% Zn, 1% Mn, and the balance Mg. Within this composition ratio range, the solid solubility is good and no particles are precipitated; at this ratio, the magnesium matrix component content is high, retaining its favorable properties such as low density and good heat dissipation. When the mass percentage of Mn is controlled at 1%, the tensile strength of the prepared magnesium alloy can reach above 370 MPa. Further increasing the Mn ratio results in a decrease in the tensile strength of the resulting magnesium alloy.

[0019] Further preferably, in step (2), the circumferential speed of the roller in the single-roll strip-spinning method is 5 m / s. At this speed, the deposition rate of the magnesium alloy strip produced by rapid cooling is moderate, and a magnesium alloy strip of uniform thickness can be continuously formed without particle precipitation or defects, which can be further processed to obtain other products. Increasing the circumferential speed results in more defects in the alloy strip, making the defective sections unusable and difficult to measure their properties, resulting in a waste of raw materials.

[0020] Further preferably, the method for preparing the magnesium alloy further comprises step (3): heating the magnesium alloy strip obtained in step (2) at 200°C for 50 hours and cooling to obtain a high-strength magnesium alloy. This heat treatment is artificial aging, and the magnesium alloy strip is prepared based on a 1% by mass Mn content and a single-roller strip spinning speed of 5 m / s. The peak point of the aging time-Vickers hardness curve at 200°C is 50 hours. After heat treatment under these conditions, the mechanical properties are further improved.

[0021] Further preferably, the high-strength magnesium alloy obtained in step (3) has a tensile strength of 400 MPa or greater. The artificial aging treatment can eliminate internal stress in the magnesium alloy, stabilize the structure and size, and improve mechanical properties. After the aging treatment, the resulting magnesium alloy can precipitate a large amount of γ″ basal plane precipitation phase, and the tensile strength is increased to 420 MPa.

[0022] Preferably, in step (2), the roller used in the single-roller belt-spinning method is a copper roller.

[0023] Further preferably, in step (2), the temperature of the copper roller in the single roller strip spinning method is room temperature. The roller temperature is maintained at 20-30°C above room temperature, so that the liquefied master alloy in contact with the roller can be quickly cooled and deposited to form a magnesium alloy strip.

[0024] Further preferably, in step (2), the cooling rate is 10 5 -10 6 K / s. Using the above-mentioned single-roller belt-spinning rapid solidification method, the cooling rate of the alloy liquid is 10 5 -10 6K / s, the cooling and solidification can be quickly completed, and the magnesium alloy product can be continuously deposited. The solid solution of Zn, Y and Mn in the Mg series alloy matrix is good at the cooling rate, the composition is uniform, the composition segregation is less, and the tensile strength is higher.

[0025] In the second aspect, the application provides a magnesium alloy prepared by the preparation method of the high-strength magnesium alloy. The magnesium alloy prepared by the preparation method of the magnesium alloy is subjected to rapid solidification treatment, the solid solution of Mn is good and the strength is high, and after further artificial aging treatment, the tensile strength can reach more than 400 MPa, the magnesium alloy has the advantages of high strength and light weight, and the application field of the magnesium alloy is widened.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] The method of the application can achieve a tensile strength of more than 400 MPa without solid solution treatment and multiple rolling deformation processes through rapid solidification and artificial aging of the alloy, and compared with the Mg-Gd-Y-Ag alloy prepared by adding Ag with a high price and subjected to subsequent multiple rolling deformation, the preparation steps are saved and the alloy cost is reduced when the same tensile strength is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The aging time-hardness curve of the magnesium alloy prepared in Example 1. DETAILED DESCRIPTION

[0029] In order to better illustrate the purpose, technical scheme and advantages of the application, the application will be further described below in combination with specific examples. Unless otherwise specified, other materials, reagents and the like used in the examples can be obtained from commercial channels.

[0030] Example 1

[0031] The preparation method of the high-strength magnesium alloy according to the embodiment of the application comprises the following specific steps:

[0032] (1) The metal raw materials are weighed: pure Mg (99.9wt.%), pure Zn (99.9wt.%), Mg-30% Gd (wt.), Mg-25% Y (wt.) and Mg-10% Mn (wt.), in mass percentage, including 1% Mn, 9.63% Gd, 4.17% Y and 1.13% Zn, and the balance is Mg and unavoidable impurities;

[0033] The above metal raw materials are stirred and melted at 740°C under argon protection, and then cast to obtain an alloy ingot.

[0034] (2) The alloy ingot is broken into small pieces, the surface oxide layer is removed, and the ingot is heated to 740°C under argon protection to melt into liquid. The liquid alloy is continuously sprayed onto the surface of a high-speed rotating copper roller with a circumferential speed of 5 m / s. The ingot is rapidly cooled and solidified to obtain a magnesium alloy strip.

[0035] (3) The magnesium alloy strip is artificially aged by heating at 200°C, keeping the temperature for 50 hours, and cooling to obtain a magnesium alloy.

[0036] The aging time-Vickers hardness curve of magnesium alloy strip at 200℃ is as follows: Figure 1 .

[0037] The obtained magnesium alloy has no defects or particle precipitation, contains a high-density γ″ basal plane precipitation phase, and has a tensile strength of 420 MPa.

[0038] Example 2

[0039] The only difference between Example 2 and Example 1 is that no artificial aging treatment is performed.

[0040] The obtained magnesium alloy has no defects or particle precipitation and has a tensile strength of 370 MPa.

[0041] Example 3

[0042] The only difference between Example 3 and Example 1 is that the circumferential speed of the copper roller is 15 m / s.

[0043] The resulting magnesium alloy has many defects and is difficult to process further.

[0044] The magnesium alloy strip obtained by rapid cooling and forming by the single-roll strip-spinning method has a tensile strength of 376 MPa.

[0045] Example 4

[0046] A method for preparing a high-strength magnesium alloy according to an embodiment of the present invention comprises the following specific steps:

[0047] (1) Prepare the following metal raw materials: pure Mg (99.9 wt.%), pure Zn (99.9 wt.%), Mg-30% Gd (wt.), Mg-25% Y (wt.), and Mg-10% Mn (wt.). Weigh the metal raw materials so that, by mass percentage, they comprise 2% Mn, 9.22% Gd, 3.99% Y, and 1.33% Zn, with the remainder being Mg and unavoidable impurities.

[0048] Under argon protection, the above metal raw materials are stirred, melted, and kept warm at 740° C., and then cast to obtain alloy ingots.

[0049] (2) The alloy ingot is broken into small pieces, the surface oxide layer is removed, and the alloy is melted into liquid state at 740℃ under argon protection. The liquid alloy is continuously sprayed onto the surface of a high-speed rotating copper roller, the circumferential speed of the copper roller is 5m / s, and the magnesium alloy strip is obtained by rapid cooling and solidification.

[0050] The obtained magnesium alloy has no defects or particle precipitation, and the tensile strength is 359.7MPa.

[0051] Example 5

[0052] The preparation method of the high-strength magnesium alloy in the embodiment of the application comprises the following steps:

[0053] (1) The following metal raw materials are prepared: pure Mg (99.9wt.%), pure Zn (99.9wt.%), Mg-30%Gd (wt.), Mg-25%Y (wt.) and Mg-10%Mn (wt.). The metal raw materials are weighed so that the mass percentage of the metal raw materials comprises 2%Mn, 9.5%Gd, 4%Y and 1.2%Zn, and the balance is Mg and inevitable impurities;

[0054] The above metal raw materials are stirred and melted at 740℃ under argon protection, and then the alloy ingot is obtained by pouring and holding.

[0055] (2) The alloy ingot is broken into small pieces, the surface oxide layer is removed, and the alloy is melted into liquid state at 740℃ under argon protection. The liquid alloy is continuously sprayed onto the surface of a high-speed rotating copper roller, the circumferential speed of the copper roller is 15m / s, and the magnesium alloy strip is obtained by rapid cooling and solidification.

[0056] The obtained magnesium alloy has many defects and is difficult to be further processed.

[0057] The magnesium alloy strip obtained by the single-roller strip casting method has a tensile strength of 364.4MPa.

[0058] Comparative Example 1

[0059] The difference between Comparative Example 1 and Example 1 is that the artificial aging treatment time is 200h.

[0060] The obtained magnesium alloy has no defects or particle precipitation, but due to the long aging time, the length of the γ″ basal plane precipitated phase increases, and a large number of γ' precipitated phases and β' precipitated phases are generated, and the tensile strength is 360MPa, which is reduced instead.

[0061] Comparative Example 2

[0062] The difference between Comparative Example 2 and Example 4 is that the obtained strip-shaped magnesium alloy is subjected to peak artificial aging treatment to obtain a magnesium alloy, the temperature is 200℃, and the time is 30h.

[0063] The obtained magnesium alloy has no defects or particle precipitation, contains a high-density γ″ basal plane precipitation phase, and has a tensile strength of 348 MPa.

[0064] Comparative Example 3

[0065] The difference between Comparative Example 3 and Example 1 is that the circumferential speed of the copper roller is 25 m / s.

[0066] The single-roller strip-throwing method cannot form a complete magnesium alloy strip with rapid cooling, and there are too many defects, making it difficult to measure its tensile strength.

[0067] Comparative Example 4

[0068] The difference between Comparative Example 4 and Example 1 is that the alloy is directly spray-casted in a copper mold without adopting the single-roller strip-spinning method for rapid solidification and then subjected to artificial aging treatment.

[0069] The obtained magnesium alloy has no defects or particle precipitation and has a tensile strength of 120 MPa.

[0070] Table 1 Tensile strength of magnesium alloys prepared in Examples and Comparative Examples

[0071]

[0072]

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high-strength magnesium alloy, characterized in that: The following steps are involved: (1) melting and casting a metal raw material in a protective atmosphere to obtain an alloy ingot; the metal raw material comprises the following components in percentage by mass: 9.22-9.63% Gd, 3.99-4.17% Y, 1.13-1.33% Zn, 1% Mn, and the balance Mg; (2) heating and melting the alloy ingot obtained in step (1), and rapidly solidifying it by a single-roll strip-spinning method to obtain a magnesium alloy strip; (3) heating the magnesium alloy strip obtained in step (2) at 200° C. for 50 h and cooling to obtain the high-strength magnesium alloy; The single roller strip method is as follows: the molten alloy ingot is sprayed onto the surface of a rotating roller, and rapidly cooled and solidified; in the single roller strip method, the circumferential speed of the roller is 5 m / s; the cooling rate is 10 5 -10 6 K / s.

2. The method for preparing a high-strength magnesium alloy according to claim 1, wherein: The tensile strength of the high-strength magnesium alloy obtained in step (3) is above 400 MPa.

3. The method for preparing a high-strength magnesium alloy according to claim 1, wherein: In the step (2), the roller used in the single-roller belt-spinning method is a copper roller.

4. The method for preparing a high-strength magnesium alloy according to claim 3, wherein: In the step (2), the temperature of the copper roller in the single-roller belt-spinning method is room temperature.

5. The magnesium alloy prepared according to the method for preparing a high-strength magnesium alloy according to any one of claims 1 to 4.

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