High-toughness wrought magnesium alloy and preparation method thereof

Abstract

The invention belongs to the technical field of non-ferrous metal materials, and particularly relates to a high-toughness wrought magnesium alloy and a preparation method thereof. The high-toughness wrought magnesium alloy comprises the following components in percentage by mass: 92.15-93.2% of Mg, 5.8-6.3% of Zn, 0.6-0.9% of Zr, 0.4-0.6% of Y and inevitable impurities, an RJ-5 flux is added for smelting and casting to obtain a magnesium alloy casting rod, the magnesium alloy casting rod is homogenized and then water-cooled to room temperature, and then hot extrusion, heat treatment and cooling are sequentially performed to obtain the high-toughness wrought magnesium alloy. The tensile strength of the obtained high-toughness wrought magnesium alloy bar and plate can reach 340 MPa, the yield strength can reach 300 MPa, and the ductility can reach 13% at the room temperature, the tensile strength of the high-toughness wrought magnesium alloy pipe can reach 310 MPa, the yield strength can reach 260 MPa, and the ductility can reach 9% at the room temperature, and the high-toughness wrought magnesium alloy pipe has wide application prospects in the aerospace military industry field.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal materials, and more specifically relates to a high-strength and toughness deformable magnesium alloy and a preparation method thereof. Background Art

[0002] Magnesium alloy is a relatively light structural metal in industrial applications. The density of pure magnesium is 1.74 g cm -3 It is 2 / 3 of aluminum and 1 / 4 of steel. It has the advantages of high specific stiffness, good thermal conductivity and electrical conductivity, damping and vibration reduction, electromagnetic shielding, easy processing and forming, and easy recycling. It has increasingly important application value and broad application prospects in the fields of automobiles, 3C products, aerospace, national defense and military industry.

[0003] However, due to the poor mechanical properties of magnesium alloys, the problem of not being able to take into account both strength and toughness at the same time has limited its development in industrial applications to a certain extent. In response to the above problems, domestic and foreign researchers often use alloying, plastic deformation and heat treatment methods to control the microstructure of magnesium alloys in order to prepare magnesium alloy materials with excellent high strength and toughness. Although a certain strengthening and toughening effect is achieved, it is very important to further improve the strengthening and toughening properties of magnesium alloys in order to meet the needs of multiple fields. Summary of the invention

[0004] The purpose of the present invention is to provide a high-strength and toughness deformable magnesium alloy and a preparation method thereof, which solves the problems existing in the above-mentioned prior art by regulating the types and contents of alloying elements and combining the hot extrusion method, and realizes the preparation of high-strength and toughness magnesium alloy materials, which has a significant significance for broadening the application of magnesium alloy materials.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is to provide a high-strength and toughness deformable magnesium alloy, which comprises, by mass percentage:

[0007] Mg 92.15-93.2%, Zn 5.8-6.3%, Zr 0.6-0.9% and Y 0.4-0.6%, and inevitable impurities.

[0008] Optionally, the high-strength and toughness deformable magnesium alloy comprises, by mass percentage, 6% Zn, 0.75% Zr and 0.6% Y, with the remainder being Mg and unavoidable impurities.

[0009] Optionally, the high-strength and toughness deformable magnesium alloy comprises, by mass percentage, 6.3% Zn, 0.8% Zr and 0.4% Y, with the remainder being Mg and unavoidable impurities.

[0010] Optionally, the high-strength and toughness deformable magnesium alloy comprises, by mass percentage, 6.4% Zn, 0.9% Zr and 0.5% Y, with the remainder being Mg and unavoidable impurities.

[0011] The second technical solution of the present invention is to provide a method for preparing a high-strength and toughness deformable magnesium alloy, the steps comprising:

[0012] According to the composition ratio of the high-strength and toughness deformable magnesium alloy, pure magnesium, pure zinc, magnesium-zirconium master alloy and magnesium-yttrium master alloy are weighed, RJ-5 flux is added for smelting, and magnesium alloy casting rods are obtained after casting;

[0013] homogenizing the magnesium alloy casting rod, and then cooling it with water to room temperature to obtain a homogenized magnesium alloy casting rod;

[0014] The homogeneous magnesium alloy casting rod is hot-extruded, heat-treated and cooled to obtain the high-strength and toughness deformable magnesium alloy.

[0015] Furthermore, the amount of the RJ-5 flux used is 7% of the mass of the pure magnesium.

[0016] Furthermore, the smelting temperature is 690-710°C, and the heating rate is 120°C / h.

[0017] Furthermore, the homogenization treatment is carried out at a temperature of 415-425°C, for 14 hours, and at a heating rate of 200°C / h.

[0018] Homogenization treatment can improve the segregation problem inside the cast rod and improve the hot extrusion performance of the material. Homogenization treatment also allows the low-temperature phase in the cast rod to be dissolved in the matrix, which has a precipitation strengthening effect in the subsequent heat treatment process.

[0019] Furthermore, the die for hot extrusion needs to be preheated to 450-460°C, and the temperature of the homogeneous magnesium alloy product during hot extrusion is 390-410°C.

[0020] Furthermore, the extrusion ratio of the hot extrusion is 13-41:1, and the extrusion speed is 0.4-0.7 mm / s.

[0021] After hot extrusion, magnesium alloy bars, magnesium alloy sheets or magnesium alloy tubes can be obtained.

[0022] Optionally, when a magnesium alloy rod is obtained after hot extrusion, the extrusion ratio of the hot extrusion is 13.98:1, and the extrusion speed is 0.7 mm / s.

[0023] Optionally, when a magnesium alloy sheet is obtained after hot extrusion, the extrusion ratio of the hot extrusion is 13.03:1, and the extrusion speed is 0.7 mm / s.

[0024] Optionally, when a magnesium alloy tube is obtained after hot extrusion, the extrusion ratio of the hot extrusion is 40.23:1, and the extrusion speed is 0.4 mm / s.

[0025] Hot extrusion treatment can improve the crystal structure of the cast rod, refine the grains, and also improve defects such as looseness and pores inside the cast rod, and form the required profile through the extrusion die.

[0026] Furthermore, the heat treatment temperature is 190° C. and the time is 16 hours.

[0027] Heat treatment can precipitate a second phase in the material. During the deformation of the material, the second phase will hinder the movement of dislocations and play a strengthening role.

[0028] The third technical solution of the present invention is to provide an application of the above-mentioned high-strength and toughness deformable magnesium alloy in aerospace and military industries.

[0029] The present invention discloses the following technical effects:

[0030] The high-strength and toughness deformable magnesium alloy rods and plates of the present invention have a tensile strength of up to 340 MPa, a yield strength of up to 300 MPa, and an elongation of up to 13% at room temperature; the high-strength and toughness deformable magnesium alloy tubes of the present invention have a tensile strength of up to 310 MPa, a yield strength of up to 260 MPa, and an elongation of up to 9% at room temperature, and have broad application prospects in the aerospace and military fields.

[0031] The present invention effectively refines the grains in the magnesium alloy matrix structure by regulating the types and contents of alloying elements and combining the methods of hot extrusion and post-extrusion heat treatment, increases the number of magnesium alloy grain boundaries, and hinders the slip of dislocations; in addition, the magnesium alloy matrix structure is made denser through the hot extrusion process, and finally a high-strength and tough magnesium alloy material is obtained.

[0032] The method of the invention has simple process and high production efficiency and can realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0034] Figure 1 Schematic diagram of the process flow for preparing high-strength and toughness wrought magnesium alloy;

[0035] Figure 2 The metallographic structure diagrams of the magnesium alloy casting rod of Example 1 before and after homogenization treatment, wherein (a) is before homogenization treatment, and (b) is after homogenization treatment;

[0036] Figure 3The TD-ND microstructure diagrams of the magnesium alloy rods, plates and tubes to be heat treated prepared by hot extrusion in Example 1, wherein (a) is a rod, (b) is a plate, and (c) is a tube;

[0037] Figure 4 TD-ND microstructure diagrams of the high-strength and toughness deformable magnesium alloy rods, plates and tubes prepared in Example 1, where (a) is a rod, (b) is a plate, and (c) is a tube. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0043] The purity of pure magnesium (magnesium ingot) used in the specific implementation scheme of the present invention is 99.99%; the purity of pure zinc (zinc ingot) is 99.99%; the mass fraction of zirconium in the magnesium-zirconium master alloy is 30%; the mass fraction of yttrium in the magnesium-yttrium master alloy is 30%.

[0044] The alloying efficiency of pure zinc used in the specific embodiment of the present invention is 100%, the alloying efficiency of magnesium-zirconium master alloy is 40%, and the alloying efficiency of magnesium-yttrium master alloy is 95%.

[0045] Unless otherwise specified, the "room temperature" and "normal temperature" referred to in the specific embodiments of the present invention refer to 20-30°C.

[0046] Figure 1 Schematic diagram of the process flow for preparing high-strength and toughness deformed magnesium alloy.

[0047] Example 1

[0048] The preparation steps of high strength and toughness deformable magnesium alloy include:

[0049] S1. Prepare magnesium ingots, zinc ingots, magnesium-zirconium master alloys and magnesium-yttrium master alloys according to the ratio of Mg-6Zn-0.75Zr-0.6Y, and RJ-5 flux with a mass percentage of 7% of the magnesium ingots for standby use;

[0050] S2, a magnesium ingot and 6.5% RJ-5 flux by mass of the magnesium ingot are mixed and heated to 710°C for stirring and melting. After the magnesium ingot is completely melted, a zinc ingot, a magnesium-zirconium master alloy, a magnesium-yttrium master alloy and 0.5% RJ-5 flux by mass of the magnesium ingot are added, and the mixture is kept warm for 15 minutes for smelting. After the heat preservation is completed, argon gas is introduced into the melt for 10 minutes for refining treatment. After the refining is completed, the mixture is kept warm for 10 minutes and then cast into a cast rod;

[0051] S3, placing the magnesium alloy casting rod in an induction resistance furnace and heating it to 420° C., keeping the temperature for 14 hours, and cooling it to room temperature with water after the end of the heat preservation to obtain a homogeneous magnesium alloy casting rod;

[0052] S4, placing the homogeneous magnesium alloy casting rod into a resistance furnace and heating it to 400°C, and preheating the mold to 460°C for hot extrusion;

[0053] Among them, the extrusion ratio of the rod die is 13.98:1, and the extrusion speed is 0.7mm / s; the extrusion ratio of the plate die is 13.03:1, and the extrusion speed is 0.7mm / s; the extrusion ratio of the pipe die is 40.23:1, and the extrusion speed is 0.4mm / s;

[0054] S5. The extruded rods, plates and tubes are heat treated in a heat treatment furnace respectively. The heat treatment process is heating to 190°C, keeping warm for 16 hours, and naturally cooling to room temperature to obtain Mg-6Zn-0.75Zr-0.6Y high-strength and toughness deformable magnesium alloy rods, bars and tubes.

[0055] Examples 2 to 3 and Comparative Examples 1 to 9

[0056] Compared with Example 1, the difference lies in the different ratios of the alloy elements, as shown in Table 1.

[0057] Table 1

[0058] Element proportion / wt.% Mg Zn Zr Y Example 2 margin 6.3 0.8 0.4 Example 3 margin 6.4 0.9 0.5 Comparative Example 1 margin 6 0.75 -- Comparative Example 2 margin 6 -- 0.5 Comparative Example 3 margin -- 0.75 0.5 Comparative Example 4 margin 6.5 0.75 0.5 Comparative Example 5 margin 5.6 0.75 0.5 Comparative Example 6 margin 6 1.0 0.5 Comparative Example 7 margin 6 0.5 0.5 Comparative Example 8 margin 6 0.75 0.75 Comparative Example 9 margin 6 0.75 0.35

[0059] Comparative Example 10

[0060] Compared with Example 1, the only difference is that the hot extrusion is directly cooled without subsequent heat treatment.

[0061] Test example

[0062] The mechanical properties of the high-strength and toughness deformable magnesium alloy rods, bars and tubes prepared in Examples 1 to 3 and Comparative Examples 1 to 10 were measured, wherein the rods are shown in Table 2, the plates are shown in Table 3, and the tubes are shown in Table 4.

[0063] Table 2 Mechanical properties of bars

[0064] sample Tensile strength / MPa Yield strength / MPa Elongation / % Example 1 352 308 13.5 Example 2 350 303 13.2 Example 3 345 301 13.3 Comparative Example 1 332 280 10 Comparative Example 2 320 278 8.2 Comparative Example 3 280 200 9.1 Comparative Example 4 360 320 10.3 Comparative Example 5 338 288 14.2 Comparative Example 6 348 295 15.1 Comparative Example 7 320 290 15.2 Comparative Example 8 355 310 9.8 Comparative Example 9 345 278 11.9 Comparative Example 10 302 242 14.8

[0065] Table 3 Mechanical properties of the plates

[0066]

[0067]

[0068] Table 4 Mechanical properties of pipes

[0069] sample Tensile strength / MPa Yield strength / MPa Elongation / % Example 1 315 264 9.9 Example 2 313 260 9.4 Example 3 312 262 10.0 Comparative Example 1 313 252 8.8 Comparative Example 2 310 236 6.9 Comparative Example 3 268 188 6.0 Comparative Example 4 345 272 6.5 Comparative Example 5 317 254 7.8 Comparative Example 6 326 266 8.1 Comparative Example 7 308 243 7.8 Comparative Example 8 321 267 6.9 Comparative Example 9 328 231 8.1 Comparative Example 10 289 230 11.2

[0070] It can be seen from Table 1 that the tensile strength of the high-strength and toughness deformed magnesium alloy rods and plates prepared in the embodiment of the present invention can reach 340 MPa, the yield strength can reach 300 MPa, and the elongation can reach 13%. The tensile strength of the high-strength and toughness deformed magnesium alloy tube can reach 310 MPa, the yield strength can reach 260 MPa, and the elongation can reach 9%.

[0071] The metallographic structures of the magnesium alloy cast rods and high-strength and toughness deformable magnesium alloy rods, plates and tubes prepared in Example 1 were observed respectively.

[0072] Figure 2 The metallographic structure diagrams of the magnesium alloy casting rod before and after homogenization treatment in Example 1, where (a) is before homogenization treatment and (b) is after homogenization treatment. It can be seen from the figure that some low-melting point coarse second phases appearing on the grain boundary of the homogenization treatment melt into the matrix, improving the extrudability of the material and preparing for subsequent extrusion.

[0073] Figure 3The TD-ND microstructure diagram of the magnesium alloy rod, plate and tube to be heat treated prepared by hot extrusion in Example 1, wherein (a) is the rod, (b) is the plate, and (c) is the tube. It can be seen from the figure that the strong plastic deformation process of hot extrusion effectively refines the grains in the magnesium alloy matrix structure and increases the number of magnesium alloy grain boundaries; in addition, the hot extrusion process makes the magnesium alloy matrix structure more dense.

[0074] Figure 4 The TD-ND microstructure diagram of the high-strength and toughness deformable magnesium alloy rods, plates and tubes prepared in Example 1, where (a) is a rod, (b) is a plate, and (c) is a tube. It can be seen from the figure that after the extruded profile is heat treated, the flat fiber structure inside the material is reduced, and the crystal undergoes obvious recovery and recrystallization. Secondly, fine second phases are precipitated inside the material grains. These second phases hinder the movement of dislocations during the subsequent plastic deformation process, greatly improving the mechanical properties of the material.

[0075] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0076] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-strength and tough deformable magnesium alloy, characterized in that: In terms of mass percentage, the components include: Mg 92.15-93.2%, Zn 5.8-6.3%, Zr 0.6-0.9% and Y 0.4-0.6%, and inevitable impurities.

2. The high-strength and toughness deformable magnesium alloy according to claim 1, characterized in that: Calculated by mass percentage, the components include: Zn 6%, Zr 0.75% and Y 0.6%, and the balance is Mg and inevitable impurities.

3. The high strength and toughness deformable magnesium alloy according to claim 1, characterized in that: Calculated by mass percentage, the components include: Zn 6.3%, Zr 0.8% and Y 0.4%, and the balance is Mg and inevitable impurities.

4. The high-strength and toughness deformable magnesium alloy according to claim 1, characterized in that: Calculated by mass percentage, the components include: Zn 6.4%, Zr 0.9% and Y 0.5%, and the balance is Mg and inevitable impurities.

5. A method for preparing a high-strength and tough deformable magnesium alloy, characterized in that the steps include: According to the composition ratio of the high-strength and toughness deformable magnesium alloy according to any one of claims 1 to 4, pure magnesium, pure zinc, magnesium-zirconium master alloy, and magnesium-yttrium master alloy are weighed, RJ-5 flux is added for smelting, and magnesium alloy casting rods are obtained after casting; The magnesium alloy casting rod is homogenized and then water-cooled to room temperature to obtain a homogenized magnesium alloy casting rod; The homogeneous magnesium alloy casting rod is hot-extruded, heat-treated and cooled to obtain the high-strength and toughness deformable magnesium alloy.

6. The preparation method according to claim 5, characterized in that: The amount of the RJ-5 flux is 7% of the mass of the pure magnesium; and / or, The smelting temperature is 690-710°C, and the heating rate is 120°C / h; and / or, The temperature of the homogenization treatment is 415-425° C., the time is 14 hours, and the heating rate is 200° C. / h.

7. The preparation method according to claim 5, characterized in that: The die for hot extrusion needs to be preheated to 450-460°C, and the temperature of the homogeneous magnesium alloy product during hot extrusion is 390-410°C.

8. The preparation method according to claim 5, characterized in that: The extrusion ratio of the hot extrusion is 13-41:1, and the extrusion speed is 0.4-0.7 mm / s.

9. The preparation method according to claim 5, characterized in that: The heat treatment temperature is 190° C. and the time is 16 hours.

10. Application of the high-strength and toughness deformable magnesium alloy according to any one of claims 1 to 4 in aerospace and military industries.

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