Preparation method of high-plasticity magnesium alloy and product thereof

Abstract

The invention relates to the field of metal material magnesium alloys, in particular to a preparation method of a high-plasticity magnesium alloy and a product thereof. The second phase of the grain boundary is controlled to be a quasi-crystal phase by regulating and controlling alloy components, and the preferred growth orientation surface of the magnesium alloy is regulated and controlled to be a conical surface through directional solidification, and the growth orientation is that grains are typical columnar crystals; the size and distribution of the second phase are adjusted by changing the growth speed, and segregation of the second phase in the crystal is reduced. And finally, the quasicrystal second phase is dispersed and distributed in the crystal by regulating and controlling the temperature and time of heat treatment. In this way, the high-plasticity magnesium alloy is successfully prepared, and the yield strength of the high-plasticity magnesium alloy ranges from 170 MPa to 200 MPa; the tensile strength is 180 to 212MPa, the plasticity reaches 31.0 to 42.2 percent, and the product of strength and elongation is 5580 to 8947MPa.%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metal material magnesium alloy, and particularly relates to a preparation method of high plasticity magnesium alloy and a product thereof. BACKGROUND

[0002] With the rapid development of society, the pursuit of material life of human beings is continuously improved, and the industries closely related to the quality of human life such as automobiles, aerospace and rail transportation are developing rapidly, and the demand for metal materials is continuously rising. However, the traditional steel material has been difficult to meet the demand of human beings for lighter and more convenient life due to its high density and large mass under the same volume, and therefore it is an inevitable requirement for the development of society to develop new light metal materials. As the metal structural material with the smallest density at present, magnesium alloy has the advantages of high specific strength and good heat dissipation performance, and shows a broad application prospect.

[0003] Magnesium is a hexagonal close-packed (HCP) crystal structure, and its plastic deformation is mainly basal plane, cylindrical, conical slip and conical twinning. At room temperature, only basal plane Two independent slip systems are activated, and independent deformation mechanism of insufficiently coordinated C-axis deformation is lacked, and non-basal slip is difficult to be activated, and the minimum number (5 independent slip systems) of uniform deformation of grain boundary in Von-Mises criterion cannot be met. The poor plasticity of magnesium alloy is not conducive to subsequent processing forming process, and greatly limits the further development and application of magnesium alloy.

[0004] To this end, domestic and foreign scholars put forward the following solutions: 1) by adding some rare earth elements to regulate, so that the non-basal slip system in the magnesium cell is activated, thereby meeting the requirement of at least 5 independent slip systems, however, most of the rare earth elements are high in price, thereby increasing the production cost of magnesium alloy; 2) through the forming path of plastic processing to prepare high-performance magnesium alloy, however, the way of improving the performance of magnesium alloy through plastic processing needs to be carried out under high temperature and low speed conditions, and faces problems such as high cost, low precision and difficult organization control, and the production cost is further increased. Therefore, it is of great significance to design and develop a high-plasticity and low-cost magnesium alloy casting or processing method. SUMMARY

[0005] The purpose of the present application is to overcome the problem of poor plasticity of magnesium alloy in the prior art, and to provide a preparation method of high-plasticity magnesium alloy and a product thereof.

[0006] In one aspect, the present application provides a preparation method of high-plasticity magnesium alloy, which specifically comprises the following steps: aging treatment of the magnesium alloy after directional solidification to obtain the high-plasticity magnesium alloy; the high-plasticity magnesium alloy comprises Mg, Zn and Y;

[0007] In the magnesium alloy, the total content of Zn and Y is 2.4-6.0% by mass fraction, and the rest is Mg; the mass ratio of Zn to Y is 5-7;

[0008] The preferred growth orientation surface of the magnesium alloy after directional solidification is a conical surface The growth orientation is

[0009] In an optional embodiment, the temperature of the aging treatment is 150-250℃, and the time is 12-18h;

[0010] Further, the temperature of the aging treatment is 180-220℃.

[0011] In an optional embodiment, the preparation method of the magnesium alloy after directional solidification comprises the following steps: melting the raw material to obtain a magnesium alloy melt, and directionally solidifying the magnesium alloy melt to obtain the magnesium alloy after directional solidification.

[0012] In an optional embodiment, the raw material comprises Mg ingot, Zn ingot and Mg-Y intermediate alloy.

[0013] Further, the Mg-Y intermediate alloy is selected from Mg-30Y.

[0014] In the present application, the burning loss rate of Mg is calculated as 5%.

[0015] Further, the raw materials are all subjected to the treatment process of removing oxide skin and drying before use, and the melting process comprises the process of alcohol cleaning and drying the equipment.

[0016] In an alternative embodiment, the melting temperature in the melting process is 750-790℃.

[0017] In an alternative embodiment, the melting process is carried out under the protection of protective gas.

[0018] Preferably, the protective gas is selected from Ar.

[0019] In an alternative embodiment, the temperature gradient of the solidification direction in the process of directional solidification of the magnesium alloy melt is 70-90K / cm, and the grain growth rate is 30-200μm / s.

[0020] Further, the grain growth rate is 80-170μm / s.

[0021] In an alternative embodiment, the average grain size of the directional solidification magnesium alloy substrate after aging treatment is 200-250μm.

[0022] The second aspect of the present application further provides a high plasticity magnesium alloy prepared by the above preparation method.

[0023] Preferably, the high plasticity magnesium alloy prepared by the above preparation method has a yield strength of 170-200MPa, a tensile strength of 180-212MPa, a plasticity of 31.0-42.2%, and a strength-plasticity product of 5580-8947MPa·%.

[0024] The high plasticity magnesium alloy provided by the present application has strip-shaped quasicrystals distributed on the grain boundary and granular quasicrystal phases dispersed in the grain.

[0025] The present application has the following beneficial effects:

[0026] The present application provides a preparation method of a high plasticity magnesium alloy, which specifically comprises the following steps: aging treatment of a directional solidification magnesium alloy to obtain the high plasticity magnesium alloy; the high plasticity magnesium alloy comprises Mg, Zn and Y; wherein the total content of Zn and Y in the magnesium alloy is 2.4-6.0% by mass fraction, and the rest is Mg; the mass ratio of Zn to Y is 5-7; and the preferred growth orientation surface of the directional solidification magnesium alloy is a conical surface. The growth orientation is The present application uses directional solidification technology and aging to prepare Mg-Zn-Y alloy with second phase of quasicrystal, further coordinates deformation to increase the plasticity of magnesium alloy, so that the alloy exhibits ultra-high plasticity while having high strength, and the method is simple and low in cost. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0028] Figure 1 The metallographic diagrams of the alloys of examples 1 and 2 and comparative examples 1 and 2 of the present application;

[0029] Figure 2 The grain boundary and intracrystalline second phase form and composition diagram of the high plasticity magnesium alloy of example 2 of the present application;

[0030] Figure 3 The tensile strength and elongation after fracture of the alloys of examples 1 and 2 and comparative examples 1 and 2 of the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] The specific experimental steps or conditions not mentioned in the embodiments can be performed according to the conventional experimental steps or conditions described in the literature in the art. The reagents or instruments not mentioned by the manufacturer are conventional reagent products that can be obtained by purchase.

[0033] The Mg ingot, Zn ingot and Mg-30Y used in the examples and comparative examples were all subjected to a process of removing oxide scale and drying before use, and the process of alcohol cleaning and drying of the equipment was included in the melting process.

[0034] Example 1

[0035] The embodiment provides a preparation method of a high-plasticity magnesium alloy, and comprises the following steps:

[0036] (1) 114g of Mg ingot, 3.6g of Zn ingot and 2.4g of Mg-30Y are melted under Ar protection at 780 DEG C, and then the melt is directionally solidified under a temperature gradient of 70K / cm, and the grain growth speed is 83um / s; and a magnesium alloy after directional solidification is obtained;

[0037] (2) the magnesium alloy after directional solidification is aged at 200 DEG C for 12h, and the high-plasticity magnesium alloy is obtained.

[0038] The magnesium alloy obtained by the above method contains 2.96% of Zn and 0.56% of Y in mass fraction, and the rest is Mg, which is measured actually. The average size of the high-plasticity magnesium alloy prepared under the condition is 214um, and the preferred growth orientation surface is a conical surface The growth orientation is

[0039] Embodiment 2

[0040] The embodiment provides a preparation method of a high-plasticity magnesium alloy, and comprises the following steps:

[0041] (1) 113.28g of Mg ingot, 4.32g of Zn ingot and 2.4g of Mg-30Y are melted under Ar protection at 780 DEG C, and then the melt is directionally solidified under a temperature gradient of 70K / cm, and the grain growth speed is 166um / s; and a magnesium alloy after directional solidification is obtained;

[0042] (2) the magnesium alloy after directional solidification is aged at 180 DEG C for 12h, and the high-plasticity magnesium alloy is obtained.

[0043] The high-plasticity magnesium alloy obtained by the above method contains 3.46% of Zn and 0.55% of Y in mass fraction, and the rest is Mg, which is measured actually. The average size of the high-plasticity magnesium alloy prepared under the condition is 232um, and the preferred growth orientation surface is a conical surface The growth orientation is

[0044] Embodiment 3

[0045] (1) 113.28g of Mg ingot, 4.32g of Zn ingot and 2.4g of Mg-30Y are melted under Ar protection at 780 DEG C, and then the melt is directionally solidified under a temperature gradient of 70K / cm, and the grain growth speed is 166um / s; and a magnesium alloy after directional solidification is obtained;

[0046] (2) the magnesium alloy after directional solidification is aged at 220℃ for 15h, to obtain the high plasticity magnesium alloy.

[0047] The high plasticity magnesium alloy obtained by the above method has a preferred growth orientation surface of a conical surface The growth orientation is

[0048] Example 4

[0049] (1) 113.28g of Mg ingot, 4.32g of Zn ingot and 2.4g of Mg-30Y are melted at 780℃ under Ar protection, and then the melt is subjected to directional solidification under a temperature gradient of 70K / cm, with a grain growth speed of 166μm / s, to obtain the magnesium alloy after directional solidification;

[0050] (2) the magnesium alloy after directional solidification is aged at 180℃ for 18h, to obtain the high plasticity magnesium alloy.

[0051] The high plasticity magnesium alloy obtained by the above method has a preferred growth orientation surface of a conical surface The growth orientation is

[0052] Comparative Example 1

[0053] The present comparative example provides a method for preparing a magnesium alloy, comprising the following steps:

[0054] 114g of Mg ingot, 3.6g of Zn ingot and 2.4g of Mg-30Y are melted at 780℃ under Ar protection, and then the melt is subjected to directional solidification under a temperature gradient of 70K / cm, with a grain growth speed of 83μm / s, to obtain the magnesium alloy.

[0055] The magnesium alloy obtained by the comparative example has a preferred growth orientation surface of a conical surface The growth orientation is

[0056] Comparative Example 2

[0057] The present comparative example provides a method for preparing a magnesium alloy, comprising the following steps:

[0058] 113.28g of Mg ingot, 4.32g of Zn ingot and 2.4g of Mg-30Y are melted at 780℃ under Ar protection, and then the melt is subjected to directional solidification under a temperature gradient of 70K / cm, with a grain growth speed of 166μm / s, to obtain the magnesium alloy.

[0059] The magnesium alloy obtained by the comparative example has a preferred growth orientation surface of a conical surface The growth orientation is

[0060] Comparative Example 3

[0061] The present comparative example provides a preparation method of a magnesium alloy, comprising the following steps:

[0062] (1) 113.28 g of Mg ingot, 4.32 g of Zn ingot and 2.4 g of Mg-30Y were melted at 780°C under Ar protection, and then the melt was naturally solidified to obtain a solidified magnesium alloy;

[0063] (2) The solidified magnesium alloy was aged at 200°C for 12 h to obtain the magnesium alloy.

[0064] Comparative Example 4

[0065] The present comparative example provides a preparation method of a magnesium alloy, comprising the following steps:

[0066] 113.28 g of Mg ingot, 4.32 g of Zn ingot and 2.4 g of Mg-30Y were melted at 780°C under Ar protection, and then the melt was naturally solidified to obtain a solidified magnesium alloy.

[0067] Test Example

[0068] Morphology analysis:

[0069] Figure 1 In FIG. a1 and b1, a1 and b1 are the crystal phase structures of the directional solidification experimental alloy with a grain growth rate of 83 μm / s before and after aging treatment in Example 1. As shown in FIG. a1, before aging treatment, the second phase mainly distributed on the grain boundary and presented as strips, and there were some large-sized granular second phases in the crystal. As shown in FIG. b1, with the aging treatment, more dispersed and fine granular second phases began to appear in the crystal, and there was no obvious change on the grain boundary.

[0070] Figure 1 In FIG. a2 and b2, a2 and b2 are the crystal phase structures of the directional solidification experimental alloy with a grain growth rate of 166 μm / s before and after aging treatment in Example 2. As shown in FIG. a2, before heat treatment, there were many large-sized granular second phases in the crystal, and the second phases were distributed in strips on the grain boundary. As shown in FIG. b2, after aging treatment, the second phases in the crystal were no longer simply large-sized second phases, but more dispersed and fine second phases were distributed around the large-sized granular second phases, and these second phases gradually tended to be homogenously and dispersedly distributed with the heat treatment.

[0071] Performance test

[0072] The standard tensile sample with a gauge length of 25 cm was stretched along the direction of directional solidification, and the stretching speed was 1×10 - 4 s -1Yield strength, tensile strength, and elongation after fracture were tested under the specified conditions. The test results are shown in Table 1. The trends of tensile strength and elongation after fracture are as follows: Figure 3 As stated above.

[0073] Table 1

[0074] Yield strength / MPa Tensile strength / MPa Elongation after break / % Example 1 175 182 38.65 Example 2 196 210 41.52 Example 3 178 205 36.42 Example 4 195 212 31.26 Comparative Example 1 125 156 22.30 Comparative Example 2 152 173 26.10 Comparative Example 3 120 156 8.25 Comparative Example 4 95 120 6.80

[0075] The second phase of Example 2 was measured:

[0076] Figure 2 The image shown is a scanning electron microscope (SEM) image of the high-ductility magnesium alloy in Example 2. Figure 2 a1 shows that the second phase of the magnesium alloy has a strip-shaped quasicrystalline structure uniformly distributed at the grain boundaries. Figure 2 b1 is its composition energy spectrum), through Figure 2 a2 shows that a large number of granular quasicrystalline phases are dispersed within the grains. Figure 2 b2 is its compositional energy spectrum. These quasicrystalline phases significantly affect the microstructure and mechanical properties of the alloy.

[0077] In summary, this method controls grain orientation and growth through directional solidification, optimizes the directionally solidified magnesium alloy sample through aging treatment, and further regulates the distribution of the second phase, thereby significantly improving the plasticity of the magnesium alloy while maintaining its strength.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for producing a high plasticity magnesium alloy, characterized by, Specifically, the following steps are included: The high-ductility magnesium alloy is obtained by aging treatment of the directionally solidified magnesium alloy; the high-ductility magnesium alloy contains Mg, Zn, and Y. The total content of Zn and Y in the magnesium alloy is 2.4-6.0% by mass fraction, with the remainder being Mg; the mass ratio of Zn to Y is (5-7):

1. The preferred growth orientation surface of the directional solidification magnesium alloy is a conical surface The growth orientation is 2. The method for preparing a high-ductility magnesium alloy according to claim 1, characterized in that, The aging treatment is performed at a temperature of 150-250℃ for 12-18 hours. Preferably, the aging treatment temperature is 180-220℃.

3. The method for preparing a high-ductility magnesium alloy according to claim 1 or 2, characterized in that, The method for preparing the directionally solidified magnesium alloy includes the following steps: melting the raw materials to obtain a magnesium alloy melt, and directionally solidifying the magnesium alloy melt to obtain the directionally solidified magnesium alloy.

4. The method for preparing a high-ductility magnesium alloy according to any one of claims 1-3, characterized in that, The raw materials used in the preparation include Mg ingots, Zn ingots, and Mg-Y master alloys; Preferably, the Mg-Y master alloy is selected from Mg-30Y.

5. The method for preparing a high-ductility magnesium alloy according to any one of claims 1-4, characterized in that, The melting temperature is 750-790℃.

6. The method for preparing a high-ductility magnesium alloy according to any one of claims 1-5, characterized in that, The melting process is carried out under the protection of a protective gas. Preferably, the protective gas is selected from Ar.

7. The method for preparing a high-ductility magnesium alloy according to any one of claims 1-6, characterized in that, The process of directional solidification of magnesium alloy melt involves controlling the temperature gradient in the solidification direction to be 70-90 K / cm and the grain growth rate to be 30-200 μm / s. Preferably, the grain growth rate is 80-170 μm / s.

8. The method for preparing a high-ductility magnesium alloy according to any one of claims 1-7, characterized in that, The average grain size of the magnesium alloy matrix after directional solidification is 200-250 μm.

9. A high-ductility magnesium alloy, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The high-ductility magnesium alloy according to claim 9, characterized in that, The high-plasticity magnesium alloy has a yield strength of 170-200 MPa, a tensile strength of 180-212 MPa, a plasticity of 31.0-42.2%, and a strength-ductility product of 5580-8947 MPa.

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