Mg-zr intermediate alloy and preparation method and application thereof

Abstract

The application provides a Mg-Zr intermediate alloy and a preparation method and application thereof, and relates to the technical field of cast magnesium alloy. The preparation method of the Mg-Zr intermediate alloy comprises the following steps: preparing a Mg-Zr alloy melt with a Zr content of 10-20wt%; subjecting the Mg-Zr alloy melt to mechanical force stirring at 50-100rpm; cooling and forming the Mg-Zr alloy melt after filtering through a ceramic filter block to obtain a Mg-Zr alloy ingot; and subjecting the Mg-Zr alloy ingot to solid solution treatment to obtain the Mg-Zr intermediate alloy. The Mg-Zr intermediate alloy prepared by the preparation method can improve the problems of the current Mg-Zr intermediate alloy, such as coarse Zr particles, high agglomeration ratio, and many inclusions, and can achieve the effects of slag removal and Zr particle reduction of the Mg-Zr intermediate alloy, so as to significantly improve the refining effect of Zr on the magnesium alloy.

Description

Technical Field

[0001] This invention relates to the technical field of cast magnesium alloys, and more particularly to a Mg-Zr master alloy, its preparation method, and its application. Background Technology

[0002] Magnesium alloys are currently the lightest metallic structural materials used in practical applications. They possess advantages such as high specific strength and specific stiffness, good vibration damping, and strong electromagnetic shielding. Therefore, magnesium alloys have been widely used in aerospace, transportation, and 3C products. Refining the grain size of magnesium alloys can not only further improve their overall mechanical properties but also control the microstructure during solidification, thereby improving casting performance. This is of great significance in promoting the development of magnesium alloys towards thinner walls, more complex structures, and larger sizes.

[0003] Zr is the most effective grain refiner for magnesium alloys (excluding elements such as Al, Si, Fe, and Mn). The addition of Zr can significantly refine the grains and improve the strength, toughness, and resistance to hot cracking of magnesium alloys. Zr exists in magnesium alloys mainly in two forms: undissolved particulate Zr and solute Zr dissolved in the matrix. Particulate Zr mainly achieves grain refinement through the heterogeneous nucleation effect (increasing the nucleation rate), while solute Zr mainly achieves grain refinement through the compositional supercooling effect (promoting grain nucleation and inhibiting grain growth).

[0004] Industrially, magnesium alloys are primarily refined by adding Mg-Zr master alloys. However, Zr in Mg-Zr master alloys mainly exists in particulate form. Traditional Mg-Zr master alloys often have coarse, inhomogeneous microstructures with significant agglomeration, making them prone to sedimentation during the refinement process. This leads to refinement degradation and low Zr yield. Furthermore, Mg-Zr master alloys often contain numerous inclusions, creating a conflict between refinement and purification. Therefore, a solution is urgently needed to address these issues. Summary of the Invention

[0005] The purpose of this invention is to provide a Mg-Zr master alloy, its preparation method, and its application, which can improve the problems of large Zr particles, high agglomeration ratio, and many inclusions in the current Mg-Zr master alloy. It can synergistically improve the purification of particle Zr, solute Zr, and magnesium alloy melt, and achieve the effect of slag removal and Zr particle sedimentation in Mg-Zr master alloy, thereby significantly improving the Zr refinement effect on magnesium alloy.

[0006] In a first aspect, the present invention provides a method for preparing a Mg-Zr master alloy, comprising the following steps:

[0007] Prepare Mg-Zr alloy melt with Zr content of 10-20 wt%;

[0008] The Mg-Zr alloy melt is stirred at 50-100 rpm under mechanical force.

[0009] The stirred Mg-Zr alloy melt was filtered through a ceramic filter block and then cooled and shaped to obtain Mg-Zr alloy ingots.

[0010] The Mg-Zr alloy ingot was subjected to solution treatment to obtain a Mg-Zr master alloy.

[0011] The beneficial effects of the method for preparing a Mg-Zr master alloy provided by this invention are as follows: By adjusting the mass fraction of Zr in the alloy melt and mechanically stirring the Mg-Zr alloy melt, the agglomerated Zr can be dispersed and the particulate Zr can be refined, increasing the proportion of Zr particles in the 1-5μm effective nucleation range; filtration of the Mg-Zr alloy melt using a ceramic filter block can purify the alloy melt and improve the problem of mutual restriction between refinement and purification in the alloy melt; and solution treatment can further dissolve Zr particles in the Mg matrix, maximizing the concentration of Zr solute atoms, exerting a better compositional supercooling effect, and synergistically enhancing the refinement effect of the Mg-Zr master alloy; that is, the preparation method proposed in this invention can achieve synergistic improvement of particulate Zr, solute Zr and melt purification, while eliminating the need for repeated remelting of the Mg-Zr master alloy, improving the convenience of preparing Mg-Zr master alloys, and making it suitable for large-scale industrial production.

[0012] Optionally, the step of preparing the Mg-Zr alloy melt with a Zr content of 10-20 wt% includes: crushing and shot-blasting the Mg-Zr commercial master alloy and commercial pure magnesium ingot, and then placing them in a vacuum medium-frequency induction furnace for vacuum melting at 780-800°C. The beneficial effects are: it can improve the surface cleanliness of the Mg-Zr commercial master alloy and commercial pure magnesium ingot, while facilitating their melting, and it is more conducive to the dissolution of Zr at high temperatures.

[0013] Optionally, the process of filtering the stirred Mg-Zr alloy melt through a ceramic filter block and then cooling and shaping it to obtain a Mg-Zr alloy ingot includes: the pore density of the ceramic filter block is 10-20 PPI. Its beneficial effect is that the filtration of the alloy melt by the ceramic filter block can improve the defects of excessive inclusions in the Mg-Zr intermediate alloy, thus achieving purification of the alloy melt.

[0014] Optionally, the process of filtering the stirred Mg-Zr alloy melt through a ceramic filter block and then cooling it to form a Mg-Zr alloy ingot includes: the cooling rate during cooling is 20-200℃ / s. Its beneficial effect is that rapid cooling of the Mg-Zr alloy melt can prevent the precipitation of a large amount of Zr solute, which is more conducive to subsequent solution treatment so that Zr particles dissolve in the Mg matrix.

[0015] Secondly, the present invention provides a Mg-Zr master alloy prepared using any of the above-mentioned optional preparation methods. Its advantage lies in its applicability to large-scale industrial production.

[0016] Thirdly, this invention provides an application of the Mg-Zr master alloy prepared by any of the above-mentioned optional preparation methods in the preparation of magnesium alloys. Its beneficial effects are: it can improve the grain refinement degree in magnesium alloys and enhance the mechanical properties of the prepared magnesium alloys.

[0017] Optionally, the process includes the following steps: preheating the Mg-Zr master alloy and placing it in a filter container, then placing the filter container in the molten magnesium alloy until the Mg-Zr master alloy melts, removing the filter container, stirring the melt, and maintaining the temperature; wherein the pore size of the filter container is 1-3 mm. Its beneficial effects are: it can further reduce the influence of impurities on the molten magnesium alloy and weaken the refining degradation effect caused by Zr sedimentation.

[0018] Optionally, the Mg-Zr master alloy can be preheated in an environment of 300-400°C. This has the advantage of accelerating the dissolution of the Mg-Zr master alloy in the magnesium alloy melt and preventing sedimentation.

[0019] Optionally, the Zr in the magnesium alloy has a mass fraction of 0.1-1%. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating a method for preparing a Mg-Zr master alloy according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram illustrating the use of a filter container when applying the Mg-Zr master alloy in magnesium alloy preparation according to an embodiment of the present invention.

[0022] Figure 3 This is a microstructure diagram of the Mg-Zr master alloy in Example 1 of the present invention;

[0023] Figure 4 This is a microstructure diagram of the commercial Mg-Zr master alloy used in Comparative Example 1 of this invention;

[0024] Figure 5The image shows the metallographic microstructure of the Mg-6.0wt%Zn-0.6wt%Zr alloy in Example 2 of this invention.

[0025] Figure 6 The image shows the metallographic microstructure of the Mg-6.0wt%Zn-0.6wt%Zr alloy in Comparative Example 1 of this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0027] Reference Figure 1 This invention provides a method for preparing a Mg-Zr master alloy, comprising the following steps:

[0028] S1. Content adjustment: Prepare Mg-Zr alloy melt with Zr content of 10-20wt%;

[0029] S2. Mechanical stirring: Apply mechanical force to the Mg-Zr alloy melt and stir at 50-100 rpm;

[0030] S3. Alloy ingot forming: After stirring, the Mg-Zr alloy melt is filtered through a ceramic filter block and then cooled and formed to obtain Mg-Zr alloy ingots.

[0031] S4. Solution treatment: After solution treatment of Mg-Zr alloy ingot, Mg-Zr master alloy is obtained.

[0032] In some embodiments, when performing step S1, the Mg-Zr commercial master alloy and commercial pure magnesium ingot are crushed and shot-blasted, and then placed in a vacuum medium-frequency induction furnace for vacuum melting in an environment of 780-800°C and 0.5Pa.

[0033] In some further embodiments, when performing step S1, the Mg-Zr commercial master alloy is selected as a Mg-30wt%Zr master alloy with a Zr content of 30%. Further, when performing step S1, the mass ratio of the Mg-30wt%Zr commercial master alloy to commercial pure magnesium ingot is 2:(1-4).

[0034] In some further embodiments, when performing step S1, a suitable mass of Mg-30wt% Zr commercial master alloy and commercial pure magnesium ingot are weighed according to the required Zr mass content in the Mg-Zr master alloy to be prepared.

[0035] In some embodiments, when performing step S1, a vacuum medium-frequency induction furnace equipped with a mechanical stirring device is selected to prepare the alloy melt.

[0036] In some embodiments, when performing step S2, the Mg-Zr alloy melt is stirred at a speed of 50-100 rpm for 2-5 minutes.

[0037] In some embodiments, when performing step S2, the stirring material located in the Mg-Zr alloy melt and performing substantial disturbance is a high-melting-point material, so as to avoid the stirring material melting into the alloy melt and causing melt contamination.

[0038] In some embodiments, when performing step S2, the Mg-Zr alloy melt is stirred by applying mechanical force, which can be done by electromagnetic stirring or motor-driven stirring.

[0039] In some embodiments, when performing step S3, the ceramic filter block selected has a pore density of 10-20 PPI (Pores Per Linear Inch).

[0040] In some embodiments, during step S3, the stirred Mg-Zr alloy melt is filtered through a ceramic filter block and then injected into a molding die for cooling and molding. Specifically, the molding die can be a water-cooled copper mold.

[0041] In some embodiments, during step S3, the alloy melt is cooled at a rate of 20-200°C / s during the cooling and forming process of the alloy ingot. Specifically, the alloy ingot can be cooled rapidly using water cooling, air cooling, or other heat exchange media.

[0042] In some embodiments, when performing step S3, a ceramic filter block is placed in advance at the opening of the molding die, so that the Mg-Zr alloy melt is poured onto the ceramic filter block. After being filtered by the ceramic filter block, the alloy melt enters the molding die.

[0043] In some embodiments, during step S4, the Mg-Zr alloy ingot is embedded in MgO powder for solution treatment. This serves two purposes: firstly, it thermodynamically inhibits the oxidation reaction of the Mg matrix in the Mg-Zr master alloy; secondly, since the MgO powder gradually sinters during high-temperature heat treatment, the sintered MgO powder provides support and protection for the Mg-Zr master alloy, isolating it from air and preventing the alloy from collapsing and overflowing due to occasional melting during heat treatment.

[0044] In some embodiments, when performing step S4, Mg-Zr alloy ingots and MgO powder are placed in a box-type resistance furnace and heated to 600-650°C and held for 6 hours to carry out a solid solution reaction.

[0045] In some embodiments, when performing step S4, the Mg-Zr alloy ingot and MgO powder are heated and dissolved in an inert protective gas atmosphere.

[0046] In some embodiments, when performing step S4, after the fixing process, the treated alloy ingot is taken out and air-cooled to room temperature.

[0047] The present invention also provides a Mg-Zr master alloy prepared by the preparation method in any of the above embodiments.

[0048] This invention also provides the application of the Mg-Zr master alloy prepared by the preparation method in any of the above embodiments in the preparation of magnesium alloys. The magnesium alloys include, but are not limited to, Mg-Y-Zr, Mg-Gd-Zr, Mg-Gd-Zr, Mg-Nd-Zr, Mg-Zn-Zr, and Mg-Gd-Y-Zr.

[0049] See Figure 2 The Mg-Zr master alloy provided by the present invention, when preparing magnesium alloy, includes: preheating the Mg-Zr master alloy 1 and placing it in a filter container 2, and placing the filter container 2 in the magnesium alloy melt 3. After the Mg-Zr master alloy melts, the filter container 2 is taken out, and the melt is stirred and kept warm; wherein, the pore size of the filter container is 1-3mm.

[0050] In some embodiments, when preheating the Mg-Zr master alloy, the Mg-Zr master alloy is placed in an environment of 300-400°C for preheating.

[0051] In some embodiments, the filter container can be a steel filter container. In practice, the material of the filter container only needs to ensure that it will not melt into the molten metal.

[0052] In some embodiments, when preparing magnesium alloys using Mg-Zr master alloys, the mass fraction of Zr in the magnesium alloy is 0.1-1%.

[0053] Example 1

[0054] This embodiment 1 provides a method for preparing a Mg-15wt% Zr master alloy, including the following steps:

[0055] S1. Content Adjustment: Weigh 10 kg of Mg-30wt% Zr commercial master alloy and 10 kg of commercial pure magnesium ingot. After crushing and shot blasting the Mg-30wt% Zr commercial master alloy and commercial pure magnesium ingot, place them in a vacuum medium-frequency induction furnace with an ultimate vacuum degree of 0.5 Pa and melt them at 780-800℃ to obtain Mg-15wt% Zr alloy melt.

[0056] S2. Mechanical stirring: Apply mechanical force to the Mg-15wt%Zr alloy melt in S1 and stir at 80rpm for 4min.

[0057] S3. Alloy Ingot Forming: The Mg-15wt%Zr alloy melt after stirring in S2 is filtered through a ceramic filter block and then poured into a water-cooled copper mold. It is cooled and formed at a cooling rate of 100-120℃ / s to obtain the Mg-15wt%Zr alloy ingot. The pore density of the ceramic filter block is 10-20PPI.

[0058] S4. Solution treatment: The Mg-15wt%Zr alloy ingot formed in S3 is embedded in MgO powder. After the MgO powder and alloy ingot are completely covered with aluminum foil, they are placed in a box-type resistance furnace with inert protective gas. The furnace is heated to 600-650℃ and held for 6 hours. The treated alloy ingot is then removed and air-cooled to room temperature to obtain the Mg-15wt%Zr master alloy.

[0059] Composition determination: The chemical composition of the commercial Mg-30wt%Zr master alloy and the Mg-15wt%Zr master alloy treated in Example 1 were analyzed using a direct-reading spectrometer. The specific chemical compositions of the two are shown in Table 1. Observation Figure 3 and Figure 4 The microstructure of the intermediate alloy shown is presented. The proportions of Zr particles (1-5 μm), Zr clusters, and impurities are statistically analyzed. The proportions of solute Zr in the Mg-Zr intermediate alloy treated in Example 1 and the commercial Mg-30wt% Zr intermediate alloy are also analyzed using energy dispersive spectroscopy (EDS), as shown in Table 2.

[0060] Table 1 Chemical composition of commercial master alloy and master alloy treated in Example 1

[0061]

[0062] Table 2. Statistics on the proportion of various Zr types in commercial master alloys and master alloys treated in Example 1.

[0063]

[0064] Referring to Table 2, the Mg-15wt% Zr master alloy prepared in Example 1 has a particle Zr content of approximately 71.33% in the 1-5μm range, a cluster Zr content of approximately 1.55%, a solute Zr content of approximately 2.21%, and an impurity content of approximately 0.49%. It can be seen that treating the Mg-30wt% commercial master alloy using the preparation method provided by this invention can increase the particle Zr content in the effective heterogeneous nucleation region of the Mg-Zr master alloy by approximately 41.27%, reduce the cluster Zr content by approximately 31.08%, reduce the impurity content by 0.49%, and after solution treatment, the solute Zr content that exerts the compositional supercooling effect increases by approximately 1.83%.

[0065] Example 2

[0066] This embodiment 2 provides a method for preparing magnesium alloys using the Mg-15wt%Zr master alloy prepared in embodiment 1, specifically for preparing Mg-6.0wt%Zn-0.6wt%Zr alloys, including the following steps:

[0067] D1. Batching: Weigh out pure magnesium ingots, pure zinc ingots and Mg-15wt%Zr master alloy according to the target composition ratio of Mg-6.0wt%Zn-0.6wt%Zr. Place the pure magnesium ingots and pure zinc ingots in an environment of 100-200℃ for preheating, and place the Mg-15wt%Zr master alloy in an environment of 300-400℃ for preheating.

[0068] D2. Alloy Melting: Spread a layer of commercial No. 5 solvent at the bottom of a crucible at 500℃. Then, place the preheated pure magnesium ingot from D1 into the crucible and spread commercial No. 5 solvent on the surface of the pure magnesium ingot again. During the melting of the pure zinc ingot, introduce a mixture of 1 vol.% SF6 and CO2 gas. After uniformly heating the crucible to 710-730℃, when the pure magnesium ingot is completely melted, add the preheated pure zinc ingot from D1. After the pure zinc ingot melts, stir for 2 minutes, then uniformly heat the crucible to 780-800℃, and add the preheated SF6 and CO2 gas from D1. The heated Mg-15wt%Zr master alloy was placed in a steel filter container, which was then immersed in the melt in the crucible, ensuring the Mg-15wt%Zr master alloy was submerged. After the Mg-15wt%Zr master alloy melted, the steel filter container was removed, and the melt in the crucible was stirred for 3-5 minutes. The crucible was then held at 780℃ for 5 minutes. The steel filter container was specifically a steel filter screen with dimensions of 80×60×50mm and a pore size of 1-3mm.

[0069] D3. Refining and Casting: After uniformly reducing the temperature of the melt in the crucible in D2 to 750℃, a refining agent is added to refine the melt in the crucible. Ar gas is introduced during the refining process to remove the slag inside and on the surface of the melt. After refining, the temperature of the melt is controlled at 710℃ and held for 10 minutes. The chemical composition of the alloy melt is then determined. If it is qualified, the melt is poured into a preheated mold to cool and form, thus obtaining a Mg-6.0wt%Zn-0.6wt%Zr alloy. The refining agent is a mixture of commercial No. 5 solvent and fluorite powder in a weight ratio of 5:1.

[0070] After measurement, and see Figure 5 In the Mg-6.0wt%Zn-0.6wt%Zr alloy prepared in Example 2, the average grain size is 68.64 micrometers.

[0071] Comparative Example 1

[0072] Comparative Example 1 provides a method for preparing a Mg-6.0wt%Zn-0.6wt%Zr alloy. The difference between Comparative Example 1 and Example 2 is that Comparative Example 1 uses a Mg-30wt% commercial master alloy instead of the Mg-15wt%Zr master alloy in Example 2. In Comparative Example 1, when adding the Mg-30wt% commercial master alloy in step D2, a steel filter container is not used. Instead, the Mg-30wt% commercial master alloy is directly added to the melt.

[0073] After measurement, and see Figure 6 In the magnesium alloy prepared in Comparative Example 1, the average grain size was 118.6 micrometers.

[0074] It can be seen that the Mg-Zr master alloy provided by the present invention greatly improves the grain refinement effect of magnesium alloy. The grain size of the Mg-6.0wt%Zn-0.6wt%Zr magnesium alloy provided by the present invention is refined by about 42.12% compared with the ordinary Mg-6.0wt%Zn-0.6wt%Zr magnesium alloy. At the same time, by introducing a filter container during the preparation of magnesium alloy, the influence of impurities in the master alloy on the alloy melt can be further reduced, and the grain refinement decay effect caused by Zr precipitation can be avoided, thus improving the defect of mutual restriction between the refinement and purification of magnesium alloy.

[0075] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for preparing a Mg-Zr master alloy, characterized in that, Includes the following steps: Prepare Mg-Zr alloy melt with Zr content of 10-20 wt%; The Mg-Zr alloy melt is stirred at 50-100 rpm under mechanical force. After stirring, the Mg-Zr alloy melt is filtered through a ceramic filter block with a pore density of 10-20 PPI and then cooled and shaped at a cooling rate of 20-200℃ / s to obtain Mg-Zr alloy ingots. The Mg-Zr alloy ingot was subjected to solution treatment to obtain a Mg-Zr master alloy.

2. The preparation method according to claim 1, characterized in that, The steps for preparing the Mg-Zr alloy melt with a Zr content of 10-20 wt% include: After crushing and shot blasting, commercial Mg-Zr intermediate alloy and commercial pure magnesium ingots are placed in a vacuum medium-frequency induction furnace for vacuum melting at 780-800℃.

3. A Mg-Zr master alloy prepared by the preparation method according to any one of claims 1 to 2.

4. The application of a Mg-Zr master alloy prepared by the preparation method according to any one of claims 1 to 2 in the preparation of magnesium alloys.

5. The application according to claim 4, characterized in that, Includes the following steps: After preheating the Mg-Zr master alloy, it is placed in a filter container, and then the filter container is placed in the magnesium alloy melt. After the Mg-Zr master alloy melts, the filter container is removed, and the melt is stirred and kept at a constant temperature. The pore size of the filter container is 1-3 mm.

6. The application according to claim 5, characterized in that, The Mg-Zr master alloy is preheated in an environment of 300-400℃.

7. The application according to claim 5, characterized in that, The Zr content in the magnesium alloy is 0.1-1% by mass.

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