CN116770109A

CN116770109A - Mg-Zr intermediate alloy and preparation method and application thereof

Info

Publication number: CN116770109A
Application number: CN202310698976.XA
Authority: CN
Inventors: 刘勇; 曾刚; 刘洪�; 李建龙
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2023-06-13
Filing date: 2023-06-13
Publication date: 2023-09-19

Abstract

The invention provides an Mg-Zr intermediate alloy, 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 an Mg-Zr alloy melt with the Zr content of 10-20wt%; stirring the Mg-Zr alloy melt at 50-100rpm by applying mechanical force; filtering the stirred Mg-Zr alloy melt through a ceramic filter block, and cooling and forming to obtain an Mg-Zr alloy ingot; and carrying out solution treatment on the Mg-Zr alloy ingot to obtain the Mg-Zr intermediate alloy. The Mg-Zr intermediate alloy prepared by the preparation method provided by the invention can solve the problems of coarse Zr particles, high agglomeration proportion, multiple inclusions and the like in the existing Mg-Zr intermediate alloy, so that the synergistic improvement of purification of granular Zr, solute Zr and magnesium alloy melt can achieve the effects of deslagging the Mg-Zr intermediate alloy and reducing sedimentation of Zr particles, and further the refinement effect of Zr on the magnesium alloy is remarkably improved.

Description

Mg-Zr intermediate alloy and preparation method and application thereof

Technical Field

The invention relates to the technical field of cast magnesium alloy, in particular to an Mg-Zr intermediate alloy and a preparation method and application thereof.

Background

The magnesium alloy is the lightest metal structural material in the actual application at present, has the advantages of high specific strength and specific rigidity, good shock absorption, strong electromagnetic shielding property and the like, and therefore, the magnesium alloy is widely applied to the fields of aerospace, transportation, 3C products and the like. The grain refinement of the magnesium alloy can further improve the comprehensive mechanical property of the magnesium alloy, and can regulate and control the structure morphology of the alloy in the solidification process, thereby improving the casting performance, and having great significance for pushing the magnesium alloy to develop towards thin walls, complexity and large trends.

Zr is the most effective grain refiner of magnesium alloy (without Al, si, fe, mn and other elements), and the addition of Zr can obviously refine grains, improve the strength, toughness, hot cracking resistance and the like of the magnesium alloy. Zr mainly exists in the magnesium alloy in two forms of undissolved particles Zr and solute Zr dissolved in the matrix. Grain Zr realizes grain refinement mainly through heterogeneous nucleation effect (improving nucleation rate), while solute Zr realizes grain refinement mainly through component supercooling effect (promoting grain nucleation, inhibiting grain growth).

The magnesium alloy is refined mainly by adding the Mg-Zr intermediate alloy in industry, however, zr mainly exists in a particle form in the Mg-Zr intermediate alloy, the traditional Mg-Zr intermediate alloy is often coarse and uneven in structure, obvious in agglomeration, easy to subside in the refining process, and the phenomena of refining decline, low Zr yield and the like are caused, and meanwhile, more inclusions in the Mg-Zr intermediate alloy are often caused, so that the problem of mutual restriction of refining and purifying is easy to occur. It is therefore desirable to provide a solution to the above-mentioned problems.

Disclosure of Invention

The invention aims to provide a Mg-Zr intermediate alloy, a preparation method and application thereof, which can solve the problems of coarse Zr particles, high agglomeration proportion, multiple inclusions and the like in the existing Mg-Zr intermediate alloy, improve the synergic purification of particle Zr, solute Zr and magnesium alloy melt, achieve the effects of deslagging the Mg-Zr intermediate alloy and reducing sedimentation of Zr particles, and further remarkably improve the refining effect of Zr on the magnesium alloy.

In a first aspect, the invention provides a preparation method of an Mg-Zr intermediate alloy, which comprises the following steps:

preparing an Mg-Zr alloy melt with the Zr content of 10-20wt%;

stirring the Mg-Zr alloy melt at 50-100rpm by applying mechanical force;

filtering the stirred Mg-Zr alloy melt through a ceramic filter block, and cooling and forming to obtain an Mg-Zr alloy ingot:

and carrying out solution treatment on the Mg-Zr alloy ingot to obtain the Mg-Zr intermediate alloy.

The preparation method of the Mg-Zr intermediate alloy provided by the invention has the beneficial effects that: by adjusting the mass fraction of Zr in the alloy melt and adopting mechanical stirring to the Mg-Zr alloy melt, the dispersion of cluster Zr can be realized, the particle Zr is refined, and the Zr particle proportion between effective nucleation areas of 1-5 mu m is improved; the Mg-Zr alloy melt is filtered by adopting a ceramic filter block, so that the purification of the alloy melt can be realized, and the problem of mutual restriction of refining and purification in the alloy melt can be solved; the Zr particles can be further dissolved in the Mg matrix through solution treatment, so that the concentration of Zr solute atoms is improved to the greatest extent, a better component supercooling effect is exerted, and the refining effect of the Mg-Zr intermediate alloy is cooperatively improved; namely, the preparation method provided by the invention can realize the synergistic improvement of the purification of the granular Zr, the solute Zr and the melt, does not need repeated remelting of the Mg-Zr intermediate alloy, can improve the convenience of preparing the Mg-Zr intermediate alloy, and can be suitable for large-scale industrialized production.

Optionally, the step of preparing the Mg-Zr alloy melt having a Zr content of 10-20wt% includes: crushing and shot blasting are carried out on the commercial Mg-Zr intermediate alloy and commercial pure magnesium ingot, and then the commercial Mg-Zr intermediate alloy and commercial pure magnesium ingot are placed in a vacuum medium-frequency induction furnace for vacuum smelting at 780-800 ℃. The beneficial effects are that: the surface cleanliness of the commercial intermediate alloy of Mg-Zr and commercial pure magnesium ingot can be improved, smelting is facilitated, and Zr dissolution is facilitated at a high temperature.

Optionally, the process of performing the cooling molding after the stirred Mg-Zr alloy melt flows through the ceramic filter block for filtering to prepare the Mg-Zr alloy ingot comprises the following steps: the ceramic filter block has a pore density of 10-20PPI. The beneficial effects are that: through the filtering effect of the ceramic filter block on the alloy melt, the defect of more impurities in the Mg-Zr intermediate alloy can be improved, and the purification of the alloy melt is realized.

Optionally, the process of performing the cooling molding after the stirred Mg-Zr alloy melt flows through the ceramic filter block for filtering to prepare the Mg-Zr alloy ingot comprises the following steps: the cooling rate is 20-200 ℃/s during cooling and molding. The beneficial effects are that: the Mg-Zr alloy melt is rapidly cooled, so that a large amount of solute Zr is prevented from being separated out, and the subsequent solid solution treatment is more facilitated, so that Zr particles are solid-dissolved in the Mg matrix.

In a second aspect, the present invention provides a mg—zr master alloy prepared using any of the above-described alternative preparation methods. The beneficial effects are that: can be suitable for large-scale industrial production.

In a third aspect, the invention provides an application of the Mg-Zr intermediate alloy prepared by any one of the optional preparation methods in preparation of magnesium alloy. The beneficial effects are that: can improve the grain refinement degree in the magnesium alloy and the mechanical property of the prepared magnesium alloy.

Optionally, the method comprises the following steps: preheating the Mg-Zr intermediate alloy, placing the Mg-Zr intermediate alloy in a filtering container, placing the filtering container in a magnesium alloy melt, taking out the filtering container after the Mg-Zr intermediate alloy is melted, stirring the melt, and preserving heat; wherein the aperture of the filtering container is 1-3mm. The beneficial effects are that: the influence of impurities on the magnesium alloy melt can be further reduced, and the thinning fading effect caused by Zr sedimentation is weakened.

Optionally, the mg—zr master alloy is preheated in an environment of 300-400 ℃. The beneficial effects are that: the dissolution of the Mg-Zr intermediate alloy in the magnesium alloy melt can be quickened, and sedimentation is avoided.

Optionally, the mass fraction of Zr in the magnesium alloy is 0.1-1%.

Drawings

FIG. 1 is a flow chart of a method for preparing an Mg-Zr intermediate alloy according to an embodiment of the invention;

FIG. 2 is a schematic diagram showing the use of a filtration vessel when the Mg-Zr intermediate alloy according to the embodiment of the invention is applied to the preparation of magnesium alloy;

FIG. 3 is a microstructure of the Mg-Zr intermediate alloy in example 1 according to the invention;

FIG. 4 is a microstructure of a commercial Mg-Zr master alloy used in comparative example 1 of the present invention;

FIG. 5 is a metallographic microstructure of Mg-6.0wt% Zn-0.6wt% Zr alloy in example 2 according to the invention;

FIG. 6 is a metallographic microstructure of a Mg-6.0wt% Zn-0.6wt% Zr alloy in comparative example 1 of the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Unless otherwise defined, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. As used herein, the word "comprising" and the like means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof without precluding other elements or items.

Referring to fig. 1, an embodiment of the present invention provides a method for preparing mg—zr intermediate alloy, including the steps of:

s1, content adjustment: preparing an Mg-Zr alloy melt with the Zr content of 10-20wt%;

s2, mechanically stirring: stirring the Mg-Zr alloy melt at 50-100rpm by applying mechanical force;

s3, forming an alloy ingot: filtering the stirred Mg-Zr alloy melt through a ceramic filter block, and cooling and forming to obtain an Mg-Zr alloy ingot;

s4, solution treatment: and carrying out solution treatment on the Mg-Zr alloy ingot to obtain the Mg-Zr intermediate alloy.

In some embodiments, when the step S1 is executed, after the commercial intermediate alloy of Mg-Zr and commercial pure magnesium ingot are crushed and shot-blasted, the commercial intermediate alloy is placed in a vacuum medium-frequency induction furnace, and vacuum smelting is carried out in an environment of 780-800 ℃ and 0.5 Pa.

In some further embodiments, step S1 is performed using a commercial Mg-Zr master alloy comprising 30% by weight of Zr as the Mg-30% by weight of Zr master alloy. Further, when the step S1 is executed, the mass ratio of the commercial intermediate alloy of Mg-30wt% Zr to the commercial pure magnesium ingot is 2: (1-4).

In some further embodiments, step S1 is performed to prepare a Mg-Zr master alloy based on the mass content of Zr in the Mg-Zr master alloy as desired, to weigh suitable masses of Mg-30wt% Zr commercial master alloy and commercial pure magnesium ingot.

In some embodiments, when step S1 is performed, a vacuum medium frequency induction furnace equipped with a mechanical stirring device is selected for preparing the alloy melt.

In some embodiments, step S2 is performed by stirring the Mg-Zr alloy melt at a speed of 50-100rpm for 2-5 minutes.

In some embodiments, when step S2 is performed, the material of the stirring portion that is located in the mg—zr alloy melt and performs substantial disturbance is a high melting point material, so as to avoid melt contamination caused by the stirring material being melted into the alloy melt.

In some embodiments, when step S2 is performed, the Mg-Zr alloy melt is stirred by applying mechanical force, and may be stirred by electromagnetic stirring or motor driven stirring.

In some embodiments, the ceramic filter block selected for step S3 has a pore density of 10-20PPI (average pore number per inch length, pores Per Linear Inch).

In some embodiments, when step S3 is performed, the stirred Mg-Zr alloy melt is filtered by a ceramic filter block, and then is injected into a forming mold to be cooled and formed. Specifically, the forming die may be a water-cooled copper die.

In some embodiments, the alloy melt is cooled at a cooling rate of 20-200 ℃/S during the cooling and forming of the alloy ingot when step S3 is performed. Specifically, the alloy ingot can be cooled rapidly by water cooling, air cooling or other heat exchange media.

In some embodiments, when step S3 is performed, the ceramic filter block is placed at the opening of the forming mold in advance, so that the mg—zr alloy melt is poured onto the ceramic filter block, and after the filtering action of the ceramic filter block, the alloy melt enters the forming mold.

In some embodiments, step S4 is performed by embedding mg—zr alloy ingots in MgO powder for solution treatment. Therefore, on one hand, the oxidation reaction of the Mg matrix in the Mg-Zr intermediate alloy can be inhibited from the thermodynamic aspect, and on the other hand, the MgO powder is gradually sintered and formed in the high-temperature heat treatment process, so that the MgO powder after the sintering and forming has certain supporting and protecting effects on the Mg-Zr intermediate alloy, the air is isolated, and meanwhile, the phenomenon that the alloy collapses and overflows due to the fact that the Mg-Zr intermediate alloy is molten occasionally in the heat treatment process is avoided.

In some embodiments, when step S4 is performed, the mg—zr alloy ingot and MgO powder are placed in a box-type resistance furnace, and heated to 600-650 ℃ and kept for 6 hours to perform a solid solution reaction.

In some embodiments, when step S4 is performed, the mg—zr alloy ingot and MgO powder are placed in an atmosphere of inert shielding gas for heating and solid solution.

In some embodiments, when step S4 is performed, after the fixing process, the processed alloy ingot is taken out and cooled to room temperature.

The invention also provides the Mg-Zr intermediate alloy prepared by the preparation method in any embodiment.

The invention also provides an application of the Mg-Zr intermediate alloy prepared by the preparation method in any embodiment in preparation of magnesium alloy. Wherein the magnesium alloy comprises, but is not limited to, mg-Y-Zr, mg-Gd-Zr, mg-Nd-Zr, mg-Zn-Zr and Mg-Gd-Y-Zr.

Referring to fig. 2, the mg—zr intermediate alloy provided by the present invention includes, when preparing a magnesium alloy: preheating the Mg-Zr intermediate alloy 1, placing the Mg-Zr intermediate alloy in a filter container 2, placing the filter container 2 in a magnesium alloy melt 3, taking out the filter container 2 after the Mg-Zr intermediate alloy is melted, stirring the melt, and preserving heat; wherein the pore diameter of the filtering container is 1-3mm.

In some embodiments, the Mg-Zr master alloy is preheated by placing the Mg-Zr master alloy in an environment of 300-400 ℃.

In some embodiments, the filtration vessel may be a steel filtration vessel. In practice, the material of the filter vessel need only ensure that it does not melt in the melt itself.

In some embodiments, the Mg-Zr intermediate alloy is used to prepare a magnesium alloy, where the mass fraction of Zr in the magnesium alloy is 0.1-1%.

Example 1

This example 1 provides a method for preparing a Mg-15wt% Zr intermediate alloy comprising the steps of:

s1, content adjustment: weighing 10kg of commercial intermediate alloy of Mg-30wt% Zr and 10kg of commercial pure magnesium ingot, crushing and shot blasting the commercial intermediate alloy of Mg-30wt% Zr and the commercial pure magnesium ingot, placing the commercial intermediate alloy of Mg-30wt% Zr and the commercial pure magnesium ingot in a vacuum medium frequency induction furnace with the ultimate vacuum degree of 0.5Pa, and melting the commercial intermediate alloy of Mg-30wt% Zr in the environment of 780-800 ℃ to prepare a melt of the alloy of Mg-15wt% Zr;

s2, mechanically stirring: applying mechanical force to the Mg-15wt% Zr alloy melt in the step S1, and stirring for 4min at the rotating speed of 80 rpm;

s3, forming an alloy ingot: filtering the Mg-15wt% Zr alloy melt subjected to stirring treatment in the step S2 through a ceramic filter block, injecting the filtered Mg-15wt% Zr alloy melt into a water-cooled copper mold, and cooling and molding at a cooling rate of 100-120 ℃/S to obtain an Mg-15wt% Zr alloy ingot; wherein the pore density of the ceramic filter block is 10-20PPI;

s4, solution treatment: embedding the Mg-15wt% Zr alloy ingot molded in the step S3 into MgO powder, using aluminum foil to integrally cover the MgO powder and the alloy ingot, placing the MgO powder and the alloy ingot into a box-type resistance furnace filled with inert protective gas, heating to 600-650 ℃ along with the furnace, preserving heat for 6 hours, taking out the processed alloy ingot, and cooling to room temperature by air to obtain the Mg-15wt% Zr intermediate alloy.

Component measurement: the chemical compositions of the commercial Mg-30wt% Zr intermediate alloy and the Mg-15wt% Zr intermediate alloy treated in example 1 were analyzed by a direct-reading spectrometer, and the specific chemical compositions of the two are shown in Table 1; the master alloy microstructure plots shown in FIGS. 3 and 4 were observed, and the 1-5 μm particle Zr duty, cluster Zr duty and impurity duty were counted, and the duty ratio of the Mg-Zr master alloy treated in example 1 to the solute Zr in the commercial Mg-30wt% Zr master alloy was examined using energy spectrum analysis/EDS, as shown in Table 2.

TABLE 1 chemical compositions of commercial master alloys and of treated master alloys of example 1

TABLE 2 statistics of the Zr duty cycle of the various types in commercial master alloys and the master alloys after treatment in example 1

As shown in Table 2, in the Mg-15wt% Zr intermediate alloy prepared in this example 1, the 1-5 μm interval of the particle Zr was about 71.33%, the cluster Zr was about 1.55%, the solute Zr was about 2.21%, and the impurity content was about 0.49%; it can be seen that the preparation method provided by the invention is used for treating the commercial intermediate alloy with the content of Mg-30wt%, the particle Zr ratio between effective heterogeneous nucleation regions in the Mg-Zr intermediate alloy can be improved by about 41.27%, the cluster Zr ratio is reduced by about 31.08%, the impurity ratio is reduced by 0.49%, and the solute Zr content which plays a role of supercooling of components is increased by about 1.83% after solution treatment.

Example 2

This example 2 provides a method for preparing a magnesium alloy using the Mg-15wt% zr master alloy prepared in example 1, specifically for preparing Mg-6.0wt% zn-0.6wt% zr alloy, comprising the steps of:

d1, proportioning: weighing a pure magnesium ingot, a pure zinc ingot and a Mg-15wt% Zr intermediate alloy according to the target component proportion of Mg-6.0wt% Zn-0.6wt% Zr, preheating the pure magnesium ingot and the pure zinc ingot in an environment of 100-200 ℃, and preheating the Mg-15wt% Zr intermediate alloy in an environment of 300-400 ℃;

d2, alloy smelting: spreading a layer of commercial No. 5 solvent at the bottom of a crucible at 500 ℃, then putting the preheated pure magnesium ingot in D1 into the crucible, spreading the commercial No. 5 solvent again on the surface of the pure magnesium ingot, and introducing 1vol.% SF in the smelting process of the pure zinc ingot ₆ And CO ₂ Mixing the gases; uniformly heating a crucible to 710-730 ℃, adding the preheated pure zinc ingot in D1 after pure magnesium ingot is completely melted, uniformly heating the crucible to 780-800 ℃ after stirring for 2min after pure zinc ingot is melted, placing the preheated Mg-15wt% Zr intermediate alloy in S1 in a steel filter container, immersing the steel filter container in a melt in the crucible, submerging the Mg-15wt% Zr intermediate alloy in the melt, taking out the steel filter container after the Mg-15wt% Zr intermediate alloy is melted, stirring the melt in the crucible for 3-5min, and then placing the crucible at 780 ℃ for 5min; wherein, the steel filter container is specifically a steel filter screen, the size of the steel filter screen is 80 multiplied by 60 multiplied by 50mm, and the aperture size is 1-3mm:

and D3, refining and casting molding: uniformly reducing the temperature of the melt in the crucible in D2 to 750 ℃, adding a refining agent to refine the melt in the crucible, introducing Ar gas in the refining process, removing scum in and on the melt, controlling the temperature of the melt at 710 ℃ after the refining is finished, preserving the temperature for 10min, measuring the chemical components of the alloy melt, pouring the melt into a preheated die after the melt is qualified, and cooling and forming to obtain Mg-6.0wt% Zn-0.6wt% Zr alloy; wherein the refining agent is commercial No. 5 solvent and fluorite powder according to the weight ratio of 5: 1.

As determined, and referring to FIG. 5, the average grain size in the Mg-6.0wt% Zn-0.6wt% Zr alloy prepared in this example 2 was 68.64. Mu.m.

Comparative example 1

This comparative example 1 provides a method for preparing an Mg-6.0wt% zn-0.6wt% zr alloy, which is different from example 2 in that Mg-30wt% commercial master alloy is used instead of Mg-15wt% zr master alloy in example 2 in comparative example 1, and Mg-30wt% commercial master alloy is added in step D2 in comparative example 1, a steel filter vessel is not used, but Mg-30wt% commercial master alloy is directly put into melt.

The average grain size in the magnesium alloy prepared in this comparative example 1 was determined to be 118.6 μm, see fig. 6.

According to the Mg-Zr intermediate alloy provided by the invention, the refining effect on the magnesium alloy is greatly improved, the grain size of the Mg-6.0wt% Zn-0.6wt% Zr magnesium alloy is about 42.12% finer than that of the common Mg-6.0wt% Zn-0.6wt% Zr magnesium alloy, and meanwhile, in the preparation process of the magnesium alloy, the influence of impurities in the intermediate alloy on alloy melt can be further weakened by introducing a filtering container, the refining fading effect generated by Zr sedimentation can be avoided, and the defect that the refining and purifying of the magnesium alloy are mutually restricted is overcome.

While embodiments of the present invention have been described in detail hereinabove, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. It is to be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the following claims. Moreover, the invention described herein is capable of other embodiments and of being practiced or of being carried out in various ways.

Claims

1. A method for preparing Mg-Zr master alloy, which is characterized in that it includes the following steps:

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

Apply mechanical force to the Mg-Zr alloy melt and stir it at 50-100 rpm;

The stirred Mg-Zr alloy melt is filtered through a ceramic filter block, and then cooled and shaped to obtain an Mg-Zr alloy ingot;

The Mg-Zr alloy ingot is subjected to solid solution treatment to prepare an Mg-Zr master alloy.

2. The preparation method according to claim 1, characterized in that the step of preparing the Mg-Zr alloy melt with a Zr content of 10-20 wt% includes:

After the Mg-Zr commercial master alloy and commercial pure magnesium ingot are crushed and shot blasted, they are placed in a vacuum medium frequency induction furnace for vacuum melting at 780-800°C.

3. The preparation method according to claim 1, wherein the process of filtering the stirred Mg-Zr alloy melt through a ceramic filter block and then cooling and shaping it to obtain the Mg-Zr alloy ingot includes:

The pore density of the ceramic filter block is 10-20PPI.

4. The preparation method according to claim 1, wherein the process of filtering the stirred Mg-Zr alloy melt through a ceramic filter block and then cooling and shaping it to obtain the Mg-Zr alloy ingot includes:

The cooling rate during cooling molding is 20-200°C/s.

5. A Mg-Zr master alloy prepared by the preparation method according to any one of claims 1 to 4.

6. Application of the Mg-Zr master alloy prepared by the preparation method according to any one of claims 1 to 4 in the preparation of magnesium alloys.

7. The application according to claim 6, characterized in that it includes the following steps:

Preheat the Mg-Zr master alloy and place it in a filter container, and place the filter container in the magnesium alloy melt. After the Mg-Zr master alloy melts, take out the filter container, stir the melt and keep it warm; wherein, the filter The hole diameter of the container is 1-3mm.

8. The application according to claim 7, characterized in that the Mg-Zr master alloy is placed in an environment of 300-400°C for preheating.

9. The application according to claim 7, characterized in that the mass fraction of Zr in the magnesium alloy is 0.1-1%.