A Ce-containing master alloy refiner suitable for magnesium alloys and its preparation method

Abstract

A Ce-containing intermediate alloy refiner suitable for magnesium alloys and a preparation method thereof belong to the technical field of magnesium and magnesium alloy modification. The preparation of the refiner includes the following steps: Al powder, CeO2 powder, and graphite powder are placed in a planetary ball mill and mixed evenly; the mixed powder is filled into a pure Al tube and sealed to prevent overflow; the Al tube sealed with the mixed powder is subjected to multiple hot rolling to obtain a preform to achieve an effective combination of the mixed powder and the aluminum tube; the hot-rolled preform, pure aluminum, and pure magnesium are placed in a medium frequency furnace for smelting, and after the reaction is complete, they are cast into a steel mold to finally form the intermediate alloy refiner. The technical solution of the present invention can overcome the non-wettability between aluminum liquid and graphite and effectively improve the reaction efficiency; it is beneficial to reduce the agglomeration of effective particles and increase the particle yield. The preparation method of the refiner is simple, the raw materials are readily available, and it is suitable for large-scale industrial production applications.

Description

Technical Field

[0001] The invention belongs to the field of processing and modification of magnesium and magnesium alloys, and particularly relates to a grain refiner for magnesium alloys and a preparation process thereof. Background Art

[0002] Studies have found that grain refinement can significantly increase the strength of magnesium alloys while also effectively improving the plasticity of magnesium alloys. This is of great significance for improving the microstructure of the alloy, enhancing its plastic forming ability and mechanical properties. On the other hand, grain refinement can result in a higher volume fraction of dendrite overlap points in the solidified alloy, which is beneficial to the shrinkage feeding of the liquid alloy and improves the fluidity of the alloy. It can be seen that grain refinement is an extremely ideal means to improve the comprehensive properties of magnesium alloys. Therefore, research on grain refinement of magnesium alloys has received widespread attention. The research and development of grain refiners is of great significance to improving the performance of Mg-Al alloys and promoting the application of magnesium alloy products.

[0003] The main methods for grain refinement during the solidification of Mg-Al alloys can be simply divided into physical and chemical methods. Physical methods include melt superheating, rapid solidification, and external field treatment, while chemical methods include the Elfinal (FeCl3) method, alloying, and the addition of intermediate alloy refiners containing nucleating particles. Physical refinement methods are limited by complex equipment requirements and cumbersome processes, making them difficult to adapt to industrial production needs. The most popular chemical refinement method is the addition of intermediate alloy refiners containing particle phases. However, to date, a grain refiner that is both cost-effective, simple to process, and provides stable grain refining effects suitable for commercial application has not yet been developed.

[0004] Currently, the main preparation processes for intermediate alloy refiners include molten salt-assisted synthesis, high-temperature self-propagating method, and reactive sintering method. The molten salt-assisted synthesis method produces a large amount of reaction smoke, which causes environmental pollution, and its preparation cost is relatively high. The disadvantages of the high-temperature self-propagating method are that the reaction is not easily controllable, a large number of pores are present within the alloy, and it is difficult to achieve a uniform distribution of the effective particle phase. The disadvantages of the reactive sintering method are that the process is relatively cumbersome, the equipment requirements are high, the yield is low, and it is difficult to achieve large-scale production. Therefore, the development of a magnesium alloy grain refiner that is simple to prepare, convenient to add, highly stable, and highly applicable is an important issue that needs to be addressed. Summary of the Invention

[0005] In view of the shortcomings of the existing master alloy preparation process and the need for fine grain strengthening and toughening of magnesium alloys, the purpose of the present invention is to provide a grain refiner suitable for magnesium alloys and its preparation process, which can not only significantly refine the grain size of magnesium alloys, but also has wide applicability and good resistance to refinement decay, and provides some new ideas and options for the preparation of magnesium alloy refiners and the research on fine grain strengthening and toughening of magnesium and magnesium alloys.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] An Al-CeO2-C-Mg grain refiner suitable for magnesium alloys is characterized in that the raw material components of the Al-CeO2-C-Mg grain refiner include, by weight percentage, 70-95% pure aluminum, 1%-10% cerium dioxide, 1%-10% graphite and 1%-10% pure magnesium.

[0008] Among them, pure aluminum is used as aluminum source, ceria is used as cerium source and oxygen source, graphite is used as carbon source, and pure magnesium is used as magnesium source;

[0009] The Al-CeO2-C-Mg alloy refiner ingot structure contains Al 11 Ce3 phase, MgAl2O4 particle phase and Al4C3 particle phase, among which MgAl2O4 and Al4C3 particle phases serve as heterogeneous nucleation sites of α-Mg, promoting efficient nucleation during the solidification process of magnesium alloy.

[0010] A rolling-melting-casting composite preparation method of an Al-CeO2-C-Mg grain refiner suitable for magnesium alloys comprises the following steps:

[0011] (1) First, aluminum powder, cerium dioxide powder, and graphite powder are dried, and the mixed powder is placed in a planetary ball mill for ball milling;

[0012] (2) The mixed powder after ball milling is sealed into a pure aluminum tube. The aluminum tube containing the mixed powder is then placed in a box furnace for preheating and kept warm for a period of time. After the insulation is completed, it is subjected to multi-directional rolling. The pure aluminum tube containing the mixed powder is rolled to a thickness of 1 to 3 mm to form a refiner precursor, and the refiner precursor is placed in a drying oven for drying.

[0013] (3) heating pure aluminum ingots and pure magnesium ingots to 780-950°C in a pit-type resistance furnace to obtain aluminum melt, then adding a refiner precursor, and heat-insulating the melt. During the heat-insulating process, stirring is performed at intervals; finally, the fully reacted melt is poured into a preheated steel mold, and demolded after solidification to obtain an Al-CeO2-C-Mg grain refiner;

[0014] The aluminum powder, pure aluminum tube, and pure aluminum ingot are aluminum sources, with the aluminum source accounting for 70%-95% of the total raw materials. The amount of cerium dioxide powder used is 1%-10% of the total raw materials, the amount of graphite used is 1%-10% of the total raw materials, and the amount of pure magnesium ingot used is 1%-10% of the total raw materials. Among the aluminum sources, aluminum powder accounts for 5%-15% of the total raw materials, pure aluminum tube accounts for 25%-45% of the total raw materials, and pure aluminum ingot accounts for 30%-50% of the total raw materials.

[0015] The refiner is applied to AZ31 magnesium alloy, specifically, different contents of Al-CeO2-C-Mg master alloy refiner are added to the AZ31 alloy melt, stirred, and cast into a steel mold after insulation to obtain the refined magnesium alloy.

[0016] Furthermore, the Al-CeO2-C-Mg refiner is designed to include, by weight, 70-95% pure aluminum (aluminum source), 1-10% ceria (Ce source and O source), 1-10% graphite (C source), and 1-10% pure magnesium (Mg source). The resulting ingot structure of the master alloy refiner contains an Al-Ce phase, MgAl2O4 particle phase, and Al4C3 particle phase.

[0017] Furthermore, the preparation method comprises the following steps:

[0018] (1) Raw materials for preparing the master alloy refiner are selected: pure aluminum tube as aluminum source, aluminum powder as supplementary aluminum source and reaction medium (accounting for 10% to 50% of the total weight of the powder); cerium dioxide powder as Ce source and O source (accounting for 1% to 50% of the total weight of the powder); graphite powder as C source (accounting for 1% to 50% of the total weight of the powder);

[0019] (2) First, the aluminum powder, cerium dioxide powder, and graphite powder after optimization are dried, and a certain amount of mixed powder is weighed and loaded into a planetary ball mill for ball milling;

[0020] (3) Weigh a certain amount of the mixed powder after ball milling and seal it in a pure aluminum tube. Then put the aluminum tube containing the mixed powder into a box furnace and preheat it to 550°C and keep it warm for 30 minutes. After the insulation is completed, it is subjected to multi-directional rolling treatment. Finally, the pure aluminum tube containing the mixed powder is rolled to a thickness of 1 to 3 mm to form a "refining agent precursor", and the "refining agent precursor" is placed in a drying oven for drying;

[0021] (4) A certain amount of pure aluminum ingot and pure magnesium ingot were weighed and heated to 780-950°C in a pit-type resistance furnace to obtain an aluminum melt. A certain amount of "refining agent precursor" was then added and kept warm. During the holding process, stirring was performed every 20 minutes. Finally, the fully reacted melt was poured into a preheated steel mold and demolded after solidification to obtain an Al-CeO2-C-Mg grain refiner.

[0022] Compared with the prior art, the present invention has the following obvious substantial features and advantages:

[0023] The preparation of the refiner introduces a rolling process, which can pre-mix the experimental raw materials in advance, providing a process basis for subsequent sufficient reaction. Specifically, the following steps are included: Al powder, CeO2 powder, and graphite powder are placed in a planetary ball mill and mixed evenly; the mixed powder is filled into a pure Al tube and sealed to prevent overflow; the Al tube sealed with the mixed powder is subjected to multiple hot rolling to obtain a preform to achieve an effective combination of the mixed powder and the aluminum tube; the hot-rolled preform, pure aluminum, and pure magnesium are placed in a medium frequency furnace for melting, and after the reaction is complete, they are cast into a steel mold to finally form an intermediate alloy refiner. The technical solution of the present invention can overcome the non-wettability between aluminum liquid and graphite and effectively improve the reaction efficiency; it is beneficial to reduce the agglomeration of effective particles and increase the particle yield. The preparation method of the refiner is simple, the raw materials are easily available, and it is suitable for large-scale industrial production applications.

[0024] 1. The preparation process of the master alloy refiner of this invention is innovative, based on improvements to the high-temperature self-propagating heat transfer method and reactive sintering, overcoming the drawbacks of uncontrollable reaction systems, complex processes, and high costs. Furthermore, compared to direct powder casting, the new rolling-melting-casting hybrid process improves the wettability between the mixed powder and the aluminum melt, increasing the reaction contact area and significantly enhancing the efficiency of the melt reaction. The preparation process does not generate toxic gases, and the melt temperature fluctuates minimally, facilitating operator operation.

[0025] 2. The master alloy refiner of the present invention exhibits significant grain refining effects on AZ31 magnesium alloy. The diverse particle phases dispersed within the master alloy refiner (Al-Ce phase, MgAl2O4 particle phase, and Al4C3 particle phase) reduce the average grain size of the AZ31 magnesium alloy from 378 μm to 74 μm, achieving a refinement efficiency of 80.4%. Considering that grain refinement becomes increasingly challenging for AZ31 magnesium alloys below 150 μm, significant changes in grain size are difficult to achieve, the refiner of the present invention demonstrates its exceptional effectiveness.

[0026] 3. The master alloy refiner of the present invention has good resistance to refinement decay in the AZ31 magnesium alloy melt. When the AZ31 magnesium alloy melt is kept in the magnesium alloy melt for 10 minutes, 30 minutes and 60 minutes, the grain size of the AZ31 magnesium alloy does not change much, all at around 80 μm. Compared with the unrefined magnesium alloy, the grain refining effect is still obvious.

[0027] 4. The new rolling-melt-casting composite process for preparing Al-CeO2-C-Mg master alloy refiners effectively reduces particle floating, agglomeration, and uneven raw material reaction associated with directly placing the reaction raw material powders into the melt, while also improving the particle yield and significantly promoting the synthesis of effective master alloy particle phases. This new rolling-melt-casting composite process developed in this invention overcomes many shortcomings of existing processes, promotes sufficient reaction between raw materials, and improves particle yield, possessing high practical value.

[0028] 5. The second phase contained in the prepared Al-CeO2-C-Mg master alloy refiner is Al4C3, MgAl2O4 and Al 11 Ce3 is the key to grain refinement. The solute limitation of Ce element and the Al4C3 and MgAl2O4 particle phases can serve as heterogeneous nucleation sites for α-Mg, promoting grain refinement. Figure 5 The figure shows the interface morphology and lattice matching relationship between MgAl2O4 particle phase and α-Mg in the magnesium alloy matrix, which directly proves the heterogeneous nucleation effect of MgAl2O4 particle phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram showing the effect of directly placing the reaction raw material powder into the melt to prepare the Al-4CeO2-1.6C-3Mg refiner in Example 1 of the present invention.

[0030] Figure 2 This is an SEM image of the Al-4CeO2-1.6C-3Mg refiner in Example 2 of the present invention.

[0031] Figure 3 This is an SEM image of the Al-6.7CeO2-3.3C-3Mg refiner in Example 3 of the present invention.

[0032] Figure 4 This is the microstructure diagram of the AZ31 alloy in Example 4 of the present invention before and after treatment with 1 wt.% Al-6.7CeO2-3.3C-3Mg refiner.

[0033] Figure 5 This is a diagram showing the interface morphology and lattice matching relationship between the MgAl2O4 particle phase and α-Mg in the magnesium alloy matrix after the AZ31 alloy in Example 4 of the present invention is treated with 1 wt.% Al-6.7CeO2-3.3C-3Mg refiner.

[0034] Figure 6 These are the microstructure diagrams of the AZ31 alloy in Example 5 of the present invention after being treated with 1 wt.% Al-6.7CeO2-3.3C-3Mg refiner and kept warm for different lengths. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto:

[0036] Example 1

[0037] The objectives of the present invention are achieved through the following technical solution: an Al-CeO2-C-Mg master alloy refiner is prepared by directly placing reaction raw material powders into a melt. The Al-CeO2-C-Mg master alloy refiner is designed to comprise, by weight, 70-95% pure aluminum (aluminum source), 1-10% ceria (Ce source and O source), 1-10% graphite (C source), and 1-10% pure magnesium (Mg source). The resulting master alloy refiner ingot contains an Al-Ce phase, a MgAl2O4 particle phase, and an Al4C3 particle phase.

[0038] The preparation method comprises the following steps:

[0039] (1) Raw materials for preparing the master alloy refiner were selected: aluminum powder (32 g) as aluminum source and reaction medium; cerium dioxide powder (12 g) as Ce source and O source; graphite powder (5 g) as C source;

[0040] (2) The optimized aluminum powder, cerium dioxide powder, and graphite powder were mixed evenly and loaded into a planetary ball mill for ball milling with a ball-to-material ratio of 5:1 and a ball milling time of 6 h;

[0041] (3) Weigh 130g of pure aluminum ingot and 9g of pure magnesium ingot and heat them to 780℃ to obtain aluminum-magnesium melt. Then, preheat the mixed powder after ball milling and add it directly to the Mg-Al melt. Keep it warm for 2h. During the heat preservation process, stir it every 20 minutes. Finally, pour the fully reacted melt into a steel mold preheated to 200℃. The preparation process diagram and refiner microstructure diagram are shown in the figure. Figure 1 As shown, Figure 1 (a)-(d) show the reaction process between the powder raw material and the melt when the reaction raw material powder is directly placed in the melt. It can be seen that after the powder is added to the melt, due to the poor wettability between them, it is difficult to eliminate this non-wetting phenomenon even with long-term heat preservation and stirring. Figure 1 (e)-(d) show the microstructure of Al-CeO2-C-Mg refiner prepared by traditional powder casting process. It is observed that the yield of particle phase in the refiner is very small, and there is unreacted cerium dioxide powder and carbon powder on the alloy matrix, which proves that this process for preparing refiner will waste raw materials and produce relatively few effective particle phases, which is not conducive to production application.

[0042] Example 2

[0043] The present invention achieves its objectives through the following technical solution: an Al-CeO2-C-Mg grain refiner suitable for magnesium alloys, characterized in that the Al-CeO2-C-Mg grain refiner comprises, by weight, 70-95% pure aluminum (aluminum source), 1-10% ceria (Ce source and O source), 1-10% graphite (C source), and 1-10% pure magnesium (Mg source). The resulting ingot microstructure of the master alloy refiner contains an Al-Ce phase, a MgAl2O4 particle phase, and an Al4C3 particle phase.

[0044] The preparation method comprises the following steps:

[0045] (1) Raw materials for preparing the master alloy refiner: optimized pure aluminum tube as aluminum source, with an outer diameter of 3 cm and an inner diameter of 1.5 cm; aluminum powder as aluminum source and reaction medium; cerium dioxide powder as Ce source and O source; graphite powder as C source;

[0046] (2) The optimized aluminum powder, cerium dioxide powder, and graphite powder were mixed evenly and loaded into a planetary ball mill for ball milling for 6 hours;

[0047] (3) Weigh a certain amount of the mixed powder after ball milling, seal it into a pure aluminum tube, and seal it. Then, place the aluminum tube containing the mixed powder in a box furnace and preheat it to 550°C and keep it warm for 30 minutes. After the insulation is completed, it is subjected to multi-directional rolling. Finally, the pure aluminum tube containing the mixed powder is rolled to a thickness of 1 to 3 mm to form a "fine-refining agent precursor", and the "fine-refining agent precursor" is placed in a drying oven for drying.

[0048] (4) Weigh a certain amount of pure aluminum ingot and pure magnesium ingot and heat them to 780℃ to obtain aluminum-magnesium melt, then add the dried precursor and keep it warm for 2h. During the heat preservation process, stir it every 20 minutes. Finally, pour the completely reacted melt into a steel mold preheated to 200℃, demold it after solidification to obtain Al-4CeO2-1.6C-3Mg grain refiner, such as Figure 2 shown.

[0049] Example 3

[0050] (1) Raw materials for preparing the master alloy refiner: selected pure aluminum tube as aluminum source, with an outer diameter of 3 cm and an inner diameter of 1.5 cm; aluminum powder as aluminum source and reaction medium; cerium dioxide powder as Ce source and O source; graphite powder (10 g) as C source;

[0051] (2) The optimized aluminum powder, cerium dioxide powder, and graphite powder were mixed evenly and loaded into a planetary ball mill for ball milling for 6 hours;

[0052] (3) Weigh a certain amount of the mixed powder after ball milling, seal it into a pure aluminum tube, and seal it. Then, place the aluminum tube containing the mixed powder in a box furnace and preheat it to 550°C and keep it warm for 30 minutes. After the insulation is completed, it is subjected to multi-directional rolling. Finally, the pure aluminum tube containing the mixed powder is rolled to a thickness of 1 to 3 mm to form a "refining agent precursor", and the "refining agent precursor" is placed in a drying oven for drying.

[0053] (4) Weigh a certain amount of pure aluminum ingot and pure magnesium ingot and heat them to 780℃ to obtain aluminum-magnesium melt, then add the dried precursor and keep it warm for 2h. During the heat preservation process, stir it every 20 minutes. Finally, pour the completely reacted melt into a steel mold preheated to 200℃, demould it after solidification to obtain Al-6.7CeO2-3.3C-3Mg grain refiner, such as Figure 3 shown.

[0054] Compared with Example 1, Examples 2 and 3 adopt a new rolling-melting composite process to prepare Al-CeO2-C-Mg intermediate alloy refiner, which can effectively reduce the particle phase floating, agglomeration and uneven raw material reaction caused by direct powder casting, and improve the yield of the particle phase, which has a significant promoting effect on the synthesis and preparation of the effective particle phase of the intermediate alloy.

[0055] Example 4

[0056] The grain refining effect of the master alloy refiner prepared in Example 2 was evaluated by applying it to a commercial AZ31 alloy. The specific method includes the following steps:

[0057] (1) A certain amount of pure magnesium was weighed, and the surface oil and oxide scale were removed. The magnesium was placed in a stainless steel crucible, sprinkled with RJ-2 type covering agent, and smelted in a 780℃ pit-type resistance furnace to obtain a magnesium melt. Subsequently, appropriate amounts of pure aluminum, pure Zn, and Mg-5Mn master alloy were weighed and added to the magnesium melt. The mixture was kept warm for 15 minutes, and the oxide slag on the surface of the melt was then cleaned to obtain an AZ31 magnesium alloy melt.

[0058] (2) The Al-6.7CeO2-3.3C-3Mg master alloy refiner from Example 2 (0 wt.%, 0.5 wt.%, 1.0 wt.%, 1.5 wt.%, and 2.0 wt.% of the magnesium alloy) was weighed and added to a magnesium melt at 730°C. The mixture was kept warm for 5 minutes to allow the refiner to melt and distribute throughout the magnesium melt. Mechanical stirring was then performed for 2 minutes to uniformly distribute the refiner throughout the magnesium melt. After stirring, the mixture was allowed to stand for a period of time, and the melt temperature was lowered to approximately 710°C. The surface slag of the melt was then removed, and the melt was finally cast into a steel mold preheated to 200°C. The grain refining effect of the Al-6.7CeO2-3.3C-3Mg master alloy refiner on the AZ31 magnesium alloy was investigated.

[0059] (3) As a comparison, an AZ31 magnesium alloy sample that has not been refined with an intermediate alloy refiner was prepared according to the smelting process in this embodiment.

[0060] (4) In order to make the grain boundaries more obvious and facilitate the comparison of grain size, the magnesium alloy before and after refinement was subjected to solid solution treatment.

[0061] (5) Preparation of samples before and after refinement: The magnesium alloy after solid solution was ground with sandpaper, then polished, and finally corroded in picric acid-acetic acid solution to obtain the metallographic images of AZ31 magnesium alloy before and after refinement, as shown in Figure 5. Figure 4 shown. Figure 4 (a)-(e) represent the microstructure of AZ31 alloy after refinement treatment with 0wt%, 0.5wt%, 1.0wt%, 1.5wt% and 2wt% Al-6.7CeO2-3.3C-3Mg refiner, respectively. It can be seen that the addition of refiner can effectively reduce the grain size of AZ31 alloy.

[0062] (6) The existence of a good matching relationship between the particle phase and the magnesium matrix is ​​an important basis for the particle phase to serve as a heterogeneous nucleation site for the nucleation phase. In order to prove the refining effect of the effective particle phase in the refiner, the AZ31 alloy after adding 1.5wt% Al-6.7CeO2-3.3C-3Mg refiner was subjected to transmission microstructure analysis. Figure 5 (a)-(b) show the morphology and transmission electron microscopy images of a thinned Mg matrix containing MgAl2O4 particles. Selected area electron diffraction (SEED) in region A in the lower right corner confirms that the particle phase is MgAl2O4. The transmission electron microscopy image shows a smooth interface between the MgAl2O4 particles and the Mg matrix, demonstrating a good bonding between them. Figure 5 (c) is a high-resolution transmission image of region B, further demonstrating the good interface bonding between MgAl2O4 and α-Mg. Figure 5 The analysis results of (d) show that there is a definite orientation relationship between MgAl2O4 and α-Mg: the (440) crystal plane of MgAl2O4 and the (440) crystal plane of α-Mg There is an angle of 5.2° between them, which proves that the MgAl2O4 particle phase can serve as a heterogeneous nucleation site for α-Mg, which can promote the efficient nucleation of the melt to achieve the purpose of grain refinement.

[0063] Example 5

[0064] The results of Example 3 indicate that a 1 wt.% Al-6.7CeO2-3.3C-3Mg master alloy refiner is the optimal refiner addition. In this example, a 1 wt.% Al-6.7CeO2-3.3C-3Mg master alloy refiner addition was selected to investigate its anti-fading properties in AZ31 magnesium alloy refinement. The raw material mix and smelting process in this example were identical to those in Example 3, with the exception that the melt after refiner addition was held at room temperature for 10, 20, 30, and 60 minutes, without any stirring during the holding period.

[0065] The observation of the grain size of the refined AZ31 alloy at different holding times is as in steps (4) and (5) of Example 3, and the metallographic diagrams of the AZ31 magnesium alloy at different holding times are finally obtained, as shown in FIG. Figure 6 As shown. Figure 6 (a)-(d) show the microstructures of the AZ31 alloy after the addition of the refiner and holding for 10, 20, 30, and 60 minutes, respectively. Although varying the holding time has some influence on the refinement effect of the refiner, the refiner still maintains high efficiency, demonstrating the excellent resistance to refinement decay of the refiner.

[0066] The results from all the examples above demonstrate that the prepared refiners containing Al-Ce phases, MgAl2O4 particles, and Al4C3 particles all exhibit significant refinement effects on AZ31 magnesium alloy and exhibit effective resistance to refinement degradation. Their preparation and addition methods are simple, making them suitable for large-scale industrial applications.

[0067] The above describes the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Any other modifications, modifications, substitutions, combinations, and simplifications that do not violate the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A rolling-melting-casting composite preparation method of an Al-CeO2-C-Mg grain refiner suitable for magnesium alloys, characterized by: The raw material components of the refiner include, by weight percentage, 70-95% pure aluminum, 1-10% cerium dioxide, 1-10% graphite and 1-10% pure magnesium; Among them, pure aluminum is used as aluminum source, ceria is used as cerium source and oxygen source, graphite is used as carbon source, and pure magnesium is used as magnesium source; The Al-CeO2-C-Mg alloy refiner ingot structure contains Al 11 Ce3 phase, MgAl2O4 particle phase and Al4C3 particle phase, among which MgAl2O4 and Al4C3 particle phases act as heterogeneous nucleation sites for α-Mg, promoting efficient nucleation during the solidification process of magnesium alloy; The method comprises the following steps: (1) First, aluminum powder, cerium dioxide powder, and graphite powder are dried, and the mixed powder is placed in a planetary ball mill for ball milling; (2) The mixed powder after ball milling is sealed into a pure aluminum tube. The aluminum tube containing the mixed powder is then placed in a box furnace for preheating. After the insulation is completed, it is subjected to multi-directional rolling. The pure aluminum tube containing the mixed powder is rolled to a thickness of 1-3 mm to form a refiner precursor, and the refiner precursor is placed in a drying oven for drying. (3) Pure aluminum ingots and pure magnesium ingots are heated to 780-950°C in a pit-type resistance furnace to obtain aluminum melt, and then a refiner precursor is added and kept warm. During the heat preservation process, stirring is performed every 10-20 minutes; finally, the fully reacted melt is poured into a preheated steel mold, and demolded after solidification to obtain an Al-CeO2-C-Mg grain refiner; The aluminum powder, pure aluminum tube and pure aluminum ingot are aluminum sources, which account for 70%-95% of the total raw materials. The amount of cerium dioxide powder is 1%-10% of the total raw materials, the amount of graphite is 1%-10% of the total raw materials, and the amount of pure magnesium ingot is 1%-10% of the total raw materials.

2. The rolling-melting-casting composite preparation method of an Al-CeO2-C-Mg grain refiner suitable for magnesium alloys according to claim 1, characterized in that: In the aluminum source, aluminum powder accounts for 5%-15% of the total raw material amount, pure aluminum tube accounts for 25%-45% of the total raw material amount, and pure aluminum ingot accounts for 30%-50% of the total raw material amount.

3. An Al-CeO2-C-Mg grain refiner suitable for magnesium alloys, characterized in that: The grain refiner is prepared by the preparation method according to claim 1 or 2.

4. The use of an Al-CeO2-C-Mg grain refiner suitable for magnesium alloys according to claim 3, characterized in that: The refiner is applied to AZ31 magnesium alloy.

5. The use of the Al-CeO2-C-Mg grain refiner for magnesium alloys according to claim 3, characterized in that: The refiner is applied to AZ31 magnesium alloy, specifically, different contents of Al-CeO2-C-Mg master alloy refiner are added to the AZ31 alloy melt, stirred, and cast into a steel mold after insulation to obtain the refined magnesium alloy.

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