Rare earth-containing aluminum alloy refiner and use method thereof

Abstract

The invention discloses an aluminum alloy refiner containing rare earth and a using method thereof, the aluminum alloy refiner is composed of aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder, and the molar ratio of aluminum to titanium to carbon to copper oxide to yttrium oxide is (2.0-6.0): (0.5-1.5): (0.5-1.5): (0.2-1.5): (0.01-0.2). The use method comprises the following steps: (1) uniformly mixing the aluminum powder, the titanium powder, the carbon powder, the copper oxide powder and the yttrium oxide powder through ball milling to obtain mixed raw material powder; (2) the mixed raw material powder is subjected to compression molding and drying, and an aluminum alloy refiner block is obtained; (3) the dried aluminum alloy refiner block is pressed into an aluminum alloy melt for a high-temperature self-propagating reaction; and (4) a near liquidus temperature casting method is adopted for casting, and the aluminum alloy cast ingot with the obviously refined grain structure is obtained. According to the method, a fine and uniform equiaxed crystal structure comparable to a rapid solidification structure can be obtained under the conventional casting condition, and in-situ particles can also serve as a reinforcing phase to achieve the dispersion strengthening effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy refiner. Specifically, it is a rare earth-containing aluminum alloy refiner and its use method. BACKGROUND

[0002] With the transformation of global energy structure, there is a rigid demand for energy efficiency improvement and endurance breakthrough in transportation equipment such as new energy vehicles, rail transit, aircraft, etc. Aluminum alloy has become the preferred material for lightweight due to its low density, high specific strength and other excellent properties, and its application rate in key components such as vehicle body, chassis, battery pack, etc. is continuously rising. However, the contradictory relationship between the strength and plasticity of aluminum alloy (i.e. the bottleneck problem of imbalance between strength and toughness of aluminum alloy) makes it unable to meet the high requirements of the increasing use of aluminum alloy in the field of comprehensive performance. Various strengthening methods such as solid solution strengthening, work hardening and second phase strengthening can improve the strength of aluminum alloy while sacrificing certain plasticity indicators. Only the fine-grain strengthening method can not only improve the strength of the alloy but also slightly improve the plasticity.

[0003] Patent CN 119571127 A discloses a rare earth modified in-situ reinforced particle reinforced aluminum matrix composite material and its preparation method. The patent adds Al powder, TiO2 powder, C powder and Y2O3 powder as reinforcing phase raw materials to the aluminum alloy to generate reinforcing particles in-situ. The average grain size of the prepared aluminum matrix composite material can be refined to 45-68 μm. However, due to the poor wettability of C in molten aluminum alloy, it is difficult to completely react with TiO2 powder to generate TiC, and TiC-O solid solution will also be formed due to the residual oxygen in TiO2, which is not conducive to the improvement of the comprehensive performance of aluminum alloy.

[0004] Therefore, it is particularly important to develop high-quality and easy-to-use aluminum alloy refiner. SUMMARY

[0005] To this end, the technical problem to be solved by the present application is to provide a rare earth-containing aluminum alloy refiner and its use method, which can obtain fine and uniform equiaxed crystal structure comparable to that of rapid solidification under conventional casting conditions. In-situ particles can also act as reinforcing phase and play a role in dispersion strengthening.

[0006] To solve the above technical problems, the present application provides the following technical solutions:

[0007] A rare earth-containing aluminum alloy refiner is composed of aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder, and the molar ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide is (2.0-6.0):(0.5-1.5):(0.5-1.5):(0.2-1.5):(0.01-0.2); for example: 2.8:1:1.2:0.3:0.043, 3.5:1:1.2:1.0:0.1285, 5.4:1:1.2:1.0:0.1185, 2.8:1:1.2:0.4:0.045. If the proportion of aluminum in the rare earth-containing aluminum alloy refiner is too large, the contact area between the reactants such as titanium, carbon, copper oxide and yttrium oxide will be affected, which will cause them to not fully react in the subsequent high-temperature self-propagating reaction. If the proportion of aluminum is too small, the subsequent high-temperature self-propagating reaction will be too violent, and spattering may occur. If the proportions of titanium and carbon are too large or too small, it will be difficult for them to fully react or generate too few TiC particles, which will not achieve the ideal refinement effect. If the proportion of copper oxide is too large, it will generate too much aluminum oxide (which has a less refining effect than TiC) and less TiC, which will affect the overall refining effect of the refiner. If the proportion of copper oxide is too small, the heat generated by the thermal explosion reaction of aluminum and copper oxide will not be enough to promote the complete reaction of Ti and C, which will affect the continuation of the self-propagating reaction. In addition, if the amount of yttrium oxide is too small, the desired effect will not be achieved, and if the amount is too large, it will have a negative impact. By controlling the molar ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide in the aluminum alloy refiner within the above range, the components can interact with each other in the subsequent high-temperature self-propagating reaction, making the high-temperature self-propagating reaction more complete and the reaction process smoother, generating submicron TiC and Al2O3 particles (both particles are spherical), no large-size Al3Ti phase, and the number and distribution of the generated in-situ particles reach the ideal state, thereby fully exerting their refining effect on aluminum alloy.

[0008] A method for using a rare earth-containing aluminum alloy refiner, comprising the following steps:

[0009] Step (1), uniformly ball-milling aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder to obtain the mixed raw material powder of the above-mentioned rare earth-containing aluminum alloy refiner; using a powder mixer or a ball mill to mix the powders to ensure uniform mixing and sufficient contact of the raw material powders;

[0010] Step (2), pressing the mixed raw material powder into a block to obtain an aluminum alloy refiner block; wrapping the aluminum alloy refiner block with aluminum foil and drying;

[0011] Step (3), pressing the dried aluminum alloy refiner block into an aluminum alloy melt to perform a high-temperature self-propagating reaction, generating the required in-situ particles in the aluminum alloy melt;

[0012] Step (4), the aluminum alloy melt after reaction is appropriately stirred and cooled to a certain temperature, then melt purification treatment is carried out, when the melt temperature is reduced to close to the liquidus temperature of the alloy, near-liquidus casting is adopted, and the aluminum alloy ingot with uniform fine equiaxed crystal organization characteristics is obtained.

[0013] The lanthanum oxide is not selected because, after the lanthanum oxide is mixed with the aluminum powder, the titanium powder, the carbon powder and the copper oxide powder to prepare the refiner, when the refiner is used for the structure optimization of the aluminum-magnesium-zinc alloy, even if the ratio of the components of each refiner raw material and the processing condition of the aluminum alloy material are optimized, the size of the in-situ particle reinforced phase generated in the finally obtained aluminum alloy material is relatively large, and there are large size (tens of microns) rare earth phases, which are not suitable for being nucleating agents and reinforced phases, and affect the comprehensive performance of the aluminum alloy material.

[0014] In addition, compared with the lanthanum oxide, the yttrium oxide has the following advantages: the crystal structure of the yttrium oxide is cubic phase (Ia-3), the cubic structure is stable at room temperature to high temperature, and there is no phase change, which is beneficial to sintering densification; the crystal structure of the lanthanum oxide is unstable at high temperature, and is hexagonal phase at room temperature, and is converted into cubic phase when the temperature is greater than 600 DEG C, and the phase change at high temperature may lead to volume change; the yttrium oxide shows extremely high stability in the molten metal, and the melting point is as high as 2430 DEG C, which is one of the highest among the rare earth oxides (only next to Lu2O3), and is suitable for extremely high temperature application; the yttrium oxide is more stable when stored at room temperature, and the lanthanum oxide is easy to hydrate to form La(OH)3 when exposed to air, and needs special storage. Therefore, the Al-Ti-C-CuO-Y2O3 used as the refiner in the application is stable and not easy to hydrate when stored at room temperature and in the preheating stage, and is not easy to change phase when reacting at high temperature, which is beneficial to the preparation of high-quality as-cast structure aluminum alloy.

[0015] The Al-Ti-C-CuO-Y2O3 refiner of the present application uses titanium powder instead of commonly used titanium dioxide powder as the titanium source, because: since the interface relationship between Al2O3 and the base Al is semi-coherent, and the interface relationship between TiC and the base Al is coherent, the lattice matching relationship of the latter is better than that of the former, that is, the refining effect of TiC on the aluminum alloy material is better than that of Al2O3; for the Al-TiO2-C-Y2O3 system, TiO2 provides Ti atoms and O atoms, and the generation amount of Al2O3 and TiC is "bound" in proportion, and the adjustable freedom is low; and the wettability of C in molten aluminum alloy is extremely poor, and the problem that TiO2 and C cannot fully react easily occurs; furthermore, since TiO2 reacts with C in steps, CO gas is generated during the reaction process, and the prepared as-cast aluminum alloy also has the problem of porosity caused by the escape of CO. Most importantly, the TiC generated by the carbonization of TiO2 often forms a TiC-O solid solution due to the residual oxygen, and the existence of the solid solution will seriously affect the plasticity of the aluminum alloy.

[0016] The present application uses titanium powder instead of TiO2 in the Al-TiO2-C-Y2O3 system refiner, and further adds copper oxide powder to form an Al-Ti-C-CuO-Y2O3 refiner, which has high adjustable freedom of Al2O3 and TiC generation amount, can effectively improve the wettability of C in molten aluminum alloy by controlling the addition ratio of yttrium oxide, can promote the full reaction of Ti and C by using the heat released by the thermal explosion reaction between CuO and Al to generate more TiC with better refining effect (if CuO is not added, the heat generated by the self-reaction of Ti and C is not enough to support the complete performance of the self-propagating reaction under conventional casting conditions, resulting in insufficient TiC generation and increasing by-products to affect the refining effect); and the local high temperature environment generated by the thermal explosion reaction between CuO and Al can promote the decomposition of by-products generated during the reaction of Ti and C, thereby effectively avoiding the generation of TiC-O solid solution; the Cu generated by the thermal explosion reaction between CuO and Al can enter the base as an alloy element, which is beneficial to optimizing the alloy strength of the aluminum alloy material. In addition, the reaction of Ti and C is a direct diffusion reaction, and there is no porosity problem caused by the escape of CO during the generation of TiC.

[0017] The aluminum alloy material prepared by using the rare earth-containing aluminum alloy refiner of the present application is an original casting, and has not been processed, and a non-vacuum melting method is selected, the rare earth-containing aluminum alloy refiner undergoes a high-temperature self-propagating reaction in the aluminum alloy melt, and the generated in-situ particles are directly generated in the aluminum alloy melt, have coherent or semi-coherent interface with the base, the interface is not contaminated, has strong binding ability, and is dispersedly distributed under the action of thermal explosion reaction, which can not only refine the grain structure, but also act as a dispersion strengthening phase.

[0018] The method for using the rare earth-containing aluminum alloy refiner, in step (1), the particle size of the mixed raw material powder is 1-40 μm (favorable for obtaining small in-situ particles by reaction, and if the particle size of the mixed raw material powder is too large, the size of the in-situ particles obtained by reaction will also be large); the ball-milling mixing time is 30-90 min. Specifically, the ball-milling time is, for example but not limited to, any one of 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, or a range between any two of them.

[0019] The method for using the rare earth-containing aluminum alloy refiner, in step (2), the forming pressure is 12-18 MPa (if the forming pressure is too small, the aluminum alloy refiner block cannot be formed or is too loose, the contact between the reactants is not close enough to affect the full reaction, and the temperature of the aluminothermic reaction cannot act on the entire reaction system after being put into the aluminum alloy melt, and will be dispersed; if the forming pressure is too large, the reaction process cannot uniformly disperse the generated particles in the melt), and the pressure holding time is 90-150 s; specifically, the forming pressure is, for example but not limited to, any one of 12 MPa, 14 MPa, 14.5 MPa, 15 MPa, 15.5 MPa, 16 MPa, 17 MPa, 18 MPa, or a range between any two of them; the aluminum alloy refiner block is a cylinder with a diameter of 20-30 mm and a thickness of 5-8 mm; specifically, the reactant powder and the rare earth oxide mixed powder are pressed into a circular aluminum alloy refiner block with a diameter of, for example but not limited to, any one of 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, 30 mm, or a range between any two of them; the reactant powder and the rare earth oxide mixed powder are pressed into a circular aluminum alloy refiner block with a thickness of, for example but not limited to, any one of 5 mm, 6 mm, 7 mm, 8 mm, or a range between any two of them; during the drying treatment, the drying treatment temperature is 100-200 ℃, and the drying treatment time is 30-60 min; the drying treatment temperature is, for example but not limited to, any one of 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, or a range between any two of them; the drying treatment time is, for example but not limited to, any one of 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or a range between any two of them;

[0020] The method for using the rare earth-containing aluminum alloy refiner, in step (3), the amount of the aluminum alloy refiner block is 0.5-10 wt.% of the mass of the aluminum alloy melt (if the amount of the aluminum alloy refiner block is too small, the refining effect of the aluminum alloy refiner on the aluminum alloy is not significant, and if the amount of the aluminum alloy refiner is too large, the plasticity of the finally prepared aluminum alloy will be significantly reduced); preferably 3-10 wt.%, the amount of the aluminum alloy refiner block is 3.0 wt.%, 3.5 wt.%, 4.0 wt.%, 4.5 wt.%, 5.0 wt.%, 5.5 wt.%, 6.0 wt.%, 6.5 wt.%, 7.0 wt.%, 7.5 wt.%, 8.0 wt.%, 8.5 wt.%, 9.0 wt.%, 9.5 wt.%, 10.0 wt.% or the like but not limited to; the temperature of the aluminum alloy melt is controlled at 900-950 ℃ during the high-temperature self-propagating reaction, at which the high-temperature self-propagating reaction rate of the aluminum alloy refiner block is moderate, which can ensure the full reaction of the components and make the generated in-situ particles uniformly and dispersedly distributed in the aluminum alloy melt, which is beneficial to the full play of the refining effect of the aluminum alloy refiner on the aluminum alloy.

[0021] The method for using the rare earth-containing aluminum alloy refiner, in step (4), the purification treatment is performed when the temperature of the aluminum alloy melt is reduced to 700-800 ℃, then the temperature is continuously reduced to 650-680 ℃ for casting, the metal mold is preheated to 100-150 ℃ before casting; and the castings are air-cooled to room temperature after casting. The casting temperature is, for example, but not limited to, any one of 650 ℃, 660 ℃, 670 ℃, 680 ℃ or a range between any two of them; and the preheating temperature of the metal mold is, for example, but not limited to, any one of 100 ℃, 120 ℃, 140 ℃, 150 ℃ or a range between any two of them.

[0022] The method for using the rare earth-containing aluminum alloy refiner, in step (3), the aluminum alloy melt is prepared by preparing alloy raw materials according to the design composition of the base aluminum alloy, and melting under normal temperature and pressure by using a non-vacuum melting method to obtain the aluminum alloy melt.

[0023] The method for using the rare earth-containing aluminum alloy refiner, in step (3), in the base aluminum alloy: the mass fraction of magnesium is 4.40-5.60wt.%, the mass fraction of zinc is 2.40-3.60wt.%, the mass fraction of silicon is less than or equal to 0.08wt.%, the mass fraction of iron is less than or equal to 0.08wt.%, the mass fraction of manganese is less than or equal to 0.08wt.%, and the balance is aluminum and inevitable impurities. Specifically, the Zn content of the base alloy is, for example but not limited to, any one of or a range between any two of 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6 in percentage by weight; the Mg content of the base alloy is, for example but not limited to, any one of or a range between any two of 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6 in percentage by weight.

[0024] The method for using the rare earth-containing aluminum alloy refiner, in step (3), the melting temperature of the alloy raw material is 900-950℃, and the melting time is 20-40min. Specifically, the melting temperature is, for example but not limited to, any one of or a range between any two of 900℃, 910℃, 920℃, 930℃, 940℃, 950℃;

[0025] The method for using the rare earth-containing aluminum alloy refiner, in step (1), in the mixed raw material powder, the amount-of-substance ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide is 2.8:1:1.2:0.3:0.043; the aluminum powder is passed through a 700-mesh sieve, the titanium powder is passed through a 500-mesh sieve, the carbon powder is passed through a 500-mesh sieve, the copper oxide powder is passed through a 700-mesh sieve, and the average particle size of the yttrium oxide powder is 1.0μm; the ball-milling mixing time is 60min;

[0026] In step (2), the forming pressure is 16MPa, and the pressure holding time is 120s; the aluminum alloy refiner block is a cylinder with a diameter of 20-30mm and a height of 5-8mm; during the drying treatment, the drying treatment temperature is 150℃, and the drying treatment time is 40min;

[0027] In step (3), the preparation method of the aluminum alloy melt is: preparing alloy raw materials according to the design composition of the base aluminum alloy, and melting the alloy raw materials under normal temperature and pressure by using a non-vacuum melting method to obtain an aluminum alloy melt; in the base aluminum alloy: the mass fraction of magnesium is 5.0wt.%, the mass fraction of zinc is 3.0wt.%, the mass fraction of silicon is less than or equal to 0.08wt.%, the mass fraction of iron is less than or equal to 0.08wt.%, the mass fraction of manganese is less than or equal to 0.08wt.%, and the balance is aluminum; the melting temperature of the alloy raw material is 950℃, and the melting time is 30min;

[0028] In step (3), the amount of the aluminum alloy refiner block is 8wt.% of the mass of the aluminum alloy melt, and the temperature of the aluminum alloy melt is controlled at 950 DEG C during the high-temperature self-propagating reaction;

[0029] In step (4), the purification treatment is performed when the temperature of the aluminum alloy melt is reduced to 700 DEG C, and then the temperature is continuously reduced to 650 DEG C close to the liquidus temperature for casting, and the casting metal mold is preheated to 150 DEG C before casting; and the casting is air-cooled to room temperature after completion.

[0030] The high-strength high-plasticity aluminum alloy material prepared by the above method is used for the preparation of parts of transportation equipment.

[0031] The technical scheme of the present application achieves the following beneficial technical effects:

[0032] 1. The rare earth-containing aluminum alloy refiner and its use method add rare earth oxides (Y2O3) to the Al-Ti-C-CuO reaction system and control the proportion of each component to form the rare earth-containing aluminum alloy refiner, use the activity of rare earth to affect the reaction path of high-temperature self-propagating reaction, refine the reaction product, increase the number of nucleation, and obtain better refined organization effect. Using the rare earth-containing aluminum alloy refiner in the present application, aluminum alloy with uniform and fine equiaxed crystal organization characteristics can be prepared under normal pressure and room temperature conditions by using conventional casting equipment, the grain refinement degree is comparable to that of rapid solidification technology, and the high comprehensive performance demand of related fields can be met.

[0033] 2. The rare earth-containing aluminum alloy refiner and its use method in the present application use the in-situ particles generated by high-temperature self-propagating reaction, which have a size of submicron and have a coherent or semi-coherent interface with the aluminum magnesium zinc alloy matrix, and under the action of copper-aluminum thermal explosion reaction, the in-situ particles can be dispersed in the melt, which not only promotes nucleation but also hinders the growth of crystal nucleus in the subsequent crystallization process, thereby producing significant refinement effect, and the in-situ particles can also serve as a dispersion strengthening phase to improve the comprehensive performance of the aluminum alloy material. Therefore, the Al-Ti-C-CuO refiner of the present application has the dual effects of fine-grain strengthening and dispersion strengthening, and provides an economical and effective way for the synergistic improvement of aluminum alloy strength and toughness.

[0034] 3. The rare earth-containing aluminum alloy refiner and its use method in the present application are selected by non-vacuum melting method under normal pressure and room temperature conditions, and the aluminum alloy ingot with uniform and fine equiaxed crystal organization characteristics is obtained by casting with a metal mold near the liquidus temperature of the aluminum alloy, that is, it can be realized under conventional processing conditions, the preparation method is simple and easy to operate, and there is no special requirement for equipment and environment, the process flow is simple, and it has the prospect of subsequent large-scale production and use.

[0035] 4、The Al-Ti-C-CuO-Y2O3 refiner used in the present application can be understood as a rare earth modified aluminum alloy refiner, which is adding trace amount of yttrium oxide in the Al-Ti-C-CuO system, the added yttrium oxide not only participates in the high temperature self-propagating reaction but also refines the reaction product, significantly increases the nucleation site, and obtains better refined structure effect; the trace amount of yttrium oxide is added in the form of rare earth oxide, which can obtain significant effect of refining grain structure under the premise of a small amount of cost increase; this reflects the special role of the activity of rare earth in the field of refiner: further refining the ceramic particle size generated by the refiner.

[0036] 5、The Al-Ti-C-CuO-Y2O3 refiner system is used for refining Al-5Mg-3Zn (wt.%), and by controlling the process parameters, submicron TiC and micron Al2O3 particles can be prepared, both of which are spherical; the added rare earth element Y exists around the TiC particles; the Cu element in the Al-Ti-C-CuO-Y2O3 refiner system is combined with the original strengthening phase T-Mg 32 (Al,Zn) 49 into the T-Mg 32 (Al,Zn,Cu) 49 phase containing Cu element, the size of which is nanometer to submicron level and the shape is circular / elliptical. Under the condition that the amount of aluminum alloy refiner is the same, the hardness value of the alloy prepared by the Al-Ti-C-CuO-Y2O3 refiner system is generally higher than that of the alloy prepared by the Al-TiO2-C-Y2O3 refiner system, and the corrosion potential and corrosion current of the Al-5Mg-3Zn alloy prepared by the Al-Ti-C-CuO-Y2O3 refiner system are significantly higher than those of the Al-5Mg-3Zn alloy prepared by the Al-TiO2-C-Y2O3 refiner system. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The flow chart of the rare earth-containing aluminum alloy refiner and the using method thereof in the embodiment 1 of the present application;

[0038] Figure 2 The grain structure diagram of the Al-5Mg-3Zn aluminum alloy prepared in the embodiment 1 of the present application;

[0039] Figure 3 The grain structure diagram of the Al-5Mg-3Zn aluminum alloy prepared in the embodiment 2 of the present application;

[0040] Figure 4 The grain structure diagram of the Al-5Mg-3Zn aluminum alloy prepared in the comparative example 1 of the present application;

[0041] Figure 5A TiC particle morphology chart in the Al-5Mg-3Zn aluminum alloy prepared in Example 1 of the present application;

[0042] Figure 6 An Al2O3 particle morphology chart in the Al-5Mg-3Zn aluminum alloy prepared in Example 1 of the present application;

[0043] Figure 7 A TEM morphology and energy spectrum result chart of a TiC particle in the Al-5Mg-3Zn aluminum alloy prepared in Example 1 of the present application;

[0044] Figure 8 A TEM morphology and energy spectrum result chart of another TiC particle in the Al-5Mg-3Zn aluminum alloy prepared in Example 1 of the present application;

[0045] Figure 9 A TEM morphology chart of precipitated phases in the Al-5Mg-3Zn aluminum alloy prepared in Example 1 and Comparative Example 2 of the present application; in the chart, (a), (b), (c) and (d) correspond to Example 1; (e), (f), (g) and (h) correspond to Comparative Example 2;

[0046] Figure 10 A morphology and energy spectrum analysis of a second precipitated phase in the Al-5Mg-3Zn aluminum alloy prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0047] Example 1

[0048] The rare earth-containing aluminum alloy refiner and the use method thereof of the present embodiment comprise the following steps:

[0049] Step (1), 3.777 g of aluminum powder, 2.394 g of titanium powder, 0.721 g of carbon powder, 1.193 g of copper oxide powder and 0.486 g of yttrium oxide powder are placed in a ball mill for ball milling and uniformly mixing to obtain mixed raw material powder; in the mixed raw material powder, the amount-of-substance ratio of Al, Ti, C, CuO and Y2O3 is 2.8:1:1.2:0.3:0.043; the aluminum powder is passed through a 700-mesh screen, the titanium powder is passed through a 500-mesh screen, the carbon powder is passed through a 500-mesh screen, the copper oxide powder is passed through a 700-mesh screen, and the average particle size of the yttrium oxide powder is 1.0 μm; the time for ball milling and mixing is 60 min;

[0050] Step (2), the mixed raw material powder is pressed and formed at 16 MPa for 120 s to obtain a round sheet-shaped aluminum alloy refiner block with a diameter of 25 mm, a thickness of 7 mm and a weight of 6 g; the aluminum alloy refiner block is wrapped with aluminum foil paper to isolate air and impurity pollution and is placed in a drying dish for use; the aluminum alloy refiner block is placed in a box-type resistance furnace for drying treatment at 150℃ for 40 min to completely remove the moisture of the aluminum alloy refiner block;

[0051] Step (3), prepare alloy raw materials (75 g in total) according to the design composition of the base aluminum alloy (Al-5Mg-3Zn), and melt by using a non-vacuum melting method at normal temperature and pressure to obtain an aluminum alloy melt; during melting, first heat the crucible resistance furnace to a preheating temperature of 950°C, put the alloy raw materials into a graphite crucible, and place the crucible in the preheated crucible resistance furnace to melt at a temperature of 950°C, and the melting time is 30 min to melt the alloy raw materials;

[0052] In this embodiment, the mass fraction of magnesium in the base aluminum alloy is 5.0wt.%, the mass fraction of zinc is 3.0wt.%, the mass fraction of silicon is less than or equal to 0.05wt.%, the mass fraction of iron is less than or equal to 0.05wt.%, the mass fraction of manganese is less than or equal to 0.05wt.%, and the balance is aluminum;

[0053] Put the dried aluminum alloy refiner block into the aluminum alloy melt with a crucible tongs, and press it into the molten aluminum alloy melt with a graphite bell jar, ignite the reaction system at high temperature to perform high-temperature self-propagating reaction, and obtain an aluminum alloy material melt; the preheating temperature of the aluminum alloy melt is controlled at 950°C during high-temperature self-propagating reaction; the reactants of high-temperature self-propagating reaction are metal elements or metal oxides, which are in the form of powder and can ensure the full reaction; the in-situ reaction product particles are uniformly distributed in the aluminum alloy melt under the action of thermal explosion reaction;

[0054] Step (4), when the aluminum alloy melt is lowered to 700°C, use the pre-prepared hexachloroethane to refine and degas, and remove the dross suspended on the surface of the melt to perform melt purification treatment, then continue to lower the temperature to near the liquidus temperature of the aluminum alloy (650°C), and use a metal mold (a steel mold preheated to 150°C) to perform casting, after casting is completed, air cooling to room temperature, and an aluminum alloy ingot with uniform and fine equiaxed crystal organization characteristics is obtained.

[0055] In this embodiment, a non-vacuum melting method is used, and the rare earth-containing refiner generates high-temperature self-propagating reaction in the aluminum alloy melt, and the generated in-situ particles are directly dispersed in the aluminum alloy melt under the action of thermal explosion reaction, which not only refines the grain organization, but also serves as a dispersion strengthening phase. The aluminum alloy prepared in this embodiment is a raw casting, which is not further processed, and the in-situ particles have a coherent or semi-coherent interface relationship with the matrix, the interface is not polluted and has strong bonding ability. Figure 2 As can be seen from the above, the aluminum alloy prepared in this embodiment has fine equiaxed crystal organization, and the average grain size is about 40μm.

[0056] Example 2

[0057] The only difference between this embodiment and embodiment 1 is that in step (1), 3.777g of aluminum powder, 2.394g of titanium powder, 0.721g of carbon powder, 1.591g of copper oxide powder and 0.508g of yttrium oxide powder are placed in a ball mill and ball-milled to mix evenly to obtain a mixed raw material powder; in the mixed raw material powder, the molar ratio of Al, Ti, C, CuO and Y2O3 is 2.8:1:1.2:0.4:0.045.

[0058] The other steps, process parameters, raw material sources, and equipment used are exactly the same as in Example 1.

[0059] from Figure 3 As can be seen from the data, the aluminum alloy material prepared in this embodiment has a fine equiaxed crystal structure with an average grain size of nearly 50 μm.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Examples 1 and 2 is that no aluminum alloy refining agent block was added, and the Al-5Mg-3Zn as-cast alloy was prepared by casting using the process equipment and parameter conditions of Example 1.

[0062] from Figure 4 As can be seen, the aluminum alloy grains prepared in this comparative example are equiaxed, but their size distribution range is large, with an average grain size of nearly 110 μm.

[0063] Comparing Comparative Example 1 with Examples 1 and 2, it can be seen that the aluminum alloy using the rare earth-containing aluminum alloy refining agent of the present invention has a more significant effect on grain structure optimization.

[0064] In summary, this invention can achieve the preparation and microstructure control of Al-5Mg-3Zn alloy by adding a rare earth-containing aluminum alloy refining agent and using a high-temperature self-propagating reaction. The rare earth-containing aluminum alloy refining agent used in this invention has a significant effect on optimizing the microstructure of Al-5Mg-3Zn alloy.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that in step (1), 4.212g of aluminum powder, 3.995g of titanium dioxide powder, 0.721g of carbon powder and 0.474g of yttrium oxide powder are placed in a ball mill and mixed evenly to obtain a mixed raw material powder; in the mixed raw material powder, the molar ratio of Al, TiO2, C and Y2O3 is 3.15:1:1.2:0.042.

[0067] The other steps, process parameters, raw material sources, and equipment used are exactly the same as in Example 1.

[0068] The aluminum alloy material prepared in this embodiment has a fine equiaxed grain structure with an average grain size of nearly 60 μm.

[0069] The hardness and corrosion resistance of the Al-5Mg-3Zn as-cast aluminum alloys prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested. The results showed that the Brinell hardness of the Al-5Mg-3Zn as-cast aluminum alloys prepared in Example 1, Comparative Example 1, and Comparative Example 2 were 96.4 HBV, 78.6 HBV, and 89.3 HBV, respectively. Compared with Comparative Example 1, the corrosion potential and corrosion current density of the Al-5Mg-3Zn as-cast alloys prepared in Example 1 and Comparative Example 2 were increased to varying degrees, and the corrosion potential and corrosion current of the Al-5Mg-3Zn alloy prepared in Example 1 were significantly higher than those of the Al-5Mg-3Zn alloy prepared in Comparative Example 2.

[0070] Therefore, the Al-5Mg-3Zn alloy prepared in Example 1 exhibits superior mechanical and corrosion resistance properties compared to the Al-5Mg-3Zn alloy prepared in Comparative Example 2. To investigate the reasons for this excellent performance, a detailed analysis of the microstructure of the Al-5Mg-3Zn alloy prepared in Example 1 was conducted.

[0071] Figure 5 The microstructure of TiC particles in the alloy prepared in Example 1 is shown. The results show that the TiC particles generated by the in-situ reaction of the Al-Ti-C-CuO-Y2O3 refining agent system are spherical, with most having a diameter of about 500-600 nm. This is likely mainly due to the high temperature generated by the aluminothermic reaction and the combined effect of rare earth elements, which improves the wettability of carbon in the aluminum melt and promotes the complete reaction of the system.

[0072] Figure 6 The morphology of Al2O3 particles in the alloy prepared for Example 1 is shown in the figure. It can be seen from the figure that there are large TiC particles around the Al2O3 particles. It is believed that the Al2O3 is generated by the aluminothermic reaction between Al and CuO and a large amount of heat is released, which improves the wetting properties of C and Al.

[0073] from Figure 7 As can be seen, the TiC particles are approximately the same size but less than 1 μm, and are spherical. Surrounding the TiC particles are some Al₂O₃ particles, with a size similar to that of the TiC particles. From... Figure 8 As can be seen, the TiC particle size is approximately 500 nm, and the added rare earth element Y can be observed around the TiC particles. In this section, the TiC particle size is approximately 500 nanometers (nm), and the presence of added rare earth element Y is clearly visible around the TiC particles. The addition of these rare earth elements may have a certain impact on the formation and properties of TiC particles.

[0074] from Figure 9As can be seen from the figure, compared with Comparative Example 2, the size of the precipitated phase in the Al-5Mg-3Zn alloy prepared in Example 1 gradually decreases, while its shape changes from a long rod to an elliptical shape. Diffraction spot identification of the precipitated phases in Figures (b) and (f) shows the presence of the T'' / T' phase in the alloy. Furthermore, the precipitated phase of the alloy prepared in Example 1 contains trace amounts of Cu in addition to Al-5Mg-3Zn, while the precipitated phase of the alloy prepared in Comparative Example 2 contains only Al-5Mg-3Zn. The presence of Cu can significantly affect the microstructure evolution of the Al-5Mg-3Zn (wt.%) alloy; the GP region serves as the nucleation site for the T' phase, and the Cu-containing GP region has a higher number density, resulting in the formation of T-Mg... 32 (Al,Zn,Cu) 49 The precipitates are small and round, which is more beneficial to the improvement of the mechanical properties of the alloy.

[0075] Figure 10 Morphology and energy dispersive spectroscopy (EDS) analysis of the alloy precipitates prepared in Example 1. Figure 10 It is known that the T phase of the alloy contains Cu. The matrix alloy itself does not contain Cu. During the in-situ reaction of the Al-Ti-C-CuO-Y2O3 system within the Al-5Mg-3Zn (wt.%) aluminum alloy matrix to generate in-situ particles, the Al-CuO reaction releases a large amount of heat, igniting the high-temperature self-propagating reaction of the system and generating Al2O3 particles to further refine the alloy microstructure. The displaced Cu element interacts with the original strengthening phase T-Mg of the matrix alloy. 32 (Al,Zn) 49 Combined to form Cu-containing T-Mg 32 (Al,Zn,Cu) 49 Compared to the strengthening phases prepared in the Al-TiO2-C-Y2O3 system, the Cu-containing T-Mg phase is finer, more dispersed, and more circular / elliptical in shape, exhibiting a better promoting effect on alloy performance. 32 (Al,Zn,Cu) 49 The formation of the Cu-containing T-Mg phase will hinder the formation of the S phase in the alloy. The S phase, acting as a cathode phase, accelerates the corrosion and dissolution of the alloy in corrosive media. Therefore, under the preparation process parameters and alloy system of this invention, the Cu-containing T-Mg... 32 (Al,Zn,Cu) 49 The presence of the phase will be beneficial to improving the corrosion resistance of the alloy.

[0076] 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 the claims of this patent application.

Claims

1. A rare earth-containing aluminum alloy refining agent, characterized in that, It is composed of aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder, and the molar ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide is (2.0~6.0):(0.5~1.5):(0.5~1.5):(0.2~1.5):(0.01~0.2).

2. A method for using a rare earth-containing aluminum alloy refining agent, characterized in that, Includes the following steps: Step (1): Ball mill and mix aluminum powder, titanium powder, carbon powder, copper oxide powder and yttrium oxide powder evenly to obtain the mixed raw material powder of rare earth aluminum alloy refining agent as described in claim 1. Step (2): Press the mixed raw material powder into shape to obtain aluminum alloy refining agent block; wrap the aluminum alloy refining agent block with aluminum foil and dry it; Step (3): Press the dried aluminum alloy refining agent block into the aluminum alloy melt for a high-temperature self-propagating reaction to generate the required in-situ particles; Step (4): The reacted aluminum alloy melt is cast using a near-liquidothermal temperature casting method. After casting, an aluminum alloy with refined grain structure is obtained.

3. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (1), the particle size of the mixed raw material powder is 1~40μm; the ball milling time is 30~90min.

4. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (2), the forming pressure is 12~18MPa and the holding time is 90~150s; the aluminum alloy refining agent block is a cylinder with a diameter of 20~30mm and a thickness of 5~8mm; during the drying process, the drying temperature is 100~200℃ and the drying time is 30~60min.

5. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (3), the amount of aluminum alloy refining agent block is 0.5~10wt.% of the mass of aluminum alloy melt; the temperature of aluminum alloy melt is controlled at 900~950℃ during high-temperature self-propagating reaction.

6. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (4), the aluminum alloy melt temperature is reduced to 700~800℃ for purification treatment, and then the temperature is further reduced to 650~680℃ for casting. Before casting, the casting metal mold is preheated to 100~150℃; after casting, it is air-cooled to room temperature.

7. The method of using the rare earth-containing aluminum alloy refining agent according to claim 2, characterized in that, In step (3), the method for preparing the aluminum alloy melt is as follows: prepare alloy raw materials according to the design composition of the base aluminum alloy, and melt them at room temperature and pressure using a non-vacuum melting method to obtain the aluminum alloy melt.

8. The method of using the rare earth-containing aluminum alloy refining agent according to claim 7, characterized in that, In step (3), in the base aluminum alloy: the mass fraction of magnesium is 4.40~5.60 wt.%, the mass fraction of zinc is 2.40~3.60 wt.%, the mass fraction of silicon is less than or equal to 0.08 wt.%, the mass fraction of iron is less than or equal to 0.08 wt.%, the mass fraction of manganese is less than or equal to 0.08 wt.%, and the balance is aluminum.

9. The method of using the rare earth-containing aluminum alloy refining agent according to claim 7, characterized in that, In step (3), the melting temperature of the alloy raw materials is 900~950℃ and the melting time is 20~40min.

10. The method of using the rare earth-containing aluminum alloy refining agent according to any one of claims 2-9, characterized in that, In step (1), the molar ratio of aluminum, titanium, carbon, copper oxide and yttrium oxide in the mixed raw material powder is 2.8:1:1.2:0.3:0.043; aluminum powder passes through a 700-mesh sieve, titanium powder passes through a 500-mesh sieve, carbon powder passes through a 500-mesh sieve, copper oxide powder passes through a 700-mesh sieve, and the average particle size of yttrium oxide powder is 1.0 μm; the ball milling time is 60 min. In step (2), the forming pressure is 12~18MPa and the holding time is 120s; the aluminum alloy refining agent block is a cylinder with a diameter of 25mm and a height of 7mm; during the drying process, the drying temperature is 150℃ and the drying time is 40min. In step (3), the method for preparing the aluminum alloy melt is as follows: prepare alloy raw materials according to the designed composition of the base aluminum alloy, and melt them at room temperature and pressure using a non-vacuum melting method to obtain the aluminum alloy melt; in the base aluminum alloy: the mass fraction of magnesium is 5.0 wt.%, the mass fraction of zinc is 3.0 wt.%, the mass fraction of silicon is less than or equal to 0.08 wt.%, the mass fraction of iron is less than or equal to 0.08 wt.%, the mass fraction of manganese is less than or equal to 0.08 wt.%, and the balance is aluminum; the melting temperature of the alloy raw materials is 950℃, and the melting time is 30 min; In step (3), the amount of aluminum alloy refining agent block is 8 wt.% of the mass of the aluminum alloy melt; the temperature of the aluminum alloy melt is controlled at 950℃ during the high-temperature self-propagating reaction; In step (4), the aluminum alloy melt temperature is reduced to 700°C for purification treatment, and then the temperature is further reduced to 650°C for casting. Before casting, the casting metal mold is preheated to 150°C; after casting, it is air-cooled to room temperature.

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