Hypoeutectic and eutectic Al-Mg2Si composite material and preparation method thereof

Abstract

The invention discloses a hypoeutectic and eutectic Al-Mg2Si composite material and a preparation method thereof. The hypoeutectic and eutectic Al-Mg2Si composite material is prepared from the following components in percentage by mass: 4.3 to 8.6 percent of Mg, 3.0 to 11.0 percent of Si, 0 to 1.0 percent of Cu, 0.1 to 0.9 percent of Fe, 0 to 0.4 percent of Mn, 0 to 0.1 percent of Ti, 0.001 to 0.005 percent of Be, 0.008 to 0.05 percent of Sr, 0.02 to 0.10 percent of RE, less than or equal to 0.15 percent of impurities and the balance of Al. The mass ratio of Mg to Si is less than or equal to 1.5; rE is selected from at least one of La and Ce. According to the hypoeutectic and eutectic Al-Mg2Si composite material disclosed by the invention, the eutectic Mg2Si is modified, so that the strength and plasticity of the composite material can be improved.

Description

Technical Field

[0001] The invention belongs to the field of materials, and in particular relates to a hypoeutectic and eutectic Al-Mg2Si composite material and a preparation method thereof. Background Art

[0002] In recent years, Al-Mg2Si composite materials formed by in-situ formation of a controllable amount of Mg2Si phase in aluminum alloys have attracted extensive attention from scholars at home and abroad. Compared with traditional Al-Mg-Si alloys, Mg2Si particle-reinforced aluminum-based composite materials have higher specific stiffness, specific strength, wear resistance and other excellent properties, and have broad application prospects in aerospace and automotive fields with high requirements for lightweight.

[0003] However, under ordinary casting conditions, the eutectic Mg2Si is mainly composed of a network of thin blades interconnected. Due to the high hardness of Mg2Si, there is a large strain mismatch between it and the matrix, and cracks are easily generated when subjected to force. At the same time, the network interconnected structure splits the matrix, becomes a medium for crack expansion, and accelerates the failure of the component. In order to solve this problem, domestic and foreign researchers have improved the morphology of the eutectic Mg2Si by adding modifiers, such as Sr, Bi, Sc, Er, Y, B, Sb, P, etc., and have achieved certain results. For example, CN108300884A discloses a method for modifying and refining a hypoeutectic Al-Mg2Si alloy. The method improves the morphology of the eutectic Mg2Si phase by adding metal particles Bi. The principle is to use the extremely low solubility of Bi in Al. When Al-Mg2Si undergoes a eutectic reaction, it is easy to adsorb and aggregate at the front of the growth interface of the first precipitated eutectic phase, triggering a large number of new concave angle twins, changing the branch growth rate and direction, thereby achieving the purpose of refining the eutectic phase and improving the performance of the composite material. CN109112368A discloses a Sc-containing cast hypoeutectic Al-Mg2Si alloy and a production method thereof, and believes that the mechanism of action of Sc is similar to that of Bi, improving the morphology of eutectic Mg2Si. Similarly, CN111118355A discloses a rare earth element erbium-modified cast hypoeutectic Al-Mg2Si alloy and a preparation method thereof.

[0004] In the above method, the addition of Bi, Sc and Er can significantly change the morphology of eutectic Mg2Si, thereby improving the performance of the alloy. However, Bi has a low melting point and forms an overburned structure during the heat treatment of aluminum alloy. Sc and Er are both rare and precious rare earth elements, and the added content of Sc is 0.15-0.35% and the content of Er is 0.1-0.3%. The modification cost is high, which is not conducive to large-scale application. Summary of the invention

[0005] In order to overcome the problems existing in the above-mentioned prior art, one of the objectives of the present invention is to provide a hypoeutectic and eutectic Al-Mg2Si composite material.

[0006] A second object of the present invention is to provide a method for preparing hypoeutectic and eutectic Al-Mg2Si composite materials.

[0007] The third object of the present invention is to provide the application of the above-mentioned hypoeutectic and eutectic Al-Mg2Si composite materials and their preparation methods in the automotive, communication, electronic or aerospace fields.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] The first aspect of the present invention provides a hypoeutectic and eutectic Al-Mg2Si composite material, wherein the hypoeutectic and eutectic Al-Mg2Si composite material is composed of the following components in mass percentage: Mg 4.3% to 8.6%, Si 3.0% to 11.0%, Cu0 to 1.0%, Fe 0.1 to 0.9%, Mn 0 to 0.4%, Ti 0 to 0.1%, Be 0.001 to 0.005%, Sr 0.008 to 0.05%, RE 0.02 to 0.10%, impurities ≤ 0.15%, and Al as the balance;

[0010] The mass ratio of Mg to Si is ≤1.5; RE is selected from at least one of La and Ce;

[0011] The hypoeutectic and eutectic Al-Mg2Si composite materials contain Mg2Si.

[0012] In the present invention, the mass ratio of Mg to Si is ≤1.5, Mg reacts with Si to generate Mg2Si, and the Si element that does not react to generate Mg2Si can improve the fluidity of the composite material, so that the composite material can have better fluidity during casting.

[0013] In the present invention, the mass percentage of Mg is 4.3% to 8.6%, for example, it can be selected from 4.3%, 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%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%. In the present invention, the Mg content cannot exceed the eutectic point (8.8%) to ensure that primary Mg2Si is substantially not generated.

[0014] In the present invention, the mass percentage of Si is 3.0% to 11.0%, for example, can be selected from 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%.

[0015] In the present invention, the mass percentage of Cu is 0-1.0%, for example, it can be selected from 0%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1.0%. Cu can improve the mechanical properties of the composite material in the present invention, so that the composite material has a higher strength. In addition, if the addition amount of Cu exceeds 1%, it will affect the fluidity and liquidus of the composite material, which is not conducive to casting.

[0016] In the present invention, the mass percentage of Fe is 0.1-0.9%, for example, it can be selected from 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%. In order to improve the recycling efficiency of aluminum recovery material after removing Zn, the present invention can achieve a significant increase in the tolerance of Fe element in the composite material to 0.9% by optimizing the composition and preparation method, and set the corresponding Mn and its content by thermodynamic calculation to determine the formation temperature of Al(FeMn)Si quaternary phase, ensure that the temperature is close to the Al-Mg2Si eutectic temperature, so as to obtain Al-Mg2Si-Al(FeMn)Si ternary eutectic structure, reduce the harm of Fe phase, and improve the sticky mold property of composite material during casting, and broaden the application of composite material.

[0017] In the present invention, the mass percentage of Mn is 0-0.4%, for example, it can be selected from 0%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%. In the present invention, if the composite material needs to improve the mold adhesion during subsequent processing and molding, a certain amount of Mn needs to be added to the composite material; if the composite material does not need to improve the mold adhesion during subsequent processing and molding, Mn does not need to be added.

[0018] In the present invention, the mass percentage of Ti is 0-0.1%, for example, it can be selected from 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%. Ti can refine the grains of the primary α-Al matrix generated in the composite material in the present invention.

[0019] In the present invention, the mass percentage of Be is 0.001-0.005%, for example, it can be selected from 0.001%, 0.0015%, 0.002%, 0.0025%, 0.003%, 0.0035%, 0.004%, 0.0045%, 0.005%. In the present invention, the Be element can reduce the burning loss of Mg, Sr, and RE during the smelting process, and at the same time, Be can change the type of the iron-rich phase during the solidification process, promote the beneficial transformation of the iron-rich phase, thereby increasing the allowable content of Fe in the composite material.

[0020] In the present invention, the mass percentage of Sr is 0.008-0.05%, for example, it can be selected from 0.008%, 0.01%, 0.015%, 0.020%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%. In the present invention, Sr is added in the form of Al-Sr-RE alloy.

[0021] In the present invention, the mass percentage of RE is 0.02-0.10%, for example, it can be selected from 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.10%. In the present invention, RE is added in the form of Al-Sr-RE alloy.

[0022] Preferably, the mass percentage of Mg2Si is ≤13.9% based on the total mass percentage of the hypoeutectic and eutectic Al-Mg2Si composite material as 100%. According to the binary phase diagram of Al-Mg2Si, the eutectic point of Mg2Si is 13.9%. When the mass fraction of Mg2Si is higher than this value, it is called a hypereutectic alloy, and the structure contains a primary phase and a eutectic phase. On the contrary, when the mass fraction of Mg2Si is not higher than this value, the structure contains a hypoeutectic or eutectic alloy, and only a eutectic Mg2Si phase exists.

[0023] The second aspect of the present invention provides a method for preparing the hypoeutectic and eutectic Al-Mg2Si composite materials according to the first aspect of the present invention, comprising the following steps:

[0024] S1: heating and melting part of the raw materials, and then refining to obtain melt A;

[0025] S2: adding Al-Be alloy to the melt A, and then adding Mg, and optionally Ti and Mn, and melting to obtain a melt B;

[0026] S3: refining the melt B, then adding the Al-Sr-RE composite modifier into the melt B for melting, and casting to obtain the hypoeutectic or eutectic Al-Mg2Si composite material.

[0027] In the present invention, the mass percentage of Mg2Si is ≤13.9%, and the microstructure contains hypoeutectic or eutectic alloy, which only needs to be modified by Al-Sr-RE composite modifier, that is, by adding a trace amount of Al-Sr-RE master alloy, the master alloy contains Al4 (SrRE) and Al doped with Sr and RE. 11 (SrRE)3, by virtue of its higher formation temperature and high chemical activity, aggregates at the solid-liquid interface of the eutectic Mg2Si phase, inhibits the lateral growth of the eutectic Mg2Si, promotes its twinning transformation, and ultimately obtains fine whisker-like and granular eutectic Mg2Si, significantly improving the plasticity of the alloy.

[0028] Preferably, the refining step in step S1 is: refining by introducing a halide salt refining agent with an inert gas as a carrier.

[0029] Preferably, the amount of the halide salt refining agent added is 0.08-0.12% of the mass of melt A.

[0030] Preferably, the halide salt refining agent mainly contains NaCl, KCl and Na3AlF6.

[0031] Preferably, the refining step in step S3 is: refining by introducing a sodium-free halide salt refining agent with an inert gas as a carrier. The use of a sodium-free halide salt refining agent for refining can eliminate the adverse effects of the sodium-containing halide salt refining agent on the high-Mg melt.

[0032] Preferably, the sodium-free halide salt refining agent mainly contains MgCl2, KCl, and K3AlF6.

[0033] Preferably, the amount of the sodium-free halide salt refining agent added is 0.08-0.12% of the mass of the melt B.

[0034] Preferably, the inert gas is selected from at least one of nitrogen, argon and xenon.

[0035] Preferably, based on the mass percentage of the Al-Sr-RE composite modifier being 100%, the total mass percentage of Sr and RE is 10-18%.

[0036] Preferably, the part of raw materials includes aluminum recycling material after Zn is removed; further preferably, the part of raw materials includes aluminum recycling material after Zn is removed, aluminum ingot, Cu, and Si. The present invention uses aluminum recycling material after Zn is removed as the main raw material, and prepares the components of the target hypoeutectic or eutectic Al-Mg2Si composite material by adding aluminum ingot, magnesium ingot, Si, Mn, Cu, Al-Be, and Al-Sr-RE composite modifier.

[0037] Preferably, the temperature of the heating and melting in step S1 is 750-850°C.

[0038] Preferably, the preparation method further comprises the step of adding raw materials until the alloy composition is qualified; the step of adding raw materials until the alloy composition is qualified is located between step S1 and step S2 and / or between step S2 and step S3.

[0039] Preferably, the step S1 further comprises the steps of degassing, filtering and removing impurities; the steps of degassing, filtering and removing impurities are located after the refining step.

[0040] The third aspect of the present invention provides the application of the preparation method of the hypoeutectic and eutectic Al-Mg2Si composite materials described in the first aspect of the present invention and / or the hypoeutectic and eutectic Al-Mg2Si composite materials described in the second aspect of the present invention in the automotive, communication, electronics or aerospace fields.

[0041] The beneficial effects of the present invention are as follows: the hypoeutectic and eutectic Al-Mg2Si composite materials in the present invention can improve the strength and plasticity of the composite materials by modifying the eutectic Mg2Si, thereby meeting the use requirements of composite materials in the fields of automobiles, communications, electronics, aerospace, etc. The performance that the hypoeutectic and eutectic Al-Mg2Si composite materials in the present invention can achieve is specifically: the tensile strength in the gravity casting state is 180-200MPa, the yield strength is 100-106MPa, and the elongation is 8-11.5%; the tensile strength in the T6 state is 270-340MPa, the yield strength is 220-280MPa, and the elongation is 6-9.5%.

[0042] The present invention uses Al-Sr-RE composite modifier to modify eutectic Mg2Si, which can significantly improve the micromorphology of eutectic Mg2Si, thereby improving the strength and plasticity of the obtained hypoeutectic and eutectic Al-Mg2Si composite materials. In addition, the phases formed by Ce, La and Sr in the Al-Sr-RE composite modifier have a good promoting effect on the growth and twin transformation of eutectic Mg2Si, and the prices of Ce, La and Sr are the lowest, slightly higher than the price of Al, which significantly reduces the preparation cost of hypoeutectic and eutectic Al-Mg2Si composite materials. In addition, the preparation method is simple and easy to operate, and is suitable for industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the metallographic phase diagram of the eutectic Al-Mg2Si composite material in Example 1.

[0044] Figure 2 This is the metallographic image of the eutectic Al-Mg2Si composite material in Comparative Example 1.

[0045] Figure 3 This is the XRD diagram of the eutectic Al-Mg2Si composite material in Example 1. DETAILED DESCRIPTION

[0046] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0047] Example 1

[0048] This example provides a eutectic Al-Mg2Si composite material, which is composed of the following components in mass percentage: Mg 8.5%, Si 6.0%, Cu 0.6%, Fe 0.5%, Mn 0.3%, Ti 0.05%, Be 0.002%, Sr 0.008%, Ce 0.025%, and the balance is Al and inevitable trace impurities.

[0049] The eutectic Al-Mg2Si composite material in this example is prepared by the following preparation method, and the specific steps include:

[0050] (1) Batching: The amount of each raw material is calculated according to the mass percentage of the target product. When recycled aluminum is used as the main raw material, the Zn waste in the recycled aluminum needs to be removed. The target product composition is prepared by adding aluminum ingots, magnesium ingots, Si, Mn agent, Cu, Al-Be and Al-Sr-Ce master alloy.

[0051] (2) Melting: Most of the recycled aluminum, Al, Si and alloy materials that are not easily burned are added into a melting furnace, and then the temperature is raised to 800°C for melting.

[0052] (3) Refining: Add the remaining raw materials and adjust the melt temperature to 750°C; use 99.99% pure nitrogen as a carrier, introduce 0.1% of the total mass of the melt into a halide refining agent (commercially available product, its main components are NaCl, KCl, Na3AlF6), and degas and remove impurities for 15 minutes; at the same time, turn on the electromagnetic stirring system at the bottom of the furnace for 5 minutes; then add Al-Be alloy;

[0053] (4) Composition adjustment: remove the surface slag and test the composition. According to the test results, replenish the raw materials and add Mg. It is not necessary to add Fe agent. Use thermodynamic calculation to design the Mn content, add Mn and Ti, and turn on the electromagnetic stirring system for 2 minutes. Test the alloy composition for the second time and adjust the alloy composition to meet the requirements.

[0054] (6) Refining: Using 99.99% pure argon as a carrier, introduce a Na-free halide refining agent (commercially available product, whose main components are MgCl2, KCl, K3AlF6) accounting for 0.1% of the total mass of the melt, and purify for 15 minutes;

[0055] (7) Composite modification: add 0.3% Al-8Sr-8Ce composite modifier to the total mass of the melt (the mass percentage of Sr is 8% and the mass percentage of Ce is 8% based on the mass percentage of the composite modifier as 100%), turn on the electromagnetic stirring system for 2 minutes, and then keep it warm and stand for 30 minutes;

[0056] (8) Casting: The scum on the surface of the melt is removed, and the melt is introduced into a flow channel. After rotary degassing and double-layer filtration, the melt is introduced into a holding furnace and directly supplied to a casting equipment for casting to obtain the eutectic Al-Mg2Si composite material in this example.

[0057] In this example, taking the mass percentage of the eutectic Al-Mg2Si composite material as 100%, the mass percentage of Mg2Si is 13.8%.

[0058] Example 2

[0059] This example provides a hypoeutectic Al-Mg2Si composite material, which is composed of the following components in mass percentage: Mg 4.3%, Si 3.5%, Cu 0.3%, Fe 0.1%, Ti 0.03%, Be 0.002%, Sr 0.01%, La 0.04%, and the balance is Al and inevitable trace impurities.

[0060] The hypoeutectic Al-Mg2Si composite material in this example is prepared by the following preparation method, and the specific steps include:

[0061] (1) Batching: The amount of each raw material is calculated according to the mass percentage of the target product. When recycled aluminum is used as the main raw material, the Zn waste in the recycled aluminum needs to be removed. The target alloy composition is prepared by adding aluminum ingots, magnesium ingots, Si, Cu, Al-Be and Al-Sr-La master alloys.

[0062] (2) Melting: Most of the recycled aluminum, Al, Si and alloy materials that are not easily burned are added into a melting furnace, and then the temperature is raised to 780°C for melting.

[0063] (3) Refining: Add the remaining raw materials and adjust the melt temperature to 740°C; use 99.99% pure nitrogen as a carrier, introduce 0.1% of the total mass of the melt into a halide refining agent (commercially available product, its main components are NaCl, KCl, Na3AlF6), and degas and remove impurities for 20 minutes; at the same time, turn on the electromagnetic stirring system at the bottom of the furnace for 4 minutes; then add Al-Be alloy;

[0064] (4) Composition adjustment: Remove the surface slag and test the composition. According to the test results, replenish the raw materials and add Mg and Ti. There is no need to add Fe, and turn on the electromagnetic stirring system for 3 minutes. Test the alloy composition for the second time and adjust the alloy composition to meet the requirements.

[0065] (6) Refining: Using 99.99% pure argon as a carrier, introduce 0.1% of the total mass of the melt into a Na-free halide refining agent (commercially available product, whose main components are MgCl2, KCl, K3AlF6), and purify for 12 minutes;

[0066] (7) Composite modification: add 0.4% Al-6Sr-10La composite modifier to the total mass of the melt (the mass percentage of Sr is 6% and the mass percentage of La is 10% based on the mass percentage of the composite modifier as 100%), turn on the electromagnetic stirring system for 3 minutes, and then keep it warm and stand for 20 minutes;

[0067] (8) Casting: The scum on the surface of the melt is removed, and the melt is introduced into a flow trough. After rotary degassing and double-layer filtration, the melt is introduced into a semi-continuous casting device and cast into a rod, which is the hypoeutectic Al-Mg2Si composite material in this example.

[0068] In this example, taking the mass percentage of the hypoeutectic Al-Mg2Si composite material as 100%, the mass percentage of Mg2Si is 7.2%.

[0069] Example 3

[0070] This example provides a hypoeutectic Al-Mg2Si composite material, which is composed of the following components in mass percentage: Mg 8.0%, Si 11.0%, Fe 0.8%, Be 0.005%, Sr 0.03%, RE 0.09%, and the balance is Al and inevitable trace impurities, wherein the mass ratio of Ce to La in RE is 3:1.

[0071] The hypoeutectic Al-Mg2Si composite material in this example is prepared by the following preparation method, and the specific steps include:

[0072] (1) Batching: The amount of each raw material is calculated according to the mass percentage of the target product. When recycled aluminum is used as the main raw material, the Zn waste in the recycled aluminum needs to be removed. The target alloy composition is prepared by adding aluminum ingots, magnesium ingots, Si, Al-Be and Al-Sr-RE master alloys.

[0073] (2) Melting: Most of the recycled aluminum, Al, Si and alloy materials that are not easily burned are added into a melting furnace, and then the temperature is raised to 820°C for melting.

[0074] (3) Refining: Add the remaining raw materials and adjust the melt temperature to 760°C; use 99.99% pure nitrogen as a carrier, introduce 0.1% of the total mass of the melt into a halide refining agent (commercially available product, its main components are NaCl, KCl, Na3AlF6), and degas and remove impurities for 25 minutes; at the same time, turn on the electromagnetic stirring system at the bottom of the furnace for 6 minutes; then add Al-Be alloy;

[0075] (4) Composition adjustment: remove the surface scum and test the composition. According to the test results, replenish the raw materials and add Mg. There is no need to add Fe, and turn on the electromagnetic stirring system for 4 minutes. Test the alloy composition for the second time and adjust the alloy composition to meet the requirements.

[0076] (6) Refining: Using 99.99% pure argon as a carrier, 0.1% of the total mass of the melt was introduced into a Na-free halide refining agent (commercially available product, whose main components are MgCl2, KCl, K3AlF6), and purified for 20 minutes;

[0077] (7) Composite modification: add 0.8% Al-5Sr-9Ce-3La composite modifier to the total mass of the melt (the mass percentage of Sr is 5%, the mass percentage of Ce is 9%, and the mass percentage of La is 3%, based on the total mass percentage of the composite modifier being 100%), turn on the electromagnetic stirring system for 5 min, and then keep it at a temperature for 40 min;

[0078] (8) Casting: Remove the scum on the surface of the melt, introduce the melt into a flow channel, and after rotary degassing and double-layer filtration, introduce it into a circulating casting mold to cast an ingot, which is the hypoeutectic Al-Mg2Si composite material in this example.

[0079] In this example, taking the mass percentage of the hypoeutectic Al-Mg2Si composite material as 100%, the mass percentage of Mg2Si is 12.7%.

[0080] Example 4

[0081] This example provides a hypoeutectic Al-Mg2Si composite material, which is composed of the following components in mass percentage: Mg6%, Si 5.5%, Cu 1.0%, Fe 0.4%, Mn 0.4%, Ti 0.03%, Be 0.002%, Sr 0.05%, RE 0.04%, and the balance is Al and inevitable trace impurities, wherein the mass ratio of La to Ce in RE is 4:3.

[0082] The hypoeutectic Al-Mg2Si composite material in this example is prepared by the following preparation method, and the specific steps include:

[0083] (1) Batching: The amount of each raw material is calculated according to the mass percentage of the target product. When recycled aluminum is used as the main raw material, the Zn waste in the recycled aluminum needs to be removed. The target alloy composition is prepared by adding aluminum ingots, magnesium ingots, Si, Mn agents, Cu, Al-Be and Al-Sr-RE master alloys.

[0084] (2) Melting: Most of the recycled aluminum, Al, Si and alloy materials that are not easily burned are added into a melting furnace, and then the temperature is raised to 810°C for melting.

[0085] (3) Refining: Add the remaining raw materials and adjust the melt temperature to 750°C; use 99.99% pure nitrogen as a carrier, introduce 0.1% of the melt mass of a halide refining agent (commercially available product, its main components are NaCl, KCl, Na3AlF6), degas and remove impurities for 10 minutes; at the same time, turn on the electromagnetic stirring system at the bottom of the furnace for 5 minutes; then add Al-Be alloy;

[0086] (4) Composition adjustment: remove the surface slag and test the composition. According to the results, replenish the raw materials and add Mg. According to the measured Fe content, add Mn and Ti agents, and turn on the electromagnetic stirring system for 5 minutes. Test the alloy composition for the second time and adjust the alloy composition to meet the requirements.

[0087] (6) Refining: Using 99.99% pure argon as a carrier, introduce 0.1% of the melt mass of a Na-free halide refining agent (a commercial product, whose main components are MgCl2, KCl, and K3AlF6) for purification for 20 minutes;

[0088] (7) Composite modification: add 0.6% Al-9Sr-4La-3Ce composite modifier (the total mass percentage of the composite modifier is 100%, the mass percentage of Sr is 5%, the mass percentage of La is 5%, and the mass percentage of Ce is 4%) to the melt, turn on the electromagnetic stirring system for 3 minutes, and then keep it warm and stand for 30 minutes;

[0089] (8) Casting: The scum on the surface of the melt is removed, and the melt is introduced into a flow trough. After rotary degassing and double-layer filtration, the melt is introduced into a semi-continuous casting device and cast into rods to obtain the hypoeutectic Al-Mg2Si composite material in this example.

[0090] In this example, taking the mass percentage of the hypoeutectic Al-Mg2Si composite material as 100%, the mass percentage of Mg2Si is 9.5%.

[0091] Comparative Example 1

[0092] The only difference between the preparation method of the eutectic Al-Mg2Si composite material in this example and that in Example 1 is that step (7) of this example does not contain the step of adding an Al-Sr-Ce composite modifier.

[0093] In this example, taking the total mass percentage of the eutectic Al-Mg2Si composite material as 100%, the mass percentage of Mg2Si is 13.9%.

[0094] Comparative Example 2

[0095] The preparation method of the eutectic Al-Mg2Si composite material in this example is different from that in Example 1 only in that an equal amount of Al-Sr is used in step (7) of this example to replace the Al-Sr-Ce composite modifier in Example 1.

[0096] Comparative Example 3

[0097] The preparation method of the eutectic Al-Mg2Si composite material in this example is different from that in Example 1 only in that an equal amount of Al-Ce is used in step (7) of this example to replace the Al-Sr-Ce composite modifier in Example 1.

[0098] Comparative Example 4

[0099] The preparation method of the eutectic Al-Mg2Si composite material in this example is different from that in Example 1 only in that in step (7) of this example, Al-Sr and Al-Ce are used to replace the Al-Sr-Ce composite modifier in Example 1.

[0100] Performance Test:

[0101] The metallographic phase diagrams of the eutectic Al-Mg2Si composite materials in Example 1 and Comparative Example 1 were tested respectively, and the specific test results are as follows: Figure 1 and Figure 2 As shown by Figures 1-2 It can be seen that compared with Comparative Example 1, the eutectic Mg2Si in Example 1 is significantly refined.

[0102] The XRD data of the eutectic Al-Mg2Si composite material in Example 1 was tested by X-ray diffractometer. The specific test results are as follows: Figure 3 As shown by Figure 3 It can be seen that in the eutectic Al-Mg2Si composite material in Example 1, Mg and Si react in situ to generate Mg2Si.

[0103] The hypoeutectic and eutectic Al-Mg2Si composite materials in Examples 1 to 4 and Comparative Examples 1 to 4 were subjected to gravity casting and T6 heat treatment. The T6 heat treatment process was: 540±5°C, heat preservation for 8h, water quenching and heating to 175°C, and heat preservation for 9h. The tensile test was carried out according to the method listed in the national standard GB / T 228.1-2021 "Tensile test of metal materials Part 1: Room temperature test method", and the test results are listed in Table 1.

[0104] Table 1 Mechanical properties test results of hypoeutectic and eutectic Al-Mg2Si composites

[0105]

[0106] As shown in Table 1, compared with Comparative Examples 1 to 4, after Examples 1 to 4 were treated with Al-Sr-RE composite modifier, the plasticity of the hypoeutectic and eutectic Al-Mg2Si composite materials was significantly improved, and the elongation reached 8 to 11.5% in the gravity casting state and 6 to 9.5% in the T6 state. Compared with Comparative Example 1 (without Al-Sr-RE composite modifier), the tensile strength, yield strength and elongation of Example 1 were significantly improved, and the elongation was increased by 3.2 times. Compared with Comparative Example 2 (using Al-Sr), Example 1 was treated with Al-Sr-RE composite modifier, and the elongation was increased by 2 times. Compared with Comparative Example 3 (using Al-Ce), Example 1 was treated with Al-Sr-RE composite modifier, and the elongation was increased by 1.63 times. In addition, the modification effect of Sr and Ce on eutectic Al-Mg2Si is also closely related to the addition method. Compared with comparative example 4, the elongation of the composite material prepared by adding Al-Sr-RE is increased by 38.1% and 37.5%.

[0107] The average equivalent circular diameter of the eutectic Mg2Si of the hypoeutectic and eutectic Al-Mg2Si composite materials of Examples 1 to 4 and Comparative Examples 1 to 3 was tested respectively. The specific testing method was as follows: image processing software was used to test and analyze Mg2Si in 5 to 30 50 to 500 times magnification metallographic photographs. The statistically measured average equivalent circular diameter data were shown in Table 2 below.

[0108] Table 2 Average equivalent circle diameter of eutectic Mg2Si

[0109]

[0110] It can be seen from Table 2 that, compared with Comparative Examples 1 to 3, the size of the eutectic Mg2Si in Example 1 is significantly refined, and the average equivalent circle diameter is less than 3 μm.

[0111] In summary, the hypoeutectic and eutectic Al-Mg2Si composite materials in the present invention can improve the strength and plasticity of the composite materials by modifying the eutectic Mg2Si, so that the composite materials can meet the use requirements of aluminum alloy materials in the fields of automobiles, communications, electronics, aerospace, etc. The performance that can be achieved by the hypoeutectic and eutectic Al-Mg2Si composite materials in the present invention is specifically: the tensile strength in the gravity casting state is 180-200MPa, the yield strength is 100-106MPa, and the elongation is 8-11.5%; the tensile strength in the T6 state is 270-340MPa, the yield strength is 220-280MPa, and the elongation is 6-9.5%. The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A hypoeutectic and eutectic Al-Mg2Si composite material, characterized in that: The hypoeutectic and eutectic Al-Mg2Si composite material is composed of the following components in mass percentage: Mg 4.3%-8.6%, Si 3.0%-11.0%, Cu 0-1.0%, Fe 0.1-0.9%, Mn 0-0.4%, Ti 0-0.1%, Be 0.001-0.005%, Sr 0.008-0.05%, RE 0.02-0.10%, impurities ≤0.15%, and Al as the balance; The mass ratio of Mg to Si is ≤1.5; RE is selected from at least one of La and Ce; The hypoeutectic and eutectic Al-Mg2Si composite materials contain Mg2Si.

2. The hypoeutectic and eutectic Al-Mg2Si composite material according to claim 1, characterized in that: Taking the total mass percentage of the hypoeutectic and eutectic Al-Mg2Si composite material as 100%, the mass percentage of the Mg2Si is ≤13.9%.

3. The method for preparing the hypoeutectic and eutectic Al-Mg2Si composite material according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1: heating and melting part of the raw materials, and then refining to obtain melt A; S2: adding Al-Be alloy to the melt A, and then adding Mg, and optionally Ti and Mn, and melting to obtain a melt B; S3: refining the melt B, then adding the Al-Sr-RE composite modifier into the melt B for melting, and casting to obtain the hypoeutectic and eutectic Al-Mg2Si composite materials.

4. The method for preparing the hypoeutectic and eutectic Al-Mg2Si composite material according to claim 3, characterized in that: The refining step in step S1 is: introducing a halide salt refining agent with an inert gas as a carrier for refining; And / or, the refining step in step S3 is: refining by introducing a sodium-free halide salt refining agent using an inert gas as a carrier.

5. The method for preparing the hypoeutectic and eutectic Al-Mg2Si composite material according to claim 3, characterized in that: Taking the mass percentage of the Al-Sr-RE composite modifier as 100%, the total mass percentage of Sr and RE is 10-18%.

6. The method for preparing the hypoeutectic and eutectic Al-Mg2Si composite material according to claim 3, characterized in that: The part of raw materials includes aluminum recovery materials after Zn is removed.

7. The method for preparing the hypoeutectic and eutectic Al-Mg2Si composite material according to claim 3, characterized in that: The temperature of the heating and melting in the step S1 is 750-850°C.

8. The method for preparing the hypoeutectic and eutectic Al-Mg2Si composite material according to claim 3, characterized in that: The preparation method further comprises the step of adding raw materials until the alloy composition is qualified; the step of adding raw materials until the alloy composition is qualified is located between step S1 and step S2, and / or between step S2 and step S3.

9. The method for preparing the hypoeutectic and eutectic Al-Mg2Si composite material according to claim 3, characterized in that: The step S1 also includes the steps of degassing, filtering and removing impurities; the steps of degassing, filtering and removing impurities are located after the refining step.

10. Application of the hypoeutectic and eutectic Al-Mg2Si composite material according to any one of claims 1 to 2 and / or the method for preparing the hypoeutectic and eutectic Al-Mg2Si composite material according to any one of claims 3 to 9 in the automotive, communication, electronic or aerospace fields.

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