A high-yield die-casting aluminum alloy material, preparation method and application

Abstract

The present invention provides a high-yield die-casting aluminum alloy material, a preparation method and an application, belonging to the technical field of high-pressure die-casting aluminum alloy materials. The components of the high-yield die-casting aluminum alloy material of the present invention are calculated by weight percentage as follows: 6.0% to 10.0% Si, 4.0% to 8.0% Zn, 1.0% to 4.0% Mg, 0.2% to 1.0% Fe, 0.1% to 0.6% Mn, 0.1% to 2.0% Cu, 0.15% to 0.3% Sr, and 0% to 0.01% Re, with the balance being Al; Re includes Sm and Pr, and the mass ratio of Sm to Pr is 0.2 to 5:1. Sm and Pr optimize the tissue morphology and improve the strength and toughness of the alloy; the addition of Mn improves the toughness and corrosion resistance of the alloy, and each element jointly offsets the defects brought by the high content of iron elements and improves the alloy performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-pressure die-casting aluminum alloy materials, and particularly relates to a high-yield die-casting aluminum alloy material, a preparation method and an application thereof. Background Art

[0002] As the internal core support structure of a smart phone, the middle plate of the mobile phone needs to have both high strength, high thermal conductivity and the ability to form complex thin walls. With the rapid development of mobile phones towards lightweight, full-screen and ultra-thin directions, in order to maintain the body strength and support for large screens, a metal middle frame with higher strength is required. Therefore, ordinary stamped aluminum middle plates can no longer meet the design requirements. Die-casting and molding methods can cope with the complex structures inside the mobile phone and can form ultra-thin high-strength mobile phone structural components. However, with traditional materials and die-casting formation methods, the yield strength can only reach about 160 MPa, the elongation rate is less than 1%, and the thermal conductivity is less than 100 W / (m·K), far from meeting customer requirements.

[0003] With the requirement of low carbon emissions for cast aluminum alloys put forward, in order to reduce the carbon emissions in the manufacturing process of aluminum alloys, it is necessary to use recycled aluminum as raw materials to produce cast aluminum alloys. However, the Fe content in most recycled aluminum is greater than 0.15%, and it is necessary to consider preparing medium-strength die-casting aluminum alloy materials for mobile phone middle plates under the condition of relatively high Fe content.

[0004] Therefore, there is an urgent need to develop a new type of die-casting aluminum alloy with both high yield, high thermal conductivity and low cost to meet the requirements of high-performance structural components of the new generation of mobile phones. Summary of the Invention

[0005] In view of the technical problems existing in the prior art, the present invention aims to provide a high-yield die-casting aluminum alloy material, a preparation method and an application thereof.

[0006] One of the purposes of the present invention is to provide a high-yield die-casting aluminum alloy material, which is characterized in that the components of the high-yield die-casting aluminum alloy material are calculated by weight percentage as follows: 6.0% - 10.0% Si, 4.0% - 8.0% Zn, 1.0% - 4.0% Mg, 0.2% - 1.0% Fe, 0.1% - 0.6% Mn, 0.1% - 2.0% Cu, 0.15% - 0.3% Sr, and 0% - 0.01% Re, with the balance being Al; Re includes Sm and Pr, and the mass ratio of Sm to Pr is 0.2 - 5:1.

[0007] Preferably, the components of the high yield die-casting aluminum alloy material are as follows by weight percentage: 7.0% - 9.0% Si, 4.0% - 6.0% Zn, 2.0% - 4.0% Mg, 0.4% - 0.6% Fe, 0.3% - 0.5% Mn, 0.5% - 1.0% Cu, 0.15% - 0.3% Sr, and 0% - 0.01% Re, with the balance being Al; Re includes Sm and Pr, and the mass ratio of Sm to Pr is 0.2 - 5:1.

[0008] Preferably, the mass ratio of Sm to Pr is 2:3.

[0009] The second object of the present invention is to provide a preparation method of a high yield die-casting aluminum alloy material, and the preparation method includes:

[0010] First, melt the raw materials according to the components of the high yield die-casting aluminum alloy material and the weight percentages of each component to obtain a melt, and then subject the melt to refining and die-casting treatment to obtain the high yield die-casting aluminum alloy material.

[0011] Preferably, the raw materials include:

[0012] Industrial waste aluminum, pure aluminum ingots, industrial crystalline silicon, aluminum-zinc alloy, pure magnesium ingots, aluminum-manganese alloy, aluminum-copper alloy, aluminum-strontium alloy, Al-Sm master alloy, and Al-Pr master alloy.

[0013] Preferably, the melting includes:

[0014] Melt the pure aluminum ingots, then add industrial waste aluminum and crystalline silicon. After complete melting, stir thoroughly and remove the surface scum. Set the temperature of the aluminum liquid at 750 - 760 °C, and add the aluminum-zinc alloy, aluminum-manganese alloy, and aluminum-copper alloy in batches, and maintain for 25 minutes, with continuous stirring during this period; adjust the temperature of the aluminum liquid to 720 - 730 °C, and add the pure magnesium ingots, Al-Sm master alloy, and Al-Pr master alloy in batches until complete melting.

[0015] Preferably, the refining includes first adding a K2ZrF6 refining agent to the aluminum liquid at a temperature of 700 - 720 °C, refining for 10 minutes to obtain the first refined aluminum liquid, and then adding an aluminum-strontium alloy to the first refined aluminum liquid at a temperature of 700 - 710 °C, refining for 5 minutes to obtain the second refined aluminum liquid.

[0016] Preferably, the addition amount of the K2ZrF6 refining agent is 0.10% of the total weight of the aluminum liquid, and the addition amount of the aluminum-strontium alloy is 0.05% of the total weight of the first refined aluminum liquid.

[0017] Preferably, the refining is carried out in a high-purity argon environment.

[0018] The third object of the present invention is to provide an application of the high yield die-casting aluminum alloy material in the middle plate of a mobile phone.

[0019] Beneficial effects of the present invention:

[0020] The invention provides a high yield die-casting aluminum alloy material, a preparation method and an application thereof. The high yield die-casting aluminum alloy material comprises the following components by weight percentage: 6.0% to 10.0% Si, 4.0% to 8.0% Zn, 1.0% to 4.0% Mg, 0.2% to 1.0% Fe, 0.1% to 0.6% Mn, 0.1% to 2.0% Cu, 0.15% to 0.3% Sr and 0% to 0.01% Re, with the remainder being Al; Re comprises Sm and Pr, and the mass ratio of Sm to Pr is 0.2 to 5:1.

[0021] The addition of Sm and Pr can optimize the microstructure. The combined effect of the two changes the interface conditions and solute distribution during the solidification process of the alloy. This makes the iron-containing phase, which is originally easy to form harmful forms such as needles and flakes, transform into a relatively small, dispersed, blocky form with a more uniform distribution.

[0022] The addition of Sm and Pr can also improve the mechanical properties. High iron content usually reduces the grain boundary strength, while Al3Pr makes up for this defect, making it more difficult for the grain boundary to crack and expand when subjected to stress. Sm refines the grains and increases the grain boundary area, allowing more Al3Pr to be distributed at the grain boundary, further enhancing the contribution of the grain boundary to the mechanical properties and weakening the grain boundary weakening problem caused by the iron-containing phase. In addition, Sm and Pr significantly improve the strength of the alloy through fine grain strengthening and dispersion strengthening. Fine grain strengthening increases the obstruction of dislocation movement by grain boundaries, and dispersion strengthening causes dislocations to be obstructed by second phase particles such as Al3Pr. After the overall strength of the alloy is improved, it can better resist the embrittlement caused by the brittle phase formed by the high iron content, and it is more difficult to crack and break due to the stress concentration of the iron-containing phase when subjected to stress.

[0023] At the same time, the addition of Mn not only reduces the tendency of castings to stick to the mold and improves production efficiency, but also Mn can transform the needle-shaped iron-containing phase into a Chinese character-shaped or fine spherical α-Fe phase, greatly improving the adverse effects of Fe and improving the toughness and corrosion resistance of the alloy.

[0024] Without heat treatment, the tensile strength of high yield die-cast aluminum alloy material is greater than 380MPa, the yield strength is greater than 280MPa, the elongation is greater than 3%, and the thermal conductivity is greater than 150W / (m·K). It has good thermal conductivity and maintains high strength performance, which is very suitable for the production of complex thin-walled, high-yield, low-cost mobile phone mid-plate structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope analysis diagram of the high yield die-cast aluminum alloy material of Example 1. DETAILED DESCRIPTION

[0026] According to the first aspect of the present invention, a high yield die-cast aluminum alloy material is provided, and the components of the high yield die-cast aluminum alloy material are, by weight percentage, 6.0% to 10.0% Si, 4.0% to 8.0% Zn, 1.0% to 4.0% Mg, 0.2% to 1.0% Fe, 0.1% to 0.6% Mn, 0.1% to 2.0% Cu, 0.15% to 0.3% Sr and 0% to 0.01% Re, with the remainder being Al; Re includes Sm and Pr, and the mass ratio of Sm to Pr is 0.2 to 5:1.

[0027] In the present invention, the addition of Sm and Pr can optimize the organizational morphology. Sm forms a large number of fine grains in the Al-Si alloy by promoting grain nucleation and increasing the nucleation rate. Although Pr does not directly promote nucleation like Sm, it provides better conditions for grain refinement by reducing lattice distortion and stabilizing grain boundaries. The combined effect of Sm and Pr makes the grain size in the alloy finer than when Sm or Pr is added alone. The refined grains can inhibit the generation and aggregation of coarse iron-containing phases at positions such as grain boundaries, because the grain boundaries increase and are more uniform after grain refinement, which limits the growth space of the iron-containing phase and makes it difficult to form a continuous, coarse phase, thereby avoiding the deterioration of alloy properties caused by coarse iron-containing phases.

[0028] After Sm and Pr are added together, Sm changes the nucleation and growth process of the alloy during solidification, and Pr is enriched at the grain boundary to form Al3Pr compounds. The two work together to change the interface conditions and solute distribution during the alloy solidification process. This makes the iron-containing phase, which is easy to form in harmful forms such as needles and flakes, transform into a relatively small, dispersed, blocky form with a more uniform distribution.

[0029] The addition of Sm and Pr can improve the mechanical properties. First, the Al3Pr compound formed by Pr is enriched at the grain boundary, which can enhance the bonding force and stability of the grain boundary. High iron content usually reduces the grain boundary strength, and the presence of Al3Pr can make up for this defect, making it more difficult for the grain boundary to crack and expand when subjected to stress. Sm refines the grains and increases the grain boundary area, so that more Al3Pr is distributed at the grain boundary, further enhancing the contribution of the grain boundary to the mechanical properties and weakening the grain boundary weakening problem caused by the iron-containing phase. In addition, Sm and Pr significantly improve the strength of the alloy through fine grain strengthening and dispersion strengthening. Fine grain strengthening increases the obstruction of dislocation movement by grain boundaries, and dispersion strengthening causes dislocations to be obstructed by second phase particles such as Al3Pr. After the overall strength of the alloy is improved, it can better resist the embrittlement caused by the brittle phase formed by the high iron content. When subjected to stress, it is more difficult to crack and break due to stress concentration around the iron-containing phase, thereby improving the elongation of the material.

[0030] Within the range of the mass ratio of Sm to Pr being 0.2 - 5:1, it can not only generate an appropriate amount of strengthening phases to effectively improve the strength, but also synergistically refine the grains to make the alloy structure more uniform. Moreover, it can achieve a good balance in terms of corrosion resistance, heat resistance, processing performance, etc. If the mass ratio is lower than 0.2:1, the content of Sm is insufficient, and the effects of strengthening and grain refinement are poor, and the improvement of corrosion resistance is also limited. When it is higher than 5:1, excessive Sm will increase the brittleness of the alloy, coarsen the structure, and also lead to an increase in cost.

[0031] Meanwhile, the addition of Mn not only reduces the tendency of the casting to stick to the mold and improves production efficiency, but also Mn can transform the acicular iron-containing phase into a Chinese character-shaped or fine spherical α-Fe phase, greatly improving the adverse effects of Fe, and enhancing the toughness and corrosion resistance of the alloy. At the same time, Zn forms strengthening phases such as MgZn2 with other elements and precipitates during aging, further enhancing the alloy strength; Si forms a eutectic structure with Al, improving the casting performance and hardness, and to a certain extent increasing the alloy strength and wear resistance; an appropriate amount of Cu forms a strengthening phase Al2Cu, which greatly improves the alloy strength through age hardening and can also improve the thermal conductivity.

[0032] As a modifier, Sr can transform the eutectic silicon in the Al-Si alloy from thick needles into fine fibrous or granular shapes, improving the mechanical properties and processing performance of the alloy. The refined eutectic silicon improves the fluidity of the alloy, is conducive to filling the mold cavity during die casting, reduces the problem of poor filling caused by high Fe content, and improves production efficiency and product quality. Moreover, with the reasonable combination of various elements, while ensuring high strength, complex phases that affect heat conduction are not introduced too much, and the good thermal conductivity characteristics of the aluminum alloy are retained. The optimized structure reduces the hindrance of grain boundaries to heat conduction, achieving high thermal conductivity performance.

[0033] Si, Zn, Mg, Fe, Mn, Cu, etc. in the components and the weight percentages of each component are all common and low-cost aluminum alloy additive elements. On the basis of ensuring performance, by precisely controlling the content ranges of each element and not overusing expensive special elements, it has successfully achieved the preparation of a new type of die-casting aluminum alloy at low cost.

[0034] In a preferred embodiment of the present invention, the components of the high-yield die-casting aluminum alloy material are by weight percentage: 7.0 - 9.0% Si, 4.0 - 6.0% Zn, 2.0 - 4.0% Mg, 0.4% - 0.6% Fe, 0.3 - 0.5% Mn, 0.5 - 1.0% Cu, 0.15 - 0.3% Sr, and 0 - 0.01% Re, with the balance being Al; Re includes Sm and Pr, and the mass ratio of Sm to Pr is 0.2 - 5:1.

[0035] In a preferred embodiment of the present invention, the mass ratio of Sm to Pr is 2:3.

[0036] In the present invention, when Sm and Pr are compounded and added in a mass ratio of 2:3, the nucleation and growth during the solidification of the alloy can reach the best balance, the grains can be refined to the greatest extent, which helps the more reasonable distribution of Sm and Pr in the alloy, improves the phase structure in the alloy better, makes the iron-containing phase, silicon phase, etc. become finer, more dispersed and more uniform, effectively avoids the formation of coarse phases, and reduces the damage to the continuity of the alloy matrix. The mass ratio of 2:3 can make the effects of fine grain strengthening and dispersion strengthening reach the best combination, making the comprehensive mechanical properties such as the tensile strength, yield strength, elongation rate, etc. of the alloy reach the optimal state, and enhancing the ability of the alloy to resist deformation and fracture more than other ratios. At this ratio, Sm and Pr may have more favorable interactions with other elements (such as Mg, Zn, etc.) in the alloy, further improving the corrosion resistance and stability of the alloy in different environments, and enabling a denser and more uniform oxide film to form on the alloy surface to prevent the intrusion of external corrosive media.

[0037] According to the second aspect of the present invention, a preparation method of a high-yield die-casting aluminum alloy material is provided. The preparation method includes:

[0038] First, melt the raw materials according to the components of the high-yield die-casting aluminum alloy material and the weight percentages of each component to obtain a melt, and after refining the melt, perform die-casting treatment to obtain the high-yield die-casting aluminum alloy material.

[0039] In the present invention, for the preparation method of the high-yield die-casting aluminum alloy material, without performing heat treatment, an aluminum alloy material with complex thin walls, high yield, high thermal conductivity and low cost can be obtained.

[0040] In a preferred embodiment of the present invention, the raw materials include industrial waste aluminum, pure aluminum ingots, industrial crystalline silicon, aluminum-zinc alloy, pure magnesium ingots, aluminum-manganese alloy, aluminum-copper alloy, aluminum-strontium alloy, Al-Sm master alloy and Al-Pr master alloy.

[0041] In the present invention, as one of the raw materials of the high-yield die-casting aluminum alloy material, industrial waste aluminum not only realizes the secondary utilization of aluminum resources, but also effectively utilizes elements such as Zn, Cu, Mg, etc. in industrial waste aluminum to form strengthening phases such as MgZn2, Al2Cu and Al2CuMg, thereby enhancing the alloy properties.

[0042] In a preferred embodiment of the present invention, the melting includes:

[0043] Melt the pure aluminum ingots and then add industrial waste aluminum and crystalline silicon. After all are melted, stir well and remove the surface scum. Set the temperature of the aluminum liquid at 750 - 760 °C, add the aluminum-zinc alloy, aluminum-manganese alloy and aluminum-copper alloy in batches, and keep for 25 minutes, with continuous stirring during this period; adjust the temperature of the aluminum liquid to 720 - 730 °C, and add the pure magnesium ingots, Al-Sm master alloy and Al-Pr master alloy in batches until all are melted.

[0044] In a preferred embodiment of the present invention, the refining includes first adding K2ZrF6 refining agent to aluminum liquid at a temperature of 700-720°C, refining for 10 minutes to obtain a first refined aluminum liquid, and then adding aluminum strontium alloy to the first refined aluminum liquid at a temperature of 700-710°C, refining for 5 minutes to obtain a second refined aluminum liquid.

[0045] In the present invention, K2ZrF6 refining agent and aluminum strontium alloy are used for double refining, which can not only quickly and efficiently remove gas and oxide slag in aluminum melt and improve the quality of aluminum melt, but also prevent the growth of α-Al phase, increase the number of dendrites and make them round, improve the morphology of eutectic silicon and the interface between eutectic silicon and α-Al, make them distributed in fine flakes, fibers and granules, and increase the number of α-Al, which greatly reduces the hindering effect on electrons, thereby enhancing the mechanical properties and thermal conductivity of the alloy.

[0046] The strontium element in the aluminum-strontium alloy can further remove some impurities that may remain in the aluminum liquid, such as alkali metals. These impurities will have an adverse effect on the performance of the aluminum alloy. Through the action of strontium, they can be removed or their content can be reduced, thereby improving the purity of the aluminum liquid. Strontium is an effective modifier that can significantly change the morphology and distribution of the silicon phase in the aluminum alloy. For aluminum alloys containing silicon, after adding aluminum-strontium alloy, strontium can transform the silicon phase from coarse flakes or needles to fine, uniform fibers or particles, thereby improving the mechanical properties of the aluminum alloy, especially toughness and ductility. At the same time, strontium can also improve the fluidity of the aluminum alloy, which is beneficial to the subsequent die-casting process, so that the quality and dimensional accuracy of the castings can be better controlled.

[0047] In a preferred embodiment of the present invention, the amount of K2ZrF6 refining agent added is 0.10% of the total weight of the aluminum liquid, and the amount of aluminum strontium alloy added is 0.05% of the total weight of the first refined aluminum liquid.

[0048] In a preferred embodiment of the present invention, the refining is performed in a high-purity argon environment.

[0049] In the present invention, aluminum and its alloy elements have active chemical properties and are easy to react with oxygen in the air at high temperatures, while high-purity argon can isolate the air, prevent the aluminum liquid and alloy elements from being oxidized, and reduce oxide inclusions and burning of alloy elements; at the same time, when the bubbles formed by argon rise in the aluminum liquid, they can not only adsorb impurities to make them float, but also stir the aluminum liquid to make the composition and temperature more uniform, thereby playing a role in assisting refining; in addition, the high-purity argon environment can reduce interference with the refining agent, allowing the refining agent to fully react with impurities in the aluminum liquid, thereby improving the refining efficiency, stabilizing the reaction process, and facilitating precise control of the refining effect.

[0050] In a preferred embodiment of the present invention, the preparation method of the high yield die-casting aluminum alloy material specifically includes:

[0051] (1) Alloy batching: According to the components of the high yield die-casting aluminum alloy material and the weight percentages of each component, a certain amount of recycled industrial waste aluminum that has been pretreated and electromagnetically sorted, as well as the required pure aluminum ingots, industrial crystalline silicon, aluminum-zinc alloy, pure magnesium ingot, aluminum-manganese alloy, aluminum-copper alloy, aluminum-strontium alloy, Al-Sm master alloy, and Al-Pr master alloy are weighed for aluminum alloy batching.

[0052] (2) Alloy melting:

[0053] ① Put the pure aluminum ingots into the crucible and heat them by electricity, set the temperature to 780 °C, and check the materials and tools to ensure they are clean and dry.

[0054] ② After all the pure aluminum ingots are melted, add the industrial waste aluminum and crystalline silicon, and keep warm for 30 minutes.

[0055] ③ After all the industrial waste aluminum and crystalline silicon are melted, stir well for 2 minutes and remove the surface dross, set the aluminum liquid temperature to 750 - 760 °C, add alloys such as aluminum-zinc, aluminum-manganese, and aluminum-copper in batches, and keep for 25 minutes, continuously stir during this period to accelerate the melting and diffusion of alloy elements.

[0056] ④ Adjust the aluminum liquid temperature to 720 - 730 °C, add pure magnesium ingots, Al-Sm, and Al-Pr master alloys in batches. When adding the magnesium ingots, press the pure magnesium ingots into the aluminum liquid to melt, reduce burning loss, continuously stir during this period to accelerate the melting and diffusion of alloy elements.

[0057] ⑤ After all the above batching is melted, the aluminum liquid temperature is 720 °C, stir and skim the dross, detect the aluminum liquid composition and adjust it.

[0058] (3) Melt treatment:

[0059] ① First refining: The aluminum liquid temperature is 700 - 720 °C, add the K2ZrF6 refining agent, use a titanium tube to add powder and blow air to purify the aluminum liquid, the refining gas is high-purity argon, the dosage of the refining agent is 0.10% of the total weight of the aluminum liquid, the refining time is 10 minutes. After the refining is completed, let it stand for 2 - 3 minutes and thoroughly skim the dross.

[0060] ② Second refining: The aluminum liquid temperature is 700 - 710 °C, add the aluminum-strontium alloy, and use a titanium tube to add powder and blow air to purify the aluminum liquid, the refining gas is high-purity argon, the dosage of the refining agent is 0.05% of the total weight of the aluminum liquid, the refining time is 5 minutes. After the refining is completed, let it stand for 2 - 3 minutes and thoroughly skim the dross.

[0061] (4) Die-casting production:

[0062] ① Mold treatment: The surface of the mold cavity needs to be cleaned thoroughly. Release agent is sprayed inside the cavity, and lubricant is sprayed on the injection punch. The mold is preheated to 250 - 300 °C.

[0063] ② Die casting production: Ensure that the temperature of the die-cast aluminum liquid is 680 ± 10 °C, and the test bar mold temperature is 250 - 300 °C for die casting production.

[0064] ③ Cooling: Immediately after die casting production, the sample is directly placed in cooling water at 25 ± 5 °C and cooled to room temperature.

[0065] According to the third aspect of the present invention, there is provided an application of a high yield die-cast aluminum alloy material in a mobile phone middle plate.

[0066] Example 1

[0067] A high yield die-cast aluminum alloy material, comprising the following components by weight percentage: 8.50% Si, 6% Zn, 3.0% Mg, 0.5% Fe, 0.3% Mn, 0.8% Cu, 0.15% Sr, 0.002% Sm, and 0.003% Pr, with the balance being Al and unavoidable impurities.

[0068] The high yield die-cast aluminum alloy material is prepared by the following preparation method:

[0069] (1) Alloy batching: According to the components and weight percentages of the high yield die-cast aluminum alloy material, a certain amount of recycled industrial waste aluminum that has been pretreated and electromagnetically sorted, as well as the required pure aluminum ingots, industrial crystalline silicon, aluminum-zinc alloy, pure magnesium ingot, aluminum-manganese alloy, aluminum-copper alloy, aluminum-strontium alloy, Al-Sm master alloy, and Al-Pr master alloy are weighed for aluminum alloy batching.

[0070] (2) Alloy melting:

[0071] ① The pure aluminum ingot is put into the crucible and heated by electricity, with the temperature set at 780 °C, and the materials and tools are inspected to ensure they are clean and dry.

[0072] ② After all the pure aluminum ingots are melted, industrial waste aluminum and crystalline silicon are added, and kept warm for 30 min.

[0073] ③ After all the industrial waste aluminum and crystalline silicon are melted, stir thoroughly for 2 min and remove the surface scum. Set the aluminum liquid temperature at 750 - 760 °C, and add aluminum-zinc, aluminum-manganese, aluminum-copper and other alloys in batches, and keep for 25 min, with continuous stirring during this period to accelerate the melting and diffusion of alloy elements.

[0074] ④ Adjust the aluminum liquid temperature to 720 - 730 °C, and add pure magnesium ingots, Al-Sm, and Al-Pr master alloys in batches. When adding the magnesium ingot, press the pure magnesium ingot under the aluminum liquid to melt it to reduce burning loss, with continuous stirring during this period to accelerate the melting and diffusion of alloy elements.

[0075] ⑤After melting all the above ingredients, the temperature of the molten aluminum is 720 °C. Stir and skim the slag, then detect and adjust the composition of the molten aluminum.

[0076] (3)Melt treatment:

[0077] ①First refining: The temperature of the molten aluminum is 700 - 720 °C. Add K2ZrF6 refining agent, and use a titanium tube to add powder and blow gas to purify the molten aluminum. The refining gas is high-purity argon. The dosage of the refining agent is 0.10% of the total weight of the molten aluminum, and the refining time is 10 minutes. After the refining is completed, let it stand for 2 - 3 minutes and thoroughly skim the slag.

[0078] ②Second refining: The temperature of the molten aluminum is 700 - 710 °C. Add aluminum strontium alloy, and use a titanium tube to add powder and blow gas to purify the molten aluminum. The refining gas is high-purity argon. The dosage of the refining agent is 0.05% of the total weight of the molten aluminum, and the refining time is 5 minutes. After the refining is completed, let it stand for 2 - 3 minutes and thoroughly skim the slag.

[0079] (4)Die casting production:

[0080] ①Mold treatment: The surface of the mold cavity needs to be cleaned thoroughly. Spray release coating inside the cavity and lubricating coating on the injection punch. Preheat the mold to 250 - 300 °C.

[0081] ②Die casting production: Ensure that the temperature of the die-casting molten aluminum is 680 ± 10 °C, and carry out die-casting production with the temperature of the test bar mold at 250 - 300 °C.

[0082] ③Cooling: Immediately put the sample completed by die-casting production into cooling water at 25 ± 5 °C and cool it to room temperature.

[0083] (5)Performance testing: After standing the die-cast test bar for 24 h, conduct a tensile test.

[0084] The high-yield die-casting aluminum alloy material prepared in this example is analyzed by a scanning electron microscope (Scanning Electron Microscope, SEM), and the results are as Figure 1 shown.

[0085] Example 2

[0086] A high-yield die-casting aluminum alloy material, including the following components by weight percentage: 10.0% Si, 8.0% Zn, 4.0% Mg, 0.5% Fe, 0.6% Mn, 2.0% Cu, 0.15% Sr, 0.002% Sm, and 0.003% Pr, with the balance being Al and unavoidable impurities.

[0087] The remaining preparation method is the same as that of Example 1.

[0088] Example 3

[0089] A high-yield die-casting aluminum alloy material comprises the following components by weight percentage: 6.0% Si, 4.0% Zn, 1.0% Mg, 0.5% Fe, 0.1% Mn, 0.1% Cu, 0.15% Sr, 0.002% Sm, and 0.003% Pr, with the balance being Al and inevitable impurities.

[0090] The remaining preparation method is the same as that of Example 1.

[0091] Example 4

[0092] A high-yield die-casting aluminum alloy material comprises the following components by weight percentage: 7.0% Si, 4.0% Zn, 1.0% Mg, 0.4% Fe, 0.3% Mn, 0.5% Cu, 0.15% Sr, 0.004% Sm, and 0.006% Pr, with the balance being Al and inevitable impurities.

[0093] The remaining preparation method is the same as that of Example 1.

[0094] Example 5

[0095] A high-yield die-casting aluminum alloy material comprises the following components by weight percentage: 9.0% Si, 6.0% Zn, 2.0% Mg, 0.6% Fe, 0.5% Mn, 1.0% Cu, 0.15% Sr, 0.004% Sm, and 0.006% Pr, with the balance being Al and inevitable impurities.

[0096] The remaining preparation method is the same as that of Example 1.

[0097] Example 6

[0098] A high-yield die-casting aluminum alloy material comprises the following components by weight percentage: 8.50% Si, 6% Zn, 3.0% Mg, 0.5% Fe, 0.3% Mn, 0.8% Cu, 0.15% Sr, 0.005% Sm, and 0.001% Pr, with the balance being Al and inevitable impurities.

[0099] The remaining preparation method is the same as that of Example 1.

[0100] Example 7

[0101] A high-yield die-casting aluminum alloy material comprises the following components by weight percentage: 8.50% Si, 6% Zn, 3.0% Mg, 0.5% Fe, 0.3% Mn, 0.8% Cu, 0.15% Sr, 0.001% Sm, and 0.005% Pr, with the balance being Al and inevitable impurities.

[0102] The remaining preparation method is the same as that of Example 1.

[0103] Example 8

[0104] A high-yield die-casting aluminum alloy material, comprising the following components by weight percentage: 8.50% Si, 6% Zn, 3.0% Mg, 0.5% Fe, 0.3% Mn, 0.8% Cu, 0.15% Sr, 0.003% Sm, and 0.0045% Pr, with the balance being Al and unavoidable impurities.

[0105] The remaining preparation method is the same as that of Example 1.

[0106] Comparative Example 1

[0107] A high-yield die-casting aluminum alloy material, comprising the following components by weight percentage: 8.50% Si, 6% Zn, 3.0% Mg, 0.5% Fe, 0.3% Mn, 0.8% Cu, 0.15% Sr, and 0.003% Pr, with the balance being Al and unavoidable impurities.

[0108] The remaining preparation method is the same as that of Example 1.

[0109] Comparative Example 2

[0110] A high-yield die-casting aluminum alloy material, comprising the following components by weight percentage: 8.50% Si, 6% Zn, 3.0% Mg, 0.5% Fe, 0.3% Mn, 0.8% Cu, 0.15% Sr, and 0.002% Sm, with the balance being Al and unavoidable impurities.

[0111] The remaining preparation method is the same as that of Example 1.

[0112] Comparative Example 3

[0113] A high-yield die-casting aluminum alloy material, comprising the following components by weight percentage: 8.50% Si, 6% Zn, 3.0% Mg, 0.5% Fe, 0.3% Mn, 0.8% Cu, and 0.15% Sr, with the balance being Al and unavoidable impurities.

[0114] The remaining preparation method is the same as that of Example 1.

[0115] Performance Test

[0116] Performance tests were carried out in accordance with GB / T 228.1 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature for metallic materials".

[0117] Table 1 Performance test results of Examples 1-8 and Comparative Examples 1-3

[0118]

[0119] As can be seen from Table 1, the use of Sm-Pr composite modification can significantly improve the mechanical properties of the alloy. Compared with the individual addition of Sm and Pr, the combined addition of Sm and Pr has a more excellent effect and more significantly improves the properties.

[0120] As Figure 1 can be seen, after two-stage refining with a K2ZrF6 refining agent and high-purity argon, the α-Al phase in the aluminum matrix is approximately equiaxed, and most of the eutectic silicon phases are fibrous or short rod-shaped. The interface between α-Al and eutectic silicon is rounded, and the quantity of α-Al increases, greatly reducing the hindrance to electrons, thereby enhancing the mechanical properties and thermal conductivity of the alloy. Sm has an extremely low solubility in Al, high chemical activity, and surface adsorption. Therefore, when Sm is added to the melt, due to its low solubility in Al, there is a significant enrichment of Sm at the solid-liquid interface front, causing solute redistribution and resulting in constitutional supercooling, promoting grain nucleation and growth, and the nucleation rate is higher than the grain growth rate, so the grains are refined. In addition, Sm can reduce the interfacial tension of the melt, thereby reducing the nucleation work of grains, increasing the nucleation rate, and refining the grains. In addition, the partially precipitated AlCu7Sm2 phase is distributed at the grain boundaries, playing a role in hindering the growth of α-Al and refining the grain size. The atomic radius of Pr is larger than that of Al. To maintain the lowest free energy and reduce the occurrence of lattice distortion, only a small amount of Pr dissolves into α-Al, and most of the rest accumulates at the grain boundaries and forms the rare-earth compound Al3Pr. Therefore, the addition of Pr can play a role in refining grains and increasing the dispersion of the second phase. Therefore, the use of Sm-Pr composite modification can significantly improve the strength of the Al-Si alloy through grain refinement strengthening and dispersion strengthening.

Claims

1. A high yield die-cast aluminum alloy material, characterized in that: The high yield die-cast aluminum alloy material comprises, by weight percentage, 6.0% to 10.0% Si, 4.0% to 8.0% Zn, 1.0% to 4.0% Mg, 0.2% to 1.0% Fe, 0.1% to 0.6% Mn, 0.1% to 2.0% Cu, 0.15% to 0.3% Sr and 0.005% to 0.01% Re, with the remainder being Al; the Re comprises Sm and Pr, and the mass ratio of Sm to Pr is 0.2 to 5:1; the addition of Sm and Pr transforms the iron-containing phase in the alloy from a needle-like or lamellar shape into a fine and dispersed block shape, and the grains are refined.

2. The high yield die-cast aluminum alloy material according to claim 1, characterized in that: The high yield die-casting aluminum alloy material comprises, by weight percentage, 7.0% to 9.0% Si, 4.0% to 6.0% Zn, 2.0% to 4.0% Mg, 0.4% to 0.6% Fe, 0.3% to 0.5% Mn, 0.5% to 1.0% Cu, 0.15% to 0.3% Sr and 0.005% to 0.01% Re, with the remainder being Al; the Re comprises Sm and Pr, and the mass ratio of Sm to Pr is 0.2 to 5:

1.

3. The high yield die-cast aluminum alloy material according to claim 1, characterized in that: The mass ratio of the Sm to the Pr is 2:

3.

4. A method for preparing a high yield die-cast aluminum alloy material according to any one of claims 1 to 3, characterized in that: The preparation method comprises: According to the components of the high yield die-casting aluminum alloy material and the weight percentage of each component, the raw material is firstly melted to obtain a melt, and the melt is subjected to die-casting treatment after refining to obtain the high yield die-casting aluminum alloy material.

5. The method for preparing a high yield die-cast aluminum alloy material according to claim 4, characterized in that: The raw materials include: Industrial scrap aluminum, pure aluminum ingots, industrial crystalline silicon, aluminum-zinc alloy, pure magnesium ingots, aluminum-manganese alloy, aluminum-copper alloy, aluminum-strontium alloy, Al-Sm master alloy and Al-Pr master alloy.

6. The method for preparing a high yield die-cast aluminum alloy material according to claim 4, characterized in that: The smelting comprises: After melting the pure aluminum ingot, add industrial waste aluminum and crystalline silicon. After all are melted, stir thoroughly and remove the surface scum. Set the aluminum liquid temperature to 750~760℃, add aluminum-zinc alloy, aluminum-manganese alloy and aluminum-copper alloy in batches, and keep it for 25 minutes while stirring continuously; adjust the aluminum liquid temperature to 720~730℃, add pure magnesium ingot, Al-Sm master alloy and Al-Pr master alloy in batches until all are melted.

7. The method for preparing a high yield die-cast aluminum alloy material according to claim 4, characterized in that: The refining includes firstly adding K2ZrF6 refining agent into aluminum liquid at a temperature of 700-720°C, refining for 10 minutes to obtain the first refined aluminum liquid, and then adding aluminum strontium alloy into the first refined aluminum liquid at a temperature of 700-710°C, refining for 5 minutes to obtain the second refined aluminum liquid.

8. The method for preparing a high yield die-cast aluminum alloy material according to claim 7, characterized in that: The amount of the K2ZrF6 refining agent added is 0.10% of the total weight of the aluminum liquid, and the amount of the aluminum strontium alloy added is 0.05% of the total weight of the first refined aluminum liquid.

9. The method for preparing a high yield die-cast aluminum alloy material according to claim 7, characterized in that: The refining is carried out in a high-purity argon environment.

10. Application of a high yield die-cast aluminum alloy material in mobile phone mid-plate.

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