Die-casting aluminum alloy capable of being strengthened through T6 heat treatment and production method and application thereof

Abstract

The invention provides a die-casting aluminum alloy capable of being strengthened through T6 heat treatment and a production method and application of the die-casting aluminum alloy. An aluminum alloy capable of being subjected to T6 heat treatment strengthening and used for die casting is prepared from, by weight, 7.5%-8% of silicon, 0.3%-0.35% of magnesium, 0.1%-0.3% of iron, 0.05% of vanadium, 0.05% of zirconium, 0.1%-0.3% of rare earth elements, 0.001%-0.005% of beryllium and the balance aluminum and inevitable impurities. According to the production method, the tensile strength of the aluminum alloy product obtained after T6 heat treatment can reach 270-285MPa, and the ductility is improved to 8%-10%.

Description

Technical Field

[0001] This disclosure relates to the field of aluminum alloy materials technology, and in particular to a die-casting aluminum alloy that can be strengthened by T6 heat treatment, its production method and application. Background Technology

[0002] In automotive manufacturing, aluminum alloys are often used for integrated die casting of the car body and its components to achieve weight reduction and increased strength. However, most conventional aluminum alloys currently available have the following problems when used for integrated die casting: First, existing aluminum alloys have poor feeding properties, making the cast parts prone to shrinkage cavities and surface cracks, which seriously affect the quality of the castings; second, they have poor fluidity, failing to flow smoothly through the mold cavity when forming castings with small cavities; third, the integrated die casting process makes the molten aluminum alloy prone to absorbing air, resulting in surface pinhole defects and subcutaneous porosity defects inside the casting, making T6 heat treatment impossible.

[0003] T6 heat treatment (solution treatment + artificial aging) is an important process for improving material strength. However, in existing technologies, there are significant defects in the matching between aluminum alloy composition design and T6 strengthening process, making it difficult for aluminum alloys to simultaneously meet the performance requirements of no shrinkage cracks and small deformation after T6 heat treatment. The reasons are as follows: 1. Although traditional high-silicon aluminum alloys (Si content 11%~12%) can be adapted to T6 heat treatment by adding Mg to form a Mg2Si strengthening phase, the Mg2Si phase is prone to coarsening and segregation at grain boundaries in a high-silicon environment, forming stress concentration areas. During the T6 heat treatment process, the high temperature in the solution stage will aggravate the precipitation of coarse and brittle phases, and the structural stress in the aging stage will further induce hot cracking or cold cracking, especially in thin-walled areas of complex casting structures, where the tendency to crack increases significantly. 2. Low-silicon aluminum alloys (Si content 6.5%~7%) have a high coefficient of thermal expansion due to insufficient eutectic structure. During the solution cooling and aging process of T6 heat treatment, the large thermal shrinkage rate leads to internal thermal stress concentration, which can easily cause overall deformation or local shrinkage cracks in the casting, making it difficult to meet the stringent requirements for dimensional accuracy. In summary, existing conventional grade aluminum alloys are prone to shrinkage cracks or significant deformation after T6 strengthening, failing to meet the requirements for high strength and high dimensional stability in castings. Summary of the Invention

[0004] This disclosure provides a die-casting aluminum alloy that can be strengthened by T6 heat treatment, its production method, and its application, in order to at least solve one of the technical problems existing in the prior art.

[0005] In one aspect, this application provides a die-casting aluminum alloy that can be strengthened by T6 heat treatment, comprising, by weight percentage: 7.5%–8% silicon, 0.3%–0.35% magnesium, 0.1%–0.3% iron, 0.05% vanadium, 0.05% zirconium, 0.1%–0.3% rare earth elements, 0.001%–0.005% beryllium, with the balance being aluminum and unavoidable impurities.

[0006] In one embodiment, the rare earth element is yttrium or lanthanum.

[0007] In one embodiment, the silicon comprises 7.6% to 7.9% by weight.

[0008] In one embodiment, the magnesium content is 0.31% to 0.34% by weight.

[0009] In one embodiment, the iron has a weight percentage of 0.15% to 0.25%.

[0010] In one embodiment, the alloy further includes a modifier comprising phosphorus, calcium, and sodium, wherein the weight percentage of each of the phosphorus, calcium, and sodium in the die-casting aluminum alloy is less than or equal to 10 ppm.

[0011] In one embodiment, the phosphorus in the die-casting aluminum alloy is 6-10 ppm by weight, the calcium in the die-casting aluminum alloy is 7-10 ppm by weight, and the sodium in the die-casting aluminum alloy is 7-10 ppm by weight.

[0012] Secondly, a method for producing a die-casting aluminum alloy that can be strengthened by T6 heat treatment is also provided, comprising the following steps: Raw material preparation: Prepare each raw material according to the percentage of each element in the die-casting aluminum alloy; Crucible pretreatment: Clean the crucible and preheat it to 150-200℃; Alloy smelting: First, add aluminum raw material to a crucible and heat to 720-750℃ to completely melt the aluminum; add the corresponding raw materials in the order of silicon, iron, magnesium, vanadium, zirconium, rare earth elements, and beryllium, controlling the stirring speed at 150-200 r / min during the addition process; after all raw materials have completely melted, raise the temperature to 760-780℃ and hold for 15-20 min to obtain aluminum alloy melt; Melt treatment: The aluminum alloy melt is degassed and refined; Modification treatment: When the temperature of the aluminum alloy melt after melt treatment drops to 720-740℃, add phosphorus, calcium and sodium modifiers evenly and dispersedly; after the addition is completed, stir for 3-5 minutes; Forming: The modified aluminum alloy melt is poured into a mold preheated to 200-250℃, and the casting temperature is controlled at 700-720℃; after casting, it is naturally cooled to room temperature to obtain aluminum alloy castings. T6 heat treatment: The aluminum alloy casting is subjected to T6 heat treatment.

[0013] In one embodiment, during the T6 heat treatment process, the solution treatment temperature is 535°C and the solution treatment time is 9 hours, while the artificial aging treatment requires an aging temperature of 175°C and an aging time of 11 hours. The degassing and refining of the aluminum alloy melt includes degassing the aluminum alloy melt by rotary jetting argon gas, with the argon gas flow rate controlled at 8-10 L / min and the jetting time at 10-20 min; simultaneously, a refining agent is added, with the amount of refining agent added being 0.5%-0.8% of the mass of the aluminum alloy melt, and the refining time being 15-20 min.

[0014] Thirdly, the application of die-casting aluminum alloys obtained by the above-mentioned generation method or one of the above-mentioned die-casting aluminum alloys that can be strengthened by T6 heat treatment in automotive structural parts.

[0015] Compared with existing technologies, the advantages of this application are as follows: 1) In the aluminum alloy of this application, the silicon content is controlled at 7.5% to 8%. This proportion of silicon allows the alloy to absorb some shrinkage stress through eutectic reaction during solidification, resulting in a fine microstructure, reduced overall thermal stress, and fewer cracks. The magnesium content is controlled at 0.3% to 0.35%. This proportion of magnesium can synergistically work with silicon to promote the formation of fine and uniform Mg2Si strengthening phases, further improving the alloy's strength and elongation. The addition of iron, vanadium, and zirconium can refine the microstructure and improve the overall performance of the alloy. The addition of rare earth elements can refine the grains, improve the alloy's microstructure, reduce the negative impact of impurity elements, enhance thermal stability, and further improve the alloy's elongation. The addition of beryllium can reduce the surface tension of the aluminum alloy, improve melt fluidity, make the solidification microstructure more uniform, reduce internal defects, and improve elongation.

[0016] 2) Aluminum alloys with the above-mentioned composition ratio exhibit a hypereutectic phase, refined primary silicon, resulting in a more uniform grain structure, high density, and low apparent porosity. When applied to piston casting, they significantly improve the piston's high-temperature performance, wear resistance, and dimensional stability. Cast structural components exhibit high strength, high weldability and corrosion resistance, good casting mechanical properties, good heat resistance, and good flow properties of molten aluminum. They can be heat-treated for strengthening, resulting in high mechanical properties at both high and room temperature.

[0017] 3) Aluminum alloys with the above-mentioned component ratios have a low coefficient of thermal expansion. After solidification, the castings exhibit dimensional stability, good casting performance, no tendency to hot cracking, high airtightness, and low linear shrinkage. This meets the material performance requirements of castings.

[0018] 4) This application effectively reduces shrinkage cracks and deformation of castings during T6 heat treatment by optimizing the aluminum alloy composition and production process. For small, relatively simple integrated aluminum alloy castings, the linear deformation after T6 heat treatment is controlled within ±0.1% to ±0.3%; for large, complex integrated aluminum alloy castings, the linear deformation is controlled within ±0.3% to ±0.8%, with good dimensional stability, meeting the stringent requirements for forming accuracy.

[0019] 5) This application effectively solves the problem of large performance differences in different positions of the casting during the die casting process by optimizing the alloy composition and improving the production process, ensuring consistent performance in each position of the casting and improving the reliability and stability of product quality. 6) The aluminum alloy provided in this application overcomes the defects of existing aluminum alloys that are prone to shrinkage cracking, large deformation and low elongation after T6 heat treatment. After T6 heat treatment, the aluminum alloy of this application can not only achieve excellent performance of no shrinkage cracking and small deformation, meeting the stringent requirements for forming accuracy, but also increase the elongation to 8% to 10%, while ensuring that the performance of each position of the casting is consistent, effectively solving the problem of large performance differences at different positions during the die casting process.

[0020] 7) In the production method of this application, the aluminum alloy melt does not absorb air for a long time, has good fluidity, slow self-solidification time, and can flow smoothly through the casting cavity such as the gap of the spiral tube, and can form castings with small cavities; it has good feeding performance, is not prone to shrinkage porosity, and has high casting quality; it has a low coefficient of expansion, and after the casting is solidified, the casting dimensions are stable, the casting performance is good, there is no tendency to hot crack, the air tightness is high, the linear shrinkage is small, and the casting performance is excellent.

[0021] 8) The aluminum alloy products obtained by using the production method of this application and after T6 heat treatment have a tensile strength of 270-285MPa and an elongation of 8%-10%. It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0022] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0023] Figure 1 The deformation curves of the aluminum alloy samples prepared in Examples 1-3 of this disclosure are shown. Figure 2 A 100x metallographic image of the aluminum alloy sample obtained after T6 heat treatment according to Embodiment 1 of this disclosure is shown. Detailed Implementation

[0024] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0025] In a first aspect, this application provides a die-casting aluminum alloy that can be strengthened by T6 heat treatment, comprising the following components by weight percentage: silicon 7.5%–8%, magnesium 0.3%–0.35%, iron 0.1%–0.3%, vanadium 0.05%, zirconium 0.05%, rare earth elements 0.1%–0.3%, beryllium 0.001%–0.005%, with the balance being aluminum and unavoidable impurities.

[0026] The silicon content is controlled at 7.5%–8%. This proportion of silicon allows the alloy to absorb some shrinkage stress through eutectic reaction during solidification, resulting in a finer microstructure, reduced overall thermal stress, and fewer cracks. Compared to low-silicon alloys, the proportion of primary α-Al is moderate, leading to a more reasonable coefficient of thermal expansion and lower shrinkage stress. The magnesium content is controlled at 0.3%–0.35%. This proportion of magnesium works synergistically with silicon to promote the formation of fine and uniform Mg2Si strengthening phases, further improving the alloy's strength and elongation. It avoids cracking caused by coarse or unevenly distributed Mg2Si phases due to high silicon content and also solves the problems of insufficient eutectic reaction and high shrinkage leading to cracking in low-silicon alloys. The iron content is maintained at 0.1%–0.3%, and the contents of vanadium and zirconium are 0.05% each. These elements refine the microstructure and improve the overall performance of the alloy. Rare earth elements can refine grains, improve the alloy's microstructure, reduce the negative impact of impurity elements, enhance thermal stability, and further improve the alloy's elongation. In addition, the addition of beryllium at a content of 0.001% to 0.005% reduces the surface tension of aluminum alloys, improves melt fluidity, makes the solidification structure more uniform, reduces internal defects, and increases elongation.

[0027] Therefore, the aluminum alloy with the above-mentioned proportions provided in this application overcomes the defects of existing aluminum alloy castings, such as easy shrinkage cracking, large deformation, and low elongation after T6 heat treatment. The aluminum alloy castings of this application, after T6 heat treatment, not only achieve excellent properties such as no shrinkage cracking and small deformation, meeting stringent requirements for forming accuracy, but also increase the elongation to 8%–10%, while ensuring consistent performance at every location of the casting. Furthermore, the tensile strength is increased to 275–280 MPa, and the surface porosity is reduced to 0.02–0.03%. The aluminum alloy products obtained after T6 heat treatment can be integrally die-cast to produce automobile bodies and other components, effectively solving the problem of large performance differences at different locations during the die-casting process.

[0028] In one embodiment, the rare earth element is yttrium or lanthanum. The total amount of unavoidable impurities is <0.5%.

[0029] Preferably, the weight percentage of silicon is 7.6% to 7.9%.

[0030] Preferably, the magnesium content is 0.31% to 0.34% by weight.

[0031] Preferably, the weight percentage of iron is 0.15% to 0.25%.

[0032] In this invention, the silicon content is moderate. The addition of magnesium in the aforementioned proportion has a synergistic effect, promoting the formation of fine and uniform Mg2Si strengthening phases. This results in a continuous and uniform eutectic structure, reducing localized stress concentration and improving crack resistance. It avoids cracks caused by coarse or unevenly distributed Mg2Si phases in high-silicon environments and also solves the problems of insufficient eutectic reaction, large shrinkage, and susceptibility to cracking in low-silicon environments. The addition of magnesium refines the grains and ensures uniform precipitation of the strengthening phase, resulting in uniform stress distribution and improved crack resistance. The addition of vanadium and zirconium further refines the microstructure and enhances overall performance.

[0033] In one embodiment, the T6 heat-treatable aluminum alloy of this application further includes a modifier comprising phosphorus, calcium, and sodium, wherein the weight percentage of phosphorus, calcium, and sodium in the die-casting aluminum alloy is less than or equal to 10 ppm. Preferably, the weight percentage of phosphorus in the die-casting aluminum alloy is 6-10 ppm, the weight percentage of calcium in the die-casting aluminum alloy is 7-10 ppm, and the weight percentage of sodium in the die-casting aluminum alloy is 7-10 ppm.

[0034] The modifier phosphorus refines grains and primary silicon, calcium improves the morphology of eutectic silicon and enhances thermal stability, and sodium further refines eutectic silicon and improves casting performance. In this invention, the modifiers phosphorus, calcium, and sodium are all present in aluminum alloys at a content of less than or equal to 10 ppm. These three modifiers work synergistically to form uniformly dispersed microcrystalline nuclei in the molten aluminum alloy. During solidification, this induces the formation of numerous fine grains. Compared to aluminum alloys treated with conventional modifier ratios, this significantly improves the material's strength and hardness while reducing deformation.

[0035] Secondly, this application also provides a method for producing a die-casting aluminum alloy that can be strengthened by T6 heat treatment, the method comprising the following steps: Step 1) Raw material preparation: Prepare each raw material according to the percentage of each element in the die-casting aluminum alloy; Step 2) Crucible pretreatment: Clean the crucible and preheat it to 150-200℃ to remove moisture and impurities; Step 3) Alloy melting: First, add aluminum raw material to the crucible and heat to 720-750℃ to completely melt the aluminum; add the corresponding raw materials in the order of silicon, iron, magnesium, vanadium, zirconium, rare earth elements, and beryllium, controlling the stirring speed at 150-200 r / min during the addition process; after all raw materials have completely melted, raise the temperature to 760-780℃ and hold for 15-20 min to obtain aluminum alloy melt; Step 4) Melt treatment: Degas and refine the aluminum alloy melt; Step 5) Modification treatment: When the temperature of the aluminum alloy melt after melt treatment drops to 720-740℃, add phosphorus, calcium and sodium modifiers evenly and dispersedly; after the addition is completed, stir gently for 3-5 minutes. Step 6) Molding: Pour the modified aluminum alloy melt into a mold preheated to 200-250℃, and control the casting temperature at 700-720℃; after casting, allow it to cool naturally to room temperature to obtain the aluminum alloy casting. Step 7) T6 heat treatment: Perform T6 heat treatment on the aluminum alloy casting to obtain the aluminum alloy product.

[0036] For example, in step 3) alloy melting, the stirring speed is controlled at 150-200 r / min. This stirring speed can make each element fully and uniformly integrated into the aluminum matrix, ensuring that the composition of each part of the aluminum alloy is consistent and avoiding compositional segregation, thereby ensuring the stability and consistency of the aluminum alloy performance. After all the raw materials have been completely melted, the temperature is raised to 760-780℃ and held for 15-20 minutes, which can make the aluminum alloy composition fully homogenized.

[0037] For example, in step 4), the degassing and refining of the aluminum alloy melt includes degassing the aluminum alloy melt by rotary argon blowing, with the argon flow rate controlled at 8-10 L / min and the blowing time at 10-20 min; at the same time, a refining agent is added, with the amount of refining agent added being 0.5%-0.8% of the mass of the aluminum alloy melt, and the refining time being 15-20 min.

[0038] Step 4) In the melt treatment, degassing can effectively remove gases such as hydrogen from the aluminum alloy melt, reducing the formation of porosity inside the casting. The refining agent used is a commonly used degassing and slag-removing refining agent in existing technology (selecting a common high-efficiency degassing and slag-removing refining agent on the market).

[0039] For example, in step 5) modification treatment, phosphorus, calcium and sodium modifiers are added to the aluminum alloy melt in a uniformly dispersed manner, and then stirred gently for 3 to 5 minutes. This step can help the modifiers form uniformly dispersed micro-crystal nuclei in the aluminum alloy melt, so that a large number of fine grains are induced to form during the solidification of the aluminum alloy, optimizing the microstructure of the aluminum alloy, thereby improving the strength, hardness and deformation resistance of the aluminum alloy.

[0040] For example, in step 6), preheating the mold can reduce the temperature difference between the aluminum alloy melt and the mold, and avoid cracks in the casting caused by rapid temperature changes. The casting temperature is controlled at 700-720℃. After casting, the casting is naturally cooled to room temperature to obtain the aluminum alloy casting.

[0041] For example, in step 7), the aluminum alloy casting undergoes T6 heat treatment. T6 heat treatment is a commonly used strengthening heat treatment process for aluminum alloys, which mainly includes solution treatment, quenching and cooling, and artificial aging steps.

[0042] Preferably, during the T6 heat treatment process, the solution treatment temperature is 535°C and the solution treatment time is 9 hours, while the artificial aging treatment requires an aging temperature of 175°C and an aging time of 11 hours.

[0043] This application effectively reduces shrinkage cracking and deformation of aluminum alloy castings during the T6 heat treatment process by optimizing the composition and production method. For small, relatively simple integrated aluminum alloy castings, the linear deformation after T6 treatment is controlled within ±0.1% to ±0.3%; for large, complex integrated aluminum alloy castings, the linear deformation is controlled within ±0.3% to ±0.8%, exhibiting good dimensional stability and meeting stringent requirements for forming accuracy. Therefore, the die-casting aluminum alloy of this application can be applied to automotive structural components, including but not limited to automotive bodies.

[0044] The present application will be further described in detail below with reference to specific embodiments: Example 1 A die-casting aluminum alloy that can be strengthened by T6 heat treatment, the composition of which, by weight percentage, comprises 7.6% silicon, 0.31% magnesium, 0.15% iron, 0.05% vanadium, 0.05% zirconium, 0.15% yttrium, 0.002% beryllium, with the remainder being aluminum and unavoidable impurities (total impurities < 0.5%); it also includes modifiers comprising phosphorus, calcium, and sodium, wherein phosphorus is 8 ppm, calcium is 7 ppm, and sodium is 10 ppm.

[0045] The method for producing this die-casting aluminum alloy includes the following steps: Step 1), Raw material preparation: Based on the percentage of each element in the above aluminum alloy, accurately weigh pure aluminum, ferrosilicon alloy, magnesium ingot, ferrovanadium alloy, zirconium master alloy, yttrium master alloy, beryllium copper master alloy, and modifier raw materials containing phosphorus, calcium, and sodium. Step 2), Crucible pretreatment: Select a suitable crucible, clean it thoroughly to remove surface oil, impurities, etc., and then place it in a heating furnace to preheat to 180°C and maintain for 30 minutes to ensure that moisture and impurities are completely removed; Step 3) Alloy melting: Place the preheated crucible into the melting furnace, add pure aluminum, and heat to 730℃. After the aluminum is completely melted, add the corresponding raw materials in the order of silicon, iron, magnesium, vanadium, zirconium, yttrium, and beryllium. During the addition process, turn on the stirring device and control the stirring speed at 180 r / min to ensure that each element is fully and evenly incorporated into the aluminum matrix. After all the raw materials are completely melted, raise the temperature to 770℃ and hold for 18 minutes to ensure that the alloy composition is fully homogenized; thus, an aluminum alloy melt is obtained. Step 4) Melt treatment: The aluminum alloy melt is degassed using a rotary jet of argon gas. The argon gas flow rate is adjusted to 9 L / min, and the jetting time is set to 18 minutes to effectively remove gases such as hydrogen from the melt. At the same time, 0.6% of the mass of the aluminum alloy melt is added as a refining agent (using a commonly available high-efficiency degassing and slag-removing refining agent) for 18 minutes to further remove impurities from the melt. Step 5) Modification treatment: When the temperature of the aluminum alloy melt after step 4) melt treatment drops to 730°C, add phosphorus, calcium and sodium modifiers evenly and dispersedly into the aluminum alloy melt; after the addition is completed, use a stirring paddle to stir gently for 4 minutes to promote the formation of uniformly dispersed micro crystal nuclei in the melt. Step 6) Molding: Pour the modified aluminum alloy melt into a mold preheated to 200-250℃. Preheating the mold can reduce the temperature difference between the melt and the mold, and avoid cracks in the casting caused by rapid temperature changes. The casting temperature is controlled at 700-720℃. After casting, let it cool naturally to room temperature to obtain the aluminum alloy casting. Step 7) Heat treatment: The aluminum alloy casting is subjected to T6 heat treatment, wherein the solution treatment temperature is set at 535℃ and the solution treatment time is 9 hours; after solution treatment, it is quickly quenched and cooled, and then artificial aging treatment is performed at 175℃ and the aging time is 11 hours.

[0046] In Example 1, an aluminum alloy sample for die casting (hereinafter referred to as "aluminum alloy sample" or "sample") was prepared.

[0047] Performance testing The aluminum alloy samples prepared in Example 1 were subjected to tensile tests in accordance with GB / T228.1 "Metallic materials - Tensile testing - Part 1: Test method at room temperature" to detect tensile strength and elongation. The apparent porosity of the samples was determined by metallographic analysis according to GB3489-2015. The appearance of the samples was observed for shrinkage cracks and deformation, and the relevant data were recorded.

[0048] The results showed that the aluminum alloy sample obtained in Example 1 had a tensile strength of 280 MPa, an elongation of 9%, no shrinkage cracks on the surface, a deformation of less than 0.2%, and a surface porosity of 0.02%.

[0049] Example 2 A die-casting aluminum alloy that can be strengthened by T6 heat treatment, the composition of which, by weight percentage, includes 7.7% silicon, 0.33% magnesium, 0.2% iron, 0.05% vanadium, 0.05% zirconium, 0.2% lanthanum, 0.003% beryllium, with the remainder being aluminum and unavoidable impurities (total impurities < 0.5%); it also includes modifiers, the amount of which is 6 ppm phosphorus, 7 ppm calcium, and 8 ppm sodium.

[0050] The production method of this die-casting aluminum alloy includes: Step 1) Raw material preparation: Same as in Example 1, accurately prepare all kinds of raw materials; Step 2) Crucible pretreatment: Clean and preheat the crucible to 160°C and keep it at that temperature for 40 minutes; Step 3) Alloy melting: Place the preheated crucible into the melting furnace, add pure aluminum, and heat to 720℃ to melt it; add the corresponding raw materials in the order of silicon, iron, magnesium, vanadium, zirconium, lanthanum, and beryllium, and control the stirring speed at 160 r / min during the addition process; after all the raw materials have completely melted, heat to 760℃ and hold for 20 minutes to obtain aluminum alloy melt; Step 4) Melt treatment: The aluminum alloy melt is degassed by rotary argon blowing, with the argon flow rate controlled at 8L / min and the blowing time at 16 minutes; at the same time, a refining agent is added, with the amount of refining agent added being 0.7% of the mass of the aluminum alloy melt, and the refining time being 16 minutes. Step 5) Modification treatment: When the temperature of the aluminum alloy melt after step 4) melt treatment drops to 720℃, add phosphorus, calcium and sodium modifiers evenly and dispersedly. After the addition is completed, stir gently for 5 minutes. The molding and heat treatment steps in steps 6 and 7 are the same as in Example 1.

[0051] In Example 2, an aluminum alloy sample for die casting was prepared.

[0052] Based on the above performance testing methods, the performance of the die-casting aluminum alloy sample prepared in Example 2 was tested. The results showed that its tensile strength was 275 MPa, elongation was 8.5%, surface had no shrinkage cracks, deformation was less than 0.2%, and surface porosity was 0.03%.

[0053] Example 3 A die-casting aluminum alloy that can be strengthened by T6 heat treatment, the composition of which, by weight percentage, contains 7.8% silicon, 0.34% magnesium, 0.25% iron, 0.05% vanadium, 0.05% zirconium, 0.25% yttrium, 0.004% beryllium, with the remainder being aluminum and unavoidable impurities (total impurities < 0.5%); it also includes a modifier, the amount of which is 9 ppm phosphorus, 10 ppm calcium, and 7 ppm sodium.

[0054] The production method of this die-casting aluminum alloy includes: Step 1) Raw material preparation: Refer to Example 1 and accurately weigh each raw material; Step 2) Crucible pretreatment: After cleaning the crucible, preheat it to 200℃ and keep it at that temperature for 20 minutes; Step 3) Alloy melting: Place the preheated crucible into the melting furnace, then add pure aluminum to the crucible and heat to 750℃ to melt the aluminum; add the corresponding raw materials in the order of silicon, iron, magnesium, vanadium, zirconium, yttrium, and beryllium, controlling the stirring speed at 200 r / min during the addition process; after all the raw materials have completely melted, heat to 780℃ and hold for 15 minutes to obtain aluminum alloy melt; Step 4) Melt treatment: The aluminum alloy melt is degassed by rotary argon blowing at a flow rate of 10 L / min for 20 minutes. At the same time, a refining agent is added at a rate of 0.8% of the mass of the aluminum alloy melt for 20 minutes. Step 5) Modification treatment: When the temperature of the aluminum alloy melt after melt treatment drops to 740℃, add phosphorus, calcium and sodium modifiers evenly and dispersedly, and stir gently for 3 minutes after the addition is completed; The molding and heat treatment steps in steps 6) to 7) are the same as in Example 1.

[0055] In Example 3, an aluminum alloy sample for die casting was prepared.

[0056] Based on the above performance testing methods, the performance of the die-casting aluminum alloy sample prepared in Example 3 was tested. The results showed that its tensile strength was 278 MPa, elongation was 9.5%, surface had no shrinkage cracks, deformation was less than 0.2%, and surface porosity was 0.025%.

[0057] Comparative Example 1 Aluminum alloy composition: by weight percentage, it contains 7.5% silicon, 0.25% magnesium, 0.1% iron, 0.05% vanadium, 0.05% zirconium, with the remainder being aluminum and unavoidable impurities (total impurities < 0.5%); it also includes modifiers, the amount of which is the same as in Example 1, 8 ppm phosphorus, 7 ppm calcium, and 10 ppm sodium.

[0058] The production method of this aluminum alloy is the same as that in Example 1 of this invention, including raw material preparation, crucible pretreatment, alloy smelting, melt treatment, modification treatment, forming, and heat treatment. The same process parameters are strictly followed to ensure consistency in all conditions except for composition.

[0059] Aluminum alloy samples were prepared in Comparative Example 1.

[0060] Performance testing: The aluminum alloy sample of Comparative Example 1 was tested according to the above performance testing standards. The results showed that its tensile strength was 260 MPa, elongation was 6%, there were a few microcracks on the surface, and the surface porosity was 0.04%. Due to the low magnesium content, insufficient formation of strengthening phases, and lack of rare earth elements and beryllium to improve the microstructure, the strength and elongation were low, and the crack resistance was poor.

[0061] Comparative Example 2 The aluminum alloy composition is as follows: silicon 7.5%, magnesium 0.3%, iron 0.1%, vanadium 0.05%, zirconium 0.05%, yttrium 0.15%, with the remainder being aluminum and unavoidable impurities (total impurities < 0.5%). It also includes a modifier, with the same amount added as in Example 1. The rare earth element yttrium was added, but beryllium was not added.

[0062] The production method of this aluminum alloy is completely consistent with the production method of Example 1.

[0063] Aluminum alloy samples were prepared in Comparative Example 2.

[0064] Performance testing: The aluminum alloy sample of Comparative Example 2 was tested according to the above standards. The results showed that the tensile strength was 270 MPa, the elongation was 7.5%, there was no obvious shrinkage crack, and the surface porosity was 0.03%. The addition of the rare earth element yttrium refined the grains and improved some properties, but due to the lack of beryllium to improve melt flowability and microstructure uniformity, the elongation still did not reach 8% to 10%.

[0065] Comparative Example 3 The aluminum alloy composition is as follows: silicon 7.5%, magnesium 0.3%, iron 0.1%, vanadium 0.05%, zirconium 0.05%, beryllium 0.002%, with the remainder being aluminum and unavoidable impurities (total impurities < 0.5%). The amount of modifier added is the same as in Example 1. Beryllium was added, but rare earth elements were not added.

[0066] The production method of this aluminum alloy is completely consistent with the production method of Example 1.

[0067] Aluminum alloy samples were prepared in Comparative Example 3.

[0068] Performance testing: The aluminum alloy sample of Comparative Example 3 was tested according to the above standards. The results showed that its tensile strength was 265 MPa, elongation was 7%, with slight deformation and surface porosity of 0.035%. Beryllium improved the melt flowability, but due to the lack of rare earth elements to refine the grains and enhance thermal stability, the overall performance improvement was limited, and the elongation did not meet the standard.

[0069] The above test results are summarized in Table 1 as follows: Table 1. Performance test results of aluminum alloy samples prepared in each embodiment and comparative example.

[0070] As can be seen from the comparison between Examples 1-3 and Comparative Examples 1-3, the optimized alloy composition in this application, especially the addition of rare earth elements and beryllium, combined with specific production processes, has a significant effect on improving the tensile strength, elongation, crack resistance and reducing surface porosity of aluminum alloys.

[0071] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this disclosure can be achieved, and this is not limited herein.

[0072] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0073] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A die-casting aluminum alloy that can be strengthened by T6 heat treatment, characterized in that, By weight percentage, it includes: silicon 7.5%–8%, magnesium 0.3%–0.35%, iron 0.1%–0.3%, vanadium 0.05%, zirconium 0.05%, rare earth elements 0.1%–0.3%, beryllium 0.001%–0.005%, with the balance being aluminum and unavoidable impurities.

2. The die-casting aluminum alloy that can be strengthened by T6 heat treatment according to claim 1, characterized in that, The rare earth element is yttrium or lanthanum.

3. The die-casting aluminum alloy that can be strengthened by T6 heat treatment according to claim 1, characterized in that, The silicon content is 7.6% to 7.9% by weight.

4. The die-casting aluminum alloy that can be strengthened by T6 heat treatment according to claim 1, characterized in that, The magnesium content is 0.31% to 0.34% by weight.

5. The die-casting aluminum alloy that can be strengthened by T6 heat treatment according to claim 1, characterized in that, The iron content is 0.15% to 0.25% by weight.

6. The die-casting aluminum alloy that can be strengthened by T6 heat treatment according to claim 1, characterized in that, It also includes modifiers, which include phosphorus, calcium and sodium, wherein the weight percentage of each of the phosphorus, calcium and sodium in the die-casting aluminum alloy is less than or equal to 10 ppm.

7. The die-casting aluminum alloy that can be strengthened by T6 heat treatment according to claim 6, characterized in that, The phosphorus content in the die-casting aluminum alloy is 6-10 ppm by weight, the calcium content in the die-casting aluminum alloy is 7-10 ppm by weight, and the sodium content in the die-casting aluminum alloy is 7-10 ppm by weight.

8. A method for producing a die-casting aluminum alloy that can be strengthened by T6 heat treatment according to any one of claims 1-7, characterized in that, Includes the following steps: Raw material preparation: Prepare each raw material according to the percentage of each element in the die-casting aluminum alloy; Crucible pretreatment: Clean the crucible and preheat it to 150-200℃; Alloy smelting: First, add aluminum raw material to a crucible and heat to 720-750℃ to completely melt the aluminum; add the corresponding raw materials in the order of silicon, iron, magnesium, vanadium, zirconium, rare earth elements, and beryllium, controlling the stirring speed at 150-200 r / min during the addition process; after all raw materials have completely melted, raise the temperature to 760-780℃ and hold for 15-20 min to obtain aluminum alloy melt; Melt treatment: The aluminum alloy melt is degassed and refined; Modification treatment: When the temperature of the aluminum alloy melt after melt treatment drops to 720-740℃, add phosphorus, calcium and sodium modifiers evenly and dispersedly; after the addition is completed, stir for 3-5 minutes; Forming: The modified aluminum alloy melt is poured into a mold preheated to 200-250℃, and the casting temperature is controlled at 700-720℃; after casting, it is naturally cooled to room temperature to obtain aluminum alloy castings. T6 heat treatment: The aluminum alloy casting is subjected to T6 heat treatment.

9. The production method according to claim 8, characterized in that, During the T6 heat treatment process, the solution treatment temperature is 535℃ and the solution treatment time is 9 hours, while the artificial aging treatment requires an aging temperature of 175℃ and an aging time of 11 hours. The degassing and refining of the aluminum alloy melt includes degassing the aluminum alloy melt by rotary jetting argon gas, with the argon gas flow rate controlled at 8-10 L / min and the jetting time at 10-20 min; simultaneously, a refining agent is added, with the amount of refining agent added being 0.5%-0.8% of the mass of the aluminum alloy melt, and the refining time being 15-20 min.

10. The application of a die-casting aluminum alloy that can be strengthened by T6 heat treatment according to any one of claims 1-7 or a die-casting aluminum alloy obtained by the production method according to claim 8 or 9 in automotive structural parts.

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