Heat-treatment-free aluminum alloy and preparation method thereof

Abstract

The invention relates to the technical field of metal materials, in particular to a heat-treatment-free aluminum alloy and a preparation method thereof. The aluminum alloy comprises the following components in percentage by weight: 7wt% to 10wt% of Si, 0.1 wt% to 1wt% of Ni, 0.4 wt% to 0.7 wt% of Mn, 0.25 wt% to 0.5 wt% of Mg, 0.08 wt% to 0.2 wt% of Fe, 0.02 wt% to 0.1 wt% of Cr, 0.1 wt% to 0.2 wt% of Cu, 0.001 wt% to 0.05 wt% of Zr, 0.08 wt% to 0.15 wt% of Ti, 0.015 wt% to 0.03 wt% of B, 0.005 wt% to 0.025 wt% of Sr, 0.03 wt% to 0.3 wt% of rare earth metal elements and the balance of aluminum and inevitable impurity elements. The aluminum alloy provided by the invention has excellent mechanical properties and die-casting properties.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, specifically to a heat-free aluminum alloy and its preparation method. Background Technology

[0002] In recent years, with the rapid development of new energy vehicles and the advancement of the automotive lightweighting development strategy, the development of die casting equipment and process technology has been promoted. High vacuum die casting has become an important way for new energy vehicles to achieve lightweighting of load-bearing structural components.

[0003] Currently, Al-Si-Mg alloys combined with T6 / T7 heat treatment are commonly used to strengthen and toughen automotive aluminum alloy die-cast structural parts. However, T6 / T7 heat treatment often leads to deformation and increased costs for large, thin-walled structural parts. To improve the strength and reduce the cost of thin-walled structural parts, using heat-treatable aluminum alloys is an important direction in automotive development. This requires heat-treatable aluminum alloys to possess not only high yield strength, high toughness, and high fatigue strength, but also good die-casting fluidity, overall dimensional stability, and specific stiffness. However, in the process of industrialization, heat-free die-cast aluminum alloys still face several key technical challenges: First, the strength properties of the material, especially the yield strength, are still difficult to fully meet the mechanical requirements of large structural components under lightweight design; second, the die-casting fluidity of the alloy is insufficient, which easily leads to defects such as cold shuts and poor filling in the far-end areas of the integrated die-cast parts; third, although the strength of the components is improved after the baking paint process, the elongation often decreases significantly, even falling below the standard limit, affecting the service safety of the parts; fourth, large castings are prone to deformation during the cooling process, and must be cooled to a specific temperature below the mold temperature before the mold can be opened, which leads to a longer production cycle and seriously restricts the increase in production capacity.

[0004] Based on its material properties, heat-free strengthened aluminum alloy die-cast structural parts are easily connected to other body parts through bonding, FDS, riveting, and press riveting, significantly reducing part weight compared to traditional steel parts and improving the driving range and handling performance of new energy vehicles. As the integration level of structural parts in new energy vehicles increases, heat-free die-cast aluminum alloy materials have become an important choice. Die-cast aluminum alloys for automotive body structural parts possess excellent comprehensive performance, requiring excellent die-casting performance, high yield strength, high toughness, and excellent thermal stability simultaneously. In terms of material design, die-casting performance is generally achieved by adding silicon to meet its fluidity requirements; high strength in the as-cast state requires the addition of solid solution strengthening elements; and high toughness requires minimizing the volume fraction of the second phase and reducing lattice distortion. These three aspects are difficult to balance simultaneously. Furthermore, body structural parts need to be connected to other parts, and dimensional and performance stability must be maintained during painting and service. Developing new alloy systems with excellent thermal stability has become one of the key technological challenges currently facing the market. Summary of the Invention

[0005] The purpose of this invention is to overcome the limitations of existing aluminum alloys that, under heat-free conditions, struggle to simultaneously achieve high strength, high toughness, and good die-casting performance, and which suffer from problems such as decreased elongation after painting, deformation of large castings, and extended production cycle time. This invention provides a heat-free aluminum alloy and its preparation method. This heat-free aluminum alloy exhibits excellent mechanical and die-casting properties.

[0006] To achieve the above objectives, the first aspect of the present invention provides a heat-free aluminum alloy, comprising, based on the total mass of the heat-free aluminum alloy: 7wt%–10wt% Si, 0.1wt%–1wt% Ni, 0.4wt%–0.7wt% Mn, 0.25wt%–0.5wt% Mg, 0.08wt%–0.2wt% Fe, 0.02wt%–0.1wt% Cr, 0.1wt%–0.2wt% Cu, 0.001wt%–0.05wt% Zr, 0.08wt%–0.15wt% Ti, 0.015wt%–0.03wt% B, 0.005wt%–0.025wt% Sr, and 0.03wt%–0.3wt% rare earth metal elements, with the remainder being aluminum and unavoidable impurity elements.

[0007] The second aspect of this invention provides a method for preparing the heat-free aluminum alloy described in the first aspect of this invention, comprising the following steps: Aluminum-containing raw materials, nickel-containing raw materials, boron-containing raw materials, titanium-containing raw materials, copper-containing raw materials, manganese-containing raw materials, chromium-containing raw materials, zirconium-containing raw materials, rare earth metal-containing raw materials, silicon-containing raw materials, magnesium-containing raw materials, and strontium-containing raw materials are heated and melted to obtain aluminum alloy liquid; the aluminum alloy liquid is refined to obtain heat-free aluminum alloy.

[0008] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The heat-free aluminum alloy prepared by this invention has important industrial application value: the heat-free aluminum alloy has excellent properties such as tensile strength ≥290MPa, yield strength ≥140MPa and elongation ≥12% under die-casting conditions, and can achieve good die-casting performance, which can meet the application requirements of large thin-walled body structural parts in the new energy vehicle industry.

[0009] 2. The heat-free aluminum alloy of this invention achieves excellent properties in the as-cast state, with tensile strength ≥290MPa, yield strength ≥140MPa, and elongation ≥12%. Compared with existing heat-treatable alloys, it can reduce the heat treatment process of parts, thereby improving the qualification rate of castings and reducing the cost of castings.

[0010] 3. The heat-free aluminum alloy of the present invention can be cooled quickly (mold opening), which can greatly shorten the production cycle. The alloy composition design can reduce the overall cycle by 10-15s. After composition and process design, the cycle can be reduced to 100s compared with the traditional one-piece die casting process (120s-180s). Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] The first aspect of this invention provides a heat-free aluminum alloy, comprising, based on the total mass of the heat-free aluminum alloy: 7wt% to 10wt% Si, 0.1wt% to 1wt% Ni, 0.4wt% to 0.7wt% Mn, 0.25wt% to 0.5wt% Mg, 0.08wt% to 0.2wt% Fe, 0.02wt% to 0.1wt% Cr, 0.1wt% to 0.2wt% Cu, 0.001wt% to 0.05wt% Zr, 0.08wt% to 0.15wt% Ti, 0.015wt% to 0.03wt% B, 0.005wt% to 0.025wt% Sr, and 0.03wt% to 0.3wt% rare earth metal elements, with the remainder being aluminum and unavoidable impurity elements.

[0013] In this invention, the components of the aluminum alloy are controlled to be adjusted within the above-defined range. This aluminum alloy can reduce the heat treatment process of the parts and can better balance the yield strength, tensile strength and elongation under die-cast conditions, thereby obtaining a heat-treatable strengthened aluminum alloy with high yield strength, high tensile strength and high elongation. Compared with existing heat-treatable alloys, it can reduce the heat treatment process of the parts, thereby improving the qualification rate of castings and reducing the cost of castings.

[0014] According to the present invention, the Si content in the heat-free aluminum alloy can be 7wt%, 7.5wt%, 8wt%, 8.2wt%, 8.6wt%, 9wt%, 9.2wt%, 9.5wt%, 10wt%, or any combination of two of the above values. The addition of Si mitigates the problem of reduced elongation caused by the presence of reinforcing phases in the alloy. Furthermore, controlling the Si content within the range of the present invention can better increase the fluidity of the aluminum alloy, thereby ensuring lower macroscopic defects and thus guaranteeing the mechanical properties of the aluminum alloy.

[0015] According to the present invention, the Ni content in the heat-free aluminum alloy can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or any two of the above values. In some embodiments, the Ni content in the heat-free aluminum alloy is preferably 0.2wt%-0.5wt%. By optimizing the composition system of the aluminum alloy, the Ni content can be controlled within the range of the present invention, and the heat resistance of the aluminum alloy can be optimized and upgraded at a specific Ni content, breaking through the performance bottleneck of traditional single Ni strengthening. Moreover, the lower Ni content can not only significantly reduce the cost of alloy raw materials, but also more effectively suppress the risk of excessive Ni forming coarse and brittle NiSi phase, Ni2Si phase and other harmful phases with Si, avoiding metallurgical defects such as decreased alloy toughness, stress concentration and deterioration of corrosion resistance caused by such phases, and ensuring the stability of product service. Furthermore, controlling the Ni content within the above range can better cooperate with rare earth metal elements to synergistically strengthen the system.

[0016] According to the present invention, the Mn content in the heat-free aluminum alloy can be 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, or any combination of two of the above values. Controlling the Mn content within the range of the present invention can better enhance the mechanical properties of the aluminum alloy in the as-cast state.

[0017] According to the present invention, the Mg content in the heat-free aluminum alloy can be 0.25wt%, 0.3wt%, 0.35wt%, 0.45wt%, 0.5wt%, or any combination of two of the above values. By controlling the Mg content within the range of the present invention, the mechanical properties of the aluminum alloy can be directly improved without heat treatment.

[0018] According to the present invention, the Fe content in the heat-free aluminum alloy can be 0.08wt%, 0.1wt%, 0.12wt%, 0.14wt%, 0.15wt%, 0.16wt%, 0.18wt%, 0.2wt%, or any combination of two of the above values. Controlling the Fe content within the range of the present invention can better improve the as-cast properties of the aluminum alloy, eliminating the need for traditional heat treatment steps.

[0019] According to the present invention, the Cr content in the heat-free aluminum alloy can be 0.02wt%, 0.03wt%, 0.04wt%, 0.055wt%, 0.06wt%, 0.08wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.17wt%, 0.2wt%, or any range of two of the above values. Controlling the Cr content within the range of the present invention can better enhance the mechanical properties of the aluminum alloy in the as-cast state.

[0020] According to the present invention, the Cu content in the heat-free aluminum alloy can be 0.1wt%, 0.12wt%, 0.14wt%, 0.15wt%, 0.17wt%, 0.18wt%, 0.2wt%, or any combination of two of the above values. Controlling the Cu content within the range of the present invention can better guarantee the strength of the aluminum alloy casting.

[0021] According to the present invention, the Zr content in the heat-free aluminum alloy can be 0.001 wt%, 0.004 wt%, 0.006 wt%, 0.008 wt%, 0.01 wt%, 0.02 wt%, 0.04 wt%, 0.05 wt%, or any combination of two of the above values. Controlling the Zr content within the range of the present invention can better guarantee the strength and toughness of the aluminum alloy casting.

[0022] According to the present invention, the Ti content in the heat-free aluminum alloy can be 0.08 wt%, 0.1 wt%, 0.12 wt%, 0.15 wt%, or any combination of two of the above values. Controlling the Ti content within the range of the present invention can better enhance the mechanical properties of the aluminum alloy in the as-cast state.

[0023] According to the present invention, the content of B in the heat-free aluminum alloy can be 0.015wt%, 0.018wt%, 0.02wt%, 0.023wt%, 0.025wt%, 0.028wt%, 0.03wt%, or any range of two of the above values. Controlling the content of B within the range of the present invention can better enhance the mechanical properties of the aluminum alloy in the as-cast state.

[0024] According to the present invention, the Sr content in the heat-free aluminum alloy can be 0.005 wt%, 0.008 wt%, 0.01 wt%, 0.015 wt%, 0.018 wt%, 0.02 wt%, 0.023 wt%, 0.025 wt%, or any range of two of the above values. Controlling the Sr content within the range of the present invention can better enhance the mechanical properties of the aluminum alloy in the as-cast state.

[0025] According to the present invention, the rare earth metal elements in the heat-free aluminum alloy can be 0.03wt%, 0.05wt%, 0.07wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.18wt%, 0.2wt%, 0.23wt%, 0.25wt%, 0.28wt%, 0.3wt%, or any two of the above values. In this invention, rare earth elements enhance the density and interfacial bonding of the aluminum alloy matrix through solid solution strengthening and grain boundary purification. Furthermore, by regulating the precipitation behavior of Ni-based strengthening phases at specific contents—promoting the dispersed distribution of thermally stable intermetallic compounds such as Al3Ni and Al7Cu4Ni, and inhibiting their coarsening and aggregation at high temperatures—they synergistically enhance the strengthening effect of Ni on the heat resistance of the aluminum alloy. The present invention, verified by a long-term heat exposure test at 150℃ / 1000h, shows that the attenuation rate of the room temperature and high temperature mechanical properties (tensile strength, yield strength) of the heat-free aluminum alloy can be controlled within 6%, and the amount of Ni added is significantly reduced.

[0026] According to the present invention, in some embodiments, the rare earth metal element includes La and / or Ce. Using La and / or Ce rare earth metal elements allows for a better construction of a multi-element synergistic strengthening system within the specific system of the present invention.

[0027] According to the present invention, in some embodiments, the rare earth metal elements include La and Ce. Preferably, in the heat-free aluminum alloy, the mass ratio of La to Ce is 1:(2-4), for example, 1:2, 1:2.3, 1:2.5, 1:2.8, 1:3, 1:3.2, 1:3.5, 1:3.8, 1:4, or any range of two of the above ratios. While optimizing the metal elements and their content in the heat-free aluminum alloy, the present invention further optimizes and controls the rare earth metal elements in the heat-free aluminum alloy to be La and Ce, and controls the mass ratio of La to Ce within the above range. This enables the construction of a multi-element synergistic strengthening system in the specific system of the present invention without heat treatment, and achieves optimized and upgraded heat resistance performance with better synergy with Ni at low Ni content, breaking through the performance bottleneck of traditional single Ni strengthening. It is particularly suitable for large, structurally complex die-cast parts.

[0028] According to the present invention, in some embodiments, the mass ratio of Si to Ni in the heat-free aluminum alloy is greater than 10:1, for example, 12:1, 15:1, 17:1, 17.2:1, 18:1, 20:1, 25:1, 30:1, 35:1, 40:1, 43:1, 45:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 120:1, 150:1, 160:1, 172:1, 180:1, etc., and there is no specific limitation. In the present invention, by optimizing the metal elements and their contents in the heat-free aluminum alloy, the Ni content can be better reduced. Furthermore, by controlling the mass ratio of Si to Ni within the above-mentioned range, the precipitation of nickel-based brittle phases can be better avoided, thereby increasing the elongation and other properties of the heat-free aluminum alloy.

[0029] According to the present invention, in some embodiments, the mass ratio of Mn to Cr in the heat-free aluminum alloy is not less than 4:1, for example, 4:1, 5:1, 5.8:1, 6:1, 8:1, 10:1, 12:1, etc., and is not specifically limited. The present invention optimizes the metal elements and their contents in the heat-free aluminum alloy, while further optimizing and controlling the mass ratio of Mn to Cr within the above-mentioned range. This allows for better assurance of the mechanical strength and other properties of the aluminum alloy parts without heat treatment, making it particularly suitable for large, complex die-cast parts.

[0030] According to the present invention, in some embodiments, the mass ratio of Ni to rare earth metal elements in the heat-free aluminum alloy is (2-6):1, for example, 2:1, 3:1, 4:1, 5:1, 6:1, etc. In this invention, while optimizing the metal elements and their content in the heat-free aluminum alloy, the mass ratio of Ni to rare earth metal elements is further optimized and controlled within the above range, which can better balance the elongation and strength of the aluminum alloy. The reason for this is that this ratio range ensures a reasonable distribution and interaction of Ni and rare earth metal elements in the aluminum matrix, which can improve the material's strength and toughness by forming a dispersed and stable strengthening phase, and also reduce the alloy's hot cracking tendency, reducing or eliminating the need for subsequent heat treatment.

[0031] According to some embodiments of the present invention, the content of unavoidable impurity elements in the heat-free aluminum alloy does not exceed 0.25 wt%.

[0032] According to the present invention, since it is difficult to achieve 100% purity in raw materials, and impurities are likely to be introduced during the preparation process, aluminum alloys typically contain unavoidable impurities. The "unavoidable impurity elements" mentioned in this invention refer to impurity components commonly found in aluminum alloys, generally including but not limited to at least one of V, P, Ca, and Zn. Further, in some embodiments, the content of a single unavoidable element impurity in the heat-free aluminum alloy does not exceed 0.05 wt%. Therefore, it can be well ensured that the various properties of the aluminum alloy meet the requirements and will not have a negative impact on the aluminum alloy.

[0033] Furthermore, a second aspect of the present invention provides a method for preparing a heat-free aluminum alloy, used to prepare the heat-free aluminum alloy described in the first aspect of the present invention, comprising the following steps: Aluminum-containing raw materials, nickel-containing raw materials, boron-containing raw materials, titanium-containing raw materials, copper-containing raw materials, manganese-containing raw materials, chromium-containing raw materials, zirconium-containing raw materials, rare earth metal-containing raw materials, silicon-containing raw materials, magnesium-containing raw materials, and strontium-containing raw materials are heated and melted to obtain aluminum alloy liquid; the aluminum alloy liquid is refined to obtain heat-free aluminum alloy.

[0034] The preparation method of this invention can produce heat-free aluminum alloys with excellent mechanical and die-casting properties.

[0035] In addition, the alloy composition design of the aluminum alloy in this invention can reduce the overall cycle time of the preparation method of this invention by 10-15s, and the die casting of the heat-free aluminum alloy obtained can directly obtain the required mechanical properties without a long and expensive heat treatment process after casting. This can directly eliminate the heat treatment process that takes several hours in the traditional process, and reduce the cycle time to 100s compared with the traditional one-piece die casting process (120s-180s).

[0036] In addition, the raw materials of general heat-free aluminum alloys usually contain iron, which means that the final aluminum alloy will contain iron. If it is not enough, it can be supplemented. Here, Al-Fe master alloy is supplemented.

[0037] According to some embodiments of the present invention, the method for preparing the heat-free aluminum alloy includes the following steps: (1) After heating and melting the aluminum-containing raw material, the nickel-containing raw material, the boron-containing raw material, the titanium-containing raw material, the copper-containing raw material, the manganese-containing raw material, the chromium-containing raw material, the zirconium-containing raw material, the rare earth metal-containing raw material and the silicon-containing raw material are added and then heated and melted to obtain the first aluminum alloy melt; (2) Add magnesium-containing raw materials to the first aluminum alloy melt for first melting, and then add strontium-containing raw materials for second melting to obtain a second aluminum alloy melt; (3) The second aluminum alloy melt is refined to obtain a heat-free aluminum alloy.

[0038] According to the present invention, in some embodiments, in step (1), the heating and melting temperature is 745℃-765℃, for example 745℃, 750℃, 755℃, 760℃, 765℃, etc., and there is no specific limitation.

[0039] According to the present invention, in some embodiments, in step (2), the temperature of the first melting is 680℃-700℃, for example, 680℃, 685℃, 690℃, 695℃, 700℃, etc., and there is no specific limitation. That is, after obtaining the first aluminum alloy liquid, the temperature is cooled to 680℃-700℃ and then magnesium-containing raw materials are added for the first melting.

[0040] According to the present invention, in some embodiments, in step (2), the temperature of the second melting is 700℃-730℃, for example, 700℃, 705℃, 710℃, 715℃, 720℃, 725℃, 730℃, etc., and there is no specific limitation. That is, after the first melting is completed, the temperature is raised to 700℃-730℃ and strontium-containing raw materials are added for the second melting.

[0041] According to the present invention, in some embodiments, in step (3), the refining method includes: using a rotary jetting device to introduce Ar with refining agent into the second aluminum alloy melt for powder refining, slag removal and degassing.

[0042] According to the present invention, the refining agent can be any refining agent known in the art. In some embodiments, the refining agent includes, but is not limited to, magnesium chloride and / or calcium chloride. Further, in some embodiments, the mass of the refining agent is 0.05%-0.1% of the mass of the second aluminum alloy melt, for example, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, etc., and there is no specific limitation.

[0043] According to the present invention, in some embodiments, the conditions for the above-mentioned powder spraying refining include: a rotation speed of 300 r / min-500 r / min (e.g., 300 r / min, 400 r / min, 500 r / min), an argon pressure of 0.25 ± 0.05 MPa, and a time of 8-15 minutes (e.g., 8 minutes, 10 minutes, 12 minutes, 15 minutes).

[0044] According to the present invention, the above-mentioned method for removing slag and gas is a means well known to those skilled in the art, such as removing slag after standing for 10-15 minutes after refining.

[0045] After refining, the alloy can be poured into an alloy mold to form an alloy ingot, and then the required aluminum alloy structural parts can be obtained through conventional die casting.

[0046] According to the present invention, the density equivalent of aluminum alloy must be <2% and the K-mold value must be <0.1 before die casting; furthermore, it is generally kept at 690℃-710℃ (e.g., 690℃, 695℃, 700℃, 705℃, 710℃) before die casting.

[0047] According to the present invention, in some embodiments, the die-casting conditions include: an injection speed of 3 m / s-6 m / s, a release agent to water ratio of 1:(20-100), a mold temperature of 180℃-240℃, a spot cooling temperature of 5℃-15℃, and a casting pressure of 25 MPa-80 MPa. The aforementioned release agent is any well-known release agent in the art.

[0048] According to the present invention, in preparing heat-free aluminum alloys, to avoid gas absorption, it is necessary to ensure that the raw materials are free of moisture. This can be achieved by preheating and drying the raw materials. The preheating and drying methods are conventional in the art, typically with a preheating temperature of 150℃-200℃. Specifically, aluminum-containing, nickel-containing, boron-containing, titanium-containing, copper-containing, manganese-containing, chromium-containing, zirconium-containing, rare earth metal-containing, silicon-containing, magnesium-containing, and strontium-containing raw materials are preheated and dried at 150℃-200℃ to ensure the alloy is free of moisture before use.

[0049] According to the present invention, there are no special restrictions on the sources of the above-mentioned raw materials, and they can be flexibly selected according to actual needs. For example, aluminum-containing raw materials and silicon-containing raw materials can be provided in the form of pure Al and pure Si, while nickel-containing raw materials, boron-containing raw materials, titanium-containing raw materials, copper-containing raw materials, manganese-containing raw materials, chromium-containing raw materials, zirconium-containing raw materials, rare earth metal-containing raw materials, magnesium-containing raw materials, and strontium-containing raw materials can be provided in the form of elements or master alloys. Specifically, in some embodiments, aluminum-containing raw materials include pure Al, silicon-containing raw materials include pure Si, nickel-containing raw materials include Al-Ni master alloys, boron-containing and titanium-containing raw materials include Al-Ti-B master alloys, copper-containing raw materials include Al-Cu master alloys, manganese-containing raw materials include Al-Mn master alloys, chromium-containing raw materials include Al-Cr master alloys, zirconium-containing raw materials include Al-Zr master alloys, rare earth metal-containing raw materials include aluminum-rare earth element master alloys (e.g., Al-10Ce master alloys, Al-10La master alloys), magnesium-containing raw materials include Al-50Mg master alloys, and strontium-containing raw materials include Al-10Sr master alloys.

[0050] Specifically, the preparation method of the above-mentioned heat-free aluminum alloy includes the following steps: (1) Prepare the required raw materials: pure Al, pure Si, Al-Ni master alloy, Al-Ti-B master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Cr master alloy, Al-Zr master alloy, Al-10Ce master alloy, Al-10La master alloy, Al-50Mg master alloy, and Al-10Sr master alloy. Preheat and dry them in a drying oven at 150℃-200℃ to ensure that the raw material alloys are free of moisture. (2) After the pure Al is melted by heating to 745℃-765℃ for the first time, Al-Ni master alloy, Al-Ti-B master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Cr master alloy, Al-Zr master alloy, Al-10Ce master alloy, Al-10La master alloy and pure Si are added and heated to continue melting to obtain the first aluminum alloy melt; (3) After the first aluminum alloy melt cools down to 680℃-700℃, the Al-50Mg master alloy is pressed into the bottom of the melt to melt. After it is completely melted, the alloy melt is heated to 700℃-730℃, and the Al-10Sr master alloy is pressed into the bottom of the melt to melt, thus obtaining the second aluminum alloy melt. (4) Using a rotary jetting device, Ar with refining agent is introduced into the second aluminum alloy melt for powder spraying refining, slag removal and degassing. The rotation speed is 300r / min-500r / min, the argon pressure is 0.25±0.05MPa, the time is 8-15 minutes, and the mass of the refining agent is 0.05%-0.1% of the mass of the second aluminum alloy melt. After the powder spraying refining is completed, the melt is allowed to stand for 10-15 minutes and then the slag is removed to obtain the refined melt. After complete melting, the melt is allowed to stand for 10-15 minutes and then the temperature of the melt is reduced to 690℃-710℃ and kept at that temperature to obtain aluminum alloy liquid. (5) The molten aluminum alloy is poured into an alloy mold to form an alloy ingot, and then die-cast to obtain a surface-heat-treated aluminum alloy product; wherein, the die-casting conditions include: injection speed of 3m / s-6m / s, release agent to water ratio of 1:(20-100), mold temperature of 180℃-240℃, spot cooling temperature of 5℃-15℃, and casting pressure of 25MPa-80MPa. The aforementioned release agent is any well-known release agent in the art.

[0051] The present invention will be described in detail below through embodiments. Unless otherwise specified, the instruments, reagents, and materials involved in the following embodiments are all conventional instruments, reagents, and materials that can be obtained through legitimate commercial channels.

[0052] Example 1 After the batching calculation, each standard intermediate alloy and elemental metal are weighed by weight, and then ingots are obtained according to the aluminum alloy preparation method provided below. The mass content of the main elements of the die-cast aluminum alloy products is shown in Table 1.

[0053] Preparation of aluminum alloy products: (1) Prepare the required raw materials: pure Al, pure Si, Al-Ni master alloy, Al-Ti-B master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Cr master alloy, Al-Zr master alloy, Al-10Ce master alloy, Al-10La master alloy, Al-50Mg master alloy, and Al-10Sr master alloy. Preheat and dry them in a 180℃ drying oven to ensure that the raw material alloys are free of moisture. (2) After the pure Al is melted by heating to 750℃ for the first time, Al-Ni master alloy, Al-Ti-B master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Cr master alloy, Al-Zr master alloy, Al-10Ce master alloy, Al-10La master alloy and pure Si are added and heated to continue melting to obtain the first aluminum alloy melt. (3) After the first aluminum alloy melt cools down to 590°C, the Al-50Mg master alloy is pressed into the bottom of the melt to melt. After it is completely melted, the alloy melt is heated to 720°C, and the Al-10Sr master alloy is pressed into the bottom of the melt to melt, thus obtaining the second aluminum alloy melt. (4) Using a rotary jetting device, Ar with refining agent is introduced into the second aluminum alloy melt for powder spraying refining, slag removal and degassing. The rotation speed is 400 r / min, the argon pressure is 0.25 MPa, the time is 15 minutes, and the mass of the refining agent is 0.05% of the mass of the second aluminum alloy melt. After the powder spraying refining is completed, the melt is allowed to stand for 15 minutes and then the slag is removed to obtain the refined melt. After complete melting, the melt is allowed to stand for 10 minutes and then the temperature of the melt is reduced to 690℃ and kept at that temperature to obtain aluminum alloy liquid. (5) Pour the aluminum alloy liquid into the alloy mold to form an alloy ingot, and then perform die casting to obtain surface heat-treated aluminum alloy products; wherein, the die casting conditions include: injection speed of 4m / s, release agent to water ratio of 1:50, mold temperature of 220℃, spot cooling temperature of 10℃, and casting pressure of 28MPa.

[0054] Examples 2-5, Comparative Examples 1-5 After calculating the ingredients, each standard intermediate alloy and elemental metal were weighed by weight, and then ingots were obtained according to the aluminum alloy preparation method provided in Example 1. The aluminum alloy products corresponding to Examples 2-5 and Comparative Examples 1-5 were obtained by die casting. The mass content of the main elements is shown in Table 1.

[0055] Table 1 In Table 1, the remaining elements are unavoidable impurity elements and the balance aluminum. In Examples 1-5, the total content of unavoidable impurity elements does not exceed 0.25 wt%.

[0056] Performance testing Mechanical property testing: The tensile strength, yield strength and elongation of the die-cast aluminum alloy products in Examples 1-5 and Comparative Examples 1-5 were tested in accordance with GB / T 228.1-2010 Metallic Materials Tensile Testing Part 1: Room Temperature Test Method.

[0057] The die-cast aluminum alloy products from Examples 1-5 and Comparative Examples 1-5 were treated at 150°C for 1000 hours, and their tensile strength, yield strength, and elongation were tested according to the mechanical property testing methods described above.

[0058] The properties of Silafont-36 and Castasil-37 alloys are taken from the properties provided on the official website of the material.

[0059] The specific results are shown in Table 2. Table 2 The performance test results above show that the tensile strength, yield strength, and elongation of the samples prepared by die casting of the aluminum alloy according to the present invention all meet the following requirements: tensile strength ≥ 290 MPa, yield strength ≥ 140 MPa, and elongation ≥ 12%. In Comparative Example 1, when the Si and Mg contents are low, although the elongation of the aluminum alloy sample does not change significantly compared to the example, its strength decreases. Compared to Comparative Example 1, Comparative Example 2 shows an increase in strength with increasing Mg content, but the elongation shows a decreasing trend. In Comparative Example 3, excessive Fe content leads to a significant decrease in both strength and elongation. Therefore, under these conditions, the aluminum alloy sample has the lowest mechanical properties, with a tensile strength of 247.8 MPa, a yield strength of 128.2 MPa, and an elongation of 8.7%. In Comparative Example 4, the elongation of the aluminum alloy sample decreased to 10.8%, indicating that the tensile strength of the sample prepared by die casting of the present invention is lower than that of the example. In the invention system, a low Si / Ni ratio (Si / Ni=7.2) carries the risk of increasing brittle phases. Although the aluminum alloy of Comparative Example 5 has a high elongation, elongation is not the core guarantee of product strength and safety, and it is difficult to meet the requirements of load-bearing structural components. Compared with Comparative Example 5, the aluminum alloy of the present invention significantly improves the overall strength (especially the yield strength) while maintaining the elongation that fully meets the requirements of structural components. This directly determines the load-bearing capacity and initial deformation threshold of the structure under load. At the same time, the production cost of the present invention is lower than that of Comparative Example 5. That is, the aluminum alloy of the present invention has both performance advantages and economic benefits.

[0060] Furthermore, according to embodiments of the present invention, in the alloy system of the present invention, rare earth elements (La, Ce) combined with Ni can better increase the strength of the alloy, and further combined with components such as Si can weaken the problem of reduced elongation caused by possible strengthening phase alloys in the system. By increasing the fluidity of the alloy, it is ensured that the alloy has low macroscopic defects. That is, by controlling the various components and their contents of the aluminum alloy within the scope of the present invention, and further controlling the proportion of some elements in the alloy, the comprehensive mechanical properties of the aluminum alloy can be better guaranteed.

[0061] A comparison of performance before and after long-term heat exposure testing (150℃×1000h) shows that the aluminum alloy of this invention exhibits significantly higher thermal stability and mechanical properties, especially strength and elongation, compared to traditional alloys Silafont-36 and Castasil-37. Furthermore, the overall mechanical properties and performance after long-term heat exposure testing (150℃×1000h) of this invention are superior to the comparative example. For instance, in the embodiments of this invention, after long-term heat exposure testing (150℃×1000h), the tensile strength increased by approximately 0.87% to 1.96%, the yield strength increased by approximately 4.8% to 5.5%, and the elongation decreased by approximately 1.6% to 8.5%. In contrast, in the comparative example, after long-term heat exposure testing (150℃×1000h), the tensile strength increased by -2% to 3.5%, the yield strength increased by approximately 2% to 8%, and the elongation decreased by approximately 2% to 20%.

Claims

1. A heat-treat-free aluminum alloy characterized by, The heat treatment-free aluminum alloy contains, based on the total mass of the heat treatment-free aluminum alloy, 7wt%-10wt% of Si, 0.1wt%-1wt% of Ni, 0.4wt%-0.7wt% of Mn, 0.25wt%-0.5wt% of Mg, 0.08wt%-0.2wt% of Fe, 0.02wt%-0.1wt% of Cr, 0.1wt%-0.2wt% of Cu, 0.001wt%-0.05wt% of Zr, 0.08wt%-0.15wt% of Ti, 0.015wt%-0.03wt% of B, 0.005wt%-0.025wt% of Sr, 0.03wt%-0.3wt% of rare earth metal elements, and the rest of aluminum and inevitable impurity elements.

2. The heat treatment free aluminum alloy of claim 1, wherein, The rare earth metal elements include La and / or Ce.

3. The heat treatment free aluminum alloy of claim 2, wherein, The rare earth metal elements include La and Ce, and the mass ratio of La to Ce in the heat treatment-free aluminum alloy is 1:(2-4).

4. The heat treatment free aluminum alloy of claim 1, wherein, The mass ratio of Si to Ni in the heat treatment-free aluminum alloy is greater than 10:

1. The mass ratio of Mn to Cr in the heat treatment-free aluminum alloy is not less than 4:

1. The mass ratio of Ni to the rare earth metal elements in the heat treatment-free aluminum alloy is (2-6):

1.

5. The heat treatment free aluminum alloy according to any one of claims 1-4, wherein, The content of the inevitable impurity elements in the heat treatment-free aluminum alloy is not more than 0.25wt%. The inevitable impurity elements include at least one of V, P, Ca and Zn. The content of a single inevitable element impurity in the heat treatment-free aluminum alloy is not more than 0.05wt%.

6. A method of producing the heat-treatable aluminium alloy according to any one of claims 1 to 5, characterised in that, The method comprises the following steps: The aluminum-containing raw material, the nickel-containing raw material, the boron-containing raw material, the titanium-containing raw material, the copper-containing raw material, the manganese-containing raw material, the chromium-containing raw material, the zirconium-containing raw material, the rare earth metal-containing raw material, the silicon-containing raw material, the magnesium-containing raw material and the strontium-containing raw material are heated and melted to obtain an aluminum alloy liquid; the aluminum alloy liquid is refined to obtain the heat treatment-free aluminum alloy.

7. The method of producing a heat-treatable aluminium alloy according to claim 6, c h a r a c t e r i s e d i n t h a t The method for preparing the heat treatment-free aluminum alloy comprises the following steps: (1) the aluminum-containing raw material is heated and melted, and then the nickel-containing raw material, the boron-containing raw material, the titanium-containing raw material, the copper-containing raw material, the manganese-containing raw material, the chromium-containing raw material, the zirconium-containing raw material, the rare earth metal-containing raw material and the silicon-containing raw material are added and continuously heated and melted to obtain a first aluminum alloy melt; (2) the magnesium-containing raw material is added to the first aluminum alloy melt for first melting, and then the strontium-containing raw material is added for second melting to obtain a second aluminum alloy melt; (3) the second aluminum alloy melt is refined to obtain the heat treatment-free aluminum alloy.

8. The method of producing a heat-treatable aluminium alloy according to claim 7, c h a r a c t e r i s e d i n t h a t In step (1), the temperature for heating and melting is 745°C-765°C; In step (2), the temperature for the first melting is 680°C-700°C; In step (2), the temperature for the second melting is 700°C-730°C; In step (3), the refining method comprises: using a rotary spraying device to introduce Ar with a refining agent into the second aluminum alloy melt for powder spraying refining, deslagging and degassing.

9. The method of producing a heat-treatable aluminium alloy according to claim 8, c h a r a c t e r i s e d i n t h a t The refining agent comprises magnesium chloride and / or calcium chloride. And / or, the mass of the refining agent is 0.05%-0.1% of the mass of the second aluminum alloy melt; The conditions of the powder injection refining include: the rotating speed is 300r / min-500r / min, the argon pressure is 0.25±0.05MPa, and the time is 8-15 minutes.

10. The method of producing a heat-treatable aluminium alloy according to any one of claims 6 to 9, c h a r a c t e r i s e d i n t h a t The aluminum-containing raw material includes pure Al, the silicon-containing raw material includes pure Si, the nickel-containing raw material includes Al-Ni intermediate alloy, the boron-containing raw material and the titanium-containing raw material include Al-Ti-B intermediate alloy, the copper-containing raw material includes Al-Cu intermediate alloy, the manganese-containing raw material includes Al-Mn intermediate alloy, the chromium-containing raw material includes Al-Cr intermediate alloy, the zirconium-containing raw material includes Al-Zr intermediate alloy, the rare earth metal-containing raw material includes aluminum-rare earth element intermediate alloy, the magnesium-containing raw material includes Al-50Mg intermediate alloy, and the strontium-containing raw material includes Al-10Sr intermediate alloy.

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