High-performance heat-treatment-free recoverable gravity or low-pressure casting aluminum alloy and manufacturing method

Abstract

The invention discloses a high-performance heat-treatment-free recoverable gravity or low-pressure casting aluminum alloy and a manufacturing method thereof. The aluminum alloy comprises the following elements in percentage by mass: 3-10wt% of Zn; 0.25 to 3 wt% of Mg; 0.5 to 3 wt% of Ca; si: 0.05 to 2 wt%; fe: 0.05 to 2 wt%; not more than 0.15 wt% of unavoidable inclusions; and the balance of Al; the gravity / low-pressure casting as-cast state yield strength of the alloy is larger than or equal to 210 MPa, the tensile strength is larger than or equal to 280 MPa, the ductility is larger than or equal to 5%, the mechanical property of an industrial A356 cast aluminum alloy T6 in a heat treatment state is achieved, high-performance components can be manufactured without heat treatment, energy conservation and cost reduction benefits are remarkable, meanwhile, the alloy has the high-speed rail tolerance limit and recoverability, and the production cost is reduced. And the method has a huge application prospect in lightweight, green and low-cost manufacturing of key structural parts in the fields of automobiles and aviation.

Description

Technical Field

[0001] The invention relates to the technical field of metal casting, and in particular to a high-performance heat-treatment-free recyclable gravity or low-pressure casting aluminum alloy and a manufacturing method thereof. Background Art

[0002] Aluminum alloys have been widely used in many fields such as automobile industry, aerospace, communication electronics, mechanical equipment and construction due to their low density, high strength, excellent thermal conductivity, strong corrosion resistance, easy processing and recycling. Especially in the automotive field, aluminum alloys have been widely used in the automotive field since the 1970s and have become a key material for lightweight automobiles.

[0003] In recent years, as the cost pressure of automobile parts manufacturing in the automotive industry continues to increase, high-performance gravity / low-pressure cast aluminum alloy automobile parts are developing in the direction of economy and low cost. At present, gravity / low-pressure cast aluminum alloy automobile parts must undergo heat treatment to improve performance. However, the heat treatment process requires a large amount of energy and time costs, generally accounting for more than 20% of the manufacturing cost of automobile parts. In order to reduce manufacturing costs and achieve green manufacturing, the development of high-performance heat-free green recyclable aluminum alloys is imminent. In addition, heat-free aluminum alloy components do not require long-term high-temperature heat treatment, effectively avoiding high-temperature heat treatment deformation, and can manufacture medium and large thin-walled metal components, which has great application prospects.

[0004] Since 2020, the integrated high-pressure die-casting of large, lightweight, thin-walled components is leading the fourth revolution in automobile manufacturing technology. However, large, lightweight, thin-walled components have the problem of difficult-to-control deformation during heat treatment, especially high-temperature solution heat treatment, which has driven the integrated high-pressure die-casting field to begin using heat-treatment-free alloys to solve this problem. At present, heat-treatment-free high-pressure die-casting aluminum alloys are mainly Al-Si-Mg and Al-Mg-Si aluminum alloys. Under the high cooling rate of 500-1000K / s in high-pressure die-casting, the grains and phase structure are fine, and the solid solution strengthening effect is strong. Among them, the yield strength of Al-Si-Mg heat-treatment-free high-pressure die-casting aluminum alloys can reach 120-150MPa, and the yield strength of Al-Mg-Si heat-treatment-free high-pressure die-casting aluminum alloys can reach 150-180MPa. However, in the field of gravity / low-pressure casting, there has not yet been a successful development and application of high-strength heat-treatment-free gravity / low-pressure casting aluminum alloys. Due to the low cooling rate during gravity / low-pressure casting, which is usually 0.5-10K / s, the grain size and phase structure of the casting are coarse, the solid solution strengthening effect is poor, and the casting defect rate is high. If it is not heat treated, the casting mechanical properties are poor, especially the strength is low, and it is difficult to meet the performance requirements. For example, the existing automotive parts subframe is made of A356 aluminum alloy through low-pressure casting and subsequent T6 heat treatment strengthening. Its yield strength is about 210MPa, tensile strength is about 280MPa, and elongation is about 5%; if it is not heat treated, its cast yield strength is only about 105MPa, and the tensile strength is only about 200MPa. The strength is significantly lower than the T6 heat treatment state, and the yield strength is only half of the T6 heat treatment state, which cannot meet the performance requirements. At the same time, the brittle Fe phase structure formed under the low cooling rate of about 0.5-10K / s in gravity / low pressure casting is coarse, which makes the tolerance limit of existing gravity / low pressure casting aluminum alloys to Fe elements low, generally less than 0.15wt%, resulting in the inability to recycle existing gravity / low pressure casting aluminum alloys and making it difficult to adapt to the development trend of green manufacturing. Therefore, it is urgent to develop a high-performance heat-free green recyclable gravity / low pressure casting aluminum alloy system to fill the gap in the application of high-performance heat-free green recyclable aluminum alloys in the field of gravity / low pressure casting, while significantly reducing manufacturing costs.

[0005] It should be pointed out that high pressure die casting and gravity / low pressure casting are different casting processes; there is a significant difference in the cooling rate between the two, and the cooling rate of high pressure die casting is about 2 orders of magnitude higher than that of gravity / low pressure casting; and the alloy composition of the two is different. High pressure die casting aluminum alloy must contain a higher content of about 0.6wt% of Mn element to prevent the alloy from sticking to the mold under high pressure, and gravity / low pressure casting aluminum alloy usually contains a lower content of about 0.1wt% of Mn to reduce the formation of brittle Fe phase. The existing publicly available heat-treatment-free aluminum alloy is a high pressure die casting aluminum alloy, and the alloy system is mainly Al-Si-Mg and Al-Mg-Si system. For Al-Si-Mg system heat-treatment-free high-pressure die-casting aluminum alloy, invention patent CN 117488145A discloses an Al-Si-Mg system heat-treatment-free high-pressure die-casting aluminum alloy, wherein the main components range are: Si: 6%-11%, Mg: 0.1%-0.8%, Mn: 0.2%-0.8%; invention patent CN117026023A discloses an Al-Si-Mg system heat-treatment-free high-strength and high-toughness high-pressure die-casting aluminum alloy, wherein the main components range are: Si: 8.2-10.5 wt%; Mg: 0.5-2.0 wt%; Cu: 1.4-3.2 wt%; Mn: 0.3-1.0wt%. For Al-Mg-Si system heat-treatment-free high-pressure die-casting aluminum alloy, invention patent CN118600290A discloses an Al-Mg-Si system heat-treatment-free high-pressure die-casting aluminum-magnesium-silicon alloy based on recycled materials, wherein the main components range from Mg: 4.5-6.5%, Si: 2.0-3.0%, Mn: 0.6-0.9%; invention patent CN118563183A discloses an Al-Mg-Si system heat-treatment-free aluminum alloy suitable for high-pressure die-casting, wherein the main components range from Mg: 4% to 6%, Si: 0.5% to 2%. However, the existing Al-Si-Mg and Al-Mg-Si system high pressure die casting heat-free aluminum alloys have coarse grain size and poor performance under the low cooling rate conditions of gravity / low pressure casting, which cannot meet the performance requirements. Therefore, Al-Si-Mg and Al-Mg-Si system high pressure die casting heat-free aluminum alloys cannot be applied to gravity / low pressure casting, resulting in the lack of gravity / low pressure casting heat-free aluminum alloys. Therefore, it is urgent to develop a new heat-free gravity / low pressure casting aluminum alloy that is different from the existing Al-Si-Mg and Al-Mg-Si system heat-free high pressure die casting aluminum alloys to meet the performance requirements.

[0006] In summary, it is imperative to develop high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloys and manufacturing methods with cast yield strength ≥210MPa, tensile strength ≥280MPa, and elongation ≥5%. Summary of the invention

[0007] In order to solve the defects and shortcomings in the above-mentioned prior art, the present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: High-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy, characterized in that the mass percentage of each element in the aluminum alloy satisfies: Zn: 3-10 wt %; Mg: 0.25-3 wt %; Ca: 0.5-3 wt %; Si: 0.05-2 wt %; Fe: 0.05-2 wt %; Unavoidable inclusions not exceeding 0.15 wt%; and the balance Al.

[0009] As a further preferred embodiment of the present invention, the mass percentage of each element in the aluminum alloy satisfies: Zn: 3-8 wt %; Mg: 0.5-2.5 wt %; Ca: 0.5-2.5 wt %; Si: 0.05-2 wt %; Fe: 0.15-1.5 wt %; Unavoidable inclusions not exceeding 0.15 wt %; and the balance Al.

[0010] As a further preferred embodiment of the present invention, the mass percentage of each element in the aluminum alloy satisfies: Zn: 4-8 wt %; Mg: 0.75-2.25 wt %; Ca: 0.5-2 wt %; Si: 0.25-1.75 wt %; Fe: 0.25-1 wt %; Unavoidable inclusions not exceeding 0.15 wt %; and the balance Al.

[0011] As a further preferred embodiment of the present invention, the mass percentage of each element in the aluminum alloy satisfies: Zn: 5-8 wt %; Mg: 1-2 wt %; Ca: 0.5-1.5 wt %; Si: 0.5-1.5 wt %; Fe: 0.45-0.8 wt %; Unavoidable inclusions not exceeding 0.15wt%; and the balance Al.

[0012] As a further preferred embodiment of the present invention, the mass percentage of each element in the aluminum alloy satisfies: the ratio of the sum of the masses of Zn and Mg to the sum of the masses of Ca, Si and Fe is in the range of 7:3 to 8:1.

[0013] As a further preferred embodiment of the present invention, the mass percentage of each element in the aluminum alloy satisfies: the ratio of the sum of the masses of Ca and Si to the mass of Fe is in the range of 1.5:1 to 6:1.

[0014] As a further preferred embodiment of the present invention, in the aluminum alloy, The raw materials for providing Al, Mg and Zn elements are in the form of pure metal blocks; The raw materials for providing the Ca, Si and Fe elements are in the form of Al-Ca master alloy, Al-Si master alloy and Al-Fe master alloy respectively.

[0015] Furthermore, the present invention also provides a method for manufacturing a high-performance heat-treatment-free and recyclable gravity or low-pressure cast aluminum alloy, which is characterized by comprising the following steps: Step S1: weighing a pure metal block of Al according to a stoichiometric ratio, and smelting it at 700-730° C. for 0.5-3 h to form an Al melt; Step S2: weighing pure metal blocks of Mg and Zn according to a stoichiometric ratio, and selecting Al-Ca master alloy, Al-Fe master alloy and Al-Si master alloy according to a stoichiometric ratio, and adding them to the Al melt obtained in step S1 to obtain a prefabricated Al alloy melt; Step S3: heating the prefabricated Al alloy melt obtained in step S2 to 740-770° C. and refining the prefabricated Al alloy melt for 5-25 min under a refining agent condition to remove gas and inclusions in the prefabricated Al alloy melt to obtain a purified Al alloy melt; Step S4: The purified Al alloy melt obtained in step S3 is subjected to gravity or low-pressure casting to obtain a high-performance, heat-treatment-free, green, recyclable cast aluminum alloy in a cast state.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention include: 1) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method, which can manufacture high-performance gravity / low-pressure cast aluminum alloy components with cast yield strength ≥210MPa, tensile strength ≥280MPa, and elongation ≥5% without heat treatment, and has significant energy-saving and cost-reduction benefits. At the same time, the alloy has a high Fe tolerance limit (≥0.45wt%Fe), thereby breaking through recyclability, and is suitable for lightweight, low-cost and green manufacturing of key structural parts in key fields such as automobiles, aerospace, etc.

[0017] 2) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method, which improves the casting performance and cast mechanical properties of the gravity / low-pressure cast aluminum alloy by using the composite addition of Zn, Mg, Ca, Si, and Fe elements, and breaks through the Fe tolerance limit and recyclability of the gravity / low-pressure cast aluminum alloy.

[0018] 3) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method. The composite addition of Zn and Mg elements improves the fluidity of the alloy and the solid solution strengthening effect of the alloy. At the same time, Al-Zn-Mg and Mg-Zn compound phases are formed on the grain boundaries to enhance the second phase strengthening effect and improve the corrosion resistance of the alloy.

[0019] 4) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method, which induces the in-situ precipitation of Al-Ca-Fe heterogeneous nucleation particles through the composite addition of Ca and Fe elements to refine the α-Al grains, inhibit the formation of coarse columnar crystals, refine the grains, improve the shrinkage cavities, shrinkage porosity, thermal cracking and other defects of the alloy, and synergistically improve the casting performance, strength and toughness of the alloy.

[0020] 5) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method. A low initial crystallization temperature Al-Zn-Si-Ca phase is formed by the composite addition of Zn, Si and Ca elements, and the effective solidification and crystallization temperature range of the alloy is reduced to 45 ºC, which is about 30% lower than the effective solidification and crystallization temperature range of 62 ºC of the existing gravity / low-pressure cast aluminum alloy. The shrinkage cavity, shrinkage porosity, thermal cracking and other defects of the alloy are significantly improved, the casting performance of the alloy is improved, and the second phase strengthening effect and toughness of the alloy are improved.

[0021] 6) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method. The existing gravity or low-pressure cast aluminum alloy adopts the addition of Mn elements to reduce the formation of long flake-shaped brittle Fe phases, which is effective when the Fe content is low (≤0.15wt%), but it is difficult to effectively reduce the formation of long flake-shaped brittle Fe phases when the Fe content is ≥0.25wt%, resulting in the inability to recycle the existing gravity / low-pressure cast aluminum alloys. Different from the existing gravity / low-pressure cast aluminum alloys, the alloy of the present invention does not add Mn elements, nor does it add Sr elements that must be added to the existing heat-treatment-free high-pressure die-cast aluminum alloys, especially Al-Si-Mg series treatment-free high-pressure die-cast aluminum alloys, and does not add Cr, Mo, V, rare earth and other precious metal elements that are often added to the existing heat-treatment-free high-pressure die-cast aluminum alloys. Through Ca, Si The composite addition of Al-Ca-Si-Fe and Fe elements forms a short block of non-brittle Al-Ca-Si-Fe phase, completely eliminating the formation of long flake-like coarse brittle Fe phase that is unfavorable to toughness, greatly improving the Fe tolerance limit of the alloy to more than 0.45wt%, breaking through the recyclability of the alloy, and at the same time improving the second phase strengthening effect and toughness of the alloy. In addition, the elimination of long flake-like coarse brittle Fe phase improves the alloy's shrinkage cavities, shrinkage porosity, thermal cracking and other defects, and improves the alloy's casting performance.

[0022] 7) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method. The existing industrially commonly used gravity / low-pressure cast aluminum alloy has a cast yield strength of only about 105MPa and a tensile strength of only about 200MPa, which cannot achieve heat-treatment-free manufacturing of high-performance gravity / low-pressure cast aluminum alloy components. The high-performance heat-treatment-free green recyclable gravity / low-pressure cast aluminum alloy manufactured by the present invention has a cast yield strength of ≥210MPa, a tensile strength of ≥280MPa, and an elongation of ≥5%, reaching the strength and toughness of the T6 heat-treated state of the A356 gravity / low-pressure cast aluminum alloy widely used in industry, and can achieve heat-treatment-free manufacturing of high-performance gravity / low-pressure cast aluminum alloy components.

[0023] 8) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method. The obtained high-performance heat-treatment-free green recyclable gravity / low-pressure cast aluminum alloy does not require a heat treatment process, and has significant advantages in energy consumption and time costs. At the same time, there is no problem of heat treatment deformation, and it can be used for the manufacture of large and ultra-large components. In addition, the alloy has a high Fe tolerance limit (≥0.45wt%Fe) and recyclability; it can be used for lightweight, low-cost and green manufacturing of large and ultra-large key components in key fields such as automobiles, aerospace, etc., and has great application prospects.

[0024] 9) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure casting aluminum alloy and a manufacturing method. The existing high-pressure die-casting heat-treatment-free aluminum alloy has a cast yield strength of 120-180MPa under the high cooling rate of 500-1000K / s for high-pressure die-casting, while the castings obtained under the low cooling rate of 0.5-10K / s for gravity / low-pressure casting have coarse grains and a cast yield strength significantly lower than 120-180MPa, which cannot meet the performance requirements of a yield strength of ≥210MPa for gravity / low-pressure casting components. Therefore, the existing high-pressure die-casting aluminum alloys that do not require heat treatment cannot be applied to the heat-treatment-free manufacturing of gravity / low-pressure casting components; the alloy of the present invention is a gravity / low-pressure casting aluminum alloy that does not require heat treatment, which is different from the existing high-pressure die-casting aluminum alloys that do not require heat treatment. Under the low cooling rate conditions of gravity / low-pressure casting, the cast yield strength is ≥210MPa, the tensile strength is ≥280MPa, and the elongation is ≥5%, achieving the strength and toughness of the T6 heat-treated state of the A356 gravity / low-pressure casting aluminum alloy widely used in industry, and is suitable for the heat-treatment-free manufacturing of gravity / low-pressure casting components.

[0025] 10) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure casting aluminum alloy and a manufacturing method. The heat-treatment-free gravity / low-pressure casting aluminum alloy obtained by the present invention has an alloy system different from other heat-treatment-free aluminum alloys. The disclosed heat-treatment-free aluminum alloys are mainly Al-Si-Mg and Al-Mg-Si system heat-treatment-free high-pressure die-casting aluminum alloys, the main elements of which are Si or Mg, and Mn is a necessary element to prevent high-pressure die-casting from sticking to the mold. The alloy of the present invention is a novel Al-Zn-(Ca, Mg, Si, Fe) system aluminum alloy, the main element of which is Zn. In addition to Si and Mg contained in the existing heat-treatment-free high-pressure die-casting aluminum alloy, other elements also contain Ca, Si and Fe elements that play a key role in the microstructure and mechanical properties of the alloy of the present invention, and no Mn element is contained; wherein Zn is the main element to ensure the fluidity of the alloy; the composite addition of Ca and Fe elements induces in-situ precipitation of Al-Ca-Fe heterogeneous nucleation particles to refine α-Al grains, inhibits the formation of coarse columnar crystals, refines grains, and improves shrinkage cavities, shrinkage porosity, thermal cracking and other defects of the alloy; the composite addition of Zn, Si and Ca elements forms an Al-Zn-Si-Ca phase with a low initial crystallization temperature, reduces the effective solidification and crystallization temperature range of the alloy to 45°C, which is 62°C lower than the effective solidification and crystallization temperature range of the existing gravity / low-pressure casting aluminum alloy. Compared with the aluminum alloy cast by gravity / low pressure casting, the temperature is reduced by about 30%, which significantly improves the shrinkage cavity, shrinkage porosity, hot cracking and other defects of the alloy, improves the casting performance of the alloy, and at the same time improves the second phase strengthening effect and toughness of the alloy; the composite addition of Ca, Si and Fe elements forms a short block non-brittle Al-Ca-Si-Fe phase, completely eliminates the formation of long flake-like coarse brittle Fe phase that is unfavorable to toughness, and greatly increases the Fe tolerance limit of the alloy to more than 0.45wt%, breaking through the recyclability of gravity / low pressure casting aluminum alloy, and at the same time improves the second phase strengthening effect and toughness of the alloy; in addition, the elimination of long flake-like coarse brittle Fe phase improves the shrinkage cavity, shrinkage porosity, hot cracking and other defects of the alloy, and improves the casting performance of the alloy.

[0026] 11) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method. The heat-treatment-free gravity / low-pressure cast aluminum alloy obtained by the scheme provided by the present invention has a different composition range and composition ratio from the existing heat-treatment-free high-pressure die-cast aluminum alloy. For example, the composition range of the existing heat-treatment-free high-pressure die-cast aluminum alloy includes Si: 6%-11%, Mg: 0.1%-0.8%, Mn: 0.2%-0.8%; Si: 8.2-10.5 wt%; Mg: 0.5-2.0 wt%; Cu: 1.4-3.2 wt%; Mn: 0.3-1.0 wt%; Mg: 4.5-6.5%, Si: 2.0-3.0%, Mn: 0.6-0.9%; Mg: 4%~6%, Si: 0.5% to 2%, etc., while in the alloy of the present invention, Zn: 3-10wt%, Mg: 0.25-3wt%, Ca: 0.5-3wt%, Si: 0.05-2wt%, Fe: 0.05-2wt%, wherein the mass ratio of (Zn+Mg) to (Ca+Si+Fe) is in the range of 7:3 to 8:1, and the mass ratio of (Ca+Si) to Fe is in the range of 1.5:1 to 6:1, and only when the mass ratio of (Zn+Mg) to (Ca+Si+Fe) and the mass ratio of (Ca+Si) to Fe are satisfied can the characteristics and excellent mechanical properties of the gravity / low-pressure casting aluminum alloy with high performance, heat treatment-free, green and recyclable characteristics described in the present invention be achieved.

[0027] 12) The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy and a manufacturing method, which effectively realizes the lightweight, green and low-cost manufacturing of high-performance gravity / low-pressure cast aluminum alloy parts. The present invention adopts the composite addition of Zn, Mg, Ca, Si, and Fe elements to improve the casting performance and cast mechanical properties of gravity / low-pressure cast aluminum alloys, and breaks through the recyclability of gravity / low-pressure cast aluminum alloys. Among them, the composite addition of Zn and Mg elements improves the fluidity of the alloy, improves the solid solution strengthening and second phase strengthening effects of the alloy, and improves the corrosion resistance of the alloy; the composite addition of Ca and Fe elements induces the in-situ precipitation of Al-Ca-Fe heterogeneous nucleation particles to refine the α-Al grains, inhibit the formation of coarse columnar crystals, refine the grains, improve the shrinkage cavities, shrinkage porosity, thermal cracking and other defects of the alloy, and synergistically improves the casting performance, strength and toughness of the alloy; the composite addition of Zn, Si and Ca elements forms a low initial crystallization temperature Al-Zn-Si-Ca phase, which reduces the effective solidification of the alloy The crystallization temperature range improves the defects of the alloy such as shrinkage cavity, shrinkage porosity, and thermal cracking, improves the casting performance of the alloy, and at the same time improves the second phase strengthening effect and toughness of the alloy; in addition, the existing gravity / low-pressure casting aluminum alloy adopts the addition of Mn elements to reduce the formation of long flake-shaped brittle Fe phase, which is effective when the Fe content is low (≤0.15wt%), but it is difficult to effectively reduce the formation of long flake-shaped brittle Fe phase when the Fe content is ≥0.25wt%, resulting in the inability to recycle the existing gravity / low-pressure casting aluminum alloy. Different from the existing gravity / low-pressure casting aluminum alloy, the alloy of the present invention does not add Mn elements, and through Ca, Si The composite addition of the element and Fe forms a short block non-brittle Al-Ca-Si-Fe phase, completely eliminating the formation of the long flake brittle Fe phase that is unfavorable to toughness, greatly improving the Fe tolerance limit of the alloy to more than 0.45wt%, breaking through the recyclability of gravity / low-pressure cast aluminum alloys, and improving the second phase strengthening effect and toughness of the alloy; finally, the alloy of the present invention does not add precious metal elements such as Cr, Mo, V, and rare earth, and the material cost is low. The alloy of the present invention achieves excellent mechanical properties of gravity / low-pressure casting cast yield strength ≥210MPa, tensile strength ≥280MPa, and elongation ≥5%. At the same time, it can manufacture high-performance components without heat treatment, with significant energy-saving and cost-reduction benefits. It has great application prospects in the lightweight, green and low-cost manufacturing of key structural parts in key fields such as new energy vehicles and aerospace. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a diagram showing the intracrystalline solid solution strengthening and grain boundary second phase strengthening effects of the elements Zn, Mg, Ca, Si and Fe in the present invention.

[0029] Figure 2 It is a metallographic diagram of the existing gravity or low-pressure cast aluminum alloy in the cast state, in which the α-Al grains are coarse columnar crystals.

[0030] Figure 3 It is a metallographic phase diagram of the alloy of the present invention in the cast state, in which the α-Al grains are refined equiaxed crystals.

[0031] Figure 4 It is a comparison chart of the difference in effective solidification crystallization temperature range between the alloy of the present invention and the existing gravity or low-pressure casting aluminum alloy.

[0032] Figure 5 The metallographic diagram is of an Al-Zn-Si-Ca phase with a low initial crystallization temperature and a short blocky non-brittle Al-Ca-Si-Fe Fe-containing phase formed by the composite action of adding Ca, Si, Fe and Zn elements in the present invention.

[0033] Figure 6 It is the role of elements in the high-performance heat-treatment-free green recyclable gravity or low-pressure cast aluminum alloy of the present invention and the manufacturing flow chart of the alloy and its components. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings.

[0035] The present invention provides a high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy, wherein the mass percentage of each element in the aluminum alloy satisfies: Zn: 3-10%; Mg: 0.25-3%; Ca: 0.5-3%; Si: 0.05-2%; Fe: 0.05-2%; Unavoidable inclusions not exceeding 0.15%; and the balance Al.

[0036] As a further preference, the mass percentage of each element in the aluminum alloy in this embodiment can be further limited to satisfy: Zn: 3-8%; Mg: 0.5-2.5%; Ca: 0.5-2.5%; Si: 0.05-2%; Fe: 0.15-1.5%; Unavoidable inclusions not exceeding 0.15%; and the balance Al.

[0037] As a further preference, the mass percentage of each element in the aluminum alloy in this embodiment can be further limited to satisfy: Zn: 4-8%; Mg: 0.75-2.25%; Ca: 0.5-2%; Si: 0.25-1.75%; Fe: 0.25-1%; Unavoidable inclusions not exceeding 0.15%; and the balance Al.

[0038] As a further preference, the mass percentage of each element in the aluminum alloy in this embodiment can be further limited to satisfy: Zn: 5-8%; Mg: 1-2%; Ca: 0.5-1.5%; Si: 0.5-1.5%; Fe: 0.45-0.8%; Unavoidable inclusions not exceeding 0.15wt%; and the balance Al.

[0039] In this embodiment, the mass percentage of each element in the aluminum alloy satisfies: the ratio of the sum of the masses of Zn and Mg to the sum of the masses of Ca, Si and Fe is in the range of 7:3 to 8:1, and the mass percentage of each element in the aluminum alloy satisfies: the ratio of the sum of the masses of Ca and Si to the mass of Fe is in the range of 1.5:1 to 6:1. Only by satisfying the above-mentioned range of the mass ratio of (Zn+Mg) to (Ca+Si+Fe) and the range of the mass ratio of (Ca+Si) to Fe can the characteristics and excellent mechanical properties of the gravity / low-pressure cast aluminum alloy with high performance, heat treatment-free, green and recyclable characteristics described in this embodiment be achieved.

[0040] Furthermore, in the raw materials for making the aluminum alloy in this embodiment, The raw materials for providing Al, Mg and Zn elements are in the form of pure metal blocks; The raw materials for providing the Ca, Si and Fe elements are in the form of Al-Ca master alloy, Al-Si master alloy and Al-Fe master alloy respectively.

[0041] The specific role of each element in the aluminum alloy obtained in this application is further explained below in conjunction with the drawings of the present application specification: like Figure 1-3 As shown: Figure 1 This is a diagram showing the effects of solid solution strengthening and second phase strengthening achieved by the elements Zn, Mg, Ca, Si and Fe in the present invention; Figure 2 It is a metallographic diagram of the existing gravity / low-pressure cast aluminum alloy in the cast state, in which the α-Al grains are coarse columnar crystals; Figure 3The metallographic diagram of the alloy of the present invention in the state of casting shows that the α-Al grains are refined equiaxed crystals. A more specific description of the alloy strengthening based on the elements of Zn, Mg, Ca, Si, and Fe is as follows: The addition of Zn and Mg elements can be dissolved in the Al matrix to achieve solid solution strengthening and form Al-Zn-Mg and Mg-Zn compounds on the grain boundaries to achieve the second phase strengthening of the alloy, such as Figure 1 As shown; by adding Ca, Si, and Fe elements to form Al-Zn-Si-Ca and Al-Ca-Si-Fe phases on the grain boundaries, the second phase strengthening of the alloy is enhanced and Al-Ca-Fe heterogeneous nucleation particles are precipitated in situ, as shown Figure 1 As shown, the α-Al grains are refined and the formation of equiaxed grains is promoted, as shown in Figure 2 , 3 As shown, in the existing gravity / low-pressure casting aluminum alloy, there is a fairly wide columnar grain area (~2-5 mm) and large grains (about 2 mm) in the center part. In the alloy of the present invention, a fine grain structure is observed in the cast state, and there are no columnar grains, achieving the α-Al grain refinement strengthening effect, improving the strength and toughness of the alloy. The refinement can also reduce defects such as shrinkage cavities, shrinkage porosity, and thermal cracking, thereby improving the casting performance of the alloy.

[0042] like Figure 4-5 As shown: Figure 4 This is a comparison chart of the difference between the effective solidification and crystallization temperature ranges of the alloy of the present invention and the existing gravity / low-pressure casting aluminum alloy; Figure 5 It is a metallographic diagram of Al-Zn-Si-Ca phase with low initial crystallization temperature and short blocky non-brittle Al-Ca-Si-Fe Fe-containing phase formed by the composite action of Ca, Si, Fe and Zn elements added in the present invention. Based on the composite action of Ca, Si, Fe and Zn elements, the casting performance and mechanical properties of gravity / low-pressure casting aluminum alloy are improved, and the recyclability of gravity / low-pressure casting aluminum alloy is broken through. The more specific description is as follows: The composite addition of Zn, Si and Ca elements forms Al-Zn-Si-Ca phase with low initial crystallization temperature, which reduces the effective solidification crystallization temperature range of the alloy to 45 ºC, which is about 30% lower than the effective solidification crystallization temperature range of 62 ºC of existing gravity / low-pressure casting aluminum alloys. Figure 4 and 5 As shown in the figure, the shrinkage cavity, shrinkage porosity, thermal cracking and other defects of the alloy are significantly improved, the casting performance of the alloy is improved, and the second phase strengthening effect and toughness of the alloy are improved; the composite addition of Ca, Si and Fe elements forms a short block-shaped non-brittle Al-Ca-Si-Fe phase, which completely eliminates the formation of long flake-shaped coarse brittle Fe phase that is unfavorable to toughness, as shown in the figure. Figure 5As shown in the figure, by changing the long lamellar coarse brittle Fe phase into a short block-shaped non-brittle Al-Ca-Si-Fe Fe-containing phase, the Fe tolerance limit of the gravity / low-pressure cast aluminum alloy is greatly improved to more than 0.45wt%, breaking through the recyclability of the gravity / low-pressure cast aluminum alloy, while improving the second phase strengthening effect and toughness of the alloy. In addition, the elimination of the long lamellar coarse brittle Fe phase improves the shrinkage cavity, shrinkage porosity, thermal cracking and other defects of the alloy, and improves the casting performance of the alloy.

[0043] The sources of the raw materials for the provision of the above-mentioned metal elements are as follows: the Al, Mg and Zn raw materials are provided in the form of pure metal blocks; the raw materials of the Ca, Si and Fe are provided in the form of Al-Ca master alloy, Al-Si master alloy and Al-Fe master alloy respectively, and meet the weight percentage requirements of Al, Zn, Mg, Ca, Si and Fe components in the high-performance heat treatment-free green recyclable gravity / low-pressure cast aluminum alloy. The grades of the Al-Ca master alloy, Al-Si master alloy and Al-Fe master alloy can be selected from the corresponding raw material grades in the prior art, as long as the Al master alloy contains the relevant metal elements and meets the weight percentage requirements of each component.

[0044] [Second embodiment] The second embodiment of the present invention further provides a method for manufacturing the high-performance heat-treatment-free and recyclable gravity or low-pressure cast aluminum alloy mentioned in the first embodiment, comprising the following steps: Step S1: weighing a pure metal block of Al according to a stoichiometric ratio, and smelting it at 700-730° C. for 0.5-3 h to form an Al melt; Step S2: weighing pure metal blocks of Mg and Zn according to a stoichiometric ratio, and selecting Al-Ca master alloy, Al-Fe master alloy and Al-Si master alloy according to a stoichiometric ratio, and adding them to the Al melt obtained in step S1 to obtain a prefabricated Al alloy melt; Step S3: heating the prefabricated Al alloy melt obtained in step S2 to 740-770° C. and refining the prefabricated Al alloy melt for 5-25 min under a refining agent condition to remove gas and inclusions in the prefabricated Al alloy melt to obtain a purified Al alloy melt; Step S4: The purified Al alloy melt obtained in step S3 is subjected to gravity or low-pressure casting to obtain a high-performance, heat-treatment-free, green, recyclable cast aluminum alloy in a cast state.

[0045] The following is an introduction to a high-performance heat-treatment-free green recyclable gravity / low-pressure cast aluminum alloy and a manufacturing method thereof according to the present invention, and a specific embodiment and test results are introduced: Take low pressure casting as an example to test the performance of the corresponding alloy composition: Example 1: A heat-treatment-free low-pressure cast aluminum alloy component, the mass percentage of each element in the alloy is (unit: wt%): 5.02Zn, 1.02Mg, 0.75Ca, 0.75Si, 0.52Fe, and the balance is Al; Example 2: A heat-treatment-free low-pressure cast aluminum alloy component, wherein the mass percentage of each element in the alloy is (unit: wt%): 6.03Zn, 1.25Mg, 1.01Ca, 0.98Si, 0.62Fe, and the balance is Al; Example 3: A heat-treatment-free low-pressure cast aluminum alloy component, the mass percentage of each element in the alloy is (unit: wt%): 7.05Zn, 1.51Mg, 1.25Ca, 0.98Si, 0.68Fe, and the balance is Al; Example 4: A heat-treatment-free low-pressure cast aluminum alloy component, wherein the mass percentage of each element in the alloy is (unit: wt%): 8.02Zn, 1.75Mg, 1.45Ca, 1.26Si, 0.75Fe, and the balance is Al; Existing process 1: low-pressure casting of A356 aluminum alloy components without heat treatment, the mass percentage of each element in the alloy is (unit: wt%): 7Si, 0.3Mg, 0.12Fe, 0.08Mn, 0.08Zn, 0.12Ti, and the balance is Al; Existing process 2: T6 heat treatment (540℃ solution treatment for 8 hours + 70℃ hot water quenching + 170℃ artificial aging treatment for 8 hours) low pressure casting A356 aluminum alloy components, the mass percentage of each element in the alloy is (unit wt%): 7Si, 0.3Mg, 0.11Fe, 0.07Mn, 0.09Zn, 0.12Ti, and the balance is Al; Table 1 Low pressure casting tensile properties test table As shown in Table 1, there are the tensile performance test tables of the cast state of Examples 1-4 of the present invention, the existing process 1, and the tensile performance test table of the T6 heat-treated state of the existing process 2. Compared with the existing gravity / low-pressure cast aluminum alloy with a cast performance yield strength of 107 MPa, a tensile strength of 202 MPa, and an elongation of 5.4%, the high-performance heat-treatment-free green recyclable gravity / low-pressure cast aluminum alloy of the present invention has a cast yield strength of ≥210 MPa, a tensile strength of ≥280 MPa, and an elongation of ≥5%. Compared with the existing process 1, the cast yield strength is significantly improved by about one-fold, and the mechanical properties of the existing gravity / low-pressure cast aluminum alloy in the T6 heat-treated state are achieved, and the heat-treatment-free manufacturing of high-performance components can be realized, with significant energy-saving and cost-reduction benefits. At the same time, the alloy has a high iron tolerance limit and recyclability, and is suitable for lightweight, low-cost, and green manufacturing of key structural parts in key fields such as automobiles and aerospace.

[0046] The above describes the basic principles and main features of the present invention. It is particularly noted that for those skilled in the art, the present invention is not limited to the above embodiments, and can be modified and improved without departing from the concept and scope of the present invention. These modifications and improvements belong to the scope of protection claimed by the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. High performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy, characterized by: The mass percentage of each element in the aluminum alloy satisfies: Zn: 3-10wt%; Mg: 0.25-3 wt %; Ca: 0.5-3 wt %; Si: 0.05-2 wt %; Fe: 0.05-2 wt %; Unavoidable inclusions not exceeding 0.15 wt%; and the balance Al.

2. The high-performance heat-treatment-free recyclable gravity or low-pressure cast aluminum alloy according to claim 1, characterized in that: The mass percentage of each element in the aluminum alloy satisfies: Zn: 3-8 wt %; Mg: 0.5-2.5 wt %; Ca: 0.5-2.5 wt %; Si: 0.05-2 wt %; Fe: 0.15-1.5 wt %; Unavoidable inclusions not exceeding 0.15 wt %; and the balance Al.

3. The high performance heat treatment-free recyclable gravity or low pressure casting aluminum alloy according to claim 2, characterized in that: The mass percentage of each element in the aluminum alloy satisfies: Zn: 4-8 wt %; Mg: 0.75-2.25 wt %; Ca: 0.5-2 wt %; Si: 0.25-1.75 wt %; Fe: 0.25-1 wt %; Unavoidable inclusions not exceeding 0.15 wt %; and the balance Al.

4. The high performance heat treatment-free recyclable gravity or low pressure casting aluminum alloy according to claim 3, characterized in that: The mass percentage of each element in the aluminum alloy satisfies: Zn: 5-8 wt %; Mg: 1-2 wt %; Ca: 0.5-1.5 wt %; Si: 0.5-1.5 wt %; Fe: 0.45-0.8 wt %; Unavoidable inclusions not exceeding 0.15wt%; and the balance Al.

5. The high performance heat treatment-free recyclable gravity or low pressure cast aluminum alloy according to any one of claims 1 to 4, characterized in that: The mass percentage of each element in the aluminum alloy satisfies that the ratio of the sum of the mass of Zn and Mg to the sum of the mass of Ca, Si and Fe is in the range of 7:3 to 8:

1.

6. The high performance heat treatment-free recyclable gravity or low pressure cast aluminum alloy according to any one of claims 1 to 4, characterized in that: The mass percentage of each element in the aluminum alloy satisfies that the ratio of the sum of the masses of Ca and Si to the mass of Fe is in the range of 1.5:1 to 6:

1.

7. The high performance heat treatment-free recyclable gravity or low pressure cast aluminum alloy according to any one of claims 1 to 4, characterized in that: In the aluminum alloy, The raw materials for providing Al, Mg and Zn elements are in the form of pure metal blocks; The raw materials for providing the Ca, Si and Fe elements are in the form of Al-Ca master alloy, Al-Si master alloy and Al-Fe master alloy respectively.

8. The method for producing a high-performance heat-treatment-free and recyclable gravity or low-pressure cast aluminum alloy according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1: weighing a pure metal block of Al according to a stoichiometric ratio, and smelting it at 700-730° C. for 0.5-3 h to form an Al melt; Step S2: weighing pure metal blocks of Mg and Zn according to a stoichiometric ratio, and selecting Al-Ca master alloy, Al-Fe master alloy and Al-Si master alloy according to a stoichiometric ratio, and adding them to the Al melt obtained in step S1 to obtain a prefabricated Al alloy melt; Step S3: heating the prefabricated Al alloy melt obtained in step S2 to 740-770° C. and refining the prefabricated Al alloy melt for 5-25 min under a refining agent condition to remove gas and inclusions in the prefabricated Al alloy melt to obtain a purified Al alloy melt; Step S4: The purified Al alloy melt obtained in step S3 is subjected to gravity or low-pressure casting to obtain a high-performance, heat-treatment-free, green, recyclable cast aluminum alloy in a cast state.

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