Cast and weldable near eutectic Al-Fe-Ni aluminum alloy and preparation method thereof

Abstract

The invention discloses a cast and weldable near eutectic Al-Fe-Ni aluminum alloy and a preparation method of the cast and weldable near eutectic Al-Fe-Ni aluminum alloy. The invention discloses a castable and weldable near-eutectic Al-Fe-Ni aluminum alloy which comprises the following components in percentage by mass: 1.0%-2.0% of iron, 1.0%-1.5% of nickel, 0.1%-7.8% of calcium, 0.1%-1.0% of magnesium, 0.1%-1.0% of silicon, 0.1%-3.0% of zinc, 0.1%-1.0% of cerium, 0.1%-1.0% of lanthanum and inevitable impurities 1t. 0.3%, and the balance being aluminum. The castable and weldable aluminum alloy provided by the invention has higher melting point, mechanical property and flowability, and can be suitable for the industries of vacuum brazing, casting molding and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy materials, in particular to a castable and weldable near-eutectic Al-Fe-Ni aluminum alloy and a preparation method thereof. BACKGROUND

[0002] With the strengthening of energy-saving and environmental protection trend, the mechanical properties and high thermal conductivity, high corrosion resistance and other performance requirements of lightweight aluminum structural parts in the field of new energy vehicles and 5G communication are becoming higher and higher. Although the commonly used cast Al-Si alloy has excellent casting performance, its melting point is too low to realize subsequent vacuum brazing, and its thermal conductivity is not enough, so the conventional die-casting Al-Si alloy cannot meet the needs of the project. 6063 aluminum alloy is a wrought aluminum alloy, which has poor casting performance and has a tendency to crack, so it can only be formed by forging or machining, resulting in large machining allowance and low forming efficiency. The above problems need to be solved urgently. SUMMARY

[0003] The present application provides a castable and weldable near-eutectic Al-Fe-Ni aluminum alloy and a preparation method thereof, aiming at the problems of high quality, short process in the processing of complex high-precision aluminum alloy parts, and the problems of high strength, high toughness and high thermal conductivity in lightweight aluminum alloy structural parts. The Al-Fe-Ni aluminum alloy provided by the present application has high melting point, high casting and weldability, and the aluminum alloy can be used for casting and high-temperature brazing.

[0004] The first object of the present application is to provide a castable and weldable near-eutectic Al-Fe-Ni aluminum alloy, which comprises the following components in mass fraction: 1.0%-2.0% of iron, 1.0%-1.5% of nickel, 0.1%-7.8% of calcium, 0.1%-1.0% of magnesium, 0.1%-1.0% of silicon, 0.1%-3.0% of zinc, 0.1%-1.0% of cerium, 0.1%-1.0% of lanthanum, <0.3% of unavoidable impurities, and the balance of aluminum.

[0005] The effects of each component in the present application are as follows:

[0006] For iron and nickel: by adding 1.0%-2.0% of iron, the sticking phenomenon during casting can be reduced, and it can also be added as an alloying element. A small amount of Fe can form Al3Fe intermetallic compounds as heterogeneous nucleation cores, refine the grains and improve the casting performance, but excessive Fe will form coarse needle-like or flaky Al3Fe phases, resulting in a significant decrease in alloy plasticity and toughness. By adding 1.0%-1.5% of nickel, when Fe and Ni exist in the aluminum alloy at the same time, they can form Al9FeNi composite intermetallic compounds, which have stronger nucleation ability and can be used as heterogeneous nucleation cores to refine the grains, and at the same time, the morphology is more uniform, reducing stress concentration and improving the strength of the alloy.

[0007] For magnesium and silicon: 0.1%-1.0% of magnesium is added to the aluminum-iron-nickel alloy to strengthen the alloy. Mg atoms can be dissolved in the Al9FeNi phase edge, improve the interface bonding of the phase and the Al matrix, reduce stress concentration, alleviate the adverse effect of Al9FeNi phase on plasticity, and balance strength and plasticity to some extent. Appropriate amount of Mg can inhibit the coarsening of Al9FeNi phase and promote its distribution in a finer and more uniform form; but excessive Mg (such as >1.2%) is easy to form Mg3Al2 phase with Al, increase the tendency of casting hot crack, and may cause organization segregation. The strengthening phase formed by adding Mg alone is easy to soften above 300°C, and the high-temperature strength retention rate is low. By adding 0.1% to 1% mass fraction of silicon, Al-Si eutectic reaction is promoted, the flowability of the alloy is greatly improved, the casting performance of the alloy is improved, and Mg2Si precipitation strengthening phase can be formed with Mg, which can significantly improve the strength and hardness of the alloy. Appropriate amount of Mg can also inhibit the acicular growth of β phase by promoting Mg2Si precipitation and changing the solidification path, so that the Fe-Si phase tends to be blocky, thereby weakening its negative impact on mechanical properties. At the same time, the addition of Mg and Si can combine with Fe and Ni to form (AlSi)5FeNi phase, improve the morphology of iron-rich phase, and make the iron-rich phase more evenly distributed.

[0008] For calcium: by adding 0.1%-7.8% of calcium, the grain size of α-Al is refined, and high-density Mg2Si and Al2Ca particles are induced to precipitate in the as-cast α-Al grains. At the same time, calcium can affect the morphology of iron-rich phase, making it more fine and uniform, thereby improving the microstructure of the alloy. Due to the refining effect of Ca element on the alloy, the number of grain boundaries increases, hindering the movement of dislocations, so that the strength and toughness of the alloy are improved; on the other hand, the addition of Ca makes the alloy generate uniformly distributed Al2Ca high-melting-point compounds, which not only increases the melting point of the alloy, but also plays a role in dispersion strengthening. When the addition amount of Ca element is in the appropriate range, due to the grain refinement effect and the reduction of alloy melt viscosity, the resistance of the alloy liquid is reduced during flow. At the same time, the addition of Ca plays a role in modifying the eutectic silicon phase, making the morphology of the eutectic silicon phase change from coarse acicular to fine fibrous, which significantly improves the flowability of the alloy.

[0009] For zinc: Zn can improve the room temperature mechanical properties of the alloy through solid solution strengthening. Its atomic radius is close to that of Al, and it can be uniformly dissolved in the Al matrix, increasing the resistance to dislocation movement, thereby improving the tensile strength and yield strength of the alloy. At the same time, the addition of Zn can reduce the surface tension of the alloy melt (when the Zn content is in the range of 0.1%-3.0%, the surface tension of the melt is reduced by 5%-8% compared with the alloy without Zn), which helps to improve fluidity. In addition, Zn can promote the uniform precipitation of Mg2Si phase, reduce the agglomeration of Mg2Si phase, and further optimize the strengthening effect of the alloy. It is important to note that the Zn content must be controlled below 3.0%. When the Zn content exceeds 3.0%, it easily forms an Al-Zn eutectic phase (melting point approximately 575℃) with Al, leading to a decrease in the overall melting point of the alloy (below 630℃), which fails to meet the requirements for vacuum brazing. Furthermore, excessive Zn increases the alloy's susceptibility to intergranular corrosion, increasing the risk of intergranular cracking in humid or corrosive environments (such as the coolant in contact with the water-cooled housing of new energy vehicles). In addition, the synergistic effect of Zn and Ca is particularly important. Ca alone has a limited and unstable effect on the modification of Fe phases (such as β-Al5FeSi). The addition of Zn, by altering the melt structure, interfacial energy, and solidification path, works in conjunction with Ca to promote the transformation of acicular Fe-rich phases into smaller, more complex phases such as α-Al8Fe2Si. The combined effect of the two makes the solidification process smoother and the eutectic structure more uniform, thereby further reducing the hot cracking sensitivity of the casting and improving the casting qualification rate. At the same time, the combination of the two forms a complex and stable (Al, Zn)4Ca phase, which improves the fluidity of the alloy while reducing the negative impact of Zn on the thermal conductivity of the alloy, and further enhances the role of Ca in improving the alloy performance.

[0010] For lanthanum and cerium: by adding 0.1%-1.0% lanthanum, the eutectic point temperature of aluminum-lanthanum alloys is above 640℃; by adding 0.1%-1.0% cerium, the eutectic point temperature of aluminum-cerium alloys is above 640℃. This results in aluminum alloys with added lanthanum and cerium having high melting points, reaching above 630℃. The temperature for vacuum brazing aluminum alloys is around 600℃. At this temperature, the melting point of this type of aluminum alloy is higher than the vacuum brazing temperature, so it will not melt during vacuum brazing and is suitable for vacuum brazing. Furthermore, Ce can significantly refine the as-cast microstructure of Al-Mg-Si alloys. When 0.2% Ce is added to the alloy, Ce-rich metallic compounds exist at the grain boundaries, effectively inhibiting the nucleation and growth of primary phases. Ce can transform the coarse AlFeSi phase into granular and short rod-shaped phases, making them finer and more uniform, thereby improving the alloy's fluidity and mechanical properties, but the degree of improvement is limited.

[0011] This invention utilizes the synergistic effect of calcium, magnesium, silicon, zinc, cerium, and lanthanum on aluminum-iron-nickel alloys to generate Mg2Si reinforcing phase and high-melting-point Al2Ca phase. This improves the alloy's melting point and mechanical properties while refining the grains and enhancing its fluidity. The alloy's properties meet the requirements for casting (such as sand casting, metal mold casting, anti-gravity casting, and vacuum casting), and its ultra-high melting point allows it to be applied in the field of vacuum welding.

[0012] The aluminum alloy proposed in this invention has aluminum as its base material, and the sum of the mass percentages of all components is 100%. Unavoidable impurities may include impurities introduced from the raw materials and impurities introduced during the manufacturing process by various production equipment and tooling, such as, but not limited to, one or at least two combinations of chromium, beryllium, cobalt, vanadium, tin, and lead. To avoid affecting the final properties of the aluminum alloy, the content of unavoidable impurities must be controlled below 0.3%, and further, below 0.15%. This can be achieved, for example, by controlling the purity of the raw materials and the cleanliness of the equipment used in the manufacturing process. Furthermore, the maximum allowable content of a single impurity must be specified: Be ≤ 0.0005% (Be is toxic and easily leads to hot cracking of the alloy; exceeding this content will significantly increase the casting defect rate), Cr ≤ 0.05% (Cr and Fe easily form coarse Al-Cr-Fe ternary compounds; exceeding 0.05% will lead to a decrease in alloy elongation of more than 15%), Co ≤ 0.03% (Co... It will reduce the thermal conductivity of the alloy, and when it exceeds 0.03%, the thermal conductivity will decrease by more than 8%); V≤0.02%, Sn≤0.01%, Pb≤0.01%; at the same time, it is necessary to control the synergistic effect between impurities. When Cr and Fe coexist and the total content exceeds 2.05%, the Cr content needs to be further reduced to below 0.03% to avoid the formation of a large number of brittle intermetallic compounds.

[0013] Preferably, the near-eutectic Al-Fe-Ni aluminum alloy comprises, by mass fraction, the following components: 1.2%-1.8% iron, 1.0%-1.4% nickel, 0.7%-2.0% calcium, 0.3%-1.0% magnesium, 0.4%-1.0% silicon, 0.9%-1.2% zinc, 0.2%-0.8% cerium, 0.2%-0.8% lanthanum, unavoidable impurities <0.15%, and the balance being aluminum.

[0014] Further preferably, the near-eutectic Al-Fe-Ni aluminum alloy comprises, by mass fraction, the following components: iron 1.7%-1.8%, nickel 1.2%-1.4%, calcium 1.6%-2.0%, magnesium 0.5%-0.9%, silicon 0.6%-0.9%, zinc 1.0%-1.2%, cerium 0.2%-0.8%, lanthanum 0.2%-0.8%, unavoidable impurities <0.15%, and the balance being aluminum.

[0015] A second objective of this invention is to provide a method for preparing the near-eutectic Al-Fe-Ni aluminum alloy, comprising the following steps:

[0016] (1) Prepare raw materials according to alloy composition. First, put pure aluminum ingots into a melting container for melting to obtain aluminum liquid. Then, add components iron, nickel, silicon, calcium, magnesium, zinc, cerium and lanthanum to the aluminum liquid in sequence. Heat up to melt the various components to obtain alloy melt.

[0017] (2) The alloy melt obtained in step (1) is subjected to slag removal and degassing treatment to obtain a pure alloy melt;

[0018] (3) After cooling the pure alloy melt to 720°C-730°C, it is cast into shape and then naturally cooled and solidified to obtain the near-eutectic Al-Fe-Ni aluminum alloy.

[0019] In step (3), casting includes sand casting, metal mold casting, anti-gravity casting, vacuum die casting, etc. A portion of the alloy melt is subjected to fluidity testing and vacuum brazing and tunnel welding tests. The resulting aluminum alloy material has a high melting point, can be used for vacuum brazing, and also has good mechanical properties and casting effect.

[0020] Preferably, the components iron, nickel, silicon, calcium, magnesium, zinc, cerium and lanthanum in step (1) are respectively made of intermediate alloys Al-20Fe, Al-10Ni, Al-20Si, Al-10Ca, Al-5Mg, Al-10Zn, Al-10Ce and Al-10La.

[0021] Preferably, step (1) is as follows: first, put pure aluminum ingots into a melting container, heat to 700°C-750°C for melting to obtain aluminum liquid, then add components iron, nickel, silicon, calcium, magnesium, zinc, cerium and lanthanum to the aluminum liquid in sequence, heat to 780°C-790°C and hold for 16-20 min to melt the various components and obtain alloy melt.

[0022] Further optimization, the specific steps of step (1) are as follows: first, put pure aluminum ingots into a melting container, heat to 750°C for melting to obtain aluminum liquid, then add components iron, nickel, silicon, calcium, magnesium, zinc, cerium and lanthanum to the aluminum liquid in sequence, heat to 780°C and hold for 18 min to melt various components, thereby obtaining alloy melt.

[0023] Preferably, the specific steps of slag removal and degassing in step (2) are as follows: the temperature of the alloy melt is reduced to 740°C, aluminum refining agent is added and stirred, and after the aluminum refining agent adsorbs the oxide impurities in the alloy melt, the aluminum refining agent is scraped off, and then argon gas is introduced for degassing. The argon gas flow rate is 0.8-1.2 L / min, the gas introduction time is 8-12 min, and the argon gas tube is inserted into the alloy melt to a depth of 2 / 3 of the alloy melt depth to ensure that the bubbles are evenly dispersed. After degassing is completed, it is left to stand for 8-12 min to allow the residual bubbles to float to the surface and obtain a pure alloy melt.

[0024] Further optimization involves lowering the temperature of the alloy melt to 740℃, adding an aluminum refining agent and stirring. After the aluminum refining agent adsorbs oxide impurities in the melt, the refining agent is scraped off, and then argon gas is introduced for degassing. The argon gas flow rate is 1 L / min, the gas introduction time is 10 min, and the argon gas tube is inserted into the melt to a depth of 2 / 3 of the melt depth to ensure that the bubbles are evenly dispersed. After degassing, the melt is allowed to stand for 10 min to allow the residual bubbles to float to the surface, resulting in a pure alloy melt.

[0025] Further preferred, the aluminum refining agent is a mixture of sodium chloride and potassium chloride in a mass ratio of 1:1, and the amount of aluminum refining agent added is 0.4%-0.6% of the mass of the alloy melt.

[0026] Further optimization involves adding aluminum refining agent at a rate of 0.5% of the alloy melt mass.

[0027] The third objective of this invention is to provide the application of the near-eutectic Al-Fe-Ni aluminum alloy in the manufacture of complex, high-precision aluminum alloy parts.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The castable and weldable aluminum alloy proposed in this invention has high melting point, mechanical properties and fluidity, and can be applied to industries such as vacuum brazing and casting.

[0030] 2. The castable and weldable aluminum alloy proposed in this invention has good casting and welding properties, and its application scenarios cover many fields that require complex component shapes and reliable connections, such as vacuum brazing, transportation, automobile manufacturing, rail transportation, and agricultural machinery. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the aluminum alloy flowability testing mold provided by the present invention;

[0032] Figure 2 This is a flowchart of the method for preparing aluminum alloy materials proposed in this invention;

[0033] Figure 3This is a comparative schematic diagram of the flowability results of aluminum alloy materials obtained from Example 2 and A356 alloy of the present invention; wherein, Figure e is the flowability result diagram of A356 alloy; and Figure f is the flowability result diagram of alloy from Example 2.

[0034] Figure 4 This is a microscopic morphology diagram of the aluminum alloy material obtained in Example 2 of the present invention;

[0035] Figure 5 This is a casting effect diagram of the aluminum alloy obtained in Example 2 of the present invention;

[0036] Figure 6 This is a schematic diagram of the casting after vacuum brazing is completed according to Embodiment 2 of the present invention;

[0037] Figure 7 This is a schematic diagram of the tensile strength of the aluminum alloy material after vacuum brazing, obtained in Example 2 of the present invention;

[0038] Figure 8 This is a schematic diagram of the weld seam after vacuum brazing of the aluminum alloy material obtained in Embodiment 2 of the present invention;

[0039] Explanation of reference numerals in the attached diagram: a) Flow mold gate; b) Positioning hole; c) Flow channel; d) Handle. Detailed Implementation

[0040] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0041] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental materials and reagents used herein are commercially available products conventionally available in this technical field.

[0042] Figure 2 An exemplary flowchart of the preparation method of aluminum alloy material in the embodiments or comparative examples is shown. The specific manufacturing process may include:

[0043] Pure aluminum ingots with a purity of 99.99% are selected to ensure that the purity of the aluminum matrix meets the performance requirements of subsequent alloying processes and to reduce the interference of impurities on the alloy microstructure and properties. Alloying elements are added in the form of an intermediate alloy, specifically Al-20Fe (20% iron by mass), Al-10Ni (10% nickel by mass), Al-10Ca (10% calcium by mass), Al-5Mg (5% magnesium by mass), Al-20Si (20% silicon by mass), Al-10Zn (10% zinc by mass), Al-10Ce (10% cerium by mass), and Al-10La (10% lanthanum by mass). The intermediate alloy has a uniform and stable composition, allowing for precise control of the content of each element in the alloy.

[0044] The aluminum refining agent consists of sodium chloride (NaCl) and potassium chloride (KCl) in a 1:1 mass ratio, and is used to remove impurities and gases from the alloy melt. A sodium-free refining agent is available as a backup and can be selected for use according to the required purity of the melt.

[0045] The smelting equipment is a pit-type crucible smelting furnace with a rated power of 5 kW and a temperature control accuracy of ±5℃. It can achieve stable melting and heat preservation of aluminum ingots and intermediate alloys, avoiding element burn-off caused by excessive local temperature.

[0046] Example 1

[0047] A castable and weldable near-eutectic Al-Fe-Ni aluminum alloy comprises, by mass fraction, the following components: 1.2% iron, 1.1% nickel, 1.0% calcium, 0.3% magnesium, 0.4% silicon, 1.0% zinc, 0.2% cerium, 0.2% lanthanum, unavoidable impurities <0.15%, and the balance being aluminum.

[0048] The preparation method of Al-Fe-Ni aluminum alloy includes the following steps:

[0049] (1) Prepare raw materials according to the formula. First, put pure aluminum ingots into a graphite crucible melting furnace and heat to 750°C to melt them to obtain aluminum liquid. Then, add Al-20Fe, Al-10Ni, and Al-20Si master alloys to the aluminum liquid in sequence, heat to 780°C and hold for 10 min to ensure that the above master alloys are completely dissolved. Then add Al-10Ca, Al-5Mg, Al-10Zn, Al-10Ce, and Al-10La master alloys and continue to hold for 8 min. During this period, gently stir with a graphite rod 2-3 times to make the alloy elements evenly distributed, thereby obtaining the alloy melt.

[0050] (2) Reduce the temperature of the alloy melt to 740℃, add 0.5% of the alloy melt mass of aluminum refining agent (about 5g / 1kg melt), stir with a graphite rod for 5 min to make the refining agent fully contact the melt, and after the aluminum refining agent adsorbs the oxide impurities in the melt, let it stand for 3 min, scrape off the surface slag with a graphite spoon, and then introduce argon gas (purity 99.99%) for degassing. The argon gas flow rate is 1 L / min, the gas introduction time is 10 min, and the argon gas tube is inserted into the melt to a depth of 2 / 3 of the melt depth to ensure that the bubbles are evenly dispersed. After degassing, let it stand for 10 min to allow the residual bubbles to float to the surface and obtain a pure alloy melt.

[0051] (3) After cooling the pure alloy melt to 730°C, slowly pour it into the H13 steel circular mold preheated to 200°C. After naturally cooling to room temperature, demold to obtain a cylindrical aluminum alloy casting with a diameter of 50 mm and a height of 100 mm, which is used for mechanical property and microstructure testing.

[0052] Flowability test: Pour pure alloy melt at 730℃ at a uniform rate (pouring speed 50 mL / s) into a flowability test mold preheated to 200℃. After complete solidification, open the mold, remove the flowability sample, and measure the length of the melt filling the runner. Repeat the test 3 times and take the average value as the alloy flowability index. To better illustrate the superiority of this alloy, the flowability of A356 alloy under the same conditions is used as a reference.

[0053] Example 2

[0054] Same as Example 1, except that:

[0055] A castable and weldable near-eutectic Al-Fe-Ni aluminum alloy comprises, by mass fraction, the following components: 1.7% iron, 1.2% nickel, 2.0% calcium, 0.5% magnesium, 0.6% silicon, 1.0% zinc, 0.2% cerium, 0.2% lanthanum, unavoidable impurities <0.15%, and the balance being aluminum.

[0056] Based on the above component ratios, accurately calculate the weighing mass of each raw material (pure aluminum ingot, master alloy). For example, to prepare 1 kg of aluminum alloy, the following are required: 335 g pure aluminum ingot, 85 g Al-20Fe (containing 17 g Fe), 110 g Al-10Ni (containing 11 g Ni), 200 g Al-10Ca (containing 20 g Ca), 100 g Al-5Mg (containing 5 g Mg), 30 g Al-20Si (containing 6 g Si), 100 g Al-10Zn (containing 10 g Zn), 20 g Al-10Ce (containing 2 g Ce), and 20 g Al-10La (containing 2 g La).

[0057] The preparation method of Al-Fe-Ni aluminum alloy is the same as in Example 1.

[0058] Example 3

[0059] Same as Example 1, except that:

[0060] A castable and weldable near-eutectic Al-Fe-Ni aluminum alloy comprises, by mass fraction, the following components: 1.8% iron, 1.4% nickel, 1.6% calcium, 0.9% magnesium, 0.9% silicon, 1.2% zinc, 0.8% cerium, 0.8% lanthanum, unavoidable impurities <0.15%, and the balance being aluminum.

[0061] The preparation method of Al-Fe-Ni aluminum alloy is the same as in Example 1.

[0062] Example 4

[0063] Same as Example 1, except that:

[0064] A castable and weldable near-eutectic Al-Fe-Ni aluminum alloy, comprising the following components by mass fraction: 1.7% iron, 1.0% nickel, 1.0% calcium, 1.0% magnesium, 1.0% silicon, 1.0% zinc, 0.2% cerium, 0.2% lanthanum, unavoidable impurities <0.15%, and the balance being aluminum.

[0065] The preparation method of Al-Fe-Ni aluminum alloy is the same as in Example 1.

[0066] Example 5

[0067] Same as Example 1, except that:

[0068] A castable and weldable near-eutectic Al-Fe-Ni aluminum alloy comprises, by mass fraction, the following components: 1.7% iron, 1.2% nickel, 0.7% calcium, 0.5% magnesium, 1.0% silicon, 0.9% zinc, 0.2% cerium, 0.2% lanthanum, unavoidable impurities <0.15%, and the balance being aluminum.

[0069] The preparation method of Al-Fe-Ni aluminum alloy is the same as in Example 1.

[0070] Example 6

[0071] A castable and weldable near-eutectic Al-Fe-Ni aluminum alloy is prepared, comprising the following components by mass fraction: 1.0% iron, 1.0% nickel, 7.8% calcium, 0.1% magnesium, 0.1% silicon, 0.1% zinc, 0.1% cerium, 0.1% lanthanum, unavoidable impurities <0.3%, and the balance being aluminum.

[0072] The preparation method of Al-Fe-Ni aluminum alloy includes the following steps:

[0073] (1) Prepare raw materials according to the formula. First, put pure aluminum ingots into a graphite crucible melting furnace and heat it to 700°C to melt it to obtain aluminum liquid. Then, add Al-20Fe, Al-10Ni, and Al-20Si master alloys to the aluminum liquid in sequence, heat it to 780°C and hold it for 11 min to ensure that the above master alloys are completely dissolved. Then add Al-10Ca, Al-5Mg, Al-10Zn, Al-10Ce, and Al-10La master alloys and continue to hold it for 9 min. During this period, gently stir it 2-3 times with a graphite rod to make the alloy elements evenly distributed, thereby obtaining the alloy melt.

[0074] (2) Reduce the temperature of the alloy melt to 740℃, add 0.4% aluminum refining agent by mass of the alloy melt, stir with a graphite rod for 5 min to ensure that the refining agent is in full contact with the melt, and let it stand for 3 min. Then scrape off the surface scum with a graphite spoon and then introduce argon gas (purity 99.99%) for degassing. The argon gas flow rate is 0.8 L / min and the gas introduction time is 12 min. The argon gas tube is inserted into the melt to a depth of 2 / 3 of the melt depth to ensure that the bubbles are evenly dispersed. After degassing, let it stand for 10 min to allow the residual bubbles to float to the surface and obtain a pure alloy melt.

[0075] (3) After cooling the pure alloy melt to 720°C, slowly pour it into the mold and let it cool naturally to obtain Al-Fe-Ni aluminum alloy.

[0076] Example 7

[0077] A castable and weldable near-eutectic Al-Fe-Ni aluminum alloy, comprising the following components by mass fraction: 2.0% iron, 1.5% nickel, 0.1% calcium, 0.1% magnesium, 1.0% silicon, 3.0% zinc, 1.0% cerium, 1.0% lanthanum, unavoidable impurities <0.3%, with the balance being aluminum.

[0078] The preparation method of Al-Fe-Ni aluminum alloy includes the following steps:

[0079] (1) Prepare raw materials according to the formula. First, put pure aluminum ingots into a graphite crucible melting furnace and heat to 750°C to melt them to obtain aluminum liquid. Then, add Al-20Fe, Al-10Ni, and Al-20Si master alloys to the aluminum liquid in sequence, heat to 790°C and hold for 9 min to ensure that the above master alloys are completely dissolved. Then add Al-10Ca, Al-5Mg, Al-10Zn, Al-10Ce, and Al-10La master alloys and continue to hold for 7 min. During this period, gently stir with a graphite rod 2-3 times to make the alloy elements evenly distributed, thereby obtaining the alloy melt.

[0080] (2) Reduce the temperature of the alloy melt to 740℃, add 0.6% aluminum refining agent by mass of the alloy melt, stir with a graphite rod for 5 min to ensure that the refining agent is in full contact with the melt, and let it stand for 3 min. Then scrape off the surface scum with a graphite spoon and then introduce argon gas (purity 99.99%) for degassing. The argon gas flow rate is 1.2 L / min and the gas introduction time is 8 min. The argon gas tube is inserted into the melt to a depth of 2 / 3 of the melt depth to ensure that the bubbles are evenly dispersed. After degassing, let it stand for 10 min to allow the residual bubbles to float to the surface and obtain a pure alloy melt.

[0081] (3) After cooling the pure alloy melt to 720°C, slowly pour it into the mold and let it cool naturally to obtain Al-Fe-Ni aluminum alloy.

[0082] Comparative Example 1

[0083] Similar to Example 2, except that in the raw material smelting stage, the raw materials with the lower melting point are added first.

[0084] Comparative Example 2

[0085] Similar to Example 2, except that: instead of using an intermediate phase alloy as a compounding material, pure component raw materials are used directly.

[0086] Comparative Example 3

[0087] Same as Example 2, except that the mass percentages of each component are: iron 1.7%, nickel 1.2%, magnesium 0.5%, silicon 0.6%, zinc 3.0%, cerium 0.2%, lanthanum 0.2%, unavoidable impurities <0.15%, and the balance is aluminum.

[0088] Comparative Example 4

[0089] Same as Example 2, except that the mass percentages of each component are: iron 1.7%, nickel 1.2%, calcium 3.0%, magnesium 0.5%, silicon 0.6%, cerium 0.2%, lanthanum 0.2%, unavoidable impurities <0.15%, and the balance is aluminum.

[0090] Comparative Example 5

[0091] Same as Example 2, except that the mass percentages of each component are: iron 1.7%, nickel 1.2%, calcium 2.0%, silicon 1.1%, zinc 1.0%, cerium 0.2%, lanthanum 0.2%, unavoidable impurities <0.15%, and the balance is aluminum.

[0092] Comparative Example 6

[0093] Same as Example 2, except that the mass percentages of each component are: iron 1.7%, nickel 1.2%, calcium 2.0%, magnesium 1.1%, zinc 1.0%, cerium 0.2%, lanthanum 0.2%, unavoidable impurities <0.15%, and the balance is aluminum.

[0094] Comparative Example 7

[0095] Same as Example 2, except that the mass percentages of each component are: iron 1.75%, nickel 1.25%, magnesium, calcium, lanthanum, cerium 0%, silicon 0.5%, zinc 0.5%, copper 0.5%, unavoidable impurities <0.15%, and the balance is aluminum.

[0096] Comparative Example 8

[0097] Same as Example 2, except that the mass percentages of each component are: iron 1%, lanthanum 4%, cerium 5.5%, titanium diboride 0.7%, manganese 0.1%, magnesium 0.4%, silicon 0.09%, nickel, calcium, zinc 0%, unavoidable impurities <0.15%, and the balance is aluminum.

[0098] Comparative Example 9

[0099] Same as Example 2, except that the mass percentages of each component are: iron 1.0%, nickel 1.0%, magnesium 5.5%, silicon 1.5%, unavoidable impurities <0.15%, and the balance is aluminum.

[0100] The materials obtained in Examples 1-7 and Comparative Examples 1-9 were tested.

[0101] The alloy melt was subjected to flowability tests and vacuum brazing and tunnel welding tests.

[0102] A schematic diagram of the aluminum alloy flowability test mold is shown below. Figure 1 As shown, the material of the flow mold is H13 steel. To facilitate mold opening and positioning, four handles and three positioning holes b are designed. Before conducting the flow test, a coating should be evenly applied to the inner wall of the mold channel to prevent the introduction of impurities, and then preheated at 200℃. Pure alloy melt is slowly and evenly poured into the mold from the gate a. The alloy melt flows along the flow channel c. After the melt solidifies, the handle d is lifted, the mold is opened, and the flow sample is taken out. The flowability of the alloy is evaluated based on the length of the melt in the channel when it finally solidifies.

[0103] To avoid introducing impurities and ensure casting quality during metal mold casting, a water-based coating is evenly applied to the inner surface of the mold before pouring and the mold is preheated to 200°C to prevent quenching and splashing of molten aluminum. The resulting pure melt is then poured into an H13 steel circular mold. After natural cooling and solidification, a near-eutectic Al-Fe-Ni alloy that is both castable and weldable is obtained. The water-based coating consists of (ZnO + Na2O·nSiO2), and the coating thickness is controlled at 0.1-0.2 mm. After application, it is dried in a 120℃ oven for 30 minutes to ensure that there is no moisture residue on the inner surface of the mold. The mold preheating temperature needs to be adjusted for castings of different thicknesses: when the casting thickness is <5 mm, the preheating temperature is 180℃-200℃ (to avoid rapid solidification of thin walls leading to material shortage); when the casting thickness is 5-20 mm, the preheating temperature is 200℃-220℃; when the casting thickness is >20 mm, the preheating temperature is 220℃-240℃ (to reduce shrinkage defects inside thick-walled castings). In sand casting, the prepared sand mold is precisely closed to ensure a good seal. The refined and degassed pure alloy melt is poured into the pouring cup. The molten metal flows into the mold cavity through the sprue, gating system, and ingate. It is then allowed to cool and solidify within the mold cavity. After solidification, the sand mold is broken to remove the casting. The risers and gating gates are removed, and any adhering sand and burrs on the casting surface are cleaned to obtain the sand-cast part. In anti-gravity casting, a metal mold is used. After installing the riser pipe, it is ensured to seal well with the crucible and mold. A coating is applied, and the mold is preheated to 200℃-220℃. Gas is introduced into the crucible to apply low pressure, causing the pure alloy melt in the crucible to slowly rise along the riser pipe to the mold gate. The pressure is adjusted to ensure the molten metal fills the mold cavity at a uniform speed. The mold cavity pressure is maintained until the casting completely solidifies, resulting in an anti-gravity cast part. During vacuum die casting, connect the mold vacuum interface to the die casting machine's vacuum pipeline, ensuring no leaks. Then preheat the mold to 200℃-220℃. Inject pure alloy melt into the injection chamber. The injection punch slowly moves forward to expel air from the injection chamber. After the punch seals the gating gate, activate the vacuum system to evacuate air from the cavity. When the molten metal approaches the ingate, the punch advances at high speed to force the molten metal into the cavity. The vacuum system is shut off when the molten metal fills the end of the cavity. The injection punch maintains pressure to replenish the solidified molten metal. The mold cooling system cools the casting to a solid state. After mold opening, the casting is removed via the ejector mechanism. Clean the gating gate and flash to obtain the vacuum die-cast part. The castings from these different casting processes have the same shape. Figure 5 As shown.

[0104] For alloy fluidity testing, pure molten alloy is slowly and evenly poured into a fluidity mold preheated to 200°C. After the melt solidifies, the mold is opened and the fluidity sample is removed. This operation is repeated three times, and the average length of the three fluidity samples is used as the basis for alloy fluidity evaluation. The flow channel length of the fluidity mold is 800-1000 mm, the width is 8-12 mm, and the thickness is 4-6 mm. The mold material is H13 steel. The pouring speed is controlled at 50±5 mL / s to avoid excessive speed causing turbulent melt flow or excessive speed causing premature solidification. The fluidity test must be matched with the actual casting size. When the minimum wall thickness of the actual casting is 4-6 mm, a flow channel mold with a thickness of 4-6 mm is selected to ensure that the test results reflect the actual casting fluidity. All required mold parameters will not be elaborated further.

[0105] According to the tensile specimen standard, L30 and φ5 standard tensile specimens were processed and subjected to room temperature tensile tests at a rate of 0.5 mm / min on an MTS CMT5105 universal testing machine.

[0106] Aluminum alloy samples with dimensions of 50mm×20mm×5mm were processed using 4343 brazing filler metal (melting point 577-600℃) and brazed in a vacuum brazing furnace at a brazing temperature of 600℃, a holding time of 15min, a vacuum degree of 5×10⁻³Pa, and a cooling rate of 5℃ / min.

[0107] The forming equipment includes an H13 steel circular mold (inner diameter 50mm, height 100mm) for casting aluminum alloy samples; and a flowability test mold, made of H13 steel. For specific mold parameters, please refer to the relevant documentation.

[0108] The testing equipment includes a vacuum brazing furnace (ultimate vacuum 5×10⁻³Pa, temperature control accuracy ±2℃), used to simulate the actual vacuum brazing process. A schematic diagram of a vacuum brazed casting is shown below. Figure 6 As shown, the tensile strength, yield strength, and elongation of the alloy were tested using a universal testing machine (range 0-500kN, accuracy grade 0.5); a metallographic microscope (magnification 50-2000x) was used to observe the microstructure of the alloy; a differential scanning calorimeter (DSC, heating rate 10℃ / min, temperature range 25-800℃) was used to determine the melting point of the alloy; and a laser thermal conductivity meter (accuracy ±5%) was used to test the thermal conductivity of the alloy.

[0109] Brazing process parameters: The aluminum alloy castings of Examples 1-7 and Comparative Examples 1-9 were machined into samples with dimensions of 50mm×20mm×5mm. 4343 brazing filler metal (melting point 577-600℃) was used, and brazing was performed in a vacuum brazing furnace. The brazing temperature was 600℃, the holding time was 15min, the vacuum degree was 5×10⁻³Pa, and the cooling rate was 5℃ / min.

[0110] In summary, the alloy compositions of Examples 1-7 and Comparative Examples 1-9 are shown in Table 1 below:

[0111] Table 1

[0112] The test results are as follows:

[0113] 1. The melting point, fluidity, and thermal conductivity of aluminum alloy castings are tested, and the results are listed in Table 2 below.

[0114] Table 2

[0115] As can be seen from Table 2, the melting point of the aluminum alloys in Examples 1-5 is all above 630℃, which is higher than the vacuum brazing temperature of 600℃. There is no melting phenomenon during the brazing process, which meets the requirements of vacuum brazing.

[0116] like Figure 3 The figure shows a comparison of the fluidity of alloy A356 (Figure e) and Example 2 (Figure f). The fluidity of Example 2 is 568 mm, which is 44 mm higher than that of alloy A356 (524 mm), meeting the requirements of die casting of complex components. In contrast, due to the absence of Ca to refine the grains and reduce the melt viscosity, the fluidity of Comparative Example 7 is only 475 mm, which makes it prone to defects such as material shortage and cold shut during molding.

[0117] Example 2 has a thermal conductivity of 192 W / (m·K), while Comparative Examples 7-9 have a maximum thermal conductivity of only 159 W / (m·K), and A356 has a thermal conductivity of 146 W / (m·K). As can be seen from the above data, this alloy has higher fluidity and thermal conductivity than the comparative examples and A356 alloy, and has great application advantages in casting and vacuum brazing scenarios.

[0118] 2. The tensile strength and elongation of the aluminum alloy materials in Examples 1-7 and Comparative Examples 1-9 were tested under different casting processes (sand casting, metal mold casting, anti-gravity casting, vacuum die casting) and after vacuum brazing and tunnel welding. The test results are listed in Tables 3 and 4.

[0119] The tensile strength is shown in Table 3:

[0120] Table 3 Tensile Strength (MPa)

[0121] Table 4. Elongation (%)

[0122] As can be seen from the data in Tables 2-4, the overall performance of the aluminum alloy castings corresponding to Examples 1-5 is higher than that of Comparative Examples 7-9.

[0123] 3. Microstructure analysis of aluminum alloys

[0124] like Figure 4 The images show the as-cast microstructures of Example 2 and Comparative Example 1 as observed under a 500x metallographic microscope. Example 2 exhibits fine and uniform α-Al matrix grains with uniformly distributed black, fine-grained Al₂Ca phases, and good dispersion of the secondary phases. In Comparative Example 1, the α-Al matrix grains are coarser, and a large number of coarse (AlSi)₅(FeNi) phases are present. These phases are prone to stress concentration, leading to decreased alloy plasticity and reduced tensile strength. Figure 8 This is a schematic diagram of the weld after vacuum brazing in Example 2. It can be observed that there are no obvious cracks at the weld joint. Figure 7 The diagram shows the tensile strength after vacuum brazing in Example 2, illustrating that the materials bond well and retain their properties well after vacuum brazing in Example 2.

[0125] Obviously, the aluminum alloy material of this invention refines the grains with Ca and improves the melt flowability with Si, achieving a flowability of 540-570 mm, which meets the requirements of various casting processes such as sand casting, metal mold casting, and vacuum die casting. With a melting point above 640℃, it is fully suitable for vacuum brazing environments. After brazing, the tensile strength of the weld is 170-200 MPa, and the yield strength and elastic modulus remain at a high level. The thermal conductivity is 150-180 W / (m・K), solving the problems of conventional Al-Si alloys being unable to be brazed and the poor casting performance of deformed aluminum alloys.

[0126] 4. Taking the preparation of 1 kg of alloy as an example, the raw material costs (2025 market prices) of the aluminum alloy proposed in this invention are compared with those of A356 alloy and 6063 alloy. Table 5 shows the comparison.

[0127] Table 5

[0128] Although the cost of the alloy of this invention is slightly higher than that of A356, 6063 alloys and Comparative Examples 7-9, considering that it can simultaneously meet the requirements of casting and vacuum brazing, without the need for subsequent welding process improvements or material replacements, it can reduce the overall component manufacturing cost and has a significant cost-performance advantage.

[0129] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A castable and weldable near-eutectic Al-Fe-Ni aluminum alloy, characterized in that, By mass fraction, it comprises the following components: iron 1.0%-2.0%, nickel 1.0%-1.5%, calcium 0.1%-7.8%, magnesium 0.1%-1.0%, silicon 0.1%-1.0%, zinc 0.1%-3.0%, cerium 0.1%-1.0%, lanthanum 0.1%-1.0%, unavoidable impurities <0.3%, and the balance being aluminum.

2. The near-eutectic Al-Fe-Ni aluminum alloy according to claim 1, characterized in that, By mass fraction, it comprises the following components: iron 1.2%-1.8%, nickel 1.0%-1.4%, calcium 0.7%-2.0%, magnesium 0.3%-1.0%, silicon 0.4%-1.0%, zinc 0.9%-1.2%, cerium 0.2%-0.8%, lanthanum 0.2%-0.8%, unavoidable impurities <0.15%, and the balance being aluminum.

3. The near-eutectic Al-Fe-Ni aluminum alloy according to claim 2, characterized in that, By mass fraction, it comprises the following components: iron 1.7%-1.8%, nickel 1.2%-1.4%, calcium 1.6%-2.0%, magnesium 0.5%-0.9%, silicon 0.6%-0.9%, zinc 1.0%-1.2%, cerium 0.2%-0.8%, lanthanum 0.2%-0.8%, unavoidable impurities <0.15%, and the balance being aluminum.

4. The method for preparing the near-eutectic Al-Fe-Ni aluminum alloy according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Prepare raw materials according to alloy composition. First, put pure aluminum ingots into a melting container for melting to obtain aluminum liquid. Then, add components iron, nickel, silicon, calcium, magnesium, zinc, cerium and lanthanum to the aluminum liquid in sequence. Heat up to melt the various components to obtain alloy melt. (2) The alloy melt obtained in step (1) is subjected to slag removal and degassing treatment to obtain a pure alloy melt; (3) After cooling the pure alloy melt to 720°C-730°C, it is cast into shape and then naturally cooled and solidified to obtain the near-eutectic Al-Fe-Ni aluminum alloy.

5. The preparation method according to claim 4, characterized in that, The components iron, nickel, silicon, calcium, magnesium, zinc, cerium and lanthanum mentioned in step (1) are respectively made using intermediate alloys Al-20Fe, Al-10Ni, Al-20Si, Al-10Ca, Al-5Mg, Al-10Zn, Al-10Ce and Al-10La.

6. The preparation method according to claim 4 or 5, characterized in that, Step (1) The specific steps are as follows: First, put the pure aluminum ingot into the melting container and heat it to 700°C-750°C for melting to obtain aluminum liquid. Then, add the components iron, nickel, silicon, calcium, magnesium, zinc, cerium and lanthanum to the aluminum liquid in sequence, heat it to 780°C-790°C and keep it at that temperature for 25-30 minutes to melt the various components and obtain the alloy melt.

7. The preparation method according to claim 4, characterized in that, The specific steps for slag removal and degassing in step (2) are as follows: the temperature of the alloy melt is reduced to 740℃, aluminum refining agent is added and stirred. After the aluminum refining agent adsorbs the oxide impurities in the alloy melt, the aluminum refining agent is scraped off, and then argon gas is introduced for degassing. The argon gas flow rate is 0.8-1.2 L / min, the gas introduction time is 8-12 min, and the argon gas tube is inserted into the alloy melt to a depth of 2 / 3 of the alloy melt depth to ensure that the bubbles are evenly dispersed. After degassing is completed, it is left to stand for 8-12 min to allow the residual bubbles to float to the surface and obtain a pure alloy melt.

8. The preparation method according to claim 7, characterized in that, The aluminum refining agent is a mixture of sodium chloride and potassium chloride in a mass ratio of 1:

1. The amount of aluminum refining agent added is 0.4%-0.6% of the mass of the alloy melt.

9. The application of the near-eutectic Al-Fe-Ni aluminum alloy according to any one of claims 1-3 in the preparation of complex high-precision aluminum alloy parts.

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