A high-strength cast aluminum alloy and a method for manufacturing the same

Abstract

The application belongs to the technical field of metal materials, and specifically discloses a high-strength and high-toughness cast aluminum alloy and a preparation method thereof; the aluminum alloy contains the following elements and has the following mass percentages: 6.80%-7.10% of Si, 0.28%-0.32% of Mg, 0.10%-0.20% of Ti, 0.005%-0.015% of B, 0.010%-0.020% of Sr, 0.003%-0.012% of La, ≤0.15% of Fe, ≤0.15% of Cu, ≤0.05% of the rest of impurities, ≤0.15% of the total of the rest of impurities, and the rest is Al; the preparation method uses A356.2 aluminum alloy ingots as a matrix; Al-5Ti-1B-1La alloy is used as a refiner, the A356.2 aluminum alloy ingots are smelted at 720 DEG C, then the Al-5Ti-1B-1La intermediate alloy refiner is added, the Al-10Sr modifier is added after uniform stirring, and the aluminum alloy is poured and formed after heat preservation; the formed aluminum alloy is subjected to solid solution at 540 DEG C for 4 hours, water quenching at 80 DEG C for 120 seconds, and aging treatment at 130 DEG C for 3 hours; the high-strength and high-toughness cast aluminum alloy and the preparation method thereof have higher hardness, ultimate tensile strength and elongation than the existing conventional A356.2 (T6) cast aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of new aluminum alloy materials, and in particular to a high-strength and high-toughness cast aluminum alloy and its preparation method. Background Technology

[0002] With the increasing popularity of new energy vehicles, two major improvement directions (batteries and lightweighting) have become popular optimization areas. A crucial branch of automotive lightweighting research is the lightweighting improvement of car wheels. Currently, most non-heavy-duty car wheels are made of aluminum alloy, making the improvement and optimization of aluminum alloy car wheels an important research direction. Lightweighting research on aluminum alloy car wheels mainly focuses on two major areas: material improvement and process improvement.

[0003] Currently, over 80% of the aluminum alloys used in low-pressure casting and spin casting of automotive wheels are A356 hypoeutectic aluminum-silicon alloys. This alloy, after appropriate heat treatment, can be used for most automotive wheel materials, but there is still room for improvement in its mechanical properties. Because the A356.2 aluminum alloy currently used in low-pressure casting and spin casting wheel production, after refining with traditional Al-5Ti-1B refining agents and undergoing conventional heat treatment processes, generally has a hardness of 65HBW-80HBW, making it difficult to exceed 80HBW. However, some low-pressure casting and spin casting wheel applications now require material hardness close to or even exceeding 80HBW. At the same time, some spin casting wheel applications require an elongation of ≥10%, which is almost the limit of elongation for conventional alloys (generally 7%-10%). Therefore, for automotive wheel applications with high mechanical performance requirements, traditional A356.2 aluminum alloys are still insufficient to fully meet the demands. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength and high-toughness cast aluminum-silicon alloy and its preparation method, which can further refine the α-Al grains and secondary dendrite arms in the hypoeutectic aluminum-silicon alloy, and at the same time make the eutectic Si particles in the alloy body more uniformly distributed. Compared with the existing A356.2 aluminum alloy preparation methods, the aluminum-silicon alloy prepared by this invention has an average grain size of 320.9μm-334.7μm and an average secondary dendrite spacing of 26.8μm-36.6μm, which improves the tensile strength, elongation and hardness to a certain extent.

[0005] The technical problem solved by this invention is achieved through the following technical solution:

[0006] A high-strength and high-toughness cast aluminum alloy, characterized in that: the elemental composition and their mass percentage in the aluminum alloy are: 6.80%-7.10% Si, 0.28%-0.32% Mg, 0.10%-0.20% Ti, 0.005%-0.015% B, 0.010%-0.020% Sr, 0.003%-0.012% La, Fe≤0.15%, Cu≤0.15%, other impurities ≤0.05% individually, the sum of other impurities ≤0.15%, and the balance is Al.

[0007] Furthermore, the aluminum alloy has an average grain size of 320.9 μm-334.7 μm, an average secondary dendrite spacing of 26.8 μm-36.6 μm, a hardness of 81.78 HBW-83.48 HBW, an ultimate tensile strength of 276.59 MPa-281.93 MPa, and an elongation of 19.72%-22.17%.

[0008] A method for preparing a high-strength and high-toughness cast aluminum alloy, the method comprising the following steps:

[0009] 1) Ingredients: A356.2 aluminum-silicon alloy was used as the main material; Al-5Ti-1B-1La master alloy refiner was used for refining treatment, with an addition amount of 0.5%-1%; Al-10Sr master alloy modifier was used for modification treatment, with an addition amount of 0.14%.

[0010] 2) Prepare materials: Calculate the proportions of A356.2 aluminum-silicon alloy, Al-5Ti-1B-1La master alloy, Al-10Sr master alloy, and industrial refining agent and slag remover and prepare them for use.

[0011] 3) Melting: The prepared A356.2 aluminum alloy ingot is put into the melting furnace for heating and melting. After the temperature of the aluminum liquid rises to 720℃ and the aluminum ingot is fully melted, nitrogen is used to blow in the refining agent for powder refining treatment. Then, slag removal treatment is performed. After the treatment is completed, the temperature is held for 30 minutes. Then, the prepared Al-5Ti-1B-1La master alloy is added and stirred continuously for 20 minutes. Then, Al-10Sr master alloy is added and stirred continuously for 20 minutes. Then, the slag removal agent is added and stirred continuously, while nitrogen is introduced for degassing and slag removal treatment. After the slag removal is completed, the temperature is held for 30 minutes.

[0012] 4) Casting: Heat the casting mold to 420℃; pour the molten aluminum into the mold and let it cool naturally until it solidifies and takes shape. Then remove it and water-cool it with 80℃ water for 20 seconds, and then let it cool naturally to room temperature.

[0013] 5) Heat treatment: the casting is solution treated at 540℃ for 4 hours; then quenched in water at 80℃ for 120 seconds; and then aged at 130℃ for 3 hours.

[0014] Furthermore, the A356.2 aluminum-silicon alloy used comprises the following components by mass percentage: 6.9%-7.3% Si, 0.35%-0.45% Mg, 0.2%-0.3% Ti, Fe≤0.15%, Cu≤0.15%, other impurities individually≤0.05%, other impurities total≤0.15%, and the balance being aluminum.

[0015] Furthermore, the preparation method of the Al-5Ti-1B-1La master alloy includes the following steps:

[0016] 1.1) Raw materials: Al-5Ti-1B master alloy is used as raw material. The Al-5Ti-1B master alloy raw material includes the following components by mass percentage: 5.0%-5.2% Ti, 1.0%-1.2% B, and the remainder is aluminum; industrial pure lanthanum, purity 99%;

[0017] 1.2) Material preparation: Prepare materials with 1.0%-1.2% La by weight, and the balance being Al-5Ti-1B master alloy raw material;

[0018] 1.3) Melting: Place the prepared Al-5Ti-1B intermediate alloy raw material and La into the melting furnace, evacuate the furnace, and then introduce industrial-grade high-purity argon gas; continue heating to 1000℃ and then mechanically stir for 30 minutes; hold at that temperature for 30 minutes.

[0019] 1.4) Casting: Heat the casting mold to 420°C and perform vacuum casting, then cool it to room temperature.

[0020] 1.5) Prepare an Al-5Ti-1B-1La master alloy. The prepared Al-5Ti-1B-1La master alloy contains the following components in mass percentage: 4.9%-5.1% Ti, 0.95%-1.05% B, and 0.9%-1.1% La.

[0021] Furthermore, the Al-10Sr master alloy modifier comprises the following components by mass percentage: 10% Sr and 90% aluminum.

[0022] The advantages and beneficial effects of this invention are as follows:

[0023] 1. The present invention provides a method for preparing high-strength and high-toughness cast aluminum-silicon alloy. This method refines A356.2 aluminum alloy ingots by preparing a new Al-5Ti-1B-1La master alloy refiner. Compared to the traditional Al-5Ti-1B master alloy refiner, the α-Al grains and secondary dendrite arms are refined to a certain extent, with an average grain size of 320.9 μm-334.7 μm and a secondary dendrite arm spacing reduced to 26.8 μm-36.6 μm. Simultaneously, the eutectic silicon distribution becomes more uniform.

[0024] 2. The method for preparing high-strength and high-toughness cast aluminum-silicon alloy of the present invention uses Al-5Ti-1B master alloy as a base and adds La element to it by vacuum melting to prepare Al-5Ti-1B-1La master alloy. The preparation conditions of the Al-5Ti-1B-1La master alloy refiner are relatively low and the preparation process is industrially feasible.

[0025] 3. The preparation method of the high-strength and high-toughness cast aluminum-silicon alloy of the present invention uses A356.2 casting hypoeutectic aluminum-silicon alloy ingot as the matrix, uses the above-mentioned Al-5Ti-1B-1La master alloy as a refining agent to refine the α-Al grains and secondary dendrites, uses Al-10Sr master alloy as a eutectic silicon modifier to modify the eutectic silicon, and performs heat treatment operations by solution treatment at 540℃ for 4 hours, water quenching at 80℃ for 120 seconds, and aging at 130℃ for 3 hours, and finally obtains the high-strength and high-toughness cast aluminum-silicon alloy.

[0026] 4. The invention provides a high-strength and high-toughness cast aluminum-silicon alloy. Experiments have shown that the high-strength and high-toughness aluminum alloy prepared by this invention can achieve an ultimate tensile strength of 281.93 MPa and an elongation of 22.17% under optimal conditions. At the same time, the hardness can reach 83.48 HBW. The above mechanical properties all exceed those of aluminum alloys prepared by traditional methods.

[0027] 5. The high-strength and high-toughness cast aluminum-silicon alloy and its preparation method of the present invention have improved hardness, ultimate tensile strength and elongation to a certain extent compared with traditional hypoeutectic cast aluminum alloys. The preparation process can be improved based on the existing industrial preparation of aluminum alloys. The present invention provides a new option for the selection of materials for cast aluminum alloy automobile wheels and has good application prospects. Attached Figure Description

[0028] Figure 1 Here is a photograph of a casting sample of high-strength and high-toughness cast aluminum alloy manufactured by the method of this invention:

[0029] Figure 1 (a) is a photograph of the casting sample of Example 1;

[0030] Figure 1(b) is a photograph of the casting sample from Example 2;

[0031] Figure 1 (c) is a photograph of the casting sample of Example 3;

[0032] Figure 1 (d) is a photograph of the casting sample from Example 4;

[0033] Figure 1 (e) is a picture of the actual casting sample of Comparative Example 1;

[0034] Figure 2 These are metallographic polarized light microscope comparison images of the grain morphology of the high-strength and high-toughness cast aluminum alloy of this invention and a traditional cast aluminum alloy:

[0035] Figure 2 (a) is a metallographic polarized light microscope image of the grain morphology observed in Example 1;

[0036] Figure 2 (b) is a metallographic polarized light microscope image of the grain morphology observed in Comparative Example 1.

[0037] Figure 3 This is a comparison diagram of grain size and secondary dendrite arm spacing between the high-strength and high-toughness cast aluminum alloy of this invention and traditional cast aluminum alloy:

[0038] Figure 3 (a) is a comparison diagram of grain size distribution between Example 1 and Comparative Example 1;

[0039] Figure 3 (b) is a comparison diagram of the size distribution of the secondary dendrite arm spacing between Example 1 and Comparative Example 1;

[0040] Figure 4 This is a comparison diagram of the tensile fracture morphology of the high-strength and high-toughness cast aluminum alloy of this invention and the traditional cast aluminum alloy: [Image showing the tensile fracture morphology of the alloy compared to the traditional cast aluminum alloy]

[0041] Figure 4 (a) is a fracture morphology image of Example 1 taken by scanning electron microscope at 15x magnification;

[0042] Figure 4 (b) is a fracture morphology image of Example 1 taken by scanning electron microscope at 500x magnification;

[0043] Figure 4 (c) is a fracture morphology image of Example 1 taken by scanning electron microscope at 2000x magnification;

[0044] Figure 4 (d) is a fracture morphology image of Comparative Example 1 taken by scanning electron microscope at 15x magnification;

[0045] Figure 4 (e) is a fracture morphology image of Comparative Example 1 taken by scanning electron microscopy at 500x magnification;

[0046] Figure 4 (f) is a fracture morphology image of Comparative Example 1 taken by scanning electron microscope at 2000x magnification;

[0047] Figure 5 This is a comparison chart of the mechanical properties of the high-strength and high-toughness cast aluminum alloy of the present invention (Examples 1-4) and the traditional cast aluminum alloy (Comparative Example 1). Detailed Implementation

[0048] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0049] A high-strength and high-toughness cast aluminum alloy comprises the following components by mass percentage: 6.80%-7.10% Si, 0.28%-0.32% Mg, 0.10%-0.20% Ti, 0.005%-0.015% B, 0.010%-0.020% Sr, 0.003%-0.012% La, Fe≤0.15%, Cu≤0.15%, other impurities ≤0.05% individually, and the total of other impurities ≤0.15%, with the balance being Al. The high-strength and high-toughness aluminum alloy has an average grain size of 320.9 μm-334.7 μm, an average secondary dendrite spacing of 26.8 μm-36.6 μm, a hardness of 81.78 HBW-83.48 HBW, an ultimate tensile strength of 276.59 MPa-281.93 MPa, and an elongation of 19.72%-22.17%.

[0050] A method for preparing the high-strength and high-toughness cast aluminum alloy as described above, the method comprising the following steps:

[0051] 1) Preparation of master alloy: Prepare Al-5Ti-1B master alloy and industrially pure lanthanum. The Al-5Ti-1B master alloy comprises the following components by mass percentage: 5.0%-5.2% Ti, 1.0%-1.2% B, and the remainder being aluminum; industrially pure lanthanum with a purity greater than 99%. The proportion of industrially pure lanthanum is 1.0%-1.2% La, and the remainder is Al-5Ti-1B master alloy.

[0052] 2) Preparation of Al-5Ti-1B-1La master alloy refiner: The prepared Al-5Ti-1B master alloy rod was cut into appropriate sizes and placed in a melting furnace. At the same time, the weighed lanthanum block was also added to the melting furnace. After evacuation, argon gas was introduced as a protective gas. The temperature was continuously raised to 1000℃ and then mechanically stirred for 30 minutes to make it uniform. After holding at the temperature for 30 minutes, it was vacuum cast into a mold with a preheated temperature of 420℃ and naturally cooled to room temperature to obtain the Al-5Ti-1B-1La master alloy. The obtained Al-5Ti-1B-1La master alloy contains the following components by mass percentage: 4.9%-5.1% Ti, 0.95%-1.05% B, and 0.9%-1.1% La.

[0053] 3) Aluminum alloy preparation ingredients: Prepare A356.2 aluminum alloy ingots as the main preparation material, which includes the following components by mass percentage: 6.9%-7.3% Si, 0.35%-0.45% Mg, 0.2%-0.3% Ti, Fe≤0.15%, Cu≤0.15%, other impurities ≤0.05% individually, and the total of other impurities ≤0.15%, with the balance being aluminum; use a modified Al-5Ti-1B-1La master alloy refiner for refining treatment, with an addition amount of 0.5%-1%; prepare Al-10Sr master alloy, which includes the following components by mass percentage: 10% Sr, 90% aluminum, with an addition amount of 0.14%; prepare refining agents and slag removers for industrial aluminum alloy smelting.

[0054] 4) Aluminum alloy preparation and batching: Prepare the required A356.2 aluminum alloy ingots, Al-5Ti-1B-1La master alloy, Al-10Sr master alloy rods, industrial refining agents and slag removers according to the requirements. The raw materials are prepared according to the calculated proportions and ready for use.

[0055] 5) Aluminum alloy smelting: The prepared A356.2 aluminum alloy is put into the smelting furnace for heating and melting; after the temperature of the aluminum liquid rises to 720℃ and the aluminum ingot is fully melted, nitrogen is used to blow in the refining agent for powder refining treatment; then slag removal treatment is performed; after the treatment is completed, the temperature is held for 30 minutes; then the prepared Al-5Ti-1B-1La master alloy is added and mechanically stirred continuously to make the aluminum liquid composition more uniform, and the stirring time is 20 minutes; then Al-10Sr master alloy is added and stirred continuously, and the stirring time is 20 minutes; then the slag remover is added and stirred continuously, while nitrogen is introduced for degassing and slag removal treatment; after the slag removal is completed, the temperature is held and allowed to stand for 30 minutes.

[0056] 6) Pouring: Pour into a mold preheated to 420°C, let it cool naturally until it solidifies and takes out, then water-cool it with 80°C water for 20 seconds, and then let it cool naturally to room temperature.

[0057] 7) Heat treatment of aluminum alloy: The casting is solution treated at 540℃ for 4 hours; then water quenched at 80℃ for 120 seconds; then aged at 130℃ for 3 hours to obtain a high-strength and tough cast aluminum alloy.

[0058] The present invention relates to a high-strength and high-toughness cast aluminum alloy with a Si content controlled at 6.80%-7.10%. Aluminum alloys within this range have good plasticity and are more suitable for the processing of cast wheel hubs.

[0059] The Mg content is controlled between 0.28% and 0.32%. Mg can promote the precipitation of Si, so the alloy strength is better within this range. If it is lower than this range, the alloy strength will be reduced to a certain extent, while if it is higher than this range, it will lead to a decrease in plasticity and a decrease in processing performance.

[0060] The Ti content is controlled at 0.10%-0.20%. The presence of Ti is to form compounds such as TiAl3 and TiB2 with B and Al in the matrix, which act as nucleation cores, accelerate the nucleation of α-Al, and thus refine the α-Al grains.

[0061] The boron content is controlled between 0.005% and 0.015% to form TiB2 with Ti and LaB6 with La, which together serve as heterogeneous nucleation cores to promote the refinement of α-Al grains. Excessive boron will reduce the plasticity of aluminum alloys and affect their processing performance.

[0062] The Sr content is controlled at 0.010%-0.020% to refine the eutectic Si particles, making the Si particles more rounded and thus improving mechanical properties. Excessive Sr will cause Sr segregation and thus affect the mechanical properties of the final product.

[0063] Example 1

[0064] A high-strength and high-toughness cast aluminum alloy comprises the following components by mass percentage: 6.964% Si, 0.304% Mg, 0.126% Ti, 0.013% B, 0.015% Sr, 0.005% La, 0.116% Fe, 0.046% Cu, with individual impurities ≤0.05% and the total of other impurities ≤0.15%, and the balance being Al. The high-strength and high-toughness aluminum alloy has an average grain size of 320.9 μm, an average secondary dendrite spacing of 26.8 μm, a hardness of 83.48 HBW, an ultimate tensile strength of 281.93 MPa, and an elongation of 22.17%.

[0065] A method for preparing the above-mentioned high-strength and high-toughness cast aluminum alloy includes the following steps:

[0066] 1) Preparation of master alloy ingredients: Prepare Al-5Ti-1B master alloy, including the following components by mass percentage: 5.1% Ti, 1.1% B, and the remainder being aluminum; prepare industrial pure lanthanum with a purity greater than 99%; its proportion is 1.2% La, and the remainder being Al-5Ti-1B master alloy.

[0067] 2) Preparation of Al-5Ti-1B-1La master alloy refiner: The prepared Al-5Ti-1B master alloy rod was cut into appropriate sizes and placed in a melting furnace. At the same time, the weighed lanthanum block was also added to the melting furnace. After evacuation, argon gas was introduced as a protective gas. The temperature was continuously raised to 1000℃ and then mechanically stirred for 30 minutes to make it uniform. After holding at the temperature for 30 minutes, it was vacuum cast into a mold with a preheated temperature of 420℃ and naturally cooled to room temperature to obtain the Al-5Ti-1B-1La master alloy. The obtained Al-5Ti-1B-1La master alloy contains the following components by mass percentage: 4.92% Ti, 0.98% B, and 1.10% La.

[0068] 3) Aluminum alloy preparation ingredients: Prepare A356.2 aluminum alloy ingots as the main preparation material, which includes the following components by mass percentage: 7.02% Si, 0.38% Mg, 0.20% Ti, 0.12% Fe, 0.13% Cu, with individual impurities ≤0.05% and total impurities ≤0.15%, with the balance being aluminum; use a modified Al-5Ti-1B-1La master alloy refining agent for refining treatment; prepare Al-10Sr master alloy, which includes the following components by mass percentage: 10% Sr, 90% aluminum, with an addition amount of 0.14%; prepare refining agents and slag removers for industrial aluminum alloy smelting.

[0069] 4) Aluminum alloy preparation and batching: Prepare the required A356.2 aluminum alloy ingots, Al-5Ti-1B-1La master alloy, Al-10Sr master alloy rods, industrial refining agents and slag removers according to the requirements. The raw materials are prepared according to the calculated proportions and ready for use.

[0070] 5) Aluminum alloy smelting: The prepared A356.2 aluminum alloy is put into the smelting furnace for heating and melting; after the temperature of the aluminum liquid rises to 720℃ and the aluminum ingot is fully melted, nitrogen is used to blow in the refining agent for powder refining treatment; then slag removal treatment is performed; after the treatment is completed, the temperature is held for 30 minutes; then the prepared Al-5Ti-1B-1La master alloy is added and mechanically stirred continuously to make the aluminum liquid composition more uniform, the addition amount is 0.8%, and the stirring time is 20 minutes; then Al-10Sr master alloy is added and stirred continuously for 20 minutes; then the slag remover is added and stirred continuously, while nitrogen is introduced for degassing and slag removal treatment; after the slag removal is completed, the temperature is held and allowed to stand for 30 minutes.

[0071] 6) Pour into a mold preheated to 420°C, let it cool naturally until it solidifies and sets, then remove it and water-cool it with 80°C water for 20 seconds, then remove it and let it cool naturally to room temperature;

[0072] 7) Aluminum alloy heat treatment: The casting was solution treated at 540℃ for 4 hours; then quenched in water at 80℃ for 120 seconds; followed by aging treatment at 130℃ for 3 hours to obtain a high-strength and high-toughness cast aluminum alloy. Alloy samples are attached. Figure 1 (a).

[0073] When using the intermediate alloy ingot prepared in step (2) during the smelting process, select the middle part and remove the top and bottom parts to avoid the introduction of impurities. In step (5) during the smelting process, use a medium-frequency melting furnace and a graphite crucible for smelting, use mechanical stirring, and avoid open melting to prevent excessive oxidation. In step (5) during the smelting process, slag removal refers to cleaning the slag on the surface of the aluminum liquid. Before adding the intermediate alloy refiner, take an appropriate amount of aluminum liquid from the middle of the aluminum liquid, cool it, and measure its composition to see if it is within the qualified range. If the Mg content is low, supplement it with industrial pure Mg particles beforehand. The molds in steps (2) and (6) are ordinary stainless steel molds with a wall thickness of 1.5 cm.

[0074] Example 2

[0075] A high-strength and high-toughness cast aluminum alloy comprises the following components by weight percentage: 6.816% Si, 0.282% Mg, 0.104% Ti, 0.005% B, 0.010% Sr, 0.003% La, 0.092% Fe, 0.032% Cu, with individual impurities ≤0.05% and the total of other impurities ≤0.15%, and the balance being Al. The high-strength and high-toughness aluminum alloy has an average grain size of 326.4 μm, an average secondary dendrite spacing of 36.6 μm, a hardness of 82.43 HBW, an ultimate tensile strength of 276.59 MPa, and an elongation of 19.72%.

[0076] A method for preparing the above-mentioned high-strength and high-toughness cast aluminum alloy includes the following steps:

[0077] 1) Preparation of master alloy ingredients: Prepare Al-5Ti-1B master alloy, including the following components by mass percentage: 5.0% Ti, 1.0% B, and the remainder being aluminum; prepare industrial pure lanthanum with a purity greater than 99%; its proportion is 1.0% La, and the remainder being Al-5Ti-1B master alloy.

[0078] 2) Preparation of Al-5Ti-1B-1La master alloy refiner: The prepared Al-5Ti-1B master alloy rod was cut into appropriate sizes and placed in a melting furnace. At the same time, the weighed lanthanum block was also added to the melting furnace. After evacuation, argon gas was introduced as a protective gas. The temperature was continuously raised to 1000℃ and then mechanically stirred for 30 minutes to make it uniform. After holding at the temperature for 30 minutes, it was vacuum cast into a mold with a preheated temperature of 420℃ and naturally cooled to room temperature to obtain the Al-5Ti-1B-1La master alloy. The obtained Al-5Ti-1B-1La master alloy contains the following components by mass percentage: 4.90% Ti, 0.95% B, and 0.90% La.

[0079] 3) Aluminum alloy preparation ingredients: Prepare A356.2 aluminum alloy ingots as the main preparation material, which includes the following components by mass percentage: 6.90% Si, 0.35% Mg, 0.2% Ti, 0.12% Fe, 0.10% Cu, with individual impurities ≤0.05% and total impurities ≤0.15%, with the balance being aluminum; use a modified Al-5Ti-1B-1La master alloy refining agent for refining treatment; prepare Al-10Sr master alloy, which includes the following components by mass percentage: 10% Sr, 90% aluminum, with an addition amount of 0.14%; prepare refining agents and slag removers for industrial aluminum alloy smelting.

[0080] 4) Aluminum alloy preparation and batching: Prepare the required A356.2 aluminum alloy ingots, Al-5Ti-1B-1La master alloy, Al-10Sr master alloy rods, industrial refining agents and slag removers according to the requirements. The raw materials are prepared according to the calculated proportions and ready for use.

[0081] 5) Aluminum alloy smelting: The prepared A356.2 aluminum alloy is put into the smelting furnace for heating and melting; after the temperature of the aluminum liquid rises to 720℃ and the aluminum ingot is fully melted, nitrogen is used to blow in the refining agent for powder refining treatment; then slag removal treatment is performed; after the treatment is completed, the temperature is held for 30 minutes; then the prepared Al-5Ti-1B-1La master alloy is added and mechanically stirred continuously to make the aluminum liquid composition more uniform, the addition amount is 0.5%, and the stirring time is 20 minutes; then Al-10Sr master alloy is added and stirred continuously for 20 minutes; then the slag remover is added and stirred continuously, while nitrogen is introduced for degassing and slag removal treatment; after the slag removal is completed, the temperature is held and allowed to stand for 30 minutes.

[0082] 6) Pour into a mold preheated to 420°C, let it cool naturally until it solidifies and sets, then remove it and water-cool it with 80°C water for 20 seconds, then remove it and let it cool naturally to room temperature;

[0083] 7) Aluminum alloy heat treatment: The casting was solution treated at 540℃ for 4 hours; then quenched in water at 80℃ for 120 seconds; followed by aging treatment at 130℃ for 3 hours to obtain a high-strength and high-toughness cast aluminum alloy. Alloy samples are attached. Figure 1 (b)

[0084] When using the intermediate alloy ingot prepared in step (2) during the smelting process, select the middle part and remove the top and bottom parts to avoid the introduction of impurities. In step (5) during the smelting process, use a medium-frequency melting furnace and a graphite crucible for smelting, use mechanical stirring, and avoid open melting to prevent excessive oxidation. In step (5) during the smelting process, slag removal refers to cleaning the slag on the surface of the aluminum liquid. Before adding the intermediate alloy refiner, take an appropriate amount of aluminum liquid from the middle of the aluminum liquid, cool it, and measure its composition to see if it is within the qualified range. If the Mg content is low, supplement it with industrial pure Mg particles beforehand. The molds in steps (2) and (6) are ordinary stainless steel molds with a wall thickness of 1.5 cm.

[0085] Example 3

[0086] A high-strength and high-toughness cast aluminum alloy comprises the following components by weight percentage: 7.037% Si, 0.318% Mg, 0.182% Ti, 0.015% B, 0.018% Sr, 0.011% La, 0.082% Fe, 0.096% Cu, with individual impurities ≤0.05% and the total of other impurities ≤0.15%, and the balance being Al. The high-strength and high-toughness aluminum alloy has an average grain size of 334.7 μm, an average secondary dendrite spacing of 34.2 μm, a hardness of 81.78 HBW, an ultimate tensile strength of 278.46 MPa, and an elongation of 20.23%.

[0087] A method for preparing the above-mentioned high-strength and high-toughness cast aluminum alloy includes the following steps:

[0088] 1) Preparation of master alloy ingredients: Prepare Al-5Ti-1B master alloy, including the following components by mass percentage: 5.2% Ti, 1.2% B, and the remainder being aluminum; prepare industrial pure lanthanum with a purity greater than 99%; its proportion is 1.2% La, and the remainder being Al-5Ti-1B master alloy.

[0089] 2) Preparation of Al-5Ti-1B-1La master alloy refiner: The prepared Al-5Ti-1B master alloy rod was cut into appropriate sizes and placed in a melting furnace. At the same time, the weighed lanthanum block was also added to the melting furnace. After evacuation, argon gas was introduced as a protective gas. The temperature was continuously raised to 1000℃ and then mechanically stirred for 30 minutes to make it uniform. After holding at the temperature for 30 minutes, it was vacuum cast into a mold with a preheated temperature of 420℃ and naturally cooled to room temperature to obtain the Al-5Ti-1B-1La master alloy. The obtained Al-5Ti-1B-1La master alloy contains the following components by mass percentage: 5.10% Ti, 1.05% B, and 1.10% La.

[0090] 3) Aluminum alloy preparation ingredients: Prepare A356.2 aluminum alloy ingots as the main preparation material, which includes the following components by mass percentage: 7.30% Si, 0.45% Mg, 0.30% Ti, 0.11% Fe, 0.15% Cu, with individual impurities ≤0.05% and total impurities ≤0.15%, with the balance being aluminum; use a modified Al-5Ti-1B-1La master alloy refiner for refining treatment; prepare Al-10Sr master alloy, which includes the following components by mass percentage: 10% Sr, 90% aluminum, with an addition amount of 0.14%; prepare refining agents and slag removers for industrial aluminum alloy smelting.

[0091] 4) Aluminum alloy preparation and batching: Prepare the required A356.2 aluminum alloy ingots, Al-5Ti-1B-1La master alloy, Al-10Sr master alloy rods, industrial refining agents and slag removers according to the requirements. The raw materials are prepared according to the calculated proportions and ready for use.

[0092] 5) Aluminum alloy smelting: The prepared A356.2 aluminum alloy is put into the smelting furnace for heating and melting; after the temperature of the aluminum liquid rises to 720℃ and the aluminum ingot is fully melted, nitrogen is used to blow in the refining agent for powder refining treatment; then slag removal treatment is performed; after the treatment is completed, the temperature is held for 30 minutes; then the prepared Al-5Ti-1B-1La master alloy is added and mechanically stirred continuously to make the aluminum liquid composition more uniform, the addition amount is 1.0%, and the stirring time is 20 minutes; then Al-10Sr master alloy is added and stirred continuously for 20 minutes; then the slag remover is added and stirred continuously, while nitrogen is introduced for degassing and slag removal treatment; after the slag removal is completed, the temperature is held and allowed to stand for 30 minutes.

[0093] 6) Pour into a mold preheated to 420°C, let it cool naturally until it solidifies and sets, then remove it and water-cool it with 80°C water for 20 seconds, then remove it and let it cool naturally to room temperature;

[0094] 7) Aluminum alloy heat treatment: The casting was solution treated at 540℃ for 4 hours; then quenched in water at 80℃ for 120 seconds; followed by aging treatment at 130℃ for 3 hours to obtain a high-strength and high-toughness cast aluminum alloy. Alloy samples are attached. Figure 1 (c)

[0095] When using the intermediate alloy ingot prepared in step (2) during the smelting process, select the middle part and remove the top and bottom parts to avoid the introduction of impurities. In step (5) during the smelting process, use a medium-frequency melting furnace and a graphite crucible for smelting, use mechanical stirring, and avoid open melting to prevent excessive oxidation. In step (5) during the smelting process, slag removal refers to cleaning the slag on the surface of the aluminum liquid. Before adding the intermediate alloy refiner, take an appropriate amount of aluminum liquid from the middle of the aluminum liquid, cool it, and measure its composition to see if it is within the qualified range. If the Mg content is low, supplement it with industrial pure Mg particles beforehand. The molds in steps (2) and (6) are ordinary stainless steel molds with a wall thickness of 1.5 cm.

[0096] Example 4

[0097] A high-strength and high-toughness cast aluminum alloy comprises the following components by weight percentage: 6.964% Si, 0.304% Mg, 0.126% Ti, 0.013% B, 0.015% Sr, 0.005% La, 0.116% Fe, 0.046% Cu, with individual impurities ≤0.05% and the total of other impurities ≤0.15%, and the balance being Al. The high-strength and high-toughness aluminum alloy has an average grain size of 321.0 μm, an average secondary dendrite spacing of 31.9 μm, a hardness of 82.21 HBW, an ultimate tensile strength of 280.68 MPa, and an elongation of 21.06%.

[0098] A method for preparing the above-mentioned high-strength and high-toughness cast aluminum alloy includes the following steps:

[0099] 1) Preparation of master alloy ingredients: Prepare Al-5Ti-1B master alloy, including the following components by mass percentage: 5.1% Ti, 1.1% B, and the remainder being aluminum; prepare industrial pure lanthanum with a purity greater than 99%; its proportion is 1.0% La, and the remainder being Al-5Ti-1B master alloy.

[0100] 2) Preparation of Al-5Ti-1B-1La master alloy refiner: The prepared Al-5Ti-1B master alloy rod was cut into appropriate sizes and placed in a melting furnace. At the same time, the weighed lanthanum block was also added to the melting furnace. After evacuation, argon gas was introduced as a protective gas. The temperature was continuously raised to 1000℃ and then mechanically stirred for 30 minutes to make it uniform. After holding at the temperature for 30 minutes, it was vacuum cast into a mold with a preheated temperature of 420℃ and naturally cooled to room temperature to obtain the Al-5Ti-1B-1La master alloy. The obtained Al-5Ti-1B-1La master alloy contains the following components by mass percentage: 4.97% Ti, 1.01% B, and 0.92% La.

[0101] 3) Aluminum alloy preparation ingredients: Prepare A356.2 aluminum alloy ingots as the main preparation material, which includes the following components by mass percentage: 7.16% Si, 0.42% Mg, 0.27% Ti, 0.13% Fe, 0.09% Cu, with individual impurities ≤0.05% and total impurities ≤0.15%, with the balance being aluminum; use a modified Al-5Ti-1B-1La master alloy refining agent for refining treatment; prepare Al-10Sr master alloy, which includes the following components by mass percentage: 10% Sr, 90% aluminum, with an addition amount of 0.14%; prepare refining agents and slag removers for industrial aluminum alloy smelting.

[0102] 4) Aluminum alloy preparation and batching: Prepare the required A356.2 aluminum alloy ingots, Al-5Ti-1B-1La master alloy, Al-10Sr master alloy rods, industrial refining agents and slag removers according to the requirements. The raw materials are prepared according to the calculated proportions and ready for use.

[0103] 5) Aluminum alloy smelting: The prepared A356.2 aluminum alloy is put into the smelting furnace for heating and melting; after the temperature of the aluminum liquid rises to 720℃ and the aluminum ingot is fully melted, nitrogen is used to blow in the refining agent for powder refining treatment; then slag removal treatment is performed; after the treatment is completed, the temperature is held for 30 minutes; then the prepared Al-5Ti-1B-1La master alloy is added and mechanically stirred continuously to make the aluminum liquid composition more uniform, the addition amount is 0.7%, and the stirring time is 20 minutes; then Al-10Sr master alloy is added and stirred continuously for 20 minutes; then the slag remover is added and stirred continuously, while nitrogen is introduced for degassing and slag removal treatment; after the slag removal is completed, the temperature is held and allowed to stand for 30 minutes.

[0104] 6) Pour into a mold preheated to 420°C, let it cool naturally until it solidifies and sets, then remove it and water-cool it with 80°C water for 20 seconds, then remove it and let it cool naturally to room temperature;

[0105] 7) Aluminum alloy heat treatment: The casting was solution treated at 540℃ for 4 hours; then quenched in water at 80℃ for 120 seconds; followed by aging treatment at 130℃ for 3 hours to obtain a high-strength and high-toughness cast aluminum alloy. Alloy samples are attached. Figure 1 (d)

[0106] When using the intermediate alloy ingot prepared in step (2) during the smelting process, select the middle part and remove the top and bottom parts to avoid the introduction of impurities. In step (5) during the smelting process, use a medium-frequency melting furnace and a graphite crucible for smelting, use mechanical stirring, and avoid open melting to prevent excessive oxidation. In step (5) during the smelting process, slag removal refers to cleaning the slag on the surface of the aluminum liquid. Before adding the intermediate alloy refiner, take an appropriate amount of aluminum liquid from the middle of the aluminum liquid, cool it, and measure its composition to see if it is within the qualified range. If the Mg content is low, supplement it with industrial pure Mg particles beforehand. The molds in steps (2) and (6) are ordinary stainless steel molds with a wall thickness of 1.5 cm.

[0107] Comparative Example 1

[0108] A cast aluminum alloy comprises the following components by weight percentage: 6.862% Si, 0.316% Mg, 0.196% Ti, 0.011% B, 0.019% Sr, 0.103% Fe, 0.041% Cu, with individual impurities ≤0.05% and the total of impurities ≤0.15%, and the balance being Al. The aluminum alloy has an average grain size of 432.9 μm, an average secondary dendrite spacing of 49.0 μm, a hardness of 76.27 HBW, an ultimate tensile strength of 272.57 MPa, and an elongation of 10.14%.

[0109] A method for preparing the above-mentioned cast aluminum alloy, the method comprising the following steps:

[0110] 1) Aluminum alloy preparation materials: Prepare A356.2 aluminum alloy ingots as the main preparation material, which includes the following components by mass percentage: 7.09% Si, 0.38% Mg, 0.25% Ti, 0.15% Fe, 0.11% Cu, with individual impurities ≤0.05% and total impurities ≤0.15%, with the balance being aluminum; use Al-5Ti-1B master alloy refining agent for refining treatment, which includes the following components by mass percentage: 4.97% Ti, 1.01% B, with the balance being aluminum; prepare Al-10Sr master alloy, which includes the following components by mass percentage: 10% Sr, 90% aluminum, with an addition amount of 0.14%; prepare refining agents and slag removers for industrial aluminum alloy smelting.

[0111] 2) Aluminum alloy preparation and batching: Prepare the required A356.2 aluminum alloy ingots, Al-5Ti-1B master alloy, Al-10Sr master alloy rods, industrial refining agents and slag removers according to the requirements. The raw materials are prepared according to the calculated proportions and ready for use.

[0112] 3) Aluminum alloy smelting: The prepared A356.2 aluminum alloy is put into the smelting furnace for heating and melting; after the temperature of the aluminum liquid rises to 720℃ and the aluminum ingot is fully melted, nitrogen is used to blow in the refining agent for powder refining treatment; then slag removal treatment is performed; after the treatment is completed, the temperature is held for 30 minutes; then the prepared Al-5Ti-1B master alloy is added and mechanically stirred continuously to make the aluminum liquid composition more uniform, the addition amount is 0.8%, and the stirring time is 20 minutes; then Al-10Sr master alloy is added and stirred continuously for 20 minutes; then the slag remover is added and stirred continuously, while nitrogen is introduced for degassing and slag removal treatment; after the slag removal is completed, the temperature is held and allowed to stand for 30 minutes.

[0113] 4) Pour into a mold preheated to 420°C, let it cool naturally until it solidifies and sets, then remove it and water-cool it with 80°C water for 20 seconds, then remove it and let it cool naturally to room temperature;

[0114] 5) Aluminum alloy heat treatment: The casting was solution treated at 540℃ for 4 hours; then quenched in water at 80℃ for 120 seconds; followed by aging treatment at 130℃ for 3 hours to obtain the above-mentioned cast aluminum alloy. Alloy samples are attached. Figure 1 (e).

[0115] In step (3), during the smelting process, a medium-frequency melting furnace and a graphite crucible are used for smelting. Mechanical stirring is employed, and open-mouth smelting is avoided to prevent excessive oxidation. In step (3), slag removal refers to cleaning the slag floating on top of the molten aluminum. Before adding the intermediate alloy refiner, a suitable amount of molten aluminum must be taken from the middle of the molten aluminum, cooled, and its composition measured to ensure it is within the acceptable range. If the Mg content is low, industrial pure Mg particles are used to supplement it beforehand. The molds used in step (4) are all ordinary stainless steel molds with a wall thickness of 1.5 cm.

[0116] Metallographic preparation and observation were performed on the physical specimen from Example 1. Mechanical polishing was followed by electrolytic polishing using a 10% perchloric acid-ethanol solution at 25V and 0.2A for 10 seconds. Anodizing was then performed using a 2.5% fluoroboric acid aqueous solution at 25V and 0.2A for 90 seconds. The prepared metallographic specimen was observed under a polarizing microscope, and the resulting metallographic images are shown in the appendix. Figure 2It can be seen that the grains of the aluminum alloy have been refined to a certain extent, especially the secondary dendrites. Measurements showed that the average grain size of the aluminum-silicon alloy in Example 1 was 320.9 μm, and the average secondary dendrite spacing was 26.8 μm, which represents a reduction of 25.9% and 45.3% respectively compared to the cast aluminum alloy of Comparative Example 1 (average grain size: 432.9 μm, secondary dendrite arm spacing: 49.0 μm). See the attached comparison figures for relevant information. Figure 3 .

[0117] The fracture surface of the tensile specimen from Example 1 after fracture was observed using a scanning electron microscope (SEM). The SEM images are shown in the attached image. Figure 4 It can be seen that the dimple depth in the fracture surface of the aluminum alloy of Example 1 is deeper than that of the aluminum alloy of Comparative Example 1; the cleavage surface and dimples coexist in Example 1 and are more evenly distributed than those in Comparative Example 1. This phenomenon can explain that the ultimate tensile strength and elongation of the aluminum alloy of Example 1 are improved to a certain extent compared with those of the aluminum alloy of Comparative Example 1.

[0118] The mechanical property comparison charts obtained by comparing the above Examples 1-4 with the comparative examples are shown in the appendix of the instruction manual. Figure 5 Comparative analysis shows that after using a master alloy as a refining agent, the resulting aluminum alloy exhibits improvements in hardness, elongation, and ultimate tensile strength compared to aluminum alloys using traditional master alloys. In particular, Example 1, with a La addition of 0.005 wt.%, demonstrates higher hardness, elongation, and ultimate tensile strength than other examples. Its ultimate tensile strength is 281.93 MPa, a 3.4% increase compared to the cast aluminum alloy of Comparative Example 1 (272.57 MPa); its elongation is 22.17%, a 119% increase compared to the cast aluminum alloy of Comparative Example 1 (10.14%); and its hardness is 83.48 HBW, a 9.5% increase compared to the cast aluminum alloy of Comparative Example 1 (76.27 HBW).

[0119] Although the embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for preparing a high-strength and high-toughness cast aluminum alloy, characterized in that: The elemental composition and their mass percentage in the aluminum alloy are as follows: 6.80%-7.10% Si, 0.28%-0.32% Mg, 0.10%-0.20% Ti, 0.005%-0.015% B, 0.010%-0.020% Sr, 0.003%-0.012% La, Fe≤0.15%, Cu≤0.15%, other impurities ≤0.05% individually, total impurities ≤0.15%, and the balance is Al; The preparation method of the high-strength and high-toughness cast aluminum alloy includes the following steps: 1) Ingredients: A356.2 hypoeutectic aluminum-silicon alloy ingot is used as the main preparation material; Al-5Ti-1B-1La master alloy refiner is used for refining treatment, with an addition amount of 0.5%-1%; Al-10Sr master alloy modifier is used for modification treatment, with an addition amount of 0.14%. 2) Prepare materials: Calculate the proportions of A356.2 aluminum-silicon alloy, Al-5Ti-1B-1La master alloy, Al-10Sr master alloy, and industrial refining agent and slag remover and prepare them for use. 3) Melting: The prepared A356.2 aluminum alloy ingot is put into the melting furnace for heating and melting. After the temperature of the aluminum liquid rises to 720℃ and the aluminum ingot is fully melted, nitrogen is used to blow in the refining agent for powder refining treatment. Then, slag removal treatment is performed. After the treatment is completed, the temperature is held for 30 minutes. Then, the prepared Al-5Ti-1B-1La master alloy is added and stirred continuously for 20 minutes. Then, Al-10Sr master alloy is added and stirred continuously for 20 minutes. Then, the slag removal agent is added and stirred continuously, while nitrogen is introduced for degassing and slag removal treatment. After the slag removal is completed, the temperature is held for 30 minutes. 4) Casting: Heat the casting mold to 420℃; pour the molten aluminum into the mold, let it cool naturally until it solidifies and takes shape, then remove it and water-cool it with 80℃ water for 20 seconds, then let it cool naturally to room temperature. 5) Heat treatment: The casting is solution treated at 540℃ for 4 hours; then quenched in water at 80℃ for 120 seconds; then aged at 130℃ for 3 hours. The preparation method of the Al-5Ti-1B-1La master alloy includes the following steps: 1.1) Raw materials: Al-5Ti-1B master alloy is used as raw material. The Al-5Ti-1B master alloy raw material includes the following components by mass percentage: 5.0%-5.2% Ti, 1.0%-1.2% B, and the remainder is aluminum; industrial pure lanthanum, purity 99%; 1.2) Material preparation: Prepare materials with 1.0%-1.2% La by weight, and the balance being Al-5Ti-1B master alloy raw material; 1.3) Melting: Place the prepared Al-5Ti-1B intermediate alloy raw material and La into the melting furnace, evacuate the furnace, and then introduce industrial-grade high-purity argon gas; continue heating to 1000℃ and then mechanically stir for 30 minutes; hold at that temperature for 30 minutes. 1.4) Casting: Heat the casting mold to 420°C and perform vacuum casting, then cool to room temperature; 1.5) An Al-5Ti-1B-1La master alloy was prepared. The Al-5Ti-1B-1La master alloy contained the following components by mass percentage: 4.9%-5.1% Ti, 0.95%-1.05% B, and 0.9%-1.1% La.

2. The method for preparing high-strength and high-toughness cast aluminum alloy according to claim 1, characterized in that: The aluminum alloy has an average grain size of 320.9 μm-334.7 μm, an average secondary dendrite spacing of 26.8 μm-36.6 μm, a hardness of 81.78 HBW-83.48 HBW, an ultimate tensile strength of 276.59 MPa-281.93 MPa, and an elongation of 19.72%-22.17%.

3. The method for preparing high-strength and high-toughness cast aluminum alloy according to claim 1, characterized in that: The A356.2 aluminum-silicon alloy used comprises the following components by mass percentage: 6.9%-7.3% Si, 0.35%-0.45% Mg, 0.2%-0.3% Ti, Fe≤0.15%, Cu≤0.15%, other impurities individually≤0.05%, other impurities total≤0.15%, and the balance being aluminum.

4. The method for preparing high-strength and high-toughness cast aluminum alloy according to claim 1, characterized in that: The Al-10Sr master alloy modifier comprises the following components by mass percentage: 10% Sr, 90% aluminum.

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