High-strength and high-toughness aluminum alloys, their preparation methods and applications

Abstract

This invention relates to the field of alloy materials technology, and in particular to a high-strength and high-toughness aluminum alloy, its preparation method, and its applications. The high-strength and high-toughness aluminum alloy, by mass percentage, comprises the following components: Si 7%–8%, Mg 0.45%–0.55%, Ti 0.15%–0.3%, Be 0.15%–0.3%, Sc 0.15%–0.45%, Ce 0.15%–0.25%, B 0.01%–0.03%, Fe≤0.2%, Zn≤0.2%, Mn≤0.1%, Cu≤0.2%, Zr≤0.2%, with the balance being Al and unavoidable impurities. The high-strength and high-toughness aluminum alloy of this invention, through the control of its composition, exhibits good fluidity, meeting the requirements of investment casting for complex structures; simultaneously, the alloy possesses high strength and toughness at temperatures ranging from -56 to 300°C.

Description

Technical Field

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

[0002] Investment casting is an advanced casting process developed based on the traditional lost-wax casting method. Its main process includes: first, using wax to make a wax model that matches the shape of the part; then, coating the surface of the wax model with refractory material layer by layer to form a shell with a certain thickness; next, softening the wax model by heating or high-temperature steam treatment and allowing it to flow out completely, thereby obtaining a hollow refractory shell; then, firing the shell at high temperature to ceramicize it and give it sufficient strength; finally, pouring molten metal into the shell and cooling it to obtain a precision-formed casting.

[0003] In the investment casting process of aluminum alloys, molten aluminum alloy is poured into a refractory mold. Due to the poor thermal conductivity of refractory materials, the alloy cools relatively slowly, making the alloy's casting properties crucial to the metallurgical quality of the final casting. Furthermore, to improve the mechanical properties of aluminum alloys, alloying elements are usually added. While this improves the material's mechanical properties, it also increases the risk of casting defects such as porosity, gas bubbles, and segregation.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength and high-toughness aluminum alloy, its preparation method and application. The high-strength and high-toughness aluminum alloy of this invention, by controlling the alloy composition, gives the alloy good fluidity, which can meet the needs of investment casting of complex structures. At the same time, the alloy has high strength and toughness, and has excellent mechanical properties in the range of -56 to 300°C.

[0006] To achieve the above-mentioned objectives of the present invention, a first aspect of the present invention provides a high-strength and high-toughness aluminum alloy comprising, by mass percentage, the following components: Si 7%–8%, Mg 0.45%–0.55%, Ti 0.15%–0.3%, Be 0.15%–0.3%, Sc 0.15%–0.45%, Ce 0.15%–0.25%, B 0.01%–0.03%, Fe ≤0.2%, Zn ≤0.2%, Mn ≤0.1%, Cu ≤0.2%, Zr ≤0.2%, with the balance being Al and unavoidable impurities.

[0007] In a specific embodiment of the present invention, the high-strength and high-toughness aluminum alloy comprises, by mass percentage, the following components: Si 7.3%–7.7%, Mg 0.47%–0.53%, Ti 0.18%–0.25%, Be 0.18%–0.25%, Sc 0.2%–0.3%, Ce 0.17%–0.23%, B 0.015%–0.025%, Fe ≤0.2%, Zn ≤0.2%, Mn ≤0.1%, Cu ≤0.2%, Zr ≤0.2%, with the balance being Al and unavoidable impurities.

[0008] In a specific embodiment of the present invention, the as-cast microstructure of the high-strength and high-toughness aluminum alloy has the following characteristics: the eutectic silicon is mainly in the form of fine short fibers; Al3Sc particles, Al3Ti particles, Al3Ce particles, and TiB2 particles are present in the as-cast microstructure, with Al3Sc particles and Al3Ti particles distributed near the grain boundaries.

[0009] The second aspect of the present invention provides a method for preparing the high-strength and high-toughness aluminum alloy of the first aspect of the present invention, comprising the following steps:

[0010] (a) Prepare raw materials according to the alloy composition; melt pure aluminum and Al-Si master alloy, and after all the raw materials have melted, add the remaining master alloy and perform a first refining; then add magnesium and perform a second refining to obtain aluminum alloy liquid;

[0011] (b) Casting the molten aluminum alloy.

[0012] In a specific embodiment of the present invention, step (a) includes melting pure aluminum and Al-Si master alloy in a furnace, and then sequentially adding Al-Sc master alloy, Al-Ce master alloy, Al-Ti master alloy, Al-Ti-B master alloy and Al-Be master alloy for melting.

[0013] In a specific embodiment of the present invention, the temperature during the first refining process is 720–740°C and the time is 10–20 min.

[0014] In a specific embodiment of the present invention, a rotary jet refining process is used in the primary refining stage. Further, in the rotary jet refining, the rotational speed is 250–500 r / min, and the argon pressure is 0.1–0.5 MPa.

[0015] In a specific embodiment of the present invention, the secondary refining process is carried out at a temperature of 720–740°C for 10–20 minutes.

[0016] In a specific embodiment of the present invention, a rotary jet refining process is used in the secondary refining. Further, in the rotary jet refining, the rotational speed is 250–500 r / min, and the argon pressure is 0.1–0.5 MPa.

[0017] In a specific embodiment of the present invention, in step (b), the temperature of the aluminum alloy liquid is adjusted to 680-720°C for casting.

[0018] In a specific embodiment of the present invention, during the casting process, the molten aluminum alloy is poured into a shell or ingot mold.

[0019] In a specific embodiment of the present invention, the method further includes: performing solution treatment and aging treatment on the casting obtained by casting. Further, the solution treatment includes: holding at 536±5℃ for 10–16 hours, followed by water cooling; the aging treatment includes: holding at 175±5℃ for 4–8 hours, followed by air cooling.

[0020] The third aspect of the present invention provides the application of the high-strength and high-toughness aluminum alloy provided in the first aspect of the present invention in investment casting.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The high-strength and high-toughness aluminum alloy of the present invention has good fluidity by controlling the alloy composition, which can meet the needs of investment casting of complex structures; at the same time, the alloy has high strength and toughness in the range of -56 to 300°C. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a microstructure diagram of the heat-treated casting provided in Embodiment 1 of the present invention;

[0025] Figure 2 This is a microstructure diagram of the heat-treated casting provided in Embodiment 2 of the present invention;

[0026] Figure 3 This is a microstructure diagram of the heat-treated casting provided in Embodiment 3 of the present invention;

[0027] Figure 4 This is a microstructure diagram of the heat-treated casting provided in Embodiment 4 of the present invention;

[0028] Figure 5 This is a microstructure diagram of the heat-treated casting provided in Embodiment 5 of the present invention;

[0029] Figure 6 This is a microstructure diagram of the heat-treated casting provided in Embodiment 6 of the present invention;

[0030] Figure 7 This is a microstructure diagram of the heat-treated casting provided in Embodiment 7 of the present invention;

[0031] Figure 8 This is a microstructure diagram of the heat-treated casting provided in Comparative Example 1 of the present invention.

[0032] Figure 9 This is a microstructure diagram of the heat-treated casting provided in Comparative Example 2 of the present invention;

[0033] Figure 10 This is a microstructure diagram of the heat-treated casting provided in Comparative Example 3 of the present invention.

[0034] Figure 11 This is a microstructure diagram of the heat-treated casting provided in Comparative Example 4 of the present invention. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0036] For aluminum-silicon alloys, improving their mechanical properties hinges on refining the morphology of their eutectic silicon. While the introduction of silicon improves the alloy's fluidity, the eutectic silicon formed during solidification (typically lamellar or needle-like) severely disrupts the matrix. Eutectic silicon is a brittle phase, making it highly susceptible to fatigue crack propagation, thus impairing the alloy's mechanical properties. Adding modifiers can alter the growth pattern of eutectic silicon. Commonly used modifiers include Na, Sr, and Sb. Na exhibits good modifying effects, but its duration is short, generally showing a good effect only within 40 minutes after addition, and essentially failing after 2 hours. Sr, on the other hand, provides a persistent modifying effect that persists even after repeated melting, but its tendency to absorb gas can lead to excessive porosity in castings. While Sb also provides a persistent modifying effect, its effect is relatively limited.

[0037] In the high-strength and high-toughness aluminum alloy of the present invention, Ce and Sc elements are introduced as modifiers. The combination of the two elements, within a certain range of addition, has a lasting and effective modification effect. At the same time, a certain amount of Ti, B and other elements are introduced to refine the grains. A certain amount of Mg element is added to the alloy, which generates the Mg2Si phase during the solidification process of the metal and precipitates to the grain boundaries after heat treatment. Through the combination of multiple factors, the performance of the aluminum alloy is significantly improved while ensuring that the fluidity of the alloy meets the requirements of investment casting.

[0038] Based on this, the first aspect of the present invention provides a high-strength and high-toughness aluminum alloy, comprising the following components by mass percentage: Si 7%–8%, Mg 0.45%–0.55%, Ti 0.15%–0.3%, Be 0.15%–0.3%, Sc 0.15%–0.45%, Ce 0.15%–0.25%, B 0.01%–0.03%, Fe ≤0.2%, Zn ≤0.2%, Mn ≤0.1%, Cu ≤0.2%, Zr ≤0.2%, with the balance being Al and unavoidable impurities.

[0039] The high-strength and high-toughness aluminum alloy of the present invention has good fluidity by controlling the alloy composition, which can meet the needs of investment casting of complex structures; at the same time, the alloy has high strength and toughness in the range of -56 to 300°C and meets the requirements of high metallurgical quality.

[0040] In one specific embodiment, the high-strength and high-toughness aluminum alloy includes 7% to 8% Si by mass percentage, for example, 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8%, or any combination thereof, preferably 7.3% to 7.7%. Si can lower the melting point of the alloy and improve its fluidity, making it easier to fill complex cavities in investment casting. Simultaneously, within the above range, Si can form an appropriate amount of eutectic silicon, which, in conjunction with the other components, improves the morphology of the eutectic silicon and avoids its negative impact on mechanical properties. When the Si content is too low, fluidity is difficult to guarantee; when the Si content is too high, excessive brittle phases will severely fracture the aluminum matrix, leading to a significant deterioration in the alloy's toughness and ductility.

[0041] In one specific embodiment, the high-strength and high-toughness aluminum alloy includes 0.45% to 0.55% Mg by mass percentage, for example, it can be 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.5%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, or any combination thereof, preferably 0.47% to 0.53%. The introduction of an appropriate amount of Mg can form the intermetallic compound Mg₂Si with Si. With a certain solution treatment, Mg₂Si can dissolve into the matrix. During aging treatment, fine, dispersed Mg₂Si phases precipitate at grain boundaries, effectively hindering dislocation movement, thereby achieving a strengthening effect and significantly improving the strength of the alloy. When the Mg content is too low, it is difficult to form a sufficient amount of Mg₂Si phase, and the improvement in strength is not significant; when the Mg content is too high, on the one hand, Mg increases the melt viscosity, leading to a decrease in fluidity; on the other hand, excessive Mg may form other brittle phases, affecting toughness.

[0042] In one specific embodiment, the high-strength and high-toughness aluminum alloy includes 0.15% to 0.3% Ti by mass percentage, for example, it can be 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, or any combination thereof, preferably 0.18% to 0.25%. The introduction of an appropriate amount of Ti can refine the grains of the as-cast aluminum alloy, improve the alloy's mechanical properties, and reduce casting defects. When the Ti content is too low, its grain-refining effect is not significant; when the Ti content is too high, coarse Al3Ti is easily formed, leading to a decrease in alloy properties. Simultaneously, excessive Ti will react with boron (B), consuming B and affecting the grain-refining effect of B.

[0043] In one specific embodiment, the high-strength and high-toughness aluminum alloy includes 0.15% to 0.3% Be by mass percentage, for example, it can be 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, or any combination thereof, preferably 0.18% to 0.25%. The introduction of an appropriate amount of Be can improve the properties of the oxide film, prevent melt oxidation, and reduce defects such as oxide inclusions and porosity in castings. When the Be content is too low, the effect is not obvious; when the Be content is too high, it will affect the grain refinement effect of Ti, B, etc., leading to coarse as-cast microstructure, affecting mechanical properties and hot cracking tendency.

[0044] In one specific embodiment, the high-strength and high-toughness aluminum alloy includes 0.15% to 0.45% Sc by mass percentage, for example, in the range of 0.15%, 0.16%, 0.17%, 0.18%, 0.2%, 0.22%, 0.23%, 0.45%, or any combination thereof, preferably 0.2% to 0.3%; and 0.15% to 0.25% Ce by mass percentage, for example, in the range of 0.15%, 0.16%, 0.17%, 0.18%, 0.2%, 0.22%, 0.23%, 0.25%, or any combination thereof, preferably 0.17% to 0.23%. The introduction of appropriate amounts of Ce and Sc elements can significantly improve the morphology of the eutectic silicon and refine the matrix structure. Specifically, Ce enriches at the growth front of eutectic silicon, inhibiting its anisotropic growth and thus altering its coarse, acicular structure. Combined with the grain-refining effects of Ti and B, this contributes to enhanced low-temperature performance of the alloy. Sc refines the primary grains of the aluminum alloy matrix, providing more dispersed nucleation sites for eutectic silicon growth and inhibiting its growth and coarsening. Simultaneously, the Al3Sc particles formed by Sc are distributed near grain boundaries, effectively hindering dislocation movement and pinning subgrain boundaries, significantly improving the alloy's high-temperature stability. Under the combined action of Ce and Sc, the eutectic silicon morphology gradually transforms from a harmful lamellar / acicular structure to a skeletal or short rod-like morphology. Combined with heat treatment, the edges of the eutectic silicon are further passivated and tend towards spheroidization, resulting in a fine, uniform, and nearly spherical eutectic silicon structure. This significantly reduces the cutting effect of eutectic silicon on the matrix and broadens the alloy's operating temperature range. However, excessive amounts of either element degrade the modification effect, leading to a decrease in mechanical properties.

[0045] In one specific embodiment, the high-strength and high-toughness aluminum alloy includes 0.01% to 0.03% B by mass percentage, for example, it can be 0.01%, 0.012%, 0.015%, 0.018%, 0.02%, 0.022%, 0.025%, 0.028%, 0.03%, or any combination thereof, preferably 0.015% to 0.025%. The addition of an appropriate amount of B can react with Ti in the alloy to form dispersed TiB2 or (Al,Ti)B2 particles, which can refine the grain size. When the B content is too low, the grain refining effect is not significant; when the B content is too high, coarse and brittle phases are easily formed, leading to a deterioration in the performance of the aluminum alloy.

[0046] In one specific embodiment, the high-strength and high-toughness aluminum alloy comprises, by mass percentage, the following components: Si 7.3%–7.7%, Mg 0.47%–0.53%, Ti 0.18%–0.25%, Be 0.18%–0.25%, Sc 0.2%–0.3%, Ce 0.17%–0.23%, B 0.015%–0.025%, Fe ≤0.2%, Zn ≤0.2%, Mn ≤0.1%, Cu ≤0.2%, Zr ≤0.2%, with the balance being Al and unavoidable impurities.

[0047] Fe, Zn, Mn, Cu, and Zr may be absent or introduced in appropriate amounts (or as impurities), as long as their upper limits are controlled to not exceed the above-mentioned limits. Among unavoidable impurities, the content of a single impurity is ≤0.05%, and the total content of impurities is ≤0.15%.

[0048] In one specific embodiment, the as-cast microstructure of the high-strength and high-toughness aluminum alloy has the following characteristics: the eutectic silicon mainly exists in the form of fine short fibers, with a small amount existing in short rods; the as-cast microstructure contains Al3Sc, Al3Ti, Al3Ce, and TiB2 particles, with Al3Sc and Al3Ti particles distributed near the grain boundaries. The phrase "eutectic silicon mainly exists in the form of fine short fibers" means that at least half of the eutectic silicon exhibits a fine short fiber structure.

[0049] The second aspect of the present invention provides a method for preparing the high-strength and high-toughness aluminum alloy of the first aspect of the present invention, comprising the following steps:

[0050] (a) Prepare raw materials according to the alloy composition; melt pure aluminum and Al-Si master alloy, and after all the raw materials have melted, add the remaining master alloy and perform a first refining; then add magnesium and perform a second refining to obtain aluminum alloy liquid;

[0051] (b) Casting the molten aluminum alloy.

[0052] In one specific embodiment, Si is introduced into the high-strength and high-toughness aluminum alloy in the form of Al-Si master alloy; Mg is introduced in the form of pure magnesium; Ti is introduced in the form of Al-Ti master alloy and / or Al-Ti-B master alloy; Be is introduced in the form of Al-Be master alloy; Sc is introduced in the form of Al-Sc master alloy; Ce is introduced in the form of Al-Ce master alloy; and B is introduced in the form of Al-Ti-B master alloy. In actual operation, all raw materials can be pretreated (including but not limited to baking at 400°C) before smelting to remove surface oil and moisture.

[0053] In one specific embodiment, the Al-Si master alloy includes, but is not limited to, Al-Si20 master alloy; the Al-Ti master alloy includes, but is not limited to, Al-Ti10 master alloy; the Al-Ti-B master alloy includes, but is not limited to, Al-Ti5-B1 ​​master alloy; the Al-Be master alloy includes, but is not limited to, Al-Be5 master alloy; the Al-Sc master alloy includes, but is not limited to, Al-Sc2 master alloy; and the Al-Ce master alloy includes, but is not limited to, Al-Ce30 master alloy.

[0054] In one specific embodiment, in step (a), the smelting includes: melting pure aluminum and Al-Si master alloy in a furnace, and then sequentially adding Al-Sc master alloy, Al-Ce master alloy, Al-Ti master alloy, Al-Ti-B master alloy and Al-Be master alloy for melting.

[0055] In one specific embodiment, the temperature is 720–740°C and the time is 10–20 minutes during one refining cycle. The specific refining time can be adjusted according to the dosage.

[0056] In one specific embodiment, a rotary jet refining process is employed in the primary refining stage. Further, in the rotary jet refining, the rotational speed is 250–500 r / min, and the argon pressure is 0.1–0.5 MPa. For example, the rotational speed can be within the range of 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, or any combination thereof; the argon pressure can be within the range of 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, or any combination thereof. The argon gas is high-purity argon gas with a purity ≥ 99.99%.

[0057] In one specific embodiment, the secondary refining process is carried out at a temperature of 720–740°C for 10–20 minutes. The specific secondary refining time can be adjusted according to the dosage.

[0058] In one specific embodiment, a rotary jet refining process is employed in the secondary refining. Further, in the rotary jet refining, the rotational speed is 250–500 r / min, and the argon pressure is 0.1–0.5 MPa. For example, the rotational speed can be within the range of 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, or any combination thereof; the argon pressure can be within the range of 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, or any combination thereof. The argon gas is high-purity argon gas with a purity ≥ 99.99%.

[0059] In one specific embodiment, in step (b), the temperature of the molten aluminum alloy is adjusted to 680–720°C for pouring. Specifically, the temperature of the molten aluminum alloy used for pouring can be 680°C, 690°C, 700°C, 710°C, 720°C, or any combination thereof.

[0060] In one specific embodiment, during casting, molten aluminum alloy is poured into a mold or ingot mold. After cooling in the ingot mold to obtain an aluminum ingot, the ingot can be repeatedly melted and used to cast the final product.

[0061] In one specific embodiment, the method further includes: performing solution treatment and aging treatment on the casting obtained by casting. Further, the solution treatment includes: holding at 536±5℃ for 10 to 16 hours and water cooling; the aging treatment includes: holding at 175±5℃ for 4 to 8 hours and air cooling.

[0062] The heat treatment process of this invention can further passivate and spheroidize the edges of the eutectic silicon, resulting in a fine, uniform, and nearly spherical eutectic silicon structure, which significantly reduces the cutting effect on the matrix. The Mg2Si strengthening phase can fully dissolve into the aluminum matrix during the solid solution stage, forming a supersaturated solid solution. During aging, it disperses and precipitates at the grain boundaries, hindering dislocation movement and thus improving the strength of the alloy.

[0063] In one specific embodiment, in the as-cast microstructure of the high-strength and tough aluminum alloy of the present invention, the eutectic silicon is in the form of fine short fibers, with a small amount in the form of short rods, and after heat treatment, it mainly presents as short rods and spheres; the Al3Sc particles and Al3Ti particles in the as-cast microstructure are distributed near the grain boundaries, and after heat treatment, fine Mg2Si phase is dispersedly precipitated.

[0064] In one specific embodiment, the heat-treated microstructure of the high-strength and high-toughness aluminum alloy of the present invention has the following characteristics: the eutectic silicon is mainly distributed in short rod-shaped and spherical shapes; the secondary dendrite spacing is 15-22 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm or any combination thereof; the average grain size is 22-30 μm, such as 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm or any combination thereof.

[0065] The third aspect of the present invention provides the application of the high-strength and high-toughness aluminum alloy provided in the first aspect of the present invention in investment casting.

[0066] Example 1

[0067] This embodiment provides a high-strength and high-toughness aluminum alloy, which, by mass percentage, comprises the following components:

[0068] The composition is as follows: Si 7.5%, Mg 0.5%, Ti 0.22%, Be 0.22%, Sc 0.25%, Ce 0.2%, B 0.02%, Fe≤0.2%, Zn≤0.2%, Mn≤0.1%, Cu≤0.2%, Zr≤0.2%, with the balance being Al and unavoidable impurities; among the unavoidable impurities, the content of a single impurity is ≤0.05%, and the total content of impurities is ≤0.15%.

[0069] The method for preparing the high-strength and high-toughness aluminum alloy in this embodiment includes the following steps:

[0070] (1) Prepare raw materials according to the above alloy composition; the raw materials include pure aluminum (purity above 99.98%), pure magnesium (purity above 99.99%), Al-Si20 master alloy, Al-Ti10 master alloy, Al-Ti5-B1 ​​master alloy, Al-Be5 master alloy, Al-Sc2 master alloy, and Al-Ce30 master alloy.

[0071] (2) Place all raw materials into an electric resistance furnace and bake at 400°C for 30 minutes to remove surface oil and moisture.

[0072] (3) Load pure aluminum and Al-Si20 master alloy into the furnace and melt them at a temperature of 775°C. Melt the metal under stirring conditions. Adjust the temperature of the aluminum liquid to 720-740°C (e.g., 730°C). Then add Al-Sc2 master alloy, Al-Ce30 master alloy, Al-Ti10 master alloy, Al-Ti5-B1 ​​master alloy, and Al-Be5 master alloy in sequence. Press each master alloy into the aluminum liquid. After all the metal has melted, let it stand for 10 minutes and adjust the temperature of the aluminum liquid to 720-740°C (e.g., 730°C). Refine the metal at this temperature using a rotary jet refining process. The gas is high-purity argon (argon purity ≥ 99.99%), the argon pressure is 0.3 MPa, the rotor speed is 300 r / min, and the refining time is 15 minutes.

[0073] (4) Add pure magnesium to the aluminum liquid in step (3), press the pure magnesium into the aluminum liquid, and let it melt completely. After standing for 10 minutes, control the temperature of the aluminum liquid to 730℃, and use a rotary jet refining process at this temperature for refining. The gas is high-purity argon (argon purity ≥ 99.99%), the argon pressure is 0.3MPa, the rotor speed is 300r / min, and the refining time is 15min.

[0074] (5) Let the aluminum liquid stand, adjust its temperature to 700℃, and pour it into the mold shell to obtain an aluminum alloy sample.

[0075] (6) The sample obtained in step (5) is subjected to T6 heat treatment; T6 heat treatment includes: holding at 536℃ for 12h, water cooling; then holding at 175℃ for 6h, air cooling.

[0076] Example 2

[0077] This embodiment refers to the high-strength and tough aluminum alloy and its preparation method in Embodiment 1, the only difference being that the composition of the high-strength and tough aluminum alloy is different.

[0078] The high-strength and high-toughness aluminum alloy of this embodiment comprises the following components by mass percentage:

[0079] The composition is as follows: Si 7%, Mg 0.45%, Ti 0.15%, Be 0.15%, Sc 0.15%, Ce 0.15%, B 0.01%, Fe≤0.2%, Zn≤0.2%, Mn≤0.1%, Cu≤0.2%, Zr≤0.2%, with the balance being Al and unavoidable impurities; among the unavoidable impurities, the content of a single impurity is ≤0.05%, and the total content of impurities is ≤0.15%.

[0080] Example 3

[0081] This embodiment refers to the high-strength and tough aluminum alloy and its preparation method in Embodiment 1, the only difference being that the composition of the high-strength and tough aluminum alloy is different.

[0082] The high-strength and high-toughness aluminum alloy of this embodiment comprises the following components by mass percentage:

[0083] The composition is as follows: Si 8%, Mg 0.55%, Ti 0.3%, Be 0.3%, Sc 0.45%, Ce 0.25%, B 0.03%, Fe≤0.2%, Zn≤0.2%, Mn≤0.1%, Cu≤0.2%, Zr≤0.2%, with the balance being Al and unavoidable impurities; among the unavoidable impurities, the content of a single impurity is ≤0.05%, and the total content of impurities is ≤0.15%.

[0084] Example 4

[0085] This embodiment refers to the high-strength and tough aluminum alloy and its preparation method in Embodiment 1. The only difference is that the T6 heat treatment parameters in step (6) are different in its preparation method.

[0086] In this embodiment, the T6 heat treatment includes: holding at 525°C for 12 hours, followed by water cooling; then holding at 175°C for 6 hours, followed by air cooling.

[0087] Example 5

[0088] This embodiment refers to the high-strength and tough aluminum alloy and its preparation method in Embodiment 1. The only difference is that the T6 heat treatment parameters in step (6) are different in its preparation method.

[0089] In this embodiment, the T6 heat treatment includes: holding at 536°C for 12 hours, followed by water cooling; then holding at 190°C for 6 hours, followed by air cooling.

[0090] Example 6

[0091] This embodiment refers to the high-strength and tough aluminum alloy and its preparation method in Embodiment 1. The only difference is that the T6 heat treatment parameters in step (6) are different in its preparation method.

[0092] In this embodiment, the T6 heat treatment includes: holding at 542°C for 14 hours, followed by water cooling; then holding at 165°C for 6 hours, followed by air cooling.

[0093] Example 7

[0094] This embodiment refers to the high-strength and tough aluminum alloy and its preparation method in Embodiment 1. The only difference is that the T6 heat treatment parameters in step (6) are different in its preparation method.

[0095] In this embodiment, the T6 heat treatment includes: holding at 536°C for 12 hours, followed by water cooling; then holding at 175°C for 10 hours, followed by air cooling.

[0096] Comparative Example 1

[0097] Comparative Example 1 refers to the high-strength and high-toughness aluminum alloy and its preparation method in Example 1, the only difference being that the composition of the aluminum alloy is different, as detailed below.

[0098] In Comparative Example 1, the aluminum alloy does not contain Sc, and the mass percentage of Ce is 0.4%; its preparation method does not include the raw material Al-Sc2 master alloy.

[0099] Comparative Example 2

[0100] Comparative Example 2 refers to the high-strength and high-toughness aluminum alloy and its preparation method in Example 1, the only difference being that the composition of the aluminum alloy is different, as detailed below.

[0101] In Comparative Example 2, the aluminum alloy does not contain Ce, and the mass percentage of Sc is 0.4%; its preparation method does not include the raw material Al-Ce30 master alloy.

[0102] Comparative Example 3

[0103] Comparative Example 3 refers to the high-strength and high-toughness aluminum alloy and its preparation method in Example 1, the only difference being that the composition of the aluminum alloy is different, as detailed below.

[0104] In the aluminum alloy of Comparative Example 3, the mass percentage of Ce is 0.27% and the mass percentage of Sc is 0.47%.

[0105] Comparative Example 4

[0106] Comparative Example 4 refers to the high-strength and high-toughness aluminum alloy and its preparation method in Example 1, the only difference being that the composition of the aluminum alloy is different, as detailed below.

[0107] In the aluminum alloy of Comparative Example 4, the mass percentages of Ce and Sc elements are both 0%.

[0108] Experimental Example

[0109] The tensile properties of single-cast specimens prepared in different embodiments and comparative examples at low temperature (-56℃), room temperature, and high temperature (300℃) were tested, and the test results are shown in Table 1.

[0110] Table 1 Performance test results of different samples

[0111]

[0112] In the as-cast microstructure of Example 1 of this invention, the eutectic silicon is in the form of fine short fibers, with a small amount in short rods. The as-cast microstructure contains Al3Sc, Al3Ti, Al3Ce, and TiB2 particles, with Al3Sc and Al3Ti particles distributed near the grain boundaries. To compare and illustrate the influence of different compositions on the microstructure of aluminum alloys, the metallographic structures of the heat-treated castings of the examples and comparative examples were observed and statistically analyzed. The results are as follows: Figures 1 to 11 As shown in Table 2. Figures 1 to 7 The images shown are microstructure images of the heat-treated castings provided in Examples 1 to 7 of this invention. Figures 8-11 The images shown are microstructure diagrams of the heat-treated castings provided in Comparative Examples 1 to 4 of this invention.

[0113] Table 2. Microstructure of castings in different heat-treated states

[0114]

[0115] The test results above show that the high-strength and high-toughness aluminum alloy of the present invention, through the control of alloy composition, exhibits good fluidity, which can meet the requirements of investment casting for complex structures; at the same time, the alloy has high strength and toughness, and excellent mechanical properties in the range of -56 to 300℃. Further control of heat treatment conditions can further passivate and spheroidize the eutectic silicon edges, helping to obtain a fine, uniform, and nearly spherical eutectic silicon structure, thus improving the performance of the aluminum alloy.

[0116] The alloys were cast and heat-treated according to the alloy composition and method of Example 1 and Comparative Example 4, respectively. The main body samples were taken from the castings and subjected to smooth high-cycle fatigue performance under room temperature conditions. The test was carried out in accordance with HB 5287-1996 "Metallic Materials Axial Loading Fatigue Test Method". The stress conditions in the test were 200MPa and 160MPa. The test results are shown in Table 3.

[0117] Table 3. Results of High-Cycle Fatigue Performance Tests for Smooth Surfaces

[0118]

[0119] As can be seen from the high-cycle fatigue performance test results in Table 3, the fatigue performance of the high-strength and high-toughness aluminum alloy obtained by controlling the alloy composition in this invention is significantly improved.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high strength aluminum alloy characterized by, consists of, in mass percent, Si 7% to 8%, Mg 0.45% to 0.55%, Ti 0.15% to 0.3%, Be 0.15% to 0.3%, Sc 0.15% to 0.45%, Ce 0.15% to 0.25%, B 0.01% to 0.03%, Fe ≤ 0.2%, Zn ≤ 0.2%, Mn ≤ 0.1%, Cu ≤ 0.2%, Zr ≤ 0.2%, and the balance of Al and inevitable impurities; The as-cast structure of the high strength and toughness aluminum alloy has the following characteristics: the eutectic silicon is mainly in the form of fine short fibers; Al3Sc particles, Al3Ti particles, Al3Ce particles and TiB2 particles exist in the as-cast structure, and the Al3Sc particles and Al3Ti particles are distributed near the grain boundaries; In the preparation of the high strength and toughness aluminum alloy, the castings obtained by pouring are subjected to solid solution treatment and aging treatment; the solid solution treatment comprises: heat treatment at 536 ± 5 ℃ for 10 to 16 h, and water cooling; the aging treatment comprises: heat treatment at 175 ± 5 ℃ for 4 to 8 h, and air cooling.

2. The high toughness aluminum alloy of claim 1, wherein, The high strength and toughness aluminum alloy comprises, in mass percent, Si 7.3% to 7.7%, Mg 0.47% to 0.53%, Ti 0.18% to 0.25%, Be 0.18% to 0.25%, Sc 0.2% to 0.3%, Ce 0.17% to 0.23%, B 0.015% to 0.025%, Fe ≤ 0.2%, Zn ≤ 0.2%, Mn ≤ 0.1%, Cu ≤ 0.2%, Zr ≤ 0.2%, and the balance of Al and inevitable impurities.

3. The method of producing a high toughness aluminum alloy as claimed in any one of claims 1 to 2, characterized by, comprising the following steps: (a) preparing raw materials according to alloy components; melting pure aluminum and Al-Si intermediate alloy, after the raw materials are completely melted, adding the remaining intermediate alloy, and performing primary refining; then adding magnesium, performing secondary refining, and obtaining aluminum alloy liquid; (b) pouring the aluminum alloy liquid; and further comprising: subjecting the castings obtained by pouring to solid solution treatment and aging treatment; the solid solution treatment comprises: heat treatment at 536 ± 5 ℃ for 10 to 16 h, and water cooling; the aging treatment comprises: heat treatment at 175 ± 5 ℃ for 4 to 8 h, and air cooling.

4. The production method according to claim 3, characterized by, In step (a), the melting comprises: loading pure aluminum and Al-Si intermediate alloy into a furnace and melting, and then sequentially adding Al-Sc intermediate alloy, Al-Ce intermediate alloy, Al-Ti intermediate alloy, Al-Ti-B intermediate alloy and Al-Be intermediate alloy for melting.

5. The preparation method according to claim 3, characterized in that, has at least one of the following characteristics: (1) in the primary refining, the temperature is 720 to 740 ℃, and the time is 10 to 20 min; (2) in the primary refining, a rotary blowing refining process is used; in the rotary blowing refining, the rotating speed is 250 to 500 r / min, and the argon gas pressure is 0.1 to 0.5 MPa; (3) in the secondary refining, the temperature is 720 to 740 ℃, and the time is 10 to 20 min; (4) the secondary refining adopts a rotary injection refining process; in the rotary injection refining process, the rotating speed is 250-500 r / min, and the argon pressure is 0.1-0.5 MPa.

6. The preparation method according to claim 3, characterized in that, In step (b), the temperature of the aluminum alloy liquid is regulated to 680-720 ℃, and the pouring is performed.

7. The preparation method according to claim 3, characterized in that, In the pouring, the aluminum alloy liquid is poured into a mold shell or an ingot mold.

8. Use of the high-strength and high-toughness aluminum alloy according to any one of claims 1-2 in investment casting.

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