A new die-casting aluminum-silicon alloy containing multifunctional crystal seeds and a preparation method thereof

Abstract

This invention relates to the field of non-ferrous metal materials technology, specifically a novel die-cast aluminum-silicon alloy containing multifunctional seed crystals and its preparation method. The alloy's chemical composition, by mass percentage, is: Zr 0.5%~1.5%, Ce 0.3%~3%, Si 5%~12%, B 0.5%~2%, Ti 0.5%~2.5%, with the remainder being Al and unavoidable impurities. Among the unavoidable impurities, the content of a single impurity element is ≤0.05%, and the total content of impurity elements is ≤0.25%. The microstructure of this invention integrates a refining phase (Al3Zr), a modified phase (Ce-Si), and a strengthening phase (Ce-B), simultaneously achieving α-Al grain refinement, eutectic Si modification, and dispersion strengthening. This completely avoids the "Sr-B poisoning" effect of traditional Al-Ti-B and Al-Sr mixtures, ensuring the alloy's strength and toughness from the source.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal materials technology, specifically a novel die-cast aluminum-silicon alloy containing multifunctional seed crystals and its preparation method. Background Technology

[0002] With the development of new energy vehicles towards lightweighting and integration, integrated die casting technology has become a revolutionary trend in vehicle body structure manufacturing. This technology requires aluminum alloy materials to possess excellent mechanical properties in the die-cast state to avoid problems such as part deformation, dimensional deviations, surface blistering, increased energy consumption, and extended production cycles caused by subsequent heat treatment processes. Therefore, the development of high-performance, heat-treatable die-cast aluminum alloys has become a research hotspot and urgent need in the industry.

[0003] Currently, to improve the as-cast properties of die-cast aluminum alloys, the industry commonly employs the method of adding multiple intermediate alloys or elemental elements to the melt, aiming to achieve effects such as grain refinement and eutectic silicon modification. Mainstream technical approaches typically include adding Al-Ti-B series grain refiners, Al-Sr or Al-Sb eutectic silicon modifiers, and strengthening phase-forming elements such as Al-Zr and Al-Cr. However, existing technologies face multiple challenges: key alloying elements such as Zr and Re, due to their high density and chemical reactivity, are prone to segregation, oxidation, and burn-off during the smelting process, resulting in low element yields and poor process stability, severely affecting performance reproducibility; simultaneously, there is a severe "Sr-B poisoning" effect between widely used Al-Ti-B refining agents and Al-Sr modifiers. Sr reacts with B to form SrB6 compounds, which not only renders Sr's modifying function ineffective and keeps the eutectic silicon in a coarse lamellar shape, thus deteriorating plasticity, but also causes the failure of TiB2 heterogeneous nucleation sites, leading to a decline in the α-Al grain refining effect; furthermore, multiple additives need to be added in batches according to a specific order and temperature window, resulting in complex processes, cumbersome operations, and high dependence on personnel experience, introducing a large number of uncontrollable factors, making it difficult to guarantee the quality consistency of large-scale production; finally, for large integrated die-cast parts, existing additives are prone to sedimentation, agglomeration, or dissolution degradation during long-process filling, resulting in significant differences in microstructure and mechanical properties at different locations of the part, making it difficult to meet the requirements for remote performance.

[0004] In conclusion, although there is an urgent need for heat-free die-cast aluminum alloys, existing technologies are limited by inherent defects in material systems and preparation processes, making it difficult to stably and efficiently produce alloys that simultaneously possess high strength, high toughness, and uniform properties. Therefore, developing a novel die-cast aluminum-silicon alloy and its preparation method that can comprehensively solve all the above-mentioned problems is of vital importance for breaking through current technological bottlenecks and promoting industry development. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel die-cast aluminum-silicon alloy containing multifunctional seed crystals and its preparation method.

[0006] This invention is achieved using the following technical solution: A novel die-cast aluminum-silicon alloy containing multifunctional seed crystals has the following chemical composition by mass percentage: Zr 0.5%~1.5%, Ce 0.3%~3%, Si 5%~12%, B 0.5%~2%, Ti 0.5%~2.5%, with the remainder being Al and unavoidable impurities; among the unavoidable impurities, the content of a single impurity element is ≤0.05%, and the total content of impurity elements is ≤0.25%.

[0007] Its mechanical properties meet the following requirements: tensile strength ≥ 280 MPa, yield strength ≥ 140 MPa, and elongation ≥ 8%.

[0008] A method for preparing a novel die-cast aluminum-silicon alloy containing multifunctional seed crystals, the method comprising the following steps: 1) Raw material preparation: Accurately weigh pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, Al-10Zr master alloy, Al-10Ti master alloy, and Al-2B master alloy according to their chemical composition. 2) Melting: Pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, and Al-10Zr master alloy are placed in a crucible for melting for 40 minutes. After melting, Al-10Ti master alloy and Al-2B master alloy are added, and the Al-10Ti master alloy and Al-2B master alloy are pressed into the bottom of the melt using clamps and held for 30 minutes. 3) Refining: High-purity argon gas is introduced through a rotary degasser to refine the melt under an argon atmosphere for 15 minutes. After refining, the melt is allowed to stand for 2 minutes before slag removal. 4) Electromagnetic stirring: Adjust the melt temperature to 720℃~750℃, and then transfer the melt to an electromagnetic stirrer for electromagnetic stirring; the electromagnetic stirring process parameters are: magnetic field strength 30mT~60mT, stirring frequency 60Hz~90Hz, and stirring time 5min. 5) Casting: The molten material is aligned with the gate of the high-pressure die-casting machine for casting; the casting process parameters are: casting temperature 700℃, mold temperature 250℃±10℃, and the working temperature of the core filling area of ​​the cavity and the inner gate is controlled at 200℃~300℃. 6) Die casting: The melt is die cast using a high-pressure die casting machine; the die casting process parameters are: injection time 3s, first speed position 120mm, second speed position 160mm, pressure boosting position 190mm, tracking position 320mm, mold dwell time 10s, and rapid energy storage pressure of the injection system 125bar. 7) Performance testing: Room temperature tensile mechanical properties of the die-cast parts are tested.

[0009] The microstructure of this invention integrates a refining phase (Al3Zr), a modified phase (Ce-Si), and a strengthening phase (Ce-B), simultaneously achieving α-Al grain refinement, eutectic Si modification, and dispersion strengthening. This completely avoids the "Sr-B poisoning" effect of traditional Al-Ti-B and Al-Sr mixtures, ensuring the alloy's strength and toughness from the source. The composition is stable, and the yield is high: the smelting process uses a pre-alloying method, where active elements such as Zr and Ce are encapsulated within the Al matrix, greatly reducing the oxidation and burn-off of effective elements. The element yield is consistently above 95%, far exceeding that of traditional elemental addition methods (which typically yield 60%~80%), achieving precise composition control and high process reproducibility.

[0010] This invention ensures the ultimate dispersion of nano-reinforcing phases in die-cast aluminum-silicon alloys, effectively solving the problem of "Sr-B poisoning" effect in die-cast aluminum-silicon alloys. It achieves α-Al grain refinement, eutectic Si phase fiberization, Fe-rich phase spheroidization, and nano-dispersion strengthening in one step. This invention innovatively employs an integrated electromagnetic stirring coupled high-pressure die casting process (ES-HPDC). Through multi-physics field control of electromagnetic stirring, it achieves uniform dispersion of micro- and nano-functional phases throughout the melt. Combined with the high-speed filling and rapid solidification characteristics of high-pressure die casting, the uniform microstructure regulated by the melt is in situ inherited into the integrated die-cast part. The resulting alloy exhibits excellent strength and toughness, and stable performance, making it particularly suitable for large integrated die-cast structural parts for new energy vehicles with extremely high strength and toughness requirements. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of steps 3) to 6) in this invention. Detailed Implementation Example 1

[0012] A novel die-cast aluminum-silicon alloy containing multifunctional seed crystals has the following chemical composition by mass percentage: Zr 0.5%, Ce 0.3%, Si 5%, B 0.5%, Ti 0.5%, with the remainder being Al and unavoidable impurities; wherein the content of a single impurity element is ≤0.05%, and the total content of impurity elements is ≤0.25%.

[0013] Its mechanical properties meet the following requirements: tensile strength 326MPa, yield strength 163MPa, and elongation 8.5%.

[0014] A method for preparing a novel die-cast aluminum-silicon alloy containing multifunctional seed crystals, the method comprising the following steps: 1) Raw material preparation: Accurately weigh pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, Al-10Zr master alloy, Al-10Ti master alloy, and Al-2B master alloy according to their chemical composition. 2) Melting: Pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, and Al-10Zr master alloy are placed in a crucible for melting for 40 minutes. After melting, Al-10Ti master alloy and Al-2B master alloy are added, and the Al-10Ti master alloy and Al-2B master alloy are pressed into the bottom of the melt using clamps and held for 30 minutes. 3) Refining: High-purity argon gas is introduced through a rotary degasser to refine the melt under an argon atmosphere for 15 minutes. After refining, the melt is allowed to stand for 2 minutes before slag removal. 4) Electromagnetic stirring: Adjust the melt temperature to 720℃, and then transfer the melt to an electromagnetic stirrer for electromagnetic stirring; the electromagnetic stirring process parameters are: magnetic field strength 30mT, stirring frequency 60Hz, and stirring time 5min. 5) Casting: The molten material is aligned with the gate of the high-pressure die-casting machine for casting; the casting process parameters are: casting temperature 700℃, mold temperature 250℃±10℃, and the working temperature of the core filling area of ​​the cavity and the inner gate is controlled at 200℃. 6) Die casting: The melt is die cast using a high-pressure die casting machine; the die casting process parameters are: injection time 3s, first speed position 120mm, second speed position 160mm, pressure boosting position 190mm, tracking position 320mm, mold dwell time 10s, and rapid energy storage pressure of the injection system 125bar. 7) Performance testing: Room temperature tensile mechanical properties of the die-cast parts are tested.

[0015] In this embodiment, the purity of the pure aluminum ingot is 99.99%; the rotation speed of the rotary degasser is 300 rpm; and the flow rate of high-purity argon is 5 L / min. Example 2

[0016] A novel die-cast aluminum-silicon alloy containing multifunctional seed crystals has the following chemical composition by mass percentage: Zr 1%, Ce 1.5%, Si 8%, B 1%, Ti 1.5%, with the remainder being Al and unavoidable impurities; wherein the content of a single impurity element is ≤0.05%, and the total content of impurity elements is ≤0.25%.

[0017] Its mechanical properties meet the following requirements: tensile strength 290MPa, yield strength 150MPa, and elongation 9.4%.

[0018] A method for preparing a novel die-cast aluminum-silicon alloy containing multifunctional seed crystals, the method comprising the following steps: 1) Raw material preparation: Accurately weigh pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, Al-10Zr master alloy, Al-10Ti master alloy, and Al-2B master alloy according to their chemical composition. 2) Melting: Pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, and Al-10Zr master alloy are placed in a crucible for melting for 40 minutes. After melting, Al-10Ti master alloy and Al-2B master alloy are added, and the Al-10Ti master alloy and Al-2B master alloy are pressed into the bottom of the melt using clamps and held for 30 minutes. 3) Refining: High-purity argon gas is introduced through a rotary degasser to refine the melt under an argon atmosphere for 15 minutes. After refining, the melt is allowed to stand for 2 minutes before slag removal. 4) Electromagnetic stirring: Adjust the melt temperature to 750℃, and then transfer the melt to an electromagnetic stirrer for electromagnetic stirring; the electromagnetic stirring process parameters are: magnetic field strength 60mT, stirring frequency 90Hz, and stirring time 5min. 5) Casting: The molten material is aligned with the gate of the high-pressure die-casting machine for casting; the casting process parameters are: casting temperature 700℃, mold temperature 250℃±10℃, and the working temperature of the core filling area of ​​the cavity and the inner gate is controlled at 300℃. 6) Die casting: The melt is die cast using a high-pressure die casting machine; the die casting process parameters are: injection time 3s, first speed position 120mm, second speed position 160mm, pressure boosting position 190mm, tracking position 320mm, mold dwell time 10s, and rapid energy storage pressure of the injection system 125bar. 7) Performance testing: Room temperature tensile mechanical properties of the die-cast parts are tested.

[0019] In this embodiment, the purity of the pure aluminum ingot is 99.99%; the rotation speed of the rotary degasser is 300 rpm; and the flow rate of high-purity argon is 5 L / min. Example 3

[0020] A novel die-cast aluminum-silicon alloy containing multifunctional seed crystals has the following chemical composition by mass percentage: Zr 1.5%, Ce 2.5%, Si 12%, B 2%, Ti 2.5%, with the remainder being Al and unavoidable impurities; wherein the content of a single impurity element is ≤0.05%, and the total content of impurity elements is ≤0.25%.

[0021] Its mechanical properties meet the following requirements: tensile strength 285MPa, yield strength 145MPa, and elongation 10%.

[0022] A method for preparing a novel die-cast aluminum-silicon alloy containing multifunctional seed crystals, the method comprising the following steps: 1) Raw material preparation: Accurately weigh pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, Al-10Zr master alloy, Al-10Ti master alloy, and Al-2B master alloy according to their chemical composition. 2) Melting: Pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, and Al-10Zr master alloy are placed in a crucible for melting for 40 minutes. After melting, Al-10Ti master alloy and Al-2B master alloy are added, and the Al-10Ti master alloy and Al-2B master alloy are pressed into the bottom of the melt using clamps and held for 30 minutes. 3) Refining: High-purity argon gas is introduced through a rotary degasser to refine the melt under an argon atmosphere for 15 minutes. After refining, the melt is allowed to stand for 2 minutes before slag removal. 4) Electromagnetic stirring: Adjust the melt temperature to 730℃, and then transfer the melt to an electromagnetic stirrer for electromagnetic stirring; the electromagnetic stirring process parameters are: magnetic field strength 50mT, stirring frequency 70Hz, and stirring time 5min. 5) Casting: The molten material is aligned with the gate of the high-pressure die-casting machine for casting; the casting process parameters are: casting temperature 700℃, mold temperature 250℃±10℃, and the working temperature of the core filling area of ​​the cavity and the inner gate is controlled at 250℃. 6) Die casting: The melt is die cast using a high-pressure die casting machine; the die casting process parameters are: injection time 3s, first speed position 120mm, second speed position 160mm, pressure boosting position 190mm, tracking position 320mm, mold dwell time 10s, and rapid energy storage pressure of the injection system 125bar. 7) Performance testing: Room temperature tensile mechanical properties of the die-cast parts are tested.

[0023] In this embodiment, the purity of the pure aluminum ingot is 99.99%; the rotation speed of the rotary degasser is 300 rpm; and the flow rate of high-purity argon is 5 L / min.

[0024] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A novel die-cast aluminum-silicon alloy containing multifunctional seed crystals, characterized in that: The chemical composition by mass percentage is: Zr 0.5%~1.5%, Ce 0.3%~3%, Si 5%~12%, B 0.5%~2%, Ti 0.5%~2.5%, with the remainder being Al and unavoidable impurities; among the unavoidable impurities, the content of a single impurity element is ≤0.05%, and the total content of impurity elements is ≤0.25%.

2. The novel die-cast aluminum-silicon alloy containing multifunctional seed crystals according to claim 1, characterized in that: Its mechanical properties meet the following requirements: tensile strength ≥ 280 MPa, yield strength ≥ 140 MPa, and elongation ≥ 8%.

3. A method for preparing a novel die-cast aluminum-silicon alloy containing multifunctional seed crystals, the method being used to prepare the novel die-cast aluminum-silicon alloy containing multifunctional seed crystals as described in claim 1, characterized in that: The method includes the following steps: 1) Raw material preparation: Accurately weigh pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, Al-10Zr master alloy, Al-10Ti master alloy, and Al-2B master alloy according to their chemical composition. 2) Melting: Pure aluminum ingots, Al-40Si master alloy, Al-20Ce master alloy, and Al-10Zr master alloy are placed in a crucible for melting for 40 minutes. After melting, Al-10Ti master alloy and Al-2B master alloy are added, and the Al-10Ti master alloy and Al-2B master alloy are pressed into the bottom of the melt using clamps and held for 30 minutes. 3) Refining: High-purity argon gas is introduced through a rotary degasser to refine the melt under an argon atmosphere for 15 minutes. After refining, the melt is allowed to stand for 2 minutes before slag removal. 4) Electromagnetic stirring: Adjust the melt temperature to 720℃~750℃, and then transfer the melt to an electromagnetic stirrer for electromagnetic stirring; the electromagnetic stirring process parameters are: magnetic field strength 30mT~60mT, stirring frequency 60Hz~90Hz, and stirring time 5min. 5) Casting: The molten material is aligned with the gate of the high-pressure die-casting machine for casting; the casting process parameters are: casting temperature 700℃, mold temperature 250℃±10℃, and the working temperature of the core filling area of ​​the cavity and the inner gate is controlled at 200℃~300℃. 6) Die casting: The melt is die cast using a high-pressure die casting machine; the die casting process parameters are: injection time 3s, first speed position 120mm, second speed position 160mm, pressure boosting position 190mm, tracking position 320mm, mold dwell time 10s, and rapid energy storage pressure of the injection system 125bar. 7) Performance testing: Room temperature tensile mechanical properties of the die-cast parts are tested.

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