Heat-treatment-free high-toughness Al-Si-Mg alloy and preparation method thereof

Abstract

The invention belongs to the technical field of metal preparation, and particularly relates to a heat-treatment-free high-toughness Al-Si-Mg alloy and a preparation method. The alloy comprises the following components in percentage by mass: 7 to 8 weight percent of Si, 0.5 to 1.0 weight percent of Mg, 0.3 to 0.8 weight percent of Cu, 0.2 to 0.6 weight percent of Mn, 0.1 to 0.5 weight percent of Zn, 0.1 to 0.3 weight percent of Mo, 0.1 to 0.25 weight percent of Zr, 0.1 to 0.18 weight percent of La, 0.05 to 0.1 weight percent of V, 0.03 to 0.05 weight percent of B and the balance of Al and inevitable impurities, and the total weight percent is 100 percent. According to the invention, Al-Si-Mg is taken as a matrix, and mechanical properties and strong plasticity are improved by adding various alloy elements to cooperate with microalloying, so that the Al-Si-Mg alloy can be widely applied as a main bearing structural member.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal preparation, and in particular relates to a high-strength and tough Al-Si-Mg alloy that does not require heat treatment and a preparation method thereof. Background Art

[0002] In the industrial production of traditional Al-Si-Mg alloys, achieving high strength and toughness requires a T6 heat treatment process. However, this process has significant drawbacks: high-temperature solution treatment consumes significant energy, complex components are prone to dimensional deformation exceeding 0.3% during heat treatment, and surface oxide layers exceeding 5μm in thickness require additional processing. The development of heat-treatment-free alloys in recent years avoids this heat treatment step.

[0003] Traditional Al-Si-Mg alloys improve fluidity through high silicon content, but the eutectic Si phase in the cast state is in the form of coarse flakes or needles, which severely cuts the matrix, resulting in an elongation generally below 8%, making it difficult to meet the plasticity requirements of complex structural parts. Although Mg strengthens the alloy through the Mg2Si phase, it has a high tendency to segregate and easily forms a Chinese character-shaped eutectic phase, which impairs plasticity. Existing technology requires limiting the Mg content to below 0.6% to avoid embrittlement. Although a high Cu content can form an age-strengthening phase (such as Al2Cu), in heat-treatment-free alloys, the Al-Cu eutectic phase formed during solidification cannot be refined by heat treatment, but instead reduces plasticity and corrosion resistance.

[0004] Zr forms a high-melting-point Al3Zr phase in the aluminum melt, which serves as a heterogeneous nucleation substrate for α-Al, significantly enhancing the grain refinement of the aluminum alloy. Furthermore, Zr has a high solid solubility and low diffusion coefficient in the aluminum matrix, allowing it to precipitate into nanoscale Al3Zr dispersed phases during subsequent heat treatment. These precipitated phases effectively enhance the alloy's high-temperature mechanical properties by inhibiting recovery and recrystallization and hindering dislocation motion. For hypoeutectic Al-Si alloys with silicon contents exceeding 5%, the eutectic silicon phase exhibits a needle-like morphology, leading to severe matrix fracture and requiring modification.

[0005] Among traditional modifiers, Al-Ti-B refiners are prone to "silicon poisoning" in high-silicon alloys, forming coarse Ti-Si compounds, leading to grain coarsening and decreased mechanical properties. Sr modifiers, on the other hand, have unstable effects on eutectic Si and are prone to burnout and hydrogen absorption, which increases the porosity of castings. Existing heat-treatment-free alloys rely on expensive rare earth elements, resulting in high costs and poor compatibility with recycled aluminum. For example, Sc-containing alloys cost 3 to 5 times more than conventional alloys, restricting their large-scale application.

[0006] In summary, although Al-Si-Mg alloys are widely used, they generally face the problems of insufficient tensile strength in the cast state and low elongation. The addition of precious metals such as Ag and Sc significantly increases the cost, and traditional modifiers are prone to failure due to their short half-life. Summary of the Invention

[0007] To address these issues, the present invention provides a heat-treatment-free, high-strength and tough Al-Si-Mg alloy and its preparation method. Using Al-Si-Mg as the matrix, the invention employs microalloying with the addition of multiple alloying elements to improve the mechanical properties and strength of the Al-Si-Mg alloy, enabling its wider application as a primary load-bearing structural component.

[0008] The present invention solves the above technical problems through the following technical solutions.

[0009] A first object of the present invention is to provide a high-strength and tough Al-Si-Mg alloy that does not require heat treatment. The components of the Al-Si-Mg alloy are, by mass percentage, Si: 7wt.% to 8wt.%, Mg: 0.5wt.% to 1.0wt.%, Cu: 0.3wt.% to 0.8wt.%, Mn: 0.2wt.% to 0.6wt.%, Zn: 0.1wt.% to 0.5wt.%, Mo: 0.1wt.% to 0.3wt.%, Zr: 0.1wt.% to 0.25wt.%, La: 0.1wt.% to 0.18wt.%, V: 0.05wt.% to 0.1wt.%, B: 0.03wt.% to 0.05wt.%, and the remainder is Al and unavoidable impurity elements, totaling 100%.

[0010] A second object of the present invention is a method for preparing the above-mentioned high-strength and tough Al-Si-Mg alloy without heat treatment, comprising the following steps: S1. According to the mass percentage of high-strength and tough Al-Si-Mg alloy, pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy and Al-5Zr master alloy are weighed.

[0011] S2. After the pure Al is heated and melted for the first time, each intermediate alloy is added in sequence and heated and melted for the second time. After the alloy is completely melted, the first stirring, refining and degassing process is carried out. After the degassing is completed, the La-VB composite modifier is added, and the second stirring and standing are carried out to keep the temperature. Then, impurities are removed to obtain a melt.

[0012] S3. When the melt is cooled to 710° C. to 715° C., a titanium alloy rod is inserted, and ultrasonic treatment and die casting are performed in sequence. After die casting, the melt is cooled to obtain an ingot.

[0013] S4. Performing aging treatment on the ingot to obtain a high-strength and tough Al-Si-Mg alloy that does not require heat treatment.

[0014] Furthermore, the temperature of the first heating and melting and the second heating and melting is 720°C to 750°C.

[0015] Furthermore, the degassing method is: introducing hexachloroethane for 10 minutes to 15 minutes.

[0016] Furthermore, the second stirring time is 25 minutes to 35 minutes, and the standing and heat preservation time is 10 minutes to 15 minutes.

[0017] Furthermore, before the titanium alloy rod is inserted, the titanium alloy rod is preheated to 395° C. to 405° C., and the insertion depth of the titanium alloy rod is 28 mm to 32 mm.

[0018] Furthermore, the ultrasonic treatment time is 5 min to 6 min.

[0019] Furthermore, the die casting is injected into the mold cavity at 4m / s to 6m / s, the pressure is 115Mpa to 125Mpa, the mold temperature is 200℃ to 250℃, and the cooling is done by water mist cooling, and the water mist cooling rate is >100℃ / s.

[0020] Furthermore, the aging treatment temperature is 545° C. to 555° C., and the aging treatment time is 3.9 h to 4.1 h.

[0021] Furthermore, before being heated and melted, the pure Al and the master alloy are polished to remove the surface oxide layer, and then preheated to 200°C to 300°C.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The heat-treatment-free, high-strength and tough Al-Si-Mg alloy provided by the present invention uses Al-Si-Mg as a matrix, introduces Cu, Mn, and Zn to improve strength, and selects Zr and Mo / V as microalloying elements. Through the synergistic strengthening of the nanophase of elements such as Zr, Mo, and V and the three-dimensional confinement effect of La-VB composite modification, the strength-plasticity contradiction of the cast alloy is overcome. In the composition design, gradient-distributed Cu, Mn, and Zn are introduced to construct a multi-scale strengthening network, in which Cu forms an Al2Cu dispersed phase and Mn suppresses the harmful effects of Fe by generating a T-Al6Mn phase. The key microalloying elements Zr and Mo / V form Al3(Zr,Mo / V) nano-precipitates with a size of less than 20nm during solidification, and their grain boundary pinning effect refines the grain size to 15-20μm. The composite modifiers La and VB achieve three-dimensional confined growth of eutectic silicon phase through synergistic action: LaB6 as a heterogeneous nucleation substrate reduces the activation energy of silicon phase growth by 35%, and the V element induces fractal growth of the silicon phase (fractal dimension > 1.6), ultimately achieving the refinement of the eutectic silicon size. By adding multiple alloying elements for synergistic microalloying, the mechanical properties of the Al-Si-Mg alloy are improved, as well as the strength and plasticity of the Al-Si-Mg alloy, enabling it to be more widely used as a main load-bearing structural component.

[0023] This invention modifies an Al-Si-Mg alloy by adding multiple alloying elements. By optimizing the casting process and integrating heat treatment-free processes (such as high-pressure die-casting followed by rapid cooling), the alloy achieves T6-grade mechanical properties directly in the as-cast state, with a tensile strength of ≥300 MPa and an elongation of ≥8%. Compared to existing technologies, aluminum alloy products derived from this novel alloy exhibit superior strength. Furthermore, the production cost is low due to the minimal addition of alloying elements and the lack of complex processing methods and procedures. Therefore, this novel magnesium alloy has the potential for commercial production.

[0024] The preparation method employed in this invention adheres to the principles of safety and environmental protection during the manufacturing process, without causing any pollution. While ensuring that alloy composition deviations and impurity elements meet regulatory requirements, products exceeding their service life can be recycled and reused through secondary smelting, thereby saving costs. The resulting alloy is suitable for integrated die-cast structural components for new energy vehicles (such as battery pack housings and door inner panels), as well as precision castings for aerospace applications (avionics brackets and hydraulic valve bodies). It is expected to replace the existing rare earth-containing 7075-T6 alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the process of preparing the Al-Si-Mg alloy according to the present invention. DETAILED DESCRIPTION

[0026] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0028] In the industrial production of traditional Al-Si-Mg alloys, achieving high strength and toughness requires a T6 heat treatment process. However, this process has significant drawbacks: high-temperature solution treatment consumes significant energy, complex components are prone to dimensional deformation exceeding 0.3% during heat treatment, and surface oxide layers exceeding 5μm require additional processing. While heat-treatment-free alloys developed in recent years avoid the heat treatment process, they generally face technical bottlenecks such as insufficient as-cast tensile strength and low elongation. Some solutions require the addition of precious metals such as Ag and Sc, significantly increasing costs. Traditional Sr modifiers, due to their short half-life, are prone to degradation failure.

[0029] Based on this, the present invention proposes an innovative solution based on multi-element synergistic microalloying and non-equilibrium solidification control, which improves the mechanical properties of Al-Si-Mg alloys by adding multiple alloying elements for synergistic microalloying. Specifically: a high-strength and tough Al-Si-Mg alloy that does not require heat treatment. The components of the Al-Si-Mg alloy are, by mass percentage, Si: 7wt.%~8wt.%, Mg: 0.5wt.%~1.0wt.%, Cu: 0.3wt.%~0.8wt.%, Mn: 0.2wt.%~0.6wt.%, Zn: 0.1wt.%~0.5wt.%, Mo: 0.1wt.%~0.3wt.%, Zr: 0.1wt.%~0.25wt.%, La: 0.1wt.%~0.18wt.%, V: 0.05wt.%~0.1wt.%, B: 0.03wt.%~0.05wt.%, and the remainder is Al and unavoidable impurity elements, totaling 100%.

[0030] The present invention is based on Al-Si-Mg based alloys, because Al-Si-Mg based alloys are currently widely used, have stable casting properties, and have high room temperature strength and good corrosion resistance. Due to its excellent forming properties, the present invention improves the Al-Si-Mg alloy used as the base alloy in the main load-bearing structural parts, making it capable of producing complex structural parts. With Al-Si-Mg as the matrix, Cu, Mn and Zn are introduced to improve the strength, and Zr, Mo / V are selected as microalloying elements. Through the three-dimensional confinement effect of the nano-phase synergistic strengthening of elements such as Zr, Mo, and V and the La-VB composite modification, the strength-plasticity contradiction of the cast alloy is broken. In the composition design, with Al-8Si-0.6Mg as the matrix, gradient-distributed Cu, Mn and Zn are introduced to construct a multi-scale strengthening network, wherein Cu forms an Al2Cu dispersed phase, and Mn suppresses the harmful effects of Fe by generating a T-Al6Mn phase. During solidification, the key microalloying elements Zr and Mo / V form Al3(Zr,Mo / V) nanoprecipitates with a size of less than 20 nm. Their grain boundary pinning effect refines the grain size to 15-20 μm. The composite modifiers La and VB synergistically enable the three-dimensional confined growth of the eutectic silicon phase: LaB6 acts as a heterogeneous nucleation substrate, reducing the activation energy for silicon growth by 35%, while V induces fractal growth of the silicon phase (fractal dimension >1.6), ultimately refining the eutectic silicon size.

[0031] Al-Si-Mg alloys are modified by adding various alloying elements. The design principles for these element additions are as follows: Si forms a eutectic with Al, thereby increasing the alloy's strength and hardness. It also improves castability, reduces shrinkage, and prevents hot cracking. Si also enhances the alloy's high-temperature moldability, improving tensile strength, hardness, and machinability. Mg forms a solid solution in Al-Cu alloys, enhancing the alloy's mechanical properties through solid solution strengthening. Mg refines the grain size, forms a stable phase structure during heat treatment, and improves the alloy's corrosion resistance. Cu exhibits significant solid solution strengthening and aging strengthening effects in aluminum alloys. The addition of Cu increases the alloy's tensile strength and yield strength, improving its machinability. Zn enhances strength and hardness in aluminum alloys, especially when added together with Mg, forming a strengthening phase called MgZn2, which significantly strengthens the alloy. Mo forms fine dispersed phases in aluminum alloys, which contribute to the alloy's strength during die casting. The addition of Mo also improves the alloy's wear resistance by promoting the formation of a harder surface phase. In addition, Mo is also used to improve the corrosion resistance of the alloy. Zr forms a high melting point Al3Zr phase in the Al melt, which can serve as a heterogeneous nucleation substrate for α-Al, significantly refining the alloy grains. The refined grain structure not only improves the room temperature strength of the alloy, but also improves its plasticity and fatigue resistance. The addition of Zr can indirectly regulate the morphology of eutectic silicon, reduce the coarsening tendency of the eutectic silicon phase, and alleviate the cutting effect of needle-shaped silicon on the matrix, thereby improving the fracture toughness of the alloy, while synergizing with elements such as Mg and Si to form a composite synergistic strengthening effect. Therefore, in summary, the present invention adopts Cu, Mo, Zn and other elements to add to the Al-Si-Mg alloy, designs a new low-cost Al-Si-Mg-Cu-Mo-Zr-La-VB alloy, and smelts it to prepare aluminum alloy main load-bearing structural parts.

[0032] The second object of the present invention is to provide a method for preparing the above-mentioned high-strength and tough Al-Si-Mg alloy without heat treatment, the preparation process is as follows: Figure 1 As shown, the following steps are included: S1. According to the mass percentage of high-strength and tough Al-Si-Mg alloy, pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy and Al-5Zr master alloy are weighed.

[0033] S2. After the pure Al is heated and melted for the first time, each intermediate alloy is added in sequence and heated and melted for the second time. After the alloy is completely melted, the first stirring, refining and degassing process is carried out. After the degassing is completed, the La-VB composite modifier is added, and the second stirring and standing are carried out to keep the temperature. Then, impurities are removed to obtain a melt.

[0034] S3. When the melt is cooled to 710° C. to 715° C., a titanium alloy rod is inserted, and ultrasonic treatment and die casting are performed in sequence. After die casting, the melt is cooled to obtain an ingot.

[0035] S4. Performing aging treatment on the ingot to obtain a high-strength and tough Al-Si-Mg alloy that does not require heat treatment.

[0036] This invention uses a La-VB composite modifier to introduce La, V, and B into an Al-Si-Mg alloy, with a La:B mass ratio of 3:1. This optimizes the Si phase and α-Al grains, achieving three-dimensional confined growth of the eutectic silicon phase through a synergistic effect: La and B form LaB6 to refine the primary α-Al, while V and B form VB2 to pin the eutectic Si phase. This dual effect inhibits silicon poisoning and optimizes the eutectic microstructure. Furthermore, the La-VB system replaces the traditional Sr modifier, reducing hydrogen absorption and improving modification stability.

[0037] This invention modifies an Al-Si-Mg alloy by adding multiple alloying elements. By optimizing the casting process and integrating heat treatment-free processes (such as high-pressure die-casting followed by rapid cooling), the alloy achieves T6-grade mechanical properties directly in the as-cast state, with a tensile strength of ≥300 MPa and an elongation of ≥8%. Compared to existing technologies, aluminum alloy products derived from this novel alloy exhibit superior strength. Furthermore, the production cost is low due to the minimal addition of alloying elements and the lack of complex processing methods and procedures. Therefore, this novel magnesium alloy has the potential for commercial production.

[0038] The preparation method employed in this invention adheres to the principles of safety and environmental protection during the manufacturing process, without causing any pollution. While ensuring that alloy composition deviations and impurity elements meet regulatory requirements, products exceeding their service life can be recycled and reused through secondary smelting, thereby saving costs. The resulting alloy is suitable for integrated die-cast structural components for new energy vehicles (such as battery pack housings and door inner panels), as well as precision castings for aerospace applications (avionics brackets and hydraulic valve bodies). It is expected to replace the existing rare earth-containing 7075-T6 alloy.

[0039] In some embodiments, the temperature of the first heating and melting and the second heating and melting is 720°C to 750°C.

[0040] In some embodiments, the refining agent used in refining is aluminum chloride, and the amount of aluminum chloride used is 0.5 wt.% to 0.6 wt.% of the aluminum alloy melt.

[0041] In some embodiments, degassing is performed by introducing hexachloroethane for 10 to 15 minutes. This method achieves deep purification of the aluminum alloy melt through the synergistic effects of chemical reactions (hydrogen removal and oxide reduction) and physical effects (bubble adsorption), significantly improving the density and mechanical properties of the casting.

[0042] In some embodiments, the second stirring time is 30 minutes, and the standing and heat preservation time is 10 minutes to 15 minutes.

[0043] In some embodiments, before the titanium alloy rod is inserted, the titanium alloy rod is preheated to 395° C. to 405° C., and the insertion depth of the titanium alloy rod is 28 mm to 32 mm.

[0044] In some embodiments, the ultrasonic treatment time is 5 to 6 minutes. The present invention utilizes ultrasonic treatment to significantly improve melt quality, refine solidification structure, and enhance final performance through ultrasonic energy. After ultrasonic melt treatment, large-scale samples can be cast with few internal defects, and can be used for the preparation of primary load-bearing structural products.

[0045] In some embodiments, die casting is performed by injecting the material into the mold cavity at a speed of 4 to 6 m / s, a pressure of 115 to 125 MPa, a mold temperature of 200°C to 250°C, and water mist cooling at a rate of >100°C / s. The present invention utilizes water mist cooling to inhibit grain growth and stabilize the microstructure.

[0046] In some embodiments, the aging treatment temperature is 545°C to 555°C and the aging treatment time is 3.9 hours to 4.1 hours. The present invention controls the aging treatment temperature and time to form fine, dispersed, and evenly distributed precipitates in the supersaturated solid solution matrix, thereby eliminating dendritic segregation and improving its mechanical properties.

[0047] In some embodiments, pure Al and the master alloy are polished to remove surface oxide layers before being heated and melted, and then preheated to 200° C. to 300° C.

[0048] Polishing is the process of mechanically polishing the surface of pure Al and master alloys until the surface presents a metallic luster and removes the surface oxide layer. After mechanical polishing, the aluminum is placed in a resistance furnace for preheating at 200℃ to 300℃ to evaporate the surface moisture.

[0049] The following is further described through specific examples.

[0050] Example 1 A high-strength and tough Al-Si-Mg alloy that does not require heat treatment. The components of the Al-Si-Mg alloy are, by mass percentage, Si: 7.3wt.%, Mg: 0.58wt.%, Cu: 0.35wt.%, Mn: 0.28wt.%, Zn: 0.18wt.%, Mo: 0.16wt.%, Zr: 0.14wt.%, La: 0.12wt.%, V: 0.07wt.%, B: 0.04wt.%, and the remainder is Al and unavoidable impurity elements, which together account for 100%.

[0051] The method for preparing the above-mentioned high-strength and tough Al-Si-Mg alloy without heat treatment comprises the following steps: S1. Weigh pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy according to the mass percentage of the high-strength and toughness Al-Si-Mg alloy. Mechanically polish the surfaces of the weighed pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy until they exhibit a metallic luster and remove the surface oxide layer. After mechanical polishing, preheat the alloy in a resistance furnace at 250°C for 1 hour.

[0052] S2. Melt the aluminum ingot in a pit-type resistance melting furnace. When the temperature of the resistance furnace reaches the set temperature of 730°C, place the preheated aluminum ingot into the melting crucible of the pit furnace and let it stand for 15 minutes. After the standing period, the aluminum ingot is completely melted. Then, preheated Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy and Al-5Zr master alloy are quickly added in sequence, and then the melting temperature is increased to 730°C and allowed to stand for 10 minutes.

[0053] S3. After the standing and heat preservation is completed, an alloy solution is obtained, and the alloy solution is stirred and refined. A refining agent, aluminum chloride, is added to the alloy solution. The amount of aluminum chloride is 0.55 wt.% of the aluminum alloy melt. The melt is continuously stirred during the addition process. After the addition is completed, the temperature is raised to 750° C. and then kept at this temperature for 10 minutes.

[0054] S4. After S3 is completed, hexachloroethane is introduced into the alloy solution for 10 minutes for degassing.

[0055] S5. After degassing, add La-VB composite modifier. The amount of La-VB composite modifier is 0.28wt.% of the mass of the alloy solution. The mass ratio of La, V and B in the La-VB composite modifier is 15:8:5. Electromagnetic stirring is performed for 30 minutes to make the composition uniform. After stirring evenly, let it stand for 10 minutes.

[0056] S6. After the standing period in S5 is completed, slag removal is started. Overburned products and impurities on the surface are removed using a stainless steel spoon, and then the melt is allowed to stand for 10 minutes. When the melt temperature drops to 710°C, a titanium alloy rod preheated to 400°C is inserted into the melt (depth of about 30mm). After ultrasonic treatment for 5 minutes, the ultrasonic device is removed. At this time, the melt temperature is about 695°C.

[0057] S7. After the standing still in S6 is completed, die casting is started. A 2800T die casting machine is used to fill the mold at a high speed (5m / s), a pressure of 120Mpa, and a mold temperature of 200℃. After die casting, water mist cooling (cooling rate>100℃ / s) is immediately performed to inhibit grain growth and fix the microstructure to obtain an ingot, that is, a high-strength and tough Al-Si-Mg alloy that does not require heat treatment.

[0058] Example 2 A high-strength and tough Al-Si-Mg alloy that does not require heat treatment, wherein the components of the Al-Si-Mg alloy are, by mass percentage, Si: 7.3wt.%, Mg: 0.58wt.%, Cu: 0.35wt.%, Mn: 0.28wt.%, Zn: 0.18wt.%, Mo: 0.16wt.%, Zr: 0.14wt.%, La: 0.12wt.%, V: 0.07wt.%, B: 0.04wt.%, with the remainder being Al and unavoidable impurity elements, totaling 100%. The method for preparing the high-strength and tough Al-Si-Mg alloy that does not require heat treatment comprises the following steps:

[0059] S1. Weigh pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy according to the mass percentage of the high-strength and toughness Al-Si-Mg alloy. Mechanically polish the surfaces of the weighed pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy until they exhibit a metallic luster and remove the surface oxide layer. After mechanical polishing, preheat the alloy in a resistance furnace at 250°C for 1 hour.

[0060] S2. Melt the aluminum ingot in a pit-type resistance melting furnace. When the temperature of the resistance furnace reaches the set temperature of 730°C, place the preheated aluminum ingot into the melting crucible of the pit furnace and let it stand for 15 minutes. After the standing period, the aluminum ingot is completely melted. Then, preheated Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy and Al-5Zr master alloy are quickly added in sequence, and then the melting temperature is increased to 730°C and allowed to stand for 10 minutes.

[0061] S3. After the standing and heat preservation is completed, an alloy solution is obtained, and the alloy solution is stirred and refined. A refining agent, aluminum chloride, is added to the alloy solution. The amount of aluminum chloride is 0.55 wt.% of the aluminum alloy melt. The melt is continuously stirred during the addition process. After the addition is completed, the temperature is raised to 750° C. and then kept at this temperature for 10 minutes.

[0062] S4. After S3 is completed, hexachloroethane is introduced into the alloy solution for 10 minutes for degassing.

[0063] S5. After degassing, add La-VB composite modifier. The amount of La-VB composite modifier is 0.28wt.% of the mass of the alloy solution. The mass ratio of La, V and B in the La-VB composite modifier is 15:8:5. Electromagnetic stirring is performed for 30 minutes to make the composition uniform. After stirring evenly, let it stand for 10 minutes.

[0064] S6. After the standing period in S5 is completed, slag removal is started. Overburned products and impurities on the surface are removed using a stainless steel spoon, and then the melt is allowed to stand for 10 minutes. When the melt temperature drops to 710°C, a titanium alloy rod preheated to 400°C is inserted into the melt (depth of about 30mm). After ultrasonic treatment for 5 minutes, the ultrasonic device is removed. At this time, the melt temperature is about 695°C.

[0065] S7. After the standing still in S6 is completed, die casting is started. A 2800T die casting machine is used to fill the mold at a high speed (5m / s), a pressure of 120Mpa, and a mold temperature of 200℃. After die casting, water mist cooling (cooling rate>100℃ / s) is immediately performed to inhibit grain growth and fix the microstructure to obtain an ingot.

[0066] S8. The ingot is aged at 550°C for 4 hours to eliminate dendritic segregation and obtain a high-strength and tough Al-Si-Mg alloy that does not require heat treatment.

[0067] Example 3 A high-strength and tough Al-Si-Mg alloy that does not require heat treatment. The components of the Al-Si-Mg alloy are, by mass percentage, Si: 7.5wt.%, Mg: 0.72wt.%, Cu: 0.55wt.%, Mn: 0.38wt.%, Zn: 0.49wt.%, Mo: 0.22wt.%, Zr: 0.21wt.%, La: 0.13wt.%, V: 0.07wt.%, B: 0.04wt.%, and the remainder is Al and unavoidable impurity elements, which together account for 100%.

[0068] The method for preparing the above-mentioned high-strength and tough Al-Si-Mg alloy without heat treatment comprises the following steps: S1. Weigh pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy according to the mass percentage of the high-strength and toughness Al-Si-Mg alloy. Mechanically polish the surfaces of the weighed pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy until they exhibit a metallic luster and remove the surface oxide layer. After mechanical polishing, preheat the alloy in a resistance furnace at 250°C for 1 hour.

[0069] S2. Melt the aluminum ingot in a pit-type resistance melting furnace. When the temperature of the resistance furnace reaches the set temperature of 730°C, place the preheated aluminum ingot into the melting crucible of the pit furnace and let it stand for 15 minutes. After the standing period, the aluminum ingot is completely melted. Then, preheated Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy and Al-5Zr master alloy are quickly added in sequence, and then the melting temperature is increased to 730°C and allowed to stand for 10 minutes.

[0070] S3. After the standing and heat preservation is completed, an alloy solution is obtained, and the alloy solution is stirred and refined. A refining agent, aluminum chloride, is added to the alloy solution. The amount of aluminum chloride is 0.55 wt.% of the aluminum alloy melt. The melt is continuously stirred during the addition process. After the addition is completed, the temperature is raised to 750° C. and then kept at this temperature for 10 minutes.

[0071] S4. After S3 is completed, hexachloroethane is introduced into the alloy solution for 10 minutes for degassing.

[0072] S5. After degassing, add La-VB composite modifier. The amount of La-VB composite modifier is 0.28wt.% of the mass of the alloy solution. The mass ratio of La, V and B in the La-VB composite modifier is 15:8:5. Electromagnetic stirring is performed for 30 minutes to make the composition uniform. After stirring evenly, let it stand for 10 minutes.

[0073] S6. After the standing period in S5 is completed, slag removal is started. Overburned products and impurities on the surface are removed using a stainless steel spoon, and then the melt is allowed to stand for 10 minutes. When the melt temperature drops to 710°C, a titanium alloy rod preheated to 400°C is inserted into the melt (depth of about 30mm). After ultrasonic treatment for 5 minutes, the ultrasonic device is removed. At this time, the melt temperature is about 695°C.

[0074] S7. After the standing still in S6 is completed, die casting is started. A 2800T die casting machine is used to fill the mold at a high speed (5m / s), a pressure of 120Mpa, and a mold temperature of 200℃. After die casting, water mist cooling (cooling rate>100℃ / s) is immediately performed to inhibit grain growth and fix the microstructure to obtain an ingot.

[0075] S8. The ingot is aged at 550°C for 4 hours to eliminate dendritic segregation and obtain a high-strength and tough Al-Si-Mg alloy that does not require heat treatment.

[0076] Example 4 A high-strength and tough Al-Si-Mg alloy that does not require heat treatment. The components of the Al-Si-Mg alloy are, by mass percentage, Si: 7.9wt.%, Mg: 0.92wt.%, Cu: 0.77wt.%, Mn: 0.56wt.%, Zn: 0.48wt.%, Mo: 0.28wt.%, Zr: 0.24wt.%, La: 0.17wt.%, V: 0.08wt.%, B: 0.04wt.%, and the remainder is Al and unavoidable impurity elements, which together account for 100%.

[0077] The method for preparing the above-mentioned high-strength and tough Al-Si-Mg alloy without heat treatment comprises the following steps: S1. Weigh pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy according to the mass percentage of the high-strength and toughness Al-Si-Mg alloy. Mechanically polish the surfaces of the weighed pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy until they exhibit a metallic luster and remove the surface oxide layer. After mechanical polishing, preheat the alloy in a resistance furnace at 250°C for 1 hour.

[0078] S2. Melt the aluminum ingot in a pit-type resistance melting furnace. When the temperature of the resistance furnace reaches the set temperature of 730°C, place the preheated aluminum ingot into the melting crucible of the pit furnace and let it stand for 15 minutes. After the standing period, the aluminum ingot is completely melted. Then, preheated Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy and Al-5Zr master alloy are quickly added in sequence, and then the melting temperature is increased to 730°C and allowed to stand for 10 minutes.

[0079] S3. After the standing and heat preservation is completed, an alloy solution is obtained, and the alloy solution is stirred and refined. A refining agent, aluminum chloride, is added to the alloy solution. The amount of aluminum chloride is 0.55 wt.% of the aluminum alloy melt. The melt is continuously stirred during the addition process. After the addition is completed, the temperature is raised to 750° C. and then kept at this temperature for 10 minutes.

[0080] S4. After S3 is completed, hexachloroethane is introduced into the alloy solution for 10 minutes for degassing.

[0081] S5. After degassing, add La-VB composite modifier. The amount of La-VB composite modifier is 0.28wt.% of the mass of the alloy solution. The mass ratio of La, V and B in the La-VB composite modifier is 15:8:5. Electromagnetic stirring is performed for 30 minutes to make the composition uniform. After stirring evenly, let it stand for 10 minutes.

[0082] S6. After the standing period in S5 is completed, slag removal is started. Overburned products and impurities on the surface are removed using a stainless steel spoon, and then the melt is allowed to stand for 10 minutes. When the melt temperature drops to 710°C, a titanium alloy rod preheated to 400°C is inserted into the melt (depth of about 30mm). After ultrasonic treatment for 5 minutes, the ultrasonic device is removed. At this time, the melt temperature is about 695°C.

[0083] S7. After the standing still in S6 is completed, die casting is started. A 2800T die casting machine is used to fill the mold at a high speed (5m / s), a pressure of 120Mpa, and a mold temperature of 200℃. After die casting, water mist cooling (cooling rate>100℃ / s) is immediately performed to inhibit grain growth and fix the microstructure to obtain an ingot.

[0084] S8. The ingot is aged at 550°C for 4 hours to eliminate dendritic segregation and obtain a high-strength and tough Al-Si-Mg alloy that does not require heat treatment.

[0085] Comparative Example 1 A heat treatment-free Al-Si-Mg alloy comprises, by mass percentage, 8 wt.% Si, 0.6 wt.% Mg, 0.7 wt.% Cu, 0.6 wt.% Mn, 0.5 wt.% Zn, 0.1 wt.% Mo, and 0.1 wt.% Zr, with the remainder being Al and unavoidable impurity elements, which together account for 100%.

[0086] The method for preparing the above-mentioned Al-Si-Mg alloy without heat treatment comprises the following steps: S1. Weigh pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy according to the mass percentage of the high-strength and toughness Al-Si-Mg alloy. Mechanically polish the surfaces of the weighed pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy, and Al-5Zr master alloy until they exhibit a metallic luster and remove the surface oxide layer. After mechanical polishing, preheat the alloy in a resistance furnace at 250°C for 1 hour.

[0087] S2. Melt the aluminum ingot in a pit-type resistance melting furnace. When the temperature of the resistance furnace reaches the set temperature of 730°C, place the preheated aluminum ingot into the melting crucible of the pit furnace and let it stand for 15 minutes. After the standing period, the aluminum ingot is completely melted. Then, preheated Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy and Al-5Zr master alloy are quickly added in sequence, and then the melting temperature is increased to 730°C and allowed to stand for 10 minutes.

[0088] S3. After the standing and heat preservation is completed, an alloy solution is obtained, and the alloy solution is stirred and refined. A refining agent, aluminum chloride, is added to the alloy solution. The amount of aluminum chloride is 0.55 wt.% of the aluminum alloy melt. The melt is continuously stirred during the addition process. After the addition is completed, the temperature is raised to 750° C. and then kept at this temperature for 10 minutes.

[0089] S4. After S3 is completed, hexachloroethane is introduced into the alloy solution for 10 minutes for degassing. After the degassing is completed, the surface slag is removed using a stainless steel spoon; finally, the furnace temperature is lowered to 730°C.

[0090] S5. When the melt temperature drops to 710°C, insert a titanium alloy rod preheated to 400°C into the melt (depth of about 30mm). After ultrasonic treatment for 5 minutes, remove the ultrasonic device. At this time, the melt temperature is about 695°C.

[0091] S6. After the static state in S5 is completed, die casting is started. A 2800T die casting machine is used to fill the mold at a high speed (5m / s), a pressure of 120Mpa, and a mold temperature of 200℃. After die casting, water mist cooling (cooling rate>100℃ / s) is immediately performed to inhibit grain growth and fix the microstructure to obtain an ingot, which is an Al-Si-Mg alloy.

[0092] The structures and properties of the Al-Si-Mg alloys prepared in Examples 1 to 4 and Comparative Example 1 were tested, and the results are as follows: The composition of the new high-strength cast aluminum alloy obtained in Examples 1 to 4 of the present invention and Comparative Example 1 was detected using a spectrum analyzer, wherein: In Examples 1 to 2, the components of the Al-Si-Mg alloy are, by mass percentage, Si: 7.3±0.05wt%, Mg: 0.6±0.02wt%, Cu: 0.35±0.02wt%, Mn: 0.28±0.02wt%, Zn: 0.18±0.02wt%, Mo: 0.16±0.01wt%, Zr: 0.14±0.01wt%, La: 0.12±0.01wt.%, V: 0.07±0.01wt.%, B: 0.04±0.01wt.%, and the remainder is Al and unavoidable impurity elements, totaling 100%.

[0093] In Example 3, the components of the Al-Si-Mg alloy are, by mass percentage, Si: 7.5±0.05wt%, Mg: 0.7±0.02wt%, Cu: 0.55±0.02wt%, Mn: 0.38±0.02wt%, Zn: 0.5±0.02wt%, Mo: 0.22±0.01wt%, Zr: 0.2±0.01wt%, La: 0.13±0.01wt.%, V: 0.07±0.01wt.%, B: 0.05±0.01wt.%, and the remainder is Al and unavoidable impurity elements, totaling 100%.

[0094] In Example 4, the components of the Al-Si-Mg alloy are, by mass percentage, Si: 7.9±0.05wt%, Mg: 0.9±0.02wt%, Cu: 0.77±0.02wt%, Mn: 0.56±0.02wt%, Zn: 0.5±0.02wt%, Mo: 0.28±0.01wt%, Zr: 0.24±0.01wt%, La: 0.17±0.01wt.%, V: 0.08±0.01wt.%, B: 0.04±0.01wt.%, and the remainder is Al and unavoidable impurity elements, totaling 100%.

[0095] In Comparative Example 1, the components of the Al-Si-Mg alloy are, by mass percentage, Si: 7.3±0.05wt%, Mg: 0.6±0.02wt%, Cu: 0.35±0.02wt%, Mn: 0.28±0.02wt%, Zn: 0.18±0.02wt%, Mo: 0.16±0.01wt%, Zr: 0.14±0.01wt%, and the remainder is Al and unavoidable impurity elements, totaling 100%.

[0096] The mechanical properties of the samples prepared in Examples 1 to 4 and Comparative Example 1 were tested. The Al-Si-Mg alloy was processed into tensile test specimens for tensile test. The tensile test method complies with the GB / T228.1-2010 standard. The experiment was repeated three times to ensure the accuracy of the data. The results are shown in Table 1.

[0097] Table 1 Mechanical properties of Examples 1 to 4 and Comparative Example 1 As shown in Table 1, the mechanical properties of the alloy have broken through the tensile strength of the cast alloy and are expected to reach 300MPa, the yield strength ≥280MPa, and the elongation is stable at 7% to 9%. The comprehensive performance exceeds that of the traditional T6 heat-treated AlSi7Mg 0.3 Alloy (typical values: tensile strength 250MPa~280MPa / elongation 3%~8%).

[0098] Compared to the traditional T6 process, this invention offers cost and energy advantages. The heat-treatment-free process reduces production energy consumption by 30% and eliminates heat-treatment deformation (dimensional fluctuation <0.05%). The La-VB composite modifier costs only 12% to 15% of that of Sc-containing alloys and exhibits excellent compatibility with recycled aluminum (performance retention >95% when scrap aluminum is incorporated at a ratio of up to 50%).

[0099] The microstructural stability test of the Al-Si-Mg alloy prepared in Example 2 shows that the average size of the eutectic silicon phase is refined to 1 μm to 1.2 μm (conventional T6 (AlSi7Mg 0.3 )>5μm), effectively alleviating the matrix splitting effect. Al3(Zr,Mo) nano-precipitates (size 15nm-20nm) have excellent thermal stability below 300℃, with a strength decay rate of <3% after thermal exposure at 200℃ / 100h, significantly better than traditional Al-Si-Cu alloys (decay rate >10%).

[0100] In summary, the present invention uses Al-Si-Mg as the matrix, introduces Cu, Mn, and Zn to enhance strength, and selects Zr, Mo / V as microalloying elements. Through the synergistic strengthening of the nanophase of elements such as Zr, Mo, and V and the three-dimensional confinement effect of La-VB composite modification, the strength-plasticity contradiction of the cast alloy is overcome. By adding multiple alloying elements to form a synergistic microalloying, the mechanical properties of Al-Si-Mg alloys are improved, as well as the strength and plasticity of Al-Si-Mg alloys, enabling them to be more widely used as primary load-bearing structural components.

[0101] It should be noted that when numerical ranges are mentioned in the present invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints may be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0102] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A high-strength and tough Al-Si-Mg alloy that does not require heat treatment, characterized in that: In terms of mass percentage, the composition of Al-Si-Mg alloy is: Si: 7wt.%~8wt.%, Mg: 0.5wt.%~1.0wt.%, Cu: 0.3wt.%~0.8wt.%, Mn: 0.2wt.%~0.6wt.%, Zn: 0.1wt.%~0.5wt.%, Mo: 0.1wt.%~0.3wt.%, Zr: 0.1wt.%~0.25wt.%, La: 0.1wt.%~0.18wt.%, V: 0.05wt.%~0.1wt.%, B: 0.03wt.%~0.05wt.%, the remainder is Al and unavoidable impurity elements, totaling 100%.

2. A method for preparing a high-strength and tough Al-Si-Mg alloy that does not require heat treatment according to claim 1, characterized in that: The following steps are involved: According to the mass percentage of high-strength and tough Al-Si-Mg alloy, pure Al, Al-20Si master alloy, Al-50Cu master alloy, Al-10Mn master alloy, Al-30Zn master alloy, Al-10Mo master alloy, Al-5V master alloy and Al-5Zr master alloy were weighed; After the pure Al is heated and melted for the first time, each master alloy is added in sequence and heated and melted for the second time. After the alloy is completely melted, the first stirring, refining and degassing process is carried out. After the degassing is completed, the La-VB composite modifier is added, and the second stirring and static insulation are carried out, and then impurities are removed to obtain a melt; When the melt is cooled to 710°C to 715°C, a titanium alloy rod is inserted, and ultrasonic treatment and die casting are performed in sequence. After die casting, the melt is cooled to obtain an ingot. The ingot is subjected to aging treatment to obtain a high-strength and tough Al-Si-Mg alloy that does not require heat treatment.

3. The method for preparing a high-strength and tough Al-Si-Mg alloy that does not require heat treatment according to claim 2, characterized in that: The temperature of the first heating and melting and the second heating and melting is 720℃~750℃.

4. The method for preparing a high-strength and tough Al-Si-Mg alloy without heat treatment according to claim 2, characterized in that: The degassing method is: passing hexachloroethane for 10 minutes to 15 minutes.

5. The method for preparing a high-strength and tough Al-Si-Mg alloy that does not require heat treatment according to claim 2, wherein: The second stirring time is 25min to 35min, and the standing and heat preservation time is 10min to 15min.

6. The method for preparing a high-strength and tough Al-Si-Mg alloy without heat treatment according to claim 2, characterized in that: Before inserting the titanium alloy rod, the titanium alloy rod is preheated to 395° C. to 405° C., and the insertion depth of the titanium alloy rod is 28 mm to 32 mm.

7. The method for preparing a high-strength and tough Al-Si-Mg alloy that does not require heat treatment according to claim 2, wherein: The ultrasonic treatment time is 5 min to 6 min.

8. The method for preparing a high-strength and tough Al-Si-Mg alloy that does not require heat treatment according to claim 2, wherein: Die casting is done by injecting liquid into the mold cavity at a speed of 4m / s to 6m / s, with a pressure of 115Mpa to 125Mpa, a mold temperature of 200℃ to 250℃, and water mist cooling at a rate of >100℃ / s.

9. The method for preparing a high-strength and tough Al-Si-Mg alloy without heat treatment according to claim 2, characterized in that: The temperature of the aging treatment is 545°C to 555°C, and the time is 3.9h to 4.1h.

10. The method for preparing a high-strength and tough Al-Si-Mg alloy that does not require heat treatment according to claim 2, wherein: Before heating and melting, pure Al and master alloys are polished to remove the surface oxide layer and then preheated to 200℃~300℃.

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