Al-zn heat treatment-free aluminum alloy, preparation method and application thereof

Abstract

The application relates to the technical field of metal materials, and discloses an Al-Zn heat treatment-free aluminum alloy and a preparation method and application thereof. The Al-Zn heat treatment-free aluminum alloy is composed of the following components in percentage by mass: Zn: 8.0-18.0%, Si: 4.0-9.0%, Cu: 0.5-4.0%, Mn: 0.3-1.2%, Zr: 0.1-0.5%, V: 0.1-0.9%, Er: 0.1-0.4%, Sr: 0.05-0.6%, TiC / TiB2: 1.0-3.0%, and the balance of Al and inevitable impurities. The Al-Zn heat treatment-free aluminum alloy provided by the application has the advantages of compact structure, small grain size, uniform distribution of solute elements, excellent mechanical properties and the ability to meet the application requirements of aluminum alloy materials in the automobile and aerospace fields.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, and in particular to an Al-Zn-based heat-treatable aluminum alloy, its preparation method, and its applications. Background Technology

[0002] The continuous development of fields such as 3C electronics and new energy vehicles has placed higher demands on the forming performance and quality of die-cast aluminum alloys. Currently, the commonly used Al-Mg-Si series alloys have sufficient plasticity to meet application requirements, but their strength properties remain unstable. In Al-Zn series alloys, by rationally controlling the content of elements such as Zn, Si, and Cu, and adding small amounts of trace elements as needed, the mechanical properties of the alloy can be significantly improved; however, the porosity and shrinkage defects in the alloy are still difficult to overcome.

[0003] In the automotive engine and aerospace fields, the local structure of components is quite complex. In the traditional die casting process, due to the fast filling speed of the molten metal and the high pressure during molding, the turbulence generated by the molten metal will hinder the timely discharge of gas. As a result, the high-speed flowing molten metal and the entrained gas are compressed by the huge pressure at the same time. In the end, the gas that cannot be discharged in time will solidify together with the molten metal, which will seriously affect the molding quality and performance of the casting. Die castings are also prone to blistering and deformation during heat treatment. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one objective of the present invention is to provide an Al-Zn-based heat-treatable aluminum alloy; a second objective is to provide a method for preparing such an Al-Zn-based heat-treatable aluminum alloy; and a third objective is to provide applications of such an Al-Zn-based heat-treatable aluminum alloy.

[0005] The basic principles of this invention are explained as follows:

[0006] (1) The addition ratio of Zn, Si and Cu elements has an important influence on the performance of Al-Zn alloys. In this invention, Zn, Si and Cu elements are added in a specific ratio to ensure that the solute elements are dissolved in the matrix to the maximum extent and to form a second phase strengthening phase through interaction between the solute elements, thereby improving the strength and plasticity of the alloy. Specifically: at the eutectic temperature (approximately 577℃), Zn has a high solid solubility (31.6%) in the matrix. During solidification, 50-60% of Zn will dissolve into the matrix, playing a solid solution strengthening role. The remaining 40-50% of Zn will form a CuZn4 strengthening phase with Cu at the grain boundaries (when the element ratio is (3-4):1), playing a second-phase strengthening role. At high temperatures, the solid solubility of Cu in the matrix is ​​5.46%. In addition, when the Cu to Al ratio is (1-2):1, an AlCu / Al2Cu phase will be formed in the matrix, which can also play a second-phase strengthening role. When the Si content is 6-8%, it can improve the alloy strength and melt fluidity, and also ensure that the casting has good plasticity. If the Si content exceeds 10%, the alloy plasticity will decrease significantly.

[0007] (2) This invention adds trace elements Mn, V, Zr, and Er in specific proportions. Mn, V, Zr, and Er are trace elements of the alloy. The introduction of trace elements can effectively improve the microstructure of the alloy and enhance its mechanical properties. When the Mn content is 0.6-1.0%, the alloy's strength and plasticity can reach their maximum value, and the formation of needle-like Fe-rich phase can be inhibited, Fe impurities can be dissolved, and (Fe,Mn)Al6 phase can be formed. When the Mn content exceeds 1.0%, it will reduce the alloy's... The thermal conductivity is improved. When the addition ratio of V, Zr and Er elements is 1:(1-2):1, the (AlSi)3ZrV phase and the core-shell Al3(Er, Zr) phase, which are thermally stable phases, will be formed in the alloy matrix. They can serve as the substrate for heterogeneous nucleation of the alloy and significantly refine the grain structure. In particular, when the addition ratio of Er and Zr elements is 1:(1-2.5), the Al3(Er, Zr) phase plays a good role in dispersion strengthening in the alloy and can significantly improve the fracture toughness of the alloy.

[0008] (3) In this invention, TiC / TiB2 nanoparticles are added in a specific ratio. The in-situ generated TiC / TiB2 nanoparticles can effectively avoid chemical reaction with Si elements, thus preventing the "poisoning" phenomenon and hindering the heterogeneous nucleation process of α-Al dendrites. When the content of TiC / TiB2 nanoparticles is 1.0-3.0%, they can fully interact with the matrix and play a role in refining the grains. When the content of TiC / TiB2 particles is too low (less than 1.0%), the refining effect is insufficient and the performance improvement is not obvious. When the content is too high (greater than 3.0%), clusters are easily formed in the matrix, resulting in enrichment and a decrease in plasticity. In addition, the TiC and TiB2 particles are in a completely coherent state with the matrix interface. The lattice distortion generated with the matrix triggers the formation of dislocations. The TiC and TiB2 nanoparticles hinder the movement of dislocations. The Orovan strengthening effect can greatly improve the mechanical properties of the alloy.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] The first aspect of the present invention provides an Al-Zn-based heat-treatable aluminum alloy composed of the following components in weight percentage: Zn: 8.0-18.0%, Si: 4.0-9.0%, Cu: 0.5-4.0%, Mn: 0.3-1.2%, Zr: 0.1-0.5%, V: 0.1-0.9%, Er: 0.1-0.4%, Sr: 0.05-0.6%, TiC / TiB2: 1.0-3.0%, with the balance being Al and unavoidable impurities.

[0011] Preferably, the Al-Zn-based heat-treatable aluminum alloy is composed of the following components by mass percentage: Al: 71.35-78.3%, Zn: 12.0-16.0%, Si: 4.0-9.0%, Cu: 0.5-2.0%, Mn: 0.6-1.2%, Zr: 0.1-0.4%, V: 0.1-0.8%, Er: 0.1-0.3%, Sr: 0.05-0.4%, TiC / TiB2: 1.0-2.0%, and unavoidable impurities <0.04%.

[0012] More preferably, the Al-Zn-based heat-treatable aluminum alloy is composed of the following components by mass percentage: Al: 71.35-78.3%, Zn: 13.0-15.0%, Si: 6.0-8.0%, Cu: 0.5-1.5%, Mn: 0.6-1.0%, Zr: 0.1-0.3%, V: 0.1-0.4%, Er: 0.15-0.25%, Sr: 0.05-0.2%, TiC / TiB2: 1.2-2.0%, and unavoidable impurities <0.04%.

[0013] Preferably, the unavoidable impurities include Fe, C, O and Ca.

[0014] Preferably, the mass percentage content of any single impurity among the unavoidable impurities is less than 0.01%.

[0015] Preferably, the Al-Zn-based heat-free aluminum alloy comprises the following raw materials: pure aluminum, pure zinc, master alloy, modifier, and refining agent.

[0016] Preferably, the aluminum content in the pure aluminum is ≥99.999 wt%.

[0017] Preferably, the zinc content in the pure zinc is ≥99.999 wt%.

[0018] Preferably, the intermediate alloy comprises Al-Si, Al-Cu, Al-Mn, Al-Zr, Al-V, and Al-Er alloys; more preferably, the intermediate alloy comprises Al-20%Si, Al-50%Cu, Al-20%Mn, Al-10%Zr, Al-4%V, and Al-10%Er alloys.

[0019] Preferably, the modifier comprises an Al-Sr modifier; more preferably, the modifier comprises an Al-10%Sr modifier.

[0020] Preferably, the refining agent comprises Al-TiC / TiB2 nanoparticles; more preferably, the refining agent comprises Al-30% TiC / TiB2 nanoparticles.

[0021] The second aspect of the present invention provides a method for preparing the Al-Zn-based heat-treatable aluminum alloy described in the first aspect of the present invention, comprising the following steps:

[0022] S1. Pure aluminum, intermediate alloy and pure zinc are added in sequence and smelted to obtain alloy liquid;

[0023] S2. Add the modifier and refiner to the alloy liquid in sequence and refine it to obtain a refined liquid;

[0024] S3. The refining liquid is stirred, poured and die-cast to obtain the Al-Zn series heat-free aluminum alloy.

[0025] Preferably, in step S1, the smelting process conditions include at least one of the following:

[0026] 1) The smelting temperature after adding pure aluminum is 710-800℃, and the smelting time is 1-4h;

[0027] 2) The melting temperature after adding the intermediate alloy is 730-790℃, and the melting time is 0.5-2.5h;

[0028] 3) The smelting temperature after adding pure zinc is 630-730℃, and the smelting time is 1-2h.

[0029] More preferably, in step S1, the smelting process conditions include at least one of the following:

[0030] 1) The smelting temperature after adding pure aluminum is 740-790℃, and the smelting time is 1-3h;

[0031] 2) The melting temperature after adding the intermediate alloy is 740-780℃, and the melting time is 0.5-2h;

[0032] 3) The smelting temperature after adding pure zinc is 650-720℃, and the smelting time is 0.2-1.5h.

[0033] More preferably, in step S1, the smelting process conditions include at least one of the following:

[0034] 1) The smelting temperature after adding pure aluminum is 750-780℃, and the smelting time is 1.5-2.5h;

[0035] 2) The melting temperature after adding the intermediate alloy is 745-760℃, and the melting time is 1-1.5h;

[0036] 3) The smelting temperature after adding pure zinc is 670-700℃, and the smelting time is 0.3-0.8h.

[0037] Preferably, in step S1, an intermediate alloy is added when the remaining pure aluminum melts to 40-60 wt%.

[0038] Preferably, in step S1, pure zinc is added when the pure aluminum and intermediate alloy are completely melted.

[0039] Preferably, in step S2, the refining process conditions include at least one of the following:

[0040] 1) The refining temperature after adding the modifier is 630-750℃, and the refining time is 0.1-1h;

[0041] 2) The refining temperature after adding the refining agent is 690-760℃, and the refining time is 0.1-1h.

[0042] More preferably, in step S2, the refining process conditions include at least one of the following:

[0043] 1) The refining temperature after adding the modifier is 660-740℃, and the refining time is 0.1-0.5h;

[0044] 2) The refining temperature after adding the refining agent is 700-750℃, and the refining time is 0.1-0.5h.

[0045] More preferably, in step S2, the refining process conditions include at least one of the following:

[0046] 1) The refining temperature after adding the modifier is 690-730℃, and the refining time is 0.2-0.4h;

[0047] 2) The refining temperature after adding the refining agent is 730-740℃, and the refining time is 0.2-0.4h.

[0048] Preferably, in step S3, the stirring method includes ultrasonic vibration stirring.

[0049] Preferably, the parameters of the ultrasonic vibration stirring include at least one of the following:

[0050] 1) The power of the ultrasonic vibration is 500-3000W;

[0051] 2) The resonant frequency of the ultrasonic vibration is 15-35kHz;

[0052] 3) The duration of the ultrasonic vibration is 3-10 minutes.

[0053] More preferably, the parameters of the ultrasonic vibration stirring include at least one of the following:

[0054] 1) The power of the ultrasonic vibration is 1000-2500W;

[0055] 2) The resonant frequency of the ultrasonic vibration is 20-30kHz;

[0056] 3) The duration of the ultrasonic vibration is 3-8 minutes.

[0057] Specifically, ultrasonic vibration stirring of the refining liquid can fully utilize the cavitation effect, uniformly dispersing the nanoparticle refining agent in the melt, and achieving better heterogeneous nucleation during solidification. The parameters of ultrasonic vibration stirring have a significant impact on the process effect. If the power is too high or the frequency is too high, it can easily lead to huge instantaneous pressure, causing liquid splashing and gas entrainment; if the power is too low or the frequency is too low, it will result in uneven vibration stirring, affecting the distribution of the refining agent.

[0058] Preferably, in step S3, after the stirring is completed, the refining liquid is further subjected to a step of skimming off the slag and allowing it to stand.

[0059] Preferably, the settling time is 3-25 minutes; more preferably, the settling time is 4-16 minutes; and even more preferably, the settling time is 8-15 minutes.

[0060] Preferably, in step S3, the casting process conditions include at least one of the following:

[0061] 1) The pouring temperature is 660-780℃;

[0062] 2) The pouring speed is 0.4-1.6 m / s.

[0063] More preferably, in step S3, the casting process conditions include at least one of the following:

[0064] 1) The pouring temperature is 690-750℃;

[0065] 2) The pouring speed is 0.5-1.4 m / s.

[0066] More preferably, in step S3, the casting process conditions include at least one of the following:

[0067] 1) The pouring temperature is 700-730℃;

[0068] 2) The pouring speed is 0.6-1.0 m / s.

[0069] Preferably, the casting process is carried out in a mechanically automatic tilting melting furnace, and the refined liquid is poured into the die-casting mold after being allowed to stand. The die-casting mold is provided with a pouring cup at the upper end.

[0070] Specifically, selecting a lower pouring temperature and a higher pouring speed during the die casting process can reduce the supercooling required for alloy solidification and decrease the contact time with air. This avoids defects such as shrinkage cavities, porosity, gas holes, and sand adhesion in the casting due to excessively high pouring temperatures, or incomplete filling defects due to poor alloy fluidity caused by excessively low pouring temperatures. Furthermore, the pouring speed of this invention ensures that the molten alloy quickly and completely fills the mold cavity, preventing defects such as cold shuts or incomplete filling during the pouring process.

[0071] Preferably, in step S3, the die-casting process conditions include at least one of the following:

[0072] 1) The die casting is vacuum die casting, with a vacuum degree of 1-50 kPa;

[0073] 2) The injection speed of the die casting is 4-6.5 m / s;

[0074] 3) The injection pressure of the die casting is 100-600 MPa;

[0075] 4) The temperature of the die-casting mold is 100-300℃.

[0076] More preferably, in step S3, the die-casting process conditions include at least one of the following:

[0077] 1) The die casting is vacuum die casting, with a vacuum degree of 5-30 kPa;

[0078] 2) The injection speed of the die casting is 4-6 m / s;

[0079] 3) The injection pressure of the die casting is 200-400 MPa;

[0080] 4) The temperature of the die-casting mold is 100-200℃.

[0081] Specifically, using a relatively high vacuum during the die casting process can prevent gas from being trapped in the molten alloy during stirring, which could lead to defects such as porosity in the ingot. As for the injection pressure in die casting, if it is too low, the gas trapped inside the casting may not be able to escape, while if it is too high, the casting may generate excessive residual stress, which is not conducive to molding. Therefore, it is necessary to ensure that the pressure is appropriate.

[0082] Preferably, step S3 further includes a pressure holding step after die casting.

[0083] Preferably, the pressure holding time is 1-15 min; more preferably, the pressure holding time is 2-12 min; even more preferably, the pressure holding time is 5-10 min.

[0084] The basic principle of the preparation method of Al-Zn based heat-free aluminum alloys is explained as follows:

[0085] (1) By melting pure aluminum, intermediate alloy and pure zinc in batches, the present invention can ensure that pure aluminum and pure zinc are fully melted, solute elements are evenly distributed in the melt, and overheating does not occur.

[0086] (2) By using in-situ TiC / TiB2 nanoparticles for refinement, the initial solidification temperature of aluminum liquid can be significantly increased and the supercooling required for solidification can be reduced.

[0087] (3) By controlling the temperature and time of smelting, smelting efficiency and product quality can be improved;

[0088] (4) The vacuum die casting method can significantly improve the cleanliness and density of the alloy, eliminate structural defects such as porosity and inclusions, ensure that the resulting alloy castings are free of inclusions, avoid the adverse effects of inclusions on alloy performance, and thus prepare aluminum alloys with good tensile strength, yield strength and elongation.

[0089] The third aspect of the present invention provides the application of the Al-Zn heat-free aluminum alloys described in the first aspect of the present invention in the automotive and aerospace fields.

[0090] Compared with the prior art, the beneficial effects of the present invention are:

[0091] 1) The Al-Zn-based heat-treatable aluminum alloy provided by this invention, by controlling the content range of Zn, Si, and Cu elements, maximizes the solidification of solute elements into the matrix and utilizes the interaction between solute elements to form a second-phase strengthening phase, thereby improving the strength and plasticity of the alloy; by controlling the content range of trace alloying elements Mn, Zr, V, and Er, the microstructure of the alloy is improved, and the mechanical properties of the alloy are enhanced; by controlling the content range of nanoparticles TiC / TiB2, the grains of the alloy are refined, and the mechanical properties are improved; this invention, through the microstructure control of the main alloying elements and in-situ nanoparticles, obtains an aluminum alloy with dense microstructure, fine grains, uniform distribution of solute elements, and few casting defects;

[0092] 2) The method for preparing Al-Zn-based heat-free aluminum alloys provided by this invention adopts a batch melting method to ensure uniform distribution of solute elements; by controlling the melting temperature and time of each batch, the melting efficiency and product quality are improved; by ultrasonically vibrating and stirring the refining liquid, a melt with uniform composition and no impurities is obtained; and by using a vacuum die casting process, high-quality die castings with high cleanliness and density and few structural defects such as porosity are obtained.

[0093] 3) The Al-Zn series heat-free aluminum alloy provided by this invention, after being die-cast, has a tensile strength of 388MPa, a yield strength of 272MPa, an elongation of 6.2%, and few defects such as porosity and shrinkage. The product quality is high and can meet the performance requirements of heat-free aluminum alloy die-castings in the automotive and aerospace fields. Attached Figure Description

[0094] Figure 1 The image shows the microstructure of the Al-Zn-based heat-free aluminum alloy ingot prepared in Example 1.

[0095] Figure 2 The image shows the microstructure of the Al-Zn-based heat-free aluminum alloy ingot prepared in Comparative Example 1.

[0096] Figure 3 The image shows the microstructure of the Al-Zn-based heat-free aluminum alloy ingot prepared in Comparative Example 3.

[0097] Figure 4 The image shows the microstructure of the Al-Zn-based heat-free aluminum alloy ingot prepared in Comparative Example 4. Detailed Implementation

[0098] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0099] Example 1

[0100] This embodiment prepares an Al-Zn-based heat-treatable aluminum alloy. The composition of the Al-Zn-based heat-treatable aluminum alloy is shown in Table 1:

[0101] Table 1. Composition and content of Al-Zn heat-free aluminum alloy in Example 1

[0102] Components Content (wt%) Components Content (wt%) Zn 13.5 Sr 0.08 Si 6.5 <![CDATA[TiC / TiB2]]> 1.5 Cu 0.9 Al 75.80 Mn 1.0 Fe ＜0.01 Zr 0.2 C ＜0.01 V 0.3 O ＜0.01 Er 0.2 Ca ＜0.01

[0103] The raw materials for preparing Al-Zn-based heat-treatable aluminum alloys are:

[0104] Pure aluminum ingots (aluminum content ≥99.999wt%, industrial grade), pure zinc ingots (zinc content ≥99.999wt%, industrial grade);

[0105] Master alloys: Al-20%Si, Al-50%Cu, Al-20%Mn, Al-10%Zr, Al-4%V and Al-10%Er alloys;

[0106] Modifier: Al-10%Sr modifier;

[0107] Refining agent: Al-30% TiC / TiB2 nanoparticles.

[0108] The preparation steps for Al-Zn-based heat-treatable aluminum alloys are as follows:

[0109] S11. According to the formula of Al-Zn series heat-free aluminum alloy, add pure aluminum ingots into the resistance furnace, heat to 770℃, and hold for 2 hours. At this time, the pure aluminum ingots are half melted. Add intermediate alloy, cool down to 750℃, and hold for 1.5 hours. After the pure aluminum ingots and intermediate alloys are completely melted, cool down to 690℃, add pure zinc ingots, and melt for 0.5 hours to obtain alloy liquid.

[0110] S21. The alloy liquid in S11 is subjected to modification and refinement treatment. The temperature is raised to 720℃, a modifier is added, the mixture is stirred thoroughly, and the temperature is maintained for 0.3h. Then the temperature is raised to 735℃, a refiner is added, and the temperature is maintained for 0.3h to obtain a refined liquid.

[0111] S31. The refining liquid in S21 is subjected to ultrasonic vibration stirring (vibration power of 1000W, resonant frequency of 20kHz, vibration time of 5min). After vibration, slag is removed, and after standing for 10min, it is poured and die-cast. The entire die-casting mold is sealed with a vacuum hood. The refining liquid is poured into the pressure chamber at 730℃ and a speed of 1.0m / s. The pressure chamber is sealed with an injection punch. The vacuum degree is controlled at 20kPa, the high-pressure injection speed is 4m / s, the injection pressure is 300MPa, the mold temperature is 150℃, and the holding time is 5min to obtain Al-Zn system heat-free aluminum alloy ingot.

[0112] Example 2

[0113] This embodiment prepares an Al-Zn-based heat-treatable aluminum alloy. The composition of the Al-Zn-based heat-treatable aluminum alloy is shown in Table 2:

[0114] Table 2. Composition and content of Al-Zn-based heat-free aluminum alloys in Example 2

[0115] Components Content (wt%) Components Content (wt%) Zn 13.5 Sr 0.08 Si 6.5 <![CDATA[TiC / TiB2]]> 1.5 Cu 0.9 Al 75.79 Mn 1.0 Fe ＜0.01 Zr 0.2 C ＜0.01 V 0.3 O ＜0.01 Er 0.2 Ca ＜0.01

[0116] The raw materials for preparing Al-Zn-based heat-treatable aluminum alloys are:

[0117] Pure aluminum ingots (aluminum content ≥99.999wt%, industrial grade), pure zinc ingots (zinc content ≥99.999wt%, industrial grade);

[0118] Master alloys: Al-20%Si, Al-50%Cu, Al-20%Mn, Al-10%Zr, Al-4%V and Al-10%Er alloys;

[0119] Modifier: Al-10%Sr modifier;

[0120] Refining agent: Al-30% TiC / TiB2 nanoparticles.

[0121] The preparation steps for Al-Zn-based heat-treatable aluminum alloys are as follows:

[0122] S11. According to the formula of Al-Zn series heat-free aluminum alloy, add pure aluminum ingots into the resistance furnace, heat to 770℃, and hold for 2 hours. At this time, the pure aluminum ingots are half melted. Add intermediate alloy, cool down to 750℃, and hold for 1.5 hours. After the pure aluminum ingots and intermediate alloys are completely melted, cool down to 690℃, add pure zinc ingots, and melt for 0.5 hours to obtain alloy liquid.

[0123] S21. The alloy liquid in S11 is subjected to modification and refinement treatment. The temperature is raised to 720℃, a modifier is added, the mixture is stirred thoroughly, and the temperature is maintained for 0.3h. Then the temperature is raised to 735℃, a refiner is added, and the temperature is maintained for 0.3h to obtain a refined liquid.

[0124] S31. The refining liquid in S21 is subjected to ultrasonic vibration stirring (vibration power of 1000W, resonant frequency of 20kHz, vibration time of 5min). After vibration, slag is removed, and after standing for 10min, it is poured and die-cast. The entire die-casting mold is sealed with a vacuum hood. The refining liquid is poured into the pressure chamber at 730℃ and a speed of 1.0m / s. The pressure chamber is sealed with an injection punch. The vacuum degree is controlled at 5kPa, the high-pressure injection speed is 4m / s, the injection pressure is 300MPa, the mold temperature is 150℃, and the holding time is 5min to obtain Al-Zn series heat-free aluminum alloy ingot.

[0125] Example 3

[0126] This embodiment prepares an Al-Zn-based heat-treatable aluminum alloy. The composition of the Al-Zn-based heat-treatable aluminum alloy is shown in Table 3.

[0127] Table 3. Composition and content of Al-Zn-based heat-free aluminum alloys in Example 3

[0128]

[0129]

[0130] The raw materials for preparing Al-Zn-based heat-treatable aluminum alloys are:

[0131] Pure aluminum ingots (aluminum content ≥99.999wt%, industrial grade), pure zinc ingots (zinc content ≥99.999wt%, industrial grade);

[0132] Master alloys: Al-20%Si, Al-50%Cu, Al-20%Mn, Al-10%Zr, Al-4%V and Al-10%Er alloys;

[0133] Modifier: Al-10%Sr modifier;

[0134] Refining agent: Al-30% TiC / TiB2 nanoparticles.

[0135] The preparation steps for Al-Zn-based heat-treatable aluminum alloys are as follows:

[0136] S11. According to the formula of Al-Zn series heat-free aluminum alloy, add pure aluminum ingots into the resistance furnace, heat to 770℃, and hold for 2 hours. At this time, the pure aluminum ingots are half melted. Add intermediate alloy, cool down to 750℃, and hold for 1.5 hours. After the pure aluminum ingots and intermediate alloys are completely melted, cool down to 690℃, add pure zinc ingots, and melt for 0.5 hours to obtain alloy liquid.

[0137] S21. The alloy liquid in S11 is subjected to modification and refinement treatment. The temperature is raised to 720℃, a modifier is added, the mixture is stirred thoroughly, and the temperature is maintained for 0.3h. Then the temperature is raised to 735℃, a refiner is added, and the temperature is maintained for 0.3h to obtain a refined liquid.

[0138] S31. The refining liquid in S21 is subjected to ultrasonic vibration stirring (vibration power of 1000W, resonant frequency of 20kHz, vibration time of 5min). After vibration, slag is removed, and after standing for 10min, it is poured and die-cast. The entire die-casting mold is sealed with a vacuum hood. The refining liquid is poured into the pressure chamber at 730℃ and a speed of 1.0m / s. The pressure chamber is sealed with an injection punch. The vacuum degree is controlled at 20kPa, the high-pressure injection speed is 4m / s, the injection pressure is 300MPa, the mold temperature is 150℃, and the holding time is 5min to obtain Al-Zn system heat-free aluminum alloy ingot.

[0139] Example 4

[0140] This embodiment prepares an Al-Zn-based heat-treatable aluminum alloy. The composition of the Al-Zn-based heat-treatable aluminum alloy is shown in Table 4.

[0141] Table 4. Composition and content of Al-Zn heat-free aluminum alloy in Example 4

[0142]

[0143]

[0144] The raw materials for preparing Al-Zn-based heat-treatable aluminum alloys are:

[0145] Pure aluminum ingots (aluminum content ≥99.999wt%, industrial grade), pure zinc ingots (zinc content ≥99.999wt%, industrial grade);

[0146] Master alloys: Al-20%Si, Al-50%Cu, Al-20%Mn, Al-10%Zr, Al-4%V and Al-10%Er alloys;

[0147] Modifier: Al-10%Sr modifier;

[0148] Refining agent: Al-30% TiC / TiB2 nanoparticles.

[0149] The preparation steps for Al-Zn-based heat-treatable aluminum alloys are as follows:

[0150] S11. According to the formula of Al-Zn series heat-free aluminum alloy, add pure aluminum ingots into the resistance furnace, heat to 770℃, and hold for 2 hours. At this time, the pure aluminum ingots are half melted. Add intermediate alloy, cool down to 750℃, and hold for 1.5 hours. After the pure aluminum ingots and intermediate alloys are completely melted, cool down to 690℃, add pure zinc ingots, and melt for 0.5 hours to obtain alloy liquid.

[0151] S21. The alloy liquid in S11 is subjected to modification and refinement treatment. The temperature is raised to 720℃, a modifier is added, the mixture is stirred thoroughly, and the temperature is maintained for 0.3h. Then the temperature is raised to 735℃, a refiner is added, and the temperature is maintained for 0.3h to obtain a refined liquid.

[0152] S31. The refining liquid in S21 is subjected to ultrasonic vibration stirring (vibration power of 2000W, resonant frequency of 25kHz, vibration time of 8min). After vibration, slag is removed, and after standing for 10min, it is poured and die-cast. The entire die-casting mold is sealed with a vacuum hood. The refining liquid is poured into the pressure chamber at 730℃ and a speed of 1.0m / s. The pressure chamber is sealed with an injection punch. The vacuum degree is controlled at 20kPa, the high-pressure injection speed is 4m / s, the injection pressure is 300MPa, the mold temperature is 150℃, and the holding time is 5min to obtain Al-Zn system heat-free aluminum alloy ingot.

[0153] Comparative Example 1

[0154] This comparative example prepared an Al-Zn-based heat-treatable aluminum alloy. The composition of the Al-Zn-based heat-treatable aluminum alloy is shown in Table 5.

[0155] Table 5. Composition and content of Al-Zn heat-free aluminum alloys in Comparative Example 1

[0156]

[0157]

[0158] The raw materials for preparing Al-Zn-based heat-treatable aluminum alloys are:

[0159] Pure aluminum ingots (aluminum content ≥99.999wt%, industrial grade), pure zinc ingots (zinc content ≥99.999wt%, industrial grade);

[0160] Intermediate alloys: Al-20%Si and Al-50%Cu alloys.

[0161] The preparation steps for Al-Zn-based heat-treatable aluminum alloys are as follows:

[0162] S11. According to the formula of Al-Zn series heat-free aluminum alloy, add pure aluminum ingots into the resistance furnace, heat to 770℃, and hold for 2 hours. At this time, the pure aluminum ingots are half melted. Add intermediate alloy, cool down to 750℃, and hold for 1.5 hours. After the pure aluminum ingots and intermediate alloys are completely melted, cool down to 690℃, add pure zinc ingots, and melt for 0.5 hours to obtain alloy liquid.

[0163] S31. The alloy liquid in S11 is subjected to ultrasonic vibration stirring (vibration power of 1000W, resonant frequency of 20kHz, vibration time of 5min). After vibration, slag is removed, and after standing for 10min, it is poured and die-cast. The entire die-casting mold is sealed with a vacuum hood. The refined liquid is poured into the pressure chamber at 730℃ at a speed of 1.0m / s. The pressure chamber is sealed with an injection punch. The vacuum degree is controlled at 20kPa, the high-pressure injection speed is 4m / s, the injection pressure is 300MPa, the mold temperature is 150℃, and the holding time is 5min to obtain Al-Zn system heat-free aluminum alloy ingot.

[0164] Comparative Example 2

[0165] This comparative example prepared an Al-Zn-based heat-treatable aluminum alloy. The composition of the Al-Zn-based heat-treatable aluminum alloy is shown in Table 6.

[0166] Table 6. Composition and content of Al-Zn heat-free aluminum alloys in Comparative Example 2

[0167] Components Content (wt%) Components Content (wt%) Zn 6.5 Sr 0.02 Si 4.5 <![CDATA[TiC / TiB2]]> 0.5 Cu 0.4 Al 87.25 Mn 0.4 Fe ＜0.01 Zr 0.2 C ＜0.01 V 0.1 O ＜0.01 Er 0.1 Ca ＜0.01

[0168] The raw materials for preparing Al-Zn-based heat-treatable aluminum alloys are:

[0169] Pure aluminum ingots (aluminum content ≥99.999wt%, industrial grade), pure zinc ingots (zinc content ≥99.999wt%, industrial grade);

[0170] Master alloys: Al-20%Si, Al-50%Cu, Al-20%Mn, Al-10%Zr, Al-4%V and Al-10%Er alloys;

[0171] Modifier: Al-10%Sr modifier;

[0172] Refining agent: Al-30% TiC / TiB2 nanoparticles.

[0173] The preparation steps for Al-Zn-based heat-treatable aluminum alloys are as follows:

[0174] S11. According to the formula of Al-Zn series heat-free aluminum alloy, add pure aluminum ingots into the resistance furnace, heat to 770℃, and hold for 2 hours. At this time, the pure aluminum ingots are half melted. Add intermediate alloy, cool down to 750℃, and hold for 1.5 hours. After the pure aluminum ingots and intermediate alloys are completely melted, cool down to 690℃, add pure zinc ingots, and melt for 0.5 hours to obtain alloy liquid.

[0175] S21. The alloy liquid in S11 is subjected to modification and refinement treatment. The temperature is raised to 720℃, a modifier is added, the mixture is stirred thoroughly, and the temperature is maintained for 0.3h. Then the temperature is raised to 735℃, a refiner is added, and the temperature is maintained for 0.3h to obtain a refined liquid.

[0176] S31. The refining liquid in S21 is subjected to ultrasonic vibration stirring (vibration power of 1000W, resonant frequency of 20kHz, vibration time of 5min). After vibration, slag is removed, and after standing for 10min, it is poured and die-cast. The entire die-casting mold is sealed with a vacuum hood. The refining liquid is poured into the pressure chamber at 730℃ and a speed of 1.0m / s. The pressure chamber is sealed with an injection punch. The vacuum degree is controlled at 20kPa, the high-pressure injection speed is 4m / s, the injection pressure is 300MPa, the mold temperature is 150℃, and the holding time is 5min to obtain Al-Zn system heat-free aluminum alloy ingot.

[0177] Comparative Example 3

[0178] This comparative example prepared an Al-Zn-based heat-treatable aluminum alloy. The composition of the Al-Zn-based heat-treatable aluminum alloy is shown in Table 7.

[0179] Table 7. Composition and content of Al-Zn heat-free aluminum alloys in Comparative Example 3

[0180] Components Content (wt%) Components Content (wt%) Zn 13.5 Sr 0.08 Si 6.5 <![CDATA[TiC / TiB2]]> 1.5 Cu 0.9 Al 75.81 Mn 1.0 Fe ＜0.01 Zr 0.2 C ＜0.01 V 0.3 O ＜0.01 Er 0.2 Ca ＜0.01

[0181] The raw materials for preparing Al-Zn-based heat-treatable aluminum alloys are:

[0182] Pure aluminum ingots (aluminum content ≥99.999wt%, industrial grade), pure zinc ingots (zinc content ≥99.999wt%, industrial grade);

[0183] Master alloys: Al-20%Si, Al-50%Cu, Al-20%Mn, Al-10%Zr, Al-4%V and Al-10%Er alloys;

[0184] Modifier: Al-10%Sr modifier;

[0185] Refining agent: Al-30% TiC / TiB2 nanoparticles.

[0186] The preparation steps for Al-Zn-based heat-treatable aluminum alloys are as follows:

[0187] S11. According to the formula of Al-Zn series heat-free aluminum alloy, add pure aluminum ingots into the resistance furnace, heat to 770℃, and hold for 2 hours. At this time, the pure aluminum ingots are half melted. Add intermediate alloy, cool down to 750℃, and hold for 1.5 hours. After the pure aluminum ingots and intermediate alloys are completely melted, cool down to 690℃, add pure zinc ingots, and melt for 0.5 hours to obtain alloy liquid.

[0188] S21. The alloy liquid in S11 is subjected to modification and refinement treatment. The temperature is raised to 720℃, a modifier is added, the mixture is stirred thoroughly, and the temperature is maintained for 0.3h. Then the temperature is raised to 735℃, a refiner is added, and the temperature is maintained for 0.3h to obtain a refined liquid.

[0189] S31. The refining liquid in S21 is mechanically stirred. After stirring, the slag is removed and the mixture is allowed to stand for 10 minutes before being poured and die-cast. The entire die-casting mold is sealed with a vacuum hood. The refining liquid is poured into the pressure chamber at 730℃ and a speed of 1.0 m / s. The pressure chamber is sealed with an injection punch. The vacuum degree is controlled at 20 kPa, the high-pressure injection speed is 4 m / s, the injection pressure is 300 MPa, the mold temperature is 150℃, and the holding time is 5 minutes to obtain an Al-Zn series heat-free aluminum alloy ingot.

[0190] Comparative Example 4

[0191] This comparative example prepared an Al-Zn-based heat-treatable aluminum alloy. The composition of the Al-Zn-based heat-treatable aluminum alloy is shown in Table 8.

[0192] Table 8. Composition and content of Al-Zn heat-free aluminum alloys in Comparative Example 4

[0193] Components Content (wt%) Components Content (wt%) Zn 14.5 Sr 0.2 Si 8.0 <![CDATA[TiC / TiB2]]> 2.0 Cu 1.5 Al 71.83 Mn 1.0 Fe ＜0.01 Zr 0.3 C ＜0.01 V 0.4 O ＜0.01 Er 0.25 Ca ＜0.01

[0194] The raw materials for preparing Al-Zn-based heat-treatable aluminum alloys are:

[0195] Pure aluminum ingots (aluminum content ≥99.999wt%, industrial grade), pure zinc ingots (zinc content ≥99.999wt%, industrial grade);

[0196] Master alloys: Al-20%Si, Al-50%Cu, Al-20%Mn, Al-10%Zr, Al-4%V and Al-10%Er alloys;

[0197] Modifier: Al-10%Sr modifier;

[0198] Refining agent: Al-30% TiC / TiB2 nanoparticles.

[0199] The preparation steps for Al-Zn-based heat-treatable aluminum alloys are as follows:

[0200] S11. According to the formula of Al-Zn series heat-free aluminum alloy, add pure aluminum ingots into the resistance furnace, heat to 770℃, and hold for 2 hours. At this time, the pure aluminum ingots are half melted. Add intermediate alloy, cool down to 750℃, and hold for 1.5 hours. After the pure aluminum ingots and intermediate alloys are completely melted, cool down to 690℃, add pure zinc ingots, and melt for 0.5 hours to obtain alloy liquid.

[0201] S21. The alloy liquid in S11 is subjected to modification and refinement treatment. The temperature is raised to 720℃, a modifier is added, the mixture is stirred thoroughly, and the temperature is maintained for 0.3h. Then the temperature is raised to 735℃, a refiner is added, and the temperature is maintained for 0.3h to obtain a refined liquid.

[0202] S31. The refining liquid in S21 is subjected to ultrasonic vibration stirring (vibration power of 1000W, resonant frequency of 20kHz, vibration time of 5min). After vibration, slag is removed, and after standing for 10min, it is poured and die-cast. The entire die-casting mold is sealed with a vacuum hood. The refining liquid is poured into the pressure chamber at 700℃ and a speed of 1.0m / s. The pressure chamber is sealed with an injection punch without starting the vacuum. The high-pressure injection speed is 4m / s, the injection pressure is 100MPa, the mold temperature is 100℃, and the holding time is 5min to obtain Al-Zn system heat-free aluminum alloy ingot.

[0203] Performance testing

[0204] 1. The microstructure of the Al-Zn-based heat-free aluminum alloy ingots prepared in Example 1, Comparative Example 1, Comparative Example 3, and Comparative Example 4 was observed using a metallographic microscope:

[0205] Figure 1 The image shows the microstructure of the Al-Zn-based heat-treatable aluminum alloy ingot prepared in Example 1. Figure 1 It can be seen that the Al-Zn-based heat-free aluminum alloy in Example 1 has a dense microstructure, fine grains, and uniform distribution of solute elements.

[0206] Figure 2 The image shows the microstructure of the Al-Zn-based heat-treatable aluminum alloy ingot prepared in Comparative Example 1. Figure 2 It can be seen that the Al-Zn-based heat-free aluminum alloy in Comparative Example 1 has a coarse microstructure, uneven grain distribution, and coarse α-Al dendrites. This is because no trace alloying elements were added in Comparative Example 1, so a second phase containing trace alloying elements could not be formed in the alloy matrix, thus failing to play a role in refining the grains.

[0207] Figure 3 The image shows the microstructure of the Al-Zn-based heat-treatable aluminum alloy ingot prepared in Comparative Example 3. Figure 3It can be seen that the Al-Zn-based heat-free aluminum alloy in Comparative Example 3 exhibits severe segregation and enrichment of solute elements. This is because Comparative Example 3 did not use ultrasonic vibration stirring, resulting in uneven distribution of nanoparticles and solute elements in the melt. During the die casting process, segregation is easily generated under rapid cooling.

[0208] Figure 4 The image shows the microstructure of the Al-Zn-based heat-treatable aluminum alloy ingot prepared in Comparative Example 4. Figure 4 It can be seen that the Al-Zn-based heat-free aluminum alloy in Comparative Example 4 has a large number of porosity and inclusion defects. This is because the die-casting process parameters in the preparation process of Comparative Example 4 are not within the scope of this invention, and the process was not carried out in a vacuum atmosphere, resulting in low cleanliness and density of the alloy.

[0209] As can be seen, by adding Zn, Si, Cu, and trace alloying elements Mn, Zr, V and Er in a specific ratio, and by introducing in-situ TiC / TiB2 nanoparticles combined with ultrasonic vibration stirring, a melt with uniform composition and no impurities was obtained. Combined with vacuum die casting process, the resulting alloy ingot has a dense structure, fine grains and uniform distribution of solute elements.

[0210] 2. Mechanical property tests were performed on the Al-Zn-based heat-treatable aluminum alloy ingots prepared in Examples 1-4 and Comparative Examples 1-4:

[0211] The tensile test was performed on a WGW-100H universal testing machine. The specific test method was as follows:

[0212] 1) Tensile strength was tested according to GB-T228-2002 "Metallic Materials - Tensile Testing at Room Temperature";

[0213] 2) Yield strength was tested in accordance with GB-T228-2002 "Metallic Materials - Tensile Testing at Room Temperature";

[0214] 3) The elongation rate is tested in accordance with GB / T 17737.308-2018 "Coaxial Communication Cables" Part 1-308: Mechanical Test Methods - Tensile Strength and Elongation Test of Copper-Clad Metals.

[0215] Table 9. Mechanical property test results of Al-Zn-based heat-free aluminum alloy ingots prepared in Examples 1-4 and Comparative Examples 1-4

[0216] Examples / Comparative Examples Tensile strength / MPa Yield strength / MPa Elongation / % Example 1 378 264 6.5 Example 2 388 272 6.2 Example 3 364 255 5.9 Example 4 370 267 6.0 Comparative Example 1 324 201 7.6 Comparative Example 2 336 220 4.8 Comparative Example 3 319 229 4.9 Comparative Example 4 330 231 5.1

[0217] Table 9 shows the mechanical property test results of the Al-Zn-based heat-free aluminum alloy ingots prepared in Examples 1-4 and Comparative Examples 1-4. As can be seen from Table 9, the tensile strength of the Al-Zn-based heat-free aluminum alloy ingots in Examples 1-4 is 364-388 MPa, the yield strength is 255-272 MPa, and the elongation is 5.9-6.5%. The alloy has good tensile strength, yield strength and elongation, and excellent mechanical properties.

[0218] Comparative Example 1, which did not contain any trace alloying elements, had a tensile strength of 324 MPa, a yield strength of 201 MPa, and an elongation of 7.6%, with mechanical properties significantly worse than those of Example 1. This demonstrates that the addition of trace alloying elements plays an important role in improving the mechanical properties of the alloy.

[0219] The amount of alloying elements added in Comparative Example 2 is not within the range provided by this invention. The tensile strength of the alloy is 336 MPa, the yield strength is 220 MPa, and the elongation is 4.8%. The mechanical properties are significantly worse than those in Example 1, indicating that alloying elements need to be added in a specific ratio to better improve the mechanical properties of the alloy.

[0220] In Comparative Example 3, after the addition of a nanoparticle refiner, the melt was not treated with ultrasonic vibration stirring. The tensile strength of the alloy was 319 MPa, the yield strength was 229 MPa, and the elongation was 4.9%. The mechanical properties were significantly worse than those in Example 1, indicating that ultrasonic vibration stirring plays an important role in the uniform distribution of nanoparticles and solute elements, which is beneficial to improving the mechanical properties of the alloy.

[0221] The die-casting process conditions of Comparative Example 4 are not within the scope of this invention. The tensile strength of the alloy is 330 MPa, the yield strength is 231 MPa, and the elongation is 5.1%. The mechanical properties are significantly worse than those of Example 3. This shows that by using a die-casting process with specific parameters, castings with dense structure and fewer defects such as porosity and inclusions can be obtained, which is beneficial to improving the mechanical properties of the alloy.

[0222] This invention adds Zn, Si, and Cu elements in specific proportions to synergistically regulate and enhance solid solution strengthening and second-phase strengthening, thereby improving the mechanical properties of the alloy. It also introduces trace alloying elements Mn, V, Zr, and Er in specific proportions. Mn elements form Al6Mn compounds, which disperse and recrystallize into dispersed particles that hinder recrystallization grain growth. Simultaneously, (Fe,Mn)Al6 is formed, reducing the harmful effects of Fe-rich phases. V, Zr, and Er elements effectively increase the nucleation temperature and undercooling of primary α-Al, raising the recrystallization temperature of the alloy by forming Si2V, Al3Zr, Zr2Si, and Al3Er phases. The formation of (AlSi)3ZrV and core-shell Al3(Er,Zr) phases provides dispersion strengthening. Finally, in-situ self-generated TiC / TiB2 nanoparticles are selected as grain refiners, simultaneously refining the grains and improving the mechanical properties of the alloy.

[0223] This invention achieves good elongation while ensuring alloy strength by controlling the content range of Zn, Si, Cu, trace alloying elements, and nanoparticle refiners, combined with an optimized preparation process. The resulting Al-Zn-based heat-free aluminum alloy has a dense structure, fine grains, and is free from defects such as porosity and shrinkage. The product has high quality and can meet the high requirements of the automotive and aerospace industries for aluminum alloy materials.

Claims

1. An Al-Zn based heat-treatable aluminum alloy, characterized in that, Composed of the following components by mass percentage composition: Al: 71.35-78.3%, Zn: 13.0-15.0%, Si: 6.0-8.0%, Cu: 0.5-1.5%, Mn: 0.6-1.0%, Zr: 0.1-0.3%, V: 0.1-0.4%, Er: 0.15-0.25%, Sr: 0.05-0.2%, TiC / TiB2: 1.2-2.0%, unavoidable impurities <0.04%; wherein, the unavoidable impurities include Fe, C, O and Ca; the mass percentage content of any single impurity is less than 0.01%; The Al-Zn-based heat-free aluminum alloy comprises the following raw materials: pure aluminum, pure zinc, master alloy, modifier, and refining agent; The Al-Zn-based heat-treatable aluminum alloy is prepared by a method comprising the following steps: S1. Pure aluminum, intermediate alloy and pure zinc are added in sequence and smelted to obtain alloy liquid; S2. Add the modifier and refiner to the alloy liquid in sequence and refine it to obtain a refined liquid; S3. The refining liquid is subjected to ultrasonic vibration stirring, pouring and vacuum die casting to obtain the Al-Zn system heat-free aluminum alloy. In step S3, the ultrasonic vibration stirring power is 500-3000W, the resonant frequency is 15-35kHz, and the time is 3-10min; the pouring temperature is 660-780℃, and the speed is 0.4-1.6m / s; the vacuum degree of the vacuum die casting is 1-50kPa, the injection speed is 4-6.5m / s, the injection pressure is 100-600MPa, and the mold temperature is 100-300℃.

2. The Al-Zn-based heat-treatable aluminum alloy according to claim 1, characterized in that, The intermediate alloys include Al-Si, Al-Cu, Al-Mn, Al-Zr, Al-V, and Al-Er alloys.

3. The Al-Zn-based heat-treatable aluminum alloy according to claim 1, characterized in that, The modifier includes an Al-Sr modifier.

4. The Al-Zn-based heat-treatable aluminum alloy according to claim 1, characterized in that, The refining agent includes Al-TiC / TiB2 nanoparticles.

5. The Al-Zn-based heat-treatable aluminum alloy according to claim 1, characterized in that, In step S1, the smelting process conditions include at least one of the following: 1) The smelting temperature after adding pure aluminum is 710-800℃, and the smelting time is 1-4h; 2) The melting temperature after adding the intermediate alloy is 730-790℃, and the melting time is 0.5-2.5h; 3) The smelting temperature after adding pure zinc is 630-730℃, and the smelting time is 1-2h.

6. The Al-Zn-based heat-treatable aluminum alloy according to claim 1, characterized in that, In step S2, the refining process conditions include at least one of the following: 1) The refining temperature after adding the modifier is 630-750℃, and the refining time is 0.1-1h; 2) The refining temperature after adding the refining agent is 690-760℃, and the refining time is 0.1-1h.

7. The application of the Al-Zn heat-free aluminum alloy according to any one of claims 1-6 in the automotive and aerospace fields.

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