Al-zn casting alloy with near-p texture and high strength and high yield ratio and preparation method thereof

Abstract

The application provides an Al-Zn casting alloy, which comprises the following components in percentage by mass: Zn 4.3-5.2%, Mg 1.2-1.8%, Cu 0.50-0.85%, Ti 0.15-0.25%, Zr 0.10-0.25%, V 0.10-0.25%, Si≤0.2%, Fe≤0.2%, Mn≤0.2%, and the balance of Al; the sum of the percentage by mass of the components is 100%. The application reasonably designs the component proportion of the alloy, controls Zn, Mg and Cu and other elements and uniformizes and solid-solutes coupling process treatment through a special casting process, so that the Al-Zn casting alloy with high strength and high yield ratio can be obtained by means of the particle excitation nucleation effect of the coupled second phase, the grains are refined at the same time, and a high proportion of near P texture is formed.

Description

Technical Field

[0001] This invention relates to the field of high-performance cast aluminum alloy materials and their processing technology, and in particular to an Al-Zn cast alloy with near-P texture, high strength and high yield strength ratio, and its preparation method. Background Technology

[0002] In achieving lightweighting of automobiles using aluminum alloys, maintaining material strength and improving material utilization are major challenges in the automotive industry's transformation. To achieve these goals, a high yield-to-strength ratio is required. Materials with a high yield-to-strength ratio not only effectively improve material utilization but also possess greater resistance to deformation, preventing the vehicle from easily deforming during service and allowing it to maintain its original shape. Currently, developing aluminum alloy materials with high strength and a high yield-to-strength ratio is a significant technological challenge for significantly improving the service performance of automobiles.

[0003] Several technological inventions have been developed to address the aforementioned technical problems. However, most of these inventions utilize Al-Mg or Al-Mg-Si series casting alloys, which suffer from insufficient strength and yield strength ratio, making it difficult to meet the demands of automotive materials, especially automotive parts, in more demanding service environments. If high strength and a high yield strength ratio are the primary key performance indicators for automotive materials / parts, Al-Zn series casting alloys are a better choice. Currently, there are already some Al-Zn series casting alloys available for automotive applications.

[0004] In Chinese patent CN201410768910.4, the Al-Zn aluminum alloy melt comprises: 1.4–2 wt% Cu, 0.2–0.6 wt% Mn, 1.8–2.8 wt% Mg, 0.1–0.25 wt% Cr, 5.0–6.5 wt% Zn, and the balance Al. The alloy composition of the aluminum alloy melt is optimized during the casting process, improving the flaw detection pass rate of the aluminum alloy ingot (higher than 90%). Chinese patent CN201310724624.3 discloses an Al-Zn-Mg-Zr aluminum alloy ingot and its casting process. First, the Ti content in the aluminum alloy melt is adjusted. Then, Al-5Ti-1B blocks are added and the temperature of the aluminum alloy melt is controlled. Next, Al-5Ti-1B wire is added again. Finally, the melt is cast and the casting speed is controlled to obtain an aluminum alloy ingot with a grain size of 1–2.

[0005] Chinese patent CN201010034149.3 discloses an Al-Zn-Mg-Cu-Sc-Zr-RE alloy and its preparation method, which can be used as an ultra-high strength cast aluminum alloy. This alloy, by employing higher Zn and Mg content, Sc and Zr composite microalloying, and the addition of trace amounts of rare earth elements Er and / or Yb, achieves the goals of increasing the eutectic phase ratio, refining the grain structure, suppressing dendrite growth, and altering the alloy's solidification mode, thereby reducing the alloy's hot cracking tendency and significantly improving its casting performance. Chinese patent CN89107816.9 develops a combined casting and forging process for Al-Zn-Mg alloys. First, prepared liquid metal is poured into a mold. Then, the cleaned casting is placed in a preheated forging die and subjected to pressure, causing the casting to deform and fill the entire die. After pressure processing, pores and shrinkage cavities are flattened or fused, increasing the casting density and refining the grain size.

[0006] Most of the above patents improve the alloy's flaw detection pass rate by changing the composition, adding complex rare elements, and using complex casting and heat treatment methods, or by controlling the grain size to improve the strength of aluminum alloys. However, the existing patent methods are technically complex, making it difficult to achieve large-scale production of high yield strength ratio Al-Zn casting alloys, and they do not effectively utilize texture control to deeply improve the alloy's yield strength ratio. Therefore, this application is filed. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art and provide an Al-Zn casting alloy and its preparation method, thereby improving the strength and yield strength ratio of aluminum alloy materials.

[0008] This invention provides the following technical solution:

[0009] This invention provides an Al-Zn casting alloy comprising the following components by mass percentage: Zn 4.3-5.2%, Mg 1.2-1.8%, Cu 0.50-0.85%, Ti 0.15-0.25%, Zr 0.10-0.25%, V 0.10-0.25%, Si≤0.2%, Fe≤0.2%, Mn≤0.2%, with the balance being Al; the sum of the mass percentages of all components is 100%.

[0010] The present invention also provides a method for preparing the Al-Zn cast alloy, comprising the following steps:

[0011] S1. Charge proportioning: Charge proportioning is based on the target alloy composition;

[0012] S2, Smelting: Smelting is carried out by adding 4.5-7% refining agent and 0.15-0.29% covering agent to the furnace charge according to the total raw material mass;

[0013] S3. Casting: After melting, let stand for 5-10 minutes, degas, remove slag, and cast to obtain alloy castings;

[0014] S4. Coupled heat treatment: The alloy casting is first homogenized, and then solution and water quenching are performed.

[0015] S5. Timeliness processing.

[0016] Furthermore, in step S1, the furnace charge is made of pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy.

[0017] Furthermore, the refining agent is hexachloroethane, and the covering agent comprises the following components by mass percentage: 13% calcium fluoride, 18% potassium chloride, and 69% sodium chloride.

[0018] Furthermore, in step S2, the crucible is preheated to 200-300°C before melting, and then a protective coating is applied to clean the melting tools.

[0019] Furthermore, in step S2, the smelting process parameters are: melting temperature of 710–730°C, refining temperature of 690–710°C, and refining treatment of 3–5 min.

[0020] Furthermore, in step S3, the mold is preheated to 250°C before casting, and the casting temperature is 690-710°C.

[0021] Further, step S4 specifically involves: first, homogenization treatment at 456-479℃ for 24-50 hours, followed by solution treatment at 470-493℃ for 0.5-2.8 hours, and finally water quenching treatment, with the water temperature controlled within the range of 20-60℃.

[0022] Furthermore, in step S5, the aging temperature is 120±5℃, the holding time is 12-25 hours, and finally air cooling is performed.

[0023] The principle of this invention is as follows:

[0024] Firstly, the smelting method employed in this invention effectively controls the hydrogen and oxygen content in the molten aluminum and suppresses bubble formation, thus significantly improving the casting quality of the aluminum alloy. Secondly, through the above composition design, three phases—η(MgZn2), T(Al2Mg2Zn3), and S(Al2MgCu)—are formed during the casting cooling process. The formation of these phases provides strong attachment sites for crystal nuclei, increasing the nucleation rate and refining the grains. Furthermore, the subsequent homogenization and solution-coupled two-stage heat treatment allows these three types of secondary phases to fully dissolve back into the aluminum matrix, ensuring the amount of strengthening phase precipitated during subsequent aging and effectively improving the alloy's strength. Furthermore, while improving the alloy's strength, the particle-induced nucleation effect induced by the three phases η(MgZn2), T(Al2Mg2Zn3), and S(Al2MgCu) leads to the formation of a texture with a relatively high proportion and an Euler angle of (55° 45°) during the dissolution of the second phase aluminum matrix. This texture is close to the P(65° 45°) texture and is called the near-P texture. This texture can stably exist in the subsequent aging process, thus obtaining a high-strength near-P texture in the aged plate. This texture has good resistance to deformation and can effectively improve the alloy's yield strength, thereby increasing the alloy's yield strength ratio. Under the action of the above mechanisms, the alloy strength and yield strength ratio of the Al-Zn casting alloy are simultaneously improved, showing good prospects for industrial applications.

[0025] The present invention has the following beneficial effects:

[0026] In the aged state of the Al-Zn cast alloy described in this invention, the near-P texture accounts for 34.8% to 62.4% of the total texture, and the average grain size is 37.9 to 67.5 μm. The prepared Al-Zn cast alloy aged material has a tensile strength of 408.3 to 429.7 MPa, a yield strength of 386.5 to 394.2 MPa, a yield ratio of 0.927 to 0.954, and an elongation of 2.07 to 2.63%, which has good application value in the automotive industry. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The (220), (200), and (111) pole figures provided for the final aged state of the substrate in Embodiment 1 of the present invention;

[0029] Figure 2Orientation distribution function (ODF) diagram provided for the final aged state of the plate material in Embodiment 1 of the present invention;

[0030] Figure 3 The orientation distribution function (ODF) diagram provided for the final aged state of the plate material in Comparative Example 1 of this invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides an Al-Zn-Mg-Cu alloy comprising the following components by mass percentage: Zn 4.3-5.2%, Mg 1.2-1.8%, Cu 0.50-0.85%, Ti 0.15-0.25%, Zr 0.10-0.25%, V 0.10-0.25%, Si≤0.2%, Fe≤0.2%, Mn≤0.2%, with the balance being Al; the sum of the mass percentages of all components is 100%.

[0033] This invention also provides a method for preparing the Al-Zn cast alloy, comprising the following steps:

[0034] S1. Charge proportioning: Charge proportioning is based on the target alloy composition;

[0035] S2, Smelting: Smelting is carried out by adding 4.5-7% refining agent and 0.15-0.29% covering agent to the furnace charge according to the total raw material mass;

[0036] S3. Casting: After melting, let stand for 5-10 minutes, degas, remove slag, and cast to obtain alloy castings;

[0037] S4. Coupled heat treatment: The alloy casting is first homogenized, and then solution and water quenching are performed.

[0038] S5. Timeliness processing.

[0039] In a specific embodiment: In step S1, the furnace charge is made of pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy and Al-V master alloy.

[0040] In a specific embodiment: the refining agent is hexachloroethane, and the covering agent comprises the following components by mass percentage: 13% calcium fluoride, 18% potassium chloride and 69% sodium chloride.

[0041] In a specific embodiment: In step S2, the crucible is preheated to 200-300°C before melting, and then a protective coating is applied to clean the melting tools.

[0042] In a specific embodiment: In step S2, the smelting process parameters are: melting temperature of 710-730℃, refining temperature of 690-710℃, and refining treatment of 3-5 minutes.

[0043] In a specific embodiment: In step S3, the mold is preheated to 250°C before pouring, and the pouring temperature is 690-710°C.

[0044] In a specific embodiment: Step S4 is as follows: first, a homogenization treatment is performed at 456-479℃ for 24-50h, then a solution treatment is performed at 470-493℃ for 0.5-2.8h, and finally a water quenching treatment is performed, with the water temperature controlled within the range of 20-60℃.

[0045] In a specific embodiment: In step S5, the aging temperature is 120±5℃, the temperature is maintained for 12-25 hours, and finally air cooling is performed.

[0046] The present invention will now be described through specific embodiments:

[0047] In the following examples and comparative examples, the refining agent used was hexachloroethane, and the covering agent used was 13 wt% calcium fluoride, 18 wt% potassium chloride, and 69 wt% sodium chloride.

[0048] Example 1

[0049] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 4.5%, Mg 1.7%, Cu 0.60%, Ti 0.25%, Zr 0.12%, V 0.15%, Si 0.13%, Fe 0.2%, Mn 0.15%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0050] The specific preparation process of this alloy is as follows:

[0051] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0052] Step S2, Melting: Preheat the crucible to 250℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 6% refining agent and 0.21% covering agent. The melting temperature is 720℃, the refining temperature is 705℃, and the refining time is 3.5 minutes.

[0053] Step S3, casting: After melting, let stand for 7 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 700℃.

[0054] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 456℃ for 30h, then solution treated at 479℃ for 1.2h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0055] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 20 hours. Finally, air cooling is performed.

[0056] The near-P texture accounted for 51.7% of the cast alloy aged material, with an average grain size of 60.4 μm; the tensile strength was 408.3 MPa, the yield strength was 388.9 MPa, the yield ratio was 0.952, and the elongation was 2.1%.

[0057] Example 2

[0058] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 5.1%, Mg 1.8%, Cu 0.50%, Ti 0.15%, Zr 0.12%, V 0.1%, Si 0.05%, Fe 0.19%, Mn 0.12%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0059] The specific preparation process of this alloy is as follows:

[0060] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0061] Step S2, Melting: Preheat the crucible to 290℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 5.5% refining agent and 0.16% covering agent. The melting temperature is 715℃, the refining temperature is 698℃, and the refining time is 4 minutes.

[0062] Step S3, casting: After melting, let stand for 9 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 708℃.

[0063] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 468℃ for 42h, then solution treated at 483℃ for 0.5h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0064] Step S5, Aging Treatment: The temperature is 120±5℃, and the temperature is maintained for 15 hours. Finally, air cooling is performed.

[0065] The near-P texture accounted for 54.3% of the cast alloy aged material, with an average grain size of 52.6 μm; the tensile strength was 409.1 MPa, the yield strength was 389.4 MPa, the yield-to-tensile ratio was 0.952, and the elongation was 2.07.

[0066] Example 3

[0067] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 5.2%, Mg 1.2%, Cu 0.70%, Ti 0.17%, Zr 0.22%, V 0.19%, Si 0.02%, Fe 0.1%, Mn 0.03%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0068] The specific preparation process of this alloy is as follows:

[0069] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0070] Step S2, Melting: Preheat the crucible to 210℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 6.5% refining agent and 0.29% covering agent. The melting temperature is 719℃, the refining temperature is 695℃, and the refining time is 5 minutes.

[0071] Step S3, casting: After melting, let stand for 9.5 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 697.5℃.

[0072] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 479℃ for 29h, then solution treated at 490℃ for 2.5h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0073] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 12 hours. Finally, air cooling is performed.

[0074] The near-P texture accounted for 61.2% of the aged cast alloy material, with an average grain size of 37.9 μm; the tensile strength was 413.2 MPa, the yield strength was 394.2 MPa, the yield ratio was 0.954, and the elongation was 2.04%.

[0075] Example 4

[0076] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 4.3%, Mg 1.2%, Cu 0.85%, Ti 0.15%, Zr 0.25%, V 0.25%, Si 0.2%, Fe 0.09%, Mn 0.2%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0077] The specific preparation process of this alloy is as follows:

[0078] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0079] Step S2, Melting: Preheat the crucible to 200℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Melt pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy with the addition of 7% refining agent and 0.18% covering agent. The melting temperature is 730℃, the refining temperature is 690℃, and the refining time is 3 minutes.

[0080] Step S3, casting: After melting, let stand for 5 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 710℃.

[0081] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 479℃ for 24h, then solution treated at 470℃ for 2.8h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0082] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 12 hours. Finally, air cooling is performed.

[0083] The near-P texture of the aged cast alloy was found to be 46.0%, with an average grain size of 39.2 μm; the tensile strength was 412 MPa, the yield strength was 386.9 MPa, the yield-to-tensile ratio was 0.939, and the elongation was 2.18%.

[0084] Example 5

[0085] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 4.6%, Mg 1.75%, Cu 0.65%, Ti 0.15%, Zr 0.15%, V 0.19%, Si 0.03%, Fe 0.06%, Mn 0.17%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0086] The specific preparation process of this alloy is as follows:

[0087] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0088] Step S2, Melting: Preheat the crucible to 300℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 6.8% refining agent and 0.17% covering agent. The melting temperature is 730℃, the refining temperature is 698℃, and the refining time is 5 minutes.

[0089] Step S3, casting: After melting, let stand for 9 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 702℃.

[0090] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 459℃ for 28h, then solution treated at 486℃ for 1.9h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0091] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 20 hours. Finally, air cooling is performed.

[0092] The near-P texture accounted for 39.5% of the cast alloy aged material, with an average grain size of 50.3 μm; the tensile strength was 421.1 MPa, the yield strength was 391.3 MPa, the yield-to-tensile ratio was 0.929, and the elongation was 2.36%.

[0093] Example 6

[0094] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 4.5%, Mg 1.7%, Cu 0.79%, Ti 0.21%, Zr 0.10%, V 0.25%, Si 0.17%, Fe 0.13%, Mn 0.19%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0095] The specific preparation process of this alloy is as follows:

[0096] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0097] Step S2, Melting: Preheat the crucible to 300℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 4.5% refining agent and 0.29% covering agent. The melting temperature is 710℃, the refining temperature is 690℃, and the refining time is 5 minutes.

[0098] Step S3, casting: After melting, let stand for 10 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 710℃.

[0099] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 479℃ for 29h, then solution treated at 470℃ for 2.8h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0100] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 25 hours. Finally, air cooling is performed.

[0101] The near-P texture of the aged cast alloy was found to be 34.8%, with an average grain size of 67.5 μm; the tensile strength was 418.3 MPa, the yield strength was 387.6 MPa, the yield ratio was 0.927, and the elongation was 2.54%.

[0102] Example 7

[0103] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 4.9%, Mg 1.3%, Cu 0.80%, Ti 0.21%, Zr 0.19%, V 0.15%, Si 0.19%, Fe 0.2%, Mn 0.12%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0104] The specific preparation process of this alloy is as follows:

[0105] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0106] Step S2, Melting: Preheat the crucible to 289℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 4.9% refining agent and 0.25% covering agent. The melting temperature is 716℃, the refining temperature is 699℃, and the refining time is 5 minutes.

[0107] Step S3, casting: After melting, let stand for 8 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 697℃.

[0108] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 469℃ for 28h, then solution treated at 482℃ for 2.5h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0109] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 25 hours. Finally, air cooling is performed.

[0110] The near-P texture accounted for 39.2% of the aged cast alloy material, with an average grain size of 42.9 μm; the tensile strength was 429.7 MPa, the yield strength was 400.1 MPa, the yield-to-tensile ratio was 0.931, and the elongation was 2.5%.

[0111] Example 8

[0112] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 5.2%, Mg 1.2%, Cu 0.81%, Ti 0.21%, Zr 0.17%, V 0.13%, Si 0.2%, Fe 0.05%, Mn 0.07%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0113] The specific preparation process of this alloy is as follows:

[0114] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0115] Step S2, Melting: Preheat the crucible to 200℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 4.7% refining agent and 0.15% covering agent. The melting temperature is 715℃, the refining temperature is 692℃, and the refining time is 3 minutes.

[0116] Step S3, casting: After melting, let stand for 5 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 690℃.

[0117] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 459℃ for 30h, then solution treated at 493℃ for 0.5h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0118] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 19 hours. Finally, air cooling is performed.

[0119] The near-P texture accounted for 62.4% of the cast alloy aged material, with an average grain size of 61.3 μm; the tensile strength was 412.6 MPa, the yield strength was 388.7 MPa, the yield ratio was 0.942, and the elongation was 2.43%.

[0120] Example 9

[0121] This embodiment prepares an Al-Zn casting alloy. The target mass percentage of each component of the alloy is as follows: Zn 4.9%, Mg 1.8%, Cu 0.50%, Ti 0.22%, Zr 0.16%, V 0.25%, Si 0.03%, Fe 0.17%, Mn 0.09%, with the balance being Al; the sum of the mass percentages of each component is 100%.

[0122] The specific preparation process of this alloy is as follows:

[0123] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0124] Step S2, Melting: Preheat the crucible to 290℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 6.8% refining agent and 0.21% covering agent. The melting temperature is 713℃, the refining temperature is 705℃, and the refining time is 4.5 minutes.

[0125] Step S3, casting: After melting, let stand for 7.6 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 698℃.

[0126] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 465℃ for 45h, then solution treated at 486℃ for 2.1h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0127] Step S5, Aging Treatment: The temperature is 120±5℃, and the temperature is maintained for 25 hours. Finally, air cooling is performed.

[0128] The near-P texture accounted for 53.7% of the cast alloy aged material, with an average grain size of 58.0 μm; the tensile strength was 410.9 MPa, the yield strength was 390.3 MPa, the yield ratio was 0.95, and the elongation was 2.09%.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0130] Comparative Example 1

[0131] This comparative example prepares an Al-Zn casting alloy with the following target mass percentages: Zn 3.3%, Mg 1.1%, Cu 0.30%, Ti 0.1%, Zr 0.09%, V 0.10%, Si 0.17%, Fe 0.12%, Mn 0.16%, with the balance being Al; the sum of the mass percentages of all components is 100%.

[0132] The specific preparation process of this alloy is as follows:

[0133] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0134] Step S2, Melting: Preheat the crucible to 250℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 4.6% refining agent and 0.18% covering agent. The melting temperature is 720℃, the refining temperature is 695℃, and the refining time is 5 minutes.

[0135] Step S3, casting: After melting, let stand for 9 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 698℃.

[0136] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 472℃ for 30h, then solution treated at 482℃ for 1.9h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0137] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 22 hours. Finally, air cooling is performed.

[0138] The near-P texture of the aged cast alloy was 3.9%, the average grain size was 97.5 μm, the tensile strength was 364.1 MPa, the yield strength was 311.7 MPa, the yield ratio was 0.856, and the elongation was 1.66%.

[0139] Comparative Example 2

[0140] This comparative example prepares an Al-Zn casting alloy with the following target mass percentages: Zn 4.5%, Mg 1.7%, Cu 0.60%, Ti 0.24%, Zr 0.12%, V 0.15%, Si 0.14%, Fe 0.1%, Mn 0.17%, with the balance being Al; the sum of the mass percentages of all components is 100%.

[0141] The specific preparation process of this alloy is as follows:

[0142] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0143] Step S2, Melting: Preheat the crucible to 310℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 4.3% refining agent and 0.31% covering agent. The melting temperature is 700℃, the refining temperature is 685℃, and the refining time is 2 minutes.

[0144] Step S3, casting: After melting, let stand for 3 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 685℃.

[0145] Step S4, Coupled heat treatment: The alloy casting is first homogenized at 447℃ for 20h, then solution treated at 495℃ for 1.8h, and then water quenched, with the water temperature controlled in the range of 20-60℃.

[0146] Step S5, Aging treatment: The temperature is 120±5℃, and the temperature is maintained for 26 hours. Finally, air cooling is performed.

[0147] The near-P texture of the aged cast alloy was found to be 5.6%, with an average grain size of 135.7 μm; the tensile strength was 407.6 MPa, the yield strength was 329.5 MPa, the yield ratio was 0.808, and the elongation was 1.78%.

[0148] Comparative Example 3

[0149] This comparative example prepares an Al-Zn casting alloy with the following target mass percentages: Zn 4.5%, Mg 1.7%, Cu 0.50%, Ti 0.25%, Zr 0.10%, V 0.10%, Si 0.13%, Fe 0.2%, Mn 0.15%, with the balance being Al; the sum of the mass percentages of all components is 100%.

[0150] The specific preparation process of this alloy is as follows:

[0151] Step S1, Charge Proportioning: Proportion the charge according to the target alloy composition;

[0152] Step S2, Melting: Preheat the crucible to 205℃, then clean the melting tools by applying a protective coating; then proceed with melting and refining. Pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy are melted with the addition of 0.17% refining agent and 0.26% covering agent. The melting temperature is 715℃, the refining temperature is 700℃, and the refining time is 5 minutes.

[0153] Step S3, casting: After melting, let stand for 10 minutes, degas, remove slag, preheat the mold to 250℃ before casting, and then cast the casting and sample at a casting temperature of 710℃.

[0154] Step S4, Heat Treatment: The alloy casting is directly subjected to heat treatment at 485℃ for 30 hours, followed by water quenching with the water temperature controlled between 20-60℃; then aging treatment is performed at 120±5℃ for 24 hours, and finally air cooling is performed.

[0155] The near-P texture of the aged cast alloy was 1.2%, the average grain size was 109.4 μm, the tensile strength was 419.5 MPa, the yield strength was 286.1 MPa, the yield ratio was 0.682, and the elongation was 1.81%.

[0156] Test analysis description:

[0157] The pole figure tests for (220), (200), and (111) in the examples and comparative examples were performed using a Bruker D8 X-ray diffractometer with a copper target. The test voltage was 40kV and the current was 40mA. Then, an incomplete pole figure (0-70°) was obtained using the reflection method. Based on the data from the three incomplete pole figures (220), (200), and (111), the orientation distribution function (ODF) was obtained using the spherical harmonic series expansion method. The volume fraction of the near-P texture was calculated using the integral method based on the Euler space partition. In the comparative examples of this patent, orientations within 20° of the near-P texture belong to this type of texture. The average grain size was obtained based on the GB / T6394-2017 standard. The mechanical properties (tensile strength, yield strength, yield ratio, elongation) were obtained based on the GB / T228.1-2010 standard.

[0158] Taking Example 1 and Comparative Example 1 as examples, from Figure 1 It can be seen from the data that the aged plate exhibits a strong orientation concentration effect. By synthesizing the ODF diagrams of (220), (200), and (111), it can be seen that the near-P texture intensity in Example 1 is relatively high (e.g., Figure 2 As shown in the figure, the proportion of near-P texture reaches 51.7%. Figure 3 The texture distribution of the final aged state of the plate in Comparative Example 1 is shown. It can be seen that the overall texture distribution is weak, with the near-P texture accounting for only 3.9%.

[0159] Table 1 shows the near-P texture ratio, average grain size, tensile strength, yield strength, yield ratio, and elongation data of the final aged state plates of Comparative Examples 1-9 and 1-3 of this invention.

[0160] Table 1

[0161]

[0162] As can be seen from Table 1, the proportion of near-P texture in Examples 1-9 is 34.8% to 62.4%, which is much higher than that in the comparative examples. The average grain size of the examples is smaller than that of the comparative examples. This is because: Comparative Example 1 does not use the proportions of the present invention, and the three phases η(MgZn2), T(Al2Mg2Zn3), and S(Al2MgCu) cannot be formed in a relatively ideal manner, thus failing to produce the specific coupled particle-induced nucleation effect. Therefore, it is difficult to form a near-P texture, and the yield strength and yield ratio do not achieve the effects of the embodiments of the present invention. In Comparative Example 2, the addition of refining agent and covering agent is outside the scope of the present invention, and the casting temperature is too low. This will result in insufficient purity of the obtained ingot. The aluminum impurities formed therefrom will have a significant impact on the directional induction of near-P texture formation of the three phases η(MgZn2), T(Al2Mg2Zn3), and S(Al2MgCu). Furthermore, the subsequent coupled heat treatment temperature is outside the scope of the invention patent, thus making it difficult to form a near-P texture and resulting in an unsatisfactory yield ratio of the alloy. In Comparative Example 3, because it does not use a coupled heat treatment method, it cannot effectively exert the coupled particle-induced nucleation effect, and therefore it is also difficult to achieve the effects of the embodiments of the present invention. It should be noted that the tensile strength of the embodiments is not superior to that of some comparative examples (such as Comparative Examples 2 and 3), but the yield strength and yield strength ratio of the embodiments are significantly higher than those of the comparative examples. This indicates that high-strength, high-yield-strength-ratio alloys can be obtained within the scope of protection of this invention.

Claims

1. An Al-Zn casting alloy, characterized in that, The composition includes the following components by mass percentage: Zn 4.3-5.2%, Mg 1.2-1.8%, Cu 0.50-0.85%, Ti 0.15-0.25%, Zr 0.10-0.25%, V 0.10-0.25%, Si≤0.2%, Fe≤0.2%, Mn≤0.2%, with the balance being Al; the sum of the mass percentages of all components is 100%. The preparation method of the Al-Zn casting alloy includes the following steps: S1. Charge proportioning: Charge proportioning is based on the target alloy composition; S2, Smelting: Smelting is carried out by adding 4.5-7% refining agent and 0.15-0.29% covering agent to the furnace charge according to the total raw material mass; S3. Casting: After melting, let stand for 5-10 minutes, degas, remove slag, and cast to obtain alloy castings; S4. Coupled heat treatment: The alloy casting is first homogenized, and then solution and water quenching are performed. S5. Time-sensitive processing; Specifically, step S4 involves: first, homogenization treatment at 456-479℃ for 24-50 hours, followed by solution treatment at 470-493℃ for 0.5-2.8 hours, and finally water quenching with the water temperature controlled within the range of 20-60℃; in step S5, the aging temperature is 120±5℃, the holding time is 12-25 hours, and finally air cooling is performed. In the aged state of the Al-Zn cast alloy, the near-P texture accounts for 34.8% to 62.4% of the total texture, and the average grain size is 39.2 to 67.5 μm. The tensile strength of the prepared Al-Zn cast alloy aged material is 408.3 to 429.7 MPa, the yield strength is 386.5 to 394.2 MPa, the yield strength ratio is between 0.927 and 0.954, and the elongation is between 2.07 and 2.63%.

2. The Al-Zn casting alloy as described in claim 1, characterized in that: In step S1, the furnace charge is made of pure aluminum, pure magnesium, pure zinc, Al-Cu master alloy, Al-Ti-B master alloy, Al-Zr master alloy, and Al-V master alloy.

3. The Al-Zn casting alloy as described in claim 1, characterized in that: The refining agent is hexachloroethane, and the covering agent comprises the following components by mass percentage: 13% calcium fluoride, 18% potassium chloride, and 69% sodium chloride.

4. The Al-Zn casting alloy as described in claim 1, characterized in that: In step S2, the crucible is preheated to 200-300℃ before melting, and then a protective coating is applied to clean the melting tools.

5. The Al-Zn casting alloy as described in claim 1, characterized in that: In step S2, the smelting process parameters are: melting temperature of 710-730℃, refining temperature of 690-710℃, and refining treatment of 3-5 minutes.

6. The Al-Zn casting alloy as described in claim 1, characterized in that: In step S3, the mold is preheated to 250°C before pouring, and the pouring temperature is 690-710°C.

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