A heat treatment free high strength and toughness die casting Al-Si-Mg alloy and a preparation method thereof

Abstract

This invention discloses a heat-treatment-free high-strength and high-toughness die-cast Al-Si-Mg alloy and its preparation method. The die-cast Al-Si-Mg alloy comprises the following components by mass fraction: Si 7.8~8.3%, Mg 1.5~3.0%, Fe 0.4~0.6%, Mn 0.3~0.6%, Hf 0.05~0.15%, Yb 0.1~0.3%, with the remainder being Al and unavoidable impurities. This invention can obtain high-strength and high-toughness Al-Si-Mg alloy die-castings without heat treatment, avoiding defects caused by heat treatment and ensuring the forming quality of the die-castings.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, and in particular to a heat-free high-strength and high-toughness die-cast Al-Si-Mg alloy and its preparation method. Background Technology

[0002] Al-Si-Mg alloys are widely used in the automotive and 5G communication fields due to their low density, light weight, and good corrosion resistance. High-pressure die casting technology, with its advantages of high production efficiency and low production cost, has become the main processing technology for manufacturing Al-Si-Mg alloy parts. With the rapid development of the automotive industry, the demand for lightweight thin-walled parts is increasing, and the requirements for their high strength and toughness are also increasing. Currently, Al-Si-Mg alloys commonly used in high-pressure die casting, including A356, AlSi10Mg, and YL104, can no longer meet the requirements for high strength and toughness. Although heat treatment can further improve the tensile strength of the alloy, it reduces the elongation of the alloy; at the same time, after high-temperature heat treatment, thin-walled parts are prone to dimensional deformation and surface bubbles due to uneven temperature and stress, which not only affect the surface quality of the parts but also the dimensional accuracy. Subsequent secondary processing and straightening are required to ensure their dimensional and assembly requirements, increasing production costs. Therefore, there is an urgent need for a heat-treatment-free, high-strength and high-toughness die-cast Al-Si-Mg alloy to solve the shortcomings of existing technologies. Summary of the Invention

[0003] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a heat-free high-strength and high-toughness die-casting Al-Si-Mg alloy and its preparation method, which can obtain Al-Si-Mg alloy die castings with high strength and good toughness without heat treatment, avoid the defects caused by heat treatment, and ensure the forming quality of the die castings.

[0004] The present invention provides a heat-free, high-strength and high-toughness die-cast Al-Si-Mg alloy, comprising the following components by mass fraction: Si 7.8~8.3%, Mg 1.5~3.0%, Fe 0.4~0.6%, Mn 0.3~0.6%, Hf 0.05~0.15%, Yb 0.1~0.3%, with the remainder being Al and unavoidable impurities.

[0005] Furthermore, this invention also provides a method for preparing the heat-free, high-strength, high-toughness die-cast Al-Si-Mg alloy as described above, comprising the following steps: 1) Weigh each component raw material according to its mass fraction; 2) Under a protective atmosphere, the raw materials of each component are melted to obtain an alloy melt; the melting temperature is 700℃~720℃; 3) Hold the alloy melt at a certain temperature for a period of time to lower the temperature of the alloy melt to the target temperature, and then pour it into the die casting chamber of the die casting equipment; 4) Adjust the injection parameters so that the alloy melt solidifies rapidly under the cooling effect of the mold, and the target part is obtained.

[0006] Furthermore, in step 2), the protective atmosphere is an argon atmosphere.

[0007] Furthermore, in step 2), the alloy melt is subjected to degassing, slag removal, and slag skimming treatment.

[0008] Furthermore, in step 3), the heat preservation time is 20-40 minutes; the target temperature is 650-670℃.

[0009] Furthermore, in step 4), the injection parameters include die casting pressure of 0~40MPa, injection speed of 0~7m / s, and mold preheating temperature of 0~250℃.

[0010] Compared with the prior art, the beneficial effects of the present invention are: The die-casting Al-Si-Mg alloy of the present invention incorporates Si, Mg, Fe, Mn, Hf and Yb based on alloying concepts and composition calculations, and designs an Al-Si-Mg alloy with high strength and high toughness. Hf element eliminates the tendency for hot cracking caused by increased Mg content, achieving high elongation at high Mg content. Simultaneously, Mg-Si clusters (GP zones) form during room temperature storage, causing yield strength fluctuations over time. Due to its extremely low diffusion coefficient, Hf acts as a trap to capture vacancies, significantly delaying room temperature diffusion of Mg atoms and preventing fluctuations in the alloy's mechanical properties over extended periods.

[0011] Yb elements preferentially adsorb at the growth twin grooves of the Si phase, blunting the edges of the Si phase; at the same time, a Yb-rich film is formed at the Al / Si interface, allowing dislocations to pass through the interface under stress instead of generating cracks at the Si tips, thereby improving both strength and plasticity.

[0012] This application utilizes a specific ratio of alloying elements and a coupling mechanism of solid solution strengthening, vacancy trapping effect, and grain boundary passivation lubrication to eliminate the need for heat treatment while obtaining Al-Si-Mg alloy die castings with excellent tensile strength and elongation. This avoids defects caused by heat treatment and ensures the forming quality of the die castings.

[0013] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0014] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 Here is a flowchart of the preparation method; Figure 2 A schematic diagram of the Al-Si-Mg alloy die casting prepared by the preparation method of the present invention; Figure 3 Metallographic image of the Al-Si-Mg alloy die casting prepared in Example 1; Figure 4 The stress-strain curve of the Al-Si-Mg alloy die casting prepared in Example 1; Figure 5 The stress-strain curve of the Al-Si-Mg alloy die casting prepared in Example 2. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] The embodiments of the present invention provide a heat-free, high-strength and high-toughness die-cast Al-Si-Mg alloy, comprising the following components by mass fraction: Si 7.8~8.3%, Mg 1.5~3.0%, Fe 0.4~0.6%, Mn 0.3~0.6%, Hf 0.05~0.15%, Yb 0.1~0.3%, with the remainder being Al and unavoidable impurities.

[0018] Also, please refer to Figures 1-2 The present invention also provides a method for preparing the heat-free high-strength and high-toughness die-cast Al-Si-Mg alloy as described above, comprising the following steps: 1) Weigh each component raw material according to its mass fraction; 2) Under a protective argon atmosphere, the raw materials of each component are melted. During the melting process, degassing, slag removal, and slag skimming are performed to obtain an alloy melt. The melting temperature is 700℃~720℃. 3) Hold the alloy melt at a constant temperature for 20-40 minutes, then reduce the temperature of the alloy melt to 650-670℃ and pour it into the die casting chamber of the die casting equipment; 4) Adjust the injection parameters to make the die casting pressure 0~40MPa, the injection speed 0~7m / s, and the mold preheating temperature 0~250℃; under the cooling effect of the mold, the alloy melt solidifies rapidly to obtain the target part.

[0019] In this embodiment, Si, Mg, Fe, Mn, Hf and Yb are added to the Al-Si-Mg alloy. The addition of Si increases the fluidity of the melt, which meets the filling requirements of the die casting. The addition of Mg element increases the solid solution strengthening effect on the matrix, and at the same time forms Mg2Si precipitate with Si element, which enhances precipitation strengthening effect and thus improves the strength of die castings. The addition of Fe element reduces the adhesion of Al-Si-Mg alloy to steel mold during die casting, reduces mold sticking, improves the demolding effect of Al-Si-Mg alloy, and thus improves the die casting effect. The addition of Mn element improves the morphology of iron-containing intermetallic compounds, reduces the cutting effect on the aluminum matrix, and thus improves the plasticity of Al-Si-Mg alloy; The addition of Hf element eliminates the tendency for hot cracking caused by increased Mg content, achieving high elongation at high Mg content. Simultaneously, Mg-Si clusters (GP regions) form during room temperature storage, causing yield strength fluctuations over time. Due to the extremely low diffusion coefficient of Hf element, it acts as a trap to capture vacancies, significantly delaying the room temperature diffusion of Mg atoms and preventing fluctuations in the mechanical properties of the alloy over long periods. The addition of Yb preferentially adsorbs at the growth twin grooves of the Si phase, blunting the edges of the Si phase; at the same time, it also forms a Yb-rich film at the Al / Si interface, allowing dislocations to pass through the interface under stress instead of generating cracks at the Si tips, thereby improving both strength and plasticity.

[0020] The Al-Si-Mg alloy prepared in this application has a tensile strength of 330~360MPa and an elongation of 9.8~11.7%.

[0021] Example 1

[0022] The raw materials used are commercially available pure Al ingots, pure Mg ingots, Al-Si master alloys, Al-Fe master alloys, Al-Mn master alloys, Al-Hf master alloys, and Al-Yb master alloys. The purity of the pure Al ingots is 99.99%, the purity of the pure Mg ingots is 99.99%, the Al-Si master alloy is Al-30Si master alloy, the Al-Fe master alloy is Al-10Fe master alloy, the Al-Mn master alloy is Al-5Mn master alloy, the Al-Hf master alloy is Al-5Hf master alloy, and the Al-Yb master alloy is Al-20Yb master alloy.

[0023] Weigh each component raw material according to its mass fraction; unavoidable impurities include Ti ≤ 0.02% and other impurity elements ≤ 0.01% by mass fraction; other impurity elements include Cr and Zr; under a protective argon atmosphere, melt the raw materials to obtain an alloy melt; the melting temperature is 700℃~720℃; after holding at this temperature for 30 minutes, lower the alloy melt temperature to 660℃ and pour the alloy melt into the die-casting chamber of the die-casting equipment; adjust the injection parameters and perform die casting, wherein the die-casting pressure is 35MPa, the injection speed is 3.5m / s, and the mold preheating temperature is 200℃. Under the cooling effect of the mold, the alloy melt solidifies rapidly to obtain the target part.

[0024] The metallographic results of the die-cast sample are as follows Figure 3 As shown; its stress-strain curve is as follows. Figure 4 As shown in the figure; its measured alloy composition is shown in Table 1; its tensile strength is 359.8 MPa and its elongation is 11.7%.

[0025] Table 1: Measured Alloy Composition Table

[0026] Example 2

[0027] The only difference from Example 1 was the die-casting pressure of 30 MPa and the injection speed of 5.0 m / s. The tensile strength of the die-cast sample was 341.9 MPa, and the elongation was 9.9%.

[0028] In the description of this specification, the terms "one embodiment," "some embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0029] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A heat-treasure-free, high-strength, high-toughness die-cast Al-Si-Mg alloy, characterized in that, The composition by mass fraction includes the following components: Si 7.8~8.3%, Mg 1.5~3.0%, Fe 0.4~0.6%, Mn 0.3~0.6%, Hf 0.05~0.15%, Yb 0.1~0.3%, with the remainder being Al and unavoidable impurities.

2. A method for preparing a heat-tough, high-strength, die-cast Al-Si-Mg alloy as described in claim 1, characterized in that, Includes the following steps: 1) Weigh each component raw material according to its mass fraction; 2) Under a protective atmosphere, the raw materials of each component are melted to obtain an alloy melt; the melting temperature is 700℃~720℃; 3) Hold the alloy melt at a certain temperature for a period of time to lower the temperature of the alloy melt to the target temperature, and then pour it into the die casting chamber of the die casting equipment; 4) Adjust the injection parameters so that the alloy melt solidifies rapidly under the cooling effect of the mold, and the target part is obtained.

3. The preparation method according to claim 2, characterized in that, In step 2), the protective atmosphere is an argon atmosphere.

4. The preparation method according to claim 2, characterized in that, In step 2), the alloy melt is subjected to degassing, slag removal, and slag skimming.

5. The preparation method according to claim 2, characterized in that, In step 3), the heat preservation time is 20-40 minutes; the target temperature is 650-670℃.

6. The preparation method according to claim 2, characterized in that, In step 4), the injection parameters include die casting pressure of 0~40MPa, injection speed of 0~7m / s, and mold preheating temperature of 0~250℃.

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