Die-cast aluminum alloy, method of making and structural member

Abstract

The application provides a die-casting aluminum alloy, which comprises, in percentage by weight: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10-50 ppm, and the balance of Al. The die-casting aluminum alloy has excellent tensile strength, yield strength and elongation, and no surface cracking phenomenon, and has small size change before and after heat treatment, which is beneficial to its use. The application also provides a preparation method and a structural member of the die-casting aluminum alloy.

Description

Technical Field

[0001] This application relates to the field of die-cast aluminum alloy technology, and in particular to die-cast aluminum alloys, their preparation methods, and structural components. Background Technology

[0002] Die-cast aluminum alloys are widely used due to their excellent mechanical properties and corrosion resistance. However, significant problems exist in the forming performance of die-cast aluminum alloys, such as poor die-casting fluidity and a tendency to hot cracking, resulting in low die-casting yields and affecting their application. Summary of the Invention

[0003] In view of this, this application provides a die-cast aluminum alloy, its preparation method and structural component. The die-cast aluminum alloy has excellent strength, good elongation, small dimensional changes before and after heat treatment, good fluidity during die casting, and no cracks on the surface of the die-cast aluminum alloy, which is more conducive to its use.

[0004] In a first aspect, this application provides a die-cast aluminum alloy, which, by weight, comprises: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10ppm-50ppm, and the balance Al.

[0005] The die-cast aluminum alloy provided in this application contains specific elemental components and contents, which makes the die-cast aluminum alloy have excellent tensile strength, yield strength and elongation. In addition, the surface of the die-cast aluminum alloy is free from cracking, and the dimensional changes before and after heat treatment are small, which is beneficial to the use of the die-cast aluminum alloy.

[0006] Optionally, the weight ratio of the sum of Sr and Mo to Si in the die-cast aluminum alloy is 1:(50-150).

[0007] Optionally, the weight ratio of the sum of Mn and Cr to Ga in the die-cast aluminum alloy is 40-70.

[0008] Optionally, the weight ratio of Mg to Si in the die-cast aluminum alloy is greater than 1.73 and less than 2.5.

[0009] Optionally, the weight ratio of the sum of Mn and Cr to Fe in the die-cast aluminum alloy is greater than 2.5 and less than 10.

[0010] Optionally, the weight percentage of Mg is 5.7%-6.3%.

[0011] Optionally, the weight percentage of Si is 2.4%-2.8%.

[0012] Optionally, the weight percentage of Zn is 1.1%-1.5%.

[0013] Optionally, the weight percentage of Mn is 0.6%-0.8%.

[0014] Optionally, the weight percentage of Ti is 0.1%-0.2%.

[0015] Optionally, the weight percentage of Cr is 0.1%-0.25%.

[0016] Optionally, the weight percentage of Sr is 0.01%-0.03%.

[0017] Optionally, the weight percentage of Ga is 0.013%-0.017%.

[0018] Optionally, the weight percentage of Mo is 0.008%-0.012%.

[0019] Optionally, the weight percentage of Hf is 0.05%-0.7%.

[0020] Optionally, the grain size of the die-cast aluminum alloy is 15μm-20μm.

[0021] Optionally, the die-cast aluminum alloy has a yield strength greater than or equal to 280 MPa, a tensile strength greater than or equal to 370 MPa, and an elongation greater than or equal to 6%.

[0022] Secondly, this application provides a method for preparing a die-cast aluminum alloy, comprising: melting and refining an aluminum source, a magnesium source, a silicon source, a zinc source, a manganese source, a titanium source, a chromium source, and a gallium source to obtain an alloy melt; adding a strontium source, a tin source, a molybdenum source, a hafnium source, a boron source, and a nitrogen source to the alloy melt, stirring, casting, and cooling to obtain a die-cast aluminum alloy, wherein, by weight ratio, the die-cast aluminum alloy comprises: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10ppm-50ppm, and the balance Al.

[0023] Optionally, the step of adding a strontium source, a tin source, a molybdenum source, a hafnium source, a boron source, and a nitrogen source to the alloy melt, stirring, and then casting includes: adding a modifier containing the strontium source, the tin source, and the molybdenum source to the alloy melt for modification treatment, and then adding a grain refiner containing the hafnium source, the boron source, and the nitrogen source for grain refinement treatment before casting.

[0024] The method for preparing die-cast aluminum alloys provided in this application is easy to operate and has a simple preparation process, which can realize the industrial production of die-cast aluminum alloys and obtain die-cast aluminum alloys with excellent properties.

[0025] Thirdly, this application provides a structural component made of die-cast aluminum alloy, wherein, by weight, the die-cast aluminum alloy comprises: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10ppm-50ppm, and the balance Al.

[0026] The structural components provided in this application are made of die-cast aluminum alloy, which has excellent performance, which is beneficial to the performance of the structural components and facilitates their use. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0028] Figure 1 This is a flowchart illustrating a method for preparing a die-cast aluminum alloy according to an embodiment of this application.

[0029] Figure 2 The image shows the metallographic structure of the die-cast aluminum alloy obtained in Example 2.

[0030] Figure 3 The image shows the metallographic structure of the die-cast aluminum alloy prepared in Comparative Example 11.

[0031] Figure 4 Cooling curves of the die-cast aluminum alloys obtained in Example 2 and Comparative Example 11. Detailed Implementation

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0033] This application provides a die-cast aluminum alloy, comprising, by weight: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10ppm-50ppm, and the balance Al. This die-cast aluminum alloy exhibits excellent tensile strength, yield strength, and elongation. Furthermore, the surface of the die-cast aluminum alloy is free of cracking, and the dimensional changes before and after heat treatment are minimal, which is beneficial for the application of die-cast aluminum alloys.

[0034] In this application, magnesium (Mg) is an important alloying element that can form strengthening phases with elements such as aluminum and silicon, thereby improving the strength of die-cast aluminum alloys. For example, Mg forms the Al3Mg2 strengthening phase with Al and the Mg2Si strengthening phase with Si. In die-cast aluminum alloys, the weight percentage of Mg is 4%-9%. If the Mg content is too low, the strengthening effect of the die-cast aluminum alloy is not significant, failing to improve the yield strength and causing large dimensional differences before and after heat treatment. If the Mg content is too high, it will affect the toughness, elongation, and thermal conductivity of the die-cast aluminum alloy, leading to hot cracking. Therefore, 4%-9% Mg helps improve the strength, toughness, and thermal conductivity of die-cast aluminum alloys, improves die-casting fluidity, avoids hot cracking, reduces dimensional differences before and after heat treatment, and improves the overall performance of the die-cast aluminum alloy. Specifically, the weight percentage of Mg in the die-cast aluminum alloy can be, but is not limited to, 4%, 4.53%, 4.76%, 5%, 5.38%, 5.81%, 6%, 6.25%, 6.69%, 7%, 7.33%, 7.85%, 8%, 8.47%, 8.95%, or 9%. In one embodiment of this application, the weight percentage of Mg in the die-cast aluminum alloy can be, but is not limited to, 5%-7%, 5.7%-6.3%, 4.86%-8.43%, 5.25%-8.61%, 4%-6.3%, 6%-7.5%, 6%-8%, or 6.5%-9%. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Mg in the die-cast aluminum alloy can be 5.7%-6.3%. This can further improve the yield strength and tensile strength of the die-cast aluminum alloy, while further reducing the dimensional deviation of the die-cast aluminum alloy before and after heat treatment.

[0035] In die-cast aluminum alloys, the weight percentage of silicon (Si) is 1.6%-2.8%. Too low a Si content reduces the yield strength of the die-cast aluminum alloy and results in poor thermal stability, leading to significant dimensional changes before and after heat treatment, which is detrimental to its use. Too high a Si content causes crystal precipitation, forming hard spots, reducing elongation, and causing hot cracking. Therefore, a Si content of 1.6%-2.8% is beneficial for improving the yield strength and thermal stability of die-cast aluminum alloys, ensuring elongation, and avoiding hot cracking. Specifically, the weight percentage of Si in die-cast aluminum alloys can be, but is not limited to, 1.67%, 1.7%, 1.78%, 1.8%, 1.84%, 1.9%, 2%, 2.19%, 2.33%, 2.45%, 2.5%, 2.72%, 2.85%, or 2.8%, etc. In one embodiment of this application, the weight percentage of Si in the die-cast aluminum alloy can be, but is not limited to, 1.6%-2%, 1.85%-2.2%, 2%-2.3%, 2.4%-2.8%, 2.45%-2.76%, 2.5%-2.7%, 2.6%-2.8%, or 2.68%-2.8%, etc. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Si in the die-cast aluminum alloy can be 2.4%-2.8%. This can further improve the yield strength and elongation of the die-cast aluminum alloy, while further reducing the dimensional deviation of the die-cast aluminum alloy before and after heat treatment, and avoiding hot cracking problems.

[0036] In this application, silicon and magnesium can form a reinforcing phase, thereby playing a role in second-phase reinforcement. By setting 4%-9% Mg and 1.6%-2.8% Si, the reinforcing effect of the Mg2Si reinforcing phase is ensured, improving the yield strength and tensile strength of the die-cast aluminum alloy, while ensuring the high plasticity and casting performance of the die-cast aluminum alloy. In one embodiment of this application, the weight ratio of Mg to Si in the die-cast aluminum alloy is greater than 1.73 and less than 2.5. This avoids the influence of excess Si on the toughness of the die-cast aluminum alloy, and also avoids the increase in hot cracking tendency due to excess Mg. In this case, the Mg2Si reinforcing phase in the die-cast aluminum alloy can improve toughness on the basis of enhancing strength, further improving the performance of the die-cast aluminum alloy. Specifically, the weight ratio of Mg to Si in the die-cast aluminum alloy can be, but is not limited to, 1.75, 1.8, 1.82, 1.85, 1.9, 2, 2.12, 2.2, 2.3, 2.4, or 2.47, etc. In one embodiment of this application, the weight ratio of Mg to Si in the die-cast aluminum alloy can be 1.75-2, 1.8-2.17, 1.93-2.25, 2-2.3, or 2.1-2.46, etc.

[0037] In this application, zinc (Zn) can improve the strength of die-cast aluminum alloys, particularly by synergistically strengthening with magnesium (Mg). The weight percentage of Zn in die-cast aluminum alloys is 1.1%-2%. Too low a Zn content results in poor die-casting fluidity, hindering alloy preparation; too high a Zn content increases high-temperature brittleness, leading to severe hot cracking and affecting elongation. Therefore, 1.1%-2% Zn helps improve fluidity and elongation, preventing hot cracking and mitigating sticking during prolonged die-casting. Specifically, the weight percentage of Zn in the die-cast aluminum alloy can be, but is not limited to, 1.15%, 1.2%, 1.28%, 1.33%, 1.38%, 1.45%, 1.5%, 1.63%, 1.7%, 1.85%, 1.9%, or 2%. In one embodiment of this application, the weight percentage of Zn in the die-cast aluminum alloy can be, but is not limited to, 1.1%-1.5%, 1.15%-1.7%, 1.2%-1.4%, 1.3%-1.7%, 1.4%-1.8%, 1.5%-2%, 1.6%-1.9%, or 1.7%-1.95%, etc. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Zn in the die-cast aluminum alloy can be 1.1%-1.5%. This can further improve the elongation and thermal stability of the die-cast aluminum alloy.

[0038] In one embodiment of this application, the weight ratio of Zn to Mg in the die-cast aluminum alloy is greater than 0.1 and less than 0.5. This promotes the formation of the MgZn2 phase, further improving the fluidity of the die-cast aluminum alloy. Specifically, the weight ratio of Zn to Mg in the die-cast aluminum alloy can be, but is not limited to, 0.1, 0.14, 0.18, 0.2, 0.27, 0.35, 0.4, 0.49, or 0.5. In another embodiment of this application, the weight ratio of Zn to Mg in the die-cast aluminum alloy can be 0.15-0.45, 0.15-0.3, 0.18-0.25, 0.2-0.4, 0.3-0.49, or 0.35-0.42.

[0039] In this application, manganese (Mn) can improve the strength of die-cast aluminum alloys, particularly by synergistically strengthening with magnesium (Mg). The weight percentage of Mn in die-cast aluminum alloys is 0.5%-1.5%. Too low a Mn content results in poor die-casting fluidity, hindering alloy preparation and causing significant dimensional differences before and after heat treatment. Too high a Mn content leads to severe hot cracking and negatively impacts elongation. Therefore, 0.5%-1.5% Mn helps improve the fluidity and elongation of die-cast aluminum alloys, avoids hot cracking, and reduces dimensional differences before and after heat treatment. Specifically, the weight percentage of Mn in die-cast aluminum alloys can be, but is not limited to, 0.5%, 0.65%, 0.72%, 0.89%, 0.95%, 1%, 1.25%, 1.37%, 1.4%, 1.45%, or 1.5%. In one embodiment of this application, the weight percentage of Mn in the die-cast aluminum alloy can be, but is not limited to, 0.55%-1.2%, 0.6%-0.8%, 0.65%-1.1%, 0.63%-0.76%, 0.8%-1%, 0.72%-1.3%, or 0.75%-1%. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Mn in the die-cast aluminum alloy can be 0.6%-0.8%. This can further reduce the dimensional differences of the die-cast aluminum alloy before and after heat treatment.

[0040] In this application, titanium (Ti) is used as a refining agent to refine α-Al. In die-cast aluminum alloys, the weight percentage of Ti is 0.1%-0.3%. Too low a Ti content results in poor die-casting fluidity, hindering the preparation of the die-cast aluminum alloy and causing significant dimensional differences before and after heat treatment. Too high a Ti content leads to severe hot cracking in the die-cast aluminum alloy and also affects its elongation. Therefore, 0.1%-0.3% Ti helps improve the fluidity and elongation of the die-cast aluminum alloy, avoids hot cracking, and reduces dimensional differences before and after heat treatment. Specifically, the weight percentage of Ti in the die-cast aluminum alloy can be, but is not limited to, 0.1%, 0.13%, 0.15%, 0.17%, 0.2%, 0.24%, 0.26%, 0.29%, or 0.3%, etc. In one embodiment of this application, the weight percentage of Ti in the die-cast aluminum alloy can be, but is not limited to, 0.1%-0.2%, 0.15%-0.25%, 0.17%-0.28%, or 0.2%-0.3%, etc. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Ti in the die-cast aluminum alloy can be 0.1%-0.2%.

[0041] In die-cast aluminum alloys, the weight percentage of chromium (Cr) is 0.001%-0.3%. Cr can form intermetallic compounds with Al, Mn, and Fe, playing a strengthening role and improving the toughness and hot cracking resistance of the die-cast aluminum alloy. Specifically, the weight percentage of Cr in the die-cast aluminum alloy can be, but is not limited to, 0.001%, 0.01%, 0.02%, 0.05%, 0.1%, 0.16%, 0.2%, 0.25%, or 0.3%. In one embodiment of this application, the weight percentage of Cr in the die-cast aluminum alloy can be, but is not limited to, 0.1%-0.25%, 0.01%-0.1%, 0.05%-0.1%, 0.15%-0.23%, or 0.25%-0.3%. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Cr in the die-cast aluminum alloy can be 0.1%-0.25%.

[0042] In this application, iron (Fe) originates from smelting impurities and is an unavoidable element. Fe can react with Al to form FeAl3 crystals, providing nucleation sites for solidification and promoting grain refinement. In die-cast aluminum alloys, the weight percentage of Fe is 0.1%-0.3%. Excessive Fe content reduces the fluidity of die-cast aluminum alloys and can prevent the formation of needle-like Al9Fe2Si2 phases. The aforementioned Fe content ensures the mechanical properties and fluidity of die-cast aluminum alloys.

[0043] In this application, the addition of Mn and Cr can promote the phase transformation of Fe-containing impurities at high temperatures, reducing the harmful effects of Fe generation. In one embodiment of this application, the weight ratio of the sum of Mn and Cr to Fe is greater than 2.5 and less than 10. That is, the weight ratio of (Mn+Cr) / Fe is greater than 2.5 and less than 10, which can completely transform the Al9Fe2Si2 phase into Al. 12 Fe3Si is used to avoid the harmful effects of Fe. Specifically, the weight ratio of the sum of Mn and Cr to Fe can be, but is not limited to, 2.7, 3, 3.5, 4, 5, 6, 7, 8, or 9.5. In one embodiment of this application, the weight ratio of the sum of Mn and Cr to Fe can be 3-9, 4-8, 3.5-6, 5-8.5, or 6-9.

[0044] In die-cast aluminum alloys, the weight percentage of strontium (Sr) is 0.01%-0.1%. As a modifier, Sr can lower the eutectic temperature of the die-cast aluminum alloy, slow down the eutectic plateau, and allow for more effective feeding during the later stages of solidification, thus reducing hot cracking. Specifically, the weight percentage of Sr in the die-cast aluminum alloy can be, but is not limited to, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, or 0.09%. In one embodiment of this application, the weight percentage of Sr in the die-cast aluminum alloy can be, but is not limited to, 0.01%-0.03%, 0.01%-0.05%, 0.03%-0.06%, 0.02%-0.08%, or 0.06%-0.1%. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Sr in the die-cast aluminum alloy can be 0.01%-0.03%.

[0045] In die-cast aluminum alloys, the weight percentage of tin (Sn) is 0.1%-0.3%, which can significantly improve die-casting forming, prevent hot cracking, and combine with Ti-CB seed crystals during the preparation process, resulting in a significant refinement of Mg2Si, Mg2Sn, and Mg2(Si,Sn) phases, exhibiting a fine granular distribution and significantly improving formability. Specifically, the weight percentage of Sn in die-cast aluminum alloys can be, but is not limited to, 0.1%, 0.14%, 0.17%, 0.2%, 0.24%, 0.25%, 0.29%, or 0.3%. In one embodiment of this application, the weight percentage of Sn in die-cast aluminum alloys can be, but is not limited to, 0.1%-0.2%, 0.15%-0.25%, 0.18%-0.2%, or 0.2%-0.3%. This is beneficial for further improving the performance of die-cast aluminum alloys.

[0046] In die-cast aluminum alloys, the weight percentage of gallium (Ga) is 0.01%-0.02%, which ensures the mechanical properties and elongation of the die-cast aluminum alloy. Specifically, the weight percentage of Ga in the die-cast aluminum alloy can be, but is not limited to, 0.011%, 0.012%, 0.014%, 0.015%, 0.017%, 0.019%, or 0.02%. In one embodiment of this application, the weight percentage of Ga in the die-cast aluminum alloy can be, but is not limited to, 0.01%-0.015%, 0.015%-0.02%, 0.013%-0.017%, or 0.014%-0.019%. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Ga in the die-cast aluminum alloy can be 0.013%-0.017%, which can further ensure the mechanical properties and elongation of the die-cast aluminum alloy.

[0047] In one embodiment of this application, the weight ratio of the sum of Mn and Cr to Ga is 40-70. That is, the weight ratio of (Mn+Cr) / Ga is 40-70. This reduces Ga enrichment at grain boundaries and prevents F enrichment at α-Al grain boundaries, resulting in a dispersed Ga distribution without segregation. This reduces the tendency of the aluminum alloy to exhibit the Rehbinder effect, improves the alloy's microstructure, and enhances material properties. Specifically, the weight ratio of the sum of Mn and Cr to Ga can be, but is not limited to, 40, 45, 48, 50, 52, 57, 60, 65, 69, or 70. In one embodiment of this application, the weight ratio of the sum of Mn and Cr to Ga can be 40-55, 50-65, 50-70, 60-70, or 55-70.

[0048] In die-cast aluminum alloys, a molybdenum (Mo) weight percentage of 0.0015%-0.015% can significantly improve the elongation of the die-cast aluminum alloy. Specifically, the weight percentage of Mo in the die-cast aluminum alloy can be, but is not limited to, 0.0015%, 0.003%, 0.005%, 0.0075%, 0.009%, 0.001%, 0.0012%, or 0.0015%. In one embodiment of this application, the weight percentage of Mo in the die-cast aluminum alloy can be, but is not limited to, 0.008%-0.012%, 0.005%-0.01%, 0.006%-0.012%, or 0.002%-0.007%. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Mo in the die-cast aluminum alloy can be 0.008%-0.012%, which can further improve the elongation of the die-cast aluminum alloy.

[0049] In this application, by adding Sr and Mo for composite modification treatment, the morphology of Mg2Si can be improved, thereby enhancing the performance of die-cast aluminum alloys. In one embodiment of this application, the weight ratio of the sum of Sr and Mo to Si is 1:(50-150). That is, the weight ratio of (Sr+Mo) / Si is 1:(50-150), which causes an adsorption-poisoning mechanism to occur during the crystal growth stage, changing the nucleation mode from heterogeneous nucleation to homogeneous nucleation. The morphology of Mg2Si changes from a needle-like structure to a dispersed granular structure, reducing the cutting effect of the needle-like structure on the aluminum matrix, thereby significantly improving the hot cracking tendency of the die-cast aluminum alloy. Specifically, the weight ratio of the sum of Sr and Mo to Si can be, but is not limited to, 1:50, 1:75, 1:90, 1:100, 1:115, 1:130, 1:140, or 1:150, etc. In one embodiment of this application, the weight ratio of the sum of Mn and Cr to Fe can be 1:(50-100), 1:(100-150), 1:(80-135), 1:(75-125), or 1:(90-130), etc.

[0050] In die-cast aluminum alloys, the weight percentage of hafnium (Hf) is 0.03%-0.1%. The addition of Hf causes the Mg2Si phase in the die-cast aluminum alloy to exhibit a regular, Chinese character-like distribution. When the Hf content is too low, the Mg2Si phase fractures and becomes irregularly distributed; when the Hf content is too high, the Mg2Si phase segregates towards the grain boundaries, exhibiting granularity, which is detrimental to improving the performance of the die-cast aluminum alloy. Specifically, the weight percentage of Hf in the die-cast aluminum alloy can be, but is not limited to, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. In one embodiment of this application, the weight percentage of Hf in the die-cast aluminum alloy can be, but is not limited to, 0.03%-0.05%, 0.05%-0.07%, 0.06%-0.09%, or 0.07%-0.1%. This is beneficial for further improving the performance of the die-cast aluminum alloy. In one embodiment, the weight percentage of Hf in the die-cast aluminum alloy can be 0.05%-0.07%, the alloy modification effect is significant, the Chinese character-shaped Mg2Si phase disappears and becomes dispersed, the refinement effect is enhanced, which is conducive to further improving the performance of the die-cast aluminum alloy.

[0051] In a die-cast aluminum alloy, the weight percentage of boron (B) is 0.0001%-0.004%, which can prevent excessive B from reacting with Sr to weaken the refining and modification effects. Meanwhile, adding titanium and boron in the form of an Al-Ti-C-B master alloy is conducive to ensuring the refining and modification effects. Specifically, the weight percentage of B in the die-cast aluminum alloy can be, but is not limited to, 0.0001%, 0.0005%, 0.001%, 0.002%, 0.0025%, 0.003%, 0.0035% or 0.004%. In an embodiment of the present application, the weight percentage of B in the die-cast aluminum alloy can be, but is not limited to, 0.0001%-0.0005%, 0.001%-0.002% or 0.002%-0.003%. This arrangement is beneficial to further improving the performance of the die-cast aluminum alloy.

[0052] In a die-cast aluminum alloy, the content of nitrogen (N) is 10ppm-50ppm. Nitrogen can act as a heterogeneous nucleation site, enhance the refining effect and improve the performance of the die-cast aluminum alloy. Specifically, the content of N in the die-cast aluminum alloy can be, but is not limited to, 10ppm, 15ppm, 20ppm, 25ppm, 30ppm, 35ppm, 40ppm or 50ppm. In an embodiment of the present application, the content of N in the die-cast aluminum alloy can be, but is not limited to, 10ppm-25ppm, 25ppm-50ppm, 10ppm-50ppm or 10ppm-50ppm. This arrangement is beneficial to further improving the performance of the die-cast aluminum alloy.

[0053] In an implementation of the present application, the contents of N, B and Hf satisfy 9.8N+B<Hf<60N+B. That is, the content of Hf is greater than the sum of the content of B and 9.8 times the content of N, and less than the sum of the content of B and 60 times the content of N, so that deposition caused by the interaction of N, B and Hf can be avoided, thereby ensuring the refining effect and improving the performance of the die-cast aluminum alloy. In an embodiment of the present application, the contents of N, B and Hf satisfy 12N+B<Hf<50N+B, 15N+B<Hf<45N+B, 30N+B<Hf<60N+B or 40N+B<Hf<55N+B, etc.

[0054] In the present application, impurity elements are inevitably introduced during the preparation of the die-cast aluminum alloy. In an implementation of the present application, the content of impurity elements in the die-cast aluminum alloy is less than 0.2%, so as to avoid the influence of impurity elements on the performance of the die-cast aluminum alloy as much as possible. In an embodiment, the content of impurity elements in the die-cast aluminum alloy is less than 0.1%.

[0055] In this application, aluminum (Al) is used as the main element in the die-cast aluminum alloy, ensuring its performance. In one embodiment, the weight percentage of Al in the die-cast aluminum alloy is greater than 83%. In another embodiment, the weight percentage of Al in the die-cast aluminum alloy is greater than 85%. In yet another embodiment, the weight percentage of Al in the die-cast aluminum alloy is greater than 88%. In still another embodiment, the weight percentage of Al in the die-cast aluminum alloy is greater than 90%. In yet another embodiment, the weight percentage of Al in the die-cast aluminum alloy is greater than 91%.

[0056] The die-cast aluminum alloy provided in this application has a main microstructure of α-Al-based solid solution and aluminum-silicon eutectic structure. Within the matrix, Al3Mg2 and Mg2Si precipitates enhance the alloy's strength. In one embodiment, the die-cast aluminum alloy also contains a MnFe phase.

[0057] In one embodiment of this application, the grain size of the die-cast aluminum alloy is 15μm-20μm, which gives the die-cast aluminum alloy excellent strength and plasticity, which is beneficial to its use. In one embodiment, the grain size of the die-cast aluminum alloy is 15μm-18μm, 15μm-17μm, 17μm-20μm, or 18μm-20μm, etc.

[0058] In one embodiment of this application, the yield strength of the die-cast aluminum alloy is greater than or equal to 270 MPa. In one embodiment, the yield strength of the die-cast aluminum alloy is 270 MPa-350 MPa. Specifically, the yield strength of the die-cast aluminum alloy may be, but is not limited to, 280 MPa, 295 MPa, 300 MPa, 305 MPa, 315 MPa, 320 MPa, 325 MPa, or 330 MPa.

[0059] In one embodiment of this application, the tensile strength of the die-cast aluminum alloy is greater than or equal to 370 MPa. In one embodiment, the tensile strength of the die-cast aluminum alloy is 370 MPa-430 MPa. Specifically, the tensile strength of the die-cast aluminum alloy may be, but is not limited to, 375 MPa, 380 MPa, 390 MPa, 400 MPa, 405 MPa, 415 MPa, 420 MPa, or 430 MPa.

[0060] In one embodiment of this application, the elongation of the die-cast aluminum alloy is greater than or equal to 6%. In one embodiment, the elongation of the die-cast aluminum alloy is 6%-8%. Specifically, the elongation of the die-cast aluminum alloy may be, but is not limited to, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.3%, 7.5%, or 7.7%, etc.

[0061] In one embodiment of this application, the thermal conductivity of the die-cast aluminum alloy is greater than 125 W / (m•K), exhibiting excellent heat dissipation performance, which is beneficial for the use of die-cast aluminum alloys. In one embodiment, the thermal conductivity of the die-cast aluminum alloy is greater than 130 W / (m•K). In another embodiment, the thermal conductivity of the die-cast aluminum alloy is greater than 140 W / (m•K). In yet another embodiment, the thermal conductivity of the die-cast aluminum alloy is greater than 150 W / (m•K).

[0062] The die-cast aluminum alloy provided in this application has high yield strength and tensile strength. At the same time, the die-cast aluminum alloy has good plasticity, high elongation, high thermal conductivity, and avoids hot cracking problems. The dimensional difference before and after heat treatment is small, which is beneficial to the use of die-cast aluminum alloy.

[0063] This application also provides a method for preparing a die-cast aluminum alloy to obtain the die-cast aluminum alloy in any of the above embodiments. Please refer to... Figure 1 The flowchart below shows a method for preparing a die-cast aluminum alloy according to an embodiment of this application, including: S101: An alloy melt is obtained by melting and refining aluminum, magnesium, silicon, zinc, manganese, titanium, chromium and gallium sources; S102: Strontium, tin, molybdenum, hafnium, boron, and nitrogen sources are added to the alloy melt, stirred, and then cast. After cooling, a die-cast aluminum alloy is obtained. The die-cast aluminum alloy comprises, by weight: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10ppm-50ppm, and the balance Al.

[0064] Understandably, the amount of each element added during the preparation process is determined based on the content of each component in the final die-cast aluminum alloy. The aluminum source can be metallic aluminum (such as pure aluminum ingots) or aluminum alloy; the magnesium source can be metallic magnesium; the silicon source can be at least one of metallic silicon and aluminum-silicon master alloys; the zinc source can be metallic zinc; the manganese source can be at least one of aluminum-manganese master alloys and manganese additives; the titanium source can be at least one of aluminum-titanium master alloys and titanium additives; the chromium source can be aluminum-chromium master alloys; the gallium source can be aluminum-gallium master alloys; the strontium source can be aluminum-strontium master alloys; the tin source can be metallic tin; the molybdenum source can be aluminum-molybdenum master alloys; the hafnium source can be aluminum-hafnium master alloys; the boron source can be aluminum-boron master alloys; and the nitrogen source can be aluminum-nitrogen master alloys.

[0065] In S101, an alloy melt is obtained by mixing, melting, and refining various raw materials. During the melting process, easily fusible materials can be added first, followed by difficult-to-fuss materials, or materials with less burn-off can be added first, followed by easily burn-off materials, which is beneficial to the melting process.

[0066] In one embodiment of this application, aluminum can be added, the temperature raised to 710℃-730℃, and an aluminum-silicon master alloy can be added. The temperature is then raised to above 800℃, and aluminum-manganese, aluminum-chromium, aluminum-titanium, and aluminum-gallium master alloys, along with zinc, are added and stirred. After refining, magnesium is added at 720℃-730℃ to obtain an alloy melt. Stirring can be performed every 8-12 minutes for 2-5 minutes each time to ensure thorough mixing of the raw materials. After stirring, the mixture can be allowed to stand for 5-10 minutes. In another embodiment of this application, a portion of the aluminum can be added, followed by silicon, zinc, manganese, titanium, chromium, and gallium sources, and then the remaining aluminum can be added.

[0067] In one embodiment of this application, the refining process includes adding a refining agent. Specifically, the refining agent can be 0.5%-2% of the alloy melt mass, the refining temperature can be, but is not limited to, 730℃-750℃, and the refining agent can be, but is not limited to, hexafluoroethane, aluminum refining agent ZS-AJ01C, etc. In another embodiment of this application, the refining process includes treatment with an inert gas and the addition of a refining agent. The inert gas can be, but is not limited to, argon, nitrogen, etc. In this application, after the refining process, the slag is simply skimmed off. The refining process can remove some impurities and improve the purity of the alloy melt. In one embodiment, a calcium remover can also be added during the refining process to prevent excessive calcium from affecting the performance of the die-cast aluminum alloy.

[0068] In S102, the remaining raw materials are added, stirred, and then cast to obtain a die-cast aluminum alloy.

[0069] In one embodiment of this application, a modifier containing strontium, tin, and molybdenum sources is added to the alloy melt for modification treatment, followed by a grain refiner containing hafnium, boron, and nitrogen sources for grain refinement treatment before casting. Modification and refinement treatments can alter the brittle phases, change the grain morphology and distribution, refine the grains, and improve the performance of the die-cast aluminum alloy. In one embodiment of this application, a modifier containing aluminum-strontium master alloy, metallic tin, and aluminum-molybdenum master alloy is added to the alloy melt for modification treatment. In one embodiment, the modification treatment temperature can be 700℃-740℃ (e.g., 700℃, 710℃, 720℃, 730℃, 740℃, etc.). In the modification treatment, the aluminum-strontium master alloy can be added first, which is beneficial for improving the effect of the modification treatment. In one embodiment of this application, after modification treatment, a grain refiner containing an aluminum-hafnium master alloy, an aluminum-titanium-carbon-boron alloy (TCB seed alloy), and an Al-AlN / TiB2 nano-ceramic phase is added to the alloy melt for grain refinement. In one embodiment, the refinement temperature can be 710℃-730℃ (e.g., 710℃, 715℃, 720℃, 725℃, 730℃, etc.). By adding the aluminum-titanium-carbon-boron alloy, the boron content can be accurately controlled, preventing the reaction between B and Sr. Simultaneously, the addition of the small and dispersed Al-AlN / TiB2 nano-ceramic phase provides nucleation sites, increasing the number of nucleation sites and causing collisions during crystal growth. This inhibits the growth rate of the crystals, resulting in fine grains and improving the mechanical and machinability of the die-cast aluminum alloy.

[0070] In one embodiment of this application, the casting temperature is 650℃-750℃. Specifically, the casting temperature can be, but is not limited to, 665℃, 680℃, 690℃, 700℃, 710℃, 720℃, or 745℃. In one embodiment, the casting temperature can be 680℃-720℃, and the holding time is 1s-3s. In one embodiment of this application, the casting speed can be 1.5m / s-2.5m / s. Specifically, the casting speed can be, but is not limited to, 1.6m / s, 1.7m / s, 1.8m / s, 1.9m / s, 2m / s, or 2.2m / s. The casting can be carried out in a die-casting machine. In one embodiment, the casting speed can be 1.6m / s-2m / s. In one embodiment, the temperature of the die-casting machine mold can be 300℃-320℃ to ensure the die-casting process.

[0071] In one embodiment of this application, the die-cast aluminum alloy is further subjected to an aging treatment to improve its performance. In one embodiment, the aging treatment includes allowing the die-cast aluminum alloy to age naturally for 24-48 hours, followed by hot pressing at 250-270°C and then allowing it to stand for 24-72 hours. This reduces the gas content, avoids high-temperature blistering and deformation problems, stabilizes performance, and improves the surface smoothness of the die-cast aluminum alloy.

[0072] This application also provides a structural component made of the die-cast aluminum alloy described in any of the above embodiments. The component made of the aforementioned high-strength, medium-toughness die-cast aluminum alloy exhibits excellent mechanical properties and good formability, which is beneficial for the use of the structural component. Specifically, the structural component may be, but is not limited to, parts in vehicles, parts in electronic products, etc.

[0073] The present application will be further described below through specific embodiments.

[0074] Example 1 Prepare the raw materials according to the element content of the die-cast aluminum alloy. Add a portion of pure aluminum to the melting furnace, and when the temperature reaches 720℃, add an aluminum-silicon master alloy. After the temperature rises above 800℃, add aluminum-manganese master alloy, aluminum-chromium master alloy, aluminum-titanium master alloy, aluminum-gallium master alloy, and zinc. Stir every 10 minutes for 3 minutes each time, and let it stand for about 8 minutes after stirring. Then add the remaining pure aluminum, adjust the melting temperature to 760℃, and add refining agents to refine the melt. After refining, remove the surface... After removing surface slag and ensuring the alloy is completely melted, an alloy melt is obtained. Pure magnesium is added at 720℃, followed by Al-Sr alloy (10% Sr by mass), elemental Sn, and Al-Mo master alloy (8% Mo by mass) for modification treatment. Al-AlN / TiB2 nano-ceramic phase, Al-Ti-CB alloy, and Al-Hf (10.45% Hf by mass) are added at 720℃ for refinement treatment. After complete melting, the mixture is thoroughly stirred and allowed to stand for 1 minute. Then, it is cast in a die-casting machine at 700℃ under vacuum. After casting, it is allowed to age naturally for 1 day, then hot-pressed in a metal mold at 270℃ and left to stand for 2 days to obtain the die-cast aluminum alloy.

[0075] Examples 2-37 and Comparative Examples 1-25 were prepared according to the method in Example 1, except that the element content in the die-cast aluminum alloys was different from that in Example 1.

[0076] The weight percentages of each element in the die-cast aluminum alloys prepared in the above embodiments and comparative examples are shown in Table 1, wherein the weight percentage of unavoidable impurities is less than 0.1%, and the balance is Al.

[0077] Table 1. Weight percentage (%) of each element in die-cast aluminum alloys

[0078] The surface cracking of the die-cast aluminum alloys prepared in the above embodiments and comparative examples was observed to determine the hot cracking resistance of the die-cast aluminum alloys. The yield strength, tensile strength, and elongation of the die-cast aluminum alloys prepared in the above embodiments and comparative examples were tested according to GB / T 228.1-2010. Specifically, the die-cast aluminum alloys prepared in the above embodiments and comparative examples were die-cast into tensile test bars (diameter 6.4 mm). Tensile properties were tested using a CMT5105 electronic universal testing machine with a gauge length of 50 mm and a loading rate of 2 mm / min. Measurement data were recorded. Six samples were tested at each formulation point. The yield strength, tensile strength, and elongation were the average of the six data points. The relative standard deviation of yield strength was the percentage of the ratio of the standard deviation of the six yield strength data points to the average. The relative standard deviation of tensile strength was the percentage of the ratio of the standard deviation of the six tensile strength data points to the average. In the preparation process of the above examples and comparative examples, the same spiral mosquito coil mold was used to prepare die-cast aluminum alloys, resulting in corresponding mosquito coil mold products. The products obtained in the comparative examples and comparative examples were... The fluidity of die-cast aluminum alloys is judged by the length of the coils, with more coils indicating better fluidity. The die-cast aluminum alloys obtained in the above examples and comparative examples were hot-pressed at 260℃ for 15 seconds. The length, width, and diagonal dimensions of the die-cast aluminum alloys were measured using an OMM image measuring instrument. The rate of change of length, width, and diagonal dimension before and after heat treatment was calculated. The average of the rate of change of length, width, and diagonal dimension for the same die-cast aluminum alloy was taken as the dimensional change rate (‰). Before heat treatment, the die-cast aluminum alloys provided in the above examples and comparative examples had the same dimensions (rectangular surface, length 148mm, width 70mm). The results are shown in Table 2.

[0079] Table 2 Performance Test Results

[0080] As shown in Table 2, compared with the comparative examples, the die-cast aluminum alloys provided in this application exhibit superior yield strength and tensile strength, excellent elongation, and no surface cracking, avoiding hot cracking problems. They also have good fluidity, which is beneficial for die casting, and exhibit small dimensional differences before and after heat treatment, demonstrating good stability, which is advantageous for the use of die-cast aluminum alloys. Furthermore, compared with Examples 30-37, the die-cast aluminum alloys provided in Examples 1-29 have better overall performance. Simultaneously, the thermal conductivity of the die-cast aluminum alloys obtained in the examples was tested, and all were greater than 125 W / (m•K), demonstrating excellent thermal conductivity.

[0081] The die-cast aluminum alloys obtained in the above embodiments and comparative examples were observed using a metallographic microscope. Figure 2The image shows the metallographic structure of the die-cast aluminum alloy obtained in Example 2. Figure 3 The metallographic images of the die-cast aluminum alloy prepared in Comparative Example 11 are shown. Both are observed at the same magnification. It can be seen that in Comparative Example 11, the absence of Sr resulted in coarse and aggregated grains. In Example 2, the addition of Sr resulted in a more uniform and dispersed grain distribution, thus improving the performance of the die-cast aluminum alloy. Furthermore, the grain sizes of the die-cast aluminum alloys prepared in Examples 1-3 were 16 μm, 17 μm, and 18 μm, respectively, while the grain size of the die-cast aluminum alloy prepared in Comparative Example 11 was 30 μm.

[0082] The die-cast aluminum alloys prepared in Example 2 and Comparative Example 11 were heated to 650°C and then naturally cooled. The temperature of the die-cast aluminum alloys was measured at different times to obtain cooling curves, as shown below. Figure 4 As shown, adding Sr can lower the eutectic temperature of the alloy, slow down the eutectic plateau, and allow the die-cast aluminum alloy to achieve more effective feeding in the later stages of solidification, thus reducing hot cracking.

[0083] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A die-cast aluminum alloy, characterized in that, By weight, the die-cast aluminum alloy comprises: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10ppm-50ppm, and the balance Al.

2. The die-cast aluminum alloy as described in claim 1, characterized in that, The weight ratio of the sum of Sr and Mo to Si in the die-cast aluminum alloy is 1:(50-150).

3. The die-cast aluminum alloy as described in claim 1, characterized in that, The weight ratio of the sum of Mn and Cr in the die-cast aluminum alloy to Ga is 40-70.

4. The die-cast aluminum alloy as described in claim 1, characterized in that, The weight ratio of Mg to Si in the die-cast aluminum alloy is greater than 1.73 and less than 2.

5.

5. The die-cast aluminum alloy as described in claim 1, characterized in that, The weight ratio of the sum of Mn and Cr in the die-cast aluminum alloy to the weight of Fe is greater than 2.5 and less than 10.

6. The die-cast aluminum alloy as described in claim 1, characterized in that, The weight percentage of Mg is 5.7%-6.3%; The weight percentage of Si is 2.4%-2.8%; The weight percentage of Zn is 1.1%-1.5%; The weight percentage of Mn is 0.6%-0.8%; The weight percentage of Ti is 0.1%-0.2%; The weight percentage of Cr is 0.1%-0.25%; The weight percentage of Sr is 0.01%-0.03%; The weight percentage of Ga is 0.013%-0.017%; The weight percentage of Mo is 0.008%-0.012%; The weight percentage of Hf is 0.05%-0.07%.

7. The die-cast aluminum alloy as described in claim 1, characterized in that, The grain size of the die-cast aluminum alloy is 15μm-20μm.

8. The die-cast aluminum alloy as described in claim 1, characterized in that, The die-cast aluminum alloy has a yield strength greater than or equal to 270 MPa, a tensile strength greater than or equal to 370 MPa, and an elongation greater than or equal to 6%.

9. A method for preparing a die-cast aluminum alloy, characterized in that, include: The alloy melt is obtained by smelting and refining aluminum, magnesium, silicon, zinc, manganese, titanium, chromium and gallium sources. Strontium, tin, molybdenum, hafnium, boron, and nitrogen sources are added to the alloy melt, and after stirring, it is cast and cooled to obtain a die-cast aluminum alloy. The die-cast aluminum alloy, by weight, comprises: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10ppm-50ppm, and the balance Al.

10. The preparation method according to claim 9, characterized in that, The process of adding strontium, tin, molybdenum, hafnium, boron, and nitrogen sources to the alloy melt, stirring, and then casting includes: The alloy melt is modified by adding a modifier containing the strontium source, the tin source and the molybdenum source, and then refined by adding a grain refiner containing the hafnium source, the boron source and the nitrogen source before casting.

11. A structural component, characterized in that, The structural component is made of die-cast aluminum alloy, which, by weight, comprises: Mg 4%-9%, Si 1.6%-2.8%, Zn 1.1%-2%, Mn 0.5%-1.5%, Ti 0.1%-0.3%, Cr 0.001%-0.3%, Fe 0.1%-0.3%, Sr 0.01%-0.1%, Sn 0.1%-0.3%, Ga 0.01%-0.02%, Mo 0.0015%-0.015%, Hf 0.03%-0.1%, B 0.0001%-0.004%, N 10ppm-50ppm, and the balance Al.

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