High-strength, high-toughness and high-fluidity die-casting aluminum alloy and preparation method and application thereof

Abstract

The invention provides a high-strength, high-toughness and high-fluidity die-casting aluminum alloy as well as a preparation method and application thereof. The metallographic structure of the die-casting aluminum alloy comprises eutectic silicon, an iron-rich phase and an aluminum matrix, the die-casting aluminum alloy comprises the following chemical components: Al, Si, Fe, Cu, Mn, Mg, Zn, Ti and Sr. According to the mass percent, the content of Si in the die-casting aluminum alloy is 8.5 wt%-9.5 wt%, and the content of Zn in the die-casting aluminum alloy is 0.35 wt%-1.35 wt%. The preparation method comprises the steps of material preparation, melting, refining and die casting which are carried out in sequence. According to the die-casting aluminum alloy provided by the invention, by reasonably regulating and controlling the contents of Si and Zn, the fluidity is improved on the premise that the cost is relatively low, thin-wall die casting is realized, and the die-casting aluminum alloy has high-strength and high-toughness as-cast mechanical properties and is beneficial to large-scale popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy materials and relates to a die-casting aluminum alloy, and in particular to a high-strength, high-toughness, and high-fluidity die-casting aluminum alloy and a preparation method and application thereof. Background Art

[0002] With the rapid development of new energy vehicles, the proportion of aluminum alloy used in automobiles as the main lightweight material has increased rapidly, especially the rise of integrated die-casting technology, which helps to reduce the number of processes, shorten the supply chain, and save the development cycle. At present, aluminum alloy die-castings are developing in the direction of large-scale, thin-walled, complex, high-precision, and high-toughness. Generally speaking, the thinner the die-casting, the higher the strength of the die-casting material needs to be to meet the strength requirements of the product. In addition, the thinner the die-casting, the easier it is for the aluminum liquid to cool during the filling process, which can easily cause poor filling problems.

[0003] In order to solve the above technical problems, the industry continues to develop high-strength, high-toughness, and high-fluidity die-cast aluminum alloys. WO2005071127A1 discloses a currently used one-piece die-casting heat-treatment-free alloy, which improves the elongation by reducing the silicon content to 6.5%, but the too low silicon content leads to poor die-casting processability, which is manifested in poor fluidity and easy casting defects when casting thin-walled parts. CN109750191A effectively improves the fluidity and strength of the material by adding 2.6-4% of Mg elements, but the elongation is only 6%; the aluminum alloy disclosed in CN111575545A also belongs to the Al-Si-Mg system, with a higher Mg content, so the elongation is lower; CN1537961A reduces the magnesium content to 0.06% to improve the elongation, but it also leads to the low strength of the obtained aluminum alloy, the strength of the cast and baked state is less than 120MPa, and the wall thickness attenuation is obvious. For test pieces with a thickness of 5mm or more, the yield strength is only about 95MPa.

[0004] In addition to Mg, Zn, Ni and rare earth elements can also improve the fluidity of aluminum alloys. For example, CN117568679A adds 6.5-13% Zn elements to the Al-Si system, and the yield strength of the resulting aluminum alloy is greater than 285MPa, the minimum wall thickness is 0.45mm, but the elongation is only 2.5%. Similarly, the Al-Ni-Mn system alloy disclosed in CN116536545A has a yield strength greater than 200MPa, a minimum wall thickness of 0.5mm, but a low elongation. CN114438377A and CN117965968A select rare earths such as La, Ce, Y, and Sm as alloying elements. Although they improve the elongation and fluidity of aluminum alloys, the cost is high.

[0005] It can be seen that the existing technology mainly has a difficult-to-reconcile contradiction between strength-toughness-fluidity-cost. Based on this, how to provide a die-cast aluminum alloy with good fluidity, low cost, and high strength and toughness in the cast state has become an urgent problem that technicians in this field need to solve. Summary of the invention

[0006] The purpose of the present invention is to provide a high-strength, high-toughness and high-fluidity die-casting aluminum alloy and a preparation method and application thereof. By reasonably regulating the content of Si and Zn, the fluidity is improved at a low cost, thin-wall die-casting is achieved, and it has both high-strength and high-toughness cast mechanical properties, which is conducive to large-scale promotion and application.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a high-strength, high-toughness and high-fluidity die-cast aluminum alloy, the metallographic structure of the die-cast aluminum alloy comprising eutectic silicon, an iron-rich phase and an aluminum matrix.

[0009] The chemical components of the die-casting aluminum alloy include: Al, Si, Fe, Cu, Mn, Mg, Zn, Ti and Sr.

[0010] Measured in terms of mass percentage, the Si content in the die-casting aluminum alloy is 8.5-9.5wt%, and the Zn content is 0.35-1.35wt%.

[0011] The die-cast aluminum alloy provided by the present invention has eutectic silicon, iron-rich phase and aluminum matrix as main metallographic structures, wherein the eutectic silicon and iron-rich phase as hard phases help to improve the strength of the material; the aluminum matrix is ​​the main component of the aluminum alloy, and the characteristics of its soft phase determine the toughness of the material.

[0012] In addition, the present invention further improves the fluidity of the obtained aluminum alloy by reasonably regulating the content of Si and Zn and under the synergistic effect of other specific types of doping elements. The elongation after fracture is above 7.5%, thin-walled die casting is achieved, and the minimum wall thickness is 1.2 mm. It has both high-strength and high-toughness cast mechanical properties, with a yield strength of more than 150 MPa and a tensile strength of more than 300 MPa. At the same time, it significantly reduces material costs, improves economic benefits, and is conducive to large-scale promotion and application.

[0013] Preferably, the eutectic silicon is in a fibrous shape.

[0014] Preferably, the iron-rich phase is in the shape of a block and / or a Chinese character.

[0015] Preferably, the aluminum matrix is ​​an equiaxed crystal or a doped dendrite.

[0016] Preferably, the average size of the eutectic silicon is ≤5 μm.

[0017] Preferably, the average size of the iron-rich phase is ≤5 μm.

[0018] Preferably, the average size of the aluminum matrix is ​​≤100 μm.

[0019] Preferably, the chemical composition of the die-casting aluminum alloy includes, by mass percentage:

[0020]

[0021] The balance is Al and inevitable impurities.

[0022] Preferably, the total content of the impurities is ≤0.15wt%.

[0023] Preferably, the content of a single impurity is ≤0.05wt% in terms of mass percentage.

[0024] In a second aspect, the present invention provides a method for preparing the die-cast aluminum alloy as described in the first aspect, wherein the preparation method comprises sequentially performing material preparation, melting, refining and die-casting.

[0025] Preferably, the material preparation comprises: mixing pure aluminum ingots with different types of doping alloys according to the mass percentage of chemical components.

[0026] Preferably, the purity of the pure aluminum ingot is ≥99.5wt%.

[0027] Preferably, the elements in the different kinds of doping alloys include Si, Fe, Cu, Mn, Mg, Zn, Ti and Sr.

[0028] Preferably, the melting includes: adding pure aluminum ingots and different types of doped alloys into a smelting furnace for melting and heat preservation to obtain an aluminum melt.

[0029] Preferably, the temperature of the melting and heat preservation treatment is ≥ 700°C.

[0030] Preferably, the refining comprises: introducing nitrogen and / or argon into the aluminum melt to perform degassing refining and remove slag.

[0031] Preferably, the degassing refining is carried out at a temperature of 720-750° C. and for a time of 10-20 min.

[0032] Preferably, the die casting comprises: pouring aluminum melt into a mold for die casting.

[0033] Preferably, the temperature of the aluminum melt is 650-700° C., the temperature of the mold is 150-250° C., and the wall thickness of the die-casting molding is ≥1.2 mm.

[0034] As a preferred technical solution of the second aspect of the present invention, the preparation method comprises the following steps:

[0035] (1) Material preparation: mixing pure aluminum ingots with different types of doped alloys according to the mass percentage of chemical components, wherein the purity of the pure aluminum ingots is ≥99.5wt%, and the elements in the different types of doped alloys include Si, Fe, Cu, Mn, Mg, Zn, Ti and Sr;

[0036] (2) Melting: pure aluminum ingots and different types of doped alloys are added into a melting furnace, melted and kept warm at above 700°C to obtain aluminum melt;

[0037] (3) Refining: nitrogen and / or argon are introduced into the aluminum melt, and degassing and refining is performed at 720-750°C for 10-20 minutes, after which the slag is removed;

[0038] (4) Die casting: Pour aluminum melt at a temperature of 650-700°C into a mold at a temperature of 150-250°C for die casting, and control the wall thickness of the die casting to be ≥1.2mm.

[0039] In a third aspect, the present invention provides an application of the die-cast aluminum alloy as described in the first aspect, wherein the die-cast aluminum alloy is used to manufacture body structural parts of automobiles, including floors, engine compartments or shock towers.

[0040] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The die-cast aluminum alloy provided by the present invention has eutectic silicon, iron-rich phase and aluminum matrix as the main metallographic structures, wherein the eutectic silicon and iron-rich phase as hard phases help to improve the strength of the material; the aluminum matrix is ​​the main component of the aluminum alloy, and the characteristics of its soft phase determine the toughness of the material.

[0043] (2) The present invention further improves the fluidity of the obtained aluminum alloy by reasonably regulating the content of Si and Zn and under the synergistic effect of other specific types of doping elements, with an elongation of more than 7.5% after fracture, and realizes thin-walled die casting with a minimum wall thickness of 1.2 mm. It has both high-strength and high-toughness cast mechanical properties, with a yield strength of more than 150 MPa and a tensile strength of more than 300 MPa. At the same time, it significantly reduces material costs, improves economic benefits, and is conducive to large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1is a metallographic structure photograph of the die-cast aluminum alloy provided in Example 1;

[0045] Figure 2 This is a microscopic morphology of the iron-rich phase in the die-cast aluminum alloy provided in Example 1. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] In order to solve the difficult-to-reconcile contradictions between strength, toughness, fluidity and cost of die-cast aluminum alloys, the present invention provides a high-strength, high-toughness and high-fluidity die-cast aluminum alloy, the metallographic structure of the die-cast aluminum alloy includes eutectic silicon, iron-rich phase and aluminum matrix.

[0048] The chemical components of the die-casting aluminum alloy include: Al, Si, Fe, Cu, Mn, Mg, Zn, Ti and Sr.

[0049] In terms of mass percentage, the Si content in the die-casting aluminum alloy is 8.5-9.5wt%, for example, it can be 8.5wt%, 8.6wt%, 8.7wt%, 8.8wt%, 8.9wt%, 9.0wt%, 9.1wt%, 9.2wt%, 9.3wt%, 9.4wt% or 9.5wt%, and the Zn content is 0.35-1.35wt%, for example, it can be 0.35wt%, 0.45wt%, 0.55wt%, 0.65wt%, 0.75wt%, 0.85wt%, 0.95wt%, 1.05wt%, 1.15wt%, 1.25wt% or 1.35wt%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] The die-cast aluminum alloy provided by the present invention has eutectic silicon, iron-rich phase and aluminum matrix as main metallographic structures, wherein the eutectic silicon and iron-rich phase as hard phases help to improve the strength of the material; the aluminum matrix is ​​the main component of the aluminum alloy, and the characteristics of its soft phase determine the toughness of the material.

[0051] In addition, the present invention further improves the fluidity of the obtained aluminum alloy by reasonably regulating the content of Si and Zn and under the synergistic effect of other specific types of doping elements. The elongation after fracture is above 7.5%, thin-walled die casting is achieved, and the minimum wall thickness is 1.2 mm. It has both high-strength and high-toughness cast mechanical properties, with a yield strength of more than 150 MPa and a tensile strength of more than 300 MPa. At the same time, it significantly reduces material costs, improves economic benefits, and is conducive to large-scale promotion and application.

[0052] In certain embodiments, the eutectic silicon is in a fibrous form.

[0053] In certain embodiments, the iron-rich phase is in the shape of blocks and / or Chinese characters.

[0054] In some embodiments, the aluminum matrix is ​​an equiaxed crystal or a doped dendrite.

[0055] In some embodiments, the average size of the eutectic silicon is ≤5μm, for example, it can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In some embodiments, the average size of the iron-rich phase is ≤5μm, for example, it can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] In some embodiments, the average size of the aluminum substrate is ≤100μm, for example, it can be 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] The present invention helps to further refine the grains by strictly limiting the size range of various metallographic structures, and grain refinement can improve the yield strength and tensile strength of the material while maintaining better toughness.

[0059] In some embodiments, the chemical composition of the die-cast aluminum alloy includes, by mass percentage:

[0060]

[0061]

[0062] The balance is Al and inevitable impurities.

[0063] Wherein, the content of Si is 8.5-9.5wt%, for example, it can be 8.5wt%, 8.6wt%, 8.7wt%, 8.8wt%, 8.9wt%, 9.0wt%, 9.1wt%, 9.2wt%, 9.3wt%, 9.4wt% or 9.5wt%, the content of Fe is 0.05-0.15wt%, for example, it can be 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.10wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt% or 0.15wt%, and the content of Cu is 0-0.1w t%, for example, it can be 0wt%, 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt% or 0.1wt%, the content of Mn is 0.5-0.7wt%, for example, it can be 0.5wt%, 0.52wt%, 0.54wt%, 0.56wt%, 0.58wt%, 0.6wt%, 0.62wt%, 0.64wt%, 0.66wt%, 0.68wt% or 0.7wt%, and the content of Mg is 0.15-0.35wt%, for example, it can be 0.1 %, 0.5wt%, 0.16wt%, 0.18wt%, 0.2wt%, 0.22wt%, 0.24wt%, 0.26wt%, 0.28wt%, 0.3wt%, 0.32wt%, 0.34wt% or 0.35wt%, the Zn content is 0.35-1.35wt%, for example, it can be 0.35wt%, 0.45wt%, 0.55wt%, 0.65wt%, 0.75wt%, 0.85wt%, 0.95wt%, 1.05wt%, 1.15wt%, 1.25wt% or 1.35wt%, and the Ti content is 0.05-0.08wt%, for example, it can be It is 0.05wt%, 0.055wt%, 0.06wt%, 0.065wt%, 0.07wt%, 0.075wt% or 0.08wt%, and the Sr content is 0.015-0.035wt%, for example, it can be 0.015wt%, 0.016wt%, 0.018wt%, 0.020wt%, 0.022wt%, 0.024wt%, 0.026wt%, 0.028wt%, 0.030wt%, 0.032wt%, 0.034wt% or 0.035wt%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] In the present invention, Al is the main component of the aluminum alloy, and the characteristics of its soft phase determine the toughness of the material.

[0065] In the present invention, Si is the main alloying element, and its unique shrinkage rate has a good shrinkage compensation effect on casting, and the closer to the eutectic point, the better the fluidity of the Al-Si alloy, but the worse the toughness of the material. Taking fluidity and toughness into consideration, the present invention specifically limits the content of Si to 8.5-9.5wt%.

[0066] In the present invention, Fe, as a common impurity, has a low solubility in Al (0.05wt.%), so most of the Fe exists in the form of an iron-rich phase. Usually, this type of iron-rich phase is positively correlated with the Fe content and exists in the form of strips or needles, thereby affecting the toughness, fatigue and corrosion resistance of the material. Therefore, the present invention specifically limits the Fe content to 0.05-0.15wt%.

[0067] In the present invention, Cu has the effects of solid solution and aging strengthening on aluminum alloy, and the higher the Cu content, the higher the strength of the aluminum alloy, but the lower the toughness, so the present invention specifically limits the Cu content to 0-0.1wt%.

[0068] In the present invention, Mn is used as a modifying element of the iron-rich phase to change it from strip or needle shape to square or Chinese character shape. Mn also has an anti-mucosal effect, so the present invention specifically limits the content of Mn to 0.5-0.7wt%.

[0069] In the present invention, the role of Mg is similar to that of Cu, so it will not be described in detail here. The present invention specifically limits the content of Mg to 0.15-0.35wt%.

[0070] In the present invention, Zn can improve the material strength and fluidity of the aluminum alloy, but too high a Zn content will coarsen Si particles and lead to a decrease in toughness, so the present invention specifically limits the Zn content to 0.35-1.35wt%.

[0071] In the present invention, Ti, as a refining element of Al grains, can improve the morphology and grain size of Al grains, so the present invention specifically limits the content of Ti to 0.05-0.08wt%.

[0072] In the present invention, Sr, as a modification element of Si particles, can improve the morphology and size of Si particles, so the present invention specifically limits the content of Sr to 0.015-0.035wt%.

[0073] In some embodiments, the total content of the impurities is ≤0.15wt%, for example, it can be 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt%, 0.1wt%, 0.12wt%, 0.14wt% or 0.15wt%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0074] In some embodiments, the content of a single impurity is ≤0.05wt% as a percentage by mass, for example, it may be 0.005wt%, 0.01wt%, 0.015wt%, 0.02wt%, 0.025wt%, 0.03wt%, 0.035wt%, 0.04wt%, 0.045wt% or 0.05wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0075] In the present invention, the impurity elements are very likely to react with other elements in the alloy to form harmful intermetallic compounds or metallographic structures, thereby reducing the plasticity and toughness of the alloy and increasing its brittleness. By strictly limiting the total impurity content and the content of a single impurity, it is beneficial to avoid the formation of the above-mentioned harmful structures, ensure the purity of the alloy, thereby improving its mechanical properties and corrosion resistance, and at the same time optimize the casting properties of the alloy, reduce casting defects, and improve the yield rate of castings.

[0076] The present invention also provides a method for preparing the above die-casting aluminum alloy, which comprises sequentially performing material preparation, melting, refining and die-casting.

[0077] In some embodiments, the material preparation includes: mixing pure aluminum ingots with different types of doping alloys according to the mass percentage of chemical components.

[0078] In some embodiments, the purity of the pure aluminum ingot is ≥99.5wt%, for example, it can be 99.5wt%, 99.55wt%, 99.6wt%, 99.65wt%, 99.7wt%, 99.75wt%, 99.8wt%, 99.85wt%, 99.9wt% or 99.95wt%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0079] In some embodiments, the elements in the different types of doping alloys include Si, Fe, Cu, Mn, Mg, Zn, Ti, and Sr.

[0080] In some embodiments, the melting includes: adding pure aluminum ingots and different types of doped alloys into a smelting furnace for melting and heat preservation to obtain an aluminum melt.

[0081] In some embodiments, the temperature of the melting and heat preservation treatment is ≥ 700°C, for example, it can be 700°C, 705°C, 710°C, 715°C, 720°C, 725°C, 730°C, 735°C, 740°C, 745°C or 750°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0082] In certain embodiments, the refining includes: introducing nitrogen and / or argon into the aluminum melt to perform degassing refining and remove dross.

[0083] In some embodiments, the degassing refining temperature is 720-750°C, for example, it can be 720°C, 725°C, 730°C, 735°C, 740°C, 745°C or 750°C, and the time is 10-20 min, for example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0084] In some embodiments, the die casting includes: pouring aluminum melt into a mold for die casting.

[0085] In some embodiments, the temperature of the aluminum melt is 650-700°C, for example, it can be 650°C, 655°C, 660°C, 665°C, 670°C, 675°C, 680°C, 685°C, 690°C, 695°C or 700°C, the temperature of the mold is 150-250°C, for example, it can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C or 250°C, and the wall thickness of the die-casting is ≥1.2mm, for example, it can be 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm or 2mm, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0086] The present invention also provides an application of the die-cast aluminum alloy, wherein the die-cast aluminum alloy is used to manufacture vehicle body structural parts, including a floor, a cabin or a shock tower.

[0087] Examples 1-6

[0088] This group of embodiments respectively provides a high-strength, high-toughness, and high-fluidity die-cast aluminum alloy and a preparation method thereof. The chemical composition of the die-cast aluminum alloy provided in each embodiment is shown in Table 1 below.

[0089] Table 1

[0090]

[0091] The balance is Al and unavoidable impurities, and in the die-casting aluminum alloy provided in each embodiment, the total content of impurities is ≤0.15wt%, and the content of a single impurity is ≤0.04wt%.

[0092] Figure 1This is a metallographic structure photograph of the die-cast aluminum alloy obtained in Example 1. Figure 2 This is the microscopic morphology of the iron-rich phase.

[0093] Depend on Figure 1 and Figure 2 It can be seen that the metallographic structure of the die-cast aluminum alloy obtained in Example 1 includes eutectic silicon, iron-rich phase and aluminum matrix, and the eutectic silicon is fibrous, the iron-rich phase is block-shaped and Chinese character-shaped, and the aluminum matrix is ​​equiaxed crystal and doped dendrite.

[0094] According to a rough estimate, the average size of the eutectic silicon is ≤5 μm, the average size of the iron-rich phase is ≤5 μm, and the average size of the aluminum matrix is ​​≤100 μm.

[0095] The metallographic structure of the die-cast aluminum alloy obtained in Examples 2-6 is similar to that in Example 1, so it will not be described here in detail.

[0096] The die-cast aluminum alloys provided in this group of embodiments are respectively prepared by the following methods, and the specific steps are as follows:

[0097] (1) Material preparation: pure aluminum ingots and different types of doped alloys are mixed according to the mass percentage of chemical components, wherein the purity of the pure aluminum ingot is 99.8wt%, and the elements in the different types of doped alloys include Si, Fe, Cu (only Example 5 does not contain Cu), Mn, Mg, Zn, Ti and Sr;

[0098] (2) Melting: pure aluminum ingots and different types of doped alloys are added into a melting furnace, melted and heat-insulated at 750°C to obtain aluminum melt;

[0099] (3) Refining: nitrogen is introduced into the aluminum melt, and degassing and refining is carried out at 725°C for 15 minutes, after which the slag is removed;

[0100] (4) Die casting: Pour aluminum melt at a temperature of 680°C into a mold at a temperature of 200°C for die casting.

[0101] Comparative Examples 1-6

[0102] This group of comparative examples respectively provides a die-casting aluminum alloy and a preparation method thereof. The chemical composition of the die-casting aluminum alloy provided by each comparative example is shown in Table 2 below.

[0103] Table 2

[0104]

[0105] The balance is Al and unavoidable impurities, and in the die-casting aluminum alloys provided in each comparative example, the total content of impurities is ≤0.15wt%, and the content of a single impurity is ≤0.04wt%.

[0106] The preparation method of the die-cast aluminum alloy provided in this group of comparative examples is the same as that of Examples 1-6, except that the addition amount of various doping alloys is adjusted accordingly according to the chemical composition of the obtained die-cast aluminum alloy, so it is not repeated here.

[0107] Performance Testing

[0108] After testing, the performance parameters and determination results of the die-casting aluminum alloys obtained in Examples 1-6 and Comparative Examples 1-6 are shown in Table 3 below.

[0109] Table 3

[0110]

[0111]

[0112] In the above table, the tests of tensile strength, yield strength and elongation after fracture are all based on the standard GB / T 228.1-2010.

[0113] It can be seen that the present invention further improves the fluidity of the obtained aluminum alloy by reasonably regulating the content of Si and Zn and under the synergistic effect of other specific types of doping elements, and the elongation after fracture is above 7.5%, and thin-walled die casting is achieved with a minimum wall thickness of 1.2 mm. It has both high-strength and high-toughness cast mechanical properties, a yield strength of more than 150 MPa, and a tensile strength of more than 300 MPa. At the same time, it significantly reduces material costs, improves economic benefits, and is conducive to large-scale promotion and application.

[0114] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A high-strength, high-toughness and high-fluidity die-casting aluminum alloy, characterized in that: The metallographic structure of the die-cast aluminum alloy includes eutectic silicon, iron-rich phase and aluminum matrix; The chemical composition of the die-casting aluminum alloy includes: Al, Si, Fe, Cu, Mn, Mg, Zn, Ti and Sr; Measured in terms of mass percentage, the Si content in the die-casting aluminum alloy is 8.5-9.5wt%, and the Zn content is 0.35-1.35wt%.

2. The die-cast aluminum alloy according to claim 1, characterized in that: The eutectic silicon is in a fibrous shape.

3. The die-cast aluminum alloy according to claim 1, characterized in that: The iron-rich phase is in the shape of a block and / or a Chinese character.

4. The die-cast aluminum alloy according to claim 1, characterized in that: The aluminum matrix is ​​an equiaxed crystal or a doped dendrite.

5. The die-cast aluminum alloy according to claim 1 or 2, characterized in that: The average size of the eutectic silicon is ≤5 μm.

6. The die-cast aluminum alloy according to claim 1 or 3, characterized in that: The average size of the iron-rich phase is ≤5 μm.

7. The die-cast aluminum alloy according to claim 1 or 4, characterized in that: The average size of the aluminum matrix is ​​≤100 μm.

8. The die-cast aluminum alloy according to claim 1, characterized in that: The chemical composition of the die-cast aluminum alloy includes, by mass percentage: The balance is Al and inevitable impurities.

9. The die-cast aluminum alloy according to claim 8, characterized in that: Calculated by mass percentage, the total content of the impurities is ≤0.15wt%.

10. The die-cast aluminum alloy according to claim 9, characterized in that: Measured by mass percentage, the content of a single impurity is ≤0.05wt%.

11. A method for preparing the die-cast aluminum alloy according to any one of claims 1 to 10, characterized in that: The preparation method comprises material preparation, melting, refining and die casting which are performed in sequence.

12. The preparation method according to claim 11, characterized in that: The material preparation includes: mixing pure aluminum ingots with different types of doping alloys according to the mass percentage of chemical components.

13. The preparation method according to claim 12, characterized in that: The purity of the pure aluminum ingot is ≥99.5wt%.

14. The preparation method according to claim 12, characterized in that: The elements in the different kinds of doping alloys include Si, Fe, Cu, Mn, Mg, Zn, Ti and Sr.

15. The preparation method according to claim 11, characterized in that: The melting process includes: adding pure aluminum ingots and different types of doped alloys into a smelting furnace for melting and heat preservation to obtain aluminum melt.

16. The preparation method according to claim 15, characterized in that: The temperature of the melting and heat preservation treatment is ≥700°C.

17. The preparation method according to claim 11, characterized in that: The refining comprises: introducing nitrogen and / or argon into the aluminum melt to perform degassing refining and remove slag.

18. The preparation method according to claim 17, characterized in that: The degassing refining is carried out at a temperature of 720-750° C. and for a time of 10-20 minutes.

19. The preparation method according to claim 11, characterized in that: The die casting comprises: pouring aluminum melt into a mold for die casting.

20. The preparation method according to claim 19, characterized in that: The temperature of the aluminum melt is 650-700° C., the temperature of the mold is 150-250° C., and the wall thickness of the die-casting is ≥1.2 mm.

21. The preparation method according to any one of claims 11 to 20, characterized in that: The preparation method comprises the following steps: (1) Material preparation: mixing pure aluminum ingots with different types of doped alloys according to the mass percentage of chemical components, wherein the purity of the pure aluminum ingots is ≥99.5wt%, and the elements in the different types of doped alloys include Si, Fe, Cu, Mn, Mg, Zn, Ti and Sr; (2) Melting: pure aluminum ingots and different types of doped alloys are added into a melting furnace, melted and kept warm at above 700°C to obtain aluminum melt; (3) Refining: nitrogen and / or argon are introduced into the aluminum melt, and degassing and refining is performed at 720-750°C for 10-20 minutes, after which the slag is removed; (4) Die casting: Pour aluminum melt at a temperature of 650-700°C into a mold at a temperature of 150-250°C for die casting, and control the wall thickness of the die casting to be ≥1.2mm.

22. An application of the die-casting aluminum alloy according to any one of claims 1 to 10, characterized in that: The die-cast aluminum alloy is used to manufacture body structural parts of automobiles, including floors, engine compartments or shock towers.

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