Heat-treatment-free die-casting aluminum alloy, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a heat-treatment-free die-casting aluminum alloy, and a preparation method therefor and the use thereof. The aluminum alloy comprises the following components: Si: 7 wt.%-11 wt.%; Mn: 0.3 wt.%-0.8 wt.%; Mg: 0.1 wt.%-0.8 wt.%; Cr: 0.04 wt.%-0.2wt.%; Zr: 0-0.3 wt.%; Mo: 0.02 wt.%-0.2wt.%; Sr: 0.01 wt.%-0.04 wt.%; Fe: <0.8 wt.%; and the balance of Al. In the present invention, by means of the optimization of the alloying components, a stable α phase can be formed, the generation of a harmful phase can be prevented, the tolerance to the impurity Fe can be greatly improved, the alloy is allowed to have relatively ideal mechanical properties when being in an as-cast state, and the yield strength can also be greatly improved after low-temperature baking; and the alloy can be used for preparing automotive components.

Description

Heat treatment free die casting aluminum alloy, preparation method and application thereof TECHNICAL FIELD

[0001] The present application belongs to the technical field of alloy materials, and particularly relates to a heat treatment free die casting aluminum alloy, a preparation method and application thereof. BACKGROUND

[0002] The integrated die casting forming process is gradually becoming one of the important processes in the automotive industry due to its superior efficiency and cost-effectiveness. The integrated die casting forming process combines multiple links such as stamping, welding, painting and assembly in the production of traditional aluminum parts into one, greatly shortening the manufacturing cycle of the casting, reducing the manufacturing cost, and effectively reducing the weight of the vehicle body. Therefore, this process provides a low-cost and high-efficiency way to achieve vehicle lightweighting.

[0003] Although the integrated die casting technology has obvious advantages, it still faces many technical barriers in practical application, mainly focusing on the following four aspects: first, the heat treatment free die casting aluminum alloy suitable for integrated die casting; second, the development and application of large die casting machines; third, the design and manufacture of die casting molds; fourth, the optimization of vacuum die casting process. Among them, the development of special heat treatment free aluminum alloy materials suitable for integrated die casting is the key technical difficulty.

[0004] Traditional die casting aluminum alloys usually improve the mechanical properties such as yield strength and elongation through heat treatment technology (high temperature solid solution + artificial aging). However, heat treatment technology has significant limitations when applied to large integrated die casting structural parts; specifically, when the die casting structural parts are subjected to solid solution strengthening treatment, the casting needs to be heated to a temperature close to the solidus, and due to the large size of the integrated die casting parts, the cooling speed of each part is significantly different, which is prone to form large thermal stress during the subsequent cooling process. These thermal stresses not only may cause thermal deformation of the casting, but also significantly reduce the dimensional accuracy and positional accuracy of the casting. In order to correct these deformations, multiple trimming processes are usually introduced, which not only increases the production cost, but also reduces the production efficiency, and the effect is also difficult to guarantee.

[0005] Therefore, the development of a new type of aluminum alloy material that can achieve ideal performance without heat treatment after die casting forming is beneficial to realize large-scale application of integrated die casting process, making it possible to develop and apply large integrated die casting structural parts, and providing a new solution for the lightweight development of the automotive industry.

[0006] However, the current non-heat treatment die casting aluminum alloy material still has significant problems in application, for example, its tolerance to impurity element iron (Fe) is not high, and the weight percentage of iron must be controlled below 0.16wt.%. This strict requirement requires that the raw material used for production must be high-purity electrolytic aluminum, which increases the production energy consumption and cost, and is not conducive to the recycling of aluminum alloy materials and the realization of environmental protection goals. SUMMARY

[0007] The purpose of the present application is to provide a heat treatment die casting aluminum alloy and a preparation method thereof, which has higher tolerance to impurity Fe and excellent mechanical properties.

[0008] To achieve the above-mentioned purpose, the technical solutions provided by the present application are as follows:

[0009] In a first aspect, the present application provides a non-heat treatment die casting aluminum alloy, comprising the following components:

[0010] Si: 7wt.%-11wt.%; Mn: 0.3wt.%-0.8wt.%; Mg: 0.1wt.%-0.8wt.%; Cr: 0.04wt.%-0.2wt.%; Zr: 0-0.3wt.%; Mo: 0.02wt.%-0.2wt.%; Sr: 0.01wt.%-0.04wt.%; Fe: <0.8wt.%; total amount of unavoidable impurities <0.2wt.%, and content of any single impurity element <0.1wt.%; and the balance of Al.

[0011] In a second aspect, the present application provides a non-heat treatment die casting aluminum alloy, comprising the following components:

[0012] Si: 7wt.%-11wt.%; Mn: 0.3wt.%-0.8wt.%; Mg: 0.1wt.%-0.8wt.%; Cr: 0.04wt.%-0.2wt.%; Zr: 0-0.3wt.%; Mo: 0.06wt.%-0.2wt.%; Sr: 0.01wt.%-0.04wt.%; Fe: <0.8wt.%; total amount of unavoidable impurities <0.2wt.%, and content of any single impurity element <0.1wt.%; and the balance of Al.

[0013] In one or more embodiments, at least two of Cr, Mo, and Zr in the aluminum alloy form a dispersed phase dispersed in the aluminum matrix.

[0014] In one or more embodiments, a blocky α-Al(Cr,Fe)Si phase is formed in the aluminum alloy.

[0015] In one or more embodiments, the (Al,Si)3Zr phase of rod shape is formed in the aluminum alloy.

[0016] In one or more embodiments, the α-Al(Mo,Fe)Si phase is formed in the aluminum alloy and dispersed in the aluminum matrix.

[0017] In one or more embodiments, the Cr in the aluminum alloy can change the solidification sequence of the aluminum alloy, and form the α-Al(FeMnCr)Si phase dispersed in the aluminum matrix.

[0018] In a third aspect, the present application provides a preparation method of the heat treatment-free die casting aluminum alloy as described above, which comprises:

[0019] The raw materials are prepared according to the component proportions of the aluminum alloy, and the prepared raw materials are added into a melting furnace for heating and melting, and stirred uniformly to obtain an alloy melt; a protective gas is applied to the alloy melt, a refining agent is added, and refining is performed to remove impurities; a Sr-containing raw material is added into the refined alloy melt, and modification treatment is performed; a refining agent is added into the alloy melt after modification treatment, and refining is performed to remove gas and impurities; and the treated alloy melt is subjected to die casting to obtain an aluminum alloy casting.

[0020] In one or more embodiments, the prepared raw materials are added into a melting furnace for heating and melting, and stirred uniformly to obtain an alloy melt, which specifically comprises:

[0021] The aluminum ingot and the Si-containing raw material are added into a melting furnace for heating and melting, and the temperature of the melt is adjusted to 720-780℃ after the aluminum ingot and the Si-containing raw material are melted; the Cr-containing raw material, the Mn-containing raw material, the Zr-containing raw material and the Mo-containing raw material are added into the melt, and the temperature is lowered to 700-760℃ after complete melting; the Mg-containing raw material is added into the melt, the Mg-containing raw material is immersed below the liquid surface and melted, and the alloy melt is obtained after uniform stirring.

[0022] In one or more embodiments, the refining, degassing and impurity removal method specifically comprises: degassing with a rotor and adding a refining agent, the degassing time is 5-40 min, the degassing pressure is 0.1-0.5 MPa, the degassing speed is 300-500 r / min, the degassing temperature is 710-750℃, the refining agent is added within 1-5 min before the end of the degassing process, and the slag is removed after degassing.

[0023] In one or more embodiments, the method further comprises: baking the aluminum alloy casting obtained by die casting at a temperature in the range of 150-240℃ for 30-90 min.

[0024] In a fourth aspect, the present application further provides a use of the heat treatment-free die casting aluminum alloy as described above in the preparation of automobile parts.

[0025] Compared with the prior art, the heat treatment-free die-casting aluminum alloy and the preparation method thereof have the following advantages:

[0026] (1) The stable alpha phase is formed by Mn, Cr and Mo and Fe, the harmful phase is prevented from being generated, and the tolerance to impurity Fe can be greatly improved;

[0027] (2) The yield strength of the alloy in the as-cast state reaches 130-160 MPa, the tensile strength reaches 260-290 MPa, and the elongation reaches 7-15 %;

[0028] (3) The yield strength can be increased by 20-30 % (30-40 MPa) after low-temperature baking (150-240 DEG C / 30-90 min);

[0029] (4) Under the test conditions of stress ratio R=-1, loading frequency 40 Hz and 100 million cycles, the fatigue strength of the alloy in the as-cast state reaches 110 MPa or above. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0031] Fig. 1 is a micro-alloy structure diagram of the aluminum alloy prepared in Example 1 of the present application (scale 100 μm);

[0032] Fig. 2 is a micro-alloy structure diagram of the aluminum alloy prepared in Example 1 of the present application (scale 20 μm);

[0033] Fig. 3 is a micro-alloy structure diagram of the aluminum alloy prepared in Example 2 of the present application (scale 100 μm);

[0034] Fig. 4 is a micro-alloy structure diagram of the aluminum alloy prepared in Example 2 of the present application (scale 20 μm);

[0035] Fig. 5 is a micro-alloy structure diagram of the aluminum alloy prepared in Example 3 of the present application (scale 100 μm);

[0036] Fig. 6 is a micro-alloy structure diagram of the aluminum alloy prepared in Example 3 of the present application (scale 20 μm);

[0037] Fig. 7 is a tensile test stress-strain curve diagram of the aluminum alloy prepared in Example 2 of the present application;

[0038] Fig. 8 is a VDA test result diagram of the aluminum alloy prepared in Examples 1-3 of the present application. DETAILED DESCRIPTION

[0039] In order to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts should fall within the protection scope of the present application.

[0040] It should be noted that in the following description, the "wt.%" representing the amount is based on weight unless otherwise specified. Unless otherwise indicated, all numbers expressing quantities and physical characteristics in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the description and the claims are approximations. Those skilled in the art can obtain the required properties sought with variations to the described parameters, as the desired properties can be obtained by appropriate variation of the described parameters within the scope of the present disclosure. The use of the term "about" in the description and the claims should be understood to allow for variations that are due to expected variations in manufacturing and other factors, such as variations in the manufacturing process, variations in the materials used, and the like.

[0041] The manufacturing process of traditional aluminum parts involves multiple links such as stamping, welding, painting and assembly, which not only increases the manufacturing cycle and cost, but also limits the further reduction of the body weight. To solve these problems, the integrated die casting forming process emerges as the times require, which combines the above-mentioned multiple links, greatly shortens the manufacturing cycle, reduces the cost, and significantly reduces the body weight. However, this technology faces multiple technical barriers, among which the more important one is to develop a special heat treatment-free aluminum alloy material suitable for integrated die casting.

[0042] In the prior art, traditional die casting aluminum alloys usually rely on heat treatment technology (high temperature solid solution + artificial aging) to improve the yield strength and elongation of the alloy. However, for large-sized die casting structural parts, large thermal stress and thermal deformation are easily generated during the heat treatment process, resulting in the decline of the position accuracy and dimensional accuracy of the castings, and the need to introduce multiple shaping processes, which further increases the cost and reduces the efficiency. In addition, the existing heat treatment-free die casting aluminum alloys have low tolerance to impurity Fe, requiring the weight percentage of Fe to be ≤0.16wt.%, which makes the raw material for production must be high-purity electrolytic aluminum, which is not conducive to reducing energy consumption and recycling of aluminum alloy materials, and also leads to high cost of the corresponding products.

[0043] To solve the problems in the prior art, the application provides a heat treatment-free die-casting aluminum alloy. By scientifically optimizing the proportion of alloy components, in particular, adding Si, Mn, Mg, Cr, Zr, Mo and Sr elements in a specific proportion, and controlling the content of Fe and other impurities, the aluminum alloy can obtain ideal mechanical properties without heat treatment. Specifically, Si improves the strength and casting performance of the alloy, Mn, Cr and Mo form stable alpha phase with Fe to prevent the generation of harmful phases, Mg improves the strength and ductility through solid solution strengthening and precipitation hardening, Zr refines the grains, Mo prevents the generation of coarse intermetallic compounds, and Sr refines the eutectic silicon phase. The synergistic effect of the components improves the overall performance of the alloy.

[0044] Through the above-mentioned component optimization design, the aluminum alloy of the application can obtain relatively ideal high strength and high ductility without high-temperature solid solution and artificial aging treatment after casting, thereby reducing thermal stress and thermal deformation problems, ensuring the dimensional accuracy and position accuracy of the casting, reducing production cost and energy consumption, and achieving the lightweight goal. The heat treatment-free die-casting aluminum alloy not only improves the manufacturing efficiency and performance consistency of the casting, but also promotes the recycling of aluminum alloy materials, meets the requirements of environmental protection and sustainable development, and provides an efficient and low-cost solution for the lightweight of the automobile industry.

[0045] The heat treatment-free die-casting aluminum alloy in an embodiment of the application includes the following components: Si: 7wt.%-11wt.%; Mn: 0.3wt.%-0.8wt.%; Mg: 0.1wt.%-0.8wt.%; Cr: 0.04wt.%-0.2wt.%; Zr: 0-0.3wt.%; Mo: 0.02wt.%-0.2wt.%; Sr: 0.01wt.%-0.04wt.%; Fe: <0.8wt.%; total amount of unavoidable impurities <0.2wt.%, and content of any single impurity element <0.1wt.%; and the balance of Al. The unavoidable impurities refer to other impurity elements except Fe.

[0046] The heat treatment-free die-casting aluminum alloy in an embodiment of the application includes the following components:

[0047] Si: 7wt.%-11wt.%; Mn: 0.3wt.%-0.8wt.%; Mg: 0.1wt.%-0.8wt.%; Cr: 0.04wt.%-0.2wt.%; Zr: 0-0.3wt.%; Mo: 0.04wt.%-0.2wt.%; Sr: 0.01wt.%-0.04wt.%; Fe: <0.8wt.%; total amount of unavoidable impurities <0.2wt.%, and content of any single impurity element <0.1wt.%; and the balance of Al.

[0048] It should be noted that the present application can realize dispersion phase formation and Fe phase regulation by adding elements of Cr, Mo and Zr in combination, thereby realizing the double promotion of alloy strength and plasticity, and also allowing the aluminum alloy to accommodate more impurity elements Fe.

[0049] In practice, in the system of the present application, transition elements Cr, Mo and Zr have a low diffusion rate in the α-Al matrix (for example, Cr, Mo and Zr at 400℃ are 1.29×10 -21 m 2 s -1 , 5.52×10 -23 m 2 s -1 , 1.20×10 -20 m 2 s -1 , respectively, which is better than the commonly used dispersion phase initiator Mn (6.24×10 -19 m 2 s -1 ), so the dispersion phase obtained from Cr, Mo and Zr has good anti-coarsening performance in the aluminum alloy of the present application, which also conforms to the Lifshitz, Slyozov and Wagner theory, and the ideal dispersion phase should have low interface energy (low lattice and matrix mismatch degree), low diffusion rate and solubility limit, to prevent coarsening by bulk diffusion at high temperature.

[0050] In the Al-Si alloy of the present application, the addition of Cr can effectively inhibit the sticking tendency and convert the needle-like β-Al5FeSi into blocky α-Al(Cr,Fe)Si phase, in addition, during heat treatment, the supersaturated Cr solute atoms in the aluminum matrix will precipitate in the form of dispersion phase. Zr can form balanced rod-shaped D023 type (Al, Si)3Zr precipitated phase. In the Al-Si alloy of the present application, Mo is an effective Fe neutralizer, which can inhibit the β-Al5FeSi and π phase transformation, form fine and dispersed α-Al(Mo,Fe)Si phase, and uniformly distribute in the aluminum matrix, which can effectively hinder dislocation movement and improve the strength of the alloy.

[0051] Under the alloy system of the present application, Mg, Zr and Mo can effectively improve the strength of the alloy, Mn, Mo and Cr can effectively control the morphology of intermetallic compounds, and the proportion of Mn, Mo and Cr can effectively control the proportion of intermetallic compounds with different morphologies. By adding Cr to change the solidification sequence of single Mo-containing composition, the area percentage of alpha-Al(FeMnCr)Si phase is increased, and part of the Fe content in the alloy is consumed, thereby avoiding the problem of intermetallic compound particle coarsening caused by single addition of Mo element, reducing the organization difference of the alloy under different process conditions, and improving the uniformity of the microstructure and performance of the casting. On the other hand, the content of Cr can effectively avoid the generation of pi phase and beta-Fe phase, and the needle-like beta-Al(Fe,Cr)Si phase can also be avoided by optimizing the composition window, and only fine alpha-Al(FeMnCr)Si phase is formed.

[0052] Solidification sequence refers to the transition sequence of metal or alloy from liquid phase to solid phase during cooling process. The addition of different elements can change the solidification sequence of the alloy, thereby affecting the final microstructure and phase composition. The addition of Cr (chromium) and Mo (molybdenum) elements has different effects on the solidification sequence. Mo is prone to form larger intermetallic compound particles in aluminum alloys, such as beta phase (β-Al5FeSi) and pi phase (Al8FeMg3Si6). These large particles will gradually grow during the cooling process, leading to a decrease in strength and ductility of the material. The addition of Cr forms new intermetallic compounds such as alpha-Al(FeMnCr)Si phase, which makes Cr, Fe, Mn and Si form new stable phases, thereby avoiding the formation of large intermetallic compound particles when Mo exists alone.

[0053] Alpha-Al(FeMnCr)Si phase is a stable intermetallic compound with fine and uniform morphology, which can effectively disperse in the aluminum matrix, thereby improving the strength and hardness of the alloy. By adding Cr, the formation of alpha phase is promoted, and its area percentage in the alloy is increased. The presence of this phase helps to refine the microstructure of the alloy, hinders dislocation movement, and improves the mechanical properties of the material. The addition of Cr causes a part of Fe to form stable alpha phase with Cr and other elements, thereby reducing the opportunity for Fe to form unfavorable beta phase and pi phase (beta-Fe phase and pi phase are usually needle-like, and the presence of these phases will adversely affect the ductility and toughness of the material).

[0054] The present application can eliminate large-size Mo-containing phases in the alloy on the basis of obtaining sufficient strength (addition of Mg, Zr and Mo), reduce the process sensitivity of the alloy, and avoid the generation of pi phase and beta-Fe phase by adding Cr. In addition, the needle-like beta-Al(Fe,Cr)Si phase can also be avoided by optimizing the composition window, and only fine alpha-Al(FeMnCr)Si phase is formed. Moreover, by introducing Cr element, the pi phase in the alloy is greatly reduced, realizing Mg strengthening while reducing the damage of Mg element to ductility.

[0055] Chromium (Cr) has multiple roles in aluminum alloys, mainly including grain refinement, corrosion resistance enhancement, and mechanical property improvement. In the aluminum alloy system of the present invention, Cr can form α-Al(FeMnCr)Si phase with Fe, Mn and other elements, which has a stable crystal structure and can effectively inhibit the formation of β phase (brittle phase). In addition, the addition of Cr can also improve the high temperature stability and creep resistance of the alloy.

[0056] In order to obtain fine and uniformly distributed α-Al(FeMnCr)Si phase during casting, while avoiding the formation of β-Al(Fe,Cr)Si phase, the present invention selects to control the Cr content in the range of 0.04wt.%-0.2wt.%. The Cr content in this range can ensure the formation of the required α phase during casting, and also avoid excessive intermetallic compounds, ensuring the toughness and ductility of the alloy.

[0057] Cr content is too low (less than 0.04wt.%) will lead to insufficient formation of α-Al(FeMnCr)Si phase, resulting in an increase in the formation of β phase. The presence of β phase will significantly reduce the mechanical properties of the alloy, especially ductility and toughness. In addition, lack of sufficient Cr will also reduce the high temperature stability and creep resistance of the alloy.

[0058] Cr content is too high (more than 0.2wt.%) will lead to excessive intermetallic compounds. These compounds will form coarse grains and secondary phases during casting, resulting in a significant reduction in the toughness and ductility of the alloy. At the same time, too high Cr content will also increase the hardness of the alloy, making the processing and forming process more difficult.

[0059] Zirconium (Zr) mainly plays a role in refining grains and improving heat resistance in aluminum alloys. Zr can form fine (Al,Si)3Zr phase with Al, which can effectively hinder the movement of grain boundaries during solid solution process, thereby refining grains and improving the mechanical properties and high temperature performance of the alloy. In addition, (Al,Si)3Zr phase also has high melting point and stability, which can maintain stable crystal structure at high temperature and prevent grain coarsening.

[0060] The present invention selects to control the Zr content in the range of 0-0.3wt.%, the purpose is to achieve grain refinement and high temperature performance improvement by adding appropriate amount of Zr, while avoiding the negative effects of excessive addition. Zr content is too high (more than 0.3wt%) will lead to the formation of a large amount of (Al,Si)3Zr phase, which may form coarse particles in the supersaturated state, weakening the ductility and toughness of the alloy. In addition, excessive Zr will increase the hardness of the alloy, making the processing and forming process more difficult.

[0061] Molybdenum (Mo) is mainly used in aluminum alloys to prevent the coarsening of intermetallic compounds and improve the high-temperature performance and strength of the alloy. Mo can form stable intermetallic compounds with other elements such as Fe, Mn, Cr, etc., which have high stability at high temperatures and can effectively prevent grain growth. In addition, Mo also has good solid solution strengthening effect, which can improve the comprehensive mechanical properties of the alloy.

[0062] The present application selects the Mo content to be controlled in the range of 0.02wt.%-0.2wt.% (for example, it can be 0.06wt.%-0.2wt.%), the purpose is to realize the refinement and stability of intermetallic compounds by adding appropriate amount of Mo, improve the high-temperature performance and strength of the alloy, and avoid the negative effects caused by excessive addition.

[0063] If the Mo content is too low, it will lead to insufficient formation of intermetallic compounds, which cannot effectively prevent grain coarsening, especially in high temperature environment, the mechanical properties and dimensional stability of the alloy will decrease significantly. In addition, the lack of sufficient Mo will also reduce the solid solution strengthening effect of the alloy, making the strength and hardness of the alloy insufficient.

[0064] If the Mo content is too high, it will lead to the formation of too much intermetallic compounds, which may form coarse particles in the supersaturated state, weakening the toughness and ductility of the alloy. In addition, excessive Mo will significantly increase the hardness of the alloy, making the processing and forming process more difficult, and may cause processing stress and crack problems.

[0065] In a preferred embodiment of the present application, the heat treatment-free die casting aluminum alloy includes the following components: Si: 7wt.%-11wt%; Mn: 0.5wt.%-0.6wt.%; Mg: 0.15wt.%-0.2wt.%; Cr: 0.04wt.%-0.1wt.%; Zr: 0-0.15wt.%; Mo: 0.04wt.%-0.12wt.%; Sr: 0.01wt.%-0.03wt.%; Fe: 0.2wt.%-0.8wt.%; the total amount of unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance of Al.

[0066] In a preferred embodiment of the present application, the heat treatment free die casting aluminum alloy comprises the following components: Si: 7wt.%-9wt%; Mn: 0.5wt.%-0.7wt%; Mg: 0.1wt.%-0.2wt%; Cr: 0.04wt.%-0.1wt%; Mo: 0.04wt.%-0.12wt%; Sr: 0.01wt.%-0.03wt%; Fe: 0.2wt.%-0.5wt%; total amount of unavoidable impurities <0.2wt%, and content of any single impurity element <0.1wt%; and the balance of Al.

[0067] In a preferred embodiment of the present application, the heat treatment free die casting aluminum alloy comprises the following components: Si: 8wt.%-9wt%; Mn: 0.4wt.%-0.7wt%; Mg: 0.1wt.%-0.6wt%; Cr: 0.05wt.%-0.1wt%; Zr: 0.04wt.%-0.2wt%; Mo: 0.06wt.%-0.15wt%; Sr: 0.01wt.%-0.03wt%; Fe: <0.8wt%; total amount of unavoidable impurities <0.2wt%, and content of any single impurity element <0.1wt%; and the balance of Al.

[0068] In a preferred embodiment of the present application, the heat treatment free die casting aluminum alloy comprises the following components: Si: 8wt.%-9wt%; Mn: 0.45wt.%-0.65wt%; Mg: 0.1wt.%-0.3wt%; Cr: 0.05wt.%-0.1wt%; Zr: 0-0.1wt%; Mo: 0.04wt.%-0.15wt%; Sr: 0.01wt.%-0.03wt%; Fe: 0.3wt.%-0.6wt%; total amount of unavoidable impurities <0.2wt%, and content of any single impurity element <0.1wt%; and the balance of Al.

[0069] In a more preferred embodiment of the present application, the heat treatment free die casting aluminum alloy comprises the following components: Si: 9wt.%-10wt%; Mn: 0.4wt.%-0.6wt%; Mg: 0.1wt.%-0.3wt%; Cr: 0.06wt.%-0.08wt%; Zr: 0.06wt.%-0.1wt%; Mo: 0.06wt.%-0.1wt%; Sr: 0.01wt.%-0.03wt%; Fe: <0.8wt%; total amount of unavoidable impurities <0.2wt%, and content of any single impurity element <0.1wt%; and the balance of Al.

[0070] In a preferred embodiment of the present application, the heat treatment free die casting aluminum alloy comprises the following components: Si: 9wt.%-11wt.%; Mn: 0.45wt.%-0.65wt.%; Mg: 0.1wt.%-0.3wt.%; Cr: 0.05wt.%-0.1wt.%; Zr: 0.05wt.%-0.1wt.%; Mo: 0.04wt.%-0.12wt.%; Sr: 0.01wt.%-0.03wt.%; Fe: 0.3wt.%-0.6wt.%; unavoidable impurities: total content <0.2wt.% and content of any single impurity <0.1wt.%; and the balance of Al.

[0071] In an embodiment of the present application, a preparation method of the aforementioned heat treatment free die casting aluminum alloy is provided, which specifically comprises the following steps:

[0072] S101: ingredients are proportioned according to the component proportioning of the aluminum alloy.

[0073] The raw materials can include pure Al ingot (electrolytic aluminum ingot or recycled aluminum ingot), Al-Si intermediate alloy or industrial pure silicon or instant silicon, pure Mg ingot, Al-Cr intermediate alloy, Al-Mn intermediate alloy or manganese agent, Al-Zr intermediate alloy, Al-Mo intermediate alloy, Al-Sr intermediate alloy, etc.

[0074] S102: the proportioned raw materials are added into a smelting furnace for heating and melting, and stirred uniformly to obtain an alloy melt.

[0075] Specifically, the aluminum ingot and Si-containing raw material are added into a smelting furnace for heating and melting, and the temperature of the melt is adjusted to 720-780℃ after the aluminum ingot and Si-containing raw material are melted; Cr-containing raw material, Mn-containing raw material, Zr-containing raw material and Mo-containing raw material are added into the melt, and the temperature is lowered to 700-760℃ after complete melting; then Mg-containing raw material is added into the melt, so that the Mg-containing raw material is immersed below the liquid level and melted, and stirred uniformly to obtain an alloy melt.

[0076] S103: protective gas is applied to the alloy melt, and a refining agent is added for refining and impurity removal.

[0077] Specifically, the refining agent is weighed according to 1‰-1.5‰ of the mass of the alloy melt, and 99.99% nitrogen / argon is used for blowing refining; the refining pressure is 0.05-0.2MPa, and the refining speed is 0.5-2kg / min; after the refining is completed, the slag is removed after standing for 5-20min, and the temperature of the alloy melt is set to 720-750℃ after the slag removal, and the melt is stirred to make the temperature uniform, and then the alloy melt is placed into a transfer ladle after standing.

[0078] S104: Sr-containing raw material is added into the refined alloy melt for modification treatment.

[0079] Specifically, the transfer package is baked to 720-750℃ and weighed, and after discharging, it is weighed again, and Al-Sr intermediate alloy is added according to the mass of the melt to carry out modification treatment.

[0080] S105: Add a refining agent to the modified alloy melt to carry out refining, degassing and impurity removal.

[0081] Specifically, the rotor is degassed and a refining agent is added at 1-3‰ of the mass of the melt, the degassing time is 5-40 min, the degassing pressure is 0.1-0.5 MPa, the degassing speed is 300-500 r / min, the degassing temperature is 710-750℃, and the refining agent (Al5TiB or TCB) is added within 1-10 minutes before the end of the degassing process, and the slag is removed after degassing.

[0082] It should be noted that after refining, degassing and impurity removal, the aluminum liquid in the transfer package is poured into the machine-side furnace, a filter screen is added before feeding the machine-side furnace; mushroom-shaped samples, K-shaped samples, and hydrogen samples are taken, and if the composition is unqualified, the alloy composition is adjusted to qualified, if the K-shaped sample is unqualified, the slag removal process is repeated, and if the hydrogen content is unqualified, the rotor degassing process is repeated, until the alloy melt is qualified.

[0083] S106: The treated alloy melt is pressure cast to obtain an aluminum alloy casting.

[0084] Specifically, the conditions for pressure casting include: temperature 680℃-720℃; mold vacuum degree controlled below 80 mbar (for example, can be controlled at 1-80 mbar); mold temperature 170-250℃; casting pressure 40-150 MPa; injection speed low speed section 0.1-0.5 m / s, high speed section 3-5 m / s. The amount of soup is adjusted and determined according to the thickness of the material handle being 20%-30% of the diameter of the barrel, and the mold holding pressure holding time is 1-20 s.

[0085] An embodiment of the present application provides a preparation method of the aforementioned heat treatment-free pressure casting aluminum alloy, which specifically comprises the following steps:

[0086] (1) The ingredients of the aluminum alloy are proportioned according to the ingredient ratio.

[0087] The raw materials can include pure Al ingot (electrolytic aluminum ingot or recycled aluminum ingot), Al-Si intermediate alloy or industrial pure silicon or instant silicon, pure Mg ingot, Al-Cr intermediate alloy, Al-Mn intermediate alloy or manganese agent, Al-Zr intermediate alloy, Al-Mo intermediate alloy, Al-Sr intermediate alloy, etc.

[0088] (2) Melting

[0089] The aluminum ingot and Si-containing raw material are added into a smelting furnace for heating and melting, and after the aluminum ingot and Si-containing raw material are melted, the temperature of the melt is adjusted to 720-780 ℃; the Cr-containing raw material, Mn-containing raw material, Zr-containing raw material and Mo-containing raw material are added into the melt, and after complete melting, the temperature is lowered to 700-760 ℃; then the Mg-containing raw material is added into the melt, so that the Mg-containing raw material is immersed below the liquid level and melted, and stirred uniformly to obtain an alloy melt.

[0090] (3) Refining and degassing:

[0091] The temperature of the melt is lowered to 700-720 ℃, the weighed Al-Sr intermediate alloy is added, and stirred to completely melt, and then the temperature is kept constant. Then the temperature of the melt is increased to 720-730 ℃ to start degassing. The refining agent is weighed according to 0.1%-0.15% of the mass of the melt, and added into the refining agent automatic adding funnel of the rotor degassing machine. The degassing is carried out by using the rotor degassing machine, the refining agent adding speed is 400-600 r / min, the degassing speed is 300-500 r / min, the high-purity Ar flow rate of the degassing machine is 15-40 L / min, and the degassing time is 10-50 min. After the degassing is completed, the alloy composition sample and the reduced-pressure solidification gas measurement sample are taken after standing for 1-20 min;

[0092] (4) Die casting

[0093] After the degassing meets the standard and the composition is qualified, the temperature of the melt is adjusted to 680-720 ℃, and die casting is carried out on the die casting machine. The die casting parameters are as follows: the mold temperature is 165-200 ℃, the mold fullness is 25%-36%, the vacuum degree is 20-80 mBar, the low-speed section injection speed is 0.1-0.5 m / s, the high-speed section injection speed is 3-5 m / s, the casting pressure is 40-150 MPa, and the mold holding and pressure maintaining time is 1-20 s.

[0094] It should be noted that according to the actual performance requirements and assembly process arrangement of the aluminum alloy castings, the aluminum alloy castings can be baked at a temperature in the range of 180-230 ℃ for 30-90 min to further improve the yield strength (the yield strength can be improved by 30-40 MPa by the present application).

[0095] The present application will be further described below in combination with specific examples.

[0096] Preparation of the aluminum alloy

[0097] (1) Batching: batching according to the total amount of 300 kg, and according to the calculated values of the batching table, the pure Al ingot, AlSi20 intermediate alloy, 95% fast-acting silicon, pure Mg ingot, AlMn10 intermediate alloy, AlCr10 intermediate alloy, AlMo5 intermediate alloy, AlZr10 intermediate alloy, AlSr10 intermediate alloy, AlV10 intermediate alloy and grain refiner TCB intermediate alloy are weighed and prepared for use;

[0098] (2) Melting: pure Al ingot and AlSi20 intermediate alloy were first added in a 300 kg capacity crucible furnace with furnace temperature rising; after complete melting, the melt temperature was increased to 765℃, and 95% instant silicon was added in batches by bell jar pressing; after complete melting of instant silicon, AlCr10 intermediate alloy, AlMn10 intermediate alloy, AlMo5 intermediate alloy, AlZr10 intermediate alloy, and AlV10 intermediate alloy were added according to the actual alloying of the alloy, and a preheated ladle was used for stirring to make it uniform; after complete melting of the intermediate alloy, the temperature was decreased to 720℃, and pure Mg ingot was pressed below the melt surface by bell jar, and after complete melting of the pure Mg ingot, it was stirred uniformly;

[0099] (3) Refining and degassing: the melt temperature was decreased to 710℃, and AlSr10 intermediate alloy was added after weighing, and stirred to completely melt, and kept for 5 minutes. Then the melt temperature was increased to 720℃-730℃ to start degassing. According to the 0.1%-0.15% of the melt quality, the refining agent was weighed and added into the refining agent automatic adding funnel of the rotor degassing machine. Degassing was carried out by using the rotor degassing machine, the refining agent adding speed was 500r / min, the degassing speed was 400r / min, the high purity Ar flow rate of the degassing machine was 25L / min, and the degassing time was 25min. After degassing, it was placed for 10min, and the alloy composition sample and the reduced pressure solidification gas measurement sample were taken;

[0100] (4) Die casting: after the degassing was qualified and the composition was qualified, the melt temperature was adjusted to 690℃-705℃, and die casting was carried out on a 400 ton die casting machine. The die casting parameters were: mold temperature 170℃, mold fullness 33%, vacuum degree 60mBar, low speed section injection speed 0.2m / s, high speed section 3.9m / s, casting pressure 80MPa, and mold holding pressure time 6s.

[0101] (5) Low temperature aging: the temperature of the holding furnace was set to 200℃, and after the temperature was reached, it was kept for 1h to stabilize the furnace temperature, and the die casting was placed, and after the temperature rose to 200℃, it was kept for 60min.

[0102] The aluminum alloy compositions shown in Table 1 were used to prepare the aluminum alloys of each example and comparative example, and then the aluminum alloys of each example and comparative example were prepared according to the aforementioned aluminum alloy preparation method.

[0103] Table 1 - Al-Si alloy composition table

[0104] The mechanical properties of the aluminum alloys prepared in each example and comparative example in the as-cast state and after low temperature aging were tested, and the specific test results are shown in Table 2.

[0105] Table 2 - Performance test results of aluminum alloy in as-cast state and after low temperature aging

[0106] As shown in Table 2, the aluminum alloy prepared by the embodiment of the present application can significantly improve the mechanical properties of the aluminum alloy through the synergistic effect of each component.

[0107] Fig. 1 and Fig. 2 are microstructure diagrams of the aluminum alloy prepared in Example 1 under different scales, Fig. 3 and Fig. 4 are microstructure diagrams of the aluminum alloy prepared in Example 2 under different scales, and Fig. 5 and Fig. 6 are microstructure diagrams of the aluminum alloy prepared in Example 3 under different scales. As shown in Fig. 1-6, in addition to the inevitable pre-crystallization in the barrel due to the high-pressure casting process itself, the alloy organization of the present application is fine and dense, most of the α-Al dendrite size is below 20 μm; the eutectic silicon modification effect is good, most of which is fine network structure; there is almost no needle-like Fe phase, and the Fe phase is basically all converted into fine granular α-Fe phase instead of needle-like β-Fe phase.

[0108] Fig. 7 is a tensile test stress-strain curve diagram of the aluminum alloy prepared in Example 1 of the present application. As shown in Fig. 7, the tensile property numerical value of the aluminum alloy prepared in Example 1 is yield strength δ 0.2 > 140 MPa, tensile strength δ b > 285 MPa, and elongation A% > 13.

[0109] Fig. 8 is a VDA test result diagram of the aluminum alloy prepared in Examples 1-3 of the present application. As shown in Fig. 8, the bending angle of the aluminum alloy prepared in Examples 1-3 is all above 20°, and Example 2 can reach above 25°.

[0110] The aluminum alloy sample prepared in Example 2 of the present application was subjected to high-cycle fatigue test, and the test conditions were stress ratio R = -1, frequency = 40 Hz, cycle period was 100 million times, and amplitude (load) = 90 MPa, 100 MPa, 105 MPa, 110 MPa, 115 MPa, 120 MPa could all be tested, and the probability of passing 110 MPa was > 90%.

[0111] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

[0112] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as exactly that endpoint point. Any of the endpoints of the ranges or the separate values should be understood as not solely the precision as disclosed for that endpoint but also values so close thereto as to be considered equivalent to the disclosed value for the range or separate value. For values whose endpoints contain the term "about", the exact value of the endpoint is also included in the disclosure.

Claims

1. A heat-free die-cast aluminum alloy, characterized in that, Includes the following ingredients: Si: 7wt.%-11wt.%; Mn: 0.3wt.%-0.8wt.%; Mg: 0.1wt.%-0.8wt.%; Cr: 0.04wt.%-0.2wt.%; Zr: 0-0.3wt.%; Mo: 0.02wt.%-0.2wt.%; Sr: 0.01wt.%-0.04wt.%; Fe: <0.8wt.%; total unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance Al; At least two of the Cr, Mo, and Zr elements in the aluminum alloy form dispersed phases in the aluminum matrix. The aluminum alloy contains α-Al(Cr,Fe)Si phase, D023 type (Al,Si)3Zr phase, and α-Al(Mo,Fe)Si phase and α-Al(FeMnCr)Si phase dispersed in the aluminum matrix, respectively.

2. A heat-treatable die-cast aluminum alloy, characterized in that, Includes the following ingredients: Si: 7wt.%-11wt.%; Mn: 0.3wt.%-0.8wt.%; Mg: 0.1wt.%-0.8wt.%; Cr: 0.04wt.%-0.2wt.%; Zr: 0-0.3wt.%; Mo: 0.02wt.%-0.2wt.%; Sr: 0.01wt.%-0.04wt.%; Fe: <0.8wt.%; total unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance Al.

3. The heat-free die-cast aluminum alloy according to claim 1 or 2, characterized in that, The heat-free die-cast aluminum alloy contains 0.06 wt.% to 0.2 wt.% Mo.

4. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, At least two of the Cr, Mo, and Zr elements in the aluminum alloy form a dispersed phase dispersed in the aluminum matrix.

5. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The aluminum alloy contains a bulk α-Al(Cr,Fe)Si phase.

6. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The aluminum alloy contains rod-shaped D023-type (Al,Si)3Zr phases.

7. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The aluminum alloy contains an α-Al(Mo,Fe)Si phase dispersed in the aluminum matrix.

8. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The Cr in the aluminum alloy can change the solidification sequence of the aluminum alloy, forming the α-Al(FeMnCr)Si phase dispersed in the aluminum matrix.

9. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The heat-free die-cast aluminum alloy comprises the following components: Si: 7wt.%-11wt%.; Mn: 0.5wt.%-0.6wt.%; Mg: 0.15wt.%-0.2wt.%; Cr: 0.04wt.%-0.1wt.%; Zr: 0-0.15wt.%; Mo: 0.04wt.%-0.12wt.%; Sr: 0.01wt.%-0.03wt.%; Fe: 0.2wt.%-0.8wt.%; total unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance Al.

10. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The heat-free die-cast aluminum alloy comprises the following components: Si: 7wt.%-9wt.%; Mn: 0.5wt.%-0.7wt.%; Mg: 0.1wt.%-0.2wt.%; Cr: 0.04wt.%-0.1wt.%; Mo: 0.04wt.%-0.12wt.%; Sr: 0.01wt.%-0.03wt.%; Fe: 0.2wt.%-0.5wt.%; total unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance Al.

11. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The heat-free die-cast aluminum alloy comprises the following components: Si: 8wt.%-9wt.%; Mn: 0.4wt.%-0.7wt.%; Mg: 0.1wt.%-0.6wt.%; Cr: 0.05wt.%-0.1wt.%; Zr: 0.04wt.%-0.2wt.%; Mo: 0.04wt.%-0.15wt.%; Sr: 0.01wt.%-0.03wt.%; Fe: <0.8wt.%; total unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance Al.

12. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The heat-free die-cast aluminum alloy comprises the following components: Si: 8wt.%-9wt.%; Mn: 0.45wt.%-0.65wt.%; Mg: 0.1wt.%-0.3wt.%; Cr: 0.05wt.%-0.1wt.%; Zr: 0-0.1wt.%; Mo: 0.04wt.%-0.15wt.%; Sr: 0.01wt.%-0.03wt.%; Fe: 0.3wt.%-0.6wt.%; total unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance Al.

13. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The heat-free die-cast aluminum alloy comprises the following components: Si: 9wt.%-10wt.%; Mn: 0.4wt.%-0.6wt.%; Mg: 0.1wt.%-0.3wt.%; Cr: 0.06wt.%-0.08wt.%; Zr: 0.06wt.%-0.1wt.%; Mo: 0.04wt.%-0.1wt.%; Sr: 0.01wt.%-0.03wt.%; Fe: <0.8wt.%; total unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance Al.

14. The heat-free die-cast aluminum alloy according to claim 2, characterized in that, The heat-free die-cast aluminum alloy comprises the following components: Si: 9wt.%-11wt.%; Mn: 0.45wt.%-0.65wt.%; Mg: 0.1wt.%-0.3wt.%; Cr: 0.05wt.%-0.1wt.%; Zr: 0.05wt.%-0.1wt.%; Mo: 0.04wt.%-0.12wt.%; Sr: 0.01wt.%-0.03wt.%; Fe: 0.3wt.%-0.6wt.%; total unavoidable impurities <0.2wt.%, and the content of any single impurity element <0.1wt.%; and the balance Al.

15. A method for preparing a heat-free die-cast aluminum alloy according to any one of claims 1 to 14, characterized in that, The preparation method includes: preparing materials according to the composition ratio of aluminum alloy, first preparing an alloy melt, refining and modifying the alloy melt, and then die-casting to obtain an aluminum alloy casting.

16. The method for preparing heat-free die-cast aluminum alloy according to claim 15, characterized in that, The embodiments for preparing the aluminum alloy casting include: Prepare the ingredients according to the composition ratio of the aluminum alloy; The prepared raw materials are added to a melting furnace, heated and melted, and stirred evenly to obtain an alloy melt; A protective gas is applied to the alloy melt, and a refining agent is added to refine and remove impurities. Add Sr-containing raw materials to the refined alloy melt for modification treatment; A refining agent is added to the modified alloy melt for refining, degassing, and impurity removal. The treated alloy melt is die-cast to obtain aluminum alloy castings.

17. The method for preparing heat-free die-cast aluminum alloy according to claim 16, characterized in that, The embodiments for preparing the alloy melt include: Aluminum ingots and Si-containing raw materials are added to a smelting furnace and heated to melt. After the aluminum ingots and Si-containing raw materials have melted, the melt temperature is adjusted to 720-780℃. Add Cr-containing raw materials, Mn-containing raw materials, Zr-containing raw materials, and Mo-containing raw materials to the melt, and after complete melting, lower the temperature to 700-760℃; Add Mg-containing raw materials to the melt, allowing the Mg-containing raw materials to be immersed below the liquid surface and melted. Stir evenly to obtain an alloy melt.

18. The method for preparing heat-free die-cast aluminum alloy according to claim 16, characterized in that, The implementation methods for the refining, degassing, and impurity removal include: The degassing process involves using a rotor and adding a refining agent. The degassing time is 5-40 minutes, the degassing pressure is 0.1-0.5 MPa, the degassing speed is 300-500 r / min, and the degassing temperature is 710-750℃. A refining agent is added 1-5 minutes before the end of the degassing process. After degassing, the slag and impurities are removed.

19. The method for preparing heat-free die-cast aluminum alloy according to claim 15, characterized in that, The preparation method further includes: The aluminum alloy castings obtained by die casting are baked and held at a temperature range of 150-240℃ for 30-90 minutes.

20. The use of a heat-free die-cast aluminum alloy according to any one of claims 1 to 14 in the manufacture of automotive parts.

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