Al-mg-fe series as-cast high strength and toughness alloy and preparation method thereof

Abstract

The application belongs to the technical field of cast aluminum alloy, and discloses an Al-Mg-Fe series as-cast high-strength and high-toughness alloy and a preparation method thereof.The Al-Mg-Fe series as-cast high-strength and high-toughness alloy contains the following components in percentage by mass: Mg: 4.0%-5.0%, Fe: 1.2%-1.8%, trace elements: 0.2%-0.8%, Si: ≤0.1%, and the balance of Al; the trace elements include at least one of Zr, Cu, Zn, Mn and Cr.The application also discloses a preparation method of the Al-Mg-Fe series as-cast high-strength and high-toughness alloy.The application improves the mechanical properties of the alloy, the strength and the plasticity of the alloy in the as-cast state by adding trace elements to form a strengthening phase or improve the original alloy microstructure on the basis of the Al-Mg-Fe alloy.The method is simple and easy to implement, and the cost is low.The comprehensive performance of the prepared alloy can meet the demand of automobile structural parts.

Description

Technical Field

[0001] This invention belongs to the field of cast aluminum alloys and discloses an Al-Mg-Fe system as-cast high strength and toughness alloy and its preparation method. Background Technology

[0002] With the growing demand for lightweight automobiles and miniaturized 3C products, aluminum alloys, due to their advantages such as low density, high specific strength, and good corrosion resistance, have been widely used in the automotive and 3C consumer electronics industries. In the new energy vehicle industry, integrated die casting can achieve one-time molding of lightweight automotive structural parts, significantly simplifying processes, reducing overall costs, and improving production efficiency, precisely meeting the automotive industry's needs for large-scale mass production and lightweight, low-carbon development. However, traditionally cast aluminum alloys generally have low strength and require heat treatment processes such as solution treatment and aging to achieve the required mechanical properties. But the heat treatment process can easily lead to defects such as deformation, cracking, and porosity in the castings, affecting the product qualification rate.

[0003] To address the aforementioned issues, heat-treatable cast aluminum alloys have gradually become a research hotspot. Currently, heat-treatable cast aluminum alloys are mainly divided into two core series: Al-Si and Al-Mg. While Al-Si alloys offer superior casting performance, Al-Mg alloys, with their excellent ductility, toughness, and corrosion resistance, have become another type of heat-treatable aluminum alloy material attracting considerable attention in this field. Al-Mg alloys suffer from shortcomings in casting performance and machinability, which restricts their application in high-performance castings. Furthermore, the recycling of recycled aluminum resources is receiving increasing attention in current technologies. Recycled aluminum typically contains a certain amount of Fe impurities. How to rationally utilize the Fe element in recycled aluminum and avoid its detrimental effects on alloy properties has become a current research hotspot in the aluminum alloy industry.

[0004] Introducing Fe into Al-Mg alloys can induce the precipitation of fine eutectic Al6Fe phase. This phase not only improves the alloy's mechanical properties and casting fluidity but also enables the high-value utilization of Fe impurities inevitably introduced from recycled aluminum alloys, ultimately achieving the dual optimization goals of alloy performance enhancement and impurity element resource utilization. However, existing Al-Mg-Fe studies either fail to effectively control the morphology of the Fe phase, resulting in insufficient alloy toughness, or have unreasonable alloy composition ratios, leading to low alloy strength that cannot meet the requirements of high-performance components in the automotive and 3C industries. Therefore, improving the strength and plasticity of the alloy has become crucial for the current research and development of heat-free Al-Mg-Fe aluminum alloys. Summary of the Invention

[0005] To overcome the shortcomings and deficiencies of existing technologies, this invention improves the strength and plasticity of Al-Mg-Fe alloys in the as-cast state by precisely controlling the main alloy components, introducing micro-alloying to form strengthening phases, or improving the original alloy microstructure, so as to meet their application requirements in the automotive, communications, electronics, or aerospace fields.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An Al-Mg-Fe as-cast high-strength and high-toughness alloy, wherein the Al-Mg-Fe alloy is composed of the following by mass percentage: Mg: 4.0%~5.0%, Fe: 1.2%~1.8%, trace elements: 0.2%~0.8%, Si≤0.1%, and the balance being Al; wherein the trace elements include at least one of the following: Zr, Cu, Zn, Mn and Cr; when the trace elements include multiple elements, the content of each trace element is 0.2%~0.8%, and the total amount of trace elements added is ≤1.0%.

[0008] When trace elements include Zr, the Zr content is 0.2%~0.4%; when trace elements include Cu, the Cu content is 0.2%~0.8%; when trace elements include Zn, the Zn content is 0.2%~0.8%; when trace elements include Mn, the Mn content is 0.2%~0.5%; when trace elements include Cr, the Cr content is 0.2%~0.8%; when trace elements include multiple elements, the total amount of trace elements added is ≤1.0%.

[0009] The trace elements are preferably Cr or, more preferably, Cu and Zn.

[0010] When the trace element is Cr, the Cr content is preferably 0.4~0.8%.

[0011] When the trace elements are Cu and Zn, the Cu content is preferably 0.4% to 0.7% and the Zn content is 0.4% to 0.7%.

[0012] The preparation method of the Al-Mg-Fe system as-cast high-strength and high-toughness alloy includes the following steps:

[0013] S1. Pure aluminum, Al-Fe master alloy, and Al-trace element master alloy are mixed and completely melted to obtain the first melt; after cooling, pure magnesium blocks are added until completely melted, stirred evenly, and kept at a constant temperature to obtain the second melt; the Al-trace element master alloy is Al-Zr master alloy, Al-Cu master alloy, Al-Mn and / or Al-Cr master alloy; when the trace element contains Zn, pure zinc granules are added together with pure magnesium blocks until completely melted;

[0014] S2. The second melt is refined and slag removed, then cast to obtain an as-cast Al-Mg-Fe alloy casting.

[0015] The Al-Fe master alloy mentioned in step S1 is Al-20Fe master alloy, Al-Zr master alloy is Al-10Zr master alloy, Al-Cu master alloy is Al-50Cu master alloy, and Al-Mn master alloy is Al-10Mn master alloy.

[0016] The temperature at which the pure aluminum, Al-Fe master alloy and Al-trace element master alloy are completely melted in step S1 is 780℃-800℃.

[0017] In step S1, the temperature of the melt when adding magnesium blocks is 725~735℃, and the magnesium blocks and zinc granules are wrapped in aluminum foil when added. The stirring time is 2-5 minutes, and the standing and heat preservation time is 10-20 minutes.

[0018] The refining and slag removal in step S2 specifically involves adding a slag remover to the second melt using an argon gas blowing method. The slag remover is a mixture of commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1, with a total addition amount of 1% of the weight of the second melt. After refining and slag removal, the melt is allowed to stand for 2-10 minutes, and the melt temperature is controlled within the range of 720℃-740℃. Then, the floating slag on the surface of the alloy melt is removed.

[0019] The casting method described in step S2 is to keep the second melt after refining and slag removal at 720℃-740℃ and cast it into a metal mold preheated to 250℃-300℃.

[0020] principle:

[0021] Mg (Mg) mainly exists in the Al matrix in solid solution form, playing a role in solid solution strengthening. Its addition is limited to 4.0%–5.0%. A small amount of Al3Mg2 phase is formed in the later stages of alloy solidification, with minimal impact on the alloy's strength and corrosion resistance. Adding Fe (Fe) helps prevent sticking during die casting and forms fine Al6Fe eutectic phases, significantly improving the alloy's strength and toughness. The solidification range also decreases, enhancing the alloy's casting performance. However, as the Fe content increases, the formation of primary Al-Fe phases severely deteriorates the alloy's mechanical properties. Extensive experimentation has shown that controlling the Fe content at 1.2%–1.8% limits the formation of primary Al-Fe phases while simultaneously forming a large amount of Al6Fe eutectic, thus improving the alloy's mechanical properties.

[0022] The content of trace elements is controlled at 0.2%~0.8%. Zr plays a role in forming fine Al3Zr phase during the solidification process of aluminum alloy, which serves as a heterogeneous crystallization nucleus and promotes grain refinement. Cu and Zn elements work together with Mg elements in the alloy to form sufficient metal strengthening phase in the alloy, which improves the hardness and strength of the alloy. By controlling their addition amount, the size of the metal strengthening phase is improved, thereby improving the strength and toughness of the alloy. Mn and Cr elements improve the mechanical properties of Al-Mg-Fe alloy by controlling the morphology and volume fraction of eutectic Fe phase.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] (1) The present invention prepares an Al-Mg-Fe system as-cast high strength and toughness alloy. The high strength in the as-cast state mainly comes from the solid solution strengthening effect of Mg element and the strengthening effect of fine eutectic Al6Fe second phase, as well as the formation of strengthening phase by adding trace elements or improving the original alloy microstructure.

[0025] (2) This invention optimizes the composition ratio and Fe phase morphology of Al-Mg-Fe system cast alloys. By adjusting the content of Mg and Fe main elements, fine eutectic Al6Fe second phase is formed to strengthen the mechanical properties of the alloy. By adding trace elements, a strengthening phase is formed or the original alloy microstructure is improved.

[0026] (3) The cast aluminum alloy prepared by this invention exhibits excellent high strength and high toughness in the as-cast state, with a yield strength of up to 133 MPa and a tensile strength of up to 295 MPa, and an elongation of 22%. This alloy is compatible with a variety of casting processes (such as die casting) and has excellent recyclability. As a lightweight structural material, it can be applied on a large scale in the fields of new energy vehicles and aerospace. Attached Figure Description

[0027] Figure 1 Optical microstructure of the Al-4.5Mg-1.5Fe alloy prepared by conventional metal mold casting in Comparative Example 1;

[0028] Figure 2 Optical microstructure of the Al-4.5Mg-2.0Fe alloy prepared by conventional metal mold casting in Comparative Example 2;

[0029] Figure 3 Optical microstructure of the Al-6.0Mg-1.5Fe alloy prepared by conventional metal mold casting in Comparative Example 3;

[0030] Figure 4 The image shows the optical microstructure of the Al-4.5Mg-1.5Fe-0.3Zr alloy prepared by conventional metal mold casting in Example 1.

[0031] Figure 5 The image shows the optical microstructure of the Al-4.5Mg-1.5Fe-0.5Cu alloy prepared by conventional metal mold casting in Example 2.

[0032] Figure 6 The image shows the optical microstructure of the Al-4.5Mg-1.5Fe-0.5Zn alloy prepared by conventional metal mold casting in Example 3.

[0033] Figure 7 The image shows the optical microstructure of the Al-4.5Mg-1.5Fe-0.5Cu-0.5Zn alloy prepared by conventional metal mold casting in Example 4.

[0034] Figure 8 The image shows the optical microstructure of the Al-4.5Mg-1.5Fe-0.5Mn alloy prepared by conventional metal mold casting in Example 5.

[0035] Figure 9 The image shows the optical microstructure of the Al-4.5Mg-1.5Fe-0.5Cr alloy prepared by conventional metal mold casting in Example 6. Detailed Implementation

[0036] The present invention will be described in further detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0037] Comparative Example 1: Preparation of Al-4.5Mg-1.5Fe alloy (mass percentage content, Mg: 4.5%, Fe: 1.5%, as per the entire text):

[0038] The alloy prepared in this comparative example is an Al-4.5Mg-1.5Fe alloy, with the following mass percentage content: Mg: 4.5%, Fe: 1.5%, and the balance being Al. Pure aluminum, pure magnesium, and Al-20Fe master alloy were used as raw materials for batching and smelting to prepare the Al-4.5Mg-1.5Fe alloy melt, which was then cast into shape.

[0039] Specific steps:

[0040] (1) Alloy preparation: Based on the target composition Al-4.5Mg-1.5Fe alloy, calculate and weigh the pure aluminum, pure magnesium, and Al-20Fe alloy raw materials required to prepare the target alloy.

[0041] (2) Alloy smelting: The weighed pure aluminum and Al-20Fe master alloy raw materials are melted in the furnace at a melting temperature of 780℃. After all the materials are melted (the melting time is 60 min), pure Mg blocks wrapped in aluminum foil are added and stirred for 2 min to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 min to obtain the desired Al-4.5Mg-1.5Fe melt.

[0042] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag removal agent (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Let stand and keep warm for 2 minutes.

[0043] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-4.5Mg-1.5Fe alloy casting. Finally, samples are taken from the casting for analysis.

[0044] Comparative Example 2: Preparation of Al-4.5Mg-2.0Fe alloy

[0045] (1) Alloy preparation: Based on the target composition Al-4.5Mg-2.0Fe alloy (mass percentage content, Mg: 4.5%, Fe: 2.0%, balance Al), calculate and weigh the pure aluminum, pure magnesium, and Al-20Fe alloy raw materials required to prepare the target alloy.

[0046] (2) Alloy smelting: The weighed pure aluminum and Al-20Fe master alloy raw materials are melted in the furnace at a melting temperature of 780℃. After they are completely melted, the temperature is lowered to 730℃, pure Mg blocks wrapped in aluminum foil are added, and the mixture is stirred for 2 minutes to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 minutes to obtain the desired Al-4.5Mg-2.0Fe melt.

[0047] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag remover (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Keep it standing for 2 minutes.

[0048] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-4.5Mg-2.0Fe alloy casting. Finally, samples are taken from the casting for analysis.

[0049] Comparative Example 3: Preparation of Al-6.0Mg-1.5Fe alloy

[0050] (1) Alloy preparation: Based on the target composition Al-6.0Mg-1.5Fe alloy (mass percentage content, Mg: 6.0%, Fe: 1.5%, balance Al), calculate and weigh the pure aluminum, pure magnesium, and Al-20Fe alloy raw materials required to prepare the target alloy.

[0051] (2) Alloy smelting: The weighed pure aluminum and Al-20Fe master alloy raw materials are melted in a furnace at a melting temperature of 780℃. After they are completely melted, the temperature is lowered to 730℃, pure Mg blocks wrapped in aluminum foil are added, and the mixture is stirred for 2 minutes to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 minutes to obtain the required Al-6.0Mg-1.5Fe melt.

[0052] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag removal agent (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Let stand and keep warm for 2 minutes.

[0053] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-6.0Mg-1.5Fe alloy casting. Finally, samples are taken from the casting for analysis.

[0054] Example 1: Preparation of Al-4.5Mg-1.5Fe-0.3Zr alloy

[0055] (1) Alloy preparation: Based on the target composition Al-4.5Mg-1.5Fe-0.3Zr alloy (mass percentage content, Mg: 4.5%, Fe: 1.5%, Zr: 0.3%, balance Al), calculate and weigh the pure aluminum, pure magnesium, Al-20Fe, and Al-10Zr alloy raw materials required to prepare the target alloy.

[0056] (2) Alloy smelting: The weighed pure aluminum, Al-20Fe and Al-10Zr intermediate alloy raw materials are melted in a furnace at a melting temperature of 780℃. After they are completely melted, the temperature is lowered to 730℃. Pure Mg blocks wrapped in aluminum foil are added and stirred for 2 minutes to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 minutes to obtain the required Al-4.5Mg-1.5Fe-0.3Zr melt.

[0057] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag removal agent (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Let stand and keep warm for 2 minutes.

[0058] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-4.5Mg-1.5Fe-0.3Zr alloy casting. Finally, samples are taken from the casting for analysis.

[0059] Example 2: Preparation of Al-4.5Mg-1.5Fe-0.5Cu alloy

[0060] (1) Alloy preparation: Based on the target composition Al-4.5Mg-1.5Fe-0.5Cu alloy (mass percentage content, Mg: 4.5%, Fe: 1.5%, Cu: 0.5%, balance Al), calculate and weigh the pure aluminum, pure magnesium, Al-20Fe, and Al-50Cu alloy raw materials required to prepare the target alloy.

[0061] (2) Alloy smelting: The weighed pure aluminum, Al-20Fe and Al-50Cu intermediate alloy raw materials are melted in a furnace at a melting temperature of 780℃. After they are completely melted, the temperature is lowered to 730℃. Pure Mg blocks wrapped in aluminum foil are added and stirred for 2 minutes to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 minutes to obtain the desired Al-4.5Mg-1.5Fe-0.5Cu melt.

[0062] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag removal agent (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Let stand and keep warm for 2 minutes.

[0063] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-4.5Mg-1.5Fe-0.5Cu alloy casting. Finally, samples are taken from the casting for analysis.

[0064] Example 3: Preparation of Al-4.5Mg-1.5Fe-0.5Zn alloy

[0065] (1) Alloy preparation: Based on the target composition Al-4.5Mg-1.5Fe-0.5Zn alloy (mass percentage content, Mg: 4.5%, Fe: 1.5%, Zn: 0.5%, balance Al), calculate and weigh the pure aluminum, pure magnesium, pure zinc, and Al-20Fe alloy raw materials required to prepare the target alloy.

[0066] (2) Alloy smelting: The weighed pure aluminum and Al-20Fe master alloy raw materials are melted in a furnace at a melting temperature of 780℃. After they are completely melted, the temperature is lowered to 730℃. Pure Mg blocks and pure Zn particles wrapped in aluminum foil are added and stirred for 2 minutes to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 minutes to obtain the desired Al-4.5Mg-1.5Fe-0.5Zn melt.

[0067] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag removal agent (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Let stand and keep warm for 2 minutes.

[0068] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-4.5Mg-1.5Fe-0.5Zn alloy casting. Finally, samples are taken from the casting for analysis.

[0069] Example 4: Preparation of Al-4.5Mg-1.5Fe-0.5Cu-0.5Zn alloy

[0070] (1) Alloy preparation: Based on the target composition Al-4.5Mg-1.5Fe-0.5Cu-0.5Zn alloy (mass percentage content, Mg: 4.5%, Fe: 1.5%, Cu: 0.5%, Zn: 0.5%, balance Al), calculate and weigh the pure aluminum, pure magnesium, pure zinc, Al-20Fe, and Al-50Cu alloy raw materials required for preparing the target alloy.

[0071] (2) Alloy smelting: The weighed pure aluminum, Al-20Fe, and Al-50Cu intermediate alloy raw materials are melted in a furnace at a melting temperature of 780℃. After they are completely melted, the temperature is lowered to 730℃. Pure Mg blocks and pure Zn granules wrapped in aluminum foil are added and stirred for 2 minutes to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 minutes to obtain the desired Al-4.5Mg-1.5Fe-0.5Cu-0.5Zn melt.

[0072] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag removal agent (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Let stand and keep warm for 2 minutes.

[0073] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-4.5Mg-1.5Fe-0.5Cu-0.5Zn alloy casting. Finally, samples are taken from the casting for analysis.

[0074] Example 5: Preparation of Al-4.5Mg-1.5Fe-0.5Mn alloy

[0075] (1) Alloy preparation: Based on the target composition Al-4.5Mg-1.5Fe-0.5Mn alloy (mass percentage content, Mg: 4.5%, Fe: 1.5%, Mn: 0.5%, balance Al), calculate and weigh the pure aluminum, pure magnesium, Al-20Fe, and Al-10Mn alloy raw materials required to prepare the target alloy.

[0076] (2) Alloy smelting: The weighed pure aluminum, Al-20Fe and Al-10Mn intermediate alloy raw materials are melted in a furnace at a melting temperature of 780℃. After they are completely melted, the temperature is lowered to 730℃. Pure Mg blocks wrapped in aluminum foil are added and stirred for 2 minutes to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 minutes to obtain the required Al-4.5Mg-1.5Fe-0.5Mn melt.

[0077] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag removal agent (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Let stand and keep warm for 2 minutes.

[0078] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-4.5Mg-1.5Fe-0.5Mn alloy casting. Finally, samples are taken from the casting for analysis.

[0079] Example 6: Preparation of Al-4.5Mg-1.5Fe-0.5Cr alloy

[0080] (1) Alloy preparation: Based on the target composition Al-4.5Mg-1.5Fe-0.5Cr alloy (mass percentage content, Mg: 4.5%, Fe: 1.5%, Cr: 0.5%, balance Al), calculate and weigh the pure aluminum, pure magnesium, Al-20Fe, and Al-10Cr alloy raw materials required to prepare the target alloy.

[0081] (2) Alloy smelting: The weighed pure aluminum, Al-20Fe and Al-10Cr intermediate alloy raw materials are melted in a furnace at a melting temperature of 780℃. After they are completely melted, the temperature is lowered to 730℃. Pure Mg blocks wrapped in aluminum foil are added and stirred for 2 minutes to make the composition uniform. Then, a sodium-free covering agent is added and the mixture is kept at a constant temperature for 10 minutes to obtain the required Al-4.5Mg-1.5Fe-0.5Cr melt.

[0082] (3) Refining and slag removal of melt: Remove the floating slag from the surface of the alloy melt after melting in step (2), control the melt temperature in the range of 720℃~740℃, add slag removal agent (commercially available YT-J-1 refining agent and YT-D-4 refining agent) by argon gas blowing method to refine and remove slag. The ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent is 1:1, and the total amount added is 1% of the melt weight. Let stand and keep warm for 2 minutes.

[0083] (4) Melt casting: The temperature of the melt in step (3) is controlled at 720°C, and then it is cast into a metal mold preheated to 250°C to obtain an Al-4.5Mg-1.5Fe-0.5Cr alloy casting. Finally, samples are taken from the casting for analysis.

[0084] Performance testing:

[0085] Tensile tests were conducted on the alloy castings of Comparative Examples 1-3 and Examples 1-6 according to the methods listed in the national standard GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature". The specific results are shown in Table 1 below:

[0086] Table 1 Performance Test Data

[0087]

[0088] Furthermore, the optical microstructure images of the alloy castings of Comparative Examples 1-3 and Examples 1-6 are shown below. Figure 1-9 As shown;

[0089] Figure 1 The metallographic microstructure of the Al-4.5Mg-1.5Fe alloy prepared for Comparative Example 1 is shown. This alloy does not contain any trace elements, and the contents of Mg and Fe are within the limited range. The second phase is mainly fine rod-shaped and granular eutectic Al6Fe, with a small amount of Al3Mg2 phase. These fine second phases are beneficial to improving the strength and toughness of the alloy.

[0090] Figure 2 The metallographic structure of the Al-4.5Mg-2.0Fe alloy prepared for Comparative Example 2 is compared with that of Comparative Example 1 ( Figure 1 Compared to other alloys, when the Fe content exceeds the limit, a primary Al3Fe phase is formed, the eutectic Al6Fe morphology transformation layer is fine needle-like, and the primary Al3Fe phase is coarse needle-like. These will severely rupture the Al matrix, causing stress concentration and forming crack initiation; reducing the strength and toughness of the alloy.

[0091] Figure 3 The metallographic structure of the Al-6.0Mg-1.5Fe alloy prepared in Comparative Example 3 is compared with that of Comparative Example 1 ( Figure 1 In contrast, when the Mg content exceeds the limit, a large amount of Al3Mg2 phase is generated, and the morphology of the eutectic Al6Fe changes to coarse needle-like, which will seriously deteriorate the mechanical properties of the alloy.

[0092] Figure 4 The metallographic structure of the Al-4.5Mg-1.5Fe-0.3Zr alloy prepared in Example 1 is compared with that of Comparative Example 1 ( Figure 1 Compared to the eutectic Al6Fe phase, the eutectic phase did not change significantly, appearing as fine rod-shaped or granular. Meanwhile, Zr played a role in refining the grains, further improving the mechanical properties of the alloy.

[0093] Figure 5 The metallographic structure of the Al-4.5Mg-1.5Fe-0.5Cu alloy prepared in Example 2 is compared with that of Comparative Example 1 ( Figure 1 Compared to the Al₂Fe₃, the eutectic Al₆Fe phase did not change significantly, appearing as fine rod-shaped or granular structures. Meanwhile, the formation of fine blocky and worm-like S-Al₂CuMg phases and the partial solid dissolution of Cu elements in the Al matrix improved the strength and toughness of the alloy.

[0094] Figure 6 The metallographic structure of the Al-4.5Mg-1.5Fe-0.5Zn alloy prepared in Example 3 is compared with that of Comparative Example 1 ( Figure 1Compared to the Al6Fe phase, the eutectic Al6Fe phase did not change significantly, appearing as fine rod-shaped and granular structures. At the same time, the formation of fine blocky and granular T-AlZnMg phases and the partial dissolution of Zn elements in the Al matrix improved the strength and toughness of the alloy.

[0095] Figure 7 The metallographic structure of the Al-4.5Mg-1.5Fe-0.5Cu-0.5Zn alloy prepared in Example 4 is compared with that of Comparative Example 1 ( Figure 1 Compared to the Al6Fe phase, the eutectic phase did not change significantly, appearing as fine rod-shaped and granular structures. Meanwhile, the formation of fine blocky and worm-like T-AlZnMgCu phases and the solid dissolution of some Cu and Zn elements in the Al matrix improved the strength and toughness of the alloy.

[0096] Figure 8 The metallographic structure of the Al-4.5Mg-1.5Fe-0.5Mn alloy prepared in Example 5 is compared with that of Comparative Example 1 ( Figure 1 Compared to the previous method, the eutectic second phase increases, transforming from fine rod-shaped and granular eutectic Al6Fe phase to fine blocky and granular eutectic Al6(Mn,Fe) phase. At the same time, some Mn elements are dissolved in the Al matrix, improving the strength and toughness of the alloy.

[0097] Figure 9 The metallographic structure of the Al-4.5Mg-1.5Fe-0.5Cr alloy prepared in Example 6 is compared with that of Comparative Example 1 ( Figure 1 Compared to the previous method, the eutectic second phase increases, transforming from fine rod-shaped and granular eutectic Al6Fe phase to fine blocky and granular eutectic Al6(Cr,Fe) phase. At the same time, fine blocky Al7Cr is generated, and some Cr elements are dissolved in the Al matrix, which greatly improves the strength and toughness of the alloy.

[0098] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An Al-Mg-Fe as-cast high-strength and high-toughness alloy, characterized in that: It contains the following components by mass percentage: Mg: 4.0%~5.0%, Fe: 1.2%~1.8%, trace elements: 0.2%~0.8%, Si≤0.1%, and the balance is Al; wherein the trace elements include at least one of the following: Zr, Cu, Zn, Mn and Cr; when the trace elements include multiple elements, the content of each trace element is 0.2%~0.8%, and the total amount of trace elements added is ≤1.0%.

2. The Al-Mg-Fe as-cast high-strength and high-toughness alloy according to claim 1, characterized in that: When trace elements include Zr, the Zr content is 0.2%~0.4%; when trace elements include Cu, the Cu content is 0.2%~0.8%; when trace elements include Zn, the Zn content is 0.2%~0.8%; when trace elements include Mn, the Mn content is 0.2%~0.5%; when trace elements include Cr, the Cr content is 0.2%~0.8%; when trace elements include multiple elements, the total amount of trace elements added is ≤1.0%.

3. The Al-Mg-Fe as-cast high-strength and high-toughness alloy according to claim 2, characterized in that: The trace element is Cr or a mixture of Cu and Zn; When the trace element is Cr, the Cr content is 0.4%~0.8%; When the trace elements are Cu and Zn, the content of Cu is 0.4%~0.7% and the content of Zn is 0.4%~0.7%.

4. The method for preparing the Al-Mg-Fe system as-cast high-strength and high-toughness alloy according to any one of claims 1 to 3, characterized in that: Includes the following steps: S1. Pure aluminum, Al-Fe master alloy, and Al-trace element master alloy are mixed and completely melted to obtain the first melt; after cooling, pure magnesium blocks are added until completely melted, stirred evenly, and kept at a constant temperature to obtain the second melt; the Al-trace element master alloy is Al-Zr master alloy, Al-Cu master alloy, Al-Mn master alloy, and / or Al-Cr master alloy; when the trace element contains Zn, pure zinc granules are added together with pure magnesium blocks until completely melted; S2. The second melt is refined and slag removed, then cast to obtain an as-cast Al-Mg-Fe alloy casting.

5. The method for preparing the Al-Mg-Fe system as-cast high-strength and high-toughness alloy according to claim 4, characterized in that: The Al-Fe master alloy mentioned in step S1 is Al-20Fe master alloy, Al-Zr master alloy is Al-10Zr master alloy, Al-Cu master alloy is Al-50Cu master alloy, and Al-Mn master alloy is Al-10Mn master alloy. The temperature at which the pure aluminum, Al-Fe master alloy and Al-trace element master alloy are completely melted in step S1 is 780℃-800℃.

6. The method for preparing the Al-Mg-Fe system as-cast high-strength and high-toughness alloy according to claim 4, characterized in that: In step S1, the temperature of the melt when adding magnesium blocks is 725~735℃, and the magnesium blocks or magnesium blocks and zinc granules are wrapped in aluminum foil when added; the stirring time is 2-5 minutes, and the standing and heat preservation time is 10-20 minutes.

7. The method for preparing the Al-Mg-Fe system as-cast high-strength and high-toughness alloy according to claim 4, characterized in that: The refining and slag removal in step S2 specifically involves adding a slag remover to the second melt using an argon gas blowing method. The slag remover is a mixture of commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1, with a total addition amount of 1% of the weight of the second melt. After refining and slag removal, the melt is allowed to stand for 2-10 minutes, and the melt temperature is controlled within the range of 720℃-740℃. Then, the floating slag on the surface of the alloy melt is removed.

8. The method for preparing the Al-Mg-Fe system as-cast high-strength and high-toughness alloy according to claim 4, characterized in that: The casting method described in step S2 is to keep the second melt after refining and slag removal at 720℃-740℃ and cast it into a metal mold preheated to 250℃-300℃.

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