Die-casting Mg-Al-Zn-RE alloy material as well as preparation method and application thereof

Abstract

The invention provides a die-casting Mg-Al-Zn-RE alloy material as well as a preparation method and application thereof, and belongs to the technical field of alloy materials. According to the die-casting magnesium alloy and the preparation method thereof, the flowability of the die-casting magnesium alloy can be improved by adding the Al element, an Al11Ce3 phase, an Al2Ce phase and a (Al, Mg) 2Ce phase can be separated out at the grain boundary while grains are refined by Ce, and the yield strength of the alloy is improved; zn and Mn can respectively form an Al2CeZn2 precipitated phase and an Al10Ce2Mn7 precipitated phase with Al and Ce, so that the yield strength of the alloy material is improved; and the trace Sb and Sr can obviously refine the crystal grains of the alloy material, so that the mechanical property of the alloy material is improved. The result of the embodiment shows that the tensile strength of the die-casting Mg-Al-Zn-RE alloy material at the room temperature is 270-300 MPa, the yield strength of the die-casting Mg-Al-Zn-RE alloy material at the room temperature is 180-200 MPa, and the ductility of the die-casting Mg-Al-Zn-RE alloy material at

Description

Technical Field

[0001] The present invention relates to the technical field of alloy materials, and in particular to a die-cast Mg-Al-Zn-RE alloy material, a preparation method thereof, and an application thereof. Background Art

[0002] Magnesium alloy is the lightest metal structural material, with a density only 2 / 3 of that of aluminum alloy and 1 / 4 of that of steel. It is one of the most potential lightweight metal materials. Its large-scale application has very important strategic significance for energy conservation and emission reduction, alleviating the shortage of China's metal mineral resources, etc. The demand for lightweighting of traditional automobiles and new energy vehicles is extremely urgent, and magnesium alloy has great application potential in automobile lightweighting. With the upgrading of materials and process equipment, small and medium-sized magnesium alloy parts are gradually transforming into large and extra-large ones, and many key automobile magnesium alloy components are developing in the directions of "extra-large size", "structural integration" and "functional integration". The lightweighting effect of integrated extra-large magnesium alloy components will be more significant. The integrated forming technology of extra-large magnesium alloy castings can greatly simplify the complex processes of the original multi-component production and multi-component connection, and greatly improve the dimensional stability of components. It not only saves time cost and production manufacturing cost, but also reduces production line cost and labor cost, and the energy conservation and emission reduction benefits are more obvious, which has become an important development trend in the future. In June 2022, the currently world's largest tonnage HDC8800-ton die-casting machine jointly developed by Meridian Technology and Haitian Metal was successfully mass-produced for large automobile aluminum alloy rear floor components. In June 2023, Chongqing University, Meridian Technology and Chongqing Boao successfully trial-produced two types of integrated extra-large magnesium alloy die-castings, and the projected areas are both larger than 2.2m 2 。

[0003] The application potential of integrated die-cast magnesium alloy components in the automobile industry is huge. However, with the development of technology, the mechanical properties requirements for integrated die-cast magnesium alloy components are getting higher and higher. At present, the mechanical properties of the obtained integrated die-cast magnesium alloy components are average and it has been difficult to meet the technical requirements. Therefore, how to improve the mechanical properties of integrated die-cast magnesium alloy components has become an urgent technical problem in this field. Summary of the Invention

[0004] The purpose of the present invention is to provide a die-cast Mg-Al-Zn-RE alloy material, a preparation method thereof, and an application thereof. The die-cast Mg-Al-Zn-RE alloy material provided by the present invention has excellent mechanical properties, can strictly meet the requirements of automobiles for components, and is free of heat treatment, thus replacing some die-cast aluminum alloy products.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a die-cast Mg-Al-Zn-RE alloy material, which comprises the following chemical components by mass percentage: Al: 8.0-8.5%, Ce: 1.0-1.6%, Zn: 0.5-0.9%, Mn: 0.21-0.28%, Sb: 0.18-0.36%, Sr: 0.06-0.12% and the balance of Mg; wherein, the mass ratio of Sb to Sr is (2-4):1.

[0007] Preferably, by mass percentage, the die-cast Mg-Al-Zn-RE alloy material comprises the following chemical components: Al: 8.3-8.5%, Ce: 1.0-1.3%, Zn: 0.6-0.8%, Mn: 0.21-0.25%, Sb: 0.18-0.32%, Sr: 0.06-0.08% and the balance of Mg.

[0008] Preferably, by mass percentage, the die-cast Mg-Al-Zn-RE alloy material comprises the following chemical components: Al: 8.3%, Ce: 1.19%, Zn: 0.74%, Mn: 0.21%, Sb: 0.18%, Sr: 0.06% and the balance of Mg.

[0009] Preferably, the mass ratio of Sb to Sr is 3:1.

[0010] The present invention provides a preparation method of the die-cast Mg-Al-Zn-RE alloy material described in the above technical solution, which comprises the following steps:

[0011] (1) Melting alloy raw materials to obtain an alloy melt;

[0012] (2) Die-casting the alloy melt obtained in the step (1) to obtain a die-cast Mg-Al-Zn-RE alloy material.

[0013] Preferably, in the step (1), the alloy raw materials include pure magnesium ingots, pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy and Mg-Sr master alloy.

[0014] Preferably, the melting in the step (1) comprises the following steps:

[0015] 1) Preheating a melting furnace to obtain a preheated melting furnace;

[0016] 2) Coating a release agent on the inner wall of a low-carbon steel crucible, and then drying the low-carbon steel crucible to obtain a dried low-carbon steel crucible;

[0017] 3) Place the pure magnesium ingot into the dried low-carbon steel crucible obtained in step 2), and then place the dried low-carbon steel crucible into the preheated melting furnace obtained in step 1). Under a protective atmosphere, heat up to 750 - 780 °C. After the pure magnesium ingot melts, successively add pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy, and Mg-Sr master alloy. After the alloy raw materials are completely melted, remove the surface scum to obtain a preliminary alloy melt;

[0018] 4) Add a refining agent to the preliminary alloy melt obtained in step 3) for refining, and then perform slagging treatment to obtain an alloy melt;

[0019] There is no sequence relationship between step 1) and step 2).

[0020] Preferably, the protective atmosphere in step 3) is a mixed gas of CO2 and SF6; the volume ratio of CO2 to SF6 is 100:(0.5 - 2).

[0021] Preferably, the die-casting temperature in step (2) is 720 - 740 °C, and die-casting is carried out using a 650T die-casting machine.

[0022] The present invention provides the application of the die-cast Mg-Al-Zn-RE alloy material described in the above technical solution or the die-cast Mg-Al-Zn-RE alloy material prepared by the preparation method described in the above technical solution in the fields of automobiles, aerospace, and national defense and military industry.

[0023] The present invention provides a die-cast Mg-Al-Zn-RE alloy material, which, by mass percentage, includes the following chemical components: Al: 8.0 - 8.5%, Ce: 1.0 - 1.6%, Zn: 0.5 - 0.9%, Mn: 0.21 - 0.28%, Sb: 0.18 - 0.36%, Sr: 0.06 - 0.12%, and the balance is Mg; wherein, the mass ratio of Sb to Sr is (2 - 4):1. In the present invention, the addition of Al element can improve the fluidity of the die-cast magnesium alloy, and the addition of Ce element can precipitate Al 11 Ce3 phase, Al2Ce, and (Al,Mg)2Ce phases at the grain boundaries while refining the grains, thereby further improving the yield strength of the alloy material; the addition of Zn element and Mn element can respectively form Al2CeZn2 and Al 10The Ce2Mn7 precipitated phase can also significantly improve the yield strength of the alloy material; the addition of trace amounts of Sb and Sr elements can significantly refine the grains of the alloy material, thereby further improving the comprehensive mechanical properties of the alloy material. The results of the examples show that the die-cast Mg-Al-Zn-RE alloy material provided by the present invention has a tensile strength of 270-300 MPa, a yield strength of 180-200 MPa, and an elongation of 9-14% at room temperature, and has good application prospects in the fields of automobiles, aerospace, and national defense industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the stress-strain curve of the die-cast Mg-Al-Zn-RE alloy material obtained in Example 1 of the present invention;

[0025] Figure 2 is the stress-strain curve of the die-cast Mg-Al-Zn-RE alloy material obtained in Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention provides a die-cast Mg-Al-Zn-RE alloy material, which includes the following chemical components by mass percentage: Al: 8.0-8.5%, Ce: 1.0-1.6%, Zn: 0.5-0.9%, Mn: 0.21-0.28%, Sb: 0.18-0.36%, Sr: 0.06-0.12%, and the balance of Mg; wherein, the mass ratio of Sb to Sr is (2-4):1.

[0027] By mass percentage, the die-cast Mg-Al-Zn-RE alloy material provided by the present invention includes Al: 8.0-8.5%. As an embodiment of the present invention, the mass percentage of Al in the die-cast Mg-Al-Zn-RE alloy material can be 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, or 8.5%. In the present invention, the Al element is one of the matrix elements of the alloy material and can improve the fluidity of the die-cast magnesium alloy.

[0028] By mass percentage, the die-cast Mg-Al-Zn-RE alloy material provided by the present invention includes Ce: 1.0-1.6%. As an embodiment of the present invention, the mass percentage of Ce in the die-cast Mg-Al-Zn-RE alloy material can be 1.0%, 1.05%, 1.1%, 1.15%, 1.19%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, or 1.6%. In the present invention, the addition of the Ce element can precipitate Al 11 Ce3 phase, Al2Ce, and (Al,Mg)2Ce phases at the grain boundaries while refining the grains, thereby further improving the yield strength of the alloy material.

[0029] By mass percentage, the die-casting Mg-Al-Zn-RE alloy material provided by the present invention includes Zn: 0.5-0.9%. As an embodiment of the present invention, the mass percentage of Zn in the die-casting Mg-Al-Zn-RE alloy material can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.74%, 0.8%, 0.85% or 0.9%.

[0030] By mass percentage, the die-casting Mg-Al-Zn-RE alloy material provided by the present invention includes Mn: 0.21-0.28%. As an embodiment of the present invention, the mass percentage of Mn in the die-casting Mg-Al-Zn-RE alloy material can be 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27% or 0.28%.

[0031] In the present invention, the addition of Zn element and Mn element can respectively form Al2CeZn2 and Al 10 Ce2Mn7 precipitation phases with Al and Ce, and can also significantly improve the yield strength of the alloy material.

[0032] By mass percentage, the die-casting Mg-Al-Zn-RE alloy material provided by the present invention includes Sb: 0.06-0.36%. As an embodiment of the present invention, the mass percentage of Sb in the die-casting Mg-Al-Zn-RE alloy material can be 0.18%, 0.20%, 0.22%, 0.24%, 0.26%, 0.28%, 0.30%, 0.32%, 0.34% or 0.36%.

[0033] By mass percentage, the die-casting Mg-Al-Zn-RE alloy material provided by the present invention includes Sr: 0.06-0.12%. As an embodiment of the present invention, the mass percentage of Sr in the die-casting Mg-Al-Zn-RE alloy material can be 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11% or 0.12%.

[0034] In the present invention, the mass ratio of Sb to Sr is (2-4):1. As an embodiment of the present invention, the mass ratio of Sb to Sr can be 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 3.9:1 or 4.0:1.

[0035] In the present invention, the addition of trace amounts of Sb and Sr elements and the control of their dosage relationship can significantly refine the grains of the alloy material, thereby further improving the comprehensive mechanical properties of the alloy material; when the mass ratio of Sb to Sr is in the range of (2 to 4):1, compared with other ranges, the mechanical properties of the die-cast Mg-Al-Zn-RE alloy material obtained are better.

[0036] By mass percentage, the die-cast Mg-Al-Zn-RE alloy material provided by the present invention includes the balance of Mg. In the present invention, the Mg element is the matrix material of the alloy material.

[0037] By mass percentage, the die-cast Mg-Al-Zn-RE alloy material provided by the present invention preferably further includes impurities. In the present invention, the mass percentage of the impurities is preferably ≤0.01%. The present invention does not have special limitations on the types of the impurities, which are inevitable impurities well-known to those skilled in the art when preparing alloy materials.

[0038] In the present invention, the addition of the Al element can improve the fluidity of the die-cast magnesium alloy, and the addition of the Ce element can precipitate Al 11 Ce3 phase, Al2Ce and (Al,Mg)2Ce phases at the grain boundaries while refining the grains, thereby further improving the yield strength of the alloy material; the addition of the Zn element and the Mn element can respectively form Al2CeZn2 and Al 10 Ce2Mn7 precipitation phases with Al and Ce, which can also significantly improve the yield strength of the alloy material; the addition of trace amounts of Sb and Sr elements can significantly refine the grains of the alloy material, thereby further improving the comprehensive mechanical properties of the alloy material.

[0039] The present invention also provides a preparation method of the die-cast Mg-Al-Zn-RE alloy material according to the above technical solution, including the following steps:

[0040] (1) Melting alloy raw materials to obtain an alloy melt;

[0041] (2) Die-casting the alloy melt obtained in the step (1) to obtain a die-cast Mg-Al-Zn-RE alloy material.

[0042] The present invention melts alloy raw materials to obtain an alloy melt.

[0043] In the present invention, the alloy raw materials preferably include pure magnesium ingots, pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy and Mg-Sr master alloy. The present invention does not have special limitations on the specific dosages of the alloy raw materials, which are determined according to the common technical knowledge of those skilled in the art and can ensure that the chemical composition of the obtained die-cast Mg-Al-Zn-RE alloy material meets the requirements.

[0044] In the present invention, the alloy raw materials are preferably polished and dried before melting. In the present invention, the polishing method is preferably to use a grinding wheel grinder to remove the oxide layer on the surface of the alloy raw materials. The temperature of the drying treatment is preferably 200 - 300 °C; the time of the drying treatment is preferably 20 - 60 min; the drying is preferably carried out in a drying oven. As an embodiment of the present invention, the temperature of the drying treatment can be 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C or 300 °C; the time of the drying treatment can be 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min. By the polishing and drying treatment, the present invention can remove the oxides and moisture on the surface of the alloy raw materials.

[0045] In the present invention, the melting preferably includes the following steps:

[0046] 1) Preheat the melting furnace to obtain a preheated melting furnace;

[0047] 2) Coat the inner wall of the low-carbon steel crucible with a release agent, and then dry the low-carbon steel crucible to obtain a dried low-carbon steel crucible;

[0048] 3) Put the pure magnesium ingot into the dried low-carbon steel crucible obtained in step 2), and then put the dried low-carbon steel crucible into the preheated melting furnace obtained in step 1). Under a protective atmosphere, heat up to 750 - 780 °C. After the pure magnesium ingot melts, sequentially add pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy and Mg-Sr master alloy. After the alloy raw materials are completely melted, remove the surface scum to obtain a preliminary alloy melt;

[0049] 4) Add a refining agent to the preliminary alloy melt obtained in step 3) for refining, and then perform slagging treatment to obtain an alloy melt;

[0050] Steps 1) and 2) have no sequence relationship.

[0051] The present invention preferably preheats the melting furnace to obtain a preheated melting furnace.

[0052] The present invention has no special limitation on the specific model and source of the melting furnace, and a commercially available melting furnace well-known to those skilled in the art can be used.

[0053] In the present invention, the preheating temperature is preferably 480 - 520 °C, more preferably 500 °C; the preheating time is preferably 40 - 80 min, more preferably 60 min. Through preheating in the present invention, subsequent smelting is facilitated.

[0054] In the present invention, the mold release agent is preferably applied to the inner wall of the low-carbon steel crucible, and then the low-carbon steel crucible is dried to obtain a dried low-carbon steel crucible.

[0055] In the present invention, the mold release agent is preferably composed of boron nitride and alcohol mixed in a mass ratio of 1:2. In the present invention, the method of applying the mold release agent is preferably uniform application using a brush. The present invention has no special limitation on the coating amount of the mold release agent, which can be determined according to the common technical knowledge of those skilled in the art. By applying the mold release agent in the present invention, subsequent demolding is facilitated.

[0056] The present invention has no special limitation on the specific operation of the drying, which can be determined according to the common technical knowledge of those skilled in the art as long as the mold release agent can be dried.

[0057] After obtaining the preheated smelting furnace and the dried low-carbon steel crucible, in the present invention, pure magnesium ingots are preferably put into the dried low-carbon steel crucible, and then the dried low-carbon steel crucible is put into the preheated smelting furnace. Under a protective atmosphere, the temperature is raised to 750 - 780 °C. After the pure magnesium ingots are melted, pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy, and Mg-Sr master alloy are added in sequence. After the alloy raw materials are completely melted, the surface scum is removed to obtain a preliminary alloy melt.

[0058] In the present invention, the protective atmosphere is preferably a mixed gas of CO2 and SF6; the volume ratio of CO2 to SF6 is preferably 100:(0.5 - 2), more preferably 100:(1 - 1.5). By carrying out smelting in a protective atmosphere in the present invention, oxidation of the metal can be avoided.

[0059] In the present invention, the method of removing the surface scum is preferably to use a long-handled low-carbon steel ladle coated with the mold release agent to remove the surface scum. In the present invention, the mold release agent is preferably the same as the aforementioned mold release agent, which will not be elaborated here. By removing the surface scum in the present invention, impurities can be reduced.

[0060] After obtaining the preliminary alloy melt, in the present invention, a refining agent is preferably added to the preliminary alloy melt for refining, and then slagging treatment is carried out to obtain an alloy melt.

[0061] In the present invention, the refining agent is preferably the No. 5 refining agent; the dosage of the refining agent is preferably 2% of the total mass of the preliminary alloy melt; the refining agent is preferably subjected to a drying treatment; the drying treatment is preferably drying in a pit furnace at 250 °C for 30 min. By adding the refining agent, the present invention can remove oxides in the alloy melt and further reduce the content of impurities.

[0062] In the present invention, the adding method of the refining agent is preferably to send the refining agent to the bottom of the preliminary alloy melt with a long-handled low-carbon steel spoon, stir it up and down for 2 - 3 min, and then rotate and stir for 3 - 5 min. By the above adding method, the present invention can ensure that the refining agent is evenly mixed.

[0063] In the present invention, the refining temperature is preferably 740 - 750 °C.

[0064] The present invention has no special limitation on the specific operation of the slag skimming treatment, which can be determined according to the common technical knowledge of those skilled in the art.

[0065] After obtaining the alloy melt, the present invention performs die casting on the alloy melt to obtain a die-cast Mg-Al-Zn-RE alloy material.

[0066] In the present invention, the temperature of the die during die casting is preferably 180 - 250 °C, more preferably 200 - 220 °C. By increasing the temperature of the die, the present invention avoids too fast a cooling rate of the alloy melt during die casting.

[0067] In the present invention, the die casting temperature is preferably 720 - 740 °C; the die casting is preferably carried out using a 650T die casting machine. By high-pressure die casting, the present invention can directly obtain an integrally die-cast super-large component with excellent performance.

[0068] The preparation method provided by the present invention is simple. By high-pressure die casting, an integrally die-cast super-large component with excellent performance can be directly obtained, and the obtained super-large component has excellent mechanical properties, having good application prospects in the fields of automobiles, aerospace, and national defense industry, etc.

[0069] The present invention also provides the application of the die-cast Mg-Al-Zn-RE alloy material described in the above technical solution or the die-cast Mg-Al-Zn-RE alloy material prepared by the preparation method described in the above technical solution in the fields of automobiles, aerospace, and national defense industry.

[0070] The present invention has no special limitation on the specific manner of the application, which can be determined according to the common technical knowledge of those skilled in the art.

[0071] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0072] Embodiment 1

[0073] A die-casting Mg-Al-Zn-RE alloy material, by mass percentage, has a chemical composition of: Al: 8.3%, Ce: 1.19%, Zn: 0.74%, Mn: 0.21%, Sb: 0.18%, Sr: 0.06% and the balance of Mg; the mass ratio of the Sb and Sr is 3:1;

[0074] The preparation method of the die-casting Mg-Al-Zn-RE alloy material comprises the following steps:

[0075] (1) Use a grinding wheel grinder to remove the oxide layer on the surface of the alloy raw materials, then dry them in a drying oven at 250 °C for 30 min, and then carry out melting to obtain an alloy melt;

[0076] (2) Let the alloy melt obtained in step (1) stand for 30 min at 740 °C, and then use a 650T die-casting machine to carry out die-casting on the alloy melt to obtain a die-casting Mg-Al-Zn-RE alloy material, and the shape of the die-casting Mg-Al-Zn-RE alloy material is rod-shaped; the temperature of the die during die-casting is 200 °C;

[0077] The melting in step (1) comprises the following steps:

[0078] 1) Preheat the melting furnace at 500 °C for 60 min to obtain a preheated melting furnace;

[0079] 2) Mix boron nitride and alcohol in a mass ratio of 1:2 to form a release agent, evenly apply the release agent on the inner wall of a low-carbon steel crucible with a brush, and then dry the low-carbon steel crucible to obtain a dried low-carbon steel crucible;

[0080] 3) Put pure magnesium ingots into the dried low-carbon steel crucible obtained in step 2), and then put the dried low-carbon steel crucible into the preheated melting furnace obtained in step 1). Under a protective atmosphere, heat up to 780 °C. After the pure magnesium ingots are melted, sequentially add pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy and Mg-Sr master alloy. After the alloy raw materials are completely melted, use a long-handled low-carbon steel spoon coated with a release agent to remove the surface scum to obtain a preliminary alloy melt; the protective atmosphere is a mixed gas of CO2 and SF6, and the volume ratio of CO2 and SF6 is 100:1;

[0081] 4) Control the temperature of the preliminary alloy melt at 750 °C, add a refining agent to the preliminary alloy melt obtained in step 3) for refining, and then perform slag removal treatment to obtain an alloy melt; the refining agent is No. 5 refining agent; the dosage of the refining agent is 2% of the total mass of the preliminary alloy melt; the refining agent is dried in a pit furnace at 250 °C for 30 min; the adding method of the refining agent is to send the refining agent to the bottom of the preliminary alloy melt with a long-handled low-carbon steel spoon, stir it up and down for 2 min, and then rotate and stir for 3 min.

[0082] Perform a room-temperature mechanical tensile test on the die-cast Mg-Al-Zn-RE alloy material obtained in Example 1. The test method is as follows: Two groups (denoted as 1# and 2# respectively) of the die-cast Mg-Al-Zn-RE alloy materials obtained in Example 1 are processed into standard room-temperature tensile specimens according to the national standard GB / T228.1-2021 and stretched on a room-temperature tensile testing machine CMT-5105. Tensile conditions: Polish the surface of the die-cast Mg-Al-Zn-RE alloy material specimen brightly with sandpaper and stretch it at a rate of 3.6 mm / min. The stress-strain curve obtained is as Figure 1 shown, and the mechanical property results are shown in Table 1:

[0083] Table 1 Mechanical properties of the die-cast Mg-Al-Zn-RE alloy material obtained in Example 1

[0084] Tensile strength / MPa Yield strength / MPa Elongation / % 1# 297 196 11.6 2# 285 187 10.4

[0085] From Figure 1 and Table 1, it can be seen that under room-temperature conditions, the room-temperature tensile strength and yield strength of the die-cast Mg-Al-Zn-RE alloy material obtained in Example 1 are at a relatively high level; the yield strength of the rod-shaped die-cast Mg-Al-Zn-RE alloy material is as high as 196 MPa, the tensile strength reaches 297 MPa, and the elongation is 11.6%.

[0086] Example 2

[0087] A die-cast Mg-Al-Zn-RE alloy material, by mass percentage, the chemical composition is: Al: 8.3%, Ce: 1.19%, Zn: 0.74%, Mn: 0.21%, Sb: 0.18%, Sr: 0.06% and the balance of Mg; the mass ratio of the said Sb and Sr is 3:1;

[0088] The preparation method of the die-cast Mg-Al-Zn-RE alloy material is the following steps:

[0089] (1) Use a grinding wheel grinder to remove the oxide layer on the surface of the alloy raw materials, then dry them in a drying oven at 250 °C for 30 min, and then carry out melting to obtain an alloy melt;

[0090] (2) Let the alloy melt obtained in step (1) stand for 30 min at 740 °C, and then use a 650T die-casting machine to carry out die-casting on the alloy melt to obtain a die-cast Mg-Al-Zn-RE alloy material. The shape of the die-cast Mg-Al-Zn-RE alloy material is plate-shaped (with thicknesses of 3 mm, 4 mm, and 5 mm respectively); the temperature of the mold during die-casting is 200 °C;

[0091] The melting in step (1) is the following steps:

[0092] 1) Preheat the melting furnace at 500 °C for 60 min to obtain a preheated melting furnace;

[0093] 2) Mix boron nitride and alcohol in a mass ratio of 1:2 to form a mold release agent. Use a brush to evenly apply the mold release agent on the inner wall of a low-carbon steel crucible, and then dry the low-carbon steel crucible to obtain a dried low-carbon steel crucible;

[0094] 3) Put pure magnesium ingots into the dried low-carbon steel crucible obtained in step 2), and then put the dried low-carbon steel crucible into the preheated melting furnace obtained in step 1). Under a protective atmosphere, raise the temperature to 780 °C. After the pure magnesium ingots melt, successively add pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy, and Mg-Sr master alloy. After the alloy raw materials are completely melted, use a long-handled low-carbon steel spoon coated with a mold release agent to remove the surface scum to obtain a preliminary alloy melt; the protective atmosphere is a mixed gas of CO2 and SF6, and the volume ratio of CO2 to SF6 is 100:1;

[0095] 4) Control the temperature of the preliminary alloy melt to be 750 °C, add a refining agent to the preliminary alloy melt obtained in step 3) for refining, and then carry out slag removal treatment to obtain an alloy melt; the refining agent is No. 5 refining agent; the dosage of the refining agent is 2% of the total mass of the preliminary alloy melt; the refining agent is dried in a pit furnace at 250 °C for 30 min; the addition method of the refining agent is to use a long-handled low-carbon steel spoon to send the refining agent to the bottom of the preliminary alloy melt, stir it up and down for 2 min, and then rotate and stir for 3 min.

[0096] The die-cast Mg-Al-Zn-RE alloy materials with thicknesses of 3 mm, 4 mm, and 5 mm obtained in Example 2 were subjected to a room-temperature mechanical tensile test. The test method was as follows: The die-cast Mg-Al-Zn-RE alloy materials obtained in Example 2 were processed into standard room-temperature tensile specimens in accordance with the national standard GB / T228.1-2021 and then tensile tested on a room-temperature tensile testing machine CMT-5105. Tensile conditions: The surface of the specimen was polished bright with sandpaper and tensile tested at a rate of 3.6 mm / min. The engineering stress-strain curves of the die-cast Mg-Al-Zn-RE alloy materials obtained were as Figure 2 shown, and the mechanical property results of the die-cast Mg-Al-Zn-RE alloy materials are shown in Table 2:

[0097] Table 2 Mechanical properties of the die-cast Mg-Al-Zn-RE alloy materials obtained in Example 2

[0098] Thickness Tensile strength / MPa Yield strength / MPa Elongation / % 3 mm 271 196 9.1 4 mm 265 180 10.3 5 mm 267 173 12.3

[0099] As can be seen from Figure 2 and Table 2, at room temperature, the room-temperature tensile strength and yield strength of the die-cast Mg-Al-Zn-RE alloy materials obtained in Example 2 are still at a relatively high level; as the thickness of the tensile specimen increases, the yield strength of the die-cast Mg-Al-Zn-RE alloy material gradually decreases, the tensile strength decreases, and the elongation increases. When the thickness of the tensile specimen is 3 mm, the strength is relatively high, with a yield strength of 196 MPa and a tensile strength of 271 MPa; when the thickness of the tensile specimen is 5 mm, the elongation of the die-cast Mg-Al-Zn-RE alloy material is the highest, reaching 12.3%. Therefore, the die-cast Mg-Al-Zn-RE alloy material provided by the present invention can strictly meet the requirements of the automobile for components and is free of heat treatment, thus replacing some die-cast aluminum alloy products.

[0100] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A die-cast Mg-Al-Zn-RE alloy material, by mass percentage, includes the following chemical components: Al: 8.0 - 8.5%, Ce: 1.0 - 1.6%, Zn: 0.5 - 0.9%, Mn: 0.21 - 0.28%, Sb: 0.18 - 0.36%, Sr: 0.06 - 0.12% and the balance of Mg; wherein, The mass ratio of Sb to Sr is (2 - 4):

1.

2. The die-cast Mg-Al-Zn-RE alloy material according to claim 1, characterized in that, By mass percentage, it includes the following chemical components: Al: 8.3 - 8.5%, Ce: 1.0 - 1.3%, Zn: 0.6 - 0.8%, Mn: 0.21 - 0.25%, Sb: 0.18 - 0.32%, Sr: 0.06 - 0.08% and the balance of Mg.

3. The die-cast Mg-Al-Zn-RE alloy material according to claim 1, characterized in that, By mass percentage, it includes the following chemical components: Al: 8.3%, Ce: 1.19%, Zn: 0.74%, Mn: 0.21%, Sb: 0.18%, Sr: 0.06% and the balance of Mg.

4. The die-cast Mg-Al-Zn-RE alloy material according to claim 1, wherein, The mass ratio of Sb to Sr is 3:

1.

5. The preparation method of the die-casting Mg-Al-Zn-RE alloy material according to any one of claims 1 to 4, characterized in that It includes the following steps: (1) Melting alloy raw materials to obtain an alloy melt; (2) Die-casting the alloy melt obtained in step (1) to obtain a die-cast Mg-Al-Zn-RE alloy material.

6. The preparation method according to claim 5, wherein In step (1), the alloy raw materials include pure magnesium ingots, pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy and Mg-Sr master alloy.

7. The preparation method according to claim 6, wherein, The melting in step (1) includes the following steps: 1) Preheating the melting furnace to obtain a preheated melting furnace; 2) Coating a release agent on the inner wall of a low-carbon steel crucible, and then drying the low-carbon steel crucible to obtain a dried low-carbon steel crucible; 3) Putting pure magnesium ingots into the dried low-carbon steel crucible obtained in step 2), and then putting the dried low-carbon steel crucible into the preheated melting furnace obtained in step 1). Under a protective atmosphere, heating to 750 - 780 °C. After the pure magnesium ingots melt, successively adding pure Al, pure Zn, pure Sb, Mg-Ce master alloy, Mg-Mn master alloy and Mg-Sr master alloy. After the alloy raw materials are completely melted, removing the surface scum to obtain a preliminary alloy melt; 4) Adding a refining agent to the preliminary alloy melt obtained in step 3) for refining, and then performing slag removal treatment to obtain an alloy melt; Steps 1) and 2) have no sequence relationship.

8. The preparation method according to claim 7, characterized in that, The protective atmosphere in step 3) is a mixed gas of CO2 and SF6; the volume ratio of CO2 to SF6 is 100:(0.5 - 2).

9. The preparation method according to claim 5, characterized in that, The die-casting temperature in step (2) is 720 - 740 °C, and die-casting is carried out using a 650T die-casting machine.

10. Application of the die-cast Mg-Al-Zn-RE alloy material described in any one of claims 1 - 4 or the die-cast Mg-Al-Zn-RE alloy material prepared by the preparation method described in any one of claims 5 - 9 in the fields of automobiles, aerospace and national defense industries.

Images