CN108977711B

CN108977711B - Die-casting magnesium alloy material and preparation method thereof

Info

Publication number: CN108977711B
Application number: CN201810812693.2A
Authority: CN
Inventors: 王渠东; 魏杰; 雷川
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2018-07-23
Filing date: 2018-07-23
Publication date: 2020-11-17
Anticipated expiration: 2038-07-23
Also published as: CN108977711A

Abstract

The invention belongs to the field of metal structure materials, and particularly relates to a die-casting magnesium alloy material and a preparation method thereof. The material consists of the following elements in percentage by mass: al in a%, one or more of La, Ce and Pr in b%, Mn in c%, one or more of RE rare earth elements Gd, Y, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy and Yb in d%, impurities in a total amount of less than 0.2%, and Mg in the balance, wherein a, b, c and d meet the following condition that a is more than or equal to 3.5 and less than or equal to 4.5; b is more than or equal to 3.5 and less than or equal to 4.5; c is more than or equal to 0.2 and less than or equal to 0.5; d is more than or equal to 0.01 and less than or equal to 3.0. The material has excellent mechanical property and good casting property, and widens the application field of magnesium alloy materials. The preparation process provided by the invention has good stability and high controllability.

Description

Die-casting magnesium alloy material and preparation method thereof

Technical Field

The invention belongs to the field of metal structure materials, and particularly relates to a die-casting magnesium alloy material and a preparation method thereof.

Background

With the increasingly prominent problems of global energy shortage, environmental pollution and the like, automobile energy conservation and emission reduction become inevitable choices for dealing with major challenges of resources and environment in the world. The world automobile association reports that the oil consumption of the self weight of the automobile accounts for 70 percent of the total oil consumption of the automobile, the fuel oil consumption can be reduced by 6 to 8 percent and the emission can be reduced by 5 to 6 percent when the weight of the automobile is reduced by 10 percent, so that the light weight of the automobile body becomes an important development trend of the current automobile body materials. Magnesium and its alloy are the lightest metal structure materials that can be used in industry at present, have the advantages of small density (about 2/3 for aluminum and 1/4 for steel), high specific strength and specific stiffness, good damping, machinability and casting performance, and have been widely used in the fields of automobiles, communication electronics, aerospace, and the like. But the absolute strength and plasticity are low, so that the magnesium and the magnesium alloy are mainly used as non-bearing or bearing members, and further popularization and application of the magnesium and the magnesium alloy are restricted.

AE44(Mg-4Al-4RE, wt.%) magnesium alloy is commercial magnesium alloy so far, and has excellent room temperature mechanical property (die-casting state, tensile strength sigma)_b>240MPa, elongation>10.0%), and has good high-temperature creep resistance. Chinese patent CN101440450A discloses a heat-resistant die-casting magnesium alloy containing lanthanum AE series, which contains Al with the component content (wt.%) of 3.5% -4.5%,1 to 6 percent of La, 0.2 to 0.6 percent of Mn, less than 0.03 percent of impurity element total amount and the balance of magnesium. Chinese patent CN101158002B discloses an AE heat-resistant die-casting magnesium alloy containing cerium and lanthanum, which contains (wt.%) 3-5% of Al, 0.4-2.6% of Ce, 0.4-2.6% of La, 0.2-0.6% of Mn, and the balance of magnesium. These patents are addressed by increasing Al₁₁RE₃The high-temperature performance of the alloy is improved through the heat stability, but the room-temperature performance of the alloy can hardly meet the application requirement of the high-strength and high-toughness magnesium alloy. Al in traditional AE series magnesium alloy structure₁₁RE₃The phase is needle-shaped, the needle-shaped tip is easy to generate stress concentration and crack in the service process, and the mechanical property of the material is deteriorated, while the alloy in the patent takes the AE series alloy high temperature property as the starting point, but (1) for Al₁₁RE₃The morphology of the needle-shaped phase is not improved; (2) no introduction of a novel room temperature strengthening phase; (3) casting alone, lacking subsequent heat treatment. Thus how to modify Al₁₁RE₃The key problems of improving the room-temperature toughness of the AE series magnesium alloy are that a needle phase, a novel strengthening phase are introduced and the alloy can be promoted to be thermally treated. We have found that: samarium, gadolinium, yttrium and other rare earth elements (1) and aluminum element form fine high-melting-point Al at the early stage of solidification₂The RE phase as a heterogeneous nucleation core can obviously refine the matrix and introduce a fine novel strengthening phase; (2) solute distribution coefficient k in magnesium<1, enrichment on a solid-liquid interface in the solidification process hinders growth of a matrix and a second phase, and the matrix can be further obviously refined and the morphology of the second phase can be granulated; (3) the magnesium has high solid solubility and solid solution strengthening effect; (4) the solid solubility is reduced along with the temperature change, and the aging strengthening effect is achieved. At present, the rare earth elements with the characteristics are added to carry out the structural modification and modification on the AE magnesium alloy and introduce a novel strengthening phase to improve the toughness of the alloy, which is not reported at home and abroad.

Disclosure of Invention

The invention aims to provide a die-casting magnesium alloy material which has excellent mechanical property and good casting property and widens the application field of the magnesium alloy material.

The invention also aims to provide a preparation method of the die-casting magnesium alloy material, which has good process stability.

The purpose of the invention can be realized by the following technical scheme:

a die-casting magnesium alloy material is characterized in that: the material consists of the following elements in percentage by mass: a percent of Al, b percent of one or a plurality of La, Ce and Pr, c percent of Mn, d percent of one or a plurality of RE rare earth elements Gd, Y, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy and Yb in total, less than 0.2 percent of impurities in total and the balance of Mg, a, b, c and d satisfy the following formulas (1) to (4),

(1)3.5≤a≤4.5；

(2)3.5≤b≤4.5；

(3)0.2≤c≤0.5；

(4)0.01≤d≤3.0。

preferably, the range of d in the formula (4) is: d is more than or equal to 0.1 and less than or equal to 3.0. Gd. Y, Sm, the solid solubility of the rare earth elements in Mg is high, the addition of d in the formula (4) is more than or equal to 0.1, so that the aging strengthening effect is more obvious, but the addition of d is more than 3.0, so that the second phase is coarsened, the matrix is cut in the service process, and the mechanical property of the material is seriously deteriorated as a crack initiation point.

Wherein, 1) aluminum is used for balancing the strength and plasticity of the alloy and improving the casting process performance, so that the invention is suitable for industrial batch production. 2) La, Ce and Pr are used for improving the mechanical property of the alloy, and the La, Ce and Pr elements and aluminum preferentially generate Al₁₁RE₃Phase, inhibiting the formation of Mg having poor thermal stability₁₇Al₁₂Phase, improving the room temperature and high temperature mechanical properties of the alloy; in addition, the La, Ce and Pr can remove impurities in the magnesium alloy melt during smelting, and the effects of degassing, refining and purifying the melt are achieved. 3) Manganese is used for improving the corrosion resistance of the alloy, and can form a compound with iron or other heavy metal elements in the magnesium alloy, so that most of manganese can be removed as slag; in addition, manganese can promote the aging strengthening effect of the alloy, form Al-Mn nano aging phase and further improve the toughness of the alloy. 4) Rare earth elements such as Gd, Y, Sm and the like have high solid solubility in Mg, and mainly exist in three forms in AE series magnesium alloy: solid solution in the matrix; segregation is in grain boundary, phase boundary and dendrite boundary; by dissolving in or forming a solid solution in the compoundA compound (I) is provided. The addition of the rare earth elements into the alloy can play a role in solid solution strengthening and strength improvement. Solute distribution coefficient k of the above rare earth elements in Mg<1, the rare earth elements have extremely strong chemical activity, can be partially aggregated and adsorbed on a growing grain interface or a dendritic crystal interface to block the growth of grains and dendritic crystals, and can obviously refine the grains and granulate Al₁₁RE₃The needle-shaped phase greatly improves the performance, especially the plasticity of the alloy. Further increasing the content of the rare earth can generate fine granular high melting point Al with the Al element preferentially₂The RE intermetallic compound can be used as heterogeneous nucleation core refined grains and is dispersed in the matrix, so that the crack initiation position and the expansion path in the alloy fracture process are changed, and the plasticity of the alloy is further improved. In addition, the addition of rare earth elements such as Gd, Y, Sm and the like can promote the aging strengthening effect of the AE series magnesium alloy, and further improve the strength of the alloy.

Preferably, in the magnesium alloy material, the b + d is more than or equal to 3.6 percent and less than or equal to 7.5 percent. More preferably, in the magnesium alloy material, b + d is more than or equal to 4.5% and less than or equal to 6.0%. The addition of b and d determines various properties of the final magnesium alloy material.

Preferably, the combination of La and Ce is selected from the three elements of b%, so that the material structure is more uniform and the mechanical property is better.

Preferably, the types of the d% RE elements are Gd, Y, Sm and Nd elements, the mass ratio of the Gd, the Y, the Sm and the Nd elements is 40-81:31-52:16-30:11-24, and the proper types and the proportion of the rare earth elements are favorable for refining grains and modifying and granulating acicular second phase Al₁₁RE₃And the coarsening of the second phase is avoided, and the mechanical property of the alloy can be greatly improved.

A preparation method of a die-casting magnesium alloy material comprises the following steps,

s1: smelting alloy, namely preheating pure Mg, pure Al, magnesium rare earth intermediate alloy and aluminum manganese or magnesium manganese intermediate alloy respectively;

preferably, in the step S1, the preheating temperature is 200 to 250 ℃, and the preheating time is 2 to 6 hours. The preheating temperature and time can effectively remove the moisture of the raw materials and can avoid the problem of excessive oxidation of the surfaces of the raw materials in the preheating process.

Preferably, in step S1, the magnesium-rare earth intermediate alloy is one or a combination of several intermediate alloys selected from a magnesium-cerium-rich mischmetal intermediate alloy, a magnesium-lanthanum intermediate alloy, a magnesium-cerium intermediate alloy, a magnesium-praseodymium intermediate alloy, a magnesium-samarium intermediate alloy, a magnesium-gadolinium intermediate alloy, a magnesium-yttrium-rich mischmetal intermediate alloy, a magnesium-neodymium intermediate alloy, a magnesium-praseodymium-neodymium mixed rare earth intermediate alloy, a magnesium-erbium intermediate alloy, a magnesium-europium intermediate alloy, a magnesium-holmium intermediate alloy, a magnesium-thulium intermediate alloy, a magnesium-lutetium intermediate alloy, a magnesium-dysprosium intermediate alloy, and a magnesium-ytterbium intermediate alloy.

The cerium-rich mischmetal contains three rare earth elements of Ce, La and Pr.

S2: completely melting the preheated pure Mg in a protective atmosphere; adding preheated pure Al, Al-Mn or Mg-Mn intermediate alloy at 670-690 ℃; when the temperature rises to 720-740 ℃, adding the preheated magnesium rare earth intermediate alloy; heating to 720-740 ℃ after the magnesium rare earth intermediate alloy is completely melted, adding a refining agent for refining, standing at 710-730 ℃ after refining, cooling to 680-700 ℃, skimming scum to obtain a magnesium alloy melt, or pouring to obtain a magnesium alloy ingot;

preferably, in step S2, a refining agent is added to refine the mixture, and the mixture is allowed to stand at 720 ℃ after refining. The refining temperature is 720 ℃, the refining effect is optimal, and the gas and slag can be removed to the greatest extent and the melt can be purified.

S3: and (4) remelting the magnesium alloy melt or the magnesium alloy ingot in the step S2, and then carrying out vacuum die casting or non-vacuum die casting to obtain a magnesium alloy casting.

Preferably, the vacuum die-casting process conditions include remelting magnesium alloy melt or magnesium alloy ingots, and die-casting at 680-700 ℃ to obtain magnesium alloy castings, wherein the effective vacuum pressure of a cavity is 1-10 kPa, the mold temperature is 200-300 ℃, the low-speed is 0.2-0.4 m/s, the high-speed is 1.0-3.0 m/s, and the pressurizing injection force is 20-50 MPa; the casting produced by vacuum die casting has good density and few internal hole defects, and can be effectively strengthened by heat treatment.

Preferably, the non-vacuum die casting process conditions include remelting magnesium alloy melt or magnesium alloy ingots, and die casting at 680-700 ℃ to obtain magnesium alloy castings, wherein the temperature of a metal mold is 200-300 ℃, the low-speed is 0.2-0.4 m/s, the high-speed is 1.0-3.0 m/s, and the pressurizing injection force is 20-50 MPa. The melt pouring temperature and the metal mold temperature enable the melt to have good fluidity and feeding property in the die-casting process; the low-speed and the high-speed can reduce the gas entrainment of the melt to the maximum extent and avoid the defect of excessive holes in the casting; the pressurizing injection force can compact the structure in the melt solidification process, and finally, a healthy die casting with few defects is obtained.

The protective atmosphere of the step S2 is SF₆And CO₂The mixed gas of (1). Preferably, the SF₆And CO₂Is 1: 99.

the refining agent of the step S2 is a magnesium alloy refining agent containing inorganic salts, preferably, an inorganic salt magnesium alloy refining agent containing sodium salt, potassium salt, fluorine salt or hexachloroethane.

Preferably, the refining agent is added in an amount of 1-5% of the total mass of all raw materials.

The preparation method of the die-casting magnesium alloy material further comprises the steps of carrying out solution treatment and artificial aging treatment on the magnesium alloy casting prepared in the step S3;

preferably, the temperature of the solution treatment is 300-500 ℃, and the time of the solution treatment is 0.1-4 hours; the temperature of the artificial aging treatment is 175-225 ℃, and the time of the aging treatment is 1-32 hours. The solution treatment process can dissolve the second phase into the magnesium matrix to the maximum extent on the premise of avoiding bubbling or deformation of the casting; the aging treatment process can enable the casting to obtain obvious aging strengthening effect.

Or directly carrying out artificial aging treatment on the magnesium alloy casting prepared in the step S3, wherein the temperature of the aging treatment is 175-225 ℃, and the time of the aging treatment is 1-32 hours.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention is madeCompared with the prior art, the prepared magnesium alloy material has the advantages that the structure is obviously refined, the second phase is changed into particles from needle-shaped deterioration, and a new phase Al is introduced₂RE, the toughness of the alloy is obviously improved, and the alloy is at room temperature.

2. The mechanical property of the magnesium alloy material is effectively improved after the alloy is subjected to direct aging (T5) or solid solution and artificial aging (T6).

3. The preparation method is simple, the process stability is good, and the process controllability is high.

Drawings

FIG. 1 is a microstructure of the core of the alloy of comparative example 1, in which the morphology of the second phase is a typical needle-like phase.

FIG. 2 is a microstructure of the surface layer of the alloy of comparative example 1, which is a typical equiaxed dendrite.

FIG. 3 is a microstructure diagram of the alloy core of example 5 of the present invention, in which the second phase is refined and is in the form of fine particles.

FIG. 4 is a microstructure of the surface layer of the alloy of example 5 of the present invention, which is significantly refined into fine equiaxed dendrites and columnar dendrites.

FIG. 5 is a tensile stress-strain curve of the alloy core of example 5.

FIG. 6 is a tensile stress-strain curve of the alloy surface layer of example 5 of the present invention.

Detailed Description

The invention will now be further illustrated by reference to the following examples:

the various intermediate alloys used in the invention are all commercial products, and the magnesium rare earth intermediate alloy is purchased from Ganzhou Feiteng light alloy Co., Ltd.

Example 1:

the die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.82% of Al, 2.11% of Ce, 1.08% of La, 0.98% of Pr, 0.01% of Sm, 0.32% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

The embodiment relates to a smelting method of a conventional rare earth magnesium alloy and an alloy die casting method in the invention:

wherein the smelting process is carried out in SF₆And CO₂Mixed gas protectorThe method is carried out under the protection condition and comprises the following steps:

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(2) melting magnesium: putting the dried pure magnesium into SF₆/CO₂Melting in a crucible resistance furnace under the protection of gas;

(3) adding pure aluminum and magnesium-manganese intermediate alloy: when the pure magnesium is completely melted and the temperature reaches 670 ℃, adding preheated pure aluminum, magnesium and manganese intermediate alloy;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 720 ℃, adding the preheated magnesium-cerium-rich mischmetal intermediate alloy and magnesium-samarium intermediate alloy;

(5) after the magnesium rare earth intermediate alloy is melted, adding a refining agent for refining when the temperature of the melt is raised back to 720 ℃, standing at 720 ℃ after refining, cooling to 680 ℃, and skimming scum to obtain a magnesium alloy melt;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 680 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 300 ℃, the low-speed is 0.2m/s, the high-speed is 1.0m/s, and the pressurizing injection force is 50 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 1 of the invention were tested by using a universal tensile testing machine, and the test results are shown in table 1.

Example 2:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.74% of Al, 2.06% of Ce, 1.04% of La, 1.01% of Pr, 0.44% of Sm, 0.12% of Nd, 0.03% of Er, 0.30% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

wherein the smelting process is carried out in SF₆And CO₂The method is carried out under the protection of mixed gas and comprises the following steps:

(1) drying materials: preheating smelting raw materials for 2 hours at 250 ℃;

(2) melting magnesium: putting the dried pure magnesium intoSF₆/CO₂Melting in a crucible resistance furnace under the protection of gas;

(3) adding pure aluminum and magnesium-manganese intermediate alloy: when the pure magnesium is completely melted and the temperature reaches 680 ℃, adding preheated pure aluminum, magnesium and manganese intermediate alloy;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 730 ℃, adding the preheated magnesium-cerium-rich mischmetal intermediate alloy, the magnesium samarium intermediate alloy, the magnesium neodymium intermediate alloy and the magnesium erbium intermediate alloy;

(5) after the magnesium rare earth intermediate alloy is melted, adding a refining agent for refining when the temperature of the melt is raised to 730 ℃, standing at 720 ℃ after refining, cooling to 690 ℃, and skimming scum to obtain a magnesium alloy melt;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 690 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 250 ℃, the low-speed is 0.3m/s, the high-speed is 2.0m/s, and the pressurizing injection force is 30 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 2 of the invention were tested by using a universal tensile testing machine, and the test results are shown in table 1.

Example 3:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.94% of Al, 4.09% of La, 1.09% of Sm, 0.19% of Nd, 0.04% of Er, 0.34% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 6 hours at 200 ℃;

(3) adding pure aluminum and magnesium-manganese intermediate alloy: when the pure magnesium is completely melted and the temperature reaches 690 ℃, adding the preheated pure aluminum, magnesium and manganese intermediate alloy;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 740 ℃, adding the preheated magnesium-lanthanum intermediate alloy, magnesium-samarium intermediate alloy, magnesium-neodymium intermediate alloy and magnesium-erbium intermediate alloy;

(5) after the magnesium rare earth intermediate alloy is melted, adding a refining agent for refining when the temperature of the melt is raised to 740 ℃, standing at 720 ℃ after refining, cooling to 700 ℃, and skimming scum to obtain a magnesium alloy melt;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 700 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 200 ℃, the low-speed is 0.3m/s, the high-speed is 2.0m/s, and the pressurizing injection force is 30 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 3 of the invention were tested by using a universal tensile testing machine, and the test results are shown in table 1.

Example 4:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 4.11% of Al, 2.11% of Ce, 2.14% of La, 0.43% of Gd, 0.01% of Dy, 0.02% of Yb, 0.50% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(3) adding pure aluminum and aluminum-manganese intermediate alloy: when the pure magnesium is completely melted and the temperature reaches 670 ℃, adding preheated pure aluminum and aluminum-manganese intermediate alloy;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 720 ℃, adding the preheated magnesium lanthanum intermediate alloy, the preheated magnesium cerium intermediate alloy, the preheated magnesium gadolinium intermediate alloy, the preheated magnesium dysprosium intermediate alloy and the preheated magnesium ytterbium intermediate alloy;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 680 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 300 ℃, the low-speed is 0.2m/s, the high-speed is 2.0m/s, and the pressurizing injection force is 40 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 4 of the invention were tested by using a universal tensile testing machine, and the test results are shown in table 1.

Example 5:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.94% of Al, 1.92% of Ce, 1.01% of La, 1.06% of Pr, 0.86% of Gd, 0.02% of Dy, 0.03% of Yb, 0.34% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 740 ℃, adding the preheated magnesium cerium-rich mischmetal intermediate alloy, the magnesium gadolinium intermediate alloy, the magnesium dysprosium intermediate alloy and the magnesium ytterbium intermediate alloy;

the die casting process comprises the following steps:

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 5 of the present invention were tested by using a universal tensile testing machine, and the test results are shown in table 1.

Example 6:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.88 percent of Al, 1.81 percent of Ce, 0.93 percent of La, 0.92 percent of Pr, 1.29 percent of Gd, 0.03 percent of Dy, 0.05 percent of Yb, 0.29 percent of Mn, less than 0.2 percent of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(3) adding pure aluminum and aluminum-manganese intermediate alloy: when the pure magnesium is completely melted and the temperature reaches 680 ℃, adding preheated pure aluminum and aluminum-manganese intermediate alloy;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 730 ℃, adding the preheated magnesium cerium-rich mischmetal intermediate alloy, the magnesium gadolinium intermediate alloy, the magnesium dysprosium intermediate alloy and the magnesium ytterbium intermediate alloy;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 690 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 250 ℃, the low-speed is 0.3m/s, the high-speed is 2.0m/s, and the pressurizing injection force is 20 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 6 of the present invention were tested by using a universal tensile testing machine, and the test results are shown in table 1.

Example 7:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.94% of Al, 1.76% of Ce, 0.90% of La, 0.94% of Pr, 1.72% of Gd, 0.04% of Dy, 0.06% of Yb, 0.29% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 720 ℃, adding the preheated magnesium cerium-rich mischmetal intermediate alloy, the magnesium gadolinium intermediate alloy, the magnesium dysprosium intermediate alloy and the magnesium ytterbium intermediate alloy;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 680 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 300 ℃, the low-speed is 0.4m/s, the high-speed is 3.0m/s, and the pressurizing injection force is 20 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 7 of the present invention were measured using a universal tensile tester, and the test results are shown in table 1.

Example 8:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.50% of Al, 1.72% of Ce, 0.88% of La, 0.91% of Pr, 2.58% of Gd, 0.05% of Dy, 0.07% of Yb, 0.20% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(3) adding pure aluminum and aluminum-manganese intermediate alloy: when the pure magnesium is completely melted and the temperature reaches 690 ℃, adding preheated pure aluminum and aluminum-manganese intermediate alloy;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 700 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 200 ℃, the low-speed is 0.3m/s, the high-speed is 2.0m/s, and the pressurizing injection force is 50 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 8 of the present invention were tested by using a universal tensile testing machine, and the test results are shown in table 1.

Example 9:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 4.50% of Al, 2.21% of Ce, 1.13% of La, 1.17% of Pr, 0.40% of Y, 0.06% of Er, 0.03% of Ho, 0.01% of Tm, 0.41% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 730 ℃, adding the preheated magnesium-cerium-rich mischmetal intermediate alloy, magnesium-yttrium intermediate alloy, magnesium-erbium intermediate alloy, magnesium-holmium intermediate alloy and magnesium-thulium intermediate alloy;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 690 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 250 ℃, the low-speed is 0.3m/s, the high-speed is 3.0m/s, and the pressurizing injection force is 30 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 9 of the present invention were measured using a universal tensile tester, and the test results are shown in table 1.

Example 10:

the die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.94% of Al, 1.92% of Ce, 2.07% of La, 0.40% of Gd, 0.31% of Y, 0.16% of Sm, 0.11% of Nd and 0.34% of Mn, and the balance of Mg, wherein the content of other inevitable impurities is less than 0.2%.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 740 ℃, adding the preheated magnesium-lanthanum intermediate alloy, magnesium-cerium intermediate alloy, magnesium-gadolinium intermediate alloy, magnesium-yttrium intermediate alloy, magnesium-samarium intermediate alloy and magnesium-neodymium intermediate alloy;

the die casting process comprises the following steps:

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 10 of the present invention were tested by using a universal tensile testing machine, and the test results are shown in table 1.

Example 11:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 4.02% of Al, 1.86% of Ce, 1.94% of La, 0.81% of Gd, 0.52% of Y, 0.30% of Sm, 0.24% of Nd, 0.37% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 730 ℃, adding the preheated magnesium-lanthanum intermediate alloy, magnesium-cerium intermediate alloy, magnesium-gadolinium intermediate alloy, magnesium-yttrium intermediate alloy, magnesium-samarium intermediate alloy and magnesium-neodymium intermediate alloy;

the die casting process comprises the following steps:

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 11 of the present invention were measured using a universal tensile tester, and the test results are shown in table 1.

Example 12:

the novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.95% of Al, 1.72% of Ce, 0.88% of La, 0.93% of Pr, 2.42% of Y, 0.33% of Er, 0.19% of Ho, 0.04% of Tm, 0.02% of Lu, 0.24% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 720 ℃, adding the preheated magnesium-cerium-rich mischmetal intermediate alloy and the preheated magnesium-yttrium-rich mischmetal intermediate alloy;

the die casting process comprises the following steps:

and die-casting the magnesium alloy melt at 680 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 300 ℃, the low-speed is 0.4m/s, the high-speed is 2.0m/s, and the pressurizing injection force is 20 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 12 of the present invention were measured using a universal tensile tester, and the test results are shown in table 1.

Comparative example 1

Comparative example 1 alloy composition (mass percentage) of die-cast magnesium alloy: 3.94% of Al, 1.92% of Ce, 1.01% of La, 1.06% of Pr, 0.34% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

wherein the content of the first and second substances,the smelting process is carried out in SF₆And CO₂The method is carried out under the protection of mixed gas and comprises the following steps:

(1) drying materials: preheating smelting raw materials for 3 hours at 200 ℃;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 740 ℃, adding the preheated magnesium cerium-rich mischmetal intermediate alloy;

the die casting process comprises the following steps:

The die-cast magnesium alloy obtained in comparative example 1 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile tester, and the test results are shown in table 1.

Comparative example 2

Comparative example 2 alloy composition (mass percentage) of die-cast magnesium alloy: 3.94% of Al, 1.92% of Ce, 2.07% of La, 0.40% of Gd, 0.31% of Y, 0.16% of Sm, 0.11% of Nd and 0.34% of Mn, and the balance of Mg, wherein the content of other inevitable impurities is less than 0.2%.

(1) drying materials: preheating the smelting raw materials at 200 ℃ for more than 3 hours;

(2) melting magnesium: purifying the dried pureMagnesium in SF₆/CO₂Melting in a crucible resistance furnace under the protection of gas;

(3) adding pure aluminum and magnesium-manganese intermediate alloy: when the pure magnesium is completely melted and the temperature reaches 690 ℃, adding preheated pure aluminum, magnesium-manganese and aluminum-titanium intermediate alloy;

the die casting process comprises the following steps:

The die-cast magnesium alloy obtained in comparative example 2 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile testing machine, and the test results are shown in table 1. The result shows that the mechanical property of the alloy is not beneficial to the addition of Ti, and no Ti element is found by detecting the alloy elements by using an inductively coupled plasma spectrometer, because the solid solubility of Ti in Mg is almost zero, the Ti is difficult to be added into the alloy. In addition, the addition of Ti to the alloy further increases the use cost of the alloy.

Comparative example 3

Comparative example 3 alloy composition (mass percentage) of die-cast magnesium alloy: 3.94% of Al, 1.92% of Ce, 2.07% of La, 0.40% of Gd, 0.31% of Y, 0.16% of Sm, 0.11% of Nd and 0.34% of Mn, and the balance of Mg, wherein the content of other inevitable impurities is less than 0.2%.

(3) adding pure aluminum and magnesium-manganese intermediate alloy: when the pure magnesium is completely melted and the temperature reaches 690 ℃, adding preheated pure aluminum, magnesium-manganese and aluminum-niobium intermediate alloy;

the die casting process comprises the following steps:

The die-cast magnesium alloy obtained in comparative example 3 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile testing machine, and the test results are shown in table 1. The result shows that the addition of Nb is not beneficial to the mechanical property of the alloy, and no Nb element is found by detecting the alloy elements by using an inductively coupled plasma spectrometer, because the solid solubility of Nb in Mg is almost zero, Nb is difficult to be added into the alloy. In addition, the addition of Nb to the alloy further increases the use cost of the alloy.

Table 1 results of mechanical properties at room temperature of the whole, surface and core regions of the novel high strength and toughness die-cast magnesium alloys obtained in examples 1 to 12 of the present invention and the die-cast magnesium alloys obtained in comparative examples 1 to 3.

As can be seen from Table 1, the novel high-strength and high-toughness die-casting magnesium alloy obtained by the embodiment of the invention has excellent room-temperature mechanical properties, and the strength and the plasticity are simultaneously improved. The performance improvements of example 10 are particularly significant.

Example 13

The novel high-strength and high-toughness die-casting magnesium alloy comprises the following alloy components in percentage by mass: 3.94% of Al, 1.92% of Ce, 1.01% of La, 1.06% of Pr, 1.09% of Sm, 0.19% of Nd, 0.04% of Er, 0.34% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(3) adding pure aluminum and magnesium-manganese intermediate alloy: when pure magnesium is completely melted and the temperature reaches 670-690 ℃, adding preheated pure aluminum, magnesium and manganese intermediate alloy;

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 720-740 ℃, adding the preheated magnesium cerium-rich mixed rare earth intermediate alloy, the preheated magnesium samarium intermediate alloy, the preheated magnesium praseodymium neodymium mixed rare earth intermediate alloy and the preheated magnesium erbium intermediate alloy;

(5) after the magnesium rare earth intermediate alloy is melted, adding a refining agent for refining when the temperature of the melt is raised to 720-740 ℃, standing at 720 ℃ after refining, cooling to 680-700 ℃, skimming scum to obtain a magnesium alloy melt, and pouring to obtain a magnesium alloy ingot;

the die casting process comprises the following steps:

and remelting the magnesium alloy ingot, and carrying out vacuum die casting at 680-700 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 200-300 ℃, the effective vacuum pressure of a cavity is 10kPa, the low-speed is 0.3m/s, the high-speed is 2.0m/s, and the pressurizing injection force is 3 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 13 of the present invention were measured using a universal tensile tester, and the test results are shown in table 2.

Example 14:

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 720-740 ℃, adding the preheated magnesium cerium-rich mischmetal intermediate alloy, the magnesium gadolinium intermediate alloy, the magnesium dysprosium intermediate alloy and the magnesium ytterbium intermediate alloy;

the die casting process comprises the following steps:

and remelting the magnesium alloy ingot, and carrying out vacuum die casting at 680-700 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 200-300 ℃, the effective vacuum pressure of a cavity is 4kPa, the low-speed is 0.2m/s, the high-speed is 3.0m/s, and the pressurizing injection force is 30 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 14 of the present invention were measured using a universal tensile tester, and the test results are shown in table 2.

Example 15

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 720-740 ℃, adding the preheated magnesium-lanthanum intermediate alloy, magnesium-cerium intermediate alloy, magnesium-gadolinium intermediate alloy, magnesium-yttrium intermediate alloy, magnesium-samarium intermediate alloy and magnesium-neodymium intermediate alloy;

the die casting process comprises the following steps:

and remelting the magnesium alloy ingot, and carrying out vacuum die casting at 680-700 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 200-300 ℃, the effective vacuum pressure of a cavity is 1kPa, the low-speed is 0.3m/s, the high-speed is 1.0m/s, and the pressurizing injection force is 50 MPa.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 15 of the present invention were measured using a universal tensile tester, and the test results are shown in table 2.

Comparative example 4

Comparative example 4 alloy composition (mass percentage) of die-cast magnesium alloy: 3.94% of Al, 1.92% of Ce, 1.01% of La, 1.06% of Pr, 0.34% of Mn, less than 0.2% of other inevitable impurities and the balance of Mg.

(4) adding magnesium rare earth intermediate alloy: when the temperature rises to 720-740 ℃, adding the preheated magnesium cerium-rich mischmetal intermediate alloy;

the die casting process comprises the following steps:

and remelting the magnesium alloy ingot, and carrying out vacuum die casting at 680-700 ℃ to obtain a magnesium alloy casting, wherein the temperature of a metal die is 200-300 ℃, the effective vacuum pressure of a cavity is 3kPa, the low-speed is 0.3m/s, the high-speed is 2.0m/s, and the pressurizing injection force is 30 MPa.

The die-cast magnesium alloy obtained in comparative example 4 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile testing machine, and the test results are shown in table 2.

Table 2 shows the room temperature mechanical property test results of the whole, surface region and core region of the novel high strength and toughness die-cast magnesium alloys obtained in examples 13 to 15 of the present invention and the die-cast magnesium alloy obtained in comparative example 4.

As can be seen from table 2, the die-cast magnesium alloy obtained in the example of the present invention has excellent room temperature mechanical properties.

Example 16

The novel high-strength and high-toughness die-cast magnesium alloy obtained in the embodiment 15 of the invention is subjected to aging treatment at 175 ℃ for 32 hours, and the cooling mode of the aging treatment is water cooling.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 16 of the present invention were measured using a universal tensile tester, and the test results are shown in table 3.

Example 17

The novel high-strength and high-toughness die-cast magnesium alloy obtained in the embodiment 15 of the invention is subjected to aging treatment for 16 hours at 200 ℃, and the cooling mode of the aging treatment is water cooling.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 17 of the present invention were measured using a universal tensile tester, and the test results are shown in table 3.

Example 18

The novel high-strength and high-toughness die-cast magnesium alloy obtained in the embodiment 15 of the invention is subjected to aging treatment at 225 ℃ for 1 hour, and the cooling mode of the aging treatment is water cooling.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 18 of the present invention were measured using a universal tensile tester, and the test results are shown in table 3.

Example 19

The novel high-strength and high-toughness die-cast magnesium alloy obtained in the embodiment 15 of the invention is subjected to solution treatment at 300 ℃ for 4 hours and aging treatment at 175 ℃ for 32 hours, wherein the cooling mode of the solution treatment and the aging treatment is water cooling.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 19 of the present invention were measured using a universal tensile tester, and the test results are shown in table 3.

Example 20

The novel high-strength and high-toughness die-cast magnesium alloy obtained in the embodiment 15 of the invention is subjected to solution treatment at 400 ℃ for 2 hours and aging treatment at 200 ℃ for 16 hours, wherein the cooling mode of the aging treatment is water cooling.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 20 of the present invention were measured using a universal tensile tester, and the test results are shown in table 3.

Example 21

The novel high-strength and high-toughness die-cast magnesium alloy obtained in the embodiment 15 of the invention is subjected to solution treatment for 0.1 hour at 500 ℃ and aging treatment for 1 hour at 225 ℃, and the cooling mode of the solution treatment and the aging treatment is water cooling.

The room temperature mechanical properties of the whole, surface region and core region of the novel high-toughness die-cast magnesium alloy obtained in example 21 of the present invention were measured using a universal tensile tester, and the test results are shown in table 3.

Comparative example 5

The die cast magnesium alloy obtained in comparative example 4 was subjected to an aging treatment at 175 ℃ for 32 hours, and the cooling method of the aging treatment was water cooling.

The die-cast magnesium alloy obtained in comparative example 5 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile tester, and the test results are shown in table 3.

Comparative example 6

The die-cast magnesium alloy obtained in comparative example 4 was subjected to an aging treatment at 200 ℃ for 16 hours, and the cooling method of the aging treatment was water cooling.

The die-cast magnesium alloy obtained in comparative example 6 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile tester, and the test results are shown in table 3.

Comparative example 7

The die-cast magnesium alloy obtained in comparative example 4 was subjected to an aging treatment at 225 ℃ for 1 hour, and the cooling method of the aging treatment was water cooling.

The die-cast magnesium alloy obtained in comparative example 7 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile tester, and the test results are shown in table 3.

Comparative example 8

The die cast magnesium alloy obtained in comparative example 4 was subjected to a solution treatment at 300 ℃ for 4 hours and an aging treatment at 175 ℃ for 32 hours, and the cooling method of the solution and aging treatment was water cooling.

The die-cast magnesium alloy obtained in comparative example 8 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile tester, and the test results are shown in table 3.

Comparative example 9

The die-cast magnesium alloy obtained in comparative example 4 was subjected to a solution treatment at 400 ℃ for 2 hours and an aging treatment at 200 ℃ for 16 hours, the cooling method of the aging treatment being water cooling.

The die-cast magnesium alloy obtained in comparative example 9 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile tester, and the test results are shown in table 3.

Comparative example 10

The die-cast magnesium alloy obtained in comparative example 4 was subjected to a solution treatment at 500 ℃ for 0.1 hour and an aging treatment at 225 ℃ for 1 hour, the cooling method of the aging treatment being water cooling.

The die-cast magnesium alloy obtained in comparative example 10 was tested for mechanical properties at room temperature in the whole, surface region and core region by a universal tensile tester, and the test results are shown in table 3.

Table 3 results of mechanical properties at room temperature of die-cast magnesium alloys after direct aging treatment (T5) or solid solution + artificial aging treatment (T6) obtained in inventive examples 16 to 21 and comparative examples 5 to 10.

Table 3 shows that the novel high-toughness die-cast magnesium alloy obtained by the present invention has significant solution aging strengthening effect after direct aging treatment (T5) or solution and artificial aging treatment (T6), and can effectively improve the mechanical properties of the alloy at room temperature.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention, and the present invention should not be limited by the disclosure of the preferred embodiments. Therefore, it is intended that all equivalents and modifications which do not depart from the spirit of the invention disclosed herein are deemed to be within the scope of the invention.

Claims

1. A die-casting magnesium alloy material is characterized in that: the material consists of the following elements in percentage by mass: al in a percent, one or a mixture of more of La, Ce and Pr in b percent, Mn in c percent, RE rare earth elements in d percent, impurities with the total amount less than 0.2 percent, and Mg in the balance, wherein a, b, c and d satisfy the following formulas (1) to (4),

（1）3.5 ≤ a ≤ 4.5；

（2）3.5 ≤ b ≤ 4.5；

（3）0.2 ≤ c ≤ 0.5；

（4）0.01 ≤ d ≤ 3.0，

the types of the d% RE elements are Gd, Y, Sm and Nd elements, and the mass ratio of the Gd, the Y, the Sm and the Nd elements is 40-81:31-52:16-30: 11-24;

in the preparation process of the die-casting magnesium alloy material, a magnesium alloy casting is obtained by adopting a vacuum die-casting or non-vacuum die-casting process;

remelting a magnesium alloy melt or a magnesium alloy ingot, and die-casting at 680-700 ℃ to obtain a magnesium alloy casting, wherein the effective vacuum pressure of a cavity is 1-10 kPa, the mold temperature is 200-300 ℃, the low-speed is 0.2-0.4 m/s, the high-speed is 1.0-3.0 m/s, and the pressurizing injection force is 20-50 MPa;

the non-vacuum die-casting process conditions comprise remelting magnesium alloy melt or magnesium alloy ingots, and die-casting at 680-700 ℃ to obtain magnesium alloy castings, wherein the temperature of a metal die is 200-300 ℃, the low-speed is 0.2-0.4 m/s, the high-speed is 1.0-3.0 m/s, and the pressurizing injection force is 20-50 MPa.

2. The production method of a die-cast magnesium alloy material according to claim 1, comprising the step of,

3. The method for producing a die-cast magnesium alloy material according to claim 2, characterized in that: in the step S1, the preheating temperature is 200-250 ℃ and the preheating time is 2-6 hours.

4. The method for producing a die-cast magnesium alloy material according to claim 2, characterized in that: in the step S1, the magnesium-rare earth intermediate alloy is a combination of several intermediate alloys selected from among magnesium-cerium-rich mixed rare earth intermediate alloy, magnesium-lanthanum intermediate alloy, magnesium-cerium intermediate alloy, magnesium-praseodymium intermediate alloy, magnesium-samarium intermediate alloy, magnesium-gadolinium intermediate alloy, magnesium-yttrium-rich mixed rare earth intermediate alloy, magnesium-neodymium intermediate alloy, and magnesium-praseodymium-neodymium mixed rare earth intermediate alloy.

5. The method for producing a die-cast magnesium alloy material according to claim 2, characterized in that: the protective atmosphere of the step S2 is SF₆And CO₂The mixed gas of (1).

6. The method for producing a die-cast magnesium alloy material according to claim 2, characterized in that: the adding amount of the refining agent in the step S2 is 1-5% of the total mass of all raw materials.

7. The method for producing a die-cast magnesium alloy material according to claim 2, characterized in that: the preparation method also comprises the step of carrying out solid solution treatment and artificial aging treatment on the magnesium alloy casting prepared in the step S3;

the temperature of the solution treatment is 300-500 ℃, and the time of the solution treatment is 0.1-4 hours;

the temperature of the artificial aging treatment is 175-225 ℃, and the time of the aging treatment is 1-32 hours.

8. The preparation method of the die-casting magnesium alloy material according to claim 2, characterized by further comprising the step of subjecting the magnesium alloy casting prepared in the step S3 to direct aging treatment, wherein the temperature of the aging treatment is 175-225 ℃, and the time of the aging treatment is 1-32 hours.