Differential pressure casting flame-retardant magnesium alloy, preparation method and application thereof

Abstract

The application relates to a differential pressure casting flame-retardant magnesium alloy and a preparation method and application thereof. The application belongs to the flame-retardant magnesium alloy field. The purpose of the application is to provide a differential pressure casting flame-retardant magnesium alloy and a preparation method and application thereof. The magnesium alloy of the application is composed of the following components in percentage by mass: Gd: 6.5-11%, Nd: 2.8-3.0%, Zn: 0.3-0.5%, Zr: 0.3-0.5%, and the balance of Mg and inevitable impurities. The method of the application is as follows: taking magnesium ingots and Mg-30Gd, Mg-30Nd, Mg-30Zn and Mg-30Zr intermediate alloys as raw materials to carry out smelting, and obtaining alloy liquid after refining and deslagging; and adopting a differential pressure casting process to carry out forming. The magnesium alloy obtained by the application has high strength and toughness and excellent flame retardancy, and is applied to the fields of aerospace and automobiles.

Description

Technical Field

[0001] This invention belongs to the field of flame-retardant magnesium alloys, specifically relating to a differential pressure casting flame-retardant magnesium alloy, its preparation method, and its application. Background Technology

[0002] Magnesium alloys are widely used in aerospace, automotive, and other fields due to their lightweight and high specific strength. However, their susceptibility to oxidation and combustion at high temperatures limits their applications. Existing technologies improve flame retardancy by adding flame-retardant elements (such as Be and Ca), but these methods suffer from toxicity, brittleness, and defects like porosity and shrinkage during casting. To overcome these problems, researchers have developed various high-strength, heat-resistant magnesium alloys by adding rare earth elements and transition elements. However, these alloys still have shortcomings in flame retardancy, and their manufacturing processes are complex and costly. Differential pressure casting technology, by applying external pressure, can significantly improve the alloy's filling properties and solidification structure, making it particularly suitable for producing magnesium alloy castings with complex structures and high performance requirements. However, existing magnesium alloy composition designs fail to fully utilize the advantages of differential pressure casting. Summary of the Invention

[0003] To overcome the above-mentioned technical defects, the present invention provides a differential pressure casting flame-retardant magnesium alloy, its preparation method and application.

[0004] The technical solution of the present invention is as follows:

[0005] One of the objectives of this invention is to provide a differential pressure casting flame-retardant magnesium alloy composed of the following components by mass percentage: Gd: 6.5-11%, Nd: 2.8-3.0%, Zn: 0.3-0.5%, Zr: 0.3-0.5%, with the balance being Mg and unavoidable impurities.

[0006] Further specifying, the Gd content in magnesium alloys is 8.5-11%.

[0007] The second objective of this invention is to provide a method for preparing a differential pressure casting flame-retardant magnesium alloy, the method comprising the following steps:

[0008] S1: Magnesium ingots and Mg-30Gd, Mg-30Nd, Mg-30Zn and Mg-30Zr master alloys are used as raw materials. The alloy liquid is obtained after smelting under the protection of SF6+CO2 mixed gas and refining and slag removal.

[0009] S2: After the mold is preheated, differential pressure casting is used for forming. During the filling stage, the pressure difference is controlled at 0.6-1.2MPa and the filling speed is 20-40cm / s. After filling is completed, the pressure difference is increased to 2.5-3.5MPa and the pressure is held until solidification is completed to obtain magnesium alloy.

[0010] Further specified, in S1, magnesium ingots are melted and heated to 720-740℃ before the intermediate alloy is added.

[0011] Further specified, after slag removal in S1, the temperature is lowered to 680℃ and kept warm.

[0012] Further specified, the mold in S2 is preheated to 300-350℃.

[0013] Further restrictions are imposed, with the pressure difference during the filling stage of S2 controlled at 0.8-1.0 MPa and the filling speed at 30 cm / s.

[0014] Further, after the filling process in S2 is completed, the pressure difference is increased to 3.0-3.5 MPa.

[0015] Further restrictions are imposed, with a boost time delay of 5-10 seconds in S2.

[0016] The third objective of this invention is to provide an application of the above-mentioned flame-retardant magnesium alloy in the aerospace and automotive fields.

[0017] The advantages of this invention compared to existing technologies are:

[0018] (1) This invention provides a novel differential pressure casting flame-retardant magnesium alloy. Through optimized composition design, the flame-retardant properties of this alloy are significantly improved while maintaining good mechanical and casting properties. The differential pressure casting process can effectively reduce casting defects, and the process is simple and suitable for industrial production.

[0019] (2) The magnesium alloy obtained by the present invention has high strength and toughness and excellent flame retardancy, with tensile strength ≥340MPa and elongation ≥6%; it does not continue to burn after being exposed to air at 750℃ for 10 minutes; in addition, the flame-retardant magnesium alloy obtained by the method of the present invention has a fine structure with a grain size ≤25μm (Zr and differential pressure casting synergistic refinement).

[0020] (3) This invention eliminates shrinkage defects caused by high Gd content through the synergistic optimization of composition and process, and improves the yield by more than 20%. Attached Figure Description

[0021] Figure 1 Here is a SEM image of the flame-retardant magnesium alloy obtained in Example 1;

[0022] Figure 2 Here is a SEM image of the flame-retardant magnesium alloy obtained in Example 2;

[0023] Figure 3 This is a cross-sectional view of the oxide layer of the magnesium alloy obtained in Example 1 after oxidation at 600℃ for 30 min;

[0024] Figure 4This is a cross-sectional view of the oxide layer of the magnesium alloy obtained in Example 2 after oxidation at 600℃ for 30 min;

[0025] Figure 5 This is a cross-sectional view of the oxide layer of the magnesium alloy obtained in the comparative example after oxidation at 600℃ for 30 min. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0028] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0029] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0030] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0031] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0032] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] In the following examples, the magnesium ingots and Mg-30Gd, Mg-30Nd, Mg-30Zn and Mg-30Zr master alloys are all 99.95% industrial grade raw materials, and the Mg-30Gd master alloy, Mg-30Nd master alloy, Mg-30Zn master alloy and Mg-30Zr master alloy are all mass percentages.

[0034] Example 1

[0035] The preparation method of the differential pressure casting flame-retardant magnesium alloy in this embodiment is carried out according to the following steps:

[0036] (1) Prepare raw materials according to the following alloy ratio (mass percentage): Gd 11.0%, Nd 3.0%, Zn 0.5%, Zr 0.3%, balance Mg.

[0037] (2) Using magnesium ingots and Mg-30Gd master alloy, Mg-30Nd master alloy, Mg-30Zn master alloy and Mg-30Zr master alloy as raw materials, the alloy is smelted under the protection of SF6+CO2 mixed gas (v:v=1:99). In order to avoid Gd segregation, the magnesium ingots are melted and heated to 740℃. Then, Mg-30Gd master alloy, Mg-30Nd master alloy, Mg-30Zn master alloy and Mg-30Zr master alloy are added in sequence. After stirring, the alloy is allowed to stand for 15 minutes, refined and slag removed, and then cooled to 680℃ and held to obtain alloy liquid.

[0038] (3) After the mold is preheated to 320°C, differential pressure casting process is used for forming. The pressure difference is controlled at 0.8MPa during the filling stage and the filling speed is 30cm / s. After filling, the mold is left to stand for 5s, and then the pressure difference is increased to 3.5MPa within 8s to alleviate the decrease in fluidity of high Gd content. The pressure is held until solidification is completed to obtain magnesium alloy.

[0039] The obtained magnesium alloy was tested and found to have a tensile strength of 368 MPa and an elongation of 4.8%. In flame retardancy testing, it showed no spontaneous combustion after being incubated at 780°C in air. The SEM image of the obtained magnesium alloy is shown below. Figure 1 As shown.

[0040] Example 2

[0041] The preparation method of the differential pressure casting flame-retardant magnesium alloy in this embodiment is carried out according to the following steps:

[0042] (1) Prepare raw materials according to the following alloy ratio (mass percentage): Gd 6.5%, Nd 3.0%, Zn 0.5%, Zr 0.3%, balance Mg.

[0043] (2) Using magnesium ingots and Mg-30Gd master alloy, Mg-30Nd master alloy, Mg-30Zn master alloy and Mg-30Zr master alloy as raw materials, the alloy is smelted under the protection of SF6+CO2 mixed gas (v:v=1:99). In order to avoid Gd segregation, the magnesium ingots are melted and heated to 740℃. Then, Mg-30Gd master alloy, Mg-30Nd master alloy, Mg-30Zn master alloy and Mg-30Zr master alloy are added in sequence. After stirring, the alloy is allowed to stand for 15 minutes, refined and slag removed, and then cooled to 680℃ and held to obtain alloy liquid.

[0044] (3) After the mold is preheated to 320°C, differential pressure casting process is used for forming. The pressure difference is controlled at 0.8MPa during the filling stage and the filling speed is 30cm / s. After filling, the mold is left to stand for 5s, and then the pressure difference is increased to 3.5MPa within 8s to alleviate the decrease in fluidity of high Gd content. The pressure is held until solidification is completed to obtain magnesium alloy.

[0045] The obtained magnesium alloy was tested and found to have a tensile strength of 352 MPa and an elongation of 7.2%. In flame retardancy testing, it showed no spontaneous combustion after being incubated at 750°C in air. The SEM image of the obtained magnesium alloy is shown below. Figure 2 As shown.

[0046] Comparative Example

[0047] The preparation method of the differential pressure casting magnesium alloy in this comparative example is carried out according to the following steps:

[0048] (1) Prepare raw materials according to the following alloy ratio (mass percentage): Gd 1.0%, Nd 3.0%, Zn 0.5%, Zr 0.3%, balance Mg.

[0049] (2) Using magnesium ingots and Mg-30Gd master alloy, Mg-30Nd master alloy, Mg-30Zn master alloy and Mg-30Zr master alloy as raw materials, the alloy is smelted under the protection of SF6+CO2 mixed gas (v:v=1:99). In order to avoid Gd segregation, the magnesium ingots are melted and heated to 740℃. Then, Mg-30Gd master alloy, Mg-30Nd master alloy, Mg-30Zn master alloy and Mg-30Zr master alloy are added in sequence. After stirring, the alloy is allowed to stand for 15 minutes, refined and slag removed, and then cooled to 680℃ and held to obtain alloy liquid.

[0050] (3) After the mold is preheated to 320°C, differential pressure casting process is used for forming. The pressure difference is controlled at 0.8MPa during the filling stage and the filling speed is 30cm / s. After filling, the mold is left to stand for 5s, and then the pressure difference is increased to 3.5MPa within 8s to alleviate the decrease in fluidity of high Gd content. The pressure is held until solidification is completed to obtain magnesium alloy.

[0051] The magnesium alloy was tested and found to have a tensile strength of 335 MPa and an elongation of 8.5%. The flame retardancy test showed that the alloy could burn when heated to 720°C in air.

[0052] Cross-sectional views of the oxide layer of the magnesium alloys obtained in the comparative examples and Examples 1 and 2 after oxidation at 600°C for 30 min are shown below. Figure 3-5 As shown in the figure, the comparison shows that with the increase of Gd content, the Gd2O3 content in the oxide layer is higher, the oxide layer is more dense, and the oxidation resistance is higher.

[0053] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A differential pressure casting flame-retardant magnesium alloy, characterized in that, Composed of the following components by mass percentage composition: Gd: 6.5-11%, Nd: 2.8-3.0%, Zn: 0.3-0.5%, Zr: 0.3-0.5%, balance Mg and unavoidable impurities.

2. The magnesium alloy according to claim 1, characterized in that, Gd content in magnesium alloys: 8.5-11%.

3. The method for preparing the magnesium alloy according to claim 1 or 2, characterized in that, The method described: S1: Magnesium ingots and Mg-30Gd, Mg-30Nd, Mg-30Zn and Mg-30Zr master alloys are used as raw materials. The alloy liquid is obtained after smelting under the protection of SF6+CO2 mixed gas and refining and slag removal. S2: After the mold is preheated, differential pressure casting is used for forming. During the filling stage, the pressure difference is controlled at 0.6-1.2MPa and the filling speed is 20-40cm / s. After filling is completed, the pressure difference is increased to 2.5-3.5MPa and the pressure is held until solidification is completed to obtain magnesium alloy.

4. The method according to claim 3, characterized in that, In S1, magnesium ingots are melted and heated to 720-740℃ before an intermediate alloy is added.

5. The method according to claim 3, characterized in that, After slag removal in S1, the temperature is lowered to 680℃ and then kept warm.

6. The method according to claim 3, characterized in that, In S2, the mold is preheated to 300-350℃.

7. The method according to claim 3, characterized in that, In S2, the pressure difference during the filling stage is controlled at 0.8-1.0 MPa, and the filling speed is 30 cm / s.

8. The method according to claim 3, characterized in that, After filling in S2, increase the pressure difference to 3.0-3.5 MPa.

9. The method according to claim 3, characterized in that, The boost time delay in S2 is 5-10 seconds.

10. The application of the magnesium alloy according to claim 1 or 2 in the aerospace and automotive fields.

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