High-strength flame-retardant rare earth magnesium alloy and preparation method thereof

Abstract

The invention discloses a high-strength flame-retardant rare earth magnesium alloy and a preparation method thereof, and belongs to the technical field of flame-retardant magnesium alloys. The technical problem that an existing rare earth magnesium alloy is poor in mechanical property, casting property and flame retardant property is solved. The flame-retardant rare earth magnesium alloy comprises the following chemical components in percentage by mass: 0.5 to 15 percent of Yb, 0.5 to 15 percent of La, Ce, Y, Gd, Nd, Sm or Ho, 0.03 to 0.8 percent of Zr or 0.03 to 0.5 percent of Mn, and the balance of Mg and inevitable impurities. According to the invention, Yb is taken as a main flame-retardant element, and Yb and other rare earth elements are introduced into the flame-retardant magnesium alloy, so that the flame-retardant and casting properties of the rare earth magnesium alloy are effectively improved, and meanwhile, the mechanical properties of the alloy are also improved. The flame-retardant point of the developed flame-retardant rare earth magnesium alloy is higher than 1050 DEG C, and the developed flame-retardant rare earth magnesium alloy is wide in application range and suitable for large-scale industrial production and application.

Description

Technical Field

[0001] The invention belongs to the technical field of flame-retardant magnesium alloys, and in particular relates to a high-strength flame-retardant rare earth magnesium alloy and a preparation method thereof. Background Art

[0002] In recent years, with the development of the aviation field, aviation vehicles have put forward an urgent need for weight reduction. As the lightest "green" metal structural material, magnesium alloy has the advantages of low density, high specific strength / specific stiffness, good thermal conductivity, good damping and shock absorption performance, excellent electromagnetic shielding performance, easy processing, and recyclable reuse. It has become a widely used material in rail transportation, aerospace and other fields. In addition to lightweight, manned spacecraft, such as large aircraft, flying cars and other aviation equipment, also require lightweight materials to have higher safety, which requires further improvement of the flame retardant properties of magnesium alloys. To this end, researchers have developed a variety of methods. The most effective method at present is to add alkaline earth elements Be and Ca. Be is harmful to the human body and is generally not recommended for actual industrial application. The addition of Ca element often requires more than 2wt% to make the magnesium alloy have good flame retardant properties, but this content of Ca addition often significantly increases the thermal cracking tendency of magnesium alloys, resulting in the flame retardant magnesium alloys with Ca addition often unable to prepare large-sized or complex components, and unable to apply the mainstream casting process on the market to prepare products, resulting in the Ca-added flame retardant magnesium alloys having no high practical application value. Therefore, some researchers have added rare earth elements to magnesium alloys to prepare flame-retardant rare earth magnesium alloys to improve flame retardancy, and have achieved good results. As a result, rare earth magnesium alloys have received great attention in the aviation field. However, with the rapid development of aviation technology, higher requirements have been put forward for rare earth magnesium alloys used in aviation aircraft, especially commercial manned aircraft. In addition to having excellent mechanical properties, the flame retardancy of rare earth magnesium alloys must also be further improved.

[0003] Conventional rare earth magnesium alloys use Gd and Y rare earth elements as the main flame retardant elements. Although they can improve the flame retardant properties, they reduce the fluidity of the alloy melt, the casting properties of the alloy and the mechanical properties of the components, and also increase the production cost of the magnesium alloy. High-abundance rare earth elements such as La and Ce can improve the flame retardancy of magnesium alloys to a certain extent, but the degree of improvement is limited. Therefore, it is of great significance to develop a rare earth magnesium alloy with excellent mechanical properties, casting properties and flame retardant properties. Summary of the invention

[0004] In order to solve the technical problem that the existing rare earth magnesium alloy has poor mechanical properties, casting properties and flame retardant properties, the present invention provides a high-strength flame retardant rare earth magnesium alloy and a preparation method thereof.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] One of the purposes of the present invention is to provide a high-strength flame-retardant rare earth magnesium alloy, the chemical composition of which, by weight percentage, includes: Yb: 0.5-15%, M: 0.5-15%, Zr: 0.03-0.8% or Mn: 0.03-0.5%, and the balance is Mg and inevitable impurities.

[0007] It is further defined that M is La, Ce, Y, Gd, Nd, Sm or Ho.

[0008] The second object of the present invention is to provide a method for preparing a high-strength flame-retardant rare earth magnesium alloy, comprising:

[0009] S1. Descaling and preheating the Mg-Zr master alloy or Mg-Mn master alloy, Mg-Yb master alloy, Mg-M master alloy and magnesium ingot;

[0010] S2, putting magnesium ingot, Mg-Yb master alloy and Mg-M master alloy into a crucible furnace as charge, and passing protective gas;

[0011] S3, heating to a certain temperature, adding Mg-Zr master alloy or Mg-Mn master alloy after the charge is completely melted, and stirring;

[0012] S4, adjusting the furnace temperature to a certain temperature, and performing gravity casting or high pressure die casting after the melt is allowed to stand to obtain a magnesium alloy ingot;

[0013] S5. Using the magnesium alloy ingot as a flame retardant rare earth magnesium alloy, or using the magnesium alloy ingot obtained by gravity casting as a flame retardant rare earth magnesium alloy after post-treatment.

[0014] It is further defined that the preheating temperature in S1 is 200-300° C. and the time is 40-80 min.

[0015] It is further defined that the protective gas in S2 is CO2 containing 1 to 10 vol% SF6.

[0016] It is further defined that the temperature in S3 is raised to 700-800°C.

[0017] It is further defined that the stirring time in S3 is 5 to 10 minutes.

[0018] It is further defined that in S4, the furnace temperature is adjusted to 690-710°C.

[0019] It is further defined that the melt temperature during high pressure die casting in S4 is 685-695°C.

[0020] It is further defined that the post-treatment method in S5 is solution aging or solution extrusion.

[0021] It is further defined that the solution temperature during the solution aging process is 450-540°C, and the solution temperature during the solution extrusion process is 450-540°C.

[0022] It is further defined that the parameters of the solid solution extrusion process are: extrusion ratio of 7 to 28, extrusion speed of 0.1 to 1 mm / s, mold temperature of 250 to 350°C, and ingot temperature of 300 to 520°C.

[0023] The beneficial effects achieved by the present invention are as follows:

[0024] (1) The rare earth flame retardant magnesium alloy provided by the present invention does not use conventional elements such as Ca, Be, Gd, and Y as the main flame retardant elements to achieve the purpose of flame retardancy, but uses Yb as the main flame retardant element. The affinity of Yb to oxygen is much greater than the affinity of magnesium to oxygen, so Yb will react with oxygen on the surface of the rare earth flame retardant magnesium alloy melt before Mg to form a dense ytterbium oxide film layer. Ytterbium oxide has excellent high temperature resistance and low thermal cracking tendency, so that the ytterbium oxide film layer will not crack at high temperatures. In addition, Yb diffuses faster in the magnesium melt and has the characteristic of surface diffusion. Therefore, under high-temperature burning conditions, as time goes by, the ytterbium oxide film layer formed by Yb on the surface of the rare earth flame retardant magnesium alloy melt becomes thicker, thereby effectively isolating the contact between magnesium and oxygen, increasing the ignition temperature of the rare earth flame retardant magnesium alloy, and achieving a better flame retardant effect.

[0025] (2) In addition to Yb, the present invention further adds La, Ce, Y, Gd, Nd, Sm or Ho. The addition of the second rare earth element in addition to Yb can further improve the toughness and heat resistance of the ytterbium oxide film layer on the surface of the rare earth flame retardant magnesium alloy melt, thereby further reducing the cracking tendency of the ytterbium oxide flame retardant film layer formed on the surface. At the same time, the second rare earth element added in the present invention can also form a corresponding oxide film layer with oxygen, further increasing the thickness of the oxide flame retardant film layer and improving the protective effect of the oxide film layer. The addition of Zr can refine the grains, while the addition of Mn can remove impurities.

[0026] (3) In the present invention, for the rare earth flame retardant alloy obtained by gravity casting, Yb and Mg form high melting point Mg2Yb, which hinders the growth of grains during solidification, thereby refining the alloy grains and improving the strength of the rare earth flame retardant alloy. In particular, after solution and aging treatment, a large number of dispersed nano-sized Mg2Yb particles are formed in the magnesium matrix, which can further improve the strength of the alloy. At the same time, the addition of the second rare earth element will also introduce a conventional β series precipitation phase into the magnesium matrix, while the addition of Mn and Zr can refine the grains, promote aging precipitation, and refine the size of the precipitation phase, thereby improving the strength of the flame retardant rare earth magnesium alloy.

[0027] (4) In the present invention, for the rare earth flame retardant alloy obtained by high pressure die casting, Yb forms high melting point Mg2Yb at the grain boundary and forms a semi-continuous network second phase structure, thereby improving the strength of the alloy. The introduction of the second rare earth element further increases the volume fraction of the second phase in the alloy and changes the composition of the grain boundary network structure, so that the deformation of different second phases (the new structure formed after the addition of the second rare earth element and Mg2Yb) is effectively coordinated, which hinders the movement of dislocations, thereby strengthening the alloy and improving the strength of the flame retardant rare earth magnesium alloy.

[0028] (4) In the present invention, for the deformed alloy obtained by solution extrusion treatment, the deformation itself can greatly refine the alloy grains, and the addition of Yb can further promote the dynamic recrystallization of the alloy, refine the recrystallized grains, and at the same time form a large number of dynamic precipitation phases at the grain boundaries, further strengthening the grain boundaries. The addition of the second rare earth element will also introduce conventional β series precipitation phases into the magnesium matrix, and the addition of Mn and Zr can refine the casting grains, thereby refining the deformed structure. In addition, the addition of Mn and Zr will also promote aging precipitation and refine the size of the precipitation phase, thereby improving the strength of the flame-retardant rare earth magnesium alloy. Therefore, the flame-retardant rare earth magnesium alloy provided by the present invention has higher strength than traditional rare earth magnesium alloys.

[0029] (6) The flame-retardant rare earth magnesium alloy provided by the present invention has good flame-retardant properties, with a flame-retardant point higher than 1050°C, and has excellent casting properties, especially die-casting properties. It can meet various casting process conditions such as conventional gravity casting, high-pressure casting, semi-continuous casting, etc., is harmless to the human body, and is suitable for large-scale industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1a This is a SEM image of the high-strength flame-retardant rare earth magnesium alloy prepared in Example 1;

[0031] Figure 1b This is a SEM image of the alloy ingot prepared in Example 2;

[0032] Figure 1c This is a SEM image of a high-strength flame-retardant rare earth magnesium alloy prepared by solid solution extrusion in Example 2;

[0033] Figure 1d This is a SEM image of the high-strength flame-retardant rare earth magnesium alloy prepared in Example 3;

[0034] Figure 1e This is a SEM image of the alloy ingot prepared in Example 4;

[0035] Figure 1f This is the SEM image of the high-strength flame-retardant rare earth magnesium alloy prepared by solid solution extrusion in Example 4. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in combination with the embodiments of the specification. In the following description, many specific details are elaborated to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0038] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0039] The purity of the magnesium ingot and zinc ingot used in the following examples is greater than 99.9%.

[0040] Example 1

[0041] Weigh and prepare the ingredients according to the mass ratio of the alloy components, wherein Yb: 1.5%, Y: 4%, Nd: 3%, Zr: 0.8%, and the balance is Mg and inevitable impurities, descaling the magnesium ingot, Mg-30Yb master alloy, Mg-30Y master alloy, Mg-20Nd master alloy and Mg-30Zr master alloy, preheat at 250° C. for 30 min, then put the magnesium ingot, Mg-30Yb master alloy, Mg-20Nd master alloy and Mg-30Y master alloy into a crucible furnace, introduce CO2 containing 2 vol% SF6, raise the furnace temperature to 730° C., completely melt the charge to be added, add the Mg-30Zr master alloy, continue to introduce the protective gas, stir for 10 min, adjust the furnace temperature to 700° C., let the melt stand for 30 min, perform gravity casting, and obtain a Mg-Y-Nd-Yb-Zr alloy ingot;

[0042] The Mg-Y-Nd-Yb-Zr alloy ingot was solution treated at 520°C for 10 hours, then hot water quenched, and then aged at 200°C for 72 hours to obtain a peak aged alloy, namely, Mg-Y-Nd-Yb-Zr flame retardant rare earth magnesium alloy.

[0043] Example 2

[0044] Weigh and prepare the ingredients according to the mass ratio of the alloy components, wherein Yb: 4%, Gd: 9%, Zr: 0.5%, and the balance is Mg and inevitable impurities, descaling the magnesium ingot, Mg-30Yb master alloy, Mg-30Gd master alloy, and Mg-30Zr master alloy, preheat at 250° C. for 30 min, then put the magnesium ingot, Mg-30Yb master alloy, and Mg-30Gd master alloy into a crucible furnace, introduce CO2 containing 2 vol% SF6, raise the furnace temperature to 730° C., completely melt the charge to be added, add the Mg-30Zr master alloy, continue to introduce the protective gas, stir for 10 min, adjust the furnace temperature to 705° C., let the melt stand for 30 min, and then perform gravity casting to obtain a Mg-30Gd-Yb-Zr alloy ingot;

[0045] The Mg-30Gd-Yb-Zr alloy ingot was solution treated at 500℃ for 10h and then subjected to differential temperature extrusion. The ingot temperature was 500℃, the extrusion temperature was 300℃, the extrusion ratio was 7, the extrusion speed was 0.1mm / s, and the ingot was kept in a constant temperature furnace at 500℃ for 2h before extrusion. The temperature of the extrusion barrel and the mold was 300℃ to obtain the extruded sample, i.e., Mg-30Gd-Yb-Zr flame retardant rare earth magnesium alloy.

[0046] Example 3

[0047] Weigh and prepare the ingredients according to the mass ratio of the alloy components, wherein Yb: 3.5%, La: 2.6%, Mn: 0.5%, and the balance is magnesium and inevitable impurities, descaling the magnesium ingot, Mg-30Yb master alloy, Mg-20La master alloy, and Mg-5Mn master alloy, preheat at 250° C. for 30 min, then put the magnesium ingot, Mg-30Yb master alloy, and Mg-20La master alloy into a crucible furnace, introduce CO2 containing 2 vol% SF6, raise the furnace temperature to 720° C., completely melt the charge to be added, add the Mg-5Mn master alloy, continue to introduce the protective gas, stir for 10 min, adjust the furnace temperature to 690° C., let the melt stand for 30 min, and obtain a Mg-30Yb-La-Mn alloy melt;

[0048] The Mg-30Yb-La-Mn alloy melt was subjected to high-pressure die casting, the melt temperature was maintained at 690°C, the injection pressure was 120 MPa, the injection rate was 8 m / s, the pressurization time was 15 ms, the holding pressure was 55 MPa, the holding time was 12 s, the die-casting mold was 60mm×80mm×2.6mm thin plate and dog-bone shaped tensile rod with a gauge length of 60mm, a diameter of 6mm, and a clamping end diameter of 10mm; the mold temperature was 220°C, and the Mg-30Yb-La-Mn flame retardant rare earth magnesium alloy was obtained by die casting.

[0049] Example 4

[0050] Weigh and prepare the ingredients according to the mass ratio of the alloy components, wherein Yb: 0.5%, Gd: 9%, Y: 3%, Zr: 0.3%, and the balance is magnesium and inevitable impurities, descaling the magnesium ingot, Mg-30Yb master alloy, Mg-30Gd master alloy, Mg-30Y master alloy and Mg-30Zr master alloy, preheat at 250° C. for 30 min, then put the magnesium ingot, Mg-30Yb master alloy, Mg-30Y master alloy and Mg-30Gd master alloy into a crucible furnace, introduce CO2 containing 2 vol% SF6, raise the furnace temperature to 730° C., completely melt the charge to be added, add the Mg-30Zr master alloy, continue to introduce the protective gas, stir for 5 min, adjust the furnace temperature to 700° C., let the melt stand for 30 min, perform gravity casting, and obtain a Mg-30Gd-Y-Yb-Zr alloy ingot;

[0051] The Mg-30Gd-Y-Yb-Zr alloy ingot was solution treated at 500℃ for 6h and then subjected to differential temperature extrusion. The ingot temperature was 480℃, the extrusion temperature was 250℃, the extrusion ratio was 7, the extrusion speed was 0.1mm / s, and the ingot was kept in a constant temperature furnace at 480℃ for 2h before extrusion. The temperature of the extrusion barrel and the mold was 250℃ to obtain the extruded sample, i.e., Mg-30Gd-Y-Yb-Zr flame retardant rare earth magnesium alloy.

[0052] Example 5

[0053] The ingredients are weighed and prepared according to the mass ratio of the alloy components, wherein Yb: 15%, Nd: 3%, Mn: 0.5%, and the balance is magnesium and inevitable impurities. The magnesium ingot, Mg-30Yb master alloy, Mg-20Nd master alloy, and Mg-5Mn master alloy are descaled and preheated at 250° C. for 30 minutes. Then, the magnesium ingot, Mg-30Yb master alloy, and Mg-20Nd master alloy are placed in a crucible furnace, and CO2 containing 2 vol% SF6 is introduced. The furnace temperature is raised to 720° C., and the charge to be added is completely melted, and the Mg-5Mn master alloy is added. The protective gas is continued to be introduced. After stirring for 10 minutes, the furnace temperature is adjusted to 690° C., and the melt is gravity casted after being allowed to stand for 30 minutes to obtain a Mg-30Yb-Nd-Mn alloy ingot.

[0054] Example 6

[0055] Weigh and prepare the ingredients according to the mass ratio of the alloy components, wherein Yb: 4.5%, Gd: 5%, Zr: 0.5%, and the balance is magnesium and inevitable impurities, descaling the magnesium ingot, Mg-30Yb master alloy, Mg-30Zr master alloy and Mg-30Gd master alloy, preheat at 250° C. for 30 min, then put the magnesium ingot, Mg-30Yb master alloy and Mg-30Gd master alloy into a crucible furnace, introduce CO2 containing 2 vol% SF6, raise the furnace temperature to 730° C., completely melt the charge to be added, add the Mg-30Zr master alloy, continue to introduce the protective gas, stir for 10 min, adjust the furnace temperature to 700° C., let the melt stand for 30 min, then perform gravity casting to obtain a Mg-30Yb-Gd-Zr alloy ingot;

[0056] The Mg-30Yb-Gd-Zr alloy ingot was solution treated at 520℃ for 6h and then subjected to differential temperature extrusion. The ingot temperature was 520℃, the extrusion temperature was 350℃, the extrusion ratio was 28, the extrusion speed was 0.1mm / s, and the ingot was kept in a constant temperature furnace at 520℃ for 2h before extrusion. The temperature of the extrusion barrel and the mold was 350℃ to obtain the extruded sample, i.e., Mg-30Yb-Gd-Zr flame retardant rare earth magnesium alloy.

[0057] Comparative Example 1

[0058] Weigh and prepare the ingredients according to the mass ratio of the alloy components, wherein Gd: 9%, Y: 3%, Zr: 0.5%, and the balance is magnesium and inevitable impurities, descaling the magnesium ingot, Mg-30Gd master alloy, Mg-30Y master alloy and Mg-30Zr master alloy, preheat at 250° C. for 30 min, then put the magnesium ingot, Mg-30Gd master alloy and Mg-30Y master alloy into a crucible furnace, introduce CO2 containing 2 vol% SF6, raise the furnace temperature to 730° C., completely melt the charge to be added, add the Mg-30Zr master alloy, continue to introduce the protective gas, stir for 10 min, adjust the furnace temperature to 700° C., let the melt stand for 30 min, then perform gravity casting to obtain a Mg-30Gd-Y-Zr alloy ingot;

[0059] The Mg-30Gd-Y-Zr alloy ingot was solution treated at 500℃ for 6h and then subjected to differential temperature extrusion. The ingot temperature was 500℃, the extrusion temperature was 300℃, the extrusion ratio was 7, the extrusion speed was 0.1mm / s, and the ingot was kept in a constant temperature furnace at 500℃ for 2h before extrusion. The temperature of the extrusion barrel and the mold was 300℃ to obtain the extruded sample, i.e., Mg-30Gd-Y-Zr magnesium alloy.

[0060] Comparative Example 2

[0061] Weigh and prepare the ingredients according to the mass ratio of the alloy components, wherein Y: 4%, Nd: 3%, Zr: 0.5%, and the balance is magnesium and inevitable impurities, descaling the magnesium ingot, Mg-30Y master alloy, Mg-20Nd master alloy and Mg-30Zr master alloy, preheat at 250° C. for 30 min, then put the magnesium ingot, Mg-30Y master alloy and Mg-20Nd master alloy into a crucible furnace, introduce CO2 containing 2 vol% SF6, raise the furnace temperature to 730° C., completely melt the charge to be added, add the Mg-30Zr master alloy, continue to introduce the protective gas, stir for 10 min, adjust the furnace temperature to 690° C., let the melt stand for 30 min, then perform gravity casting to obtain a Mg-Y-Nd-Zr alloy ingot;

[0062] The Mg-Y-Nd-Zr alloy ingot was solution treated at 520°C for 10 hours, then quenched in hot water, and then aged at 200°C for 48 hours to obtain a peak aged alloy, namely, Mg-Y-Nd-Zr alloy.

[0063] Comparative Example 3

[0064] Weigh and prepare the ingredients according to the mass ratio of the alloy components, wherein La: 2.6%, Sm: 1.8%, Mn: 0.3%, and the balance is magnesium and inevitable impurities, and perform descaling treatment on the magnesium ingot, Mg-20La master alloy, Mg-20Sm master alloy and Mg-5Mn master alloy, and then put the magnesium ingot, Mg-20La master alloy and Mg-20Sm master alloy into a crucible furnace, introduce CO2 containing 2 vol% SF6, raise the furnace temperature to 730°C, completely melt the charge to be added, add the Mg-5Mn master alloy, continue to introduce the protective gas, stir for 10 minutes, adjust the furnace temperature to 690°C, and let the melt stand for 30 minutes to obtain a Mg-20La-Sm-Mn alloy melt;

[0065] The Mg-20La-Sm-Mn alloy melt was subjected to high-pressure die casting. The melt temperature was maintained at 690°C, the injection pressure was 120 MPa, the injection rate was 8 m / s, the pressurization time was 15 ms, the holding pressure was 55 MPa, the holding time was 12 s, the die-casting mold was 60 mm × 80 mm × 2.6 mm, the mold temperature was 220°C, and a conventional ALa44 (AE44 type) alloy sample was obtained by die casting.

[0066] The mechanical properties and ignition point tests were performed on the alloys in Examples 1 to 6 and Comparative Examples 1 to 3.

[0067] Mechanical properties test method:

[0068] The high-strength flame-retardant rare earth magnesium alloys obtained in Examples 1 to 2, Examples 4 to 6, and Comparative Examples 1 to 3 were mechanically processed to obtain dog-bone-shaped tensile rods with a gauge length of 36 mm, a gauge diameter of 6 mm, and a clamping section thread of M10 for mechanical property testing. In Example 3, a dog-bone-shaped tensile rod with a gauge length of 36 mm and a gauge diameter of 6 mm was prepared in the high-pressure die-casting stage, and its clamping end was processed into M10 for testing; the mechanical property test was carried out in accordance with the standard of GB / T 228.1-2010 "Uniaxial Tensile Test Method for Metallic Materials", and the room temperature mechanical properties of the high-strength flame-retardant rare earth magnesium alloy were tested, and the test results are shown in Table 1.

[0069] Fire point test:

[0070] The high-strength flame-retardant rare earth magnesium alloys obtained in Examples 1 to 2, Examples 4 to 6, and Comparative Examples 1 to 3 were machined to obtain 60 mm × 80 mm × 2.6 mm thin plates for ignition point testing. The thin plates in Example 3 were prepared during the high-pressure die-casting stage and can be directly used for ignition point testing. The ignition point test method was based on ASTM E659-17 "Standard Test Method for Autoignition Temperature of Liquid Chemicals". The test results are shown in Table 1.

[0071] Table 1 Mechanical properties and ignition point test results of rare earth magnesium alloys prepared in Examples 1 to 6 and Comparative Examples 1 to 3

[0072]

[0073]

[0074] It can be seen from the data in Table 1 that the rare earth magnesium alloys prepared in Examples 1 to 6 of the present invention did not burn at a high temperature of 1050°C, and had a good flame retardant effect. Although the rare earth magnesium alloys prepared in Comparative Examples 1 to 2 had good mechanical properties, they burned at 1000°C and 1050°C, respectively, and had a poor flame retardant effect. The rare earth magnesium alloy prepared in Comparative Example 3 burned at 900°C, and its yield strength was also lower than that of the rare earth magnesium alloy provided by the present invention.

[0075] By comparing Example 1 with Comparative Example 2, it is found that after solution aging treatment, the yield strength, tensile strength and elongation of the rare earth magnesium alloy provided in Comparative Example 2 are lower than those in Example 1, and the mechanical properties are worse than those of the rare earth magnesium alloy in Example 1. In addition, the rare earth magnesium alloy provided in Comparative Example 2 burns at 1050°C, and the flame retardant performance is also lower than that of Example 1.

[0076] By comparing Examples 2, 4 or 6 with Comparative Example 1, it is found that the yield strength, tensile strength and elongation of the rare earth magnesium alloys prepared in Examples 2 and 4 are higher than those in Comparative Example 1, and none of them burn at 1050°C, while the rare earth magnesium alloy in Comparative Example 1 not only has inferior mechanical properties to those in Examples 2 and 4, but also burns at 1000°C, and its flame retardant properties are not as good as those in Examples 2 and 4 of the present invention; although the yield strength and tensile strength of the rare earth magnesium alloy prepared in Example 6 are lower than those in Comparative Example 1, its elongation is much higher than that in Comparative Example 1, and its flame retardant properties are also better than those of the rare earth magnesium alloy prepared in Comparative Example 1.

[0077] By comparing Example 3 or 5 with Comparative Example 3, it is found that although the magnesium alloy ingot has not been post-treated, it also has a certain strength and can meet the subsequent processing needs. The yield strength of the rare earth magnesium alloy prepared in Example 3 and Example 5 is higher than that of Comparative Example 3, and the rare earth magnesium alloy prepared in Comparative Example 3 burns at 900°C, and its flame retardant performance is worse than that of Example 3 and Example 5.

[0078] In summary, the rare earth magnesium alloy prepared by the present invention has both good flame retardant properties and mechanical properties, can be formed into different shapes through a casting process, and has good casting properties.

[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A high-strength flame-retardant rare earth magnesium alloy, characterized in that: The chemical composition of the alloy includes, by weight percentage, 0.5-15% Yb, 0.5-15% M, 0.03-0.8% Zr or 0.03-0.5% Mn, and the balance is Mg and unavoidable impurities; The M is La, Ce, Y, Gd, Nd, Sm or Ho.

2. A method for preparing the high-strength flame-retardant rare earth magnesium alloy according to claim 1, characterized in that: include: S1. Descaling and preheating the Mg-Zr master alloy or Mg-Mn master alloy, Mg-Yb master alloy, Mg-M master alloy and magnesium ingot; S2, putting magnesium ingot, Mg-Yb master alloy and Mg-M master alloy into a crucible furnace as charge, and passing protective gas; S3, heating to a certain temperature, adding Mg-Zr master alloy or Mg-Mn master alloy after the charge is completely melted, and stirring; S4, adjusting the furnace temperature to a certain temperature, and performing gravity casting or high pressure die casting after the melt is allowed to stand to obtain a magnesium alloy ingot; S5. Using the magnesium alloy ingot as a flame retardant rare earth magnesium alloy, or using the magnesium alloy ingot obtained by gravity casting as a flame retardant rare earth magnesium alloy after post-treatment.

3. The preparation method according to claim 2, characterized in that: The preheating temperature in S1 is 200-300°C and the time is 20-40 minutes.

4. The preparation method according to claim 2, characterized in that: The protective gas in S2 is CO2 containing 1 to 10 vol% SF6.

5. The preparation method according to claim 2, characterized in that: In S3, the temperature is raised to 700-800°C; the stirring time is 5-10 minutes.

6. The preparation method according to claim 2, characterized in that: In S4, the furnace temperature is adjusted to 690-710°C.

7. The preparation method according to claim 2, characterized in that: During S4 medium and high pressure die casting, the melt temperature is 685-695°C.

8. The preparation method according to claim 2, characterized in that: The post-treatment method in S5 is solution aging or solution extrusion.

9. The preparation method according to claim 8, characterized in that: The solution temperature during solution aging is 450-540°C, and the solution temperature during solution extrusion is 450-540°C.

10. The preparation method according to claim 8 or 9, characterized in that: The process parameters of the solid solution extrusion are: extrusion ratio of 7 to 28, extrusion speed of 0.1 to 1 mm / s, mold temperature of 250 to 350°C, and ingot temperature of 300 to 520°C.

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