A nano-oxide dispersion strengthened magnesium alloy and its preparation method

Abstract

The present invention discloses a nano-oxide dispersion strengthened magnesium alloy and a preparation method thereof. Among them, the nano-oxide dispersion strengthened magnesium alloy comprises the following elements in mass percentages: O: 0.05 - 1.50%, Ca: 0.03 - 2.50%, Al: 0.1 - 11.0%, RE: 0.1 - 10.0%, Zr: 0.01 - 1.50%, Mn: 0.05 - 1.50%, and the balance is Mg and inevitable impurities; RE is a rare earth element. The present invention provides a nano-oxide dispersion strengthened magnesium alloy and a preparation method thereof. Through the alloy composition design containing rare earth elements, and by using an oxygen supersaturated aluminum alloy precursor powder to introduce solid-solution oxygen into the solidified magnesium alloy ingot, the rare earth elements combine with oxygen to precipitate in solid phase to form nano-oxide particles, thereby obtaining a nano-oxide dispersion strengthened high-temperature magnesium alloy. It overcomes the deficiencies of the existing heat-resistant magnesium alloys, breaks through the problem of the nano-oxide dispersion distribution in magnesium alloys, realizes the high-number density nano-oxide dispersion strengthening in magnesium alloys, and simultaneously improves its thermal strength, thermal stability and corrosion resistance characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of alloys, and particularly to a nano-oxide dispersion strengthened magnesium alloy and a preparation method thereof. Background Art

[0002] Magnesium is one of the most abundant metallic elements on the earth. It is the fourth most abundant metallic element in the earth's crust after aluminum, iron, and calcium, with a content of 2.33%. Magnesium has low strength and plasticity. Magnesium alloys formed by adding elements such as aluminum, zinc, manganese, calcium, rare earths, and zirconium are currently the lightest metallic structural materials. Their density is only one-fourth that of steel and two-thirds that of aluminum. They have high specific strength, specific stiffness, good damping and shock absorption performance, electromagnetic shielding performance, biocompatibility, and excellent casting performance, and have broad application prospects in the fields of transportation, aerospace, biomedicine, and the electronics industry.

[0003] However, compared with aluminum alloys, magnesium alloys have disadvantages such as relatively low absolute strength, insufficient heat resistance, and easy corrosion, which limit their commercial applications. Developing high-strength, tough, and heat-resistant magnesium alloys is the key to realizing the wide application of magnesium alloys. Currently, commercial heat-resistant magnesium alloys mainly improve their heat resistance by adding rare earth elements. For example, Y, Gd, etc. are added to commercial magnesium alloys WE43, WE54, and WE94, which can be applied at room temperature to below 300°C. Rare earth elements have a low diffusion rate in magnesium alloys, and have the effects of refining grain size, strengthening grain boundaries, and solid solution strengthening, and can form intermetallic compounds and ordered phases during the aging process to improve the strength of magnesium alloys. By controlling the content of rare earth elements and the aging process, the thermal strength and corrosion resistance of magnesium alloys can be optimized. For example, in patents CN102187004A, CN100383271C, CN101532107B, and CN1289703C, higher heat resistance and corrosion resistance characteristics are obtained through the design of rare earth element content and process optimization. However, the thermal strength of heat-resistant rare earth magnesium alloys is still significantly lower than that of aluminum alloys, which limits their industrial applications. At the same time, the intermetallic compounds formed by rare earth elements in magnesium are mainly distributed at grain boundaries and have relatively large sizes. While improving the thermal strength, the deformation ability becomes worse. In addition, the addition amount of rare earth elements in existing rare earth magnesium alloys usually reaches more than 10%, which not only increases the density of magnesium alloys but also greatly increases the production cost of magnesium alloys. Therefore, developing high-strength, tough, and low-cost heat-resistant magnesium alloys is an important direction for the research and development of magnesium alloy technology.

[0004] Nano-oxide dispersion strengthening is an effective method to simultaneously improve the hot strength and thermal stability of alloys. Oxides have excellent thermal stability, can effectively pin dislocations and interface migration, and reduce the diffusion rate of alloying elements, thereby improving the hot strength and thermal stability of alloys. Compared with solid-solution strengthening, intermetallic compound and ordered-phase strengthening, nano-oxide dispersion strengthening is more obvious in improving heat resistance. For example, the nano-oxide dispersion strengthened NiCoCr alloy prepared by laser cladding additive manufacturing in the paper (Nature, Vol 617, 513-518, 2023) has far better strength, creep properties and oxidation resistance than traditional nickel-based superalloys at 1093 °C. The nano-MgO particle dispersion strengthened aluminum alloy prepared by powder metallurgy in the paper (Nature Materials, Vol 23, 747-754, 2024) has significantly better strength and creep properties than age-hardened aluminum alloys at 500 °C. However, in the existing literature and patents, the prior art has not disclosed nano-oxide dispersion strengthened magnesium alloys and their preparation methods.

[0005] Nano-oxide dispersion strengthened alloys are usually prepared by powder metallurgy or chemical synthesis of reducible metals. The core technical difficulty lies in how to achieve the dispersion distribution of nano-oxides in the alloy matrix. There are two dispersion methods for oxides. One is to physically disperse nano-oxide powders into the alloy matrix by ball milling. For example, in patent CN107699811A, SiO2 nano-powders are added to alloy powders for ball milling, and then the ball-milled powders are hot isostatically pressed or hot extruded to obtain oxide dispersion strengthened steel. This method is applicable to alloy matrices mainly composed of Fe, Ni, Mo, etc. The other is to prepare by chemical reaction. For example, patent CN1092240C discloses a method of mixing TiO2 powder and aluminum powder and performing high-energy ball milling to prepare alumina dispersion strengthened titanium alloy by the reaction of oxide and metal reducing agent. This method is applicable to alloy matrices mainly composed of Ti, Cu, etc. For magnesium alloys, it is difficult to achieve the dispersion distribution of nano-oxides by the above two methods. The main reason is that magnesium is a very active metal with the characteristics of flammability, explosiveness and irreducibility. If the powder metallurgy method is used, it is difficult to avoid self-oxidation of magnesium powder during ball milling to form tissue defects such as inclusions, which seriously reduces the plasticity of the material. At the same time, because magnesium cannot be reduced, the chemical synthesis method cannot be used either. Summary of the Invention

[0006] In view of the above-mentioned defects of the prior art, the technical problems to be solved by the present invention are the insufficient performance of heat-resistant magnesium alloys in existing nano-oxide dispersion-strengthened alloys and the difficulty of nano-oxide dispersion distribution in magnesium alloys. The present invention provides a nano-oxide dispersion-strengthened magnesium alloy and a preparation method thereof. Through the alloy composition design containing rare earth elements and using oxygen supersaturated aluminum alloy precursor powder to introduce solid solution oxygen into the solidified magnesium alloy ingot, rare earth elements combine with oxygen to precipitate in solid phase to form nano-oxide particles, obtaining a nano-oxide dispersion-strengthened high-temperature magnesium alloy. This alloy has good high-temperature strength, creep life, thermal stability and corrosion resistance. Its service temperature can reach 400 °C, overcoming the deficiencies of existing heat-resistant magnesium alloys and breaking through the problem of nano-oxide dispersion distribution in magnesium alloys, achieving high-number-density nano-oxide dispersion strengthening in magnesium alloys and simultaneously improving its thermal strength, thermal stability and corrosion resistance.

[0007] To achieve the above object, the present invention provides a nano-oxide dispersion-strengthened magnesium alloy, including the following elements in mass percentages: O: 0.05~1.50%, Ca: 0.03~2.50%, Al: 0.1~11.0%, RE: 0.1~10.0%, Zr: 0.01~1.50%, Mn: 0.05~1.50%, and the balance is Mg and inevitable impurities; RE is a rare earth element.

[0008] Further, the rare earth element includes one or more of lanthanum La, yttrium Y, cerium Ce, gadolinium Gd, erbium Er, neodymium Nd, praseodymium Pr, terbium Tb, samarium Sm, dysprosium Dy or scandium Sc elements.

[0009] Further, the weight ratio of O / (RE + Ca + Al + Zr) in the final composition of the alloy is 1 / (1~50).

[0010] Further, it contains high-number-density nano-oxide particles, the average size of the particles is less than 5 nm, and the number density is not less than 5×10 23 m -3 .

[0011] In another preferred embodiment of the present invention, a preparation method of a nano-oxide dispersion-strengthened magnesium alloy is provided, including the following steps:

[0012] Mix Al metal powder, oxide powder and rare earth metal powder according to the ratio and carry out mechanical alloying under a high-purity argon protection atmosphere to obtain oxygen supersaturated aluminum alloy precursor powder;

[0013] Spray the oxygen supersaturated aluminum alloy precursor powder into the magnesium alloy master alloy to obtain an oxygen-containing magnesium alloy melt;

[0014] After skimming the dross and covering agent on the surface of the oxygen-containing magnesium alloy melt, a nano-oxide dispersion-strengthened magnesium alloy ingot is obtained by direct casting, die casting or continuous casting and rolling.

[0015] Further, Al metal powder, oxide powder and rare earth metal powder are mixed according to the ratio and mechanically alloyed under a high-purity argon protective atmosphere to obtain an oxygen supersaturated aluminum alloy precursor powder. Among them, the percentage of rare earth metal powder in the total mass of the precursor powder is 0.1-20.0%, the percentage of oxide in the total mass of the precursor powder is 0.1-35.0%, and the balance is Al metal powder; the oxide is one or a combination of CaO, MnO or rare earth oxides; the ball-to-material ratio of mechanical alloying is 5:1-50:1, the ball milling time is 8-72 hours, and the ball milling medium is corundum balls or zirconia balls.

[0016] Further, the oxygen supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy melt to obtain an oxygen-containing magnesium alloy melt. Specifically, the oxygen supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy melt by using an inert carrier gas. The dosage of the oxygen supersaturated aluminum alloy precursor powder accounts for 1-100 kg / ton of the weight of the magnesium alloy master alloy melt; the melt temperature is controlled at 690±20 °C and kept warm for 5-10 minutes. During the melting process, a mixed protective gas of SF6 and CO2 is introduced to prevent the melt from oxidizing; the oxygen supersaturated aluminum alloy precursor powder prepared in the above S1 is sprayed into the magnesium alloy master alloy melt by using an inert carrier gas, and the dosage of the oxygen supersaturated aluminum alloy precursor powder is 1-100 kg / ton of magnesium alloy.

[0017] Further, the oxygen supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy to obtain a magnesium alloy master alloy melt. Specifically, the oxygen supersaturated aluminum alloy precursor powder is pressed into blocks and then put into the magnesium alloy melt, or is pre-placed in a melting crucible and melted together with the raw material blocks, and the components contained in the precursor powder are uniformly dissolved in the melt by stirring.

[0018] Further, the percentages of the components of the magnesium alloy master alloy in the total mass are respectively: Ca: 0-2.0%, Al: 0-10.0%, RE: 0-10.0%, Zr: 0-1.50%, Mn: 0-1.50%, and the balance is Mg and unavoidable impurities.

[0019] Further, it also includes performing a deformation treatment on the alloy ingot according to the usage requirements: after keeping the alloy ingot at 450-480 °C for 8-10 h, it is cooled to 400-420 °C and then extruded or forged.

[0020] Technical effects

[0021] A nano-oxide dispersion-strengthened magnesium alloy and a preparation method thereof provided by the present invention propose an idea significantly different from the solid solution strengthening, intermetallic compound and ordered phase strengthening in traditional rare-earth magnesium alloys. Based on the design of oxygen-containing and rare-earth-containing components and unique preparation techniques, supersaturated solid solution oxygen and solid solution rare-earth elements are introduced into the solidification structure of the magnesium alloy through a rare-earth-containing oxygen supersaturated aluminum alloy precursor powder. Utilizing the interstitial solid solution of oxygen in aluminum and its strong affinity with rare-earth elements, a high number density dispersion distribution of nano-oxides in the magnesium alloy is achieved in the form of solid-phase precipitation. The nano-oxides pin the grain boundaries, inhibit grain growth, reduce the diffusion rate of elements at the grain boundaries, increase the dislocation slip resistance and promote the activation of more slip systems, simultaneously improving the strength, toughness and corrosion resistance of the magnesium alloy, and significantly improving the creep life and thermal stability of the magnesium alloy.

[0022] When the nano-oxide dispersion-strengthened magnesium alloy provided by the present invention is used as a casting alloy, at the T6 state, the room-temperature tensile yield strength of the nano-oxide dispersion-strengthened magnesium alloy is 230 - 260 MPa, the tensile strength is 370 - 410 MPa, and the elongation is greater than 13%; the high-temperature tensile yield strength at 400 °C is 206 - 217 MPa, the tensile strength is 236 - 259 MPa, and the elongation is greater than 15%; using the ASTM B117 standard salt spray test, the corrosion rate is less than 30 Mpy, and the above performances are significantly better than those of existing heat-resistant magnesium alloys; the service temperature of the nano-oxide dispersion-strengthened magnesium alloy can reach 400 °C, which is 50 - 100 °C higher than that of existing heat-resistant magnesium alloys.

[0023] The mass percentage content of rare-earth elements in the nano-oxide dispersion-strengthened magnesium alloy provided by the present invention is not more than 10% at most, reducing the dosage of rare-earth elements and reducing the cost while reducing the density of the magnesium alloy.

[0024] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the drawings to fully understand the purpose, features and effects of the present invention. Description of the Drawings

[0025] Figure 1 It is a transmission electron microscopy imaging picture of a preferred embodiment (Embodiment 3) of the present invention, showing the high number density dispersion morphology of nano-oxides in the nano-oxide dispersion-strengthened magnesium alloy. Detailed Embodiments

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] In the following description, specific details such as specific internal programs and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0028] The present invention provides a nano-oxide dispersion strengthened magnesium alloy, which comprises the following elements in mass percentages: O: 0.05 - 1.50%, Ca: 0.03 - 2.50%, Al: 0.1 - 11.0%, RE: 0.1 - 10.0%, Zr: 0.01 - 1.50%, Mn: 0.05 - 1.50%, and the balance is Mg and inevitable impurities; RE is a rare earth element. Among them, the rare earth element includes one or more of lanthanum La, yttrium Y, cerium Ce, gadolinium Gd, erbium Er, neodymium Nd, praseodymium Pr, terbium Tb, samarium Sm, dysprosium Dy, or scandium Sc elements. The weight ratio of O / (RE + Ca + Al + Zr) in the final composition of the alloy is 1 / (1 - 50). The alloy contains high-density nano-oxide particles, the average particle size is less than 5 nm, and the number density is not less than 5×10 23 m -3 . When used as a casting alloy, the room-temperature tensile yield strength of the nano-oxide dispersion strengthened magnesium alloy in the T6 state is 230 - 260 MPa, the tensile strength is 370 - 410 MPa, and the elongation is greater than 13%; the high-temperature tensile yield strength at 400 °C is 206 - 217 MPa, the tensile strength is 236 - 259 MPa, and the elongation is greater than 15%; using the ASTM B117 standard salt spray test, the corrosion rate of the nano-oxide dispersion strengthened magnesium alloy described in the present invention is less than 30 Mpy.

[0029] The nano-oxide dispersion strengthened magnesium alloy of the present invention is also applicable to deformation (forging) alloy applications.

[0030] In another preferred embodiment of the present invention, a preparation method of a nano-oxide dispersion strengthened magnesium alloy is provided, which comprises the following steps:

[0031] S1, mixing Al metal powder, oxide powder, and rare earth metal powder according to the ratio and performing mechanical alloying under a high-purity argon protective atmosphere to obtain an oxygen supersaturated aluminum alloy precursor powder; wherein, the percentage of the rare earth metal powder in the total mass of the precursor powder is 0.1 - 20.0%, the percentage of the oxide in the total mass of the precursor powder is 0.1 - 35.0%, and the balance is Al metal powder; the oxide is one or more combinations of CaO, MnO, or rare earth oxides; the ball-to-material ratio of mechanical alloying is 5:1 - 50:1, the ball milling time is 8 - 72 hours, and the ball milling medium is corundum balls or zirconia balls.

[0032] S2. The oxygen supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy to obtain a magnesium alloy master alloy melt. Specifically, the oxygen supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy melt by using an inert carrier gas to obtain the magnesium alloy master alloy melt. The dosage of the oxygen supersaturated aluminum alloy precursor powder accounts for 1 - 100 kg / ton of the weight of the magnesium alloy master alloy melt. The melt temperature is controlled at 690 ± 20 °C and held for 5 - 10 minutes. During the melting process, a mixed protective gas of SF6 and CO2 is introduced to prevent the melt from oxidation. The oxygen supersaturated aluminum alloy precursor powder prepared in S1 is sprayed into the magnesium alloy master alloy melt by using an inert carrier gas, and the dosage of the oxygen supersaturated aluminum alloy precursor powder is 1 - 100 kg / ton of magnesium alloy. The powder spraying process is specifically as follows: the oxygen supersaturated aluminum alloy precursor powder is sprayed at a high speed into the magnesium alloy melt by using an inert carrier gas, and the spraying speed of the oxygen supersaturated aluminum alloy precursor powder is 1 - 50 kg / min. Among them, the percentages of the components of the magnesium alloy master alloy in the total mass are respectively: Ca: 0 - 2.0%, Al: 0 - 10.0%, RE: 0 - 10.0%, Zr: 0 - 1.50%, Mn: 0 - 1.50%, and the balance is Mg and unavoidable impurities.

[0033] In addition, the oxygen supersaturated aluminum alloy precursor powder is pressed into blocks and then put into the magnesium alloy melt, or is pre - placed in the melting crucible and melted together with the raw material blocks, and the components contained in the precursor powder are uniformly dissolved in the melt by stirring.

[0034] S3. After skimming the scum and covering agent on the surface of the oxygen - containing magnesium alloy melt, a nano - oxide dispersion - strengthened magnesium alloy ingot is obtained by direct casting, die - casting or continuous casting and rolling.

[0035] It also includes performing a deformation treatment on the alloy ingot according to the usage requirements: after holding the alloy ingot at 450 - 480 °C for 8 - 10 h, it is cooled to 400 - 420 °C and then extruded or forged.

[0036] Example 1:

[0037] In the nano - oxide dispersion - strengthened magnesium alloy provided by the embodiment of the present invention, the percentages of the components in the total mass are respectively: O: 0.21%, Ca: 0.32%, Al: 5.0%, Y: 0.50%, Zr: 0.05%, Mn: 0.10%, and the balance is Mg and unavoidable impurities. The above components are the designed contents of the elements in the final alloy material.

[0038] First, prepare an oxygen supersaturated aluminum alloy precursor powder by mechanical alloying: Mix Al metal powder, rare earth Y metal powder, CaO, and Y2O3 oxide powder according to the ratio and perform mechanical alloying under a high-purity argon protective atmosphere to obtain the oxygen supersaturated aluminum alloy precursor powder. In the precursor powder raw materials, the percentage of rare earth Y metal powder in the total mass of the precursor powder is 4.5%, the percentage of CaO powder in the total mass of the precursor powder is 9.0%, the percentage of Y2O3 powder in the total mass of the precursor powder is 7.0%, and the balance is Al metal powder; the ball-to-material ratio for mechanical alloying is 25:1, the ball milling time is 25 hours, and the ball milling medium is corundum balls.

[0039] Melt the magnesium alloy master alloy: The percentages of each component in the master alloy in the total mass are as follows: Al: 1.00%, Zr: 0.05%, Mn: 0.10%, and the balance is Mg and unavoidable impurities.

[0040] Then, spray the oxygen supersaturated aluminum alloy precursor powder prepared by mechanical alloying into the magnesium alloy master alloy: Control the temperature of the master alloy melt to be 690 ± 20 °C, hold for 5 - 10 minutes, and introduce a mixed protective gas of SF6 and CO2 during the melting process to prevent the melt from oxidizing; use argon to spray the oxygen supersaturated aluminum alloy precursor powder into the magnesium alloy master alloy melt, and the dosage of the oxygen supersaturated aluminum alloy precursor powder is 50 kg / ton of magnesium alloy, and the spraying speed of the precursor powder is 50 kg / min.

[0041] Solidify to obtain a nano-oxide dispersion-strengthened magnesium alloy ingot: After skimming the scum and covering agent on the surface of the alloy liquid, obtain the nano-oxide dispersion-strengthened magnesium alloy ingot by die casting.

[0042] Perform deformation treatment on the alloy ingot: Keep the alloy ingot at 460 °C for 8 h, then cool it to 410 °C and forge it to obtain the final deformed nano-oxide dispersion-strengthened magnesium alloy.

[0043] Through transmission electron microscopy imaging analysis (TEM) and three-dimensional atom probe (APT) testing, the number density of nano-oxides in the final solid-state structure of the nano-oxide dispersion-strengthened magnesium alloy in this example is 9.7×10 23 m -3 , the average particle size is 2.9 nm, and the main components of the particles are Y-Mg-Ca-Al-O; using GB / T 228.1-2021 room temperature tensile and GB / T228.2-2015 high temperature tensile mechanical property tests, its room temperature tensile yield strength is 238 MPa, the tensile strength is 387 MPa, and the elongation is 15.7%; the 400 °C high temperature tensile yield strength is 209 MPa, the tensile strength is 243 MPa, and the elongation is 16.7%; using the ASTM B117 standard salt spray test, the corrosion rate is 25 Mpy.

[0044] Example 2:

[0045] The main difference between the embodiment of the present invention and the first embodiment is that in this embodiment, the oxygen content and the rare earth content are further increased to obtain a higher number density of nano-oxides, further improving the corrosion resistance of the material, but the elongation of the material decreases.

[0046] In the nano-oxide dispersion strengthened magnesium alloy provided by the embodiment of the present invention, the percentages of each component in the total mass are respectively: O: 0.65%, Ca: 0.75%, Al: 5.50%, RE: 3.10% (where Y: 1.30%, Gd: 1.80%), Zr: 0.15%, Mn: 0.10%, and the balance is Mg and inevitable impurities.

[0047] First, prepare an oxygen supersaturated aluminum alloy precursor powder by mechanical alloying: mix Al metal powder, Gd metal powder, CaO, and Y2O3 oxide powder according to the ratio and perform mechanical alloying under a high-purity argon protective atmosphere to obtain the oxygen supersaturated aluminum alloy precursor powder. The percentage of rare earth Gd metal powder in the total mass of the precursor powder is 18.0%, the percentage of CaO powder in the total mass of the precursor powder is 10.5%, the percentage of Y2O3 powder in the total mass of the precursor powder is 16.5%, and the balance is Al metal powder; the ball-to-material ratio of mechanical alloying is 30:1, the ball milling time is 35 hours, and the ball milling medium is corundum balls.

[0048] Smelt the magnesium alloy master alloy: The percentages of each component in the master alloy in the total mass are respectively: Zr: 0.15%, Mn: 0.10%, and the balance is Mg and inevitable impurities.

[0049] Then spray the oxygen supersaturated aluminum alloy precursor powder obtained by mechanical alloying into the magnesium alloy master alloy: control the temperature of the master alloy melt to be 690±20°C, keep it warm for 5-10 minutes, and introduce a mixed protective gas of SF6 and CO2 during the smelting process to prevent the melt from oxidizing; use argon to spray the oxygen supersaturated aluminum alloy precursor powder into the magnesium alloy master alloy melt, and the dosage of the oxygen supersaturated aluminum alloy precursor powder is 100 kg / ton of magnesium alloy, and the spraying speed of the precursor powder is 25 kg / min.

[0050] Solidify to obtain a nano-oxide dispersion strengthened magnesium alloy ingot: After skimming the scum and covering agent on the surface of the alloy liquid, obtain the nano-oxide dispersion strengthened magnesium alloy ingot by die casting.

[0051] After transmission electron microscopy imaging analysis (TEM) and three-dimensional atom probe (APT) testing, the number density of nano-oxides in the final solid state structure of the nano-oxide dispersion strengthened magnesium alloy in this embodiment is 2.3×10 24 m -3, the average particle size is 3.2 nm, and the main components of the particles are Y-Gd-Mg-Ca-Al-O; the room temperature tensile test is carried out according to GB / T 228.1-2021 and the high temperature tensile mechanical property test is carried out according to GB / T 228.2-2015. Its room temperature tensile yield strength is 248 MPa, the tensile strength is 401 MPa, and the elongation is 13.7%; the high temperature tensile yield strength at 400 °C is 215 MPa, the tensile strength is 252 MPa, and the elongation is 15.3%; the corrosion rate is 19 Mpy by the ASTM B117 standard salt spray test.

[0052] Example 3:

[0053] The main difference between the embodiment of the present invention and Example 2 is that in this embodiment, the contents of Ca, Al and Zr are increased, and the RE content is reduced. While maintaining the high strength and toughness of the alloy, the cost can be further reduced, but the corrosion resistance decreases slightly.

[0054] In the nano-oxide dispersion strengthened magnesium alloy provided by the embodiment of the present invention, the percentages of each component in the total mass are: O: 0.65%, Ca: 2.30%, Al: 9.50%, RE: 0.30% (where Y: 0.27%, Gd: 0.03%), Zr: 0.45%, Mn: 0.10%, and the balance is Mg and unavoidable impurities.

[0055] First, an oxygen supersaturated aluminum alloy precursor powder is prepared by mechanical alloying: the Al metal powder, Gd metal powder, CaO and Y2O3 oxide powder are mixed according to the ratio and mechanically alloyed under a high-purity argon protective atmosphere to obtain an oxygen supersaturated aluminum alloy precursor powder. The percentage of the rare earth Gd metal powder in the precursor powder raw material in the total mass of the precursor powder is 0.3%, the percentage of the CaO powder in the total mass of the precursor powder is 20.0%, the percentage of the Y2O3 in the total mass of the precursor powder is 3.5%, and the balance is the Al metal powder; the ball-to-material ratio of the mechanical alloying is 20:1, the ball milling time is 30 hours, and the ball milling medium is zirconia balls.

[0056] Melting the magnesium alloy master alloy: the percentages of each component in the master alloy in the total mass are: Al: 1.90%, Ca: 0.90%, Zr: 0.45%, Mn: 0.10%, and the balance is Mg and unavoidable impurities.

[0057] Then, the oxygen supersaturated aluminum alloy precursor powder prepared by mechanical alloying is sprayed into the magnesium alloy master alloy: control the temperature of the master alloy melt to be 690 ± 20 °C, keep it warm for 5-10 minutes, and introduce a mixed protective gas of SF6 and CO2 during the melting process to prevent the melt from oxidizing; use argon to spray the oxygen supersaturated aluminum alloy precursor powder into the magnesium alloy master alloy melt, and the dosage of the oxygen supersaturated aluminum alloy precursor powder is 100 kg / ton of magnesium alloy, and the spraying speed of the precursor powder is 25 kg / min.

[0058] Obtaining a nanometer oxide dispersion strengthened magnesium alloy ingot by solidification: After skimming the dross and covering agent on the surface of the alloy liquid, a nanometer oxide dispersion strengthened magnesium alloy ingot is obtained by die casting.

[0059] Through transmission electron microscopy imaging analysis (TEM) and three-dimensional atom probe (APT) testing, the number density of nanometer oxides in the final solid-state structure of the nanometer oxide dispersion strengthened magnesium alloy in this example is 2.6×10 24 m -3 , the average particle size is 3.5 nm, and the main components of the particles are Y-Ca-Al-Zr-O. The transmission electron microscopy imaging pictures of the sample are as shown in Figure 1 ; The room temperature tensile and high temperature tensile mechanical properties are tested according to GB / T228.1-2021 and GB / T228.2-2015. Its room temperature tensile yield strength is 242 MPa, the tensile strength is 407 MPa, and the elongation is 13.9%; The high temperature tensile yield strength at 400 °C is 207 MPa, the tensile strength is 249 MPa, and the elongation is 15.6%; The corrosion rate is 27 Mpy by the ASTM B117 standard salt spray test.

[0060] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A nano-oxide dispersion strengthened magnesium alloy, characterized in that: The invention discloses a method for preparing a magnesium alloy ingot containing a rare earth element by designing an alloy composition containing rare earth elements and using an oxygen-supersaturated aluminum alloy precursor powder to introduce solid-solution oxygen into a solidified magnesium alloy ingot, so that the rare earth elements combine with oxygen to precipitate in a solid phase to form nano-oxide particles; specifically, Al metal powder, oxide powder and rare earth metal powder are mixed according to a proportion and mechanically alloyed under a high-purity argon protective atmosphere to obtain an oxygen-supersaturated aluminum alloy precursor powder, wherein the oxide is one or more combinations of CaO, MnO or rare earth oxides; the oxygen-supersaturated aluminum alloy precursor powder is sprayed into a magnesium alloy master alloy melt to obtain an oxygen-containing magnesium alloy melt; after skimming off the scum and covering agent on the surface of the oxygen-containing magnesium alloy melt, a nano-oxide dispersion-strengthened magnesium alloy ingot is obtained by direct casting, die casting or cast-rolling; The invention comprises the following elements in percentage by mass: O: 0.05-1.50%, Ca: 0.03-2.50%, Al: 0.1-11.0%, RE: 0.1-10.0%, Zr: 0.01-1.50%, Mn: 0.05-1.50%, and the balance is Mg and unavoidable impurities; the RE is a rare earth element; the weight ratio of O / (RE+Ca+Al+Zr) in the final composition of the alloy is 1 / (1-50); the alloy comprises high number density nano oxide particles, the average particle size is less than 5 nm, and the number density is not less than 5×10 23 m -3 .

2. The nano-oxide dispersion strengthened magnesium alloy according to claim 1, characterized in that: The rare earth element includes one or more of lanthanum La, yttrium Y, cerium Ce, gadolinium Gd, erbium Er, neodymium Nd, praseodymium Pr, terbium Tb, samarium Sm, dysprosium Dy or scandium Sc.

3. A method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Al metal powder, oxide powder and rare earth metal powder are mixed according to a ratio and mechanically alloyed under a high-purity argon protective atmosphere to obtain oxygen-supersaturated aluminum alloy precursor powder; wherein the percentage of rare earth metal powder to the total mass of the precursor powder is 0.1-20.0%, the percentage of oxide to the total mass of the precursor powder is 0.1-35.0%, and the balance is Al metal powder; the oxide is one or more combinations of CaO, MnO or rare earth oxides; the mechanical alloying ball-to-material ratio is 5:1-50:1, the ball milling time is 8-72 hours, and the ball milling medium is corundum balls or zirconia balls; S2. spraying the oxygen-supersaturated aluminum alloy precursor powder into the magnesium alloy master alloy melt to obtain an oxygen-containing magnesium alloy melt; S3. After skimming off the slag and covering agent on the surface of the oxygen-containing magnesium alloy melt, a nano-oxide dispersion-strengthened magnesium alloy ingot is obtained by direct casting, die casting or casting and rolling; The invention comprises the following elements in percentage by mass: O: 0.05-1.50%, Ca: 0.03-2.50%, Al: 0.1-11.0%, RE: 0.1-10.0%, Zr: 0.01-1.50%, Mn: 0.05-1.50%, and the balance is Mg and unavoidable impurities; the RE is a rare earth element; the weight ratio of O / (RE+Ca+Al+Zr) in the final composition of the alloy is 1 / (1-50); the alloy comprises high number density nano oxide particles, the average particle size is less than 5 nm, and the number density is not less than 5×10 23 m -3 .

4. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 3, characterized in that: An oxygen-supersaturated aluminum alloy precursor powder is sprayed into a magnesium alloy master alloy melt to obtain an oxygen-containing magnesium alloy melt. Specifically, the oxygen-supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy melt using an inert carrier gas, and the weight percentage of the oxygen-supersaturated aluminum alloy precursor powder to the magnesium alloy master alloy melt is 1-100 kg / ton; the temperature of the oxygen-containing magnesium alloy melt is controlled to be 690±20°C, and the temperature is kept for 5-10 minutes. During the smelting process, a mixed protective gas of SF6 and CO2 is introduced to prevent oxidation of the melt.

5. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 3, characterized in that: The oxygen-supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy to obtain a magnesium alloy master alloy melt. Specifically, the oxygen-supersaturated aluminum alloy precursor powder is pressed into a block and then put into the magnesium alloy melt, or is pre-placed in a melting crucible and melted together with the raw material block, and the components contained in the precursor powder are uniformly dissolved in the melt by stirring.

6. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 3, characterized in that: The percentages of the components of the magnesium alloy master alloy in the total mass are: Ca: 0-2.0%, Al: 0-10.0%, RE: 0-10.0%, Zr: 0-1.50%, Mn: 0-1.50%, and the balance is Mg and unavoidable impurities.

7. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 3, characterized in that: The method also includes deforming the alloy ingot according to the use requirements: after keeping the alloy ingot at 450-480°C for 8-10 hours, cooling it to 400-420°C and extruding or forging it.

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