Nano oxide dispersion strengthened magnesium alloy and preparation method thereof

Abstract

The invention discloses a nano oxide dispersion strengthened magnesium alloy and a preparation method thereof, and the nano oxide dispersion strengthened magnesium alloy comprises the following elements in percentage by mass: 0.05 to 1.50 percent of O, 0.03 to 2.50 percent of Ca, 0.1 to 11.0 percent of Al, 0.1 to 10.0 percent of RE, 0.01 to 1.50 percent of Zr, 0.05 to 1.50 percent of Mn and the balance of Mg and inevitable impurities. RE is a rare earth element. According to the nanometer oxide dispersion strengthening magnesium alloy and the preparation method thereof, through the design of alloy components containing rare earth elements, solid solution oxygen is introduced into a solidified magnesium alloy cast ingot through oxygen supersaturated aluminum alloy precursor powder, so that the rare earth elements and oxygen are combined, and a solid phase is separated out to form nanometer oxide particles; and the nanometer oxide dispersion strengthening high-temperature magnesium alloy is obtained. The heat-resistant magnesium alloy overcomes the defects of the performance of the existing heat-resistant magnesium alloy, breaks through the problem of dispersion distribution of nano-oxides in the magnesium alloy, realizes dispersion strengthening of high-number-density nano-oxides in the magnesium alloy, and synchronously improves the heat resistance, heat stability and corrosion resistance of the magnesium alloy.

Description

Technical Field

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

[0002] Magnesium is one of the most abundant metal elements on earth, and the fourth most abundant metal 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 aluminum, zinc, manganese, calcium, rare earth, zirconium and other elements are currently the lightest metal structural materials, with a density of only one-fourth of steel and two-thirds of aluminum. They have high specific strength and 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 electronics industries.

[0003] However, compared with aluminum alloys, magnesium alloys have disadvantages such as low absolute strength, insufficient heat resistance and easy corrosion, which limit their commercial application. The development of high-strength and tough heat-resistant magnesium alloys is the key to achieving widespread application of magnesium alloys. At present, 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 used at room temperature to below 300°C. Rare earth elements have a low diffusion rate in magnesium alloys, and have the functions of refining grain size, strengthening grain boundaries and solid solution strengthening. They can also form intermetallic compounds and ordered phases during aging, thereby improving the strength of magnesium alloys. Through the control of rare earth element content and aging process, the thermal strength and corrosion resistance of magnesium alloys can be optimized. For example, in patents CN102187004A, CN100383271C, CN101532107B, and CN1289703C, high heat resistance and corrosion resistance are obtained through rare earth element content design 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 on the grain boundaries and are large in size. While improving 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, the development of high-strength, 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 thermal 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 thermal strength and thermal stability of alloys. Compared with solid solution strengthening and intermetallic compound and ordered phase strengthening, nano-oxide dispersion strengthening has a more obvious improvement in 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 strength, creep properties and oxidation resistance far exceeding traditional nickel-based high-temperature alloys 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 aging-strengthened aluminum alloys at 500°C. However, in existing literature and patents, the prior art does not disclose 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 ways to disperse oxides. One is to physically disperse nano-oxide powders into the alloy matrix by ball milling. For example, patent CN107699811A proposes adding SiO2 nano-powders to alloy powders for ball milling, and then hot isostatic pressing or hot extrusion of the ball-milled powders to obtain oxide dispersion-strengthened steel. This method is suitable for alloy matrices with Fe, Ni, Mo, etc. as the main components; the other is to prepare by chemical reaction. For example, patent CN1092240C discloses a method for preparing aluminum oxide dispersion-strengthened titanium alloy by mixing TiO2 powder with aluminum powder and performing high-energy ball milling, and reacting oxides with metal reducing agents. This method is suitable for alloy matrices with Ti, Cu, etc. as the main components. For magnesium alloys, it is difficult to achieve dispersed distribution of nano-oxides by the above two methods. The main reason is that magnesium is a very active metal that is flammable, explosive and cannot be reduced. If powder metallurgy is used, magnesium powder will inevitably oxidize itself during ball milling to form structural defects such as inclusions, which will seriously reduce the plasticity of the material. At the same time, because magnesium cannot be reduced, it cannot be prepared by chemical synthesis. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is that the existing nano-oxide dispersion-strengthened alloys have insufficient performance of heat-resistant magnesium 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. The alloy composition is designed to contain rare earth elements, and oxygen-supersaturated aluminum alloy precursor powder is used to introduce solid solution oxygen into the solidified magnesium alloy ingot, so that the rare earth elements and oxygen are combined to form nano-oxide particles in the solid phase, and a nano-oxide dispersion-strengthened high-temperature magnesium alloy is obtained. The alloy has good high-temperature strength, creep life, thermal stability and corrosion resistance, and its use temperature can reach 400°C, overcoming the shortcomings of the existing heat-resistant magnesium alloy performance, and breaking through the difficulty of nano-oxide dispersion distribution in magnesium alloys, realizing high-density nano-oxide dispersion strengthening in magnesium alloys, and simultaneously improving its thermal strength, thermal stability and corrosion resistance.

[0007] To achieve the above-mentioned object, the present invention provides a nano-oxide dispersion strengthened magnesium alloy, comprising 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 being Mg and unavoidable impurities; RE is a rare earth element.

[0008] Furthermore, 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.

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

[0010] Furthermore, it contains 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 .

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

[0012] 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 oxygen-supersaturated aluminum alloy precursor powder;

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

[0014] 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.

[0015] Furthermore, 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 oxygen-supersaturated aluminum alloy precursor powder, wherein 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 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.

[0016] Furthermore, 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 by 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 melt temperature 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; the oxygen-supersaturated aluminum alloy precursor powder prepared by the above S1 is sprayed into the magnesium alloy master alloy melt by using an inert carrier gas, and the amount of the oxygen-supersaturated aluminum alloy precursor powder is 1-100 kg / ton of magnesium alloy.

[0017] Furthermore, 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 through stirring.

[0018] Furthermore, the percentage of each component of the magnesium alloy master alloy in the total mass is: 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] Furthermore, the method further includes subjecting the alloy ingot to deformation treatment according to the use requirements: the alloy ingot is kept at 450-480° C. for 8-10 hours, and then cooled to 400-420° C. for extrusion molding or forging. Technical Effects

[0020] The invention provides a nano-oxide dispersion-strengthened magnesium alloy and a preparation method thereof, which proposes a significantly different idea from the solid solution strengthening and intermetallic compound and ordered phase strengthening in the traditional rare earth magnesium alloy. Based on the design of oxygen-containing rare earth components and a unique preparation technology, supersaturated solid solution oxygen and solid solution rare earth elements are introduced into the solidified structure of the magnesium alloy through oxygen-supersaturated aluminum alloy precursor powder containing rare earths, and the interstitial solid solution of oxygen in aluminum and its strong affinity with rare earth elements are utilized to realize the high number density dispersion distribution of nano-oxides in the magnesium alloy by solid phase precipitation. The nano-oxides pin the grain boundaries, inhibit the growth of grains, reduce the diffusion rate of elements on the grain boundaries, increase the sliding resistance of dislocations and promote the activation of more slip systems, and simultaneously improve the strength, toughness and corrosion resistance of the magnesium alloy, and significantly improve the creep life and thermal stability of the magnesium alloy.

[0021] When the nano-oxide dispersion-strengthened magnesium alloy provided by the present invention is 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 400°C high temperature tensile yield strength is 206-217 MPa, the tensile strength is 236-259 MPa, and the elongation is greater than 15%; the corrosion rate is less than 30Mpy in the ASTM B117 standard salt spray test, and the above performance is significantly better than that of the existing heat-resistant magnesium alloy; the use temperature of the nano-oxide dispersion-strengthened magnesium alloy can reach 400°C, which is 50-100°C higher than that of the existing heat-resistant magnesium alloy.

[0022] The mass percentage content of rare earth elements in the nano-oxide dispersion-strengthened magnesium alloy provided by the present invention does not exceed 10%, thereby reducing the amount of rare earth elements used, and reducing the density of the magnesium alloy while reducing the cost.

[0023] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a transmission electron microscopic image of a preferred embodiment (Embodiment 3) of the present invention, showing the high number density of nano-oxide dispersion morphology in the nano-oxide dispersion strengthened magnesium alloy. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] In the following description, specific details such as specific internal procedures and techniques are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may 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 prevent unnecessary details from obstructing the description of the present invention.

[0027] The present invention provides a nano-oxide dispersion-strengthened magnesium alloy, comprising 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; RE is a rare earth element. 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. 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 ASTMB117 standard salt spray test, the corrosion rate of the nano-oxide dispersion-strengthened magnesium alloy of the present invention is less than 30Mpy.

[0028] The nano-oxide dispersion-strengthened magnesium alloy of the present invention is also suitable for deformation (forging) alloy applications.

[0029] In another preferred embodiment of the present invention, a method for preparing a nano-oxide dispersion-strengthened magnesium alloy is provided, comprising the following steps:

[0030] S1, Al metal powder, oxide powder and rare earth metal powder are mixed according to a proportion and mechanically alloyed in a high-purity argon protective atmosphere to obtain oxygen-supersaturated aluminum alloy precursor powder; wherein 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 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.

[0031] S2, spraying oxygen-supersaturated aluminum alloy precursor powder into a magnesium alloy master alloy to obtain a magnesium alloy master alloy melt; specifically, using an inert carrier gas to spray the oxygen-supersaturated aluminum alloy precursor powder into the magnesium alloy master alloy melt to obtain the magnesium alloy master alloy melt, and the weight percentage of the oxygen-supersaturated aluminum alloy precursor powder to the magnesium alloy master alloy melt is 1~100kg / ton; controlling the melt temperature to 690±20℃, keeping warm for 5~10 minutes, and introducing a mixed protective gas of SF6 and CO2 during the smelting process to prevent oxidation of the melt; using an inert carrier gas to spray the oxygen-supersaturated aluminum alloy precursor powder prepared in the above S1 into the magnesium alloy master alloy melt, and the amount of the oxygen-supersaturated aluminum alloy precursor powder is 1~100kg / ton of magnesium alloy; the powder spraying process is specifically: using an inert carrier gas to spray the oxygen-supersaturated aluminum alloy precursor powder into the magnesium alloy melt at a high speed, and the oxygen-supersaturated aluminum alloy precursor powder is sprayed out at a speed of 1~50kg / min. 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.

[0032] In addition, the oxygen-supersaturated aluminum alloy precursor powder is pressed into a 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.

[0033] 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 cast-rolling.

[0034] 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.

[0035] Embodiment 1:

[0036] In the nano-oxide dispersion-strengthened magnesium alloy provided by the embodiment of the present invention, the percentage of each component in the total mass is: 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 each element in the final alloy material.

[0037] First, oxygen-supersaturated aluminum alloy precursor powder is prepared by mechanical alloying: Al metal powder, rare earth Y 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 oxygen-supersaturated aluminum alloy precursor powder. The percentage of rare earth Y metal powder in the precursor powder raw material 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 mechanical alloying ball-to-material ratio is 25:1, the ball milling time is 25 hours, and the ball milling medium is corundum ball.

[0038] Smelting magnesium alloy master alloy: the percentage of each component of the master alloy in the total mass is: Al: 1.00%, Zr: 0.05%, Mn: 0.10%, and the balance is Mg and unavoidable impurities.

[0039] Then, the oxygen-supersaturated aluminum alloy precursor powder prepared by mechanical alloying steel is sprayed into the magnesium alloy master alloy: the temperature of the master 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 the melt from oxidation; the oxygen-supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy melt using argon gas, the amount of the oxygen-supersaturated aluminum alloy precursor powder is 50kg / ton of magnesium alloy, and the precursor powder spraying speed is 50kg / min.

[0040] Solidification to obtain nano-oxide dispersion-strengthened magnesium alloy ingots: After skimming off the scum and covering agent on the surface of the alloy liquid, the nano-oxide dispersion-strengthened magnesium alloy ingots are obtained by die-casting.

[0041] The alloy ingot is subjected to deformation treatment: after the alloy ingot is kept at 460° C. for 8 hours, it is cooled to 410° C. and forged to obtain the final deformation nano-oxide dispersion strengthened magnesium alloy.

[0042] According to transmission electron microscopy (TEM) and three-dimensional atom probe (APT) tests, the number density of nano-oxides in the final solid structure of the nano-oxide dispersion-strengthened magnesium alloy in this embodiment is 9.7×10 23 m -3 The average particle size is 2.9nm, and the main components of the particles are Y-Mg-Ca-Al-O; the room temperature tensile test of GB / T 228.1-2021 and the high temperature tensile test of GB / T228.2-2015 are adopted, and the room temperature tensile yield strength is 238 MPa, the tensile strength is 387 MPa, and the elongation is 15.7%; the high temperature tensile yield strength of 400℃ is 209 MPa, the tensile strength is 243MPa, and the elongation is 16.7%; the corrosion rate of ASTM B117 standard salt spray test is 25Mpy.

[0043] Embodiment 2:

[0044] The main difference between the embodiment of the present invention and the first embodiment is that in the present embodiment, the oxygen content and the rare earth content are further increased to obtain nano-oxides with a higher number density, thereby further improving the corrosion resistance of the material, but the elongation of the material is reduced.

[0045] In the nano-oxide dispersion strengthened magnesium alloy provided by the embodiment of the present invention, the percentage of each component in the total mass is: O: 0.65%, Ca: 0.75%, Al: 5.50%, RE: 3.10% (including Y: 1.30%, Gd: 1.80%), Zr: 0.15%, Mn: 0.10%, and the balance is Mg and unavoidable impurities.

[0046] First, oxygen-supersaturated aluminum alloy precursor powder is prepared by mechanical alloying: 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 oxygen-supersaturated aluminum alloy precursor powder. The percentage of rare earth Gd metal powder in the precursor powder raw material 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 mechanical alloying ball-to-material ratio is 30:1, the ball milling time is 35 hours, and the ball milling medium is corundum ball.

[0047] Smelting magnesium alloy master alloy: the percentage of each component of the master alloy in the total mass is: Zr: 0.15%, Mn: 0.10%, and the balance is Mg and inevitable impurities.

[0048] Then, the oxygen-supersaturated aluminum alloy precursor powder prepared by mechanical alloying steel is sprayed into the magnesium alloy master alloy: the temperature of the master 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 the melt from oxidation; the oxygen-supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy melt using argon gas, the amount of the oxygen-supersaturated aluminum alloy precursor powder is 100kg / ton of magnesium alloy, and the precursor powder spraying speed is 25kg / min.

[0049] Solidification to obtain nano-oxide dispersion-strengthened magnesium alloy ingots: After skimming off the scum and covering agent on the surface of the alloy liquid, the nano-oxide dispersion-strengthened magnesium alloy ingots are obtained by die-casting.

[0050] According to transmission electron microscopy (TEM) and three-dimensional atom probe (APT) tests, the number density of nano-oxides in the final solid structure of the nano-oxide dispersion-strengthened magnesium alloy in this embodiment is 2.3×10 24 m -3The average particle size is 3.2nm, and the main components of the particles are Y-Gd-Mg-Ca-Al-O; the room temperature tensile test of GB / T 228.1-2021 and the high temperature tensile test of GB / T228.2-2015 show that the 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 of 400℃ is 215 MPa, the tensile strength is 252 MPa, and the elongation is 15.3%; the corrosion rate is 19Mpy using the ASTM B117 standard salt spray test.

[0051] Embodiment three:

[0052] The main difference between the embodiment of the present invention and the second embodiment is that in the present embodiment, the contents of Ca, Al and Zr are increased and the content of RE is reduced, which can further reduce the cost while maintaining the high strength and toughness of the alloy, but the corrosion resistance is slightly reduced.

[0053] In the nano-oxide dispersion strengthened magnesium alloy provided by the embodiment of the present invention, the percentage of each component in the total mass is: O: 0.65%, Ca: 2.30%, Al: 9.50%, RE: 0.30% (including Y: 0.27%, Gd: 0.03%), Zr: 0.45%, Mn: 0.10%, and the balance is Mg and unavoidable impurities.

[0054] First, oxygen-supersaturated aluminum alloy precursor powder is prepared by mechanical alloying: 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 oxygen-supersaturated aluminum alloy precursor powder. The percentage of rare earth Gd metal powder in the precursor powder raw material is 0.3%, the percentage of CaO powder in the total mass of the precursor powder is 20.0%, the percentage of Y2O3 in the total mass of the precursor powder is 3.5%, and the balance is Al metal powder; the mechanical alloying ball-to-material ratio is 20:1, the ball milling time is 30 hours, and the ball milling medium is zirconia ball.

[0055] Smelting magnesium alloy master alloy: the percentage of each component of the master alloy in the total mass is: Al: 1.90%, Ca: 0.90%, Zr: 0.45%, Mn: 0.10%, and the balance is Mg and unavoidable impurities.

[0056] Then, the oxygen-supersaturated aluminum alloy precursor powder prepared by mechanical alloying steel is sprayed into the magnesium alloy master alloy: the temperature of the master 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 the melt from oxidation; the oxygen-supersaturated aluminum alloy precursor powder is sprayed into the magnesium alloy master alloy melt using argon gas, the amount of the oxygen-supersaturated aluminum alloy precursor powder is 100kg / ton of magnesium alloy, and the precursor powder spraying speed is 25kg / min.

[0057] Solidification to obtain nano-oxide dispersion-strengthened magnesium alloy ingots: After skimming off the scum and covering agent on the surface of the alloy liquid, the nano-oxide dispersion-strengthened magnesium alloy ingots are obtained by die-casting.

[0058] According to transmission electron microscopy (TEM) and three-dimensional atom probe (APT) tests, the number density of nano-oxides in the final solid structure of the nano-oxide dispersion-strengthened magnesium alloy in this embodiment is 2.6×10 24 m -3 The average particle size is 3.5nm, and the main components of the particles are Y-Ca-Al-Zr-O. The transmission electron microscopy image of the sample is as follows Figure 1 As shown; using GB / T228.1-2021 room temperature tensile test and GB / T228.2-2015 high temperature tensile mechanical property test, the room temperature tensile yield strength is 242 MPa, the tensile strength is 407 MPa, and the elongation is 13.9%; the 400℃ high temperature tensile yield strength is 207 MPa, the tensile strength is 249 MPa, and the elongation is 15.6%; using ASTM B117 standard salt spray test, the corrosion rate is 27Mpy.

[0059] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A nano-oxide dispersion strengthened magnesium alloy, characterized in that: 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.

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. The nano-oxide dispersion strengthened magnesium alloy according to claim 1, characterized in that: The weight ratio of O / (RE+Ca+Al+Zr) in the final composition of the alloy is 1 / (1~50).

4. The nano-oxide dispersion strengthened magnesium alloy according to claim 1, characterized in that: Contains high number density nano oxide particles, with an average particle size of less than 5 nm and a number density of not less than 5×10 23 m -3 .

5. A method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. 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-saturated aluminum alloy precursor powder; 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 cast-rolling.

6. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 5, characterized in that: Al metal powder, oxide powder and rare earth metal powder are mixed according to a proportion and mechanically alloyed in a high-purity argon protective atmosphere to obtain oxygen-supersaturated aluminum alloy precursor powder, wherein 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 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 ball or zirconia ball.

7. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 5, 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.

8. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 5, 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.

9. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 5, 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.

10. The method for preparing a nano-oxide dispersion-strengthened magnesium alloy according to claim 5, 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.

Images