Atomized magnesium alloy powder

Abstract

The present application provides atomized magnesium alloy powder, which can be used to manufacture complex geometric shapes and hollow lattice structures that are difficult to achieve by traditional casting or forging through additive manufacturing technologies such as laser powder bed melting, realize extremely high strength / weight ratio, and overcome the poor formability problem of magnesium alloy. The atomized magnesium alloy powder is in a powder state, and the alloy in the powder state is composed of the following components in percentage by weight: 3.7-4.3 yttrium Y; 2.0-2.5 neodymium Nd; 1.0-1.5 heavy rare earth mixture HRE; 0.4-1.0 zirconium Zr; the rest is magnesium Mg; wherein the impurity limit: Fe iron ≤0.005, nickel Ni ≤0.002, copper Cu ≤0.03, and the total content of other impurities ≤0.01; the powder state magnesium alloy is produced by electrode induction melting gas atomization or plasma rotating electrode atomization to obtain atomized magnesium alloy powder.

Description

Technical Field

[0001] This invention relates to the technical field of additive manufacturing materials, specifically atomized magnesium alloy powder. Background Technology

[0002] Additive manufacturing is a digital manufacturing technology that creates solid parts by depositing materials layer by layer based on three-dimensional model data, in contrast to traditional subtractive manufacturing methods. This technology includes two typical processes: direct energy deposition and powder bed fusion, enabling near-net-shape forming of complex structural parts and finding applications in aerospace, automotive, and medical fields.

[0003] Additive manufacturing can utilize a variety of materials, including metals, plastics, ceramics, and biomaterials. Among these, metallic materials primarily include titanium alloys, aluminum alloys, and iron-based alloys. In practice, magnesium alloys play a crucial role in modern lightweighting technologies. However, the reliable application of magnesium alloys in additive manufacturing is not yet feasible. Magnesium alloys possess excellent casting properties, machinability, damping properties, and thermal stability, as well as good electromagnetic radiation resistance and superior biocompatibility. How to combine magnesium alloys with additive manufacturing technology for widespread application in the automotive, aerospace, and orthopedic materials fields is a pressing technical challenge that needs to be addressed in the materials science of additive manufacturing. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides atomized magnesium alloy powder, which, through additive manufacturing technologies such as laser powder bed melting, can produce complex geometric shapes and hollow lattice structures that are difficult to achieve with traditional casting or forging, achieving an extremely high strength-to-weight ratio and overcoming the traditional problem of poor formability of magnesium alloys.

[0005] Atomized magnesium alloy powder, characterized in that: it is in powder form, and the alloy components in the powder form are proportioned by weight percentage as follows: Yttrium Y with a strength of 3.7-4.3 2.0-2.5 Nd; 1.0-1.5% heavy rare earth element mixture HRE; 0.4-1.0 zirconium (Zr); The remainder is magnesium (Mg); Among them, the impurity limits are: Fe (iron) ≤ 0.005, Ni (nickel) ≤ 0.002, Cu (copper) ≤ 0.03, and the total content of other impurities ≤ 0.01. Magnesium alloys in powder form are produced by atomizing molten gas through electrode induction or by plasma rotating electrode atomization to obtain atomized magnesium alloy powder.

[0006] Its further features are: The particle size distribution of the magnesium alloy particles is 15-63 μm, preferably 15-53 μm or 20-63 μm; Magnesium alloy particles have a sphericity of ≥95%, a smooth surface, and few satellite spheres and adhering bodies; Its theoretical density does not exceed 1.84 g / cm³. 3 The density in the loose state is ≥ 1.5 g / cm³. 3 The density under tapped condition is ≥ 1.7 g / cm³. 3 ; Its oxygen content is ≤ 500ppm. Oxygen will form magnesium oxide inclusions, which will become crack sources and seriously deteriorate mechanical properties and corrosion resistance. Mechanical properties, especially fatigue and ductility, must be protected by inert gas throughout the entire process of powder production, storage, transportation and use.

[0007] The process for using atomized magnesium alloy powder in additive manufacturing is characterized by additive manufacturing via laser powder bed melting, and the process parameters are as follows: The laser power ranges from 100 to 300W, depending on the spot size and scanning speed. The scanning speed is 500-1500 mm / s; The layer thickness is 20-50μm; The chamber temperature is heated to 150-200℃. Preheating by chamber temperature can reduce printing thermal stress, prevent cracking, and help with degassing.

[0008] The heat treatment process of the product after additive manufacturing is characterized by including solution treatment and artificial aging. The process parameters for solution treatment are: 525℃±5℃, heat preservation for 4-8 hours, followed by water quenching; The process parameters for artificial aging are: 250℃±5℃, heat preservation for 16-24 hours, and air cooling.

[0009] Through additive manufacturing technologies such as laser powder bed melting, it can produce complex geometric shapes and hollow lattice structures that are difficult to achieve by traditional casting or forging, achieving an extremely high strength-to-weight ratio and overcoming the traditional problem of poor formability of magnesium alloys. Detailed Implementation

[0010] Atomized magnesium alloy powder, which is in powder form, has the following composition of alloy components in powder form according to weight percentage: Yttrium (Y) with a strength of 3.7-4.3 g / L is the core strengthening element. It forms a stable dispersed phase with magnesium, improving room temperature and high temperature strength and creep resistance. Neodymium (Nd) of 2.0-2.5 g / L is a key rare earth strengthening element. It forms a strengthening precipitate phase, enhancing the precipitation strengthening effect. Heavy rare earth element (HRE) mixtures of 1.0-1.5% are key to high-temperature strengthening. These mixtures typically contain gadolinium, dysprosium, and erbium. The slow diffusion of elements within these HRE mixtures allows them to form highly thermally stable precipitates, which are the main contributors to creep resistance. Zirconium (Zr) of 0.4-1.0 g is used as a grain refiner. During solidification, it acts as a heterogeneous nucleation site, strongly refining the grains in both as-cast and printed states, significantly improving strength and plasticity. The remainder is magnesium (Mg); The impurity limits are as follows: Fe (iron) ≤ 0.005, Ni (nickel) ≤ 0.002, Cu (copper) ≤ 0.03, and the total content of other impurities ≤ 0.01. Powder is produced by atomizing molten gas through electrode induction EIGA or plasma rotating electrode atomization PREP to obtain atomized magnesium alloy powder.

[0011] In a specific embodiment, the typical chemical composition of high-purity powder (by weight percentage) is as follows: 4.0±0.2% Yttrium (Y), 2.2±0.2% Neodymium (Nd), 1.2±0.2% HRE (heavy rare earth element mixture), 0.6±0.2% Zirconium (Zr), and the remainder is magnesium (Mg). The impurity limits are as follows: Fe ≤ 0.003, Ni ≤ 0.001, Cu ≤ 0.01, and the total content of other impurities ≤ 0.005.

[0012] The control of impurity elements Fe, Ni, and Cu in powders is extremely stringent because the large specific surface area of ​​powders amplifies the negative impact of impurities on corrosion resistance, and the rapid solidification process in additive manufacturing can form harmful localized micro-cells. Top-grade powders typically require Fe+Ni content below 50 ppm.

[0013] The particle size distribution of magnesium alloy powder is 15-53μm or 20-63μm; these two particle size distribution ranges are the golden range for laser powder bed melting process. The content of fine powder with a particle size of <15μm needs to be low (usually <10%), because fine powder can exacerbate agglomeration, worsen flowability, and increase the risk of printing fumes and explosions.

[0014] The content of coarse powder with a particle size greater than 80μm needs to be low, as this may lead to defects such as uneven powder spreading and lack of fusion.

[0015] Its theoretical density does not exceed 1.84 g / cm³. 3 It is far lower than aluminum's 2.7 g / cm³. 3 And titanium 4.5g / cm 3 Its main advantage is that its density in the loose state is ≥ 1.5g / cm³. 3 The density under tapped condition is ≥ 1.7 g / cm³. 3 ; Magnesium alloy particles have a sphericity ≥95%, a smooth surface, and few satellite spheres and agglomerates. In practice, atomized magnesium alloy powder is produced by electrode induction melting gas atomization (EIGA). The electrode induction melting gas atomization (EIGA) method is free from crucible contamination and is the preferred method for producing high-purity powders of highly active metals (such as titanium and magnesium), resulting in a particle sphericity >95% and good flowability.

[0016] Its flowability was measured using a Hall effect flowmeter, with a specific embodiment showing a flowability of <35s / 50g. This excellent flowability is a prerequisite for ensuring a uniform and dense powder layer. Its sphericity and low moisture content are key to its excellent flowability.

[0017] Its oxygen content must be ≤500 ppm. Oxygen will form magnesium oxide inclusions, which will become crack sources and seriously deteriorate mechanical properties and corrosion resistance. Mechanical properties, especially fatigue and ductility, must be protected by inert gas throughout the entire process of powder production, storage, transportation and use.

[0018] Its atomized magnesium alloy powder has extremely low moisture content. Moisture will react with magnesium to produce hydrogen gas (which has an explosion risk) and magnesium oxide, resulting in printing porosity and performance degradation. Therefore, the powder needs to be stored in a vacuum-sealed or dry inert gas environment.

[0019] Due to the following characteristics of atomized magnesium alloy powder, a specific additive manufacturing process is required for additive production: High reflectivity and high thermal conductivity: Magnesium has high reflectivity to common fiber lasers (1μm wavelength) and fast thermal conductivity, requiring high laser energy input to achieve a stable molten pool; b. High vapor pressure and low boiling point: Magnesium has a low boiling point (approximately 1090℃), which makes it prone to volatilization, generating smoke and splashing under high laser energy density. Parameter optimization is needed to reduce splashing. c. Oxidation sensitivity: The printing chamber must maintain a high-purity inert atmosphere (oxygen content <100 ppm).

[0020] The process of using atomized magnesium alloy powder for additive manufacturing involves laser powder bed melting for additive manufacturing, and the process parameters are as follows: The laser power ranges from 100 to 300 W, depending on the spot size and scanning speed. The scanning speed is 500-1500 mm / s; The layer thickness is 20-50μm; The chamber temperature is heated to 150-200℃. Preheating by chamber temperature can reduce printing thermal stress, prevent cracking, and help with degassing.

[0021] The heat treatment process of the product after additive manufacturing is characterized by including solution treatment and artificial aging. The process parameters for the solid solution treatment are: 525℃±5℃, heat preservation for 4-8 hours, followed by water quenching. The purpose is to dissolve the unevenly distributed rare earth compounds in the printed state back into the magnesium matrix to obtain a supersaturated solid solution. The process parameters for artificial aging are: 250℃±5℃, heat treatment for 16-24 hours, and air cooling. This promotes the dispersion and precipitation of fine and uniform β'' and β' phases from the supersaturated matrix, resulting in a strong precipitation strengthening effect.

[0022] The properties of the additively manufactured product obtained after heat treatment using this invention are as follows: The room temperature mechanical properties include ultimate tensile strength, yield strength, elongation, elastic modulus, and fatigue limit. The ultimate tensile strength is 250-320 MPa; the yield strength is 150-220 MPa; the elongation is 8%-15%; the elastic modulus does not exceed 45 GPa; the fatigue limit is high-cycle fatigue, R=-1, which is about 30-40% of the UTS, and is strongly dependent on internal defects and surface quality. Internal defects include porosity and unfused structures. Its high-temperature mechanical properties at 200-300℃: At 250℃, its tensile strength can still be maintained above 200 MPa, and its creep resistance is significantly better than that of AZ and ZK series magnesium alloys. This is due to the thermally stable precipitates formed by heavy rare earth elements.

[0023] Its corrosion resistance is excellent among magnesium alloys, far superior to the AZ series. This is due to the rare earth elements purifying the alloy and forming a more stable surface film. However, in harsh chloride ion environments (such as seawater), a coating is still required for protection. As a biodegradable biomaterial, its degradation rate in simulated body fluids is relatively controllable, at approximately 0.3-0.6 mm / year. This can be further adjusted through surface modification, including micro-arc oxidation and coating application.

[0024] Biocompatibility: Rare earth elements such as yttrium and neodymium exist in trace amounts in the human body. This material contains yttrium and neodymium, which has good tissue compatibility and bone integration ability. Moreover, the local concentration of its degradation products can be controlled and can be metabolized or excreted, making it suitable as a biodegradable orthopedic implant material. Its thermal conductivity is less than 51 W / (m·K), giving it excellent heat dissipation performance; Its coefficient of thermal expansion is less than 26 × 10⁻⁶ in environments ranging from 25 to 200°C. -6 / K; Through additive manufacturing technologies such as laser powder bed melting, it can produce complex geometric shapes and hollow lattice structures that are difficult to achieve by traditional casting or forging, achieving an extremely high strength-to-weight ratio and overcoming the traditional problem of poor formability of magnesium alloys.

[0025] Its main application areas include: Aerospace: Weight-sensitive shells, brackets, cabin structures, UAV components, satellite camera mounts, etc.; utilizing their lightweight and mid-temperature performance; Defense and military industry: individual soldier equipment, helmet frames, portable equipment shells, missile components; Biomedical applications: biodegradable bone screws, bone plates, and vascular stents; their strength and modulus match bone, and they can gradually degrade in the human body, avoiding the need for secondary surgery for removal; High-end racing cars and motorcycles: engine and gearbox housings, rocker arms, wheel hubs, etc., pursue ultimate lightweighting; Precision instruments and electronics: require lightweight, well-ventilated optical instrument stands, high-end camera bodies, laptop casings, etc.

[0026] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0027] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Atomized magnesium alloy powder, characterized in that: It is in powder form, and the alloy composition in powder form is as follows by weight percentage: Yttrium Y with a strength of 3.7-4.3 2.0-2.5 Nd; 1.0-1.5% heavy rare earth element mixture HRE; 0.4-1.0 zirconium (Zr); The remainder is magnesium (Mg); Among them, the impurity limits are: Fe (iron) ≤ 0.005, Ni (nickel) ≤ 0.002, Cu (copper) ≤ 0.03, and the total content of other impurities ≤ 0.

01. Magnesium alloys in powder form are produced by atomizing molten gas through electrode induction or by plasma rotating electrode atomization to obtain atomized magnesium alloy powder.

2. The atomized magnesium alloy powder of claim 1, wherein: The particle size distribution of the magnesium alloy particles is 15-63 μm.

3. The atomized magnesium alloy powder of claim 2, wherein: The particle size distribution of magnesium alloy particles is 15-53μm or 20-63μm.

4. The atomized magnesium alloy powder of claim 1, wherein: Magnesium alloy particles have a sphericity of ≥95%, a smooth surface, and few satellite spheres and adhering bodies.

5. The atomized magnesium alloy powder of claim 1, wherein: The theoretical density formed thereby is not more than 1.84 g / cm 3 , the density in a loose state is ≥ 1.5 g / cm 3 , the density in a tapped state is ≥ 1.7 g / cm 3 .

6. The atomized magnesium alloy powder of claim 1, wherein: Its oxygen content is ≤ 500 ppm.

7. Process for the additive manufacturing of atomized magnesium alloy powders, characterized in that, It uses atomized magnesium alloy powder as described in any one of claims 1-6, and is additively manufactured by laser powder bed melting. The process parameters are as follows: The laser power ranges from 100 to 300 W, depending on the spot size and scanning speed. The scanning speed is 500-1500 mm / s; The layer thickness is 20-50μm; The chamber temperature is heated to 150-200℃. Preheating by chamber temperature can reduce printing thermal stress, prevent cracking, and help with degassing.

8. Process for the heat treatment of a product obtained by additive manufacturing, made with the atomized magnesium alloy powder according to any one of claims 1-6, characterized in that: It includes solution treatment and artificial aging; The process parameters for solution treatment are: 525℃±5℃, heat preservation for 4-8 hours, followed by water quenching; The process parameters for artificial aging are: 250℃±5℃, heat preservation for 16-24 hours, and air cooling.