阅读说明：本技术 一种用于增材制造的镁合金粉末及其制备方法与应用 (Magnesium alloy powder for additive manufacturing and preparation method and application thereof ) 是由 郑玉峰 边东 张余 马立敏 楚晓 于 2021-07-07 设计创作，主要内容包括：本发明公开了一种用于增材制造的镁合金粉末及其制备与应用。所述镁合金粉末是以Mg为主要成分,含有稀土元素RE,所述稀土元素RE为Y、La、Ce、Pr、Gd、Ho、Er、Lu中的至少一种,所述稀土元素RE所占的比重为0.1～7wt.％,所述镁合金粉末表面的含氧量低于5wt.％。本发明的镁合金粉纯净度高、含氧量低、球形度好、粒径均匀,可适用于多种3D打印方法,打印过程中合金元素蒸发少,产生的烟雾少,最终3D打印件致密、无缺陷,成分可控,且性能优异,可适用于多种临床场景。(The invention discloses magnesium alloy powder for additive manufacturing and preparation and application thereof. The magnesium alloy powder is mainly composed of Mg and contains a rare earth element RE, wherein the rare earth element RE is at least one of Y, La, Ce, Pr, Gd, Ho, Er and Lu, the proportion of the rare earth element RE is 0.1-7 wt.%, and the oxygen content of the surface of the magnesium alloy powder is lower than 5 wt.%. The magnesium alloy powder disclosed by the invention is high in purity, low in oxygen content, good in sphericity and uniform in particle size, can be suitable for various 3D printing methods, is less in evaporation of alloy elements in the printing process, generates less smoke, is compact and free of defects in a final 3D printed piece, is controllable in components, has excellent performance, and can be suitable for various clinical scenes.)

1. A magnesium alloy powder for additive manufacturing, characterized by: the magnesium alloy powder is mainly composed of Mg and contains rare earth element RE, wherein the rare earth element RE is at least one of Y, La, Ce, Pr, Gd, Ho, Er and Lu, and the proportion of the rare earth element RE is 0.1-7 wt.%.

2. The magnesium alloy powder for additive manufacturing of claim 1, wherein: the surface of the magnesium alloy powder has an oxygen content of less than 5 wt.%.

3. The magnesium alloy powder for additive manufacturing according to claim 1 or 2, wherein: the magnesium alloy powder further contains 0-0.5 wt.% of an alloying element Zr.

4. The magnesium alloy powder for additive manufacturing according to claim 1 or 2, wherein: the contents of impurity elements Fe, Cu, Ni, Co, Be and Al in the magnesium alloy powder are all lower than 100 ppm.

5. The magnesium alloy powder for additive manufacturing according to claim 1 or 2, wherein: the magnesium alloy powder is composed of countless fine particles, the particles are regular in shape and are spherical or quasi-spherical/approximately spherical, the average particle size of the particles is within the range of 1-300 mu m, and the length-diameter ratio of the particles is not more than 2.

6. A method of preparing a magnesium alloy powder for additive manufacturing according to any one of claims 1 to 5, characterized by comprising the steps of:

(1) high-purity metal Mg, RE and Zr or high-purity Mg-RE and Mg-Zr intermediate alloy are adopted as raw materials, and the metal raw materials are smelted and cast under the protection of inert gas to obtain high-purity magnesium alloy ingots with required components;

(2) under the protection of inert gas, melting the magnesium alloy ingot to obtain a uniform melt; and then atomizing the melt under a controllable atmosphere to prepare powder, rapidly cooling fine metal liquid drops to obtain magnesium alloy powder, and screening, bagging and vacuum packaging the powder to obtain a magnesium alloy powder product for 3D printing.

7. The method of preparing a magnesium alloy powder for additive manufacturing according to claim 6, wherein: the inert gas is Ar or CO₂And SF₆The mixed gas of (3); the controllable atmosphere is Ar gas, He gas or the mixed gas of the Ar gas and the He gas; the oxygen content and the humidity of the atomization environment are both lower than 10 ppm; the melting temperature is 700-850 ℃.

8. Use of a magnesium alloy powder for additive manufacturing according to any one of claims 1 to 5, wherein: the magnesium alloy powder is used as an additive manufacturing raw material, a selective laser melting technology, a selective laser sintering technology or an electron beam melting technology is adopted, and 3D printing is carried out under an inert protective atmosphere to obtain a 3D printed magnesium alloy part which is used as a personalized implant material or instrument.

9. Use of a magnesium alloy powder for additive manufacturing according to claim 8, characterized in that: the magnesium alloy powder is used as a main raw material for additive manufacturing, another metal powder, bioactive ceramic powder or degradable polymer material is doped, a selective laser melting technology, a selective laser sintering technology, an electron beam melting technology or an adhesive spray forming technology is adopted, and 3D printing is carried out under the condition of selectively using inert protective atmosphere, so that the 3D printing degradable magnesium-based implant material or instrument is obtained and is used for repairing hard tissues or soft tissues.

10. Use of a magnesium alloy powder for additive manufacturing according to claim 9, characterized in that: the other metal powder is Zn or Zn alloy powder; the bioactive ceramic powder is preferably one or a mixture of more than two of hydroxyapatite, beta-tricalcium phosphate, magnesium silicate or calcium silicate; the degradable polymer material is preferably one or more than two copolymers or blends of polylactic acid, polyglycolic acid, polylactic-glycolic acid or polycaprolactone.

Technical Field

The invention belongs to the technical field of metal additive manufacturing, and particularly relates to magnesium alloy powder for additive manufacturing and a preparation method and application thereof.

Background

With the development of science and technology, medical innovation and the higher demand of human beings for disease treatment, the personalized innovative implant materials and apparatus industries aiming at precise treatment enter a high-speed development stage. The development of such versatile innovative implant materials/devices requires the selection of appropriate materials, design and manufacturing methods. Magnesium and magnesium alloys are currently considered the most prominent degradable metals due to their mechanical properties matching those of human bones, degradability in body fluids, and ability to stimulate tissue growth. Additive manufacturing AM (i.e., 3D printing) can exploit computer-aided design to design implant materials/instruments with complex structures according to patient-specific anatomical data, and enable their fabrication quickly within a reasonable range of dimensional accuracy. Therefore, it is a current research trend to develop ideal biodegradable magnesium-based devices for precise treatment through additive manufacturing methods.

For example, patent (CN104762541B) discloses a rare earth magnesium alloy material for 3D printing and a preparation method thereof, which is to mix and melt Mg, Mn, and RE, and then atomize to obtain the rare earth magnesium alloy material. However, melting under a non-protective atmosphere (requiring the use of covering agents) may bring about oxidation and inclusions (low purity) in the metal matrix, which are not advantageous for medical implants; secondly, the oxygen content and humidity in the atomization powder making environment are not controlled, the specific surface area of the magnesium alloy powder is large, moisture absorption and oxidation are easy to occur, the oxidized powder is not beneficial to subsequent 3D printing, and the performance of a printed piece is adversely affected; furthermore, the evaporation loss of alloying elements in the powder (mismatch of evaporation losses of different alloying elements) during 3D printing is not taken into account and may result in too large a difference in composition of the final 3D print from the initial alloying powder composition, deviating from the expected setting, affecting performance.

At present, in the 3D printing process of magnesium alloy, high energy (laser, electron beam and the like) acts on powder, the powder is melted, micro melts are connected with each other, and the micro melts are cooled and solidified to finally form a macro 3D printing piece. However, there are still difficulties in preparing magnesium-based implants using additive manufacturing (3D printing) methods, concentrated in: (1) compared with additive manufacturing raw materials of other metals, the high-quality magnesium powder for 3D printing of the magnesium alloy has fewer sources, easily oxidized surface and poorer performance stability; if the oxygen content of the surface of the magnesium alloy powder is higher or the surface of the magnesium alloy powder contains an oxide layer, the melting and spreading of the powder are seriously influenced, the mutual connection among melts is influenced, and the performance of a 3D printing piece is finally influenced. (2) High-energy treatment in the additive manufacturing process easily causes raw materials to be overheated, ablated, vaporized and evaporated, element loss abnormality caused by vaporization and evaporation causes the components and the microstructure of a final printed piece to deviate from expectations, and the final performance does not reach the standard; when multiple alloying elements are present, the evaporation rates of the different alloying elements differ, even more so, and the chemical composition of the final 3D print may deviate far from that of the starting powder. Moreover, the microstructure of the alloy is sensitive to the composition, and the 3D printing piece structure may deviate from the expected setting due to the evaporation loss of the alloy elements, so that the overall controllability is poor. Furthermore, for 3D prints of magnesium alloys for use as implant materials/instruments, it is also required to control the impurity content in the material matrix in order to obtain good in vivo degradation behavior. Therefore, the research and development of the magnesium alloy powder with high purity, low surface oxygen content and less element evaporation loss in the 3D printing process is very important for obtaining a high-quality medical magnesium alloy 3D printing product.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides magnesium alloy powder for additive manufacturing and a preparation method and application thereof.

The purpose of the invention is realized by the following technical scheme:

the magnesium alloy powder for additive manufacturing (3D printing) contains a rare earth element RE with Mg as a main component, wherein the rare earth element RE is at least one of Y, La, Ce, Pr, Gd, Ho, Er and Lu, and the proportion of the rare earth element RE is 0.1-7 wt.%.

The surface of the magnesium alloy powder has an oxygen content of less than 5 wt.%.

The rare earth element RE is preferably La, Ce, Pr or Gd.

The magnesium alloy powder further contains 0-0.5 wt.% of an alloying element Zr.

The contents of impurity elements Fe, Cu, Ni, Co, Be and Al in the magnesium alloy powder are all lower than 100 ppm.

The magnesium alloy powder is composed of countless fine particles, the particles are regular in shape and are spherical or quasi-spherical/approximately spherical, the average particle size of the particles is within the range of 1-300 mu m, and the length-diameter ratio of the particles is not more than 2.

Preferably, the content of impurity elements (Fe, Cu, Ni, Co, Be and Al) in the powder is less than 50ppm, the surface oxygen content of the powder is less than 4 wt.%, the average particle diameter of particles in the magnesium alloy powder is in the range of 10-150 μm, and the aspect ratio of the particles is not more than 1.5.

The preparation method of the magnesium alloy powder for additive manufacturing (3D printing) comprises the following steps:

(1) high-purity metals (Mg, RE and Zr) or high-purity Mg-RE and Mg-Zr intermediate alloys are adopted as raw materials, and under the protection of inert gas, the metal raw materials are smelted and cast to obtain high-purity magnesium alloy ingots with required components;

(2) under the protection of inert gas, melting the magnesium alloy ingot to obtain a uniform melt; and then atomizing the melt under a controllable atmosphere to prepare powder, rapidly cooling fine metal liquid drops to obtain magnesium alloy powder, and screening, bagging and vacuum packaging the powder to obtain a magnesium alloy powder product for 3D printing.

In the step (1), theThe inert gas is Ar or CO₂And SF₆The mixed gas of (1). Smelting and pouring are carried out under the protection of inert gas, so that element loss can be reduced, and alloy oxidation and inclusion can be reduced. The tantalum crucible is preferably adopted for smelting and pouring, so that the introduction of impurities can Be reduced, and the contents of impurity elements such as Fe, Cu, Ni, Co, Be, Al and the like which are unfavorable for corrosion performance are controlled to Be lower than 100 ppm. The magnesium alloy ingot is qualified through component detection, and is melted and atomized after being pickled or mechanically polished to remove the dirt or oxide layer on the surface of the ingot, so as to reduce the introduction of impurities.

In the step (2), the inert gas is Ar or CO₂And SF₆The mixed gas of (3); the controllable atmosphere is inert atomization gas, namely Ar gas, He gas or the mixed gas of the Ar gas and the He gas. The melting temperature is 700-850 ℃.

In the step (2), in the atomization process, the high-temperature (700-850 ℃) melt is sprayed out through a narrow nozzle and is impacted with low-temperature (0-20 ℃) inert atomization gas (Ar, He) to form fine metal droplets, and the metal droplets are rapidly cooled and solidified before being gathered, so that the magnesium alloy powder which is good in sphericity, uniform in particle size distribution, good in surface quality (no oxidation/slight oxidation) and highly dispersed is obtained. Before atomization, the atomization gas is dehydrated/dried and deoxidized, and then is introduced into an atomization bin, so that the oxygen content and humidity of the environment where the melt is atomized are lower than 10ppm, and oxidation and corrosion of powder are avoided/reduced. The powder is sieved under the protection of inert gas, and vacuum packaging ensures that the magnesium alloy powder does not absorb moisture, oxidize and agglomerate after being stored for a long time, so that the powder has stable performance and can be used after being opened.

The application of the magnesium alloy powder for additive manufacturing is that the magnesium alloy powder is used as a raw material for additive manufacturing, and 3D printing is carried out under inert protective atmosphere (such as nitrogen or argon) by adopting a selective laser melting technology (SLM), a selective laser sintering technology (SLS) or an electron beam melting technology (EBM) to obtain a 3D printed magnesium alloy part which is used as a personalized implant material or instrument.

The application of the magnesium alloy powder for additive manufacturing further comprises the steps of taking the magnesium alloy powder as a main raw material for additive manufacturing, doping another metal powder, bioactive ceramic powder or degradable polymer material, and then performing 3D printing under the condition of selectively using inert protective atmosphere (such as nitrogen or argon) by adopting a selective laser melting technology (SLM), a selective laser sintering technology (SLS), an electron beam melting technology (EBM) or a Binder jet forming technology (Binder jet forming) to obtain a 3D printing degradable magnesium-based implant material or device for repairing hard tissues or soft tissues.

Preferably, the other metal powder is Zn or Zn alloy powder; the bioactive ceramic powder is preferably Hydroxyapatite (HA), beta-tricalcium phosphate (beta-TCP), magnesium silicate (Mg)₂SiO₄) Or calcium silicate (CaSiO)₃) One or a mixture of two or more of them; the degradable polymer material is preferably one or more of polylactic acid, polyglycolic acid, polylactic-glycolic acid or polycaprolactone copolymer or blend.

The principle of the invention is as follows:

(1) in the 3D printing process of the magnesium alloy, magnesium alloy powder is melted under the action of high-energy treatment (laser, electron beams and the like), micro melts flow and spread and are mutually connected, and a macroscopic 3D printing piece is obtained by cooling and repeating the processes. If the oxygen content of the surface of the magnesium alloy powder is higher or an oxide layer exists, the melting of the powder is hindered, the flowability of the micro melt is influenced, and the 3D printing process is further influenced. In addition, oxygen-containing inclusions exist in grain boundaries, which adversely affect the mechanical properties and corrosion properties of 3D prints. Therefore, the control of the oxygen content of the surface of the magnesium alloy powder is beneficial to the development of the 3D printing process, and the comprehensive performance of the 3D printing piece can be improved fundamentally. The invention reduces the oxidation and inclusion of the base material by controlling the alloy component design and the ingot preparation process, controls the atmosphere and the oxygen content and the humidity of the environment in the atomization powder preparation stage, and effectively avoids/reduces the oxidation of the magnesium alloy powder, thereby improving the powder performance.

(2) The rare earth elements Y, La, Ce, Pr, Gd, Ho, Er and Lu adopted by the invention have high boiling points, low saturated vapor pressure and low evaporation rate, the evaporation loss in the atomization powder preparation and 3D printing processes is less, the printing material is not easy to burn/oxidize, the generation of smoke is reduced, the components of the final 3D printing piece and the initial powder are basically consistent, and the high-quality magnesium alloy 3D printing piece with preset components and structures is easy to obtain. And moreover, the rare earth can refine grains, so that the mechanical property and the corrosion resistance of the 3D printing piece are improved, and meanwhile, a small amount of biocompatible element Zr is added into the powder, so that the fluidity of the powder after melting can be improved, the grains are refined, and the microstructure and the performance of the 3D printing piece are regulated and controlled. Therefore, a high-purity, low-oxygen magnesium alloy powder containing the above rare earth elements and Zr is suitable as a base material for 3D printing of magnesium alloys.

Compared with the prior art, the invention has the following advantages and effects:

(1) the magnesium alloy powder disclosed by the invention is high in purity, less in impurities, slight in surface oxidation, excellent in flame retardant property and suitable for 3D printing, the evaporation of alloy elements in the 3D printing process is less, the components of a 3D printed piece are consistent with those of the powder, no obvious component deviation exists, and the components are controllable.

(2) The magnesium alloy powder has good fluidity after being melted by laser treatment, can be rapidly spread, and is compact and flawless in 3D printing.

(3) The invention prepares powder by atomization under a controlled atmosphere (low oxygen and low humidity), avoids powder aggregation/agglomeration and pollution caused by electrostatic attraction, moisture absorption, impurity introduction and surface oxidation in the conventional ball milling powder preparation (the direct mixing of simple substance powder also needs to be uniformly mixed by ball milling), and has stable powder performance.

(4) The method has the advantages that the impurities are controlled in the whole process, the purity of the magnesium alloy powder is high, the corrosion performance of the final 3D printed piece is guaranteed, and the method is suitable for medical application; moreover, the powder is sealed and packaged, and can be used immediately after being opened, the powder does not need to be heated and dried in advance, and the product is simple and convenient to use.

(5) The implant material/instrument obtained by 3D printing of the magnesium alloy powder has excellent comprehensive performance (high mechanical strength, corrosion resistance and good biocompatibility) and can be suitable for various clinical scenes.

Drawings

FIG. 1 is a Mg-1Pr alloy powder for 3D printing; wherein, the left picture is the appearance photograph of the hermetically packaged Mg-1Pr alloy powder, and the right picture is the appearance of the powder under an optical microscope.

FIG. 2 is a Mg-4Y-0.4Zr alloy powder for 3D printing; wherein the left graph is the appearance of the Mg-4Y-0.4Zr alloy powder under an optical microscope, and the right graph is the corresponding particle size distribution of the powder particles.

FIG. 3 is a magnesium alloy bone tissue engineering scaffold obtained by 3D printing of Mg-Y-Gd-Zr alloy powder according to the present invention; wherein, the left picture is a macroscopic picture of the stent, and the right picture is the local magnification and detail display of the stent.

Detailed Description

In order that the invention may be readily understood, reference will now be made in detail to the specific embodiments of the invention. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that, for a person skilled in the art, many variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Unless defined otherwise, all technical and scientific terms used herein are to be interpreted as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Example 1

High-purity Mg (99.99 wt.%) and high-purity Pr (99.9 wt.%) are selected as smelting raw materials, and a tantalum crucible is selected according to different mass fraction ratios (the proportion of Pr is 0.1-7 wt.%, and the balance is Mg), and smelting is carried out in a medium-frequency induction furnace. Firstly, vacuumizing to 10^-2Pa, recharging high-purity Ar gas or CO₂+SF₆And (3) taking the mixed gas as a protective atmosphere, heating to 800 ℃ for raising the temperature, stirring the melt, pouring the uniform melt into a graphite mold, preheating the graphite mold at 200 ℃ in advance, and cooling along with the furnace to obtain high-purity Mg-Pr alloy ingots with different Pr contents (0.1-7 wt.%). Pickling to remove oxidation and dirt on the surface of the cast ingot, and then carrying out acid pickling on the cast ingot again at 750-85 DEG CMelting at 0 deg.C, and atomizing the molten magnesium alloy liquid by an atomizer. Controlling the oxygen content and humidity in the atomizing environment to be lower than 10ppm, spraying high-temperature metal liquid through a nozzle, meeting high-pressure Ar gas, pneumatically atomizing into Mg-Pr alloy powder, and rapidly cooling and screening to obtain the Mg-Pr alloy powder with uniform particle size. The low oxygen, low humidity atmosphere minimizes oxidation of the powder. Adjusting atomization parameters (such as the size of a nozzle, the pressure of Ar gas and the included angle between the direction of Ar gas and the metal liquid flow) to obtain Mg-Pr alloy powder with different particle sizes (the average particle size is in the range of 1-300 mu m, and the length-diameter ratio is less than 2). And bagging and vacuum packaging the powder to obtain the Mg-Pr alloy powder product which can be directly used for 3D printing. As shown in fig. 1, Mg-1Pr powder, in which Pr is present in 1 wt.%, has an average particle size of 25.37 ± 12.16 μm, and an aspect ratio of less than 1.2. X-ray energy spectrum analysis (EDS) under a Scanning Electron Microscope (SEM) shows that the oxygen content of the surface is low and less than 5 wt.%, and the visible powder has uniform granularity, good sphericity and good dispersion.

Example 2

High-purity Mg (99.99 wt.%), high-purity Mg-20Y master alloy and high-purity Mg-20Zr master alloy are selected as smelting raw materials, and Mg-Y-Zr alloy ingots with different Y contents (0.1-7 wt.%) and Zr contents (0-0.5 wt.%) are obtained according to the smelting and casting method described in example 1. Removing the surface dirt and oxidation of the cast ingot, remelting again at the temperature of 700-800 ℃, and obtaining the required Mg-Y-Zr alloy powder after pneumatic atomization (controlling the oxygen content and the humidity in the atomization environment to be lower than 10 ppm). As shown in FIG. 2, the Mg-4Y-0.4Zr alloy powder has an average particle size of 53.64 + -20.60 μm, an aspect ratio of less than 1.5 and a surface oxygen content of less than 4 wt.%, and has uniform particle size distribution, high sphericity and good dispersion. The actual composition of the precursor alloy of the powder shown in fig. 2 was found to contain 4.12 wt.% Y, 0.42 wt.% Zr, as measured by composition. The magnesium alloy powder prepared from the alloy ingot contains 4.17 wt.% of Y and 0.43Zr through inductively coupled plasma mass spectrometry (ICP-MS), and the content of the alloy element (Y, Zr) is consistent with the height of the as-cast alloy base metal. In addition, the impurity levels (0.0039 wt.% Fe, 0.0012 wt.% Cu, 0.0021 wt.% Ni, 0.0047 wt.% Si, 0.00099 wt.% Mn, 0.0031 wt.% Al, 0.00027 wt.% Co) in the resulting powder were all below 50ppm, with high purity of the powder.

Example 3

Referring to the relevant steps in examples 1-2, Mg-Y-Gd-Zr (1-4 wt.% Y, 0-3 wt.% Gd, 0-0.5 wt.% Zr) alloy powders were prepared and obtained by an alloy melting method and a melt atomization method (700-. Selecting powder with typical components (4.12 wt.% Y, 1.05 wt.% Gd, 0.43 wt.% Zr) for 3D printing, obtaining Mg-Y-Gd-Zr alloy 3D printing parts (as shown in figure 3) by laser powder bed fusion technology (LPBF), wherein the actual components of the 3D printing parts are 4.21 wt.% Y, 1.09 wt.% Gd, 0.41 wt.% Zr, the loss of alloy elements is very little, and the components are consistent with the powder parent metal in height. The material density in the 3D printing piece can exceed 99%, the grain size of the finally obtained 3D printing piece is less than or equal to 20 mu m due to the action of alloy elements (Y, Gd and Zr) in the powder and the rapid cooling in the 3D printing process, the grain size can even reach a submicron level (less than 1 mu m), and the macro-micro components and the structure are uniform, and the performance is uniform.

Comparative example 1

Referring to the alloy melting method in examples 1 to 3, an Mg-1Pr alloy ingot was prepared. Remelting the cast ingot at the temperature of 750-850 ℃, atomizing the molten magnesium alloy liquid by a conventional atomizing device, and obtaining Mg-1Pr alloy powder without requiring the oxygen content and the humidity in the atomizing device (both are more than 100 ppm). The shape, size and particle size distribution of the powder were not significantly different from the powder described in example 1. However, the above alloy powder was tested to have an oxygen content on the surface of more than 8 wt.%, which is much higher than the surface oxygen content (<5 wt.%) of the magnesium alloy powder in examples 1-3, and oxidation of the powder surface was detrimental to the subsequent 3D printing.

The above description is only an example of the present invention, but the present invention is not limited to the above example, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention and are equivalent to each other are included in the protection scope of the present invention.