Nanometer ceria reinforced biologic magnesium alloy and preparation method thereof
By introducing nano-cerium oxide into Mg-Al magnesium alloys and using selective laser melting technology to form aluminum-cerium phase and dense product film, the problem of excessively rapid degradation of magnesium alloys was solved, and the degradation resistance of magnesium alloys was significantly improved.
Patent Information
- Application Number
- CN202211353484.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-01
- Publication Date
- 2026-02-03
- Estimated Expiration
- 2042-11-01
AI Technical Summary
Mg-Al magnesium alloys degrade too quickly in the human body, failing to meet the requirements for clinical applications. This rapid degradation is mainly due to microgalvanic corrosion and the formation of porous degradation product films.
A bio-magnesium alloy reinforced with nano-cerium oxide was constructed by selective laser melting (SLM) to incorporate nano-cerium oxide into a Mg-6Al-0.5Zn alloy, forming an aluminum-cerium phase to suppress microgalvanic corrosion. Furthermore, the nano-cerium oxide increased the density of the degradation product film, preventing the intrusion of corrosive liquids.
It significantly improved the degradation resistance of magnesium alloys, reducing the degradation rate from 1.60 mm/year to 0.11-0.19 mm/year, and significantly improved the density of the corrosion product film.
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Figure CN115582554B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of medical implant material preparation technology, and particularly relates to a nano-cerium oxide reinforced bio-magnesium alloy and its preparation method. Background Technology
[0002] Magnesium alloys have densities and elastic moduli similar to those of human cortical bone, effectively preventing stress shielding after implantation. Furthermore, magnesium alloys gradually degrade within the body, avoiding the need for secondary surgery. The magnesium ions released after degradation are essential trace elements that participate in bone tissue metabolism, promoting bone growth and healing. Therefore, magnesium alloys have broad application prospects in the field of bone implants. Among them, magnesium-aluminum (Mg-Al) alloys have attracted widespread attention due to their excellent mechanical strength. However, Mg-Al alloys are multiphase alloys, mainly composed of a magnesium matrix and a magnesium-aluminum phase. In body fluid environments, the magnesium matrix readily forms micro-galvanic corrosion with the magnesium-aluminum phase. Simultaneously, the degradation product film formed after degradation is composed of magnesium hydroxide, which is porous and does not provide adequate protection for the matrix. Therefore, Mg-Al alloys degrade too rapidly in the body, failing to meet the requirements for clinical application. Thus, improving the degradation resistance of Mg-Al alloys and controlling their degradation rate has become a pressing problem to be solved for their application in bone implants.
[0003] The density of the degradation product film formed by the micro-galvanic corrosion and degradation between the second phase and the magnesium matrix plays a decisive role in the degradation resistance of Mg-Al magnesium alloys. The degree of micro-galvanic corrosion is mainly determined by the cathodic strength of the second phase relative to the matrix; the stronger the cathodic strength of the second phase relative to the matrix, the greater the degree of micro-galvanic corrosion; the weaker the cathodic strength of the second phase relative to the matrix, the smaller the degree of micro-galvanic corrosion. In Mg-Al magnesium alloys, the magnesium-aluminum phase is distributed in a coarse, semi-continuous network in the matrix and has a large potential difference with the matrix, exhibiting strong cathodic activity. It usually forms strong micro-galvanic corrosion with the matrix. At the same time, the degradation product layer formed during the degradation process is loose and porous, and the corrosive liquid is in continuous contact with the matrix, leading to the continuous and rapid degradation of Mg-Al magnesium alloys in the physiological environment. Therefore, if the strongly cathodic magnesium-aluminum phase in Mg-Al magnesium alloys can be transformed into a weakly cathodic second phase, while increasing the density of the degradation product film and isolating the matrix from continuous contact with the corrosive liquid, it is expected to improve the degradation resistance of Mg-Al magnesium alloys.
[0004] Currently, common methods to improve the degradation resistance of Mg-Al magnesium alloys include alloying, composite coating, and surface coating. Alloying primarily reduces the cathodic nature of the second phase by controlling its composition and morphology, thus inhibiting microgalvanic corrosion and improving degradation resistance. Composite coating mainly increases the density of the degradation product layer, isolating the substrate from continuous contact with the etching solution and improving degradation resistance. However, these two methods only address a single aspect and have limited effectiveness in improving degradation resistance, failing to meet the requirements for clinical applications of magnesium alloys. Using surface coating to improve the degradation resistance of Mg-Al magnesium alloys may result in the coating itself not degrading, leading to no alloy degradation, or slow degradation in the initial implantation stage. Once the coating breaks down, forming a large cathode and small anode, the degradation of the magnesium alloy may accelerate later, resulting in a faster degradation rate. Summary of the Invention
[0005] To overcome the drawback of excessively rapid degradation rates in existing Mg-Al magnesium alloys, this invention aims to provide a nano-cerium oxide-reinforced bio-magnesium alloy and its preparation method. This method synergistically enhances the degradation resistance of magnesium alloys by suppressing galvanic corrosion and increasing the density of the degradation product film. This invention utilizes selective laser melting (SLM) technology to incorporate nano-cerium oxide into a Mg~6Al~0.5Zn (AZ61) alloy. During laser melting, some of the nano-cerium oxide is reduced to cerium by magnesium. The cerium combines with aluminum in the matrix to form an aluminum-cerium phase, inhibiting the precipitation of the magnesium-aluminum phase. Compared to the magnesium-aluminum phase, the aluminum-cerium phase exhibits weak cathodic activity towards the magnesium matrix, and this second-phase transformation suppresses micro-galvanic corrosion. Simultaneously, the remaining nano-cerium oxide detaches after the magnesium matrix degrades and enters the degradation product film, increasing the density of the product film and blocking the intrusion of corrosive liquids. These two factors work together to significantly improve the degradation resistance of the magnesium alloy.
[0006] This invention relates to a nano-cerium oxide-reinforced bio-magnesium alloy and its preparation method, wherein the bio-magnesium alloy is composed of a magnesium matrix, an aluminum cerium phase, and nano-cerium oxide.
[0007] This invention discloses a nano-cerium oxide-reinforced bio-magnesium alloy and its preparation method, comprising the following steps:
[0008] (1) The nano-cerium oxide powder and AZ61 powder were mixed in a ball mill and ball milled under an argon protective atmosphere to obtain a uniform mixed powder. The ball mill speed was 300~800 rpm and the ball milling time was 4~8 hours. The mass fraction of nano-cerium oxide in the mixed powder was 2~14 wt.%.
[0009] (2) Using the above mixed powder as raw material, under an argon protective atmosphere, nano-cerium oxide-reinforced bio-magnesium alloy is prepared by selective laser melting technology. During the preparation process, the laser power is controlled at 60~140 W, the scanning rate at 200~600 mm / min, and the scanning distance at 40~240 μm.
[0010] In step (1), the preferred ball mill speed is 400-600 rpm and the ball milling time is 5-7 hours, and the preferred ball mill speed is 500 rpm and the ball milling time is 6 hours.
[0011] In step (1), the preferred mass fraction of nano-cerium oxide is 6~10% wt.%, and more preferably 8 wt.%.
[0012] In step (2), the laser power is preferably 80~120 W, the scanning rate is 300~500 mm / min, and the scanning spacing is 100~180 μm. More preferably, the laser power is 100 W, the scanning rate is 400 mm / min, and the scanning spacing is 140 μm.
[0013] The particle size of the nano-cerium oxide is 5~150 nm, preferably 20~100 µm, and more preferably 40~60 nm.
[0014] The AZ61 magnesium alloy has a particle size of 10~300 μm, preferably 20~200 µm, and more preferably 50~100 μm.
[0015] The bio-magnesium alloy designed and prepared in this invention can be applied in the biomedical field.
[0016] The principles and advantages of this invention:
[0017] This invention is the first to attempt to use nano-cerium oxide as a reinforcing phase, and to prepare a bio-magnesium alloy reinforced with a composite of aluminum-cerium phase and nano-cerium oxide using selective laser melting technology. During the laser melting process, some nano-cerium oxide is reduced to cerium by magnesium. The cerium combines with aluminum in the matrix to form an aluminum-cerium phase, which inhibits the precipitation of the magnesium-aluminum phase. Compared with the magnesium-aluminum phase, the aluminum-cerium phase exhibits weak cathodic activity to the magnesium matrix, and the transformation of the second phase can inhibit microgalvanic corrosion. At the same time, the remaining nano-cerium oxide detaches after the magnesium matrix degrades and enters the degradation product film, increasing the density of the product film and blocking the invasion of corrosive liquid. The combined effect of these two factors significantly improves the degradation resistance of the magnesium alloy.
[0018] Currently, "cerium oxide reinforced magnesium alloys" are mainly prepared using casting and powder metallurgy methods. Casting, due to its long forming time, is prone to defects such as nano-cerium oxide agglomeration, uneven dispersion of the reinforcing phase, and shrinkage cavities in the matrix. Powder metallurgy, with its lower forming temperature, results in incomplete melting of the metal powder, preventing the reduction reaction between cerium oxide and magnesium. In contrast, the selective laser melting technology in this invention rapidly melts and solidifies the uniformly mixed composite powder in micro-areas. During forming, the laser provides a very high energy density to the powder instantaneously, and before forming, nano-cerium oxide is already uniformly dispersed around the magnesium particles. Under the high temperature provided by the laser, the nano-cerium oxide can undergo a sufficient reduction reaction with the magnesium melt, promoting the full formation of the aluminum-cerium phase in the alloy and inhibiting the precipitation of the magnesium-aluminum phase. Furthermore, during rapid laser melting, the high melting temperature gradient and the resulting Marango convection in the melt promote the uniform dispersion of nano-cerium oxide in the magnesium melt. Under suitable ball milling and laser process parameters, uniformly distributed aluminum-cerium phases and nano-cerium oxide are formed in the prepared bulk material. This not only inhibits micro-galvanic corrosion but also increases the density of the degradation product film, significantly improving the degradation resistance of the magnesium alloy. When the laser power is too low, the magnesium alloy powder fails to melt completely, resulting in a porous and loose magnesium alloy bulk, which accelerates the degradation of the magnesium alloy. When the laser power is too high, the low-melting-point alloying elements in the magnesium alloy vaporize, and the formed aluminum-cerium phase becomes coarse and its precipitation increases. At the same time, excessive thermal stress cracks are generated, leading to increased micro-galvanic corrosion and corrosion liquid intrusion, thus accelerating the degradation of the magnesium alloy.
[0019] In this invention, nano-cerium oxide and magnesium alloy powder are mixed by ball milling. By optimizing the ball milling process parameters, the agglomeration of nano-cerium oxide is avoided and its dispersion is promoted. However, when the ball milling process parameters are below the range selected in this invention, severe agglomeration of nano-cerium oxide occurs, resulting in agglomeration of nano-cerium oxide in the alloy after forming, uneven distribution of the aluminum-cerium phase, and deterioration of the alloy's degradation performance. When the ball milling parameters are above the range selected in this invention, the intense collision between the powder and the grinding balls during ball milling causes powder particle deformation and reduced sphericity, affecting the powder flowability during selective laser melting powder spreading. This results in poor forming quality or even defects in the obtained magnesium alloy, which also worsens the alloy's degradation resistance.
[0020] The content of nano-cerium oxide determines the formation and distribution of the aluminum-cerium phase in the alloy. By controlling the content of nano-cerium oxide, alloys with high, medium, and low nano-cerium oxide contents can all contain the aluminum-cerium phase and uniformly distributed nano-cerium oxide. When the content is below the range selected in this invention, the aluminum-cerium phase formed in the magnesium alloy is small and has limited refining effect on the magnesium-aluminum phase. The second phase still consists of a large amount of coarse magnesium-aluminum phase and a small amount of aluminum-cerium phase, which has limited improvement on the degradation resistance of the magnesium alloy. When the content is above the range selected in this invention, the formed aluminum-cerium phase is coarse and the precipitation content increases. At the same time, excessive nano-cerium oxide agglomerates, forming pores in the matrix, ultimately leading to increased microgalvanic corrosion and corrosion liquid intrusion, and reduced degradation resistance. By changing the nano-cerium oxide content, the content of the aluminum-cerium phase and the distribution of nano-cerium oxide in the alloy can be controlled simultaneously, achieving complete transformation of the magnesium-aluminum phase into the aluminum-cerium phase, while the nano-cerium oxide particles are dispersed, thereby endowing the magnesium alloy with good degradation resistance.
[0021] Smaller nano-cerium oxide particles have larger surface areas and higher surface energy, leading to more severe particle agglomeration and decreased resistance to degradation in the alloy. Conversely, excessively large nano-cerium oxide particles result in uneven distribution after ball milling, insufficient reduction reaction with the magnesium matrix during forming, limited and uneven formation of the aluminum-cerium phase, which is detrimental to improving the degradation resistance of magnesium alloys.
[0022] In summary, the selection of parameters such as the selective laser melting process, ball milling process, and nano-cerium oxide content in this invention is not arbitrary, but rather the culmination of countless experiments and creative efforts by the inventors. This invention, through the synergistic effect of controlling the nano-cerium oxide content, combined with high-speed ball milling and a unique selective laser melting process, prepares a nano-cerium oxide-reinforced bio-magnesium alloy. By inhibiting galvanic corrosion and increasing the density of the degradation product film, the degradation resistance of the magnesium alloy is synergistically improved, and it is expected to be applied in the biomedical field. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Appendix Figure 1 Microstructure of AZ61 alloy and the product obtained in Example 1;
[0025] Appendix Figure 2 Cross-sectional morphology of degradation products of AZ61 alloy and the product obtained in Example 1. Detailed Implementation
[0026] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.
[0027] Example 1
[0028] 9.2 g of AZ61 powder (particle size 50–100 μm) and 0.8 g of nano-cerium oxide powder (particle size 40–60 nm) were weighed and placed in a ball mill. The mixture was ball-milled under an argon protective atmosphere at a speed of 500 rpm for 6 hours to obtain a homogeneous powder. Using this mixed powder as raw material, nano-cerium oxide-reinforced bio-magnesium alloys were prepared via selective laser melting (SLM). During the preparation process, the laser power was controlled at 100 W, the scanning speed at 400 mm / min, and the scanning interval at 140 μm.
[0029] Tests revealed that the prepared alloy contained fine grains, acicular aluminum-cerium phase, and uniformly dispersed nano-cerium oxide particles. Figure 1 Degradation rate tests revealed that, compared to AZ61 alloy, the magnesium alloy containing acicular aluminum-cerium phase and uniformly distributed nano-cerium oxide decreased in degradation rate from 1.60 mm / year for AZ61 to 0.11 mm / year. The corrosion product film was also more uniform and dense, with the corrosion layer thickness decreasing from 20.7 μm for AZ61 to 6.05 μm. Figure 2 ).
[0030] Example 2
[0031] 8.6 g of AZ61 powder (particle size 50–100 μm) and 1.4 g of nano-cerium oxide powder (particle size 40–60 nm) were weighed and placed in a ball mill. The mixture was ball-milled under an argon protective atmosphere at a speed of 500 rpm for 6 hours to obtain a homogeneous powder. Using this mixed powder as raw material, nano-cerium oxide-reinforced bio-magnesium alloys were prepared via selective laser melting (SLM). During the preparation process, the laser power was controlled at 100 W, the scanning speed at 400 mm / min, and the scanning interval at 140 μm.
[0032] Tests revealed the formation of fine grains, acicular aluminum-cerium phase, and uniformly dispersed nano-cerium oxide particles in the prepared alloy. Degradation rate tests showed that, compared to the AZ61 alloy, the magnesium alloy containing the acicular aluminum-cerium phase and nano-cerium oxide decreased in degradation rate from 1.60 mm / year for AZ61 to 0.13 mm / year, with a uniform and dense corrosion product film and a corrosion layer thickness decreasing from 20.7 μm for AZ61 to 6.35 μm.
[0033] Example 3
[0034] 9.2 g of AZ61 powder (particle size 50–100 μm) and 0.8 g of nano-cerium oxide powder (particle size 40–60 nm) were weighed and placed in a ball mill. The mixture was ball-milled under an argon protective atmosphere at a speed of 500 rpm for 6 hours to obtain a homogeneous powder. Using this mixed powder as raw material, nano-cerium oxide-reinforced bio-magnesium alloys were prepared via selective laser melting (SLM). During the preparation process, the laser power was controlled at 130 W, the scanning speed at 500 mm / min, and the scanning interval at 140 μm.
[0035] Tests revealed the formation of fine grains, acicular aluminum-cerium phase, and uniformly dispersed nano-cerium oxide particles in the prepared alloy. Degradation rate tests showed that, compared to the AZ61 alloy, the magnesium alloy containing the acicular aluminum-cerium phase and nano-cerium oxide decreased in degradation rate from 1.60 mm / year for AZ61 to 0.15 mm / year, with a uniform and dense corrosion product film and a corrosion layer thickness decreasing from 20.7 μm for AZ61 to 6.55 μm.
[0036] Example 4
[0037] 9.2 g of AZ61 powder (particle size 50–100 μm) and 0.8 g of nano-cerium oxide powder (particle size 40–60 nm) were weighed and placed in a ball mill. The mixture was ball-milled under an argon protective atmosphere at 700 rpm for 8 hours to obtain a homogeneous powder. Using this mixed powder as raw material, nano-cerium oxide-reinforced bio-magnesium alloys were prepared via selective laser melting (SLM). During the preparation process, the laser power was controlled at 100 W, the scanning speed at 400 mm / min, and the scanning interval at 140 μm.
[0038] Tests revealed the formation of fine grains, acicular aluminum-cerium phase, and uniformly dispersed nano-cerium oxide particles in the prepared alloy. Degradation rate tests showed that, compared to the AZ61 alloy, the magnesium alloy containing acicular aluminum-cerium phase and nano-cerium oxide exhibited a degradation rate decrease from 1.60 mm / year for AZ61 to 0.19 mm / year, with a more uniform and dense corrosion product film and a corrosion layer thickness reduced from 20.7 μm for AZ61 to 6.85 μm.
[0039] During the development of this invention, the following solutions were also tried, but the performance of the resulting products was far inferior to that of the embodiments.
[0040] Comparative Example 1
[0041] All other conditions were the same as in Example 1, except that 8.0 g of AZ61 powder and 2.0 g of nano-cerium oxide powder were weighed. Tests revealed that the prepared alloy formed more and larger needle-like aluminum-cerium phases, and the nano-cerium oxide aggregated into pores. The corrosion rate of the alloy increased from 1.60 mm / year for AZ61 to 2.59 mm / year.
[0042] Comparative Example 2
[0043] All other conditions were the same as in Example 1, except that the laser power was controlled at 50 W and the scanning speed at 800 mm / min during the preparation process. Tests revealed that the prepared alloy had a lower density, which was attributed to the laser energy density failing to completely melt the AZ61 powder. The degradation rate of the alloy increased from 1.60 mm / year for AZ61 to 3.83 mm / year.
[0044] Comparative Example 3
[0045] All other conditions were the same as in Example 1, except that the ball mill speed was 200 rpm and the ball milling time was 2 hours. Tests revealed that the acicular aluminum-cerium phase in the AZ61 alloy was unevenly distributed, and nano-cerium oxide agglomerates were observed. Tests also showed that the corrosion rate of the prepared alloy increased from 1.60 mm / year for AZ61 to 2.71 mm / year.
Claims
1. A method for preparing a nano-cerium oxide-reinforced bio-magnesium alloy, wherein the bio-magnesium alloy comprises a magnesium matrix, an aluminum-cerium phase, and nano-cerium oxide; characterized in that, Includes the following steps: (1) The nano-cerium oxide powder and AZ61 powder are mixed and placed in a ball mill, and ball milled under an argon protective atmosphere to obtain a uniform mixed powder. The ball mill speed is 300-800 rpm and the ball milling time is 4-8 hours. The mass fraction of nano-cerium oxide in the mixed powder is 2-14 wt.% and the particle size of nano-cerium oxide powder is 5-150 nm. (2) Using the above mixed powder as raw material, a nano-cerium oxide-reinforced bio-magnesium alloy was prepared by selective laser melting technology under an argon protective atmosphere. During the preparation process, the laser power was controlled at 60-140W, the scanning rate at 200-600mm / min, and the scanning distance at 40-240μm.
2. The method for preparing a nano-cerium oxide-reinforced bio-magnesium alloy according to claim 1, characterized in that, In step (1), the ball mill speed is 400-600 rpm and the ball milling time is 5-7 hours.
3. The method for preparing a nano-cerium oxide-reinforced bio-magnesium alloy according to claim 1, characterized in that, In step (1), the mass fraction of nano-cerium oxide is 6-10 wt.%.
4. The method for preparing a nano-cerium oxide-reinforced bio-magnesium alloy according to claim 1, characterized in that, In step (2), the laser power is 80-120W, the scanning rate is 300-500mm / min, and the scanning spacing is 100-180μm.
5. The method for preparing a nano-cerium oxide-reinforced bio-magnesium alloy according to claim 1, characterized in that, The particle size of the AZ61 powder is 10–300 μm.