An ultra-thin degradable Fe-Se alloy stent and a preparation method thereof

Abstract

The application discloses an ultra-thin degradable Fe-Se alloy stent and a preparation method thereof. Fe particles and Fe-Se intermediate alloy powder are taken, Fe-Se ingots are obtained through smelting, the Fe-Se ingots are poured into a mold after being melted, Fe-Se rod materials are obtained, annealing treatment is conducted on the Fe-Se rod materials, annealed rod blanks are obtained, the annealed rod blanks are extruded to obtain extruded rod blanks, the extruded rod blanks are drawn in multiple passes to obtain Fe-Se tubular materials, and the Fe-Se tubular materials are processed to obtain the Fe-Se alloy stent. The Fe-Se alloy stent provided by the application has excellent mechanical properties and good degradation performance.

Description

Technical Field

[0001] This invention belongs to the field of biomedical iron-based alloy technology, and specifically relates to an ultrathin biodegradable Fe-Se alloy scaffold and its preparation method. Background Technology

[0002] Biodegradable iron alloys have great application potential in the field of implantable medical devices for hard tissues due to their excellent biocompatibility and functionality. Iron (Fe), an essential trace element for the human body, participates in the synthesis of oxygen transport proteins (hemoglobin and myoglobin), the composition of functional enzymes, immune regulation, electron transport, the formation of heme enzymes and iron-binding enzymes, and the maintenance of normal hematopoietic function. The content and RDI of Fe in the human body are approximately 3-5g and 0.9mg, respectively, with a plasma concentration of 6.3-26.9μM and an IC50 of 66.7mM for endothelial cells. Absorbable stents are considered the fourth revolution in cardiovascular interventional therapy. As one of the main materials for absorbable vascular stents, pure iron has the advantage of easily improving strength through modification compared to polymers and magnesium-based alloys; its inherent disadvantages are slow in vivo corrosion and absorption, the reasons and mechanisms of which are not yet clear. Therefore, the challenge lies in achieving mechanical properties comparable to permanent stents with the least amount of iron and the thinnest wall thickness, while simultaneously matching the in vivo degradation curve to the healing time of diseased blood vessels, enabling complete absorption as quickly as possible after complete degradation. Currently, the main methods to improve the degradation rate of pure iron are: (1) adding alloying elements other than noble metals, such as Mn, Co, C, B, and S, within the solubility range of iron; (2) generating fine and dispersed metallic intermediate phases by adding noble metal alloying elements. These metallic intermediate phases act as cathodes in the iron matrix, causing micro-current corrosion, thereby improving the degradation rate; (3) introducing porous structures into the iron matrix to increase the effective contact area with the corrosive environment and thus improve its degradation rate. However, since iron contains iron oxide and iron hydroxide corrosion products during the degradation process, it will prevent further corrosion. Therefore, simply preparing porous iron cannot significantly improve the degradation rate. By adding appropriate alloying elements, in addition to improving its degradation rate, it is also possible to improve its mechanical properties and biocompatibility, which is a promising approach.

[0003] Selenium (Se) is one of the essential trace elements for the human body. It can form glutathione peroxidase, protecting cell tissues, maintaining cell membrane function, and playing an antioxidant role. Selenium has a strong binding affinity for metals, resisting the toxic effects of cadmium on the kidneys, gonads, and central nervous system. As a negatively charged non-metallic ion, selenium can combine with positively charged harmful metal ions in the body to form metalloselenoprotein complexes, directly excreting harmful metal ions that can induce carcinogenesis, thus neutralizing the toxicity of metal ions and playing a detoxification role. Furthermore, the level of selenium in the blood is closely related to the occurrence of cancer. Selenium can reduce the toxicity of aflatoxin (which can induce liver cancer), and a higher selenium level in the body is associated with a lower risk of cancer. Therefore, selenium can reduce the risk of cancer. In addition, selenium can also reduce the risk of diseases such as diabetes and cataracts, maintain muscle nutrition, and reduce the incidence of leukoma.

[0004] Based on the solid solution theory of the Fe-Se alloy phase diagram, the formation of Se-rich precipitates in the matrix is ​​expected to induce micro-electrochemical corrosion, thereby significantly increasing the degradation rate. From a biological perspective, Se ions possess anti-tumor properties and do not pose a direct or serious risk to human health. The phase diagram shows that Fe has a melting point of 1538℃, while Se has a melting point of 220℃ and a boiling point of 685℃. Fe has low melting and boiling points, high volatility, and is difficult to dissolve. More importantly, the melting points of Fe and Se differ significantly, and their solid solution capacity is also poor. To date, no ultrathin biodegradable Fe-Se alloy materials have been reported. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the first objective of this invention is to provide a method for preparing an ultrathin biodegradable Fe-Se alloy scaffold. This invention obtains an ultrathin biodegradable Fe-Se alloy scaffold with a thickness ≤80μm by melting, extruding, and then drawing.

[0006] The second objective of this invention is to provide an ultrathin biodegradable Fe-Se alloy scaffold prepared by the above-described preparation method, wherein the provided Fe-Se alloy scaffold possesses both excellent mechanical properties and good degradation performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention discloses a method for preparing an ultrathin biodegradable Fe-Se alloy scaffold. The method involves preparing Fe granules and Fe-Se intermediate alloy powder, melting them to obtain an Fe-Se ingot, pouring the melted Fe-Se ingot into a mold to obtain Fe-Se rods, annealing the Fe-Se rods to obtain annealed billets, extruding the annealed billets to obtain extruded billets, and drawing the extruded billets through multiple passes to obtain Fe-Se tubing. The Fe-Se tubing is then processed to obtain an Fe-Se alloy scaffold. The Fe-Se alloy scaffold contains a Se mass fraction of 0.1-2.0% wt.

[0009] This invention uses FeSe master alloy powder and Fe particles as raw materials to obtain Fe-Se alloy rods through melting and casting. By introducing Se elements to modify the alloy degradation rate, and combining the cold work hardening effect of extrusion and drawing processes, the strength of FeSe alloy can be greatly improved while maintaining good plastic deformation ability, so that Fe-Se alloy supports can be obtained by further machining.

[0010] Since the present invention provides an Fe-Se alloy support, further processing is required to obtain the Fe-Se tubing to meet the design drawings. Therefore, the obtained Fe-Se tubing not only needs an ultra-thin wall thickness, but also needs to have processing deformation properties. During the experimental exploration process, the inventors tried a large number of deformation processes and found that only by first casting the Fe-Se alloy rod and then extruding and drawing can the required Fe-Se tubing be obtained. If deformation processes such as rolling are used, the required thickness of Fe-Se tubing cannot be obtained.

[0011] In a preferred embodiment, the smelting process is as follows: iron foil is wrapped around Fe-Se master alloy powder and placed in a vacuum arc melting furnace. Then, Fe particles are placed on top of the Fe-Se master alloy powder. The Fe particles are first melted with a current of 90-100A to obtain Fe liquid, which wraps around the Fe-Se master alloy powder underneath. Then, the current is increased to 150-250A and the smelting is repeated to obtain an ingot.

[0012] This invention employs a vacuum arc melting furnace. First, a small current is used to ignite the arc. When the arc from this small current strikes the surface of the Fe particles, the Fe slowly melts. As time progresses, the molten Fe completely encapsulates the underlying Fe-Se master alloy, allowing it to melt and preventing volatilization. Subsequently, the current is increased for repeated melting, resulting in a more uniform mixing and melting of the two alloys.

[0013] In a further preferred embodiment, the number of repeated melting processes is 6 to 8 times.

[0014] In the preferred embodiment, the Fe-Se ingot is placed at the edge of the casting mold in a vacuum arc melting furnace, an arc is ignited, and the current is increased to 250-300A to melt the ingot and pour it into the mold to obtain Fe-Se rods.

[0015] Using the aforementioned current to melt the ingot and pour it into the mold ensures that the molten alloy flows smoothly and completely into the mold, avoiding overheating and the formation of pores, thus obtaining the desired Fe-Se rod.

[0016] In a preferred embodiment, the annealing temperature is 600-800℃ and the annealing time is 20-30 minutes.

[0017] The resulting bars from the alloy after casting have relatively coarse grains and an uneven microstructure. Annealing can make the material's microstructure and composition more uniform, eliminate structural defects, reduce residual stress, and decrease the tendency for deformation and cracking. However, annealing parameters need to be effectively controlled. If the annealing temperature is too high, it will cause grain growth, resulting in an uneven internal structure and a decrease in tensile strength and hardness, thus affecting the metal's service life and performance. If the annealing temperature is too low, the internal stress of the metal cannot be fully released, affecting the metal's ability to recover its microstructure and plastically deform. The grain growth rate will slow down, easily leading to uneven grain growth and a decrease in metal strength and toughness. If the annealing time is too long, the grain growth rate will accelerate, and the corresponding grain size will increase, resulting in a reduction in grain boundary area and the formation of a thick grain structure, which in turn reduces the plasticity, toughness, and ductility of the Fe-Se alloy. If the annealing time is too short, it will affect the alloy's performance, as internal stress cannot be completely eliminated, easily leading to cracking.

[0018] In a further preferred embodiment, the annealing process is followed by water quenching. After annealing, the annealed billet is immediately placed in water for quenching. This prevents the annealed billet from undergoing a phase transformation and allows it to maintain its high-temperature structural state after cooling to room temperature, thus avoiding further grain growth.

[0019] In a preferred embodiment, the annealed billet is preheated at 550-600℃ for 45-60 minutes, and then hot extruded. The hot extrusion temperature is 550-620℃, the extrusion ratio is 10-25:1, and the extrusion speed is 1-2 mm / s.

[0020] In the hot extrusion process of this invention, the heating is first controlled above the recrystallization temperature of the Fe-Se alloy, and then the hot extrusion is controlled within the temperature range of this invention. After preheating, the grains can be prevented from growing significantly during the short extrusion period, thereby preventing the Fe-Se alloy grains from becoming coarse and cracks from forming on the surface after extrusion. Thus, under the action of the extrusion rod, the material is deformed through the die hole to obtain a bar of the required size.

[0021] Extrusion temperature directly affects extrusion strength. Excessively high extrusion temperatures can soften the Fe-Se alloy, increasing extrusion difficulty and increasing the risk of overheating. Conversely, excessively low extrusion temperatures can lead to material embrittlement and breakage. If the extrusion ratio is too high, the extruder may stall due to excessive pressure, preventing normal extrusion, damaging the sample, and even destroying the equipment, thus affecting the experiment. Conversely, if the extrusion ratio is too low, it is difficult to obtain samples with uniform microstructure and properties.

[0022] In a preferred embodiment, the multi-pass drawing process is as follows: preheating at 500-550℃ for 15-30 minutes, followed by air cooling and drawing, with heat treatment performed between passes. The temperature of the last heat treatment between passes is 600-650℃, and the temperature of the heat treatment between the remaining passes is 500-550℃, with each heat treatment lasting 15-30 minutes.

[0023] The drawing process of this invention involves preheating the Fe-Se alloy above its recrystallization temperature, followed by air cooling to obtain a ferrite and pearlite microstructure, which is a near-equilibrium microstructure. Drawing at the recrystallization temperature eliminates work hardening, non-equilibrium microstructure, and coarse grains caused during the drawing process, facilitating further drawing and resulting in more uniform mechanical properties of the Fe-Se alloy. The drawing process is then repeated in multiple passes. With each pass, the strain increases, the grains are elongated, and significant refinement occurs, further reducing the diameter and wall thickness to achieve the desired thickness. During the final inter-pass heat treatment, the temperature is increased to eliminate work hardening from the previous draw, stabilizing and maintaining the microstructure, ultimately yielding an Fe-Se alloy tube with the required wall thickness and excellent reprocessing properties.

[0024] In a preferred embodiment, during the multi-pass drawing process, the deformation amount per pass is controlled to be 15%-20%, and the total deformation amount is ≤90%.

[0025] In this invention, a small amount of deformation is used between single passes and a small partial compression ratio is used across multiple passes during drawing. This allows the microstructure in the Fe-Se alloy to undergo plastic bending and axial rotation during the drawing process. Even when the total compression ratio reaches 90%, the microstructure can still be elongated along the drawing direction without cracking. However, if the deformation amount in a single pass is too large, the ferrite will almost completely break, resulting in brittleness in the Fe-Se alloy material.

[0026] The preferred method is to obtain an Fe-Se alloy bracket by laser cutting and polishing Fe-Se pipe.

[0027] In a preferred embodiment, the wall thickness of the Fe-Se alloy scaffold is ≤80μm, preferably 70-80μm.

[0028] In a preferred embodiment, the mass fraction of Se in the Fe-Se alloy scaffold is 0.5-1.2 wt%.

[0029] The present invention also provides an Fe-Se alloy scaffold prepared by the above preparation method.

[0030] Principles and advantages

[0031] This invention uses FeSe master alloy powder and Fe particles as raw materials to obtain Fe-Se alloy rods through melting and casting. By introducing Se element to modify the alloy degradation rate and combining it with the cold work hardening effect of extrusion and drawing processes, the strength of the FeSe alloy can be significantly improved while maintaining good plastic deformation capacity. The obtained FeSe tubes are then straightened and polished, and laser-cut patterns to obtain ultra-thin Fe-Se alloy supports with a thickness of only 70-80 μm. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0033] Figure 1 The tensile deformation curves of pure Fe and Fe-0.6Se alloy supports after hot extrusion drawing are shown.

[0034] Figure 2 The image shows the potentiodynamic polarization curves of the Fe-0.6Se alloy scaffold after hot extrusion drawing, obtained by testing in simulated body fluid (Hank's solution).

[0035] Figure 3 Cell viability of Fe-0.6Se alloy scaffold in MG63 osteoma cells and MC3T3-E1 normal cells.

[0036] Figure 4 It is a finished Fe-0.6Se alloy scaffold with a thickness of 70-80μm. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] Example 1 (Fe-0.6Se)

[0039] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0040] The prepared Fe-0.6Se bars were annealed at 650℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. To ensure uniform alloy temperature during extrusion, the Fe-0.6Se bars were preheated at 600℃ for 1 hour, and then immediately hot-extruded at 550℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. The extruded rods are cut and cleaned, then subjected to multiple drawing passes at 550-650℃. First, the rods are held at 550℃ for 15 minutes for the first drawing. Then, for the second drawing, the temperature is raised to 550℃ and held for 15-30 minutes. This heating-holding-drawing-heating-holding-drawing process is repeated five times. In the final pass, the drawing temperature is increased to 650℃ and held for 15 minutes before drawing. The drawn material is then straightened and mechanically polished to obtain Fe-0.6Se tubing with an outer diameter of 4mm and a wall thickness of 0.09mm. The FeSe tubing is then laser-cut and polished to produce an ultrathin Fe-0.6Se alloy support with a diameter of 3mm, a nominal length of 18mm, and a thickness of 80μm.

[0041] Specific data

[0042] 1. X-ray fluorescence spectroscopy (XRF) was used to determine that the relative mass content of Se in the Fe-0.6Se alloy prepared in this example was 0.54%, and the rest was Fe.

[0043] 2. Figure 1The figures show the tensile deformation curves of pure Fe and Fe-0.6Se alloy stents after hot extrusion drawing. After hot extrusion drawing, the tensile mechanical properties and hardness of the Fe-0.6Se alloy stents are significantly improved, with tensile yield strength (YS), tensile ultimate strength (UTS), elongation, and hardness values ​​of 844.1 MPa, 885.5 MPa, 17.7%, and 256 HV, respectively.

[0044] 3. Figure 2 The image shows the potentiodynamic polarization curves of the Fe-0.6Se alloy scaffold after hot extrusion drawing in simulated body fluid (Hank's solution). Electrochemical tests in Hank's solution revealed that the corrosion potential, corrosion current density, and corrosion rate of extruded pure Fe were -0.598 V and 4.478 μA / cm, respectively. 2 The corrosion potential, corrosion current density, and corrosion rate of the Fe-0.6Se support after extrusion and drawing are -0.557 V, 8.516 μA / cm, and 0.036 mm / y. 2 The corrosion rate was 0.068 mm / y. After introducing Se and undergoing hot extrusion and drawing, the iron alloy stent exhibited a faster corrosion potential, higher corrosion current density, and corrosion rate, demonstrating superior degradation performance. Immersion experiments in Hank's solution showed that the corrosion rate of pure Fe after extrusion and drawing was 0.12 mm / y, while the corrosion rate of the Fe-0.6Se alloy stent was 0.26 mm / y, consistent with the trends observed in electrochemical experiments.

[0045] 4. Figure 3To assess the cell viability of Fe-0.6Se alloy scaffolds in MG63 osteoma cells and MC3T3-E1 normal cells, the extruded and drawn Fe-0.6Se alloy was immersed in culture medium for 48 hours. The culture medium was then diluted to different concentrations (100%, 25%, and 12.5%) and cultured with MG63 and MC3T3-E1 cells for 5 days. Cell viability was then measured. The results showed that MC3T3-E1 cells exhibited over 100% viability at a 12.5% ​​dilution, indicating that the alloy at this concentration had zero cytotoxicity to MC3T3-E1 cells and possessed complete biocompatibility. When the immersion solution was diluted to 12.5% ​​and 25%, the viability of MG63 cells decreased. Furthermore, significant apoptosis was observed when cell morphology was assessed using fluorescent live / dead staining and 4'-6-diamidinyl-2-phenylindole (DAPI) staining, demonstrating that the Fe-0.6Se alloy scaffold can effectively combat tumor cells. In mouse platelet-ischemic plasma (PPP) containing osteocarcinoma cells, the Fe-0.6Se alloy scaffold, after compression and stretching, achieved a 1.42% survival rate inactivating osteocarcinoma cells. This indicates a certain rate of osteocarcinoma inactivation, meeting the requirements for clinical medical biomaterials and possessing superior biomedical value.

[0046] 5. Three months after implantation of the Fe-0.6Se alloy stent into the rabbit abdominal aorta, morphological analysis of hard tissue sections showed that the myocardial cells, hepatocytes, spleen tissue, and lung tissue exhibited normal morphology and clear cell arrangement, without obvious necrosis, tissue edema, or inflammatory cell infiltration. This indicates that the Fe-0.6Se alloy stent did not adversely affect the rabbit's circulatory or immune organs. Microscopic CT morphology of the degradation products showed that the Fe-0.6Se alloy stent began to corrode gradually after implantation. After three months, a layer of degradation products completely covered the stent, indicating that the alloy stent underwent partial degradation in vivo and possesses suitable corrosion resistance.

[0047] Example 2 (Fe-1.2Se)

[0048] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-1.2%Se alloy. 100g of Fe was melted at a time, and 2.4g of FeSe powder was weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. During melting, the current of the vacuum arc furnace was adjusted to control the melting temperature. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0049] The prepared Fe-1.2Se bars were annealed at 650℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. To ensure uniform alloy temperature during extrusion, the Fe-1.2Se bars were preheated at 600℃ for 1 hour, and then immediately hot-extruded at 550℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. The extruded rods are cut and cleaned, then subjected to multiple drawing passes at 550-650℃. First, the rods are held at 550℃ for 15 minutes for the first drawing. Then, for the second drawing, the rods are heated to 550℃ again and held for 15-30 minutes. This heating-holding-drawing-heating-holding-drawing process is repeated five times. In the final pass, the drawing temperature is increased to 650℃ and held for 15 minutes before drawing. The heat treatment time between each pass is 15-30 minutes, and the drawing process is repeated five times. The drawn material is then straightened and mechanically polished to obtain Fe-1.2Se tubing with an outer diameter of 4mm and a wall thickness of 0.09mm. The FeSe tubing is then laser-cut and polished to produce an ultrathin Fe-1.2Se alloy support with a diameter of 3mm, a nominal length of 18mm, and a thickness of 80μm.

[0050] Implementation effect

[0051] X-ray fluorescence spectroscopy (XRF) revealed that the relative mass content of Se in the Fe-1.2Se alloy prepared in this embodiment was 1.14%, with the remainder being Fe. After hot extrusion and drawing, the tensile mechanical properties and hardness of the Fe-1.2Se alloy scaffold showed significant improvements, with tensile yield strength (YS), ultimate tensile strength (UTS), elongation, and hardness values ​​of 794.3 MPa, 801.2 MPa, 16.2%, and 241 HV, respectively. Electrochemical tests in Hank's solution showed that the corrosion potential, corrosion current density, and corrosion rate of the extruded Fe-1.2Se scaffold were -0.572 V and 9.142 μA / cm, respectively. 2The corrosion rate was 0.075 mm / y. After introducing Se and undergoing hot extrusion and drawing, the iron alloy scaffold exhibited a faster corrosion potential, higher corrosion current density, and corrosion rate, demonstrating superior degradation performance. Immersion experiments in Hank's solution showed that the corrosion rate of the Fe-1.2Se alloy scaffold was 0.31 mm / y, consistent with the variation observed in electrochemical experiments. After immersing the extruded and drawn Fe-1.2Se alloy in culture medium for 48 hours, the culture medium was diluted to different concentrations of 100%, 25%, and 12.5%, and cultured with MG63 and MC3T3-E1 cells for 5 days, respectively. Cell viability was then assessed. The results showed that when the immersion medium was diluted to 12.5%, the cell viability of MC3T3-E1 cells was higher than 100%, indicating that the alloy at this concentration had zero cytotoxicity to normal MC3T3-E1 cells and exhibited complete biocompatibility. When the MG63 cells were diluted to 12.5% ​​and 25% in the soaking solution, cell viability decreased. Furthermore, significant apoptosis was observed when cell morphology was assessed using fluorescent live / dead staining and 4'-6-diamidinyl-2-phenylindole (DAPI) staining, demonstrating that the Fe-1.2Se alloy scaffold can effectively combat tumor cells. In mouse ischemic platelet plasma (PPP) containing osteocarcinoma cells, the Fe-1.2Se alloy scaffold achieved a 2.11% survival rate inactivating osteocarcinoma cells after compression and stretching. This indicates a certain rate of osteocarcinoma inactivation, meeting the requirements for clinical medical biomaterials and possessing superior biomedical value. Three months after implantation of the Fe-1.2Se alloy scaffold into the rabbit abdominal aorta, hard tissue sections showed normal morphology and arrangement of cardiomyocytes, hepatocytes, spleen tissue, and lung tissue, with clear cells and no obvious necrosis, tissue edema, or inflammatory cell infiltration. This indicates that the Fe-1.2Se alloy scaffold did not adversely affect the rabbit's circulatory or immune organs. The microscopic CT morphology of the degradation products showed that the Fe-1.2Se alloy stent began to corrode gradually after implantation. After 3 months, a layer of degradation products could be observed to completely cover the stent, indicating that the alloy stent underwent partial degradation in the implanted body and had suitable corrosion resistance.

[0052] Comparative Example 1 (using cold extrusion)

[0053] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0054] The prepared Fe-0.6Se rods were annealed at 550℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. The Fe-0.6Se rods were then placed in an extrusion die and cold-extruded at room temperature with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. It was found that the samples cracked during extrusion at room temperature, and the extrusion deformation was very small, making it impossible to proceed with further experiments.

[0055] Comparative Example 2 (samples not annealed at high temperature before extrusion)

[0056] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0057] Fe-0.6Se rods were preheated at 600℃ for 1 hour and then immediately hot-extruded at 550℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. It was subsequently found that the extruded rods were cracked and bent, and very few samples could be obtained, making it impossible to conduct the next pull-out test.

[0058] Comparative Example 3 (Extrusion Temperature Too High)

[0059] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0060] The prepared Fe-0.6Se rods were annealed at 650℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. To ensure uniform alloy temperature during extrusion, the Fe-0.6Se rods were preheated at 600℃ for 1 hour, and then immediately hot-extruded at 850℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. Overheating was observed on the surface of the rods, resulting in blackening and rust flaking, making further experiments impossible.

[0061] Comparative Example 4 (Excessive number of pull-out passes)

[0062] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0063] The prepared Fe-0.6Se bars were annealed at 650℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. To ensure uniform alloy temperature during extrusion, the Fe-0.6Se bars were preheated at 600℃ for 1 hour, and then immediately hot-extruded at 550℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. The extruded rods were cut and cleaned, then subjected to multiple drawing passes at 550-650℃. The first drawing was performed by holding the rod at 550℃ for 15 minutes. For the second drawing, the rod was reheated to 550℃ and held for 15-30 minutes. This heating-holding-drawing-heating-holding-drawing process was repeated eight times. In the final draw, the drawing temperature was increased to 650℃ and held for 15 minutes before drawing. The heat treatment time between each pass was 15-30 minutes, and the total number of drawing passes was eight. As the number of drawing passes increased, the sample diameter gradually decreased, and the thickness also became thinner. After more than six passes, the drawing effect gradually weakened, the sample diameter became too small to continue drawing, and due to excessive deformation, the plasticity was poor, making it prone to breakage and preventing further experiments.

[0064] Comparative Example 5 (drawing temperature too low)

[0065] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0066] The prepared Fe-0.6Se bars were annealed at 650℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. To ensure uniform alloy temperature during extrusion, the Fe-0.6Se bars were preheated at 600℃ for 1 hour, and then immediately hot-extruded at 550℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. The extruded bars were cut and cleaned, and then drawn at 300℃ with a heat treatment time of 15-30 minutes between each pass. It was found that the bars were difficult to deform during the drawing process, the sample diameter was difficult to reduce, and the desired thickness could not be achieved, making it impossible to proceed to the next step of the experiment.

[0067] Comparative Example 6 (Drawing temperature too high)

[0068] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0069] The prepared Fe-0.6Se bars were annealed at 650℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. To ensure uniform alloy temperature during extrusion, the Fe-0.6Se bars were preheated at 600℃ for 1 hour, and then immediately hot-extruded at 550℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. The extruded rods were cut and cleaned, and then drawn at 850℃ with a heat treatment time of 15-30 minutes between each pass. It was found that the rods were overheated, with black rust on the surface. The samples were also brittle after high-temperature drawing and could not be used as supports for expansion, so further experiments could not be carried out.

[0070] Comparative Example 7 (Drawing Heat Treatment Time)

[0071] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0072] The prepared Fe-0.6Se bars were annealed at 650℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. To ensure uniform alloy temperature during extrusion, the Fe-0.6Se bars were preheated at 600℃ for 1 hour, and then immediately hot-extruded at 550℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. The extruded rods were cut and cleaned, then drawn at 550-650℃. First, the rods were held at 550℃ for 15 minutes for the first drawing. Then, for the second drawing, the temperature was raised to 550℃ and held for 15-30 minutes. This heating-holding-drawing-heating-holding-drawing process was repeated five times. In the final draw, the drawing temperature was increased to 650℃ and held for 15 minutes before drawing. The heat treatment time between each pass was 15-30 minutes, and the drawing process consisted of five passes. During the subsequent straightening and mechanical polishing process, it was found that the samples cracked and became brittle, making them unsuitable for use as expansion supports and preventing further experiments.

[0073] Comparative Example 7 (same temperature for the final drawing pass)

[0074] Fe particles with a purity of 99.95%, Fe-Se master alloy powder with a purity of 99.95%, and Fe foil with a purity of 99.95% and a thickness of 0.05 mm were weighed according to the mass ratio of a binary Fe-0.6% Se alloy. 100g of FeSe powder was melted at a time, with 1.2g of FeSe powder weighed out. When weighing the Fe particles, the mass of the Fe foil coating the FeSe powder was removed. Melting was carried out in a vacuum arc furnace under argon protection. Before melting, the coated FeSe powder and Fe particles were placed in the crucible tank in the order of lower melting point first, followed by higher melting point. The melting temperature was controlled by adjusting the current of the vacuum arc furnace. First, a current of 100A was used to melt the pure Fe particles, coating the underlying FeSe powder. Then, the current was increased to 250A, and the melting process was repeated 8 times. After melting, the sample is placed in the casting mold opening inside the furnace, the arc is continued to be struck, and the current is increased to 300A, so that the liquid is slowly poured into the mold to obtain a cylindrical bar of 10mm*90mm.

[0075] The prepared Fe-0.6Se bars were annealed at 650℃ for 30 minutes in a vacuum tube furnace, and then rapidly water-cooled. To ensure uniform alloy temperature during extrusion, the Fe-0.6Se bars were preheated at 600℃ for 1 hour, and then immediately hot-extruded at 550℃ with an extrusion ratio of 10:1 and an extrusion speed of 2 mm / s. The extruded rods were cut and cleaned, then drawn at 550℃. The rods were held at 550℃ for 15 minutes for the first drawing. For the second drawing, the rods were reheated to 550℃ and held for 15-30 minutes. This heating-holding-drawing-heating-holding-drawing process was repeated 5 times. The heat treatment time between each pass was 15-30 minutes, and the number of drawing passes was 5. The drawn material was then straightened. However, during straightening, it was found that the bending could not be effectively corrected, and some work hardening remained, making it impossible to obtain a completely bendable and straightened support.

Claims

1. A method for preparing an ultrathin biodegradable Fe-Se alloy scaffold, characterized in that: Fe granules and Fe-Se intermediate alloy powder are prepared and smelted to obtain Fe-Se ingots. The Fe-Se ingots are melted and poured into a mold to obtain Fe-Se rods. The Fe-Se rods are annealed to obtain annealed billets. The annealed billets are extruded to obtain extruded billets. The extruded billets are drawn in multiple passes to obtain Fe-Se tubes. The Fe-Se tubes are processed to obtain Fe-Se alloy supports. In the Fe-Se alloy supports, the mass fraction of Se is 0.1-2.0%wt. The annealing temperature is 600-800℃, and the annealing time is 20-30 minutes; After the annealing process, water quenching is performed. The annealed billet is preheated at 550-600℃ for 45-60 minutes, and then hot extruded. The hot extrusion temperature is 550-620℃, the extrusion ratio is 10-25:1, and the extrusion speed is 1-2 mm / s. The multi-pass drawing process is as follows: preheating at 500-550℃ for 15-30 minutes, followed by air cooling and drawing, with heat treatment between passes. The temperature of the last heat treatment between passes is 600-650℃, and the temperature of the heat treatment between the remaining passes is 500-550℃. The heat treatment time between passes is 15-30 minutes. During the multi-pass drawing process, the deformation amount of a single pass is controlled to be 15%-20%, and the total deformation amount is ≤90%.

2. The method for preparing an ultrathin biodegradable Fe-Se alloy scaffold according to claim 1, characterized in that: The smelting process is as follows: Fe-Se master alloy powder is wrapped in iron foil and placed in a vacuum arc melting furnace. Then, Fe particles are placed on top of the Fe-Se master alloy powder. The Fe particles are first melted with a current of 90-100A to obtain Fe liquid, which wraps the Fe-Se master alloy powder underneath. Then, the current is increased to 150-250A and the smelting is repeated to obtain an ingot. The number of smelting cycles is 6 to 8.

3. The method for preparing an ultrathin biodegradable Fe-Se alloy scaffold according to claim 1 or 2, characterized in that: Fe-Se ingots are placed on the edge of a casting mold in a vacuum arc melting furnace, an arc is ignited, and the current is increased to 250-300A to melt the ingots and pour them into the mold to obtain Fe-Se bars.

4. The method for preparing an ultrathin biodegradable Fe-Se alloy scaffold according to claim 1 or 2, characterized in that: Fe-Se alloy supports are obtained by laser cutting and polishing Fe-Se pipes.

5. A method for preparing an ultrathin biodegradable Fe-Se alloy scaffold according to claim 1 or 2, characterized in that: The wall thickness of the Fe-Se alloy scaffold is ≤80μm. In the Fe-Se alloy scaffold, the mass fraction of Se is 0.5-1.2 wt%.

6. The Fe-Se alloy scaffold prepared by the preparation method according to any one of claims 1-5.

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