A biodegradable zinc alloy thin-walled microtube and a preparation method and application thereof

Abstract

The present application relates to the technical field of metallurgical and plastic processing of biomaterials, and provides a biodegradable zinc alloy thin-walled microtube and a preparation method and application thereof.The present application uses zinc and zinc intermediate alloy as raw materials, prepares a zinc alloy hollow ingot through vacuum melting and pouring casting, and then prepares the biodegradable zinc alloy thin-walled microtube through hot spinning-drawing.The alloying elements in the obtained thin-walled microtube include one, two or three of Mg, Mn, Cu and Ti, and the total mass fraction of the alloying elements is not more than 0.5%.The preparation method provided by the present application has a short process flow and low cost, and the mechanical properties, degradation performance and surface quality of the obtained thin-walled microtube can completely meet the processing and service requirements of cardiovascular stents, and thus has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of metallurgical and plastic processing technology of biomaterials, and in particular to a biodegradable zinc alloy thin-walled microtube, its preparation method and application. Background Technology

[0002] Zinc alloys, due to their excellent mechanical properties, biocompatibility, and suitable degradation rate, hold potential as fourth-generation biodegradable cardiovascular stent materials. Pure zinc itself has low strength and poor ductility, failing to meet the high strength and high ductility requirements of cardiovascular stents. Currently, biodegradable biomedical zinc alloys generally improve their overall performance by adding various alloying elements. However, most alloying elements have low solid solubility in the zinc matrix, and the actual added content often exceeds their solid solubility range, leading to the precipitation of a large amount of second phase within the alloy. Cardiovascular stents made from such zinc alloys containing second phases are prone to uneven degradation after implantation, easily leading to premature stent failure, thus affecting treatment outcomes and even threatening patient lives. Conversely, insufficient addition of alloying elements results in inadequate alloy strengthening and substandard mechanical properties, also failing to meet clinical application requirements. Therefore, reducing or even eliminating the second phase in zinc alloys while ensuring their high strength and ductility is a prerequisite for the use of zinc alloys in biodegradable cardiovascular stents.

[0003] Furthermore, the fabrication technology of zinc alloy thin-walled microtubes, as precursors to biodegradable cardiovascular stents, is still in its early stages. Existing research has produced zinc alloy thin-walled tubes of different systems through various processes such as extrusion-drawing, single extrusion, and drilling-cold rolling-drawing. However, the tubes prepared by the above processes are difficult to simultaneously meet the comprehensive mechanical performance indicators of yield strength ≥200MPa, tensile strength ≥300MPa, and elongation after fracture ≥20%.

[0004] A related technology provides a zinc alloy thin-walled microtube fabrication technique, which includes multiple processes such as conventional casting, magnetic levitation melting, homogenization heat treatment, free forging, die forging, extrusion billet preparation, mechanical polishing, three-roll cold rolling, annealing, and fixed core drawing. The resulting zinc alloy thin-walled microtubes have mechanical properties and in vivo degradation performance that meet the actual service standards of cardiovascular stents. However, this fabrication process is long and complex, with many variables affecting production control, leading to high production costs and unstable product quality, which is not conducive to industrial production. Summary of the Invention

[0005] In view of this, the present invention provides a biodegradable zinc alloy thin-walled microtube, its preparation method, and its application. The preparation method provided by the present invention has a short process flow and low cost, and the mechanical properties, degradation performance, and surface quality of the obtained thin-walled microtubes fully meet the processing and service requirements of cardiovascular stents.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing biodegradable zinc alloy thin-walled microtubes includes the following steps: Metallic zinc and zinc master alloy are vacuum melted to obtain an alloy melt; the zinc master alloy is one, two or three of zinc-magnesium master alloy, zinc-manganese master alloy, zinc-titanium master alloy and zinc-copper master alloy. The alloy melt is poured and cast to obtain a zinc alloy hollow ingot; The zinc alloy hollow ingot is sequentially subjected to hot spinning forging and drawing to obtain the biodegradable zinc alloy thin-walled microtubes. The hot spinning forging includes a first hot spinning forging, a second hot spinning forging, and a third hot spinning forging. The initial temperature of the first hot spinning forging is 300±10℃, and the total deformation is not less than 75%. The initial temperature of the second hot spinning forging is 200±10℃, and the total deformation is not less than 75%. The initial temperature of the third hot spinning forging is 100±10℃, and the total deformation is not less than 80%. The deformation per drawing pass is 5~15%, and the total deformation is not less than 75%. The chemical composition of the biodegradable zinc alloy thin-walled microtube includes Zn and alloying elements, wherein the alloying elements include one, two or three of Mg, Mn, Cu and Ti; the total mass fraction of the alloying elements in the biodegradable zinc alloy thin-walled microtube does not exceed 0.5%, and the balance is Zn.

[0007] Preferably, the purity of the zinc metal is 99.999% or higher, and the purity of the zinc master alloy is 99.999% or higher.

[0008] Preferably, the zinc-magnesium master alloy has a magnesium mass fraction of 30-55% and the balance is zinc; the zinc-manganese master alloy has a manganese mass fraction of 5-20% and the balance is zinc; the zinc-titanium master alloy has a titanium mass fraction of 1-5% and the balance is zinc; and the zinc-copper master alloy has a copper mass fraction of 2-10% and the balance is zinc.

[0009] Preferably, the vacuum melting pressure is 20~40 kPa, and the vacuum melting is carried out in an inert atmosphere.

[0010] Preferably, the deformation amount per pass in the first, second, and third hot rotary forgings is 25-35%; the first hot rotary forging is held at the initial temperature of the first hot rotary forging for 20-30 minutes; the second hot rotary forging is held at the initial temperature of the second hot rotary forging for 15-20 minutes; and the third hot rotary forging is held at the initial temperature of the third hot rotary forging for 10-15 minutes.

[0011] Preferably, the drawing is cold drawing.

[0012] The present invention also provides a biodegradable zinc alloy thin-walled microtube prepared by the preparation method described above, wherein the average grain size of the biodegradable zinc alloy thin-walled microtube is less than 1 μm and the grain orientation is non-basal texture.

[0013] Preferably, the biodegradable zinc alloy thin-walled microtube has an outer diameter of 2.5~3.0 mm, a wall thickness of 0.12~0.16 mm, a wall thickness standard deviation ≤0.005 mm, an outer surface roughness Ra ≤0.05 μm, and an inner surface roughness Ra ≤0.1 μm.

[0014] Preferably, the biodegradable zinc alloy thin-walled microtube has a tensile strength of 320~380MPa, a yield strength of 260~320MPa, and an elongation of not less than 20%.

[0015] The present invention also provides the application of the biodegradable zinc alloy thin-walled microtubes described above in the preparation of vascular stents.

[0016] This invention provides a method for preparing biodegradable zinc alloy thin-walled microtubes, comprising the following steps: vacuum melting of metallic zinc and a zinc master alloy to obtain an alloy melt; wherein the zinc master alloy is one, two, or three of zinc-magnesium master alloy, zinc-manganese master alloy, zinc-titanium master alloy, and zinc-copper master alloy; casting the alloy melt to obtain a hollow zinc alloy ingot; and sequentially hot-forging and drawing the hollow zinc alloy ingot to obtain the biodegradable zinc alloy thin-walled microtubes; wherein the hot-forging includes a first hot-forging, a second hot-forging, and a third hot-forging; and the initial temperature of the first hot-forging is 300± The initial temperature of the first hot forging is 10℃, and the total deformation is not less than 75%; the initial temperature of the second hot forging is 200±10℃, and the total deformation is not less than 75%; the initial temperature of the third hot forging is 100±10℃, and the total deformation is not less than 80%; the deformation per pass of the drawing is 5~15%, and the total deformation is not less than 75%; the chemical composition of the biodegradable zinc alloy thin-walled microtube includes Zn and alloying elements, wherein the alloying elements include one, two, or three of Mg, Mn, Cu, and Ti; the total mass fraction of the alloying elements in the biodegradable zinc alloy thin-walled microtube does not exceed 0.5%, and the balance is Zn. This invention prepares hollow zinc alloy ingots through vacuum melting and casting, and then uses a short-process method of hot rotary forging and drawing to produce biodegradable zinc alloy thin-walled microtubes. Hot rotary forging features multi-directional and high-frequency forging, combining rotational and axial compression motions to gradually reduce the cross-section and shape of the hollow zinc alloy ingot, achieving die-free forging or near-net-shape forming. During forging, the ingot is under triaxial compressive stress, effectively improving the plasticity of hexagonal close-packed (HCP) zinc alloys. Simultaneously, high-frequency forging refines the grains, resulting in a uniform and fine microstructure within the zinc alloy tube, significantly improving its processing and mechanical properties. The subsequent drawing after hot rotary forging improves the dimensional accuracy and surface quality of the forged zinc alloy tube, ensuring dimensional consistency along its entire length and cross-section. Furthermore, it allows for further diameter and wall reduction, producing high-precision, high-performance zinc alloy thin-walled microtubes suitable for cardiovascular stents. In addition, this invention strictly controls the number of alloying elements to no more than 3 and the total content to ≤0.5wt%. The added alloying elements are basically in a solid solution state in the zinc matrix, with no obvious second phase precipitation, resulting in a single-phase or quasi-single-phase structure. The prepared zinc alloy thin-walled microtubes can degrade uniformly, avoiding the problems of local accelerated corrosion and premature failure of the stent caused by the second phase, and significantly improving implantation safety and service stability.

[0017] In summary, the preparation method provided by this invention has a short process flow and low cost, and the mechanical properties, degradation properties and surface quality of the obtained thin-walled microtubes can fully meet the processing and service requirements of cardiovascular stents, and have broad application prospects. Attached Figure Description

[0018] Figure 1 The image shows the microstructure of the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in Example 1. Figure 2 The grain size distribution diagram is shown for the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in Example 1. Figure 3 The grain orientation diagram of the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in Example 1; Figure 4 The room temperature tensile curve of the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in Example 1; Figure 5 The room temperature tensile curve of the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in Example 1 after being placed at room temperature for 12 months; Figure 6 The room temperature tensile curve of the Zn-0.04Mg binary alloy thin-walled microtube prepared in Example 1 is shown. Figure 7 The room temperature tensile curve of the Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtube prepared as a control example 2. Detailed Implementation

[0019] This invention provides a method for preparing biodegradable zinc alloy thin-walled microtubes, comprising the following steps: Metallic zinc and zinc master alloy are vacuum melted to obtain an alloy melt; the zinc master alloy is one, two or three of zinc-magnesium master alloy, zinc-manganese master alloy, zinc-titanium master alloy and zinc-copper master alloy. The alloy melt is poured and cast to obtain a zinc alloy hollow ingot; The zinc alloy hollow ingot is sequentially subjected to hot spinning forging and drawing to obtain the biodegradable zinc alloy thin-walled microtubes. The hot spinning forging includes a first hot spinning forging, a second hot spinning forging, and a third hot spinning forging. The initial temperature of the first hot spinning forging is 300±10℃, and the total deformation is not less than 75%. The initial temperature of the second hot spinning forging is 200±10℃, and the total deformation is not less than 75%. The initial temperature of the third hot spinning forging is 100±10℃, and the total deformation is not less than 80%. The deformation per drawing pass is 5~15%, and the total deformation is not less than 75%. The chemical composition of the biodegradable zinc alloy thin-walled microtube includes Zn and alloying elements, wherein the alloying elements include one, two or three of Mg, Mn, Cu and Ti; the total mass fraction of the alloying elements in the biodegradable zinc alloy thin-walled microtube does not exceed 0.5%, and the balance is Zn.

[0020] This invention involves vacuum melting of metallic zinc and a zinc master alloy to obtain an alloy melt. In this invention, the purity of the metallic zinc is preferably 99.999% or higher; the zinc master alloy is preferably one, two, or three of the following: zinc-magnesium master alloy, zinc-manganese master alloy, zinc-titanium master alloy, and zinc-copper master alloy; the magnesium mass fraction in the zinc-magnesium master alloy is preferably 30-55%, specifically 40% or 50%, with the balance being zinc; the manganese mass fraction in the zinc-manganese master alloy is 5-20%, specifically 10% or 20%, with the balance being zinc; the titanium mass fraction in the zinc-titanium master alloy is 1-5%, specifically 2% or 5%, with the balance being zinc; the copper mass fraction in the zinc-copper master alloy is 2-10%, specifically 5%, with the balance being zinc; the purity of the zinc master alloy is preferably 99.999% or higher.

[0021] In this invention, the vacuum melting pressure is preferably 20-40 kPa, and the vacuum melting is preferably carried out in an inert atmosphere, preferably argon; the vacuum melting is specifically vacuum induction melting; in a specific embodiment of this invention, the vacuum degree of the vacuum induction melting furnace is preferably first evacuated to 2.0 × 10⁻⁶ kPa. -3 After purging with argon gas to 20~40 kPa, vacuum melting is carried out.

[0022] After obtaining the alloy melt, the present invention performs casting to obtain a zinc alloy hollow ingot. In the present invention, the mold used for casting is preferably a water-cooled iron mold; the present invention preferably waits until all the raw materials are melted, then electromagnetically stirs the alloy melt evenly, then lets it stand for 15 minutes before casting.

[0023] After obtaining the zinc alloy hollow ingot, the present invention sequentially performs hot spinning forging and drawing on the zinc alloy hollow ingot to obtain the biodegradable zinc alloy thin-walled microtube. In a specific embodiment of the present invention, it is preferable to first turn the zinc alloy hollow ingot and then perform hot spinning forging.

[0024] In this invention, the hot rotary forging includes a first hot rotary forging, a second hot rotary forging, and a third hot rotary forging; the initial temperature of the first hot rotary forging is 300±10℃, and it is preferable to hold the first hot rotary forging at the initial temperature for 20~30min before the first hot rotary forging, and the total deformation of the first hot rotary forging is not less than 75%, preferably 75%~87%, specifically 80%, 85%, or 87%; the initial temperature of the second hot rotary forging is 200±10℃, and it is preferable to hold the second hot rotary forging at the initial temperature for 15~20min before the second hot rotary forging, and the total deformation of the second hot rotary forging is not less than 75%, preferably 75%~85%, specifically 80% or 82%; the initial temperature of the third hot rotary forging is 100±10℃, and it is preferable to hold the third hot rotary forging at the initial temperature for 10~15min before the third hot rotary forging, and the total deformation of the third hot rotary forging is not less than 80%, preferably 80%~86%, specifically 85% or 86%. The microstructure of hollow zinc alloy ingots is relatively coarse, resulting in poor low-temperature plastic deformation capacity. This invention first performs a first hot rotary forging at 300±10℃, which can improve its plastic deformation capacity. At the same time, dynamic recrystallization refines the coarse cast microstructure, reducing millimeter-level grains to hundreds of micrometers, which is beneficial for subsequent plastic deformation. Then, the temperature is lowered to 200±10℃ for a second hot rotary forging, which can refine the hundreds of micrometer-level grains to tens of micrometers. Finally, the temperature is lowered to 100±10℃ for a third hot rotary forging, which refines the grains to below 10 micrometers, thus facilitating subsequent room-temperature drawing plastic deformation. Ultimately, a zinc alloy thin-walled microtube with certain specifications, microstructure, and performance meets the requirements for cardiovascular stents is prepared.

[0025] In this invention, the deformation amount per pass of the first, second, and third hot rotary forgings is preferably 25-35%. In an embodiment of this invention, the deformation amount per pass of the first hot rotary forging is 30-35%, specifically 30%, 32%, or 35%, the deformation amount per pass of the second hot rotary forging is 28-30%, and the deformation amount per pass of the third hot rotary forging is 25-26%. This invention controls the deformation amount per pass of hot rotary forging, which can reduce the number of forming passes, improve production efficiency, and also help to keep the start and end temperatures of rotary forging consistent. More importantly, it can refine the internal structure of the alloy, improve the uniformity of the structure, and help improve the subsequent forming performance of the zinc alloy.

[0026] In this invention, the deformation amount per drawing pass is 5-15%, specifically 8%, 10%, or 12%, and the total deformation amount is preferably not less than 75%, preferably 75-86%, specifically 75%, 80%, or 86%. This invention controls the deformation amount per drawing pass and the total deformation amount, which helps to ensure that the tube does not break during the drawing process, thereby achieving the forming of thin-walled microtubes. At the same time, it can achieve the refinement and uniform distribution of the grain size of the thin-walled microtube matrix, thereby ensuring the mechanical properties and degradation uniformity of the product.

[0027] In this invention, the drawing is cold drawing, that is, the drawing temperature is room temperature.

[0028] The present invention also provides a biodegradable zinc alloy thin-walled microtube prepared by the preparation method described above. In the present invention, the chemical composition of the biodegradable zinc alloy thin-walled microtube includes Zn and alloying elements. The alloying elements include one, two, or three of Mg, Mn, Cu, and Ti. The total mass fraction of the alloying elements in the biodegradable zinc alloy thin-walled microtube does not exceed 0.5%, and the balance is Zn.

[0029] In this invention, the alloying element can specifically be Mg, or Mg and Mn, or Mg, Cu and Ti. In specific embodiments of this invention, when the alloying element is Mg, the mass fraction of Mg in the biodegradable zinc alloy thin-walled microtube is preferably 0.3%~0.5%, specifically 0.4%. When the alloying element is Mg and Mn, the mass fraction of Mg in the biodegradable zinc alloy thin-walled microtube is preferably 0.04%~0.06%, specifically 0.05%, and the mass fraction of Mn is preferably 0.1%~0.2%, specifically 0.18%. When the alloying element is Mg, Cu and Ti, the mass fraction of Mg in the biodegradable zinc alloy thin-walled microtube is preferably 0.03%~0.04%, specifically 0.035%, the mass fraction of Cu is preferably 0.2%~0.4%, specifically 0.3%, and the mass fraction of Ti is preferably 0.03%~0.05%, specifically 0.04%.

[0030] In this invention, the content of unavoidable impurities in the biodegradable zinc alloy thin-walled microtubes is ≤20ppm.

[0031] In this invention, the average grain size of the biodegradable zinc alloy thin-walled microtube is less than 1 μm, and the grain orientation is non-basal texture; the alloy structure of the biodegradable zinc alloy thin-walled microtube is equiaxed.

[0032] In this invention, the outer diameter of the biodegradable zinc alloy thin-walled microtube is preferably 2.5~3.0 mm, the wall thickness is preferably 0.12~0.16 mm, the standard deviation of the wall thickness is ≤0.005 mm, the outer surface roughness Ra is ≤0.05 μm, and the inner surface roughness Ra is ≤0.1 μm.

[0033] In this invention, the tensile strength of the biodegradable zinc alloy thin-walled microtube is preferably 320~380MPa, the yield strength is preferably 260~320MPa, and the elongation is preferably not less than 20%, more preferably 20%~38%. The strength change of the biodegradable zinc alloy thin-walled microtube after being placed at room temperature for 12 months does not exceed ±5%.

[0034] In this invention, the biodegradable zinc alloy thin-walled microtubes can achieve uniform degradation, with a degradation rate of no more than 0.004 mm / year in simulated body fluid (SBF) at 37°C.

[0035] This invention also provides the application of the biodegradable zinc alloy thin-walled microtubes described above in the fabrication of vascular stents. The zinc alloy thin-walled microtubes provided by this invention possess excellent mechanical and degradation properties, and can be used in the fabrication of cardiovascular stents, showing broad application prospects.

[0036] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] In the embodiments of the present invention, the purity of metallic Zn is 99.999%, the purity of Zn-Mg, Zn-Mn, Zn-Cu and Zn-Ti master alloys is 99.999%, and the purity of the graphite crucible is 99.999%.

[0038] In this embodiment of the invention, the component analysis was performed using an Optima 4300DV inductively coupled plasma atomic emission spectrometer (ICP-AES) manufactured by PE Corporation, USA.

[0039] In this embodiment of the invention, the tensile test adopts the national standard GB / T 228-2002 "Metallic materials, room temperature tensile test method", and the equipment is the AG-X50kN electronic universal testing machine manufactured by Shimadzu Corporation.

[0040] In this embodiment of the invention, the equipment used for tissue analysis is a Crossbeam 550 field emission scanning electron microscope manufactured by Zeiss, equipped with a backscattered electron diffractometer (EBSD).

[0041] The simulated body fluid used in this embodiment of the invention was prepared according to standard ISO / FDIS 23317. The preparation process used a 1 L solution as a baseline, a plastic beaker, and deionized water as the solvent, in a constant temperature bath at 37℃. The required reagent masses and their order of addition for 1 L of solution were as follows: NaCl, 8.035 g; NaHCO3, 0.355 g; KCl, 0.225 g; K2HPO4·3H2O, 0.231 g; MgCl2·6H2O, 0.311 g; 1 mol / L hydrochloric acid solution, 39 mL; CaCl2, 0.292 g; Na2SO4, 0.072 g; TRIS, 6.118 g. After adding the above reagents, the pH of the solution was adjusted to 7.40 with 0–5 mL of HCl solution (1 mol / L). During the preparation process, the reagents were added sequentially, with continuous stirring using a stirring rod, and the next reagent was added only after the previous one had fully dissolved.

[0042] Example 1 The composition of the biodegradable Zn-Mg binary alloy thin-walled microtubes prepared in this embodiment, by mass percentage, is as follows: Mg 0.04%, unavoidable impurities ≤20ppm, and the balance being Zn.

[0043] The preparation method of biodegradable Zn-Mg binary alloy thin-walled microtubes is as follows: (1) Using metallic Zn and Zn-40Mg master alloy as raw materials, metallic Zn and Zn-40Mg master alloy were loaded into a graphite crucible and the vacuum degree was evacuated to 2.0×10 -3 Pa, after purging with argon gas to 20~40 kPa, vacuum melting is carried out; (2) After the voltage is increased to 350 KV and it is completely melted, it is stirred evenly by electromagnetic stirring, then left to stand for 15 minutes, and then cast into a water-cooled iron mold to obtain a hollow Zn-0.04Mg alloy ingot. (3) After machining the hollow ingot, it is held at 300±10℃ for 20 minutes, and then rotary forged with a total deformation of 85% and a per-pass deformation of 35%; then it is held at 200±10℃ for 15 minutes and rotary forged with a total deformation of 80% and a per-pass deformation of 30%; finally it is held at 100±10℃ for 10 minutes and rotary forged with a total deformation of 85% and a per-pass deformation of 25%, thus obtaining a Zn-0.04Mg alloy hollow tube with a larger specification. (4) The hot-forged tubes are drawn at room temperature, with the deformation per pass controlled at 10% and the total deformation controlled at 75%, to obtain biodegradable Zn-0.04Mg binary alloy thin-walled microtubes. The Mg content at different locations (upper outer and inner surfaces, middle outer and inner surfaces, and bottom outer and inner surfaces) of the Zn-0.04Mg alloy hollow ingot was tested, and the results are shown in Table 1.

[0044] Table 1 Results of Mg content uniformity test According to the data in Table 1, the Mg content at different locations of the hollow ingot is basically maintained at 0.04±0.002%, with a standard deviation of only 0.0015wt%. The alloy composition is uniformly distributed, and the loss of Mg is effectively controlled.

[0045] The biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in this embodiment have an outer diameter of 2.8 mm, a standard deviation of 0.004 mm, a wall thickness of 0.15 mm, an outer surface roughness Ra of 0.0385 μm, and an inner surface roughness Ra of 0.0875 μm, as tested.

[0046] The biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in this embodiment have a microstructure composed of fine equiaxed crystals, such as... Figure 1 As shown, the average grain size is 0.96 μm, mainly concentrated in the range of 0.3–2.0 μm, and the distribution is relatively uniform. Figure 2 As shown.

[0047] The grain orientation of the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in this embodiment is as follows: Figure 3 As shown, the grains form a non-basal plane texture at a certain angle to the basal plane, which significantly improves the plasticity of the alloy.

[0048] The room temperature tensile curve of the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in this embodiment is shown in the figure. Figure 4 As shown, its yield strength is 302 MPa, tensile strength is 355 MPa, and elongation is 21.7%, which fully meets the requirements of biodegradable cardiovascular stents.

[0049] The room temperature tensile curve of the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in this embodiment after being placed at room temperature for 12 months is shown below. Figure 5 As shown, its yield strength is 314 MPa, tensile strength is 354 MPa, and elongation is 20.1%. The yield strength increased by 4%, and the tensile strength decreased by 0.28%, with the strength variation not exceeding ±5%.

[0050] The degradation performance of the biodegradable Zn-0.04Mg binary alloy thin-walled microtubes prepared in this embodiment was tested. The results showed that its degradation rate in simulated body fluid in vitro was 0.003463 mm·year. -1 .

[0051] Example 2 The composition of the biodegradable Zn-Mn-Mg ternary alloy thin-walled microtubes prepared in this embodiment, by mass percentage, is as follows: Mn 0.18%, Mg 0.05%, unavoidable impurities ≤20ppm, and the balance is Zn.

[0052] The preparation method of biodegradable Zn-Mn-Mg ternary alloy thin-walled microtubes is as follows: (1) Using metallic Zn, Zn-20Mn, and Zn-40Mg master alloys as raw materials, metallic Zn, Zn-20Mn, and Zn-40Mg master alloys were loaded into a graphite crucible, and the vacuum degree was evacuated to 2.0 × 10⁻⁶. -3 Pa, after purging with argon gas to 20~40 kPa, vacuum melting is carried out; (2) After the voltage is increased to 350 KV and it is completely melted, it is stirred evenly by electromagnetic stirring, then left to stand for 15 minutes, and then cast into a water-cooled iron mold to obtain a hollow Zn-0.18Mn-0.05Mg alloy ingot. (3) After machining the hollow ingot, it is held at 300±10℃ for 30 min, and then rotary forging is performed to open the billet. The total deformation is 80% and the deformation per pass is 30%. Then, after holding at 200±10℃ for 20 min, rotary forging is performed to obtain a total deformation of 80% and a deformation per pass of 30%. Finally, after holding at 100±10℃ for 15 min, rotary forging is performed to obtain a total deformation of 85% and a deformation per pass of 26%, thus obtaining a Zn-0.18Mn-0.05Mg alloy hollow tube with a larger specification. (4) The tubes after rotary forging are drawn at room temperature, with the deformation per pass controlled at 8% and the total deformation controlled at 80%, to obtain biodegradable Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtubes; The Mn and Mg contents of different locations (upper outer and inner surfaces, middle outer and inner surfaces, and bottom outer and inner surfaces) of the Zn-0.18Mn-0.05Mg alloy hollow ingot were tested, and the test results are shown in Table 2.

[0053] Table 2 Results of Mn and Mg content uniformity test According to the data in Table 2, the Mg content at different locations is basically maintained at 0.05±0.003%, with a standard deviation of only 0.0017wt%, and the Mn content at different locations is basically maintained at 0.18±0.015%, with a standard deviation of only 0.010wt%. The alloy composition is uniformly distributed, and the loss of alloying elements is effectively controlled.

[0054] Testing revealed that the biodegradable Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtubes prepared in this embodiment have an outer diameter of 3.0 mm, a standard deviation of 0.0035 mm, and a wall thickness of 0.12 mm. The outer surface roughness Ra of the microtubes is 0.0425 μm, and the inner surface roughness Ra is 0.0915 μm.

[0055] Testing revealed that the biodegradable Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtubes prepared in this embodiment consisted of fine equiaxed crystals with an average grain size of 0.84 μm, mainly concentrated between 0.1 and 1.8 μm, and relatively uniformly distributed. Furthermore, the grain orientation formed a non-basal plane texture at a certain angle to the basal plane, significantly improving the alloy's plasticity.

[0056] Testing revealed that the biodegradable Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtubes prepared in this embodiment have a yield strength of 316 MPa, a tensile strength of 376 MPa, and an elongation of 37.6%, fully meeting the requirements for biodegradable cardiovascular stents.

[0057] Testing revealed that the biodegradable Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtubes prepared in this embodiment, after being stored at room temperature for 12 months, exhibited a yield strength of 307 MPa, a tensile strength of 371 MPa, and an elongation of 30.4%. The yield strength decreased by 2.8%, and the tensile strength decreased by 1.3%, with the strength variation not exceeding ±5%.

[0058] The degradation performance of the biodegradable Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtubes prepared in this embodiment was tested. The results showed that its degradation rate in simulated body fluid in vitro was 0.003524 mm·year. -1 .

[0059] Example 3 The composition of the biodegradable Zn-Cu-Ti-Mg quaternary alloy thin-walled microtubes prepared in this embodiment, by mass percentage, is as follows: Cu 0.3%, Ti 0.04%, Mg 0.035%, unavoidable impurities ≤20ppm, and the balance is Zn.

[0060] The preparation method of biodegradable Zn-Cu-Ti-Mg quaternary alloy thin-walled microtubes is as follows: (1) Using metallic Zn, Zn-5Cu and Zn-50Mg, Zn-5Ti master alloys as raw materials, metallic Zn, Zn-5Cu and Zn-50Mg, Zn-5Ti master alloys were loaded into a graphite crucible and the vacuum degree was evacuated to 2.0×10 -3 Pa, after purging with argon gas to 20~40 kPa, vacuum melting is carried out; (2) After the voltage is increased to 350 KV and the material is completely melted, it is stirred evenly by electromagnetic stirring, then left to stand for 15 minutes, and then cast into a water-cooled iron mold to obtain a hollow Zn-0.3Cu-0.04Ti-0.035Mg alloy ingot. (3) After machining the hollow ingot, it is held at 300±10℃ for 25 minutes, and then rotary forging is performed. The total deformation is 87% and the deformation per pass is 32%. Then, after holding at 200±10℃ for 15 minutes, rotary forging is performed. The total deformation is 82% and the deformation per pass is 28%. Finally, after holding at 100±10℃ for 10 minutes, rotary forging is performed. The total deformation is 86% and the deformation per pass is 25%, thus obtaining a large-sized Zn-0.3Cu-0.04Ti-0.035Mg alloy hollow tube. (4) The tubes after rotary forging are drawn at room temperature, with the deformation per pass controlled at 12% and the total deformation controlled at 84%, to obtain biodegradable Zn-0.3Cu-0.04Ti-0.035Mg quaternary alloy thin-walled microtubes; The Cu, Ti, and Mg contents of Zn-0.3Cu-0.04Ti-0.035Mg alloy hollow ingots at different locations (outer and inner surfaces at the top, outer and inner surfaces in the middle, and outer and inner surfaces at the bottom) were tested, and the results are shown in Table 3.

[0061] Table 3 Results of the uniformity test for Cu, Ti, and Mg contents According to the data in Table 3, the Cu content at different locations of the hollow ingot is basically maintained at 0.3±0.02%, with a standard deviation of only 0.014wt%; the Ti content is basically maintained at 0.04±0.0025%, with a standard deviation of only 0.0018wt%; and the Mg content at different locations is basically maintained at 0.035±0.0025%, with a standard deviation of only 0.015wt%. The alloy composition is uniformly distributed, and the loss of alloying elements is effectively controlled.

[0062] The biodegradable Zn-0.3Cu-0.04Ti-0.035Mg quaternary alloy thin-walled microtubes prepared in this embodiment have an outer diameter of 3.0 mm, an outer diameter standard deviation of 0.003 mm, a wall thickness of 0.16 mm, an outer surface roughness Ra of 0.0432 μm, and an inner surface roughness Ra of 0.0726 μm.

[0063] The biodegradable Zn-0.3Cu-0.04Ti-0.035Mg quaternary alloy thin-walled microtubes prepared in this embodiment have a microstructure composed of fine equiaxed crystals with an average grain size of 0.78 μm, mainly concentrated between 0.15 and 1.78 μm, and relatively uniformly distributed. Furthermore, the grain orientation forms a non-basal plane texture at a certain angle to the basal plane, significantly improving the alloy's plasticity.

[0064] The biodegradable Zn-0.3Cu-0.04Ti-0.035Mg quaternary alloy thin-walled microtubes prepared in this embodiment have a yield strength of 276 MPa, a tensile strength of 336 MPa, and an elongation of 25.0%, which fully meet the requirements of biodegradable cardiovascular stents.

[0065] The biodegradable Zn-0.3Cu-0.04Ti-0.035Mg quaternary alloy thin-walled microtubes prepared in this embodiment had a yield strength of 269 MPa, a tensile strength of 332 MPa, and an elongation of 31.0% after being placed at room temperature for 12 months. The yield strength decreased by 2.5%, and the tensile strength decreased by 1.2%, with the strength change not exceeding ±5%.

[0066] The degradation performance of the biodegradable Zn-0.3Cu-0.04Ti-0.035Mg quaternary alloy thin-walled microtubes prepared in this embodiment was tested. The results showed that its degradation rate in simulated body fluid in vitro was 0.003152 mm·year. -1 .

[0067] Compare with Example 1 Compared to Example 1, the hot rotary forging process was changed to: after the hollow ingot was turned, it was held at 300±10℃ for 20 minutes, and then rotary forging was performed to open the billet, with a total deformation of 65%; then it was held at 200±10℃ for 15 minutes and then rotary forged, with a total deformation of 60%; finally, it was held at 100±10℃ for 10 minutes and then rotary forged, with a total deformation of 65%.

[0068] The room temperature tensile curve of the Zn-0.04Mg binary alloy thin-walled microtube prepared according to Example 1 is shown below. Figure 6 As shown, its yield strength is 273 MPa, tensile strength is 282 MPa, and elongation is 31.0%. According to... Figure 6 It can be seen that after the total deformation of rotary forging is reduced, the mechanical properties of the resulting alloy decrease significantly. The Zn-0.04Mg binary alloy thin-walled microtubes prepared in Example 1 have superior mechanical properties.

[0069] Compare with Example 2 Compared to Example 2, only the forging temperature was changed to 300±10℃, while the total deformation remained unchanged, resulting in biodegradable Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtubes.

[0070] The room temperature tensile curve of the Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtube prepared in Example 2 is shown below. Figure 7As shown, its yield strength is 268 MPa, tensile strength is 276 MPa, and elongation is 20%. The results in Comparative Example 2 show that changing the forging temperature at different stages significantly reduces the mechanical properties of the resulting alloy. The Zn-0.18Mn-0.05Mg ternary alloy thin-walled microtubes prepared in Example 2 have superior mechanical properties.

[0071] The results of the above embodiments show that the present invention uses a short-process method of vacuum casting-hot spinning forging-drawing to prepare high-strength, uniformly degradable zinc alloy thin-walled microtubes. The preparation process is simple and low-cost, and the resulting thin-walled microtubes have good mechanical properties and can be uniformly degraded. They can be used for the processing of medical biodegradable zinc alloy vascular stents and have broad application prospects.

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing biodegradable zinc alloy thin-walled microtubes, characterized in that, Includes the following steps: Metallic zinc and zinc master alloy are vacuum melted to obtain an alloy melt; the zinc master alloy is one, two or three of zinc-magnesium master alloy, zinc-manganese master alloy, zinc-titanium master alloy and zinc-copper master alloy. The alloy melt is poured and cast to obtain a zinc alloy hollow ingot; The zinc alloy hollow ingot is sequentially subjected to hot spinning forging and drawing to obtain the biodegradable zinc alloy thin-walled microtubes. The hot spinning forging includes a first hot spinning forging, a second hot spinning forging, and a third hot spinning forging. The initial temperature of the first hot spinning forging is 300±10℃, and the total deformation is not less than 75%. The initial temperature of the second hot spinning forging is 200±10℃, and the total deformation is not less than 75%. The initial temperature of the third hot spinning forging is 100±10℃, and the total deformation is not less than 80%. The deformation per drawing pass is 5~15%, and the total deformation is not less than 75%. The chemical composition of the biodegradable zinc alloy thin-walled microtube includes Zn and alloying elements, wherein the alloying elements include one, two or three of Mg, Mn, Cu and Ti; the total mass fraction of the alloying elements in the biodegradable zinc alloy thin-walled microtube does not exceed 0.5%, and the balance is Zn.

2. The preparation method according to claim 1, characterized in that, The purity of the zinc metal is above 99.999%, and the purity of the zinc master alloy is above 99.999%.

3. The preparation method according to claim 1, characterized in that, The zinc-magnesium master alloy has a magnesium mass fraction of 30-55%, with the balance being zinc; the zinc-manganese master alloy has a manganese mass fraction of 5-20%, with the balance being zinc; the zinc-titanium master alloy has a titanium mass fraction of 1-5%, with the balance being zinc; and the zinc-copper master alloy has a copper mass fraction of 2-10%, with the balance being zinc.

4. The preparation method according to claim 1, characterized in that, The vacuum melting pressure is 20~40 kPa, and the vacuum melting is carried out in an inert atmosphere.

5. The preparation method according to claim 1, characterized in that, The deformation amount per pass in the first, second, and third hot rotary forgings is 25-35%; the first hot rotary forging is held at the initial temperature of the first hot rotary forging for 20-30 minutes; the second hot rotary forging is held at the initial temperature of the second hot rotary forging for 15-20 minutes; and the third hot rotary forging is held at the initial temperature of the third hot rotary forging for 10-15 minutes.

6. The preparation method according to claim 1, characterized in that, The drawing process is cold drawing.

7. The biodegradable zinc alloy thin-walled microtube prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The biodegradable zinc alloy thin-walled microtubes have an average grain size of less than 1 μm and a non-basal texture grain orientation.

8. The biodegradable zinc alloy thin-walled microtube according to claim 7, characterized in that, The biodegradable zinc alloy thin-walled microtubes have an outer diameter of 2.5~3.0 mm, a wall thickness of 0.12~0.16 mm, a wall thickness standard deviation ≤0.005 mm, an outer surface roughness Ra≤0.05 μm, and an inner surface roughness Ra≤0.1 μm.

9. The biodegradable zinc alloy thin-walled microtube according to claim 7, characterized in that, The biodegradable zinc alloy thin-walled microtubes have a tensile strength of 320~380MPa, a yield strength of 260~320MPa, and an elongation of not less than 20%.

10. The application of the biodegradable zinc alloy thin-walled microtubes according to any one of claims 7 to 9 in the preparation of vascular stents.

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