A biodegradable Zn-Mg binary alloy and a preparation method and application thereof

Abstract

The application relates to the field of metallurgical and plastic processing of biomaterials, and provides a biodegradable Zn-Mg binary alloy and a preparation method and application thereof. The biodegradable Zn-Mg binary alloy is prepared by adopting a method of smelting-semi-continuous casting-forging-rolling-reverse extrusion and taking metal Zn and Zn-Mg intermediate alloy as raw materials. The Zn-Mg binary alloy prepared by the application has good mechanical properties, and the strength and ductility can meet the requirements of medical implant devices. Meanwhile, the Mg is added in the form of Zn-Mg intermediate alloy, so that the burning loss of the Mg can be effectively controlled, and the uniformity of the alloy composition and structure is improved. Further, high-purity raw materials are selected, and high-purity graphite crucibles are adopted for smelting, so that the heavy metal content in the Zn-Mg binary alloy is effectively controlled, the contents of Pb, As and Cd reach the standard of drinking water, and the safety of the Zn-Mg binary alloy implant in the body is ensured.

Description

Technical Field

[0001] This invention relates to the field of metallurgy and plastic processing technology of biomaterials, and in particular to a biodegradable Zn-Mg binary alloy, its preparation method and application. Background Technology

[0002] Biodegradable zinc alloys, as a class of medical biomaterials with great application potential, have attracted much attention in the field of medical implants due to their suitable in vivo degradation rate, good biocompatibility, and mechanical properties that match human hard tissues. Currently, zinc alloy products that meet the performance requirements of medical implants are basically ternary or higher-element multi-element alloys.

[0003] Compared to multi-component alloys, binary zinc alloys have simpler compositions, which can significantly simplify the biocompatibility evaluation process and reduce development costs, giving them significant application advantages and research value. Currently, Zn-Mg alloys are considered a new generation of biodegradable binary zinc alloy materials. However, despite their good biocompatibility, the strength and ductility of Zn-Mg alloys are difficult to meet the standards for medical implant devices.

[0004] One related technology provides a Zn-1Mg binary alloy, in which hydrostatic extrusion technology can significantly improve the alloy's mechanical properties, with its yield strength, tensile strength, and elongation all meeting the mechanical performance requirements of medical implant devices. However, hydrostatic extrusion is expensive and the size of the finished product is limited, restricting its application in high-performance implant devices.

[0005] Another related technology uses a casting-extrusion-semi-solid treatment-secondary extrusion technique to prepare Zn-Mg binary alloys, by refining Mg2Zn 11 While nanoscale materials significantly improve strength, elongation does not meet the requirements for implantable devices. Furthermore, due to the volatility of Mg and its large density difference with Zn, it is difficult to effectively control the consistency between the actual Mg content and the designed composition in Zn-Mg binary alloy ingots, which can easily lead to inhomogeneities in alloy composition distribution and microstructure.

[0006] In summary, how to use low-cost preparation techniques to prepare Zn-Mg alloys with satisfactory strength and ductility, and good uniformity in alloy composition and microstructure, is a technical problem that urgently needs to be solved. Summary of the Invention

[0007] In view of this, the present invention provides a biodegradable Zn-Mg binary alloy, its preparation method, and its application. The preparation method provided by the present invention is simple to operate, low in cost, and the prepared biodegradable Zn-Mg binary alloy has high strength and ductility, and good uniformity of alloy composition and microstructure.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] A method for preparing a biodegradable Zn-Mg binary alloy includes the following steps:

[0010] Metallic Zn and Zn-Mg master alloy are smelted to obtain an alloy melt; the alloy melt is semi-continuously cast to obtain a Zn-Mg binary alloy ingot; the Zn-Mg master alloy contains 30~50wt% Mg and the balance is Zn;

[0011] The Zn-Mg binary alloy ingot is sequentially forged, rolled, and reverse extruded to obtain the biodegradable Zn-Mg binary alloy; the forging ratio of the forging is not less than 16; the deformation per pass of the rolling is 8-15%, and the total deformation is 70-85%; the extrusion temperature of the reverse extrusion is 75-205℃, and the extrusion ratio is not less than 20; the reverse extrusion is performed by holding the material at the extrusion temperature for 0.5-2 hours before extrusion.

[0012] The composition of the biodegradable Zn-Mg binary alloy, by mass percentage, is: Mg 0.03~0.8%, total unavoidable impurities ≤20ppm, and balance Zn.

[0013] Preferably, the purity of the metallic Zn is 99.999% or higher, and the purity of the Zn-Mg master alloy is 99.999% or higher.

[0014] Preferably, the melting temperature is 515~525℃; the melting is carried out in a graphite crucible with a purity of 99.999% or higher; and the pouring temperature of the semi-continuous casting is 495~505℃.

[0015] Preferably, before the semi-continuous casting, the alloy melt is further refined; the refining agent used in the refining is hexachloroethane.

[0016] Preferably, the forging is hot forging; the forging temperature of the hot forging is 330~350℃, and the temperature is held at the forging temperature for 0.5~2h before hot forging; the rolling is cold rolling.

[0017] Preferably, the extrusion speed of the reverse extrusion is 0.5~5 mm / min.

[0018] The present invention also provides a biodegradable Zn-Mg binary alloy prepared by the preparation method described above, wherein the average grain size of the biodegradable Zn-Mg binary alloy is 0.5~1.5μm.

[0019] Preferably, the content of Pb in the biodegradable Zn-Mg binary alloy does not exceed 10 ppm, the content of As does not exceed 0.1 ppm, and the content of Cd does not exceed 5 ppm.

[0020] Preferably, the biodegradable Zn-Mg binary alloy has a tensile strength of 320-380 MPa, a yield strength of 250-330 MPa, and an elongation of not less than 20%.

[0021] This invention also provides the application of the biodegradable Zn-Mg binary alloy described above in the preparation of medical implant devices.

[0022] This invention provides a method for preparing a biodegradable Zn-Mg binary alloy, comprising the following steps: smelting metallic Zn and a Zn-Mg master alloy to obtain an alloy melt; semi-continuously casting the alloy melt to obtain a Zn-Mg binary alloy ingot; the Zn-Mg master alloy contains 30-50 wt% Mg, with the balance being Zn; sequentially forging, rolling, and back-extruding the Zn-Mg binary alloy ingot to obtain the biodegradable Zn-Mg binary alloy; the forging ratio of the forging is not less than 16; the deformation per pass in the rolling is 8-15%, and the total deformation is 70-85%; the back-extrusion temperature is 75-205℃, and the extrusion ratio is not less than 20; the back-extrusion is performed at the extrusion temperature for 0.5-2 hours; the composition of the biodegradable Zn-Mg binary alloy, by mass percentage, is: 0.03-0.8% Mg, total unavoidable impurities ≤20 ppm, and the balance being Zn. This invention employs a smelting-semi-continuous casting-forging-rolling-reverse extrusion method to prepare biodegradable Zn-Mg binary alloys. Specifically, the invention first melts metallic Zn and a Zn-Mg master alloy into a uniform melt through smelting. Then, semi-continuous casting effectively controls the uniform distribution of Mg elements along the axial and radial directions of the ingot, while simultaneously achieving uniformity in the ingot microstructure (such as grain size). A large forging ratio is then used to refine the coarse as-cast microstructure, providing plastic deformation capability for subsequent cold working. After cold rolling deformation, heat treatment is performed before reverse extrusion to achieve recrystallization annealing, further refining the grains. Reverse extrusion achieves uniform deformation of the product with relatively low extrusion pressure, thereby obtaining a Zn-Mg binary alloy with a uniform and fine microstructure. In summary, the Zn-Mg binary alloy prepared by this invention exhibits a uniform and fine microstructure, good mechanical properties, and strength and ductility that meet the requirements for medical implantable devices. Furthermore, the addition of Mg as a Zn-Mg master alloy during the preparation of the Zn-Mg binary alloy effectively controls the amount of Mg lost due to burn-off, improving the uniformity of the alloy composition and microstructure. Moreover, the preparation method provided by this invention is simple to operate and low in cost.

[0023] Furthermore, this invention uses high-purity raw materials and high-purity graphite crucibles for smelting, effectively controlling the heavy metal content in the Zn-Mg binary alloy. The contents of Pb, As, and Cd meet the standards for drinking water, thereby ensuring the safety of Zn-Mg binary alloy implantation.

[0024] The results of the examples show that the Zn-Mg binary alloy prepared by the present invention has a tensile strength of 320~380MPa, a yield strength of 250~330MPa, an elongation of not less than 20%, uniform composition and microstructure, fine grain size, and a standard deviation of Mg content distribution at different locations within ±0.1wt%. The heavy metal impurities Pb does not exceed 10ppm, As does not exceed 0.1ppm, and Cd does not exceed 5ppm. It can meet the requirements of biodegradable cardiovascular stents, bone screws and plates, anastomotic staples, binding sutures and other medical implantable devices. Attached Figure Description

[0025] Figure 1 The room temperature stress-strain curve of the Zn-0.05Mg alloy prepared in Example 1;

[0026] Figure 2 Microstructure diagram of the Zn-0.05Mg alloy prepared in Example 1;

[0027] Figure 3 The grain size distribution diagram is shown for the Zn-0.05Mg alloy prepared in Example 1.

[0028] Figure 4 The grain orientation diagram of the Zn-0.05Mg alloy prepared in Example 1;

[0029] Figure 5 The room temperature stress-strain curves of the Zn-0.5Mg alloys prepared for Example 2, Comparative Example 2, and Comparative Example 3. Detailed Implementation

[0030] This invention provides a method for preparing a biodegradable Zn-Mg binary alloy, comprising the following steps:

[0031] Metallic Zn and Zn-Mg master alloy are smelted to obtain an alloy melt; the alloy melt is semi-continuously cast to obtain a Zn-Mg binary alloy ingot; the Zn-Mg master alloy contains 30~50wt% Mg and the balance is Zn;

[0032] The Zn-Mg binary alloy ingot is sequentially forged, rolled, and reverse extruded to obtain the biodegradable Zn-Mg binary alloy; the forging ratio of the forging is not less than 16; the deformation per pass of the rolling is 8-15%, and the total deformation is 70-85%; the extrusion temperature of the reverse extrusion is 75-205℃, and the extrusion ratio is not less than 20; the reverse extrusion is performed by holding the material at the extrusion temperature for 0.5-2 hours before extrusion.

[0033] The composition of the biodegradable Zn-Mg binary alloy, by mass percentage, is: Mg 0.03~0.8%, total unavoidable impurities ≤20ppm, and balance Zn.

[0034] This invention involves smelting metallic Zn and a Zn-Mg master alloy to obtain an alloy melt; then, the alloy melt is semi-continuously cast to obtain a Zn-Mg binary alloy ingot. In this invention, the purity of the metallic Zn is preferably above 99.999%, and the Mg content in the Zn-Mg master alloy is 30-50 wt%, with the balance being Zn. In specific embodiments of this invention, the Zn-Mg master alloy used is Zn-30Mg or Zn-50Mg; the purity of the Zn-Mg master alloy is preferably above 99.999%; the smelting temperature is preferably 515-525℃, specifically 520℃; the smelting is preferably carried out in a graphite crucible, and the purity of the graphite crucible is preferably above 99.999%; in specific embodiments of this invention, metallic Zn is preferably first heated to 515-525℃, and after the metallic Zn melts, the Zn-Mg master alloy is added. After all the metals have melted, the mixture is stirred until homogeneous to obtain the alloy melt. This invention uses high-purity raw materials and high-purity graphite crucibles for smelting, which can effectively control the heavy metal content in Zn-Mg binary alloys, thereby ensuring their safety when implanted in the body.

[0035] In this invention, prior to the semi-continuous casting, it is preferable to further refine the alloy melt; the refining agent used in the refining is hexachloroethane; the mass of hexachloroethane is preferably 0.1~0.2% of the mass of the alloy melt, specifically 0.15%; the refining temperature is preferably 495~505℃, specifically 500℃; the refining time is preferably 20~60min, specifically 30min; the refining is preferably carried out under static conditions. This invention, through refining, can degas the alloy melt, remove oxide inclusions, and achieve purification of the alloy melt.

[0036] In this invention, the pouring temperature for the semi-continuous casting is preferably 495~505℃, specifically 500℃. In a specific embodiment of this invention, the alloy melt is preferably first cooled to 495~505℃, and hexachloroethane is injected into the alloy melt using a graphite bell jar for refining. After refining, semi-continuous casting is performed to obtain a Zn-Mg binary alloy ingot. This invention uses semi-continuous casting, which can achieve uniform distribution of Mg element along the axial and radial directions of the alloy ingot, and also achieve uniformity in the ingot microstructure (such as grain size). In addition, it can also realize the preparation of large-sized ingots of different specifications, improving material utilization and batch stability.

[0037] After obtaining the Zn-Mg binary alloy ingot, the present invention sequentially forges, rolls, and reverse-extrudes the Zn-Mg binary alloy ingot to obtain the biodegradable Zn-Mg binary alloy. In the present invention, the Zn-Mg binary alloy ingot is preferably turned before forging; the forging is preferably hot forging; the forging temperature of the hot forging is preferably 330~350℃, specifically 340℃; the forging ratio is not less than 16, preferably 16~30, specifically 25 or 30; the holding temperature before hot forging is preferably 0.5~2h, specifically 1h; after forging, a bar stock is obtained. In the present invention, after casting, the grain size of the Zn matrix in the coarse as-cast microstructure is refined, and the second phase Mg2Zn... 11 The dimensions have also been refined, and the distribution is more diffuse and uniform.

[0038] In this invention, the rolling process is preferably cold rolling; the deformation per rolling pass is 8-15%, specifically 8%, 12%, or 15%; the total deformation is 70-85%, specifically 70% or 75%. In this invention, after cold rolling, the Zn matrix grains are elongated into a fibrous structure, generating dislocations in the Zn-Mg binary alloy and forming deformation energy storage. This provides a driving force for recrystallization during the pre-extrusion holding process, thereby refining the grains. Since zinc alloys have a close-packed hexagonal structure, their room temperature deformation capacity is much smaller than that of face-centered cubic structures. The selection of the deformation per pass is beneficial for the rolling and forming of zinc alloys. The total deformation per pass can accumulate sufficient deformation energy storage, which is beneficial for recrystallization and grain refinement during the pre-extrusion holding process.

[0039] In this invention, the extrusion ratio of the reverse extrusion is not less than 20, preferably 20-40, specifically 30 or 36; the extrusion temperature of the reverse extrusion is 75-205℃, specifically 175±5℃, 180±5℃, or 200±5℃; the extrusion speed is preferably 0.5-5mm / min, specifically 0.5, 2, or 5mm / min; the billet is held at the extrusion temperature for 0.5-2 hours before reverse extrusion, specifically 1 hour. In a specific embodiment of this invention, the rolled bar is preferably first machined, then held at the extrusion temperature, and then reverse extruded. During the reverse extrusion process, there is no relative movement between the billet and the extrusion cylinder, eliminating the friction between them, reducing the extrusion pressure, and making the metal flow more uniform during forming, thereby ensuring that the final product has a more uniform microstructure along the axial and radial directions, and greatly improving the stability and consistency of mechanical properties. By controlling the extrusion temperature, extrusion speed, and extrusion ratio, this invention can further refine the microstructure through dynamic recrystallization, making the Zn matrix grains finer and more uniform, and the second phase Mg2Zn... 11 The uniform dispersion greatly improves the mechanical properties of zinc-magnesium binary alloys.

[0040] This invention also provides a biodegradable Zn-Mg binary alloy prepared by the preparation method described above. The composition of the biodegradable Zn-Mg binary alloy, by mass percentage, is: Mg 0.03~0.8%, specifically 0.05%, 0.5%, or 0.8%, with unavoidable total impurities ≤20ppm, and the balance being Zn. In this invention, the degradation rate of the Zn-Mg binary alloy can be controlled by adjusting the Mg content. In this invention, the composition of the biodegradable Zn-Mg binary alloy is uniformly distributed, and the standard deviation of the Mg content at different locations is below ±0.1wt%, and in the examples, it is below 0.0024wt%.

[0041] In this invention, the average grain size of the biodegradable Zn-Mg binary alloy is 0.5~1.5 μm; the microstructure of the biodegradable Zn-Mg binary alloy consists of equiaxed crystals, or includes an equiaxed crystal matrix and Mg2Zn dispersed in the equiaxed crystal matrix. 11 Phase; In a specific embodiment of the present invention, the Mg2Zn 11 The phase size is 1.1~1.5μm and the mass percentage is ≤11%.

[0042] In this invention, the content of Pb in the biodegradable Zn-Mg binary alloy heavy metals does not exceed 10 ppm, the content of As does not exceed 0.1 ppm, and the content of Cd does not exceed 5 ppm.

[0043] In this invention, the biodegradable Zn-Mg binary alloy has a tensile strength of 320-380 MPa, a yield strength of 250-330 MPa, and an elongation of not less than 20%, preferably 20-35%.

[0044] This invention also provides the application of the biodegradable Zn-Mg binary alloy described above in implantable devices; in this invention, the implantable device can specifically be a vascular stent, bone screw, bone plate, anastomotic screw, or binding suture. The biodegradable Zn-Mg binary alloy provided by this invention has excellent mechanical properties and controllable degradation performance, and its composition and structure are uniform. The content of heavy metals Pb, As, and Cd meets the standards for drinking water, and it has broad application prospects in the field of medical implantable devices.

[0045] 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.

[0046] In the embodiments of the present invention, the purity of the metallic Zn is 99.999%, the purity of the Zn-Mg master alloy is 99.999%, the purity of the graphite crucible is 99.999%, and the purity of the graphite bell jar is 99.999%.

[0047] 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.

[0048] 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.

[0049] 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).

[0050] 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.

[0051] Example 1

[0052] The composition of the biodegradable Zn-Mg binary alloy prepared in this embodiment, by mass percentage, is as follows: Mg 0.05%, unavoidable impurities ≤20ppm, and the balance is Zn.

[0053] The preparation method of biodegradable Zn-Mg binary alloy is as follows:

[0054] (1) Using metallic Zn and Zn-30Mg master alloy as raw materials, metallic Zn is placed in a graphite crucible and heated to 520±5℃ to melt metallic Zn. Then Zn-30Mg master alloy is added. After all the metals are melted, the mixture is stirred until it is homogeneous to obtain the alloy melt.

[0055] (2) Cool the alloy melt to 500±5℃, press 0.15% of the melt mass of hexachloroethane into the melt using a graphite bell jar, let it stand for 30 minutes, and then use semi-continuous casting to form an ingot.

[0056] (3) After the ingot is machined, it is kept at 340±10℃ for 1 hour, and then forged with a forging ratio of 25 to obtain bar stock;

[0057] (4) The forged bar is rolled at room temperature, with a deformation per pass of 15% and a total deformation of 75%;

[0058] (5) After the rolled bar is machined, it is reverse extruded at an extrusion temperature of 180±5℃ and held for 1h. The extrusion ratio is 30 and the extrusion speed is 0.5mm / min to obtain a biodegradable Zn-Mg binary alloy, which is denoted as Zn-0.05Mg alloy.

[0059] The Mg content at different locations (the upper edge and core, the middle edge and core, and the bottom edge and core) of the ingot obtained from test step (2) is shown in Table 1. According to the data in Table 1, the Mg content at different locations is basically maintained at 0.05±0.003wt%, with a standard deviation of only 0.0016wt%, which is much lower than ±0.1wt%. The alloy composition is uniformly distributed, and the Mg yield is effectively controlled.

[0060] The contents of heavy metal impurities Pb, As, and Cd at different locations (the upper edge and center, the middle edge and center, and the bottom edge and center) of the ingot obtained in step (2) were tested, and the test results are shown in Table 2. The data in Table 2 show that the contents of Pb, As, and Cd are 8.5, 0.014, and 3.0 ppm, respectively, which fully meet the drinking water standards.

[0061] The room temperature stress-strain curve of Zn-0.05Mg alloy is shown below. Figure 1 As shown, its yield strength is 255MPa, tensile strength is 356MPa, and elongation is 29.4%, which fully meets the requirements of biodegradable cardiovascular stents, bone screws and plates, anastomotic screws, binding sutures and other implantable devices.

[0062] The microstructure of Zn-0.05Mg alloy is as follows: Figure 2 As shown, it is mainly composed of fine equiaxed crystals.

[0063] The grain size distribution of Zn-0.05Mg alloy is as follows: Figure 3 As shown, the average grain size is 1.2 μm, mainly distributed between 0.4 and 1.8 μm, and the microstructure is uniform.

[0064] The grain orientation of Zn-0.05Mg alloy is as follows: Figure 4 As shown, a non-basal surface texture is formed at a certain angle to the basal surface, which significantly improves the plasticity of the alloy.

[0065] The degradation performance of Zn-0.05Mg alloy was tested, and the results showed that the degradation rate of Zn-0.05Mg alloy in simulated body fluid in vitro was 0.02685 mm / year.

[0066] Table 1 Results of Mg content uniformity test

[0067]

[0068] Table 2 Results of heavy metal impurity content test

[0069]

[0070] Example 2

[0071] The composition of the biodegradable Zn-Mg binary alloy prepared in this embodiment, by mass percentage, is as follows: Mg 0.5%, unavoidable impurities ≤20ppm, and the balance is Zn.

[0072] The preparation method of biodegradable Zn-Mg binary alloy is as follows:

[0073] (1) Using metallic Zn and Zn-50Mg master alloy as raw materials, metallic Zn is placed in a graphite crucible and heated to 520±5℃ to melt metallic Zn. Then Zn-50Mg master alloy is added. After all the metals are melted, the mixture is stirred until it is homogeneous to obtain the alloy melt.

[0074] (2) Cool the alloy melt to 500±5℃, press 0.15% of the melt mass of hexachloroethane into the melt using a graphite bell jar, let it stand for 30 minutes, and then use semi-continuous casting to form an ingot.

[0075] (3) After the ingot is machined, it is kept at 340±10℃ for 1 hour, and then forged with a forging ratio of 30 to obtain bar stock;

[0076] (4) The forged bar is rolled at room temperature, with a deformation per pass of 12% and a total deformation of 75%;

[0077] (5) After the rolled bar is machined, it is reverse extruded at an extrusion temperature of 175±5℃ and held for 1h. The extrusion ratio is 36 and the extrusion speed is 2mm / min to obtain a biodegradable Zn-Mg binary alloy, which is denoted as Zn-0.5Mg alloy.

[0078] The Mg content at different locations (the upper edge and core, the middle edge and core, and the bottom edge and core) of the ingot obtained by test step (2) showed that the Mg content at different locations was basically maintained at 0.5±0.012wt%, with a standard deviation of only 0.002wt%, which is much lower than ±0.1wt%. The alloy composition was evenly distributed, and the Mg yield was effectively controlled.

[0079] The contents of heavy metal impurities Pb, As and Cd at different locations (the upper edge and core, the middle edge and core, and the bottom edge and core) of the ingot obtained in step (2) were tested. The results showed that the contents of Pb, As and Cd were 8.2, 0.018 and 4.2 ppm, respectively, which fully meet the drinking water standards.

[0080] Mechanical property tests were conducted on the Zn-0.5Mg alloy. The results showed that the yield strength of the Zn-0.5Mg alloy was 310 MPa, the tensile strength was 338 MPa, and the elongation was 33%, which fully meets the requirements of biodegradable cardiovascular stents, bone screws and plates, anastomotic screws, binding sutures and other implantable devices.

[0081] Microstructure observation of the Zn-0.5Mg alloy revealed that its microstructure mainly consists of fine equiaxed crystal matrix and dispersed fine Mg2Zn particles. 11 Phase (Mg2Zn) 11 The phase size is about 1.1 μm, and the mass percentage is about 6.2%. The average grain size of the Zn-0.5Mg alloy is 0.88 μm, mainly distributed between 0.25 and 1.56 μm. The microstructure is uniform, and the grain orientation forms a non-basal texture at a certain angle to the basal plane, which significantly improves the plasticity of the alloy.

[0082] The degradation performance of Zn-0.5Mg alloy was tested, and the results showed that the degradation rate of Zn-0.5Mg alloy in simulated body fluid in vitro was 0.03378 mm / year.

[0083] Example 3

[0084] The composition of the biodegradable Zn-Mg binary alloy prepared in this embodiment, by mass percentage, is as follows: Mg 0.8%, unavoidable impurities ≤20ppm, and the balance is Zn.

[0085] The preparation method of biodegradable Zn-Mg binary alloy is as follows:

[0086] (1) Using metallic Zn and Zn-50Mg master alloy as raw materials, metallic Zn is placed in a graphite crucible and heated to 520±5℃ to melt metallic Zn. Then Zn-50Mg master alloy is added. After all the metals are melted, the mixture is stirred until it is homogeneous to obtain the alloy melt.

[0087] (2) Cool the alloy melt to 500±5℃, press 0.15% of the melt mass of hexachloroethane into the melt using a graphite bell jar, let it stand for 30 minutes, and then use semi-continuous casting to form an ingot.

[0088] (3) After the ingot is machined, it is kept at 340±10℃ for 1 hour, and then forged with a forging ratio of 25 to obtain bar stock;

[0089] (4) The forged bar is rolled at room temperature, with a deformation per pass of 8% and a total deformation of 70%;

[0090] (5) After the rolled bar is machined, it is subjected to reverse extrusion at an extrusion temperature of 200±5℃ and held for 1h. The extrusion ratio is 36 and the extrusion speed is 5mm / min to obtain a biodegradable Zn-Mg binary alloy, which is denoted as Zn-0.8Mg alloy.

[0091] The Mg content at different locations (the upper edge and core, the middle edge and core, and the bottom edge and core) of the ingot obtained by test step (2) showed that the Mg content at different locations was basically maintained at 0.8±0.021wt%, with a standard deviation of only 0.0024wt%, which is much lower than ±0.1wt%. The alloy composition was evenly distributed, and the Mg yield was effectively controlled.

[0092] The contents of heavy metal impurities Pb, As and Cd at different locations (the upper edge and core, the middle edge and core, and the bottom edge and core) of the ingot obtained in step (2) were tested. The results showed that the contents of Pb, As and Cd were 8.9, 0.024 and 3.2 ppm, respectively, which fully meet the drinking water standards.

[0093] Mechanical property tests were conducted on the Zn-0.8Mg alloy. The results showed that the Zn-0.8Mg alloy had a yield strength of 326 MPa, a tensile strength of 378 MPa, and an elongation of 26%, which fully met the requirements for biodegradable cardiovascular stents, bone screws and plates, anastomotic screws, sutures and other implantable devices.

[0094] Microstructure observation of the Zn-0.8Mg alloy revealed that its microstructure mainly consists of fine equiaxed matrix and dispersed fine Mg2Zn particles. 11 Phase (Mg2Zn) 11 The phase size is approximately 1.5 μm, and the mass percentage is around 10.9%. The average grain size of the Zn-0.8Mg alloy is 0.76 μm, mainly distributed between 0.20 and 1.37 μm. The microstructure is uniform, and the grain orientation forms a non-basal texture at a certain angle to the basal plane, which significantly improves its plasticity.

[0095] The degradation performance of Zn-0.8Mg alloy was tested, and the results showed that the degradation rate of Zn-0.8Mg alloy in simulated body fluid in vitro was 0.04875 mm / year.

[0096] Compare with Example 1

[0097] The Zn-Mg binary alloy ingots with different Mg contents were prepared by adding pure Mg to zinc alloys. The specific steps are as follows:

[0098] (1) Using metallic Zn and Mg as raw materials, metallic Zn is placed in a graphite crucible and heated to 520±5℃ to melt metallic Zn. Then pure Mg is added. After all the metals have melted, the mixture is stirred until homogeneous to obtain an alloy melt.

[0099] (2) Cool the alloy melt to 500±5℃, press 0.15% of the melt mass of hexachloroethane into the melt using a graphite bell jar, let it stand for 30 minutes, and then use semi-continuous casting to form an ingot.

[0100] The Mg content at different locations on the ingot was tested, and the results are shown in Table 3.

[0101] Table 3. Test results of Mg content at different locations in Zn-Mg binary alloys

[0102]

[0103] As can be seen from Table 3, compared with Examples 1 to 3, due to the volatilization of pure Mg and the density difference with Zn, the Mg content distribution at different locations of the ingot in Comparative Example 1 is extremely uneven.

[0104] Compare with Example 2

[0105] Compared to Example 2, only the forging ratio during the forging of the Zn-0.5Mg alloy was reduced to 12. The stress-strain curve of the obtained Zn-0.5Mg alloy is as follows: Figure 5 As shown. According to Figure 5 It can be seen that the mechanical properties of the resulting alloy decrease significantly after the forging ratio is reduced, and the Zn-0.5Mg alloy prepared in Example 2 has better mechanical properties.

[0106] Compare with Example 3

[0107] Compared to Example 2, only the deformation per pass during the rolling of the Zn-0.5Mg alloy was reduced to 6%, and the total deformation was reduced to 65%. The stress-strain curve of the obtained Zn-0.5Mg alloy is shown below. Figure 5 As shown. According to Figure 5 It can be seen that after changing the deformation amount per rolling pass and the total deformation amount, the mechanical properties of the alloy decreased significantly. The Zn-0.5Mg alloy prepared in Example 2 has better mechanical properties.

[0108] In summary, this invention uses metallic Zn and Zn-Mg master alloys as raw materials and employs a smelting-semi-continuous casting-forging-rolling-reverse extrusion method to obtain a biodegradable Zn-Mg binary alloy with an impurity content of less than 20 ppm and uniform composition and structure. Furthermore, the content of heavy metals Pb, As, and Cd meets drinking water standards. Simultaneously, by controlling the forming process and optimizing the microstructure of the zinc alloy, this invention obtains a Zn-Mg binary alloy with excellent mechanical properties, meeting the service requirements of biodegradable cardiovascular stents, bone screws and plates, anastomotic staples, sutures, and other medical implantable devices.

[0109] 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 a biodegradable Zn-Mg binary alloy, characterized in that, Includes the following steps: Metallic Zn and Zn-Mg master alloy are smelted to obtain an alloy melt; the alloy melt is semi-continuously cast to obtain a Zn-Mg binary alloy ingot; the Zn-Mg master alloy contains 30~50wt% Mg and the balance is Zn; The Zn-Mg binary alloy ingot is sequentially forged, rolled, and reverse extruded to obtain the biodegradable Zn-Mg binary alloy; the forging ratio of the forging is not less than 16; the deformation per pass of the rolling is 8-15%, and the total deformation is 70-85%; the extrusion temperature of the reverse extrusion is 75-205℃, and the extrusion ratio is not less than 20; the reverse extrusion is performed by holding the material at the extrusion temperature for 0.5-2 hours; the forging is hot forging; and the rolling is cold rolling. The composition of the biodegradable Zn-Mg binary alloy, by mass percentage, is: Mg 0.03~0.8%, total unavoidable impurities ≤20ppm, and balance Zn.

2. The preparation method according to claim 1, characterized in that, The purity of the metallic Zn is above 99.999%, and the purity of the Zn-Mg master alloy is above 99.999%.

3. The preparation method according to claim 1, characterized in that, The melting temperature is 515~525℃; the melting is carried out in a graphite crucible with a purity of 99.999% or higher; the pouring temperature of the semi-continuous casting is 495~505℃.

4. The preparation method according to claim 1, characterized in that, Before the semi-continuous casting, the alloy melt is further refined; the refining agent used in the refining is hexachloroethane.

5. The preparation method according to claim 1, characterized in that, The hot forging temperature is 330~350℃, and the hot forging is carried out at the forging temperature for 0.5~2h before hot forging.

6. The preparation method according to claim 1, characterized in that, The extrusion speed of the reverse extrusion is 0.5~5 mm / min.

7. The biodegradable Zn-Mg binary alloy prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The average grain size of the biodegradable Zn-Mg binary alloy is 0.5~1.5μm.

8. The biodegradable Zn-Mg binary alloy according to claim 7, characterized in that, The biodegradable Zn-Mg binary alloy contains Pb at no more than 10 ppm, As at no more than 0.1 ppm, and Cd at no more than 5 ppm.

9. The biodegradable Zn-Mg binary alloy according to claim 7, characterized in that, The biodegradable Zn-Mg binary alloy has a tensile strength of 320~380MPa, a yield strength of 250~330MPa, and an elongation of not less than 20%.

10. The application of the biodegradable Zn-Mg binary alloy according to any one of claims 7 to 9 in the preparation of medical implantable devices.

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