Anti-aging high-toughness degradable zinc alloy rod, preparation method and application

Abstract

The application belongs to the technical field of zinc alloy, and particularly relates to an anti-aging high-strength and high-toughness degradable zinc alloy bar, a preparation method and application, which comprises the following components by weight percentage: Cu 1.5-2.0%, Mg 0.01-0.05%, and the balance of Zn; the preparation method of the anti-aging high-strength and high-toughness degradable zinc alloy bar is that zinc alloy ingots are sequentially subjected to homogenization treatment and multi-pass rotary forging treatment to obtain the anti-aging high-strength and high-toughness degradable zinc alloy bar, and the number of passes is more than 7; the application has good strength, toughness and anti-aging capacity.

Description

Technical Field

[0001] This invention belongs to the field of zinc alloy technology, specifically relating to an anti-aging, high-strength, tough, and biodegradable zinc alloy rod, its preparation method, and its application. Background Technology

[0002] Biodegradable metallic materials offer significant advantages in orthopedics, cardiovascular diseases, and other fields because they do not require secondary surgery for removal. Zinc alloys, with their excellent biocompatibility and controllable degradation rate, are considered the third generation of biodegradable metals after magnesium and iron. However, the primary problem facing most zinc alloys is their insufficient resistance to aging; that is, their plasticity decreases significantly after being left at room temperature for a period of time. Furthermore, due to the low melting point of zinc and zinc alloys, significant strain softening or uneven deformation may occur during plastic deformation or service, potentially leading to localized excessive loading or even structural damage during implantation, which could result in medical accidents.

[0003] Currently, mechanical properties are mainly improved through alloying and subsequent plastic deformation. Developed zinc alloys mainly include Zn-Mg, Zn-Li, Zn-Mn, and Zn-Cu systems, as well as various ternary and multi-component alloy systems formed based on these alloys. Patent application number 202110458281.5 discloses a high-strength, high-toughness, biodegradable zinc alloy with a high work hardening rate, comprising a Zn matrix, and refined and dispersed Zn+Mg2Zn in the Zn matrix. 11 The structure is a eutectic structure, with micron-sized YZn dispersed in the Zn matrix. 12 Zn + Mg2Zn 11 Submicron-sized YZn is dispersed in the eutectic structure. 12 and nanoscale YZn 12 Submicron YZn 12 and nanoscale YZn 12 The area ratio is no greater than 85:15; nanoscale YZn 12 The phase particles contain twins; the zinc alloy composition is: Mg: 0.8-1.7%, Y: 0.1-0.5%, with the remainder being Zn, and the mass ratio of Y to Mg in the alloy is not higher than 0.3; the micron-sized YZn 12 The particle size is >2μm; the submicron-sized YZn 12 The particle size is 0.2–1 μm; the nano-sized YZn 12 The particle size is <200 nm. The structure of this microstructure is relatively complex, and the controllable preparation of such a multi-level distribution is quite difficult. In addition, the aging phenomenon of this Zn-Mg alloy may be very severe.

[0004] Considering the unique aging phenomenon of zinc alloy, generally, the element with higher solid solubility should be considered as the first choice in alloy design. The limit solid solubility of common alloying elements in zinc alloy is as follows: Ag (8%) > Cu (2.75%) > Mn (0.8%) > Mg (0.1%), wt%. Further, considering the biocompatibility and cost of alloying elements, the Cu element with excellent antibacterial property is preferred as the first choice of alloying element. However, the Zn-Cu alloy has the problem of mismatching between strength and toughness, and it is difficult to obtain the combination of high strength and high toughness at the same time. SUMMARY

[0005] The technical problem to be solved by the present application is to provide an anti-aging high-strength and high-toughness degradable zinc alloy rod, a preparation method and an application, which have good strength, toughness and anti-aging ability.

[0006] The anti-aging high-strength and high-toughness degradable zinc alloy rod provided by the embodiment of the present application comprises the following components by weight percentage: Cu 1.5-2.0%, Mg 0.01-0.05%, and the balance being Zn. The preparation method of the anti-aging high-strength and high-toughness degradable zinc alloy rod comprises the following steps: sequentially performing homogenization treatment and multi-pass rotary forging treatment on a zinc alloy ingot to obtain the anti-aging high-strength and high-toughness degradable zinc alloy rod, wherein the number of passes is more than 7.

[0007] The present application introduces high-density twins at the initial stage of rotary forging, and with the intensification of twin dislocation interaction, non-basal slip in the twin is activated. Under the synergistic effect of twin-induced dynamic recrystallization and continuous-induced dynamic recrystallization, a heterogeneous structure is successfully prepared, the coordination between the strength and toughness of the alloy is realized, and the alloy has more sustained strain hardening capacity at large strain. The microstructure of the zinc alloy of the present application is composed of fine-grained regions formed by dynamic recrystallization and heterogeneous structures formed by alternating arrangement of residual deformation coarse-grained regions.

[0008] Preferably, Ca and / or Sr are further included, and the weight percentage of Ca and / or Sr is 0.1-0.5%.

[0009] Preferably, the weight percentage of Ca and / or Sr is 0.1-0.3%.

[0010] Preferably, the anti-aging high-strength and high-toughness degradable zinc alloy rod comprises the following components by weight percentage: Cu 1.5-2%, Mg 0.01-0.03%, Ca 0.05-0.15%, Sr 0.05-0.15%, and the balance being Zn.

[0011] Preferably, the weight ratio of Ca to Sr is 1:1.

[0012] The application provides a preparation method of the anti-aging high-strength and high-toughness degradable zinc alloy rod.

[0013] Preferably, the single-pass deformation of the rotary swaging treatment is greater than 21%, and the total deformation is greater than 379%; the temperature of the homogenization treatment is 280-300 DEG C, and the holding time is 6-12 h.

[0014] Preferably, the temperature of the rotary swaging treatment is room temperature, the passes are 7-13, and intermediate annealing treatment is not needed for each pass. The rotary swaging frequency of the rotary swaging treatment is 20-35 times / s.

[0015] Preferably, the preparation method of the zinc alloy ingot is as follows: the components are smelted, heated to 520-550 DEG C under inert gas protection, kept for 3-5 min, then cooled to 480-500 DEG C, heated to 550-570 DEG C again, and then cast. The mold used for casting is preferably a graphite mold, and the mold temperature is 200-230 DEG C. The equipment used for smelting is a graphite crucible with a melting point higher than 3000 DEG C, and the vacuum degree of smelting is not greater than 1*10 -3 Pa. Smelting is carried out by adopting electromagnetic stirring, and the frequency is 500-2000 Hz.

[0016] The application provides an application of the anti-aging high-strength and high-toughness degradable zinc alloy rod.

[0017] The zinc alloy of the application can form CuZn4 phase; the trace magnesium element is in the form of solute atoms; when the zinc alloy contains Ca and / or Sr, the zinc alloy has Zn-Cu-(Mg / Ca / Sr) alloy organization, in addition to containing η-Zn matrix and block-shaped ε-CuZn4 phase, at least one of Mg2Zn 11 phase, CaZn 13 phase and SrZn 13 phase is contained. After rotary swaging treatment, the microstructure of the zinc alloy mainly changes as follows: 1) In the initial stage of rotary swaging deformation, the Zn-Cu-(Mg / Ca / Sr) alloy with excellent thermal stability forms high-density twins to adapt to deformation and achieve the effect of dividing original parent crystals and refining grains.

[0018] 2) With the increase of the amount of rotary swaging deformation, the interaction between twins and dislocations intensifies, which is beneficial to the generation of non-basal slip. Due to the twin-induced dynamic recrystallization and its promotion effect on continuous induced dynamic recrystallization, subgrains can be formed in the twin and dislocation array in the deformation band. At the same time, subgrains can also be formed at the intersection of twins, including small-angle grain boundaries of twin boundaries.

[0019] 3) When the rotary swaging deformation amount further increases, the twin bands formed by twin-induced dynamic recrystallization, and the grain size heterostructure formed under the joint action of twin-induced dynamic and continuous induced dynamic recrystallization. The crystal orientation in the twin band has a specific orientation relationship with the matrix (such as The orientation difference between the twin and the matrix is 86° >), which can effectively refine the grain and weaken the texture.

[0020] 4) When the rotary swaging deformation amount continues to increase, the residual coarse grains will preferentially activate twins and non-basal slip under high stress concentration, and finally form a full fine grain structure.

[0021] Therefore, under the action of high strain rate and radial high-frequency short-stroke forging in the rotary swaging process, the zinc alloy gradually forms a twin heterostructure, a bimodal grain size heterostructure, a gradient grain size heterostructure, and finally a full fine grain structure. This grain size heterostructure has excellent strength and uniform elongation. Due to the difference in strain compatibility between coarse and fine grains, it has more sustained work hardening at large deformation. In addition, there will be a small galvanic corrosion between coarse and fine grains, which will accelerate the degradation of the alloy. Further by adjusting the content of Cu and alkaline earth metal elements in the alloy and the relative content of coarse and fine grains, the degradation performance of the alloy can be controlled within a certain range.

[0022] Based on the heterostructure enhancement effect brought by the specific coarse / fine grain structure, the alloy has high strength and toughness, anti-aging ability and controllable degradation, the tensile strength is 350-450 MPa, the elongation at break is 20-70%, the change of mechanical properties within 1 year is ≤5% at room temperature, and it also has excellent antibacterial performance and bone formation promoting ability.

[0023] The present application introduces high-density twins and cooperatively controls the grain size heterostructure through twin-induced dynamic recrystallization / continuous induced dynamic recrystallization, and controls the work hardening behavior through hetero-induced strengthening, which has more sustained work hardening ability in a large strain range.

[0024] The Cu element with excellent antibacterial property in the application is beneficial to improve the mechanical property and regulate the degradation rate. Further, the mechanical property is improved by micro-alloying including the third component of alkaline earth metal (Mg, Ca, Sr), and the repair and regeneration of bone tissue are promoted. While having good biocompatibility, the zinc alloy rods and wires can be prepared by room temperature high strain rate spinning instead of traditional hot processing, and intermediate annealing is not needed, energy saving is more than 30%, production efficiency is improved by more than 2 times, and it is especially suitable for efficient preparation of degradable cardiovascular stents and bone implant devices and other materials. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a metallographic photo of the as-cast alloy of example 1, wherein the average grain size of the matrix is about 216 μm, and the white second phase CuZn4 phase exists on the matrix.

[0026] Figure 2 It is the high-density twin and refined microstructure of the alloy after 2-pass room temperature high strain rate spinning of example 1, wherein Figure 2 (a) is the metallographic structure, Figure 2 (b) is the SEM structure.

[0027] Figure 3 It is the bimodal grain heterostructure formed after 7-pass room temperature high strain rate spinning of example 1, wherein Figure 3 (a) is the metallographic structure, Figure 3 (b) is the SEM structure.

[0028] Figure 4 It is the almost full fine-grained structure formed after 13-pass room temperature high strain rate spinning of example 2, wherein the fine-grained area fraction is 96%.

[0029] Figure 5 It is the activated non-basal plane <c+a> dislocation slip in the coarse-grained region of the alloy of example 1, wherein Figure 5 (a) is the dislocation morphology when g=0002, Figure 5 (b) is the dislocation morphology when g=10 0, and the red arrow indicates the <c+a> dislocation, and the white arrow indicates Dislocations, indicated by yellow arrows <c>Dislocations.

[0030] < / c> Figure 6 It is the mechanical property of the alloy after 0, 2, 7, and 13-pass room temperature high strain rate spinning of the as-cast alloy of example 1: wherein Figure 6 (a) is the room temperature tensile stress-strain curve, Figure 6 (b) is the work hardening rate curve of the deformed alloy. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be described in detail below in combination with some specific embodiments. The specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0032] Embodiment 1 A medical degradable Zn-Cu-Mg alloy, with the element mass fraction of Cu: 2%, Mg: 0.025%, and the balance being Zn.

[0033] The preparation method is as follows: (1) batching: batching and weighing according to the above components, the raw materials including pure zinc ingot, Zn-2Cu intermediate alloy and Zn-2Mg intermediate alloy; (2) melting: melting the pure zinc ingot, zinc copper intermediate alloy and zinc magnesium intermediate alloy under the protection of high-purity argon to obtain a zinc alloy ingot; Specifically, a graphite crucible with a melting point higher than 3000 ℃ is used, the vacuum degree of melting is ≤1×10 -3 Pa; the melting is carried out in two steps, first heating to 550 ℃, holding for 4 min, then cooling to 500 ℃, then quickly heating to 570 ℃ again, while electromagnetic stirring is carried out, the frequency of electromagnetic stirring is 1000 Hz, after the temperature of the melt reaches 570 ℃, the melt is quickly poured and cast into a graphite mold; the mold temperature is controlled at 200 ℃, and a zinc alloy ingot is obtained.

[0034] (3) homogenization treatment: homogenization treatment is carried out on the above zinc alloy ingot, the homogenization temperature is 300 ℃, and the holding time is 12 h.

[0035] (4) room temperature high strain rate rotary swaging processing: a rod with a diameter of 20 mm is turned from the above homogenized zinc alloy ingot, then the zinc alloy rod is rotary swaged for 7 passes, and finally a zinc alloy rod with a diameter of 8 mm is obtained; the rotary swaging frequency is 25 times / s, the single pass deformation of rotary swaging processing is 21~30%, and the total deformation is 379%~400%.

[0036] The zinc alloy has a heterogeneous structure of grain size, and the area ratio of coarse grain zone (diameter ≥5 μm) and fine grain zone (diameter <5 μm) is 42:58.

[0037] The total content of alloying elements (i.e. the total content of magnesium and copper) of the zinc alloy is within 2.1%, which fully plays the role of solid solution strengthening of copper elements in the zinc matrix, and the addition of trace magnesium elements further significantly improves the mechanical properties. The increase of uniform elongation is due to the deformation hardening caused by the mismatch of the deformation compatibility of coarse and fine grains in the heterogeneous structure, so that it has a more sustained strain hardening capacity during the tensile load process. Therefore, under the heterogeneous induced strengthening effect of the bimodal structure in the present application, the zinc alloy obtains the combination of high strength and toughness and high work hardening rate, which can effectively avoid the fracture phenomenon of the zinc alloy implant at local positions due to excessive deformation. In addition, due to the solid solution of a certain amount of high-melting-point Cu elements and trace Mg elements in the low-melting-point zinc as the matrix material, the thermal stability of the Zn matrix can be greatly improved, thereby greatly improving the anti-aging performance of the Zn alloy.

[0038] The application of the high-strength and high-toughness degradable zinc alloy with the heterogeneous structure of alternating distribution of coarse and fine grains in biomedical degradable metal materials includes, but is not limited to, cardiovascular stents, bone screws and the like.

[0039] Example 2 Compared with Example 1, the difference is that: 1. In the room temperature high strain rate rotary forging process of step (4), the pass is 13 times, and finally a zinc alloy rod with a diameter of 3 mm is obtained.

[0040] The other aspects are the same as those in Example 1.

[0041] The zinc alloy has a heterogeneous structure of grain size, and the area ratio of the coarse grain region (diameter ≥ 5 μm) to the fine grain region (diameter < 5 μm) is 4:96.

[0042] The mass of elements in the Zn-Cu-Mg alloy in Example 2 and the rotary forging pass in the preparation method are adjusted. The other aspects are consistent with those in Example 2, and the mechanical properties of each product are measured. The results are shown in Table 1.

[0043] Table 1 Comparison of mechanical properties of zinc alloys

[0044] The unit of tensile strength (UTS) is MPa, and the unit of fracture elongation (TE) is %.

[0045] The step (4) of Comparative Example 6 is: A 20 mm diameter bar was machined from the homogenized zinc alloy ingot. This bar was then subjected to nine passes of room temperature rotary forging, followed by annealing in a vacuum annealing furnace for 10 minutes at 200°C. After annealing, the bar was further rotary forged up to 13 passes, ultimately yielding a 3 mm diameter zinc alloy bar. The rotary forging frequency was 25 times per second. Other procedures were the same as in Example 2.

[0046] As can be seen from Table 1, a low copper content will significantly reduce tensile strength.

[0047] With a high copper content, the addition of trace amounts of magnesium further enhances the ultimate tensile strength.

[0048] While the addition of Ca or Sr in this invention reduces tensile strength to some extent, the reduction is limited, remaining above 350 MPa, with a strength decrease of less than 22%. Simultaneously, Ca or Sr significantly improves the elongation at break and plasticity of zinc alloys, increasing the elongation at break to over 42%. The inventors further discovered that the simultaneous addition of Ca and Sr results in an even smaller decrease in tensile strength and a greater increase in elongation at break. A Ca:Sr ratio of 1:1 further minimizes the decrease in tensile strength while effectively improving elongation at break.

[0049] The amount of Ca and / or Sr added in this invention is required to be between 0.1% and 0.5% in total. Exceeding this amount will result in a significant decrease in strength, while below this amount will result in no improvement in elongation at break, or a significant decrease in the improvement rate.

[0050] The inventors discovered that adding other elements, such as Fe, would decrease both strength and elongation at break.

[0051] In this invention, annealing cannot be performed during rotary forging, as annealing will lead to static recrystallization, which will severely reduce the dislocation density and significantly reduce the strength.

[0052] The following description is provided in conjunction with the embodiments and accompanying drawings: The zinc alloy blocks and subsequent profiles such as bars, tubes, and wires obtained by this invention have a gradient grain size heterogeneous structure.

[0053] like Figure 1 The image shown is a metallographic photograph of the Zn-2Cu-0.025Mg as-cast alloy in Example 1 of this invention. The average grain size of the zinc matrix is ​​about 216 μm, and a white second phase CuZn4 phase exists on the matrix.

[0054] like Figure 2The image shows the metallographic and SEM structures of the zinc alloy after two passes of room temperature high strain rate rotary forging in Example 1, revealing high-density twins and refined microstructure. High-density twins were initially formed in the alloy before rotary forging. The activation of different twin morphologies, such as parallel and intersecting twins, facilitates grain segmentation and refinement of the original coarse grains.

[0055] With increasing forging passes, the interaction between twins and dislocations intensifies, facilitating the activation of non-basal plane slip. Due to twin-induced dynamic recrystallization (TDRX) and its promoting effect on continuous-induced dynamic recrystallization (CDRX), subgrains can form within twins and dislocation arrays in deformation bands. Furthermore, subgrains, including twin boundaries and small-angle grain boundaries, can also form at twin interfaces. When the forging passes increase to 7, the alloy microstructure is as follows... Figure 3 The image shows a typical bimodal grain heterostructure. Figure 3 The presence of numerous twinning zones confirms that it originates from initial high-density twinning nucleation, i.e., the formation of numerous dynamically recrystallized grains under the action of TDRX, which have an 86° angle with the matrix. The orientation relationship is used to effectively weaken the texture.

[0056] Figure 4 The microstructure formed in Example 2 after 13 passes of high strain rate rotary forging at room temperature is almost entirely fine-grained, with a fine grain area fraction of 96%. The strength of the Zn-Cu-Mg alloy can be further improved by increasing the number of rotary forging passes.

[0057] Figure 5 Analysis of the dislocation types activated in the coarse-grained region in Embodiment 1 of the present invention confirms that the coarse-grained region activates non-basal planes.<c+a> Dislocation slip.

[0058] Figure 6 The mechanical properties of the Zn-2Cu-0.025Mg alloys in Examples 1-2 of this invention after 2, 7, and 13 passes of room temperature high strain rate rotary forging are shown in Figure (a) as the room temperature tensile stress-strain curve and (b) as the work hardening rate curve of the deformed alloy. With the increase of the number of passes in the room temperature high strain rate rotary forging, both the strength and elongation at break increase, while the uniform elongation is the highest at 7 passes. Alloying Cu and Mg elements onto pure Zn can significantly improve its mechanical properties and control the degradation rate.

[0059] As can be seen, the addition of Cu, an element with high solid solubility and excellent antibacterial properties, in this invention improves mechanical properties and regulates degradation rate. Further, microalloying with alkaline earth metals (Mg, Ca, Sr) as a tertiary element enhances mechanical properties, promotes bone tissue repair and regeneration, and exhibits good biocompatibility. Various zinc alloy bars and wires are prepared by replacing traditional hot working with room-temperature high-strain-rate rotary forging. High-density twinning is introduced to regulate the heterogeneous structure of grain size, and heterogeneous induction strengthening regulates work hardening behavior, resulting in more sustained work hardening capacity over a wide strain range. While exhibiting good biocompatibility, the preparation process eliminates the need for intermediate annealing, saving over 30% energy and increasing production efficiency by more than 2 times.

[0060] The specific embodiments and comparative examples of the present invention have been described above to facilitate a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. Those skilled in the art should understand that the present invention is not limited to the specific embodiments described above, and various modifications or variations can be made within the scope of the claims, all of which fall within the protection scope of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the protection scope of the appended claims. Therefore, the scope of protection of this invention patent should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. An anti-aging, high-strength, tough, biodegradable zinc alloy rod, characterized in that, It includes the following components by weight percentage: Cu 1.5–2.0%, Mg 0.01–0.05%, and the balance being Zn; The method for preparing the anti-aging, high-strength, tough, and biodegradable zinc alloy bar is as follows: the zinc alloy ingot is subjected to homogenization treatment and multiple passes of rotary forging treatment in sequence to obtain the anti-aging, high-strength, tough, and biodegradable zinc alloy bar, with the number of passes being more than 7.

2. The anti-aging, high-strength, tough, and biodegradable zinc alloy rod as described in claim 1, characterized in that, It also includes Ca and / or Sr, with a weight percentage of Ca and / or Sr of 0.1 to 0.5%.

3. The anti-aging, high-strength, tough, and biodegradable zinc alloy rod as described in claim 2, characterized in that, The weight percentage of Ca and / or Sr is 0.1% to 0.3%.

4. The anti-aging, high-strength, tough, and biodegradable zinc alloy rod as described in claim 2, characterized in that, It includes the following components by weight percentage: Cu 1.5–2%, Mg 0.01–0.03%, Ca 0.05–0.15%, Sr 0.05–0.15%, with the balance being Zn.

5. The anti-aging, high-strength, tough, and biodegradable zinc alloy rod as described in claim 2, characterized in that, The weight ratio of Ca to Sr is 1:

1.

6. A method for preparing an anti-aging, high-strength, tough, biodegradable zinc alloy rod as described in any one of claims 1-5, characterized in that, The zinc alloy ingot is subjected to homogenization treatment and multiple rotary forging processes to obtain anti-aging, high-strength, tough, and biodegradable zinc alloy bars, with a number of processes of more than 7.

7. The preparation method according to claim 6, characterized in that, The single-pass deformation of the rotary forging process is greater than 21%, and the total deformation is greater than 379%. The homogenization treatment is carried out at a temperature of 280–300°C for 6–12 hours.

8. The preparation method according to claim 6, characterized in that, The rotary forging process is performed at room temperature, with 7 to 13 passes; the rotary forging frequency is 20 to 35 times per second.

9. The preparation method according to claim 6, characterized in that, The zinc alloy ingot is prepared by melting the components, heating it to 520-550 °C under inert gas protection, holding it at that temperature for 3-5 minutes, then cooling it to 480-500 °C, then heating it again to 550-570 °C, and then casting it.

10. An application of the anti-aging, high-strength, tough, biodegradable zinc alloy rod as described in any one of claims 1-5, characterized in that, The anti-aging, high-strength, tough, and biodegradable zinc alloy rod is used to manufacture medical devices that can be implanted in the body.

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