A biodegradable zinc alloy semi-solid billet and a method of making the same

Abstract

The application discloses a kind of biodegradable zinc alloy semi-solid billets and preparation method thereof, belong to zinc alloy material processing technical field, to Zn-Mg-Bi-Ca-Sr biological zinc alloy ingot is carried out homogenization annealing treatment;Then to Zn-Mg-Bi-Ca-Sr biological zinc alloy ingot is carried out three-dimensional compression pre-deformation, obtain the three-dimensional free upsetting billet of uniform severe deformation;Three-dimensional free upsetting billet is carried out semi-solid isothermal holding treatment again, obtains semi-solid slurry.The application uses strain-induced melting activation method to semi-solid processing to zinc alloy with narrow liquid-solid region, by three-dimensional forging uniform severe deformation and subsequent isothermal spheroidization treatment to obtain a kind of Zn-Mg-Bi-Ca-Sr biological zinc alloy semi-solid structure with best organizational state, and grain spheroidization effect is remarkable.

Description

Technical Field

[0001] This invention belongs to the field of zinc alloy material processing technology, specifically relating to a biodegradable zinc alloy semi-solid billet and its preparation method. Background Technology

[0002] In recent years, zinc-based biomedical materials have attracted close attention from materials scientists. From a biosafety perspective, zinc is an essential trace element for the human body, with a normal content of 2.5g, of which 85% is found in bones and muscles. For a healthy adult, the daily zinc intake is approximately 15mg / day. Zinc plays a crucial role in the structure of numerous macromolecules and in over 300 enzymatic reactions. In the bone environment, zinc within osteoblasts promotes protein synthesis by activating tRNA synthetase and stimulating gene expression, while also increasing intracellular DNA levels, thereby promoting new bone formation and mineralization. Furthermore, zinc promotes osteoclast apoptosis by regulating calcium ion signaling pathways. Zinc ultimately increases bone mass by promoting bone formation and inhibiting bone resorption, and compared to other trace elements, zinc has the lowest toxicity in bone metabolism. Simultaneously, zinc's standard electrode potential is -0.763V, falling between magnesium's -2.37V and iron's -0.44V, indicating a more suitable degradation rate and adjustable biodegradation potential than magnesium and iron.

[0003] From a mechanical property perspective, pure zinc has poor mechanical properties. It has low strength (UTS < 50 MPa), poor plasticity (Elongation < 1%), and is hard and brittle; therefore, pure zinc is difficult to use directly. Alloying is an effective and simple method to improve the mechanical properties of metals. Furthermore, through deformation processing and heat treatment, the mechanical properties of zinc alloys are greatly improved. This also expands the application range of zinc alloys.

[0004] Therefore, the research and development of biodegradable zinc alloys has irreplaceable advantages. Improving the strength and plasticity of zinc alloys through large plastic deformation has become a research focus and hot topic for scientific and technological workers. However, the hexagonal close-packed (HCP) crystal structure and fewer slip systems of zinc alloys, along with their high-level fault energy, make it difficult for traditional zinc alloys to undergo plastic deformation at low and room temperature conditions. The application of cast zinc alloys is also limited by the limitations of forming processes. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a biodegradable zinc alloy semi-solid billet and its preparation method. This addresses the difficulties in plastic deformation of traditional zinc alloys under low-temperature and room-temperature conditions, and the limitations of casting zinc alloy applications due to the constraints of forming processes. This technology solves the technical challenges of narrow liquid-solid and semi-solid regions in biodegradable zinc alloys, difficulty in controlling the solid fraction in the preparation of semi-solid slurries, and low sphericity shape factor of semi-solid grains in biodegradable zinc alloys. It employs a three-dimensional free forging continuous compensation and heat preservation technique to achieve uniform and large plastic deformation of difficult-to-deform zinc alloys, high internal energy storage during deformation, and precise control of the isothermal treatment of pre-deformed semi-solid zinc alloys. This significantly improves the strength, toughness, and other mechanical properties of Zn-Mg-Bi-Ca-Sr biodegradable zinc alloys and enables their application in semi-solid forming processing.

[0006] The present invention adopts the following technical solution:

[0007] A method for preparing a biodegradable zinc alloy semi-solid billet includes the following steps:

[0008] The Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot was subjected to homogenization annealing treatment; then the Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot was subjected to triaxial compression pre-deformation to obtain triaxial free upsetting billet; then the triaxial free upsetting billet was subjected to semi-solid isothermal heat preservation treatment to obtain semi-solid slurry.

[0009] Specifically, the Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot is as follows:

[0010] Under the protection of high-purity argon, the raw material is heated to 550-600℃, stirred repeatedly, and kept at this temperature for 25-30 minutes. After standing, it is refined and slag is removed, and then poured into a preheated mold to obtain Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingots.

[0011] Specifically, the homogenization annealing temperature is 320℃±5℃, and the holding time is greater than or equal to 3h.

[0012] Specifically, the triaxial compression pre-deformation of the Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot is as follows:

[0013] The Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot is heated to 230-250℃. Under the condition of heat preservation and precise temperature compensation, the compression rate is controlled at 1.2-2.5 mm / s along the X direction to perform free upsetting, thus completing the first pass of free upsetting.

[0014] When the upsetting compression deformation reaches 38% to 45%, the first-pass free upsetting sample is kept at 230 to 250℃ for 10 minutes, and then the second-pass free upsetting is carried out.

[0015] When the upsetting deformation reaches 38% to 45%, the second-pass free upsetting sample is heated to 250℃ and held for 10 minutes, and then the third-pass free upsetting is carried out to finally obtain a three-dimensional free upsetting billet with a square structure.

[0016] Furthermore, the second free upsetting process specifically involves:

[0017] The first-pass free upsetting sample is rotated to the Y direction for the second-pass free upsetting.

[0018] Furthermore, the third free upsetting process specifically involves:

[0019] The sample was rotated to the Z-direction for the third free upsetting, and then air-cooled.

[0020] Specifically, samples were taken from the same deformation location of the triaxial free upsetting billet as dendrite crushing pre-compression samples and subjected to semi-solid isothermal heat preservation treatment.

[0021] Specifically, the heating rate of the semi-solid isothermal heat treatment is 10-15℃ / min, the heating temperature is 370-395℃, the heat treatment is held for 15-90 minutes, and the product is immediately water quenched after removal.

[0022] Specifically, the composition of the Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot is as follows: Zn-1.2wt.%, Mg-0.8~1.5wt.%, Bi-0.18wt.%, Ca-0.12wt.%, Sr; the weight of the Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot is 1000g.

[0023] Another technical solution of the present invention is a biodegradable zinc alloy semi-solid billet.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] A method for preparing biodegradable zinc alloy semi-solid billets has the following beneficial effects:

[0026] 1. The original dendrites of the zinc alloy used for triaxial upsetting pre-deformation are completely broken. The strengthening phase is fully stretched, broken and refined under the action of internal friction during the deformation and flow of the matrix grains. The microstructure is evenly distributed, the entire sample and microstructure are uniformly deformed, the pre-deformation effect is significant, and the deformation storage energy is large.

[0027] 2. Obtain a semi-solid billet with fine structure and good spherical grain structure (average grain diameter reaches 20μm, which is nearly 150 times smaller than the original dendrite size).

[0028] 3. Homogenization annealing treatment avoids uneven chemical composition in the alloy, improves the material flowability of triaxial upsetting pre-deformation, and reduces solute segregation.

[0029] 4. Under the same isothermal semi-solid treatment temperature, as the isothermal holding time increases, the microstructure evolution goes through five stages: dislocation cell merging, substructure formation, subgrain boundary and intergranular liquid phase region formation, solid particle isolation and spheroidization, complete spheroidization, and finally partial spheroid crystal merging. Triaxial upsetting pre-deformation and isothermal treatment can efficiently obtain spheroid grains, and the solid phase ratio during the spheroidization process exceeds 60%.

[0030] 5. Improved the spheroidization rate and preparation efficiency of semi-solid slurry for biodegradable zinc alloys, with the shape factor of spherical grains reaching over 0.85. The spherical grains of the slurry exhibit excellent stability, and the reinforcing phase is uniformly distributed in dispersed granular form within the spherical grains.

[0031] In summary, this invention achieves a semi-solid microstructure of Zn-Mg-Bi-Ca-Sr bio-zinc alloy with optimal microstructure through triaxial forging, uniform and severe deformation, and subsequent isothermal spheroidization treatment, resulting in significant grain spheroidization.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1 This is an optical microstructure diagram of Embodiment 1 of the present invention;

[0034] Figure 2 This is an optical microstructure diagram of Embodiment 2 of the present invention;

[0035] Figure 3 This is an optical microstructure diagram of Embodiment 3 of the present invention;

[0036] Figure 4 This is an optical microstructure diagram of Embodiment 4 of the present invention;

[0037] Figure 5 This is an optical microstructure diagram of Embodiment 5 of the present invention;

[0038] Figure 6 This is an optical microstructure diagram of Embodiment 6 of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0041] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0042] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0043] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0044] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0045] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0046] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0047] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0048] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0049] Semi-solid forming technology utilizes the low shear stress and low viscosity of metals within the solid-liquid temperature range for processing and shaping. The most crucial step in semi-solid forming is preparing a semi-solid billet with a certain solid volume fraction. Strain-Induced Melt Activation (SIMA) is a promising semi-solid billet preparation method. Its process involves: first, obtaining a metal ingot; then applying sufficient large strain plastic deformation to the ingot to fully break down the coarse low-melting-point phases and developed dendrites in the original cast billet, refining the matrix grain size, generating stress concentration and high-density dislocations within the deformed metal, storing a certain amount of deformation energy; then heating the deformed metal to a temperature where solid and liquid phases coexist, performing isothermal holding treatment, and immediately water quenching after a certain holding time, ultimately obtaining a semi-solid billet with a fine spherical or near-spherical solid phase structure. SIMA preparation process is simple and does not require complex equipment. Its essence is that plastic deformation fully deforms, breaks and refines the matrix grains and low-melting-point phases, storing high strain energy inside the grains. Subsequently, it recrystallizes and spheroidizes during isothermal heat treatment to obtain a semi-solid structure with spherical fine grains.

[0050] This invention provides a biodegradable zinc alloy semi-solid billet and its preparation method. The method uses strain-induced melt activation (SIMA) to semi-solidify zinc alloys with narrow liquid-solid regions. Through triaxial forging for uniform and severe deformation and subsequent isothermal spheroidization treatment, a Zn-Mg-Bi-Ca-Sr biodegradable zinc alloy semi-solid microstructure with optimal microstructure is obtained, and the grain spheroidization effect is significant.

[0051] This invention discloses a method for preparing a biodegradable zinc alloy semi-solid billet. First, a Zn-Mg-Bi-Ca-Sr biodegradable zinc alloy ingot is cast in a controlled atmosphere pit-type resistance furnace. Then, the ingot undergoes homogenization treatment. Next, the sample is subjected to triaxial free upsetting rough deformation on a servo-controlled intelligent press. The billet after triaxial free upsetting is obtained from the same location using wire cutting. It is then subjected to isothermal holding treatment at the same holding temperature but different times. Immediately after the isothermal holding treatment, it is water-quenched. The specific steps are as follows:

[0052] S1, Raw Material Preparation

[0053] Raw materials such as pure zinc, pure magnesium, pure bismuth, pure calcium, and pure strontium are put into a controlled atmosphere pit-type resistance furnace and melted under the protection of high-purity argon gas at 550-600℃. After stirring several times, the mixture is held at the temperature for 25-30 minutes, then allowed to stand for refining and slag removal. The mixture is then poured into a preheated graphite mold to obtain a square-structured Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot.

[0054] S2, Material homogenization annealing treatment

[0055] The Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot obtained in step S1 was subjected to homogenization annealing treatment in a vacuum heat treatment furnace (temperature 320℃±5℃, holding time 3h). The sample was cooled with the furnace. Through homogenization treatment, the elements in the zinc alloy underwent sufficient solid-state diffusion to reduce the inhomogeneity of chemical composition.

[0056] S3, Material triaxial free upsetting coarse deformation

[0057] S301. The ingot was heated to 230-250℃ in a heating furnace and held for 10 minutes. The Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot was then transferred to the mold position on the press workbench. The upper and lower parts of the sample were heated with heating plates for precise temperature compensation, and the outer part was insulated with high-temperature insulation cotton. Temperature compensation was monitored by a temperature sensor. Then, the sample was quickly upset on the press (the first pass was in the X direction). The upsetting compression rate was 1.2-2.5 mm / s. The sample deformed uniformly and no cracking was observed.

[0058] S302. When the upsetting compression deformation reaches 38% to 45%, the first-pass free upsetting sample is kept at 230 to 250℃ for 10 minutes before the second-pass free upsetting is performed.

[0059] The second stage of free upsetting is specifically as follows:

[0060] Rotate the first-stage deformed sample 90° and place it on the press (in the Y direction of the sample), and perform the second-stage free upsetting in the Y direction.

[0061] S303. When the upsetting deformation reaches 38% to 45%, the second-pass free upsetting sample is heated to 250℃ and held for 10 minutes, and then the third-pass free upsetting is performed to finally obtain a three-way free upsetting billet with a square structure.

[0062] The third stage of free upsetting is specifically as follows:

[0063] The sample was rotated 90° (Z direction) after the second pass of free upsetting and then subjected to a third pass of free upsetting. After the three-dimensional upsetting, it was air-cooled and treated in the same way as the previous two passes.

[0064] S4, semi-solid isothermal insulation treatment

[0065] The triaxial free upsetting billet obtained in step S3 is sampled and cut into dendritic crushing pre-compression samples with dimensions of 10mm×10mm×10mm at the same deformation location. The dendritic crushing pre-compression samples are subjected to semi-solid isothermal heat preservation treatment to obtain semi-solid slurry.

[0066] After triaxial free upsetting deformation, the matrix grains and the second phases Mg3Bi2 and Mg(Ca,Sr) in the microstructure of the pre-deformed ingot )2 Bi2 was significantly elongated, fragmented, and refined. The triaxial upsetting process completely broke down the dendritic matrix and significantly improved the morphology, distribution, and size of the strengthening phase. Large cumulative strain was achieved within the high-deformation zinc alloy, which is conducive to the formation of a spherical semi-solid structure.

[0067] The semi-solid isothermal heat treatment process was carried out in a vacuum heat treatment furnace at a heating rate of 10-15℃ / min. The isothermal heat treatment temperature is the solid-liquid coexistence temperature range. Based on the Zn-Mg phase diagram and experimental exploration, the semi-solid temperature for isothermal heat treatment was determined to be 380℃. Based on the fixed isothermal heat treatment temperature, the isothermal heat treatment process was carried out at different heat treatment times: 15 min, 30 min, 45 min, 60 min, 75 min, and 90 min. After reaching the predetermined heat treatment time, the sample was immediately water quenched.

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0069] Example 1

[0070] This embodiment provides a method for preparing a semi-solid billet of Zn-Mg-Bi-Ca-Sr bio-zinc alloy, including the following steps:

[0071] S1. Place raw materials such as pure zinc, pure magnesium, pure bismuth, pure calcium, and pure strontium into an atmosphere-controlled pit-type resistance furnace. Under the protection of high-purity argon, heat the furnace to 550°C to melt them. After stirring multiple times, keep the furnace at the temperature for 30 minutes, let it stand to refine and remove slag, and pour it into a preheated graphite mold to obtain a square ingot.

[0072] S2. The ingot is homogenized in a vacuum heat treatment furnace (temperature 320℃, holding time 3h), and the sample is cooled with the furnace; the homogenization treatment allows the elements in the zinc alloy to undergo sufficient solid-state diffusion, thereby reducing the inhomogeneity of chemical composition.

[0073] S3. First, heat the ingot to 230℃ in an atmosphere heat treatment furnace and hold for 10 minutes. Then, transfer the Zn-Mg-Bi-Ca-Sr bio-zinc alloy ingot to the mold position on the press table. Heating plates are used for precise temperature compensation on both the top and bottom of the sample, and high-temperature insulation cotton is used for external insulation. Temperature compensation is monitored by a temperature sensor. Subsequently, rapid free upsetting (X direction) is performed on the press table mold. Heating plates are used for precise temperature compensation on both the top and bottom of the sample, and high-temperature insulation cotton is used for external insulation. Temperature compensation is monitored by a temperature sensor. Then, the press descends at a controlled speed. After the ingot upsetting compression rate reaches 38% at a speed of 1.2 mm / s, the first-pass free upsetting sample is heated to 230℃ and held for 10 minutes before the second-pass free upsetting. Specifically, the first-pass deformed sample is rotated 90° and placed on the press mold (Y direction) for the second-pass free upsetting deformation. Then, the third-pass free upsetting is carried out by rotating the second-pass free upsetting sample 90° (Z direction) and repeating the upsetting at a predetermined rate and deformation amount. After completing the three-pass three-dimensional upsetting, the sample is air-cooled to obtain a square-structured three-dimensional free upsetting billet.

[0074] S4. The pre-deformed sample was wire-cut into 10mm×10mm×10mm pieces, obtained from the same location on the zinc alloy large-deformation billet. The semi-solid isothermal treatment process was carried out in a vacuum heat treatment furnace at a heating rate of 10℃ / min; the isothermal holding temperature was 380℃, and the isothermal holding time was 15min. Immediately after the isothermal holding time was completed, the sample was removed and water-quenched. The optical microstructure was as follows: Figure 1 As shown, triaxial free upsetting achieved uniform large deformation of the bio-zinc alloy, resulting in extremely fine recrystallized grains during subsequent isothermal treatment of the bio-zinc alloy in a narrow liquid-solid region. From Figure 1 It can be seen that the banded structure obtained after triaxial free upsetting of the alloy, after holding at temperature for 15 minutes, shows that the elongated grains in the alloy's large deformation structure gradually melt and break into small polygonal grains, and some solid phase grains are absorbed by the liquid phase Mg2Zn. 11 The eutectic structure is isolated. This means that it has undergone a process of dislocation cell merging and substructure gradually forming.

[0075] Example 2

[0076] This embodiment provides a method for preparing a semi-solid billet of Zn-Mg-Bi-Ca-Sr bio-zinc alloy, including the following steps:

[0077] S1. Pure zinc, pure magnesium, pure bismuth, pure calcium, pure strontium and other raw materials are put into an atmosphere-controlled pit-type resistance furnace. Under argon protection, the temperature is raised to 600℃ to melt them. After stirring several times, the temperature is kept for 25 minutes. After standing, refining and removing slag, the mixture is poured into a preheated graphite mold to obtain a square-structured ingot.

[0078] S2. The ingot is subjected to homogenization annealing treatment in a heat treatment furnace (temperature 320℃, holding time 3h), and the sample is cooled with the furnace; this allows the elements in the zinc alloy to undergo sufficient solid-state diffusion, thereby reducing the inhomogeneity of chemical composition.

[0079] S3. First, the ingot is heated to 250℃ and held for 10 minutes in an atmosphere heat treatment furnace. The upper and lower parts of the sample are heated with heating plates for precise temperature compensation, and the outer part is insulated with high-temperature insulation cotton. Temperature compensation is monitored by a temperature sensor. Then, free upsetting (X direction) is performed on the mold of the press workbench. The press descends at a speed of 2.5 mm / s. After the ingot upsetting compression rate reaches 45%, the first free upsetting sample is heated to 250℃ and held for 10 minutes before the second free upsetting. Specifically, the first deformation sample is rotated 90° and placed on the press mold (Y direction) for the second free upsetting deformation. Then, the third free upsetting is performed according to the above operation. Specifically, the second free upsetting sample is rotated 90° (Z direction) and upsetting is repeated at a predetermined rate and deformation amount. After completing the three-pass three-dimensional upsetting, the sample is air-cooled to obtain a square three-dimensional free upsetting billet.

[0080] S4. The pre-deformed sample was wire-cut into 10mm×10mm×10mm pieces, obtained from the same part of the zinc alloy large deformation billet. The semi-solid isothermal treatment process was carried out in a vacuum heat treatment furnace at a heating rate of 15℃ / min. The isothermal holding temperature was 380℃, and the isothermal holding time was 30min. After the isothermal holding time was completed, the sample was immediately removed and water-quenched. The optical microstructure was as follows: Figure 2 As shown, triaxial free upsetting achieved uniform large deformation of the bio-zinc alloy, with high deformation energy storage. Subsequent isothermal treatment of the bio-zinc alloy in a narrow liquid-solid region resulted in well-integrity recrystallized spherical grains with uniform grain distribution. From... Figure 2 As can be seen, with the extension of the holding time, the heat input of the system continuously increases, and some of the blocky Mg2Zn11 eutectic phase melts at the grain boundaries with high distortion energy, forming local liquid phase regions. The separation of solid phase grains is mainly due to the wetting and expansion of the liquid phase along the solid phase grain boundaries. The formed solid phase particles are of varying sizes and have uneven surfaces.

[0081] Example 3

[0082] This embodiment provides a method for preparing a semi-solid billet of Zn-Mg-Bi-Ca-Sr bio-zinc alloy, including the following steps:

[0083] S1. Pure zinc, pure magnesium, pure bismuth, pure calcium, pure strontium and other raw materials are put into an atmosphere-controlled pit-type resistance furnace. Under argon protection, the temperature is raised to 560℃ to melt them. After stirring several times, the temperature is kept for 28 minutes. After standing, refining and removing slag, the mixture is poured into a preheated graphite mold to obtain a square ingot.

[0084] S2. The ingot is homogenized in a heat treatment furnace (temperature 320℃, holding time 3h), and the sample is cooled with the furnace; this allows the elements in the zinc alloy to undergo sufficient solid-state diffusion, thereby reducing the inhomogeneity of the chemical composition.

[0085] S3. First, heat the ingot to 235℃ in an atmosphere heat treatment furnace and hold for 10 minutes. Then, transfer the sample to the mold position on the press table. The upper and lower parts of the sample are heated with heating plates for precise temperature compensation, and the outer part is insulated with high-temperature insulation cotton. Temperature compensation is monitored by a temperature sensor. Then, the sample is quickly subjected to free upsetting (X direction) on the press table mold. The press descends at a speed of 2.0 mm / s. After the ingot upsetting compression rate reaches 40%, the sample from the first free upsetting stage is heated to 235℃ and held for 10 minutes before the second free upsetting stage. Specifically, the sample from the first stage is rotated 90° and placed on the press mold (Y direction) for the second free upsetting deformation. Then, the third free upsetting stage is performed according to the above operation. Specifically, the sample from the second stage is rotated 90° (Z direction) and upsetting is repeated at a predetermined rate and deformation amount. After completing the three-stage three-way upsetting, the sample is air-cooled to obtain a square three-way free upsetting billet.

[0086] S4. The pre-deformed sample was wire-cut into 10mm×10mm×10mm pieces, obtained from the same location on the zinc alloy large-deformation billet. The semi-solid isothermal treatment process was carried out in a vacuum heat treatment furnace at a heating rate of 11℃ / min; the isothermal heat treatment temperature was 380℃, and the isothermal holding time was 45min. Immediately after the isothermal treatment time, the sample was removed and water-quenched. The optical microstructure was as follows: Figure 3 As shown, triaxial free upsetting achieved uniform large deformation of the bio-zinc alloy, resulting in fine recrystallized grains during subsequent isothermal treatment in a narrow liquid-solid region, significantly improving the solidity during the semi-solid process. From Figure 3 It can be seen that when the holding time is extended to 45 minutes, grains larger than the average size continue to grow, while grains smaller than the average size gradually disappear, and the matrix grains gradually become more uniform. Moreover, a diffusely distributed liquid phase pool appears within the grains.

[0087] Example 4

[0088] This embodiment provides a method for preparing a semi-solid billet of Zn-Mg-Bi-Ca-Sr bio-zinc alloy, including the following steps:

[0089] S1. Pure zinc, pure magnesium, pure bismuth, pure calcium, pure strontium and other raw materials are put into an atmosphere-controlled well-type resistance furnace. Under argon protection, the temperature is raised to 580℃ to melt them. After stirring several times, the temperature is kept for 27 minutes. After standing, refining and removing slag, the mixture is poured into a preheated graphite mold to obtain a square ingot.

[0090] S2. The ingot is homogenized in a heat treatment furnace (temperature 320℃, holding time 3h), and the sample is cooled with the furnace; this allows the elements in the zinc alloy to undergo sufficient solid-state diffusion, thereby reducing the inhomogeneity of the chemical composition.

[0091] S3. First, heat the ingot to 240℃ in an atmosphere heat treatment furnace and hold for 10 minutes. Then, transfer the sample to the mold position on the press table. The upper and lower parts of the sample are heated with heating plates for precise temperature compensation, and the outer part is insulated with high-temperature insulation cotton. Temperature compensation is monitored by a temperature sensor. Then, the sample is quickly subjected to free upsetting (X direction) on the press table mold. The press descends at a speed of 2.1 mm / s. After the ingot upsetting compression rate reaches 41%, the sample from the first free upsetting stage is heated to 240℃ and held for 10 minutes before the second free upsetting stage. Specifically, the sample from the first stage is rotated 90° and placed on the press mold (Y direction) for the second free upsetting deformation. Then, the third free upsetting stage is performed according to the above operation. Specifically, the sample from the second stage is rotated 90° (Z direction) and upsetting is repeated at a predetermined rate and deformation amount. After completing the three-stage three-way upsetting, the sample is air-cooled to obtain a square three-way free upsetting billet.

[0092] S4. The pre-deformed sample was wire-cut into 10mm×10mm×10mm pieces, obtained from the same part of the zinc alloy large deformation billet. The semi-solid isothermal treatment process was carried out in a vacuum heat treatment furnace at a heating rate of 12℃ / min. The isothermal holding temperature was 380℃, and the isothermal holding time was 60min. After the isothermal treatment time was completed, the sample was immediately removed and water-quenched. The optical microstructure was as follows. Figure 4 As shown, triaxial free upsetting achieved uniform large deformation of the bio-zinc alloy. Subsequent isothermal treatment of the bio-zinc alloy in a narrow liquid-solid region yielded fine recrystallized grains. The semi-solid process significantly improved the solid fraction, further enhanced the shape factor, and resulted in good grain spheroidization and uniform dispersion. From... Figure 4 It can be seen that after 60 minutes of holding time, the semi-solid structure, along with the release of stored energy, shows that the liquid phase gradually spreads along the boundaries of the solid grains, forming solid particles that are separated by the liquid phase and are of uneven size and irregular shape. The number of small liquid phase pools within the grains increases. The growth of large grains and the melting and disappearance of small grains are still ongoing.

[0093] Example 5

[0094] This embodiment provides a method for preparing a semi-solid billet of Zn-Mg-Bi-Ca-Sr bio-zinc alloy, including the following steps:

[0095] S1. Pure zinc, pure magnesium, pure bismuth, pure calcium, pure strontium and other raw materials are put into an atmosphere-controlled pit-type resistance furnace. Under argon protection, the temperature is raised to 570℃ to melt them. After stirring several times, the temperature is kept for 29 minutes. After standing, refining and removing slag, the mixture is poured into a preheated graphite mold to obtain a square ingot.

[0096] S2. The ingot is homogenized in a heat treatment furnace (temperature 320℃, holding time 3h). The sample is cooled with the furnace to allow the elements in the zinc alloy to undergo sufficient solid-state diffusion in order to reduce the inhomogeneity of chemical composition.

[0097] S3. First, heat the ingot to 245℃ in an atmosphere heat treatment furnace and hold for 10 minutes. Transfer the sample to the mold position on the press table. Use heating plates on the top and bottom of the sample for precise temperature compensation, and use high-temperature insulation cotton for insulation. Temperature compensation is monitored by a temperature sensor. Then, quickly perform free upsetting (X direction) on the press table mold. The press descends at a speed of 2.4 mm / s. After the ingot upsetting compression rate reaches 44%, heat the first free upsetting sample to 245℃ and hold for 10 minutes before performing the second free upsetting. Specifically, rotate the first deformation sample 90° and place it on the press mold (Y direction) for the second free upsetting deformation. Then, continue the above operation for the third free upsetting. Specifically, rotate the second free upsetting sample 90° (Z direction) and repeat the upsetting at a predetermined rate and deformation amount. After completing the three-pass three-dimensional upsetting, air cool to obtain a square three-dimensional free upsetting billet.

[0098] S4. The pre-deformed sample was wire-cut into samples with dimensions of 10mm × 10mm × 10mm, obtained from the same part of the zinc alloy large deformation billet; the semi-solid isothermal treatment process was carried out in a vacuum heat treatment furnace, with a heating rate of 13℃ / min; the isothermal heat treatment temperature was 380℃, and the isothermal holding time was 75min. After the isothermal treatment time was completed, the sample was immediately removed and water-quenched. The optical microstructure was as follows: Figure 5 As shown, triaxial free upsetting achieved uniform large deformation of the bio-zinc alloy, significantly improving the solid fraction, further enhancing the shape factor, and resulting in good grain spheroidization with the strengthening phase dispersed within the spherical grains during subsequent isothermal treatment in the narrow liquid-solid region. Figure 5 It can be seen that as the isothermal heat treatment time continues to extend, under the combined effect of surface tension and solid-phase interface curvature, the solid-phase grains transform into spheres with the lowest surface energy. The liquid phase thickness between the solid-phase interfaces is uniform, and the liquid phase molten pools within the grains grow due to solute diffusion and infiltration merging. The solid-liquid phase ratio in the semi-solid structure reaches an equilibrium state.

[0099] Example 6

[0100] This embodiment provides a method for preparing a semi-solid billet of Zn-Mg-Bi-Ca-Sr bio-zinc alloy, including the following steps:

[0101] S1. Pure zinc, pure magnesium, pure bismuth, pure calcium, pure strontium and other raw materials are put into an atmosphere-controlled pit-type resistance furnace. Under argon protection, the temperature is raised to 590℃ to melt them. After stirring several times, the temperature is kept for 26 minutes. After standing, refining and removing slag, the mixture is poured into a preheated graphite mold to obtain a square ingot.

[0102] S2. The ingot is homogenized in a heat treatment furnace (temperature 220℃, holding time 3h). The sample is cooled with the furnace to allow the elements in the zinc alloy to undergo sufficient solid-state diffusion in order to reduce the inhomogeneity of chemical composition.

[0103] S3. First, heat the ingot to 250℃ in an atmosphere heat treatment furnace and hold for 10 minutes. Then, transfer the sample to the mold position on the press table. The upper and lower parts of the sample are heated with heating plates for precise temperature compensation, and the outer part is insulated with high-temperature insulation cotton. Temperature compensation is monitored by a temperature sensor. Then, the sample is quickly subjected to free upsetting (X direction) on the press table mold. The press descends at a speed of 1.8 mm / s. After the ingot upsetting compression rate reaches 39%, the sample from the first free upsetting stage is heated to 250℃ and held for 10 minutes before the second free upsetting stage. Specifically, the sample from the first stage is rotated 90° and placed on the press mold (Y direction) for the second free upsetting deformation. Then, the third free upsetting stage is performed according to the above operation. Specifically, the sample from the second stage is rotated 90° (Z direction) and upsetting is repeated at a predetermined rate and deformation amount. After completing the three-stage three-way upsetting, the sample is air-cooled to obtain a square three-way free upsetting billet.

[0104] S4. The pre-deformed sample was wire-cut into 10mm×10mm×10mm pieces, obtained from the same location on the zinc alloy large-deformation billet. The semi-solid isothermal treatment process was carried out in a vacuum heat treatment furnace at a heating rate of 14℃ / min. The isothermal heat treatment temperature was 380℃, and the isothermal holding time was 90min. Immediately after the isothermal treatment time, the sample was removed and water-quenched. The optical microstructure was as follows: Figure 6 As shown, triaxial free upsetting achieved uniform large deformation of the bio-zinc alloy, which significantly improved the solid fraction during the subsequent isothermal treatment of the bio-zinc alloy in the narrow liquid-solid region, resulting in good grain spheroidization and a dispersed distribution of the strengthening phase within the spherical grains. As can be seen from the figure, the solid-liquid phase ratio remained constant, and the solid grains reduced the system's free energy through Ostwald ripening and coalescence, maintaining the system's dynamic equilibrium.

[0105] In summary, this invention provides a biodegradable zinc alloy semi-solid billet and its preparation method. This technology utilizes temperature compensation to achieve multi-directional upsetting coarse deformation of the difficult-to-deform biodegradable zinc alloy, resulting in high storage energy and uniform pre-deformation. During isothermal treatment of the semi-solid phase, the biodegradable zinc alloy with a narrow liquid-solid region achieves a high solid fraction, high shape factor, and uniformly distributed spherical grain semi-solid slurry. This method offers high preparation efficiency, low cost, and excellent precise control over the shape factor and the shape of the narrow liquid-solid region semi-solid zinc alloy slurry. This invention employs a strain-induced melting activation method to semi-solidify the zinc alloy with a narrow liquid-solid region. A semi-solid microstructure of the biodegradable zinc alloy is obtained through triaxial forging uniform and severe deformation followed by isothermal spheroidization. Furthermore, the evolution mechanism of the semi-solid microstructure of the biodegradable zinc alloy is investigated by holding it at a constant temperature for different times to better determine the optimal semi-solid microstructure.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing a biodegradable zinc alloy semi-solid billet, characterized by, The method comprises the following steps: The Zn-Mg-Bi-Ca-Sr biological zinc alloy ingot is subjected to homogenization annealing treatment, and the Zn-Mg-Bi-Ca-Sr biological zinc alloy ingot is specifically: Under the protection of high-purity argon, the raw materials are heated to 550-600 DEG C, and after stirring for several times, the temperature is maintained for 25-30 minutes, the slag is refined by standing, and the Zn-1.2wt.% Mg-0.8-1.5wt.% Bi-0.18wt.% Ca-0.12wt.% Sr biological zinc alloy ingot is poured into the preheated mold, the balance is zinc and unavoidable impurities, and the weight of the Zn-Mg-Bi-Ca-Sr biological zinc alloy ingot is 1000g; Then the Zn-Mg-Bi-Ca-Sr biological zinc alloy ingot is heated to 230-250 DEG C, and then the free upsetting is carried out along the X direction at a compression rate of 1.2-2.5 mm / s under the conditions of temperature compensation and accurate temperature maintenance, and the first pass free upsetting is completed; When the upsetting compression deformation reaches 38%-45%, the first pass free upsetting sample is maintained at 250 DEG C for 10 min, and the second pass free upsetting is carried out. When the upsetting deformation reaches 38%-45%, the second pass free upsetting sample is heated to 230-250 DEG C and maintained for 10 min, the third pass free upsetting is carried out, and the three-way free upsetting blank with square structure is obtained. The three-way free upsetting blank is subjected to semi-solid isothermal heat preservation treatment, the heating rate of the semi-solid isothermal heat preservation treatment is 10-15 DEG C / min, the heating temperature is 370-395 DEG C, the heat preservation time is 15-90 min, and the semi-solid slurry is obtained after water quenching immediately after taking out.

2. The method of claim 1, wherein the biodegradable zinc alloy semi-solid billet is prepared by a method comprising: The temperature of the homogenization annealing treatment is 320 DEG C ± 5 DEG C, and the heat preservation time is greater than or equal to 3h.

3. The method of claim 1, wherein the biodegradable zinc alloy semi-solid billet is prepared by a method comprising: The second pass free upsetting is specifically: The first pass free upsetting sample is rotated to the Y direction for the second pass free upsetting.

4. The method of claim 1, wherein the biodegradable zinc alloy semi-solid billet is prepared by a method comprising: The third pass free upsetting is specifically: The second pass free upsetting sample is rotated to the Z direction for the third pass free upsetting, and then air cooling is carried out.

5. The method of claim 1, wherein the biodegradable zinc alloy semi-solid billet is prepared by a method comprising: The three-way free upsetting blank is sampled at the same deformation position as the dendrite breaking pre-pressing sample for semi-solid isothermal heat preservation treatment.

6. The biodegradable zinc alloy semi-solid blank prepared by the method according to any one of claims 1 to 5.

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