Medical magnesium alloy plate and preparation method thereof

Abstract

The invention provides a medical magnesium alloy plate and a preparation method of the medical magnesium alloy plate. The average grain size of the medical magnesium alloy plate ranges from 3.2 micrometers to 5 micrometers, and the flatness range is smaller than or equal to 0.04 mm. The average grain size of the medical magnesium alloy plate is 3.2-5 [mu] m, so that the medical magnesium alloy plate has excellent mechanical properties and corrosion degradation properties, and the promotion effect on pitting corrosion caused by too small grain size can be avoided; an in-vivo implantation instrument made of the magnesium alloy plate cannot be perforated or fractured in advance due to pitting corrosion after being implanted into a body; and meanwhile, excessive grain boundaries caused by too small grain sizes are avoided. In addition, the planeness range of the medical magnesium alloy plate is controlled to be 0.04 mm or below, and it is indicated that the medical magnesium alloy plate has high planeness.

Description

Technical Field

[0001] The present application relates to the technical field of medical materials, and in particular to a medical magnesium alloy plate and a preparation method of the medical magnesium alloy plate. Background Art

[0002] With the continuous advancement of science and technology, the medical industry's technical level is rapidly improving, and the medical materials industry is booming. Among them, medical metal materials, with their excellent properties such as high strength and toughness, fatigue resistance, easy processing and molding, and high reliability, account for over 40% of medical device materials. Traditional metal implants are made of inert metal materials and remain in the human body for a long time after implantation, or require secondary surgery to remove. However, the demand for many implants during service is only temporary. To address the adverse effects of long-term implant retention, biodegradable implants have entered the spotlight.

[0003] Degradable implantable devices are made from degradable implantable materials. These materials include degradable polymers, degradable ceramics, and degradable metals. Metals have attracted considerable attention due to their high strength, toughness, and ease of processing. Degradable metal materials can be further categorized as degradable magnesium alloys, degradable zinc alloys, and degradable iron alloys. Among these, degradable magnesium alloys offer the best biocompatibility and the broadest clinical application prospects. Furthermore, the degradation properties of degradable implantable devices are also a key factor influencing their practicality.

[0004] At present, the traditional preparation process of magnesium alloy industrial plates is usually to cast and press the magnesium alloy ingots, then perform multiple rolling processes, and finally mechanically level them. Traditional industrial magnesium alloy plates are widely used in automobile manufacturing, electronic products, aerospace and other fields.

[0005] However, it is currently difficult to obtain medical magnesium alloy sheets that can balance degradation performance and mechanical properties while having high flatness based on traditional process flows, and there is a lack of suitable preparation processes in the field of medical magnesium alloy implants. Summary of the Invention

[0006] Based on this, the present application provides a medical magnesium alloy sheet material and a method for preparing the medical magnesium alloy sheet material that can take into account both degradation performance and mechanical properties and has high flatness.

[0007] A first aspect of the present application provides a medical magnesium alloy plate, wherein the average grain size of the medical magnesium alloy plate is 3.2 μm-5 μm and the flatness range is ≤0.04 mm.

[0008] In some embodiments, the average grain size of the medical magnesium alloy plate is 3.9 μm-5 μm.

[0009] In some embodiments, the degradation rate in vivo of the in-vivo implant device made of the medical magnesium alloy sheet is 0.08 mm / year - 0.1 mm / year.

[0010] The second aspect of the present application provides a preparation method of a medical magnesium alloy sheet, comprising the following steps:

[0011] Perform a first heat preservation treatment and hot extrusion on the homogenized and heat-treated magnesium alloy ingot in sequence to prepare a plate-shaped blank;

[0012] Perform cold rolling or room-temperature drawing on the plate-shaped blank;

[0013] Perform a second heat preservation treatment and hot press leveling on the plate-shaped blank after cold rolling or room-temperature drawing in sequence to prepare the medical magnesium alloy sheet;

[0014] Among them, the rolling speed of the cold rolling is 0.3 m / s - 1 m / s, the reduction ratio per pass of the cold rolling is 6% - 10%, the temperature of the second heat preservation treatment is 310°C - 500°C, the average grain size of the medical magnesium alloy sheet is 3.2 μm - 5 μm, and the flatness tolerance ≤ 0.04 mm.

[0015] In some embodiments, the pressure of the hot press leveling is 10 MPa - 30 MPa, and the pressure holding time is 5 min - 20 min.

[0016] In some embodiments, the time of the second heat preservation treatment is 5 min - 25 min.

[0017] In some embodiments, the temperature of the cold rolling is 20°C - 26°C, the rolling speed is 0.5 m / s - 1 m / s, and the number of passes is 1 pass - 3 passes; and / or

[0018] The drawing speed of the room-temperature drawing is 0.1 m / s - 2 m / s, and the deformation rate per pass ≤ 10%.

[0019] In some embodiments, the temperature of the first heat preservation treatment is 300°C - 400°C, and the time is 1 hour - 1.5 hours.

[0020] In some embodiments, the extrusion speed of the hot extrusion is 0.1 m / s - 0.5 m / s, and the pressure is 150 MPa - 250 MPa.

[0021] In some embodiments, the thickness of the plate-shaped blank after cold rolling or room-temperature drawing is 0.1 mm - 2 mm.

[0022] In some embodiments, the preparation method further comprises the step of performing homogenization heat treatment on the magnesium alloy ingot; among them, the temperature of the homogenization heat treatment is 520°C - 550°C, and the time is 8 hours - 12 hours.

[0023] In some embodiments, the leveling fixture used for hot pressing and leveling includes a lower mold and an upper mold. The lower mold is a cube with a groove provided on one side surface. The groove is used to hold the plate-shaped blank to be leveled, and the upper mold can cover the groove.

[0024] In some embodiments, the wall thickness of the groove is 10 mm, and the depth of the groove is 12 mm - 25 mm; and / or

[0025] The length, width, and height of the lower mold are 100 mm - 140 mm, 60 mm - 100 mm, and 20 mm - 30 mm respectively, and the length, width, and height of the upper mold are 90 mm - 130 mm, 40 mm - 80 mm, and 25 mm - 35 mm respectively.

[0026] For the above-mentioned medical magnesium alloy sheet, since its average grain size is 3.2 μm - 5 μm, it can not only ensure that the medical magnesium alloy sheet has excellent mechanical properties and corrosion degradation properties, but also avoid fracture due to fatigue cracks under the influence of cyclic mechanical movements such as breathing and movement after the device is implanted into the human body. In addition, since its flatness deviation is controlled below 0.04 mm, it can ensure that the medical magnesium alloy sheet has a high flatness.

[0027] The beneficial effects of the preparation method of the above-mentioned medical magnesium alloy sheet are as follows. First, by hot extrusion, a plate-shaped blank is obtained, and its size is close to the size required for the final product. A fine-grained sheet with a grain size less than 5 μm can be obtained, which greatly improves the performance of the sheet. Since magnesium alloy has poor deformability, magnesium plate, a low-plasticity metal, is prone to brittle fracture under tensile stress and is more likely to crack and have cracked edges during the plastic forming process. However, in hot extrusion, a triaxial compressive stress makes the microcracks or defects inside the material in a closed state, reducing stress concentration, thereby delaying or preventing the expansion of cracks. Under high pressure, the voids and defects inside the material are compressed, and the microstructure becomes denser, improving the mechanical properties and surface quality of the sheet.

[0028] Since after hot extrusion, the material will undergo thermal expansion at high temperatures, and its size will increase with the increase in temperature. During the hot extrusion process, the material is in a high-temperature state (usually close to or higher than the recrystallization temperature). Therefore, when it cools after being removed from the mold, its size will shrink, but at the moment of extrusion, the material size may be larger than the mold size. During the extrusion process, the material is restricted by the mold, and while undergoing plastic deformation, it will also undergo elastic deformation. When the material is removed from the mold, the elastic deformation part will recover, resulting in a slightly larger size of the finished product. Through this step of hot extrusion, the size of the sheet is initially controlled.

[0029] Further, the sheet obtained after hot extrusion can be cold-rolled or drawn at room temperature in 1-2 passes to precisely adjust the product thickness and obtain a thickness dimension with high precision.

[0030] During cold rolling, the material is at a relatively low temperature, and the deformation process is more stable, making it less likely to undergo dynamic recovery and recrystallization. Cold rolling also results in a higher surface quality of the sheet, with less oxidation and fewer defects. Moreover, cold rolling significantly increases the dislocation density through plastic deformation, enabling a large accumulation of true strain, inducing a large number of dislocations within the microstructure of the magnesium alloy ingot, thereby refining the grains and enhancing the hardness and strength of the magnesium alloy. At the same time, grain refinement affects its degradation rate, thus achieving the organic unity of its mechanical properties and degradation properties.

[0031] When magnesium alloys are drawn at room temperature, they mainly rely on two dislocation movement modes: basal slip and pyramidal slip. Compared with hot forming, dynamic recovery is suppressed during cold deformation, resulting in the continuous accumulation of dislocations to form a grid structure. This self-strengthening hardening effect makes it more difficult for the sheet to develop local necking during subsequent deformation.

[0032] The present invention uses cold rolling or drawing at room temperature in 1-2 passes, which has a shorter process flow and improves the product stability.

[0033] Finally, through the hot pressing and leveling process, the flatness can be improved while eliminating the internal stress introduced by the previous processing step, and the comprehensive properties of the magnesium alloy sheet can be appropriately regulated to meet the requirements of high mechanical properties and high flatness needed for the preparation of implantable devices; and due to stress elimination, premature cracking caused by metal corrosion of the magnesium alloy under the action of stress can be effectively avoided, preventing the implantable device from failing prematurely before the treatment site heals. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application and more comprehensively understand the present application and its beneficial effects, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative efforts.

[0035] Figure 1 It is a process flow chart of the preparation of a medical magnesium alloy sheet provided by an embodiment.

[0036] Figure 2 It is a schematic structural diagram of a leveling die provided by an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to related embodiments. The following gives the preferred embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of the present application more thorough and comprehensive.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0039] As used herein, the alternatives of the terms "and / or", "or / and", and "and / or" include any one of two or more related listed items, as well as any and all combinations of the related listed items. The said any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items. It should be noted that when connecting at least three items with at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in this application, this technical solution undoubtedly includes the technical solution connected by "logical AND", and also undoubtedly includes the technical solution connected by "logical OR".

[0040] In the present application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, as well as an open technical solution containing the listed features.

[0041] In the present application, regarding the numerical range, unless otherwise specified, the above numerical range is considered continuous and includes the minimum value and the maximum value of this range, as well as each value between such minimum value and maximum value. Further, when the range refers to an integer, it includes each integer between the minimum value and the maximum value of this range. In addition, when providing multiple ranges to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0042] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recorded.

[0043] The temperature parameters in this application, unless otherwise specified, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows for temperature fluctuations within the precision range of instrument control. Fluctuations within the ranges of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0044] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc. shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0045] In this application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0046] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0047] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0048] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0049] Unless otherwise specified, all steps of the present application can be performed sequentially or randomly, preferably sequentially.

[0050] Biodegradable magnesium alloy materials have the best biocompatibility and are currently the most widely used biodegradable implant material. However, the preparation of medical magnesium alloy sheets in related technologies has the following problems: (1) Magnesium alloys are close-packed hexagonal metals. Compared with widely used iron alloys, aluminum alloys, copper alloys, etc., they have poor room temperature formability and are prone to cracking and other defects during processing, resulting in a low yield rate; and multiple annealing and other heat treatments can easily lead to coarse tissue of the prepared products, thereby reducing mechanical properties. Traditional magnesium alloy sheet preparation technology is not perfect and cannot obtain medical magnesium alloy sheets with high mechanical properties and high flatness. (2) The traditional magnesium alloy profile preparation process is complex, with many processing and heat treatment passes, so the production cost is high and the product quality stability is difficult to control.

[0051] Based on the above problems, in this application, first, a plate-shaped blank is obtained by hot extruding a homogenized heat-treated magnesium alloy ingot, so that the size of the plate-shaped blank is close to the size required for the final product. At the same time, the forming method of triaxial compressive stress in hot extrusion is used to obtain fine grains and high performance. Secondly, the forming thickness of the sheet blank is precisely controlled by cold rolling or room-temperature drawing, and the mechanical properties of the sheet blank are further improved to achieve further shape control and property control. Finally, a hot pressing and leveling process is applied to the sheet blank to eliminate the internal stress introduced by the previous processing step while improving the flatness of the sheet, and the mechanical properties of the alloy can be appropriately adjusted to meet the requirements of high performance and high flatness required for the preparation of implantable devices.

[0052] One or more embodiments of this application provide a medical magnesium alloy sheet. The average grain size of the medical magnesium alloy sheet is 3.2μm - 5μm, and the flatness variation ≤ 0.04mm.

[0053] It should be noted that the flatness variation refers to the maximum vertical distance between the highest point and the lowest point on the surface of the sample when the sample is placed flat on an ideal plane. The ideal plane refers to a two-dimensional surface that is completely flat, infinitely extended, and has no deviation.

[0054] As a non-limiting example, the average grain size of the medical magnesium alloy sheet can be, but is not limited to, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5μm, or the range between any two of the above particle sizes, etc.

[0055] The flatness variation of the medical magnesium alloy sheet can be, but is not limited to, 0.005mm, 0.01mm, 0.015mm, 0.02mm, 0.025mm, 0.03mm, 0.035mm, 0.04mm, or the range between any two of the above values, etc.

[0056] Understandably, for the medical magnesium alloy sheet provided in this application, since its average grain size is between 3.2 μm and 5 μm, it can not only ensure that the medical magnesium alloy sheet has excellent mechanical properties and corrosion degradation properties, but also avoid the promotion effect on pitting corrosion caused by too small grain size, so that the in-vivo implant device made of this magnesium alloy sheet will not perforate or break prematurely due to pitting corrosion after being implanted into the body; at the same time, it will not produce too many grain boundaries due to too small grain size. If there are too many grain boundaries, stress concentration is likely to occur at the grain boundaries, becoming the initiation point of fatigue cracks, resulting in the fracture of the device after being implanted into the human body under the influence of cyclic mechanical movements such as breathing and movement. In addition, since its flatness deviation is controlled below 0.04 mm, it can ensure that the medical magnesium alloy sheet has a high flatness.

[0057] In some embodiments, the average grain size of the medical magnesium alloy sheet is 3.9 μm - 5 μm.

[0058] In some embodiments, the degradation rate of the in-vivo implant device made of the medical magnesium alloy sheet in the body is 0.08 mm / year - 0.1 mm / year; for example, it can be, but is not limited to, 0.08 mm / year, 0.082 mm / year, 0.084 mm / year, 0.086 mm / year, 0.088 mm / year, 0.09 mm / year, 0.092 mm / year, 0.094 mm / year, 0.096 mm / year, 0.098 mm / year, 0.1 mm / year or the range between any two of the above degradation rates, etc. Thus, the degradation period of the implant device can be effectively matched with the degradation rate of the implant environment.

[0059] One or more embodiments of this application provide a preparation method of a medical magnesium alloy sheet, which can be used to prepare the above-mentioned medical magnesium alloy sheet. The preparation method includes the following steps:

[0060] Perform a first heat preservation treatment and hot extrusion on the homogenized heat-treated magnesium alloy ingot in sequence to prepare a plate blank; perform cold rolling or room-temperature drawing on the plate blank; perform a second heat preservation treatment and hot pressing and leveling on the plate blank after cold rolling or room-temperature drawing to prepare a medical magnesium alloy sheet; wherein, the rolling speed of cold rolling is 0.3 m / s - 1 m / s, the single-pass reduction rate of cold rolling is 6% - 10%, the temperature of the second heat preservation treatment is 310 °C - 500 °C, the average grain size of the medical magnesium alloy sheet is 3.2 μm - 5 μm, and the flatness deviation ≤ 0.04 mm.

[0061] As a non-limiting example, the temperature of room-temperature drawing is 20 °C - 26 °C; for example, it can be, but is not limited to, 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, 25 °C, 26 °C or the range between any two of the above temperatures, etc.

[0062] The rolling speed of cold rolling can be, but is not limited to, 0.3 m / s, 0.35 m / s, 0.4 m / s, 0.45 m / s, 0.5 m / s, 0.55 m / s, 0.6 m / s, 0.65 m / s, 0.7 m / s, 0.75 m / s, 0.8 m / s, 0.85 m / s, 0.9 m / s, 0.95 m / s, 1 m / s, or the range between any two of the above rolling speeds, etc. When the rolling speed of cold rolling is within the above range, it is beneficial to balance the production efficiency, surface quality, and mechanical properties of rolling.

[0063] The reduction per pass of cold rolling can be, but is not limited to, 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, 8%, 8.2%, 8.4%, 8.6%, 8.8%, 9%, 9.2%, 9.4%, 9.6%, 9.8%, 10%, or the range between any two of the above reduction rates, etc. The reduction per pass of cold rolling facilitates the biting-in of magnesium alloy and will not generate cracks during the rolling process.

[0064] The temperature of the second heat treatment can be, but is not limited to, 310 °C, 320 °C, 340 °C, 360 °C, 380 °C, 400 °C, 420 °C, 440 °C, 460 °C, 480 °C, 500 °C, or the range between any two of the above temperatures, etc. When the temperature of the second heat treatment is within the above range, this temperature is above the recrystallization temperature of the processed material, which is beneficial to promoting grain refinement and improving the mechanical properties of the material.

[0065] It can be understood that in the preparation method of the medical magnesium alloy sheet provided by this application, plastic deformation such as hot extrusion and cold rolling or room temperature drawing is performed on the homogenized heat-treated magnesium alloy ingot, which can achieve a large true strain accumulation, induce a large number of dislocations inside the microstructure of the magnesium alloy ingot, thereby refining the grains and achieving the purpose of improving the mechanical properties of the magnesium alloy sheet; at the same time, grain refinement will affect its degradation rate, thereby achieving the organic unity of its mechanical properties and degradation properties. Finally, through the hot pressing and leveling process, the flatness can be improved while eliminating the internal stress introduced by the previous processing step, and the comprehensive properties of the magnesium alloy sheet can be appropriately regulated to meet the requirements of high mechanical properties and high flatness required for the preparation of implantable devices; and due to stress elimination, premature cracking caused by metal corrosion of magnesium alloy under stress can be effectively avoided, preventing the implantable device from failing prematurely before the treatment site heals. In addition, this preparation method has a short process flow, low production cost, high yield, and high quality stability of the product.

[0066] It can be understood that the medical magnesium alloy sheet prepared by this preparation method has similar technical solutions and advantages to the aforementioned medical magnesium alloy sheet, which will not be elaborated here again.

[0067] As shown Figure 1 in some exemplary embodiments, the method for preparing a medical magnesium alloy sheet comprises the following steps: performing a first heat preservation treatment and hot extrusion forming on a homogenized and heat-treated magnesium alloy ingot to obtain a plate blank; performing cold rolling or room-temperature drawing on the plate blank; and performing a second heat preservation treatment and hot pressing and leveling on the plate blank after cold rolling or room-temperature drawing to prepare a medical magnesium alloy sheet.

[0068] As a non-limiting example, the magnesium alloy ingot can be, but is not limited to, at least one of a medical EK30 magnesium alloy ingot and a medical WE43 magnesium alloy ingot.

[0069] In some embodiments, the pressure for hot pressing and leveling is 10 MPa - 30 MPa; for example, it can be, but is not limited to, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa, 25 MPa, 26 MPa, 27 MPa, 28 MPa, 29 MPa, 30 MPa, or the range between any two of the above pressures, etc. When the pressure for hot pressing and leveling is within the above range, the flatness of the magnesium alloy can be effectively and rapidly improved, and the magnesium alloy will not flow out of the mold due to excessive pressure and cause serious deformation.

[0070] As a possible embodiment, the pressure holding time for hot pressing and leveling is 5 min - 20 min; for example, it can be, but is not limited to, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, or the range between any two of the above pressure holding times, etc. When the pressure holding time for hot pressing and leveling is within the above range, the flatness of the magnesium alloy can be effectively improved, and the magnesium alloy will not adhere to each other due to too long a pressure holding time.

[0071] It should be noted that the pressure and pressure holding time for hot pressing and leveling can be combined in any suitable manner, and both can be selected from any of the pressures and pressure holding times for hot pressing and leveling described herein.

[0072] As a possible embodiment, the time for the second heat preservation treatment is 5 min - 25 min; for example, it can be, but is not limited to, 5 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 25 min, or the range between any two of the above times, etc.

[0073] It should be noted that the temperature and time of the second heat preservation treatment can be combined in any suitable manner, and both can be selected from any temperature and time of the second heat preservation treatment described herein respectively.

[0074] Before hot pressing and flattening, when the temperature and time for heat preservation of the plate-shaped blank are within the above ranges respectively, it is beneficial to keep the magnesium alloy within a suitable range of mechanical properties, facilitating the improvement of its flatness during hot pressing and flattening.

[0075] In some embodiments, the temperature of cold rolling is 20°C - 26°C; for example, it can be, but is not limited to, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, or the range between any two of the above temperatures, etc. When the temperature of cold rolling is within the above range, there is no need to use a heating furnace and roll heating, and the desired effect can be achieved at a lower cost.

[0076] As a possible embodiment, the rolling speed of cold rolling is 0.5 m / s - 1 m / s; for example, it can be, but is not limited to, 0.5 m / s, 0.55 m / s, 0.6 m / s, 0.65 m / s, 0.7 m / s, 0.75 m / s, 0.8 m / s, 0.85 m / s, 0.9 m / s, 0.95 m / s, 1 m / s, or the range between any two of the above rolling speeds, etc. When the rolling speed of cold rolling is within the above range, it is beneficial to balance the production efficiency, surface quality, and mechanical properties of rolling.

[0077] In some of these embodiments, the number of cold rolling passes is 1 - 3 passes; for example, it can be, but is not limited to, 1 pass, 2 passes, 3 passes, or the range between any two of the above values, etc.

[0078] In some embodiments, the drawing speed of room-temperature drawing is 0.1 m / s - 2 m / s; for example, it can be, but is not limited to, 0.1 m / s, 0.2 m / s, 0.3 m / s, 0.4 m / s, 0.5 m / s, 0.6 m / s, 0.7 m / s, 0.8 m / s, 0.9 m / s, 1 m / s, 1.1 m / s, 1.2 m / s, 1.3 m / s, 1.4 m / s, 1.5 m / s, 1.6 m / s, 1.7 m / s, 1.8 m / s, 1.9 m / s, 2 m / s, or the range between any two of the above drawing speeds, etc. When the drawing speed of room-temperature drawing is within the above range, it is beneficial to balance the production efficiency, surface quality, and mechanical properties of rolling.

[0079] As a possible implementation, the single-pass deformation rate of room-temperature drawing is ≤ 10%; for example, it can be but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range between any two of the above reduction rates, etc. Thus, the fracture of the magnesium alloy during drawing can be avoided.

[0080] In some embodiments, the temperature of the first heat preservation treatment is 300°C - 400°C; for example, it can be but not limited to 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C or the range between any two of the above temperatures, etc.

[0081] As a possible implementation, the time of the first heat preservation treatment is 1 hour - 1.5 hours; for example, it can be but not limited to 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours or the range between any two of the above times, etc.

[0082] It should be noted that the temperature and time of the first heat preservation treatment can be combined in any suitable way, and both can be selected from any of the temperatures and times of the first heat preservation treatment described herein respectively.

[0083] The "first heat preservation treatment", "second heat preservation treatment", etc. mentioned in the context are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0084] Before hot extrusion, when the temperature and time for heat preservation of the magnesium alloy ingot are within the above ranges respectively, it is beneficial for the magnesium alloy ingot to have sufficient time to fully heat up, and it will not lead to too low mechanical properties due to too long heat preservation time.

[0085] In some embodiments, the extrusion speed of hot extrusion is 0.1 m / s - 0.5 m / s; for example, it can be but not limited to 0.1 m / s, 0.15 m / s, 0.2 m / s, 0.25 m / s, 0.3 m / s, 0.35 m / s, 0.4 m / s, 0.45 m / s, 0.5 m / s or the range between any two of the above extrusion speeds, etc. When the extrusion speed of hot extrusion is within the above range, magnesium alloy sheets with better surface quality can be extruded, and it is not easy to produce wavy warping.

[0086] As a possible implementation, the pressure of hot extrusion is 150 MPa - 250 MPa; for example, it can be, but is not limited to, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 190 MPa, 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa, or the range between any two of the above pressures, etc. When the pressure of hot extrusion is within the above range, the deformation resistance of the magnesium alloy can be overcome, the material flow can be promoted, and the production efficiency, surface quality and workpiece loss can reach a balance.

[0087] It should be noted that the extrusion speed and pressure of hot extrusion can be combined in any suitable manner, and both can be selected from any of the extrusion speeds and pressures of hot extrusion described herein respectively.

[0088] In some embodiments, the thickness of the plate blank after cold rolling or room temperature drawing is 0.1 mm - 2 mm; for example, it can be, but is not limited to, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, or the range between any two of the above thicknesses, etc. Thus, a plate blank with a suitable thickness can be selected according to the final product to be prepared.

[0089] In some embodiments, the method for preparing the medical magnesium alloy sheet further includes a step of performing homogenization heat treatment on the magnesium alloy ingot.

[0090] In some alternative embodiments, the temperature of the homogenization heat treatment is 520 °C - 550 °C; for example, it can be, but is not limited to, 520 °C, 530 °C, 540 °C, 550 °C, or the range between any two of the above temperatures, etc.

[0091] In some alternative embodiments, the time of the homogenization heat treatment is 8 hours - 12 hours; for example, it can be, but is not limited to, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, or the range between any two of the above times, etc.

[0092] It should be noted that the temperature and time of the homogenization heat treatment can be combined in any suitable manner, and both can be selected from the temperature and time of the homogenization heat treatment described herein respectively.

[0093] In some embodiments, such as Figure 2As shown in the figure, the leveling fixture used for hot pressing leveling includes a lower mold 21 and an upper mold 22. The lower mold 21 is a cube with a groove 211 provided on one side surface. The groove 211 is used to hold the plate-shaped blank 212 to be leveled, and the upper mold can cover the groove.

[0094] In some alternative embodiments, the wall thickness of the groove 211 is 10 mm, and the depth of the groove 211 is 12 mm - 25 mm. Specifically, the depth of the groove can be, but is not limited to, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 25 mm, or the range between any two of the above depths, etc.

[0095] In some alternative embodiments, the length, width, and height of the lower mold 21 are 100 mm - 140 mm, 60 mm - 100 mm, and 20 mm - 30 mm respectively, and the length, width, and height of the upper mold 22 are 90 mm - 130 mm, 40 mm - 80 mm, and 25 mm - 35 mm respectively.

[0096] As a non-limiting example, the length of the lower mold 21 can be, but is not limited to, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, or the range between any two of the above values, etc. The width of the lower mold 21 can be, but is not limited to, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, or the range between any two of the above values, etc. The height of the lower mold 21 can be, but is not limited to, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, 30 mm, or the range between any two of the above values, etc.

[0097] The length of the upper mold 22 can be, but is not limited to, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, or the range between any two of the above values, etc. The width of the upper mold 22 can be, but is not limited to, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, or the range between any two of the above values, etc. The height of the upper mold 22 can be, but is not limited to, 25 mm, 27 mm, 30 mm, 33 mm, 35 mm, or the range between any two of the above values, etc.

[0098] The technical solutions of the present application will be described in detail below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. For the experimental methods without specific conditions in the following embodiments, the guidance given in the present application is preferably referred to, and it can also be carried out according to the experimental manuals or conventional conditions in the art, or according to the conditions recommended by the manufacturer, or by referring to the experimental methods known in the art.

[0099] In the following specific embodiments, regarding the measurement parameters of raw material components, without special instructions, there may be slight deviations within the weighing accuracy range. Regarding temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0100] I. Preparation of Medical Magnesium Alloy Sheets

[0101] Example 1

[0102] Step S1: Select a medical EK30 magnesium alloy ingot material and perform homogenization heat treatment by holding the material at 540 °C for 10 hours.

[0103] Step S2: Hold the homogenized medical EK30 magnesium alloy ingot at 350 °C for 1 hour, and then perform hot extrusion according to an extrusion ratio of 50:1 to obtain a plate-shaped blank with a thickness of 1.5 mm. Among them, the extrusion speed of hot extrusion is 0.2 m / s, and the pressure is 150 MPa.

[0104] Step S3: Perform one-pass cold rolling on the plate-shaped blank, control its thickness after rolling to be 1.4 mm, and then perform cutting to obtain small plates with a width of 60 mm and a length of 100 mm. Among them, the temperature of cold rolling is 24 °C, and the rolling speed is 0.5 m / s.

[0105] Step S4: Heat the small plate obtained after cutting to 400 °C and hold it for 20 min, and then perform hot press leveling. The pressure applied for leveling is 30 MPa, and the pressure holding time is 10 min to obtain a medical magnesium alloy sheet.

[0106] Example 2

[0107] Step S1: Select a medical WE43 magnesium alloy ingot material and perform homogenization heat treatment by holding the material at 550 °C for 9 hours.

[0108] Step S2: Hold the homogenized medical WE43 magnesium alloy ingot at 400 °C for 1 hour, and then perform hot extrusion according to an extrusion ratio of 50:1 to obtain a plate-shaped blank with a thickness of 1.2 mm. Among them, the extrusion speed of hot extrusion is 0.3 m / s, and the pressure is 200 MPa.

[0109] Step S3: Perform one-pass cold rolling on the plate-shaped blank, control its thickness after rolling to be 1.1 mm, and then perform cutting to obtain small plates with a width of 100 mm and a length of 100 mm. Among them, the temperature of cold rolling is 25 °C, and the rolling speed is 0.8 m / s.

[0110] Step S4: Heat the small plate obtained after cutting to 400 °C and hold it for 20 min, and then perform hot press leveling. The pressure applied for leveling is 25 MPa, and the pressure holding time is 15 min to obtain a medical magnesium alloy sheet.

[0111] Example 3

[0112] Step S1: Select a medical WE43 magnesium alloy ingot material and perform homogenization heat treatment on the material at 520 °C for 12 hours to achieve uniform heat treatment.

[0113] Step S2: Keep the medical WE43 magnesium alloy ingot after homogenization heat treatment at 400 °C for 1.5 hours, and then perform hot extrusion according to an extrusion ratio of 50:1 to obtain a plate-shaped blank with a thickness of 1.4 mm. Among them, the extrusion speed of hot extrusion is 0.4 m / s, and the pressure is 150 MPa.

[0114] Step S3: Perform one-pass room-temperature drawing on the plate-shaped blank, control its thickness after room-temperature drawing to be 1.35 mm, and then perform cutting to obtain small plates with a width of 80 mm and a length of 100 mm. Among them, the temperature of room-temperature drawing is 20 °C, and the room-temperature drawing speed is 1 m / s.

[0115] Step S4: Heat the small plate obtained after cutting to 350 °C and keep it warm for 25 min, and then perform hot pressing and leveling. The pressure applied for leveling is 30 MPa, and the pressure holding time is 10 min to obtain a medical magnesium alloy sheet.

[0116] Comparative Example 1

[0117] The preparation methods of Comparative Example 1 and Example 1 are similar, the difference is that: in step S4 of Comparative Example 1, mechanical leveling is used instead of hot pressing and leveling; others are the same. The specific steps of step S4 in Comparative Example 1 are as follows:

[0118] Use a mechanical leveling machine for experiments. The leveling machine has 20 rolls arranged alternately. The leveling force is 3 KN. The sheet is placed along the rolling direction. The inlet roll gap is 0.4 mm, and the outlet roll gap is 1.3 mm. Repeat leveling 3 times, and it is impossible to achieve ideal flatness and mechanical properties.

[0119] Comparative Example 2

[0120] The preparation methods of Comparative Example 2 and Example 1 are similar, the difference is that: in step S3 of Comparative Example 2, hot rolling is used instead of cold rolling, and others are the same. The specific steps of step S3 in Comparative Example 2 are as follows:

[0121] Step S3: Perform one-pass hot rolling on the plate-shaped blank, control its thickness after rolling to be 1.4 mm, and then perform cutting to obtain small plates with a width of 60 mm and a length of 100 mm. Among them, the temperature of hot rolling is 300 °C, and the rolling speed is 0.5 m / s.

[0122] Comparative Example 3

[0123] The preparation methods of Comparative Example 3 and Example 1 are similar, the difference is that: in Comparative Example 3, step S3 is not performed, and others are the same.

[0124] Comparative Example 4

[0125] The preparation methods of Comparative Example 4 and Example 1 are similar, the difference lies in: in step S4 of Comparative Example 4, the heat preservation temperature is 250°C, and others are the same. The specific steps of step S4 in Comparative Example 4 are as follows:

[0126] Step S4: Heat the small plate obtained after cutting to 250°C, keep it warm for 20 min, then perform hot pressing and leveling. The pressure applied for leveling is 30 MPa, and the pressure holding time is 10 min, to obtain a medical magnesium alloy sheet.

[0127] II. Structure and performance tests

[0128] 1. Flatness range test

[0129] Perform flatness range tests on the medical magnesium alloy sheets prepared in the above-mentioned examples and Comparative Examples 1 and 4. The test method is: place the sample on a marble measuring platform, use a micrometer to measure 9 points on the sample, the points are arranged in a nine-square grid, and subtract the minimum value from the maximum value to obtain the range test result as shown in Table 1.

[0130] Table 1

[0131]

[0132] From the comparison of the results of Examples 1-3 and Comparative Example 1 in Table 1, it can be seen that in the preparation method of the medical magnesium alloy sheet provided in this application, the flatness range of the medical magnesium alloy sheet prepared by hot pressing and leveling is less than 0.04 mm; while the flatness range of the medical magnesium alloy sheet prepared by traditional mechanical leveling is unstable, and the maximum flatness range can reach about 0.15 mm. From the comparison of the results of Examples 1-3 and Comparative Example 4, it can be seen that in the process of preparing the medical magnesium alloy sheet in this application, by regulating the heat preservation temperature, it is beneficial to further reduce the flatness range and improve the flatness of the sheet.

[0133] 2. Average grain size test

[0134] Perform average grain size tests on the medical magnesium alloy sheets prepared in the above-mentioned examples and Comparative Examples 2 and 3-4. The test method is: after the sample is corroded by a special corrosion agent for JDBM magnesium alloy, it is measured by the straight-line intercept method under a metallographic microscope. The test results are shown in Table 2.

[0135] Table 2

[0136]

[0137] As can be seen from the results in Table 2, the average grain size of the medical magnesium alloy sheets prepared in this application is below 5 μm, indicating that the preparation method of this application is beneficial to grain refinement and reduces the average grain size of the medical magnesium alloy sheets. From the comparison of the results of Example 1 and Comparative Example 2, it can be seen that the average grain size of the medical magnesium alloy sheets prepared by hot rolling is large and cannot reach the ideal average grain size range.

[0138] 3. Tensile property test

[0139] Tensile property tests were carried out on the medical magnesium alloy sheets prepared in the above-mentioned examples and comparative examples. The test method was as follows: a universal tensile testing machine was used, and the tensile specimens were prepared according to GBT 16865-2023. The test results are shown in Table 3.

[0140] Table 3

[0141]

[0142] As can be seen from the results in Table 3, the preparation method of this application can effectively improve the mechanical properties of the medical magnesium alloy sheets. From the comparison of the results of Example 1 and Comparative Example 1, it can be seen that mechanical leveling cannot achieve the ideal mechanical properties.

[0143] From the comparison of the results of Example 1 and Comparative Example 2, it can be seen that when hot rolling is used instead of cold rolling, there is no obvious difference in the mechanical properties of the prepared magnesium alloy sheets. However, hot rolling requires the addition of equipment such as a holding furnace and a hot rolling mill, and the power consumption and time cost are far higher than those of cold rolling. Therefore, its production cost is higher than that of cold rolling.

[0144] 4. Degradation rate test

[0145] Degradation rate tests were carried out on the medical magnesium alloy sheets prepared in the above-mentioned examples and comparative examples. The test method was as follows: weight loss corrosion test was carried out using hank’s solution, the test referred to ASTM G31, and the solution formula referred to YY / T0695-2008. The test results are shown in Table 4.

[0146] Table 4

[0147]

[0148] As can be seen from the results in Table 4, the degradation rate of the in-vivo implant devices made of the medical magnesium alloy sheets prepared in this application is in the range of 0.08 mm / year - 0.1 mm / year, which can effectively avoid human magnesium element poisoning caused by too fast degradation rate of the in-vivo implant devices, and realizes the organic unity of mechanical properties and degradation properties.

[0149] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0150] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A medical magnesium alloy sheet, characterized in that, The average grain size of the medical magnesium alloy plate is 3.2 μm-5 μm, and the flatness range is ≤0.04 mm.

2. The medical magnesium alloy sheet according to claim 1, characterized in that, The average grain size of the medical magnesium alloy plate is 3.9 μm to 5 μm; and / or The degradation rate of the in vivo implantable device made of the medical magnesium alloy plate is 0.08 mm / year to 0.1 mm / year.

3. A preparation method of a medical magnesium alloy sheet, characterized in that, The steps include: The magnesium alloy ingot after homogenization heat treatment is subjected to a first heat preservation treatment and hot extrusion in sequence to prepare a plate-shaped blank; cold rolling or room temperature drawing the plate-shaped blank; The plate-shaped blank after cold rolling or room temperature drawing is subjected to a second heat preservation treatment and hot pressing and leveling in sequence to prepare the medical magnesium alloy plate; Among them, the rolling speed of the cold rolling is 0.3m / s-1m / s, the single-pass reduction rate of the cold rolling is 6%-10%; the temperature of the second insulation treatment is 310℃-500℃, the average grain size of the medical magnesium alloy plate is 3.2μm-5μm, and the flatness range is ≤0.04mm.

4. The preparation method according to claim 3, characterized in that, The pressure of hot pressing leveling is 10MPa-30MPa, and the holding time is 5min-20min.

5. The preparation method according to claim 3, characterized in that, The second heat preservation treatment time is 5min-25min.

6. The preparation method according to claim 3, characterized in that, The cold rolling temperature is 20°C-26°C, the rolling speed is 0.5m / s-1m / s, and the number of passes is 1-3; and / or The drawing speed of room temperature drawing is 0.1m / s-2m / s, and the single-pass deformation rate is ≤10%.

7. The preparation method according to claim 3, characterized in that, The temperature of the first heat preservation treatment is 300° C.-400° C., and the time is 1 hour-1.5 hours.

8. The preparation method according to claim 3, characterized in that, The extrusion speed of hot extrusion is 0.1m / s-0.5m / s, and the pressure is 150MPa-250MPa.

9. The preparation method according to claim 3, characterized in that, The thickness of the plate-shaped blank after cold rolling or room temperature drawing is 0.1 mm to 2 mm.

10. The preparation method according to any one of claims 3 to 9, characterized in that, The leveling fixture used in the hot pressing leveling includes a lower mold and an upper mold. The lower mold is a cube with a groove on one side surface. The groove is used to hold the plate-shaped blank to be leveled, and the upper mold can cover the groove.

11. The preparation method according to claim 10, characterized in that, The wall thickness of the groove is 10 mm, and the depth of the groove is 12 mm to 25 mm; and / or The length, width and height of the lower mold are 100mm-140mm, 60mm-100mm and 20mm-30mm respectively, and the length, width and height of the upper mold are 90mm-130mm, 40mm-80mm and 25mm-35mm respectively.

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