A three-dimensional controllable directional degradation medical metal material and a preparation method thereof

Abstract

The application discloses a three-dimensional controllable directional degradation medical metal material and a preparation method thereof. The metal material has an inner-outer layered coating structure; an interface layer is formed between the inner and outer layers of the metal material; and a sub-region differential micro-nano structure layer is further formed on the surface of the outer layer of the metal material. The sub-region differential micro-nano structure layer is distributed with n unit corrosion zones (n=1-5) from one end to the other end in the longitudinal direction, and each unit corrosion zone is sequentially composed of an induced corrosion zone, a stable corrosion zone and a final corrosion zone in the longitudinal direction. The inner layer of the metal material is Mg, a Mg alloy, Zn or a Zn alloy, and the outer layer of the metal material is Mg, a Mg alloy, Zn, a Zn alloy, Fe or a Fe alloy. The three-dimensional controllable directional degradation metal material prepared by the application can be applied to the field of tissue repair of organisms, including the repair of orthopedics, cardiology and other fields, and meets the needs of different implant environments.

Description

Technical Field

[0001] The present invention relates to the technical field of laser surface modification and composite material processing, and in particular to a method for preparing a three-dimensional controllable directionally degradable magnesium / zinc composite medical metal material. Background Art

[0002] With the aging of my country's population and the improvement of living standards, fractures caused by accidental falls, traffic accidents, and other factors are increasing year by year. Internal fixation is an important method for treating fractures. Currently, internal fixation implants used clinically are primarily composed of corrosion-resistant metals such as stainless steel, titanium alloys, and cobalt-chromium alloys. Since these implants remain in the body as foreign bodies for a long time after implantation, they can irritate surrounding tissues to varying degrees, causing adverse reactions such as inflammation and even allergies, often requiring secondary surgical removal. To address this challenge, a key approach is the development of biodegradable medical metal materials. However, a major challenge facing the widespread application of biodegradable metals is the uneven degradation, which leads to increased instability in their degradation cycle and mechanical properties. For implants, to maintain structural and mechanical integrity during the initial implantation phase and achieve rapid degradation during the later stages, it is desirable for corrosion to begin at certain non-critical locations and proceed in a specific order. Therefore, regulating the degradation sequence of biodegradable metal materials has become a key focus for researchers in this field.

[0003] CN1085255022A discloses a fast directional biodegradable hemostatic clip and a preparation method thereof, which realizes directional degradation from the outside to the inside by laser modification treatment of the outer surface and side of the hemostatic clip (iron-based material). However, it is a laser treatment of the outer surface and side as a whole, which cannot regulate the starting position of corrosion degradation, nor can it realize directional degradation from the end to the center. CN103892884A discloses a directional degradable and absorbable tube bracket and a preparation method thereof, which makes the outside and inside of the vascular clamp material have different microstructures and potential differences through rolling and heat treatment, and the grain size of the outside is larger than the grain size of the inside, thereby realizing directional degradation from the outside to the inside. However, this method can only treat the surface of the material as a whole, and cannot accurately regulate different areas, that is, it cannot realize directional degradation of corrosion induced from a specific part. CN111939327A discloses a coated metal material with controlled temporal and spatial degradation and its preparation method. By applying a polymer coating to the surface of the degradable metal and modifying the interface layer to enhance the coating's bonding ability, the material achieves directional degradation from the coating to the base metal. The degradation time can be adjusted by varying the coating thickness. However, this method only coats the entire surface of the material and has no effect on regulating the degradation behavior of the base metal after the coating material has completely degraded.

[0004] In summary, the currently reported methods for regulating the degradation sequence of degradable metals can only achieve layered degradation from the outer layer to the inner layer, and the corrosion behavior of each layer of material is uncontrollable, and cannot achieve corrosion degradation from a specific site and in a specific direction, that is, three-dimensional controllable directional degradation of degradable metal materials cannot be achieved. SUMMARY

[0005] The present application aims to overcome the deficiency that the degradation sequence of current degradable metal materials cannot be accurately regulated, and provides a three-dimensional controllable directional degradation medical metal material, which is composed of two degradable metals with different compositions in an inner-outer layered coating structure, and the surface of the outer layer metal is longitudinally arranged from the end to the center as a groove-shaped structure surface, a periodic nano-wavy structure surface, and a polished surface. A preparation method of the three-dimensional controllable directional degradation medical metal material is also provided, which first prepares a layered coated degradable metal material by rolling process, controls the coating rate and interface performance by changing the rolling process, and then prepares different micro-nano structures on the material surface by using ultrafast pulsed laser, and controls the structure morphology and proportion by changing the laser process. The three-dimensional controllable directional degradation metal material prepared by the present application can be applied to the field of tissue repair of living organisms, including repair in the fields of orthopedics, cardiovascular surgery, etc., and meets the needs of different implant environments.

[0006] The technical scheme of the present application is:

[0007] A three-dimensional controllable directional degradation medical metal material, which has an inner-outer layered coating structure; in the inner-outer layered coating structure, the interface between the inner and outer layers is a diffusion layer or a reaction layer; the surface of the outer layer metal material further has a regionally differentiated micro-nano structure layer, which is longitudinally distributed with n unit corrosion zones (n=1-5) from one end to the other end, each unit corrosion zone is sequentially an induced corrosion zone, a stable corrosion zone, and a final corrosion zone, wherein the induced corrosion zone is a groove-shaped structure surface, the stable corrosion zone is a periodic nano-wavy structure surface, and the final corrosion zone is a polished surface; the thickness of the regionally differentiated micro-nano structure layer is 0.01-20 μm.

[0008] The width of the unit corrosion zone ranges from 2 to 50 mm.

[0009] The thickness ratio of the outer layer material to the inner layer material in the inner-outer layered coating structure is 2:3-7:3; the thickness of the inner layer metal ranges from 0.6 to 6 mm.

[0010] The electrode potential of the inner layer metal material is lower than that of the outer layer metal material, forming a certain potential difference; the potential difference is preferably 0.05-1.2 V.

[0011] The surface of the induced corrosion area is a groove-like structure, with a single groove width between 40 and 70 μm and a depth between 1 and 20 μm; the groove has arc-shaped transverse stripes, and the spacing between the arc-shaped transverse stripes is 10 to 30 μm; the surface of the stable corrosion area is a periodic nano-corrugated structure, with a corrugation period between 400 and 600 nm.

[0012] In the surface of the outer metal material, the area ratio of the grooved structure surface, the nano-corrugated structure surface and the polished surface is preferably between 1:0.8:0.6 and 1:1.2:0.8.

[0013] The thickness of the interface layer is 1 to 50 μm.

[0014] The diffusion layer interface layer is a Mg solid solution, a Zn solid solution or a Fe solid solution layer; the reaction layer interface layer is a Mg-Zn intermediate phase layer or a Fe-Zn intermediate phase layer;

[0015] The inner layer metal material is Mg, Mg alloy, Zn or Zn alloy, the outer layer metal material is Mg, Mg alloy, Zn, Zn alloy, Fe or Fe alloy, and the inner and outer layer metals have different compositions.

[0016] In the Mg alloy, the alloying elements are one or more of Zn, Ca, Li, Al, Cu, Fe, Mn, and Zr; in the Zn alloy, the alloying elements are one or more of Mg, Ca, Li, Si, Fe, Mn, and Zr; in the Fe alloy, the alloying elements are one or more of Mn, Si, Cr, and Co.

[0017] The method for preparing the three-dimensional controllable directionally degradable medical metal material comprises the following steps:

[0018] 1) heating the outer layer-coated inner layer layered composite billet to 200-300° C., keeping the temperature for 10-30 minutes, and then rolling the billet for 3-6 passes, with a deformation of 20-35% per pass and a total deformation of 45-85%, to obtain a medical metal material with an inner and outer layered coating structure;

[0019] The total thickness of the composite blank is 15 to 80 mm, and the thickness of the inner metal blank is 5 to 40 mm;

[0020] 2) Heat treatment: one of the following two methods:

[0021] Method 1: When the inner layer is a layered cladding structure metal material of Mg and its alloys or Zn and its alloys and the outer layer is a layered cladding structure metal material of Mg and its alloys or Zn and its alloys, the heat treatment temperature is 250-320°C and the time is 10-30 minutes; a reaction layer interface or a diffusion layer interface is obtained;

[0022] Alternatively, in the second method, when the inner layer is a layered cladding structure metal material of Mg and its alloys or Zn and its alloys and the outer layer is Fe and its alloys, the heat treatment temperature is 280-330°C and the time is 15-40 minutes to obtain a reaction layer interface or a diffusion layer interface;

[0023] 3) Laser treatment: grinding and polishing the metal material obtained in step 2), and ultrasonically cleaning it in alcohol for 10 to 15 minutes;

[0024] The prepared plate is placed on a nanosecond pulse laser processing table, and the protector is turned on for laser processing. The average laser power is 50-90W, the pulse frequency is 10-50kHz, the pulse width is 6-270ns, and the scanning speed is 500-1000mm / s to prepare a groove structure in the induced corrosion area; then the plate is placed on a femtosecond pulse laser processing table, and the protective gas is turned on for laser processing. The laser wavelength is 960-1030nm, the average power is 0.1-0.6W, the pulse frequency is 1-5000Hz, the pulse width is 140-300fs, and the scanning speed is 0.05-4mm / s to prepare a periodic nano-corrugated structure in the stable corrosion area.

[0025] Step 3) The protective gas is argon, and the flow rate is preferably 3 to 10 L / min.

[0026] The essential features of the present invention are:

[0027] The application adopts rolling compounding method and ultrafast pulse laser to prepare degradable metal material with layer compounding structure and surface partition differentiation structure, and realizes three-dimensional controllable directional degradation function. The application solves the problem that traditional degradable metal material cannot be accurately controlled in three-dimensional space degradation. The material takes layer compounding structure as a matrix, controls the potential difference between inner and outer layers to be between 0.05-1.2V, so that the degradation rate of the inner layer metal is faster than that of the outer layer metal, and meanwhile, serious galvanic corrosion does not occur between the two metals, directional degradation from the inner layer to the outer layer is realized. By controlling the thickness ratio of the outer layer material to the inner layer material to be 2:3-7:3, the outer layer metal can still play a mechanical supporting role after the inner layer metal disappears. By nanosecond laser modification treatment, the induced corrosion area of the outer layer metal has a groove-shaped surface morphology, the roughness of the area is increased, the exposed surface area is increased, and the thermal effect of the nanosecond laser causes the material surface to react to generate a small amount of oxide and form a micro galvanic corrosion with the matrix, so that the part preferentially corrodes. At the same time, by femtosecond laser modification treatment, a stable corrosion area with periodic nanometer ripple structure is prepared in the adjacent area of the induced corrosion area. The structure also increases the roughness of the sample, but the change of the induced corrosion area is not large, and the cold working effect of the femtosecond laser does not change the phase composition of the material surface, forming a stable corrosion area, and starting to corrode and degrade after the induced corrosion area is corroded. The polished surface without laser treatment has the smallest roughness and constitutes the final corrosion area. The area ratio of the three parts is preferably between 1:0.8:0.6 and 1:1.2:0.8, to ensure that the outer layer metal realizes the degradation of the induced corrosion area, the stable corrosion area and the final corrosion area in sequence. At the same time, by adopting a heat treatment process to optimize the bonding interface of the inner and outer layers, a diffusion layer interface or a reaction layer interface is obtained, the interface layer thickness is between 1-20um, which ensures the bonding strength of the two metals, and also does not affect the overall degradation order.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] 1) Three-dimensional controllable directional degradation of medical metal material is realized. The application adopts rolling compounding to successfully prepare degradable metal material with layer compounding structure, and adopts pulse laser to successfully construct surface partition differentiation structure, so as to realize three-dimensional controllable directional degradation from the inner layer to the outer layer, then from the end to the center, and designable, predictable and controllable material degradation behavior.

[0030] 2) The maximum structural and mechanical integrity of the material is maintained during the degradation process. The present application adopts an inner-outer layered composite structure, the inner layer metal preferentially corrodes and degrades, and the outer layer metal maintains structural integrity and provides sufficient mechanical support during this process; when the inner layer metal completely disappears, the outer layer metal starts to corrode and degrade from the designed end induced corrosion zone to the central part, avoiding the phenomenon of partial material falling off and loss of structural and mechanical integrity caused by uneven corrosion.

[0031] 3) Excellent interface bonding performance. The inner and outer layers of the material in the present application are both metal materials, and good metallurgical bonding is formed through interface atomic diffusion during rolling, avoiding the poor interface bonding performance caused by the large difference in material performance (such as metal and polymer coating, metal and ceramic coating, etc.), which is prone to interface cracking, falling off and inducing crevice corrosion during the degradation process, thereby ensuring the three-dimensional directional degradation of the prepared material.

[0032] 4) High processing precision. The present application uses pulsed laser to perform surface modification treatment on the material, and the laser beam motion is controlled by adjusting the laser scanning galvanometer, and the minimum processing path distance can be controlled to 0.1 mm, and the thermal stress and heat affected zone during processing are very small, avoiding the destruction of the surface of the adjacent area; and the partitioned differential structure processing of the complex structure surface can be realized.

[0033] 5) Good application prospect. The three-dimensional controllable directional degradation metal material prepared by the present application can be applied to the field of tissue repair of biological body, including repair in the field of orthopedics, cardiovascular department, etc. At the same time, the present application can adjust the thickness ratio of the inner and outer layers, and the area ratio of different surface structure regions to control the degradation rate and time, and meet the needs of different implant environments. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A schematic diagram of the three-dimensional controllable directional degradation medical metal structure designed by the present application;

[0035] Figure 2 The surface morphology of the induced corrosion zone of the outer layer metal in Example 1;

[0036] Figure 3 The surface morphology of the stable corrosion zone of the outer layer metal in Example 1.

[0037] Wherein, 1 - induced corrosion zone; 2 - stable corrosion zone; 3 - final corrosion zone; 4 - outer layer metal; 5 - inner layer metal. DETAILED DESCRIPTION

[0038] The technical solutions in the examples of the present application will be described clearly and completely in combination with the drawings in the examples of the present application, and the described examples are only part of the embodiments of the present application, and are not a limitation on the protection scope of the present application.

[0039] As Figure 1 indicated, the three-dimensional controllable directional degradation medical metal material provided by the application is composed of an inner layer metal and an outer layer metal. Overall, the degradation process of the medical metal can be described as follows:

[0040] Since the standard electrode potential of the inner layer metal is lower, its degradation rate is faster, so the inner metal will degrade preferentially, at which time the outer metal is still intact and can provide effective mechanical support. The first part of the outer metal to contact the body fluid is the surface layer part treated by laser, and the induced corrosion zone 1 at the end will preferentially degrade due to its rougher surface and partial oxides. Subsequently, the degradation process is guided from zone 1 to zone 2, and zone 3 has a relatively lower surface roughness due to the nature of the polished surface, so the degradation sequence is after zones 1 and 2, thereby achieving a three-dimensional controllable directional degradation sequence. In this way, the required mechanical integrity can be maintained within a certain degradation period, and after completing the service purpose, the implant will completely degrade and disappear in the body.

[0041] Referring to Figure 1 , the application provides a preparation method of a three-dimensional controllable directional degradation metal material, which specifically comprises the following steps:

[0042] S1, selecting two metal materials with a potential difference of 0.05-1.2V as a blank, the outer layer material has a higher potential, and the inner layer material has a lower potential, to form an inner-outer layer composite blank;

[0043] S2, heating the composite blank, and then performing multiple rolling processing and precision finishing to obtain an inner-outer layer composite plate or rod;

[0044] S3, heat treating the composite plate or rod, and then polishing and polishing it, and placing it in alcohol for ultrasonic cleaning for 10-15 minutes;

[0045] S4, dividing the polished composite plate into 1-5 unit corrosion zones in sequence along the longitudinal direction, and each corrosion zone is divided into an induced corrosion zone, a stable corrosion zone, and a final corrosion zone in sequence along the longitudinal direction; placing the composite plate on a nanosecond laser workstation, opening the protective gas, and performing nanosecond laser modification treatment to obtain a groove-shaped structure and form the induced corrosion zone;

[0046] S5, placing the composite plate on a femtosecond laser workstation, opening the protective gas, and performing femtosecond laser modification treatment to obtain a periodic nanometer ripple structure and form the stable corrosion zone morphology; the polished surface not treated by laser forms the final corrosion zone.

[0047] Specifically, in step S1, two metal materials with a potential difference of 0.05-1.2V are selected as the blank, the outer layer material has a higher potential, and the inner layer material has a lower potential.

[0048] In the preparation method of the three-dimensional controllable directional degradation metal material provided in the embodiment of the application, the raw materials are magnesium and its alloys, zinc and its alloys, and iron and its alloys.

[0049] The alloying elements of magnesium are one or more of Zn, Ca, Li, Al, Cu, Fe, Mn and Zr; the alloying elements of zinc are one or more of Mg, Ca, Li, Si, Fe, Mn and Zr; and the alloying elements of iron are one or more of Mn, Si and Cr.

[0050] The potential difference of the selected materials should be between 0.05-1.2V. If the potential difference is lower than 0.05V, the degradation speed of the inner and outer layer materials will not be significantly different, and the degradation sequence from the inside to the outside cannot be ensured. If the potential difference is higher than 1.2V, serious galvanic corrosion will occur between the inner and outer layer materials, which will interfere with the degradation process. Since the degradation speed of the degradable metal is inversely proportional to the standard electrode potential, the lower the potential, the faster the degradation speed. Therefore, to ensure the degradation sequence from the inside to the outside, the potential of the inner layer material should be lower than that of the outer layer material.

[0051] In step S2, the composite blank is heated and then subjected to multiple rolling processes and precision sizing to obtain a composite sheet with an inner and outer layer.

[0052] Since rolling can increase the plasticity of the material, the composite ingot needs to be heated before rolling. The heating is performed in a resistance furnace, and the heating temperature is controlled at 200-300℃, and the holding time is 10-30min. The selection of the heating temperature should aim to reduce the deformation resistance of the material and ensure the coordinated deformation of the two metals in the subsequent rolling process. At the same time, the heating temperature should not be too high, otherwise overheating or overburning may occur, or a thick brittle phase layer may be generated in the interface area due to atomic diffusion reaction. The holding time should not be too long to improve the production efficiency.

[0053] In the rolling process, the single pass deformation amount should not be too large to avoid defects on the surface of the material, and the thickness ratio of the inner and outer layers should be controlled. The thickness of the outer layer material accounts for 40%-70% of the total thickness of the layered composite material. If the outer layer material is too thin, the outer layer metal will not be able to provide mechanical support after the degradation of the inner layer structure. If the outer layer metal is too thick, the overall degradation process will be affected.

[0054] In step S3, the composite sheet is subjected to heat treatment, and then cut to a suitable length by wire cutting and polished and placed in alcohol for ultrasonic cleaning for 10-15min.

[0055] The composite plate is heat treated to optimize the composite interface, to obtain a reaction layer interface or a diffusion layer interface, and to reduce and overcome the mismatch factors of the bonding site.

[0056] In step S4, the polished composite plate is sequentially divided into 1-5 single-unit corrosion zones along the longitudinal direction, each of which is sequentially divided into an induced corrosion zone, a stable corrosion zone, and a final corrosion zone. The composite plate is placed on a nanosecond laser workstation, a protective gas is turned on, and nanosecond laser modification treatment is performed to obtain a groove-shaped structure and form the induced corrosion zone.

[0057] The laser parameters are selected as follows: a laser output central wavelength of 1064(±1) nm, an average power of 50-90 W, a pulse frequency of 10-50 kHz, a pulse width of 6-270 ns, and a scanning speed of 500-1000 mm / s.

[0058] In step S5, the composite plate is placed on a femtosecond laser workstation, a protective gas is turned on, and femtosecond laser modification treatment is performed to obtain a periodic nanometer ripple structure and form the stable corrosion zone morphology. The polished surface without laser treatment forms the final corrosion zone.

[0059] The laser parameters are selected as follows: a laser wavelength of 960-1030 nm, a pulse width of 140-300 fs, a pulse frequency of 1-5000 Hz, a power of 0.1-0.6 W, and a scanning speed of 0.05-4 mm / s.

[0060] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further illustrated below with specific examples.

[0061] Example 1

[0062] In this example, AZ31 magnesium alloy is used as the inner layer metal, and its chemical mass percentage is as follows: Al: 3%, Zn: 0.8%, Mn: 0.4%, and the rest is Mg. The thickness of the inner layer is 10 mm. Industrial pure zinc (≥99.79 wt.%) is used as the outer layer cladding material. The potential difference between the inner and outer layers is 0.81 V, and the total thickness of the composite blank is 36 mm.

[0063] The zinc-coated magnesium composite blank is placed in a resistance heating furnace and heated to 300℃, and then heat treated for 10 min. Then, multi-pass rolling treatment is performed. The rolling passes are 4 passes, the single-pass deformation amount is 25%, and the total deformation amount is 76%. A zinc-coated magnesium composite plate with a length of 230 mm, a width of 40 mm, a total thickness of 8.8 mm, an inner layer metal thickness of 3.5 mm, and a thickness ratio of the outer layer to the inner layer of 3:2 is obtained.

[0064] The composite sheet was placed in a muffle furnace for heat treatment at 280°C for 20 minutes, and then cooled to room temperature. Metallographic microscope observation revealed that a Mg-Zn intermediate phase reaction layer interface was obtained between the inner and outer metal layers, with a thickness of 4.2 μm. The composite sheet was then wire-cut to a length of 90 mm, and was ground and polished with 2000 mesh sandpaper, and ultrasonically cleaned in alcohol for 15 minutes.

[0065] Afterwards, the composite plate was placed on the laser workbench, the protective gas was turned on at a flow rate of 4 L / min, and the induced corrosion area and the stable corrosion area were processed in sequence from one end to the center (longitudinal direction) of the composite plate using nanosecond laser and femtosecond laser, respectively, and part of the center was retained as a polished surface, thereby forming a unit corrosion area, as shown in the attached figure. Figure 1 As shown in the figure, at the same time, the same process is used on the other end of the composite plate to process the induced corrosion area and the stable corrosion area from the end to the center in sequence, and form another unit corrosion area with the polished surface reserved in the center, so that a total of two unit corrosion areas are obtained on the material surface. Among them, the nanosecond laser parameters are: laser wavelength 1064nm, pulse frequency 50kHz, pulse width 210ns, laser power 90W, scanning speed 600mm / s, to obtain a grooved structure surface, forming an induced corrosion area, the groove width is 70μm, the depth is 20μm, and the arc corrugation spacing is 12μm, as shown in the attached figure. Figure 2 As shown, the surface area of ​​the groove structure in each unit corrosion zone is 13 cm 2 .

[0066] The femtosecond laser parameters are: laser wavelength 1030nm, pulse frequency 1000Hz, pulse width 160fs, power 0.1W, scanning speed 0.5mm / s, to obtain a nano-corrugated surface structure, forming a stable corrosion area, the corrugation period is 400nm, and the depth is 11nm. Figure 3 As shown, the surface area of ​​the corrugated structure of each unit corrosion zone is 13cm 2 The area ratio of the grooved surface, nano-corrugated surface, and polished surface in each unit corrosion zone is 1:1:0.8. The grooved surface is light gray, the nano-corrugated surface is gray-black, and the polished surface has a metallic luster.

[0067] The prepared material was tested in vitro and indoor immersion experiments according to ASTM G31-21. Samples were first weighed and recorded, then immersed in simulated body fluid (SBF). An electrically heated constant-temperature water tank maintained the sample temperature at 37°C. The SBF solution was replaced every two days, and the pH was monitored using a pH meter to maintain a constant pH of approximately 7.4. The results showed that after seven days of immersion in the simulated body fluid, the inner metal layer of the material corroded and lost approximately 30% of its weight, while the outer metal structure remained intact. After 20 days, the inner metal layer disappeared, while the induced corrosion zone of the outer metal exhibited severe corrosion, while the nano-ripple structure remained visible on the surface of the stable corrosion zone. After 50 days, the induced corrosion zone of the outer metal disappeared, while the stable corrosion zone exhibited severe corrosion, and pitting corrosion was observed in the final corrosion zone. This demonstrated a directional degradation effect, first from the inner layer to the outer layer, and then from the ends toward the center.

[0068] Example 2

[0069] In this embodiment, Mg-0.5Zn alloy is selected as the inner layer metal with a thickness of 6mm; Zn-0.5Li is used as the outer layer coating material, the potential difference between the inner and outer metal layers is 0.65V, and the total thickness of the composite blank is 20mm.

[0070] The zinc-clad magnesium composite billet was placed in a resistance heating furnace and heated to 250°C, kept warm for 15 minutes, and then subjected to multi-pass rolling treatment, with 3 rolling passes, a single pass deformation of 22%, and a total deformation of 50%. A zinc-clad magnesium composite sheet with a length of 216 mm, a width of 31 mm, a total thickness of 9.9 mm, an inner layer metal thickness of 4.5 mm, and a thickness ratio of the outer layer to the inner layer of 6:5 was obtained.

[0071] The composite sheet was placed in a muffle furnace for heat treatment at 320°C for 15 minutes, and then cooled to room temperature with the furnace. A Mg-Zn intermediate phase reaction layer interface with a thickness of 8.2 μm was obtained between the inner and outer metal layers. The composite sheet was then wire-cut to a length of 90 mm, and was ground and polished with 2000 mesh sandpaper, and ultrasonically cleaned in alcohol for 15 minutes.

[0072] Afterwards, the composite sheet was placed on a laser workbench, and the protective gas was turned on at a flow rate of 6L / min. Nanosecond laser and femtosecond laser were used to process the induced corrosion area and stable corrosion area along the longitudinal direction of the composite sheet from one end to the other, respectively. The other end retained the polished surface, thereby obtaining a total of one unit corrosion area on the material surface. Among them, the nanosecond laser parameters were: laser wavelength 1064nm, pulse frequency 10kHz, pulse width 270ns, laser power 80W, scanning speed 700mm / s, obtaining a grooved surface structure, forming an induced corrosion area, with a groove width of 60μm, a depth of 15μm, and an arc corrugation spacing of 20μm. The grooved surface area of ​​the unit corrosion area was 30cm2 The femtosecond laser parameters are: laser wavelength 960nm, pulse frequency 3000Hz, pulse width 280fs, power 0.2W, scanning speed 1mm / s, to obtain a nano-corrugated surface structure, forming a stable corrosion area, with a corrugation period of 450nm and a depth of 16nm. The surface area of ​​the corrugated structure of a unit corrosion area is 24cm 2 The area ratio of the grooved structure surface, nano-corrugated structure surface and polished surface in the unit corrosion area is 1:0.8:0.6.

[0073] After immersion in simulated body fluid for seven days, the inner metal layer of the material corroded and lost about 25% of its weight, while the outer metal structure remained intact. After 14 days, only about 30% of the inner metal remained, and pitting corrosion occurred in the induced corrosion zone of the outer metal. After 25 days, the inner metal disappeared, and the induced corrosion zone of the outer metal suffered severe corrosion, while the stable corrosion zone and the final corrosion zone remained structurally intact. After 60 days, the induced corrosion zone of the outer metal disappeared, the stable corrosion zone corroded more severely, and pitting corrosion occurred in the final corrosion zone. This achieved a directional corrosion degradation effect, first from the inner layer to the outer layer, and then from one end to the other.

[0074] Example 3

[0075] In this embodiment, Mg-0.5Ca alloy is selected as the inner layer metal with a thickness of 20 mm; Zn-1Mg is used as the outer layer coating material, the potential difference between the inner and outer metal layers is 0.58 V, and the total thickness of the composite blank is 50 mm.

[0076] The zinc-clad magnesium composite billet was placed in a resistance heating furnace and heated to 200°C, kept warm for 30 minutes, and then subjected to multi-pass rolling treatment, with 6 rolling passes, a single pass deformation of 25%, and a total deformation of 82%. A zinc-clad magnesium composite sheet with a length of 225 mm, a width of 41 mm, a total thickness of 9.1 mm, an inner layer metal thickness of 4.9 mm, and a thickness ratio of the outer layer to the inner layer of 5:6 was obtained.

[0077] The composite sheet was placed in a muffle furnace for heat treatment at 280°C for 30 minutes, and then cooled to room temperature with the furnace. A Mg-Zn intermediate phase reaction layer interface with a thickness of 5.1 μm was obtained between the inner and outer metal layers. The composite sheet was then wire-cut to a length of 90 mm, and was ground and polished with 2000 mesh sandpaper, and ultrasonically cleaned in alcohol for 15 minutes.

[0078] Afterwards, the composite sheet was placed on a laser workbench, and the protective gas was turned on at a flow rate of 5L / min. Nanosecond laser and femtosecond laser were used to process the induced corrosion area and the stable corrosion area along the longitudinal direction of the composite sheet from one end to the other, respectively. The polished surface was retained at the other end, thereby obtaining a total of one unit corrosion area along the longitudinal direction of the material. Among them, the nanosecond laser parameters are: laser center output wavelength of 1064nm, pulse frequency of 20kHz, pulse width of 180ns, power of 70W, scanning speed of 800mm / s, obtaining a grooved surface structure, forming an induced corrosion area, with a groove width of 50μm, a depth of 10μm, and an arc corrugation spacing of 25μm. The grooved surface area of ​​the unit corrosion area is 24cm 2 The femtosecond laser parameters are: laser wavelength 1030nm, pulse frequency 5000Hz, pulse width 200fs, power 0.4W, scanning speed 2mm / s, to obtain a nano-corrugated surface structure, forming a stable corrosion area, the corrugation period 550nm, and the corrugated surface area of ​​a unit corrosion area is 30cm 2 The area ratio of the grooved structure surface, nano-corrugated structure surface and polished surface in the unit corrosion area is 1:1.2:0.8.

[0079] When the material was immersed in simulated body fluid, it achieved obvious directional corrosion degradation effect from the inner layer to the outer layer and then from one end to the other over time.

[0080] Example 4

[0081] In this embodiment, Mg-0.5Zr alloy is selected as the inner layer metal with a thickness of 10 mm; Zn-0.5Mn is used as the outer layer coating material. The potential difference between the inner and outer metal layers is 0.83 V, and the total thickness of the composite blank is 36 mm.

[0082] The parameters selected in step S4 are: laser center output wavelength 1064nm, pulse frequency 30kHz, pulse width 270ns, power 50W, scanning speed 800mm / s; the grooved surface is obtained with a groove width of 40μm, a depth of 5μm, an arc corrugation spacing of 30μm, and a grooved surface area of ​​25cm 2 The parameters selected in step S5 are: laser wavelength 960 nm, pulse width 300 fs, power 0.6 W, scanning speed 4 mm / s; a nano-corrugated surface is obtained with a corrugation period of 600 nm.

[0083] The remaining step parameters are the same as those in Example 1.

[0084] When the material is immersed in simulated body fluid, it achieves a directional degradation effect from the inner layer to the outer layer and then from both ends to the center over time.

[0085] Example 5

[0086] This example uses AZ31 magnesium alloy as the inner layer metal with a thickness of 26mm; industrial pure zinc (≥99.79wt.%) is used as the outer layer coating material, the potential difference between the inner and outer metal layers is 0.81V, and the total thickness of the composite billet is 40mm.

[0087] The zinc-clad magnesium composite billet was placed in a resistance heating furnace and heated to 250°C, kept warm for 30 minutes, and then subjected to multi-pass rolling treatment. The rolling passes were 5, the pass deformation was 28%, the total deformation was 81%, and a zinc-clad magnesium composite sheet with a length of 227 mm, a width of 41 mm, a total thickness of 7.7 mm, an inner layer metal thickness of 6.1 mm, and a thickness ratio of the outer layer to the inner layer of 1:4 was obtained.

[0088] The remaining step parameters are the same as those in Example 1.

[0089] After the material was immersed in simulated body fluids for 7 days, the inner metal layer lost about 20% of its weight due to corrosion, while the outer metal structure remained intact; after 20 days, only about 20% of the inner metal remained, and pitting corrosion occurred in the outer metal-induced corrosion zone; after 32 days, the inner metal disappeared, and the outer metal-induced corrosion zone was severely corroded and pitting corrosion occurred in the stabilized corrosion zone. Due to its thin thickness, the material fell off in blocks, destroying its structural and mechanical integrity, and failing to achieve a directional corrosion degradation effect.

[0090] Example 6

[0091] In this example, AZ31 magnesium alloy is selected as the inner layer metal with a thickness of 10 mm; industrial pure zinc (≥99.79 wt.%) is used as the outer layer coating material. The potential difference between the inner and outer metal layers is 0.81 V, and the total thickness of the composite billet is 36 mm.

[0092] The nanosecond laser parameters in step S4 were changed to: laser output center wavelength 1064 nm, average power 10 W, pulse frequency 50 kHz, pulse width 270 ns, scanning speed 1200 mm / s, to obtain a grooved surface structure with a groove width of 30 μm, a depth of 2 μm, and an arc-shaped corrugation spacing of 50 μm.

[0093] In step S5, the femtosecond laser parameters were changed to: laser wavelength 960 nm, pulse frequency 6000 Hz, laser power 0.7 W, scanning speed 0.25 mm / s; no corrugated structure was obtained, but a series of conical protrusion structures with a diameter of 500-1500 nm were obtained.

[0094] The remaining step parameters are the same as those in Example 1.

[0095] After being immersed in simulated body fluids for 7 days, the inner metal layer of the material corroded and lost about 30% of its weight, while the outer metal structure remained intact; after 20 days, the inner metal layer disappeared, the induced corrosion zone of the outer metal underwent severe corrosion, and pitting corrosion occurred in the stable corrosion zone and the final corrosion zone; after 50 days, the induced corrosion zone of the outer metal disappeared, and obvious corrosion pits appeared on the surface of the stable corrosion zone and the final corrosion zone, and were unevenly distributed, and directional corrosion degradation was not achieved.

[0096] Example 7

[0097] The difference between this embodiment and embodiment 1 is that the grooved surface structure obtained in step S4 has a surface area of ​​4 cm2 in each unit corrosion zone. 2 The surface corrugation structure obtained by S5 has a surface area of ​​8 cm2 in each unit corrosion zone. 2 The area ratio of the grooved structure surface, corrugated structure surface and polished surface in each unit corrosion area is 1:2:6.

[0098] After being immersed in simulated body fluids for 7 days, the inner metal layer of the material corroded and lost about 30% of its weight, while the outer metal structure remained intact; after 14 days, only about 20% of the inner metal remained, and obvious pitting corrosion occurred in the induced corrosion zone and final corrosion zone of the outer metal; after 20 days, the inner metal disappeared, and obvious corrosion pits appeared in the final corrosion zone of the outer metal and were unevenly distributed, and directional corrosion degradation was not achieved.

[0099] In Examples 5-7, in Example 5, the thickness ratio of the outer layer to the inner layer does not meet the ratio of the claim, which causes the outer metal of the composite material to fall off in non-uniform blocks after the corrosion degradation of the inner metal is completed, thereby destroying the structural and mechanical integrity and causing the directional corrosion degradation effect to disappear; in Example 6, the surface structure of the stable corrosion area on the outer metal surface does not meet the periodic stripe structure of the claim, which causes corrosion to occur simultaneously in the stable corrosion area and the final corrosion area, thereby causing the directional corrosion degradation effect to disappear; in Example 7, the area ratio of the grooved structure surface, the corrugated structure surface and the polished surface on the outer metal surface does not meet the ratio of the claim, which causes corrosion to occur simultaneously in the induced corrosion area and the final corrosion area, thereby causing the directional corrosion degradation effect to disappear.

[0100] Through the above examples, it can be seen that the material obtained by the present invention, under the implantation environment, based on the potential difference between the different component materials, the metal with low potential in the inner layer corrodes first, and the outer metal maintains structural integrity; when the inner metal is completely corroded and disappears, based on the differences in different surface micro-nanostructures and physical phases, corrosion first occurs on the surface of the grooved structure, and corrosion degradation is carried out in the order of the grooved structure, periodic nano-corrugated structure, and polished surface, thereby achieving a staged three-dimensional controllable directional degradation from the inner layer to the outer layer, and then from the end to the center (or one end to the other). This material avoids the phenomenon of uneven corrosion and maximizes the structural and mechanical integrity of the material; at the same time, the degradation rate and time can be regulated by adjusting the thickness ratio of the inner and outer layers and the area ratio of different surface structure regions to meet the needs of different implantation environments.

[0101] The above is only an implementation method of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

[0102] Matters not covered by the present invention are known technologies.

Claims

1. A three-dimensional controllable directional degradation medical metal material, characterized by The metal material has an inner and outer layered coating structure; in the inner and outer layer coating structure, a diffusion layer interface layer or a reaction layer interface layer is formed between the inner and outer metal layers; the surface of the outer metal material further has a regionally differentiated micro-nanostructure layer, wherein the regionally differentiated micro-nanostructure layer has n unit corrosion zones (n=1-5) distributed longitudinally from one end to the other, and each unit corrosion zone is sequentially an induced corrosion zone → a stable corrosion zone → a final corrosion zone, wherein the surface of the induced corrosion zone has a grooved structure, the surface of the stable corrosion zone has a periodic nano-corrugated structure, and the final corrosion zone has a polished surface; The inner layer metal material is Mg, Mg alloy, Zn or Zn alloy, the outer layer metal material is Mg, Mg alloy, Zn, Zn alloy, Fe or Fe alloy, and the inner and outer layers have different metal compositions; In the unit corrosion zone, the surface of the induced corrosion area is a groove structure, and the width of a single groove is between 40 and 70 μm, and the depth is between 1 and 20 μm; The groove has arc-shaped horizontal stripes, and the spacing between the arc-shaped horizontal stripes is 10-30 μm; The surface of the stable corrosion area is a periodic nano-corrugated structure, and the corrugation period is 400-600nm.

2. The three-dimensional controllable directionally degradable medical metal material as described in claim 1, characterized in that the alloying elements in the Mg alloy are one or more of Zn, Ca, Li, Al, Cu, Fe, Mn, and Zr; the alloying elements in the Zn alloy are one or more of Mg, Ca, Li, Si, Fe, Mn, and Zr; and the alloying elements in the Fe alloy are one or more of Mn, Si, Cr, and Co.

3. The three-dimensional controllable directionally degradable medical metal material according to claim 1, wherein the thickness of the regionally differentiated micro-nanostructure layer is 0.01-20 μm; The thickness of the interface layer is 1-20 μm; the interface layer of the diffusion layer is a Mg solid solution, a Zn solid solution or a Fe solid solution layer; and the interface layer of the reaction layer is a Mg-Zn intermediate phase layer or a Fe-Zn intermediate phase layer.

4. The three-dimensional controllable directionally degradable medical metal material as described in claim 1, characterized in that the width of the unit corrosion zone ranges from 2 to 50 mm.

5. The three-dimensional controllable directionally degradable medical metal material as described in claim 1 is characterized in that the thickness ratio of the inner layer material to the outer layer material of the inner and outer layer coating structure is: 2:3~7:3; the thickness range of the inner layer metal is 0.6~6mm.

6. The three-dimensional controllable directionally degradable medical metal material as described in claim 1, characterized in that the electrode potential of the inner layer metal material is lower than that of the outer layer metal material, forming a certain potential difference; the potential difference is 0.05~1.2V.

7. The three-dimensional controllable directionally degradable medical metal material according to claim 1, characterized in that In the surface of the outer metal material, the area ratio of the groove structure surface, the nano-corrugated structure surface and the polished surface is between 1:0.8:0.6 and 1:1.2:0.

8.

8. The method for preparing a three-dimensional controllable directionally degradable medical metal material according to claim 1, wherein the method comprises the following steps: 1) Heating the outer layer-coated inner layer layered composite billet to 200-300°C, keeping the temperature for 10-30 minutes, and then rolling it, with 3-6 rolling passes, a pass deformation of 20-35%, and a total deformation of 45-85%, to obtain an inner and outer layer-coated medical metal material; Among them, the total thickness of the composite blank is 15~80mm, and the thickness of the inner metal layer is 5~40mm; 2) Heat treatment: one of the following two methods: Method 1: When the inner layer is a layered cladding structure metal material of Mg and its alloys or Zn and its alloys and the outer layer is a layered cladding structure metal material of Mg and its alloys or Zn and its alloys, the heat treatment temperature is 260-320°C and the time is 10-30 minutes; a reaction layer interface or a diffusion layer interface is obtained; Alternatively, in method 2, when the inner layer is a layered cladding structure metal material with Mg and its alloys or Zn and its alloys and the outer layer is Fe and its alloys, the heat treatment temperature is 280-330°C and the time is 15-40 minutes to obtain a reaction layer interface or a diffusion layer interface; 3) Laser treatment: The metal material obtained in step 2) is ground and polished, and then ultrasonically cleaned in alcohol for 10-15 minutes; The prepared plate was placed on a nanosecond pulse laser processing table and laser processing was performed with the protector turned on. The average laser power was 50-90W, the pulse frequency was 10-50kHz, the pulse width was 6-270ns, and the scanning speed was 500-1000mm / s to prepare a groove structure in the induced corrosion area. The plate was then placed on a femtosecond pulse laser processing table, and the protective gas was turned on for laser processing. The laser wavelength was 960~1030nm, the average power was 0.1~0.6W, the pulse frequency was 1~5000Hz, the pulse width was 140~300fs, and the scanning speed was 0.05~4mm / s to produce a periodic nano-corrugated structure in a stable corrosion area.

9. The method for preparing the three-dimensional controllable directionally degradable medical metal material according to claim 8, characterized in that Step 3) The protective gas is argon, and the flow rate is preferably 3-10 L / min.

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