Gradient porous magnesium alloy, preparation method and application thereof

Abstract

The present application relates to the technical field of medical metal materials, in particular to a gradient porous magnesium alloy, a preparation method and application thereof, the gradient porous magnesium alloy comprises the following components by weight percentage: 0.2-0.5wt.% of Ag, 0.6-2.4wt.% of Y, 0.6-1.2wt.% of Zn, 7.0-10.6wt.% of Gd, and the balance of Mg and inevitable impurity elements; wherein the gradient porous magnesium alloy is formed by additive manufacturing, and has element gradient, microstructure gradient and pore structure gradient distributed along a preset direction in the inside. It can realize spatial controllable adjustment of corrosion behavior of medical magnesium alloy in a body fluid environment, and meet the comprehensive performance requirements of bone nail, bone plate and other bone fixation implants in mechanical support at the initial implantation stage and gradual degradation at the later stage.

Description

Technical Field

[0001] This invention relates to the field of medical metal materials technology, specifically to a gradient porous magnesium alloy, its preparation method, and its application. Background Technology

[0002] Magnesium and its alloys are considered ideal biodegradable orthopedic implant materials due to their elastic modulus being similar to that of human bone tissue, good biocompatibility, and the ability to be gradually degraded and absorbed in the body. They are widely used in temporary bone fixation devices such as bone nails and bone plates.

[0003] However, existing medical magnesium alloys still suffer from problems such as uncontrollable corrosion rates, uneven degradation, and insufficient retention time of mechanical properties, which severely limit their clinical application. On the one hand, magnesium alloys are prone to rapid corrosion in body fluid environments, leading to a significant decline in the mechanical properties of implants in the early stages of bone healing; on the other hand, traditional manufacturing processes make it difficult to achieve spatial differentiation of the internal properties of components, failing to meet the clinical requirement of "slow corrosion in the early stages and gradual degradation in the later stages."

[0004] In recent years, additive manufacturing technology has provided a new means for the structural design of medical magnesium alloys. However, the forming process easily leads to high roughness, spheroidized particles, and residual stress on the surface of components, which can become the starting point for localized corrosion and weaken the control effect of gradient structures. In addition, existing surface treatment technologies have not yet been systematically integrated with additive manufacturing structures and corrosion control, leaving considerable room for improvement.

[0005] In existing technologies, some patents for 3D-printed biodegradable magnesium alloys only regulate the degradation rate and mechanical decay period of the magnesium alloy in vivo through porous structures, without involving the design of compositional gradient changes. In the initial stage of service, the degradation rate and mechanical strength decline of such magnesium alloys are mainly determined by the increased specific surface area caused by the uniform initial composition and porous structure, lacking active control over local degradation behavior. Therefore, in the complex biomechanical and chemical microenvironment of the human body, implants may experience premature local failure (such as rapid disintegration in stress concentration areas) or premature loss of overall support, making it difficult to achieve an ideal temporal and spatial match between the degradation process and the rate of new bone growth. Summary of the Invention

[0006] The purpose of this invention is to provide a gradient porous magnesium alloy, its preparation method and application, which enables spatially controllable adjustment of the corrosion behavior of medical magnesium alloys in body fluid environment, and meets the comprehensive performance requirements of bone fixation implants such as bone nails and bone plates in the early stage of implantation and in the later stage of gradual degradation.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention discloses a gradient porous magnesium alloy, which, by weight percentage, comprises the following components: 0.2~0.5 wt.% Ag, 0.6~2.4 wt.% Y, 0.6~1.2 wt.% Zn, 7.0~10.6 wt.% Gd, with the balance being Mg and unavoidable impurity elements;

[0009] The gradient porous magnesium alloy is formed by additive manufacturing and has an elemental gradient, microstructure gradient and pore structure gradient distributed along a preset direction inside.

[0010] In one embodiment, the gas alloying element is further included, which is selected from one or more of oxygen, nitrogen and hydrogen, wherein the oxygen content is 50-2000 ppm, the nitrogen content is 20-1000 ppm, and the hydrogen content is 1-100 ppm.

[0011] In one embodiment, at least one of Ag, Y, Zn and Gd elements is distributed in a gradient along a predetermined direction inside the gradient porous magnesium alloy.

[0012] In one embodiment, the porosity of the gradient porous magnesium alloy is 10-60%, and the average pore size is [missing information]. The porosity and / or the pore size vary in a gradient along the preset direction.

[0013] In one embodiment, the surface region of the gradient porous magnesium alloy is a fine-grained structure layer formed by surface deformation treatment, and the grain size of the surface region is smaller than that of the internal region.

[0014] In one embodiment, after the surface deformation treatment, a layer with a thickness of [thickness missing] is formed on the surface of the component. The fine-grained structure layer of plastic deformation.

[0015] Secondly, the present invention discloses a method for preparing the above-mentioned gradient porous magnesium alloy, which includes the following steps:

[0016] S1, Prepare raw material powder, wherein the raw material powder includes Mg-30Y master alloy powder, Mg-30Gd master alloy powder, Zn powder and Ag powder;

[0017] S2, additive manufacturing, uses selective laser melting or binder spraying to form components layer by layer. During the forming process, by controlling the powder ratio, laser power, scanning speed and pore unit structure design, element gradient, microstructure gradient and pore structure gradient are formed inside the component.

[0018] S3, the surface deformation treatment is carried out on the formed component to form a fine-grained structure layer in the surface area;

[0019] S4, heat treatment is performed on the component that has undergone surface deformation treatment.

[0020] In one embodiment, the surface deformation treatment in step S3 includes sandblasting and / or grinding.

[0021] In one embodiment, during the additive manufacturing and / or heat treatment process, a gaseous alloying element is introduced by controlling the forming atmosphere, so that the gaseous alloying element is distributed in a gradient within the component; the gaseous alloying element is selected from one or more of oxygen, nitrogen, and hydrogen.

[0022] Thirdly, the present invention discloses the application of the above-mentioned gradient porous magnesium alloy in the preparation of biodegradable bone fixation implants, characterized in that: the biodegradable bone fixation implants include one or more of bone nails, bone plates, bone screws, and bone plates. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0024] Figure 1 This is a schematic flowchart illustrating the preparation method of gradient porous magnesium alloy provided in the embodiments of this application.

[0025] Figure 2 Metallographic images of different locations of the gradient porous magnesium alloy prepared in Example 1 of this application. Detailed Implementation

[0026] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0027] In one embodiment, this application provides a gradient porous magnesium alloy, which, by weight percentage, comprises the following components: 0.2~0.5 wt.% Ag, 0.6~2.4 wt.% Y, 0.6~1.2 wt.% Zn, 7.0~10.6 wt.% Gd, with the balance being Mg and unavoidable impurity elements; wherein, the gradient porous magnesium alloy is formed by additive manufacturing, and its interior has an elemental gradient, microstructure gradient, and pore structure gradient distributed along a predetermined direction.

[0028] The design principles of each chemical element are as follows:

[0029] Silver (Ag): Ag can effectively enhance the age-hardening effect of magnesium alloys. During solution treatment and artificial aging, it promotes the precipitation of dispersed strengthening phases, thereby significantly improving the strength and hardness of the alloy. Simultaneously, Ag is beneficial for improving the heat resistance and high-temperature stability of magnesium alloys and possesses certain antibacterial properties. Considering the strengthening effect, microstructure stability, and preparation cost, when the Ag content is below 0.2 wt.%, its strengthening effect is not significant, making it difficult to fully utilize the age-hardening effect. When the Ag content is above 0.5 wt.%, it easily forms coarse primary or secondary phases, leading to inhomogeneity in the matrix structure, while also impairing alloy plasticity and significantly increasing material costs. Therefore, controlling the Ag content within the range of 0.2~0.5 wt.% can ensure the strengthening effect while also considering microstructure stability and economy.

[0030] Yttrium (Y): Y is a rare earth element that can significantly refine the grains of magnesium alloys, effectively improving the as-cast and modified microstructures. Simultaneously, Y can enhance the high-temperature strength, creep resistance, and corrosion resistance of alloys, and effectively suppress grain boundary weakening, comprehensively optimizing the overall mechanical properties of the alloy. Experimental verification shows that when the Y content is below 0.6 wt.%, its grain-refining and heat-strengthening effects are limited; when the Y content exceeds 2.4 wt.%, it easily forms brittle rare earth phases, leading to a decrease in plasticity and processing performance. Therefore, limiting the Y content to the range of 0.6~2.4 wt.% achieves a good balance between strengthening and toughness.

[0031] Zinc (Zn): Zn is a commonly used strengthening element in magnesium alloys, enhancing alloy strength through both solid solution strengthening and precipitation strengthening mechanisms. Simultaneously, Zn can synergistically interact with elements such as Ag and Y, promoting the uniform and dispersed precipitation of strengthening phases, thereby improving the mechanical properties and microstructure stability of the alloy. Furthermore, Zn exhibits good biocompatibility, which is beneficial for promoting bone tissue growth. A reasonable Zn content is crucial for maximizing its effectiveness. When the Zn content is below 0.6 wt.%, the solid solution strengthening effect is insufficient, making it difficult to effectively improve the matrix strength; when the Zn content is above 1.2 wt.%, it easily forms a continuous brittle second phase, potentially increasing the tendency for hot cracking and reducing plasticity. Therefore, controlling the Zn content within the range of 0.6~1.2 wt.% is beneficial for maximizing its strengthening effect while avoiding adverse effects.

[0032] Gadolinium (Gd): Gd plays a crucial role in magnesium alloys by refining grain size, improving mechanical properties, and enhancing heat resistance and corrosion resistance. It is one of the important alloying elements in high-performance magnesium alloys. Pure magnesium or ordinary magnesium alloys have poor corrosion resistance and are prone to pitting corrosion. The addition of Gd reduces the electrochemical activity of the magnesium alloy matrix and refines the oxide film structure, promoting the formation of a denser and more continuous Gd-containing oxide film on the surface (e.g., gadolinium, gd ... ), hindering corrosive media (such as The presence of rare earth elements (Gd) enhances the corrosion resistance of the alloy. When the Gd content is below 7.0 wt.%, the improvement in corrosion resistance is limited; when the Gd content is above 10.6 wt.%, excessive rare earth phases are easily formed, reducing plasticity and increasing cost. Therefore, controlling the Gd content within the range of 7.0~10.6 wt.% can comprehensively optimize both mechanical and corrosion resistance.

[0033] Magnesium (Mg): As a matrix element, Mg has the closest elastic modulus to that of human bone, which can greatly avoid the stress shielding effect. At the same time, after completing its bone repair mission, magnesium alloy implants can be gradually and completely degraded and absorbed in the body without the need for a second surgery to remove them. This effectively reduces patient pain, lowers medical costs, and avoids the infection risk associated with a second surgery.

[0034] By rationally proportioning the aforementioned alloying elements and combining them with the elemental, microstructural, and pore structure gradients created through additive manufacturing, precise spatial control of corrosion behavior is achieved. Specifically, the surface region of the component, through the synergistic effect of high Gd / Ag content, fine grain structure, and low porosity, can rapidly form a dense and stable oxide film, effectively blocking the intrusion of corrosive media and significantly reducing the surface corrosion rate. The core region, through a precise design of low Gd / Ag content, suitable grain size, and high porosity, accelerates the penetration of bodily fluids and alloy degradation. This gradual corrosion pattern, characterized by slow external corrosion and rapid internal corrosion, effectively avoids a significant decline in the mechanical properties of the implant due to premature corrosion in the early stages of bone healing, providing stable and continuous mechanical support for fracture healing.

[0035] Furthermore, this invention achieves a dynamic match between the mechanical properties of the implant and the bone healing process through the synergistic design of multi-dimensional structure and composition. Specifically, the rational design of the gradient distribution of Zn and Y elements precisely meets the strength requirements of high-stress areas of the implant; the gradient arrangement of the pore structure causes the porosity to change in stages along a predetermined direction. In the initial stage of implantation, the low-porosity region provides sufficient mechanical support, ensuring stability after fracture reduction. Later, the high-porosity region preferentially degrades, allowing the mechanical support force to gradually and smoothly transfer to the newly formed bone tissue, achieving an orderly transfer of mechanical load. Simultaneously, the surface fine-grained tissue (grain size...) It can significantly improve the fatigue strength and stress corrosion resistance of implants, while the appropriate internal grain size effectively ensures the toughness of the alloy. The synergistic effect of the three makes the mechanical decay curve of the implant highly consistent with the new bone growth curve, which not only avoids the inhibition of new bone growth by the "stress shielding effect" but also prevents premature failure of the implant.

[0036] Furthermore, this invention significantly enhances the biocompatibility and osseointegration capacity of the implant through gradient optimization of composition and structure, achieving excellent in vivo biological response. The gradient distribution of Ag elements gives the implant surface good antibacterial function, which can effectively inhibit the growth of bacteria around the implant and reduce the risk of postoperative infection; Zn elements themselves have excellent biofriendly properties and can actively promote osteoblast proliferation and bone tissue growth; the gradient design of the pore structure takes into account the needs of cell adhesion and bone tissue ingrowth. The surface pores provide a suitable microenvironment for cell adhesion and proliferation, while the internal macropores are conducive to vascularization and bone tissue ingrowth. The synergistic effect of the three significantly promotes the rapid and stable integration of the bone-implant interface and accelerates the bone repair process.

[0037] In a preferred embodiment, the gradient porous magnesium alloy provided in this application further includes a gas alloying element selected from one or more of oxygen, nitrogen, and hydrogen, wherein the oxygen content is 50~2000ppm, the nitrogen content is 20~1000ppm, and the hydrogen content is 1~100ppm.

[0038] The gas alloying elements exist in the alloy matrix in a solid solution or dispersed phase form, providing auxiliary effects on the stability of the microstructure and the regulation of corrosion behavior. The specific design principle is as follows:

[0039] Oxygen (O): In magnesium alloys, oxygen mainly exists in solid solution or as a dispersed oxide phase (such as MgO, O). , Oxygen exists in the form of ) . Appropriate amounts of oxygen can refine grains, pin grain boundaries, and inhibit grain growth, thereby improving the microstructure stability of the alloy; simultaneously, oxygen participates in the formation of the surface oxide film, synergistically promoting the formation of a denser composite oxide film with Gd elements. This improves corrosion resistance. When the oxygen content is below 50 ppm, its contribution to microstructure refinement and oxide film densification is limited; when the oxygen content is above 2000 ppm, it easily forms excessive coarse oxide inclusions, becoming a source of corrosion initiation and reducing plasticity. Therefore, controlling the oxygen content within the range of 50~2000 ppm can ensure microstructure stability while avoiding adverse effects.

[0040] Nitrogen (N): Nitrogen in magnesium alloys mainly exists in solid solution or as dispersed nitride phases (such as... Nitrogen exists in the form of GdN. Appropriate amounts of nitrogen can form fine, dispersed second-phase particles, resulting in dispersion strengthening and increased alloy strength. Simultaneously, the nitride phase acts as a corrosion barrier, hindering the diffusion path of corrosive media. When the nitrogen content is below 20 ppm, its dispersion strengthening effect is not significant; when the nitrogen content is above 1000 ppm, continuous nitride phases are easily formed, leading to increased brittleness and reduced processing performance. Therefore, controlling the nitrogen content within the range of 20–1000 ppm achieves a balance between strengthening effect and plasticity.

[0041] Hydrogen (H): In magnesium alloys, hydrogen mainly exists in solid solution or hydride form. Trace amounts of hydrogen can occupy interstitial positions in the crystal lattice, hindering dislocation movement and producing a solid solution strengthening effect. Simultaneously, under controlled content, hydrogen can regulate local electrochemical activity, aiding in the gradient control of corrosion rates. When the hydrogen content is below 1 ppm, its effect is negligible; when the hydrogen content is above 100 ppm, it easily forms hydride phases and introduces hydrogen embrittlement risk, significantly reducing the alloy's plasticity and toughness. Therefore, strictly controlling the hydrogen content within the range of 1–100 ppm can leverage its auxiliary regulatory role while avoiding hydrogen embrittlement.

[0042] It should be noted that the gas alloying elements mainly originate from the protective atmosphere or forming environment during the additive manufacturing process, and their content is precisely controlled through process parameter adjustment. In some embodiments, the gas alloying elements work synergistically with metallic elements (Ag, Y, Zn, Gd) to further enhance the corrosion control effect of the gradient structure.

[0043] In a preferred embodiment, at least one of Ag, Y, Zn, and Gd elements is distributed in a gradient along a predetermined direction within the gradient porous magnesium alloy. This elemental gradient distribution is achieved by layer-by-layer control of process parameters such as powder feeding rate, laser power, and scanning speed during additive manufacturing, resulting in a continuous or stepwise variation of the alloy element content along the predetermined direction.

[0044] Ag is distributed in a gradient along a predetermined direction, with a higher Ag content in the surface region (e.g., 0.4–0.5 wt.%) and a lower Ag content in the core region (e.g., 0.2–0.3 wt.%). The high Ag content in the surface promotes the precipitation of the dispersion strengthening phase, improving surface hardness and wear resistance; simultaneously, the antibacterial properties of Ag are concentrated in the surface, effectively inhibiting bacterial infection around the implant. The low Ag content in the core avoids the formation of coarse second phases, ensuring internal toughness and plasticity. This achieves a functional gradient design of "surface antibacterial reinforcement and core toughness support."

[0045] The rare earth element (Y) exhibits a gradient distribution along a predetermined direction, with higher Y content (e.g., 1.5–2.4 wt.%) in high-stress regions and lower Y content (e.g., 0.6–1.2 wt.%) in low-stress regions. The high-Y content regions show significant grain refinement, resulting in excellent high-temperature strength and creep performance, suitable for high-stress load-bearing requirements. The low-Y content regions avoid excessive formation of brittle rare earth phases, ensuring processing performance and toughness. This achieves optimized matching between mechanical properties and stress distribution at the implantation site.

[0046] The Zn element exhibits a gradient distribution along a predetermined direction, with a lower Zn content in the surface region (e.g., 0.6–0.8 wt.%) and a higher Zn content in the core region (e.g., 0.9–1.2 wt.%). The low Zn content in the surface layer prevents the formation of a continuous second phase, reducing corrosion initiation sources; the high Zn content in the core enhances overall strength through solid solution strengthening and precipitation strengthening. Simultaneously, the gradient distribution of Zn's bio-friendly properties promotes gradual ingrowth of bone tissue from the surface inwards. This achieves a gradient balance between corrosion resistance and mechanical strength.

[0047] The Gd element exhibits a gradient distribution along a predetermined direction, with a higher Gd content in the surface region (e.g., 8.5–10.6 wt.%) and a lower Gd content in the core region (e.g., 7.0–9.0 wt.%). The high Gd content in the surface region promotes the formation of a denser Gd-containing oxide film. This significantly reduces the surface corrosion rate; the low Gd content in the core avoids excessive rare earth phases that reduce plasticity while ensuring mechanical support in the later stages of corrosion, and also guarantees appropriate corrosion resistance. This achieves a gradual corrosion pattern of slow external corrosion and rapid internal corrosion, preventing early localized failure of the implant.

[0048] In a preferred embodiment, the porosity of the gradient porous magnesium alloy is 10-60%, and the average pore size is [missing information]. Furthermore, the porosity and / or the pore size exhibit a gradient change along the preset direction.

[0049] When the porosity is below 10%, the porous structure is not obvious, the increase in specific surface area is limited, and the effect on regulating corrosion rate and bone tissue ingrowth is weak. When the porosity is above 60%, the mechanical strength of the alloy decreases significantly, making it difficult to meet the initial support requirements of bone fixation implants. Therefore, controlling the porosity within the range of 10-60% can achieve a balance between mechanical properties and biological function.

[0050] When the average aperture is lower When the average pore size is higher than a certain value, cells have difficulty growing into the pores, resulting in limited bone tissue integration. When the hole wall thickness decreases, the mechanical strength drops significantly, and stress concentration is easily formed. Therefore, the average hole diameter is controlled within a certain range. Within this range, it can take into account both the needs for bone ingrowth and the needs for mechanical support.

[0051] In a preferred embodiment, the surface region of the gradient porous magnesium alloy is a fine-grained microstructure layer formed through surface deformation treatment, wherein the grain size of the surface region is smaller than that of the internal region. Surface deformation treatment removes surface-attached particles and molten pool ripples formed during additive manufacturing, smoothing the component surface and forming a plastic deformation layer of a predetermined thickness on the component surface, thereby refining the surface grains and forming a fine-grained microstructure region. This fine-grained surface region, in conjunction with the elemental gradient, microstructure gradient, and pore structure gradient within the component, effectively reduces the localized corrosion susceptibility of the component's surface region.

[0052] Furthermore, after the surface deformation treatment, a layer with a thickness of [thickness missing] is formed on the surface of the component. The plastic deformation fine-grained structure layer. The grain size in the fine-grained structure layer is significantly refined, the dislocation density is increased, and a dense protective oxide film is formed. This film works synergistically with the elemental gradient and pore structure gradient inside the component to effectively reduce the local corrosion sensitivity of the component surface area, while improving the surface mechanical properties and biocompatibility.

[0053] When the thickness of the fine-grained structure layer during plastic deformation is less than At that time, the effects of fine grain strengthening, corrosion resistance improvement, and residual compressive stress stabilization are all significantly reduced, failing to achieve the expected technical effects.

[0054] When the thickness of the fine-grained structure layer during plastic deformation exceeds At that time, the risks of brittleness, loss of dimensional accuracy, pore blockage, and increased costs become significant, and the overall performance actually declines.

[0055] In one embodiment, this application provides a method for preparing a gradient porous magnesium alloy, see below. Figure 1 As shown, the method includes the following steps:

[0056] S1. Prepare raw material powder according to the designed composition ratio. The raw material powder includes Mg-30Y master alloy powder, Mg-30Gd master alloy powder, Zn powder and Ag powder.

[0057] The powder is prepared by gas atomization, with specific process parameters including: the atomization medium is a high-purity inert gas, the gas pressure is 0.3~0.5 MPa, and the temperature of the molten metal is... The prepared powder has a particle size of To meet the powder particle size requirements of selective laser melting or binder jet additive manufacturing; the sphericity of the powder is ≥90%, and the loose packing density is [not specified]. This ensures the flowability and uniformity of the powder.

[0058] S2, additive manufacturing, uses selective laser melting or binder spraying to form components layer by layer. During the forming process, by controlling the powder ratio, laser power, scanning speed and pore unit structure design, element gradient, microstructure gradient and pore structure gradient are formed inside the component.

[0059] Achieving elemental gradient: A multi-bucket powder feeding system is employed. By adjusting the powder feeding rate of each bucket (Mg-30Y, Mg-30Gd, Zn, Ag), the composition ratio of each powder layer is changed, thereby achieving a gradient distribution of Ag, Y, Zn, and Gd elements along different directions of the component. For example, when forming the surface region, the powder feeding rate of Zn powder is increased; when forming the core region, the powder feeding rate of Mg-30Gd powder is increased.

[0060] Realization of pore structure gradient: A gradient pore unit structure is designed in the 3D model. By changing the shape (spherical pores, cylindrical pores), size, and distribution density of the pore units, combined with the scanning path planning of additive manufacturing, gradient changes in porosity and pore size are achieved. For example, small-sized spherical pores are used in the bone contact layer, while large-sized cylindrical pores are used in the core layer.

[0061] Achieving microstructure gradient: Adjusting additive manufacturing process parameters, including laser power (100~300W), scanning speed (500~2000mm / s), and scanning spacing (…). ), layer thickness ( The forming atmosphere is an inert gas environment. High laser power and low scanning speed parameters can refine the grains, while low laser power and high scanning speed parameters can obtain relatively coarse grains. By controlling the process parameters in layers, a gradient distribution of microstructure can be achieved.

[0062] This application achieves integrated fabrication of elemental gradients, microstructure gradients, and pore structure gradients simultaneously in a single process by synchronously controlling powder ratio, laser power, scanning speed, and pore unit structure design. Compared with traditional multi-step fabrication, this method offers high process integration, shortens the production cycle, and avoids the problems of uneven microstructure and interface defects caused by multi-step transitions. Surface deformation treatment forms a fine-grained microstructure layer on the component surface, eliminating surface-attached particles and molten pool ripples formed during additive manufacturing, refining the surface grain size, and significantly reducing localized corrosion sensitivity. Subsequent heat treatment eliminates residual stress introduced by surface deformation treatment, stabilizing the microstructure. The synergistic effect of the fine-grained surface microstructure and the internal gradient structure achieves optimized comprehensive performance of external corrosion resistance and internal toughness.

[0063] S3 involves surface deformation treatment of the formed component to form a fine-grained structure layer in the surface area.

[0064] Specifically, the additively manufactured components undergo sandblasting and grinding processes, as follows:

[0065] Sandblasting treatment: using Or SiC abrasive, with abrasive particle size of The sandblasting pressure is 0.2~0.6MPa, the sandblasting time is 5~30min, and the sandblasting angle is... Sandblasting uses the impact force to cause plastic deformation of the component's surface, breaking down coarse grains and forming a fine-grained structure. Through high-speed abrasive impact, sandblasting effectively removes surface defects such as adhering particles, molten pool ripples, and microcracks formed during additive manufacturing.

[0066] Grinding treatment: The sandblasted components are then ground in stages, with the abrasive paper grit increasing from 400 grit to 2000 grit. The grinding pressure is 0.1~0.3MPa, and the grinding speed is 50~100 r / min. Grinding treatment further refines the surface grains and improves the surface finish of the components. Through mechanical friction cutting, grinding treatment reduces surface roughness and significantly reduces corrosion initiation sources and bacterial attachment sites.

[0067] After surface deformation treatment, the surface layer of the component has a thickness of A fine-grained layer of plastic deformation, wherein the grain size of the fine-grained layer is smaller than It is significantly better than the grain size in the internal region.

[0068] S4 involves heat treatment of the surface-deformed components to eliminate residual stress on the surface and simultaneously regulate the microstructure and mechanical properties of the alloy. The specific process is as follows: heat treatment temperature is... The holding time is 1-4 hours; the cooling method is furnace cooling to room temperature; the heat treatment atmosphere can be air or argon mixed with a small amount of nitrogen. By controlling the oxygen and nitrogen content in the atmosphere, the distribution of gaseous alloying elements in the component can be further regulated. By precisely controlling the composition, concentration, and distribution of the atmosphere in the additive manufacturing forming chamber and / or heat treatment furnace, gaseous alloying elements such as oxygen, nitrogen, and hydrogen can form a spatial gradient distribution inside the component, working synergistically with the gradient of metallic elements to further optimize the corrosion behavior, mechanical properties, and biological functions of the component.

[0069] After heat treatment, the fine-grained structure on the surface of the component remains stable, the internal grain size becomes uniform, and the toughness and corrosion resistance of the alloy are further improved.

[0070] The following analysis and explanation will be based on specific examples.

[0071] Example 1: A gradient porous magnesium alloy, wherein the gradient structure of each region of the gradient porous magnesium alloy is shown in Table 1.

[0072] Table 1. Gradient structure of various regions in the gradient porous magnesium alloy of Example 1

[0073]

[0074] The preparation method of this gradient porous magnesium alloy includes the following steps:

[0075] S1. Prepare raw material powder according to the designed composition ratio. The raw material powder includes Mg-30Y master alloy powder, Mg-30Gd master alloy powder, Zn powder and Ag powder.

[0076] The powder was prepared using a gas atomization method. Specific process parameters included: the atomizing medium was a high-purity inert gas, the gas pressure was 0.4 MPa, and the temperature of the molten metal was... The prepared powder has a particle size of To meet the powder particle size requirements of selective laser melting or binder jet additive manufacturing; the sphericity of the powder is ≥90%, and the loose packing density is [not specified]. This ensures the flowability and uniformity of the powder.

[0077] S2, additive manufacturing, uses selective laser melting or binder spraying to form components layer by layer. During the forming process, by controlling the powder ratio, laser power, scanning speed and pore unit structure design, element gradient, microstructure gradient and pore structure gradient are formed inside the component.

[0078] Achieving elemental gradient: A multi-powder silo feeding system is adopted. By adjusting the powder feeding rate of each powder silo (Mg-30Y, Mg-30Gd, Zn, Ag), the composition ratio of each layer of powder is changed, thereby achieving a gradient distribution of Ag, Y, Zn, and Gd elements along different directions of the component.

[0079] Realization of pore structure gradient: A gradient pore unit structure is designed in the 3D model. By changing the shape (spherical pores, cylindrical pores), size, and distribution density of the pore units, combined with the scanning path planning of additive manufacturing, gradient changes in porosity and pore size are achieved. Small-sized spherical pores are used in the bone contact layer, while large-sized cylindrical pores are used in the core layer.

[0080] Achieving microstructure gradients: Adjusting additive manufacturing process parameters, including: scanning spacing. The layer thickness is The forming atmosphere is an inert gas environment. High laser power and low scanning speed parameters can refine the grains, while low laser power and high scanning speed parameters can obtain relatively coarse grains. By controlling the process parameters in layers, a gradient distribution of microstructure can be achieved.

[0081] S3 involves sandblasting and grinding the additively manufactured components. The specific process is as follows:

[0082] Sandblasting treatment: using Abrasive, abrasive particle size is The sandblasting pressure was 0.4 MPa, the sandblasting time was 15 minutes, and the sandblasting angle was [missing information]. .

[0083] Grinding treatment: The sandblasted components are ground in stages, with the abrasive paper grit gradually increasing from 400 grit to 2000 grit, the grinding pressure being 0.2 MPa, and the grinding speed being 75 r / min.

[0084] After surface deformation treatment, a fine-grained plastic deformation layer with a thickness of 80 μm is formed on the surface of the component. The grain size of this fine-grained layer is smaller than... It is significantly better than the grain size in the internal region.

[0085] S4. The component that has undergone surface deformation treatment is then subjected to heat treatment. The heat treatment atmosphere can be argon mixed with a small amount of nitrogen, and the heat treatment temperature is... The heat preservation time is 2.5 hours, and the cooling method is to cool to room temperature with the furnace.

[0086] The gradient porous magnesium alloy produced in this example can be used to manufacture general-purpose bone screws / plates, with an expected degradation period of 3 to 6 months.

[0087] See Figure 2 As shown, the core region has the largest grain size, exhibiting irregular polygonal shapes with clear grain boundaries, closely resembling a recrystallized or cast structure. These coarse grains typically possess good plasticity and toughness, allowing them to withstand significant loads as a matrix and preventing brittle fracture of the implant within the body.

[0088] The grain size in the transition region lies between that of the core and surface regions, exhibiting a coexistence of large and small grains and displaying transitional characteristics. This avoids stress concentration caused by excessive performance differences between the coarse grains in the core region and the fine grains in the surface region, preventing delamination or cracking and ensuring the integrity of the structure.

[0089] The grain size in the surface region is significantly smaller than that in the core region, and the deformation traces are relatively uniformly distributed; some grains show deformation characteristics. This is the direct impact area of ​​surface deformation treatments (such as sandblasting and grinding). Fine-grained strengthening improves surface hardness and strength.

[0090] The grains in the fine-grained layer resulting from plastic deformation are extremely small, even diffuse, with indistinguishable grain boundaries. Due to the intense plastic deformation, a high density of dislocations may exist within the crystal lattice. These extremely fine grains help form a denser, more uniform oxide film (passivation film) on the magnesium alloy surface, thereby significantly reducing the corrosion rate and addressing the problem of excessively rapid degradation of magnesium alloys. It also improves surface wear resistance.

[0091] Example 2: A gradient porous magnesium alloy, wherein the gradient structure of each region of the gradient porous magnesium alloy is shown in Table 2.

[0092] Table 2. Gradient structure of various regions in the gradient porous magnesium alloy of Example 2

[0093]

[0094] The preparation method of this gradient porous magnesium alloy includes the following steps:

[0095] S1. Prepare raw material powder according to the designed composition ratio. The raw material powder includes Mg-30Y master alloy powder, Mg-30Gd master alloy powder, Zn powder and Ag powder.

[0096] The powder is prepared using a gas atomization method. Specific process parameters include: the atomization medium is a high-purity inert gas, the gas pressure is 0.5 MPa, and the temperature of the molten metal is... The prepared powder has a particle size of To meet the powder particle size requirements of selective laser melting or binder jet additive manufacturing; the sphericity of the powder is ≥90%, and the loose packing density is [not specified]. This ensures the flowability and uniformity of the powder.

[0097] S2, additive manufacturing, uses selective laser melting or binder spraying to form components layer by layer. During the forming process, by controlling the powder ratio, laser power, scanning speed and pore unit structure design, element gradient, microstructure gradient and pore structure gradient are formed inside the component.

[0098] Achieving elemental gradient: A multi-powder silo feeding system is adopted. By adjusting the powder feeding rate of each powder silo (Mg-30Y, Mg-30Gd, Zn, Ag), the composition ratio of each layer of powder is changed, thereby achieving a gradient distribution of Ag, Y, Zn, and Gd elements along different directions of the component.

[0099] Realization of pore structure gradient: A gradient pore unit structure is designed in the 3D model. By changing the shape (spherical pores, cylindrical pores), size, and distribution density of the pore units, combined with the scanning path planning of additive manufacturing, gradient changes in porosity and pore size are achieved. Small-sized spherical pores are used in the bone contact layer, while large-sized cylindrical pores are used in the core layer.

[0100] Achieving microstructure gradients: Adjusting additive manufacturing process parameters, including: scanning spacing. The layer thickness is The forming atmosphere is an inert gas environment. High laser power and low scanning speed parameters can refine the grains, while low laser power and high scanning speed parameters can obtain relatively coarse grains. By controlling the process parameters in layers, a gradient distribution of microstructure can be achieved.

[0101] S3 involves sandblasting and grinding the additively manufactured components. The specific process is as follows:

[0102] Sandblasting: SiC abrasive is used, with an abrasive particle size of [missing information]. The sandblasting pressure was 0.5 MPa, the sandblasting time was 20 minutes, and the sandblasting angle was [missing information]. .

[0103] Grinding treatment: The sandblasted components are ground in stages, with the abrasive paper grit gradually increasing from 400 grit to 2000 grit, the grinding pressure being 0.3 MPa, and the grinding speed being 90 r / min.

[0104] After surface deformation treatment, the surface layer of the component has a thickness of A fine-grained layer of plastic deformation, wherein the grain size of the fine-grained layer is smaller than It is significantly better than the grain size in the internal region.

[0105] S4. The component that has undergone surface deformation treatment is subjected to heat treatment. The heat treatment atmosphere uses argon mixed with a small amount of nitrogen, and the heat treatment temperature is... The heat preservation time is 3 hours, and the cooling method is to cool to room temperature with the furnace.

[0106] This example features a highly corrosion-resistant design suitable for long-term implantation needs, with an expected degradation period of 12 to 18 months.

[0107] Example 3: A gradient porous magnesium alloy, wherein the gradient structure of each region of the gradient porous magnesium alloy is shown in Table 3.

[0108] Table 3. Gradient structure of various regions in the gradient porous magnesium alloy of Example 3

[0109]

[0110] The preparation method of this gradient porous magnesium alloy includes the following steps:

[0111] S1. Prepare raw material powder according to the designed composition ratio. The raw material powder includes Mg-30Y master alloy powder, Mg-30Gd master alloy powder, Zn powder and Ag powder.

[0112] The powder is prepared by gas atomization, with specific process parameters including: the atomization medium is a high-purity inert gas, the gas pressure is 0.35 MPa, and the temperature of the molten metal is... The prepared powder has a particle size of To meet the powder particle size requirements of selective laser melting or binder jet additive manufacturing; the sphericity of the powder is ≥90%, and the loose packing density is [not specified]. This ensures the flowability and uniformity of the powder.

[0113] S2, additive manufacturing, uses selective laser melting or binder spraying to form components layer by layer. During the forming process, by controlling the powder ratio, laser power, scanning speed and pore unit structure design, element gradient, microstructure gradient and pore structure gradient are formed inside the component.

[0114] Achieving elemental gradient: A multi-powder silo feeding system is adopted. By adjusting the powder feeding rate of each powder silo (Mg-30Y, Mg-30Gd, Zn, Ag), the composition ratio of each layer of powder is changed, thereby achieving a gradient distribution of Ag, Y, Zn, and Gd elements along different directions of the component.

[0115] Realization of pore structure gradient: A gradient pore unit structure is designed in the 3D model. By changing the shape (spherical pores, cylindrical pores), size, and distribution density of the pore units, combined with the scanning path planning of additive manufacturing, gradient changes in porosity and pore size are achieved. Small-sized spherical pores are used in the bone contact layer, while large-sized cylindrical pores are used in the core layer.

[0116] Achieving microstructure gradients: Adjusting additive manufacturing process parameters, including: scanning spacing. The layer thickness is The forming atmosphere is an inert gas environment. High laser power and low scanning speed parameters can refine the grains, while low laser power and high scanning speed parameters can obtain relatively coarse grains. By controlling the process parameters in layers, a gradient distribution of microstructure can be achieved.

[0117] S3 involves surface deformation treatment of the formed component to form a fine-grained structure layer in the surface area.

[0118] Specifically, the additively manufactured components undergo sandblasting and grinding processes, as follows:

[0119] Sandblasting treatment: using Abrasive, abrasive particle size is The sandblasting pressure was 0.35 MPa, the sandblasting time was 12 minutes, and the sandblasting angle was [missing information]. .

[0120] Grinding treatment: The sandblasted components are ground in stages, with the abrasive paper grit gradually increasing from 400 grit to 2000 grit, the grinding pressure being 0.3 MPa, and the grinding speed being 90 r / min.

[0121] After surface deformation treatment, the surface layer of the component has a thickness of A fine-grained layer of plastic deformation, wherein the grain size of the fine-grained layer is smaller than It is significantly better than the grain size in the internal region.

[0122] S4, perform heat treatment on the component after surface deformation treatment. The heat treatment atmosphere is air, and the heat treatment temperature is [temperature missing]. The heat preservation time is 2 hours, and the cooling method is to cool to room temperature with the furnace.

[0123] The gradient porous magnesium alloy prepared in this example adopts a rapid osseointegration design, which is suitable for fracture sites that heal quickly, with an expected degradation period of 4 to 8 months.

[0124] Example 4: A gradient porous magnesium alloy, wherein the gradient structure of each region of the gradient porous magnesium alloy is shown in Table 4.

[0125] Table 4. Gradient structure of various regions in the gradient porous magnesium alloy of Example 4

[0126]

[0127] The preparation method of this gradient porous magnesium alloy includes the following steps:

[0128] S1. Prepare raw material powder according to the designed composition ratio. The raw material powder includes Mg-30Y master alloy powder, Mg-30Gd master alloy powder, Zn powder and Ag powder.

[0129] The powder is prepared using a gas atomization method. Specific process parameters include: the atomization medium is a high-purity inert gas, the gas pressure is 0.5 MPa, and the temperature of the molten metal is... The prepared powder has a particle size of To meet the powder particle size requirements of selective laser melting or binder jet additive manufacturing; the sphericity of the powder is ≥90%, and the loose packing density is [not specified]. This ensures the flowability and uniformity of the powder.

[0130] S2, additive manufacturing, uses selective laser melting or binder spraying to form components layer by layer. During the forming process, by controlling the powder ratio, laser power, scanning speed and pore unit structure design, element gradient, microstructure gradient and pore structure gradient are formed inside the component.

[0131] Achieving elemental gradient: A multi-powder silo feeding system is adopted. By adjusting the powder feeding rate of each powder silo (Mg-30Y, Mg-30Gd, Zn, Ag), the composition ratio of each layer of powder is changed, thereby achieving a gradient distribution of Ag, Y, Zn, and Gd elements along different directions of the component.

[0132] Realization of pore structure gradient: A gradient pore unit structure is designed in the 3D model. By changing the shape (spherical pores, cylindrical pores), size, and distribution density of the pore units, combined with the scanning path planning of additive manufacturing, gradient changes in porosity and pore size are achieved. Small-sized spherical pores are used in the bone contact layer, while large-sized cylindrical pores are used in the core layer.

[0133] Achieving microstructure gradients: Adjusting additive manufacturing process parameters, including: scanning spacing. The layer thickness is The forming atmosphere is an inert gas environment. High laser power and low scanning speed parameters can refine the grains, while low laser power and high scanning speed parameters can obtain relatively coarse grains. By controlling the process parameters in layers, a gradient distribution of microstructure can be achieved.

[0134] S3 involves surface deformation treatment of the formed component to form a fine-grained structure layer in the surface area.

[0135] Specifically, the additively manufactured components undergo sandblasting and grinding processes, as follows:

[0136] Sandblasting: SiC abrasive is used, with an abrasive particle size of [missing information]. The sandblasting pressure was 0.6 MPa, the sandblasting time was 25 minutes, and the sandblasting angle was [missing information]. .

[0137] Grinding treatment: The sandblasted components are ground in stages, with the abrasive paper grit gradually increasing from 400 grit to 2000 grit, the grinding pressure being 0.4 MPa, and the grinding speed being 50 r / min.

[0138] After surface deformation treatment, the surface layer of the component has a thickness of A fine-grained layer of plastic deformation, wherein the grain size of the fine-grained layer is smaller than It is significantly better than the grain size in the internal region.

[0139] S4, perform heat treatment on the component after surface deformation treatment. The heat treatment atmosphere is air, and the heat treatment temperature is [temperature missing]. The heat preservation time is 4 hours, and the cooling method is to cool to room temperature with the furnace.

[0140] The graded porous magnesium alloy produced in this example features a high-strength design, making it suitable for high-stress load-bearing components (such as load-bearing bones), with an expected degradation period of 15–24 months.

[0141] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A gradient porous magnesium alloy, characterized in that, The gradient porous magnesium alloy comprises, by weight percentage, the following components: 0.2 to 0.5 wt.% Ag, 0.6 to 2.4 wt.% Y, 0.6 to 1.2 wt.% Zn, 7.0 to 10.6 wt.% Gd, with the balance being Mg and unavoidable impurity elements; The gradient porous magnesium alloy is formed by additive manufacturing and has an elemental gradient, microstructure gradient and pore structure gradient distributed along a preset direction inside.

2. The gradient porous magnesium alloy according to claim 1, characterized in that: It also includes a gas alloying element, which is selected from one or more of oxygen, nitrogen, and hydrogen. The oxygen content is 50~2000ppm, the nitrogen content is 20~1000ppm, and the hydrogen content is 1~100ppm.

3. The gradient porous magnesium alloy according to claim 1 or 2, characterized in that: At least one of Ag, Y, Zn and Gd elements is distributed in a gradient along a predetermined direction inside the gradient porous magnesium alloy.

4. The gradient porous magnesium alloy according to any one of claims 1 to 3, characterized in that: The porosity of the gradient porous magnesium alloy is 10-60%, and the average pore size is [missing information]. The porosity and / or the pore size vary in a gradient along the preset direction.

5. The gradient porous magnesium alloy according to any one of claims 1 to 4, characterized in that: The surface region of the gradient porous magnesium alloy is a fine-grained structure layer formed by surface deformation treatment, and the grain size of the surface region is smaller than that of the internal region.

6. The method for preparing gradient porous magnesium alloy according to claim 5, characterized in that: After the surface deformation treatment, a layer with a thickness of [thickness value missing] is formed on the surface of the component. The fine-grained structure layer of plastic deformation.

7. A method for preparing a gradient porous magnesium alloy as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1, Prepare raw material powder, wherein the raw material powder includes Mg-30Y master alloy powder, Mg-30Gd master alloy powder, Zn powder and Ag powder; S2, additive manufacturing, uses selective laser melting or binder spraying to form components layer by layer. During the forming process, by controlling the powder ratio, laser power, scanning speed and pore unit structure design, element gradient, microstructure gradient and pore structure gradient are formed inside the component. S3, the surface deformation treatment is carried out on the formed component to form a fine-grained structure layer in the surface area; S4, heat treatment is performed on the component that has undergone surface deformation treatment.

8. The method for preparing gradient porous magnesium alloy according to claim 7, characterized in that: The surface deformation treatment in step S3 includes sandblasting and / or grinding.

9. The method for preparing gradient porous magnesium alloy according to claim 7 or 8, characterized in that: During the additive manufacturing and / or heat treatment process, a gaseous alloying element is introduced by controlling the forming atmosphere, so that the gaseous alloying element is distributed in a gradient within the component; the gaseous alloying element is selected from one or more of oxygen, nitrogen and hydrogen.

10. The application of a gradient porous magnesium alloy as described in any one of claims 1 to 5 in the preparation of biodegradable bone fixation implants, characterized in that: The biodegradable bone fixation implant includes one or more of bone nails, bone plates, bone screws, and bone plates.

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