A composite additive manufacturing method for a medical talus implant

Abstract

The application discloses a kind of composite additive manufacturing methods of medical talus implant, in method, gradient topological structure facing laser impact forging process is designed;Laser powder bed fusion layer-by-layer printing, wherein, the three-dimensional defect model is printed using selective laser melting equipment;In-situ metastable laser impact forging, wherein, within 2000ms after each printing layer is completed, the melt pool is in metastable state but has not completely solidified, in-situ forging is carried out by applying ultrafast laser shock wave with pulse energy of 90-110 μJ to obtain a forming piece;Construct functional post-processing and bioactive interface, wherein the forming piece is heat treated at 490-510 ℃ for 3.5-4.5 h in an inert atmosphere, and then the bone contact surface is sandblasted using alumina abrasive with a particle size of 100-200 μm to obtain a bioactive microtopography with a surface roughness Sa of 1.5-2.5 μm.

Description

Technical Field

[0001] This invention relates to the field of high-end medical device technology, and in particular to a composite additive manufacturing method for a medical talus implant. Background Technology

[0002] As a key weight-bearing joint prosthesis, medical talus implants must meet multiple stringent requirements: sufficient mechanical support (compressive strength ≥120MPa), excellent osseointegration (surface roughness Sa1.5-2.5μm), and significant weight reduction (weight reduction of 30%-50%).

[0003] Additive manufacturing (3D printing) technology, particularly its ability to fabricate complex porous structures, has made lightweight and biomimetic designs possible. Related technologies (such as CN116833425A) have disclosed the application of TPMS lattice structures to orthopedic implants to leverage their porous properties and promote bone ingrowth. However, porous implants fabricated solely using additive manufacturing technology have a fatal flaw: during the layer-by-layer melting-solidification process, microcracks, pores, and interlayer residual tensile stresses as high as 80 MPa are inevitably generated. These defects make the implant highly susceptible to fatigue cracking and fatigue fracture under high-stress, complex-motion load-bearing environments such as the talus, posing a significant safety hazard.

[0004] To address the mechanical performance issues of additively manufactured parts, existing technology (CN108143475A) proposes combining laser shock peening with 3D printing. However, this technology primarily targets solid structures or structures with macroscopic reinforcing ribs, and does not reveal how to precisely and uniformly apply impact energy to thin-walled (~1mm), hollow, and geometrically complex microstructures like TPMS lattices. Inappropriate impacts can easily damage the delicate lattice structure, or fail to achieve the desired strengthening effect due to disordered reflection and attenuation of the shock wave within the complex interior.

[0005] More importantly, the current field suffers from a core pain point: a disconnect between design and manufacturing. That is, the topology optimization design of lattice structures (such as porosity and wall thickness) and subsequent strengthening processes (such as laser shock) are independent of each other, lacking synergy. An ideal topology that performs perfectly in simulation software may become worthless because it cannot withstand subsequent processing or cannot achieve effective performance improvements in subsequent processes.

[0006] Furthermore, the surface treatment of implants, such as the sandblasting technology disclosed in CN107865713A, aims to obtain extremely low roughness on the joint bearing surface to improve wear resistance. This is completely different in purpose and technical method from the specific roughness surface required for bone implants to promote osseointegration.

[0007] Therefore, there is an urgent need in this field for a composite manufacturing method that can organically combine structural design, dynamic reinforcement manufacturing, and functional surface treatment to fundamentally solve the contradiction between lightweight, high strength, and excellent biocompatibility.

[0008] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0009] To address the shortcomings or defects of the existing technology, this invention provides a medical bone implant topology design and performance optimization technology based on forging printing technology, and a composite additive manufacturing method for a medical talus implant. This invention integrates topology optimization, laser shock forging, and functional surface treatment, comprehensively and synergistically solving the challenges of synergistic optimization of lightweighting, stress control, and osseointegration in current technologies.

[0010] The objective of this invention is achieved through the following technical solutions.

[0011] A composite additive manufacturing method for a medical talus implant includes:

[0012] Design a gradient topology structure for laser shock forging process, wherein a three-dimensional defect model is constructed based on talus CT data, and a G-type three-period minimal surface lattice structure is filled inside with the outer skin set as the frozen area.

[0013] Laser powder bed melting is used for layer-by-layer printing, wherein a selective laser melting device is used to print the three-dimensional defect model;

[0014] In-situ metastable laser shock forging, wherein within 2000ms after each printing layer is completed, when the molten pool is in a metastable state but has not yet completely solidified, an ultrafast laser shock wave with a pulse energy of 90-110μJ is applied to forge the shaped part in situ.

[0015] To construct a functionalized post-treatment and bioactive interface, the molded part was heat-treated at 490-510℃ for 3.5-4.5h in an inert atmosphere, and then the bone contact surface was sandblasted with alumina abrasive with a particle size of 100-200μm to obtain a bioactive micromorphology with a surface roughness Sa of 1.5-2.5μm.

[0016] In the method described, the wall thickness of the lattice structure is 1.0-1.2 mm, and the porosity is distributed in a gradient along the main load direction, continuously transitioning from 30%-40% in the load-bearing zone to 60%-70% in the bone ingrowth zone.

[0017] In the method described, the porosity is distributed in a gradient along the main load direction. The load-bearing zone with a porosity of 30%-40% is used to bear the main mechanical load and efficiently transmit impact energy, while the bone ingrowth zone with a porosity of 60%-70% is used to promote bone tissue ingrowth and vascularization. The two zones avoid stress concentration through a continuous gradient transition.

[0018] In the method described, the wall thickness of the lattice structure is 1.1 mm, which enables the introduction of uniform plastic deformation and residual compressive stress in the wall thickness direction without damaging the structural integrity, using 100 μJ of laser shock energy.

[0019] In the method described, during layer-by-layer printing, the inner surface printing parameters are a fixed layer thickness of 50 μm, a spot diameter of 60 μm, and a scanning interval of 30 μm, ensuring a 50% overlap coverage.

[0020] In the method described, the impact parameters for in-situ forging using ultrafast laser shock waves include: a scanning speed consistent with the printing scanning speed, a scanning spacing of 25-35μm to achieve an overlap coverage of no less than 50% on the TPMS curved surface, and an impact direction perpendicular to the current printing layer.

[0021] In the method described, the metastable state is a semi-solid range where the molten pool temperature is higher than the material recrystallization temperature but lower than the liquidus line.

[0022] In the method described, the medical talus implant is made of Ti-6Al-4V material.

[0023] A medical talus implant is prepared by the composite additive manufacturing method of the medical talus implant.

[0024] In the aforementioned medical talus implant, the overall residual stress of the medical talus implant is in a compressive stress state, with an absolute value ≤50MPa, a compressive strength ≥125MPa, a weight reduction of ≥50% compared to solid structures, and a fatigue life improvement of ≥25% compared to additively manufactured parts.

[0025] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention achieves a balance between lightweight and high strength, reducing implant weight by 52% while maintaining a compressive strength of 128 MPa, far exceeding traditional processes. Superior fatigue performance is achieved through metastable laser shock irradiation, introducing a uniform residual compressive stress field within the implant, optimizing the overall residual stress from ~80 MPa (tensile stress) in traditional additive manufacturing to 45 MPa (compressive stress), fundamentally inhibiting fatigue crack initiation and increasing fatigue life by 30%. Excellent osteointegration performance is further enhanced by the gradient porosity structure combined with a functionalized sandblasted bioactive interface, providing an ideal topological space and surface environment for rapid osteoblast ingrowth and vascularization.

[0026] The description provided is merely an overview of the technical solution of this invention. In order to make the technical means of this invention clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and to make the described and other objects, features and advantages of this invention more obvious and understandable, specific embodiments of this invention are described below. Attached Figure Description

[0027] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0028] In the attached diagram:

[0029] Figure 1 This is a schematic diagram of a three-dimensional reconstruction model of the talus based on CT data in one embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the unit cell and porosity gradient distribution of a gradient G-type TPMS lattice structure in one embodiment of the present invention.

[0031] Figure 3 This is an optimized stress distribution cloud map of the talus implant in one embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram illustrating the significant improvement of forging printing compared to conventional additive manufacturing in one embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of a physical talus implant in one embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram illustrating the clinical application of a talus implant in the ankle, as shown in one embodiment of the present invention.

[0035] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0036] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0037] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "include" or "comprising" used throughout the specification and claims are open-ended and should be interpreted as including but not limited to. The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0038] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0039] To better understand, such as Figures 1 to 6 As shown, this invention discloses a composite additive manufacturing method for a medical talus implant, the method comprising,

[0040] Design a gradient topology structure for laser shock forging. A 3D defect model is constructed based on talus CT data. In Ntopology software, this solid model is shelled to obtain an 'outer skin'. With the outer skin set as a frozen region, the interior is filled with a gradient G-type three-period minimal surface lattice structure. The resulting 3D defect model is imported into engineering design / topology optimization software. The model's interior is divided into two regions: a frozen region (set as a 'frozen region', typically achieved through 'named selection', 'apply freeze constraints', or other specific functions or operations in software like xx), and a non-frozen region (the unfilled cavities within the model). The outer skin is the frozen region, and the hollow interior obtained after shelling the solid model is the non-frozen region.

[0041] Laser powder bed melting is used for layer-by-layer printing, wherein a selective laser melting device is used to print the three-dimensional defect model;

[0042] In-situ metastable laser shock forging, wherein within 2000ms after each printing layer is completed, when the molten pool is in a metastable state but has not yet completely solidified, an ultrafast laser shock wave with a pulse energy of 90-110μJ is applied to forge the shaped part in situ.

[0043] To construct a functionalized post-treatment and bioactive interface, the molded part was heat-treated at 490-510℃ for 3.5-4.5h in an inert atmosphere, and then the bone contact surface was sandblasted with alumina abrasive with a particle size of 100-200μm to obtain a bioactive micromorphology with a surface roughness Sa of 1.5-2.5μm.

[0044] In a preferred embodiment of the method, the wall thickness of the lattice structure is 1.0-1.2 mm, and the porosity is distributed in a gradient along the main load direction, continuously transitioning from 30%-40% in the load-bearing zone to 60%-70% in the bone ingrowth zone.

[0045] In a preferred embodiment of the method, the porosity is distributed in a gradient along the main load direction. The load-bearing zone with a porosity of 30%-40% is used to bear the main mechanical load and efficiently transmit impact energy, while the bone ingrowth zone with a porosity of 60%-70% is used to promote bone tissue ingrowth and vascularization. The two zones avoid stress concentration through a continuous gradient transition.

[0046] In a preferred embodiment of the method, the wall thickness of the lattice structure is 1.1 mm, so that a laser shock energy of 100 μJ can achieve uniform plastic deformation and introduction of residual compressive stress in the wall thickness direction without damaging the structural integrity.

[0047] In a preferred embodiment of the method, during layer-by-layer printing, the inner surface printing parameters are a fixed layer thickness of 50 μm, a spot diameter of 60 μm, and a scanning spacing of 30 μm, ensuring a 50% overlap coverage.

[0048] In a preferred embodiment of the method, the impact parameters for in-situ forging with ultrafast laser shock waves include: a scanning speed consistent with the printing scanning speed, a scanning spacing of 25-35μm to achieve an overlap coverage of no less than 50% on the TPMS curved surface, and an impact direction perpendicular to the current printing layer.

[0049] In a preferred embodiment of the method, the metastable state is a semi-solid region where the molten pool temperature is higher than the material recrystallization temperature but lower than the liquidus line.

[0050] In a preferred embodiment of the method, the medical talus implant is made of Ti-6Al-4V material.

[0051] In another embodiment, the present invention also discloses a medical talus implant prepared by the composite additive manufacturing method of the medical talus implant.

[0052] In a preferred embodiment of the medical talus implant, the overall residual stress of the medical talus implant is in a compressive stress state, with an absolute value ≤50MPa, a compressive strength ≥125MPa, a weight reduction of ≥50% compared to solid structures, and a fatigue life improvement of ≥25% compared to additively manufactured parts.

[0053] In one embodiment, gradient topology optimization design, laser shock blasting printing composite process, and functionalized surface treatment technology are deeply coupled and synergistically optimized. Guided by the process requirements of laser shock blasting, the method reverse-engineers a G-type TPMS lattice structure with a specific wall thickness (1.1 mm) and gradient porosity (30%-70%). Then, a specific energy (100 μJ) laser shock is applied during the metastable stage of the molten pool to achieve micro-defect healing and residual stress optimization. Finally, functionalized sandblasting is used to construct the optimal microstructure interface (Sa 1.5-2.5 μm) for osseointegration. This invention solves the technical problems of insufficient mechanical properties and design-manufacturing disconnect in traditional additive manufacturing implants. The resulting implant achieves a 52% weight reduction while maintaining a compressive strength of 128 MPa, a 30% increase in fatigue life, and excellent biocompatibility.

[0054] In one embodiment, the manufacturing-oriented structural design is as follows: a three-dimensional model is generated based on the patient's talus CT data using a topology optimization method, wherein the outer skin is set as a frozen region, and the inner optimized region is filled with a gradient G-type TPMS lattice structure. The porosity of the structure gradually changes from 30% to 70% along the load direction, and its wall thickness (e.g., 1.1 mm) matches the laser shock pulse energy described in step c) to achieve effective depth enhancement.

[0055] Laser powder bed fusion printing: The model filled with the lattice structure is printed layer by layer using a laser powder bed fusion equipment. The inner surface scanning parameters are: layer thickness 50μm, laser diameter 0.060mm, power 380W, and scanning speed 1250mm / s.

[0056] In-situ metastable laser shock forging: In the metastable stage after each layer is printed, before the molten pool is completely solidified (e.g., within 2000ms), a laser shock wave is applied for in-situ forging. The parameters include: scanning speed of 1250mm / s, scanning spacing of 30μm to obtain an overlap rate of at least 50%, pulse energy of 100μJ, and the impact direction is perpendicular to the printed layer.

[0057] Post-processing and functionalized surface construction: The molded part was subjected to argon protection heat treatment at 500℃±10℃ for 4 hours±0.5 hours, and then the bone contact surface of the implant was sandblasted with 100-200μm abrasive until a bioactive interface with a surface roughness Sa of 1.5-2.5μm was formed.

[0058] In another embodiment, the scanning speed of the laser impact forging is consistent with the scanning speed of the printing in step b), and the scanning spacing is set according to the diameter of the laser spot to ensure uniform and dead-angle-free impact coverage of the curved surface of the TPMS dot matrix structure.

[0059] For example, a lightweight medical talus implant includes a body made of medical titanium alloy material, said body having:

[0060] An external solid skin and an internal gradient G-type TPMS lattice structure, the porosity of which gradually changes from 30% to 70% along the load direction;

[0061] The deep residual compressive stress field formed in the lattice structure by the in-situ metastable laser shock forging process, which makes the overall residual stress of the implant less than 50MPa.

[0062] Its bone contact surface has a bioactive microstructure with a Sa value of 1.5-2.5 μm, which promotes osseointegration.

[0063] In one embodiment, the method includes:

[0064] Topology optimization and lattice structure design for laser forging process:

[0065] The unique aspect of this step is that the design of the lattice structure is no longer an isolated simulation optimization, but rather is based on the final laser shock forging process requirements as the core design constraint.

[0066] Model Input and Load: A 3D model of the talus defect was reconstructed based on the patient's CT data and imported into Altair HyperWorks software. The ankle joint load was set to 1000N, and a 50% reduction in volume was set as the weight reduction target.

[0067] Density method optimization: Optimization is performed with the goal of minimizing strain energy.

[0068] Structure generation designed for forging: The outer skin is set as a frozen area, while the interior is filled with a specially optimized gradient G-type TPMS lattice structure.

[0069] The wall thickness was designed collaboratively: 1.1 mm. This thickness is the result of precise calculations and experimental optimization. It ensures the stability of the structure during printing and allows the 100 μJ laser shock pulse energy in subsequent steps to effectively penetrate and act on the entire wall thickness, achieving the construction of a deep residual compressive stress field, rather than ineffective surface knocking.

[0070] A gradient porosity with dual functions: the structure's porosity gradually changes from 30% (load-bearing zone) to 70% (bone ingrowth zone) along the load direction. This gradient design is not only a biomimetic gradient simulating bone density distribution, but also a mechanical performance gradient serving the manufacturing process. The load-bearing zone with 30% porosity has a denser structural wall, which can better conduct and withstand impact energy, achieving efficient reinforcement; while the 70% bone ingrowth zone has a relatively sparse structure and lower stress requirements, thus avoiding unnecessary over-strengthening. This design achieves a precise distribution of reinforcement effect and biological function as needed.

[0071] Metastable laser shock blasting printing composite process:

[0072] This step creatively integrates printing and impact processes, achieving effective reinforcement of complex lattice structures through precise control of process windows and parameters.

[0073] Innovation in the process window—metastable impact: After each layer of powder is melted and printed, within 2000ms, while the molten pool is in a metastable state (before complete solidification), a laser shock wave is applied for in-situ forging. Compared to traditional impacting fully solidified cold metal, the metal at this stage has extremely high plasticity, requiring only very low impact energy (100μJ) to achieve effective densification of the microstructure, healing of microcracks, and to minimize the generation of residual stress during solidification. This is a significant improvement over traditional laser shock peening technology.

[0074] Parameter set for collaborative optimization:

[0075] Inner surface printing parameters: layer thickness 50μm, laser diameter 0.060mm, power 380W, scanning speed 1250mm / s.

[0076] Laser shock forging parameters:

[0077] Scanning speed: 1250mm / s (consistent with printing speed).

[0078] Scanning spacing: 30μm (based on a 60μm spot diameter, ensuring a 50% overlap rate).

[0079] Pulse energy: 100μJ (precisely matched to 1.1mm wall thickness).

[0080] Laser power and frequency: 5W power, 50kHz frequency.

[0081] This set of mutually coupled parameters is specifically optimized for handling complex curved surface lattices of gradient TPMS, ensuring seamless and uniform reinforcement of the structure and solving the technical problem of uneven propagation of shock waves within complex lattices.

[0082] Full-process post-processing and functional surface construction:

[0083] Heat treatment: The microstructure is further homogenized by heat treatment under argon protection at 500℃±10℃ for 4h±0.5h, and the residual stress is stabilized at a compressive stress state below 50MPa.

[0084] Functionalized sandblasting: Sandblasting is performed using alumina particles with a diameter of 100-200 μm. The purpose of this step is not polishing or improving wear resistance, but to construct a specific surface microstructure on the bone contact surface of the implant. The final surface roughness Sa is 1.5-2.5 μm, a range that has been validated through extensive cellular experiments as the most favorable bioactive interface for osteoblast adhesion, proliferation, and differentiation, thereby greatly promoting rapid and stable integration of the implant with the host bone.

[0085] In one embodiment, this embodiment details the process of manufacturing a talus implant using Ti-6Al-4V material:

[0086] 1. Model processing

[0087] Process objectives: Ensure the printability of the model and optimize structural stability.

[0088] Technical Content: A printability analysis of the 3D model of the implant was performed to identify overhanging structures and potential deformation areas. By optimizing the model's placement angle, reliance on overhanging structures was reduced, lowering support requirements. Support structures were added to key mechanically load-bearing areas, with appropriate gaps reserved at the support contact surfaces to prevent fusion adhesion.

[0089] 2. Slicing and Path Planning

[0090] Process objective: To achieve high-precision layering and molding path design.

[0091] Technical details: A composite process of additive manufacturing and ultrafast forging is employed to divide the 3D model into 2D slice data, adapting it to the precision requirements of the equipment. Path planning prioritizes ensuring a continuous closed contour, and a honeycomb filling strategy is used in the support areas to balance structural strength and ease of removal.

[0092] 3. Printing and shaping

[0093] Process objective: To ensure the geometric accuracy of the implant and the density of its internal tissue.

[0094] Technical control: Based on selective laser melting (SLM) technology, the system monitors the molten pool morphology and interlayer offset error in real time, and dynamically adjusts process parameters. The forming quality is tracked through infrared thermal imaging and a high-speed camera system, triggering an alarm and pausing correction if limits are exceeded.

[0095] 4. Powder removal and subsequent washing

[0096] Process objective: To thoroughly remove residual powder from the implant surface and internal cavity.

[0097] Step-by-step process:

[0098] ① Initial powder removal on the vibration table: The implant is placed on the vibration table, and the lower surface of the substrate is struck by high-frequency vibration to cause loose powder in the lattice cavity and complex structure to fall off.

[0099] ② Secondary compressed air blowing: High-pressure compressed air is used to blow the implant surface and inner dead corners in a directional manner to avoid secondary powder adhesion.

[0100] ③ Ultrasonic cleaning three times to remove powder: The implant is immersed in an ultrasonic cleaner and continuously cleaned with deionized water as the medium, using the cavitation effect to remove the deeply attached powder.

[0101] ④ Cleaning and drying with anhydrous ethanol: Soak and rinse with anhydrous ethanol to dissolve residual organic matter, and then transfer to a drying oven for thorough drying.

[0102] ⑤ After each stage of powder removal, inspect the implant with an endoscope to ensure no visible powder residue remains. After drying, the implant must be placed in a clean environment to avoid secondary contamination.

[0103] 5. Heat treatment

[0104] Process objectives: Eliminate residual stress and optimize material properties.

[0105] Technical content:

[0106] Heat treatment was performed under an argon protective atmosphere at 500℃ for 4 hours, strictly following the process requirements. After treatment, the microhardness and residual stress relief effects were verified to ensure compliance with subsequent processing requirements.

[0107] 6. Removal of supports and surface finishing

[0108] Process objective: Remove the supporting structure and achieve functional surface treatment.

[0109] Technical requirements:

[0110] ① Manual removal of supports: Use precision fitter tools to remove the support structure point by point to avoid damaging the added support surface and causing pits, defects, etc., so as to facilitate the subsequent polishing process.

[0111] ② Mechanical polishing: The implant surface is polished in stages, especially the support surface is removed, transitioning from coarse polishing to fine polishing, and finally achieving a bright surface effect.

[0112] ③ Sandblasting: The implant surface is sandblasted; for special components such as tibial prostheses, additional vibration sand removal is performed to ensure the inner cavity is clean.

[0113] 7. Final Inspection and Delivery

[0114] Process objective: To ensure that the implant meets the standards for medical implants.

[0115] Technical Specifications:

[0116] ① Geometric inspection: Verify the tolerances of key features by performing full-dimensional inspection using a coordinate measuring machine.

[0117] ②Performance verification: Fatigue tests and surface cleanliness tests are conducted in strict accordance with international medical standards.

[0118] ③ Packaging and delivery: Dustproof and moisture-proof packaging is used, complete product identification and traceability records are established, and delivery is completed in accordance with medical implant specifications.

[0119] It should be noted that, considering the inherent optical characteristics of selective laser melting equipment and the strict requirements of laser shock forging on the overlap rate, the layer thickness in all embodiments is fixed at 50 μm, the laser spot diameter is fixed at 60 μm, and the scanning interval is fixed at 30 μm (to ensure a precise 50% overlap coverage).

[0120] For example: Verification based on the lower limit of process parameters. Under the premise of fixed core equipment parameters, the lower limit of variable process parameters is selected to verify the molding and strengthening effect under low energy input conditions.

[0121] ① Gradient topology design for laser shock forging process

[0122] Model construction: A three-dimensional model was constructed based on talus CT data, defining the outer skin as the frozen area and the internal cavity as the unfrozen area.

[0123] Dot matrix filling: A gradient G-type TPMS dot matrix structure is filled in the non-frozen area, and the wall thickness of the dot matrix structure is set to 1.0 mm.

[0124] Gradient setting: The porosity gradually transitions from 30% in the load-bearing zone to 60% in the bone ingrowth zone along the main load direction.

[0125] ②Laser powder bed melting layer-by-layer printing

[0126] Fixed parameters: layer thickness 50μm, laser spot diameter 60μm.

[0127] Variable parameters: laser power 360W, scanning speed 1200mm / s.

[0128] ③ In-situ metastable laser shock forging

[0129] Impact timing: within 500ms after each printed layer is completed (when the melt pool is in a metastable state).

[0130] Fixed parameters: scanning spacing 30μm (ensuring 50% overlap).

[0131] Variable parameters: Apply an ultrafast laser shock wave with a pulse energy of 90μJ, and a scanning speed of 1200mm / s (consistent with the printing speed).

[0132] ④ Constructing a functionalized post-processing and bioactive interface

[0133] Heat treatment: Heat treatment at 490℃ for 3.5h in an inert atmosphere.

[0134] Surface treatment: The bone contact surface is sandblasted using alumina abrasive with a particle size of 100μm.

[0135] In another embodiment: verify the structural integrity and reinforcement effect under the condition of variable process parameter upper limit.

[0136] ① Gradient topology design for laser shock forging process

[0137] Dot matrix filling: Set the wall thickness of the dot matrix structure to 1.2mm.

[0138] Gradient setting: The porosity gradually transitions from 40% in the load-bearing zone to 70% in the bone ingrowth zone along the main load direction.

[0139] ②Laser powder bed melting layer-by-layer printing

[0140] Fixed parameters: layer thickness 50μm, laser spot diameter 60μm.

[0141] Variable parameters: laser power 400W, scanning speed 1300mm / s.

[0142] ③ In-situ metastable laser shock forging

[0143] Impact timing: within 1900ms after each printed layer is completed.

[0144] Fixed parameters: scanning spacing 30μm (ensuring 50% overlap).

[0145] Variable parameters: Apply an ultrafast laser shock wave with a pulse energy of 110 μJ and a scanning speed of 1300 mm / s.

[0146] ④ Constructing a functionalized post-processing and bioactive interface

[0147] Heat treatment: Heat treatment at 510℃ for 4.5h in an inert atmosphere.

[0148] Surface treatment: The bone contact surface is sandblasted using alumina abrasive with a particle size of 200μm.

[0149] In another embodiment: the optimal combination of parameters, verified by experiments, was selected to achieve the best balance between mechanical properties and biological activity while ensuring a 50% overlap rate.

[0150] ① Gradient topology design for laser shock forging process

[0151] Lattice filling: The wall thickness of the lattice structure is set to 1.1 mm. This wall thickness is precisely matched with an impact energy of 100 μJ, enabling effective reinforcement across the entire wall thickness.

[0152] Gradient setting: The porosity gradually transitions from 30% in the load-bearing zone to 70% in the bone ingrowth zone along the main load direction.

[0153] ②Laser powder bed melting layer-by-layer printing

[0154] Fixed parameters: layer thickness 50μm, laser spot diameter 60μm.

[0155] Variable parameters: laser power 380W, scanning speed 1250mm / s.

[0156] ③ In-situ metastable laser shock forging

[0157] Impact timing: within 1000ms after each printed layer is completed.

[0158] Fixed parameters: scanning spacing 30μm. The scanning spacing here is strictly set based on a spot diameter of 60μm to accurately achieve 50% overlap coverage and ensure the uniformity of impact strengthening.

[0159] Variable parameters: Apply an ultrafast laser shock wave with a pulse energy of 100μJ and a scanning speed of 1250mm / s.

[0160] ④ Constructing a functionalized post-processing and bioactive interface

[0161] Heat treatment: Heat treatment at 500℃ for 4.0h under argon protection.

[0162] Surface treatment: The bone contact surface is functionalized by sandblasting with alumina abrasive with a particle size of 100-200μm (or preferably 150μm) to obtain a bioactive microstructure of Sa1.5-2.5μm.

[0163]

[0164] The effectiveness of the embodiments was verified through testing. In all embodiments, by fixing the layer thickness, spot size, and spacing parameters, the geometric accuracy and impact coverage of the molding were guaranteed. Among them, Embodiment 3 showed the best overall performance.

[0165] Compressive strength: 128 MPa;

[0166] Residual stress: -45MPa (compressive stress);

[0167] Fatigue life increased by 30%;

[0168] Surface roughness (Sa): 2.1 μm Although there are slight fluctuations in strength or roughness in Examples 1 and 2, they both meet the basic performance requirements of medical implants (compressive strength ≥125 MPa, residual stress ≤50 MPa), verifying the stability of the present invention within the parameter range.

[0169] Furthermore, it should be noted that,

[0170] First, this invention addresses the design of a gradient G-type TPMS lattice structure driven by the reverse of laser shock forging processes, fundamentally solving the disconnect between traditional topology optimization, which focuses solely on simulation and neglects manufacturing. The wall thickness is precisely limited to 1.1mm, not arbitrarily chosen, but rather the optimal solution obtained through multiphysics coupling simulation and experimental verification based on the penetration depth and plastic deformation threshold of laser shock energy (100μJ) in titanium alloy. This thickness ensures both the forming stability of the thin-walled structure during printing and the effective penetration of the shock wave throughout the entire cross-section, inducing uniform compressive stress across the entire wall thickness range, avoiding ineffective surface impact due to insufficient energy or structural collapse caused by excessive energy. Simultaneously, the gradient porosity distribution from 30% to 70% not only biomimetically simulates the density transition from cortical to cancellous bone in the human talus but also achieves on-demand reinforcement at the manufacturing level: the high-density load-bearing zone is dense and stiff, efficiently conducting shock energy and forming a strong and tough skeleton; the low-density bone ingrowth zone is porous and has a large specific surface area, facilitating cell migration and nutrient exchange, without requiring excessive reinforcement to save on process costs. This concept of designing for manufacturing and grading for functionality is the core prerequisite for achieving performance synergy.

[0171] Secondly, the in-situ metastable laser shock blasting process is a significant innovation of traditional cold laser shock strengthening. Impact is applied within the metastable window (within 2000ms) before each molten pool has fully solidified. At this time, the metal is in a high-temperature semi-solid state, with active dislocation movement and significantly reduced yield strength. Only extremely low pulse energy (100μJ) is required to induce large-scale plastic flow, thereby efficiently healing defects such as micropores and microcracks formed during the printing process and suppressing tensile stress generated by solidification shrinkage. Compared to high-energy impacts on cooled parts (typically requiring mJ-level energy), this method has lower energy consumption, less thermal disturbance, and can simultaneously achieve microstructural densification and stress control during layer-by-layer construction. Ultimately, the overall residual stress is transformed from +80MPa (tensile) in traditional additive manufacturing to -45MPa (compressive), significantly improving fatigue resistance and increasing fatigue life by more than 30%. More importantly, the impact parameters (scanning speed, spacing, energy) are strictly synchronized and matched with the printing parameters to ensure uniform impact coverage without dead angles on the complex TPMS surface, thus overcoming the technical bottleneck of uneven scattering and attenuation of shock waves inside hollow thin-walled microstructures.

[0172] Third, functionalized sandblasting constructs a bioactive interface to precisely serve the needs of bone integration. Unlike the pursuit of ultra-smooth (Sa<0.1μm) wear-resistant treatments for joint friction surfaces, this invention deliberately retains and optimizes micron-level roughness (Sa=1.5-2.5μm) in the bone contact area. This range has been confirmed by numerous in vitro cell experiments as the golden window for the most active osteoblast adhesion, spreading, and differentiation: too low a roughness results in a lack of anchoring points, while too high a roughness easily triggers inflammatory responses. By controlling the alumina abrasive particle size (100-200μm) and blasting parameters, while preserving the gradient porous macrostructure, a rich peak-valley morphology is formed at the microscale, greatly increasing protein adsorption and cell contact area, and accelerating the early stable integration of the bone-implant interface.

[0173] In summary, this invention organically integrates three key technologies: malleable topology design, metastable in-situ forging, and functionally guided surface finishing. This not only significantly reduces the weight of the implant (-52%), but also simultaneously achieves synergistic optimization of high strength (128MPa), high fatigue life (+30%), and high osseointegration capacity (Sa1.5-2.5μm). It completely breaks through the technical dilemma of traditional additive manufacturing implants being either too light or too heavy, and difficult to balance biocompatibility. This provides a reliable and mass-producible new paradigm for the clinical application of high-performance personalized orthopedic implants.

[0174] See Figure 4 This demonstrates the significant improvement of forging printing compared to conventional additive manufacturing. Compared to conventional additive manufacturing, this invention achieves a substantial 24.7% increase in tensile strength; simultaneously, compared to the 0.00377% defect rate of conventional additive manufacturing, the defect rate of this invention is reduced to 0.00141%, a reduction of 62.6%. In summary... Figure 4 , Figure 5 Furthermore, it can be observed that the surface morphology of the talus implant prepared by this invention is also very good.

[0175] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0176] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for composite additive manufacturing of a medical talus implant, characterized in that, It includes, Design a gradient topology structure for laser shock forging process, wherein a three-dimensional defect model is constructed based on talus CT data, and a G-type three-period minimal surface lattice structure is filled inside with the outer skin set as the frozen area. Laser powder bed melting is used for layer-by-layer printing, wherein a selective laser melting device is used to print the three-dimensional defect model; In-situ metastable laser shock forging, wherein within 2000ms after each printing layer is completed, when the molten pool is in a metastable state but has not yet completely solidified, an ultrafast laser shock wave with a pulse energy of 90-110μJ is applied to forge the shaped part in situ. To construct a functionalized post-treatment and bioactive interface, the molded part was heat-treated at 490-510℃ for 3.5-4.5h in an inert atmosphere, and then the bone contact surface was sandblasted with alumina abrasive with a particle size of 100-200μm to obtain a bioactive micromorphology with a surface roughness Sa of 1.5-2.5μm.

2. The method as described in claim 1, characterized in that, The lattice structure has a wall thickness of 1.0-1.2 mm and a porosity that is gradient-distributed along the main load direction, transitioning continuously from 30%-40% in the load-bearing zone to 60%-70% in the bone ingrowth zone.

3. The method as described in claim 2, characterized in that, The porosity is distributed in a gradient along the main load direction. The load-bearing zone with a porosity of 30%-40% is used to bear the main mechanical load and efficiently conduct impact energy, while the bone ingrowth zone with a porosity of 60%-70% is used to promote bone tissue ingrowth and vascularization. The two zones avoid stress concentration through a continuous gradient transition.

4. The method as described in claim 1, characterized in that, The lattice structure has a wall thickness of 1.1 mm, which allows a laser shock energy of 100 μJ to achieve uniform plastic deformation and the introduction of residual compressive stress in the wall thickness direction without damaging the structural integrity.

5. The method as described in claim 1, characterized in that, During layer-by-layer printing, the inner surface printing parameters are a fixed layer thickness of 50μm, a spot diameter of 60μm, and a scanning spacing of 30μm to ensure 50% overlap coverage.

6. The method as described in claim 1, characterized in that, The impact parameters for in-situ forging using ultrafast laser shock waves include: scanning speed consistent with printing scanning speed, scanning spacing of 25-35μm to achieve an overlap coverage of no less than 50% on the TPMS curved surface, and impact direction perpendicular to the current printed layer.

7. The method as described in claim 1, characterized in that, The metastable state is the semi-solid range where the molten pool temperature is higher than the material recrystallization temperature but lower than the liquidus line.

8. The method as described in claim 1, characterized in that, The medical talus implant is made of Ti-6Al-4V material.

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