Additive manufacturing(AM)has revolutionized the production of metal bone implants,enabling unprecedented levels of customization and functionality.Recent advancements in surface-modification technologies have been cr...Additive manufacturing(AM)has revolutionized the production of metal bone implants,enabling unprecedented levels of customization and functionality.Recent advancements in surface-modification technologies have been crucial in enhancing the performance and biocompatibility of implants.Through leveraging the versatility of AM techniques,particularly powder bed fusion,a range of metallic biomaterials,including stainless steel,titanium,and biodegradable alloys,can be utilized to fabricate implants tailored for craniofacial,trunk,and limb bone reconstructions.However,the potential of AM is contingent on addressing intrinsic defects that may hinder implant performance.Techniques such as sandblasting,chemical treatment,electropolishing,heat treatment,and laser technology effectively remove residual powder and improve the surface roughness of these implants.The development of functional coatings,applied via both dry and wet methods,represents a significant advancement in surface modification research.These coatings not only improve mechanical and biological interactions at the implant-bone interface but also facilitate controlled drug release and enhance antimicrobial properties.Addition-ally,micro-and nanoscale surface modifications using chemical and laser techniques can precisely sculpt implant surfaces to promote the desired cellular responses.This detailed exploration of surface engineering offers a wealth of opportunities for creating next-generation implants that are not only biocompatible but also bioactive,laying the foundation for more effective solutions in bone reconstruction.展开更多
The remarkable mechanical properties exhibited by laminated structures have generated significant in-terest in the realm of additively manufactured laminated high-entropy alloys(HEAs).Despite this bur-geoning interest...The remarkable mechanical properties exhibited by laminated structures have generated significant in-terest in the realm of additively manufactured laminated high-entropy alloys(HEAs).Despite this bur-geoning interest,the nexus between process,structure,and properties within laminated HEAs remains largely uncharted.There is a vast space for investigating the effect of the typical heterogeneous interface on the macroscopic mechanical properties.This study focuses on the influence of the characteristic het-erogeneous interface on macroscopic mechanical properties of laminated HEAs,particularly anisotropy.Using the 3D-printed Fe_(50)Mn_(30)Co_(10)Cr_(10)-CoCrNi HEA as a model,we investigate the impact of interface geometry on mechanical characteristics.Tensile tests show that the reduced interface spacing increases yield strength.This laminated HEA displays significant anisotropy in strength and ductility,depending on the loading direction relative to the interface.Electron microscopic observations suggest that finer layer spacing enhances interface and dislocation strengthening,increasing yield strength.Anisotropic behaviors are confirmed to be mediated by interface orientation,explained in terms of deformation compatibility and crack development at the interface.This research offers fundamental insights into the relationship between heterogeneous interfaces and the mechanical properties in laminated HEAs.The knowledge is vital for designing,fabricating,and optimizing laminated HEAs through additive manufacturing,advancing their engineering applications.展开更多
Spinal fusion is a commonly used technique to treat acute and chronic spinal diseases by fusion of the adjacent vertebrae, aiming at achieving stability and eliminating the mobility of the objective segment. While bon...Spinal fusion is a commonly used technique to treat acute and chronic spinal diseases by fusion of the adjacent vertebrae, aiming at achieving stability and eliminating the mobility of the objective segment. While bone autografts and allografts have been conventionally used for spinal fusion, limitations persist in achieving optimization of both good osteoinductive capacity and mechanical stability. In this study, additively manufactured Zn-Li scaffolds were developed and evaluated for their potential in spinal fusion. First, three scaffold structures (BCC, Diamond, and Gyroid) were designed and verified in vitro. Due to the smooth transition surfaces and uniform degradation behavior, the Gyroid Zn-Li scaffold demonstrated mechanical integrity during degradation and enhanced cellular proliferation compared to the other two scaffolds. Subsequently, Zn-Li scaffolds (Gyroid) were selected for posterolateral lumbar fusion (L4/L5) in rabbits. Following 12 weeks of implantation, the Zn-Li scaffolds demonstrated a moderate biodegradation rate and satisfactory biocompatibility. Compared to bone allografts, the Zn-Li scaffolds significantly improved osseointegration adjacent to the transverse processes, which led to enhanced segmental stability of the fused vertebrae post posterolateral lumbar fusion. Overall, the results show that the biodegradable Zn-Li scaffold holds substantial potential as the next-generation graft for spinal fusion.展开更多
Nickel-based superalloys are indispensable for high-temperature engineering applications,yet their additive manufacturing(AM)is plagued by significant cracking defects.This review investigates crack failure mechanisms...Nickel-based superalloys are indispensable for high-temperature engineering applications,yet their additive manufacturing(AM)is plagued by significant cracking defects.This review investigates crack failure mechanisms in AM nickel-based superalloys,emphasizing methodologies to evaluate crack sensitivity and compositional design strategies to mitigate defects.Key crack types—solidification,liquation,solid-state,stress corrosion,fatigue,and creep-fatigue cracks—are analyzed,with focus on formation mechanisms driven by thermal gradients,solute segregation,and microstructural heterogeneities.Evaluation frameworks such as the Rappaz-Drezet-Gremaud(RDG)criterion,Solidification Cracking Index(SCI),and Strain Age Cracking(SAC)index are reviewed for predicting crack susceptibility through integration of thermodynamic parameters,solidification kinetics,and mechanical properties.Alloy compositional design strategies are presented,including optimization of strengthening elements(Al,Ti),grain boundary modifiers(B,Zr,Re),and impurity control(C,O),which suppress crack initiation and propagation via microstructure refinement and enhanced high-temperature resistance.Computational approaches,such as thermodynamically assisted design,high-throughput experimentation,and machine learning,are highlighted for decoding complex composition-structure-property relationships.Challenges in modeling multi-scale defect interactions and developing unified frameworks for manufacturing-and service-induced cracks are outlined.This review underscores the necessity of integrated computational-experimental strategies to advance reliable AM of nickel-based superalloys,providing insights for defect prediction,alloy optimization,and process control.展开更多
The unit cell configuration of lattice structures critically influences their load-bearing and energy absorption performance.In this study,three novel lattice structures were developed by modifying the conventional FB...The unit cell configuration of lattice structures critically influences their load-bearing and energy absorption performance.In this study,three novel lattice structures were developed by modifying the conventional FBCCZ unit cell through reversing,combining,and turning strategies.The designed lattices were fabricated via laser powder bed fusion(LPBF)using Ti-6Al-4V powder,and the mechanical properties,energy absorption capacity,and deformation behaviors were systematically investigated through quasi-static compression tests and finite element simulations.The results demonstrate that the three modified lattices exhibit superior performance over the conventional FBCCZ structure in terms of fracture strain,specific yield strength,specific ultimate strength,specific energy absorption,and energy absorption efficiency,thereby validating the efficacy of unit cell modifications in enhancing lattice performance.Notably,the CFBCCZ and TFBCCZ lattices significantly outperform both the FBCCZ and RFBCCZ lattice structures in load-bearing and energy absorption.While TFBCCZ shows marginally higher specific elastic modulus and energy absorption efficiency than CFBCCZ,the latter achieves superior energy absorption due to its highest ultimate strength and densification strain.Finite element simulations further reveal that the modified lattices,through optimized redistribution and adjustment of internal nodes and struts,effectively alleviate stress concentration during loading.This structural modification enhances the structural integrity and deformation stability under external loads,enabling a synergistic enhancement of load-bearing capacity and energy absorption performance.展开更多
A novel Additive Manufacturing(AM)-driven concurrent design strategy based on the beam characterization model considering strength constraints is proposed.The lattice topology,radius size,Building Orientation(BO),and ...A novel Additive Manufacturing(AM)-driven concurrent design strategy based on the beam characterization model considering strength constraints is proposed.The lattice topology,radius size,Building Orientation(BO),and structural yield strength can be simultaneously adjusted by integrating the overall process-structure-performance relationship of the AM process into the optimization.Specifically,the transverse isotropic material model is adopted to describe the material properties induced by the layer-by-layer manner of additive manufacturing.To bolster lattice strength performance,the stress constraints and ratio constraints of lattice struts are employed.The Tsai-Wu yield criterion is implemented to characterize the lattice strut's strength,while the P-norm method streamlines the handling of multiple constraints,minimizing computational overhead.Moreover,the gradient-based optimization model is established,where both the individual struts diameters and BO can be designed,and the buckling-prone spatial struts are strategically eliminated to improve the lattice strength further.Furthermore,several typical structures are optimized to verify the effectiveness of the proposed method.The optimized results are quite encouraging since the heterogeneous lattice structures with optimized BO obtained by the strength-based concurrent method show a remarkably improved performance compared to traditional designs.展开更多
In this work,the GW63K(Mg-6.54Gd-3.93Y-0.41Zr,wt.%)alloy wire was utilized as the feedstock material and the thin-walled component was fabricated using wire-arc additive manufacturing technology(WAAM).The microstructu...In this work,the GW63K(Mg-6.54Gd-3.93Y-0.41Zr,wt.%)alloy wire was utilized as the feedstock material and the thin-walled component was fabricated using wire-arc additive manufacturing technology(WAAM).The microstructural evolution during deposition and subsequent heat treatment was explained through multi-scale microstructural characterization techniques,and the impact of heat treatment on the strengthductility synergy of the deposited alloy was systematically compared.The results showed that the microstructure of the deposited sample was mainly composed of fine equiaxedα-Mg grains and Mg_(24)(Gd,Y)_(5) phase.The optimized solution heat treatment(450℃×2 h)had little effect on the grain size,but can effectively reduce the Mg_(24)(Gd,Y)_(5) eutectic phase on the grain boundary,resulting in a significant increase in elongation from 13.7% to 26.6%.After peak-aging treatment,the strength of the GW63K alloy increased to 370 MPa,which was significantly higher than the as-built state(267 MPa).The superior strength in this study is attributed to the refinement strengthening imparted by the fine microstructure inherited in the as-built GW63K alloy,as well as the precipitation strengthening due to the formation of dense β’precipitates with a pronounced plate-like aspect ratio.展开更多
Maraging steels are known for their exceptional strength but suffer from limited work hardening and ductility.Here,we report an intermittent printing strategy to tailor the microstructure and mechanical properties of ...Maraging steels are known for their exceptional strength but suffer from limited work hardening and ductility.Here,we report an intermittent printing strategy to tailor the microstructure and mechanical properties of maraging 250 steel via tuning the thermal history during wire-arc directed energy deposition.By introducing a dwell time between adjacent layers,the maraging 250 steel is cooled below the martensite start temperature,triggering thermally-driven martensitic transformation during the printing process.Thermal cycling during subsequent layer deposition results in the formation of reverted austenite which shows a refined microstructure and induces elemental segregation between martensite and reverted austenite.The Ni enrichment in the austenite promotes stabilization of the reverted austenite upon cooling to room temperature.The reverted austenite is metastable during deformation,leading to strain-induced martensitic transformation under loading.Specifically,a 3 min interlayer dwell time produces a maraging 250 steel with approximately 8% reverted austenite,resulting in improved work hardening via martensitic transformation induced plasticity during deformation.Meanwhile,the higher cooling rate and refined prior austenite grains lead to substantially refined martensitic grains(by approximately fivefold)together with an increased dislocation density.With 3 min interlayer dwell time,the yield strength of the printed maraging 250 steel increases from 836 MPa to 990 MPa,and the uniform elongation is doubled from 3.2% to 6.5%.This intermittent deposition strategy demonstrates the potential to tune the microstructure of maraging steels for achieving strength-ductility synergy by engineering the thermal history during additive manufacturing.展开更多
The integrated valve-controlled cylinder combines various control and execution components in hydraulic transmission systems.Its precise control and rapid response characteristics make it widely used in mobile equipme...The integrated valve-controlled cylinder combines various control and execution components in hydraulic transmission systems.Its precise control and rapid response characteristics make it widely used in mobile equipment for aerospace,robotics,and other engineering applications.Additive manufacturing provides high design freedom which can further enhance the power density of integrated valve-controlled cylinders.However,there is a lack of effective design methods to guide the additive manufacturing of valve-controlled cylinders for more efficient hydraulic energy transmission.This study accordingly introduces an energy-saving design method based on additive manufacturing for integrated valve-controlled cylinders.The method consists of two main parts:(1)redesigning the manifold block to eliminate leakage points and reduce energy losses through integrated design of the valve,cylinder,and piping;(2)establishing a pressure loss model to achieve energy savings through optimized flow channel design for bends with different parameters.Compared to traditional valve-controlled cylinders,the integrated valvecontrolled cylinder developed from our method reduces the weight by 31%,volume by 55%,and pressure loss in the main flow channel by over 30%.This indicates that the design achieves both lightweight construction and improved hydraulic transmission efficiency.This study provides theoretical guidance for the design of lightweight and energy-efficient valve-controlled cylinders,and may aid the design of similar hydraulic machinery.展开更多
The accurate characterization of anisotropy for additively manufactured materials is of vital importance for both highperformance structural design and printing processing optimization.To avoid the repetitive and redu...The accurate characterization of anisotropy for additively manufactured materials is of vital importance for both highperformance structural design and printing processing optimization.To avoid the repetitive and redundant tensile testing on specimens prepared along diverse directions,this study proposes an instrumented indentation-based inverse identification method for the efficient characterization of additively manufactured materials.In the present work,a 3D finite element model of indentation test is first established for the printed material,for which an anisotropic material constitutive model is incorporated.We have demonstrated that the indentation responses are information-rich,and material anisotropy along different directions can be interpreted by a single indentation imprint.Subsequently,an inverse identification framework is built,in which an Euclidean error norm between simulated and experimental indentation responses is minimized via optimization algorithms such as the Globally Convergent Method of Moving Asymptotes(GCMMA).The developed method has been verified on diverse printed materials referring to either the indentation curve or the residual imprint,and the superiority of this latter over the former is confirmed by a better and faster convergence of inverse identification.Experimental validations on 3D printed materials(including stainless steel 316L,aluminum alloy AlSi10Mg,and titanium alloy TC4)reveal that the developed method is both accurate and reliable when compared with material constitutive behaviors obtained from uni-axial tensile tests,regardless of the degree of anisotropy among different materials.展开更多
The effects of post heat treatment on the microstructure,aging kinetics,and room/elevated temperature mechanical properties of additively manufactured Inconel 718 superalloy were investigated.Scanning electron microsc...The effects of post heat treatment on the microstructure,aging kinetics,and room/elevated temperature mechanical properties of additively manufactured Inconel 718 superalloy were investigated.Scanning electron microscopy(SEM),electron backscattered diffraction(EBSD),and X-ray diffraction(XRD),as well as hardness,tensile,and creep testing were used for characterization.At temperatures higher than 1100°C,homogenization treatment resulted in the appearance of equiaxed grains by recrystallization and diminishing the dislocation density.The precipitation activation energy for the homogenized and aged condition was obtained as 203.2 kJ/mol,which was higher than the value of~160 kJ/mol for the as-built IN718 superalloy.Therefore,direct aging resulted in a faster aging response,which led to a significant improvement in tensile properties,as rationalized by the strengthening mechanisms.Direct aging treatment resulted in a higher elevated-temperature ultimate tensile strength(UTS)as well as the optimum creep life and the lowest minimum creep rate in comparison with other heat treatment routes,which were attributed to the presence of fine and uniformly dispersed strengthening precipitates in conjunction with the high dislocation density.展开更多
NiTi alloys fabricated by laser powder bed fusion(LPBF)additive manufacturing technology not only address the compositional instability resulting from complex processes but also solve the challenges of difficult machi...NiTi alloys fabricated by laser powder bed fusion(LPBF)additive manufacturing technology not only address the compositional instability resulting from complex processes but also solve the challenges of difficult machining of intricate aerospace structures.However,there are very few reports on the wear behavior of LPBF-NiTi alloys.In the present work,the effects of microstructure and thermal treatment,including heat treatment and frictional heat,on the wear behavior of LPBF-NiTi alloy and 100Cr6 ball were analyzed through a series of tribological experiments with different sliding speeds.As the average sliding speed increases(0.079–0.216 m/s),the wear rate of the as-built and heat-treated samples tends to decrease in the range of 2.69×10^(-3)–0.97×10^(-3)mm^(3)/m.Although the heat-treated LPBF-NiTi alloy is 46%harder than the as-built alloy is,the latter has a higher toughness(505 MJ/m^(3))and greater transformation strain of SIM(0.097).This leads to a coupling effect of heat treatment and sliding speed on the wear resistance.In addition,the wear track morphologies under different sliding speeds are asymmetric due to the 24% greater acceleration at the far end from the motor and the 2.15 mm deviation between the maximum speed position and the geometric center of the track.The wear modes of the as-built and heat-treated samples included adhesive,abrasive and delamination wear.Moreover,the wear morphologies and dominant wear modes change with the frictionally caused heat release induced by the sliding speed.展开更多
Wire arc additive manufacturing(WAAM)presents a promising approach for fabricating medium-to-large austenitic stainless steel components,which are essential in industries like aerospace,pressure vessels,and heat excha...Wire arc additive manufacturing(WAAM)presents a promising approach for fabricating medium-to-large austenitic stainless steel components,which are essential in industries like aerospace,pressure vessels,and heat exchangers.This research examines the mi-crostructural characteristics and tensile behaviour of SS308L manufactured via the gas metal arc welding-based WAAM(WAAM 308L)process.Tensile tests were conducted at room temperature(RT,25℃),300℃,and 600℃in as-built conditions.The microstructure con-sists primarily of austenite grains with retainedδ-ferrite phases distributed within the austenitic matrix.The ferrite fraction,in terms of fer-rite number(FN),ranged between 2.30 and 4.80 along the build direction from top to bottom.The ferrite fraction in the middle region is 3.60 FN.Tensile strength was higher in the horizontal oriented samples(WAAM 308L-H),while ductility was higher in the vertical ones.Tensile results show a gradual reduction in strength with increasing test temperature,in which significant dynamic strain aging(DSA)is observed at 600℃.The variation in serration behavior between the vertical and horizontal specimens may be attributed to microstructural differences arising from the build orientation.The yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)of WAAM 308L at 600℃were(240±10)MPa,(442±16)MPa,and(54±2.00)%,respectively,in the horizontal orientation(WAAM 308L-H),and(248±9)MPa,(412±19)MPa,and(75±2.80)%,respectively,in the vertical orientation(WAAM 308L-V).Fracture surfaces revealed a transition from ductile dimple fracture at RT and 300℃to a mixed ductile-brittle failure with intergranular facets at 600℃.The research explores the applicability and constraints of WAAM-produced 308L stainless steel in high-temperature conditions,offering crucial in-sights for its use in thermally resistant structural and industrial components.展开更多
Recent advances in additive manufacturing have enabled the construction of metallic lattice structures with tailored mechanical and functional properties.One potential application of metallic lattice struc-tures is in...Recent advances in additive manufacturing have enabled the construction of metallic lattice structures with tailored mechanical and functional properties.One potential application of metallic lattice struc-tures is in the impact load mitigation where an external kinetic energy is absorbed by the deformation/crushing of lattice cells.This has motivated a growing number of experimental and numerical studies,recently,on the crushing behavior of additively produced lattice structures.The present study overviews the dynamic and quasi-static crushing behavior of additively produced Ti64,316L,and AlSiMg alloy lattice structures.The first part of the study summarizes the main features of two most commonly used additive processing techniques for lattice structures,namely selective-laser-melt(SLM)and electro-beam-melt(EBM),along with a description of commonly observed process induced defects.In the second part,the deformation and strain rate sensitivities of the selected alloy lattices are outlined together with the most widely used dynamic test methods,followed by a part on the observed micro-structures of the SLM and EBM-processed Ti64,316L and AlSiMg alloys.Finally,the experimental and numerical studies on the quasi-static and dynamic compression behavior of the additively processed Ti64,316L,and AlSiMg alloy lattices are reviewed.The results of the experimental and numerical studies of the dynamic properties of various types of lattices,including graded,non-uniform strut size,hollow,non-uniform cell size,and bio-inspired,were tabulated together with the used dynamic testing methods.The dynamic tests have been noted to be mostly conducted in compression Split Hopkinson Pressure Bar(SHPB)or Taylor-and direct-impact tests using the SHPB set-up,in all of which relatively small-size test specimens were tested.The test specimen size effect on the compression behavior of the lattices was further emphasized.It has also been shown that the lattices of Ti64 and AlSiMg alloys are relatively brittle as compared with the lattices of 316L alloy.Finally,the challenges associated with modelling lattice structures were explained and the micro tension tests and multi-scale modeling techniques combining microstructural characteristics with macroscopic lattice dynamics were recommended to improve the accuracy of the numerical simulations of the dynamic compression deformations of metallic lattice structures.展开更多
High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy allo...High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy alloy and by employing advanced additive manufacturing techniques,high-performance HEACs can be fabricated.However,there is still considerable room for improvement in their performance.In this study,CoCrFeMnNi HEA powders were used as the matrix,and NiCoFeAlTi high-entropy intermetallic powders were used as the high-entropy reinforcement(HER).CoCrFeMnNi/NiCoFeAlTi HEACs were fabricated using selective laser melting technology.The study results indicate that after aging,the microstructure of HEACs with HER exhibits Al-and Ti-rich nano-oxide precipitates with an orthorhombic CMCM type structure system.After aging at 873 K for 2 h,HEACs with HER achieved excellent overall mechanical properties,with an ultimate tensile strength of 731 MPa.This is attributed to the combined and synergistic effects of precipitation strengthening,dislocation strengthening,and the high lattice distortion caused by high intragranular defects,which provide a multi-scale strengthening and hardening mechanism for the plastic deformation of HEACs with HER.This study demonstrates that aging plays a crucial role in controlling the precipitate phases in complex multi-element alloys.展开更多
Tailoring thermal history during additive manufacturing(AM)offers a feasible approach to customise the microstructure and properties of materials without changing alloy compositions or post-heat treatment,which is gen...Tailoring thermal history during additive manufacturing(AM)offers a feasible approach to customise the microstructure and properties of materials without changing alloy compositions or post-heat treatment,which is generally overlooked as it is hard to achieve in commercial materials.Herein,a customised Fe-Ni-Ti-Al maraging steel with rapid precipitation kinetics offers the opportunity to leverage thermal history during AM for achieving large-range tunable strength-ductility combinations.The Fe-Ni-Ti-Al steel was processed by laser-directed energy deposition(LDED)with different deposition strategies to tailor the thermal history.As the phase transformation and in-situ formation of multi-scale secondary phases of the Fe-Ni-Ti-Al steel are sensitive to the thermal histories,the deposited steel achieved a large range of tuneable mechanical properties.Specifically,the interlayer paused deposited sample exhibits superior tensile strength(∼1.54 GPa)and moderate elongation(∼8.1%),which is attributed to the formation of unique hierarchical structures and the in-situ precipitation of high-densityη-Ni_(3)(Ti,Al)during LDED.In contrast,the substrate heating deposited sample has an excellent elongation of 19.3%together with a high tensile strength of 1.24 GPa.The achievable mechanical property range via tailoring thermal history in the LDED-built Fe-Ni-Ti-Al steel is significantly larger than most commercial materials.The findings highlight the material customisation along with AM’s unique thermal history to achieve versatile mechanical performances of deposited materials,which could inspire more property or function manipulations of materials by AM process control or innovation.展开更多
In the present study,AlCoCrFeNi_(2.1)eutectic high-entropy alloy(EHEA)has been fabricated by laser melting deposition(LMD).The influence of laser energy density on microstructures,wear resistance and corrosion resista...In the present study,AlCoCrFeNi_(2.1)eutectic high-entropy alloy(EHEA)has been fabricated by laser melting deposition(LMD).The influence of laser energy density on microstructures,wear resistance and corrosion resistance of the alloy was systematically explored.The results indicate that the AlCoCrFeNi_(2.1)EHEA exhibited lamellar eutectic microstructures with alternating FCC and BCC phases.With the increase in laser energy density,the alloy grain size,interlamellar spacing,and volume fraction of the FCC phase increased,while the hardness of the alloy decreased.Meanwhile,the tribological performance of the alloy deteriorated with increasing laser energy density,and the combined effects of abrasive wear and adhesive wear gradually became significant.In addition,increasing laser energy density from 18.2 to 25 J/mm^(2)resulted in the increase in corrosion current density of the AlCoCrFeNi_(2.1)EHEA from 6.36×10^(−8) to 3.02×10^(−7) A/cm^(2)and the negative shift of corrosion potential from−211 to−292 mV(SCE).In summary,reducing laser energy density improved the wear and corrosion performance of the additively manufactured AlCoCrFeNi_(2.1)EHEA.展开更多
Fatigue properties of materials by Additive Manufacturing(AM) depend on many factors such as AM processing parameter, microstructure, residual stress, surface roughness, porosities, post-treatments, etc. Their evaluat...Fatigue properties of materials by Additive Manufacturing(AM) depend on many factors such as AM processing parameter, microstructure, residual stress, surface roughness, porosities, post-treatments, etc. Their evaluation inevitably requires these factors combined as many as possible, thus resulting in low efficiency and high cost. In recent years, their assessment by leveraging the power of Machine Learning(ML) has gained increasing attentions. A comprehensive overview on the state-of-the-art progress of applying ML strategies to predict fatigue properties of AM materials, as well as their dependence on AM processing and post-processing parameters such as laser power, scanning speed, layer height, hatch distance, built direction, post-heat temperature,etc., were presented. A few attempts in employing Feedforward Neural Network(FNN), Convolutional Neural Network(CNN), Adaptive Network-Based Fuzzy Inference System(ANFIS), Support Vector Machine(SVM) and Random Forest(RF) to predict fatigue life and RF to predict fatigue crack growth rate are summarized. The ML models for predicting AM materials' fatigue properties are found intrinsically similar to the commonly used ones, but are modified to involve AM features. Finally, an outlook for challenges(i.e., small dataset, multifarious features,overfitting, low interpretability, and unable extension from AM material data to structure life) and potential solutions for the ML prediction of AM materials' fatigue properties is provided.展开更多
As a potent grain refiner for steel casting,TiN is now widely used to refineγ-austenite in steel additive manufacturing(AM).However,the refining mechanism of TiN during AM remains unclear despite intensive research i...As a potent grain refiner for steel casting,TiN is now widely used to refineγ-austenite in steel additive manufacturing(AM).However,the refining mechanism of TiN during AM remains unclear despite intensive research in recent years.This work aims to boost our understanding on the mechanism of TiN in refining theγ-austenite in AM-fabricated 316 stainless steel and its corresponding effect on the mechanical behaviour.Experimental results show that addition of 1 wt.%TiN nanoparticles led to complete columnarto-equiaxed transition and significant refinement of the austenite grains to∼2μm in the 316 steel.Thermodynamic and kinetic simulations confirmed that,despite the rapid AM solidification,δ-ferrite is the primary solid phase during AM of the 316 steel andγ-austenite forms through subsequent peritectic reaction or direct transformation from theδ-ferrite.This implies that the TiN nanoparticles actually refined theδ-ferrite through promoting its heterogenous nucleation,which in turn refined theγ-austenite.This assumption is verified by the high grain refining efficiency of TiN nanoparticles in an AM-fabricated Fe-4 wt.%Siδ-ferrite alloy,in whichδ-ferrite forms directly from the melt and is retained at room temperature.The grain refinement is attributed to the good atomic matching betweenδ-ferrite and TiN.Grain refinement in the 316 steel through 1 wt.%TiN inoculation not only eliminated the property anisotropy but also led to a high strain-hardening rate upon plastic deformation and thereby a superior strengthductility synergy with yield strength of 561 MPa,tensile strength of 860 MPa and elongation of 48%.展开更多
Metal matrix composites(MMCs)are frequently employed in various advanced industries due to their high modulus and strength,favorable wear and corrosion resistance,and other good properties at elevated temperatures.In ...Metal matrix composites(MMCs)are frequently employed in various advanced industries due to their high modulus and strength,favorable wear and corrosion resistance,and other good properties at elevated temperatures.In recent decades,additive manufacturing(AM)technology has garnered attention as a potential way for fabricating MMCs.This article provides a comprehensive review of recent endeavors and progress in AM of MMCs,encompassing available AM technologies,types of reinforcements,feedstock preparation,synthesis principles during the AM process,typical AM-produced MMCs,strengthening mechanisms,challenges,and future interests.Compared to conventionally manufactured MMCs,AM-produced MMCs exhibit more uniformly distributed reinforcements and refined microstructure,resulting in comparable or even better mechanical properties.In addition,AM technology can produce bulk MMCs with significantly low porosity and fabricate geometrically complex MMC components and MMC lattice structures.As reviewed,many AM-produced MMCs,such as Al matrix composites,Ti matrix composites,nickel matrix composites,Fe matrix composites,etc,have been successfully produced.The types and contents of reinforcements strongly influence the properties of AM-produced MMCs,the choice of AM technology,and the applied processing parameters.In these MMCs,four primary strengthening mechanisms have been identified:Hall–Petch strengthening,dislocation strengthening,load transfer strengthening,and Orowan strengthening.AM technologies offer advantages that enhance the properties of MMCs when compared with traditional fabrication methods.Despite the advantages above,further challenges of AM-produced MMCs are still faced,such as new methods and new technologies for investigating AM-produced MMCs,the intrinsic nature of MMCs coupled with AM technologies,and challenges in the AM processes.Therefore,the article concludes by discussing the challenges and future interests of AM of MMCs.展开更多
基金supported by National Natural Science Foundation of China(Grant No.52275343)Natural Science Foundation of Zhejiang Province(Grant No.LY23E050003)Ningbo Youth Science and Technology Innovation Leading Talent Project(Grant No.2023QL021).
文摘Additive manufacturing(AM)has revolutionized the production of metal bone implants,enabling unprecedented levels of customization and functionality.Recent advancements in surface-modification technologies have been crucial in enhancing the performance and biocompatibility of implants.Through leveraging the versatility of AM techniques,particularly powder bed fusion,a range of metallic biomaterials,including stainless steel,titanium,and biodegradable alloys,can be utilized to fabricate implants tailored for craniofacial,trunk,and limb bone reconstructions.However,the potential of AM is contingent on addressing intrinsic defects that may hinder implant performance.Techniques such as sandblasting,chemical treatment,electropolishing,heat treatment,and laser technology effectively remove residual powder and improve the surface roughness of these implants.The development of functional coatings,applied via both dry and wet methods,represents a significant advancement in surface modification research.These coatings not only improve mechanical and biological interactions at the implant-bone interface but also facilitate controlled drug release and enhance antimicrobial properties.Addition-ally,micro-and nanoscale surface modifications using chemical and laser techniques can precisely sculpt implant surfaces to promote the desired cellular responses.This detailed exploration of surface engineering offers a wealth of opportunities for creating next-generation implants that are not only biocompatible but also bioactive,laying the foundation for more effective solutions in bone reconstruction.
基金supported by the National Natural Science Foundation of China(No.12272392 and 11790292)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040303)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2022020).
文摘The remarkable mechanical properties exhibited by laminated structures have generated significant in-terest in the realm of additively manufactured laminated high-entropy alloys(HEAs).Despite this bur-geoning interest,the nexus between process,structure,and properties within laminated HEAs remains largely uncharted.There is a vast space for investigating the effect of the typical heterogeneous interface on the macroscopic mechanical properties.This study focuses on the influence of the characteristic het-erogeneous interface on macroscopic mechanical properties of laminated HEAs,particularly anisotropy.Using the 3D-printed Fe_(50)Mn_(30)Co_(10)Cr_(10)-CoCrNi HEA as a model,we investigate the impact of interface geometry on mechanical characteristics.Tensile tests show that the reduced interface spacing increases yield strength.This laminated HEA displays significant anisotropy in strength and ductility,depending on the loading direction relative to the interface.Electron microscopic observations suggest that finer layer spacing enhances interface and dislocation strengthening,increasing yield strength.Anisotropic behaviors are confirmed to be mediated by interface orientation,explained in terms of deformation compatibility and crack development at the interface.This research offers fundamental insights into the relationship between heterogeneous interfaces and the mechanical properties in laminated HEAs.The knowledge is vital for designing,fabricating,and optimizing laminated HEAs through additive manufacturing,advancing their engineering applications.
基金supported by the National Natural Science Foundation of China(grant Nos.52301302,U22A20121,52175274,52111530042,and 5210010632)the China Postdoctoral Science Foundation(grant No.2023M732339)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(Nos.2021A1515220086,2023A1515220095,and 2024A1515012042)the Beijing Natural Science Foundation(Grant No.L212014).
文摘Spinal fusion is a commonly used technique to treat acute and chronic spinal diseases by fusion of the adjacent vertebrae, aiming at achieving stability and eliminating the mobility of the objective segment. While bone autografts and allografts have been conventionally used for spinal fusion, limitations persist in achieving optimization of both good osteoinductive capacity and mechanical stability. In this study, additively manufactured Zn-Li scaffolds were developed and evaluated for their potential in spinal fusion. First, three scaffold structures (BCC, Diamond, and Gyroid) were designed and verified in vitro. Due to the smooth transition surfaces and uniform degradation behavior, the Gyroid Zn-Li scaffold demonstrated mechanical integrity during degradation and enhanced cellular proliferation compared to the other two scaffolds. Subsequently, Zn-Li scaffolds (Gyroid) were selected for posterolateral lumbar fusion (L4/L5) in rabbits. Following 12 weeks of implantation, the Zn-Li scaffolds demonstrated a moderate biodegradation rate and satisfactory biocompatibility. Compared to bone allografts, the Zn-Li scaffolds significantly improved osseointegration adjacent to the transverse processes, which led to enhanced segmental stability of the fused vertebrae post posterolateral lumbar fusion. Overall, the results show that the biodegradable Zn-Li scaffold holds substantial potential as the next-generation graft for spinal fusion.
基金supported by the Aero Engine Corporation of China[Grant No.HFZL2022CXY029]the Young Elite Scientists Sponsorship Programby CAST[2022QNRC001]the High Performance Computing Center of Central South University,and the Project Supported by State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China。
文摘Nickel-based superalloys are indispensable for high-temperature engineering applications,yet their additive manufacturing(AM)is plagued by significant cracking defects.This review investigates crack failure mechanisms in AM nickel-based superalloys,emphasizing methodologies to evaluate crack sensitivity and compositional design strategies to mitigate defects.Key crack types—solidification,liquation,solid-state,stress corrosion,fatigue,and creep-fatigue cracks—are analyzed,with focus on formation mechanisms driven by thermal gradients,solute segregation,and microstructural heterogeneities.Evaluation frameworks such as the Rappaz-Drezet-Gremaud(RDG)criterion,Solidification Cracking Index(SCI),and Strain Age Cracking(SAC)index are reviewed for predicting crack susceptibility through integration of thermodynamic parameters,solidification kinetics,and mechanical properties.Alloy compositional design strategies are presented,including optimization of strengthening elements(Al,Ti),grain boundary modifiers(B,Zr,Re),and impurity control(C,O),which suppress crack initiation and propagation via microstructure refinement and enhanced high-temperature resistance.Computational approaches,such as thermodynamically assisted design,high-throughput experimentation,and machine learning,are highlighted for decoding complex composition-structure-property relationships.Challenges in modeling multi-scale defect interactions and developing unified frameworks for manufacturing-and service-induced cracks are outlined.This review underscores the necessity of integrated computational-experimental strategies to advance reliable AM of nickel-based superalloys,providing insights for defect prediction,alloy optimization,and process control.
基金supported by National Key Lab of Aerospace Power System and Plasma Technology Foundation of China(Grant No.APSPT202301002)National Natural Science Foundation of China(Grant No.52001038)Natural Science Foundation of Chongqing,China(Grant Nos.cstc2019jcyj-msxm X0787 and cstc2021jcyj-msxm X0011)。
文摘The unit cell configuration of lattice structures critically influences their load-bearing and energy absorption performance.In this study,three novel lattice structures were developed by modifying the conventional FBCCZ unit cell through reversing,combining,and turning strategies.The designed lattices were fabricated via laser powder bed fusion(LPBF)using Ti-6Al-4V powder,and the mechanical properties,energy absorption capacity,and deformation behaviors were systematically investigated through quasi-static compression tests and finite element simulations.The results demonstrate that the three modified lattices exhibit superior performance over the conventional FBCCZ structure in terms of fracture strain,specific yield strength,specific ultimate strength,specific energy absorption,and energy absorption efficiency,thereby validating the efficacy of unit cell modifications in enhancing lattice performance.Notably,the CFBCCZ and TFBCCZ lattices significantly outperform both the FBCCZ and RFBCCZ lattice structures in load-bearing and energy absorption.While TFBCCZ shows marginally higher specific elastic modulus and energy absorption efficiency than CFBCCZ,the latter achieves superior energy absorption due to its highest ultimate strength and densification strain.Finite element simulations further reveal that the modified lattices,through optimized redistribution and adjustment of internal nodes and struts,effectively alleviate stress concentration during loading.This structural modification enhances the structural integrity and deformation stability under external loads,enabling a synergistic enhancement of load-bearing capacity and energy absorption performance.
基金co-supported by National Key R&D Program of China(No.2022YFB4602003)Key Project of National Natural Science Foundation of China(No.12032018)+2 种基金Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110489)National Natural Science Foundation of China-China Academy of General Technology Joint Fund for Basic Research(No.52375380)National Key Research and Development Program of China(No.2022YFB3402200)。
文摘A novel Additive Manufacturing(AM)-driven concurrent design strategy based on the beam characterization model considering strength constraints is proposed.The lattice topology,radius size,Building Orientation(BO),and structural yield strength can be simultaneously adjusted by integrating the overall process-structure-performance relationship of the AM process into the optimization.Specifically,the transverse isotropic material model is adopted to describe the material properties induced by the layer-by-layer manner of additive manufacturing.To bolster lattice strength performance,the stress constraints and ratio constraints of lattice struts are employed.The Tsai-Wu yield criterion is implemented to characterize the lattice strut's strength,while the P-norm method streamlines the handling of multiple constraints,minimizing computational overhead.Moreover,the gradient-based optimization model is established,where both the individual struts diameters and BO can be designed,and the buckling-prone spatial struts are strategically eliminated to improve the lattice strength further.Furthermore,several typical structures are optimized to verify the effectiveness of the proposed method.The optimized results are quite encouraging since the heterogeneous lattice structures with optimized BO obtained by the strength-based concurrent method show a remarkably improved performance compared to traditional designs.
基金Supported by the Industrial Collaborative Innovation Project of Shanghai(Grant No XTCX-KJ-2022-2-11)the National Natural Science Foundation of China(Grant No52073176)。
文摘In this work,the GW63K(Mg-6.54Gd-3.93Y-0.41Zr,wt.%)alloy wire was utilized as the feedstock material and the thin-walled component was fabricated using wire-arc additive manufacturing technology(WAAM).The microstructural evolution during deposition and subsequent heat treatment was explained through multi-scale microstructural characterization techniques,and the impact of heat treatment on the strengthductility synergy of the deposited alloy was systematically compared.The results showed that the microstructure of the deposited sample was mainly composed of fine equiaxedα-Mg grains and Mg_(24)(Gd,Y)_(5) phase.The optimized solution heat treatment(450℃×2 h)had little effect on the grain size,but can effectively reduce the Mg_(24)(Gd,Y)_(5) eutectic phase on the grain boundary,resulting in a significant increase in elongation from 13.7% to 26.6%.After peak-aging treatment,the strength of the GW63K alloy increased to 370 MPa,which was significantly higher than the as-built state(267 MPa).The superior strength in this study is attributed to the refinement strengthening imparted by the fine microstructure inherited in the as-built GW63K alloy,as well as the precipitation strengthening due to the formation of dense β’precipitates with a pronounced plate-like aspect ratio.
基金the U.S.Army Research Laboratory under Cooperative Agreement Award No.HQ0034-15-2-0007the U.S.National Science Foundation(DMR-2207965).
文摘Maraging steels are known for their exceptional strength but suffer from limited work hardening and ductility.Here,we report an intermittent printing strategy to tailor the microstructure and mechanical properties of maraging 250 steel via tuning the thermal history during wire-arc directed energy deposition.By introducing a dwell time between adjacent layers,the maraging 250 steel is cooled below the martensite start temperature,triggering thermally-driven martensitic transformation during the printing process.Thermal cycling during subsequent layer deposition results in the formation of reverted austenite which shows a refined microstructure and induces elemental segregation between martensite and reverted austenite.The Ni enrichment in the austenite promotes stabilization of the reverted austenite upon cooling to room temperature.The reverted austenite is metastable during deformation,leading to strain-induced martensitic transformation under loading.Specifically,a 3 min interlayer dwell time produces a maraging 250 steel with approximately 8% reverted austenite,resulting in improved work hardening via martensitic transformation induced plasticity during deformation.Meanwhile,the higher cooling rate and refined prior austenite grains lead to substantially refined martensitic grains(by approximately fivefold)together with an increased dislocation density.With 3 min interlayer dwell time,the yield strength of the printed maraging 250 steel increases from 836 MPa to 990 MPa,and the uniform elongation is doubled from 3.2% to 6.5%.This intermittent deposition strategy demonstrates the potential to tune the microstructure of maraging steels for achieving strength-ductility synergy by engineering the thermal history during additive manufacturing.
基金supported by the National Natural Science Foundation of China(No.52222503)the Natural Science Foundation of Zhejiang Province(No.LD22E050003),China.
文摘The integrated valve-controlled cylinder combines various control and execution components in hydraulic transmission systems.Its precise control and rapid response characteristics make it widely used in mobile equipment for aerospace,robotics,and other engineering applications.Additive manufacturing provides high design freedom which can further enhance the power density of integrated valve-controlled cylinders.However,there is a lack of effective design methods to guide the additive manufacturing of valve-controlled cylinders for more efficient hydraulic energy transmission.This study accordingly introduces an energy-saving design method based on additive manufacturing for integrated valve-controlled cylinders.The method consists of two main parts:(1)redesigning the manifold block to eliminate leakage points and reduce energy losses through integrated design of the valve,cylinder,and piping;(2)establishing a pressure loss model to achieve energy savings through optimized flow channel design for bends with different parameters.Compared to traditional valve-controlled cylinders,the integrated valvecontrolled cylinder developed from our method reduces the weight by 31%,volume by 55%,and pressure loss in the main flow channel by over 30%.This indicates that the design achieves both lightweight construction and improved hydraulic transmission efficiency.This study provides theoretical guidance for the design of lightweight and energy-efficient valve-controlled cylinders,and may aid the design of similar hydraulic machinery.
基金Supported by National Key R&D Program of China(Grant Nos.2022YFB4603101,2022YFB3402200)Key Project of NSFC of China(Grant No.92271205)Sichuan Provincial Science and Technology Program and Fundamental Research Funds for the Central Universities of China(Grant No.D5000230049).
文摘The accurate characterization of anisotropy for additively manufactured materials is of vital importance for both highperformance structural design and printing processing optimization.To avoid the repetitive and redundant tensile testing on specimens prepared along diverse directions,this study proposes an instrumented indentation-based inverse identification method for the efficient characterization of additively manufactured materials.In the present work,a 3D finite element model of indentation test is first established for the printed material,for which an anisotropic material constitutive model is incorporated.We have demonstrated that the indentation responses are information-rich,and material anisotropy along different directions can be interpreted by a single indentation imprint.Subsequently,an inverse identification framework is built,in which an Euclidean error norm between simulated and experimental indentation responses is minimized via optimization algorithms such as the Globally Convergent Method of Moving Asymptotes(GCMMA).The developed method has been verified on diverse printed materials referring to either the indentation curve or the residual imprint,and the superiority of this latter over the former is confirmed by a better and faster convergence of inverse identification.Experimental validations on 3D printed materials(including stainless steel 316L,aluminum alloy AlSi10Mg,and titanium alloy TC4)reveal that the developed method is both accurate and reliable when compared with material constitutive behaviors obtained from uni-axial tensile tests,regardless of the degree of anisotropy among different materials.
文摘The effects of post heat treatment on the microstructure,aging kinetics,and room/elevated temperature mechanical properties of additively manufactured Inconel 718 superalloy were investigated.Scanning electron microscopy(SEM),electron backscattered diffraction(EBSD),and X-ray diffraction(XRD),as well as hardness,tensile,and creep testing were used for characterization.At temperatures higher than 1100°C,homogenization treatment resulted in the appearance of equiaxed grains by recrystallization and diminishing the dislocation density.The precipitation activation energy for the homogenized and aged condition was obtained as 203.2 kJ/mol,which was higher than the value of~160 kJ/mol for the as-built IN718 superalloy.Therefore,direct aging resulted in a faster aging response,which led to a significant improvement in tensile properties,as rationalized by the strengthening mechanisms.Direct aging treatment resulted in a higher elevated-temperature ultimate tensile strength(UTS)as well as the optimum creep life and the lowest minimum creep rate in comparison with other heat treatment routes,which were attributed to the presence of fine and uniformly dispersed strengthening precipitates in conjunction with the high dislocation density.
基金the State Key Laboratory of Robotics Technology and Systems Open Research Project(No.SKLRS-2022-KF-10)The author X.H.Huang is grateful for the financial support provided by the China Scholarship Council(No.202106230079)。
文摘NiTi alloys fabricated by laser powder bed fusion(LPBF)additive manufacturing technology not only address the compositional instability resulting from complex processes but also solve the challenges of difficult machining of intricate aerospace structures.However,there are very few reports on the wear behavior of LPBF-NiTi alloys.In the present work,the effects of microstructure and thermal treatment,including heat treatment and frictional heat,on the wear behavior of LPBF-NiTi alloy and 100Cr6 ball were analyzed through a series of tribological experiments with different sliding speeds.As the average sliding speed increases(0.079–0.216 m/s),the wear rate of the as-built and heat-treated samples tends to decrease in the range of 2.69×10^(-3)–0.97×10^(-3)mm^(3)/m.Although the heat-treated LPBF-NiTi alloy is 46%harder than the as-built alloy is,the latter has a higher toughness(505 MJ/m^(3))and greater transformation strain of SIM(0.097).This leads to a coupling effect of heat treatment and sliding speed on the wear resistance.In addition,the wear track morphologies under different sliding speeds are asymmetric due to the 24% greater acceleration at the far end from the motor and the 2.15 mm deviation between the maximum speed position and the geometric center of the track.The wear modes of the as-built and heat-treated samples included adhesive,abrasive and delamination wear.Moreover,the wear morphologies and dominant wear modes change with the frictionally caused heat release induced by the sliding speed.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)and the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea program(No.RS-2025-02603127,Innovation Research Center for Zero-carbon Fuel Gas Turbine Design,Manufacture,and Safety).
文摘Wire arc additive manufacturing(WAAM)presents a promising approach for fabricating medium-to-large austenitic stainless steel components,which are essential in industries like aerospace,pressure vessels,and heat exchangers.This research examines the mi-crostructural characteristics and tensile behaviour of SS308L manufactured via the gas metal arc welding-based WAAM(WAAM 308L)process.Tensile tests were conducted at room temperature(RT,25℃),300℃,and 600℃in as-built conditions.The microstructure con-sists primarily of austenite grains with retainedδ-ferrite phases distributed within the austenitic matrix.The ferrite fraction,in terms of fer-rite number(FN),ranged between 2.30 and 4.80 along the build direction from top to bottom.The ferrite fraction in the middle region is 3.60 FN.Tensile strength was higher in the horizontal oriented samples(WAAM 308L-H),while ductility was higher in the vertical ones.Tensile results show a gradual reduction in strength with increasing test temperature,in which significant dynamic strain aging(DSA)is observed at 600℃.The variation in serration behavior between the vertical and horizontal specimens may be attributed to microstructural differences arising from the build orientation.The yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)of WAAM 308L at 600℃were(240±10)MPa,(442±16)MPa,and(54±2.00)%,respectively,in the horizontal orientation(WAAM 308L-H),and(248±9)MPa,(412±19)MPa,and(75±2.80)%,respectively,in the vertical orientation(WAAM 308L-V).Fracture surfaces revealed a transition from ductile dimple fracture at RT and 300℃to a mixed ductile-brittle failure with intergranular facets at 600℃.The research explores the applicability and constraints of WAAM-produced 308L stainless steel in high-temperature conditions,offering crucial in-sights for its use in thermally resistant structural and industrial components.
基金the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 101034425 for the project titled A2M2TECHThe Scientific and Technological Research Council of Türkiye (TUBITAK) with grant No 120C158 for the same A2M2TECH project under the TUBITAK's 2236/B program
文摘Recent advances in additive manufacturing have enabled the construction of metallic lattice structures with tailored mechanical and functional properties.One potential application of metallic lattice struc-tures is in the impact load mitigation where an external kinetic energy is absorbed by the deformation/crushing of lattice cells.This has motivated a growing number of experimental and numerical studies,recently,on the crushing behavior of additively produced lattice structures.The present study overviews the dynamic and quasi-static crushing behavior of additively produced Ti64,316L,and AlSiMg alloy lattice structures.The first part of the study summarizes the main features of two most commonly used additive processing techniques for lattice structures,namely selective-laser-melt(SLM)and electro-beam-melt(EBM),along with a description of commonly observed process induced defects.In the second part,the deformation and strain rate sensitivities of the selected alloy lattices are outlined together with the most widely used dynamic test methods,followed by a part on the observed micro-structures of the SLM and EBM-processed Ti64,316L and AlSiMg alloys.Finally,the experimental and numerical studies on the quasi-static and dynamic compression behavior of the additively processed Ti64,316L,and AlSiMg alloy lattices are reviewed.The results of the experimental and numerical studies of the dynamic properties of various types of lattices,including graded,non-uniform strut size,hollow,non-uniform cell size,and bio-inspired,were tabulated together with the used dynamic testing methods.The dynamic tests have been noted to be mostly conducted in compression Split Hopkinson Pressure Bar(SHPB)or Taylor-and direct-impact tests using the SHPB set-up,in all of which relatively small-size test specimens were tested.The test specimen size effect on the compression behavior of the lattices was further emphasized.It has also been shown that the lattices of Ti64 and AlSiMg alloys are relatively brittle as compared with the lattices of 316L alloy.Finally,the challenges associated with modelling lattice structures were explained and the micro tension tests and multi-scale modeling techniques combining microstructural characteristics with macroscopic lattice dynamics were recommended to improve the accuracy of the numerical simulations of the dynamic compression deformations of metallic lattice structures.
基金Project supported by ClassⅢPeak Discipline of Shanghai-Materials Science and Engineering(High-Energy Beam Intelligent Processing and Green Manufacturing),China。
文摘High-entropy alloy composites(HEACs)have attracted significant attention due to their exceptional mechanical properties and chemical stability.By adjusting the content of reinforcing particles in the high-entropy alloy and by employing advanced additive manufacturing techniques,high-performance HEACs can be fabricated.However,there is still considerable room for improvement in their performance.In this study,CoCrFeMnNi HEA powders were used as the matrix,and NiCoFeAlTi high-entropy intermetallic powders were used as the high-entropy reinforcement(HER).CoCrFeMnNi/NiCoFeAlTi HEACs were fabricated using selective laser melting technology.The study results indicate that after aging,the microstructure of HEACs with HER exhibits Al-and Ti-rich nano-oxide precipitates with an orthorhombic CMCM type structure system.After aging at 873 K for 2 h,HEACs with HER achieved excellent overall mechanical properties,with an ultimate tensile strength of 731 MPa.This is attributed to the combined and synergistic effects of precipitation strengthening,dislocation strengthening,and the high lattice distortion caused by high intragranular defects,which provide a multi-scale strengthening and hardening mechanism for the plastic deformation of HEACs with HER.This study demonstrates that aging plays a crucial role in controlling the precipitate phases in complex multi-element alloys.
基金financially supported by the Career Development Fund(Grant No.C210112051)under the Agency for Science,Technology and Research(A*STAR)of Singapore2022 MTC Young Individual Research Grants(Grant No:M22K3c0097)under Singapore Research,Innovation and Enterprise(RIE)2025 Plan,led by C Tan。
文摘Tailoring thermal history during additive manufacturing(AM)offers a feasible approach to customise the microstructure and properties of materials without changing alloy compositions or post-heat treatment,which is generally overlooked as it is hard to achieve in commercial materials.Herein,a customised Fe-Ni-Ti-Al maraging steel with rapid precipitation kinetics offers the opportunity to leverage thermal history during AM for achieving large-range tunable strength-ductility combinations.The Fe-Ni-Ti-Al steel was processed by laser-directed energy deposition(LDED)with different deposition strategies to tailor the thermal history.As the phase transformation and in-situ formation of multi-scale secondary phases of the Fe-Ni-Ti-Al steel are sensitive to the thermal histories,the deposited steel achieved a large range of tuneable mechanical properties.Specifically,the interlayer paused deposited sample exhibits superior tensile strength(∼1.54 GPa)and moderate elongation(∼8.1%),which is attributed to the formation of unique hierarchical structures and the in-situ precipitation of high-densityη-Ni_(3)(Ti,Al)during LDED.In contrast,the substrate heating deposited sample has an excellent elongation of 19.3%together with a high tensile strength of 1.24 GPa.The achievable mechanical property range via tailoring thermal history in the LDED-built Fe-Ni-Ti-Al steel is significantly larger than most commercial materials.The findings highlight the material customisation along with AM’s unique thermal history to achieve versatile mechanical performances of deposited materials,which could inspire more property or function manipulations of materials by AM process control or innovation.
基金supported by the Jiangxi Provincial Key Research and Development Program(No.20232BBE50007)the Jiangxi Provincial Natural Science Foundation(No.20224BAB214018).
文摘In the present study,AlCoCrFeNi_(2.1)eutectic high-entropy alloy(EHEA)has been fabricated by laser melting deposition(LMD).The influence of laser energy density on microstructures,wear resistance and corrosion resistance of the alloy was systematically explored.The results indicate that the AlCoCrFeNi_(2.1)EHEA exhibited lamellar eutectic microstructures with alternating FCC and BCC phases.With the increase in laser energy density,the alloy grain size,interlamellar spacing,and volume fraction of the FCC phase increased,while the hardness of the alloy decreased.Meanwhile,the tribological performance of the alloy deteriorated with increasing laser energy density,and the combined effects of abrasive wear and adhesive wear gradually became significant.In addition,increasing laser energy density from 18.2 to 25 J/mm^(2)resulted in the increase in corrosion current density of the AlCoCrFeNi_(2.1)EHEA from 6.36×10^(−8) to 3.02×10^(−7) A/cm^(2)and the negative shift of corrosion potential from−211 to−292 mV(SCE).In summary,reducing laser energy density improved the wear and corrosion performance of the additively manufactured AlCoCrFeNi_(2.1)EHEA.
基金the support from the National Science and Technology Major Project, China (No. J2019IV-0014-0082)the National Key Research and Development Program of China (No. 2022YFB4600700)+1 种基金the National Overseas Youth Talents Program, China, the Research Fund of State Key Laboratory of Mechanics and Control for Aerospace Structures, China (No. MCMS-I-0422K01)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, China。
文摘Fatigue properties of materials by Additive Manufacturing(AM) depend on many factors such as AM processing parameter, microstructure, residual stress, surface roughness, porosities, post-treatments, etc. Their evaluation inevitably requires these factors combined as many as possible, thus resulting in low efficiency and high cost. In recent years, their assessment by leveraging the power of Machine Learning(ML) has gained increasing attentions. A comprehensive overview on the state-of-the-art progress of applying ML strategies to predict fatigue properties of AM materials, as well as their dependence on AM processing and post-processing parameters such as laser power, scanning speed, layer height, hatch distance, built direction, post-heat temperature,etc., were presented. A few attempts in employing Feedforward Neural Network(FNN), Convolutional Neural Network(CNN), Adaptive Network-Based Fuzzy Inference System(ANFIS), Support Vector Machine(SVM) and Random Forest(RF) to predict fatigue life and RF to predict fatigue crack growth rate are summarized. The ML models for predicting AM materials' fatigue properties are found intrinsically similar to the commonly used ones, but are modified to involve AM features. Finally, an outlook for challenges(i.e., small dataset, multifarious features,overfitting, low interpretability, and unable extension from AM material data to structure life) and potential solutions for the ML prediction of AM materials' fatigue properties is provided.
基金University of Queensland are very grateful to Australia Research Council(ARC)Discovery Project(DP210103162)program for funding support.Greta Lindwall acknowledges support from Vinnova,Formas and Energimyndigheten via LIGHTer Academy.
文摘As a potent grain refiner for steel casting,TiN is now widely used to refineγ-austenite in steel additive manufacturing(AM).However,the refining mechanism of TiN during AM remains unclear despite intensive research in recent years.This work aims to boost our understanding on the mechanism of TiN in refining theγ-austenite in AM-fabricated 316 stainless steel and its corresponding effect on the mechanical behaviour.Experimental results show that addition of 1 wt.%TiN nanoparticles led to complete columnarto-equiaxed transition and significant refinement of the austenite grains to∼2μm in the 316 steel.Thermodynamic and kinetic simulations confirmed that,despite the rapid AM solidification,δ-ferrite is the primary solid phase during AM of the 316 steel andγ-austenite forms through subsequent peritectic reaction or direct transformation from theδ-ferrite.This implies that the TiN nanoparticles actually refined theδ-ferrite through promoting its heterogenous nucleation,which in turn refined theγ-austenite.This assumption is verified by the high grain refining efficiency of TiN nanoparticles in an AM-fabricated Fe-4 wt.%Siδ-ferrite alloy,in whichδ-ferrite forms directly from the melt and is retained at room temperature.The grain refinement is attributed to the good atomic matching betweenδ-ferrite and TiN.Grain refinement in the 316 steel through 1 wt.%TiN inoculation not only eliminated the property anisotropy but also led to a high strain-hardening rate upon plastic deformation and thereby a superior strengthductility synergy with yield strength of 561 MPa,tensile strength of 860 MPa and elongation of 48%.
基金the financial support from the Australian Research Council through the Discovery Project(DP110101653 and DP130103592)Basic and Applied Basic Research Foundation of Guangdong Province,China(2022A1515140123).
文摘Metal matrix composites(MMCs)are frequently employed in various advanced industries due to their high modulus and strength,favorable wear and corrosion resistance,and other good properties at elevated temperatures.In recent decades,additive manufacturing(AM)technology has garnered attention as a potential way for fabricating MMCs.This article provides a comprehensive review of recent endeavors and progress in AM of MMCs,encompassing available AM technologies,types of reinforcements,feedstock preparation,synthesis principles during the AM process,typical AM-produced MMCs,strengthening mechanisms,challenges,and future interests.Compared to conventionally manufactured MMCs,AM-produced MMCs exhibit more uniformly distributed reinforcements and refined microstructure,resulting in comparable or even better mechanical properties.In addition,AM technology can produce bulk MMCs with significantly low porosity and fabricate geometrically complex MMC components and MMC lattice structures.As reviewed,many AM-produced MMCs,such as Al matrix composites,Ti matrix composites,nickel matrix composites,Fe matrix composites,etc,have been successfully produced.The types and contents of reinforcements strongly influence the properties of AM-produced MMCs,the choice of AM technology,and the applied processing parameters.In these MMCs,four primary strengthening mechanisms have been identified:Hall–Petch strengthening,dislocation strengthening,load transfer strengthening,and Orowan strengthening.AM technologies offer advantages that enhance the properties of MMCs when compared with traditional fabrication methods.Despite the advantages above,further challenges of AM-produced MMCs are still faced,such as new methods and new technologies for investigating AM-produced MMCs,the intrinsic nature of MMCs coupled with AM technologies,and challenges in the AM processes.Therefore,the article concludes by discussing the challenges and future interests of AM of MMCs.
