Titanium exhibits outstanding properties,particularly,high specific strength and resistance to both high and low temperatures,earning it a reputation as the metal of the future.However,because of the highly reactive n...Titanium exhibits outstanding properties,particularly,high specific strength and resistance to both high and low temperatures,earning it a reputation as the metal of the future.However,because of the highly reactive nature of titanium,metallic titanium production involves extensive procedures and high costs.Considering its advantages and limitations,the European Union has classified titanium metal as a critical raw material(CRM)of low category.The Kroll process is predominantly used to produce titanium;however,molten salt electrolysis(MSE)is currently being explored for producing metallic titanium at a low cost.Since 2000,electrolytic titanium production has undergone a wave of technological advancements.However,because of the intermediate and disproportionation reactions in the electrolytic titanium production process,the process efficiency and titanium purity according to industrial standards could not be achieved.Consequently,metallic titanium production has gradually diversified into employing technologies such as thermal reduction,MSE,and titanium alloy preparation.This study provides a comprehensive review of research advances in titanium metal preparation technologies over the past two decades,highlighting the challenges faced by the existing methods and proposing potential solutions.It offers useful insights into the development of low-cost titanium preparation technologies.展开更多
The traditional"trial and error"microstructural control method,with high cost and low efficiency,has become a key issue restricting the development of ultra-high strength and toughness titanium alloys.This s...The traditional"trial and error"microstructural control method,with high cost and low efficiency,has become a key issue restricting the development of ultra-high strength and toughness titanium alloys.This study adopts the molybdenum equivalent(Mo_([eq]))method to rapidly design Ti-xMo-4Al-4Zr-3Nb-2Cr-1Fe alloys(x=5-9).The as-cast alloys with different Mo_([eq])exhibit a single peak of theβphase in XRD.Theβgrains of 5Mo alloy(the lowest Mo_([eq]))exhibit elongated columnar grain characteristics.As the Mo_([eq])increases,theβgrains transition towards a more equiaxed form,resulting in a decrease in aspect ratio and a reduction in grain size.As the Mo_([eq])increases,the a phase content gradually decreases and the a phase is almost unobservable in 9Mo alloy(the highest Mo_([eq])).The a phase in 5Mo alloy exhibits short rod-shaped shapes with an average length of about2.4μm,while the a phase in 6Mo alloy shows an equiaxed and short rod shapes with the smallest size.The strength,plasticity,and toughness are the lowest in 5Mo alloy,with values of 867 MPa,7.3%,and 56 MPa·m^(1/2),respectively.However,it reaches its maximum in 6Mo alloy,where the strength,plasticity,and toughness increase to 984 MPa,12.8%,and 74 MPa·m^(1/2),respectively.The mechanical properties of Ti-xMo-4Al-4Zr-3Nb-2Cr-1Fe alloys are affected mainly by solid-solution strengthening of Mo element,refinement ofβgrain,and changes inα/βphase content.This study lays a certain theoretical foundation for the theoretical research and composition development of new ultra-high strength and toughness titanium alloys.展开更多
The strength-ductility synergy in heterogeneous materials offers significant advantages,though their scalable and controlled fabrication remains challenging.This study introduces an in situ fabrication strategy for he...The strength-ductility synergy in heterogeneous materials offers significant advantages,though their scalable and controlled fabrication remains challenging.This study introduces an in situ fabrication strategy for heterogeneous lamellar titanium(HLT)alloy via laser powder bed fusion of a powder mixture consisting of Ti6Al4V(TC4)and 3 wt%Fe.By periodically varying the scanning velocity between layers,a heterogeneous lamellar microstructure is achieved due to the unique Fe distribution originating from the various volumetric energy densities(VEDs).Consequently,the HLT achieves high yield strength(1036 MPa)and ultimate tensile strength(1419 MPa)without compromising uniform elongation(UE),surpassing most TC4 alloys.The high strength may be attributed to precipitation strengthening originating from the nano-sizedαandωprecipitates,while the high UE and work hardening arise from the strain-induced martensite(SIM)and strong hetero-deformation induced(HDI)stress.The denser dual-phase interfaces and smaller grains in the low VED layers contribute to the higher sensitivity to the SIM.A strain gradient between soft and hard layers evolves during loading,and it further enhances the HDI strengthening and SIM behavior.Through this work,the in situ fabrication method and the deformation mechanism of lamellar heterostructure could offer valuable reference for the optimization and application of heterogeneous materials.展开更多
Colitis-associated colorectal cancer(CAC)is a major contributor to cancer-related mortality worldwide.Titanium dioxide(TiO_(2),E171),a widely used food additive,has been insufficiently studied regarding its effects on...Colitis-associated colorectal cancer(CAC)is a major contributor to cancer-related mortality worldwide.Titanium dioxide(TiO_(2),E171),a widely used food additive,has been insufficiently studied regarding its effects on macrophages within colon tumors during CAC development.In this study,CAC mouse models were used to investigate the biological impact of dietary E171 on macrophages in vivo,while lipopolysaccharide(LPS)-stimulated RAW264.7 macrophage cell lines were employed to elucidate the underlying mechanisms in vitro.We found that dietary E171 intake accelerated CAC development,exacerbated inflammatory responses and oxidative stress,and upregulated CAC-associated genes,including S100a8,S100a9,Lcn2,S100a11,Cxcl2,and interleukin-1α(Il-1α).E171 also increased the expression of S100A8,S100A9,NOD-like receptor family pyrin domain-containing 3(NLRP3),and gasdermin-D Nterminal(GSDMD-N)in macrophages within colon tumors.In inflammatory macrophages,E171 exposure enhanced cell viability,increased reactive oxygen species(ROS)levels,and elevated the expression and secretion of S100A8 and S100A9,consistent with in vivo histological observations.Furthermore,E171-induced secretion of S100A8 and S100A9 in macrophages was suppressed by specific inhibitors,including N-acetylcysteine(NAC,ROS inhibitor),MCC950(NLRP3 inhibitor),Z-YVAD-FMK(caspase 1 inhibitor),disulfiram(GSDMD inhibitor),and transfection of NLRP3 small interfering ribonucleic acid(siRNA).These results indicate that dietary E171 promotes CAC development by activating macrophages,with S100A8 and S100A9 serving as key mediators,and the NLRP3/caspase 1/GSDMD pathway acting as a critical mechanism.展开更多
Achieving the simultaneous enhancement of strength and ductility in laser powder bed fused (LPBF-ed) titanium (Ti) is challenging due to the complex, high-dimensional parameter space and interactions between parameter...Achieving the simultaneous enhancement of strength and ductility in laser powder bed fused (LPBF-ed) titanium (Ti) is challenging due to the complex, high-dimensional parameter space and interactions between parameters and powders. Herein, a hybrid intelligent framework for process parameter optimization of LPBF-ed Ti with improved ultimate tensile strength (UTS) and elongation (EL) was proposed. It combines the data augmentation method (AVG ± EC × SD), the multi-model fusion stacking ensemble learning model (GBDT-BPNN-XGBoost), the interpretable machine learning method and the non-dominated ranking genetic algorithm (NSGA-Ⅱ). The GBDT-BPNN-XGBoost outperforms single models in predicting UTS and EL across the accuracy, generalization ability and stability. The SHAP analysis reveals that laser power (P) is the most important feature affecting both UTS and EL, and it has a positive impact on them when P < 220 W. The UTS and EL of samples fabricated by the optimal process parameters were 718 ± 5 MPa and 27.9 % ± 0.1 %, respectively. The outstanding strength-ductility balance is attributable to the forward stresses in hard α'-martensite and back stresses in soft αm'-martensite induced by the strain gradients of hetero-microstructure. The back stresses strengthen the soft αm'-martensite, improving the overall UTS. The forward stresses stimulate the activation of dislocations in hard α'-martensite and the generation of 〈c + a〉 dislocations, allowing the plastic strain to occur in hard regions and enhancing the overall ductility. This work provides a feasible strategy for multi-objective optimization and valuable insights into tailoring the microstructure for improving mechanical properties.展开更多
目的描述广东地区法布雷病患者基因型情况,对比IVS4+919G>A突变患者与非IVS4+919G>A突变患者的地域分布和临床表型差异。方法回顾性收集2022年3月1日至2025年12月31日本中心(中山大学附属第一医院)47例(IVS4+919G>A突变患者12...目的描述广东地区法布雷病患者基因型情况,对比IVS4+919G>A突变患者与非IVS4+919G>A突变患者的地域分布和临床表型差异。方法回顾性收集2022年3月1日至2025年12月31日本中心(中山大学附属第一医院)47例(IVS4+919G>A突变患者12例)已出现器官受累的法布雷病患者的相关资料,分析总体、IVS4+919G>A突变和非IVS4+919G>A突变患者的地域分布和临床表现特点。结果IVS4+919G>A突变在本中心为最常见突变(25.5%)。本中心的该突变患者有半数(50%)分布在粤东地区,起病中位年龄显著高于非IVS4+919G>A突变组,差异有统计学意义(P<0.05)。IVS4+919G>A突变患者中出现心脏受累11例(91.7%),神经系统受累2例(16.7%),美因茨严重程度评分指数(Mainz severity score index,MSSI)评分有高于非IVS4+919G>A突变组的趋势(P=0.051);MSSI总体评分和神经评分低于非IVS4+919G>A突变组,差异有统计学意义(P<0.05)。相较非IVS4+919G>A突变患者,IVS4+919G>A突变患者的心率更低、心肌肌钙蛋白浓度更高,超声提示其左心房更大、室间隔与左心室后壁更厚、二尖瓣舒张早期充盈峰速度E峰和二尖瓣舒张晚期充盈峰速度A峰比值(ratio of early diastolic transmitral inflow E-peak velocity to late diastolic mitral annulus A-peakvelocity,E/A)更低,差异有统计学意义(P<0.05)。结论IVS4+919G>A突变患者在本中心为最常见突变。本中心的该突变患者有半数分布在粤东地区,其表型以迟发型和心脏受累为主,神经系统受累较少,心肌肥厚、舒张功能下降和心肌损伤情况较其他突变群体更严重。展开更多
The development of cost-effective titanium alloys with outstanding mechanical properties has always been a primary concern of the modern aerospace industry.However,the intrinsic sensitivity of theirαprecipitates to h...The development of cost-effective titanium alloys with outstanding mechanical properties has always been a primary concern of the modern aerospace industry.However,the intrinsic sensitivity of theirαprecipitates to heat treatments proliferates the manufacturing costs to achieve desirable strength and ductility,especially in engineering occasions.In current work,a silicide-containingα+βTi-5Al-7.5V-0.5Mo-0.5Zr-0.5Si(TC5751S)alloy has been evidenced to exhibit advanced mechanical properties with reduced sensitivity to heat treatments.It is noted that more nano-scale secondaryα(αs)precipitate with a simultaneous dissolution in micron-scale primaryα(αp)and(Ti,Zr)_(5)Si_(3)silicides in the current alloy as the solution temperature increases.However,this alloy shows excellent and stabilized strength-ductility synergy in all cases(ultimate tensile strength:1335±30 MPa,yield strength:1245±30 MPa,fracture strain:9.6%±0.5%)irrespective of the aforementioned variations in the microstructure.This stabilized strength and ductility of TC5751S are rationalized based on the compensation mechanisms be-tween the contributions from silicide and heterogeneousαprecipitates.The quantitative analysis unveils that the increased α_(s)/β phase boundary strengthening(σ_(PB))is approximately offset by the decrease in silicide strengthening(σ_(silicide))due to silicide dissolution with increasing solution temperatures,leading to the strength of TC5751S in a dynamic equilibrium state.Simultaneously,the dissolution of silicides re-duces the cracking tendency and complements the ductility loss due to α_(p) reduction and α_(s) precipitation,leading to the ductility insensitive to heat treatments.Therefore,the compensating role of silicides to the effects of heterogeneousαprecipitates on both the strength and ductility of titanium alloys has been well-verified in our work,providing a novel pathway to the development of high-performance titanium alloys friendly to processing strategies.展开更多
Implant-related infections and tissue inflammation are the main factors for peri-implantitis.Lack of antibacterial activity and poor soft tissue sealing property increase the occurrence probability of peri-implantitis...Implant-related infections and tissue inflammation are the main factors for peri-implantitis.Lack of antibacterial activity and poor soft tissue sealing property increase the occurrence probability of peri-implantitis.To prevent and treat peri-implantitis,cerium-doped defective titanium oxide coatings are prepared on medical titanium surfaces by plasma electrolytic oxidation and thermal reduction treatment.In the darkness,Ce-doped defective titanium oxide coatings with micro-porous structure surface can inhibit the bacteria adhesion to some extent with antibacterial rates of 38.0%against S.aureus and 65.0%against E.coli.Under near infrared(NIR)irradiation,Ce-doped defective titanium oxide coatings show good photothermal antibacterial activity with antibacterial rates of 99.9%against S.aureus and 99.9%against E.coli.Moreover,with the increasing content of Ce-doping,the coatings exhibit higher capacity to scavenge hydrogen peroxide(H2O2)and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)radical cation(ABTS^(·+)).The coatings with enhanced antioxidant effect can protect human gingival fibroblasts from oxidative stress damage by eliminating reactive oxygen species and promoting initial cell adhesion.Besides,Ce-doped coatings can regulate the immune microenvironment by up-regulating the expression of anti-inflammatory genes and down-regulating the pro-inflammatory genes.In vivo animal experiments further confirm the good antibacterial activity of Ce-doped defective titanium oxide coatings under NIR irradiation and good biosafety.This work provides a novel surface modification strategy for implant abutment,which shows good application prospects for preventing and treating peri-implantitis.展开更多
The durability of dental implant carrier coatings is of paramount importance for the expeditious and predictable osseointegration process.The present work is based on a bionic micro/nano hierarchy struc-ture,which con...The durability of dental implant carrier coatings is of paramount importance for the expeditious and predictable osseointegration process.The present work is based on a bionic micro/nano hierarchy struc-ture,which consists of titanium surface microstructures and their internal TiO2 nanotubes(TNTs)with drug-carrying capacity.This effectively increases the wear resistance of the drug-carrying coating on the titanium surface.In comparison to untextured samples,the wear volume and wear depth of the optimal texture group are markedly diminished,resulting in a significant enhancement of wear resistance.This improvement was primarily attributed to the smaller contact area of the microstructure.Concurrently,the microstructure serves to safeguard the TNTs from damage during friction.The hydrophilic biomimetic anti-wear micro/nano hierarchies demonstrated the capacity to promote MC3T3-E1 cell adhesion and pro-liferation,while also exhibiting no cytotoxic effects.Moreover,the micro/nano hierarchical structure can be directly applied to the surface of commercialized implants.In simulated clinical conditions,the im-plant was inserted into a fresh Bama porcine mandible,and the structure of the drug-loading coatings remained intact.This structure enhances the abrasion resistance of the drug coating while minimizing alterations to the original treatment process of the implant,which is of great significance in the clinical application of implant-loaded drug delivery.展开更多
To promote early rapid osteogenesis and prevent late implant-related infection,it is critical to develop ef-fective and reliable surface treatment technologies for enhancing both osteogenic and antibacterial prop-erti...To promote early rapid osteogenesis and prevent late implant-related infection,it is critical to develop ef-fective and reliable surface treatment technologies for enhancing both osteogenic and antibacterial prop-erties of titanium alloy implants.Reduced graphene oxide(rGO)is considered a promising modification candidate.However,whether rGO retains its osteogenic and antibacterial functions after being applied to modify titanium alloy surfaces depends on the surface treatment technology employed.In this study,rGO was integrated onto the surface of Ti-35Nb-2Ta-3Zr(TNTZ)alloy through friction stir processing(FSP),yielding a consolidated TNTZ/F-rGO composite.The incorporation of rGO not only significantly im-proved the microhardness and hydrophilicity of the material,but also exhibited positive biological effects in vitro experiments:it effectively promoted the proliferation,osteogenic differentiation,alkaline phos-phatase(ALP)production and extracellular matrix mineralization of BMSCs.Furthermore,TNTZ/F-rGO ex-hibited potent antibacterial activity via surface-contact mechanisms.In summary,the rGO-modified in-tegrated titanium alloy has excellent osteogenic properties and high-efficiency antibacterial ability.This study provides new insights and strategies for the design of graphene-based biomaterials and implant surface modification technologies.展开更多
BACKGROUND Clinical studies using Trabecular Titanium™acetabular cups have shown promising short and medium-term results.This material,due to its macro and micro surface roughness,provides a substrate for osseointegra...BACKGROUND Clinical studies using Trabecular Titanium™acetabular cups have shown promising short and medium-term results.This material,due to its macro and micro surface roughness,provides a substrate for osseointegration and enhances implant stability.However,there is a lack of evidence in the literature on the use of this material in patients with femoral neck fracture.AIM To evaluate the short-term clinical-functional and radiographic outcomes in patients with femoral neck fractures undergoing total hip arthroplasty(THA)with Trabecular Titanium™acetabular cup implants.METHODS The study included 104 patients with medial femoral neck fractures who underwent THA between January 2020 and December 2020 with the Delta TT acetabular cup(Lima Corporate,Villanova di San Daniele del Friuli,Italy).The mean age of the patients was 69.57±10.16 years(range:36-85 years).The followup period ranged from a minimum of 3 to a maximum of 4 years.Three questionnaires(Harris Hip Score,Oxford Hip Score,and EQ5D)were administered along with radiographic evaluations.Statistical methods included the Student's t-test and one-way analysis of variance for comparisons(with significance set at 0.05),and the Kaplan-Meier curve for prosthetic implant survival.RESULTS The mean follow-up was 41.5 months.The Harris Hip Score(HHS)showed a mean increase of 2.74 points(mean HHS 88.52 at 6 months postoperatively and mean HHS 91.26 at the last follow-up)with statistical significance.Similarly,the Oxford Hip Score demonstrated a statistically significant difference between follow-up groups.However,the EQ5D did not show statistically significant differences among the three groups(preoperative,6-month follow-up,and last follow-up).Revision surgery was required in 6 patients.According to Moore's criteria,96%of the acetabular components were radiographically stable and well-integrated at the last follow-up.The Kaplan-Meier curve showed a 96%survival rate.CONCLUSION The clinical and radiographic results obtained in the short to medium term confirm the excellent performance of the Delta TT acetabular cup in terms of osseointegration,providing an optimal solution both for young patients with high functional recovery demands and for fragile patients requiring optimal stability of the acetabular component to reduce the risk of implant failure.展开更多
In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and ...In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and surface integrity must be considered simultaneously during the enhancement process.The current manufacturing process of hole burnishing has a relatively weak balance between the structure shape and surface integrity;therefore,it is necessary to analyze the mechanism and optimize the parameters to improve the strengthening effect of the holes.In this study,a two-dimensional longitudinal simplified model for the hole burnishing process was established,and the reasons for the surface roughness improvement of the hole wall and material accumulation on the upper surface were analyzed.Experiments were conducted to determine the influence of the burnishing parameters on the structure shape(material accumulation,shape contour,and roundness)and surface integrity(surface roughness,residual stress,and surface hardness),based on the opposite requirements of improving the structure shape and surface integrity for the burnishing depth(BD).The results showed that with an increase in the BD,the structure shape deteriorated,whereas the surface integrity improved.Fatigue behavior verification experiments were conducted,and parameter selection schemes for the collaborative improvement of the structure shape and surface integrity were discussed.For the holes of titanium alloy TB6(Ti-10V-2Fe-3Al),the fatigue life can be increased by 162%when the BD,spindle speed,and feed rate were 0.20 mm,200 r/min,and 0.2 mm/r,respectively.展开更多
In this study,Ti-6.5Al-3.5Mo-1.5Zr-0.3Si(TC11)titanium alloy samples are fabricated via arc-wire directed energy deposition(AW-DED)and laser powder bed fusion(L-PBF).The variant-selection(VS)mechanism of the𝛼g...In this study,Ti-6.5Al-3.5Mo-1.5Zr-0.3Si(TC11)titanium alloy samples are fabricated via arc-wire directed energy deposition(AW-DED)and laser powder bed fusion(L-PBF).The variant-selection(VS)mechanism of the𝛼grain boundary(α_(GB))and the intragranular microstructure are characterized via electron backscatter diffraction,and the related formation mechanisms are discussed.The continuous α_(GB) maintained Burgers orientation relationships with one of the adjacent lamellas in the AW-DED sample and the adjacent acicular α’laths in the l-PBF sample as much as possible,respectively.For the intragranular microstructure,the VS of the colony and basket-weave microstructures maintained a common{1120}pole with one of their adjacent microstructures in the AW-DED sample.The VS of the acicular α’lath in the intragranular region is maintained as the common{0001}pole and{1120}pole section as much as possible with the adjacent acicular α’lath.Type-2(60°/[1120])bound-aries dominated the colony microstructure and the basket-weave microstructure because of their low cooling rate in the AW-DED sample.By contrast,type-4(63.26°/[10553])boundaries are composed of the acicular α’lath owing to their high cooling rate in the l-PBF sample during deposition.展开更多
To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level ...To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level orthogonal experiment design of factor levels.Results show that through range analysis,the significance order of process parameters is determined as follows:solution cooling method>solution temperature>aging time>aging temperature>solution time.Considering the strength-ductility matching and engineering application requirements,the benchmark parameters are selected as solution time of 1 h,solution cooling method of air cooling(AC),aging temperature of 525℃,and aging time of 4 h.Furthermore,the effects of solution temperature in the range of 790–870℃ on the impact toughness and micro-fracture characteristics of the alloy were studied.The results reveal that the larger the area of shear lip and fibrous zone,and the smaller the area of radiation zone,the better the toughness of the alloy.With the increase in solution temperature,the length of secondary cracks on the fracture surface increases,the number of dimples increases,and the toughness is enhanced.Based on the collaborative optimization of strength and toughness,the optimal heat treatment process for TB18 alloy is determined as 870℃/1 h,AC+525℃/4 h,AC.展开更多
Ultrafine-grained(UFG)pure titanium was produced by equal channel angular pressing for 4 passes,followed by rotatory swaging at room temperature.The strain-controlled low-cycle fatigue tests of UFG and coarse-grained(...Ultrafine-grained(UFG)pure titanium was produced by equal channel angular pressing for 4 passes,followed by rotatory swaging at room temperature.The strain-controlled low-cycle fatigue tests of UFG and coarse-grained(CG)pure titanium were conducted by Instron electro-hydraulic servo fatigue testing machine in the strain amplitude range of 0.5%—1.1%at room temperature.Transmission electron microscope(TEM)and scanning electron microscope were used to investigate the microstructure and fracture surface of UFG pure titanium after fatigue tests.Results show that UFG pure titanium exhibits a longer low-cycle fatigue life,compared with the CG pure titanium.For example,at a total strain amplitude of 0.5%,UFG and CG pure titanium has fatigue life of 10850 and 4820 cycles,respectively.Significant cyclic softening occurs in UFG pure titanium,except in the case of a total strain amplitude of 0.5%.Hysteresis loop area is increased rapidly with the increase in strain amplitude.The fracture surface shows that the fatigue crack is initiated from the specimen surface.A series of fatigue striations and many microcracks exist in the propagation region.With the increase in strain amplitude,the predominant failure mode is transformed from ductile failure into quasi-cleavage failure.Dislocation slip is the main plastic deformation mechanism of UFG pure titanium during low-cycle fatigue deformation.展开更多
The direct transformation of dinitrogen(N_(2)) into nitrogen-containing organic compounds holds substantial importance.In this work,we report a titanium-promoted method for the conversion of N_(2) to N-methylimides.In...The direct transformation of dinitrogen(N_(2)) into nitrogen-containing organic compounds holds substantial importance.In this work,we report a titanium-promoted method for the conversion of N_(2) to N-methylimides.Initially,the N_(2)-bridging end-on dititanium side-on dipotassium complex[{(Tren^(TMS))Ti}_(2)(μ-η^(1):η^(1):η^(2):η^(2)-N_(2)K_(2))] underwent simultaneous disproportionation and N-methylation reactions in the presence of methyl trifluoromethanesulfonate(Me OTf),yielding [{(N^(Me,TMS)NN^(TMS)_(2))Ti}(μ-NMe)]_(2) with complete cleavage of the N≡N bond.The nucleophilicity of the N-methylated intermediate allowed it to react with electrophilic reagents such as trimethylchlorosilane(TMSCl) to form heptamethyldisilazane,or with acyl chlorides to generate N-methylimides.Moreover,nitrogen-15(^(15)N) labeled experiments provided a novel approach to synthesizing ^(15)N-labeled methylimides.展开更多
Ti-5Al-5Mo-5Cr-2Zr-xNb with different Nb(abbreviated as Ti-5552-xNb,x=3,6,9,12,wt.%)contents were stretched at 923 K to study their superplastic behavior and mechanical properties below recrystallization temperature.T...Ti-5Al-5Mo-5Cr-2Zr-xNb with different Nb(abbreviated as Ti-5552-xNb,x=3,6,9,12,wt.%)contents were stretched at 923 K to study their superplastic behavior and mechanical properties below recrystallization temperature.The microstructure of as-cast Ti-5552-xNb alloy is consisted of a singleβphase,and theβgrain size increases slightly with the increase of Nb content.The thermal effect in the process of high temperature drawing leads to the precipitation ofαphase.The addition of Nb in Ti-5552 titanium alloys reduces theα/βphase transformation temperature,which causes a decrease in the volume fraction ofαphase.Reducing theαphase content reduces incompatibility,but too low a proportion ofαphase will lead to premature fracture,so tensile strength and plasticity firstly increase and then decrease.The results show that Ti-5552-9Nb titanium alloy shows the best tensile strength(307.2 MPa)and superplasticity(106%).The superplastic mechanism of Ti-5552-9Nb alloy is mainly caused by relative sliding ofβgrain boundaries and dislocation movement.展开更多
基金financial support from the Yunnan Province Key Industries Science and Technology Special Project for Colleges and UniversitiesChina(No.FWCY-QYCT2024006)+6 种基金National Natural Science Foundation of China(Nos.52104351 and 52364051)Science and Technology Major Project of Yunnan Province,China(No.202202AG050007)the Yunnan Fundamental Research ProjectsChina(No.202401AT070314)the Key Technology Research and Development Program of Shandong Province,China(No.2023CXGC010903)Central Guidance Local Scientific and Technological Development Funds,China(No.202407AB110022)Yunnan Province Xingdian Talent Support Plan Project,China。
文摘Titanium exhibits outstanding properties,particularly,high specific strength and resistance to both high and low temperatures,earning it a reputation as the metal of the future.However,because of the highly reactive nature of titanium,metallic titanium production involves extensive procedures and high costs.Considering its advantages and limitations,the European Union has classified titanium metal as a critical raw material(CRM)of low category.The Kroll process is predominantly used to produce titanium;however,molten salt electrolysis(MSE)is currently being explored for producing metallic titanium at a low cost.Since 2000,electrolytic titanium production has undergone a wave of technological advancements.However,because of the intermediate and disproportionation reactions in the electrolytic titanium production process,the process efficiency and titanium purity according to industrial standards could not be achieved.Consequently,metallic titanium production has gradually diversified into employing technologies such as thermal reduction,MSE,and titanium alloy preparation.This study provides a comprehensive review of research advances in titanium metal preparation technologies over the past two decades,highlighting the challenges faced by the existing methods and proposing potential solutions.It offers useful insights into the development of low-cost titanium preparation technologies.
基金the financial support by the National Natural Science Foundation of China(Nos.U21A2042,52425401,U2441255,52474377)the Major Science and Technology Achievement Transformation Project in Heilongjiang Province(No.ZC2023SH0075)the Henan Provincial Key Research and Development&Promotion Special Program(No.251111231400)。
文摘The traditional"trial and error"microstructural control method,with high cost and low efficiency,has become a key issue restricting the development of ultra-high strength and toughness titanium alloys.This study adopts the molybdenum equivalent(Mo_([eq]))method to rapidly design Ti-xMo-4Al-4Zr-3Nb-2Cr-1Fe alloys(x=5-9).The as-cast alloys with different Mo_([eq])exhibit a single peak of theβphase in XRD.Theβgrains of 5Mo alloy(the lowest Mo_([eq]))exhibit elongated columnar grain characteristics.As the Mo_([eq])increases,theβgrains transition towards a more equiaxed form,resulting in a decrease in aspect ratio and a reduction in grain size.As the Mo_([eq])increases,the a phase content gradually decreases and the a phase is almost unobservable in 9Mo alloy(the highest Mo_([eq])).The a phase in 5Mo alloy exhibits short rod-shaped shapes with an average length of about2.4μm,while the a phase in 6Mo alloy shows an equiaxed and short rod shapes with the smallest size.The strength,plasticity,and toughness are the lowest in 5Mo alloy,with values of 867 MPa,7.3%,and 56 MPa·m^(1/2),respectively.However,it reaches its maximum in 6Mo alloy,where the strength,plasticity,and toughness increase to 984 MPa,12.8%,and 74 MPa·m^(1/2),respectively.The mechanical properties of Ti-xMo-4Al-4Zr-3Nb-2Cr-1Fe alloys are affected mainly by solid-solution strengthening of Mo element,refinement ofβgrain,and changes inα/βphase content.This study lays a certain theoretical foundation for the theoretical research and composition development of new ultra-high strength and toughness titanium alloys.
基金financially supported by the National Natural Science Foundation of China(No.52375347)Shanghai Pujiang Programme(No.8003PJD023)Natural Science Foundation of Ningbo(Grant No.2023J008)。
文摘The strength-ductility synergy in heterogeneous materials offers significant advantages,though their scalable and controlled fabrication remains challenging.This study introduces an in situ fabrication strategy for heterogeneous lamellar titanium(HLT)alloy via laser powder bed fusion of a powder mixture consisting of Ti6Al4V(TC4)and 3 wt%Fe.By periodically varying the scanning velocity between layers,a heterogeneous lamellar microstructure is achieved due to the unique Fe distribution originating from the various volumetric energy densities(VEDs).Consequently,the HLT achieves high yield strength(1036 MPa)and ultimate tensile strength(1419 MPa)without compromising uniform elongation(UE),surpassing most TC4 alloys.The high strength may be attributed to precipitation strengthening originating from the nano-sizedαandωprecipitates,while the high UE and work hardening arise from the strain-induced martensite(SIM)and strong hetero-deformation induced(HDI)stress.The denser dual-phase interfaces and smaller grains in the low VED layers contribute to the higher sensitivity to the SIM.A strain gradient between soft and hard layers evolves during loading,and it further enhances the HDI strengthening and SIM behavior.Through this work,the in situ fabrication method and the deformation mechanism of lamellar heterostructure could offer valuable reference for the optimization and application of heterogeneous materials.
基金supported by the National Natural Science Foundation of China(Nos.81974441 and 82203619)the Science and Technology Planning Project of Shenzhen Municipality(Nos.JCYJ20190814105619048 and JCYJ20220530154202005)。
文摘Colitis-associated colorectal cancer(CAC)is a major contributor to cancer-related mortality worldwide.Titanium dioxide(TiO_(2),E171),a widely used food additive,has been insufficiently studied regarding its effects on macrophages within colon tumors during CAC development.In this study,CAC mouse models were used to investigate the biological impact of dietary E171 on macrophages in vivo,while lipopolysaccharide(LPS)-stimulated RAW264.7 macrophage cell lines were employed to elucidate the underlying mechanisms in vitro.We found that dietary E171 intake accelerated CAC development,exacerbated inflammatory responses and oxidative stress,and upregulated CAC-associated genes,including S100a8,S100a9,Lcn2,S100a11,Cxcl2,and interleukin-1α(Il-1α).E171 also increased the expression of S100A8,S100A9,NOD-like receptor family pyrin domain-containing 3(NLRP3),and gasdermin-D Nterminal(GSDMD-N)in macrophages within colon tumors.In inflammatory macrophages,E171 exposure enhanced cell viability,increased reactive oxygen species(ROS)levels,and elevated the expression and secretion of S100A8 and S100A9,consistent with in vivo histological observations.Furthermore,E171-induced secretion of S100A8 and S100A9 in macrophages was suppressed by specific inhibitors,including N-acetylcysteine(NAC,ROS inhibitor),MCC950(NLRP3 inhibitor),Z-YVAD-FMK(caspase 1 inhibitor),disulfiram(GSDMD inhibitor),and transfection of NLRP3 small interfering ribonucleic acid(siRNA).These results indicate that dietary E171 promotes CAC development by activating macrophages,with S100A8 and S100A9 serving as key mediators,and the NLRP3/caspase 1/GSDMD pathway acting as a critical mechanism.
基金supported by the National Natural Sci-ence Foundation of China(Nos.52274359 and 52304379)the China National Postdoctoral Program for Innovative Talents(No.BX20220034)+2 种基金the China Postdoctoral Science Foundation(No.2022M720403)the AECC University Research Cooperation Project(No.HFZL2021CXY021)the Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)(No.FRF-IDRY-23-025).
文摘Achieving the simultaneous enhancement of strength and ductility in laser powder bed fused (LPBF-ed) titanium (Ti) is challenging due to the complex, high-dimensional parameter space and interactions between parameters and powders. Herein, a hybrid intelligent framework for process parameter optimization of LPBF-ed Ti with improved ultimate tensile strength (UTS) and elongation (EL) was proposed. It combines the data augmentation method (AVG ± EC × SD), the multi-model fusion stacking ensemble learning model (GBDT-BPNN-XGBoost), the interpretable machine learning method and the non-dominated ranking genetic algorithm (NSGA-Ⅱ). The GBDT-BPNN-XGBoost outperforms single models in predicting UTS and EL across the accuracy, generalization ability and stability. The SHAP analysis reveals that laser power (P) is the most important feature affecting both UTS and EL, and it has a positive impact on them when P < 220 W. The UTS and EL of samples fabricated by the optimal process parameters were 718 ± 5 MPa and 27.9 % ± 0.1 %, respectively. The outstanding strength-ductility balance is attributable to the forward stresses in hard α'-martensite and back stresses in soft αm'-martensite induced by the strain gradients of hetero-microstructure. The back stresses strengthen the soft αm'-martensite, improving the overall UTS. The forward stresses stimulate the activation of dislocations in hard α'-martensite and the generation of 〈c + a〉 dislocations, allowing the plastic strain to occur in hard regions and enhancing the overall ductility. This work provides a feasible strategy for multi-objective optimization and valuable insights into tailoring the microstructure for improving mechanical properties.
文摘目的描述广东地区法布雷病患者基因型情况,对比IVS4+919G>A突变患者与非IVS4+919G>A突变患者的地域分布和临床表型差异。方法回顾性收集2022年3月1日至2025年12月31日本中心(中山大学附属第一医院)47例(IVS4+919G>A突变患者12例)已出现器官受累的法布雷病患者的相关资料,分析总体、IVS4+919G>A突变和非IVS4+919G>A突变患者的地域分布和临床表现特点。结果IVS4+919G>A突变在本中心为最常见突变(25.5%)。本中心的该突变患者有半数(50%)分布在粤东地区,起病中位年龄显著高于非IVS4+919G>A突变组,差异有统计学意义(P<0.05)。IVS4+919G>A突变患者中出现心脏受累11例(91.7%),神经系统受累2例(16.7%),美因茨严重程度评分指数(Mainz severity score index,MSSI)评分有高于非IVS4+919G>A突变组的趋势(P=0.051);MSSI总体评分和神经评分低于非IVS4+919G>A突变组,差异有统计学意义(P<0.05)。相较非IVS4+919G>A突变患者,IVS4+919G>A突变患者的心率更低、心肌肌钙蛋白浓度更高,超声提示其左心房更大、室间隔与左心室后壁更厚、二尖瓣舒张早期充盈峰速度E峰和二尖瓣舒张晚期充盈峰速度A峰比值(ratio of early diastolic transmitral inflow E-peak velocity to late diastolic mitral annulus A-peakvelocity,E/A)更低,差异有统计学意义(P<0.05)。结论IVS4+919G>A突变患者在本中心为最常见突变。本中心的该突变患者有半数分布在粤东地区,其表型以迟发型和心脏受累为主,神经系统受累较少,心肌肥厚、舒张功能下降和心肌损伤情况较其他突变群体更严重。
基金supported by the National Key Research and Development Program of China(No.2021YFB3702604)the National Natural Science Foundation of China(No.52001258).
文摘The development of cost-effective titanium alloys with outstanding mechanical properties has always been a primary concern of the modern aerospace industry.However,the intrinsic sensitivity of theirαprecipitates to heat treatments proliferates the manufacturing costs to achieve desirable strength and ductility,especially in engineering occasions.In current work,a silicide-containingα+βTi-5Al-7.5V-0.5Mo-0.5Zr-0.5Si(TC5751S)alloy has been evidenced to exhibit advanced mechanical properties with reduced sensitivity to heat treatments.It is noted that more nano-scale secondaryα(αs)precipitate with a simultaneous dissolution in micron-scale primaryα(αp)and(Ti,Zr)_(5)Si_(3)silicides in the current alloy as the solution temperature increases.However,this alloy shows excellent and stabilized strength-ductility synergy in all cases(ultimate tensile strength:1335±30 MPa,yield strength:1245±30 MPa,fracture strain:9.6%±0.5%)irrespective of the aforementioned variations in the microstructure.This stabilized strength and ductility of TC5751S are rationalized based on the compensation mechanisms be-tween the contributions from silicide and heterogeneousαprecipitates.The quantitative analysis unveils that the increased α_(s)/β phase boundary strengthening(σ_(PB))is approximately offset by the decrease in silicide strengthening(σ_(silicide))due to silicide dissolution with increasing solution temperatures,leading to the strength of TC5751S in a dynamic equilibrium state.Simultaneously,the dissolution of silicides re-duces the cracking tendency and complements the ductility loss due to α_(p) reduction and α_(s) precipitation,leading to the ductility insensitive to heat treatments.Therefore,the compensating role of silicides to the effects of heterogeneousαprecipitates on both the strength and ductility of titanium alloys has been well-verified in our work,providing a novel pathway to the development of high-performance titanium alloys friendly to processing strategies.
基金supported by the National Natural Science Foundation of China(No.52272283)the Science and Technology Commission of Shanghai Municipality(Nos.22S31902900 and 22ZR1457600)+3 种基金Youth Innovation Promotion Association CAS(No.2023263)Young Elite Scientists Sponsorship Program by CAST(No.2022-2024QNRC001)General Research Fund of the Research Grants Council(No.17207719)the Health and Medical Research Fund(No.20190244).
文摘Implant-related infections and tissue inflammation are the main factors for peri-implantitis.Lack of antibacterial activity and poor soft tissue sealing property increase the occurrence probability of peri-implantitis.To prevent and treat peri-implantitis,cerium-doped defective titanium oxide coatings are prepared on medical titanium surfaces by plasma electrolytic oxidation and thermal reduction treatment.In the darkness,Ce-doped defective titanium oxide coatings with micro-porous structure surface can inhibit the bacteria adhesion to some extent with antibacterial rates of 38.0%against S.aureus and 65.0%against E.coli.Under near infrared(NIR)irradiation,Ce-doped defective titanium oxide coatings show good photothermal antibacterial activity with antibacterial rates of 99.9%against S.aureus and 99.9%against E.coli.Moreover,with the increasing content of Ce-doping,the coatings exhibit higher capacity to scavenge hydrogen peroxide(H2O2)and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)radical cation(ABTS^(·+)).The coatings with enhanced antioxidant effect can protect human gingival fibroblasts from oxidative stress damage by eliminating reactive oxygen species and promoting initial cell adhesion.Besides,Ce-doped coatings can regulate the immune microenvironment by up-regulating the expression of anti-inflammatory genes and down-regulating the pro-inflammatory genes.In vivo animal experiments further confirm the good antibacterial activity of Ce-doped defective titanium oxide coatings under NIR irradiation and good biosafety.This work provides a novel surface modification strategy for implant abutment,which shows good application prospects for preventing and treating peri-implantitis.
基金supported by the Beijing Natural Sci-ence Foundation(No.L242139).
文摘The durability of dental implant carrier coatings is of paramount importance for the expeditious and predictable osseointegration process.The present work is based on a bionic micro/nano hierarchy struc-ture,which consists of titanium surface microstructures and their internal TiO2 nanotubes(TNTs)with drug-carrying capacity.This effectively increases the wear resistance of the drug-carrying coating on the titanium surface.In comparison to untextured samples,the wear volume and wear depth of the optimal texture group are markedly diminished,resulting in a significant enhancement of wear resistance.This improvement was primarily attributed to the smaller contact area of the microstructure.Concurrently,the microstructure serves to safeguard the TNTs from damage during friction.The hydrophilic biomimetic anti-wear micro/nano hierarchies demonstrated the capacity to promote MC3T3-E1 cell adhesion and pro-liferation,while also exhibiting no cytotoxic effects.Moreover,the micro/nano hierarchical structure can be directly applied to the surface of commercialized implants.In simulated clinical conditions,the im-plant was inserted into a fresh Bama porcine mandible,and the structure of the drug-loading coatings remained intact.This structure enhances the abrasion resistance of the drug coating while minimizing alterations to the original treatment process of the implant,which is of great significance in the clinical application of implant-loaded drug delivery.
基金financially supported by the National Natural Science Foundation of China(Nos.52272283,52311530772,and 52274387)the Science and Technology Commission of Shanghai Municipality(No.22S31902900)+4 种基金the Shanghai Medical Key Specialty(No.2024ZDXK0048)the Medical Key Subject of Xuhui District(No.SHXHZDXK202302)the National Key Research and Development Program of China(No.2024YFE0109000)the Medical-Engineering Cross Foundation of Shanghai Jiao Tong University(No.YG2024LC04)the Institute-level Research Project of Xuhui District Dental Center(No.SHXYF202212).
文摘To promote early rapid osteogenesis and prevent late implant-related infection,it is critical to develop ef-fective and reliable surface treatment technologies for enhancing both osteogenic and antibacterial prop-erties of titanium alloy implants.Reduced graphene oxide(rGO)is considered a promising modification candidate.However,whether rGO retains its osteogenic and antibacterial functions after being applied to modify titanium alloy surfaces depends on the surface treatment technology employed.In this study,rGO was integrated onto the surface of Ti-35Nb-2Ta-3Zr(TNTZ)alloy through friction stir processing(FSP),yielding a consolidated TNTZ/F-rGO composite.The incorporation of rGO not only significantly im-proved the microhardness and hydrophilicity of the material,but also exhibited positive biological effects in vitro experiments:it effectively promoted the proliferation,osteogenic differentiation,alkaline phos-phatase(ALP)production and extracellular matrix mineralization of BMSCs.Furthermore,TNTZ/F-rGO ex-hibited potent antibacterial activity via surface-contact mechanisms.In summary,the rGO-modified in-tegrated titanium alloy has excellent osteogenic properties and high-efficiency antibacterial ability.This study provides new insights and strategies for the design of graphene-based biomaterials and implant surface modification technologies.
文摘BACKGROUND Clinical studies using Trabecular Titanium™acetabular cups have shown promising short and medium-term results.This material,due to its macro and micro surface roughness,provides a substrate for osseointegration and enhances implant stability.However,there is a lack of evidence in the literature on the use of this material in patients with femoral neck fracture.AIM To evaluate the short-term clinical-functional and radiographic outcomes in patients with femoral neck fractures undergoing total hip arthroplasty(THA)with Trabecular Titanium™acetabular cup implants.METHODS The study included 104 patients with medial femoral neck fractures who underwent THA between January 2020 and December 2020 with the Delta TT acetabular cup(Lima Corporate,Villanova di San Daniele del Friuli,Italy).The mean age of the patients was 69.57±10.16 years(range:36-85 years).The followup period ranged from a minimum of 3 to a maximum of 4 years.Three questionnaires(Harris Hip Score,Oxford Hip Score,and EQ5D)were administered along with radiographic evaluations.Statistical methods included the Student's t-test and one-way analysis of variance for comparisons(with significance set at 0.05),and the Kaplan-Meier curve for prosthetic implant survival.RESULTS The mean follow-up was 41.5 months.The Harris Hip Score(HHS)showed a mean increase of 2.74 points(mean HHS 88.52 at 6 months postoperatively and mean HHS 91.26 at the last follow-up)with statistical significance.Similarly,the Oxford Hip Score demonstrated a statistically significant difference between follow-up groups.However,the EQ5D did not show statistically significant differences among the three groups(preoperative,6-month follow-up,and last follow-up).Revision surgery was required in 6 patients.According to Moore's criteria,96%of the acetabular components were radiographically stable and well-integrated at the last follow-up.The Kaplan-Meier curve showed a 96%survival rate.CONCLUSION The clinical and radiographic results obtained in the short to medium term confirm the excellent performance of the Delta TT acetabular cup in terms of osseointegration,providing an optimal solution both for young patients with high functional recovery demands and for fragile patients requiring optimal stability of the acetabular component to reduce the risk of implant failure.
文摘In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and surface integrity must be considered simultaneously during the enhancement process.The current manufacturing process of hole burnishing has a relatively weak balance between the structure shape and surface integrity;therefore,it is necessary to analyze the mechanism and optimize the parameters to improve the strengthening effect of the holes.In this study,a two-dimensional longitudinal simplified model for the hole burnishing process was established,and the reasons for the surface roughness improvement of the hole wall and material accumulation on the upper surface were analyzed.Experiments were conducted to determine the influence of the burnishing parameters on the structure shape(material accumulation,shape contour,and roundness)and surface integrity(surface roughness,residual stress,and surface hardness),based on the opposite requirements of improving the structure shape and surface integrity for the burnishing depth(BD).The results showed that with an increase in the BD,the structure shape deteriorated,whereas the surface integrity improved.Fatigue behavior verification experiments were conducted,and parameter selection schemes for the collaborative improvement of the structure shape and surface integrity were discussed.For the holes of titanium alloy TB6(Ti-10V-2Fe-3Al),the fatigue life can be increased by 162%when the BD,spindle speed,and feed rate were 0.20 mm,200 r/min,and 0.2 mm/r,respectively.
文摘In this study,Ti-6.5Al-3.5Mo-1.5Zr-0.3Si(TC11)titanium alloy samples are fabricated via arc-wire directed energy deposition(AW-DED)and laser powder bed fusion(L-PBF).The variant-selection(VS)mechanism of the𝛼grain boundary(α_(GB))and the intragranular microstructure are characterized via electron backscatter diffraction,and the related formation mechanisms are discussed.The continuous α_(GB) maintained Burgers orientation relationships with one of the adjacent lamellas in the AW-DED sample and the adjacent acicular α’laths in the l-PBF sample as much as possible,respectively.For the intragranular microstructure,the VS of the colony and basket-weave microstructures maintained a common{1120}pole with one of their adjacent microstructures in the AW-DED sample.The VS of the acicular α’lath in the intragranular region is maintained as the common{0001}pole and{1120}pole section as much as possible with the adjacent acicular α’lath.Type-2(60°/[1120])bound-aries dominated the colony microstructure and the basket-weave microstructure because of their low cooling rate in the AW-DED sample.By contrast,type-4(63.26°/[10553])boundaries are composed of the acicular α’lath owing to their high cooling rate in the l-PBF sample during deposition.
基金Key Program of National Natural Science Foundation of China(52431001)。
文摘To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level orthogonal experiment design of factor levels.Results show that through range analysis,the significance order of process parameters is determined as follows:solution cooling method>solution temperature>aging time>aging temperature>solution time.Considering the strength-ductility matching and engineering application requirements,the benchmark parameters are selected as solution time of 1 h,solution cooling method of air cooling(AC),aging temperature of 525℃,and aging time of 4 h.Furthermore,the effects of solution temperature in the range of 790–870℃ on the impact toughness and micro-fracture characteristics of the alloy were studied.The results reveal that the larger the area of shear lip and fibrous zone,and the smaller the area of radiation zone,the better the toughness of the alloy.With the increase in solution temperature,the length of secondary cracks on the fracture surface increases,the number of dimples increases,and the toughness is enhanced.Based on the collaborative optimization of strength and toughness,the optimal heat treatment process for TB18 alloy is determined as 870℃/1 h,AC+525℃/4 h,AC.
基金Natural Science Foundation of Shaanxi Province (2023-JC-YB-312)。
文摘Ultrafine-grained(UFG)pure titanium was produced by equal channel angular pressing for 4 passes,followed by rotatory swaging at room temperature.The strain-controlled low-cycle fatigue tests of UFG and coarse-grained(CG)pure titanium were conducted by Instron electro-hydraulic servo fatigue testing machine in the strain amplitude range of 0.5%—1.1%at room temperature.Transmission electron microscope(TEM)and scanning electron microscope were used to investigate the microstructure and fracture surface of UFG pure titanium after fatigue tests.Results show that UFG pure titanium exhibits a longer low-cycle fatigue life,compared with the CG pure titanium.For example,at a total strain amplitude of 0.5%,UFG and CG pure titanium has fatigue life of 10850 and 4820 cycles,respectively.Significant cyclic softening occurs in UFG pure titanium,except in the case of a total strain amplitude of 0.5%.Hysteresis loop area is increased rapidly with the increase in strain amplitude.The fracture surface shows that the fatigue crack is initiated from the specimen surface.A series of fatigue striations and many microcracks exist in the propagation region.With the increase in strain amplitude,the predominant failure mode is transformed from ductile failure into quasi-cleavage failure.Dislocation slip is the main plastic deformation mechanism of UFG pure titanium during low-cycle fatigue deformation.
基金Financial supports from the National Natural Science Foundation of China (Nos.22025109,22371283)the National Key R&D Program of China (No.2023YFA1507902)+1 种基金CAS Project for Young Scientists in Basic Research (No.YSBR-050)the State Key Laboratory of Fine Chemicals,Dalian University of Technology (No.KF2102) are gratefully acknowledged。
文摘The direct transformation of dinitrogen(N_(2)) into nitrogen-containing organic compounds holds substantial importance.In this work,we report a titanium-promoted method for the conversion of N_(2) to N-methylimides.Initially,the N_(2)-bridging end-on dititanium side-on dipotassium complex[{(Tren^(TMS))Ti}_(2)(μ-η^(1):η^(1):η^(2):η^(2)-N_(2)K_(2))] underwent simultaneous disproportionation and N-methylation reactions in the presence of methyl trifluoromethanesulfonate(Me OTf),yielding [{(N^(Me,TMS)NN^(TMS)_(2))Ti}(μ-NMe)]_(2) with complete cleavage of the N≡N bond.The nucleophilicity of the N-methylated intermediate allowed it to react with electrophilic reagents such as trimethylchlorosilane(TMSCl) to form heptamethyldisilazane,or with acyl chlorides to generate N-methylimides.Moreover,nitrogen-15(^(15)N) labeled experiments provided a novel approach to synthesizing ^(15)N-labeled methylimides.
基金the financial support by the Major Science and Technology Achievement Transformation Project in Heilongjiang Province(ZC2023SH0075)the National Natural Science Foundation of China(52425401,U2441255,52474377,and 52371015)+1 种基金the Young Elite Scientists Sponsorship Program by·CAST(2021QNRC001)the Henan Provincial Key Research and Development&Promotion Special Program(251111231400)。
文摘Ti-5Al-5Mo-5Cr-2Zr-xNb with different Nb(abbreviated as Ti-5552-xNb,x=3,6,9,12,wt.%)contents were stretched at 923 K to study their superplastic behavior and mechanical properties below recrystallization temperature.The microstructure of as-cast Ti-5552-xNb alloy is consisted of a singleβphase,and theβgrain size increases slightly with the increase of Nb content.The thermal effect in the process of high temperature drawing leads to the precipitation ofαphase.The addition of Nb in Ti-5552 titanium alloys reduces theα/βphase transformation temperature,which causes a decrease in the volume fraction ofαphase.Reducing theαphase content reduces incompatibility,but too low a proportion ofαphase will lead to premature fracture,so tensile strength and plasticity firstly increase and then decrease.The results show that Ti-5552-9Nb titanium alloy shows the best tensile strength(307.2 MPa)and superplasticity(106%).The superplastic mechanism of Ti-5552-9Nb alloy is mainly caused by relative sliding ofβgrain boundaries and dislocation movement.
