Microstructure evolution and strengthening mechanism of high -performance powder metallurgy TA15 titanium alloy by hot rolling

Hot deformation of sintered billets by powder metallurgy(PM)is an effective preparation technique for titanium alloys,which is more significant for high-alloying alloys.In this study,Ti–6.5Al–2Zr–Mo–V(TA15)titanium alloy plates were prepared by cold press-ing sintering combined with high-temperature hot rolling.The microstructure and mechanical properties under different process paramet-ers were investigated.Optical microscope,electron backscatter diffraction,and others were applied to characterize the microstructure evolution and mechanical properties strengthening mechanism.The results showed that the chemical compositions were uniformly dif-fused without segregation during sintering,and the closing of the matrix craters was accelerated by increasing the sintering temperature.The block was hot rolled at 1200℃ with an 80%reduction under only two passes without annealing.The strength and elongation of the plate at 20–25℃ after solution and aging were 1247 MPa and 14.0%,respectively,which were increased by 24.5%and 40.0%,respect-ively,compared with the as-sintered alloy at 1300℃.The microstructure was significantly refined by continuous dynamic recrystalliza-tion,which was completed by the rotation and dislocation absorption of the substructure surrounded by low-angle grain boundaries.After hot rolling combined with heat treatment,the strength and plasticity of PM-TA15 were significantly improved,which resulted from the dense,uniform,and fine recrystallization structure and the synergistic effect of multiple slip systems.

A review and a statistical analysis of porosity in metals additively manufactured by laser powder bed fusion

Additive manufacturing(AM), or 3D printing, is an emerging technology that “adds” materials up and constructs products through a layer-by-layer procedure. Laser powder bed fusion(LPBF) is a powder-bed-based AM technology that can fabricate a large variety of metallic materials with excellent quality and accuracy. However, various defects such as porosity,cracks, and incursions can be generated during the printing process. As the most universal and a near-inevitable defect,porosity plays a substantial role in determining the mechanical performance of as-printed products. This work presents a comprehensive review of literatures that focused on the porosity in LPBF printed metals. The formation mechanisms,evaluation methods, effects on mechanical performance with corresponding models, and controlling methods of porosity have been illustrated and discussed in-depth. Achievements in four representative metals, namely Ti-6Al-4V, 316L, Inconel 718, and Al Si10Mg, have been critically reviewed with a statistical analysis on the correlation between porosity fraction and tensile properties. Ductility has been determined as the most sensitive property to porosity among several key tensile properties. This review also provides potential directions and opportunities to address the current porosity-related challenges.

A self-powered and sensitive terahertz photodetection based on PdSe_(2)

With the rapid development of terahertz technology,terahertz detectors are expected to play a key role in diverse areas such as homeland security and imaging,materials diagnostics,biology,medical sciences,and communication.Whereas self-powered,rapid response,and room temperature terahertz photodetectors are confronted with huge challenges.Here,we report a novel rapid response and self-powered terahertz photothermoelectronic(PTE)photodetector based on a lowdimensional material:palladium selenide(Pd Se_(2)).An order of magnitude performance enhancement was observed in photodetection based on PdSe_(2)/graphene heterojunction that resulted from the integration of graphene and enhanced the Seebeck effect.Under 0.1-THz and 0.3-THz irradiations,the device displays a stable and repeatable photoresponse at room temperature without bias.Furthermore,rapid rise(5.0μs)and decay(5.4μs)times are recorded under 0.1-THz irradiation.Our results demonstrate the promising prospect of the detector based on Pd Se2 in terms of air-stable,suitable sensitivity and speed,which may have great application in terahertz detection.

Effect of internal defects on tensile strength in SLM additively-manufactured aluminum alloys by simulation

This research investigates the effect of internal defects on the tensile strength of Selective Laser Melting(SLM)additively-manufactured aluminum alloy(AlSi10Mg)test parts used for civil aircraft light weight design.A Finite Element Analysis(FEA)model containing internal defects was established by combining test data and the stress concentration factor comparison method.The effect of variation in the number,location and shape of defects on the finite element results was analyzed.Its results show that it is reasonable to use spherical defect modeling.The finite element modeling and analysis methods are also applied to the study of the effect of internal defects on tensile strength in additive manufacturing of other metallic materials.According to the FEA results of single defects at different scales,the formula for calculating the weakening degree of tensile strength applicable to the defective area of less than 15%was established.The result of the procedure is reliable and conservative.This research results can guide the selection of process parameters for the additive manufacturing of aluminum alloys.Further,the research results can promote the application of metal additive manufacturing in designing light-weight civil aircraft structures.

Plain metallic biomaterials:opportunities and challenges

The‘plainification of materials’has been conceptualized to promote the sustainable development of materials.This perspective,for the first time in the field of biomaterials,proposes and defines‘plain metallic biomaterials(PMBs)’with demonstrated research and application case studies of pure titanium with high strength and toughness,and biodegradable,fine-grained and high-purity magnesium.Then,after discussing the features,benefits and opportunities of PMBs,the challenges are analyzed from both technical and regulatory aspects.Regulatory perspectives on PMB-based medical devices are also provided for the benefit of future research,development and commercialization.

Additive manufacturing of multi-morphology graded titanium scaffolds for bone implant applications

Porous Titanium scaffolds have attracted widespread attention as bone implants for avoiding the stress shielding effect and promoting bone-in-growth.In this study,multi-morphology graded scaffolds hy-bridized by Primitive and Gyroid structures with porosity of 50,60,and 70%were designed(denoted as PG50,PG60,and PG70,respectively)and fabricated by selective laser melting.The simulation results showed that the maximum von-Mises stress of hybridized scaffolds increased from 504.22 to 884.24 MPa with porosity.The permeability and average pore size of multi-morphology PG50,PG60,and PG70 were in the range of 3.58×10^(-9)-5.50×10^(-9) m^(2) and 568.1-758.4μm,respectively.The microstructure of multi-morphology graded scaffolds consisted of a fully martensiticα′phase.Tested permeabilities of PG50 and PG60 were 3.27×10^(-9) and 4.35×10^(-9) m^(2),respectively,which were within the range of human bone(0.01-12.1×10^(-9) m^(2)).Elastic modulus and compressive yield strength of PG50 and PG60 ranged within 5.93^(-9).86 and 180.06-257.08 MPa,respectively.Therein,the PG50 not only exhibited a similar elastic modulus compared to human cortical bone(10.1 GPa)but also had higher strength(257.08 vs 131 MPa).The results of in vitro biocompatibility assay showed that PG50 and PG60 have better cyto-compatibility than mono-morphology scaffolds with the same porosity.Taken together,PG50 is promising to be used for the restoration of bone defects due to its excellent mechanical properties,appropriate per-meability,and good cytocompatibility.

Biodegradable metals for bone defect repair:A systematic review and meta-analysis based on animal studies

Biodegradable metals are promising candidates for bone defect repair.With an evidence-based approach,this study investigated and analyzed the performance and degradation properties of biodegradable metals in animal models for bone defect repair to explore their potential clinical translation.Animal studies on bone defect repair with biodegradable metals in comparison with other traditional biomaterials were reviewed.Data was carefully collected after identification of population,intervention,comparison,outcome,and study design(PICOS),and following the inclusion criteria of biodegradable metals in animal studies.30 publications on pure Mg,Mg alloys,pure Zn and Zn alloys were finally included after extraction from a collected database of 2543 publications.A qualitative systematic review and a quantitative meta-analysis were performed.Given the heterogeneity in animal model,anatomical site and critical size defect(CSD),biodegradable metals exhibited mixed effects on bone defect repair and degradation in animal studies in comparison with traditional non-degradable metals,biodegradable polymers,bioceramics,and autogenous bone grafts.The results indicated that there were limitations in the experimental design of the included studies,and quality of the evidence presented by the studies was very low.To enhance clinical translation of biodegradable metals,evidence-based research with data validity is needed.Future studies should adopt standardized experimental protocols in investigating the effects of biodegradable metals on bone defect repair with animal models.

Biodegradable metals for bone fracture repair in animal models: a systematic review

Biodegradable metals hold promises for bone fracture repair.Their clinical translation requires pre-clinical evaluations including animal studies,which demonstrate the safety and performance of such materials prior to clinical trials.This evidence-based study investigates and analyzes the performance of bone fractures repair as well as degr adation properties of biodegradable metals in animal models.Data were carefully collected after identification of population,interventions,com-parisons,outcomes and study design,as well as inclusion criteria combining biodegradable metals and animal study.Twelve publications on pure Mg,Mg alloys and Zn alloys were finally included and reviewed after extraction from a collected database of 2122 publications.Compared to controls of traditional non-degradable metals or resorbable polymers,biodegradable metals showed mixed or contradictory outcomes of fracture repair and degradation in animal models.Although quantita-tive meta-analysis cannot be conducted because of the data heterogeneity,this systematic review revealed that the quality of evidence for biodegradable metals to repair bone fractures in animal models is'very low'.Recommendations to standardize the animal studies of biodegradable metals were proposed.Evidence based biomaterials research could help to both identify reliable scientific evidence and ensure future clinical translation of biodegradable metals for bone fracture repair.

Regulatory considerations for animal studies of biomaterial products

Animal studies play a vital role in validating the concept,feasibility,safety,performance and efficacy of biomaterials products during their bench-to-clinic translation.This article aims to share regulatory considerations for animal studies of biomaterial products.After briefly emphasizing the importance of animal studies,issues of animal studies during biomaterial products’translation are discussed.Animal studies with unclear purposes,flawed design and poor reporting quality could significantly reduce the translation efficiency and create regulatory challenges.Regulatory perspectives on the purpose,principle,quality and regulatory science of animal studies are also presented.Animal studies should have clear purposes,follow principles of 3R+DQ(replacement,reduction,refinement,design and quality)and execute under an efficiently operating quality management system.With the advancement of regulatory science,National Medical Products Administration of China has been developing a series of standards and guidance documents on animal studies of medical devices.Case studies of making decisions on whether to conduct animal studies are provided in the end with drug-eluting stents as examples.In summary,animal studies of biomaterial products should pay close attention to the rationale,design and quality in order to achieve their purposes.

Design and performance evaluation of additively manufactured composite lattice structures of commercially pure Ti(CP-Ti)

Ti alloys with lattice structures are garnering more and more attention in the field of bone repair or regeneration due to their superior structural,mechanical,and biological properties.In this study,six types of composite lattice structures with different strut radius that consist of simple cubic(structure A),body-centered cubic(structure B),and edge-centered cubic(structure C)unit cells are designed.The designed structures are firstly simulated and analysed by the finite element(FE)method.Commercially pure Ti(CP-Ti)lattice structures with optimized unit cells and strut radius are then fabricated by selective laser melting(SLM),and the dimensions,microtopography,and mechanical properties are characterised.The results show that among the six types of composite lattice structures,combined BA,CA,and CB structures exhibit smaller maximum von-Mises stress,indicating that these structures have higher strength.Based on the fitting curves of stress/specific surface area versus strut radius,the optimized strut radius of BA,CA,and CB structures is 0.28,0.23,and 0.30 mm respectively.Their corresponding compressive yield strength and compressive modulus are 42.28,30.11,and 176.96 MPa,and 4.13,2.16,and 7.84 GPa,respectively.The CP-Ti with CB unit structure presents a similar strength and compressive modulus to the cortical bone,which makes it a potential candidate for subchondral bone restorations.

Quality of reporting and adherence to the ARRIVE guidelines 2.0 for preclinical degradable metal research in animal models of bone defect and fracture:a systematic review

In vivo testing is crucial for the evaluation of orthopedic implant efficacy and safety.However,the translation and reproducibility of preclinical animal experiments are not always satisfactory,and reporting quality is among the essential factors that ensure appropriate delivery of information.In this study,we assessed the reporting quality of in vivo investigations that examined the use of degradable metal materials in fracture or bone defect repair.We employed scientific databases,such as PubMed,EMBASE,Web of Science,Cochrane Library,CNKI,WanFang,VIP and Sinomed to screen for in vivo investigations on fracture or bone defect repair using degradable metal materials,and extracted both epidemiological and main characteristics of eligible studies,and assessed their reporting quality using the ARRIVE guidelines 2.0.Overall,263 publications were selected,including 275 animal experiments.The overall coincidence rate of Essential 10(22 sub-items)and Recommended Set(16 sub-items)were 42.0%and 41.5%,respectively.Based on our analysis,the reporting quality of the published in vivo investigations examining fracture/bone defect repair with degradable metal materials was low,and there was a lack of transparent,accurate and comprehensive reporting on key elements of the experimental design and other elements that are meant to avoid bias.

江阴港口外来船舶压载舱沉积物中甲藻包囊种类及组成

为了探究外来船舶压载舱沉积物中甲藻休眠包囊的种类组成及外来甲藻入侵风险,本文根据包囊及其萌发细胞的形态特征辅以分子生物学信息对江阴港5艘外来船舶压载舱沉积物中的活体甲藻休眠包囊的种类进行鉴定和分析。共鉴定出甲藻休眠包囊29种(不含3种未鉴定种),包括膝沟藻类、钙甲藻类、裸甲藻类、翼甲藻类以及原多甲藻类,活体休眠包囊密度介于0.73–44.3cysts/gDW。其中塔玛亚历山大藻复合种(Alexandriumtamarense species complex)、网状原角藻(Protoceratium reticulatum)、具刺膝沟藻(Gonyaulax spinifera)等有毒有害甲藻的包囊在取样的5艘船舶中均有发现。此外还发现了多种中国近海未报道的甲藻包囊种类,其中一种经过分子手段确定为异常亚历山大藻(Alexandriuminsuetum)包囊,萌发和培养实验表明该种包囊能够在中国近海萌发并增殖,有潜在的入侵风险和暴发赤潮的可能性。