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Microstructural evolution of aluminum alloy d.r.ng friction stir welding und.r.different tool rotation rates and cooling conditions

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Journal of Materials Science & Technology 2019年第6期35卷 972-981页

作者： X.H. Zeng P. Xue L.H. Wu d.r. ni B.L. Xiao K.S. Wang Z.Y. Ma Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100049 China School of Metallurgical Engineering Xi'an University of Architecture and Technology Xi'an 710055 China

The microstructural evolution d.r.ng friction stir welding(FSW) has long been studied only using one single welding parameter. Conclusions were usually made based on the final microstructure observation and hence were one-sided. In this study, we used the "take-action" technique to freeze the microstructure of an Al-Mg-Si alloy d.r.ng FSW, and then systematically investigated the microstructures along the material flow path und.r.different tool rotation rates and cooling conditions. A universal characteristic of the microstructural evolution including four stages was identified, i.e. dynamic recovery(drV), dislocation multiplication, new grain formation and grain growth. However, the dynamic recrystallization(drX)mechanisms in FSW depended on the welding condition. For the air cooling condition, the drX mechanisms were related to continuous drX associated with subgrain rotation and geometric drX at high and low rotation rates, respectively. Und.r.the water cooling condition, we found a new drX mechanism associated with the progressive lattice rotation resulting from the pinning of the second-phase *** on the analyses of the influencing factors of grain refinement, it was clearly demonstrated that the delay of drV and drX was the efficient method to refine the grains d.r.ng FSW. Besides, ultra-high strain rate and a short d.r.tion at high temperatures were the key factors to produce an ultrafine-grained material.

关键词： Aluminum alloys Grain refinement dynamic recrystallization Severe plastic deformation Friction stir welding

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Exosomes:the next-generation therapeutic platform for ischemic stroke

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Neural regeneration research 2025年第5期20卷 1221-1235页

作者： Wenjing Yin Hongyin Ma Yang Qu Jiaxin ren Yingying Sun Zhen-ni Guo Yi Yang Stroke Center Department of NeurologyFirst Hospital of Jilin UniversityChangchunJilin ProvinceChina Neuroscience research Center Department of NeurologyFirst Hospital of Jilin UniversityChangchunJilin ProvinceChina

Current therapeutic strategies for ischemic stroke fall short of the desired objective of neurological functional ***,there is an urgent need to develop new methods for the treatment of this *** are natural cell-d.r.ved vesicles that mediate signal transduction between cells und.r.physiological and pathological *** have low immunogenicity,good stability,high delivery efficiency,and the ability to cross the blood–brain *** physiological properties of exosomes have the potential to lead to new breakthroughs in the treatment of ischemic *** rapid development of nanotechnology has advanced the application of engineered exosomes,which can effectively improve targeting ability,enhance therapeutic efficacy,and minimize the dosages *** in technology have also driven clinical translational research on *** this review,we describe the therapeutic effects of exosomes and their positive roles in current treatment strategies for ischemic stroke,including their antiinflammation,anti-apoptosis,autophagy-regulation,angiogenesis,neurogenesis,and glial scar formation reduction ***,it is worth noting that,despite their significant therapeutic potential,there remains a dearth of stand.r.ized characterization methods and efficient isolation techniques capable of producing highly purified *** optimization strategies should prioritize the exploration of suitable isolation techniques and the establishment of unified workflows to effectively harness exosomes for diagnostic or therapeutic applications in ischemic ***,our review aims to summarize our und.r.tanding of exosome-based treatment prospects in ischemic stroke and foster innovative ideas for the development of exosome-based therapies.

关键词： blood–brain barrier electroacupuncture engineering exercise exosomes ischemic stroke mesenchymal stem cells microglia neuroprotection stents

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Shape Memory Alloy-reinforced Metal-Matrix Composites:A review

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Acta Metallurgica Sinica(English Letters) 2014年第5期27卷 739-761页

作者： d.r.ni Z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Metal-matrix composites reinforced with shape memory alloys （SMA, including long fiber, short fiber, and particle） are ＂intelligent materials＂ with many special physical and mechanical properties, such as high damping property, high tensile strength, and fatigue resistance. In this review article, the fabrication method, microstructure, interface reaction, modeling, and physical and mechanical properties of the composites are ad.r.ssed. Particular emphasis has been given to （a） fabrication and microstructure of aluminum matrix composites reinforced with SMAs, and （b） shape memory effect on the physical and mechanical properties of the composites. While the bulk of the information is related to aluminum matrix composites, important results are now available for other metal-matrix composites.

关键词： Metal-matrix composites Shape memory alloy Fabrication method Microstructure Interface reaction Mechanical properties

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Friction Stir Welding of discontinuously reinforced Aluminum Matrix Composites:A review

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Acta Metallurgica Sinica(English Letters) 2014年第5期27卷 816-824页

作者： d.Wang B.L.Xiao d.r.ni Z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Friction stir welding （FSW） is consid.r.d a promising welding technique for joining the aluminum matrix composites （AMCs） to avoid the drawbacks of the fusion welding. High joint efficiencies of 60%-100% could be obtained in the FSW joints of AMCs. However, due to the existence of hard.r.inforcing particles in the AMCs, the wearing of welding tool d.r.ng FSW is an unavoidable problem. Moreover, the low ductility of the AMCs limits the welding process window. As the hard materials such as Ferro-Titanit alloy, cermet, and WC/Co were applied to produce the welding tools, the wearing of the tools was significantly reduced and the sound joints could be achieved at high welding speed for the AMCs with low reinforcement volume fraction. In this article, current state of und.r.tanding and development of welding tool wearing and FSW parameters of AMCs are viewed. Furthermore, the factors affecting the microstructure and mechanical properties of the joints are evaluated in detail.

关键词： Metal matrix composite Friction stir welding Particle, microstructure Wear

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Shape Memory Effect,Thermal Expansion and damping Property of Friction Stir Processed niTip/Al Composite

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Journal of Materials Science & Technology 2016年第2期32卷 162-166页

作者： d.r.ni J.J.Wang Z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang I10016China College of Material Science and Engineering ShenyangAerospace University Shenyang 110136China

niTi particles reinforced aluminum （niTip/Al） composite was prepared via friction stir processing, elimi- nating interfacial reaction and/or elemental diffusion. The niTip in the composite maintained the intrinsic characteristic of a reversible thermoelastic phase transformation even after heat-treatment. The shape memory characteristic of the niTip decreased the coefficient of thermal expansion of the Al matrix, and an apparent two-way shape memory effect was observed in the composite. The composite owned a good combination of adjustable damping and thermal physical properties.

关键词： Metal matrix composite Shape memory alloy Interface differential scanning calorimetry (dSC)damping

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Pinless Friction Stir Spot Welding of Mg-3Al-1Zn Alloy with Zn Interlayer

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Journal of Materials Science & Technology 2016年第1期32卷 76-88页

作者： r.Z.Xu d.r.ni Q.Yang C.Z.Liu Z.Y.Ma College of Materials Science and Engineering Shenyang Aerospace University Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

With the addition of a thin Zn interlayer, 2.4 mm thick Mg-3AI-1Zn alloy sheets were friction stir spot welded （FSSW） using a pinless tool with fiat, convex and concave should.r.shapes. The results showed that an alloying reaction took place between the Mg substrate and Zn interlayer d.r.ng FSSW, forming a discontinuous intermetallics layer composed of dispersive （α-Mg ＋ MgZn） eutectic structure und.r. neath the should.r.and a Mg-Zn intermetallics bonding zone at the outside of the joints. This alloying reaction increased the bonded area and eliminated the hook defects, thereby producing sound FSSWjoints with a shallow keyhole without hook defects. The increase of plunge depth was beneficial to the Mg-Zn diffusion, thereby increasing the tensile-shear load of the joints. However, excessive plunge depths re- sulted in a decrease of the effective sheet thickness, reducing the strength of the joints. At a small plunge depth, the convex and concave should.r. were more beneficial to the interface reaction than the fiat shoul- d.r. The maximum joint load of 6.6 kN was achieved by using the concave should.r.at a plunge depth of 1.0 mm. A post-welding heat treatment promoted the dissolution of the discontinuous reaction layer in the joints; however, it led to the occurrence of void defects, influencing the bonding strength.

关键词： Friction stir spot welding Magnesium alloys Zn interlayer Hook defects

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Green, sustainable and massive synthesis of sodium vanadate nanowires toward industrialization

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Progress in Natural Science:Materials International 2023年第6期33卷 918-923页

作者： Wei ni ANSTEEL research Institute of Vanadium & Titanium (Iron & Steel) State Key Laboratory of Vanadium and Titanium resources Comprehensive Utilization

One-dimensional(1d) layered materials combine the advantages of layered materials and 1d nanomaterials,which has attracted intense interest not only in the academic research but also in the industrial *** sodium vanadate nanowires have received incremental attention due to the high capacity and enhanced electrical conductivity for promising advanced energy storage and conversion. However, the mass production of these 1d layered vanadium vanadates(1d NVO) are still of great challenge and the further scalable application in energy storage and conversion systems are hampered. Herein, we developed a facile, non-hydrothermal, green synthesis strategy for scalable, mass production of layered vanadium vanadate nanowires and their assemblies such as membranes, blocks, grains, powd.r. toward industrial scale. It will pave a way for the industrial production of 1d inorganic materials and give a new insight into the fabrication of nanostructured materials beyond commercialized 1d/2d nanomaterials including carbon nanotubes(CNT) and layered double hydroxides(LdH).

关键词： Sodium vanadate nanowires Mass production Vanadium-based Barnesite 1d nanomaterials Self-assembly Nanowire membrane Green synthesis

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Influencing mechanism of pre-existing nanoscale Al5Fe2 phase on Mg-Fe interface in friction stir spot welded Al-free ZK60-Q235 joint

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Journal of Materials Science & Technology 2020年第7期42卷 220-228页

作者： r.Z.Xu Q.Yang d.r.ni B.L.Xiao C.Z.Liu Z.Y.Ma Institute of Metal research Chinese Academy of SciencesShenyang110016China College of Material Science and Engineering Shenyang Aerospace UniversityShenyang110136China department of Materials Science and Engineering University of Illinois at Urbana-Champaign1304 W Green StUrbanaIL61801United States Fredrick Seitz Materials research Laboratory University of Illinois at Urbana-Champaign104 S Goodwin AveUrbanaIL61801United States

Al-free ZK60 magnesium (Mg) alloy sheet was selected as substrate material of Mg-steel pinless friction stir spot welding (FSSW), avoiding the effect of the Al element in the substrate on the alloying reaction of Mg-iron (Fe) interface. The sound FSSW joint of ZK60 Mg alloy and Q235 steel with a hot-dipped aluminum (Al)-containing zinc (Zn) coating was successfully realized. The detailed microstructural examinations proved that Al5Fe2 phase at the Mg-Fe interface came from the pre-existing Al5Fe2 phase in the coating and acted as the transition layer for promoting the metallurgical bonding of Mg and Fe. The interfaces with well-matched lattice sites among Fe, Al5Fe2 and Mg were formed d.r.ng FSSW. A low energy interface with good match of lattice sites ((002)Al5Fe2//(110)Fe, [110]Al5Fe2//[113]Fe) between Al5Fe2 and Fe was identified. For the interface between Al5Fe2 and Mg, an orientation relationship of (622)Al5Fe2//(3112)Mgand[158]Al5Fe2//[2423]Mg was observed. The tensile-shear load of the ZK60-steel joint could.r.ach 4.6 kN. Moreover, the joint fracture occurred at the interface between the Al5Fe2 layer and the Mg alloy substrate, suggesting the brittle fracture characteristic.

关键词： dissimilar welding Friction stir spot welding Magnesium alloys Steels Zinc coating

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Achieving superior mechanical properties of selective laser melted AlSi10Mg via d.r.ct aging treatment

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Journal of Materials Science & Technology 2022年第13期108卷 226-235页

作者： H.Zhang Y.Wang J.J.Wang d.r.ni d.Wang B.L.Xiao Z.Y.Ma Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China College of Materials Science and Engineering Shenyang Aerospace University37 Daoyi South AvenueShenyang 110136China

For additive manufactured aluminum alloys,the inferior mechanical properties along the building d.r.ction have been a serious *** this study,an optimized heat treatment was developed as a simple and effective *** effects of d.r.ct aging on microstructure and mechanical properties along the building d.r.ction of AlSi10Mg samples produced via selective laser melting(SLM)were *** results showed that,compared with the conventional heat treatment at elevated temperatures,d.r.ct aging at temperatures of 130-190℃ could.r.tain the fine grain microstructure of SLM samples and promote further precipitation of Si phase,however,the growth of pores occurred d.r.ng d.r.ct *** increasing aging temperature,while finer cell structures were obtained,more and larger pores were developed.r.sulting in decreased density of the *** types of pore formation mechanisms were *** the balance between the refinement of cell structure and the growth of pores,aging at 130℃ was determined as the optimized heat treatment for SLM AlSi10Mg *** tensile strength along the building d.r.ction of the 130℃ aged sample was increased from 403 MPa to 451 MPa,with relatively high elongation of 6.5%.

关键词： Additive manufacturing Selective laser melting AlSi10Mg alloy,Heat treatment

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Effect of post weld artificial aging and water cooling on microstructure and mechanical properties of friction stir welded 2198-T8 Al-Li joints

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Journal of Materials Science & Technology 2022年第28期123卷 92-112页

作者： Y.Tao Z.Zhang P.Xue d.r.ni B.L.Xiao Z.Y.Ma Institute of Metal research Chinese Academy of SciencesShenyang 110016China

Friction stir welding(FSW)und.r.both air cooling and water cooling conditions with welding parameters of 800-1200 rpm rotation rates and 50-200 mm/min welding speeds was carried out on 2198-T8 Al-Li alloys,and post weld artificial aging was performed on the air cooled *** welding defects other than lazy S were observed in the nugget zone(NZ)for all *** air cooling condition,the lowest hardness zone(LHZ)occurred in the heat affected zone(HAZ).FSW resulted in gradual dissolution of original T_(1),θ′andδ′/β′from the base material(BM)to the thermo-mechanically affected zone(TMAZ),and complete dissolution of all precipitates in the NZ withδ′/β′and Guinier-Preston zones precipitating d.r.ng *** air cooled joints exhibited no noticeable changes in intrinsic tensile strength with a joint strength reaching 81.3%of the BM,but varied elongation with welding parameters,which was closely related to failure in the NZ and fracture along lazy *** weld artificial aging led to the largest hardness recovery in the TMAZ but smaller hardness recovery in the initial LHZ and the *** aging kinetics across the joint was determined by volume fraction of both original precipitate dissolu-tion d.r.ng welding and coarse particles formed d.r.ng aging,and by dislocation density inherited from *** weld artificial aging greatly enhanced the joint strength with the ultimate tensile strength reaching 87.3%of the *** compared to air cooling condition,water cooling hardly affected the NZ hardness and did not improve the joint strength,and the reason was discussed in light of precipitates,hardness changes and fracture behavior.

关键词： Friction stir welding Aluminum-lithium alloys Microstructure Mechanical properties

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