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Deformation mechanism of bimodal microstructure in Ti-6Al-4V alloy:The effects of intercritical annealing temperature and constituent hardness

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Journal of materials Science & Technology 2021年第12期71卷 138-151页

作者： Yan Chong Tilak Bhattacharjee Yanzhong Tian Akinobu Shibata Nobuhiro Tsuji Department of materials Science and Engineering Kyoto UniversityKyotoJapan Department of materials Science and Engineering University of CaliforniaBerkeleyCAUSA elements strategy initiative for structural materials(ESISM) Kyoto UniversityKyotoJapan Key Laboratory for Anisotropy and Texture of materials School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China Research Center for Metallic Wires Northeastern UniversityShenyang 110819China

The so-called bimodal microstructure of Ti-6 Al-4 V alloy,composed of primaryαgrains(α_(p))and transformed β areas(β_(trans)),can be regarded as a"dual-phase"structure to some extent,the mechanical properties of which are closely related to the sizes,volume fractions,distributions as well as nanohardness of the two *** this study,the volume fractions of primaryαgrains(vol.%(α_(p)))were systematically modified in three series of bimodal microstructures with fixed primaryαgrain sizes(0.8μm,2.4μm and 5.0μm),by changing the intercritical annealing temperature(T_(int)).By evaluating the tensile properties at room temperature,it was found that with increasing T_(int)(decreasing vol.%(α_(p))),the yield strength of bimodal microstructures monotonically increased,while the uniform elongation firstly increased with T_(int)until 910°C and then drastically decreased afterwards,thereby dividing the T_(int)into two regions,namely region I(830-910°C)and region II(910-970℃).The detailed deformation behaviors within the two regions were studied and compared,from the perspectives of strain distribution analysis,slip system analysis as well as dislocation *** bimodal microstructures in region I,due to the much lower nano-hardness ofβ_(trans)thanα_(p),there was a clear strain partitioning between the two constituents as well as a strain gradient from theα_(p)/β_(trans)interface to the grain interior ofα_(p).This activated a large number of geometrically necessary dislocations(GNDs)near the interface,mostly with components,which contributed greatly to the extraordinary work-hardening abilities of bimodal microstructures in region *** increasing T_(int),theα_(p)/β_(trans)interface length density gradually increased and so was the density of GNDs with components,which explained the continuous increase of uniform elongation with T_(int)in this *** bimodal microstructures in region II,where the nano-hardness ofβ_(trans)andα_(p)were comparable,neither a clear s

关键词： Ti-6Al-4V Bimodal microstructure Intercritical annealing temperature Strain distribution dislocation

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Grain size altering yielding mechanisms in ultrafine grained high-Mn austenitic steel:Advanced TEM investigations

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Journal of materials Science & Technology 2021年第27期86卷 192-203页

作者： Chang-Yu Hung Yu Bai Nobuhiro Tsuji Mitsuhiro Murayama Department of materials Science and Engineering Virginia TechBlacksburgVA24061USA Department of materials Science and Engineering Kyoto UniversityYoshida-honmachiSakyo-kuKyoto606-8501Japan elements strategy initiative for structural materials Kyoto UniversityYoshida-honmachiSakyo-kuKyoto606-8501Japan Institute for materials Chemistry and Engineering Kyushu UniversityKasugaFukuoka8168580Japan

The underlying mechanism of discontinuous yielding behavior in an ultrafine-grained(UFG)Fe-31 Mn-3 Al-3 Si(wt.%)austenitic TWIP steel was investigated by the use of advanced TEM technique with taking the plastic deformation mechanisms and their correlation with grains size near the macroscopic yield point into *** yield drop mechanisms such as the dislocation locking by the Cottrell atmosphere due to the presence of interstitial impurities cannot explain the origin of this phenomenon in the UFG high-Mn austenitic TWIP ***,we experimentally revealed that the plastic deformation mechanisms in the early stage of deformation,around the macroscopic yield point,show an obvious association with grain *** specifically,the main mechanism shifts from the conventional slip in grain interior to twinning nucleated from grain boundaries with decreasing the grain size down to less than 1μ*** observation indicates that the grain size dependent deformation mechanisms transition is also deeply associated with the discontinuous yielding behavior as it could govern the changes in the grain interior dislocation density of mobile dislocations around the macroscopic yield point.

关键词： Ultrafine grains TWIP steel Yield-drop phenomenon Deformation twin nucleation structural defects Transmission electron microscopy

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Effect of high pressure torsion process on the microhardness,microstructure and tribological property of Ti6Al4V alloy

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Journal of materials Science & Technology 2021年第35期94卷 183-195页

作者： Guanyu Deng Xing Zhao Lihong Su Peitang Wei Liang Zhang Lihua Zhan Yan Chong Hongtao Zhu Nobuhiro Tsuji School of Mechanical MaterialsMechatronic and Biomedical EngineeringUniversity of WollongongNSW 2500Australia Department of materials Science and Engineering Kyoto UniversityKyoto 606-8501Japan State Key Laboratory of High Performance Complex Manufacturing.Central South University Changsha 4W083China Stare Key Laboratory of Mechanical Transmissions Chongqing UniversityChongqing 400030China International Joint Laboratory for Light Alloys(MOE) College of Materials Science and EngineeringChongqing UniversityChongqing 400044China Department of materials Science and Engineering University of California BerkeleyCA 94720United States elements strategy initiative for structural materials(ESISM) Kyoto UniversityKyoto 606-8501Japan

In the present study,a fully lamellar Ti6Al4V alloy was severely deformed by high pressure torsion(HPT)process under a pressure of 7.5 GPa up to 10 *** results revealed that the microhardness of Ti6Al4V was increased remarkably by about~41%and saturated at about 432 Hv after the HPT process.A relatively uniform bulk nanostructured Ti6Al4V alloy with an average grain size of about52.7 nm was obtained eventually,and no obvious formation of metastableωphase was detected by XRD *** the first time,the tribological properties of the HPT processed Ti6Al4V alloy were investigated by a ball-on-disc test at room temperature under a dry *** was found that HPT process had a great influence on the friction and wear behaviors of Ti6Al4V *** increasing the number of HPT revolutions,both friction coefficient and specific wear rate were obviously decreased due to the reduction of abrasion and adhesion *** being deformed by 10 HPT revolutions,the friction coefficient was reduced from about 0.49 to 0.37,and the specific wear rate was reduced by about 48%.The observations in this study indicated that HPT processed Ti6Al4V alloys had good potential in structural applications owing to their greatly improved mechanical and tribological properties.

关键词： Severe plastic deformation High pressure torsion UFG microstructure Mechanical property Friction and wear Ti6Al4V alloy

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Automated estimation of materials parameter from X-ray absorption and electron energy-loss spectra with similarity measures

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npj Computational materials 2019年第1期5卷 815-821页

作者： Yuta Suzuki Hideitsu Hino Masato Kotsugi Kanta Ono Department of materials Science and Technology Tokyo University of ScienceTokyoJapan High Energy Accelerator Research Organization Institute of Materials Structure ScienceTsukubaJapan The Institute of Statistical Mathematics TokyoJapan Center for materials Research by Information Integration(CMI2) Research and Services Division of Materials Data and Integrated System(MaDIS)National Institute for Materials Science(NIMS)Tsukuba 305-0047Japan

materials informatics has significantly accelerated the discovery and analysis of materials in the past *** of the key contributors to accelerated materials discovery is the use of on-the-fly data analysis with high-throughput experiments,which has given rise to the need for accelerated and accurate automated estimation of the properties of *** this regard,spectroscopic data are widely used for materials discovery because these data include essential information about *** important requirement for the realisation of the automated estimation of materials parameters is the selection of a similarity measure,or kernel *** required measure should be robust in terms of peak shifting,peak broadening,and ***,the determination of appropriate similarity measures for spectra and the automated estimation of materials parameters from these spectra currently remain *** examined major similarity measures to evaluate the similarity of both X-ray absorption and electron energy-loss *** similarity measures show good correspondence with the materials parameter,that is,the crystal-field parameter,in all *** Pearson's correlation coefficient was the highest for the robustness against noise and peak *** obtained the regression model for the crystal-field parameter 10 Dq from the similarity of the *** regression model enabled the materials parameter,that is,10 Dq,to be automatically estimated from the *** regard to research progress in similarity measures,this methodology would make it possible to extract the materials parameter from a large-scale dataset of experimental data.

关键词： materials similarity parameter

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First-principles screening of structural properties of intermetallic compounds on martensitic transformation

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npj Computational materials 2017年第1期3卷 23-36页

作者： Joohwi Lee Yuji Ikeda Isao Tanaka Department of materials Science and Engineering Kyoto UniversityKyoto 606-8501Japan elements strategy initiative for Structure materials(ESISM) Kyoto UniversityKyoto 606-8501Japan Center for materials Research by Information Integration National Institute for Materials Science(NIMS)Tsukuba 305-0047 IbarakiJapan Nanostructures Research Laboratory Japan Fine Ceramics CenterNagoya 456-8587 AichiJapan Toyota Central R&D Laboratories Inc.Nagakute 480-1192 AichiJapan

Martensitic transformation with good structural compatibility between parent and martensitic phases are required for shape memory alloys(SMAs)in terms of functional *** this study,first-principles-based materials screening is systematically performed to investigate the intermetallic compounds with the martensitic phases by focusing on energetic and dynamical stabilities as well as structural compatibility with the parent *** B2,D0_(3),and L2_(1) crystal structures are considered as the parent phases,and the 2H and 6M structures are considered as the martensitic *** total,3384 binary and 3243 ternary alloys with stoichiometric composition ratios are *** is found that 187 alloys survive after the *** of the surviving alloys are constituted by the chemical elements already widely used in SMAs,but other various metallic elements are also found in the surviving *** energetic stability of the surviving alloys is further analyzed by comparison with the data in materials Project Database(MPD)to examine the alloys whose martensitic structures may cause further phase separation or transition to the other structures.

关键词： martensitic intermetallic alloys

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Ru complex and N,P-containing polymers confined within mesoporous hollow carbon spheres for hydrogenation of CO_(2)to formate

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Nano Research 2023年第4期16卷 4515-4523页

作者： Guoxiang Yang Yasutaka Kuwahara Kohsuke Mori Catherine Louis Hiromi Yamashita Division of materials and Manufacturing Science Graduate School of EngineeringOsaka University2-1 Yamada-okaSuitaOsaka 565-0871Japan Institute for Open and Transdisciplinary Research initiatives(OTRI) Osaka University2-1 Yamada-okaSuitaOsaka 565-0871Japan Unit of elements strategy initiative for Catalysts&Batteries(ESICB) Kyoto UniversityKatsuraKyoto 615-8520Japan JST PRESTO4-1-8 HonchoKawaguchiSaitama 332-0012Japan Sorbonne Université CNRSLaboratoire de Réactivitéde SurfaceLRSF-75005 ParisFrance

The development of reliable catalysts with both excellent activity and recyclability for carbon dioxide(CO_(2))hydrogenation is ***,a ternary hybrid heterogeneous catalyst,involving mononuclear Ru complex,N,P-containing porous organic polymers(POPs),and mesoporous hollow carbon spheres(Ru^(3+)-POPs@MHCS)is reported for CO_(2)hydrogenation to *** on comprehensive structural analyses,we demonstrated that Ru^(3+)-POPs were successfully immobilized within *** optimized Ru^(3+)-0.5POPs@MHCS catalyst,which was obtained with about 5 wt.%Ru^(3+)and 0.5 mmol POPs polymers confined into 0.3 g MHCS,exhibited high catalytic activity for CO_(2)hydrogenation to formate(turnover number(TON)>1,200 for 24 h under mild reaction conditions(4.0 MPa,120℃))and improved durability,compared to Ru^(3+)catalysts without POPs polymers(Ru^(3+)-MHCS)and unencapsulated MHCS(Ru^(3+)-0.5POPs)*** improved catalytic performance is attributed to the high surface area and large pore volume of MHCS which favors dispersion and stabilization of Ru^(3+)-***,the MHCS and POPs showed high CO_(2)adsorption ***^(3+)-POPs encapsulated into MHCS reduces the activation energy barrier for CO_(2)hydrogenation to formate.

关键词： heterogeneous catalysis porous organic polymers(POPs) mesoporous hollow carbon spheres CO_(2)hydrogenation formate synthesis

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