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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

Strain-dependence of deformation microstructures in ultra-low-C IF steel deformed to high strains by torsion at elevated temperatures

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Nano Materials Science 2020年第1期2卷 83-95页

作者： Reza Gholizadeh Daisuke Terada Akinobu Shibata nobuhiro tsuji Department of Materials Science and Engineering Kyoto UniversityYoshida HonmachiSakyo-kuKyoto606-8501Japan ESISM(Elements Strategy Initiative for Structural Materials) Kyoto UniversityYoshida HonmachiSakyo-kuKyoto606-8501Japan Department of Advanced Materials Science and Engineering Chiba Institute of TechnologyTsudanumaNarashino275-0016Japan

Single-phase bcc-ferrite in an interstitial free(IF)steel was deformed to different strains in a wide range from low to high strains(ε=1–7)by torsion under different Zener-Hollomon(Z)*** specimens were rapidly quenched after the torsion to preserve microstructures formed under different deformation *** results showed that during high-Z(low-temperature)deformation,grains were subdivided by geometrically necessary boundaries(GNBs)via the grain subdivision *** to high strains(ε>5)led to the ultrafine lamellar structures(with grain sizes1μm)were realized with decreasing *** significance of the grain subdivision and the thermally activated phenomena on the formation of various microstructures under different deformation conditions is discussed.

关键词： Severe plastic deformation Grain subdivision Ultrafine grains Zener-Hollomon parameter Boundary migration Electron backscattering diffraction(EBSD)

In-situ observation of twinning and detwinning in AZ31 alloy

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Journal of Magnesium and Alloys 2022年第12期10卷 3418-3432页

作者： Wu Gong Ruixiao Zheng Stefanus Harjo Takuro Kawasaki Kazuya Aizawa nobuhiro tsuji J-PARC Center Japan Atomic Energy Agency2-4 Shirane ShirakataTokaiNakaIbaraki 319-1195Japan Center for Elements Strategy Initiative for Structural Materials Kyoto UniversityYoshidahonmachiSakyo-kuKyoto 606-8501Japan Department of Materials Science and Engineering Kyoto UniversityYoshida-honmachiSakyo-kuKyoto 606-8501Japan School of Materials Science and Engineering Beihang UniversityBeijing 100191China

Twinning and detwinning behavior of a commercial AZ31 magnesium alloy during cyclic compression–tension deformation with a total strain amplitude of 4%(±2%) was evaluated using the complementary techniques of in-situ neutron diffraction, identical area electron backscatter diffraction, and transmission electron microscopy. In-situ neutron diffraction demonstrates that the compressive deformation was dominated by twin nucleation, twin growth, and basal slip, while detwinning dominated the unloading of compressive stresses and subsequent tension stage. With increasing number of cycles from one to eight: the volume fraction of twins at-2% strain gradually increased from 26.3% to 43.5%;the residual twins were present after 2% tension stage and their volume fraction increased from zero to 3.7% as well as a significant increase in their number;and the twinning spread from coarse grains to fine grains involving more grains for twinning. The increase in volume fraction and number of residual twins led to a transition from twin nucleation to twin growth, resulting in a decrease in yield strength of compression deformation with increasing cycles. A large number of-component dislocations observed in twins and the detwinned regions were attributed to the dislocation transmutation during the twinning and detwinning. The accumulation of barriers including twin boundaries and various types of dislocations enhanced the interactions of migrating twin boundary with these barriers during twinning and detwinning, which is considered to be the origin for increasing the work hardening rate in cyclic deformation of the AZ31 alloy.

关键词： Magnesium Neutron diffraction Twinning Detwinning Dislocation transmutation

Phase decomposition behavior and its impact on mechanical properties in bulk nanostructured Cu-20 at.%Fe supersaturated solid solution

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Journal of Materials Science & Technology 2024年第18期185卷 207-220页

作者： Maowen Liu Ruixiao Zheng Hongxing Li Qiuming Wei Chaoli Ma nobuhiro tsuji Tianmushan Laboratory Yuhang DistrictHangzhou 311115China Research Institute for Frontier Science Beihang UniversityBeijing 100191China School of Materials Science and Engineering Beihang UniversityBeijing 100191China Department of Materials Science and Engineering Kyoto UniversityYoshida HonmachiSakyo-kuKyoto 606-8501Japan Department of Mechanical Engineering University of North Carolina at Charlotte9201 University City BoulevardCharlotteNC 28223-0001USA Elements Strategy Initiative for Structural Materials(ESISM) Kyoto UniversityYoshida HonmachiSakyo-kuKyoto 606-8501Japan

Extended solid solution of immiscible systems,achieved by extreme processing approaches,can be trans-formed into nanostructured composites via phase decomposition,which are drawing great research atten-tion for their excellent thermal stability and high *** we fabricated the supersaturated solid solution of Cu-20 at.%Fe,a typical immiscible alloy,in bulk state by high pressure torsion,which pro-vides a great freedom over powders for studying the microstructure evolution and mechanical properties in the process of the phase decomposition in immiscible *** found that in the Cu-Fe solid solu-tion,spinodal decomposition of the Fe phases took place at the initial stage of annealing through volume *** process gives rise to:(1)metastableγ-Fe particles in the Cu grains with coherent Fe/Cu interface,and(2)the more stableα-Fe phase at the grain *** process was accompanied by moving boundary reaction which first proceeded in the pattern of spinodal decomposition and then changed into classical nucleation-growth mode with the depletion of Fe atoms in *** resultant Cu-Fe nanocomposites were jointly strengthened by the ultrafine Cu andα-Fe grains according to the rule of mixture,including grain boundary strengthening and the hardening of nanoscaleγ-Fe precipitates in the Cu *** effects of different strengthening mechanisms were scrutinized and their contributions to mechanical properties were quantitatively *** work sheds light onto the opportunity of designing and fabricating nanostructured composites via phase decomposition in immiscible systems.

关键词： immiscible alloy high pressure torsion annealing phase decomposition mechanical property

Understanding the Mechanism for the In-Plane Yielding Anisotropy of a Hot-Rolled Zirconium Plate

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Acta Metallurgica Sinica(English Letters) 2024年第6期37卷 1066-1076页

作者： Guodong Song Conghui Zhang Yunchang Xin nobuhiro tsuji Xinde Huang Bo Guan Xiaomei He School of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an710055China Key Laboratory for Light-Weight Materials Nanjing Tech UniversityNanjing210009China Department of Materials Science and Engineering Kyoto UniversityYoshida-honmachiSakyo-kuKyoto606-8501Japan Institute of Applied Physics Jiangxi Academy of ScienceNanchang330029China

Previously,the in-plane mechanical anisotropy of Zr hot-rolled plates is ascribed mainly to the different activities of the deformation modes activated when loading along different *** this work,a quantitative study on the deformation behavior of a pure Zr hot-rolled plate under tension along the rolling direction(RD)and transverse direction(TD)reveals that both the activities of deformation modes and the anisotropy of grain boundary strengthening account for a tensile yield strength anisotropy along the TD and *** plasticity simulations using viso-plastic self-consistent model show that prismatic slip is the predominant deformation mode for tension along the RD(RD-tension),while prismatic slip and basal slip are co-dominant deformation modes under tension along the TD(TD-tension).A low fraction of■under TD-tension,while hardly activated under *** activation of basal slip with a much higher critical resolve shear stress under TD-tension contributes to a higher yield strength along the TD than along the *** grain boundary strengthening effect under tension along the TD and RD were compared by calculating the activation stress difference(△Stress)and the geometric compatibility factor(m′)between neighboring *** results indicate a higher grain boundary strengthening for TD-tension than that for RD-tension,which will lead to a higher yield strength along the *** is,the anisotropy of grain boundary strengthening between TD-tension and RD-tension also plays an important role in the in-plane anisotropy along the RD and ***,the reasons for why there is a grain-boundary-strengthening anisotropy along the TD and RD were discussed.

关键词： Zirconium Strengthening Grain boundary Orientation

In situ neutron diffraction revealing the achievement of excellent combination of strength and ductility in metastable austenitic steel by grain refinement

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Journal of Materials Science & Technology 2024年第9期176卷 69-82页

作者： Wenqi Mao Wu Gong Stefanus Harjo Satoshi Morooka Si Gao Takuro Kawasaki nobuhiro tsuji J-PARC Center Japan Atomic Energy AgencyIbarakiJapan Department of Materials Science and Engineering Kyoto UniversitySakyo-kuKyotoJapan

The yield stress of Fe-24Ni-0.3C(wt%)metastable austenitic steel increased 3.5 times(158→551 MPa)when the average grain size decreased from 35μm(coarse-grained[CG])to 0.5μm(ultrafine-grained[UFG]),whereas the tensile elongation was kept large(0.87→0.82).In situ neutron diffraction measurements of the CG and UFG Fe-24Ni-0.3C steels were performed during tensile deformation at room temperature to quantitatively elucidate the influence of grain size on the mechanical properties and deformation *** initial stages of plastic deformation in the CG and UFG specimens were dominated by dislocation slip,with deformation-induced martensitic transformation(DIMT)also occurring in the later stage of *** show that grain refinement increases the initiation stress of DIMT largely and suppresses the rate of DIMT concerning the strain,which is attributed to the following effects.(i)Grain refinement increased the stabilization of austenite and considerably delayed the initiation of DIMT in the//LD(LD:loading direction)austenite grains,which were the most stable grains for *** a result,most of the//LD austenite grains in the UFG specimen failed to transform into martensite.(ii)Grain refinement also suppressed the autocatalytic effect of the martensitic ***,the DIMT with the low transformation rate in the UFG specimen was more efficient in increasing the flow stress and more appropriate to maintain uniform deformation than that in the CG specimen during *** above phenomena mutually contributed to the excellent combination of strength and ductility of the UFG metastable austenitic steel.

关键词： Ultrafine grain Deformation-induced martensitic transformation Metastable austenitic steel In situ neutron diffraction

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

Superior strength-ductility combination resulted from hetero-zone boundary affected region in Cu-Fe layered material

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Journal of Materials Science & Technology 2024年第14期181卷 209-219页

作者： Hao Ran Peihao Ye Fengjiao Guo Mingsai Wang Wuli Su Xue Chen Si Gao nobuhiro tsuji Yuntian Zhu Xiaochong Lu Chongxiang Huang School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065China Department of Materials Science and Engineering Kyoto UniversityYoshida HonmachiSakyo-kuKyoto 606-8501Japan Elements Strategy Initiative for Structural Materials(ESISM) Kyoto UniversityYoshida HonmachiSakyo-kuKyoto 606-8501Japan Department of Materials Science and Engineering City University of Hong KongHong KongChina Failure Mechanics and Engineering Disaster Prevention and Mitigation Key Laboratory of Sichuan Province Sichuan UniversityChengdu 610065China

The hetero-zone boundary affected region(HBAR)significantly influences the mechanical behaviors of layered materials,where the deformation mechanisms differ from those in the bulk *** this study,three kinds of heterogeneous Cu-Fe layered materials with different interface spacing but identical total thicknesses were *** effects of HBAR and strain partitioning on the tensile behavior of the lay-ered materials were *** results showed that layered materials had enhanced yield strength and uniform elongation with decreasing interface *** tensile deformation,geometrically nec-essary dislocations(GNDs)were generated at hetero-zone boundaries and piled up near them,resulting in hetero-deformation induced(HDI)strengthening and HDI work *** profilometry mea-surements showed that the Cu and Fe layers exhibited obvious strain partitioning and mutual *** decreasing interface spacing,strain partitioning is enhanced by interlayer constraint,which pre-vented strain localization at interfaces and thus improved the synergetic deformation of layers.A higher fraction of HBAR can improve the mechanical performance of heterogeneous layered *** study deepens our understanding of the relationship between HBAR and strength-ductility synergy and provides some insight into the design of layered materials.

关键词： Hetero-zone boundary affected region Layered material Strain partitioning Geometrically necessary dislocation Hetero-deformation

Platelets in liver disease, cancer and regeneration

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World Journal of Gastroenterology 2017年第18期23卷 3228-3239页

作者： Tomohiro Kurokawa nobuhiro Ohkohchi Department of Surgery Division of Gastroenterological and Hepatobiliary Surgery and Organ Transplantation Faculty of Medicine University of Tsukuba

Although viral hepatitis treatments have evolved over the years, the resultant liver cirrhosis still does not completely heal. Platelets contain proteins required for hemostasis, as well as many growth factors required for organ development, tissue regeneration and repair. Thrombocytopenia, which is frequently observed in patients with chronic liver disease(CLD) and cirrhosis, can manifest from decreased thrombopoietin production and accelerated platelet destruction caused by hypersplenism; however, the relationship between thrombocytopenia and hepatic pathogenesis, as well as the role of platelets in CLD, is poorly understood. In this paper, experimental evidence of platelets improving liver fibrosis and accelerating liver regeneration is summarized and addressed based on studies conducted in our laboratory and current progress reports from other investigators. In addition, we describe our current perspective based on the results of these studies. Platelets improve liver fibrosis by inactivating hepatic stellate cells, which decreases collagen production. The regenerative effect of platelets in the liver involves a direct effect on hepatocytes, a cooperative effect with liver sinusoidal endothelial cells, and a collaborative effect with Kupffer cells. Based on these observations, we ascertained the direct effect of platelet transfusion on improving several indicators of liver function in patients with CLD and liver cirrhosis. However, unlike the results of our previous clinical study, the smaller incremental changes in liver function in patients with CLD who received eltrombopag for 6 mo were due to patient selection from a heterogeneous population. We highlight the current knowledge concerning the role of platelets in CLD and cancer and anticipate a novel application of platelet-based clinical therapies to treat liver disease.

关键词： Platelet Liver cirrhosis Liver regeneration Cancer Thrombopoietin Thrombopoietin agonist Eltrombopag