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Lamellar aspect-ratio and thickness-dependent strength-ductility synergy in pure nickel during in-situ micro-tensile loading

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Journal of Materials Science & Technology 2023年第26期157卷 89-97页

作者： Zi-Meng Wang yun-fei jia Kai-Shang Li Yong Zhang jia-Dong Cai Xian-Cheng Zhang Hiroyuki Hirakata Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China Department of Mechanical Engineering and Science Kyoto UniversityKyoto daigaku-katsuraNishikyo-kuKyoto 615-8540Japan

In order to overcome the trade-offbetween strength and ductility in traditional metallic materials,the gradient lamellar structure was fabricated through an ultrasound-aided deep rolling technique in pure Ni with high stacking fault energy after heat treatment.The gradient lamellar Ni was successively di-vided into three regions.In-situ micro-tensile tests were performed in different regions to reveal the corresponding microscopic mechanical behaviors.Microscopic characterization techniques were adopted to explore the effects of microstructural parameters and defects on mechanical properties.This work demonstrates that the micro-tensile sample with small lamellar thickness and large aspect ratio possesses excellent strength and ductility when the loading direction is parallel to the long side of lamellar grain boundaries.The finding is helpful to the design of metallic material microstructure with superior com-prehensive properties.On one hand,the reason for high strength is that the strength increases with the decrease of lamellar thickness according to the Hall-Petch effect.Besides,initial dislocation density also participates in the strengthening mechanism.On the other hand,the deformation mechanisms include dislocation slip,grain rotation,and the effects of grain boundaries on dislocations,jointly contributing to good ductility.

关键词： Lamella In-situ micro-tensile test Strength-ductility synergy Aspect ratio Grain rotation

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Inverse Fluid-solid Interaction Scattering Problem Using Phased and Phaseless Far Field Data

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Acta Mathematicae Applicatae Sinica 2020年第1期36卷 74-94页

作者： Xia JI yun-fei jia Xiao-dong LIU LSEC Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China Academy of Mathematics and Systems Science Chinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100190China

We consider the inverse fluid-solid interaction scattering of incident plane wave from the knowledge of the phased and phaseless far field patterns.For the phased data,one direct sampling method for location and shape reconstruction is proposed.Only inner product is involved in the computation,which makes it very simple and fast to be implemented.With the help of the factorization of the far field operator,we give a lower bound of the proposed indicator functional for the sampling points inside the elastic body.While for the sampling points outside,we show that the indicator functional decays like the Bessel function as the points go away from the boundaries of the elastic body.We also show that the proposed indicator functional continuously dependents on the far field patterns,which further implies that the novel sampling method is extremely stable with respect to data error.For the phaseless data,to overcome the translation invariance,we consider the scattering of point sources simultaneously.By adding a reference sound-soft obstacle into the scattering system,we show some uniqueness results with phaseless far field data.Numerically,we introduce a phase retrieval algorithm to retrieve the phased data without the additional obstacle.The novel phase retrieval algorithm can also be combined with the sampling method for phased data.We also design two novel direct sampling methods using the phaseless data directly.Finally,some numerical simulations in two dimensions are conducted with noisy data,and the results further verify the effectiveness and robustness of the proposed numerical methods.

关键词： fluid-solid interaction scattering direct sampling method far field pattern phaseless phase retrieval

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Gradient Elastic–Plastic Properties of Expanded Austenite Layer in 316L Stainless Steel

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Acta Metallurgica Sinica(English Letters) 2018年第8期31卷 831-841页

作者： Yong jiang Yang Li yun-fei jia Xian-Cheng Zhang jian-Ming Gong School of Mechanical and Power Engineering Nanjing University of TechnologyNanjing 211816China Key Laboratory of Design and Manufacture of Extreme Pressure Equipment Nanjing 211816Jiangsu ProvinceChina Key Laboratory of Pressure System and Safety MOESchool of Mechanical and Power EngineeringEast China Universityof Science and TechnologyShanghai 200237China

The gradient mechanical properties, variation of stress with strain and surface cracking behavior of expanded austenite developed on 316L austenitic stainless steel were investigated by nanoindentation tests, X-ray residual stress analysis and scanning electron microscope observation in four-point bending tests. The results show that the plastic properties of the carburizing layer including true initial yield strengths and strain hardening exponents increase significantly from substrate to surface, while the true elastic modulus just improves slightly. Due to the onset of plastic flow, the residual stresses are almost equivalent to the true initial yield strengths from surface to the depth of ～10 lm. The results of four-point bending tests show that surface stress increases linearly with the increase in strain until the strain reaches～1.0%, after that the plastic yield happens. The expanded austenite surface layer is brittle, and the cracks will be created at the strain of ～1.4%.The cracking stress is about～2.4 GPa.

关键词： Low-temperature gaseous carburization Expanded austenite Nanoindentation Gradient elastic-plastic properties Four-point bending

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Microstructural Evolution, Mechanical Properties and Thermal Stability of Gradient Structured Pure Nickel

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Acta Metallurgica Sinica(English Letters) 2019年第8期32卷 951-960页

作者： Xiao Li Bo Guan yun-fei jia yun-Chang Xin Cheng-Cheng Zhang Xian-Cheng Zhang Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China School of Materials Science and Engineering Chongqing UniversityChongqing 400044China AECC Commercial Aircraft Engine Co.LTD Shanghai Engineering Research Center for Commercial Aircraft EngineShanghai 20110&China

The microstructural evolution of pure nickel treated by deep rolling(DR)technique with different indent depths was investigated by means of optical microscopy and transmission electron microscopy.The surface roughness,hardness and residual stress distribution along the depth from surface were measured.Moreover,the DR-treated sample was annealed at temperatures from 300 to 700℃for 2 h.The results reveal that dislocation movements are the fundamental mechanisms of gradient grain refinement during the DR process.With increasing indent depth of the DR,the gradient microhardness on the cross section of sample significantly increases,the maximum compressive residual stress decreases,and the affecting region of residual stress increases.The results of thermal stability depict that the microstructure can be stable as temperature up to 300℃,and the abnormal grain growth and annealing twins are observed at 600℃.

关键词： Deep rolling Pure nickel-Microstructural evolution Mechanical properties Thermal stability

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Influence of grain size on the small fatigue crack initiation and propagation behaviors of a nickel-based superalloy at 650℃

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Journal of Materials Science & Technology 2019年第8期35卷 1607-1617页

作者： Xumin Zhu Congyang Gong yun-fei jia Runzi Wang Chengcheng Zhang Yao Fu Shan-Tung Tu Xian-Cheng Zhang Key Laboratory of Pressure Systems and Safety Ministry of Education School of Mechanical and Power Engineering East China University of Science and Technology Shanghai 200237 China AECC Commercial Aircraft Engine Co. LTD Shanghai Engineering Research Center for Commercial Aircraft Engine Shanghai 201108 China

GH4169 at 650℃ in atmosphere was investigated by using single edge notch tensile specimens. The number of main cracks and crack initiation mechanisms at the notch surface strongly depended on the grain size. The crack initiation life accounted for more percentages of the total fatigue life for the alloy with smaller grain size. The fatigue life generally increased with increasing crack initiation life. The small crack transited to long crack when its length reached 10 times the grain size.

关键词： Fatigue crack initiation Small crack Crack growth rate Grain size effect High temperature

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Grain-refining and strengthening mechanisms of bulk ultrafine grained CP-Ti processed by L-ECAP and MDF

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Journal of Materials Science & Technology 2021年第24期83卷 196-207页

作者： Peng-Cheng Zhao Guang-jian Yuan Run-Zi Wang Bo Guan yun-fei jia Xian-Cheng Zhang Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai200237China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing400044China

The microstructural evolution and mechanical properties of ultrafine-grained(UFG)CP-Ti after an innovative large-volume equal channel angular pressing(L-ECAP)and multi-directional forging(MDF)were systematically examined using monotonic tensile tests combined with transmission electron microscope(TEM)and electron backscatter diffraction(EBSD)techniques.Substantially refined and homogeneous microstructures were achieved after L-ECAP(8-pass and 12-pass)and MDF(2-cycle and 3-cycle),respectively,where the grain size distribution conformed to lognormal distribution.The grain refinement of450℃L-ECAP is dominated by dynamic recrystallization(DRX)and dynamic recovery(DRV),while that of MDF is dominated by DRX.The iron impurities promote recrystallization by pinning-induced dislocation accumulation so that DRX is prone to occur at iron segregation regions during L-ECAP.The monotonic tensile results show that the strain hardening rate of CP-Ti increases with the decrease of grain size,while the continuous strain hardening ability decreases.The relationship between the average grain size and yield strength is in accordance with Hall-Petch relationship.Meanwhile,the individual strengthening mechanisms were quantitatively examined by the modified model.The results indicate that the strengthening contribution of dislocation accumulation to yield strength is greater than that of grain refinement.

关键词： Equal channel angular pressing Multi-directional forging Ultrafine grain Recrystallization Strain hardening Hall-Petch relation

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Effect of thermal annealing on the microstructure, mechanical properties and residual stress relaxation of pure titanium after deep rolling treatment

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Journal of Materials Science & Technology 2019年第3期35卷 409-417页

作者： Jie Huang Kai-Ming Zhang yun-fei jia Cheng-Cheng Zhang Xian-Cheng Zhang Xian-Feng Ma Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of Education School of Mechanical and Power Engineering East China University of Science and Technology AECC Commercial Aircraft Engine Co. Ltd. Shanghai Engineering Research Center for Commercial Aircraft Engine Sino-French Institute of Nuclear Engineering and Technology SunYat-Sen University

The aim of this paper was to investigate the effect of thermal annealing on the microstructure, mechanical properties, and residual stress relaxation of deep rolled pure titanium. The microstructure and mechanical properties of the surface modified layer were analyzed by metallographic microscopy, transmission electron microscope and in-situ tensile testing. The results showed that the annealed near-surface layer with fine recrystallized grains had increased ductility but decreased strength after annealing below the recrystallization temperature, where the tensile strength was still higher than that of the substrate. After annealing at the recrystallization temperature, the recrystallized near-surface layer had smaller grain size,similar tensile strength, and higher proportional limit, comparable to those of the substrate. Moreover, the residual stress relaxation showed evidently different mechanisms at three different temperature regions:low temperature(T≤ 0.2 Tm), medium temperature(T≈(0.2–0.3) Tm), and high temperature(T≥ 0.3 Tm).Furthermore, a prediction model was proposed in terms of modification of Zener-Wert-Avrami model,which showed promise in characterizing the residual stress relaxation in commercial pure Ti during deep rolling at elevated temperature.

关键词： Deep rolling Ultra-fine grain Tensile strength Microstructure Residual stress

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Treatment of bilateral developmental dysplasia of the hip joint with an improved technique:A case report

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World Journal of Clinical Cases 2024年第7期12卷 1320-1325页

作者： Xing-Xing Yu jian-Ye Chen Hong-Sheng Zhan Ming-Da Liu yun-fei Li Yu-Yan jia College of Traditional Chinese Medicine Changchun University of Traditional Chinese MedicineChangchun 130117Jilin ProvinceChina Shi's Traumatology Medical Center Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese MedicineShanghai 201203China College of Traditional Chinese Medicine The Affiliated Hospital of Changchun University of Chinese MedicineChangchun 130021Jilin ProvinceChina

BACKGROUND Developmental dysplasia of the hip(DDH)is a common osteoarticular deformity in pediatric orthopedics.A patient with bilateral DDH was diagnosed and treated using our improved technique"(powerful overturning acetabuloplasty)"combined with femoral rotational shortening osteotomy.CASE SUMMARY A 4-year-old girl who was diagnosed with bilateral DDH could not stand normally,and sought surgical treatment to solve the problem of double hip extension and standing.As this child had high dislocation of the hip joint and the acetabular index was high,we changed the traditional acetabuloplasty to"powerful turnover acetabuloplasty"combined with femoral rotation shortening osteotomy.During the short-term postoperative follow-up(1,3,6,9,12,and 15 months),the child had no discomfort in her lower limbs.After the braces and internal fixation plates were removed,formal rehabilitation training was actively carried out.CONCLUSION Our"powerful overturning acetabuloplasty"combined with femoral rotational shortening osteotomy is feasible in the treatment of DDH in children.This technology may be widely used in the clinic.

关键词： Developmental dysplasia of the hip Improved technique Case report

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RNA modifications in cellular metabolism:implications for metabolism-targeted therapy and immunotherapy

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Signal Transduction and Targeted Therapy 2024年第4期9卷 1565-1594页

作者： Wei-Wei Liu Si-Qing Zheng Tian Li yun-fei fei Chen Wang Shuang Zhang fei Wang Guan-Min jiang Hao Wang Department of Laboratory Medicine The First Affiliated Hospital of USTCDivision of Life Sciences and MedicineUniversity of Science and Technology of ChinaHefeiChina School of Clinical Medicine Shandong UniversityJinanChina Core Unit of National Clinical Research Center for Laboratory Medicine HefeiChina Neurosurgical Department The First Affiliated Hospital of USTCDivision of Life Sciences and MedicineUniversity of Science and Technology of ChinaHefeiChina Department of Clinical Laboratory The Fifth Affiliated HospitalSun Yat-sen UniversityZhuhaiChina

Cellular metabolism is an intricate network satisfying bioenergetic and biosynthesis requirements of cells.Relevant studies have been constantly making inroads in our understanding of pathophysiology,and inspiring development of therapeutics.As a crucial component of epigenetics at post-transcription level,RNA modification significantly determines RNA fates,further affecting various biological processes and cellular phenotypes.To be noted,immunometabolism defines the metabolic alterations occur on immune cells in different stages and immunological contexts.In this review,we characterize the distribution features,modifying mechanisms and biological functions of 8 RNA modifications,including N6-methyladenosine(m6A),N6,2'-O-dimethyladenosine(m6Am),N1-methyladenosine(m1A),5-methylcytosine(m5C),N4-acetylcytosine(ac4C),N7-methylguanosine(m7G),Pseudouridine(V),adenosine-to-inosine(A-to-l)editing,which are relatively the most studied types.Then regulatory roles of these RNA modification on metabolism in diverse health and disease contexts are comprehensively described,categorized as glucose,lipid,amino acid,and mitochondrial metabolism.And we highlight the regulation of RNA modifications on immunometabolism,further influencing immune responses.Above all,we provide a thorough discussion about clinical implications of RNA modification in metabolism-targeted therapy and immunotherapy,progression of RNA modification-targeted agents,and its potential in RNAtargeted therapeutics.Eventually,we give legitimate perspectives for future researches in this field from methodological requirements,mechanistic insights,to therapeutic applications.

关键词： metabolism targeted alterations

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Should we perform sigmoidoscopy for colorectal cancer screening in people under 45 years?

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World Journal of Gastrointestinal Oncology 2024年第4期16卷 1248-1255页

作者： Waiian Leong jia-Qi Guo Chun Ning fei-fei Luo Rui jiao Dong-Ye Yang Division of Gastroenterology&Hepatology The University of Hong Kong-Shenzhen HospitalShenzhen 518053Guangdong ProvinceChina Department of Accident&Emergency The University of Hong Kong-Shenzhen HospitalShenzhen 518053Guangdong ProvinceChina Department of Anatomical Pathology The University of Hong Kong-Shenzhen HospitalShenzhen 518053Guangdong ProvinceChina Endoscopy Center The University of Hong Kong-Shenzhen HospitalShenzhen 518053Guangdong ProvinceChin

BACKGROUND The strategy for preventing colorectal cancer is screening by colonoscopy,which offers a direct way for detection and removal of adenomatous polyps(APs).American College of Gastroenterology guidelines recommend that people aged≥45 years should undergo colonoscopy;however,how to deal with people aged≤45 years is still unknown.AIM To compare the prevalence of APs and high-grade neoplasia between the left and right colon in patients≤45 years.METHODS A retrospective observational study was conducted at a single tertiary III hospital in China.This study included patients aged 18-45 years with undergoing initial colonoscopy dissection and pathological diagnosis AP or high-grade neoplasia between February 2014 and January 2021.The number of APs in the entire colon while screening and post-polypectomy surveillance in following 1-3 years were evaluated.RESULTS A total of 3053 cases were included.The prevalence of APs in the left and right colon was 55.0%and 41.6%,respectively(OR 1.7,95%CI 1.6-2.4;P3 polyps(14.1%;OR 0.3,95%CI 0.1-0.6;P<0.05).CONCLUSION This study suggests that flexible sigmoidoscopy would be an optimal approach for initial screening in people aged≤45 years and would be a more cost-effective and safe strategy.

关键词： Adenomatous polyps High-grade neoplasia Colonoscopy Flexible sigmoidoscopy

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