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Nanoscale Morphology in Tensile Fracture of a Brittle Amorphous Ribbon

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Journal of Materials Science & Technology 2008年第5期24卷 745-749页

作者： xifeng li. Kaifeng ZHANG Guofeng WANG School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

The paper reports on the observation of nanoscale morphology on the tensile fracture surface of a brittle amorphous Fe-based ribbon. The formation of nanoscale damage cavity structure is a main characteristic morphology on the fracture surfaces. Approaching the ribbon boundary, these damage cavities assemble and form the nanoscale periodic corrugations, which are neither Wallner lines nor crack front waves. The periodic corrugations result from the interactions between the reflected elastic waves by the boundaries of amorphous ribbon and the stress fields of the crack tip.

关键词： Nanoscale periodic corrugation Damage cavity Tensile fracture Brittle amorphous ribbon

Overview on the Prediction Models for Sheet Metal Forming Failure:Necking and Ductile Fracture

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Acta Mechanica Solida Sinica 2018年第3期31卷 259-289页

作者： Qi Hu Feifei Zhang xifeng li Jun Chen Department of Plasticity Technology Shanghai Jiao Tong UniversityShanghai 200030China Shenzhen Institutes of Advanced Technology Chinese Academy of SciencesShenzhen 518055China

The formability of the material determines the amount of available deformation before failure and thus is important for the production of various structural components in industries. The workability of materiMs is commonly evaluated by different forms of failure mod- els during sheet metal forming （SMF） processes. In order to provide a whole picture about the prediction models for SMF failure, necking-related formability and ductile fracture-related forma- bility studies in SMF processes are systematically summarized, the applicability and limitation of each model are highlighted, and the link between forming limit diagram and ductile fracture criterion is pointed out, Conclusions about some critical issues on failure in SMF are made.

关键词： Necking Ductile fracture Failure model Sheet metal forming

Superplastic Tension Behavior of Dissimilar TC4/SP700 Laminate through Diffusion Bonding

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Acta Metallurgica Sinica(English Letters) 2024年第2期37卷 353-363页

作者： Qianwen Zhang Tianle li Yanbin Han Wei Zheng xifeng li Jianjun Wu School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an710072China AVIC Xi’an Aircraft Industry Group Company Ltd Xi’an710089China Institute of Forming Technology and Equipment School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai200030China

Superplastic forming is a practical method to manufacture complex-shaped parts of titanium alloys with large *** parts of dissimilar titanium alloys fabricated by superplastic forming can achieve excellent performance by combining the advantages of *** work displays the superplastic tension behavior and microstructural evolution of dissimilar TC4/SP700 laminate prepared by the diffusion bonding *** titanium alloys can achieve metallurgical bonding at parameters of 800℃/1 h/5 *** for dynamic recrystallization and grain growth behaviors upon superplastic tension,stress-induced phase transformation plays an important role inαtoβphase transformation apart from the elevated *** superplastic deformation can be attributed to the grain boundary sliding accommodated multiplex motion of *** addition,the retained strengths of all dissimilar TC4/SP700 laminates after superplastic deformation with different strain rates and temperatures range from 807 to 890 MPa.

关键词： TC4/SP700 laminate Diffusion bonding Microstructure Superplastic tension Strength

Specialized endoplasmic reticulum-derived vesicles in plants:Functional diversity,evolution,and biotechnological exploitation

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Journal of Integrative Plant Biology 2022年第4期64卷 821-835页

作者： Xie li xifeng li Baofang Fan Cheng Zhu Zhixiang Chen College of life Science Key Laboratory of Marine Food Quality and Hazard Controlling Technology of Zhejiang ProvinceChina Jiliang UniversityHangzhou 310018China Department of Botany and Plant Pathology Center for Plant BiologyPurdue UniversityWest Lafayette IN 47907-2054USA

A central role of the endoplasmic reticulum(ER)is the synthesis,folding and quality control of secretory *** proteins usually exit the ER to enter the Golgi apparatus in coat protein complex II(COPII)-coated vesicles before transport to different subcellular ***,in plants there are specialized ER-derived vesicles(ERDVs)that carry specific proteins but,unlike COPII vesicles,can exist as independent organelles or travel to the vacuole in a Golgi-independent *** specialized ERDVs include protein bodies and precursor-accumulating vesicles that accumulate storage proteins in the endosperm during seed *** ERDVs also include precursor protease vesicles that accumulate amino acid sequence KDEL-tailed cysteine proteases and ER bodies in Brassicales plants that accumulate myrosinases that hydrolyzes *** functionally specialized ERDVs act not only as storage organelles but also as platforms for signal-triggered processing,activation and deployment of specific proteins with important roles in plant growth,development and adaptive *** specialized ERDVs have also been exploited to increase production of recombinant proteins and *** we discuss our current understanding of the functional diversity,evolutionary mechanisms and biotechnological application of specialized ERDVs,which are associated with some of the highly remarkable characteristics important to plants.

关键词： endoplasmic reticulum-derived vesicles ER body glucosinolates myrosinases precursor accumulating vesicles precursor protease vesicles prolamins protein body ricinosomes zeins

Low-Temperature Diffusion Bonding Behavior of Hydrogenated Zr R60702

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Acta Metallurgica Sinica(English Letters) 2023年第10期36卷 1603-1618页

作者： Jialin Zheng Longteng li Huiping Wu Doudou Yang Bin Wang Dayong An xifeng li Institute of Forming Technology and Equipment School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai200030China Luoyang Ship Material Research Institute Luoyang471023China Beijing Xinghang Electro-Mechanical Equipment Co. Ltd.Beijing100074China

High temperature in diffusion bonding(DB)process severely deteriorates the performance of zirconium(Zr)R60702 in extreme chemical ***,it is important to reduce the DB temperature of Zr *** this work,low-temperature diffusion bonding of Zr R60702 at 750°C is realized by 0.3 wt%hydrogen addition while 900°C is required in DB process for unhydrogenated Zr *** shear strength of the hydrogenated joint bonded at 750°C reaches 388 MPa,which is 117.98%higher than that of the unhydrogenated joint bonded at 750°C and equal to that of the unhydrogenated joint bonded at 900°*** effects of hydrogen addition in Zr R60702 on the microstructure evolution,phase transformation temperature,interatomic bonding and self-diffusion coefficient of Zr atoms are investigated in *** results show that the optimized DB properties can be attributed to the improvements of its grain boundary diffusion,plasticity and self-diffusion coefficient of Zr atoms.

关键词： Low-temperature diffusion bonding Hydrogenation Zr R60702

Observation of the Hydrogen-Dislocation Interactions in a High-Manganese Steel after Hydrogen Adsorption and Desorption

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Acta Metallurgica Sinica(English Letters) 2023年第7期36卷 1105-1112页

作者： Dayong An Yuhao Zhou Yao Xiao Xinxi liu xifeng li Jun Chen Department of Plasticity Technology School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai200030China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China

Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic ***,explanations for the observed HE phenomena are still under *** shed light on this issue,here we investigated the hydrogen-defect interaction by comparing the dislocation structure evolution after hydrogen adsorption and desorption in a Fe-28Mn-0.3C(wt%)twinning-induced plasticity steel with an austenitic structure using in situ electron channeling contrast *** results indicate that hydrogen can strongly affect dislocation *** detail,hydrogen can promote the formation of stacking faults with a long dissociation ***,dislocation movements are frequently observed during hydrogen *** required resolved shear stress is considered to be the residual stresses rendered by hydrogen ***,the microstructural heterogeneity could lead to the discrepancy of dislocation activities even within the same materials.

关键词： Hydrogen embrittlement Stacking fault Dislocation movement High-manganese steel Electron channeling contrast imaging(ECCI)

Influence of Strain Rate on Tensile Characteristics of SUS304 Metastable Austenitic Stainless Steel

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Acta Metallurgica Sinica(English Letters) 2013年第6期26卷 657-662页

作者： xifeng li Jun CHEN liyan YE Wei DING Pengchao SONG Department of Plasticity Technology School of Materials Science and EngineeringShanghai Jiao Tong University

The microstructure characteristics and plastic deformation behavior of SUS304 metastable austenitic stainless steel sheets have been investigated during tensile process at different strain rates at room temperature. The yield stress continuously increases with strain rates due to low fraction of martensite transformed from austenite at 0.2% plastic stain. While the ultimate tensile stress （UTS） and elongation gradually decreases and then slightly increases with increase in strain rate from 0.0005 s-1 to 0.i s-1, which is attributed to the variation of the martensite fraction that is affected seriously by adiabatic heating. A higher temperature increase in the tensile specimens restricts the martensitic transformation at high strain rate. The strain rate of 0.1 s-1 is considered as a transition deformation rate from quasi-static state to plastic forming, where the transformed martensitic content is very small in a higher strain rate range. Anomalous stress peaks in the later half stage of deformation occur at a very low strain rate （i.e., 0.0005 s-1） result from X-shaped strain localization repeatedly sweeping over the specimen. With increasing strain rates, the variation of dimple number density follows similar trend as that of UTS and ductility because martensite fraction mostly influences void nucleation and growth.

关键词： SUS304 metastable austenitic stainless steel Strain rate Mechanical prop-erties Martensite fraction Dimple

Microstructural and Microhardness Variation of Amorphous Fe_(78)Si_9B_(13) Alloy during Bend Stress Relaxation

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Journal of Materials Science & Technology 2007年第2期23卷 253-256页

作者： xifeng li Kaifeng ZHANG Changli WANG Wenbo HAN Guofeng WANG School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China Advanced Manufacturing Technology Research Centre Department of Industrial and Systems Engineering The Hong Kong Polytechnic University Hung Hom Hong Kong China

The amorphous Fe78Si9B13 ribbons were bend stress relaxed at various temperature well below the crystallization temperature （Tx） for different time. The effect of pre-annealing on the subsequent bend stress relaxation was examined. The variation of the microstructure and microhardness during bend stress relaxation process was studied using X-ray diffraction （XRD）, atomic force microscopy （AFM） and Vickers microhardness test,respectively. Curvature radius of the amorphous Fe78Si9B13 ribbons decreased with increase bend stress relaxation temperature and time. The microhardness of the stress relaxed specimens increased with time at 300℃ due to the forming of nanocrystals during bend stress relaxation. The pre-annealing reduced the decrease rate of the curvature radius of stress relaxed specimens.

关键词： Bend stress relaxation Amorphous Fe78Si9B13 alloy Microstructure Microhardness

Fracture Morphologies of Advanced High Strength Steel During Deformation

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Acta Metallurgica Sinica(English Letters) 2014年第1期27卷 101-106页

作者： Ying Sun xifeng li Xiangyu Yu Delong Ge Jun Chen Jieshi Chen Department of Plasticity Technology.School of Materials Science and Engineering Shanghai Jiao Tong University

The fracture morphologies of several advanced high-strength steels （DP590, DP780, DP980, Ml180, and M1300） formed in uniaxial tension and piercing were observed by scanning electron microscope, and then quantitatively analyzed by image processing technique. The tension-induced fractographs are dominated by obvious uniform or bimodal size dimples, while shearing-induced fractographs have smooth surfaces and few dimples. The fracture zone of higher grade DP steels is smoother. As for M1180 and M1300, the fracture zones consist of very small dimples and smooth brittle surfaces. The dimple size of M1300（ ,- 1.2 tm） is smaller than that of M1180（ 1.6 tm）. Moreover, in the tensile fracture, the quantitative correlation between average dimple diameter （d） and tensile strength （a） can be represented by d = 10,502.32a-121. However, the relation between dimple density and tensile strength is not monotonic due to the appearance of bimodal size dimples with increase of tensile strength. For shearing-induced fracture during piercing, the fitted empirical model between the percentage of burnish zone （f） and tensile strength can be described asf --- 239.9a-＇36.

关键词： High strength steel Fracture morphology Dimple size Burnish zone Tensile strength