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Twin-twin geometric structure effect on the twinning behavior of an Mg-4Y-3Nd-2Sm-0.5Zr alloy traced by quasi-in-situ EBSD

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Journal of Magnesium and Alloys 2023年第4期11卷 1381-1392页

作者： Yunwei Gui Quanan Li Yibei Xue Lingxiao Ouyang School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471023China Provincial and Ministerial Co-construction of Collaborative Innovation Center for Non-ferrous Metal New Materials and Advanced Processing Technology Luoyang 471023China Department of Materials Processing Graduate School of EngineeringTohoku University6-6-11 AobaAramakiAoba-kuSendai 980-8579Japan School of Materials Science and Engineering Northwestern Polytechnical UniversityXi’an 710072China

We studied the microstructure evolution of Mg-4Y-3Nd-2Sm-0.5Zr alloy by quasi-in-situ electron backscatter diffraction(EBSD)along with several strains under compression tests,which provided direct evidence for the influence of different twin-twin geometric structure on the twinning behavior.The results showed that the mechanical properties of the alloy were higher than traditional magnesium alloys(the maximum compressive strength reaches 402.5 MPa)due to the strengthening effect of Sm and Nd elements addition on solution strengthening,precipitation strengthening,and grain refinement.Combined with the quasi-in-situ EBSD technique,two different twin-twin geometric structures,‘parallel structure’and‘cross structure’,were observed directly in the alloy.In the later stage of deformation,for‘parallel structure’,residual stress and a large number of dislocations mainly existed in the twin boundary and tip position.For the‘cross structure’,there was a lot of dislocation density in the interior of twins after fusion.The twin growth rate of‘parallel structure’was much faster than that of‘cross structure’because the stress of twins was mainly concentrated on the tip of twin.When the movement for the tip of twin was blocked,the growth rate of twin would be obviously decreased.Moreover,the‘cross structure’was easy to produce closed space.Due to the constraints of surrounding twins,the confined space was easy to stress concentration,thus inhibiting the growth of twins.At the same time,the‘cross structure’of twins needed a more external force to continue to deform,which also served as a strengthening structure.

关键词： Mg-RE alloy mechanical testing Twinning Quasi-in-situ EBSD

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Assessment of Hydrogen Embrittlement Susceptibility and Mechanism(s)in Quench and Tempered AISI 4135 Steel Using A Novel Fast Fracture Test in Bending

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Acta Metallurgica Sinica(English Letters) 2023年第7期36卷 1078-1094页

作者： Tuhin Das Salim V.Brahimi Jun Song Stephen Yue Department of Materials Engineering McGill UniversityMontrealQC H3A OC5Canada Industrial Fasteners Institute ClevelandOH 44131USA

A newly proposed rapid fracture test in four-point bending was used to evaluate the effect of tempering on the hydrogen embrittlement(HE)susceptibility of an AISI 4135 steel,where it was tempered to four different strength(or hardness)levels.It was observed that HE susceptibility increases with the increase in hardness.It was shown that there will be minimal impact of hydrogen(H)on the fracture of materials with hardness 37 HRC and below,even if they are completely saturated with H.On the other hand,H will have similar detrimental effect on fracture properties of quench and tempered(Q and T)steels having hardness higher than 45 HRC.Ductile to brittle transition behavior was observed for a critical hardness(or strength)range as well as for a critical concentration level of H.Additionally,a critical H concentration was observed to exist for each of the strength levels.Fractography was performed in addition to microstructural characterization using transmission electron microscopy(TEM).A very good correlation was observed between the fast fracture test results and fractography.The fast fracture test was further compared with a conventional incremental step load(ISL)test for the evaluation of HE susceptibility.The ISL test results and fracture surface characteristics corroborate very well with the observations from the fast fracture test.This study successfully establishes the fast fracture test as a novel technique to study HE susceptibility and mechanism(s).

关键词： Hydrogen embrittlement(HE) mechanical testing Fracture mechanics Martensitic steel Hardness Dislocation density

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Binder-and conductive additive-free Ga2O3 nanowires as a self-healing anode for lithium storage

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Progress in Natural Science:Materials International 2023年第2期33卷 203-210页

作者： Yang Gao Bin Wang CAS Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology

High-capacity anode materials have stimulated much attention to developing high-performance lithium-ion batteries. However, high-capacity anode materials commonly suffer from the pulverization matter that greatly hinders their practical applications, especially in terms of the high proportion of active materials. In this work, a Ga2O3nanowire electrode is synthesized by thermal evaporation and immediately used as an anode without the aid of binders and conductive additives. The 3D interconnected architecture of the Ga2O3nanowire electrode shortens lithium diffusion lengths and expedites reaction kinetics. The Ga2O3nanowires exhibit high elasticity and a self-healing ability which is inherited from metallic Ga formed during the electrochemical transition process, thus circumventing the formidable pulverization issue to a certain extent. Benefiting from the unique structural, mechanical, and chemical attributes, the as-grown Ga2O3nanowire electrode gives a high initial lithiation capacity of 1462 m Ah g-1under a current density of 0.1 A g-1. It delivers good cyclic stability with a reversible capacity of 445 m Ah g-1after 200 cycles at 0.5 A g-1. Furthermore, the investigation of lithium storage behaviors indicates the high rate capability of Ga2O3nanowires. This paper contributes to understanding binderand conductive additive-free electrodes consisting of high-capacity active materials from various viewpoints.

关键词： Lithium-ion battery Gallium oxide Nanowires Binder-free mechanical testing

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Serrated flow in NaI:Tl scintillator crystals

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Journal of Materials Science & Technology 2023年第22期153卷 120-127页

作者： Jamieson Brechtl Xie Xie Rui Feng Gongyao Wang Charles Melcher Mariya Zhuravleva Peter K.Liaw The Bredesen Center for Interdisciplinary Research and Graduate Education The University of TennesseeKnoxvilleTN 37996USA Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996USA Scintillation Materials Research Center The University of TennesseeKnoxvilleTN 37996USA

The serrated-flow behavior is an important phenomenon that unveils material-deformation mechanisms,as reported for various kinds of materials.NaI doped with Tl(NaI:Tl)is unique among scintillation ma-terials in that the structure contains glide planes that are linked to serration behavior.In the present work,single crystals of NaI:Tl were subjected to room-temperature compression experiments at different strain rates.The serrated flow was observed,and complexity and multifractal analyses were performed to analyze the serration behavior.The findings revealed that the strain rate had a pronounced effect on the complexity and multifractality of the serrated flow,similar to what has been found in other alloy systems.The results also indicate that there may be a strong link between the complexity of the serrated flow behavior and the heterogeneity of the underlying dynamics.It is expected that the present work could be a step toward a better understanding of the deformation behavior and forgeability of NaI:Tl single crystals.

关键词： Dislocations Ceramic material mechanical testing Numerical algorithms Scintillator

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Influence of alkaline treatment and fiber loading on the physical and mechanical properties of kenaf/polypropylene composites for variety of applications

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Progress in Natural Science:Materials International 2016年第6期26卷 657-664页

作者： Majid Niaz Akhtar Abu Bakar Sulong M.K.Fadzly Radzi N.F.Ismail M.R.Raza Norhamidi Muhamad Muhammad Azhar Khan Department of Physics COMSATS Institute of Information Technology Department of mechanical and Materials Engineering Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia Department of Basic Sciences and Humanities Muhammad Nawaz Sharief University of Engineering and Technology(MNSUET) Department of mechanical Engineering COMSATS Institute of Information Technology Department of Physics The Islamia University of Bahawalpur

Due to current trend and increasing interest towards natural based fiber products, Kenaf(Hibiscus cannabinus)fibers have been used for the developments of many products. Therefore, Kenaf fiber-reinforced composites have been widely used in engineering and industrial applications. The present work deals with the fabricating and characterization of untreated and treated kenaf/polypropylene(PP)-reinforced composites. Composites of PP reinforced with treated and untreated kenaf fibers were fabricated using the injection molding technique.Different fiber loadings of 10, 20, 30, 40, 50 wt% treated and untreated kenaf composites were also prepared. Xray diffraction(XRD), scanning electron microscopy(SEM), Fourier transform infrared(FTIR) spectroscopy and thermo gravimetric analysis(TGA) were performed on the treated, untreated kenaf fibers and kenaf/PP composites. Moreover, the alkaline-treated kenaf composites exhibit better physical, morphological, and mechanical properties because of the compatibility of kenaf with PP. However, variations in tensile and flexural properties depend on treatment and kenaf fiber contents. The percentage increase in the mechanical properties of the treated kenaf/PP composites relative to that of PP was also measured. In addition, 40 wt%kenaf fiber loading resulted in higher mechanical properties. By contrast, kenaf/PP composite with 50% fiber loading was not successfully prepared because of improper mixing and the burning of kenaf fibers in the PP matrix. To conclude, 40% kenaf/PP composites with superior physical and mechanical properties may be used in variety of applications such as automotive, sports, construction, animal bedding, and mass production industries.

关键词： Kenaf composites Microstructures Physical properties mechanical testing Injection-molding

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Effect of Prior Austenite Grain Size on the Morphology and mechanical Properties of Martensite in Medium Carbon Steel

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Journal of Materials Science & Technology 2012年第5期28卷 461-466页

作者： Y.Prawoto N.Jasmawati K.Sumeru Faculty of mechanical Engineering Universiti Teknologi Malaysia81310 UTMSkudaiJohor 81310Malaysia Dept.of Refrigeration and Air Conditioning Engineering Politeknik Negeri BandungIndonesia

In industrial application,unintentional manufacturing line troubles often consequence in heating raw materials excessively,in terms of either time or temperature.One of the effects of such occurrence is a product with a variation of prior austenite grain size,even if after the heat treatment the end result is the same,martensite.The variation of the prior austenite grain size is believed to vary the end results of the martensite.This undesirable variation includes the variation of fatigue resistance,impact strength,yield strength,hardness,etc.This research studies the effect of the prior austenite grain size on the morphology of the martensite microstructure.The results show that within the typical industrial application of temperature and holding time set up,as holding time or the temperature increases,the prior austenite average diameter increases.The block and packet sizes in the martensite also increase.The variation of mechanical property dependence on the grain size is indeed due to the different characteristics reflected in the martensite morphology.With respect to the same area,smaller grain has more blocks and packets,which agrees with higher dislocation density verified with transmission electron microscopic evaluation.

关键词： Heat treating mechanical testing Carbon/alloy steels

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Review on mechanics of ultra-high-temperature materials

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Acta Mechanica Sinica 2021年第9期37卷 1347-1370,I0001页

作者： Daining Fang Weiguo Li Tianbao Cheng Zhaoliang Qu Yanfei Chen Ruzhuan Wang Shigang Ai Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing100081China College of Engineering Peking UniversityBeijing100871China College of Aerospace Engineering Chongqing UniversityChongqing400044China School of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing401331China

Ultra-high-temperature materials have applications in aerospace and nuclear industry.They are usually subjected to complex thermal environments during service.The mechanical properties of materials in ultra-high-temperature environments have been attracted increasing attentions.However,the characterization and evaluation of ultra-high-temperature mechanical properties of materials are still challenging work.This article presents a review on the mechanical properties of materials at elevated temperatures.The experimental results and techniques on the ultra-high-temperature mechanical properties of materials are reviewed.The constitutive models of materials at elevated temperatures are discussed.The recent research progress on the quantitative theoretical characterization models for the temperature-dependent fracture strength of advanced ceramics and their composites is also given,and the emphasis is placed on the applications of the force-heat equivalence energy density principle.The thermal–mechanical-oxygen coupled computational mechanics of materials are discussed.Furthermore,the outlook and concluding remarks are highlighted.

关键词： Ultra-high-temperature materials mechanical properties mechanical testing Theoretical characterization Numerical simulation

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Non-contact tensile viscoelastic characterization of microscale biological materials

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Acta Mechanica Sinica 2018年第3期34卷 589-599页

作者： Yuhui Li Yuan Hong Guang-Kui Xu Shaobao Liu Qiang Shi Deding Tang Hui Yang Guy M.Genin Tian Jian Lu Feng Xu The Key Laboratory of Biomedical Information Engineeringof Ministry of Education School of Life Science and TechnologyXi'an Jiaotong UniversityXi'an 710049China Biomedical Engineering and Biomechanics Center(BEBC) Xi'an Jiaotong UniversityXi'an 710049China Intemational Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical StructuresXi'an Jiaotong UniversityXi'an 710049China School of Life Sciences Northwestern Polytechnical UniversityXi'an 710072China The NSF Science and Technology Center for Engineering Mechano-Biology Washington UniversitySaint LouisMO 63130.USA

Many structures and materials in nature and physiology have important ＂meso-scale＂ structures at the micron lengthscale whose tensile responses have proven difficult to characterize mechanically. Although techniques such as atomic force microscopy and micro- and nano-identation are mature for compression and indentation testing at the nano-scale, and standard uniaxial and shear rheometry techniques exist for the macroscale, few techniques are applicable for tensile-testing at the micrometre-scale, leaving a gap in our understanding of hierarchical biomaterials. Here, we present a novel magnetic mechanical testing （MMT） system that enables viscoelastic tensile testing at this critical length scale. The MMT system applies non-contact loading, avoiding gripping and surface interaction effects. We demonstrate application of the MMT system to the first analyses of the pure tensile responses of several native and engineered tissue systems at the mesoscale, showing the broad potential of the system for exploring micro- and meso-scale analysis of structured and hierarchical biological systems.

关键词： mechanical testing Hierarchical biomaterials Non-contact actuation Microscale analysis

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mechanical and tribological properties of graphene nanoplatelets-reinforced titanium composites fabricated by powder metallurgy

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Journal of Iron and Steel Research(International) 2020年第11期27卷 1357-1362页

作者： Zhen Cao Jiong-li Li Hai-ping Zhang Wen-bo Li Xu-dong Wang AECC Beijing Institute of Aeronautical Materials Beijing 100095China Beijing Institute of Graphene Technology Beijing 100094China Beijing Engineering Research Centre of Graphene Application Beijing 100095China

Titanium matrix composite reinforced by graphene nanoplatelets(GNPs)was fabricated via powder metallurgy route.Hot isostatic pressing and hot extrusion were used to consolidate the mixed powder of GNPs and TC4 titanium(Ti)alloy.The microstructures,mechanical properties and sliding wear performance of Ti/GNPs composite had been researched to evaluate the rein forcing effect of GNPs on tita nium matrix.Microstructure observation indicates that GNPs could restrain grai n growth slightly in titanium matrix.Titanium matrix and graphene exhibit a clean and firm interface formed by means of metallurgical bonding on atomic scale.Compared with the monolithic titanium alloy,the composite with 1.2 vol.%GNPs exhibits significantly improved elastic modulus and strength.The sliding wear test shows that there is an obvious enhancement in the tribological performance of Ti/GNPs composite with 1.2 vol.%GNPs.The results of this work indicate that GNP is an efficient reinforcenient material in titanium matrix.The strengthening mechanism including precipitates strengthening,load transfer and grain refinement mechanism of GNPs in titanium matrix was discussed.A modified shear-lag model was used to analyze the reinforcement contribution of the stress transfer mechanism.The calculation shows that the stress load mechanism constitutes the main strengthening mechanism in Ti/GNPs composite.

关键词： Titanium matrix composite Graphene mechanical testing Tribological property Powder metallurgy

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A Review on Friction Stir Welding of Steels

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Chinese Journal of mechanical Engineering 2021年第6期34卷 195-223页

作者： Dhanesh G Mohan ChuanSong Wu Institute of Materials Joining Shandong UniversityJinan 250016China

Friction Stir Welding(FSW)is the most promising solid-state metals joining method introduced in this era.Compared to the conventional fusion welding methods,this FSW can produce joints with higher mechanical and metallurgi-cal properties.Formerly,FSW was adopted for low melting metals like aluminum alloys.In recent years it has made significant progress in friction stir welding of steels since unfavourable phase transformations occurred in welds due to the melting of the parent and filler metals in fusion welding can be eliminated.The main advantage of FSW over traditional fusion welding is the reduction in the heat-affected zone(HAZ),and the joints exhibit excellent mechanical and corrosion resistance properties.This article reviews the progress in the relevant issues such as the FSW tool mate-rials and tool profiles for joining steels,microstructure and mechanical properties of steels joints,special problems in joining dissimilar steels.Moreover,in-situ heating sources was used to overcome the main limitations in FSW of hard metals and their alloys,i.e.,tool damages and insufficient heat generation.Different in-situ heating sources like laser,induction heat,gas tungsten arc welding assisted FSW for various types of steels are introduced in this review.On the basis of the up-to-date status,some problems that need further investigation are put forward.

关键词： Friction stir welding Steels Microstructure mechanical testing Hybrid welding

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