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Journal of Thermal Science 2024年第2期33卷 739-750页

作者： WU Gang MA Qianli WEI Lijiang JIANG Guohe WANG Tengfei LI Tie Merchant Marine College Shanghai Maritime UniversityShanghai201306China State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai200240China

In this work,particulate matter(PM) emissions from a large two-stroke,low-speed marine diesel engine were investigated when the engine was operated with low-sulfur heavy fuel oil(HFO) at various loads.Particle samples were collected in situ from the engine exhaust to determine the detailed physical and chemical properties.The nanostructure and morphology of the nanoparticles were analyzed using transmission electron microscopy images(TEM).The results show that volatile organic carbon(OC) accounts for more than 80% in the HFO particles and leads to an increase in particle size.The thermodynamic conditions of a low-speed engine favor the behavior of capturing the soluble organic components.A large number of spherical char HFO particles with aerodynamic diameters of 0.2 μm-0.5 μm and a suspected inner metal core were detected.The two peak aerodynamic diameters of the HFO nanoparticles are 15 nm and 86 nm.The morphological differences among the HFO nanoparticles in varied engine conditions represent the formation process from primary nascent particles to mature graphitized particles caused by thermodynamics.The above study will be valuable for understanding the characteristics of PM emissions from low-sulfur HFO to achieve the ship PM emissions reduction target.

关键词： low-speed diesel engine maritime regulations heavy fuel oil TEM particles size and distribution

Cooperative effect of Cr and Al elements on passivation enhancement of eutectic high-entropy alloy AlCoCrFeNi_(2.1)with precipitates

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Journal of Materials Science & Technology 2023年第5期136卷 97-108页

作者： Xiaotian Duan Tiezhuang Han Xiao Guan Yuning Wang Huhu Su Kaisheng Ming Jing Wang Shijian Zheng State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin 300130China School of Material Science and Engineering Hebei University of TechnologyTianjin 300130China

In conventional corrosion-resistant alloys,precipitation usually reduces corrosion resistance severely by weakening passive films locally.In this work,we found that the aging-treated AlCoCrFeNi_(2.1)sam-ples,which have abundant nanosized L 12 and body-centered cubic(BCC)precipitates in the lamellar face-centered cubic(FCC)and B2 phases,displayed better corrosion resistance than solution-treated AlCoCrFeNi_(2.1)samples without precipitates.In the AlCoCrFeNi_(2.1)alloy,the FCC phase with L1_(2)precipi-tates and the B2 phase with BCC precipitates were protected by passive films enriched with Cr and Al elements,respectively.Moreover,the Al-rich passive film of the B2 phase was less stable than the Cr-rich passive film of the FCC phase,so B2 phase dissolved preferentially.The Cr-rich passive film of the FCC phase remained stable with the formation of Al-rich L1_(2)precipitates inside the phase because those precipitates with the size of∼5 nm were too small to affect the composition of the Cr-rich passive film.The formation of Cr-rich BCC precipitates within the B2 phase increased the content of the Al element inside the phase,improving the stability of Al-rich passive film on the B2 phase.Furthermore,BCC precip-itates with the size of∼30 nm were protected by Cr-rich passive film,which could inhibit the expansion of corrosion pits.Thus,the corrosion resistance of eutectic high-entropy alloy AlCoCrFeN 2.1 was unprece-dentedly enhanced by the precipitation of BCC precipitates.Our study could provide an attractive strategy for designing high-entropy alloys with excellent corrosion resistance and high strength.

关键词： Eutectic high-entropy alloy Passive film Corrosion resistance Precipitates TEM

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镀锌热成形钢表面颜色及氧化物形成规律

表面技术 2023年第5期52卷 208-217页

作者：卢岳张彩东齐建军孙力马成刘艳丽熊自柳河钢材料技术研究院石家庄050023

目的研究保温时间对热成形钢镀锌层颜色及氧化物组成的影响。方法通过改变镀锌热成形22MnB5钢热处理保温时间,利用色差、辉光实验、X射线光电子能谱、粗糙度检测、扫描电子显微镜和透射电子显微镜对镀层表面及截面进行观察,利用电子... 详细信息

目的研究保温时间对热成形钢镀锌层颜色及氧化物组成的影响。方法通过改变镀锌热成形22MnB5钢热处理保温时间,利用色差、辉光实验、X射线光电子能谱、粗糙度检测、扫描电子显微镜和透射电子显微镜对镀层表面及截面进行观察,利用电子探针进行元素分析,研究保温前后镀层表面氧化物形貌及镀层元素分布规律。结果随着保温时间的增加,色差值ΔE逐渐增大。当温度处在945℃时,镀层连续性受到破坏,逐渐脱落。880℃加热过程后,镀层表面由排列均匀连贯的圆球状氧化物组成,连续覆盖表面,且呈聚集存在趋势,镀层表面氧化物厚度出现明显差异。当热加工时间超过6 min后,氧化物明显增多,表面厚度起伏大,呈现出不均匀分布趋势,裂纹萌生,并逐渐加深扩散。随着加热时间的增加,整体Zn浓度有降低的趋势。结论镀层表面主要由ZnO、FeO、Al_(2)O_(3)组成,ZnO连续铺满表面,并呈现连续分布的趋势,有效避免了在高温下镀层表面Zn的挥发。保持Zn含量在一定范围内,使得镀层具有阴极保护的作用。

关键词：热成形钢 GI镀层色差辉光 TEM 氧化物粗糙度

Local hardening and asymmetric twin growth by twin-twin interactions in a Mg alloy

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Journal of Magnesium and Alloys 2023年第1期11卷 176-191页

作者： Krishna Yaddanapudi Mariyappan Arul Kumar Jiaxiang Wang Xin Wang Timothy J.Rupert Enrique J.Lavernia Julie M.Schoenung Irene J.Beyerlein Subhash Mahajan Department of Materials Science and Engineering University of CaliforniaDavisCA 95616USA Materials Science and Technology Division Los Alamos National LaboratoryLos AlamosNM 87545USA Department of Mechanical Engineering Materials DepartmentUniversity of CaliforniaSanta BarbaraCA 93106USA Department of Materials Science and Engineering University of CaliforniaIrvineUSA Materials Department University of CaliforniaSanta BarbaraCA 93106USA

In this study,the role of twin-twin interactions on the distributions of local defects(e.g.,dislocations)and stress fields in a magnesium alloy is investigated.A co-zone(1012)-(1012)tensile twin junction in a deformed Mg-3wt.%Y alloy is analyzed using transmission electron microscopy(TEM).The results show that the morphology of the impinging(1012)twin is asymmetric,and the non-interacting boundary of the recipient(1012)twin is irregular.Detailed analysis of TEM images reveals that type-II pyramidal[1213](1212)dislocations concentrate in the vicinity of the twin-twin junction site.The samedislocations are also observed inside the interacting twin domains along with a few dislocations.Thedislocations emanating from the impinging(1012)twin boundary have edge character and are extended with faults parallel to the basal plane.In contrast,thedislocations connected to the recipient(1012)twin are predominantly screw orientation and compact.Elasto-viscoplastic fast Fourier transform based crystal plasticity calculations are performed to rationalize the observed twin morphology and local dislocation distribution.The model calculations suggest that the local stress fields generated at the junction site where the two twins meet are responsible for the experimentally observed concentration ofdislocations.The calculated stress fields are asymmetric with respect to the junction site,explaining the observed asymmetric morphology of the impinging twin.Overall,these findings show strong effects of twin-twin interactions on the distribution of dislocations as well as the evolution of the twinned microstructure and as such,can help advance understanding of twinning in Mg alloys and their effect on mechanical behavior.

关键词： Tensile twins Twin-twin intersections Mg alloys Crystal plasticity TEM

The microstructure evolution and phase transformation behavior of a β-solidifying γ-TiAl alloy during creep

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Progress in Natural Science:Materials International 2023年第2期33卷 193-202页

作者： Yan Liu Jinshan Li Bin Tang William Yi Wang Yudong Chu Lei Zhu Weiqing Bi Xiaofei Chen Hongchao Kou State Key Laboratory of Solidification Processing Northwestern Polytechnical University Chongqing Innovation Center Northwestern Polytechnical University

The microstructural evolution and creep behavior of the Ti-43.5Al–4Nb–1Mo-0.1B alloy have been investigated by scanning electron microscope(SEM) and transmission electron microscope(TEM). The excellent creep property was obtained with a fully lamellar(FL) microstructure containing the least grain boundary βophase(GB-βo).TEM results revealed that after creep testing the α2→βophase transformation was observed in the FL microstructure. The formation βophase is associated with the accumulation of Mo element, which is confirmed by the energy-dispersive X-ray spectroscopy(EDS). Moreover, the formation of βoprecipitation in α2lamellae effectively decreased the generation of dislocations in(α2/γ) lamellae, thereby improving the creep resistance. For the near gamma(NG) microstructure of the as-forged sample, a large number of dislocations and dislocation tangles were observed in the globular γ phase(γ-glob), which are considered to be the dominant creep mechanism. Moreover,the ellipsoidal ωophase was observed in the GB-βophase, accompanying with dislocations and sub-boundaries formation. In sum, the excellent creep property of the β-solidifying γ-Ti Al alloy is attributed to the fine FL structure with a small amount of GB-βophase and the formation of βoprecipitation in(α2/γ) lamellae.

关键词： TiAl alloys Creep behavior Microstructure evolution TEM Phase transformation

Formation mechanism of co-axial grain boundaries in a Mg alloy

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Journal of Magnesium and Alloys 2023年第3期11卷 1094-1101页

作者： Zhen Peng Yi Liu Lirong Xiao Yue Yang Bo Gao Mengning Xu Zhaohua Hu Yandong Yu Xuefei Chen Hao Zhou School of Materials Science and Engineering Jiangsu UniversityZhenjiang 212013China Nano and Heterogeneous Materials Center School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China Association for Science and Technology Nanjing University of Science and TechnologyNanjing 210094China Ansteel Beijing Research Institute Co. Ltd.Beijing 102209China Key Laboratory of Advanced Manufacturing and Intelligent Technology Ministry of EducationHarbin University of Science and TechnologyHarbin 150080China

Due to the insufficient slip sysTEMs in hexagonal close-packed structure,twinning is frequently activated to support stable plastic deformation of Mg alloy.In this work,we found four typical twin-like interfaces with misorientations of 102°,109°,142°and 149°,respectively,which had not only a shared[1120]zone axis of neighboring grains,but also overlapped diffraction spots similar to twins.However,highresolution transmission electron microscope(HRTEM)analysis revealed that the interfaces in real space deviated from the supposed twinning planes in reciprocal space,i.***.their overlapped diffraction spots.We clarified that the incoherent interfaces were co-axial grain boundaries(CGBs).Additionally,a special angle ofθ,close to 90°,between the interface and one side of basal plane,was frequently formed in CGBs.We proposed that interaction of multiple twinning contributes to the formation of CGBs,and theθis formed due to alternative tensile and compression twinning under a uniaxial loading.

关键词： Interface Twinning Tilt boundaries TEM Formation mechanism

Microstructural development and mechanical properties of drop tube atomized Al-2.85 wt%Fe

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Journal of Materials Science & Technology 2022年第9期104卷 41-51页

作者： Mehmet R.Abul Robert F.Cochrane Andrew M.Mullis School of Chemical&Process Engineering University of LeedsLeeds LS29JTUK

Al-2.85 wt%Fe alloy has been subjected to non-equilibrium container-less solidification using a 6.5 m drop tube.Spherical samples were collected and sieved into 7 sizes fractions ranging from 850μm to 53μm,with the estimated cooling rates being 150 to 11000 K s^(-1)respectively.XRD analysis was employed on all droplet size fractions for identification and evolution of the phases,showing that Al,Al_(6)Fe and Al_(13)Fe_(4)were formed for all sizes while Al_(5)Fe_(2)was observed only in droplets≤150μm in diameter.Microstructural evaluation was conducted by using SEM and optical microscopy,showing that droplet larger than 300μm in diameter exhibited distinct morphologies;microcellular,dendriticα-Al with inter-dendritic Al_(13)Fe_(4)eutectic and an AI-Al_(6)Fe eutectic region.With increasing cooling rate,the Al-Al_(6)Fe region disappears.EDX analysis reveals that increasing the cooling rate increased the dissolved Fe content inα-Al from 0.37 wt%Fe to 1.105 wt%Fe,and correspondingly the eutectic fraction decreased from 49.7 vol.%to 26.7 vol.%.Measurement of the lamellar spacing allowed the eutectic growth velocity and interfacial undercooling to be calculated,wherein the Al-rich boundary of the eutectic coupled zone could be reconstructed.This shows a coupled zone skewed significantly towards the intermetallic side of the eutectic.In order to understand the effect of non-equilibrium the solidification on the mechanical properties micro hardness of the droplets was measured.The micro-hardness has risen from 55.3 HV_(0.01)to 66.5 HV_(0.01)for≥850μm and≤75μm droplets,respectively.

关键词： Al-Fe alloys Container-less solidification Microstructure TEM Micro-hardness

Deformation mechanism of commercially pure titanium under biaxial loading at ambient and elevated TEMperatures

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Journal of Materials Science & Technology 2022年第31期126卷 237-251页

作者： Yuanjie Fu Yao Cheng Yun Cui Yunchang Xin Yuyao Zeng Xiao Liu Gang Chen School of Chemical Engineering and Technology Tianjin UniversityTianjin 300350China Key Laboratory for Light-weight Materials Nanjing Tech UniversityNanjingJiangsu 210009China School of Chemical Engineering and Technology Tianjin Ren’ai CollegeTianjin 301636China Tianjin Key Laboratory of Chemical Process Safety and Equipment Technology Tianjin 300350China Zhejiang Institute of Tianjin University NingboZhejiang 315201China Nuclear Power Institute of China ChengduSichuan 610015China

Commercially pure(CP)titanium is thermally processed and subjected to biaxial stress.However,the evolution of the microstructural deformation mechanisms under such circumstances is not adequately understood.In this study,the mechanical responses and microstructural deformation mechanisms of TA2 CP titanium sheets under equi-biaxial loading at room TEMperature(RT),300℃,and 400℃were studied.The activated slip and twinning sysTEMs were investigated by transmission electron microscopy(TEM)after polished cruciform specimens were biaxially tensile-tested at RT and elevated TEMperatures.The results show that{11¯22}contraction twinning and{10¯12}extension twinning are the main deforma-tion mechanisms of RT biaxial deformation,while dislocation glide is predominant in biaxial deformation at 300℃and 400℃.This difference yields varied work-hardening behaviors at RT and elevated TEM-peratures.In biaxial deformation at 400℃,the main slip trace type is multiple slip.The interaction of different slip sysTEMs in multiple slip created shear deformation concentration areas and further induced cross-slip.However,in biaxial deformation at 300℃,the amounts of simplex and multiple slip were significantly reduced compared to those at 400℃because the lower TEMperature increased the critical resolved shear stress and insufficient activated slip sysTEMs were available for grain deformation.There-fore,several stress-concentration areas were generated with the activation of cross-slip.

关键词： CP titanium Biaxial tensile tests High TEMperature Dislocation glide TEM

Passivation of corrosion product layer on AM50 Mg by corrosion inhibitor

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Journal of Magnesium and Alloys 2022年第9期10卷 2563-2573页

作者： Yan Li Xiaopeng Lu Di Mei Tao Zhang Fuhui Wang Shenyang National Laboratory for Materials Science Northeastern University3-11 Wenhua RoadShenyang 110819China School of Materials Science and Engineering and Henan Key Laboratory of Advanced Magnesium Alloy Zhengzhou University100 Kexue RoadZhengzhou 450001China

The influence of sodium dodecyl sulfate(SDS)on morphology and chemical composition of corrosion product layer formed onα-Mg matrix and cathodic Al-Mn intermetallic was sysTEMatically investigated by using FIB and TEM analysis for the first time to disclose the underlying inhibition mechanism.A porous corrosion bi-layer composed of crystalline MgO and Mg(OH)_(2)was observed on both ofα-Mg and Al-Mn intermetallic.It was found that a passive inner layer was deposited onα-Mg after immersion in SDS-containing NaCl solution,which can be ascribed to steady-state growth of magnesium and aluminum oxide under the protection of hydrophobic group of SDS.The inhibition mechanism of the inhibitor was mainly associated with formation of dense oxide layer onα-Mg matrix and preferential adsorption of SDS on the corrosion layer deposited on Al-Mn intermetallic.

关键词： Magnesium TEM FIB Inhibition mechanism

The martensitic transition pathway in steel

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Journal of Materials Science & Technology 2023年第3期134卷 244-253页

作者： Tianwei Liu Lunwei Liang Dierk Raabe Lanhong Dai State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 101408China Max-Planck-Institut für Eisenforschung DüsseldorfGermany

The martensitic transformation(MT)lays the foundation for microstructure and performance tailoring of many engineering materials,especially steels,which are with>1.8 billion tons produced per year the most important material class.The atomic-scale migration path is a long-term challenge for MT dur-ing quenching in high-carbon(nitrogen)steels.Here,we provide direct evidence of(11^(-)2)body-centred tetragonal(BCT)twinned martensite in carbon steels by transmission electron microscopy(TEM)investi-gation,and the increase in tetragonality with the C content matches X-ray diffraction(XRD)results.The specific{11^(-)2}_(BCT)twin planes which are related to the elongated c axis provide essential structural details to revisit the migration path of the atoms in MT.Therefore,the face-centred cubic(FCC)to BCT twin to body-centred cubic(BCC)twin transition pathway and its underlying mechanisms are revealed through direct experimental observation and atomistic simulations.Our findings shed new light on the nature of the martensitic transition,thus providing new opportunities for the nanostructural control of metals and alloys.

关键词： BCT twin Martensitic transformation Steels TEM Phase transformation