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Tin whisker growth from titanium-tin intermetallic and the mechanism

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Journal of materials Science & technology 2022年第34期129卷 79-86页

作者： Zhihua Tian Peigen Zhang Yan Zhang Jingwen Tang Yushuang Liu Jian Liu ZhengMing Sun Jiangsu Key Laboratory of advanced Metallic materials School of Materials Science and EngineeringSoutheast UniversityNanjing 211189China Jiangsu Key Laboratory of advanced Structural materials and Application technology School of Materials Science and EngineeringNanjing Institute of TechnologyNanjing 211167China Wuxi Lintex advanced materials co. Ltd.Wuxi 214145China

Spontaneous growth of metal whiskers, represented by tin whiskers, has haunted tin-based platings and solder joints for decades and caused huge losses to the electronics industry. Despite numerous efforts, the underlying growth mechanism has been resisting interpretation, and the whiskering phenomenon even co.tinues to expand its territory. Here, we report the growth of tin whiskers from a Ti6Sn5intermetallic.These tin whiskers share similar characteristics with those found on the platings or solder joints, but grow more and faster, with finer diameters. After tin whisker growth, Ti6Sn5retains its crystal structure,implying a dealloying process. co.bining experimental and first-principles calculation results, we analyzed the growth mechanism of tin whiskers in detail, and proposed a diffusion-based growth model.The strain energy stored in Ti6Sn5during deformation provides a driving force for whisker growth, and the short-circuit diffusion paths generated by such deformation accelerate whisker growth. These findings identify the critical role of intermetallic substrate in the whiskering phenomenon, shedding new light for co.prehensively understanding the whisker growth mechanisms. Furthermore, the plenty and rapid growth of tin whiskers also means a new method for the preparation of one-dimensional metallic materials.

关键词： Tin whisker Intermetallics Vacancy DFT

Single-phase formation mechanism and dielectric properties of sol-gel-derived Ba(Ti_(0.2)Zr_(0.2)Sn_(0.2)Hf_(0.2)Ce_(0.2))O_(3) high-entropy ceramics

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Journal of materials Science & technology 2022年第35期130卷 103-111页

作者： Jia Liu Cuiying Ma Lianli Wang Ke Ren Hongpei Ran Danni Feng Huiling Du Yiguang Wang co.lege of materials Science and Engineering Xi’an University of Science and TechnologyXi’an 710054China Institute of advanced Structure technology Beijing Institute of TechnologyBeijing 100081China State Key Laboratory of advanced materials and Electronic co.ponents Guangdong Fenghua Advanced Technology Holding Co.Ltd.Zhaoqing 526020China

Single-phase Ba(Ti_(0.2)Zr_(0.2)Sn_(0.2)Hf_(0.2)Ce_(0.2))O_(3)(BTZSHC) high-entropy ceramics(HECs) with the perovskite structure were successfully prepared via the sol-gel method.The results reveal that the as-prepared ceramics exhibit a single cubic phase belonging to the Pm3 m space group.The high entropy is the driving force of the formation of single-phase ceramics.A larger entropy(ΔS_(mix)) and a negative enthalpy(ΔH_(mix)) are co.ducive to the formation of single-phase co.pounds.Herein,ΔS_(mix)=0.323 R mole-1andΔH_(mix)=43.88 kJ/mol.The sluggish-diffusion effect ensures the thermal stability of high-entropy systems.Dielectric measurements reveal that the as-prepared BTZSHC high-entropy ceramics are relaxor ferroelectrics,and the degree of relaxor(γ) is 1.9.The relaxor behavior of the as-prepared ceramics can be ascribed to the relaxation and thermal evolution of their polar units(PUs).The findings of this work provide a theoretical basis and technical support for the preparation of single-phase high-entropy ceramics.

关键词： High-entropy ceramics Single-phase formation mechanism Perovskite structure Sol-gel method Dielectric properties

Influence of Al/Cu co.tent on grain boundary diffusion in Nd-Fe-B magnet via in-situ observation

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Journal of Rare Earths 2019年第4期37卷 398-403页

作者： Xinghua Cheng Jian Li Lei Zhou Tao Liu Xiaojun Yu Bo Li China Iron & Steel Research Institute Croup Functional materials Division Advanced Technology & Materials Co. Ltd.

The influence of aluminum and co.per co.tent in the starting Nd-Fe-B magnet on grain boundary diffusion process(GBDP) was studied by observing the phase transformation behaviors of the magnets in-situ at high temperature. A higher co.rcivity increment is disco.ered in the sample with higher AI/Cu despite the fact that its Dy diffusion amount is the same as the other. DSC analysis shows an evident melting behavior in the higher Al/Cu sample. Laser scanning co.focal microsco.y(LSCM) in-situ characterization shows a large amount of melted intergranular phase spills out to the surface simultaneously at around 600 ℃ in the high Al/Cu sample, while the phase spills out gradually one after another in the range between 623 and680 ℃ in the other sample, which indicates that the intergranular phase can be more easily melted in the sample co.taining more AI/Cu. The area fraction of matrix phase remarkably shrinks while that of intergranular phase enlarges after LSCM heating, which demonstrates the outer region of the Nd_2 Fe_(14)B grains melt at the temperature of 900 ℃. Electron probe microanalyzer result(EPMA) shows that the Nd and Dy co.centrate in edge regions and subsequently mix into the intergranular phase with the melting of the grain edge, while a large amount of AI and Cu in the intergranular phase spill out. Nevertheless, the sample with higher starting AI/Cu still remains higher residual co.tents after LSCM experiments, and that co.ld probably be the main reason why the high AI/Cu magnet shows smaller co.rcivity decrement after LSCM experiment. Overall, the increase of AI/Cu in the starting magnet optimizes the Dy distribution and the wettability of intergranular phase, enhancing co.rcivity increment effect further.

关键词： Nd-Fe-B sintered magnet Grain boundary diffusion process In-situ LSCM Melting behavior co.per Aluminum

In situ atomic-scale observation of dislocation behaviors in twin-structured Pt nanocrystals

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Science China(Technological Sciences) 2021年第3期64卷 599-604页

作者： GUO YiZhong SUN Tao FU LiBo HAO LongHu HUANG Ming WEI RuJian LUO JunFeng HE Xin WANG XingQuan XIONG XiaoDong WANG LiHua HAN XiaoDong Beijing Key Lab of Microstructure and Property of advanced materials Institute of Microstructure and Properties of Advanced MaterialsBeijing University of TechnologyBeijing 100124China Grikin advanced materials co. LTD.Beijing 102200China

The deformation mechanisms of twin-structured metallic materials have attracted great interest.Though previous theoretical predictions have suggested that the repulsive force of the twin boundary(TB)can significantly affect the deformation of twinstructured metals,it remains unclear whether this prediction applies to experimental co.ditions.In this paper,the atomic-scaled deformation process of twin-structured Pt nanocrystals was in situ observed using our home-made device in a high-resolution transmission electron microsco.e.We have shown that the plastic deformation of the twin-structured Pt nanocrystals was governed by full dislocation generation as well as Lomer dislocation(LD)lock formation and destruction.After LD locks were destructed,these full dislocations tended to move towards the surface of the nanocrystals.The findings revealed that due to the ultra-high repulsive force of TB on dislocation,there was no dislocation-TB reaction during the deformation.These findings can enrich our understanding of the dislocation behaviors of twin-structured nanocrystals.

关键词： deformation mechanism repulsive force twin boundary dislocations in situ

Enhanced hydrogen storage properties of NaBH4–Mg(BH4)2 co.posites by NdF3 addition

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Progress in Natural Science:materials International 2021年第4期31卷 521-526页

作者： Jianguang Yuan Jinting Chen Haixiang Huang Yujie Lv Bogu Liu Zhongyu Li Bao Zhang Wei Lv Ying Wu Central Iron & Steel Research Institute Advanced Technology & Materials Co. Ltd Jiangsu JITRI Advanced Energy & Materials Research Institute Co. Ltd advanced materials Research Institute North China Electric Power University Jiangsu Provincial Key Laboratory of Special Robot technology Hohai University

As two important members of co.plex hydrides,Mg(BH4)2and Na BH4have a high gravimetric capacity (14.9 and10.8 wt%,respectively).In this study,the Mg(BH4)2was synthesized by the ion exchange method.Afterwards,the Mg(BH4)2and Na BH4co.posites with different amounts (30,40 and 50 wt%) of NdF3were prepared by mechanical milling.Effects of the Nd F3on the microstructural evolution and hydrogen storage properties were investigated.The results show that Nd F3catalyst can significantly improve the dehydrogenation kinetics of the eutectic co.posites of Na BH4–Mg(BH4)2.The onset hydrogen desorption temperature of the co.posites is about88.6C,which is about 110C lower than that of Mg(BH4)2and Na BH4co.posites.Mg(BH4)2–Na BH4-0.5NdF3co.posites can released 5.2 wt%H2at 250C within 30 min,and the dehydrogenation capacity is significantly higher than that of Mg(BH4)2–Na BH4co.posites.The analysis of the dehydrogenation mechanism reveals that NdF3takes participate in the reaction to generate Na MgF3to promote the dehydrogenation reaction process of the co.posites.

关键词： Hydrogen storage materials Mg(BH 4 ) 2 NaBH 4 NdF 3 Ball-milling Hydrogen desorption performance

A Two-point Method for Multiaxial Fatigue Life Prediction

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Acta Mechanica Solida Sinica 2022年第2期35卷 316-327页

作者： Jianhui Liu Xuemei Pan Youtang Li Xiaochuang Chen School of Mechanical and Electrical Engineering Lanzhou University of TechnologyLanzhou 730050China Lanzhou Jinchuan advanced materials technology co. Ltd.Lanzhou 730101China

Fatigue fracture is one of the most co.mon failure modes of engineering co.po-nents,and the co.bined action of geometrie disco.tinuity and multiaxial loading is more likely to cause severe fatigue damage of co.ponents.This work focuses on the fatigue behavior of U-notched Q345 steel specimens with differen t notch sizes under proportional cyclic tension-torsion.Firstly,based on the co.cept of strain energy,the calculation method of critical plane is given and the equivalent stress of the specified path on the critical plane is extracted to char-acterize the equivalent stress distribution state and the stress gradient effect.Then,based on the high stress volume method and theory of critical distance,a simple method for determining the critical distance is given co.sidering the co.tribution of stress at the dangerous point and the critical point.In addition,based on the idea of stress-distance normalization,a new stress gradient impact factor is defined and a new method for predicting the multiaxial fatigue life of notched specimens is given.The prediction results of the proposed model,the local stress-strain method and the point method of theory of critical distance are co.pared with the experimental results.The co.parisons show that the prediction results of the proposed model are closer to experimentai life,and the calculation accuracy is higher.

关键词： Multiaxial fatigue Stress gradient Life prediction Critical distance method Local stress-strain method

Microstructural evolution and performance of hydrogen storage and electrochemistry of co.added La0.75Mg0.25Ni3.5-xco.(x=0,0.2,0.5 at%) alloys

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Progress in Natural Science:materials International 2017年第4期27卷 424-429页

作者： Wei Lv Yufan Shi Wanpeng Deng Jianguang Yuan Youhua Yan Ying Wu China Iron & Steel Research Institute Group Advanced Technology & Materials Co. Ltd

Microstructure, hydrogen storage and electrochemical performances of co.added LaMgNico.x = 0,0.2, 0.5 at%) alloys are studied. XRD and rietveld refinement results suggest that the samples are mainly co.posed of(LaMg)Ni,(LaMg)Niand LaNiphases, co.substitution for Ni changes the phase abundance,but not the phase co.position. With the rising of co.co.tent, the amount of(LaMg)Niphase decreases, but the amount of LaNiphase increases, while the amount of(LaMg)Niphase firstly increases and then decreases.The alloys reversibly absorb and desorb hydrogen at 298 K smoothly. When co.co.tent is 0.2 at%, the hydrogen absorption capacity reaches the maximum value of 1.14 H/M, and the absorption capacities reach 1.09 H/M and 1.03 H/M in the first minute at 298 K and 323 K, respectively. Electrochemical performance measurement results show that LaMgNico.lloys are co.pletely activated within 2 cycles, and the cyclic stability of LaMgNico.lloy approaches 63.7% after 100 charge/discharge cycles, which is higher than that(S= 60%) of LaMgNico.lloy. Thus, the LaMgNico.lloy exhibits optimum co.prehensive properties of hydrogen storage and electrochemistry.

关键词： La-Mg-Ni hydrogen storage alloy co.substitution for Ni Electrochemical property

Recent advances in improving performances of the lightweight co.plex hydrides Li-Mg-N-H system

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Progress in Natural Science:materials International 2017年第1期27卷 21-33页

作者： Bao Zhang Ying Wu China Iron & Steel Research Institute Group Advanced Technology & Materials Co. Ltd

A brief review of state-of-the art advances in improving performances of the lightweight co.plex hydrides LiMg-N-H system is reported. Among the hydrogen storage materials, Li-Mg-N-H co.bination systems are regarded as one of the most potential candidates for the vehicular applications owing to their high hydrogen storage capacity( > 5 wt% H) and a more appropriate thermodynamic properties of hydrogen absorption and desorption. In the Li-Mg-N-H systems, tremendous efforts have been devoted to improving the hydrogen storage properties by adjusting co.position, revealing reaction mechanisms, adding catalysts and refining the microstructures, etc. During the studies, different mechanisms, such as the co.rdinated two-molecule or multimolecule reaction mechanism and the ammonia-mediated mechanism, are proposed and applied under some certain co.ditions. Catalysis and nanosizing are very effective in enhancing the kinetic properties and thermodynamic destabilization of Li-Mg-N-H systems. Due to nano effects, the space-co.finement and nanoco.finement seems to be more effective for improving the hydrogen storage performance, and it is great significant to develop hydrogen storage materials by studying the nanoco.fined effects on the Li-Mg-N-H systems.

关键词： Li-Mg-N-H system Hydrogen storage Catalysis Nanosizing Mechanism

Simulation and experiment investigations on fabrication of Fe-based amorphous powders by a novel atomization process equipped with assisted gas nozzles

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Journal of Iron and Steel Research(International) 2023年第6期30卷 1142-1155页

作者： Jia-qi Liu Yan-nan Dong Pu Wang Huan Zhao Jing Pang Xiao-yu Li Jia-quan Zhang School of Metallurgical and Eco.ogical Engineering University of Science and Technology BeijingBeijing 100083China Qingdao Yunlu advanced materials technology co. Ltd.Qingdao 266232ShandongChina

Based on co.putational fluid dynamics method,the effect of atomization gas pressure on the atomization efficiency of Laval nozzle was studied,and then a discrete phase model was established and co.bined with industrial trials to study the effect of a new type of assisted gas nozzles(AGNs)on powder size distribution and amorphous powder yield.The results show that increasing the atomization pressure can effectively improve the gas velocity for the Laval nozzle;however,it will decrease the aspiration pressure,and the optimal atomization pressure is 2.0 MPa.co.pared with this,after the application of AGNs with the inlet velocity of 200 m s^(-1),assisted gas jet can increase the velocity of overall droplets in the break-up and solidification area by 40 m s^(-1) and the maximum co.ling rate is increased from 1.9×10^(4) to 2.3×10^(4) K s^(-1).The predicted particle behavior is demonstrated by the industrial trails,that is,after the application of AGNs,the median diameter of powders d50 is decreased from 28.42 to 25.56 lm,the sphericity is increased from 0.874 to 0.927,the fraction of amorphous powders is increased from 90.4% to 99.4%,and only the co.rcivity is increased slightly due to the accumulation of internal stress.It is illustrated that the AGNs can improve the yield of fine amorphous powders,which is beneficial to providing high-performance raw powders for additive manufacturing technology.

关键词： co.putational fluid dynamics Atomization Assisted gas nozzle Discrete phase model Amorphous powder