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Unveiling the grain boundary-related effects on the incipient plasticity and dislocation behavior in nanocrystalline CrCoNi medium-entropy alloy

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Journal of Materials Science & Technology 2022年第32期127卷 98-107页

作者： Shuo Sun Yang Yang Chenxu Han Guixun Sun Yan Chen Hongxiang Zong Jiangjiang Hu Shuang Han Xiaozhou Liao Xiangdong Ding Jianshe Lian Key Laboratory of Automobile Materials Ministry of EducationCollege of Materials Science and EngineeringJilin UniversityChangchun 130025China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310014China School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia

The incipient plasticity and dislocation behavior in a nanocrystalline(NC)CrCoNi medium-entropy alloy were systematically investigated in terms of pop-in events during instrumental nano-indentation tests.Quantitative statistical analysis and molecular dynamic simulations were performed to reveal the effects of grain boundaries(GBs)on initial stages of plastic deformation.Multiple pop-in events appeared during loading on the NC CrCoNi.The first pop-in that represents the initial yielding was identified to be controlled by dislocation nucleation,which is in sharp contrast to the continuous elastic-plastic transition mediated by GB mechanisms in NC pure metals.This can be attributed to the sluggish kinetics of the chemically complex GBs(CCGBs)in the NC CrCoNi that hinders diffusive GB activities but facilitates dislocation nucleation.Subsequent pop-ins were also found to be closely related to the extra dragging effects imposed by the CCGBs on dislocation propagation in the NC alloy.Moreover,the extremely small grain sizes and the consequent high-volume fraction of GBs in the NC alloy severely restrict the lengths of dislocation source and the radii of dislocation loop,giving rise to a higher critical stress,smaller activation volume and lower pop-in width as compared with its coarse-grained counterpart.These results provide new insights into the onset of nano-plasticity in concentrated multi-principal element alloys.

关键词： Medium-entropy alloy Nanocrystalline Nanoindentation Incipient plasticity Grain boundary

Enhancement of strength-ductility balance of heavy Ti and Al alloyed FeCoNiCr high-entropy alloys via boron doping

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Journal of Materials Science & Technology 2021年第16期75卷 154-163页

作者： Yongliang Qi Tinghui Cao Hongxiang Zong Yake Wu Lin He Xiangdong Ding Feng Jiang Shenbao Jin Gang Sha Jun Sun State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXi'anShanxi 710049China School of Materials Science and Engineering Nanjing University of Science and TechnologyJiangsu210094China

As one of the most effective mechanisms,precipitation-hardening is widely used to strengthen high-entropy alloys.Yet,heavy precipitation-hardened high-entropy alloys usually exhibit serious embrittlement.How to effectively achieve ultra-high strength and maintain reliable ductility remains a challenge.Here,we report a study of doping extremely little boron to meet this target.We found that adding of 30 ppm boron into the heavy Ti and Al alloyed FCC FeCoNiCr high-entropy,(FeCoNiCr)_(88) Ti_(6) Al_(6) HEA(at.%)which is strengthened mainly by both coarse BCC-based(Ni,Co)_(2) TiAl Heusler and fine L12-type FCC-based(Ni,Co)_(3) TiAl precipitates and shows ultrahigh strength but poor ductility,could significantly change the original microstructure and consequently improve mechanical performance,owing to the well-known effect of boron on reducing the energy of grain boundaries.The boron addition can(1)eliminate microcavities formed at Heusler precipitate-matrix interfaces;(2)suppress the formation and segregation of coarse BCC Heusler precipitates;(3)promote the formation of L12 nanoparticles.This changes of microstructure substantially improve the tensile ductility more than by~86%and retain comparable or even better ultimate tensile strength.These findings may provide a simple and costless solution to produce heavy precipitation-strengthened HEAs with ultrahigh strength and prevent accidental brittleness.

关键词： High-entropy alloy Precipitation strengthening Boron Ductility

Developing an interatomic potential for martensitic phase transformations in zirconium by machine learning

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npj Computational Materials 2018年第1期4卷 254-261页

作者： Hongxiang Zong Ghanshyam Pilania Xiangdong Ding Graeme J.Ackland Turab Lookman State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China Theoretical Division&Materials Science and Technology Division Los Alamos National LaboratoryLos AlamosNM 87545USA Centre for Science at Extreme Conditions(CSEC) School of Physics and AstronomyUniversity of EdinburghEdinburgh EH93FDUK

Atomic simulations provide an effective means to understand the underlying physics of structural phase transformations.However,this remains a challenge for certain allotropic metals due to the failure of classical interatomic potentials to represent the multitude of bonding.Based on machine-learning(ML)techniques,we develop a hybrid method in which interatomic potentials describing martensitic transformations can be learned with a high degree of fidelity from ab initio molecular dynamics simulations(AIMD).Using zirconium as a model system,for which an adequate semiempirical potential describing the phase transformation process is lacking,we demonstrate the feasibility and effectiveness of our approach.Specifically,the ML-AIMD interatomic potential correctly captures the energetics and structural transformation properties of zirconium as compared to experimental and density-functional data for phonons,elastic constants,as well as stacking fault energies.Molecular dynamics simulations successfully reproduce the transformation mechanisms and reasonably map out the pressure–temperature phase diagram of zirconium.

关键词： martensitic transformation zirconium

Impact of distance between two hubs on the network coherence of tree networks

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信息与电子工程前沿:英文版 2023年第9期24卷 1349-1356页

作者： Daquan LI Weigang SUN hongxiang HU School of Sciences Hangzhou Dianzi UniversityHangzhou 310018China

We study the impact of the distance between two hubs on network coherence defined by Laplacian eigenvalues.Network coherence is a measure of the extent of consensus in a linear system with additive noise.To obtain an exact determination of coherence based on the distance,we choose a family of tree networks with two hubs controlled by two parameters.Using the tree’s regular structure,we obtain analytical expressions of the coherences with regard to network parameters and the network size.We then demonstrate that a shorter distance and a larger difference in the degrees of the two hubs lead to a higher coherence.With the same network size and distance,the best coherence occurs in the tree with the largest difference in the hub’s degrees.Finally,we establish a correlation between network coherence and average path length and find that they behave linearly.

关键词： Consensus Coherence Distance Average path length

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铁弹材料孪晶变形的统计行为

中国科技论文 2017年第22期12卷 2600-2606页

作者：王霄飞宗洪祥丁向东西安交通大学金属材料强度国家重点实验室西安710049

针对铁弹材料孪晶变形过程的微观图像与动力学统计行为之间关系尚不清楚的问题,构筑了基于朗道自由能理论的原子间势函数,并应用于分子动力学模拟。研究结果表明:应变控制下铁弹材料孪晶变形过程中的统计规律和微观形貌均强烈依赖于体... 详细信息

针对铁弹材料孪晶变形过程的微观图像与动力学统计行为之间关系尚不清楚的问题,构筑了基于朗道自由能理论的原子间势函数,并应用于分子动力学模拟。研究结果表明:应变控制下铁弹材料孪晶变形过程中的统计规律和微观形貌均强烈依赖于体系的温度、弹性模量和特征尺寸。铁弹畴形貌的变化在势能曲线上表现为能量噪声。在塑性变形区,其孪晶变形的统计规律会从低温的幂律分布变化到中温的Kohlrausch分布以及高温下的Vogel-Fulcher分布。而在屈服变形区,孪晶变形在较大的温度和应变速率范围内均服从幂律分布,且能量噪声的平均形貌表现为对称的抛物线形。微观形貌分析发现,对于弹性模量较小的铁弹材料,剪切变形可以使其产生高密度的畴界,而且会随试样尺度的减小而增加,这为利用畴界的功能特性提供了1个新的思路。

关键词：材料学铁弹材料剪切变形畴界运动幂律分布 Kohlrausch分布 Vogel-Fulcher分布

Novel E2E-QoE Metric for PHY Optimization:A Cross-Layered Framework

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China Communications 2023年第4期20卷 167-179页

作者： Lei Ji Hao Wang hongxiang Xie Huawei No.156.Beiqing RoadHaidian DistrictBeijing 100095China

Existing systems use key performance indicators(KPIs)as metrics for physical layer(PHY)optimization,which suffers from the problem of overoptimization,because some unnecessary PHY enhancements are imperceptible to terminal users and thus induce additional cost and energy waste.Therefore,it is necessary to utilize directly the quality of experience(QoE)of user as a metric of optimization,which can achieve the global optimum of QoE under cost and energy constraints.However,QoE is still a metric of application layer that cannot be easily used to design and optimize the PHY.To address this problem,we in this paper propose a novel end-to-end QoE(E2E-QoE)based optimization architecture at the user-side for the first time.Specifically,a cross-layer parameterized model is proposed to establish the relationship between PHY and E2E-QoE.Based on this,an E2E-QoE oriented PHY anomaly diagnosis method is further designed to locate the time and root cause of anomalies.Finally,we investigate to optimize the PHY algorithm directly based on the E2E-QoE.The proposed frameworks and algorithms are all validated using the data from real fifth-generation(5G)mobile system,which show that using E2E-QoE as the metric of PHY optimization is feasible and can outperform existing schemes.

关键词： quality of experience(QoE) performance metric physical layer optimization cross-layer framework

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马氏体相变的分子动力学模拟

中国材料进展 2016年第6期35卷 416-422,441页

作者：宗洪祥丁向东孙军任晓兵西安交通大学金属材料强度国家重点实验室陕西西安710049

马氏体相变作为一类重要的结构转变而广泛存在于形状记忆合金、钢铁等智能材料以及工程材料中。从原子尺度去理解马氏体相变的微观响应机制对于开发和提高这类材料的性能至关重要。主要综述了利用分子动力学的手段研究马氏体相变的相关... 详细信息

马氏体相变作为一类重要的结构转变而广泛存在于形状记忆合金、钢铁等智能材料以及工程材料中。从原子尺度去理解马氏体相变的微观响应机制对于开发和提高这类材料的性能至关重要。主要综述了利用分子动力学的手段研究马氏体相变的相关工作:首先介绍了形状记忆合金中的马氏体相变行为及其尺寸效应方面的研究进展;然后讲述了结构金属材料中的马氏体相变行为,特别是极端压缩变形条件下马氏体相变与塑性变形的交互作用机制。最后简述了目前相变模拟中存在的问题以及未来的发展进行了展望。

关键词：马氏体相变尺寸效应计算机模拟形状记忆合金结构材料

理论模拟指导宽温域大回复超弹合金设计的研究进展

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智能安全

智能安全 2024年第1期3卷 10-19页

作者：丁向东杨洋陶雪飞宗洪祥西安交通大学金属材料强度国家重点实验室西安710049

中国未来的太空探测计划聚焦于月球永久阴影区探测、小行星及火星的采样返回任务、木星系和行星际穿越探测,以及太阳系边际探测等多项深空任务。这些宏大的探索活动旨在拓展中国在深空探测方面的能力,实现重大的科学突破,并显著提升国... 详细信息

中国未来的太空探测计划聚焦于月球永久阴影区探测、小行星及火星的采样返回任务、木星系和行星际穿越探测,以及太阳系边际探测等多项深空任务。这些宏大的探索活动旨在拓展中国在深空探测方面的能力,实现重大的科学突破,并显著提升国家的航天技术。深空探测任务的日趋复杂对宽温域大变形超弹性材料提出了更高的要求。综述了过去十几年来点缺陷与马氏体相变动力学的交互作用机制及其对宽温域超弹性影响规律方面的相关研究,着重介绍了计算机模拟技术在微观尺度上理解马氏体相变的形核长大动力学规律中发挥的重要作用。充分利用计算机模拟手段,结合日趋强大的人工智能技术,不仅有助于深入理解材料性能变化的机制,还将推动新材料的设计,从而为中国的深空探测事业提供更强大的支持。

关键词：宽温域大回复超弹性分子动力学相场

Why 90%of clinical drug development fails and how to improve it?

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Acta Pharmaceutica Sinica B 2022年第7期12卷 3049-3062页

作者： Duxin Sun Wei Gao hongxiang Hu Simon Zhou Department of Pharmaceutical Sciences College of PharmacyUniversity of MichiganAnn ArborMI48109USA Translational Development and Clinical Pharmacology Bristol Meyer Squibb CompanySummitNJ07920USA

Ninety percent of clinical drug development fails despite implementation of many successful strategies,which raised the question whether certain aspects in target validation and drug optimization are overlooked?Current drug optimization overly emphasizes potency/specificity using structure-activityrelationship(SAR)but overlooks tissue exposure/selectivity in disease/normal tissues using structure-tissue exposure/selectivity—relationship(STR),which may mislead the drug candidate selection and impact the balance of clinical dose/efficacy/toxicity.We propose structure-tissue exposure/selectivity—activity relationship(STAR)to improve drug optimization,which classifies drug candidates based on drug’s potency/selectivity,tissue exposure/selectivity,and required dose for balancing clinical efficacy/toxicity.ClassⅠdrugs have high specificity/potency and high tissue exposure/selectivity,which needs low dose to achieve superior clinical efficacy/safety with high success rate.ClassⅡdrugs have high specificity/potency and low tissue exposure/selectivity,which requires high dose to achieve clinical efficacy with high toxicity and needs to be cautiously evaluated.ClassⅢdrugs have relatively low(adequate)specificity/potency but high tissue exposure/selectivity,which requires low dose to achieve clinical efficacy with manageable toxicity but are often overlooked.ClassⅣdrugs have low specificity/potency and low tissue exposure/selectivity,which achieves inadequate efficacy/safety,and should be terminated early.STAR may improve drug optimization and clinical studies for the success of clinical drug development.

关键词： Drug development Drug optimization Clinical trial Structure-tissue exposure/selectivity relationship(STR) Structure-tissue exposure/selectivity—activity relationship(STAR)