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Aging and rejuvenation during high-temperature deformation in a metallic glass

Science China(Physics,Mechanics & Astronomy) 2022年第10期65卷 93-100页

作者： langting zhang Yunjiang Wang Yong Yang Jichao Qiao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical University(NPU)Xi’an 710072China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Mechanical Engineering College of EngineeringCity University of Hong KongHong Kong 999077China Department of Materials Science and Engineering College of EngineeringCity University of Hong KongHong Kong 999077China Innovation Center NPU-ChongqingChongqing 401135China

High-temperature deformation has been demonstrated as an effective measure to rejuvenate and optimize the mechanical properties of metallic glasses(MGs).Clarifying the competition between aging and rejuvenation during high-temperature deformation is helpful in rejuvenating MGs accurately.Signatures of aging and rejuvenation in a La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10)MG were investigated via high-temperature deformation and mechanical relaxation.The coupling of thermal history,aging,and mechanical disordering determines the transient deformation and the structural state of MGs.The stress overshoot and anelastic deformation induce structural rejuvenation,increasing the concentration of defects and erasing thermal history.Therefore,the eventually steady-state condition is dependent on ambient temperature and strain rate instead of the initial structure.Furthermore,the one-to-one relationship between defect concentration and strain rate clarifies the structural nature of rejuvenation in amorphous materials.Such a relationship also contributes toward a comprehensive understanding of the structural rejuvenation behavior in amorphous materials.

关键词： metallic glass aging rejuvenation homogenous flow free volume

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The anelastic origin of mechanical cycling induced rejuvenation in the metallic glass

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Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 93-100页

作者： langting zhang Yunjiang Wang Yong Yang Jichao Qiao School of Mechanics CivilEngineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 70072China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Mechanical Engineering College of EngineeringCity University of Hong KongHong Kong 999077China Department of Materials Science and Engineering College of EngineeringCity University of Hong KongHong Kong 999077China Innovation Center NPU-ChongqingChongqing 401135China

Mechanical cycling is one of the effective methods to rejuvenate metallic glasses(MGs)and improve their mechanical properties.The anelastic origin of the rejuvenation by mechanical cycling in a La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10) MG was investigated via differential scanning calorimetry(DSC)and dynamic mechanical analysis(DMA).We demonstrate that mechanical cycling promotes the activation of flow defects with short relaxation times,leading to anelastic strains and therefore considerable energy storage,which manifests itself as larger relaxation enthalpy on the DSC curves of MGs.However,the MGs release the excess relaxation enthalpy caused by anelastic strain with time,thus suppressing atomic mobility and elevating β relaxation activation energies.The strategy of mechanical cycling at small strains,as demonstrated in the current work,can expand the energy states of MGs over a wide range of relaxation enthalpies.

关键词： metallic glass mechanical cycling rejuvenation anelastic strain structural heterogeneity

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Effect of physical aging and cyclic loading on power-law creep of high-entropy metallic glass

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Journal of Materials Science & Technology 2022年第20期115卷 1-9页

作者： langting zhang Yajuan Duan Eloi Pineda Hidemi Kato Jean-Marc Pelletier Jichao Qiao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China Department of Physics Institute of Energy TechnologiesUniversitat Politècnica de Catalunya-BarcelonaTechBarcelona 08019Spain Institute for Materials Research Tohoku UniversitySendai 980-8577Japan Universitéde Lyon MATEISUMR CNRS5510Bat.B.PascalINSA-LyonVilleurbanne Cedex F-69621France Innovation Center NPU-ChongqingChongqing 401135China

The power-law relationship between creep rate decay and time is one of the intrinsic characteristics of metallic glasses.In the current work,a La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10) high-entropy metallic glass was selected as the model alloy to test the influences of physical aging and cyclic loading on the power-law creep mechanism,which was probed by the dynamic mechanical analysis in terms of the stochastic activation,and contiguous interplay and permeation of shear transformation zones.It is demonstrated that a notable discrepancy appears between thermal treatment and mechanical treatment on the power-law creep mechanism of this high-entropy metallic glass.On the one hand,physical aging below the glass transition temperature introduces the annihilation of potential shear transformation zones which contribute to creep.On the other hand,cyclic loading can tailor the“forward”jump operations competing with the“backward”ones of shear transformation zones by controlling the interval time(recovery time).The current research offers a new pathway towards understanding the creep mechanism of high-entropy metallic glasses.

关键词： High-entropy metallic glass Physical aging Cyclic loading Power-law creep Shear transformation zone

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Dynamic mechanical relaxation and thermal creep of high-entropy La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10)bulk metallic glass

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Science China(Physics,Mechanics & Astronomy) 2021年第9期64卷 93-103页

作者： langting zhang YaJuan Duan Daniel Crespo Eloi Pineda YunJiang Wang Jean-Marc Pelletier JiChao Qiao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China Department of Physics Barcelona Research Center in Multiscale Science and TechnologyInstitute of Energy TechnologiesUniversitat Politècnica de CatalunyaBarcelona 08019Spain State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 101408China MATEIS UMR CNRS5510Universitéde LyonINSA-LyonVilleurbanne Cedex F-69621

Dynamic mechanical relaxation is a fundamental tool to understand the mechanical and physical properties of viscoelastic materials like glasses.Mechanical spectroscopy shows that the high-entropy bulk metallic glass(La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10))exhibits a distinctβ-relaxation feature.In the present research,dynamic mechanical analysis and thermal creep were performed using this bulk metallic glass material at a temperature domain around theβrelaxation.The components of total strain,including ideal elastic strain,anelastic strain,and viscous-plastic strain,were analyzed based on the model of shear transformation zones(STZs).The stochastic activation of STZ contributes to the anelastic strain.When the temperature or external stress is high enough or the timescale is long enough,the interaction between STZs induces viscous-plastic strain.When all the spectrum of STZs is activated,the quasi-steady-state creep is achieved.

关键词： high-entropy bulk metallic glass mechanical relaxation creep recovery process shear transformation zone structural heterogeneity

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Influence of oscillation strain on the dynamic mechanical relaxation of a La-based metallic glass

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Science China(Technological Sciences) 2023年第11期66卷 3309-3316页

作者： LIANG ShuYi zhang langting WANG YunJiang PINEDA E QIAO JiChao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Physics Institute of Energy TechnologiesUniversitat Politècnica de Catalunya–BarcelonaTechBarcelona 08019Spain Innovation Center NPU-ChongqingChongqing 401135China

Dynamic mechanical relaxation processes,particularly secondary relaxation processes,are closely related to the mechanical and physical properties of metallic glasses.Here the effect of oscillation strain amplitude on the secondary relaxation of a typical Labased metallic glass was studied using the dynamic mechanical analysis method.The apparent activation energy of theβrelaxation is shown to increase with the oscillation strain amplitude.When it changes from 0.02%to 0.16%,the activation energy increases from 0.73 to 0.96 eV.Simultaneously,the intensity of theβrelaxation shifts toward high temperature.Additionally,the apparentβrelaxation is found to be sensitive to the physical aging below the glass transition temperature.The findings suggest a correlation between the inelastic deformation and the relaxation behavior of amorphous metals.

关键词： metallic glass dynamic mechanical analysis internal friction βrelaxation oscillation amplitude

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Tailoring the mechanical properties of bulk metallic glasses via cooling from the supercooled liquid region

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Science China(Technological Sciences) 2023年第1期66卷 173-180页

作者： zhang langting DUAN YaJuan WANG YunJiang YANG Yong QIAO JiChao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China Department of Physics Barcelona Research Center in Multiscale Science and TechnologyInstitute of Energy TechnologiesUniversitat PolitecnicadeCatalunyaBarcelona08019Spain State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Mechanical Engineering College of EngineeringCity University of Hong KongHong Kong 999077China Department of Materials Science and Engineering College of EngineeringCity University of Hong KongHong Kong 99077China Innovation Center NPU-ChongqingChongqing 401135China

Structural rejuvenation is vital and attractive for modulating the energetic state and structural heterogeneity of bulk metallic glasses(BMGs). In this paper, we show that cooling a BMG from a supercooled liquid region at laboratory rates can reverse the relaxation enthalpy lost during the preceding structural relaxation. Increasing the cooling rate is beneficial for enhancing atomic mobility and dynamic mechanical relaxation intensity. Therefore, this rejuvenation methodology promotes tailoring the mechanical properties of BMGs and provides a comprehensive understanding of the rejuvenation mechanism.

关键词： bulk metallic glass thermal rejuvenation supercooled liquid region mechanical relaxation structural heterogeneity

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内镜下注水法冷圈套器切除术在治疗5~10 mm无蒂型大肠息肉中的疗效分析

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广州医药 2024年第3期55卷 300-305,310页

作者：张宗胜陈明仁刘浪廷李卫娜韩燕燕卢敏阳春市中医院消化内科广东阳春529600 南方医科大学珠江医院消化内科广东广州510280

目的研究注水法内镜下冷圈套器切除术在5~10 mm无蒂型大肠息肉中的临床疗效。方法纳入120例阳春市中医院收治的5~10 mm无蒂型大肠息肉患者,合计246枚息肉,根据结肠息肉切除方式不同分为内镜下注水法冷圈套器切除术(UCSP)与传统内镜下冷... 详细信息

目的研究注水法内镜下冷圈套器切除术在5~10 mm无蒂型大肠息肉中的临床疗效。方法纳入120例阳春市中医院收治的5~10 mm无蒂型大肠息肉患者,合计246枚息肉,根据结肠息肉切除方式不同分为内镜下注水法冷圈套器切除术(UCSP)与传统内镜下冷圈套器切除术(CCSP)两组,每组分别纳入60例患者。比较两组息肉部位、息肉大小、术后病理诊断、完整息肉切除率、术后病理深度、息肉回收率、手术时间、术中瞬时性出血率、迟发性穿孔率、迟发性出血率以及手术时间、Boston及视觉模拟评分法(VAS)评分。结果两组息肉部位、息肉大小、术后病理诊断、完整息肉切除率、息肉回收率、术中瞬时性出血率、迟发性穿孔率、迟发性出血率以及Boston评分比较差异均无统计学意义(P>0.05);UCSP组术后病理深度[(8.80.5)mm]大于CCSP组[(5.90.4)mm](P<0.01),CCSP组手术时间[(21.32.4)min],较UCSP组[(25.71.1)min]缩短(P<0.01),VAS评分UCSP组[(2.60.7)分]优于CCSP组[(2.90.3)分](P<0.001)。结论UCSP能有效、安全5~10 mm无蒂型大肠息肉,术后深度的病理组织学评估获得更高的肌层黏膜切除深度,虽然UCSP手术时间较长,但术后腹痛发生率较低。

关键词：注水冷圈套器切除术冷圈套息肉切除术大肠息肉瞬时性出血腹痛

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多移动机械臂动力学建模及基于零空间的协作

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力学季刊 2023年第2期44卷 281-292页

作者：王朗亭张舒同济大学航空航天与力学学院上海200092

当前机械臂需要完成的任务日益复杂,单个固定机械臂或者是移动机械臂已经不能满足需求,而多移动机械臂系统结合了移动基座的灵活性和多机械臂合作的高效性,引起了学术界的广泛关注.本文研究了在多个移动机械臂抬起目标物体后,移动平台... 详细信息

当前机械臂需要完成的任务日益复杂,单个固定机械臂或者是移动机械臂已经不能满足需求,而多移动机械臂系统结合了移动基座的灵活性和多机械臂合作的高效性,引起了学术界的广泛关注.本文研究了在多个移动机械臂抬起目标物体后,移动平台因避障而改变移动轨迹导致与机械臂末端执行器产生相对位移时,如何利用零空间概念设计保持目标物体姿态稳定的控制方法.为验证该控制方法能适用于多移动机械臂系统,对其动力学进行建模,得到了与单机械臂系统形式一致的动力学方程.最后根据该控制方法,设计了多个移动机械臂协同搬运物体时保持物体稳定的控制律并进行了数值验证.

关键词：多移动机械臂动力学模型零空间

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基于准点缺陷理论探索非晶合金蠕变机制

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力学学报 2022年第6期54卷 1590-1600,I0002页

作者：徐宗睿郝奇张浪渟乔吉超西北工业大学力学与土木建筑学院西安710072

作为典型多体相互作用非平衡体系,如何明晰非晶合金多场耦合激励下变形机制,建立非晶合金变形行为、流动特性与微观结构特征本征关联始终是非晶合金力学性能的重要研究内容.本文以具有显著β弛豫行为的La_(56.16)Ce_(14.04)Ni_(19.8)Al_... 详细信息

作为典型多体相互作用非平衡体系,如何明晰非晶合金多场耦合激励下变形机制,建立非晶合金变形行为、流动特性与微观结构特征本征关联始终是非晶合金力学性能的重要研究内容.本文以具有显著β弛豫行为的La_(56.16)Ce_(14.04)Ni_(19.8)Al_(10)非晶合金作为研究载体,通过开展宽温度应力窗口蠕变实验,着重考查了蠕变柔量、准稳态蠕变速率、特征弛豫时间、蠕变应力指数及蠕变激活能演变规律,系统研究了非晶合金蠕变行为与蠕变机制.基于准点缺陷理论分析了非晶合金蠕变行为由弹性向黏弹性及黏塑性逐步转变的过程,从微观结构演化角度构建了非晶合金蠕变行为完整物理图像.研究结果表明,非晶合金高温蠕变行为是一典型热力耦合、非线性过程,其潜在蠕变机制受控于温度、应力与加载时间.应力较低时,非晶合金蠕变机制对应于热激活单粒子流动.应力较高时,蠕变机制则对应于应力诱导局部剪切变形增强与温度诱导原子扩散等复杂耦合过程.非晶合金蠕变变形过程所涉及弹塑性转变源于非晶合金准点缺陷激活、微剪切畴经热力耦合激励形核长大、扩展与不可逆融合.

关键词：非晶合金蠕变准点缺陷理论变形机制微观结构非均匀性

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牛顿流变转变为非牛顿流变行为的教学方法

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力学与实践 2023年第5期45卷 1178-1182页

作者：乔吉超梁淑一张浪渟西北工业大学力学与土木建筑学院西安710072

牛顿流变与非牛顿流变是流体力学的重要分支。本文从基本的流变模式出发,介绍了非牛顿流变的特性与分类,引入并推导非晶合金牛顿流变转变为非牛顿流变行为的力学机制。最后介绍了假塑性流体在工程实际中的应用。本文综合作者近年来对于... 详细信息

牛顿流变与非牛顿流变是流体力学的重要分支。本文从基本的流变模式出发,介绍了非牛顿流变的特性与分类,引入并推导非晶合金牛顿流变转变为非牛顿流变行为的力学机制。最后介绍了假塑性流体在工程实际中的应用。本文综合作者近年来对于无序固体高温流变力学行为的研究结果和非牛顿流变力学的教学实践,结合了学生的学习效果,从教学内容和思路逻辑方面进行讨论。文中教学方法可为讲授非牛顿流变力学课程的教师提供借鉴。

关键词：牛顿流变非牛顿流变非晶合金教学法

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