We report results of statistical and dynamic analysis of the serrated stress-time curves obtained from compressive constant strain-rate tests on two metallic glass samples with different ductility levels in an effort to extract hidden information in the seemingly irregular serrations. Two distinct types of dynamics are detected in these two alloy samples. The stress-strain curve corresponding to the less ductile $Zr_{65}Cu_{15}Ni_{10}Al_{10}$ alloy is shown to exhibit finite correlation dimension and a positive Lyapunov exponent, suggesting that the underlying dynamics is chaotic. In contrast, for the more ductile $Cu_{47.5}Zr_{47.5}Al_{5}$ alloy, the distributions of stress drop magnitudes and their time durations obey a power law scaling reminiscent of a self-organized critical state. The exponents also satisfy the scaling relation compatible with self-organized criticality. Possible physical mechanisms contributing to the two distinct dynamic regimes are discussed by drawing on the analogy with the serrated yielding of crystalline samples. The analysis, together with some physical reasoning, suggests that plasticity in the less ductile sample can be attributed to stick-slip of single shear band, while that of the more ductile sample could be attributed to the simultaneous nucleation of large number of shear bands and their mutual interactions.
Comment on: High Mixing Entropy Enhanced Energy States in Metallic Glasses
Juntao Huo等人最近的一篇论文[Chin. Phys. Lett. 39(2022)0464011]报道了三种Zr-Ti-Cu-Ni-Be金属玻璃(MG)(包括高熵金属玻璃(HEMG))的混合熵(和相应的能态)与热稳定性和机械参数之间的相关性。作者排除了对所研究的热稳定性和机械参数变化的可能的成分贡献。
The role of minor alloying in the plasticity of bulk metallic glasses
金属玻璃的微合金化是一项技术研究。一个原来的韧性Pd基单片块状金属玻璃(Pd $_{40}$ Ni $_{40}$ P $_{20}$)选择性地操纵通过添加Fe或Co的合金化效果是极端的,表现出无论是特殊的延展性Co添加或Fe添加后,在单轴压缩或3点弯曲下测试时,立即灾难性的失败。非晶结构的特点是变形前相对于其中程秩序(MRO),使用可变分辨率波动电子显微镜(VR-FEM)。我们观察到的韧性和脆性金属玻璃之间的MRO显着差异,与韧性玻璃表现出丰富的结构多样性和MRO相关长度高达6 nm。MRO的不均匀性似乎使更容易剪切带,从而提高变形能力。
Crystallization of metallic glass as a grain-boundary nucleated process: experimental and theoretical evidence for the grain structure of metallic glasses
On the role of Sm in solidification of Al-Sm metallic glasses
在Al-Sm金属玻璃凝固过程中,过冷液体原子结构随Sm浓度的增加而逐渐演化为类二十面体团簇。与液体中剩余的团簇相比,这些团簇表现出较慢的动力学,导致增强的无定形相稳定性和玻璃形成能力(GFA)。最大的二十面体排序和原子堆积密度已被发现的Al 90 Sm 10和Al 85 Sm 15合金,分别,而最小的结合能已被发现的Al 93 Sm 7这是一致的组合物的范围内(从Al 92 Sm 8到Al 84 Sm 16)实验发现具有高GFA。
Beijing Computational Science Research Center(北京计算科学研究中心);Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences(中国科学院宁波材料技术与工程研究所);State Key Laboratory of Advanced Marine Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences(中国科学院宁波材料技术与工程研究所先进海洋材料国家重点实验室);College of Materials & Environmental Engineering, Hangzhou Dianzi University(杭州电子科技大学材料与环境工程学院);State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences(中国科学院力学研究所非线性力学国家重点实验室);School of Engineering Science, University of Chinese Academy of Sciences(中国科学院大学工程科学学院)
NOMATEN Centre of Excellence, National Center for Nuclear Research(国家核研究中心 NOMATEN 卓越中心);Center for Complexity and Biosystems, Department of Physics "Aldo Pontremoli", University of Milan(米兰大学物理学院复杂性与生物系统中心);Saarland University, Chair of Metallic Materials(萨尔兰大学金属材料讲席);Glass and Time , IMFUFA, Department of Science and Environment, Roskilde University(罗斯基勒大学科学与环境学院 IMFUFA 玻璃与时间);Department of Materials Science, Montanuniversität Leoben(莱奥本矿业大学材料科学系);Erich Schmid Institute of Materials Science, Austrian Academy of Sciences(奥地利科学院埃里希·施密德材料科学研究所);Department of Materials Science and Engineering, Johns Hopkins University(约翰斯·霍普金斯大学材料科学与工程系);Department of Mechanical Engineering, Johns Hopkins University(约翰斯·霍普金斯大学机械工程系);Department of Physics and Astronomy, Johns Hopkins University(约翰斯·霍普金斯大学物理与天文学系);Hopkins Extreme Materials Institute, Johns Hopkins University(约翰斯·霍普金斯大学霍普金斯极端材料研究所);Technical University of Berlin, Chair of Metallic Materials(柏林工业大学金属材料讲席)
Nucleation of Al Nanocrystals in Solute-Substituted Al Metallic Glasses I: Structural characterization
高Al含量金属玻璃中的一次晶化是由内部结构类似于面心立方Al的纳米尺度区域驱动的。通过比较涨落电子显微镜(FEM)数据和FEM模拟的面心立方Al团簇在致密随机堆积基质中的分布,提取Al 88 Y 7 Fe 5基础玻璃和Al含量为1 at.%的玻璃中有序区域的直径和体积分数Cu替代Y或Al。纳米晶体的尺寸和密度作为等温退火时间的函数,对于相同的合金进行测量。在等温退火条件下,晶相的体积分数增加,相变不是单纯的晶粒粗化,而是晶相的体积分数低于淬火态样品中有序区的体积分数,因此并非所有有序区都起到晶核的作用。合金化有序区域的直径和体积分数的变化与结晶温度、成核速率和结晶密度的变化相关。没有观察到相分离的证据,相似组成的分子动力学淬火结构模型的FEM模拟没有显示实验中观察到的特征。
From metallic glasses to nanocrystals: Molecular dynamics simulations on the crossover from glass-like to grain-boundary-mediated deformation behaviour
Transmutation-accelerated sampling method for multi-component ZrCu(Al) metallic glasses
NOMATEN Centre of Excellence, National Center for Nuclear Research(NOMATEN卓越中心,国家核研究中心);Univ. Lyon, INSA-Lyon, CNRS, LaMCoS, UMR 5259(里昂大学,里昂国立应用科学学院,法国国家科学研究中心,LaMCoS实验室);Laboratoire de Mécanique des Solides, CNRS, Ecole Polytechnique(固体力学实验室,法国国家科学研究中心,巴黎综合理工学院);Aalto University(阿尔托大学)
Influence of Similar Atom Substitution on Glass Formation in (La-Ce)-Al-Co Bulk Metallic Glasses
采用铜模铸造法分别确定了La-Al-Co、Ce-Al-Co和准三元(La-Ce)-Al-Co系镧基和铈基块体非晶合金的玻璃形成范围。通过在(La_xCe_(1-x))_(65)Al_(10)Co_(25)合金(0<x<1)中用La逐步取代溶剂Ce,可成功地用倾斜浇注法制备出直径达25 mm的(La_(0.7)Ce_(0.3))Al_(10)Co_(25)合金全玻璃棒材。与单一镧系合金La 65 Al 10 Co 25和Ce 65 Al 10 Co 25的玻璃形成能力相比,具有相似原子尺寸和不同价电子结构的La和Ce的共存明显提高了(LaxCe 1-x)65 Al 10 Co 25非晶合金的玻璃形成能力,这不能用以往的非晶合金玻璃形成判据(如原子尺寸失配和负混合热)来解释。提出了一个热力学模型来评价这种替代效应,这对相似原子共存引起的GFA的明显提高给出了合理的解释。