Article
Materials Science, Multidisciplinary
Dihui Ruan, Sylvain Patinet, Michael L. Falk
Summary: By applying the local yield stress (LYS) method to probe local regions of three-dimensional computational glass models, high correlations were confirmed between the measured local yield stress (Delta tau(c)) and plastic events when the method was properly optimized. The optimal probing region was found to be around 5 sigma in radius, with the averaged correlation remaining positive through the first 200 identified plastic events or 1/3 of the yielding strain.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2022)
Article
Chemistry, Physical
Yuexin Chu, Guishen Zhou, Yue Zhang, Fuyu Dong, Xiaoguang Yuan, Binbin Wang, Liangshun Luo, Yanqing Su, Weidong Li, Peter K. Liaw
Summary: This study investigates the heterogeneity of Shear Transformation Zones (STZs) in Zr-based metallic glasses (MGs) using different nanoindentation methods. The results show that the calculated volume of STZs varies depending on the method used, and is influenced by the Poisson's ratio and loading rate.
Review
Chemistry, Physical
D. Sopu
Summary: The complex nature of shear banding and the disordered structure of metallic glasses pose challenges in understanding the mechanisms of strain localization and shear band formation. The percolation of shear transformation zones (STZs) is widely accepted as the atomic-scale mechanism for shear banding. This review provides an up-to-date assessment of the STZ-Vortex mechanism and its applications in understanding shear band dynamics and deformation mechanisms in metallic glasses. It also highlights unresolved issues where the STZ-Vortex model could be effectively applied.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Engineering, Mechanical
Yucong Gu, Jonathan Cappola, Jian Wang, Lin Li
Summary: This study investigates the yielding behavior of heterogeneous metallic glasses (MGs) by varying the spatial correlation and standard deviation of local shear moduli associated with clustering atoms on the nanoscale. Through computations and observations, the study proposes a Hall-Petch-like relationship where the yield stress of MGs scales inversely with the square root of the spatial correlation length. The results provide insights into the structure-property relationship of MGs and have important implications for the design of nanoscale MGs with tunable properties.
INTERNATIONAL JOURNAL OF PLASTICITY
(2023)
Article
Chemistry, Physical
Yuexin Chu, Guishen Zhou, Shaoshan Wan, Yue Zhang, Fuyu Dong, Xiaoguang Yuan, Binbin Wang, Liangshun Luo, Yanqing Su, Weidong Li, Peter K. Liaw
Summary: The relationship between shear transformation zones (STZs) and serrated flow dynamics in metallic glasses (MGs) was analyzed using nanoindentation. Different plasticity MGs were studied, and two distinct types of serrated flow dynamics were identified. MGs with easily activated STZs or low loading rates exhibited a power-law distribution, indicating a self-organized critical state. In contrast, hard MGs or high loading rates showed a Gaussian distribution, indicating a chaotic state with reduced stresses required for plastic deformation.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Materials Science, Multidisciplinary
Rong-Hao Shi, Yi-Cheng Wu, Fei Shuang, Zhi-Wei Zhang
Summary: This study unveils the nature of localized shear transformations (ST) in metallic glasses (MGs) through simulations and analysis, showing that pure shear or tension STs are well-known quadrupoles, while torsion or simple shear STs exhibit strong dipolar characteristics, providing explanations for shear-induced dilatation and shear-vortex coupling. Initial ST events involve shear and dilatation quadrupoles. As spatiotemporal coupling intensifies, ST is dominated by dipoles and vortices, leading to self-assembly and percolation. These findings enhance our understanding of the plastic deformation of MGs based on the evolution of quadrupolar/dipolar characteristics.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Jian Luo, Liping Huang, Yunfeng Shi, Binghui Deng
Summary: We conducted molecular dynamics simulations on metallic glasses to investigate the dynamics of shear band propagation. Our findings reveal that shear bands in metallic glasses exhibit supersonic propagation speed, microbranching, and velocity fluctuations, indicating intrinsic instability. The intersection of two shear bands under tension also leads to path deflection, speed slowing-down, and temperature rise at the junction region. These results suggest that shear bands in metallic glasses can be viewed as shear cracks in weakly nonlinear fracture mechanics theory.
Article
Chemistry, Physical
Xiaojun Sun, Jie He, Dunbo Yu, Yang Luo, Zilong Wang, Yuanfei Yang
Summary: This work investigates the relationship between structural heterogeneity and serrated flow in nanoscale phase separated Zr-Cu-Fe-Al bulk metallic glasses with different plasticity. The results show that as the atomic ratio of Cu to Fe increases, serration dynamics transform from a chaotic state to a self-organized critical state. This transformation is attributed to the increase in structural heterogeneity, which promotes the formation of multiple shear bands.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Review
Chemistry, Physical
Michael Atzmon, Jong Doo Ju, Tianjiao Lei
Summary: The lack of periodicity and long-range order in metallic glasses presents significant challenges in explaining their properties. By using quasi-static anelastic relaxation, researchers have obtained relaxation-time spectra for several metallic glasses, enabling them to examine the distribution and properties of shear transformation zones in microscopic detail. The results reveal an atomically-quantized hierarchy of shear transformation zones, providing insights into structural relaxation, plasticity, and the mechanisms of alpha and beta relaxation.
Article
Chemistry, Physical
Xiaojun Sun, Jie He, Hongxiang Jiang, Lili Zhang, Jiuzhou Zhao
Summary: By using microalloying elements to tailor the microstructure, a honeycomb-like heterogeneous structure is formed in Cu-Fe-Zr MGs, and the correlation between the heterogeneous structure and the deformation behavior is discussed. Nanoscale glassy particles play an interesting role in the evolution of local structure, indicating a significant decrease in the volume of shear transformation zone in heterogeneous MGs. This work is valuable for understanding the relationship between structure and property of MGs.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Materials Science, Ceramics
Yun-Long Guan, Lian-Song Dai, Jian-Li Shao, Wei-Dong Song
Summary: The research investigates the void evolution in Cu50Zr50 metallic glasses under different shock intensities through molecular dynamics simulations. Two typical mechanisms for void collapse, as well as the domination of different stress types under weak and strong shocks, are identified. Additionally, the activity and correlation of clusters in the shear transformation zones are explored, showing changes in behavior under different shock intensity levels.
JOURNAL OF NON-CRYSTALLINE SOLIDS
(2021)
Article
Materials Science, Multidisciplinary
Xiangkui Liu, Jian Kong, Xinxiang Song, Shuai Feng, Qipeng Wang, Yang Yang, Tianchi Wang
Summary: The size dependence of ductile to brittle transition in Zr-based metallic glasses was investigated through small punch test, revealing a significant difference in behavior between thin and thick samples. Two critical deformation factors, alpha(c1) and alpha(c2), were identified at sample thicknesses of 200 and 500 mm, triggering the initiation of circumferential and radial shear bands respectively. The interaction of multiple shear bands significantly enhances the ductility of samples with alpha >= alpha(c1).
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2021)
Article
Nanoscience & Nanotechnology
H. Zhang, Z. Wang, H. J. Yang, X. H. Shi, P. K. Liaw, J. W. Qiao
Summary: Based on microscopic mechanisms, a constitutive equation for crack-like propagation velocity and a flow model for bulk metallic glasses (BMGs) are derived. The model explains the fundamental deformation of BMGs and accurately predicts the transition between serrated and non-serrated flows. The results are consistent with experimental data, providing a theoretical basis for plastically processing BMGs.
SCRIPTA MATERIALIA
(2023)
Article
Multidisciplinary Sciences
Zhen Zhang, Jun Ding, Evan Ma
Summary: Plastic flow in metallic glasses is not caused by identifiable local defect regions. Through a realistic model, we found that shear transformations involve only a small percentage of atoms and their locations and distribution vary under different mechanical loading conditions.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Chemistry, Physical
Y. S. Luo, J. J. Li, Z. Wang, M. Zhang, J. W. Qiao
Summary: Based on a simple mean-field model, two distinct types of slip avalanches in serrated plastic flows of bulk metallic glasses were identified to differentiate the slipping modes of shear bands under various strain rates. Small avalanches propagate progressively, while large avalanches follow a simultaneous propagation. By defining a weakening parameter and critical size, researchers were able to characterize the completely disparate shearing modes, with larger weakening and lower critical sizes indicating more activated shear transformation zones, offering a new method to explore plasticity in bulk metallic glasses.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Materials Science, Multidisciplinary
Zhenzhen Yan, Howard Sheng, Evan Ma, Bin Xu, Jinfu Li, Lingti Kong
Summary: This study analyzed the structural evolution at the crystal/liquid interface in deeply undercooled elemental metallic liquids, focusing on the transition of DILPs preceding the growing BCC crystal and the differences between BCC and FCC forming cases. It was found that under large undercooling, the transition of DILP motifs into the expanding crystal requires cooperative and collective rearrangement with an appreciable energy barrier, while the intermediate structural motifs in FCC-forming cases primarily exist in the form of 1D chains. These differences in transitional motifs and associated activation energy barrier provide insight into the varying crystal growth speeds of BCC and FCC metals in deeply undercooled liquids.
Article
Materials Science, Multidisciplinary
Bin Xu, Michael L. Falk, Sylvain Patinet, Pengfei Guan
Summary: Research has shown that atomic nonaffinity is an effective indicator for describing the position of shear transformation zones and predicting plastic events, with high predictive capacity. Furthermore, by analyzing the angle between atomic nonaffinity and the shear loading direction, it is possible to predict the protocol-dependent response of shear transformation zones.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Zhenzhen Yan, Bin Xu, Jinfu Li, Lingti Kong
Summary: The study established a strong correlation between the density of defected atom pairs at the crystal-liquid interface and the activation energy for crystal growth, revealing that the orientations of interstitial pairs at the interface play a significant role in determining the local structure, energy, and crystal growth kinetics.
COMPUTATIONAL MATERIALS SCIENCE
(2022)
Article
Materials Science, Ceramics
Gongji Yang, Longfei Liu, Jiaojiao Yi, Lingti Kong, Jinfu Li
Summary: The surface microstructure and atomic dynamic property of a metallic glass nano pillar were investigated using molecular dynamics simulations. It was found that the surface contains a large number of unstable bonded pairs and clusters, leading to a liquid-like structural property. The atomic mobility on the surface is significantly enhanced, and the overall degree of medium-range order is lower compared to the core region. The surface can be divided into three consecutive sublayers: solid-like layer, semisolid layer, and liquid-like layer.
JOURNAL OF NON-CRYSTALLINE SOLIDS
(2022)
Article
Materials Science, Multidisciplinary
Dihui Ruan, Sylvain Patinet, Michael L. Falk
Summary: By applying the local yield stress (LYS) method to probe local regions of three-dimensional computational glass models, high correlations were confirmed between the measured local yield stress (Delta tau(c)) and plastic events when the method was properly optimized. The optimal probing region was found to be around 5 sigma in radius, with the averaged correlation remaining positive through the first 200 identified plastic events or 1/3 of the yielding strain.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2022)
Article
Materials Science, Multidisciplinary
Suhas Eswarappa Prameela, Peng Yi, Yannick Hollenweger, Burigede Liu, Joey Chen, Laszlo Kecskes, Dennis M. Kochmann, Michael L. Falk, Timothy P. Weihs
Summary: Magnesium alloys have great potential for structural applications due to their low density. The addition of other elements improves their mechanical properties and corrosion resistance. The formation of solute clusters and precipitates in the magnesium matrix significantly affects the alloy's plastic response. Plastic deformation during thermomechanical processing also impacts the formation of solute clusters and precipitates. This paper discusses the improvement of mechanical properties in magnesium alloys and strategies for optimizing microstructures.
MECHANICS OF MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Caihao Qiu, Yishi Su, Jingyu Yang, Boyang Chen, Lingti Kong, Qiubao Ouyang, Di Zhang
Summary: This study investigates the interfacial structures and formation mechanisms of precipitates in Al-Li alloys. The researchers found that the models with bridge- and hollow-stacking sequences generate the most stable energy-based interfaces. Additionally, the Al3Zr/Al interfaces possess larger Young's moduli and tensile strengths than the Al3Li/Al and Al3Li/Al3Zr interfaces.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2022)
Article
Education & Educational Research
Ramon S. Barthelemy, Madison Swirtz, Savannah Garmon, Elizabeth H. Simmons, Kyle Reeves, Michael L. Falk, Wouter Deconinck, Elena A. Long, Timothy J. Atherton
Summary: This article presents the first study on the experiences of LGBT+ physicists, highlighting the discrimination and exclusionary behavior they face in the workplace. Gender and transgender participants were found to be the most affected. The results indicate the need for further research on the challenges faced by LGBT+ physicists.
PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH
(2022)
Article
Physics, Applied
Zhenzhen Yan, Bin Xu, Feifei Wang, Jinfu Li, Ling Ti Kong
Summary: The atomic crystallization behaviors at the crystal-melt interfaces in FCC Cu and BCC Ta metals were investigated using molecular dynamics simulations. The study revealed the presence of ballistic attachments during crystal growth, with a small increment of diffusive attachments at the Ta interface leading to a significant energy barrier for crystallization. Additionally, it was found that the crystallization rate is mainly influenced by atomic transformation displacement and interfacial atomic movement rate.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Z. Fan, E. Ma, M. L. Falk
Summary: We report atomistic simulation results showing that the location of shear banding in a metallic glass can be accurately determined from the undeformed static structure. Our findings demonstrate a correlation between the initiation of shear bands and the initial distribution of density of fertile sites for stress-driven shear transformations. Furthermore, we show that the initial distribution of density of fertile sites can be used to determine whether a glass is brittle or ductile. These results validate the existence of nonlinear instabilities in shear bands of metallic glass and highlight the influence of inhomogeneities in the as-quenched glass structure. Additionally, we reveal an important detail regarding the nondeterministic nature of athermal quasistatic shear simulations.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Materials Science, Ceramics
Gongji Yang, Longfei Liu, Jiaojiao Yi, Jinfu Li, Lingti Kong
Summary: This study investigated the evolution of MRO structures in nano metallic glasses under torsion deformation using molecular dynamics simulations. The study found an interesting outside-in disintegration of MROs and explored the mechanism behind this disintegration.
JOURNAL OF NON-CRYSTALLINE SOLIDS
(2022)
Article
Nanoscience & Nanotechnology
T. T. Sasaki, J. Y. Lin, P. Yi, Z. H. Li, S. E. Prameela, A. Park, E. Lipkin, A. Lee, M. L. Falk, T. P. Weihs, K. Hono
Summary: In this study, the deformation-induced precipitation of G.P. zones in Mg-9Al and Mg-5 Zn alloys during equal channel angular extrusion has been reported. Atom probe tomography and hybrid molecular dynamics/Monte Carlo simulations suggest that strategic control of atomic-scale defects can generate novel microstructures, thereby strengthening the deformed Mg alloys.
SCRIPTA MATERIALIA
(2022)
Article
Materials Science, Multidisciplinary
W. Li, L. T. Kong, J. F. Li
Summary: This paper investigates the effect of Si addition on the crystallization behavior by preparing a series of (Al86Ni9Y5)100-xSix (x = 0, 1, 2, 3, 4, 5) amorphous ribbons. The results show that Si addition enhances the chemical heterogeneity and promotes the abnormal crystallization of α-Al. However, with the increase of Si content, the crystallization of Al3Ni and Al3Y advances, leading to the disappearance of the abnormal crystallization.
MATERIALS CHARACTERIZATION
(2022)
Article
Materials Science, Multidisciplinary
Haojie Mei, Feifei Wang, Jinfu Li, Lingti Kong
Summary: The temperature-dependent phonon dispersions of BCC iron and tungsten were measured using molecular dynamics simulations. Based on these simulations, the elastic constants and elastic anisotropy were derived. The results showed that the elastic constants decrease with increasing temperature, while the elastic anisotropy generally increases. It was found that the lattice thermal expansion dominates the decrease in elastic constants, while the lattice thermal vibration enhances the elastic anisotropy.
MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING
(2023)
Article
Chemistry, Physical
Jingyi Lin, Xin Li, Zhiliang Wang, Runlu Liu, Hui Pan, Yixin Zhao, Lingti Kong, Yao Li, Shenmin Zhu, Lianzhou Wang
Summary: This study selected low-cost 1,3,5-benzenetricarboxylic acid as a surface passivator for bismuth vanadate photoanodes, improving their performance and charge transfer efficiency through interfacial chemical bonding.
