Article
Materials Science, Multidisciplinary
Ziqiang Wang, Miaosen Yu, Xuehao Long, Chen Yang, Ning Gao, Zhongwen Yao, Xuelin Wang
Summary: In this study, molecular dynamics simulations were used to investigate the interaction mechanisms between dislocations and radiation defects in irradiated metals. Three new kinetic mechanisms were proposed, and it was found that the specific characteristics of the dislocation loops determine the dominant mechanism for the interaction with dislocation lines. The results also showed that the critical stress for the dislocation to cross the loop varied due to the interactions involved in these new mechanisms.
RESULTS IN PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Yu-Hao Li, Hong-Bo Zhou, Fei Gao, Gang Lu, Guang-Hong Lu, Feng Liu
Summary: This study uses first-principles calculations to reveal the effect of hydrogen on screw dislocations in bcc tungsten, finding that this effect depends on the concentration of hydrogen. Low concentrations of hydrogen enhance dislocation motion, while high concentrations significantly reduce dislocation mobility and lead to a transformation of dislocation structure. Similar structural transitions can be induced by other solutes.
Article
Materials Science, Multidisciplinary
T. Katiyar, E. Van der Giessen
Summary: Two-dimensional discrete dislocation plasticity (2D-DDP) is a powerful tool for studying microplasticity problems, with challenges in modifying the dislocation evolution rules for different crystal structures and mapping different dislocation mobilities to an effective mobility. A proposed 3D-to-2D procedure allows for the computation of effective 2D mobility for BCC materials based on their edge and screw mobilities, validated by comparing predicted rate sensitivity with experimental results for polycrystalline iron.
COMPUTATIONAL MATERIALS SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Peng Zhang, Pengming Cheng, Jinyu Zhang, Gang Liu, Jerome Weiss, Jun Sun
Summary: The intermittent plasticity of pure Mo microcrystals was studied to explore its dependence on external size and temperature. The study found that there is a coupled size and temperature effect on the mild-to-wild transition in plastic fluctuations. Strain-rate sensitivity tests were conducted, indicating that mild plasticity is associated with screw dislocation motions controlled by thermally activated nucleation of kink-pairs, while wild plasticity is nearly athermal. A controlling parameter based on a simple dislocation source model was proposed to unify the coupled sample size and temperature effects on the mild-to-wild transition, which could have practical significance for microscale applications.
Article
Nuclear Science & Technology
Kulbir Singh, C. Robertson, A. K. Bhaduri
Summary: The mechanical response and lifetime of nuclear structural materials are strongly affected by radiation effects. The current work models the irradiation effect to predict the dose-dependent changes in effective dislocation mobility, focusing on the defect-induced apparent temperature shift.
PROGRESS IN NUCLEAR ENERGY
(2021)
Article
Materials Science, Multidisciplinary
Rakesh Kumar Barik, Sankalp Biswal, Amlan Dutta, Debalay Chakrabarti, Abhijit Ghosh
Summary: Screw dislocation motion in bcc Fe has a significant impact on the temperature and strain rate sensitivity of flow stress, leading to the transition from ductile to brittle behavior in steel. Addition of solute atoms with attractive interaction with screw dislocations can reduce the flow stress sensitivity of Fe. This study investigates the effect of Ni and Cu solute atom distribution on screw dislocation motion in bcc Fe through molecular statics and dynamics simulations. Results show that the local distribution of Ni atoms greatly influences the Peierls stress of Fe, while Cu atom distribution has minimal effect. Furthermore, the presence of Ni/Cu atoms ahead of the dislocation line helps reduce the Peierls stress due to the attractive interaction with dislocations.
COMPUTATIONAL MATERIALS SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Sergei Starikov, Vahid Jamebozorgi, Daria Smirnova, Ralf Drautz, Matous Mrovec
Summary: Screw and edge dislocations in body-centered cubic transition metals exhibit distinct diffusion characteristics, with the migration along screw dislocations being faster due to their different atomic structures.
Article
Materials Science, Multidisciplinary
Xinran Zhou, Sicong He, Jaime Marian
Summary: Research on refractory multi-element alloys with body-centered cubic structure has shown that chemical energy fluctuations play a significant role in their strength at high temperatures, which cannot be explained by standard models. The formation of cross kinks and self-pinning have been identified as key contributors to the alloy's strength.
Article
Materials Science, Multidisciplinary
S. Rao, C. Woodward, B. Akdim
Summary: In this study, solute-dislocation interaction energies are calculated using Density Functional Theory (DFT) and the 2-D lattice Greens function approach. These predictions are then used in an extension of the Rao-Suzuki model to analyze solid solution strengthening and softening in various crystals. The refined model shows good agreement with experimental observations and can be used in designing high strength, multi-component BCC alloys for high temperature applications.
Article
Materials Science, Multidisciplinary
Xuehui Yan, Peter K. Liaw, Yong Zhang
Summary: Extraordinary strength and good tensile ductility are achieved in (Zr0.5Ti0.35Nb0.15)(100-x)Al-x alloys at room temperature. The relatively low densities exhibited in these alloys make them attractive structural materials. Designing nanoprecipitates and diversifying dislocation motions play key roles in achieving such breakthrough.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2022)
Article
Materials Science, Multidisciplinary
Soumya Sourav Sarangi, Anand K. Kanjarla
Summary: This study investigates the effect of introducing carbon atoms into the core of screw dislocations in body centered iron. The results show that the core reconstruction leads to changes in the symmetry of the dislocation core and asymmetry in the twinning-antitwinning critical resolved shear stress (CRSS). Furthermore, the loading conditions also influence the CRSS of the dislocation core.
MATERIALS TODAY COMMUNICATIONS
(2022)
Article
Materials Science, Multidisciplinary
Nikolay Zotov, Blazej Grabowski
Summary: The screw dislocation mobility in bcc Nb was studied through molecular dynamics simulations, showing that the elementary slip plane remains the same while consecutive cross-slip on different symmetry-equivalent planes leads to effective glide. The screw dislocation trajectories, velocities, and waviness depend on the crystallographic indices of the maximum resolved shear stress plane, with the waiting time for screw dislocation motion increasing exponentially with decreasing strain rate.
MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING
(2021)
Article
Physics, Condensed Matter
Jingjing Wu, Tianru Han, Xin Tang
Summary: The electronic structure and magnetic coupling mechanism of Zn vacancies in screw dislocations in zinc oxide nanowires were investigated using density functional theory. It was found that under specific strains, stable V-Zn pairs could be formed to achieve long-range ferromagnetic ordering.
SOLID STATE COMMUNICATIONS
(2021)
Article
Physics, Multidisciplinary
Wang Jin, He Xin-Fu, Cao Han, Jia Li-Xia, Dou Yan-Kun, Yang Wen
Summary: RAFM steel is a candidate material for future fusion reactors. The behavior of screw dislocation at different temperatures and the mechanism of interaction between screw dislocation and dislocation loops are temperature-dependent.
ACTA PHYSICA SINICA
(2021)
Article
Chemistry, Physical
Xu Li, Ran Zhang, Shuo Li, Yalei Wang, Lei Cui, Yaxuan Yao, Lingling Ren, Xueshen Wang, Senlin Jin, Yi Zhang, Xingfu Tao
Summary: This study investigates strains, microstructures, and dislocations at crack tips on silicon. Anisotropic strain distributions and strain concentration zones were observed at crack tips on different crystal planes. The generation of dislocations was found to be the main cause of plastic deformation and strain concentration. The presence of strain concentration zones and material resistance inhibited further crack propagation.
APPLIED SURFACE SCIENCE
(2022)
Article
Physics, Multidisciplinary
Stefanos Papanikolaou, Giacomo Po
PHYSICAL REVIEW LETTERS
(2020)
Article
Materials Science, Multidisciplinary
Sabyasachi Chatterjee, Giacomo Po, Xiaohan Zhang, Amit Acharya, Nasr Ghoniem
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2020)
Article
Nuclear Science & Technology
Michael Mahler, Giacomo Po, Yinan Cui, Nasr Ghoniem, Jarir Aktaa
Summary: The role of hierarchical defects microstructure of ferritic-martensitic steel Eurofer97 in determining hardening behavior is investigated using Dislocation Dynamics (DD) simulations. Material properties and dependence on temperature are determined, and microstructure-specific hardening parameters are extracted for simulating the properties of Eurofer97 at the engineering scale.
NUCLEAR MATERIALS AND ENERGY
(2021)
Article
Engineering, Mechanical
Pratyush Srivastava, Katherine Jiang, Yinan Cui, Edgar Olivera, Nasr Ghoniem, Vijay Gupta
Summary: Experimental results show that reducing sample size can decrease the strain rate sensitivity of plastic flow, including flow stress and strain burst statistics. Nano-sized samples exhibit more stable scaling effects, while micron-sized samples show truncated scaling effects.
INTERNATIONAL JOURNAL OF PLASTICITY
(2021)
Article
Engineering, Mechanical
Cameron McElfresh, Yinan Cui, Sergei L. Dudarev, Giacomo Po, Jaime Marian
Summary: Dislocation climb, a crucial high-temperature process in metal plasticity, is controlled by point defect diffusion and thermal activation. A new kinetic Monte Carlo model has been developed to study vacancy generation and transport kinetics in conjunction with evolving elastic fields, revealing surprising results such as dominance of vacancy emission in climb and faster climb velocities than expected. This discrete approach offers insights not captured by classical theories based on smooth vacancy fluxes.
INTERNATIONAL JOURNAL OF PLASTICITY
(2021)
Article
Materials Science, Multidisciplinary
Hengxu Song, Nina Gunkelmann, Giacomo Po, Stefan Sandfeld
Summary: A novel data-mining approach is proposed to extract energy density data from systems of discrete dislocations, resulting in energy density formulations through analysis of the data sets. This method addresses the long-standing issue of energy calculation during coarse graining of dislocation microstructures, making it crucial for continuum dislocation dynamics simulations.
MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING
(2021)
Article
Materials Science, Multidisciplinary
Yang Li, Sabyasachi Chatterjee, Enrique Martinez, Nasr Ghoniem, Giacomo Po
Summary: In the model, basal-to-prismatic cross-slip is energetically favorable, while prismatic-to-basal cross-slip is only activated under specific conditions. The proposed mechanism for basal slip of <a> screw dislocations in Zr involves the formation and lateral migration of kink pairs formed by double cross-slip.
Article
Materials Science, Multidisciplinary
Yinan Cui, Nasr Ghoniem, Giacomo Po
Summary: This study reviewed recent work on plastic deformation in irradiated materials at the nano- and micro scales using Discrete Dislocation Dynamics (DDD) simulations. The simulations provided new insights into collective dislocation-irradiation defect interactions, as well as the temporal and spatial characteristics associated with plastic instabilities. The development of theoretical models and probability models advanced the understanding of plastic flow localization in irradiated materials for the design of future radiation-resistant materials.
JOURNAL OF NUCLEAR MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Qianran Yu, Sabyasachi Chatterjee, Kenneth J. Roche, Giacomo Po, Jaime Marian
Summary: Irradiation damage alters a material's microstructure and mechanical response due to the accumulation of defect clusters. A coupled CP and SCD approach is developed to handle all instances of irradiation/deformation in irradiated materials, with SCD evolving the defect microstructure stochastically and providing a statistically-averaged defect cluster spacing parameter for CP calculations. The coupling is bi-directional, where SCD updates obstacle density and furnishes resistance stress to the CP model, while CP feeds updated dislocation densities acting as defect sinks in the SCD calculation cycles.
MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING
(2021)
Article
Materials Science, Multidisciplinary
Pratyush Srivastava, Koichi Tanaka, Brian Ramirez, Vijay Gupta
Summary: This study reports the nucleation of the Stishovite phase in shock-loaded soda-lime glass samples at a low compressive stress of 7 GPa. Experimental methods such as using a table-top setup and HRTEM imaging revealed 4 nm Stishovite crystals distributed within the amorphous SLG matrix.
Article
Engineering, Mechanical
Sabyasachi Chatterjee, Yang Li, Giacomo Po
Summary: Order strengthening in nickel-based superalloys is related to the additional stress required for dislocations to bypass gamma' precipitates in the gamma matrix. Various bypass mechanisms have been identified depending on operating conditions and microstructure, transitioning from shearing and looping to climb bypass as conditions change. A hybrid mechanism may also operate, supported by indirect experimental evidence.
INTERNATIONAL JOURNAL OF PLASTICITY
(2021)
Article
Materials Science, Multidisciplinary
Yang Li, Nasr Ghoniem, Kristopher Baker, Benjamin Ramirez Flores, Thomas Black, James Hollenbeck, Giacomo Po
Summary: We propose a novel model to study the climb/glide motion of jogged screw dislocations within the discrete dislocation dynamics (DDD) framework. We show that the model predictions are consistent with experimental data in both gamma-TiAl and Zircaloy-4. Based on simulations and a detailed examination of the predicted jog heights, we advance the hypothesis that a combination of jog dragging and dipole bypass mechanisms is necessary to reproduce the high creep rate observed in some experiments.
Article
Materials Science, Multidisciplinary
Giacomo Po, Yue Huang, Yang Li, Kristopher Baker, Benjamin Ramirez Flores, Thomas Black, James Hollenbeck, Nasr Ghoniem
Summary: This article develops a framework to investigate thermal creep and annealing in finite domains by coupling the climb motion of discrete dislocations with the diffusion of a continuum vacancy field. It formulates a model using irreversible thermodynamics and linearizes it for implementation in three-dimensional discrete dislocation dynamics simulations. The framework includes both diffusional creep and dislocation creep, and is applied to simulate annealing and estimate creep rate in various materials under different conditions.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2022)
Article
Materials Science, Multidisciplinary
Yang Li, Giacomo Po, Nasr Ghoniem