Molecular Dynamics Based Study on Ductility Enhancement Effect of Nano-scale Void in Fine-grained Metallic Materials

2012 ◽  
Vol 1470 ◽  
Author(s):  
Shin Taniguchi ◽  
Toshihiro Kameda ◽  
Toshiyuki Fujita
Keyword(s):  
Molecular Dynamics ◽  
Grain Size ◽  
Dynamics Simulation ◽  
Transgranular Fracture ◽  
Metallic Materials ◽  
Void Size ◽  
Dislocation Activity ◽  
Fine Grained ◽  
Nano Scale ◽  
Activity Enhancement

ABSTRACTIn fine-grained metallic materials, the dominant grain boundary (GB) process, such as dislocation emission, dislocation absorption, and dislocation pile-up, causes non-uniform deformation, which results in high yield stress and low ductility. When a nano-scale void is introduced, the dislocation activity enhancement around the void could inhibit GB fracture and enhance ductility. In this study, by considering nanocrystalline Cu models, the influence of an intragranular nano-scale void on the fracture process has been investigated through molecular dynamics simulation. The dependence of ductility enhancement on the grain size and void size has especially been discussed at low and room temperatures. Sufficient dislocation activity enhancement accompanied by optimal void growth causes a fracture mode transition from GB fracture to transgranular fracture. While the ductility enhancement strongly depends on the void size at low temperature, it depends on the grain size at room temperature. The strong dependence of ductility enhancement on the temperature is found in the case of relatively small grains.

Molecular dynamics simulation of grain size effect on friction and wear of nanocrystalline zirconium

2020 ◽  
pp. 135065012094507
Author(s):  
Kehao Zhu ◽  
Xiaoyu Zhang ◽  
Xinlu Yuan ◽  
Gen Li ◽  
Pingdi Ren
Keyword(s):  
Molecular Dynamics ◽  
Grain Size ◽  
Molecular Dynamics Simulation ◽  
Friction And Wear ◽  
Atomic Displacement ◽  
Dynamics Simulation ◽  
Friction Forces ◽  
Grain Sizes ◽  
Crystalline Substrate ◽  
Boundary Rotation

In this study, molecular dynamics simulation was conducted to investigate the frictional behaviors between diamond tool and zirconium (Zr) substrates at the nanoscale. The effects of grain size on friction and wear were discussed under different sliding velocities. The simulation results showed that the friction forces had similar variation tendencies under different sliding velocities. Besides, the friction responses were stronger at high sliding velocities because of the atomic adhesion while the ploughing effect was more obvious at slower sliding velocity. Moreover, both the friction forces and the wear amounts increased with the decrease in the average grain sizes of the substrates. To explain this phenomenon, the internal mechanism was investigated by using the dislocation extract algorithm and the atomic displacement analyses. The results showed that the [0001]-oriented single crystalline substrate was prone to form continuous dislocation structures moving tangentially along the sliding direction due to the characteristic of Zr's slip systems, whereas grain boundaries conducted the deformation further into the polycrystalline substrates, increasing the contact areas and causing atomic accumulation in front, both resulted in stronger friction responses and wear. Accordingly, with the decrease in average grain sizes, the substrates experienced more severe subsurface damage and the deformation mechanism of nanocrystalline Zr had evolved from dislocation emission to grain boundary rotation and sliding.

A131 Nano-scale sputtering behavior in Focused Ion Beam Processing via Large-Scale Molecular Dynamics Simulation

2006 ◽  
Vol 2006 (0) ◽  
pp. 17-18
Author(s):  
Shin-ichi Satake ◽  
Natsuki Inoue ◽  
Jun Taniguchi ◽  
Masahiko Shibahara ◽  
Tomoyuki Tsuchida ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Large Scale ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Dynamics Simulation ◽  
Nano Scale

Grain Refinement of Copper Alloys by Equal Channel Angular Pressing

2004 ◽  
Vol 449-452 ◽  
pp. 177-180 ◽  
Author(s):  
Cha Yong Lim ◽  
Jae Hyuck Jung ◽  
Seung Zeon Han
Keyword(s):  
Grain Size ◽  
Equal Channel Angular Pressing ◽  
Copper Alloys ◽  
Metallic Materials ◽  
Fine Grained ◽  
Angular Pressing ◽  
Fine Grain ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Average Grain Size

The equal channel angular pressing (ECAP) is one of the methods to refine the grain size of metallic materials. This study investigates the effect of ECAP process on the formation of the fine grain size in oxygen free Cu and Cu alloys. The average grain size has been refined from 150 µm before ECAP to 300 nm. Microstructure was analyzed by transmission electron micrography (TEM). The diffraction pattern of the selected area confirmed the formation of ultrafine-grained structure with high angle grain boundaries after 8 cycles of ECAP. Mechanical properties such as microhardness and tensile properties of the ultra-fine grained copper materials have been investigated.

Molecular Dynamics Simulation of Dislocation-Obstacle Interactions in Irradiated Materials

2007 ◽  
Vol 345-346 ◽  
pp. 947-950 ◽  
Author(s):  
Hyon Jee Lee ◽  
Jae Hyeok Shim ◽  
Brian D. Wirth
Keyword(s):  
Molecular Dynamics ◽  
Specific Interaction ◽  
Dislocation Motion ◽  
Dynamics Simulation ◽  
Face Centered Cubic ◽  
Void Size ◽  
Dislocation Interaction ◽  
Stacking Fault Tetrahedron ◽  
Face Centered ◽  
Induced Defects

The interactions of a dislocation with commonly observed irradiation induced defects such as a stacking fault tetrahedron (SFT) and a void are studied using molecular dynamics (MD) simulation methods. The simulation of an SFT interacting with a dislocation in face centered cubic (FCC) copper (Cu) reveals that an SFT is a strong obstacle against a dislocation motion, with dislocation detachment often involving an Orowan like mechanism. The resulting SFT generally involves a shear step, although partial absorption is also observed in some specific interaction geometries. Dislocation interaction with a void has been studied in body centered cubic (BCC) molybdenum (Mo). The dislocation locally annihilates upon contact with the void and then re-nucleates on the void surface as the dislocation glides past the void. The interaction results in the simple shear of the void by one Burger’s vector. The obstacle strength of the void is measured using conjugate gradient molecular statics (MS) method as a function of void size. A large increase in the obstacle strength is observed for a void size greater than 3 nm in diameter.

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