Study on displacement cascade and tensile simulation by molecular dynamics: Formation and properties of point defects

2021 ◽  
pp. 2150140
Author(s):  
Pandong Lin ◽  
Junfeng Nie ◽  
Meidan Liu
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Point Defects ◽  
Vacancy Concentration ◽  
Tensile Tests ◽  
Number Density ◽  
Displacement Cascade ◽  
Slip Bands ◽  
Dynamics Method

The molecular dynamics method is used to investigate the formation and properties of irradiation-induced damage (point defects). Displacement cascade simulations are performed to study the effects of primary knock-on atom (PKA) energy, temperature, vacancy concentration and tensile pre-strain on irradiation-induced damage in [Formula: see text]-Fe. An increase in PKA energy, vacancy concentration and tensile pre-strain can lead to an increase in defect numbers. In contrast, an increase in temperature decreases the defect numbers. After cascade collisions, tensile tests are performed to investigate the effect of point defects on mechanical properties. The yield stress and corresponding strain of irradiated Fe decrease with an increase in the number density of Frenkel pairs. Results show that irradiation accelerates damage of the internal structure, decreases the number of slip bands and increases the instability of the structure during plastic deformation.

Study on the Effect of Different Factors of Displacement Cascades in Alpha-Fe by Molecular Dynamics Simulations

2020 ◽  
Author(s):  
Pandong Lin ◽  
Junfeng Nie ◽  
Meidan Liu
Keyword(s):  
Molecular Dynamics ◽  
Tensile Strain ◽  
Vacancy Concentration ◽  
Irradiation Damage ◽  
Effect Of Temperature ◽  
Displacement Cascade ◽  
Rpv Steel ◽  
Dynamics Simulations ◽  
Dynamics Method

Abstract As the key component of RPV steel, α-Fe is under neutron irradiation during its long-term service, and lattice atoms of α-Fe are knocked by neutrons, which leads to irradiation damage. In this paper, molecular dynamics method is conducted to investigate the effect of temperature, vacancy concentration and tensile strain on irradiation-induced damage by displacement cascade simulations in α-Fe. The simulations are performed with primary knock-on atom energies ranging from 0.1 to 5 keV, temperature ranging from 100 to 500K, vacancy concentration ranging from 0% to 1% and applied tensile strain ranging from 0 to 5%. The time evolution of defects produced during displacement cascade can be obtained where the surviving number of Frenkel pairs increases rapidly at first, then decrease and comes to stability finally. The influence of these factors on defect production can be concluded as following: The increase of PKA energy, vacancy concentration and applied tensile strain can lead to the increase of defect numbers. In contrast, the increase of temperature decreases the defect numbers. Vacancies and interstitials cluster size distributions are varied in different case. The results are meaningful to describe some microcosmic mechanisms of RPV steels in nuclear system.

scholarly journals Influence of Hydrostatic Extrusion on the Mechanical Properties of the Model Al-Mg Alloys

2021 ◽  
Author(s):  
Aleksandra Towarek ◽  
Wojciech Jurczak ◽  
Joanna Zdunek ◽  
Mariusz Kulczyk ◽  
Jarosław Mizera
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Tensile Strength ◽  
Microstructural Analysis ◽  
Tensile Tests ◽  
Hydrostatic Extrusion ◽  
Microstructure Formation ◽  
Initial State ◽  
Degree Of Deformation ◽  
Al Mg Alloys

AbstractTwo model aluminium-magnesium alloys, containing 3 and 7.5 wt.% of Mg, were subjected to plastic deformation by means of hydrostatic extrusion (HE). Two degrees of deformation were imposed by two subsequent reductions of the diameter. Microstructural analysis and tensile tests of the materials in the initial state and after deformation were performed. For both materials, HE extrusion resulted in the deformation of the microstructure—formation of the un-equilibrium grain boundaries and partition of the grains. What is more, HE resulted in a significant increase of tensile strength and decrease of the elongation, mostly after the first degree of deformation.

Influence of Severe Plastic Deformation on the PLC Effect and Mechanical Properties in Al 5XXX Alloy

2006 ◽  
Vol 114 ◽  
pp. 171-176 ◽  
Author(s):  
Joanna Zdunek ◽  
Pawel Widlicki ◽  
Halina Garbacz ◽  
Jaroslaw Mizera ◽  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
True Strain ◽  
Tensile Tests ◽  
Size Reduction ◽  
Hydrostatic Extrusion ◽  
Stress Strain ◽  
Chatelier Effect

In this work, Al-Mg-Mn-Si alloy (5483) in the as-received and severe plastically deformed states was used. Plastic deformation was carried out by hydrostatic extrusion, and three different true strain values were applied 1.4, 2.8 and 3.8. All specimens were subjected to tensile tests and microhardness measurements. The investigated material revealed an instability during plastic deformation in the form of serration on the stress-strain curves, the so called Portevin-Le Chatelier effect It was shown that grain size reduction effected the character of the instability.

scholarly journals The Effects of Grain Boundary Misorientation on the Mechanical Properties and Mechanism of Plastic Deformation of Ni/Ni3Al: A Molecular Dynamics Study

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5715
Author(s):  
Jun Ding ◽  
Sheng-Lai Zhang ◽  
Quan Tong ◽  
Lu-Sheng Wang ◽  
Xia Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Grain Boundary ◽  
Misorientation Angle ◽  
Interfacial Energy ◽  
Stacking Faults ◽  
Boundary Misorientation ◽  
Grain Boundary Misorientation ◽  
Mechanisms Of Plastic Deformation

The effects of grain boundary misorientation angle (θ) on mechanical properties and the mechanism of plastic deformation of the Ni/Ni3Al interface under tensile loading were investigated using molecular dynamics simulations. The results show that the space lattice arrangement at the interface is dependent on grain boundary misorientations, while the interfacial energy is dependent on the arrangement. The interfacial energy varies in a W pattern as the grain boundary misorientation increases from 0° to 90°. Specifically, the interfacial energy first decreases and then increases in both segments of 0–60° and 60–90°. The yield strength, elastic modulus, and mean flow stress decrease as the interfacial energy increases. The mechanism of plastic deformation varies as the grain boundary misorientation angle (θ) increases from 0° to 90°. When θ = 0°, the microscopic plastic deformation mechanisms of the Ni and Ni3Al layers are both dominated by stacking faults induced by Shockley dislocations. When θ = 30°, 60°, and 80°, the mechanisms of plastic deformation of the Ni and Ni3Al layers are the decomposition of stacking faults into twin grain boundaries caused by extended dislocations and the proliferation of stacking faults, respectively. When θ = 90°, the mechanisms of plastic deformation of both the Ni and Ni3Al layers are dominated by twinning area growth resulting from extended dislocations.

Molecular Dynamics Simulation of Microcrack Healing in Copper Nano-Plate

2012 ◽  
Vol 531-532 ◽  
pp. 454-457
Author(s):  
Mei Fen Wang ◽  
Guo Jun Du ◽  
Dong Yu Xia
Keyword(s):  
Molecular Dynamics ◽  
Critical Temperature ◽  
Molecular Dynamics Simulation ◽  
Temperature Increase ◽  
Healing Time ◽  
Dynamics Simulation ◽  
Crack Healing ◽  
Slip Bands ◽  
Round Shape ◽  
Dynamics Method

The molecular dynamics method is used to simulate microcrack healing in copper nano-plate during heating. During microcrack healing, the tip of microcrack is blunted and deforms to round shape, the microcrack becomes smaller and smaller until it is healed through slip bands emitting from the pre-crack tip and expanding to the top and bottom of the copper nano-plate. The healing time is different in different temperature. The healing processes in different temperature present different slip bands for crack healing. When temperature is below 650K, the healing time decreases dramatically with temperature increase. When temperature is above 650K, the healing time decreases smoothly with temperature increase. The critical temperature of microcrack healing in copper nano-plate without pre-existing dislocations is about 400K.

scholarly journals Influence of Hydrogen Content on the Microstructure and Mechanical Properties of ER5183 Wires

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Yilong Han ◽  
Songbai Xue ◽  
Renli Fu ◽  
Lihao Lin ◽  
Zhongqiang Lin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Tensile Strength ◽  
Hydrogen Content ◽  
Tensile Tests ◽  
Plastic Strain Rate ◽  
Drawing Process ◽  
Welding Wire ◽  
Unstable Crack ◽  
Microstructure And Mechanical Properties

This work focused on the influence of hydrogen content on the microstructure and mechanical properties of ER5183 Al-Mg-Mn alloy wires for aluminum alloy welding. The hydrogen content of the ER5183 wires was measured, the macroscopic and microscopic morphologies of fractures were observed as well as the microstructure of the wires, and the tensile strength of the wires was also tested and investigated. The experimental results demonstrated three typical irregular macroscopic fractures of the wires appeared during the drawing process when the hydrogen content exceeded 0.23 μg/g. In the meantime, the aggregated pores were observed in the microstructure of the ϕ5.2 mm wire with the hydrogen content of 0.38 μg/g. Such defects may become the origin of cracks in subsequent processing and tensile tests. Moreover, higher hydrogen content in the ϕ5.2 mm welding wire will bring obvious changes in the fracture surface, which are internal cracks and micropores replacing the original uniform and compact dimples. With the higher hydrogen content, the tensile strength and plastic strain rate of ϕ1.2 mm wires would decrease. At the same time, unstable crack propagation would occur during the process of plastic deformation, leading to fracture. Considering the mechanical properties and microstructure, the hydrogen content of the ER5183 wires should be controlled below 0.23 μg/g.

scholarly journals Molecular Dynamics Simulation Study of the Mechanical Properties of Nanocrystalline Body-Centered Cubic Iron

Surfaces ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 381-391
Author(s):  
Jan Herman ◽  
Marko Govednik ◽  
Sandeep P. Patil ◽  
Bernd Markert
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Strain Rate ◽  
Tensile Tests ◽  
Dynamics Simulation ◽  
Uniaxial Tensile ◽  
Body Centered Cubic ◽  
Bcc Iron ◽  
Average Grain Size ◽  
Study Results

In the present work, the mechanical properties of nanocrystalline body-centered cubic (BCC) iron with an average grain size of 10 Å were investigated using molecular dynamics (MD) simulations. The structure has one layer of crystal grains, which means such a model could represent a structure with directional crystallization. A series of uniaxial tensile tests with different strain rates and temperatures was performed until the full rupture of the model. Moreover, tensile tests of the models with a void at the center and shear tests were carried out. In the tensile test simulations, peak stress and average values of flow stress increase with strain rate. However, the strain rate does not affect the elasticity modulus. Due to the presence of void, stress concentrations in structure have been observed, which leads to dislocation pile-up and grain boundary slips at lower strains. Furthermore, the model with the void reaches lower values of peak stresses as well as stress overshoot compared to the no void model. The study results provide a better understanding of the mechanical response of nanocrystalline BCC iron under various loadings.

Molecular Dynamics Simulation of Compressive Mechanical Behavior of Nanocrystalline Fe

2005 ◽  
Vol 475-479 ◽  
pp. 3291-3294
Author(s):  
Shi Fang Xiao ◽  
Yu Hu Wang
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Deformation Process ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Deformation Region ◽  
Embedded Atom ◽  
Boundary Atom ◽  
Strain Strengthening

The uniaxial compressive mechanical properties of nanocrystalline Fe are simulated with a molecular dynamics technique and the analytical embedded-atom method. An asymmetrical mechanical phenomenon between tensile and compressive process is found, and the yield stress and flow stress in compression are higher than those in tension simulations. The compressive deformation process can be described as three characteristic regions: quasi-elastic deformation, plastic flowing deformation, and strain strengthening. During the plastic flowing deformation region, the material shows very good compressive ductibility. The plastic deformation is mainly dominated by the grain boundary atom slide.

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