Point Defect Effects on Tensile Strength of BCC-Fe Studied by Molecular Dynamics

2020 ◽  
Author(s):  
Pandong Lin ◽  
Junfeng Nie ◽  
Meidan Liu
Keyword(s):  
Molecular Dynamics ◽  
Tensile Strength ◽  
Point Defect ◽  
Yield Stress ◽  
Point Defects ◽  
Constant Strain Rate ◽  
Tensile Load ◽  
Perfect Crystal ◽  
Defect Concentration ◽  
Rpv Steel

Abstract BCC-Fe is the critical and major component of the reactor pressure vessel (RPV) steel. With long-tern neutron irradiation, many point defects can be obtained in RPV steel. In this paper, the points defects (interstitial, vacancy and Frenkel pair) effects on the tensile strength of Fe are studied by molecular dynamics simulations at 300K. The uni-axial tensile load is along [001] direction of the Fe samples loading in constant strain rate. The Fe atoms are added or removed randomly to generate point defects. For point defects, three types of point defects can decrease the tensile strength containing yield stress and strain of Fe samples. In addition, the tensile strength decreases with the increase of point defect concentration. With the same defect concentration, interstitials decrease the yield stress the most seriously compared with the vacancies and Frenkel pairs. Apart from that, the morphology and evolution of the microstructure of Fe with point defects are also investigated under tension. Compared with the perfect crystal, the generation of dislocation decreases the tensile strength dramatically. For sample with interstitials, interstitial clusters form and evolve in dislocations loops finally. For sample with vacancis, vacancy may aggregate together and vacancy clusters form as a result, which is seen as precursors of dislocation loop. Notably, the results are meaningful to understand the effects of point defects on tensile strength of BCC-Fe.

Displacement cascade evolution in tungsten with pre-existing helium and hydrogen clusters: a molecular dynamics study

2020 ◽  
Vol 111 (8) ◽  
pp. 698-705
Author(s):  
Mohammad Abu-Shams ◽  
Jeffery Moran ◽  
Ishraq Shabib
Keyword(s):  
Molecular Dynamics ◽  
Point Defect ◽  
Radiation Damage ◽  
Point Defects ◽  
High Energy ◽  
Dynamics Simulation ◽  
Power Relationship ◽  
Hydrogen Clusters ◽  
Displacement Cascades ◽  
Hydrogen Defects

Abstract The effects of radiation damage on bcc tungsten with preexisting helium and hydrogen clusters have been investigated in a high-energy environment via a comprehensive molecular dynamics simulation study. This research determines the interactions of displacement cascades with helium and hydrogen clusters integrated into a tungsten crystal generating point defect statistics. Helium or hydrogen clusters of atoms~0.1% of the total number of atoms have been randomly distributed within the simulation model and primary knock-on-atom (PKA) energies of 2.5, 5, 7.5 and 10 keV have been used to generate displacement cascades. The simulations quantify the extent of radiation damage during a simulated irradiation cycle using the Wigner-Seitz point defect identification technique. The generated point defects in crystals with and without pre-existing helium/hydrogen defects exhibit a power relationship with applied PKA energy. The point defects are classified by their atom type, defect type, and distribution within the irradiated model. The presence of pre-existing helium and hydrogen clusters significantly increases the defects (5 - 15 times versus pure tungsten models). The vacancy composition is primarily tungsten (e. g., ~70% at 2.5 keV) in models with pre-existing helium, but the interstitials are primarily He (e. g., ~89% at 10 keV). On the other hand, models with pre-existing hydrogen have a vacancy composition that is primarily tungsten (more than 90% irrespective of PKA energy), and the interstitial composition is more balanced between tungsten (average 46%) and hydrogen (average 54%) interstitials across the PKA range. The distribution of the atoms reveals that the tungsten point defects prefer to reside close to the position of cascade initiation, but helium or hydrogen defects reside close to the positions where clusters are built.

scholarly journals On the yielding of a point-defect-rich model crystal under shear: insights from molecular dynamics simulations

Soft Matter ◽  
2021 ◽  
Author(s):  
Gaurav Prakash Shrivastav ◽  
Gerhard Kahl
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Point Defect ◽  
Point Defects ◽  
Model Crystal ◽  
Non Linear ◽  
Linear Effects ◽  
Dynamics Simulations

In real crystals and at finite temperatures point defects are inevitable. Under shear their dynamics severely influence the mechanical properties of these crystals, giving rise to non-linear effects, such as...

scholarly journals The Size Effects of Point Defect on the Mechanical Properties of Monocrystalline Silicon: A Molecular Dynamics Study

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3011
Author(s):  
Wei Wan ◽  
Changxin Tang ◽  
An Qiu ◽  
Yongkang Xiang
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Yield Strength ◽  
Point Defect ◽  
Size Effects ◽  
Constant Strain Rate ◽  
Monocrystalline Silicon ◽  
Dislocation Slip ◽  
Actual Strength ◽  
Yield Strength Variation

The molecular dynamics method was used to simulate the fracture process of monocrystalline silicon with different sizes of point defect under a constant strain rate. The mechanism of the defect size on the mechanical properties of monocrystalline silicon was also investigated. The results suggested that the point defect significantly reduces the yield strength of monocrystalline silicon. The relationships between the yield strength variation and the size of point defect fitted an exponential function. By statistically analyzing the internal stress in monocrystalline silicon, it was found that the stress concentration induced by the point defect led to the decrease in the yield strength. A comparison between the theoretical strength given by the four theories of strength and actual strength proved that the Mises theory was the best theory of strength to describe the yield strength of monocrystalline silicon. The dynamic evolution process of Mises stress and dislocation showed that the fracture was caused by the concentration effect of Mises stress and dislocation slip. Finally, the fractured microstructures were similar to a kind of two-dimensional grid which distributed along the cleavage planes while visualizing the specimens. The results of this article provide a reference for evaluating the size effects of point defects on the mechanical properties of monocrystalline silicon.

scholarly journals Point defect effects on tensile strength of α−zirconium studied by molecular dynamics simulations

2019 ◽  
Vol 20 ◽  
pp. 100683
Author(s):  
Yingying Li ◽  
Hong Chen ◽  
Yuting Chen ◽  
Yuhua Wang ◽  
Liang Shao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Tensile Strength ◽  
Molecular Dynamics Simulations ◽  
Point Defect ◽  
Dynamics Simulations

Strain Rate Effects on the Elevated-Temperature Tensile Behavior of a Bainitic 2-1/4 Cr-1 Mo Steel

1977 ◽  
Vol 99 (4) ◽  
pp. 350-358 ◽  
Author(s):  
R. L. Klueh ◽  
R. E. Oakes
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Strain Rate ◽  
Yield Stress ◽  
Uniform Elongation ◽  
Constant Strain Rate ◽  
Total Elongation ◽  
Dynamic Strain ◽  
Strain Rate Effects ◽  
Reduction Of Area

The tensile properties of a normalized-and-tempered 2-1/4 Cr-1 Mo steel were determined from 25 to 566° C and the strain rate 2.67 × 10−6 to 144/s. The specimens were taken from a 1-in. thick plate and had a microstructure that was essentially 100 percent bainite. Except at 25 and 566° C, the 0.2 percent yield stress was little affected by strain rate; at 25 and 566° C, the yield stress increased with increasing strain rate. At a constant strain rate, the yield stress decreased with increasing temperature. The effect of strain rate and temperature on the ultimate tensile strength was somewhat more complicated. A strength peak that resulted from dynamic strain aging was observed in the ultimate tensile strength-temperature relationship. The position of these peaks moved to higher temperatures with increasing strain rate. Total elongation and reduction of area were relatively constant over the range of test variables, except at 566° C, where they increased with decreasing strain rate. However, uniform elongation decreased with decreasing strain rate at 510 and 566° C, dropping to 1 and 0.6 percent, respectively.

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