Dislocation- Defect Interactions in Iron
Ngoc Le, Ioannis Mastorakos, Hussein Zbib
School of Mechanical and Materials Engineering
Washington State University, Pullman, WA 99163
Objectives
Results
•To address the mechanical properties of iron in
irradiated environments
I.
Stress (GPa)
1.40E+00
2.5 nm radius
6.00E-01
1 nm radius
4 nm radius
0.01
0.02
Strain
0.03
0.04
•As the size of the void increases, the motion of
the dislocation becomes more difficult, leading
to the hardening of the material.
Hardening vs. Void Radius
•After each pass the prismatic loop shrinks in size
and the dislocation leaves a new defect behind.
II. Dislocation – void interaction
Hardening (Gpa)
•Temperature: 350KDiameter of loop: 4 nm
80
70
60
50
40
30
20
10
0
0
1
2
3
Void Radius (nm)
4
5
• The graph of the slope of the stress-strain
curve versus the radius size shows a linear
relationship.
•Like defects cluster and anti-defects annihilate
Method
•Tools used are LAMMPS (MD Simulations) and
AtomEye (visualization).
8.00E-01
0
•Point Defects: vacancies and interstitials created
by radiation undergo reactions and aggregation
•A shear stress is applied and a dislocation moves
and interacts with defects. The resulting
mechanisms and the stress-strain curves are
extracted and studied.
No Void
0.00E+00
•Study the mechanical behavior of bcc iron
inhibited with prismatic loops and voids
•A prismatic loop or a void is generated by
removing atoms from the structure. The prismatic
loop is of [100] type.
1.00E+00
2.00E-01
•Study the dislocation – defects interaction
mechanisms
•A dislocation is formed by removing a half plane
of atoms and equilibrating the system. The
resulting dislocation lies on a [110] type plane and
moves along a <111> direction.
1.20E+00
4.00E-01
•Distinguish the critical parameters in which failure
occurs
•Vacancies: point defects in crystalline materials
and are missing atoms
1.80E+00
1.60E+00
Goals
•Dislocation: an irregularity within a crystal
structure that strongly influence the properties of
materials
2.00E+00
Dislocation - prismatic loop interaction
•To develop a capability that predicts the aging
and failure of the material under irradiation
Key Materials
Dislocation Interaction with Voids
Conclusions
•As the dislocation moves closer to the void, the
void’s free surface attracts the dislocation. The
radius of the void is 3 nm.
• The void begins to shear after the dislocation
passes through.
•When a dislocation interacts with a prismatic
loop, the loop shrinks in size with each pass and
defects are left. The defects can cluster to form
voids or prismatic loops.
•As the radius of the void increases, it becomes
harder for the dislocation to move and the
material hardens at a quicker rate. The
relationship between radius size and hardening
is linear.
This work was supported by the National Science
Foundation's Research Experience for
Undergraduates program under grant
number EEC-0754370.