Dislocation networks on ?/?

1
Dislocation networks on ?/? interface in single
crystal Ni-base superalloys
AFOSR under MEANS 2

• Ning Zhou Chen Shen Michael J. Mills Yunzhi
  Wang
• The Ohio State University

2
Stress calculation for static network

• Driving force for the formation of interfacial
  dislocation network misfit relieving and applied
  stress
• Starting with different dislocation network
  configuration and density, explore the back
  stresses in the system and its relation with the
  lattice misfit and applied stress.
• Calculate the elastic strain energy due to the
  dislocation networks, and relate dislocation
  density to the lattice misfit and applied stress.

3
Dislocation network configurations
(001) plane, ?/? interface
R. Field, T. Pollock, and W. Murphy, Superalloys,
pages 557566 (1992).
4
Dislocation configuration
Almost screw type
1280nm
010 dislocation pure edge type
extra half plane point to ?
5
?
?
?
Positive lattice misfit
extra half plane point to ? can relief misfit
stress
6
?
?
Misfit 0.3 with dislocations
Only misfit 0.3
only dislocations
7
Misfit 0.1
Average elastic energy density decrease from 0.25
to 0.20J/mol
Energy reduction by given dislocation networks
(J/mol)
Average elastic energy density increase from 2.22
to 3.04J/mol after adding dislocation network
misfit
Misfit 0.05 Average elastic energy density
increase from 0.062 to 0.12 J/mol
Misfit0.075 corresponds to the given network
configuration and density
8
Future work

• Dislocation network dynamics by glide.
• Relax certain network configurations under given
  applied stress and misfit and establish
  equilibrium network structure.
• Determine the relation between misfit applied
  stress and dislocation configuration density.
• Explore the possibility of incorporating climb
  mechanism into phase field dislocation dynamics.