The Ohio State University

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The Ohio State University Dislocation networks on γ/γ’ interface in single crystal Ni-base superalloys AFOSR under MEANS 2 Ning Zhou; Chen Shen; Michael J. Mills ; Yunzhi Wang; The Ohio State University

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 it’s 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.

Dislocation network configurations (001) plane, γ/γ’ interface R. Field, T. Pollock, and W. Murphy, Superalloys, pages 557–566 (1992).

Dislocation configuration [100] [010] (001) plane 430nm 210nm Almost screw type Sense vector Burgers vector 1280nm [010] dislocation: pure edge type extra half plane point to γ

X1 [100] X2 [010] X3 [001] γ γ γ’ γ’ Positive lattice misfit extra half plane point to γ can relief misfit stress lattice misfit:

Misfit: +0.3% with dislocations only dislocations X2 [010] X1 [100] X3 [001] 80nm 430nm 210nm Unit:117MPa T C γ γ’ On (100) cross-section 430nm 210nm γ γ’ 139nm Only misfit: +0.3% Misfit: +0.3% with dislocations only dislocations Average elastic energy density: decrease from 2.22J/mol to 1.74J/mol 0.17J/mol

Average elastic energy density decrease from 0.25 to 0.20J/mol Unit:117MPa T C Misfit: -0.3% γ’ γ 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 Misfit:+0.075% corresponds to the given network configuration and density

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.