1. AFOSR MEANS2 Working Meeting HRTEM/STEM CHARACTERIZATION
Outline:
Microstructure of 0.2% crept (tension) Rene104
Isolated faulting in ’
Intrinsic Stacking faults in the Matrix
Microstructure of 2% crept (tension) Rene104
Examination of structure of thicker twins

2. One of the feature of the 0.2% deformed microstructure
ISOLATED FAULTING
One of the feature of the 0.2% deformed microstructure
Not as prevalent as the SF on a different (111) slip plane
Faulting observed predominantly in the ’ precipitates
OBSERVATIONS
Ended at the ’ interface
Ended at a SF
Transmitted through 
100 nm

3. DETAIL OF THE ISOLATED FAULT ENDING AT THE ’ INTERFACE
[110] A C B
SESF C A C B A

4. THE INTERFACE DISLOCATION ANALYSIS
Probe Deconvoluted
Moire Fringe
Nye Tensor  
Schematic
MD Simulation
Shear Strain Ni
Ni3Al A  B A
zonalC

5. HOW DO ISOLATED FAULTS FORM? A   1)
CSF
Zonal
partial= C A A
SESF  A A 
ISF
ISF
SESF   2) A  ??
ISF
SESF
Zonal
partial= C
ESF A
ESF
ISF A
ISF

6. ISOLATED FAULT ANALYSIS
Stronger intensity in the SESF (heavier elements => partitioning)
Stronger indication of Ordering
Confirmation of SESF or CSF not possible

7. ISOLATED FAULT ANALYSIS
(-1-11)
(111)

8. STACKING FAULT ANALYSIS IN THE MATRIX
b=1/6
ISF
b=-1/6
ISF

9. EXTENDED FAULTS

10. LAYER FAULTING AT THE INTERFACE
MICROTWIN STRUCTURE
LAYER FAULTING AT THE INTERFACE
Rene 104, 677ºC 690MPa 2.0% Strain
1/6<112> pairs
14 atomic planes
11 atomic planes

11. The DO24 fault translates into decreasing the energy by
DFT comparison of MICRO-TWIN configurations
Super-cell configurations for Ni3Ti
True Twin (8 layers), Super-cell 16 layers(TTW_8_16)
Faulted True Twin (8 layers), Super-cell 16 layers(F_TTW_8_16)
TTW_8_16
F_TTW_8_16
Both super-cells were created from a perfect L12 NI3Ti by passing 1/3 [112]. (8 partials)
Energy comparison
(Super-cell energy 0K)
TTW
DO24
TTW_8_16 = eV
F_TTW_8_16 = eV
TTW
TTW
DE= -0.15eV/cell
The DO24 fault translates into decreasing the energy by
-96.5mJ/m2.

12. DFT calculation of MICRO-TWIN configurations
Super-cell configurations for Ni3Al
True Twin (8 layers), Super-cell 16 layers(TTW_8_16)
Faulted True Twin (8 layers), Super-cell 16 layers(F_TTW_8_16)
TTW_8_16
F_TTW_8_16
Both super-cells were created from a perfect NI3Al by passing 1/3 [112]. (8 partials)
Energy comparison
(Super-cell enthalpy)
TTW
DO24
TTW_8_16 = eV
F_TTW_8_16 = eV
TTW
TTW
DE= 0.13V/cell
The DO24 fault translates into increasing the energy by 83.5mJ/m2.

13. DFT comparison of MICRO-TWIN configurations
Super-cell configurations for Ni3Al
True Twin (7 layers) with adjacent one layer pseudo-twin (TTW_Pa1_19)
True Twin (7 layers), with a fault and adjacent pseudo twin (TTW_Pn1_19)
TTW_Pa1_19
TTW_Pn1_19
Both super-cells were created from a perfect NI3Al by passing 7x 1/3 [112] and 1x 1/6 [112] (in case of the TTW_Pn1_19 one plane was skipped before passing the 1/6 [112] ). ?
PTW
Energy comparison
(Super-cell energy 0K)
TTW
TTW
TTW_Pa1_19 = eV
TTW_Pn1_19 = = eV
DE= 0.08V/cell
The fault translates into increasing the energy by ~51.5mJ/m2.

14. DFT comparison of MICRO-TWIN configurations
Super-cell configurations for Ni3Ti
True Twin (7 layers) with adjacent one layer pseudo-twin (TTW_Pa1_19)
True Twin (7 layers), with a fault and adjacent pseudo twin (TTW_Pn1_19)
TTW_Pa1_19
TTW_Pn1_19
Both super-cells were created from a perfect L12 NI3Ti by passing 7x 1/3 [112] and 1x 1/6 [112] (in case of the TTW_Pn1_19 one plane was skipped before passing the 1/6 [112] ). ?
PTW
Energy comparison
(Super-cell energy 0K)
TTW
TTW
TTW_Pa1_19 = eV
TTW_Pn1_19 = = eV
Energetically the same!

15. EXTENDED FAULTS
2x 1/6[112]

16. OUTCOME AND FUTURE PLANS
ISOLATED FAULTING (UNDERSTANDING THE MECHANISM) => COMBINATION OF MICROSCOPY WORK AND PHASE FIELD)
STEM SEGREGATION STUDIES AND AB INITIO?
PAPERS
OBSERVATIONS OF ISOALTED FAULTING
MICROTWIN FAULTING AT THE INTERFACE AND COMPOSITIONAL EFFECTS