Upload
merrill
View
20
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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. - PowerPoint PPT Presentation
Citation preview
HRTEM/STEM CHARACTERIZATION
• Isolated faulting in ’• Intrinsic Stacking faults in the Matrix
Microstructure of 0.2% crept (tension) Rene104
Microstructure of 2% crept (tension) Rene104
• Examination of structure of thicker twins
AFOSR MEANS2 Working Meeting
Outline:
• One of the feature of the 0.2% deformed microstructureNot as prevalent as the SF on a different (111) slip plane
• Faulting observed predominantly in the ’ precipitates
100 nm100 nm
OBSERVATIONS
• Ended at the ’ interface• Ended at a SF• Transmitted through
ISOLATED FAULTING
ABC
ACBC
A
SESF
[110]
DETAIL OF THE ISOLATED FAULT ENDING AT THE ’ INTERFACE
Nye Tensor Nye Tensor Moire FringeMoire FringeProbe DeconvolutedProbe Deconvoluted
Ni3AlNi
AB
A
SchematicSchematic
zonalC
THE INTERFACE DISLOCATION ANALYSIS
MD SimulationMD Simulation Shear StrainShear Strain
HOW DO ISOLATED FAULTS FORM?
A
A
CSF
ISF
Zonalpartial=C
ISF
A
AESF
1)
2)
??
ISF
SESF
ESFA
A
SESF
A
ISF
Zonalpartial=C
ASESF
ISF
ISOLATED FAULT ANALYSIS
• Stronger intensity in the SESF (heavier
elements => partitioning) • Stronger indication of Ordering • Confirmation of SESF or CSF not possible
ISOLATED FAULT ANALYSIS
(111)(-
1-11
)
STACKING FAULT ANALYSIS IN THE MATRIX
ISFISF
ISFISF
b=1/6 [112]@30°
b=-1/6 [112]@30°
EXTENDED FAULTS
1/6<112> pairs
11 a
tom
ic
plan
es
MICROTWIN STRUCTURE LAYER FAULTING AT THE INTERFACE
Rene 104, 677ºC 690MPa 2.0% Strain
14 a
tom
ic
plan
es
TTW_8_16
TTW_8_16 = -416.07eV
F_TTW_8_16 = -416.22eV
TTW
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)
F_TTW_8_16
TTWTTW
DO24
•Both super-cells were created from a perfect L12 NI3Ti by passing 1/3 [112]. (8 partials)
Energy comparison(Super-cell energy 0K)
The DO24 fault translates into decreasing the energy by
-96.5mJ/m2.
E= -0.15eV/cell
TTW_8_16
TTW_8_16 = -349.19eV
F_TTW_8_16 = -349.06eV
TTW
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)
F_TTW_8_16
TTWTTW
DO24
•Both super-cells were created from a perfect NI3Al by passing 1/3 [112]. (8 partials)
Energy comparison(Super-cell enthalpy)
The DO24 fault translates into increasing the energy by
83.5mJ/m2.
E= 0.13V/cell
TTW TTW_Pa1_19 = -414.36eV
TTW_Pn1_19 = = -414.28eV
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)
PTW
TTW
?
•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] ).
Energy comparison(Super-cell energy 0K)
TTW_Pa1_19 TTW_Pn1_19
The fault translates into increasing the energy by
~51.5mJ/m2.
E= 0.08V/cell
TTW TTW_Pa1_19 = -492.76eV
TTW_Pn1_19 = = -492.75eV
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)
PTW
TTW
?
•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] ).
Energy comparison(Super-cell energy 0K)
TTW_Pa1_19 TTW_Pn1_19
Energetically the same!
EXTENDED FAULTS
2x 1/6[112]
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