tailoring of atomic-scale interphase complexions for mechanism-informed material design
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Office of Naval Research Multidisciplinary University Research Initiative Project Review Meeting December 18, 2012 ONR Topic Chief : David Shifler. Tailoring of Atomic-Scale Interphase Complexions for Mechanism-Informed Material Design . - PowerPoint PPT PresentationTRANSCRIPT
Tailoring of Atomic-Scale Interphase Complexionsfor Mechanism-Informed Material Design
Developing Predictive Thermodynamic Models …and
Validation ExperimentsPresented by Jian Luo
On Behalf of the MURI Team
Office of Naval Research Multidisciplinary University Research Initiative Project Review Meeting
December 18, 2012ONR Topic Chief: David Shifler
ONR-MURI Review 2
Based on the Feedbacks from DFT Calculations and STEM…A Revised Thermodynamic Description of Bilayers?
BBimonoS
bilayergb )()( 2
2 adsorbed Bi layers are weakly bonded
CMU: Ni annealed in Bi vapor
Deep Groov
e
Atomic Steps
Reconstruction(NOT 1 on 1)
Coherent?
DFT (CMU)Bi on Ni (111)
“4 on 9” reconstructi
on
Specific Bilayer Structure ~ OrientationOriginal
A “Coarse-Grained” Description
Bi LayerBi LayerNi LayerNi LayerNi Layer
Ni LayerNi LayerNi Layer
Cohe
rent
Inte
rfac
eSt
rong
Bi-N
i Bon
ds
Inco
here
nt In
terf
ace
Wea
k Bi
-Bi B
onds
Bilayer Stability (The Key Idea unchanged):Strong Ni-Bi (Measured by
Ni-Bi)Weak Bi-Bi
Experimental Evidence
Suggested by DFT (@CMU)
ONR-MURI Review 3
Segregation driving forces in metals:• Eelastic = f(RB/RA) • H |EB-B| - |EA-A|• EA-B - ½(EA-A + EB-B);
zN
Wynblatt & Chatain Metall. Mater. Trans. A 2006
Key Parameters for Prediction?
Strong Ni-BiWeak Bi-Bi
Science, 333: 1730 (2011)
ONR-MURI Review 4
To Predict Bilayer Stability…
Bi doped Ni
ubiquitous
An experiment designed in Feb. 2012 (@ a MURI meeting at TMS)
observed, but in a narrow window NOT observed
Ni-Bi = -14.8 kJ/molCu-Bi = +14.2 kJ/molFe-Bi = +72.3 kJ/molMiedema:
Ni-Bi = -16.4 kJ/molCu-Bi = +34.8 kJ/molFe-Bi = +91.6 kJ/molDFT (CMU):
Bilayers are…
Gao & Widom( 4Hmix
0.5)
Subsequently, specimens were made at Clemson and characterized at Lehigh; we observed that:
Bi Bi BiNi Cu Fe
Bi doped Cu Bi doped Fe
Reducing Bilayer Stability Predicted…
Large Eelastic Large |EB-B| - |
EA-A|Varying A-B EA-B - ½(EA-A +
EB-B)
ONR-MURI Review 5
Ni-Bi
Cu-Bi
Fe-Bi
Fe-Bi = 91.6 kJ/mol(DFT, Gao & Widom)
Fe
Fe
“Clean”
Cu-Bi = 34.8 kJ/mol(DFT, Gao & Widom)
Ni-Bi = -16.4 kJ/mol(DFT, Gao & Widom)
Scripta Mater. 2013
Science 2011
Clemson Updates
MURI Review: 5/17/2012 6
Wynblatt et al.’s Multilayer GB Segregation Model Wynblatt, Chatain et al. [JMS 2005; 2006, MMA 2006]
GB Core:
Inside:
Segregation Enthalpy
Same Crystal Structure
Weak Segregation Systems?
“Solid-State” Complexion Transition
Clemson Updates
MURI Review: 5/17/2012 7
The Most Recent Modeling Results using the Wynblatt Model [See the description of the Model: Wynblatt & Chatain, Metall.
Mater. Trans. A 2006]
1E-3 0.01 0.1 1
0.0
0.5
1.0
1.5
2.0
2.5 Ni-Bi Cu-Bi Fe-Bi Ni-Bi CalPhad
(#
of m
onol
ayer
)
X %
DFT para.(CMU)
CalPhaD
1E-4 1E-3 0.01 0.1 10.00
0.25
0.50
0.75
1.00
1.25
1.50 Ni-Bi Cu-Bi Fe-Bi Ni-Bi CalPhad
GB/
(0)
GB
X (%)
XBi(0)
(Cu-Bi)
XBi10-6 10-5 10-4 10-3 10-2
10-6 10-5 10-4 10-3 10-2 XBi
XBi(0)
(Ni-Bi)XBi
(0)
(Fe-Bi)
Approx.Solid
SolubilityLimit
XBi(0)
(Ni-Bi)
The Wynblatt Model
(111)FCC or (110)BCC high-angle (low-
symmetry) twist GBs
T/Tm =0.563Fe-Bi
Cu-Bi Ni-Bi
Consistent with
Experiment
In the Meta-Stable Supersaturated Region:
Effective GB 0 “Equilibrium” Grain Size
(Weissmuller, Johnson, Kirchheim, Schuh et al.)
Clemson Updates
MURI Review: 5/17/2012 8
Stabilization of Nanocrystralline Alloys via GB Segregation (a.k.a. Complexion)
Kinetic Stabilization• Solute drag• Second phase pinning• Chemical ordering• …
Thermodynamic Stabilization (reducing GB, ideally to ~ 0?)
competing
New Insight: The complexion theory argued that segregation induced interfacial
disordering can increase GB mobiles (demonstrated in Al2O3, Al-Ga etc.)
From the late Dr. Rowland
Cannon (2004 GRC)
A GB transition?
Schuh & co-workers’ recent work (Science 2012)
Can we pursue a more quantitative “CalPhaD for Nanocrystalline
Alloys”
Show the importance
of simultaneously evaluating bulk and GB thermodyna
mics
This MURI revealed (for Ni-Bi)…Bi adsorption reduce GB of Ni
significantly (not yet 0)Bi inhibits Ni GG at low T, but Promote
GG at high T!
ONR-MURI Review 9
Background: Developing Design Tools for the Materials Genome Initiative
CalPhaD for “Complexions” & “Nano-Phases”2 related but different tasks
Melting T for Au
Nanoparticles
Binary
T. Tanaka et al. 2001
Premelting(Complexion)
Related, but
different phenomen
a
A Successful Example of Predictive Modeling (AFOSR Project)To predict the stabilization of nanoscale quasi-liquid
intergranular films (complexions)
ONR-MURI Review 10
Developing A New “Materials Genome” Tool for Designing Nanocrystalline Alloys?
“CalPhaD for Nanocrystalline Alloy” DiagramGB
Complexion Model
(Wynblatt model for this case)
Bulk CalPhaD
(Computational Thermodynamics)
+
Metastable nanocrystalline alloys possible,
but probably impractical for Ni-
Bi…
Cu-BiMayr & Bedorf
Phys. Rev. B 2007
Consistent with
Experiment
ONR-MURI Review 11
A More Practical Case“CalPhaD for Nanocrystalline Alloy” Diagram for Fe-Zr
Consistent with Prior ExperimentsNo fitting/free parameters used other than the CalPhaD data obtained in
literature!
ONR-MURI Review 12
100 200 300 400 500 600 700 800 900 10001
10
100
1000
10000
100000
Log 10
Gra
in S
ize
(nm
)
T(oC)
Ni Ni(Bi) Ni-W Ni-W(Bi)
Grain Growth (GG): Intriguing Results
Bi inhibits GG at low T’s?
CMU High-Purity Ni (930C)
Bi promote GG (no AGG) at high T’s
Clemson High-Purity Ni (1100C)
~20 m~40 m
Clemson Electrodeposited Ni & Ni-WIsothermally annealed w/ or w/o Bi vapor, 4 hrs
Pure Ni: 137 mNi (+ Bi liquid): 159 m
UIUC GB diffusion measurements showed the consistent trends
earlier…
? Confirmed
SEMXRD, confirmed by
SEM
STEM in progress at
UIUC & Lehigh
Current Explanation:At low T’s: Bi inhibits grain growth due to the reduction of
driving force (GB/GB(0) = ¼) and solute drag (given the large
adsorption amount)At high T’s: Bilayers become more “liquid-like” the kinetic
effect due to disorder overwhelms the thermodynamic stabilization and solute drag
ONR-MURI Review 13
Bi doped Ni W doped NiRBi = 1.78Å RNi =
1.25Å
Bi Ni
RW = 1.39Å RNi = 1.25Å
W Ni
H |EBi-Bi| - |ENi-Ni| < 0
: small negative
Eel big RB/RA = 1.42
H |EW-W| - |ENi-Ni| > 0
: small negative
Eel moderate RB/RA = 1.11
• Reduce GB moderately• Stabilize nano grain size • Good mechanical properties
Strong SegregationLimited Solubility
Weak SegregationLarge Solubility
Nanocrystalline W-Ni (Schuh et al. & others)
• Reduce GB significantly• Promote GG at high T; inhibit GG at low T• Severe embrittlement
ONR-MURI Review 14
Dangling bonds(incoherent interface)
High-energy W broken bonds W depletion at the very core?
Possible Complexion Structure in Ni-W (Following Wynblatt et al.’s Multilayer GB Segregation Model)
H = +0.3 Hel = -0.2 (eV/atom)
H = 0Hel = -0.05 (eV/atom)
• Inhibit grain growth• No severe embrittlement
Non-equilibrium W segregation possible during
electrodeposition
Ni-W (made by electrodeposition) Supersaturated with W
Heat Treatment:700C for 4 hrs + 400C for 24 hrs
To verify/disapprove this prediction:
Specimens made at Clemson
STEM Characterization current in progress at
Lehigh…
ONR-MURI Review 15
Concluding Remarks
“Simple” thermodynamic models can predict useful trends• Predicted decreasing bilayer stability in Ni-Bi, Cu-Bi and Fe-Bi
verified by experiments• DFT (and atomistic) calculations are useful for providing
thermodynamic parameters (particularly in cases where experimental data are not available)
A new “CalPhaD for Nanocrystalline Alloys” method has been developed – in the spirit of the “Materials Genome” initiative?• Combining complexion models & bulk CalPhaD • Initial validation with literature data & our experiments
An Intriguing New Discovery • Bi inhibits the grain growth of Ni at low T, but promotes grain
growth at high T.
ONR-MURI Review 16
Backup Slides
ONR-MURI Review 17
Electrodeposited Ni specimens, annealed at 900 C, 4 hrs
Ni
Niin Bi vapor
Grain Size Increases