50nm

200nm

Qu

ickTim

e™

and

aTIF

F (U

nco

mpre

sse

d) d

eco

mp

resso

rare

need

ed to

see th

is pic

ture

.

Secondary ´

Tertiary ´ Matrix

Atom probe studies of linear cooled samples (Rene 104) - some observations

Motivation for work:

•Understand effects of cooling rate on microstructure

•Microstructural changes can induce changes in deformation mechanisms Typical 3D atom

probe reconstruction

Rene 104 Ni Co Cr Al Ti Ta B C Nb Mo W Nominal 49 20.08 14.34 7.27 4.37 0.73 0.13 0.24 0.55 2.23 0.64 ´ 63 9.90 2.09 11.66 8.72 1.58 0.00 0.00 1.05 0.83 0.50 36 29.97 26.37 2.18 0.61 0.13 0.00 0.00 0.13 3.80 0.80

30oF/min 250oF/min 400oF/min

0

10

20

30

40

50

60

70

-10 -8 -6 -4 -2 0 2 4Distance [nm]

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4Distance [nm]

0

10

20

30

40

50

60

70

-10 -8 -6 -4 -2 0 2 4Distance [nm]

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4Distance [nm]

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4

Element concentration (at. %)

Distance (nm)

(precipitate)

Ni

Co

Cr

Al

Ti

Ta

W

Mo

0

10

20

30

40

50

60

70

-10 -8 -6 -4 -2 0 2 4

Element concentration (at. %)

Distance (nm)

Proximity histograms (proxigrams)

0.1

1

10

Ni Co Cr Al Ti Ta Nb Mo

Partitioning ratio

250oF/min

mat

rix

p

has

e

Which elements in to which phase

•Partitioning of an element to an element can be different of different alloys (Sudbrak et al’s work)

Partitioning ratio

Used on non-planar interfaces

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4Distance [nm]

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4Distance [nm]

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4

Element concentration (at. %)

Distance (nm)

Ta

W

Mo

Tantalum concentration profile

400oF/min250oF/min30oF/min

’

•Tantalum concentration variation extends beyond other element concentration profiles

•Extended even for aged sample

•Also seen by Sudbrack et al with Cr 400oF/min + aged

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4

Distance [nm]

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4Distance [nm]

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4Distance [nm]

0

0.5

1

1.5

2

2.5

3

3.5

-10 -8 -6 -4 -2 0 2 4

Element concentration (at. %)

Distance (nm)

Ta

W

Mo

W - segregation

400oF/min

250oF/min

30oF/min

400oF/min + 1480oC/8hrs

0

0.5

1

1.5

2

-10 -5 0 5 10

Tu

ng

ste

n c

on

cen

tra

tion

(a

t.%

)

Distance (nm)

0

0.5

1

1.5

2

-10 -5 0 5 10

Tu

ng

ste

n c

on

cen

tra

tion

(a

t.%

)

Distance [nm]

W

400oF/min

•Sudbrak et al. 2006 observed W enrichmentDisappeared after ageing at 800oC/1hr

•Dieter et al 2004 found no enrichment observed in Rene 88 DT

•Rhenium has been found to segregate to the g/g’ interface in Blade alloys

0

10

20

30

40

50

60

70

80

-15 -10 -5 0 5

cNicCrcTi

Distance [nm]

0

10

20

30

40

50

60

70

80

-10 -5 0 5 10

cNicTicCr

Distance [nm]

Compositional profile of tertiary ’ (from 30 precipitates)

Compositional profile across a secondary ’ and matrix interface

Results indicate a wider /’ interface for the tertiary ’ than for the larger secondary ’

’

’

Interface width

Contour plot of ISF energy versus at.% concentration of Co and Cr

Total Co and Cr concentration ~50at.% in -matrix (a lot) more than NiMatrix contains 30 at. Cr and 25 at.% Co.

Based on old experimental results from Beeston et al, Smallman al and Harris et al

Significance of phase composition

ISF energy is around 25mJ/m2

Al

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

650 655 660 665 670 675 680

NiAlTi

Distance (Angstroms)

Ti

Ni

Crystal ordering

Site occupancy concentration of Ti in Al sublattice is high

What are the effects of Ti on CSF energy ?

Ni3Al (L12) and Ni3TI (DO24) have different crystal structures

Little work in the literature

R.C Reed suggest that Ti increases APB ?

Cooled Cooled + aged Cooled + really aged

Localized coarsening(unaffected by secondaries)

Global coarsening(affected by secondaries)

Effect of ageing on cooled samples

How does the initial “cooling tertiaries” number density affect number density and thus final volume fraction of tertiary ’ ?

Questions and possible future work with atom probe tomography

• What are the implications of diffuse / ’ interfaces ?• How can this and other parameters be used in models

• How significant and prevalent are these ultra ultra fine (~1nm) ’ precipitates w.r.t. creep?

• How stable are these ’ precipitates ?• Are they sub or supercritical nuclei ?

• Can altering the cooling profile (linear. Non-linear) alter the Vf and number density of the tertiary ’ precipitates?

• What are the affects of Ti of CSF energy

•Apply atom probe analysis to stacking faultsIs there segregation at these faults?

•Isothermal ageing studies to understand:

growth kinetics (for phase-field group)

Critical nucleation size