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In -s i t u Sc at t er ing St udy o fPhase Trans form at ion K ine t ic s

Xun-Li Wang

Neutron Scattering Science Division

Oak Ridge National Laboratory

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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY

Out l ine

Why are phase transformations of interest?

Why kinetics?How are neutrons used to study phase

transformations?

Future opportunities

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The s t ruc t u re o f a m at er ia l a t

var ious lengt h sc a les

Graphite Diamond Metallic Glass

Nanoscale clusters Nanocrystalline Ni

TRIP Steel

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St ruc t ure Af fec t s Proper t ies

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St ruc t ura l c hange dur ing c ur ing o f

cemen t

(Chakomakous et al.,Acta Cryst. 1992)

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St ruc t u re o f m et a l l i c g lass?

crystalline amorphous?

Miracle, Nature Mat.

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The s t ruc t u re o f a m at er ia l a t

var ious lengt h sc a les

Graphite Diamond Metallic Glass

Nanoscale clusters Nanocrystalline Ni

TRIP Steel

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OAK

RIDGE

NATIONAL

LABORATORY

U. S. DEPARTMENT OF ENERGY

NANOCLUSTERS IN IRON MATRIX

The nanoclusters were estimated to be 2-3 nm in diameterwith a spacing of 12 nm in agreement with APT.

2nm4nm

14YWT 1 h at 1000C

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OAK

RIDGE

NATIONAL

LABORATORY


Sm al l Ang le Neut ron Sc at t e r ing

show ed a b i-m odal s ize d is t r ibut ion

0 5 10 15

0.000

0.005

0.010

0.015

0.020

0.025

ParticleSizeDistributionFunction(N*v)

Particle Size Radius (nm)

and thermally stable up to 1400 C

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Wang et al., 1999

St ruc t ure Det erm ines Proper t ies

- Mic rost r uc t ureCross-section of a friction stir weld showing distinct microstructure

zones generated by heat and mechanical work

Hardness profile through thedifferent microstructure zonesreflects the changes inmicrostructure

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Mic rost ruc t ure o f TRIP St ee l

TRansformation Induced Plasticity steels

Retained austenite transforms into martensite (a hard phase) during deformation

Hard martensite delays the onset of necking resulting in high total elongation

Extremely high fatigue endurance

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Why K inet i c s?

Because we must ! Mechanisms of nucleation

Mechanisms of growth Nature of intermediate and meta-stable phase

Ultimate goal is achieve structure control Effect on properties

Because we can ! In-situ time-resolved measurements

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What w e a re int e res t ed in a reevolu t ion o f t he st ruc t u res a t

m u l t ip le leng t h sc a les

Length & Time

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Examples

Kinetic study of order-disorder phasetransformation in Ni3Mn (1986)

Kinetic study of phase transformation inMn (1999)

Fatigue-induced phase transition (on-going)Transient behavior during welding

Crystallization of bulk metallic glass

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How are neut rons used t o det e rm ine

s t ruc tu res?

Grain morphology andsize distribution

small angle scattering

wide angle diffraction

+ data-- refined-- error| peak position

(100)

(110)

(111)

(200)

(210)

(211)

(220)

+ data-- refined-- error| peak position

(100)

(110)

(111)

(200)

(210)

(211)

(220)

Ni (Al, Fe)

Fe

Al

Ni

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Order-disorder phaset rans fo rm at ion in N i

3Mn

Very difficult to studywith X-ray

Mn Z=25 Ni Z=28

Ideal for neutrons

Ni b=10.3 fm Mn b=-3.8 fm

Tc=510 C

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Real -t im e m easurem ent s

peak w idt h

(211) reflection

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K ine t i c s tudy o f phaset rans fo rm at ion in Mn

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K ine t i c s tudy o f phaset rans fo rm at ion in Mn

Experiments done onHRPD at ISIS

100 m instrument Very high d/dresolution of ~ 4 10-4

Time resolution: 5 minutesper data set

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Mul t iphase Riet veld ana lysis t oy ield volume f rac t ion

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Mul t iphase Riet veld ana lysis t oy ield volume f rac t ion

Tremendous difference in growth rates

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Grow t h behav io r fol low s sc a l ing byJ ohnson-Mehl -Avram i t heory

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Phase t ransform at ion induc ed byc yc l ic loading (fa t igue)

hcp

fcc

*Source: Binary Alloy Phase Diagrams, ASM, Metals Park, OH, 1986, vol.1, p. 759.

The Case of ULTIMET

54Co-26Cr-9Ni-5Mo-3Fe-2W (wt%)

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TransverseDetector Bank

AxialDetector Bank

IncidentNeutron Beam

SpecimenLoad Frame

In -s i t u Neut ron Di f f rac t ion

ENGIN-X at theISIS facility, UK.

Pulsed neutron

source.

40 minute counttimes, Co scatters

poorly.

Sampling volume:

~120 mm3.

M. Benson et al., Powder Diffraction 2005

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Strain-controlledfatigue: R = -1,

tension-compression(R is the ratio of the

minimum strain to

maximum strain).

Total strain range,

= 2.5 %.

Cycling frequency,

f = 0.5 Hz.

Cylindrical specimensof 8 mm gage

diameter, 24 mm gage

length, M12 threadedends.

In -s i t u Neut ron Di f f rac t ion

Collimator

Extensometer

Specimen


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-1,500

-1,000

-500

0

500

1,000

1,500

-1.5 -1 -0.5 0 0.5 1 1.5

250 cycles

Overlay of the axial detector bank diffractionpatterns measured at point 1.

100 cycles

75 cycles50 cycles30 cycles12 cycles

8 cycles4 cycles1 cycle0 cycles

500 cycles

X

111

101102103

311220

200

hcpfcc

Evolut ion of t he hc p phase dur ingfat igue t es t


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Inc rease in t he HCP Peak In t ens i t y as aFunc t ion o f Fat igue Cyc les

Demonstrates the

incubation period found in

austenitic stainless steelsduring low cycle fatigue*.

Demonstrates increase involume fraction as fatigue

progresses and strainaccumulates.

Similar trends in both theaxial and transversedetector banks.

Attributed to the interactionof stacking faults during lowcycle fatigue.**

Increase in intensity of the hcp (101) peak.

Axial Detector Bank

Transverse Detector Bank

* Source: ASM Handbook, Vol. 18. ASM International, 1997.

**Source: L. Jiang, C. R. Brooks, P. K Liaw, J. Dunlap, C. J.

Rawn, R. A. Peascoe, and D. L. Klarstrom, Met Trans A (2004)35 3 785-796.

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Bulk Met a l l ic Glass Mat er ialsEx h ib it Unc onvent ional Proper t ies

Excellent mechanical properties Controllable magnetic properties

-2000 -1000 0 1000 2000

-10

-5

0

5

10

15

M(k

Am

2kg

-1)

H (kAm-1)

as-cast

723 K

748 KRibbon

Nd-Fe-Co-Al

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OAK RIDGE NATIONAL LABORATORY


Part ia l ly Cryst a l l ized Bulk Met a l l ic Glass Cont a insHigh-densi t y Nanom et er Sized Cryst a l l i t es

e.g., upon isothermal

annealing Density 1023-1024 m-3

Crystallite size ~10-50

nm Even for temperatures

close to Tg

Sim ul t aneous Di f f rac t ion and Sm al l Angle

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Sim ul t aneous Di f f rac t ion and Sm al l AngleSc at t er ing in Bu lk Met a l l i c Glass Show

Conc urrent St ruc t ura l and Chem ic a l Order ing

Diffraction SAXS

Wang et al., Phys. Rev. Letter., 2003

Wang et al., unpublished

amorphous crystalline

Structural changes in two length scales

Q(A-1) Tim

e(sec)

Q(A-1)Ti

me(s

ec)

I i t N t Di f f t i M t R l d

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In -s i t u Neut ron Di f f rac t ion Measurem ent s Revealedfor the f i rs t t im e St ress and Tem perat ure Prof i lesdur ing Fr ic t ion St i r Weld ing

x

y

z

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VULCAN Tec hnic a l Dat a

Flight paths Incident ~ 43.5 m Scatting ~ 2 m

Satellite building

Resolution ~ 0.2%

~ 0.9-3.5 Flux on sample (n/s/cm2/)

3107 in high-reso. mode 1.2108 in high-int. mode

Wide angle detectorcoverage, 60-150

SANS Q-range 0.01 0.2 -1

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Summary

Next generation neutron scatteringinstruments, with high flux, will lead to major

breakthroughs in our understanding and,ultimately, the control of structural evolution inmaterials.

07 wang kinetics 070418

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