Phase transformation kinetics in a near-β titanium alloy · PDF filePhase transformation...

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Phase transformation kinetics in a near-β titanium alloy P. Barriobero Vila (a) , F. Warchomicka (a) , G. Requena (a) , M. Stockinger (b) , Thomas Buslaps (c) (a) Institute of Materials Science and Technology, Vienna University of Technology, Karlsplatz 13/308, A-1040 Vienna, Austria (b) Böhler Schmiedetechnick GmbH & Co KG , Mariazeller Strasse 25, A-8605 Kapfenberg, Austria (c) ID15, European Synchrotron Radiation Facility, Rue J. Horowitz, 38042 Grenoble, France [email protected] München, 12.09.2012

Transcript of Phase transformation kinetics in a near-β titanium alloy · PDF filePhase transformation...

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Phase transformation kinetics in a near-β titanium alloy

P. Barriobero Vila (a), F. Warchomicka (a), G. Requena (a),

M. Stockinger (b), Thomas Buslaps (c) (a) Institute of Materials Science and Technology, Vienna University of Technology, Karlsplatz 13/308, A-1040 Vienna, Austria

(b) Böhler Schmiedetechnick GmbH & Co KG , Mariazeller Strasse 25, A-8605 Kapfenberg, Austria

(c) ID15, European Synchrotron Radiation Facility, Rue J. Horowitz, 38042 Grenoble, France

[email protected]

München, 12.09.2012

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1- Goal 2- Experimental 2.1. Material

2.2. Techniques: - In Situ High Energy Synchrotron X-ray Diffraction (XRD) - Differential Scanning Calorimetry (DSC)

3- Results 3.1. Bimodal microstructure

3.2. Lamellar microstructure 3.3. Beta quenched microstructure

4- Summary

Content

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1- Goal

To study the phase transformation kinetics during continuous heating of a near-β titanium alloy with

different initial microstructures

Methods Differential Scanning Calorimetry (DSC) Identification of precipitation and dissolution processes In situ High Energy Synchrotron X-ray diffraction (XRD) Identification AND quantification of microstructural phases

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β transus

Temperature

Mo eq. (wt.%)

β Stabilizers Characteristics Aplications

808ºC 10,81%

• Excellent

Forgeability

• High strength

• High toughness

(air, salt water)

Aerospace industry

(variety of components)

2- Experimental

Ti-10V-2Fe-3Al

Near-β alloy

Leyens, 2003

2.1. Material

Handbook of Titanium Alloys, 2007

R.R. Boyer, JOM 2010

Boeing 777

Lütjering, 2007

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2- Experimental 2.1. Material: Initial microstructures

50µm 40µm

Large α Lamellae

Lamellar

5 k/min

T (°C)

t (min)

TβTRANSUS

Ar Atmosphere

10µm

Small α Lamellae

Bimodal

3µm

T (°C)

t (h)

TβTRANSUS 763°C / 2 h

510°C / 8 h

Ar Atmosphere

Secondary α-lamellae

Primary α

50µm

Metastable β grains

Beta quenched

α‘‘ martensite

Water

quenching

T (°C)

t (min)

TβTRANSUS

Ar Atmosphere

ωath

β

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2- Experimental 2.2. Techniques: In Situ High Energy X-ray Diffraction

E. Aeby-Gautier, JOM 2007

MAUD

Quantitative

phase analysis

(Rietveld)

Image

processing

2D analysis

(calibration/integration/

image analysis)

20 k/min

T (°C)

t (min)

TβTRANSUS

Ar Atmosphere

900ºC ID15-ESRF

E= 87keV ʎ= 0.1426Å

Slit size = 0.3x0.3 mm²

Acquisition time = 2s

Readout time = 1s

Sample size = 4x4x10 mm³

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Reference Sample

Alumina

Crucible

Alumina

Ti1023

Sample

Ø=5mm

L=1,6mm

2- Experimental 2.2. Techniques: DSC

20 k/min

T (°C)

t (min)

TβTRANSUS

Ar Atmosphere

900ºC

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3- Results

Bimodal

f (T)

2-Theta (°)

T (°C)

α (100)

α (002)

β (110)

α (101)

α (100)

α (002)

β (110)

α (101)

α+β→ β

Lamellar

f (T)

T (°C)

2-Theta (°)

Beta quenched

f (T)

T (°C)

2-Theta (°) α‘‘ (110)

α (100)

α (002)

α (101)

α‘‘ (020)

β (110)

α‘‘ (002)

α‘‘ (111)

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TβTRANSUS α+β→ β

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3- Results 3.1. Bimodal microstructure

Two dissolution processes may indicate sequential dissolution of α secondary α primary Ti64, P. Barriobero Vila, Diplomarbeit

Start α+β→ β DSC T~ 425-450 °C XRD T~ 450-500°C

End α+β→ β DSC T~ 875°C

aβ shows a sudden increase

at T=500°C Diffusion of alloying elements

Primary α

50µm

3µm

Secondary α-lamellae

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exo

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50µm 40µm

Large α Lamellae

10µm

Small α Lamellae

3- Results 3.2. Lamellar microstructure

Assymetric endotermic peak may indicate sequential dissolution of smaller and larger lamellae

Ti17, E. Aeby-Gautier, JOM 2007

Content of alpha increases from ~ 65wt% to ~75wt% during heating up to 600°C Slightly higher than for Bimodal (~ 70 wt%)

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exo

Start α+β→ β DSC T~ 500-550°C XRD T ~ 575°C

End α+β→ β DSC T~ 875°C

aβ shows a sudden increase at

T=500°C

Diffusion of alloying elements

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900°C β

exo

Metastable β grains

α‘‘ martensite

ω

282°C ω+β +α’’

Start α+β→ β DSC T~ 575 °C

End α+β→ β DSC T~ 855°C XRD: Beta quenched microstructure shows the

presence of stable α and β

plus metastable ωath, ω, α’’, α’’iso phases at different stages during heating

3- Results 3.3. Beta quenched microstructure

390°C ω+β +α’’

α

577°C β+α

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437°C β + α’’iso.

• Ivasishin, Materials

Science and

Engineering 2005

• E. Aeby-Gautier,

Journal of Alloys and

Compounds 2012

Azim

uth

(°)

2-Theta (°)

150°C

β α‘‘

ωath.(TEM)+β+α’’

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4- Summary

• In Situ High Energy XRD:

Reveals the phases and its weight/volume fraction as f(T)

The faster increase of the aβ cell parameter at a threshold temperature of 500ºC

may be due to the diffusion of alloying elements into β phase (Al, Fe and/or V)

• DSC:

Reveals that the α phase (identified by XRD) dissolves at different stages

depending on its morphology fine lamella start to dissolve earlier than coarse

lamellae or globular α

- The bimodal and lamellar microstructures show the presence of α and β

phases at different stages during heating (no metastable phases were

observed)

- The beta quenched microstructure presents a much more complex phase

transformation kinetics as a consequence of the formation of the metastable

phases α’’, α’’iso, ωath, ω 12/14

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4- Summary

Bimodal starts earlier due to the presence of smaller α-lamellae higher surface energy

Outlook:

- Metallography of microstructures frozen at different stages during

heating needs to be done to confirm the dissolution sequence of the

different α morphologies

- The complex phase transformation kinetics of the Beta quenched

microstructure will be quantified by Rietveld analysis.

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Microstructure

Start α+β→ β Temperature (ºC)

aβ Increasing

temperature

(ºC)

End α+β→ β Temperature (ºC)

DSC XRD DSC

Bimodal 425-450 450-500 500 875

Lamellar 500-550 575 500 875

Beta quenched 575 - - 850

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David Lorrain (DSC), Georg Fiedler (Programming), David

Canelo (XRD data processing), Martin Stockinger (Ti-alloys),

Sabine Schwarz (TEM), Fernando Warchomicka, Guillermo

Requena

Beamline Scientist:

Thomas Buslaps (ESRF-ID15)

Acknowledgements

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