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Biomechanical Behaviour
of SPD-Processed (Ti-) Materials
Michael J. Zehetbauer
University Vienna, Faculty of Physics
Research Group Physics of Nanostructured Materials
Tutorial Lecture within BIOTINET Summer School
Barcelona
June 3 – June 8, 2012
Lowering the E-Modul by Alloying
Material E(GPa) UTS (MPa)
Bone 20-40 90-140
CP Ti 105 785
-Ti alloys 60-90 600-1000
+ Ti6Al4V 110 960-970
Stainless steel
316L
210 465-950
Co-Cr alloy 230 600-1795
M. Long, H.J. Rack / Biomaterials 19 (1998) 1621-1639
Question:
How to make a material strong without change of
elastic moduli ?
Answer:
Grain refinement by Severe Plastic Deformation
S P D !!
Equal
Channel
Angular
Pressing
(V. Segal, R. Valiev)
Hydrostatic
Extrusion
(M. Pachla, K.
Kurzydlowski) V
High
Pressure
Torsion
(N.Bridgman,
R.Valiev) Accum. Roll
Bonding (N. Tsuji)
SPD – methods
SPD-induced Nanocrystallisation (v = van Mises strain, P = hydrost. pressure,
EBSP method, R. Pippan et al., ESI - ÖAW Leoben, 2002)
T. Waitz,
H.P.Karnthaler
Metallic glasses (TiNi) made by SPD
011
101
110
3 nm
T. Waitz, V. Kazykhanov, H.P. Karnthaler, Acta Mater. (2003)
Composite Model (H. Mughrabi,1979, 1983)
B
A
(large plastic strains – “SPD”):
Polarized Tilt Walls (“PTW’s“) :
Break of Symmetry (at A and B),
“Birth” of new crystallite
(small plastic strains):
Polarized Dipole Walls (“PDW’s“) :
Full Symmetry
Schafler, Zehetbauer, Ungar; Acta Mater 2006
0 20 40 60 800,0
0,4
0,8
1,2
1,6
stage IVstage III
Mw
[ MPa ]
0 20 40 60 80
1
2
3
[ MPa ]
IVIII
2/
2
order in dislocation
arrangement
fluctuations
in dislocation density
2nd order – phase transition !
1211
CC
d
d
2211 ff
Modelling of Stages IV and V (Zehetbauer, Acta metall. mater. 1993,
for SPD: Zehetbauer et al. AEM, 2003)
5
222432 )]0([
CC
d
d
„composite model“:
volume fractions fi , stresses ,
dislocation densities ,
disloc. arrang. parameters
areas with dislocations of type i
compatibility of strains i
hardening/softening by
screws dislocations edges
2211 ff
iii bG
21
most important fit parameter CC44::
Annihilation of edge dislocations by
diffusion-driven climb (low temperature deformation):
C4
= c / [(/2 .(1- )) ½ . exp ((Hmig + p )) / kBT)
.(2-
2(=0)) . d/dt . k
BT .
24 b2 3/( D
c0)]
...atomic volume, p ... hydrostatic pressure
T ... deformation temperature, d/dt ... applied strain rate
(Hmig + p ): “effective” enthalpy of vacancy migration
c : actual conc. deformation induced vacancies ( 10-5 / = 1)
Dc0
: coefficient of dislocation core diffusion ( 10-6 m2 s-1)
Rules to obtain
miminum crystallite size / maximum in strength:
SUPPRESS ANNIHILATION OF DISLOCATIONS !!
• low SPD processing temperature, high strain rate
• high hydrostatic pressure
• high alloy content
• apply > 2 SPD modes with different deformation path
Advantages of SPD – Nanomaterials
(1) Bulk materials for applications
(2) No noxious handling with powders, 100% dense & pore-free
(3) strong, but also ductile or even superplastic materials,
high fatigue strength & life
(4) Typical properties of nanomaterials retained:
enhanced strength, mechanical alloying, excellent
functional properties (magnetic, thermoelectric etc.), enhanced
diffusion (e.g. hydrogen: increased storage &
ab/desorption)
(5) SPD specific additional advantages:
create new phases and new phase transitions
Y.Wang,
M.Chen,
F.Zhou,
En Ma,
Nature 419,
912-915
(2002)
High Strength AND High Ductility of SPD Nanomaterials
Example:
Cu 99.99%
Advanced mechanical properties by SPD
R.Z.Valiev et al., J. Mater. Res. 17, 5-8 (2002)
Application:
SPD of Ti (-X)
Biomaterials
Mechanical Properties - CP Titan
0
200
400
600
800
1000
1200
sta
nd
ard
T
i a
nn
ea
led
na
no
SP
D
Ti
1p
as
s
na
no
SP
D
Ti
10
pa
ss
na
no
SP
D
Ti 10p
ass
+
Ro
llin
g
sta
nd
ard
T
i6A
l4V
EL
I a
nn
ea
led
sta
nd
ard
T
i6A
l4V
EL
I a
ge
d
Fe
sti
gk
eit
[M
Pa
]
0
5
10
15
20
25
30
Du
kti
litä
t [%
]
Rm
Rp02
A5
I
Cooperation with AIT Health & Environment Department
Biomedical Systems, Wr. Neustadt, Austria
(after R.Z.Valiev, V. Stolyarov et al. (2004))
CP2 Ti
UFG Ti processed
by Hydro-Extrusion
UFG Ti, Ti-6Al-4V ELI processed
by ECAP
Fatigue behaviour of SPD
processed Ti (-alloys)
0
1
2
3
4
5
6
-250 -200 -150 -100 -50 0 50 100 150
Temperature, oC
Imp
act
tou
gh
ness
, k
gx
m/c
m2
1
2
From: V.V. Stolyarov, Valiev, L. Zeipper, G. Korb, Fracture Toughness of
bulk ultrafine-grained CP-Titanium processed by SPD (1) coarse grained (2) SPD processed nano-material.
Proc. of the 10th Inter. Conf. on Titanium held in Hamburg, Germany,13-18 July 2003.
Plate implants for pipe bone osteosynthesis
From: R.Z. Valiev, IPAM, Ufa State Aviat. Techn.Univ.(2004)
R.Z. Valiev, Mater.Sci.Eng. A (2007)
Micro-engine
Parts of the micro-engine
(1 m - 2÷3 mm)
Scale of MEMS
Application of SPD-nanostructured materials for micromechanical systems (MEMS)
MEMS applications:
• Aircraft pressure probes, gyroscopes, etc.
• Muscle stimulator, implanted indicators of arterial pressure, cardiostimulators, instruments for microsurgery, etc.
• Micro-engines, micro-pumps, micro-robots, etc.
From: R.Z. Valiev, Mater.Sci.Eng. A (2007)
SPD processing:
Micro & Macro
R.Z.Valiev et al., Ufa State Aviation
TU Ufa, Russia
Y.Estrin et al., Monash Univ.
Melbourne, Australia
(2006)
&
SPD – equipment at the Erich Schmid Institute
Equal Channel Angular Pressing (ECAP)
15 x 15 mm , 10 x 10 mm
nanoSPD Ti Materials:
– CP-Ti (grade 2) & Ti6Al4V ELI
– Diameter: 52, 32, 18 mm
1cm
ECAP CP-Ti
Bolts from UFA Aviation
Technological University, Russia
Start up-Production AIT Biomedical
Systems, Wr. Neustadt, Austria
R. Srinivasan et al. (Mater.Sci.Forum 2006)
ECAP with parallel channels ECAP-Conform
New modifications of ECA pressing
RZ Valiev and TG Langdon, Progr. Mater.Sci.,2006
Outlines of (a) Conshearing and (b) C2S2 processes.
(from: Tsuji et al., Adv.Eng.Mater. 5 (5), 338 (2003)
Cu, Ni, Fe
New HPT-Equipment at ESI Leoben (Pippan et al.)
-196°C < T < 450°C, max. pressure 8 GPa
Sample diameter d = 15, 25, 35mm, Sample thickness = 2, 4, 5mm
Application:
SPD of Gum Biometals
SPD of Bulk Materials within BioTiNet (A. Panigrahi et al.)
Ti alloys [wt%] Phases
Ti-13Nb-13Zr Metastable β
Ti-45 Nb β
Ti-low wt% Nb
(IFW Dresden)
α + β
GUM METAL
Ti-36Nb-2Ta-3Zr-0.30 (mass%)
by Ball Milling & Cold Isost. Pressing
p 400 MPa, T = 1300 C
• Ultra low elastic modulus
• low strength
• small work hardening
Furuta et al., IJMR 2009
Application:
SPD-TiNi
Shape Memory Biomaterials
Shape Memory Effect (SME): Unique martensitic morphology of nc NiTi …
Waitz et al.,
Mater.Sci.Eng. (2008), PNM Univ. Vienna
Waitz et al., Europhys. Lett. (2005)
strain energy density
…leads to increased driving force Eb for MT,
managed by undercooling, and…
-50 0 50 100 150 200 250
-0,4
-0,2
0,0
0,2
0,4
Heat flow
[W
/g]
Temperature [°C]
NiTiHf
G. Steiner
Waitz et al., 2007
CG
UFG
nc
M
s
Transformation of bulk nanocrystalline NiTi
Ultrafine grained / nanocrystalline NiTi
Kockar, Karaman
et al., 2008
Tsuchiya et al., 2009
…to enhanced cyclic stability & superelasticity, and…
Corrosion / Biocompatibility of
SPD Biomaterials ?
• UFG Ti: less corrosion in HCl and H2SO4 solution than
CG Ti, due to enhanced formation of passive films in
case of UFG Ti, because of SPD-induced surface
lattice defects;
• However, impurities/segregations in UFG crystallite
boundaries may enhance corrosion in comparison to CG
materials !
Proliferation of pre-osteoblastic MC3T3-E1 cells extracted from
mice embryos as expressed by light absorbance in MTT assays.
Values E570 – E630 represented by the columns correspond to mean
values also shown in the table below the diagrams. The grey columns
represent the as-received commercial purity Ti as a reference and
the red ones the ECAP processed material. Error bars are also
indicated (Estrin and Zehetbauer (2009)).
Biocompatibility SPD-CP-Ti
Conclusions
• SPD processing of Ti-biomaterials is to provide taylored
high strengths at unchanged Young‘s moduli
• SPD processed Ti–biomaterials appear to allow for
enhanced cell growth in comparison with coarse-grained Ti
– without adding of special surface layers
• SPD processed Ti–biomaterials seem to have a higher
corrosion resistance unless segregations enter the
crystallite boundaries
Open Questions
• SPD may change the fraction of phases, and thus affect
the elastic modulus as a whole (this summerschool) –
learn to handle that effect or even use it !?
• SPD processing of amorphous Ti-Alloys – this is an
actual reserach issue, is not yet settled (and fills
another whole lecture !)
„SPD“ for all the life !
Thank you for your attention !
Quiz for ESRs: A New Biomaterial ?
Biodegradable Mg Stents – need higher strength SPD !
Flow curves for different HPT pressures 2 - 8 GPa
32
31
R
Q
Mres
d
RMres
Measured & fitted disl. densities (Holzleithner et al., UFG 2006)
))()(
()(
1)(
2
2
22
2
1
11
2
ff
Gb
Fe-Cu: Y. Sauvage, F. Wetscher, P. Pareige, Acta Mater. 53, 2127 (2005)
Neue Phasen, z.B. atomar gemischte Legierungen
M. Zehetbauer, D. Trattner, Mater.Sci.Eng. A (1986)
Modelling of HPT of Cu
• Fitting in-situ flow curves under
different hydrostatic pressures
• Fitting Dislocation Densities under
different hydrostatic pressures
• Simul. of Vacancy Concentration...
• Simul. of Grain/Cell and Wall Size...
21
11
LL
Lf
])()(
[)(
1)(
2
2
2
22
2
1
2
11
2
ff
b
3
21
11 ][
LL
Lf
c
)1( 12 ff
i
iiC
2
or
fit of exp. disloc. density
( interaction coeff. i )
fit of flow curve
( disl. storage rates i )
derivation of structural
element sizes
with volume fractions
derivation of activ. enthalpy
for screw annihilation
kT
G
D e C
w
1
3
i
ii
i
ii
ß
2
Dependence of volume fraction on different pressures ((Cu), XPA)
f2 (0.8 GPa) = 0.184
f2 (2 GPa) f2 (8 GPa) =
= 0.164
1
1
12 L
f
LL
Simulation of Structural Size during in-situ deformation
1
2
11
1
111
ßL
p = 0.1 MPa (Holzleithner et al.
UFG 2006)
Simulation of Structural Size during in-situ deformation
1
1
12 L
f
LL
p = 2 GPa
1
2
11
1
111
ßL
Simulation of Structural Size during in-situ deformation
1
1
12 L
f
LL
1
2
11
1
111
ßL
p = 4 GPa
Simulation of Structural Size during in-situ deformation
1
1
12 L
f
LL
1
2
11
1
111
ßL
p = 8 GPa
D.A. Hughes, N. Hansen: Acta mater. 45, 3871
(1997)
Cu, RT cold rolled 50 %
D.A. Hughes, N. Hansen: Acta mater. 48, 2985 (2000)
Summary
Simulation of Sizes: Cell Wall, Grain
• Mean free path of screw dislocations corresponds to grain size (= lattice areas tilted by at least 1°). Screws change into edges which increase the misorientation!
• The measured XPA domain size corresponds to the thickness of grain/cell walls. From simulation, the latter equals to the area occupied by the originally generated edge dislocations.
Eigenschaften
Superplastische nanoSPD Al-Legierung
(nach Furukawa et al., Mater.Sci.Eng. A, 2002)
Enhanced Superplasticity in SPD processed Nanomaterials
M.Furukawa, Z.Horita, M.Nemoto, T.G.Langdon, Mater.Sci.Eng. A324, 82-89 (2002)
Steigerung der Umformbarkeit - Al 1420 (Al-Mg-Li)
Exzellente Kaltwalzbarkeit nach ECAP + Warmwalzen (bei <<500nm Korngröße, Bleche von 0.9mm auf 0.15mm Dicke)
Verbesserte Superplastizität (Bruchdehnung bei 450°C, d/dt=10-3/s von 270% auf 480% bei einer Kraftreduktion um 35% von 22N auf 14N)
Walztemperatur von nanoSPD Al 1420 wurde um 200°C gesenkt
standard 1420 Al
nanoSPD 1420 Al
Gewalzt bei 300°C
mit 82% Reduktion 10mm
Anwendungen
FS (W) = Friction Stir (Welding)
TMAZ = Thermomechanically Affected
Zone
FS (W) = Friction Stir (Welding)
TMAZ = Thermomechanically Affected Zone
YAG-LB = YAG Laser Beam welding
GTA = Gas Tungsten Arc welding
Y.S.Sato et al. NanoSPD3 (Mater.Sci.Forum 2006)
Beschreibung:
Nanomaterial – Gruppe der
Univ. Wien
und weitere
Nanomaterial – Gruppen in
Österreich
European Nanobusiness Association stated an
Impact of Nanotechnology for 2005: 150 Billion EURO
Classical European Metal Producing/Applying Industry (Transport,
Machinery) has a turnover of
1000 Billion EURO / year
„NANO“ : Zahlen – Daten -Fakten
Phase shift achieved by ECAP
Magnesium alloy AM60
Mg- 6%wtAl- 0.13%wtMn
(Kulyasova et al.
Universities Vienna & Ufa,
J.Mater.Sci. 2007
Minimization of coercivity:
Thin foils of soft magnetic nc alloys
(G. Herzer, Physica Scripta 1993)
property conventional SPD-target
Yield strength 195 – 490 MPa at least + 30% up to + 100%
Tensile strength 260 – 515 MPa at least + 30% up to + 100%
Fracture strain 0,11 – 0,25 less than -10%
Low cycle fatigue life time 12.000 1) less than -20%
High cycle fatigue life time 3,5x104 2) at least + 50%, up to +700%
1) at a plastic strain amplitude of 1x10-3
2) at a stress amplitude of 200 MPa
Al alloys: 2XXX, 5XXX, 6XXX, 7XXX, AlMgSc,
Mg alloys: AZ31, AZ61, ZK60
Cu HPT deformed
(Zehetbauer et al. (2003),
Pippan et al. (2004))
resolved shear strain res
0 100 200 300 400
reso
lved
shea
r stre
ss re
s [MPa
]
0
100
200
300
400
500
600
8 GPa
4 GPa
2 GPa
0.1 MPa
0 5 10 15
0
200
400
600
res
0 20 40 60 80 100
res [
MP
a]
100
120
140
160
180
0.8 GPa
2 GPa
4 GPa
8 GPa
0.1 MPa
0 5 10 15 20
120
140
160
180
NanoSPD 3, Mater.Sci.Forum 2006
Plastische Verformung kristalliner Materialien
Verfestigung – „Mecking“ - Plot
Q versus
d
dQ versus
= true = F/Atrue
= ln (l/lo) = - ln do/d
Fließkurve (Bereiche I – V)
)( f
Polycrystalline
Polycrystalline
Zehetbauer Model Stages IV-V
Screw Dislocations () in Cells
Edge Dislocations ( )
in Cell Boundaries
II
III
IV
V
S S Cr Cr
b1
c1
f'
f /E'
HCF
LCF
Conventional grain size
Ultrafine grain size
2 Nt log 2 Nf2 Nf = 1
(HCF) (LCF)
t/2 = (2 Nf)b + f (2 Nf)
c''f
Elo
g
t/2
Schematic illustration of enhanced high-cycle fatigue (HCF) life (albeit
reduced low-cycle fatigue (LCF) life) typical of SPD - UFG materials,
in comparison to conventional ones. Note also the reduced transition
fatigue life Nt. E = Young’s modulus.
From: H. Mughrabi et al., MRS Fall Meeting, Boston, U.S.A. (2001)
Grain size effect : Wöhler (S-N)-Plot, UFG Al
(H.W.Höppel et al., Mater.Sci.Forum 2006)
102
103
104
105
106
107
0
50
100
150
200 CG Al, d
grain 170 µm
Al, dgrain
200 µm,
Thompson & Backofen, (1971)
Al, dgrain
20 µm,
Thompson & Backofen, (1971)
UFG Al, dgrain
850 nm
UFG Al, dgrain
350 nm
/2 /
MP
a
cycles to failure, Nf
20 µm200 µm
?
104
105
106
107
108
109
60
90
120
150
180
Ma
x s
tre
ss, M
Pa
Number of cycles
Homogenized
ECAP at 350 0C
ECAP at 210 0C
ECAP at 150 0C
O. Kulyasova (USATU) et al., M. Zehetbauer et al. (Univ. Vienna) (2008)
Enhanced Fatigue Strength in ECAPed Mg-Al AM 60 alloy
Table 1. Distribution of topical emphases in publications on severe plastic deformation from 1990-
2002
Topic Number of publications as of August 1999
Number of publications as of December 2002
Microstructures 144 490
Properties 78 445
Synthesis and processing methods 44 255
Modeling 18 102
Applications and products 18 73
(from T.C.Lowe, Y.T.Zhu, Adv.Eng.Mater. 5 (5), 373 (2003)
European Nanobusiness Association stated an
Impact of Nanotechnology for 2005: 150 Billion EURO
Classical European Metal Producing/Applying Industry (Transport,
Machinery) has a turnover of
1000 Billion EURO / year
only 10 ppm for SPD-designed metals results in a turnover of
10 Mio EURO / year
„NANO“ : Numbers & Dates & Facts
Superplastische nanoSPD Al-Legierung
(nach Furukawa et al., Mater.Sci.Eng. A, 2002)
Effect of Nanoscaling on thermally induced martensitic phase
T.Waitz, D.Spisak,
J.Hafner, H.P.Karnthaler,
Europhys.Lett. (2005)
‘Forbidden‘ twin structure
of martensite formed in
nanocrystalline NiTi
Project coordinator:
Michael J. ZEHETBAUER
Research Group Physics of Nanostr. Materials
Faculty of Physics, University of Vienna
High Performance Bulk
Nanocrystalline Materials
National Research Network NFN- S10400
Austrian Academy of
Science
Erich Schmid-
Institute of
Material Science
Project 02
University of
Vienna
Physics of Nanostructured
Materials
Projects 01, 03 Vienna University
of Technology
Institute of Solid
State Physics
Project 06
Karl-Franzens-
University Graz
Institute of Physics
Project 07
Graz University
of Technology
Institute of
Materials Physics
Project 04, 05
X. Sauvage
Rouen, France
D. Jiles
Cardiff, Great Britain
Austrian Research
Network
„High Performance Bulk
Nanocrystalline Materials“
J. Shirai
Osaka, Japan
C. Koch
Raleigh, USA
J. Eckert
Dresden, Germamy
J. Weissmüller
Karlsruhe, Germany
Tunable properties by electronic interface charging
Voltage-induced excess
at interfaces
High number of interfaces in
nanocrystalline materials
H. Gleiter, J. Weissmüller, O. Wollersheim, and
R. Würschum, Acta Mater. 49 (2001) 737.
Electrochemical double layer at the
nanocrystal–electrolyte interface:
Charge variation in surface
layer of several 1/10 e- / atom
Nanomaterials
with tunable properties
(magnetic, electronic, optical…)
Concept
resistance susceptibility
H. Drings, R. Würschum et al.
Appl. Phys. Lett. 88 (2006) 253103.
M. Sagmeister, R. Würschum et al.
Phys. Rev. Letters 96 (2006) 156601.
electron
excess
electron
excess
J. Weißmüller, R. Würschum et al.
Science 300 (2003) 312.
length
electron
excess
Pt Pt Pd
mechanic electronic magnetic
State of Research: Tunable Properties of nanocrystalline metals
M. Weisheit et al., Science, Jan. 07:
Field-induced modification of
magnetism of thin films
„Effect of equal channel angular pressing on
tensile properties and fracture modes of casting
Al–Cu alloys“
MSE A, 426, 305-313
D.R. Fang, Z.F. Zhang, S.D. Wu, C.X. Huang, H.
Zhang, N.Q. Zhao and J.J. Li
Table 1. Distribution of topical emphases in publications on severe plastic deformation from 1990-
2002
Topic Number of publications as of August 1999
Number of publications as of December 2002
Microstructures 144 490
Properties 78 445
Synthesis and processing methods 44 255
Modeling 18 102
Applications and products 18 73
(from T.C.Lowe, Y.T.Zhu, Adv.Eng.Mater. 5 (5), 373 (2003)
Feste
Wasserstoff-speicher für Brennstoffzell-Technologie
Nano-Pulver erhöhte Diffusion und Kinetik
durch mehr Kristallitgrenzen
kleinere Desorptionstemperatur
Oberflächen-Kontamination
Kommerzielle teure Technologie, Umweltrisken
Massive NM
T.Klassen, et al., Z. Metallkd., 94, 610 (2003)
Grobkristalline
Struktur Nanokristalle
Cooperation:
PNM University Vienna
AIT Biomedical Systems,
TU Ufa & Industry
Construction of an ECAP
tool for processing of
nanoSPD-materials
120° Channel Angle
20 mm Diameter
Processing Temp.
1000°C
From: M.Skripnyuk, E.Rabkin, Y.Estrin, R.Lapovok, Acta mater. 52, 405 (2004)
(a) Grain size effect to H2-desorption kinetics
(b) Catalysator effect to H2-desorption kinetics
(a) (b)
Effects to desorption kinetics in ECAPed ZK 60
(Krystian et al., 2008)
From: M.Skripnyuk, E.Rabkin, Y.Estrin, R.Lapovok, Acta mater. 52, 405 (2004)
RF plasma nitriding of SPD deformed Fe-based alloys
(H. Ferkel, Y. Estrin, R.Z. Valiev et al. (MSE A, 2003)
HPT achieves doubling of thickness of nitrided layer
High-pressure-torsion die with a sample size of 10 mm in diameter and 0.8 mm in height
placed in the center of a 40 mm die. The sample chamber is filled with a setup of a 2 mm wide
bar of metallic glass next to two cuts of polymer. (b) Optical microscopy image of a cross-
section of an Au-based metallic glass / HDPE composite processed by two turns in high-
pressure torsion
(A. Kündig, J.Löffler, ETH Zürich, coop.with IMP Vienna and ESI Leoben)
Metallic glass / polymer composites by co-processing at similar viscosities
Nanokristalle absorbieren
Bestrahlungsdefekte
M.Rose, A.G.Balogh, H.Hahn (1997)
Sizes: Magn. Domains & Grains in SPD steel P800
300 nm
R. Pippan et al.,
Mater.Sci.Forum
2006
Hc measured by ring test as function of grain size D measured by SEM- BSE
(Scheriau et al., 2010). Full lines: Models (Herzer, Physica Scripta 1993).
Coercivity in soft magnetic HPT Fe and Fe alloys
Application of Thermoelectrics
Properties needed for
Thermoelectrics
Produceable by a synthesis
process
High TE properties (high ZT)
Thermal stability and reliability
Sufficient mechanical strength
for device integration (stress)
Stiffness (Young‘s, shear, bulk
modulus)
High density (>95%)
TEG VW
Ulysses Spacecraft Thermosflask
air cooler
figure of merit efficiency
ZT = S2T/(κ)
S: Seebeck coefficient - thermopower
: Electrical resistivity
(S2/): Power factor
: Thermal conductivity
= e+ l
e: electronic thermal conductivity (e= L0T/)
l: lattice thermal conductivity …….. phonon scattering
- filling with “rattling” atoms
- introducing defects, GBs nanograins)
h
ca
a
h
ch
T
TZT
ZT
T
TT
)(1
1)(1
Tc: temperature at cold site
Th: temperature at hot site
Cooperation PNM IPCh , Univ. Vienna
Skutterudite: cubic structure with formula TPn3
T = Co, Fe, Ni … Pn = P, As or Sb
Space group : Im –3 ; sites: T: 8c (¼, ¼, ¼) , Pn: 24g (0, y, z), void: 2a (0,0,0) or (½,
½, ½).
T
(Co,Fe,Ni...)
Pn (P,As,Sb) Filler atom
p- and n-type filled skutterudites
Nanocrystallization by Ball Milling, BM (Zhang et al., 2010)
ZT = S2T/(κ)
Zusammenfassung
Herstellung massiver nanokristalliner Materialien mittels der Methode der
„Severe Plastic Deformation“ – formkonstante plastische Hochverformung unter
erhöhtem hydrostatischen Druck
Besondere Eigenschaften von SPD-hergestellten Nanomaterialien:
Mechanisch, Magnetisch, Elektrisch, H-Speicherung
- Anwendungen von SPD Nanometallen
Al- und Mg-Legierungen: (ermüdungs)festeres Material f. d. Auto- und
Flugzeugindustrie (Gewicht !),
raschere Herstellung von Tiefziehprodukten (z.B. Druckbehälter)
Mg-Legierungen: Verbesserte Speicherg. H2 (Brennstoffzellen - Technologie)
Fe-Legierungen: festeres Material f. d. Autoindustrie, verbesserter Magnetismus
für Polschuhe (Motoren), Ton/Videoköpfe, Mechatronik
Ti, Ti und Mg- Legierungen): Festeres biokompatibles Material für Prothesen,
Implantate und Stents
- Anwendungen von SPD Nichtmetallen: Verbesserte thermoelektrische Energiequellen
- Anwendungen als MEMS (Micro-Electro-Mechanical-Systems) mit verbesserten
mechanischen und magnetischen Eigenschaften
4.750 4.775 4.800 4.825
10 3
10 4
<111>
Arb
itra
ry U
nits
K [ 1/nm ]
4% Planar Faults
Extrinsic Intrinsic Twins
X-Ray Bragg Peak Profile Analysis (XPA) : Versetzungen, planare Gitterdefekte (Zwillinge, Stapelfehler)
(T.Ungar, TMS 06, Symposium UFG IV)
Cu single crystal deformed
in compression
In-situ deformation
X-ray Bragg Profile Analysis
with Synchrotron radiation
(Beamline SAXS of ÖAW,
ELETTRA, Trieste
M.Zehetbauer, T.Ungar,
E.Schafler et al. 1999 ff.)
E. Schafler, T. Ungar,
M. Zehetbauer et al.
to be published (2004) K
I/IMAX
0 25 50 750
100
200
300
IVIII
d/
d
[ M
Pa
]
[ MPa ]
Present data
Göttler [??]
Cu single crystal deformed in compression
(E. Schafler et al, Acta Mater.( January 2005)
MEMS: Forcefill between IC‘s as an applied case of ECAP
(after R. Hellmig, Y. Estrin, Clausthal University, Germany (2003)
Gum metal in scientific community
Saito and coworkers have developed this multifunctional alloy
Saito et.al. Materials Science Forum Vols. 426-432 (2003) pp 681-688
Cold worked sample Tensile test of cold working specimen Annealed sample
