Assessment of Shape Memory Alloys

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– FROM ATOMS TO ACTUATORS –

VIA IN SITU NEUTRON DIFFRACTION

Othmane Benafan

Structures and Materials Division NASA Glenn Research Center

Cleveland, OH 44135

The ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, September 8-10, 2014 – Newport, Rhode Island

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It Takes a Team…

S.A. Padula II, R.D. Noebe, A. Garg, D.J. Gaydosh, G.S. Bigelow and T.J. Halsmer

Structures and Materials Division NASA Glenn Research Center

R. Vaidyanathan and D. E. Nicholson Advanced Materials Processing and Analysis Center

Materials Science and Engineering Department University of Central Florida

B. Clausen and D. Brown Los Alamos Neutron Science Center

Los Alamos National Laboratory

K. An and H.D. Skorpenske Spallation Neutron Source Oak Ridge National Laboratory Acknowledgment

• NASA Fundamental Aeronautics Program, Fixed-Wing and Aeronautical Sciences Projects • Basic Energy Sciences (DOE)

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Motivation and Objectives

• We examine microstructures of:

• Conventional structural materials by quenching in the high temperature structure and examining at room temperature.

• This cannot be done for SMA’s because of the diffusionless phase transformation (austenite/martensite) cannot be suppressed by quenching

• Shape memory alloys (SMAs) have strong surface effects: thin films

and surface methods (e.g., SEM, x-ray) are of limited use. Neutrons are

a microscopic bulk probe: high penetration allows the examination of

the interior of bulk materials.

• Neutrons are non-destructive: complete, intact specimens/ components

can be studied in small samples (~mm) or in bigger engineering

components (~m)

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Length Scale in Engineering Materials

Where Does Neutron Diffraction Fit?

10-10 ₁₀-9 ₁₀-8 ₁₀-7 ₁₀-6 ₁₀-5 ₁₀-4 ₁₀-3 ₁₀-2 nm Pm mm Å m TEM SEM / FIB OM 10-1 ₁₀0 HRTEM / STEM

ATOM PROBE / FIM

NEUTRON / X-RAY DIFFRACTION

STRUCTURAL SCALE (COMPONENTS) MICRO-SCALE (MICROSTRUCTURES) ATOMIC SCALE (NANOMATERIALS) LOAD FRAMES 0 200 400 600 800 0 5 10 15 20 stre ss ( M Pa) strain (%) 15% 10% 5% 8% 13% 18% (b) 0%

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Chemistry Physics Engineering Life sciences Biosciences Materials science Geological sciences Archeology Chemistry Engineering Materials science

W. Kockelmanna et al. _{Courtesy: Mario Bieringer}

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Neutrons at the Experimental Area

sample detector neutron beam 0, 0 E kk _{E k}_,_k 0 4 sin Q k k S T O 4 sin k k sin

2 2

0 2 0 2 k k E E E m Z ' ₂ 0 2 Z Z k: wavevector E: energy Q: scattering vector

h: reduced Planck constant m: mass (1.67 x 10-24_g)

O: wavelength

2T: scattering angle

Nomenclature

• Now we have neutrons, what next?

• Neutron beam with a known

wavevector (k₀) and energy

(E₀)

• Detect number of scattered

neutrons with a wavevector (k) as a function of the scattering function S(Q,ω) INCIDENT NEUTRON BEAM D ETEC TO R DIFFRACTED BEAM D ETEC TO R BEAM STOP LOADING AXIS LATTICE PLANES // AND A d k₀ k 2T nO= 2dsinT

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1.0 2.0 3.0 lattice plane spacing (Å)

n o rm a li zed in te n sit y ( a rb it ra ry u n it s) 100 11 0 111 data and Rietveld fit difference curve peak positions 200 210 21 1 no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) no rm aliz e d in te n s it y d-spacing (Å) ¾Peak position

•Elastic lattice strain •Intergranular strains ¾Peak intensity •Texture changes •Phase fraction ¾Peak width •Qualitative information

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Isothermal Deformation - Loading Actuators

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Isothermal Deformation - Loading Actuators

Binary 55NiTi d-spacing (Å) intensity (a.u.) strain (% ) load unload intensity (a.u.) strain (% ) load unload (01 1) M (100) M (1 10) M (020) M (111 ) M (1 11 ) M (120) M (121) M (120) M (030) M (031) M (013) M (230) M (150) M (141) M 1 1.5 2 2.5 3 1 1.5 2 2.5 3 planes // planes A (b)

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Isothermal Deformation - Loading Actuators

300 400 500 600 200 300 400 temperature (ºC) 0.2% off se t-st re ss ( M P a ) _{4.14 10}4 330 T SIM T e V u u u Elastic* SIM _{3.09 10}3 1003 T pl T e V u u u Plastic <100>{001} <100>{110} <22-1>{114} <-1-11>{112} Slip: Twinning: M_d 0 200 400 600 800 1000 0 5 10 15 20 st re ss ( M P a) strain (%) Region II Region III Region IV Region I Ni49.9Ti50.1 Room temperature Self-accommodated Martensite Reverse reorientation Reorientation and detwinning (20-1)B19' twinning system Possible slip

Martensite

Austenite

• Deformation mechanisms revealed- complexity and multiplicity of mechanisms can’t be resolved another way

• e.g., reorientation planes/limits, stress- induced-martensite region, martensite desist...

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• No major differences in transformation strains • Large strain evolution (ratcheting) difference

Isothermal Deformation – Where to Load

Actuators? Does it Matter?

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SMA Properties – Can they be Optimized for

Actuators?

1. Material and Geometry‡

• Binary 55NiTi → I = 5.08mm (0.2in) • Stress free transformation temperatures

• • • •

• Effective coefficient of thermal expansion •

•

• Effective elastic moduli •

•

• Effective Poisson’s ratios • • * 6 * 6 13.0 10 / 6.4 10 / A M C C D D u q u q * * 74 50 A M E GPa E GPa * * 0.33 0.387 A M Q Q 92 105 71 55 s f s f A C A C M C M C q q q q 0.10 0.15 0.20 0.25 0.30 0 50 100 150 200 250 heating cooling St ra in (% ) Temperature (ºC) * M D * A D 0 100 200 300 400 500 600 0 1 2 3 4 5 6 austenite martensite St re ss ( M P a ) Strain (%) A s V M f V M s V A E M E

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Transformation Temperatures: DSC vs.

Strain-Temperature vs. Neutrons

d-spacing (Å) 1 1.5 2 2.5 3 0 1 0 1 in te n sit y ( a .u .) (b) (c) te mp er at u re ( ºC ) 30 he a ti n g co o lin g 230 in te n sit y (a .u .) 30 As Af M_s M_f (100) A (1 10) A (111 )A (210) A (221) A (2 1 1 )A (0 1 1 )M (100) M (1 10) M (111 )M (1 10) M (111 )M (102) M (030) M (202) M (320) A re ta in ed B1 9 ' Asneutron 0 40 80 120 160 200 str a in (% ) temperature (ºC) 0.1% in situ ex situ (a) heating cooling

• Transformation temperatures during the reverse transformation measured from strain-temperature and DSC data were found to differ from the actual onset of transformation as revealed from neutron spectra.

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Dynamic Young’s Modulus for Ni

_49.9

Ti

_50.1

50 60 70 80 90 0 40 80 120 160 200 Y o ung 's mod u lus (GP a ) temperature (ºC) cooling (a) T = 200 ºC/h. L =50 h =4 w = 3 heating 50 60 70 80 90 0 40 80 120 160 200 Y o ung 's mod u lus (GP a ) temperature (ºC) heating (b) T = 765 ºC/h. L =50 w = 4.9 w 50 60 70 80 90 0 40 80 120 160 200 Y o ung 's mod u lus (GP a ) temperature (ºC) heating (c) T = 200 ºC/h. L =50.2 d = 4.95 50 60 70 80 90 0 40 80 120 160 200 Y o ung 's mod u lus (GP a ) temperature (ºC) heating (d) T = 200 ºC/h. L = 50 h = 4 5

• Dynamic Young’s modulus data obtained from the impulse excitation of vibration tests. • The average dynamic modulus of martensite at room temperature was about 70 GPa, but

decreased with increasing temperature with an average minimum value of 60 GPa at ~80 ºC.

O. Benafan et al., Scripta Materialia, 2013 68(18), p. 571–574 ASTM E1876-09

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0.2% Offset “Yield” Stress Behavior of Ni

_49.9

Ti

_50.1

0 200 400 600 800 0 4 8 12 16 180 ºC 150 ºC 160 ºC 120 ºC 100 ºC 80 ºC 90 ºC 70 ºC 60 ºC 50 ºC 40 ºC 30 ºC st re ss ( M P a ) strain (%) (a) 100 200 300 400 0 40 80 120 160 200 0.2% offse t-st ress ( M P a ) temperature (ºC) (b)

• The onset of inelastic deformation (generally referred to as ‘yield’) in the martensite phase is dominated by

reorientation and detwinning mechanisms.

• Decrease with increasing temperature, reaching an averaged minimum value of 140 MPa between 65 and 80 ºC. • The onset stress then sharply increased

in the two-phase region and reached near saturation (with a still slightly

positive slope) at 350 MPa near 130 ºC. • Inelastic deformation over this

temperature range (~90 – 130 ºC), which includes the B19'→ B2 phase transition, is attributed to the nearly concurrent operation of stress-induced martensite and plastic deformation.

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Transformation Temperatures: DSC vs.

Strain-Temperature vs. Neutrons

d-spacing (Å) 1 1.5 2 2.5 3 0 1 0 1 in te n sit y ( a .u .) (b) (c) te mp er at u re ( ºC ) 30 he a ti n g co o lin g 230 in te n sit y (a .u .) 30 As Af M_s M_f (100) A (1 10) A (111 )A (210) A (221) A (2 1 1 )A (0 1 1 )M (100) M (1 10) M (111 )M (1 10) M (111 )M (102) M (030) M (202) M (320) A re ta in ed B1 9 ' Asneutron 0 40 80 120 160 200 str a in (% ) temperature (ºC) 0.1% in situ ex situ (a) heating cooling

• Transformation temperatures during the reverse transformation measured from strain-temperature and DSC data were found to differ from the actual onset of transformation as revealed from neutron spectra.

• The austenite phase starting to form at ~75 ºC, O. Benafan et al, Scripta Materialia, 2013 68(18), p. 571–574

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Thermomechanical Cycling of Actuators

(400)H ZA:[110]B2||[010]H (001)B2 200nm 500nm 0 30 60 90 120 150 180 210 240 270 300 330 {110}_A lattic e str a in (% ) 0.5 0 -0.5 55NiT i NiT iPd NiT iHf Outcome In situ diffraction Electron diffraction 10 nm precipitates 20 nm precipitates 114M,T 110T 002T 112T 110M 002M 112M –0.0 –_5.0 –2.5 2 0 cy cl es 50 c y cl es 0 c y cl es –0.0 –_3.0 –1.5

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SMA Properties – Can they be Optimized for

Actuators?

• • • •

•

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Coefficient of Thermal Expansion:

Large Anisotropy

-0.4 -0.2 0 0.2 0.4 20 40 60 80 100

calculation (isotropic average)

extensometry self-consistent model lat tic e st ra in (% ) temperature (°C) B19' NiTi (heating) 110 001 101 111 020 111 120

solid symbols: neutron data solid lines: calculation

201 (a) 0.20 0.25 0.30 0.35 0 20 40 60 80 100 20 40 60 80 100 120 140 160 heating (strain%) cooling (strain%) heating (vol.%) cooling (vol.%) ma c ros copic s tra in (%) temperature (°C) vol u me pe rc ent of B1 9' N iTi (%)

• Atomic scale measurements of thermal strains

Heating (10-6/qC) Cooling (10-6/qC) B19' NiTi Thermal expansion tensor components D11 -47.2 -30.8 D₂₂ 43.8 32.1 D33 22.7 27.3 D31 29.0 32.4 CTE* _6.4 _9.5 CTE† 8.1 10.9 CTE (extensometry) 10.3 9.0 B2 NiTi CTE* _13.0 _13.1 CTE (extensometry) 12.4 12.3

*_{isotropic average}†_{self-consistent model}

• Outcome

• First report on NiTi CTE tensor (monoclinic martensite) including negative expansion in certain crystal orientations

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Coefficient of Thermal Expansion:

Large Anisotropy

• Similar observation in HTSMAs (e.g., NiTiPt – B19)

-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 40 80 120 160 200 240 la tt ic e s tr a in ( % ) temperature (oC) B19 Ni 29Ti50Pt21 heating

solid symbols: neutron data solid lines: calculation

... extensometry 011 030 013 121 111 102 120 0 0.05 0.1 0.15 240 260 280 300 320 340 100 110 111 210 la tt ic e s tr a in (% ) temperature (oC)

solid symbols: neutron data

. . . extensometry

---calculation (isotropic average)

B2 Ni

29Ti50Pt21 (heating)

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SMA Properties – Can they be Optimized for

Actuators?

• • • •

•

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Elastic Moduli: Hard and Soft Orientations

-400 -200 0 200 400 -4 -2 0 2 4 6 stress (MP a ) strain (%) macroscopic detwinning start macroscopic detwinning start -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 -400 -200 0 200 400 100 012 102 100 model 012 model 102 model 100 single crystal 012 single crystal 102 single crystal lattice strain (%) applied s tress(MP a ) macroscopic detwinning start macroscopic detwinning start

• Strain anisotropy and texture measurements

• Outcome

• First validation of ab initio calculation • Entire compliance matrix, not just a

Young's modulus

• Revealed mechanisms responsible for deflated modulus values obtained from conventional macroscopic tests

# of points R 100 128.2 129.8 132.2 6 0.997 012 136.0 146.7 145.4 6 0.978 102 157.3 152.8 167.1 6 0.999 -120 33.8 106.0 101.4 6 0.997 121 84.2 116.3 104.6 6 0.996 -112 177.6 147.6 165.1 6 0.999 -122 120.2 143.7 110.5 5 0.991 -111 85.9 130.2 104.7 5 0.999 011 175.9 155.7 117.1 6 0.995 -121 53.4 122.0 93.3 5 1.000 -110 41.0 105.1 78.2 6 0.997

Single crystal Model

hkl crystal Neutron diffraction hkl E neutron hkl E model hkl E

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Elastic Moduli: Hard and Soft Orientations

0 200 400 600 800 1000 0 1 2 3 4 5 6 7 50Ti 50.5Ti stress (M Pa ) strain (%) 0 200 400 600 800 1000 1200 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 011 002 111 120 102 121 030 013 122 032 ap p lied stres s (M Pa) lattice strain (%)

NiTiPt

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Elastic Moduli: Hard and Soft Orientations

O. Benafan et al., unpublished work

NiTiPt

0 50 100 150 200 250 -0.1 0 0.1 0.2 0.3 0.4 011 002 111 120 102 121 030 013 122 032 ap p lied stres s (M Pa) lattice strain (%)

E

₀₁₁

=257.8 GPa R=0.985

E

₀₀₂

=138.7 GPa R=0.994

E

₁₁₁

=99.2 GPa R=0.997

E

₁₂₀

=55.1 GPa R= 0.988

E

₁₀₂

=138.3 GPa R=0.993

E

₁₂₁

=75.3 GPa R=0.995

E

₀₃₀

=173.0 GPa R=0.998

E

₀₁₃

=132.3 GPa R=0.988

E

₁₂₂

=88.3 GPa R=0.996

E

₀₃₂

=218.6 GPa R=0.886

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Optimization of Two-Way Shape Memory Effect

• Uniaxial deformation at room temperature followed by free recovery

• Outcome

• Established a quick and efficient method for creating a strong and stable TWSME • Texture maps were used to determine

deformation modes – correlated with TWSME stability and magnitude (not possible another way)

strain (%) stress (M P a) 50 100 150 200 0 2 4 6 8 10 12 14 16 18 20 22 0 100 200 300 400 500 600 700 800 900 1 2 3 4 5 6 7 A B C D 0.00 3.50 3.00 0.50 1.00 1.50 2.00 2.50 0.00 8.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0.0 0.5 1.0 1.5 2.0 2.5 0 2 4 6 8 10 12 cycle number (#) H = 6% H = 22% H = 20% H = 18% H = 16% H = 14% H = 10% tran sf ormation strai n (%) (a)

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Shape Setting of SMA Actuators

heating cooling pre-strain 1 pr H 1 pr H

• In situ neutron diffraction during shape setting of bulk polycrystalline NiTi

• Outcome

• Guidelines for shape setting any actuator: stress and temperature limits for shape setting

• Neutrons revealed mechanisms responsible for the stress generation and relaxation during

shape setting. -0.4 0.0 0.4 0.8 100 200 300 400 100 110 111 210 211 220 221 311 CTE (c) str a in ( % ) temperature (ºC) heating CTE B2 planes A to loading direction

0 100 200 300 400 0 100 200 300 400 s tre s s (M Pa ) temperature (oC) 2nd shape set 1st shape set T = 30 ºC T = 300 ºC [1] O. Benafan et al. (2012)

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Torsional Characteristics of 55NiTi

0 20 40 60 80 100 300 330 360 390 420 450 T = 5.17 N-m temperature (K) (a) an gle o f tw is t (d eg ) heating cooling 0 20 40 60 80 100 300 330 360 390 420 450 temperature (K) (b) an gle o f tw is t (d eg ) heating cooling T = 0 N-m (TWSME) 0 20 40 60 80 100 300 330 360 390 420 450 temperature (K) (d) an gle o f tw is t (d eg ) heating cooling T = 0 N-m (TWSME) 0 20 40 60 80 100 300 330 360 390 420 450 temperature (K) (c) an gle o f tw is t (d eg ) heating cooling T = 5.17 N-m Solid tube d-spacing (Å) No rm alized intens ity (a .u.) 1.0 2.0 3.0

data and Rietveld fit

difference curve peak positions 303 K 438 K {100} {110} {111} {210} {221} (011) (100) (110) (120) (120) (111) B2 austenite B19' martensite (030) (e)

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Extension of Neutrons to Novel High

Temperature SMAs

• Microstructural evolution during isothermal and isobaric deformation of NiTiHf

• Outcome

• High work output and dimensional stability

• Texture measurements were correlated to the lack of evolution in this alloy

• Confirmed relationship of microstructure and load-biased tests: From Neutron spectra

• Neutrons showed why training of Hf alloy is not necessary

lattice plane spacing (Å)

(100) (021) (121) (102) (1 10) 1.0 2.0 3.0 n o rm a li zed in te n sit y ( a rb it ra ry u n it s) (111 )

data and Rietveld fit

difference curve peak positions (a) (0 11 ) p reci p it a te s 2.16 Å

400 MPa thermal cycle 2

0 MPa initial 0 MPa initial

400 MPa no thermal cycle

400 MPa thermal cycle 3 400 MPa no thermal cycle

210 110 120 020 130 012 210 110 120 020 130 012

0 MPa after no load thermal cycle 0 MPa after no load thermal cycle

4.00 3.75 3.50 3.25 3.00 2.75 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0.00 9.00 8.50 8.00 7.50 7.00 6.50 6.00 5.50 5.00 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 1 2 3 4 0 100 200 300 400 heating (cycle 1) cooling (cycle 1) heating (cycle 2) cooling (cycle 2) heating (cycle 3) cooling (cycle 3) str a in (%) temperature (ºC) 400 MPa

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-150 MPa/25 °C, Cycle 0 -150 MPa/25 °C, Cycle 1 -150 MPa/25 °C, Cycle 4

-4 MPa/25 °C, Cycle 7 -4 MPa/25 °C, Cycle 8

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• The role of retained martensite during thermal-mechanical cycling in NiTiPd high temperature shape memory alloy was revealed

• Outcome

• Direct correlations were made between

macroscopic changes in actuator performance parameters, and atomic-scale evolution from neutron spectra

• The rate of evolution of texture and volume fraction of the retained martensite plays a key role in the stability of the actuator

-4 -3 -2 -1 0 0 50 100 150 200 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 Cycle 7 Cycle 8 s tr a in (%) temperature (°C) (b) NiTiPd loading 2.8 2.9 3 3.1 3.2 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 Cycle 7 B19 (011) B19 (100) B2 (100) d-spacing (Å) no rmalize d i n ten s it y (d) NiTiPd 2.8 2.9 3 3.1 3.2 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 Cycle 7 B19 (011) B19 (100) B2 (100) d-spacing (Å) no rmalize d i n ten s it y (c) NiTiPd

Extension of Neutrons to Novel High

Temperature SMAs

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Neutrons can be used to study most

actuator forms

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