We are Nitinol.™
TiNi
Shape
Memory
Alloys
Duerig,
Pelton
Materials
Properties
Handbook
Titanium
Alloys
pp.
1035‐1048
1994
www.nitinol.com
47533 Westinghouse Drive
Fremont, California 94539
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Ti-Ni Shape Memory Alloys 11 035
I Ti-Ni Shape Memory Alloys
T.w. Duerig and A.R. Pelton, Nitino/ Development CofpoIation
Effect of phase transformation
This datasheet describes some of the key properties of equiatomic and n ear-equiatomic tita·
nium-nickel alloys with compositions yielding
shape memory and superelastic properties. Shape
memory and superelasticity per se will not be reo
viewed; readers are referred to Ref 1 to 3 for basic
information on these subjects. These alloys are
commonly referred to as nickel-titanium, tita·
nium-nickel, Tee-nee, Memorite...., Nitinol, Tinel"',
and Flexon"". These terms do not refer to single al·
loys or alloy compositions, but to a family ofalloys
with properties that greatly depend on exact compositional make-up, processing history, and small
ternary additions. Each manufacturer has its own
series of alloy designations and specifications
within the "Ti·N i~ r ange.
A second complication that readers must acknowledge is that all properties change significantly at the transformation temperatures M M r,
"
~, and Ar (see figure on the right and the section
"Tensile Properties~). Moreover, these temperatures depend on applied stress. Thus. any given
property depends on temperature, stress, and his·
''''y.
Produc t Fo rm s
Bnd
Applications
Specia l
Properties
~
C~i
D
Auslenile {pa.ent)
Manensile
DHeating
..'
j
"
Typica lly 20 ~
M, .. Manensl1e stan
temperature
A, lIAr ~ Man ensite linish
temperalure
A" "Stan of reverse
transformation of manGnsHe
A. = Fin iS!' ot lI!Verse
transformatIon 01 martens;t
Temperatu re
->
Sd"Iemane "U$tra~OI'1 of It.. ",Heels on a phase transformation on
!tie phySical prope~s ofT,·Ni. All ~t properties eilibit a dos·
continully, d'\ar.JCt~rized by !he translormation tempe<att/fes
"""'
"- C.M. Wayman and ToW. Duerig. Engineenng Asped5 of
Source:
Shape M!mofy Aloys. T.W. Duerig. et aI.. Ed.• BoMerworfl·Henemann,t990, ptO
Titaniwn-nickel is most commonly used in the
form of cold drawn wire (down to 0.02 mm) or as
barstock. Other commercially available forms not
yet sold as standard product would include tubing
(dov,n to 0.3 mm 00), strip (down to 0.04 mm in
thickness). and sheet (widths to 500 mm and thick·
nesses down to 0.5 mm). Castings (Ref 4), forgings
and powder metallw-gy (Ref 5) products have not
yet been brought from the research laboratory.
Typical Conditions, Titanium·nickel is most
commonly used in a cold worked and partially an·
nealed condition. This partial anneal does not recrystallize the material , but does bring about the
onsel of recovery processes. The extent of the postcold worked recovery depends on many aspects of
the application, such as the desired stiffness, fa ·
tigue life, ductility, recovery stress, etc. Fully annealed conditions are used almost exclusively
when a maximum Ms is needed. Although the cold
worked condition does not transfonn and does not
exhibit shape memory, it is highly elastic and has
been considered for many applications (Ref6).
R esponse to Heat Treatment. Re<:overy
processes begin at temperatures as low as 275 "C
(525 oF). Recrystallization begins between 500 and
800 °C (930 and 1470 oF), depending on alloy composition and the degree of cold work.
Aging of Wlstable (nickel-rich) compositions
begins ot 250 "C (525 "F), causing the precipitation
of a complex sequence of nickel-rich precipitates
(Ref7), as these products leach nickel from the matrix, their general effect is to increase the Ms temperature. The solvus tem;leratw-e is about 550 °C
(1020 oF).
Applications for t itanium -nickel alloys can be
convenient ly divided into four categories (Ref 8):
Free recofJery(motion) applications are thoS(' i:l
which a shape memory romponent is allowed
to free ly recover its original shape during he:!!ing, thus generating a recovery strain (Rcf9 .
Many shape memory-related properties are
discussed in subsequent sections (transformation
temperatures. superelasticity, etc.). Sume pro perties, however, are ~ tric tly peculiar to shupe men!-
Constrained recovery (force) applications ar!!
those in which the recovery is prevented, con·
straining the materiru in its martensitic, or
cold, form whil~ recovering (Ref 9). Although
no strain is rer,)vered, large recovery stress,'~
are developed. These applications include fa s·
teners and pipe couplings and are the oldest
I1J1d most widespread type uf practicru usc.
Actuators (work) applications are those in
which there is both a recovered strain ar.d
stress during heating, such as in the case of n
titanium-nickel spring being warmed to lift n
ball (Ref10l.ln these cases, work is being done.
Such applications are onen further catego'
rized according to their actuation mode. e.g..
electrical or thermal.
Supereiasticity (eTU!rgy storage) refers to the
highly exaggerated elasticity, or springbacK.
observed in m Rny Ti-Ni alloys deformed abo..-e
A. and below Md (Ref 11). The fundion of t I:.e
material in such cnses is to store mcchan: ::u
energy. Although limited to a rather small i.e
perature range, these alloys cun delivcr 0' 'r
15 times the elastic motion of a spring steeL
1C361 Advanced Materials
ory aUoys and cannot be conveniently categorized
in standard outline fOrIDs. The more important of
these properties are discussed below.
Free-recoverable stram in polycrystalline
titanium-nickel can reach 8%, but is limited to a
maximum of6% if complete recovery is expected.
Applied stresses opposing recovery reduce
recoverable strain. Clearly, stronger alloys will be
affected less by opposing stresses. Work output is
mrucimized at intennediate stresses and strains.
Recoverable stresses generally reach 80 to
90% of yield stress. In fact, alloy behavior depends
on numerous factors, including the compliance of
the resisting force and the constraining strain (Ref
9 and 12). 1)rpical values are as follows:
Condition
"'"
''''
Co~~~b~k~cd
OISOO ·C(930"F)
Cold ""Ot\(od wi~:umr:.oJod ~l
5
Effecls of opposing stresses on recovery strain
~
~
M
W
"
lS
Work output of a li·N I alloy
Applied stress. ksi
Applied stress. ksi
~
10
TOlal deformalion strain, 'Y.
'T1·NI-Fe be rslock wi\tl SO a1.% NI8/1d 30/. Fe fuU)' annealed. tested
In unlilldal tltf"lslon. An", deforming 'T1-Ni to various lotal slrnil'lS Ixaxis). the malerial S!>f\ngs bae!< to \tie ptastic strain I~"s shown by
\lie open cirdes. A~er hea~ng above A,. most oI"e strain Is recov·
ered, but $OffiO amonla pertlSIS. lhe differenoe between the plas·
tie slrain IW'd the amnesia is the reoove<abIB Slrain (dosed ordes).
Source: J.L Proft and T.W. DuerIg. E:ngi1eeMg Aspects 01 Shape
MemoIy Alloys. T.W. Duerig fll 8/" Ed., Bunerworfl·Heinemann,
London, 1990.p 115
'000
4OQ°cnso·F)
10
•
•
Recovery 5tree~. MPa
AMQlcd b;.ntoo;k
o
Free recovery behavior
ro
~
o
10
~
~
O' ~~~~
o
Applied stress, MPa
T\.Nl-Fe tlarstock with SO at.% Ni and 3% Fo fUly anr.&aled, tested
in unia;cialleflSiot>.
Source: J.L. Proll and T.W. Ouertg, Fngneering AspecI$ 01 Shap6
Memory Alloys. T.W. Ouetlg ~, aI.• Ed., Bunerworth-Hl!Iinernatln,
LoMon. 1990,p 11S
t OO
~
~
~
ro
~
__~__~__~--J
200
A~plied
300
400
500
600
stress. MPa
To·Ni·Fe barslock wil:l150 al.~~ Ni and 3"10 Fe in II wor!<·harclened
condition, tesled in unill.lllatlens4on.
Source: J.L Prof! and T.W. Outlig. Enginee<fngAspeclsolSt!ape
~ AIof$. TW. OuePg e/ 61.• Ed. BuftetWOllh·Heinemann.
London. 1990,plIS
Chemistry and Density
Density, 6.4510 6.5 glcm3
Titanium-nickel is extremely sensitive to the
precise titanium/nickel ratio (see figure below).
~neral1y, alloys with 49.0 to 50.7 at.% titanium
are commercially common, with superelastic al·
loys in the range of 49.0 to 49.4 at.% and shape
memory alloys in the range of19. 7 to 50.7 at. %. Binary alloys with less t han 49.4 at.% titanium are
generally Wlstable. Ductility drops ropidly A8
nickel is increased.
Binary alloys are commonly available with :\Its
Ti·Ni Shape Memory A lloys 11 037
temperat.ures bet.ween -50~ and +100 ·C (-58 to
212 -F). Commercially available temary alloys are
available wit.h M.. temperatures down to-200·C
(-330 -F). Tit.aniwn·nickel is also quite sensitive to
alloying addibons.
Oxygen forms a Ti.Ni 20.., inclusion (Ref 13).
tending to deplete the matrix in titanium. lower
Ms , rct.o.rd grain growth, and increase strength.
Levels usually are cootrolled to <500 ppm. Nitrogen forms the same compound and has an additive
effect to ox.ygen.
Fe. AI, Cr, Co, an.d V tend to substitute for
nickel, but sharply depress Ms (Ref 14 to 16), with
V and Co being the weakest suppressants and Cr
the strongest. These elements are added to suppress M, while maintaining stability ar.d ductility.
Their practicu.l effect is to stiffen a supereJastic al·
loy, to create a cryogenit: shape memory alloy. or to
increase the separation of the R-phase from
martensite.
Pt aDd Pd tend to det:rease M, in small quan·
tities (-5 to 10%), then tend to increase :'vI•• eventually achieving temperatures as high as 350 °C(660
' F)(Refl7).
Zr acd Hi occasionally have been reported to
increase M., but are generally neutral when sub·
stituted for titanium on an atomic basis.
Nb Illld Cu are used to control hysteresis and
Central Portion
of Ti-NiPhase
Diagram
.
0 $4""
,
~
,~
p
,;
•,
•
~
"'"
,..
•,
• ",
.P ",
•
'00
.'0<
.,
. '5(
os
50
Nick,l. al.%
•~
i
~
••
"
.5(
.,
.'•
~b'
&
~
.'
·'00
,
·200
" " "
M. lemptralu,os 111 niek4ll·til;nivm alloys alII extremery s.er1silive 10
CIOI'IIposIllonl! Y8~a~on, per1ievlarty al rll!1'er nIc~el conlenls_
SoYroo: K.N. Mollon,
E~ Aspects Of SI!SOe
Mer7IOt'Y Al-
loys, ToW. Ouerlg (II iii., Ed., avn(ll'WO<1h-~. 1990. p 10
martensitie strength. Nb is added to increase hys.·
teresis (desirable for coupling and fastener appli·
cations), and copper (Ref 19) is added to reduce
hysteresis (for actuator applications).
.
AS)(. IS87
L
o 148.,
1 300~
,.
W(,lgh : Percent Nickel
,,
UOO J
Effect 01 composition on M.
i
o I'P<or
;
IWO
i
,
I
~
,,•
•,
•
,:1
~
E
t!.
,
,
TINI
•
,
too~
••
eoo~
lOOj
,
II-."IO-C---_.....;.
-.. _. -_.. -_..... _-_ ...-.... _- ..-.-o- -. ---._- ----- -_.. -._-_.
..,I
"
10
d
so
Atom ic Percent Nick('1
Phases and Structures
Crystal
Structure
$!o
.
"
•.
The high·temperature austenitic phase (Jl>' has a
B2. oresCI ordered structure with no ",,3.015 A. The
most common martensitic structure !BIg') hu a
complex monoclinic structure with 4 = 2.889 A. 0
4.120 A. c 4.622 A, and ~ = 96.8" (Ref 20), The Ms
can range from <-200 to +lOO°C (-328 to 212 ~ F). It
=
=
is worth noting that there is aho a "trnnsitioll~
structure that preceded the mllltcnsite. called the
R.phssc with n rhomboheUral StruL1.ure (Ref 2U.
Although this R phose e:<.hiiJils a number of inU'"
('sting properties, it will not be reviewed e:dem·
sivcly here.
10~
I Advanced Materials
Ti me-lemperature-transformation curve
OOO--~~----------------------------------------------~'100
0
TiN;
• 0
TiN; . Ti!!Ni!.,," r~iJ
0
TiNi • 11zNiJ .. rlN~ •
• TiNI "" TinNi!.
0
• TiN;. r~~
0
0
•
• TiNi . TiN~
0
0
•
''''''
~
•
~
•ri
0
0
•
IlOO
~
•
•
500
•
•
•
...,
•
•
•
•
•
•
•
•
.
•
•
·
0
, • ''..
•
•
•
••
f
J
HOO ~
•
•
t200
•
•
'000
•
0.'
0.01
•
. • ..
•
•
10
"00
100
Aging dm" h
"000
r.,...t,""*,,tur&-transfonnalion CUMlIor Ti-51Ni, 'o'dIictt shows p-ecipiIallorl reacIiOo& IS a lunctiOn 01 ten..-arure and lime.
Source: M. N"1Shida. C.M. Wa~ andT. Horma, MetaII. ThIns.. A. Vol 17, 1986, P 1505
Transformatio n
Products
The T-T-T diagram shows the aging reactions
in tulstable (>50.6% Ni) titanium-nickel alloys
(Ref 7). in general, TiNi - t TiuNil", -+ 112Ni3 ~
TiNi3 as the aging temperature increases or aa
time increases at a constant temperature. Thesc
precipitation reactions can be readily monitored
via transformation temperature or mecharucaJproperty measuremenle.
Physical Properties
Damping
Characteristics
Internal friction and damping of titaniwnnickel alloys are dramatico.lly affected by temperature changes (see figure on left). Cooling (or
heating) produces peaks, which correspond to the
trnnsformation temperatures. At higher temperatures, a very sharp increase is observed during
cooling through the M •. These usuaJly high damping characteristics (Ref 22) havc been studied for
some time, but have not been used un a commercial basis due to their limited temperature range
and rapid fatigue degradation.
Elastic
Co n stants
Dyno.m.ically measured moduli (Ref23 and 24)
change markedly with the martensitic transformation and premartensitic effects (see figure on
right). Tytca1 values of clastic modul i are 40 GPa
(5.8 x 10 psi) for martensite and 75 CPa nO.8 x
106 psil for uustenitc. From a pmctical point of
TI -NI-Cu
alloy damping characteristics
DynamiC Young's modulus vs temperature
Ttmptratur,. OF
Temperatu.e. "F
10"
·200
".~~-".~>oo~-".'~OO"-~'"--"';
OOC-"2~00"--"~~--,
!""
•0•
.;
•
~
~
.~
•
-100
100
200
300
400
..
I:J ~
•
12 ~
-/---':f-----=---l .;
,
II i
--- --'---"1
,-
0
>
.,
0
-,J
L~____-"~______"-______-',-____
·200
a
-100
100
200
_170
Internal friction of 44 .7T.. 29.3N"26 Cu (wt'!\.) du~ng coofing wi",
rne6suretnet\t trequeney of - t Hz.
Source: O. M,rtilll' arxl E. lOr6k, J. Phys., Vol C·4 (No. 43). 1982, p
C~'"
·10
30
Tempenlture. ·c
Temperature. "C
'"
A: n.s6Ni (wr"o). 8 : 44.7T..29..3N1·26Co (wI'I'.). C: 44_9T.. S1.7Ni-
3.4Fe ('<01%).
SoJroe: O. MerOer. K.N. Melton, R. Gontlartl. i!f1d A. Kulik. Proc..InL
CMl. StJid.-Sotia PPIa:M TllWroommions. ....I. AAr01SOl. D_E. 1..aug>lin, A.F. s..6fka, andC .M. Wa.,man, Ed.AtME. 1982, P t259
Shape Memo ry Allo ys / 1039
T i~Ni
view, however, modulus is oClittie value; apparent
elasticity is more controlled by the t ransfonna tion
and by mechanical twinning. Poisson's ratio, Jl., is
0.33 (Ref25).
Electrical
Resistivity
General values fo r electrical resistivity of the
two primary phases are as follows (Ref26):
p (martensite) = 76 x 10-6 n · cm
p (austenite) 82 x 10-6 n· cm
Variations in resistivity wit h temperature are
complex functions of composition and thermomechanical processing (see figure). Note also
the pronounced effect of the R-phase on resistivity.
=
Magne tic
Characteristics
Magnetic susceptibility also undergoes a dis·
cont inuity during phase transition (Ref 26). Typi.
cal values are:
X(manensite) = 2.4 x 10-6 emu/g
X(austenite)::: 3.7 x 10-0 emuJg
Electrical resistance vs tempera ture
Temperature , OF
-200
-I "
0
'"
,
A
M,
"I
I
•~
•••
M,~
,
••
•" r-J-
~
200
"I
~~
M.
1
T,
T, ~
,T- •
,
1
T-
••
I '
c
'\~
·170 · 140 · 110 ,80
·SO
·20
10
40
70
100
130
Temp erature , · C
Electrical resistance \IS ternperalure <;IJI'Ves lor a TI-50.6N; (at."-) al·
loy IhlIt WIIS thermomecha"ie8~y treated as ;r'!d;cated. A: Ouend1ed
tram l ooo ·C (1830 .F). B: Oue;'1dledfrom l(xx)'C (1830 'F), aged
at400 "C (750 ' F). C; Dlr&dIy aged at 4OO "C (750"F). TR;$ thetran ·
s1tlon tempertltUfe from austenite lQ the rOOmbohedral A pt1as.e. r R
Corrosion
Titanium·nickel generally fonns a passive
TiD2 (rutile) surface layer (Ref27). Like titaniwn
alloys, there is a transition temperature of about
500 °C (930 oF), above which the oxide layer will be
dissolved and absorbed into the material. Unlike
titaniwn alloys, however, eoa case is fonned. Titanium-rockel will also react with nitrogen during
heat tnatments, fonning a TiN layer.
is the shifted transition temperature IrQ(ll prcx:essing eMects. Arbitrary units lor ~eef1ical resistance.
Soun::.: S. Moyauki 3nd K. Otsulo.a. Melal. Trans. A.VoI 17. 1986.
,53
General
Corrosion
The rest potential of titanium~nickel in a dilute
sodium chloride solution is around 0.23 V (SCE),
which compares with 0.38 V Cor type 304 stainless
steeL This puts titanium·nickel on the noble or
protected .side of strunless steel in t he galvanic series. A passive oxide/nitride surface film LS the ba·
sis of the corrosion resistance of titani1,;ltt·nickel
all oys, similar to stainless steels. Specific environmcnts can cause the passive film to break down,
thus subjecting the base material to attack. A 8um~
m ary ortitaniwn·nickel r ea ctions in various environments rollows (Re[28).
Seawatcr. Titanium-nickel is not affected
when immersed in flowing seawater; however, in
stagnant 5eawater, such as found in creviccs, the
~rotcctive film can break down, which results in
pitting corTosion.
Acetic acid (CH3CDDH) attacks titaniumnickel at a modest rate of 2.5 x 10- 2 to 7.6 x 10- 2
mm/year (mpy) over the temperature range 30 °C
(86 oF) to the boiling point and over the concentration range 50 to 99.5%.
Me thanol (CH3DHl appears to attack tita~
mum nickel only when diluted with low concentra·
tions of water and halides. This impure methanol
solution leads to pitting and tunneling corrosion
simi lar to that found in titanium alloys.
Cupric chloride (CuCI2 ) at 70 "C (160 oF) at-
tacks titanium-nickel at 5.5 mpy.
Feme chlorid e (FeCI3) at 70 "C (160 OF) and
8% concentration attacks titanium-nickel a t 8.9
mpy. Titaniwn·nickel is attacked at a rate of 2.8
mpy in a solut ion of l.5% FeCla with 2.5% HCI.
Hydrochlo ric acid (HC!) has a variety of ef·
fects on the corrosion of titanium· nickel alloys depending on temperature, acid concentration, and
specific alloy composition. With 3% He l at 100 "C
(212 OF) and a range of alloy compositions, t he rate
of attack was as low as 0.36 mpy and as high as 3.3
rnpy. At 25°C (77 OF) and 7M solution, titanium·
nicke l~iro n alloys can lose up to 457 mpy.
Nitric acid (HND.1) is more aggressive toward
titanium-nickel than type 304 stainless steel. At
30 °C (86 OF), 10% liND3 attacks at a rate of2.5 x
10-2 mpy; 60% solution attacks at 0.25 mpy; 5%
HND3 at its boiling point attacks at 2 mpy.
Biocompatibility studies have been oonducted in various media chosen to simulate the
conditions of the mouth and the human body. In
general, no corrosion of titanium· nickel "!loy.'! has
been reported. For example, in tests where cou'
pon! oftitaniwn-nickel were sealed at 37 °C (97 "F)
for 72 h, the mass corrosion rute was on the order
of 1~ mpy for such media as synt hetic saliva, :lyn ·
t hetic sweat, 1% NaCl solution, 1% lactic acid,.llld
0.1% HNaS04 acid (Hef29); see also Ref30.
Hydrogen
Damage
The interaction between hydrogen and tita·
nium·nickel is sensitive to both concentration and
lemperat~e (Ref 31). In general, hydrogen levels
in excess of 20 ppm by weight can ue considered
detrimental to ductility, with levels in ~xce!\s o f200
ppm severely impru!ing. Undcr certain conditions,
1040 I Advanced Ma terials
hydrogen can be absor bed during pickling, plating, and caustic cleaning. The exact conditions required for hydrogen absorption are not well defined , 80 it is advisable to exercise care when
perfonning any ofthese operations.
Substantial amounts of hydrogen also can be
absorbed in hydrogenated waleI' at elevated temperatures and pressures, such as would be found
in pressurized water reactor primary water sys·
terns. Relatively short exposure times have been
shown to produce hydrogen levels well in excess of
1000 ppm (Ref32).
Thermal Properties
Heat Capacity
Latent
Heats
A typical plot of specific heat (C ) versus temperature fo r a 50.2% Ti alloy (see figure) shows a
discontinuity at the M! temperature of90 °C (195
OF) (Ref 3). The peak and onset temperatures for
the peaks are often used to characterize the transfonnntion temperatures of an alloy. Care must be
taken however, (Ref 33), because the presence of
an R-phsse prior thermal cycling, and residual
stresses from sample cutting can tend to complicate the CW""Ves and introduce spurious peaks.
The latent heat of the martensitic transfonnstion strongly depends on the transformation temperature and stress rate (doldT) through the form ula
doldT = iiliKOF.n
Typical values for 6H are 4 to 12 caUg and values for do/dT range from 3 to 10 MPaJOC.
The latent heat of fusion can be expressed 8S:
llH -34,000 J/mol (Ref34).
=
Thermal
Expansion
The thennal coefficient of linear expansion can
SpecifiC heal (C p )
3
• 00
-200
,
,
,i
,:
25 - - , -- ,--
,
5
"
,
,
,
Temperature. ' F
200
400
600
0
--
t--
-, ,
~
,
·270 · 180 ·SlO
I
I
,
I
i"
,
,
5
-t- _L~~ _-
I
! !, I
:
:
900
I
I
I
I
,
I I I
I
i,
,,, "
, "
!
"
,
0
90 1110 210 360 "50
T,mper.uu-e. ~
~O
SpedIc tltat (II T0-49.8Nj (at ~.l. with a sharp peak ~ he spociIic
heiLt at 90 "C (195 ' F) GOTeS4)Ol'ld"ng tl t-.e M. ~ture_
Scurc.: C.M. hd< __ • H.J. W;q>er. and R.J . wasilewski. NASA
fIepott. NASA-SP5110. 1912
be expressed 8s(Ref23):
(l (martensite) = 6.6 x lO--orC
a (austenite) = 11 x l~I"C
The volume change on phase transformation
(6 V) (from austenite to martensite) is -0.16% (Ref
35).
Transition Temperatures
Melti ng Point
Martensitic
Tran s formation
Temp eratures
Characteristic transformation temperatures
depend strongly on composition (see table on
next page and the previous section on chemi,try). Typical hysteresis widths r ange from 10 °C
(18 OF ) for certain titanium-nickel-copper alloys,
to 40 to 60 °C (72 to 108 OF ) for binary alloys, to
100 °C (180 OF ) for titanium-nickel-niobium alloys.
Transformation temperatures are measured
by a number off.echniques, including electrical resistivity, latent heat of transformation by differential scanning calorimetry, elastic modulus, yield
strength, and strain. However, the most useful
measurement technique is to monitor the strain
on cooling under a constant load and the recovery
on heating.
Other important relationships of transforma-
tion temperatures are as follows. Applied stre!lses
increase transformation temperatures according
to the stress rate (see the next section on tensile
properties). Martensitic deformations increase
the stress-free A, temperatures, particularly in alloys with low yield stre!lS(>S. The increase is temporary, returning to the previous value after the first
heating cycle. Increasing cold work tends to reducc
transformation temperatures. The R-phase trans·
formation temperature is much more constant
thao t hose for marten site, typically 20 to 40 °C (68
to 105 OF ) in binary alloys.
Md, which is dertncd as the temperature above
which martensite cannot be stress-induced, may
be about 25 to 50 °C (50 to 100 OF) higher than Af·
Ti-Ni Shape Memory Allo ys I 1041
M. temperature as a functio n of cold working
Strain of a Ti -Ni-Nb specimen
Tempe ra t... re. 'F
·300
-200
· 100
0
100
200
,.r;~~~C--"~--~--~~--~
.'
~
.;;
~
~
" !•&
.
2
,
-
-"-
"
-2
,.L-____________________- - J
·200
"00
o
·20
" "
'00
Tem perat ... re, ' C
Strain after delOfmlng and unloading, measured on tne first and
MCOrld h.ating cyd es. Note lMe cl"1ange in A, and 1M. rteOVfIry
strain .
20
25
Co td work, %
30
" "
Q1angeln lt1e M. temperatureol a Ti·SO.eNi ai oy cold worked 9 .2
to 4004 and 5ubseq ... ently anneated at 500 'C (9X1' F) tor 30 min.
SoI.Irot: G.A. Zact10 and T.W. o...erig, """p"'b'is.hed rI!$earch
Scuret: K.N. Menon, J. L. Prell. and T.W. DtJerlg, MRS Int. Mee~ng
on Actvanoed Materiats. \1019, K. Otsuka and K. SNmiru, Ed., Mat,.
fIaIs Rtseartll Scciely, 1989. p 165
Ti·NI shape memory transformation temperatu res
Mel. which is defined as th e temperatu re above which martensite cannot be stre ss induced, may be abo... tlrom 25 10 50 "C
(SO to l 00 "F) higher than AtCompa. ition
• t,':iN;
....
".
...
"'2
",,..
,,~
[SIMcll
IBOMiJI
[68 W;anl
[79OlcI
.9.4
".,
"'.,
49.7
'""'. ,
"'.,
"
48.1
48.6
49.0
,,~
"'~
".
Thn\perature. "C
"-
>f,
A.
"
""
""
'-'"
_lI
-",
""
"
-"
-lO
"
-"
"
)7
D
-"
-'"
~
21
"
.,'"
_liO
..
"
- 9._29
2O tol!i
.
' 00
'".,
,
.:!!
))
..
0
03
->l
''''
"
""
".'",.,
"
-"
.,
""
-lO
"
..,
-'"•
T""'hniq ....
'"'"
'"
..
J2
-"
m
,"''''
"
..'",
Elcc1ri.:al. ""'8n<:lic
n
fIRlPC ""
Eb:ui<:>.l ""i'livi!)'
..""
-J'
Compilation UoIXI Ph.;..DiavamsofBiruu:- TIlaniu", A/kIyI, (J .L :'dW11l),. Ed.), ASM InternotionAl, 1987, p203. la )CiIed rcl.-~ &I'\!
loS rouo .....: 11 Kor. LL Kornilo¥, Yo:. V. Kachur, ... d O.K. &010\11.0", "Dilatation An.a]ys;,O!'1"ran'(omIltion in the CompoundTlNi: F iz. M d .
M rl41UwtJ. . 32(2), 42().422 (1971) in Ruuian; TR: Phyr. Mff. M nolkKr.• 32(21, 19I)..193 ( 197U. 81 l i e! : KX Melton and O. l l emer. "'The
MechaNcal Propertiet o(NiTI.Bued Slape Memory AlIo)'t.~ llcIo Mtlo U., 29. 393-3981 19811. 80 Mil: RY. l{;lI ipn. "O.lf!rmination of
Phue n.nsroro>ation 'ThlXlperat.u.resor TI.'1i U.mg Oilfef"eflti.a] Thmn.al An.a]y.i••~1'i tani ... m"80. Ti Sci.1kh.. Proc. lnt. Con(. Kyoto, J".
pM. M.yl8.22, T. Kiltluzi, Ed., 14S 1-1467f1980J. 68W&n: F.£. Wang,B.r. OeSa"age,MrlW.J. But'hler. lllo: ' n-evtTSibl .. Critiaol RIInJ{f' ;"
the Til'll n-..osltion: J . Appl. PII)'$ .• 39(5). 216&2115 (l9681. "19Che: D.B. Chlll"TlO'l', Yu .l . p"pal, V.E. G)'\lnter.LA ~"",,sevio:h. "nd E.~1.
lMvil-lkii. 1"he Mwtiplicity or Stroctunoll'raMil.ioaa iD A110)'t &5o:d on
DoIIL lU ..d. NOIlIt. SS$R, 24;.854-851 ( 19191in It....i. ..;
'I"R:Sot.r. Ph:#- DolL, 24{S I. 664-066(19i91
n:-o,:
1042/ Adva nced Materials
Tensile Properties
In general, a superelastic curve is characterized by regions of nearly constant stress upon
iooding(referre<i to the loading plateau stress) and
wliooding (unloading plateau stresa). These plateau stress values are better indicators of mechanical strength than the traditional yield stress.
Typical values ace shown (see table).
Schematic of superelasticity descriptors
Ti-Ni shape memory: Typi cal loading and unloading
characteristics
..,.
l.oadi:Il pl:lllliIU
UIIIoadin. pI=u
MIUimwn ~prtn8~k
MWrnum defQrm;l.tiQI1 with %
45OlO1OOMh
Up.o 250 MP>.
pcrmanc:m~
M.ulmwn lIOItd enon'
"
$our«: T.W. Dumng and C.R. Zadno. E~TlffriT16 Mptc1' of
Slwtpe M~mcryNlay., T.W. Dueriget ...1., Ed., Butterwon..b.t!4m.
mann, London. 1990, p 369
Above M.;t
~ is defined as the temperature above which
martensite cannot be stress-induced. Consequently, titaniwn-nickel remains austenite
throughout an entire tensile test above~. Tensile
strengths depend strongly on alloy condition, and
the ultimate tensile strength, yield strength, and
ductility of cold worked titanium-nickel 'Ni.re depend on final annealing temperatures (see figure).
Ductility drops sharply as compositions become nickel-rich. A review of othec facton controlling ductility can be found in Ref36.
Strain
SthemllIie dilgam ~ key dHcrIptors 01 superetastidty: 0u
(l.WlIOIIcing jtateau mtasured aslhe inIe<:tionpoinl), o,(IoDIg pta.
tQu rne&$Ul'1!d IS 1M ;"tIection point). (, (lota! deIofmation sIrai'I).
I, (permanent se~ or ..-mesiaJ and Ihe stored energy (shftded
•.
~
Soutce: T.W. OIJerig tnd GR Zachl. Et>ginetriJg ~ cI
Shape Memcvy -/'So T.W. Duerig ef ai. Ed~ 8uUeI .. OI1h-4Ieinemam. LoncIon. 1990. P 369
Aging of nickel-rich alloys increases llu!>terutic
strength to a typical peak strength of800 MPa ( 11 6
keD. Surprisingly, ductility is also increased dur o
ing the aging process.
Yield strength vs anneal temperature
Mechanical properti es vs anneal temperature
.,,, ,
Temperature, OF
le'";800~,,~'~"~__'"OCO~__C'~'''ec__~''~''~___'~'~'' SO
r Ducti~ty
UTS
I
"
'co
I
I
......--- I
600
700
Tempal3ture , 'C
500
&
800
900
Theinlluenceol~*'9lemperal\.O'uonrned\arOcal~HoI
0.5 111m (0.02 In.) T~SO.6Ni wire ..... '" 40% eok1 WOI1t and aMNlecI
3Ominat~tur..
~:
500
'"
'"
"'
• •••
"•
'" ,,
•"•
~
~
..~~.~.~--~j~::::::::::::::::::J"
<CO
,
,co
,;
109
l%YS
300
Temperature. OF
100 200 300
G,A. Zact-o and T.W. Duerig.l..I"IpUbIished research
"00
,
roo
300
Theinll..e-lced ll'f'ttoa6rlg~on/1"!fd"larblproperliesolli·
($j -..o1<.....-.eMd 30 ...... at 1emper.1IUu.
50.6Ni
"""40"'10
Scuroe: G.A. Zadno and T.W. Ouerig. t.npUbished re$eardl
BelowMs
Titanium-nickel yield stresses are controlled
by the "friction& of the martensite twin interfaces.
Typical yields stresses are 120 to 160 MPa (17 to 23
ksi) for binary alloye and as low as 60 to 90 MPa (9
to 13 \esi) foe titanium-nickel-copper alloys. Ultimale tensile strengths and ductilities nre similar
to austenitic values.
Ti-Ni Shape Memory Alloys /1043
Superelasticlty (Between M. and Mdl
Effect of
Temperature
Between M. and ~, the material transrorms
from austenite to martensite during tensile test·
ing. Yield strengths vary continuously from Ma to
Md (see figure). The rate of stress increase is called
the stress rate, varying from 3 to 20 MParC, with
rates generally increasing with M•.
Superelasticity, or pseudoelasticity. is an en·
hanced elasticity when unloading between ~ and
~'1ct. The Md transition is generally defined as the
temperature above which stress-induced marten·
site can no longer be formed. On a stress·tempera·
ture graph, Md is the temperature where the stress
begins to level off.
Superelasticity is also highly temperature de·
pendent (see figures). Changing alloy composition
and heat treatment can shift the temperature
range of superelastic behavior from -100 to +100
°C (-148 to 212 OF).
This datasheet describes some of the key properties of equiatomic and near-equiatomic titanium-nickel alloys with compositions yielding
Permanent se t 0 1s uperelastic wire
shape memory and superelastic properties. Shupe
memory and s uperelnticity per se will not be reo
viewed; readers are rererred to ncf 1 to 3 for basic
titanium·nickel,
Tee'MI',
information
on
Memorite™, Nitinol, Tine'nl, and FlexonTIoI .
These terms do not rerer to single alloys or alloy
compositions, but to a family of al loys with properties that greatly depend on exact compositional
make·up, processing history, and small ternary ad·
ditions. Each manufacturer has its own series or
alloy designations and specifications within the
"Ti.·Ni" range.
A second compucation that readers must ac·
knowledge is t hat all properties change signifi·
cantly at the transfonnation temperatures M Mr,
"
A., and Ar (see fib'Uro). Moreover, thege temperatures depend on applied stres!. Thus any giv~n
property depends on temperature, stre!II, and his·
tory. Superclasticily is an enhanced elasticity oc·
curring when unloading between AI and ?t'ld (see
the section '!ensile Properties~ in thls da1asheet.l
Loading and unloading plateau heights in Ti·Ni wire
Temoera!ure. OF
-300
·200
·100
0
100
Tempe"lu' •. OF
200
300
.:)00
"~
0
100
200
JOO
,.- ,
•
i"
~
-200
·200 ·100
-'00
o
\
'00
200
Temperat",re. "C
Pt!Tn¥oent 5et 01 sup8felU!ic: binary titari~..we defotmld
8.3% Ind..no.ded al various t~hJt'M. TI-N ~.....". 50.8
lit% NI CCIIdv.olled 4(W.and amealed a!500 "C (930 oF) fOI' 2 min.
The wperNoStic window is roughly <10°C (70 oF} In wiatrI.
Sam;,,: T.W. Outrig lI/'Id G.R. la(ho, EngineMlg Aspects 01
SNpe ~ Aloys. T.W. Ouerig el aL. Ed.. eunerworth-~
fT\8M, l.ondo'\. 1gg(j. P 3S9
_~,oo[==:_,:o=o:::::-·o~-=-=,~oo::::_J,,;,
Te-mper~lVra.
"C
SO.8 at.'" Ni cold ~.., <IO"o;Jt'tl ameaIed al SOO "C 1m "F) lor
2min. Slres$rat• • 5.7 t.!Par'C.
SooIcI: T.W. Duerig and G.Ft Zedno. EngirIeering Asperu 01
Shape Memory A.Io)s. T.W OI.oerig ., ... Ed .. e",netWOf#l·Heir'oemann.LondOn.lgg(j.p369
10441 Advanced Materials
High-Temperature Behavior
Stress relaxation
,.
~----------------,
Creep, Very few creep measurements have
been made on titanium-nickel, although creep
mechanisms have been proposed (Ref37),
Stress relaxation is critical in many constrained recovery applications. Several measurements have been made (Ref9, 12, 38). 'Ib summarize, relaxation of stable titanium-nickel alloys is
extremely slow below 350 "C (660 "F ) and becomes
very rapid by 425 "C (795 oF).
o.
o.
CJo " 564 MPa
o.
o.
i o.
0.'
0.'
o
0.'
o. ~~~~~~~__~~~
·1.0 ·0.5 0 .0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Jog (". h
Stress rel&lCOlion 01 a Ni.rll",Fe) attoy at 375 ' e (705 ' F) measured
ir1 a dynamieally oontroll&d Cteep mact1ioe. Round specimens YAIh
gage lengIh 01 6 mm. hAy annealed.
Source: J. Pro!! and T.W. Duerlg. Engineering Aspet;1s 01 SI!~
Memory AIo}'$. T.W. Ouerig e/ aI., Ed .• Butte<WOl1h·He!nemam,
199Q,pl15
Fatigue Properties
The fatigue behavior of titanium-nickel alloys
is extremely complex and encompasses m8J)Y dif·
ferent topics. 'Ib summarize, titanium-nickel excels in low-cycle, strain-controUed environments,
and does relatively poorly in high-cycle, stress·
controlled environments. The superclastic meehl!.msms accommodate high strains without excessive stresses , but cannot accommodate high
stresses wit hout excessively high strains.
Stress
Controffed
Isothennal stress-controlled testing is important in many constrained recovery applications in
which the shape memory effect is only \;sed as a
mode of installation, e.g., fasteners and couplings,
in which the nlloys are used exclusively Ilhove the
Md temperature. Although fatigue has been exten-
sively characterized by the coupling and fastene r
industries , much of the data remains largely unpublished or highly application specific. Typical S·
N behavior for vruious alloy compositions tested
weH above lheir Md temperatures is shown below
(see figure on next pnge).
Strain
Controlled
Isothermal strain-controiled behavior is highly
dependent on the testing temperature relative to
the alloy transformation temperature, Fracture
follows the Coffin·Manson relationship:
lar interest is superelastic cycling (strain-control ·
led testing between AI and l'v1.!:). There are severnl
modes of degradation that occur under these cir·
cumsto.nces (see figure), Again, these depend
strongly on specific alloy conditions and the needs
of the application, Further data arc provided in
Ref39.
NI' • .,,=C
where C and pareconstants;N is the number ofcycles to failure; and 6£p is the applied strain amplitude (see figure). One specific example of particuThermal
Fatigue
Thermal cycling both with and without applied
loads such a s found in actuators or heat engines, is
certainly the most complex mode to analyze. Although it has been studied extensively. it remains
difficult to predict failW'e, largely because failure
can consist of fracture, ratcheting, migTation of
transformation temperatures, changes in reset
force, etc. Moreover, damage accumulation depends on stress, strain, temperature change, heat-
ing methods , heating and cooling rates, and even
orientation (hori:tontal or vertical I.
Failure too is nebulous. Various degradation
modes can occur, including a shift. in transforma'
tion temperature, a reduction in the avnilablc
strain, walking (or rntcheting), and fracture itself.
Thermo.! cycling with no applied lood can even result in some degradation. See Ref 10 to 13 for fur ther information.
Ti·Ni Shape Memory A lloys 11045
Typical S·N curves
Low.c:ycle fatigue behavior
"." "--- - - - - - -- - -.. ,
,
M.2.70 · C
•
•
Electron beam melting
o
o
••
•
T;'5O.5 Ni
T ..5O.7 Ni
Ti·5O.9 Ni
,
•
High--lrequency
T;'51.0 Ni vacuum induction melting
10
j} ,,0. 176
~
r..so.& Ni
10'
II = 0.155
~10"
... .
10)
M.,,·t20~
,
~
(l &11.216
j},,0.167
-30,,'L_ _~_~~_~:__-...J
101
M..,·oo~
0
•
,.".~::;~t::-,,:~~~:.~-,
M, .. .. 7.S · C
5
10·t L_
10'
_
~_ _ _,-;-_
10
Cycles 10 failure
...,:-_-1
_
103
lot
10'
Cycles to failure
titanium-niCkel aIToys of varioo.s CO'TIposiUons (at.~.) prepared In
varioos fashionsl! lsothermaJlytested in sI1eet form. Tes~ng is done
well above M~. SMeal specimens loaded and unloaded (R = 0). Cy·
l.J:lw-.<:yOe lallgue bMal'lor of titanium·nlckel alloys at room tern·
perature testGCI in tllnsion-eompression (R ", -1). The M, tem pera·
turM 01 the alloys are ill(iiQJted.
SOurce: K.N. Melton and O. Mercier. SIrength of Marais and Alloys.
P. Haa$eO ellJl., Ed., Pergi'lmon Pres.s. 1979. p 1246
de-dat 6O · C (140 ·~.
Source: S. Miyazaki. Y. Sugaya. and K. Otsuka . MRS 1,,1. MeeUng
on Adv.moed Male<'lals, Vd 9. 1(. Otsu<a arid 1(. ShimizU, Ed., Metetlals Researd'l Soeiely, 1989.p2S7
Effects of isothennal supe r elastic cycling
••
,•, ,
,
•,•
<
0
•
•
.. ,
-2
• • • , • ,
• • , ,
,
, ,
, , , , ,
•
•
,
12°C
•
26
. •,
•>•
2
.. , '.•
g-
0
o
"
,
,
,
12°C
,,'C
,.'C
.
"
"
,
'"
'00
Cycles to failure
•
•
••
°c
" ·C
4(FO,--GN
'.
•
•" • •
•
"
25
• •
••
•
• •••
•
o
0
0
0
0
'00
Cycles 10 railllr~
'" '"
(b)
(.)
,,------------------------,
~ooo
••
12
o •
••
0 .... 0 0
•,
• • • •
• • •
• • • •
,
•
•
0
•
o
•
•
..
, ,
t•
,
50 Cycles to 'a~ure ""
'"
(.)
THIs 01 a superelastic ~tamm~ "'r8 at Itvee tempeBtures. AJloyccnl:illf\$ 50.6 at.% noc~e.. Throe modes of deg'adalion oa:ur' sirooItan&ously do..oing Itre isolhennal superelastic eycIing 01 titanio..nl·nidte! alloys: v.9I<.ing. 01 an aocumulallon 01 permanent Sol! (lOp). a chaoge in yield
s!JeSS (middle) and a reduction in :tle hysteresis wiaIrr (bottom).
Source: S . Miyazaki, EngiIleemgAspecfsolShapeMemotyAlloy$, T.W. Ouerig ~ aI., Ed., BuHerworths, 1990. p400
,0461 Advanced Materials
Fracture
Fatigue Crack
Propagation
Strcss-inducing martensite at the tip of a
propagating crack has been shown to significantly
slow crack growth (Ref 44). Othcr sources ofdala
include Ref 45.
Toughness
Although Charpy impact testing on titaniwnnickel has been conducted (Ref3, 46). very little Kfc
or JIc data exist. Indications are strong that a
ure).
sharp toughness minimum exist.OJ at Md (see fig·
Fatigue crack propagation
,,'
0
•
,•
,,'
Stable marten$ite
Stable austenite
Irreversible stress-induced mallMsite
Reversible stress·induced marte Mite
ii,,{"J
.! 10
•
r
One laltice spaOng eer eycI.!...
_ _""""
•
310"~
•
10'''[
o
•
•
,,.
"
Slless-itU:ensity range (,6,,1(). MPa,:m
FaSg\:e crac;Ii: ptepaga:ion ra:esin 1000titanit.m.ndlel iIIIo)'$.(~ staJ:H~~le"';:hM. > tOoI'\'I ~tufe. stabl6'3USkYIiIe"';lh M"
room tempetalu'e. ~ stress~manMSiIiJ-M!h M. < room tempefalVrc < I\- and ~e sR$.$-it)ducedmar/ensi9..,;th 1\ <
roorn:~1\.We <M". fHtedwilh R .. 0.1 on 10mm~Cf~ at SOH! lJI"oI$efCQlldlion$oIckocJusingM
SoI.roe: RH. Oaus!caIl1t. lW. Ouerig. and A.O. RIChie, MRS tnt. Mee~ngon Mvanced Mate<lals, 'lot 9, K. Otsuka and K. Shimi~u. Ed. Ma!CIials
Rcsearctl Society, t 989, P 243
«
Processing
Frac ture energy vs temperature
Bulk Working
Flow Stress. Upset forging tests conducted on
seven different alloys at strain rates ranging from
10~ to 102 indicate that the material has a very
high hot ductility and is not highly strain rate dependent. The £low stresses can be characterized by
the relation:
Temper ature, ' F
,
'"
200
OS
•
0,30
0.25
m
a=kr. exp(-Q1R11
where a is the flow stress; r. is the strain rate; Q is an
activation energy (50,000 cal/mole); and m andk are
constants. Values for m were found to range from 0.1
to 0.17 with increasing temperature (see figure for
typical data ofan equiatomic binary alloy).
Extrusion. Both solid bar and large tube (50
mm mameter with 8 mm wall truckneB$) have been
extruded from titanium-nickel. Parameters remain proprietary.
Forging. Titanium-nickel has been succesfully forged into large cups. Parameters remain
proprietary.
Rolling. Titanium-nickel can be hot rolled
with relative ease, but iB difficult to cold roll, especially in thin, wide sections.
Fracture
energv
•E
~
.'" !"
" ••
.
"J
~-.-' -
Yiekl ~rength (0.2%)
,
·eo
OS
Temperature. 'C
00
eo
''''
Vac:u!.m ~ meiled alloy hot VoOI1Ied and <'Mea!ed lor I h;l.1
950 "C and aircooled. SlandardCha'll'lV.1'IOId1 impacl speeirnen$
were mac:hine<l The ~ 01 ~I",", on IracIUfa ~
ness 01 44Ti-4gN:·5Cu·2F. (~). No:e tha i It>a n'Iir'oImo,.on in the
tractu-e energyoccut'S ju1! below M". "Qetermined lrom theQ)IJ~
sponcing O.r.'. ~tld ~ and Ultimate len5ile slronglh meas·
"""""".
Soun::e:
K.N. Mellon and O. Mertier, Ada Metal.• Vd 29, t962, P
""
Ti·Ni S h ape Memory Alloys 1 1047
Fab rication
References
Casting. Although some unreported experi·
ment:i have been conducted, casting has not been
done on a commercial leveL
Powder Metallurgy. Although a great deal of
experimentation has taken place wit h both ele·
mental and prealloyed powders, nothing hns
reached near·production levels. Refe rence 5 provides a review of methods.
Forming. Titanium-nickel sheet has been successfully fonned into a range of complex shapes,
both in the martensite and austenitic phases.
Springback is high, as is die wear and friction. Pa·
rameters remain proprietary.
Machining. Titanium-nickel is very difficult
to machine. Very low speeds and a great deal of
coolant is required, and tool wear is very ra pid.
Milling and drilling are particularly difficult. Producers of couplings have demonstrated that largescole machining production is possible.
Heat Treatment. Titonium·nickel can be heat
treated in air up to -500 "C (930 "F). No 0: case is
formed, but a surface oxide of rutile develops
quickly. Above 500 °C (930 oF), the oxide layer be·
gins to flake (depending on time). Nitrogen and hydrogen at mospheres are not recommended. Argon,
helium, and vacuum heat treatments are com·
monly used to preserve bright finishes.
Recrystallization is ext remely rapid above 700
°C (1290 OF ). Solution treatment requi res tern·
peratures of at least 550 "C (1020 "F). Stress relief
is usually accomplished at temperatures as low as
300 °C (570 oF). A Tn' diagram is shown in the
previous section "Phases and Structures. ~
Fully annealed bar stock has a typical hardness of 60 HRA. Vicker numbers range from 190
HV in the annealed condition to 240 HV after 15%
cold work (Ref3).
Flow stress measurements
•
,
•
V1 8ls ~
--
~
>
5.
;
;;:
5.
o
0.11315
O.OIZ3Is
S
..
•
' .5,'-"-_ _ _ __ _ _ _ __ - '
0.'
0.'
'.0
"
lfT x 1000
"
"
Nal~(81Iog (In)
al fiow stress is shown la var, linea ~y with the in·
Yellie al abSOllil e temperalvre. 12. mm x 8 mm diameler specimens
lesfed In oompres.si()n I.nder isothermal condilKlf1S (healed dies) at
!hit I!!mp&ralvres and slraon ra les shown.
SOvree: T.W. Dvttti9 . unputllisheddala
Joining. Titanium·nickel is difficult tojoin be·
cause most mating materiuls cannol tolerate the
large strains experienced by the alloy. Most applications rely on crimped bonds. It can be welded to
itself with relative ease by resistance and TIC
methods. Welding to other materials is ext remely
diffic ult. although proprietary methods do exist
and are practiced in large volumes in lhe produc.
tion of eyeglass frames.
Brazing can only be accomplished after re-en'
force ment and plating. Again , methods are pro·
prietary; large-scale production is practiced by the
eyeglass frame industry.
.
1. T.W. Duerig et al.. Ed .. Engineering A spects of
Shape Memory Alloys, Butte rworth-Heine·
maM, London, 1990
2. J. Perkins, Ed.. Shape Memory Effects in Allay.';;, Plenum Press, 1975
3. C:M. Jackson . H.J. Wagner, and RJ.
Wasilewski, NASA Report, :-iASA·SP 5110,
1972
4. J. Takahashi, :\1 Oka;reki, K Hiroshi, and Y.
FUIllta. private communication. 1984
5. T.W. Duerig, in Aduan.ced S_vnthesis of Materi·
als, J. Moore, Ed., 1993, to be published
6. G.R Zadno and T.w. Duerig. Engineering As·
pects of Shape .\femory Alloys. T.W. Duerig et
ai.. Buttenvorth-Heinemann. London, 1990, p
4 14
7. M. Nishida, C.M. Wayman and T. Honma, Met·
all. 1rans. A , Vol 17, 1986, p 1505
8. TW Duerig and KN. :Vlelton,?roc. ofSMA'86,
C. Youyi et ai., Ed., China Academic Publishers. 1986, p 397
9. J.L. Prott and T.W. Duerig, Engineering As·
pects of Shape Memory Alloys. T.W Duerig et
al., Butterworth·Heinemann. London, 1990, p
115
10. A. Keeley, D. StOckel, and T.\V. Dueng, Engineering Aspect.~ of Shape .vfemory Alloys, T.W.
Duorig et of., Ed., Butterworth-Heinemann ,
London, 1990, P 181
11. T.W. Dueng ami G.R. Zadno. E llyincl'nnl! A~ ·
peets of Shape JJemory All())".~. T.w. Duerig cl
al .. Ed., Butterworth-Heinemnnn, London,
1990, p 369
12. C.R Such. 'The Charnctenmtion of the Reversion Stress in XiTi," M.S. Thesis. Naval Post
Graduate School. Monterrev. CA. 1974
13. M.V. r>:evitt. Thln.~. Met. SOC. AlME, Vol 218,
1960, p327
14. D.M. Goldstein, W.J. Buehler. and R.C. Wiley,
Effects of Alloying upon Certain Properties of
55. 1 Nitinol, NOLTR 64·235, 1964
15. H.K Eckelmever. Sandia Labs Report 7404 18.1974
.
16. D.D. Chemovet ai.. Dohl. Aked. ,va.uk. SSSR ,
Vol 245 (:'-io. 2). 1979, p 360
17. P.G. Lindquist and C.M. Wayman. Enginccr.
ing Aspects of Shape Mem,:.-y Alloys. TW.
Dueng et al.. Butt.cI"Worth-Heincmann, Lon·
don, 1990, p 58
18. T.w. Dueng and KN. Melton. The Marten.~i!c
Transformu.ti!lTl in Science and Technology, E.
H om~l.!Ien und H. Jost, Ed ., Deutsche Gesell·
schall. :l..!r !Iiolclallkunde, Gcrmuny. 1988, p 191
19. W. MO!H.!rly and K. Melton, Engineering A~ ·
pcc:l.~ ot" S hnpe .\femllry Alloys. T \V. Duorig et
1048/ Advanced Materials
ai., Ed., Butterworth.Heinemann, London,
1990,p46
ZO. O. Matsumoto, S. Miyazaki, K Otsuka, and H.
Tamura,Acta Meta ll., VollS, 1987, p 2137
21. H.C. Li.ogand R. Kaplow,Metall. ThJn$. A, Vol
12,1981, p 2101
22. L. Kaufman, SA Kulin, P. Neshe, and R
Salzbrenner. ShaIN Memory Effects in Alloys,
J. Perkins, Ed.., Plenum Press, 1975, p 547
23. S. Spinner and AG. Hozner, J. Acoust. Soc.
Am., Vol 40, 1966, P 1009
24. R.J. Wasilewski, 'Ihm.s. AIME, Vol 233, 1965, p
1691
25. O.K Belousov,Russ. Metall.. Vo12, 1981, p 204
26. J .E. Hanlon, S.R. Butler, andR.J. Wasilewski,
']}ans. AlME, Vol 239, 1967, p 1323
27. CoM. Chan, S. Trigwell, and T.W. Duerig, Surf.
InterfaceAncl. Vol IS, 1990, p 349
28. J.D. Harrison, ~ychem Report, 1991
29. S. Lu, Engineering Aspects of Shape Memory
Alloys, T.W. DuerigetaI., Ed.. Butterworth-Heinemann. London, 1990, p 445
30. L.S. Castleman, S.M. Motzkin. F.P. Alicandri,
VL. Bonawit, and AA Johnson, J. Biomed.
Mater. Res., Vol 10, 1976, p 695
31. R Burch and N.B. Mason, J.e.s. FarcuJ.ay I,
Vol 75, 1979, p 561; RB. Burch and N.B. Mason,J.e .S. Faraday I, Vol 75. 1979, p578
32. AR Pelton and TW. Duerig, "'AIl Analysis of
Crofit Couplings After One·Year Service at
Seabrook,8 Raychem Proprietary Report, 1991
33. G. Ai.roldi and B.Rivolta,Phys. Scn'pto , Vol 37,
1988, P 891
34. J.C. Gachon and J. Hertz, CALPHAD, Vol 7,
1983, P 1
35. K Otsuka, T. Sawamura, K Shimizu, and
C.M. Wayman, Metail. '1h:Jns., Vol 2, 1971, P
2583
36. S. Miyazakiet al., Mater:. Sci. Fomm, Vol 56-58,
1990,p765
37. A.K MukhcJjee, J . Appl. Phys., Vol 39 (No. 5),
1968.p220 1
38. A. Thrui et ai., Nip. Kihai Gakhai ROllbunshu,
A Hen, Vol 51 (Nu. 462), 1985, p 488
39. G.R Zadno. W. Yu, and T.W. Duerig. MaU!rials
Scknce Forum, Vol 56-58, D.C. Muddle, Ed.,
1990, p771
40. H. Tamura, Y. Suzuki and T. 'Ibdoroki, Prot.
lot. Con£. MartensiticTro.nsrormations, Japan
Institute orMetals, 1986, p 736
41. Y. Furuya et ai., MRS Int. Meeting on Advanced Materials, Vol 9, K. Otsuka and K.
Shimizu. Ed., Materials Research Society,
1989, p269
42. Y. Suzuki and H. Tamura, Engineering A<;pect.<;
ofShapeMemoryA1.10ys, T.w. Dueriget 0.1. , Ed.,
l3utterworth-Heinemann, London, 1990, p 256
43. J.L. Pratt, K.N. Melton, and T.w. Duerig, MRS
Int. Meeting on Advanced Materials, Vol 9, K
Otsuka and K Shimizu. Ed., Material s Research Society, 1989, p 159
44. R.H. Dauskardt, TW. Duerig. and RO. Richie.
Jl..{RS Int . Meeting on Advanced Materials, Vol
9, K Otsuka and K Shimizu. Ed., Materials
Resetl.n:h Society, 1989, p251
45. S. Miyazaki. Y. Sugaya, a.nd K. Otsuka, MRS
lnt. Meeting on Advanced Materinls, Vol 9, K
Otsuka and K Shimizu, Ed.. Materials Hesearch Society. 1989, p 251
46. K N. Melton and O. Mercier, Acta Metall ., Vol
29, 1982, p 393