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`TiNi
Shape
Memory
Alloys

`
`

`
`Duerig,
Pelton

`
`

`
`Materials
Properties
Handbook
Titanium
Alloys

`pp.
1035‐1048

`
`

`
`1994

`
`www.nitinol.com
`
`47533 Westinghouse Drive Fremont, California 94539 t 510.683.2000 f 510.683.2001
`
`Letterhead (scale 80%) Option #1
`
`Edwards Exhibit 1028, p. 1
`
`

`

`I Ti-Ni Shape Memory Alloys
`
`Ti-Ni Shape Memory Alloys 11 035
`
`Product Forms
`Bnd
`Applications
`
`T.w. Duerig and A.R. Pelton, Nitino/ Development CofpoIation
`
`This datasheet describes some of the key prop(cid:173)
`erties 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 com(cid:173)
`positional 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 ac(cid:173)
`knowledge is that all properties change signifi(cid:173)
`Mr,
`cantly at the transformation temperatures M
`"
`~, and Ar (see figure on the right and the section
`"Tensile Properties~). Moreover, these tempera(cid:173)
`tures depend on applied stress. Thus. any given
`property depends on temperature, stress, and his·
`''''y.
`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 re(cid:173)
`crystallize the material , but does bring about the
`onsel of recovery processes. The extent of the post(cid:173)
`cold worked recovery depends on many aspects of
`the application, such as the desired stiffness, fa ·
`tigue life, ductility, recovery stress, etc. Fully an(cid:173)
`nealed 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 com(cid:173)
`position 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 ma(cid:173)
`trix, their general effect is to increase the Ms tem(cid:173)
`perature. The solvus tem;leratw-e is about 550 °C
`
`Effect of phase transformation
`
`Manensile
`
`D-
`Heating .. '
`"
`
`j
`
`~ C~i
`
`D
`
`Auslenile {pa.ent)
`Typica lly 20 ~
`
`M, .. Manensl1e stan
`temperature
`A, lIAr ~ Manensite linish
`temperalure
`A" "Stan of reverse
`transformation of manGnsHe
`A. = FiniS!' ot lI!Verse
`transformatIon 01 martens;t
`
`Temperature ->
`
`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
`
`Source: C.M. Wayman and ToW. Duerig. Engineenng Asped5 of
`Shape M!mofy Aloys. T.W. Duerig. et aI .. Ed .• BoMerworfl·Hene(cid:173)
`mann,t990, ptO
`
`"""'"-
`
`(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:!!(cid:173)
`ing, thus generating a recovery strain (Rcf9 .
`
`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 mRny 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
`
`Special
`Properties
`
`Many shape memory-related properties are
`discussed in subsequent sections (transformation
`
`temperatures. superelasticity, etc.). Sume proper(cid:173)
`ties, however, are ~ tric tly peculiar to shupe men!-
`
`Edwards Exhibit 1028, p. 2
`
`

`

`1 C361 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
`AMQlcd b;.ntoo;k
`Co~~~b~k~cd
`OISOO ·C(930"F)
`Cold ""Ot\(od wi~:umr:.oJod ~l
`4OQ°cnso·F)
`
`Recovery 5tree~. MPa
`
`"'" ''''
`
`'000
`
`Free recovery behavior
`
`•
`•
`
`lS
`10
`5
`TOlal deformalion strain, 'Y.
`
`"
`
`'T1·NI-Fe berslock wi\tl SO a1.% NI8/1d 30/. Fe fuU)' annealed. tested
`In unlilldal tltf"lslon. An", deforming 'T1-Ni to various lotal slrnil'lS Ix(cid:173)
`axis). 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 $OffiO amonla pertlSIS. lhedifferenoe between the plas·
`tie slrain IW'd the amnesia is the reoove<abIB Slrain (dosed ordes).
`Source: J.L Proft and T.W. DuerIg. E:ngi1eeMg Aspects 01 Shape
`MemoIy Alloys. T. W. Duerig fll 8/" Ed., Bunerworfl·Heinemann,
`London, 1990.p 115
`
`Effecls of opposing stresses on recovery strain
`
`Work output of a li·NI alloy
`
`Applied stress. ksi
`10 ~ ~ ~ M W
`
`o
`
`ro ~
`
`o
`
`Applied stress. ksi
`10 ~ ~ ~ ~ ~ ro ~
`
`Applied stress, MPa
`
`O'~~~~ __ ~ __ ~ __ ~--J
`o
`tOO
`200
`300
`400
`500
`600
`A~plied stress. MPa
`
`T\.Nl-Fe tlarstock with SO at.% Ni and 3% Fo fUly anr.&aled, tested
`in unia;cialleflSiot>.
`Source: J.L. Proll and T.W. Ouertg, Fngneering AspecI$ 01 Shap6
`Memory Alloys. T.W. Ouetlg ~, aI .• Ed., Bunerworth-Hl!Iinernatln,
`LoMon. 1990,p 11S
`
`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. %. Bi(cid:173)
`nary 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
`
`Edwards Exhibit 1028, p. 3
`
`

`

`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.Ni20.., 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. Nitro(cid:173)
`gen 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 sup(cid:173)
`press 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 •• eventu(cid:173)
`ally 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
`
`Ti·Ni Shape Memory A lloys 11 037
`
`Effect 01 composition on M.
`
`~ ,.
`
`•
`• ,
`",
`
`•
`,
`
`, ~
`
`p
`
`,; •
`~
`&
`~
`• .5(
`
`.P ",
`~b'
`
`.' "
`
`.'0<
`.,
`
`. '5(
`
`os
`
`.,
`
`50
`Nick,l. al.%
`
`"'"
`,..
`
`'00
`
`•
`~
`i
`~
`•
`•
`
`•
`.'
`,
`" " "
`
`·'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(cid:173)
`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 i
`
`.. , ,
`
`W(,lgh : Percent Nickel
`
`..
`
`0 $4""
`o 148.,
`o I'P<or
`
`L
`
`• •
`
`,
`,
`
`TINI
`
`•
`
`Central Portion
`ofTi-NiPhase
`Diagram
`
`UOO J
`
`• , ,
`• ,
`• ~
`E
`t!.
`
`1 300~ ,
`;
`IWO i
`I ,
`~ ,:1
`
`,
`
`too~
`
`eoo~
`
`lOOj ,
`..,I
`"
`
`-.. _. -_ .. -_ ..... _-_ ... -.... _-.. -.-- -. ---._-------_ .. -._-_. ---_ ..... ;
`so
`"
`d
`Atom ic Percent Nick('1
`
`o
`
`10
`
`$!o
`
`II-."IO-C
`
`..
`
`.
`
`Phases and Structures
`
`•.
`
`Crystal
`Structure
`
`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.
`
`Edwards Exhibit 1028, p. 4
`
`

`

`10~ I Advanced Materials
`
`Ti me-lemperature-transformation curve
`
`OOO--~~----------------------------------------------~'100
`TiN;
`•
`0
`0
`• TiN; . Ti!!Ni!.,," r~iJ
`TiNi • 11zNiJ .. rlN~ •
`0
`• TiNI "" TinNi!.
`• TiN;. r~~
`• TiNi . TiN~
`
`• . · .
`
`.
`
`0
`
`•
`
`•
`
`•
`
`•
`•
`
`HOO ~
`
`'''''' • •
`t200 f
`J
`
`'000
`
`0
`
`•
`•
`
`0
`
`0
`
`•
`
`•
`•
`
`0
`
`•
`
`0
`
`•
`•
`
`•
`
`• ''' .. •
`
`• •
`. ,
`
`0
`0
`
`•
`•
`•
`•
`
`•
`•
`
`•
`•
`•
`•
`•
`
`•
`
`~
`~
`i
`•
`r
`~ IlOO
`
`500
`...,
`
`0.01
`
`0.'
`
`"000
`
`"00
`100
`10
`Aging dm" h
`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
`
`Transformation
`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 mecharucaJ(cid:173)
`property measuremenle.
`
`Physical Properties
`
`Damping
`Characteristics
`
`Internal friction and damping of titaniwn(cid:173)
`nickel alloys are dramatico.lly affected by tem(cid:173)
`perature changes (see figure on left). Cooling (or
`heating) produces peaks, which correspond to the
`trnnsformation temperatures. At higher tempera(cid:173)
`tures, a very sharp increase is observed during
`
`cooling through the M •. These usuaJly high damp(cid:173)
`ing characteristics (Ref 22) havc been studied for
`some time, but have not been used un a commer(cid:173)
`cial basis due to their limited temperature range
`and rapid fatigue degradation.
`
`Elastic
`Con stants
`
`Dyno.m.ically measured moduli (Ref23 and 24)
`change markedly with the martensitic transfor(cid:173)
`mation 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
`
`T emperatu.e. "F
`".~~-".~>oo~-".'~OO"-~'"--"';OOC-"2~00"--"~~--,
`10" !""
`
`., L~ ____ -"~ ______ "-______ -',-____ -,J
`a
`·200
`-100
`100
`200
`Temperature. "C
`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~'"
`
`DynamiC Young's modulus vs temperature
`Ttmptratur,. OF
`0
`100
`200
`
`·200
`
`-100
`
`300
`
`400 ..
`
`•
`•
`0
`.; •
`~
`~
`
`.~ , -• 0 >
`
`I:J ~
`•
`12 ~
`-/---':f-----=---l .;
`,
`II i
`
`--- --'---"1
`
`'"
`
`_170
`
`·10
`
`30
`Tempenlture. ·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>(cid:173)
`lin, A.F. s..6fka, andC.M. Wa.,man, Ed.AtME. 1982, P t259
`
`Edwards Exhibit 1028, p. 5
`
`

`

`T i~Ni Shape Memory Alloys / 1039
`
`Electrical resistance vs temperature
`Temperature, OF
`0
`-I "
`
`-200
`
`'"
`
`200
`
`M,
`I
`
`"I
`
`•
`~
`
`• • •
`• r-J-
`•
`•
`" ~
`
`"I
`
`M.
`1
`
`A
`
`T, ~
`
`•
`
`,
`M,~
`,
`~ ~ ,
`,
`T, T-
`1
`T-
`• •
`I ' c
`
`'\~
`
`·170 · 140 · 110
`
`,80
`
`10
`·20
`·SO
`Temp erature, · C
`
`40
`
`70
`
`100 130
`
`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). T R;$ thetran·
`s1tlon tempertltUfe from austenite lQ the rOOmbohedral A pt1as.e. r R
`is the shifted transition temperature IrQ(ll prcx:essing eMects. Arbi(cid:173)
`trary units lor ~eef1ical resistance.
`Soun::.: S. Moyauki 3nd K. Otsulo.a. Melal. Trans. A.VoI 17. 1986.
`,53
`
`view, however, modulus is oClittie value; apparent
`elasticity is more controlled by the t ransfonnation
`and by mechanical twinning. Poisson's ratio, Jl., is
`0.33 (Ref25).
`
`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
`ther(cid:173)
`momechanical processing (see figure). Note also
`the pronounced effect of the R-phase on resistivity.
`
`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
`
`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. Tita(cid:173)
`nium-rockel will also react with nitrogen during
`heat tnatments, fonning a TiN layer.
`
`Electrical
`Resistivity
`
`Magnetic
`Characteristics
`
`Corrosion
`
`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 se(cid:173)
`ries. 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 environ(cid:173)
`mcnts can cause the passive film to break down,
`thus subjecting the base material to attack. A 8um~
`mary ortitaniwn·nickel reactions in various envi(cid:173)
`ronments 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 titanium(cid:173)
`nickel 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 concentra(cid:173)
`tion range 50 to 99.5%.
`Methanol (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 at 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 de(cid:173)
`pending 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 oon(cid:173)
`ducted 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,
`
`Edwards Exhibit 1028, p. 6
`
`

`

`1040 I Advanced Materials
`
`hydrogen can be absor bed during pickling, plat(cid:173)
`ing, and caustic cleaning. The exact conditions re(cid:173)
`quired for hydrogen absorption are not well de(cid:173)
`fined , 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 tem(cid:173)
`peratures 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).
`
`SpecifiC heal (Cp)
`
`Temperature. ' F
`200
`400
`
`0
`
`3
`
`25 -
`
`5
`
`"
`
`:
`:
`,
`
`~
`
`I
`
`i"
`
`5
`
`"
`"
`"
`
`,
`
`• 00
`-
`900
`600
`200
`,
`,
`,
`I
`,
`i
`:
`,
`I
`- ,-- ,---- t--
`-t-_L~~ _-
`,
`,
`,
`- -
`I
`,
`,
`,
`,
`,
`,
`I
`,
`,
`I
`,
`! !
`I
`I
`!
`,
`I
`I
`,
`I I I i
`,
`1110 210 360 "50 ~O
`90
`0
`T,mper.uu-e. ~
`
`Thermal Properties
`
`Heat Capacity
`
`Latent
`Heats
`
`Thermal
`Expansion
`
`A typical plot of specific heat (C ) versus tem(cid:173)
`perature 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 trans(cid:173)
`fonnntion 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 compli(cid:173)
`cate the CW""Ves and introduce spurious peaks.
`
`The latent heat of the martensitic transfonns(cid:173)
`tion strongly depends on the transformation tem(cid:173)
`perature and stress rate (doldT) through the for(cid:173)
`mula
`doldT = iiliKOF.n
`Typical values for 6H are 4 to 12 caUg and val(cid:173)
`ues for do/dT range from 3 to 10 MPaJOC.
`The latent heat of fusion can be expressed 8S:
`llH = -34,000 J/mol (Ref34).
`
`The thennal coefficient of linear expansion can
`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
`
`·270 · 180
`
`·SlO
`
`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
`
`Melting Point
`
`Martensitic
`Transformation
`Temp eratures
`
`Characteristic transformation temperatures
`depend strongly on composition (see table on
`next page and the previous section on chemi,(cid:173)
`try). Typical hysteresis widths range 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 re(cid:173)
`sistivity, latent heat of transformation by differen(cid:173)
`tial 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 al(cid:173)
`loys with low yield stre!lS(>S. The increase is tempo(cid:173)
`rary, 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·
`
`Edwards Exhibit 1028, p. 7
`
`

`

`Ti-Ni Shape Memory Alloys I 1041
`
`Strain of a Ti-Ni-Nb specimen
`
`M. temperature as a function of cold working
`
`Tempe ra t ... re. 'F
`200
`100
`0
`-200
`·300
`· 100
`,.r;~~~C--"~--~--~~--~
`
`.' ~ .;;
`
`,
`
`2
`
`- -"-
`
`,.L-____________________ --J
`
`·200
`
`o
`"00
`Tem perat ... re, ' C
`
`'00
`
`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 .
`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
`
`~
`~
`" • &
`! ..
`"
`
`·20
`
`"
`
`-2
`
`" " 20
`
`25
`Cotd 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!$earch
`
`Ti·NI shape memory transformation temperatures
`Mel. which is defined as the temperature above which martensite cannot be stress induced, may be abo ... tlrom 25 10 50 "C
`(SO to l00 "F) higher than At-
`
`Compa.ition
`• t,':iN;
`
`.... ". ... "'2 " ,,~
`
`49.7
`
`,,..
`.9.4 "., "'.,
`'" "'. , "'.,
`" 48.1
`
`48.6
`49.0
`,,~
`
`"'~ ".
`
`[SIMcll
`
`IBOMiJI
`
`[68 W;anl
`
`[79OlcI
`
`21
`
`"-
`" )7
`D -" -'" ~
`" '" _liO ., ..
`'" .. ., ,
`
`"
`
`- 9._29
`2O tol!i
`
`' 00
`
`.:!!
`
`Thn\perature. "C
`>f,
`A.
`
`T""'hniq ....
`
`"
`"
`"
`'"
`-'"
`_lI
`,
`-"
`
`-lO
`->l
`
`-"
`.,
`"
`"
`"
`..,
`
`-lO
`
`03
`
`))
`0
`
`"
`"
`"
`..
`-"
`"
`-" "
`'''' "
`""
`'"
`".
`,.,
`"
`•
`-'"
`
`'" '" '" J2 -" .. m
`
`'''' " ,
`
`" .. ,
`'" " " .. -J'
`
`Elcc1ri.:al. ""'8n<:lic
`fIRlPCn""
`Eb:ui<:>.l ""i'livi!)'
`
`Compilation UoIXI Ph.;..DiavamsofBiruu:- TIlaniu", A/kIyI, (J .L :'dW11l),. Ed.), ASM InternotionAl, 1987, p203. la )CiIed rcl.-~ &I'\!
`loS rouo ..... : 11 Kor. LL Kornilo¥, Yo:. V. Kachur, ... d O.K. &010\11.0", "Dilatation An.a]ys;,O!'1"ran'(omIltion in the CompoundTlNi: F iz. Md .
`Mrl41UwtJ. . 32(2), 42().422 (1971) in Ruuian; TR: Phyr. Mff. MnolkKr .• 32(21, 19I)..193 ( 197U. 81 l i e!: KX Melton and O. l l emer. "'The
`MechaNcal Propertiet o(NiTI.Bued Slape Memory AlIo)'t.~ llcIo Mtlo U., 29. 393-3981 19811. 80 Mil: RY. l{;lI ipn. "O.lf!rmination of
`Phue n.nsroro>ation 'ThlXlperat.u.resor TI.'1i U.mg Oilfef"eflti.a] Thmn.al An.a]y.i •• ~1'i tani ... m"80. Ti Sci.1kh .. Proc. lnt. Con(. Kyoto, J".
`pM. M.yl8.22, T. Kiltluzi, Ed., 14S1-1467f1980J. 68W&n: F.£. Wang,B.r. OeSa"age,MrlW.J. But'hler. lllo: ' n-evtTSibl .. Critiaol RIInJ{f' ;"
`the Til'll n-..osltion: J . Appl. PII)'$ .• 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 n:-o,: DoIIL lU .. d. NOIlIt. SS$R, 24;.854-851 ( 19191 in It .... i . .. ;
`'I"R:Sot.r. Ph:#- DolL, 24{S I. 664-066(19i91
`
`Edwards Exhibit 1028, p. 8
`
`

`

`1042/ Adva nced Materials
`
`Tensile Properties
`
`In general, a superelastic curve is charac(cid:173)
`terized by regions of nearly constant stress upon
`iooding(referre<i to the loading plateau stress) and
`wliooding (unloading plateau stresa). These pla(cid:173)
`teau stress values are better indicators of me(cid:173)
`chanical strength than the traditional yield stress.
`Typical values ace shown (see table).
`
`Schematic of superelasticity descriptors
`
`Ti-Ni shape memory: Typical loading and unloading
`characteristics
`
`l.oadi:Il pl:lllliIU
`UIIIoadin. pI=u
`MIUimwn ~prtn8~k
`MWrnum defQrm;l.tiQI1 with %
`pcrmanc:m~
`M.ulmwn lIOItd enon'
`
`45OlO1OOMh
`Up.o 250 MP>.
`
`, .. ..
`
`$our«: T.W. Dumng and C.R. Zadno. E~TlffriT16 Mptc1' of
`Slwtpe M~mcryNlay., T.W. Dueriget ... 1., Ed., Butterwon..b.t!4m.
`mann, London. 1990, p 369
`
`Strain
`
`"
`
`Above M.;t
`
`~ is defined as the temperature above which
`martensite cannot be stress-induced. Conse(cid:173)
`quently,
`titaniwn-nickel
`remains
`austenite
`throughout an entire tensile test above~. Tensile
`strengths depend strongly on alloy condition, and
`the ultimate tensile strength, yield strength, and
`ductility of cold worked titanium-nickel 'Ni.re de(cid:173)
`pend on final annealing temperatures (see figure).
`
`Ductility drops sharply as compositions be(cid:173)
`come nickel-rich. A review of othec facton control(cid:173)
`ling ductility can be found in Ref36.
`
`SO
`
`Mechanical properties vs anneal temperature
`Temperature, OF
`--
`;800~,,~'~"~ __ '"OCO~ __ C'~'''ec __ ~''~''~ __ '~'~''
`le'"
`_
`r Ducti~ty
`I
`
`UTS
`
`"
`• ,;
`109
`&
`
`I
`l%YS I
`...... ---
`I
`.. ~~.~.~--~j~::::::::::::::::::J"
`
`300
`
`<CO
`
`700
`600
`500
`Tempal3ture , 'C
`
`800
`
`900
`
`SthemllIie dilgam ~ key dHcrIptors 01 superetastidty: 0u
`(l.WlIOIIcing jtateau mtasured aslhe inIe<:tionpoinl), o,(IoDIg pta.
`tQu rne&$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-4Ieine(cid:173)
`mam. 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 duro
`ing the aging process.
`
`Yield strength vs anneal temperature
`
`.,,, ,
`
`,co
`
`500
`
`Temperature. OF
`100
`200
`
`300 ,
`"'
`
`'"
`'"
`'" , ,
`" • • ~
`
`'co
`• • •
`" •
`~
`
`,
`
`"00
`
`roo
`
`300
`
`Theinlluenceol~*'9lemperal\.O'uonrned\arOcal~HoI
`0.5 111m (0.02 In.) T~SO.6Ni wire ..... '" 40% eok1 WOI1t and aMNlecI
`3Ominat~tur..
`~: G,A. Zact-o and T.W. Duerig.l..I"IpUbIished research
`
`Theinll..e-lced ll'f'ttoa6rlg~on/1"!fd"larblproperliesolli·
`
`50.6Ni """40"'10 ($j -..o1<.....-.eMd 30 ...... at 1emper.1IUu.
`Scuroe: G.A. Zadno and T.W. Ouerig. t.npUbished re$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. Ulti(cid:173)
`male tensile strengths and ductilities nre similar
`to austenitic values.
`
`Edwards Exhibit 1028, p. 9
`
`

`

`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 prop(cid:173)
`erties of equiatomic and near-equiatomic tita(cid:173)
`nium-nickel alloys with compositions yielding
`
`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
`information
`on
`titanium·nickel,
`Tee'MI',
`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 proper(cid:173)
`ties 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·
`Mr,
`cantly at the transfonnation temperatures M
`"
`A., and Ar (see fib'Uro). Moreover, thege tempera(cid:173)
`tures 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
`
`Permanent set 01 superelastic wire
`
`Loading and unloading plateau heights in Ti·Ni wire
`
`-300
`
`·200
`
`Temoera!ure. OF
`·100
`0
`100
`
`200
`
`300
`
`.:)00
`
`·200
`
`Tempe"lu' •. OF
`·100
`0
`100 200
`
`JOO
`
`" ~ •
`~
`
`\
`
`o
`Temperat",re. "C
`
`'00
`
`200
`
`-200
`
`-'00
`
`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 CC