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Response Characteristics and Adiabatic Heating during High Strain Rate for TRIP Steel and DP Steel
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ５,２ ２( １):４ ８ Ｇ ５ ４
Re s s eCha r a c t e r i s t i c sandAd i aba t i cHe a t i ngdu r i ngHi pon gh S t r a i nRa t ef o rTRIPS t e e landDPS t e e l YiGAO, ChaoXU, Zhong Ｇ i ng HE, Yan Ｇ l i n HE, L i nLI p
( Schoo lo fMa t e r i a l sSc i enc eandEng i ne e r i ng,Shangha iUn i ve r s i t i２０００７２,Ch i na) y,Shangha Ab s t r a c t:Byus i ngas t a t i candh i Ｇ spe edma t e r i a lt e s t i ngma ch i ne,t ens i l ede f o rma t i onbehav i o r so ftwok i ndso fS i Ｇ gh MnTRIP ( t r ans f o rma t i oni nduc edp l a s t i c i t t e e l sandDP ( dua lpha s e)s t e e lwe r es t ud i edi nal a r angeo fs t r a i n y)s ger r a t e s( ０ ００１－２０００s－１ )．Tempe r a t u r eva r i a t i ondu r i ngad i aba t i che a t i ngandt heamoun to fr e t a i nedaus t en i t ea t f r a c t u r ewe r eme a su r edbyani n f r a r edt he rmome t e randanXＧ r ays t r e s sana l s e r,r e spe c t i ve l c r o s t r uc t u r eo f y y．Themi s t e e l swa sobs e r vedbyop t i c a lmi c r o s c opy ( OM)ands c ann i nge l e c t r on mi c r o s c opy ( SEM)be f o r eanda f t e rt ens i l e t e s t． I twa sf oundf r omt heexpe r imen t a lr e s u l t st h a tt h et e n s i l es t r e ng t ho ft h e s es t e e l si n c r e a s e d,a ndt h ef r a c t u r ee l ong a Ｇ t i onf i r s t l c r e a s edandsubs e t l nc r e a s ed,a st hes t r a i nr a t ei nc r e a s edi nt her angeo f０ １－２０００s－１ ．The yde quen yi t empe r a t u r er a i s eddu r i ngad i aba t i che a t i ngo fTRIPs t e e lwa si nt her angeo f１００－３００ ℃ ,wh i l et ha to ft heDPs t e e l wa si nt her angeo f１００－２２０ ℃．Thet empe r a t u r er i s eo ft he s es t e e l si nc r e a s edwi t hi nc r e a s i ngt hes t r a i nr a t e,a s we l la st heamoun to ft het r ans f o rmedr e t a i nedaus t en i t ei nTRIPs t e e l s． I twa sc on f i rmedt ha taus t en i t et oma r t ens i t e t r ans f o rma t i oni sno tsupp r e s s edbyad i aba t i che a t i ng． Ke r d s:s t r a i nr a t e;TRIPs t e e l;ad i aba t i che a t i ng;r e t a i nedaus t en i t e ywo
I no r d e rt oimp r o v ep a s s e ng e rs a f e t e du c ewe i t y,r gh , ( andd e c r e a s ef u e lc on s ump t i on TRI P t r a n s f o rma t i on i nduc edp l a s t i c i t t e e l,wh i chs imu l t aneous l Ｇ y)s ypos s e s s e sh i t r eng t h and duc t i l i t s be en p r o Ｇ gh s y,ha duc edbyt hec oope r a t i ono fs t e e lg r oupsandau t o Ｇ [ １－４] mo t i vei ndus t r ．Howeve r,mo s to fi nve s t i Ｇ y ga t i onsont h i ss t e e la r er e l a t edt ot he me chan i c a lbe Ｇ hav i o randt hes t ab i l i t fr e t a i nedaus t en i t eunde r yo s t a t i co rqua s i Ｇ s t a t i cc ond i t i ons．The r ea r eon l ew yaf r epo r t s de a l i ng wi t ht he me chan i c a l behav i o ro f TRIPs t e e la th i t r a i nr a t e．Thes t r a i nr a t eha sa ghs r e a ti n f l uenc eont he me chan i c a lp r ope r t i e so fma Ｇ g , t e r i a l s．The r e f o r e t her e s e a r cho ft her e l a t i onsh i p be twe ent he me chan i c a lbehav i o rands t r a i nr a t ei s ve r r t an tf o rt hes imu l a t i ono fc a rc r a shand yimpo h i Ｇ spe edmo l d i ng． gh Du r i ngt hef o rmi ngo fs t ruc t u r a lpa r t sandt he c r a sh i ngo ft heau t omob i l ebody,t hes t r a i nr a t e sa r e －１ －１ ２ ３ －１ [ ５, ６] , i nt her angeo f１０ －１０s and１０ －１０ s r e spe c t i ve l I nh i t r a i nr a t ede f o rma t i on,t head Ｇ y． ghs i aba t i cc ond i t i onsc an ber e a ched．The me chan i c a l
behav i o ro fTRIPs t e e l si sdependen tont her e t a i ned , aus t en i t et r ans f o rma t i on wh i chi sve r ens i t i vet o ys t empe r a t ur e．The r e f o r e,i no rde rt os t udyt hedy Ｇ nami cp r ope r t i e so fTRIPs t e e l s,ad i aba t i ct empe r a Ｇ t ur er i s emus tbea c cur a t e l a sur ed． y me The r ea r et hr e eequ i t sf o r me a sur i ngt he pmen i ns t an t aneoust empe r a t ur edur i ngad i aba t i che a t i ng: t he rmocoup l e,l i i dc r t a lf i lm andi n f r a r edt he r Ｇ qu ys
mome t e r．I n f r a r ed t he rmome t e r me a sur emen ti s non Ｇ con t a c t,r e spons e sve r f a s ta n dh a sl a r es i Ｇ y g g na l Ｇno i s er a t i o．Th i sequ i twa sus edi nt hepr e s Ｇ pmen en texpe r imen t． I nt h i s wo rk,６００and９００ MPa g r ade TRIP s t e e l swe r es t ud i ed． I no rde rt oana l z et hef unc t i on y o fr e t a i nedaus t en i t e,DP ( dua lpha s e)s t e e l,wh i ch ha st hes amecompos i t i onwi t h６００ MPag r adeTRIP s t e e lbu tdoe sno texh i b i tpha s et r ans i t i ondur i ngde Ｇ f o rma t i on,wa sa l soi nve s t i t ed．Byus i ngane l e c Ｇ ga t r on i cun i ve r s a lt e s t i ng ma ch i ne MTSandah i Ｇ gh spe edt ens i l et e s t i ng ma ch i neZwi ckHTM５０２０,t he me chan i c a lp r ope r t i e so fs t e e l s we r e de t e rmi ned．
Founda t i onI t em: I t em Spons o r edbyNa t i ona lNa t ur a lSc i enc eFounda t i ono fCh i na ( ５０９３４０１１,５０９７１１３７);Na t i ona lBa s i cRe s e a r chPr og r amo f Ch i na ( ２０１０CB６３０８０２) B i o r aphy: YiGAO,Do c t o rCand i da t e,Sen i o rEng i ne e r; E Ｇma i l: i＠ans t e e l c omcn; Re c e i v e dDa t e:Sep t embe r２９,２０１３ gaoy g
I s sue１ Re spons eCha r a c t e r i s t i c sandAd i aba t i cHe a t i ngdu r i ng Hi t r a i nRa t ef o rTRIPS t e e landDPS t e e l ４９ ghS
Comb i nedt her e su l to fad i aba t i ct empe r a t u r er i s e du r i ngd e f o rma t i on w i t ht h e mi c r o s t r u c t u r eo fs t e e l s, wh i c hwe r eob s e r v e dbyop t i c a lmi c r o s c opy ( OM)and ( ) , s c ann i nge l e c t r onmi c r o s c opy SEM me chan i smo f me chan i c a lpr ope r t i e schange swa sana l z ed． I nadd i Ｇ y t i on,t heamoun to fr e t a i nedaus t en i t ei nTRIPs t e e l wa sme a su r edbyus i nganXＧ r ays t r e s sana l z e r． y
１ Exp e r imen t a l
１ １ Expe r ime n t a lma t e r i a landt e n s i l et e s t Ac omme r c i a l l i l ab l ec o l dr o l l ed TRIP A y ava ( ６００ MPag r ade)she e ts t e e landal abo r a t o r r e Ｇ yp r edTRIPB ( ９００ MPag r ade)she e ts t e e lwe r eex Ｇ pa S t e e l
C
Tab l e１ Ch emi c a lc ompo s i t i on ( ma s s％ )andh e a tt r e a tmen tpa r ame t e r so fs t e e l st e s t e d
S i
Mn
P
S
TRIP A
０ １１ １ ２
１ ５ ０ ０１
０ ００５
TRIPB
０ ２２ ０ ７ １ ６５ ０ ０５
０ ００４
DP A
ami nedi nt h i ss t udy．Thet h i ckne s so fTRIPAshe e t s t e e li sabou t１ ５mm．TheTRIPBs t e e lwa sc a s tby us i nga１１０kg med i umf r equenc nduc t i onf urna c e, yi , f o r n t o２５－３０ mm b l ank andt henhe a t eda t gedi １２００ ℃f o r１h,mu l t i Ｇ s sho tr o l l edi n t o４－６mm pa t h i ckne s s wi t haf i n i sh i ngt empe r a t ur eo f９００ ℃ , , andcoo l edt or oomt empe r a t ur ep i ck l edi n１０％ hy Ｇ d r och l o r i ca c i dso l u t i on,andt hen mu l t i Ｇ s sco l d pa r o l l ed (wi t hi n t e rmed i a t e anne a l i ng)t o１ ２ mm t h i ckne s s．The s es t e e l s we r e he a tt r e a t edi ns a l t ba t h．Thechemi c a lcompos i t i onandhe a tt r e a tmen t r ame t e r so ft he s es t e e lshe e t sa r el i s t edi nTab l e１． pa Thes ke t c ho fZwi c kHTM５０２０i ss howni nF i １． g
０ １１ １ ２
１ ５ ０ ０１
０ ００５
Ni
０ １
Al
N
He a tt r e a tmen tp r o c e s s
≤０ ０３
≤０ ００３５
７８５ ℃×３ mi n＋４２５ ℃×３ mi n＋wa t e rquench i ng[７]
０ ５６
≤０ ００３５
８００ ℃×３ mi n＋４００ ℃×５ mi n＋wa t e rquench i ng
≤０ ０３
≤０ ００３５
７８５ ℃×３ mi n＋wa t e rquench i ng
Tak i ngt hecond i t i ons o ft hecommon au t omo t i ve she e tf o rmi ngp r oc e s sandco l l i s i oni n t oa c coun t,t he dynami cp r ope r t i e si n１２d i f f e r en ts e t so fs t r a i nr a t e s we r es t ud i ed．Thes t r a i nr a t ewa ss e tt obe０ ００００５, ０ ０００５,０ ００５,０ ００１,０ ０５,１００,２００,３００,６００, －１ , １０００ １５００and２０００s i nt h i st e s t．
F i １ Sk e t cho fZwi ckHTM５０２０ ′ sd e v i c e g
Spe c imen wa sf i xedbyg r i adandde f o rmedby p he , a c c e l e r a t edg r i ad wh i chwa sc on t r o l l edbyas e r Ｇ phe vo Ｇhyd r au l i cs t em．The pa r ame t e r so fs t r e s sand ys s t r a i no fspe c imenwe r er e c o r dedbyus i ngal oadc e l l andad i sp l a c emen tt r ansduc e r．I nt h i ss t udy,dy Ｇ nami ct ens i l espe c imenswe r ema ch i neda sshowni n F i ２．Qu a s i Ｇ s t a t i cme c h a n i c a lp r op e r t i e so ft h e s es t e e l s g we r eob t a i nedi nan MTS８０９t ens i l et e s t i ng ma ch i ne．
１ ２ Ad i aba t i che a t i ngt e s te i t qu pmen Tempe r a t ur er i s edur i ngad i aba t i che a t i ng wa s me a sur ed by CTLa s e r ３M i n f r a r ed t he rmome t e r． Theme a sur emen tr angeo ft heequ i ti sf r om５０ pmen , t o４００ ℃ andi tope r a t e swi t h２ ３μmsho r twave Ｇ l eng t hde t e c t o r sandadua ll a s e rt a r t i ngs t em． ge ys Theop t i c a lr e so l u t i oni supt o３００∶１,andr e spons e t imei s１ms．Thes t ema c cur a c ft h i sequ i t ys yo pmen i sabou t±０ ３％ ,andt hemi n imumr ad i uso fme a s Ｇ ur ab l ea r e ai s０ ７ mm． １ ３ Mi c r o s t r u c t u r eob s e r va t i on By op t i c a l mi c r os copy and Hi t a ch i SUＧ １５１０ SEM,t he mi c r os t ruc t ur eo ft he s et hr e es t e e lspe c i Ｇ mensa f t e rhe a tt r e a tmen twa sobs e r ved．Comb i ned wi t ht heana l i so fXＧ r ayd i f f r a c t i on,t heamoun to f ys s e si nt he s es t e e lwa sme a sur ed． pha
２ Re s u l t sandDi s c u s s i on
F i ２ Dimen s i on so fs e c imen swi t hat h i ckn e s so f g p １ ５mmf o rZwi ckHTM５０２０ ( un i t:mm)
２ １ Mi c r o s t r u c t u r e The mi c r os t ruc t ur e mo r l og i e so fTRIP A, pho TRI PBandDPAs t e e l sa r es howni nF i s ３( a)－３( c), g whe r e,t hewh i t ep a r ti sf e r r i t eandd a r kandg r eypa r t s
５０
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
( a),( d)TRIP As t e e l; ( b),( e)DP As t e e l; ( c),( f)TRIPBs t e e l．
F i ３ Op t i c a lmi c r o r aph sandSEM mi c r o r aph so ft e s t e ds t e e l s g g g
a r e ba i n i t e and r e t a i ned aus t en i t er e spe c t i ve l n yi TRIPs t e e l． I nDPAs t e e l,t hef e r r i t epha s eappe a r s i nwh i t ec o l o randt hema r t ens i t ei sda rk． F i ３( d)－３( f)we r ea c i r edbyus i ngSEM gs qu i ns t rumen t,f r om wh i chi tc anbes e ent ha tba i n i t e andr e t a i nedaus t en i t ea r e ma i n l i s t r i bu t eda tt he yd f e r r i t eg r a i nbounda r i e si nTRIPs t e e landma r t ens i t e i sembeddedi nf e r r i t ema t r i xi nDPs t e e l． Byu s i ngqu a n t i t a t i v e me t a l l o r a ndX Ｇ r a i f Ｇ g phya yd f r a c t i o na n a l s i s( Th es s t ema c c u r a c sa b o u t ±３％), y y yi t heamoun to fe a chpha s e wa sde t e rmi ned．TRI PA , s t e e lwa sc ompo s e do f６０ ４v o l ％ f e r r i t e １０ １v o l ％ r e t a i ned aus t en i t e and ２９ ５vo l ％ ba i n i t e; DP A s t e e lc ons i s t edo f６０ ８vo l ％ f e r r i t eand３９ ２v o l ％ ma r t e n s i t ea ndTRI PBs t e e lc on t a i n e d３６ ４v o l ％ f e r Ｇ r i t e,１７ １v o l ％ r e t a i n e da u s t e n i t ea nd４６ ５％ b a i n i t e． ２ ２ Te n s i l epr ope r t i e sund e rqua s i Ｇ s t a t i cc ond i t i on Thequa s i Ｇ s t a t i cs t r e s s Ｇ s t a i ncu r ve so ft hes t e e l s a r epr e s en t edi nF i ４．Ay i e l dp l a t e auwa sobs e r ved g ont hecu r veon l o rTRIP As t e e l,wh i l eTRIPB yf [] s t e e lshowedac on t i nuousy i e l dch a r a c t e r i s t i c s． Sh i８
F i ４ Qua s i Ｇ s t a t i ct en s i l es t r e s s Ｇ s t r a i nc u r v eo f g TRIPAs t e e l,TRIPBs t e e landDPAs t e e l
i n t edou tt ha t,a sc a rboncon t en ti nc r e a s e s,t he po i e l dp l a t e au g r adua l l come ssho r t e rand even y y be d i s appe a r si nt hes amet fs t e e l s． ypeo I tc ana l sobes e enf r om F i ４t ha tt hee l onga Ｇ g t i ono fTRIPAs t e e li sa lmos tt hr e et ime st hant ha t o fDPAs t e e l,wh i chi sc aus edbyt hes t r a i ni nduc ed ma r t ens i t et r ans f o rma t i on and s imu l t aneous l he yt i nduc edp l a s t i c i t y． F i ５s howst hef r a c t u r emo r l ogyo ft h r e es t e e l s g pho
( a)TRIP As t e e l; ( b)DP As t e e l; ( c)TRIPBs t e e l．
F i ５ Fe a t u r e so ff r a c t u r es u r f a c eo ft e s t e ds t e e l s g
I s sue１ Re spons eCha r a c t e r i s t i c sandAd i aba t i cHe a t i ngdu r i ng Hi t r a i nRa t ef o rTRIPS t e e landDPS t e e l ５１ ghS
a f t e rs t r e t ch i ng．Thetwo TRIPs t e e l shaveduc t i l e f r a c t u r echa r a c t e r i s t i c s．Thesma l l e randde epe rd imＧ l e sf r a c t u r e so fTRIPs t e e l sexh i b i t edgoodp l a s t i c p de f o rma t i on c apa c i t r ed wi t ht he TRIP y．Compa s t e e l,DP A s t e e lhad poo rduc t i l i t c aus eo fi t s y be b i e ra n ds h a l l o w e rd i m l e s ． gg p ２ ３ Te n s i l epr ope r t i e sund e rdynami cc ond i t i on F i ６s h o w st h er e l a t i o n s h i b e t w e e nt ens i l e g p s t r eng t hands t r a i nr a t eo ft he s es t e e l s．I tc an be s e ent ha t wi t hi nc r e a s i ng s t r a i nr a t e,t he s es t e e l s , showah i rt ens i l es t r eng t h．Gene r a l l hep l a s Ｇ ghe y t t i cde f o rma t i onr e l i s l o c a t i on mo t i on,i nc l u Ｇ ysond d i ngt he rma la c t i va t i on movemen tandc r o s ss l i f po
d i s l oc a t i on．Duet ot hesho r tt ime,d i s l oc a t i on mo Ｇ t i oni ssupp r e s s eda th i t r a i nr a t e,r e su l t i ngi n ghs t he de c r e a s eo f duc t i l i t nc r e a s eo ff l ow y and i [ ９, １０] ( ) , s t r e s s ．Fr om F i ６ d t het ens i l es t r eng t ho f g TRIP A s t e e lchanged obv i ous l t hi nc r e a s i ng y wi s t r a i nr a t e． I ts e emst ha tt hes t r a i nr a t es ens i t i v i t f yo TRIP A s t e e li st heb i s t．Th i s phenomenoni s gge c aus edbyt hel ow dens i t fd i s l oc a t i ona s we l la s yo t heh i h w o r k h a r d e n i n c a a c i t o ff e r r i t e ． S i n c e g g p y t heh i s tamoun to ff e r r i t eex i s t edi n TRIP A ghe s t e e l,i tco r r e spondst ot heh i s two rkha rden i ng ghe e f f e c t．The r ewa sa l soh i to ff e r r i t ei nDP ghamoun As t e e l．Howeve r,t heha rdpha s ema r t ens i t ed i s s e v Ｇ e r e dt hema t r i x,h i nd e r e dd i s l oc a t i onmov i ngandl owＧ
( a)TRIP As t e e l; ( b)DP As t e e l; ( c)TRIPBs t e e l; ( d)Thr e es t e e l s．
F i ６ Ten s i l es t r eng t ho ft e s t e ds t e e l sa td i f f e r en ts t r a i nr a t e s g
e r edt hewo rkha r den i ngc apa c i t y． F i ７showst her e l a t i onsh i twe enf r a c t ur e g p be e l onga t i onr a t eands t r a i nr a t e．Ast hes t r a i nr a t ei n Ｇ c r e a s ed,t hef r a c t u r ee l onga t i onr a t eo fs t e e l sde Ｇ c r e a s eda tf i r s tandsubs equen t l nc r e a s ed．When yi －１ , t hes t r a i nr a t e wa sabou t６００s t hee l onga t i on r a t eo fa l ls t e e l sr e a cheda mi n imum va l ue．Shae t [ ] a l １０ po i n t ed ou tt ha t de f o rma t i on l o c a l i z a t i on wou l dl e adt ot hede c r e a s eo fe l onga t i onunde rdy Ｇ [ ] nami ct ens i on,wh i l es omer e s e a r che r s１１－１３ c ons i d Ｇ e r edt ha tt head i aba t i ct empe r a t u r er i s e wou l dimＧ r ove ma t e r i a le l onga t i ondu r i ng ma t e r i a lde f o rma Ｇ p
t i on．Wi t ht he s etwooppos i t eme chan i sms,t heun Ｇ de r s t and i ngont hei nve r s echangeo ft hee l onga t i on be c ameve r i f f i cu l tdur i ng dynami cde f o rma t i on． yd Ove r a l l,t hedynami cf r a c t ur ee l onga t i on o f TRIP s t e e lwa sl owe rt hant ha to ft hes t a t i cs t a t e．Th i s [ １４, １５] “ ” mi tbet ha tt he g r adua lt r ans f o rma t i on o f gh r e t a i nedaus t en i t ewa si nh i b i t edi ndynami ct ens i on． TRIPAs t e e lhadt heb i s ts t r a i nr a t es ens i t i v i t gge y be c aus ei t sf r a c t ur ee l onga t i onwa st hemos tf l uc t u Ｇ an t．Compa r edwi t ht hes i t ua t i onunde rs t a t i ct ens i l e l oad,t hef r a c t ur ee l onga t i ono fDP As t e e lbe c ame b i runde rdynami ccond i t i on． gge
５２
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
( a)TRIP As t e e l; ( b)DP As t e e l; ( c)TRIPBs t e e l; ( d)Thr e es t e e l s．
F i ７ Fr a c t u r ee l ong a t i ono ft e s t e ds t e e l sa td i f f e r en ts t r a i nr a t e s g
２ ４ Ad i aba t i ct empe r a t u r er i s e F i ８s h o w st h er e l a t i o n s h i e twe e ns t r a i nr a t e g pb anda d i a b a t i ct emp e r a t u r er i s e． I tc a nb es e e nt h a ta d i a Ｇ b a t i ct emp e r a t u r er i s ei nbo t hDPandTRIPs t e e l sa r e i n f l uenc edbys t r a i nr a t e．Ast hes t r a i nr a t ei nc r e a s e s , dur i ng dynami ct ens i on t head i aba t i ct empe r a t ur e r i s e s． I nF i ８( d),t her ange so fad i aba t i ct empe r a Ｇ g t ur er i s ea r e１００－３００ ℃ f o rTRIPs t e e l sand１００－ ２２０ ℃ f o rDPs t e e l,r e s e c t i v e l et emp e r a t u r eo f p y．Th TRI Ps t e e lr i s e dh i e rt h a nt h a to fDPs t e e l,wh i ch gh mayb ec a u s e dbyt h el a r e rd e f o rma t i ono fTRI Ps t e e l． g ２ ５ Re t a i ne dau s t e n i t et r an s f o rma t i ona td i f f e r en t s t r a i nr a t e s By us i ngan XRD me a su r emen t,t het r ans f o r Ｇ ma t i onamoun to fr e t a i nedaus t en i t ei ndynami c a l l y de f o rmedTRIPs t e e li nt hene ck i ngz onewa sde t e r Ｇ mi ned．Ther e su l t sa r eshowni nF i ９． g I tc anbef oundt ha tt heamoun to fr e t a i nedaus Ｇ t en i t eo fTRIPs t e e li nc r e a s edwi t hi nc r e a s i ngs t r a i n r a t ea f t e rexc l ud i ng t hei nd i v i dua lun r e l i ab l e da t a i n t s．Re t a i nedaus t en i t ei nt hetwos t e e l si nc r e a s ed po [ ] wi t hi nc r e a s i ng s t r a i nr a t e．Somer e s e a r che r s１６－１８ be l i evedt ha tt head i aba t i ct empe r a t u r er i s ewi l li n Ｇ
h i b i to rr e t a rdt heg r owt ho fma r t ens i t eembr Ｇ yodur i ngdynami ct ens i onandl e adt ot hel a r ee l o n a t i o n g g r a t e． Bu tt h i si n t e r r e t a t i oni scon t r a r oHsu ′ st he Ｇ p yt [ １９] o r oundt ha t ma r t ens i t epha s et r ans f o r Ｇ y ,whof ma t i onha sf i n i shedbe f o r ead i aba t i ct empe r a t ur er i s Ｇ i ng,be c aus e ma r t ens i t i ct r ans f o rma t i on wa s ve r y f a s t( １０－７ s)andt he rma lconduc t i on ne edssome t imet ocomp l e t e．Th i sv i ewpo i n twa scon f i rmedex Ｇ r imen t a l l nt h i ss t udy． pe yi
３ Conc l u s i on s
( １)Thet ens i l es t r eng t ho fTRIPs t e e l si nc r e a Ｇ s e swi t hi nc r e a s i ngt hes t r a i nr a t ei nt her angeo f －１ ０ ００１－２０００s ．Thef r a c t ur ee l onga t i ono fTRIP s t e e l sf i r s t l c r e a s e s wi t hi nc r e a s i ng s t r a i nr a t e, y de
t heni nc r e a s e sa st her a t esur s s e s６００s－１ ．TRIPA pa s t e e lha st heb i s ts t r a i nr a t es ens i t i v i t gge y． ( ２)Thead i aba t i ct empe r a t ur er i s eo fTRIP s t e e l si si nt her angeo f１００－３００ ℃ wh i l et ha to f DPs t e e li si nt her angeo f１００－２２０ ℃．Thead i aba t Ｇ i ct empe r a t ur er i s eo fTRIPs t e e land DPs t e e li n Ｇ c r e a s e swi t hi nc r e a s i ngs t r a i nr a t e． ( ３)Thet r ans i t i on o fr e t a i nedaus t en i t ei n Ｇ c r e a s edwi t hi nc r e a s i ngs t r a i nr a t e． I twa scon f i rmed
I s sue１ Re spons eCha r a c t e r i s t i c sandAd i aba t i cHe a t i ngdu r i ng Hi t r a i nRa t ef o rTRIPS t e e landDPS t e e l ５３ ghS
( a)TRIP As t e e l; ( b)DP As t e e l; ( c)TRIPBs t e e l; ( d)Thr e es t e e l s．
F i ８ Temp e r a t u r er i s edu r i ngad i aba t i ch e a t i ngo ft e s t e ds t e e l sa td i f f e r en ts t r a i nr a t e s g
( a)TRIP As t e e l; ( b)TRIPBs t e e l．
F i ９ Re t a i n e dau s t en i t et r an s f o rma t i oni nn e ck i ngz on ea td i f f e r en ts t r a i nr a t e s g
t ha t ma r t ens i t et r ans f o rma t i on wa sno tsupp r e s s ed byad i aba t i che a t i ng． Re f e r enc e s:
[ １] A．Wa s i l kowska,P．Ts i i d i s,E A．We r ne r,A． P i ch l e r,S． pour Tr a i n t,J．Ma t e r．Pr o c e s s．Te chno l． １５７ Ｇ １５８ ( ２００４)６３３ Ｇ ６３６． [ ２] P．Ve r l eys en,J． Pe i r s,J．VanS l Fa e s,L． Duchene,J． yken,K． Ma t e r．Pr o c e s s．Te chno l． ２１１ ( ２０１１)１４５７ Ｇ １４６４． [ ３] L．L i,P．Wo l l an t s,Z Y．Xu,B C．DeCooman,X D． Zhu,J． Ma t e r． Sc i．Te chno l． １９ ( ２００３)２７３ Ｇ ２７７．
[ ４] C．Ga r c i a ＧMa t eo,F G．Caba l l e r o,J．Chao,C．Capdev i l a,C． Ga r c i adeAnd r e s,J．Ma t e r． Sc i． ４４ ( ２００９)４６１７ Ｇ ４６２４．
[ ５] J Y．Sh i,Dynami c Me chan i c a lPr ope r t i e so fS t e e landI t sAp Ｇ l i c a t i on,Me t a l l ur i c a lI ndus t r e s s,Be i i ng,１９９３． p g yPr j [ ６] X C．We i,Q．Xi e,R Y． Fu,L． L i,Ch i ne s eJ our na lo fMa t e r i Ｇ a lRe s e a r ch２０ ( ２００６)５５５ Ｇ ５６０． [ ７] S．We n,S t udyont h eMi c r o s t r u c t u r ea ndPr op e r t i e so fLowCa r bon LowS i l i c on TRIPS t e e lCon t a i n i ng Vanad i um,Shangha iUn i Ｇ ve r s i t i,２００６． y,Shangha [ ８] D K． Sh i,Fundamen t a l so f Ma t e r i a l sSc i enc e,Ch i na Ma ch i ne Pr e s s,Be i i ng,２００３． j [ ９] MT．Ma,Dup l exS t e e l,Me t a l l ur i c a lI ndus t r e s s,Be i i ng, g yPr j ２００９． [ １０] GY．Sha,X G．Sun,T．L i u,Ch i ne s eJ our na lo f Ma t e r i a l s Re s e a r ch２４ ( ２０１０)５６７ Ｇ ５７１．
５４
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
[ １１] GL．Mo s s,R B．Pond,Me t a l l．Tr ans．A ６ ( １９７５)１２２３ Ｇ １２３５． [ １２] KA．Ha r t l ey,J． Du f f H．Hawl ey,J．Me ch． Phys． So l i ds y,R ３５ ( １９８７)２８３ Ｇ ３０１． [ １３] D．Ma c douga l l,Exp．Me ch． ４０ ( ２０００)２９８ Ｇ ３０６． [ １４] S．Ha ami,T． Fu r uk awa, i n:Un i onCa r b i d eCo r r a t i on,Me t a l s y po Di v i s i on ( Eds ),Mi c r oa l l oy i ng７５:Pr o c e ed i ngso fanI n t e r na Ｇ t i ona lSympo s i um on Hi Ｇ s t r eng t h,LowＧ a l l oy S t e e l s, Mi Ｇ gh c r oa l l oy i ng７５,USA,１９７７,pp． ７８ Ｇ ８７． [ １５] J．Wa ng,S．Va nDe rZwa a t a l l．Ma t e r．T r a n s．A３２ ( ２００１) g,Me １５２７ Ｇ １５３９．
[ １６] I Y．Pychmi n t s ev,R A． Sav r a i,B C．DeCooman,O．Mo r i Ｇ au,i n:B C．DeCoom ( Eds ),Pr o c e ed i ngso ft heI n t e r na Ｇ t i ona lCon f e r enc eon TRIP Ｇ a i ded Hi t r eng t h Fe r r ous Al Ｇ ghS l oys,Gr i chen,２００２,pp． ２９９ Ｇ ３０３． ps,Aa [ １７] X C．We i,Th eDyn ami cT e n s i l eCh a r a c t e r i s t i c so fHi t r e ng t h ghS Low Al l oyS i ＧMn TRIPS t e e l s,Shangha iUn i ve r s i t Ｇ y,Shang ha i,２００２． [ １８] X．We i,R．Fu,L．L i,Ma t e r．Sc i．Eng．A４６５ ( ２００７)２６０ Ｇ ２６６． [ １９] T Y．Hs u,Ma r t e n s i t i cT r a n s f o rma t i on a nd Ma r t e n s i t e,S c i e n c e Pr e s s,Be i i ng,１９９９． j
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ５,２ ２( １):４ ８ Ｇ ５ ４
Re s s eCha r a c t e r i s t i c sandAd i aba t i cHe a t i ngdu r i ngHi pon gh S t r a i nRa t ef o rTRIPS t e e landDPS t e e l YiGAO, ChaoXU, Zhong Ｇ i ng HE, Yan Ｇ l i n HE, L i nLI p
( Schoo lo fMa t e r i a l sSc i enc eandEng i ne e r i ng,Shangha iUn i ve r s i t i２０００７２,Ch i na) y,Shangha Ab s t r a c t:Byus i ngas t a t i candh i Ｇ spe edma t e r i a lt e s t i ngma ch i ne,t ens i l ede f o rma t i onbehav i o r so ftwok i ndso fS i Ｇ gh MnTRIP ( t r ans f o rma t i oni nduc edp l a s t i c i t t e e l sandDP ( dua lpha s e)s t e e lwe r es t ud i edi nal a r angeo fs t r a i n y)s ger r a t e s( ０ ００１－２０００s－１ )．Tempe r a t u r eva r i a t i ondu r i ngad i aba t i che a t i ngandt heamoun to fr e t a i nedaus t en i t ea t f r a c t u r ewe r eme a su r edbyani n f r a r edt he rmome t e randanXＧ r ays t r e s sana l s e r,r e spe c t i ve l c r o s t r uc t u r eo f y y．Themi s t e e l swa sobs e r vedbyop t i c a lmi c r o s c opy ( OM)ands c ann i nge l e c t r on mi c r o s c opy ( SEM)be f o r eanda f t e rt ens i l e t e s t． I twa sf oundf r omt heexpe r imen t a lr e s u l t st h a tt h et e n s i l es t r e ng t ho ft h e s es t e e l si n c r e a s e d,a ndt h ef r a c t u r ee l ong a Ｇ t i onf i r s t l c r e a s edandsubs e t l nc r e a s ed,a st hes t r a i nr a t ei nc r e a s edi nt her angeo f０ １－２０００s－１ ．The yde quen yi t empe r a t u r er a i s eddu r i ngad i aba t i che a t i ngo fTRIPs t e e lwa si nt her angeo f１００－３００ ℃ ,wh i l et ha to ft heDPs t e e l wa si nt her angeo f１００－２２０ ℃．Thet empe r a t u r er i s eo ft he s es t e e l si nc r e a s edwi t hi nc r e a s i ngt hes t r a i nr a t e,a s we l la st heamoun to ft het r ans f o rmedr e t a i nedaus t en i t ei nTRIPs t e e l s． I twa sc on f i rmedt ha taus t en i t et oma r t ens i t e t r ans f o rma t i oni sno tsupp r e s s edbyad i aba t i che a t i ng． Ke r d s:s t r a i nr a t e;TRIPs t e e l;ad i aba t i che a t i ng;r e t a i nedaus t en i t e ywo
I no r d e rt oimp r o v ep a s s e ng e rs a f e t e du c ewe i t y,r gh , ( andd e c r e a s ef u e lc on s ump t i on TRI P t r a n s f o rma t i on i nduc edp l a s t i c i t t e e l,wh i chs imu l t aneous l Ｇ y)s ypos s e s s e sh i t r eng t h and duc t i l i t s be en p r o Ｇ gh s y,ha duc edbyt hec oope r a t i ono fs t e e lg r oupsandau t o Ｇ [ １－４] mo t i vei ndus t r ．Howeve r,mo s to fi nve s t i Ｇ y ga t i onsont h i ss t e e la r er e l a t edt ot he me chan i c a lbe Ｇ hav i o randt hes t ab i l i t fr e t a i nedaus t en i t eunde r yo s t a t i co rqua s i Ｇ s t a t i cc ond i t i ons．The r ea r eon l ew yaf r epo r t s de a l i ng wi t ht he me chan i c a l behav i o ro f TRIPs t e e la th i t r a i nr a t e．Thes t r a i nr a t eha sa ghs r e a ti n f l uenc eont he me chan i c a lp r ope r t i e so fma Ｇ g , t e r i a l s．The r e f o r e t her e s e a r cho ft her e l a t i onsh i p be twe ent he me chan i c a lbehav i o rands t r a i nr a t ei s ve r r t an tf o rt hes imu l a t i ono fc a rc r a shand yimpo h i Ｇ spe edmo l d i ng． gh Du r i ngt hef o rmi ngo fs t ruc t u r a lpa r t sandt he c r a sh i ngo ft heau t omob i l ebody,t hes t r a i nr a t e sa r e －１ －１ ２ ３ －１ [ ５, ６] , i nt her angeo f１０ －１０s and１０ －１０ s r e spe c t i ve l I nh i t r a i nr a t ede f o rma t i on,t head Ｇ y． ghs i aba t i cc ond i t i onsc an ber e a ched．The me chan i c a l
behav i o ro fTRIPs t e e l si sdependen tont her e t a i ned , aus t en i t et r ans f o rma t i on wh i chi sve r ens i t i vet o ys t empe r a t ur e．The r e f o r e,i no rde rt os t udyt hedy Ｇ nami cp r ope r t i e so fTRIPs t e e l s,ad i aba t i ct empe r a Ｇ t ur er i s emus tbea c cur a t e l a sur ed． y me The r ea r et hr e eequ i t sf o r me a sur i ngt he pmen i ns t an t aneoust empe r a t ur edur i ngad i aba t i che a t i ng: t he rmocoup l e,l i i dc r t a lf i lm andi n f r a r edt he r Ｇ qu ys
mome t e r．I n f r a r ed t he rmome t e r me a sur emen ti s non Ｇ con t a c t,r e spons e sve r f a s ta n dh a sl a r es i Ｇ y g g na l Ｇno i s er a t i o．Th i sequ i twa sus edi nt hepr e s Ｇ pmen en texpe r imen t． I nt h i s wo rk,６００and９００ MPa g r ade TRIP s t e e l swe r es t ud i ed． I no rde rt oana l z et hef unc t i on y o fr e t a i nedaus t en i t e,DP ( dua lpha s e)s t e e l,wh i ch ha st hes amecompos i t i onwi t h６００ MPag r adeTRIP s t e e lbu tdoe sno texh i b i tpha s et r ans i t i ondur i ngde Ｇ f o rma t i on,wa sa l soi nve s t i t ed．Byus i ngane l e c Ｇ ga t r on i cun i ve r s a lt e s t i ng ma ch i ne MTSandah i Ｇ gh spe edt ens i l et e s t i ng ma ch i neZwi ckHTM５０２０,t he me chan i c a lp r ope r t i e so fs t e e l s we r e de t e rmi ned．
Founda t i onI t em: I t em Spons o r edbyNa t i ona lNa t ur a lSc i enc eFounda t i ono fCh i na ( ５０９３４０１１,５０９７１１３７);Na t i ona lBa s i cRe s e a r chPr og r amo f Ch i na ( ２０１０CB６３０８０２) B i o r aphy: YiGAO,Do c t o rCand i da t e,Sen i o rEng i ne e r; E Ｇma i l: i＠ans t e e l c omcn; Re c e i v e dDa t e:Sep t embe r２９,２０１３ gaoy g
I s sue１ Re spons eCha r a c t e r i s t i c sandAd i aba t i cHe a t i ngdu r i ng Hi t r a i nRa t ef o rTRIPS t e e landDPS t e e l ４９ ghS
Comb i nedt her e su l to fad i aba t i ct empe r a t u r er i s e du r i ngd e f o rma t i on w i t ht h e mi c r o s t r u c t u r eo fs t e e l s, wh i c hwe r eob s e r v e dbyop t i c a lmi c r o s c opy ( OM)and ( ) , s c ann i nge l e c t r onmi c r o s c opy SEM me chan i smo f me chan i c a lpr ope r t i e schange swa sana l z ed． I nadd i Ｇ y t i on,t heamoun to fr e t a i nedaus t en i t ei nTRIPs t e e l wa sme a su r edbyus i nganXＧ r ays t r e s sana l z e r． y
１ Exp e r imen t a l
１ １ Expe r ime n t a lma t e r i a landt e n s i l et e s t Ac omme r c i a l l i l ab l ec o l dr o l l ed TRIP A y ava ( ６００ MPag r ade)she e ts t e e landal abo r a t o r r e Ｇ yp r edTRIPB ( ９００ MPag r ade)she e ts t e e lwe r eex Ｇ pa S t e e l
C
Tab l e１ Ch emi c a lc ompo s i t i on ( ma s s％ )andh e a tt r e a tmen tpa r ame t e r so fs t e e l st e s t e d
S i
Mn
P
S
TRIP A
０ １１ １ ２
１ ５ ０ ０１
０ ００５
TRIPB
０ ２２ ０ ７ １ ６５ ０ ０５
０ ００４
DP A
ami nedi nt h i ss t udy．Thet h i ckne s so fTRIPAshe e t s t e e li sabou t１ ５mm．TheTRIPBs t e e lwa sc a s tby us i nga１１０kg med i umf r equenc nduc t i onf urna c e, yi , f o r n t o２５－３０ mm b l ank andt henhe a t eda t gedi １２００ ℃f o r１h,mu l t i Ｇ s sho tr o l l edi n t o４－６mm pa t h i ckne s s wi t haf i n i sh i ngt empe r a t ur eo f９００ ℃ , , andcoo l edt or oomt empe r a t ur ep i ck l edi n１０％ hy Ｇ d r och l o r i ca c i dso l u t i on,andt hen mu l t i Ｇ s sco l d pa r o l l ed (wi t hi n t e rmed i a t e anne a l i ng)t o１ ２ mm t h i ckne s s．The s es t e e l s we r e he a tt r e a t edi ns a l t ba t h．Thechemi c a lcompos i t i onandhe a tt r e a tmen t r ame t e r so ft he s es t e e lshe e t sa r el i s t edi nTab l e１． pa Thes ke t c ho fZwi c kHTM５０２０i ss howni nF i １． g
０ １１ １ ２
１ ５ ０ ０１
０ ００５
Ni
０ １
Al
N
He a tt r e a tmen tp r o c e s s
≤０ ０３
≤０ ００３５
７８５ ℃×３ mi n＋４２５ ℃×３ mi n＋wa t e rquench i ng[７]
０ ５６
≤０ ００３５
８００ ℃×３ mi n＋４００ ℃×５ mi n＋wa t e rquench i ng
≤０ ０３
≤０ ００３５
７８５ ℃×３ mi n＋wa t e rquench i ng
Tak i ngt hecond i t i ons o ft hecommon au t omo t i ve she e tf o rmi ngp r oc e s sandco l l i s i oni n t oa c coun t,t he dynami cp r ope r t i e si n１２d i f f e r en ts e t so fs t r a i nr a t e s we r es t ud i ed．Thes t r a i nr a t ewa ss e tt obe０ ００００５, ０ ０００５,０ ００５,０ ００１,０ ０５,１００,２００,３００,６００, －１ , １０００ １５００and２０００s i nt h i st e s t．
F i １ Sk e t cho fZwi ckHTM５０２０ ′ sd e v i c e g
Spe c imen wa sf i xedbyg r i adandde f o rmedby p he , a c c e l e r a t edg r i ad wh i chwa sc on t r o l l edbyas e r Ｇ phe vo Ｇhyd r au l i cs t em．The pa r ame t e r so fs t r e s sand ys s t r a i no fspe c imenwe r er e c o r dedbyus i ngal oadc e l l andad i sp l a c emen tt r ansduc e r．I nt h i ss t udy,dy Ｇ nami ct ens i l espe c imenswe r ema ch i neda sshowni n F i ２．Qu a s i Ｇ s t a t i cme c h a n i c a lp r op e r t i e so ft h e s es t e e l s g we r eob t a i nedi nan MTS８０９t ens i l et e s t i ng ma ch i ne．
１ ２ Ad i aba t i che a t i ngt e s te i t qu pmen Tempe r a t ur er i s edur i ngad i aba t i che a t i ng wa s me a sur ed by CTLa s e r ３M i n f r a r ed t he rmome t e r． Theme a sur emen tr angeo ft heequ i ti sf r om５０ pmen , t o４００ ℃ andi tope r a t e swi t h２ ３μmsho r twave Ｇ l eng t hde t e c t o r sandadua ll a s e rt a r t i ngs t em． ge ys Theop t i c a lr e so l u t i oni supt o３００∶１,andr e spons e t imei s１ms．Thes t ema c cur a c ft h i sequ i t ys yo pmen i sabou t±０ ３％ ,andt hemi n imumr ad i uso fme a s Ｇ ur ab l ea r e ai s０ ７ mm． １ ３ Mi c r o s t r u c t u r eob s e r va t i on By op t i c a l mi c r os copy and Hi t a ch i SUＧ １５１０ SEM,t he mi c r os t ruc t ur eo ft he s et hr e es t e e lspe c i Ｇ mensa f t e rhe a tt r e a tmen twa sobs e r ved．Comb i ned wi t ht heana l i so fXＧ r ayd i f f r a c t i on,t heamoun to f ys s e si nt he s es t e e lwa sme a sur ed． pha
２ Re s u l t sandDi s c u s s i on
F i ２ Dimen s i on so fs e c imen swi t hat h i ckn e s so f g p １ ５mmf o rZwi ckHTM５０２０ ( un i t:mm)
２ １ Mi c r o s t r u c t u r e The mi c r os t ruc t ur e mo r l og i e so fTRIP A, pho TRI PBandDPAs t e e l sa r es howni nF i s ３( a)－３( c), g whe r e,t hewh i t ep a r ti sf e r r i t eandd a r kandg r eypa r t s
５０
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
( a),( d)TRIP As t e e l; ( b),( e)DP As t e e l; ( c),( f)TRIPBs t e e l．
F i ３ Op t i c a lmi c r o r aph sandSEM mi c r o r aph so ft e s t e ds t e e l s g g g
a r e ba i n i t e and r e t a i ned aus t en i t er e spe c t i ve l n yi TRIPs t e e l． I nDPAs t e e l,t hef e r r i t epha s eappe a r s i nwh i t ec o l o randt hema r t ens i t ei sda rk． F i ３( d)－３( f)we r ea c i r edbyus i ngSEM gs qu i ns t rumen t,f r om wh i chi tc anbes e ent ha tba i n i t e andr e t a i nedaus t en i t ea r e ma i n l i s t r i bu t eda tt he yd f e r r i t eg r a i nbounda r i e si nTRIPs t e e landma r t ens i t e i sembeddedi nf e r r i t ema t r i xi nDPs t e e l． Byu s i ngqu a n t i t a t i v e me t a l l o r a ndX Ｇ r a i f Ｇ g phya yd f r a c t i o na n a l s i s( Th es s t ema c c u r a c sa b o u t ±３％), y y yi t heamoun to fe a chpha s e wa sde t e rmi ned．TRI PA , s t e e lwa sc ompo s e do f６０ ４v o l ％ f e r r i t e １０ １v o l ％ r e t a i ned aus t en i t e and ２９ ５vo l ％ ba i n i t e; DP A s t e e lc ons i s t edo f６０ ８vo l ％ f e r r i t eand３９ ２v o l ％ ma r t e n s i t ea ndTRI PBs t e e lc on t a i n e d３６ ４v o l ％ f e r Ｇ r i t e,１７ １v o l ％ r e t a i n e da u s t e n i t ea nd４６ ５％ b a i n i t e． ２ ２ Te n s i l epr ope r t i e sund e rqua s i Ｇ s t a t i cc ond i t i on Thequa s i Ｇ s t a t i cs t r e s s Ｇ s t a i ncu r ve so ft hes t e e l s a r epr e s en t edi nF i ４．Ay i e l dp l a t e auwa sobs e r ved g ont hecu r veon l o rTRIP As t e e l,wh i l eTRIPB yf [] s t e e lshowedac on t i nuousy i e l dch a r a c t e r i s t i c s． Sh i８
F i ４ Qua s i Ｇ s t a t i ct en s i l es t r e s s Ｇ s t r a i nc u r v eo f g TRIPAs t e e l,TRIPBs t e e landDPAs t e e l
i n t edou tt ha t,a sc a rboncon t en ti nc r e a s e s,t he po i e l dp l a t e au g r adua l l come ssho r t e rand even y y be d i s appe a r si nt hes amet fs t e e l s． ypeo I tc ana l sobes e enf r om F i ４t ha tt hee l onga Ｇ g t i ono fTRIPAs t e e li sa lmos tt hr e et ime st hant ha t o fDPAs t e e l,wh i chi sc aus edbyt hes t r a i ni nduc ed ma r t ens i t et r ans f o rma t i on and s imu l t aneous l he yt i nduc edp l a s t i c i t y． F i ５s howst hef r a c t u r emo r l ogyo ft h r e es t e e l s g pho
( a)TRIP As t e e l; ( b)DP As t e e l; ( c)TRIPBs t e e l．
F i ５ Fe a t u r e so ff r a c t u r es u r f a c eo ft e s t e ds t e e l s g
I s sue１ Re spons eCha r a c t e r i s t i c sandAd i aba t i cHe a t i ngdu r i ng Hi t r a i nRa t ef o rTRIPS t e e landDPS t e e l ５１ ghS
a f t e rs t r e t ch i ng．Thetwo TRIPs t e e l shaveduc t i l e f r a c t u r echa r a c t e r i s t i c s．Thesma l l e randde epe rd imＧ l e sf r a c t u r e so fTRIPs t e e l sexh i b i t edgoodp l a s t i c p de f o rma t i on c apa c i t r ed wi t ht he TRIP y．Compa s t e e l,DP A s t e e lhad poo rduc t i l i t c aus eo fi t s y be b i e ra n ds h a l l o w e rd i m l e s ． gg p ２ ３ Te n s i l epr ope r t i e sund e rdynami cc ond i t i on F i ６s h o w st h er e l a t i o n s h i b e t w e e nt ens i l e g p s t r eng t hands t r a i nr a t eo ft he s es t e e l s．I tc an be s e ent ha t wi t hi nc r e a s i ng s t r a i nr a t e,t he s es t e e l s , showah i rt ens i l es t r eng t h．Gene r a l l hep l a s Ｇ ghe y t t i cde f o rma t i onr e l i s l o c a t i on mo t i on,i nc l u Ｇ ysond d i ngt he rma la c t i va t i on movemen tandc r o s ss l i f po
d i s l oc a t i on．Duet ot hesho r tt ime,d i s l oc a t i on mo Ｇ t i oni ssupp r e s s eda th i t r a i nr a t e,r e su l t i ngi n ghs t he de c r e a s eo f duc t i l i t nc r e a s eo ff l ow y and i [ ９, １０] ( ) , s t r e s s ．Fr om F i ６ d t het ens i l es t r eng t ho f g TRIP A s t e e lchanged obv i ous l t hi nc r e a s i ng y wi s t r a i nr a t e． I ts e emst ha tt hes t r a i nr a t es ens i t i v i t f yo TRIP A s t e e li st heb i s t．Th i s phenomenoni s gge c aus edbyt hel ow dens i t fd i s l oc a t i ona s we l la s yo t heh i h w o r k h a r d e n i n c a a c i t o ff e r r i t e ． S i n c e g g p y t heh i s tamoun to ff e r r i t eex i s t edi n TRIP A ghe s t e e l,i tco r r e spondst ot heh i s two rkha rden i ng ghe e f f e c t．The r ewa sa l soh i to ff e r r i t ei nDP ghamoun As t e e l．Howeve r,t heha rdpha s ema r t ens i t ed i s s e v Ｇ e r e dt hema t r i x,h i nd e r e dd i s l oc a t i onmov i ngandl owＧ
( a)TRIP As t e e l; ( b)DP As t e e l; ( c)TRIPBs t e e l; ( d)Thr e es t e e l s．
F i ６ Ten s i l es t r eng t ho ft e s t e ds t e e l sa td i f f e r en ts t r a i nr a t e s g
e r edt hewo rkha r den i ngc apa c i t y． F i ７showst her e l a t i onsh i twe enf r a c t ur e g p be e l onga t i onr a t eands t r a i nr a t e．Ast hes t r a i nr a t ei n Ｇ c r e a s ed,t hef r a c t u r ee l onga t i onr a t eo fs t e e l sde Ｇ c r e a s eda tf i r s tandsubs equen t l nc r e a s ed．When yi －１ , t hes t r a i nr a t e wa sabou t６００s t hee l onga t i on r a t eo fa l ls t e e l sr e a cheda mi n imum va l ue．Shae t [ ] a l １０ po i n t ed ou tt ha t de f o rma t i on l o c a l i z a t i on wou l dl e adt ot hede c r e a s eo fe l onga t i onunde rdy Ｇ [ ] nami ct ens i on,wh i l es omer e s e a r che r s１１－１３ c ons i d Ｇ e r edt ha tt head i aba t i ct empe r a t u r er i s e wou l dimＧ r ove ma t e r i a le l onga t i ondu r i ng ma t e r i a lde f o rma Ｇ p
t i on．Wi t ht he s etwooppos i t eme chan i sms,t heun Ｇ de r s t and i ngont hei nve r s echangeo ft hee l onga t i on be c ameve r i f f i cu l tdur i ng dynami cde f o rma t i on． yd Ove r a l l,t hedynami cf r a c t ur ee l onga t i on o f TRIP s t e e lwa sl owe rt hant ha to ft hes t a t i cs t a t e．Th i s [ １４, １５] “ ” mi tbet ha tt he g r adua lt r ans f o rma t i on o f gh r e t a i nedaus t en i t ewa si nh i b i t edi ndynami ct ens i on． TRIPAs t e e lhadt heb i s ts t r a i nr a t es ens i t i v i t gge y be c aus ei t sf r a c t ur ee l onga t i onwa st hemos tf l uc t u Ｇ an t．Compa r edwi t ht hes i t ua t i onunde rs t a t i ct ens i l e l oad,t hef r a c t ur ee l onga t i ono fDP As t e e lbe c ame b i runde rdynami ccond i t i on． gge
５２
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
( a)TRIP As t e e l; ( b)DP As t e e l; ( c)TRIPBs t e e l; ( d)Thr e es t e e l s．
F i ７ Fr a c t u r ee l ong a t i ono ft e s t e ds t e e l sa td i f f e r en ts t r a i nr a t e s g
２ ４ Ad i aba t i ct empe r a t u r er i s e F i ８s h o w st h er e l a t i o n s h i e twe e ns t r a i nr a t e g pb anda d i a b a t i ct emp e r a t u r er i s e． I tc a nb es e e nt h a ta d i a Ｇ b a t i ct emp e r a t u r er i s ei nbo t hDPandTRIPs t e e l sa r e i n f l uenc edbys t r a i nr a t e．Ast hes t r a i nr a t ei nc r e a s e s , dur i ng dynami ct ens i on t head i aba t i ct empe r a t ur e r i s e s． I nF i ８( d),t her ange so fad i aba t i ct empe r a Ｇ g t ur er i s ea r e１００－３００ ℃ f o rTRIPs t e e l sand１００－ ２２０ ℃ f o rDPs t e e l,r e s e c t i v e l et emp e r a t u r eo f p y．Th TRI Ps t e e lr i s e dh i e rt h a nt h a to fDPs t e e l,wh i ch gh mayb ec a u s e dbyt h el a r e rd e f o rma t i ono fTRI Ps t e e l． g ２ ５ Re t a i ne dau s t e n i t et r an s f o rma t i ona td i f f e r en t s t r a i nr a t e s By us i ngan XRD me a su r emen t,t het r ans f o r Ｇ ma t i onamoun to fr e t a i nedaus t en i t ei ndynami c a l l y de f o rmedTRIPs t e e li nt hene ck i ngz onewa sde t e r Ｇ mi ned．Ther e su l t sa r eshowni nF i ９． g I tc anbef oundt ha tt heamoun to fr e t a i nedaus Ｇ t en i t eo fTRIPs t e e li nc r e a s edwi t hi nc r e a s i ngs t r a i n r a t ea f t e rexc l ud i ng t hei nd i v i dua lun r e l i ab l e da t a i n t s．Re t a i nedaus t en i t ei nt hetwos t e e l si nc r e a s ed po [ ] wi t hi nc r e a s i ng s t r a i nr a t e．Somer e s e a r che r s１６－１８ be l i evedt ha tt head i aba t i ct empe r a t u r er i s ewi l li n Ｇ
h i b i to rr e t a rdt heg r owt ho fma r t ens i t eembr Ｇ yodur i ngdynami ct ens i onandl e adt ot hel a r ee l o n a t i o n g g r a t e． Bu tt h i si n t e r r e t a t i oni scon t r a r oHsu ′ st he Ｇ p yt [ １９] o r oundt ha t ma r t ens i t epha s et r ans f o r Ｇ y ,whof ma t i onha sf i n i shedbe f o r ead i aba t i ct empe r a t ur er i s Ｇ i ng,be c aus e ma r t ens i t i ct r ans f o rma t i on wa s ve r y f a s t( １０－７ s)andt he rma lconduc t i on ne edssome t imet ocomp l e t e．Th i sv i ewpo i n twa scon f i rmedex Ｇ r imen t a l l nt h i ss t udy． pe yi
３ Conc l u s i on s
( １)Thet ens i l es t r eng t ho fTRIPs t e e l si nc r e a Ｇ s e swi t hi nc r e a s i ngt hes t r a i nr a t ei nt her angeo f －１ ０ ００１－２０００s ．Thef r a c t ur ee l onga t i ono fTRIP s t e e l sf i r s t l c r e a s e s wi t hi nc r e a s i ng s t r a i nr a t e, y de
t heni nc r e a s e sa st her a t esur s s e s６００s－１ ．TRIPA pa s t e e lha st heb i s ts t r a i nr a t es ens i t i v i t gge y． ( ２)Thead i aba t i ct empe r a t ur er i s eo fTRIP s t e e l si si nt her angeo f１００－３００ ℃ wh i l et ha to f DPs t e e li si nt her angeo f１００－２２０ ℃．Thead i aba t Ｇ i ct empe r a t ur er i s eo fTRIPs t e e land DPs t e e li n Ｇ c r e a s e swi t hi nc r e a s i ngs t r a i nr a t e． ( ３)Thet r ans i t i on o fr e t a i nedaus t en i t ei n Ｇ c r e a s edwi t hi nc r e a s i ngs t r a i nr a t e． I twa scon f i rmed
I s sue１ Re spons eCha r a c t e r i s t i c sandAd i aba t i cHe a t i ngdu r i ng Hi t r a i nRa t ef o rTRIPS t e e landDPS t e e l ５３ ghS
( a)TRIP As t e e l; ( b)DP As t e e l; ( c)TRIPBs t e e l; ( d)Thr e es t e e l s．
F i ８ Temp e r a t u r er i s edu r i ngad i aba t i ch e a t i ngo ft e s t e ds t e e l sa td i f f e r en ts t r a i nr a t e s g
( a)TRIP As t e e l; ( b)TRIPBs t e e l．
F i ９ Re t a i n e dau s t en i t et r an s f o rma t i oni nn e ck i ngz on ea td i f f e r en ts t r a i nr a t e s g
t ha t ma r t ens i t et r ans f o rma t i on wa sno tsupp r e s s ed byad i aba t i che a t i ng． Re f e r enc e s:
[ １] A．Wa s i l kowska,P．Ts i i d i s,E A．We r ne r,A． P i ch l e r,S． pour Tr a i n t,J．Ma t e r．Pr o c e s s．Te chno l． １５７ Ｇ １５８ ( ２００４)６３３ Ｇ ６３６． [ ２] P．Ve r l eys en,J． Pe i r s,J．VanS l Fa e s,L． Duchene,J． yken,K． Ma t e r．Pr o c e s s．Te chno l． ２１１ ( ２０１１)１４５７ Ｇ １４６４． [ ３] L．L i,P．Wo l l an t s,Z Y．Xu,B C．DeCooman,X D． Zhu,J． Ma t e r． Sc i．Te chno l． １９ ( ２００３)２７３ Ｇ ２７７．
[ ４] C．Ga r c i a ＧMa t eo,F G．Caba l l e r o,J．Chao,C．Capdev i l a,C． Ga r c i adeAnd r e s,J．Ma t e r． Sc i． ４４ ( ２００９)４６１７ Ｇ ４６２４．
[ ５] J Y．Sh i,Dynami c Me chan i c a lPr ope r t i e so fS t e e landI t sAp Ｇ l i c a t i on,Me t a l l ur i c a lI ndus t r e s s,Be i i ng,１９９３． p g yPr j [ ６] X C．We i,Q．Xi e,R Y． Fu,L． L i,Ch i ne s eJ our na lo fMa t e r i Ｇ a lRe s e a r ch２０ ( ２００６)５５５ Ｇ ５６０． [ ７] S．We n,S t udyont h eMi c r o s t r u c t u r ea ndPr op e r t i e so fLowCa r bon LowS i l i c on TRIPS t e e lCon t a i n i ng Vanad i um,Shangha iUn i Ｇ ve r s i t i,２００６． y,Shangha [ ８] D K． Sh i,Fundamen t a l so f Ma t e r i a l sSc i enc e,Ch i na Ma ch i ne Pr e s s,Be i i ng,２００３． j [ ９] MT．Ma,Dup l exS t e e l,Me t a l l ur i c a lI ndus t r e s s,Be i i ng, g yPr j ２００９． [ １０] GY．Sha,X G．Sun,T．L i u,Ch i ne s eJ our na lo f Ma t e r i a l s Re s e a r ch２４ ( ２０１０)５６７ Ｇ ５７１．
５４
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
[ １１] GL．Mo s s,R B．Pond,Me t a l l．Tr ans．A ６ ( １９７５)１２２３ Ｇ １２３５． [ １２] KA．Ha r t l ey,J． Du f f H．Hawl ey,J．Me ch． Phys． So l i ds y,R ３５ ( １９８７)２８３ Ｇ ３０１． [ １３] D．Ma c douga l l,Exp．Me ch． ４０ ( ２０００)２９８ Ｇ ３０６． [ １４] S．Ha ami,T． Fu r uk awa, i n:Un i onCa r b i d eCo r r a t i on,Me t a l s y po Di v i s i on ( Eds ),Mi c r oa l l oy i ng７５:Pr o c e ed i ngso fanI n t e r na Ｇ t i ona lSympo s i um on Hi Ｇ s t r eng t h,LowＧ a l l oy S t e e l s, Mi Ｇ gh c r oa l l oy i ng７５,USA,１９７７,pp． ７８ Ｇ ８７． [ １５] J．Wa ng,S．Va nDe rZwa a t a l l．Ma t e r．T r a n s．A３２ ( ２００１) g,Me １５２７ Ｇ １５３９．
[ １６] I Y．Pychmi n t s ev,R A． Sav r a i,B C．DeCooman,O．Mo r i Ｇ au,i n:B C．DeCoom ( Eds ),Pr o c e ed i ngso ft heI n t e r na Ｇ t i ona lCon f e r enc eon TRIP Ｇ a i ded Hi t r eng t h Fe r r ous Al Ｇ ghS l oys,Gr i chen,２００２,pp． ２９９ Ｇ ３０３． ps,Aa [ １７] X C．We i,Th eDyn ami cT e n s i l eCh a r a c t e r i s t i c so fHi t r e ng t h ghS Low Al l oyS i ＧMn TRIPS t e e l s,Shangha iUn i ve r s i t Ｇ y,Shang ha i,２００２． [ １８] X．We i,R．Fu,L．L i,Ma t e r．Sc i．Eng．A４６５ ( ２００７)２６０ Ｇ ２６６． [ １９] T Y．Hs u,Ma r t e n s i t i cT r a n s f o rma t i on a nd Ma r t e n s i t e,S c i e n c e Pr e s s,Be i i ng,１９９９． j