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Microstructures and Mechanical Properties of X100 Pipeline Steel Strip
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ４,２ １( ２):２ ２ ７ Ｇ ２ ３ ２
Mi c r o s t r u c t u r e sand Me chan i c a lPr ope r t i e so fX１００P i l i neS t e e lS t r i pe p ２ L i n Ｇ naDUAN１ ２ , YuCHEN３ , Qi ng Ｇ Ｇ unJ IA２ , Cheng Ｇ changJ IA１ youLIU , Shu j ,
( i i ng１０００８３, i ve r s i t fSc i enc eandTe chno l ogyBe i i ng,Be １． Schoo lo fMa t e r i a lSc i enc eandEng i ne e r i ng,Un j yo j Ch i na; ２． I ns t i t u t ef o rEng i ne e r i ngS t e e l,Cen t r a lI r onandS t e e lRe s e a r chI ns t i t u t e,Be i i ng１０００８１,Ch i na; j ３．Ch i naPe t r o l eum Eng i ne e r i ngandCons t r uc t i onCo r r a t i on,Be i i ng１００１２０,Ch i na) po j
Ab s t r a c t:Dyn ami cCCT ( c on t i nuou sc o o l i ngt r a n s f o rma t i on)c u r v e sa nde f f e c t so f mi c r o s t r u c t u r e sa nd M/Ai s l a nd so f X１００ho tr o l l eds t r i chan i c a lp r ope r t i e swe r es t ud i edbyme anso fat he rma ls imu l a t o r,as c ann i nge l e c t r onmi Ｇ ponme c r o s c ope ( SEM),at r a n smi s s i one l e c t r onmi c r o s c op e( TEM),ad i i t a lmi c r o Ｇh a r dn e s st e s t e ra ndIma e ＧPr oP l usana l s i s g g y s o f twa r e．Ther e su l t sshowt ha th i on t en t so fCandMoc anmaket r ans f o rma t i onl i ne so fa c i cu l a rf e r r i t eandba i n Ｇ ghc i t esh i f tr i twa r d．Hi e s t eds t r i sh i rs t r eng t handmi c r o Ｇha r dne s sandl owe rt oughne s st hant heo t he r gh gh Mot pha ghe onebe c aus el a t hba i n i t eappe a r si ns t e ado fqua s i Ｇpo l lf e r r i t e．T e s t e ds t r i i t hg r a nu l a rb a i n i t e,l a t hb a i n i t ea nd ygona pw M/Ai s l andsha sbe t t e rme chan i c a lp r ope r t i e sandi nt he mi c r o s t r uc t u r e sl a t hba i n i t ec on t en ti sa r ound３６ ５％ and M/Ai s l andsa r ef i neandd i spe r s ei nt hema t r i x． Ke r d s:X１００ho tr o l l eds t r i r ve;g r anu l a rba i n i t e;l a t hba i n i t e;M/Ai s l and p;CCTcu ywo
Al ong wi t ht head us tmen to fene r t ruc t ur e j gys , andt hei nc r e a s eo fene r d e m a n d X １ ０ ０ i e l i n e gy pp s t e e l sf o rh i e s su r e, l a r i ame t e randl ongd i s Ｇ ghpr ged t anc eo i landga sp i l i ne shavebe endeve l opedr ap Ｇ pe [ １] i d l r ed wi t ht he X８０ a c i cu l a rp i l i ne y ．Compa pe s t e e l,X１００s t e e lc anr educ et hec o s tf r om s av i ng ma t e r i a l s,impr ov i ng t r ans f e rp r e s su r e,r educ i ng , cons t ruc t i on quan t i t owe r i ng ma i n t enanc ec os t, y l [ ２] op t imi z i ngp r o e c ts t r a t egyands oon ．The r e f o r e, j mo r eandmo r ee f f o r t shavebe enpu tont her e s e a r ch onX１００p i l i nes t e e l． pe Fr omt hepr ev i ousexpe r i enc e,mi c r o s t ruc t ur e s o fX１００ p i l i nes t e e la r eba i n i t e wh i chc ons i s t so f pe r anu l a rba i n i t e andl a t h ba i n i t e．Con t en t so f C, g Mn,Nband Moo fX１００s t e e la r eh i rt hant hos e ghe o fX８０ s t e e li no r de rt o ob t a i n ba i n i t e wi t hh i gh [] s t r e ng t h３ ．Howe v e r,t h ec on f l i c t sb e twe e ns t r e ng t h andt oughne s swou l dbemo r eou t s t and i ng,e spe c i a l Ｇ l f o rX １ ０ ０h o t r o l l e ds t r i w i t h l a r e t h i c k n e s s ． M i Ｇ y p g c r os t ruc t u r e so ftwos t e e l s wi t hd i f f e r en tchemi c a l
compos i t i onsa r eana l z edandt her e l a t i onso f mi Ｇ y c r os t ruc t ur e swi t hs t r eng t handt oughn e s sa r es t ud i e d i nt h i sp a e r．Thes t udyi s me an i ng f u lf o rr e s e a r c hon p mi c r o s t r u c t u r e sand me chan i c a lp r ope r t i e so f X１００ i l i nes t e e landl owc a rbonba i n i t i cs t e e l s． p pe
１ Exp e r imen t a lMa t e r i a l sandPr o c e du r e s
Compos i t i onde s i ftwot e s t eds t e e l si sl ow gno CＧMn ＧNb ＧMoandt hede t a i l edchemi c a lcompos i t i on i sg i veni nTab l e１．Thet e s t eds t e e l swe r econ t i nu Ｇ ous l a s ta f t e rconve r t e rsme l t i ngandLFr e f i n i ng yc l usRHva cuumdega s s i ngandt h i ckne s so fcon t i nu Ｇ p ousc a s t i ngs l absi s２３０mm．Dynami cCCT ( con t i n Ｇ uouscoo l i ngt r ans f o rma t i on)cur ve swe r eme a sur ed onaGl e e b l e Ｇ １５００Dt he rma ls imu l a t o r． ϕ８mm×１２mm s imu l a t i onspe c imens we r ecu tf r om t he mi dd l eo f t hec a s ts l abs．Asshowni ns chema t i ci l l us t r a t i ono f t he rmo Ｇme chan i c a ls imu l a t i on (F i １), d i f f e r en t g coo l i ngr a t e s we r eadop t edi nt het e s t．D i l a t ome t r i c , c u r v e swe r er e c o r d e d pha s et r ans f o rma t i ont empe r a Ｇ
Tab l e１ Ch emi c a lc ompo s i t i ono ft h et e s t e ds t e e l s (ma s spe r c en t,％ )
S t e e l No １ No ２
C
０ ０５ ０ ０６
S i
０ ２１ ０ ２１
Mn
１ ９６ ２ ０５
P
０ ００９ ０ ０１３
S
０ ００２０ ０ ００２５
Mo
０ ２５ ０ ２９
Cr
０ ３０ ０ ３１
Ni
０ ３９ ０ ２６
Cu
Nb＋V＋Ti
０ ２３
≤０ １５
０ ２１
≤０ １５
Als
０ ０２０ ０ ０２３
Founda t i onI t em: I t emSpon s o r e dbyNa t i on a lKe e c hno l o s e a r c ha ndDe v e l opme n tPr o r ami n１２ t hF i v e Ｇ e a rP l a no fCh i n a( ２０１１BAE３５B０１) yT gy Re g y B i o r aphy: L i n Ｇ naDUAN,Do c t o rCand i da t e; E Ｇma i l: duan l i nna ８３＠s i na c omcn; Re c e i v e dDa t e:Ap r i l１１,２０１３ g
２２８
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 ２１
F i １ S ch ema t i ci l l u s t r a t i ono ft h e rmo Ｇme chan i c a ls imu l a t i on g
t ur e s we r eob t a i ned byt angen t i a l me t hodanddy Ｇ nami cCCTcu r ve swe r ebu i l ta tl a s t． Con t i nuousc a s t i ngs l abswe r ec on t r o l l edr o l l ed i nr e c r s t a l l i z a t i o na n dn o n Ｇ r e c r s t a l l i z a t i o nz o n e st o y y １５ ３mmt h i c ka nd１５５０ mm w i d ea ndt h e nwe r ec on Ｇ t r o l l e dc o o l e da ndc o i l e d．Ac c o r d i ngt o AP Is t a nd a r d,
t he me chan i c a lpr ope r t i e so ft e s t eds t r i r eex Ｇ ps we ( ) ami nedbyt ens i l et e s t sa l ongr o l l i ngd i r e c t i on RD , t r ansve r s ed i r e c t i on ( TD)and３０ °wi t hr o l l i ngd i r e c Ｇ t i ona tr oom t empe r a t u r eand Cha r no t chimＧ py VＧ c tt e s t si nt h et emp e r a t u r er a ng ef r om２０t o－６０ ℃． pa WEＧ ３００hyd r au l i ct ens i l et e s t i ng ma ch i neandJBNＧ ３００Bimpa c tt e s t i ng ma ch i newe r eus edr e spe c t i ve l y． Spe c imenst akenf r om twot e s t eds t r i l ong psa r o l l i ngd i r e c t i onwe r ee t chedi n３％ n i t a ls o l u t i ona f Ｇ t e rg r i nd i nga ndpo l i s h i ngi nt h i c kn e s sd i r e c t i on．Mi c r o Ｇ
ha rdne s swa st e s t eda t２１spo t sun i f o rml i s t r i bu Ｇ yd t edi nt h i ckne s sd i r e c t i onus i ngFMＧ ３００d i i t a lmi c r o Ｇ g ha r dn e s st e s t e r．Mi c r o s t r u c t u r e s we r e ob s e r v e da t９ z on e sbya HITACHI S Ｇ ４３００c o l d Ｇ f i e l demi s s i onSEM ( s c ann i ng e l e c t r on mi c r o s c op e)．Vo l umef r a c t i on o f /aus ma r t ens i t e t en i t e (M/A)i s l andswa ss t a t i s t i c a l l y e s t ima t edbyImage ＧPr oP l usso f twa r e．Mi c r os t ruc Ｇ t ur e mo r l ogy wa sobs e r ved by an HＧ ８００ TEM pho ( t r ansmi s s i one l e c t r onmi c r os cope)．
２ Exp e r imen t a lRe s u l t s
２ １ Dynami cCCTcu r v e Dynami cCCT cur ve so ftwot e s t eds t e e l sa r e showni nF i ２．Be c aus eo fs imi l a rchemi c a lcompo Ｇ g , s i t i on t r endso fCCT cur ve so ftwos t e e l sa r et he s ame．Wi t ht hei nc r e a s eo fcoo l i ngr a t e,po l l ygona f e r r i t e( PF),pe a r l i t e( P),a c i cu l a rf e r r i t e (AF), r anu l a rba i n i t e( GB)andl a t hba i n i t e( LB)appe a r g
i no rde randt he r ea r e no obv i ousc r i t i c a l po i n t s． S t a r t i ng t empe r a t ur eo ft r ans f o rma t i on o ft e s t ed s t e e lNo ２i sl owe rt hant ha to ft e s t eds t e e lNo １ owi ngt oh i rc a rboncon t en ti nt e s t eds t e e lNo ２． ghe Hi i anexpandAFandba i n i t e( B) gh Moandh ghNic t r ans f o rma t i onz oneandt hee f f e c to fMoi smo r ee f Ｇ f e c t i vet hanNi,soc r i t i c a lcoo l i ngr a t eo ft e s t eds t e e l No ２i sl owe r．Duet ot hed i f f e r enc eo fmi c r os t ruc Ｇ t ur e s,mi c r o Ｇha rdne s so ft e s t eds t e e lNo ２i sh i r ghe
( a)Te s t eds t e e lNo １; ( b)Te s t eds t e e lNo ２．
F i ２ CCTc u r v e so ftwot e s t e ds t e e l s g
t hant ha to ft e s t eds t e e lNo １． ２ ２ Me chan i c a lpr ope r t i e s T a b l e２l i s t sy i e l ds t r e ng t h,t e n s i l es t r e ng t h,e l on Ｇ a t i ona ndy i e l dr a t i oo ftwot e s t e ds t r i s． I ti sobv i ous g p t ha tt ens i l es t r eng t h and y i e l ds t r eng t ho ft e s t ed s t r i ２a r eh i rt hant ha to fNo １,bu te l onga Ｇ p No ghe t i ona f t e rf r a c t u r eo ft e s t eds t r i ２i sl e s s．The p No
s t anda rd APISPEC５Lr e i r e st e n s i l es t r e ng t hand qu i e l ds t r e ng t ho fX１００p i e l i n es t e e la r e７６０－９９０ MPa y p and６９０－８４０MPar e spe c t i ve l i e l dr a t i oi sl e s s yandy t han０ ９７．The r e f o r e,on l e s t eds t r i ２ me e t s yt p No t he s er equ i r emen t s． Mi c r o Ｇha rdne s s cur ve sa td i f f e r en t pos i t i ons a c r os st het h i ckne s sd i r e c t i ono ftwot e s t eds t r i r e psa showni nF i ３． I ti sf oundt ha tave r agemi c r o Ｇha rd Ｇ g
I s sue２ Mi c r o s t r uc t u r e sand Me chan i c a lPr ope r t i e so fX１００P i l i neS t e e lS t r i pe p
２２９
Tab l e２ Ro omt emp e r a t u r et en s i l et e s tr e s u l t so ft e s t e ds t r i s p S t r i p
No １
No ２
Ro l l i ngd i r e c t i on
Tens i l es t r eng t h/MPa
Yi e l ds t r eng t h/MPa
/％ El onga t i ona f t e rf r a c t ur e
Yi e l dr a t i o
RD
７３４
５９６
３２ ５
０ ８１
TD
８７５
TD
３０ ° RD
３０ °
７５６ ７１４
８８０
８６０
６５７ ５７３
７１５
７３０ ７００
３１ ０ ３５ ０
２４ ０
２８ ０ ２７ ０
０ ８７ ０ ８０
０ ８２
０ ８３ ０ ８１
２ ３ Mi c r o s t r u c t u r e s F i s ５a n d６s how t heSEM mo r l og i e so f g pho mi c r os t ruc t ur e si nt het h i ckne s sd i r e c t i onf r om t op t obo t t om o ftwot e s t eds t r i e spe c t i ve l c r o Ｇ psr y．Mi s t ruc t ur e so ft e s t eds t r i N o １c o n s i s t i n o ft i c a p g yp l ( ) GBandl i t t l equa s i Ｇ l lf e r r i t e QF i n who l e po ygona c r os s Ｇ s e c t i ona r ehomogeneousande l onga t edduet o r o l l i ng．M/Ai s l andsun i f o rml i spe r s ei nt heg r a i ns yd o ront heg r a i nbounda r i e swi t ht heshapeo fsphe r i c Ｇ i t rsphe r o i d i c i t hes i z ei sa r ound１μm．Mi Ｇ yo yandt c r os t ruc t ur e so ft e s t eds t r i ２cons i s to fGBand p No F i ３ Mi c r o Ｇha r dn e s sc u r v e si nt h et h i ckn e s sd i r e c t i on g LBanda r ee l onga t edt oo．La t hba i n i t i cpa cke t sa r e f r omt opt obo t t omo ftwot e s t e ds t r i s p r a l l e land g r anu l a ro ra c i cu l a r M/Ai s l andsex i s t pa be twe enba i n i t i cpa cke t so rba i n i t i cl a t hs． I nt e s t ed ne s so ft e s t eds t r i ２i s７０ HV h i rt hant ha t p No ghe s t r i ２,GBi smo r et hanLBandvo l umef r a c t i on p No o fs t r i １． p No o fLBi nbo t t om sur f a c ei sl owe rt hant ha to ft op Cha r no t chimpa c tt e s t( CVN)r e su l t so f py VＧ sur f a c ebu th i rt hant ha to fs t r i en t e r．Di f f e r Ｇ ghe pc t e s t eds t r i r eshowni nF i ４． CVNene r ftwo psa g gyo enc eo fmi c r os t ruc t ur et so ftwos t r i sc aus ed ype psi t e s t eds t r i e tt her equ i r emen to fAPISPEC５L psme byd i f f e r en tcon t en t so fCand Mo．Ha rdenab i l i t n Ｇ yi (Whent het e s tt empe r a t u r ei s－２０ ℃ ,CVNene r gy c r e a s e swi t ht hei nc r e a s eo fCcon t en tandMoi sab l e i sh i rt han２８０J)．CVN ene r ft e s t eds t r i ghe gy o p t op i nγ/αi n t e r f a c e movemen t,pos t Ｇ αt r ans Ｇ poneγ No １i sa lmo s ts t ab l ea tt he s et e s tt empe r a t u r e sand [] f o rma t i on４ ,i nh i b i tma s s i vef e r r i t ef o rma t i on,and h i rt hant ha to fNo ２． CVNene r ft e s t eds t r i ghe gyo p r omo t eAFandBt r ans f o rma t i on．Chang i ngt r ends p No ２de c r e a s e sa l ong wi t ht hede c r e a s eo ft e s tt emＧ o fM/Ai s l andcon t en ti nt het h i ckne s sd i r e c t i ono f r a t ur e．Espe c i a l l r c r e a s e sr ap i d l pe y,CVN ene gyde y / twot e s t eds t r i sa r es h o w ni n F i ７．M Ai s l a n d p g f r om２５８t o１５０Jwhent het e s tt empe r a t u r echange s con t en to fs t r i en t e ri sh i rt hant ha to ft opand pc ghe f r om －４０t o －６０ ℃．The r e f o r e,bo t ht e s t eds t r i ps bo t t om sur f a c e sand M/A i s l and con t en ti ns t r i p haveexc e l l en tc r i ct oughne s sbu tduc t i l e Ｇ b r i t t l e yogen No ２i sl e s s． t r ans i t i ont empe r a t u r eo ftwot e s t eds t r i sd i f f e r Ｇ psi , en t wh i chi sl owe rt han －６０ ℃ andbe twe en －４０ ３ Ana l s i sandDi s c u s s i on y and －６０ ℃ r e spe c t i ve l y．
F i ４ S e r i e simpa c tt e s t e dr e s u l t so ft e s t e ds t r i s g p
X１００p i l i nes t e e lwh i chi sob t a i nedby mi c r o Ｇ pe a l l oy i nge f f e c tand TMCP ( t he rmo Ｇme chan i c a lcon Ｇ t r o lp r oc e s s)i sak i ndo fl ow c a rbonba i n i t i cs t e e l． Compa r ed wi t ht r ad i t i ona ls t e e l,h i t r eng t ho f gh s X１００p i e l i n es t e e l r e l i e sn o to n l o nt h e i n c r e a s eo f p y , Ccon t en t bu ta l soonba i n i t ema t r i xwi t hh i Ｇ ghden s i t i s l oc a t i on,d i s l oc a t i onsubs t ruc t ur e, M/Ai s Ｇ yd l andha rden i ngpha s eandc a rbonn i t r i dep r e c i i t a t i on p [ ,] wi t h Ti and Nb a f t e r pha s et r ans f o rma t i on５ ６ ． Tr ans f o rma t i on ha rden i ng i st he mos timpo r t an t s t r eng t hen i ng me chan i sms．Ba i n i t ei soneo fmed i um
２３０
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 ２１
( a)Topsur f a c e; ( b)１/８; ( c)１/４; ( d)３/８; ( e)１/２; ( f)５/８; ( h)７/８; ( i)Bo t t omsur f a c e． g)３/４; (
F i ５ SEM mi c r o r aph so ft h emi c r o s t r u c t u r ei nt h et h i ckn e s sd i r e c t i ono ft e s t e ds t r i １ g g pNo
( a)Topsur f a c e; ( b)１/８; ( c)１/４; ( d)３/８; ( e)１/２; ( f)５/８; ( h)７/８; ( i)Bo t t omsur f a c e． g)３/４; (
F i ６ SEM mi c r o r aph so ft h emi c r o s t r u c t u r ei nt h et h i ckn e s sd i r e c t i ono ft e s t e ds t r i ２ g g pNo
I s sue２ Mi c r o s t r uc t u r e sand Me chan i c a lPr ope r t i e so fX１００P i l i neS t e e lS t r i pe p
２３１
Tab l e３ Vo l umef r a c t i on so fmi c r o s t r u c t u r e so f twot e s t e ds t r i s ％ p S t r i p
QF
No ２
０
No １
F i ７ Chang et r end so fM/Ai s l andc on t en ti nt h e g t h i ckn e s sd i r e c t i ono ftwot e s t e ds t r i s p
t empe r a t u r e pha s et r ans f o rma t i on p r oduc t sandi s ob t a i ned a tl owe rt r ans f o rma t i on t empe r a t u r eo r h i rt r ans f o rma t i onc oo l i ngr a t et hanf e r r i t e．Di s Ｇ ghe l oc a t i ondens i t s l andc on t en ti nba i n i t e yand M/Ai , a r eh i rt hant ho s ei n QF s oba i n i t es t r eng t hi s ghe h i rt han QFs t r eng t h．Con t en t so fd i f f e r en tmi Ｇ ghe c r os t ruc t u r e swe r es t a t i s t i c a l l e s t i m a t e do n l i nt h e y y c en t r eo ftwot e s t eds t r i omi c r o s t ruc t u r ei n Ｇ psduet homogene i t nt h i ckne s sd i r e c t i on．Ther e su l t sa r e yi showni n Tab l e３．Mi c r o s t ruc t u r e so ft e s t eds t r i p , No ２c ons i s to fGBandl i t t l eLBi ns t e ado fQF so i t ss t r eng t hi sh i rt hant ha to fs t r i １ bu t ghe p No t oughne s si sl owe r．
２４
GB
LB
M/Ai s l and
５３ ６
３６ ５
９ ９
６２ ７
０
１３ ３
La t hba i n i t econs i s t so fl a t hpa cke t swi t hd i f f e r Ｇ en to r i en t a t i onsandl a t h pa cke tcons i s t so fpa r a l l e l ( ) l a t hs． I t s mo r l ogyi sshowni nF i ８ a ．Mo r e pho g subs t ruc t ur e sand d i s l oc a t i on ex i s ti nl a t h( F i ８ g ( b))andg r anu l a ro ra c i cu l a rM/Ai s l andsappe a ri n , andbe twe enl a t hs．Compa r ed wi t hLB s t r eng t ho f GBi sl owe rbe c aus ema t r i xi sequ i axedandd i s l oc a Ｇ t i ondens i t ssma l l e r．Howeve r,t oughne s so fLBi s yi l owe rt hant ha to fGBbe c aus eh i i t fd i s l o Ｇ ghdens yo c a t i onandpa r a l l e lba i n i t el a t hi nc r e a s et her e s i s t anc e t od i s l oc a t i onmo t i onandd i s l oc a t i ons l i owt ho f p．Gr LBi sr e s t r i c t ed be c aus et hef o rma t i on o fa g r e a t t i t fg r anu l a rba i na t ei se a r l i e rt hant ha to f quan yo , LBandGBha sbe t t e rt oughne s s LB＋GBi scons i d Ｇ e r edt ob ei d e a lmi c r o s t r u c t u r e so fX１００p i e l i n es t e e l． p M/A i s l andsi sanimpo r t an t mi c r os t ruc t ur e cha r a c t e r i s t i ci np i l i nes t e e l．TEM pho t og r apho f pe M/Ai s l andi sshowni nF i ９． B l a c kp a r ti nt hef i r e g gu /g i sma r t en i t eandwh i t e r aypa r ti nma r t e n s i t ei sau s Ｇ
( a)La t hba i n i t e; ( b)Di s l o c a t i onc l us t e r．
F i ８ TEM pho t o so ft h es t e e l g
t en i t e．M/Ai s l andsf o rm unde rt hec ond i t i ono fC / conc en t r a t i oni nγ αi n t e r f a c ebe c aus eh i Ｇ gh Ccon t en t make s aus t en i t e mo r es t ab l e and aus t en i t e t r ans f o rms ma r t ens i t ea tl owe rt empe r a t u r e,even someaus t en i t er ema i nsa tr oomt empe r a t u r e．M/A i s l andsa r ec ons i de r eda saha r d pha s e wi t hh i r ghe / s t r eng t ht hanma t r i x．Howeve r,h i hc o n t e n to fM g [] Ai s l andi sun f avo r ab l ef o rt oughne s s７ i fc on t i nu i t y o f ma t r i x mi c r o s t ruc t u r ei s de s t r oyed by M/A i s l ands．La t t i c ed i s t o r t i oni n ma t r i xc aus edby M/A
i s l andscou l d gene r a t e mi c r o Ｇ c r a ck be twe en M/A i s l andsandma t r i xandt hef o rmedmi c r o Ｇ c r a ckcou l d [] e a s i l r opaga t ea l ong t hei n t e r f a c e８ ．Espe c i a l l yp y coa r s e mu l t i Ｇ ang l e M/A i s l andsa r e de l e t e r i oust o t oughne s sbe c aus es t r e s sconc en t r a t i ona r oundsuch M/Ai s l andsi sc apab l eo ff a c i l i t a t i ng M/Ai s l ands [] be comi ngc r a cki n i t i a t i onpo i n t９ ．M/Ai s l andcon Ｇ / t en to ft e s t eds t r i １i sh i rand M Ai s l ands p No ghe o ft e s t eds t r i １a r eb i rt hant ha to fs t r i p No gge p No ２． Shapeo fM/Ai s l andsi sr egu l a rsphe r i c i t o r y
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 ２１
２３２
F i ９ TEM pho t o r aphyo fM/Ai s l and g g
sphe r o i d i c i t heya r ed i spe r s edon ma t r i xwh i l e yandt / someM Ai s l andsi nt e s t eds t r i ２a r ea c i cu l a r p No andappe a rt obepa r a l l e lt oba i n i t el a t h．Ac i cu l a rM/
Ai s l andsa r ede l e t e r i oust ot oughne s sbe c aus et hey [ １０] mayt u rnt ot hepa t ho fc r a ckp r opaga t i on ．The r e Ｇ f o r e,adve r s ee f f e c to f M/Ai s l andont oughne s si n t e s t eds t r i ２i smo r es e r i ous． I no r de rt ol owe r p No , , adve r s ee f f e c tont oughne s s su i t ab l eshape c on t en t [ ] ands i z eo fM/Ai s l andsa r es i i f i c an t１１ ． gn
４ Conc l u s i on s
( １)Hi on t en t so fCand Moc ande c r e a s e ghc t he s t a r t i ng t empe r a t u r eo f pha s et r ans f o rma t i on andmakec r i t i c a lc oo l i ngr a t eo fAFandBl i ne ssh i f t r i twa r d． gh ( ２)X１００ho tr o l l e ds t r i so f１５ ３ mmi nt h i c k Ｇ p n e s swe r epr oduc edus i ngtwos t age sc on t r o l l edr o l l Ｇ i ng．Yi e l ds t r eng t hi sh i rt han７００ MPa,andt en Ｇ ghe
s i l es t r eng t hi sh i rt han８６０ MPa．Tens i l er a t i oi s ghe l owe rt han０ ８３,CVN ene r s２８２Ja t －２０ ℃ gyi andbr i t t l e Ｇ t o Ｇ duc t i l et r ans i t i ont empe r a t ur ei sl owe r t han －４０ ℃． ( ３)Mi c r os t ruc t ur e so fX１００ho tr o l l eds t r i p cons i s to fGB,LBand M/Ai s l ands．Whenequ i axed GBi smo r eandLB wi t hh i i t fd i s l oc a t i on ghdens yo i sl e s s,op t imumcomb i na t i ono fs t r eng t handt oughＧ ne s si sgua r an t e ed． ( ４)Shape,con t en tands i z eo fM/Ai s l anda r e impo r t an tt os t r eng t h and t oughne s so fp i l i ne pe s t e e l．Regu l a randf i neM/Ai s l andsa r ebene f i c i a lt o s t r eng t ho fp i l i nes t e e landensur er equ i r edt oughＧ pe ne s so fp i l i nes t e e l． pe Re f e r enc e s:
[ １] L． Zheng,J Y．Fu,I r onandS t e e l４１ ( ２００６)No １０,１ Ｇ １０． [ r on C．Zhang,HB．Wu,D．Tang,I ２] L B．Wang,Y．Ren,P andS t e e l４３ ( ２００８)No １,８０ Ｇ ８４． [ ３] S J． J i a,L N．Duan,QL．L i u,Tr ans a c t i onso fMa t e r i a l sand He a tTr e a tmen t３３ ( ２０１２)No １２,７６ Ｇ ８１． [ ４] H． Sun,We l dedP i ２０１０)No ８,６６ Ｇ ７１． peandTube３３ ( [ t aMe t a l l． S i n． ５] MC． Zhao,YY． Shan,J B．Qu,K．Yang,Ac ３７ ( ２００１)No ２,１７９ Ｇ １８３． [ ６] HF．Lan,L X．Du,Z．L i,YC．L i u,X H．L i u,Tr ans a c Ｇ t i onso fMa t e r i a l sandHe a tTr e a tmen t３０ ( ２００９)No １,６１ Ｇ ６５． [ ７] S F．Yu,B N．Qi an,Ch i ne s eJ our na lo fMa t e r i a l sRe s e a r ch１８ ( ２００４)No ４,４０６ Ｇ ４１１． [ R．Wu,Mi c r oa l l oyedS t e e l:Phys i c a l ８] QL．Yong,MT．Ma,B and Me chan i c a l Me t a l l ur i na Ma ch i ne Pr e s s,Be i i ng, gy,Ch j
１９８９． [ ９] K．Wa l l i n,T．Sa a r i o,K．To r r onen,I n t e r na t i ona lJ our na lo f Fr a c t ur e３２ ( １９８７)２０１ Ｇ ２０９． [ our na lo f Me Ｇ １０] QB．Yu,Y．Sun,HX．Ni,KF．Zhang,J chan i c a lEng i ne e r i ng４５ ( ２００９)No １２,２８４ Ｇ ２８７． [ １１] M． Zhou,QH．Ma,L X． Du,X H． L i u,J．No r t he a s t．Un i v． Na t． S c i． ３０ ( ２００９)No ７,９８５ Ｇ ９８８．
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ４,２ １( ２):２ ２ ７ Ｇ ２ ３ ２
Mi c r o s t r u c t u r e sand Me chan i c a lPr ope r t i e so fX１００P i l i neS t e e lS t r i pe p ２ L i n Ｇ naDUAN１ ２ , YuCHEN３ , Qi ng Ｇ Ｇ unJ IA２ , Cheng Ｇ changJ IA１ youLIU , Shu j ,
( i i ng１０００８３, i ve r s i t fSc i enc eandTe chno l ogyBe i i ng,Be １． Schoo lo fMa t e r i a lSc i enc eandEng i ne e r i ng,Un j yo j Ch i na; ２． I ns t i t u t ef o rEng i ne e r i ngS t e e l,Cen t r a lI r onandS t e e lRe s e a r chI ns t i t u t e,Be i i ng１０００８１,Ch i na; j ３．Ch i naPe t r o l eum Eng i ne e r i ngandCons t r uc t i onCo r r a t i on,Be i i ng１００１２０,Ch i na) po j
Ab s t r a c t:Dyn ami cCCT ( c on t i nuou sc o o l i ngt r a n s f o rma t i on)c u r v e sa nde f f e c t so f mi c r o s t r u c t u r e sa nd M/Ai s l a nd so f X１００ho tr o l l eds t r i chan i c a lp r ope r t i e swe r es t ud i edbyme anso fat he rma ls imu l a t o r,as c ann i nge l e c t r onmi Ｇ ponme c r o s c ope ( SEM),at r a n smi s s i one l e c t r onmi c r o s c op e( TEM),ad i i t a lmi c r o Ｇh a r dn e s st e s t e ra ndIma e ＧPr oP l usana l s i s g g y s o f twa r e．Ther e su l t sshowt ha th i on t en t so fCandMoc anmaket r ans f o rma t i onl i ne so fa c i cu l a rf e r r i t eandba i n Ｇ ghc i t esh i f tr i twa r d．Hi e s t eds t r i sh i rs t r eng t handmi c r o Ｇha r dne s sandl owe rt oughne s st hant heo t he r gh gh Mot pha ghe onebe c aus el a t hba i n i t eappe a r si ns t e ado fqua s i Ｇpo l lf e r r i t e．T e s t e ds t r i i t hg r a nu l a rb a i n i t e,l a t hb a i n i t ea nd ygona pw M/Ai s l andsha sbe t t e rme chan i c a lp r ope r t i e sandi nt he mi c r o s t r uc t u r e sl a t hba i n i t ec on t en ti sa r ound３６ ５％ and M/Ai s l andsa r ef i neandd i spe r s ei nt hema t r i x． Ke r d s:X１００ho tr o l l eds t r i r ve;g r anu l a rba i n i t e;l a t hba i n i t e;M/Ai s l and p;CCTcu ywo
Al ong wi t ht head us tmen to fene r t ruc t ur e j gys , andt hei nc r e a s eo fene r d e m a n d X １ ０ ０ i e l i n e gy pp s t e e l sf o rh i e s su r e, l a r i ame t e randl ongd i s Ｇ ghpr ged t anc eo i landga sp i l i ne shavebe endeve l opedr ap Ｇ pe [ １] i d l r ed wi t ht he X８０ a c i cu l a rp i l i ne y ．Compa pe s t e e l,X１００s t e e lc anr educ et hec o s tf r om s av i ng ma t e r i a l s,impr ov i ng t r ans f e rp r e s su r e,r educ i ng , cons t ruc t i on quan t i t owe r i ng ma i n t enanc ec os t, y l [ ２] op t imi z i ngp r o e c ts t r a t egyands oon ．The r e f o r e, j mo r eandmo r ee f f o r t shavebe enpu tont her e s e a r ch onX１００p i l i nes t e e l． pe Fr omt hepr ev i ousexpe r i enc e,mi c r o s t ruc t ur e s o fX１００ p i l i nes t e e la r eba i n i t e wh i chc ons i s t so f pe r anu l a rba i n i t e andl a t h ba i n i t e．Con t en t so f C, g Mn,Nband Moo fX１００s t e e la r eh i rt hant hos e ghe o fX８０ s t e e li no r de rt o ob t a i n ba i n i t e wi t hh i gh [] s t r e ng t h３ ．Howe v e r,t h ec on f l i c t sb e twe e ns t r e ng t h andt oughne s swou l dbemo r eou t s t and i ng,e spe c i a l Ｇ l f o rX １ ０ ０h o t r o l l e ds t r i w i t h l a r e t h i c k n e s s ． M i Ｇ y p g c r os t ruc t u r e so ftwos t e e l s wi t hd i f f e r en tchemi c a l
compos i t i onsa r eana l z edandt her e l a t i onso f mi Ｇ y c r os t ruc t ur e swi t hs t r eng t handt oughn e s sa r es t ud i e d i nt h i sp a e r．Thes t udyi s me an i ng f u lf o rr e s e a r c hon p mi c r o s t r u c t u r e sand me chan i c a lp r ope r t i e so f X１００ i l i nes t e e landl owc a rbonba i n i t i cs t e e l s． p pe
１ Exp e r imen t a lMa t e r i a l sandPr o c e du r e s
Compos i t i onde s i ftwot e s t eds t e e l si sl ow gno CＧMn ＧNb ＧMoandt hede t a i l edchemi c a lcompos i t i on i sg i veni nTab l e１．Thet e s t eds t e e l swe r econ t i nu Ｇ ous l a s ta f t e rconve r t e rsme l t i ngandLFr e f i n i ng yc l usRHva cuumdega s s i ngandt h i ckne s so fcon t i nu Ｇ p ousc a s t i ngs l absi s２３０mm．Dynami cCCT ( con t i n Ｇ uouscoo l i ngt r ans f o rma t i on)cur ve swe r eme a sur ed onaGl e e b l e Ｇ １５００Dt he rma ls imu l a t o r． ϕ８mm×１２mm s imu l a t i onspe c imens we r ecu tf r om t he mi dd l eo f t hec a s ts l abs．Asshowni ns chema t i ci l l us t r a t i ono f t he rmo Ｇme chan i c a ls imu l a t i on (F i １), d i f f e r en t g coo l i ngr a t e s we r eadop t edi nt het e s t．D i l a t ome t r i c , c u r v e swe r er e c o r d e d pha s et r ans f o rma t i ont empe r a Ｇ
Tab l e１ Ch emi c a lc ompo s i t i ono ft h et e s t e ds t e e l s (ma s spe r c en t,％ )
S t e e l No １ No ２
C
０ ０５ ０ ０６
S i
０ ２１ ０ ２１
Mn
１ ９６ ２ ０５
P
０ ００９ ０ ０１３
S
０ ００２０ ０ ００２５
Mo
０ ２５ ０ ２９
Cr
０ ３０ ０ ３１
Ni
０ ３９ ０ ２６
Cu
Nb＋V＋Ti
０ ２３
≤０ １５
０ ２１
≤０ １５
Als
０ ０２０ ０ ０２３
Founda t i onI t em: I t emSpon s o r e dbyNa t i on a lKe e c hno l o s e a r c ha ndDe v e l opme n tPr o r ami n１２ t hF i v e Ｇ e a rP l a no fCh i n a( ２０１１BAE３５B０１) yT gy Re g y B i o r aphy: L i n Ｇ naDUAN,Do c t o rCand i da t e; E Ｇma i l: duan l i nna ８３＠s i na c omcn; Re c e i v e dDa t e:Ap r i l１１,２０１３ g
２２８
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 ２１
F i １ S ch ema t i ci l l u s t r a t i ono ft h e rmo Ｇme chan i c a ls imu l a t i on g
t ur e s we r eob t a i ned byt angen t i a l me t hodanddy Ｇ nami cCCTcu r ve swe r ebu i l ta tl a s t． Con t i nuousc a s t i ngs l abswe r ec on t r o l l edr o l l ed i nr e c r s t a l l i z a t i o na n dn o n Ｇ r e c r s t a l l i z a t i o nz o n e st o y y １５ ３mmt h i c ka nd１５５０ mm w i d ea ndt h e nwe r ec on Ｇ t r o l l e dc o o l e da ndc o i l e d．Ac c o r d i ngt o AP Is t a nd a r d,
t he me chan i c a lpr ope r t i e so ft e s t eds t r i r eex Ｇ ps we ( ) ami nedbyt ens i l et e s t sa l ongr o l l i ngd i r e c t i on RD , t r ansve r s ed i r e c t i on ( TD)and３０ °wi t hr o l l i ngd i r e c Ｇ t i ona tr oom t empe r a t u r eand Cha r no t chimＧ py VＧ c tt e s t si nt h et emp e r a t u r er a ng ef r om２０t o－６０ ℃． pa WEＧ ３００hyd r au l i ct ens i l et e s t i ng ma ch i neandJBNＧ ３００Bimpa c tt e s t i ng ma ch i newe r eus edr e spe c t i ve l y． Spe c imenst akenf r om twot e s t eds t r i l ong psa r o l l i ngd i r e c t i onwe r ee t chedi n３％ n i t a ls o l u t i ona f Ｇ t e rg r i nd i nga ndpo l i s h i ngi nt h i c kn e s sd i r e c t i on．Mi c r o Ｇ
ha rdne s swa st e s t eda t２１spo t sun i f o rml i s t r i bu Ｇ yd t edi nt h i ckne s sd i r e c t i onus i ngFMＧ ３００d i i t a lmi c r o Ｇ g ha r dn e s st e s t e r．Mi c r o s t r u c t u r e s we r e ob s e r v e da t９ z on e sbya HITACHI S Ｇ ４３００c o l d Ｇ f i e l demi s s i onSEM ( s c ann i ng e l e c t r on mi c r o s c op e)．Vo l umef r a c t i on o f /aus ma r t ens i t e t en i t e (M/A)i s l andswa ss t a t i s t i c a l l y e s t ima t edbyImage ＧPr oP l usso f twa r e．Mi c r os t ruc Ｇ t ur e mo r l ogy wa sobs e r ved by an HＧ ８００ TEM pho ( t r ansmi s s i one l e c t r onmi c r os cope)．
２ Exp e r imen t a lRe s u l t s
２ １ Dynami cCCTcu r v e Dynami cCCT cur ve so ftwot e s t eds t e e l sa r e showni nF i ２．Be c aus eo fs imi l a rchemi c a lcompo Ｇ g , s i t i on t r endso fCCT cur ve so ftwos t e e l sa r et he s ame．Wi t ht hei nc r e a s eo fcoo l i ngr a t e,po l l ygona f e r r i t e( PF),pe a r l i t e( P),a c i cu l a rf e r r i t e (AF), r anu l a rba i n i t e( GB)andl a t hba i n i t e( LB)appe a r g
i no rde randt he r ea r e no obv i ousc r i t i c a l po i n t s． S t a r t i ng t empe r a t ur eo ft r ans f o rma t i on o ft e s t ed s t e e lNo ２i sl owe rt hant ha to ft e s t eds t e e lNo １ owi ngt oh i rc a rboncon t en ti nt e s t eds t e e lNo ２． ghe Hi i anexpandAFandba i n i t e( B) gh Moandh ghNic t r ans f o rma t i onz oneandt hee f f e c to fMoi smo r ee f Ｇ f e c t i vet hanNi,soc r i t i c a lcoo l i ngr a t eo ft e s t eds t e e l No ２i sl owe r．Duet ot hed i f f e r enc eo fmi c r os t ruc Ｇ t ur e s,mi c r o Ｇha rdne s so ft e s t eds t e e lNo ２i sh i r ghe
( a)Te s t eds t e e lNo １; ( b)Te s t eds t e e lNo ２．
F i ２ CCTc u r v e so ftwot e s t e ds t e e l s g
t hant ha to ft e s t eds t e e lNo １． ２ ２ Me chan i c a lpr ope r t i e s T a b l e２l i s t sy i e l ds t r e ng t h,t e n s i l es t r e ng t h,e l on Ｇ a t i ona ndy i e l dr a t i oo ftwot e s t e ds t r i s． I ti sobv i ous g p t ha tt ens i l es t r eng t h and y i e l ds t r eng t ho ft e s t ed s t r i ２a r eh i rt hant ha to fNo １,bu te l onga Ｇ p No ghe t i ona f t e rf r a c t u r eo ft e s t eds t r i ２i sl e s s．The p No
s t anda rd APISPEC５Lr e i r e st e n s i l es t r e ng t hand qu i e l ds t r e ng t ho fX１００p i e l i n es t e e la r e７６０－９９０ MPa y p and６９０－８４０MPar e spe c t i ve l i e l dr a t i oi sl e s s yandy t han０ ９７．The r e f o r e,on l e s t eds t r i ２ me e t s yt p No t he s er equ i r emen t s． Mi c r o Ｇha rdne s s cur ve sa td i f f e r en t pos i t i ons a c r os st het h i ckne s sd i r e c t i ono ftwot e s t eds t r i r e psa showni nF i ３． I ti sf oundt ha tave r agemi c r o Ｇha rd Ｇ g
I s sue２ Mi c r o s t r uc t u r e sand Me chan i c a lPr ope r t i e so fX１００P i l i neS t e e lS t r i pe p
２２９
Tab l e２ Ro omt emp e r a t u r et en s i l et e s tr e s u l t so ft e s t e ds t r i s p S t r i p
No １
No ２
Ro l l i ngd i r e c t i on
Tens i l es t r eng t h/MPa
Yi e l ds t r eng t h/MPa
/％ El onga t i ona f t e rf r a c t ur e
Yi e l dr a t i o
RD
７３４
５９６
３２ ５
０ ８１
TD
８７５
TD
３０ ° RD
３０ °
７５６ ７１４
８８０
８６０
６５７ ５７３
７１５
７３０ ７００
３１ ０ ３５ ０
２４ ０
２８ ０ ２７ ０
０ ８７ ０ ８０
０ ８２
０ ８３ ０ ８１
２ ３ Mi c r o s t r u c t u r e s F i s ５a n d６s how t heSEM mo r l og i e so f g pho mi c r os t ruc t ur e si nt het h i ckne s sd i r e c t i onf r om t op t obo t t om o ftwot e s t eds t r i e spe c t i ve l c r o Ｇ psr y．Mi s t ruc t ur e so ft e s t eds t r i N o １c o n s i s t i n o ft i c a p g yp l ( ) GBandl i t t l equa s i Ｇ l lf e r r i t e QF i n who l e po ygona c r os s Ｇ s e c t i ona r ehomogeneousande l onga t edduet o r o l l i ng．M/Ai s l andsun i f o rml i spe r s ei nt heg r a i ns yd o ront heg r a i nbounda r i e swi t ht heshapeo fsphe r i c Ｇ i t rsphe r o i d i c i t hes i z ei sa r ound１μm．Mi Ｇ yo yandt c r os t ruc t ur e so ft e s t eds t r i ２cons i s to fGBand p No F i ３ Mi c r o Ｇha r dn e s sc u r v e si nt h et h i ckn e s sd i r e c t i on g LBanda r ee l onga t edt oo．La t hba i n i t i cpa cke t sa r e f r omt opt obo t t omo ftwot e s t e ds t r i s p r a l l e land g r anu l a ro ra c i cu l a r M/Ai s l andsex i s t pa be twe enba i n i t i cpa cke t so rba i n i t i cl a t hs． I nt e s t ed ne s so ft e s t eds t r i ２i s７０ HV h i rt hant ha t p No ghe s t r i ２,GBi smo r et hanLBandvo l umef r a c t i on p No o fs t r i １． p No o fLBi nbo t t om sur f a c ei sl owe rt hant ha to ft op Cha r no t chimpa c tt e s t( CVN)r e su l t so f py VＧ sur f a c ebu th i rt hant ha to fs t r i en t e r．Di f f e r Ｇ ghe pc t e s t eds t r i r eshowni nF i ４． CVNene r ftwo psa g gyo enc eo fmi c r os t ruc t ur et so ftwos t r i sc aus ed ype psi t e s t eds t r i e tt her equ i r emen to fAPISPEC５L psme byd i f f e r en tcon t en t so fCand Mo．Ha rdenab i l i t n Ｇ yi (Whent het e s tt empe r a t u r ei s－２０ ℃ ,CVNene r gy c r e a s e swi t ht hei nc r e a s eo fCcon t en tandMoi sab l e i sh i rt han２８０J)．CVN ene r ft e s t eds t r i ghe gy o p t op i nγ/αi n t e r f a c e movemen t,pos t Ｇ αt r ans Ｇ poneγ No １i sa lmo s ts t ab l ea tt he s et e s tt empe r a t u r e sand [] f o rma t i on４ ,i nh i b i tma s s i vef e r r i t ef o rma t i on,and h i rt hant ha to fNo ２． CVNene r ft e s t eds t r i ghe gyo p r omo t eAFandBt r ans f o rma t i on．Chang i ngt r ends p No ２de c r e a s e sa l ong wi t ht hede c r e a s eo ft e s tt emＧ o fM/Ai s l andcon t en ti nt het h i ckne s sd i r e c t i ono f r a t ur e．Espe c i a l l r c r e a s e sr ap i d l pe y,CVN ene gyde y / twot e s t eds t r i sa r es h o w ni n F i ７．M Ai s l a n d p g f r om２５８t o１５０Jwhent het e s tt empe r a t u r echange s con t en to fs t r i en t e ri sh i rt hant ha to ft opand pc ghe f r om －４０t o －６０ ℃．The r e f o r e,bo t ht e s t eds t r i ps bo t t om sur f a c e sand M/A i s l and con t en ti ns t r i p haveexc e l l en tc r i ct oughne s sbu tduc t i l e Ｇ b r i t t l e yogen No ２i sl e s s． t r ans i t i ont empe r a t u r eo ftwot e s t eds t r i sd i f f e r Ｇ psi , en t wh i chi sl owe rt han －６０ ℃ andbe twe en －４０ ３ Ana l s i sandDi s c u s s i on y and －６０ ℃ r e spe c t i ve l y．
F i ４ S e r i e simpa c tt e s t e dr e s u l t so ft e s t e ds t r i s g p
X１００p i l i nes t e e lwh i chi sob t a i nedby mi c r o Ｇ pe a l l oy i nge f f e c tand TMCP ( t he rmo Ｇme chan i c a lcon Ｇ t r o lp r oc e s s)i sak i ndo fl ow c a rbonba i n i t i cs t e e l． Compa r ed wi t ht r ad i t i ona ls t e e l,h i t r eng t ho f gh s X１００p i e l i n es t e e l r e l i e sn o to n l o nt h e i n c r e a s eo f p y , Ccon t en t bu ta l soonba i n i t ema t r i xwi t hh i Ｇ ghden s i t i s l oc a t i on,d i s l oc a t i onsubs t ruc t ur e, M/Ai s Ｇ yd l andha rden i ngpha s eandc a rbonn i t r i dep r e c i i t a t i on p [ ,] wi t h Ti and Nb a f t e r pha s et r ans f o rma t i on５ ６ ． Tr ans f o rma t i on ha rden i ng i st he mos timpo r t an t s t r eng t hen i ng me chan i sms．Ba i n i t ei soneo fmed i um
２３０
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 ２１
( a)Topsur f a c e; ( b)１/８; ( c)１/４; ( d)３/８; ( e)１/２; ( f)５/８; ( h)７/８; ( i)Bo t t omsur f a c e． g)３/４; (
F i ５ SEM mi c r o r aph so ft h emi c r o s t r u c t u r ei nt h et h i ckn e s sd i r e c t i ono ft e s t e ds t r i １ g g pNo
( a)Topsur f a c e; ( b)１/８; ( c)１/４; ( d)３/８; ( e)１/２; ( f)５/８; ( h)７/８; ( i)Bo t t omsur f a c e． g)３/４; (
F i ６ SEM mi c r o r aph so ft h emi c r o s t r u c t u r ei nt h et h i ckn e s sd i r e c t i ono ft e s t e ds t r i ２ g g pNo
I s sue２ Mi c r o s t r uc t u r e sand Me chan i c a lPr ope r t i e so fX１００P i l i neS t e e lS t r i pe p
２３１
Tab l e３ Vo l umef r a c t i on so fmi c r o s t r u c t u r e so f twot e s t e ds t r i s ％ p S t r i p
QF
No ２
０
No １
F i ７ Chang et r end so fM/Ai s l andc on t en ti nt h e g t h i ckn e s sd i r e c t i ono ftwot e s t e ds t r i s p
t empe r a t u r e pha s et r ans f o rma t i on p r oduc t sandi s ob t a i ned a tl owe rt r ans f o rma t i on t empe r a t u r eo r h i rt r ans f o rma t i onc oo l i ngr a t et hanf e r r i t e．Di s Ｇ ghe l oc a t i ondens i t s l andc on t en ti nba i n i t e yand M/Ai , a r eh i rt hant ho s ei n QF s oba i n i t es t r eng t hi s ghe h i rt han QFs t r eng t h．Con t en t so fd i f f e r en tmi Ｇ ghe c r os t ruc t u r e swe r es t a t i s t i c a l l e s t i m a t e do n l i nt h e y y c en t r eo ftwot e s t eds t r i omi c r o s t ruc t u r ei n Ｇ psduet homogene i t nt h i ckne s sd i r e c t i on．Ther e su l t sa r e yi showni n Tab l e３．Mi c r o s t ruc t u r e so ft e s t eds t r i p , No ２c ons i s to fGBandl i t t l eLBi ns t e ado fQF so i t ss t r eng t hi sh i rt hant ha to fs t r i １ bu t ghe p No t oughne s si sl owe r．
２４
GB
LB
M/Ai s l and
５３ ６
３６ ５
９ ９
６２ ７
０
１３ ３
La t hba i n i t econs i s t so fl a t hpa cke t swi t hd i f f e r Ｇ en to r i en t a t i onsandl a t h pa cke tcons i s t so fpa r a l l e l ( ) l a t hs． I t s mo r l ogyi sshowni nF i ８ a ．Mo r e pho g subs t ruc t ur e sand d i s l oc a t i on ex i s ti nl a t h( F i ８ g ( b))andg r anu l a ro ra c i cu l a rM/Ai s l andsappe a ri n , andbe twe enl a t hs．Compa r ed wi t hLB s t r eng t ho f GBi sl owe rbe c aus ema t r i xi sequ i axedandd i s l oc a Ｇ t i ondens i t ssma l l e r．Howeve r,t oughne s so fLBi s yi l owe rt hant ha to fGBbe c aus eh i i t fd i s l o Ｇ ghdens yo c a t i onandpa r a l l e lba i n i t el a t hi nc r e a s et her e s i s t anc e t od i s l oc a t i onmo t i onandd i s l oc a t i ons l i owt ho f p．Gr LBi sr e s t r i c t ed be c aus et hef o rma t i on o fa g r e a t t i t fg r anu l a rba i na t ei se a r l i e rt hant ha to f quan yo , LBandGBha sbe t t e rt oughne s s LB＋GBi scons i d Ｇ e r edt ob ei d e a lmi c r o s t r u c t u r e so fX１００p i e l i n es t e e l． p M/A i s l andsi sanimpo r t an t mi c r os t ruc t ur e cha r a c t e r i s t i ci np i l i nes t e e l．TEM pho t og r apho f pe M/Ai s l andi sshowni nF i ９． B l a c kp a r ti nt hef i r e g gu /g i sma r t en i t eandwh i t e r aypa r ti nma r t e n s i t ei sau s Ｇ
( a)La t hba i n i t e; ( b)Di s l o c a t i onc l us t e r．
F i ８ TEM pho t o so ft h es t e e l g
t en i t e．M/Ai s l andsf o rm unde rt hec ond i t i ono fC / conc en t r a t i oni nγ αi n t e r f a c ebe c aus eh i Ｇ gh Ccon t en t make s aus t en i t e mo r es t ab l e and aus t en i t e t r ans f o rms ma r t ens i t ea tl owe rt empe r a t u r e,even someaus t en i t er ema i nsa tr oomt empe r a t u r e．M/A i s l andsa r ec ons i de r eda saha r d pha s e wi t hh i r ghe / s t r eng t ht hanma t r i x．Howeve r,h i hc o n t e n to fM g [] Ai s l andi sun f avo r ab l ef o rt oughne s s７ i fc on t i nu i t y o f ma t r i x mi c r o s t ruc t u r ei s de s t r oyed by M/A i s l ands．La t t i c ed i s t o r t i oni n ma t r i xc aus edby M/A
i s l andscou l d gene r a t e mi c r o Ｇ c r a ck be twe en M/A i s l andsandma t r i xandt hef o rmedmi c r o Ｇ c r a ckcou l d [] e a s i l r opaga t ea l ong t hei n t e r f a c e８ ．Espe c i a l l yp y coa r s e mu l t i Ｇ ang l e M/A i s l andsa r e de l e t e r i oust o t oughne s sbe c aus es t r e s sconc en t r a t i ona r oundsuch M/Ai s l andsi sc apab l eo ff a c i l i t a t i ng M/Ai s l ands [] be comi ngc r a cki n i t i a t i onpo i n t９ ．M/Ai s l andcon Ｇ / t en to ft e s t eds t r i １i sh i rand M Ai s l ands p No ghe o ft e s t eds t r i １a r eb i rt hant ha to fs t r i p No gge p No ２． Shapeo fM/Ai s l andsi sr egu l a rsphe r i c i t o r y
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 ２１
２３２
F i ９ TEM pho t o r aphyo fM/Ai s l and g g
sphe r o i d i c i t heya r ed i spe r s edon ma t r i xwh i l e yandt / someM Ai s l andsi nt e s t eds t r i ２a r ea c i cu l a r p No andappe a rt obepa r a l l e lt oba i n i t el a t h．Ac i cu l a rM/
Ai s l andsa r ede l e t e r i oust ot oughne s sbe c aus et hey [ １０] mayt u rnt ot hepa t ho fc r a ckp r opaga t i on ．The r e Ｇ f o r e,adve r s ee f f e c to f M/Ai s l andont oughne s si n t e s t eds t r i ２i smo r es e r i ous． I no r de rt ol owe r p No , , adve r s ee f f e c tont oughne s s su i t ab l eshape c on t en t [ ] ands i z eo fM/Ai s l andsa r es i i f i c an t１１ ． gn
４ Conc l u s i on s
( １)Hi on t en t so fCand Moc ande c r e a s e ghc t he s t a r t i ng t empe r a t u r eo f pha s et r ans f o rma t i on andmakec r i t i c a lc oo l i ngr a t eo fAFandBl i ne ssh i f t r i twa r d． gh ( ２)X１００ho tr o l l e ds t r i so f１５ ３ mmi nt h i c k Ｇ p n e s swe r epr oduc edus i ngtwos t age sc on t r o l l edr o l l Ｇ i ng．Yi e l ds t r eng t hi sh i rt han７００ MPa,andt en Ｇ ghe
s i l es t r eng t hi sh i rt han８６０ MPa．Tens i l er a t i oi s ghe l owe rt han０ ８３,CVN ene r s２８２Ja t －２０ ℃ gyi andbr i t t l e Ｇ t o Ｇ duc t i l et r ans i t i ont empe r a t ur ei sl owe r t han －４０ ℃． ( ３)Mi c r os t ruc t ur e so fX１００ho tr o l l eds t r i p cons i s to fGB,LBand M/Ai s l ands．Whenequ i axed GBi smo r eandLB wi t hh i i t fd i s l oc a t i on ghdens yo i sl e s s,op t imumcomb i na t i ono fs t r eng t handt oughＧ ne s si sgua r an t e ed． ( ４)Shape,con t en tands i z eo fM/Ai s l anda r e impo r t an tt os t r eng t h and t oughne s so fp i l i ne pe s t e e l．Regu l a randf i neM/Ai s l andsa r ebene f i c i a lt o s t r eng t ho fp i l i nes t e e landensur er equ i r edt oughＧ pe ne s so fp i l i nes t e e l． pe Re f e r enc e s:
[ １] L． Zheng,J Y．Fu,I r onandS t e e l４１ ( ２００６)No １０,１ Ｇ １０． [ r on C．Zhang,HB．Wu,D．Tang,I ２] L B．Wang,Y．Ren,P andS t e e l４３ ( ２００８)No １,８０ Ｇ ８４． [ ３] S J． J i a,L N．Duan,QL．L i u,Tr ans a c t i onso fMa t e r i a l sand He a tTr e a tmen t３３ ( ２０１２)No １２,７６ Ｇ ８１． [ ４] H． Sun,We l dedP i ２０１０)No ８,６６ Ｇ ７１． peandTube３３ ( [ t aMe t a l l． S i n． ５] MC． Zhao,YY． Shan,J B．Qu,K．Yang,Ac ３７ ( ２００１)No ２,１７９ Ｇ １８３． [ ６] HF．Lan,L X．Du,Z．L i,YC．L i u,X H．L i u,Tr ans a c Ｇ t i onso fMa t e r i a l sandHe a tTr e a tmen t３０ ( ２００９)No １,６１ Ｇ ６５． [ ７] S F．Yu,B N．Qi an,Ch i ne s eJ our na lo fMa t e r i a l sRe s e a r ch１８ ( ２００４)No ４,４０６ Ｇ ４１１． [ R．Wu,Mi c r oa l l oyedS t e e l:Phys i c a l ８] QL．Yong,MT．Ma,B and Me chan i c a l Me t a l l ur i na Ma ch i ne Pr e s s,Be i i ng, gy,Ch j
１９８９． [ ９] K．Wa l l i n,T．Sa a r i o,K．To r r onen,I n t e r na t i ona lJ our na lo f Fr a c t ur e３２ ( １９８７)２０１ Ｇ ２０９． [ our na lo f Me Ｇ １０] QB．Yu,Y．Sun,HX．Ni,KF．Zhang,J chan i c a lEng i ne e r i ng４５ ( ２００９)No １２,２８４ Ｇ ２８７． [ １１] M． Zhou,QH．Ma,L X． Du,X H． L i u,J．No r t he a s t．Un i v． Na t． S c i． ３０ ( ２００９)No ７,９８５ Ｇ ９８８．