,ll.h'tmls ,~l mmi' aml F nglm'mmll, ,4 /'~h i, I t~q2 ) fl t - 7h l~ On the mierostmctture and thermomechanieal processing of tita[fium alloy IM1685 Z. X. (3uo ~ ancl T. N. Baker l h'Dlll IH tt'Hl ~1 [i I~'rallm ~,~' and I~ H,~mt't'rt.g ,,~ htl('~ ml, s, I. Iml'~'~,~tt~'~ I .VI~~tl/H 'lvd~ ', ( ;/a,s't,~ ~t P ( ,'1 I A ,rV (I ,'h) ,Reeep, l'd N~veml.'r 2~4, i~H411 irl revP,l'd h~rm lillllJ.ii~ .~, lilt)21 Ahslrat'l 'T'IIe micr~)~,lrut'lurt~ (~1 nt'ar ~T Illanlum alhws i,, ve~, ,~en,Mlivc It~ Ihe IIlt'rrn~rnefhanlt'al pr~ce,,,~lng t'~ndllll)rl% which m lu[n h;.lvt, il Mgnlllt';irll inl]uenct' lln Ihe meehanit'lJl prt.perlne,, ~1 lilt' malerlal II i,, rt%'llgnlzed Ihal a ~maller 13nt~r [112,r.lln ,,i/u i~ Iht' kt'y mlt'lllhllut'lUlLII It'alurt' rlt't'e,%%ar V h) at'hlt'Ve an implanted t'(lmhlnallllri i~t pr;~perlle% bul rl'hnlrlg Iht' glalll ,,ize i,, .~ dithcull la;,k 'Thu presenl w l)tk inve,dl!/,dle~, him Ihe grain i..,.r~wlh hehav,,Jr oi a near u Illanltlm ,flh~% IMIh:4'~, ,Jnd Ihert Ihe eflet'l Ill VII[I(lU,~ Iherm;)met'hank'ul rlllJle{~ llrl iIS mlL'[OSIfut'llJle, In an allt'mpI Io rt~fine Ihe [2,rain %lruclure H,)lh i)pllcal and I[;Jn,~ml~Ml~n elt'clr~m mwro%c~pv were used lit examine Ihe mlcrllMllJCIIJrlJl v;JrllJllqtrl'~ durin R each ~lep ~d the Iherm, mwcharncul Irealn'ienl T'hc rc,.tJIl~,,.,how Ihal gram rt'hnemenl t,, very diltlcull In Ihe ea~,c ~1 [I ~r upper ~t +/J pr~t'cs.,ing, ,~wing I~ in!,,uH~cienl dynamic recrv,,lalhzalion durmg hol delorrrialt~m and I~ Ihe rapid l:,ram i..,r~wlh dunng Iht' ,~-I '..~hJlll~n Irealmerll (jralri rehn,'menl ha,, been citer'lively achieved u,,ml.., a h~wer u + 11 pr~wvs,,ml: , r,.Jle, and Iht' du,. red lamella r m~~r ph~ ~1~ ~gVca n he rel.,,,Jt ned I%, mear=,, ~1 a j'~ ,,. ~1Ul. m Ireal mvnl I. Inlroduclion 'Ttlanitim IMIhK5 in ()ne I~I Ihe c~lnlmercial neat ~ alhw,,, desngned h. high temperature applicali~ms in Ihe net~space induslrv II I, ll,'., sticct'sst~rs are IMIN2~4 and IMI83,-I 'The alhw has a n~)mmal c~.np~stl._m ~I Ti-hwl"/;,Al-'qwt,"/,,Ml~-l125wt'%,St, winch gtvcs all (~t+[3)-/Itlansus(~lab(~ul 1()211"(.'lll. ['tie ~t-(tt +[~) Iransus has m~l been accuralel~ delermmed, a~, a Irut' single ~t phase ns n~t readily ~fl~tained m Ihns alhw F:'ven wiIh a sh~w c~.~hng I~ loom lernperalule, Ihere re.really exists a Jew pel t'elFI ~)1 less i~1 melaslable [3 phase allel /3 s(~lultl~n Itealrneril Wtth regald h~ Ihe equivalenl aluFnm~um c~nlenl, tl may he said Ihal aFI equthhrtum ~t-l~t +/J) transus .,h~uld he helween ~,~2~ and '47S "(.' 121, ,-. Ihe/J phase w(~uld be dramallcally reduced I'whlw IhJs lemperalure range Aller high lemperalure prlwessmg near or above Ihe fl IlallSUS, Ihc alhw generally exhlblls a lamellar mict~slru¢lure, consisling ol ~t platelels wtlh an inter plalelel /3 phase (Fig, I) 'Tilts larnellar slruclure ill heal ~ alh~vs ts charaelerized by I I-C,~l (I) g~.~d creep pr~perlies, due t~ the resislant'e ~)1 the ~t-lalh b~und arnes (as well as the s~lnd s~lulti~ri eflecl)h) dnsh)calnlm m()vemenl (dishwali()ri creep has heen noted hi he the ~F'rt',,t, ril addrt'~,,~ rFeparlmenl ~1 Malernal,,, I lrlnvcr,,llV ~1 (_)~,h)rd, (_)xh~rd (_),~ I ~PH, I_IK dommanl mechanism, wllh a htgh n value I(Dr slress dependence, m amflhel near-~t alh~y 1'= h2,42 ]1() I, (2) g,q~,~d t,~ul?,hness and crack pr,~pagalt, lrl reMslant'e, due h~ Ihe devialton ~t crack path, crack Nunling and/l~r branching, hy Ihe ~t plalelel and b~undarv /I layer 17-111, and ('~) a relatively hlw dut'Ithly and p(.. restslarlce Io h~w-cyele laligue t'rat-k iniltal.m, because tl is easy 1~ pr~)dut'e sites,'., c~mcenlralt~ns ~r dish,ca I.m pile-Lips al hq~undarles and Irlple p~finls in lilt' lanlellar slruclure I,-I L. F'~r a l,,ivt'n alhw, Ihc patltt'ular rn~)rphl~hLgy ~1 life lamt'llat" MrlJt'lurt' vanes wilh Ihe prot'essm~ t'~mdl II~)ns 171, Ihe anrleahng leriFp~.'lall.lrt' and Ihe c~Hdlng tale l I, ~,, 121, a,,llluslraledln Fig, I Relaltvelylhlck +t L'(II(tlllL'% alL' I(ulrled when the o.flln/?, lille I% I~)l) Ii~w afler /3 st~llJll~m Irt'allnenl, ~)1 when c~t)llng slal-ls idler a i~t'rnll(.I ~1 h(~hJing m life h~wcl (~ +/I)-I:_)llase lield (Equtaxed ~e grams are rarely ~fl~served in tins alhw, hecause ~)1 lift' citer'Is (~1 Ihe alhwlug elemenls trlw~h'ed ) In t'lHIIrasl, FnarlellSlll(' slruclures can lestill Ir~rll a VelV lasl o.~llng lale, palllculallv allel a hlfld in,L~ lempelnlure In tilt'/I ~)1 upper it + ['~ held (Fig. I(c)) When c(.~lt'd al an inlt~rlnedialc c(~htF!..,, tale Ii~m lhe:,e li¢lds, Ihe ,Mrut'lure may c~mst,sl i~l relaltvelv large t'~hmws ~)I ahgned Ihm . plalclel,,, wtlhm a prnln /J gram I.~undanv ~r dfflelenllv olncnlcd small c~h m~es (~t ~t pl;.llt'lel~, In a I~;.i,~kel we;ive nF~rpll~hL~.,,y F i.gute I(t~) represent,,; m(~le ~1 aFF ali!?ned ~t Ihan a haskel-weave ¢~ I~U2 I "~II~3/~-b/'~ TM IH) .1 lUL,k2 - E,l,,~.,r %equl.a All rq:hl,,, ru,,erved