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MechanicaIP｢ope｢tiesoTFriction-Sli｢WddedT11aniumJoint
HidetoshiFUjii,HideakiKato,Kazuhi｢oNakaIaandKiyoshiNogi
JoiningandWddingResearchlnstitute,OsakaUniversity
ll-IMihogaoka,Ibaraki,Osaka,567-0047,Japan
ABSTRACT
TheCommerciaIpuTitytitanium(cp-Ti)ｐＩ紐teswitha2mmthickness,werebutt-weIded
byITiclion-stirweIding(FSW).UsingaWaIIoytooI,FSWwasperIbnnedat200rpmand50-300
ｍｍ/min・Themechanicalpropertieso｢thejointswereevaIuatedusingtensiIetestsandVicke庵
micro-hardnesstests、ThemicroslructurewasobseTvedbyopticaImicmscopy（０Ｍ)，neld
emissioliscannmgelectronmicroscopy(l7E-SEM)andlransmissionelectronmicFoscopy(TEM)．
AneIect｢onback-scatleringpattem(EBSP)tecI1niquewasaIsousedintheFE-SEMlocIaTiIythe
crystaⅡogmphicにatu唾ｓｏ「themicrostTucIure・ThelensiIestTengtho「jointssignincantIy
increaseswiththeincreasingweldingspeedbecauselhegminsizedecreaseandthedislocation
densityincreases・ThctensiIestremgtho｢thespecimenweldedat200mm/minexcecdslhatorthe
basemetaI・andlhereIbTethespecimenliracturedinlhebasemetalduringthclensiIctests・
HowevemhedefbctswensIbrmedinＩｈｅｓｐｅｃｉｍｅｎａｔ３００ｍｍ/minleadinglodecTeaseintensiIe
stmcnglh・TheITiction-sti「weIdedcp-Timicrostrucluにconsistso｢だcrystaⅡizedgminswithmany
disIocalions,andthedisIocationdensityincrCasedwiththeincreasingweIdingspee。(decにasing
heatinput）FoTpureAIorIFsteel,にwdislocationsareobservedbecausｅｔｈｅにcoveryoccuTs
duringcooling・AccordingIy,ｔｈｅｃｈａｎｇｅｉｎｓｔｒengtboflhestirzonebyvalyingheaｔｉｎｐｕｔｓｉｓ
ｇ正alerlb｢cp-TilhanIbrpuにAIorIFstceI．
lNTRODUCTION
Theliriction-stirweldsoflowmeItingpoimtmaterialｓｓｕｃｌ１ａｓＡｌＩ=０，Ｍ85.6,Cu7have
beenwidelyinvestigatedsinceilsdeveIopmentbyTheWbldingII1slitute（TWI）inI991
ReccnIIy・WeldingresearchactivitiesonhighmcltingpointmateriaIssuchaslFsleel8，and
caTbonsteel9~'２，andstainlesssteeIl3~I6haveaIsostarted・Howeve風theにａｒｃ化ｗ「℃portson
weIdingofTiI7~2owhoscmeltingpointishigher【hanIhatofsteeI・LeeI7andRamirezIllsucceeded
inweldingpureTiplaにs(u-T1)andjointedT1-6AI-4V(u-6Ti),TespectivelyJohnI9investigaに。
the正siduaIstlEsso「FSWedTi-6Al-4VandReynoIdszoreportedlheIextuにｏｆｌｈｅＦＳＷｅｄＴＹ
ｍｅｔａｌ２１Ｓ(BTi）
Tiiswidelyusedinaerospaceindusｔｒｙｂｅｃａｕｓｅｉｔｉｓｎｏｔｏｎｌｙａｌｉｇｈｔｗｅｉghtandhigb
strenglhmateriaIbulalsohassuperiorheatresistance，Moreover,Ｔｉｉｓｕｓｅｄｉｎtheseawaler
environmentandfbrlluepetrochemistrydueloitshighcolTosionresistance､Inaddition,Ｔｉｉｓａｌｓｏ
Ｉ
5１
）
「
MechanicalProperIiesofF｢iction-StirWeIdedTitaniumJoinｔ
usedlbrbiomedicalimpIanIsmaleriaIsduetoilsgoodcompatibiIilytoＩｈｅｈｕｍａｎｂｏｄｙ,and
morcappIicalionsarccxpeclcdintheInture・ＷｈｅｎＦＳＷｉｓｐｅ｢IbrmcdIbrT1aIloys,atoolwilha
hightcmperaturcstrengthis】】ecessalybecauseofitsexceIlcntmechanicalpropertiesasinthe
previousstudyl7~'R･zo・AmatmosphereconlroIisaIsoneedcdbecauseTiisveryeasiIyoxidizcd
TheclystaIstn1clureofT1isahexagonaIclosedpacked(hcp)structureunder880oCandabody
cenlcrcdcubic(b6c)structu肥over880oCAsmnlIernumbcro｢sIipsystemsinIhehcpstruclu｢ｅ
ｔｈａｎｉｎｌｈｅｂｃｃｏｒｍｃｃｚｏstructuresmayalIbctthedefbrmationbehavio凪aIthoughfiiction-sti「
weIdinghasbeenaIにadyuscdIbrMg5も.ahcpmclal
lnthisstudy,thecp-Tiplateswercsuccessn1Ⅱylriction-stirweIded､TI1eefIbcto「the
weIdingcondilionsonthcmechanicalprope｢tiesandmicrostructureofthejoinlsisaIso
irwestiga(essoIhatthebeslweldingconditionscouldbedetermined．
ＥＸＰＥＲＩＭＥＮＴＡＬＰＲＯＣＥＤＵＲＥ
ＣｏｍｍｃＴｃｉａIpurityTipIatcswith300mmIcng(h，ｓ０ｍｍｗｉｄｔｈ，and2mmthickness，
wemebutt-weldedbyfrictio冊stirwcIdingThcchemicaIcomposition(wt％)ｏ『lhcbasemaleriaI
wasO､007％Ｃ,00013％Ｂ,ｑ０８％0,0.004％Ｎ,0.05％ＦｅａｎｄｂａｌａｎｃｅＴｉ・TmeuItimatetcnsile
slrenglh,02％ｐToo｢s(｢engtb,eIongalionandhardnessofbasematerialwere4I8MPa,３１１MPa，
39％･I46HvrcspectiveIy・AWalloyloolwithshouIderdiameleｒｏｒｌ５ｍｍ,probediametero｢６
ｍｍ,andprobcIengthof1､８ｍｍ､wasuscdatarolation｢ａｌｅｏｆ２００ｍｍ・Theweldingspeedwas
varicdat50-3００ｍｍ/mintoconlToIlheI1catinpuLDuringwelding,anArgaswasthrownaround
theloollbrtheatmosphemetopにventTi6ombeingoxidized・
Afterwelding，anclectricaIdischargemachinｅｗａｓｕｓｅｄｔｏｆｂｍｌｔｈｅｔｅｎｓｉＩｃｌｃｓｔ
ｓｐecimcmsandc｢oss-sectionsperpcndiculartolheweIdingdirectionIbrthehardnesslest・The
conngu｢ationandsizＣＯ「lhctransve応ctensiIcspecimenswereprcparedaccordingtoFigurcI，
whereRSandASdenolelheretreatingsideandadvancingside,respectiveIy,Ｔｈｅtype(a)in
Fig､lwasuscdIbralIspecimcns,andtype(b)wasusedlbrspecimcns200mm/minbecauscthe
type(A)spccimcnwasbrokenatthcbasemetaI。uringthelensiIetesls・Thecrossheadspeedwas
lmm/minduringthetcnsilctests・ThcVicke応microha｢dnessesweremeasuredunderaIoadｏｆ
0.98Nlbrl5sccondsaIongu1ecenle｢Iinesofthecross-scc(ionwiUBaspacingo｢０．５ｍｍ・
ＴｈｅmicTostructurcwasobscrvedbyfieIdcmissionscanningeIectronmicroscopy
(FE-SEM),transmissionelectronmicroscopy(TEM).Ａnclectronbackscatteringpattem(EBSP）
technipuewasalsousedinthel7E-SEMtoclariIylhecrystalIographic化aturesofthe
micmsIructurc・Anercross-sectionsofUlesIirzoneperpendicula「totheweldingdi唾ctionwere
cutoITfbTtheEBSRtheyｗｅにpoIishedbyemerypapersandelectTochemicaIpolishedusinga
twinjeteIectropoIishingmaChine
１１
５２．Characte｢izationandControIofInterfacesforHighQualityAdvancedMateriaIsIl
）
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一瞬’壜⑰，‐，．’‐，，．‐‐‐．●‐‐‐ｒ‐Ⅲ０■Ｂ■Ｉｌ０６１６ＰｔＢ６０１６００
MechanicaIPropertiesofFriction-StirWeIdedTitaniumJoint
▲．……，ｉｌｉ，陰…・
○討
一
■■４ｂ７ＩｄＶＤ・・ｄｕｐ■ＢＴＩ・ローⅡＩｄ４■・ｐ０ｉ凸ＢＢＴＰ５■十ｐｐ０ｔ６ｌＶＩｉ
Figu妃１.Conngurationandsizeo｢thelensiIelestsusedIblr(a)ａⅡspecimems(b)onlyspecimens
weldedat200mm/ｍin．
ＩＤ蕊蕊戸
◆
●
－－－－－-－-－－－■-－－－
◆
◆
FigKme〕ｓｈｏｗｓ【heVickersmicm
cross-3ec【ions・TluebrokenIineindicaIes
hardneＳＳＯ「ｔｌｌｅｂａｓｅｍｅｔａＭｎｃｏｍｍｏｎｗｉｔｈＵＤｅ
ｌensiIestrcmgth，theI1aTdnessincreaseswi(hthe
increasingweldingspeed（dec庇asmgheat
input).Thehardestvalueofaboul200I1vwas
obtainedat300mm/ｍin．
シエー⑩の①巨巨の工
haTdnessesalongthecenleTIinesonIhe
００００
５０５００
２２１１５０
WardnessDislributionso｢Joints
＄＄●
-10－５０５１０
DislanceiromweIdcenIer,ｍｍ
’０‐’－－，０００Ⅱロー■■００口。■０ⅡＤ０Ｉ００ｕ■ロロⅡＢ００９６口■１０１口■口Ⅱ■８Ｆ日■■ロ・‐』■ＰＧ‐Ⅱ‐Ｌ■Ⅱ口
Ｆｉｇｕｒｅ３・HardnessdisInbulionofcpTi．
Characterization
andControlofInterfacesforHighQualityAdvancedMateriaIsI１．５３
１１１「‐Ｉ
「
MechanicaIPropeItiesofFriction-StirWeIdedTitaniumJoint
TEMobservation
Figure4showsTEMbrigIulfieIdimagesatthecenにｒｏ「stirzone・Incommonwithlhe
EBSIDanaIysis,lhccIystalgrainsbecomeIinerwithIheincreasingweIdingspeed・Furthermorc，
thedisIocationdcnsilyincreascｄｗｉｌｈｌｈｃｉｎｃ正nsingweIdingspecd，ltisconsideredthatthc
disIocationsalahighweldingspcedwerenolrccognizedastheIowangleboundalyduelotI1c
smalIdiITbrenccinlhco｢ienlaIion・Ｔｈｉｓ「esuItcIearIyindicaleslhalcp-TiwHsdynamic
reclCsIaⅡizcdduTingweldingbygeUinggrea【dcaIofslrain．
Figure4・ＴＥＭｐＩ１ｏｔｏｇｒａｐｈｓｏｆＦＳＷｅｄｃｐ－Ｔｉ
ＣＯＮＣＬＵＳｌＯＮＳ
(1)CommercialpurityTi(cp-Ti)wassucccsslillIyfriction-sIirweldedat50mm/ｍｉｎｔｏ
３００ｍｍ/ｍin，ThemechaluicalpropertiesorIheFSWedcp-TiincrcaseswiUltheinc唾asillg
weldingspeedbecauselhegminsizedecreaseHandU1edisIocationdel1sityincreasesduelolhe
pIasticdefbrmationundertheweldingconditionSlnthisstudy，thehighesttensiIesl正ngthwas
oblaiIledat200mm/ｍin・becauseasmalIdc血ｃｔｗａｓｆｂｒｍｅｄａｔ３００ｍｍ/、in．
(2)llUthestirzoneofFSWed,cP-TiequiaxinIgraillswithIotsofdislocationswere
observed・indicatillgthatdynamic配c正slaⅡiza(ionoccurre｡．
ＡＣＫＮＯＷＬＥＤＧＥＭＥＮＴＳ
Ｔｈｅａｕｔｈｏ応'AfishtoacknowledgethellnancialsuppoTtofthcTolnayScienccFolmdatiom
aOmnt-im-AidfbrthecooperativeReseamchPrQjectofNalionwidejoint-UseResearchInslilutes
onI〕evelopmentBascofJoiningTecbnoｌｏｇｙｆｂｒＮｃｗＭｃｍⅡicGIassesandlmorganicMaterials，
``PriorilyAssistanceoftheFomlauonofWorldwideRellownedCenlersoTRcsea比h-The21st
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MaにriaIsDesign)“IiomtheMinislryo｢EducnlioLSp⑪rls,Culture,ScienceandTechnologyof
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５４．CharacterizationandControIofInterIacesforHighQuaIityAdvancedMaterialsII
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