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1、JOURNALOFAPPLIEDELECTROCHEMISTRY6(1976)477-483OntheelectrochemicalmachiningofsometitaniumalloysinbromideelectrolytesJ.BANNARDDepartmentofMetallurgyandMaterialsScience,UniversityofNottingham,Nottingham,U.K.Received22September1975Thecurrentefficiencywasdeterminedforthedissol
2、utionofanumberoftitaniumalloys(IMI115,230,318and550)inavarietyofelectrolytesbasedonpotassiumbromide.Itwasfoundthatthesematerialsingeneraldissolvedatefficienciessomewhatgreaterthan100%basedonthe4-valentdissolutionreac-tion:Ti-*Ti4+,althoughatlowercurrentdensitiestheefficien
3、cywasalittlelower.Usingsodiumchlorideasanadditivetothepotassiumbromide,slightimprovementsinthestray-currentattackpropertiesoftheelectrolyteandinthesurfacefinishwereobtained.Allthealloysdissolvedinthetranspassiveregionofthepolariz-ationcurvebutproducedetchedsurfaces,andevid
4、enceispresentedtoshowthatthedissolutionkineticsismodifiedbyacidgenerationattheanodeand,inthecaseofthetwo-phasealloys,alsobytheoccur-enceofdifferentialdissolution.1.Introductionwasnotrotationdependentshowingthatthedis-solutionprocesswasnotadissolution-precipitationTitaniuma
5、nditsalloysarebecomingincreasinglymechanismbutratherwasduetosurfaceadsorp-importantintheaerospaceindustriesbecause,intion.Titaniumowesitscorrosionresistancetotheadditiontoofferinggoodtensile,creepandcor-existenceofasurfacefilmoftenacious,passivatingrosionproperties,themate
6、rialshaveverylowden-oxide.Thiscorrosionresistancepresentsaproblemsitiesandveryhighstrength/weightratiosaretotheelectrochemicalmachinistinfindinganattainable.Problems,however,existwiththeelectrolytewhichwilldissolvethemetalatanmechanicalmachiningofthesealloysduetotheaccepta
7、blylowvoltage.Ithasbeenshown[6]thatformationofsurfacecracksandtheapplicationoftheorderofaggressivenessofthehalideionsto-electrochemicalmachining(ECM)hasconsiderablewardtitaniumisintheorderI->Br->C1->F-.potential.Thecorrosionresistanceoftitaniumhasbeenin-Astudyofthethermody
8、namicbehaviour[1]creasedevenfurtherbyalloyingwithPd[7],andoftitaniumshowsittobeabasemetal