简介:Stationaryshoulderfrictionstirlapwelding(SSFSLW)wassuccessfullyusedtoweld6005A-T6aluminumalloyinthispaper.EffectofpinrotatingspeedoncrosssectionmorphologiesandlapshearstrengthoftheSSFSLWjointsweremainlydiscussed.Resultsshowthatjointswithoutflashandshouldermarkscanbeobtainedbythestationaryshoulder.CrosssectionoftheSSFSLWjointpresentsabasin-likemorphologyandlittlematerialloss.Byincreasingtherotatingspeedfrom1000rpmto1600rpm,botheffectivesheetthicknessandlapwidthincrease,whilelapshearfailureloadfirstlydecreasesandthenincreases.Themaximumfailureloadof14.05kNisattainedwhen1000rpmisused.AllSSFSLWjointspresentshearfracturemode.
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简介:Nb-24Ti-18Si-2Al-2Hf-4CrandNb-24Ti-18Si-2Al-2Hf-8Cralloyswerepreparedbyarcmeltinginawater-cooledcrucibleunderargonatmosphere.Microstructuralcharacteristicsandoxidationresistanceofthealloysat1250℃wereinvestigated.Theresultsshowthat,whentheCrcontentis4at%,themicrostructuresconsistof(Nb,Ti)_(ss)andNb_5Si_3;asCrcontentincreasesto8at%,C14LavesphaseCr_2Nbisformed.Theisothermaloxidationtestsshowthattheoxidationkineticsofthetwoalloysfollowsimilarfeatures.Theweightgainsofthetwoalloysafteroxidationat1250℃for100hare235.61and198.50mg·cm~(-2),respectively.Duringoxidation,SiO_2,TiO_2,Nb_2O_5andCrNbO_4areformedatfirst.Then,Ti_2Nb_(10)O_(29)isformedafteroxidationfor20minandbeginstochangeintoTiNb_2O_7astheoxidationproceeds.SiO_2isformedassolidstateatfirstbutlaterevolvesintoglassystatetoimprovethecohesionofthescale.Afteroxidationfor100h,oxidationproductsconsistofSiO_2,TiNb_2O_7,Nb_2O_5andCrNbO_4.