az31b镁合金电子束焊接接头组织与疲劳断裂行为的分析

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1、万方数据太原理工大学硕士研究生学位论文RESEARCH0NMICROS删Cn爪EANDR6mGUEFRACTUREBEHAVIOR0FELECTRONBEAMWELDEDJOINTSOFAZ3lBMAGNESrL7MALLOYABSTRACTBasedonthelightweight，highstrength，easytorecycleandotherexcellentcharacteristics，magnesiumalloyhasakeadybeenwellknownastheprospect

2、ivegreenengineeringstructurematerialsinthe21stcentury,Thedevelopmentofstructuralmaterialsmustdependontheweldingtechnique．Vacuumelectronbeamwelding(EBW)technologyisverysuitableforweldingmagnesiumalloymaterialwhichhavealotofadvantagessuchashil曲energyden

3、sity,highpenetrationability,largeweldingspeed，vacuumstate，etc．Thecorrelativedataindicatesthat70％to90％offailureaccidentsinvolvingweldingstructuresarecausedbythefatiguefractureofweldedjoints．Thecrackinitiationandpropagationhaveanimprovementaffectonfatig

4、uepropertiesandlifeofweldingstructure．Therefore，fatiguepropertyandfatiguecrackpropagationrateofmagnesiumalloyelectronbeamsignificanceandpracticalvalue．weldingjointshasimportanttheoreticalInthispaper,themicrostructure，fatigueperformanceandfatiguecrackp

5、ropagationrateoftheAZ31Bmagnesiumalloyelectronbeamweldingjointwerestudied．TheresultsofEDSanalysisshowsthatthecontentofMgandZnreducedandtherelativecontentofA1andMnincreased．TheanalysisofX—RDindicatethatfusionzoneconsistsofsingle-phaseofa-Mg,thereisnoob

6、viousMgl7All2phase．ThemicrostructureofEBWseamismainlycomposedoffineequal-axedgrainsanddendriticcrystals，besides，thegrainsinHAZgrowedsli曲tly,butthewidthoftheHAZisverynarrow．Themicrohardnessresultsshowthattheaveragehardnessoftheweldedjointswas59．5HVo．1’

7、andthehardnessofheataffectedzonewas53．7HV0．1，thehardnessofthebasemetalwas54．6HVo．1，themicrohardnessvaluesofweldcross．sectionalmostnochangefromthetoptothebottom．V万方数据太原理工大学硕士研究生学位论文Tensiletestingofweldedjointsshowedthattheyieldstrengthandtensilestrengt

8、hofEBWjointsare144MPaand242MParespectively,whicharesli曲tlyhigherthanthatofthebasemetal．Thejointofstrength，plasticityandtoughnessareimproved．Tensilefracturemorphologymainlyfordimple，showstoughnessfracturecharacteristics．Itisconcludedthatthefati