一種AZ31鎂合金管材擠壓-剪切-擴徑成形工藝（英文）

一種AZ31鎂合金管材擠壓-剪切-擴徑成形工藝（文Extrusion-Shear-ExpansionFormingProcessforAZ31MagnesiumAlloyTubesInrecentyears,magnesiumalloyshavegainedincreasingattentionduetotheirhighstrength-to-weightratio,goodcastability,andexcellentcorrosionresistance.Amongdifferentprocessingmethods,extrusioniswidelyusedtoproducemagnesiumalloytubesduetoitshighproductivity,excellentproductquality,andfavorablemechanicalproperties.However,extrudedtubesoftenhavelimiteddimensionalaccuracyandsurfacequality,whichrequiresadditionalmachiningprocessesandincreasesproductioncosts.Inthisstudy,anovelextrusion-shear-expansionformingprocesswasdevelopedforAZ31magnesiumalloytubes,aimingtoimprovethedimensionalaccuracy,surfacequality,andmechanicalpropertiesoftheextrudedtubes.Theprocessconsistsofthreemainstages:extrusion,shearcutting,andexpansionforming.Theeffectsofprocessparametersonthemicrostructureevolution,mechanicalproperties,andsurfacequalityoftheformedtubeswereinvestigated.Theresultsshowedthattheextrusion-shear-expansionformingprocesscouldeffectivelyimprovethemechanicalpropertiesoftheAZ31magnesiumalloytubeswithoutsacrificingthedimensionalaccuracyandsurfacequality.Magnesiumalloyshavebeenwidelyusedinvariousapplications,suchasaerospace,automotive,andbiomedicalfields,duetotheirexcellentmechanicalproperties,goodcastability,andbiocompatibility.Inparticular,theAZ31magnesiumalloy,whichcontains3%aluminumand1%zinc,isapopularchoiceforstructuralcomponentsduetoitshighstrength-to-weightratio,goodcorrosionresistance,andfavorableprocessingproperties.Amongdifferentprocessingmethods,extrusionhasbeenwidelyusedtoproducemagnesiumalloytubesduetoitshighproductivity,excellentproductquality,andfavorablemechanicalproperties.However,extrudedtubesoftenhavelimiteddimensionalaccuracyandsurfacequality,whichrequiresadditionalmachiningprocessesandincreasesproductioncosts.Toaddresstheseissues,variousapproacheshavebeendevelopedtoimprovetheextrusionprocess,suchasoptimizingthediedesign,controllingtheextrusiontemperatureandspeed,andusinglubricantsandsurfacetreatments.However,theseapproacheshavelimitedeffectsonthemechanicalpropertiesandsurfacequalityoftheextrudedtubes.Inthisstudy,anovelextrusion-shear-expansionformingprocesswasdevelopedtoimprovethedimensionalaccuracy,surfacequality,andmechanicalpropertiesoftheAZ31magnesiumalloytubes.MaterialsandTheAZ31magnesiumalloytubeswerepreparedbyextrusion-shear-expansionformingprocess,whichconsistsofthreemainstages:extrusion,shearcutting,andexpansionforming.Theextrusionprocesswasconductedusinganextrusionmachinewithahollowdie,whichwasdesignedtohaveasquare-shapedcross-section.Theextrudedtubeswerethencutusingashearcuttingtooltoremovetheenddefectsandimprovethesurfacequality.Finally,thetubeswereexpandedusingatube-expandingmachine,whichformedthetubesintoaroundshapeandimprovedthemechanicalproperties.Theeffectsofprocessparameters,suchasextrusiontemperature,extrusionspeed,shearcuttingclearance,andexpansionratio,onthemicrostructureevolution,mechanicalproperties,andsurfacequalityoftheformedtubeswereinvestigated.Themicrostructureofthetubeswasanalyzedbyopticalmicroscopyandscanningelectronmicroscopy(SEM).Themechanicalproperties,suchastensilestrengthandelongation,weremeasuredusingamechanicaltester.Thesurfacequalityofthetubeswasevaluatedbysurfaceroughnessmeasurementsandvisualinspection.ResultsandTheextrusion-shear-expansionformingprocesswasfoundtosignificantlyimprovethemechanicalpropertiesoftheAZ31magnesiumalloytubescomparedtotheextrusionprocessalone.Theoptimalprocessparametersweredeterminedtobeanextrusiontemperatureof350°C,anextrusionspeedof8mm/s,aclearancebetweentheshearcuttingtoolanddieof0.2mm,andanexpansionratioof1.2.Themicrostructureanalysisshowedthattheextrudedtubeshadafine-grainedstructurewithsomeresidualgrainboundariesduetothelimitationsoftheextrusionprocess.However,aftertheshearcuttingandexpansionformingprocesses,thegrainboundariesweresignificantlyrefinedandthegrainsweremoreequiaxed,leadingtoamoreuniformmicrostructureandimprovedmechanicalproperties.Themechanicaltestingresultsshowedthattheextrusion-shear-expansionformingprocesssignificantlyincreasedthetensilestrengthandelongationoftheAZ31magnesiumalloytubescomparedtotheextrudedtubes.Specifically,thetensilestrengthincreasedfrom195MPato238MPa,andtheelongationincreasedfrom5.6%to10.2%.Theseimprovementswereattributedtotherefinedmicrostructureandthereductionofenddefectsandinternalstressesbytheshearcuttingandexpansionformingprocesses.Thesurfacequalityevaluationshowedthattheextrusion-shear-expansionformingprocesssignificantlyimprovedthesurfaceroughnessoftheAZ31magnesiumalloytubescomparedtotheextrusionprocessalone.Thesurfaceroughnesswasreducedfrom4.5μmto2.1μm,indicatingasmoothersurfaceandbettersurfaceintegrity.Inthisstudy,anovelextrusion-shear-expansionformingprocesswasdevelopedforAZ31magnesiumalloytubes,whicheffectivelyimprovedthedimensionalaccuracy,surfacequality,andmechanicalpropertiesoftheextrudedtubes.Theprocessco