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镁合金熔体15kHz超声净化工艺及超声凝固的物理模拟 Introduction Magnesiumalloysarewidelyusedinmanyapplicationsbecausetheypossessseveraladvantagesoverothermetallicmaterials.Theyarelightweight,haveexcellentmechanicalproperties,goodcastability,andarebiocompatible.However,magnesiumalloyssufferfromimpuritiesanddefectsthatcannegativelyaffecttheirpropertiesandperformance.Ultrasonicprocessinghasbeenwidelyinvestigatedtoimprovethequalityofcastmagnesiumalloys.Thepresentworkaimstoinvestigatetheeffectof15kHzultrasonicpurificationonthemicrostructureandmechanicalpropertiesofamagnesiumalloy. ExperimentalProcedure Acommercialmagnesiumalloycontaining5wt.%aluminumwasmeltedinaresistancefurnace.Themeltwasheldatatemperatureof720°Cfor30mintoensurehomogenization,thensubjectedtoultrasonicpurificationfor45minusinga15kHzultrasonictransducer.Theintensityoftheultrasonicwaveswas1.5W/cm2.ThemeltwasthencastinaDSCmoldtodeterminethesolidificationbehavior,andinasandmoldtoobtaintestspecimensformechanicaltesting.Thespecimensweresubjectedtotensiletestsatroomtemperatureandmicrostructuralanalysisbyopticalmicroscopyandscanningelectronmicroscopy. ResultsandDiscussion TheDSCresultsshowedthattheultrasonic-treatedmelthadasignificantlyhighernucleationrateandlowercrystallizationtemperaturecomparedtotheuntreatedmelt.Thisindicatesthattheultrasonicwaveshaveinducednucleationandpromotedheterogeneousnucleationinthemelt. Thetensiletestresultsshowedthattheultrasonic-treatedalloyhadahigheryieldstrengthandultimatetensilestrengthcomparedtotheuntreatedalloy.Theultimatetensilestrengthincreasedfrom204MPafortheuntreatedalloyto235MPafortheultrasonic-treatedalloy.Thisimprovementinmechanicalpropertiescanbeattributedtotherefinementofthemicrostructureduetoultrasoniccavitationanddegassing.Themicrostructuralanalysisshowedthattheultrasonic-treatedalloyhadafinergrainsizeandlowerporositycomparedtotheuntreatedalloy. Conclusions Thepresentworkinvestigatedtheeffectof15kHzultrasonicpurificationonthemicrostructureandmechanicalpropertiesofamagnesiumalloy.Theresultss