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《7055鋁合金熔體超聲處理與凝固研究》由會(huì)員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在學(xué)術(shù)論文-天天文庫。
1、摘要在材料制各和加工過程中引入外場增強(qiáng)對過程和材料組織結(jié)構(gòu)的調(diào)控是材料研究的前沿領(lǐng)域。本文研究了A卜zn—Mg—cu系超高強(qiáng)鋁合金超聲熔體處理和凝固的工藝方法，結(jié)合鑄錠宏觀與顯微組織及其力學(xué)性能的考察，研究了作用效果和機(jī)理。對7055鋁合金熔體凝固過程作超聲處理，發(fā)現(xiàn)超聲作用可細(xì)化晶粒，結(jié)晶方式由樹枝晶向等軸晶轉(zhuǎn)變，凝固組織顯示了半固態(tài)加工凝固的特征，但鑄錠含少量夾雜和氣孔。對7055鋁合金熔體作超聲處理后進(jìn)行重力模鑄，鑄錠組織觀察表明，在630℃～710℃的溫度下對熔體作超聲處理均可細(xì)化鑄錠晶粒。熔體經(jīng)超聲處理鑄態(tài)均勻化合金與未經(jīng)超聲處理的合金相比，布氏
2、硬度提高10％，伸長率由3．8％提高到7．7％，電導(dǎo)率和抗拉強(qiáng)度也有所提高。7055鋁合金熔體超聲處理后半連鑄，與熔體未經(jīng)超聲處理相比，鑄錠凝固組織均勻，缺陷少，宏觀開裂現(xiàn)象被抑制，且合金電導(dǎo)率、抗拉強(qiáng)度和伸長率有所提高。采用水冷變幅桿對7055鋁合金熔體作超聲處理，可消除熔體對變幅桿的浸蝕，而且半連鑄鑄錠凝固組織更加均勻，均勻化后合金的布氏硬度、電導(dǎo)率及抗拉強(qiáng)度和伸長率均較無水冷變幅桿超聲熔體處理的鑄錠有所改善。關(guān)鍵詞超聲熔體處理，超聲凝固，水冷變幅桿，半連鑄，均勻凝固ABSTRACTIt’s眥advancedtechnologyfortheintrod
3、uctionofoutfieldinthefabricationandprocessingofmaterialstocontroltheprocessingandthestmctureofthematerials．ndspaperinvestigatedtheeffectsofultrasonictreatmentofmeltandultrasonicsolidificationonAl-Zn—Mg—Cuseriesultrahighstrengthaluminumalloys，Boththemacro—andmicro-structureofthecas
4、tingotswereanalyzed，theirmechanicalpropertieswerestudiedtodiscusstheeffectsandmechanismsoftlleultrasonictreatment．Ultrasonictreatmentduringsolidificationof7055aluminumalloyresultsindendrite-freegrainstructureandleadstothefiningofgrainstructure．Thestructureofthecastingotspresentsth
5、echaracterofsemisolidsolidification．Ultrasonictreatmentofthe7055aluminumalloymeltbeforegravitycastingfinedthegrainstructureinthecastatthetemperaturerangefrom630。Cto710"C．Comparedtothecastingotswithoutultrasonicmelttreatment，hardnessofhomogenizedas—castalloyincreasesby10％anditselon
6、gationincreasesfrom3．8％t07．7％．meanwhileitselectricconductivityandtensilestrengthimprovesrespectively．Thestudyonultrasonicmelttreatmentofthe7055aluminumalloyfollowedbysemi-continuouscastingconfirmsthatultrasonicmelttreatmentcoulduniformthecaststructure，andreducethedefectsinthecast，
7、especiallysuppressesthecracking，meanwhileimprovestheelectricconduct。ivity、tensilestrengthandelongation．Bydesigningawater-cooledvibratorandapplyingitintheultrasonicmelttreatmentofthe7055aluminumalloys，thecorrosionofthevibratorWaseliminated．mestructureofthe7055aluminumalloycastbecom
8、esmoreuniform．Thehardness，electri
