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1、第14卷第6期中国有色金属学报2004年6月Vol.14No.6TheChineseJournalofNonferrousMetalsJun.2004文章编号:10040609(2004)06093906①AZ91D镁合金的快速凝固特征徐锦锋1,2,翟秋亚1,袁森1(1.西安理工大学材料科学与工程学院,西安710048;2.西北工业大学应用物理系,西安710072)摘要:采用单辊实验技术研究了AZ91D镁合金的急冷快速凝固特征。合金条带的凝固组织沿厚度方向分为3个晶区:近辊面细晶区、内部柱状晶区和自由面等轴晶区。XRD分析表明,在快速凝固条件下,L→α2Mg+β2Mg1
2、7Al12的共晶反应受到抑制,条带凝固组织由过饱和的单相α2Mg固溶体组成。TEM分析发现,α2Mg晶内和晶界上离散分布着的少量Mg17Al12质点,系α2Mg固溶体在连续冷却过程中脱溶析出的产物;α2Mg中存在着大量的位错线和位错胞。随着辊速增大,晶粒更加细化,柱状晶区减小,位错密度增大,条带强度增加,塑性降低,电阻率增大。关键词:镁合金;快速凝固;晶体生长;组织与性能中图分类号:TG146.2文献标识码:ARapidsolidificationcharacteristicsofmelt2spunAZ91DmagnesiumalloyXUJin2feng1,2,ZHA
3、IQiu2ya1,YUANSen1(1.SchoolofMaterialsScienceandEngineering,Xi′anUniversityofTechnology,Xi′an710048,China;2.DepartmentofAppliedPhysics,NorthwesternPolytechnicalUniversity,Xi′an710072,China)Abstract:Theribbonsofmelt2spunAZ91Dmagnesiumalloywiththicknessof4070μmandlengthof80100mmwereob2taine
4、dbyasinglerollerapparatus.Accordingtothegrainmorphology,therapidsolidificationmicrostructureofmel2tspunmagne2siumalloyisroughlysubdividedintothreecrystalzonesthroughthethicknesssection:thefineequiaxedzoneneartherollersu2rface,theinnercolumnarzoneandtheouterequiaxedzonenearthefreesurface.
5、TheX2rayanalysisresultsindicatethatthemi2crostructureofthealloyiscomposedofthesinglephaseα2MgsupersaturatedsolidsolutionandtheeutecticreactionofL→α2Mg+β2Mg17Al12issuppressedduetorapidsolidification.TEManalysisrevealsthatalittleamountofβ2Mg17Al12compound,whichdispersesinsidetheα2Mggrainsa
6、ndlocatesatthegrainboundaries,istheproductofprecipitationfromsupersaturatedα2Mgsol2idsolutionduringcoolingprocesses.Lotsofdislocationsanddislocationcellsexistinα2Mggrains.Withtheincreasingofrollervelocity,theα2Mggrainsbecomegraduallyfinerandtheinnercolumnarzonetendstoelimination,andthede
7、nsityofdislocationinsidethegrainsincreases,andhencethestrengthandelectricalresistivityofthealloyincreaseremarkably,whiletheelongationofthealloydecreases.Keywords:magnesiumalloy;rapidsolidification;crystalgrowth;microstructuresandproperties镁合金比强度高,比弹性模量大,导热性和成广泛应用于汽车、电子及航空
