Modification effect of pure rare earth metal La on as-cast hypereutectic Al-17%Si alloys

1　INTRODUCTIONImprovedpropertiesandlightweightareincreas inglybecomingthemaingoalsofautomotiveandaerospaceindustries[1] .Forthesakeofachievingthesecharacteristics,manyeffortshavebeenfocusedonaluminumalloysandtheirpropertiesundersevereconditions.Applyingaluminumalloystoautomotivepartssuchaspistons ,cylinderliners ,engineblocksanddifferentpartsofthermalmotors ,combinativeimprovementofthestrengthtomassratio ,wearre sistance,heatresistance ,andlowheatexpansionisanimportantgoal[2 ] .Al Siallo…     

Microstructures of worn surface and wear debris of as-cast Al-17Si-xLa alloys under unlubricated conditions

1　INTRODUCTIONAl Sialloyshavebeenwidelyusedasthetribo logicalcomponentsininternalcombustionenginesfortheirhighresistancetowearandseizure ,andhighspecificstrength .Therefore ,thewearbehaviorsofAl Sialloysagainstvariouscounterfaces (typicallyacastironcounterface)havebeeninvestigatedexten sively[16 ] .Themutualtransferofmaterialbetweentwoslidingcounterfacesisinvariablyinvolvedinawearprocess ,especiallyunderdryorunlubricatedconditions ,leadingtotheformationofamechanicallymixedlayerattheworn…     

Al-17Si-xLa合金室温阻尼-应变振幅行为研究

研究了过共晶Al-17Si-xLa合金在室温下不同频率的阻尼一应变振幅行为。Al-17Si-xLa合金通过常规的铸造和喷射成形工艺制备,并采用动态热机械分析仪(DMTA)对其阻尼行为进行研究。结果表明大多数铸态以及喷射成形态Al-17Si-xLa合金显示了类似的室温应变振幅-阻尼行为：即随振幅的增加,阻尼先不增大,然后明显升高出现阻尼峰,最后回落,可以用G-L位错阻尼理论加以解释;铸态下添加La对Al-17Si合金的阻尼行为影响不大,过量La(6％(质量分数))添加明显降低阻尼性能。La的添加明显提高喷射成形态Al-Si合金阻尼性能。喷射成形态Al-Si合金的阻尼明显比相应铸态Al-Si合金的阻尼高。     

应变振幅对过共晶Al-Si-xLa合金室温阻尼行为的影响

研究了过共晶A1—Si—xLa合金在室温下不同频率的阻尼-应变振幅行为。A1—Si合金通过常规的铸造和喷射成形工艺制备，并采用动态热机械分析仪(DMTA)对其阻尼行为进行研究。结果表明：大多数铸态以及喷射成形态过共晶A1—Si—xLa合金显示了类似的室温应变振幅-阻尼行为，即随振幅的增加，阻尼先不增大，然后明显升高出现阻尼峰，最后回落，此行为可以用G—L位错阻尼理论加以解释；铸态下添加La对A1—17Si合金的阻尼行为影响不大，过量La(6％)添加明显降低阻尼性能，而La的添加明显提高喷射成形态Al-Si合金阻尼性能；Si含量高的铸态A1—25Si合金的阻尼比铸态A1—17Sl合金的阻尼降低，所需振幅大，而喷射成形态A1—Si合金的阻尼明显比相应铸态A1—Si合金的阻尼高。     

微量Mg,Ag对Al—Li—Cu系合金性能和组织的影响

在ＡＡ２１９５标准成分基础上,通过加入微量元素Ｍｇ和Ａｇ,研究了各合金薄板材料在１８０℃不同时效时间下的室温拉伸性能和湿微组织特征,实验结果表明：单独加入Ｍｇ和单独加入Ａｇ对Ａｌ－Ｌｉ合金都有强化效果,但Ａｇ的单独作用显然比Ａｇ要大得多。Ｍｇ和Ａｇ共同加入则产生最大的强化效应,这说明Ｍｇ和Ａｇ之间有强烈相互作用。     

Influence of La on microstructures of hypereutectic Al-Si alloys

1　INTRODUCTIONThemicrostructureofhypereutecticAl Sialloys ,preparedbyconventionalcastingroutines ,usuallyconsistsofcoarseSicrystals[112 ] ,leadingtothepoorextrudability ,machinability ,strengthandductili ty[1315] .Therefore ,structuralmodificationmustbedonethroughtwo generalways :1)alloyingaddi tions ,and /or ;2 )syntheticalternatives .Accordingtothedimensionalconditionofaneffectivemodifier ,theradiusratiooftheagenttoSishouldbeabout1.6 5 [16 ] ,La ,withtheratioof 1.5 9,ispossiblycon sid…