简介:Therulessuchasprocessparametersaffectingjointpropertiesandtheevolutionprincipleofweld'smicrostructurehavebeenresearchedbyadoptingdiffusionweldingprocesstoconnectSiCw/6061Alcomposite.ExperimentalresultsshowthatthereexistsacriticaltemperatureregionbetweensolidandliquidphaselineofSiCw/6061Alcomposite,andtheregionwillshrinkwiththeincreasingofweldingpressure.Whendiffusionweldingoccurredunderthecriticaltemperatureregion,weldingjointexhibitsbadpropertyofbonding,andthematrixandthereinforcementcan'tbondeffectively.Whendiffusionweldingoccurredinthecriticaltemperatureregion,thestrengthofweldingjointchangeswidelywiththevariationofweldingtemperature.Whenweldingtemperaturevariesin10℃,thestrengthofweldingjointwillchangeobviously.Onlywhenweldingtemperatureishigherthanthecriticaltemperatureregion,stablejointpropertiescanbeobtained.Simultaneouslythematrixandthereinforcementhasbetterinterfacialbondedindiffusionweldinginterface,andnoobviousinterfacereactionoccurred,andthusdiffusionweldingofSiCw/6061Alcompositecanbesuccessfullyrealized.
简介:ThemixturemodelofAl85Y4Nd4Ni7alloyinwhichapartiallycrystallizedamorphousalloyisregardedasananocompositeofanAlnanoparticleandaremainingamorphousmatrixispresented.Itsevolutionintheprocessofcrystallizationhasbeeninvestigatedbydifferentialscanningcalorimetry(DSC),X-raydiffraction(XRD),andtransmissionelectronmicroscopy(TEM).Mainlyamorphousstructurewithα-Alnanocrystalsembeddedintheamorphousmatrixhasbeenrevealedbymeltspiningthealloy.Crystallizationisshowedtooccurinthreestages:(1)crystallizationofamorphousalloyandformationofAlNiY,AlNdNiandunknowncrystallinephases,(2)formationofAl3YandAl3Nd,and(3)formationofAl3Ni.
简介:采用扫描电镜、能谱仪以及X射线衍射仪对具有WC+β(β为钴基粘结相)两相结构的WC-11Co-0.71Cr3C2-0.06RE(RE为含La、Ce、Pr、Nd的混合稀土)硬质合金烧结体表面进行观察与分析。结果表明,在烧结过程中合金中的La、Ce、Pr、Nd通过定向迁移与烧结炉内气氛中的S、O等杂质元素结合,在合金烧结体表面形成RE2S3(主)和RE2O2S(少量)弥散相。从合金中Cr3C2的热力学稳定性、Cr在Co中的溶解度特性以及稀土原子激发等3个方面,对稀土迁移活性的激发机制和稀土原子的定向迁移机制进行分析与讨论。
简介:Theeffectofnonmetallicinclusionsinthedropletofthestainlesssteelcoveredelectrodeontheporositywasresearched.Theresultshowsthatthenonmetallicinclusionsinthedropletarespherical,theircompositionisdifferentfromtheoneofslagandtheinclusionshavethecharacterof"innerformation".Whentheratioofrutiletoilmeniteinthecoatedmaterialisincreased,thedropletbecomescoarse,thecontentofnonmetallicinclusioninthedropletdecreases,andtheporositysensitivityintheweldmetalalsodecreases.Whentheratiooffledspartoilmeniteinthecoatedmaterialisincreased,thedropletbecomesfine,thecontentofnonmetallicinclusioninthedropletincreases,andtheporositysensitivityintheweldmetalincreases.WhentheratioofFe2O3toilmeniteinthecoatedmaterialisincreased,thedropletbecomesfine,thecontentofnonmetallicinclusiondecreases,whiletheporositysensitivitydoesnotreduce.
简介:WeldingresearchofA6N01S-T5aluminumalloyprofileforhigh-speedtrainwasdonebyusinglaser-MIGhybridweldingandMIGweldingindividually.Andtheweldappearance,weldingdistortion,mechanicalpropertiesofthejointsandmicrostructureswereanalyzed.Thetestresultsdemonstratedthathigh-efficientweldingfortheprofilecanbeachievedbyusinglaser-MIGhybridwelding,thespeedofwhichcanbeover3.0m/min.Theprocessinghadagoodgapbridgingability,evenifthegapofthebuttjointwasupto2.0mm,agoodweldappearancecanalsobegot.Whilethehybridweldingspeedwasgreaterthan2.5m/min,theweldingdistortionofthelaser-tandemMIGhybridjointswasjustabout33%ofthatoftheMIGjoints,buttheweldingefficiencywasover3timesofMIGwelding.Andtensilestrengthofthehybridjointswas85%ofthatofA6N01S-T5basemetal,9%higherthanthatoftheMIGjoints.Fatiguepropertieswastestedindividuallywithpulsedtensilefatiguemethodintheconditionof1×107lifetime.Thetestresultsdemonstratedthatthefatiguestrengthofthejointswasalittlelowerthanthatofbasematerial,whichcouldbeupto115MPa.Butthefatiguestrengthofhybridweldingjointswas107.5MPa,whichwas23%higherthan87MPaofMIGweldingjoints.
简介:介绍一种金属/合金的生产方法,用于恒电流和恒电位条件下由混合硫化物(Cu2S,NiS)生产Cu-Ni合金,称为直接电化学还原(DER)。研究槽电压和槽电流等工艺参数对还原得到的化合物组成的影响,以生产工业所需的CuNi10,CuNi20和CuNi30等合金。在1200°C下采用循环伏安法(CV)考察Cu2S和NiS在CaCl2熔体中的电化学行为。根据CV研究结果,Cu2S的阴极还原是一步完成的,即Cu2S?Cu;NiS的阴极还原则分两步进行,即NiS?Ni3S2?Ni。恒电流研究表明,在10A电流下电解15min,可制备出最高硫含量为320×10-6的高纯CuNi10合金。扫描电子显微镜以及能量色散X射线能谱和光学发射光谱(OES)测试结果表明,在2.5V电压下直接电化学还原15min,可制备出杂质含量低(即硫含量小于60×10-6)的所选成分的Cu-Ni合金。