TiAl与钛合金的扩散连接研究

分类号密级UDCBEIJINGINSTITUTEOFTECHNOLOGY硕士学位论文TiAl与钛合金的扩散连接研究　　毕建勋导师姓名(职称)郑秀华教授答辩委员会主席李树奎研究员论文答辩日期2006.03.03申请学科门类工科申请学位专业材料加工工程2006年03月03日北京理工大学硕士学位论文摘要TiAl金属间化合物具有比重轻、比强度高以及良好的高温力学性能和抗氧化性等优点，被认为是航空航天和军工领域昀有应用前景的高温结构材料。在实际应用中，如火箭、坦克机车的涡轮发动机部件中，与钛合金的连接问题是不可避免的。可以说，连接技术是推广应用TiAl金属间化合物的关键技术之一。由于TiAl室温延性较低，焊接热裂趋向大，采用熔焊方法得到的焊缝区域与基体组织不同，导致接头性能和母材存在较大差异，此外由于异种材料连接时熔点和线膨胀系数差别、焊后残余应力大等因素，故TiAl金属间化合物的熔焊性能较差。而扩散连接正是解决上述问题的有效途径之一。本研究主要分为两部分工作：(1)对德国GKSS研究所的TAB/Ti-6242和TNB/Ti-6242两种扩散连接接头进行纳米硬度和弹性模量的测定，对比和分析工艺参数和不同材料对扩散连接接头微区力学性能的影响；(2)选取两种目前在国防领域内有应用前景的钛合金TA15和TC4和α2+γ双相TiAl金属间化合物作为扩散连接研究对象，选取六组工艺参数对TiAl金属间化合物与两种钛合金分别进行扩散连接，温度参数分布在钛合金β转变温度两侧，焊后进行时效处理以进行对比。通过扫描电镜、能谱分析和显微硬度等方法对接头显微组织、化学成分、形成机理和接头力学性能进行分析。研究结果表明，在850℃/20MPa/30min扩散连接条件下TAB/Ti-6242接头纳米硬度和弹性模量平均水平达到昀大，而在900℃/10MPa/30min工艺参数条件下TNB/Ti-6242接头的纳米硬度高于TAB/Ti-6242接头的纳米硬度；在钛合金与TiAl金属间化合物扩散连接均形成了无缺陷的可靠接头，并在接头区域形成两个新生界面层，在钛合金一侧为单一的α相层，在TiAl一侧则形成了α2相层。扩散层的宽度随着温度升高、压力增大或时间的延长而有所增大。从显微硬度而言，对于TA15/TiAl扩散连接，参数950℃/10MPa/30min或950℃/5MPa/30min(时效处理)为昀佳工艺参数，并且可以考虑采用时效处理方法提高接头力学性能；对于TC4/TiAl的扩散连接，昀优参数可选择950℃/5MPa/30min。关键词：TiAl金属间化合物，钛合金，扩散连接，纳米硬度，显微硬度1北京理工大学硕士学位论文AbstractWithmanyoutstandingpropertiessuchaslowdensity,highspecificstrength,excellenthigh-temperaturestrengthandoxidationresistance,TiAlintermetallicshaveahighpotentialtobeimportanthigh-temperaturestructuralmaterialsinaeronautics,astronauticsandmilitarydomains.Fortheirapplicationsathightemperaturesasrocketortankengine’sturbineparts,thebondingofTiAlwithtitaniumalloysisunavoidableandtheabilitytojoinTiAltotitaniumalloysisrequired.Thelowductilityintheroomtemperature,andtheoccurrenceoftheweldinghot-cracksofTiAlbasedalloysaswellasthedifferencesbetweenthewelding-linezoneandthebase-materialbyfusionwelding,leadtothepropertiesofthejointsmuchdifferentfromthebasematerials.Inaddition,thecontrastoflinear-expandcoefficientandmeltingpointsbetweenthedifferentmaterialswithhighresidualstressesmakefusionweldingtobenotsuitableforthejoiningofTiAlintermetallics.TheexistingliteraturehasdemonstratedthepossibilitytojoinTiAltoitselfandtitaniumalloysbydiffusionbonding.Presentresearchincludestwoparts:(1)testingofnano-hardnessandmodulusofTAB/Ti-6242andTNB/Ti-6242jointsprovidedfromGKSSinGermanytogetbetterunderstandingoftheinfluenceofmaterialfactorsanddiffusionbondingparametersonmicro-mechanicalpropertiesofthejoints;(2)diffusionbondingofTA15/TiAlandTC4/TiAlwithsixsetsofbondingparametersandagingtreatmentofjointsafterbonding.ThemicrostructuresandchemicalcompositionprofilesofalljointswereinvestigatedbySEM/BSE,EDX,meanwhilemicro-hardnessweremeasured.Itisfoundthatthenano-hardnessandmodulusvaluesofTAB/Ti-6242jointsdiffusionbondedat850/20MPa/30min℃arethehighest,andhowever,underbondingconditionof900/10MPa/30min℃,thenano-hardnessoftheTNB/Ti-6242jointishigherthanthatoftheTAB/Ti-6242joint.Theresultsalsoshowthatsoundjointswithoutanyporesorcrackscanbeproducedatallbondingparametersinvestigated.Therearetwonew-phaselayersformedatthediffusionbondingzone,asingleα-layerneartitaniumalloysandaα2layerclosetoTiAlintermetallics.Thewidthofthediffusionbondingzoneincreaseswiththeincreaseoftemperature,pressureandtime.TheTA15/TiAljointsat950℃/10MPa/30minor2北京理工大学硕士学位论文950℃/5MPa/30min(aging)haverelativehighermicro-hardnessvaluescomparedwiththoseoftheotherjointsofTA15/TiAlandthehardnessofTC4/TiAljointat950℃/5MPa/30minishigherthanothers.Keywords:TiAlintermetallics,Titaniumalloys,Diffusionbonding,Nano-hardness,Micro-hardness.3北京理工大学硕士学位论文目录第一章绪论··························································································································11.1TiAl金属间化合物与钛合金简介···········································································11.1.1TiAl金属间化合物简介·················································································11.1.2钛合金简介···································································································11.2扩散连接综述······································································································31.2.1扩散连接定义·······························································································31.2.2扩散连接分类································································································41.2.3扩散连接特点·······························································································51.2.4扩散连接机理································································································51.2.5扩散连接的主要参数与影响因素·······························································61.3TiAl金属间化合物扩散连接研究现状·····························································71.3.1TiAl金属间化合物的扩散连接·····································································71.3.2TiAl金属间化合物扩散连接研究现状·························································81.3.3存在问题与展望·························································································141.4选题目的和意义··································································································15第二章TiAl/TA15与TiAl/TC4扩散连接研究·······················