TC4钛合金微观组织与绝热剪切敏感性关系研究

分类号密级UDC硕士学位论文TC4钛合金微观组织与绝热剪切敏感性关系研究胡阳光导师姓名(职称)才鸿年教授答辩委员会主席刘颖教授申请学科门类工学论文答辩日期2008年6月15日申请学位专业材料加工工程2008年6月15日StudyontherelationbetweenmircostructureandadiabaticshearsensitivityinTi-6Al-4VHuYang-guangAdvisor:Prof.CaiHong-nianSpecialty:MaterialsScienceSchoolofMaterialsScienceandEngineeringBeijingInstituteofTechnologyJune2008研究成果声明本人郑重声明：所提交的学位论文是我本人在指导教师的指导下进行的研究工作获得的研究成果。尽我所知，文中除特别标注和致谢的地方外，学位论文中不包含其他人已经发表或撰写过的研究成果，也不包含为获得北京理工大学或其它教育机构的学位或证书所使用过的材料。与我一同工作的合作者对此研究工作所做的任何贡献均已在学位论文中作了明确的说明并表示了谢意。特此申明。签名：胡阳光日期：2008年6月15日关于学位论文使用权的说明本人完全了解北京理工大学有关保管、使用学位论文的规定，其中包括：①学校有权保管、并向有关部门送交学位论文的原件与复印件；②学校可以采用影印、缩印或其它复制手段复制并保存学位论文；③学校可允许学位论文被查阅或借阅；④学校可以学术交流为目的,复制赠送和交换学位论文；⑤学校可以公布学位论文的全部或部分内容（保密学位论文在解密后遵守此规定）。签名：胡阳光日期：2008年6月15日导师签名：才鸿年日期：2008年6月15日北京理工大学硕士学位论文摘要本文主要研究了四种典型微观组织（等轴组织，双态组织，层片组织和淬火时效组织）TC4钛合金的动态力学行为特性和绝热剪切敏感性。对双态组织和层片组织帽形试样中绝热剪切带（ASB）的演化机制进行了分析。研究表明：四种组织TC4钛合金均没有明显的应变强化效应，有一定的应变率强化效应。随着应变率增加，四种组织TC4钛合金的应变率强化效应均逐渐减小，其中层片组织的降低幅度最大，双态组织的降低幅度最小。对四种组织的绝热剪切敏感性进行比较后发现其从大到小顺序为：层片组织，淬火时效组织，等轴组织，双态组织。分析表明，通过调节热处理制度，获得微观组织中板条α相与等轴α相具有合适比例的双态组织能得到具有最低绝热剪切敏感性的TC4钛合金组织。通过对双态组织和层片组织的帽形试样进行控制条件强迫剪切实验，得到了两种组织中处于不同发展阶段的ASB。研究表明：从51µs到80µs这个阶段，双态组织中ASB的形成原因是ASB中晶粒的拉长和碎化；层片组织中ASB在51µs到60µs这个阶段处于晶粒的拉长和碎化阶段，而从60µs到80µs这个阶段，ASB中以碎化的亚晶为核，发生了动态再结晶。经分析，造成双态组织和层片组织中ASB在同样加载条件下，演化机制不同的原因为组织中晶粒的形状和尺寸差异过大，细小的板条状晶粒更有利于ASB中形成细小的亚晶，而粗大的等轴晶粒明显不容易细化、破碎。层片组织在同样的加载条件下形成的ASB比双态组织发展得更为充分，因此，层片组织比双态组织表现出比更大的绝热剪切敏感性。关键词：钛合金；绝热剪切带；绝热剪切敏感性；动态再结晶I北京理工大学硕士学位论文ABSTRACTThispapermainlystudiedthedynamicmechanialperformanceandadiabaticshearsensitivityofTC4titaniumalloywhichistreatedtofourtypicalmicrostructures:equiaxedmicrostructure,bimodalmicrostructure,lamelarmicrostructureandquenchingageingmicrostructure.theevolutionmechanismofAdiabaticshearbands(ASB)inhat-typesampleofbimodalmicrostructureandlamelarmicrostructureisanalysed.Theresearchindicatedthatfourtypetitaniumalloydon’tshowdistinctstrainstrengtheningeffect,andshowsomestrainratestrengtheningeffect.withtheincreasingofstrainrate,thestrain-ratestrengtheningeffectoffourtypeTC4titaniumalloyisdecreasing,lamelarmicrostructurehavethemostquickydecreasingrate,bimodalhavetheleast.Theadiabaticshearsensitivityoffourtypemicrostructrearrangefromstrongtoweak:lamelarmicrostructure,quenchingageingmicrostructure,equiaxedmicrostructure,bimodalmicrostructure.it’sindicatedthatadjustingtheproportionoflath-shapedmatrixandequiaxialmatrixbyheattreatingcanobtainthemostweakadiabaticshearsensitivityinTC4titaniumalloy.ThrouththeconditioncontrollingforcedshearexperimentbySplitHopkinsonPressBar(SHPB)ofhattypesampleofbimodalmicrostructureandlamelarmicrostructure,obtainingthedifferentevolutionstageASBsinthetwomicrostructures.Thestudiesindicatedthat:form51µsto80µs,theevolutionmodeofASBinbimodalmicrostructureareprolonging、breakingofcrystalgrain.DislocationplayaroleintheevolutionofASBinbimodalmicrostructure.from51µsto60µs,theevolotionmodeofASBinlamelarmicrostructureareprolonging,breakingofcrystalgrain,butfrom60µsto80µs,dynamicrecrystallizationoccurredintheASB,thenucleationisthebreakingsuperfinesubgrain.afterafteranalyse,themainreasonforthedifferentevolutionmechanisminthetwomicrostructuresarethedifferentshapeandsizeofgrains,thefinelath-shapedgrainismoreeasytobreakintosubgrainswhicharethenucleationsofdynamicrecrystallization,thebigequiaxedgrainsarehardtorefiningandbreak.TheASBinlamelarmicrostructureevolutionmoresufficientlythebimodalmicrostructureunderthesameloadingcontion,soII北京理工大学硕士学位论文lamelarmicrostructureismoreeasytoformingASBthanbimodalmicrostructure.Keywords:Titaniumalloy,Adiabaticshearband(ASB),Adiabaticshearsensitivity,dynamicrecrystallizationIII北京理工大学硕士学位论文目录摘要·································································································································IABSTRACT·······················································································································II目录·······························································································································IV第1章前言······················································································································11.1TC4钛合金简介及钛合金军事应用······························································11.1.1TC4钛合金及其热处理简介·································································11.1.2钛合金在战斗部壳体上的应用现状···················································31.2绝热剪切现象·····································································································41.3绝热剪切带中微观组织演化研究现状··························································51.4本课题的研究的目的与意义·········································································13第2章材料和实验·······································································································152.1实验材料···········································································································152.2分离式HOPKINSON压杆(SHPB)简介·························································172.3动态压缩实验···············································