蠕变本构理论

jiecun-liang高温蠕变本构及其微观机理扩散蠕变机理扩散蠕变机理位错运动机理位错运动机理高温蠕变本构高温蠕变本构010203jiecun-liang高温蠕变：温度应力mTT5.0s恒应力，初始蠕变阶段稳态蠕变阶段加速蠕变阶段恒应变速率初始蠕变阶段稳态蠕变阶段加速蠕变阶段constconstssssjiecun-liangnA1)exp(2RTQAc)exp()(3RTQEAcnjiecun-liang滑移增值攀移湮灭位错运动机理Frank-Read源异号刃位错攀移jiecun-liang位错运动机理低温：外应力内应力高温：外应力+热激活内应力ijiecun-liang热激活滑移与回复蠕变000,,)/ln(TTTTabkTFii，)/ln(00kFT其中：T≤T0，热激活滑移，外力克服长程内应力和一部分局部障碍T=T0，回复控制蠕变，外力只需克服长程内应力jiecun-liang第一个回复蠕变模型第一个回复蠕变模型WeertmanIvanovBlumWeertmanIvanovBlumWeertman考虑亚晶界McLeanBurtonMcLeanBurton亚晶内网络回复蠕变理论)exp()(3RTQkTGbGAsdnssn≈5?jiecun-liangOrowan方程(位错运动与宏观变形关系)考虑位错总体运动：进而：考虑滑移-攀移过程：313dxNb3212dxdxdxNdx31dxdxN113bdxbl13bvdVLcdVbLcjiecun-liangweertman模型位错源密度×每个源的偶极子数目×一个位错环平均长度dLdMLLdLM2)22)((12dML21d2/13)(MddbVdVbLccdGbGbdkTbDVc3kTGbGMbD35.45.05.3jiecun-liang考虑亚晶界模型Ivanov本征5次Blumweertman一：刃位错可通过螺位错交滑移湮灭，而蠕变速率仍受攀移控制二：螺位错可滑移足够长距离，停止准则-超割阶达到临界长度┴┴┴┬┬┬L2/HH31LHLNHLNL14/1HVLHLdVbLccbkTbDVc3kTGbGbD332)(GbH┴┴┴┬┬┬21HNLHLHLN21kTGbGbD342)(┴┴┴┴┴┬┬┬┬┬31LHLNNGbLNHLNNHdbkTDbNVc3kTGbGbLbD33302kTGbGbD352jiecun-liangMcleanBurton基于亚晶内位错网络的模型Friedel理论：kTGbDdtd32GbMclean假定：回复速率：324GkTDbdtd加工硬化系数：2GhBailey-Orowan方程：33238GkTGbbDhr2/由orowan方程bv根据硬化-软化动态平衡22)/exp(1cgMMGccrittt2认为：]1ln[12132GbMGbtgcrit322GbMtcc332GkTGbbDAjiecun-liangBoJakobsenetal.Formationandsubdivisionofdeformationstructuresduringplasticdeformation.Sciencevol31212may2006jiecun-liang扩散蠕变特点：温度高，应力低，机制：受拉处空位浓度高，受压空位浓度低，空位梯度导致原子定向扩散kTdD2其中D为自扩散系数，Ω为一个原子体积，djiecun-liangS.M.KeralavarmaandA.A.Benzerga.High-temperaturediscretedislocationplasticityJournaloftheMechanicsandPhysicsofSolids82(2015)1–22M.E.Kassner.Five-power-lawcreepinsinglephasemetalsandalloys.ProgressinMaterialsScience45(2000)1-102jiecun-liangA—位错滑移B—幂率蠕变D—Nabarro-Herring蠕变E—弹性晶粒尺寸为100μm铜的本构关系总图M.E.Kassner.Five-power-lawcreepinsinglephasemetalsandalloys.ProgressinMaterialsScience45(2000)1-102jiecun-liangInsituSEMimagingattemperaturesashighas1450°C困难：高温下大量光子电子逸出导致信噪比降低低来源：1—电阻丝2—样品表面3—氧化铝罩上表面解决方案：1—氧化铝罩2—屏蔽系统3—探测器JournalofElectronMicroscopy51(6):347–352(2002)jiecun-liangjiecun-liangjiecun-liang