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Enhanced thermal isolation in porous thermal barrier coatings by the formation of pore guided thermal-shock cracks

Science China(Technological Sciences) 2023年第4期66卷 1007-1017页

作者： ZHEN Yu WU KaiJin LIU MengQi ZHENG SongLin HE LingHui YU Yin NI Yong CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsCAS Center for Excellence in Complex System MechanicsUniversity of Science and Technology of ChinaHefei 230026China National Key Laboratory of Shock Wave and Detonation Physics China Academy of Engineering PhysicsInstitute of Fluid PhysicsMianyang 621900China

Pore structure design is an effective strategy to tailor the thermal isolation capability of thermal barrier coatings(TBCs).Pursuing optimal porosity is crucial to balance the requirements of thermal isolation and mechanical reliability since the pore structure shields thermal heat transfer but increases mechanical degradation.In this work,we investigate how thermal heat transfer couples with fracture propagation in porous TBCs by the using thermo-mechanical coupling phase field model for fracture.The simulated results show that cracks induced by thermal shock favor deflection that is sometimes perpendicular to the direction of heat flow.The thermal conductivity degradation by the transverse cracks significantly impedes thermal heat transfer,leads to enhanced reduction of the effective thermal conductivity of TBCs,decreases the average thermal stress of the substrate,and thus decreases the risk of the crack penetrating into the substrate.The numerical results demonstrate that the phase field method fully considering the thermo-mechanical interaction between cracks and pores can be a useful tool to improve the thermal isolation of porous TBCs under extreme thermal shock loadings through pore structure design.

关键词： Phasefield TBCs porosity thermal shock cracks

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Phase-field-lattice Boltzmann simulation of dendrite growth under natural convection in multicomponent superalloy solidification

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Rare Metals 2020年第2期39卷 147-155页

作者： Cong Yang Qing-Yan Xu Bai-Cheng Liu Key Laboratory for Advanced Materials Processing Technology(Ministry of Education) School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

The thermosolutal convection can alter segregation pattern,change dendrite morphology and even cause freckles formation in alloy solidification.In this work,the multiphase-field model was coupled with lattice Boltzmann method to simulate the dendrite growth under melt convection in superalloy solidification.In the isothermal solidification simulations,zero and normal gravitational accelerations were applied to investigate the effects of gravity on the dendrite morphology and the magnitude of melt flow.The solute distribution of each alloy component along with the dendrite tip velocity during solidification was obtained,and the natural convection has been confirmed to affect the microsegregation pattern and the dendrite growth velocity.In the directional solidification simulations,two typical temperature gradients were applied,and the dendrite morphology and fluid velocity in the mushy zone during solidification were analyzed.It is found that the freckles will form when the average fluid velocity in the mushy zone exceeds the withdraw velocity.

关键词： Dendrite growth Natural convection Phasefield model Lattice Boltzmann method

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