Tungsten(W)is a promising candidate material for the plasma-facing components in future fusion reactors.However,it has issues regarding the intrinsic brittleness as well as operational embrittlement.Tungsten fiber rei...Tungsten(W)is a promising candidate material for the plasma-facing components in future fusion reactors.However,it has issues regarding the intrinsic brittleness as well as operational embrittlement.Tungsten fiber reinforced tungsten(W_(f)/W)composites overcome these issues by using extrinsic toughening mechanisms.Due to neutron irradiation and high-temperature recrystallization during fusion operation,the ductility of the fibers may degrade over a long period of service.Therefore,it is necessary to investigate the fracture behavior of W_(f)/W composites with brittle fibers.In the present work,the tungsten fibers were embrittled by carbonization.Subsequently,the continuous brittle W_(f)/W composite with yttrium oxide(Y_(2)O_(3))interface was fabricated by the field-assisted sintering technology process.The microstructure of the prepared W_(f)/W composites was characterized.The fracture behavior and toughening mechanisms were discussed in detail based on the experimental results of 3-point bending tests and the corresponding finite element simulation.The composites show a pseudo-ductile fracture behavior.Cracks are hindered and deflected by the de-bonded fiber-matrix interface.The extrinsic toughening mechanisms of interface de-bonding,crack bridging,and fiber pull-out are active.This indicates the reinforcement concept still works even though all components in the W_(f)/W are brittle.展开更多
A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC...A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.展开更多
基金funded by the European Union via the Euratom Research and Training Programme(Grant Agreement No 101052200-EUROfusion)financially supported by the China Scholarship Council(CSC)(No.202007000034)。
文摘Tungsten(W)is a promising candidate material for the plasma-facing components in future fusion reactors.However,it has issues regarding the intrinsic brittleness as well as operational embrittlement.Tungsten fiber reinforced tungsten(W_(f)/W)composites overcome these issues by using extrinsic toughening mechanisms.Due to neutron irradiation and high-temperature recrystallization during fusion operation,the ductility of the fibers may degrade over a long period of service.Therefore,it is necessary to investigate the fracture behavior of W_(f)/W composites with brittle fibers.In the present work,the tungsten fibers were embrittled by carbonization.Subsequently,the continuous brittle W_(f)/W composite with yttrium oxide(Y_(2)O_(3))interface was fabricated by the field-assisted sintering technology process.The microstructure of the prepared W_(f)/W composites was characterized.The fracture behavior and toughening mechanisms were discussed in detail based on the experimental results of 3-point bending tests and the corresponding finite element simulation.The composites show a pseudo-ductile fracture behavior.Cracks are hindered and deflected by the de-bonded fiber-matrix interface.The extrinsic toughening mechanisms of interface de-bonding,crack bridging,and fiber pull-out are active.This indicates the reinforcement concept still works even though all components in the W_(f)/W are brittle.
基金This study was supported by the National Natural Science Foundation of China(Grant No.11975296)the Natural Science Foundation of Ningbo City(Grant No.2021J199)+3 种基金We would like to recognize the support from the Ningbo 3315 Innovative Teams Program,China(Grant No.2019A-14-C)Peter TATARKO gratefully acknowledges the financial support of the project APVV-17-0328this study was performed as part of the implementation of the project“Building-up Centre for advanced materials application of the Slovak Academy of Sciences”and ITMS project(Grant No.313021T081)supported by the Research&Innovation Operational Programme funded by the ERDF.
文摘A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.
