B_(4)C/Al composites are widely utilized as neutron absorbing materials for the storage and transportation of spent nuclear fuel.In order to improve the high-temperature mechanical properties of B_(4)C/Al composites,i...B_(4)C/Al composites are widely utilized as neutron absorbing materials for the storage and transportation of spent nuclear fuel.In order to improve the high-temperature mechanical properties of B_(4)C/Al composites,in-situ nano-Al_(2)O_(3)was introduced utilizing oxide on Al powder surface.In this study,the Al_(2)O_(3)content was adjusted by utilizing spheroid Al powder with varying diameters,thereby investigating the impact of Al_(2)O_(3)content on the tensile properties of(B_(4)C+Al_(2)O_(3))/Al composites.It was found that the pinning effect of Al_(2)O_(3)on the grain boundaries could hinder the recovery of dislocations and lead to dislocation accumulation at high temperature.As the result,with the increase in Al_(2)O_(3)content and the decrease in grain size,the high-temperature strength of the composites increased significantly.The finest Al powder used in this investigation had a diameter of 1.4μm,whereas the resultant composite exhibited a maximum strength of 251 MPa at room temperature and 133 MPa at 350℃,surpassing that of traditional B_(4)C/Al composites.展开更多
To investigate the influence of W and Al on the microstructure and mechanical properties of a high-W superalloy,the Thermo-Calc calculation was utilized to simulate the microstructure with various W and Al contents.Th...To investigate the influence of W and Al on the microstructure and mechanical properties of a high-W superalloy,the Thermo-Calc calculation was utilized to simulate the microstructure with various W and Al contents.The results indicated that the concentration of W and Al exceeded 15.7 wt%and 5.9 wt%,respectively,the abnormal tungsten-richα-W phase would precipitate.Compared with the results of orthogonal experiment,the precipitation ofα-W phase is consistent with thermodynamic calculation results.The presence of Al not only influenced the precipitation ofα-W phase but also impacted the eutectic content and theγʹ-size,both of which showed an increase with higher Al concentrations.Excessive W and Al contents promoted the precipitation ofα-W phase,escalating the site of crack nucleation,and ultimately decreasing the plasticity.In the process of creep deformation(975℃/235 MPa),the raftedγ'phases were more continuous with increasing W contents,which increased the difficulty of dislocation climbing.As Al content increased,the density of interfacial dislocation network increased.The dislocations were entangled with each other,and the hindrance of dislocation movement was enhanced,which improved the stress rupture life.However,the precipitation of the hard and brittleα-W phase was attributed to the excessive W and Al,which increased the tendency of crack formation and significantly diminished the stress rupture life.The alloy exhibited the highest stress rupture life of 110.46 h when the W and Al contents were 15.7 wt%and 5.9 wt%,respectively.展开更多
This study presents a multiscale method to evaluate the transverse tensile strength and failure mechanism of SiC_(f)/TC17 cruciform specimen machined from a large-size ring.The mechanical properties and failure of the...This study presents a multiscale method to evaluate the transverse tensile strength and failure mechanism of SiC_(f)/TC17 cruciform specimen machined from a large-size ring.The mechanical properties and failure of the specimen were evaluated through a macroscale model under transverse tensile loading at 200°C.A mesoscale model was developed to analyze the transverse tensile behavior and failure of the composite specimen.Interfacial debonding,plastic deformation of matrix and cladding,and damage to the composite core were incorporated into the mesoscopic and macroscopic models.The stress–strain curves and fracture modes obtained from the numerical simulation showed good agreement with the experimental curves,acoustic emission test results,and fracture morphology.The simulation results suggested that the damage to the central region interface and the plastic deformation of the matrix initiated first and propagated outwards.Subsequently,the interfacial failure,matrix failure,and formation of macro-crack developed,which led to the crack of the titanium matrix composite core.Finally,cladding was plastically deformed and crack developed,which led to the severe failure of the cruciform specimen.展开更多
The hot deformation behavior of a newly developed Ni–W–Cr superalloy for use in 800℃molten salt reactors(MSRs)was looked into by isothermal compression tests in the temperature range of 1050–1200℃with a strain ra...The hot deformation behavior of a newly developed Ni–W–Cr superalloy for use in 800℃molten salt reactors(MSRs)was looked into by isothermal compression tests in the temperature range of 1050–1200℃with a strain rate of 0.001–1 s^(−1)under a true strain of 0.693.An Arrhenius-type model for the Ni–W–Cr superalloy was constructed by fitting the corrected flow stress data.In this model,the effect of dispersion of solid solution elements during thermal deformation on microstructure evolution was considered,as well as the effects of friction and adiabatic heating on the temperature and strain rate-dependent variation of flow stresses.The hot deformation activation energy of the Ni–W–Cr superalloy was 323 kJ/mol,which was less than that of the Hastelloy N alloy(currently used in MSRs).According to the rectified flow stress data,processing maps were created.In conjunction with the corresponding deformation microstructures,the flow instability domains of the Ni–W–Cr superalloy were determined to be 1050–1160℃/0.03–1 s^(−1)and 1170–1200℃/0.001–0.09 s^(−1).In these deformation conditions,a locally inhomogeneous microstructure was caused by flow-i.e.,incomplete dynamic recrystallization and hot working parameters should avoid sliding into these domains.The ideal processing hot deformation domain for the Ni–W–Cr superalloy was determined to be 1170–1200℃/0.6–1 s^(−1).展开更多
In the present study,2219-T87 Al alloy plates,4 mm in thickness,were subjected to bobbin tool friction stir welding(BTFSW)under relatively high welding speeds of 200 and 400 mm/min,with the aim to analyze the effect o...In the present study,2219-T87 Al alloy plates,4 mm in thickness,were subjected to bobbin tool friction stir welding(BTFSW)under relatively high welding speeds of 200 and 400 mm/min,with the aim to analyze the effect of welding speeds on fatigue properties of the joints.The results showed that the tension–tension high-cycle fatigue performance of the BT-FSW joints at room temperature was significantly enhanced compared to that of other joints of 2xxx series Al alloys counterparts.Particularly at a high welding speed of 400 mm/min,the fatigue strength of the joint reached 78%of the base material together with a high tensile strength of 311 MPa.It was found that the joint line remnants had no effects on the fatigue properties of the BT-FSW joints due to the elimination of root flaws under the action of the lower shoulder.Most of the samples with the welding speed of 200 mm/min failed at the thermo-mechanical zone(TMAZ)during fatigue tests,attributable to the coarsened grains and precipitates,but all of the samples with high welding speed of 400 mm/min randomly failed at the nugget zone due to the improved hardness value in the TMAZ.展开更多
Multi-principal element alloys(MPEAs)composed of thermally stable high-density cuboidal nanoparticles have revealed great potential for high-temperature applications.In this work,we systematically studied the growth b...Multi-principal element alloys(MPEAs)composed of thermally stable high-density cuboidal nanoparticles have revealed great potential for high-temperature applications.In this work,we systematically studied the growth behavior and coarsening kinetics of the cuboidal nanoparticles in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA.In the initial stage of isothermal aging,the nanoparticles exhibit growth and split behavior,resulting in the improvement of mechanical performance,then the cuboidal nanoparticles retain superior thermal and mechanical stability during long-term isothermal aging.The 288 kJ/mol activation energy of Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA,which is higher than that in Ni-based superalloys,reveals the obvious elemental sluggish diffusion in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA.Meanwhile,coarsening rate constant determined by the volume diffusion mechanism in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA is 1–2 orders of magnitude less than that of the traditional Ni-based superalloys.The shortterm regulation and long-term stability of the cuboidal nanoparticles endow the Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA with superior mechanical performance and thermal stability for high temperature applications.展开更多
基金supported by the National Key R&D Program of China(Grant No.2023YFB3710601)the National Natural Science Foundation of China(Grant Nos.52203385 and 52171056)+2 种基金the CNNC Science Fund for Talented Young Scholars,the Institute of Metal Research(IMR)Innovation Fund(Grant No.2021-ZD02)the Natural Science Foundation of Liaoning Province(Grant No.2022-BS-009)Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20220225).
文摘B_(4)C/Al composites are widely utilized as neutron absorbing materials for the storage and transportation of spent nuclear fuel.In order to improve the high-temperature mechanical properties of B_(4)C/Al composites,in-situ nano-Al_(2)O_(3)was introduced utilizing oxide on Al powder surface.In this study,the Al_(2)O_(3)content was adjusted by utilizing spheroid Al powder with varying diameters,thereby investigating the impact of Al_(2)O_(3)content on the tensile properties of(B_(4)C+Al_(2)O_(3))/Al composites.It was found that the pinning effect of Al_(2)O_(3)on the grain boundaries could hinder the recovery of dislocations and lead to dislocation accumulation at high temperature.As the result,with the increase in Al_(2)O_(3)content and the decrease in grain size,the high-temperature strength of the composites increased significantly.The finest Al powder used in this investigation had a diameter of 1.4μm,whereas the resultant composite exhibited a maximum strength of 251 MPa at room temperature and 133 MPa at 350℃,surpassing that of traditional B_(4)C/Al composites.
基金financial support received from the National Key Research and Development Program of China(2022YFB3705000)the National Natural Science Foundation of China(No.52303394)the Liaoning Provincial Natural Science Foundation(No.2023-BS-015).
文摘To investigate the influence of W and Al on the microstructure and mechanical properties of a high-W superalloy,the Thermo-Calc calculation was utilized to simulate the microstructure with various W and Al contents.The results indicated that the concentration of W and Al exceeded 15.7 wt%and 5.9 wt%,respectively,the abnormal tungsten-richα-W phase would precipitate.Compared with the results of orthogonal experiment,the precipitation ofα-W phase is consistent with thermodynamic calculation results.The presence of Al not only influenced the precipitation ofα-W phase but also impacted the eutectic content and theγʹ-size,both of which showed an increase with higher Al concentrations.Excessive W and Al contents promoted the precipitation ofα-W phase,escalating the site of crack nucleation,and ultimately decreasing the plasticity.In the process of creep deformation(975℃/235 MPa),the raftedγ'phases were more continuous with increasing W contents,which increased the difficulty of dislocation climbing.As Al content increased,the density of interfacial dislocation network increased.The dislocations were entangled with each other,and the hindrance of dislocation movement was enhanced,which improved the stress rupture life.However,the precipitation of the hard and brittleα-W phase was attributed to the excessive W and Al,which increased the tendency of crack formation and significantly diminished the stress rupture life.The alloy exhibited the highest stress rupture life of 110.46 h when the W and Al contents were 15.7 wt%and 5.9 wt%,respectively.
基金This work was supported by the National Science and Technology Major Project(HT-J2019-VI-0007-0121)the CAS Project for Young Scientists in Basic Research(YSBR-025)the National Natural Science Foundation of China(No.52101164).
文摘This study presents a multiscale method to evaluate the transverse tensile strength and failure mechanism of SiC_(f)/TC17 cruciform specimen machined from a large-size ring.The mechanical properties and failure of the specimen were evaluated through a macroscale model under transverse tensile loading at 200°C.A mesoscale model was developed to analyze the transverse tensile behavior and failure of the composite specimen.Interfacial debonding,plastic deformation of matrix and cladding,and damage to the composite core were incorporated into the mesoscopic and macroscopic models.The stress–strain curves and fracture modes obtained from the numerical simulation showed good agreement with the experimental curves,acoustic emission test results,and fracture morphology.The simulation results suggested that the damage to the central region interface and the plastic deformation of the matrix initiated first and propagated outwards.Subsequently,the interfacial failure,matrix failure,and formation of macro-crack developed,which led to the crack of the titanium matrix composite core.Finally,cladding was plastically deformed and crack developed,which led to the severe failure of the cruciform specimen.
基金supported by the National Key R&D Program of China(Nos.2021YFB3700601 and 2019YFA0705304)the IMR Innovation Fund(No.2023-PY08).
文摘The hot deformation behavior of a newly developed Ni–W–Cr superalloy for use in 800℃molten salt reactors(MSRs)was looked into by isothermal compression tests in the temperature range of 1050–1200℃with a strain rate of 0.001–1 s^(−1)under a true strain of 0.693.An Arrhenius-type model for the Ni–W–Cr superalloy was constructed by fitting the corrected flow stress data.In this model,the effect of dispersion of solid solution elements during thermal deformation on microstructure evolution was considered,as well as the effects of friction and adiabatic heating on the temperature and strain rate-dependent variation of flow stresses.The hot deformation activation energy of the Ni–W–Cr superalloy was 323 kJ/mol,which was less than that of the Hastelloy N alloy(currently used in MSRs).According to the rectified flow stress data,processing maps were created.In conjunction with the corresponding deformation microstructures,the flow instability domains of the Ni–W–Cr superalloy were determined to be 1050–1160℃/0.03–1 s^(−1)and 1170–1200℃/0.001–0.09 s^(−1).In these deformation conditions,a locally inhomogeneous microstructure was caused by flow-i.e.,incomplete dynamic recrystallization and hot working parameters should avoid sliding into these domains.The ideal processing hot deformation domain for the Ni–W–Cr superalloy was determined to be 1170–1200℃/0.6–1 s^(−1).
基金financially supported by the LiaoNing Revitalization Talents Program under grant No.XLYC2002099the LiaoNing Province Excellent Youth Foundation(No.2021-YQ-01)+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.Y2021061)the IMR Innovation Fund(No.2022-PY11).
文摘In the present study,2219-T87 Al alloy plates,4 mm in thickness,were subjected to bobbin tool friction stir welding(BTFSW)under relatively high welding speeds of 200 and 400 mm/min,with the aim to analyze the effect of welding speeds on fatigue properties of the joints.The results showed that the tension–tension high-cycle fatigue performance of the BT-FSW joints at room temperature was significantly enhanced compared to that of other joints of 2xxx series Al alloys counterparts.Particularly at a high welding speed of 400 mm/min,the fatigue strength of the joint reached 78%of the base material together with a high tensile strength of 311 MPa.It was found that the joint line remnants had no effects on the fatigue properties of the BT-FSW joints due to the elimination of root flaws under the action of the lower shoulder.Most of the samples with the welding speed of 200 mm/min failed at the thermo-mechanical zone(TMAZ)during fatigue tests,attributable to the coarsened grains and precipitates,but all of the samples with high welding speed of 400 mm/min randomly failed at the nugget zone due to the improved hardness value in the TMAZ.
基金This work was financially supported by the National Key Research and Development Program(2018YFB0703402)the Chinese Academy of Sciences(ZDBS-LY-JSC023)+1 种基金the Industrialization Innovation Team of the Industrial Technology Research Institute of the Chinese Academy of Sciences in Foshan(ZK-TD-2019-04)the Key Specialized Research and Development Breakthrough-Unveiling and Commanding the Special Project Program in Liaoning Province under Grant(2021JH15).
文摘Multi-principal element alloys(MPEAs)composed of thermally stable high-density cuboidal nanoparticles have revealed great potential for high-temperature applications.In this work,we systematically studied the growth behavior and coarsening kinetics of the cuboidal nanoparticles in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA.In the initial stage of isothermal aging,the nanoparticles exhibit growth and split behavior,resulting in the improvement of mechanical performance,then the cuboidal nanoparticles retain superior thermal and mechanical stability during long-term isothermal aging.The 288 kJ/mol activation energy of Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA,which is higher than that in Ni-based superalloys,reveals the obvious elemental sluggish diffusion in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA.Meanwhile,coarsening rate constant determined by the volume diffusion mechanism in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA is 1–2 orders of magnitude less than that of the traditional Ni-based superalloys.The shortterm regulation and long-term stability of the cuboidal nanoparticles endow the Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA with superior mechanical performance and thermal stability for high temperature applications.
