Precipitates in an 11% Cr ferritic/martensitic steel containing Nd with tempering and creep conditions were investigated using transmission electron microscope with energy-dispersive X-ray spectroscopy. The precipitat...Precipitates in an 11% Cr ferritic/martensitic steel containing Nd with tempering and creep conditions were investigated using transmission electron microscope with energy-dispersive X-ray spectroscopy. The precipitates in the steel with a tempering condition were identified to be Cr-rich M23C6 carbide, Nb-rich/V-rich/Ta–Nb-rich MX carbides, Nbrich MX carbonitride, and Fe-rich M5C2 carbide. Nd-rich carbonitride, which is not known to have been reported previously in steels, was also detected in the steel after tempering. Most of the Nb-rich MX precipitates were dissolved, whereas the amount of Ta-rich MX precipitates was increased significantly in the steel after a creep test at 600 °C at an applied stress of180 MPa for 1,100 h. No Fe2 W Laves phase has been detected in the steel after tempering.（Fe, Cr）2W Laves phase with a relatively large size was observed in the steel after the creep test.展开更多
12Cr ferritic/martensitic steels with 0, 0.1 wt%, 0.2 wt% and 0.3 wt% theoretical yttrium(Y) additions were fabricated by vacuum inducting melting and casting method. Solubilities of Y in the 12Cr steels are0.027, 0.0...12Cr ferritic/martensitic steels with 0, 0.1 wt%, 0.2 wt% and 0.3 wt% theoretical yttrium(Y) additions were fabricated by vacuum inducting melting and casting method. Solubilities of Y in the 12Cr steels are0.027, 0.078 and 0.17 for 12Cr-0.1 Y, 12Cr-0.2 Y and 12Cr-0.3 Y, respectively. Phase transformations and microstructure characteristics under different heat-treatment schedules were investigated. The starting temperature of ferrite-to-austenite transformation A^(c1) are maintained about 850℃, but the finishing temperature of ferrite-to-austenite transformation A^(c3) are about 950, 970, 980 and 1000℃ for 12Cr-0 Y,12Cr-0.1 Y, 12Cr-0.2 Y and 12Cr-0.3 Y, respectively, which indicates that A^(c3) increases gradually with the addition of Y. Martensite accompanied with a few δ-ferrite is the dominant structure in all the steels. The amount of δ-ferrite shows a strong dependence with the Y content and austenitizing temperature. Area fraction of δ-ferrite increases with the content of Y, which is the ferrite favouring element. The minimum amount of δ-ferrite are achieved at 950℃ for 12Cr-0 Y, 12Cr-0.1 Y, 12Cr-0.2 Y and 1000℃ for 12Cr-0.3 Y.Besides, more carbides precipitate along the martensite laths and grain boundaries in the Y-bearing steel due to the redistribution of carbon between austenite and ferrite resulting from the ferrite favouring element of Y.展开更多
Helium ion irradiation at 350℃was performed to study equilibrium segregation and radiation-induced segregation(RIS)of Cr at grain boundaries in reduced activation ferritic/martensitic steels.Cr concentration at grain...Helium ion irradiation at 350℃was performed to study equilibrium segregation and radiation-induced segregation(RIS)of Cr at grain boundaries in reduced activation ferritic/martensitic steels.Cr concentration at grain boundary was measured by scanning transmission electron microscopy with an energy-dispersive spectrometer.The measured Cr concentration at grain boundaries in heat treated zone was 11.7 and 12.8 wt.%in irradiated zone,respectively,which matched well to the calculated results from Mclean and modified Perk model.Equilibrium segregation and RIS of Cr mechanisms were theoretically analysed.The analysis indicates that as temperature rises,equilibrium Cr segregation decreases monotoni-cally,while RIS of Cr has a bell-shape profile,which increases first and then decreases.It is also shown that at low and high temperatures,equilibrium segregation of Cr is higher than that of RIS;at intermediate temperatures,equilibrium Cr segregation is lower than RIS.展开更多
Based on a 00Cr11NbTi ferritic stainless steel plate produced by Baosteel,the plasma arc welding was performed without filler wire. The mechanical properties of the welded joints were tested,as a result,the transverse...Based on a 00Cr11NbTi ferritic stainless steel plate produced by Baosteel,the plasma arc welding was performed without filler wire. The mechanical properties of the welded joints were tested,as a result,the transverse tensile strength of the welded joints decreased to a certain extent in comparison with that of the base metal,but the bending performance and plasticity of the welded joint were good.展开更多
In view of developing novel alloys for applications in supercritical water-cooled reactor fuel cladding and in-core components, a 12%Cr reduced activation ferrite/martensite(RAFM) steel with good corrosion resistance ...In view of developing novel alloys for applications in supercritical water-cooled reactor fuel cladding and in-core components, a 12%Cr reduced activation ferrite/martensite(RAFM) steel with good corrosion resistance and irradiation performance was developed. V and Ta were added to form fine MX type carbonitrides and enhance the high temperature creep rupture strength. Microstructure stability of the steel during long-term aging at 650 C was studied experimentally combined with the simulation of ThermoCalc and DICTRA software. The results show that the precipitates in the steel during long-term aging contain M23C6, MX and Laves phase. M23C6 carbides play a major role in the stabilization of the tempered martensite lath structure by exerting a large Zener pinning force as compared with MX and Laves phase.Adding V and Ta in the steel can not only promote MX precipitation, but also refine M23C6 carbides and thus improve the thermal stability of lath/subgrains, which is beneficial to the improvement of high temperature microstructure stability of the 12%Cr RAFM steel.展开更多
基金financially supported by Key Program of National Natural Science Foundation of China (No. 51034011)ITER-National Magnetic Confinement Fusion Program (No.2011GB113001)National Science and Technology Major Project (No.2011ZX06004-009)
文摘Precipitates in an 11% Cr ferritic/martensitic steel containing Nd with tempering and creep conditions were investigated using transmission electron microscope with energy-dispersive X-ray spectroscopy. The precipitates in the steel with a tempering condition were identified to be Cr-rich M23C6 carbide, Nb-rich/V-rich/Ta–Nb-rich MX carbides, Nbrich MX carbonitride, and Fe-rich M5C2 carbide. Nd-rich carbonitride, which is not known to have been reported previously in steels, was also detected in the steel after tempering. Most of the Nb-rich MX precipitates were dissolved, whereas the amount of Ta-rich MX precipitates was increased significantly in the steel after a creep test at 600 °C at an applied stress of180 MPa for 1,100 h. No Fe2 W Laves phase has been detected in the steel after tempering.（Fe, Cr）2W Laves phase with a relatively large size was observed in the steel after the creep test.
基金Project supported by the National Key Research and Development Program of China(2017YFB0702400)
文摘12Cr ferritic/martensitic steels with 0, 0.1 wt%, 0.2 wt% and 0.3 wt% theoretical yttrium(Y) additions were fabricated by vacuum inducting melting and casting method. Solubilities of Y in the 12Cr steels are0.027, 0.078 and 0.17 for 12Cr-0.1 Y, 12Cr-0.2 Y and 12Cr-0.3 Y, respectively. Phase transformations and microstructure characteristics under different heat-treatment schedules were investigated. The starting temperature of ferrite-to-austenite transformation A^(c1) are maintained about 850℃, but the finishing temperature of ferrite-to-austenite transformation A^(c3) are about 950, 970, 980 and 1000℃ for 12Cr-0 Y,12Cr-0.1 Y, 12Cr-0.2 Y and 12Cr-0.3 Y, respectively, which indicates that A^(c3) increases gradually with the addition of Y. Martensite accompanied with a few δ-ferrite is the dominant structure in all the steels. The amount of δ-ferrite shows a strong dependence with the Y content and austenitizing temperature. Area fraction of δ-ferrite increases with the content of Y, which is the ferrite favouring element. The minimum amount of δ-ferrite are achieved at 950℃ for 12Cr-0 Y, 12Cr-0.1 Y, 12Cr-0.2 Y and 1000℃ for 12Cr-0.3 Y.Besides, more carbides precipitate along the martensite laths and grain boundaries in the Y-bearing steel due to the redistribution of carbon between austenite and ferrite resulting from the ferrite favouring element of Y.
文摘Helium ion irradiation at 350℃was performed to study equilibrium segregation and radiation-induced segregation(RIS)of Cr at grain boundaries in reduced activation ferritic/martensitic steels.Cr concentration at grain boundary was measured by scanning transmission electron microscopy with an energy-dispersive spectrometer.The measured Cr concentration at grain boundaries in heat treated zone was 11.7 and 12.8 wt.%in irradiated zone,respectively,which matched well to the calculated results from Mclean and modified Perk model.Equilibrium segregation and RIS of Cr mechanisms were theoretically analysed.The analysis indicates that as temperature rises,equilibrium Cr segregation decreases monotoni-cally,while RIS of Cr has a bell-shape profile,which increases first and then decreases.It is also shown that at low and high temperatures,equilibrium segregation of Cr is higher than that of RIS;at intermediate temperatures,equilibrium Cr segregation is lower than RIS.
文摘Based on a 00Cr11NbTi ferritic stainless steel plate produced by Baosteel,the plasma arc welding was performed without filler wire. The mechanical properties of the welded joints were tested,as a result,the transverse tensile strength of the welded joints decreased to a certain extent in comparison with that of the base metal,but the bending performance and plasticity of the welded joint were good.
基金supported by the National Basic Research Program of China (Grant No. 2007CB209801)the National Natural Science Fundation of China (Grant No. 51371030)the National High Technology Research and Development Program of China (Grant No. 2013AA031601)
文摘In view of developing novel alloys for applications in supercritical water-cooled reactor fuel cladding and in-core components, a 12%Cr reduced activation ferrite/martensite(RAFM) steel with good corrosion resistance and irradiation performance was developed. V and Ta were added to form fine MX type carbonitrides and enhance the high temperature creep rupture strength. Microstructure stability of the steel during long-term aging at 650 C was studied experimentally combined with the simulation of ThermoCalc and DICTRA software. The results show that the precipitates in the steel during long-term aging contain M23C6, MX and Laves phase. M23C6 carbides play a major role in the stabilization of the tempered martensite lath structure by exerting a large Zener pinning force as compared with MX and Laves phase.Adding V and Ta in the steel can not only promote MX precipitation, but also refine M23C6 carbides and thus improve the thermal stability of lath/subgrains, which is beneficial to the improvement of high temperature microstructure stability of the 12%Cr RAFM steel.
