The goal of the present work was to optimize the phase-structural composition and microstructure of binary Ti0.8-0.9V0.2-0.1 alloys with respect to their hydrogen sorption properties. Application of these alloys is fo...The goal of the present work was to optimize the phase-structural composition and microstructure of binary Ti0.8-0.9V0.2-0.1 alloys with respect to their hydrogen sorption properties. Application of these alloys is for hydrogen absorption from gaseous mixtures containing substantial amounts of carbon monoxide （CO） at high temperatures. Irrespective of alloy composition, both α（HCP） and β（BCC） phases in Ti0.8-0.9V0.2-0.1 formed single phase FCC hydrides upon hydrogenation in pure H2. An in situ synchrotron X-ray diffraction study showed that only the β-phase transformed to the corresponding hydride when the alloy was hydrogenated in a mixture of H2＋10%CO. Rapid solidification （RS） of the alloy resulted in refined grain sizes both in the Ti0.8V0.2 and Ti0.9V0.1 alloys. Furthermore, RS was found to increase the β-phase fraction in Ti0.9V0.1, being twice larger than that of the as-cast alloy. Ti0.9V0.1 had a platelike microstructure as observed by scanning electron microscopy （SEM）, the plates were about 300 nm thick. The microstructure refinement resulted in a faster kinetics of H desorption as observed by temperature desorption spectroscopy （TDS）.展开更多
Through the solubility product theory of the ternary secondary phase,classical nucleation theory,and Ostwald ripening theory,a model was established to describe the thermodynamics and kinetics of(Ti,V)C precipitates i...Through the solubility product theory of the ternary secondary phase,classical nucleation theory,and Ostwald ripening theory,a model was established to describe the thermodynamics and kinetics of(Ti,V)C precipitates in austenite/ferrite(y/α)matrices.The model was used to calculate the volume fraction,precipitation-temperature-time(PTT)curve,and nucleation rate-temperature(NrT)curve of MC(M=Ti,V)precipitates in γ/α matrices in Ti-V microalloyed steels with various Ti/V ratios,which is verified by hardness tester,transmission electron microscopy and energy-dispersive X-ray spectroscopy.The calculations indicate that,by decreasing Ti/V ratio from Ti4V0 steel to Ti0V4 steel,the complete-dissolution temperature decreases monotonically from 1226 to 830℃,and the equilibrium volume fraction of MC pre-cipitated from austenite decreases from 0.333%to 0.091%at 900℃.Moreover,the maximum nucleation temperature of MC precipitated from α matrix decreases from 748 to 605℃and the fastest precipitation temperature decreases from 844 to 675℃as Ti/V ratio decreases.PTT and NrT diagrams of MC precipitated from α matrices in different Ti-V microalloyed steels all exhibit C-shaped and inverse C-shaped curves.In addition,both theoretical calculation and experimental results show that when tempered at 600℃for 100 h,Ti2V2 steel shows the largest hardness value of 312 HV among the three steels tested because it has a larger volume fraction(0.364%),a larger precipitate density(1689 μm-2),and the smallest average size(8.4 nm)of(Ti,V)C precipitates.The theoretical calculations are consistent with experimental results,which indicates that the thermodynamics and kinetics model for(Ti,V)C precipitates is reliable and accurate.展开更多
In this paper, the effects of Si and Ce on the microstructure and hydrogen storage property of Ti26.5 Cr20V45Fe8.5Ce0.5 alloy were studied, respectively. First of all, effects of Si on the microstructure and hydrogen ...In this paper, the effects of Si and Ce on the microstructure and hydrogen storage property of Ti26.5 Cr20V45Fe8.5Ce0.5 alloy were studied, respectively. First of all, effects of Si on the microstructure and hydrogen storage properties of Ti26.5Cr20(V45Fe8.5)1?xSixCe0.5 (x = 0, 0.5, 1.0, 1.5 and 2.0 at%) alloys were studied by X-ray diffraction, scanning electron microscopy and P-C isotherm measurements. As the Si addition increases, the hydrogen absorption capacities of alloys decrease but the equilibrium pressure increases, due to the formation of Laves phase. Secondly, the effect of Ce on Ti26.5Cr20 (V45Fe8.5)0.98Si2 alloy was studied. It was found that Ce addition is an effective way to eliminate the effect of Si on the hydrogen storage properties of the alloy.展开更多
Microstructures and mechanical properties of Ti-V micro-alloyed TRIP（ transformation-induced plasticity） steel with different compositions were investigated by tensile test,scanning electron microscopy（ SEM）,trans...Microstructures and mechanical properties of Ti-V micro-alloyed TRIP（ transformation-induced plasticity） steel with different compositions were investigated by tensile test,scanning electron microscopy（ SEM）,transmission electron microscopy（ TEM）,X-ray diffraction（ XRD） and thermodynamic calculation（ TC）. The results indicated that the steel exhibited high ultimate tensile strength（ 1 079MPa）,sufficient ductility（ 28%） and the highest product of strength and ductility（ 30 212 MPa·%） heat treated after intercritical annealing at 800℃ for 3 min and bainitic annealing at 430 ℃ for 5 min. In addition,the change of volume fraction of retained austenite（ VF-RA） versus tensile strain was measured using in-situ analysis by X-ray stress apparatus and micro-electronic universal testing machine. It was concluded that a-value could be used to evaluate the stability of retained austenite（ S-RA） in the investigated Ti-V micro-alloyed TRIP steel. The smaller a-value indicated the higher stability of retained austenite（ S-RA） and the higher mechanical properties of Ti-V micro-alloyed TRIP steel.展开更多
Due to the largely inhomogeneous deformation among constituent phases, the advanced high-strength multi-phase steels are always facing challenges when applied to automotive parts where local formability is critically ...Due to the largely inhomogeneous deformation among constituent phases, the advanced high-strength multi-phase steels are always facing challenges when applied to automotive parts where local formability is critically required. In this work, two characteristic microstructures were produced from a low carbon Ti-V microalloyed steel by varying the cooling path. In the ferrite single-phase microstructure resulted from "ultra-fast cooling(UFC) + furnace-cooling(FC)", the hole-expanding ratio of 200% and tensile strength of 647 MPa were achieved. In the ferrite-bainite-martensite(F+B+M) multi-phase microstructure produced by "UFC + air-cooling(AC) + UFC", the ferrite has been strengthened by Ti-V carbides to promote the strain partitioning, which resulted in the tensile strength of ≥780 MPa, a moderate elongation and hole-expanding ratio of 93%. The strengthening contributions of Ti-V carbides were calculated to be 126 MPa and 149 MPa in the ferrite single-phase and F+B+M multi-phase microstructure, respectively.展开更多
The Panzhihua,Hongge,and Baima Fe-Ti-V oxide deposits in the Panzhihua-Xichang(Panxi) region are hosted in large layered mafic-ultramafic intrusions.The layered intrusions intrude either the Neoproterozoic Dengying Fo...The Panzhihua,Hongge,and Baima Fe-Ti-V oxide deposits in the Panzhihua-Xichang(Panxi) region are hosted in large layered mafic-ultramafic intrusions.The layered intrusions intrude either the Neoproterozoic Dengying Formation,composed mainly of limestone,or the Paleoproterozoic Hekou Formation,composed of meta-sedimentary-volcanic rocks.It remains unclear if the wall rocks have been involved during the fractionation of magmas and have affected the sequence of crystallization of Fe-Ti oxide.Volatiles and their C-H-O isotopic compositions of magnetite,apatite,clinopyroxene,and plagioclase of different types of ores from the three intrusions are analyzed using a technique of stepwise heating mass spectrometer to evaluate the role of wall rocks in the formation of Fe-Ti oxide ores.Volatiles released from magnetite are composed mainly of H 2 O and CO 2,whereas the other minerals are composed mainly of H 2 O,CO 2 and H 2.At 800-1200°C temperature interval,the average 13 C values of CO 2 of all the minerals from the three intrusions range from 7.7‰ to 13.5‰ and the average 18 O CO 2 values from 19.1‰ to 19.5‰,which are scattered in a mixed field with basalt and the two types of wall rocks as end-members,indicating that CO 2 from the wall rocks may have been involved in the magmas from which the three intrusions formed.At 400-800 C temperature interval,both 13 C values(13.7‰ to 17.9‰ on the average) and 18 O values(16.2‰ to 19.2‰ on the average) of CO 2 of all the minerals are lower than those for 800-1200 C temperature interval,and much closer to the values of the wall rocks.Abundant H 2 O released at the 400-800 C temperature interval has relatively low D values ranging from 90‰ to 115‰,also indicating the involvement of fluids from the wall rocks.The average bulk contents of volatiles released from magnetite of the Hongge,Baima,and Panzhihua intrusions are 4891,2996,and 1568 mm 3 STP/g,respectively,much higher than those released from other minerals in total,which are 382,600,and 379 mm 3 STP/g,res展开更多
基金Project "Integrated Process for Hydrogen Production and Separation" supported by Norwegian Research Council and Statoil, Norway
文摘The goal of the present work was to optimize the phase-structural composition and microstructure of binary Ti0.8-0.9V0.2-0.1 alloys with respect to their hydrogen sorption properties. Application of these alloys is for hydrogen absorption from gaseous mixtures containing substantial amounts of carbon monoxide （CO） at high temperatures. Irrespective of alloy composition, both α（HCP） and β（BCC） phases in Ti0.8-0.9V0.2-0.1 formed single phase FCC hydrides upon hydrogenation in pure H2. An in situ synchrotron X-ray diffraction study showed that only the β-phase transformed to the corresponding hydride when the alloy was hydrogenated in a mixture of H2＋10%CO. Rapid solidification （RS） of the alloy resulted in refined grain sizes both in the Ti0.8V0.2 and Ti0.9V0.1 alloys. Furthermore, RS was found to increase the β-phase fraction in Ti0.9V0.1, being twice larger than that of the as-cast alloy. Ti0.9V0.1 had a platelike microstructure as observed by scanning electron microscopy （SEM）, the plates were about 300 nm thick. The microstructure refinement resulted in a faster kinetics of H desorption as observed by temperature desorption spectroscopy （TDS）.
基金supported by the National Key Research and Development Program of China(Nos.2017YFB0305100 and 2017YFB0304700)the National Natural Science Foundation of China(Nos.51704008 and 51974003)+1 种基金the Open Research Fund of State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization(No.18100009)the Open Research Fund from the State Key Laboratory of Rolling and Automation,Northeastern University(No.2018RALKFKT006).
文摘Through the solubility product theory of the ternary secondary phase,classical nucleation theory,and Ostwald ripening theory,a model was established to describe the thermodynamics and kinetics of(Ti,V)C precipitates in austenite/ferrite(y/α)matrices.The model was used to calculate the volume fraction,precipitation-temperature-time(PTT)curve,and nucleation rate-temperature(NrT)curve of MC(M=Ti,V)precipitates in γ/α matrices in Ti-V microalloyed steels with various Ti/V ratios,which is verified by hardness tester,transmission electron microscopy and energy-dispersive X-ray spectroscopy.The calculations indicate that,by decreasing Ti/V ratio from Ti4V0 steel to Ti0V4 steel,the complete-dissolution temperature decreases monotonically from 1226 to 830℃,and the equilibrium volume fraction of MC pre-cipitated from austenite decreases from 0.333%to 0.091%at 900℃.Moreover,the maximum nucleation temperature of MC precipitated from α matrix decreases from 748 to 605℃and the fastest precipitation temperature decreases from 844 to 675℃as Ti/V ratio decreases.PTT and NrT diagrams of MC precipitated from α matrices in different Ti-V microalloyed steels all exhibit C-shaped and inverse C-shaped curves.In addition,both theoretical calculation and experimental results show that when tempered at 600℃for 100 h,Ti2V2 steel shows the largest hardness value of 312 HV among the three steels tested because it has a larger volume fraction(0.364%),a larger precipitate density(1689 μm-2),and the smallest average size(8.4 nm)of(Ti,V)C precipitates.The theoretical calculations are consistent with experimental results,which indicates that the thermodynamics and kinetics model for(Ti,V)C precipitates is reliable and accurate.
基金Supported by the National Hi-Tech Research and Development Program of China ("863" Project) (Grant No. 2006AA05Z144)
文摘In this paper, the effects of Si and Ce on the microstructure and hydrogen storage property of Ti26.5 Cr20V45Fe8.5Ce0.5 alloy were studied, respectively. First of all, effects of Si on the microstructure and hydrogen storage properties of Ti26.5Cr20(V45Fe8.5)1?xSixCe0.5 (x = 0, 0.5, 1.0, 1.5 and 2.0 at%) alloys were studied by X-ray diffraction, scanning electron microscopy and P-C isotherm measurements. As the Si addition increases, the hydrogen absorption capacities of alloys decrease but the equilibrium pressure increases, due to the formation of Laves phase. Secondly, the effect of Ce on Ti26.5Cr20 (V45Fe8.5)0.98Si2 alloy was studied. It was found that Ce addition is an effective way to eliminate the effect of Si on the hydrogen storage properties of the alloy.
基金supported by the Shanghai Municipal Science and Technology Commission(Grant No.15DZ2260300,15DZ2260301)Shanghai Municipal Natural Science Foundation(17ZR1410400)
文摘Microstructures and mechanical properties of Ti-V micro-alloyed TRIP（ transformation-induced plasticity） steel with different compositions were investigated by tensile test,scanning electron microscopy（ SEM）,transmission electron microscopy（ TEM）,X-ray diffraction（ XRD） and thermodynamic calculation（ TC）. The results indicated that the steel exhibited high ultimate tensile strength（ 1 079MPa）,sufficient ductility（ 28%） and the highest product of strength and ductility（ 30 212 MPa·%） heat treated after intercritical annealing at 800℃ for 3 min and bainitic annealing at 430 ℃ for 5 min. In addition,the change of volume fraction of retained austenite（ VF-RA） versus tensile strain was measured using in-situ analysis by X-ray stress apparatus and micro-electronic universal testing machine. It was concluded that a-value could be used to evaluate the stability of retained austenite（ S-RA） in the investigated Ti-V micro-alloyed TRIP steel. The smaller a-value indicated the higher stability of retained austenite（ S-RA） and the higher mechanical properties of Ti-V micro-alloyed TRIP steel.
基金Funded by the National Natural Science Foundation of China(51204048)the Fundamental Research Funds for the Central Universities(N150704006)
文摘Due to the largely inhomogeneous deformation among constituent phases, the advanced high-strength multi-phase steels are always facing challenges when applied to automotive parts where local formability is critically required. In this work, two characteristic microstructures were produced from a low carbon Ti-V microalloyed steel by varying the cooling path. In the ferrite single-phase microstructure resulted from "ultra-fast cooling(UFC) + furnace-cooling(FC)", the hole-expanding ratio of 200% and tensile strength of 647 MPa were achieved. In the ferrite-bainite-martensite(F+B+M) multi-phase microstructure produced by "UFC + air-cooling(AC) + UFC", the ferrite has been strengthened by Ti-V carbides to promote the strain partitioning, which resulted in the tensile strength of ≥780 MPa, a moderate elongation and hole-expanding ratio of 93%. The strengthening contributions of Ti-V carbides were calculated to be 126 MPa and 149 MPa in the ferrite single-phase and F+B+M multi-phase microstructure, respectively.
基金supported by the Main Direction Program of Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No. KZCX2-YW-Q04-06)National Basic Research Program of China (Grant No. 2011CB808903)+1 种基金National Natural Science Foundation of China (Grant No. 41073030)Hundred Talents Program of the Chinese Academy of Sciences to CYW
文摘The Panzhihua,Hongge,and Baima Fe-Ti-V oxide deposits in the Panzhihua-Xichang(Panxi) region are hosted in large layered mafic-ultramafic intrusions.The layered intrusions intrude either the Neoproterozoic Dengying Formation,composed mainly of limestone,or the Paleoproterozoic Hekou Formation,composed of meta-sedimentary-volcanic rocks.It remains unclear if the wall rocks have been involved during the fractionation of magmas and have affected the sequence of crystallization of Fe-Ti oxide.Volatiles and their C-H-O isotopic compositions of magnetite,apatite,clinopyroxene,and plagioclase of different types of ores from the three intrusions are analyzed using a technique of stepwise heating mass spectrometer to evaluate the role of wall rocks in the formation of Fe-Ti oxide ores.Volatiles released from magnetite are composed mainly of H 2 O and CO 2,whereas the other minerals are composed mainly of H 2 O,CO 2 and H 2.At 800-1200°C temperature interval,the average 13 C values of CO 2 of all the minerals from the three intrusions range from 7.7‰ to 13.5‰ and the average 18 O CO 2 values from 19.1‰ to 19.5‰,which are scattered in a mixed field with basalt and the two types of wall rocks as end-members,indicating that CO 2 from the wall rocks may have been involved in the magmas from which the three intrusions formed.At 400-800 C temperature interval,both 13 C values(13.7‰ to 17.9‰ on the average) and 18 O values(16.2‰ to 19.2‰ on the average) of CO 2 of all the minerals are lower than those for 800-1200 C temperature interval,and much closer to the values of the wall rocks.Abundant H 2 O released at the 400-800 C temperature interval has relatively low D values ranging from 90‰ to 115‰,also indicating the involvement of fluids from the wall rocks.The average bulk contents of volatiles released from magnetite of the Hongge,Baima,and Panzhihua intrusions are 4891,2996,and 1568 mm 3 STP/g,respectively,much higher than those released from other minerals in total,which are 382,600,and 379 mm 3 STP/g,res
