Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocataly...Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocatalysts have been widely investigated toward hydrogen oxidation reaction(HOR)under alkaline electrolytes,these studies are mostly limited to conventional hexagonal-close-packed(hcp)phase,mainly arising from the lack of sufficient synthesis strategies.In this study,we report the precise synthesis of metastable binary RuW alloy with face-centered-cubic(fcc)phase.We find that the introduction of W can serve as fcc phase seeds and reduce the formation energy of metastable fcc-RuW alloy.Impressively,fcc-RuW exhibits remarkable alkaline HOR performance and stability with the activity of 0.67 mA cm_(Ru)^(-2)which is almost five and three times higher than that of hcp-Ru and commercial Pt/C,respectively,which is attributed to the optimized binding strength of adsorbed hydroxide intermediate derived from tailored electronic structure through W doping and phase engineering.Moreover,this strategy can also be applied to synthesize other metastable fcc-RuCr and fcc-RuMo alloys with enhanced HOR performances.展开更多
Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using sc...Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDS), X-ray diffractometry(XRD) and mechanical properties tests. The results show that the maximum values of hardness and strength are HV 1124 and 2466 MPa respectively when 0.4% TaC is added. When the content of TaC is more than 0.6%, the grain size of WC is no longer affected by the amount of TaC, and(W,Ta)C occurs as well. Moreover, the strength and fracture toughness increase and the(Ta+W) content decreases with the increase of TaC content. The dependence of(Ta+W) content on the mechanical properties indicates that(Ta+W) content in Co should be decreased as low as possible to improve the mechanical properties of coarse grained WC-TaC-9Co cemented carbides with the microstructure of WC+γ two phase regions.展开更多
Two experimental single crystal superalloys, Ru-free alloy and Ru-containing alloy with [001] orientation, other alloying element contents being basically kept same, were cast in the directionally solidified furnace. ...Two experimental single crystal superalloys, Ru-free alloy and Ru-containing alloy with [001] orientation, other alloying element contents being basically kept same, were cast in the directionally solidified furnace. The effect of Ru on the stress rupture properties of the single crystal superalloy was investigated at （980 ℃, 250 MPa）, （1100 ℃, 140 MPa） and （1120 ℃, 140 MPa）. The results show that Ru can enhance high temperature stress rupture properties of single crystal superalloy. The improvement effect of Ru addition on stress rupture properties decreases with increasing test temperature. The γ′ coarsening and rafting directionally are observed in Ru-free alloy and Ru-containing alloy after stress rupture test. Needle shaped TCP phases precipitated in both of alloys after stress rupture test at （1100 ℃, 140 MPa） and （1120 ℃, 140 MPa） and no TCP phase was observed in both of alloys after stress rupture test （980 ℃, 250 MPa）. The precipitate volume fraction of TCP phases is significantly decreased by the addition of Ru. At last, the relationship between the microstructure change with Ru addition and improvement of stress rupture properties was discussed.展开更多
TA2/TA15 graded structural material（GSM） was fabricated by the laser additive manufacturing（LAM） process. The chemical composition, microstructure and micro-hardness of the as-deposited GSM were investigated. The ...TA2/TA15 graded structural material（GSM） was fabricated by the laser additive manufacturing（LAM） process. The chemical composition, microstructure and micro-hardness of the as-deposited GSM were investigated. The results show that the TA2 part of exhibiting near-equiaxed grains was Widmanst？tten α-laths microstructure. The TA15 part containing large columnar grains was fine basket-weave microstructure. The graded zone was divided into four deposited layers with 3000 μm in thickness. As the distance from the TA2 part increases, the alloy element contents and the β phase volume fraction increase, the α phase volume fraction decreases and the microstructure shows the evolution from Widmanst？tten α-laths to basket-weave α-laths gradually. The micro-hardness increases from the TA2 part to the TA15 part due to the solid solution strengthening and grain boundary strengthening.展开更多
The dynamic globularization kinetics of TA15（Ti-6Al-2Zr-1Mo-1V） titanium alloy with a colony α microstructure during deformation at temperature range of 860-940 ℃ and strain rate range of 0.01-10 s-1 was quantitat...The dynamic globularization kinetics of TA15（Ti-6Al-2Zr-1Mo-1V） titanium alloy with a colony α microstructure during deformation at temperature range of 860-940 ℃ and strain rate range of 0.01-10 s-1 was quantitatively studied through isothermal compression tests.It is found that the dynamic globularization kinetics and the kinetics rate of TA15 are sensitive to deformation parameters.The dynamic globularized fraction increases with increasing strain,temperature but decreasing strain rate.The variation of globularized fraction with strain approximately follows an Avrami type equation.Using the Avrami type equation,the initiation and completion strains for dynamic globularization of TA15 were predicted to be 0.34-0.59 and 3.40-6.80.The kinetics rate of dynamic globularization increases with strain at first,then decreases.The peak value of kinetics rate,which corresponds to 20%-33% globularization fraction,increases with increasing temperature and decreasing strain rate.展开更多
The microstructure, phase composition and cold shut defect of thick titanium alloy electron beam welded joint were studied. The results showed that the microstructure of weld zone was composed of α′ phase; the heat ...The microstructure, phase composition and cold shut defect of thick titanium alloy electron beam welded joint were studied. The results showed that the microstructure of weld zone was composed of α′ phase; the heat affected zone was divided into fine-grained zone and coarse-grained zone, the microstructure of fine-grained zone was primary α phase ＋ β phase ＋ equiaxed α phase, and the microstructure of coarse-grained zone was primary α phase ＋ acicular α′ phase; the microstructure of base metal zone basically consisted of primary α phase, and a small amount of residual β phase sprinkled. The forming. reason of cold shut was analyzed, and the precaution of cold shut was proposed.展开更多
The effects of Si addition on microstructures, mechanical and shape memory properties of Ti-55Ta biomedical alloy were investigated. The results show that the microstructures consist of mainly α′′ martensite and a ...The effects of Si addition on microstructures, mechanical and shape memory properties of Ti-55Ta biomedical alloy were investigated. The results show that the microstructures consist of mainly α′′ martensite and a little β phase, and the grain size decreases obviously with increasing Si addition. When x = 0.2, small （Ti, Ta）3Si precipitates are formed at grain boundaries. With further increasing Si content, the amount of the precipitates gradually increases. The tensile and yield strength of Ti-55Ta-xSi alloys gradually increase with increasing Si addition, whereas elongation decreases. Ti-55Ta-0.1Si alloy exhibits the lowest elastic modulus and the best shape memory recoverable strain. It is revealed that the refinement of grain and the precipitation of （Ti, Ta）3Si phase are responsible to the changes of their mechanical and shape memory properties.展开更多
The difference of energy and electronic structure of V, Nb, and Ta in different crystalline structures were investigated by different methods in density functional theory （DFT）. Lattice constants, total energies, an...The difference of energy and electronic structure of V, Nb, and Ta in different crystalline structures were investigated by different methods in density functional theory （DFT）. Lattice constants, total energies, and densities of states of these metals were calculated using the plane-wave pseudopotential method in DFT. Results were compared with those of projector augmented wave method, CALPHAD method, and experiments. Total energy and electronic structure analyses showed that valence electrons mostly transferred from s to p or d state, changing obviously with both the crystal structure and the elemental period number from V to Ta and leading to stronger cohesion, higher cohesive energy and more stable lattice of heavier metals.展开更多
基金the support from the National Natural Science Foundation of China(22272121,21972107)the National Key Research and Development program of China(2021YFB4001200)。
文摘Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocatalysts have been widely investigated toward hydrogen oxidation reaction(HOR)under alkaline electrolytes,these studies are mostly limited to conventional hexagonal-close-packed(hcp)phase,mainly arising from the lack of sufficient synthesis strategies.In this study,we report the precise synthesis of metastable binary RuW alloy with face-centered-cubic(fcc)phase.We find that the introduction of W can serve as fcc phase seeds and reduce the formation energy of metastable fcc-RuW alloy.Impressively,fcc-RuW exhibits remarkable alkaline HOR performance and stability with the activity of 0.67 mA cm_(Ru)^(-2)which is almost five and three times higher than that of hcp-Ru and commercial Pt/C,respectively,which is attributed to the optimized binding strength of adsorbed hydroxide intermediate derived from tailored electronic structure through W doping and phase engineering.Moreover,this strategy can also be applied to synthesize other metastable fcc-RuCr and fcc-RuMo alloys with enhanced HOR performances.
基金Project(2013zzts025)supported by the Fundamental Research Funds for the Central Universities of China
文摘Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDS), X-ray diffractometry(XRD) and mechanical properties tests. The results show that the maximum values of hardness and strength are HV 1124 and 2466 MPa respectively when 0.4% TaC is added. When the content of TaC is more than 0.6%, the grain size of WC is no longer affected by the amount of TaC, and(W,Ta)C occurs as well. Moreover, the strength and fracture toughness increase and the(Ta+W) content decreases with the increase of TaC content. The dependence of(Ta+W) content on the mechanical properties indicates that(Ta+W) content in Co should be decreased as low as possible to improve the mechanical properties of coarse grained WC-TaC-9Co cemented carbides with the microstructure of WC+γ two phase regions.
文摘Two experimental single crystal superalloys, Ru-free alloy and Ru-containing alloy with [001] orientation, other alloying element contents being basically kept same, were cast in the directionally solidified furnace. The effect of Ru on the stress rupture properties of the single crystal superalloy was investigated at （980 ℃, 250 MPa）, （1100 ℃, 140 MPa） and （1120 ℃, 140 MPa）. The results show that Ru can enhance high temperature stress rupture properties of single crystal superalloy. The improvement effect of Ru addition on stress rupture properties decreases with increasing test temperature. The γ′ coarsening and rafting directionally are observed in Ru-free alloy and Ru-containing alloy after stress rupture test. Needle shaped TCP phases precipitated in both of alloys after stress rupture test at （1100 ℃, 140 MPa） and （1120 ℃, 140 MPa） and no TCP phase was observed in both of alloys after stress rupture test （980 ℃, 250 MPa）. The precipitate volume fraction of TCP phases is significantly decreased by the addition of Ru. At last, the relationship between the microstructure change with Ru addition and improvement of stress rupture properties was discussed.
基金Project(2010CB731705)supported by the National Basic Research Program of China
文摘TA2/TA15 graded structural material（GSM） was fabricated by the laser additive manufacturing（LAM） process. The chemical composition, microstructure and micro-hardness of the as-deposited GSM were investigated. The results show that the TA2 part of exhibiting near-equiaxed grains was Widmanst？tten α-laths microstructure. The TA15 part containing large columnar grains was fine basket-weave microstructure. The graded zone was divided into four deposited layers with 3000 μm in thickness. As the distance from the TA2 part increases, the alloy element contents and the β phase volume fraction increase, the α phase volume fraction decreases and the microstructure shows the evolution from Widmanst？tten α-laths to basket-weave α-laths gradually. The micro-hardness increases from the TA2 part to the TA15 part due to the solid solution strengthening and grain boundary strengthening.
基金Project(50935007)supported by the National Natural Science Foundation of ChinaProject(2010CB731701)supported by the National Basic Research Program of China
文摘The dynamic globularization kinetics of TA15（Ti-6Al-2Zr-1Mo-1V） titanium alloy with a colony α microstructure during deformation at temperature range of 860-940 ℃ and strain rate range of 0.01-10 s-1 was quantitatively studied through isothermal compression tests.It is found that the dynamic globularization kinetics and the kinetics rate of TA15 are sensitive to deformation parameters.The dynamic globularized fraction increases with increasing strain,temperature but decreasing strain rate.The variation of globularized fraction with strain approximately follows an Avrami type equation.Using the Avrami type equation,the initiation and completion strains for dynamic globularization of TA15 were predicted to be 0.34-0.59 and 3.40-6.80.The kinetics rate of dynamic globularization increases with strain at first,then decreases.The peak value of kinetics rate,which corresponds to 20%-33% globularization fraction,increases with increasing temperature and decreasing strain rate.
基金Project (2010CB731704) supported by the National Basic Research Program of China
文摘The microstructure, phase composition and cold shut defect of thick titanium alloy electron beam welded joint were studied. The results showed that the microstructure of weld zone was composed of α′ phase; the heat affected zone was divided into fine-grained zone and coarse-grained zone, the microstructure of fine-grained zone was primary α phase ＋ β phase ＋ equiaxed α phase, and the microstructure of coarse-grained zone was primary α phase ＋ acicular α′ phase; the microstructure of base metal zone basically consisted of primary α phase, and a small amount of residual β phase sprinkled. The forming. reason of cold shut was analyzed, and the precaution of cold shut was proposed.
基金Project(50771086) supported by the National Natural Science Foundation of ChinaProject(NCET) supported by Program for New Century Excellent Talents in University, China+1 种基金Project(NCETFJ) supported by Program for New Century Excellent Talents in Fujian Province University, ChinaProject(2009H0039) supported by Fujian Provincial Department of Science and Technology, China
文摘The effects of Si addition on microstructures, mechanical and shape memory properties of Ti-55Ta biomedical alloy were investigated. The results show that the microstructures consist of mainly α′′ martensite and a little β phase, and the grain size decreases obviously with increasing Si addition. When x = 0.2, small （Ti, Ta）3Si precipitates are formed at grain boundaries. With further increasing Si content, the amount of the precipitates gradually increases. The tensile and yield strength of Ti-55Ta-xSi alloys gradually increase with increasing Si addition, whereas elongation decreases. Ti-55Ta-0.1Si alloy exhibits the lowest elastic modulus and the best shape memory recoverable strain. It is revealed that the refinement of grain and the precipitation of （Ti, Ta）3Si phase are responsible to the changes of their mechanical and shape memory properties.
基金ACKNOWLEDGMENTS This work was supported by the Doctoral Discipline Foundation of the Ministry of Education of China （No.20070533118） and the National Natural Science Foundation of China （No.50871124）. The authors acknowledge Dr. Y. Z. Nie for his useful discussion in calculations.
文摘The difference of energy and electronic structure of V, Nb, and Ta in different crystalline structures were investigated by different methods in density functional theory （DFT）. Lattice constants, total energies, and densities of states of these metals were calculated using the plane-wave pseudopotential method in DFT. Results were compared with those of projector augmented wave method, CALPHAD method, and experiments. Total energy and electronic structure analyses showed that valence electrons mostly transferred from s to p or d state, changing obviously with both the crystal structure and the elemental period number from V to Ta and leading to stronger cohesion, higher cohesive energy and more stable lattice of heavier metals.
