The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The re...The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The result showed that crack pacing turns much smaller underthe condition of pure heating, especially for crack tips. The healing effect is well related to thelength of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, ironand carbon atoms must diffuse at the high speed in steel to realize that plasticity deformationenergy exceeds and overcomes surface tensile force energy. In addition, phase transformation andstress-stain relationship also have positive effects on the process.展开更多
The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed . The electrochemical properties such as cycling stability, activation property, and the plateau v...The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed . The electrochemical properties such as cycling stability, activation property, and the plateau voltage of the alloy which was heat-treated in various temperatures and times had different changes during the cycle process, the optimum heat-treatment conditions of this alloy were determined by this work.展开更多
The influences of annealing treatment on the electrochemical and structural properties of La 0.75Mg 0.25- Ni 2.8Co 0.5 hydrogen storage alloy were investigated by means of electrochemical studies and X-ray diffraction...The influences of annealing treatment on the electrochemical and structural properties of La 0.75Mg 0.25- Ni 2.8Co 0.5 hydrogen storage alloy were investigated by means of electrochemical studies and X-ray diffraction(XRD) analyses. The XRD results reveal that the peak width gets narrower with increasing annealing temperature, which can be ascribed to the structural change and more homogeneous composition after being annealed. Electrochemical studies show that the discharge capacity and the cycle stability of the alloy electrodes increase after being annealed. The maximum discharge capacity, exchange current density J 0 and limiting current density J L of the as-cast alloy are 388 mA·h/g, 340.5 mA/g and 3 068 mA/g, respectively, and they are increased to 400 mA·h/g, 372.1 mA/g and 3 399 mA/g for the alloy annealed at 1 123 K for 8 h, respectively. Meanwhile, as the discharge current density is 1 250 mA/g, the high rate dischargeability(HRD) increases from 77.4% for the as-cast alloy to 83.3% for the alloy annealed at 1 123 K.展开更多
The transformation behavior of a TiNiCu shape memory alloy electrolyticallycharged with hydrogen was investigated by means of different scanning calorimetry (DSC), opticalmicroscope and X-ray diffraction (XRD). The re...The transformation behavior of a TiNiCu shape memory alloy electrolyticallycharged with hydrogen was investigated by means of different scanning calorimetry (DSC), opticalmicroscope and X-ray diffraction (XRD). The results showed that inter- and inner-granular hydridesformed after charging with hydrogen, and the hydrides suppressed martensitic transformation. Theelectrolytically charged hydrogen can be easily released by heat treatment and the transformationoccurred again, which was verified by the DSC and XRD experiments.展开更多
Fuel cell using borohydride as the fuel has received much attention. AB5-type hydrogen storage alloy used as the anodic material instead of noble metals has been investigated. In order to restrain the generation of hy...Fuel cell using borohydride as the fuel has received much attention. AB5-type hydrogen storage alloy used as the anodic material instead of noble metals has been investigated. In order to restrain the generation of hydrogen and enhance the utilization of borohydride, Ti/Zr metal powders has been added into the parent LmNi4.78Mn0.22 （where Lm is La-richened mischmetal） alloy （LNM） by ball milling and heat treatment methods. It is found that the addition of Ti/Zr metal powders lowers the electrochemical catalytic activity of the electrodes, at the same time, restrains the generation of hydrogen and enhances the utilization of the fuel. All the results show that the hydrogen generation rate or the utilization of the fuel is directly relative to the electrochemical catalytic activity or the discharge capability of the electrodes. The utilization of the fuel increases with discharge current density. It is very important to find a balance between the discharge capability and the utilization of the fuel.展开更多
Hydrogen plays an important role in the formation of quench cracks of structural steels. To clarify hydrogen ab- sorption and desorption during heat treatment of AISI 4140 steel, thermal desorption spectrometry （TDS...Hydrogen plays an important role in the formation of quench cracks of structural steels. To clarify hydrogen ab- sorption and desorption during heat treatment of AISI 4140 steel, thermal desorption spectrometry （TDS） analysis was carried out for the specimens in the as-rolled, as quenched, and quenched and tempered conditions. Results show that hydrogen content increased from 0. 127 ×10 6 in the as-rolled specimen to 0. 316 × 10-6 in the as-oil-quenched specimen. After tempering at 200 ℃, the hydrogen content in the oil-quenched specimen decreased to 0. 155 × 10-6 , and the peak temperature of hydrogen desorption increased from 200 to 360 ℃. From the dependence of hydrogen content in the as-quenched specimens on austenitizing time, it can be deduced that hydrogen absorption occurs during austenitizing. The simulation of hydrogen absorption contributes to a better understanding on the distribution of hy- drogen during the heat treatment in structural steels.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.59971011) and "973" Science Foundation of China (No. 19990650).
文摘The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The result showed that crack pacing turns much smaller underthe condition of pure heating, especially for crack tips. The healing effect is well related to thelength of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, ironand carbon atoms must diffuse at the high speed in steel to realize that plasticity deformationenergy exceeds and overcomes surface tensile force energy. In addition, phase transformation andstress-stain relationship also have positive effects on the process.
文摘The effect of heat-treatment process on the properties of Mm0.8Mg0.2(NiCoAlMn)3.5 hydrogen storage alloy was discussed . The electrochemical properties such as cycling stability, activation property, and the plateau voltage of the alloy which was heat-treated in various temperatures and times had different changes during the cycle process, the optimum heat-treatment conditions of this alloy were determined by this work.
文摘The influences of annealing treatment on the electrochemical and structural properties of La 0.75Mg 0.25- Ni 2.8Co 0.5 hydrogen storage alloy were investigated by means of electrochemical studies and X-ray diffraction(XRD) analyses. The XRD results reveal that the peak width gets narrower with increasing annealing temperature, which can be ascribed to the structural change and more homogeneous composition after being annealed. Electrochemical studies show that the discharge capacity and the cycle stability of the alloy electrodes increase after being annealed. The maximum discharge capacity, exchange current density J 0 and limiting current density J L of the as-cast alloy are 388 mA·h/g, 340.5 mA/g and 3 068 mA/g, respectively, and they are increased to 400 mA·h/g, 372.1 mA/g and 3 399 mA/g for the alloy annealed at 1 123 K for 8 h, respectively. Meanwhile, as the discharge current density is 1 250 mA/g, the high rate dischargeability(HRD) increases from 77.4% for the as-cast alloy to 83.3% for the alloy annealed at 1 123 K.
基金This project is financially supported by the National Natural Science Foundation of China (No.10175042) and by the Pro-gram for New Century Excellent Talents in Universities.
文摘The transformation behavior of a TiNiCu shape memory alloy electrolyticallycharged with hydrogen was investigated by means of different scanning calorimetry (DSC), opticalmicroscope and X-ray diffraction (XRD). The results showed that inter- and inner-granular hydridesformed after charging with hydrogen, and the hydrides suppressed martensitic transformation. Theelectrolytically charged hydrogen can be easily released by heat treatment and the transformationoccurred again, which was verified by the DSC and XRD experiments.
文摘Fuel cell using borohydride as the fuel has received much attention. AB5-type hydrogen storage alloy used as the anodic material instead of noble metals has been investigated. In order to restrain the generation of hydrogen and enhance the utilization of borohydride, Ti/Zr metal powders has been added into the parent LmNi4.78Mn0.22 （where Lm is La-richened mischmetal） alloy （LNM） by ball milling and heat treatment methods. It is found that the addition of Ti/Zr metal powders lowers the electrochemical catalytic activity of the electrodes, at the same time, restrains the generation of hydrogen and enhances the utilization of the fuel. All the results show that the hydrogen generation rate or the utilization of the fuel is directly relative to the electrochemical catalytic activity or the discharge capability of the electrodes. The utilization of the fuel increases with discharge current density. It is very important to find a balance between the discharge capability and the utilization of the fuel.
基金Item Sponsored by National Basic Research Program(973 Program)of China(2010CB630800)
文摘Hydrogen plays an important role in the formation of quench cracks of structural steels. To clarify hydrogen ab- sorption and desorption during heat treatment of AISI 4140 steel, thermal desorption spectrometry （TDS） analysis was carried out for the specimens in the as-rolled, as quenched, and quenched and tempered conditions. Results show that hydrogen content increased from 0. 127 ×10 6 in the as-rolled specimen to 0. 316 × 10-6 in the as-oil-quenched specimen. After tempering at 200 ℃, the hydrogen content in the oil-quenched specimen decreased to 0. 155 × 10-6 , and the peak temperature of hydrogen desorption increased from 200 to 360 ℃. From the dependence of hydrogen content in the as-quenched specimens on austenitizing time, it can be deduced that hydrogen absorption occurs during austenitizing. The simulation of hydrogen absorption contributes to a better understanding on the distribution of hy- drogen during the heat treatment in structural steels.
