Pulse Electric Discharging (PED) is a novel technique that can modify solidifying structure and reduce grain size. ItS effectsapplied to the high carbon liquid steel were presented here. The macrostructure and microst...Pulse Electric Discharging (PED) is a novel technique that can modify solidifying structure and reduce grain size. ItS effectsapplied to the high carbon liquid steel were presented here. The macrostructure and microstructure of the high carbon alloy steel werealso observed. Results show that (1 ) the length of columnar crystal at the edge of ingot without PED treatment is much longer than thatwith PED, and (2) the perlite lamellae of steel billets after deposed by PED are twisted and shortened. An explanation of those experimental results is given.展开更多
A new technique-series electro-pulse discharge (SEPD)-was developed as a sur-face coating process. In this technique, both positive and negative poles of a pulse power were used as the depositing electrodes with the s...A new technique-series electro-pulse discharge (SEPD)-was developed as a sur-face coating process. In this technique, both positive and negative poles of a pulse power were used as the depositing electrodes with the substrate alloy as an induction electrode. Fe-Cr and Fe-Cr-Y2O3 micro-crystalline coatings were deposited on stain-less steel (Fe-18Cr-8Ni) surfaces. Oxidation at 950℃ in ambient air showed that the coatings greatly improved the oxidation resistance of the steel. The addition of dis-persed Y2O3 nano-particles into the alloy coatings was found to further reduce the scaling rate and enhance the adhesion of oxide scales.展开更多
Electro-pulse modification(EPM) was used to change the dendritic structure of AlSi7Mg alloy to globular one.The effects of the modified temperature,electro-pulse frequency and time on the solidified structure were exa...Electro-pulse modification(EPM) was used to change the dendritic structure of AlSi7Mg alloy to globular one.The effects of the modified temperature,electro-pulse frequency and time on the solidified structure were examined.The results show that these parameters play an important role in the solidified microstructures.That is to say,under the same modified temperature,the solidified microstructure will be improved greatly with the increase of electro-pulse frequency and time,but when they exceed to limit values,the solidified microstructure will become worse,resulting from the decrease of the ratio of nucleation.The experimental results indicate that the suitable modified temperature of AlSi7Mg alloy is 720 °C,and the appropriate electro-pulse frequency and time are 5 Hz and 40 s,respectively.Then the microstructures produced by suitable EPM process were reheated at temperatures between liquidus and solidus,the primary-Al grains ripen further and become more spherical,which is favorable to the semi-solid forming of AlSi7Mg alloy.展开更多
A new technique-series electro-pulse discharg e (SEPD)-was developed as a kind of surface coating process. In this technique, both positive and negative poles of a pulse power were used as the depositing electrodes...A new technique-series electro-pulse discharg e (SEPD)-was developed as a kind of surface coating process. In this technique, both positive and negative poles of a pulse power were used as the depositing electrodes with the substrate allo y as an induction electrode. Micro-crystalline Co-Cr and Co-Cr dispersed wit h Y 2O 3 coatings were deposited on Fe-18Cr-8Ni stainless steel surface by using Co30Cr alloy as the depositing electrodes. Oxidation at 950 ℃ in ambie nt air shows that these coatings greatly improve the oxidation resistance of the steel. The addition of dispersed Y 2O 3 nano-particles into the alloy coati ngs was found to further reduce the scaling rate and enhance the adhesion of oxi de scales.展开更多
A new technique—series electro-pulse discharge (SEPD)—was developed as a surface coating process. In this process, both positive and negative poles of a pulse power were used as the depositing electrodes and the sub...A new technique—series electro-pulse discharge (SEPD)—was developed as a surface coating process. In this process, both positive and negative poles of a pulse power were used as the depositing electrodes and the substrate alloy was used as an induction electrode. The physical process for such SEPD was tested by measuring the relationship between the discharge voltages and gaps in a pin-plate-pin system. Microcrystalline Ni20Cr alloy coatings and oxidedispersed Ni20Cr alloy coatings were prepared on Ni20Cr alloy surface by using a vibrating SEPD device. Oxidation at 950°C in ambient air showed that the microcrystalline Ni20Cr alloy coatings greatly improved the oxidation resistance of the substrate alloy. The addition of dispersed Y2O3 nano-particles into the microcrystalline coatings was found to further reduce the oxidation rate and enhance the oxide spallation resistance.展开更多
Heat treatment is an effective method to improve the intergranular corrosion resistance of the sensitized Al–Mg alloy due to dissolution of the grain boundary precipitates above the solvus temperature ofβ-phase.The ...Heat treatment is an effective method to improve the intergranular corrosion resistance of the sensitized Al–Mg alloy due to dissolution of the grain boundary precipitates above the solvus temperature ofβ-phase.The grain boundary precipitates will grow and coarsening below the solvus temperature.In this study,the in-situ intergranular corrosion performance regeneration of the sensitized Al–Mg alloy can be realized by low-density electro-pulsing treatment below the solvus temperature ofβ-phase.Our findings show that the dissolution of grain boundary precipitates by electro-pulsing treatment is accelerated at relatively low temperature in comparison to traditional heat treatment.The athermal effect produced by the interaction between atoms and electrons on the dissolution of grain boundary precipitates is the main reason for the improved corrosion resistance below the solvus temperature ofβ-phase.展开更多
文摘Pulse Electric Discharging (PED) is a novel technique that can modify solidifying structure and reduce grain size. ItS effectsapplied to the high carbon liquid steel were presented here. The macrostructure and microstructure of the high carbon alloy steel werealso observed. Results show that (1 ) the length of columnar crystal at the edge of ingot without PED treatment is much longer than thatwith PED, and (2) the perlite lamellae of steel billets after deposed by PED are twisted and shortened. An explanation of those experimental results is given.
基金This project was supported by The National Natural Science Foundation of China (Grant No. 59801002).
文摘A new technique-series electro-pulse discharge (SEPD)-was developed as a sur-face coating process. In this technique, both positive and negative poles of a pulse power were used as the depositing electrodes with the substrate alloy as an induction electrode. Fe-Cr and Fe-Cr-Y2O3 micro-crystalline coatings were deposited on stain-less steel (Fe-18Cr-8Ni) surfaces. Oxidation at 950℃ in ambient air showed that the coatings greatly improved the oxidation resistance of the steel. The addition of dis-persed Y2O3 nano-particles into the alloy coatings was found to further reduce the scaling rate and enhance the adhesion of oxide scales.
基金Project(07KJD460007) supported by the Educational Science Foundation of Jiangsu Province,China
文摘Electro-pulse modification(EPM) was used to change the dendritic structure of AlSi7Mg alloy to globular one.The effects of the modified temperature,electro-pulse frequency and time on the solidified structure were examined.The results show that these parameters play an important role in the solidified microstructures.That is to say,under the same modified temperature,the solidified microstructure will be improved greatly with the increase of electro-pulse frequency and time,but when they exceed to limit values,the solidified microstructure will become worse,resulting from the decrease of the ratio of nucleation.The experimental results indicate that the suitable modified temperature of AlSi7Mg alloy is 720 °C,and the appropriate electro-pulse frequency and time are 5 Hz and 40 s,respectively.Then the microstructures produced by suitable EPM process were reheated at temperatures between liquidus and solidus,the primary-Al grains ripen further and become more spherical,which is favorable to the semi-solid forming of AlSi7Mg alloy.
文摘A new technique-series electro-pulse discharg e (SEPD)-was developed as a kind of surface coating process. In this technique, both positive and negative poles of a pulse power were used as the depositing electrodes with the substrate allo y as an induction electrode. Micro-crystalline Co-Cr and Co-Cr dispersed wit h Y 2O 3 coatings were deposited on Fe-18Cr-8Ni stainless steel surface by using Co30Cr alloy as the depositing electrodes. Oxidation at 950 ℃ in ambie nt air shows that these coatings greatly improve the oxidation resistance of the steel. The addition of dispersed Y 2O 3 nano-particles into the alloy coati ngs was found to further reduce the scaling rate and enhance the adhesion of oxi de scales.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59801002).
文摘A new technique—series electro-pulse discharge (SEPD)—was developed as a surface coating process. In this process, both positive and negative poles of a pulse power were used as the depositing electrodes and the substrate alloy was used as an induction electrode. The physical process for such SEPD was tested by measuring the relationship between the discharge voltages and gaps in a pin-plate-pin system. Microcrystalline Ni20Cr alloy coatings and oxidedispersed Ni20Cr alloy coatings were prepared on Ni20Cr alloy surface by using a vibrating SEPD device. Oxidation at 950°C in ambient air showed that the microcrystalline Ni20Cr alloy coatings greatly improved the oxidation resistance of the substrate alloy. The addition of dispersed Y2O3 nano-particles into the microcrystalline coatings was found to further reduce the oxidation rate and enhance the oxide spallation resistance.
基金financially supported by the National Natural Science Foundation of China(Nos.51601011,51571013 and 51971019)the Beijing Laboratory of Metallic Materials and Processing for Modern Transportation,China。
文摘Heat treatment is an effective method to improve the intergranular corrosion resistance of the sensitized Al–Mg alloy due to dissolution of the grain boundary precipitates above the solvus temperature ofβ-phase.The grain boundary precipitates will grow and coarsening below the solvus temperature.In this study,the in-situ intergranular corrosion performance regeneration of the sensitized Al–Mg alloy can be realized by low-density electro-pulsing treatment below the solvus temperature ofβ-phase.Our findings show that the dissolution of grain boundary precipitates by electro-pulsing treatment is accelerated at relatively low temperature in comparison to traditional heat treatment.The athermal effect produced by the interaction between atoms and electrons on the dissolution of grain boundary precipitates is the main reason for the improved corrosion resistance below the solvus temperature ofβ-phase.
