Room temperature and high temperature microstructural and mechanical properties of arc melted Ni Al-28Cr-6Mo eutectic alloys doped with 0.1% Fe, 0.2% Fe and 0.5% Fe(mole fraction) were investigated. The homogenization...Room temperature and high temperature microstructural and mechanical properties of arc melted Ni Al-28Cr-6Mo eutectic alloys doped with 0.1% Fe, 0.2% Fe and 0.5% Fe(mole fraction) were investigated. The homogenization heat treatment of the alloys was conducted at 1300℃ in Ar atmosphere. Microscopic analyses, hardness measurements, XRD measurements and compression tests were used to characterize the alloys. As-cast and homogenized alloys exhibit fine cellular eutectic structures with coarse intercellular eutectic structure. The increase in the content of Fe results in coarsening eutectic layers and the decrease in eutectic cells. All alloys have very high compressive stress and strain at room temperature. The addition of Fe has small negative impact on the strength and ductility of the alloys at room temperature. However, the addition of Fe increases the high temperature strength of the alloy. High temperature XRD patterns show that peaks shift to lower Bragg angles. This indicates that the lattice parameter of the alloys increases.展开更多
Theductility and hardness of AA6011/SiCp composites using NaCl, SnCl2, NH4Cl and PdCl2 as wetting reagents were investigated. SiCp was cleaned with the wetting reagents, and used as reinforcement in AA6011 alloy using...Theductility and hardness of AA6011/SiCp composites using NaCl, SnCl2, NH4Cl and PdCl2 as wetting reagents were investigated. SiCp was cleaned with the wetting reagents, and used as reinforcement in AA6011 alloy using the stir casting method. Ductility and hardness responses of the composites were measured using standard methods. Microstructural features were examined using scanning electron microscopy and the phases were determined with the help of an X-ray diffractometer. The results show that for all wetting agents, the increase in cleaning time leads to initial increase in ductility to a certain value, but a decrease afterwards with further increase in cleaning time. The best combination of hardness （BHN 57.88） and ductility （11.91%） was shown under conditions of 40 g/L SnCl2and cleaning time of 60 min. A minor formation of Al4C3was noted in diffraction patterns, indicating that the formation of deleterious precipitate was hindered by the cleaning process.展开更多
The modification of A356 aluminum-silicon alloy using yttrium oxide (Y2O3) was studied. Addition levels of up to 2.5 wt.% Y2O3 were investigated. A premixed powder of Al-30wt.%Y2O3 was added to the melt at about 750℃...The modification of A356 aluminum-silicon alloy using yttrium oxide (Y2O3) was studied. Addition levels of up to 2.5 wt.% Y2O3 were investigated. A premixed powder of Al-30wt.%Y2O3 was added to the melt at about 750℃ using vortex method. Samples were then poured in sand mold. The results showed that evident modification was obtained using the Y2O3 addition. The optimum level was 1.5 wt.%, and was corresponding to a eutectic temperature depression from 568 to 557℃. The eutectic Si particles were refined in length from 44.8 to 8.3 μm, and modified in aspect ratio from 6.8 to 0.98. Higher additions of Y2O3 caused de-modification of the eutectic Si particles. The ductility of the modified specimens was enhanced by more than 20% compared to the unmodified ones. This was associated with a gradual transfer from cleavage to a more ductile mode of fracture.展开更多
This article introduces the recent advances of China in the fields of process technology of delayed coking, enlarged equipment size, hydraulic decoking, automatic control and environmental protection. By the end of 20...This article introduces the recent advances of China in the fields of process technology of delayed coking, enlarged equipment size, hydraulic decoking, automatic control and environmental protection. By the end of 2004 the total capacity of delayed coking uniis in China had reached 37.24 Mt/a with the maximum coke drum diameter equating to 9.4 m. This article also presents the investmerit in delayed cokers and the current production status while pointing out the existing problems and future development trends.展开更多
The substantive characteristics of the connotation of ＂State＂ include two parts： （I） the relatively perpetual and impersonalized political system; （II） the ductility of organization forms within the space and p...The substantive characteristics of the connotation of ＂State＂ include two parts： （I） the relatively perpetual and impersonalized political system; （II） the ductility of organization forms within the space and politics. And the later part is the absolute attribute of this connotation while the former part tends to show with different forms. Therefore, it is more suitable for the former one to be the objective for study on the evolution process of the connotation of ＂State＂ at different stages. Based on this understanding, the author discusses the specific political system at different stages and the relatively perpetual and impersonalized methods for the realization of the system, then tries to define the connotation of the early state, ancient state and modem state in Chinese history.展开更多
基金Tubitak for their financial support under Contract No. 213M247
文摘Room temperature and high temperature microstructural and mechanical properties of arc melted Ni Al-28Cr-6Mo eutectic alloys doped with 0.1% Fe, 0.2% Fe and 0.5% Fe(mole fraction) were investigated. The homogenization heat treatment of the alloys was conducted at 1300℃ in Ar atmosphere. Microscopic analyses, hardness measurements, XRD measurements and compression tests were used to characterize the alloys. As-cast and homogenized alloys exhibit fine cellular eutectic structures with coarse intercellular eutectic structure. The increase in the content of Fe results in coarsening eutectic layers and the decrease in eutectic cells. All alloys have very high compressive stress and strain at room temperature. The addition of Fe has small negative impact on the strength and ductility of the alloys at room temperature. However, the addition of Fe increases the high temperature strength of the alloy. High temperature XRD patterns show that peaks shift to lower Bragg angles. This indicates that the lattice parameter of the alloys increases.
基金the University of Lagos, Nigeria, for providing the platform for the Tetfund Research Grant (CRC/ TETFUND/No.2011/2013) used for this research
文摘Theductility and hardness of AA6011/SiCp composites using NaCl, SnCl2, NH4Cl and PdCl2 as wetting reagents were investigated. SiCp was cleaned with the wetting reagents, and used as reinforcement in AA6011 alloy using the stir casting method. Ductility and hardness responses of the composites were measured using standard methods. Microstructural features were examined using scanning electron microscopy and the phases were determined with the help of an X-ray diffractometer. The results show that for all wetting agents, the increase in cleaning time leads to initial increase in ductility to a certain value, but a decrease afterwards with further increase in cleaning time. The best combination of hardness （BHN 57.88） and ductility （11.91%） was shown under conditions of 40 g/L SnCl2and cleaning time of 60 min. A minor formation of Al4C3was noted in diffraction patterns, indicating that the formation of deleterious precipitate was hindered by the cleaning process.
基金financial support from the Central Metallurgical Research and Development Institute (CMRDI), Ministry of Scientific Research, Egypt
文摘The modification of A356 aluminum-silicon alloy using yttrium oxide (Y2O3) was studied. Addition levels of up to 2.5 wt.% Y2O3 were investigated. A premixed powder of Al-30wt.%Y2O3 was added to the melt at about 750℃ using vortex method. Samples were then poured in sand mold. The results showed that evident modification was obtained using the Y2O3 addition. The optimum level was 1.5 wt.%, and was corresponding to a eutectic temperature depression from 568 to 557℃. The eutectic Si particles were refined in length from 44.8 to 8.3 μm, and modified in aspect ratio from 6.8 to 0.98. Higher additions of Y2O3 caused de-modification of the eutectic Si particles. The ductility of the modified specimens was enhanced by more than 20% compared to the unmodified ones. This was associated with a gradual transfer from cleavage to a more ductile mode of fracture.
文摘This article introduces the recent advances of China in the fields of process technology of delayed coking, enlarged equipment size, hydraulic decoking, automatic control and environmental protection. By the end of 2004 the total capacity of delayed coking uniis in China had reached 37.24 Mt/a with the maximum coke drum diameter equating to 9.4 m. This article also presents the investmerit in delayed cokers and the current production status while pointing out the existing problems and future development trends.
文摘The substantive characteristics of the connotation of ＂State＂ include two parts： （I） the relatively perpetual and impersonalized political system; （II） the ductility of organization forms within the space and politics. And the later part is the absolute attribute of this connotation while the former part tends to show with different forms. Therefore, it is more suitable for the former one to be the objective for study on the evolution process of the connotation of ＂State＂ at different stages. Based on this understanding, the author discusses the specific political system at different stages and the relatively perpetual and impersonalized methods for the realization of the system, then tries to define the connotation of the early state, ancient state and modem state in Chinese history.
