The microstructure ofthe Mg/MmNi5-x (CoAlMn )x composite hydrogen storage material preparedby the method of mechanical alloyingwas characterized by X-ray diffraction, SEM and particle size distribution analysis. By me...The microstructure ofthe Mg/MmNi5-x (CoAlMn )x composite hydrogen storage material preparedby the method of mechanical alloyingwas characterized by X-ray diffraction, SEM and particle size distribution analysis. By measuring PCTcurves, the hydrogen absorption properties of the composite was evaluated.The results show that nanocrystallinecomposite structure can be obtainedunder adequate ball milling condition. The reactive activation and hydrogen absorption capacity are improved compared with the sole MmNi5-x(CoAlMn)x alloy. The effect ofmagnesium on the microstructure andhydrogen absorption properties of thecomposite were also evaluated.展开更多
Three nanocrystalline alloys, Fe50Al50, Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20 (molar fraction, %), were synthesized from elemental powders by high-energy ball milling. The structural evolutions and morphological chan...Three nanocrystalline alloys, Fe50Al50, Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20 (molar fraction, %), were synthesized from elemental powders by high-energy ball milling. The structural evolutions and morphological changes of the milled powders were characterized by X-ray diffractometry(XRD), transmission electron microscopy(TEM) and scanning electron microscopy(SEM). The effects of different Ti, B additions on the structure and phase transformation in these alloys were also discussed. It is observed that the diffusion of Al, Ti, B atoms into Fe lattice occurs during milling, leading to the formation of a BCC phase identified as Fe(Al) or Fe(Al, Ti, B) supersaturated solid solution. Fe-based solid solution with nanocrystalline structure is observed to be present as the only phase in all the alloy compositions after milling. Furthermore, the contents of Ti, B affect the formation of mechanical alloying products, changes in the lattice parameter as well as the grain size.展开更多
We have systematically studied the microstructure and mechanical properties of Ni-5wt%Al and Ni-20wt%Al composite coat- ings fabricated on 6061-T6 aluminum alloy sheet by twin-wire arc spraying under different experim...We have systematically studied the microstructure and mechanical properties of Ni-5wt%Al and Ni-20wt%Al composite coat- ings fabricated on 6061-T6 aluminum alloy sheet by twin-wire arc spraying under different experimental conditions. The abrasive wear be- havior and interface diffusion behavior of the composite coatings were evaluated by dry/wet rubber wheel abrasive wear tests and heat treat- ment, respectively. Experimental results indicate that the composite coatings exhibit features of adhesive wear. Besides, the Vickers micro- hardness of NiA1 and Ni3AI intermetallic compounds is relatively larger than that of the substrate, which is beneficial for enhancing the wear resistance. With the increase of annealing temperature and time, the interface diffusion area between the Ni-Al coating and the substrate gradually expands with the formation of NiAl3 and Ni2Al3 phases, and is controlled by diffusion of aluminum atoms. The grain growth ex- ponent n of diffusion kinetics of the Ni-Al coating, calculated via a high-temperature diffusion model at 400, 480, and 550℃, is between 0.28 and 0.38. This satisfies the cubic law, which is consistent with the general theoretical relationship of high-temperature diffusion.展开更多
A sub-microstructure titanium aluminide alloy /Al2O3 (3A) composite was obtained by crystallization of the amorphous powders, which were prepared by mechanical alloying (MA) in a planetary ball milling system using Ti...A sub-microstructure titanium aluminide alloy /Al2O3 (3A) composite was obtained by crystallization of the amorphous powders, which were prepared by mechanical alloying (MA) in a planetary ball milling system using Ti-Al-TiO2 as raw materials. The experimental results show that, when the milling time increases up to 30 h, the hcp Ti(Al) supersaturated solid solution disappears, only amorphous phase is left. The compact samples were synthesized by hot-press to 1 200℃with the amorphous as a precursor; the final phases of the matrix and strengthened phase areγ-TiAl and Al2O3. The phases come from in situ crystallization and transformation. The samples, fabricated from the amorphous phase by hot press sintering, have high bending strength and fracture toughness.展开更多
Mo5Si3-20%Al2O3 （mass fraction） nanocomposite was synthesized by mechanical alloying （MA） of mixture of MoO3,Mo,Si and Al powders.The structural evolutions of powder particles during mechanical alloying were studi...Mo5Si3-20%Al2O3 （mass fraction） nanocomposite was synthesized by mechanical alloying （MA） of mixture of MoO3,Mo,Si and Al powders.The structural evolutions of powder particles during mechanical alloying were studied by X-ray diffractometry （XRD）,scanning electron microscopy （SEM）,transmission electron microscopy （TEM） and differential thermal analysis （DTA）.Results show that Mo5Si3-20%Al2O3 was obtained after 10 h of milling.The spontaneous reaction of powders takes place in an explosive mode.The crystallite sizes of Mo5Si3 and Al2O3 after milling for 30 h were 36.3 nm and 21.9 nm,respectively.With longer milling time,the intensities of Mo5Si3 and Al2O3 peaks decreased and became broad due to the decrease in crystallite size.Thermal analysis results and XRD analysis results show that the Mo5Si3-Al2O3 nanocomposite powders are very stable during milling （up to 30 h） and heating （up to 1 000℃） and no transformation takes place.展开更多
文摘The microstructure ofthe Mg/MmNi5-x (CoAlMn )x composite hydrogen storage material preparedby the method of mechanical alloyingwas characterized by X-ray diffraction, SEM and particle size distribution analysis. By measuring PCTcurves, the hydrogen absorption properties of the composite was evaluated.The results show that nanocrystallinecomposite structure can be obtainedunder adequate ball milling condition. The reactive activation and hydrogen absorption capacity are improved compared with the sole MmNi5-x(CoAlMn)x alloy. The effect ofmagnesium on the microstructure andhydrogen absorption properties of thecomposite were also evaluated.
基金Project(050440704) supported by the Natural Science Foundation of Anhui Province, ChinaProject(103-037016) supported by the Technological Innovation Foundation of Hefei University of Technology, China
文摘Three nanocrystalline alloys, Fe50Al50, Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20 (molar fraction, %), were synthesized from elemental powders by high-energy ball milling. The structural evolutions and morphological changes of the milled powders were characterized by X-ray diffractometry(XRD), transmission electron microscopy(TEM) and scanning electron microscopy(SEM). The effects of different Ti, B additions on the structure and phase transformation in these alloys were also discussed. It is observed that the diffusion of Al, Ti, B atoms into Fe lattice occurs during milling, leading to the formation of a BCC phase identified as Fe(Al) or Fe(Al, Ti, B) supersaturated solid solution. Fe-based solid solution with nanocrystalline structure is observed to be present as the only phase in all the alloy compositions after milling. Furthermore, the contents of Ti, B affect the formation of mechanical alloying products, changes in the lattice parameter as well as the grain size.
基金financially supported by the International Cooperation Project of the Ministry of Science and Technology of China(ICPMSTPRC,No.2008DFR50070)
文摘We have systematically studied the microstructure and mechanical properties of Ni-5wt%Al and Ni-20wt%Al composite coat- ings fabricated on 6061-T6 aluminum alloy sheet by twin-wire arc spraying under different experimental conditions. The abrasive wear be- havior and interface diffusion behavior of the composite coatings were evaluated by dry/wet rubber wheel abrasive wear tests and heat treat- ment, respectively. Experimental results indicate that the composite coatings exhibit features of adhesive wear. Besides, the Vickers micro- hardness of NiA1 and Ni3AI intermetallic compounds is relatively larger than that of the substrate, which is beneficial for enhancing the wear resistance. With the increase of annealing temperature and time, the interface diffusion area between the Ni-Al coating and the substrate gradually expands with the formation of NiAl3 and Ni2Al3 phases, and is controlled by diffusion of aluminum atoms. The grain growth ex- ponent n of diffusion kinetics of the Ni-Al coating, calculated via a high-temperature diffusion model at 400, 480, and 550℃, is between 0.28 and 0.38. This satisfies the cubic law, which is consistent with the general theoretical relationship of high-temperature diffusion.
基金Projects(50432010, 50372037) supported by the National Natural Science Foundation of Chinaproject(SUST-B14) supported by the Scientific Research Foundation of Shaanxi University of Science and Technology, China
文摘A sub-microstructure titanium aluminide alloy /Al2O3 (3A) composite was obtained by crystallization of the amorphous powders, which were prepared by mechanical alloying (MA) in a planetary ball milling system using Ti-Al-TiO2 as raw materials. The experimental results show that, when the milling time increases up to 30 h, the hcp Ti(Al) supersaturated solid solution disappears, only amorphous phase is left. The compact samples were synthesized by hot-press to 1 200℃with the amorphous as a precursor; the final phases of the matrix and strengthened phase areγ-TiAl and Al2O3. The phases come from in situ crystallization and transformation. The samples, fabricated from the amorphous phase by hot press sintering, have high bending strength and fracture toughness.
基金Project(3ZS061-A25-038) supported by the Natural Science Foundation of Gansu Province,China
文摘Mo5Si3-20%Al2O3 （mass fraction） nanocomposite was synthesized by mechanical alloying （MA） of mixture of MoO3,Mo,Si and Al powders.The structural evolutions of powder particles during mechanical alloying were studied by X-ray diffractometry （XRD）,scanning electron microscopy （SEM）,transmission electron microscopy （TEM） and differential thermal analysis （DTA）.Results show that Mo5Si3-20%Al2O3 was obtained after 10 h of milling.The spontaneous reaction of powders takes place in an explosive mode.The crystallite sizes of Mo5Si3 and Al2O3 after milling for 30 h were 36.3 nm and 21.9 nm,respectively.With longer milling time,the intensities of Mo5Si3 and Al2O3 peaks decreased and became broad due to the decrease in crystallite size.Thermal analysis results and XRD analysis results show that the Mo5Si3-Al2O3 nanocomposite powders are very stable during milling （up to 30 h） and heating （up to 1 000℃） and no transformation takes place.
