We systematically investigate the internal friction properties of a Fe-(43 at.%)Al powder mixture compact during the heating process with the expectation to understand the phase formation and transition process.Three ...We systematically investigate the internal friction properties of a Fe-(43 at.%)Al powder mixture compact during the heating process with the expectation to understand the phase formation and transition process.Three internal friction peaks are successively observed during the heating process from room temperature to 750℃,but almost completely disappear in the subsequent cooling process.Three internal friction peaks exhibit obvious measuring frequency dependence,which increases with decreasing the frequency.The first internal friction peak originates from the micro-sliding of weak bonding interface between Al particles corresponding to a recr.ystallization process of deformed Al particles.The second internal friction peak is attributed to a phase formation process associated with the formation of the intermediate phase Fe2Al5.The third internal friction peak is considered to result from the formation of the FeAl intermetallic compound owing to the reaction of Fe2Al5 and residual Fe initiated by a dramatic thermal explosion reaction.展开更多
Amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 pow...Amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were investigated by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, and differential scanning calorimetry（DSC）. The isothermal crystallization kinetics was analyzed by the Johnson-Mehl-Avrami equation. In the results, the supercooled liquid region of the amorphous alloy is as high as 81 K, as determined by-non-isothermal DSC curves. The activation energy for crystallization is as high as 312.6 kJ ·mol1 obtained by Kissinger and Ozawa analyses. The values of Avrami exponent（n） imply that the crystallization is dominated by interface-controlled three-dimensional growth in the early stage and the end stage and by diffusion-controlled two- or three-dimensional growth in the middle stage. In addition, the amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were sintered under 2 GPa at temperatures of 673 K and 723 K. The results show that the Vickers hardness of the compacted powders is as high as Hv 1215.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.51661032 and 51301150the Special Program of Science and Technology New Star of Shaanxi Province under Grant No.2013KJXX-11。
文摘We systematically investigate the internal friction properties of a Fe-(43 at.%)Al powder mixture compact during the heating process with the expectation to understand the phase formation and transition process.Three internal friction peaks are successively observed during the heating process from room temperature to 750℃,but almost completely disappear in the subsequent cooling process.Three internal friction peaks exhibit obvious measuring frequency dependence,which increases with decreasing the frequency.The first internal friction peak originates from the micro-sliding of weak bonding interface between Al particles corresponding to a recr.ystallization process of deformed Al particles.The second internal friction peak is attributed to a phase formation process associated with the formation of the intermediate phase Fe2Al5.The third internal friction peak is considered to result from the formation of the FeAl intermetallic compound owing to the reaction of Fe2Al5 and residual Fe initiated by a dramatic thermal explosion reaction.
基金financially supported by the National Natural Science Foundation of China(No.51371167)
文摘Amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were investigated by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, and differential scanning calorimetry（DSC）. The isothermal crystallization kinetics was analyzed by the Johnson-Mehl-Avrami equation. In the results, the supercooled liquid region of the amorphous alloy is as high as 81 K, as determined by-non-isothermal DSC curves. The activation energy for crystallization is as high as 312.6 kJ ·mol1 obtained by Kissinger and Ozawa analyses. The values of Avrami exponent（n） imply that the crystallization is dominated by interface-controlled three-dimensional growth in the early stage and the end stage and by diffusion-controlled two- or three-dimensional growth in the middle stage. In addition, the amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were sintered under 2 GPa at temperatures of 673 K and 723 K. The results show that the Vickers hardness of the compacted powders is as high as Hv 1215.
