The effect of rare earth (RE) elements on the morphologies and sizes of Si phases in the hypereutectic A1-Si alloys modified with P was investigated. The results show that the addition of La element to the hypereute...The effect of rare earth (RE) elements on the morphologies and sizes of Si phases in the hypereutectic A1-Si alloys modified with P was investigated. The results show that the addition of La element to the hypereutectic A1-Si alloys can enhance the effect of P element on the modification of the primary Si phases. In the multiplex modification of RE-P, the primary Si phase is refiner and the shape of the eutectic Si is changed from long needle-like to short rod-like. Moreover, the agglomeration rate of the primary Si phase is slowed greatly. Even the melt is held for 6 h, the average size of the primary Si phase is still satisfied. The results analyzed by scanning electron microscope (SEM) indicate that La is richer at A1-Si interface than that in α-A1 or primary Si phase. The higher the La content in the A1-Si interface, the smaller the primary Si phase.展开更多
Hypereutectic Al-17.5Si (wt pct) and Al-25Si (wt pct) alloys with various content of rare earth Er were prepared by conventional casting technique. The effect of Er on the microstructure and properties of the hype...Hypereutectic Al-17.5Si (wt pct) and Al-25Si (wt pct) alloys with various content of rare earth Er were prepared by conventional casting technique. The effect of Er on the microstructure and properties of the hypereutectic Al-Si alloys was investigated using optical microscopy, scanning electron microscopy as well as friction and wear tests. It was found that optimal amount of Er exists in modifying the hypereutectic Al-Si alloys. An appropriate addition of Er improved the anti-wear properties, and reduced the friction coefficient of the hypereutectic Al-Si alloys studied. The primary silicon crystals in the hypereutectic Al-Si alloys were refined with the suitable addition of Er element. The modification mechanism was also discussed in this paper.展开更多
The Mg-A1 hydrogen storage alloy was suc- cessfully prepared by combustion synthesis (CS) method. The formation of alloy phases during the CS process was studied using X-ray diffraction (XRD), scanning electron mi...The Mg-A1 hydrogen storage alloy was suc- cessfully prepared by combustion synthesis (CS) method. The formation of alloy phases during the CS process was studied using X-ray diffraction (XRD), scanning electron microscope (SEM), and differential scanning calorimetry (DSC). When the time increases from 0, 0.5, 1.0 to 2.0 h at 733 K, the products are Mg and A1; Mg2A13, Mg and A1; Mgl7All2, Mg2A13; and Mg; and eventually only MgI7A112, respectively. Combined with three peaks in the DSC traces, it is concluded that the formation of MglyAll2 during the CS includes three processes, namely, the formation of MgzA13 first; then the unsaturated solid solution, MglvAla2; and finally the complete MglvA112 alloy. The formation of MgzA13 prior to MglvA112 in this work is different from those prepared by mechanical alloying. This is thought to be related to the instant high temperature during the ther- mal explosion of CS.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.50075051)
文摘The effect of rare earth (RE) elements on the morphologies and sizes of Si phases in the hypereutectic A1-Si alloys modified with P was investigated. The results show that the addition of La element to the hypereutectic A1-Si alloys can enhance the effect of P element on the modification of the primary Si phases. In the multiplex modification of RE-P, the primary Si phase is refiner and the shape of the eutectic Si is changed from long needle-like to short rod-like. Moreover, the agglomeration rate of the primary Si phase is slowed greatly. Even the melt is held for 6 h, the average size of the primary Si phase is still satisfied. The results analyzed by scanning electron microscope (SEM) indicate that La is richer at A1-Si interface than that in α-A1 or primary Si phase. The higher the La content in the A1-Si interface, the smaller the primary Si phase.
基金supported by the National Key Technology R&D Program of China(No.2009BAE80B00)
文摘Hypereutectic Al-17.5Si (wt pct) and Al-25Si (wt pct) alloys with various content of rare earth Er were prepared by conventional casting technique. The effect of Er on the microstructure and properties of the hypereutectic Al-Si alloys was investigated using optical microscopy, scanning electron microscopy as well as friction and wear tests. It was found that optimal amount of Er exists in modifying the hypereutectic Al-Si alloys. An appropriate addition of Er improved the anti-wear properties, and reduced the friction coefficient of the hypereutectic Al-Si alloys studied. The primary silicon crystals in the hypereutectic Al-Si alloys were refined with the suitable addition of Er element. The modification mechanism was also discussed in this paper.
基金financially supported by the National Natural Science Foundation of China(Nos.51071085 and 51171079)Specialized Research Fund for the Doctoral Program of High Education(No.20093221110008)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The Mg-A1 hydrogen storage alloy was suc- cessfully prepared by combustion synthesis (CS) method. The formation of alloy phases during the CS process was studied using X-ray diffraction (XRD), scanning electron microscope (SEM), and differential scanning calorimetry (DSC). When the time increases from 0, 0.5, 1.0 to 2.0 h at 733 K, the products are Mg and A1; Mg2A13, Mg and A1; Mgl7All2, Mg2A13; and Mg; and eventually only MgI7A112, respectively. Combined with three peaks in the DSC traces, it is concluded that the formation of MglyAll2 during the CS includes three processes, namely, the formation of MgzA13 first; then the unsaturated solid solution, MglvAla2; and finally the complete MglvA112 alloy. The formation of MgzA13 prior to MglvA112 in this work is different from those prepared by mechanical alloying. This is thought to be related to the instant high temperature during the ther- mal explosion of CS.