The effect of cooling rate on the transition of dendrite morphology of a Mg-6Gd （wt%） alloy was semiquantitatively analyzed under a constant temperature gradient by using synchrotron X-ray radiographic technique. Re...The effect of cooling rate on the transition of dendrite morphology of a Mg-6Gd （wt%） alloy was semiquantitatively analyzed under a constant temperature gradient by using synchrotron X-ray radiographic technique. Results show that equiaxed dendrites, including exotic ＇butterfly-shaped＇ dendrite morphology, dominate at high cooling rate （〉1 K/s）. When the cooling rate decreases in the range of 0.5-1 K/s, the equiaxed-to-columnar transition takes place, and solute segregates at the center of two long dendrite arms （LDA） of the ＇butterfly-shaped＇ dendrite. When the cooling rate is lower than 0.3 K/s, directional solidification occurs and the columnar dendritic growth direction gradually rotates from the crystalline axis to the thermal gradient direction with an increase in cooling rate. Meanwhile, interface moves faster but the dendrite arm spacing decreases. Floating, collision and rotation of dendrites under convection were also studied in this work.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
在轨道交通控制系统中,为了保证车辆控制稳定和运行数据及故障记录准确可靠,其关键部件——中央控制单元(Central Control Unit,CCU)和数据记录单元(Event Record Machine,ERM)采用嵌入式实时操作系统VxWorks。一般情况下,该系统启动时...在轨道交通控制系统中,为了保证车辆控制稳定和运行数据及故障记录准确可靠,其关键部件——中央控制单元(Central Control Unit,CCU)和数据记录单元(Event Record Machine,ERM)采用嵌入式实时操作系统VxWorks。一般情况下,该系统启动时需要先启动DOS,之后再被当作一般软件调用启动。在系统启动失败、前面板6个灯常亮故障的基础上,研究DOS对电子盘的读写对其启动过程的影响,提出并验证一种可以直接在FAT32格式电子盘上启动解决方案,避免系统启动失败问题。然后结合作者遇到的不同版本VxWorks在应用过程中的UDP单播问题、FTP文件传输问题、启动检查DBR及读写LBA扇区问题进行测试,并提出了解决方案。展开更多
基金financially supported by the Program of Shanghai Subject Chief Engineering (No. 14XD1425000)the National Natural Science Foundation of China (No. 51304135)the Chinese Scholarship Council and DOE (No. DE-FG02-07ER46417)
文摘The effect of cooling rate on the transition of dendrite morphology of a Mg-6Gd （wt%） alloy was semiquantitatively analyzed under a constant temperature gradient by using synchrotron X-ray radiographic technique. Results show that equiaxed dendrites, including exotic ＇butterfly-shaped＇ dendrite morphology, dominate at high cooling rate （〉1 K/s）. When the cooling rate decreases in the range of 0.5-1 K/s, the equiaxed-to-columnar transition takes place, and solute segregates at the center of two long dendrite arms （LDA） of the ＇butterfly-shaped＇ dendrite. When the cooling rate is lower than 0.3 K/s, directional solidification occurs and the columnar dendritic growth direction gradually rotates from the crystalline axis to the thermal gradient direction with an increase in cooling rate. Meanwhile, interface moves faster but the dendrite arm spacing decreases. Floating, collision and rotation of dendrites under convection were also studied in this work.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
文摘在轨道交通控制系统中,为了保证车辆控制稳定和运行数据及故障记录准确可靠,其关键部件——中央控制单元(Central Control Unit,CCU)和数据记录单元(Event Record Machine,ERM)采用嵌入式实时操作系统VxWorks。一般情况下,该系统启动时需要先启动DOS,之后再被当作一般软件调用启动。在系统启动失败、前面板6个灯常亮故障的基础上,研究DOS对电子盘的读写对其启动过程的影响,提出并验证一种可以直接在FAT32格式电子盘上启动解决方案,避免系统启动失败问题。然后结合作者遇到的不同版本VxWorks在应用过程中的UDP单播问题、FTP文件传输问题、启动检查DBR及读写LBA扇区问题进行测试,并提出了解决方案。
