Equi-axed growth and related segregations in cast metallic alloys

Full-scale trials of DC ingots and laboratory scale directional solidification experiments have been performed to study the effect of grain structure on macro-segregation in industrial cast products. An Al alloy sheet ingot was cast with constant casting conditions (speed, superheat, cooling rate) except for the grain refiner: the first half of the ingot was non-inoculated, while the second half was inoculated. The results indicate that the extent and intensity of the centreline segregation is modified via the grain-refinement treatment: the finer the grains are, the more intense is the macro-segregation.

Numerical simulations of directional solidification of binary Al-Cu alloys have been carried out with the help of a 2D finite volume software which takes account of the movement of the liquid with respect to the solid in the mushy zone. It is possible to account for the segregation pattern of the directionally solidified ingots that exhibit columnar or coarse equi-axed grain structures. Contrarily, the intense segregation of the fine-grained ingots is not yet understood.     

机器人精密装配实验系统的研究

介绍了由作者研究的仿生型超精密平面驱动器ＢＵＰＡ、机器人微驱动末端操作器ＦＰＷＭ和具有主被动适应功能的主从微操作器ＡＰＭＭ，将它们与普通的工业机器人组成宏／微操作系统，分别成功地完成了机器人自动精密配作业。     

Modelling inclusion evolution in Al–Ti-killed steels during ladle mixing process

A reaction model was developed to better understand the evolution of inclusions in Al–Ti-killed steels during the ladle mixing process. The fluctuation of steel chemistry gave rise to the transient evolution of inclusions during the mixing process. The formed Al₂O₃ in the steel can be hardly influenced by the addition of FeTi, while adding Al can effectively modify the TiO_x-containing oxides to solid Al₂O₃. The formation of Al₂O₃–TiO_x inclusions can be suppressed by increasing Al and lowering Ti in the steel. The alloying sequence of adding Ti after the Al addition is beneficial to improve the recovery of Ti. The one-point strong air absorption may cause the formation of the unwanted Al₂O₃–TiO_x inclusions in Al–Ti-killed steels. The critical oxygen contents in the molten steel with varying Al and Ti concentrations were predicted to avoid the formation of Al₂O₃–TiO_x inclusions and Ti loss.