中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 25 No. 2 February 2015 |
（1. School of Mechanical and Materials Engineering, North China University of Technology, Beijing 100144, China;
2. State Key laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:The solid-liquid interfacial morphology evolution was investigated in directional solidification (DS) of Al-1.5%Cu alloy (mass fraction). The results show that the solidified microstructural evolution is gradual other than sharp, and the microstructure patterns are interesting and diversiform at the pulling rate ranging from 30 mm/s to 1500 mm/s. Indeed, dendrite to cell transition follows this sequence: dendrites→banded cellular dendrites→elongated cells and part of dendrites→main elongated cells and little dendrites. Moreover, the present microstructure is not normal microstructure as we saw before. Further, according to the experimental phenomenon, the dendrite to cell transition was studied theoretically. Dendrite tip shape is an important parameter to characterize the dendrite to cell transition. As the dendrite to cell transition is far from equilibrium solidification, non-equilibrium solidification is taken into consideration in calculation. Finally, it is speculated that the dendrite to cell transition would occur at the minimum tip radius.
Key words: Al-Cu alloy; dendrite to cell transition; directional solidification; pulling rate; interface morphology
