中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 10 No. 6 December 2000 |
（1. School of Materials Science and Engineering, Shanghai Jiaotong University,
Shanghai 200030, P.R.China;
2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University,
Xi′an 710072, P.R.China）
Abstract:The solidification process of undercooled Cu70Ni30 alloy melt in a cylindrical crucible was investigated by high speed cinematography. In the experiment, nucleation location was controlled at one end of the sample by means of artificial triggering. The results show that the equiaxed dendritic crystals obtained at low undercooling form in sequential solidification, rather than simultaneously in the entire sample, and the morphology of the recalescence front frequently changes with time. If increment of undercooling results in that the dendrite growth is controlled by thermal diffusion, the primary dendrite arms propagate parallel to each other in〈100〉, and eventually directional solidification microstructure is obtained. At higher undercooling, dendrite growth is destabilized due to solidification contraction, and the microstructure develops into fine quasi-spherical grains through recrystallization, however, the massive nucleation is not found.
Key words: undercooled alloy; solidification; high speed cinematography; microstructure evolution
