Real time observation of nucleation and detachment of crystal from chilling surface Part I – effects of vibration

Abstract

The nucleation and detachment of grains from a chilling surface were observed in real time in a model NH₄Cl solution system. The effects of vibration frequency and amplitude on the detachment behaviour and crystallographic morphology of grains were also studied. The results show that partial dendrite arms were broken off under low frequency vibration, whereas the entire dendrite was broken off at its root under high frequency vibration. The higher the frequency and amplitude, the thinner the detached grains. The effect of frequency on the morphology of grains is much greater than that of amplitude, thus increasing vibration frequency is effective in forming fine granular grains, but not amplitude. The amount of detached grains increases with increasing vibration frequency and amplitude up to 1200 Hz and 80 μm; further increase in vibration frequency or amplitude reduced the amount of detached grains.

Keywords:

• NUCLEATION
• SOLIDIFICATION
• DENDRITIC GROWTH
• CRYSTALLOGRAPHY
• VIBRATION