In situ nucleation and detachment of dendrites to form equiaxed grains stirred by vibration

摘要

A novel method for nucleation and detachment of dendrites from a vibrating chilling solid surface inserted into the NH_4Cl-H_2O alloy melt has been proposed to further increase the proportion of equiaxed grains in the solidification microstructure. The surface nucleation and evolution behaviours of dendrites on the chilling generator with vibration were observed, and the effects of vibration frequency as well as amplitude on the equiaxed crystallographic morphology were also experimentally studied. The results show that exerting vibration to the chilling generator is helpful to not only prevent the formation of solidifying shell but also promote to form equiaxed grains microstructure, and that the higher vibration frequency and amplitude are, the much finer equiaxed grains are obtained.