Fractal characteristics of dendrite and cellular structure in nickel-based superalloy at intermediate cooling rate

摘要

The fractal characteristics of dendrite and cellular structure of nickel-based superalloy K5 are investigated under directional solidification. Results show that the fractal dimension of the dendrite increases from 1.228 to 1.418 as the withdraw speeds change from 40 to 264?μm/s, whereas the fractal dimension of the cellular changes little as the withdraw speeds from 600 to 952?μm/s. The physical significance of the fractal dimension is analyzed by fractal theory. Based on this, a new idea is proposed that both the fractal dimension and the dendrite arm spacing or cellular spacing be considered to describe the evaluation of the solidification structure completely and integrally.