Microstructure and fractal characteristics of the solid-liquid interface forming during directional solidification of Inconel 718

摘要

The solidification microstructure and fractal characteristics of the solid-liquid interfaces of Inconel718, under different cooling rates during directional solidification, were investigated by using SEM. Results showedthat 5 μm/s was the cellular-dendrite transient rate. The prime dendrite arm spacing (PDAS) was measured byImage Tool and it decreased with the cooling rate increased. The fractal dimension of the interfaces was calculatedand it changes from 1.204310 to 1.517265 with the withdrawal rate ranging from 10 to 100 μm/s. The physicalsignificance of the fractal dimension was analyzed by using fractal theory. It was found that the fractal dimensionof the dendrites can be used to describe the solidification microstructure and parameters at low cooling rate, butboth the fractal dimension and the dendrite arm spacing are needed in order to integrally describe the evaluationof the solidification microstructure completely