Nucleation mode selection during formation and growth of molten removal particles in Al2O3 ceramics laser cutting

Because of the multiple selections on different crystalline faces in nucleation process of α-alumina, it is necessary to confirm the nucleation mode and growth mechanism of molten removal particles produced by alumina ceramics laser cutting. A model based on driving force of Helmholtz and Gibbs free energies is built to compare different critical nucleation sizes and corresponding nucleation barriers among several crystal planes. The calculation shows that when alumina ceramic is cooled and solidified from a molten state, the material is preferably nucleated in the parallelepiped model with extension and stack along the (112¯0) plane. X-ray diffraction and scanning electron microscopy detections are taken to verify the nucleation mode that the morphologies thereof are shown as corners of an octahedron or edges of hexagons in different section directions. A pyramid stacking growth mode of spherical particles is proposed to coincide with the hollow micro morphology. The analysis concludes this model is feasible and it makes contribution to the potential application of removal particles for the field of ceramic powder metallurgy during laser processing.