Use of computer simulation to aid the understanding of microstructural changes observed in heat-treated AIN ceramics

A parametric computational study, using the Monte Carlo method, was performed to examine the effect of γ_s1/γ_ss value and Monte Carlo step (MCS) on the key microstructural characteristics of aluminum nitride (AlN)/yttrium aluminate system. The γ_s1/γ_ss values studied in the simulation ranged from 0.1 to 1.0 and covered the non-wetting and wetting situations for this liquid phase sintered material. Grain morphology and contiguity of the resultant microstructures were determined. Validation experiments were performed on sintered and heat-treated AlN ceramics to study the effect of time, temperature, and grain boundary phase level on the microstructural development. In addition to contiguity, dihedral angle and grain boundary phase chemistry were also measured. The mimicking of experimental and computational results suggested that the remarkable microstructural changes observed during heat treatment at 1800°C might be the result of variations in the γ_s1/γ_ss value with temperature. There was also good agreement between the simulated microstructures and the AlN ceramics with different liquid phase fractions. Dihedral angle measurements of the ceramic materials confirmed the appropriateness of the γ_s1/γ_ss values used in the simula-tion.