Abstract:

To investigate the mechanism of preparing dense fine-grained alumina ceramics using different sintering methods，Al₂O₃ ceramics were prepared using conventional high-temperature and atmospheric pressure sintering，high-pressure forming and atmospheric pressure sintering，and high-temperature and high-pressure sintering methods with 0.20 μm Al₂O₃ as the raw materials.The crystal structure，microstructure，and properties of the obtained Al₂O₃ ceramics were analyzed and characterized by X-ray diffraction，scanning electron microscopy，density，and Vickers hardness tests.The sintering mechanisms of high-pressure forming，atmospheric pressure sintering，and high-temperature high-pressure sintering were also explored.The results showed that dense Al₂O₃ ceramics could be obtained by all three sintering methods，and the relative densities of the samples were 96.64%，97.12% and 97.87%，respectively.Due to forming under a pressure of 5 GPa，the relative density of Al₂O₃ ceramic green body reached 60.02%.High pressure could make Al₂O₃ particles move closer quickly，accelerate plastic slip，eliminate small pores between grains，strengthen diffusion，and promote densification.Al₂O₃ ceramic with a grain size of only 0.22 μm was obtained after sintering at a lower temperature（1 000 ℃），which was slightly larger than the grain size of the raw Al₂O₃ powder，and the grain size was uniform.In high temperature and high pressure sintering，applied pressure could increase the driving force of sintering，and dense samples could be obtained at low temperatures for a short time.Since the grain size of the samples formed at high pressure and sintered at normal pressure was the smallest，the samples showed the largest Vickers hardness，which was 1 835.

Key words: Al₂O₃ ceramics, high pressure forming, high temperature and high pressure sintering, microstructure, sintering mechanism