Effects of heating rate on the microstructure and mechanical properties of rapid vacuum sintered translucent alumina

Abstract

Translucent polycrystalline alumina ceramics were fabricated by rapid vacuum sintering using commercial α-Al2O3 as a starting powder and MgO as an additive. Effect of heating rate on the sintering behavior, microstructure and properties of translucent alumina was investigated. It was shown that with increasing the heating rate from 50 to 150°C/min, grain growth was inhibited due to the restrained surface diffusion, and densification was promoted due to the enhanced vacancy diffusion. The grain size decreased from 14.8μm to 4μm, and the flexural strength increased from 352MPa to 570MPa correspondingly. Further increase of the heating rate led to the increase of residual pores, which was owing to the insufficient rearrangement of the Al2O3 particles. The in-line transmission was related to the porosity and grain size.