Thermal Wave Effect and Sintering Activation Energy at the Initial Stage of Field Assisted Sintering Process for Non-conductive Al₂O₃ Powders

张龙^1,2，ZHANG Xiaomin²，ZHENG Hengwei¹

1. Department of Theoretical and Applied Mechanics, Chongqing University of Science and Technology2. Department of Engineering Mechanics, Chongqing University

摘 要：The effect of thermal wave at the initial stage for non-conductive Al₂ O₃ powders compact in field assisted sintering technique（FAST） was investigated. The Lord and Shulman type generalized thermoselastic theory was introduced to describe the influence of thermal-mechanical interaction, as well as the heat transport and thermal focusing caused by thermal wave propagation. The expression of vacancy concentration difference of the particles was deduced by considering transient thermal stress. Subsequently, the relationship between activation energy and vacancy concentration difference was obtained. The mechanism of surface diffusion, volume diffusion, simultaneous surface and volume diffusion was analyzed. The numerical simulations indicate that low sintering temperature can obtain high local temperature by the superposition effect of thermal wave. Vacancy concentration differences were improved during FAST compared with hot-pressure and pressureless sintering, thereby decreasing the sintering time. By contrast, the activation energy declined with the decrease of vacancy concentration difference in the neck growth process.

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