脉冲电流烧结Al_2O_3颗粒的广义热弹性分析

Thermoelastic analysis of Al_2O_3 powder in pulse electric current sintering

脉冲电流烧结过程的颈部形成机理,特别是非导电粉末材料,是需要着重研究的核心问题。以非导电Al_2O_3粉末为研究对象,引入L-S(Lord and Shulman)型广义热弹性方程,初步探究烧结初期非导电粉末颈部局部高温形成以及快速烧结机理。利用Comsol Multiphysics模拟得到脉冲电流烧结过程中颗粒内部的温度场和应力场分布以及烧结颈部的化学势和空位浓度变化规律。数值结果表明,热以波的形式在烧结颈部产生叠加,形成局部高温。化学势变化表明:烧结初期表面扩散占主要作用,空位浓度差的突变使烧结颈部产生局部空位浓度梯度,促进烧结颈长过程,缩短烧结时间。

The neck growth mechanism of pulse electric current sintering （PECS）, especially for non- conductive powder, is a key problem to study. In this paper, the rapid sintering mechanism and local high temperature of the neck at the initial stage in pulse electric current sintering was investigated for non- conductive Al2O3 powders based on the L-S （Lord and Shulman） generalized thermoelastic theory. The Comsol Multiphysics was applied to numerically simulate temperature, stress distribution, and the chemical potential and the vacancy concentration of sintering neck. The results show that the heat propagated with a finite velocity, and superposition was produced at sintering neck, so local high temperature generates. The chemical potential on the edge and center of sintering neck shows that surface diffusion is main diffusion mechanism. Local vacancy concentration gradient is present on the sintering neck, promoting the sintering process and reducing the sintering time.