ABSTRACT

We propose an innovative methodology to quantify the dependence of grain growth with respect to current density during flash sintering of zirconia (3YSZ) (field set under a nominal current limit of 150 mA mm⁻². This was achieved by using a notch (0.5 mm deep and 1.5 mm wide) located in the middle of a dog-bone specimen, allowing an uneven current distribution (ranging from 3 to 670 mA mm⁻²) while maintaining a fairly homogeneous temperature (1420–1500 °C). Microstructure observations nearby the notch tip confirmed localised overheating. The modelling approach decoupled thermal and electrical field effects identifying the long questioned athermal electric field effects in flash sintering. Increased current density seems to weakly restrain grain growth, to accelerate densification, to promote defects healing (i.e. notch, cracks and pores) and inter-particle bond formation. These results could rationalise the athermal effects occurring during FS and flash joining.

摘要

我们提出了一种创新的方法来量化氧化锆 (3YSZ) 闪烧过程中晶粒生长与电流密度的相关性（场设置在 150 mA mm ^-2的标称电流限制下。这是通过使用凹口（0.5 mm深和 1.5 毫米宽）位于狗骨样本的中间，允许不均匀的电流分布（范围从 3 到 670 mA mm ^-2) 同时保持相当均匀的温度 (1420–1500 °C)。缺口尖端附近的微观结构观察证实了局部过热。建模方法将热和电场效应解耦，确定了闪烧中长期受到质疑的非热电场效应。增加的电流密度似乎微弱地抑制晶粒生长，加速致密化，促进缺陷愈合（即缺口、裂纹和孔隙）和颗粒间键的形成。这些结果可以使 FS 和闪光连接期间发生的无热效应合理化。