Abstract

The interdiffusion kinetics of Cu-Ni system and the influence of porous structure on atomic diffusion kinetics during spark plasma sintering (SPS) were investigated. The interdiffusion coefficient of the Cu-Ni system annealed under SPS is much higher than that without current when the temperature exceeds 700 °C. By comparing the interdiffusion behaviors between Ni powder/Cu foil interface and Ni foil/Cu foil interface, the interdiffusion rate at the foil/powder interface was found to be significantly higher than that at the foil/foil interface during SPS. The diffusion process at the Ni powder/Cu foil interface shows two clearly identified stages: a high diffusion rate at the initial stage with high porosity and a slower diffusion rate at the mid-late stage with low porosity. The diffusion coefficient at the initial stage is nearly 5.2 times higher than that of the mid-late stage, demonstrating that the diffusion rate at the foil/powder interface decreases with the gradual reduction of porosity during the SPS densification process. The porous structure leads to an extremely high local current density at the neck area, which results in a high density of crystal defects at the diffusion interface and subsequently accelerates atomic diffusion.

中文翻译：

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火花等离子体烧结过程中多孔结构对Cu-Ni体系互扩散动力学的影响

摘要

研究了Cu-Ni体系的相互扩散动力学以及多孔结构对火花等离子体烧结（SPS）过程中原子扩散动力学的影响。当温度超过700°C时，在SPS下退火的Cu-Ni系统的互扩散系数要比没有电流时高。通过比较Ni粉/ Cu箔界面和Ni箔/ Cu箔界面之间的互扩散行为，发现在SPS期间，箔/粉末界面处的互扩散速率显着高于箔/箔界面处的互扩散速率。Ni粉末/ Cu箔界面的扩散过程显示出两个明确确定的阶段：孔隙率高的初始阶段的扩散速率高，孔隙率低的中晚期的扩散速率较慢。初始阶段的扩散系数接近5。比中后期高2倍，表明在SPS致密化过程中，箔/粉体界面的扩散速率随着孔隙度的逐渐降低而降低。多孔结构导致在颈部区域的极高的局部电流密度，这导致了扩散界面处的晶体缺陷的高密度，并随后加速了原子扩散。