Abstract: One of the critical challenges in additive manufacturing or powder metallurgy is the efficient reuse of metallic powders, particularly those exhibiting surface oxidation or irregular shapes. In the present study, we attempted to address this challenge by utilizing time-resolved three-dimensional imaging of the traditional sintering process. Specifically, a mixture of recycled elongated aluminum alloy powder and spherical commercial aluminum alloy powder was selected as the raw materials. The in situ sintering process was observed in four dimensions (time plus) using laboratory X-ray microscopy, integrated with a self-designed spark plasma sintering apparatus. Both the powder morphology and surface oxygen doping were characterized, with a focus on their impact on pore evolution and sintering kinetics. Through qualitative and quantitative analyses, the relationship between the dynamics of the sintering neck and both oxygen doping and sintering mechanics was established. Notably, the dynamic sintering behavior can be accurately predicted based on the transient changes in the morphology of the sintering neck. The present study therefore provides a comprehensive four-dimensional quantitative analysis and is expected to advance the understanding of the effects of powder morphology and oxygen doping on the kinetics of spark plasma sintering of metallic powders.

Key words: Aluminum alloy powder, Laboratory X-ray microscopy, Spark plasma sintering