X-ray observation study of the influence of binder deposition on sintering process of aluminum binder jetting

Using transmission synchrotron X-ray imaging, we have dynamically visualized the influence of binder deposited inside green bodies on the sintering densification process in aluminum binder jetting. Specifically, green bodies with both binder-containing and binder-free regions were prepared using a binder jet printer, and the densification behavior of the different regions during heating was observed in the same field of view. We identified the binder-free region from the characteristic particle arrangement revealed by X-ray computed tomography before performing dynamic synchrotron X-ray imaging. A series of observations showed that while densification by particle rearrangement in liquid phase sintering occurs, it is somewhat suppressed in regions where binder is deposited. The results also demonstrate that, following the sintering process, regions where the degree of densification is insufficient do not necessarily coincide with regions of binder deposition, possibly due to leakage of the liquid phase. These results of this study not only suggest the importance of developing alternative binders with good pyrolysability and of optimizing the particle size distribution to guarantee sufficient strength for handling but will also be useful for investigating binder deposition patterns for densification during aluminum sintering, such as core–shell printing and line-and-space printing.