Pressureless sintering techniques for aluminum (Al) powder have become essential to apply it to binder jetting (BJT) additive manufacturing. Liquid phase sintering of Al powder using Al-Cu eutectic alloy powder (Al-Cu aid) can achieve a relative density over 97%, regardless of the initial relative density. Various in-situ observations suggested that good wettability between Al particles and Al-Cu liquid phase plays a crucial role in sintering behaviors. In this study, a Monte Carlo (MC) simulation was employed to reproduce the liquid phase sintering behavior of Al powder using the Al-Cu aid. Furthermore, solid-liquid interfacial energy (γSL) was virtually varied to investigate the effect of wettability on the sintering behaviors. γSL was determined so that the MC simulation reproduces the experimental data, and was so low that it did not balance with the grain boundary energy. It means that the liquid phase can form a continuous liquid film between adjacent Al grains. In addition, an increment in γSL had a slight effect on the densification but significantly suppressed the grain growth. This suggested that the continuous liquid film between adjacent Al grains promotes the solution-reprecipitation kinetics (Ostwald ripening).
Kusunoki et al. (Thu,) studied this question.