Sintering of Aluminum Powder at Its 2/3 Tm via Sonication Assisted Mixing and Liquid Metal Sintering Method

Powder metallurgy is an ideal technique for manufacturing metal matrix composites, owing to its capacity for near-net shape production and minimal material waste. However, a characteristic feature of the aluminum green compacts during the sintering process is the presence of natural oxide films on the surfaces of aluminum powders, which limits the application of aluminum powder metallurgy technology. To address this, we propose a sonication-assisted mixing and liquid metal sintering strategy by which aluminum powder can be easily sintered at the temperature as low as 623 K, two-thirds of the melting point of aluminum. The present investigation demonstrates that the molten gallium enhances metallurgical bonding between the aluminum particles by acting as a “bridge” between adjacent aluminum particles and disrupting the oxide film inevitably existing on the outermost layer of aluminum powder. According to the performance analysis results, when the sintering temperature is as low as two-thirds of the melting point of aluminum, the compressive strength of the Al-5Ga sample increases by 62.5% compared with that of pure aluminum. This innovation will help powder metallurgy researchers to pursue sintering at low-temperature and has a sweeping impact on a wide range of powder metallurgy applications.