The ability to produce a dense part of Al-based metal matrix nanocomposites using binder jetting followed by infiltration was investigated. A green density above 1.58 g/cm3 was determined to be necessary for spontaneous direct liquid infiltration to commence, and a press-compaction-assisted binder jetting process is needed to achieve this benchmark. A green density of 1.64±0.02 g/cm³ only resulted in a density of 1.65±0.03 g/cm³ by sintering at 1050 °C, which showed that densification is not possible with sintering alone. However, infiltration with Al-6061 produced specimens with a density of 2.74±0.04 g/cm³, which corresponded to a density improvement of 65%. Moreover, the infiltrated specimens had a low open porosity of 2.71±0.95% and a high hardness of 54 HRA. This study suggests that it is feasible to manufacture parts with complex shapes and superior mechanical properties using binder Jetting followed by infiltration.

The increasing number of gasoline direct injection (GDI) vehicles on the roads has drawn attention to their particulate matter (PM) emissions, which are greater both in number and mass than port fuel injected (PFI) spark ignition (SI) engines [1]. Regulations have been proposed and implemented to reduce exposure to PM, which has been shown to have negative impacts on both human health and the environment [2, 3]. Currently, the gasoline particulate filter (GPF) is the proposed method of reducing the amount of PM from vehicle exhaust, but modifications to improve the filtration efficiency (FE) and reduce the pressure drop across the filter are yet needed for implementation of this solution in on-road vehicles. This work evaluates the impacts of wall thickness and cell density on filtration efficiency and backpressure using a benchtop filtration system. For both unmodified and modified GPFs, the filtration efficiency was studied using a scanning mobility particle sizer (SMPS), and the pressure drop across the filter was obtained using a differential pressure transducer. The performance of the unmodified GPFs were investigated at three space velocities: 15,000 hr^-1, 30,000 hr^-1, and 60,000 hr^-1. Increasing space velocity through unmodified GPFs results in decreasing FE by approximately 5% for every 15,000 hr^-1 increase, which means a GPF has its lowest FE and highest pressure drop at 60,000 hr^-1. The GPF with lowest initial FE and pressure drop, 300-10, was modified by preloading calcium sulfate (CaSO₄) to form a cake layer <!-- Not hyphenated -->on the walls. The improvement of about 10% to the filtration efficiency and increase of about 6% to the pressure drop when loaded to 20 g/L indicates that a preloaded cake layer can improve performance with less penalty than increasing wall thickness.

This technical brief reports an experimental investigation on the effect of feed region density on resultant sintered density and intermediate densities (powder bed density and green density) during the binder jetting additive manufacturing process. The feed region density was increased through compaction. The powder bed density and green density were determined by measuring the mass and dimension. The sintered density was measured with the Archimedes’ method. As the relative feed region density increased from 44% to 65%, the powder bed density increased by 5.7%, green density by 8.5%, and finally sintered density by 4.5%. Statistical testing showed that these effects were significant. This study showed that compacting the powder in the feed region is an effective method to alter the density of parts made via binder jetting additive manufacturing.

The ability to produce metal matrix nanocomposites via pressing and infiltration was validated. Al/TiC nanocomposite was used as the model material. Pressing the powder in a die yielded cylindrical specimens with a green density of 1.98 ± 0.05 g/cm³, which was increased to only 2.11 ± 0.12 g/cm³ by sintering. Direct infiltration of the pressed specimens at 1050 °C for 3.5 h yielded specimens with a density of 3.07 ± 0.08 g/cm³, an open porosity of 3.06 ± 1.40%, and an areal void fraction of 8.09 ± 2.67%. The TiC nanoparticles were verified to be well dispersed using energy-dispersive X-ray spectroscopy. The measured hardness of 64 ± 3 HRA makes it a promising material for structural applications in industries such as aerospace and automotive.