Modeling the Filler Phase Interaction with Solidification Front in Al(TiC) Composite Produced by the In Situ Method

This paper presents simulation results of the interaction of TiC nanoparticle in liquid aluminum. The behavior of the TiC particle in the frontal interaction region stems from the operation of a system of such forces as gravity, viscous flow drag force, and Saffman force. The difference in density between the TiC and the aluminum matrix makes the particle fall, regardless of the radius dimension; while the Saffman force—which accounts for the local velocity gradient of the liquid aluminum—causes that particles with the smallest radii considered in the calculations 6.4 × 10−8 m; 7 × 10−8 m; 7.75 × 10−8 m; 9.85 × 10−8 m are repelled from the solidification front and the particles with 15.03 × 10−8 m are attracted to it. The viscosity growth in the course of casting caused by the lowering temperature reduces this effect, though the trend is maintained. The degree to which the particle is attracted to the front clearly depends on the velocity gradient of the liquid phase. For a very small gradient of 0.00001 m/s, the particle is at its closest position relative to the front.

Effect of Nanoparticle Content on the Microstructural and Mechanical Properties of Forged and Heat-Treated TiC/2219 Nanocomposites

In this study, castings of TiC nanoparticle reinforced 2219 aluminum matrix composites with different TiC nanoparticle contents (0, 0.5, 0.9, 1.3, and 1.7 wt.%) prepared using an ultrasound-assisted stirring technology were deformed by multidirectional forging at 510 °C followed by T6 aging treatment. The microstructural evolution and mechanical properties of the 2219 alloy and its composites were investigated and compared. Optical microscopy and scanning electron microscopy revealed that the composite with 0.9 wt.% TiC nanoparticle content possessed finer grains and the lowest amount of Al2Cu phases. The electron backscattered diffraction (EBSD) was used to characterize the sub-grains. The precipitation microstructures of the 2219 alloy and composites with different nanoparticle contents were characterized by differential scanning calorimetry and transmission electron microscopy. It was found that 0.9 wt.% TiC/2219 nanocomposites contained the highest amount of θ″ and θ′ phases with shorter lengths. This might imply that the nanoparticles uniformly dispersed in the matrix could facilitate the precipitation of θ″ and θ′ phases during aging. Thus, the 0.9 wt.% TiC/2219 nanocomposite showed the best mechanical properties. The ultimate tensile strength, yield strength, and elongation of the 0.9 wt.% TiC/2219 nanocomposite increased by 24.2, 46.1, and 37.2%, respectively, compared to those of the 2219 alloy.