The Effect of Melt Ultrasound Treatment on the Microstructure and Age Hardenability of Al-4 Wt Pct Cu/TiC Composite

In the present work, Al-4 wt pct Cu/TiC composite was synthesized by the molten salt route that contains submicron-sized TiC particles in the Al-4 wt pct Cu matrix. The concentration of the TiC particle in the base alloy is 7.5 wt pct. Melt ultrasound treatment was done by remelting the as-cast composite at 1023 K (750 °C) in a view to refine the size of TiC particles to nanoscale and distribute them evenly in the matrix. The microstructure and age hardenability of the untreated and ultrasound-treated composites were investigated. The TiC particles accelerate the precipitation kinetics of CuAl₂ phase in Al-4 wt pct Cu alloy. In the present study, the hardness obtained for untreated Al-4 wt pct Cu/TiC composite is 120 VHN within 5 hours of peak aging time, which is higher than the hardness of the monolithic Al-4 wt pct Cu, which is 104 VHN at 35 hours of peak aging time. Melt ultrasound treatment of Al-4 wt pct Cu/TiC composite shows no significant effect on the distribution and refinement of TiC particles in the matrix. However, it partially disintegrates the TiC into Al₃Ti and Al₄C₃ particles. The ultrasound-treated composite showed an improved hardness of about 132 VHN at 5 hours of peak aging, in comparison to that of the untreated composite, by forming denser and homogeneous CuAl₂ precipitates.