Effects of ultrasound assisted solidificaiton on the microstructure and mechanical properties of nano-sized TiB2/Al-4.5Cu composites

Ultrasound assisted solidification (UAS) was applied in the fabrication of nano-sized TiB2p/Al-4.5Cu composites with the aim of decreasing the aggregation of TiB2 particles at alpha-Al grain boundaries (GBs) and inducing more TiB2 particles to distribute within grains. Experimental results showed that UAS could remarkably refine microstructure of Al-4.5Cu matrix and induced more TiB2 particles to distribute within alpha-Al grains, leading to the further improvement in both strength and ductility of composites. This research indicated that ultrasound was able to promote the nucleation of alpha-Al on more TiB2 particles and made TiB2 particles more susceptible to engulfment by moving solid/liquid interface during the solidification. Curve regression fitting method was conducted based on the strengthening model considering yield strength of composites, by which it was found that the ratio of TiB2 particles playing strengthening effects was increased from 0.035 to 0.06 with UAS treatment, indicating that the improvement in mechanical properties of composites treated with UAS was mainly attributed to the distribution of more nano-sized TiB2 particles within alpha-Al grains.