Tunning the L-L Phase Separation of Al-Bi-TiB ₂ Multiphase Composites Through Heterogeneous Nucleation and Ultrasound Cavitation

Abstract

The liquid-liquid (L-L) separation leads to severe inhomogeneity of Al-Bi monotectic alloys. In this study we developed an Al-Bi-TiB₂ multiphase composites, in which TiB₂ particles act as the substrates, to stimulate heterogeneous nucleation of Bi-rich phase. Further, ultrasonic cavitation and acoustic streaming can improve the dispersion of TiB₂ particles, leading to spheroidization of the refined Bi-rich dispersoids. The incorporation of TiB₂ and ultrasonic vibration treatment (UVT) reduces the average diameter of Bi-rich phase from 81.9 μm to 6.8 μm, with the sphericity increasing from 75% to 90%. Divergent trends in the Young’s moduli has been recorded as a function of the Bi content in the composites with and without UVT. The results demonstrate that through nucleants and ultrasonic activation, one can affect the L-L phase separation of monotectic alloys.

Keywords: Al-Bi-TiB2 composites, In-situ reaction, Ultrasonic vibration, Acoustic cavitation, Solidification process