Dispersion of TiB2 Particles in Al–Ni–Sc–Zr System Under Rapid Solidification

The dispersion behavior of ceramic particles in aluminum alloys during rapid solidification critically affects the resulting microstructure and mechanical performance. In this study, we investigated the nucleation and growth of Al3(Sc,Zr) on TiB2 surfaces in a 2TiB2/Al–8Ni–0.6Sc–0.1Zr alloy, fabricated via wedge-shaped copper mold casting and laser surface remelting. Thermodynamic calculations were employed to optimize alloy composition, ensuring sufficient nucleation driving force under rapid solidification conditions. The results show that the formation of Al3(Sc,Zr)/TiB2 composite interfaces is highly dependent on cooling rate and plays a pivotal role in promoting uniform TiB2 dispersion. At an optimal cooling rate (~1200 °C/s), Al3(Sc,Zr) nucleates heterogeneously on TiB2, forming core–shell structures and enhancing particle engulfment into the α-Al matrix. Orientation relationship analysis reveals a preferred (111)α-Al//(0001)TiB2 alignment in Sc/Zr-containing samples. A classical nucleation model quantitatively explains the observed trends and reveals the critical cooling-rate window for composite interface formation. This work provides a mechanistic foundation for designing high-performance aluminum-based composites with uniformly dispersed reinforcements for additive manufacturing applications.