Work

On the microstructures evolution and interface structures of Al-17Si-4Cu alloys prepared by spray deposition upon the addition of TiB2

Year: 2025

Type: article

Abstract: This study investigates the influence of TiB₂ content on the microstructural evolution and interface structure of Al-17Si-4Cu alloy prepared by spray deposition. Using in-situ synthesis of intermediate alloys and a subsequent spray deposition process, we successfully achieved a uniform dispersion of TiB₂ in the melt and prepared Al-17Si-4Cu composites containing 0, 3, and 5 wt% TiB₂ as a reinforcing phase. Various techniques, including XRD, SEM, and TEM, characterized their microstructures and properties. The results indicate that TiB₂ content exerts a significant effect on the material properties: an increase in TiB₂ content leads to a rise in the viscosity of the semi-solid slurry. In the discrete molten droplets (during atomization), high viscosity results in increased surface roughness and decreased sphericity of the atomized droplets, along with a tendency for coarsening of primary Si. In the deposited state, TiB₂ acts as a heterogeneous nucleation core, which significantly promotes the nucleation of primary Si by providing effective nucleation sites. The refinement effect is enhanced with the increase of TiB₂ content: at 5 wt% TiB₂, the average size of primary Si is reduced to 4.74μm, while simultaneously the material density decreases to 2.31 g/cm³ and the porosity increases to 14.2%. Furthermore, TiB₂ forms semi-coherent interfaces with α-Al and primary Si, with mismatch degrees of 5.79% and 12.58%, respectively. The θ-Al 2 Cu phase also forms a semi-coherent interface with primary Si, with a mismatch degree of 15.15%. The semi-coherent interfaces formed by TiB₂ particles provide favorable lattice matching for Si nucleation, thereby refining the grains by lowering the nucleation barrier and restricting their growth. This constitutes the primary microscopic mechanism of grain refinement.

Source: Materials Today Communications

DOI: 10.1016/j.mtcomm.2025.114255