Diffusion-controlled mechanical property-enhancement of Al-20wt.%Si ribbon annealed under high static magnetic fields, from the microscale to the atomic scale

Abstract

Al-20wt.%Si hypereutectic alloys were designed in order to study how a high static magnetic field (HSMF) during annealing affected the microstructure evolution, atomic diffusion, and resultant mechanical properties from the microscale to the atomic scale. Our results indicate that the size of the primary silicon particles (PSPs) increased with increasing temperature, while it decreased with increasing magnetic flux density (MFD). The solid solubilities of the Al matrix were 0.84 wt% and 0.53 wt% for the ribbons annealed at 0 T and 8 T, respectively. HSMF decreased the precipitation rate of Al from the PSPs and retained the solute trapping effect in the PSPs during annealing. After annealing the ribbon, the Al matrix retained the lattice distortions under the HSMF. Applying a HSMF led to the coexistence of grain boundary strengthening, particle strengthening, dislocation strengthening, and solid solution strengthening, so the hardness and elastic modulus increased with increasing MFD. Compared with the ribbon annealed at 8 T, the ribbon annealed at 0 T had a hardness and elastic modulus improved by 139.47% and 1053.2%, respectively. This paper presents a new way to design heat treatments and even solidification processes for metallic materials by controlling their diffusion by applying an HSMF.