Study on continuous solid solution of Al and Si elements of a high current pulsed electron beam treated hypereutectic Al17.5Si alloy

This paper reports, for the first time, an interesting phenomenon associates with the high current pulsed electron beam (HCPEB) treatment: continuous solid solution of Al and Si elements of Al17.5Si alloy. The Al17.5Si alloy is treated by HCPEB in order to see the effect of the fairly recent technology on coarse primary Si of the alloy. After HCPEB treatment, no new phase forms in modified layer and nearly all diffraction peaks become broader than that of initial sample, Al diffraction peaks move to higher angles after treatment. Besides, coarse primary Si nearly disappears due to diffusion of Si and Al elements, Al and Si elements diffuse mutually and form continuous solid solution of Al and Si. The chemical compositions of Al and Si elements tend to gradually distribute, presenting “halos” morphology by EPMA analysis. Meanwhile, the microhardness of primary Si from the center to edge of halos microstructure also shows gradual distribution.