Synergistic effects of Mn and B on iron-rich intermetallic modification of recycled Al alloy
Dongfu Song, Yuliang Zhao, Yiwang Jia, Xintao Li, Yanan Fu, Weiwen Zhang
Abstract
Individual manganese (Mn) modification cannot prevent the formation of coarse and blocky Iron-rich phases in recycled Al–Si alloys. In the present work, scanning/transmission electron microscopy (SEM/TEM), thermodynamic calculations, and synchrotron X-ray imaging were comprehensively applied to reveal the synergistic effect of Mn and B (boron) on Iron-rich phase formation in Al–Si–Fe alloys during solidification. The results showed that with addition of Mn and B, the morphology of Iron-rich phase translated from the coarse primary into a uniform and hollow-shaped multibranched Chinese-script morphology. An appropriate boron amount significantly reduced the initial nucleation temperature of the primary Iron-rich phase and increased the number of nucleation cites. The TEM results show that there was no obvious orientations relationship between the AlB2 and α-Al15(MnFe)3Si2 phases. The main modification mechanism is that B was adsorbed on the oxide film surface, which hindered the formation of the Iron-rich phase at high temperature. This Mn + B compound modification method provides an alternative way to enhance the mechanical properties of recycled Al–Si alloys in industry.