An anti Si/Zr-poisoning strategy of Al grain refinement by the evolving effect of doped complex

The issue of how to avoid the poisoning phenomenon of α-Al grain refinement caused by special elements (such as Si and Zr) has always been the focus of research attention. In this work, the anti Si/Zr-poisoning of α-Al grain refinement was achieved by the evolving effect of a doped TCB complex, which is constituted by B-doped TiC (B-TiC) and C-doped TiB₂ (C-TiB₂). The results indicate that B-TiC in the TCB complex can release Ti atoms in Al melts, and the unique C-TiB₂ particles have a reproduction subsequently. The released Ti atoms by B-TiC during the evolution process act as the solute, limiting the grain growth and assisting in the refinement of the α-Al grains. Furthermore, the density functional theory calculations show that the C atoms in the interior of C-TiB₂ tend to enhance the adhesion energy of the C-TiB₂/Al interface, improving the nucleation potency for α-Al on C-TiB₂ in the Al-Si alloys or Zr-containing Al alloys. The average grain sizes of Al-7Si-0.4Mg and Al-5Cu-0.15Zr with inoculated TCB complex can be refined to 84 ± 7 μm and 63 ± 4 μm from 784 ± 58 μm and 402 ± 32 μm, respectively. Thus, the anti Si/Zr-poisoning of Al grain refinement is synergistically realized based on the dynamically evolving TCB complex. These findings provide a new direction for the grain refinement of the Al-Si alloys or Zr-containing Al alloys, as well as guidance on further research and development of grain refiners.