Fabrication of Al-Si-Sc alloy bearing AlSi2Sc2 phase using ultrasonically assisted molten salt electrolysis

In this work, an Al-7Si-1.5Sc alloy bearing the strengthening AlSi2Sc2 phase was successfully prepared by the addition of Sc through ultrasonically assisted molten salt electrolysis. The ultrasound transforms the lamellar and network-like AlSi2Sc2 phase into the short-bar shapes. The average size of AlSi2Sc2 phase reduces from similar to 1500 mm down to similar to 150 mm. The mechanical properties of the Al-7Si-Sc alloys have been greatly improved. The Vickers hardness of the Al-7Si-Sc alloy prepared with ultrasound assistance increase from 49 HV up to 85 HV. The ultrasound can enhance nucleation of the pre-existed Al3Sc nuclei that serve as the nucleating substrates for the ternary AlSi2Sc2 phase (through peritectic reaction). Furthermore, the pre-existed Al3Sc nuclei get dispersed under the ultrasound-enhanced melt flow and mass transfer. The final ternary strengthening AlSi2Sc2 phase correspondingly disperse in the Al based matrix. It provides a potential shorter and more effective approach to fabricate Al based alloys with uniformly distributed and refined strengthening particles. (C) 2019 Elsevier B.V. All rights reserved.