Microstructures and mechanical properties of the Al-Cu-Sc alloys prepared by ultrasound-assisted molten salt electrolysis

An Al-4Cu-Sc alloy bearing the strengthening ternary W- (Al, Cu, Sc) phase has been successfully prepared by molten salt electrolysis (MSE) assisted by ultrasound. Modification of the morphology at W(Al, Cu, Sc) ternary phase and mechanical properties of the Al-4Cu-Sc alloy are comprehensively studied in this work. Without the presence of ultrasound, a quantity of large-clustered eutectic W-phase precipitate around grain boundaries, accompanied by a small amount of bulk peritectic W-phase nucleating on the substrate of pre-existed Al3Sc. Both the eutectic and peritectic W-phase get significant refinement and dispersion in the presence of ultrasound. The size of W-phase cluster reduces from length similar to 150 mu m and width similar to 30 mu m down to diameter about 30 mu m. The refining mechanism of W-phase should be attributed to the enhanced nucleation rate for pre-existed Al3Sc as well as the uniform distribution of solute in the presence of ultrasound. The values of Vickers hardness and yield strength of the alloy prepared by synergetic ultrasound assisted electrolysis and solidification process are about 68 H V and 157 MPa, approximately 36% and 67% higher than those of the MSE alloy. It should be due to the ultrasound-enhanced refinement and dispersion of fine W-phase, serving as strengthening phase. (C) 2019 Elsevier B.V. All rights reserved.