Sub-Rapid-Solidification Dominated Microstructure Modification and Strength Increment for Wire-Arc Directed Energy Deposited Al-Ce-Mg Alloys

Abstract

Conventional cast Al-Ce alloys are challenged by the increasing demand for improved mechanical properties. To address this issue, in this study, wire-arc directed energy deposition (WA-DED) is employed for the fabrication of Al-15Ce-3Mg (wt%) alloy components. We aimed to tune the microstructure and mechanical properties via the inherent sub-rapid-solidification effect of WA-DED. In addition to significant microstructure refinement, a decrease in arc heat input leads to a larger cooling rate, up to 346 °C/s, and triggers the transition from hypereutectic to near-eutectic α-Al/Al11Ce3 microstructures with the suppression of primary Al11Ce3 intermetallics. Such microstructural modification improves the mechanical properties, resulting in higher yield and ultimate tensile strengths than those of the as-cast counterpart alloy. The fracture process involves the formation of dimples around Al11Ce3, cracking of large Al11Ce3 particles, and growth, merging, and fracture of pores. The strength increment is mainly contributed by particle-size strengthening mediated by microstructure refinement as well as the targeted formation of near-eutectic α-Al/Al11Ce3 microstructures.