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

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.