Process-specific design strategy enables exceptional as-deposited strength-ductility synergy in novel Al–Ce alloys via additive friction stir deposition (AFSD)

A process-specific alloy design strategy was employed to achieve exceptional as-deposited strength-ductility synergy in Al-Ce alloys, eliminating the need for post-aging treatments. Al-Ce alloys are inherently suited for high-temperature aerospace applications due to their excellent creep resistance and thermal stability, attributed to the thermally stable Al11Ce3​ intermetallic phase in Al- Al11Ce3​ eutectic microstructures. Using CALPHAD simulations, new alloy composition was designed to incorporate solid solution and precipitation strengthening, in addition to composite strengthening achieved by Al11Ce3 phase in Al-matrix. Additive friction stir deposition (AFSD) was employed on cast material to fabricate 3D builds, significantly refining the microstructure through fragmentation of Al11Ce3 lamellae into smaller, uniformly dispersed particles, while inducing Al3Sc nanoprecipitates during deposition. Microstructures and tensile behavior of the cast and AFSD materials were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atom probe tomography (APT), and small-scale tensile testing. The AFSD alloy demonstrated remarkable improvements in mechanical properties: while the cast alloy fractured prematurely at 230 MPa with no ductility, the AFSD alloy achieved a yield strength of 385 MPa, a UTS of 530 MPa, and 12.6% plastic strain under tension. The as-deposited properties surpassed those of cast, extruded/Hot isostatically pressed (HIP’d), or laser powder bed fusion (LPBF)/direct energy deposited (DED) Al-Ce based alloys reported so far, even after their aging. This approach leverages process-specific dynamics, such as deformation and localized high temperatures, to achieve in-situ precipitation and microstructural refinement. The strategy represents a transformative pathway for designing energy-efficient, high-performance materials for additive manufacturing.