Microstructure Evolution during Creep Deformation of Laser Powder Bed Fused Al-Ce based Alloys

Many applications in automotive, aerospace and energy sectors require lightweight high temperature aluminum alloys. Aluminum-Cerium (Al-Ce) based alloys have shown promise for these applications due to their demonstrated high temperature properties and amenability to various manufacturing processes, including additive manufacturing. This presentation focuses on the microstructural evolution observed in selective Al-Ce based alloys during creep deformation. These Al-Ce based alloys were manufactured by laser powder bed fusion (LPBF) using gas atomized powders. The mechanical properties and creep properties of various Al-Ce alloys will be compared. In the as-built state, rapid solidification leads to a microstructure consisting of fine eutectic solid solution Al and intermetallic Al₁₁Ce₃ structures, well distributed within the melt pool and along the melt pool boundaries. After creep deformation, a segregation between the Al and eutectic structure was observed, manifested by the formation of a thin layer of nearly-pure Al along the grain boundaries. The magnitude of the layer was dependent on the creep deformation conditions. Notably, no such segregation was observed in the same alloy, which underwent only heat treatment under same conditions but without the application of stress. The formation mechanisms of the segregation will be elucidated with respect to the microstructural evolution and diffusion at creep conditions, and its impact on the creep properties of Al-Ce based alloys will be discussed.