High-Temperature Mechanical Behavior of a Precipitation-Strengthened Aluminum-Cerium Hypoeutectic Alloy

This study examines the high-temperature mechanical behavior of a cast Al-Ce-Er-Sc-Zr alloy designed for applications requiring exceptional thermal stability and mechanical performance. The alloy underwent peak aging via a double-aging heat treatment, first at 300 °C for 48 hours and then at 400 °C for 24 hours. This treatment produced a microstructure comprising a hypoeutectic mixture of α-Al and Al 11 Ce 3 intermetallic phases, along with L1 2 -ordered nanoprecipitates. Based on the alloy composition and prior literature on comparable Al-Er-Sc-Zr alloys, these precipitates are inferred to be Al 3 (Er,Sc,Zr). Tensile tests conducted at room temperature, 200 °C, and 300 °C indicated a significant increase in strength resulting from the combined contributions of these phases. The alloy demonstrated 47% strength retention at 300 °C, comparable to similar high-performance Al-Ce-based alloys. Creep experiments performed at 300, 350, and 400 °C yielded apparent stress exponents of 11.96, 8.15, and 6.29, respectively, indicating a threshold stress and suggesting that creep is primarily dislocation-controlled. Scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, and X-ray diffraction were used to characterize the eutectic and nanoscale strengthening phases. Fractography and longitudinal cross-sections show that fracture evolves from mixed ductile/brittle failure associated with Al 11 Ce 3 -rich eutectic regions at room temperature to more ductile void growth and coalescence at 200-300 °C. Creep rupture occurs through damage accumulation at Al/Al 11 Ce 3 interfaces and eutectic/interdendritic regions, with more pronounced boundary-adjacent cavitation at 400 °C.