Revealing the grain refinement and strengthening mechanisms of Al-Ce-Zr alloy via in-situ synchrotron X-ray imaging and diffraction

Al-Ce alloys are promising for high-temperature applications due to their thermally stable Al₁₁Ce₃ eutectic phase, yet their strength-ductility trade-off remains a critical challenge. This study introduces Zr to Al-5wt.%Ce hypoeutectic alloys to address this limitation. Combining thermodynamic calculations, microstructure characterization, and in-situ synchrotron X-ray imaging and diffraction, we elucidate the mechanisms of Zr-induced grain refinement and strengthening. Increasing Zr content promotes the formation of primary Al₃Zr phases, which act as heterogeneous nucleation sites, refining the average grain size from 576 ± 182 μm (Zr-free) to 452 ± 148 μm (0.5 wt% Zr). The Al-5Ce-0.5Zr alloy achieves optimized mechanical properties, with ultimate tensile strength increasing from 126 MPa to 137 MPa and elongation improving from 32 % to 37 %. In-situ experiments reveal that load transfer to the Al₁₁Ce₃ phase and enhanced strain hardening in both α-Al and Al₁₁Ce₃ contribute synergistically to strength and ductility. A quantitative model confirms that stress partitioning to Al₁₁Ce₃ rises from 170 MPa to 210 MPa with Zr addition. These findings provide critical insights for designing high-performance Al-Ce alloys via grain refinement and eutectic phase strengthening, advancing their potential in casting and additive manufacturing.