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Microstructural origin of abnormal grain growth suppression in extruded Mg–Al–Ca–Mn alloy with trace cerium addition
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DOI：10.1016/j.jre.2026.07.028.png)
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Abstract
En 中文
Trace Ce microalloying (0.1 wt%) markedly enhances the thermal stability of an extruded Mg-Al-Ca-Mn alloy during thermal exposure at 350 °C. Despite similar initial grain sizes (∼1.9 μm), the 01Ce retains a much finer microstructure after exposure (∼2.31 μm), whereas the 0Ce coarsens to ∼6.61 μm with pronounced abnormal grain growth (AGG). Quasi-in-situ electron back-scattered diffraction (EBSD) result shows that AGG in the 0Ce originates from the local coupling of elevated grain-boundary curvature and strong stored-energy gradients. In contrast, Ce addition suppresses abnormal growth by increasing the resistance to grain-boundary migration and reducing the local growth advantage arising from grain-boundary curvature and stored-energy heterogeneity. High-angle annular dark-field scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (HAADF-STEM/EDS) analyses further reveal that Ce promotes the formation of fine, thermally stable Al8CeMn4-containing particles, which provide effective Zener pinning, while Al/Ca segregation at dislocations and low-angle grain boundaries (LAGBs) contributes to an additional drag to boundary migration. As a result, the 01Ce exhibits a much higher post-exposure yield strength (∼220.6 MPa vs. ∼164.3 MPa), and the loss in yield strength is reduced from ∼128.0 to ∼46.9 MPa. The present work demonstrates a Ce-induced stabilization mechanism in fine-grained Mg alloys based on the synergistic suppression of grain-growth driving force and grain-boundary mobility.
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