The inhibition mechanism of abnormal grain growth in dilute Mg–Al–Ca–Mn alloy through trace Gd addition

作者：Shi Liu, Honglong Ning, Cheng Wang, Kai Guan, Zhao-Yuan Meng, Haixiao Zhang, Huiyuan Wang · 发表于：Journal of Magnesium and Alloys · 年份：2025 · DOI：10.1016/j.jma.2025.07.010 · 被引用次数：18 · 研究领域：Magnesium Alloys: Properties and Applications、Aluminum Alloys Composites Properties、Metal and Thin Film Mechanics

• The AGG phenomenon is attributed to the diminished Zener pinning forces near the abnormally coarsened Al₈Mn₅. • The addition of Gd promotes the formation of uniform, fine Al₈Mn₄Gd precipitates, enhancing grain stability. • The preferential growth of Al₈Mn₅ adjacent to Al₂Ca during the homogenization process induces heterogeneous distrubution of Al₈Mn₅. • Al₈Mn₄Gd has a lower Gibbs free energy than Al₈Mn₅, resulting in more uniform and stable growth behavior. Abnormal grain growth (AGG), a prevalent phenomenon in dilute magnesium (Mg) alloys during elevated-temperature processing, significantly compromises mechanical performance through microstructural degradation. This study investigates AGG evolution in a heat-treatable Mg–1Al–0.3Ca–0.5Mn (wt.%) alloy, revealing its fundamental mechanism through phase interaction analysis. The AGG initiation is predominantly driven by Zener pinning force attenuation around abnormally coarsened Al₈Mn₅ precipitates. Mechanistically, this heterogeneous coarsening stems from preferential Al₈Mn₅ phase growth kinetics adjacent to Al₂Ca phase during homogenization treatment, creating localized pinning force discontinuities. However, addition of 0.2 wt.% Gd facilitates phase transformation from Al₈Mn₅ to thermally stable Al₈Mn₄Gd with lower Gibbs free energy, thereby promoting a more uniform and refined precipitate distribution. Consequently, the Gd-containing alloy exhibits enhanced grain thermal stability, maintaining a refined microstructure wi...