4D grain growth evolution and statistical tracking in a magnesium alloy using lab-based diffraction contrast tomography (LabDCT)

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Grain growth governs the strength, ductility and creep performance of metals, yet spatial heterogeneity and mechanisms of abnormal grain growth (AGG) remain debated. We coupled 4 D LabDCT with our newly developed grain-tracking toolbox (Track-4DGG) to investigate grain growth in a WE43 Mg alloy during interrupted annealing. The grain feature evolution can be extracted from the tracking results, at both individual grain and grain cluster scales. We observe pronounced spatial differences in growth kinetics, with the surface section suppressing normal coarsening but promoting AGG rates. Contrarily, the inner section contains more AGG occurrences but with lower growth rates. More than 50% of the grains within two grain diameters of the initial surface are consumed, and the surviving grains are larger than their interior counterparts. This divergence in growth kinetics is attributed to a ring-like second-phase free band (SPFB) forming towards the surface during annealing.