Tracking the emergence and persistence of abnormal grain growth in aluminum

A polycrystal manifests abnormal grain growth (AGG) when a subset of grains grows rapidly into an environment of largely stagnant matrix grains. If allowed to proceed to completion, the final microstructure can be orders of magnitude coarser than in the initial state. AGG is far from a rare occurrence, but its underlying mechanism(s) continue to confound researchers—the primary problem being a lack of time-resolved experimental data revealing the migration of abnormal/matrix interfaces in 3D. Evidence suggests that local inhomogeneities in the distribution of crystallographic orientations as well as second-phase pinning particles play a decisive role in determining where in a specimen AGG occurs and how fast. By combining DCT + PCT scans, performed between sequential anneals of a commercial-grade aluminum alloy, we gain access to both distributions in 4D, which promises to deliver a robust experimental basis for resolving some of the open questions surrounding the phenomenon of AGG.