Decoding the role of lattice strain on abnormal grain growth

Why abnormal grain growth (AGG), where only few grains grow large, happens is a pending question in the field. Theories relate AGG to local chemical fluctuations or grain boundary (GB) crystallography, but both cannot explain AGG in pure metals, and why the growth advantage maintains. Contrary, our preliminary experiments suggest local strains to serve as an important origin of AGG. 3D(4D)-XRD revealed local strains of ~10-4 – equal to several 10 MPa stress – in well annealed metals. Applying stresses of this magnitude uniformly during annealing in a dilatometer, already led to a significant grain size increase compared to the solely annealed counterparts. Local strain hot spots and their evolution with time may thus trigger AGG. Here we aim to track the local strain distribution of fully recrystallized nickel samples in-situ using 3DXRD and dark-field X-ray microscopy to understand how they affect the initiation and progression of AGG, to unravel this peculiar phenomenon.