Microstructure and texture evolution during annealing a cryogenic-SPD processed Al-alloy with a nanoscale lamellar HAGB grain structure

GH Zahid, Y Huang, PB Prangnell - Acta Materialia, 2009 - Elsevier
Acta Materialia, 2009Elsevier
The grain structure and texture evolution during annealing a Al–0.13% Mg submicron-
grained alloy, deformed by plane-strain compression (PSC) at cryogenic temperatures, has
been investigated by transmission electron microscopy and electron backscatter diffraction.
After deformation the alloy contained a lamellar grain structure with a high-angle grain
boundary (HAGB) spacing of 190nm and an area fraction of∼ 80%. On annealing the grain
structure coarsened and transformed from lamellar to equiaxed. Remarkably, the fraction of …
The grain structure and texture evolution during annealing a Al–0.13% Mg submicron-grained alloy, deformed by plane-strain compression (PSC) at cryogenic temperatures, has been investigated by transmission electron microscopy and electron backscatter diffraction. After deformation the alloy contained a lamellar grain structure with a high-angle grain boundary (HAGB) spacing of 190nm and an area fraction of ∼80%. On annealing the grain structure coarsened and transformed from lamellar to equiaxed. Remarkably, the fraction of low-angle grain boundaries (LAGBs) progressively increased during annealing, to ∼50% above 300°C, leading to instability and discontinuous recrystallization at higher temperatures. This resulted in a “bimodal grain structure” comprised of bands of coarser grains and fine subgrains, arising as a result of the increase in proportion of lower-mobility LAGBs. The surprisingly large increase in LAGB fraction on annealing is shown to be related to orientation impingement, originating from the strong texture present after PSC in liquid nitrogen.
Elsevier
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