Microstructural Parameter-Based Characterization of Annealing Behaviour in Metals Deformed to High Strains
The transition from discontinuous recrystallization to a continuous recovery process during annealing of aluminium deformed to high plastic strains has been investigated by following several different microstructural parameters. Samples were examined following equal channel angular extrusion (ECAE), accumulated roll bonding (ARB) and high-strain conventional rolling (HSCR). Local variations in the uniformity of coarsening have been characterized by an analysis of grain size distributions, obtained from electron backscatter pattern investigations. Except for at the lowest strains the distributions were not obviously bimodal. Methods of separating the distributions into two parts based on the mean value have therefore also been examined. The results suggest that the presence of a high fraction of high angle boundaries (>15o) in the microstructure may be a necessary but not sufficient condition for continuous recovery during annealing. The annealing behaviour can be related in part to the heterogeneity of the deformed microstructures, which can be pronounced even after strains of ≈ 10 (ECAE). The presence of oxide particles in the ARB sample has a beneficial effect in limiting the grain growth.
B. Bacroix, J.H. Driver, R. Le Gall, Cl. Maurice, R. Penelle, H. Réglé and L. Tabourot
Q. Liu et al., "Microstructural Parameter-Based Characterization of Annealing Behaviour in Metals Deformed to High Strains", Materials Science Forum, Vols. 467-470, pp. 387-392, 2004