Thermal Stability of CP-Aluminium during Annealing after ECAE
Samples of a hot-rolled AA1050 Aluminium alloy have been deformed by ECAE for 4 and 8 passes following route C. The structural stability of the samples after annealing treatments in the range 200°C to 350°C during 1 to 1000 minutes has been investigated. After 4 ECAE passes, the microstructure is not homogeneous. EBSD-scans show that the former grains can still be identified and that these grains show a different stage of subdivision. After 8 passes the structure is more homogeneous. During subsequent annealing the (sub)structure changes following a common pattern, but with different kinetics in all former grains. At first the dislocation density decreases, illustrated by an increase in image quality of the EBSD-scans and a sharpening of the (sub)structure can be observed. The (sub)grain size remains practically constant during this phase. At a given time, different from one (original) grain to another, some (sub)grains start to grow following an ‘abnormal grain growth’ pattern. This happens at all investigated temperatures. The kinetics and mechanisms of this microstructural evolution will be discussed.
B. Bacroix, J.H. Driver, R. Le Gall, Cl. Maurice, R. Penelle, H. Réglé and L. Tabourot
S. Poortmans and B. Verlinden, "Thermal Stability of CP-Aluminium during Annealing after ECAE", Materials Science Forum, Vols. 467-470, pp. 1319-1324, 2004