Recrystallization and Grain Growth in Al-Li Alloys Subjected to Severe Plastic Deformation
Equal channel angular extrusion (ECAE) was used to obtain ultrafine grain structures in two aluminium- lithium alloys. The specimens were subjected to severe plastic deformation up to strain value of 9,2 at room temperature. After ECAE deformation, the grain size was reduced from an initial value of 300 µm to 1 µm. The main purpose of this study was to examine the recrystallization characteristics of ECAE treated specimens at temperatures of T = 0,5 and T = 0,7 Tm. At each temperature the specimens were heated for 1, 10, 100 seconds. The microstructure, texture and microhardness were examined in the as-deformed condition and after the annealing. The TEM observations indicate that in the Al-0.7 wt. % Li and Al-1.6 wt. % Li alloys, recrystallization has a continuous character. The microhardness results show that the lithium content increases, in an essential way, the mechanical properties of the alloys after severe plastic deformation and subsequent annealing. During ECAE process, a well pronounced texture with the orientation of the (441)[ 12 4 ], (145)[ 7 31] and (321)[ 3 4 6 ] types are formed within about ¼ volume of the material. After the annealing the grains acquire orientations other than those observed typically in these alloys when deformed by classical straining techniques followed by recrystallization.
B. Bacroix, J.H. Driver, R. Le Gall, Cl. Maurice, R. Penelle, H. Réglé and L. Tabourot
J. Mizera et al., "Recrystallization and Grain Growth in Al-Li Alloys Subjected to Severe Plastic Deformation", Materials Science Forum, Vols. 467-470, pp. 1301-1306, 2004