Twin recrystallization mechanisms in magnesium-rare earth alloys

Binary Mg-1 wt.% Gd and Mg-1 wt.% Ce wrought alloys, with basal type starting texture, are subjected to plane strain compression. Specially oriented specimens invoking c-axis extension (In Plane Compression) and c-axis compression (through thickness compression) were deformed to 6% and 13% respectively. Deformation in Mg-1Gd under in plane compression (IPC) led to evolution of sharp 'prismatic fiber' texture, whereas a weak basal texture was witnessed for Mg-1 Ce. In case of through thickness compression (TTC), Mg-1Gd gave rise to a split basal component, whereas Mg-1Ce resulted in a weak basal component with large off-basal spread. Microstructurally, Mg-1Gd displayed unequivocal activation of both {10 (1) over bar2} tension twinning and {10 (1) over bar1} compression twinning during IPC, while profuse {10 (1) over bar1} compression twinning for the ITC mode. Majority of the compression twins underwent second generation {10 (1) over bar2} tension twinning to give rise to {10 (1) over bar1}-{10 (1) over bar2} double twins. Compression and double twinned regions showed strong slip activity leading to the formation of fine recovered sub-structure. On the contrary, Mg-1Ce exhibited a conventional deformation response with twinning being predominantly of {10 (1) over bar2} tension type. Annealing led to preservation of the deformation texture components along with strong texture weakening. Recrystallization in Mg-1Gd commenced discontinuously in compression and double twins, which at higher temperatures showed favorable growth behavior consuming the still deformed matrix and tension twins. Mg-1Ce displayed continuous recrystallization marked by recovery and growth of orientationally soft tension twins along with nucleation in the vicinity of particles. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.