Twin recrystallization mechanisms in magnesium-rare earth alloys

Abstract

Binary Mg-1wt.% Gd and Mg-1wt.% 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-1Ce. 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 {101¯2} tension twinning and {101¯1} compression twinning during IPC, while profuse {101¯1} compression twinning for the TTC mode. Majority of the compression twins underwent second generation {101¯2} tension twinning to give rise to {101¯1}–{101¯2} 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 {101¯2} 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.