Formation of nanocrystalline grain structure in an Mg-Gd-Y-Zr alloy processed by high-pressure torsion

In this paper, the microstructural and hardness evolutions of an Mg-5.91Gd-3.29Y-0.54Zr (wt%) alloy during high-pressure torsion (HPT) were investigated. Deformation twinning played a crucial role in HPT-induced grain subdivision process. 1/8-revolution disk, 101¯1 101¯2 twins with different twin variants, 101¯1−101¯2 secondary twin-twin interactions activated. Primary prevailed at very central region while much finer multiple formed edge disk corresponding to area subjected relatively large plastic strain. Besides, dislocation cell substructures also developed. Nanocrystalline structure was attained after 5-revolution HPT processing, maximum reached ~120 Hv which is higher than that achieved from other traditional deformation methods.