High-pressure torsion processing of Zn–3Mg alloy and its hybrid counterpart: A comparative study

Processing of metal hybrid nanocomposites have emerged in the recent years by means of solid-state reactions through severe plastic deformation techniques, resulting in heterogenous microstructures and mechanical properties. Despite the increased scientific interest in these unusual materials, little is known regarding their comparative attributes with respect to a homogeneous material having equivalent nominal composition. This work provides a direct comparison of the microstructure and the hardness evolution between a Zn–3Mg (wt.%) alloy and its hybrid counterpart, after high-pressure torsion (HPT) and after HPT followed by a post-deformation annealing (PDA) treatment. Experimental results indicate that both the alloy and the hybrid reach a similar level of grain refinement after HPT processing, however, grain growth follows different trends after PDA. The HPT-processed alloy exhibits clusters of Mg₂Zn₁₁ nanocrystalline domains that coalesce into coarser grains maintaining a unimodal GS distribution after PDA. On the other hand, the hybrid after PDA displays a multimodal GS distribution consisting of ultrafine Mg-rich grains containing MgZn₂ and Mg₂Zn₁₁ nanoscale intermetallics, in a matrix of coarser dislocation-free Zn grains. These observations were supported by kernel average misorientation (KAM) maps and pole figures obtained through electron backscattered diffraction (EBSD) analysis.