Effect of subgrain and the associated DRX behaviour on the texture modification of Mg-6.63Zn-0.56Zr alloy during hot tensile deformation

Abstract

The individual effect of DRXed grains, subgrains and deformed grains on the basal texture of Mg–Zn–Zr alloy during hot tensile deformation was systematically studied by extracting corresponding grains. The results show that the final texture was the result of compromise between the randomized texture of DRXed grains and preferred texture of subgrains and deformed grains. The texture attribute of subgrain did not change fundamentally compared with that of deformed grain, both of which dominated the final texture profile. Prismatic <a> dislocations exerted a profound effect on the compatible deformation of unDRXed grains, giving rise to a sharp [011‾0] fiber. Few basal <a> dislocations could be detected in the unDRXed grains due to the premature exhaustion of such slip operation and subsequent substitution by non-basal slips. Subgrains, in terms of DDRX, were caused by the interaction between basal and non-basal dislocations, resulting in the protrusions segmented by the subgrain boundaries (sub-GBs) whose misorientation increased gradually as trapping dislocation proceeded. As a result, these protrusions were segregated from the parent grains and transformed into DRXed grains. CDRX proceeded by high activity of profuse dislocations. In this case, sub-GBs came from the realignment and incorporation of the accumulated dislocations in the vicinity of dislocation forest, which subdivided one grain into several subgrains that could be converted into DRXed grains in situ via the transformation from LAGBs to HAGBs by consecutively absorbing dislocations. Besides, twinning deformation was an auxiliary way of compatible deformation, which could reorientate parent grains so as to reactivate the slip systems. The contribution of resulting {101‾2} twins to the final texture was not significant yet. Ultimately, the selection of {101‾2} twin variants was also discussed.