Microstructural evolution in Mg-3Gd during accumulative roll-bonding

An Mg-3Gd (wt. %) alloy has been deformed by accumulative roll bonding through four cycles to an equivalent strain of 3.2. The deformed microstructure has been fully characterized by advanced electron microscopy techniques and the mechanical properties are determined by tensile testing. Three characteristic microstructures have been identified and characterized as: cell blocks, twin blocks and nanograins, all with boundary spacings of 100-200 nm. These structures illustrate a structural subdivision by low angle dislocation boundaries and high angle boundaries, which shows a clear resemblance with deformation microstructures in fcc and bcc metals deformed to high strains. The structural evolution has its origin in dislocation and twinning based plasticity which is quantified. The structure-strength relationship of this low-alloyed Mg-3Gd is analysed.