Deformation dynamics and pre-compression effects on Mg-3Al-1Zn alloy: An in situ synchrotron-based multiscale study

In situ synchrotron diffraction is used to investigate deformation dynamics during unloading and reverse loading (tension) in Mg-3Al-1Zn alloy pre-compressed to different strains. The specimens are compressed along the transverse direction (TD) to -4.8% and -9.8% true strains and then stretched along TD to failure. Bulk-scale stress-strain curves, X-ray diffraction and total strain field mapping via digital image correlation are obtained simultaneously. Electron backscatter diffraction characterization is performed as a complement. Detwinning occurs immediately after unloading, and dominates the deformation upon unloading and reverse tension, and more grains are involved in the detwinning with the increase of stress, accelerating the detwinning rate. The large pre-compression strain (-9.8%) boosts the twin boundary-dislocation interaction, which impedes twin boundary motion and reduces the detwinning rate and proportion. When deformation twins are almost exhausted via detwinning, dislocation motion dominates the plastic deformation, and the transition of deformation modes leads to variations in strain hardening rate.