In situ analysis of multi-twin morphology and growth using synchrotron polychromatic X-ray microdiffraction

Synchrotron polychromatic X-ray microdiffraction (micro-XRD) was applied to study in situ deformation twinning of commercially AZ31 (Mg-3Al-1Zn) strip subjected to uniaxial tension. The morphology and growth of twins were analyzed in situ under the load level from 64 to 73 MPa. The X-ray microdiffraction data, collected on beamline 12.3.2 at the Advanced Light Source, were then used to map an area of 396 mu m x 200 mu m within the region of interest. The experimental set-up and X-ray diffraction microscopy with a depth resolution allow the position and orientation of each illuminated grain to be determined at the submicron size. A list of parent grains sorted by crystallographic orientation were selected to examine their twinning behavior. The results depict twin variant selection, local misorientation fluctuation and mosaic spread for multi-twins within the same parent grain. As load increases, the amplitude of misorientation fluctuation along twin trace keeps increasing. This is attributable to the accumulation of geometrically necessary dislocations.