In situ observation of cross-grain twin pair formation in pure magnesium

Cross-grain twin pairing was studied utilising in situ optical microscopy and ex situ electron backscatter diffraction in extruded pure magnesium subjected to tension in the direction perpendicular to the extrusion direction. A twin chain spanning over seven grains was rapidly developed through twin propagation and conjoining. Formation of cross-grain twin pair by twin thickening was in/ex situ observed for the first time. It was confirmed that variant selection of the cross-grain twins that carry high Schmid factors, formed either by twin propagation or by twin thickening, was dominated by the strain compatibility between the neighbouring grains.