Electron backscatter diffraction observations of twinning–detwinning evolution in a magnesium alloy subjected to large strain amplitude cyclic loading

• Compression/double twins can be easily induced under cyclic loading.
• Formation of compression/double twins under cyclic loading do not lead to immediate fracture of the material.
• Twin nucleation is promoted by cyclic loading whereas twin growth and twin shrinkage are inhibited.
• Residual twins are trivial even at a large strain amplitude.

An extruded ZK60 magnesium alloy was subjected to fully-reversed strain-controlled cyclic loading at a strain amplitude of 4.0% in the extrusion direction in ambient air. Electron backscatter diffraction (EBSD) analyses were conducted on samples taken from companion specimens terminated at different loading cycles to study the twinning–detwinning process and the evolution of the twin structures at different stages of cyclic deformation. It is observed that the twin nucleation sites are increased whereas twin growth/shrinkage is inhibited due to repeated twinning–detwinning. The enhanced twin nucleation sites are responsible for the observed increase in the number of twin lamellae and the increased twin volume fraction with loading cycles. Cyclic loading enhances formation of compression and double twins which do not result in immediate fracture of the material. With increasing number of loading cycles, more and larger sized residual tension twin lamellae can be detected by EBSD, but the total volume fraction of the residual twins is trivial.