Mechanical twinning and detwinning in pure Ti during loading and unloading – An in situ high-energy X-ray diffraction microscopy study

Far-field high-energy X-ray diffraction microscopy (HEDM) was used to study {1 0 1‾ 2}〈1‾ 0 1 1〉 twinning in Ti. Twin nucleation within a bulk parent grain is observed at a resolved shear stress (RSS) of 225 MPa. During unloading, the RSS on the twin plane reversed sign, providing a driving force for detwinning. Formation of the twin, however, prevented the parent grain from returning to its original stress state even after complete unloading. The twin morphology and surrounding environment were examined using near-field HEDM.