Field ion microscopy observation of mechanical twinning in pure iridium

Mechanical twins were observed in pure Ir using field ion microscopy. The twinning plane and shear direction were determined to be {111} and 16〈112〉 respectively. Results of the morphological examination of the twin boundaries and of the coincident site lattice analysis of the twin-matrix lattice relationship suggest that these twins were formed via the stepwise nucleation and growth mechanism rather than the dislocation pole mechanism.