Twinned 2H martensite was observed in Cu-based shape memory alloys together with basal and non-basal plane stacking faults. Knowledge of the twin-boundary structure and its interaction with the faults was important to understand the deformation mechanism by twin coalescence. High-resolution electron microscopy coupled with image simulations were used for these studies. The interface of the type I twinning in 2H martensite exhibited an atomic configuration with mirror antisymmetry. An atomic plane was shared by the twinned variants in such a way that the distance between the (¯121) planes, parallel to the interface, was unchanged at the boundary and the mean atomic volume was conserved. The interaction of the boundary with a basal plane fault generated a shift in the interface. A mirror antisymmetrical boundary was maintained by introducing an imperfect interface dislocation.

Interaction of Twin Boundaries with Stacking Faults in 2H Martensite - a High-Resolution Electron Microscopy Study. A.M