The reorientation of the 2H martensite phase in Cu–Al–Mn shape memory single crystal alloy

Regarding the deformation processes in shape memory alloys, large amount of experimental data on stress-induced martensitic transformations exist in the literature. Much less evidence is available on the mechanics of the twinning processes in the martensitic phases (particularly the level and orientation dependence of twinning stresses), although they provide recoverable strains of the same order. In this work, twinning deformation processes in the 2H martensite phase in Cu–Al–Mn shape memory alloy single crystals were investigated. It was found that out of the three possible twinning modes (compound, type-I and type-II), the type-II twinning mode prevails for most of the load axis orientations in compression. The reason is the relatively large twinning stress for compound twinning in Cu–Al–Mn comparable to that for type-II twinning.