  We study a system of classical particles in two dimensions interacting
through an isotropic pair potential that displays a martensitic phase
transition between a triangular and a rhomboidal structure upon the change of a
single parameter. Previously it was shown that this potential is able to
reproduce the shape memory effect and super-elasticity, among other well known
features of the phenomenology of martensites. Here we extend those previous
studies and describe the development of the more subtle two-way shape memory
effect. We show that in a poly-crystalline sample, the effect can be associated
to the existence of retained martensite within the austenite phase. We also
study the case of a single crystal sample where the effect is associated to
particular orientations of the dislocations, either induced by training or by
an ad hoc construction of a starting sample.
