Mechanism for the Pseudoelastic Behavior of FCC Shape Memory Nanowires

Pseudoelasticity and shape memory have been recently discovered in single-crystalline FCC nanowires of Cu, Ni, Au and Ag. The deformation mechanism responsible for this novel behavior is surface-stress-driven reorientations of the FCC lattice structure. A mechanism-based continuum model has been developed for the lattice reorientation process during loading through the propagation of a single twin boundary. Here, this model is extended to the nucleation, propagation and annihilation of multiple twin boundaries associated with the reverse reorientation process during unloading. The extended model captures the major characteristics of the loading and unloading behavior and highlights the dominating effect of the evolution of twin boundary structure on the pseudoelasticity.