Reversible Nanoscale Deformation In Compositionally Graded Shape Memory Alloy Films

Reversible deformation through the thickness of a compositionally graded shape memory alloy (SMA) film was observed at the nanoscale. Recovery of deformation caused by nanoindentation was characterized at low temperature using atomic force microscopy with in situ heating and cooling. The film was indented at various depths so recovery due to martensite transformations through the thickness could be studied. Tests performed on a homogenous SMA film showed that the recovery exhibited a one-way shape memory effect. The compositionally graded SMA film exhibited a two-way shape memory effect resulting from the variation in the coexistence of the martensite and austenite phases.