P. Palanisamy, M. Fox, R. Vaidyanathan, University of Central Florida, Orlando, FL; A. Antoniou, A. Misra, Los Alamos National Laboratory, Los Alamos, NM; S. Padula, G. Bigelow, R. Noebe, NASA Glenn Research Center, Cleveland, OH
Conventional mechanical testing, nano- and micro-indentation, and in situ neutron diffraction at stress and temperature were used to investigate superelasticity and the shape-memory effect across geometrical and microstructural length scales. Aspects addressed in the context of superelasticity in NiTi include: homogeneous vs. heterogeneous deformation and the role of dislocation and interfaces vis-a-vis misfit strain accommodation, elastic strain energy, and frictional resistance contributions to the thermodynamics of the stress-induced phase transformation. In the case of shape-memory behavior, comparisons are made between results from micron-scaled wires and bulk cm-scaled specimens. Results from monotonic loading and constrained recovery (heating under load) experiments in a NiTiPd shape memory alloy are presented with emphasis placed on specimen fabrication and electropolishing methodologies.
Summary: Conventional mechanical testing, nano- and micro-indentation, and in situ neutron diffraction at stress and temperature were used to investigate superelasticity and the shape-memory effect across geometrical and microstructural length scales. Aspects addressed in the context of superelasticity in NiTi include: homogeneous vs. heterogeneous deformation and the role of dislocation and interfaces vis-a-vis misfit strain accommodation, elastic strain energy, and frictional resistance contributions to the thermodynamics of the stress-induced phase transformation. In the case of shape-memory behavior, comparisons are made between results from micron-scaled wires and bulk cm-scaled specimens. Results from monotonic loading and constrained recovery (heating under load) experiments in a NiTiPd shape memory alloy are presented with emphasis placed on specimen fabrication and electropolishing methodologies.
