Functionally Graded Ni-Ti Shape Memory - Production And Characterization

A functionally graded shape memory alloy was investigated by thermal, mechanical, thermomechanical and structural analysis, namely using in-situ synchrotron-based x-ray diffraction during cyclic tensile load/unload. Diffraction patterns were recorded under applied stress during the stress-induced martensitic transformation, analyzed and interpreted in view of the evolution of microstructure. The phase transformations temperatures were determined by DSC analyses. The thermomechanical behavior was analyzed by three-point bending test. The present study focusses on the localized heat treatment (Joule heat effect) of NiTi wires, using an equipment that gives a large variety of graded treatments. Structural, mechanical and thermomechanical characterization is presented in order to get a perspective of the optimization parameters for the adequate graded functionality.